Papers by Author: Li Ping Du

Abstract: From the aspect of the fastest exit speed of the ball and through the collision model of mechanics, we analyzed the best hitting point which results in the fastest exit speed of the ball and the change of the best hitting point. Based on this model, we gave a very practical definition of the sweet spot, and we also found out the effect of the baseball bat’s material on the sweet spot. The distances from the best hitting point to the end of the baseball bat result from the three different materials, which are the bat’s original material, aluminum and the corked material. Through the sensitivity analysis, three parameters affecting the hitting position resulting in the ball’s fastest exit speed are the weight of the bat, the center of mass and the moment-of-inertia. In the process of the three parameters’ calculation, the infinitesimal method is used. As can be found out that the length of the sweet spot results from the corked and the aluminum are much longer than results from the original material. The longer the length of sweet spot, the possibility that the hitter hits the fast ball is higher. Also ball hit by the aluminum bat is faster than that hit by the bat made out of the original material. The above analysis can explain that why the aluminum bat and corked bat are prohibited by Major League Baseball

Abstract: For the structure failure of pressurized cylindrical shell under laser irradiation, studied with axial semi-elliptical surface crack of cylindrical shell under the combined action of laser radiation and pressure, analysis of its thermal force coupling of stress and material for the 30CrMnSiA steel. According to of static fracture toughness and based on theof estimated impact dynamic fracture toughness, the application of finite element method to study the fracture problem under dynamic load. Analyzing the crack initiation propagation and static dynamic initiation based on fracture criterion and dynamic fracture criterion for crack initiation propagation, provides a useful research of the analysis to a certain extent on the structure in thermal force coupling failure mechanism.