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Thermal diffusivity evaluation for carbon-carbon composites using infrared thermography.

机译：使用红外热成像技术评估碳-碳复合材料的热扩散系数。

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摘要

This paper presents a flash infrared and a step-heating thermography technique for the determination of the whole-field thermal diffusivity of anisotropic Carbon/Carbon (C/C) brakes. Quick set-up and a portable system provide a powerful tool that can realize on-site non-destructive measurement of thermal diffusivity. In the flash thermography method, heat was provided by two flash lamps and was applied to one side of the sample (e.g. fraction surface of the C/C brake), while the temperature response of the opposite surface was monitored by an infrared camera. Thus, by analyzing real-time digital infrared thermal images and the temperature evolution on one of the two surfaces, one can obtain the whole-field through-thickness thermal diffusivity in a single experiment. The experiments were conducted on two types of nonplate like sub-scale C/C and Al-6061 brakes that have an inner step along the axial direction. The influence on the evaluation of the thermal diffusivity caused by the specific geometry of the brakes was studied based upon the Finite Element Analysis (FEA) modeling. The FEA software ANSYS 8.0 was used to generate and analyze models of the composite disks, which helped to predict the measurement bias and determine the inspection procedure such as estimation of experimental time. The diffusivity evaluation was then corrected based on FEA results. Moreover, the resulting diffusivity value was compared with the value measured from the same brake by the conventional laser flash method. This flash infrared technique also was used on full-scale C/C and Al bulk samples for through-thickness measurement.;For the measurement of in-plane thermal diffusivity, the proposed method uses infrared thermography with a periodic mask. The principal characteristic is that a thermal gradient across the testing plane has to be generated. Here, heat is still applied to the front face of the sample by flash lamps and the periodic mask is added between the specimen and the lamps. After flashing, the heat is periodically distributed over the image area with such a grid pattern. The masks were specially designed to determine the radial and circumferential diffusivities of carbon disk by generating heat diffusion along these two orthotropic directions on the carbon disk sample. The period was carefully chosen as a function of sample thickness and an estimation of the ratio of through-thickness and in-plane diffusivity. The in-plane thermal diffusivity profile is then obtained by doing a Fourier transform analysis over one period of the grid mask. The results represented the average diffusivity value in that one period area. The tests have been conducted for aluminum plate and half C/C specimen. The resulting in plane diffusivity then compared with the value obtained from conventional laser flash method and literatures.;Another method, called step heating, is an alternative technique to the known flash method, which is based on the application of an instantaneous constant heat flux on the front face of the sample and measurement of the temperature response at the rear face. This work will extend the applicability of the step-heating technique to large dimension of the thick sample. The through-thickness thermal diffusivities were determined for 3-D C/C disk and Al 6061 alloy samples.
机译：本文介绍了一种闪光红外和步进加热热成像技术，用于确定各向异性碳/碳（C / C）制动器的全场热扩散率。快速设置和便携式系统提供了强大的工具，可以实现现场热扩散率的无损测量。在闪光热成像方法中，热量由两个闪光灯提供并施加到样品的一侧（例如，C / C制动器的部分表面），而相对表面的温度响应由红外照相机监控。因此，通过分析实时数字红外热像和两个表面之一上的温度变化，可以在一个实验中获得全视场厚度的热扩散率。实验是在两种类型的非盘式C / C和Al-6061制动器上进行的，这些制动器沿轴向方向有一个内台阶。基于有限元分析（FEA）模型，研究了制动器的特定几何形状对热扩散系数评估的影响。 FEA软件ANSYS 8.0用于生成和分析复合磁盘的模型，从而有助于预测测量偏差并确定检查程序，例如估算实验时间。然后根据FEA结果校正扩散性评估。此外，将所得的扩散率值与通过常规激光闪光法从同一制动器测得的值进行比较。这种闪光红外技术还用于全尺寸C / C和Al块状样品的厚度测量。;对于平面内热扩散率的测量，该方法使用带有周期性掩模的红外热成像技术。主要特征是必须在整个测试平面上产生热梯度。在这里，仍然通过闪光灯将热量加热到样品的正面，并且在样品和灯之间添加了周期性的掩模。在闪烁之后，热量以这种网格图案周期性地分布在图像区域上。这些面罩经过特殊设计，可通过在碳盘样品上沿这两个正交各向异性方向产生热扩散来确定碳盘的径向和周向扩散率。根据样品厚度以及厚度和面内扩散率之比来仔细选择周期。然后，通过在网格掩模的一个周期内进行傅立叶变换分析来获得平面内热扩散率曲线。结果表示在那个周期区域内的平均扩散率值。已经对铝板和半个C / C样品进行了测试。然后将所得的平面扩散率与从常规激光闪光方法和文献中获得的值进行比较。另一种方法，称为分步加热，是已知闪光方法的另一种技术，该方法基于在工件上施加瞬时恒定热通量的方法。样品的正面和背面的温度响应测量。这项工作将逐步加热技术的适用范围扩展到大尺寸的厚样品。测定了3-D C / C圆盘和Al 6061合金样品的全厚度热扩散率。

著录项

  • 作者

    Zhang, Ying.;

  • 作者单位

    Southern Illinois University at Carbondale.;

  • 授予单位 Southern Illinois University at Carbondale.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 120 p.
  • 总页数 120
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

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