Research On Key Technologies And Application Of Digital Image Correlation Based On Fiber Bundle

Digital Image Correlation(DIC)can measure the shape and deformation of a target in a non-contact manner,and has the advantages of high accuracy,high efficiency and ease of implementation,thus it is widely used in scientific research and engineering applications.However,it is difficult to apply DIC technology to these special scenarios because the electronic components of the camera are subject to interference in underwater,high temperature and strong electromagnetic interference environments.In order to increase the operability and flexibility of DIC measurement system,this thesis combined Fiber Bundle(FB)with DIC technology to establish a new measurement system.Because of its flexibility,high temperature resistance,corrosion resistance and electromagnetic interference resistance,the FB offers the possibility of multichannel detection and remote monitoring in environments where conventional cameras have difficulty working,which is especially important for DIC applications in underwater,high temperature and strong electromagnetic interference scenarios.In this thesis,we delved into the design and application of DIC measurement system based on FB and proposed a misalignment correction algorithm based on image alignment.The main research contents are as follows:(1)A single-camera threedimensional digital image correlation(3D-DIC)measurement system based on FB was developed to realize single-camera stereo measurement.In the thesis,the imaging and measurement characteristics of the proposed system were described from the optical path design and measurement principles,and the feasibility and accuracy of the system in reconstructing morphology and measuring deformation were verified through specific experiments.In addition,we also proposed an innovative optimization scheme based on image processing to further improve the measurement accuracy of the proposed system.The system is characterized by flexible spatial structure and the possibility of long-distance measurement,which provides a novel idea for the measurement in special scenarios;(2)A feature recognition-based misalignment correction method for coherent fiber bundle(COFB)was proposed and validated.Through the experimental design and algorithm development,the image misalignment problem caused by the spatial arrangement in the FB imaging system was solved.Subsequent experiments have demonstrated that the misalignment correction can not only effectively correct misalignment,but also mitigate the effect of fixed honey-comb patterns,thus improving the image transmission accuracy and measurement accuracy of the established system.This work provides new technical support to solve the image misalignment problem in the field of FB imaging technology,and provides a strong guarantee for the further application of COFB in the field of high precision optical measurement;(3)An ultra-long baseline video extensometer based on FB was established.The FB was used as a field-of-view(FOV)separation tool in this structure,successfully removing the FOV limitation of the system and smoothly increasing the scale length of single-camera video extensometer from 5120 pixels to 13600 pixels,effectively increasing the use of camera image resolution.The flexibility of the established system to be freely assembled opens up new paths for the measurement of large span specimens/shaped parts;(4)The preliminary study of simultaneous deformation field/temperature field at high temperature was completed.The technical difficulties and solutions of high-temperature DIC and spectral color temperature measurement were summarized through high-temperature deformation measurement experiments and high-temperature measurement experiments,respectively.The structural design and working principle of the simultaneous measurement scheme were described in the thesis,and the measurement scheme was given.Based on the above study,the technical difficulties of the simultaneous measurement were summarized and the optimization scheme was proposed in a targeted manner,which lays the foundation for the application of FB to the simultaneous measurement of high-temperature deformation field/temperature field.