Preparation And Characteristics Of Potassium Hexatitanate Whisker Reinforced Heavy Duty Dry Clutch Facing

The automobile clutch is an important component to ensure the vehicle starts stably,shift smoothly and handle lightly.The clutch facing is the key part of the clutch assembly.The performance of the clutch facing affects the clutches’ lifetime as well as the efficiency,comfort and stability of power transmission directly.Domestic and foreign experts and scholars have conducted in-depth analysis and research on the influence of friction and wear performance of clutch facing,surface temperature,the effect of load and speed on friction coefficient;as well as the differences in friction and wear performance of different material formulas.However there is still a lack of comprehensive systematic research on friction and wear performance,thermal load performance,clutch facing life estimation,and start-up judder of the heavy duty dry clutch,which becomes a bottleneck restricting the development of heavy-duty trucks.High-end heavy-duty truck clutches have always been relied on the imported.Meanwhile High-end clutch facing have been monopolized by the three major foreign companies: Sachs,Schaeffler and Valeo.Therefore,it is imperative to study the performance of heavy truck clutch facing.The purpose of this thesis is to improve the excellent performance in terms of hightemperature resistance,wear resistance,low noise and other aspects of brake braking friction materials based on the urgent needs of the heavy truck market and by drawing on potassium hexatitanate whiskers.Through the positive development of a potassium hexatitanate whisker reinforce heavy truck dry clutch friction facing to solve the early abnormal wear of the existed clutch friction facing,ablation,start-up judder and other failures of clutch.That will be a theoretical guidance and data support for future research and development of clutch friction facings,research of clutch system friction pairs and selection of clutch friction materials.The main research and innovative results of this article are followings:(1)Based on the new introduction of QFD tools to determine the customer important requirements of heavy truck dry clutch facing and obtain the important evaluation indicators of heavy truck clutch facing such as slipping,burning,abnormal wear,environmental protection and noise.To develop a new environmentally friendly clutch facing formula to meet the importance needs of heavy truck customers by introducing the reinforced material with Potassium titanate whisker and using orthogonal optimization design method.(2)To analyze the influence of different material formulas and different potassium hexatitanate ingredient on the physical properties,internal shear strength,mechanical properties,wear performance and transmission noise of friction materials by applying the method of orthogonal testing design.The testing of small batch samples,bench testing and road testing proved that it can achieve the best resistance to thermal degradation,minimum wear and tear as well as reduce starting vibration by adding 8% to 10% potassium hexatitanate whisker in clutch facing.(3)A new green preparation technology of friction material is presented.During the preparation of the Potassium hexatitanate whisker reinforced heavy duty dry clutch facing,using the potassium hexatitanate whisker environmental protection materials instead of the copper,lead and other heavy metals at design source.The production process adopts solvent-free extruded environmental protection technology to replace the current non-environmental protection of organic solvent impregnation technology,waste recycling,etc.There is no exhaust gas,heavy metal and industrial solid waste pollution in the whole process of the new formula clutch facing,which meets the national energy saving and environmental protection requirements.(4)Bench testing confirmed that the potassium hexatitanate whisker reinforced heavy duty dry clutch friction material was significantly more resistant to thermal degradation than ordinary friction materials.Through the clutch bench test and the surface morphology analysis of the ablated friction facing as well as the tribology theory,the thermal decay of the friction plate was explained.It is revealed that the high temperature thermal decomposition of phenolic resin is the main reason for the thermal decomposition of heavy duty vehicle’s friction materials.(5)Based on the principles of the heat generation and transmission of clutch friction facing,a dynamic model of the heavy-duty starts the clutch was established to calculate the sliding wear,wear volume,and the start-up temperature rise generated by the clutch engagement at the starting.A formula for calculating the clutch wear life was concluded.According to the sliding wear to calculate the wear volume of the clutch at the first start,then calculate the average wear amount per kilometer.Thereby the wear life mileage was calculated from the allowed total wear amount of the clutch facing.And a prediction formula for estimating the lifetime mileage of the heavy truck dry clutch was proposed.(6)Established a judder model for automobile starting and pay important attention to the judder caused by self-excited oscillation of the clutch friction material itself.Judder bench testing proved that friction materials contain 8% potassium titanate whiskers could significantly reduce the starting judder.The method to reduce or eliminate starting judder was to develop and select friction materials with negative damping factors.Moreover the smaller the negative value of the average damping factor and the maximum damping factor of the clutch facing was,the better it had a significant attenuation effect on the starting judder.