Rossmann Lin, Sarley Brooke, Hernandez Johnathan, Kenesei Peter, Köster Alain, Wischek Janine, Almer Jonathan, Maurel Vincent, Bartsch Marion, Raghavan Seetha
Department of Materials Science and Engineering, University of Central Florida, Orlando, Florida 32816, USA.
Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816, USA.
Rev Sci Instrum. 2020 Mar 1;91(3):033705. doi: 10.1063/1.5124496.
This work presents a novel method of obtaining in situ strain measurements at high temperature by simultaneous digital image correlation (DIC), which provides the total strain on the specimen surface, and synchrotron x-ray diffraction (XRD), which provides lattice strains of crystalline materials. DIC at high temperature requires specialized techniques to overcome the effects of increased blackbody 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, remotely and simultaneously with synchrotron XRD measurements. The heater included a window for camera access, and the light of the heater lamps is used as illumination. High-temperature paint is used to apply a random speckle pattern to the sample to allow the tracking of displacements and the calculation of the DIC strains. An inexpensive blue theatrical gel filter is used to block interfering visible and infrared light at high temperatures. This technique successfully produces properly exposed images at 870 °C and is expected to perform similarly at higher temperatures. The average strains measured by DIC were validated by an analytical calculation of the theoretical strain. Simultaneous DIC and XRD strain measurements of Inconel 718 (IN718) tensile test specimens were performed under thermal and mechanical loads and evaluated. This approach uses the fact that with DIC, the total strain is measured, including plastic strain, while with XRD, only elastic strain is captured. The observed differences were discussed with respect to the effective deformation mechanisms.
这项工作提出了一种通过同步数字图像相关（DIC）在高温下获得原位应变测量值的新方法，DIC可提供试样表面的总应变，同时结合同步加速器X射线衍射（XRD），XRD可提供晶体材料的晶格应变。高温下的DIC需要专门技术来克服黑体辐射增加带来的影响，否则会使图像过度曝光。本文提出的技术独具特色，它可用于置于红外加热器中的样品，能与同步加速器XRD测量远程且同步地进行。加热器设有用于相机观察的窗口，加热器灯的光用作照明。高温漆用于在样品上施加随机散斑图案，以便跟踪位移并计算DIC应变。一种廉价的蓝色戏剧凝胶滤光片用于在高温下阻挡干扰的可见光和红外光。该技术在870℃成功产生了曝光适当的图像，预计在更高温度下也能有类似表现。通过理论应变的解析计算验证了DIC测量的平均应变。对因科镍合金718（IN718）拉伸试样在热载荷和机械载荷下同时进行了DIC和XRD应变测量并进行了评估。该方法利用了这样一个事实，即DIC测量的是总应变，包括塑性应变，而XRD仅捕获弹性应变。针对有效的变形机制对观察到的差异进行了讨论。
