Winger1984
Mechanical
Hello Everyone
I have a question about the best method of calculating the effect of Internal or External Pressure on Tubes of short overall sectional length.
If you Click the drawing I have uploaded below you will see a generic example of what I am talking about.
I have two pieces of tube, threaded with a stub acme thread which can withstand the piston effects of the applied pressures.
The pressure is retained by use of an elastomeric O-ring with polymeric back up rings due to the pressures I go to.
Normal I use Von Mises stress criterian on this as I know the geometry of the part and from this can work out my principal stress, Axial, Hoop & Radial.
I calculate my stress due to Burst (Internal) pressure through the section with the yellow line drawn in and my stress due to Collapse (External) pressure though the section marked in red.
My thought process was these are the thinnest sections so if my components can withstand at these points then the significantly thicker sections will be fine, with the obvious provision of checking if I am close to the transition point of thick and thin walled vessels.
Recently at a design review with vendors they claimed a higher pressure rating than I expected possible using the material selected. When questioned they had said they neglected the thin sections as they are well supported by the thick sections on either side. My personal view is this need to be proven mathematically or by testing.
Do any of you fine people have any experience at this sort of mathematical calculation or can you point me in the direction of some good reference material.
Regards
Daniel
I have a question about the best method of calculating the effect of Internal or External Pressure on Tubes of short overall sectional length.
If you Click the drawing I have uploaded below you will see a generic example of what I am talking about.
I have two pieces of tube, threaded with a stub acme thread which can withstand the piston effects of the applied pressures.
The pressure is retained by use of an elastomeric O-ring with polymeric back up rings due to the pressures I go to.
Normal I use Von Mises stress criterian on this as I know the geometry of the part and from this can work out my principal stress, Axial, Hoop & Radial.
I calculate my stress due to Burst (Internal) pressure through the section with the yellow line drawn in and my stress due to Collapse (External) pressure though the section marked in red.
My thought process was these are the thinnest sections so if my components can withstand at these points then the significantly thicker sections will be fine, with the obvious provision of checking if I am close to the transition point of thick and thin walled vessels.
Recently at a design review with vendors they claimed a higher pressure rating than I expected possible using the material selected. When questioned they had said they neglected the thin sections as they are well supported by the thick sections on either side. My personal view is this need to be proven mathematically or by testing.
Do any of you fine people have any experience at this sort of mathematical calculation or can you point me in the direction of some good reference material.
Regards
Daniel
