Research On High-precision Thermal Expansion Rate Measurement Technology For Near-zero-expansion Structures

The development of aerospace is the embodiment of a country's science and technology and economic strength.The working environment of spacecraft is harsh,and the requirements for manufacturing materials are very high.Near zero expansion structure is widely used in aerospace products,which can adapt to harsh environment and ensure normal performance.In this paper,the thermal expansion rate of near zero expansion structure is measured,and the digital image correlation method is determined to be used for the test through the selection of a variety of thermal expansion coefficient measurement methods.From the principle analysis,digital image correlation(DIC)includes three-dimensional matching,system calibration and displacement solution.The test platform is built through the selection of test materials,acquisition system and heating system.The influencing factors of thermal expansion rate measurement are summarized from three aspects: calculation formula of thermal expansion rate,test process of digital image correlation method and environmental factors in the test process.The influencing factors can be optimized.Four environmental factors are summarized,including light intensity,light wavelength,airflow disturbance and environmental vibration.Four kinds of environmental factors are analyzed from the influence mechanism.After the mechanism analysis,the thermal expansion coefficient of single factor in the temperature field is measured from the complex environment.The wavelength of light and vibration coupling test are added.Through the measurement test,the rule is summarized,the test is optimized,and the measurement accuracy is improved.The function model of the experiment of adding influence factors in the temperature field is established,and the appropriate function is fitted.The expressions of temperature and influencing factors are written by using appropriate fitting function.The influence of environmental factors on digital image correlation always exists.It is of great significance to explore its influence law for the development of digital image correlation.