Dissipative Visco-plastic Deformation in Dynamic Fracture: Tip Blunting and Velocity Selection

TL;DR

This paper presents a dynamical theory combining visco-plasticity and linear elasticity to explain phenomena in dynamic fracture, including tip blunting and velocity-dependent fracture energy, with implications for understanding crack propagation.

Contribution

It introduces a simple coupled visco-plasticity and elasticity model that explains tip blunting and velocity selection in dynamic fracture.

Findings

Predicts crack tip radius of curvature dynamically

Demonstrates velocity-dependent fracture energy

Identifies fracture energy in fixed-grip geometry

Abstract

Dynamic fracture in a wide class of materials reveals "fracture energy" $\Gamma$ much larger than the expected nominal surface energy due to the formation of two fresh surfaces. Moreover, the fracture energy depends on the crack velocity, $\Gamma=\Gamma(v)$. We show that a simple dynamical theory of visco-plasticity coupled to asymptotic pure linear-elasticity provides a possible explanation to the above phenomena. The theory predicts tip blunting characterized by a dynamically determined crack tip radius of curvature. In addition, we demonstrate velocity selection for cracks in fixed-grip strip geometry accompanied by the identification of $\Gamma$ and its velocity dependence.