| The brake drum and the brake pad are the most important components of the brake system.There is a strong study effort to improve their service life by reducing the wear.The bionic brake drum processed by laser technology has improved wear resistance and service life compared with normal brake drum.However,it also intensifies the wear of the brake pad as the friction coupling part,reduces the service life of the brake pad,and impacts the service life and maintenance cost of the brake system.Therefore,it is necessary to study the friction and wear between the bionic brake drum and the brake pad in order to master their wear law,control the wear rate,and match their service life reasonably for effective reducing brake maintenance cost.It has been proved in this dissertation that reasonable matching brake drum and brake pad wear is very important based on the theoretical analysis and calculation examples.The wear between the brake drum and the brake pad has been studied through the test based on the closed actual working condition.By analyzing the wear-resistance surface of some creatures,it is found that the biological surface combined with hard and soft characteristic has the advantage of the wear-resistance.By simulating such biological body surface,some hard unit bodies are processed on the brake drum base body which forms hard and soft surface features.This kind of brake drum is called a bionic brake drum.The acting force between the surface unit body of the bionic brake drum and the brake pad is analyzed by setting up a mechanical model which explains the reason why the bionic brake drum increases the wear of the brake pad.Through computer simulation and experiments,the influence of the bionic brake drum surface parameters on the mutual wear between the brake drum and the brake pad is studied.Based on those analyses and study,a new bionic brake drum has been developed,and the bionic brake drum is further optimized through test bench in order to reduce brake maintenance cost.The main research work in this dissertation is shown below,1.The reasonable matching of the service life of the brake drum and the brake pad is studied,and the reasonable matching relationship under the condition of reducing the maintenance cost of the brake is obtained.The calculation example and experimential mearurment show that setting the service life of the brake drum and brake pad based on this relationship can effectively reduce the brake maintenance cost.2.Experimental study on friction and wear between brake drum and brake pad is performed.The thermal fatigue factors based on the actual working condition are considered in this study.By comparing and studying the friction and wear of the normal brake drum and the bionic brake drum with the brake pad before and after thermal fatigue,it is found that the unit body on the bionic brake drum blocks the generation and expansion of cracks,improves its own thermal fatigue and wear resistance.However,contrarily,the wear of the brake pad has been increased and its service life has been shortened.For the grid unit bionic brake drum after 600 times thermal fatigues,compared with untreated brake dram,this bionic brake drum wear is reduced by approximately 42%,the length of the longest crack is reduced by 50%,and the number of cracks longer than 2mm is reduced by 52.4%.The law of friction and wear between the bionic brake drum and the brake pad is found,and the mechanism of reducing wear of the bionic brake drum is clarified,which created favorable conditions for the rational design of the bionic brake drum.3.Research on the contact mechanics between the bionic brake drum unit body and the brake pad was conducted.According to the different shape of the unit bodies on the bionic brake drum surface,the force and deformation between the unit body and the brake pad are analyzed by establishing the contact mechanics model.Based on this model,the friction and wear caused by the unit body to the brake pad are studied according to the Preston-Theory.The wear of the brake pad causedd by the point unit body is increased by more than 50%,and the wear of the brake pad caused by the striped unit body is increased by about 27%.The presence of unit bodies makes the original two-dimensional plane contact become a three-dimensional space surface contact,the two-dimensional plane friction becomes the three-dimensional space surface friction,which increases the normal pressure and the friction force between the brake drum and the brake pad,as well as the wear of the brake pad.This explains the reason why the bionic brake drum increases the wear of the brake pad.4.The influence of bionic brake drum surface topography parameters on friction and wear were researched.Through computer simulation analysis and experimental study of contact stress between the bionic brake drum and brake pad,the influence rule of bionic brake drum surface morphology parameters(unit body shape,height,arrangement spacing,arrangement pattern,and arrangement angle)on the force between the bionic brake drum and the brake pad and their wear is found.The influence mechanism of bionic brake drum surface morphology parameters on friction and wear is clarified,which creates the necessary condition for adjusting the wear matching relationship between them.5.Influences of the matrix material of the brake drum on its own wear and wear of the brake pad were studied.It is found that the graphite type and carbon content of the matrix material of the brake drum have a great impact on its thermal fatigue resistance,the self-wear resistance and the wear of brake pad.With the increasing carbon content of the brake drum material without biomimetic treatment,its own wear resistance is decreased,and further decreased after thermal fatigue.For the bionic brake drum with the low carbon content before thermal fatigue and after thermal fatigue,its wear is increased with the carbon content increase.When the carbon content exceeds 3.41%,the brake drum wear begins to decrease with the carbon content increase,which is opposite to the wear of brake pad.The change of pearlite content has little effect on the wear of the brake drum itself and on the wear of the brake pads,which does not exceed 5%.The hardness of the unit body has the positive contribution to increase the wear resistance of the bionic brake drum and the wear of the brake pad.The influence law of brake drum matrix material on wear is found,and the influence mechanism is clarified.The bionic brake drum matrix material can be determined according to this law reasonably.6.Bionic brake drum development and bench test research are performed.In this dissertation,the surface parameters and the material of the bionic brake drum are reasonably determined,and the bionic brake drum is developed according to the law of frictional wear between the bionic brake drum and the brake pad.Based on the test bench result,it is indicated that the thermal fatigue life of the developed bionic brake drum is increased by 27%(stripe feature)and 38%(grid feature)respectively,compared with the untreated brake drum.The wear of the bionic brake drum is reduced by 58%(stripe feature)and 62%(grid feature)compared with the untreated brake drum.The braking torque of bionic brake drum is more than that of untreated brake drum.When the moving speed of the truck is 60 km/h,the braking torque of the bionic brake drum of the stripe unit body is increased by 5%.The braking torque of the bionic brake drum of the grid unit body is increased by 9.5%,which improves the braking performance.On this basis,an optimized double-spacing unit body bionic model is proposed.Comparing with the original bionic brake drum,the bench test result of this double-spacing unit body bionic brake drum shows that its thermal fatigue life is increased by 13% and its wear is reduced by 5%.Through actual measurement and analysis,it is found that the bionic brake drum using the optimized model can reduce the brake maintenance cost by 3%.By reasonably matching the service life relationship between the brake drum and the brake pad,the overall maintenance cost of the brake is reduced by 8% furthermore. |
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