a b s t r a c tClassical nonlinear vibration methods used for structural damage detection are often based on higher-and sub-harmonic generation. However, nonlinearities arising from sources other than damage -e.g. boundary conditions or a measurement chain -are a primary concern in these methods. This paper focuses on localisation of damage-related nonlinearities based on higher harmonic generation. Numerical and experimental investigations in longitudinal vibration of beams with breathing cracks are presented. Numerical modelling is performed using a two-dimensional finite element approach. Different crack depths, locations and boundary conditions are investigated. The results demonstrate that nonlinearities in cracked beams are particularly strong in the vicinity of damage, allowing not only for damage localisation but also for separation of crack induced nonlinearity from other sources of nonlinearities.

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A method of simulation is developed for studying the dynamics of the structures with discontinuities using Matlab-Simulink. The concept of dynamic compliance is used for modeling the continuous elements of the structure and the local discontinuity is modeled as nonlinear feedback. As an example, a one-dimensional model of cracked bar under harmonic loading is considered for the simulation purpose.

Structural health monitoring is receiving much attention as a means to prevent catastrophic failure in structures in operating conditions. In most cases fracture is caused by the growth of crack, which cannot be precluded in many engineering structures. Moreover, to have an accurate quantitative estimate of crack tolerance of a structure to prevent fracture of load bearing components, an effective non-destructive evaluation procedure becomes necessary to monitor the structure under working conditions.

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