Technology Research Of Material Defect Detection Based On Linear Array Thermopile

Infrared thermal wave nondestructive testing is a nondestructive testing technology, it has been used widely in aviation, aerospace, machinery and other areas of the defect detection in materials. According to the infrared thermal wave nondestructive testing technique, different heat sources are used to heat the detected material actively. And then, different surface temperatures are caused by different thermal characteristics on the defect and non-defect of material. Based on different materials have different thermal radiation properties, the defects'information of the material can be obtained through scanning record or observation the material surface temperature differences in the rate of change.At present, the thermal imager is used in most nondestructive testing system as the core component, which has high practical value in terms of military and civilian. However, thermal imager also has many deficiencies, such as complex, expensive and difficult to promotion. The paper is aimed at analyzing the response characteristics of the thermopile infrared sensor based on the infrared nondestructive testing platform, and improving the defect detection accuracy of the system by the software processing.Firstly, based on the comprehensive analysis of the infrared radiation theory and heat wave theory, the linear array probe group with high sensitivity thermopile sensor is made up. According to the characteristics of thermopile sensor selected in the system,the temperature drift of operational amplifier in the preamplifier circuit and non-uniformity among sensors are analyzed, which are the two main factors affecting system test accuracy. Accordingly, the preamplifier and the subsequent processing circuit are designed to acquire weak infrared signals. Besides, the quadratic curve fitting correction, the cooling curve's differential curve and angle information of the differential curve are applied. The system's defect detection accuracy is improved by these methods. Finally, the samples of fiber board and rubber sheet were detected by infrared thermal wave. By analyzing the angle information, an analysis report is made. The result shows that the defect of the materials can be detected effectively by the angle information analysis.