(a) Loading part of thirteen load-depth (-) plots at different loading rates at an ultralow peak load of 1 N, (b) exploded view of Figure 2(a) showing the presence of multiple micro-pop-in and micro-pop-out events at typical 4 selected loading rates (10−3, 10−2, 10−1, 100 N·s−1), (c) exploded view of Figure 2(b) showing the variation of serrations with the loading rates, and (d) exploded view of Figure 2(c) showing clearly the occurrences of more number of serrations at lower loading rates and lesser number of serrations at higher loading rates.
