AN EVALUATION OF IMAGE TECHNIQUES IN THE ULTRASONIC INSPECTION OF MATERIAL

摘要

This report evaluates the application of ultrasonic image techniques in the field of nondestruc¬tive testing with emphasis on the possibility of reducing radiographic film costs. The physical basis for sonography is developed in terms of the transmission characteristics of ultrasonic waves through an elastic medium: the reflection and refraction at boundaries, diffraction, the minute particle displacements, and the low attenuation. The evolution of various ultrasonic inspection methods is traced and computations are made to show the effectiveness and sensitivity of the image technique as compared to the most advanced current ultrasonic method, the probe technique. Since the success of the image method depends upon the development of an image converter, a survey and evaluation is made of the various principles by which an ultrasonic image might be converted to an optical image. The work on the Naval Ordnance Laboratory image converter is described briefly and its operation is illustrated. A conclusion is reached that an electronic type converter is feasible, but considerable work remains to complete a practical image tube. To assess the significance of the ultrasonic image inspection technique, the charac¬teristics of two other important nondestructive test methods, Magnaflux and radiography, are described. The further development of X-ray image converters and other filmless detection methods appears to be a more direct solution to the radiographic film problem. However-, the ultrasonic image technique would have important applications because of its probable convenience, sensitivity, and economy