Research And Application Of Full Field Strain Measurement Method Based On DIC Technology

The development level of large equipment such as aero-engines and aerospace vehicles is an important strategic guarantee for national security.It is also a concentrated expression of a country’s scientific and technological level and comprehensive national strength.Its performance development not only promotes the rapid development of the aerospace field,but also promotes the rapid development of materials,machinery and other fields.However,largescale complex equipment works under extremely complex conditions for a long time.The strain load generated by high temperature and high pressure can easily cause cracks and fatigue in the core components,which has an extremely adverse effect on the working state and life of the core components.How to measure the mechanical parameters of core components and restore the strain field in a space-constrained environment has become an urgent problem to be solved.In this paper,based on the digital image correlation method,a full-field strain analysis platform,a double-mirror imaging device and a movable optical image acquisition device are built.A 2DDIC full-field strain measurement method based on virtual camera array and a 3D-DIC fullfield strain measurement method based on correlation splicing algorithm are proposed.The specific research contents are as follows :(1)In order to meet the strain measurement requirements of the core components of the equipment,this paper builds a full-field strain measurement system based on the digital image correlation method.Firstly,the strain measurement device is tested and built.Then,based on the strain measurement system,the optical system image acquisition device and the double mirror imaging device are integrated.Finally,the strain measurement system is simulated and optimized to improve the measurement performance of the device.(2)In order to realize the strain measurement of large field of view with ultra-high resolution of camera,a 2D-DIC full-field strain analysis method based on virtual camera array is proposed.In order to eliminate the out-of-plane motion introduced by the eccentric loading of the test fixture in the 2D-DIC strain analysis,a double mirror imaging technique is proposed.In order to eliminate the continuous change of strain field by image stitching,a speckle matching fusion algorithm is proposed.Finally,the static error analysis experiment and the uniform strain field analysis experiment are designed to verify the feasibility and effectiveness of the full-field strain measurement method.The axial and transverse average strain errors of this method are 0.68% and 0.64% respectively,and the experimental simulation results are good.(3)In order to realize three-dimensional full-field strain measurement and eliminate the strain error caused by the non-verticality of the optical axis of the camera and the surface of the measured object,this paper proposes a 3D-DIC full-field strain measurement method based on correlation stitching algorithm.The multi-camera 3D-DIC method collects images in different regions of the sample,and proposes a correlation stitching algorithm to stitch the collected images into a panoramic image to restore the complete displacement field and strain field of the sample.In order to verify the feasibility and effectiveness of the method,this paper designs comparative experiments of movable 2D-DIC,3D-DIC and camera array-based DIC methods,and analyzes the simulation results and error causes.The experimental results show that the lateral and longitudinal strain errors of this method are 0.64% and 0.61%,respectively,which are less than 1.07% and 1.01% of the DIC method based on camera array and 0.97% and 0.87%of the movable 2D-DIC method,which proves the effectiveness of the full-field strain measurement method.