Experimental and Numerical Study on the Multiaxial Fatigue Properties of the Udimet 720Li Under Elevated Thermal Conditions

The turbine disc works under high-temperature and high-stress conditions, making it a key component in aero-engine strength assessment. In particular, its fatigue life—especially the low-cycle fatigue (LCF) life at the disc's central region—has drawn significant attention. Due to the substantial thickness of some turbine disc centers, this region experiences a typical bi-axial stress state. In this study, a cross shaped biaxial specimen was designed and tested based on the stress state at the center of the disk to evaluate the fatigue performance of powder nickel based high-temperature alloy Udimet 720Li. Furthermore, the Ohno–Wang constitutive model was introduced to simulate the elastic–plastic mechanical behavior of materials, corresponding to digital image correlation (DIC) technology. In this work, a novel multiaxial fatigue life prediction model, which considered the octahedral stress component, was proposed and obtained satisfied life prediction results regards of the new designed cross shaped specimens.