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Simulation of ultrasonic wave in the composite aircraft structures
Cimrhanzl, Jan ; Koštial, Rostislav (oponent) ; Šplíchal, Jan (vedoucí práce)
In the present thesis, SHM methods used in aviation are described, and series of FEM simulations of UGW propagation in the thin-walled composite aircraft structure have been performed. For the simulation, pitch-catch SHM method is used. Experimental simulations are performed on two panels from a different material, and each of those two materials is tested with three configurations of crack and one configuration without a crack. For the simulation preprocessor MSC.Patran and two post processors MSC.Nastran and MSC.Dytran are used for comparison of results. Simulations showed that cracks in the panel are affecting velocity and amplitude of waves. In configurations with crack, velocity and amplitude are lower than in the case without a crack. In FEM simulations, post processor MSC.Nastran showed more accurate and easier data for reading for further study of UGW propagation.
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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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Lokalizace zdrojů akustické emise na geometricky řídkých konstrukcích
Chlada, Milan ; Převorovský, Zdeněk
V posledních letech nabývá na významu moderní filozofie tzv. sledování stavu konstrukcí (SHM - Structural Health Monitoring). SHM systémy jsou dnes postupně integrovány např. do leteckých či mostních konstrukcí a stávají se nově také součástí některých moderních budov, u nichž by zhroucení způsobilo velké materiální nebo lidské ztráty. Jednou z efektivních metod včasné výstrahy je sledování akustické emise (AE). V příspěvku je pro případ „geometricky řídkých“ konstrukcí diskutováno využití umělých neuronových ve srovnání se segmentovou lokalizací na základě chronologie příchodu elastické vlny k vybraným skupinám snímačům AE. Obě metody a jejich výsledky jsou demonstrovány na případě experimentu s postupným zatěžováním části střešní konstrukce až do finálního kolapsu.
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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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