热障涂层复阻抗谱影响参数的有限元模拟

发布时间：2018-02-16 08:09

本文关键词： 热障涂层复阻抗谱电场分布有限元　出处：《湘潭大学》2015年硕士论文　论文类型：学位论文

【摘要】：热障涂层(Thermal Barrier Coatings,简称TBCs)是一种绝热陶瓷涂层,已成功应用在航空发动机的涡轮叶片,以提高涡轮叶片的服役温度和耐腐蚀性能。然而,TBCs结构复杂,在恶劣的服役环境下会发生脱落和失效,这不但影响航空发动机效率,而且严重威胁航空发动机的安全运行。为预防上述情况发生,复阻抗谱检测(Impedance Spectroscopy,简称IS)作为一种无损检测方法已被应用于热障涂层的结构检测和寿命预测中。尽管如此,复阻抗谱检测在航空发动机热障涂层中的应用还存在以下两个问题:1.对复阻抗谱结果的分析缺乏稳定可靠的研究工具。2.实验中采用的非对称电极对复阻抗谱检测结果的影响不明确。因此,本文引入有限元法对热障涂层的复阻抗谱检测进行模拟分析,进一步研究复阻抗谱测量环境和TBCs结构变化对热障涂层复阻抗谱测量结果的影响。主要研究内容及所得结果如下:1.根据有限元结果、实验测量结果以及复阻抗谱理论,详细地分析测量电压、测量温度以及测量电极大小对TBCs复阻抗谱的影响。此外,对复阻抗谱进行等效电路拟合,得到YSZ和TGO的测量厚度。最后,综合测量电压、测量温度以及测量电极大小的影响,确定TBCs复阻抗谱最佳的测量电压为1 V,测量温度为400°C,测量所用的Pt电极直径为3~5 mm。2.根据有限元结果、实验结果及复阻抗谱理论,分析YSZ、TGO厚度和电导率对TBCs复阻抗谱检测的影响。通过比较测量厚度与模型所设厚度,确定检测的大致误差,结果表明:在根据复阻抗谱计算YSZ和TGO厚度时,不应直接采用Pt电极面积作为测量区域面积,而应选取比Pt电极面积大的值。如当Pt电极直径为3 mm时,用于计算YSZ厚度的测量区域面积取值应比Pt电极面积大10%,此时得到的结果测量误差更小。同理,对于计算TGO厚度,测量区域面积取值则应比Pt电极面积大60%。3.采用COMSOL软件模拟TBCs复阻抗谱测量过程,同时分析不同条件下TBCs的复阻抗谱及其内部的电场分布。结果表明:非对称电极的使用导致TBCs内电场线发散,该发散是复阻抗谱检测误差存在的重要原因之一。测量温度、测量电极大小、YSZ和TGO的厚度以及电导率对复阻抗谱的影响可从两个角度解释:(1)通过本身数值的改变影响TBCs的复阻抗谱;(2)通过改变测量区域面积影响TBCs的复阻抗谱。
[Abstract]:Thermal Barrier Coatingsis an adiabatic ceramic coating, which has been successfully used in aero-engine turbine blades to improve the service temperature and corrosion resistance of turbine blades. However, the structure of TBCs is complex. Shedding and failure will occur in harsh service conditions, which not only affect the efficiency of aero-engines, but also seriously threaten the safe operation of aero-engines. Complex Impedance Spectroscopy (ISS) has been used as a nondestructive testing method for structural testing and life prediction of thermal barrier coatings. Application of complex Impedance Spectroscopy in Aero-engine Thermal Barrier Coatings: 1. The analysis of complex impedance spectrum results is short of a stable and reliable research tool .2. the asymmetric electrode pair complex impedance spectrum detection used in the experiment. The effect of the outcome is not clear. In this paper, the finite element method is introduced to simulate the measurement of complex impedance spectrum of thermal barrier coatings. The influence of complex impedance spectrum measurement environment and structure change of TBCs on the measurement results of thermal barrier coating complex impedance spectrum is further studied. The main contents and results are as follows: 1. According to the finite element results, the experimental results and the complex impedance spectrum theory, The influence of measurement voltage, temperature and electrode size on TBCs complex impedance spectrum is analyzed in detail. In addition, the measurement thickness of YSZ and TGO is obtained by the equivalent circuit fitting of complex impedance spectrum. Finally, the comprehensive measurement voltage is obtained. The optimum measurement voltage of TBCs complex impedance spectrum is 1 V, the measurement temperature is 400 掳C, and the diameter of Pt electrode is 3 ~ 5 mm. 2. According to the finite element results, the experimental results and the complex impedance spectrum theory are used. The influence of the thickness and conductivity of YSZ TGO on the measurement of TBCs complex impedance spectrum is analyzed. By comparing the thickness between the measured thickness and the thickness set up by the model, the approximate error of the detection is determined. The results show that the thickness of YSZ and TGO is calculated according to the complex impedance spectrum. The area of Pt electrode should not be used as the measuring area directly, but the value larger than that of Pt electrode should be chosen. For example, when the diameter of Pt electrode is 3 mm, The area of the measuring area used to calculate the thickness of YSZ should be 10 times larger than the area of Pt electrode, and the measurement error of the result obtained at this time is smaller. In the same way, for calculating the thickness of TGO, The area of measurement area should be 60% larger than that of Pt electrode. The COMSOL software is used to simulate the measurement process of TBCs complex impedance spectrum. At the same time, the complex impedance spectrum of TBCs and its internal electric field distribution under different conditions are analyzed. The results show that the use of asymmetric electrode leads to the divergence of electric field line in TBCs, which is one of the important reasons for the existence of complex impedance spectrum measurement error. The influence of the thickness of YSZ and TGO and the conductivity of the electrode on the complex impedance spectrum can be explained from two angles: (1) the complex impedance spectrum of TBCs can be affected by the change of its own value. (2) the complex impedance spectrum of TBCs can be affected by changing the area of measurement area.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ174.758.16

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