时间： 2017-07-08 来源： 信息员
应机械结构强度与振动国家重点实验室的邀请，约翰霍普金斯大学(Johns Hopkins University)机械工程系Jaafar A. El-Awady教授来访我院并作学术报告。
报告人： Jaafar A. El-Awady教授
报告题目： Evolution of Fatigue Microstructure and Crack Initiation in Ni and Ni-base
Prof. El-Awady is an Associate Professor of Mechanical Engineering at Johns Hopkins University (JHU). Dr. El Awady received his B.S. in 2001 and M.S. in 2003, with a major in Aeronautic and Astronautic Engineering from Cairo University, Egypt, and his Ph.D. in Aerospace Engineering from the University of California, Los Angles (UCLA) in 2008. Prior to joining JHU in 2010, Dr. El-Awady was a visiting scientist at the Wright Patterson Air Force Research Laboratory in Dayton Ohio. Dr. El-Awady’s research group focuses on developing multiscale simulation techniques, and microscale experiments to predict the underlying deformation, damage, and failure mechanisms in materials. Prof. El-Awady is the recipient of multiple awards including: the DARPA Young Investigator Program in 2012, the ASME Orr Early Career Award in 2014, and the National Science Foundation CAREER Award in 2015.
A fundamental understanding of fatigue mechanisms is essential to predict the usable life of engineering components in aerospace applications. While conventional bulk scale fatigue tests provide a way to quantify the fatigue life of materials, specific microstructural features that result in failure are difficult to ascertain. To overcome these limitations, here we will present the detailed results of the evolution of the dislocation microstructure in cyclically loaded Ni single crystals as predicted by large scale three-dimensional discrete dislocation dynamics simulations in Ni single crystals. In addition, we will also present a novel in situ, high frequency fatigue testing methodology to investigate crack initiation, propagation, fracture, fracture life, and the mechanical response of microcrystal Ni and Ni-based superalloy (Rene-N5) under different strain amplitudes. The crack initiation and propagation in the microcrystals is monitored by observing changes in the beam's dynamic stiffness and continuous scanning electron microscope (SEM) imaging.