(1) Division 1's Pressure Vessels can be Designed with Division 2's Design by Analysis
Elastic-Plastic Stress Analysis Method of Division 2 can be used to qualify Division 1 vessels by elevating the design factors from 2.4 (Division 2) to 3.5 (Division 1).
Stress-strain curves of any materials used in elastic-plastic analysis shall be computed according to ASME, Section VIII, Division 2, Annex 3-D STRENGTH PARAMETERS (2019, page 148). Don’t use measured stress-strain curves.
For linear elastic analysis, there is no converged stress at the areas with stress concentration. The maximum stress is infinite just as the theory predicts. Thus, if there is stress concentration, the maximum stress in a linear elastic analysis is not a useful criterion to validate the structure.
(1) Use Three or More Layers of Reduced 8-node Elements in the Thickness Direction
For example, if three layers of reduced elements are used, the computed tip deflection is 4.828 mm; if four layers, 4.581 mm. The computed deflection is reasonable, but they are still larger than the theoretical value (4.281 mm).
(2) Use Two or More Layers of Reduced 20-node Elements or One or More Layer of Fully Integrated 20-node Elements in the Thickness Direction
The reduced integration of linear 8-node solid elements leads to numerical difficulty called hourglassing because the reduced 8-node solid elements tend to be excessively flexible. For example, if two layers of reduced 8-node elements in the thickness direction are used, the computed tip deflection of the beam example in Shear Locking is 5.713 mm, which is much larger than 4.281 mm.