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

ABSTRACT 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.