Diaphragm/volute calcs

[adamko]

Hi I have a diaphragm of non regular shape to analyze for stress and deflection. Imagine a circular plate(5 mm thickness) a hole in the middle. From the hole on the top of the plate there is a spiral wall, which grows in diameter (from D 50 to D 240) and in depth from 0 up to 10mm. The wall is only 3 mm thick. I need to perform stress analysis and deflection analysis by hand as well as in Catia or Ansys. I am not sure how to do the hand analysis. Shall I simplify the shape to calculate simple diaphragm with uniform presure on top?(This diaphragm is a volute in centrifugal pump, that is clamped on edges and has pressure applied on to surface.
Thanks
Oxana

 

[rb1957]

stresses in a curved surface under pressure are "reasonably" easy to work out. Roark has info.

it maybe sufficient to simplify your geometry to a simpler form (say a hemisphere).

one problem you may encounter is the fixed base ... the membrane will want to expand under pressure (and this is what the hand calcs assume). but near the base this radial expansion is prevented; maybe it's enough to hand calc away from the base (as a surface under pressure), and then hand calc near the base (axial tension and enforced radial displacement in the membrane, cantilevered at the base)