The problem of openings in cylinders
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The openings on the cylinder are non-radial; the circumferential opening ratio is greater than 0.5, while the axial opening ratio is less than 0.5. The ratio of the long axis to the short axis of these openings is less than 2. When performing strength calculations, in accordance with GB150 standards, equal-area reinforcement can be applied (GB150 takes into account a long-axis-to-short-axis ratio of less than 2 as well as the axial opening ratio). However, when using SW6 for calculations, it turns out that whenever the openings are non-radial, the HG20582-1998 standards must be used. What should be done in such cases? Note: However, the \"Training Manual for Pressure Vessel Design Engineers\" edited by Professor Li Shiyu states that the pressure area method cannot yet be used as a legitimate basis for design; when the openings exceed the requirements specified in GB150, the pressure area method can only be used as a reference
Based on experience, equal-area reinforcement should be feasible; it is recommended to use a method of overall thickening for reinforcement, while finite element analysis can be used to assess its local strength.
The calculation standard adopted by SW6 for non-radial openings is HG20582-1998 P108, which deals with the reinforcement calculation for openings in non-radial fittings. Essentially, the equal-area reinforcement method specified in GB150 is still used, with only a F-stress correction factor introduced into the formulas; the opening diameter of the radial fitting is determined as the chord length at the intersection of the midplane of the calculated thickness of the shell or head and the inner wall of the fitting, plus twice the additional thickness of the fitting. Then, the calculations are performed separately in the direction parallel to the cylinder axis and in the direction of the cross-section at 90° to the cylinder, ensuring that both cases meet the reinforcement requirements.
What if the ratio is greater than 2? If the software cannot perform the calculation, is finite element analysis the only option?