Dished pipe cap (head) is also called spherical pipe cap with folded edge. It consists of three parts: sphere with radius m, transition arc with radius R and straight edge with height H. Because of the existence of the transition section, the depth of the pipe cap is reduced, which is convenient for stamping, hand beating and back spinning forming, and has good economy and processability. However, due to the existence of the transition zone, the curvature radius of the joint changes abruptly, resulting in large edge stress. Considering the stress concentration and processing conditions, it is specified that the spherical radius Ri of the dished cap is not more than the cylinder diameter Di, and R / DI is not less than 0.1, while the transition arc radius R is not less than 3 times the thickness of the cap. When Tong = 0.9di, r = 0.17di, it is called standard dished cap. The thickness shall not be less than 0.15% of the inner diameter of the cap, and the thickness of other dished caps shall not be less than 0.30%. When the elastic instability under internal pressure is considered, it is not limited.
