Crack spacing threshold of double cracks propagation for large-module rack

Abstract

Large-module rack of the Three Gorges shiplift is manufactured by casting and machining, which is unable to avoid slag inclusions and surface cracks. To ensure its safety in the future service, studying on crack propagation rule and the residual life estimation method of large-module rack is of great significance. The possible crack distribution forms of the rack in the Three Gorges shiplift were studied. By applying moving load on the model in FRANC3D and ANSYS, quantitative analyses of interference effects on double cracks in both collinear and offset conditions were conducted. The variation rule of the stress intensity factor (SIF) influence factor, R_K, of double collinear cracks changing with crack spacing ratio, R_S, was researched. The horizontal and vertical crack spacing threshold of double cracks within the design life of the shiplift were obtained, which are 24 and 4 times as large as half of initial crack length, c₀, respectively. The crack growth rates along the length and depth directions in the process of coalescence on double collinear cracks were also studied.

Keywords

large-module rack / double cracks / fatigue crack propagation / crack spacing threshold / moving load

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