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Stress analysis of the ceramic head of hip joint endoprosthesis under different loading

Fuis V., Houfek M., Navrat T., Hlavon P.

Modelling and Optimization of Physical Systems

2007

z. 6

47--50

Using the system approach, the paper deals with the problems of ceramic head of hip joint endoprosthesis destructions, and with assessing the impact of shape deviations of conical surfaces on the tensile stress under different loading. Concerned are shape deviations from the ideal conical surfaces of the stem and the head of the endoprosthesis, which - when the head is put on the stem and the endoprosthesis loaded - form a contact configuration. The shape deviations may be modelled at the macro-level - this concerns model shape inaccuracies such as deviation from the nominal degree of taper, ovality, and their combination, or, possibly, at the micro-level - when the stochastic distribution of unevenness on the contact areas is respected. The problem of stress in ceramic heads was solved using the algorithm of the finite element method for spatial contact tasks. In the paper are presented and analysed the results of solution of the micro-level shape deviations, obtained from measurements made on the cones of stems and heads under the loading obtained from the experiments [1] and under ISO 7206-5 loading [2].

Using of the long squeeze film dampers in rotor systems

Hlavon P., Houfek L.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

2003

nr 21

79-84

The present paper focuses on the issues of rotor systems with hydrodynamic dampers known as sąueeze film dampers (SFD), which are non-linear hydraulic binding elements between the rotor and stator. The hydrodynamic dampers, with maximum discharged layer, have recently been applied more and more often thanks to their favourable characteristics, mainly in the rotor systems of aircraft engines. In principal, the dampers decrease amplitude of the actuated oscillations, primarily when crossing the critical speed. They tend to shift the amplitude-frequency characteristic of the whole system to lower values due to the supplementary material of oil film, preventing thus the transmission of vibrations on to the machine frame and, in fact, reducing noisiness of the whole equipment.