Coalescence judgment criteria for the interaction between two close surface cracks by WES2805 and its safety margin for brittle fracture assessment

Abstract

It is important to consider the interaction between multiple cracks in evaluating the reliability of a structure. In this study, the stress intensity factor (K value) is evaluated using the finite element method for interacting surface cracks. Although there are an infinite number of possible conditions of the locations and sizes of two close cracks, the cracks shall be located parallel to each other and have the same dimensions for simplification in this study. The K values on the crack front are calculated under various aspect ratios and relative locations. When there is a strong interaction (ΔKmax ≥ 10%), fracture analysis is generally performed after the coalescence of the two cracks by the FFS standard. As a result of the investigation of the critical condition of the positional parameters for coalescence, judgement criteria were introduced in WES2805 with some simplification. It was revealed that the coalescence process in WES2805 provides a safety margin.

Keywords

• stress intensity factor; finite element method; interaction; aspect ratio; safety margin