Research On Measurement Techniques Of Material Mechanical Properties In High Temperature Test Based On DIC

Digital Image Correlation(DIC) is an optical measurement method, which has the advantages of non-contact, full field and low requirements for experimental environment, so that it is widely used for measuring mechanical parameters of materials at high temperature test in many areas. For example, engine, aerospace, national defense. After studying the correlation algorithm and the existing DIC system for high temperature test, a new DIC system is established and used to measure mechanical parameters of materials in high temperature test. By analyzing thermal expansion coefficients of Austenitic chromium nickel stainless steel sample at different temperatures, the system is verified to be feasible. The specific research are as follows:1) This paper research the performance comparison of some typical correlation algorithms of DIC, and proposes an improved Hill-climbing algorithm by adding threshold value judgment and more climbing points, because Hill-climbing algorithm has disadvantage of obtaining local optimal solution. Comparing with Hill-climbing algorithm, this new algorithm can improve the accuracy and guarantee searching speed meanwhile.2) Based on black-body radiation theory, a method using UV illumination and UV filter is applied in imaging at high temperature test. The experiment verifies that this imaging method reduces the effect of heat radiation more greatly than the blue light imaging method.3) Analyzing the effect of thermal airflow turbulence in high temperature test, and By combining pneumatic device and gray average algorithm, effect of thermal airflow turbulence to imaging system is reduced.4) A DIC software is designed based on Visual Studio 2010, and a new DIC system is established for high temperature test. Then, experiments of rigid body displacement and tensile measurement at room temperature are conducted to analyze the accuracy of the software, experiment of thermal strain is also conducted to analyze the feasibility of the hardware, and finally it is proved that the new DIC system is effective for measuring mechanical parameters of materials.