| Friction lining, serving as the key component of friction hoists, can absorb load from the wire rope and rope terminal and can drive the lifting system by providing the friction force. Therefore, the properties of friction lining directly influence on the working capacity, lifting efficiency, safety and reliability of hoists. Based on the white-box method and using VW9000 high-speed camera, the reciprocating and sliding frictional experiments were carried out aimed at lining materials and the whole processes were recorded and observed real-timely. The occurrence and developing processes of all sorts of micro phenomena in the frictional interface were observed. Moreover, the micro contact properties of friction lining were studied and the micro wear mechanism was analyzed. Eventually,works can offer basic reference and gist to study the friction mechanism of friction lining and wire rope.Friction linings K25, G30 and GM-3, widely used by the domestic friction hoists at current, were chosen as research subjects. The reciprocating and sliding frictional experiments were operated under the condition of the various loads and sliding speeds. After utilizing contact properties, the varieties of surface morphology, friction coefficient and SEM analysis for studying micro friction mechanism, the main results are listed as follow:(1) Friction lining is considered as a viscoelastic material, the surface micro bulges are deformed consequently similar to the deformation of hard grinding pairs. As the load increases in the yield limit, the deformation of friction lining and the real contact area of the friction pair increase. This phenomenon is the main reason to explain the increase of contact area. With the increase of sliding speed, the real contact area increases first and then decreases. As sliding speed reaches 1mm/s, the preliminary and terminal real contact area of friction lining share a same variety law in a single period; after sliding speed reaches 5mm/s, the stick-slip vibration phenomenon occurs in the middle and terminal periods; moreover, the shape of the real contact region presents an irregular serrated wave, and the fluctuated amplitude increases with increasing sliding speed,and happen along with friction noise.(2) The sliding process of friction lining can be divided into three stages. First of all, the first stage is defined as adhesion stage. As sheet glass trends to slide, no relative displacement exists in the interface of the friction pair and molecular chains in the surface of contact region are stretched to deform along the sliding direction. Then, in the stick-slip transition stage, relative slide occurs at the edge section of the back contact region along the slip direction, and sliding region gradually expands to the center; viscous situation still exists at the center section and molecular chains are sustained to be stretched to deform. Finally, in the completely sliding stage, no adhesion migration is generated in the contact region and sliding situation reaches a stable stage. Furthermore, adhesion displacement in the center region is bigger than that in the edge section.(3) The friction coefficients of friction lining GM-3 increase first and then decrease with the increase of the load. Friction coefficient of lining G30 and K25 slightly decreasing with load. The friction coefficients of friction linings increase first and then decrease with the increase of spread,stick-slip fluctuations reduced friction coefficient。(4) surface material of friction lining GM-3 can be molten easily under the influence of friction heat. Thus lining GM-3 can generate more abrasives and serious wear than others under the same condition. Friction lining G30 possesses the best heat resistance and a middle surface wear than three lining materials. Friction lining K25 possesses an excellent elasticity conducive to spread load. Moreover, the surface stress of lining K25 is smaller than others under the same load. A high thermal decomposition temperature of lining K25 can help its surface reduce the influence from friction heat. Consequently, lining K25 possesses the slightest surface wear, minimum abrasive and best wear resistance. Friction lining is mainly dominated by adhesion wear under the low-load and low-speed conditions. Additionally, the wear mechanism of lining is adhesion wear, abrasive wear and fatigue wear with rolling particls under the high-load or high-speed conditions.(5) All the three kinds of lining can produce rolling abrasives under a certain load and speed. The procedure for formation of rolling abrasives can be divided into four stages. In the first stage, adhesion phenomenon occurs in the interface of sheet glass and lining. In the second stage, fatigue cracks are generated in the surface of lining under the periodic alternating stress. In the third stage, surface material peels off to form rolling abrasives with the propagation of cracks. In the fourth stage, abrasives are pushed to roll in the interface of the friction pair, and the surface of lining eventually generates some indentations similar to the shape of abrasives. |
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