Unreasonable rail section causes bolt hole crack

According to the relevant data, the design of the rail section is unreasonable, and the rail waist is too thin, which is a cause of bolt hole cracks. The rail rail waist thickness is only 33, such thickness, under the action of the wheel rail, is prone to fatigue damage, resulting in bolt hole cracks. Wedge connection of rail joints.

China's rail joints are wedge-shaped joints. This type of joint can cause upward tensile stress on the rails when the bolts are too tight. According to the stress analysis of the round holes, it is easy to cause oblique cracks between the bolt holes, especially Especially in the first bolt hole at the rail end, in the actual maintenance, if the maintenance of the joint bolt is neglected, the bolt torque can not meet the requirements, resulting in poor joint rigidity, the two ends can not be evenly stressed, and it is easy to form dynamic irregularity. Long-term permanent geometric irregularity is formed. Under the impact of the wheel, the interaction between the splint and the rail hole is increased, and the bolt hole is cracked. At the same time, the torque is too small, and the rail is generated in the splint when passing the train. Excessive slippage causes the screw to contact the wall of the extrusion hole, causing plastic deformation of the hole wall to form stress concentration and cause cracks.

Especially in the northeast of China, it is located in a cold zone, the temperature is low, the rail shrinks, the space between the rail and the splint is reduced, the force of the hole wall is increased, and the crack is more likely to occur. There are weak places where the stress is concentrated in the bolt hole wall. If there are cracks, burrs, sharp corners, etc., there is no or no treatment during the replacement. Under the repeated action of the train load, stress concentration is easy to occur, resulting in rail hole damage.

There are weak links in the rail joints, such as low joints, wrong teeth, joint rail surface blockage, wear, ballast plate knots, joints and dark pits. Unevenness occurs on the surface of the rail head. Under the action of the train impact load, it is easy to increase the dynamic force between the wheel and rail and increase the damage to the weak links such as the hole wall of the rail bolt.

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