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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