Research On Braking And Wear Resistance Properties Of Cu-based Friction Plate

Brake pad is the key part to ensure the safety operation of vehicle.At present,the high speed brake disc depends on the import in our country.It lead to the high cost and it is an urgent need for localized friction plates to replace foreign products.In this paper,the Cu-based friction plate at particle enhancement,fiber hybrid and lubricating components is analyzed.The effects of particle reinforcement,fiber hybrid and lubricating elements on the wear resistance of Cu-base friction plates are studied separately under different loads and speeds.The surface microstructure of the specimens after friction is observed and the friction and wear mechanism is analyzed.The addition of Fe and Al copper matrix has an obvious enhancement than the pure copper matrix.And it greatly improves the friction and wear properties of the sample.The friction coefficient of the pure copper matrix is the most unstable and the wear rate reaches the maximum.The copper matrix samples with Fe and Al have relatively stable friction coefficient and lower wear rate.With the adding of Al into the Cu-based friction materials,aluminum bronze can be formed by combining Al with Cu elements.Aluminum bronze can increase the hardness of friction material.However,too many Al elements can lead to a blocky distribution due to liquid aggregation.The Fe element is not only combined with the Cu and Al in the matrix,but also is scattered in the debris.Fe can form a dispersed distribution of the micro convex body on the worn surface during the friction process,which makes the copper matrix strengthened.The micro convex body is embedded on the Cu-base friction material to form a surface which is hard to wear.It can isolate the direct contact between the sample and the dual surface,and plays a role of inhibiting wear.The curves of friction coefficient for Fe+Al specimens are more stable,and the wear rate varies little,showing the best tribological properties.The content of carbon fiber and copper fiber has little effect on the hardness of the specimen.And working layer with more iron and poor copper can be formed on the surface of Cu-based friction plate by iron-collecting effect of copper fiber and reduce the wear.The lubrication effect of carbon fiber is the most significant under high load.The combination of carbon fiber and a bit of copper fiber can stabilize the friction coefficient of the composite.At the same time,it can improve the brake and wear resistance of the copper matrix composite.The lubricating film formed by 5% graphite and 2% BN is relatively tight.These lubricating films have the effect to reduce the friction coefficient and wear rate.It can improve the wear resistance of Cu-base friction plates.Graphite has excellent lubricity at room temperature.BN can stabilize the friction coefficient of samples and improve the wear resistance of samples at high temperature.The friction and wear properties of Cu-based powder metallurgy friction materials can be improved effectively by the combination of h-BN and graphite with better friction performance than their use alone.A three-dimensional model of a car disc brake is established based on ABAQUS.And the stress distribution of the disc brakes under the action of the mechanical field(pressure stress and friction shear stress)and thermal stress field is analyzed.The effect of thermal stress is far greater than other stresses,and it plays a leading role in the analysis of the failure of disc brake.