Nonlinear analysis formulation > Failure criteria > The Von-Misses criterion

This criterion taking into accounts the all three principal shear stress into account. In this case the yield function is given by:

		(147)

or in terms of the so-called equivalent stress

as

		(148)

where

		(149)

For plane strain applications assuming no plastic volume change:

		(150)

whereas under triaxial conditions:

		(151)

where cu is the undrained "cohesion" or shear strength of the soil.

Fig.40. von Misses criterion in principal stress space

When plotted in three-dimensional principal stress space the yield surface depicts a cylinder parallel to the hydrostatic axis

as shown in Figure 40.

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