梯形交变加载作用下聚碳酸酯的应变与寿命

STUDY ON THE STRAIN AND BREAKING LIFE OF POLYCARBONTE UNDER TRAPEZOIDAL WAVE LOAD

对聚碳酸酯在交变 持久载荷复合作用下应变与寿命研究表明 ,其疲劳 蠕变曲线与纯蠕变曲线十分相似 .加载时间周期越短和交变载荷变化越频繁 ,普弹应变阶段的斜率和应变越小 ,进入延迟弹性变形的平台应变阶段越早 .随每一次循环中的最大载荷加载保持时间延长 ,聚碳酸酯断裂寿命减小 .以最大载荷为恒载荷一直加载的纯蠕变曲线 ,平台最高 ,断裂时间最早 .而最大载荷加载作用时间为 0的纯疲劳曲线 ,平台最低 ,断裂时间最迟 .在交变 持久载荷复合作用下聚碳酸酯存在疲劳和蠕变的交互损伤 ,其断裂寿命N Nf 和 ∑t tr比纯疲劳或纯蠕变的断裂寿命低 ;断裂寿命减小 .并且 ,疲劳 蠕变的交互损伤程度与温度密切相关 .聚碳酸酯在较低温度的疲劳 蠕变交互损伤作用大于较高温度的交互损伤作用 .随温度升高 ,疲劳

The strain and breaking life of polycarbonate under loading of trapezoidal wave shape were investigated for analysing the behavior of polymers under the co\|act ion of cyclic and constant loadings.It was found that the fatigue/creep curv es u nder trapezoidal loading are similar to the pure creep curves under constant loa ding.A strain platform was observed before the break of the samples.With increas ing the time len gth of maximum load in each cycle the platform strain value increases,and the br eak life decreases.Under trapezoidal loading the break life of polycarbonate wa s not simply determined by the contributions of pure creep and pure fatigue,and a term reflecting the co\|action of the two demage types should be considered.Th e co\|action term is more evident at low temperature.A decrease of breaking life of the samples was observed with raising temperature and was explained as the r esult of increase of individual effects of pure creep or pure fatigue.