| In the field of automotive braking,friction material is one of the indispensable functional devices.The low-metal friction material is produced by a hot press process using metal fibers or reduced iron powder as a matrix,and it has the advantages of good thermal conductivity,stable friction coefficient,and low production cost.With the ever-increasing requirements for driving safety and comfort of passenger vehicles,the effectiveness and stability of braking materials for friction materials on brake pads have become a research hotspot for automobile and its parts and components companies,and the wear rate of low-metallic friction materials is high.High noise has always been a problem for engineers.Therefore,improving the braking performance of low-metallic friction materials through process research is of great significance for the development and application of new products.In this paper,based on the low-metallic friction material formula,DOE experiments were conducted by changing the friction-increasing materials and fiber-reinforced materials in the basic formulas to compare the effect of different material components on the characteristics of the friction material powder and the physical properties of the friction material.As a friction material formulation with stone,alumina particles,and iron oxide black as the friction-increasing material,a drying process must be added to reduce the moisture content of the powder.The stiffness and compression tests show that the hardness of the friction material and the hardness of the friction-increasing material are not in a binary linear relationship.With the same volume fraction,cellulosic fibers,steel fibers,and aramid pulp were used as hybrid fibers,and chromite was used as a friction-increasing material.The pressed brake pads had larger compression values and hardness values.At present,many scholars use the method of constant speed testing machine to study the friction and wear properties of friction materials.The test results are different from the actual driving brake.Therefore,this paper adopts bench simulation to evaluate the friction and wear of friction materials.The test procedure adopts Europe standard SAE J2522,the test results show that the average friction coefficient of the eight groups of friction materials is about 0.43 under braking at the normal road speed,and the friction coefficient is negatively correlated with speed and pressure.By analyzing the braking effect of the friction-increasing material group,it was found that a group with a larger friction material hardness has higher wear resistance,but the friction coefficient is not necessarily larger.The use of cellulose fiber and aramid pulp as reinforcing materials in the four commonly used fibers in the formulation can enhance the strength of the matrix and improve the thermal decay resistance of the friction material.The NVH(Noise,Vibration,Harshness)test is used to simulate the noise performance of the actual braking process.It is analyzed that the thermal decay reduces the friction coefficient of the material and also reduces the braking noise.Using cellulosic fiber and aramid pulp,or using acrylic fiber pulp and aramid pulp as the low-metal friction material,the pressed brake pad has good noise performance.The use of chamfered,riveted silencers can effectively reduce and eliminate brake noise. |
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