Experimental investigation of a breathing crack in a plate under different excitations

Structures in real-life scenarios like industrial robots, spaceships, aircrafts, submarines, bridges, and pressure vessels undergo different loading conditions. These structures are prone to damage due to the risks related to fatigue and aging. Small cracks may appear in these complex structures and prove to be fatal. These cracks may open and close, hence termed as breathing cracks, exhibiting nonlinear behavior under load. Various nonlinear techniques exist for the detection and severity estimation of breathing crack in one-dimensional structures such as beams. However, in plate-like (2D) structures these types of cracks are difficult to identify. Moreover, most of the research has been conducted in plate-like structures with a through crack. However, it becomes a challenge when the breathing crack is not only part-through but localized in the central region of the plate. This paper presents the Hilbert transform to identify a central part-through breathing crack in 2D structure. The appearance of nonlinearities in the response spectrum helps in crack detection which depends primarily on the type of excitation. The impulse and harmonic excitation tend to enhance the nonlinearity whereas the random excitation makes the nonlinearity difficult to detect in the response spectrum. This paper presents the numerical and experimental investigations of a plate with part-through crack under different excitation signals. Furthermore, the proposed techniques have also been applied on random response of plate to achieve identification and severity of the crack.