The function of the connecting rod group is to turn the repeated movement of the piston rod into the rotational fitness movement of the engine crankshaft and send the force on the piston rod to the engine crankshaft. The load borne by the connecting rod is: tension and compression fatigue load; Bending load; Extra load. Therefore, the design scheme of connecting rod group shall consider the following provisions: Dalian marine parts

A) Reduce the net weight as much as possible while ensuring sufficient compressive strength and bending stiffness;

B) Large and small end rolling bearings are reliable in operation and have good wear resistance;

C) Connecting rod bolt connection is reliable and has high fatigue strength; Easy to manufacture and low cost.

Connecting rod structure and model selection common structures of connecting rod include: straight wound connecting rod, oblique wound connecting rod, separated connecting rod, side-by-side connecting rod, etc

Connecting rod raw materials and processing technology

The raw materials of connecting rod shall have high fatigue strength and fracture toughness. Generally, medium carbon steel or high toughness carbon steel shall be selected. The wool embryo is formed by free forging. The direction of the chemical fiber of the metal material macroeconomic mechanism in the longitudinal section of the connecting rod shall follow the connecting rod management center and conform to the appearance design of the connecting rod. The microscope mechanism shall be a symmetrical fine crystal structure.

In order to better improve the fatigue strength of connecting rod, the following perfect mechanism can be selected:

(1) According to raw materials, select effective heat treatment methods to improve the compressive strength of forged steel connecting rod.

(2) Surface shot peening can cause residual reduced in-situ stress on the surface, which can significantly improve the fatigue strength of parts.

The checking of connecting rod in application includes: checking of pre tightening torque of connecting rod bolt; Connecting rod appearance and surface crack inspection; Inspection for different centrality of connecting rod big end; Inspection of rolling bearings at large and small ends of connecting rods, etc. to distinguish the conditions of connecting rods

Connecting rod bolt is the key connecting bolt for connecting the big end of connecting rod and connecting rod cap. Connecting rod bolts shall be subject to the effect of pre tightening force during installation. The pre tightening force shall ensure that the middle of the two split surfaces are inseparable, so that they will not be separated under the large reciprocating inertia moment and other lashing effects.

In order to better improve the fatigue strength of connecting rod bolts, connecting rod bolts are of soft structure.

Excessive pre tightening force of connecting rod bolts or uneven pre tightening force of each bolt will endanger its credibility in work. Therefore, it must be carried out according to the specified tightening method and process.