Invalid area opening problem

The best position of the saddle - A ≤ 0.2L and try to make A ≤ 0.5Ri 1) In order to reduce the maximum bending moment of the cylinder at the support and make the stress distribution appropriate, make the support span center equal to the maximum bending moment of the support (M1 = M2). The distance between the support center and the tangent line of the head is deduced A = 0.207L (L - cylinder length). If the design deviates from this value, the axial bending stress at the support will increase significantly.； 2) The rigidity of the head is generally greater than that of the cylinder, and it has a local strengthening effect on the cylinder. Tests have proved that when A≤0.5Ri, the head has a strengthening effect on the cylinder. Therefore, the optimal position of the support should be under the condition of A≤0.2L, and try to make A≤0.5Ri. 3) When A>0.5Ri or the cylinder has insufficient rigidity without strengthening measures, under the action of the circumferential bending moment, the cylinder will collapse at the saddle.: The cylinder on the saddle is deformed, as if "flattened". The cylinder at the saddle has no load-bearing function and becomes an ineffective zone. This will not only increase the various stresses in the cylinder at the saddle, but also move the maximum action point of the axial combined stress, tangential shear stress and circumferential combined compressive stress downwards.

I think the so-called "invalid area" refers to the area with large bending moment. The opening reinforcement considers the hoop stress, and the bending moment causes the axial stress. If the stress caused by the internal pressure and bending moment is less than the hoop stress after the superposition, it can be calibrated according to the internal pressure. Otherwise, it can be calibrated according to the equivalent internal pressure method.