RAILWAY APPLICATIONS OF ULTRASONIC WAVE VISUALISATION TECHNIQUES.

Problems encountered in the ultrasonic inspection of materials have been examined by the technique of photoelastic visualization. Certain aspects of range calibration of flaw detectors have been explained and possible dangers in selecting cylindrical holes as reference standards demonstrated. Direct reflections and indirect or 'delayed' reflections have been recorded. The sources of these have been identified using a glass model; in one example wave mode conversions from the sidewalls were shown to be responsible for 'delayed' signals. Two practical problems have been selected as examples of the model technique. The design of a high speed rail flaw detection vehicle has been aided by this technique. In particular some effects related to the lateral position of the probe have been demonstrated.