Figure 4.

Local deformation analysis for strain and strain energy density. Columns 1–2 compare one surface-removed and one surface-intact sample at first cut, i.e. with similar bulk force. Alternatively, columns 2–3 compare the same two samples, but at similar blade depths (i.e. prior to the first cut for the surface-intact sample). Row 1 shows the raw confocal images, row 2 shows the resulting Lagarange strain norm, and row 3 shows the corresponding strain energy density. Note that both strain and strain energy are in deformed coordinates. In the force-controlled comparison, strain fields are distinct between surface-intact and -removed, but the strain energy fields are more similar. The opposite is true (similar strain but distinct strain energy) for the depth-controlled comparison. Arrows highlight differences in how the strain field spreads across the surface layer.