scispace - formally typeset
Search or ask a question

Showing papers on "Acoustic emission published in 1989"



Journal ArticleDOI
TL;DR: Monitoring of cutting tool wear based on time series analysis of acoustic emission signals suggests that tool wear detection can be achieved by monitoring the evolution of the model parameter vector during machining processes.
Abstract: :This paper discusses th.e monitoring of cutting tool wear based on time series analysis of acoustic emission signals. In cutting operations, acoustic emission provides useful information concerning the tool wear condition because of the fundamental dif­ ferences between its source mechanisms in the rubbing friction on the wear land and the dislocation action in the shear zones. In this study, a signal processing scheme is developed which uses an autoregressive time-series to model the acoustic emission generated during cutting. The modeling scheme is implemented with a stochastic gradient algorithm to update the model parameters adaptively and is thus a suitable candidate for in-process sensing applications. This technique encodes the acoustic emission signal features into a time varying model parameter vector. Ex­ periments indicate that the parameter vector ignores the change of cutting param­ eters, but shows a strong sensitivity to the progress of cutting tool wear. This result suggests that tool wear detection can be achieved by monitoring the evolution of the model parameter vector during machining processes.

189 citations


Journal ArticleDOI
TL;DR: In this article, the authors count acoustic emissions and measure compressional wave velocities while a sample is heated to a maximum temperature of 300°C under confining pressures up to 55 MPa.
Abstract: We have developed a comprehensive experimental capability to study thermally induced microfractures in rock. We count acoustic emissions and measure compressional wave velocities while a sample is heated to a maximum temperature of 300°C under confining pressures up to 55 MPa. After a heating cycle we measure crack porosity and crack compressibility. We count the cracks under an SEM, sorting them by grain boundary and intragranular types and by mineral pair occurrence. Our observations reveal that (1) significant thermal cracking occurs in granites heated above 200° or 250°C under 28 and 55 MPa and above 100°C in granites heated under 7 MPa, (2) most newly created thermal cracks close at pressures below 40 MPa (1.5 km depth), (3) grain boundaries between quartz grains or between quartz and another mineral are preferentially cracked, (4) the threshold temperature for acoustic emissions is a positive, linear function of pressure, (5) total acoustic emission counts in Westerly granite heated to 300°C are slightly lower under 55 than 28 MPa confining pressure and are substantially lower under 28 than 7 MPa, (6) the compressional velocity decreases 22% as Westerly granite is heated to 300°C at 7 MPa, 15% at 28 MPa, and 10% at 55 MPa, and (7) greater hysteresis in compressional velocities occurs in samples heated at lower pressures. The acoustic emission counts in Westerly granite during heating show one or more peaks of activity as a function of temperature, with more peaks at lower pressures. We interpret this result to mean that additional crack populations are able to open at lower confining pressures. The curves of acoustic emission count rates can be fit by summing one to three Gaussian density functions.

161 citations


Journal ArticleDOI
TL;DR: In this article, an acoustic emission (AE) technique was used to locate the positions of fiber breaks and determine the lenght distribution of the fiber fragments resulting when a composite specimen containing a single fiber is loaded to failure.

77 citations


Journal ArticleDOI
TL;DR: In this paper, the acoustic emission (AE) technique has been applied to study scale-damage processes during thermal cycling of a tube, preferentially between 600 and 300°C in air, oxygen, and air + 0.5% SO2.
Abstract: The acoustic-emission (AE) technique has been applied to study scale-damage processes during thermal cycling of a tube, preferentially between 600 and 300°C in air, oxygen, and air + 0.5% SO2. The AE measurements were accompanied by optical and electron-optical investigations on tube rings exposed to the same cycling conditions. During the first period of cycling, a scale rich in hematite is formed. It suffers compressive stresses during cooling. The result is a buckled multilayered scale with separated lamellae. The scaling rate is lower than under isothermal conditions. AE signals start after 175°C cooling. After longer exposure times, the scale contains an increasing amount of magnetite and becomes more compact. The scaling rate increases and is comparable to that under isothermal conditions. AE signals are already observed after 50°C cooling and are correlated with crack formation in the magnetite caused by tensile stresses there. The addition of SO2 to air enhances the crack-healing process due to higher Fe diffusion in FeS. The scale is more compact.

60 citations


Journal ArticleDOI
22 Jun 1989-Nature
TL;DR: In this paper, the authors describe acoustic emissions and shear instabilities that are associated with the β-Sn → simple-hexagonal phase transformation in Si and Ge to pressures as high as 70 GPa, well above the brittle-ductile transitions of both elements.
Abstract: ACOUSTIC emissions are commonly observed at low pressures as they are characteristic of brittle deformation1,2. Most solids are ductile above a few gigapascals (GPa), and acoustic emissions have not been recorded from solids above 5 GPa. Here we describe acoustic emissions and shear instabilities that are associated with theβ-Sn → simple-hexagonal phase transformation in Si and Ge to pressures as high as 70 GPa, well above the brittle–ductile transitions of both elements. We propose that the events are driven by rapid atomic motions across displacive phase transformations, and not by fracturing or cracking of the samples. These phenomena may be relevant to the processes that generate deep-focus seismicity in the Earth's mantle.

56 citations


Patent
17 Jan 1989
TL;DR: In this article, a system and method for nondestructively inspecting and monitoring materials that indicate the structural integrity of the material is disclosed, which includes the following steps: First, the material to be subsequently monitored, is tagged by dispersing a small amount of finely divided particles throughout the material.
Abstract: A system and method for nondestructively inspecting and monitoring materials that indicates the structural integrity of the material is disclosed. The inspection method includes the following steps. First, the material to be subsequently monitored, is tagged by dispersing a small amount of finely divided particles throughout the material. The tagged material is then applied in accordance with its application, such as adhesive material to two pieces to be joined to form an adhesive joint. When the adhesive joint or other material is to be inspected, the tagged particles are activated to cause an inherent structural resonance in the tagged material. The activation and structural resonance of the material is then monitored and measured with a probe. Finally, the structure resonance of the material is related to the structural integrity of the adhesive joint, the matrix-reinforcement interface integrity of a composite material, or the state of cure of a resin. The tagged particles may be ferromagnetic particles and the probe either an electromagnetic field coil and an actuator or an electromagnetic field coil and an acoustic emission probe. The tagged particles may be piezoelectric particles and the probe either an electric field and an acelerometer or an electric field and an acoustic emission probe. Alternately, the tagged particles may be acoustic impedance mismatch particles and the probe is an ultrasonic inspection probe.

55 citations


Journal ArticleDOI
01 Apr 1989-Wear
TL;DR: In this paper, the authors measured acoustic emission in severe sliding of metallic specimens with a view to determining relationships, if any, between AE and wear-friction parameters, and found that AE is readily observed in dry sliding and that emission rates and cumulative count data are sensitive to the external variables which influence tribological contact conditions.

52 citations



Journal ArticleDOI
TL;DR: In this paper, it was shown that in a nonlinear elastic semi-infinite medium possessing the property of self-focusing of shear waves, besides bulk nonlinear shear wave, new surface acoustic waves exist, localization of which near the boundary is entirely due to nonlinear effects.

43 citations


Journal ArticleDOI
TL;DR: In this paper, the acoustic emission technique has been applied to identify scale cracking during thermal cycling of tubes of 2.25Cr-1Mo steel, and the scale morphology and failure mode were investigated by light and electron optical methods.
Abstract: The acoustic emission (AE) technique has been applied to identify scale cracking during thermal cycling of tubes of 2.25Cr-1Mo steel. The scale morphology and failure mode were investigated by light and electron optical methods. The scale formed at 600°C in water vapor consists of an outer magnetite and an inner, chromium-containing spinel layer. Cooling leads to tensile stresses in the scale that cause macro and microcrack formation in the scale. At constant-cycle parameters, a characteristic set of crack length and crack density is established. Changes in the cycle parameters also change the crack length and crack density. The experimental results can be described by a model developed by Hasselmann assuming a large number of noninteracting microcracks in a ceramic plate.

Journal ArticleDOI
TL;DR: In this paper, the authors model some terrestrial material as an elastic medium consisting of randomly distributed inclusions with a considerable concentration, and the waves incident on such an inhomogeneous medium undergo multiple scattering due to the presence of inclusions.
Abstract: In seismic exploration, elastic waves are sent to investigate subsurface geology. However, the transmission and interpretation of the elastic wave propagation is complicated by various factors. One major reason is that the earth can be a very complex medium. Nevertheless, in this paper, we model some terrestrial material as an elastic medium consisting of randomly distributed inclusions with a considerable concentration. The waves incident on such an inhomogeneous medium undergo multiple scattering due to the presence of inclusions. Consequently, the wave energy is redistributed thereby reducing the amplitude of the coherent wave.

Journal ArticleDOI
TL;DR: In this paper, an acoustic emission and force-based sensor fusion system involving pattern recognition analysis has been used to detect tool breakage, chip form and a threshold level of tool flank wear in turning.

Journal ArticleDOI
TL;DR: In this paper, a neural network is trained using simulated acoustic emission signals generated by a normal force acting on a thick plate to which information about the source related to its location and characteristics was appended.
Abstract: This article describes a novel approach for analyzing elastic wave signals to obtain a solution to simple inverse source problems. By using a simulated intelligent system that resembles the structure of a neural network and an acoustic source with its associated field of elastic waves in a plate, a set of pattern vectors is generated. The memory of the system is formed through a learning process in which a systematic series of experiments is presented to the system. In the experiments described here, the system was trained using simulated acoustic emission signals generated by a normal force acting on a thick plate to which information about the source related to its location and characteristics was appended. It is demonstrated, using such a trained system, that one can recover the characteristics of an unknown source from the acoustic signals emitted by it. It is also shown that one can synthesize from the memory the acoustic signals corresponding to an arbitrary source without using any elastodynamic th...

Journal ArticleDOI
TL;DR: In this paper, acoustic emission (AE) generated during turning was detected and analyzed in order to study tool wear development during metal cutting and investigate the possibility of applying AE techniques for in-process sensing of tool wear.


Journal ArticleDOI
TL;DR: In this article, the authors describe a method by which a point-like source of acoustic emission can be located in an anisotropic plate with arbitrary symmetry as long as the principal acoustic axes of the material are known a priori.
Abstract: In this paper is described a method by which a pointlike source of acoustic emission can be located in an anisotropic plate. The method is applicable for a source in an anisotropic solid of arbitrary symmetry as long as the principal acoustic axes of the material are known a priori. It is shown that from the time‐of‐flight differences of particular features in the waveforms detected by any pair of sensors, a set of nonlinear transcendental equations can be formed in which the coefficient of each term in the equations is related to the time‐of‐flight differences, the geometrical parameters of the array, and the wave speeds of quasiwaves propagating along each source/receiver path. For waves propagating in principal planes, the analytical expressions for the wave speed values are used. Extension to nonprincipal planes is obtained by computing the eigenvalues of the Green–Christoffel tensor. Determination of the optimum location of the source is found by minimizing the Euclidean functional associated with th...

Journal ArticleDOI
TL;DR: In this article, the failure behavior of spray coatings is characterized by using acoustic emission (AE) methodology, which is performed by using a set of acoustic emission sensors. But this method is not suitable for the case of plasma sprayed coatings, which are produced by the overlaying of many molten or semi-molten particles.
Abstract: Plasma sprayed coatings have a complex structure which is produced by the overlaying of many molten or semi-molten particles in the diameter range of 20 to 120 µm. There is a need to characterize the failure behaviour of coatings and this has been carried out by using acoustic emission (AE) methodology.

PatentDOI
TL;DR: An acoustic emission sensor comprising a piezoelectric material that is integral with a tooling or machine element in which acoustic emissions are to be sensed is described in this article.
Abstract: An acoustic emission sensor comprising a piezoelectric material that is integral with a tooling or machine element in which acoustic emissions are to be sensed.

Journal ArticleDOI
TL;DR: A model relating the velocity shifts of surface acoustic waves (SAW) to the six tensor components of quasistatic stresses makes it possible to define a family of quartz cuts with potentially low stress and temperature sensitivities for oscillator applications.
Abstract: A model is presented, relating the velocity shifts of surface acoustic waves (SAW) to the six tensor components of quasistatic stresses. Stress sensitivity is then defined through six independent coefficients, whatever the origin of the stress (direct external forces, thermoelastic stresses) might be. These coefficients, depending on crystal anisotropy, are computed for different cut angles and propagation directions of quartz crystal, and represented as a contour-line mapping. The determination of SAW quartz cuts compensated for both planar isotropic stresses and first-order temperature effects make it possible to define a family of quartz cuts with potentially low stress and temperature sensitivities for oscillator applications. >

Journal ArticleDOI
TL;DR: In this paper, an automatic acoustic emission (AE) source location algorithm has been developed for downhole AE measurement of subsurface cracks by using the triaxial hodogram method.
Abstract: An automatic acoustic emission (AE) source location algorithm has been developed for downhole AE measurement of subsurface cracks by using the triaxial hodogram method. The P-wave arrival time is detected by analyzing crosscorrelation coefficients among three components of AE signal energy; the P-wave direction is determined by the method of least squares. For detection of S-wave arrival time, a maximum‐likelihood method analyzes a distribution of instantaneous values of the SH-wave component amplitude. This algorithm can locate an AE source as accurately as human analysis. For field measurements, it takes less than 4 s to locate an AE source using a 16-bit personal computer with a program in C language. Automatic AE source location by the triaxial hodogram method has been realized with this algorithm.

Journal ArticleDOI
TL;DR: In this article, the authors used acoustic emission methods to study the multiple fracture process of carbon fiber/epoxy cross-ply laminates with the objective of making valid assignments for the failure of the transverse layer.

Journal ArticleDOI
TL;DR: In this paper, the F-111 Cold Proof Test Station Acoustic Emission Monitoring System has several innovative features, including a colour CRT which displays the exact location of AE events in real time on simultaneous overhead and side views of the aircraft.
Abstract: Significant portions of the F-111 aircraft were fabricated of D6AC steel, which is now known to have a fairly small critical crack size. To prove structural flight-worthiness the Air Force built a chamber at McClellan AFB, where all F-111 aircraft are periodically chilled to 40°C and stressed to 7.3g and3.0g. Recently the chamber was modernized, and Physical Acoustics Corporation was selected to supply an acoustic emission system to locate any sources of structural failure. The new F-111 Cold Proof Test Station Acoustic Emission Monitoring System has several innovative features, including a colour CRT which displays the exact location of AE events in real time on simultaneous overhead and side views of the F-111. The events are coloured green, yellow and red according to their severity, as calculated from their amplitude and energy. A monochromatic CRT is used concurrently with the colour CRT to display severity information on AE events which only arrive at one sensor. Alarms also audibly alert the operator to crucial events, using two tones to distinguish the degree of severity.

Journal ArticleDOI
TL;DR: In this article, the frequency spectra corresponding to various stages of plastic deformation with the physical phenomena occurring were analysed in frequency domain and it was shown that during continuous type AE emission, the extent of waiting time of mobile dislocations at short range obstacles is mainly responsible for the predominant frequencies observed.

Journal Article
A. Chichibu, K. Jo, M. Nakamura, T. Goto, M. Kamata 
TL;DR: In this paper, an ambankment and an unstable natural slope were monitored by using AE monitoring and traditional field techniques, and the results showed that the period of AE occurrence approximately coincides with the movement of the embankment.
Abstract: An ambankment and an unstable natural slope were monitored by using AE monitoring and traditional field techniques. AE characteristics of the two slopes were different. Results from the embankment showed that the period of AE occurrence approximately coincides with the movement of the embankment. In the natural slope, significant increases in levels of AE count rate were recorded at least two months before the observation of detectable ground movement. In the prediction of slope failure, it is important to take the differences of earth structures into consideration



Journal ArticleDOI
TL;DR: In this article, acoustic emission was measured during subcritical crack growth of Fe, Ni, 304 SS, a tool steel, and an Fe−Si single crystal, and it was concluded that the short discontinuous crack jumps were not detectable with the AE monitoring equipment.
Abstract: Acoustic emission (AE) has been measured during subcritical crack growth of Fe, Ni, 304 SS, a tool steel, and an Fe−Si single crystal. Tests were conducted using compact tension type samples in a variety of environments. Iron with two levels of S and P grain boundary concentrations was tested in Ca(NO3)2 at +750mV; Ni with P segregation was tested in 1N H2SO4 at +900 mV; two heats of 304 SS were tested in Na2S2O3 at open circuit potentials; Fe and Ni with S-enriched grain boundaries were tested in 1N H2SO4 at cathodic potentials; and RDS tool steel and an [001] oriented Fe−Si single crystal were tested in gaseous hydrogen at a pressure of 1 atm. The number of AE events/mm2 of crack extension increased with an increase in transgranular fracture for all of these test conditions with the exception of the Fe−Si single crystal. In this case, crack extension was 100 pct transgranular, but the number of events/mm2 was negligible. It was concluded that the short, discontinuous crack jumps were not detectable with the AE monitoring equipment. Likewise, for the intergranular subcritical crack growth, it was concluded that crack extension was either anodic dissolution with no accompanying AE or short, discontinuous crack jumps with nondetectable AE. It also was postulated that the transgranular fracture surfaces accompanying the intergranular subcritical crack growth resulted from ligaments which fractured behind the advancing crack front.

Journal ArticleDOI
TL;DR: In this paper, the authors focused on the quantitative analyses of martensitic growth events in an Fe-30 pct Ni alloy in order to determine the growth velocity and the final size of single transformation events directly and simultaneously.
Abstract: Previous studies of the growth velocity in athermal martensitic transformations were of an indirect nature in which the size of individual martensite plates could not be determined with precision. The present study focuses on the quantitative analyses of martensitic growth events in an Fe-30 pct Ni alloy in order to determine the growth velocity and the final size of single transfor-mation events directly and simultaneously. Both magnetic induction and acoustic emission (AE) techniques have been employed, and the corresponding analytical methods have been developed. While efforts have been made to minimize possible distortions of transformation signals caused by detectors and signal processing apparatus, it is recognized that the media in which the signals propagate impose a significant distortion on the signals. We have proposed methods to cope with the effect of eddy currents in the magnetic measurements and the frequency-dependent media attenuation in the AE measurements. Two independent experiments in our study have shown a consistent trend of the growth velocity and the final size of martensitic transformation events as a function of temperature. The growth velocity ranges from 0.25 to 0.65 of the shear wave velocity in the material. Several possibilities responsible for the velocity scatter are dis-cussed, and it is suggested that the varying strain conditions under which the martensitic growth events take place play a decisive role in determining the actual growth velocity.

PatentDOI
Schulze Guenther Dr1
TL;DR: In this paper, a commercially available accelerometer having at least one piezoelectric element and one seismic mass is coupled to the structural part in a frequency range substantially from 0.1 MHz to 2 Mhz.
Abstract: A transducer acoustic emission testing of a structural part includes a commercially available accelerometer having at least one piezoelectric element and one seismic mass. The accelerometer is typically tuned to a resonant frequency substantially between 1 kHz and 100 kHz. The accelerometer is coupled to the structural part in a frequency range substantially from 0.1 MHz to 2 Mhz.