Curve Offset in LS-DYNA

LS-DYNA offers ability to offset a defined curve. This helps us to for example to define an arbitrary fire time for airbags by simply changing the offset value rather than to change the entire curve. Depending on the type of curve, LS-DYNA adds two points at the beginning of the curve for positive offsets and NONE for a negative offset value when the offsets are applied to the Abscissa. If the curve represents a time history curve (default) and the offset is greater than zero, then LS-DYNA add two points: one at ZERO and the other at 0.999*OFFSET_VALUE to ensure that the ordinate (function) is zero until a x-value of 0.999*OFFSET_VALUE. The following is depicted below.

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Initially in Contact – TIEBREAK contacts

When using TIEBREAK contacts, options other than 1, ties nodes ONLY if the nodes are initially in contact. Nodes not initially in contact will not be tied but can interact with master segments like the traditioanal compression-only contacts. To enforce the “initially” in contact condition, the [initial_separation-(slave_thickness+master_thickness)*0..5] < 0 which causes the initial penetration or initially in contact condition. If this value is greater than zero, you can use SST or MST values to enforce the condition.

The only method to verify if the intended nodes are actually tied is a quick normal mode analysis.