Reasons Analysis on Early Fatigue Fracture of Forging Transition Section of 200 km·h-1 Railway Turnout 60AT Switch Rail

For the situation that the forging transition section of 60AT switch rail for 200 km·h-1 railway turnout fractured early when fatigue test refering to TB/T 1354-1979, macro analysis and physicochemical performance test were done to the fractured rail, and the finite element solid model of the rail fatigue test piece was established and FEM force analysis was done. The results show that the biggest Mises equivalent stress ratio of rail bottom short leg and long leg was 2.26, and the maximum stress value obtained by finite element solution was 1.2 times of that by ayalytic method. The maximum stress position appeared at the short leg of variable cross-section beginning location. It coincided with the rail fracture source location during the fatigue test. So it could be conduded that the excessive load was the main reason of early fracture of forging transition section of the 60AT switch rail in fatigue test.