Study And Application Of Digital Image Correlation Method For Structural Deformation Measurement

Digital Image Correlation(DIC)is a traditional optical measurement method.As an engineering structural deformation measurement method,it has the advantages of high measurement accuracy,full field measurement and non-contact.Thanks to the development of computer and image vision technology,DIC technology began to emerge in the 1980s and has attracted extensive attention from scholars at home and abroad.So far,the theoretical system has been more comprehensive,and in practical application is becoming more and more popular.Such as:material testing,civil engineering,medical research,aerospace and so on.It can be said that digital image related methods have broad prospects,is a significant research significance of the emerging discipline.Digital image correlation method has its advantages,but also has its disadvantages,such as the limitations of the algorithm itself,the measurement accuracy is still a certain gap compared with the strain gauge,and the speed of calculation needs to be improved.Based on the existing research results,this paper further studies the accuracy and speed of digital images by consulting a large number of literature materials.The main contents are as follows:1.The basic principle of digital image correlation method is expounded.This paper introduces several common whole pixel search methods,such as step by step,thick and thin,and cross search.At the same time,the surface fitting method,gradient method and Newton rappson method in the sub-pixel search method are also introduced in detail,and the characteristics of computing speed,displacement accuracy and anti-noise performance between them are analyzed and compared by simulating speckle map.2.Summarized the existing situation of particle swarm optimization algorithm.Particle swarm optimization algorithm based on particle swarm optimization has the advantages of good robustness,global optimization,avoiding falling into local optimization,and the algorithm is easy to understand and program.Two methods for calculating subpixel displacement are proposed,starting from rigid body displacement measurement.Compared with the classical subpixel displacement method,the numerical simulation results show that the PIP method is feasible.3.Considering the complex displacement field of elastic displacement deformation of structure,the p-g method is proposed in this paper.The comparative experiment of simulating speckle pattern verifies its advantage in computing efficiency.Furthermore,the adaptability of the algorithm in noise resistance,non-uniform deformation and complex deformation is also tested.4.Based on MATLAB platform,the relevant calculation software of the algorithm was written.The deflection deformation of the beam is measured on site and compared with the traditional experimental method.