摘要
为了测试碳/碳复合材料的热扩散系数,本文提出了非线性拟合用于透射式脉冲红外检测的数据处理方法.非线性拟合通过循环迭代的方法持续调整拟合参数,让理论值不断逼近实验值,直至获得最佳结果.传统的透射式脉冲红外成像技术利用半高时间法测试材料的热扩散系数,但通常会受到采集时间不足和信噪比差的限制.本文提出的非线性拟合方法可以有效消除或减弱这两种影响.在使用该方法之前,首先选用常见的304不锈钢评估了该方法的测量精度及拟合长度对测试结果的影响.结果显示304不锈钢的测量精度达到0.3%,且当拟合长度不小于半高时间法采集时间的1/5时,拟合长度对非线性拟合结果影响很小.随后使用该拟合方法测试了不同厚度的碳/碳复合材料试件,并通过热扩散系数测量结果分析了试件之间的热参数差异性和材料自身的均匀性.
In order to measure diffusivity of carbon/carbon composite, a nonlinear fitting method for data processing of transmission pulsed infrared thermography is proposed. It is a kind of method of comparing the experimental data with the theoretical values under a fitting parameter and obtaining the optimal result by an iteration method. Traditional half rise time method calculates the diffusivity through searching the half maximum temperature rise time, which is very difficult when a long capture time is required or a big temperature rise is needed. Unlike the traditional half rise time method, the nonlinear data fitting method can effectively eliminate the capture time restriction and weaken the badsignal-to-noise ratio effects. Before applying this method to carbon/carbon composite examination, a common stainless steel 304 specimen that has reliable diffusivity indicated in the literature, is employed to evaluate the measurement accuracy and confirm the effect of fitting length on the fitting results. The examination results illustrate that the measurement accuracy of stainless steel 304 is as high as 0.3%, and the influence is very small if the fitting data length keeps no less than 1/5 that of half rise time method（t_（1/2））. Specifically, the fitting result changes less than 1% when the fitting length varies from 1 to 4 times of t_（1/2）. With this evaluation result, the nonlinear fitting method is further applied to testing 6 carbon/carbon composite specimens from both sides of each specimen. Furthermore, the diffusivity differences among the specimens and the uniformities of the materials are analyzed through the thermal diffusivity results gained from the examination. The results demonstrate that average diffusivity values of both sides are similar, but the diffusivities among the specimens are different greatly. Of the diffusivities of specimens, the diffusivity value 5.125 is the smallest, while the diffusivity value 6.915 is the biggest. The gap between them is nearly 30% of their mean value.Some nonuniformity areas are also examined from the diffusivity images of carbon/carbon composite samples. So we can obtain not only diffusivity values but also uniformity information of the carbon/carbon composite from this nonlinear fitting transmission thermography examination.
作者
李晓丽
Sun Jian-Gang
陶宁
曾智
赵跃进
沈京玲
张存林
Li Xiao-Li Sun Jian-Gang Tao Ning Zeng Zhi Zhao Yue-Jin Shen Jing-Ling Zhang Cun-Lin(Beijing Key Lab. for Precision Optoelectronic Measurement Instrument and Technology, School of Optoelectronics, Beijing Institute of Technology, Beijing 100081, China Nuclear Engineering Division, Argonne National Laboratory, IL 60439, USA Beijing Advanced Innovation Center for Imaging Technology, Beijing Key Lab for Terahertz Spectroscopy and Imaging., Key Lab of Terahertz Optoelectronics, Ministry of Education, Department of Physics, Capital Normal Universit3~ Beijing 100048, China Robot and Intelligent Equipment Engineering Research Center, College of Computer and Information Science Chongqing Normal University, Chongqing 400047, China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2017年第18期268-275,共8页
Acta Physica Sinica
基金
北京市教育部市属高校创新能力建设项目(批准号:TJSHG201510028008)
国家自然科学基金(批准号:U1233120)资助的课题~~
关键词
非线性拟合
透射式脉冲红外检测
碳/碳复合材料
热扩散系数
nonlinear data fitting
transmission pulsed thermography
carbon/carbon composites
diffusivity measurement
