The Use of Strain Measurement Techniques at Elevated Temperatures

This paper discusses the use of both extrinsic Fabry-Perot interferometry and digital image correlation method to measure strain at elevated temperatures. Strain measurements of TC4 Titanium Alloy under 500 °C have been performed based on extrinsic Fabry-Perot interferometry approach. The results show that the maximum absolute error was 0.052 × 10−3 compared with theoretical strain. When the load was higher than 0.2 × 10−3, the performance of EFPI sensor was better than that of the conventional resistance strain gauge, and the relative error was less than 14%. Digital image correlation method was also applied to a 310S stainless steel subjected to a uniaxial tensile test at 400 °C. Noticeable in-plane strain heterogeneities were highlighted throughout the test. These spatial heterogeneities were clearly visible from the beginning of the test and markedly intensified at the last stages before the macroscopic fracture. Comments on the investigated techniques and suggestions for future work are finally discussed.