scholarly journals A Study on Compressive Anisotropy and Nonassociated Flow Plasticity of the AZ31 Magnesium Alloy in Hot Rolling

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Guoqiang Wang ◽  
Xiaolei Qian ◽  
Xuefei Li ◽  
Haijing Hou ◽  
Yi Liu ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Constitutive Model ◽  
Hot Rolling ◽  
Yield Function ◽  
Lateral Spread ◽  
Az31 Magnesium Alloy ◽  
Flow Rule ◽  
Strip Rolling ◽  
Satisfactory Description ◽  
Plastic Deformation Behavior

Effect of anisotropy in compression is studied on hot rolling of AZ31 magnesium alloy with a three-dimensional constitutive model based on the quadratic Hill48 yield criterion and nonassociated flow rule (non-AFR). The constitutive model is characterized by compressive tests of AZ31 billets since plastic deformations of materials are mostly caused by compression during rolling processes. The characterized plasticity model is implemented into ABAQUS/Explicit as a user-defined material subroutine (VUMAT) based on semi-implicit backward Euler's method. The subroutine is employed to simulate square-bar rolling processes. The simulation results are compared with rolled specimens and those predicted by the von Mises and the Hill48 yield function under AFR. Moreover, strip rolling is also simulated for AZ31 with the Hill48 yield function under non-AFR. The strip rolling simulation demonstrates that the lateral spread generated by the non-AFR model is in good agreement with experimental data. These comparisons between simulation and experiments validate that the proposed Hill48 yield function under non-AFR provides satisfactory description of plastic deformation behavior in hot rolling for AZ31 alloys in case that the anisotropic parameters in the Hill48 yield function and the non-associated flow rule are calibrated by the compressive experimental results.

scholarly journals Application of an Evolving Non-Associative Anisotropic-Asymmetric Plasticity Model for a Rare-Earth Magnesium Alloy

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1013 ◽  
Author(s):  
Armin Abedini ◽  
Cliff Butcher ◽  
Michael Worswick
Keyword(s):  
Plastic Deformation ◽  
Rare Earth ◽  
Magnesium Alloy ◽  
Constitutive Model ◽  
Magnesium Alloys ◽  
Yield Function ◽  
Flow Rule ◽  
Proportional Loading ◽  
Plastic Potential ◽  
Stress States

Magnesium sheet metal alloys have a hexagonal close packed (hcp) crystal structure that leads to severe evolving anisotropy and tension-compression asymmetry as a result of the activation of different deformation mechanisms (slip and twinning) that are extremely challenging to model numerically. The low density of magnesium alloys and their high specific strength relative to steel and aluminum alloys make them promising candidates for automotive light-weighting but standard phenomenological plasticity models cannot adequately capture the complex plastic response of these materials. In this study, the constitutive plastic behavior of a rare-earth magnesium alloy sheet, ZEK100 (O-temper), was considered at room temperature, under quasi-static conditions. The CPB06 yield criterion for hcp materials was employed along with a non-associative flow rule in which the yield function and plastic potential were calibrated for a range of plastic deformation levels to account for evolving anisotropy under proportional loading. The non-associative flow rule has not previously been applied to magnesium alloys which require the use of flexible constitutive models to capture the severe anisotropy and its evolution with plastic deformation. The non-associative flow rule can provide the required flexibility by decoupling the yield function and plastic potential. For the associative flow rule, such flexibility can only be achieved by multiple linear transformations of the stress tensor resulting in expensive models for calibration and simulations. The constitutive model was implemented as a user material subroutine (UMAT) within the commercial finite element software, LS-DYNA, for general 3-D stress states along with an interpolation technique to consider the evolution of anisotropy based upon the plastic work. To evaluate the accuracy of the implemented model, predictions of a single-element model were compared with the experimental results in terms of flow stresses and plastic flow directions under various proportional loading conditions and along different test directions. Finally, to assess the predictive capabilities of the model, full-scale simulations of coupon-level formability experiments were performed and compared with experimental results in terms of far-field load-displacement and local strain paths. Using these experiments, the constitutive model was evaluated across the full range of representative stress states for sheet metal forming operations. It was shown that the predictions of the model were in very good agreement with experimental data.

SUPERPLASTIC FORMABILITY OF AZ31 MAGNESIUM ALLOY SHEETS PRODUCED BY TWIN ROLL CASTING AND SEQUENTIAL HOT ROLLING

2013 ◽  
Vol 27 (19) ◽  
pp. 1341020
Author(s):  
YANDONG YU ◽  
KAI LIN ◽  
PENG JIANG
Keyword(s):  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Hot Rolling ◽  
Tensile Testing ◽  
Az31 Magnesium Alloy ◽  
Twin Roll Casting ◽  
Roll Casting ◽  
Three Stages ◽  
The Common ◽  
Twin Roll

In this paper, superplastic tensile testing and gas bulging forming of AZ31 and AZ31 + Y + Sr magnesium alloys produced by twin roll casting (TRC) and sequential hot rolling were carried out. At 673 K, the superplastic formability of the TRC AZ31 magnesium alloy sheets added Y and Sr elements has improved significantly compared to the common TRC AZ31 sheets. Formations of cavities on the bulging part go through three stages of the nucleation, growth and aggregation, finally cavities merging lead to rupture at the top of the bulging part.

scholarly journals Non-orthogonal elastoplastic constitutive model for sand with dilatancy

2021 ◽  
Author(s):  
Jingyu Liang ◽  
Dechun Lu ◽  
Xiuli Du ◽  
Wei Wu ◽  
Chao Ma
Keyword(s):  
Constitutive Model ◽  
Plastic Flow ◽  
Flow Direction ◽  
Model Performance ◽  
Yield Function ◽  
Flow Rule ◽  
Shear Process ◽  
Hardening Parameter ◽  
Elastoplastic Constitutive Model ◽  
Plastic Flow Rule

A non-orthogonal elastoplastic constitutive model for sand with dilatancy is presented in the characteristic stress space. Dilatancy of sand is represented by the direction of plastic flow, which can be directly determined by applying the non-orthogonal plastic flow rule to an improved elliptic yield function. A new hardening parameter is developed to describe the contractive and dilative volume change during the shear process, which is co-ordinated with the non-orthogonal plastic flow direction. The combination of the non-orthogonal plastic flow rule and the proposed hardening parameter renders the proposed model with the ability to reasonably describe the stress-strain relationship of sand with dilatancy. The model performance is evaluated by comparing with the experimental data of sand under triaxial stress conditions.

scholarly journals The modified temperature term on Johnson-Cook constitutive model of AZ31 magnesium alloy with {0002} texture

2020 ◽  
Vol 8 (1) ◽  
pp. 172-183 ◽  
Author(s):  
Feng Zhang ◽  
Zheng Liu ◽  
Yue Wang ◽  
Pingli Mao ◽  
Xinwen Kuang ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Constitutive Model ◽  
Az31 Magnesium Alloy

scholarly journals A Thermodynamic Constitutive Model for Saturated Sand

Entropy ◽  
2019 ◽  
Vol 21 (2) ◽  
pp. 136
Author(s):  
Shize Xiao ◽  
Xiaohui Cheng ◽  
Zhou Yang
Keyword(s):  
Constitutive Model ◽  
Soil Mechanics ◽  
Constitutive Models ◽  
Yield Function ◽  
Flow Rule ◽  
Saturated Sand ◽  
Coupling Energy ◽  
Dissipative Mechanism ◽  
Nonlinear Elastic ◽  
Undrained Shear

This paper establishes a non-equilibrium thermodynamic constitutive model that can predict the undrained shear behavior of saturated sand. Starting from the basic laws of thermodynamics, the model does not require the classical concepts in elasto-plastic models, such as the yield function, the flow rule, and the hardening rule. It is also different from the existing thermodynamic constitutive models in soil mechanics literatures. The model does not use a complex nonlinear elastic potential as usually and introduces a coupling energy dissipative mechanism between the viscosity and elasticity relaxation, which is essential in granular materials. Then this model was used to simulate the undrained shear test of Toyoura sand. The model can predict the critical state, dilatancy-contraction and hardening-softening characteristics of sand during undrained triaxial shearing.

Hot Rolling of AZ31 Magnesium Alloy to Sheet Gauge

2006 ◽  
Author(s):  
Elhachmi Essadiqi ◽  
Claude Galvani ◽  
Javaid Amjad ◽  
Guowu Shen ◽  
Kevin Spencer ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Hot Rolling ◽  
Az31 Magnesium Alloy
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