Compression Permanent Deformation of Rail Pads on Fastener System Stiffness
Q1: What factors determine the compression set of under-rail pads?
A1: Material formula, hardness, service temperature, load magnitude and action time jointly determine it. Rubber pads are more prone to large permanent deformation than polyurethane pads.
Q2: Why does deformation lead to a decrease in clip clamping force?
A2: Thinning of the pad moves the clip working point downward, reduces the clip deformation, and thus reduces the clamping force. The rail restraint is weakened, and both gauge stability and lateral resistance decrease.
Q3: What impact does stiffness degradation have on track vibration and noise?
A3: Poor pad elasticity and increased stiffness reduce vibration absorption capacity, increase wheel-rail impact, and significantly raise vibration and radiation noise, affecting riding comfort and surrounding environment.
Q4: Why does permanent deformation of pads develop faster in high-temperature seasons?
A4: High temperature softens the material, reduces creep resistance, accelerates the accumulation of plastic deformation under continuous train load, and the deformation is significantly higher than that at normal temperature.
Q5: How to delay pad permanent deformation through material selection?
A5: Select high-elasticity, low-creep polyurethane pads or modified rubber pads; reasonably control pad hardness; prioritize long-life high-performance pads for important lines.