Papers by Author: Yong Jin Guo

Abstract: The influence of forming condition on crash performance of thin-walled structures is investigated, in which high strength low alloy steel HSLA340 and dual phase steel DP590 are considered. Stamping and knife-edge-bending process were carried out respectively to form hat channels, and then, impact tests were performed on the spot-welded top-hat sections subjected to quasi-static and dynamic axial loading conditions to identify the forming effect on the crashworthiness. Regular progressive buckling (quasi-inextensional mode) was observed for knife-edge-bent specimens, while the stamped specimens showed peculiar collapse mode, especially, global instability existed for all the specimens under dynamic impacting and their energy absorption capacity was significantly reduced. The result demonstrates that for accurate assessing the structural performance detailed stamping history of sheet metal components should be taken into consideration.

Abstract: The cell model with twenty-five random dispersion voids was employed to analyze the damage and fracture mechanism of the nodular cast iron. The results show that the growth velocity of the voids has obvious difference with each other due to the random dispersion of voids. In the early stage of the deformation, the growth of the voids is mainly determined by the distance of the voids since the triaxiality stress parameter of the matrix around the voids is approximately equal. With the increase of the triaxiality stress parameter of the matrix materials around the void, the evolution velocity of the voids increases quickly. At the same time, this will influence the neighboring voids to grow quickly. The chain reaction of the rapidly increase of voids lead to the final material failure. The results can explain the fracture appearance of the smooth bar specimens under uniaxial tensile load really.