Analysis of residual stresses in main crankshaft bearings after induction surface hardening and finish grinding

The exact pattern of residual stresses will depend on the heat treatment temperatures employed, the depth of hardening and the type of quenchant. Process conditions that give rise to compressive residual stresses on the surface of heat-treated components are favourable. This type of residual stress delays the initiation of fatigue cracking in service, which typically occurs on the surface of the part under the action of cyclic tensile stresses. The last phase in the manufacturing of crankshafts is finish grinding in order to achieve the desirable condition of the surface and the subsurface layer, i.e. suitable dimensions, suitable surface roughness and the corresponding distribution of relative grinding residual stress in the subsurface have to be ensured. By correct selection of the grinding wheel and grinding conditions, taking into account the physical and mechanical properties of the workpiece material, the very favourable compressive residual stresses in the hardened surface layer will be retained after grinding.