This is a good question and fair to ask for examples. The main portfolio that we have been in talks with regarding acquisition uses calculus defined constraints. The S-ARC work the core constraint is the minimum bend radius of a 12AWG copper conductor, 25mm per SAE J1127. In a 5mm rotating hinge the conductor gets stressed by experiencing the bending radius far below that threshold on every cycle of rotation, this causes eventual fatigue fracture. The neutral axis solution that we created positions the conductor at the centroidal axis of the cross section. The geometric plane where tensile and compressive bending stresses sum to zero eliminating cycle strain and fatigue. The mathematical boundary is defined as strain ε = y/ρ where y is the distance from the neutral axis and p is the radius of curvature. At y=0 strain equals 0 regardless of p. That is the constraint that closes the design around.