| The electrified railway has become a main type of China's railway transportation due to its excellent characteristics such as high speed,large transport capacity and the advantages of safety and comfort.The pantograph/catenary system is one of the most important parts of the electrified railway,and it is also one of the key technologies needed to be broken through with the increasing speed of the electrified locomotive.The pantograph strip and the contact wire make up a pair of high-speed sliding friction with electrical current in complicated environments.The pantograph strip of the electrified locomotive obtains electric energy from the catenary wire through sliding electric contact of at the pantograph/catenary system high speeds.However,the service life of the pantograph strip is short due to its serious wear in bad service conditions.Therefore,it is of great practical significance to study the friction and wear behaviors of the pantograph strip/catenary with electrical current,which is the basis to develop the electrified railway.A series of tests on the friction and wear behaviors of the pantograph carbon strip/catenary with electrical current have been conducted on a ring-on-block friction and wear sliding tester at a high speed in this paper.The effects of voltage on the friction and wear behaviors and temperature rise of the pantograph carbon strip have been studied mainly,and the following conclusions are obtained:1.The temperature rise of the carbon strip and the arc discharge energy between the carbon strip and contact wire increase with the increasing of the voltage,and show a trend of increasing sharply first and then kept stable gradually for different normal forces and sliding speeds.The current-carrying efficiency also increases with the increasing of the voltage,and shows a trend of approximately linear increasing with the voltage.2.The wear rate of the carbon strip increases with the increasing of the voltage,and shows a trend of increasing sharply first and then kept stable gradually with the voltage,The friction coefficient of the carbon strip is higher than the friction coefficient without voltage.The friction coefficient of the carbon strip decreases with the increasing of the voltage,and then is close to the friction coefficient without voltage.The wear rate of the carbon strip presents a strong and positive linear correlation with the temperature rise of the carbon strip and the arc discharge energy.The correlation coefficients are 0.94651 and 0.96248,respectively.3.The wear morphology of the carbon strip shows great differences under different voltages.When the voltage is 3.5 V,the main friction mechanism of the pantograph/catenary system is mechanical wear and slight electric ablation appeared in the contact area.When the voltage is 167 V,the wear of the carbon strip is mainly caused by arc erosion,and the surface of the carbon strip showed a large number of uneven arc ablation pits and a small number of cracks.When the voltage is 667 V,uniform arc ablation pits and a large number of tiny cracks are observed on the surface of carbon strip.In this case that time,serious arc erosion is a main wear mechanism.4.Within the presence of electrical current,the increasing of the normal force can improve the friction and wear behaviors of the carbon strip,and the voltage is greater,the effect of this promotion is more obvious.The increasing of sliding speed aggravates wear of the carbon strip.When the sliding speed is bigger than 150 km/h,the wear of the carbon strip is more serious.The effect of the sliding speed on the friction and wear behaviors of the carbon strip is due to the instantaneous change of the normal force between the carbon strip and the contact wire,which changes the stability of the pantograph strip/catenary system.Compared with those effects of the normal force and the sliding speed,the effect of the voltage on the friction and wear behaviors of the carbon strip is more significant. |
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