超声疲劳裂纹扩展与摩擦生热研究

在高频循环载荷作用下,材料疲劳裂纹的萌生与扩展过程伴随着明显的温度变化,该温度变化反映材料内部结构的损伤特征。通过20 kHz的超声疲劳试验,研究一种碳锰钢在超高周疲劳加载条件下的内部疲劳裂纹萌生与扩展过程中温度的演化过程。通过对该材料在疲劳损伤过程中,内部裂纹间的摩擦生热机理分析,从微观角度出发,结合分形理论,建立内部裂纹微观结构的摩擦模型,数值模拟超声疲劳过程中材料内部疲劳裂纹面间的摩擦生热情况,并定量地计算该过程中由裂纹间摩擦所导致的温度上升,将模拟结果与试验结果进行比较。探究高频疲劳载荷下微裂纹扩展与摩擦生热的关系,并结合超高周疲劳裂纹扩展公式,建立超声疲劳过程中的裂纹扩展与裂纹面温度演化关系的模型。

Research on Propagation and Frictional Heat of Crack in Ultrasonic Fatigue Loading

The initiation and propagation of the fatigue crack coupled with slightly temperature evolution under high frequency cyclic loading. The evolution of temperature reflects the characteristics of fatigue damage. The evolution of temperature during the initiation and propagation of internal crack in a kind of carbon manganese steel under very high cycle fatigue loading is observed by the 20 kHz ultrasonic fatigue test. A friction modeling of micro-structure of internal fatigue crack is introduced based on heat analysis of internal crack friction during the fatigue damage process of material. Numerical simulation of the friction of internal crack is presented with the fractal theory at the micro scale, and the frictional heat of the process is calculated. The comparison of simulation results with experiment result is presented. The relationship between the micro-crack propagation and frictional heat is discussed. A model of the relationship between crack propagation and temperature evolution of crack surface in ultrasonic fatigue is constructed with considering of the Paris-Hertzberg-McClintock crack growth rate law.