谱载荷下的短裂纹扩展规律及疲劳损伤的研究

GROWTH BEHAVIOUR OF SHORT CRACK AND FATIGUE DAMAGE UNDER SPECTRUM LOADING

本文研究了一种谱载荷作用下的短裂纹扩展规律，并对谱载荷下的疲劳损伤进行了预测与分析。实验发现：谱载荷下的单边穿透短裂纹和缺口短裂纹都能够在长裂纹的门槛值以下以较高的速率扩展，表现出与常幅下短裂纹相似的扩展规律．但谱载荷下的短裂纹扩展速率略低于常幅下的短裂纹扩展速率，谱载荷下长裂纹的扩展速率远低于常幅下长裂纹的扩展速率．利用特征值方法和常幅疲劳实验预测了冰载荷谱下的疲劳损伤，提出了预测冰载荷谱下的疲劳损伤较为合理的方法。

Study has been carried out of the growth behaviour of short crack under spectrum loading. Meanwhile,fatigue damage and life prediction under spectrum loading have also been made.The results show that both single─edge short cracks and short cracks from notchs under spectrum loading can propagate at higher rate below the long crack growth threshold,and indicate the same growth tendency as short cracks under constant amplitude test. However, short crack growth rate under spectrum loading is slightly lower than that of constant amplitude loading. Furthermore, growth rate for long crack under spectrum loading is even lower than that of constant amplitude loading. According to the statistical approach and the constant amplitude fatigue tests, the prediction for fatigue damage under ice spectrum loading has been made, and a reasonable method for fatigue damage under ice spectrum loading has been put forward.