/DT/INTER/Keyword3/Iflag

Engine Keyword Interface time step control.

Format

/DT/INTER/Keyword3/IflagIflag

$Δ T_{s c a}$ $Δ T_{\min}$

If using /DT/INTER/AMS/1, insert the next line.

Tol_AMS

Definitions

Data	Description	SI Unit Example
`Keyword3`	Time step control type. 1: `CST` Use default constant time step method, /DT/INTER/CST2. `CST1` Nodal mass of interface secondary node is increased to maintain the constant time step $Δ T_{\min}$ . `CST2` (Default) Nodal mass of interface secondary node is increased to maintain the constant time step $Δ T_{\min}$ . Improved formulation. `DEL` The impacting secondary node is deleted from the contact interface so that constant time step $Δ T_{\min}$ can be maintained. `STOP` The run will stop if the time step reaches $Δ T_{\min}$ and a restart file will be written. `AMS` Advanced Mass Scaling is used on the interface secondary nodes to maintain the constant time step $Δ T_{\min}$ . If `Keyword3` is not specified, i.e. /DT/INTER, then $Δ T_{\min}$ is not used and $Δ T_{s c a}$ is used for TYPE7 contacts only.
`Iflag`	Number of additional (optional) cards. Only used when `Keyword3`=`AMS`. = 0 or blank Only $Δ T_{s c a}$ and $Δ T_{\min}$ is read. = 1 Additional card for `Tol_AMS` is read.
$Δ T_{s c a}$	Scale factor on critical time step for interface. Default = 0.9
$Δ T_{\min}$	Minimum time step.
`Tol_AMS`	Tolerance for AMS convergence - only used for /DT/INTER/AMS/1. Default = 10^-3

Comments

For all Keyword3 options, the time step control will be activated when the time step of the node controlling the time step of the simulation becomes less than:
$\frac{Δ T_{\min}}{Δ T_{s c a}}$
All Keyword3 options are only applicable for TYPE7, TYPE10, TYPE11, and TYPE19 interfaces.
Keyword3= STOP also applies to TYPE21 interfaces.
Both /DT/INTER/CST and /DT/INTER/AMS can be used at the same time as /DT/INTER/DEL or /DT/INTER/STOP.
/DT/INTER/Keyword3 can be combined with /DT/NODA or /DT/NODA/CST.
For Keyword3=AMS
- Advanced Mass Scaling does not modify the global mass, so that the global momentum of the related nodes is conserved. Therefore, /DT/INTER/AMS is more accurate than /DT/INTER/CST, /DT/INTER/CST1 and /DT/INTER/CST2.
- /DT/INTER/AMS is compatible with the following kinematic conditions: boundary conditions, imposed velocities, imposed displacements, imposed accelerations, tied interfaces (/INTER/TYPE2), rigid bodies, fixed rigid walls, rigid links and cylindrical joints.
- /DT/INTER/AMS is compatible with dynamic relaxation (/DAMP) and Rayleigh damping (/DAMP).
- /DT/INTER/AMS will not work if applied to nodes involving rivets (/RIVET) or Lagrange multipliers (e.g. /MPC and /GJOINT). In such cases, an error is output by the Radioss Engine.
- The rigid bodies which are connected to nodes where AMS applies can be activated/deactivated during Radioss Engine run through /RBODY/ON and /RBODY/OFF, but not with sensors.
- /DT/INTER/AMS always applies to the whole model, except that it is possible to use Elementary time step for AMS (/DT/AMS) on a part group and to use /DT/INTER/AMS at the same time: /DT/INTER/AMS will then apply to nodes which are not belonging to the part group.
  For example:
  - /DT/AMS/1
  - $Δ T_{s c a}$ $Δ T_{\min}$
  - Tol_AMS
  - /DT/INTER/AMS
  - $Δ T_{s c a}$ $Δ T_{\min}$
- Elementary time step for Advanced Mass Scaling will apply on the part group declared in /AMS of the Radioss Starter Input deck, but /DT/INTER/AMS will apply to nodes which do not belong to the part group.