(e) Estimate the average pressure loading on the pressure vessel and use the standard equations for thin-walled pressure vessels to make an estimate by hand calculation of the pressure vessel wall thickness required to give a Factor of Safety of not less than 2 using whichever of the two failure criteria gives the safer result.
Conclusion
- The weight is calculated with accuracy of -0.22(%) for the empty vessel.
- The weight is calculated with accuracy of -0.05(%) for the filled vessel.
- The calculated stress is verified by its comparison with hand calculated membrane stress.
- Von Mises and Tresca criteria are applied to upper and lower spherical part of the pressure vessel, with FOS larger than 2.
- Von Mises and Tresca criteria are applied to the cylindrical part of the pressure vessel, using an average Mises stress, with FOS smaller than 2.
- Von Mises and Tresca criteria are applied to lower spherical part of the pressure vessel, with FOS larger than 2.
- After the verification of stress level at the cylindrical part of the pressure vessel, with Von Mises criterion, the required thickness is calculated as 0.042(m).
- If this pressure vessel were made with a spherical shape, FOS might have been larger than 2 as a whole.
- The wall of a pressurized spherical vessel is subjected to uniform tensile stresses in all directions.
- When a cylindrical pressure vessel is to designed, care must be taken especially failure strength of a cylindrical part.
- The longitudinal welding might better be replaced by a helical welding.
References
[1] unit 3 riveted joints-IGNOU,
[online] Available at:<http://www.ignou.ac.in/upload/Unit-3-60.pdf>
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[2] Timoshenko and Woinowsky-Krieger, 1959: Theory of Plates and Shells,
[online] Available at:<http://155.207.34.6/files/Timoshenko.pdf>
[Accessed 21 Dec 2013 ].
[3] Introduction to ASME Codes and Standards,
[online] Available at:
<http://faculty.uml.edu/pavitabile/22.302/web_download/ASME_Into_to_Codes_and_Standards_1028.pdf>
[Accessed 21 Dec 2013 ].
[4] Spherical Pressure Vessels,
[online] Available at:<http://academic.uprm.edu/pcaceres/Courses/MMII/IMoM-6A.pdf>
[Accessed 21 Dec 2013 ].
[5] Brittle and Ductile Behavior,
[online] Available at:<http://dolbow.cee.duke.edu/TENSILE/tutorial/node10.html>
[Accessed 21 Dec 2013 ].
[6] von Mises yield criterion,
[online] Available at:<http://en.wikipedia.org/wiki/Von_Mises_yield_criterion>
[Accessed 21 Dec 2013 ].
[7] Maximum Shear Stress Criterion,
[online] Available at:<http://andriandriyana.files.wordpress.com/2008/03/yield_criteria.pdf>
[Accessed 21 Dec 2013 ].
