During the life of a structure impact by foreign objects can be expected to occur during manufacturing, service and maintenance operations. An example of in service impact occurs during aircrafts takeoffs and landing. During the manufacturing process or during maintenance tools can be dropped on the structure, in this case the impact energy is small, laminated structures are more susceptible to impact damage often cannot be detected by visual inspection. This internal damage can severe reductions in strength and further reductions occur under the load. Therefore the effects of foreign object impact on composite structure must be understood and proper measures should be taken in the design process to account for expected events. Concerns about the effects of impact on the performance of composite structures have been a factor in limiting the use of composite materials. For these reasons the problem of impact has received considerable attention in the literature. The process of impact damage initiation and growth, and identify the governing parameters are important for the formulation of numerical models for damage prediction, for designing impact resistant structures and for developing improved material systems. An important aspect of a model for predicting the impact dynamics is to accurately describe the behavior of the target under impact loading conditions. For some simple cases the structural loading can be modeled by a simple spring-mass system or by using the quasi-static behavior and considering the energy balance for a system. But in general more sophisticated beam, plate or shell theories are required to model the structure. .Keywords: FEA, Low-velocity impact, LS DYNA, Modeling, Simulation
Study on Low Velocity Impact on Composite MaterialsJakir Hossen
An investigation was performed on impact damage in laminated composites caused by low-velocity impact. The major objective of the study was to fundamentally understand the failure mechanisms and mechanics of fiber-reinforced composites resulting from impact and to identify the essential parameters governing the impact damage.
International Refereed Journal of Engineering and Science (IRJES) is a peer reviewed online journal for professionals and researchers in the field of computer science. The main aim is to resolve emerging and outstanding problems revealed by recent social and technological change. IJRES provides the platform for the researchers to present and evaluate their work from both theoretical and technical aspects and to share their views.
Application of fuzzy logic reasoning model for determining adhesive strength ...IJAMSE Journal
This paper shows a elaborates new methodology for calculating Adhesive Strength of thin film coating
using approximate fuzzy reasoning. This approach mainly focuses on nano and micro thin films for evaluating adhesion strength. The influence of various coating parameters(Critical force, loading rate,Displacement rate, Coefficient of friction, Tip radius and Tip wear) on quality of adhesion strength isconsidered. is used Modeling and Simulation is done with the help of fuzzy logic toolbox and results are shown.
This document discusses modeling the elastic properties of laminated composites. It first defines composites as materials made of two or more distinct constituent materials. It then discusses various properties of composites like strength and corrosion resistance. It classifies composites based on their matrix material and reinforcement type. It also discusses volume and weight fractions. Rules of mixture are presented for calculating longitudinal and transverse modulus. Stress-strain relationships and analysis methods for orthotropic laminates are described. Forces, moments, and the inverse of the stiffness matrix for laminated composites are defined. Computer simulation of composite modeling allows for virtual testing of multiple design scenarios.
Improvement of the Shell Element Implemented in FEASTSMTiosrjce
The paper deals with shear locking problem in shell element. Shear locking does not mean complete
rigidity, it refers to unwanted high-stiffness behavior that influences the solution but does not over whelm it, so
that convergence with mesh refinement is slowed but not prevented. In the present study the Bilinear
Degenerated Shell (BDS) element model is improved based on the bubble function for membrane strain energy
and selective integration for the shear energy. After formulation of the shell element, implementation is carried
out in FEASTSMT (FINITE ELEMENT ANALYSIS OF STRUCTURES). Result of the shell element without any
bubble function terms showed sensitivity to shear locking problem. Use of bubble functions and selective
integration greatly improves the element performance. The results were compared with those available in
literatures.
This document discusses the use of cohesive zone modeling to simulate fatigue crack growth and retardation. Cohesive zone models define cohesive stresses around a crack tip that are related to crack opening width. Crack propagation occurs when cohesive stresses reach a failure value. The models can account for material properties through a cohesive law. Finite element implementations use cohesive elements located at crack fronts. The models can simulate crack closure effects, wedge effects, and predict crack growth under various loading conditions like overloads through an unloading-reloading hysteresis. Cohesive theory provides a unified way to model long cracks under constant loading as well as short cracks and overloads.
Computational analysis of effect of stacking orientation on low velocity impa...eSAT Publishing House
This document summarizes a study on the effect of stacking orientation on the low velocity impact behavior of glass fiber reinforced plastic (GFRP) composite laminates using finite element analysis. The study used ABAQUS to model GFRP laminates with different stacking orientations impacted by a rigid sphere. Results showed that maximum contact force increased with increasing difference between orientation angles at equal impact energy. Orientations with higher bending stiffness like [00/750/-750/900]s had higher maximum contact forces. The model can be extended to predict failure modes like delamination using damage criteria.
A composite material can be defined as a combination of two or more materials that
gives better properties than those of the individual components used alone. In contrast to
metallic alloys, each material retains its separate chemical, physical, and mechanical
properties. The two constituents are reinforcement and a matrix. The main advantages of
composite materials are their high strength and stiffness combined with low density when
compared to classical materials. Micromechanical approach is found to be more suitable for
the analysis of composite materials because it studies the volume proportions of the
constituents for the desired lamina stiffness and strength.
Study on Low Velocity Impact on Composite MaterialsJakir Hossen
An investigation was performed on impact damage in laminated composites caused by low-velocity impact. The major objective of the study was to fundamentally understand the failure mechanisms and mechanics of fiber-reinforced composites resulting from impact and to identify the essential parameters governing the impact damage.
International Refereed Journal of Engineering and Science (IRJES) is a peer reviewed online journal for professionals and researchers in the field of computer science. The main aim is to resolve emerging and outstanding problems revealed by recent social and technological change. IJRES provides the platform for the researchers to present and evaluate their work from both theoretical and technical aspects and to share their views.
Application of fuzzy logic reasoning model for determining adhesive strength ...IJAMSE Journal
This paper shows a elaborates new methodology for calculating Adhesive Strength of thin film coating
using approximate fuzzy reasoning. This approach mainly focuses on nano and micro thin films for evaluating adhesion strength. The influence of various coating parameters(Critical force, loading rate,Displacement rate, Coefficient of friction, Tip radius and Tip wear) on quality of adhesion strength isconsidered. is used Modeling and Simulation is done with the help of fuzzy logic toolbox and results are shown.
This document discusses modeling the elastic properties of laminated composites. It first defines composites as materials made of two or more distinct constituent materials. It then discusses various properties of composites like strength and corrosion resistance. It classifies composites based on their matrix material and reinforcement type. It also discusses volume and weight fractions. Rules of mixture are presented for calculating longitudinal and transverse modulus. Stress-strain relationships and analysis methods for orthotropic laminates are described. Forces, moments, and the inverse of the stiffness matrix for laminated composites are defined. Computer simulation of composite modeling allows for virtual testing of multiple design scenarios.
Improvement of the Shell Element Implemented in FEASTSMTiosrjce
The paper deals with shear locking problem in shell element. Shear locking does not mean complete
rigidity, it refers to unwanted high-stiffness behavior that influences the solution but does not over whelm it, so
that convergence with mesh refinement is slowed but not prevented. In the present study the Bilinear
Degenerated Shell (BDS) element model is improved based on the bubble function for membrane strain energy
and selective integration for the shear energy. After formulation of the shell element, implementation is carried
out in FEASTSMT (FINITE ELEMENT ANALYSIS OF STRUCTURES). Result of the shell element without any
bubble function terms showed sensitivity to shear locking problem. Use of bubble functions and selective
integration greatly improves the element performance. The results were compared with those available in
literatures.
This document discusses the use of cohesive zone modeling to simulate fatigue crack growth and retardation. Cohesive zone models define cohesive stresses around a crack tip that are related to crack opening width. Crack propagation occurs when cohesive stresses reach a failure value. The models can account for material properties through a cohesive law. Finite element implementations use cohesive elements located at crack fronts. The models can simulate crack closure effects, wedge effects, and predict crack growth under various loading conditions like overloads through an unloading-reloading hysteresis. Cohesive theory provides a unified way to model long cracks under constant loading as well as short cracks and overloads.
Computational analysis of effect of stacking orientation on low velocity impa...eSAT Publishing House
This document summarizes a study on the effect of stacking orientation on the low velocity impact behavior of glass fiber reinforced plastic (GFRP) composite laminates using finite element analysis. The study used ABAQUS to model GFRP laminates with different stacking orientations impacted by a rigid sphere. Results showed that maximum contact force increased with increasing difference between orientation angles at equal impact energy. Orientations with higher bending stiffness like [00/750/-750/900]s had higher maximum contact forces. The model can be extended to predict failure modes like delamination using damage criteria.
A composite material can be defined as a combination of two or more materials that
gives better properties than those of the individual components used alone. In contrast to
metallic alloys, each material retains its separate chemical, physical, and mechanical
properties. The two constituents are reinforcement and a matrix. The main advantages of
composite materials are their high strength and stiffness combined with low density when
compared to classical materials. Micromechanical approach is found to be more suitable for
the analysis of composite materials because it studies the volume proportions of the
constituents for the desired lamina stiffness and strength.
This document summarizes a study on developing a fracture mechanics model to predict the insertion force of needles cutting through tissue. Experimental tests were conducted to determine the fracture toughness, shear modulus, frictional force, and crack length for different size needles inserted at various speeds into porcine skin. A force model was developed incorporating these parameters and validated against experimental force measurements, with errors less than 0.2 N. The model accurately predicts insertion forces and shows that 61% of the force comes from creating a crack in the tissue, while 21% is from friction and 18% from spreading the tissue. Increasing insertion speed was found to not reduce force for porcine skin.
The document describes an investigation of the modal parameters of rectangular cantilever beams using experimental modal analysis. Modal parameters such as natural frequencies, damping ratios, and mode shapes were determined experimentally for cantilever beams made of mild steel and aluminum. Theoretical modal analysis was also performed and results were found to correlate well with experimental findings. Frequency response functions were measured and used to extract modal data using LabVIEW software.
Multi-Objective Genetic Topological Optimization for Design of composite wall...Sardasht S. Weli
The aim of this presentation is to show the utilization of Topology Optimization to optimize a wall barrier thickness and its resistance under the extreme environment which is blast loading.
Idealized solid propellant is models is analysed for thick sphere subjected to internal
pressure, whose casing is made of composite materials,. Results obtained from present
elements are compared with analytical results and 8 noded counterpart of MARC. Solid
Rocket Motor (SRM) is developed based on casting method where solid propellant grains
are cast into a composite or metallic casing. Generally, SRMs are exposed to extreme
loading scenarios during storage, transportation, and firing, leading to cracks in the solid
propellants. In this paper, Computational Finite Element Analysis is performed with
developed 8 node quadrilateral, 9 node quadrilateral and 6 node triangular elements
using Herrmann formulation to analyze stress and strain variations in the mid segments
of the typical SRM subjected to pressure loading. The obtained results are compared with
commercially available Finite element software
Abstract. Ensuring of permanent and continuous working process of oil-gas and field equipment alongside with the other factors, depends also on reliability of sealing units. A problem of deterioration modeling of a sealing element of a packer including into an oil field equipment complex is considered in this paper.
Dynamic Relaxation (DR) method is presented for the analysis of geometrically linear laterally loaded, rectangular laminated plates. The analysis uses the Mindlin plate theory which accounts for transverse shear deformations. A computer program has been compiled. The convergence and accuracy of the DR solutions of isotropic, orthotropic, and laminated plates for elastic small deflection response are established by comparison with different exact and approximate solutions. The present Dynamic Relaxation (DR) method shows a good agreement with other analytical and numerical methods used in the verification scheme. It was found that: The convergence and accuracy of the DR solution were dependent on several factors which include boundary conditions, mesh size and type, fictitious densities, damping coefficients, time increment and applied load. Also, the DR small deflection program using uniform meshes can be employed in the analysis of different thicknesses for isotropic, orthotropic or laminated plates under uniform loads in a fairly good accuracy.
Strength and Mechanical behavior of FRC laminaKartik_95
This document discusses failure modes and strength criteria for fiber reinforced composite lamina. It begins by describing typical failure mechanisms like matrix cracking, fiber breakage, and debonding. It then discusses determining the lamina's effective strengths under different stress states like tension and shear. Several strength criteria are presented for predicting lamina failure under multiaxial loading conditions, including the maximum stress criterion, maximum strain criterion, and quadratic interaction criteria. Graphs of experimental data are shown comparing predicted failure surfaces to test results for different composites.
This document discusses theories of composite plates and numerical methods used for bending and buckling analysis of laminated plates. It summarizes different plate theories including classical laminate theory (CLPT), first-order shear deformation theory (FSDT), and higher-order shear deformation theory (HSDT). Numerical methods covered include finite difference method (FDM), dynamic relaxation (DR), and finite element method (FEM). The document concludes that FEM can provide acceptable accuracy for modeling composite plates and is applicable to complex geometries.
1) The document discusses modeling fiber-reinforced membrane materials using continuum mechanics. Two tasks are presented: modeling the stresses in a textile membrane used in lightweight roof constructions, and modeling stresses in the aorta under blood pressure.
2) The model uses a strain energy potential that accounts for the isotropic matrix and transversely isotropic behavior of the fiber reinforcement. Boundary conditions and simplifying assumptions are applied to solve for the relevant stresses and strains.
3) In the first task, the model is applied to a textile membrane under external pressure to solve for hoop and axial stresses and strains. In the second task, the same approach is used to model stresses in the aorta wall under blood pressure and compare
IRJET- Computation of Failure Index Strength of FML and FRB CompositesIRJET Journal
This document discusses the computation of failure indices of fiber metal laminate (FML) and fiber reinforced polymer (FRP) composites with different fiber orientations. It first provides background on FRP, FML, and different types of laminate configurations. It then outlines the methodology used, which involves using classical lamination theory (CLT) and the ANSYS software to predict stresses in FML and FRP laminates under in-plane tensile loading. Specific laminate stacking sequences of [Al/45/-45/Al] and [00/45/-45/00] are analyzed. Stresses are calculated in the layers and failure indices are determined using Tsai-Wu criterion for the FRP layers and
This document presents a study analyzing the static flexural behavior of thick isotropic beams using a higher order shear deformation theory. The theory considers axial displacement as consisting of elementary bending theory displacement plus a hyperbolic shear deformation term. Governing differential equations are derived through the principle of virtual work. Numerical results for axial displacement, transverse displacement, stresses are obtained for cantilever beams under transverse loading and compared to other theories.
Determination Of Geometric Stress Intensity Factor For A Photoelastic Compac...Anupam Dhyani
Experimental and analytical studies with finite elements was done on a polycarbonate transparent material as a forerunner to a similar study on transparent glass -epoxy composites
1. The paper studies electron transport through magnetic tunnel junctions using the non-equilibrium Green's function method. It models a multi-layer structure of magnetic/non-magnetic/magnetic layers.
2. Increasing the binding strength of the insulating layer increases the electron density and disruption of energy levels. A broader band connection disrupts the insulating layer more, changing it from a non-conductor to a semiconductor or even conductor.
3. The results show that electron transport can be controlled in the non-conducting layers by changing properties of the three layers to maximize the transmission function.
Micromechanical Modeling of the Macroscopic Behavior of Soft Ferromagnetic Co...IJMERJOURNAL
ABSTRACT: Soft ferromagnetic composites consist of ferromagnetic particles embedded within nonmagnetic electrically insulating matrix. The aims of this article are twofold. In the first one, multiaxial nonlinear isothermal constitutive equations that govern the behavior of soft ferromagnetic materials are generalized to include the temperature and hysteretic effects. The second aim consists of developing a micromechanical analysis which takes into account the detailed interaction between the phases, and establishes the instantaneous concentration tensors which relate between the local magneto-thermo-elastic field and the externally applied loading. The ferromagnetic particles constituents employed in the micromechanical analysis are governed by the developed magneto-thermo-elastic coupled hysteretic constitutive relations. With the established concentration tensors, the macroscopic (global) re- sponse of the composite can be readily determined at any instant of loading. The offered micromechanical modeling is capable of predicting the response of soft ferromagnetic composites that are subjected to various types of magneto-thermo-elastic loadings, and it can be employed by the designerto easily determine the composite response for a particular desired application.
This document discusses various mechanical properties of engineering materials including hardness, creep, elasticity, hardening, and plasticity. It defines each property and describes methods for measuring hardness, factors that influence creep, the hardening process, and how plastic deformation occurs at the atomic level resulting in a permanent change in shape even after removal of stress. Measurement techniques for hardness include Rockwell, Brinell, Vickers, Knoop, and shore hardness tests. Creep is influenced by load, temperature, composition, grain size, and heat treatment. Hardening increases hardness through metallurgical processes.
1. The document analyzes damage tolerance of a fuselage stiffened panel using finite element analysis. It calculates stress intensity factors for longitudinal cracks initiated at rivet holes under internal pressurization loads.
2. The stress intensity factor is calculated using the modified virtual crack closure integral method for crack lengths from 50mm to 1000mm. The stress intensity factor increases with crack length but decreases when the crack reaches frames.
3. For a crack length of 900mm, the calculated stress intensity factor is below the material's fracture toughness, indicating the design is safe for the analyzed internal pressurization loads.
The document discusses stress analysis in restorative dentistry using finite element analysis. It provides an overview of finite element analysis, including its history, basic concepts, advantages, and limitations. It also discusses mechanical properties of dental materials and various studies that have used finite element analysis to analyze stresses in dental structures and restorations. The document aims to present finite element analysis as a useful tool for stress analysis in restorative dentistry.
Coercivity, saturation magnetisation and Size dependent properties of Nano pa...Eswaran Murugesan
Coercivity, saturation magnetisation and Size dependent properties of Nano particles
Magnetic hysteresis
Magnetic induction field lags behinds Magnetic field intensity
Hysteresis loop
If an alternating magneric field is applied to the material it’s magnetic induction will traceout a loop called HYSTERESIS LOOP
Saturation of magnetization
Increase in applied external magnetic field (H) cannot increase the magnetization of material further
Retentivity of magnetization
Remaining magnetization when external magnetic field (H)
Co-ercivity of magnetization
Magnetization (B) =0 for negative to the external magnetic field (H)
Size dependent properties of nano particles
SIZE plays vital role on the mechanical properties
Plastic deformation of nanostructure coating strictly depends on the grain size
With decrease in grain size beyond certain limit, Hall-Petch eqn doesn’t apply
this indicates particular material will become softer
Reduction of granule size has remarkable effect on improvement of resistant against erosion in nanostructure and composite materials
Erosion behavior under low and average loading condition in nano-materials shows that , because of higher stiffness, erosion resistance of these materials is more than that of materials with large size.
Effect of size on Mechanical properties
It is differ from conventional or bulk structures
Effective elastic properties of these small-scale structural elements strongly depends on their size.
Small-scale structures are very sensitive to the micro-structural features of the material such as the GRAIN SIZE , the finite NUMBER OF GRAINS ,BOUNDARY LAYER THICKNESS , TEXTURE and DISLOCATION STRUCTURE .
Research studies have shown that when particles ‘ size reaches to the dimension of nanometer , remarkable improvement can be observed in strength of composites
In nanoscale bars and plates effective elastic properties of structural elements strongly depend on their size
It was found that a nano-whisker can have a mechanical strength approaching to the theoretical strength values
Strength increase becomes appreciable only on diameter less than 10microns
thanks
This document summarizes a research paper analyzing the sustainability opportunities and challenges of the biofuels industry in India. The paper aims to answer three questions: 1) What are some significant sustainability opportunities and challenges of the biofuels industry? 2) What is the current state of biofuel operations in India? 3) What initial steps can be taken toward sustainable biofuel development? The response analyzes strategic sustainable development approaches and tools like the Natural Step Framework. Key points discussed include economic, environmental and social sustainability assessments of biomass and biofuels, including issues of profitability, efficiency, equity, energy balance, greenhouse gas emissions and life cycle assessments. Challenges in implementing ethanol blending programs in India like taxation and availability of
This document presents a method called Joint Sentiment and Topic Detection (JST) that can simultaneously detect sentiment and topic from text without requiring labeled training data. JST extends the Latent Dirichlet Allocation (LDA) topic model by adding an additional sentiment layer. It assumes words are generated from a joint distribution conditioned on both a sentiment label and topic. The document evaluates JST on movie reviews and product reviews using domain independent sentiment lexicons as prior information. Experimental results show JST can accurately classify sentiment at the document level and detect topics for different domains.
This document provides a review of face recognition techniques and several face video databases. It discusses four main face video databases: NRC-IIT, Honda/UCSD, Choke Point, and McGill. For each database, it describes the image characteristics, subjects, environment, limitations, and relevant research. It also reviews approaches for face detection, feature extraction, and recognition in video-based systems. Common techniques discussed include Viola-Jones detection, SIFT features, and combining detection with tracking across frames. The performance of these methods on the different video datasets is analyzed and areas for future improvement are identified.
This document summarizes a laboratory study on treating and reusing greywater. The study involved collecting greywater from bathroom sinks and washing areas of an apartment building. The greywater was treated using a system with sedimentation, sand filtration, and storage tanks. Water quality parameters like pH, turbidity, COD, DO were tested on the raw and treated greywater. Results showed the treated greywater met standards for reuse for gardening, toilet flushing and street washing after reductions in turbidity, COD and other parameters. The study concluded greywater treatment and reuse is an effective small-scale method to reduce water usage and demands on municipal supplies.
This document summarizes a study on developing a fracture mechanics model to predict the insertion force of needles cutting through tissue. Experimental tests were conducted to determine the fracture toughness, shear modulus, frictional force, and crack length for different size needles inserted at various speeds into porcine skin. A force model was developed incorporating these parameters and validated against experimental force measurements, with errors less than 0.2 N. The model accurately predicts insertion forces and shows that 61% of the force comes from creating a crack in the tissue, while 21% is from friction and 18% from spreading the tissue. Increasing insertion speed was found to not reduce force for porcine skin.
The document describes an investigation of the modal parameters of rectangular cantilever beams using experimental modal analysis. Modal parameters such as natural frequencies, damping ratios, and mode shapes were determined experimentally for cantilever beams made of mild steel and aluminum. Theoretical modal analysis was also performed and results were found to correlate well with experimental findings. Frequency response functions were measured and used to extract modal data using LabVIEW software.
Multi-Objective Genetic Topological Optimization for Design of composite wall...Sardasht S. Weli
The aim of this presentation is to show the utilization of Topology Optimization to optimize a wall barrier thickness and its resistance under the extreme environment which is blast loading.
Idealized solid propellant is models is analysed for thick sphere subjected to internal
pressure, whose casing is made of composite materials,. Results obtained from present
elements are compared with analytical results and 8 noded counterpart of MARC. Solid
Rocket Motor (SRM) is developed based on casting method where solid propellant grains
are cast into a composite or metallic casing. Generally, SRMs are exposed to extreme
loading scenarios during storage, transportation, and firing, leading to cracks in the solid
propellants. In this paper, Computational Finite Element Analysis is performed with
developed 8 node quadrilateral, 9 node quadrilateral and 6 node triangular elements
using Herrmann formulation to analyze stress and strain variations in the mid segments
of the typical SRM subjected to pressure loading. The obtained results are compared with
commercially available Finite element software
Abstract. Ensuring of permanent and continuous working process of oil-gas and field equipment alongside with the other factors, depends also on reliability of sealing units. A problem of deterioration modeling of a sealing element of a packer including into an oil field equipment complex is considered in this paper.
Dynamic Relaxation (DR) method is presented for the analysis of geometrically linear laterally loaded, rectangular laminated plates. The analysis uses the Mindlin plate theory which accounts for transverse shear deformations. A computer program has been compiled. The convergence and accuracy of the DR solutions of isotropic, orthotropic, and laminated plates for elastic small deflection response are established by comparison with different exact and approximate solutions. The present Dynamic Relaxation (DR) method shows a good agreement with other analytical and numerical methods used in the verification scheme. It was found that: The convergence and accuracy of the DR solution were dependent on several factors which include boundary conditions, mesh size and type, fictitious densities, damping coefficients, time increment and applied load. Also, the DR small deflection program using uniform meshes can be employed in the analysis of different thicknesses for isotropic, orthotropic or laminated plates under uniform loads in a fairly good accuracy.
Strength and Mechanical behavior of FRC laminaKartik_95
This document discusses failure modes and strength criteria for fiber reinforced composite lamina. It begins by describing typical failure mechanisms like matrix cracking, fiber breakage, and debonding. It then discusses determining the lamina's effective strengths under different stress states like tension and shear. Several strength criteria are presented for predicting lamina failure under multiaxial loading conditions, including the maximum stress criterion, maximum strain criterion, and quadratic interaction criteria. Graphs of experimental data are shown comparing predicted failure surfaces to test results for different composites.
This document discusses theories of composite plates and numerical methods used for bending and buckling analysis of laminated plates. It summarizes different plate theories including classical laminate theory (CLPT), first-order shear deformation theory (FSDT), and higher-order shear deformation theory (HSDT). Numerical methods covered include finite difference method (FDM), dynamic relaxation (DR), and finite element method (FEM). The document concludes that FEM can provide acceptable accuracy for modeling composite plates and is applicable to complex geometries.
1) The document discusses modeling fiber-reinforced membrane materials using continuum mechanics. Two tasks are presented: modeling the stresses in a textile membrane used in lightweight roof constructions, and modeling stresses in the aorta under blood pressure.
2) The model uses a strain energy potential that accounts for the isotropic matrix and transversely isotropic behavior of the fiber reinforcement. Boundary conditions and simplifying assumptions are applied to solve for the relevant stresses and strains.
3) In the first task, the model is applied to a textile membrane under external pressure to solve for hoop and axial stresses and strains. In the second task, the same approach is used to model stresses in the aorta wall under blood pressure and compare
IRJET- Computation of Failure Index Strength of FML and FRB CompositesIRJET Journal
This document discusses the computation of failure indices of fiber metal laminate (FML) and fiber reinforced polymer (FRP) composites with different fiber orientations. It first provides background on FRP, FML, and different types of laminate configurations. It then outlines the methodology used, which involves using classical lamination theory (CLT) and the ANSYS software to predict stresses in FML and FRP laminates under in-plane tensile loading. Specific laminate stacking sequences of [Al/45/-45/Al] and [00/45/-45/00] are analyzed. Stresses are calculated in the layers and failure indices are determined using Tsai-Wu criterion for the FRP layers and
This document presents a study analyzing the static flexural behavior of thick isotropic beams using a higher order shear deformation theory. The theory considers axial displacement as consisting of elementary bending theory displacement plus a hyperbolic shear deformation term. Governing differential equations are derived through the principle of virtual work. Numerical results for axial displacement, transverse displacement, stresses are obtained for cantilever beams under transverse loading and compared to other theories.
Determination Of Geometric Stress Intensity Factor For A Photoelastic Compac...Anupam Dhyani
Experimental and analytical studies with finite elements was done on a polycarbonate transparent material as a forerunner to a similar study on transparent glass -epoxy composites
1. The paper studies electron transport through magnetic tunnel junctions using the non-equilibrium Green's function method. It models a multi-layer structure of magnetic/non-magnetic/magnetic layers.
2. Increasing the binding strength of the insulating layer increases the electron density and disruption of energy levels. A broader band connection disrupts the insulating layer more, changing it from a non-conductor to a semiconductor or even conductor.
3. The results show that electron transport can be controlled in the non-conducting layers by changing properties of the three layers to maximize the transmission function.
Micromechanical Modeling of the Macroscopic Behavior of Soft Ferromagnetic Co...IJMERJOURNAL
ABSTRACT: Soft ferromagnetic composites consist of ferromagnetic particles embedded within nonmagnetic electrically insulating matrix. The aims of this article are twofold. In the first one, multiaxial nonlinear isothermal constitutive equations that govern the behavior of soft ferromagnetic materials are generalized to include the temperature and hysteretic effects. The second aim consists of developing a micromechanical analysis which takes into account the detailed interaction between the phases, and establishes the instantaneous concentration tensors which relate between the local magneto-thermo-elastic field and the externally applied loading. The ferromagnetic particles constituents employed in the micromechanical analysis are governed by the developed magneto-thermo-elastic coupled hysteretic constitutive relations. With the established concentration tensors, the macroscopic (global) re- sponse of the composite can be readily determined at any instant of loading. The offered micromechanical modeling is capable of predicting the response of soft ferromagnetic composites that are subjected to various types of magneto-thermo-elastic loadings, and it can be employed by the designerto easily determine the composite response for a particular desired application.
This document discusses various mechanical properties of engineering materials including hardness, creep, elasticity, hardening, and plasticity. It defines each property and describes methods for measuring hardness, factors that influence creep, the hardening process, and how plastic deformation occurs at the atomic level resulting in a permanent change in shape even after removal of stress. Measurement techniques for hardness include Rockwell, Brinell, Vickers, Knoop, and shore hardness tests. Creep is influenced by load, temperature, composition, grain size, and heat treatment. Hardening increases hardness through metallurgical processes.
1. The document analyzes damage tolerance of a fuselage stiffened panel using finite element analysis. It calculates stress intensity factors for longitudinal cracks initiated at rivet holes under internal pressurization loads.
2. The stress intensity factor is calculated using the modified virtual crack closure integral method for crack lengths from 50mm to 1000mm. The stress intensity factor increases with crack length but decreases when the crack reaches frames.
3. For a crack length of 900mm, the calculated stress intensity factor is below the material's fracture toughness, indicating the design is safe for the analyzed internal pressurization loads.
The document discusses stress analysis in restorative dentistry using finite element analysis. It provides an overview of finite element analysis, including its history, basic concepts, advantages, and limitations. It also discusses mechanical properties of dental materials and various studies that have used finite element analysis to analyze stresses in dental structures and restorations. The document aims to present finite element analysis as a useful tool for stress analysis in restorative dentistry.
Coercivity, saturation magnetisation and Size dependent properties of Nano pa...Eswaran Murugesan
Coercivity, saturation magnetisation and Size dependent properties of Nano particles
Magnetic hysteresis
Magnetic induction field lags behinds Magnetic field intensity
Hysteresis loop
If an alternating magneric field is applied to the material it’s magnetic induction will traceout a loop called HYSTERESIS LOOP
Saturation of magnetization
Increase in applied external magnetic field (H) cannot increase the magnetization of material further
Retentivity of magnetization
Remaining magnetization when external magnetic field (H)
Co-ercivity of magnetization
Magnetization (B) =0 for negative to the external magnetic field (H)
Size dependent properties of nano particles
SIZE plays vital role on the mechanical properties
Plastic deformation of nanostructure coating strictly depends on the grain size
With decrease in grain size beyond certain limit, Hall-Petch eqn doesn’t apply
this indicates particular material will become softer
Reduction of granule size has remarkable effect on improvement of resistant against erosion in nanostructure and composite materials
Erosion behavior under low and average loading condition in nano-materials shows that , because of higher stiffness, erosion resistance of these materials is more than that of materials with large size.
Effect of size on Mechanical properties
It is differ from conventional or bulk structures
Effective elastic properties of these small-scale structural elements strongly depends on their size.
Small-scale structures are very sensitive to the micro-structural features of the material such as the GRAIN SIZE , the finite NUMBER OF GRAINS ,BOUNDARY LAYER THICKNESS , TEXTURE and DISLOCATION STRUCTURE .
Research studies have shown that when particles ‘ size reaches to the dimension of nanometer , remarkable improvement can be observed in strength of composites
In nanoscale bars and plates effective elastic properties of structural elements strongly depend on their size
It was found that a nano-whisker can have a mechanical strength approaching to the theoretical strength values
Strength increase becomes appreciable only on diameter less than 10microns
thanks
This document summarizes a research paper analyzing the sustainability opportunities and challenges of the biofuels industry in India. The paper aims to answer three questions: 1) What are some significant sustainability opportunities and challenges of the biofuels industry? 2) What is the current state of biofuel operations in India? 3) What initial steps can be taken toward sustainable biofuel development? The response analyzes strategic sustainable development approaches and tools like the Natural Step Framework. Key points discussed include economic, environmental and social sustainability assessments of biomass and biofuels, including issues of profitability, efficiency, equity, energy balance, greenhouse gas emissions and life cycle assessments. Challenges in implementing ethanol blending programs in India like taxation and availability of
This document presents a method called Joint Sentiment and Topic Detection (JST) that can simultaneously detect sentiment and topic from text without requiring labeled training data. JST extends the Latent Dirichlet Allocation (LDA) topic model by adding an additional sentiment layer. It assumes words are generated from a joint distribution conditioned on both a sentiment label and topic. The document evaluates JST on movie reviews and product reviews using domain independent sentiment lexicons as prior information. Experimental results show JST can accurately classify sentiment at the document level and detect topics for different domains.
This document provides a review of face recognition techniques and several face video databases. It discusses four main face video databases: NRC-IIT, Honda/UCSD, Choke Point, and McGill. For each database, it describes the image characteristics, subjects, environment, limitations, and relevant research. It also reviews approaches for face detection, feature extraction, and recognition in video-based systems. Common techniques discussed include Viola-Jones detection, SIFT features, and combining detection with tracking across frames. The performance of these methods on the different video datasets is analyzed and areas for future improvement are identified.
This document summarizes a laboratory study on treating and reusing greywater. The study involved collecting greywater from bathroom sinks and washing areas of an apartment building. The greywater was treated using a system with sedimentation, sand filtration, and storage tanks. Water quality parameters like pH, turbidity, COD, DO were tested on the raw and treated greywater. Results showed the treated greywater met standards for reuse for gardening, toilet flushing and street washing after reductions in turbidity, COD and other parameters. The study concluded greywater treatment and reuse is an effective small-scale method to reduce water usage and demands on municipal supplies.
This document proposes and evaluates a context-based access control (CBAC) mechanism for Android systems. The CBAC mechanism allows users to set configuration policies over applications' usage of device resources and services based on the user's context. The proposed system uses context sensing and machine learning to classify contexts and then dynamically grants or revokes application privileges. Experiments show the CBAC mechanism incurs negligible energy overhead compared to the stock Android system. The CBAC framework provides improved privacy and security over existing location-based policy systems.
This document reviews techniques for automated extraction of regions of interest (ROIs) from histopathology images. It begins with an overview of the clinical workflow for histopathological image analysis, including tissue sample collection, preprocessing, embedding, sectioning, staining, and visualization. It then discusses challenges in automated analysis, particularly ROI extraction, and reviews several existing techniques including thresholding, hidden Markov models, watershed algorithms, and cellular automata active contours. Specifically, it examines works that use downsampling, multiscale processing, and object detection to extract ROIs. Overall, the document provides a summary of current approaches for automated ROI extraction from whole slide histopathology images.
This document summarizes a study on the effects of occupational stress on the work performance of police officers in Nakuru police division, Kenya. The study found that police officers experience high levels of occupational stress due to factors like role overload and ambiguity. It also found that their work performance was rated as only fair. The study established that high occupational stress negatively impacts the work performance of police officers. Additionally, it was found that police officers lack adequate welfare support despite the stressful nature of their work. The study recommends that the National Police Service Commission implement policies and mechanisms to reduce work-related stress and improve police officers' work performance.
This document discusses testing and loss measurement techniques in optical fiber communication systems. It describes how optical time domain reflectometry (OTDR) is commonly used to characterize optical fibers and locate faults by measuring backscattered light. OTDR can measure splice and connector losses, fiber quality, and reflectance. Other techniques mentioned include using a light source and power meter to check continuity and measure insertion loss. The document provides a table comparing the capabilities of different fiber testing equipment and concludes that both OTDR and optical loss test sets provide important loss measurement information to ensure healthy optical fiber communication.
This document presents a second order integral sliding mode control approach for speed control of a DC motor system. The DC motor system is modeled as a second order system with uncertainty and disturbances. Three controllers are designed and compared - a second order integral sliding mode controller, a conventional sliding mode controller, and a PID controller. Simulation results show that the proposed second order integral sliding mode controller has the fastest response time, no overshoot, smooth control input, and drives the sliding surface to zero, performing better than the other controllers in terms of robustness and disturbance rejection.
This document describes the design of a low noise amplifier (LNA) for wideband wireless receivers operating in the S-band frequency range of 2-4 GHz. It first discusses designing an LNA using lumped elements, achieving a maximum gain of 10 dB at 2.5 GHz and minimum noise figure of 2.4 dB at 4 GHz. It then presents an improved design using microstrip matching networks, obtaining a lower minimum noise figure of 0.424 dB at 2.6 GHz and higher maximum gain of 10.84 dB at 2.4 GHz. The microstrip design demonstrates better performance for noise figure and gain across the 2-4 GHz band compared to the lumped element approach.
Nuclear Magnetic Resonance (NMR) Analysis of D - (+) - Glucose: A Guide to Sp...IOSR Journals
NMR spectroscopy has a wide range of applications including exchange phenomena, the
identification and structural studies of complex biomolecules. 1D 1H-NMR without water suppression, 1D
Carbon, 1D 13C-DEPT135, 2D Cosy, 2D HSQC, 2D TOCSY, 2D HMQC, and 2D HMBC techniques were used
to completely elucidate the structure of glucose with spectral induced at 400MHz.. The spectral were analysed
using spinworks 3. The results obtained from the spectral data were systematically combined to elucidate the
structure of the D-glucose. Full characterisation of D-glucose was achieved by assigning 1H and 13C signals,
starting from the known to unknown signals.
This document discusses serial communication interfaces and error detection techniques. It begins with an introduction to serial communication interfaces and some common interfaces like RS-232, I2C, and SPI. It then discusses the differences between synchronous and asynchronous serial communication. The bulk of the document focuses on using Hamming codes for error detection and correction in serial transmission. It provides an example of how Hamming codes can be used to detect and correct single bit errors in transmitted data. The document concludes by stating that error correction can improve the reliability and fault tolerance of integrated circuits.
The document summarizes a study of different microstrip patch antenna configurations with slotted ground planes. Three antenna designs were proposed and their performance evaluated through simulation: a conventional square patch, an elliptical patch, and a star-shaped patch. All antennas were mounted on an FR4 substrate. The effects of adding different slot patterns to the ground plane on resonance frequency, bandwidth, gain and efficiency were analyzed parametrically. Key findings were that reshaping the patch and adding slots increased bandwidth and shifted resonance frequency. The elliptical and star patches in particular performed better than the conventional design. Three antenna configurations were selected for fabrication and measurement based on the simulations: a conventional patch with a slot under the patch, an elliptical patch with slots
This document describes an online signature verification system that uses vector quantization and hidden Markov models. Signatures are collected using a graphics tablet and preprocessed to reduce noise and normalize size and phase. Features like velocity, acceleration, and pressure are extracted from segments of each signature. K-means clustering is used to generate a codebook, and vector quantization maps signatures to code words. Hidden Markov models are trained on the code words using the Baum-Welch algorithm. In verification, the forward algorithm calculates the probability that a signature was generated by a claimed user's model. The system achieved an equal error rate of 14% for verification.
This document discusses performance of matching algorithms for signal approximation. It begins by introducing matching pursuit algorithms like Orthogonal Matching Pursuit (OMP) and Stagewise Orthogonal Matching Pursuit (StOMP) which are greedy algorithms that approximate sparse signals. It then describes the Non-Negative Least Squares algorithm which solves non-negative least squares problems. Finally, it discusses Extranious Equivalent Detection (EED), a modification of OED that incorporates non-negativity of representations by using a non-negative optimization technique instead of orthogonal projection.
This document describes a genetic algorithm approach for automatically generating fuzzy rules for classification problems. The genetic algorithm uses rule importance as the fitness criteria, calculated as the rule's support for each class. The algorithm encodes rules using fuzzy membership set numbers for antecedents and consequents. It iterates for a set number of generations or until a minimum number of rules are fired, selecting high-fitness rules to generate offspring via crossover. The offspring replace lower-fitness rules, and the new rule population is evaluated in the next generation. The approach aims to consistently generate optimal fuzzy rules for classification using genetic search.
Comparative Assessment of Two Thermodynamic Cycles of an aero-derivative Mari...IOSR Journals
Abstract: This paper explores the gas turbine potentials that are fully enhanced by the use of intercooling and
thermal recuperation as an engineering option available in the design of gas turbines and offered for marine
applications. It examines the off-design performance of two different cycle designs of a 25MW aero-derivative
engine by modelling and simulating each of them to operate under conditions other than those of their design
point. The simple cycle model consists of a single-spool dual shaft layout while the advanced model is
represented by an intercooled-recuperated cycle that runs on a dual-spool and is driven through a three shaft
configuration. In each case, the output shaft is coupled to a power turbine through which the propulsion power
may be transmitted to the propeller of the vessel to operate in a virtual marine environment. An off-design
performance simulation of both engines has been conducted in order to investigate and compare the effect of
ambient temperature variation during their part-load operation and particularly when subjected to a variety of
marine operating conditions. The study assesses the techno-economic impact of the complex design of the
advanced cycle over its simple cycle counterpart and demonstrates its potential for improved operating cost
through reduced fuel consumption as a significant step in the current drive for establishing the marine gas
turbine engine as a viable alternative to traditional prime movers in the ship propulsion industry.
The document describes a proposed framework called UPS for privacy-preserving personalized web search. The UPS framework aims to generalize user profiles for each query according to user-specified privacy requirements, while balancing privacy risk and personalization utility. Two key contributions of the proposed system are: 1) Supporting runtime profiling to dynamically generalize user profiles on a per-query basis; and 2) Allowing for customization of privacy requirements by users to designate sensitive topics in their profiles. Algorithms are proposed to generalize profiles to optimize these metrics during the personalization process.
This document discusses quality technical and vocational education and training (TVET) as a tool for self-reliance. It begins by defining TVET and identifying skills and knowledge as important for economic growth. The study aims to investigate factors that contribute to quality TVET for self-reliance, including student factors, school factors, instructional materials, and government strategies. A questionnaire was administered to 36 TVET teachers. The results found that students often lack background in TVET and confidence in it as a career. Schools have inadequate facilities, materials, and practical periods. Instructional materials like tools, textbooks, and ICT resources are also insufficient. The document recommends that governments prioritize TVET curriculum planning and ensure qualified teaching staff
This document summarizes a research paper that proposes a new algorithm for maintaining the shape and integrity of bio-signals over a body sensor network. The algorithm uses set theory operations instead of interpolation to synchronize signals. It also proposes a secure key management scheme to enhance security in wireless body area networks and analyzes energy consumption. The paper reviews related work in body sensor networks, describes the methodology used in the research, and presents results on evaluating the proposed algorithm's energy efficiency and effectiveness compared to previous methods.
This document discusses conducting a finite element analysis using LS-DYNA software to study the effects of low velocity impacts on composite materials. It outlines the objectives, which include reviewing literature on low velocity impacts on composites, conducting simple analyses on composite plates and comparing the results to existing research. It also describes the methodology, which involves determining contact forces, applying forces to model dynamic response, and refining the finite element model. Key steps in using LS-DYNA like modeling the composite laminate, assigning materials, defining boundary and initial conditions, and controlling time steps are summarized. The goal is to predict damage initiation and propagation from impacts and study how factors like impactor mass and velocity influence the response.
Investigations on material casualty of plates under impact load conditionseSAT Journals
This document summarizes an investigation into the material damage of plates under impact load conditions. Finite element models of tungsten fragments impacting mild steel and titanium plates were created in LS-DYNA. The kinetic energy, velocity, von mises stress, effective plastic strain, and hole diameter damage of the plates were measured for impact velocities of 300, 500, 700, and 1000 mm/ms. Higher impact velocities led to greater decreases in fragment velocity and kinetic energy upon impact, indicating more energy was absorbed by the plates. Von mises stresses and plastic strains in the plates and fragment increased only slightly with higher velocities. Greater impact velocities produced larger holes in the plates, showing higher damage.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
This document summarizes research on modeling the low velocity impact behavior of fiberglass reinforced laminate composites using finite element analysis. Finite element models were created using ANSYS/LS-DYNA software to simulate drop tower impact tests and characterize the damage induced in laminates. Both shell and solid elements were used to model laminate targets and a spherical impactor. Results from the models were able to reasonably predict impact forces and energies compared to experimental testing. The models provide an initial understanding of the stresses and strains in laminates under different impact conditions.
Static structural and dynamic analysis of cracks in composite materialsIRJET Journal
This document summarizes a study on analyzing cracks in composite materials using static and dynamic finite element analysis. It discusses:
1) Modeling a cracked and uncracked composite beam in ANSYS and analyzing their stress distributions and natural frequencies under static and dynamic loading. The cracked beam showed higher stresses and lower natural frequencies.
2) Conducting a case study on modeling and analyzing a cracked bicycle crank made of carbon fiber reinforced polymer. The crank was meshed and its stress fields were analyzed to study the effect of cracks on its strength and failure behavior.
3) The study aims to better understand how cracks influence the static and dynamic characteristics of composite materials like beams and crank arms, which is important for
International Journal of Engineering Research and Development (IJERD)IJERD Editor
This document reviews several studies that analyzed bolted joints in composite laminates. It discusses how clamping force and laminate stacking sequence can affect failure mechanisms and strength. The review examines both experimental and modeling/simulation approaches. Studies investigated topics like bearing strength, fatigue characteristics, stress distributions, and the effects of parameters like bolt-hole clearance and clamping loads. Overall, the review indicates that while modeling techniques have improved understanding, further work is still needed to optimize bolted joint design given composites' brittle failure modes.
The document describes an optimal design project to maximize the specific energy absorption of thin-walled square tube structures using LS-OPT. Crash simulations were performed in LS-DYNA to determine the internal energy and crushing force for different tube thickness values. A kriging meta-model and genetic algorithm in LS-OPT were used to optimize the thickness for maximum specific energy absorption subject to a crushing force constraint. The results showed specific energy absorption greater than predicted for thicknesses from 1.93-2 mm, with a maximum crushing force below the constraint. However, only two iterations were completed, so the optimal thickness was not fully converged.
This document discusses various methods for analyzing steel space frames, including first-order elastic analysis, second-order elastic analysis, first-order inelastic (plastic) analysis, and second-order inelastic (plastic) analysis. It notes that first-order elastic analysis is commonly used but does not account for important second-order effects from frame deflections. Second-order elastic analysis more accurately considers these effects through methods like elastic buckling analysis or full second-order analysis. Advanced second-order inelastic analyses may also consider effects of plastic behavior, residual stresses, and imperfections, though they are rarely done in practice. The document explores these analysis methods in more detail.
IRJET- Design & Development of Bending Fatigue Testing Machine for Composite ...IRJET Journal
1. The document describes the design of a bending fatigue testing machine for composite materials. It aims to provide a low-cost option for generating fatigue data of composites.
2. The machine was designed with a simple operating mechanism using a crank-linkage driven by a V-belt that applies alternating displacement on composite specimens clamped in bending. Strain gauges measure the force and compensate for temperature effects.
3. The machine will help engineers study the behavior of composite components subjected to bending loads, like airplane bodies, at a lower cost than existing commercial machines. This could generate fatigue data to evaluate composite designs.
INTERFACIAL STRESS ANALYSIS OF EXTERNALLY PLATED RC BEAMSIjripublishers Ijri
has become a popular retrofit method due to its rapid, simple and other advantages. However, debonding along the
Steel-RC beam interface can lead to premature failure of the structures. The interfacial stresses play a significant role
in understanding this premature debonding failure of such repaired structures. This paper presents a careful finite
element investigation into interfacial stresses in the adhesive layer bonding RC beam and soffit plate. Finite element
modelling issues like proper selection of contact between adherents and symmetry conditions are first
discussed, with particular attention on appropriate finite element meshes for the accurate determination of interfacial
stresses. The interfacial stress behaviour at plate end has been analysed for two cases of loading taken one by applying
uniformly distributed load and the other with a two point loading. Two special cases are considered in two point
loading – for the cases when the plate terminates with-in the constant moment region (CMR) and for the case when
plate is extended beyond constant moment region where bending moment is minimal. The interfacial stresses are
increasing with a reduction in adhesive layer thickness where as the stresses are increasing with the increase in soffit
plate thickness. Carbon fibre reinforced polymer (CFRP) has shown a significant reduction in interfacial stresses
when compared to steel plate. The interfacial stresses for the plate restricted within the constant moment region are very
high near the plate end leading to flexural debonding compared to the case where plate is extended beyond constant
moment region where bending moment is minimal. The concentration of stresses in the adhesive layer near the plate
end explained the significance in considering their influence in flexural debonding.
INTERFACIAL STRESS ANALYSIS OF EXTERNALLY PLATED RC BEAMSIjripublishers Ijri
Strengthening reinforced concrete (RC) beams by bonding steel or fibre reinforced polymer (FRP) on its tension face
has become a popular retrofit method due to its rapid, simple and other advantages. However, debonding along the
Steel-RC beam interface can lead to premature failure of the structures. The interfacial stresses play a significant role
in understanding this premature debonding failure of such repaired structures. This paper presents a careful finite
element investigation into interfacial stresses in the adhesive layer bonding RC beam and soffit plate. Finite element
modelling issues like proper selection of contact between adherents and symmetry conditions are first
discussed, with particular attention on appropriate finite element meshes for the accurate determination of interfacial
stresses. The interfacial stress behaviour at plate end has been analysed for two cases of loading taken one by applying
uniformly distributed load and the other with a two point loading. Two special cases are considered in two point
loading – for the cases when the plate terminates with-in the constant moment region (CMR) and for the case when
plate is extended beyond constant moment region where bending moment is minimal. The interfacial stresses are
increasing with a reduction in adhesive layer thickness where as the stresses are increasing with the increase in soffit
plate thickness. Carbon fibre reinforced polymer (CFRP) has shown a significant reduction in interfacial stresses
when compared to steel plate. The interfacial stresses for the plate restricted within the constant moment region are very
high near the plate end leading to flexural debonding compared to the case where plate is extended beyond constant
moment region where bending moment is minimal. The concentration of stresses in the adhesive layer near the plate
end explained the significance in considering their influence in flexural debonding.
Keywords-- Interfacial stresses, flexural debonding, constant moment region, soffit plate, finite element method.
Today, retrofitting of the old structures is important. For this purpose, determination of capacities for these buildings, which mostly are non-ductile, is a very useful tool. In this context, non-ductile RC joint in concrete structures, as one of the most important elements in these buildings are considered, and the shear capacity, especially for retrofitting goals can be very beneficial. In this paper, three famous soft computing methods including artificial neural networks (ANN), adaptive neuro-fuzzy inference system (ANFIS) and also group method of data handling (GMDH) were used to estimating the shear capacity for this type of RC joints. A set of experimental data which were a failure in joint are collected, and first, the effective parameters were identified. Based on these parameters, predictive models are presented in detail and compare with each other. The results showed that the considered soft computing techniques are very good capabilities to determine the shear capacity.
Effect of lamination angle on maximum deflection of simply supported composit...RAVI KUMAR
In this project a composite laminated beam is studied with glass-epoxy and graphite-epoxy combination. The beam is composed of four layers of different combination of composite material (glass epoxy and graphite epoxy composite). The beam is simply supported at both the ends and is subjected to uniformly distributed load along the length. Transverse deflection is computed for different lamination angle (0^0-〖90〗^0) by using Euler- Bernoulli’s theory (or CLPT). Maximum transverse deflection analysis is carried out using derived analytical expressions. The research carried out in this project will enable to determine the beam strength due to bending loads. The importance of fibre reinforcement in the manufacturing of the beam is studied in terms of bending strength of the beam. MATLAB codes are generated to implement analytical expiations of the composite beam.
The main objective of the paper is to find out the lamination angle at which minimum deflection is obtained & to find out the effect of lamination angle on maximum transverse deflection of the beam.
Dynamics Behaviour of Multi Storeys Framed Structures by of Iterative Method AM Publications
Dynamics refers to the branch of mechanics that deals with the movement of objects and the forces that drive that movement. Structural analysis which covers the behaviour of structures subjected to dynamic (actions having high acceleration) loading. Dynamic loads include people, wind, waves, traffic, earthquakes, and blasts. Any structure can be subjected to dynamic loading. Dynamic analysis can be used to find dynamic displacements, time history, and the frequency content of the load. One analysis technique for calculating the linear response of structures to dynamic loading is a modal analysis. In modal analysis, we decompose the response of the structure into several vibration modes. A mode is defined by its frequency and shape. Structural engineers call the mode with the shortest frequency (the longest period) the fundamental mode. This paper presents a study on mode shape, inertia force, spring force and deflection of multi storied framed structures by comparison of stodola’s and Holzer method. This study involves in examination of theoretical investigations of multi storied framed structures. Overall four storey multi storied framed structures and two methods were analysed & comparison of all the mode shape, inertia force, spring force and deflection at the critical cross-section with same configuration loading by keeping all other parameters constant. The theoretical data are calculated using code IS 1893, IS 4326, IS 13920. The all storey mass and stiffens are analysed under the cantilever condition. The research project aims to provide which method is most accuracy to find the mode shape, spring force deflection and inertia force. The studies reveal that the theoretical investigations Stodola’s method is most accuracy compare to the Holzer method. The maximum mode shape, spring force, spring deflection and inertia force is 87.29%, 80 %, 89% and 72% is higher the Stodola’s method compare than Holzer method in same configuration.
Research on Air-wake of Large Diameter Non-metallic High-speed DiskIJRES Journal
Good performance of intelligent power grid user equipment is the necessary condition to ensure the smooth implementation of smart grid, due to the influence of outside air damping, non-metallic of large diameter disk as the key components of the smart grid sensor will easy cause the problem of deformation and damage in the working process. At present, the usually method of researching the aspect of inspection, performance comparison and optimization design of disk are testing but not computer software. In this paper, non-metallic of large diameter disk are analyzed from the aspect of velocity, pressure and stress through the software of ANSYS WORKBENCH, which lay the foundation for the structure optimization.
IRJET- Dynamic Stability Analysis of Functionally Graded MaterialsIRJET Journal
The document summarizes a study on the dynamic stability analysis of functionally graded materials (FGM) plates subjected to in-plane periodic loading. It discusses how FGMs have graded material properties that vary continuously from one surface to another, making them advantageous over conventional composite materials. A finite element model is developed using higher-order shear deformation theory to analyze the dynamic stability of FGM plates under different loading and boundary conditions. Parameters like volume fraction index, temperature rise, loading amplitude are varied to understand their influence on the stability boundaries of the FGM plates.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document provides an overview of composite materials and nanocomposites. It discusses the properties of materials including stress, strain, Young's modulus, and Poisson's ratio. It describes different types of composite materials like fibrous, laminated, and particulate composites. Examples of applications in aerospace, automotive, civil engineering are presented. Methods for fabricating composites like open mold, pultrusion, and sheet molding are covered. Predictions for the properties of composites using rules of mixtures are also summarized.
This document describes various analysis methods for modeling active and passive damping in structures using NX I-deas and NX Nastran software. It discusses modeling constrained layer damping, piezoelectric fibers, and viscoelastic damping materials to increase structural damping. Examples are provided of applying these methods to design damping treatments for a spacecraft and liquid rocket engine. The key methods allow identifying important vibration modes, estimating modal damping contributions of candidate materials, and predicting changes to modal damping and forced response with added damping treatments.
FRP Laminated Composite Plate with Central Circular Hole: Structural and Buck...IRJET Journal
The document discusses a finite element analysis of thin fiber reinforced plastic (FRP) rectangular composite plates with central circular holes under compressive loading. The analysis examines the effect of plate dimension ratio (L/W), stacking sequence, and hole diameter on the structural characteristics and buckling behavior. The results show that the critical load increases with L/W ratio up to a ratio of 4. The critical load also decreases as the hole diameter increases. The stacking sequence is found to impact the critical load values for different buckling modes. The findings provide insights into how composite plates perform under compression loads.
Similar to To study the effect of low velocity impacts on composite material buy using Finite element analysis software LSDYNA (20)
This document provides a technical review of secure banking using RSA and AES encryption methodologies. It discusses how RSA and AES are commonly used encryption standards for secure data transmission between ATMs and bank servers. The document first provides background on ATM security measures and risks of attacks. It then reviews related work analyzing encryption techniques. The document proposes using a one-time password in addition to a PIN for ATM authentication. It concludes that implementing encryption standards like RSA and AES can make transactions more secure and build trust in online banking.
This document analyzes the performance of various modulation schemes for achieving energy efficient communication over fading channels in wireless sensor networks. It finds that for long transmission distances, low-order modulations like BPSK are optimal due to their lower SNR requirements. However, as transmission distance decreases, higher-order modulations like 16-QAM and 64-QAM become more optimal since they can transmit more bits per symbol, outweighing their higher SNR needs. Simulations show lifetime extensions up to 550% are possible in short-range networks by using higher-order modulations instead of just BPSK. The optimal modulation depends on transmission distance and balancing the energy used by electronic components versus power amplifiers.
This document provides a review of mobility management techniques in vehicular ad hoc networks (VANETs). It discusses three modes of communication in VANETs: vehicle-to-infrastructure (V2I), vehicle-to-vehicle (V2V), and hybrid vehicle (HV) communication. For each communication mode, different mobility management schemes are required due to their unique characteristics. The document also discusses mobility management challenges in VANETs and outlines some open research issues in improving mobility management for seamless communication in these dynamic networks.
This document provides a review of different techniques for segmenting brain MRI images to detect tumors. It compares the K-means and Fuzzy C-means clustering algorithms. K-means is an exclusive clustering algorithm that groups data points into distinct clusters, while Fuzzy C-means is an overlapping clustering algorithm that allows data points to belong to multiple clusters. The document finds that Fuzzy C-means requires more time for brain tumor detection compared to other methods like hierarchical clustering or K-means. It also reviews related work applying these clustering algorithms to segment brain MRI images.
1) The document simulates and compares the performance of AODV and DSDV routing protocols in a mobile ad hoc network under three conditions: when users are fixed, when users move towards the base station, and when users move away from the base station.
2) The results show that both protocols have higher packet delivery and lower packet loss when users are either fixed or moving towards the base station, since signal strength is better in those scenarios. Performance degrades when users move away from the base station due to weaker signals.
3) AODV generally has better performance than DSDV, with higher throughput and packet delivery rates observed across the different user mobility conditions.
This document describes the design and implementation of 4-bit QPSK and 256-bit QAM modulation techniques using MATLAB. It compares the two techniques based on SNR, BER, and efficiency. The key steps of implementing each technique in MATLAB are outlined, including generating random bits, modulation, adding noise, and measuring BER. Simulation results show scatter plots and eye diagrams of the modulated signals. A table compares the results, showing that 256-bit QAM provides better performance than 4-bit QPSK. The document concludes that QAM modulation is more effective for digital transmission systems.
The document proposes a hybrid technique using Anisotropic Scale Invariant Feature Transform (A-SIFT) and Robust Ensemble Support Vector Machine (RESVM) to accurately identify faces in images. A-SIFT improves upon traditional SIFT by applying anisotropic scaling to extract richer directional keypoints. Keypoints are processed with RESVM and hypothesis testing to increase accuracy above 95% by repeatedly reprocessing images until the threshold is met. The technique was tested on similar and different facial images and achieved better results than SIFT in retrieval time and reduced keypoints.
This document studies the effects of dielectric superstrate thickness on microstrip patch antenna parameters. Three types of probes-fed patch antennas (rectangular, circular, and square) were designed to operate at 2.4 GHz using Arlondiclad 880 substrate. The antennas were tested with and without an Arlondiclad 880 superstrate of varying thicknesses. It was found that adding a superstrate slightly degraded performance by lowering the resonant frequency and increasing return loss and VSWR, while decreasing bandwidth and gain. Specifically, increasing the superstrate thickness or dielectric constant resulted in greater changes to the antenna parameters.
This document describes a wireless environment monitoring system that utilizes soil energy as a sustainable power source for wireless sensors. The system uses a microbial fuel cell to generate electricity from the microbial activity in soil. Two microbial fuel cells were created using different soil types and various additives to produce different current and voltage outputs. An electronic circuit was designed on a printed circuit board with components like a microcontroller and ZigBee transceiver. Sensors for temperature and humidity were connected to the circuit to monitor the environment wirelessly. The system provides a low-cost way to power remote sensors without needing battery replacement and avoids the high costs of wiring a power source.
1) The document proposes a model for a frequency tunable inverted-F antenna that uses ferrite material.
2) The resonant frequency of the antenna can be significantly shifted from 2.41GHz to 3.15GHz, a 31% shift, by increasing the static magnetic field placed on the ferrite material.
3) Altering the permeability of the ferrite allows tuning of the antenna's resonant frequency without changing the physical dimensions, providing flexibility to operate over a wide frequency range.
This document summarizes a research paper that presents a speech enhancement method using stationary wavelet transform. The method first classifies speech into voiced, unvoiced, and silence regions based on short-time energy. It then applies different thresholding techniques to the wavelet coefficients of each region - modified hard thresholding for voiced speech, semi-soft thresholding for unvoiced speech, and setting coefficients to zero for silence. Experimental results using speech from the TIMIT database corrupted with white Gaussian noise at various SNR levels show improved performance over other popular denoising methods.
This document reviews the design of an energy-optimized wireless sensor node that encrypts data for transmission. It discusses how sensing schemes that group nodes into clusters and transmit aggregated data can reduce energy consumption compared to individual node transmissions. The proposed node design calculates the minimum transmission power needed based on received signal strength and uses a periodic sleep/wake cycle to optimize energy when not sensing or transmitting. It aims to encrypt data at both the node and network level to further optimize energy usage for wireless communication.
This document discusses group consumption modes. It analyzes factors that impact group consumption, including external environmental factors like technological developments enabling new forms of online and offline interactions, as well as internal motivational factors at both the group and individual level. The document then proposes that group consumption modes can be divided into four types based on two dimensions: vertical (group relationship intensity) and horizontal (consumption action period). These four types are instrument-oriented, information-oriented, enjoyment-oriented, and relationship-oriented consumption modes. Finally, the document notes that consumption modes are dynamic and can evolve over time.
1) The document describes a study conducted to improve call drop rates in a GSM network through RF optimization.
2) Drive testing was performed before and after optimization using TEMS software to record network parameters like RxLevel, RxQuality, and events.
3) Analysis found call drops were occurring due to issues like handover failures between sectors, interference from adjacent channels, and overshooting due to antenna tilt.
4) Corrective actions taken included defining neighbors between sectors, adjusting frequencies to reduce interference, and lowering the mechanical tilt of an antenna.
5) Post-optimization drive testing showed improvements in RxLevel, RxQuality, and a reduction in dropped calls.
This document describes the design of an intelligent autonomous wheeled robot that uses RF transmission for communication. The robot has two modes - automatic mode where it can make its own decisions, and user control mode where a user can control it remotely. It is designed using a microcontroller and can perform tasks like object recognition using computer vision and color detection in MATLAB, as well as wall painting using pneumatic systems. The robot's movement is controlled by DC motors and it uses sensors like ultrasonic sensors and gas sensors to navigate autonomously. RF transmission allows communication between the robot and a remote control unit. The overall aim is to develop a low-cost robotic system for industrial applications like material handling.
This document reviews cryptography techniques to secure the Ad-hoc On-Demand Distance Vector (AODV) routing protocol in mobile ad-hoc networks. It discusses various types of attacks on AODV like impersonation, denial of service, eavesdropping, black hole attacks, wormhole attacks, and Sybil attacks. It then proposes using the RC6 cryptography algorithm to secure AODV by encrypting data packets and detecting and removing malicious nodes launching black hole attacks. Simulation results show that after applying RC6, the packet delivery ratio and throughput of AODV increase while delay decreases, improving the security and performance of the network under attack.
The document describes a proposed modification to the conventional Booth multiplier that aims to increase its speed by applying concepts from Vedic mathematics. Specifically, it utilizes the Urdhva Tiryakbhyam formula to generate all partial products concurrently rather than sequentially. The proposed 8x8 bit multiplier was coded in VHDL, simulated, and found to have a path delay 44.35% lower than a conventional Booth multiplier, demonstrating its potential for higher speed.
This document discusses image deblurring techniques. It begins by introducing image restoration and focusing on image deblurring. It then discusses challenges with image deblurring being an ill-posed problem. It reviews existing approaches to screen image deconvolution including estimating point spread functions and iteratively estimating blur kernels and sharp images. The document also discusses handling spatially variant blur and summarizes the relationship between the proposed method and previous work for different blur types. It proposes using color filters in the aperture to exploit parallax cues for segmentation and blur estimation. Finally, it proposes moving the image sensor circularly during exposure to prevent high frequency attenuation from motion blur.
This document describes modeling an adaptive controller for an aircraft roll control system using PID, fuzzy-PID, and genetic algorithm. It begins by introducing the aircraft roll control system and motivation for developing an adaptive controller to minimize errors from noisy analog sensor signals. It then provides the mathematical model of aircraft roll dynamics and describes modeling the real-time flight control system in MATLAB/Simulink. The document evaluates PID, fuzzy-PID, and PID-GA (genetic algorithm) controllers for aircraft roll control and finds that the PID-GA controller delivers the best performance.
This document provides a review of synthetic aperture radar (SAR) engineering. It begins with an introduction to SAR and its uses in remote sensing and defense. It then discusses designs for SAR systems and antennas. The document reviews recent literature on SAR, including works discussing antenna mask design to optimize SAR performance, polarimetric SAR for mapping terrain changes, and using SAR to monitor cryospheric regions. It concludes that SAR is a useful technique for achieving good image quality through optimized antenna design.
Batteries -Introduction – Types of Batteries – discharging and charging of battery - characteristics of battery –battery rating- various tests on battery- – Primary battery: silver button cell- Secondary battery :Ni-Cd battery-modern battery: lithium ion battery-maintenance of batteries-choices of batteries for electric vehicle applications.
Fuel Cells: Introduction- importance and classification of fuel cells - description, principle, components, applications of fuel cells: H2-O2 fuel cell, alkaline fuel cell, molten carbonate fuel cell and direct methanol fuel cells.
Optimizing Gradle Builds - Gradle DPE Tour Berlin 2024Sinan KOZAK
Sinan from the Delivery Hero mobile infrastructure engineering team shares a deep dive into performance acceleration with Gradle build cache optimizations. Sinan shares their journey into solving complex build-cache problems that affect Gradle builds. By understanding the challenges and solutions found in our journey, we aim to demonstrate the possibilities for faster builds. The case study reveals how overlapping outputs and cache misconfigurations led to significant increases in build times, especially as the project scaled up with numerous modules using Paparazzi tests. The journey from diagnosing to defeating cache issues offers invaluable lessons on maintaining cache integrity without sacrificing functionality.
A review on techniques and modelling methodologies used for checking electrom...nooriasukmaningtyas
The proper function of the integrated circuit (IC) in an inhibiting electromagnetic environment has always been a serious concern throughout the decades of revolution in the world of electronics, from disjunct devices to today’s integrated circuit technology, where billions of transistors are combined on a single chip. The automotive industry and smart vehicles in particular, are confronting design issues such as being prone to electromagnetic interference (EMI). Electronic control devices calculate incorrect outputs because of EMI and sensors give misleading values which can prove fatal in case of automotives. In this paper, the authors have non exhaustively tried to review research work concerned with the investigation of EMI in ICs and prediction of this EMI using various modelling methodologies and measurement setups.
Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
The presentation also covers the positive and negative aspects of inductive bias, along with strategies for mitigating potential drawbacks. We'll explore examples of how bias manifests in algorithms like neural networks and decision trees.
By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
CHINA’S GEO-ECONOMIC OUTREACH IN CENTRAL ASIAN COUNTRIES AND FUTURE PROSPECTjpsjournal1
The rivalry between prominent international actors for dominance over Central Asia's hydrocarbon
reserves and the ancient silk trade route, along with China's diplomatic endeavours in the area, has been
referred to as the "New Great Game." This research centres on the power struggle, considering
geopolitical, geostrategic, and geoeconomic variables. Topics including trade, political hegemony, oil
politics, and conventional and nontraditional security are all explored and explained by the researcher.
Using Mackinder's Heartland, Spykman Rimland, and Hegemonic Stability theories, examines China's role
in Central Asia. This study adheres to the empirical epistemological method and has taken care of
objectivity. This study analyze primary and secondary research documents critically to elaborate role of
china’s geo economic outreach in central Asian countries and its future prospect. China is thriving in trade,
pipeline politics, and winning states, according to this study, thanks to important instruments like the
Shanghai Cooperation Organisation and the Belt and Road Economic Initiative. According to this study,
China is seeing significant success in commerce, pipeline politics, and gaining influence on other
governments. This success may be attributed to the effective utilisation of key tools such as the Shanghai
Cooperation Organisation and the Belt and Road Economic Initiative.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
Redefining brain tumor segmentation: a cutting-edge convolutional neural netw...IJECEIAES
Medical image analysis has witnessed significant advancements with deep learning techniques. In the domain of brain tumor segmentation, the ability to
precisely delineate tumor boundaries from magnetic resonance imaging (MRI)
scans holds profound implications for diagnosis. This study presents an ensemble convolutional neural network (CNN) with transfer learning, integrating
the state-of-the-art Deeplabv3+ architecture with the ResNet18 backbone. The
model is rigorously trained and evaluated, exhibiting remarkable performance
metrics, including an impressive global accuracy of 99.286%, a high-class accuracy of 82.191%, a mean intersection over union (IoU) of 79.900%, a weighted
IoU of 98.620%, and a Boundary F1 (BF) score of 83.303%. Notably, a detailed comparative analysis with existing methods showcases the superiority of
our proposed model. These findings underscore the model’s competence in precise brain tumor localization, underscoring its potential to revolutionize medical
image analysis and enhance healthcare outcomes. This research paves the way
for future exploration and optimization of advanced CNN models in medical
imaging, emphasizing addressing false positives and resource efficiency.
Redefining brain tumor segmentation: a cutting-edge convolutional neural netw...
To study the effect of low velocity impacts on composite material buy using Finite element analysis software LSDYNA
1. IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE)
e-ISSN: 2278-1684,p-ISSN: 2320-334X, Volume 9, Issue 5 (Nov. - Dec. 2013), PP 01-09
www.iosrjournals.org
www.iosrjournals.org 1 | Page
To study the effect of low velocity impacts on composite material
buy using Finite element analysis software LSDYNA
Mr.Nayeemuddin1
, Mr. Abdul Nazeer2
(Department of mechanical engineering, KBN college of engineering Gulbarga, Karnataka, India)
Abstract: During the life of a structure impact by foreign objects can be expected to occur during
manufacturing, service and maintenance operations. An example of in service impact occurs during aircrafts
takeoffs and landing. During the manufacturing process or during maintenance tools can be dropped on the
structure, in this case the impact energy is small, laminated structures are more susceptible to impact damage
often cannot be detected by visual inspection. This internal damage can severe reductions in strength and
further reductions occur under the load. Therefore the effects of foreign object impact on composite structure
must be understood and proper measures should be taken in the design process to account for expected events.
Concerns about the effects of impact on the performance of composite structures have been a factor in limiting
the use of composite materials. For these reasons the problem of impact has received considerable attention in
the literature.
The process of impact damage initiation and growth, and identify the governing parameters are
important for the formulation of numerical models for damage prediction, for designing impact resistant
structures and for developing improved material systems. An important aspect of a model for predicting the
impact dynamics is to accurately describe the behavior of the target under impact loading conditions. For some
simple cases the structural loading can be modeled by a simple spring-mass system or by using the quasi-static
behavior and considering the energy balance for a system. But in general more sophisticated beam, plate or
shell theories are required to model the structure.
.Keywords: FEA, Low-velocity impact, LS DYNA, Modeling, Simulation
I. Introduction
Problem statement: To study the effect of low velocity impacts on composite material buy using Finite
element analysis software LSDYNA
Problem Definition:- Low-velocity impact is defined as events which can be treated as quasi-static,
the upper limit of which can vary from one to tens of ms-1
depending on the target stiffness, material
properties and the impactor‟s mass and stiffness.
Objective:
To review the literature on the low velocity impact on laminated composite.
To study the relevant analytical and experimental models which are available in the literature.
To conduct a simple analysis of rigid ball impact the steel plate and compare the obtained results with
existing journal.
To conduct the simple analysis on carbon fiber reinforced plastic (CFRP) plate by varying the mesh density
of plate.
To conduct the analysis on carbon fiber reinforced plastic (CFRP) plate by varying the mass and velocity of
impactor.
To conduct the analysis on the hybrid composite plate impacted by a rigid impactor.
To predict the initiation and propagation of crack due to bending and delamination in laminated composite
structure.
Parametric studies involving impactor mass, velocity, laminate characteristics,boundary conditions etc.
examining their influence on the impact response and on the extant of resulting damage.
The obtained results are then compared with existing journal.
II. Methodologies:
A methodology describes different approaches to analyze the impact and the prediction of impact
induced damage by means of the finite-element method can be categorized into the following steps:
2. To study the effect of low velocity impacts on composite material buy using LSDYNA
www.iosrjournals.org 2 | Page
Determining the contact force between impacting mass and the plate element as a function of time. This
contact force cannot be determined explicitly as it depends on the relative approach of the two contacting
bodies.
Applying the contact force to find the transient dynamic response of the impacted structure as a function of
position and time (displacements, strains, stresses, etc.) which depends on the mass and velocity of the
impactor and the laminate characteristics (geometry, boundary conditions, ply arrangement, elastic
properties etc.).
Refinement and pre-processing of the finite element model of a plate and sphere is carried out using LS
DYNA.
The finite element model impact simulation is carried out using LSDYNA as a solver.
Reviewing the results is done using LS-PrePOST as a post processor.
Comparing the obtained results with the existing journal.
.
III. LS DYNA SOFTWARE
Introduction to LS DYNA : LSDYNA is an explicit Finite Element program and is designed for transient
dynamic analysis of highly nonlinear problems. In LS-DYNA the transient dynamic equilibrium equation is
solved by the central difference method. Similar to ANSYS, LS-DYNA also uses Newton-Raphson method to
solve the nonlinear problems including the contact and impact problems. For the contact problems, three distinct
methods are used to handle such problems, includes the kinematic constraint method, the penalty method and
the distributed parameter method.
Advantages and Disadvantages of LS-Dyna
The main advantages of LS-DYNA is that it is one of the most robust programs currently available,
when simulating problems of nonlinear loading, which includes fluid structure interaction and impact problems.
LS-DYNA has the capabilities to stand non linearity of the impact problem and possesses a wide database with
different kind of material formulations. Also it has the ability to work with different kinematic
descriptions and element types for dynamic analysis. The main disadvantage of this code is that it is not user-
friendly and used a large number of variables and parameters to build a model.
LS-DYNA has a variety of element types, which include four-node tetrahedron and eight node solid elements,
beam elements, three-node and four-node shell elements, eight-node solid shell elements, truss elements,
membrane elements, discrete elements and rigid bodies. A variety of element formulations are also available for
each element type. The most advantageous capability of LS-DYNA over other explicit finite element codes is its
included contact algorithm. Several types of contact interfaces can be defined in LS-DYNA including surface to
surface, nodes to surface, nodes tied to surface, and surface tied to surface contacts etc.
To solve the impact problems by LS-DYNA, the required input data can be classified into the following three
categories:
a. Material properties: identified the material properties for the impactor and target object, can be a rigid
body, isotropic material or composite material.
b. Initial and boundary conditions: specified the initial conditions for the impactor such as impact velocity,
acceleration; boundary conditions for the target object such as clamped or simple support.
c. Contact conditions: defined the type of contact and friction coefficient, there are 18 different types of
contact can be chosen to accurately represent the physical model, among them surface to surface (STS) and
node to surface (NTS) is the most common use.
3. Low velocity impact of a rigid impactor on steel plate
To verify the accuracy of LS-DYNA, a steel plate impacted by a rigid ball. Here the contact force is calculated
for the different mesh density keeping the same dimensions of the plate and impactor. The obtained results are
compared with literature result.
4. Geometric modeling of steel plate and rigid impactor
3. To study the effect of low velocity impacts on composite material buy using LSDYNA
www.iosrjournals.org 3 | Page
Figure 4.1: Geometric model of rigid impactor and steel plate
Figure 4.1 shows the geometric modeling of a rigid impactor and steel plate where the mesh density of the plate
and sphere is varied from a corase mesh to a fine mesh with a clamped boundary condition the mesh density is
varied in order to calculate the effect of mesh density on contact force.
Parameters Units
Length unit Millimeter(mm)
Time unit Millisecond(msec)
Mass unit Kilogram(Kg)
Force unit Kilo Newton(kN)
Young‟s Modulus Giga pascal(Gpa)
Density Kg/mm³
Velocity mm/msec
Table 4.1: Parameters and units
Table 4.2: Material Properties of Steel plate and Rigid Sphere
5. Assigning material in Ls-dyna
The modeling meshing of composite plate is done in the Hypermesh 9.0 version preprocessor. The composite
plate is modeled using Belytschko-Tsay shell elements there are wide range of material model in Ls-dyna the
material model selected for assigning to plate is MAT_22 composite damage. The rigid sphere is modeled using
Hughes-Liu solid elements material model assigned is MAT_20 MAT_RIGID the elements chosen are solid
element. SMA wires are modeled using MAT_30 SHAPE_MEMORY.
The orientation and the through thickness location of the shape memory alloy (SMA) wires was used in order to
minimize the maximum transverse deflection of the hybrid composite plate during the low-velocity impact
phenomena.
To ensure the accuracy of the present model, the contact force determined from LS-Dyna model is compared to
existing literature shokuhfar[2].
6. Initial and Boundary conditions
Material properties for plate Symbol (Unit) Value
Young‟s modulus E (GPa) 200
Poisson‟s ratio γ 0.3
Density ρ (kg/mm³) 7.83𝑒−6
Yield stress fy (GPa) 0.2
Material properties for Sphere Symbol (Unit) Value
Young‟s modulus E (GPa) 207
Poisson‟s ratio γ 0.3
Density ρ (kg/mm³) 7.85𝑒−6
Radius R (mm) 10
Velocity V (mm/ms) 1
4. To study the effect of low velocity impacts on composite material buy using LSDYNA
www.iosrjournals.org 4 | Page
Figure III.2: Possible Boundary Conditions along an Edge of the Plate
Figure 6.11 shows the boundary conditions .initially (time≤0), the displacement and velocity at every point of
the plate are zero.
Thus, the initial conditions are
ui=0 𝑢i=o throughout the plate at t ≤ 0
where i = 1, 2, 3
At the start of the simulation (immediately time>0), the nodes that are in contact with the impactor are given the
initial impact velocity, as well as the distributed mass of the projectile. Each edge of the plate may be clamped,
simply supported or free. The boundary conditions corresponding to these types of support are
Clamped edge
u3=0 un=0 on the surface of the edge
Simply supported edge
U3=0 un=0 along the mid-line of the edge
7. Defining laminated composite in LS DYNA
By default, shells in LS-DYNA make the assumption of uniform transverse shear strain. This assumption is
invalid for foam core composites or any stack up with lamina comprised of different materials with largely
varying stiffness.
To correctly calculate the stiffness of sandwich composites (particularly foam cores) using shells, laminate
theory must be invoked in LS-DYNA by any one of several means:
Use MAT_22, 54, or55
Use MAT_114, a plasticity model patterned after MAT_24.
Use MAT_116, a resultant layup-theory model.
8. Modeling multi-layer composites
There are several options for modeling layered composites with shell elements. The simplest and least
general is to use the BETA option of SECTION_SHELL to define the material direction for each integration
point through the element thickness. A userdefined integration rule should also be used to control the layer
thicknesses. (IRID of SECTION_SHELL and INTEGRATION_SHELL).
If a composite is made up layers of different materials, a more general composite can be modeled by specifying
a different part ID for each integration point (INTEGRATION_SHELL). Each part can refer to a different
material model with the restriction that all materials must be of the same type. This method allows different
material constants to be used in the different layers, but still does not allow completely general mixing of
material types in a single shell element. In order to obtain the correct membrane and bending stiffness for the
whole composite element, define a separate integration rule for each element in the composite with appropriate
weights and through thickness locations.
9. Assigning materials
After creating and meshing the model the next step is to assign the material to the plate and sphere. LS-
DYNA is having a wide range of material and equation of state model each with a unique of history variables
from the material library material model named MAT_PIECEWISE_LINEAR_PLASTICITY is used for the
Sphere. A brief description of this particular material model is given below.
MAT_PIECEWISE_LINEAR_PLASTICITY (Mat type 24)
This is an Elasto-plastic material with an arbitrary stress versus strain curve and arbitrary strain rate dependency.
The stress-strain relation for this material is defined with eight stress-vs.-strain points. With these material
models, failure based on a plastic strain or a minimum time step size can be defined. In the FE model, this
material is primarily used for the Sphere.
5. To study the effect of low velocity impacts on composite material buy using LSDYNA
www.iosrjournals.org 5 | Page
MAT_COMPOSITE_DAMAGE (Mat type22)
An orthotropic material with optional brittle failure for composite can be defined following the suggestion of
[Chang 1987a, 1987b].Three failure criteria are possible.
The Matrix Cracking Failure Criteria
Fmatrix = (σ/S2)² + 𝜁
Where Failure is assumed Whenever Fmatrix>1.If Fmatrix>1 then the material constants E2, G12, υ1 and υ2 are
set to zero.
The compression Failure Criteria is given as.
Fcomp=(σ2/2S12)² +[(C2/2S12)²-1]σ2/C2 + 𝜁
Where Failure is assumed whenever Fcomp=>1. If Fcomp>1 then the material constants E2, υand υare set to
zero.
The Final Failure mode is due to fiber breakage
Ffiber= (σ1/S1)² + 𝜁
Where Failure is assumed whenever Ffiber>1. If Ffiber>1 then the material constants E1,E2, G12, υand υare
set to zero.
By using the user defined integration rule,INTEGRATION_SHELL the constitutive constants can vary through
the shell thickness. For all shell, except the DKT formulation, laminated shell theory can be activated to
properly model the transverse shear deformation.
Material Properties and Element Formulation
After the material is assigned to the plate and sphere it is necessary to specify the properties of the material.
SECTION_SHELL is used for composite and SECTION_SOLID is used for Steel sphere.
Shell element formulation: Element formulations are affiliated to the „section properties of the respective
elements type used. Following are the two types of shell element formulations used in the FE model.
Type 2(ELFORM 2/ EQ.2)- Belytschko-Tsay, used for composite plate.
Type 1(ELFORM1/EQ.1) - Hughes-Liu used for Steel sphere.
10. Boundary Conditions
Boundary conditions includes defining contacts, constraints etc. In this case contact between Steel ball and a
composite plate are defined. Contact type used in LS-DYNA for impact is
CONTACT_AUTOMATIC_NODES_TO_SURFACE. In LS-DYNA a contact is defined by identifying what
locations are to be checked for potential penetration of a „slave‟ node through a „master‟ segment. As presently
implemented, one surface of the interface is identified as a master surface and the other as slave. By using
number of different algorithm, a search for penetration is carried out during the execution of solution In general,
an input for the contact-impact algorithm, only the slave surface is defined and each node in the surface is
checked each node in the surface is checked each time step to ensure that it does not penetrate through the
surface. Internal logic identifies a master segment for each slave node and a slave segment for each master node
and updates this information every time step as the slave and master nodes slide along their respective surfaces.
Here the all the side of the plate is constrained to both translation and rotational moments i: e plate is clamped
along all four sides.
11. Defining Control time step
The time step of an explicit analysis is determined as the minimum stable time steps in any deformable
finite element in the mesh. For shell element the time step is given by the equation as shown below:
Δte =
𝐿𝑠
𝐶
Where, Ls is the characteristic length and
C is the sound speed
Time step for shell element can also be prevented by the equation as shown below
Δt
Where, Δx = Characteristic length
E = Young‟s modulus
ρ = Density of the material
12. Defining Database_Binary_Option
The D3PLOT, D3PART, D3DRLF and the INTFOR files contain plotting information to plot data over
the three dimensional geometry of the model. This database can be plotted with LS-PREPOST. The D3THDT
file contains time history data for element subsets as well as global information.
Defining ASCII outputs
6. To study the effect of low velocity impacts on composite material buy using LSDYNA
www.iosrjournals.org 6 | Page
ASCII output files (i.e. database files) are optional but necessary to obtain output files containing the results
information. Below are some of the output flies which are specified:
GLSTAT: This file gives the global data. The output components for this file include kinetic energy, internal
energy, total energy, ratio, stone-wall energy spring and damper energy, hourglass energy, sliding interface
energy, external work, X, Y, Z- direction velocities.
MATSUM: This file outputs the individual material energies. The output components for this file includes
Kinetic energy, Internal energy, hourglass energy, X,Y,Z-direction momentum, X,Y,Z- direction rigid body
velocity of individual components with total kinetic energy, total internal energy, total hourglass energy.
NODOUT: This file gives the nodal point data. Output such as displacement in X, Y, Z directions, velocities in
X, Y, Z direction, acceleration values in this direction with X, Y, Z direction rotation, rotational velocities and
rotational acceleration can be obtained.
SECFORC: Cross sectional forces are obtained from the ASCII file SECFORC output such as forces in X, Y, Z
direction, momentum in X, Y, Z direction, Cross sectional area after deformation, resultant force acting on the
section specified can be obtained by this option.
RCFORC: This file gives the Resultant interface forces in X, Y, Z directions used for impact problems the
resultant interface force is nothing but the contact force.
SLEOUT: This file gives the Sliding interface forces. This option is used for to find out the Slave energy and
master energy.
IV. RESULT AND DISCUSSION
Low-Velocity Impact on steel plate with rigid impactor
The analysis is carried out on a steel plate. A rigid ball is impacted on a steel plate with different mesh
density. The material properties of plate and Sphere is defined in Table 6.2 the plate with length 200 mm, width
200 mm and thickness 8 mm is clamped along the four edges. Mesh 1 with 20 (length) x 20 (width) x 2 (height)
= 800 elements in plate and 32 elements in impactor. Mesh 2 with 40 (length) x 40 (width) x 2 (height) = 3200
elements in plate and 32 elements in impactor. Mesh 3 with 80 (length) x 80 (width) x 2 (height) =12,800
elements in plate and 256 elements in impactor. LS-DYNA is capable of calculating the transient responses and
provides the displacements and stresses distributions for both impactor and plate.
Once the model was made in Msc/Pattern and the key file was edited the model was run on a solver for
solving the given loading and boundary constraints. The results were studied in post- solver LS-POST and
compared with the results in the literature and good co relation was found between the simulations and results of
SHIUH-CHUAN HER [7]
The impact analysis on a steel plate with the meshing of 20x20x2
Figure 2.1: Stress plot for Steel plate at time 1ms with (20x20x2,) mesh size and impactor velocity 1mm/ms
7. To study the effect of low velocity impacts on composite material buy using LSDYNA
www.iosrjournals.org 7 | Page
20x20x2
Time (ms)
-0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14
Contactforce(kN)
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Shuih result
Present result
Karas result
Figure 2.2: Comparison of contact force of present result and karas and shiuh[7]
Figure2.1 illustrate the damage caused to the Steel plate due to impactor with velocity 1m/s the region in red
shows maximum stress condition. As the impact analysis is carried on different mesh density first we consider
the coarse mesh to plate and sphere as 20x20x2=800 elements and 32 elements in sphere. Figure7.2 shows the
comparison of contact force vs time between the present result and the result obtained from Shuih and karas as it
can been seen that there is the difference in contact force obtained from Fem and Experimental result obtained
from Karas.
The impact analysis on a steel plate with the meshing of 40x40x2
Figure 3.1: Stress plot for Steel plate at time 1ms with (40x40x2) mesh size and impactor velocity 1mm/ms
40x40x2
Time (ms)
-0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14
Contactforce(kN)
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Shiuh result
Present result
karas result
Figure 3.2: Comparison of contact force of present result and karas and shiuh[7]
8. To study the effect of low velocity impacts on composite material buy using LSDYNA
www.iosrjournals.org 8 | Page
Figure 3.2 illustrate the damage caused to the steel plate due to impactor with velocity. 1m/s the region in red
shows maximum stress condition as it can be seen from the figure 7.3 the maximum stress in red region is not
below the impactor but it is away from the impact point. figure 7.4 shows the comparison between the result
obtained from FEM and the Experimental result obtained by Karas there is a slight variation in the contact force.
So it is seen that as the mesh density of plate is refined the contact force is increased and it is nearer to the result
obtained by the Karas and Shuih.
The impact analysis on a steel plate with the meshing of 80x80x2
1)
Figure 4.1: Stress plot for Steel plate at time 1ms with (80x80x2) mesh size and impactor velocity 1mm/ms
80x80x2
Time (ms)
-0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14
Contactforce(kN)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Shiuh result
Present result
Karas result
Figure 4.2: Comparison of contact force of present result and karas and shiuh[7]
Figure 4.1 illustrate the damage caused to the Steel plate due to impactor with velocity 1m/s the region in red
shows maximum stress condition. Figure7.6 shows the comparison of contact force of present result and Karas
and shuih and the result obtained by FEM is matching well with the literature [7]. So it can concluded the
meshing of plate and sphere play very important role in analyzing the impact problem
Table 4.1: Comparison of FEM and Experimental Peak force
Mesh Size
FEM Simulation
Peak Impact Load (kN)
Experimental Simulation
Peak Impact Load (kN)
20x20x2 1.004 1.41
40x40x2 1.05 1.41
80x80x2 1.1 1.41
V. CONCLUSION
A numerical analysis procedure for simulating the impact response of laminated composite Plates using
finite elements codes has been presented. The present formulation has been used to predict the transient
response of laminated composite plates and the obtained results have been successfully compared with existing
9. To study the effect of low velocity impacts on composite material buy using LSDYNA
www.iosrjournals.org 9 | Page
experimental data and other theoretical solutions in the literature. In comparison with experimental
measurements of the contact force histories for different impact conditions, the current predictions appear to be
found fair agreement.
Firstly the analysis is carried out on a steel plate impacted by rigid impactor for different mesh density of plate
and impactor. So it has been found that as mesh density increses the accuracy also increased. As shown from the
figures2.2,3.2,and 4.2 the numerical results obtained by LS-DYNA can converge to the analytical solution
Karas, upon the mesh being refined.
REFERENCES
[1]. IK-HYEON CHOI, “LOW-VELOCITY IMPACT ANALYSIS OF COMPOSITE LAMINATES UNDER INITIAL IN-PLANE LOAD” COMPOSITE
STRUCTURES 86 (2008) 251–257
[2]. Shokuhfar.A, “Analysis and optimization of smart hybrid composite plates subjected to low-velocity impact using the response
surface methodology (RSM)” Thin-Walled Structures 46 (2008) 1204– 1212
[3]. Tiebreak .R.a, Bachene.M b, Rechak S.c, Necib.B “Damage prediction in composite plates subjected to low velocity impact”
Composite Structures 83 (2008) 73–82
[4]. SADIGHI. M, H. POURIAYEVALI, SAADATI.M “Response of fully backed sandwich beams to low velocity transverse impact”
World Academy of Science, Engineering and Technology 36 2007
[5]. Hosur.M.V, “Studies on the low-velocity impact resip/;ponse of woven hybrid composites” Composite Structures 67 (2005) 253–
262
[6]. Ik Hyeon Choi, “Low-velocity impact analysis of composite laminates using linearized contact law” Composite Structures 66
(2004) 125–132
[7]. Shiuh-Chuan Her, “The finite element analysis of composite laminates and shell structures subjected to low velocity impact”
Composite Structures 66 (2004) 277–285
[8]. Giovanni Belingardi, “Low velocity impact tests of laminate glass-fiber-epoxy matrix composite material plates” International
Journal of Impact Engineering 27 (2002) 213–229
[9]. Krishnamurthy.K.S, “A parametric study of the impact response and damage of laminated cylindrical composite shells” Composites
Science and Technology 61 (2001) 1655–1669
[10]. Parhi.P.K, Bhattacharyya.S.K and Shina.P.K:“Failure analysis of multiple delaminated composite plates due to bending and impact”
Bull. Mater. Sci., Vol. 24, No. 2, April 2001, pp. 143–149
[11]. Mili.F, Necib.B, “Impact behaviour of cross-ply laminated composite plates under low velocities” composite structure 51 (2001)
237-244
[12]. Wade c. jackson and C.C. Poe.jr “The use of impact force as a scale parameter for the impact response of composite laminates”
Nasa Technical Memorandum 104189 Avscom Technical Report 92-B-001
[13]. Silva M.A.G. and Cismaşiu.C Centro de Investigação em Estruturas e Construção – UNIC, Faculdade de Ciências e
Tecnologia,sUniversidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal.
[14]. Sheng-Tsong Chiu, “Low velocity impact behavior of prestressed composite laminates” Materials Chemistry and Physics 47 (1997)
268-272
[15]. Vaziri.R, Quan.X and Olson.M.D “Impact analysis of laminated composite plates and shells by super finite elements Int. J. Impact
Enon9 Vol. 18, Nos 7 8, pp. 765-782, 1996
[16]. Jeffery.S.N, Paine and Craig A. Rogers. Centre for intelligent material system and structure virginia Tech Blacksburg, Virginia
24061-0261 vol-5 july 1994
[17]. Delfosse, D, Vaziri, R, Pierson M.O, and Poursartip, A., Analysis of the non-penetrating impact behavior of CFRP laminates.
Proceedings of the 9th International Conference on Composite Materials, Madrid, Spain, July 1993, pp. 366-373
[18]. Liu.G.R and Quek.S.S “The finite element method A practicle course”
[19]. LS-DYNA KEYWORD USER‟S MANUAL”, Version-971, Livermore Software Technology Corporation,2006
[20]. http://www.lsdyna.com