Preload was tested at 21, 26, and 30 lbf. As shown in the graph, increasing preload results in a corresponding increase in suction force, rising from 8.8 lbf to 15.3 lbf.
Varying the loading rate from 0.15 to 0.25 in/s results in minimal change in suction force, as shown in the graph.
The unloading rate was varied between 0.15, 0.20, and 0.25 in/s, with no significant effect on suction force.