A hybrid formulation for 3D fracture analysis

Structures with multiple load paths experiencing either isolated cracking, widespread fatigue damage or repairs to multi-site damage can experience changes in the load path resulting from changes in stiffness due to either the cracking or the associated structural repair. To account for this effect, the present paper develops a new 3D hybrid formulation capable of representing this change in stiffness, thereby enabling an accurate analysis of multiple load path structures containing three-dimensional flaws. This formulation has been prompted by the advent of cluster based computing which means that it is now desirable to develop new computational techniques for assessing structural integrity. This procedure has been validated by comparison with results available in literature and with results obtained using the alternating finite element technique. For the surface crack problems considered it was found that, if symmetry considerations were used, then accurate results could be obtained with only 65 elements, including the “hybrid element”.