Cyclic loading from ocean waves makes fatigue damage and cracking common issues for marine structures. Crack arrest holes (CAH) often have been used as a temporary repair method to retard crack growth until a permanent repair can be performed. Due to the variation of the effectiveness of CAH approach, it often requires more frequent inspection, which could be costly to the owner with respect to both time and money. Cold expansion is an alternative solution that has the potential to reduce these costs. The cold expansion process involves drilling a CAH in front of the crack tip and then cold expanding the hole while simultaneously installing a bushing. The cold expansion causes a radial plastic flow of material that results in plastic deformation. The material just beyond the plastically deformed hole constrains the plastic region and provides an annular zone of residual compressive stress. This paper covers the history of cold expanded CAH technology, a case study on a vessel in operation, and an engineering critical assessment for crack propagation. Results from these studies show promising potential for cold expanded CAH as a "long-term" temporary crack repair solution.
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Feasibility Study of Cold Expansion to Retard Crack Growth
Paper presented at the SNAME Maritime Convention, Houston, Texas, October 2017.
Paper Number: SNAME-SMC-2017-037
Published: October 24 2017
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Echols, Diana, Hsiang, Judy, Lee, Aikuo, Libhart, Ryan, and Joy Ransom. "Feasibility Study of Cold Expansion to Retard Crack Growth." Paper presented at the SNAME Maritime Convention, Houston, Texas, October 2017.
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