不锈钢在扭转／拉伸复合载荷下近门槛值的疲劳裂纹扩展行为

NEAR-THRESHOLD FATIGUE CRACK PROPAGATION IN STAINLESS STEEL UNDER COMBINED TORSION AND TENSION

研究了带环状预裂纹的奥氏体不锈钢圆棒试样在循环扭转／拉伸复合载荷下,门槛值附近的疲劳裂纹扩展行为,分析了复合加载时不同载荷比对裂纹扩展的影响,对裂纹扩展的初始阶段进行了详细研究,用应力强度因子表征了裂纹扩展开始的门槛值,提出了椭圆方程表达的疲劳裂纹扩展开始的门槛值模型,该方程可在裂纹尖端位移准则的基础上导出,疲劳裂纹扩展停止的门槛值条件也可用椭圆方程表达。

Near-threshold fatigue crack propagation tests were conducted under combined torsion and tension on a circumferentially pre-cracked round bar of an austenite stainless steel. The propagation behavior was studied extensively under various combinations of cyclic loads. The threshold condition of fatigue crack extension was expressed by a quarter-elliptic function in terms of the stress intensity factor ranges for mode I and III. The equation can be derived on the basis of the crack-tip displacement criterion. The threshold condition for fracture is also expressed by another quarter-elliptic function.