自紧身管临界裂纹尺寸的概率断裂力学研究

Probabilistic Fracture Mechanics Analysis to Critical Crack Size of Autofrettaged Gun Barrel

基于概率断裂力学理论和MonteCarlo模拟方法,本文进行了自紧身管临界裂纹尺寸的可靠性研究。自紧身管内表面的疲劳裂纹考虑为半椭圆形式。裂纹尖端处的应力强度因子由内压和自紧残余应力共同产生。自紧残余应力采用了符合身管材料具有强化和包辛格效应性能推导的公式计算,它产生的应力强度因子通过权函数方法得到。根据断裂准则,可计算出自紧身管的临界裂纹尺寸。实例分析表明,对数正态分布为临界裂纹尺寸的最佳分布,同时给出了在各种置信度和可靠度下自紧身管的临界裂纹尺寸。

Based on probabilistic fracture mechanics theory and Monte Carlo simulation, a reliability analysis method for critical crack size of autofrettaged gun barrel is proposed, where the form of fatigue cracks in bore of autofrettaged gun barrel are considered as semi-elliptical cracks, and the stress intensity factors at the tip of crack are considered the sum of SIF under internal pressure and autofrettaged residual stress. The autofrettaged residual stress solution is suitable for gun barrel made of steel with strain hardening and bauschinger effect. The stress intensity factor under the autofrettaged residual stress is calculated with weight function method. According to fracture criterion, critical crack size of autofrettaged gun barrel is calculated. An evaluated example shows that lognormal distribution is the optimum for the sample of critical crack size, critical crack size of autofrettaged gun barrel under the conditions of different reliabilities and confidences are given.