engleski

Interaction modelling of multiple fatigue cracks in stiffened panels

This paper presents a model for prediction of the fatigue growth of multiple cracks in stiffened panels under cyclic tension, where the interaction of long cracks and secondary bending was considered. In damaged stiffened panels under tension out-of-plane displacements occur due to the geometric eccentricities introduced by the cracked cross-section. As a result, secondary bending occurs, which is unfavourable for the fatigue properties of a structure. An incremental crack growth simulation procedure, based on the integration of the Paris equation, which takes account of the secondary bending and interaction of several propagating crack tips, was introduced. The Mode I stress intensity factors (SIF), KI, associated with the plate free surface on which positive bending stresses occur is determined from membrane SIF values calculated by the ANSYS FE software and the ratio of local bending and membrane stresses in the vicinity of a crack tip. Crack propagation lives were simulated for stiffened panel specimens with a single crack and with three collinear cracks and compared to fatigue test results. It was observed that bending stresses significantly increase KI values and crack propagation rate.

multiple site damage (MSD); crack growth interaction; secondary bending; stress intensity factor

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