Microstructure Evolution Investigation Of Materials Based On Digital Image Processing

The microstructural evolution and its effect on macroscopic mechanical properties are current one of the focus in material and mechanics science. The experimental investigation in situ is a difficulty thing. Hence, based on digital speckle correlation and image processing, we try to develop the experiment method that the microstructural evolution can be live surveyed. Some worth results are obtained by applying this method on the simple tensile test of polycrystalline metallic materials.Based on digital speckle correlation method, microscopic local strains are gotten. The error compared with electrical measure is analyzed and some improvement are proposed.A professional program based on MATLAB workbench is compiled to draw the outline of grain. When uneven gray, fuzzy boundaries and scratch exist in the images, a distinctive outline can yet be acquired. Also, the relations between applied loads and the shape parameters of grain are demonstrated after the shape of a grain is simulated as ellipse.For aluminum material, the strain field is measured within grain, and the change of strain across grain can be observed. The mutual relations among applied load, mean strain in grain and shape evolution of grain are displayed. The results show that the change of mean strain along with load is similar to macroscopic stress-strain curve and the shape parameter changes linearly along with inner mean strain.