Abstract
To study the influence of nano-additives on the friction-wear characteristics of friction materials, the nano-sized silicon carbide particles which have excellent chemical and physical properties are considered to add in composite to form the modified friction material. The influence of the silicon carbide nanoparticles (SCN) on the friction-wear characteristics of copper-based friction materials (CBFM) is investigated via the SAE#2 (made in Hangzhou, China) clutch bench test with the applied pressure, rotating speed, and automatic transmission fluid (ATF) temperature taken into account. Moreover, the variations of friction torque and temperature are considered to evaluate the friction performance, and the variable coefficient is employed to describe the friction stability. The wear characteristics of friction materials are investigated by the disc changes in thickness and micro-morphology. The results show that the CBFM with SCN can provide a higher friction torque, which increased by 30% to 50% compared with CBFM. The variable coefficient of CBFM with SCN changes from 674 to 52 with the rotating speed raised from 600 rpm to 3000 rpm, which shows that the friction stability is relatively worse. Furthermore, the micromorphology shows that the CBFM with SCN has lower porosity and surface roughness, which increases the microscopic contact area and the coefficient of friction (COF). Simultaneously, the reduction in porosity also leads to a decrease in the cooling quality, bringing about a rapid temperature rise. Thus, the wear amount of CBFM with SCN increases significantly, especially for the friction disc in the axial middle position.
Highlights
The wet clutches are mainly used to transfer and cut off the torque from the engine to the axle, change gear, and locking-up components to prevent motion [1,2,3]
Friction materials play an important role in the wet clutch which is required to have an adequate coefficient of friction (COF) and a low wear rate [7,8,9]
The copper-based friction materials (CBFM) is a kind of material that consists of the copper matrix, abradant, lubricant, and pores [13]
Summary
The wet clutches are mainly used to transfer and cut off the torque from the engine to the axle, change gear, and locking-up components to prevent motion [1,2,3]. Wet clutches used in heavy vehicles are under high energy density friction conditions which should possess stable and excellent friction-wear characteristics to ensure effective work performance and the long service life [4,5,6]. Friction materials play an important role in the wet clutch which is required to have an adequate COF and a low wear rate [7,8,9]. Compared with PBFM, CBFM has better compact resistance, a steady COF, and excellent mechanical properties [11,12]. The copper matrix is the main component of CBFM, and the physical and mechanical properties of the matrix largely determine the overall friction-wear performance of friction materials [14]. The excellent physical and chemical properties of copper provide good thermal conductivity, stable friction performance, and low wear of CBFM [15]
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