Here’s a slight modification that should work better:
kangaroo_Test2.gh (16.6 KB)
The strange behaviour you were seeing was because the Angle strength was a couple of orders of magnitude higher than the Length strength.
In general, for simulating something like bending of a thin rod, the axial stiffness (Length) needs to be higher than the bending resistance (Angle). If you think of bending as stretching on one side of the cross section and compression on the other, the amount of material deformation it takes to curve the rod is very small compared to the deformation involved in actually stretching the whole thing axially to change its length. So I don’t think you could ever have a material in real life that was this much harder to bend than it is to stretch.
Like the rest of Grasshopper, Kangaroo isn’t affected by the units of your Rhino doc. If you want to set forces in real life units, you just need to be consistent, so if your Rhino file is in m, your forces should be in N, and Young’s modulus in Pa (see also my reply here).
I don’t think this is relevant here though, since it seems this simulation doesn’t need to be based on actual known numerical strengths. So just choose what works for the effect you want. As a general rule of thumb, keep Length strength higher than Angle strength when simulating bending.