Scattering of Lamb waves from a rivet hole with edge cracks

Lamb waves propagating in an infinite plate containing a circular hole, with or without edge cracks, are investigated both theoretically and experimentally in this paper. The theoretical analysis is accomplished by means of a hybrid method called the global local finite element method, in which a bounded region enclosing the hole and the cracks is discretized into finite elements, while the field external to this region is represented analytically in terms of Lamb wave modes. The scattered field is calculated through the application of the boundary conditions at the interface between the discretized region and the unbounded exterior. In the experiments the incident Lamb wave of a specific mode is generated by means of a wedge transducer and the waves scattered by the hole is recorded in conventional contact type transducers located on the plate surface. The measured time histories and amplitude spectra of the transmitted and reflected waves are compared with those calculated from the hybrid model. The agreement between the theoretical and experimental results is found to be excellent in the cases considered. Application of the technique to non-destructive evaluation (NDE) of corrosion and fatigue induced defects in aging structural components is discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.