Modified maximum tangential stress criterion for fracture behavior of zirconi...dentalid
The veneering porcelain sintered on zirconia is widely used in dental prostheses, but
repeated mechanical loadings may cause a fracture such as edge chipping or delamination.
In order to predict the crack initiation angle and fracture toughness of zirconia/veneer bilayered
components subjected to mixed mode loadings, the accuracy of a new and
traditional fracture criteria are investigated. A modified maximum tangential stress
criterion considering the effect of T-stress and critical distance theory is introduced, and
compared to three traditional fracture criteria. Comparisons to the recently published
fracture test data show that the traditional fracture criteria are not able to properly predict
the fracture initiation conditions in zirconia/veneer bi-material joints. The modified
maximum tangential stress criterion provides more accurate predictions of the experimental
results than the traditional fracture criteria
Vibration analysis of a cantilever beam with crack depth and crack location e...editorijrei
This document summarizes a study that analyzed the natural frequency of a cracked cantilever beam made of different metal alloys using finite element analysis. The researchers varied the crack depth and location in the beam and measured the resulting changes in natural frequency. They found that increasing crack depth or moving the crack location closer to the fixed end resulted in decreasing natural frequency. Aluminum alloy beams exhibited the highest natural frequencies while magnesium alloy beams had the lowest.
Coupling the bionic surface friction contact performance and wear resistance ...eSAT Publishing House
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.
All structures are subjected to degenerative effects that may
cause initiation of structural defects such as cracks which,
as time progresses, lead to the catastrophic failure or
breakdown of the structure. Thus, the importance of
inspection in the quality assurance of manufactured
products is well understood.
ICMCTF2011: Micro-scratch testing for interface characterizations of diamond-...The University of Alabama
This document summarizes research on characterizing the adhesion of diamond coatings on tungsten carbide substrates through scratch testing and finite element modeling. Key findings include:
1) Scratch testing identified a critical load range of 4-6N for delamination initiation, detected by increased acoustic emission and tangential force.
2) Finite element modeling of the scratch process, using a cohesive zone model at the interface, produced stress distributions consistent with experimental observations of delamination.
3) Both experiments and simulations provide methods to evaluate coating/substrate interface properties relevant to delamination behavior.
The document discusses the ring compression test method for determining the coefficient of friction between a die and workpiece. It investigates the friction factors of aluminum rings under dry and lubricated conditions. The key findings are:
1) Lubrication reduces interface friction coefficients compared to dry conditions.
2) Friction coefficients decrease with reductions in ring height and outer radius but increase with increases in inner radius.
3) Molybdenum disulfide and zinc stearate provide the lowest friction, while dry conditions provide the highest, according to experimental, theoretical and analytical analyses.
Experimental and numerical evaluation of plasticity model with ductile damage...IJERA Editor
This work aims to develop a methodology for numerical evaluation via finite elements applied to projects shields sheet metal. To validate the methodology physical test were conduct and were compare with the numerical simulation. In the simulation, a plasticity material modelit was used at high strain rates, besides the insertion of a damage model through forming limit diagram (FLD) to capture the initiation of damage and energy criteria for propagation of the fracture. The tested shielding design is for the II-A protection level using the type 9mm ammunition.
FRACTURE MECHANICS OF NANO-SILICA PARTICLES IN REINFORCED EPOXIES Jordan Suls
This document summarizes a study that used finite element modeling to examine how different levels of particle dispersion (evenly dispersed, moderately clumped, and severely clumped) affect the fracture mechanics of nanosilica particle reinforced epoxies. Three models were created in Abaqus with the different dispersion levels and subjected to tensile loading. The results found that the evenly dispersed model had the highest fracture toughness, as indicated by its ability to withstand a greater force at similar displacements. This was because the clumped models developed large stress regions around the clumps that caused earlier debonding of the particle-matrix interfaces and faster crack propagation.
Modified maximum tangential stress criterion for fracture behavior of zirconi...dentalid
The veneering porcelain sintered on zirconia is widely used in dental prostheses, but
repeated mechanical loadings may cause a fracture such as edge chipping or delamination.
In order to predict the crack initiation angle and fracture toughness of zirconia/veneer bilayered
components subjected to mixed mode loadings, the accuracy of a new and
traditional fracture criteria are investigated. A modified maximum tangential stress
criterion considering the effect of T-stress and critical distance theory is introduced, and
compared to three traditional fracture criteria. Comparisons to the recently published
fracture test data show that the traditional fracture criteria are not able to properly predict
the fracture initiation conditions in zirconia/veneer bi-material joints. The modified
maximum tangential stress criterion provides more accurate predictions of the experimental
results than the traditional fracture criteria
Vibration analysis of a cantilever beam with crack depth and crack location e...editorijrei
This document summarizes a study that analyzed the natural frequency of a cracked cantilever beam made of different metal alloys using finite element analysis. The researchers varied the crack depth and location in the beam and measured the resulting changes in natural frequency. They found that increasing crack depth or moving the crack location closer to the fixed end resulted in decreasing natural frequency. Aluminum alloy beams exhibited the highest natural frequencies while magnesium alloy beams had the lowest.
Coupling the bionic surface friction contact performance and wear resistance ...eSAT Publishing House
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.
All structures are subjected to degenerative effects that may
cause initiation of structural defects such as cracks which,
as time progresses, lead to the catastrophic failure or
breakdown of the structure. Thus, the importance of
inspection in the quality assurance of manufactured
products is well understood.
ICMCTF2011: Micro-scratch testing for interface characterizations of diamond-...The University of Alabama
This document summarizes research on characterizing the adhesion of diamond coatings on tungsten carbide substrates through scratch testing and finite element modeling. Key findings include:
1) Scratch testing identified a critical load range of 4-6N for delamination initiation, detected by increased acoustic emission and tangential force.
2) Finite element modeling of the scratch process, using a cohesive zone model at the interface, produced stress distributions consistent with experimental observations of delamination.
3) Both experiments and simulations provide methods to evaluate coating/substrate interface properties relevant to delamination behavior.
The document discusses the ring compression test method for determining the coefficient of friction between a die and workpiece. It investigates the friction factors of aluminum rings under dry and lubricated conditions. The key findings are:
1) Lubrication reduces interface friction coefficients compared to dry conditions.
2) Friction coefficients decrease with reductions in ring height and outer radius but increase with increases in inner radius.
3) Molybdenum disulfide and zinc stearate provide the lowest friction, while dry conditions provide the highest, according to experimental, theoretical and analytical analyses.
Experimental and numerical evaluation of plasticity model with ductile damage...IJERA Editor
This work aims to develop a methodology for numerical evaluation via finite elements applied to projects shields sheet metal. To validate the methodology physical test were conduct and were compare with the numerical simulation. In the simulation, a plasticity material modelit was used at high strain rates, besides the insertion of a damage model through forming limit diagram (FLD) to capture the initiation of damage and energy criteria for propagation of the fracture. The tested shielding design is for the II-A protection level using the type 9mm ammunition.
FRACTURE MECHANICS OF NANO-SILICA PARTICLES IN REINFORCED EPOXIES Jordan Suls
This document summarizes a study that used finite element modeling to examine how different levels of particle dispersion (evenly dispersed, moderately clumped, and severely clumped) affect the fracture mechanics of nanosilica particle reinforced epoxies. Three models were created in Abaqus with the different dispersion levels and subjected to tensile loading. The results found that the evenly dispersed model had the highest fracture toughness, as indicated by its ability to withstand a greater force at similar displacements. This was because the clumped models developed large stress regions around the clumps that caused earlier debonding of the particle-matrix interfaces and faster crack propagation.
Effect of angle of repose of aggregate on strength of bituminous mixIJARIIT
The major constituent of the bituminous mix are
aggregates. The characteristics of the bituminous mix are
mainly affected by properties of aggregates. The angle of
repose of aggregates of different sizes and sources have
been designed in the present study. Further, an attempt has
been made to study the effect of angle of repose to the
strength of bituminous mix. Indirect tensile strength has
been used as the measure of the strength of bituminous mix,
subsequently, the statistical relationship has been proposed
between the overall angles of repose of the aggregates used
in the bituminous mix to its indirect tensile strength.
Seminar Report on Brittle Fracture of ShipsVISHAL SHARMA
This study investigates the sinking of the Titanic from the theory of Brittle Fracture and
Engineering Failures. This study offers a subjectivist perspective of mental inertia to
understand the Titanic Disaster. Specifically, this study argue that the fall of the Titanic was
mainly due to Brittle Fracture of Rivets and the Hull Steel. Metallurgical and Mechanical
Analysis were performed on steel and rivet samples recovered from the wreck of the RMS
Titanic. It is found that the steel possessed a ductile-to-brittle transition temperature that was
very high with respect to the service temperature, making the material very brittle at ice-water
temperatures. This had been attributed to both chemical and microstructural factors. It is also
been found that the wrought iron rivets used in the construction of Titanic contained an elevated
amount of incorporated slag, and that the orientation of the slag within the rivets may hold an
explanation for how the ship accumulated damage during its encounter with the iceberg.
Keywords- Brittle fracture, Rivets, Hull Steel, Metallurgical Failure, Titanic Disaster.
This document discusses the use of cohesive zone modeling to simulate fatigue crack growth and retardation. Cohesive zone models define cohesive stresses around a crack tip that are related to crack opening width. Crack propagation occurs when cohesive stresses reach a failure value. The models can account for material properties through a cohesive law. Finite element implementations use cohesive elements located at crack fronts. The models can simulate crack closure effects, wedge effects, and predict crack growth under various loading conditions like overloads through an unloading-reloading hysteresis. Cohesive theory provides a unified way to model long cracks under constant loading as well as short cracks and overloads.
This document summarizes a numerical study of indentation-induced cracking in brittle coatings on ductile substrates. Finite element modeling was used to simulate indentation with a spherical indenter. The coating was modeled as linear elastic, the substrate as elastic-perfectly plastic, and cracks in the coating were modeled using cohesive surfaces. Circumferential cracks were found to initiate at the coating surface near the contact edge due to high tensile radial stresses. The first crack caused a kink in the load-displacement curve. The spacing between cracks was on the order of the coating thickness. The effects of material properties and cohesive parameters on crack initiation and spacing were also investigated.
Influence of contact friction conditions on thin profile simulationVan Canh Nguyen
The paper presents the development of the Finite Element model for simulation of thin
aluminium profile extrusion of both solid and hollow shapes. The analysis has shown that the material
flow in simulation is very dependent on the friction model. Experimental and theoretical studies show
that friction traction on the interface between the tool and the deformed material can be represented as
a combination of adhesive friction force and the force that is required to deform surface asperities. In
aluminium extrusion we can clearly distinguish two different areas with respect to friction conditions
such as sticking and sliding and transient zones between them. The lengths of these zones are also
dependent on variation of the choke angle and actual thickness of the profile. To get these values the
material flow problem is to be coupled with the simulation of the tools deformation. A series of
experiments with specially designed tools have been done to investigate how the bearing length and
choke angle may influence the extension of different friction zones and by these means vary the
material flow pattern. The friction models have also been tested with industrial profiles of complex
shapes and have shown good correspondence to reality.
MSEC2013- Interface delamination of diamond-coated carbide tools considering ...The University of Alabama
Interface delamination is the major failure mode of diamond-coated carbide tools in machining. On the other hand, coating cracking is possibly accompanied during a tribological process that induces the delamination phenomenon. However, such an influence between the two failure behaviors has not been investigated in a quantitative way to better understand and design diamond coating tools.
In this study, a three-dimensional (3D) indentation model combining cohesive interactions and extended finite element method (XFEM) was developed to investigate the diamond-coating, carbide-substrate interface behavior with the incorporation of coating cracking. The cohesive interaction was based on a cohesive zone model (CZM) with a bilinear traction-separation law. XFEM was applied to the coating domain to model cracking in the diamond coating with a damage criterion of the maximum principal stress. Deposition stresses were also included to investigate their effect on the coating delamination and fractures. The model was implemented in finite element (FE) codes to analyze the cone crack in brittle coatings, as well as the interface delamination of diamond coated carbide tools. The XFEM model was validated by the indentation testing data from literature in crack initiation and propagation in brittle materials. FE results from the indentation on diamond-coated tools show that the interface delamination size and loading force become smaller when coating fractures are incorporated in the model, and the deposition stresses will increase the initial crack radius and the critical load for delamination in diamond coatings.
A fracture mechanics based method for prediction ofSAJITH GEORGE
The document presents a fracture mechanics-based method for predicting cracking in circular and elliptical concrete rings undergoing restrained shrinkage. It describes an experimental program using different ring geometries and material tests to determine properties. A numerical model is developed using ANSYS to model the restrained shrinkage process and calculate stress intensity factors. The model uses a fictitious temperature field to simulate shrinkage and determines cracking age by comparing driving and resistance curves. It finds cracking occurs earlier in elliptical rings and the method accurately predicts experimental cracking ages.
The document summarizes a study on heterogeneous deformation and dislocation dynamics in compressed copper micropillars using multi-scale discrete dislocation plasticity modeling. The model couples 3D finite element analysis to calculate stress distributions and image stresses with 3D discrete dislocation dynamics. It captures size effects, hardening behavior, and the influence of boundary conditions. Results show hardening is due to dislocation entanglement and stagnation, with stress concentrations affecting heterogeneous deformation.
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
IRJET - Behaviour of Rectangular SFRC Beam Specimens Under Combined State of ...IRJET Journal
This document summarizes a study that investigated the behavior of steel fiber reinforced concrete (SFRC) beams under combined flexure, compression, and shear loading. Rectangular SFRC beams of varying fiber content (0%, 0.5%, 0.75%, 1% by volume) were tested. Beams were subjected to four levels of compression (0 kN, 40 kN, 50 kN, 60 kN) and flexural loading. Test results found that as fiber content and compression level increased, ultimate bending strength and deflection increased. The ductility of beams also increased with higher fiber content and compression. Including steel fibers improved the compressive strength, splitting tensile strength, and flexural behavior of the concrete
The effective width in multi girder composite steel beams with web openingsIAEME Publication
This document summarizes a study on the effective width of multi-girder composite steel beams with web openings through finite element analysis. Several 3D models were developed to examine the effects of varying slab thickness, slab width, span length, and load type. The analysis found that thicker slabs experience less shear lag due to higher shear stiffness. Wider slabs and shorter spans also decreased shear lag effects. Different load types produced varying stress distributions across the slab width, affecting the effective width.
Vibrational Analysis Of Cracked Rod Having Circumferential Crack IDES Editor
The frequency ratio of torsional vibration of a rod without crack and of rod with crack subjected to torque at the free end for various crack depth and varying crack location is investigated. It is found that even a cracked of small depth is
dangerous at the fixed end, also as the crack depth is increases more than 50% of diameter of rod there is a considerable drop in natural frequency of the rod .
1. Surface engineering aims to modify the properties of material surfaces to improve functionality, such as corrosion resistance, wear resistance, and friction reduction. Common surface engineering techniques include coatings, thermal treatments, and surface texturing.
2. Controlling friction through surface texturing has gained interest, as microscale dimples or grooves can reduce friction. However, the effects of texturing parameters like shape, depth, width, and orientation on friction are still being studied. Surface roughness parameters provide a way to characterize topography but may not fully describe surfaces.
3. The document discusses various surface roughness parameters defined by ISO standards and how they can characterize surface topography features relevant to friction, such as peaks, valleys
1) The document describes a finite element analysis of the superplastic blow-forming of Ti-6Al-4V titanium alloy sheet into a closed ellip-cylindrical die.
2) The simulations investigate the effects of shear friction factor, die entry radius, die height, and die short-axis length on thickness distribution, stress, strain, and damage within the formed product.
3) The results confirm the suitability of using the DEFORMTM 3D finite element software to model superplastic blow-forming of Ti-6Al-4V titanium alloy.
Structural Changes in the Surface Layer of Deep Rolled Samples Due to Thermal...IJERA Editor
Deep rolling processes initiate plastic deformations in the surface layer. The local characteristics of deformation are dependent on the induced stress expressed by the local stress tensor. Equivalent stresses above yield strength cause plastic deformation. Additionally the intrinsic energy, e. g. the dislocation density, is enhanced and the residual stress state is changed. The effects to a deep rolled surface from an increase in temperature are mainly dependent on the material, the microstructure, the initial residual stress state, the inclusion density, the distribution of soluted alloying elements and the plastic deformation. In the described experiments the interactions between deformation and temperature of the steel grade AISI 4140 (42 CrMo 4) used for all further experiments in a transregional Collaborative Research Center (CRC) were to be examined. The most simple investigation methods were chosen deliberately to allow a better statistical support of correlations between introduced strains and material reactions for a wide variation of process parameters. Since the visual effects by light microscopy in AISI 4140 were very small, the experiments were repeated with german grade 18 CrNiMo 7-6 (comparable to AISI 4820). This paper focuses on the micro structural changes in defined deep rolled surface regions due to an increase in temperature. The work described is part of the Collaborative Research Center “Process Signatures”, collaboration between Bremen University, Technical University Aachen, Germany and Oklahoma State University Stillwater, USA.
This document reviews the effect of knitted composite structure and properties. It finds that tensile strength is highest for plain knits with longer loop lengths and lower stitch densities, which reduces stress concentrations. Compressive strength improves slightly with these same parameters as they allow for higher fiber buckling loads. Modulus is largely independent of structure. Overall, knitted composites have properties dominated by the matrix, but structure can be optimized to improve strengths by reducing stress concentrations.
This document summarizes a range of aerospace cleaning chemicals for components. It describes four products: HDL Precision Cleaning Solvent which can safely clean precision components and electrical parts and meets various approvals. Lemsolv 860 RI is designed for cleaning turbine blades and removing semi-cured adhesives. Lemsolv CX1 is a citrus-based solvent that removes fingerprints and markings from pre-inspection components. Lemsolv CX4 removes sealants, adhesives, and ink and meets a helicopter approval. All products are manufactured and supplied by Oil Technics Ltd.
Due to year on year exceptional growth, Oil Technics Ltd have expanded their Sales Team and in June we will be joined by a dedicated Fire Foam Sales Manager.... Watch this space.
The documentary "Lifers" explores the daily lives of convicted killers in prison as they undergo rehabilitation programs. It airs on Channel 4 on June 25, 2012 at 9pm and runs for 47 minutes and 34 seconds. The documentary aims to show how criminals live in prison following their crimes and consequences. Its message is to discourage killing by showing viewers how their lives would turn out in prison. It profiles several convicted criminals and interviews experts to analyze prisoner behavior. It uses techniques like handheld cameras, interviews, archival footage, and montage editing to create a sense of realism.
Ben Turner commented on logo examples for a unit on digital graphics for print media. The logos represented past and contemporary styles used in the music industry. Most logos become iconic as the band's success increases. Common features included a focus on being uniquely crafted, using black and other colors like white, vertically-rainbow and light blue, and themes of graffiti, funky and pop designs.
The document discusses magazine advertisement samples created by graphic designers for the media industry. It notes that magazine ads can include more detailed information about events than posters. It also states that the ads relate to how pop and rock bands assemble and convey their ideas through the magazine advertising format.
Effect of angle of repose of aggregate on strength of bituminous mixIJARIIT
The major constituent of the bituminous mix are
aggregates. The characteristics of the bituminous mix are
mainly affected by properties of aggregates. The angle of
repose of aggregates of different sizes and sources have
been designed in the present study. Further, an attempt has
been made to study the effect of angle of repose to the
strength of bituminous mix. Indirect tensile strength has
been used as the measure of the strength of bituminous mix,
subsequently, the statistical relationship has been proposed
between the overall angles of repose of the aggregates used
in the bituminous mix to its indirect tensile strength.
Seminar Report on Brittle Fracture of ShipsVISHAL SHARMA
This study investigates the sinking of the Titanic from the theory of Brittle Fracture and
Engineering Failures. This study offers a subjectivist perspective of mental inertia to
understand the Titanic Disaster. Specifically, this study argue that the fall of the Titanic was
mainly due to Brittle Fracture of Rivets and the Hull Steel. Metallurgical and Mechanical
Analysis were performed on steel and rivet samples recovered from the wreck of the RMS
Titanic. It is found that the steel possessed a ductile-to-brittle transition temperature that was
very high with respect to the service temperature, making the material very brittle at ice-water
temperatures. This had been attributed to both chemical and microstructural factors. It is also
been found that the wrought iron rivets used in the construction of Titanic contained an elevated
amount of incorporated slag, and that the orientation of the slag within the rivets may hold an
explanation for how the ship accumulated damage during its encounter with the iceberg.
Keywords- Brittle fracture, Rivets, Hull Steel, Metallurgical Failure, Titanic Disaster.
This document discusses the use of cohesive zone modeling to simulate fatigue crack growth and retardation. Cohesive zone models define cohesive stresses around a crack tip that are related to crack opening width. Crack propagation occurs when cohesive stresses reach a failure value. The models can account for material properties through a cohesive law. Finite element implementations use cohesive elements located at crack fronts. The models can simulate crack closure effects, wedge effects, and predict crack growth under various loading conditions like overloads through an unloading-reloading hysteresis. Cohesive theory provides a unified way to model long cracks under constant loading as well as short cracks and overloads.
This document summarizes a numerical study of indentation-induced cracking in brittle coatings on ductile substrates. Finite element modeling was used to simulate indentation with a spherical indenter. The coating was modeled as linear elastic, the substrate as elastic-perfectly plastic, and cracks in the coating were modeled using cohesive surfaces. Circumferential cracks were found to initiate at the coating surface near the contact edge due to high tensile radial stresses. The first crack caused a kink in the load-displacement curve. The spacing between cracks was on the order of the coating thickness. The effects of material properties and cohesive parameters on crack initiation and spacing were also investigated.
Influence of contact friction conditions on thin profile simulationVan Canh Nguyen
The paper presents the development of the Finite Element model for simulation of thin
aluminium profile extrusion of both solid and hollow shapes. The analysis has shown that the material
flow in simulation is very dependent on the friction model. Experimental and theoretical studies show
that friction traction on the interface between the tool and the deformed material can be represented as
a combination of adhesive friction force and the force that is required to deform surface asperities. In
aluminium extrusion we can clearly distinguish two different areas with respect to friction conditions
such as sticking and sliding and transient zones between them. The lengths of these zones are also
dependent on variation of the choke angle and actual thickness of the profile. To get these values the
material flow problem is to be coupled with the simulation of the tools deformation. A series of
experiments with specially designed tools have been done to investigate how the bearing length and
choke angle may influence the extension of different friction zones and by these means vary the
material flow pattern. The friction models have also been tested with industrial profiles of complex
shapes and have shown good correspondence to reality.
MSEC2013- Interface delamination of diamond-coated carbide tools considering ...The University of Alabama
Interface delamination is the major failure mode of diamond-coated carbide tools in machining. On the other hand, coating cracking is possibly accompanied during a tribological process that induces the delamination phenomenon. However, such an influence between the two failure behaviors has not been investigated in a quantitative way to better understand and design diamond coating tools.
In this study, a three-dimensional (3D) indentation model combining cohesive interactions and extended finite element method (XFEM) was developed to investigate the diamond-coating, carbide-substrate interface behavior with the incorporation of coating cracking. The cohesive interaction was based on a cohesive zone model (CZM) with a bilinear traction-separation law. XFEM was applied to the coating domain to model cracking in the diamond coating with a damage criterion of the maximum principal stress. Deposition stresses were also included to investigate their effect on the coating delamination and fractures. The model was implemented in finite element (FE) codes to analyze the cone crack in brittle coatings, as well as the interface delamination of diamond coated carbide tools. The XFEM model was validated by the indentation testing data from literature in crack initiation and propagation in brittle materials. FE results from the indentation on diamond-coated tools show that the interface delamination size and loading force become smaller when coating fractures are incorporated in the model, and the deposition stresses will increase the initial crack radius and the critical load for delamination in diamond coatings.
A fracture mechanics based method for prediction ofSAJITH GEORGE
The document presents a fracture mechanics-based method for predicting cracking in circular and elliptical concrete rings undergoing restrained shrinkage. It describes an experimental program using different ring geometries and material tests to determine properties. A numerical model is developed using ANSYS to model the restrained shrinkage process and calculate stress intensity factors. The model uses a fictitious temperature field to simulate shrinkage and determines cracking age by comparing driving and resistance curves. It finds cracking occurs earlier in elliptical rings and the method accurately predicts experimental cracking ages.
The document summarizes a study on heterogeneous deformation and dislocation dynamics in compressed copper micropillars using multi-scale discrete dislocation plasticity modeling. The model couples 3D finite element analysis to calculate stress distributions and image stresses with 3D discrete dislocation dynamics. It captures size effects, hardening behavior, and the influence of boundary conditions. Results show hardening is due to dislocation entanglement and stagnation, with stress concentrations affecting heterogeneous deformation.
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
IRJET - Behaviour of Rectangular SFRC Beam Specimens Under Combined State of ...IRJET Journal
This document summarizes a study that investigated the behavior of steel fiber reinforced concrete (SFRC) beams under combined flexure, compression, and shear loading. Rectangular SFRC beams of varying fiber content (0%, 0.5%, 0.75%, 1% by volume) were tested. Beams were subjected to four levels of compression (0 kN, 40 kN, 50 kN, 60 kN) and flexural loading. Test results found that as fiber content and compression level increased, ultimate bending strength and deflection increased. The ductility of beams also increased with higher fiber content and compression. Including steel fibers improved the compressive strength, splitting tensile strength, and flexural behavior of the concrete
The effective width in multi girder composite steel beams with web openingsIAEME Publication
This document summarizes a study on the effective width of multi-girder composite steel beams with web openings through finite element analysis. Several 3D models were developed to examine the effects of varying slab thickness, slab width, span length, and load type. The analysis found that thicker slabs experience less shear lag due to higher shear stiffness. Wider slabs and shorter spans also decreased shear lag effects. Different load types produced varying stress distributions across the slab width, affecting the effective width.
Vibrational Analysis Of Cracked Rod Having Circumferential Crack IDES Editor
The frequency ratio of torsional vibration of a rod without crack and of rod with crack subjected to torque at the free end for various crack depth and varying crack location is investigated. It is found that even a cracked of small depth is
dangerous at the fixed end, also as the crack depth is increases more than 50% of diameter of rod there is a considerable drop in natural frequency of the rod .
1. Surface engineering aims to modify the properties of material surfaces to improve functionality, such as corrosion resistance, wear resistance, and friction reduction. Common surface engineering techniques include coatings, thermal treatments, and surface texturing.
2. Controlling friction through surface texturing has gained interest, as microscale dimples or grooves can reduce friction. However, the effects of texturing parameters like shape, depth, width, and orientation on friction are still being studied. Surface roughness parameters provide a way to characterize topography but may not fully describe surfaces.
3. The document discusses various surface roughness parameters defined by ISO standards and how they can characterize surface topography features relevant to friction, such as peaks, valleys
1) The document describes a finite element analysis of the superplastic blow-forming of Ti-6Al-4V titanium alloy sheet into a closed ellip-cylindrical die.
2) The simulations investigate the effects of shear friction factor, die entry radius, die height, and die short-axis length on thickness distribution, stress, strain, and damage within the formed product.
3) The results confirm the suitability of using the DEFORMTM 3D finite element software to model superplastic blow-forming of Ti-6Al-4V titanium alloy.
Structural Changes in the Surface Layer of Deep Rolled Samples Due to Thermal...IJERA Editor
Deep rolling processes initiate plastic deformations in the surface layer. The local characteristics of deformation are dependent on the induced stress expressed by the local stress tensor. Equivalent stresses above yield strength cause plastic deformation. Additionally the intrinsic energy, e. g. the dislocation density, is enhanced and the residual stress state is changed. The effects to a deep rolled surface from an increase in temperature are mainly dependent on the material, the microstructure, the initial residual stress state, the inclusion density, the distribution of soluted alloying elements and the plastic deformation. In the described experiments the interactions between deformation and temperature of the steel grade AISI 4140 (42 CrMo 4) used for all further experiments in a transregional Collaborative Research Center (CRC) were to be examined. The most simple investigation methods were chosen deliberately to allow a better statistical support of correlations between introduced strains and material reactions for a wide variation of process parameters. Since the visual effects by light microscopy in AISI 4140 were very small, the experiments were repeated with german grade 18 CrNiMo 7-6 (comparable to AISI 4820). This paper focuses on the micro structural changes in defined deep rolled surface regions due to an increase in temperature. The work described is part of the Collaborative Research Center “Process Signatures”, collaboration between Bremen University, Technical University Aachen, Germany and Oklahoma State University Stillwater, USA.
This document reviews the effect of knitted composite structure and properties. It finds that tensile strength is highest for plain knits with longer loop lengths and lower stitch densities, which reduces stress concentrations. Compressive strength improves slightly with these same parameters as they allow for higher fiber buckling loads. Modulus is largely independent of structure. Overall, knitted composites have properties dominated by the matrix, but structure can be optimized to improve strengths by reducing stress concentrations.
This document summarizes a range of aerospace cleaning chemicals for components. It describes four products: HDL Precision Cleaning Solvent which can safely clean precision components and electrical parts and meets various approvals. Lemsolv 860 RI is designed for cleaning turbine blades and removing semi-cured adhesives. Lemsolv CX1 is a citrus-based solvent that removes fingerprints and markings from pre-inspection components. Lemsolv CX4 removes sealants, adhesives, and ink and meets a helicopter approval. All products are manufactured and supplied by Oil Technics Ltd.
Due to year on year exceptional growth, Oil Technics Ltd have expanded their Sales Team and in June we will be joined by a dedicated Fire Foam Sales Manager.... Watch this space.
The documentary "Lifers" explores the daily lives of convicted killers in prison as they undergo rehabilitation programs. It airs on Channel 4 on June 25, 2012 at 9pm and runs for 47 minutes and 34 seconds. The documentary aims to show how criminals live in prison following their crimes and consequences. Its message is to discourage killing by showing viewers how their lives would turn out in prison. It profiles several convicted criminals and interviews experts to analyze prisoner behavior. It uses techniques like handheld cameras, interviews, archival footage, and montage editing to create a sense of realism.
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Texture and crack growth behaviour
1. Crystallographic texture correlation with
fracture toughness and fatigue crack growth
behaviour
Term Paper for the course of
Texture in Engineering Materials
Department of Metallurgical and Materials Engineering
IIT KHARAGPUR
2. Introduction
In this report, a short review of influence of material texture on crack propagation is
presented. Material texture results in anisotropy of material properties which impact its
fracture toughness and crack initiation and propagation rate. A number of papers are
reviewed ranging from initial macrotexture experiments to recently developed
microtexture methods. Dynamic crack propagation and crack arrest is an important
factor in determining structural integrity. Focus is usually placed on the initiation step
(KIc) to avoid catastrophic failures of structures. Structural materials manufactured in
industrial processes do not produce defect free materials. Due to residual stresses and
strain inhomogeneities, nanoscale cracks or defects may be present. Thus for safety
analysis, it is better to consider cracks inherently present in the material and focus on
retarding crack growth. It is important to know whether or not the material will be able to
arrest that crack before it goes through the entire structure. To answer this question it is
essential to understand cleavage micromechanisms during crack propagation.1 It is
known that crack propagation is arrested by grain boundaries: boundaries act like a pile
up of dislocations blocking further movement of dislocations into other grains. But this
does not consider micro-texture effects like grain boundary misorientation on crack
growth. Fatigue cracks are assumed to form in the most favourably oriented grains on
the surface of the specimen and propagate through less well oriented grains. In this
report, the effect of texture on crack propagation has been analysed with a multiscale
approach. It starts with macrotexture and bulk orientation and goes deeper into local
texture and grain boundary.
Crystallography and Local Failure
Consider (fig. 1).2 The crack on reaching the triple point in a
grain boundary has 2 choices for further propagation. It will
either continue along one of the grain boundaries or continue
on directly through the grain. The path selection will depend
on the character of the grain boundaries as well as the
orientation of the grain with respect to the imposed stress
state. The latter factor depends upon the Schmid factor or the
Taylor factor of the preferential slip planes. Depending on the
crack propagation trajectory two types of fracture are
possible:
Figure Error! No sequence
specified.: schematic of
crack propagation
3. Transgranular fracture
gA with respect to the stress state is critical, i.e. the resolved shear stress on
crystallographic planes in grain A. For a polycrystalline material, grains having slip
planes with lower Taylor factor will undergo transgranular fracture.
Intergranular fracture
The orientation of boundary plane (nAB and nAC) with respect to the stress state and the
misorientation between the grains(ΔgAB and ΔgAC) separated by the boundary are
critical. Also some grain boundaries may be weaker than the others due to lattice
incompatibility and impaired strain transfer across the boundary.
Effect of Macro-Texture on Crack Growth Behaviour
AZ61 Mg alloy is considered. Mg and other hcp metals have preferable slip in the basal
plane. During rolling of Mg, the rolling plane aligns parallel to the basal plane.[3] Due to
this uniformity in texture; it is experimentally easier in hcp metals to explore the effect of
fatigue crack orientation and loading direction on crack propagation rate. The following
observations are observed in AZ61 and also have been verified in other hcp systems
like Ti alloys. The specimen orientations are shown in fig. 2.
The longitudinal specimen, where the basal plane is parallel to the loading axis,
indicated high fatigue limit compared to the 45° and transverse specimens [4]. This is
due to the absence of slip systems at 45° in the longitudinal specimen.
In the near-threshold region the longitudinal specimen indicated high fatigue crack
growth resistance and high threshold value (fig. 3). For long cracks spanning more than
one grain, the crack growth rate becomes roughly independent of the orientation [5]. In
fig. 4, crack growth rate is plotted against (ΔKeff) effective stress intensity factor. The
plots approximately coincide for short or long cracks. Thus, the effect of texture is
mainly due to the difference of crack closure in different crack growth orientation.
Figure 2: Orientations of specimens taken
4. Figure 3: Crack growth rate vs. stress intensity
factor range
Figure 4: Crack growth range vs. effective
stress intensity factor range
A bimodal TiAl6V4 alloy is considered with 50% αp (hcp) and 50% of αs in β grains of
average grain size of 15 microns [6]. Fig. 6 is an optical microscope image of an etched
sample. It shows 2 distinct dark and clear patches of roughly 1mm size throughout the
surface which have been labelled as macrozone 1 and 2. X-ray diffraction shows that
macrozones have different αp phase texture. It is observed that short cracks produced
coincide either with basal or prismatic planes of αp grains depending upon the resolved
shear stress. As shown in (fig. 7), the sudden increase of crack length corresponds to
crack coalescence. Thus, in macrozones exhibiting a high crack density, a major
contribution of crack coalescence to crack growth was observed. The orientation of
macrozones governs the crack initiation on slip bands in αp grains, but has no significant
effect on crack growth in the Paris regime.
Figure 5: Scanning electron micrograph of
the electrolytically polished TiAl6V4
Figure 6: optical micrograph of the TiAl6V4
etched by an ethanol solution of 0.5% HF.
5. Figure 7: Crack length vs. number of cycles
Crack Tip
Fatigue crack propagation is presented for high strength steel. Dislocations generated in
slip bands, because of the plastic deformation, can pile up against the high-angle grain
boundaries and form micro-voids. Crack growth occurs by incorporation of these voids
in the main crack [7]. Two maps are constructed: Grain reference orientation deviation
(GROD) and Grain orientation spread (GOS) [8]. GROD measures angular deviation of
each point relative to a reference orientation. GOS shows the distribution of orientation
spread within a grain. Fig. 8 shows the predominant presence of HAGB surrounding the
crack tip [9]. Fig.9 shows that cracking occurs through the grains with the least lattice
rotation and it deflects when the grains have misorientation higher than 7°. From fig.10 it
can be inferred that the least strained grains are affecting the crack path direction. It is
presumed to be due to the hardening of highly deformed grains. It can be seen from fig.
11 that in the immediate vicinity of the crack there are grains with very low Taylor factor, thus
these grains can be deformed easily. But the crack trajectory also coincides with grains that
have high Taylor factor values. By comparing identical regions in Fig. 9, 10, 11, it is observed
that be seen that most of the grains with high Taylor factor which the crack propagated through
are either strained or rotated. In the Schmid factor map, the red area is indicative of large scale
yield and plasticity that may have activated a number of slip systems around the crack
trajectory.
6. Fig. 8: Low medium and high
angle grain boundaries in the
crack tip region
Fig. 9: Grain reference
orientation deviation (GROD)
map with respect to the lowest
average kernel misorientation
Fig.10: Grain orientation
spread (GOS) with respect to
all data points
inside a grain.
Fig.11: Taylor factor map of crack region Fig.12: Schmid factor map of crack region
Conclusion
Crack propagation mechanism has been studied. It is observed that orientation has impact on
short fatigue cracks but not on large cracks. Texture causes difference in fatigue crack closure
for different orientations. Further analysis of crack trajectory and tip mechanism is to be carried
out which should include impact of grain boundary types like tilt and twist and also various types
of CSL boundaries.
7. References
[1] Bouyne, E et al. "Use of EBSD technique to examine microstructure and cracking in
a bainitic steel." Scripta Materialia 39.3 (1998): 295-300.
[2] Wright, Stuart I, and David P Field. "Recent studies of local texture and its influence
on failure." Materials Science and Engineering: A 257.1 (1998): 165-170.
[3] T. Mukai, M. Yamanoi, H. Watanabe, K. Higashi “Ductility enhancement in Z31
magnesium alloy by controlling its grain structure” Scripta Materilia, 45 (2001), 89–94
[4] Sajuri, Zainuddin Bin et al. "Effects of Mn content and texture on fatigue properties of
as-cast and extruded AZ61 magnesium alloys." International journal of mechanical
sciences 48.2 (2006): 198-209.
[5] Navarro, A, and ER De Los Rios. "Short and long fatigue crack growth: a unified
model." Philosophical Magazine A 57.1 (1988): 15-36.
[6] Le Biavant, K, S Pommier, and C Prioul. "Local texture and fatigue crack initiation in
a Ti‐6Al‐4V titanium alloy." Fatigue & Fracture of Engineering Materials & Structures
25.6 (2002): 527-545.
[7] Tanaka, K, and T Mura. "A dislocation model for fatigue crack initiation." Journal of
Applied Mechanics 48.1 (1981): 97-103.
[8] Kobayashi, S. "Orientation dependence of local lattice rotations at precipitates."
2010. <http://www.sciencedirect.com/science/article/pii/S1359645410005446>
[9] Azar, Amin S, Lars-Erik Svensson, and Bård Nyhus. "Effect of crystal orientation
and texture on fatigue crack evolution in high strength steel welds." International Journal
of Fatigue 77 (2015): 95-104.