Research On Crack Identification Of Rail Tread Based On Dynamic And Static Response

As a component of the track structure that directly carries the train,rail will be subjected to a series of multiple cycles of dynamic and static loads,temperature loads,environmental factors,and possible base sinking during service.These loads make the rail susceptible to generate fatigue cracks or further enlarge the existing defects.If not in the early formation and expansion of rail cracks in the stage of timely detection,positioning and treatment,may eventually lead to serious defects and even failure of the rail structure,threatening the safety of traffic and leading to accidents when serious.According to the investigation results of the rail condition monitoring method,the current rail cracks detection methods can only perform periodic detection but not online monitoring.It is necessary to propose a new idea of online identification of rail tread cracks by using technical means such as distributed optical fiber sensors to investigate the feasibility of this idea by using finite element analysis method theoretically.In this paper,the static and dynamic simulations of the nondestructive rail and the rail with tread cracks are carried out by the finite element method.The static strain and strain modal results of the rail by constructing a damage index based on the strain information are analyzed.Taking the crack position,load position,crack depth and other information as variables,the ability of damage index to identify the crack position is investigated.The main research work and results of this paper are as follows:1.Based on the elastic foundation beam theory,the force and constraint characteristics of rail in track structure are analyzed theoretically;based on the theory of fracture mechanics,the redistribution characteristics of strain field at crack tip are analyzed theoretically;according to the actual rail cross section data of high-speed railway,local simplified finite element simulation models of nondestructive rail and rail with tread crack are constructed.2.The damage indexes based on static and dynamic strain response signals are constructed to carry out the identification and localization of cracks in rails under static and dynamic excitation,respectively.The results indicate that the damage indexes have a high ability to identify the crack location,and there is a positive correlation between the value of the damage index and the crack depth.Through the analysis of the results found that the restraint of fastener located in rail sleeper will have a greater impact on the identification of cracks.