线性调频激励的红外热波成像检测技术

线性调频激励的红外热波成像检测技术是一种基于线性调制热波信号处理的主动式红外热成像技术，能够弥补传统红外锁相热像检测的单一调制热波只能探测相应扩散深度缺陷的不足，可准确检测不同深度范围内的缺陷形状及尺寸。阐述了线性调频红外热波成像检测技术的原理、分析方法和实验。采用有限元方法对线性调频啁啾(Chirp)规律变化热流在构件中的传递过程进行了分析。利用相关算法计算了表面温度(热波)信号的相关峰值及其对应的时间，形成了表面温度相关峰值图像与峰值时间图像。利用Chirp规律调制卤素光源作为热激励源对金属平底孔试件进行激励加载，通过Jade MWIR 550 焦平面红外热像仪进行图像序列采集。分别利用时域相关处理与频域FFT扫描得到了表面温度(热波)信号的相关峰值及对应时间图像和不同频率下的相位图像。试验结果表明，在给定激励条件下，相关峰值图像和频域相位图像能够可靠地确定不同深度缺陷的几何特征。

Technology of linear frequency modulation infrared thermal-wave imaging for nondestructive testing

Linear frequency modulation infrared thermal-wave imaging(LFMITWI) is an active infrared thermography based on linear frequency modulation thermal-wave signal processing,which makes up for the disadvantage of traditional lock-in thermography that only detects the limited depth of subsurface defects by using a single frequency modulation thermal-wave.The theory,mathematics analysis and experiments in support of the LFMITWI for nondestructive subsurface defects detection in solids were described.The finite element modeling was used to analyze the thermal-wave behavior generated by linear frequency modulation chirp heat flux.The cross correlation peak value and its time were calculated by the use of cross correlation between surface temperature signal and reference chirp signal,and the peak value image and its time image were obtained.In experimental study,the law of chirp modulated halogen lamp was used as active heat source into metal flat-bottom holes sample,and the thermal-wave image sequences were collected with Jade MWIR 550 FPA infrared camera.The cross correlation processing of time field and Fourier transform scanning of frequency field were used to obtain the peak value image,peak value time image and phase image respectively.The experimental results show that the peak value image and phase image are helpful to identify the geometric characteristic of different depths′ defects under the condition of given chirp thermal stimulation.