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本文首先通过对试件表面和内部裂纹扩展情况不同的原因的分析指出,在疲劳裂纹扩展过程中,试件表面和内部裂纹扩展情况不同的本质是扩展速率不等,不是滞后问题;然后,通过直三点弯曲试件da/dN测试实验,指出由于表面与内部裂纹长度的差别而引起的ΔK误差是不可忽视的。因而需对表面直读法进行修正,并提出了简便易行的修正公式和修正方法。最后讨论了直三点弯曲试件在ds/dN测试中裂纹长度的合理取值范围。
This paper first analyzes the reasons for the different crack propagation on the surface and the interior of the specimen, and points out that in the process of fatigue crack growth, the difference between the crack propagation on the surface and the interior of the specimen is that the expansion rates are not equal and not the hysteresis. Then, The straight three-point bending test da / dN test experiment, pointed out that due to the difference between the surface and the internal crack length caused by the ΔK error can not be ignored. Therefore, it is necessary to correct the surface direct reading method and put forward a simple and easy correction formula and correction method. Finally, the reasonable value range of the crack length in ds / dN test of straight three-point bending specimens is discussed.