高分子材料的极限断裂强度和破坏性能的研究——Ⅱ.蠕变持久强度的动力学模型理论

A STUDY ON THE ULTIMATE FRACTURE STRENGTH AND FRACTURE BEHAVIOR OF POLYMERIC MATERIALS——Ⅱ.A KINETIC MODEL THEORY OF CREEP TENSILE STRENGTH

本文对当前蠕变持久强度的表征进行了系统总结,指出了它是高分子材料的可形变性、分子链应力集中情况和应力集中链断链滑移动力学三者统一的体现。基于这种破坏概念,推导出一种能表征半晶态、玻璃态和弹性体等聚合物的蠕变持久强度动力学模型理论和一般化断裂状态方程。当该方程引入一、二级近似条件后,该式就分别还原为准脆性状态下粘弹性蠕变断裂方程,受迫高弹性状态下蠕变断裂方程和高弹性状态下蠕变断裂方程。

The failure phenomena of viscoelastic materials consist of three factors:1)the time dependences of the bulk stress-strain relation;2)the time dependences of the fail-ure initation mechanism-the formation of overstressed polymer chains in local plastic are-as;and 3)the kinetics of the molecular flow and bond rupture of the overstressed polymerchains.Actually both three factors are freguently of simultaneous occureuce and it is diffi-cult to separate them.Based on the ideas of failure phenomena,the theory of Eyring reac-tion rate and the theeory of rubber elasticity at large deformations,a new kinetic modeltheory of creep tensile strength for polymeric materials was proposed.A kinetic equationfor bond rupture and molecular flow of overstressed polymer chains is established by usingthe coefficient of overstressed polymer chains as a variable.After integration and simplifi-cation a general relationship among the tensile strength at the ultimate elongation,tempera-ture and the parameters of structure was derived from the theory.Taking the first and sec-ond approximation the general equation reduces,respectively,to the realtion of Zhurkov,Bartenew and Larson-Miller.