The paper deals with mathematical modelling of dynamic response of the electric locomotive wheelset drive caused by short-circuit traction motor torque. The individual wheelset drive is composed of five subsystems - rotor of the traction motor with driving gear, driven gear, stator of the traction motor with gear housing, hollow graduated shaft with clutches and wheelset. The couplings between subsystems are linearized in dependence on longitudinal creepage and locomotive forward velocity before sudden short-circuit in the asynchronous traction motor. In comparison with previous models of the wheelset drives, the rotor of the electromotor is characterized by flexible shaft suppported on flexible rolling-element bearings. The sheet metal packjet of cylindrical shape is connected by parallel cooper bars with two short circuit rings. In conseqquence of strong excitation an interruption of gear mesh can be observed. This nonlinear effect and dynamic load of individual wheelset drive with large number of DOF is investigated using the condensed mathematical model created by model synthesis method. and Obsahuje seznam literatury
The paper deals with the mathematical modelling and the computer simulation of forced vibrations of the reactor core barrel excited by pressure pulsations generated by main circulation pumps. The modelling is focused on a possible core barrel flange slip along a pressure vessel flange. The slip in this internal reactor linkage is analysed providing the solid friction and the backlash between slip tongues of the pressure vessel flange and grooves in the core barrel flange. The impact motion can produce an excessive abrasive wear of the tongues and grooves. A guarantee of the fail-safe operation is achieved by calculated pre- stressing of toroidal tubes inserted between the upper flange of the core barrel and the pressure vessel cover. and Obsahuje seznam literatury
This paper is devoted to a new approach to the dynamic response of Soil-Structure System (SSS), the far field of which is meshed by decay or mapped elastodynamic infinite elements, based on scaling modified Bessel shape functions to be calculated. These elements are appropriate for Soil-Structure Interaction problems, solved in time or frequency domain and can be treated as a new form of the recently proposed elastodynamic infinite elements with united shape functions (EIEUSF) infinite elements. Here the time domain form of the equations of motion is demonstrated and used in the numerical example. In the paper only the formulation of 2D horizontal type infinite elements (HIE) is used, but by similar techniques 2D vertical (VIE) and 2D corner (CIE) infinite elements can also be added. Continuity along the artificial boundary (the line between finite and infinite elements) is discussed as well and the application of the proposed elastodynamical infinite elements in the Finite element method is explained in brief. A numerical example shows the computational efficiency and accuracy of the proposed infinite elements, baeed on scaling Bessel shape functions. and Obsahuje seznam literatury
The paper deals with the modelling of forced vibrations of reactor components excited by pressure pulsations generated by main circulation pumps. For the vibration analysis a new generalised model of the reactor with spatial localization of the nuclear fuel assemblies and protection tubes, continuously mass distribution of beam type components and more accurate model of the linear stepper drives for actuation of control cassettes was applied. Slightly different pump revolutions are sources of the heating which causes an amplification of vibration and possibility of the contact loss in internal linkages of the core barrel. and Obsahuje seznam literatury
The paper deals with the dynamic transmission error (ТЕ) measurements of a simple gear set at gearbox operational conditions that means under load and during rotation.
The analysis method is focused on the processing of impulse signals generated by incremental rotary encoders attached to the gears in mesh. The analysis technique benefits from demodulation of a phase-modulated signal. The theory is illustrated by experiments with a car gearbox and measurement errors are discussed. and Obsahuje seznam literatury
The paper deals with derivation of the dynamical model of the turbochargers with rotor supported on the two floating ring bearings. The model respects the bearing forces acting upon the journals and floating bearing rings by means of inner and outer oil-films. The gyroscopic effects, external and internal damping of the flexible rotor shaft and the rigid turbine and compressor wheels are respected. The modal analysis and the Campbell diagram is used in the turbocharger linearized model to find the critical speeds. and Obsahuje seznam literatury
Position actuator with small DC motor, torque 1 Nm, range 210 grad, using dynamic superposition of vibrations for decreasing of friction effect and clearances in gear box. and Polohový servomechanismus s malým stejnosměrným motorkem, točivý moment 1 Nm, rozsah 210 grad, využívající dynamické superposice vibrací pro potlačení vlivu tření a vůlí v převodovce.
H. Weyl, jeden z prvních, kdo se zabýval rolí symetrie v kvantové mechanice, podal následující definici symetrie [1]: „Věc je symetrická, pokud se s ní dá něco udělat tak, že i po dokončení toho udělání vypadá stejně jako před tím.“ Tato věta se dá přeložit do poněkud exaktnějšího jazyka pomocí teorie grup - matematické disciplíny, která byla ještě na začátku 20. století považována za nepraktickou, spíše poněkud exotickou doménu ryze teoretického bádání. Především zásluhou fyziků se v následujících desetiletích z teorie grup stal jeden z nejdůležitějších nástrojů k uchopení reality. Fyzikální svět je plný symetrií!, Pavel Cejnar., and Obsahuje seznam literatury
In celestial mechanics interactions of radiation and small bodies in Solar system can be classified as scattering, absorption, radiation drag and thermal emission. The final one, in particular, induces important secular changes of orbits and rotation states of asteroids and meteoroids, as supported by a number of astronomical observations., Miroslav Brož., and Obsahuje seznam literatury