Study On Influence Of Hot Air Flow On Digital Image Correlation And Its Correction

In recent years,digital image correlation measurement methods have been widely used in high temperature environments.When using digital image correlation measurements in a hot environment,the air density directly affects the refractive index of the light in the air,and the air density varies with the ambient temperature.Convective motion occurs between the air of different densities,so when In a non-closed environment,due to the uneven heating between air molecules,it will definitely cause a change in the refractive index of the air,which in turn causes problems such as blurring and blurring of images collected by digital cameras.In response to this problem,I will study the measurement errors of the displacement and strain fields caused by the hot gas flow when measured with DIC in the hot environment.By studying the distortion field pattern and systematic physical parameters,the physical parameters mainly include the distance between the test piece and the heat source L,the uneven refractive index field width W,and the temperature gradient in the imaging area_?x^?T.The fixed calculation method is used to achieve the consistency of measurement results,ensuring the reliability and correctness of the measurement results,and making the digital image correlation measurement methods truly become a kind of test tools that can be widely used in various environments,as well as improving the environmental adaptability of digital image-related full-field measurement and meeting the accuracy requirements related to full-field deformation measurement,which is of great significance for accelerating the universal application of digital image correlation measurement technology.In this paper,the influence of hot airflow on digital image correlation measurement is carried out,and then the pneumatic device correction method and code point correction method are proposed.The main contents and research results of this paper mainly include the following three parts:?1?The theoretical background of the influence of hot airflow on the digital image correlation method was introduced.The results of the study indicate that the experimental error of the 3D-DIC measurement caused by the hot gas flow is the result of the combined action of these three variables.These three variables are distance between the test piece and the heat source L,the width of the uneven refractive index field W,and the temperature gradient in the imaged area_?x^?T.?2?The effects of ambient airflow on the measurement of 3D digital image correlation were studied.The camera self-heating experiment and wind environment experiment were designed to systematically evaluate the influence of ambient airflow on digital image correlation measurement.Through the experiment of the influence of camera self-heating on digital image correlation measurement,the method of preheating the camera to the thermal equilibrium state and then conducting the experiment is proposed.The experiment of the influence of airflow interference on the digital image correlation measurement is carried out by simulating the actual air flow with a smooth airflow,indicating the environment airflow has little effect on digital image-related measurements,and these errors are negligible when using DICin normal temperature application experiments.?3?Systematically studied the influence of hot air flow on digital image correlation measurement,and introduced the normalized distance.When the heat source is under the test piece,it is recorded as“0”.When the heat source is under the camera,it is recorded as“1”.The influence of the hot airflow on the digital image correlation measurement is proposed.I propose two correction methods,namely the pneumatic device correction method and the code point correction method,and evaluate the effectiveness of the two correction methods.The experimental results show that the effect of the code point correction method is obviously better than the pneumatic device correction method.The correction rate is up to 70%,and the correction effect is obvious.The measuring device of the code point correction is simple and the experiment is easy to operate.The code point correction method has the irreplaceable superiority of the pneumatic device correction method.