What’s a crankshaft?
Crank shaft is main rotating parts of engine,is installed on the connecting rod,can undertake the (reciprocating) up and down movement into circulation movement (rotation) of connecting rod.Is an important part on the engine,and its material is made of carbon steel or nodular cast iron,there are two important parts of crankshaft:main journal,connecting rod journal,(and other).Main journal is installed on the cylinder block, connecting rod connected with the big hole,neck connecting rod small hole is connected to the cylinder piston, is a typical slider-crank mechanism.Lubrication of the crankshaft is mainly refers to the lubrication of bearing between the rocker arms and the lubrication of two fixed point.The rotation of the crankshaft is the power source of the engine. Is also the driving force of the whole mechanical system.
Main causes of crankshaft fracture:
1.Individual users due to improper selection of engine oil,or do not pay attention cleaning and replacement,oil long-term use of metamorphism;Serious overloading, super hung, causing engine overload operation for a long time and appear the tile burning failure. Because of tile burning,engine crankshaft is resulted in serious wear and tear.Users could choose to repair damaged crankshaft for standby application,and buy a new one installed.Some users consider more about cost and time,will find a small factory in the local to repair,will seriously do surfacing welding,processing,whole heat treatment and grinding on the serious wear section of the crankshaft.Due to repair methods and process problems,changes will be caused at the connecting round corner of crank pin,main journal and crank armround,causing local stress concentration.As the crankshaft is made of 45# steel with closed die forging,surfacing welding will also make metallographic texture changed.So above two factors will cause second fracture of crankshaft.
2.After reparing of engine,overload ultra hang without passing run-in period and overload woking for a long time,will make overload of crankshaft beyond allowable limit.
3.In the repair of crankshaft adopts surfacing welding,destroyed the dynamic balance of crankshaft,nor do the balance calibration,casuing the big vibration of the engine,lead to fracture of the crankshaft.
4.Due to the poor road conditions,serious overload ultra hang,also causes the crankshaft torsional vibration fatigue failure and fracture.