Fig. 3.

Example data from a single typical quasi-static rate experiment with 2D-DIC. (a) Time-history of the mean axial Lagrangian strain (E₂₂), with example images selected at zero compression and 50 % compressive strain. The red dashed box indicates the region of interest used for DIC. (b) Example 2D-DIC displacement fields (u₁, top, and u₂, bottom) on the specimen surface at approximately 10 % axial strain. Note that u₁ is nominally symmetric about the vertical centerline and the u₂ component is minimum at the bottom edge and maximum at the top edge, since the uniaxial compression is applied between a fixed top platen and moving bottom platen. (c) Analogously to (b), the 2D-DIC displacement fields (u₁, top, and u₂, bottom) on the specimen surface at approximately 50 % axial strain, showing a small amount of frictional confinement on the upper platen in u₁. (d) The axial engineering stress and mean transverse Lagrangian strain plotted against the mean axial Lagrangian strain for one example. Standard uncertainty on stress is circa ±0.18 kPa.