ยทForce equilibrium of the Triple Bellows
Figure 3c shows the section force diagram of the Triple Bellows.
The force caused by pressure, the elastic force from tube deformation, the equivalent component forces of \(F_i\)  and the equivalent force couple \(M_i\)  follow the same law as Equation  (S20)-(S24).
The equilibrium equations about axis-b and axis-r are