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Assessment of Properties of Sheet Metals Using Digital Image Correlation

Digital image correlation (DIC) is a new technique developed for sheet material tensile test strain measurement. This optical, noncontact, full-field measurement technique was used for the tensile testing of different advanced high-strength steels (AHSS) in this study. Previously, the traditional technique involved an extensometer that produced strain data by recording the motion of two points at gage marks on the specimen. The obtained strain measurements represented the averaged value of the strain over the gage length. The measured strain was valid only up to the uniform strain limit. DIC, however, is a full-field technique that can be used to measure strain over a very small gage length and is particularly well suited for measuring non-homogeneous strain distribution, as well as for highlighting the localized strain near the fracture zone, which cannot be measured by traditional extensometer technology. The objectives of this paper are to investigate the properties of different AHSS sheet metals, especially in the diffuse neck region, which will provide a guideline for the extrapolation of conventional stress-strain curves, as well as to demonstrate the effect of gage length on the strain-stress curves.

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