为探讨光热辐射(PTR)技术检测金属材料亚表面缺陷的能力, 理论分析了双层材料在强度调制激光束激励下产生的热波幅值和相位, 实验检测了阶梯型钢板样品、铝/钢质盲孔阵列样品和钢质填锡盲孔样品的光热辐射信号。对于直径分别为2.5, 2.0, 1.5 mm, 孔底厚度分别为0.2, 0.4, 0.6 mm的铝质盲孔阵列样品, 实验得到的光热辐射相位分布显示了盲孔直径和孔底厚度的可区分性。对于钢质盲孔阵列样品, 在盲孔填锡前后的光热辐射相位分布显示出一定区别。实验结果表明: 聚焦光斑的光热辐射检测能探测到深度小于或约等于面层材料热扩散长度, 截面积约等于或大于光斑面积的铝或钢内气孔缺陷。

To investigate the ability of photothermal radiometry (PTR) testing on the subsurface of metal materials, the amplitude and phase of thermal wave generated from a double layer material which is excited by intensity modulated laser are analyzed theoretically. Besides, the PTR signals of stepped steel samples, aluminum/steel samples with blind hole array, and steel samples with blind hole filled tin are tested in experiments. For the aluminum samples with blind hole array with diameters of 2.5, 2.0, 1.5 mm and hole bottom thickness of 0.2, 0.4, 0.6 mm, the PTR phase distributions obtained by the experiment show that the diameter of the blind hole and the hole bottom thickness are distinguishable. For the steel samples with blind hole array, the PTR phase distribution before and after the blind hole filling with tin shows a certain difference. The experimental results show that the PTR detection of the focused spot can detect the stoma defect in aluminum or steel. The depth of the stoma defect should be less than or approximately equal to the thermal diffusion length of the surface material, and the cross-sectional area of the stoma defect should be approximately equal to or greater than the spot.