Research On Image Processing Algorithms Of High Temperature Video Extensometer

With the development of material science and technology,the increasing demands for reliable methods of material mechanical properties testing in complex environments.However,the material mechanical properties testing exists deficiency at high temperature.For instance,the traditional contact extensometer cannot measure non-standard specimen with a small gauge length,it also cannot be suitable for testing in high temperature environment.This article studies the high temperature video extensometer test system.For video extensometer encounters problems such as thermal radiation and stray light which affect the imaging quality at high temperature,the optical design is conducted.In order to achieve trace facility,the non-standard specimen with sharp corners is designed.The dissertation introduces dual detected crossing lines algorithm of simplified F?rstner,improved algorithm of Curvature Scale Space and Improved algorithm of Harris corner detection for feature tracking.For the purpose of reducing influences of image noise and improving the measuring accuracy of video extensometer,image processing methods such as bilateral filtering algorithm and morphological filtering algorithm are applied to image smooth denoising.Sub-pixel edge detection algorithm based on hyperbolic tangent fitting is presented to increase accuracy of edge positioning.The high temperature video extensometer test system has the advantages of non-contact,non-loss,high precision and could test the material mechanical properties of metallic materials under the harsh condition in high temperature.To verify the feasibility of the image processing algorithms for high temperature video extensometer studied in this thesis.The experimental platform of high temperature video extensometer is set up to carry out tensile test at room temperature and high temperature.Software interface and modules mainly program in C++ or C#.Elongation curves are obtained from comparison experiments between Dantec Q400 test system and the proposed system.The dissertation researches on algorithms of high temperature video extensometer which has achieved well expectation of testing performance by the verification results.