用夏比冲击试验评估低周疲劳损伤程度

损伤力学给予我们评估材料的损伤程度及预测剩余寿命以有力的理论依据和手段。但是 ,评估材料损伤程度的损伤参量的确定却是比较困难的。人们对疲劳过程中材料的微观组织结构变化已进行了大量的表象的研究 ,但是这些变化与材料损伤程度之间的关系却是不很明确的 ,特别是由驻留滑移带转化为微观裂纹这一阶段。作者采用不同程度的低周疲劳后再进行冲击试验的方法 ,可以从冲击试验的载荷 挠度曲线及扫描电镜断口照片上清晰地看到随着低周疲劳损伤程度的增加 ,沿晶断裂及二次裂纹的百分数增加 ,并且由此导致了撕裂功的增加。所以 ,对于低周疲劳损伤程度的评估 ,可以用冲击韧性试验再配合以扫描电镜断口分析的方法来获得。

EVALUATION OF LOW CYCLE FATIGUE DAMAGE BY CHARPY IMPACT TESTING

The damage mechanics provides us a better means to evaluate the damage degree and the remaining lifetime of materials. But the damage parameters are very difficult to choose since they must be sensitive, measurable and reproducible. For fatigue damage, plenty research work on phenomenological observations by optical and electron microscope has been done. But the dislocation structure changes are not closely related to the macro-property changes of materials. In the present paper, the charpy impact test was introduced to characterize the damage degree of low cycle fatigue of materials by means of the tearing energy variation and the fraction variation of brittle fracture on the broken surface in SEM.