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Monitoring of fatigue crack growth in riveted aircraft structures by acoustic emission
Chlada, Milan ; Převorovský, Zdeněk
In principle, the acoustic emission (AE) represents one of NDT and structure health monitoring (SHM) methods for the detection and identification of growing material defects. Different types of signals detected by the AE method are supposed to correspond to different types of defects or operational noises. Monitoring of structures by acoustic emission needs new robust and fast methods for emission source location and classification. Recently proposed AE source location method using so called signal arrival time profiles and artificial neural networks (ANN) was applied for monitoring of growing defects during long term fatigue testing of riveted aircraft wing flange. The potentialities of the method regarding the on-line monitoring of dangerous crack growth in selected critical parts of aircraft structures are discussed.
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Corrosion damage evaluation by acoustic emission monitoring and nonlinear elastic wave spectroscopy testing
Kober, Jan ; Převorovský, Zdeněk
The development of local corrosion damage can lead to serious malfunctions and even to irreparable damage to whole structural parts. A reliable operation of a structure has to be secured, if a failure can cause health hazards and significant economic losses, i.e. in power, chemical and aerospace industry. This work is dealing with the application of acoustic emission method and a NEWS method for detection and monitoring of corrosion damage growth. The acoustic emission was recorded in situ during corrosion process. The measurement by NWMS method was performed in between corrosion tests. It was observed that the current dynamics of a corrosion process was determined by AE and that the amount of corrosion damage was corresponding to the nonlinear parameters obtained by NWMS. Both methods have already been used for fatigue damage evaluation therefore they form a universal system for non-destructive structural inspection.
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Structural Health Monitoring in aerospace and civil engineering supported with two ultrasonic NDT methods - AE and NEWS
Převorovský, Zdeněk ; Krofta, Josef ; Farová, Zuzana ; Chlada, Milan
Structural Health Monitoring (SHM) becomes today an important technology improving reliability and safety of aeronautical and civil structures. Combining of two ultrasonic NDT methods - Acoustic Emission (AE) with Nonlinear Elastic Wave Spectroscopy (NEWS) - in SHM systems brings many advantages. AE enables real-time detection and localization of initiation and progression under operational stimulations, and NEWS methods provide retrieval of structural faults and complete information on AE sources. Examples of a complex SHM system design for critical parts of both aircraft and building roofs are discussed in this paper. The NEWS pseudo-tomography procedure, based on Time Reversal Mirrors (TRM) with Excitation Symmetry Analysis Method (ESAM), enabled zone-location of initiating defects, not detectable by other classical NDT procedures.Our results reflect good robustness of both techniques, and support their helpfulness in SHM of aircraft and building structures.
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Nondestructive evaluation of corrosion damage of Al-alloys by in-situ AE monitoring and nonlinear elastic wave spectroscopy testing
Kober, Jan ; Převorovský, Zdeněk
This work investigates the possibilities of monitoring ongoing corrosion process by acoustic emission (AE) and of determining overall corrosion damage by the nonlinear wave modulation spectroscopy method (NWMS). Specimens made of Al-alloy L-beams simulating stringer reinforcements of airplane structure were studied. The samples were repeatedly immersed in sea salt solution. The acoustic emission activity was recorded in situ during corrosion process. Nonlinear parameters of the samples were measured in between corrosion tests by NWMS method. The current dynamics of a corrosion process was determined by AE, the amount of corrosion damage was corresponding to the nonlinear parameters obtained by NWMS.
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Detection of AE Sources During Long-term Fatigue Tests of Riveted Aircraft Wing Flange
Chlada, Milan ; Převorovský, Zdeněk
Fracture is the primary threat to the integrity, safety, and performance of nearly all highly stressed mechanical structures, e.g., aircrafts, building units or pressure vessels. Contemporary exacting demands on reliability and safety of material structures are not realizable without effective means of NDT and continuous state monitoring. AE monitoring of structures needs new robust and fast methods for emission source location and classification. Recently proposed AE source location method using so-called signal arrival time profiles and artificial neural networks (ANN) was applied for monitoring of growing defects during long-term fatigue testing of riveted aircraft wing flange. The potentialities of the method regarding the on-line monitoring of dangerous crack growth in selected critical parts of aircraft structures are discussed.
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Damage detection in Mg-alloys by nonlinear ultrasonic spectroscopy
Kober, Jan ; Převorovský, Zdeněk ; Trojanová, Z.
The localization of acoustic emission (AE) sources by procedures using artificial neural networks (ANN) represents today highly effective alternative approach to classical triangulation algorithms. The main problems are in the collecting sufficiently extensive training and testing data sets together with the non portability of particular trained network to any other object. Recently, the ANN based AE source location method has been improved by using so-called signal arrival time profiles to overcome both limitations. This way of signal arrival time characterization enables ANN training on numerical models and allows the application of learned ANN on real structures of various scales and materials. In this paper, the method is upgraded and localization results are illustrated on experimental data obtained during pen-tests on a model roof I-beam and an aircraft structure part. General application possibilities of the method variations for different sensor configurations are also discussed.
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