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Analysis of crack formation in T-joint structures under dynamic loading

T-joints play a vital role in the hulls of ships and bulkheads made of sandwich materials. Their design aspects and crack detection are important in preserving the safety of ships navigating through violent sea waves. In this work, an overview of the state-of-the-art of design aspects of T-joints used mainly in ship structures is first provided. The design aspects are focused on estimating static and quasi-static failure loads, fracture and fatigue characteristics. This study also develops a reduced order dynamic model for identification of cracks in T-joints. The reduced model constitutes three modal equations with piecewise-linear asymmetric characteristics in which the influence of the crack appears in terms of its length parameter. In particular, it is shown that the presence of a crack essentially affects both the amplitude and frequency content of the dynamic response due to nonlinear coupling between normal modes. Under external dynamic loading with a frequency close to the first mode frequency, the development of a crack is identified by the evolution of attractors on the configuration planes created by different combinations of modal coordinates.