Research On Infrared Thermal Wave Nondestructive Testing Device Based On Excitation Of Semiconductor Laser

As an emerging material,composite materials have been widely used in various fields of industrial production in recent years due to their high strength,light weight,thermal insulation.However,it may occur defects such as debonding and pore during processing and use.These problems will cause the performance of composite materials to decline rapidly,and ultimately affect the reliability of the materials.Although the destructive test detection method can better complete the quality inspection of the material,it destroys the structure of the composite material and can only be sampled for detection,and it cannot achieve online real-time detection.Therefore,the application of advanced non-destructive testing technology to achieve the detection and determination of composite defects is of great practical significance.As one of the important technologies of non-destructive testing,infrared thermal wave non-destructive testing technology provides a new method for the non-destructive testing of composite surface and sub-surface defects by virtue of its better defect recognition efficiency,convenient experimental operation and non-contact.Therefore,this thesis takes the gypsum board composite material as an example,analyzes the theory of active infrared heat wave non-destructive testing,builds a testing device based on semiconductor laser excitation and tests its performance,achieves accurate detection of surface and subsurface defects of composite materials through effective processing and segmentation of infrared image sequences.The research results of this thesis can be extended to the defect detection of other kinds of composite materials,and the specific research content is as follows:(1)Based on the relevant theoretical foundations such as heat transfer,the surface temperature field of the semi-infinite plate member with defects is deduced and analyzed under the condition of pulse thermal excitation,which provides a theoretical basis for experimental research.When the thermal excitation source is incident perpendicularly,the thermal distribution of the heat-insulating and the heat-conducting defective material is analyzed.According to the requirements of the inspection task,the pulse thermal imaging method would be selected in the thesis for infrared thermal wave non-destructive testing.The advantages of laser heating are analyzed and compared,and the semiconductor laser is finally selected as the excitation source for thermal wave non-destructive testing.(2)This thesis builds an experimental platform of infrared thermal wave nondestructive testing device based on semiconductor laser excitation,which can realize the fast and reliable detection of the tested specimen,and test and analyze the controllable performance and uniformity of the thermal excitation source system.The results show that the laser thermal excitation system constructed has the advantages of strong controllability and uniform excitation,and the test piece can produce an effective temperature difference to achieve non-destructive testing of the composite material.(3)In this thesis,the Kernel Principal Component Analysis—Fuzzy C-Means clustering image processing algorithm is used to effectively process and analyze the infrared image sequences and realizes the identification of the surface and subsurface defects of the gypsum board composite material.The experimental results show that the reconstructed image of the image sequence of the test specimen generated by the algorithm is clearer and the signal-to-noise ratio is enhanced.The algorithm has good anti-noise ability,and realizes the accurate identification of the defects of the tested specimens.The detected defects have a high degree of agreement with the actual defects and the segmentation accuracy is high.