SEPARATION OF PRINCIPAL STRESSES IN DYNAMIC PHOTOELASTICITY
动态光弹性方法的主应力分离的研究

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 transient prin-cipal stresses in the whole domain and the principal stresses along the free boundary can besolved.In addition,the method of caustics is a very powerful technique for measuring theconcentrative load.Then,the sum of the principal stresses is calculated by the boundaryintegral equation which is derived from the Laplace integral transform of the wave equation.So,the transient principal stresses can be determined from the experimental and numericalresults. As an example,the transient principal stresses in a polycarbonate disk under animpact load is resolved.