Research on the mechanical behavior of high-speed railway gear steel 20CrNi2Mo: Experimental and theoretical investigation

Gears are key components in the transmission system of high-speed railway trains, and their reliability is critical for the safe operation of trains. This study investigates the commonly used high-speed railway gear steel, 20CrNi2Mo, through systematic experimental and theoretical analysis. Based on the experimental results, it was found that the viscous effects of 20CrNi2Mo steel can be neglected, while the material exhibits significant changes in the hysteresis loop shape under cyclic loading. As the number of loading cycles increases, the hysteresis loop gradually becomes shorter and wider. Even when the applied stress is below the yield limit, initial deformation is primarily elastic, but plastic deformation and hysteresis loops develop over time. This phenomenon demonstrates a gradual reduction in the yield stress of the material under identical loading conditions, accompanied by a decline in elastic modulus. It further elucidates the evolution mechanism from elastic deformation to plastic failure during the fatigue process. Based on these experimental findings, the proposed constitutive model integrates improved fatigue damage evolution laws and coupling methods, incorporating elastic modulus and yield stress as damage factors. This model effectively explains material softening, hysteresis loop rotation, and widening observed during the fatigue process. Simulation results confirm that the model accurately captures the mechanical behavior at each stage of fatigue, with predicted life expectancy closely aligning with experimental outcomes. These findings provide a solid theoretical foundation and valuable reference for the failure analysis of gear transmission.