|
|
Simulation and Evaluation of the UHMWPE Surface Wear
Franta, L. ; Jeníková, Z. ; Sieber, D. ; Synková, Hana ; Pražák, Josef ; Suchánek, J.
The goal of this research project is to increase the lifetime of total knee joint replacement. Therefore the “In vitro“ simulation of realistic physiological conditions is important. For the knee joint replacement experiments, a KKK ELO 98001 simulator is used. The simulator enables the combination of rolling and sliding motion of replacement components with sinusoidal loading. During the experiment, a considerable amount of wear particles of the UHMWPE component is produced and the friction surfaces are irreversibly changed. Initially, the irregularities of tibia component are smoothed. Consequently, large amounts of UHMWPE wear are released. The surface changes of specimens were evaluated.
|
|
|
Elastic tubes in the mode of self-excited oscillation
Chlup, Hynek ; Maršík, František ; Konvičková, S.
Our paper studies experimentally the self-excited oscillations of thin-walled elastic tubes with respect to the Korotkoff sounds. The self-excited oscillation is a phenomenon, when an elastic tube looses stability of its shape and starts to oscillate, loaded only by continual flow, therefore without any external excitation. The mean flow rates, pressures at the ends of the tube, external pressures and photographs of the shape in two planes were recorded under various modes of oscillation. The effective cross-section and Young’s modulus of the tube wall were calculated by simplified formulas. The data analysis showed an increase of the oscillation frequency with a decrease of the tube wall compliance. It means the frequency of the oscillation is dependent on ratio of the wall thickness and the tube diameter. The mode of the oscillation is also influenced by the transmural pressure. The influence of the axial pretension of the tube is being studied now.
|
|
|
Účinek motoru s omezeným výkonem na kmitání systému s blízkými rezonancemi
Půst, Ladislav
The paper discusses dynamic behaviour of two degrees of freedom system excited by centrifugal force of unbalance. electric motor with limited power drives the rotor with unbalance. This "weak" property of energy source strongly influences the responses of vibrating system, especially if its eigenfrequencies are close each other. This is often case in technical praxis, mainly in rotating machinery, where the stiffness anisotropy of rotors supports leads to interesting dynamic phenomena. Particular attention is given also to the internal dynamic interaction of mechanical part of electric motor with the processes in the electromagnetic part at the non-stationary vibrations.
|
|
| |
|
| |
guest ::
