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Abstract

<u>INTRODUCTION</u> <br>Ultrasonic testing employs high-frequency mechanical waves to detect various material variables. These variables can be surface o r internal variables, and their locations and/or geometries can be reasonably delineated. <br>Ultrasonic testing is unique i n several areas, Ultrasonics and radiography provide deep, internal inspection capabilities. Normally ultrasonics provides the deepest penetration. (The penertration of X-rays in steel is measured in inches, ultrasonic beams can penetrate twenty feet or more.) Ultrasonics does not require an intrusion of a foreign substance into a material, such as high energy photons of an X-ray beam, but it consists of simple movements of the internal atoms already there. Therefore, ultrasonics can be considered to be the safest of all the inspection methods and is especially adaptable for medical use. Ultrasonic testing has very few restrictions on the kinds of materials it can inspect. The materials do not have to be magnetic (as they must be for magnetic particle testing), they do not have to be electrically conductive (as for eddy current testing) , and they do not have to exhibit an adhesive affinity for a liquid (as required for liquid penetrant testing). They do not even have to be a solid. Any volumetrically elastic material can be inspected by this method. <br>Ultrasonic testing can involve a wide variety of variables. Material variables relating to flaws, voids, inclusions, bonding, thicknesses, and densities can almost always be effectively inspected by ultrasonics. Therefore, ultrasonics is one of the basic nondestructive test methods. <br>This chapter provides the fundamental principles and guides associated with ultrasonictesting. It includes the theory of operation, the type of equipment, the advantages and disadvantages of the method, various applications and standards, and guides for specific disciplines. The information contained in Chapter 1 should be included with this chapter for - general guidelines to the employment of all NDT methods as it for a more complete understanding of ultrasonic testing as it compares with other basic methods.