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Layout optimisation method for active structural health monitoring
Červenka, Miroslav ; Koštial, Rostislav
This paper describes optimisation method for designing sensoric layout for Active Structural Health Monitoring (A-SHM) by Ultrasonic Guided Waves (UGW) on metal and non-metal (composite) materials. The SHM sensors need to be placed optimally in order to detect structural damage with high probability before the damage turns critical. Configuration of used optimisation algorithm for such task is not straightforward. Differential Evolution (DE) has two configuration parameters – the mutation factor F and the crossover rate CR – whose settings largely influence the solution quality the optimisation process can yield. For that matter we describe an elaborated a method to guide this selection towards good results using visual heat maps with the intent to select best DE’s variant and particular configuration to receive the most optimal SHM sensorics layout.
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Simulation of ultrasonic wave in the composite aircraft structures
Cimrhanzl, Jan ; Koštial, Rostislav (referee) ; Šplíchal, Jan (advisor)
V této diplomové práci jsou popsané SHM metody používané v letectví a dále jsou udělány MKP simulace šíření ultrazvoukových vln v celokompozitním tenkostěnném materiálu používaném u leteckých konstrukcí. Pro simulaci byla zvolena SHM metoda nazývaná pitch-catch. Simulace byla provedena na dvou různých kompozitových materiálech a každý z nich byl testován třemí různými konfiguracemi s trhlinou a jednou konfigurací bez trhliny. Jako prepocessor byl použit MSC.Patran a jako post processory byli použity MSC.Nastran a MSC.Dytran, jejichž výsledky byli na závěr porovnány. Simulace prokázali, že rychlost šíření a amplituda vln šířících se v simulovaném panelu je trhlinami ovlivněna. Při konfiguracích s trhlinami rychlost šíření i amplituda vln byli menší, než v případě bez trhliny. Jako vhodnější post processor při MKP simulacích se ukázal MSC.Nastran, jehož výsledky byli přesnější a zárověň bylo i snažší správně odečítat hodnoty dat z grafů pro podrobnější pozorování šíření vln.
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Changes of dynamic properties of a timber frame due to simulated seismic load: a case study
Bayer, Jan ; Pospíšil, Stanislav ; Urushadze, Shota ; Kasal, B.
The data from a laboratory seismic resistance test of a three-story timber frame stiffened with steel joints were used to compare sweep and random excitation techniques on the platform of experimental modal analysis. The changes of mechanical properties due to increasing seismic load of the timber structure are demonstrated on corresponding changes of vibration modes and on changes of averaged frequency response functions. The comparison of averaged frequency response functions turned out to be at least as efficient tool for damage indication as the comparison of modal properties in this case. The experiences obtained in this case study are aimed at increasing the efficiency of dynamic tests and methods of Structural Health Monitoring.
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Location of acoustic emission sources in geometrically sparce structures
Chlada, Milan ; Převorovský, Zdeněk
In recent years, the importance of modern philosophy of Structural Health Monitoring (SHM) is increasing. SHM systems are gradually integrated into, e.g., aircraft or bridge structures and also become newly a part of certain modern buildings, where the break down would cause significant material or human losses. One of the effective prewarning methods is the detection of acoustic emission (AE). The paper yields the discussion about the utilization of artificial neural networks in comparison with the segment location based on the chronology of signal arrivals to selected groups of AE sensors for “geometrically sparse” structures. Both methods and their results are demonstrated in case of experiment with gradual loading of a part of a roof construction until the final breakdown.
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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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