Uncertainty in monitoring deformations of a planar surface has been among the major components that contribute to the overall positional error and thus must be minimized especially for small strains. This Study develops a Radon transform (RT)-based image processing for measuring elastic strain. A theoretical investigation is accomplished to propose a proper configuration of the marked lines and its in-between distance on the specimen surface. The method is applied to simulated strained image generated by MATLAB™ and verified using ASTM E83 for extensometer verification. In addition to measuring the axial and lateral strain of tensile testing, the Young’s modulus and Poisson’s ratio are measured. It demonstrates further that the integration of RT with cubic spline interpolation in detection of linear features enables high spatial resolution and less time of computation. Eventually, the method presented is insensitive to illumination variation and to in-plane rotation of specimen.

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