Assessing the Estimated Life of UD Drum of Automatic Transmission Using Material Properties Evaluated by Stress Rupture Testing

High-cycle fatigue testing under different stress conditions must be performed in fatigue test methodology, and this requires expenditure both of money and time. The high-cycle fatigue test methodology also has the limitation of being a statistical approach to assessing estimated life that is not based on material properties. Thus to evaluate the estimated life of structural materials in transmissions in use, we need a novel assessment method that is economical, effective, easy to apply, and based on the material properties. In this study, we derive the relation between rupture stress and tensile properties taking into account fatigue rupture time, and developed a methodology for evaluating the estimated life of structural materials of transmission. Using this methodology, we performed stress rupture and fatigue tests for automatic transmission UD drum steels.