Influence of Anisotropic Yield Functions on Parameters of Yoshida-Uemori Model

2013 ◽  
Vol 554-557 ◽  
pp. 2440-2452 ◽  
Author(s):  
Hirotaka Kano ◽  
Jiro Hiramoto ◽  
Toru Inazumi ◽  
Takeshi Uemori ◽  
Fusahito Yoshida
Keyword(s):  
Effective Strain ◽  
Yield Function ◽  
Strain Response ◽  
Material Parameters ◽  
International Conference ◽  
Polynomial Type ◽  
Calculated Stress ◽  
Yield Functions ◽  
Order Polynomial ◽  
Von Mises

Yoshida-Uemori model (Y-U model) can be used with any types of yield functions. The calculated stress strain response will be, however, different depending on the chosen yield function if the yield function and the effective strain definition are inappropriate. Thus several modifications to Y-U model were proposed in the 10th International Conference on Technology of Plasticity. It was ascertained that in the modified Y-U model, the same set of material parameters can be used with von Mises, Hill’s 1948, and Hill’s 1990 yield function. In this study, Yld2000-2d and Yoshida’s 6th-order polynomial type 3D yield function were examined and it was clarified that the same set of Y-U parameters can be used with these yield functions.

An Investigation of Yield Potentials In Superplastic Deformation

1999 ◽  
Vol 122 (1) ◽  
pp. 93-97 ◽  
Author(s):  
Marwan K. Khraisheh
Keyword(s):  
Effective Strain ◽  
Yield Function ◽  
Yield Potential ◽  
Anisotropic Yield Function ◽  
Superplastic Alloy ◽  
Degree Of Anisotropy ◽  
Anisotropic Function ◽  
Experimental Yield ◽  
Dynamic Yield ◽  
Von Mises

Recent results (Khraisheh et al., 1995 and 1997) have indicated that superplastic materials exhibit a strong degree of anisotropy and that the plastic flow cannot be described by the isotropic von Mises flow rules. In this study, the yield potential for the model Pb-Sn superplastic alloy is constructed experimentally for different effective strain rates using combined tension/torsion tests. A generalized anisotropic “dynamic” yield function is also proposed to represent the experimentally constructed yield potentials. The anisotropic function is not only capable of describing the initial anisotropic state of the yield potential, it can also describe its evolution through the evolution of unit vectors defining the direction of anisotropy. The anisotropic yield function includes a set of material constants which determine the degree of deviation of the yield potential from the isotropic von Mises yield surface. It is shown that the anisotropic yield function successfully represents the experimental yield potentials, especially in the superplastic region. [S0094-4289(00)01401-8]

A Critical Reexamination of Classical Metal Plasticity

2001 ◽  
Vol 69 (1) ◽  
pp. 63-68 ◽  
Author(s):  
C. D. Wilson
Keyword(s):  
Finite Element ◽  
Hydrostatic Stress ◽  
Yield Function ◽  
Nonlinear Finite Element ◽  
Compressive Yield Strength ◽  
Systematic Effect ◽  
Finite Element Analyses ◽  
Yield Functions ◽  
Classical Plasticity ◽  
Von Mises

P. W. Bridgman’s early work on flow and fracture in the presence of hydrostatic pressure showed no systematic effect on strain hardening. This experimental observation led to the conclusions that yielding does not depend on hydrostatic stress and that the yielded material is incompressible. Classical plasticity theory was largely built on these observations. New experiments and nonlinear finite element analyses of 2024-T351 aluminum notched round bars has quantified the effect of hydrostatic tensile stresses on yielding. Nonlinear finite element analyses using the von Mises (yielding is independent of hydrostatic stress) and the Drucker-Prager (yielding is linearly dependent on hydrostatic stress) yield functions was performed. The von Mises results overestimated experimental load-displacement curves by 10–65 percent. The Drucker-Prager results essentially matched the experimental results. The only additional data requirement for the Drucker-Prager yield function is the compressive yield strength.

Influence of Parameter Identification of Anisotropic Yield Function on Spring-Back Prediction in Finite Element Simulation of Sheet Metal Forming Process

2011 ◽  
Vol 189-193 ◽  
pp. 1465-1471 ◽  
Author(s):  
Shun Lai Zang ◽  
Lai Teng ◽  
Chen Guo
Keyword(s):  
Yield Function ◽  
Plastic Behavior ◽  
Spring Back ◽  
Forming Process ◽  
Material Parameters ◽  
Anisotropic Yield Function ◽  
Element Simulation ◽  
Yield Functions ◽  
Metal Forming Process ◽  
Anisotropic Plastic

The anisotropic plastic behavior of metallic sheet has a significant influence on spring-back, and is usually modeled by anisotropic yield function in numerical simulation. Material parameters of anisotropic yield function are generally identified either by yield stresses or by r-values, or both of them. For Hill1948 and Yld89 anisotropic yield functions, r-values are still widely used to calibrate their material parameters in spring-back prediction. Here, yield stresses and r-values were respectively used to calibrate them, and the differences of the spring-back simulated by these two identification methods were discussed. To evaluate their accuracy, the simulation results were compared with the spring-back calculated by Yld2000-2d anisotropic yield function. The result shows that when yield stresses were used to identify the material parameters of Hill1948 and Yld89 yield functions, the simulated spring-back was closer to that of Yld2000-2d yield function.

Elasto-Plastic Analysis of Reissner-Mindlin Plates

1990 ◽  
Vol 43 (5S) ◽  
pp. S40-S50 ◽  
Author(s):  
Panayiotis Papadopoulos ◽  
Robert L. Taylor
Keyword(s):  
Yield Function ◽  
Rate Equations ◽  
Test Problems ◽  
Field Equations ◽  
Element Analysis ◽  
Linear Hardening ◽  
Nonlinear Version ◽  
Plastic Analysis ◽  
Von Mises ◽  
Predictor Corrector

A finite element analysis of elasto-plastic Reissner-Mindlin plates is presented. The discrete field equations are derived from a nonlinear version of the Hu-Washizu variational principle. Associative plasticity, including linear hardening, is employed by means of a generalized von Mises-type yield function. A predictor/corrector scheme is used to integrate the plastic constitutive rate equations. Numerical simulations are conducted for a series of test problems to illustrate performance of the formulation.

Effect of Material Frame Rotation on the Hardening of an Anisotropic Material in Simple Shear Tests

2018 ◽  
Vol 85 (12) ◽  
Author(s):  
Kelin Chen ◽  
Stelios Kyriakides ◽  
Martin Scales
Keyword(s):  
Simple Shear ◽  
Plastic Anisotropy ◽  
Yield Function ◽  
Strain Response ◽  
Shear Tests ◽  
Stress Strain ◽  
Anisotropic Yield Function ◽  
Torsion Experiment ◽  
Thin Walled Tube ◽  
Material Frame

The shear stress–strain response of an aluminum alloy is measured to a shear strain of the order of one using a pure torsion experiment on a thin-walled tube. The material exhibits plastic anisotropy that is established through a separate set of biaxial experiments on the same tube stock. The results are used to calibrate Hill's quadratic anisotropic yield function. It is shown that because in simple shear the material axes rotate during deformation, this anisotropy progressively reduces the material tangent modulus. A parametric study demonstrates that the stress–strain response extracted from a simple shear test can be influenced significantly by the anisotropy parameters. It is thus concluded that the material axes rotation inherent to simple shear tests must be included in the analysis of such experiments when the material exhibits anisotropy.

scholarly journals Study on the biomechanical responses of the loaded bone in macroscale and mesoscale by multiscale poroelastic FE analysis

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
WeiLun Yu ◽  
XiaoGang Wu ◽  
HaiPeng Cen ◽  
Yuan Guo ◽  
ChaoXin Li ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Fluid Velocity ◽  
Fluid Pressure ◽  
Biological Information ◽  
Von Mises Stress ◽  
Fe Model ◽  
Heterogeneous Distribution ◽  
Material Parameters ◽  
Mesoscopic Models ◽  
Von Mises

Abstract Background Bone is a hierarchically structured composite material, and different hierarchical levels exhibit diverse material properties and functions. The stress and strain distribution and fluid flow in bone play an important role in the realization of mechanotransduction and bone remodeling. Methods To investigate the mechanotransduction and fluid behaviors in loaded bone, a multiscale method was developed. Based on poroelastic theory, we established the theoretical and FE model of a segment bone to provide basis for researching more complex bone model. The COMSOL Multiphysics software was used to establish different scales of bone models, and the properties of mechanical and fluid behaviors in each scale were investigated. Results FE results correlated very well with analytical in macroscopic scale, and the results for the mesoscopic models were about less than 2% different compared to that in the macro–mesoscale models, verifying the correctness of the modeling. In macro–mesoscale, results demonstrated that variations in fluid pressure (FP), fluid velocity (FV), von Mises stress (VMS), and maximum principal strain (MPS) in the position of endosteum, periosteum, osteon, and interstitial bone and these variations can be considerable (up to 10, 8, 4 and 3.5 times difference in maximum FP, FV, VMS, and MPS between the highest and the lowest regions, respectively). With the changing of Young’s modulus (E) in each osteon lamella, the strain and stress concentration occurred in different positions and given rise to microscale spatial variations in the fluid pressure field. The heterogeneous distribution of lacunar–canalicular permeability (klcp) in each osteon lamella had various influence on the FP and FV, but had little effect on VMS and MPS. Conclusion Based on the idealized model presented in this article, the presence of endosteum and periosteum has an important influence on the fluid flow in bone. With the hypothetical parameter values in osteon lamellae, the bone material parameters have effect on the propagation of stress and fluid flow in bone. The model can also incorporate alternative material parameters obtained from different individuals. The suggested method is expected to provide dependable biological information for better understanding the bone mechanotransduction and signal transduction.

Response, Localization, and Rupture of Anisotropic Tubes Under Combined Pressure and Tension

2020 ◽  
Vol 88 (1) ◽  
Author(s):  
Martin Scales ◽  
Kelin Chen ◽  
Stelios Kyriakides
Keyword(s):  
Constitutive Model ◽  
Ductile Failure ◽  
Failure Criteria ◽  
Yield Function ◽  
Local Deformation ◽  
Al Alloys ◽  
Biaxial Stress ◽  
Image Correlation ◽  
Element Analysis ◽  
Von Mises

Abstract The inelastic response and failure of Al-6061-T6 tubes under combined internal pressure and tension is investigated as part of a broader study of ductile failure of Al-alloys. A custom experimental setup is used to load thin-walled tubes to failure under radial paths in the axial-hoop stress space. All loading paths achieve nominal stress maxima beyond which deformation localizes into a narrow band. 3D digital image correlation (DIC) was used to monitor the deformations in the test section and successfully captured the rapid growth of strain within the localization bands where they burst. The biaxial stress states generated are first used to calibrate the nonquadratic anisotropic Yld04-3D yield function (Barlat et al., 2005, “Linear Transformation-based Anisotropic Yield Functions,” Int. J. Plasticity, 21(5), pp. 1009–1039). The constitutive model is then incorporated through a UMAT into a finite element analysis and used to simulate numerically the experiments. The same calculations were performed using von Mises (VM) and an isotropic nonquadratic yield function. The material hardening responses adopted were extracted for each constitutive model from the necked zone of a tensile test using an inverse method. The use of solid elements captures the evolution of local deformation deep into the localizing part of the response, producing strain levels that are required in the application of failure criteria. The results demonstrate that the adoption of a nonquadratic yield function, together with a correct material hardening response are essential for large deformation predictions in localizing zones in Al-alloys. Including the anisotropy in such a constitutive model produces results that are closest to the experiments.

Characterization and Variational Modeling of Ionic Polymer Transducers

2006 ◽  
Vol 129 (1) ◽  
pp. 113-120 ◽  
Author(s):  
Miles A. Buechler ◽  
Donald J. Leo
Keyword(s):  
Variational Approach ◽  
Electromechanical Coupling ◽  
Structural Model ◽  
A Priori ◽  
Effective Strain ◽  
Polymer Materials ◽  
Beam Model ◽  
Frequency Dependent ◽  
Ionic Polymer ◽  
Material Parameters

Ionomeric polymers are a promising class of intelligent material which exhibit electromechanical coupling similar to that of piezoelectric bimorphs. Ionomeric polymers are much more compliant than piezoelectric ceramics or polymers and have been shown to produce actuation strain on the order of 2% at operating voltages between 1V and 3V (Akle et al., 2004, Proceedings IMECE). Their high compliance is advantageous in low force sensing configurations because ionic polymers have a very little impact on the dynamics of the measured system. Here we present a variational approach to the dynamic modeling of structures which incorporate ionic polymer materials. To demonstrate the method a cantilever beam model is developed using this variational approach. The modeling approach requires a priori knowledge of three empirically determined material properties: elastic modulus, dielectric permittivity, and effective strain coefficient. Previous work by Newbury and Leo has demonstrated that these three parameters are strongly frequency dependent in the range between less than 1Hz to frequencies greater than 1kHz. Combining the frequency-dependent material parameters with the variational method produces a second-order matrix representation of the structure. The frequency dependence of the material parameters is incorporated using a complex-property approach similar to the techniques for modeling viscoelastic materials. A transducer is manufactured and the method of material characterization is applied to determine the mtaerial properties. Additional experiments are performed on this transducer and both the material and structural model are validated. Finally, the model is shown to predict sensing response very well in comparison to experimental results, which supports the use of an energy-based variational approach for modeling ionomeric polymer transducers.

REALIZATION OF COUPLINGS IN A POLYNOMIAL TYPE MIXED-MODE CELLULAR NEURAL NETWORK

2003 ◽  
Vol 13 (06) ◽  
pp. 443-452 ◽  
Author(s):  
MIKA LAIHO ◽  
ARI PAASIO ◽  
ASKO KANANEN ◽  
KARI HALONEN
Keyword(s):  
Neural Network ◽  
Mixed Mode ◽  
Cellular Neural Network ◽  
Third Order ◽  
Device Mismatch ◽  
Polynomial Type ◽  
Order Polynomial

In this paper realization of couplings between cells in a polynomial type mixed-mode cellular neural network (CNN) is analyzed. The choice of the multiplier is discussed and two multiplier types are analyzed. Also, two circuits for generating the second and third order polynomial terms of cell output are described. The accuracy of the multipliers and polynomial circuits at the presence of device mismatch is analyzed.

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