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Vliv svalové dysbalance na migraci kyčelního implantátu
Kytýř, Daniel ; Jírová, Jitka ; Vyčichl, Jan ; Jíra, J.
In general all orthopaedic operations may cause the change of muscle balance. This dysbalance various not only range of movement but also the loading vector during the movement. In case of hemiarthroplasty when the new joint is created by femoral replacement and intact acetabulum could be the dysbalance very dangerous. Migration of the implant head after hemiarthoplasty is the problem which observed to nearly at all patients. Muscle dysbalance and shape of acetabulum are the two main problems solved by numerical analysis of hip joint FE model.
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Stanovení kritéria poškození hlavy pomocí konečnoprvkového modelu
Jiroušek, Ondřej ; Jíra, J.
Paper presents a detailed finite element model of human head used for head injury criteria assessment. Today most used HICs are based on the history of linear acceleration only. However, the rotational acceleration plays also important role, due to the rupture of bridging veins involved in the relative motion between the skull and the brain. Presented model allows for new approach to define the HIC based on either strain energy or on combination of linear and rotational acceleration history. The model is based on a series of CT and MRI scans of a cadaver head of high resolution and is composed of three different regions: 1. skull, 2. brain and 3. subarachnoidal space. Discussion on material properties of these four distinct regions is given in the paper.
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Vliv tvaru pánevní kosti na pole napění po implantaci cerkvikokapitální endoprotézy
Kytýř, Daniel ; Jírová, Jitka ; Micka, Michal ; Jíra, J.
Migration of the implant head after hemiarthoplasty is a problem which appertain to nearly all patients. Article deals with development and utilization of parametrical FE model of the hip joint for numerical analysis of implant head migration. There are two main input parameters for the stress analysis. CE angle representing the shape of acetabulum and direction of the femoral replacement loading. To assess the influence of selected parameters on the implant migration and to enable easy comparison to patients X-Ray scanning, the analysis was carried out as axially symmetric 2D and 3D contact problem. Ultimate values of first principal stress, third principal stress and sum of displacements were used as a reference magnitude.
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Interaction of pelvic bone and acetabular component
Vyčichl, Jan ; Jiroušek, Ondřej ; Jíra, J.
The article deals with development and validation of complex FE model of pelvic bone and acetabular component. The model of pelvic bone is constructed on basis of CT data of high resolution. Different designs of acetabular components are then incorporated in the FE model using Boolean operations. Comparative study of different acetabular components (spherical, conical and spherical cemented) is presented. Contact stresses in the underlying pelvic bone are compared for each of the cup designs.
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Analysis of local defects of high-pressure pipelines
Micka, Michal ; Jíra, Josef
In their surroundings the local defects of pipelines influence stress and strain state in the pipe wall. They are significant concentrators of the stress and they have fundamental effect on load-carrying capacity and service life of the pipe. The field of the stress and strain in the surroundings of defects may be detected experimentally or it may be used numerical modelling by FEM. In this paper are presented results of the numerical modelling of the stress state in the pipe wall due to ovality of the pipe also in the surroundings of corrosion pits and further at the place of local inward denting (buckling) of the pipe wall.
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