Evaluation of high-temperature tensile behavior for metal foils by a novel resistance heating assisted tensile testing system using samples with optimized structures

Abstract

To evaluate the tensile behavior of metal foils by resistance heating (RH) assisted tensile testing system accurately, this study proposed to embed a digital image correlation (DIC) system with laser speckles for the measurement of full-field strain distribution. Furthermore, the sample structures were optimized to achieve uniform temperature and strain distribution. An infrared camera was used to monitor the temperature distribution. Rectangular samples instead of dog-bone shaped samples were proposed. A model for calculating the temperature distribution was established to optimize the sample structure. The parameters that influence the temperature distribution and tensile behavior were studied. As results, compared to the strain measured by a non-contact extensometer, the maximum deviation of the strain measured by DIC was less than 6% when the nominal strain was larger than 0.013. It is confirmed that the proposed tensile testing system is reliable for measuring the temperature and full-field strain distributions. Sample shape influenced temperature distributions of smaller samples while it almost had no influence on the temperature distributions of larger samples. The temperature difference was not affected by the material type but by the sample size. The proposed rectangular shape was validated to be feasible for RH assisted tensile testing. The sample length was successfully optimized for a more uniform temperature distribution by the established model. Although the tensile deformation was not influenced by the sample shape, the temperature distribution resulted in a non-uniform strain distribution before achieving ultimate tensile strength. Longer effective sample length between two clamping jigs contributed to a more uniform temperature distribution and material deformation. A more accurate evaluation of high-temperature tensile behavior for metal foils can be achieved by the proposed RH assisted tensile testing system using rectangular samples with an optimized structure.