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Napjatostní a deformační analýza keramické hlavice totální kyčelní endoprotézy s tvarovými odchylkami kontaktních ploch
Fajfr, M. ; Fuis, Vladimír
The problem of the stress in the head of the hip joint endoprosthesis is solved by FEM. These shape variants of the contact areas were taken into account: accurate variant, deviation from the nominal conicalness, no roundness contact surfaces (modelling by the help of elliptically shaped), indirectness of contact surfaces, combination of no roundness and conicalness. The maximum of the first principal stress in the ceramic head decreases with the increasing of the angle of the loading. Deflections of the type no roundness create the highest values of maximum stresses in the head.
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Calculation of the Ceramics Material Parameters from the Testing Destructions of the Heads
Fuis, Vladimír ; Návrat, Tomáš ; Hlavoň, Pavel
This paper deals with increasing of the computation modelling level of the reliability problem of ceramic heads of total hip joint endoprostheses. The solution to this problem was invoked by recent more frequent failures of these heads in clinical practice. Results of computational and experimental modelling have shown a substantial influence of shape deviations in the conical connection between stem and head on the initiation of ceramic head fractures. The fracture probability was evaluated step by step for various macroscopic shape deviations in the conical connection and then for microscopic shape deviations superposed on the macroscopic deviations.
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Manufacturing accuracy versus reliability of the hip joint endoprosthesis ceramic head
Fuis, Vladimír
The paper deals with the problems of the stress and failure probability of the ceramic head of hip joint endoprosthesis. Computational modeling is used to solve the problem - stress states are calculated by FEM, failure probability is based on the Weibull weakest link theory. The ceramic head is pressed on the stem cone under ISO 7206-5 conditions. There are considered the macro and micro shape deflections of the contacted cone areas, the values are given from the 3D measured device IMS UMPIRE.
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Napjatostní analýza keramické hlavice kyčelní endoprotézy s reálnými tvarovými odchylkami
Fuis, Vladimír
The paper deals with the problems of ceramic head of hip joint endoprosthesis destructions, and with assessing the impact of shape deflections of conical surfaces on the probability of this failure. Concerned are shape deflections 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.
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Experimental evaluation of the weibull paramaters of the bioceramics strength
Fuis, Vladimír
The solution to the problem of ceramic head reliability requires realization of two computational models: one for determination of stress states and another one for evaluation of the fracture probability. Material characteristics of ceramics used in fracture probability evaluation have been determined by a 3-point-bending test till now. Within the framework of this paper is that the characteristics will be determined by destruction tests of ceramic heads.
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