The Influence of the Dynamic-Static Stiffness Ratio of Rail Pads on Track Vibration Reduction Performance
Q1: What is the dynamic-static stiffness ratio of under-rail pads?
A1: Static stiffness is the stiffness under slow loading, dynamic stiffness is the stiffness under high-frequency train vibration, and the dynamic-static stiffness ratio is the ratio of the two. The smaller the ratio, the smaller the stiffness change of the pad under high-speed vibration, and the more stable the vibration reduction effect.
Q2: What problems are caused by an excessively high dynamic-static stiffness ratio?
A2: When the train passes at high speed, the pad stiffness rises sharply, the vibration reduction ability decreases, the wheel-rail impact increases, and the vibration transmitted to the sleepers and foundation is intensified. At the same time, the dynamic load of clips, bolts and other components increases, and fatigue damage accelerates.
Q3: Why are high-speed lines more stringent on the dynamic-static stiffness ratio?
A3: Under high speed, the vibration frequency is high and the impact is strong. If the pad stiffness increases significantly with frequency, it will destroy the track smoothness, cause vehicle shaking and noise increase, and even affect driving stability. Therefore, the dynamic-static stiffness ratio must be controlled at a low level.
Q4: What is the difference in dynamic-static stiffness ratio between rubber and polyurethane pads?
A4: The stiffness of ordinary rubber pads increases significantly at high frequencies, and the dynamic-static stiffness ratio is large; polyurethane pads have better material internal friction characteristics, smaller dynamic-static stiffness ratio, more stable stiffness, and are more suitable for lines with high smoothness requirements.
Q5: How to judge whether the pad is aging through the dynamic-static stiffness ratio on site?
A5: After aging, the pad has poor elasticity and hardened material, the dynamic stiffness rises faster, and the dynamic-static stiffness ratio increases significantly. If the stiffness ratio exceeds the standard range, the vibration reduction performance has attenuated and should be replaced in a timely manner.