Research On The Influence Of Microscopic Characteristics Of Contacts On The Contact Performance Of Railway Relay

The railway system plays an increasingly important role in people’s daily travel.Railway relays are widely used in railway control systems and are an important component of railway systems.Their long-term safety and reliability directly affect the stable transportation of railways.Therefore,it is necessary to study the contact performance of railway relays.Contact surface morphology changes and pollution directly affect the contact performance of the contacts.In this paper,the railway relay after constant temperature stress accelerated life test is taken as the research object,focusing on two aspects of the contact surface micro-topography and surface contaminant composition,to analyze the mechanism that affects the contact performance of the contact.Firstly,this article briefly describes the test plan and test conditions,and briefly describes the internal structure and working principle of the relay.Secondly,the relays after the test are disassemble,and the three-dimensional roughness parameters of the dynamic and static contacts are calculated.The gray correlation analysis method is used to analyze the correlation between the contact resistance and the roughness parameters S_z,S_a,S_q,S_p,and S_v.The analysis shows that the contact resistance of the relay has a strong correlation with each roughness parameter.The roughness of the dynamic and static contacts surface affects the value of the contact resistance.Compared with the static contact,the change of the topography of the moving contact surface has a stronger correlation with the contact resistance,and has a greater influence on the contact resistance of the relay.Then,the image processing is applied to the extraction of the contact ablation area,and the perimeter and area of the ablation area are calculated.In order to improve the accuracy of detection,various pre-processing is performed on the topography of the contact surface.The relationship between the size of the ablated area and the contact resistance was analyzed using the gray correlation analysis method.The results show that the size of the ablation area on the surface of moving contact is more closely related to the contact resistance than the static contact.Combined with the analysis results of the correlation between roughness and contact resistance,it can be seen that the change in the topography of moving contact surface has a greater impact on the contact performance of the relay.Finally,scanning electron microscopy and X-ray photoelectron spectroscopy analysis methods are used to analyze the element composition and valence state of the contact surface after the test to infer the source of compounds and surface contaminants generated on the contact surface.After the test,a significant material transfer phenomenon from the static contact to the dynamic contact occurs between the contacts.After elemental analysis of the contact surface,it is found that a contaminated film is formed on the contact surface after the test.After the test,Si pollution was introduced into the contact part;under the action of arc discharge,the organic matter in the contact surface and the environment burned to generate C-containing substances to deposit on the contact surface;the contact surface after the test have Ag element,Ag₂O and Ag₂CO₃,and there is a substance conversion between the two;the surface silver material oxidizes,and the O element is mostly located in the contact part.At the same time,the surface material of the contact also chemically reacts with the corrosive atmosphere in the air,generating compounds with poor conductivity such as Ag Cl,which makes the surface resistance of the contact surface increase and the contact performance deteriorates.In this paper,through the analysis of the micro-topography characteristics and pollutant composition of the surface of dynamic and static contacts after the test,from the perspective of the mechanism that affects the contact performance of the relay,it is obtained that the surface morphology and pollution both affect the contact performance of the relay It has certain theoretical guiding significance for the improvement of relay contact materials,the production and processing technology of contacts and the degradation of relay contact performance.