WTC2005-63363 EXPERIMENTAL THERMAL STUDY OF CONTACT WITH THIRD BODY

ABSTRACT The thermal study of sliding contact is complex due to numerous physical aspects highly coupled. Heat generation mechanisms are still badly known due to the complex interactions between mechanical, thermal and physico-chemical behaviours and surface degradations. In the goal to better appreciate the third body role on the thermal aspect, an experimental set-up has been realized. It consists in two rings sliding to each other, the first one is made of sapphire (rotating ring) and the second one is made of steel (fixed ring). The temperatures are obtained by an infrared camera scanning through the sapphire and by thermocouples on the contact surface specially realized for this experimental setup. The contact surfaces of the two rings have been observed with a scanning electronic microscope. Comparison between the thermal scene and the surface observations has allowed connecting the third body accumulation with local surface heating. INTRODUCTION The study of dry friction between rubbing surfaces is generally closely related to the debris behavior of the interface. The debris particles have often been considered as worn particles from the contact area. The concept of third body was introduced in tribology by M. Godet [1] in order to define physically the components of a friction system and the mechanical interaction between them. Numerous experimental observations emphasized the complexity of the existing mechanisms in a sliding contact (third body distinction in granular form and in sheet microplates, third body flows, etc.

WTC2005-63363 EXPERIMENTAL THERMAL STUDY OF CONTACT WITH THIRD BODY

ABSTRACT The thermal study of sliding contact is complex due to numerous physical aspects highly coupled. Heat generation mechanisms are still badly known due to the complex interactions between mechanical, thermal and physico-chemical behaviours and surface degradations. In the goal to better appreciate the third body role on the thermal aspect, an experimental set-up has been realized. It consists in two rings sliding to each other, the first one is made of sapphire (rotating ring) and the second one is made of steel (fixed ring). The temperatures are obtained by an infrared camera scanning through the sapphire and by thermocouples on the contact surface specially realized for this experimental setup. The contact surfaces of the two rings have been observed with a scanning electronic microscope. Comparison between the thermal scene and the surface observations has allowed connecting the third body accumulation with local surface heating. INTRODUCTION The study of dry friction between rubbing surfaces is generally closely related to the debris behavior of the interface. The debris particles have often been considered as worn particles from the contact area. The concept of third body was introduced in tribology by M. Godet [1] in order to define physically the components of a friction system and the mechanical interaction between them. Numerous experimental observations emphasized the complexity of the existing mechanisms in a sliding contact (third body distinction in granular form and in sheet microplates, third body flows, etc.

Influence of chloromequat chloride application on the content of selected microelements in quinoa seeds (Chenopodium quinoa Willd.)

Analizowano wpływ zastosowanego terminu oprysku i dawek retardanta Antywylegacza Płynnego 675 SL chlorku chlorocholiny (CCC) na zmiany akumulacji wybranych mikroelementów (Fe, Cu, Mn, Zn) w nasionach komosy ryżowej. Zbadano dwa terminy wykonania oprysku na etapie fazy rozwojowej roślin Sili par liści. Dawkę retardanta oceniano na trzech poziomach: l, 2 i 3 dm3•ha-1, które porównano z badaniem kontrolnym - bez zastosowania preparatu. Stwierdzono istotny wpływ badanych czynników na zawartość wybranych mikroelementów w nasionach komosy ryżowej. Najwyższą zawartość Fe i Mn zaobserwowano na obiektach z dawką 3 dm3•ha-1 CCC i była ona wyższa w fazie 8 par liści. Jednocześnie zastosowanie CCC w uprawie komosy ryżowej stymulowało nieznaczne zmniejszenie zawartości Cu i Zn.An influence of spraying time and chloromequat chloride (CCC) retardant doses on changes in the accumulation of selected micronutrients (Fe, Cu, Mn, Zn) in quinoa seeds was analyzed. Two time deadlines for retardant spraying at the stage of 8 and 11 pairs of leaves plant development phase was checked. The retardant dose was evaluated in three levels at l, 2 and 3 dm3 ha-1, which was compared to the control test without the use of preparation. A significant influence of examined factors on the content of selected micronutrients in seeds of quinoa was confirmed. The highest content of Fe and Mn was observed on objects with a dose of 3 dm3-ha"' CCC and was higher in the 8 pairs of leaves stagc. At the same time the use of CCC in the cultivation of quinoa stimulated a slight reduction of Cu and Zn content

Monitoring of Transient Phenomena in Sliding Contact Application to Friction Brakes

International audienceAbstract This work focuses on the study of transient phenomena, in particular the non-uniformity and space-time variation of friction forces and surface temperature of a brake disc during stop-braking. Friction tests were conducted on a braking tribometer. The friction forces in the contact were measured using a 3D piezoelectric sensor, while the disc surface temperature was investigated by means of a high frequency fibre-optic two-colour pyrometer. An optical lap-top device was used to keep track of disc revolutions, and an original programme was written to plot the space-time variations of the measured parameters. This new original approach helps better understand the coupling between thermal and tribological phenomena occurring during braking