任意曲面物体表面物性及深度轮廓的激光光热检测技术研究

项目名称： 任意曲面物体表面物性及深度轮廓的激光光热检测技术研究

项目编号： No.60877063

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 王钦华

作者单位： 苏州大学

项目金额： 32万元

中文摘要： 本项目系统研究了基于格林函数方法的激光光热技术进行层状曲面物体（包括柱面和球面）的物理性质和以及物理性质的深度轮廓重建的机理和方法。系统建立了对应不同几何形状复合结构样品的格林函数以及对应的热波温度场的计算方法。对各种热波场相对于材料的热物理性质，材料的几何尺寸以及测量方法和方位角的依赖关系进行了详细研究。基于本项目建立的理论模型，首次提出和验证了一种"相似归一化"方法对非均匀曲面样品进行表面物性及其深度轮廓重建的方法。采用层状柱面、球面和平面样品的热波模型，具体研究了从热波信号中消除样品曲面因素的原理和物理机理，发现了经过"相似归一化"后曲面样品的热波场与平面样品热波场的等价原理，并对样品的相对曲率半径，表面非均匀层厚度以及测量方位角对该等价原理的适用条件进行了系统研究。基于曲面样品理论和等价的平面理论，对不同尺寸表面硬化的柱形样品的表面热物理性质及其深度轮廓重建技术进行了实验研究。实验结果证实了等价原理的正确性。该项目的研究结果开辟了利用现有简单的平面样品的深度轮廓重建方法进行曲面样品的深度轮廓重建技术，使得光热技术对任意曲面样品的检测成为可能。

中文关键词： 激光光热辐射；任意曲面样品；热波场等价原理；相似归一化方法；热物理参数深度轮廓.

英文摘要： Photothermal characterization of multi-layer cylindrical and spherical curved solids using Green function method is investigated systematically. A theoretical methodology of calculating the thermal-wave Green's function and the thermal-wave field corresponding to the composite structures of both cylindrical and spherical geometries is established. The general characteristics of the thermal-wave field with respect to the thermophysical properties of the material, the geometry dimensions of the sample, and the measurement scheme are studied in detail. Based on the theoretical models that are established in this project, a generalized similarity normalization (SN) methodology for characterizing depth profiles of continuously varying thermophysical properties in curvilinear (cylindrical and spherical) solids is proposed and demonstrated for the first time, in which equivalence principle of the normalized thermal-wave fields between curved and flat surfaces under certain conditions has been found. Specifically, the principle and the physical mechanism of the elimination of the surface curvature effect from the overall photothermal signal is introduced based on theoretical models of cylindrical, spherical and flat solids with multi-layer structures. The effects of the relative values of radii of curvature of the curvilinear solid, the thickness of the inhomogeneous surface layer and the measurement azimuthal angle on the validity of the technique are discussed in detail. Experimental reconstructions of thermophysical depth profiles of hardened cylindrical steel rods of various diameters are performed based on both curvilinear theory and the equivalent flat surface theory. The reconstructed results are compared and validated. The mechanism and methodology introduced in this project cover a full solution of characterizing curved solids including theoretical thermal fields of homogeneous, 2-layer(thin film system), and multi-layer(or continuously varying) system, experimental demonstration and the reconstruction method of depth profile of arbitrary curved solids. The equivalence methodology opens and paves a new way of characterizing arbitrary curved solids using existing inversion techniques for flat solids on the basis of the similarity normalization photothermal technique proposed in this project. This is significant in that it enables the application of photothermal depth profilometric techniques to inhomogeneous solids of arbitrary geometries.

英文关键词： photothermal;arbitrary curvilinear sample;equivalence of thermalwave fields; similarity normalization; depth profilimetry of thermophysical parameters