1. Force analysis and design basis
The design of Track bolts is based on the precise analysis of the force of the track system. The track will be subjected to a variety of complex forces during operation, such as vertical pressure, lateral impact force, longitudinal traction and braking force generated by the train. For vertical pressure, the design of Track bolts must ensure that they can firmly fix the track to the foundation structure to prevent the track from sinking or deforming. This requires that the bolts have sufficient tensile strength to withstand the huge pressure transmitted by the track in the vertical direction.
When considering the lateral impact force, the connection structure and size of the bolts play a key role. For example, at the curve of the railway, the centrifugal force of the train will generate a large lateral force on the track. At this time, the design of the head and rod of the Track bolts must be able to effectively resist this lateral force and prevent the track from lateral displacement. Generally speaking, a larger bolt head size or a special lateral force resistance structure is used to evenly distribute the lateral force to the track and foundation components.
2. Material and strength matching
In order to meet the force requirements of the track system, the selection of Track bolt materials is crucial. High-strength alloy steel is one of the commonly used materials, which has high yield strength and tensile strength. During the design process, the minimum strength required for the bolt is calculated based on the maximum expected force that the track system will bear. For example, for heavy-duty railway tracks, the bolts need to withstand great pressure and impact force, so the yield strength of the selected alloy steel material may reach more than 800MPa.
The toughness of the material is also an important factor. During the long-term operation of the track, the bolts will be subjected to frequent alternating stresses, especially in sections where trains frequently start and stop. If the bolt material is not tough enough, fatigue fracture is prone to occur. Therefore, the selection of materials should take into account both strength and toughness. Through a reasonable heat treatment process, the bolt material can meet the strength requirements while having good toughness and can withstand long-term alternating stress without damage.
3. Structural design and force dispersion
The structural design of track bolts has a direct impact on meeting the force requirements. The shape and size of the bolt head are carefully designed, such as the hexagonal head or square head design, which is convenient for tightening with tools and also provides a large contact area. When connected to the track and foundation components, the washer or gasket under the head can further disperse the pressure to avoid damage to the components due to excessive local pressure.
The design of the threaded part is also critical. The thread type, pitch and length of the thread are closely related to the force transmission. For example, the use of fine thread can provide more bearing area under the same diameter and enhance the shear resistance of the bolt. Moreover, sufficient thread length can ensure that the bolt forms a stable connection between the track and the foundation component, so that the tension and pressure are evenly distributed on the entire connection surface, preventing the connection from failing due to stress concentration.
4. Preload and dynamic force adaptation
The preload design of Track bolts is an important part of meeting the force requirements. Appropriate preload can make the bolt in a preloaded state when the track is not subjected to external force, thereby enhancing the tightness of the connection. During the operation of the track, when subjected to dynamic external force, the preload can ensure that the bolt connection is always tight and prevent loosening.
When designing the preload, the dynamic force of the track system needs to be considered. For example, on the track where high-speed trains run, the vibration and impact force generated are large due to the high speed of the train. At this time, the preload force of the track bolts should be calculated and adjusted according to factors such as the maximum speed of the train, the operating frequency, and the vibration characteristics of the track to ensure that the bolts can meet the force requirements of the track system in a dynamic environment.
