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Other methods there are many other methods of

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Other Methods There are many other methods of nondestructive testing, including optical methods such as holography, shearography and moiré imaging; material identification methods such as chemical spot testing, spark testing and spectroscopy; strain gaging; and acoustic methods such as vibration analysis and tapping. 12 Acoustic Emission Testing
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Selection of Acoustic Emission Testing 4 Acoustic emission testing is an important method within the broad field of nondestructive materials testing. Acoustic emission test techniques usually fall into one of the following categories: pressure (or acceptance) testing, diagnostics, condition monitoring and leak detection. Some techniques can be subdivided even further. Condition monitoring, for example, can be divided into machinery monitoring, process monitoring and health monitoring. Proof testing is the most widely used application as applied to new and inservice pressure vessels as well as a variety of equipment used in various industries. Acoustic emission instrumentation is designed to detect the structural or liquid borne sound generated by a source within a material, sound that can be caused by crack initiation, crack tip yielding, crack extension, certain phase changes, turbulent flow or leakage, boiling, chemical reaction, friction or fretting, impact, matrix cracking, delamination, disbonding or fiber breakage. Many specific applications have been developed using acoustic emission. Detection of discontinuities is the largest class of applications. Specific applications include detecting discontinuities formed during welding; detecting tool wear and undesired tool contact during automated machining; detecting wear and loss of lubrication in rotating equipment; detecting loose parts inside operating equipment; detecting, locating and assessing leaks; detecting when cavitation occurs; determining when fluid flow becomes turbulent; acceptance testing of new equipment; and pressure testing of inservice equipment. Advantages of Acoustic Emission Testing Modern acoustic emission test techniques offer an economical means for high speed, large scale testing of materials and structures such as those found in nearly every industry. In a typical test, a controlled mechanical load is used to stimulate acoustic emission in the test object. Nearly every kind of material generates acoustic emission under load. When properly instrumented, an entire structure can be tested by applying loads equal to or slightly greater than those experienced during normal operation. For this reason, acoustic emission testing is often used to test structures as they are being operated. The test has minimal impact on operations. The method also lends itself to initial acceptance testing, as in hydrostatic testing of new vessels.
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  • Fall '19
  • Nondestructive testing, Acoustic Emission

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