Bending fatigue analysis of cast iron crankshafts in consideration of fillet rolling effects

As fillet rolling hardening technique has been widely used to enhance the bending fatigue strength of cast iron crankshaft, the residual stress due to fillet rolling must be considered in fatigue analysis. For a fillet-rolled cast iron crankshaft, a three dimensional roller-multidiameter shaft contact finite element model was established, and both bodies were flexible. The roller were used to simulate the rolling process by pressing in the roller, applying a relative revolution and unloading, and then the residual stresses induced by fillet rolling were obtained. After that, the bending stresses and strains near fillet by the action of bending moment in the fatigue test were computed by a finite element static analysis of the crankshaft section. In order to describe the properties of cast iron, the material model that has the different behaviors in tension and compression were used the rolling and bending calculation. The monotonic tension and compression stress-strain curves were chosen in rolling analysis, but the cyclic curves were used in bending computation. Finally the life of critical position near fillet region was got by the local stress/strain fatigue analysis method, in which the amplitude of strain was used as a basic parameter and the residual stress caused by fillet rolling was treated as a mean stress. The results agree with the bending fatigue test results of crankshaft sections well.