抄録
For increase in the bending and torsion fatigue limit of Crank shaft, it is important to produce high hardness and introduce large compressive residual stress under the surface of Crank shaft pin fillet-R and Oil holes. For this purpose, surface treatment methods, such as Nitrocaburizing (NH), Induction hardening (IH) and etc. are useful techniques. Therefore, the authors conducted an experiment using the following five types of surface treated Crank shaft for heavy duty diesel engine : a)NH b)IH c)IH+Shot peening (SP) d)NH+IH e)NH+IH+SP. And evaluated their surface characteristics and fatigue limits. The main results are as follows : 1) Extremely high bending fatigue limit of IH+SP Crank shaft, i.e. 31% higher limit than the NH Crank shaft. 2) Considerably increased torsion fatigue limit of NH and NH+IH+SP Crank shaft, i.e. 90% and 107% higher than the IH Crank shaft, respectively.
