Abstract: A new and effective method that is used to separate the transient prin-cipal st resses for dynamic photoelast ic ity was. prop osed.This is a hybrid met ho d combin-ing the optical method of dynamic caustics and the boundary element numerical method.Firstlyt a modified Cranz-Schardin spark camera is presented to record simultaneously theisochromatic fringe patterns of photoelasticity and the shadow spot patterns in the dynamicprocess. By means of the isochromatic fringe patterns,the difference between trans...