高分子材料的极限断裂强度和破坏性能的研究——Ⅳ.等速拉伸下屈服强度动力学模型理论

STUDY ON THE ULTIMATE FRACTURE STRENGTH AND FRACTURE BEHAVIOR OF POLYMERIC MATERIALS——Ⅳ.A Kinetic MOdel Theory Of Yielding Under Constant Rate Extension

本文从高聚物结构多重性和形变不均一性出发,结合应力集中区的形变具有受迫高弹性和高弹性的动力学本质及分子运动松弛特征,将等速拉伸下的应力-应变关系式与应力集中链及断链动力学方程联系起来,推导出等速拉伸屈服状态方程,并讨论了屈服破坏机理。

The yielding phenomena of viscoelastic materials consist of three factors:1)the time dependence of the bulk stress-strain relation;2)the time dependence of the yield-ing initation mechanism;and 3)the kinetics of the molecular flow and bond rupture of theoverstressed polymer chains.Actually all three factors are frequently of simultaneousoccurence and it is diffcult to separate them.Based on the ideas of yielding phenomena,thetheory of Eyring reaction rate and the theory of rubber elasticity at large deformation,anew kinetic model theory of yielding for polymeric materials was proposed.A kinetic equa-tion for bond repture and molecular flow of overstressed polymer chains is established byusing the coefficient of overstressed polymer chains as a varible.After integraion and sim-plification a general state equation for yielding under constant rate extension was derivedfrom the theory.