Von Mises Material Properties

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Biaxial stress-strain curve. In the

 biaxial case, any combination of 

stress inside the initial yield

surface (surface A) is in the elasticregion. Once the part is taken

 beyond the initial yield surface, the

 part experiences plasticdeformation.

With isotropic hardening, the

center of the yield surface remains

fixed but the size of the surface

increases. Any stress state inside

the new yield surface (surface B)

will experience elasticdeformation; new plastic

deformation occurs when the stressstate reaches surface B.

Figure 1: Isotropic Hardening

Uniaxial stress-strain curve. If the

 part is taken beyond the yield

stress, it begins to deform

 plastically. If taken to a maximumstress (point A) and the load is

released, it unloads along the

dashed line. If the part is loaded

again, no additional plastic

deformation occurs until the stressreaches point A.

If the part is put into compression,

it compresses elastically along the

dashed line until it reaches point B,and then it yields in compression.

With kinematic hardening, the

change in stress from point A to point B is twice the yield stress.

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strain hardening modulus =Ultimate Strength - Yield Strength

(Elongation at 2 in)/100 - yield strain

where yield strain is the strain corresponding to the yield strength, or yield strain = (Yield

Strength) / (Modulus of Elasticity). The Ultimate Strength, Yield Strength, Elongation at 2 in,

and Modulus of Elasticity are stored in the material library.