Research On Key Technology Of Material Testing In High Temperature Environment Based On Digital Image Correlation

Digital image correlation(DIC)method is a kind of displacement and strain measurement technique based on visible light illumination.It can realize non-contact and full-field measurement with lower requirements on the measurement environment,thus it's widly used in testing and research for mechanical properties of materials at high temperature,especially in aerospace,engine and shipbuilding applications.But there are many factors affecting the measurement accuracy due to the complexity of the high temperature environment,of which the influence of the thermal disturbance on digital image correlation method is the most obvious.In order to improve the measurement accuracy of DIC in high temperature environment,this paper studies the related compensation methods and thermal disturbance elimination methods,and builds a high temperature DIC measurement system and applies it to the high temperature mechanical properties test of materials.At the same time,the accuracy and feasibility of the proposed method are verified by displacement and strain experiments.The specific research work is as follows:(1)The technical principle and basic concepts of the DIC method are introduced.Moreover,We analyzed the commonly used integer pixel localization and sub-pixel search algorithm,and selected the relevant search algorithm combination applicable to the system.(2)The influence of thermal lens effect on high temperature measurement is studied,and a compensation method based on adjustable mirror is proposed,in DIC system,an angle-adjustable mirror is added to compensate the displacement of x and y direction caused by the thermal lens effect.(3)A new error elimination method for thermal disturbance is proposed.We use a color camera to separate the error caused by thermal disturbance from the actual measurement results,and then establish a mathematical model to correct the measurement results of the measured object in the heat flow field.(4)A set of testing software is written based on Visual Studio 2010 and Opencv compiler environment,and a high-temperature DIC measurement system is built and experimental research is carried out.The accuracy and effectiveness of the system are verified by analyzing the data of rigid body motion experiment and tensile test in room temperature and high temperature.