Research On Low-Cost And Non-Contact Infrared Nondestructive Testing Technology

Infrared nondestructive testing technology is one of the hot research topic in the field of nondestructive testing.It has wide development prospects for it’s unique advantages of fast,non-contact,accurate and intuitive testing.In this paper,an infrared nondestructive testing system that is based on infrared thermopile sensors and can detect internal defects with large depth width ratio of several composite materials was developed.The system has function of analysising infrared nondestructive testing and characteristics of low cost,wide used and high flexibility,which meets demand of real-time detection of industrial material.This article firstly carried out the overall design of the system according to the requirements of system.In addition,the noise characteristics of resistance and operational amplifier was analyzed,the low noise amplifier circuit and low-pass filter circuit was designed according to the performance parameters of infrared thermopile sensors.Secondly the wireless data transmission circuit was designed to transmit data encrypted according to the requirements.Then the the multi-channel high-speed sampling A/D conversion circuit,low ripple coefficient power circuit,PC Labview data display program,FPGA controller module and control program of data collection was designed.Thirdly,an improved calibration algorithm of sensors’ heterogeneity was presented in view of the inhomogeneity problems of linear array infrared thermopile sensors.This algorithm is based on traditional two point calibration algorithm and can be used in a wide temperature range.A good effect was achieved through utilizing this calibration algorithm.Finally,the infrared non-destructive testing experiment using high-power heating lamp on three different thermal diffusion coefficient material carbon-carbon composite materials,carbon fiber composite materials and glass fiber composite materials was made.It is concluded from the result that the system noise index is 0.067mV,SNR is 89dB and the retio of depth to width of internal defect can detected are:carbon-carbon composite materials is o.4,carbon fiber composite materials is 0.5 and glass fiber composite materials is 0.8,which shows that this system has characteristics of low cost,wide applicable scope,high flexibility and can detect internal defect with large ratio of depth to width.