This only works for a single element. The loops where `sigmav` is used won't work for more than one element.

[dcelisgarza]

https://github.com/dcelisgarza/EasyDD/blob/31a74cd3bcd1d84713a5293f30029636af09d0a5/src/wip/DanielCelisGarza/Evaluating SegSeg forces via FEM/Test_SegSegForcesViaFEM.m#L8-L8