A Modified Closed Form Energy Based Framework for Axial Isothermal Mechanical Fatigue Life Assessment for Aluminum 6061 T6

Abstract

In the present investigation, the applicability of a previously developed closed form energy based framework to predict low cycle fatigue (LCF) life of aluminum 6061T6 was extended from room temperature to elevated temperature. The three different elevated temperatures considered in the present investigation were 75 آ°C, 100 آ°C, and 125 آ°C which were below the creep activation temperature for aluminum 6061T6. Like the room temperature life assessment framework, the elevated temperature life assessment framework involved computation of the Ramberg–Osgood cyclic parameters from the average plastic strain range and the average plastic energy obtained from an axial isothermalmechanical fatigue (IMF) test. The temperature dependent cyclic parameters were computed for 25 آ°C (room temperature), 75 آ°C, and 100 آ°C and then extrapolated to 125 آ°C utilizing functions describing the dependence of the cyclic parameters on temperature. For aluminum 6061T6, the cyclic parameters were found to decrease with increase of temperature in a quadratic fashion. Furthermore, the present energy based axial IMF framework was found to be able to predict the LCF life of aluminum 6061T6 at both room and elevated temperatures with excellent accuracy.