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疲劳裂纹在残余压应力场中的扩展可藉助于裂纹闭合力来描述。采用板状试样相变温度下急冷以获得长程残余压应力场。应用动态测定法可同时测得裂纹闭合力和扩展速率。结果表明,残余压应力的最大值位置与扩展速率的最低值和闭合力的峰值所对应的裂纹长度基本相同。可以认为残余压应力提高了裂纹的闭合力,它使最小有效应力强度因子 K_(eff min)升高,从而减小了裂纹的扩展驱动力△K_(eff),这是裂纹扩展速率降低的主要原因。
The propagation of fatigue cracks in the residual compressive stress field can be described by means of the crack closure force. The plate specimen was quenched with phase transition temperature to obtain long-range residual compressive stress field. Applying the dynamic measurement method, the crack closing force and the expansion rate can be measured at the same time. The results show that the maximum compressive residual stress is basically the same as the crack length corresponding to the minimum value of the expansion rate and the peak value of the closing force. It can be considered that the residual compressive stress increases the closing force of the crack, which increases the minimum effective stress intensity factor K effmin and decreases the extended driving force ΔK eff of the crack, which is the main factor that reduces the crack growth rate the reason.