The Numerical Simulation For Hot-preflex Heavy Rail Straightening

Railway transportation is in rapid development period in China,especially the high-speed railway develops more rapidly in recent years. Increasinglyfast, frequent, large-capacity, and even heavy load of railway development demandsheavy rail with high purity, high straightness, high strength and high surface quality.In heavy rail production, hot-preflex cooling and compound straightening, as the lasttwo deformation processes, directly influence the shape of rail size, the residual stressand qualified rate.The ANSYS implicit thermal analysis software is adapted to simulate U75Vheavy rail cooling process. From the temperature field, stress field and bendingdeformation analyze the three stages of heavy rail cooling process, such as fastcooling stage, solid phase changing stage and slow cooling deformation stage; itfound the heavy rail deformation rule that bending trend is toward "rail head-railbottom-rail head-rail bottom-rail head", and the conclusion that preflex deflectionhas no effect on general rules in cooling process. Then, simulation temperature andstress are tally with the measured ones at value and distributed rules.Secondly, with the ANSYS/LS-DYNA explicit dynamics analysis softwarebeing used in compound straightening process, it analyzes the rules of the longitudinalresidual stress and straightness changing when heavy rail experienced the13plasticdeformation periods in succession, and those of compounded heavy rail whichconform to the measured at distributed rules. In order to search for the optimalregulation of compound straightening, the uniform experiment design method isadapted in paper, and with Microsoft Visual Basic program and SPSS for Windowssoftware, the experiment results are analyzed in visual analysis and regressionanalysis. It is found that the optimal regulation of heavy rail preflex-cooling-straightening, which concretes as preflex deflection of3.83mm, cooling12000seconds and straightening rollers reduction of19.2mm-11.2mm-7.9mm-3.5mm-12.0mm-6.0mm-2.5mm, and the conditioning methods of straighteningreduction for the optimal residual stress and straightness.Finally, this paper introduces the ANSYS implicit to ANSYS/LS-DYNA explicittransition method for heavy rail model converting between system, and theexploratory method of explicit-implicit solution for the elastic energy release instraightening system.In this paper, the numerical simulation and rule exposition for heavy rail coolingand compound straightening process have solved many left problems, complete theunderstanding of deflection rule and residual stress mechanism; it possesses theorybasis and reference value for establishment and optimization of heavy rail productionregulation; as to similar engineering numerical simulation, especially, the problem ofANSYS implicit-explicit, explicit-implicit and couple-physical field conversion and solution, it introduces the complete operation method and develops new idea.