FOCUSING TECHNIQUES FOR LONG RANGE ULTRASONIC GUIDED WAVE INSPECTION OF PIPELINES

摘要

The goal of our work is to develop a long range ultrasonic guided wave focusing technique for pipelines with improved defect signal amplitude signal to noise ratio, and penetration power. Focusing techniques consequently reduces the false alarm rate, increases the probability of detection, hence inspection confidence, and also leads to excellent defect circumferential length and depth measurement potential. The focusing techniques include frequency tuning for axisymmetric loading of the pipe, natural focusing as a result of partial loading around the circumference of the pipe, and phased array focusing via multi-element array excitation and receiving with time delay profiling. Inspection consequences of bitumen coated pipe versus uncoated pipe will be made along with a discussion on the aspects of longitudinal versus torsional mode selection. Sensor and instrumentation requirements will also be given. Sample results will be offered that points out the significant advantages of beam focusing in pipeline inspection compared to current inspection techniques.