The nondestructive testing (NDT) techniques active thermography and terahertz time domain spectroscopy (THz-TDS) are both newcomers to the large range of established NDT methods: Both are contactless imaging techniques and well suited for analysing layered materials e.g. ceramic coatings, polymer laminates and glued materials. These two methods are compared for characterising ceramic coatings. Measurement results show these two methods are practicable and complimentary for NDT applications of layered structures. The pulse-thermography is suitable for fast screening inspection and THz-TDS imaging performs well for the detailed investigation of coatings and boundary variations.
This paper examines pulse thermographic nondestructive evaluation of flat bottom holes of isotropic materials. Different combinations of defect diameters and depths are considered. Thermographic Signal Reconstruction (TSR) method [1] is used to analyze these results. In addition, a new normalization procedure is used to remove the dependence of thermographic results on the material properties and instrumentation settings during these experiments. Hence the normalized results depend only on the geometry of the specimen and the defects. These thermographic NDE procedures were also simulated using finite element technique for a variety of defect configurations. The data obtained from numerical simulations were also processed using the normalization scheme. Excellent agreement was seen between the results obtained from experiments and numerical simulations. Therefore the scheme is extended to introduce a correlation technique by which numerical simulations are used to quantify the defect parameters.Acknowledgement:
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