MATHEMATICAL ANALYSIS OF THE TENSILE BEHAVIOR OF DP 980 STEEL USING DIGITAL IMAGE CORRELATION (DIC)

This paper presents an analysis tool and preliminary, high-resolution results of material behavior and surface features during the tensile test of DP 980 steel specimen. The ultimate goal is a method for detection of localized through-thickness necking in stamping and welding samples based on measurement of the sample geometry and analyzing the evolution of surface features. It is thought that the onset of necking can be detected more precisely through characterization of the changes in the geometry of surface coordinate measurements than strain-based metrics. In this work, a MATLAB-based analysis tool was created to extract information from the ample data generated by DIC in tension testing. The results shown highlight the level of detail and granularity possible from DIC data. Several analysis results, such as the evolution of strains in x, y, and z directions, development of stress-strain cures, temporal surface profile, and curvature evolution, were presented for 201 surface points along the sample. The nature of the stress-strain behavior was plotted for every 0.25 mm along the sample, showing the increase in stress and strain at varying degrees in the diffuse neck. Surface profile and curvature evolution were shown at each 0.5-second time step. Comparing the temporal results of all points revealed the location of the diffuse neck on the sample.