Investigate Of Design And Brake Properties For Resin Based Friction Materials

As the key part of the brake,the performance of the brake friction material is directly related to the safety and stability of the braking system.However,for the brake friction material of the existing mine mechanical brake system,there are some problems to a certain extent such as low friction coefficient,poor braking performance and short service life,difficult to meet the brake requirements especially in mining machinery such as large braking torque,high frequency braking and poor mining conditions.Aiming at the above problems,through theoretical and experimental research,the self-prepared resin based brake materials as the research object,this paper explores the effect of resin matrix,hybrid fiber,working conditions on the braking performance of friction materials and friction and wear mechanism,in order to provide theoretical and experimental basis for the research and application of high-friction and long-service-life resin based friction material.The straight phenolic resin（PF）,cashew nut shell oil modified phenolic resin（CNSLPF）,and epoxy modified phenolic resin（EMPF）matrix friction materials were prepared by P/M method.The tribological properties were investigated at different braking loads and speeds.The results indicated that CNSLPF specimen showed most stable friction coefficients and lowest specific wear rates;brake wheel matched with CNSLPF specimen showed lower wear.and friction film is relatively smooth and uniform,wear forms mainly to micro-plough and fatigue spalling.Four different contents of cashew nut shell oil modified phenolic resin matrix brake materials were prepared by P/M method.The results indicated that the hardness of the brake pads obviously increased with the increase of resin content.Friction coefficient and temperature on friction surface increased at first and subsequently decreased with the increase of brake loads and speeds.Higher surface temperature is helpful to reduce the friction coefficient fluctuation With the resin content of 26%²8%,the materials present excellent friction and wear properties at different braking loads and speeds.With cashew shell oil modified phenolic resin of 28% volume fraction as binder,using ceramic fibers,carbon fibers,minerals fibers,aramid fibers as reinforcing components,the orthogonal optimization design is performed by using L₉（3⁴）orthogonal test table.The effect of factors on friction materials is discussed through signal to noise ratio analysis and variance analysis and the final fiber ratio is determined.Research has shown that aramid fiber is the most significant factor,which can increase friction coefficient and reduce wear to the greatest extent;Ceramic fibers and mineral fibers is so brittle that it is not conducive to the improvement of friction material wear;Carbon fiber has a significant effect on wear because its lubricity and high thermal conductivity has important influence on the friction surface layer.Finally,under the two braking conditions of dry and wet,the variation of friction coefficient and wear rate with different braking pressure and braking speed were studied,and the wear mechanism was discussed.Under dry sliding conditions,the fluctuation range of friction coefficient is 0.36⁰.5,and the range of friction factor is 0.2⁰.4 under water braking conditions.Under dry and wet braking conditions,friction coefficient increases first and then decreases with increasing sliding speed,the maximum of friction coefficient move to the origin of coordinates with the increase of braking load.Under the condition of low-load braking,the variation curve of the friction coefficient is only the rising part,and the variation curve of the friction coefficient is decreased only under the condition of high load braking.Under dry sliding condition,the distribution of more debris and poor quality of friction contact surface,wear mechanism for three body wear,and accompanied by the generation and dissipating of secondary constant plateau,friction performance is unstable and wear is larger.Under water braking conditions,friction surface is smooth and surface quality is better,wear mechanism for cracks and furrows,lubrication,cooling and permeability of water helps to reduce friction coefficient and wear.