Consequence of stiffness and damping coefficients of suspension system on critical speed of a rail vehicle running on straight and curved track

One of the most important cases in moving of trains especially in high speed trains is critical speed on straight and curved track. Generally for investigation of critical speed in railway vehicles, wheelset, bogie and or car body can be analyzed separately. In this paper a four axle rail vehicle is considered and equations of motion for complete vehicle and its single two axle bogie are derived separately on curved track. A computer program is developed in MATLAB software and these equations are solved in time domain and the critical speed is determined using response method. Effect of stiffness and damping coefficients of primary and secondary suspension system has been investigated on critical speed for the complete vehicle model and comprised with its single bogie model. Also, the effect of car body mass, wheel conicity and radius and also curve radius on critical speed have been studied. After analyzing of equations and obtaining graphs, it has been shown that changing of damping coefficient has more effect on critical speed than changing of stiffness coefficient. Increasing the radius of wheelset doesn’t have significant effect on critical speed. Also, decreasing of wheel conicity, increases stability but also it increases corrosion.