TSTEPNX

Bulk Data Entry Defines additional parameters for geometric nonlinear implicit dynamic analysis.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
TSTEPNX ID TA0 DTA DTTH NPRINT RFILE      
  SOLV TSCTRL DTMIN DTMAX LSMETH RREFIF NCYCLE FIXTID/TOUT  
  DYNA ALFA BETA GAMA SMDISP        
  ITW DTSCI LDTN DTSCD LARC        

Example 1

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
TSTEPNL 99   0.01            

Example 2

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
TSTEPNL 99   0.01            
TSTEPNX 99   0.1            
  NEWT ARC 1.e-4 0.1          

Example 3

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
TSTEPNL 99   0.01   3   PW    
    0.01 0.01            
TSTEPNX 99   0.1            
  NEWT ARC 1.e-4 0.1          
  NEWM   0.25 0.5          

Definitions

Field Contents SI Unit Example
ID An associated TSTEPNL entry identification number.

No default (Integer > 0)

  
TA0 Start time for writing animation files.

Default = 0.0 (Real ≥ 0)

  
DTA Output time step for animation files. If zero, no output. 3

Default = DT (Real ≥ 0)

  
DTTH Output time step for time history files. If zero, no output. 3

Default = 0.1*DT (Real ≥ 0)

  
NPRINT Print every NPRINT iterations. If negative, to .out and standard output; if positive, only to .out file.

Default = -1 (Integer)

  
RFILE Cycle frequency to write restart file for nonlinear iteration.

Default = 5000 (Integer > 0)

  
SOLV Geometric nonlinear implicit solution method
NEWT (Default)
Modified Newton.
BFGS
BFGS quasi-Newton method.

(Character)

  
TSCTRL Time step control.
ARC (Default)
Arc-length is used to accelerate and control the convergence. The time step is determined by displacement norm control (arc-length).
SIMP
Simple time step control.
NONE
No time step control. A warning will be issued. In the case of divergence, the time step will be repeated with half the step size. The run will be terminated according to DTMIN and NCYCLE.

(Character)

  
DTMIN Minimum geometric nonlinear implicit time step. If DTMIN is reached, simulation will be terminated. 3

Default = 1e-5*DT (Real ≥ 0)

  
DTMAX Maximum geometric nonlinear implicit time step from which time step is set constant. 3

Default = 3*DT (Real > 0)

  
LSMETH Line search method.
NONE
FORCE
ENERGY (Default)
AUTO

(Character)

  
RREFIF Special residual force computation with contact interfaces present.
0
Aggressive (modified entirely by the out-of-balance value).
1
Average (modified each time with 200% maximum).
2
Light (modified each time with 20% maximum).
3
No change.
4
No change; except for the first contact.
5
Modified automatically (for imposed displacement only).

Default = no special treatment (Integer)

  
NCYCLE Maximum number of time steps. If reached, solution will be terminated, NCYCLE=0 means no limit.

Default = no limit (Integer ≥ 0)

  
FIXTID A TABLEDi entry identification number. The x values of the table define fixed time points that the automatic time step control will adhere to.

(Integer > 0)

  
TOUT The method to determine the fixed time point.
AUTO (Default)
Fully automatic time step control.
NLOAD
The time points in all TABLEDi that are referenced by NLOAD1 in one subcase.
  
DYNA Implicit transient solution methods.
HHT (Default)
α-HHT method
NEWM
General Newmark method.

(Character)

  
ALFA Parameter in α-HHT Method (DYNA = HHT).

Default = -0.05 (Real, -1/3 < ALFA < 0.0)

  
BETA Parameter in general Newmark method (DYNA=NEWM).

Default = 0.25 (Real, -2 * BETA ≤ GAMA < 0.5)

  
GAMA Parameter in general Newmark method (DYNA=NEWM).

Default = 0.5 (Real, -2 * BETA ≤ GAMA ≤ 0.5)

  
SMDISP Perform small displacement and rotation analysis instead of geometric nonlinear analysis. PARAM, SMDISP, YES overwrites this definition.
OFF (Default)
Geometric nonlinear analysis.
ON
Small displacements and small rotations analysis.
(Character)		  
ITW If the solution of a time step converges within ITW iterations, the next time step will be increased by a factor controlled by DTSCI.

Default = 6 for TSCTRL=ARC

Default = 2 for TSCTRL=SIMP

(Integer > 0)

  
DTSCI Maximum scale factor for increasing the time step (TSCTRL=ARC). Scale factor for TSCTRL=SIMP.

Default = 1.1 (Real > 0)

  
LDTN Maximum number of iterations before resetting and decreasing the time step by a factor of DTSCD.

Default = 20 for TSCTRL=ARC

Default = 15 for TSCTRL=SIMP

(Integer > 0)

  
DTSCD Scale factor for decreasing the time step (TSCTRL=ARC or SIMP).

Default = 0.67 (Real > 0)

  
LARC Input arc-length for TSCTRL=ARC.

Default = automatic computation (Real)

  

Comments

  1. The TSTEPNX Bulk Data Entry is selected by the Subcase Information command TSTEP=option. There must also be a TSTEPNL Bulk Data Entry with the same ID. It is only used in geometric nonlinear implicit dynamic analysis (ANALYSIS=IMPDYN); it is ignored in other analyses.
  2. The solution method for geometric nonlinear implicit analysis is selected by SOLV. The frequency of stiffness matrix updates is controlled by TSTEPNL, KSTEP. For highly nonlinear problems, it is recommended to reduce KSTEP for better performance. KSTEP=1 means full Newton.
  3. The initial time step DTINI=DT is defined by TSTEPNL.
  4. For more information about geometric nonlinear analysis, refer to Explicit Dynamic Analysis (Radioss Integration) in the Users Guide.
  5. This card is represented as a loadcollector in HyperMesh.