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A direct method for the simultaneous characterization of thermal diffusivities of a bi-layer material consisting of a thin coating deposited on a substrate
Applied Mathematical Modelling ( IF 5 ) Pub Date : 2021-03-01 , DOI: 10.1016/j.apm.2020.09.049
Elissa El Rassy , Yann Billaud , Didier Saury

Abstract This work presents a method dedicated to the simultaneous identification of the thermal diffusivities of coatings or thin film materials. To ensure non-destructive thermal characterization of the coating, the present method also implies the identification of the substrate thermal properties, which may be orthotropic. The estimation of thermal diffusivities is based on the resolution of an inverse problem by minimizing the quadratic difference between the response of a 3D semi-analytical model and the measurements resulting from a single ‘3D flash method’ type experiment, using a stochastic based optimization algorithm. A unique non-intrusive test, that consists in recording the temperature change cartography on one face of the sample by means of an infrared camera, is required. The evolution of the temperatures within the material is generated by a non-uniform and almost instantaneous excitation imposed by a CO2 laser on the measured face. The difficulties related to the control of the excitation, in terms of the distribution of the imposed flux or the energy absorbed by the material, are overcome by estimating the parameters associated to the excitation simultaneously with the thermal diffusivities. The developed method is applied to estimate the thermal diffusivity of a coating used in thermographic phosphor thermometry to measure wall surface temperatures and heat fluxes in combustion environments. The method is first evaluated on simulated data as a function of the measuring/excitation face in order to ensure the feasibility, the robustness and accuracy of the current method and to establish the best experimental configuration. Experimental results are then exploited and the estimation results are compared with other methods results.

中文翻译:

一种同时表征由沉积在基板上的薄涂层组成的双层材料的热扩散率的直接方法

摘要 这项工作提出了一种专门用于同时识别涂层或薄膜材料的热扩散率的方法。为了确保涂层的非破坏性热表征,本方法还暗示了基材热特性的识别,其可能是正交各向异性的。热扩散率的估计是基于通过最小化 3D 半分析模型的响应与单个“3D 闪光方法”类型实验产生的测量值之间的二次差来解决的逆问题,使用基于随机的优化算法. 需要一种独特的非侵入式测试,即通过红外摄像机记录样品一个面上的温度变化图。材料内温度的变化是由 CO2 激光施加在被测面上的非均匀且几乎是瞬时的激发产生的。通过估计与激发相关的参数和热扩散率,克服了与激发控制有关的困难,即施加的通量分布或材料吸收的能量。所开发的方法用于估计热成像磷光体测温法中使用的涂层的热扩散率,以测量燃烧环境中的壁面温度和热通量。该方法首先在模拟数据上作为测量/激励面的函数进行评估,以确保可行性,当前方法的稳健性和准确性,并建立最佳实验配置。然后利用实验结果并将估计结果与其他方法的结果进行比较。
更新日期:2021-03-01
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