Crack Propagation in the Power-Law Nonlinear Viscoelastic Material

An analysis on crack creep propagation problem of power-law nonlinear viscoelastic materials is presented, The creepincom pressibility assumption is used,To simulate fracture behavior of craze region, it is assumed that in the fracture process zone near the crack tip, the cohesive stress б_f acts upon the crack surfaces and resists crack opening. Through a perturbation method, i, e.,by superposing the Mode-I applied force onto a referential uniform stress state, which has a trivial solution and gives no effect on the solution of the original problem,the nonlinear viscoelastic problem is reduced to linear problem, For weak non-linear materials, for which,the power-law ind,ea n≌1, the expressions of stress and crack surface displace went are derived. Then, the fracture process zone local energy criterion is proposed and on the basis of which the for mulae of crac-king incubation time t^* and crack slow propagation velocity a are derived.