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The process of cutting of an aluminum alloy has been monitored by the acoustic emission method. Single-crystal natural and synthetic diamond tools have been used in the investigation. The comparative analysis has demonstrated that...
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The process of cutting of an aluminum alloy has been monitored by the acoustic emission method. Single-crystal natural and synthetic diamond tools have been used in the investigation. The comparative analysis has demonstrated that the correlation model of acoustic emission, which was put forward by Pan and Dornfeld, is valid for the conditions of fine diamond turning of aluminum alloys.
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Abstract Brittleness has an important effect on the deformation and failure behavior of rocks. In this study, a brittleness evaluation index (Bp) based on the prepeak stress–strain curves of rock was proposed, and its effectivene...
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Abstract Brittleness has an important effect on the deformation and failure behavior of rocks. In this study, a brittleness evaluation index (Bp) based on the prepeak stress–strain curves of rock was proposed, and its effectiveness was verified by triaxial and uniaxial compression tests on different types of rocks. Based on the newly proposed index, the brittleness effect on the acoustic emission (AE) characteristics, such as the AE b-value, AE energy, average frequency (AF), and the ratio of the rise time to the peak amplitude (RA) of rocks under uniaxial loading was analyzed. The results show that the Bp has a linear negative correlation with the AE b-value. The stronger the brittleness of the rock, the smaller the AE b-value and the higher the ratio of macro to microcracks generated during rock failure. The brittleness effect on the variation law of the AE b-value is reflected during unstable crack propagation. In addition, rock brittleness affects the AF value but had no obvious influence on the RA value. The more brittle the rock is, the higher the proportion of tensile cracks in the fracture process. The research results could further enrich the evaluation system for rock brittleness and contribute to a better understanding of rock damage.
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The paper addresses the dependence of acoustic emission produced in rolled hafnium GFE-1 under tensile deformation on the material’s structural state. A correlation has been established between the material structure, the level o...
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The paper addresses the dependence of acoustic emission produced in rolled hafnium GFE-1 under tensile deformation on the material’s structural state. A correlation has been established between the material structure, the level of mechanical properties and the values of acoustic parameters. Acoustic emission in non-recrystallized hafnium under tensile deformation is recorded only at the stages that precede fracture. Upon recrystallization annealing at temperatures of 1123 and 1373 K acoustic emission occurs at all the stages of tensile deformation. The highest level of acoustic emission activity in hafnium is observed during the transition from elastic to elastic-plastic strain.
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An algorithmic approach to improve the accuracy of acoustic emission (AE) source location was demonstrated by using a large database of wideband-AE-modeled signals and wavelet-transform (WT) results. The AE-signal database was cre...
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An algorithmic approach to improve the accuracy of acoustic emission (AE) source location was demonstrated by using a large database of wideband-AE-modeled signals and wavelet-transform (WT) results. The AE-signal database was created by a three-dimensional, finite-element code. These signals represented the out-of-plane displacements from buried dipole AE sources in aluminum plates of 4.7 mm thickness and large lateral dimensions. The AE signals included eight different source types, six or seven source depths (below the plate surface), and seven different radiation angles (0° to 90°). The surface displacement signals were measured at three propagation distances (i.e., 60, 120, and 180 mm) and were filtered with a 40 kHz high-pass filter. The WT results consisted of WT magnitudes (i.e., WT coefficients) as a function of both time and frequency. The regions of greatest WT magnitude were found to occur at or very near three key frequencies (60, 270, and 522 kHz), and these regions were typically representative of the first fundamental antisymmetric mode (A_0) or the first fundamental symmetric mode (S_0). Additionally, a plot of the signal-propagation distances as a function of the WT-peak-based arrival times created slope-based velocities that corresponded quite closely to the relevant theoretical group velocities for the A_0 or S_0 modes. It was determined that the key frequency having the greatest WT peak magnitude always corresponded to a known mode having a known group velocity. The remaining two key frequencies had their associated modes determined by means of a newly devised algorithm (which could be computer-automated) that considers the arrival times of the WT peak magnitudes but requires knowledge of neither the propagation distance nor the AE-source-operation time. The algorithm also computed a range (i.e., linear distance) from a measured signal to the AE source.
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So sensitive is the human ear that sound pressures light enough to vibrate the eardrum by mere tenths of an angstrom generate waves that are amplified in the cochlea and then passed on to the brain as electrical signals. Although ...
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So sensitive is the human ear that sound pressures light enough to vibrate the eardrum by mere tenths of an angstrom generate waves that are amplified in the cochlea and then passed on to the brain as electrical signals. Although details are murky at the cellular level, the basic physics of hearing is straightforward: Vibrational motion of the stapes bone in the middle ear creates a pressure difference across the basilar membrane, an elastic ribbon that partitions the fluid-filled cochlea lengthwise into two chambers. The pressure difference creates a slow traveling wave along the membrane, whose elasticity acts as a restoring force.
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Acoustic emission signals in non-coherent addition of waves and coherent addition of displacement were analysed. It is shown that for non-coherent addition of waves the area under a curve of a temporary course of acoustic emission...
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Acoustic emission signals in non-coherent addition of waves and coherent addition of displacement were analysed. It is shown that for non-coherent addition of waves the area under a curve of a temporary course of acoustic emission intensity does not depend on the entry speed of the load. For an acoustic emission, which is calculated by addition of displacement impulses, the area under a curve of change of effective amplitude in time does not depend on the entry speed of the load.
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A database of wideband acoustic emission (AE) modeled signals was used to continue to examine the use of wavelet-transform (WT) results to accomplish identification of AE sources. The AE signals in the database were created by use...
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A database of wideband acoustic emission (AE) modeled signals was used to continue to examine the use of wavelet-transform (WT) results to accomplish identification of AE sources. The AE signals in the database were created by use of a validated three-dimensional finite-element code. These signals represented the out-of-plane displacements from buried dipole sources in aluminum plates 4.7 mm thick with large lateral dimensions. The surface displacement signals at three distances (60, 120, and 180 mm) were filtered with a 40 kHz high-pass filter prior to applying the WT. The WTs were calculated with a freeware software program. The WT peak magnitudes were calculated at three key frequencies (i.e., 60, 270, and 522 kHz) for all the signals generated by three different source types (i.e., in-plane dipole, microcrack initiation, and balanced shear). The signal database covered seven different radiation angles (from 0° to 90° and six or seven depths for each source type. The fundamental Lamb modes that corresponded to the WT peak magnitudes were also determined. It was concluded that the variation of the normalized peak WT magnitudes as a function of the radiation angles was effectively constant for the various source depths. This effective independence of source depth was demonstrated for a fixed source type, propagation distance, and key frequency-mode combination. The fact that the radiation-angle dependence varied among source types for particular frequency-mode combinations allowed ratios of the WT peak magnitudes at different radiation angles to be used to uniquely distinguish the different source types.
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This paper concerns the use of Modal Acoustic Emission (MAE) on composite overwrapped pressure vessels (COPY). It investigates the physics of this approach, defined as a promising method that can provide further information to cla...
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This paper concerns the use of Modal Acoustic Emission (MAE) on composite overwrapped pressure vessels (COPY). It investigates the physics of this approach, defined as a promising method that can provide further information to classical acoustic emission technique. The investigations are achieved on a small coupon and full scale specimens extracted from a COPY. The separation mode was previously performed using Pencil Lead Breaks (PLBs) based on Continuous Wavelet Transform (CWT) analysis. It has been shown that extensional (S-0) and flexural (A(0)) modes were successfully splitted and their frequency bandwidths are defined. After that, an appropriate algorithm was developed based on CWT analysis of the extracted AE signals coming from the region of damage. Results obtained by this method show a good agreement regarding the nature of damage and predominant mode expected during tensile test. (C) 2016 Elsevier Ltd. All rights reserved.
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The article presents the results of applying the signal time reversal method in the ultrasound (similar to 130 kHz) under strong spot heating conditions (>250 degrees C) and deformation of the investigated sample-a steel plate. It...
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The article presents the results of applying the signal time reversal method in the ultrasound (similar to 130 kHz) under strong spot heating conditions (>250 degrees C) and deformation of the investigated sample-a steel plate. It is shown that the distortions of the time-reversed signal during propagation, caused by changes in the sample properties, can be significantly reduced by reducing the duration of the processed signals and by using several receivers.
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Immersed mechanical resonators are well suited for probing the properties of fluids, since the surrounding environment influences the resonant characteristics of such oscillators in several ways. Quartz tuning forks have gained mu...
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Immersed mechanical resonators are well suited for probing the properties of fluids, since the surrounding environment influences the resonant characteristics of such oscillators in several ways. Quartz tuning forks have gained much popularity in recent years as the resonators of choice for studies of liquid helium. They have many superior properties when compared to other oscillating bodies conventionally used for this purpose, such as vibrating wires. However, the intricate geometry of a tuning fork represents a challenge for analyzing their behavior in a fluid environment--analytical approaches do not carry very far. In this article the characteristics of immersed quartz tuning fork resonators are studied by numerical simulations. We account for the compressibility of the medium, that is acoustic phenomena, and neglect viscosity, with the aim to realistically model the oscillator response in superfluid helium. The significance of different tuning fork shapes is studied. Acoustic emission in infinite medium and acoustic resonances in confined volumes are investigated. The results can aid in choosing a quartz tuning fork with suitable properties for experiments, as well as interpreting measured data.
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