Acoustic Emission Signal Parameters Research Articles

Features of Recording Energy Parameters of Acoustic Emission Signals from Materials

The acoustic emission method is used as a means of analyzing the state of materials and structures, non-destructive testing and diagnosing them during operation. An important advantage over other methods is that it reacts only to the development of truly dangerous defects and is capable of monitoring large volumes and surfaces without scanning them. The article presents the results of the development of methods and algorithms designed to analyze the energy characteristics of acoustic signals. The use of spectral methods is justified.

Innovative acoustic emission method for monitoring the quality and integrity of ferritic steel gas pipelines

Abstract This article presents a comprehensive improvement in the experimental analysis of cracking processes in smooth and sharp V-notched samples taken from gas transport pipelines, utilizing the acoustic emission (AE) method. The research aimed to establish a robust correlation between the failure mechanisms of uni-axially tensile samples and the distinct characteristics of AE signals for enhanced quality management in pipeline integrity. The study encompassed materials from two different straight pipe sections, encompassing both long-term used materials and new, unused materials. Through the application of the k-means grouping method to AE signal analysis, we achieved the identification of AE signal parameters characteristic of various stages of the material destruction process. This advancement introduces a significant improvement in monitoring and managing the operational safety of pipeline networks, offering a methodology that leverages advanced acoustic emission signal analysis. The outcomes present significant implications for the pipeline industry by proposing methods to enhance safety systems and more effectively manage the integrity and quality of gas infrastructure.

Comprehensive assessment and monitoring of bond deterioration in GFRP-reinforced concrete beams using guided wave and acoustic emission techniques

The debonding between glass fiber-reinforced polymer (GFRP) rebars and concrete significantly reduces the bond strength and jeopardizes the safety and durability of GFRP-reinforced concrete (GFRP-RC) structures. As a result, it is imperative to monitor the structural integrity of infrastructures being built using these composite materials in structural elements during their service lives. Previous studies have primarily focused on artificially induced debonding scenarios for guided wave (GW)-based monitoring, which has resulted in an inability to capture debonding events that arise naturally due to external loads. Furthermore, flexural bond test investigations simulating real loading scenarios in GFRP-RC structures have not been linked with acoustic emission (AE) and GW monitoring. The present study addresses these research gaps by comprehensively examining the flexural bond integrity in GFRP-RC structural elements subjected to realistic loading conditions using a hybrid approach combining GW and AE as active and passive structural health monitoring techniques, respectively. A series of bond tests, conforming to RILEM specifications, have been performed to investigate various parameters (including rebar surface characteristics, embedment length, and confinement conditions) that affect the flexural bond degradation response of GFRP-RC members. Damage indices based on GW and AE signal parameters have been developed to evaluate the characteristics of confined and unconfined specimens distinctly. It has been observed from the test results that the L (0,3) GW mode is more sensitive to debonding than other modes and that a threshold of 25% has been established for the GW damage index to denote significant bond damage. Furthermore, AE damage indices have provided valuable insights into concrete damage, including splitting and damage at the rebar-concrete interface. Thus, a thorough understanding of bond deterioration in GFRP-RC structures has been developed by combining GW and AE health monitoring techniques, with implications for enhancing structural safety and durability.

Mechanical and acoustic characteristics of sandstone failure at different immersion heights under tailings water erosion conditions

To investigate the influence of tailings water immersion height on the failure process of rocks, intact yellow sandstone samples and yellow sandstone samples with prefabricated fissures were prepared. Uniaxial compression tests were conducted on these sandstone samples with varying immersion heights, and the failure processes were simultaneously monitored using a camera and an acoustic emission monitoring system. Based on the test results, the crack propagation and failure characteristics of the yellow sandstone samples under uniaxial loading at different immersion heights were determined. The relationships between the immersion height and peak strength and between the immersion height and elastic modulus were characterized. Additionally, the intrinsic connection between sandstone damage and acoustic emission signal parameters was revealed. The experimental results indicate that the uniaxial compressive strength and elastic modulus of the sandstone samples decrease continuously with increasing immersion height, but the rate of decrease gradually slows. The presence of water is the primary reason for the deterioration of mechanical properties, and the chemical components in the tailings water are significant factors that cannot be ignored. The initiation location and propagation of cracks in intact samples depend on the immersion height, while the fracture behaviour of fissured samples after immersion is mainly influenced by the prefabricated fissures. As the immersion height increases, the longitudinal wave velocity increases, while the number of acoustic emission events, peak frequency, and amplitude exhibit a decreasing trend that is initially rapid and then slows. A damage evolution model based on acoustic emission ringing counts at different immersion heights was established. It was also found that the acoustic emission signals of these yellow sandstone samples mainly show the characteristics of abrupt signals under any immersion water height.

Tension and Shear Behaviour of Basalt Fiber Bio-Composites with Digital Image Correlation and Acoustic Emission Monitoring.

This research investigates the mechanical behavior and damage evolution in cross-ply basalt fiber composites subjected to different loading modes. A modified Arcan rig for simultaneous acoustic emission (AE) monitoring was designed and manufactured to apply quasi-isotropic shear, combined tensile and shear loading, and pure tensile loading on specimens with a central notch. Digital image correlation (DIC) was applied for high-resolution strain measurements. The measured failure strengths of the bio-composite specimens under different loading angles are presented. The different competing failure mechanisms that contribute to the local reduction in stress concentration are described. Different damage mechanisms trigger elastic waves in the composite, with distinct AE signatures that closely follow the sequence of fracture mechanisms. AE monitoring is employed to capture signals associated with structural damage initiation and progression. The characteristic parameters of AE signals are correlated with crack modes and damage mechanisms. The evolution of AE parameters during the peak load transition is presented, which enables the timely AE detection of the maximum load transition. The combination of DIC and AE monitoring improves understanding of the mechanical response and failure mechanisms in cross-ply basalt fiber composites, offering valuable insights for possible performance monitoring and structural reliability in diverse engineering applications.

Comprehensive analysis of bond stress transfer mechanisms in glass fiber-reinforced polymer-reinforced concrete beams using acoustic emission monitoring

The present study investigates the critical bond characteristics between glass fiber-reinforced polymer (GFRP) bars, which is essential for the application bars as corrosion-resistant components in structural concrete. The interfacial bond deterioration and stress transfer mechanisms have been investigated in the present study by employing acoustic emission (AE) monitoring in hinged-type GFRP-reinforced concrete (GFRP-RC) beam specimens. The bond strength of the test specimens, governed by chemical adhesion, mechanical interlocking, and frictional resistance, has been intricately examined. Various AE signal parameters as well as historic and severity indices derived from the AE signal parameters have been meticulously evaluated and correlated with bond stress and rebar slip variations. The present study has also introduced an innovative approach of using the sentry function for the assessment of bond deterioration and associated mechanisms. The results of the present study demonstrate the reliability of AE parameters in monitoring debonding and bond strength variation, the effectiveness of the sentry function in evaluating damage progression, and the utility of historic and severity indices in capturing micro-mechanism transformations. The accurate localization of debonding and the qualitative distribution of bond stress have also been demonstrated by through correlations between cumulative AE parameters and rebar slip, Additionally, the present study also highlights the significance of peak frequency variations in AE signals, serving as a crucial tool for quantifying the mechanical interlocking and interfacial friction. The results contribute significantly to precise assessments and development of effective strategies for mitigating bond deterioration in GFRP-RC elements.

Acoustic emission for exploring loading rate impact on type I fracture mechanism of engineering cementitious composites after subjected to sub-high temperature

To investigate the crack extension mechanism of engineered cementitious composite (ECC) after sub-high temperature. This paper studies the mode I fracture properties of ECC after sub-high temperatures (20 °C, 100 °C, 200 °C) at three strain rates (2 × 10-5s-1,10-4s-1,10-3s-1), and monitors the damage process in real-time by acoustic emission (AE) technology. Crack evolution and failure modes of ECC during loading are investigated by AE signal parameters. The results show that compared with 20 °C, the fracture energy of ECC increases after 100 °C, and decreases after 200 °C. The damage characteristics of ECC after 100 °C are similar to those at room temperature. Due to the bridging effect of the PVA fibers, their internal microcracks spread around from the tip of the prefabricated cracks. The percentage of shear type cracks gradually increases. The damage types are dominated by matrix cracking and fiber pull-out. While the PVA fibers deteriorated after 200 °C, the damage within the ECC was more concentrated, and the width of the fracture process zone was reduced. The crack types were dominated by tensile cracks. The failure mode was dominated by fiber pull-off and matrix cracking. Construction of an AE energy-based damage model. The b-value can reflect the whole process of crack evolution from multi-cracks to main cracks within ECC.

Acoustic emission diagnostics of a hull structures by a system of integrating fiber-optic sensors for the aircraft and spacecraft safe operation

A variant of aircraft and spacecraft state of hull structures acoustic emission diagnostics method based on a system of distributed fiber-optic sensors is considered. Such systems can be sources of information for a technical means of ensuring safety at aerospace facilities. The Green's function for a single sensor is found, and the features of its operation under the influence of pulsed acoustic emission signals are considered. The capabilities of the sensor system under consideration in estimating the coordinates and parameters of acoustic emission signals are determined. The results of experimental studies demonstrating the possibility of detecting emission signals under conditions of specific interference are reported.

TESTING OF D16T DURALUMIN SAMPLES UNDER STATIC LOADING USING THE ACOUSTIC EMISSION METHOD

Tests of samples made of D16T duralumin were carried out under static loading until failure under normal conditions, at positive and negative temperatures. Information was recorded using the acoustic emission method. In this case, a stable location of signals from defects corresponding to the beginning of sample destruction was observed. It was shown that at a low temperature of –50 oС the number of recorded signals increased, but the energy of the high-frequency component of the AE signals decreased, and the maximum energy was in the frequency band 550…600 kHz. At a temperature of +80 oC, the number of recorded signals decreased. Wavelet scalograms were constructed at various temperatures and loads. The sensitivity of the main informative parameters of acoustic emission signals, which made it possible to determine the onset of destruction of the sample material, was analyzed.

Experimental study on multiple characteristics of multi-source AE signals during cavitation process of waterjet propulsion pump

In order to investigate the cavitation-induce acoustic emission (AE) characteristics of a waterjet propulsion pump, a synchronous experimental system consisting of a test pump, a high-speed camera, and acoustic emission sensors has been established. The characteristic parameters of AE signals are extracted to established the quantitative relationships between cavitation status and AE signals. These characteristic parameters mainly consist of the ringing count rate Rc , energy release rate Er , and Hurst index Hi . The cavitation status of the test pump is reflected in the characteristic parameters of the AE signals obtained by the sensors installed at different locations. The incipient blade suction side (SS) cavitation as well as the blade tip gap cavitation can be detected through the change of characteristic parameters of AE signals at impeller inlet. The start of head drop can be reflected by the variety of characteristic parameters of AE signals at impeller middle. Large-scale cavitation will lead to the breakdown of pump performance and dramatically characteristic parameters’ change of AE signals can be measured by the sensors located at impeller outlet.

Prediction of wool fibre breaking strength based on acoustic emission signal parameters and combined noise reduction method

ABSTRACT The accurate original signals of fibre fracture and the veritable correlation between the signal parameters and the fibre tensile stress are investigated in this paper based on a suitable noise reduction method. The physical properties of materials can be indirectly characterised through fracture acoustic emission signals, such as fibres. However, it makes the characterisation difficult and inaccurate due to the fracture signals of most fibres are weaker than the background noise. A suitable noise reduction method based on complete ensemble empirical mode decomposition with adaptive noise and wavelet packet transform denoising is proposed to reduce the noise of the fibre fracture signals and obtain the exact raw signals. The fibre fracture signals are decomposed into several intrinsic mode function series and categorised into two groups. The two groups of series are denoised by different thresholds to minimise the level of noise. The two sets of denoised series are reconstructed as the original fibre fracture signals. The results show the proposed combined denoising method can reduce the noise components and well preserve the components of fibre fracture signals. The signal parameters denoised by the combined noised reduction method have a better correlation with the fibre breaking strength and higher prediction accuracy.

Investigation of the features of destruction of fillers of structures made of reinforced polymer composite materials

The paper presents the results of experimental studies of the destruction of fillers of polymer composite materials (PCM) with the control of acoustic emission (AE) signal parameters. As object of research were considered silica filaments К11С6-180, carbon filaments UKN-M-12K-1-7-380 and aramid technical fiber Rusar-С600 type А. Based on the experimental data obtained, acoustic emission portraits of the destruction processes of various types of PCM fillers were obtained. This allows, when loading a structure made of PCM with AE control, to fix the destruction of the filler, and, consequently, to increase the reliability and safety of operation of products made of PCM.

USING THE ACOUSTIC EMISSION METHOD, STRAIN GAUGE AND FRACTOGRAPHY TO ANALYZE THE PROCESSES OF DESTRUCTION OF SAMPLES FROM CARBON FIBER

Static loading of Torayca T800 carbon fiber samples to failure was carried out, during which defects were registered using a microprocessor-based diagnostic acoustic emission (AE) system. The location of AE signals began in the area of the stress concentrator at loads not exceeding 30 kN. The analysis of the destruction process of samples at negative (–50 C) and positive (+80 C) temperatures was carried out. During their heating and cooling, thermal chambers were used, located in the region of a stress concentrator with a diameter of 12 mm. In the process of testing at a temperature of T = –50 C, an active location of AE signals was observed, corresponding, as shown by fractography, to delamination and destruction of the upper monolayers of carbon fiber. During tests carried out at a temperature of T = +80 C, AE signals were localized, caused by lateral delaminations located at the edges of the samples. Using wavelet transforms, an analysis was made of the features of changes in the main informative parameters of AE signals, and their relationship with the growth of damage (matrix, fiber, delamination) of the carbon fiber material.

Display of WEDM Quality Indicators of Heat-Resistant Alloy Processing in Acoustic Emission Parameters.

The widespread nature of heat-resistant alloys is associated with the difficulties in their mechanical machining. It forces the use of the wire electrical discharge machining to be wider. The productivity, roughness, and dimensions of the modified layer of the machined surfaces are indicators of the machining quality. The search for new diagnostic parameters that can expand the information content of the operational monitoring/diagnostics of wire electrical discharge machining and accompany the currently used electrical parameters' data is an urgent research task. The article presents the studies of the relationship between the parameters of acoustic emission signals accompanying wire electrical discharge machining of heat-resistant alloys, process quality indicators, and characteristics of discharge pulses. The results are presented as mathematical expressions and graphs demonstrating the experimentally obtained dependencies. The research focuses on the formed white layer during wire electrical discharge machining. Pictures of thin cross-sections of the machined surfaces with traces of the modified layer are provided. The issues of crack formation in the modified layer and base materials are considered.

Gaussian mixture model in clustering acoustic emission signals for characterizing osteoarthritic knees

High-frequency acoustic waves produced by the sudden release of energy within a material caused by mechanical loading, deformation, corrosion, or other forms of damage are detected by Acoustic Emission (AE). It is a non-destructive testing technique utilized to monitor the structural health of materials and components and to detect and locate defects or damage that could lead to failure. Researchers in the biomedical field have lately focused on AE due to its potential for early detection, tracking, and managing various health issues, such as identifying and evaluating joint disorders, tissue damage, etc. However, due to the variance in AE signals produced from complex structures like knee joints, a general statistical method frequently finds it difficult to differentiate between distinct types of AE signals from different kinds of damage. In such instances, machine learning (ML) and deep learning (DL) can be beneficial for differentiating these signals. In this study, the application of Gaussian mixture model (GMM) clustering with principal component analysis (PCA) for dimension reduction was proposed to detect knee osteoarthritis (OA) from AE data. Four groups of participants, Group A (age 20–39), Group B (age 40–59), and Group C (age 60+), along with diagnosed OA as Group D, were included in this study. Avoiding overlapping AE signal parameters from different groups of participants is a significant challenge. GMM was applied to identify and eliminate the coinciding data points to address this issue. Moreover, the impact of this approach on clustering was also investigated in this research, and by utilizing GMM and PCA, compact clustering of the AE data potentially ensured the efficiency and effectiveness of early diagnosis of OA using the AE Technique (AET).

Mechanical and Acoustic Response of Low-Permeability Sandstone under Multilevel Cyclic Loading-Unloading Stress Paths

Low-permeability sandstone reservoirs have been widely used as a gas storage medium worldwide. Compared with the high porosity and high permeability of sandstone, low-permeability sandstone may present different mechanical (deformation, damage or failure) and acoustic responses under cyclic loading-unloading processes caused by the high-rate injection–production of underground gas storage. In this paper, multistage triaxial loading–unloading tests with a continuously increased upper limit of stress were carried out on low-permeability sandstone under six different confining pressures. The results showed that the superposition of stress–strain curves become much denser in the process of each level of stress. Based on the variation of the elastic modulus of low-permeability sandstone under alternating loads, the mechanical behavior of low-permeability sandstone under cyclic loading is divided into three stages: cyclic hardening, stability and cyclic softening. According to the evolution of acoustic emission (AE) signal parameters, AE counts appear intensively at the initial stage of each level of stress and then gradually stabilize. The peak frequency presents the zonal distribution, which is divided into low-frequency, intermediate-frequency and high-frequency zones. Low confining pressure leads to a small b-value. The RA–AF distribution implies that the mixed tensile–shear cracks are continuously generated in low-permeability sandstone during the cyclic loading process, and the shear cracks are more obviously developed.

Development of an empirical model for damage degree assessment of steel specimens based on the results of acoustic emission signal flow statistical processing

The study is devoted to acoustic emission (AE) method application for monitoring the state of structural materials at the inelastic and ultimate deformation stages. The possibilities of using the standard AE signal parameters recorded at the inelastic and ultimate deformation stages to assess the damage degree of steel specimens were investigated. It was shown that such parameters as the maximum amplitude of the recorded AE signals and their AE activity did not have a clear correlation with the damage degree of products made of structural steel and alloys. This makes it difficult to apply standard methods for assessing the damage degree of structural steels. The feasibility of monitoring the state of damage of 30KhGSA alloyed steel at the inelastic and ultimate stages by the evaluation of partial activity of the high-energy AE signals weight content was presented. The Kolmogorov-Smirnov criterion was used to separate the processes of ductile and brittle fracture.

Analysis of the destruction processes of carbon fiber samples using acoustic emission and tensometry

With samples made of carbon fiber, static tests were carried out to failure. Defects were controlled using acoustic emission and tensometry. Four wire strain gauges were glued to each sample in the area of the hole, and four piezoelectric gauges were installed along its edges, forming the working zone of control. Registration of signals associated with the destruction of the composite material of the samples, and their location was carried out by the acoustic emission system. In the process of testing, the tensometric system recorded loads and deformations, at which the process of destruction of carbon plastics began. The types of destruction were determined during the analysis of micro-glyphs, which were made from location zones. The main informative parameters (amplitude, dominant frequency, MARSE, structural coefficient) of acoustic emission signals were associated with the type of failure of carbon fiber reinforced plastics.

Experimental Study on the Damage and Failure Characteristics of High-Temperature Granite after Liquid-Nitrogen Cooling

To analyze the influence of liquid-nitrogen cooling on the damage and failure of high-temperature granite, granite samples were heated to 150~600 °C for natural cooling and liquid-nitrogen cooling treatment. Brazilian splitting tests were carried out as the samples returned to room temperature, and basic tensile and energy evolution parameters were obtained. Acoustic emission signal parameters during loading were recorded. The experimental results showed that the heating process caused damage to the granite samples, and liquid-nitrogen cooling further increased the degree of damage. Specifically, the ultrasonic velocity of liquid-nitrogen-cooled samples was lower than that of naturally cooled samples at each heating temperature. With an increase in heating temperature, the AE ring-down counts of liquid-nitrogen-cooled samples were higher than that of naturally cooled samples. At the same heating temperature, the dissipated energy of naturally cooled samples was greater than that of liquid-nitrogen-cooled samples. Liquid-nitrogen cooling could effectively promote the propagation of microcracks inside high-temperature granite and result in a reduction in the mechanical strength of granite, which could be conducive to the efficient fracture of high-temperature rock during fracturing.

Investigation of Situational Correlations of Wire Electrical Discharge Machining of Superhard Materials with Acoustic Emission Characteristics

The purpose of this research is to find relationships between the parameters of the acoustic emission signals accompanying the electroerosive processing with a wire electrode of metals and hard alloys and the most important process indicators. These indicators include an increase in the concentration of erosion products in the interelectrode gap, an increase in the probability of wire electrode breakage, the efficiency of the supplied energy, the current productivity. This article presents the results of the study of acoustic emission signals during the processing of hard alloys with a cutting machine. The main focus is on the period preceding the breakage of the wire electrode. Changes in the parameters of acoustic emission a few seconds before failure are shown, and the possibility of preventing wire breakage by monitoring the parameters of acoustic emission signals is established. To evaluate the efficiency of the energy supplied to the processing zone, a dynamic model is proposed, with the help of which the processing efficiency is estimated by changing the transmission coefficients in one or several frequency ranges. To explain the situation that occurs in the processing zone with an increase in the concentration of erosion products, the article draws a parallel between electroerosive and laser processing, related to technologies of processing with concentrated flows of energy. Studies have shown that acoustic emission signals can be used to search for rational processing modes and improve automatic control systems for electroerosive equipment.