National Repository of Grey Literature 33 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Measurement of dry friction coefficient
Meško, Marek ; Brablc, Martin (referee) ; Rubeš, Ondřej (advisor)
This thesis describes modelling of dry friction and determining appropriate friction coefficients. The theoretical part of the thesis is devoted to the basic models of dry friction. The aim of the practical part of this thesis is to create devices for measuring friction coefficients and subsequently to measure the corresponding friction coefficients using these devices.
Wear analysis of the sliding surface material of large-scale hydrostatic bearings
Daněk, Lukáš ; Robenek, Dětřich (referee) ; Svoboda, Petr (advisor)
This thesis focuses on the experimental investigation of the wear behavior of sliding surface materials in large-scale hydrostatic bearings during oil supply failure. The aim is to clarify the influence of materials and surface treatments on friction and wear. For this purpose, a testing methodology was designed and implemented in laboratory conditions. An experimental module was developed for the tribometer to simulate a critical state and a new procedures were established for evaluating the behavior of the contact. Wear results were observed using a profilometer, precise scales, and a microscope. A set of suitable materials for pad sliding surfaces was created, which were tested under critical conditions. The selected materials were representatives of construction steel and anticorrosion treatments (galvanization), soft and hard (aluminium) bronzes, composite bearing linings (Babbitt), polymers (UHMWPE), and composite materials (PTFE). The experimental results show the dependence of friction on sliding velocity, wear rate, and other phenomena repeatedly measured on a statistical sample of selected materials. The final result is a list of characteristics, limitations, and recommendations for the tested sliding materials, which can be used for more effective design and operation of large-scale hydrostatic bearings.
Design of a simulator for studying eye friction and lubrication
Snopek, Lukáš ; Horák, Zdeněk (referee) ; Vrbka, Martin (advisor)
This work deals with the design of a tribometer, which simulates the interaction between the human eye and the eyelid, and simultaneously measures the friction between them and the thickness of the tear film. The tribometer will be used for research and development of artificial tears based on hyaluronic acid. The aim of the work was to design experimental conditions, conceptual and design solutions, as well as to ensure the production, assembly, and validation of the device. The experimental conditions were determined based on critical research. Four different conceptual solutions were proposed, of which two were selected for further development in the design solution. Based on the engineering documentation, the production of non-standardized components and assembly were ensured. Validation experiments demonstrated that the simulator enables the measurement of friction and tear film thickness at the contact area under the desired conditions, with both conforming and non-conforming types of contact. The contribution of this work lies in the construction of a new device that allows for measuring the coefficient of friction and film thickness during conforming contact, offering new opportunities in the study of human eye biotribology.
Friction investigation of coated materials for joint implants
Gelnar, Adam ; Streďanská, Alexandra (referee) ; Nečas, David (advisor)
This bachelor thesis deals with the comparison of the coefficient of friction of different types of DLC coatings applied on two materials used for joint replacements. The experiments also aim to compare the friction as a function of the material pair combination. The friction tests were performed on a Bruker UMT TriboLab tribometer in a pin-on-plate configuration. The surface topography before and after the tests were also analyzed. The measured results show that the pins have lower friction coefficient values against the UHMWPE plate than against the glass. The uncoated samples, although having lower friction values, showed some signs of wear after the tests, while the pins with DLC coatings did not. In view of these findings, it can therefore be assumed that surface modification of commonly used materials with DLC coatings can lead to an extension of the lifetime of joint replacements, and therefore to significant advances in implantology.
Impact of joint implant surface structure on friction behaviour
Kučera, Ondřej ; Nečas, David (referee) ; Ranuša, Matúš (advisor)
In osteoarthritis of small joints, the use of total endoprosthesis is currently being developed to ensure physiological movement, but it provides only a limited-service life. The use of microstructures on the implant surface may improve tribological properties, but this issue is not described enough. Thus, this work addresses the impact of microstructures on friction coefficient, lubricant thickness in the contact area, wear, as well as surface topography and geometry of the structures. Furthermore, the influence of DLyte electrochemical machining on the change of microstructures geometry and tribological properties is investigated. Measurements were performed using a reciprocal tribometer, interferometry and optical profilometry. The textured samples achieved an increase in both friction coefficient and lubricant thickness in the contact area. Furthermore, a correlation between the height of the texture edges and the measured lubricant thickness was demonstrated. DLyte significantly reduces these edges, also reducing wear, however, it degrades the surface of the CoCrMo samples. Implant texturing can lead to reduced wear, prolonged life, and thus improved quality of life for many patients. Texturing of Ti6Al4V alloy in combination with DLyte shows great potential.
Influencing of the Pile-Up and the Sink-In by the Coefficient of Friction in the Nanoindentation Test
Kovář, J. ; Fuis, Vladimír ; Čtvrtlík, Radim
The influence of the coefficient of friction between an indenter and a specimen on the height of the pile-up or depth of the sink-in during the nanoindentation test is discussed in this paper. When the indenter is pressed into the hard material, the sink-in behavior causes the bending of the specimen’s surface under the indenter. When the indenter is pressed into the soft material, the deformed material accumulates under the sides of the indenter and makes a pile-up region. The pile-up or sink-in behavior influences the contact area. In this paper, the finite element method was used for calculation of the dependency between the depth of the sink-in or height of the pile-up and the coefficient of friction. The results showed that while there is not any dependency between the friction and the depth of the sink-in, there is a strong dependency between the friction and the height of the pile-up until a specific value of the coefficient of friction. When the pile-up behavior occurs, the friction influences the contact area and should be included into the calculation of the contact area.
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.
Comparison of frictional properties of cosmetic massage products
Dohnal, Petr ; Čípek, Pavel (referee) ; Vrbka, Martin (advisor)
This bachelor’s thesis examines tribological properties of massage products (creams and oils). Its aim is to create a comparison of the selected products. Tribometer in the pin-on-plate configuration was used for the experiment because of its ability to simulate the process of rubbing the product on the skin. Cowhide was used as a model of human skin. The attributes of products were compared based on the characteristics of the coefficient of friction during the measurements. Through the experiments a suitable parameter was found for easy comparison of the product's durability. According to the results the best oil was selected in terms of durability and lubrication. The thesis could be used as a basis for creating a standardised method for evaluation and selection of products suitable for massage purposes.
Design of a belt grinder for robotic grinding
Šimara, Vít ; Vetiška, Jan (referee) ; Pavlík, Jan (advisor)
This bachelor thesis focuses on stationary robotic belt grinder. The grinder is designed to be tiltable in multiple axes, to guarantee its versatility. The theoretical part describes the belt grinder’s working principle and the fundamentals of robotic grinding. In addition, current trends in this branch are described. At the beginning of the practical part, the concept of the grinder is configured, part by part. This configuration is based on the theoretical research and the choice of the best option. The mechanical design follows, supported by calculations, indispensable to ensure the right functionality of the machine. This thesis’s outlet is a 3D model of the mechanical construction of the grinder with a partial drawing and technical documentation.
Influence of surface microstructure on implant lubrication processes in contact
Matovič, Martin ; Odehnal, Lukáš (referee) ; Ranuša, Matúš (advisor)
This bachelor thesis deals with the lubrication of microstructured prostheses of the first metatarsophalangeal joint. The aim of the research is the service life of joint replacements by creating a microstructure on the surface of the material. The work focuses on the influence of microstructures on lubrication processes in contact and coefficient of friction. Fluorescence microscopy in combination with a reciprocating tribometer with the possibility of recording frictional and loaded forces was used to observe the contact area. The number and average particle size of albumin, which plays an important role in contact lubrication, were then examined to record the camera. The testing was performed on two material combinations, namely CoCrMo - Glass B270 (hard pair) and CoCrMo - PMMA (soft pair), which were only four different microstructures. Elsewhere, the influence of microstructures on lubrication processes in contact for hard and soft pairs is indicated, which can be used to design further measurements.

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