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本文提出用带表面裂纹的试样来显示氯化及滚压试样的表面强化层的疲劳裂纹扩展抗力并解释和近似处理了半椭圆表面裂纹及其折回(Turn Back)现象。试验结果表明在裂纹扩展速率10~(-4)～10~(-5)mm/周范围内,氮化及滚压均提高弯曲载荷下的疲劳裂纹扩展抗力,且滚压效果优于氮化处理,而氮化试样表面的白层对疲劳抗力影响甚微。试验结果还表明其试验范围内(0.19<α/2c<0.38),半椭圆表面裂纹长轴端应力强度因子与短半轴无关。与传统的试验方法相比,这是显示表面强化层疲劳裂纹扩展抗力的有效方法,可以应用于其他表面强化层性能测试上去。
In this paper, the fatigue crack growth resistance of the surface strengthened layer of chlorinated and rolled specimens is demonstrated by the specimens with surface cracks and the semi-elliptical surface cracks and their turn-back phenomena are explained and approximated. The results show that both the nitriding and rolling increase the fatigue crack propagation resistance under flexural load and the rolling effect is better than that of nitriding at the crack growth rate of 10 -4 to 10 -5 mm / While the white layer on the surface of the nitrided sample has little effect on the fatigue resistance. The experimental results also show that within the experimental range (0.19 <α / 2c <0.38), the stress intensity factor at the long axis of the semi-elliptical surface crack has nothing to do with the short axis. Compared with the traditional test methods, this is an effective method to show the fatigue crack propagation resistance of the surface strengthened layer and can be applied to other surface strengthening layer performance tests.