The GR3 Method for the Stress Analysis of Weldments

Abstract

Determination of the fatigue life of a component requires knowledge of the local maximum fluctuation stress and the through-thickness stress distribution acting at the critical cross-section. This has traditionally been achieved through the use of stress concentration factors. More recently finite element methods have been used to determine the maximum stress acting on a weldment. Unfortunately, meshing large and complicated geometries properly requires the use of fine meshes and can be computationally intensive and time consuming. An alternative method for obtaining maximum stress values using coarse three-dimensional finite element meshes and the hot spot stress concept will be examined in this paper.

Coarse mesh stress distributions were found to coincide with fine mesh stress distributions over the inboard 50% of a cross-section. It was also found that the moment generated by stress distribution over the inboard half of the cross-section accounted for roughly 10% of the total moment acting in all of the cases studied. As a result of this, the total moment acting on a cross-section may be predicted using knowledge of the stress distribution over the inboard 50% of a structure.

Given the moment acting on a cross-section, the hot spot stress may be found. Using bending and membrane stress concentration factors, the maximum stress value may be found. Finally, given the maximum stress data, the fatigue life of a component may be determined using either the strain-life approach or fatigue crack growth methods.