Acoustic Emission Signal Parameters Research Articles

Analysis of damage characteristics of steel fiber-reinforced concrete based on acoustic emission

Steel fiber-reinforced concrete (SFRC) has been widely used as a building material worldwide. The macroscopic destruction of this material is a manifestation of the internal microdamage evolution. Hence, investigating the internal damage evolution process in concrete for monitoring in-service concrete has considerable significance in terms of safety. This study investigates the damage characteristics of SFRC with different steel fiber contents (0, 15, 30, 45, and 60 kg/m3) using Brazilian disk splitting tests and acoustic emission (AE) techniques. The changing trend of the characteristic parameters (counts and energy, respectively) of AE signals throughout the failure process of concrete is analyzed. Then, the moment tensor method is used to determine the temporal and spatial evolution of microcracks in SFRC. Research results show that the AE characteristic parameters are closely related to the internal damage of concrete specimens, and show different characteristics of AE signals in different failure stages. When the matrix cracks, the AE counts become denser, the values increase sharply, and the energy is closely related to fiber content (the lower the fiber content, the higher the energy value, and the minimum AE energy is 1.80e5 aJ (in SFRC60)). According to the moment tensor method, the cumulative microcracks are first appear to near the central axis and then dispersed to the surrounding area in the SFRC with the effect of steel fiber, effectively weakening the local damage. Based on the R-value method, the proportion analysis results of microcracks show that tensile damage is the primary destruction mechanism throughout the failure process of the Brazilian disk. The minimum proportion for tensile microcracks is 56.67%.

Acoustic Emission Test of Marble Powder Concrete

Uniaxial compression tests were carried out based on acoustic emission technology to study the rule and process of the damage evolution of marble powder concrete (MPC) under compression. The fracture characteristics of MPC are examined by analyzing the variation characteristics of acoustic emission signal parameters. The damage evolution model of MPC is established based on the characteristic parameters. The results showed that the strength loss rate of MPC decreased with the curing time, and the maximum strength loss rate of 28 d was 6.2% when the substitution percentage was 15%. According to the analysis of acoustic emission parameters, the compression failure process of MPC can be divided into three stages, the acoustic emission activity is higher in the early stage of loading, the relative stress during critical instability failure is reduced, and the substitution percentage is reduced by 4.2% at 15%. MPC is mainly fractured by tensile failure. With the increase in marble powder substitution percentage, the proportion of tensile mode cracks in stages I and II decreased. The proportion in stage III showed an increasing trend, and the failure characteristics gradually changed from brittleness to ductility. The fluctuation amplitude of the b-value increased with the substitution percentage, and the highest volatility was 18.5% when the substitution percentage was 15%. The crack propagation behavior gradually changed from stable growth to unstable growth. When the substitution percentage is lower than 15%, the damage development of MPC in the middle of stress (relative stress 20~70%) is relatively slow, and the damage development is accelerated in the late stress stage.

Analysis of the Significance of Changes in the Number and Energy Parameters of Acoustic Emission Signals on the Assessment of the Strength of Fibre-Cement Boards.

The article presents the results of three-point bending tests carried out for samples cut from full-size fibre–cement boards subjected to typical and exceptional conditions. The tests were carried out with the simultaneous acquisition of acoustic emission signals. It has been noted that some factors significantly deteriorate the strength parameters of the samples as well as cause the occurrence of differences in the number of acoustic emission signals of various classes and their energy parameters. A statistical analysis was carried out in order to repeat the relationship between the strength parameters of the samples and the acoustic emission parameters. Based on the research, it was found that the MOR bending strength for specimens exposed to fire and high temperature is more than 50% lower than for air-dried specimens and specimens exposed to water. The increased number of freeze–thaw cycles also has an impact on the strength of the specimens. Components exposed to more than 10 freeze–thaw cycles had a strength more than 30% smaller than the reference specimens soaked in water and exposed to bath-drying cycles. A similar dependency was indicated by the number of signals of the individual classes, their energy parameters and their frequencies. The number, strength, duration and frequency also decreased along with the increase in the test case number. On this basis, conclusions were drawn concerning the suitability of acoustic emission for the evaluation of the strength of fibre–cement elements.

Condition Monitoring of Spur Gear Box based on Acoustic Emission Signal Analysis

Abstract: Monitoring the condition of rotating machinery, such as gearbox is an important task in order to enhance its performance. Acoustic Emission (AE) and vibration analyses are some of the most accomplished techniques used for this purpose. Acoustic emission technique has the ability to detect the initial phase of component degradation. This paper presents the experimental investigation of gearbox condition using acoustic emission techniques. AE signals of gearbox under different conditions are acquired. AE signal parameters such as RMS, amplitude and rise time have provided information about the condition of the gearbox. Hence, AE technique can also be used for monitoring the gearbox.

Acoustic emission characteristics of Pykrete under uniaxial compression

Pykrete is a special building material suitable for cold regions. It has attracted extensive attention in recent years owing to its high strength and toughness. However, for structures constructed using Pykrete, appropriate damage detection and evaluation methods have rarely been investigated. As with most materials, the destruction of the Pykrete structure releases energy as stress waves and produces acoustic emission (AE) signals, which help understand the damage process and evaluate the degree of damage to the Pykrete. In this study, the AE technique was employed to monitor and evaluate the damage to different types of Pykretes and matrix subjected to uniaxial compression. Combined with the load-time curve, the conventional parameters of AE signals obtained from Pykretes and matrix were analyzed first. Furthermore, the failure modes of Pykretes and the matrix were investigated via the relationship between the ratio of the rise time to the waveform amplitude and the average frequency. The b-value was also calculated using the least-squares method to evaluate the failure process of Pykretes and matrix. The results show that the AE technique can qualitatively assess the damage process of Pykretes and has the potential to detect damage to actual Pykrete structures in situ.

Mineral Composition and Grain Size Effects on the Fracture and Acoustic Emission (AE) Characteristics of Rocks Under Compressive and Tensile Stress

The influence of rock mineral composition and mineral grain size on basic rock strength performance and AE characteristics have been studied, 13 different rocks microstructures are analyzed in an optical microscope thin section using petrographic image analysis, making it possible to determine the mineral composition and mineral texture characteristics of rocks. Then, the basic strength parameters of rock and AE signals generated during fracture propagation were obtained by UCT (uniaxial compression test) and BIT (Brazilian intension test). Finally, the relationship between basic strength parameters and AE characteristics of rock with mineral composition and grain size was analyzed. The results showed that different mineral constituents have significant effects on rock strength. The positive influence of plagioclase content on igneous strength was obtained. Sedimentary rocks strength increases initially and then decreases with the increase of plagioclase content. Besides, with the increase in quartz and K-feldspar content, the strength of the rock was weakened obviously. It is also found that the greater the dimensional deviation of mineral grain, the greater the strength of the rock. The strength of igneous rocks was inversely proportional to the mineral grain size, but there is no correlation between the sedimentary rocks strength and the mineral grain size. Furthermore, the tension–shear crack propagation of rock can effectively distinguish by judging that the data set of the AF–RA density graph was nearby the AF axis or RA axis and the peak frequency data sets of below 100 kHz or more than. Alterations in the rock nature are the main key reasons for the differences between AE hit rate, AE count rate, AE energy, and cumulative energy. The plagioclase content and grain size play a decisive role in AE signal characteristics and failure mode.

Developing a new acoustic emission source classification criterion for concrete structures based on signal parameters

Acoustic emission (AE) signal parameters can be used to classify the source type in concrete structures. However, signal parameters are influenced by the wave propagation from the source to the receiver, leading to wrong source classification results, especially for monitoring large concrete structures. This paper experimentally evaluates the influence of wave travel distance on signal parameters on a full-scale shear test of a reinforced concrete beam. The evaluated signal parameters include the RA value, average frequency, peak frequency, frequency centroid, and partial power. The evaluation reveals the limitation of using RA value - average frequency trends in large scale structural concrete members. Based on the evaluation, we propose a new source classification criterion using peak frequency or partial power, which can effectively classify the source type. The new criterion is also validated in a reinforced concrete slab test, which is another structural type. Based on the new criterion, we suggest a sensor layout that is suitable for source classification for large concrete structures. The results of this paper can help developing a reliable solution for real-time source classification for large concrete structures in general.

Influence of Propagation Distance on Characteristic Parameters of Acoustic Emission Signals in Concrete Materials Based on Low‐Frequency Sensor

Acoustic emission is a nondestructive testing technology based on the propagation of transient elastic waves captured by acoustic emission sensors. The acoustic emission signal depends not only on the distance and quality of the propagation path of the transient elastic wave but also on the sensitivity and frequency bandwidth of the receiving sensor that converts the transient elastic wave into a voltage signal. The frequency range of damage signals in concrete materials is generally in the low‐frequency band. If high‐frequency sensors are used, the low sensitivity to low‐frequency signals will cause measurement errors, while the bandwidth of general commercial acoustic emission sensors is relatively narrow. Therefore, a high‐sensitivity, low‐frequency acoustic emission sensor is proposed, whose bandwidth is almost four times that of commercial sensors. Based on the customized sensor, we quantitatively analyzed the influence of propagation distance on the characteristic parameters of acoustic waves propagating in concrete. The results show that the different propagation modes of acoustic waves in concrete have different attenuation with the propagation distance, related to the position relationship between the acoustic source and the sensor and the propagation path and path quality. This result gives us a better understanding of the propagation mechanism of acoustic emission signals in concrete materials.

Analysis of the parameters of acoustic emission signals localized under static loading of carbon fiber specimens with impact damage

Analysis of the parameters of acoustic emission signals localized under static loading of carbon fiber specimens with impact damage

Research of the parameters of acoustic emission signals during the destruction of the liner material and the power shell of a metal-composite high-pressure cylinder

To The article provides information on the results of studying the parameters of acoustic emission signals during the destruction of the liner material and micro-plastic of the power shell of a metal-composite high-pressure cylinder. B-200 within the framework of a complex of studies to create an acoustic-emission portrait of metal-composite high-pressure cylinders. It was found that the most informative parameter when carrying out technical diagnostics of a liner is the signal amplitude recorded in the private range of 60-80 kHz, and a sign of microplastic rupture is the emission of acoustic emission signals reaching 82 dB.

Quality control of adjustment of clearances of ball bearing supports, dynamic devices rotor-type, according to parameters of acoustic emission signals

The article is devoted to increasing the bearing life of dynamic rotary-type machines by controlling the uniformity of the distribution of the value of the preliminary axial load acting on the rolling bearings of the rotation axis of the power unit. The possibility of monitoring the axial load using acoustic emission (AE) signals is considered. The results of experimental studies of the kinematics of the ball movement relative to other bearing parts, depending on the tightening torque of bolted joints, estimated by the parameters of AE signals, are presented.

Three Stages of Composite Specimen Destruction in Static Failure

Abstract The paper presents the results of standard specimen fracture made of anisotropic carbon fiber plastic with an epoxy matrix. Static stepwise loading of the specimen was carried out on an Instron 8801 testing machine to determine the characteristics of ductile fracture G1C in the first mode in accordance with ASTM D5528. During loading, the parameters of acoustic emission (AE) signals, such as AE impulse amplitudes and their energy were synchronously recorded. At the same time, the magnitude of the opening and the growth of the crack initiated by the artificial cut at the end of the specimen were recorded. According to the analysis of the acoustic emission signals, three zones with different G1C behaviour were identified: initial crack propagation, its stationary growth and accelerated fracture of the specimen. The zonal character of the change in the acoustic emission signals made it possible to determine the energy of the acoustic emission signals as diagnostic evidence for the onset of rapid destruction of the specimen. The amplitude of the AE-signals in the zones, however, remained constant. Online monitoring of changes in the energy of acoustic emission signals will prevent the onset of rapid destruction of an object in places of its deformations. The paper does not aim at defining G1C as usual. It presents the investigation of the fracture stages for a composite material using an acoustic emission method.

Influence of additional dielectric coatings on the electrode surfaces on selected parameters of acoustic emission signals in high-voltage gas insulation systems

The paper is devoted to the study of impact of additional dielectric coatings placed on the surface of the electrodes on the operation of a high-voltage insulation system with air as insulating medium. The study mainly focused on measurement of partial discharges (PDs) with the use of acoustic emission method. Tests were conducted in various levels of chamber pressure. Applicable parameters of recorded signals were analyzed with the use of applications developed in the environment of MATLAB software. The results of analyses clearly show that presence of additional coatings has impact on signal parameters and thus indirectly on PDs. The use of coatings reduces the duration of a single pulse (event) and increases its amplitude. Furthermore, the influence of degradation of the coating caused by individual discharges on the values of the analyzed parameters was analyzed. The study has shown, however, that this effect is negligible.

Wavelet Processing of Acoustic Emission of VT 1-0 Titanium Alloy under Tension

The paper proposes a method for processing acoustic emission signals for calculating informative signal parameters characterizing the stages of plastic deformation and fractures in a loaded titanium alloy. The proposed method has a complex structure that includes digital signal processing algorithms and multivariate data analysis methods. The acoustic emission signals are processed using the mathematical apparatus of the multilevel discrete wavelet transform to obtain the approximation coefficients of the 10-level decomposition. These coefficients characterize the low-frequency features of acoustic emission at various stages of samples loading. The approximation coefficients are further used as informative parameters of acoustic emission signals. Principal components analysis is used to investigate the informative parameters and establish their quantitative relationship with the stages of plastic deformation of titanium by clustering the processed results. Differences in the informative parameters at different stages of plastic deformation of the material are revealed by the following analysis of the clustered results.
 The obtained results can be used to develop a new generation of diagnostic devices for acoustic emission measurements.

Magnetoacoustic fusion life prediction method for retired components based on D-S evidence theory

Prediction of the remaining life of remanufacturing blanks is crucial to evaluate their remanufacturability. To overcome the deficiency of obtaining insufficient fatigue damage characteristic information using a single non-destructive testing method, a new magnetoacoustic fusion life prediction method based on Dempster-Shafer (D-S) evidence theory optimised by a weighted fusion algorithm is proposed. The characteristic parameters of metal magnetic memory (MMM) and acoustic emission (AE) signals are first extracted on the basis of a fatigue experiment and data layer fusion is carried out to establish the mapping relationship between MMM and AE characteristic parameters and specimen life based on a back-propagation (BP) neural network. The basic probability distribution of the life is assigned in a fuzzy manner according to the normal distribution and the reliability function of each life interval is obtained by data fusion based on D-S evidence theory. Furthermore, the basic probability distribution value is modified based on a weighted fusion algorithm and the corrected data are fused to obtain a more accurate life prediction result.

Experimental Study on the Characteristics of Acoustic Emission Source of Rock under Uniaxial Compression

One of the main research problems in acoustic emission (AE) monitoring technology is to identify the source of the acoustic emission. Processing the acoustic emission signal is the only way to solve this problem, and then to achieve the purpose of identifying the material destruction mode. Using acoustic emission monitoring technology, the acoustic emission of granite under uniaxial compression was monitored and analyzed, and the coupling characteristics between the acoustic emission signal parameters of granite under different loading rates were obtained. The results show that during the process of rock shear failure, the peak intensity of the rock, the peak value of the absolute energy of acoustic emission, the cumulative amount of acoustic emission and the loading rate showed a positive correlation. The correlation diagram of the AE ringing count and the duration shows a triangular distribution, and as the rock loading rate decreases, the angle of the triangle top angle of the correlation diagram increases. The distribution relationship between the absolute energy of AE and the duration can be fitted using a unary quadratic function, and as the loading rate decreases, the opening of the fitting curve gradually increases, and the width of the correlation graph gradually decreases. The correlation graph of absolute energy and amplitude of AE is linearly distributed, and as the loading rate decreases, the slope of the fitted line of absolute energy and amplitude of AE gradually decreases, and the width of the linear channel of the correlation graph decreases. It is found that there is a good regularity between the correlation graphs of different parameters of the acoustic emission of the rock during the uniaxial compression failure process, which is an effective method to identify the characteristics of the source of the acoustic emission. Therefore, establishing the correspondence between the characteristics of the AE source and the loading conditions will promote the development of acoustic emission technology in the monitoring of the stability of the surrounding rock of underground projects.

Acoustic Emission at Properties Change of Composite Destructed by von Mises Criterion

The results of theoretical studies influence the parameter characterizing the composite properties on acoustic emission signals parameters during composite material fracture by a shear force using von Mises criterion are considered. It has been determined that with increase of influencing parameter, there is decrease the maximum amplitude and duration of generated acoustic emission signals. In this case, a decrease the maximum amplitude of acoustic emission signals is ahead of decrease in their duration. It has been determined that the regularities of acoustic emission signals maximum amplitude and duration decrease with an increase the parameter characterizing the composite material properties are well described by power functions.

Erratum to: Experimental Estimation of the Waveguide Effect on the Acoustic Emission Signal Parameters in Monitoring Facilities with a Long Surface Radius of Curvature

An Erratum to this paper has been published: https://doi.org/10.3103/S1052618821030134

Acoustic emission monitoring of composite specimens with impact damage during static compression test

The standard specimens have been made by anisotropic carbon fiber plastic with an epoxy matrix. The specimens were subject to static load after its shock impact. During static compression loading, the parameters of acoustic emission (AE) signals were synchronously recorded: AE impulse amplitudes, its energy and the number of oscillations. According to the analysis of the acoustic emission signals the following events were observed: matrix cracking, fiber delamination and fiber destruction. The character of the AE signals change made it possible to determine the energy of the acoustic emission signals as a diagnostic witness of the onset of two moments of the specimen destruction. The first = near 70% of ultimate load’s (the destruction of matrix) and total destruction under ultimate static load.

Flexural ductility and crack-controlling capacity of polypropylene fiber reinforced ECC thin sheet with waste superfine river sand based on acoustic emission analysis

Engineered cementitious composite (ECC) with waste superfine river sand (WSRS) and polypropylene (PP) fiber is an economical and sustainable cement-based composite material (WSRSPP-ECC), which has the deformation hardening and multi-cracking characteristics, and affinity for engineering promotion. In this study, acoustic emission (AE) technology was used to monitor the flexural damage process of WSRSPP-ECC thin sheets with different deformability. Based on AE signal features, the damage development and accumulation of WSRSPP-ECC thin sheet under flexural load were analyzed. The results showed that AE signal parameters can capture and describe the transition of different damage stages of WSRSPP-ECC thin sheets. The b-value analysis further showed that the internal micro-cracks characteristics of WSRSPP-ECC thin sheets with various deformability were different in the flexural damage process, which was mainly related to the ability of fibers controlling stable cracking. In view of the smaller fluctuation of AE signals in the first two stages of flexural damage process, three modified indirect AE signal feature parameters including average energy, average waveform coefficient and average frequency were proposed. Then the quantitative relationship models between these three indirect AE signal parameters and flexural ductility as well as crack-controlling capacity of WSRSPP-ECC thin sheet were established. Moreover, through the economic analysis, it is corroborated that WSRSPP-ECC has the higher comprehensive cost performance, and it is a new economical cement-based material suitable for practical engineering application. The production of WSRSPP-ECC by replacing PVA fiber and silica sand with PP fiber and WSRS can not only save cost, and also keep the physical performances, which effectively solves the problems of river channel sedimentation and blocking.