Showing papers on "Acoustic emission published in 2013"
TL;DR: In this article, the crack initiation stress and damage stress of the Beishan granite under uniaxial and triaxial compressions were determined, and they were shown to be independent of each other.
235 citations
TL;DR: In this article, the acoustic emission parameters of amplitude, rise time, average frequency and signal strength were used to classify the damage and to determine the damage level in a beam with an increasing loading cycle.
196 citations
TL;DR: In this paper, fracture experiments on cementitious specimens are conducted, where the fracture mode is controlled by modifying the experiment geometry and the process is monitored by acoustic emission, and the distinct signature of the cracking modes is reflected on acoustic waveform parameters like the amplitude, RA-value and frequency.
165 citations
TL;DR: This work presents a novel classification technique designed for real-time applications inspired by the sequential k-means procedure, i.e., both the number of clusters and their elements are inferred from the data distribution in a multi-dimensional metric space.
131 citations
TL;DR: In this paper, the authors used non-linear theory for cylindrical shell to derive motion equation under simply supported boundary condition and solved the motion equation by using Galerkin method that resulted in a system of nonlinear equations with 6 degrees of freedom.
119 citations
TL;DR: In this paper, the authors used acoustic emission (AE) to characterize cracks in concrete, masonry, and rock materials and checked the extension for similar schemes in real size structures with a multiscale methodology.
Abstract: Acoustic emission (AE) is a Non Destructive Inspection Technique, widely used for monitoring of structural condition of different materials like concrete, masonry and rock. It utilizes the transient elastic waves after each fracture occurrence, which are captured by sensors on the surface. Several parameters of the AE behavior enlighten the damage stage within the material. These may be the cumulative AE activity, which is connected to the density of cracks and the emission energy which is connected to the cracks’ intensity. Additionally, AE waveform parameters like duration and frequency content depend on the motion of the crack tip and therefore, carry information about the mode of the crack. Study of the AE indices enlightens the fracture process, enabling predictions on the remaining life. However, the experimental conditions crucially affect the waveforms captured by the sensors. Specimen size, as well as sensor type and sensors separation distance exercise strong influence in the acoustic emission parameters. Since AE features like amplitude and energy are used for characterization purposes in the framework of an energy density approach and frequency is used in cracking mode classification schemes, the influence of the above mentioned experimental parameters should be certainly taken into account in order to lead to more accurate results and increase reliability. This would help to expand the use of AE in situ which so far is hindered by geometric and other technical reasons that allow only a case-specific approach. In the present paper fracture experiments in different specimen sizes of cementitious and rock materials are described while the sensor location relatively to the cracking zone is altered. The aim of this study is to validate the use of cracking characterization in laboratory and check the extension for similar schemes in real size structures with a multiscale methodology.
118 citations
TL;DR: In this article, a detailed experimental study and detailed mechanistic interpretations of the tensile behavior of one representative 3D non-crimp orthogonal woven (3DNCOW) carbon/epoxy composite is presented.
116 citations
TL;DR: In this paper, the physics of laboratory earthquake precursors in a biaxial shear configuration were investigated at room temperature and humidity in which we shear layers of glass beads under applied normal loads of 2-8"MPa and with shearing rates of 5-10"µm/s.
Abstract: [1] We investigate the physics of laboratory earthquake precursors in a biaxial shear configuration. We conduct laboratory experiments at room temperature and humidity in which we shear layers of glass beads under applied normal loads of 2–8 MPa and with shearing rates of 5–10 µm/s. We show that above ~ 3 MPa load, acoustic emission (AE), and shear microfailure (microslip) precursors exhibit an exponential increase in rate of occurrence, culminating in stick-slip failure. Precursors take place where the material is in a critical state—still modestly dilating, yet while the macroscopic frictional strength is no longer increasing.
115 citations
TL;DR: In this paper, the authors used acoustic emission (AE) to detect and locate the early stages of corrosion and macro-cracks and furthermore classify different crack types to aid maintenance priorities.
113 citations
TL;DR: In this article, continuous acoustic emission (AE) monitoring is applied to a cyclic wet and dry test of reinforced concrete beams and a relation between kinematical information of AE sources and nucleation of micro-cracks inside is identified by the SiGMA analysis and observed by the stereo-microscope.
111 citations
TL;DR: In this paper, the role of dislocation slip and deformation twinning as deformation mechanisms in magnesium alloys was clarified by monitoring acoustic emission (AE) in conjunction with a novel signal categorization technique in Mg alloy ZK60.
TL;DR: The Hilbert–Huang transform is used for the extraction of new relevant damage descriptor to be adopted for Acoustic Emission (AE) pattern recognition in order to help understanding the damage process.
TL;DR: In this paper, the authors report on the acoustic emission monitoring during laboratory hydraulic fracture studies conducted on Lyons sandstone samples under different applied external stress, and they compute AE hypocenter locations, analyze event frequency content and compute focal mechanisms (FMS).
TL;DR: In this paper, a review of current progress in condition monitoring of wind turbine gearboxes and generators is presented, as an input to the design of a new continuous condition monitoring system with automated warnings based on a combination of vibrational and acoustic emission (AE) analysis.
TL;DR: In this paper, an acoustic emission (AE) is used for monitoring the bending failure of concrete beams reinforced by external layers of different composite materials, which gives a clear depiction of the surface strain field and its transient changes according to stress redistribution which occurs after fracture moments.
TL;DR: In this article, a methodology for fast, reliable and experimentally economic determination of the fatigue limit in monolithic and composite materials by means of combined usage of two nondestructive inspection methods, namely infrared (IR) lock-in thermography and acoustic emission (AE), was introduced.
TL;DR: In this paper, the effects of axial thermal residual stresses, cyclic loading and presence of notches on the tensile performance of a SiC-fiber-reinforced barium-magnesium-alumina-silicate (BMAS) ceramic matrix composite were investigated.
Abstract: This study reports on the effects of axial thermal residual stresses, cyclic loading and presence of notches on the tensile performance of a SiC-fiber-reinforced barium–magnesium–alumina–silicate (BMAS) ceramic matrix composite. The residual stress state of the composite was experimentally measured by interrogation of the tensile curves at a uniquely well-defined common intersection point of unloading–reloading cycles in the tensile domain. Notch presence was critical on the material’s mechanical response and promoted catastrophic failure shortly after the achievement of a saturated matrix crack state. The result of cyclic loading was an increase by 20% in sustainable stress throughout loading, as compared to pure tension. Scatter in elastic properties within specimens of different notch-to-width ratios was reconciled with theoretical expectations by application of a translation vector approach in the stress–strain plane, based on the material’s residual stress state. Acoustic emission and infrared thermography provided valuable insight into damage identification, location and sequence.
TL;DR: In this paper, the authors designed and validated a monitoring system based on a sparse array of piezoelectric transducers to receive acoustic emissions distributed across the wall and a statistical pattern recognition algorithm capable of identifying critical structural conditions.
Abstract: Reinforced concrete shear walls are critical structural components in gravity and lateral force resisting systems. The objective of this work is to design and validate a monitoring system capable of rapid and automated damage assessment of reinforced concrete shear walls. The proposed system is based on a sparse array of piezoelectric transducers to receive acoustic emissions distributed across the wall and a statistical pattern recognition algorithm capable of identifying critical structural conditions to inform decision makers on the need for repair to ensure safe operation of the structure. The proposed system was validated on a full-scale reinforced concrete shear wall subjected to quasi-static cyclic loading.
TL;DR: In this article, the potential of data fusion in structural damage detection, identification and remaining-life estimation is investigated by integrating heterogeneous monitoring techniques and extracting damage-specific information using a hybrid non-destructive testing system relying on the combination of acoustic emission, digital image correlation and infrared thermography.
TL;DR: In this paper, the authors investigated the correlation between absorbed, released and acoustic emission energies, and obtained the complete load vs displacement curves up to complete failure, evidencing very different post-peak responses by varying the material, even for the same size and slenderness.
TL;DR: In this article, acoustic emission (AE) measurements were performed during room temperature tensile deformation of high-alloyed cast model steels with different austenite stability and stacking fault energy for better understanding of the kinetics of TRIP/TWIP-assisted plastic deformation.
TL;DR: In this article, the authors developed a first-arrival automatic determination technique based on Akaike information criterion (AIC) for thin metal plates and compared this technique with another AIC approach, STA/LTA method (shortterm average/long-term average) and a standard threshold-crossing technique.
TL;DR: In this article, an application of the acoustic emission signal features in the structure health monitoring (SHM) fields is described, which can be used in health monitoring of vital concrete structures such as bridges and any RC member subjected to bending load.
TL;DR: In this paper, a Gaussian filter is proposed to improve the interpretation of b-value data obtained during the test and a cluster analysis based on the k-means is presented to automatically classify the signal into tensile and shear cluster.
Abstract: In the last two decades, several efforts have been made to monitor the cracking behavior in RC structures. A technique that shows promise is acoustic emission (AE). This paper presents the results of an experimental study aimed at monitoring fracture processes in a large-scale RC shear wall using one of the most important AE parameters, that is, the b-value. The specimen was subjected to a displacement controlled reversed cyclic loading. A Gaussian filter is proposed to improve the interpretation of b-value data obtained during the test. In addition, a cluster analysis based on the k-means is presented to automatically classify the signal into tensile and shear cluster. Finally, a new algorithm called Sifted b-value (Sb) analysis is introduced to monitor the evolution of each crack mode. The proposed approach is capable to identify the initial yielding and eventually provide an early warning for the planning and implementation of remedial action to the structure at a point at which it is less expe...
TL;DR: In this article, Acoustic emission (AE) signals were analyzed to identify the classes of reinforced concrete (RC) beam corresponding to a specific crack mode and the relationship between average frequency and RA value indicated clear trend with respect to crack classifications.
TL;DR: In this paper, the post peak behavior of specimens with chemically treated fibers is more closely related to matrix cracking, while untreated fibers exhibit clear shear behavior due to pullout, and it is concluded that coating effectively contributes to the deflection of the cracks from the fiber-matrix interphase into the concrete matrix.
TL;DR: In this paper, the uniaxial compressive strength (UCS), Young's modulus and Poisson's ratio, both static and dynamic, of the seismogenic Triassic Evaporites of the Northern Apennines were reported.
TL;DR: In this article, the authors developed a methodology for the detection and monitoring of damage and fractures in building materials in the prospects of energetic renovation by using digital image correlation (DIC) and acoustic emission (AE) monitoring.
TL;DR: In this paper, the authors present details and results of experimental investigations conducted for characterizing the brittle failure processes induced in a rock due to monocyclic uniaxial compression on loading of two types of sandstone core samples saturated in NaCl brines of varying concentration (0, 2, 5, 10 and 15% NaCl by weight).
Abstract: Acoustic emissions (AE) and stress–strain curve analysis are well accepted ways of analysing crack propagation and monitoring the various failure stages (such as crack closure, crack initiation level during rock failure under compression) of rocks and rock-like materials. This paper presents details and results of experimental investigations conducted for characterizing the brittle failure processes induced in a rock due to monocyclic uniaxial compression on loading of two types of sandstone core samples saturated in NaCl brines of varying concentration (0, 2, 5, 10 and 15 % NaCl by weight). The two types of sandstone samples were saturated under vacuum for more than 45 days with the respective pore fluid to allow them to interact with the rocks. It was observed that the uniaxial compressive strength and stress–strain behaviour of the rock specimens changed with increasing NaCl concentration in the saturating fluid. The acoustic emission patterns also varied considerably for increasing ionic strength of the saturating brines. These observations can be attributed to the deposition of NaCl crystals in the rock’s pore spaces as well some minor geo-chemical interactions between the rock minerals and the brine. The AE pattern variations could also be partly related to the higher conductivity of the ionic strength of the high-NaCl concentration brine as it is able to transfer more acoustic energy from the cracks to the AE sensors.
TL;DR: In this article, a numerical model of coupled thermo-hydrologic-mechanical damage (THMD) in the failure process of rock is proposed using elastic damage mechanics, thermal-elastic theory and seepage mechanics.