Study On Friction And Wear Performance Of Brake Blocks For Oil Drilling Machine

During the working process of oil drilling brake system,the whole system needs to be braked frequently.The energy generated during braking is rapidly converted into heat energy,which causes the surface temperature of the brake block to rise rapidly.Therefore,the friction and wear resistance and thermal degradation resistance of the brake block materials directly affect the stability and safety of the brake system.At present,the oil drilling brake system is mainly disc brake system.In the oil drilling deep well operation,the brake time of disc brake system is longer,so the friction contact surface temperature is higher,and the performance of the brake block material is also required higher.The traditional oil drilling brake block contains asbestos,which is widely used because of its stable friction coefficient,good wear resistance,low cost and non damage dual material.However,in the use process,asbestos and its high temperature decomposition products have strong carcinogenic effect,so the friction products containing asbestos have been listed in the elimination products.Therefore,the research and development of new wear-resistant and heat-resistant friction brake materials which can replace asbestos is the development direction of friction materials at present,and is also the further guarantee for the safety and stability of oil exploitation.In this paper,a certain amount of glass fiber is used instead of asbestos to form a non asbestos hybrid fiber friction composite with phenolic resin and wear-resistant filler as the main components.The friction and wear properties of the brake block reinforced with glass fiber and asbestos are compared and analyzed under the same conditions of other components.The temperature field and stress field of the two materials under friction braking are simulated and analyzed by using ANSYS software.The influence of braking load,friction speed and time on the temperature field and stress field is discussed,which provides theoretical and experimental basis for glass fiber replacing asbestos.The results show that:1.Under 130?170N load and 200r/min?400r/min test conditions,the friction coefficients of glass fiber and asbestos materials are the same with the change of load,and with the increase of load,the friction coefficients increase.However,the change of friction coefficient with friction velocity is not obvious when the load is fixed.The friction coefficient of glass fiber material is between 0.33 and 0.40,and that of asbestos material is between 0.35 and 0.43.In comparison,the friction coefficient of asbestos type brake block is slightly higher and the variation range is smaller.The difference of friction coefficient between the two materials is very small,which meets the performance requirements of friction coefficient of friction brake materials.2.The comparison of the wear rate of the two friction materials shows that the wear rate increases with the increase of load when the friction speed is fixed.However,when the load is fixed,the wear rate is basically the same as that at low speed with the increase of friction speed.Under the experimental conditions,the wear rate of glass fiber brake block is 0.140-0.243x10^-7mm³/m,and that of asbestos brake block is 0.138-0.242x10^-7mm³/m.Compared with asbestos type material,the wear rate of glass fiber type material is slightly higher under certain load and certain friction speed,but the difference is very small,and the wear amount is in an order of magnitude.3.In the braking process of petroleum drilling brake system,the friction surface stress of glass fiber type and asbestos type friction materials increases with the braking time,and the stress value increases.At the beginning,the stress of the contact friction surface is not obvious,and presents irregular distribution.With the increase of friction time,the stress distribution gradually reaches a stable state,and the maximum stress always appears at the contact surface of the brake disc and the friction plate.The instantaneous maximum stress of glass fiber brake block is lower than that of asbestos brake block.4.The longer the friction braking time is,the higher the temperature is.The temperature of asbestos brake block is always higher than that of glass fiber brake block.Under the condition of 0.4MPa external braking force and 200r/min braking speed,the temperature of glass fiber type brake block is 57?,the temperature of asbestos type brake block is 75?,and the temperature difference reaches 18?,which is caused by the poor thermal conductivity of asbestos.5.The finite element analysis of temperature field shows that the temperature of brake block increases with the increase of friction coefficient.When the friction coefficient of glass fiber brake block increases by 0.035,the temperature increases by about 10%,and when the friction coefficient of asbestos brake block increases by 0.04,the temperature increases by about 13.5%,which is in direct proportion to the change of friction coefficient.The glass fiber type brake block has better heat resistance.6.According to the results of experiment and simulation analysis,the friction composite of non asbestos hybrid fiber type designed and prepared in this paper has good impact performance,friction and wear performance and heat aging resistance,and its density,impact strength,friction coefficient and wear value meet the requirements of service performance of oil drilling brake block.