NLCTRL

Bulk Data Entry Uses keywords to define various control parameters for both Nonlinear Static and Nonlinear Transient Analysis.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
NLCTRL ID PARAM1 VALUE PARAM2 VALUE PARAM3 VALUE
PARAM4 VALUE PARAM5 VALUE PARAM6 VALUE
etc.

Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
NLCTRL 23 TTERM 1.0 DT 0.1
NCUTS 5 DTMAX 0.2 DTMIN 1.0E-5
TOLU 0.01
TOLF 0.005

Definitions

Field Description SI Unit Example
ID Each NLCTRL Bulk Data Entry should have a unique ID.

No default (Integer > 0)

TTERM Subcase termination time.

Default = 1.0 (Real > 0.0)

DT Initial time increment.

Default = 1.0 (Real > 0.0)

NINC Number of increments for determining DT. 4

Default = 1 (Integer > 0)

DTMIN Minimum time increment allowed.

The default value is given as the termination time multiplied by a scaling factor of 1.0E-5.

(Real > 0.0)

DTMAX Maximum time increment allowed. It is ignored in the first increment.

(Real > 0.0)

DIRECT Adaptive time increment. 5
NO (Default)
Use adaptive time increment scheme. Cutback is triggered if the time increment does not converge.
YES
Use fixed time increment. In case of divergence, the run will stop immediately.
TOLF Tolerance for force convergence criterion. 6

Default = 0.005 (Real > 0.0)

TOLU Tolerance for displacement convergence criterion. 7

Default = 0.01 (Real > 0.0)

TOLM Tolerance for moment convergence criterion.

Default = 0.005 (Real > 0.0)

TOLR Tolerance for rotation convergence criterion.

Default = 0.01 (Real > 0.0)

ITER Iteration number starting from which alternative force and moment convergence tolerance (TOLFLI and TOLMLI) are checked. 9

Default = 9 (Integer > 0)

TOLFLI Alternative tolerance for force convergence criterion with large iteration numbers (greater than or equal to ITER). 9

Default = 0.02 (Real > 0.0)

TOLMLI Alternative tolerance for moment convergence criterion with large iteration numbers (greater than or equal to ITER). 9

Default = 0.02 (Real > 0.0)

TOLUZF Alternative tolerance for displacement convergence criterion in case of zero force. 10

Default = 0.001 (Real > 0.0)

TOLRZM Alternative tolerance for rotation convergence criterion in case of zero moment. 10

Default = 0.001 (Real > 0.0)

REFF Reference force. 11

(Real > 0.0)

REFM Reference moment. 11

(Real > 0.0)

MAXITER Maximum allowed number of iterations in each increment. 17, 18

Default = 25 (Integer > 0)

MAXINC Maximum number of increments to analyze.

(Integer > 0)

MAXLS Maximum number of line searches. 12

Default = 0 (Integer > 0)

LSTOL Line search tolerance. 12

Default = 1.0E-3 (Real > 0.0)

NCUTS Number of cutbacks allowed to reduce the time increment. 19

Default = 5 (Integer > 0)

NOPCL Number of grids allowed to have open-close contact status change.

(Integer ≥ 0)

NSTSL Number of grids allowed to have stick-slip contact status change.

No default (Integer ≥ 0)

EXTRA Extrapolation of the solution at the beginning of an increment. 13
LINEAR
Activate linear extrapolation
NO (Default)
No extrapolation
STABILIZ Add stabilization energy. 14
MAXAUG Number of allowed augmentations within each time increment when the augmented Lagrange multiplier method for nonlinear contact is activated. 17

Default = 50 (Integer > 0)

Comments

  1. The NLCTRL Bulk Data Entry is selected by the Subcase Information Entry NLCTRL=ID.
  2. A nonlinear implicit subcase uses one of the following control entries: NLPARM, NLCTRL or TSETPNL Bulk Data Entries. TSTEPNL is used for a nonlinear transient subcase. NLCTRL Bulk Data Entry is an alternative for the NLPARM Bulk Data Entry to control the convergence, based on considerations illustrated in the following comments, and can improve convergence for the nonlinear solver. Many field options that are supported in NLPARM and NLADAPT can also be used directly in NLCTRL through keywords.
  3. TTERM is the duration of time until the subcase is terminated. In the case of subcase continuation, it is the local subcase time that is different between the start time and the final time of the subcase. In a nonlinear transient subcase, the specified value of TTERM is computed depending on the Ni and DTi fields of the TSTEP Bulk Data Entry, if they are specified.
  4. DT is the user-specified initial time. If NINC and DT are specified at the same time, then the NINC file is ignored.
  5. DIRECT=NO is used for activating the adaptive time increment scheme in both Nonlinear Static Analysis and Nonlinear Transient Analysis. The time step in the next increment is adjusted based on the number of iterations. The time step is changed if there are highly nonlinear difficulties in geometry and material calculations. In Nonlinear Transient Analysis, the automatic time stepping is checked to control the displacement error related to velocity and acceleration. At the end, the smaller value from both will be chosen. For more details, refer to the TSTEP Bulk Data Entry.
  6. For those subcases using NLCTRL, the special time adjustment of expert system PARAM,EXPERTNL will be ignored. However, if PARAM,EXPERTNL,CNTSTB is specified, contact stabilization is performed in those subcases with NLCTRL.
  7. TOLF is the tolerance of force criterion. The relative error of force is defined as:
    E F = R max F r e f T O L F MathType@MTEF@5@5@+= feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyramaaBa aaleaacaWGgbaabeaakiabg2da9maalaaabaGaamOuamaaBaaaleaa ciGGTbGaaiyyaiaacIhaaeqaaaGcbaGaamOramaaBaaaleaacaWGYb GaamyzaiaadAgaaeqaaaaakiabgsMiJkaadsfacaWGpbGaamitaiaa dAeaaaa@4580@
    Where,
    R max MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOuamaaBa aaleaaciGGTbGaaiyyaiaacIhaaeqaaaaa@39CB@
    Maximum residual force of any degree of freedom in translational direction
    F r e f MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaBa aaleaacaWGYbGaamyzaiaadAgaaeqaaaaa@39B7@
    Reference force which can be specified directly or calculated by OptiStruct for the model based on the loading history
    For the adaptive time increment scheme, F r e f MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaBa aaleaacaWGYbGaamyzaiaadAgaaeqaaaaa@39B7@ is the time average force, F t i m , a v g MathType@MTEF@5@5@+= feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaBa aaleaacaWG0bGaamyAaiaad2gacaGGSaGaamyyaiaadAhacaWGNbaa beaaaaa@3D40@ , over a number of increments, which can be expressed as:
    F t i m , a v g = 1 N a v g i = 1 N a v g ( F a v g , i ) MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaBa aaleaacaWG0bGaamyAaiaad2gacaGGSaGaamyyaiaadAhacaWGNbaa beaakiabg2da9maalaaabaGaaGymaaqaaiaad6eadaWgaaWcbaGaam yyaiaadAhacaWGNbaabeaaaaGcdaaeWbqaaiaacIcacaWGgbWaaSba aSqaaiaadggacaWG2bGaam4zaiaacYcacaWGPbaabeaakiaacMcaaS qaaiaadMgacqGH9aqpcaaIXaaabaGaamOtamaaBaaameaacaWGHbGa amODaiaadEgaaeqaaaqdcqGHris5aaaa@5275@
    Where,
    F a v g , i MathType@MTEF@5@5@+= feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaBa aaleaacaWGHbGaamODaiaadEgacaGGSaGaamyAaaqabaaaaa@3B55@
    Spatial average force of the model in the i MathType@MTEF@5@5@+= feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyAaaaa@36E1@ increment
    N a v g MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOtamaaBa aaleaacaWGHbGaamODaiaadEgaaeqaaaaa@39C0@
    Number of active increments

    The spatial average force, F a v g MathType@MTEF@5@5@+= feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaBa aaleaacaWGHbGaamODaiaadEgaaeqaaaaa@39B7@ , is the average value of the degrees-of-freedom with significant non-zero force when you check all grid forces and element forces, including applied force, reaction force and element internal force.

    F a v g = 1 N a c t i = 1 N a c t f a c t MathType@MTEF@5@5@+= feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaBa aaleaacaWGHbGaamODaiaadEgaaeqaaOGaeyypa0ZaaSaaaeaacaaI XaaabaGaamOtamaaBaaaleaacaWGHbGaam4yaiaadshaaeqaaaaakm aaqahabaGaamOzamaaBaaaleaacaWGHbGaam4yaiaadshaaeqaaaqa aiaadMgacqGH9aqpcaaIXaaabaGaamOtamaaBaaameaacaWGHbGaam 4yaiaadshaaeqaaaqdcqGHris5aaaa@4BED@
    Where, N a c t MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOtamaaBa aaleaacaWGHbGaam4yaiaadshaaeqaaaaa@39BA@ is the number of active degrees-of-freedom.

    Moment convergence criterion in the rotational direction is handled separately and in the same way as force convergence criterion.

  8. TOLU is the tolerance of displacement criterion. The relative error of displacement is calculated only based on the current increment:
    E U = δ U max Δ U max T O L U MathType@MTEF@5@5@+= feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyramaaBa aaleaacaWGvbaabeaakiabg2da9maalaaabaGaeqiTdqMaamyvamaa BaaaleaaciGGTbGaaiyyaiaacIhaaeqaaaGcbaGaeuiLdqKaamyvam aaBaaaleaaciGGTbGaaiyyaiaacIhaaeqaaaaakiabgsMiJkaadsfa caWGpbGaamitaiaadwfaaaa@48C3@
    Where,
    δ U max MathType@MTEF@5@5@+= feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqiTdqMaam yvamaaBaaaleaaciGGTbGaaiyyaiaacIhaaeqaaaaa@3B72@
    Maximum displacement correction in one iteration.
    Δ U max MathType@MTEF@5@5@+= feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeuiLdqKaam yvamaaBaaaleaaciGGTbGaaiyyaiaacIhaaeqaaaaa@3B33@
    Maximum displacement change in the current increment for one single degree of freedom in translational direction.
    The rotation convergence criterion is handled separately in the same way as the displacement criterion.
  9. Alternative tolerances TOLFLI and TOLMLI are used in iteration numbers equal to or larger than ITER.
  10. Alternative tolerances TOLUZF and TOLRZM are used in iterations when the time average value of force and moment are insignificant which means there is no active loading.
  11. If the reference force REFF or the reference moment REFM is specified, the reference value is replaced with a specified value and remains constant throughout the analysis:
    F r e f = R E F F MathType@MTEF@5@5@+= feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaBa aaleaacaWGYbGaamyzaiaadAgaaeqaaOGaeyypa0JaamOuaiaadwea caWGgbGaamOraaaa@3DFD@
    or
    M r e f = R E F M MathType@MTEF@5@5@+= feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamytamaaBa aaleaacaWGYbGaamyzaiaadAgaaeqaaOGaeyypa0JaamOuaiaadwea caWGgbGaamytaaaa@3E0B@
  12. Line search method using MAXLS and LSTOL is only supported in SMDISP NLSTAT. For more information, refer to the NLPARM Subcase Information Entry.
  13. When EXTRA=YES the linear extrapolation of displacement is performed at the beginning of an increment, based on the displacement change in the last increment. This option is only supported in LGDISP NLSTAT.
  14. For the STABLIZ option, refer to the NLADAPT Bulk Data Entry.
  15. Both NLPARM and NLCTRL Bulk Data Entries can not be specified together in the same nonlinear implicit subcase.
  16. Detailed convergence check information for implicit nonlinear subcases, increments, and Newton-Raphson iterations are printed in the _nl.out file. Additional options for checking Nonlinear Analysis run information and monitoring progress of Nonlinear Implicit Analysis jobs are listed in Runtime Monitoring in the User Guide.
  17. For more information on the augmented Lagrange multiplier method, refer to Augmented Lagrange Multiplier (ALM) Method (Nonlinear Analysis) in the User Guide.
  18. When the augmented Lagrange multiplier method for nonlinear contact is activated, MAXITER is respected within each augmentation of a time increment.
  19. If cutback occurs, the time increment is immediately reduced to 25% of the current time increment. Subsequently, if an increment converges without issue, the scaling factor for the time increment is successively increased from 1.0 to 1.5 in the next few increments, aiming to achieve a stable solution path.