Associate Professor, Vice Dean of State Key Laboratory of Traction Power, Southwest Jiaotong University, China

Biography: Bing Yang received his Ph.D. from Southwest Jiaotong University, Chengdu, China in 2011. He then worked as an Associate Professor in State Key Laboratory of Traction Power (TPL) at Southwest Jiaotong University. He is currently the vice dean of TPL and has published more than 50 research papers. He also serves as a reviewer for many journals such as International Journal of Fatigue, Materials and Design. His major research interests involve strength theory of vehicle structures, fatigue and fracture of materials etc.

Speech Title: Study on Short Fatigue Crack Behavior of LZ50 Steel under Non-Proportional Loading

Abstract. The low cycle fatigue tests using replica technique for LZ50 steel under non-proportional cyclic loading were carried out, and eight groups of effective test data were obtained. The evolution behavior of short cracks was studied based on the effective short crack criterion. The results show that short fatigue cracks generally originate in the grain or along the grain boundary. At the microstructural short crack stage, the crack propagation is affected strongly by the microstructure of the material, and the growth rate of short crack slows down for several times according to the number of grain boundary obstacles encountered. At the physical short crack stage, the crack propagation overcomes the microstructural constraints after breaking through the banded structure of pearlite. Thus, the dominant effective short fatigue crack is formed and the crack growth rate increases rapidly. Furthermore, on the basis of critical plane criterion, four commonly-used crack growth models were compared. It is found that the predicted crack growth rates using FS model or CBC model are less dispersive than that using Tomkins model or SWT model, and the predicted life calculated by the first two models is closer to the test data.

Keywords: LZ50 steel; replica test; non-proportional loading; critical plane criterion