DSpace Kolekce:http://hdl.handle.net/11025/116672024-03-28T21:40:18Z2024-03-28T21:40:18ZDry friction damping couple at high frequenciesPůst, LadislavPešek, LuděkKošina, JanRadolfová, Alenahttp://hdl.handle.net/11025/116772021-09-22T08:43:33Z2014-01-01T00:00:00ZNázev: Dry friction damping couple at high frequencies
Autoři: Půst, Ladislav; Pešek, Luděk; Košina, Jan; Radolfová, Alena
Abstrakt: The contribution deals with the application of dry friction couples for noise and vibration damping at high fre-
quency of several kHz what brings new problems connected with the small amplitudes of relative slipping motion
of contact surfaces. The most important information from the experimental results is knowledge that the value of
evaluated friction coefficient can have different physical sense according to the magnitude of excitation force and
to the frequency of applied vibrations. If amplitudes of motion are very small, then the external harmonic force
produces only elastic micro-deformations of contacting bodies, where no slip occurs and then the traction contact
force is proportional only to elastic deformation of the sample.2014-01-01T00:00:00ZPůst, LadislavPešek, LuděkKošina, JanRadolfová, AlenaApplication of the Monte Carlo method for investigation of dynamical parameters of rotors supported by magnetorheological squeeze film damping devicesZapoměl, JaroslavFerfecki, PetrKozánek, Janhttp://hdl.handle.net/11025/116762021-09-22T08:43:34Z2014-01-01T00:00:00ZNázev: Application of the Monte Carlo method for investigation of dynamical parameters of rotors supported by magnetorheological squeeze film damping devices
Autoři: Zapoměl, Jaroslav; Ferfecki, Petr; Kozánek, Jan
Abstrakt: A flexible suspension with damping devices is an efficient technological tool for reducing forces transmitted be-
tween the rotor and its frame. To achieve optimum performance of the damping elements, their damping effect
must be adaptable to the current operating conditions. In practical rotordynamic applications this is offered by
magnetorheological squeeze film dampers. Some of parameters, which determine behaviour of rotors, may have
uncertain character. Then a probabilistic approach is needed for analysis of such systems. In this paper there is
investigated the vibration amplitude of a rigid rotor damped by two magnetorheological squeeze film dampers and
magnitude of the force transmitted to the stationary part during the steady state operating regime. The uncertain
parameters of the studied system are the rotor unbalance and speed of its rotation. The Monte Carlo method was
employed for this analysis.2014-01-01T00:00:00ZZapoměl, JaroslavFerfecki, PetrKozánek, JanDouble pendulum contact problemŠpička, JanHynčík, LuděkHajžman, Michalhttp://hdl.handle.net/11025/116752021-09-22T08:43:34Z2014-01-01T00:00:00ZNázev: Double pendulum contact problem
Autoři: Špička, Jan; Hynčík, Luděk; Hajžman, Michal
Abstrakt: The work concerns contact problems focused on biomechanical systems modelled by a multibody approach. The
example is modelling of impact between a body and an infrastructure. The paper firstly presents algorithm for
minimum distance calculation. An analytical approach using a tangential plain perpendicular to an initial one is
applied. Contact force generated during impact is compared by three different continuous force models, namely
the Hertz’s model, the spring-dashpot model and the non-linear damping model. In order to identify contact
parameters of these particular models, the method of numerical optimization is used. Purpose of this method is to
find the most corresponding results of numerical simulation to the original experiment. Numerical optimization
principle is put upon a bouncing ball example for the purpose of evaluation of desirable contact force parameters.
The contact modelling is applied to a double pendulum problem. The equation of motion of the double pendulum
system is derived using Lagrange equation of the second kind with multipliers, respecting the contact phenomena.
Applications in biomechanical research are hinted at arm gravity motion and a double pendulum impact example.2014-01-01T00:00:00ZŠpička, JanHynčík, LuděkHajžman, MichalDevelopment of aerodynamic bearing support for application in air cycle machinesŠimek, JiříLindovský, P.http://hdl.handle.net/11025/116742021-09-22T08:43:34Z2014-01-01T00:00:00ZNázev: Development of aerodynamic bearing support for application in air cycle machines
Autoři: Šimek, Jiří; Lindovský, P.
Abstrakt: Air cycle machines (ACM) are used in environmental control system of aircrafts to manage pressurization of the
cabin. The aim of this work is to gain theoretical and experimental data enabling replacement of rolling bearings,
which require lubrication and have limited operating speed, with aerodynamic bearing support. Aerodynamic
bearings do not pollute process air and at the same time allow achieving higher operating speed, thus enabling
to reduce machine mass and dimensions. A test stand enabling the verification of aerodynamic bearing support
properties for prospective ACM was designed, manufactured and tested with operating speeds up to 65 000 rpm.
Some interesting features of the test stand design and the test results are presented. A smaller test stand with
operating speed up to 100 000 rpm is in design stage.2014-01-01T00:00:00ZŠimek, JiříLindovský, P.