Do Principal Stresses and Strains Align in Plane Stress States?

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SUMMARY

In plane stress states, principal stresses and strains align in the same direction, as demonstrated through the application of Hooke's Law. The relationship is established using the equations for principal stress and strain, specifically tan(2θ) = 2δ/(\sigmax - \sigmay) for stresses and tan(2θ) = \gammaxy/(\epsilonx - \epsilony) for strains. The alignment is confirmed by manipulating these equations under the condition that σz equals zero, revealing that the ratio of shear to normal stresses remains consistent. Understanding this relationship is crucial for accurately analyzing material behavior under plane stress conditions.

PREREQUISITES
  • Understanding of Hooke's Law for Plane Stress States
  • Familiarity with the concepts of principal stresses and strains
  • Knowledge of the relationship between shear modulus (G) and Young's modulus (E)
  • Basic proficiency in trigonometric identities and transformations
NEXT STEPS
  • Study the derivation of Hooke's Law for Plane Stress States in detail
  • Learn about the implications of setting σz to zero in stress analysis
  • Explore the relationship between shear and normal stresses in more complex loading scenarios
  • Investigate numerical methods for solving plane stress problems in finite element analysis
USEFUL FOR

Mechanical engineers, structural analysts, and students studying material mechanics who are focused on understanding stress-strain relationships in plane stress conditions.

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Homework Statement



For a plane stress state, show that the principal stresses and strains occur in the same direction?

Homework Equations



Hookes Law for PLane Stress States
Principal Stress is tan(2θ)=2δ/(\sigmax-\sigmay)
Principal Strain is tan(2θ)=\gammaxy/(\epsilonx-\epsilony)
\gamma=\tau/G
G=E/(2(1+v))


The Attempt at a Solution



tan(2θ)*(\epsilonx-\epsilony)=tan(2θ)*(\sigmax-\sigmay)2(1+v)/2E

I cannot see how to get rid of (1+v)/E, can anyone help me out please.
 
Physics news on Phys.org
What do the Hooke's law equations for each of the stresses explicitly in terms of the strains reduce to when σz is set equal to zero?
 

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