Skip to content

!STEP

Analysis step settings

Required for nonlinear static analysis and nonlinear dynamic analysis

If this definition is omitted for analyses other than those above, all boundary conditions are enabled and the calculation is performed in one step

For viscoelastic and creep material properties, specify TYPE=VISCO and set the calculation-time conditions

Parameters

TYPE     = STATIC(default) / VISCO (quasi-static analysis)
SUBSTEPS = number of substeps for boundary conditions (default: 1)
CONVERG  = convergence criterion threshold (default: 1.0e-6)
MAXITER  = maximum number of iterations in nonlinear analysis (default: 50)
AMP      = time function name (specified by !AMPLITUDE)
INC_TYPE = FIXED (fixed increment, default) / AUTO (automatic increment)
MAXRES   = maximum allowable residual (default: 1.0e+10)
TIMEPOINTS = time-point list name (specified by !TIME_POINTS, NAME)
AUTOINCPARAM = automatic-increment parameter set name (specified by !AUTOINC_PARAM, NAME)
MAXCONTITER = maximum number of contact iterations in contact analysis (default: 10)

** 2nd line **

When INC_TYPE=FIXED (may be omitted when TYPE=STATIC)

(2nd line) DTIME, ETIME
Variable Attribute Description
DTIME R Time increment (default: 1/SUBSTEPS)
ETIME R Step time span (default: 1)

When INC_TYPE=AUTO (specified regardless of TYPE)

(2nd line) DTIME_INIT, ETIME, MINDT, MAXDT
Variable Attribute Description
DTIME_INIT R Initial time increment
ETIME R Step time span
MINDT R Lower limit of time increment
MAXDT R Upper limit of time increment

** 3rd line and later **

  BOUNDARY, id                                  id=GRPID defined by !BOUNDARY, !VELOCITY, !ACCELERATION
  LOAD, id                                      id=GRPID defined by !CLOAD, !DLOAD, !SPRING, !TEMPERATURE
  CONTACT, id                                   id=GRPID defined by !CONTACT

Example

Example using fixed time increments

!STEP, CONVERG=1.E-8
  0.1, 1.0
  BOUNDARY, 1
  LOAD, 1
  CONTACT, 1

Enable automatic increment adjustment and set the initial time increment to 0.01, the step time span to 2.5, the lower time-increment limit to 1E-5, the upper time-increment limit to 0.3, and the maximum number of substeps to 200

    !STEP, INC_TYPE=AUTO, SUBSTEPS=200
    0.01, 2.5, 1E-5, 0.3

Enable automatic increment adjustment and specify time-point list TP1 as the calculation and result-output times

    !STEP, INC_TYPE=AUTO, TIMEPOINTS=TP1
    0.1, 2.0, 1E-3, 0.2

Notes

  • With automatic increment adjustment, SUBSTEPS is treated as the maximum number of substeps
  • The time-point list name TIMEPOINTS and automatic-increment parameter set name AUTOINCPARAM are valid only when INC_TYPE=AUTO
  • When TIMEPOINTS is specified, the referenced !TIME_POINT must be defined before the !STEP card.
  • When AUTOINCPARAM is specified, the referenced !AUTOINC_PARAM must be defined before the !STEP card. If this parameter is omitted, the default automatic-increment parameter set is used.
  • If !STEP is omitted in dynamic analysis, the analysis is treated as a one-step analysis based on n_step and t_delta of !DYNAMIC, and the defined boundary conditions and loads are enabled. This behavior is provided for backward compatibility; defining !STEP is recommended for new input.
  • For fixed increments in dynamic analysis, specifying DTIME, ETIME on the second line of !STEP to control the time increment and step time span is recommended. n_step and t_delta of !DYNAMIC are treated as defaults when !STEP is omitted or for backward compatibility.
  • When INC_TYPE=AUTO is specified in dynamic analysis, the time increment is controlled using DTIME_INIT, ETIME, MINDT, and MAXDT on the second line. Automatic increments and cutback are used mainly in nonlinear implicit dynamic analysis.
  • In dynamic analysis, !BOUNDARY, !VELOCITY, and !ACCELERATION can be enabled step by step with the BOUNDARY line, and !CLOAD and implicit-method !SPRING can be enabled step by step with the LOAD line.