DIGITAL IMAGE CORRELATION AND COMPLEX BIAXIAL LOADING TESTS ON THERMAL ENVIRONMENT AS A METHOD TO DETERMINE THE MECHANICAL PROPERTIES OF GH738 USING WARM HYDROFORMING

摘要

This paper mainly designs a high-precision digital image correlation (DIC) system and combines biaxial tensile tests with a DIC measuring system, which is successfully applied to determine the mechanical properties of the GH738 material subjected to multistage temperatures and complex loading paths. Firstly, uniaxial tensile tests of 2024 aluminum were made under different heat treatment conditions to validate the performance of the measuring system. Then, with the aim of ensuring the accuracy and reliability of the DIC measuring system, a series of GH738 biaxial tensile tests were made on a thermal environment biaxial tensile machine. In biaxial tensile tests, a GH738 cruciform specimen was designed and it was heated accurately from room temperature up to 1000℃ using a heating furnace. Digital images of the GH738 cruciform specimen are recorded and subsequently processed by the DIC measuring system to extract a full-field true stress-strain curve which was calculated for different temperature phases and loading paths. The results indicate that in different temperature and loading path states, the mechanical properties of GH738 show obvious differences providing accurate mechanical properties data for hydroforming simulation and experiment. Based on the mechanical properties of GH738 measured by the high-temperature DIC system, the W-shaped seal ring, which is a vital component of jet engines, is simulated and tested with a good effect.