Abstract
Crack growth of a single crack or a periodical array of cracks initiated at the stiffeners in a stiffened panel has been investigated. Using stiffened panel specimens, fatigue crack propagation tests have been carried out with cyclic stress of constant amplitude and frequency. A procedure for simulation of crack propagation for multiple cracks was introduced. The stress intensity factors have been calculated by a FEM program. From experimental a-N data of flat plate specimens, the fatigue crack propagation rate was obtained, and the Paris' constants have been determined. By means of the material constants and the stress intensity factors, the fatigue crack growth has been simulated for all test specimens. The experiment and numerical simulation have shown that in case of a stiffened panel with three cracks, the crack growth rate is higher compared with a stiffened panel having a single crack, because in case of three cracks the net sectional area is reduced, and also the adjacent cracks interact with each other. For an actual deck of a ship structure, the ratios of crack growth lives for multiple site damage and a single crack damage have been investigated. In case of multiple site damage it is found that the crack propagation rate is several times higher than the single site damage.
