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根据线弹性断裂力学基本理论,分别讨论了由位移法和能量法确定裂纹尖端应力强度因子的具体步骤;计算分析了试件在承受超声疲劳载荷(R=-1)和超声疲劳载荷叠加平均应力(R>-1)两种情况下的应力强度因子随裂纹长度变化的关系.分析结果表明,应用能量法研究确定超声疲劳载荷下的裂纹尖端应力强度因子,具有简明和计算精度高等突出优点,并能正确描述疲劳裂纹扩展对固有振动模态影响的规律.还实验研究了钛合金的疲劳裂纹扩展行为及超声疲劳载荷下的裂纹扩展机理.
According to the basic theory of linear elastic fracture mechanics, the concrete steps of determining the stress intensity factor of crack tip by the displacement method and the energy method are respectively discussed; and the average stress of ultrasonic fatigue load (R = -1) and superposition of ultrasonic fatigue load (R> -1), the relationship between the stress intensity factor and the crack length is analyzed.The results show that the stress intensity factor at the crack tip under ultrasonic fatigue loading is studied by the energy method, which has the outstanding advantages of conciseness and high accuracy of calculation, And can correctly describe the rule of the fatigue crack propagation on the natural vibration modal.It is also studied experimentally that the fatigue crack propagation behavior of titanium alloy and the crack propagation mechanism under ultrasonic fatigue load.