Max Von Mises Stress Calculation for Pipe Bend

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Discussion Overview

The discussion centers on calculating the maximum von Mises stress in a 90-degree pipe bend, specifically under conditions of internal pressure. Participants explore the theoretical aspects of stress analysis in pipe bends, with a focus on static analysis and the implications of various loading conditions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks guidance on calculating von Mises stress for a pipe bend, indicating familiarity with straight pipes but uncertainty regarding bends.
  • Another participant questions the specific loads involved in the analysis.
  • Internal pressure of around 4 bar is mentioned as a relevant loading condition.
  • A suggestion is made to consult the Roark handbook for stress and strain, noting that while a direct solution for the bend may not exist, there are solutions for simple shells of revolution under internal pressure that could be adapted.
  • Concerns are raised about the effects of fluid flow and thrust on the pipeline, emphasizing the importance of considering these factors in practical applications.
  • A participant clarifies that their analysis is theoretical and static, stating that they do not need to consider thrust or fluid flow for their specific calculation.
  • Another participant expresses the opinion that flow forces are often overlooked in pipe design, citing potential serious consequences from inadequate thrust block provision and neglect of buoyancy or support forces.

Areas of Agreement / Disagreement

Participants express differing views on the relevance of flow forces and thrust in the context of the theoretical analysis. While some emphasize the importance of these factors, the original poster maintains that their focus is solely on calculating the maximum von Mises stress without considering flow.

Contextual Notes

The discussion highlights the complexity of stress analysis in pipe bends and the potential for varying interpretations of loading conditions. There is an acknowledgment of the limitations of existing resources and the need for careful consideration of assumptions in the analysis.

dfitz1000
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Hi, I'm trying to calculate the max (von Mises) stress in a 90o pipe bend. Now I know (I think) how to do it for a straight pipe, but can anyone point me in the right direction as to where I can find this analysis for a pipe bend?

Thanks in advance.
 
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Given what loads?
 
minger said:
Given what loads?

The internal pressure is around 4 bar.
 
Have you taken a look for any analytical/empirical solutions such as in the Roark handbook for stress and strain?

I doubt there is a solution for your exact pipe bend, but I know there are solutions for simple shells of revolution under internal pressure. Perhaps you can adjust the solution for the bend.
 
That's pretty much what I'm looking for minger. Roark's handbook you say, do you know any other books with a similar analysis? Thanks for your help so far.
 
Don't forget that if your pipe fitting is under pressure, presumabably there is also fluid flowing. This exerts a thrust on the pipeline, which resists in bending, unless there is a suitably placed thrust block, in which case there is a direct force on the fitting.

Look in any standard hydraulics or fluids testbook for thrust block design.

Obviously it will make a difference whether the pipe is horizontal or vertical so the question 'what loads' remains open.
 
Well, it's just a theoretical question. I need to find the maximum theoretical stress in the 90o pipe bend under 4 bar internal pressure. It's a static analysis I'm doing so there's no need to consider thrust or anything like that. I do appreciate your reply though.
 
In my opinion, forces from the flow exerted on the pipes are too often ignored or not taught.

I have seen really serious consequences ensue as a result of inadequate thrust block provision.

I have also seen serious damage ensue from neglect of bouyancy, self weight or support forces in soft goround.
 
Studiot said:
In my opinion, forces from the flow exerted on the pipes are too often ignored or not taught.

I have seen really serious consequences ensue as a result of inadequate thrust block provision.

I have also seen serious damage ensue from neglect of bouyancy, self weight or support forces in soft goround.

I don't doubt what you're saying but I just need to calculate the max von Mises stress in the bend. Just assume there is no flow.
 

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