Showing papers on "Acoustic emission published in 2007"
TL;DR: In this article, a coupled numerical method is used to study acoustic emission (AE) and microseismic (MS) events at the Kannagawa underground powerhouse cavern in Japan, where two codes, Fast Lagrangian Analysis of Continua (FLAC) and Particle Flow Code (PFC), a distinct element code, are coupled.
321 citations
TL;DR: In this article, the authors investigated the self-healing of cracks in an ultra high performance concrete, considered as a model material, and carried out an experimental program to quantify the phenomenon, which has been mainly highlighted by means of water permeability tests until now.
286 citations
TL;DR: In this article, the acoustic emission technique is applied to identify defects and damage in reinforced concrete structures and masonry buildings and a particular methodology has been put forward for crack propagation monitoring and damage assessment, in structural elements under service conditions.
265 citations
TL;DR: In this paper, an experimental investigation on spur gears in which natural pitting was allowed to occur was conducted, and it was observed that based on the analysis of root mean square (rms) levels only the acoustic emission technique was more sensitive in detecting and monitoring pitting than either the vibration or spectrometric oil analysis (SOA) techniques.
252 citations
TL;DR: In this paper, a novel method is developed to back-calculate rock mass strength parameters from acoustic emission (AE) monitoring data in combination with FEM stress analysis, based on the important concept of generalized AE initiation threshold of rock masses.
163 citations
25 Jul 2007-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, tension and compression tests were conducted for AZ31, AZ61 and AZ80 alloys at room temperature, and the distinctive tension/compression asymmetry in the yield behavior was analyzed for textured samples from extruded bars with various grain sizes.
Abstract: Tensile and compression tests were conducted for AZ31, AZ61 and AZ80 alloys at room temperature. The distinctive tension/compression asymmetry in the yield behaviour was analysed for textured samples from extruded bars with various grain sizes. Parallel measurements of the acoustic emission were carried out to gather information about the relative activity of twinning and dislocation glide during deformation. The acoustic emission data are used to elaborate on the possible roles of grain size and aluminium content on the deformation behaviour.
163 citations
TL;DR: In this paper, acoustic emission (AE) measurements along the gauge length indicated important critical intra and inter laminar damage occurring as early as 27% of ultimate tensile strength (UTS), typically 0.3% ultimate strain, for laminates with 90° layers.
142 citations
TL;DR: An alternative approach based on an optimization scheme is proposed to locate the point of impact in isotropic and anisotropic plates and it is investigated how the prediction would change if the plate is assumed to have some anisotropy.
Abstract: It is shown in this paper that the conventional triangulation technique is not very reliable for locating the impact point even in isotropic plates when the sensors are placed close to the point of strike for two reasons: First, it is difficult to pinpoint the exact time of arrival of the signal and, second, the Lamb modes in a plate are dispersive. Dispersive signals attenuate differently at various frequencies and propagate with different speeds causing distortions in the received signals, and thus introduce error in the time of flight measurement. The triangulation technique assumes that wave speeds in all directions are the same, which is not true for anisotropic plates. Here an alternative approach based on an optimization scheme is proposed to locate the point of impact in isotropic and anisotropic plates. A formulation is presented for the general anisotropic case. Experiments are carried out with an aluminum plate by dropping balls on the plate and picking up acoustic signals at different locations. The impact points predicted by the conventional triangulation technique and the proposed modified method are compared for this isotropic plate. Then it is investigated how the prediction would change if the plate is assumed to have some anisotropy.
127 citations
TL;DR: In this paper, three composites materials, Glare 2 fiber metal laminates, graphite/epoxy (Gr/Ep) and carbon/carbon (C/C) have been tested mechanically under quasi-static loading in uniaxial and bending modes using uniform and notched specimens.
120 citations
TL;DR: In this article, the collective dislocation dynamics in various single crystals was investigated using acoustic emission and high-resolution extensometry, and it was shown that the dislocation avalanches are limited in size by a nontrivial finite size effect resulting from the lamellar character of avalanches.
Abstract: Plasticity, a key property in the mechanical behavior and processing of crystalline solids, has been traditionally viewed as a smooth and homogeneous flow. However, using two experimental methods, acoustic emission and high-resolution extensometry, to probe the collective dislocation dynamics in various single crystals, we show that its intermittent critical-like character appears as a rule rather than an exception. Such intermittent, apparently scale-free plastic activity is observed in single-slip as well as multislip conditions and is not significantly influenced by forest hardening. Strain bursts resulting from dislocation avalanches are limited in size by a nontrivial finite size effect resulting from the lamellar character of avalanches. This cutoff explains why strain curves of macroscopic samples are smooth, whereas fluctuations of plastic activity are outstanding in submillimetric structures.
119 citations
TL;DR: In this article, the authors used acoustic emission and X-ray tomography to identify the mechanisms of damage and the fracture process during compressive loading on concrete specimens, in relation with the microstructure of the material.
TL;DR: In this article, the authors constructed a novel apparatus based on subharmonic ultrasound for the accurate imaging of closed cracks, where linear and nonlinear responses not only from the tip but also from other parts of cracks were observed in fundamental and sub-harmonic images, which were changed with varying closure stress.
Abstract: The authors constructed a novel apparatus based on subharmonic ultrasound for the accurate imaging of closed cracks. Linear and nonlinear responses not only from the tip but also from other parts of cracks were observed in fundamental and subharmonic images, which were changed with varying closure stress. The subharmonic images always gave an accurate length of partially closed cracks, in contrast to the fundamental images in which the crack length was underestimated. Significant similarities in generation and resonance phenomena of subharmonic waves, acoustic emission, and the vibration of microbubbles are discussed.
TL;DR: In this paper, the structural stability of three medieval towers, Torre Sineo (Torre Astesiano), Torre Bonino and Torre Staro, was investigated.
TL;DR: In this article, a technique based on acoustic emission (AE) signal wavelet analysis is proposed for tool condition monitoring, where the local characterize of frequency band, which contains the main energy of AE signals, is depicted by the wavelet multi-resolution analysis, and the singularity of the signal is represented by wavelet resolution coefficient norm.
Abstract: It is believed that the acoustic emission (AE) signals contain potentially valuable information for tool wear and breakage monitoring and detection. However, AE stress waves produced in the cutting zone are distorted by the transmission path and the measurement systems and it is difficult to obtain an effective result by these raw acoustic emission data. In this article, a technique based on AE signal wavelet analysis is proposed for tool condition monitoring. The local characterize of frequency band, which contains the main energy of AE signals, is depicted by the wavelet multi-resolution analysis, and the singularity of the signal is represented by wavelet resolution coefficient norm. The feasibility for tool condition monitoring is demonstrated by the various cutting conditions in turning experiments.
TL;DR: In this article, the authors investigated the applicability of acoustic emission (AE) technique to detect and locate the corrosion-induced failure of high-strength steel tendons of prestressed concrete structures.
TL;DR: In this article, a triaxial compression test was conducted on the basalt from Mount Etna (Italy) under an effective confining pressure representative of conditions under a volcanic edifice (40 MPa), and at a constant strain rate of 5 similar to 10(-6) s(-1).
Abstract: We have deformed basalt from Mount Etna (Italy) in triaxial compression tests under an effective confining pressure representative of conditions under a volcanic edifice (40 MPa), and at a constant strain rate of 5 similar to 10(-6) s(-1). Despite containing a high level of pre-existing microcrack damage, Etna basalt retains a high strength of 475 MPa. We have monitored the complete deformation cycle through contemporaneous measurements of axial strain, pore volume change, compressional wave velocity change and acoustic emission (AE) output. We have been able to follow the complete evolution of the throughgoing shear fault without recourse to any artificial means of slowing the deformation. Locations of AE events over time yields an estimate of the fault propagation velocity of between 2 and 4 mm. s(-1). We also find excellent agreement between AE locations and post-test images from X-ray microtomography scanning that delineates deformation zone architecture.
TL;DR: In this article, the authors proposed the use of active waveguides for monitoring the stability of soil slopes, where developing shear surfaces generate acoustic emission (AE) in the soil.
Abstract: In soil slopes, developing shear surfaces generate acoustic emission (AE). The authors have previously proposed the use of active waveguides for monitoring the stability of such slopes. Active wave...
TL;DR: In this paper, a wavelet-based methodology was proposed for the monitoring of grinding wheel condition based on acoustic emission (AE) signals, which achieved 97% clustering accuracy for the high material removal rate condition, 86.7% for the low material removal ratio condition, and 76.7 % for the combined grinding conditions if the base wavelet, the decomposition level, and the GA parameters were properly selected.
Abstract: Grinding wheel surface condition changes as more material is removed. This paper presents a wavelet-based methodology for grinding wheel condition monitoring based on acoustic emission (AE) signals. Grinding experiments in creep feed mode were conducted to grind alumina specimens with a resinoid-bonded diamond wheel using two different conditions. During the experiments, AE signals were collected when the wheel was 'sharp' and when the wheel was 'dull'. Discriminant features were then extracted from each raw AE signal segment using the discrete wavelet decomposition procedure. An adaptive genetic clustering algorithm was finally applied to the extracted features in order to distinguish different states of grinding wheel condition. The test results indicate that the proposed methodology can achieve 97% clustering accuracy for the high material removal rate condition, 86.7% for the low material removal rate condition, and 76.7% for the combined grinding conditions if the base wavelet, the decomposition level, and the GA parameters are properly selected.
TL;DR: By conducting experiments in the presence of background electrolytes and also using non-ionic surfactants, the importance of electrostatic effects has been revealed and provides further mechanistic evidence for the interpretation of the effect of surface-active solutes on acoustic cavitation and hence on the mechanism of sonochemistry.
Abstract: The effect of adding surface-active solutes to water being insonated at 515 kHz has been investigated by monitoring the acoustic emission from the solutions. At low concentrations (<3 mM), sodium dodecyl sulfate causes marked changes to the acoustic emission spectrum which can be interpreted in terms of preventing bubble coalescence and declustering of bubbles within a cavitating bubble cloud. By conducting experiments in the presence of background electrolytes and also using non-ionic surfactants, the importance of electrostatic effects has been revealed. The results provide further mechanistic evidence for the interpretation of the effect of surface-active solutes on acoustic cavitation and hence on the mechanism of sonochemistry. The work will be valuable to many researchers in allowing them to optimize reaction and process conditions in sonochemical systems.
TL;DR: In this paper, an acoustic emission (AE) sensor and a piezoelectric dynamometer were used to monitor the diamond-ground optical glasses to correlate the processing characteristics with the generated surface and subsurface integrities, which were characterized by atomic force microscope (AFM), scanning electronic microscope (SEM), and nanoindentation technique.
Abstract: In order to investigate the surface and subsurface integrity of diamond-ground optical glasses, a Tetraform ‘C’ machine tool featuring high close-loop stiffness was used to conduct the ultra-precision machining of fused silica and fused quartz assisted with electrolytic in-process dressing (ELID). An acoustic emission (AE) sensor and a piezoelectric dynamometer were used to monitor the grinding process to correlate the processing characteristics with the generated surface and subsurface integrities, which were characterized by atomic force microscope (AFM), scanning electronic microscope (SEM), and nano-indentation technique. Experimental results showed that for optical glasses the fracture toughness value can be used to predict the machinability while its bigger value always means a better surface and subsurface integrity. During the grinding process of optical glasses, the smaller amplitude and RMS values of AE signal, as well as the smaller grinding forces and the ratio of normal force to tangential force, correspond to a better surface and subsurface integrity. With selected machining parameters and a 6–12 μm grain-sized diamond-grinding wheel, nanometric quality surfaces (Ra
TL;DR: In this article, acoustic emission (AE) analysis is applied to monitor the deterioration progress of a reinforced concrete beam under loading in a laboratory test, and the location capability decreases when cracking of the concrete occurs.
TL;DR: In this article, the authors investigated the correlation between micro-fractures and acoustic emission (AE) and demonstrated the advantages of the combined use of acoustic emission and detailed petrographic study of thin rock slices, showing the pre-peak damage evolution caused by macro-compressive and macro-tensile stresses in rock material.
TL;DR: The spatial distribution of the acoustic amplitude in a sonochemical reactor has been numerically calculated using the finite element method (FEM) and it is revealed that the thin (thick) glass or stainless steel wall is nearly a free (rigid) boundary and that the glass wall is freer than the Stainless steel wall.
TL;DR: In this paper, acoustic emission (AE) sensing was employed for on-line detection of workpiece status and to improve the process stability and workpiece quality by minimising associated defects.
TL;DR: In this paper, numerical results based on a Rock Failure Process Analysis code (RFPA2D) are presented, which show the nucleation and growth of macro-cracks in relatively homogeneous and heterogeneous specimens under uniaxial tension.
TL;DR: In this article, a tensile rig for in situ tomography was used to understand the significance of acoustic emission signals, recorded simultaneously, during image acquisition on the same sample, and a continuous in situ tensile test was compared with the standard step-by-step procedure.
TL;DR: In this paper, a case study concerning both numerical modeling and in-situ monitoring of a retrofitted RC beam with non-rectangular cross-section is presented before retrofitting, non-destructive techniques, such as pull-out and impact tests, were used to estimate the mechanical parameters of concrete at the same time, a long-term monitoring with the Acoustic Emission (AE) technique was carried out in order to investigate on creep effects and micro-cracking phenomena Then, after a complete removal of the overload and retrofitting with FRP sheets, an in-
Abstract: A case study concerning both numerical modeling and in-situ monitoring of a retrofitted RC beam with non-rectangular cross-section is presented Before retrofitting, non-destructive techniques, such as pull-out and impact tests, were used to estimate the mechanical parameters of concrete At the same time, a long-term monitoring with the Acoustic Emission (AE) technique was carried out in order to investigate on creep effects and microcracking phenomena Then, after a complete removal of the overload and retrofitting with FRP sheets, an in-situ loading test was performed At that stage, the AE technique was again profitably used for the analysis of the cracking progression leading to FRP debonding A numerical model of the structure is then proposed in the framework of the FE discretization with mechanical parameters estimated according to an inverse analysis on the monitored mechanical behavior of the structure before retrofitting According to this model it is shown that, when the flexural inertia of the retrofitted beam is considerably higher than that of the unrepaired beam, snap-back instabilities can take place Finally, considering the self-similarity between the acoustic emission phenomenon and seismicity, an analogy between the snap-back instability of the FRP delamination and that occurring during fault growth is proposed
TL;DR: In this paper, two source location techniques, a traditional wave velocity-based and an energy-based technique, using triangular sensor arrays, are used to locate source positions on the cylinder head of a 74kW diesel engine using simulated sources (pencil lead break) and real sources (e.g. injectors and exhaust valves during engine running).
TL;DR: In this paper, an asymmetric Lamb wave propagation representing acoustic emissions (AE) is modelled based on a superposition of plate bending vibration modes, and a two-neuron prototype is built and tested using a simulated AE source (a pencil lead break) on a riveted aluminium joint and on a composite plate.
TL;DR: In this paper, cylindrical coal samples were subjected to three successive cycles of sorption-desorption processes of a single gas (CO2, CH4). Acoustic emission (AE) and strains were simultaneously recorded during the sorption and desorption process.