Extending Image Processing Strain Measurement System to Evaluate Fracture Behavior of Wall-Thinned Pipes

概要

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In this paper, an image processing strain measurement system was extended so that fracturebehavior of wall-thinned pipes, such as out of plane and large plastic deformation observed in bulging,can be evaluated by the system. Regular grids with nominal size of 10 x 10 mm were marked on 100Acarbon steel pipes and the images taken with 6 CCD cameras of 15 million pixels were correlated toachieve resolution of 0.3% strain. Strain of the cylinder outer surface was evaluated by 1) modeling thegrids as a cylindrical shell, 2) measuring deformation of the grid on a projected plane, and 3) applyingan updated Lagrangian method. The results indicate the possibility that the method is effective for themeasuring large strains of wall thinned pipes observed before failure.