Why Bolts Break？

Bolts, as a kind of fasteners, are still used in many places in daily life, but the same is true for bolts when people are poor. The needs of ordinary use scenarios and special use scenarios are different. No matter how good the bolt is , if the use requirements are not standardized, it is very likely to cause breakage, so today, Xiaorui will give you an example to understand.

  Example: The connecting rod bolts of the diesel engine are for one-time use and are not allowed to be reused.

        If the connecting rod bolts are used repeatedly, due to the large force, the bolts will be elongated, and it is very easy to cause the rolling pad burning accident of the bearing pad due to insufficient tightening force of the bolts; Increase, resulting in low oil pressure, resulting in excessive wear of bearing pads and occurrence of pad burning accidents.

        The diesel engine is a high-strength diesel engine. The connecting rod is subjected to a large impact load, which is much larger than that of an ordinary diesel engine. Repeated use of the connecting rod bolts can easily lead to breakage, damage the engine cylinder block, and cause the engine to be scrapped. Although some units have replaced the connecting rod bolts, there are also fracture failures, and some connecting rod bolts suddenly break during the operation of individual engines.

  Cause of failure:

  ①When assembling, the tightening torque is too large and the force is uneven. Since there is no strict matching torque wrench in the assembly, and the specific tightening torque is not well understood, I think the tighter the better; the tightening rod bolts use a longer booster rod, and the tightening torque is too large, exceeding the bolt material. The yield limit causes the connecting rod bolts to yield and deform, causing them to break due to excessive elongation under the action of impact loads. It should be emphasized that the connecting rod bolts must be tightened according to the standard, and never think that the tighter and the greater the strength, the better.

  ② Diesel engine connecting rods are divided into different grades, and care should be taken not to replace connecting rods of different grades during maintenance. If the connecting rod cover is messed up or installed incorrectly due to sloppy care during maintenance, it will cause the joint surface of the big end of the connecting rod to not fit tightly, and the connecting rod cover will become loose during engine operation, resulting in the breakage of the connecting rod bolts. The large end of the connecting rod of WD615 series diesel engine is obliquely cut, and the oblique angle is 45°. The joint surface of the connecting rod cover and the large end of the connecting rod adopts a 60° zigzag positioning structure. This structure has the advantages of tight fit, accurate positioning, reliability and compact structure. specialty. If the connecting rod cover is messed up or installed incorrectly during maintenance, it will inevitably lead to poor positioning of the joint surface serrations, which will easily cause the loosening of the connecting rod cover during engine operation, resulting in the breakage of the connecting rod bolts.

  ③Diesel engine runs out of speed or the piston burns to death in the cylinder during operation, and the connecting rod bolts are broken. If the engine has a speeding failure during use, a comprehensive inspection of the engine should be carried out, and it is best to replace the connecting rod bolts; if some cylinders have serious scuffing during operation, the connecting rod should also be replaced when replacing the cylinder piston assembly. Bolt replacement.

  ④Material problems, processing defects and heat treatment process problems will also cause the connecting rod bolts to break during engine operation.