Application Of Digital Image Correlation Method In The Research Of Material Mechanical Properties

As a full field,non-contact modern optical measurement method,digital image correlation method can obtain the actual deformation of an object by comparing the changes of surface gray information before and after deformation.DIC theory after decades of continuous development and improvement,the application of related methods has become increasingly mature,and is widely used in scientific research and practical engineering,such as nondestructive testing,road and bridge,aerospace and other fields.Fish skin is a common biological material,and studying its specific mechanical properties has great reference value for the development of bionic materials in the future.In order to further study the carp skin and analyze its mechanical parameters,this paper compares and analyzes the specific performance of carp skin in different stretched states based on the digital image correlation method,and the specific application of DIC related methods and the use of bionic materials foundation.In view of the importance of search algorithm in digital image correlation,this paper studies the implementation principle and process of several basic search algorithms based on the basic principle,shape function and correlation criterion function of digital image correlation.In order to further improve the accuracy of DIC correlation method,three interpolation methods in Sub-pixel Search stage are introduced and compared.It is considered that bicubic polynomial interpolation method has better effect.Besides,focused on the performance of Newton-Raphson(NR)and inverse compositional-Gauss Newton(IC-GN)under different displacements,windows,and initial values,it is concluded that the IC-GN algorithm has better efficiency without loss of accuracy.Aiming at the IC-GN algorithm requiring accurate initial values to quickly converge to accurate results,an initial value estimation method based on feature matching is proposed,first,match the corresponding coordinate point pairs in the images before and after the deformation,and then use affine transformation to calculate the initial deformation parameters based on the matched point pairs,and use this initial value as the iterative initial value of IC-GN to calculate the precise deformation parameters.Based on the Q-400 strain measurement system and horizontal tensile machine,a related experimental platform was built to realize continuous stretching and image acquisition of carp skin.Using the algorithm and strain measurement system in this paper to analyze and calculate fish skins in different stretched states.The experimental results show that the algorithm in this paper meets the relevant requirements in speed and accuracy,and provides support for the wider application of DIC method.