The Minimum Elastic Energy Density Criterion in Dynamic Problems of Propagating Cracks

In a previous paper by the authors the minimum elastic strain energy density criterion was studied by considering the general case where both K_I and K_II-components of the stress intensity factor are operative when the crack is stationary, and static elastic fracture theory is valid. In this paper the dynamic case was considered. The influence of the velocity of a propagating slant crack in a homogeneous and elastic plate was taken into account. The dynamic stress intensity factors K_I^d and K_II^d were accurately determined by using the method of reflected caustics and the dynamic initial curve was defined to delineate the boundary of the core region, which is assumed to be the limiting curve, along which the energy density should be evaluated. It was shown that, in particular cases, important corrections to the position of this minimum and its size should be introduced in order to take care of the dynamic influence.