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Investigation on yield behavior of 7075‑T6 Aluminum Alloy at Elevated Temperatures

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Chinese Journal of Mechanical Engineering 2020年第5期33卷 225-236页

作者： Jianping Lin Xingyu Bao Yong Hou Junying Min Xinlei Qu Zhimin Tao Jiajie Chen School of Mechanical Engineering Tongji UniversityShanghai 201804China Shandong Nanshan Aluminum Co. LtdShandong 265706China Pan Asia Technical Automotive Center Shanghai 202106China

Aluminum alloys have drawn considerable attention in the area of automotive *** strength aluminum alloys are usually deformed at elevated temperatures due to their poor formability at room *** this work,the yield behavior of 7075 aluminum alloy in T6 temper(AA7075-T6)within the temperature ranging from 25°C to 230°C was *** and biaxial tensile tests with the aid of induction heating system were performed to determine the stress *** curves and the yield loci of AA7075-T6 at elevated temperatures,*** Mises,Hill48 and Yld2000-2d yield criteria were applied to predicting yield loci which were compared with experimentally measured yield loci of the *** show that yield stress corresponding to the same equivalent plastic strain decreases with increasing temperature within the investigated temperature range and the shape of yield loci evolves nearly *** experimental yield locus expands with an increase of equivalent plastic strain at the same temperature and the work hardening rate of AA7075-T6 exhibits obvious *** nonquadratic Yld2000-2d yield criterion describes the yield surfaces of AA7075-T6 more accurately than the quadratic von Mises and Hill48 yield criteria,and an exponent of 14 in the Yld2000-2d yield function gives the optimal predictions for the AA7075-T6 at all investigated temperatures.

关键词： Aluminum alloy yield behavior Biaxial tensile test Warm condition

Three-dimensional dissipative stress space considering yield behavior in deviatoric plane

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Science China(Technological Sciences) 2013年第11期56卷 1999-2009页

作者： YAO YangPing CUI WenJie WANG NaiDong School of Transportation Science and Engineering Beihang University

Naturally deposited soils are always found in the complex three-dimensional stress *** models developed for modeling the three-dimensional mechanical behavior of soils should obey the basic laws of thermo-mechanical *** on the incremental dissipation function,a new deviatoric shift stress is derived and then introduced into the existing constitutive models to describe the yield behavior in the deviatoric plane for *** adopting the proposed shift stress,the relationship between dissipative stress tensors and true stress tensors can be ***,the threedimensional plastic strain can be calculated reasonably through the associated flow rule in the three-dimensional dissipative stress *** the same time,three methods that are conventionally adopted for generalizing constitutive models to model the three-dimensional stress-strain relationships are examined under the thermo-mechanical *** TS(transformed stress)method is shown to obey the thermo-mechanical rules and the TS space adopted in TS method is actually a translational three-dimensional dissipative stress ***,it is illustrated that the other two approaches,the method of using failure criterion directly and the method of using g()function,violate the basic rules of thermo-mechanical theories although they may bring convenience and simplicity to numerical analysis for geotechnical *** between model predictions and experimental data confirms the validity of the proposed three-dimensional dissipative stress space.

关键词： soils thermo-mechanics yield behavior shift stress stress space three-dimension

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Non‑associated and Non‑quadratic Characteristics in Plastic Anisotropy of Automotive Lightweight Sheet Metals

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Automotive Innovation 2023年第3期6卷 364-378页

作者： Yong Hou Junying Min Myoung‑Gyu Lee Department of Materials Science and Engineering and RIAM Seoul National UniversitySeoul 08826South Korea School of Mechanical Engineering Tongji UniversityShanghai 201804China

Lightweight sheet metals are highly desirable for automotive applications due to their exceptional strength-to-density *** accurate description of the pronounced plastic anisotropy exhibited by these materials in finite element analysis requires advanced plasticity *** recent years,significant efforts have been devoted to developing plasticity models and numeri-cal analysis methods based on the non-associated flow rule(non-AFR).In this work,a newly proposed coupled quadratic and non-quadratic model under non-AFR is utilized to comprehensively investigate the non-associated and non-quadratic characteristics during the yielding of three lightweight sheet metals,i.e.,dual-phase steel DP980,TRIP-assisted steel QP980,and aluminum alloy *** materials are subjected to various proportional loading paths,including uniaxial tensile tests with a 15°increment,uniaxial compressive tests with a 45°increment,in-plane torsion tests,and biaxial tensile tests using laser-deposited arm-strengthened cruciform *** show that the non-AFR approach provides an effective means for accurately modeling the yield behavior,including yield stresses and the direction of plastic strain rates,simultaneously,utilizing two separate functions and a simple calibration *** introduction of the non-quadratic plastic potential reduces the average errors in angle when predicting plastic strain directions by the quadratic plastic potential ***,for DP980,the average error is reduced from 3.1°to 0.9°,for QP980 it is reduced from 6.1°to 3.9°,and for AA5754-O it is reduced from 7.0°to 0.2°.This highlights the importance of considering the non-quadratic characteristic in plasticity modeling,especially for aluminum alloys such as AA5754-O.

关键词： yield behavior Non-associated flow rule Non-quadratic Lightweight sheet metal

Biaxial mechanical behavior of closed-cell aluminum foam under combined shear-compression loading

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Transactions of Nonferrous Metals Society of China 2020年第1期30卷 41-50页

作者： Zhi-bin LI Xue-yan LI Yu-xuan ZHENG College of Liberal Arts and Sciences National University of Defense TechnologyChangsha 410073China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

Combined shear-compression tests and simulations were performed on a closed-cell aluminum foam over a wide range of loading angles in order to probe their yield behaviors under biaxial loading *** shear-compression tests were carried out by using a pair of cylindrical bars with beveled *** yield surfaces were experimentally measured and compared with various theoretical yield surface *** cellular structures of closed-cell aluminum foams were modeled as tetrakaidecahedrons and their biaxial crushing behaviors were simulated by the finite element *** results show that,yield initiates from the stress-concentrated corners in the specimens under combined shear-compression loading and the stress distribution is no longer uniform at the specimen/bar *** the range of cell sizes studied,the larger the foam cell size is,the higher the yield stress *** foam density is found to be the dominant factor on its mechanical properties compared with the cell size and is much more significant in engineering practice.

关键词： combined shear-compression closed-cell aluminum foam yield surface biaxial loading yield behavior