用光塑性方法确定工程构件的疲劳裂纹扩展荷载门槛值

Determination of the Threshold Value for Fatigue Crack Extension Load by Photo Plasticity Method

提出疲劳裂纹尖端塑性核半径门槛值Ｒｔｈ的概念及计算方法，Ｒｔｈ是材料性质。在满足光塑性相似关系要求及模型与原型几何形状尺寸相同的前提下，模型与原型间的相似系数ｎ为两种材料屈服极限之比。鉴于疲劳裂纹扩展的机理分析并不涉及惯性力和冲击效应，在偏光仪上测出模型裂纹尖端的塑性核尺寸达到原型材料的Ｒｔｈ时所受的静载值。

In this paper, a concept for the radius of plastic core at the top of a fatigue crack is raised. It is shown that by examining this radius of plastic core for a model at static load with a polarizing optical instrument, the threshold value of the fatigue crack extension load for the prototype of a engineering part can be deduced on the basis of similarity law.