Elastodynamic and viscoplastic-dynamic fracture-mechanics analyses

The principal objective of this research program is to assist the HSST Program in obtaining reliable material fracture-toughness data and analysis procedures for the prediction of crack arrest at high-toughness (upper-shelf) conditions. The research combines finite-element analyses with small-scale fracture experimentation and the wide-plate testing being performed at the National Bureau of Standards (NBS). The focal point is a dynamic-viscoplastic finite-element analysis model because 1) unless the crack jump length is small, dynamic effects can significantly influence a run-arrest event in a laboratory test and 2) rapid crack propagation will induce rate-sensitive inelastic deformation that will require strain-rate effects to be taken into account. The basic research issue centers on the quantification of a kinetic crack-growth criterion for these conditions