A Robust Image Processing Algorithm for Optical-Based Stress–Strain Curve Corrections after Necking

Abstract To determine the stress–strain curve of a ductile material up to fracture from tensile test, necking contour is measured by an optical measurement technique. The radius minimal cross-sectional area and curvature are used as input for analytical corrections curve, well finite element inverse simulations. Due increasing surface roughness that develops during testing, precise determination specimen very challenging. This crucial, since second derivative required estimating curvature. A dedicated contour-tracking algorithm was developed deal with painted white black background found provide enough contrast. new implemented in software, which made available open source. Tests were isotropic, commercially pure aluminum alloy axisymmetric, peak aged AA6082 alloy, based on image recording digital camera synchronized force measurements. Modeling simulations performed assess accuracy curves modeling designing robust algorithm.