How to get stresses in a beam with known deflection

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Discussion Overview

The discussion revolves around determining the stresses in an elastically bedded beam subjected to a point load, given that the deflection of the beam has been calculated. Participants explore the relationship between deflection and stress, considering boundary conditions and the implications of the beam's support characteristics.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant inquires whether the known deflection can be used to derive stress in the beam.
  • Another participant asks for clarification on the boundary conditions affecting the beam's behavior.
  • A participant suggests determining the shear force or bending moment at a specific point to calculate the stress contribution, given the stated boundary conditions.
  • There is a mention of the complexity of the problem and a recommendation to consult "Roark's Formulas for Stress and Strain" for additional insights on beams on elastic foundations.
  • A participant references a related problem involving torsional stress in a ring mounted on a shaft, indicating a desire to simplify the original problem to focus on the beam's deflection and stress relationship.

Areas of Agreement / Disagreement

Participants express varying approaches to the problem, with no clear consensus on the best method to relate deflection to stress. Multiple viewpoints on boundary conditions and the need for additional resources indicate ongoing debate.

Contextual Notes

Participants have not fully resolved the implications of the boundary conditions on stress calculations, and there are references to external resources that may contain relevant equations or methodologies.

ladil123
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Hello!

I have a elastically bedded beam that is subjected to a pointload on the top of the beam.
I have managed to solve for the deflection in the beam.

Can I use this deflection to get the stress somehow?

Thanks
 
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ladil123 said:
Hello!

I have a elastically bedded beam that is subjected to a pointload on the top of the beam.
I have managed to solve for the deflection in the beam.

Can I use this deflection to get the stress somehow?

Thanks

Yes. What are the boundary conditions?

Take a look here for the equations to use:

http://www.efunda.com/formulae/solid_mechanics/beams/theory.cfm

CS
 
My beam is positioned on a elastic material that gives the "elastic bedded" part to the problem, My boundary conditions are that the beam doesn't have any moment at the outer lengths of the beam and no shear forces there as well.

Should I determine the shear force or bending moment at some point with my formula for the deflection to get the stress contribution ?
 
ladil123 said:
My beam is positioned on a elastic material that gives the "elastic bedded" part to the problem, My boundary conditions are that the beam doesn't have any moment at the outer lengths of the beam and no shear forces there as well.

Should I determine the shear force or bending moment at some point with my formula for the deflection to get the stress contribution ?

Is it a finite-length beam?

It gets rather involed so it may be best to take a look at "Roark's Formula's for Stress and Strain" as they have a whole section on beams on elastic foundations.

CS
 
Its really this problem I wanted to solve:
https://www.physicsforums.com/showthread.php?t=293368

But I have "simplified" the problem to a beam that is on a elastic bed with a point load as said before.
As seen in the problem in the link above that's a cross section of a ring mounted on a shaft. So what I really want is the torsional stress in the lower part of the ring.
http://www.roarksformulas.com/ didnt work for the moment, but I´ll try to check it out later.
 

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