数字图像相关技术在高温热膨胀系数测量中的应用

目的测量热结构材料在高温环境下的热膨胀系数,方法将数字图像相关(DIC)技术和通电加热技术相结合,建立高温热变形测量系统。该系统使用CCD相机采集不同温度下试样的表面图像,经DIC方法分析处理得到被测材料随温度升高产生的变形和应变,进一步计算得到相应温度下的热膨胀系数。测量紫铜、石墨分别在600~800℃,600~1200℃范围内的热膨胀系数,并与文献数据进行比较。结果使用该实验系统测量得到了紫铜和石墨分别在600~800℃,600~1200℃范围内的热膨胀系数,与文献参考值吻合较好。结论该测量方法可精确得到导电材料的热应变及热膨胀系数,测量温度上限可达1200℃。

Application of Digital Image Correlation Technique in Measuring Coefficient of Thermal Expansion at High Temperature

Objective To measure thermal expansion coefficient (CTE) of heat structures materials at high temperature.Me-thods Combining the digital image correlation (DIC) method and energized resistance heating technology, a test system for measuring high-temperature deformation and strain was established. After recording the surface images at different temperatures by a CCD camera, DIC method was used to analyze all the images to obtain the deformation and strain along with increasing temperature, and the corresponding thermal expansion coefficients at different temperatures were further calculated. This paper measured the thermal expansion coefficients of copper in the range of 600~800℃, and measured the graphite′s CTE in the range of 600 ~1200℃, comparing with literature data.Results The CTE of copper was in the range of 600 ~800℃ and gra-phite in the range of 600~1200℃ as, measured by this system, showing that the data were in good agreement with the litera-ture.Conclusion This method showed the ability to accurately measure thermal strain and CTE of conductive material, and its temperature limit reached up to 1200℃.