Contact Interface Time Step Control

The contact interface time step can be controlled using the Engine options:

/DT/INTER/Keyword3/Iflag
$Δ T_{s c a}$ $Δ T_{\min}$

For all the Keyword3 options, the action taken will occur when

$Δ T_{\min} \geq Δ T_{s c a} * Δ t_{int e r f a c e}$ where,

$Δ t_{i n t e r f a c e} = \min (Δ t_{i n t e r n o d a l}, Δ t_{k i n})$ is the minimum of contact stiffness time step and the kinetic time step as defined in Contact Interface Time Step. If Iflag=1, then a second line with additional input is entered for /DT/INTER/AMS.

Note: This control is only used with contact interfaces with nonlinear stiffness, TYPE7, TYPE10, TYPE11, TYPE19, and TYPE21.

/DT/INTER/CST

Automatically increases the mass of nodes involved in contact to maintain the entered value. Normally this option is not useful since contact secondary nodes with low time steps typically have high penetration into the contact gap and when mass is added their kinetic energy increases which causes increased penetration and thus model instability. The amount of added mass should be monitored during and checked after the simulation in the same manner as /DT/NODA/CST.

/DT/INTER/DEL

Removes nodes involved in a contact interface that are causing the time step of the simulation to drop below $Δ T_{\min}$ . This option can be very useful to maintain a specified time step, but if the number of removed nodes is too large, then the contact will not be correct, and the results may not be accurate.

/DT/INTER/STOP

Stops the simulation when the contact interface time step drops below the entered $Δ T_{\min}$ value. Many times, a reduction in time step is caused by a model's instability, so stopping the simulation can be useful to diagnose the issue.

/DT/INTER/AMS

Applies Advanced Mass Scaling to interface secondary nodes to maintain the constant time step, $Δ T_{\min}$ . Refer to Advanced Mass Scaling (AMS) for more information.