An Evaluation of Finite Element Methods for the Computation of Elastic Stress Intensity Factors

摘要

The report summarizes the first phase of the development of computer programs for calculating elastic stress intensity factors at the critical (fatigue-prone) details of pressure hulls. The work is part of a broader study aimed at the development of analytical methods for fatigue and fracture analysis of submarine hulls. Two new techniques are introduced. One is based on direct application of the linear elastic fracture mechanics relations between the stress intensity factors and the near crack tip displacement fields utilizing two-term series expansion. The stress intensity factors are computed directly from the nodal displacements obtained previously from the finite element program. The second technique is based on direct incorporation into the finite element computer program of the strain energy of the singular element enclosing the crack tip. Examples of the application of such methods to several simply axisymmetric and two-dimensional plane strain problems are presented along with recommendations for future studies and applications. (Author)