MULTI-AXIAL LOADING EFFECTS IN A NICKEL-BASED DISC SUPERALLOY SUBJECT TO PROPORTIONAL AND NON-PROPORTIONAL LOAD PATHS

摘要

The structural integrity of rotating components is paramount to the safe operation of aero-gas turbine engines. Specifically, high-pressure spool turbine discs are an example of safety critical parts. Disc spinning tests are used to declare a safe life for a given component geometry through a typical engine flight cycle. These are normally performed under isothermal conditions and can only apply multi-axial loads to the disc in a proportional manner. In an attempt to understand the response of disc materials to more complex modes of loading, a series of strain and load-controlled tests were conducted on a nickel-based superalloy. Constitutive deformation and low-cycle fatigue behaviour for both proportional and non- proportional load paths were investigated using a tension-torsion test machine and thin-walled tubular specimens. Additional cyclic hardening was found to exist under non-proportional loading when compared to the equivalent proportional conditions. Low-cycle fatigue lives were sensitive to both proportionality and applied stress magnitude.