Finite difference 3D model for structural health monitoring of single lap joints

This work is centered on the development of a 3D Finite Difference (FD) model to simulate Single Lap Joints (SLJs) excited by Lamb waves. An approach based on transient waves is proposed for assessing debonding area in aluminum SLJ typically used in aerospace industry. This approach is based on the interference of elastic waves generated by Piezo Wafer Active Sensors (PWAS) attached to an adhesively bonded thin joint and travelling through the adhesion area: destructive interference conditions are promoted when the adhesive is partially debonded and they reveal a specific damage length. The mathematical model is the Cauchy-Navier equation of linear elasticity with variable Lamé moduli, solved in a regular and relatively simple domain. The main advantage of the proposed 3D numerical model is the mathematical ability to easily reproduce the presence of a damage (debonding) as a discontinuity in velocity values. Numerical results and experimental data are presented in order to validate the obtained novel reduced-order FD 3D model that appears leaner, cleaner and more simplified than FE one. Moreover, the simplicity and low computational cost of the proposed method make it particularly interesting for industrial applications (i.e., online Structural Health Monitoring on working structures).