nldiag

Mapdl.nldiag(label='', key='', maxfile='', **kwargs)

Sets nonlinear diagnostics functionality.

APDL Command: NLDIAG

Parameters
label

Diagnostic function:

NRRE - Store the Newton-Raphson residuals information.

EFLG - Identify or display elements or nodes that violate the criteria.

CONT - Write contact information to a single Jobname.cnd diagnostic text file during

solution.

key

Diagnostic function characteristics:

OFF or 0 - Suppresses writing of diagnostic information (default).

ON or 1 - Writes diagnostic information to the Jobname.ndxxx, Jobname.nrxxx, or

Jobname.cnd file. (If Label = CONT, this option is the same as the SUBS option described below.)

ITER - Writes contact diagnostic information at each iteration. Valid only when Label

= CONT.

SUBS - Writes contact diagnostic information at each substep. Valid only when Label =

CONT.

LSTP - Writes contact diagnostic information at each load step. Valid only when Label

= CONT.

STAT - Lists information about the diagnostic files in the current working directory.

DEL - Deletes all diagnostic files in the current working directory.

maxfile

Maximum number of diagnostic files to create. Valid values are 1 through 999. Default = 4. Valid only when Label = NRRE or EFLG.

Notes

The NLDIAG command is a nonlinear diagnostics tool valid for nonlinear structural analyses. It is a debugging tool for use when you must restart after an unconverged solution. The command creates Jobname.ndxxx, Jobname.nrxxx, or Jobname.cnd files in the working directory to store the information you specify.

For more information, see Performing Nonlinear Diagnostics.

Issue the NLDIAG,NRRE,ON command to create Jobname.nrxxx diagnostic files (for each equilibrium iteration after the first) in which to store the relevant Newton-Raphson residual information of forces/moments Fx, Fy, Fz, Mx, My and Mz for the last MAXFILE equilibrium iterations.

Issue a NLDPOST,NRRE,STAT command to list the load step, substep, time, and equilibrium iteration corresponding to each of the Jobname.nrxxx diagnostic files in the working directory, then issue a PLNSOL,NRRES,,,,FileID command to point to the file from which you want to create a contour plot of your Newton-Raphson residuals.

If you restart or issue a new SOLVE command, any Jobname.nrxxx diagnostic files in the current (working) directory are overwritten.

Issue a NLDIAG,EFLG,ON command to create Jobname.ndxxx diagnostic files which store IDs for elements violating the following criteria:

Too large a distortion (HDST)

Elements contain nodes that have near zero pivots (PIVT) for nonlinear analyses

Too large a plastic/creep (EPPL/EPCR) strain increment (CUTCONTROL)

Elements for which mixed u-P constraints are not satisfied (mixed U-P option of 18x solid elements only) (MXUP)

Hyperelastic element (EPHY), cohesive zone material (EPCZ), or damage strain (EPDM) not converged

Radial displacement (RDSP) not converged

MPC184 multipoint constraint elements using KEYOPT(1) = 6 through 16 with the Lagrange multiplier option fail to satisfy constraint conditions (184J)

For NLDIAG,EFLG,ON, all Jobname.ndxxx diagnostic files (for each equilibrium iteration after the first) in the current (working) directory are deleted when you issue a new SOLVE command (or restart).

In the solution processor (/SOLU), use the STAT option to list the active status of this command. In the postprocessor (/POST1), issue a NLDPOST,EFLG,STAT command to list the load step, substep, time, and equilibrium iteration corresponding to each of the Jobname.ndxxx diagnostic files in the working directory, then issue a NLDPOST,EFLG,CM,FileID command to create element components that violate the criteria.

Issue the NLDIAG,CONT,ON command to create a Jobname.cnd diagnostic file which stores contact information for all defined contact pairs at all substeps. Alternatively, you may issue one of the following commands to store contact information at a specific frequency:

NLDIAG,CONT,ITER to write at each iteration

NLDIAG,CONT,SUBS to write at each substep (default)

NLDIAG,CONT,LSTP to write at each load step

Contact diagnostic information is available for elements CONTA171 through CONTA177; it is not available for CONTA178.

Diagnostic file Jobname.cnd is written during solution and lists, on a pair-base, the following contact information:

Contact pair ID[1]

Number of contact elements in contact[2]

Number of contact elements in “sticking” contact status

Maximum chattering level

Maximum contact penetration/Minimum gap[3]

Maximum closed gap

Maximum normal contact stiffness

Minimum normal contact stiffness

Maximum resulting pinball

Maximum elastic slip distance

Maximum tangential contact stiffness

Minimum tangential contact stiffness

Maximum sliding distance

Maximum contact pressure

Maximum friction stress

Average contact depth

Maximum closed penetration

Number of contact points having too much penetration

Contacting area

Maximum contact damping pressure

Maximum tangential contact damping stress

Maximum total sliding distance (GSLID), including near-field

Minimum total sliding distance (GSLID), including near-field

Maximum fluid penetration pressure on contact surface

Maximum fluid penetration pressure on target surface

Total volume lost due to wear for the contact pair

Total strain energy due to contact constraint

Total frictional dissipation energy

Total contact stabilization energy

ANSYS Workbench contact pair ID[4]