Method for conducting in situ high temperature DIC with simultaneous synchrotron measurements under thermomechanical load

Rossmann, L. and Sarley, B. and Hernandez, J. and Kenesei, P. and Almer, J. and Wischek, J. and Bartsch, M. and Kösterk, A. and Maurel, V. and Raghavan, S.

Volume: Pages:
DOI: 10.2514/6.2018-1375
Published: 2018

This work presents a novel method of obtaining in situ strain measurements at high temperature by simultaneous digital image correlation (DIC), which provides global strain, and synchrotron x-ray diffraction (XRD), which provides lattice strains. Digital image correlation at high temperature requires specialized techniques to overcome the effects of increased black body radiation that would otherwise overexpose the images. The technique presented herein is unique in that it can be used with a sample enclosed in an infrared heater that cannot be illuminated with additional lighting. A small hole was drilled into the heater to serve as a window for the camera, and the light of the heater lamps is used as illumination. High-temperature paint is used to apply a speckle pattern to the sample to allow the tracking of displacements and the calculation of strains. An inexpensive blue theatrical gel filter is used to block the orange, red, and infrared light at high temperatures. This technique successfully produces properly exposed sample images at 870 ◦C; this temperature was determined by the requirements of the experiment, not a limitation of the technique. Another feature of this method is that the camera is controlled remotely, allowing focusing and image capture during synchrotron XRD measurements. The results were validated by an analytical calculation of the theoretical strain. Simultaneous DIC and XRD measurements of Inconel 718 (IN718) were taken under thermal and mechanical loads. The combination of global and lattice strains can provide important information on the anisotropy of the material. © 2018 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

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