NLHIST

NLHIST, Key, Name, Item, Comp, NODE, ELEM, SHELL, LAYER, STOP_VALUE, STOP_COND
Specify results items to track during solution.

SOLUTION: Nonlinear Options

Key

Specifies the command operation:

NSOL	—	Nodal solution data.
ESOL	—	Element nodal data.
PAIR	—	Contact data (for pair-based contact).
GCN	—	Contact data (for general contact).
RSEC	—	Result section data.
STAT	—	Displays a list of items to track.
OFF or 0	—	Deactivates tracking of all variables. This value is the default.
ON or 1	—	Activates tracking of all variables. Tracking also activates whenever any specification changes.
DEL	—	Removes the specified variable from the set of result items to track. If `Name` = ALL (default), all specifications are removed.

Name

The 32-character user-specified name.

Item, Comp

Predetermined output item and component label for valid elements. See the Element Reference for more information.

NODE

Number identifying one of the following:

Valid node number (if Key = NSOL or ESOL).

Valid real constant set number identifying a contact pair (if Key = PAIR).

Valid section ID number identifying a surface of a general contact definition (if Key = GCN).

Valid real constant set number identifying a result section (if Key = RSEC).

NODE is required input when Key = NSOL, ESOL, PAIR, GCN, or RSEC.

ELEM

Valid element number for element results. Used for ESOL items. If ELEM is specified, then a node number that belongs to the element must also be specified in the NODE field.

SHELL

Valid labels are TOP, MID or BOT. This field can specify the location on shell elements for which to retrieve data. Used only for element nodal data (ESOL).

LAYER

Layer number (for layered elements only). Used only for element nodal data (ESOL).

STOP_VALUE

Critical value of the tracked variable. This value is used to determine if the analysis should be terminated.

STOP_COND

Specifies the conditional relationship between the variable being tracked and the STOP_VALUE upon which the analysis will be terminated:

-1	—	Terminate the analysis when the tracked variable is less than or equal to `STOP_VALUE`.
0	—	Terminate the analysis when the tracked variable equals `STOP_VALUE`.
1	—	Terminate the analysis when the tracked variable is greater than or equal to `STOP_VALUE`.

Notes

The NLHIST command is a nonlinear diagnostics tool that enables you to monitor diagnostics results of interest in real time during a solution.

You can track a maximum of 50 variables during solution. The specified result quantities are written to the file Jobname.nlh. Nodal results and contact results are written for every converged substep (irrespective of the OUTRES command setting), while element results are written only at time points specified via the OUTRES command. Result section data is written only at time points specified via the OUTPR,RSO,Freq command.

For time points where element results data is not available, a very small number is written instead. If the conditions for contact to be established are not satisfied, 0.0 will be written for contact results.

Results tracking is available for:

nonlinear structural analyses (static or transient)
nonlinear steady-state thermal analyses
transient thermal analyses (linear or nonlinear)
nonlinear coupled structural-thermal analyses (static or transient)

All results are tracked in the Solution Coordinate System (that is, nodal results are in the nodal coordinate system and element results are in the element coordinate system).

Contact results can be tracked for elements CONTA172, CONTA174, CONTA175, and CONTA177; they cannot be tracked for CONTA178.

Result section data can be tracked for elements CONTA172 and CONTA174.

When contact results (Key = PAIR or GCN) or result section data (Key = RSEC) are tracked , the user-specified name (Name argument) is used to create a user-defined parameter. This enables you to monitor the parameter during solution. As an example, you can use a named parameter to easily convert the contact stiffness units from FORCE/LENGTH³ to FORCE/LENGTH based on the initial contact area CAREA. Be sure to specify Name using the APDL parameter naming convention.

The STOP_VALUE and STOP_COND arguments enable you to automatically terminate the analysis when a desired value for a tracked contact result or section result has been reached.

The Jobname.nlh file is an ASCII file that lists each time point at which a converged solution occurs along with the values of the relevant result quantities.

The GUI option Solution> Results tracking provides an interface to define the result items to be tracked. The GUI also allows you to graph one or more variables against time or against other variables during solution. You can use the interface to graph or list variables from any .nlh file generated by Mechanical APDL.

You can also track results during batch runs. Either access the launcher and select Run Results Tracker Utility from the Tools menu, or type nlhist242 at the command line. Use the supplied file browser to navigate to your Jobname.nlh file, and click on it to invoke the tracking utility. You can use this utility to read the file at any time, even after the solution is complete (the data in the file must be formatted correctly).

Table 196: NLHIST - Valid NSOL Item and Component Labels

Item	Comp	Description
U	X, Y, Z	X, Y, or Z structural displacement.
ROT	X, Y, Z	X, Y, or Z structural rotation.
F	X, Y, Z	X, Y, or Z structural reaction force.
M	X, Y, Z	X, Y, or Z structural reaction moment.
TEMP [1]	-	Temperature.
TEMP	MAX, MIN	Maximum or minimum temperature in the model.
HEAT [2]	-	Reaction heat flow.

For SHELL131 and SHELL132 elements with KEYOPT(3) = 0 or 1, use the labels TBOT, TE2, TE3, . . ., TTOP instead of TEMP.
For SHELL131 and SHELL132 elements with KEYOPT(3) = 0 or 1, use the labels HBOT, HE2, HE3, . . ., HTOP instead of HEAT.

Table 197: NLHIST - Valid ESOL Item and Component Labels

Item	Comp	Description
S	X, Y, Z, XY, YZ, XZ	Component stress.
"	1, 2, 3	Principal stress.
"	INT	Stress intensity.
"	EQV	Equivalent stress.
EPEL	X, Y, Z, XY, YZ, XZ	Component elastic strain.
"	1, 2, 3	Principal elastic strain.
"	INT	Elastic strain intensity.
"	EQV	Elastic equivalent strain.
EPPL	X, Y, Z, XY, YZ, XZ	Component plastic strain.
"	1, 2, 3	Principal plastic strain.
"	INT	Plastic strain intensity.
"	EQV	Plastic equivalent strain.
EPCR	X, Y, Z, XY, YZ, XZ	Component creep strain.
"	1, 2, 3	Principal creep strain.
"	INT	Creep strain intensity.
"	EQV	Creep equivalent strain.
EPTH	X, Y, Z, XY, YZ, XZ	Component thermal strain.
"	1, 2, 3	Principal thermal strain.
"	INT	Thermal strain intensity.
"	EQV	Thermal equivalent strain.
EPDI	X, Y, Z, XY, YZ, XZ	Component diffusion strain.
"	1, 2, 3	Principal diffusion strain.
"	INT	Diffusion strain intensity.
"	EQV	Diffusion equivalent strain.
NL	SEPL	Equivalent stress (from stress-strain curve).
"	SRAT	Stress state ratio.
"	HPRES	Hydrostatic pressure.
"	EPEQ	Accumulated equivalent plastic strain.
"	CREQ	Accumulated equivalent creep strain.
"	PSV	Plastic state variable.
"	PLWK	Plastic work/volume.
TG	X, Y, Z, SUM	Component thermal gradient or vector sum.
TF	X, Y, Z, SUM	Component thermal flux or vector sum.

ETABLE items are not supported for ESOL items.

PAIR solution quantities are output on a "per contact pair" basis. GCN solution quantities are output on a “per general contact section” basis. (See Comparison of Pair-Based Contact and General Contact.) As a consequence, the corresponding values listed in the Jobname.nlh file represent a minimum or a maximum over the associated contact pair or general contact surface, as detailed in the table below.

Table 198: NLHIST - Valid Contact (PAIR or GCN) Item and Component Labels

Item Comp Description

CONT

ELCN

If >0, number of contact elements in contact. Other values are interpreted as follows:

0 indicates the contact pair (or GCN surface) is in near-field contact status.

-1 indicates the contact pair (or GCN surface) is in far-field contact status.

-2 indicates that the contact pair (or GCN surface) is inactive (symmetric to asymmetric contact).

" ELST Number of contact elements in sticking contact status

" CNOS Maximum chattering level

" PENE Maximum penetration (or minimum gap) [1]

" CLGP Maximum geometric gap

" SLID Maximum total sliding distance (algebraic sum)

" SLMX Maximum total sliding distance for closed contact in the current substep

" ESLI Maximum elastic slip distance

" KNMX Maximum normal contact stiffness

" KTMX Maximum tangential contact stiffness

" KNMN Minimum normal contact stiffness

" KTMN Minimum tangential contact stiffness

" PINB Maximum pinball radius

" PRES Maximum contact pressure

" SFRI Maximum frictional stress

" CNDP Average contact depth

" CLPE Maximum geometric penetration

" LGPE Number of contact points having too much penetration

" CAREA Contacting area

" NDMP Maximum contact damping pressure

" TDMP Maximum tangential contact damping stress

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

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

" FPSC Maximum normal fluid penetration pressure on contact surface

" FPST Maximum normal fluid penetration pressure on target surface

" WEAR Total volume lost due to wear for the contact pair (not available for general contact, Key = GCN )

" CTEN Total strain energy due to contact constraint [2]

" CFEN Total frictional dissipation energy [2]

" CDEN Total contact stabilization energy [2]

" CFNX Total force due to contact pressure - X component [4]

" CFNY Total force due to contact pressure - Y component [4]

" CFNZ Total force due to contact pressure - Z component [4] [5]

" CFSX Total force due to tangential stress - X component [4]

" CFSY Total force due to tangential stress - Y component [4]

" CFSZ Total force due to tangential stress - Z component [4] [5]

" CTRQ Maximum torque in an axisymmetric analysis with MU = 1.0

" LGSL Number of contact points having too much sliding for small sliding contact

" NORM Pair-based force convergence norm [3]

" CRIT Pair-based force convergence criterion [3]

" FPTC Maximum tangential fluid penetration pressure on contact surface

" FPTT Maximum tangential fluid penetration pressure on target surface

For PENE, a positive value indicates a penetration, and a negative value indicates a gap. If the contact pair (or GCN surface) has a far-field contact status, penetration and gap are not available, and the value stored for PENE is the current pinball radius.
The pair-based dissipation energy (CFEN) and stabilization energy (CDEN) do not include contributions from contact elements that are in far-field. The pair-based strain energy (CTEN) does not include the frictional dissipation energy and stabilization energy; it only contains an elastic recovery energy when the contact status changes from closed to open.
The program uses a default tolerance value of 0.1 to calculate the pair-based force convergence norm and pair-based force convergence criterion. This is not a check for local convergence. It is for monitoring purposes only and is useful for nonlinear contact diagnostics.

If the specified contact pair is a rigid surface or force-distributed constraint that includes stress stiffening effects, this quantity represents a total constraint force or moment at the pilot node as shown below:

CFNX	Total constraint force - X component
CFNY	Total constraint force - Y component
CFNZ	Total constraint force - Z component
CFSX	Total constraint moment - X component
CFSY	Total constraint moment - Y component
CFSZ	Total constraint moment - Z component

For the case of 2D axisymmetric with torsion (CONTA172 with a ROTY DOF), CFNZ and CFSZ represent moments along the Y direction.

Table 199: NLHIST - Valid Result Section (RSEC) Item and Component Labels

Item	Comp	Description
REST	SECF	Total section force
"	SECM	Total section moment
"	AXST	Section axial stress
"	BDST	Section bending stress
"	SPTX	Section center X coordinate
"	SPTY	Section center Y coordinate
"	SPTZ	Section center Z coordinate
"	THXY	Rotation about local z
"	THYZ	Rotation about local x
"	THZX	Rotation about local y

Menu Paths

Main Menu>Solution>Results Tracking