MODELING OF GUIDED WAVE PROPAGATION IN A LAYERED HALF-SPACE USING DISTRIBUTED POINT SOURCE METHOD

Propagating guided waves in a layered half-space are modeled with the semi-analytical Distributed Point Source Method (DPSM). For nondestructive evaluation of solid structures using ultrasonic waves it is necessary to have an ultrasonic field model for the damage-free structure. This solution can be used as a baseline or benchmark solution. Any distortion in the ultrasonic field from this baseline should indicate the presence of one or more anomalies inside the structure. Distributed Point Source Method which is a Green's function based mesh-free technique is adopted here to generate the ultrasonic field inside the layer and the half-space when the layered structure is excited by an ultrasonic transducer of finite dimension. Unlike elastic half-space a layered half-space is a dispersive medium and several guided wave modes travel through the layer and the adjacent half-space. Numerical examples are given for an aluminum half-space attached to a layer made of a different material when the structure is excited by a bounded ultrasonic beam. It is also shown how the presence of an anomaly can influence the wave field inside the layered half-space. Displacements and stresses inside copper and epoxy layers and in the aluminum half-space are computed and presented as visual images.