Research On Thermal Shock Damage Mechanism And Detection Method Of Carbon Strip Of Pantograph

As a major national economic artery and mass transit,high-speed railways play an important role in China’s economic and social development.As a key collector element for energy acquisition by high-speed trains,an accurate understanding of its damage mechanism and condition testing is essential to ensure that the pantograph network is reliably subjected to flow.Statistics show that Joule heat and thermal shock caused by arcs during high currentcarrying capacity operation of the pantograph network have become important causes of structural damage to the material properties of the slider.Therefore,based on the operational characteristics of the sliding electrical contact of the bow network system of high-speed trains,it is of great theoretical research significance and engineering application value for the development of high-speed railways to carry out research on the mechanism of pantograph sliding plate thermal shock resistance performance and effective thermal shock damage detection.The pantograph network relationship is one of the three fundamental relationships of high-speed railways.The simulation test platform established in this paper originates from the two types of operating conditions that the train field operation requires the pantograph sliding plate to be able to adapt to: current-carrying friction conditions when the bow network is in good contact and off-line arc erosion conditions when the bow network is in poor contact.With the significant increase in train speed and traction power,the thermal erosion between the pantograph networks is significantly increased and arcs are frequent when running highspeed trains.The pantograph sliding plate is subject to thermal shock from the pantograph system,causing porosity or cracks in the internal structure of the sliding plate,resulting in chipped edges and even fractures.These pantograph sliding plates are abnormally damaged,causing frequent failures and seriously affecting the safe and stable operation of electric locomotives.In this paper,based on the establishment of a thermal shock test platform for pantograph sliding plates under simulated operating conditions,the effects of thermal shock on the surface morphology,internal structure,electrical and mechanical properties of the carbon material of the sliding plates are comprehensively analysed,and a thermal shock damage model for contact current-carrying/offline arcing of pantograph sliding plates is constructed.Long-time thermal shock simulation tests were carried out to investigate the effect of thermal shock temperature difference on the porosity,friction coefficient and compressive and flexural strength of the material,to analyse the thermal shock performance of the carbon material under current-carrying friction conditions,and to explain the thermal shock damage mechanism of the carbon material.A short-time off-line arc thermal shock simulation test was designed for skateboards.The effect of arc thermal erosion time on the material phase morphology,mass loss rate and resistivity was investigated,and the key factors influencing the thermal shock resistance of skateboard carbon materials under extreme arc conditions were revealed.A comprehensive study of the change pattern and mechanism of action of thermal shock on the damage characteristics of pantograph carbon skids reveals that the electrical and mechanical properties of pantograph skids exhibit different degrees of deterioration after thermal shock,and that the traditional apparent inspection methods are unable to identify internal thermal shock damage,requiring the development of new methods for damage detection.Through systematic experiments,it is found that porosity can be used as a characterization parameter for thermal shock damage of carbon materials in pantograph sliding plates,and a method for in-situ detection of thermal shock damage using ultrasonic waves is proposed.The mapping relationship between ultrasonic parameters and thermal shock damage and the correlation mechanism between structural characteristics-detection parameters-mechanical properties were established to quantitatively assess the thermal shock damage of the pantograph sliding plate material.The ultrasonic technique is used for the in-situ inspection of carbon porous materials to transfer the change in porosity of the carbon material to the change in interfacial properties,thus quantitatively characterising the structural property damage of the carbon porous material caused by the thermal shock.The ultrasonic wave velocity slows down with increasing thermal shock differential during pantograph slide plate thermal shock damage detection.A method is proposed to evaluate the degree of thermal shock damage to the carbon-based porous material of the pantograph slide,which provides strong support for ensuring the service safety of the arch network system.