Tribological Characteristics Of Electrically Controlled Friction Damped Vibration Isolation Spherical Bearing For High Speed Rail Bridges

Spherical bearing has excellent bearing capacity,low friction coefficient and large corner,which is considered to have good seismic isolation capacity.However,the frictional wear effect of the spherical bearing developed at home and abroad is very limited under the actual service conditions,which causes the spherical bearing to be unable to play an effective role in seismic isolation when the seismic intensity is too large.at the same time,the spherical bearing also exhibits a wear effect lower than the design life in the normal environment.In this paper,we propose a spherical bridge bearing with low frictional wear in the conventional non-seismic condition,and actively increase the friction coefficient in high intensity earthquakes,which can increase the seismic energy dissipation by improving the frictional damping to achieve the purpose of seismic isolation.The specific research contents are as follows:Firstly,considering the real-time of regulating the friction coefficient,it was decided to regulate the growth of friction coefficient by means of electric current-carrying(Electric friction control),and the ionic liquid(IL)with good electrical conductivity was selected to replace the traditional insulating silicone grease as the basic lubrication response medium between the bearing friction subsets according to the current-carrying conditions,and nanoparticles were used as the reinforcing phase to synthesize and prepare the nanofluid composite lubrication response medium(IL-based nanofluids),and then the tribological test platform based on the current-carrying conditions was built to investigate the electronically controlled friction-increasing performance of the response media under the current-carrying environment and the lubrication and wear-reducing ability in the normal environment.The friction coefficient of IL under current-carrying conditions would change significantly under the action of current,and when the current strength reached a certain critical value,the friction coefficient would increase,and within a certain range,the higher the current strength,the more significant the frictional effect,it should be noted that too high a current strength would cause the accumulation of heat,softening the surface of metal materials to cause more serious adhesive wear,and the final determination of the current strength should not exceed 30 A.The addition of nanoparticles could further increase the friction coefficient of IL,which could be increased several times in a very short period of time.On the other hand,the longer the alkyl side chain of the IL,the weaker the effect of current on the IL,the smaller the increase of the friction coefficient with current under the same current intensity.And as the applied normal load increased,the effect of current on the friction coefficient gradually decreased,so that the effect of current on IL was most significant at the light load.Meanwhile,the effect of current on the growth of friction coefficient during the current-carrying process was real-time and reversible,and the growth and fall back of friction coefficient could be controlled by adjusting the strength of output current,while the mechanism of electronically controlled friction was the controlled formation and failure of lubricating adsorption oil film under the action of current.In the normal environment,IL showed excellent lubrication ability,compared with dry friction,when using IL lubrication between the friction pairs could maintain a low coefficient of friction and very low wear,the wear mechanism was dominated by abrasive wear.The addition of nanoparticles helped to further improve the lubricating effect of IL,and the higher the concentration of nanoparticles,the more significant the wear reduction effect.On the other hand,as the length of alkyl side chains of IL grew,the friction coefficient decreased and the lubrication and wear reduction effect became more excellent,while in a certain range,the higher reciprocating speed was also conducive to the better lubrication and wear reduction effect of IL.The higher normal load would lead to part of the lubricating medium was squeezed out of the friction contact area,which was not conducive to the performance of IL lubrication and wear reduction ability.The software Solidworks was used to establish the spherical bearing model,and the finite element software Workbench was used to carry out the static and dynamic analysis;the research results showed that: the improved material of the spherical bearing could still meet the design of the load-bearing requirements,and had a better ability to frictional energy consumption.