Can Maximum Bending Strain Be Calculated Without Knowing Young's Modulus?

AI Thread Summary
Determining maximum bending strain in a beam typically requires knowledge of Young's modulus, as it directly influences strain calculations. While bending stress can be calculated using equations that do not depend on material properties, such as Euler's model, the resulting strain and deflection are contingent on Young's modulus. The discussion highlights that while stresses can be evaluated from known dimensions and forces, the question specifically asks for maximum bending strain, which necessitates incorporating Young's modulus. Therefore, the answer may be expressed in terms of known stresses and Young's modulus. Ultimately, calculating maximum bending strain without Young's modulus is not feasible.
maniaciswicke
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Very simply put.
Is it possible to determine bending stress in a beam without knowing the young's modulus of the material used? All equations I've seen seem to include in some form an E value ( young's modulus), which is used in conjunction with a stress value to evaluate the strain.
 
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The forces and therefore the stresses in many beams are statically determinate so they do not depend on the material. Euler's model of beam bending gives.

\frac \sigma y = \frac M I

Where \sigma is the stress, y is the offset from the neutral axis, M is the bending moment and I is the 2nd moment of area.

The Euler-Timoshenko model also includes shear stresses.

The strains, and therefore the amount of deflection of the beam, DO depend on Young's modulus.
 
This is what i thought.
It is a homework problem but i wasn't asking for the answer, merely if it was possible to solve. The dimensions of the beam are known so i agree the stresses are quite straightforward. The question very clearly asks for the "maximum bending strain" though. Could i perhaps give the answer in terms of the known stresses and E?
 

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