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Improving friction of lubricated contacts by modifying thermal conductivity
Šnevajs, Matěj ; Hartl, Martin (referee) ; Šperka, Petr (advisor)
This thesis deals with an experimental study regarding the effects of the thermal conductivity of contact bodies on the friction, lubricant film thickness and temperature distribution in EHL contact. The thesis focuses on the configuration of the ball on disc contact. The contact body materials are characterized by a wide range of thermal properties. New contact pairs are proposed and used in the study in order to make the contact bodies’ thermal properties dependent on the behaviour of EHL contact. The colorimetric interferometry method is used to measure the lubricant film thickness and the infrared thermography method is used to observe the temperature distribution in EHL contact. The author presents the assumed mechanism of heat transfer within EHL contact on the basis of different heat transfer mechanisms. The same conditions – such as the Hertz pressure, mean entrainment speed, sliding speed and ambient temperature – are induced for all the contact pair combinations. That is why the differences in the results are attributed to the different thermal phenomena in the contact, caused by the thermal properties of the contact bodies. In the case of contact bodies with a reduced heat dissipation capability, a reduction of the friction coefficient of up to 50 % is observed, which is attributed to an increase in the lubricant temperature, resulting in a decrease in its viscosity. This is confirmed by the infrared thermography method, whereby a significantly higher lubricant temperature is observed in the case of a combination of contact materials with a lower heat dissipation capability.
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Heat treatement of gear steels
Šnevajs, Matěj ; Řehořek, Lukáš (referee) ; Jan, Vít (advisor)
This bachelor thesis deals with suitable types of heat and heat-chemical treating of case hardening steel for production of gear wheels. The experimental part focuses on examination of two specific gear wheels made of 14 224 and ZF1A steel, which were donated by the company TATRA TRUCKS a.s. This bachelor thesis presents results of their hardenability, microstructure, hardness and microhardness of the case hardening layer.
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Improving friction of lubricated contacts by modifying thermal conductivity
Šnevajs, Matěj ; Hartl, Martin (referee) ; Šperka, Petr (advisor)
This thesis deals with an experimental study regarding the effects of the thermal conductivity of contact bodies on the friction, lubricant film thickness and temperature distribution in EHL contact. The thesis focuses on the configuration of the ball on disc contact. The contact body materials are characterized by a wide range of thermal properties. New contact pairs are proposed and used in the study in order to make the contact bodies’ thermal properties dependent on the behaviour of EHL contact. The colorimetric interferometry method is used to measure the lubricant film thickness and the infrared thermography method is used to observe the temperature distribution in EHL contact. The author presents the assumed mechanism of heat transfer within EHL contact on the basis of different heat transfer mechanisms. The same conditions – such as the Hertz pressure, mean entrainment speed, sliding speed and ambient temperature – are induced for all the contact pair combinations. That is why the differences in the results are attributed to the different thermal phenomena in the contact, caused by the thermal properties of the contact bodies. In the case of contact bodies with a reduced heat dissipation capability, a reduction of the friction coefficient of up to 50 % is observed, which is attributed to an increase in the lubricant temperature, resulting in a decrease in its viscosity. This is confirmed by the infrared thermography method, whereby a significantly higher lubricant temperature is observed in the case of a combination of contact materials with a lower heat dissipation capability.
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Heat treatement of gear steels
Šnevajs, Matěj ; Řehořek, Lukáš (referee) ; Jan, Vít (advisor)
This bachelor thesis deals with suitable types of heat and heat-chemical treating of case hardening steel for production of gear wheels. The experimental part focuses on examination of two specific gear wheels made of 14 224 and ZF1A steel, which were donated by the company TATRA TRUCKS a.s. This bachelor thesis presents results of their hardenability, microstructure, hardness and microhardness of the case hardening layer.
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