The connecting rod is an important part in the automobile and ship engine, it connects the piston and the crankshaft. In addition, its function is to convert the reciprocating motion of the piston into the rotational motion of the crankshaft, and to transmit the force acting on the piston to the crankshaft.

The connecting rod is consisted by the connecting rod body, big head cover, small head bushing, big end bearing shell and rod bolts (or screws). The connecting rod group is subjected to the gas force from the piston pin, the size and direction of these forces are periodic. Therefore, the connecting rod China Dongfeng auto parts is subjected to cyclic loading such as compression and tension. Connecting rod must have sufficient fatigue strength and structural stiffness. If the fatigue strength is not enough, the connecting rod body or rod bolt will be broken, then the significant accident will occur.

Rod part of the connecting rod mechanism are respectively hinged with the active and the driven member to transfer the movement and the force. For example, in a reciprocating piston type power machine and compressor, a connecting rod is used to connect Coolant Sensor and the crank. Connecting rod for steel parts, the main part of the cross section is circular or I-shaped, both ends of the hole, the hole with bronze bushings or needle roller bearings for axle load and a hinged pin.

The Connecting rod in the work bears the pressure from the combustion chamber gas, but also it bears the vertical and horizontal inertia force. Therefore, the connecting rod works in a complex stress state, it is not only affected by the alternating tension and compression stress, but also by the bending stress. The main damage form of connecting rod is fatigue fracture and excessive deformation. Usually the location of fatigue fracture is in the three high-stress region of the connecting rod. The working condition of connecting rod requires high strength and anti-fatigue properties, also require a sufficient rigidity and toughness.

In the traditional processing technology, the material of the connecting rods is 45 steel,40Cr or 40MnB, but now in the foreign, the advanced conrod fracture splitting is widely used, which requires high brittleness and hardness. Although the alloy steel has a very high strength, but the stress concentration is very sensitive, therefore, in the connecting rod shape, excessive fillet need to be strict, it also should pay attention to the surface processing quality in order to improve the China Dongfeng Commercial Vehicle fatigue strength, otherwise the application of high strength alloy steel can not achieve the desired results.

1, the Inspection of connecting rod appearance

• The connecting rod and bearing cap can not be cracked or damaged.
• The bearing cover and the bearing seat should be close together, and the joint surface is not damaged。
• Check the gap between the two ends of the connecting rod and the crank arm with a feeler gauge. The size should be in accordance with the regulations, otherwise it should be replaced.
• Check the connecting rod bolts and nuts. If the bolt has cracks or obvious defects, the gap between the bolt with the nut is too large, all of these should be replaced.

2, Inspection of deformation of connecting rod

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