学术活动

首页  > 学术活动

Cyclic Deformation and Fatigue of Magnesium Alloys

来源:牵引动力国家重点实验室  作者:吴东阁     日期:2017/5/24 15:25:55   点击数:729  

时间:2017-05-25 09:00--2017-05-25 11:00

地点:牵引动力国家重点实验室红楼218会议室

报告人:蒋炎尧

 



内容提要:

Magnesium is the fourth most common element on the Earth and is a green material due to its lightweight, nontoxicity, and recyclability. With two-thirds the density of aluminum, magnesium alloys are the lightest metals that can be used for load-bearing structures. A wrought magnesium alloy, either rolled or extruded, differs from a conventional metal in two major aspects: deformation twins and material anisotropy. The current presentation will cover characteristic cyclic deformation and fatigue behavior observed on several typical wrought magnesium alloys (AZ31B, AZ61A, AZ90, ZK60) under strain- and stress-controlled uniaxial, torsional, and combined axial-torsion loading. For a given loading path under the fully reversed strain-controlled condition, a distinguishable kink point in the strain-life fatigue curve demarcates the involvement of twinning-detwinning deformation. The influence of twinning is significant on fatigue behavior of a magnesium alloy when the loading amplitude exceeds the kink point. Twinning-detwinning in a magnesium alloy is often reflected in an asymmetric sigmoidal-shaped stress-strain hysteresis loop during cyclic loading.  As a result, there is a tensile or compressive mean stress, dependent on the material orientation, under fully reserved strain-controlled tension-compression loading. Cyclic twinning-detwinning deformation leads to significant cyclic hardening particularly under stress-controlled loading. Under pure shear loading, the stress-strain hysteresis loops are symmetric although twinning-detwinning occurs at high shear strain amplitudes. When a magnesium alloy is subjected to combined axial-torsion loading, asymmetric shear stress-shear strain hysteresis loops are observed due to alternative occurrence of twinning and detwinning with reversed axial stress. No nonproportional hardening is observed on the magnesium alloys but the fatigue life is reduced significantly under nonproportional loading as compared to that under proportional loading with the same equivalent strain magnitude. Material orientation- and amplitude-dependent cyclic deformation and fatigue behavior of magnesium alloys will be presented together with an assessment of the existing multiaxial fatigue criteria for the application to the magnesium alloys. The crack growth characteristics of magnesium alloys with the influence of twinning deformation and material anisotropy will be briefly discussed.

 

报告人简介:

Yanyao Jiang is Professor in the Mechanical Engineering Department at the University of Nevada, Reno (UNR).  He received his B.S. degree in Mechanical Engineering at the Northeast University in China in 1983, M.S. degree in Solid Mechanics from the Zhejiang University in 1996, and Ph.D. degree in the Department of Mechanical Engineering at the University of Illinois at Urbana-Champaign in 1993.  Professor Jiang has made significant contributions in cyclic plasticity, fatigue and fracture, rolling contact, and durability of bolted joints.  His research work has led to an understanding of the relationship between cyclic plasticity and fatigue failure. Professor Jiang has done pioneering research on the inhomogeneous cyclic plastic deformation and ratcheting deformation.  His approach for crack growth predictions bridges the crack initiation stage and the crack growth stage in fatigue research.

Professor Jiang is an ASME Fellow.  He was the recipient of the US NSF CAREER award, the Ford University Research Program, the Alexander von Humboldt Foundation Fraunhofer Bessel Research Award, and the Joint Research Fund for Overseas Chinese Young Scholars from the National Natural Science Foundation of China.  He served as an Associate Editor of the ASME Journal of Engineering Materials and Technology and is a member of the Editorial Board for the International Journal of Plasticity and the International Journal of Fatigue.

 

欢迎广大师生积极参听!

                                                                       


                                                                                                                                                                                                            主办:研究生院

                                                                                                                                                                                                            承办:牵引动力国家重点实验室

                                                                                                                                                                                                                                                                                                                                      力学与工程学院