Ultrasound reflection from, and transmission through, stratified media with rough interfaces: Its relevance to ultrasonic defect detection

Ultrasonic inspection is used to detect and size defects in pressure vessels and pipework. These defects are generally in the vicinity of welds, and may be put into one of two classes from a fracture-mechanics point of view: those which are potentially dangerous and those which are not. In the first group are crack-like defects orientated in the through-thickness direction, whereas in the second are such things as manganese sulphide inclusions. These non-metallic inclusions are formed into flat plates parallel to pressure-retaining surfaces by the forging and rolling processes used during manufacture. Such laminar defects may not be especially dangerous since (a) they contain the direction of maximum stress and (b) they do not grow during service