基于"紫外成像"数字图像相关方法的高温视频引伸计研制

The real-time, accurate measurement of surface strain of alloys、ceramics structural materials served under the condition of extreme high temperature and loading during mechanical properties tests is the key point to obtain the basic mechanical parameters. Among strain measurement technologies, applied with mechanics experimental machine, the video extensometer of traditional digital image processing method based on feature extraction has low precision at high temperature, generally only used at room temperature. In recent years, digital image correlation based on speckle grayscale matching although has a great potential, problems of high temperature blackbody radiation, speckle instability and “heat haze” exist. For the urgent need to solve the technical problems of high temperature strain measurement, this project aims to develop high temperature video extensometer based on “UV imaging” digital image correlation to realize the real-time、accurate deformation measurement of high temperature structural materials. The project will focus on solving problems as follows: 1) the thermal radiation of the hot object leading to the deccorrelation in digital image correlation; 2) the fabrication of super-stable speckle pattern at elevated temperature; 3) image distortion due to the hot air refractive index inhomogeneity in the imaging optical path between lens and hot sample. The developed high temperature video extensometer is expected to be verified and applied in the mechanical properties test of structural materials of high temperature alloy、ceramics.

在对高温合金、陶瓷等在极端高温条件下使用的结构材料进行高温力学性能测试时，其表面力热耦合下应变的实时、准确测量是获得基本力学参数的关键。应变测量技术中，与力学试验机配合使用的基于特征提取的传统数字图像处理方法的视频引伸计高温下测量精度差、普遍只用于常温测量。近年来基于散斑灰度匹配的数字图像相关方法虽然具有很大潜力，但高温下，黑体热辐射、散斑不稳定和“热雾”问题存在。基于高温应变测量迫切需要解决的技术难题，本项目拟开发和研制基于“紫外成像”数字图像相关方法的高温视频引伸计，以实现高温力学试验中应变的实时、高精度测量。拟解决如下关键问题：1)高温物体的黑体热辐射增强导致的图像退相关性；2)高温环境下超稳定散斑的制作；3)镜头与加热试样之间存在的温度梯度导致的图像畸变。本项目研制的高温视频引伸计将有望在高温合金、陶瓷材料等结构材料的力学性能测试中得到验证和应用。

本项目研制了基于“紫外成像”数字图像相关方法的高温视频引伸计，以实现高温力学试验中应变的实时、高精度测量。解决如下关键问题：1)高温物体的黑体热辐射增强导致的图像退相关性；2)高温环境下超稳定散斑的制作；3)镜头与加热试样之间存在的温度梯度导致的图像畸变。本项目首次对散斑制备和评价进行了长篇综述。散斑制备方法从“增材制造”和“减材制造”两种分类进行了论述。首次利用新开发的UV立体DIC系统及自然纹理散斑在1868℃高温电弧风洞加热下获得了高温结构的全场三维形貌，退移量等重要数据。在石英灯前表面加热下对高温镍基合金进行了1050℃下的热变形测量，解决了石英灯前表面加热测试困难的问题。对镍基高温合金在980℃下进行了65h蠕变行为测试。结果与激光位移传感器（LDS）测量的应变的结果具有一致性证明了方法的可靠性。