Research On Variable Force Crankshaft Rolling And Deformation Rule

Crankshaft is one of the most important components in internal-combustion engine. The main function of crankshaft is transmitting and outputting power, driving the mechanism and accessories. Mostly, the failure mode of crankshaft is bending fatigue fracture, the crankshaft fatigue crack is almost caused by the location of stress concentration in the fillet between crank web and crank journal, therefore, the strengthening of the fillet is the key point of prolonging crankshaft's life. Fillet rolling have no obvious effects for steel crankshaft, but for nodular graphite cast iron crankshaft, it can improve the crank strength greatly, and the cost of nodular graphite cast iron crankshaft is only 2/3 comparing with steel crankshaft. Therefore, considering the economical efficiency and reliability, it is a good choice to use nodular graphite cast iron crankshaft with fillet rolling instead of steel crankshaft. The process of fillet rolling is the main trend of crankshafts' development currently.The means of finite analysis has the capability of high efficiency and reliability. All kinds of load can be calculated automatically by the use of Ansys. So technician's work is reduced. The models of stress, strain and displacement can be predicted by a computer only without any other material and equipment. Once a program is designed, parameter of a load can be changed conveniently, and then, the law of the stress and the load can be found more easily.In this thesis, according to the crankshaft's working condition, a analysis of crankshaft fillet rolling which depend on the fatigue strengthen theory has been done with the ANSYS and LS-DYNA. According to the calculated result, the relationship of rolling force & crankshaft's fatigue life and rolling force & crankshaft's deformation have been discussed. The conclusion is that 15KN is the better rolling force for QT800. Also, there has a discuss about crankshaft's straightening from constant force rolling and variable force rolling. Little force is better than big one for variable force rolling.