Rail Pad Material Properties and Cushioning Effect
- What are the common materials for under - rail pads? What are their cushioning characteristics?
Common materials include natural rubber, which has good elasticity and excellent cushioning performance, can effectively absorb train vibration, and is suitable for high - speed railways, but has poor oil resistance and aging resistance. Styrene - butadiene rubber has lower cost, slightly inferior cushioning performance to natural rubber, and improved aging resistance, often used in ordinary railways. Chloroprene rubber has good weather resistance and wear resistance, stable cushioning effect, and is suitable for harsh environments such as humidity and dust. In addition, polyurethane material has adjustable hardness, strong bearing capacity and long - lasting cushioning performance, suitable for heavy - haul railways.
- What impact does the hardness of the material have on the cushioning effect of under - rail pads?
The cushioning effect is the best when the material hardness is moderate. For example, rubber pads with Shore hardness of 60 - 70 degrees can produce moderate deformation when bearing load and absorb impact energy. If the hardness is too high (exceeding 75 degrees), the pad has high rigidity, the cushioning capacity decreases, and the train vibration is directly transmitted to the sleeper, aggravating component wear. If the hardness is too low (below 55 degrees), the pad is prone to excessive compression, leading to excessive rail sinking, affecting track smoothness, and shortening the service life of the pad.
- What are the differences in requirements for the cushioning effect of under - rail pads in different line types?
High - speed railways require excellent cushioning effect of pads, which need to reduce the train vibration acceleration by more than 30% to ensure driving stability, and high - elastic rubber or polyurethane pads are mostly used. Heavy - haul railways need to balance cushioning and bearing, requiring the pad to maintain stable cushioning performance under large loads, and chloroprene rubber pads with hardness of 65 - 70 degrees are usually selected. Urban rail transit has high requirements for noise reduction, requiring the pad to have both cushioning and sound absorption functions, and porous rubber pads are often used.
- How to test the cushioning effect of under - rail pads?
Dynamic compression test can be carried out to simulate train load applying alternating pressure to the pad, measure the deformation and rebound speed of the pad. Those with moderate deformation and fast rebound have good cushioning effect. Through vibration test, install the pad on the test track and measure the vibration amplitude when the train passes. The more the amplitude decreases, the better the cushioning effect. The dynamic - static stiffness ratio of the pad can also be tested. The smaller the ratio, the more stable the cushioning performance, and generally the ratio is required to be no more than 1.5.
- How do environmental factors affect the cushioning performance of under - rail pads?
High - temperature environment will soften the rubber pad, reduce its hardness, and make the cushioning performance unstable. In high - temperature areas, high - temperature resistant materials should be selected. Low - temperature environment will cause rubber to harden, reduce elasticity, and decrease the cushioning effect. In cold areas, low - temperature resistant rubber should be selected. Humid environment may make the pad absorb water and expand, affect dimensional stability, and reduce the cushioning effect. It is necessary to select materials with good waterproof performance, such as chloroprene rubber.