## Card 16 - Impulsive Constraint "Snag" – Veh1, Veh2

Optional impulsive constraints that resist the relative motions of the two vehicles during a portion of the collision contact. In many impacts, the two colliding vehicles may momentarily interlock, independent of the magnitude of the compressive collision forces and therefore their behavior is not adequately modeled with simple inter-vehicle friction. This option has been added to permit the modeling of an impulsive constraint on the relative motion. (Input cards 16, 18.)

Inputs for a "Snag" Impulsive Restraint are entered on Cards 16, 18, and 19.

 TSBEG TSWIND FSOPO XSPI YSPI AKSP DELSPM Qembed AKSP2 16 Card:  Field Variable Description Original Units Metric Units 16:1 TSBEG "SNAG" Impulsive Restraint Optional Input For SNAG, you specify a point in either V1 (FSOPO=1,2) or V2 (FSOPO=11,12) and at the start time for the snag (TSBEG) the location of the point specified is determined either in the other vehicle (FSOPO=2,12) or in space (FSOPO=1,11). Then an impulsive constraint is applied to the vehicle(s), based on the stiffness AKST, to attempt to minimize the separation of the points during the pusle width (TSWIND). See DISCUSSION – Snag Option Time to begin reaction and to begin use of  DTCOLL. Sec 16:2 TSWIND Pulse width, or duration of reaction. Sec 16:3 FSOPO Option =  0 -  no reaction.                 1 -  Point specified in V1, reaction point fixed in space.                 2 -  Point specified in V1, reaction point fixed in V2.                 5 -  Point specified in V1, Pole reaction.                      (If Pole chosen, then must include card 19)                 11 -  Point specified in V2, reaction point fixed in space.                 12 -  Point specified in V2, reaction point fixed in V1. 16:4 XSPI X coordinate of force application point in either V1 (FSOPO=1 or 2), in V2 (FSOPO=11,12)  or for Pole option (FSOPO=5) the space fixed location X location of the pole center. inches mm 16:5 YSPI Y coordinate of force application point in either V1 (FSOPO=1 or 2), in V2 (FSOPO=11,12)  or for Pole option (FSOPO=5) the space fixed location X location of the pole center. inches mm 16:6 AKSP Linear load-deflection characteristic of impulsive force.  (Only for FSOPO not equal to 5.) lb/inch N/cm 16:7 DELSPM Deflection at which saturation of  impulsive force occurs. NOTE: Maximum value of Impulse = AKSP*DELPSM*TSWIND inches Mm 16:8 Qembed For use with Pole Option: Embedment distance. inches Mm 16:9 AKSP2 Normally with DELSPM the force saturates at AKSP*DELPSM. Setting AKSP2 > 0 applies a secondary resistance for deflections > DELSPM. Lb/inch N/cm

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Card 16, Seq 1 - Impulsive Restraint "Snag" - Veh3