脉冲相位法及其在复合材料无损检测中的应用

为了抑制各种因素的干扰,提高脉冲热像无损检测对复合材料的缺陷探测能力,研究了基于像素点时间信号FFT(Fast Fourier Transform)的脉冲相位法及其在复合材料结构检测中的应用.介绍了利用脉冲相位法进行脉冲热像数据处理的原理,讨论了信号处理中的频域混叠和频谱泄漏问题,进行了碳纤维增强塑料试件的脉冲相位法检测实验,以信噪比为指标对图像处理效果进行了定量比较.通过实验说明脉冲相位法不仅具有快速获取原始热像、对表面加热不均不敏感、无需预先知道无缺陷区的位置的优点,而且对随机噪声有较好的抗干扰能力,所得的相位图像有较高的信噪比,因此是复合材料结构无损检测和评估的有效方法.

Pulsed phase thermography and its application in the NDT of composite materials

To suppress various interference and increase the detection capability of pulsed thermography for defect inspection of composite materials,PPT(pulsed phase thermography) based on FFT(fast Fourier transform) for the time history of each pixel and its application to composite structures were studied.The principle of PPT for processing pulsed thermographic data was described;the problems of frequency domain aliasing and frequency spectrum leakage in the signal processing were discussed.A PPT experiment was made on a carbon fibre reinforced plastic sample,and the image processing effects were quantitatively compared by the signal-to-noise ratio.The experimental results show that PPT not only has the advantages of rapid image acquisition,less sensitivity to inhomogeneities of surface heating,non-necessity to know a prior position of a sound area,but also has good robustness to random noise and greater signal-to-noise ratio,so it is an effective method for NDT & E(nondestructive testing and evaluation) of composite structures.