Use of Plane-Strain Tension and Shear Tests to Evaluate Yield Surfaces for AA1050 Aluminium Sheet

2014 ◽  
Vol 794-796 ◽  
pp. 596-601
Author(s):  
Kai Zhang ◽  
Bjørn Holmedal ◽  
Odd Sture Hopperstad ◽  
Stéphane Dumoulin
Keyword(s):  
Experimental Data ◽  
Plane Strain ◽  
Yield Function ◽  
Isotropic Hardening ◽  
Flow Rule ◽  
Shear Tests ◽  
Anisotropic Plasticity ◽  
Type Iii ◽  
Plane Strain Tension ◽  
Force Displacement

Plane-strain tension and shear tests were carried out for a fully annealed AA1050 sheet. The tests were simulated numerically with a commercial finite element method (FEM) code using an anisotropic plasticity model including the Yld2004-18p yield function, the associated flow rule and isotropic hardening. The advanced yield function was calibrated by three different methods: using uniaxial tension data combined with FC-Taylor model predictions of the equibiaxial yield stress and r-value, using 201 virtual yield points in stress space, and using a combination of experimental data and virtual yield points (i.e., a hybrid method). The virtual stress points at yielding were provided by the recently proposed Alamel model with the so-called Type III relaxation (Alamel Type III model). FEM simulations of the tests were then made with parameters of Yld2004-18p identified by these three methods. Predicted force-displacement curves were compared to the experimental data, and the accuracy of the parameter identification methods for Yld2004-18p was evaluated based on these comparisons.

Finite Element Calculation of Anisotropy of Hole Expansion in a Thin Steel Sheet with Six Degrees Polynomial Yield Function

2019 ◽  
Vol 794 ◽  
pp. 260-266
Author(s):  
Seung Yong Yang ◽  
Wei Tong
Keyword(s):  
Finite Element ◽  
Plastic Strain ◽  
Strain Ratio ◽  
Yield Function ◽  
Sixth Order ◽  
Isotropic Hardening ◽  
Flow Rule ◽  
Anisotropic Plasticity ◽  
Plastic Strain Ratio ◽  
Hole Expansion

A sixth order yield function was used to analyze the anisotropic plasticity behavior of sheet metal forming. Based on a complete sixth order homogenous polynomial in plane stress, the yield function was implemented as user material subroutines in the FE code ABAQUS Explicit and Standard. The associated flow rule and isotropic hardening were assumed. Material parameter values in the yield function were decided by uniaxial yield stresses and plastic strain ratios along 7 different loading orientations and plane strain yield and equal biaxial stresses and plastic strain ratio. To show the superiority of the sixth order yield function, the hole expansion test by Kuwabara et al.[1] was considered. The results of finite element simulation using the sixth order yield function showed a better agreement with the test results than YLD2000-2D yield function with M=6.

Damage Theoretical Analysis of 2.5D C/SiC Composites under Tensile and Shear Loading

2010 ◽  
Vol 150-151 ◽  
pp. 330-333
Author(s):  
Yan Jun Chang ◽  
Ke Shi Zhang ◽  
Gui Qiong Jiao ◽  
Jian Yun Chen
Keyword(s):  
Constitutive Model ◽  
Damage Evolution ◽  
Yield Function ◽  
Shear Loading ◽  
Isotropic Hardening ◽  
Shear Tests ◽  
Energy Equivalence ◽  
Damage Constitutive Model ◽  
Sic Composites ◽  
Nonlinear Hardening

An anisotropic damage constitutive model is developed to describe the damage behavior of C/SiC composites. Different kinematic and isotropic hardening functions were employed in damage yield function to describe accurately the damage nonlinear hardening. The damage variable is defined by the principle of energy equivalence. The degradation of stiffness and the unrecoverable deformation induced by micro-crack propagation were considered in this model. The constants of constitutive model are identified and the damage evolution processes under tensile and shear loading. Uniaxial tension and shear tests have been used to valid the constitutive model to C/SiC composites.

Effect of Yield Surface Curvature on Necking and Failure in Porous Plastic Solids

1986 ◽  
Vol 53 (3) ◽  
pp. 491-499 ◽  
Author(s):  
R. Becker ◽  
A. Needleman
Keyword(s):  
Plane Strain ◽  
Volume Fraction ◽  
Kinematic Hardening ◽  
Constitutive Models ◽  
Ductile Failure ◽  
Isotropic Hardening ◽  
Void Coalescence ◽  
Potential Surfaces ◽  
Plane Strain Tension ◽  
Path Dependent

The effect of material path dependent hardening on neck development and the onset of ductile failure is analyzed numerically. The calculations are carried out using an elastic-viscoplastic constitutive relation that has isotropic hardening and kinematic hardening behaviors as limiting cases and that accounts for the weakening due to the growth of micro-voids. Final material failure is incorporated into the constitutive model by the dependence of the plastic potential on void volume fraction. Results are obtained for both axisymmetric and plane strain tension. Failure is found to initiate by void coalescence at the neck center in axisymmetric tension and within a shear band in plane strain tension. The increased curvature of flow potential surfaces associated with the kinematic hardening solid leads to somewhat more rapid diffuse neck development than occurs for the isotropic hardening solid. However, a much greater difference between the predictions of the two constitutive models is found for the onset of ductile failure.

Plane-Strain Tension Tests on Aluminum Alloy Sheet

1995 ◽  
Vol 117 (2) ◽  
pp. 168-171 ◽  
Author(s):  
Fadi Taha ◽  
Alejandro Graf ◽  
William Hosford
Keyword(s):  
Aluminum Alloy ◽  
Plane Strain ◽  
Yield Criterion ◽  
Alloy Sheet ◽  
Isotropic Hardening ◽  
Aluminum Alloy Sheet ◽  
Strain Measurements ◽  
Plane Strain Tension ◽  
Tension Tests ◽  
High Exponent

A simple way of making plane-strain tension tests on sheet specimens has been developed. This method was used to test sheets of aluminum alloy 2008 T4 and the results were analyzed in terms of a high exponent yield criterion and isotropic hardening. Experimentally measured forces agreed with those calculated from strain measurements using uniaxial tension test curves.

scholarly journals Hole-Expansion: Sensitivity of Failure Prediction on Plastic Anisotropy Modeling

2021 ◽  
Vol 5 (2) ◽  
pp. 28
Author(s):  
Jinjin Ha ◽  
Yannis P. Korkolis
Keyword(s):  
Stress State ◽  
Uniaxial Tension ◽  
Plane Strain ◽  
Biaxial Tension ◽  
Plastic Anisotropy ◽  
Yield Function ◽  
Hydraulic Press ◽  
Image Correlation ◽  
Hole Expansion ◽  
Plane Strain Tension

The influence of yield function parameters on hole-expansion (HE) predictions are investigated for an anisotropic AA6022-T4 aluminum sheet. The HE experiment is performed in a fully-instrumented double-action hydraulic press with a flat-headed punch. Full strain fields are measured by a stereo-type digital image correlation (DIC) system. The stress state gradually changes from uniaxial to plane-strain tension to biaxial tension in the radial direction. Besides HE, the plastic anisotropy of AA6022-T4 is characterized by uniaxial tension and plane-strain tension experiments. Uniaxial tension is considered as the most important, since it is the stress state along the hoop direction in the hole. For the finite element (FE) simulation, the Yld2000-2d non-quadratic anisotropic yield function is used with two different parameter sets, calibrated by: (1) uniaxial tension only (termed Calib1) and, (2) both uniaxial and plane-strain tension (Calib2). The strain field predictions show a good agreement with the experiments only for Calib2, which takes into account plane-strain as well uniaxial tension. This indicates the importance of biaxial modes, and in particular plane-strain tension, for the adopted yield function to produce accurate HE simulations.

scholarly journals Prediction of Strain Path Changing Effect on Forming Limits of AA 6111-T4 Based on A Shear Ductile Fracture Criterion

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 546
Author(s):  
Silin Luo ◽  
Gang Yang ◽  
Yanshan Lou ◽  
Yongqian Xu
Keyword(s):  
Ductile Fracture ◽  
Uniaxial Tension ◽  
Plane Strain ◽  
Strain Path ◽  
Fracture Criterion ◽  
Kinematic Hardening ◽  
Isotropic Hardening ◽  
Ductile Fracture Criterion ◽  
Plane Strain Tension ◽  
Strain Paths

Strain path changing is a phenomenon in the stamping of complex panels or multiple-step stamping processes. In this study, the influence of the strain path changing effect was investigated and assessed for an aluminum alloy of 6111-T4 with a shear ductile fracture criterion. Plastic deformation of the alloy was modeled by an anisotropic Drucker yield function with the assumption of normal anisotropy. Then the shear ductile fracture criterion was calibrated by the fracture strains at uniaxial tension, plane strain tension and equibiaxial tension under proportional loading conditions. The calibrated fracture criterion was utilized to predict forming limit curves (FLCs) of the alloy stretched under bilinear strain paths. The analyzed bilinear strain paths included biaxial tension after uniaxial tension, plane strain tension and equibiaxial tension. The predicted FLCs of bilinear strain paths were compared with experimental results. The comparison showed that the shear ductile fracture criterion could reasonably describe the effect of strain path changing on FLCs, but its accuracy was poor for some bilinear paths, such as uniaxial tension followed by equibiaxial tension and equibiaxial tension followed by plane strain tension. Kinematic hardening is suggested to substitute the isotropic hardening assumption for better prediction of FLCs with strain path changing effect.

scholarly journals Sheet metal forming simulation using finite elastoplasticity with mixed isotropic/kinematic hardening

2011 ◽  
pp. 427-453
Author(s):  
Sami Chatti ◽  
Narjess Chtioui
Keyword(s):  
Metal Forming ◽  
Kinematic Hardening ◽  
Yield Function ◽  
Shear Tests ◽  
Anisotropic Plasticity ◽  
Cyclic Shear ◽  
Forming Simulation ◽  
Non Linear ◽  
Numerical Formulation ◽  
Finite Elastoplasticity

A numerical formulation is presented for anisotropic elastoplasticity behavior in finite strain with non-linear isotropic/kinematic hardening model. Non-linear kinematic hardening is modeled by the Lemaitre-Chaboche law with the aim of considering cyclic deformation phenomena. User-defined material subroutines are developed based on Hill’s quadratic yield function for both ABAQUS-Explicit (VUMAT) and ABAQUS-Standard (UMAT). For validation purpose, the tension-compression and cyclic shear tests are simulated. Several sheet forming processes including contact, anisotropic plasticity, elastic modulus variation with plastic strain and springback effects are simulated. Numerical results are compared with experimental data.

Elastic-Plastic Plane-Strain Solutions With Separable Stress Fields

1969 ◽  
Vol 36 (3) ◽  
pp. 528-532
Author(s):  
D. B. Bogy
Keyword(s):  
Stress Field ◽  
Plane Strain ◽  
Yield Criterion ◽  
A Priori ◽  
Equivalent Plastic Strain ◽  
Uniaxial Stress ◽  
Stress Fields ◽  
Isotropic Hardening ◽  
Flow Rule ◽  
Elastic Plastic

A stress field σij(χ, t) depending on position χ and time t will be called separable if the time-dependence enters only through a scalar multiplier; i. e., if σij(χ,t)=s(χ,t)σˆij(χ). It is shown here that elastic-plastic plane-strain solutions in the infinitesimal (flow) theory of plasticity satisfying Tresca’s yield criterion and associated flow rule with linear isotropic hardening, based on either equivalent plastic strain or total plastic work, can occur with separable stress fields only in the following instances: (a) solutions with uniaxial stress fields, as in bending, (b) solutions with stress fields such that the entire domain changes from elastic to plastic at the same time, and (c) solutions with stress fields for which the elastic-plastic boundary coincides with a principal shear stress trajectory. Whether or not a plasticity solution has a separable stress field can be determined a priori by examining the corresponding elasticity solution.

Stress update algorithm for non-associated flow metal plasticity

2012 ◽  
Vol 3 (2) ◽  
pp. 106-110
Author(s):  
Mohsen Safaei ◽  
Wim De Waele
Keyword(s):  
Plastic Strain ◽  
Yield Stress ◽  
Kinematic Hardening ◽  
Quadratic Function ◽  
Yield Function ◽  
Plastic Strain Rate ◽  
Isotropic Hardening ◽  
Flow Rule ◽  
Strain Rate Tensor ◽  
Incremental Change

. In this paper we present the continuum plasticity model based on non-Associated Flow Rule (nonAFR) for Hill’s48 quadratic yield function. In case of non-AFR, Hill’s quadratic function used as plasticpotential function, makes use of plastic strain ratios to determine the direction of effective plastic strain rate.In addition, the yield function uses direction dependent yield stress data. Therefore more accuratepredictions are expected in terms of both yield stress and strain ratios at different orientations. Weimplemented a modified version of the non-associative flow rule originally developed by Stoughton [1] intothe commercial finite element code ABAQUS by means of a user material subroutine UMAT. The mainalgorithm developed includes combined effects of isotropic and kinematic hardening [2]. This paper assumesproportional loading cases and therefore only isotropic hardening effect is considered. In our model theincremental change of plastic strain rate tensor is not equal to the incremental change of the compliancefactor. The validity of the model is demonstrated by comparing stresses and strain ratios obtained from finiteelement simulations with experimentally determined values for deep drawing steel DC06. A criticalcomparison is made between numerical results obtained from AFR and non-AFR based models.

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