QUANTIFICATION OF GUIDED WAVE INTERACTION EFFECTS WITH LOCALISED STRUCTURAL NONLINEARITIES IN COMPLEX, COMPOSITE STRUCTURES

Abstract eng:
The extensive usage of composite materials in modern industrial applications implies a great range of possible structural failure modes for which the structure has to be frequently and thoroughly inspected. Nonlinear guided wave inspection techniques have been continuously gaining attention during the last decade. This is primarily due to their sensitivity to very small sizes of localized damage. A number of complex transformation phenomena take place when an elastic wave impinges on a nonlinear segment, including the generation of higher and sub-harmonics. Moreover, the transmission and reflection coefficients of each wave type become amplitude dependent. In this work, a generic Finite Element (FE) based computational scheme is presented for quantifying guided wave interaction effects with Localized Structural Nonlinearities (LSN) within structures of arbitrary layering and geometric complexity. Amplitude dependent guided wave reflection, transmission and conversion is computed through a Wave and Finite Element (WFE) method. The scheme couples wave propagation properties within linear structural waveguides to a LSN and is able to compute the generation of higher and sub-harmonics for each wave type through a harmonic balance projection. A Newton-like iteration scheme is employed for solving the system of nonlinear differential equations. Numerical case studies are exhibited for a set of waveguides coupled through a joint exhibiting nonlinear mechanical behaviour.

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