Nondestructive tests ultrasonic methods

The ultrasonic testing of anisotropic austenitic steel welds is a commonly used method in nondestructive testing. Nevertheless, it is often a problem to analyze the received signals in a satisfactory way. Computer simulation of ultrasonics has turned out to be a very helpful tool to gather information and to improve the physical understanding of complicated wave phenomena inside the samples. 

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. 

Nondestructive testing (NDT) is used to assess a component or structure during its operational lifetime. Radiography, ultrasonics, eddy currents, acoustic emissions, and other methods are used to detect and monitor flaws that develop during operation (Chapter 7). 

Nondestructive Testing. Nondestructive testing (NDT) is far more economical than destructive test methods, and every assembly can be tested if desired. Several nondestructive test methods are used to check the appearance and quality of structures made with adhesives or sealants. The main methods are simple ones such as visual inspection, tap, proof, and more advanced physical monitoring such as ultrasonic or radiographic inspection. The most difficult defects to find are those related to improper curing and surface treatments. Therefore, great care and control must be exercised in surface preparation procedures and shop cleanliness. 

The test methods are subdivided into two categories, destructive and nondestructive methods. One of the latter, the ultrasonic method , is applied in special fields of adhesive technology, for example, in aircraft construction. It is based on the fact that sound waves in test pieces propagate differently, in dependence on the evenness of their structure, which can be disturbed by the presence of pores or imperfections, thus enabling the recording of failures. 

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. 

Figure 17.94 Ultrasonic C-scan of cfrp laminate showing an area of impact induced delamination white indicates negligible damage and black bad damage. Source Reprinted from Cawley P, The sensitivity of the mechanical impedance method of nondestructive testing, NDT Int, 30(4), 209-215, Aug 1987.

G. J. Curtis, Adhesively bonded structure nondestructive testing with acoustic methods, in Ultrasonic Testing, J. Szilard, Ed., John Wiley, 1980. 

Condition Evaluation of Concrete Bridges Relative to Reinforcement Corrosion. Vol. 4 Deck Membrane Effectiveness and a Method for Evaluating Membrane Integrity. Investigates membrane performance and effectiveness to develop a nondestructive test to evaluate in-place membranes. An ultrasonic pulse velocity method was developed. Conclusions indicate that properly installed and maintained preformed membrane systems reduce chloride intrusion. 143 pages. SHRP-S-326, 15... 

Plastics are susceptible to flaws that cannot always be seen thus premature failure can only be prevented if methods are available that will disclose the presence and extent of such flaws without destroying the part. Three of the more common nondestructive testing methods are ultrasonic, -radiometric, and holographic testing. 

Nondestructive Testing of Adhesive Joints. Many commercially available adhesives are based on polymers. NDT of adhesive joints (180) poses challenges because of (2) the small size of possibly deleterious defects (eg, porosity), (2) the thinness of the adhesive layers, and (3) sometimes, the size, shape, and material of the adherends. Acousto-ultrasonics (181) and various types of ultrasonics (182,183) are applicable to adhesive joints. Ultrasonics can be combined with noncontact optical methods (184) and pulsed thermography (185). However, the assessment of the quality or of the quantitative strength of the adhesive bond based on the NDT data often proves difficult. 

Ribbon Test (B.S. 1902 Pt.5.12) The lower faces of a series of bricks are heated by a linear burner 1.52m long at 980°C for 15min. The bricks are then cooled to 200°C. The reduction in modulus of elasticity (using a nondestructive ultrasonic method) after 5-10 cycles provides a measure of themal shock resistance. ASTM Cl 100 also specifies a ribbon test. 

G. J. Curtis, Nondestructive testing of adhesively bonded structures with acoustic methods. Ultrasonic Testing Non-Conventional Testing Techniques, pp. 495-554 (1982). 

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