Crack failure prediction is a prerequisite to assess the safety margin for pressure vessels with interacting parallel cracks. Therefore, an alternating iteration method with approximated image traction is employed in this study to assess the stress intensity factors of two stacked parallel cracks. The predicted crack intensity factors for these parallel cracks correlate well with the recent available solutions in literature. Maximum-energy-release-rate criterion is also utilized for converting problems of multiple cracks into a single crack in mode I. Results demonstrate that a shorter secondary parallel crack may enhance the equivalent crack primarily in the regions 0 < h/2a1 ≤ 0.8 and −1 ≤ t/a1 ≤ 1. The predicted results can be used to evaluate the conformability of simple proximity rules suggested by ASME Boiler & Pressure Vessel Code (ASME B&PV Code).

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