ASSESSMENT OF INTERMETALLIC COMPOUNDS WITHIN DISSIMILAR JOINTS USING NONLINEAR GUIDED- WAVE FEATURES

Abstract

The welding of dissimilar materials finds a wide variety of applications in the fields of industrial construction and manufacturing. One of the most prominent challenges of these techniques is the development of intermetallic compounds (IMCs) at the joint level, which reduces the strength of the welds. Nonlinear ultrasound detection methods are used as modern non-destructive testing tools for inspecting early damage in various materials. This study investigates the assessment of the thickness of the IMC layer within dissimilar joints using nonlinear guided-wave (GW) features. A numerical investigation was performed on friction-stir-welded (FSW) lap joints, between AA5052-H32 aluminum and ASTM 516-70 steel, with various intermetallic conditions/thicknesses. GWs were excited in the specimens using piezoelectric transducers placed on the aluminum side. The second-harmonic generation (SHG) among the fundamental GW modes was examined within the low-excitation-frequency range. It was found that the relative acoustic nonlinearity parameter ?′ varies linearly with the thickness of the IMC layer. The attained results prove the sensitivity of GW nonlinear features to microstructural variations, within dissimilar FSW joints, and demonstrate the capability of LWs in accurately scrutinizing their strength. Keywords: Friction stir welding, dissimilar welds, intermetallic compound, nonlinear guided waves, acoustic non-linear parameter, numerical modelling.