News

Analysis of three causes of fastener bolt fracture

Release time:

2023-01-30 15:32

Analysis of three causes of fastener bolt fracture

This article comes from Easy Tight

As we all know, it is used to connect mechanical parts. Its function on the machine is also very important. If the connection is not good, it will directly affect the normal operation of the machine. However, what disturbs many people is that bolts often break. Many users do not know what causes them. Here, China Standard Parts Network will share with you three common causes of fastener bolt fracture.

1. The tightening torque is too large and the force is uneven during assembly. Because there is no strict matching torque wrench in the assembly, and the specific tightening torque is not well understood, the tighter the better; The connecting rod bolt is fastened with a long tension rod. The tightening torque is too large, which exceeds the yield limit of the bolt material, causing the connecting rod bolt to yield deformation, and breaking due to excessive elongation under the impact load. It should be emphasized that the connecting rod bolts must be tightened according to the standard. Never think that the more tight and the greater the force, the better.

2. The connecting rod of diesel engine is divided into several levels. During maintenance, it should be noted that connecting rods of different levels cannot be replaced. If the connecting rod cap is disordered and incorrectly installed due to carelessness during maintenance, the connecting rod big end joint surface will not fit tightly, and the connecting rod cap will be loose during engine operation, resulting in the fracture of connecting rod bolts. The connecting rod big end of wd615 series diesel engine is of bevel cut type with a bevel cut angle of 45 °. The connecting rod cap and connecting rod big end joint surface adopts a 60 ° serrated positioning structure, which has the characteristics of tight fitting, accurate positioning, reliability and compact structure. If the connecting rod cap is disordered and wrongly installed during maintenance, it will inevitably lead to poor positioning of the joint surface serrations, which will easily lead to the looseness of the connecting rod cap and the fracture of the connecting rod bolts during the operation of the engine.

3. The connecting rod bolt will be pulled off when the diesel engine is running with a runaway fault or the piston is burnt in the cylinder. If the engine has a runaway fault in use, a comprehensive inspection should be carried out for the engine. It is better to replace the connecting rod bolts; If some cylinders have been seriously pulled during operation, the connecting rod bolts should also be replaced when replacing the cylinder piston assembly.