The Interaction between an Edge and an Embedded Parallel Crack in a Structural Component

Parallel cracks are often detected in various structural components using non-destructive methods. In the case of non-aligned parallel cracks, on-site service needs to decide whether they should be treated as coalesced or separate multiple cracks for Fitness-for-Service. Criteria and standards for the adjustment of multiple nonaligned cracks are very different from one another in existing resources. Furthermore, those criteria and standards are often derived from on-site service experience without rigorous and systematic verification. Based on this observation, the interaction between an edge and an embedded parallel crack is investigated to correlate criteria and standards from various resources in order to recommend the usage of those standards for the purpose of Fitness-for-Service. In this study, depending on the crack ratio a1/a2, what may be deemed conservative by one standard, leading to aligned cracks for a given separation distance, H/a2 and S/a2, may be deemed non-conservative, or non-aligned, by another standard. Examples are given to show this phenomenon.