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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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Consistency of mathematical and experimental model of the autoparametric system
Fischer, Cyril ; Náprstek, Jiří
This paper presents a long-overdue comparison of data obtained from experimental investigation of a spherical vibration absorber with the results of two mathematical models of the motion of a heavy sphere in a spherical surface. It shows that the danger posed by the potentially unstable self-parametric nature of the mathematical system is not too great in the case of realistic configurations, and that the values of the parameters describing the realistic structures remain within intervals corresponding to the stable behaviour of the absorber.
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Adaptation of methods for cyclo-stationary processes for noisy structural health data
Fischer, Cyril ; Bayer, Jan ; Náprstek, Jiří ; Urushadze, Shota
In structural health analysis, various techniques, including indirect measurement via monitoring vehicles, often yield data with significant randomness and insufficient frequency separation. Conversely, the desired attributes under scrutiny are periodic in nature. Thus, methodologies designed to identify cyclo-stationary properties within noisy data can be adapted for such scenarios, assuming an adequate length of the recorded data.
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Dynamics of a cantilever beam with piezoelectric sensor: Experimental study
Kolman, Radek ; Kylar, Jaromír ; Kotek, Vojtěch ; Cimrman, Robert ; Musil, Ladislav
Online and real-time sensing and monitoring of the health state of complex structures, such as air-craft and critical parts of power stations, is an essential part of the research in dynamics. Several types of sensors are used for sensing dynamic responses and monitoring response changes during the operation of critical parts of complex systems. The piezoelectric (PZ) materials belong to one group of electroactive materials, which transform mechanical deformation into an electrical response. For example, PZ ceramics or PVDF foils are employed for online sensing of the time history of mechanical deformation. Experimentally obtained response of a cantilever beam structure with a glued PZ sensor is the case of interest in this contribution. During the transient problem of the beam loaded by suddenly interrupted load due to the weight of a mass at the end of the beam, the time history of normal velocity at a point on the beam surface has been measured by a laser vibrometer and parallely, the output voltage on the PZ sensor has been measured by an electric device. The experimental data in the case of the first eigen-frequency is in good agreement with the value given by the formulae from the theoretical modeling of free vibration of a linear beam.
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V5: Zpráva o další programové spolupráci s R6 Panel
Joch, Jaroslav ; Štefan, Jan
Výzkumná zpráva je závazným výstupem V5 projektu TK01030108: Inovativní posuzování bezpečnosti jaderných elektráren na základě nových technologií SHM a návazných procedur - NEMENUS (NEw MEthods for NUclear Safety). Ve zprávě je prezentován program další spolupráce s R6 Panel a s dalšími zahraničními partnery, který vznikl na základě spolupráce v rámci projektu.
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V7: Souhrnná zpráva NEMENUS pro SÚJB
Štefan, Jan ; Joch, Jaroslav ; Převorovský, Zdeněk ; Gabriel, Dušan ; Krofta, Josef ; Chlada, Milan ; Kober, Jan ; Masák, Jan ; Kunz, J. ; Ashhab, B.
Toto je finální zpráva projektu TK01030108: Inovativní posuzování bezpečnosti jaderných elektráren na základě nových technologií SHM a návazných procedur - NEMENUS (NEw MEthods for NUclear Safety). Ve zprávě jsou prezentovány nejvýznamnější výsledky a výstupy projektu NEMENUS a je zde podáno souhrnné vyhodnocení přínosů ve vazbě na projektovou dokumentaci a z hlediska dlouhodobých technologických perspektiv.
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V6: Zpráva popisující funkční vzorek NEMENUS
Štefan, Jan ; Joch, Jaroslav ; Převorovský, Zdeněk ; Gabriel, Dušan ; Krofta, Josef ; Chlada, Milan ; Kober, Jan ; Masák, Jan ; Materna, A. ; Kovářík, O. ; Čech, J.
Výzkumná zpráva je součástí závazného výstupu V6: FUNKČNÍ VZOREK projektu TAČR TK01030108: Inovativní posuzování bezpečnosti jaderných elektráren na základě nových technologií SHM a návazných procedur - NEMENUS (NEw MEthods for NUclear Safety). Zpráva podává úplný technický popis sestrojeného reprezentativního funkčního vzorku, tedy „reprezentativního SHM modelu“, a popis procesu čtyřletého experimentálního vývoje RFV.
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Theoretical analysis of selected trajectories inscribed by a ball freely rolling in a spherical cavity
Náprstek, Jiří ; Fischer, Cyril
Indirect monitoring of structures is significantly complicated when an artificial vibration absorber has to be taken into account. Knowledge of the absorber’s behaviour is necessary in order to correctly distinguish the response types obtained during an drive-by measurement. In this work, the mathematical model of the ball-type vibration absorber is used, which is based on the Lagrangian formalism. Three first integrals are identified when no external excitation nor damping is assumed. The paper illustrates the power of this approach, which enables a detailed analysis of free movement of the ball in the spherical cavity. Properties of several particular trajectories depending on initial conditions are presented.
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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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