Study On Thermal Shock Damage Characteristics And Characterization Method Of Pantograph Strip

High speed railway plays an important role in social development for its advantages of fast running speed,high comfort and good punctuality.With an increment of running speed and load,the friction and wear of pantograph-catenary system and the frequent occurrence of arc would increase,resulting in the sudden increase of temperature in pantograph strip.On the other hand,the actual operation of high-speed trains might encounter such as rainfall and other natural weather changes,resulting in the pantograph strip temperature drop sharply.This sudden cold or sudden heat would lead to the thermal shock damage inside the pantograph strip,even endangering the running safety of high-speed train.At present,many scholars mainly focused on the study of thermal shock damage characteristics in rocks,concrete,ceramics and so on.There were few reports about thermal shock damage characteristics in pantograph-catenary system of high-speed railway.Only a few scholars have studied the effect of temperature rise on pantograph strip materials,but it was not clear that thermal shock effect acts solely on pantograph strip materials.Therefore,it was necessary to study the thermal shock damage characteristics of pantograph strip materials systematically,so as to provide theoretical basis for further development of pantograph strip materials with good thermal shock resistance.In addition,the complexity of the internal structure changes of pantograph strip after thermal shock damage made it difficult to evaluate its performance and damage.Therefore,the damage mechanism of strip materials under thermal shock was deeply understood,and a more scientific and reasonable evaluation method of damage degree of pantograph strip was established.It could be better solve the problems of low accuracy and low maintenance efficiency caused by current detection methods.In this paper,it will be divided into two stages to explore.The first is the research stage of thermal shock damage characteristics of strip material,and the second is the research stage of evaluation method for the damage degree of strip materials.Aiming at the first stage,the variation law of porosity of pure carbon composite strip materials was studied before and after thermal shock at different thermal shock temperatures,different cooling methods and different thermal shock times.The relationship between structural characteristics and static performance parameters(mechanical and electrical characteristics)of strip was discussed.The change process of surface morphology was observed.And the thermal shock damage mechanism of reversible damage and irreversible damage of pure carbon composite strip material was clarified.It provided a theoretical basis for reducing the thermal shock damage of pantograph carbon strip.Aiming at the research of the evaluation method for damage degree of the pantograph strip materials,in this paper,an ultrasonic evaluation method for thermal shock damage of pantograph strip was presented.The parameters of the ultrasonic probe used in the measurement were optimized by simulation modeling,and the accuracy of ultrasonic evaluation method was improved.On this basis,the ultrasonic characteristics of pantograph strip under different thermal shock damage degrees were explored,the correlation mechanism of ultrasonic-structural property-static performance was established.The accuracy of ultrasonic velocity evaluation method and ultrasonic time-frequency domain analysis method in evaluating the damage degree of pantograph carbon strip material was compared.It provided a more scientific and reasonable method for the problems of low accuracy and low maintenance efficiency in pantograph strip damage detection.