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A similarity normalization method for thermal-wave depth profiling of layered and radial continuously varying inhomogeneous thermophysical properties in cylindrical solids is investigated and related to that developed for inhomogeneous flat solids both theoretically and experimentally using photothermal radiometry. The deconvolution of the curvature effect out of the overall thermal-wave field of inhomogeneous cylindrical solids allows conventional rectilinear thermal-wave inverse-problem techniques to be applied to thermal conductivity depth profile reconstructions in layered and inhomogeneous depth-varying cylindrical solids and opens new possibilities for depth profilometry of such solids using existing flat-surface inverse techniques. [ABSTRACT FROM AUTHOR]

Motivated by increasing practical and industrial applications of photothermal techniques in the measurement of materials of various shapes with curvature, we extend the applications of photothermal diagnostics to solid spheres, in which both theoretical and experimental photothermal radiometry studies on spherical geometries and thermal diffusivity of the sample are discussed. Based on the Green function method, a full thermal-wave field distribution of a spherical solid is obtained. The characteristics of the thermal-wave field with respect to thermophysical properties of the material, the diameter of the solid, the size of the incident laser beam, and the measurement angle are discussed. Experimental results with steel spheres of different diameters exhibit good agreement between the theory and the experiments. [ABSTRACT FROM AUTHOR]

We extend the applications of the photothermal diagnostics by means of laser-infrared photothermal radiometry (PTR) to samples with curved surfaces. Specifically, we present both the theoretical and experimental PTR studies on solid cylindrical samples (surfaces). Based on the Green function method, the thermal-wave field distribution of a cylindrical surface that is under the excitation of a periodically modulated uniform beam is obtained. The laser beam, which is of a cylindrical symmetry, impinges uniformly, partially or fully, on the cylindrical surface, which is practically infinitely long along the axial direction. The characteristics of the thermal-wave field with respect to the thermal diffusivity of the material, the diameter of the sample, the size of the incident beam, and the measurement of the angle are discussed. Experimental results are in good agreement with the theory. [ABSTRACT FROM AUTHOR]

Describes a technique called nonlinear photothermal radiometry that applies the second-harmonic thermal waves to material inspection and nondestructive evaluation. Implications of the measurement results of the second-harmonic signal; Description of the theoretical model developed; Differences between the fundamental and the second-harmonic signal.

Frequency-domain photothermal radiometry has been used for the evaluation of the hardened case depth and the measurement of the thermophysical properties (thermal conductivity and diffusivity) of cylindrical C1018 heat-treated steel rods. The measurement results of several steel cylinders nominally hardened identically during a common heat-treating process were consistent with each other and also with mechanical indentation hardness test results. The application of the two-layer composite cylinder thermal-wave theory yielded an effective case depth within the discrete two-layer thermal-wave approximation. This technique provides a relatively simple noncontact and nondestructive method for evaluating the thermophysical parameters of layered cylindrical samples. The good fit of the experimental frequency scans to the two-layer thermal-wave model was shown to constitute a reasonable method for calibrating actual continuously decreasing hardness depth profiles by means of abrupt two-layer-equivalent profiles. [ABSTRACT FROM AUTHOR]