|
|
Experimental Assessment of Influence of Polyethylene Liners' Position on Plastic Deformation in the Run-in Phase of Wear
Zeman, Jakub ; Daniel, Matej (referee) ; Ranuša, Matúš (advisor)
The diploma thesis is focused on the run-in phase of total hip replacement. Mutual adjustment of contact surfaces takes place in this phase and polyethylene acetabular cup shows notable creep behaviour. The magnitude of creep deformations is assessed experimentally in relation to acetabular cups orientation in human body after its implantation. The condition of articulating surfaces is also assessed as well as resulting coefficient of friction in run-in phase. Physiological load and kinematics of the artificial joint as well as physiological conditioning is achieved by new module of existing joint simulator, which is created as part of this thesis. Deformations and condition of articulating surfaces are assessed via optical methods and SEM. Findings about the run-in phase are compared with existing FEM analyses to evaluate simplifications used in these analyses. Measurement of creep deformations has also potential to improve the accuracy of acetabular wear diagnosis in clinical practice.
|
|
|
The effect of viscoelasticity and operating conditions on friction of compliant contacts
Quinn, Cheney ; Daniel, Matej (referee) ; Nečas, David (advisor)
Poddajné kontakty obsahující polymerní nebo pryžové členy lze nalézt v technických i biologických aplikacích. I přes vývoj v této oblasti existují efekty, které ovlivňují tribologické aspekty těchto kontaktů, a je třeba je dále zkoumat. Tato práce se zabývá vlivy kinematických podmínek, konfigurace, viskoelasticity a viskozity maziva na tření v mazaných poddajných kontaktech. Výsledky byly použity k vývoji numerického modelu pro predikci kapalinového tření v poddajných kontaktech. K objasnění chování poddajných kontaktů bylo použito zařízení Mini Traction Machine (MTM) v konfiguraci ball-on-disc, což umožnilo zkoumání zmíněných vlivů. Z poznatků z technické oblasti bylo zjištěno, že viskoelasticita se projevuje ve všech konfiguracích, tedy soft-on-hard, hard-on-soft a soft-on-soft, a její efekt je nejvýznamnější v konfiguracích s poddajným diskem. Data dále ukazují, že poměr skluzu a valení má vliv na valivé tření což je v rozporu se současnou literaturou. Výsledky z biologické oblasti naznačují, že za určitých podmínek lze nahradit nativní kapalinu jednoduchým mazivem. Tyto poznatky mohou posloužit jako odrazový můstek pro další studie zabývající se poddajnými kontakty.
|
|
|
PMSM Modeling in Non-standard Situations
Daniel, Martin ; Otava, Lukáš (referee) ; Václavek, Pavel (advisor)
There is an increasing use of synchronous motors with permanent magnets in industrial applications. Therefore, it is also required simulation of the behavior of these engines in non-standard situation. We want to prevent destruction of the engine thanks to these simulations. Waveforms of signals are the result of the simulation. The bachelor thesis deals with a design of simulation schemes. Specifically, is about the short circuit phases at the input of the engine, disconnect engine from the source and change duty cycle of inverter. One part of the thesis belongs to a creation of user interface for setting the technical parameters of the engine and an activation of simulations with using the created simulation schemes.
|
|
|
Analysis of THR lubrication with the use of fluorescent microscopy
Tkadlec, Tadeáš ; Daniel, Matej (referee) ; Nečas, David (advisor)
This diploma thesis deals with an experimental analysis of lubrication of total hip joint replacement using fluorescence microscopy, focusing on so-called soft bearing pairs. Experiments were realized using a hip joint simulator, which was modified and refined for fluorescence microscopy. The aim of this diploma thesis was to determine the effect of the individual components of the synovial fluid on the lubrication mechanisms. For this purpose, different model fluids were designed to represent the composition of proteins and other synovial fluid constituents to elucidate the effect of albumin, -globulin and hyaluronic acid on the resulting lubrication performance. The experiments were separate into two categories different in type of load, dynamic (representative walking) and combined (representing standing with short walk). The experimental results were time-dependent fluorescence intensity values, representing dimensionless film thickness parameters. The values were recorded on the graphs and supplemented with fluorescence images taken during the characteristic sections of the measurements. The measured data was subsequently confronted with previously published articles. It was found that the dominant constituent responsible form film thickness is albumin, while -globulin and hyaluronic acid forms thin stable layer enhancing adsorption ability of albumin which contributes to increase of film thickness eventually.
|
|
|
Optimization in control systems
Daniel, Martin ; Václavek, Pavel (referee) ; Pohl, Lukáš (advisor)
Master’s thesis deals with using a linear matrix inequality (LMI) in control of a dynamic systems. We can define a stability of a dynamic system with a LMI. We can use a LMI for research if the poles of a system are in a given regions in the left half-plane of the complex plane with a LMI or we can use a LMI for a state feedback control. In the work we describe a desing of a controller minimizing a norm from an input to an output of the system. There is also a desing of a LQ controller with a LMI. In the end of the work, there are two examples of a design a LQ controller, which minimize the norm from the input to the output of the system and moves a poles of a dynamic system in a given regions in the complex plane, with the LMI. We use a LMI for a design a continuos LQ controller in the first example. In the second example we use a LMI for a design a discrete LQ controller.
|
|
|
Analysis of Response Variables of Bone Tissue under Mechanical Loading
Vosynek, Petr ; Daniel, Matej (referee) ; Janíček, Přemysl (referee) ; Návrat, Tomáš (advisor)
Dissertation summarizes the results of computational and experimental modeling in the field of biomechanics engineering. Analyses are focused on selected variables that complement or can supplement existing methods of prediction of bone fractures. In terms of computational modeling the variables are based on stress strain analysis. The greater part of the work has been aimed on experimental modeling which is used for monitoring the two dominant components of bone tissue, which are minerals and collagen fibers. The current most widely used variable for the description of bone loss (osteopenia, osteoporosis) is areal bone mineral density (BMD). This variable does not however provide any information about the change in total volume consequently change of mineral and collagen. Proposed mechanical values follow the loss of the two components during simulation of minerals loss (demineralization) and simulation of collagen loss (deproteinization) in vitro for long turkey bones
|
|
|
An investigation of friction and lubrication in eye/lens contact
Kulíšek, Vlastimil ; Daniel, Matej (referee) ; Nečas, David (advisor)
Millions of contact lens wearers suffer from eye irritation due to dry eye disease (DED), which is most often treated with the application of artificial tears. As the primary source of irritation and discomfort is mutual rubbing of the eye, lens and lid surface, contact lens tribology research has the potential to bring new insights into the field of DED therapy. The aim of this diploma thesis was to clarify the influence of the properties of the contact lens and the properties of the lubricant on the friction and formation of the lubricating film in the simulated contact between the contact lens and the lid. The experiments were carried out using a pin-on-plate tribometer, which can simultaneously record the coefficient of friction while simultaneously observing the lubricating film. The contact was lubricated with twelve types of lubricants differing in mucin content, buffer type, and molecular weight (MW) of hyaluronic acid (HA). The effect of lubricant type was studied on two types of contact lenses. The results showed that for lenses containing an active wetting agent, the presence of mucin in the lubricant is essential for increasing the tribological performance, while MW of HA does not play a significant role. A closer analysis of the individual tested solutions showed that the highest performance for both types of lenses was achieved by HA with an average MW of 337 kDa. However, the type of buffer played a significant role in this case. In general, it can be stated that suitable artificial tears for DED therapy should be chosen based on the type (material) of contact lenses used and the mucin content in the tear film of a particular patient.
|
|
| |
|
|
Friction and lubrication of fascia
Chmelík, Jiří ; Daniel, Matej (referee) ; Vrbka, Martin (advisor)
The diploma thesis was part of the project "Regeneration and lubrication of fascia with hyaluronan" of the company Contipro a.s., whose main goal is the development of an injectable medicinal product. The number of patients suffering from so-called myofascial lower back pain is increasing. The cause of the pain is increased hyaluronic acid, which is produced between the layers of the fascia. If the viscosity is low, the fascia layers are not affected and the coefficient of friction is low. The purpose of the product is to improve the sliding movement of the fascia and relieve patients of pain. The main component of the medicine is hyaluronic acid. The project included rheological and tribological analysis of hyaluronic acid samples. A tribological model of fascia in a pin-on-plate configuration was created for the analysis of the coefficient of friction. Based on the fascia models used, the dependence between the coefficient of friction and viscosity of native hyaluronic acid solutions was found. For models and real fascias, the native solution (Bonharen) was found to have better friction properties than hyaluronic acid derivatives. These analyzes have contributed not only to the development of the drug, but also to the emergence of other studies that would like to address the biotribology of fascia.
|
|
|
Effects of the crisis caused by Covid-19 on the operation of construction company
Daniel, Martin ; Biolek, Vojtěch (referee) ; Hanák, Tomáš (advisor)
The diploma thesis evaluates the impact of the crisis caused by covid-19 on construction companies, especially through a questionnaire survey and interviews with representatives of construction companies. The theoretical part of the work, which precedes the questionnaire survey and interviews, describes the construction company and also explains topics such as anti-epidemic restrictions, compensation programs or the state of emergency caused by the covid crisis.
|
guest ::
RSS feed.