Guided wave testing of rail

Guided wave inspection has a number of advantages over conventional ultrasonic inspection. For instance, guided waves can propagate over many tens of metres in rail, they can fully penetrate alumino-thermic welds and theyare very sensitive to cracks in the transverse-vertical plane that may cause catastrophic failure. With financial and technical support from Network Rail, the authors are developing a guided wave inspection system for rail, which is described in this paper. Experimental and finite element results showing the interaction of various guided wave modes with a wide variety of defect geometries are presented. This study has enabled characteristic mode conversion signatures for various defects and features to be obtained and these signatures will provide the basis for an automatic feature extraction algorithm. Results from laboratory tests and site trials are presented that demonstrate the ability of the system to detect a range of defects in free rail, aluminio-thermic welds and in rail at a level crossing.