拉伸作用下轴疲劳长裂纹扩展寿命分析

Analysis of the propagation life of shaft′s fatigue long crack under tension

考察了拉伸作用下不同类型表面裂纹模型(圆弧裂纹、椭圆裂纹和直裂纹)应力强度因子对轴疲劳长裂纹扩展寿命的影响,认为在计算具有表面裂纹轴类构件的疲劳寿命时,把裂纹处理为受深度比、纵横比2参数控制的椭圆裂纹比处理为仅受深度比控制的圆弧裂纹和直裂纹更加合理。在计算过程中,针对断裂韧度、裂纹扩展速率参数等的不确定性,按照它们各自的随机分布特征,应用Monte Carlo法分别对其进行抽样,采用Paris公式计算了轴寿命。

Varies types of surface cracks were taken into consideration, such as circular arc crack, elliptical crack and straight-edged crack. The influence of stress intensity factor to the shaft＇s fatigue long crack propagation life was studied. The conclusion gained through the analysis of the result shows when calculating the fatigue life of a shaft with surface crack, it＇s better to take the defect as an elliptical crack governed by two parameters, depth ration and aspect ration than circular arc crack or straight-edged crack governed only by depth ration. During the process of calculating, attention was paid to fracture toughness and crack propagation speed＇s randomicities, according to their distribution character, Monte Carlo numerical calculating method was used to sample and Paris formula was adopted to obtain the shaft＇s fatigue life.