Development of In Situ Fatigue Performance Testing Apparatus for Materials Under Coupling Conditions of High-Temperature and Combined Mechanical Loads

In order to study the high-cycle and very-high-cycle fatigue (VHCF) performance of aero-engine blade materials under conditions close to their real service, an
in situ
fatigue performance testing apparatus for materials under coupling conditions of high-temperature and combined mechanical loads (HTCMFTA) has been developed. The main functions of the apparatus include: static loads loading, ultrasonic fatigue (up to 20 kHz) loading, high-temperature field (up to 1100 °C) building, and
in situ
monitoring. A series of tests on the compressor blade material Ti-6Al-4V alloy under coupling conditions of high temperature and combined mechanical loads were carried out with the apparatus. The results show that the apparatus can accurately simulate various mechanical loads and high-temperature fields to which the blade materials are subjected. The static and dynamic mechanical properties of Ti-6Al-4V alloy under high-temperature and combined mechanical loads were also revealed. The results show that there is a synergistic effect between tension and bending; as the pretension stress increases, the bending stiffness and bending-bearing capacity of Ti-6Al-4V alloy were enhanced. A coupling effect exists between temperature, tension, and bending. Under the combined loads, the bending stiffness of Ti-6Al-4V alloy slightly weakened with the increase of temperature, but the bending-bearing capacity increased significantly. This apparatus has important practical significance and scientific value for studying the high-cycle and VHCF performance of aero-engine blade materials and ensuring its service safety.