Showing papers on "Acoustic emission published in 1982"
TL;DR: In this article, a diffuse field in a solid medium is found to partition its energy between transverse and dilatational waves in a fraction R = 2(cd/ct)3.
Abstract: A diffuse field in a solid medium is found to partition its energy between transverse and dilatational waves in a fraction R = 2(cd/ct)3. Energy flow rates from a diffuse field into a surface transducer from dilatational, transverse, and surface waves are compared. The relevance of the diffuse field concept for acoustic emission is discussed.
240 citations
TL;DR: In this article, the authors used the frequency characteristics of acoustic emissions to characterize the microfracturing processes leading to failure and found that larger cracks tend to generate events with larger amplitudes and containing lower-frequency components.
Abstract: Acoustic emission generated during the uniaxial compression of brittle rocks were counted after band-pass filtering. Throughout the whole process from application of load to failure, the count rate monitored through a low pass window was compared statistically with the monitored through a high passs window. The emission rate monitored through a low pas window increases more rapidly than that monitored through a high pass window as rock approaches failure. Two possible explanations for this effect are (1) generation of larger cracks (or coalescence of cracks into larger sizes) and (2) the relative attenuation of higher-frequency wave components. This finding is consistent with past observations, i.e., the relative number of large-amplitude events increases (i.e., a decrease in b value) as rock approaches failure. We suggest that larger cracks tend to generate events with larger amplitudes and containing lower-frequency components. The frequency characteristics of acoustic emissions are used to characterize the microfracturing processes leading to failure. The beginning of a sequence of acoustic emission activity is discussed in relation to the stress-strain curve and the onset of dilatancy. The present observations may be utilized in understanding structural instability of a region where rockbursts or earthquakes can potentially occur. If a sizable microseismicmore » population is observed through sensors placed near the fault, then a potential exists for predicting major earthquakes.« less
181 citations
TL;DR: In this paper, the analysis of acoustic emission signals generated during machining has been proposed as a technique for studying both the fundamentals of the cutting process and tool wear and as a methodology for detecting tool wear.
134 citations
TL;DR: In this article, a small non-colinear transducer array for omnidirectional acoustic emission monitoring is described, which consists of four piezoelectric sensor elements of sufficiently small diameter as to function as essentially point receivers and of sufficient frequency response as to be sensitive to the signals to be detected.
Abstract: A small non-colinear transducer array for omnidirectional acoustic emission monitoring is disclosed. The small transducer array consists of four piezoelectric sensor elements of sufficiently small diameter as to function as essentially point receivers and of sufficient frequency response as to be sensitive to the signals to be detected. The sensor elements of the transducer array are close together and are non-colinear so that the signals received by them can be used for determining the group velocity of acoustic waves on solid plates and on plate-like structures such as shells and pipes, and to permit determination of both the source direction and distance. The array is designed to monitor the region exterior to the area enclosed by the array, and the ratio of the smallest distance between sensors to the radius of a single transducer element is relatively large in order to minimize measurement errors introduced by undertainties in transducer element positions caused by large transducer sizes with respect to the acoustic waves being received.
61 citations
60 citations
Journal Article•
TL;DR: In this article, the authors combine the advantages of acoustic emission and ultrasonic methodologies in a technique which operates by introducing a repeating series of ultrasonic pulses into a material to simulate the spontaneous stress waves that would arise if the material were put under stress.
Abstract: The advantageous aspects of acoustic emission and ultrasonic methodologies are combined in a technique which operates by introducing a repeating series of ultrasonic pulses into a material. The waves introduced simulate the spontaneous stress waves that would arise if the material were put under stress as in the case of acoustic emission measurements. These benign stress waves are detected by an acoustic emission sensor. The physical arrangement of the ultrasonic (input) transducer and acoustic emission (output) sensor is such that the resultant waveform carries an imprint of morphological factors that govern or contribute to material performance. The output waveform is quite complex, but it can be quantitized in terms of a "stress wave factor". The stress wave factor, which can be defined in a number of ways, is essentially a relative measure of the efficiency of energy dissipation in a material. If flaws or other material anomalies exist in the volume being examined, their combined effect will appear in the stress wave factor.
60 citations
Patent•
19 Jan 1982
TL;DR: In this paper, an acoustic sensor is positioned at a distance from the welding zone and picks up airborne acoustic emission signals associated with the laser welding process, which are detected and analyzed to determine the quality of the weld.
Abstract: Herein disclosed is a noncontact, nondestructive method for monitoring the quality of a high energy weld, e.g., laser beam weld. In accordance with the proposed method, an acoustic sensor (32) is positioned at a distance from the welding zone (34) and picks up airborne acoustic emission signals (33) associated with the laser welding process. These acoustic signals, propagating through the air space between the welding zone (34) and the sensor (32), are detected and analyzed (36,37) to determine the quality of the weld (FIG. 3).
53 citations
TL;DR: In this article, the authors compared acceleration shock pulse transducers, acoustic emission and jerk measurements from slightly damaged bearings at medium to low speeds and showed that defects at very low speeds with an acoustic emission transducer are not easily explained.
45 citations
01 Jan 1982
TL;DR: In this article, a new method for in-process detection of cutting tool damage, such as wear, fracture and cracking, was proposed, where the acoustic emission signal from the metal cutting process was monitored in order to identify the state of the cutting tool edge.
Abstract: New method for in-process detection of cutting tool damage, such as wear, fracture and cracking was proposed. In the present study, the acoustic emission signal from the metal cutting process was monitored in order to identify the state of the cutting tool edge. The flank wear of the cutting tool was successfully measured by monitoring the gradual increase of the acoustic emission signal level. In-process detection of the cutting tool fracture was also possible by monitoring the stepwise increase in the amplitude level or the outbreak of burst-type acoustic emission signals. Finally, the feasibility of the in-process detection of tool cracking was investigated using the same sensor. Microprocessor was used to process the data obtained and to indicate the state of the cutting tool damage.
44 citations
TL;DR: In this article, the acoustic emission activity accompanying thermoelastic martensitic phase change in Au-47.5 at.% Cd alloy during the forward and reverse transformations was found to be asymmetric in energy and pulsewidth distribution.
42 citations
TL;DR: In this paper, acoustic emission (AE) monitoring is a non-destructive testing technique widely used to detect flaw development and crack propagation in metals, ceramics, polymers and composite materials.
Abstract: Acoustic emission (AE) monitoring is a non-destructive testing technique widely used to detect flaw development and crack propagation in metals, ceramics, polymers and composite materials. This paper relates the AE-strain characteristics from three softwoods tested in tension to mechanisms of deformation observed by scanning electron microscopy. All wood specimens are identical in size and radial-longitudinal in orientation, enabling the path of failure through planes of earlywood and latewood to be examined. It is found that the proportion of earlywood to latewood in each species has a marked effect on the shape of the AE-strain curves. Parana pine, containing very few latewood tracheids, exhibits a close to linear relationship between log cumulative emissions and strain until close to failure when the count rate increases rapidly. Douglas-fir, which has well-defined earlywood-latewood boundaries generates many AEs at low strain and there is greater variation in the shape of the AE characteristic between samples. Parana pine and Douglas-fir are tested at 20 °C (12.5 % EMC). Scots pine is also stressed at 20°C (12.5%EMC), 20°C (0.7%EMC) and 80°C (0.7%EMC), to assess the effect of moisture content on AE. Values of Young's modulus, stress at failure and work of fracture for the three softwoods are compared with the AE-strain data. Although the work of fracture is related to the total AEs to failure, no direct proportionality exists between the two parameters. Finally, the AE-strain data for plywood and glass-reinforced plastic (GRP), both man-made composite materials, are compared with those of wood, the natural composite material.
TL;DR: In this article, a modified Gilmore model taking into account the mass loss of the cavity can explain the rapid damping of the bubble oscillation observed in the experiments and an energy balance is considered.
Abstract: Cavitation bubble dynamics is investigated by the method of ‘optic cavitation’, i.e. the formation of single cavities in liquids by light. From the sound waves radiated upon collapse the pressure-time curve is obtained. Maximum bubble size and shock wave amplitudes are evaluated and an energy balance is considered. Numerical calculations with a modified Gilmore model taking into account the mass loss of the cavity can explain the rapid damping of the bubble oscillation observed in the experiments.
TL;DR: In this paper, the energy released following cracks and bond failures were measured for an EPON epoxy near 4.2 K. Cracking was observed to be load dependent; this may account in part for the training phenomenon observed in bringing epoxy-impregnated superconducting magnets to full design field.
TL;DR: In this article, the acoustic emission response from fine-grained polycrystalline ice subjected to constant compressive loads was examined and a model to describe the acoustic emissions in ice was developed.
TL;DR: In this article, the authors investigated the acoustic emission behavior of cast nickel aluminium bronze (NAB) in seawater by a dealuminification process similar to dezincification in brasses.
Abstract: Cast nickel aluminium bronze (NAB) can suffer severe selective phase corrosion in seawater by a dealuminification process similar to dezincification in brasses During the process, which occurs particularly in the heat-affected zones of weld repairs, copper is redeposited at the corroded areas thus making the phenomenon extremely difficult to detect by conventional non-destructive testing techniques It was considered likely that the different fracture modes of sound material and corroded material would result in differing forms of acoustic emission during deformation Acoustic emission monitoring was therefore carried out on tensile specimens of as-cast NAB, welded NAB and corroded NAB The failed specimens were then examined using optical and scanning electron microscopy It was apparent from the results that there were significant differences in the acoustic emission behaviour of the three types of material This was revealed in characteristic event counts, event amplitudes and rms energy outputs and by normalized amplitude analysis of the data These differences in behaviour have been correlated with the varying structures of NAB and their behaviour under stress
TL;DR: In this article, the locations of disturbances and quenches in a superconductor and a superconducting magnet have been determined by using a multiple set of acoustic emission (AE) sensors.
Abstract: Locations of disturbances and quenches in a superconductor and a superconducting magnet have been determined by using a multiple set of acoustic emission (AE) sensors. The letter presents an AE triangulation technique and experimental results.
01 Jan 1982
TL;DR: In this article, the authors present a guide for using acoustic emission during testing of fiber composite materials based on available information, including extraneous AE noise, signal attenuation, the Kaiser effect, specimen variability, the identification and interpretation of all potential sources, and the location of the AE source.
Abstract: The accumulation and the rate of accumulation of acoustic emission (AE) can be used to monitor early damage in fiber composites, changes of composite strength and correlations between different angle-plys and expected changes in failure mechanisms. In addition, AE can provide data for developing micro- and macro-failure models. However, reliable monitoring is required before implementing AE testing. To expedite this, extraneous AE noise, signal attenuation, the Kaiser effect, specimen variability, the identification and interpretation of all potential sources, and the location of the AE source must be investigated. Problems associated with monitoring and accepted mechanisms for handling them are found in the literature. A guide for using acoustic emission during testing of fiber composite materials based on available information is presented here.
TL;DR: In this paper, a study of the fracture behavior of sheet molding compound under tensile load using acoustic emission monitoring is presented. And the relationship between the stress/strain curve and the properties of the sheet moulding compound is discussed in terms of the results and the generation of cracks after the knee point of the curve was found to be reduced by using a matrix with high failure strain.
TL;DR: In this paper, the average energy measurements of acoustic emission events qualitatively exhibit the same behaviour as the acoustic emission measurements done by the ring-down count rate: the AE event mean energy is more important during the reverse transformation than during the direct one; the mean energy of the events is higher for the first plates of martensite than for the following plates.
Abstract: Acoustic emission (AE) characteristics have been studied during the thermoelastic martensitic transformation of Cu-Zn-Al alloy The average energy measurements of acoustic emission events qualitatively exhibit the same behaviour as the acoustic emission measurements done by the ring-down count rate: the AE event mean energy is more important during the reverse transformation than during the direct one; the mean energy of the events is higher for the transformation of the first plates of martensite than for the following plates For the reverse transformation the mean event energy is higher for the same plates which are the last to disappear
TL;DR: In this article, the initiation and growth of microcracks due to thermal stresses has been studied by applying the acoustic emission technique, which is approximately a superposition of two maxima near the phase transition of quartz and cristobalite.
Abstract: In porcelain during cooling the smaller thermal expansion coefficient of the glassy phase compared with the quartz particles causes radial tensile stresses and may create microcracks between these two components. The initiation and growth of microcracks due to thermal stresses has been studied by applying the acoustic emission technique. Different sources of microcracks are detected depending on thermal history. The acoustic emission spectrum is approximately a superposition of two maxima near the phase transition of quartz and cristobalite. Microcracking depends on particle size. With decreasing size of the quartz particles the maximum of microcrack activity shifts to lower temperatures.
TL;DR: In this paper, a simple formula is developed for the interference pattern of the spectra of two or more modes of progressing waves, which is then applied to interpret the complex frequency spectra over a wide range of frequency.
Abstract: Frequency spectra of transient Rayleigh–Lamb waves in a plate are evaluated by two methods, a direct numerical integration (FFT), and an asymptotic calculation of the theoretical responses. A simple formula is developed for the interference pattern of the spectra of two or more modes of progressing waves, which is then applied to interpret the complex frequency spectra of the waves in a plate over a wide range of frequency. These interpretive techniques may be applicable to source characterization of acoustic emission.
TL;DR: In this article, acoustic emission ringdown counting has been used to monitor sub-critical crack growth by stress corrosion of mild steel in disodium hydrogen phosphate, -brass in sodium nitrite and magnesium-7% aluminium in potassium chromate/sodium chloride mixtures, and by hydrogen embrittlement in mild steel and a 7179 T651 aluminium alloy.
Abstract: Acoustic emission ring-down counting has been used to monitor sub-critical crack growth by stress corrosion of mild steel in disodium hydrogen phosphate, -brass in sodium nitrite and magnesium–7% aluminium in potassium chromate/sodium chloride mixtures, and by hydrogen embrittlement in mild steel and a 7179 T651 aluminium alloy. The level of acoustic emission activity varies widely between different alloy/environment systems and is dependent upon microstructure, fracture path and crack growth rate. The practical significance of the results is discussed.
TL;DR: In this article, the authors show that acoustic emission (AE) produced as Pb 5 Ge 3 O 11 c -plate crystals undergo the ferroelectric hysteresis cycle results from domain wall nucleation and collapse.
TL;DR: In this paper, both acoustic emission and ultrasonic pulse velocity measurements were used to try to monitor the structural integrity of concrete, and four different concrete mixes were each tested at ages up to two years to provide a wide range of concrete strengths.
TL;DR: In this paper, a model of cleavage crack extension based on the local critical fracture stress criterion is used to interpret the emission behaviour from the materials tested. But the results indicate that incorporating AE techniques in detecting brittle fracture will enhance the fai...
Abstract: Acoustic emission (AE) monitoring, in liaison with fracture mechanics methods, is used to study cleavage crack growth in laboratory specimens of several alloy steels. Experimental results indicate that, during the onset of rapid unstable crack growth, spontaneous acoustic events are emitted. Fractographic studies on fracture surfaces have demonstrated that a large number of energetic signals resulted from the local brittle fracture at the crack tip. It is shown that the stress intensity factor corresponding to the first transor intergranular cleavage crack extension provides predictive information regarding the final unstable failure. A model of cleavage crack extension based on the local critical fracture stress criterion is used to interpret the emission behaviour from the materials tested. The difference in AE response during toughness testing is attributed to the microstructural features. These results indicate that incorporating AE techniques in detecting brittle fracture will enhance the fai...
TL;DR: In this article, it is shown that the acoustic emission obtained from plates and tube specimens for which failure is dominated by fibre fracture can be described analytically, and a means with which the importance of failure mechanisms other than fibre fracture, such as overloading, can be quantified.
Abstract: It is shown that the acoustic emission obtained from plates and tube specimens for which failure is dominated by fibre fracture can be described analytically. The approach which is taken proposes a means with which the importance of failure mechanisms other than fibre fracture can be quantified. Overloading is seen to be equivalent to an acceleration of time at the lower load. The limitations of this analysis are explored and it is shown that certain structures are not amenable to this approach.
TL;DR: In this article, the effect of heavy doping on the elastic constants of silicon is discussed, and the following device implications of this effect are discussed: Contrast between heavily doped and lightly doped regions in acoustic microscopy; change of velocity and temperature dependence of velocity of Rayleigh waves with doping; existence of Love waves in the presence of a heavily doping surface layer; interaction of surface waves with electrons controlled by a metal-oxide semiconductor (MOS) structure; determination of the carrier concentration from thermodynamic, rather than transport, properties.
Abstract: Absfroct-The effect of heavy doping on the elastic constants of silicon is well-established. The following device implications of this effect are discussed: ( l ) Contrast between heavily doped and lightly doped regions in acoustic microscopy; (2) change of velocity and temperature dependence of velocity of Rayleigh waves with doping; (3) existence of Love waves in the presence of a heavily doped surface layer; (4) interaction of surface waves with electrons controlled by a metal-oxide semiconductor (MOS) structure; (5 ) determination of the carrier concentration from thermodynamic, rather than transport, properties.
TL;DR: In this paper, the acoustic emission associated with the initiation and the growth of electrical trees in polymeric materials is examined under ac voltage application, and two kinds of acoustic emission waveform, a burst type and an impulse type, are observed, which suggest different tree-forming causes.
Abstract: The acoustic emission associated with the initiation and the growth of electrical trees inpolymeric materials is examined under ac voltage application. Two kinds of acoustic emission waveform, a burst type and an impulse type, are observed, which suggest different tree-forming causes. The procedure can provide not only a non-destructive testing technique but also a means for investigating the tree-forming mechanism.