Acoustic Emission Wave Propagation Research Articles

A lattice modelling framework for fracture-induced acoustic emission wave propagation in concrete

To date, there is no comprehensive approach available that can explicitly model the complete transient waveforms of acoustic emissions (AE) induced by fracture processes in brittle and quasi-brittle materials like concrete. The complexity of AE modelling arises from the intricate coupling between the local discontinuity of material fracturing and the global continuity of elastic wave propagation in solids. Among others, the lattice type models are promising approaches, as they are known to be a matured modelling approach to simulate the fracturing process in concrete-like materials. Nevertheless, like other discrete element methods (DEM), they are currently limited to describing the number and rate of AE events (broken elements) in the fracture process and cannot explicitly model wave generation and propagation. In this study, we propose a lattice modeling framework to simulate the propagation of complete waveforms of fracture-induced AE signals in concrete. A proportional-integral-derivative (PID) control algorithm is incorporated in an explicit time integration procedure to reduce dynamic noise from spurious oscillations. Additionally, a Rayleigh damping-based calculation method and corresponding calibration procedure are proposed to model the attenuation of AE signals due to material damping. Using the developed approach, we systematically investigate the feasibility of lattice models for elastic wave propagation simulation, the dependence of lattice mesh sizes and the choice of numerical damping parameters. These results lead to a systematic framework which can be employed in simulating wave propagation with attenuation using DEM models in general including lattice models.

Acoustic emission wave propagation in pipeline sections and analysis of the effect of coating and sensor location

ABSTRACT This paper presents an experimental investigation in which acoustic emission (AE) wave was generated through a pencil lead break as a point source on two pipeline sections made of mild steel and titanium. The pipelines (bare, epoxy phenolic coated) were of same length but had two different diameters and wall thicknesses. The recorded AE signals were analysed using time and frequency domain signals, energy levels and wavelet transform to explore time-frequency features for the identification of wave modes. It is concluded that the damping behaviour of coating restricts the peaks of waves, decreases the decay time of waves and reduces the energy level in the coated pipeline. It is concluded that monitoring of coated pipeline wave propagation could be done effectively with sensor placement directly on the pipeline surface compared to sensor placement on the coating surface. A high wall thickness of pipeline results in a higher number of reflected waves and increases the decay time of waves. The coating on pipeline resists wave propagation, and different densities of coating layer and pipeline affect the velocity of the wave. This experimental work advance towards designing an alternative way to monitor changes in pipeline structures (e.g., corrosion under insulation applications).

Quantitative Analysis of the Hsu-Nielsen Source through Advanced Measurement and Simulation Techniques

Abstract This paper presents the results from conducting a series of experiments with a Hsu-Nielsen Source, accompanied by corresponding numerical simulations on a solid block. The aim being to illustrate a Finite Element Analysis (FEA) approach for simulating Acoustic Emission (AE) wave propagation in a Hsu-Nielsen Source, by employing virtual sensors to enhance existing AE research methodologies. The objective was to examine and establish the actual unload rate derived from Pencil Lead Breaks (PLBs) by comparing results from simulations and experimental trials. These experiments and simulations were conducted using a solid cylindrical steel block, capturing the propagating Acoustic AE waves from both sources over a two-second span. When comparing the experimental data with the simulation results, it is evident that replicating the structure of an impulsive AE source is feasible for brief durations. Furthermore, both the experimental and simulated signals on the steel cylinder displayed comparable patterns in the initial 25-30 µs. The methodology presented in this study demonstrates the effectiveness of Finite Element Analysis (FEA) in precisely identifying the specific modes present in AE wave propagation, including the actual unload rates affecting the AE signals recorded.

Acoustic emission source location for composite tubes using finite element simulation and machine learning

ABSTRACT Acoustic emission is widely used in engineering structural health monitoring, where damage location based on acoustic emission have great advantages. Currently, most of the acoustic emission location work requires extensive experimental studies. In this study, acoustic emission source location model was proposed based on BP neural network and acoustic emission wave propagation simulation, thus reduced the experiments required for acoustic emission localisation and improved the location accuracy. Initially, finite element simulation was conducted to study the propagation of acoustic emission waves in composite tubes. The calculated findings showed a high level of agreement with the experimental data. Additionally, the first arrival time of the signal was extracted according to the Akaike information criterion, and the neural network was trained and tested using the simulated data, while the trained network model was validated using the experimental data. The results show that the finite element method is a reliable alternative test method. More than 94% of the sound source location results have absolute location error within ± 3 mm, and the all points is less than ± 5 mm. The deviation of the location results showed significant improvement compared to the traditional time difference of arrival method, verifying the feasibility of the method.

Acoustic emission-based assessment of weld effects on the health monitoring of the rail section: an experimental study

Railways are a vital lifeline for both passengers and freight, with an extensive network connected by robust welded joints. This study explores the potential of Acoustic Emission (AE) techniques in rail health monitoring, particularly in the context of rail sections and their relationship with welds. While AE-based health monitoring has gained attention, a significant gap exists in understanding welds’ influence. This research bridges this gap by examining the interplay between welds and health monitoring. Welds introduce complexities in AE wave propagation, crucial for precise health assessments. Through artificial AE source simulation using the Pencil Lead Break (PLB) method across diverse rail segments, specialized sensors capture AE signals. Rigorous analysis, involving signal processing and statistical methods, reveals how welds impact AE wave behaviour and health assessment accuracy. Importantly, this research underscores how welds alter AE wave propagation, ensuring accurate health evaluations. This study’s insights hold far-reaching implications, not only for enhancing current rail system maintenance but also for advancing our understanding of the critical interrelationship between welds and health monitoring, thus contributing to the longevity and reliability of rail systems.

Investigation of Acoustic Emission Wave Propagation Pattern with Defect Locations in a Multilayer Structure

Acoustic emission (AE) is used to monitor conditions of various structures across many industrial sectors, including containment vessel or storage tank of nuclear materials. Periodic monitoring, inspection, and analysis of structure conditions can help prevent failure and accidents. Understanding the transient elastic waves in multi-layered structures (planar or rounded types) has long been of great interest. This paper experimentally investigates changes in AE wave propagation patterns in multilayer planar structures (detecting and assessing the effect of coating layers, assumed surrogate of deposits or protective layer). Epoxy phenolic coated two mild steel plates were assembled (without any adhesion), and two piezoelectric AE sensors were placed on the coating layer. The pencil lead break (PLB) test was used to initiate the AE waves from the surface and cross-section of different layers. From wavelet transforms (WT) analysis, significant energy zone changes were observed up to the 450 kHz frequency level with PLB on the surface and cross-section of different layers. Love wave propagation on the coated plate structure resulted in wave pattern changes with PLB locations and layers. Wave duration, energy, energy ratio, and peak amplitude levels were also analysed to characterise the AE wave pattern relationship with defect location in a multilayer plate-like (planar) structure. The approaches used in this work could potentially be useful in providing a greater understanding of defects within multilayer nuclear containment structures, and also offering an alternative way to monitor corrosion related degradation of structures with insulations.

Effect of Hydrostatic Pressure on the Propagation of Partial Discharge Acoustic Signals in Transformer Oil

In this research article an attempt is made to investigate the effect of hydrostatic pressure on the propagation behavior of Partial Discharge (PD) Acoustic Emission (AE) signals in a simple experimental tank. A mathematical model has been developed in the form of Partial Differential Equations (PDEs) for PD acoustic wave propagation in transformer oil in a steel tank. A Finite Element Analysis tool (FEMLAB), has been used to simulate the propagation of the acoustic waves. The simulation results show that the speed of the acoustic signal varies with the depth of the source location demonstrating hydrostatic pressure affects AE wave propagation. Furthermore, the effect of hydrostatic pressure was investigated and conformed experimentally. It is concluded that the propagation speed is not constant within the tank and increases with tank depth. If the effect of increased acoustic velocities due to hydrostatic pressure is ignored then the possibility of practical PD location algorithms inferring the incorrect location in high voltage assets, such as oil filled transformers, will be increased significantly.

RETRACTED ARTICLE: Investigation on elastic guided wave propagation in a parallel axisymmetric stressed viscoelastic cylindrical waveguide

We, the Editor & Publisher of Mechanics of Advanced Materials and Structures, have retracted the following article: T. Jothi Saravana (2021) Investigation on elastic guided wave propagation in a parallel axisymmetric stressed viscoelastic cylindrical waveguide. DOI: 10.1080/15376494.2021.2017524 After publication, the author, T.J. Saravana, requested the retraction of this article due to his use of third-party data without the required permissions. Further investigations revealed that the article contained data from an unpublished thesis titled “Analyses on Acoustic Emission Wave Propagation in a Stay Cable using Semi-Analytical FEM” authored by Yang Yaohua in 2018, that was used without permission. As the reuse of data from a third party without acquiring the required permissions is a serious breach of publishing ethics, we are retracting the article from the journal. The author agrees to this retraction. We have received guidance from our policy on publishing ethics and integrity and the COPE guidelines on retractions, which have informed our decision-making process. To maintain the scholarly record, the retracted article will remain available online. We will ensure that it is identified as “Retracted” by adding a digital watermark on each page.

The influence law of concrete aggregate particle size on acoustic emission wave attenuation

Elastic waves have different attenuation laws when propagating in various materials, which is one of the important challenges in the application of non-destructive testing methods, such as acoustic emission (AE) technology in geotechnical engineering. The study presented in this paper investigated the influence mechanism of concrete composition materials and parameters on the propagation law of elastic waves using concrete specimens produced in six different particle sizes of sand or gravel. The burst AE signal was generated through the lead-breaking experiment, and ceramic piezoelectric sensors were used to record the signal waveform at different propagation distances. Through parameter analysis, spectrum analysis, and pattern recognition techniques, the influence of the concrete aggregate particle size on AE wave propagation and attenuation was revealed. The results show that the attenuation of elastic wave amplitude, energy spectral density, and frequency all were positively correlated with the aggregate particle size, and the elastic wave spectrum center of gravity generally decreased with the propagation distance. The ring count gradually decreased with the propagation distance, and the specimens with a larger aggregate particle size underwent a relatively faster ring count attenuation rate. The rise time increased rapidly with the propagation of the elastic wave, and the specimens with a larger aggregate particle size experienced a relatively rapid increase in rise time. In addition, in the feature spaces of ring count-amplitude and rise time–amplitude, the size of aggregate has an obvious influence on the distribution of these feature vector.

Acoustic emission wave propagation in honeycomb sandwich panel structures

This paper studies acoustic emission (AE) wave propagation in a glass fibre aluminium honeycomb sandwich panel (HSP). Of particular novelty is the quantification of the through-thickness propagation of AE from one surface of the HSP to the other, which is a real-world monitoring consideration for applications where AE instrumentation is only be permissible on one surface, i.e. aerofoils. Complexity was introduced to the specimens in stages to enable a thorough understanding; first investigating propagation in a large glass fibre laminated plate (GFLP) alone; then in bespoke sandwich specimens with a limited number of honeycomb cells; and, finally, in a large HSP. The results of this paper demonstrate that, whilst some energy is transmitted through the honeycomb core, AE propagating in an HSP becomes bound in the outer plates. Despite this, propagation in these outer plates differs to that in an equivalent plate of the same material in isolation due to the complex interactions with the structural elements of the HSP. Further, propagation of AE transmitted from one surface to the other was quantified for the first time, giving insight into expected attenuation rates and characteristics for practical applications.

Evaluation of Acoustic Emission Wave Propagation for Diagnosis in Homogenous Material

Evaluation of Acoustic Emission Wave Propagation for Diagnosis in Homogenous Material

On the determination of acoustic emission wave propagation velocity in composite sandwich structures

This work focuses on the rapid determination of Acoustic Emission (AE) wave propagation velocity in composite laminate and sandwich structures using a closed-form formula. Firstly, a classical closed-form model proposed in the literature is extended to determine the acoustic wave velocity in any direction in a composite laminate or sandwich structure; then a corrective factor has been defined to improve the calculation accuracy; finally, a parameter, called correlation ratio has been introduced to describe the relation between acoustic wave velocity in the composite skin and that in the sandwich panel. This strategy has been validated by two types of composite sandwich panels: one is honeycomb sandwich structures with CFRP composite laminate skins; the other is balsa sandwich with GFRP skins. It is demonstrated that acoustic wave velocity in the sandwich is dominated by the skin property, namely the elastic modulus of the skin, the density of the constituents, the core and skin thickness. Moreover, only by measuring the velocity in one direction, the velocity in any direction of composite structures can be predicted accurately and quickly. This work lays the first foundations for the establishment of numerical and experimental models necessary to improve the damage localization of composite structures.

RETRACTED ARTICLE: Investigation of guided wave dispersion characteristics for fundamental modes in an axisymmetric cylindrical waveguide using rooting strategy approach

We, the Editor & Publisher of Mechanics of Advanced Materials and Structures, have retracted the following article: T. Jothi Saravana (2020) Investigation of guided wave dispersion characteristics for fundamental modes in an axisymmetric cylindrical waveguide using rooting strategy approach. DOI: 10.1080/15376494.2020.1777601 After publication, the author, T.J. Saravana, requested the retraction of this article due to his use of third-party data without the required permissions. Further investigations revealed that the article contained data from an unpublished thesis titled "Analyses on Acoustic Emission Wave Propagation in a Stay Cable using Semi-Analytical FEM" authored by Yang Yaohua in 2018, that was used without permission. As the reuse of data from a third party without acquiring the required permissions is a serious breach of publishing ethics, we are retracting the article from the journal. The author agrees to this retraction. We have received guidance from our policy on publishing ethics and integrity and the COPE guidelines on retractions, which have informed our decision-making process. To maintain the scholarly record, the retracted article will remain available online. We will ensure that it is identified as "Retracted" by adding a digital watermark on each page.

Partial discharge localisation methodology for power transformers based on improved acoustic propagation route search algorithm

The localisation of partial discharge (PD) sources using the acoustic emission (AE) technique has attracted increasing research attention. The complicated propagation routes and wave-type conversion in power transformer can induce considerable localisation error. In this paper, the catadioptric phenomenon of AE wave propagation is explained in detail. With the incident angle varying, the wave type of the direct wave in tank wall could convert and the velocity will change accordingly. A transformer model is established in which each node refers to a suspected PD position and a shortest route search algorithm is proposed to calculate the shortest path between two nodes in this model. However, the fastest route is most significant to PD localisation rather than the shortest route when TDOA method is used. As a result, an improved propagation route search (IPRS) algorithm, which can recreate the propagation process and calculate the fastest AE routes, is proposed to localise the PD origin. To verify the feasibility of the IPRS algorithm, localisation experiments were performed in 35 and 110 kV transformers, respectively. Compared with other present localisation methods, such as the Chan algorithm, the genetic algorithm and the imperial competitive algorithm, the proposed algorithm can effectively reduce localisation error.

Propagation characteristics of acoustic emission wave in reinforced concrete

Due to the complexity of components and damage mechanism of reinforced concrete, the wave propagation characteristics in reinforced concrete are always complicated and difficult to determine. The objective of this article is to study the failure process of reinforced concrete structure under the damage caused by pencil-broken. A new method on the basis of the acoustic emission technique and the Hilbert-Huang transform theory is proposed in this work. By using acoustic emission technique, the acoustic emission wave signal is generating while the real-time damage information and the strain field of the reinforced concrete structure is receiving simultaneously. Based on the Hilbert-Huang transform (HHT) theory, the peak frequency characteristics of the acoustic emission signals were extracted to identify the damage modes of the reinforced concrete structure. The results demonstrate that this method can quantitatively investigate the acoustic emission wave propagation characteristic in reinforced concrete structures and might also be promising in other civil constructions.

Solder joint failure localization of welded joint based on acoustic emission beamforming

A localization approach of welded joint damage is proposed based on acoustic emission (AE) beamforming. In this method, a uniform line array is introduced to detect the AE signal of welded joints in specified area. In order to investigate the influence of fillet and crimping commonly existing in a welded plate structure during the AE wave propagation process, the finite element method (FEM) is applied to simulate the behavior of AE wave in the specimen. The simulation localization results indicate that the proposed localization approach can effectively localize AE sources although there exist the fillet and crimping, and it is also validated by the pencil-lead-broken test on rectangular steel tube with welded joints. Finally, the proposed method is adopted to localize the failure of solder joint in operation vibration condition. The proposed method is successful to localize the compact AE source caused by the cracked joint based on wavelet packet transform.

A novel method of identifying damage types in carbon fiber-reinforced plastic cross-ply laminates based on acoustic emission detection using a fiber-optic sensor

We applied a highly sensitive phase-shifted fiber-optic Bragg grating (PS-FBG) sensor with a broad bandwidth to acoustic emission (AE) detection in a composite material. Based on AE detection, this research proposed a novel method to identify damage types in carbon fiber-reinforced plastic (CFRP) laminates. Because the PS-FBG sensor measured pure dynamic strain, the detected AE signals had great physical reliability, which made elastic wave theory suitable for analysis of the signal. The analysis clarified the different characteristics of Lamb wave modes in three types of AEs caused by a transverse crack, delamination and fiber breakage. Additionally, the ratios of the amplitudes of the S0 mode to the A0 mode and the peak frequencies quantitatively evaluated the mode characteristics in the AE signals. Simultaneously using the two physical parameters, we identified the three types of damage among the AE signals detected in a three-point bending test. Furthermore, the finite element method-based AE wave propagation simulation agreed well with the identification results. Hence, the proposed identification method with the PS-FBG sensor has great physical reliability for evaluating damage in composite laminates.

Acoustic emission beamforming method for localizing rotor-stator rubbing fault

One of the challenges restricted rubbing quantitative diagnosis is that vibration method cannot be effective applied to rubbing fault localization. Therefore,an acoustic emission( AE) beamforming array was presented to localize rotor-stator rubbing fault of rotating machinery. Firstly,finite element simulation model of rubbing AE was established based on mechanical model of rotor-stator rubbing and the structure of rotor test-bed,which can be used to simulate AE signals and study characteristics of simulating signals and AE wave propagation. Then rubbing localization performances of AE beamforming with typical arrays,such as line array,crossed array and circular array,were studied based on simulation AE signals and propagation characteristics of rubbing AE,and that the line array was the most appropriate for rubbing localization. Aiming to the shortage of line array,the improved sensor array and localization scheme were approached. Finally,the proposed localizing method of rubbing fault was verified by experiments. The results show that AE beamforming method can achieve accurate localization of rubbing fault by choosing the right sensor array and suitable sensor arrangement.

Normalization and source separation of acoustic emission signals for condition monitoring and fault detection of multi-cylinder diesel engines

A signal processing technique is presented in this paper to normalize and separate the source of non-linear acoustic emission (AE) signals of a multi-cylinder diesel engine for condition monitoring applications and fault detection. The normalization technique presented in the paper overcomes the long-existing non-linearity problem of AE sensors so that responses measured by different AE sensors can be quantitatively analysed and compared. A source separation algorithm is also developed in the paper to separate the mixture of the normalized AE signals produced by a multi-cylinder diesel engine by utilising the system parameters (i.e., wave attenuation constant and the arrival time delay) of AE wave propagation determined by a standard pencil lead break test on the engine cylinder head. It is shown that the source separation algorithm is able to separate the signal interference of adjacent cylinders from the monitored cylinder once the wave attenuation constant and the arrival time delay along the propagation path are known. The algorithm is particularly useful in the application of AE technique for condition monitoring of small-size diesel engines where signal interference from the neighbouring cylinders is strong.

A novel acoustic emission beamforming method with two uniform linear arrays on plate-like structures

A novel acoustic emission (AE) source localization approach based on beamforming with two uniform linear arrays is proposed, which can localize acoustic sources without accurate velocity, and is particularly suited for plate-like structures. Two uniform line arrays are distributed in the x-axis direction and y-axis direction. The accurate x and y coordinates of AE source are determined by the two arrays respectively. To verify the location accuracy and effectiveness of the proposed approach, the simulation of AE wave propagation in a steel plate based on the finite element method and the pencil-lead-broken experiment are conducted, and the AE signals obtained from the simulations and experiments are analyzed using the proposed method. Moreover, to study the ability of the proposed method more comprehensive, a plate of carbon fiber reinforced plastics is taken for the pencil-lead-broken test, and the AE source localization is also realized. The results indicate that the two uniform linear arrays can localize different sources accurately in two directions even though the localizing velocity is deviated from the real velocity, which demonstrates the effectiveness of the proposed method in AE source localization for plate-like structures.