X-Ray Digital Image Correlation: A Reliable Method for Deformation Measurement at 1000 °C

Background

Digital image correlation (DIC) is widely used as a noncontact optical deformation measurement method. However, optical DIC encounters difficulties when measuring displacement and strain at high temperatures, including false deformation caused by heat haze and image overexposure caused by intense thermal radiation. X-ray imaging is not affected by these factors, so the combination of X-ray imaging and the DIC algorithm (X-DIC) holds the potential for measuring deformation during high-temperature tests.

Objective

This study investigated the ability of X-DIC to measure deformation in high-temperature experiments, expand the applicable temperature range of X-DIC, and provide a reliable method for obtaining deformation measurements in high-temperature experiments.

Methods

A combination of X-ray digital radiography (DR) images and the DIC algorithm was used to measure deformation. Numerical experiments based on synthetic images were used to evaluate the measurement accuracy of X-DIC, and the influence of different DIC parameters on the measurement error was discussed. Ductile iron and C/SiC composites were subjected to tensile tests at different temperatures from ambient temperature to 1000 °C, and different deformation measurement methods were used to simultaneously measure the deformation of the samples to verify the accuracy of the X-DIC results.

Results

In the numerical experiments, the displacement measurement error of X-DIC is less than 0.02 px. The relative error between the X-DIC and blue-light DIC measurements of the tensile deformation of ductile iron at 500 °C is 0.65%. When the deformation of the C/SiC composite materials was measured at 1000 °C, the root mean square error (RMSE) of the strain data obtained by X-DIC and optical DIC was 1.12 × 10^–4.

Conclusions

These results prove that X-DIC has high measurement accuracy. Compared with optical DIC, X-DIC is insensitive to high-temperature environments and provides alternative experimental methods for high-temperature deformation measurements.