Biaxial stresses and plane-strain elasticity

If principal stresses cri and ct2 act in a plane, in an elastic material, the strains in the 1 and 2 directions are given by 

The quantity E = E/(l — v ), the plain-strain Young s modulus , can be used in place of E in formulae for the effect of a single stress. For beams of width depth, E = E. 

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