1. Elliptical head

The circumferential stress and meridional stress of each point of the head shell will continue to change. The hoop stress at the top is equal to the axial stress and the stress on the equator. When the elliptical head is subjected to uniform internal pressure, the axial stress is constant as tensile stress and gradually decreases from the top.

2. Torispherical Head

The size of the edge stress of this head is related to the ratio of the transition zone radius to the spherical radius. The smaller the ratio, the more severe the sudden change in the curvature boundary and the greater the edge stress. When the ratio reaches the boundary, that is, the transition zone radius is 0, the torispherical head evolves into a spherical cap head and a straight cylinder.

3. Conical head

The main part of the cone is under the action of internal pressure, and the membrane stress occurs at the large end. Due to geometric discontinuity and sudden change in curvature radius, the connection between the cone and the cylinder will produce a large lateral thrust, resulting in a large edge stress and easy bending, so it needs to be strengthened.