/DT/NODA/Keyword3/Iflag
Engine Keyword Activates the nodal time step control method with the option to apply mass scaling to increase a model’s time step.
Format
 /DT/NODA/Keyword3/Iflag

$\text{\Delta}{T}_{sca}$ $\text{\Delta}{T}_{\mathrm{min}}$ initial_mass_ratio  If Iflag=1, insert the next line
 grnd_ID
Definition
Field  Contents  SI Unit Example 

Keyword3  Time step control
type. 1
If Keyword3 is not specified, as in /DT/NODA/Iflag, then the computation will use the nodal time step and $\text{\Delta}{T}_{\mathrm{min}}$ is not used. 

Iflag  Node group flag.


$\text{\Delta}{T}_{sca}$  Scale factor on
critical nodal time step. Default = 0.9 

$\text{\Delta}{T}_{\mathrm{min}}$  Minimum time step.  
initial_mass_ratio  Mass ratio increase at
the beginning of the computation used to increase the minimum
time step. This value is entered as a ratio, so a 5% increase in
mass would be entered as 0.05. Default = blank 

grnd_ID  The nodal time step method is only applied to the nodes in this node group, read only if Iflag=1. 
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 the defined timestep divided by $\text{\Delta}{T}_{sca}$ .
 Only one /DT/NODA/Keyword3 option can be used in a simulation.
 When using Nodal time step, the computation of each cycle is slightly more expensive but the time step can be higher especially for low quality meshes.
 When /DT/NODA/Iflag is used (without Keyword3), the computation will use the nodal time step method, and $\text{\Delta}{T}_{\mathrm{min}}$ and initial_mass_ratio are not used.
 For constant nodal time step
options, (Keyword3=CST,
CST1, and CST2), the time step used at the
beginning of the simulation is the maximum of $\text{\Delta}{T}_{\mathrm{min}}$
or, time step calculated with mass added by
initial_mass_ratio. The initial time step will then be
maintained during the simulation by adding additional mass, if needed.
/DT/NODA/CST 0 $\text{\Delta}{T}_{\mathrm{min}}$
The computation is done with minimal nodal time step of $\text{\Delta}{T}_{\mathrm{min}}$ value. Mass will be added to maintain this timestep. /DT/NODA/CST 0 $\text{\Delta}{T}_{\mathrm{min}}$ 0
Radioss calculates a nodal time step to give 0% of initial mass increase and uses the maximum value of this calculated time step and $\text{\Delta}{T}_{\mathrm{min}}$ .  The time step for different amounts of percent mass increase information is printed as a table and a graph in the Starter output file.
 /DT/NODA/Keyword3 is compatible with all options of /DT/Eltyp/Keyword3.
 /DT/NODA and /DT/NODA/CST* are compatible with /DT/INTER/AMS from version 2017.2.3.
 /DT/NODA/CST* is
compatible with advanced mass scaling, /DT/AMS. If used with
/DT/AMS, AMS will be applied to the part group defined in
Starter /AMS card and /DT/NODA/CST*
applied to nodes not belonging to the AMS part group.For example:
 /DT/AMS/1
 $\text{\Delta}{T}_{sca1}$ $\text{\Delta}{T}_{\mathrm{min}1}$
 Tol_AMS
 /DT/NODA/CST
 $\text{\Delta}{T}_{sca1}$ $\text{\Delta}{T}_{\mathrm{min}1}$
This is even advised in order to minimize computing time in models where AMS only applies to selected parts.Note: It is pointless to use a higher time step in AMS than the one used in classic mass scaling since the smaller time step limits the performance.