ARMY ARMAMENT RESEARCH AND DEVELOPMENT COMMAND WATERVLIET NY BENET WEAPONS LAB
The elastic and plastic singularities near a crack tip are obtained from higher order isoparametric elements. This is simply accomplished by collapsing the quadrilateral element into a triangular element and by judicious choice of adjacent mid-side nodes. Specifically for the cubic element, the elastic singularity is obtained by placing the mid-side nodes adjacent to the crack tip at 19th and 49th locations. The plastic singularity is constructed using the sliding node concept. These elements have been implemented in NASTRAN as user dummy elements.