Can strain exist without deflection?

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    Deflection Strain
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Discussion Overview

The discussion revolves around the concept of strain in materials, particularly whether strain can exist without observable deflection. Participants explore this in the context of a thick wall being pushed, examining definitions of strain and deflection, and considering the implications of stress levels and constraints.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that strain can be induced in a thick wall even without visible deflection, suggesting that surface slips may occur.
  • Others argue that the definition of strain (dL/L) implies that stress below a certain limit should not cause strain, although this view is contested.
  • A participant asserts that any stress will cause some strain, but acknowledges that if the stress is very low, the resulting strain might not be significant.
  • One participant mentions that strain can also be induced by the material's own weight, suggesting that strain is always present under certain conditions.
  • There is a request for clarification on the term "surface slips," with an explanation provided that refers to deformation at slip planes on the surface when sufficient force is applied.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between stress, strain, and deflection, indicating that multiple competing perspectives remain without a clear consensus.

Contextual Notes

Limitations include varying definitions of strain and deflection, the impact of stress levels, and the role of constraints in determining whether strain occurs without deflection.

wasif
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Lets take an example of a person pushing a thick wall, of course no deflection in the line of action of force is seen but can strains be induced in it, like surface slips?
 
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The definition of strain is dL/L. Stress less than some limit should cause no strain.
 
wasif said:
Lets take an example of a person pushing a thick wall, of course no deflection in the line of action of force is seen but can strains be induced in it, like surface slips?
What are surface slips?

Chet
 
Doug Huffman said:
The definition of strain is dL/L. Stress less than some limit should cause no strain.
This is not correct. Any stress will cause a strain. But, if the stress is very low, the strain might not be significant.

Chet
 
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via wikiapedia: http://en.wikipedia.org/wiki/Deflection_(engineering), http://en.wikipedia.org/wiki/Deformation_(mechanics),

I believe you can have a displacement at the line of action even in a thick wall. Unless there is some sort of rigid constraint that prevents that.

deflection is the degree to which a structural element is displaced under a load. It may refer to an angle or a distance.

strain is a normalized measure of deformation representing the displacement between particles in the body relative to a reference length.

So, I think it depends on the constraints. Otherwise there will be a strain under any deflection, no matter how small. Check out my picture it may help.
 

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strain will be induced due to its own weight also.So,strain will always be present.
 
Chestermiller said:
What are surface slips?

Chet

Hi chet, thanks for the reply

Surface slips by which i mean the deformation of the slip planes at the surface if the force is just enough.
 

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