NLADAPT

Bulk Data Entry Defines parameters for time-stepping and convergence criteria in Nonlinear Analysis.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
NLADAPT ID PARAM1 VALUE1 PARAM2 VALUE2 PARAM3 VALUE3    
    PARAM4 VALUE4 PARAM5 VALUE5 PARAM6 VALUE6    

Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
NLADAPT 23 NCUTS 5 DTMAX 4.0 DTMIN 1.0    

Definitions

Field Contents SI Unit Example
ID Each NLADAPT Bulk Data Entry should have a unique ID.

No default (Integer > 0)

  
NCUTS Number of cutbacks allowed to reduce the time increment.

Default = 5 (Integer > 0)

  
DTMAX Maximum time increment allowed.

No default (Real > 0.0)

  
DTMIN Minimum time increment allowed.

No default (Real > 0.0)

  
NOPCL Number of grids allowed to have open-close contact status change. 2

(Integer ≥ 0)

  
NSTSL Number of grids allowed to have stick-slip contact status change when the current time step converged.

No default (Integer ≥ 0)

  
EXTRA
LINEAR
Activates linear extrapolation in the Newton-Raphson method. The displacement value from the previous load increment is used as the initial guess for the current load increment.
NO (Default)
Extrapolation is turned off.
  
DIRECT
NO (Default)
Adopt adaptive time increment scheme. Cutback is triggered if the time increment does not converge and none of the stopping criteria are satisfied.
YES
Adopt fixed time increment. In case of divergence, the run will stop immediately.
  
STABILIZ Scale factor value to control the stabilization energy limit. 3
YES or 1.0 (Default)
Limits stabilization energy to 1.0e-4 times the strain energy. Since the strain energy can vary during the solution, the corresponding maximum stabilization energy for the YES option also varies accordingly.
Real > 0.0
The stabilization energy is limited to Scale Factor * 1.0e-4 *strain energy. For example, if STABILIZ is set to 2.0, then the stabilization energy is limited to 2.0*1.0e-4*strain energy. Since the strain energy can vary during the solution, the corresponding maximum stabilization energy for the Real > 0.0 option also varies accordingly.
Real < 0.0
The negative sign for scale factor simply indicates that the stabilization energy will remain constant throughout the solution. It is calculated using the strain energy at the beginning of the solution. The stabilization energy is equal to Abs(Scale Factor) * 1.0e-4 * (Initial strain energy) for the entire solution, where Abs (Scale Factor) indicates the absolute value of the scale factor, and Initial Strain Energy indicates that the initial value of the Strain energy is used for the calculation of stabilization energy for the entire solution. For example, if STABILIZ is set to -3.0, then the stabilization energy is set equal to (+3.0)*1.0e-4*(initial strain energy), and this value is used for the entire solution.
Note: For a “buckling” type of phenomenon, which is an unstable problem, in large displacement analysis, a fixed stabilization energy is more stable than a varying one.
  

Comments

  1. The NLADAPT Bulk Data Entry is selected by the Subcase Information Entry NLADAPT=ID. The NLADAPT Subcase Entry can be specified in any Nonlinear Subcase.
  2. The following table summarizes the support of different fields in NLADAPT for different analysis types.
    NLADAPT Field Small Displacement Nonlinear Analysis (SMDISP) Large Displacement Nonlinear Analysis (LGDISP)
    Static Transient Static Transient
    NCUTS Not Supported Not Supported Supported Supported
    DTMAX Supported Supported Supported Supported
    DTMIN Supported Supported Supported Supported
    NOPCL Supported Supported Supported Supported
    NSTSL Supported Supported Supported Supported
    EXTRA Not Supported Not Supported Supported Not Supported
    DIRECT Supported Supported Supported Supported
    STABILIZ Not Supported Not Supported Supported Supported
  3. This is a static stabilization based on viscous damping, where the viscous forces are added to the equilibrium equations. The viscous damping force ( F v MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaBa aaleaacaWG2baabeaaaaa@37E8@ ) is:(1)
    F v = c * v MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaBa aaleaacaWG2baabeaakiabg2da9iaadogacaGGQaGaamODaaaa@3B89@
    Where,
    c MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4yaaaa@36DE@
    f (Scale factor from STABILIZ, Compliance/Strain energy)
    v MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4yaaaa@36DE@
    Velocity of the nodes ( d u d t MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSaaaeaaca WGKbGaamyDaaqaaiaadsgacaWG0baaaaaa@39CB@ ) calculated from the time increment ( d t MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamizaiaads haaaa@37D8@ ).