Nondestructive testing Acoustic emission test

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). 

Test methods are used to detect flaws. As an example when flaws or cracks grow in plastic, minute amounts of elastic energy are released and propagated in the material as an acoustic wave. A nondestructive acoustic emission test has sensors placed on the surface that can detect these waves providing information about location and rate of flaw growth. These principles form the basis for nondestructive test methods such as sonic testing. 

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. 

Miller, R.K., Mclntire, P., (1987) Nondestructive Testing Handboook, Vol. 5, Acoustic Emission Testing, American Society For Nondestructive Testing, Columbus OH (USA). 

General corrosion control, prevention, and monitoring should be planned for from the onset. To detect and monitor corrosion, various methods must be used, while corrosion protection would be done by the addition of inhibition and use of protection coatings [5]. Visual examination, laser methods, the replication microscopy liquid penetration testing method, magnetic particles testing, the eddy current inspection method, acoustic emission technique, thermal methods of inspection, and nondestructive methods are the various methods to be adopted when monitoring pipeline corrosion [5]. 

Park, J.-M., Kim, D.-S. and Kim, S.-R. (2003) Interfadal properties and microfailure degradation mechanisms of bioabsorbable fibers/poly-L-lactide composites using micromechanical test and nondestructive acoustic emission. Composites Science and Technology, 63, 403 19. 

Acoustic emission (AE) has been widely used in many fields such as material behavior detecting, nondestructive testing, investigating friction and wear processes, monitoring engineering structures, and mechanical machining processes since the late 1960s. 

All pressure equipment should be tested or inspected periodically. The interval between tests or inspections is determined by the severity of the usage the equipment has received. Corrosive or otherwise hazardous service requires more frequent tests and inspections. Inspection data should be stamped on or attached to the equipment. Pressure vessels may be subjected to nondestructive inspections such as visual inspection, penetrant inspection, acoustic emissions recording, and radiography. However, hydrostatic proof tests are necessary for final acceptance. These tests should be as infrequent as possible. They should be performed before the vessel is placed in initial service, every 10 years thereafter, after a significant repair or modification, and if the vessel experiences ovrapressure or overtemperature. 

Acoustic emission can be used for testing pressure vessels and is not strictly a nondestructive test as it involves listening to the propagation of damage when subjected to an applied stress. 

Miller RK, Mclntire P (eds) (1987) Acoustic emission testing. Nondestructive testing handbook, Vol. 5. American Society for Nondestiuctive Testing. 2. Edition, p 603... 

Nondestmctive Testing Handbook, Vol. 5 Acoustic Emission Testing (1987) Miller RK Mclntire P (eds ), American Soc. for Nondestructive Testing... 

Hsu NN, Hardy SC (1978) Experiments in Acoustic Emission Waveform Analysis for Characterization of AE Sources, Sensors and Structures. Elastic Waves and Nondestructive Testing of Materials, AMD-Vol. 29 85-106... 

Ohtsu M, Okamoto T, Yuyama S (1998) Moment tensor analysis of acoustic emission for cracking mechanisms in concrete. ACI Stracmral Journal 95(2) 87-95 Ohtsu M, Ohtsuka M (1998) Damage evolution by AE in the fracture process zone of concrete. J Materials, Cone. Struct. Pavement, JSCE, 599/V-40 177-184 Ohtsu M (2000) Moment tensor analysis of AE and SiGMA code. Acoustic Emis-sion-Beyond the Millennium. Elsevier, pp 19-34 Ouyang C, Landis E, Shah SP (1992) Damage assessment in concrete using acoustic emission. Nondestructive Testing of Concrete Elements and Structures, ASCE, pp 13-24... 

Nondestructive Testing, ACI SP-112 63-82 Ohtsu M, Murakami Y, Yuyama S (1995) AE generating behavior under Concrete Ppacement and application to process control. ASNT, Proc. AECM-5 332-339 Ohtsu M (1995) The history and development of acoustic emission in concrete engineering. Concrete Library of JSCE 25 121-134 Ohtsu M, Watanabe H (2001) Quantitative damage estimation of concrete by AE. 

Most of the effectiveness of nondestructive techniques for the inspection of metal parts (such as eddy currents, X-ray) is lost when it comes to detection of flaws and cracks in composite structures, imless appropriate modifications are made to the instrumentation hardware or the inspection procedure. Ultrasoimd, laser (shearography), and acoustic emission techniques are usually preferred for inspecting the crack initialization (see Nondestructive Testing). 

The literature on NDT of polymers and PMC comprises the classes shown in Table 1. References illustrate the available range of literature or a specific topic. Omission or inclusion of a reference does not imply a rating by the authors. The amount of information available in electronic format only is steadily increasing, eg, References 2-8, and many journals feature electronic on-line editions. Electronic database searches are sensitive to spelling, eg, non-destructive yields 27, and nondestructive 384, active standards of the American Society for Testing and Materials International. Most NDT methods apply to various material classes. Those documents that explicitly mention polymers or PMC deal with effects specific to certain materials, eg, the Felicity effect in PMC (9), or with polymer products used in large quantities (10-14). Standards tend to lag behind technical developments, as discussed for acoustic emission (15), but similar arguments hold for other NDT methods. 

Acoustic Emission Testing n A nondestructive test for determining material or structural integrity by detecting and recording location, amplitude, and frequency of sound emissions as test loads are applied. 

Sachse, W., Netravali, A.N. and Baker, A.R., An enhanced, acoustic emission-based, single fiber-composite test, J. Nondestruct. Eval., 11(3/4) (1992). 

R.B. Engle, H.L. Dunegan, Acoustic emission Stress wave detection as a tool for nondestructive testing and material evaluation, Intemat. J. Nondestructive Test. 

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