Dynamic Thermal Tomograpy Detection Experimental Investigation Of Defects In Grain Cladding

Solid rocket motor has applied in many fields,such as rockets,missiles,etc.,and their stability and reliability have attracted extensive attention.As an important part of the solid rocket motor,the manufacture of grain cladding tends to be mature,and the NDT technology is still in development.The grain cladding nondestructive testing techniques such as visual analysis,X ray detection,ultrasonic detection,laser holographic detection method has the problem such as strong subjectivity,low detection efficiency,complex implementation conditions,so to find an efficient,easy implementation,high sensitivity detection method has important meaning.Dynamic thermography tomography(DTT)is one of the infrared pulse thermal wave imaging testing techniques,which provides information about the depth and lateral dimensions of defects,and make the expression of defect structure more accurate and comprehensive.In this paper,the influence of grain cladding discontinuities structure on pulse wave signal is analyzed and the pulse wave imaging algorithm simulation has been carried out,investigated the applicability of pulsed thermography testing of grain cladding.On this basis,a pulsed thermal wave imaging system and a dynamic thermal tomography Data processing platform has been designed,and the pulse thermal wave imaging testing experimental investigations and dynamic thermal tomography technology experimental investigations have been studied,and the applicability of this technique to the cladding of the column has been discussed.Firstly,in this paper,the diffusion process of pulsed heat flow in the grain cladding has been analyzed theoretically,and a one-dimensional heat transfer model was established and the influence of defect depth on thermal wave signal was analyzed;a three-dimensional heat transfer model was established,and the finite element method was used to solve the model;the influence of defect depth and lateral scale on thermal wave signal was analyzed,and the simulation test of pulse thermal wave imaging algorithm was carried out,and the applicability of pulse thermal wave imaging technique to the grain cladding was discussed.Secondly,the pulse thermal wave imaging system has been designed,including hardware selection,detection platform construction and software system design,and the debonding and porosity defects simulated samples of the grain cladding were designed.The experimental research on the influence of discontinuous structure of the grain cladding on the thermal wave signal was carried out,and the applicability of the pulsed thermal wave imaging test and dynamic thermal tomography technique to the material was determined;the experimental research on pulse thermal wave imaging algorithm was carried out to determine the applicability and existing problems of each algorithm.Finally,the experimental investigations on classical dynamic thermal tomography algorithm has been carried out,and the existing problems of this method were determined;a dynamic thermal tomography algorithm based on multiple feature maps was proposed and experimental investigations were carried out to determine the applicability of this method to the grain cladding.a tomographic technique based on wavelet transform was proposed,and corresponding experimental investigations were carried out to determine the applicability and existing problems of each algorithm.