Use Of Acoustic Emission Technique Research Articles

Examining the Use of Acoustic Emission Technique for Evaluating Partial Discharge in Power Cables: A Review

Examining the Use of Acoustic Emission Technique for Evaluating Partial Discharge in Power Cables: A Review

The use of AE technique for identifying ductility degradation against cryogenic on flexural performance of UHPC at various temperature conditions

This paper reports the flexural performance of ultra-high performance concrete (UHPC) exposure to six temperature conditions, including ambient temperature (A), after exposure to 200 °C (EA), in-situ −170 °C (DC), in-situ −170 °C after exposure to 200 °C (IDC), after exposure to −170 °C (AC), after exposure to 200 °C and −170 °C (AEC). The cracking characteristics of UHPC under the coupling effect of cryogenic and external load is identified with acoustic emission (AE) technology. The results show that DC condition is the most efficient in enhancing flexural strength and toughness due to frozen water and improved bond strength. A nonlinear relationship between first-peak deflection and first-peak flexural strength is observed because of the changed flexural modulus at different temperature conditions. The increasing shear cracks in linear-elastic stage is attributed to the fracture process of frozen water, which can account for the significant increase of first-peak strength at DC and IDC conditions. Cryogenic-induced ductility degradation is observed in the flexural behaviour of UHPCs at DC and IDC conditions, which is attributed to higher energy release rate. Furthermore, pre-exposure to 200 °C reduced the positive influence of cryogenic temperature on flexural performance and the negative effect of cryogenic temperature on ductility because of the initiated cracks around steel fibers.

Monitoring by acoustic emission the mechanical behavior of polystyrene submitted to stress cracking at different temperatures

AbstractEnvironmental stress cracking (ESC) is one of the main phenomena that limit the use of polymers, being responsible for an expressive number of premature failures in service. This occurs when mechanical loading is combined with a certain kind of chemical agent, causing surface cracks and, eventually, catastrophic failure. This issue is not widely reported in the literature, and the usual procedures for investigation involve conventional mechanical testing. Alternative tools, such as, the technique of acoustic emission (AE) to monitor the stages of fracture, are rarely used. In this work, injection molded polystyrene were submitted to stress cracking conditions, using two types of active fluids and different exposure temperatures (25, 40, and 55°C). The AE technique was applied simultaneously with the mechanical testing to monitor parameters like intensity of the hits and energy released during the deformation and fracture. The results showed that the failure by ESC was related to the fluid interaction with the polymer and was very dependent on the exposure temperature. The use of acoustic emission technique was very useful to differentiate the effects of the various exposure conditions and to explain certain fracture characteristics observed by visual inspection and by scanning electron microscopy.

Damage assessment of a titanium skin adhesively bonded to carbon fiber–reinforced plastic omega stringers using acoustic emission

This study is devoted to the use of acoustic emission technique for a comprehensive damage assessment, that is, damage detection, localization, and classification, of an aeronautical metal-to-composite bonded panel. The structure comprised a titanium panel adhesively bonded to carbon fiber–reinforced plastic omega stringers. The panel contained a small initial artificial debonding between the titanium panel and one of the carbon fiber–reinforced plastic stringers. The panel was subjected to a cyclic increasing in-plane compression load, including loading, unloading, and then reloading to a higher load level, until the final fracture. The generated acoustic emission signals were captured by the acoustic emission sensors, and digital image correlation was also used to obtain the strain field on the surface of the panel during the test. The results showed that acoustic emission can accurately detect the damage onset, localize it, and also trace its evolution. The acoustic emission results not only were consistent with the digital image correlation results, but also managed to detect the damage initiation earlier than digital image correlation. Finally, the acoustic emission signals were clustered using particle swarm optimization method to identify the different damage mechanisms. The results of this study demonstrate the capability of acoustic emission for the comprehensive damage characterization of aeronautical bi-material adhesively bonded structures.

Challenges and Limitations in the Identification of Acoustic Emission Signature of Damage Mechanisms in Composites Materials

Acoustic emission is a part of structural health monitoring (SHM) and prognostic health management (PHM). This approach is mainly based on the activity rate and acoustic emission (AE) features, which are sensitive to the severity of the damage mechanism. A major issue in the use of AE technique is to associate each AE signal with a specific damage mechanism. This approach often uses classification algorithms to gather signals into classes as a function of parameters values measured on the signals. Each class is then linked to a specific damage mechanism. Nevertheless, each recorded signal depends on the source mechanism features but the stress waves resulting from the microstructural changes depend on the propagation and acquisition (attenuation, damping, surface interactions, sensor characteristics and coupling). There is no universal classification between several damage mechanisms. The aim of this study is the assessment of the influence of the type of sensors and of the propagation distance on the waveforms parameters and on signals clustering.

Advanced signal analysis of acoustic emission data to discrimination of different corrosion forms

Aim of the present work is to give an analytical approach suitable to distinguish three different corrosion forms through the use of acoustic emission technique. Corrosion attacks have been obtained on three different types of martensitic stainless steel in a FeCl3 solution, using conditions set by the ASTM G48 standard. These martensitic stainless steel used were characterised by different mechanical, microstructural and electrochemical properties, which lead to the development of specific corrosion forms, albeit the steels were tested in the same environmental conditions. A multivariate statistical analysis approach, based on principal component analysis (PCA) and self-organising map (SOM), has been adopted to evaluate AE data and to obtain highlight damage-sensitive features. Specific clusters of variables related to specific corrosion phenomena have been identified, promoting this analysis approach as a potential procedure for discriminating onset of a specific corrosion mechanism.

The use of acoustic emission technique in the failure analysis of PET by stress cracking

Failure of polymers by environmental stress cracking is a major problem for designers and engineers but scientific work in this field might not be sufficient to fully understand its mechanisms and propose possible solutions. In this work, the failure analysis of poly(ethylene terephthalate) was conducted under tensile and stress relaxation conditions and in contact with sodium hydroxide solution. The use of acoustic emission (AE), a non-conventional technique, was shown to be very useful for monitoring the changes in the material during the experiments. It was possible to detect phenomena such as shear bands, formation and location of crazes and cracks and to evaluate the damage caused to the polymer under different experimental conditions. The acoustic events related to stresses and deformations were determined for a number of situations, being very useful in the analysis of failure by stress cracking.

Signal Analysis of Acoustic Emission for Laser Imitating Grinding Burn

Grinding burn is a common phenomenon of thermal damage that has been one of the main constraints in grinding in respect of high efficiency and quality. Use of acoustic emission technique for identifying grinding burn was reported before. However, the AE features of grinding burn are relatively weak and easily merged by other AE sources. This paper presents an investigation of the AE features of the thermal expansion induced by laser irradiation, which was designed to simulate grinding thermal behaviour. By means of the wavelet packet transforms, AE features at the grinding burn temperature can successfully be extracted without other mechanical interferential factors. These clean features can provide a firm foundation for analysing the real grinding burn AE features and for monitoring grinding burn.

Use of acoustic emission technique for the early detection of aluminum alloys exfoliation corrosion

Exfoliation corrosion of aluminum alloys is a form of localized corrosion which affects many industries, specially aeronautics. The study of this corrosion mode using only electrochemical techniques is not fully efficient for the detection and control on line of this phenomenon. Therefore, we developed a non-destructive testing technique based on the acoustic emission recordings in order to follow-up this form of corrosion on aluminum alloys. Indeed, recent works have shown the interest of the acoustic emission for the detection, the monitoring and the localization of pitting corrosion on aluminum alloys. This pitting corrosion phenomenon is currently well understood and the experimental methodology acquired during that study is transposed to the study of exfoliation corrosion of aluminum alloys. The present study is conducted on two aluminum alloys: (Al 2024 T3, and Al 7449 T6 and T7). Samples are immersed 4 days in the modified ASTM STP 1134 saline solution. Observations of the structures after tests show that the exfoliation corrosion sensitivity of alloy 7449 T6 is more important than for alloy 7449 T7 which exhibits only the presence of small and non-occluded pits. Very severe exfoliation corrosion was also observed on Al 2024 T3, but after a longer immersion time or in a more acid solution. The recording of the acoustic emission activity shows evident links between this activity and the exfoliation corrosion rate. The analysis of the signal's characteristics reveals a population corresponding to the release of hydrogen bubbles. A few more energetic signals have also been observed. Their source can be either, the cracking resulting from the separation of sheets of metal, or the development and evolution of hydrogen bubbles formed inside blisters during exfoliation corrosion.

Sound signatures assist assembly

Examines the use of acoustic emission techniques for monitoring part mating during the assembly process. The frequency recorded during a peg insertion is compared with known frequencies of successful peg insertion by a microcomputer. This allows unsuccessful alignment to be readjusted which being monitored by a digital sound analyzer. Outlines the concept of part mating which is based on the peg‐in‐hole theory developed by Simunovic and describes an acoustic emission monitoring system. Concludes that acoustic monitoring provides a relatively low cost, low complexity system for part mating monitoring but may have limitation in manufacturing environments where there is excessive background noise or machine part vibration.

Use of acoustic emission technique for identification of failure of tensioned grouted rock anchors : Bouja, A; Ballivy, G; Benmokrane, B; Piasta, Z; Feknous, N Rock Mechanics as a Multidisciplinary Science: Proc 32nd US Symposium, Norman, 10–12 July 1991P159–168. Publ Rotterdam: A A Balkema, 1991

Use of acoustic emission technique for identification of failure of tensioned grouted rock anchors : Bouja, A; Ballivy, G; Benmokrane, B; Piasta, Z; Feknous, N Rock Mechanics as a Multidisciplinary Science: Proc 32nd US Symposium, Norman, 10–12 July 1991P159–168. Publ Rotterdam: A A Balkema, 1991

Use of acoustic emission technique to study the spalling behaviour of oxide scales on Ni‐10Cr‐8AI containing sulphur and/or yttrium impurity

AbstractIt is now well established that the presence of small amounts of sulphur impurity in a NiCrAl‐based alloy causes a deleterious effect on their high temperature oxidation behaviour. It is, however, not clear whether the adverse effect is due to a decrease in the spalling resistance of the oxide scale or due to an enhanced scale growth. In order to confirm which of the factors is dominating, two independent experimental techniques were used in the investigation of the oxidation behaviour of Ni‐10Cr‐8AI containing sulphur‐ and/or yttrium additions: conventional thermogravimetry, to study the scale growth rates and acoustic emission analysis to study the scale adherence. The results indicated that the dominant factor responsible for the deleterious effect of sulphur impurity on the oxidation of a Ni‐10Cr‐8AI alloy, was a significant change in the growth rate and the composition of the scale. Addition of yttrium improved the oxidation behaviour, not only by increasing the scale adherence, but also by reducing the scale growth due to gettering of sulphur.

The use of acoustic emission techniques to monitor fracture processes in high strength precipitation hardened aluminum alloys

The ductile fracture of dispersion hardened aluminum alloy containing brittle intermetallic inclusions is briefly reviewed. The effect of the size, distribution and chemical composition of the inclusions in affecting the matrix fracture behavior is discussed. The potential of acoustic emission techniques in being able to discriminate between different microstructures produced by various thermomechanical treatment is emphasized. It is shown that processes that affect dislocation motion, i.e., cold work, precipitation, solute atom diffusion, etc., also affect the acoustic response, thus making the AE technique extremely useful for the study of flow and fracture behavior of aluminum alloys.

Acoustic emission: A means of measuring crack growth at elevated temperatures

Acoustic-emission (AE) technique has been applied to detect and continuously monitor subcritical crack growth in Zr-25% Nb. a commercial alloy for reactor-core components. The tests conducted in the dimensions of time, temperature, stress and local environment registered a significant difference in AE aclivity. The time-domain analysis of acoustic emissions suggested the crack growth to be intermittent Further investigations to interpret the AE response to cracking identified tracture mechanisms operative during slow crack growth. The analytical parameters of crack growth were then correlated with AE data which produced some confidence in the use of AE techniques to quanhtatively measure slow crack growth and crack growth rates during tracture. The results are presented to show a good fit between estimated and observed crack lengths and velocities. Finally, the viewpoints reached from AE studies were compared with tractographic observations and were found in agreement, providing a great deal of faith in the use of AE techniques.

１９Ｃｒフェライト系ステンレス鋼溶接部の機械的，や金的挙動

A study has been carried out into the mechanical and metallurgical properties of welds of the so called super-ferritics with carbon and nitrogen impurities of less than 200 ppm. The tests were carried out on three kinds of materials, one commercial grade and two kinds of 19Cr alloy with carbon and nitrogen impurities of around and less than 30ppm respectively.Tensile test specimens were so designed as to possess a TIG weld bead at the center of the gage sections. They were aged at various temperatures in order to induce 475°C embrittlement, σ-phase embrittlement, high temperature embrittlement, and an embrittlement due to fine carbide and nitride precipitation at grain boundaries. Tensile properties were obtained using an Instron-type machine at room temperature. As a result, it was found that there exist at least four kinds of embrittlement for the present weld joints: a. 475°C embrittlement b. embrittlement due to fine carbide and nitride precipitations at grain boundaries c. high temperature embrittlement d. grain boundary embrittlement due to phosphorous segregation at grain boundaries by 1350°C aging and the following water-quenching. 475°C embrittlement is not induced by welding process only. However once the embrittlement is realized by aging heat treatment, it is most severe at weld section.TIG arc-strike weld cracking test was conducted to investigate the cracking behaviour of weld nugget, especially the locations and the temperature range, the latter being monitored by use of acoustic emission technique. The cracking occurs at sub-grain boundaries at equiaxed zone of the weld nugget in the temperature range of 400-1000°C during cooling after welding. The cracking increases with the increase of heat input. The mechanism of the cracking is of the combination of matrix hardening due to high temperature embrittlement and carbon (nitrogen) segregation at sub-grain boundaries.

Application of acoustic emission in the geotechnical area

A review of the application of acoustic emission (microseismic) techniques to the geotechnical area will be given. The approach will be somewhat historical starting with the pioneering work (in the 1930's) by Obert and Duvall in the coal and metal mines and continuing up to the present where currently a host of materials and engineering problems are being investigated with acoustic emission techniques. Acoustic emission measurements in the laboratory will be described which have given insight into the mechanical behavior of rocks, soils, coal and ice. Field applications which will be dealt with include determination of the stability of mine tunnels, open pit mine slopes, underground gas storage reservoirs, and earthem dikes and dams. The use of acoustic emission techniques in earthquake prediction studies will be reviewed. [The authors' work has been supported by EPA.]

Acoustic emission studies of filament-wound carbon fibre reinforced rings and pressure vessels

Following earlier work on the use of acoustic emission techniques for studying fatigue and fracture in unidirectional plane samples of carbon fibre reinforced plastic, experiments have been carried out on filament-wound rings and pressure vessels. The hydraulic expansion to failure of rings of carbon/epoxy composites represents the first step away from the earlier studies of model systems to more realistic structures, and it appears that the rings behave in exactly the same way as tensile samples. Of greater significance, however, is the fact that polar-wound pressure vessels in the form of oblate spheroids with aluminium screw-thread end connexions also show the same kind of acoustic emission patterns. If a vessel is pressurized and held at constant pressure the acoustic output is gradually reduced until it ceases. If the vessel is unloaded and reloaded, the pressure at which emission recommences (about 93 per cent of the previous maximum) can then be considered to be a safe working pressure. The response of these vessels to monotonic loading, cyclic loading and stress relaxation is very similar to that of unidirectional tensile samples.

An evaluation of acoustic emission techniques applied to carbon-fibre composites

A study has been made of the use of acoustic emission techniques to monitor failure processes within carbon-fibre-reinforced plastics and to establish some of the limitations of the technique. The type of signal to be expected from a resonant transducer of the type most widely used is discussed, and simulation studies confirm this analysis. Bundles of different types of fibres have been broken in order to investigate the type of emission obtained when fibres fracture. Sources of extraneous emission arising from the grips and from shear damage at notch tips have also been studied.

The use of acoustic-emission techniques and liquid penetrants to detect surface cracks

The author describes a method of infiltrating surface defects with adhesive liquids. After curing, high amplitude acoustic emissions are obtained from cracking of the adhesive when the defect opens under load. Thus the defects can be found.