Debonding detection at adhesive joints using nonlinear Lamb waves mixing

Abstract

Many engineering structural elements make use of adhesively bonded joints due to its lighter weight, load distribution and transmission mechanisms. The safety of the structure relies greatly on the condition of the adhesive joint. In this paper, the detection of debonding at the adhesive joint is investigated using a nonlinear Lamb wave mixing approach. The method relies on the presence of combined harmonics as indicative of material nonlinearity due to dislocations or anharmonicity in intact specimens or contact nonlinearity produced by the defects. In this study, experiments and three-dimensional finite element simulations were conducted and demonstrated that the presence of combined frequency wave due to contact acoustic nonlinearity is effective for indicating debonding. The effect of the debonding width was investigated and the debonding width was found to correlate well with the combined harmonic energy generated due to debonding. The findings presented in this study provides physical insights into the effect of debonding mechanisms at adhesive joints in related to the nonlinear Lamb wave mixing approach, and can be used to further develop the debonding detection techniques using wave mixing.