应卢天健教授和航天航空学院邀请，美国Akron大学Gao Xiaosheng博士将来我校访问并开展学术交流。
报告时间： 2007年8月3日（星期五）下午3：00
报告地点： 教一楼南208（强度与振动教育部重点实验室会议室）
报告题目： Recent Developments on Modeling Ductile Fracture of Structural Materials

                          Abstract
Ductile fracture of many structural materials is a result of void nucleation, growth and coalescence, and it is well recognized that this material failure process depends strongly on the stress triaxiality, characterized by the ratio of the mean stress and the equivalent stress. We demonstrate through micromechanics analysis and experimental studies that the Lode angle, which can be related to the third invariant of the deviatoric stress tensor, also has significant effect on the ductile fracture process. A material failure criterion (void coalescence) is then expressed as a function of the stress triaxiality and the Lode angle (or the third invariant of the deviatoric stress tensor).

With the local material failure criterion established, two numerical approaches can be employed to simulate the ductile fracture process. In the first approach, voids are considered explicitly and modeled using refined finite elements. This approach provides a straightforward way to study the void growth mechanisms and the effects of material microstructure on fracture toughness. In the second approach, the void-containing material is considered as a homogenized continuum governed by porous plasticity models. This makes it possible to simulate extensive amount of crack propagation. As an example, a numerical approach is proposed to predict ductile crack growth in thin panels of a 2024-T3 aluminum alloy. Here, a modified Gologanu-Leblond-Devaux model is used to describe the evolution of void shape and void volume fraction and the associated material softening, and the material failure criterion is calibrated using experimental data. The calibrated computational model successfully predicts crack extension in various fracture specimens, including the compact tension specimen, middle crack tension specimens, multi-site damage specimens and the pressurized cylindrical shell specimen.

    报告人简介：高博士是美国Akron大学机械工程系的副教授，本科毕业于西安交通大学，1998年获布朗大学博士学位，1997－2000年在伊利诺斯大学Urbana校区作博士后研究，2001年至2006年担任美国Akron大学的助理教授，2006年至今担任Akron大学副教授，2002年获得美国海军青年学者奖。高博士共发表了33篇期刊论文和18篇会议论文，SCI他引300余篇次。