**yield_surface#

Description#

This option is used to create an ASCII file with the yield surface data at a load segment start or end time. Any number of yield surfaces may be given for a single test. The output files contain a list of the entire flux variable values for the surface taken in order, followed by the angle.

Syntax#

The yield surfaces to output are defined in the following manner:

**yield_surface output_file_name \(~\,\) *time time0 [ time1 time2 … ] \(~\,\) *criterion num \(~\,\) *potential num \(~\,\) *component comp1 comp2 \(~\,\) *degrees degrees \(~\,\) *angles angle0 [ angle1 angle2 … ] \(~\,\) *factor factor \(~\,\) *eps eps \(~\,\) *rate [ rate0 rate1 rate2 … ] \(~\,\) *find_offset \(~\,\) *offset offset values

*time

A list of one or more real values time0 [ time1 time2 … ] to define the time at which the yield surface is evaluated. The times can be any time from 0.0 onward. In the event that multiple times are given, the surface scans will be given in the same file separated by two blank lines.

*criterion

This gives the criterion name which will be used for the surface. They are arbitrary values to match with zero or the rate if given.

*potential

A gen_evp behavior potential which will be used for the criterion. By default all potentials input will be used to establish the material criteria for flow.

*component
1unfortunately, gradient values cannot yet be used to scan for strain space yields surfaces, etc.

Two strain names for the two flux components which are scanned 1unfortunately, gradient values cannot yet be used to scan for strain space yields surfaces, etc.. An example would be to give sig11 sig12 for the components.

*degrees

The sweep angle which will be used for each step in the surface. Note that fineness of the surface depends on this, but also that the sweep center be in the center of the surface. Being close to the surface in one point increases the number of output points because it dominates the “point of view.”

*angles

Instead of using the sweep angle to define the steps, a list of angles (in degrees) angle0 angle1 angle2 … can be specified. If both *degrees and *angles are specified, the *degrees command will be ignored.

*factor

A magnitude of the flux gradient which is considered large for the surface. Look in the output file for bad value lines (marked with a comment line). If there are bad values, increase the factor. The default value is 400.

*eps

A positive real value eps specifying the degree of convergence in the surface. The actual value depends on the strain rates as specified by the *rate command.

  • If neither *eps nor *rate commands are given, then the default value is 1.e-1.

  • If no *eps command is given, and the *rate command is given without specifying any strain rate, then the default value is 1.e-1.

  • If no *eps command is given while the *rate command is given with one or more strain rates, then the default value is 1.e-6 times the average of the specified strain rates.

  • On the other hand, if the *eps command is given, but the *rate command is not, then the actual value is eps.

  • If the *eps command is given while the *rate command is given without specifying any strain rate, then the actual value is 1.e-12 times eps.

  • Finally, if the *eps command is given, and if the *rate command specifies one or more strain rates, then the actual value is eps times the average of the strain rates.

*rate Optional

rate values for an equipotential surface. If more than one value is given, the surfaces will be placed in the same file with two blank lines between them. The default is zero.

*find_offset

This command is used to find the surface when the current position is outside of it. A large rate value will be used to hopefully expand the surface such that the current position is inside, and an average of that surface will be used to estimate the center. An optional real value following the command sets this large rate factor, while the default is quite arbitrarily 1.0.

*offset

Allows setting the actual offset flux variable (the estimated difference between current position and yield center) in place of the automated method *find_offset (not recommended). Each component of the flux tensor should be specified.

Example#

**yield_surface yield_find_offset.test
 *degrees   5.0
 *factor    1000.0
 *find_offset
 *time      0.0 50. 200. 500.
 *time      1000.
 *rate      0.0 1.e-9 1.e-6 1.e-3