Ultrasonic Inspection of Irregular Surfaces

摘要

A technique and instrument are described to overcome a number of problems in examining complex irregular surfaces. The instrument is a portable, highly accurate position-sensing arm. It can be interrogated under program control to yield a position with respect to an arbitrary set of orthogonal axes. The technique involves transformation of these coordinates into a much more useful set of values, based on a non-orthogonal set of axes derived from a triangle of points located on the specimen surface. Inspection of individual areas on the sample is done on a fine triangular matrix, whereas coverage of the whole surface is achieved by linking larger triangles of arbitrary shape in a manner not dissimilar to a patchwork quilt. Ultrasonic waveforms are collected under program control, and the data are stored in a direct-access structure on disk. Entries into the structure are calculated with respect to the triangular matrix. This facilitates rapid reconstruction of section views (in particular B-scans). The technique has been successfully demonstrated using a prototype arm.