Development of a synthetic A-scan technique for ultrasonic testing of pipelines

Multiple-boundary echoes are often seen in ultrasonic testing of materials, particularly in laminates. Although these echoes can be a problem in many situations in masking the signals of interest, they can also be used to advantage, e.g., in identifying disbonds in laminates or the presence and properties of materials beneath the test surface. However, that often requires echo comparison with signals from reference acoustic targets or templates. Making such templates is an exhaustive, and in some cases a prohibitive process, particularly when testing nonplanar materials such as pipelines. A new approach to synthesize reference signals using numerical modeling and computation is presented as an alternative method to the use of actual templates. Although the techniques described are specifically related to testing of pipelines, they can be extended to other general applications in nondestructive testing (NDT) of materials.