How does the railway equipment fish plate crack?

After the crack of the fishplate of railway equipment is generated, it starts to expand slowly under a certain alternating load. This is the slow expansion area of the crack. When the crack expands to a certain depth, the remaining cross-sectional area of the component is not enough to withstand the alternating load. When it acts, the component will produce instability and fracture to form a quick breaking zone, and these two zones generally have obvious characteristics.
From the research on the failure of the fishplate, the main factors affecting the crack growth are the load condition and the material condition, among which the load condition includes many contents, it not only includes the size of the load itself, but also includes bad working conditions and The additional impact load and other forms of external force brought to the rail joint by a certain wheel-loaded vehicle speed and vehicle type. For example, the fastening bolts do not reach the specified tightening force, or the tightening force decreases due to the increased wear of the fishplate, which will increase the additional impact force at the joint; the increase of wheel load, the increase of vehicle speed, and the unevenness of the joint will also cause Joint stress increases. The condition of the material is very obvious, and a good material can ensure that the crack expands slowly.
Another important cause of fishplate cracks is the interaction between the rail and the fishplate. Therefore, how to reduce the adverse effects of this effect is a problem that remains to be studied and solved. In addition, in recent years, some people have noticed the effect of the fishplate on the steel plate while studying the cracks in the rail bolt holes, and found that the support form of the upper and lower slopes of the fishplate, that is, the wedge-shaped support, has caused vertical tensile stress on the rail waist. , this stress aggravates the cracks in the rail bolt holes. At the same time, we believe that only by considering the fishplate and rail as an inseparable system and studying the interaction between them can we ensure that the entire line has a good joint state and improve line operation.