The nut of the connecting rod bolt starts to loose under the action of alternating load

The damage of the connecting rod bolt is usually caused by the fatigue of the material in the stress concentration part. The main factors of fatigue damage are as follows: (1) excessively tightening the nut to make the connecting rod bolt deform and elongate; (2) bearing clearance (3) mechanical damage of the connecting rod bolt; (4) the bolt head or nut of the connecting rod is not perpendicular to the bearing surface on the connecting rod; (5) the pre-tightening force of the connecting rod bolt If the specified value is not reached, the nut is too loose; (6) the bearing is overheated.

In order to avoid or reduce the above fatigue damage, the connecting rod bolts are required to select materials with high strength and good plasticity. At the same time, the outer surface should be inspected for signs of nicks, scratches, cracks, burrs or knocks before non-destructive testing. In addition, improper assembly is also an important cause of damage to the connecting rod bolts. The connecting rod bolts must be properly inspected and assembled, otherwise it will cause additional stress or local stress concentration, resulting in a fracture accident.

After the connecting rod bolt is pre-tightened, the nut is locked by the split pin. The split pin used for the nut on the connecting rod bolt shall be a standard pin made of steel, and shall not be replaced by a wire, a nail or a tapered pin. The hole through the split pin should be drilled after the connecting rod bolt is pre-tightened. The pin hole diameter should match the split pin to prevent the split pin from moving in the pin hole. If the clearance between the split pin and the pin hole is too large, the split pin will be rubbed by the reciprocating force in the pin hole to cause the split pin to wear. When the wear is severe, the split pin breaks and falls off from the pin hole, and the nut of the connecting rod bolt Under the action of the alternating load, the loosening starts, causing the connecting rod bolt to lose the fastening effect and causing fatigue fracture, resulting in a major equipment accident.

Mounting Equipment

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