透明聚碳酸酯材料疲劳断裂行为

研究不同应力比(R)以及退火处理对透明聚碳酸酯(PC)板材疲劳性能的影响规律与机理,并对聚碳酸酯疲劳裂纹扩展过程与机理进行分析。结果表明:退火后聚碳酸酯试样的残余应力明显变小,疲劳性能明显提高,这是由于机加工造成PC试样残余拉应力,而消除残余拉应力能够明显改善PC的疲劳性能;正应力比(拉拉疲劳)情况下,随着应力幅值变大,PC的疲劳性能明显下降,而负应力比(拉压疲劳)对PC的疲劳性能影响较为复杂。断口形貌分析表明,PC疲劳裂纹断口存在明显的裂纹源区、稳定扩展区与失稳区,而PC的疲劳裂纹扩展机理是首先在应力作用下产生银纹,当应力超过银纹中微纤维强度或在多次循环应力作用下疲劳而造成微纤维破坏时,银纹便发展为裂纹。

Fatigue Fracture Behaviors of Transparent Polycarbonate Materials

The effect of the different stress ratios (R) and annealing treatment on the fatigue properties of the transparent polycarbonate (PC) sheet and the mechanism behind were studied,the fatigue crack propagation (FCP) process and mechanism were analyzed.The results show that after annealing,the residual stress of the PC samples decreases obviously and the fatigue properties are greatly improved.This is because the machining process results in tensile stress in the PC samples,eliminating the tensile stress can improve the fatigue property of PC effectively;under the positive stress ratio (tensile-tensile fatigue),as the stress amplitude increases,the fatigue properties of PC decreases obviously,however,the negative stress ratio (tensile-compression fatigue) causes complex influence on the fatigue properties of PC.The fatigue fracture morphology suggests that distinct crack source,stable crack extension zone and instability zone exist obviously in fatigue fracture of PC.The mechanism of the fatigue crack propagation of PC indicates that crazes are initiated at first under the cycling stress,when the stress is higher than the strength of the fibrils in crazes or the fibrils are broken under the cycling stress,crazes develop into cracks.