Research On Digital Speckle Correlation Method And Its Application In Fish Skin Tensile Measurement

Digital Speckle Correlation Method(DSCM)is a measuring method of full-field deformation and non-contact.The surface displacement and stress change of the measured object can be obtained by image processing.It is widely used because of its low environmental requirements and high measurement accuracy.After decades of research and exploration,the relevant theories have become relatively mature and have been well applied in engineering,which has brought great help to related scientific research.Fish skin is a kind of high quality leather material,which microstructure has been applied in bionics.In order to fully understand its mechanical properties,this paper to study the tensile properties of carp skin materials with DSCM technology,so as to provide data support for its potential bionic applications.Integer pixel is the cornerstone of the digital speckle correlation method.In order to improve the search speed of the whole pixel,genetic algorithm,particle swarm algorithm and artificial fish swarm algorithm are selected in this paper.The selection of the sub-region shape function and related functions under different deformations is expounded.The search speed and matching precision of the three intelligent algorithms are verified by simulating the speckle pattern.In order to improve the measuring accuracy of sub-pixel,the paper compares the effect diagrams of different interpolation methods,put forward a sub-pixel algorithm combining fitting and bicubic spline interpolation,and compares it with the inverse compositional Gauss-Newton algorithm.It is concluded that the inverse compositional Gauss-Newton algorithm has better applicability,but the combined algorithm has better comprehensive advantages,taking into account both speed and accuracy.An experimental platform was set up for the performance test of carp skin.The platform is composed of Q-400 micro-deformation measurement system and horizontal tensile testing machine,which can realize image acquisition and storage in the stretching process.The above algorithm is used to process the acquired image.The results show that the method used in this paper is fast and accurate,which is suitable for the application of digital speckle correlation method in the measurement of carp skin deformation.The paper also analyzes the influence factors in the experimental process.It turns out that the error is within the controllable range.