## Simulation Mechanical and Multiphysics

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# Equivalent Stress

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Does anyone know how the "Equivalent Stress" is calculated?

The documentation explains it as; "Equivalent Stress: If this command is selected, the model will be shaded with the equivalent (or effective) stress. This stress value will include the effect of the size of the yield surface for the calculations."

What I am after is the calculation being used.

Senior Engineer, FEA Lead Analyst

T&T Engineering Services, Inc.

# Re: Equivalent Stress

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In short, it is von Mises stress.

For little more,

Equivalent stress (effective or generalized stress) represents an envelope of mutiaxial stress state into the “equivalent” yield condition under uniaxial load; in order to identify whether the material is elastic (Sigma < Sigma_yield) or has yielded (Sigma >= Sigma_yield).

In von Mises criteria, the von Mises Equivalent stress (Sigma_e) is computed from Sigma_e = Sqrt (3 * J_2) where J_2 is second deviatoric stress invariant.

For more, http://en.wikipedia.org/wiki/Von_Mises_yield_crite

Or check any decent solid mechanics text book on plasticity.

Jaesung