Cushion Classification and Function Classification of Track Rubber Pads

Classification of rubber pad under rail:

1.Classified according to different laying positions

The rubber pad under the rail is bounded by the iron backing plate, and is divided into the elastic cushion on the iron backing plate and the elastic cushion under the iron backing plate. An elastic cushion applied between the steel rail and the concrete sleeper, which can directly buffer and damp the load on the concrete sleeper, and at the same time improve the elasticity of the elastic cushion under the rail. This con not only reduce the sinking of the track, but also play a significant role in maintaining the smoothness of the track and reducing the workload of maintenance and repair. Among them, the elastic cushion under the iron backing plate is widely used on Chinese rails. There are mainly WJ-1 type fasteners, WJ-2 type fasteners, and WJ-7 type elastic cushion under the pillow: it is used for sleepers. A kind of elastic pad between sleeper and ballast. Laying an elastic cushion under the sleepers can effectively reduce the vehicle dynamic load transmitted to the track bed, thereby improving the dynamic load distribution performance of the track and buffering the dynamic effect of the train.

Elastic cushion under ballast: the elastic cushion under ballast can be divided into elastic cushion under ballast and elastic cushion under concrete foundation. It is a kind of elastic pad used for the surface of ballast and subgrade bed. Laying an elastic cushion under the ballast bed, reduces the compressive stress transmitted form the gravel ballast layer to the roadbed protection layer, reduces the crushing and pulverization of the ballast, thereby protecting the good geometric state of the track and improving the rail surface smoothness.

2.Classification according to different structures

The elastic cushion under the rail has a flat structure, a groove structure and a nail structure. Due to the development of the rail transit industry, the comprehensive performance of the traditional ballast bed, sleeper and elastic backing plate with flat structure has been difficult to meet the requirements of increasing total weight and axle load of heavy-duty trains in the world, and the continuous improvement of traction force. The elastic backing plate with groove and nail structure provides high resilience through deflection and shear deformation, and the elastic recovery speed is fast. Under the action of vertical dynamic force, the deformation amplitude is large and the dynamic stiffness is low, which can give full play to the elastic pad. Therefore, the groove and plate nail structure can be used to design a large elastic backing plate with good seismic isolation performance.

The function of the elastic underlayment under the rail:

The elastic cushion is an integral part of the fastening system for heavy-duty lines. Among them, the elastic cushion under the rail is applies under the rail. The system is electrically insulated.

The elastic cushion materials of heavy-duty fastener systems used at home and abroad include rubber materials, plastic materials, thermoplastic foam materials. Among them, rubber materials are easy to age and have a short service life, plastic materials have high rigidity and poor dynamic mechanical properties. Thermoplastic elastomer materials and micro-foam materials have excellent flexibility at room temperature and low temperature, excellent resistance to flex cracking, high elasticity and stress relaxation resistance, creep performance, and are more used in elastic cushions.

The elasticity of the track is mainly provided by the granular track bed and the rail cushion, which has the function of shock absorption and isolation. For concrete rail foundation, the good elasticity of the under-rail cushion is more important. The fasteners with rail underlayment used in China’s heavy-duty railways mainly include elastic type I height adjustment fasteners, elastic type II fasteners, elastic type III fasteners, WJ-I2 type fasteners, TP7 type fasteners, etc.