A facet ensemble approach for evaluation of array performance inultrasonic NDE

摘要

The use of ultrasonic array systems, in conjunction with ansynthetic aperture focusing technique (SAFT) has recognized potentialnfor flaw characterization in nondestructive evaluation (NDE). However,ndefect type, location, orientation and geometrical constraints imposednby the test specimen can reduce the effectiveness of nonoptimal arraynsystems. To assist with design, a simulation approach for evaluation ofnarray performance for NDE imaging was developed and is described in thisnpaper. In the development of the model, several key factors werenidentified as being critical in defining the response of a linearnultrasonic transducer array. These include the ultrasonic waveletngenerated by each array element, the directivity of the transducers andnthe interaction of the ultrasonic wave field with the surface which isnto be imaged. Following several simplifying assumptions, and employing anlinear systems approach, the cumulative response of all these factorsnwas formulated. Thus a low-cost, yet powerful, interactive model fornsystem design evaluation could be implemented. To illustrate the model,na range of simulation results is presented, concerning the imaging of anfatigue crack in a solid medium. The influence of array element spacingnand centre frequency is considered, in conjunction with aperture size,ndefect orientation and surface roughness. In each case, the principalnfactors governing final image quality are discussed and where possible,nrecommendations are made concerning array design and imaging strategy