关键词: 孔边角裂纹, 门槛值, 近门槛区疲劳裂纹扩展

Abstract:

Based on the features of the three-dimensional crack, an experimental method was presented to measure the near-threshold fatigue crack growth rate and threshold of the corner crack at a hole. In order to get the actual crack shape variable law, this paper firstly established the “b-a” demarcated curve for the particular specimen by the marking-line method- Refer to the standrd test method on Threshold, We just directly measured the crack size of “a” direction, the crack size of “b” direction could be calculated by the demareated curve. Then we could get two set of data separately for “a” and “b” , which represent characteristic directions of the crack. Through the experimental studies for 30CrMaSiNi2A and 2024T3 material, the method used in this paper was proved available. On the basis of test data, this paper have carried out statistical comparisons between results, and concluded: 1. the near-threshold fatigue crack grouth rates and thresholds for “a” and “b”are essentially coincident; 2. different diameters of the holes make no difference to results; 3. With the same thickness, the near-threshold fatigue crack growth rate of a specimen with the coruer-crack at a hole is higher than that of a CT Specimen, but the threshold is less.

Key words: Corner crack at the hole, Threshold, Near-threshold, fatigue crack propaga- tion