Basic Principles of Practical Ultrasonic Testing

Abstract

Ultrasonic testing, now in its fifth year in practical use, has, during that time demonstrated its ability to economically test non-destructively many materials and industrial parts. In many cases it has saved thousands of dollars of wasted machine time and labor, increased production and reduced the hazard of accidents due to defective or over-stressed parts. It is not, however, the panacea for all inspection troubles. Like all methods of non-destructive testing it has its limitations. It is just as important to know what it cannot do as what it can do, because misapplication can sometimes be more harmful than no test at all. It is doubtful that ultrasonic testing will entirely supplant other testing methods such as X-ray or magnetic particle testing. Although they overlap in their application, each has a distinctive field. Frequently they supplement each other. Using ultrasonic testing it is now possible to explore areas inside of metal sections which could not previously be tested or inspected. To apply ultrasonic testing intelligently one should have a clear understanding of the basic principle of operation, the available equipment, the techniques of application and the best procedure to follow when setting up test standards. The knowledge of basic formulae may be desirable but is certainly not necessary. One should, however, have an understanding of how the ultrasonic vibrations are generated and projected through the materials and the reaction inside the same materials.