We adopt analog simulation method of Monte Carlo in this paper. Under the circumstance of different prior information, in this paper we also make researches on the value assessment accuracy of the samples’ total parameters of up-and-down and langlie methods, and figure out the application condition and range of these two sensitivity experimental methods.
For the high speed train, safety is the most important factor. Flash welding is the primary technology for the seamless line rail in Chinese railway. So the quality of the flash welded joints is the most important. This paper presents the situation of joint fracture in rail flash welding joints and analyses the failure mechanism through macroscopic and microscopic observation. The result demonstrate that the cracking of the rail is fatigue-crack propagation,the fatigue cracking is caused by alumina calcium-Aluminates-non-metallic inclusion.
The technology of lightening manufacture for aluminum alloy train body is one key of manufacturing high-speed train . The train body is a whole bearing loading tubular structure which is welded together by the large, hollow, thin-walled aluminum extrusion. Therefore,the demand for welding quality of aluminum alloy train body is very high,and the mechanical properties of joints severely affected the overall strength of welded components. To solve this problem ,we use the 421 EXPERT forceArc MIG of PHOENIX series of German EWM company to perform three types of experiments of single pulse, double pulse, and forceArc welding ,and then effect of three welding methods on mechanical properties of Welding joint for 5083 aluminum alloy used in high-speed train body is compared.
The fracture of U71Mn rail welded butt joints on flash welding was analyzed by using visual observation, metallographic microscope, SEM and EDS from macro to micro.The results show that, the transverse fracture is rail oval flaw and the fracture mechanism of the rail is fatigue-crack propagation. The fatigue cracking is caused by silicate-non-metallic inclusions which are residues in the welded joints after flash welding.
The residual stress,which is unavoidable in the process of flash-butt-weld rails,plays important roles in the service life of the railway rails.Residual stress can and do change in service.In this paper,the distribution of initial residual stress was presented,and the redistribution was measured after 2×106cycles as well.The result shows that residual stress would change after appling fatigue loading.After 2×106cycles,the residual stress of some tested places increased while others decreased,the state of the longitudinal residual stress in the side region and the foot region has not changed,which still presented compressive,while the change of the longitudinal residual stress in the head region and the foot region does not present general tendency. In the transverse direction,residual stress in the head and side head regions decreases while the foot region shows opposite change.
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