Stress intensity factors by enriched finite elements

Abstract

The finite element method is extended to direct calculation of combined modes I and II stress intensity factors for axisymmetric and planar structures of arbitrary geometry and loading. High order conventional isoparametric elements are combined with a fracture mechanics enrichment of the same element so that a corner node is made to correspond to a crack-tip. The development is explained in detail and necessary modifications to a standard finite element computer program are identified. Stress intensity factors as well as a complete stress analysis are obtained directly from the computer printout. Few elements are generally required, minimizing engineering costs and eliminating the need for data generators. Example problems demonstrate the ease of using the method, the high accuracy to be expected from the method, and the fact that accuracy is relatively insensitive to variations of the element mesh in the vicinity of crack tips. Important applications include complex geometries for which other methods fail and situations wherein multiple crack tips may interfere with one another.