This document presents a novel methodology for developing probabilistic fatigue curves for asphalt concrete based on viscoelastic continuum damage mechanics. Several asphalt concrete specimens were tested under uniaxial loading to determine their viscoelastic and damage properties. The data was analyzed using viscoelastic continuum damage mechanics principles to predict fatigue life. Weibull and lognormal distributions were fit to the predicted fatigue lives. The Weibull distribution provided the best fit to the fatigue damage data. A 3-parameter Weibull distribution fit better than a 2-parameter distribution due to its flexibility. The probabilistic fatigue curves developed differed significantly from traditional deterministic curves. The proposed methodology combines continuum damage mechanics with probabilistic approaches.
This document summarizes research characterizing damage in thin acrylonitrile butadiene styrene (ABS) plates under uniaxial loading. Experiments were conducted on smooth and notched ABS plate specimens. Results showed mechanical properties like ultimate stress and stiffness decreased with increasing notch diameter due to stress concentration. A damage model based on the unified damage theory was applied to quantify damage. Damage increased linearly with the fraction of life and reached a maximum of 0.9 at failure. Stress concentration factor was also examined, decreasing with increasing notch to width ratio. In conclusion, the experiments and modeling successfully characterized ABS plate damage and the effects of notches on stress concentration and mechanical properties.
A study on the mechanical properties of s45 c medium type carbon steel specim...eSAT Journals
Abstract The experimental process is a fundamental technique used to determine the nature and behavior of many materials under study. In order to evaluate the fundamental properties of many engineering materials the use of mechanical testing techniques frequently play a crucial role. The development of new materials and the control of material quality are essential in the process of design and in their usage for industrial applications and construction. In this experiment, there were 2 sets (5 samples each) of medium type steel specimens S45C of 0.45% carbon content that were rigorously prepared according to ASTM standards under specific varied parameters. These parameters include the machining cutter speeds on the lathe machine and the mediums selected and temperatures set for the quenching process on the steel specimens in order to affect their overall microstructure. The specimens were then subjected to aggregate mechanical loading using a conventional tensile testing machine. The consequential effect of material structure metamorphosis under the selected quenching techniques was ultimately not part of the study as it involves microscopic analysis of grain boundaries and high-end precision equipment would be necessary to do any significant material analysis. The results of the experiment suggest that the macroscopic (not microscopic) effect of the lathe machining speeds do not significantly affect the tensile material strength of the S45 medium carbon steel specimen. Thus, the mediums and temperatures selected for the quenching process on the specimens had a marginal but significant effect on the elevated levels of tensile mechanical strength and strain of medium type carbon steel. Keywords: mechanical properties, carbon steel, lathe machine, S45C, quenching process, tensile test, stress, strain.
1) An experimental study was conducted to compare the compression behavior of normal strength concrete (NSC) and self-compacting concrete (SCC) intermediate columns.
2) Six column specimens with a cross-section of 125x125mm and a height of 1.5m were tested under axial loading. The columns varied in concrete type (NSC and SCC) and longitudinal reinforcement ratio (2.09%, 2.89%, 5.15%).
3) The results showed that as the reinforcement ratio increased, the ultimate load capacity increased and axial deformation decreased for both NSC and SCC columns. However, SCC columns exhibited higher ultimate loads and deformations than NSC columns for the same reinforcement ratio.
Probabilistic approach to study the hydroformed sheetIJERA Editor
Under the leadership of the Kyoto agreements on reducing emissions of greenhouse gases, the automotive sector was forced to review its methods and production technologies in order to meet the new environmental standards. In fuel consumption reduction is an immediate way to reduce the emission of polluting gases. In this paper, the study of the formability of sheet submitted to the hydroforming process is proposed. The numerical results are given to validate the proposed approach. To show the influence of uncertainties in the study process, we take some characteristics of the material as random and the probabilistic approach is done. The finding results are showing the effectiveness of the proposed approach.
In the past few years, a concern is observed internationally regarding the seismic mechanical
behavior of reinforced concrete walls, especially against their transverse instability under extreme
seismic loads.
This document discusses the fatigue behavior of high volume fly ash concrete (HVFAC) under constant amplitude and compound loading. It presents test results of 95 HVFAC and 100 conventional concrete prism specimens tested under constant amplitude flexural fatigue loading. It also discusses test results of 24 HVFAC specimens under compound fatigue loading to verify the validity of Miner's hypothesis for HVFAC. Probability distributions were developed from the fatigue life test results and S-N curves were established relating stress level to fatigue life for both concretes. The findings provide useful data on fatigue performance of HVFAC.
This document presents a numerical analysis of high strength concrete beams using ABAQUS finite element software. An M60 concrete beam was modeled in ABAQUS with different reinforcement configurations. The beam models were analyzed under static loading and the results were verified against experimental data. The failure loads, deflections, and load-deflection behaviors obtained from ABAQUS analysis matched closely with the experimental values, with errors of less than 10% in most cases. Stress contours from the ABAQUS models also agreed well with the failure patterns observed in experiments. The study demonstrated that ABAQUS can accurately simulate the behavior of reinforced high strength concrete beams.
Damage tolerance study of honeycomb sandwich structureeSAT Journals
Abstract
Composite materials are essential component in today’s modern world. Structural sandwich construction is one of the first form of composite structures. In this study honeycomb sandwich structure which is a peculiar type of composite structure was investigated for crashworthiness. They are manmade structures with a honeycomb geometry. It consists of three elements ; Top face sheet, Core, Bottom face sheet. They are widely used in aerospace industry, marine, rail, automotive industry, in construction field as prefabricated partition walls, mezzanine floor, doors etc. The main objective of this study was to assess the damage tolerance of honeycomb sandwich structure based on serviceability and safety of the structure ie. to understand ability of structure to sustain defects safely until repair/replacement is performed. Damage tolerance study was performed to know with how much load this structure would safely withstand and also to know till how much load this structure would be made serviceable, if a damage is caused to it. Investigations were performed on both damaged and undamaged specimens by conducting. Four point bending flexure test and Edgewise compression test based on ASTM standards. Also finite element modeling of honeycomb sandwich structure was developed and analysis of the two experiments were performed in Ansys. Ultimate load, tensile and compressive stress values etc. obtained from the two experiments were compared for both damaged and undamaged specimen. Based on the results obtained it could be inferred that the load carrying capacity of honeycomb sandwich structure reduces, if a damage is caused to it but can perform its duty with reduced efficiency.
Keywords: Honeycomb Sandwich, Crashworthiness, Four point bending and Edgewise compression.
This document summarizes research characterizing damage in thin acrylonitrile butadiene styrene (ABS) plates under uniaxial loading. Experiments were conducted on smooth and notched ABS plate specimens. Results showed mechanical properties like ultimate stress and stiffness decreased with increasing notch diameter due to stress concentration. A damage model based on the unified damage theory was applied to quantify damage. Damage increased linearly with the fraction of life and reached a maximum of 0.9 at failure. Stress concentration factor was also examined, decreasing with increasing notch to width ratio. In conclusion, the experiments and modeling successfully characterized ABS plate damage and the effects of notches on stress concentration and mechanical properties.
A study on the mechanical properties of s45 c medium type carbon steel specim...eSAT Journals
Abstract The experimental process is a fundamental technique used to determine the nature and behavior of many materials under study. In order to evaluate the fundamental properties of many engineering materials the use of mechanical testing techniques frequently play a crucial role. The development of new materials and the control of material quality are essential in the process of design and in their usage for industrial applications and construction. In this experiment, there were 2 sets (5 samples each) of medium type steel specimens S45C of 0.45% carbon content that were rigorously prepared according to ASTM standards under specific varied parameters. These parameters include the machining cutter speeds on the lathe machine and the mediums selected and temperatures set for the quenching process on the steel specimens in order to affect their overall microstructure. The specimens were then subjected to aggregate mechanical loading using a conventional tensile testing machine. The consequential effect of material structure metamorphosis under the selected quenching techniques was ultimately not part of the study as it involves microscopic analysis of grain boundaries and high-end precision equipment would be necessary to do any significant material analysis. The results of the experiment suggest that the macroscopic (not microscopic) effect of the lathe machining speeds do not significantly affect the tensile material strength of the S45 medium carbon steel specimen. Thus, the mediums and temperatures selected for the quenching process on the specimens had a marginal but significant effect on the elevated levels of tensile mechanical strength and strain of medium type carbon steel. Keywords: mechanical properties, carbon steel, lathe machine, S45C, quenching process, tensile test, stress, strain.
1) An experimental study was conducted to compare the compression behavior of normal strength concrete (NSC) and self-compacting concrete (SCC) intermediate columns.
2) Six column specimens with a cross-section of 125x125mm and a height of 1.5m were tested under axial loading. The columns varied in concrete type (NSC and SCC) and longitudinal reinforcement ratio (2.09%, 2.89%, 5.15%).
3) The results showed that as the reinforcement ratio increased, the ultimate load capacity increased and axial deformation decreased for both NSC and SCC columns. However, SCC columns exhibited higher ultimate loads and deformations than NSC columns for the same reinforcement ratio.
Probabilistic approach to study the hydroformed sheetIJERA Editor
Under the leadership of the Kyoto agreements on reducing emissions of greenhouse gases, the automotive sector was forced to review its methods and production technologies in order to meet the new environmental standards. In fuel consumption reduction is an immediate way to reduce the emission of polluting gases. In this paper, the study of the formability of sheet submitted to the hydroforming process is proposed. The numerical results are given to validate the proposed approach. To show the influence of uncertainties in the study process, we take some characteristics of the material as random and the probabilistic approach is done. The finding results are showing the effectiveness of the proposed approach.
In the past few years, a concern is observed internationally regarding the seismic mechanical
behavior of reinforced concrete walls, especially against their transverse instability under extreme
seismic loads.
This document discusses the fatigue behavior of high volume fly ash concrete (HVFAC) under constant amplitude and compound loading. It presents test results of 95 HVFAC and 100 conventional concrete prism specimens tested under constant amplitude flexural fatigue loading. It also discusses test results of 24 HVFAC specimens under compound fatigue loading to verify the validity of Miner's hypothesis for HVFAC. Probability distributions were developed from the fatigue life test results and S-N curves were established relating stress level to fatigue life for both concretes. The findings provide useful data on fatigue performance of HVFAC.
This document presents a numerical analysis of high strength concrete beams using ABAQUS finite element software. An M60 concrete beam was modeled in ABAQUS with different reinforcement configurations. The beam models were analyzed under static loading and the results were verified against experimental data. The failure loads, deflections, and load-deflection behaviors obtained from ABAQUS analysis matched closely with the experimental values, with errors of less than 10% in most cases. Stress contours from the ABAQUS models also agreed well with the failure patterns observed in experiments. The study demonstrated that ABAQUS can accurately simulate the behavior of reinforced high strength concrete beams.
Damage tolerance study of honeycomb sandwich structureeSAT Journals
Abstract
Composite materials are essential component in today’s modern world. Structural sandwich construction is one of the first form of composite structures. In this study honeycomb sandwich structure which is a peculiar type of composite structure was investigated for crashworthiness. They are manmade structures with a honeycomb geometry. It consists of three elements ; Top face sheet, Core, Bottom face sheet. They are widely used in aerospace industry, marine, rail, automotive industry, in construction field as prefabricated partition walls, mezzanine floor, doors etc. The main objective of this study was to assess the damage tolerance of honeycomb sandwich structure based on serviceability and safety of the structure ie. to understand ability of structure to sustain defects safely until repair/replacement is performed. Damage tolerance study was performed to know with how much load this structure would safely withstand and also to know till how much load this structure would be made serviceable, if a damage is caused to it. Investigations were performed on both damaged and undamaged specimens by conducting. Four point bending flexure test and Edgewise compression test based on ASTM standards. Also finite element modeling of honeycomb sandwich structure was developed and analysis of the two experiments were performed in Ansys. Ultimate load, tensile and compressive stress values etc. obtained from the two experiments were compared for both damaged and undamaged specimen. Based on the results obtained it could be inferred that the load carrying capacity of honeycomb sandwich structure reduces, if a damage is caused to it but can perform its duty with reduced efficiency.
Keywords: Honeycomb Sandwich, Crashworthiness, Four point bending and Edgewise compression.
This paper addresses the fracture toughness ( ), or also known as critical stress intensity Factor, according to
conditions of Lineal Elastic Fracture Mechanics (LEFM). The characterization of the mechanical properties in
tensile and fracture toughness of structural steel pipes API-5L used in hydrocarbons transportation was
performed. For fracture toughness, the material was tested through fatigue crack propagation on standardized
compact specimen (CT) according to ASTM E-399 norm. A thickness (B) equal to and a crack size (a) equal
to 0.5w were used. With the porpoise of establishing the adequate conditions at the crack tip, the specimens were
subjected to fatigue pre-cracking by application of repeated cycles of load in tensile-tensile and constant load
amplitude with a load ratio of R = 0.1. The experimental Compliance method was used based on data obtained
from load vs. Crack Mouth Opening Displacement (CMOD). The results show a Stress Intensity factor of 35.88
MPa√m for a 25 mm crack size specimen. The device used for testing is a MTS-810 machine with capacity of
100KN and 6 kHz sampling rate, which meets the conditions of the ASTM E-399 standard. The cracking
susceptibility of steel is influenced by the size, morphology and distribution of non-metallic inclusions,
thermochemical interaction with the environment and microstructure.
This document summarizes a study on predicting subsurface rolling contact fatigue in railway wheels using finite element modeling and fatigue analysis. A 3D finite element model of a wheel rolling on a rail segment was developed. Stresses and strains from the model were used in the Fatemi-Socie multiaxial fatigue criterion to predict fatigue initiation locations. The model predicted initiation at a depth of 0.12 inches, consistent with previous research. It also predicted a fatigue life of around 220,000 cycles and the critical crack plane orientation, matching other studies. The study concludes the model can accurately predict fatigue behavior in railway wheels.
This document reviews the use of ANSYS finite element analysis software to model reactive powder concrete (RPC). It discusses how ANSYS can be used to perform various types of structural analyses, including static, modal, transient dynamic and buckling analyses. The review then describes how RPC specimens were modeled and meshed in ANSYS, and the results obtained, including stress contours showing higher shear stresses at connections. It concludes RPC behaves in an elasto-plastic manner initially, then is plastic dominated, and that fiber reinforcement improves its shear strength through fiber pullout and dowel action.
Study of Damage to ABS Specimens Submitted To Uniaxial Loadingtheijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Theoretical work submitted to the Journal should be original in its motivation or modeling structure. Empirical analysis should be based on a theoretical framework and should be capable of replication. It is expected that all materials required for replication (including computer programs and data sets) should be available upon request to the authors.
The International Journal of Engineering & Science would take much care in making your article published without much delay with your kind cooperation.
The document describes an extension to the brittle cracking concrete material model in ABAQUS. The extension adds nonlinear compressive behavior using a user subroutine. The extended model is validated by comparing it to the original brittle cracking model and damaged plasticity model under uniaxial loading. The extended model is also shown to capture strain rate effects observed in experiments. Finally, the extended model is used to simulate benchmark cases including a notched concrete beam, demonstrating its ability to model tensile failure of concrete structures.
LITERATURE REVIEW ON FRACTURE TOUGHNESS AND IMPACT TOUGHNESSijiert bestjournal
The present paper gives a technical revi ew of fracture toughness,and impact toughness for metallic materials in terms of the linear elastic fracture mechanics. This includes the early investigations and recent advances of fracture toughness test methods and practices developed by various agencies and societies. The review describes the most important fracture mechanics parameters:such as the elastic energy release rate G,the stress intensity factor K,the J - integral,the crack - tip opening displacement (CTOD) and the crack - tip opening angle (CTOA) from the basic concept,definition,to,tes t methods. Attention is paid to guidelines on how to choose an appropriate fracture parameter to characterize fracture toughness for the material of interest,and how to measure the fracture toughness value defined either at a critical point or in a resist ance curve format using laboratory specimens. The effects of loading rate,temperature and crack - tip constraint on fracture toughness as well as fracture instability analysis are also reviewed.
This document discusses the stress-strain behavior of Ultra High Performance Concrete (UHPC) under uniaxial compression. Cylinder specimens with varying fiber contents were tested to determine their complete stress-strain curves and develop stress-strain models. The highest compressive strength of 171.3 MPa was achieved with 2% 13mm fibers. A modified toughness index was proposed and ranged from 2.64 to 4.65, indicating fiber reinforcement improved cracking resistance. The optimal fiber contents were found to be 3% 6mm fibers or 2% 13mm fibers. Several models were examined and a modified model provided the best fit for predicting the stress-strain behavior of UHPC.
Can fracture mechanics predict damage due disaster of structureseSAT Publishing House
This document discusses how fracture mechanics can be used to better predict damage and failure of structures. It notes that current design codes are based on small-scale laboratory tests and do not account for size effects, which can lead to more brittle failures in larger structures. The document outlines how fracture mechanics considers factors like size effect, ductility, and minimum reinforcement that influence the strength and failure behavior of structures. It provides examples of how fracture mechanics has been applied to problems like evaluating shear strength in deep beams and investigating a failure of an oil platform structure. The document argues that fracture mechanics provides a more scientific basis for structural design compared to existing empirical code provisions.
This document presents a new approach for determining the tensile and shear strengths of normal weight concrete. It discusses existing methods for evaluating these properties and their limitations. The author proposes using the failure patterns of two concrete cylinders under compression - with the same cross-sectional area but different heights - to define a characteristic fracture angle. This angle would be a function of the concrete's compressive strength. Equations are then developed relating the fracture angle to the tensile and shear strengths. The significance of using two cylinders is that it introduces the concept of the direction of the failure plane as a way to predict mechanical properties from a standard compression test.
This document summarizes a study that models fatigue damage in solder interconnects using a cohesive zone approach. The study simulates fatigue damage over successive loading cycles using finite element analysis. Damage is modeled to occur at interfaces using cohesive zones, which incorporate a damage variable into the constitutive law to account for material degradation over cycles. A damage evolution law is formulated to capture key damage characteristics as damage accumulates. The model predicts solder bump lifetime and shows good agreement with an empirical lifetime model. Damage distribution and stiffness loss are examined over cycles. The analysis is currently limited to 2D but aims to provide a more realistic fatigue simulation than models that assume constant material properties.
Design Evaluation and Optimization of IC Engine Connecting Rods '“ A Reviewijtsrd
Fatigue analysis and Optimization of connecting rod are the modern trend in automotive engineering industry emphasis on many parameters like total deformation, life, factor of safety, stress biaxiality and fatigue sensitivity. The main scope of this work comprises detailed review on various methods and procedures adopted by different researchers in Fatigue analysis of commercially used Engine Connecting rod. The objective of conducting fatigue analysis varies from each other like Weight reduction, Cost reduction, Shape optimization and fatigue life calculation at varying boundary conditions and loads. Fatigue analysis has a very dominant position in product design and development as more than 50% of the products, structural failures are due to fatigue concept only. The review have emphasized the importance of conducting the fatigue analysis of the connecting rod to identity its critical points, fatigue life and factor of safety etc., for its better performance and life period extension. N. Mohammed Raffic | Dr. K. Ganesh Babu | K. N. Arun Kumar"Design Evaluation and Optimization of IC Engine Connecting Rods “ A Review" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-3 , April 2018, URL: http://www.ijtsrd.com/papers/ijtsrd10814.pdf http://www.ijtsrd.com/engineering/mechanical-engineering/10814/design-evaluation-and-optimization-of-ic-engine-connecting-rods--a-review/n-mohammed-raffic
The current paper is a report on the preparation and testing of 10 reinforced concrete column specimens of (120x120) mm2 cross section and 1000 mm height, for the experimental clarification of the behavior of columns under the influence of pure axial loads. The research addresses the influences of some parameters and conditions on the mentioned behavior, including concrete type (normal strength, high strength or modified reactive powder concrete), the amount of reinforcement and the percentage of steel fibers. The effects of the above variables on the ultimate capacity, failure mode, stiffness, ductility and axial load-lateral displacement behavior were studied. It has been found that increasing the compressive strength and steel reinforcement ratio lead to increasing the ultimate capacity and stiffness of the tested columns. The effectiveness of increasing the steel fibers ratio is manifest in increasing the ultimate strength, ductility, and decreasing the stiffness and the ductility of the tested columns.
Effect of orientation and applied load on abrasive wear property of alumunIAEME Publication
1. The document investigates experimentally the effect of orientation and applied load on the abrasive wear property of an aluminum alloy (Al6061).
2. Tests were conducted using a pin-on-disc setup at various orientations (0, 30, 45, 60, 90 degrees) and loads (5-20N). Results showed that weight loss increased with increasing load at all orientations.
3. Weight loss was highest at 0 degrees orientation and lowest at 90 degrees orientation for a given load. The circumferential distance traveled was the same for all positions and loads but mass loss varied.
This document describes a study that verifies a method for improving the accuracy of simplified seismic response analysis of steel rigid frame viaducts. The study constructs an analytical model using shell elements to account for local buckling behavior. Pushover analysis is performed to evaluate seismic performance. Simplified seismic response analysis is then conducted using an equivalent single-degree-of-freedom system model with a bilinear restoring force-displacement relationship based on the Pushover analysis results. The accuracy of this simplified analysis is evaluated by comparing to results from dynamic analysis using the full analytical model. The study also examines using a trilinear model for the restoring force relationship to improve accuracy of response displacement predictions for the structure.
There are currently three approaches to characterize and quantify the fatigue behaviour of composite laminates that are, Fatigue Life Modelling and Prediction, Phenomenological and Empirical Modelling, and Progressive Damage Modelling. These approaches constitute the evolution that is driven by ever expanding industrial needs and academic pursuit and assisted by perpetual technological advances in experimentation capabilities. In the first approach of Fatigue Life Modelling and Prediction the individual material degradation mechanisms are not directly concerned with, rather the determination of stress-life relationships based on experimental data is concerned with and the failure criteria or the residual strength determination is established based on these relationships, for the specific composite laminate.
Effect of pitch and nominal diameter on load distribution and efficiency in m...eSAT Journals
Abstract Lead screws are the devices which are used for power transmission or to have linear motion. It is theoretically assumed that applied load is evenly distributed among the thread pair in contact. However, practically it is observed that load is not uniformly distributed among threads. The first thread carries the maximum load and later the load on each thread reduces. Numerous studies have been carried out for analytical calculation of the load distribution using spring stiffness method. But these studies are for screw and nut combination. Not much study has been done to find load distribution on threads of a lead screw. The maximum load acting on one thread is an important parameter in lead screw design. The load decides the fatigue life of the screw and nut. To have better life of threads, the load distribution should be uniform to have fewer loads on single thread. The load is also important to know the deflection of thread which affects the positional accuracy of the lead screw drives. This paper focuses on analyzing mathematically the various thread parameters which affects the load distribution in threads and the corresponding effect on efficiency. The spring model method proposed in [1], [4] has different constant coefficient which are depending on thread geometry and material. If there are n numbers of threads in contact, there will be (n-1) number of equations in (n-1) unknowns. These are linear difference equations and can be solved by matrix elimination method. The results obtained from analytical solution are validated with the FEM (Finite Elements Method) results. Keywords: Lead Screws, Load Distribution, Thread Parameters, Efficiency, Linear Drives
High Strain Rate Testing of Materials
Polymers, composites and some metallic materials are viscoelastic and strain-rate sensitive. Under high strain rates the micro mechanisms by which these materials deform is different than that experienced at low strain rates. Consequently, use of quasi-static stress-strain data may not produce accurate and reliable predictions, when such data is used in simulation and Finite element analysis FEA of engineering components.
This document outlines standards for plane strain fracture toughness testing of metals. It describes the test method which involves precracking a notched metal specimen using fatigue, then applying a bending or tensile load to propagate the crack. Key parameters such as specimen thickness, crack length, and stress intensity during precracking are specified. The test aims to determine the plane strain fracture toughness (KIC) value, which indicates a material's resistance to crack growth under conditions of limited plasticity. Specimen dimensions, test procedures, and validity checks are provided to ensure accurate KIC measurements.
Establishing empirical relations to predict grain size and hardness of pulsed...drboon
SS 304L, an austenitic Chromium-Nickel stainless steel offering the optimum combination of corrosion resistance, strength and ductility, is favorable for many mechanical components. The low carbon content reduces susceptibility to carbide precipitation during welding. In case of single pass welding of thinner section of this alloy, pulsed current micro plasma arc welding was found beneficial due to its advantages over the conventional continuous current process. The paper focuses on developing mathematical models to predict grain size and hardness of pulsed current micro plasma arc welded SS304L joints. Four factors, five level, central composite rotatable design matrix is used to optimize the number of experiments. The mathematical models have been developed by response surface method. The adequacy of the models is checked by ANOVA technique. By using the developed mathematical models, grain size and hardness of the joints can be predicted with 99% confidence level. Contour plots are drawn to study the interaction effect of pulsed current micro plasma arc welding parameters on fusion zone grain size and hardness of SS304L steel.
Model Development for Estimation of Failure Loads: A Case Study of Composite ...ijsrd.com
This paper deals with the study of failure loads of glass vinylester composite plates with a circular hole subjected to a traction force by a rigid pin. These are investigated for two variables, the ratio of distance from the free edge of the plate (E) to the diameter of the hole (D) and the ratio of width of the plate (W) to the diameter of the hole (D). The work consists of a numerical study of different specimens using finite element analysis package ANSYS. Also, a mathematical model has been developed to determine the failure loads of different geometry plates. The results obtained from the numerical study and the mathematical models are compared with experimental results from the existing literature and the correlations are observed for both. A comparison of the experimental results with the numerical model shows that the numerical model gives results with correlation co-efficient 0.96. A comparison of the experimental results with the mathematical model shows that the mathematical model gives results with correlation co-efficient 0.99. For estimation of the failure loads within the range of E/D and W/D considered for the study, the mathematical model developed, i.e., Full Cubic Model proves to be more efficient with the observed values of correlation co-efficient, Root Mean Square Error and Maximum Absolute Error.
Fracture mechanics based estimation of fatigue life of weldsAvinash B
This document presents an approach for predicting fatigue life in welded joints subjected to multiaxial loading. It assumes crack-like flaws exist after welding, so crack initiation is insignificant. Crack propagation analysis or fracture mechanics are used to determine fatigue limits depending on the cycle regime. A weight function method calculates stress intensity factors for a semi-elliptical surface crack near the weld toe. Finite element analysis determines the through-thickness stress distribution. Combining this information with the Paris law and fracture toughness allows predicting fatigue life in the high-low cycle regimes. Validation with S-N curves from welding standards shows the approach can derive material-specific limits for particular welding processes.
Experimental Investigation of Stress Concentration in Cross Section of Crane ...ijtsrd
Crane Hooks are highly liable components and are always subjected to failure due to the amount of stresses concentration which can eventually lead to its failure. To study the stress pattern of crane hook in its loaded condition, a solid model of crane hook is prepared with the help of solid works or Pro E software. Real time pattern of stress concentration in 3D model of crane hook is obtained. By predicting the stress concentration area, the shape of the crane is modified to increase its working life and reduce the failure rates. Hooks are employed in heavy industries to carry tonnes of loads safely. These hooks have a big role to play as far as the safety of the crane loaded is concerned. With more and more industrialization the rate at which these hooks are forged are increasing. This work has been carried out on one of the major crane hook carrying a larger load comparatively. The cad model of the crane hook is initially prepared with the help of existing drawings. It is then followed by implementation of modified cross section of hook in the static structural analysis workbench of ANSYS. The selection was based on the satisfaction of several factors in the form of load carrying capacity, stress induced and deflection Stress analysis plays a significant role in the design of parts and structures that must carry load. In this study, Crane hook which is one of lifting equipment, frequently used in material handling is investigated. Analytical Straight beam, curved beam and Winkler Bach approximation , FEM methods were used by various researchers to study stress pattern of crane hook in its loaded condition. The fatigue of the crane which leads to failure of propagation of cracks by stress concentration. Gabriel. A | Suganth. V | Dr. S. Velumani "Experimental Investigation of Stress Concentration in Cross Section of Crane Hook" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-6 , October 2020, URL: https://www.ijtsrd.com/papers/ijtsrd33640.pdf Paper Url: https://www.ijtsrd.com/engineering/mechanical-engineering/33640/experimental-investigation-of-stress-concentration-in-cross-section-of-crane-hook/gabriel-a
This paper addresses the fracture toughness ( ), or also known as critical stress intensity Factor, according to
conditions of Lineal Elastic Fracture Mechanics (LEFM). The characterization of the mechanical properties in
tensile and fracture toughness of structural steel pipes API-5L used in hydrocarbons transportation was
performed. For fracture toughness, the material was tested through fatigue crack propagation on standardized
compact specimen (CT) according to ASTM E-399 norm. A thickness (B) equal to and a crack size (a) equal
to 0.5w were used. With the porpoise of establishing the adequate conditions at the crack tip, the specimens were
subjected to fatigue pre-cracking by application of repeated cycles of load in tensile-tensile and constant load
amplitude with a load ratio of R = 0.1. The experimental Compliance method was used based on data obtained
from load vs. Crack Mouth Opening Displacement (CMOD). The results show a Stress Intensity factor of 35.88
MPa√m for a 25 mm crack size specimen. The device used for testing is a MTS-810 machine with capacity of
100KN and 6 kHz sampling rate, which meets the conditions of the ASTM E-399 standard. The cracking
susceptibility of steel is influenced by the size, morphology and distribution of non-metallic inclusions,
thermochemical interaction with the environment and microstructure.
This document summarizes a study on predicting subsurface rolling contact fatigue in railway wheels using finite element modeling and fatigue analysis. A 3D finite element model of a wheel rolling on a rail segment was developed. Stresses and strains from the model were used in the Fatemi-Socie multiaxial fatigue criterion to predict fatigue initiation locations. The model predicted initiation at a depth of 0.12 inches, consistent with previous research. It also predicted a fatigue life of around 220,000 cycles and the critical crack plane orientation, matching other studies. The study concludes the model can accurately predict fatigue behavior in railway wheels.
This document reviews the use of ANSYS finite element analysis software to model reactive powder concrete (RPC). It discusses how ANSYS can be used to perform various types of structural analyses, including static, modal, transient dynamic and buckling analyses. The review then describes how RPC specimens were modeled and meshed in ANSYS, and the results obtained, including stress contours showing higher shear stresses at connections. It concludes RPC behaves in an elasto-plastic manner initially, then is plastic dominated, and that fiber reinforcement improves its shear strength through fiber pullout and dowel action.
Study of Damage to ABS Specimens Submitted To Uniaxial Loadingtheijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Theoretical work submitted to the Journal should be original in its motivation or modeling structure. Empirical analysis should be based on a theoretical framework and should be capable of replication. It is expected that all materials required for replication (including computer programs and data sets) should be available upon request to the authors.
The International Journal of Engineering & Science would take much care in making your article published without much delay with your kind cooperation.
The document describes an extension to the brittle cracking concrete material model in ABAQUS. The extension adds nonlinear compressive behavior using a user subroutine. The extended model is validated by comparing it to the original brittle cracking model and damaged plasticity model under uniaxial loading. The extended model is also shown to capture strain rate effects observed in experiments. Finally, the extended model is used to simulate benchmark cases including a notched concrete beam, demonstrating its ability to model tensile failure of concrete structures.
LITERATURE REVIEW ON FRACTURE TOUGHNESS AND IMPACT TOUGHNESSijiert bestjournal
The present paper gives a technical revi ew of fracture toughness,and impact toughness for metallic materials in terms of the linear elastic fracture mechanics. This includes the early investigations and recent advances of fracture toughness test methods and practices developed by various agencies and societies. The review describes the most important fracture mechanics parameters:such as the elastic energy release rate G,the stress intensity factor K,the J - integral,the crack - tip opening displacement (CTOD) and the crack - tip opening angle (CTOA) from the basic concept,definition,to,tes t methods. Attention is paid to guidelines on how to choose an appropriate fracture parameter to characterize fracture toughness for the material of interest,and how to measure the fracture toughness value defined either at a critical point or in a resist ance curve format using laboratory specimens. The effects of loading rate,temperature and crack - tip constraint on fracture toughness as well as fracture instability analysis are also reviewed.
This document discusses the stress-strain behavior of Ultra High Performance Concrete (UHPC) under uniaxial compression. Cylinder specimens with varying fiber contents were tested to determine their complete stress-strain curves and develop stress-strain models. The highest compressive strength of 171.3 MPa was achieved with 2% 13mm fibers. A modified toughness index was proposed and ranged from 2.64 to 4.65, indicating fiber reinforcement improved cracking resistance. The optimal fiber contents were found to be 3% 6mm fibers or 2% 13mm fibers. Several models were examined and a modified model provided the best fit for predicting the stress-strain behavior of UHPC.
Can fracture mechanics predict damage due disaster of structureseSAT Publishing House
This document discusses how fracture mechanics can be used to better predict damage and failure of structures. It notes that current design codes are based on small-scale laboratory tests and do not account for size effects, which can lead to more brittle failures in larger structures. The document outlines how fracture mechanics considers factors like size effect, ductility, and minimum reinforcement that influence the strength and failure behavior of structures. It provides examples of how fracture mechanics has been applied to problems like evaluating shear strength in deep beams and investigating a failure of an oil platform structure. The document argues that fracture mechanics provides a more scientific basis for structural design compared to existing empirical code provisions.
This document presents a new approach for determining the tensile and shear strengths of normal weight concrete. It discusses existing methods for evaluating these properties and their limitations. The author proposes using the failure patterns of two concrete cylinders under compression - with the same cross-sectional area but different heights - to define a characteristic fracture angle. This angle would be a function of the concrete's compressive strength. Equations are then developed relating the fracture angle to the tensile and shear strengths. The significance of using two cylinders is that it introduces the concept of the direction of the failure plane as a way to predict mechanical properties from a standard compression test.
This document summarizes a study that models fatigue damage in solder interconnects using a cohesive zone approach. The study simulates fatigue damage over successive loading cycles using finite element analysis. Damage is modeled to occur at interfaces using cohesive zones, which incorporate a damage variable into the constitutive law to account for material degradation over cycles. A damage evolution law is formulated to capture key damage characteristics as damage accumulates. The model predicts solder bump lifetime and shows good agreement with an empirical lifetime model. Damage distribution and stiffness loss are examined over cycles. The analysis is currently limited to 2D but aims to provide a more realistic fatigue simulation than models that assume constant material properties.
Design Evaluation and Optimization of IC Engine Connecting Rods '“ A Reviewijtsrd
Fatigue analysis and Optimization of connecting rod are the modern trend in automotive engineering industry emphasis on many parameters like total deformation, life, factor of safety, stress biaxiality and fatigue sensitivity. The main scope of this work comprises detailed review on various methods and procedures adopted by different researchers in Fatigue analysis of commercially used Engine Connecting rod. The objective of conducting fatigue analysis varies from each other like Weight reduction, Cost reduction, Shape optimization and fatigue life calculation at varying boundary conditions and loads. Fatigue analysis has a very dominant position in product design and development as more than 50% of the products, structural failures are due to fatigue concept only. The review have emphasized the importance of conducting the fatigue analysis of the connecting rod to identity its critical points, fatigue life and factor of safety etc., for its better performance and life period extension. N. Mohammed Raffic | Dr. K. Ganesh Babu | K. N. Arun Kumar"Design Evaluation and Optimization of IC Engine Connecting Rods “ A Review" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-3 , April 2018, URL: http://www.ijtsrd.com/papers/ijtsrd10814.pdf http://www.ijtsrd.com/engineering/mechanical-engineering/10814/design-evaluation-and-optimization-of-ic-engine-connecting-rods--a-review/n-mohammed-raffic
The current paper is a report on the preparation and testing of 10 reinforced concrete column specimens of (120x120) mm2 cross section and 1000 mm height, for the experimental clarification of the behavior of columns under the influence of pure axial loads. The research addresses the influences of some parameters and conditions on the mentioned behavior, including concrete type (normal strength, high strength or modified reactive powder concrete), the amount of reinforcement and the percentage of steel fibers. The effects of the above variables on the ultimate capacity, failure mode, stiffness, ductility and axial load-lateral displacement behavior were studied. It has been found that increasing the compressive strength and steel reinforcement ratio lead to increasing the ultimate capacity and stiffness of the tested columns. The effectiveness of increasing the steel fibers ratio is manifest in increasing the ultimate strength, ductility, and decreasing the stiffness and the ductility of the tested columns.
Effect of orientation and applied load on abrasive wear property of alumunIAEME Publication
1. The document investigates experimentally the effect of orientation and applied load on the abrasive wear property of an aluminum alloy (Al6061).
2. Tests were conducted using a pin-on-disc setup at various orientations (0, 30, 45, 60, 90 degrees) and loads (5-20N). Results showed that weight loss increased with increasing load at all orientations.
3. Weight loss was highest at 0 degrees orientation and lowest at 90 degrees orientation for a given load. The circumferential distance traveled was the same for all positions and loads but mass loss varied.
This document describes a study that verifies a method for improving the accuracy of simplified seismic response analysis of steel rigid frame viaducts. The study constructs an analytical model using shell elements to account for local buckling behavior. Pushover analysis is performed to evaluate seismic performance. Simplified seismic response analysis is then conducted using an equivalent single-degree-of-freedom system model with a bilinear restoring force-displacement relationship based on the Pushover analysis results. The accuracy of this simplified analysis is evaluated by comparing to results from dynamic analysis using the full analytical model. The study also examines using a trilinear model for the restoring force relationship to improve accuracy of response displacement predictions for the structure.
There are currently three approaches to characterize and quantify the fatigue behaviour of composite laminates that are, Fatigue Life Modelling and Prediction, Phenomenological and Empirical Modelling, and Progressive Damage Modelling. These approaches constitute the evolution that is driven by ever expanding industrial needs and academic pursuit and assisted by perpetual technological advances in experimentation capabilities. In the first approach of Fatigue Life Modelling and Prediction the individual material degradation mechanisms are not directly concerned with, rather the determination of stress-life relationships based on experimental data is concerned with and the failure criteria or the residual strength determination is established based on these relationships, for the specific composite laminate.
Effect of pitch and nominal diameter on load distribution and efficiency in m...eSAT Journals
Abstract Lead screws are the devices which are used for power transmission or to have linear motion. It is theoretically assumed that applied load is evenly distributed among the thread pair in contact. However, practically it is observed that load is not uniformly distributed among threads. The first thread carries the maximum load and later the load on each thread reduces. Numerous studies have been carried out for analytical calculation of the load distribution using spring stiffness method. But these studies are for screw and nut combination. Not much study has been done to find load distribution on threads of a lead screw. The maximum load acting on one thread is an important parameter in lead screw design. The load decides the fatigue life of the screw and nut. To have better life of threads, the load distribution should be uniform to have fewer loads on single thread. The load is also important to know the deflection of thread which affects the positional accuracy of the lead screw drives. This paper focuses on analyzing mathematically the various thread parameters which affects the load distribution in threads and the corresponding effect on efficiency. The spring model method proposed in [1], [4] has different constant coefficient which are depending on thread geometry and material. If there are n numbers of threads in contact, there will be (n-1) number of equations in (n-1) unknowns. These are linear difference equations and can be solved by matrix elimination method. The results obtained from analytical solution are validated with the FEM (Finite Elements Method) results. Keywords: Lead Screws, Load Distribution, Thread Parameters, Efficiency, Linear Drives
High Strain Rate Testing of Materials
Polymers, composites and some metallic materials are viscoelastic and strain-rate sensitive. Under high strain rates the micro mechanisms by which these materials deform is different than that experienced at low strain rates. Consequently, use of quasi-static stress-strain data may not produce accurate and reliable predictions, when such data is used in simulation and Finite element analysis FEA of engineering components.
This document outlines standards for plane strain fracture toughness testing of metals. It describes the test method which involves precracking a notched metal specimen using fatigue, then applying a bending or tensile load to propagate the crack. Key parameters such as specimen thickness, crack length, and stress intensity during precracking are specified. The test aims to determine the plane strain fracture toughness (KIC) value, which indicates a material's resistance to crack growth under conditions of limited plasticity. Specimen dimensions, test procedures, and validity checks are provided to ensure accurate KIC measurements.
Establishing empirical relations to predict grain size and hardness of pulsed...drboon
SS 304L, an austenitic Chromium-Nickel stainless steel offering the optimum combination of corrosion resistance, strength and ductility, is favorable for many mechanical components. The low carbon content reduces susceptibility to carbide precipitation during welding. In case of single pass welding of thinner section of this alloy, pulsed current micro plasma arc welding was found beneficial due to its advantages over the conventional continuous current process. The paper focuses on developing mathematical models to predict grain size and hardness of pulsed current micro plasma arc welded SS304L joints. Four factors, five level, central composite rotatable design matrix is used to optimize the number of experiments. The mathematical models have been developed by response surface method. The adequacy of the models is checked by ANOVA technique. By using the developed mathematical models, grain size and hardness of the joints can be predicted with 99% confidence level. Contour plots are drawn to study the interaction effect of pulsed current micro plasma arc welding parameters on fusion zone grain size and hardness of SS304L steel.
Model Development for Estimation of Failure Loads: A Case Study of Composite ...ijsrd.com
This paper deals with the study of failure loads of glass vinylester composite plates with a circular hole subjected to a traction force by a rigid pin. These are investigated for two variables, the ratio of distance from the free edge of the plate (E) to the diameter of the hole (D) and the ratio of width of the plate (W) to the diameter of the hole (D). The work consists of a numerical study of different specimens using finite element analysis package ANSYS. Also, a mathematical model has been developed to determine the failure loads of different geometry plates. The results obtained from the numerical study and the mathematical models are compared with experimental results from the existing literature and the correlations are observed for both. A comparison of the experimental results with the numerical model shows that the numerical model gives results with correlation co-efficient 0.96. A comparison of the experimental results with the mathematical model shows that the mathematical model gives results with correlation co-efficient 0.99. For estimation of the failure loads within the range of E/D and W/D considered for the study, the mathematical model developed, i.e., Full Cubic Model proves to be more efficient with the observed values of correlation co-efficient, Root Mean Square Error and Maximum Absolute Error.
Fracture mechanics based estimation of fatigue life of weldsAvinash B
This document presents an approach for predicting fatigue life in welded joints subjected to multiaxial loading. It assumes crack-like flaws exist after welding, so crack initiation is insignificant. Crack propagation analysis or fracture mechanics are used to determine fatigue limits depending on the cycle regime. A weight function method calculates stress intensity factors for a semi-elliptical surface crack near the weld toe. Finite element analysis determines the through-thickness stress distribution. Combining this information with the Paris law and fracture toughness allows predicting fatigue life in the high-low cycle regimes. Validation with S-N curves from welding standards shows the approach can derive material-specific limits for particular welding processes.
Experimental Investigation of Stress Concentration in Cross Section of Crane ...ijtsrd
Crane Hooks are highly liable components and are always subjected to failure due to the amount of stresses concentration which can eventually lead to its failure. To study the stress pattern of crane hook in its loaded condition, a solid model of crane hook is prepared with the help of solid works or Pro E software. Real time pattern of stress concentration in 3D model of crane hook is obtained. By predicting the stress concentration area, the shape of the crane is modified to increase its working life and reduce the failure rates. Hooks are employed in heavy industries to carry tonnes of loads safely. These hooks have a big role to play as far as the safety of the crane loaded is concerned. With more and more industrialization the rate at which these hooks are forged are increasing. This work has been carried out on one of the major crane hook carrying a larger load comparatively. The cad model of the crane hook is initially prepared with the help of existing drawings. It is then followed by implementation of modified cross section of hook in the static structural analysis workbench of ANSYS. The selection was based on the satisfaction of several factors in the form of load carrying capacity, stress induced and deflection Stress analysis plays a significant role in the design of parts and structures that must carry load. In this study, Crane hook which is one of lifting equipment, frequently used in material handling is investigated. Analytical Straight beam, curved beam and Winkler Bach approximation , FEM methods were used by various researchers to study stress pattern of crane hook in its loaded condition. The fatigue of the crane which leads to failure of propagation of cracks by stress concentration. Gabriel. A | Suganth. V | Dr. S. Velumani "Experimental Investigation of Stress Concentration in Cross Section of Crane Hook" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-6 , October 2020, URL: https://www.ijtsrd.com/papers/ijtsrd33640.pdf Paper Url: https://www.ijtsrd.com/engineering/mechanical-engineering/33640/experimental-investigation-of-stress-concentration-in-cross-section-of-crane-hook/gabriel-a
System identification is an emerging area in engineering fields. To assess the present health of important structures is necessary to know the status of the health of structure and subsequently to improve the health of the structure. In this work, using the finite element software, a simple structural member like beam is modeled. A simply supported beam is taken and crack is initiated at the bottom of the beam along it’s width by reducing the cross section in different location. Free vibration analysis is performed using FEM software SAP2000. There is a difference between the frequencies of cracked and un-cracked beam. From this analysis it can be predicted that there is damage in the beam, but location of the damage cannot be detected. For this, mode shape to be found out. This concept can be used to know in the real life structure whether there is any damage or not using the non-destructive techniques.
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
Study on the effects of ceramic particulates (sic, al2 o3 and cenosphere) on ...eSAT Journals
Abstract This paper investigates the sliding wear behaviour of three different composites. Three different reinforcements are under taken for this study namely SiC, Al2O3 and Cenosphere. Along with it percentage reinforcement is also varied from 8wt% to 16wt.%. Other factors applied normal load and sliding speed are also considered. Taguchi design of experimental technique is employed for the study of sliding wear. It is observed that SiC reinforced composites show better wear resistance than Al2O3 and Cenosphere reinforced composites. Regression and artificial neural network (ANN) is used to develop a model to predict the wear loss. It is observed that artificial neural network is more efficient than regression. Keywords: A. Metal-matrix composites (MMCs); B.Wear; C.Taguchi D. Nueral Network
This document discusses several methods for estimating the fatigue life of Type 304LN stainless steel under strain-controlled cyclic loading, including the four-point correlation method, modified four-point correlation method, universal slopes method, modified universal slopes method, uniform material law, hardness method, median's method, and methods proposed by Mitchell and Basan. The results of estimating fatigue life using these methods are compared to experimental strain-controlled fatigue test results on Type 304LN stainless steel at various strain amplitudes. Most methods overestimate fatigue life except the median's method, which provides a reasonably accurate estimation of fatigue life, especially at higher strain amplitudes. Basan's method, modified universal slopes method, and uniform material law also predict fatigue life with reasonable accuracy
Interfacial delamination failure in bonded concrete overlay systems a review...IAEME Publication
This document reviews theories and modeling methods for describing delamination failure at the interface between two bonded cementitious materials. It discusses traditional stress-based and energy-based failure criteria approaches. It presents the interface cohesive zone model (ICZM) as a viable approach for describing and predicting delamination in bonded concrete overlay systems. The ICZM treats delamination as a progressive failure involving both crack initiation and propagation. It considers distinct analytical cases involving material and structural property variables. The concluding model shows that numerical values of delamination coefficients and energy release rates vary depending on overlay scale, problem type, and material property mismatches.
INTERFACIAL DELAMINATION FAILURE IN BONDED CONCRETE OVERLAY SYSTEMS - A REVIE...IAEME Publication
This study reviews the theories and modelling methods for describing interfacial delamination failure process between two bonded cementitious materials. Complex interfacial stress
conditions at discontinuities and areas of high stress concentrations were primary areas of concern. Distinct analytical cases involving intrinsic material and structural property variables were considered. An approach based on plane strain analysis within the context of Interface Cohesive
Zone Model (ICZM) was cited and presented as viable for describing and predicting delamination mode of failure in bonded concrete overlays systems (BCOs).
This document summarizes a study that used computational fluid dynamics (CFD) to model soil erosion during a hole erosion test (HET). The study used the k-epsilon turbulence model in ANSYS Fluent to simulate the turbulent flow within the HET apparatus and calculate wall shear stresses. Higher velocities were found to increase erosion rates according to an erosion law relating erosion rate to shear stress exceeding a critical value. Non-uniform erosion along the hole was predicted, unlike one-dimensional models. Results provide insight into how flow variables like velocity affect internal erosion processes.
Analysis of a thin and thick walled pressure vessel for different materialsIAEME Publication
This document analyzes thin and thick walled pressure vessels made of different materials. It discusses the thick wall theory and thin wall theory for calculating stresses in pressure vessels. For thick walled vessels, Lame's equations and maximum stress theories are applied. Stress variations through the thickness are considered. Barlow's equation is used to analyze high pressure pipes. Numerical analysis is conducted in C++ software to efficiently solve stresses in thin and thick cylinders made of ductile and brittle materials. The modeling methodology and numerical approach are discussed in detail.
ANALYSIS OF A THIN AND THICK WALLED PRESSURE VESSEL FOR DIFFERENT MATERIALS IAEME Publication
In the present work the problem of calculation of the stress developed in the thin and thick cylindrical pressure vessels is numerically solved by using software in C++. The analysis has been done for two different materials pressure vessels. The variations in the thickness of the pressure vessels have been considered for the analysis for different internal pressures. The common characteristic of the pressure vessels solved is that the radial and tangential stresses vary in the same nature of curve for different thickness of vessels.
1) The document reviews several expressions proposed by researchers to calculate the equivalent width of diagonal struts used to model masonry-infilled reinforced concrete (RC) frames.
2) It applies these expressions to a sample one-bay one-story RC frame and analyzes the results using ABAQUS software to validate the modeling approach.
3) The study finds that the Paulay and Priestley expression, which defines the equivalent strut width as one-fourth the diagonal length of the infill panel, provides an average value that gives a reasonably accurate model for further analysis of RC infilled frames.
A critical comparison of shear tests for adhesive joints.pdfssuser9f67f31
This document summarizes and compares four methods for testing the shear strength of adhesive joints: single lap shear test (SLJ), thick adherent shear test (TAST), ARCAN test, and napkin ring test. It analyzes each method based on the stress and strain distributions within the joint, and the triaxiality ratio of normal to shear stresses, using analytical calculations and finite element modeling. The goal is to determine an optimal test configuration by understanding the advantages and limitations of each method for characterizing the mechanical behavior and fatigue properties of adhesive joints.
Molecular dynamics simulation studies of mechanical properties of different c...Johan Zhi Kang Kok
This document discusses molecular dynamics simulations of the mechanical properties of carbon nanotube systems. It summarizes simulations performed on single-walled carbon nanotubes (SWCNTs) under axial tension, including the effects of varying strain rates and length-diameter ratios on the SWCNT's ultimate tensile strength and critical strain. Simulations were also conducted on double-walled carbon nanotubes (DWCNTs), including extracting the inner tube of a DWCNT and bending tests on DWCNTs with different intertube separations. The results provide insights into the mechanical behavior of carbon nanotubes at the atomic level.
The document describes an experimental investigation of the fatigue life of two bridge crane girders using the S-N method. Strain gauge measurements were performed on the girders to determine stress values under operational loads after over 50 years of use. The measurements identified a nearly 50% decrease in residual life for one girder, caused by improper welding of rails during maintenance instead of using clamps. The experimental analysis provided valuable information on the technical state and remaining fatigue life of the load-bearing structure that would be difficult to determine through analytical calculations alone due to the complex operational conditions.
Design Modification of Failure Mode Effect Analysis of Vibrating Feeder used ...ijsrd.com
Vibratin feeder technology is common in material handling applications in numerous industries. This review paper examines a problem with fatigue in the support structure of a specific type of vibrating feeder. It also reviews the theory behind vibrating feeder technology and considerations that engineers who design them need to be aware of. The finite element method is used to replicate a fatigue problem in the support structure and various design configurations are then analyzed to reduce the risk of the conditions that caused the fatigue. The results are reviewed and recommendations are made to improve the design and modify the component dimensional parameters vibrating feeder.
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity
HVOF Sprayed WC-Cocr Coating on Mild Steel: Microstructure and Wear Evaluationiosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
This document presents a study that aims to develop correlations between uniaxial compressive strength (UCS) and point load index (I50) for single and double jointed rocks. Over 180 plaster samples were prepared with different joint conditions like orientation, roughness, and number of joints. Samples were tested for UCS and I50. Statistical analysis identified two groups of jointed rocks that showed different trends between UCS and I50. Multiple linear regression was used to develop new correlation equations for each group to predict UCS from I50 for jointed rocks. The proposed equations were compared to previous studies and may be applied to actual rocks like weathered limestone.
Similar to Sharma2016 development of probabilistic fatigue curve for asphalt concrete (20)
This document provides details about the site of a four-lane highway project in Jharkhand, India. It summarizes the status of construction work done by the previous contractor, including:
- Earthwork and pavement layers were completed over 15,750-16,150 meters of the total 31,064 meter highway.
- Concrete works were partially completed on three major bridges, with foundations and parts of structures finished.
- The site will be provided in its current "as-is" condition for the new contractor to complete the remaining construction work.
The National Highways Authority of India is seeking bids for the four laning of the Barhi-Hazaribagh section of NH-33 from km 0.00 to km 40.500 in Jharkhand on an EPC basis under NHDP Phase III. The project cost is estimated at Rs. 323.72 crore and is to be completed within 21 months. The selected bidder will be responsible for designing, engineering, procurement and construction of the project as well as maintenance during the 4 year defect liability period under an EPC contract. The scope of work includes rehabilitation, upgradation and augmentation of the existing carriageway to four lanes along with construction of new and rehabilitation of existing pavements, bridges and cul
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help boost feelings of calmness, happiness and focus.
The document outlines a leave policy for SA INFRA CONSULTANTS PVT LIMITED. It details various types of leave including casual leave, earned leave, maternity leave, and paternity leave. Eligibility and entitlements are provided for each leave type. The policy aims to support a healthy work-life balance for employees and encourage use of leave for personal matters, illness, recreation, and emergencies. Guidelines are given for requesting and approving different leaves, and consequences are outlined for unapproved or extended leaves.
The document discusses rutting, cracking, and slippage issues observed on a highway project. It notes that the concessionaire did not follow the recommended plan to lay a 50mm overlay and that rutting has been observed at several locations totaling 7.1 km. Photos are provided and non-conformance reports have been issued but not addressed. Further deficiencies are expected to appear over time if issues are not resolved.
The document discusses several design issues with the NH-44 pavement project, including cracks and rutting in the main carriageway that the concessionaire did not fully address by applying the recommended 50mm overlay. It also notes issues with slip road and service road designs, including a request for FWD testing on the service road due to waterlogging issues. Pre-COD work is discussed, with 24kms of the 47km completed section needing non-compliance reports due to deficiencies like rutting.
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.
International Conference on NLP, Artificial Intelligence, Machine Learning an...gerogepatton
International Conference on NLP, Artificial Intelligence, Machine Learning and Applications (NLAIM 2024) offers a premier global platform for exchanging insights and findings in the theory, methodology, and applications of NLP, Artificial Intelligence, Machine Learning, and their applications. The conference seeks substantial contributions across all key domains of NLP, Artificial Intelligence, Machine Learning, and their practical applications, aiming to foster both theoretical advancements and real-world implementations. With a focus on facilitating collaboration between researchers and practitioners from academia and industry, the conference serves as a nexus for sharing the latest developments in the field.
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.
The CBC machine is a common diagnostic tool used by doctors to measure a patient's red blood cell count, white blood cell count and platelet count. The machine uses a small sample of the patient's blood, which is then placed into special tubes and analyzed. The results of the analysis are then displayed on a screen for the doctor to review. The CBC machine is an important tool for diagnosing various conditions, such as anemia, infection and leukemia. It can also help to monitor a patient's response to treatment.
ACEP Magazine edition 4th launched on 05.06.2024Rahul
This document provides information about the third edition of the magazine "Sthapatya" published by the Association of Civil Engineers (Practicing) Aurangabad. It includes messages from current and past presidents of ACEP, memories and photos from past ACEP events, information on life time achievement awards given by ACEP, and a technical article on concrete maintenance, repairs and strengthening. The document highlights activities of ACEP and provides a technical educational article for members.
Embedded machine learning-based road conditions and driving behavior monitoringIJECEIAES
Car accident rates have increased in recent years, resulting in losses in human lives, properties, and other financial costs. An embedded machine learning-based system is developed to address this critical issue. The system can monitor road conditions, detect driving patterns, and identify aggressive driving behaviors. The system is based on neural networks trained on a comprehensive dataset of driving events, driving styles, and road conditions. The system effectively detects potential risks and helps mitigate the frequency and impact of accidents. The primary goal is to ensure the safety of drivers and vehicles. Collecting data involved gathering information on three key road events: normal street and normal drive, speed bumps, circular yellow speed bumps, and three aggressive driving actions: sudden start, sudden stop, and sudden entry. The gathered data is processed and analyzed using a machine learning system designed for limited power and memory devices. The developed system resulted in 91.9% accuracy, 93.6% precision, and 92% recall. The achieved inference time on an Arduino Nano 33 BLE Sense with a 32-bit CPU running at 64 MHz is 34 ms and requires 2.6 kB peak RAM and 139.9 kB program flash memory, making it suitable for resource-constrained embedded systems.
UNLOCKING HEALTHCARE 4.0: NAVIGATING CRITICAL SUCCESS FACTORS FOR EFFECTIVE I...amsjournal
The Fourth Industrial Revolution is transforming industries, including healthcare, by integrating digital,
physical, and biological technologies. This study examines the integration of 4.0 technologies into
healthcare, identifying success factors and challenges through interviews with 70 stakeholders from 33
countries. Healthcare is evolving significantly, with varied objectives across nations aiming to improve
population health. The study explores stakeholders' perceptions on critical success factors, identifying
challenges such as insufficiently trained personnel, organizational silos, and structural barriers to data
exchange. Facilitators for integration include cost reduction initiatives and interoperability policies.
Technologies like IoT, Big Data, AI, Machine Learning, and robotics enhance diagnostics, treatment
precision, and real-time monitoring, reducing errors and optimizing resource utilization. Automation
improves employee satisfaction and patient care, while Blockchain and telemedicine drive cost reductions.
Successful integration requires skilled professionals and supportive policies, promising efficient resource
use, lower error rates, and accelerated processes, leading to optimized global healthcare outcomes.
Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
This paper describes a speed control device for generating electrical energy on an electricity network based on the doubly fed induction generator (DFIG) used for wind power conversion systems. At first, a double-fed induction generator model was constructed. A control law is formulated to govern the flow of energy between the stator of a DFIG and the energy network using three types of controllers: proportional integral (PI), sliding mode controller (SMC) and second order sliding mode controller (SOSMC). Their different results in terms of power reference tracking, reaction to unexpected speed fluctuations, sensitivity to perturbations, and resilience against machine parameter alterations are compared. MATLAB/Simulink was used to conduct the simulations for the preceding study. Multiple simulations have shown very satisfying results, and the investigations demonstrate the efficacy and power-enhancing capabilities of the suggested control system.
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.
Sharma2016 development of probabilistic fatigue curve for asphalt concrete
1. Development of probabilistic fatigue curve for asphalt concrete
based on viscoelastic continuum damage mechanics
Himanshu Sharma, Aravind Krishna Swamy ⇑
Department of Civil Engineering, Indian Institute of Technology Delhi, New Delhi 110016, India
Received 3 October 2015; received in revised form 21 July 2016; accepted 23 July 2016
Abstract
Due to its roots in fundamental thermodynamic framework, continuum damage approach is popular for modeling asphalt concrete
behavior. Currently used continuum damage models use mixture averaged values for model parameters and assume deterministic dam-
age process. On the other hand, significant scatter is found in fatigue data generated even under extremely controlled laboratory testing
conditions. Thus, currently used continuum damage models fail to account the scatter observed in fatigue data. This paper illustrates a
novel approach for probabilistic fatigue life prediction based on viscoelastic continuum damage approach. Several specimens were tested
for their viscoelastic properties and damage properties under uniaxial mode of loading. The data thus generated were analyzed using
viscoelastic continuum damage mechanics principles to predict fatigue life. Weibull (2 parameter, 3 parameter) and lognormal distribu-
tions were fit to fatigue life predicted using viscoelastic continuum damage approach. It was observed that fatigue damage could be best-
described using Weibull distribution when compared to lognormal distribution. Due to its flexibility, 3-parameter Weibull distribution
was found to fit better than 2-parameter Weibull distribution. Further, significant differences were found between probabilistic fatigue
curves developed in this research and traditional deterministic fatigue curve. The proposed methodology combines advantages of con-
tinuum damage mechanics as well as probabilistic approaches. These probabilistic fatigue curves can be conveniently used for reliability
based pavement design.
Ó 2016 Chinese Society of Pavement Engineering. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND
license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Keywords: Probabilistic fatigue curve; Continuum damage mechanics; Weibull distribution; Lognormal distribution
1. Introduction
Fatigue in asphalt pavement is one of the major distress
mechanisms, which is primarily caused by repeated traffic
loading. Initially, this damage starts with microcracks at
locations of higher stress (or strain) concentration. These
microcracks further coalesce into a series of interconnected
macrocracks finally leading to failure of pavement. This
degradation under cyclic loading has been characterized
in laboratory conditions using various modes of loading
including flexure [1,2], direct tension [3], indirect tension
[4] and shear [5]. One common feature among all these
loading modes is amplitude of strain (or stress) held con-
stant throughout the fatigue testing and its response is
recorded. The testing is continued until specimen fails com-
pletely. This process is repeated at other strain (or stress)
levels to obtain relationship between strain (or stress)
amplitude and number of cycles to failure. In general there
are two different approaches used for fatigue life prediction
i.e. phenomenological and mechanistic approaches.
In the phenomenological approach, a series of tests are
performed at various conditions to capture all significant
factors that contribute to the fatigue damage. Using the
http://dx.doi.org/10.1016/j.ijprt.2016.07.004
1996-6814/Ó 2016 Chinese Society of Pavement Engineering. Production and hosting by Elsevier B.V.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
⇑ Corresponding author. Fax: +91 11 2658 1117.
E-mail address: akswamy@civil.iitd.ac.in (A.K. Swamy).
Peer review under responsibility of Chinese Society of Pavement
Engineering.
www.elsevier.com/locate/IJPRT
Available online at www.sciencedirect.com
ScienceDirect
International Journal of Pavement Research and Technology xxx (2016) xxx–xxx
Please cite this article in press as: H. Sharma, A.K. Swamy, Development of probabilistic fatigue curve for asphalt concrete based on viscoelastic con-
tinuum damage mechanics, Int. J. Pavement Res. Technol. (2016), http://dx.doi.org/10.1016/j.ijprt.2016.07.004
2. data generated, regression models are developed to relate
fatigue life with other parameters like binder type, aggre-
gate type and gradation, air voids and testing method. If
one of the parameters is neglected initially, the entire set
of experiments has to be repeated to capture its effect.
Thus, careful attention is required while deciding on fac-
tors to be accounted, experimental plan and regression
model. In this approach, fatigue damage process is consid-
ered as deterministic. Even under extremely controlled con-
dition testing, fatigue test results developed show
significant scatter/variability [6].
Alternatively, mechanistic approach is more complex
which is applicable to a wide range of loading and environ-
mental conditions. Some examples for mechanistic
approach are Visco-Elastic Continuum Damage (VECD)
approach, fracture mechanics, and micromechanics.
VECD approach relates stress-strain using the principles
of thermodynamics. In the VECD approach, a damaged
body is represented by a homogeneous continuum where
the scale of the test specimen is much larger than the defect
size. These VECD models use macroscale observations to
capture the net effect of microstructural changes. Hence,
the VECD model is convenient for modeling overall behav-
ior of the material. Present day VECD models consider
material properties and damage process to be deterministic.
Improper selection of input values in these VECD models
will lead to significant deviation in predicted material
behavior. Thus, extreme care has to be exercised while
choosing input values for VECD model parameters. Prob-
abilistic fatigue analysis can account for the variability
issues like constituent materials, specimen fabrication
issues, and testing practices. Therefore, there is a need of
probabilistic approach for the fatigue life analysis within
VECD framework.
This paper presents a novel methodology for predicting
fatigue life of asphalt concrete for a given reliability based
on elastic-viscoelastic correspondence principle and VECD
mechanics. The paper is divided into 6 sections of which
this is the first section. Research work conducted by others
in area of asphalt concrete fatigue characterization, VECD
mechanics, and probabilistic fatigue modeling is discussed
in the second section. Details regarding asphalt concrete
mixtures, and specimen preparation and testing is pre-
sented in third and fourth sections, respectively. The next
two sections deal with the proposed probabilistic fatigue
analysis methodology and a case study along with statisti-
cal analysis. The last section concludes the article.
2. Previous work
Various researchers have used regression-based
approach to relate fatigue life (Nf ) and initial strain ampli-
tude (e0) as presented in Eq. (1) [7–10]. Due to its simplicity
and ease of use, this empirical model is popular among
engineering community. The regression coefficients (K
and n) in Eq. (1) are specific to the asphalt mixture type,
volumetric composition and binder type, and the test
parameters used in the laboratory evaluation. A schematic
diagram of fatigue curve developed after laboratory evalu-
ation is shown in Fig. 1. Due to mechanical compliance of
machine and pneumatic control issues, strain amplitude
during fatigue testing is not exactly constant. This small
variation in applied strain amplitude is specific to particu-
lar equipment in use. Thus, some scatter in strain ampli-
tude (in vertical direction) in fatigue curve is expected.
Further, variability in constituent materials, aggregate
microstructure, and testing procedure use will contribute
to inherent variability in failure point. Hence scatter in fati-
gue life (in horizontal direction) is always expected.
Nf ¼ k1
1
e0
k2
ð1Þ
where ki ¼ regression coefficients.
Several studies have reported that regression coefficients
in Eq. (1) are found to be very sensitive to mixture proper-
ties. Navarro and Kennedy observed that the value of K
generally ranges from 5.0 1020
to 6.5 105
while value
of n ranges between 1.2 to 6.3 [6]. Shukla and Das [11]
reported that value of K varied between 5.35 1018
and
497 while value of n ranged between 2.93 and 6.17.
Navarro and Kennedy [6] have reported Coefficient of
Variation (CV) values of fatigue life ranged between 26
and 84%. For field-extracted specimens, Monismith et al.
[12] have reported CV values between 25% and 131%. Sim-
ilarly for laboratory prepared specimens, CV values ranged
between 54% and 76% [12–13]. Thus, it can be concluded
that CV value for the fatigue life of field specimens is more
when compared to laboratory prepared specimens.
Various researchers have reported scatter in fatigue life
distribution. Miura [14], Tsai et al. [15], Sun et al. [16], Kle-
menc et al. [17] have noted that fatigue life distribution of
bituminous mixtures follows Weibull distribution. Pell and
Taylor [18] found that fatigue life follows lognormal
distribution. Zhao et al. [19] found that fatigue life distribu-
tion at a given strain magnitude is skewed to the right.
Fig. 1. Fatigue curve showing scatter in strain amplitude and fatigue life.
2 H. Sharma, A.K. Swamy / International Journal of Pavement Research and Technology xxx (2016) xxx–xxx
Please cite this article in press as: H. Sharma, A.K. Swamy, Development of probabilistic fatigue curve for asphalt concrete based on viscoelastic con-
tinuum damage mechanics, Int. J. Pavement Res. Technol. (2016), http://dx.doi.org/10.1016/j.ijprt.2016.07.004
3. Zhao et al. [19] and Bucar et al. [20] showed that the Wei-
bull or lognormal distribution could describe the statistical
scatter of the fatigue life. Current practice in fatigue studies
employ averaged values of strain (or stress) amplitude and
fatigue life alone. Hence, this practice does not account for
fatigue life variation and skewness of test data completely.
Various probabilistic approaches have been developed
to account for scatter observed in fatigue life. In order to
minimize the number of specimens required and laboratory
testing time, Ling et al. [21] proposed a maximum likeli-
hood method for estimating probabilistic fatigue curve
parameters. Klemenc et al. [17] found that Weibull param-
eters are dependent on the strain amplitude through Cof-
fin–Manson equation. Guida et al. [22] proposed
Bayesian approach for fatigue data analysis that accounts
for material properties and small sample size. Xiong
et al. [23] proposed a single-point likelihood method tech-
nique to address the paucity of data in developing a gener-
alized fatigue curve from small sample of test data. Zhao
and Liu [24] proposed Weibull modeling of the probabilis-
tic curves for rolling contact fatigue. Luo et al. [25] devel-
oped the probabilistic model for rubberized asphalt
concrete mixtures using point estimate method. These
probabilistic approaches require finding a best-fit distribu-
tion of fatigue life through statistical tests, and finally cal-
culating the distribution parameters to develop
probabilistic fatigue curves.
Use of elastic-viscoelastic correspondence principle and
VECD approach in the area of asphalt concrete modeling
was initiated by work of Kim [26]. Lee and Kim developed
a uniaxial constitutive model of non-aging asphalt aggre-
gate mixtures based on elastic-viscoelastic correspondence
principle and Schapery’s work potential theory [27]. Lee
et al. [28] developed a fatigue life prediction model using
the constitutive model. The expression to predict fatigue
life (Nf ) of asphalt concrete without rest period based on
elastic-viscoelastic correspondence principle and VECD
approach is given in Eq. (2). Daniel [3], and Daniel and
Kim [29] found that the relationship between damage
parameter (S) and pseudostiffness (C) is unique for a given
mix and is commonly referred to as damage characteristic
curve. Further, power law [C ¼ 1 C11ðSÞ
C12
] with C11
and C12 as regression coefficients was used to describe this
damage characteristic curve.
Nf ¼
f ðSf Þ
p1
p1ð0:125IC11C12Þ
a1
jEj2a1
e2a1
o ð2Þ
p1 ¼ 1 þ ð1 C12Þa1 ð3Þ
a1 ¼ 1 þ
1
m
ð4Þ
where, m = slope of the linear portion of the creep compli-
ance curve in a log-log scale, jE
j = dynamic modulus,
f = frequency, Sf = damage parameter at failure, I = ini-
tial secant pseudostiffness.
VECD approach essentially requires material properties
under undamaged and damaged condition to develop/cali-
brate constitutive model. Further, prediction at a different
test conditions is made using damage characteristic curve
and temperature shift factors. Hence VECD approach
can be conveniently used for modeling overall behavior
of the asphaltic materials under different temperature, fre-
quency, and rate of loading. Averaged values of dynamic
modulus, relaxation modulus and damage characteristic
curve are used in fatigue life prediction. Due to its deter-
ministic nature, current VECD approaches fail to capture
scatter observed in actual fatigue tests.
3. Materials, mixture design and specimen preparation
Asphalt concrete mixture used in this research was
designed as per New Hampshire Department of Trans-
portation (NHDOT) specifications using Superpave mix-
ture design approach. 12.5 mm nominal maximum
aggregate size gradation along with polyphosphoric acid
modified asphalt (PG 70-28) was used while designing mix-
ture. Aggregate and binder satisfied all engineering proper-
ties specified by NHDOT. The percentage of aggregates
passing 19.0, 12.5, 9.5, 4.75, 2.36, 1.18, 0.6, 0.3, 0.15, and
0.075 mm sieves are 100, 94.1, 73.2, 49.4, 37.0, 24.6, 16.3,
10.3, 6.7, and 3.6, respectively. The design binder content
was 4%, and dust proportion was 0.55. Further, mixture
was designed for air voids, void in mineral aggregate, and
void filled with asphalt of 4%, 17.4 and 77, respectively.
More details about materials and mixture can be found
elsewhere [30,31].
Laboratory prepared loose mixture was compacted
using Superpave gyratory compactor. After 24 h, these
compacted samples were trimmed using core cutter and
wet saw to obtain cylindrical specimens. Neatly cut speci-
mens were checked for air voids using Corelok vacuum sys-
tem as per AASHTO TP 69-04 standard. Specimens having
4 0:5% airvoids were used for subsequent instrumenta-
tion and testing. Steel end plates, and Linearly Variable
Differential Transducers (LVDTs) were glued to uniaxial
specimens using plastic epoxy glue using jigs. The LVDTs
were spaced 90° apart around the circumference of the
specimen using a 100 mm gage length. During testing, the
applied load on the specimen was measured using the load
cell attached to a closed-loop servo-hydraulic system and
the deformations were measured using LVDTs mounted
on the specimen.
4. Test methods
The testing part included non-damage inducing tests to
determine Linear Visco-Elastic (LVE) properties and dam-
age inducing tests to determine fatigue properties of
asphalt concrete. 10 specimens satisfying NHDOT specifi-
cations were tested of which 5 each were used for determin-
ing LVE properties and fatigue properties. Further, data
from 3 specimens that were close to mean value were used
for subsequent analysis. Here afterward, specimens used
for determining LVE properties are referred to as V1, V2,
H. Sharma, A.K. Swamy / International Journal of Pavement Research and Technology xxx (2016) xxx–xxx 3
Please cite this article in press as: H. Sharma, A.K. Swamy, Development of probabilistic fatigue curve for asphalt concrete based on viscoelastic con-
tinuum damage mechanics, Int. J. Pavement Res. Technol. (2016), http://dx.doi.org/10.1016/j.ijprt.2016.07.004
4. and V3, respectively. Similarly, specimens used for deter-
mining fatigue properties are referred to as F1, F2, and
F3, respectively.
The temperature sweep, and frequency sweep tests were
conducted to determine dynamic modulus and phase angles
under stress-controlled mode of loading. Temperatures of
10 °C, 0 °C, 10 °C, 20 °C, 30 °C; frequencies of 0.1 Hz,
0.2 Hz, 0.5 Hz, 1 Hz, 2 Hz, 5 Hz, 10 Hz, and 20 Hz, were
used to measure dynamic moduli and phase angles. To
limit specimen damage, testing was started at 10 °C and
terminated at 30 °C. At a particular temperature, testing
was started at a higher frequency while ending at a lower
frequency. To limit specimen damage, overall strain in
specimen was limited to 70 microstrain during testing.
The strain-controlled cyclic test under uniaxial mode of
loading was conducted to capture material behavior at
damage inducing strain levels. On-specimen displacement,
load recorded by LVDT’s and load cell, respectively were
used for computing strain and stress experienced by the
specimen. Applied crosshead strain amplitude in specimens
F1, F2, F3 is 2000 le, 1500 le and 2250 le, respectively.
Fig. 2 shows an instrumented specimen ready for testing
in the environmental chamber.
5. Methodology
This section presents the methodology for development
of probabilistic fatigue curve based on VECD approach.
Overall approach consisted of four major steps namely (i)
Determination of linear viscoelastic properties, (ii) Deter-
mination of damage properties, (iii) Determination of fati-
gue failure at different levels of strain, and (iv)
Development of probabilistic fatigue curve. These individ-
ual steps are explained using the flow chart (refer Fig. 3) in
following paragraphs.
The first step consisted of obtaining mastercurves for
viscoelastic properties. Dynamic modulus, and phase angle
mastercurves were constructed using measured stress–
strain history through time-temperature superposition
principle. The relaxation modulus mastercurve was
obtained using storage modulus (E0
) data through intercon-
version technique proposed by Park and Kim [32]. Further,
the creep compliance mastercurve was obtained from relax-
ation modulus mastercurve using interconversion tech-
nique [32].
In the second step, damage characteristics of mixture
were evaluated using VECD approach. With the computed
strain history, relaxation modulus values and reference
modulus (ER = 1), the pseudostrain was computed. The
secant pseudostiffness in any cycle i was calculated by
dividing stress corresponding to maximum pseudostrain
in each cycle by maximum pseudostrain in each cycle. To
account for the specimen-to-specimen variation, the secant
pseudostiffness history was normalized by using the initial
secant pseudostiffness. Finally, the damage parameter was
calculated using the pseudostrain history, normalized
secant pseudostiffness values, initial secant pseudostiffness
and material constant (a). The normalized pseudostiffness
was cross-plotted against damage parameter to obtain the
damage characteristic curve. Further, power law was fitted
to this damage characteristic curve.
In the third step, the number of cycles to failure for a
given strain level was predicted. Using viscoelastic proper-
ties and damage properties determined in previous steps,
fatigue life was predicted for all possible combinations of
individual specimen properties. For example, testing 3
specimens each for viscoelastic properties and damage
properties resulted in 9 combinations. All these combina-
tions will lead to 9 fatigue life prediction at a particular
strain level. This process of fatigue life prediction was
repeated at several strain levels.
In the fourth step, fatigue life at a particular strain level
for a given probability was calculated. Initially, lognormal
and Weibull distributions (2-parameter, 3-parameter) were
fitted to fatigue lives using graphical approach. Graphical
analysis (through coefficient of determination, R2
) and sta-
tistical test (Kolmogorov-Smirnov) were performed to
compare the fatigue life distribution fits. Preliminary anal-
ysis indicated that Weibull distribution describes fatigue
life better when compared to lognormal distribution.
Hence further analysis was carried out using Weibull distri-
bution. Further, Weibull distribution parameters were
obtained by Maximum Product of Spacing (MPS) method.
This was based on previous observation that MPS method
can be efficiently used with small sample sizes [33]. Fatigue
Fig. 2. Instrumented specimen ready for testing within environmental
chamber.
4 H. Sharma, A.K. Swamy / International Journal of Pavement Research and Technology xxx (2016) xxx–xxx
Please cite this article in press as: H. Sharma, A.K. Swamy, Development of probabilistic fatigue curve for asphalt concrete based on viscoelastic con-
tinuum damage mechanics, Int. J. Pavement Res. Technol. (2016), http://dx.doi.org/10.1016/j.ijprt.2016.07.004
5. life for a given probability at a given strain (S) for 3-
parameter Weibull distribution was then obtained using
the Eq. (5). When location parameter is equal to zero then
Eq. (5) changes into 2-parameter Weibull distribution.
Finally, fatigue curve at a probability level was obtained.
PðX=SÞ ¼ exp
ðX cÞ
g
b
#
( )
ð5Þ
where, c = location parameter, g = scale parameter, and
b = scale parameter.
6. Case study and discussion
This section elaborates the methodology presented in
previous section with help of a case study. As mentioned
previously, 3 specimens were used for determining LVE
properties. The dynamic modulus and phase angle master-
curves obtained for all three specimens (V1, V2, and V3)
are presented in Fig. 4a and b, respectively. The relaxation
modulus and creep compliance mastercurves obtained
using appropriate inter-conversion technique are presented
in Fig. 4c and d, respectively. Mixture averaged sigmoidal
curves for relaxation modulus mastercurve, and creep com-
pliance mastercurve are shown in Fig. 4c and d, respec-
tively. Damage characteristic curves obtained for all three
specimens (F1, F2, F3) along with mixture averaged power
law fit are presented in Fig. 5. From the non-damage
inducing and damage inducing test results it is clear that
samples prepared from the same mixture having similar
volumetric properties exhibit significant variation in their
response. As seen in Figs. 4 and 5, these variations are
dependent on reduced frequency, applied strain amplitude,
and loading history.
In the next stage, fatigue life was estimated using Eq. (2).
It is evident from Eq. (2) that predicted fatigue life depends
on numerical values of viscoelastic and damage properties.
In this research 3 specimens each were used for non-
damage and damage analysis. Thus, each combination
would result in one fatigue life estimation. All 9 combina-
tions used in this research and corresponding ID are pre-
sented in Table 1. Fatigue curves obtained for all
combinations of specimens are presented in Fig. 6. Fatigue
curves obtained using the VECD model for all combina-
tions shows significant scatter at all strain levels. Fatigue
curve obtained using mixture-averaged values (both vis-
coelastic properties and damage characteristic curve) is also
presented in Fig. 6. As seen in Fig. 6, depending on the
availability of specimen properties, fatigue curve will be
positioned within certain band with respect to fatigue curve
predicted with mixture-averaged values. Use of any combi-
nation will either underestimate or overestimate the fatigue
life. This necessitates the requirement of probabilistic
approach for efficient utilization of fatigue damage
information.
Statistical analysis of fatigue life obtained (using all 9
combinations) at different strain amplitude levels were car-
ried out. The results are presented in Table 2. Table 2 indi-
cates that standard deviation increases with decreasing
strain amplitude. Physically this implies that scatter in
Fig. 3. Flowchart of proposed methodology.
H. Sharma, A.K. Swamy / International Journal of Pavement Research and Technology xxx (2016) xxx–xxx 5
Please cite this article in press as: H. Sharma, A.K. Swamy, Development of probabilistic fatigue curve for asphalt concrete based on viscoelastic con-
tinuum damage mechanics, Int. J. Pavement Res. Technol. (2016), http://dx.doi.org/10.1016/j.ijprt.2016.07.004
6. fatigue life is more at lower strain levels. The skewness of
the distribution at all strain levels was found to be positive.
This implies that the majority of the data values falls to the
left of the mean and cluster at the lower end of the distri-
bution; the ‘‘tail” is to the right. i.e., the distribution is
skewed to the right [34]. The low value of kurtosis indicates
(a) Dynamic modulus (b) Phase angle
(c) Relaxation modulus (d) Creep compliance
0
10000
20000
30000
1.0E-03 1.0E+00 1.0E+03 1.0E+06
Dynamic
Modulus
(MPa)
Reduced Frequency (Hz)
V1
V2
V3
0.0
20.0
40.0
60.0
80.0
1.0E-03 1.0E+00 1.0E+03 1.0E+06
Phase
Angle
(Degrees)
Reduced Frequency (Hz)
V1
V2
V3
0.00001
0.0001
0.001
0.01
0.1
1.0E-08 1.0E-04 1.0E+00 1.0E+04
Creep
Compliance
(1/MPa)
Time (s)
Average
V1
V2
V3
0
10000
20000
30000
1.0E-09 1.0E-05 1.0E-01 1.0E+03
Relaxation
Modulus
(MPa)
Time (s)
Average
V1
V2
V3
Fig. 4. Mastercurves of viscoelastic properties.
0
0.2
0.4
0.6
0.8
1
0 50000 100000 150000 200000 250000 300000
Normalized
Pseudo
stiffness
Damage parameter
F1
F2
F3
Average
Fig. 5. Damage characteristic curves obtained from damage inducing cyclic tests.
Table 1
Combination of Specimens Used for Fatigue Life Estimation
Specimen ID used for LVE material characterization
V1 V2 V3
Specimen ID used for damage characterization F1 Combination 1 Combination 2 Combination 3
F2 Combination 4 Combination 5 Combination 6
F3 Combination 7 Combination 8 Combination 9
6 H. Sharma, A.K. Swamy / International Journal of Pavement Research and Technology xxx (2016) xxx–xxx
Please cite this article in press as: H. Sharma, A.K. Swamy, Development of probabilistic fatigue curve for asphalt concrete based on viscoelastic con-
tinuum damage mechanics, Int. J. Pavement Res. Technol. (2016), http://dx.doi.org/10.1016/j.ijprt.2016.07.004
7. a relatively flat distribution when compared to normal dis-
tribution. Absolute value of kurtosis value is more at lower
strain levels indicating more flat distribution at lower strain
levels.
Further, fatigue lives computed at a particular strain
level were checked for Weibull distribution and lognormal
distribution. To check the accuracy of Weibull distribution
and lognormal distribution fits, a straight line was fit to
probability plots. Further, R2
was computed using a
straight-line fit to probability plot. Kolmogorov–Smirnov
test was conducted to check goodness of fit. Summary of
both tests are presented in Table 3. Table 3 clearly indicates
that Weibull distribution describes fatigue life better than
lognormal distribution.
Further, fatigue lives computed at a particular strain
level were fitted with 2-parameter and 3-parameter Weibull
distribution using MPS method. It was observed that with
increasing strain levels, numerical value of scale parameter
exhibited decreasing trend. This implies scatter is more at
lower stain levels. Physically this implies spread in fatigue
life is increasing with decreasing strain amplitudes. The
shape parameter was found to be less than one indicating
that the distribution is skewed to the right. Similar observa-
tions regarding Weibull parameters were made by Zhao
[24] and Hwang et al. [35]. Location parameter exhibited
decreasing trend with increasing strain level. Physically this
implies that the distribution is shifting toward origin. In
general, Weibull distribution parameters were found to
vary with the strain magnitude. Similar conclusions regard-
ing Weibull distribution dependency on applied stress (or
strain) levels have been made by Zhao and Liu [24]. Oh
[36], and Tsai et al. [15].
Statistical analysis during this study indicated Weibull
distribution described fatigue life well when compared to
lognormal distribution. Thus, it was decided to use Weibull
distribution for further analysis. More details regarding the
statistical analysis can be found elsewhere [37]. The fatigue
life at various reliability levels was calculated to obtain
probabilistic fatigue curves using survival probability func-
tion (Eq. (5)). Finally, Eq. (1) was fitted to calculated fati-
gue lives using ordinary least squares approach.
Probabilistic fatigue curves obtained using 2-parameter
0
200
400
600
800
1000
1.E+00 1.E+02 1.E+04 1.E+06 1.E+08 1.E+10
Strain
(με)
Fatigue Life
Combination1
Combination 2
Combination 3
Combination 4
Combination 5
Combination 6
Combination 7
Combination 8
Combination 9
Average
Fig. 6. Fatigue lives obtained for all combinations of material properties.
Table 2
Descriptive statistics of predicted fatigue lives at different strain levels
Strain (le) Mean fatigue life Standard deviation Skewness Kurtosis
800 780 1042 1.278 0.09
500 15645 19334 1.217 0.01
400 66221 77443 1.117 0.14
300 437387 472584 0.850 0.77
200 6735763 6984958 0.624 1.55
Table 3
Results of statistical analysis of fatigue life distribution
Strain (le) Kolmogorov–Smirnov test Coefficient of determination from linear fit to probability plot
Lognormal Weibull Lognormal Weibull
200 0.37 0.51 0.83 0.87
300 0.55 0.71 0.87 0.92
400 0.47 0.61 0.88 0.93
500 0.49 0.62 0.90 0.94
800 0.84 0.88 0.92 0.96
H. Sharma, A.K. Swamy / International Journal of Pavement Research and Technology xxx (2016) xxx–xxx 7
Please cite this article in press as: H. Sharma, A.K. Swamy, Development of probabilistic fatigue curve for asphalt concrete based on viscoelastic con-
tinuum damage mechanics, Int. J. Pavement Res. Technol. (2016), http://dx.doi.org/10.1016/j.ijprt.2016.07.004
8. and 3-parameter Weibull distribution are presented in
Fig. 7a and b, respectively. Fatigue curves obtained using
mixture-averaged values are also presented in same figures.
It may be noted from Fig. 7 that fatigue curve obtained
using mixture-averaged values is conservative when com-
pared to fatigue curve obtained using Weibull distribution
at 50% reliability.
Fig. 8 presents comparison of probabilistic fatigue
curves developed using 2-parameter and 3-parameter Wei-
bull distribution. The 3-parameter Weibull distribution
provides a better fit when compared to 2-parameter Wei-
bull distribution. Fig. 8 indicates until 95% reliability level,
fatigue curves obtained using 2-parameter and 3-parameter
Weibull distribution curves are almost overlapping.
(a) Using 2-parameter distribution
(b) Using 3-parameter distribution
0
200
400
600
800
1000
1.0E+00 1.0E+02 1.0E+04 1.0E+06 1.0E+08
Strain
(με)
Fatigue Life
50% reliability
90% reliability
99% reliability
Average
0
200
400
600
800
1000
1.E+00 1.E+02 1.E+04 1.E+06 1.E+08
Strain
(με)
Fatigue Life
50% reliability
90% reliability
99% reliability
Average
Fig. 7. Probabilistic fatigue curves obtained using Weibull distribution
0
200
400
600
800
1000
1.0E-01 1.0E+01 1.0E+03 1.0E+05 1.0E+07 1.0E+09
Strain
(ms)
Fatigue Life
2-P-50%
2-P-90%
2-P-95%
2-P-99%
Average
3P-50%
3-P-90%
3-P-95%
3-P-99%
Fig. 8. Comparison of 2-parameter and 3-parameter probabilistic fatigue curves.
8 H. Sharma, A.K. Swamy / International Journal of Pavement Research and Technology xxx (2016) xxx–xxx
Please cite this article in press as: H. Sharma, A.K. Swamy, Development of probabilistic fatigue curve for asphalt concrete based on viscoelastic con-
tinuum damage mechanics, Int. J. Pavement Res. Technol. (2016), http://dx.doi.org/10.1016/j.ijprt.2016.07.004
9. However at 99% reliability, fatigue curve obtained using 2-
parameter Weibull distribution is more conservative when
compared with fatigue curve obtained using 3-parameter
Weibull distribution.
7. Summary and conclusions
Current viscoelastic continuum damage models assume
fatigue damage as deterministic process. Any predicted
material behavior using such an approach is very sensitive
to input parameters. Further, any wrong input can lead to
erroneous conclusions. Thus, careful attention is required
during fatigue testing and analysis. This article presented
a novel approach to develop probabilistic fatigue curve
for asphalt concrete mixtures using VECD approach.
Asphalt concrete specimens conforming to NHDOT speci-
fications were tested for viscoelastic and damage proper-
ties. The data gathered were used to develop fatigue
curve using VECD and probabilistic approach. Statistical
analysis indicated 3-parameter Weibull distribution, 2-
parameter Weibull distribution and lognormal distribution
can describe predicted fatigue lives well (in decreasing
order of ranking). Statistical analysis of computed Weibull
distribution parameters indicates fatigue life dependency
on applied strain amplitude. Also, fatigue life distribution
was found to be skewed. Fatigue life predicted using deter-
ministic values fails to capture underlying statistical distri-
bution in fatigue lives. Thus, probabilistic fatigue curve
development methodology presented in this article is effi-
cient and improvement over current practice of VECD
based fatigue life prediction. Use of probabilistic fatigue
curve proposed in this research can provide safety margin
in fatigue life estimation to certain extent. This methodol-
ogy can be easily merged with currently used reliability
based pavement design approaches.
Acknowledgements
The authors are grateful to Prof. Jo S. Daniel for allow-
ing use mixture testing data acquired during second
author’s PhD work at University of New Hampshire in this
research. Also, first and second authors are grateful to
Ministry of Human Resources and Development, India
and National Science Foundation, USA for their financial
support, respectively.
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tinuum damage mechanics, Int. J. Pavement Res. Technol. (2016), http://dx.doi.org/10.1016/j.ijprt.2016.07.004