Showing papers on "von Mises yield criterion published in 2010"
TL;DR: In this article, a fracture criterion is expressed in terms of the equivalent failure strain as a function of the stress triaxiality and the Lode angle (or the third invariant of the deviatoric stress deviator) and this function is calibrated for a DH36 steel plate.
Abstract: The main purpose of this paper is to demonstrate that besides the stress triaxiality parameter, the Lode angle, which can be related to the third invariant of the deviatoric stress tensor, also has an important effect on ductile fracture. This is achieved by conducting a series of micromechanics analyses of void-containing unit cells and experimental-numerical studies of carefully designed specimens experiencing a wide range of stress states. As a result, a fracture criterion is expressed in terms of the equivalent failure strain as a function of the stress triaxiality and the Lode angle (or the third invariant of the stress deviator) and this function is calibrated for a DH36 steel plate.
157 citations
TL;DR: In this paper, it was shown that the emission and outward expansion of special dislocation loops, nucleated at the surface of nanosized voids, are responsible for the outward flux of matter, promoting their growth.
157 citations
TL;DR: In this article, a class of penalty functionals that mimic a pointwise constraint on the Von Mises stress field is introduced, and a topology optimization algorithm based on these concepts is proposed, that allows for treating local stress criteria.
Abstract: The topological asymptotic analysis provides the sensitivity of a given shape functional with respect to an infinitesimal domain perturbation. Therefore, this sensitivity can be naturally used as a descent direction in a structural topology design problem. However, according to the literature concerning the topological derivative, only the classical approach based on flexibility minimization for a given amount of material, without control on the stress level supported by the structural device, has been considered. In this paper, therefore, we introduce a class of penalty functionals that mimic a pointwise constraint on the Von Mises stress field. The associated topological derivative is obtained for plane stress linear elasticity. Only the formal asymptotic expansion procedure is presented, but full justifications can be deduced from existing works. Then, a topology optimization algorithm based on these concepts is proposed, that allows for treating local stress criteria. Finally, this feature is shown through some numerical examples.
127 citations
TL;DR: Load sequence effects on low cycle multiaxial fatigue behavior of titanium are investigated in this article, where constant and variable amplitude axial, torsion, as well as in-phase and out-of-phase axial-torsion strain-controlled tests were conducted on tubular specimens made from pure titanium and titanium alloy BT9.
117 citations
TL;DR: The TWINLAW model as discussed by the authors is based on three phenomenological deformation modes for Mg AZ31B: S (slip), T (twinning), and U (untwinning), which correspond to three testing regimes: initial in-plane tension (from the annealed state), initial inplane compression, and inplane tension following compression, respectively.
106 citations
TL;DR: The cross-sectional design has a greater impact than taper or size of the instrument on the stresses developed in the instrument under either torsion or bending, taking into account the nonlinear mechanical properties of material.
99 citations
TL;DR: The present study showed that the use of different thread form designs did not affect the von Mises concentration at supporting bone structure, however, the compressive stress concentrations differ by various thread profiles.
Abstract: The biomechanical behavior of implant thread plays an important role on stresses at implant-bone interface. Information about the effect of different thread profiles upon the bone stresses is limited. The purpose of this study was to evaluate the effects of different implant thread designs on stress distribution characteristics at supporting structures. In this study, three-dimensional (3D) finite element (FE) stress-analysis method was used. Four types of 3D mathematical models simulating four different thread-form configurations for a solid screw implant was prepared with supporting bone structure. V-thread (1), buttress (2), reverse buttress (3), and square thread designs were simulated. A 100-N static axial occlusal load was applied to occlusal surface of abutment to calculate the stress distributions. Solidworks/Cosmosworks structural analysis programs were used for FE modeling/analysis. The analysis of the von Mises stress values revealed that maximum stress concentrations were located at loading areas of implant abutments and cervical cortical bone regions for all models. Stress concentration at cortical bone (18.3 MPa) was higher than spongious bone (13.3 MPa), and concentration of first thread (18 MPa) was higher than other threads (13.3 MPa). It was seen that, while the von Mises stress distribution patterns at different implant thread models were similar, the concentration of compressive stresses were different. The present study showed that the use of different thread form designs did not affect the von Mises concentration at supporting bone structure. However, the compressive stress concentrations differ by various thread profiles.
99 citations
TL;DR: In this paper, the residual stress developed in the welding region is measured using the XRD technique and the results are compared with the predictions using optical microscopy and the SEM for the metallurgical examination of the welding sites.
Abstract: Laser welding of mild steel sheets is carried out under nitrogen assisting gas ambient. Temperature and stress fields are computed in the welding region through the finite element method. The residual stress developed in the welding region is measured using the XRD technique and the results are compared with the predictions. Optical microscopy and the SEM are used for the metallurgical examination of the welding sites. It is found that von Mises stress attains high values in the cooling cycle after the solidification of the molten regions. The residual stress predicted agreed well with the XRD results.
90 citations
15 May 2010-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors simulate laser beam welding induced residual stresses and distortions using industrialally employed thermal and mechanical boundary conditions, and the welding simulation is performed with the commercial finite element software Abaqus and a Fortran program.
Abstract: Laser beam welding has recently found its application in the fabrication of aircraft structures where fuselage panels, made of thin sheets of AA 6056-T4 (an aluminium alloy), are welded with stiffeners of the same material in a T-joint configuration. The present work simulates laser beam welding induced residual stresses and distortions using industrially employed thermal and mechanical boundary conditions. Various measurements performed on small-scale welded test specimens provide a database of experimental results that serves as a benchmark for qualification of the simulation results. The welding simulation is performed with the commercial finite element software Abaqus and a Fortran programme encoding a conical heat source with Gaussian volumetric distribution of flux. A sequentially coupled temperature–displacement analysis is undertaken to simulate the weld pool geometry, transient temperature and displacement fields. The material is assumed to follow an elasto-plastic law with isotropic hardening behaviour (von Mises plasticity model). A comparison between the experimental and simulation results shows a good agreement. Finally, the residual stress and strain states in a T-joint are predicted.
87 citations
TL;DR: The yield prediction capabilities of these models using four different yield criteria are investigated, and the spread in the predicted load between the isotropic and orthotropic material models is investigated.
Abstract: High-order finite-element (FE) analyses with inhomogeneous isotropic material properties have been shown to predict the strains and displacements on the surface of the proximal femur with high accuracy when compared with in vitro experiments. The same FE models with inhomogeneous orthotropic material properties produce results similar to those obtained with isotropic material properties. Herein, we investigate the yield prediction capabilities of these models using four different yield criteria, and the spread in the predicted load between the isotropic and orthotropic material models. Subject-specific high-order FE models of two human femurs were generated from CT scans with inhomogeneous orthotropic or isotropic material properties, and loaded by a simple compression force at the head. Computed strains and stresses by both the orthotropic and isotropic FE models were used to determine the load that predicts 'yielding' by four different 'yield criteria': von Mises, Drucker-Prager, maximum principal stress and maximum principal strain. One of the femurs was loaded by a simple load until fracture, and the force resulting in yielding was compared with the FE predicted force. The surface average of the 'maximum principal strain' criterion in conjunction with the orthotropic FE model best predicts both the yield force and fracture location compared with other criteria. There is a non-negligible influence on the predictions if orthotropic or isotropic material properties are applied to the FE model. All stress-based investigated 'yield criteria' have a small spread in the predicted failure. Because only one experiment was performed with a rather simplified loading configuration, the conclusions of this work cannot be claimed to be either reliable or sufficient, and future experiments should be performed to further substantiate the conclusions.
86 citations
TL;DR: An elastic contact model for three-dimensional layered or coated materials under coupled normal and tangential loads, with consideration of partial slip effects, has been developed in this paper, where the response functions for calculating the displacements and stresses were determined in the frequency domain by using the Papkovich-Neuber potentials.
Abstract: An elastic contact model for three-dimensional layered or coated materials under coupled normal and tangential loads, with consideration of partial slip effects, has been developed in this paper. The response functions for calculating the displacements and stresses were determined in the frequency domain by using the Papkovich–Neuber potentials. The partial slip contact problem was solved by a numerical procedure based on the conjugate Gradient method and fast Fourier transform technique. The contact pressure, surface shear tractions, stick ratios, rigid body displacements, and subsurface stresses are analyzed under different conditions with variations in the material properties and coating thickness. Results show that stiffer coatings tend to decrease the stick ratios and the rigid ball tangential displacements in comparison to those with compliant coatings under the same contact conditions. For stiffer coatings, the values of the von Mises stress and compressive surface stress increase and the positions of maximum von Mises stress move up to the surface; meanwhile, the distributions of the compressive stress become asymmetric due to the action of the tangential load. DOI: 10.1115/1.4001011
Journal Article•
TL;DR: The platform-switching technique reduced the stress concentration in the area of compact bone and shifted it to the area to cancellous bone during oblique loading.
Abstract: PURPOSE The purpose of this study was to analyze and compare the implant-bone interface stresses in anisotropic three-dimensional finite element models of an osseointegrated implant with platform switching and a conventional matching-diameter implant platform and abutment in the posterior maxilla. MATERIALS AND METHODS Three-dimensional finite element models were created of a first molar section of the maxilla and embedded with a single endosseous implant (4.1 3 10 mm). One model simulated a 4.1-mm-diameter abutment connection and the other was a narrower 3.4-mm-diameter abutment connection, ie, simulating a platform-switching configuration. A gold alloy crown with 2-mm occlusal thickness was applied over the titanium abutment. Material properties of compact and cancellous bone were modeled as fully orthotropic and transversely isotropic, respectively. Oblique (200-N vertical and 40-N horizontal) occlusal loads were applied and perfect bonding was assumed at all interfaces. RESULTS Maximum von Mises, compressive, and tensile stresses in compact bone were lower in the platform-switching model than in the conventional model. However, the maximum von Mises stress in cancellous bone was higher in the platform-switching model than in the conventional model. CONCLUSION The platform-switching technique reduced the stress concentration in the area of compact bone and shifted it to the area of cancellous bone during oblique loading.
Journal Article•
TL;DR: This study compared the biomechanical behavior of the "All-on-Four" system with that of a six-implant-supported maxillary prosthesis with tilted distal implants using the three-dimensional finite element method.
Abstract: Purpose Using the three-dimensional finite element method (FEM), this study compared the biomechanical behavior of the "All-on-Four" system with that of a six-implant-supported maxillary prosthesis with tilted distal implants. The von Mises stresses induced on the implants under different loading simulations were localized and quantified. Materials and methods Three-dimensional models representing maxillae restored with an "All-on-Four" and with a six-implant-supported prosthesis were developed in three-dimensional design software and then transferred into FEM software. The models were subjected to four different loading simulations (full mouth biting, canine disclusion, load on a cantilever, load in the absence of a cantilever). The maximum von Mises stresses were localized and quantified for comparison. Results In both models, in all loading simulations, the peak stress points were always located on the neck of the distal tilted implant. The von Mises stress values were higher in the "All-on-Four" model (7% to 29%, higher, depending on the simulation). In the presence of a cantilever, the maximum von Mises stress values increased by about 100% in both models. Conclusions The stress locations and distribution patterns were similar in the two models. The addition of implants resulted in a reduction of the maximum von Mises stress values. The cantilever greatly increased the stress.
TL;DR: In this paper, the authors investigated the deformation response of metallic glass under adiabatic planar shock wave loading (one-dimensional strain) with molecular dynamics simulations, including Hugoniot (shock) states, shock-induced plasticity, and spallation.
Abstract: We investigate dynamic response of ${\text{Cu}}_{46}{\text{Zr}}_{54}$ metallic glass under adiabatic planar shock wave loading (one-dimensional strain) with molecular dynamics simulations, including Hugoniot (shock) states, shock-induced plasticity, and spallation. The Hugoniot states are obtained up to 60 GPa along with the von Mises shear flow strengths, and the dynamic spall strengths, at different strain rates and temperatures. The spall strengths likely represent the limiting values achievable in experiments such as laser ablation. For the steady shock states, a clear elastic-plastic transition is identified (e.g., in the shock velocity-particle velocity curve), and the shear strength shows strain softening. However, the elastic-plastic transition across the shock front displays transient stress overshoot (hardening) above the Hugoniot elastic limit followed by a relatively sluggish relaxation to the steady shock state, and the plastic shock front steepens with increasing shock strength. The local von Mises shear strain analysis is used to characterize local deformation, and the Voronoi tessellation analysis, the corresponding local structures at various stages of shock, release, tension and spallation. The plasticity in this glass, manifested as localized shear transformation zones, is of local structure rather than thermal origin, and void nucleation occurs preferentially at the highly shear-deformed regions. The Voronoi and shear strain analyses show that the atoms with different local structures are of different shear resistances that lead to shear localization (e.g., the atoms indexed with $⟨0,0,12,0⟩$ are most shear-resistant, and those with $⟨0,2,8,1⟩$ are highly prone to shear flow). The dynamic changes in local structures are consistent with the observed deformation dynamics.
TL;DR: In this article, a thermodynamically consistent elastic-plastic constitutive model including the von Mises yield criterion, the associated flow rule and two nonlinear isotropic hardening variables is applied to describe the behavior of the high-strength steels.
Abstract: Tensile tests on three high-strength steels exhibiting Luders band propagation are carried out at room temperature and under quasi-static loading conditions. Displacement and temperature fields on the surface of the flat samples are measured by digital image correlation and digital infrared thermography, respectively. The true stress versus true strain curves were calculated from the displacement data, while the thermal data were used to estimate the heat sources using the local heat diffusion equation. Based on these measurements the stored and dissipated energies were estimated up to diffuse necking. A thermodynamically consistent elastic-plastic constitutive model including the von Mises yield criterion, the associated flow rule and two non-linear isotropic hardening variables is applied to describe the behaviour of the high-strength steels. It is shown that this simple model is able to reproduce both the local behaviour, such as the power associated to heat sources, and the global behaviour, such as Luders band propagation and stored and dissipated energies. It is further shown that the ratio of dissipated power to plastic power varies during plastic straining and that this variation is captured reasonably well in the numerical simulations.
TL;DR: It is found that the stress shielding at the fracture site at the fully healed stages decreases when using FG bone-plates compared to Ti alloy or SS bone-plate, and the significant effects of using an FGBone-plate with a gap on the resultant Von Mises stresses on the bone underneath the plate and on theBone stress shielding should be taken into consideration during fractured bone fixation.
TL;DR: The present probabilistic and sensitivity study clearly showed that in vertebroplasty the maximum stresses in the augmented vertebral body and in bone cement depend mainly on the loading case and fracture shape.
Abstract: Fractured vertebral bodies are often stabilized by vertebroplasty. Several parameters, including fracture type, cement filling shape, cement volume, elastic moduli of cement, cancellous bone and fractured region, may all affect the stresses in the augmented vertebral body and in bone cement. The aim of this study was to determine numerically the effects of these input parameters on the stresses caused. In a probabilistic finite element study, an osteoligamentous model of the lumbar spine was employed. Seven input parameters were simultaneously and randomly varied within appropriate limits for >110 combinations thereof. The maximum von Mises stresses in cancellous and cortical bone of the treated vertebral body L3 and in bone cement were calculated. The loading cases standing, flexion, extension, lateral bending, axial rotation and walking were simulated. In a subsequent sensitivity analysis, the coefficients of correlation and determination of the input parameters on the von Mises stresses were calculated. The loading case has a strong influence on the maximum von Mises stress. In cancellous bone, the median value of the maximum von Mises stresses for the different input parameter combinations varied between 1.5 (standing) and 4.5 MPa (flexion). The ranges of the stresses are large for all loading cases studied. Depending on the loading case, up to 69% of the maximum stress variation could be explained by the seven input parameters. The fracture shape and the elastic modulus of the fractured region have the highest influence. In cortical bone, the median values of the maximum von Mises stresses varied between 31.1 (standing) and 61.8 MPa (flexion). The seven input parameters could explain up to 80% of the stress variation here. It is the fracture shape, which has always the highest influence on the stress variation. In bone cement, the median value of the maximum von Mises stresses varied between 3.8 (standing) and 12.7 MPa (flexion). Up to 75% of the maximum stress variation in cement could be explained by the seven input parameters. Fracture shape, and the elastic moduli of bone cement and of the fracture region are those input parameters with the highest influence on the stress variation. In the model with no fracture, the maximum von Mises stresses are generally low. The present probabilistic and sensitivity study clearly showed that in vertebroplasty the maximum stresses in the augmented vertebral body and in bone cement depend mainly on the loading case and fracture shape. Elastic moduli of cement, fracture region and cancellous bone as well as cement volume have sometimes a moderate effect while number and symmetry of cement plugs have virtually no effect on the maximum stresses.
TL;DR: It can be concluded that the differences between two material property assignments are significant, at least in some local regions, because of the effects of comparative parameters, loading conditions and mesh refinement.
TL;DR: In this paper, the authors focus on the important aspect of strength, quantified as minimization of the maximum von Mises stress, and find by examples that the obtained designs are close to fulfilling also strength maximization.
Abstract: For thermoelastic structures the same optimal design does not simultaneously lead to minimum compliance and maximum strength. Compliance may be a questionable objective and focus for the present paper is on the important aspect of strength, quantified as minimization of the maximum von Mises stress. With compliance defined as the product of resulting displacements and their corresponding total loads, then for thermoelastic problems compliance is different from total elastic energy. An explicit formula for this difference is derived and numerically illustrated in the optimized examples. As an alternative to mathematical programming, which with a large number of both design variables and strength constraints, is found non-practical, we choose simple recursive iterations to obtain uniform energy density and find by examples that the obtained designs are close to fulfilling also strength maximization. In compliance minimization it may be advantageous to decrease the total volume, but for strength maximization it is argued that it is advantageous to keep the total permissible volume. With the thermoelastic analysis presented directly in a finite element formulation, simple explicit formulas for equivalent thermoelastic loads are appended.
TL;DR: In this article, the Gurson model for ductile porous media is extended to incorporate the surface/interface stresses effect at the nano-scale for capillary forces, the yield surface is obtained by a mere translation of Gurson one for interface stresses obeying a von Mises criterion.
TL;DR: In this article, a reformulation of the Theory of Critical Distance (TCD) is proposed for estimating static strength of notched ductile materials subjected to multiaxial loading.
TL;DR: In this article, the authors compared the growth and detachment of drops from a capillary nozzle by high-speed imaging and found that the critical stability behavior is similar to that of Newtonian and shear-thinning drops.
Abstract: The process of growth and detachment of drops from a capillary nozzle is studied experimentally by high-speed imaging. Newtonian drops are compared to shear-thinning and viscoplastic drops. Both Newtonian and shear-thinning fluid drops grow on the end of the capillary until a maximum supportable tensile stress is reached in the drop neck, after which they become unstable and detach. The critical stress is not influenced by variations in viscosity or in the degree of shear thinning. Viscoplastic fluids show a different behavior: at low values of the yield stress, the critical stability behavior is similar to that of Newtonian and shear-thinning drops. Above a threshold value, characterized in terms of the drop size, surface tension and tensile yield-stress magnitude, yield-stress forces are larger than surface forces, and the maximum tensile stress achievable in the drop neck at the point of critical stability is governed by the von Mises criterion.
TL;DR: Rousselier et al. as discussed by the authors applied a parameter calibration procedure to obtain a good agreement with the experimental database to model anisotropic hardening in the proportional loadings of the strongly anisoustric aluminum alloy.
TL;DR: The different materials of the overdenture-retaining bar did not present considerable influence on the stress levels in the periimplant bone tissue, while the mechanical components of the system were more sensitive to the material stiffness.
Abstract: Purpose: This study evaluated the effects of different bar materials on stress distribution in an overdenture-retaining bar system with a vertical misfit between implant and bar framework.
Materials and Methods: A three-dimentional finite element model was created including two titanium implants and a bar framework placed in the anterior part of a severely reabsorbed jaw. The model set was exported to mechanical simulation software, where displacement was applied to simulate the screw torque limited by 100-μm vertical misfit. Four bar materials (gold alloy, silver-palladium alloy, commercially pure titanium, cobalt-chromium alloy) were simulated in the analysis. Data were qualitatively evaluated using Von Mises stress given by the software.
Results: The models showed stress concentration in cortical bone corresponding to the cervical part of the implant, and in cancellous bone corresponding to the apical part of the implant; however, in these regions few changes were observed in the levels of stress on the different bar materials analyzed. In the bar framework, screw, and implant, considerable increase in stress was observed when the elastic modulus of the bar material was increased.
Conclusions: The different materials of the overdenture-retaining bar did not present considerable influence on the stress levels in the periimplant bone tissue, while the mechanical components of the system were more sensitive to the material stiffness.
TL;DR: Based on the FEM analysis, both of the response surface model (RSM) and Kriging model are used to optimize an ADI upper control arm, where the weight of theupper control arm is considered as the design objective, and the maximum allowable von Mises stress the constraint objective.
Abstract: Simulation-based surrogate models have been used for a variety of applications in automotive industry. In this paper, based on the FEM analysis, both of the response surface model (RSM) and Kriging model are used to optimize an ADI upper control arm, where the weight of the upper control arm is considered as the design objective, and the maximum allowable von Mises stress the constraint objective. The initial FEM analysis shows the stress distribution and maximum stress on the upper control arm under a very severe loading condition. And, by virtue of the result of FEM analyses, fifty simulations with six design variables are performed for RSM and Kriging model to construct the approximation of the weight and maximum stress to obtain the optimum result. The optimized results obtained by using RSM and KRG are confirmed by a verified FEM analysis. In addition, a fatigue analysis is carried out to verify the durability the final design.
TL;DR: In this paper, a numerical simulation of localized deformation that can develop into necking and failure, induced by combined bending and tension in shell structures, was performed on Al-6061-T6 cylindrical shells.
TL;DR: In this paper, the unloading process of an elastic-plastic spherical contact under stick contact condition is analyzed for various material properties, including the evolution of normal and shear stress distribution at the contact area as well as the residual profile of the sphere and residual von Mises stresses inside the sphere.
TL;DR: In this paper, finite element analysis (FEA) of the shear punch testing is carried out to study the specimen deformation up to yielding and the results are compared and validated with experimental data for four different materials.
TL;DR: In this article, a constitutive model was implemented in the finite element models combining the Johnson-Cook strain-rate sensitivity model, a nonlinear isotropic-kinematic hardening model, and the Yld2000-2d anisotropic model.
TL;DR: In this article, the effect of the particle clustering behavior on the mechanical response of metal matrix composites has been analyzed based on the analysis of the von Mises effective stress and the strain in the matrix and in the particles.