Identification of thermomechanical parameters based on the virtual fields method combined with the sampling moiré method

Abstract

Thermomechanical parameters are important indicators for evaluating the mechanical properties of superalloys and generally include the coefficients of stiffness and thermal expansion at high temperatures. At present, there are few methods for simultaneously characterising the thermomechanical parameters of superalloys, especially single‐crystal superalloys. To satisfy the demand for simultaneously identifying the thermomechanical parameters of orthotropic superalloys, an optimised virtual fields method for decoupling the thermomechanical parameters was developed in this study by combining the self‐developed heat‐resistant grids and the sampling moiré method. First, several factors, including the oblique angle of the grids, image noise and thermomechanical coupling phenomena, were studied through numerical experiments to analyse their influences on the identification accuracy. Then, an optimised identification strategy was established. Finally, the thermomechanical parameters of Ni‐based polycrystalline and single‐crystal superalloys were successfully identified and comparatively studied. The identification results demonstrate that the proposed method is highly accurate and robust. This research will provide an effective way to accurately characterise the multiple parameters of superalloys at high temperatures.

Characterizing the measurement resolution and measurement bias of Sampling Moiré

“…In practice, 2D grids are generally not aligned with the rows of pixels of the camera sensor. Moving average filtering must therefore be performed using a filter defined over an oblique window, as in [28,50]. This additional operation induces some errors in the grid images.…”