Nondestructive ultrasonic penetration

Nondestructive testing techniques for welded joints usually include visual, radiographic, magnetic particle, liquid penetrant, and ultrasonic testing methods. Of interest in this paper is the radiographic testing (RT) technique. 

Stress-corrosion cracks tend to be fine, tight, and easily overlooked. Various nondestructive techniques are available to aid in the discovery of cracks, such as dye penetrant, and ultrasonic and radiographic techniques. 

Corrosion-fatigue cracks can be detected by nondestructive testing techniques such as magnetic particle inspection, radiography, ultrasonics, and dye penetrant. Corrosion-fatigue cracks may occur in numerous tubes simultaneously. Nondestructive testing of tubes at locations similar to those in which cracks are observed can be useftil. 

Gross cracks may be visually observable. Nondestructive testing for the presence of cracks includes using dye penetrant, ultrasonics, and radiography. Determination of the cracking mechanism will require metallographic analysis. 

Caitz, L. Nondestructive Testing Radiography, Ultrasonics, Liquid Penetrant, Magnetic Particle. Eddy Current, ASM International, Materials Park. OH, 1995 Cornua, R.D. Problem-Solving Surface Analysis Techniques. Advanced Materials Processes, 16 (December 1992). 

Nondestructive evaluation, also termed nondestructive testing or nondestructive inspection, is extensively used in weld testing (14). Nondestructive tests do no impair the serviceability of the material or component under stress. The most widely used tests for evaluation of welds are liquid penetrant, magnetic particle, ultrasonics, and radiography. Acoustic-emission tests are increasingly used. Nondestructive tests detect and characterize, in terms of size, shape, and location, the various types of weld discontinuities that can occur. 

The choice of the nondestructive technique used in the examination of the sample on hand also depends upon the complexity of the shape of the sample. The following order of the methods is in progressively increasing complexity of the shape of the sample to be examined acoustic microscopy, microwave method, eddy current, magnetic particle, X-ray radiography, ultrasonics, liquid penetrant and visual methods. 

Preliminary testing is done next to uncover flaws in joining, and sometimes in the metal itself. Nondestructive test methods, such as ultrasonics and X- or gamma-ray inspection, are used on main welding seams Dye penetration, hydrostatic, or air-soap tests are also used to locals leaks and cracks. Helium or Freon leak detectors are necessary fok more critical leak testing, particularly on high-vacuum equipment. 

The reactor coolant pump pressure boundary is nondestructively inspected as required by ASME Section III for Class 1 components. The pump casing inspections include complete radiography and liquid penetrant or ultrasonic testing. The pump receives a hydrostatic pressure test in the vendor s shop and with the Reactor Coolant System. Inservice inspection of the pump pressure boundary will be performed during plant life in accordance with ASME Section XI. 

Most techniques for the nondestructive evaluation of ceramic materials fall into two categories high-energy penetrating radiation (for example. X-ray) and high-frequency elastic waves (ultrasonics). Some NDE techniques have been developed for specialized applications, such as optical birefringence for transparent specimens and shearography for laminar composites. 

Nondestructive testing. An ultrasonic inspection technique is available for the detection of flaws in plate, piping, and tubing. The water-immersed pulse-echo ultrasound equipment has been adapted to highspeed use. Eddy-current, dye-penetrant, and radiogr.aphic inspection methods are also used as required. The inspected materials have included Inconel, austenitic stainless steel, INOR-8, and the Hastelloy and other nickel-molybdenum-ba.se alloys. 

ASTM G 46 also includes procedures for the nondestructive evaluation of pitied specimens. These include radiographic, electromagnetic, ultrasonic, and dye-penetrant inspection. These methods can be used to locate pits and to provide some information on thdr size, but they generally cannot detea small pits or differentiate bOween pits and other types of surface defects. 

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