非接触热波层析成像检测内部缺陷的研究

Detection of Interior Thermal Defects by Contactless Thermal Wave Imaging with Tomography

将非接触热波测试系统与计算机层析技术结合，成功检测出铜样品内部缺陷的分布。在层析成像代数模型基础上，根据热波传输的物理实质及所用实验装置的特点，分别引入几何因子消除探测器有限尺寸效应，引入透射率因子表征孤立缺陷边界对热波的作用，从而建立薪的层析重建模型，实验结果表明，对热性质突变的缺陷，该方法是成功的，带有人为空洞的样品，其内部缺陷的形状和位置得以相当精确的复现，在深度方向重迭的缺陷也得以分辨。实际样品的检测结果也证明了该模型的正确性。最后据实验结果讨论了该模型的局限性。

A contactless thermal wave sensing system has been used together withcomputer-basedtomography to successfully determine the distribution of interior defects in Cu specimens. Anew reconstruction model is proposed on the basis of an algebraic tomography model.Ac-cording to the physical essence of the thermal wave and the specific features of the experi-mental setup, a transmissivity and dimension factor each are proposed respectively to de-scribe the effects of the defects on the thermal wave and to compensate for the finite dimen-sions of the detector. It is shown that the model is successful provided that the thermal be-havior of the defects is abruptly different from that of the surroundings. For samples withartificial voids, the position and shape of the subsurface defects can be accurately repro-duced. Defects overlapping in the depth direction can also be recognked. The correctness ofthe model has been proved by the results of the actual sample.The limitations of the modelare discussed.