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Modeling for nonlinear laser vibrometry ex-periments in solids with frictional cracks
Archive ouverte : Communication dans un congrès
Edité par HAL CCSD
International audience. Modeling for processes underlying NDT and SHM by ultrasound and vibrations present certain benefits. A valid digital tool can help accept or reject a hypothesis on damage position, orientation and degree of gravity. As a final objective, a fully reconstructed damage configuration can supplement diagnostics by prognostics and help describe future evolution of damage in certain conditions. To do so, as a first step it is necessary to have a tool capable of describing acoustic waves in materials with inner contacts (cracks, delaminations, loose joints) with the account for a most pertinent phenomenon occurring in there, friction. Frictional interfaces have complex hysteretic response that depends on history of excitation. It is suggested to describe this response by using an original semianalytical method of contact mechanics called the Method of Memory Diagrams (MMD). The MMD provides boundary conditions at crack faces necessary for the wave propagation description modeled via standard FEM software. The next step is a qualitative imitation of a nonlinear acoustic NDT experiment via the proposed model. Here we have implemented the MMD-FEM principle in a 2D case similar to the one typical for nonlinear laser vibrometry experiments. A piece of plate containing a frictional crack parallel to the surfaces is excited with a harmonic signal. Contact nonlinearity of the defect generates higher harmonics, in particular, in the normal displacement field at the top surface measurable in real vibrometry experiments. We show that the spatial harmonics' distribution indicates the position and the size of the crack.
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