Safety Assessment of the Junction Between a Thick Pressure Vessel Shell and a Thinner Hemispherical Head

A junction of shell to hemispherical head whose thickness is half of that of the shell has been developed and safely used in the People’s Republic of China in the past ten years. Great achievements of mesomechanics in ductile fracture have been made in P. R. China. The load when local shear band prongs the ligament in the front of crack tip is regarded as the limit load and the direction of the maximum plastic strain along a constant radius around the crack tip might be considered as the direction of shear fracture. Based on these concepts and small-deformation elastic-plastic analysis with finite element method, safety of the junction under operating pressure, 31.4MPa, is assessed and the possible failure modes of it are forecasted. The reasonability of the design of the junction is also considered.