Mode Conversion Estimation of Filleted T-Joint Using FEM and 3D Laser Vibrometry

摘要

T-joint configurations, commonly found in aerospace applications, provide achallenge for structural health monitoring (SHM) strategies that employ wavepropagation based interrogation techniques. The challenge arises from thecomplexity of wave propagation through the T-joint interface, and the consequentmode conversion and reflections. This work presents a numerical characterizationof undamaged T-joint using simplified two-dimensional (2D) plane strain finiteelement (FE) models, where excitation from a piezoelectric actuator is simulated onone side of the T-joint. The incident and consequent reflected waveforms areseparated in the frequency-wavenumber domain, and spatially-integrated multiplecomponent mode coefficients are formulated in the frequency-spatial domain withthe intent to characterize wave reflections and mode conversions. Mode coefficientsfrom the undamaged configuration are compared to T-joints with blind side notchdamage located in the fillet radius. Trends from the 2D FE numerical studies areverified by a three dimensional (3D) Scanning Laser Vibrometer test setup for theundamaged case, which consists of an aluminum T-joint for selected fillet radius(0.6 cm) and stiffener thickness (0.3 cm). The setup enables 3D full wavefieldsurface measurements of the front and back sides of the plate, plate-stiffener radius,and stiffener. Recommendations of how to use the mode coefficient formulation asa damage quantification tool for the T-joint are given.