Cause Analysis of Crankshaft Fracture

Crankshaft fracture is a serious component failure of the engine, occurring in stress concentrated areas such as the crank pin, the connecting fillet of the main journal and the crank arm, and the journal oil hole.

Main causes of crankshaft fracture

1) Individual users do not pay attention to incorrect use of engine oil or cleaning and replacing the "three filters", resulting in long-term deterioration of engine oil; Serious overloading and overloading lead to long-term overload operation of the engine, resulting in a tile burning accident. The crankshaft is badly worn due to the burning of the engine tiles. The engine crankshaft is replaced and repaired, that is, a new crankshaft installation machine is purchased, and the damaged crankshaft is sent to the manufacturer for repair and standby. Some users find several small local factories to repair and process seriously worn crankshafts from a cost and time perspective after experiencing crankshaft wear issues on their vehicles. The severely worn crankshafts are overlayed and processed, and the entire body is subjected to heat treatment and grinding. Due to repair methods and technical problems, the connecting fillet of the crank pin, main journal, and crank arm has changed, causing local stress concentration; Due to the fact that the crankshaft is forged with precision 45 # steel, surfacing has changed the metallographic texture of the crankshaft. The above two are the main reasons for crankshaft fracture.

2) After repairing the engine, the vehicle has not passed the wear period. In other words, overload suspension, long-term overload operation of the engine, and crankshaft load exceeding the allowable limit.

3) The crankshaft is repaired by overlaying welding, which destroys the power balance of the crankshaft and does not undergo balance verification, resulting in excessive imbalance, causing greater engine vibration, and causing crankshaft fracture.

4) Due to poor road conditions and severe overloading and overtaking of vehicles, the engine is often within the limit rotational speed of torsional vibration, and the shock absorber fails, resulting in torsional vibration fatigue damage and fracture of the crankshaft.