Volume 7, number 2 (2013)
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Item Prediction of the nuclear fuel rod abrasion(University of West Bohemia, 2013) Zeman, Vladimír; Hlaváč, ZdeněkThe paper is focused on calculation of the friction forces work in the contact of nuclear fuel rods with fuel assembly spacer grid cells. This friction work is deciding factor for the prediction of the fuel rod coating abrasion. The fuel rod abrasion is caused by fuel assembly vibrations excited by pressure pulsations of the cooling liquid generated by main circulation pumps. A prediction of fuel rod coating abrasion makes use of experimentally investigated dependence of the abrasion on the friction force work in laboratory conditions. The presented original analytical-numerical method is applied for nuclear fuel rod inside of the Russian TVSA-T fuel assembly in the WWER 1000/320 type reactor core in NPP Temelin.
Item Determination of the transient vibrations of a rigid rotor attenuated by a semiactive magnetorheological damping device by means of computational modelling(University of West Bohemia, 2013) Zapoměl, Jaroslav; Ferfecki, Petr; Kozánek, JanUnbalance is the principal source of increase of time varying forces transmitted between the rotor and its stationary part. Their magnitudes can be considerably reduced if th e rotor is flexibly suspended and if the damping devices are added to the support elements. Their damping effect mu st be high for low rotor velocities and small for veloc- ities approximately higher than the critical one to minimize the transmitted forces and the vibrations amplitude. This implies to achieve maximum efficiency of the damping elements, their damping effect has to be adaptable to the current operating conditions. Such technological solutio n is offered by application of a squeeze film magne- torheological damper. Its hybrid variant consisting of two damping units (one controllable) in a serial arrangement is investigated in this paper. The damping takes place in two concentric lubricating films formed by normal and magnetorheological oils. The damper is equipped with an electric coil generating magnetic flux passing through the layer of the magnetorheological fluid. As resistanc e against its flow depends on magnetic induction, changing magnitude of the applied current enables to control the damping force. In the computational model, the rotor is considered to be absolutely rigid, unbalanced and the damping elements are represented by force couplings. The goal of the analysis is to study influence of the investigated magnetorheological damper on behaviour of a rigid rotor during different transient reg imes. A special attention is focused on passing the rotor through the critical speed and on planning the dependence of the applied current on speed of the rotor rotation to achieve the optimum compromise between minimizing the transmitted forces and maximum attenuation of the rotor vibrations.Item Torsional vibration analysis of shafts based on Adomian decomposition method(University of West Bohemia, 2013) Tabassian, RassoulIn this paper free torsional vibration of shafts is studi ed using a new approach of solving differential equations called Adomian decomposition method (ADM). Applying this method to free torsional vibration of shafts means a systematic and straightforward procedure for calculating both low and high frequency modes. In this paper different boundary conditions are app lied to both end of the shaft and firs t five natural frequencies and mode shapes are calculated for four different cases. Obtained results are compared with results presented in literature. These results demonstrate that ADM is a suitable approach for analysis of free torsional vibration of shafts which provides precise results with high order of accuracy.Item Thermal analysis of isotropic plates using hyperbolic shear deformation theory(University of West Bohemia, 2013) Shinde, B. M.; Sayyad, Atteshamuddin Shamshuddin; Kawade, A. B.Item Active structural health monitoring of composite plates and sandwiches(University of West Bohemia, 2013) Sadílek, Petr; Zemčík, Robert; Bartošek, Jan; Mandys, TomášThe aim of presented work is to design, assemble and test a functional system, that is able to reveal damage from impact loading. This is done by monitoring of change of spectral characteristics on a damaged structure that is caused by change of mechanical properties of mater ial or by change of structure’s geometry. Excitation and monitoring of structures was done using piezoelectric patches. Unidirectional composite plate was tested for eigenfrequencies using chirp signal. The eigenfreque ncies were compared to results from experiments with an impact hammer and consequently with results from finite element method. Same method of finding eigenfrequen- cies was used on a different unidirectional composite sp ecimen. Series of impacts wer e performed. Spectrum of eigenfrequencies was measured on undamaged plate and t hen after each impact. Measur ements of the plate with different level of damage were compared. Following e xperiments were performed on sandwich materials where more different failures may happen. Set of sandwich beams (cut out from one plate made of two outer composite layers and a foam core) was investigated and subjected to several impacts. Several samples were impacted in the same manner to get comparable results. The impact s were performed with growing impact energy.Item Finite element based investigation of buckling and vibration behaviour of thin walled box beams(University of West Bohemia, 2013) Ramkumar, Kandasamy; Kang, H.Thin-walled box type conventional and composite structures are having wide applications for building the structural system which are used in advanced ships, aerospace, civil, construction equipment and etc. Often these structures are subjected to vibration and buckling due to the environmental effect such as mechanical, thermal, electrical, magnetic, and acoustic or a combination of these. Also dampingmaterial and structural stiffness plays an important role for the improvement of vibration, noise control, fatigue and bulking resistance of these structures. So it is important to know the dynamic and buckling characteristics of these structures. Pre-stress in a structure affects the stiffness, which modifies the dynamic and stability characteristics of the structure. So it is also important to know the influence of pre-stress on the vibration and buckling character. In this paper, buckling and dynamic characteristics of the thin-walled box type structures are analyzed using finite element software ANSYS.Item Differential transform method to study free transverse vibration of monoclinic rectangular plates resting on Winkler foundation(University of West Bohemia, 2013) Kumar, YajuvindraThis paper analyses free transverse vibration of a monoclinic rectangular plate of uniform thickness resting onWinkler foundation using differential transform method (DTM). Two parallel edges of the plate are taken according to Levy approach i.e., simply supported and other two edges may be either clamped-clamped or clamped-simply supported. This semi-numerical-analytical technique converts the governing differential equation and boundary conditions into a set of algebraic equations. Characteristic equations have been obtained for above two combinations of boundary conditions in the form of infinite series and solved numerically by truncating these equations to finite number of terms. Robustness and convergence of the method is confirmed through numerical results. Two dimensional and three dimensional mode shapes have been plotted for both the cases.Item Identification of parameters of cohesive elements for modeling of adhesively bonded joints of epoxy composites(University of West Bohemia, 2013) Kottner, Radek; Hynek, Richard; Kroupa, TomášAdhesively bonded joints can be numerically simulated using the cohesive crack model. The critical strain energy release rate and the critical opening displacement are the parameters which must be known when cohesive elements in MSC.Marc software are used. In this work, the parameters of two industrial adhesives Hunstman Araldite 2021 and Gurit Spabond 345 for bonding of epoxy composites are identified. Double Cantilever Beam (DCB) and End Notched Flexure (ENF) test data were used for the identification. The critical opening displacements were identified using an optimization algorithm where the tests and their numerical simulations were compared.Item Investigation of the influence of air gap thickness and eccentricity on the noise of the rotating electrical machine(University of West Bohemia, 2013) Donát, MartinThis article deals with the numerical modelling of the dynamic response of the rotating electrical machine on the application of the magnetic forces. The special attention is paid to the modelling of the magnetic forces that act on the stator winding of the machine and the computational model of the modal properties of the stator winding. The created computational model was used to investigation of the influence of the nominal air gap thickness and the air gap eccentricity on the sound power radiated by outer surface of the stator of the machine. The obtained results show that the nominal air gap thickness has slightly greater influence on the sound power of the machine than eccentricity of the air gap.
