Dynamic toughness in elastic nonlinear viscous solids
The paper presents a micromechanical model proposed for void growth in a nonlinear viscous material used to study the dynamic fracture toughness in amorphous polymeric materials. It is proposed that the primary mechanism of crack propagation is rate-dependent void growth. The model is employed to simulate quasi-static steady crack growth in a homogeneous elastic nonlinear viscous solid under small-scale yielding conditions. First, the authors formulate the boundary value problem for dynamic steady crack growth of mode I under plane strain and small-scale yielding by assuming the growth and coalescence of pre-existing microvoids. The material model considers a microporous strip of elements that forms a fracture process zone (FPZ). Then for plane strain analysis of a semi-infinite crack propagating at constant velocity under mode I loading, the authors describe a solution method and an iterative finite element procedure adopted to solve the steady-state problem. The steady-state growth is a dissipative process caused by the intrinsic toughness defined by the work of separation in the FPZ and by the extrinsic toughening contribution from energy dissipation in the background material. The paper offers some insights into the relationships between dynamic fracture toughness and crack velocity. In one regime the dynamic fracture toughness can be a decreasing function of crack velocity. In another regime, it can be an increasing function of crack velocity. Both regimes can be found in the same material at different crack velocities. The existing competition is discussed in the framework of two computational models: (i) elastic background material with rate-dependent process zone, and (ii) rate-dependent background material and process zone. At low crack velocity, inelastic dissipation in the background material dominates over the work of separation and kinetic energy decreasing toughness with crack velocity. By contrast to the high crack velocity, the inelastic deformation enhanced by the internal force causes sharp increase in toughness.
scientific article; zbMATH DE number 5600182