Dynamic stress intensity factors for suddenly loaded structures using enriched finite elements

In this paper, an efficient finite element formulation for stationary cracks subjected to dynamic impact loading is presented. For impact problems, where wave propagation effects dominate, the onset of rapid crack growth is strongly influenced by inertia effects, including stress wave reflections from geometric boundaries. Dynamic stress intensity factors generally attain maximum values that can be many times greater than their static counterparts. Because of this, there is a strong motivation for developing efficient computational techniques to evaluate this type of engineering problem in a relatively straightforward manner. In order to analyze the dynamic stress intensity factor problem efficiently, a computational technique that does not require a special crack tip mesh is of considerable value. The enriched finite element approach is shown to be a practical and effective technique for obtaining dynamic stress intensity factors, especially for cracks located on bimaterial interfaces, where there is inherent coupling between the mode I and mode II stress intensity factors. The enriched crack tip element approach utilizes the analytic asymptotic crack tip fields to directly compute the stress intensity factors. In this paper, fracture problems known to have two different types of crack tip singularities, subjected to elastic wave propagation effects during impact loading, are given as examples.