It is generally believed that such a network crack is related to the magnitude of the current during electroplating and the temperature of the electrolytic solution. We have consulted the factory on this issue and the explanations obtained are not very satisfactory. We think this is actually an unsolved technical problem. Undoubtedly, similar to the hollow hole chrome-plated cylinder liner, the mesh stripe is beneficial to improve the oiliness of the journal surface, especially during the starting and loading of the diesel engine, the oil film stored in the mesh pattern acts on the journal. Better protection. However, the chrome plating of the cylinder liner forms a mesh groove obtained by reverse plating, which is different from the mesh pattern formed by the iron plating layer of the journal. The results of practice prove that the crack of the damaged journal (generally above 2mm) is greatly expanded after a medium repair period, and the crack is greatly extended, and the degree of expansion is related to its initial state. At this time, the crankshaft cannot used. Therefore, the existence of the reticular cracks makes the service life of the repaired crankshaft generally maintain a medium repair period, and there are probably few that can continue to be used. If this is a technical problem that can be solved, then the non-etching iron plating technology has a very broad prospect for the repair of high-volume, serialized diesel engine crankshafts. Otherwise, from the perspective of economy, the diesel locomotive The significance of the repair of the damaged crankshaft of the diesel engine is very debatable.
Improvement measures Through the analysis of the above bolts, we believe that new bolt mitigation technology must be adopted. To this end, we designed and manufactured a new type of anti-stay shaft bolt. The working principle of the new anti-slip shaft bolts The anti-slowing effect of the bolts is mainly achieved by a nylon sleeve. The nylon sleeve of the new bolt is unthreaded. When the bolt is screwed into the body, the motor body thread is used as the die, and the nylon sleeve is extruded out of the thread to make the threaded joint form an interference form, relying on the good elasticity of the nylon and the high The coefficient of friction, so as to achieve a slowing effect. After using this new type of anti-slow bolt, we carried out the loading test on the locomotive No. 4020 in May 2000. After a mid-term repair period, during this period, the motor was replaced several times, and there was no loss of the axle bolt. In this time, we repaired 78 bolts, and only 6 bolts were used to prevent the nylon thread. Plastic deformation occurred, the integrity rate reached 9213%, 717% of the bolts can be used after replacing the nylon sleeve.
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