Anybody help with these questions?

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Discussion Overview

The discussion revolves around a homework problem involving the calculation of maximum uniform internal pressure for a spherical pressure vessel, given specific tensile stress limits and a ratio of radius to wall thickness. The focus is on applying the thin-walled pressure vessel theory and clarifying the relevant equations.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents a problem statement and attempts a solution, suggesting a maximum internal pressure of 0.15MPa but expresses uncertainty about its correctness.
  • Another participant corrects the equation used for calculating pressure, stating it should be σ = (Pr)/t or P = σt/r.
  • A participant seeks clarification on the notation for the radius to wall thickness ratio, asking if it is denoted as 100 to 1 or 10 to 0.1.
  • Further clarification is provided regarding the radius to wall thickness ratio, confirming it as r/t = 100.
  • Another participant reiterates the correction of the equation, emphasizing the correct form as σ = p*r/(2*t) and acknowledges the context of a thin-walled cylinder.

Areas of Agreement / Disagreement

There is no consensus on the correct maximum internal pressure, as participants are focused on clarifying the equations and notation rather than reaching a final answer. Multiple viewpoints on the correct equation and notation exist.

Contextual Notes

Participants have not resolved the assumptions regarding the application of the thin-walled assumption and the implications of the radius to wall thickness ratio on the calculations.

scw1
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Anybody help with these questions?

Homework Statement



A spherical pressure vessel has been designed such that the tensile stresses in its walls should not exceed 150MPa. The ratio of the vessels radius to wall thickness is 100. Applying a thin-walled plane stress assumption, what is the maximum uniform internal pressure that the vessel is intended to contain?

Homework Equations



Thin walled pressure cylinder assumption P= sigma(s) x radius/2xt(s)

The Attempt at a Solution


i tried the answer 0.15MPa but not sure if its right can anyone help me??
 
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Your equation should read σ= (Pr)/t or P = σt/r
 


rock.freak667 said:
Your equation should read σ= (Pr)/t or P = σt/r
Hi how do you denote the radius to wall thickness, is it 100 to 1 or 10 to 0.1?
Many thanks
Stevo
 


scw1 said:
Hi how do you denote the radius to wall thickness, is it 100 to 1 or 10 to 0.1?
Many thanks
Stevo

since r is the radius and t is the wall thickness

radius to wall ratio = 100 OR r/t = 100.
 
Good advice by rock.freak667, except the equation should be sigma = p*r/(2*t).
 


nvn said:
Good advice by rock.freak667, except the equation should be sigma = p*r/(2*t).

Yes it should, I was thinking about a thin-walled cylinder.
 

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