Research On The Influential Factors For Friction And Wear Behavior Of A Pantograph-Catenary System Under Ac Passage

From the view point of ecology and economy, electrical traction is the best way in various railway tractions. The pantograph-catenary system is the key part of the electric locomotive getting driving power. With the development of electrified railway, especially the construction of high-speed railway, the pantograph-catenary system needs a better performance. Currently, the wear of the pantograph-catenary system under AC passage has become one of the key problems in the development of high-speed railway.In this dissertation, experimental study on effects of the contact pressure, velocity fluctuation and change of electric current on friction and wear behavior of carbon strip/copper contact wire under AC passage was conducted, and the abnormal wear of strips under the same contact pressure, the same sliding velocity and the same electric current was studied. A series of tests were tested on a ring-on-block test machine. The results were summarized as follows:(1) The contact pressure has an effect on the worn surface morphology. The main wear mechanisms during the sliding process under AC passage are abrasive wear, arc erosion wear and material transfer. The main wear mechanism is abrasive wear when the contact pressure is higher. And the main mechanism is arc erosion wear when the contact pressure is lower. The change of friction coefficient with time may be divided into two stages:an initial transition stage and a later stable stage. Reducing the contact pressure can increase the duration of the transition stage, in other words, the duration of the system entering a state of dynamic balance. The friction coefficient is decreased with the increase of contact pressure. The wear process may also be divided into an initial transition stage and a later stable stage. The wear rate of the strip in the transition stage is larger than that in the stable stage. The wear rate of the strip in the stable stage is first decreased and then increased with the increase of contact pressure. In addition, arc discharge power and off-line rate are decreased with the increase of contact pressure. The contact pressure in a certain values has a little bit effect on the current-carrying efficiency. The wear rate of the strip in the stable stage is directly proportional to the average energy of arc. When the contact pressure is lower, occurrence of severe arc (the arc voltage is larger than40V) is maybe attributed to a sudden change of the strip vibration amplitude.(2) With the increase of sliding velocity, the wear rate of the strip, the arc discharge power and off-line rate are increased, and the friction coefficient has a little change. With the increase of the amplitude of sliding velocity fluctuation, the change of the friction coefficient gradually trends to be regular. That is that the maximum of the friction coefficient always corresponds to the change point of the velocity from deceleration to acceleration (or from acceleration to deceleration), and the minimum of the friction coefficient arises during the process of acceleration or deceleration. When the amplitude of sliding velocity fluctuation increases to a certain value, the wear rate of the strip, off-line rate and average energy of arc are larger than those when the amplitude of sliding velocity fluctuation is zero. A constant sliding velocity is one of the methods available to reduce wear.(3) With the decrease of electric current, the friction coefficient is increased and the wear rate of the strip is decreased. Under the same electric current gradient, the gradient of the arc discharge power is the same. But the gradient of the friction coefficient under the electric current from50A to0is larger than that under the electric current from250A to50A.(4) Under the same conditions of the contact pressure, the electric current and the sliding velocity, abnormal wear of the strip in the friction sliding may be related to the acceleration in the beginning of the test. And the strip abnormal wear is related to the strip vibration, the arc ablation and the temperature distribution. The stronger the strip vibration, the more the strip wear. The larger energy of arc discharge, or the higher temperature of the strip, the more the strip wear.