After the crack of Fish Bolt occurs, it begins to expand slowly under a certain alternating load, which is the slow crack growth zone. When the crack extends to a certain depth and the remaining cross-sectional area of the member is not enough to withstand the action of the alternating load, the member will produce instability fracture and form a fast fault zone. These two regions generally have obvious characteristics.
From the failure study of Fish Bolt, the main factors affecting its crack growth are the load and material conditions, among which the load conditions include more content, including not only the size of the load itself, but also the adverse working conditions, a certain wheeling speed, vehicle type, and other additional impact loads and other forms of external forces brought to the rail joint. For example, the tightening Bolt does not reach the specified tightening force, or the tightening force decreases due to the increase in Fish Bolt wear, which will increase the additional impact force at the joint; The increase of wheel load, the increase of speed, and the uneven joint will also increase the joint stress. The condition of the material is very obvious, and the good material can ensure the slow expansion of the crack.
Another important cause of Fish Bolt cracks is the interaction between rail and Fish Bolt. Therefore, how to reduce the adverse effects of this effect is a problem to be solved. In addition, in recent years, some people have noticed the effect of Fish Bolt on steel plates while studying the hole cracks of rail bolts. It is found that the support form of the upper and lower inclined plane of Fish Bolt currently used, that is, the wedge support, causes vertical tensile stress on the rail waist, which aggravates the hole cracks of rail bolts. Railway equipment manufacturers believe that only by considering Fish Bolt and rail as an inseparable system and studying the interaction between them can they ensure that the whole line has a good joint state and improve the safety of line operation.
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