ABSTRACT
ABSTRACT: We present calculations of the static stress intensity factors of a branched crack for both antiplane and inplane configurations. The result s are applied to the problem of dynamic crack branching, using an approximated form of the dynamic stress fields. We show that the finite waves speeds in the material cause a time delay in the interaction between the branches. The time delay increases with the propagation velocity, vb, of the two branches, and causes each branch to behave as if the other branch was shorter. Despite these effects, we show that for any branching angle, the maximum energy release rate is always attained when vb 0. Following Eshelby, we show that the branching of a single propagating crack is energetically possible when its speed v exceeds a threshold value. Our calculations predict a relatively large branching angles, which is consistent with experimental observations. In addition, we show that an increasing fracture energy with the velocity results in a decrease in the critical velocity at which branching is energetically possible. Finally, we show that the principle of local symmetry and the principle of maximum energy release rate predict two different crack paths.
