Study On Speckle Characteristics And Error Analysis Of Digital Image Correlation

As a non-contact optical measurement method,digital image correlation method(DIC)has become one of the most active research fields in experimental mechanics.Because of its simple equipment requirements,low measurement environment requirements and wide application range,it is widely used in scientific research and engineering.DIC obtains full-field deformation by tracking the position of speckle before and after deformation.The speckle pattern has an important influence on accuracy and speed of DIC.Research of speckle pattern has practical significance.As an important part of quantitative research on DIC,error analysis is also a focusing problem for scholars.This paper is devoted to the research of speckle pattern and error analysis of DIC.The application method of regular pattern in DIC method is established.Theoretical model of frequency domain error is established to predict calculation error.Based on regular pattern,this paper also proposes a method to control calculation errors.In research of speckle pattern,this paper analyzes the shortcomings of traditional random pattern,proposes to apply regular pattern to DIC method and optimizes regular pattern.Numerical simulation and actual experiments show evidence on its more accuracy relative to random pattern.Based on the regular pattern,this paper also proposes a moiré fringe method based on correlation coefficient.The method obtains low-frequency moiré fringes with full-field correlation coefficients quickly,which containing information of deformation.In this paper a hybrid measurement method based on regular pattern is proposed by combining this method with DIC.The hybrid method takes the full-field deformation from moiré fringe as the initial value estimation into DIC.With the accurate initial value estimation from moiré fringe,DIC method can quickly converge to exact value.With the aspect of error analysis,the frequency domain error theory model is established from one-dimensional DIC frequency domain analytical solution.The numerical simulation demonstrates its effectiveness in analyzing DIC error.Each error is analyzed based on different forms of this model.The frequency domain random error model is a summary of several spatial domain random error models.Frequency domain systematic error model can explain how different frequency components in pattern constitute systematic error.This paper also proposes an interpolation error control method based on regular pattern,which shows well effect and application prospect.In addition,this paper researches error factors of DIC method and obtains proportion of each error.