Study On Fatigue Property Of Axle Bridge Weld Of Low-floor Light Rail

Welding is the key process of changing axle to bridge for low floor bus.In the production process of low floor bus welded axle bridge exported by Taichung group to the United States,there are different types of weld joints.The fatigue strength of the weld determines the quality of the axle bridge products,and then affects the safety and reliability.Once the fatigue failure of the weld occurs,it will seriously affect the safe operation of the vehicle.The thermal behavior of welding process is complex,and the weld toe is easy to have undercut,fine defects and stress concentration.The axle bridge of low floor passenger car is an important load-bearing and force transmission component in the operation of rail vehicles.It is particularly important to test or simulate the mechanical properties of the axle bridge in the use process,and then make a quantitative or qualitative evaluation conclusion.TIG Dressing is to repair the weld toe with proper welding specifications to improve the surface condition of the weld.TIG Dressing Technology can effectively improve the fatigue performance of welded joints and prolong the service life of welded structures with low cost.The popularization and application of this technology in the production of welded structures is of great significance.This paper analyzes the welding conditions,weldability and welding joints of low floor axle bridge materials,and carries out welding of axle bridge materials.The microstructure and mechanical properties of fillet welded joint before and after TIG Dressing and butt joint were compared.The static strength of axle bridge under different load conditions is analyzed by finite element method,and then the distribution diagram of static strength is obtained.The von Mises stress distribution diagram and fatigue life distribution diagram are obtained by finite element calculation on the basis of static strength.Finally,the change of surface temperature and fatigue life of samples under cyclic loading are analyzed by infrared thermal imaging method,and the change curve of material surface temperature under load is obtained,and the relevant data of fatigue crack initiation,propagation and failure are obtained.The fracture morphology was observed by SEM,and the improvement mechanism of TIG repair on fatigue property of joint was obtained.The relevant conclusions have certain reference value and guiding significance for the production and process optimization of similar products.