Measurement Of Mechanical Properties Of Fish Materials Based On Digital Image Correlation Method

Fish skin and scales are a kind of high-quality natural materials,among which fish scales as a kind of biological armor can provide an ability of protection,while fish skin has en edible and wearable value.In some of China's ethnic minorities,fish scales and skin have a long history of use.At present,there are few researches on fish skin and scales in China,mainly on their components and nutritional value,but few on their mechanical properties and microstructure.In this paper,based on the digital image correlation method and a set of self-built strain measurement system,the mechanical properties of fish skin and fish scales during uniaxial tension were studied and analyzed,and the surface and section microstructure of fish scales were observed by magnifying the images with the help of optical microscope.The results of this paper have certain reference value for the development of fish biomimetic materials in the future.The digital image correlation method can be divided into integer pixel part and sub-pixel part.In the integer pixel part of this paper,an improved algorithm for mountain climbing is used,the problem of local extremum in traditional mountain climbing method is improved,increased the whole pixel search range to 100 pixel.In addition,compared with the traditional method of mountain climbing,the accuracy and speed are greatly improved.The influence of search step size and measured displacement on search time of this improved method was studied,the results are shown in the search step size of 12 pixel.The larger the step size,the faster the speed,the larger the measurement displacement and the longer the search time.The subpixel part USES the reverse combination method and the simulated speckle pattern is used in the experimental measurement.A set of apparatus for measuring tensile strain of fish skin and scales was set up,the specimens with speckle treatment were tested by tensile test and data were collected.The results showed that the elastic modulus and strength of the head and middle fish scales were better than that of the tail,while the mechanical properties of the fish skin specimens were better than those of the head and middle part.