Application Of Acoustic Emission Technique Research Articles

Analyzing the Sound of Materials: Application of Acoustic Emission Technique for Monitoring Material Behavior

During the last years, some concerns have arisen in relation to the outcome of mechanisms of failure in composite materials according to its mechanical behavior. Such interest resulted in the development of new complex structures in order to enhance its mechanical resistance and the controlling of damage processes. Nevertheless, it is imperative to understand the degree of mechanical performance that these materials can achieve when under external stresses. In this regard, applying Acoustic Emission (AE) technique is widely known as a very effective technology for identifying and monitoring damage progression on different kind of materials and structures providing valuable information. AE is a non-destructive technique (NDT) capable of detecting micro damage initiation and propagation along several types of failure modes such as reinforcement/matrix interfacial debonding, matrix cracking, delamination, fracture, etc. This paper examines applications of AE regarding to composite materials where fracture processes are generally more complex and data interpretation is correspondingly more difficult. Finally, in order to continuously improve the reliability of this technique, several researches have advanced its trustworthiness through innovations in AE technology. Some perspectives are discussed.

Application of Acoustic Emission Technique (AET) to the Study of Adhesive Wear of two Aluminium Alloys 2024 and 2024-T4

The adhesive wear resistance of (2024&2024-T4) aluminium alloy under dry and lubricated conditions has been investigated by using the weighing method and the Acoustic Emission Technique (AET). Pin–on-plate reciprocating wear apparatus was used. The AET has capability of predicting an impending failure much ahead of time of its occurrence. The AE measurements are made with the help of a tape recorder system into isolated chamber from external noises. The results show that 2024-T4 alloy has higher wear resistance with three distinct stages of wear rate in comparison with 2024 alloy under the working conditions. The AE data analysis showed a clear evident that the Events Rate and Peak Amplitude value display a clear-cut distinction between the wear rate stages in dry and lubricated conditions of both alloys giving a good agreement with the weighing method results.

Fractional Fourier Transform Based Adaptive Filtering Techniques for Acoustic Emission Signal Enhancement

Acoustic emission technique (AET) is a well-known non-destructive testing method used for the detection of crack growth and monitoring structural integrity of components. The main limitation in the application of AET is the fact that acoustic emission (AE) signal is often affected by background noise. A new approach is proposed in this paper to reduce the background noise and to improve the accuracy of AE signal detection. Various noise reduction methods have been applied and studied for AE signal enhancement so far. Some of the studies proved that self-adaptive noise cancellation (SANC) and adaptive noise cancellation (ANC) are better techniques for denoising the AE signal. This paper proposes the use of ANC and SANC schemes based on Fractional Fourier Transform (FrFT) for AE signal enhancement. FrFT is the generalization of the classical Fourier Transform (FT). The use of FrFT gives an advantage of an additional degree of freedom (angle of rotation in time–frequency plane) over the traditional Fourier transform and could provide improved performance. In this method, the noisy signal is rotated in time- frequency plane to extract the signal in Fractional Fourier domain (FrFD). Two adaptive filters viz. least mean squares and normalized least mean squares are studied for FrFD based ANC approach. The performance of the proposed method is validated using real AE signals acquired from three different experiments: pencil lead break test, composite drilling test and concrete compression test. Results are compared with the time and frequency domain adaptations. Moreover, the results have also been compared with the frequency domain adaptation techniques. Results have demonstrated that FrFD based ANC approach outperforms the conventional time domain and frequency domain adaptive filtering with an improved signal to noise ratio and significantly reduces mean square error.

Monitoring of fracture propagation in brittle materials using acoustic emission techniques-A review

During the past decades, the application of acoustic emission techniques (AET) through the diagnosis and monitoring of the fracture process in materials has been attracting considerable attention. AET proved to be operative among the other non-destructive testing methods for various reasons including their practicality and cost-effectiveness. Concrete and rock structures often demand thorough and real-time assessment to predict and prevent their damage nucleation and evolution. This paper presents an overview of the work carried out on the use of AE as a monitoring technique to form a comprehensive insight into its potential application in brittle materials. Reported properties in this study are crack growth behavior, localization, damage evolution, dynamic character and structures monitoring. This literature review provides practicing engineers and researchers with the main AE procedures to follow when examining the possibility of failure in civil/resource structures that rely on brittle materials.

Application of Acoustic Emission Technique to the Evaluation of Coal Seam Hydraulic Flushing Effect

Hydraulic flushing has the advantages of reducing coal stress and improving coal seam permeability, so it is widely used in high gas outburst coal seams in China. However, the effect evaluation of stress relief and permeability enhancement will be necessary before coal mining. In this paper, an acoustic emission (AE) experiment system of coal seam hydraulic flushing was established, and the AE characteristics of coal during hydraulic flushing were studied. The results show that the changes in AE signals are basically consistent with those in load and water pressure. In addition, the quantitative relationship between the signals and the damage of coal around the borehole is revealed by the theory of damage mechanics. The in-situ AE test of hydraulic flushing was performed in the Liangbei Coal Mine, by measuring gas flow and coal stress simultaneously. The variation of AE activities and the effect evaluation of hydraulic flushing were analyzed. The results reveal that the changes in coal seam stress are basically consistent with those of AE signals. After the flushing has been completed for 1–3 h, the coal seam stress decreases rapidly, and the AE counts and intensity reach the peak. Therefore, this study proposes a new method for evaluating the effect of coal seam hydraulic flushing by AE, which has a very important practical significance.

A complex approach to assessing properties of aerated agar-fructose gels: Application of acoustic emission technique

The aim of this work was to characterise aerated gels and evaluate the possibility of applying the acoustic emission (AE) method to determine the texture of foamed products. The model system was based on aerated agar-fructose gel. The effect of different whipping times on mechanical and acoustic properties was determined. The material was aerated for 1, 2, 3, 4, 5, 8, 10 and 15 min. The measurement of acoustic emission was carried out while compressing samples. Acoustic emission was registered in the range 0.1–18 kHz using a piezoelectric accelerometer. The density and selected mechanical and textural parameters (fracture force and area, force at strain of 20%, Young modulus) decreased with whipping time. The size of bubbles decreased during aeration of the sample up to 5 min. Further whipping caused an increase and afterwards a decrease of air bubble diameter after 8 and 15 min of aeration, respectively. The porous structure of agar-fructose gels had a significant effect on acoustic emission of the gel system. Damage to pores during compression may lead to emission of an acoustic signal. The more acoustic events and the higher acoustic energy emitted during deformation of the aerated gel indicated that more small bubbles were deformed during compression.

The Application of Acoustic Emission Technique to Monitor the Early Setting Process of Cement Pastes

The obtained physico-mechanical properties (mainly flexural and compressive strength) of cement-based composite materials depend on various factors (type of mixture, its composition, standard hardening process, proper testing, handling during transportation, etc.). Important properties to be tested include in particular properties of materials in the fresh, still plastic, state, since accurate identification of defects in building materials/structures at the early stage will allow early elimination and minimization of their future consequences. The aim of this paper is the application of the acoustic emission (AE) method for the detection of high-frequency elastic waves created by physical and chemical processes accompanying setting and hardening of cement pastes. The experiment was conducted on cement pastes produced from different cements but with the same water/cement ratio. Since there are many possible sources of AE and the identification of the individual sources is difficult, the monitoring of the setting cement paste was conducted simultaneously with measurements of the internal temperature. The results of these experiments can be used to expand the understanding of the various processes occurring at the early stage of setting and hardening of cement-based materials.

Application of Acoustic Emission Technique for Bridge Cable Monitoring

Application of Acoustic Emission Technique for Bridge Cable Monitoring

Влияние структуры свинцового сплава на акустическую эмиссию при пластической деформации и разрушении

A study of acoustic emission during static stretching of lead alloy samples is presented. Test samples with various dendritic structures characterized by different sizes of the crystallites have been prepared. The values of RMS acoustic emission voltage during the process of plastic deformation and fracture are measured. Peak values occurred during the changing of strain hardening stages are discovered and analyzed. A significant influence of a sample structure on acoustic emission parameters manifests in changes of forms of acoustic emission curves for a set of samples with coarse-grained to finegrained structures. Revealed differences may be associated with the change of plastic deformation dominant mechanisms and their contribution due to changes of dendritic structure crystallites sizes. The obtained results can be further utilized in a study of plastic deformation and failure processes evolutions in the lead-based alloys. They also provide a scientific background for application of acoustic emission technique for investigating of lead alloys structure.

Acoustic emission monitoring for bond integrity evaluation of reinforced concrete under pull-out tests

This article presents the results of an experimental investigation on the application of acoustic emission technique for monitoring the steel-to-concrete bond integrity of reinforced concrete structures. A series of direct pull-out tests were performed on 54 reinforced concrete unconfined prism samples with variable rebar diameter (10, 20, and 35 mm), embedded length (50, 100, and 200 mm), and concrete cover (20, 30, and 40 mm). The samples were tested under incrementally increasing monotonic loading while being continuously monitored via attached acoustic emission sensors. These sensors were utilized to acquire different acoustic emission signal parameters emitted throughout the tests until failure. Also, an acoustic emission intensity analysis was implemented on acoustic emission signal strength data to quantify the damage resulting from loss of bond in all tested specimens. This analysis employed the signal strength of all recorded acoustic emission hits to develop two additional parameters: historic index ( H ( t)) and severity ( Sr). The results of bond behavior, mode of failure, and free end slip were compared with the recorded acoustic emission data. The results showed that the cumulative number of hits, cumulative signal strength, H ( t), and Sr had a good correlation with different stages of bond damage from de-bonding/micro-cracking until bond splitting failure and bar slippage, which caused cover cracking or delamination. The analysis of cumulative signal strength and H ( t) curves enabled early identification of two progressive stages of bond degradation (micro-cracking and macro-cracking) and recognized the various modes of failure of the tested specimens. The variations of bar diameter, concrete cover, and embedded length yielded significant impacts on both the bond behavior and acoustic emission activities. The results also presented developed intensity classification charts, based on H ( t) and Sr, to assess the bond integrity and to quantify the bond deterioration (micro-cracking, macro-cracking, and rebar slip) in reinforced concrete structures.

Relation between the plastic instability and fracture of tensile tested Cu-Sn alloys investigated with the application of acoustic emission technique

The work concerns the application of the acoustic emission (AE) method in testing the mechanical properties of continuously cast industrial tin bronze CuSn6P, which reveals tendencies to instable plastic flow connected particularly with the Portevin-Le Chatelier (PLC) effect. The relations between the jerky flow connected with the PLC effect, AE intensity and the evolution of a fracture of the investigated alloy subjected to the tensile test at a strain rate (?? ) of about 1.2·10-3s-1 in the range of temperatures (20÷400?C) has been analyzed. It has been found that the highest intensity of the oscillation of stresses, corresponding to the instability of plastic deformation PLC occurred at 200?C, whereas the maximum of the AE activity is at about 200÷250?C. The brittle intergranular fracture starts in the range of equicohersive temperature (TE) of about 200?C. Plastic deformation of the investigated alloy in the range of the temperature of minimum plasticity, amounting to about 400?C, results in intercrystalline fractures on the entire surface of the stretched samples.

A review of the application of acoustic emission technique in engineering

The use of acoustic emission (AE) technique for detecting and monitoring damages and the progress on damages in different structures is widely used and has earned a reputation as one of the most reliable and well-established technique in non-destructive testing (NDT). Acoustic Emission is a very efficient and effective technology used for fracture behavior and fatigue detection in metals, fiberglass, wood, composites, ceramics, concrete and plastics. It can also be used for detecting faults and pressure leaks in vessels, tanks, pipes, as well as for monitoring the progression of corrosion in welding. This paper reviews major research developments over the past few years in application of acoustic emission in numerous engineering fields, including manufacturing, civil, aerospace and material engineering.

Application of Acoustic Emission Technique for Bond Characterization in FRP-Masonry Systems

The acoustic emission (AE) technique is used for investigating the interfacial fracture and damage propagation in GFRP-and SRG-strengthened bricks during debonding tests. The bond behavior is investigated through single-lap shear bond tests and the fracture progress during the tests is recorded by means of AE sensors. The fracture progress and active debonding mechanisms are characterized in both specimen types with the aim of AE outputs. Moreover, a clear distinction between the AE outputs of specimens with different failure modes, in both SRG-and GFRP-strengthened specimens, is found which allows characterizing the debonding failure mode based on acoustic emission data.

Multi-sensor couplers and waveguides for efficient detection of acoustic emission behavior of snow

The efficient detection of acoustic emission (AE) activity from snow having porous and fragile character is hindered by the fact that the AE signals have small amplitudes and are typically attenuated within a short distance from the source. We therefore tested seven different types of highly sensitive resonant AE sensors and a multi-channel AE system in a wide frequency range of 1kHz–400kHz to evaluate the performance of multi-sensor coupler and waveguides with varying displacement rates. The AE generated during small fracturing of a natural snowpack, caused by a ram penetrometer, were detected using a cylindrical waveguide and a detection range of up to 16m with detection efficiency of 38dBAE were observed in snow. The AE activities produced by the snowpack were continuously recorded using a 2D-arrestor for AE in relation with the natural melt-freeze process. Prominent AE activity was observed near the phase-transition temperature of snow. Furthermore, spectral analysis of the AE signals generated by snow was carried out using the Short-time Fast Fourier Transform (ST-FFT) method. The AE behavior of snow was observed at different states of stress by varying from low to high, corresponding to different frequency ranges and grain sizes and an empirical relation was established for peak AE rates as a function of displacement rate. Apart from it, an attempt was made to monitor the real time failure of snow sample vis-à-vis AE energy with the help of an AE system and a high-speed camera. Our results are quite encouraging towards application of AE technique in the direction of slope stability evaluation and AE-based non-destructive evaluation of snow under various physical processes. The network of acoustic arrestors and waveguides can be crucial towards prediction of slope stability in view of avalanche release.

The Effect of Welding Angle for Acoustic Emission Propagation in Offshore Jacket Platform

Considering the requirement of NDT for offshore jacket platform, the effection of welding angle to the propagation characteristic of acoustic emission (AE) is studied. Amplitude and energy are the main analysis parameters for the experiment. As used wildly in jacket structure, the 90 and 45 degrees welding angle are discussed. The research result can provide references for engineering application of AE technique to locate the damage source and analyse the failure feature.

Application of Acoustic Emission Technique to Monitor the Viscosity of Single Grade Diesel Engine Lubricant Oil

This paper presents an investigation of the capability of the acoustic emission (AE) technology in the processes of monitoring and detecting the variation of diesel engine lubricant viscosity via in-situ operation. The investigations were conducted on an 8.5-hp single cylinder of four strokes with a water cooling diesel engine. One single grade engine lubricant oil condition has been put to the test; namely, SAE 40. The lubrication condition in the diesel engine was successfully monitored based on the AE signatures generated by the interaction between the piston surface and the layer of the lubricant during the time that the engine was in operation. The generated AE signatures were captured using an AE wide band transducer that was bonded outside the engine block and located at the lower part of the bottom dead centre (BDC). The captured waveform signatures were then analysed using the MATLAB software. The results of the experimental works show that the statistical analysis parameters including the root-mean-square (rms), maximum amplitude and AE energy values are capable of distinguishing the variant of the viscosity. The AE technique can assist the owner of the diesel engine in determining the diesel engine lubricant oil condition before replacing it.

Applications of Acoustic Emission Technique Associated with the Fracture Process Zone in Concrete Beam – A Review

This paper summarized the recent development within the application of acoustic emission technique in the formation of fracture process zone and the AE energy released during the fracture process in concrete beam specimens. AE technique is a non destructive technique which is a useful tool to study the energy released during the different failure mechanisms in different types of materials and fracture process is one of the failure mechanisms in concrete. Most of the researchers were applied three point bending test on plain concrete in order to determine the facture process zone of the concrete and some of them were used numerical modeling to verify their results. The results between AE data and experimental in different parameters such as specimens size and aggregate size are normally compared. As a conclusion, AE technique is a very useful tool to determine the fracture process zone in concrete.

Application of acoustic emission technique to limoges enamels for damage assessment

L'eclairage de tungstene-halide a ete mis en cause quant a son impact dans les vitrines. Un tel risque n'est pas facile a evaluer : c’est la technique d'emission acoustique qui a ete utilisee pour detecter de microdegâts sur des emaux de Limoges, puisque des recherches precedentes avaient mis en evidence la fragilite et vulnerabilite de ceux-ci. Avant d'appliquer la technique aux originaux, les echantillons d'email ont ete utilises dans des tests et exposes aux variations de temperature pour evaluer leur reponse a la deterioration induite. La distribution d'humidite relative et de temperature dans deux vitrines a ete mesuree afin d'evaluer le changement thermique. De plus, la performance de methodes actuelles pour controler l'humidite relative, le taux de renouvellement de l’air et les risques de polluants carbonyl dans les vitrines a ete aussi evaluee. Cette analyse a abouti a plusieurs modifications pour ameliorer le microenvironnement lors de la presentation-exposition.

Indentation testing and its acoustic emission response: applications and emerging trends

This review summarises the state of knowledge on acoustic emission (AE) techniques applied to material property evaluation during indentation (e.g. hardness) testing. There are two aspects of application of AE technique to indentation which makes it unique, i.e. (1) enhancing the understanding of the evolution of material accommodation mechanisms under loading and (2) qualitative and quantitative evaluation of mechanical properties such as fracture toughness and bond strength from the AE signal. Both of these aspects have the potential to improve our understanding of the structure property relationships of current and future generation materials. In addition, the knowledge developed here can be incorporated to improve the AE based condition monitoring systems for stress critical applications. This review concentrates on the phenomena which occur during indentation and how its examination can be used to study more fundamental behaviour of materials such as deformation and fracture. The uncertainty in quantifying and measuring the total crack surface in indentation makes a simple fracture mechanics based assessment of toughness difficult. It is therefore expected that correlation between AE and fracture patterns will lead to an improved method for material’s quality evaluation. The main part of this review is presented on AE of material classifications. These classifications include ceramics, glasses, composites, metals and metallic foams, thin solid films and thermally sprayed coatings. Apart from quasi‐static indentation testing, attention has also been paid to studies on various AE instrumented indentation systems so that information can be derived about the progress of deformation and cracking processes. This review discusses the studies summarising those aspects that have so far been established and the areas of controversy and/or lack of knowledge. The prospect of using AE techniques to monitor indentation tests is also assessed, taking into account those few studies that have been reported so far in different groups of materials. Although with some limitations, it is concluded that AE monitored indentation testing has considerable scope to assess in much more detail the deformation and cracking properties of materials under localised stress condition. It is possible to construct empirical relationships and develop theoretical understanding linking mechanical parameters with AE signal characteristics and its derived features. However, the occurrence of multiple events at different locations superimposing the AE signal requires more advanced signal processing techniques. With the advancement of very thin films and nanomaterials, it is anticipated that AE response measured during nanoindentation will be critical for enhancing our understanding of future generation applications, as it allows individual events to be investigated without resorting to more complex signal processing techniques. In terms of material accommodation, the understanding of physical mechanisms generating AE require a multiscale approach, e.g. correlations exist between fracture and sudden release of AE energy, dislocations and Bremsstrahlung and Frank–Reid sources, and maternsitic phase transformation with rapid variation in the shape of deformation volume generating AE exist; however, integration of continuum elastic–plastic and molecular dynamics models is necessary to enhance our understanding of the physical mechanisms generating AE response. This multiscale approach can be further helped by the experimental data using AE instrumented nanoindentation as it allows very localised and fine scale measurement in load or displacement control.

The application of acoustic emission technique to plastic deformation of low carbon steel

In present paper, using Acoustic Emission (AE) as an ultrasonic technique, the onset of plastic deformation has been investigated on smooth and notched specimens of AISI 1010 steel. AE activities (number of counts and signal energy) and stress–strain curve were measured during tests. The results show that activity of AE increases near the yield point and reaches to maximum at beginning of plastic deformation. AE activity decreases significantly with further straining. The main source of AE at all stages of deformation is associated with massive dislocation motion.