用光弹性法测定复合应力强度因子

工程结构裂纹尖端应力强度因子(SIF)由于形状、荷载的复杂性及边界条件的不确定性,难以用解析法得到,数值计算也有困难,而光弹性法弥补了上述方法的不足。本文用环氧树脂制作圆轴模型,采用机加工的方法制作圆轴模型裂纹,然后将加载模型进行应力冻结,通过光弹性实验研究分析了圆轴裂纹尖端应力分布。由于带环形裂纹的圆轴在弯扭组合变形时,离中性轴最远的裂纹尖端处于复合裂纹状态,而三维光弹性应力冻结法是测定复杂三维问题复合裂纹的有效方法。本文用双参数法测定I型应力强度因子,用切片逐次削去法测定Ⅲ型应力强度因子,实验误差较小。

Photoelastic Method for Determination of Mixed-mode Stress-intensity Factors

In engineering structures, it is difficult to determine stress-intensity factor at crack tip with analytic method and sometime also difficult with numerical method because of complexity of shape and load as well as no determinability of boundary condition. However photoelastic method remedies these deficiencies. In this paper, a cylindrical bar was made with epoxy resin, a crack in the cylindrical bar model was prepared with mechanic process, and the stress was frozen after loading the model. Photoelastic method was used to analyze stress distribution around the crack tip of the cylindrical bar. When a cylindrical bar with cyclical crack is subjected to bending and torsion, the crack top far away from the median axis of the cross section is in a situation of mixed-crack. The three-dimensional photoelastic stress-frozen method is an effective method for determination of complex threedimensional question. In this paper, the two-parameter method was used for determination of I mode stress-intensity factor and a slice cutting step-by-step method was used for determination of HI mode stress-intensity factor. The error of results is small.