|
|
Strain Stress Study of Burch-Schneider Split
Řehák, Kamil ; Horyl, Petr (referee) ; Janíček, Přemysl (referee) ; Florian, Zdeněk (advisor)
This thesis deals with problems of the hip endoprosthetics area, namely total endoprosthesis (TEP) with Burch-Schneider (BS) split, in which there are many problems in clinical practice. The hip joint load depends on the patient weight and the performed activity. Sedentary job, little exercise, a lot of stress or poor eating habits and overweight associated with it affect negatively hip joint. Increasing hip joint wear and its pain in movement is necessary in several cases to be solved by a surgical procedure in which TEP is applied. When selecting and subsequently applying individual TEP, it is important to pay attention to creating conditions which will allow good fixation. In case of worse mechanical properties of bone tissue, it is very problematic to ensure stability of the implant. Based on several classifications which assess the degree of hip joint damage, it is possible to select a suitable TEP. The BS split, on which this work is focused, is dominantly used in cases of large defects in the acetabulum area. The use of this cage allows to bridgelarge defects and create a new centre of rotation of the hip. Knowledge of the mechanical properties of hip bone tissue can significantly affect the prediction of BS split damage. For this purpose, it was necessary to perform a biomechanical study, which is focused on the influence of worse mechanical properties of bone tissue on BS split failure. The computational modelling using finite element method implemented in the ANSY S software was used for the solution, which enables to solve the mechanical interaction between bone tissue and TEP with BS split. Due to the absence of bone tissue data before application of TEP with BS split, the variants before application of TEP and after application of resurfacing and standard TEP were solved. All variants were solved with the material properties of bone tissue that were determined based on CT images. In addition, all variants were solved for the case of degraded mechanical properties. Based on the numerical simulations results and the Mechanostat hypothesis, a bone tissue analysis of the hip joint was performed before and after application of TEP and TEP with BS split. The results show the influence of the computational model level, which considers the distribution of bone tissue through the inhomogeneous model of the material. Therefore, the degraded mechanical properties have a major impact on the stability and strain of the BS split, particularly in the cranial part of the acetabulum.
|
|
|
Ductile Fracture Criteria in Multiaxial Loading – Theory, Experiments and Application
Šebek, František ; Horyl, Petr (referee) ; Španiel, Miroslav (referee) ; Petruška, Jindřich (advisor)
Práce se zabývá tvárným lomem, který je výsledkem víceosého kvazi-statického monotónního namáhání doprovázeného rozsáhlými plastickými deformacemi, přičemž pro degradaci materiálu je uvažován lokální přístup. Ve výpočtech o rozvoji poškození rozhodují použité mezní podmínky tvárného lomu. Tyto byly teoreticky studovány v úvodu práce a po výběru vhodné mezní podmínky byl stanoven postup kalibrace. Dále byl rozpracován plán měření a realizovány zkoušky při pokojové teplotě na slitině hliníku 2024-T351, zahrnující tah, krut a tlak, pro studium rozvoje poškození a věrohodnou kalibraci vybraného fenomenologického modelu tvárného porušování, vyjádřeného pomocí lomového přetvoření a závislého na hydrostatickém tlaku a deviátoru tenzoru napětí. Mezní podmínka tvárného lomu byla posléze svázána s podmínkou plasticity. Plasticita byla pro zkoumaný materiál uvažována ve tvaru zohledňujícím i stav třetího invariantu deviátoru tenzoru napětí. Celý navržený přístup, plně aplikovatelný na víceosé úlohy, byl implementován pomocí uživatelské rutiny do komerčního programu založeného na explicitní variantě metody konečných prvků. V závěru práce je předložena aplikace navrženého přístupu k modelování tvárného porušování v podobě verifikace na vybraných zkušebních testech, z níž plynou závěry a doporučení pro další práci.
|
|
|
Biomechanical Study of Hand
Krpalek, David ; Janíček, Přemysl (referee) ; Horyl, Petr (referee) ; Florian, Zdeněk (advisor)
This work deals with issue of human wrist and appropriate total wrist implant allowing a restoration of hand mobility approaching physiological condition after traumatic and degenerative diseases. Treating these diseases are very complex. These issues including a biological and medical issues. To determine the appropriate treatment method and select right total wrist implant is important to know the behavior the human wrist at all stages in terms of medical and biomechanical. For this reason, it was developed a biomechanical study including computation model of human wrist allowing solution of strain and stress of hand in physiological and pathological conditions and condition after total wrist implant. The frost remodeling of bone tissue was used for analysis of human wrist bone tissues and bone tissues after application of total wrist implant RE-MOTION™ Total Wrist.
|
|
|
Biomechanical Studies of Facial Bone
Valášek, Jiří ; Janíček, Přemysl (referee) ; Horyl, Petr (referee) ; Florian, Zdeněk (advisor)
Presented work deals with Biomechanical study of the facial skeleton. This work is focused on the fixation of the mandible after removal of a tumor from affected bone tissue. The aim of the work is to perform biomechanical study of the facial skeleton with subsequent detailed stress strain analysis of two mandible implants designed and manufactured for specific patients. The geometry model of mandible used for design of mandible implants and used for computational modelling has been obtained on the basis of CT data of two patients. A Theoretical-Clinical sub-study that deals with the comparison the CT data processing which is necessary for creating the model of geometry is a part of the thesis. Two models of mandible with applied mandible implant have been created for two specific patients with tumorous mandible bone tissue. Stress strain analysis has been performed for these two models. Results of the stress strain analysis of two models of mandibles with mandible implants are presented in the final chapters of the thesis. Findings of the biomechanical study have been published and applied in clinical practice.
|
|
|
Biomechanical Study of Interaction between Spinal Segment and Malleable Fixation Device
Manek, Filip ; Horyl, Petr (referee) ; Janíček, Přemysl (referee) ; Florian, Zdeněk (advisor)
This doctoral thesis is focused on comparative stress strain analysis of a spinal segment with a malleable fixation device and a physiologic spinal segment. In its opening a research study from available sources is carried out. It covers the contemporary state of scientific studies in the given area, anatomy of individual components of the spine, material properties, ways and magnitudes of loadings and also the most common FE model used in similar problems solved. To create a model of geometry of a spinal segment CT scans of a spinal segment of a 38-year-old woman are used. Then they are subsequently used in the modeling software SolidWorks to create the model of geometry of two lumbar vertebras L4 - L5 and a malleable fixation device. Using the computational system ANSYS Workbench, the complete computational model of the spinal motional segment with a malleable fixation device is compiled, covering models of material, loading and bonds. On the basis of the computational solution of FEM models for different ways of loading, a stress-strain analysis is performed. To compare obtained results a detailed comparative analysis with the physiological spinal segment, the segment with the degenerated disc and the segment with applied "rigid" fixation device is carried out. Within the stress strain analysis of the spinal segment with malleable fixation device, an analysis of the magnitude of the strain intensity of spongious bone tissue around the implanted transpedicular screw, depending on the cord pretension of the malleable fixation device, is performed.
|
|
|
BIOMECHANICAL STUDY OF EXTERNAL FIXATORS APPLIED TO TIBIA
Mrázek, Michal ; Horyl, Petr (referee) ; Janíček, Přemysl (referee) ; Florian, Zdeněk (advisor)
External fixators are used in a treatment of complicated fractures and their properties have a crucial impact on treatment quality. Therefore, this thesis is concerned with a biomechanical study of a bone (tibia) with applied external fixators via strain-stress analysis and their comparison with a state of tibia without applied fixator (physiological state). After creating the volume models of geometry of tibia and seven variants of external axial fixators, the corresponding finite element method (FEM) models are created. The analysis of tibia without applied fixator and tibia with all studied fixators is made for three states of load which correspond to characteristic load states during the first stage of treatment. The strain-stress analysis is made using finite element method. Furthermore, the methods of displacement and rotation evaluation during loading are proposed. One can conclude from the results of the strain-stress analysis how the different variants of fixators prevent the displacement and rotation of the bone during the different load states and the comparisons with the physiological state of bone are made. Bone tissue loading is determined from the distribution and the values of the first and the third principal stresses. Finally, comparing the results of all variants the influence of the fixator length, the gap between the fixation elements near the fracture, the number and the setting of the fixation elements on the fixation properties is analysed.
|
|
|
Biomechanical Study of Tooth Implants for Low Density Bone
Marcián, Petr ; Janíček, Přemysl (referee) ; Horyl, Petr (referee) ; Florian, Zdeněk (advisor)
This work deals with problem of dental implant area, where there are many problems at the dental implants application. The essential issue is the bone tissue quality at implant application, which sig-nificantly influences its deformation, tension and the possibility of subsequent implant failure. The knowledge of bone tissue mechanical properties of mandible and mandible with applied implant can significantly affect prediction of dental implant failure. The mechanical interaction can be described by variable determining deformation and tension of solved system. For this reason the computational modeling by using Finite Element Method was used for solving given problem. The computational model creation of solved system on the high resolution level is necessary for biomechanical assessment of implant failure, including bone tissue quality. For this purpose the biomechanical study was performed, which significantly spreads range of solved problem in this work afterwards. In this work the methodology, which describes assessment of bone tissue quality where the implant should be applied as well as mutual interaction, is presented. The results confirm necessity of bone tissue computational models creation on high resolution level including complex trabecular architecture. In this work the creation of trabecular structure computational model from data gained on micro-CT device is described. Further, the trabecular structure computational model was created on the 3D level with dental implant and the stress strain analysis was performed consequently. The last part of this work deals with introductory study of bone tissue modeling and remodeling.
|
|
|
Biomechanical Study of Human Mandible in Physiological State
Borák, Libor ; Horyl, Petr (referee) ; Bartáková, Sonia (referee) ; Janíček, Přemysl (referee) ; Florian, Zdeněk (advisor)
This study deals with the mechanical aspects of human mandible in physiological state during the occlusion. The work is focused on evaluation of stress-strain conditions of bone tissue. The emphasis is paid to the interaction of teeth with the bone. In addition, contact pres-sures in temporomandibular joints during various loading conditions were determined. The analysis of material model of some parts of the system regarding their modelling-level is pre-sented as well. The problem concerning the evaluation of stress-strain states is solved by computational simulation using the finite element method. The presented work is a detailed analysis of the parts of the masticatory system and a thorough description of their modelling is presented. Special focus is paid to modelling of cancellous bone as well as of periodontal tissue which mediates the interaction between a tooth and the alveolar bone. Three-dimensional geometry of the mandible and all its teeth has been obtained by using the digitizing of real objects, namely by using of three-dimensional optical scanner. Three various modelling levels of the material of periodontium are assessed: Linear iso-tropic model, bilinear isotropic model and linear orthotropic model. Characteristics of these models are analyzed and especially nine new constants describing orthotropic model (which is almost absent in the literature) are proposed. Two-dimensional models are used for analysis of differencies in mechanical response of cancellous bone to the tooth loading. Two cases are considered: Cancellous bone as a ho-mogenous continuous model on one hand and with detailed trabeculous architecture model on the other. Computational model is divided into four basic cases varying in level of masticatory appa-ratus geometry: A – 2D geometry of bone; B – 3D geometry of bone segment with one tooth through three teeth; C – 3D geometry of whole mandible with the only tooth; D – 3D geome-try of whole mandible with all teeth. All basic cases are further researched in different varia-tions for different material models etc.
|
|
|
Mechanical Analysis of the Influence of Fabrication Tolerances on Contact Conditions between the Acetabular Cup and the Femoral Head in Total Hip Replacement
Koukal, Milan ; Horyl, Petr (referee) ; Repko, Martin (referee) ; Janíček, Přemysl (referee) ; Florian, Zdeněk (advisor)
In endoprosthesis surgery there are typically a high percentage of implant defects, these can lead to failure of the whole prosthesis. One type of total hip replacement function loss is acetabular cup loosening from the pelvic bone. This disertation examines manufacture perturbations as one of the possible reasons for this kind of failure. Both dimension and geometry manufacturing perturbations of ceramic head and polyethylen cup were analyzed. We find that perturbations in the variables analysed here affect considered values of contact pressure and frictional moment. Furthermore, contact pressure and frictional moment are quantities affecting replacement success and durability. From obtained results it can be recommended to fit head and cup with a clearance of between 0 mm and 0.05 mm. It can not be recommend using interference type of fit because of strong deterioration of the contact conditions. Roundness perturbation of ceramic head should not exceed 0.025 mm.
|
|
| |
guest ::
