热障涂层脱粘缺陷脉冲压缩激光红外热成像检测

针对热障涂层热导率低,激光红外热成像检测效果不佳等问题,本文提出了一种基于脉冲压缩的增强型激光红外热成像方法用于热障涂层系统脱粘缺陷的检测。该方法利用频率或周期调制脉冲串激光热源,再通过信号处理将接收到的时域信号压缩成有效峰值高的窄脉冲信号,从而有效增强检测信号的信噪比。首先,建立热障涂层多层结构脉冲压缩激光红外检测有限元数值计算模型,模拟了周期调制脉冲串激光激励下结构内部热流的传播过程以及内部缺陷对温度场分布的影响,研究了不同激励参数对于温度场分布的影响。模拟结果表明,单调递减型且热激励时间为2s左右的脉冲激励形式能获得最佳的检测效果。其次,通过脉冲压缩技术对数据信号进行后处理,得到了更能反映缺陷信息的温度场分布图。最后,通过实验验证了基于脉冲压缩的增强型激光红外热成像方法对热障涂层脱粘缺陷检测的有效性,实验结果表明,该方法在一定程度上提高了缺陷检测的灵敏度与信噪比。

Detection of debonding defects of thermal barrier coatings by pulsed compression laser infrared thermal imaging

Aiming at the problems of low thermal conductivity of thermal barrier coating and poor detection effect of laser infrared thermal imaging,an enhanced laser infrared thermal imaging method based on pulse compression is proposed in this paper to detect the debonding defect of thermal barrier coating system.The frequency or period modulation pulse laser heat source is used to compress the received time domain signal into a narrow pulse signal with high effective peak value through signal processing,thus effectively enhancing the signal to noise ratio of the detection signal.Firstly,a finite element numerical model for pulsed compression laser infrared inspection of multilayer structures with thermal barrier coatings is established to simulate the propagation of heat flow inside the structure and the influence of internal defects on the temperature field distribution.The simulation results show that the best detection effects are obtained with a monotonically decreasing pulse excitation with a thermal excitation time of about 2s.Secondly,the data signal is post processed by pulse compression to obtain a temperature field distribution diagram that better reflects the defect information.Finally,the effectiveness of the enhanced laser infrared thermography method based on pulse compression for the detection of debonding defects in thermal barrier coatings was experimentally verified.The experimental results show that the method improves the sensitivity and signal to noise ratio of defect detection to a certain extent.