Showing papers on "Acoustic emission published in 1987"
TL;DR: In this paper, the critical load determined by the scratch test is widely regarded as representative of coating adhesion; however, it remains difficult to express quantitatively the adherence because the critical loads depend on several parameters related to the testing conditions and to the coating-substrate system.
399 citations
TL;DR: The acoustic emission (AE) technique as discussed by the authors uses one or more sensors to 'listen' to a wide range of events that may take place inside a solid material, which can be used to assess structural integrity.
Abstract: The technique of acoustic emission (AE) uses one or more sensors to 'listen' to a wide range of events that may take place inside a solid material. Depending on the source of this high frequency sound, there are broadly three application areas: structural testing and surveillance, process monitoring and control, and materials characterisation. In the first case the source is probably a defect which radiates elastic waves as it grows. Provided these waves are detectable, AE can be used in conjunction with other NDT techniques to assess structural integrity. Advances in deterministic and statistical analysis methods now enable data to be interpreted in greater detail and with more confidence than before. In the second area the acoustic signature of processes is monitored. In the third area, AE is used as an additional diagnostic technique for the study of, for instance, fracture, because it gives unique dynamic information on defect growth.
219 citations
TL;DR: In this article, the fracture process zone and its effect on fracture toughness were examined for Charcoal and Rockville granite, average grain sizes of 1 and 10mm, and the experimental evidence indicated an effective crack to be composed of a traction free length and a ligament process zone, which was observed to form a multiconnected region within the macrocrack.
148 citations
Journal Article•
TL;DR: A comprehensive review of the literature concerning acoustic emission produced during deformation by dislocation motion, deformation twinning, as well as inclusion fracture and decohesion can be found in this article.
Abstract: Acoustic emission is frequently produced during deformation of metals and alloys. Numerous mechanisms can be responsible for the acoustic emission activity. This report is a comprehensive review of the literature concerning acoustic emission produced during deformation by dislocation motion, deformation twinning, as well as inclusion fracture and decohesion. 232 refs., 30 figs.
108 citations
84 citations
01 Mar 1987
TL;DR: The genesis acoustic emission during slip is discussed, experimental evidence presented to the sensitivity of acoustic emission to slip between two surfaces, and use ofoustic emission signal analysis a slip detection technique is proposed.
Abstract: The detection of the onset of motion and slip between an end effector and workpiece has been of interest for some time and many schemes have been proposed. This paper reviews some of the background on slip detection methods and proposes use of acoustic emission signal analysis a slip detection technique. The genesis acoustic emission during slip is discussed and experimental evidence presented to the sensitivity of acoustic emission to slip between two surfaces. Preliminary tests with a robot gripper have also done to demonstrate the feasibility of acoustic emission slip detector.
69 citations
TL;DR: In this paper, the authors consider quantitative acoustic emission (AE) techniques with real and simulated sources as powerful tools for investigating failure processes in composite materials using a simulated source acting as a point source and one or more point receivers whose characteristics are known.
52 citations
47 citations
TL;DR: In this article, acoustic emission (AE) produced by the propagation of stress corrosion cracks in an aligned glass fibre/polyester resin composite material has been recorded and the amplitude of AE signals produced by fibre failure appears to be proportional to the fracture stress of the fibres, although further analysis requires a greater understanding of the generation, transmission and detection of acoustic signals.
Abstract: Acoustic emission (AE) produced by the propagation of stress corrosion cracks in an aligned glass fibre/polyester resin composite material has been recorded Tests have been carried out over a range of crack growth rates and the variation of AE with crack velocity/applied stress intensity has been examined The main source of AE is fibre fracture and there is a one-to-one relationship between the number of fibre fractures and the number of high-amplitude AE signals This enables crack growth to be monitored directly from acoustic emission The amplitude of AE signals produced by fibre failure appears to be proportional to the fracture stress of the fibres, although further analysis requires a greater understanding of the generation, transmission and detection of AE signals This work demonstrates that stress corrosion cracking is an ideal source for the study of AE produced by fibre fracture without complications caused by interface effects, such as fibre debonding or pullout
44 citations
TL;DR: In this paper, the ultrasonic transducers were designed to monitor pulse transmission in both the axial and lateral directions throughout a uniaxial compression test, and the waveforms received at various stages of loading were digitized, stored and analyzed after the test.
Abstract: Results of monitoring crack growth in concrete during uniaxial compression using ultrasonic methods offer the possibility of determining the internal properties of a concrete member both during and after loading without causing any damage. The ultrasonic transducers were designed to monitor pulse transmission in both the axial and lateral directions throughout a uniaxial compression test. The waveforms received at various stages of loading were digitized, stored and analysed after the test. The crack growth was inferred from the intensity of these ultrasonic waveforms. Axial stresses/strains and transverse strains were also recorded by the use of a data acquisition system. Four different mix proportions were tested and the results obtained are discussed and compared with other available results.
TL;DR: In this paper, the acoustic emission (AE) generated during Luders and Portevin-Le Chatelier (PLC) deformation bands has been studied in Al-2.5% Mg and Cu-30% Zn.
TL;DR: In this paper, the first observation of acoustic emission during crystallization was made, and the source of acoustic waves was identified as an abrupt stress release in regions of the melt occluded by spherulites during crystallisation.
Abstract: Ultrasonic emission was found to accompany several physical processes involving stress release, for example, microfracture in solids1 or cavitation and bubble collapse in liquids2. We here report the first observation of acoustic emission during crystallization. Acoustic emission was found to occur during the spherulitic crystallization of polymers from melt. The source of acoustic waves was identified as an abrupt stress release in regions of the melt occluded by spherulites during crystallization. The stress buildup in occluded areas is a result of density changes during crystallization. When the level of stress approaches the limit of the melt cohesion cavitation occurs, the stress is released and sound emitted. Because crystallization, in the form of aggregates growing simultaneously from many nuclei, always leads to the formation of occluded areas, and because the density of the melt or glass from which these aggregates grow is always lower than the crystallized matter, stress always arises. Depending on its level, the stress is either released by cavitation or remains frozen in the material. Thus acoustic emission is also expected to accompany crystallization in other, non-polymeric materials.
TL;DR: In this article, an analytical compliance method has been successfully applied to Mode I interlaminar fracture toughness tests for laminated composites, and a new double cantilever beam (DCB) specimen was designed to measure load-line crack opening displacement with high accuracy, and an interpolation function was proposed to calculate the crack length and the energy release rate from the analytical results of compliance of the DCB specimen.
TL;DR: In this paper, a quantitative approach to estimate acoustic emission (AE) source parameters with proper care taken of the frequency-dependent media attenuation is proposed, where the node frequency in the amplitude spectra and the peak time in real-time signals are found to be the most suitable for the purpose.
Abstract: Acoustic emission (AE) signals emanating from various deformation processes in materials are of a broadband nature. It is also well established that the ultrasonic attenuation caused by grain boundary scattering in polycrystalline materials is strongly frequency dependent. It is worth noting that distortions of AE signals due to grain boundary scattering (Rayleigh or stochastic type) have been inadequately treated in some previous quantitative AE studies. We propose a quantitative approach to estimating AE source parameters with proper care taken of the frequency‐dependent media attenuation. Without getting involved in the complete measurement of media attenuation, the present approach is designed to find some characteristic quantities in both the frequency and time domains that are least sensitive to attenuation. The node frequency in the amplitude spectra and the peak time in real‐time signals are found to be the most suitable for the purpose. They can be used to infer the source parameters such as the ...
TL;DR: In this paper, the damage of oxide scales formed on a low alloy steel (containing 2.25 wt.% Cr and 1 wt% Mo) at 600 °C in Ar-50%H2O, O2 and air, which occurred during cooling to 300 °C every 8 h, has been investigated using the acoustic emission (AE) technique.
TL;DR: In this article, frequency-based pattern recognition concepts using linear discriminant functions have been used in analysing acoustic emission signals generated during machining to distinguish between different signal sources, specifically chip formation, tool fracture, and chip noise.
TL;DR: In this article, the acoustic emission of lactose, sodium chloride, microcrystalline cellulose and paracetamol was monitored during compression, using an acoustic transducer coupled to a portable activity meter.
TL;DR: In this article, the minimum thickness to the composite surface roughness was 0.21-0.27 and the ratios of propagation initiation times to corresponding lives and of the propagating times to the corresponding lives were 98.6-99.9 % and 0.05-1.03%, respectively.
Abstract: 18 test bearings simulating a thrust ball bearing were run under a maximum contact pressure of 5.64 GPa at a rotational speed of 660 rpm in a mineral oil bath. The ratio of the minimum thickness to the composite surface roughness was 0.21-0.27. The propagation initiation time is the time at which acoustic emissions increase at the position of failure. The propagating time is the period from the initiation time to the time when flaking occurs. The propagating times were distributed between 1 to 25 min and the lives were from 11.47 h to 112.02 h. The ratios of propagation initiation times to the corresponding lives and of the propagating times to the lives were 98.6-99.9 % and 0.05-1.03%, respectively. According to vibration acceleration trends, flaking processes were classified into two types; the sudden occurrence of a large flaking and the rather slow development of a damage.
01 Jan 1987
TL;DR: In this paper, the authors used ultrasonic measurements of internal friction and ultrasonic attenuation in materials characterization NDE applications and found that the usual limitation to testing on specially designed specimens is probably partly responsible for the lack of field application.
Abstract: While measurements of internal friction and ultrasonic attenuation have long been known to be sensitive to material damage, applications in materials characterization NDE have been disappointingly few. The usual limitation to testing on specially designed specimens is certainly partly responsible for the lack of field application. Low accuracy in ultrasonic pulse-echo attenuation measurements may be another reason.
01 Nov 1987
TL;DR: The formation and development of a fracturing source can be detected reliably by variations of the amplitude-time spectra of AE and the variation of the statistical parameters of AE as discussed by the authors, and the similarities of the fracturing processes at different size scales allows using the predictive features detected to forecast rock bursts.
Abstract: 1.
The fracturing of rocks is a process evolving in time on the basis of a stochastic accumulation and development of cracks.
2.
Acoustic emissions allow monitoring the accumulation of the number of cracks and evaluating their sizes.
3.
For monitoring the emission of elastic energy, computerized systems are necessary, capable of real-time recording of all acoustic signals above a desired threshold and measuring their amplitude and time parameters.
4.
The formation and development of a fracturing source can be detected reliably by variations of the amplitude-time spectra of AE and the variation of the statistical parameters of AE.
5.
The similarities of the fracturing processes at different size scales allows using the predictive features detected to forecast rock bursts.
Journal Article•
TL;DR: In this article, a preliminary experiment was conducted to determine the primary parameter for controlling wood drying and furthermore demonstrates a feedback control for drying * 2Zelkova serrata*1 discs through in-process acoustic emission monitoring.
Abstract: If internal stresses could be monitored, they might warn that drying defects are about to occur. Checking caused by drying stresses can be regarded as the source of acoustic emissions that are premonitory symptoms of fracture. The rate of acoustic emission depends on drying conditions. This paper describes a preliminary experiment to determine the primary parameter for controlling wood drying and furthermore demonstrates a feedback control for drying * 2Zelkova serrata*1 discs through in-process acoustic emission monitoring. -- AATA
TL;DR: In this paper, the growth of stress corrosion cracks in aligned glass-reinforced polyester resin was monitored using the acoustic emission technique, and it was found that the average peak amplitude of the signals is a linear function of the stress intensity at the stress corrosion crack tip.
Abstract: The growth of stress corrosion cracks in aligned glass-reinforced polyester resin was monitored using the acoustic emission technique. The cracks propagated perpendicularly to the fibre direction under very low stress levels. The log-normal distribution function was applied to describe peak amplitude distributions of the acoustic emission signals produced mainly by fibre failure. It was found that the average peak amplitude of the signals is a linear function of the stress intensity K1 at the stress corrosion crack tip.
01 Jan 1987
TL;DR: In this paper, a modified Michelson interferometer is used to measure the time-dependent normal component of surface displacement at the location of that spot. But the authors do not consider the application of interferometric optical sensing techniques for acoustic emission.
Abstract: The monitoring of acoustic emission (AE) is an important technique for the nondestructive characterization of strained materials because time and frequency domain analyses of AE events yield information about the type, geometry, and location of defects, as well as how material failure may occur. The quantitative interpretation of AE event signatures is critically dependent upon the faithfulness of the acoustic transduction and signal processing system in reproducing localized stress wave amplitude as a function of time. Although the usual sensor for acoustic emission is the piezoelectric transducer, several investigators have considered the application of interferometric optical sensing techniques which offer good spatial resolution and frequency response [1,2]. These techniques typically focus one beam of a modified Michelson interferometer to a small spot on the surface of a specimen and measure the time-dependent normal component of surface displacement at the location of that spot.
TL;DR: In this paper, the authors show that the recorded acoustic emission associated with a martensite microplate is reproducible, and for each event the activity and the echoes last about 1 ms.
TL;DR: In this paper, a detailed analysis has been made of acoustic emissions detected during build-up tests in a geothermal production well in Kakkonda geothermal power plant, Japan, in 1982, 1984 and 1985.
TL;DR: In this article, a new autoadaptive system has been developed and successfully tested in industrial conditions to detect tool breakage and tool wear in turning, milling, drilling and high speed milling.
Journal Article•
TL;DR: In this paper, the reproducibility and instability of thermal cycling in a restricted temperature domain within the range of the martensitic transformation in a Cu-Zn-Al alloy (68.5:14.9:16.6 at%) have been studied by means of the acoustic emission (AE) technique.