Simulation of detecting contact nonlinearity in carbon fibre polymer using ultrasonic nonlinear delayed time reversal

摘要

A finite element method simulation of a carbon fibre reinforced polymer blockis used to analyse the nonlinearities arising from a contacting delaminationgap inside the material. The ultrasonic signal is amplified and nonlinearitiesare analysed by delayed Time Reversal -- Nonlinear Elastic Wave Spectroscopysignal processing method. This signal processing method allows to focus thewave energy onto the receiving transducer and to modify the focused wave shape,allowing to use several different methods, including pulse inversion, fordetecting the nonlinear signature of the damage. It is found that the smallcrack with contacting acoustic nonlinearity produces a noticeable nonlinearsignature when using pulse inversion signal processing, and even highersignature with delayed time reversal, without requiring any baselineinformation from an undamaged medium.