Acoustic Emission Diagnostics Research Articles

Structural–Phenomenological Concept and Acoustic-Emission Diagnostics of Composite Stringers under Three-Point Bending Conditions

Structural–Phenomenological Concept and Acoustic-Emission Diagnostics of Composite Stringers under Three-Point Bending Conditions

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.

Evaluation of the Residual Strength of Composite Products Based on the Structural-Phenomenological Concept of Damage and Acoustic Emission Diagnostics

Evaluation of the Residual Strength of Composite Products Based on the Structural-Phenomenological Concept of Damage and Acoustic Emission Diagnostics

Acoustic Emission Diagnostics of Damaged MS-21 Airplane Wingbox during Endurance Tests

Acoustic Emission Diagnostics of Damaged MS-21 Airplane Wingbox during Endurance Tests

Structural phenomenological concept of monitoring the load-bearing capacity of structural elements of composite materials

The authors demonstrate the potential of a methodological approach for monitoring the damage kinetics and evaluating the load-bearing capacity of composite structural elements based on the method of acoustic emission. This methodology was developed by specialists of the Blagonravov Mechanical Engineering Research Institute of the Russian Academy of Sciences. The methodology was implemented for a fatigue test of an aircraft panel represented by a complex hybrid structure with a lining made of layered composite and a cellular internal structure of aluminum foil with polymeric filler that has a continuous layered structure in the gripping area. Fatigue tests were carried out at 4 Hz from the zero-loading cycle with an amplitude of 145 kN. To record the accumulation of damages, R15–AST transducers by Mistral (USA) and an A-line 32D 8-channel acoustic emission system by Interunis-IT LLC were used. Comparing the weight content of location impulses with their threshold values in energy clusters characterizing the kinetics of micro-, meso-, and macro-damages of the composite material structure made it possible to determine the bearing capacity of the aircraft panel at respective stages of damage kinetics. The results of the acoustic emission diagnostics are given for the examined aircraft panel during cyclic loading, including the coordinate location of acoustic emission sources, accumulation of acoustic emission events by channels, the dynamics of partial activity changes, and weight content of location impulses at damage evolution stages of a composite material. Therefore, the acoustic emission diagnostics of the aircraft panel made it possible to identify the areas of intensive damage accumulation in the hybrid structure of the panel and control the actual bearing capacity by defining the extent of its damages at various scale and structural levels during cyclic loading. The described methodology of using acoustic emission diagnostics for monitoring the damage kinetics and actual bearing capacity of highly loaded composite elements extends the research potential of the acoustic emission method.

Evaluation of the residual strength of composite products based on the structural-phenomenological concept of damage and acoustic-emission diagnostics

A structural-phenomenological concept (SPhC) of monitoring the residual strength of composite materials is proposed. SFK was developed taking into account the kinetics of damage and destruction of polymer composite material (PCM) at the micro-, meso- and macroscale levels, which generate acoustic emission pulses (AE) recorded by the receiving transducers of the antenna array. A correspondence between the ongoing destruction of the composite material structure at the micro-, meso- and macroscale level and the AE pulses recorded at the same time and their weight content provides the possibility of monitoring of the damage kinetics in the loading mode at all structural levels, and, consequently, the possibility of control of the residual strength of the product. An algorithm and software have been developed that made it possible to divide the recorded AE signals into the clusters of lower, middle and upper energy levels corresponding to micro-, meso- and macroscale disruptions of the structure of a composite material, calculate the AE activity and the weight content of location pulses in energy clusters, thus displaying the dynamics of their changes every second. Comparison of the current values of the most informative parameters of the weight content of location pulses in energy clusters with the threshold values recorded during the destruction of the material provides monitoring of the residual strength of the product in the loading mode. The validity of the developed concept, algorithm and software was proved during tests of elementary and structurally similar samples of PCM under different loading conditions. An example of using the developed technique for revealing the areas of the most intense damage accumulation in a MS-21 fuselage panel at a stepwise increase in the compressive load is presented. In addition to the possibility of identification of the area of intensive accumulation of damage and failure of the structure of the composite material, SPhC of the AE diagnostics provides also the possibility of tracing the damage kinetics at different scale-structural levels, controlling the level of the residual strength of the panel upon the stepwise compression.

Acoustic Emission Diagnostics of Freight Car Bogie Cast Pieces

Diagnostics of freight car bogie cast parts (side frames and bolster beams) using acoustic emission (AE) method enables to locate defects (fatigue cracks, cavities, nonslithing, pores, etc.) in real time, define their danger level, on the basis of which conclusion about their further operation is made. The developed method of AE-control provides automatic calculation of AE signal source parameters. This allows defects to be detected at an early development stage. The developed loading stands and AE diagnostic systems have been introduced in 39 railway depots of Russia.

Diagnostic of Crack in Concrete with Acoustic Emission in Case of Concrete Slab with Subsoil

The development of new structural systems, materials, and technologies enables the design and the implementation of progressive buildings meeting the demanding criteria of users and architects. However, using the new design approaches implies a need for knowledge about the behavior of the materials used, including their manner of disruption. This issue is also related to existing structures, where damage and accidents also occur. One of the solutions is the advanced acoustic emission diagnostics. This paper deals with the specific role of the interaction between the concrete slab and the subsoil. The paper aims to present the identification of crack formation, where acoustic emission measurements are compared to other measurement methods. The presented spatial graphs are used to evaluate the measurement and to compare the acoustic emission.

Acoustic emission diagnostics of corrosion monitoring in prestressed concrete using hidden Markov and semi-Markov models

This article presents a framework based on hidden Markov modeling for monitoring corrosion damage in prestressed concrete structures through acoustic emission measurements. Both hidden Markov models and hidden semi-Markov models are investigated to determine the merits of each under typical challenges encountered in real-world monitoring scenarios: an unknown initial corrosion condition and an uncertain corrosion rate. To enable hidden semi-Markov models to perform effectively, they are constructed using extended state hidden Markov models in a manner which is able to easily accommodate these scenarios. Furthermore, a framework is proposed for adopting frequency- and topological-based features of acoustic emission data as indicators of corrosion for the models. Accelerated corrosion tests were carried out on two prestressed concrete specimens; one specimen was used for training the models and the other one for testing. The testing specimen was additionally subjected to accelerated weathering to approximate certain conditions found in the field. A combination of established visual inspection, mass loss measurement, and acoustic emission activity analysis was first used to obtain a benchmark corrosion assessment of the specimens. Frequency- and topological-based acoustic emission features were then used as the basis of the hidden Markov modeling framework. The results demonstrate that both hidden Markov models and hidden semi-Markov models are highly reliable under an unknown initial condition. However, in these tests, the hidden semi-Markov model showed slightly greater reliability against error in the assumed corrosion rate. To improve accuracy in this scenario, a procedure for combining predictions from various candidate corrosion rates was also proposed. The diagnostics obtained from this work may provide useful information for established prognostic models of corrosion mechanisms in prestressed concrete.

Diagnostics of aluminum alloys with friction stir welded joints based on multivariate analysis of acoustic emission signals

The acoustic emission method was applied to study aluminum-magnesium alloys produced by friction stir welding. Alloy specimens were tested under static tension with simultaneous recording of acoustic emission, applied load, and elongation. The recorded acoustic emission signals were processed using projection methods of multivariate data analysis; the informative features used were the coefficients of wavelet discrete decomposition which characterize the low-frequency form of the signal. It is shown that the proposed approach allows the partition of signals formed on different stages of plastic deformation and fracture. Strong differences in acoustic emission signals were revealed and described to be due to the formation of highly defect structure in the weld zones in different welding modes. The obtained results can be useful for acoustic emission diagnostics of welded joints in structures of metal alloys exposed to external loads.

Multilevel model of time dependences of acoustic emission parameters as the basis for nanodiagnostics of the state of technical objects

The method of acoustic emission (AE) and the information-kinetic approach to AE diagnostics are identified as the most promising from the point of view of observing the process of growth of damage and optimization of production technologies. Based on a multi-level model of the time dependence of AE parameters, estimation of elastic homogeneous fracture intensity parameters of representative structural elements of a product and universal strength nanoconstants, the approach combines the traditional experimental way of resource estimation and kinetic representations of fracture. This allows to separate the effect of macro- and nano-factors on the AE of the material, variously related to the strength and acoustic emission activity of the material. A multilevel model and an informational-kinetic approach to acoustic emission diagnostics are described, combining nano-, micro- and macro-factors affecting acoustic emission activity, reliability of technical objects and methods for assessing their resource. On the example of a welded pressure vessel, the implementation of the method of its nano-diagnosis is considered. The possibility of effective resource estimation of various technical objects based on the information-kinetic approach to their acoustic emission diagnostics is shown. As a methodological basis, a multilevel model of the time dependences of the AE parameters is taken, which describes their behavior under conditions of strength and metrological heterogeneity.

Identification of automatic systems for acoustic emission diagnostics

The difficulties of automation control, which are connected with variability of input parameters and complexity of mathematical description of internal dynamic processes in the controlled object, are noted. The features of categorical concepts of automation of control of acoustic-emission diagnostics control are formulated and marked: control object, control system, control functions. The mathematical formalism of modeling the energy spectrum of acoustic emission signals is presented. A discrete and continuous approach to describing the oscillatory properties of the internal structure of a material under load is used. The structural model of the basic stages of management is offered, which includes multidimensional input of diagnostics information, ensuring the controllability of products, informatization of diagnostic parameters, direct measurements, identification of the current state of the object. Functional purposes of the acoustic emission diagnostics system have been determined. On the basis of generalization of information on experimental studies of the effect of stresses under uniaxial loading and four-point bending on the parameters of acoustic emission signals, data on the influence of deformation processes on the information parameters of AE steels and composite materials were investigated and systematized. Areas of their application and rational use are established. It is noted that most of the experimental works in domestic and foreign practice are devoted to the influence on the material of one type of deformation measurements of the structure of materials, while during the operation of structures the material is subjected to a complex effect of complex loads. An algorithm for identification of systems for automatic control of acoustic emission diagnostics has been developed, which differs taking into account the variety of factors affecting the initial variables, the complexity of their interactions and estimates using expert evaluation, system analysis and simulation modeling.

Damage Assessment of Specimens Made of Steel 09G2S Exposed to Low-Cycle Fatigue with the Help of Acoustic Emission Monitoring Method

Cyclic impact of external parameters on the structure, such as the daily change of temperature, change of operating parameters (pressure, temperature, volumes of loaded raw material) may lead to the brittle fracture of the equipment material with fast propagation of the main crack. In view of this, there is a need to use the nondestructive test methods which allow determining the critical level of damage accumulation. The article considers the pattern of change in properties as a result of low-cyclic loading by studying the parameters of acoustic signal. Changes in acoustic emission (AE) parameters were measured in the process of uniaxial tension of specimens with different degrees of accumulated damage. Upon processing of these AE parameters, stages of damage accumulation in cyclic fatigue were determined. Thus, is was determined that acoustic-emission diagnostics is sensitive to the said changes and may be used for assessment of the damage degree of 09G2S steel specimens.

Determination of nanocharacteristics of strength based on acoustic emission diagnostics

During the period of production and exploiting of materials, complex physicochemical processes of interaction of their components with each other and with the environment take place. Identifying the mechanisms of this interaction will help to understand its various aspects and to optimize the technological processes of manufacturing materials with desired properties. The solution of this problem can be based on the interpretation of the results of acoustic emission (AE) tests from the standpoint of a multilevel model of the time dependences of the parameters of AE heterogeneous materials.

Information and kinetic approach to the acoustic emission diagnostics of technical facilities

The analysis of trends in the development of resource assessment methods is given, a multi-level information-kinetic approach to acoustic emission diagnostics is described and its methodological relationship with the traditional experimental method of resource assessment is shown. The informative multi-model diagnostic parameters associated with various scale level strength characteristics of structural materials and resource technical objects are given. The examples of resource assessment of welded joints and rolling bearings are considered.

Acoustic-emission diagnosis of technical objects based on the information and kinetic approach

An analysis of trends in the development of resource assessment methods is given, a multi-level information-kinetic approach to acoustic emission diagnostics is described, its methodological relationship with the traditional experimental method of resource assessment is shown. The informative multi-model diagnostic parameters associated with various scale level strength characteristics of structural materials and resource technical objects are given. Examples of resource assessment of welded joints and rolling bearings are considered.

Analysis of the results of acoustic emission diagnostics of a structure during helicopter fatigue tests

The study is devoted to a perspective diagnostic method, which makes it possible to deal with diagnostic tasks – the acoustic non-destructive inspection method based on acoustic emission (AE) signal parameter analysis. The practical use of this method is related to the interpretation of diagnostic measurement data. The parameters of acoustic emission (AE) signals were measured during bench tests of the tail boom structure and fin, as well as the joint areas of the fin, tail boom, and fuselage of the helicopter (joint area No.1 and No.19, frames of the tail boom and fuselage respectively).The analysis of fatigue damage kinetics was carried out in several stages for groups of bolts and for characteristic structure loading intervals. Bolt fracture was predicted at least 26 to 44 flight hours before the actual collapse. Using the AE parameters, the micro crack origin intervals identified when the bolt bearing capacity after the occurrence of the damage reached 96%.

Acoustic-Emission Diagnostics of Corrosion Defects in Materials (a Survey). Part. 2. Corrosion Cracking of Metals. Applied Aspects of Application of the Method

We analyze the results of investigations of the acoustic-emission diagnostics of corrosion defects in materials and establish the relationship between the total count, energy, amplitude of acoustic radiation and the corrosion cracking of steels and metal alloys. Examples of application of the acoustic-emission method to detection of corrosion defects of a series of industrial objects are presented.

Acoustic-Emission Diagnostics of Corrosion Defects in Materials (a Survey). Part. 1. Detection of Electrochemical Corrosion and Corrosion Fatigue

We analyze the main aspects of acoustic-emission diagnostics of the corrosion processes in structural materials and present the results of numerical investigations of the electrochemical corrosion by the method of acoustic emission. We also discuss the applicability of the method to the investigation of the corrosion fatigue of materials.

A local method for loading a tested object during acoustic-emission diagnostics

A new acoustic-emission diagnostics method in which there is no need to load an entire structure has been studied. This method of monitoring (as a conventional acoustic-emission method) is based on making a deformation of the tested surface; however in this case, the load is applied to a preliminarily chosen site of the tested object in the most dangerous area.