IGNORE is echoed in d3hsp under the heading of:
"track initial penetration in auto contacts" for IGNORE in *CONTROL_CONTACT, and 
"penetration treatment for auto contact" for IGNORE on Opt. Card C of *CONTACT.

_________________________________________


In MPP, penetrating nodes may be found in mes**** by searching on 
"Moved node" if IGNORE=0 or
"has penetration" if IGNORE=2.
Ticket#2021082010000069  
(*CONTACT_AUTOMATIC_GENERAL was used in the test case)

___________________________________________________________

To explain IGNORE=1 in words:

At time=0, the initial penetration is stored as what I'll call the reference penetration.  No contact forces are applied.
After each time step,
- If the current penetration is greater than the reference penetration, the effective penetration that creates contact force is equal to the current penetration minus reference penetration.
- If the current penetration decreases and becomes less than the reference penetration, the stored reference penetration is updated to the current penetration.   Effective penetration is zero and thus contact force is zero.
jd 11/15/13
_______________________________________________________________________
If an initial penetration is detected, the contact algorithm will, by default, move the penetrating node
soas to eliminate the penetration. This moving of nodes will obviously perturb the initial 
geometry.  No forces are applied when perturbing the initial geometry.  
If IGNORE is set to 1, geometry is NOT perturbed when initial penetrations are detected.
Rather, the local penetration is noted and compensated for by adjusting the contact thickness locally.

Similarly, if at any point during the simulation a slave node is suddenly found to be
below the master surface (say, it was moving very fast and wasn't detected before
penetration), the old style (IGNORE=0) algorithm just moves the node to
the master surface without applying any forces (we term this "shooting node logic").  
If the shooting node logic is turned off (SNLOG=1),
then you would likely get large forces suddenly appearing, and negative contact energy.
If IGNORE is set to 1 then the shooting node logic flag SNLOG has no affect.
Rather the amount of sudden penetration is noted and compensated for by
adjusting the contact thickness locally.
So at any time during the simulation, if a sudden penetration is
detected, the program doesn't apply any large forces nor are any nodes moved.
Contact forces, however, will resist FURTHER penetration. 

IGNORE=2 has the same effect as IGNORE=1.  The only difference is that when IGNORE=2,
warning messages are written to d3hsp which report the initial penetrations.

Note: Do not invoke IGNORE=1 or 2 for *contact_automatic_general (per note
in contact.13vs26).


Shooting Node Logic

shooting node logic moves nodes throughout
the calculation and in fact does not move nodes initially.  We do try to
move nodes to eliminate initial penetration, but this is not shooting
node logic.  The shooting node logic moves nodes back to the surface
when they are first found to be in contact.  If you turn shooting node
logic off, then we still move nodes initially, but not throughout the
calculation.  If the ignore option is turned on, then nodes are not
moved during initialization, and shooting node logic is turned off.




SOFT=2

Segment based contact (SOFT=2) does not use the shooting node logic
parameter.  There is no need for shooting node logic because the segment
based contact ignores initial penetrations.  Penalty forces are
proportional to penetration in excess of the initial penetration.  In
equation form, this is

   f = k*(d-di)

where f is a force, k is penalty stiffness, d the current penetration
depth, and di the initial penetration depth.

The ignore option (optional card C, or 4th card of
*CONTROL_CONTACT) causes the default contact to ignore initial
penetrations which also makes shooting node logic unnecessary.



jpd, lpb
revised 3/14/2003