Nonlinear spectroscopy of closed delaminations and surface breaking cracks: Finite element simulations of clapping and nonlinear air-coupled emission

Kissing bonds and clapping contacts, such as delaminations and surface breaking cracks, inherently demand a nonlinear diagnostic method. In order to detect such defects, it is necessary to apply a finite excitation amplitude that is large enough to overcome the activation threshold to separate the two faces of the contact. To obtain a better understanding and analysis of the macroscopic nonlinear behavior, we developed and investigated the results of a finite element model that makes use of local node splitting and implements the nonlinear constitutive behavior by means of springdamper elements with local activation thresholds at the defect interface. Numerical experiments show that subharmonics and harmonics of the excitation frequency are generated by the clapping defect if the excitation amplitude is large enough to overcome the local activation threshold. As experimentally observed in NACE experiments (Nonlinear Air-coupled Emission), these nonlinear vibrations cause emission of radiation patterns

ISBN:9780735410824

Jaar van publicatie:2012

BOF-keylabel:ja

IOF-keylabel:ja

Authors from:Higher Education