<CRITERION> ratio

Description

This is a classical type criterion which may be useful for some users seeking compatibility with other programs. Its usefulness is as a viscoplastic overstress function (i.e. when \(f>0\)).

(367)\[f_{cr} = \frac{J(\hat{\ten \sigma})}{R} - L\]

Note that \(R\) is a radius measure passed in by the controlling behavior or potential object, and would normally be an isotropic hardening function. The effective stress \(\hat{\ten \sigma}\) is likewise determined by the behavior and can include back stress influences, etc.

Syntax

The model accepts a single optional coefficient for \(L\) (named L) in order to allow the user the option of having simply a ratio of \(f\) over \(R\), which could be used to apply the isotropic hardening law as a viscosity hardening. The default value of \(L\) is 1, and the user should note that only values of 1 and 0 make sense.

Example

The following example is from rate_crit02.inp in test/Volume_test/INP.

***behavior gen_evp
**elasticity isotropic
     young 2.e9
     poisson 0.4
**potential gen_evp ev
   *criterion ratio
     L   1.0
   *flow norton
     A  1000.
     n  2.
   *isotropic by_point
     sigeq  evcum
     60.e6  0.
     1.e8   2.
     1.e8   200.
***return