Study Of Strain Measurement Based On Digital Image Processing

Compared to traditional measurement of strain, digital image measurement applied to measure strain has many advantages, such as diversification of measure object, simple operation and no-damage to materials. It will have broad perspective in the fields of deformation measure.Advanced method of strain measurement based on digital image processing had been present in this thesis. Moreover, the points of material are localized by template matching and images from last deformation and previous deformation are analyzed and compared in order to achieve displacement of material.Rubber materials as object of research were extended uniaxially. During deformation of materials, the displacements were recorded and analyzed by the method of template matching. Then, both displacements were compared. The results of compare showed that relative error from strain proceeded by template matching and practical measurement had the maximum of 7.01%, but the minimum of relative error was 2.08%. Therefore, the resolution of this method is very high and this measurement applied to engineering is feasible.Uniaxial extension of the sample was simulated with elastic-plastic large deformation of Marc soft. The stress- strain curves recorded by experimental devices were fit with the material experiment curve in Marc soft in order to compute the model parameter of rubber material. Finally, the stress-strain curve of simulation and practical measure were compared, the results showed that analysis of simulation was in good agreement with the practical measure. Therefore, it verified further that the deformation of materials measured by template matching was credible and applied to engineering was feasible.