Principle stress states question, anyone help?

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Discussion Overview

The discussion centers around a homework problem involving the calculation of principal stress states in an aluminum plate using neutron diffraction measurements of residual strains. The participants are focused on determining the values of sigma 1 and sigma 2 based on given principal strains and material properties.

Discussion Character

  • Homework-related

Main Points Raised

  • One participant presents a problem statement involving principal strains and asks for help in calculating sigma 1 and sigma 2.
  • The same participant provides initial calculated values of approximately 212 MPa and 83 MPa but expresses uncertainty about their correctness.
  • Another participant challenges the initial answer, suggesting it is incorrect and prompting a reevaluation.
  • A later reply confirms that the initial calculation was correct but notes issues with significant figures and spelling in the response.

Areas of Agreement / Disagreement

There is disagreement regarding the correctness of the initial answers, with some participants asserting the values are incorrect while others affirm the calculations were right.

Contextual Notes

Participants mention rounding and significant figures, indicating potential limitations in precision. There are also noted spelling errors in the original post that do not affect the mathematical content.

scw1
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Principle stress states question, anyone help??

Homework Statement


Neutron diffraction is used to measure the residual strains near to a weld in an aluminium plate. The aluminium has a young’s modulus E of 70GPa and a poisons ratio of 0.3. The three principal strains obtained are ε1= 2400 με ε2=0με ε3=-350με. What are the values of sigma 1 and sigma 2?


Homework Equations



Plane stress and strane equations

The Attempt at a Solution


Got an answer of an answer near to 212MPa and 83MPa
but not sure if its right
 
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[strike]Your current answer looks incorrect. Try again.[/strike]
 
Last edited:


nvn said:
Your current answer looks incorrect. Try again.

Hi there the sigma2 must be 83MPa? its all i keep getting
Many thanks
Stevo
 
My apologies, scw1. Your answer was right. Nice work. However, generally always round your final answer to three significant digits, not two significant digits. You rounded slightly too much. Also, you misspelled principal and strain, and omitted all punctuation.
 

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