Acoustic Emission Source Location Research Articles

Localization of acoustic emission sources in tensile and ct specimens using a broadband acquisition technique

The acoustic emission sources in a conventional cylindrical tensile test sample of short transversely-cut carbon manganese steel are localized. There is not always a good correlation between the localization of the first signals and the zone which eventually fractures. During the Lüder's plateau, the ae signals are emitted in the deformation band and, in the hardening range, there is no significant ae in the gauge length of the sample. In ct samples precracked by fatigue, the signals are due to the growth of the plastic zone around the crack tip, and the plastic zone size, measured by source localization, agrees with those provided by models derived from fracture mechanics.

The fracture mechanics of aluminium-alloy gas cylinders

The failure pressures of sixteen 2219 aluminum alloy gas cylinders containing intentional defects were determined experimentally and compared with fracture mechanics predictions. The failure pressures predicted by two linear elastic fracture mechanics models for axially flawed cylinders were 10–70% low when the flaw was considered to bulge and ranged from 15% high to 40% low for restrained flaws. The ASME Boiler and Pressure Vessel Code gave approx. 15–45% conservative estimates for axial flaws in all cylinders except one containing a shallow flaw. A 20% overestimate was made for this cylinder. All predictions of a model developed for the American Gas Association for steel pipelines were very conservative, particularly for long axial defects where the failure pressures were underestimated by more than 300%. A similar conservative result was obtained for circumferentially flawed cylinders. This model was modified empirically to allow closer prediction of the failure pressure of axially flawed cylinders. Further models were developed to predict the failure of two cylinders each containing a dent superimposed on an axial flaw. Acoustic emission monitoring and source location during pressurization did not identify the known defects in most tests. It permitted uncertain nondestructive defect identification on only two cylinders. The inconsistent and uncertain result would not warrant the adoption of AE as an NDT tool on these cylinders.

The application of vibration signature analysis and acoustic emission source location to on-line condition monitoring of anti-friction bearings

The mechanical noise, vibration and heat generated by defects in fabrications, process plant and machinery are a measure of component condition, and once characterised allow on-line assessment of defect severity. Unexpected failures which might threaten the entire production process can thereby be avoided. There is an increasing need for reliable and robust condition monitoring instrumentation with on-line data processing, particularly as the trend contunues towards larger production units with little or no standby capacity for use in the event of unscheduled stoppages due to mechanical failure. This article describes the detection of incipient failure of rolling element bearings by kurtosis and the location of fatigue cracks in slowly rotating bearings by acoustic emission

Deformation and failure information from composite materials via acoustic emission

An introductory literature review of the applications of acoustic emission (AE) to the study of composite materials and structures is given. This survey demonstrates the unique information that AE provides on the deformation and fracture processes which occur when composite materials are stressed. Also included in the review is a survey of the application of AE to nondestructive testing of composite materials. Following the review, new research results are presented in some areas of current research interest. The following areas are emphasized: (1) Wave propagation complications and the development of AE source location techniques in Kevlar 49/Epoxy composite pressure vessels; (2) evaluation of a special immersion type AE transducer; (3) study of couplants for AE testing of composites; and (4) application of AE to the study of a Boron/Aluminum particulate composite. [Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore Laboratory under contract No. W‐7405‐ENG‐48.]

Acoustic emission source location on a spherical or plane surface

Using the differences in time of arrival from an acoustic emission source to several sensors, the position of the source may be calculated. A mathematical method is developed which allows the location of sources on a spherical surface by using a system of coordinates which is easily applied to an industrial vessel. If the radius of the sphere is inceased to infinity, the formulae can be used for the location of sources on a plane surface. A brief discussion of the results is given, keeping in mind the industrial aspect of the technique.

Application of correlation techniques for localization of acoustic emission sources

This paper describes a new method of acoustic emission (AE) source localization based on measurement of correlation functions of AE signals. In the theoretical part the correlation properties of most common AE sources are discussed and a model for their description is proposed. The methods of communication theory are then applied for a description of the detection system and for the analysis of the conditions under which localization by correlation functions could be applied. In the experimental part of the paper, the records of correlation functions corresponding to several sorts of AE in a simplified system are described. The localization method is then represented together with a discussion of various effects which are critical for its successful application. Finally it is demonstrated that the localization capability of the complete system can be efficiently improved by the inclusion of demodulation or deconvolution in signal processing.

Acoustic emission analysis during fatigue crack growth in steel

Emissions from fatigue crack growth have been examined for three steels — A533B steel, low carbon steel and H1 weld metal — using ACEMAN, a system for acoustic emission source location and analysis. The specimen size was sufficiently large for crack propagation under plane strain conditions and for time-difference analysis using multiple acoustic sensors. Signal recognition discriminators and location resolution allowed detection of signals below background noise. Emissions, detected during 80% of the upward-going part of the load cycles, most probably arose from the region of intense plastic strain near the crack tip and from unsticking behind the tip where crack closure had occurred. Expansion of the elastic-plastic interface with crack growth was ruled out as the dominant source mechanism on several grounds. With increasing crack severity, as determined by the cyclic stress intensity factor, ΔK, the rate of emission activity increased. The event count during the creation of unit crack area was, however, independent of crack growth rate. Thus, a specific emission parameter, γ, was derived, relating emission count to new crack area. For the three steels measured, γ lay in the range 2 – 44 events per square millimetre of crack growth. Analysis of signal amplitudes in A533B steel showed that amplitude spectra varied with ΔK. At the highest ΔK (67 MN m −3 2 ) a high amplitude emission source was activated.

AE monitoring of rapid crack growth in a production-size wing fatigue test article

Acoustic emission source location techniques were successfully used on a production-size aircraft wing fatigue test article to monitor crack growths in the range from 0.25 mm to 1.6 mm per load cycle. The AE data showed good correlation with the crack length data. Analyses of these correlations show that AE monitoring has the potential for being used to determine crack length over this range of crack growth rates. The fatigue test article was constructed of 7075-T6511 aluminum alloy. The test period lasted 14 days and the results demonstrated that AE has application to aircraft structures.

Acoustic-emission source location in two dimensions by an array of three sensors

Sensors on the surface of a material under stress can detect acoustic emissions from a defect within the material. The difference in time of detection of an emission from the defect at different sensors gives a way of finding where it is. This paper shows a general method of calculating the location of defects in two dimensions from the arrival times at the sensors. The ACEMAN system, which uses this method can derive the resolution properties of a sensor array in about 7.5 min.

A multichannel acoustic emission source location system and its application to fatigue test of a reactor vessel

Electrical Engineering in JapanVolume 95, Issue 3 p. 129-137 Article A multichannel acoustic emission source location system and its application to fatigue test of a reactor vessel M. Onoe, M. Onoe Institute of Industrial Science, University of TokyoSearch for more papers by this authorK. Yamaguchi, K. Yamaguchi Institute of Industrial Science, University of TokyoSearch for more papers by this authorH. Ichikawa, H. Ichikawa Institute of Industrial Science, University of TokyoSearch for more papers by this authorT. Shimada, T. Shimada Institute of Industrial Science, University of TokyoSearch for more papers by this author M. Onoe, M. Onoe Institute of Industrial Science, University of TokyoSearch for more papers by this authorK. Yamaguchi, K. Yamaguchi Institute of Industrial Science, University of TokyoSearch for more papers by this authorH. Ichikawa, H. Ichikawa Institute of Industrial Science, University of TokyoSearch for more papers by this authorT. Shimada, T. Shimada Institute of Industrial Science, University of TokyoSearch for more papers by this author First published: 1975 https://doi.org/10.1002/eej.4390950318Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume95, Issue31975Pages 129-137 RelatedInformation