Fatigue strength assessment by using a nonlinear finite element technique

An elastic-plastic finite element procedure considering nonlinear deformation behavior is used to evaluate the fatigue strength of ductile structures. Few cycles of statically cyclic response analysis are needed to reach a steady state response with which the local deformation-related post-finite element results are used to evaluate the ductile crack initiation cycles through the use of an S-N curve obtained from uniaxial tests. The consideration of using this type of fracture parameter is based on the objective of being able to solve general ductile fatigue problems without regard to the degree of plastic deformation that exists in the structure being solved. Mechanical models of both linear and nonlinear deformations are solved separately and the results are compared.