Closed form formulae for two interacting equal parallel through-wall cracks embedded in an infinite elastic medium under normal tension

Abstract Fitness-For-Service (FFS) and regulatory codes provide rules allowing determining whether multiple flaws shall be combined into a single flaw or evaluated separately. However, these rules set thresholds beyond which flaws are replaced by an envelope sometimes over conservative. The present study aims to develop a hybrid surrogate model accounting for crack interaction in an infinite isotropic homogeneous medium subjected to a uniform stress field normal to the reference plane. The paper presents closed form formulae for interaction factors relative to parallel equal through-wall cracks subjected to normal tension. Crack shielding is analysed in detail: the equation of the shielding limit is established and mode I and mode II variations of overlapped cracks are compared. Comparison with Finite Element calculations for all configurations validate the results.