为提高脉冲相位热像法(PPT)温度序列相位的计算速度和检测效率, 对传统的傅里叶变换(FFT)进行优化, 提出了适用于PPT的相位快速计算方法, 使运算速度提高了1.9～12.4倍。为确定相位算法中温度序列的最佳采样长度和频率分量, 结合热扩散深度公式提出了最佳采样长度估算公式。对铝合金试件和钢材料试件进行了脉冲相位热波检测, 当缺陷检测效果最佳时, 热图序列最佳采样长度分别为1.1 s和3.9 s, 基频相位差有最佳的缺陷分辨能力。结果表明: 该算法显著提高了相位计算速度, 量化的最佳采样长度估算公式能直接确定热图采样长度, 减少了操作的主观性和参数设置的随机性, 有效提高了脉冲相位热像检测效率。

In order to improve the phase calculation speed and detection efficiency of Pulse Phase Thermography(PPT), a fast phase algorithm optimized from Fast Fourier Transform(FFT) was proposed, with which the calculation speed could be increased by 1.9-12.4 times. To solve the optimal sampling length of thermal image sequence and frequency ratio, the calculation method for optimal sampling length was proposed based on the heat diffusion formula. Experiment was carried out on aluminium and iron specimens. Results show that the optimal sampling length is 1.1 s and 3.9 s for aluminium and iron specimens respectively and the phase difference at fundamental frequency has the best capability to distinguish defects. The calculation speed is evidently improved by the proposed fast algorithm and the optimal sampling length can be directly calculated by the improved numerical formula. Operation subjectivity and random settings of parameters can be avoided and the detection efficiency of pulse phase thermography can be improved.