Mechanical Engineering Streeses

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Discussion Overview

The discussion revolves around calculating the maximum tensile and compressive stresses in a rectangular tube subjected to a bending moment of 20 kNm. Participants explore the relevant concepts, formulas, and assumptions necessary for solving the problem, including the second moment of area and the definition of normal stress.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses uncertainty about using the second moments of area and requests clarification on the formula needed for the problem.
  • Another participant asks for the mathematical definition of normal stress due to a bending moment.
  • A question is raised regarding the application of the bending moment and whether the tube is also experiencing torsion.
  • One participant suggests that the tube functions as a beam and implies that further research could be beneficial.
  • Links to Wikipedia articles on bending and area moment of inertia are provided as resources for additional information.
  • Another participant advises considering the neutral axis and the tension/compression sides, suggesting the use of the stress equation for symmetric bending.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the approach to solving the problem, as there are multiple questions and suggestions regarding the definitions and methods involved.

Contextual Notes

There are uncertainties regarding the assumptions about the tube's length and the nature of the applied bending moment, as well as the potential for torsion, which remain unresolved.

chrisking2021
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Mechanical Engineering Stresses

I am really struggling with the following problem:

A rectangular tube with no given length has the dimensions shown in the diagram (within the attachment). Find the maximum tensile and compressive stresses that such a section will experience due to a bending moment of 20KNm.

The attachment should be included if I've done it right.

I think i should be using "Second moments of area", but I'm not sure some clarification and possibly the formula would be gratefully received.

Thank you

Chris:confused:
 

Attachments

  • Example diagram.JPG
    Example diagram.JPG
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Last edited:
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What's the definition (mathematical) of normal stress due to a bending moment?
 
how is the bending moment applied? is the bar in torsion?
 
That tube works as a beam. From here, Google is your friend.
 
think about the neutral axis and which side is in tension/compression then use the stress equation for a beam in symmetric (assuming) bending. simple. but I've done it a few times.
 

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