动态光弹性方法的主应力分离的研究

本文提出了动态光弹性、动态焦散线实验方法同边界元法结合的混合法，并用这种方法解决了动态光弹性主应力分离的问题，首先对现有的多火花高速摄影系统进行了改造，在动态实验过程中，成功地得到了不同瞬时的清晰的动态光弹性的等差线条纹和动态焦散线系列图像，这样，便可提取不同瞬时的边界应力值、全场主应力差值及边界上的外载。继而提出用Ｌａｐｌａｃｅ变换域上的边界元法来求解在冲击载荷作用下二维弹性模型全场的主应力和。最后，以受冲击载荷作用的圆盘为例，进行实验及边界元法计算，得到了分离的主应力场。

SEPARATION OF PRINCIPAL STRESSES IN DYNAMIC PHOTOELASTICITY

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.