MSC Nastran & Patran Contact TipsheetStart by: Mica Parks (mica.parks@mscsoftware.com)

Update 9-14-16

Collection of notes and suggesting pertaining to Nastran contact. Primarily newer 3D Contact but also including older contact methods and suggestions. Intended to be used AFTER a training class or watching contact videos. This is not a standalone ‘Quick Start’ yet. Modify this document as you see fit and send me suggestion how to make it better.

Preliminary outline of videos in SimCompanion DOC10729. If you are new to Pairs and/or Contact suggest start with What’s New Patran/Nastran 2013 LnL Contact Pairs.

General contact methods vs Nastran Solutions plus mixing ‘old’ and ‘new’ contact. See 1 st Tipsheet video :Newer 3D general body to body contact ~Nastran 2008+

Linear Gap P/CGAP Slideline Node To Segment (N2S) Segment To Segment (S2S)

Variation Glue Touch Glue Touch

Comment node-to-node old

node-to-node old

1D lines of nodes, old

Master-Slave Relationship, mesh independent

(Pre-Nastran 2014 too) New Mesh Independent

Mix newer 3D contact with old No*1 Yes No contact,

No FATAL

SOL 101 Yes No No Yes Yes Yes Nastran 2014

SOL 106, 129 No Yes Yes No No No No

SOL 103, 105, 108, 109, 111, 112 (linear or linear dynamic solutions)

No No NoYes

Permanent Glue Only

NoNastran 2014.1

Permanent Glue Only

No

SOL 200 No No No Yes No No, maybe Nastran 2014.1 No

SOL 400 No Yes No contact, No FATAL Yes Yes Yes Yes

SOL 700 No No No Deck Edit Yes Deck Edit Yes

SOL 144, 145, 146 Ignored Ignored Ignored Ignored Ignored Ignored Ignored

N2S = NTS = Node To SegmentS2S = STS = Segment To Segment

General Debugging ~49% of problem contact model issues are not with contact. Something else.

o Suggest remove all contact, use unintended/unrealistic constraints to stabilize model and run to verify setup.

o If touch contact in model change it to glue and run. Again, verify there aren’t other problems. SOL 103/modes can be very helpful.

Displacement is a good indication what or where a problem(s) might be. o Plotting in Patran is nice but looking at F06 or STS can also give an idea what’s the problem.o NLPARM or NLSTEP settings to get intermediate output is another method to get at displacement. Also

using ITER (non-automatic) convergence methods can make a difference with marginally un-runnable models. But iteration settings are not magic cure all.

1 “Permanent Glue” with Linear Gaps does work. Given both must be small displacement I can’t find fault with mixing the two. But this isn’t a combination development has acknowledged. Use at your own risk.

All “Traditional” methods below can be replace with new 3D Contact SOL 101 Traditional

Linear gaps can’t be mixed with any other contact. Unlikely to ever happen. Linear gaps are binary, on or off. No springs involved, not differential spring like P/CGAP. With large number of

linear gaps, thousands, convergence can be difficult or impossible. Your millage may vary but adding stiff springs 1e6 to 1e8 (regardless of units) in series (not parallel) with gap may help.

Linear gaps have no NLPARM or equivalent. Only number of times to let it iterate and user can pre-set open/close based on previous run.

SOL 106, 129, 400 Traditional P/CGAP is a differential spring. For unstable or difficult to converge models suggest giving an open stiffness of

1.0 to 10.0 (default is 1e-20). If that works likely the problems is contact related and not some other issue in the model. Your call if open stiffness should be removed for final results or substantially lowering open stiffness value is acceptable.

2-D Slidelines are list of nodes that make a curve, contact is essentially curve-curve contact. Often times need constraints on both curves so they don’t fall off of one another (constraints in non-sliding direction). Not a very general contact method.

‘new’ 3D Contact will not be added to SOL 106/129. Instead use SOL 101, SOL 400 or SOL 700.

‘new’ 3D General Body To Body Contact Information N2S stabilized in Nastran 2010. Using it prior to this version may be problematic.

o Nastran 2013.1 LMFACT and PENFM set to 0.05% of the average diagonal terms of the stiffness (Kgg). Pre-2013.1 was 5% of ave stiffness and too stiff in some cases (NAS-14547). Has to do with Lagrange calculation. This smaller value is much better if contact nodes/mesh match. If using older Nastran, meshes match and touch contact doesn’t look correct, find LMFACT/PENFM in F06 divide by 100 or more and set as PARAMs.

N2S has concept of slave-master bodies.o Slave = soft material (foam on steel) or more likely criteria finer mesh/more nodes on contact interface.o Master = Coarse mesh or less nodes on contact interface.

S2S mesh density and hard/soft material isn’t a concern, with regard to slave-master. But slave-master is still relevant to settings, COPTS/M for example. But it’s missing some N2S output and can behave softer or harder than expected. Suggest ignoring until Nastran 2014.1 or latter except for special cases; edge-edge touch is an example or if you do not need to recover forces/stress at contact boundary but need better/smoother stress distribution at contact interface.

o S2S turned on with BCPARA,0,METHOD, SEGTOSEG (SEGLARGE also an option).. SEGSMALL instead of SEGTOSEG is supported but not documented. May run a bit faster but at

some point may be remove. SEGLARGE is effectively what SEGTOSEG is. Should still be supported but like SEGSMALL may go

away at some point.o Nastran 2014.1 add NASTRAN SEGLOG=1 to control segment-to-segment stiffness calculation. =1 is

default for Nastran 2016.0 and based on testing it is better. =0 is non-conservative. Note =1 does us a bit more memory so you may need to lower BPOOL a bit. But it will FATAL quickly if not enough memory:

=0 (default 2014.1) based on average elastic stiffness of the two contact bodies and the default error tolerance.

=1 (default 2016.0) uses PARAM PENALT and other criteria. See QRG.o Look for NAS-21539 below. This has to do with S2S SPCs on contacted element and grounding.

General high level video of when to use N2S, S2S, turn off shell thickness, how edges or 1Ds are considered. N2S & S2S default is touch contact and shell thickness is taken into account for actual contact face.

o This is for all solutions, 101, 103, 400, 700, etc. SOL 700 would seem to have different rules but it works like the others.

“Contact Pair” is a newer Patran/Nastran setup method than older “Contact Table”. o Same functionality but easier to setup and modify (in Patran and BDF). Not N2S & S2S dependent. o Pair setup far more likely to pass Patran circle test (Patran read Nastran BDF with contact and correctly

regenerated)

Linear (SOL 101) Touch Contact does not consider material nonlinearity nor large displacement. This also means it doesn’t re-compute element location which can produce strange/bad results. Run in SOL 400 if in doubt.

Linear (SOL 101) multiple subcases with touch or glue is okay for standard cases. o Tested mix but none changing combo of touch/glue across multiple cases. Answers were the same if run

multiple cases at once or run as separate jobs.o Conjecture on non-standard cases would be modifying ERROR, ICOORD or similar contact parameter

from case to case. SOL 400 is required for Breaking Glue (JGLUE), Progressive Failure Analysis (PFA), Virtual Crack Closure

Technique (VCCT), Cohesive Zone Modeling (CZM). Technically JGLUE could be run in 101 but by nature of behavior it should 400, nonlinear.

RBE2/3 mix with 3D Contact is okay. But there can be various problems if large number of RBEs are mixed with contact. Handles case by case.

o N2S will back away from RBEs depending on independent/dependent.o S2S does not need to back away.

PCOMP nor PCOMPG Z0 offset is accounted for in contact face. Total ply stack is accounted for if COPTS B=1(default). If you need to account for element offset use ZOFF (offset on element).

1D element contact requires BCBMRAD card and only works with Node-to-Segment (up to ~Nastran 2014). o For Touch this imparts a user defined radius regardless of 1D property cross section shape. Based on

documentation it can be used with CROD, CBAR, CBEAM, CBEAM3.o For Glue (yes this is odd) radius is ignored. I have no idea why. You must move the nodes onto

shell/solid face/edge, with the ERROR.o 1D should be slave if mixing with 2D/3D. If 1D to 1D fall back to finer mesh slave but need for this is not

confirmed.o BCPARA BEAMB=1 is also required for beam-beam contact. In SOL 101/400 it is off by default. It can be

written from Patran.o 1D to 2D/shell edge (N2S) is effectively beam-beam. Both BCBMRAD and BEAMB are required.

It is important to realize 2D edge is a bullnose, pshell/pcomp t/2 is used as the radius. This can lead to some unexpected contact proximity scenarios. S2S, 2D edge anyway, does not work this way when it becomes available.

o 1D to 3D Touch contact has come up lately. Yes this works. But you must have 1D nodes at or near contact face. Another way to say it, it would seem the 1D node proximity check or radius is a ball about the 1D node and not a tube along the 1D. This is unconfirmed but testing supports this.

o If edge-edge or face-edge is a problem given current radius limitation, consider making dummy shell elements to represent the edge(s). Then rules go back to face-edge or face-face.

o Future Nastran will derive contact definition from cross section. Likely seg-seg only. Not available as of Nastran 2014.1

Nastran Setting You Are Likely To Modify (roughly in order and highlights in this video) ERROR is contact distance above and below patch. If not set Nastran automatically will set ERROR to be smallest

of all bodies; 1/20th smallest edge or ¼ thickness (PSHELL/PCOMP) of shells.o BCPARA ERRBAS=1 will use ERROR per contact pair base on two bodies used. Nastran 2012.

BIAS default is 0.0 for glue, 0.9 for touch. Set to 0.99 for models that seem to chatter or if big ERROR is needed. ISEARCH control Master-Slave relationship between bodies.

o =0 is terrible (default). Double search with priority based on BCBODY IDS. 50% chance of being correct.o =1 good. Search is from Slave to Master as set on BCONECT. But you have to get Master-Slave correct.o =2 okay if BCPARA THKOFF=1 is set. Nastran bases Slave to Master on mesh density. Still iffy though.

IGLUE’s = Touch or Glue + my $0.02 (3 rd Patran/Nastran Contact Pair video ):o IGLUE = 0 is touch (default). Patran doesn’t write it.o IGLUE=2 is glue, no moment, retains initial gaps & overlaps which avoids potential grounding.o IGLUE=4 is IGLUE=2 but includes moments. Also retains initial gaps & overlaps which avoids potential of

grounding.o IGLUE=1 is glue no moment, IGLUE=3 is glue with moment. Slave nodes are moved onto Master which

can cause grounding if meshes not perfectly aligned. Add ICOORD=1 or =3 if you want Nastran to move nodes and avoid grounding. ICOORD=1 or =3 is okay with IGLUE=2,4 too.

ICOORD = Stress free Initial Contact and Delayed Slide Offo Works for Touch or Glue but key is its ‘initial’ modification of nodes. If you want to artificially move

contact boundary use CINTERF.o ICOORD=1 will move Slave nodes onto Master if they meet ERROR+BIAS requirements. Nodes moved

along Slave vector direction. Stops grounding with IGLUE=1,3. This setting is particularly useful for tube in tube, bolt in hole type situations or lumpy FEM. (N2S) you can only see where the nodes are moved to by reading results with BOTH into Patran

(regenerate model from binary results, XDB, MASTER). (S2S) does NOT move nodes. Patran read results with BOTH you will not see a difference.

Instead the contact location is moved via polygons that represent the contact. This also means the elastic foundation (formulation) is at original FEM location.

o ICOORD=2 in conjunction with SLIDE increases the footprint of the Master elements/patch. By default, without ICOORD/SLIDE, Master patch is slightly larger than node based footprint so =2 may not be necessary.

o ICOORD=3 is combination of ICOORD=1 and ICOORD=2. COPTS(slave)/COPTM(master) controls how element topology is considered.

o If shell thickness is used (default) or element-node location, is primary use. o Setup is odd, sorry. See QRG but 10*B is likely what you want to interact with, you want to change. 1061

is common if ignore thickness.o Common user error, when editing deck manually after output from Patran, swap Master-Slave and

forget there is different COPT for each. You can go in circles thinking shell thickness should be ignored but contact status says otherwise.

CINTERF is interference closure amount normal to contact surface. CINTERF >0 overlap, <0 gap.o Solid elements no real hang-ups. Shell elements if property thickness is included (default) no problems

with CINTERF.o Shell without thickness can be a problem. Nastran can get confused which side to offset. Best to keep

thickness and adjust CINTERF appropriately.o CINTERF behavior is fixed offset across entire contact body. If your model is ‘lumpy’ I’m not sure if you

can mix this with ICOORD and get smooth/consistent contact face. It also brings up the point 3D contact is based on proximity whereas P/CGAP and Linear Gap are based on displacement toward or way. To mimic this will require a clearance type option, but for large sliding effects may not be desirable.

Potato Chip – Touch contact edges lift off unexpectedly.o Still assessing this based on user input. But adjusting FNLTOL and LMFACT (N2S) or PENALT and AUGDIST

(S2S) can correct this. Likely only to be a problem with thin/soft structure face to face with much stiffer structure. The problem goes back to the fact contact ‘stiffness’ should be calculated locally but that’s computationally expense. So it’s generally based off of average model stiffness.

Nastran 2013 reduced LMFACT and PENALT. Face to face models are less likely to ‘potato chip’ for no reason. But keep it in mind.

SOL 400 rigid=linear.o This is not contact specific. But with contact I see more jobs with RBE2 (sometimes RBE3) with reduced

DOFs. Instead of 123456, 1246. With default rigid=lagran simulation will have a difficult time converging.

If rigid=linear gets the job running consider keeping it or finding a non-RBE method to make the connection, BUSH for example.

o Look up RBE3/RBE2 rules with regard to RIGID= under the RBE cards. RBE3 has limitations. AUTOSPC (RESIDUAL)=YES in SOL 400

o Not contact specific. This is roughly equivalent to SOL 101 AUTOSPC. It may help in similar manner, particularly if 101 job runs but same 400 job does not.

New to Nastran 2016 (not in videos)o Introduction of a clearance and large interference overlap functionality. The 2016 Release Guide is not

particularly clear how these work and there are card name errors.o The ‘clearance’ via BCONPRG OPINGP is the more interesting of the two. It make contact similar to

P/CGAP in that if nodes are within a tolerance (TOLINGP) they are assumed to be in contact. This can be well outside the standard ERROR+BIAS. And is uniquely calculated per segment (element), not a distance for entire body. By default TOLINGP is 100x ERROR (if OPINGP active) but you’ll probably want to set it yourself. On top of this you can add MGINGP, default 0.0. An offset on top of the assumed to be perfectly in contact distance. MGINGP > 0 introduced a gap, like PGAP initial gap opening or U0. MGINGP < 0 means overlap. You can think of this as CINTERF but there are rules you should consult QRG on. The ERROR+BIAS is present at the new face location subject to OPINGP + TOLINGP + MGINGP.

Patran MPCs (from NLOPRM) can be read in with Patran Nastran import but you need to turn off node ID offset (on by

default). Make node, not MPC offset = 0. Otherwise they all end up at 0,0,0 and it has no physical meaning. MASTER/DBALL and ‘enhanced’ OP2 (PARAM,POST,+1) has Contact Status and other contact results, as opposed

to XDB or old OP2. Technically old OP2 attached as MASTER will give you same info but not supported. Contact Status is easier to see using Plot Marker/Scalar. Fringe plot can be misleading with averaging. ‘Contact Table’ can be converted to ‘Contact Pair’ but you have to play games under Analysis. Conversely you

can write ‘Contact Table’ from ‘Contact Pair’ by setting Nastran version to 2012, but not recommended. First part of What’s New Patran/Nastran 2013 LnL Contact Pairs covers this.

Problems & Debugging BCPARA overwrites all unset/default contact pair or body-body interactions. If a specific contact interaction is

required for a pair, set it on that pair. Using BCPARA can have very unintended consequences. I do not recommend it for complex/many contact body models.

BCONTACT=ALLBODY is confusing and not recommended. Nastran does not look into corresponding BCTABLE, BCTABL1 or BCONECT but uses the defaults for all entries on BCTABLE, BCONPRG or BCONPRP.

NLOPRM NLDBG=ADVDBG,N3DBAS,N3DADV,MPCPUNCH=BEGN below CEND o Writes substantially more information about contact settings and behavior in F06. See QRG for

information. o MPCPUNCH= will write MPC to punch file for visualization in Patran or to be used with subsequent runs.

MPCPUNCH=STEP will write MPCs at end of Subcase/Step, likely what you want. MPCPUNCH=BEGN write the MPCs at the start of the run, good for Permanent Glue or

understand start contact interaction but not generally what you want, end is better. Triple stack or more of contact surfaces is possible with N2S. But special care must be taken with regard to slave-

master setup. S2S removes some of this complexity but can get in trouble if contact distance, ERROR + BIAS is too large. Best to take a look at Use Case. But general idea is make middle plate combo Master-Slave or Master-Master. Slave-Slave is bad.

Elements in contact bodies need to be mutually exclusive. Can’t have same element in multiple contact bodies. Shared nodes from elements is generally okay but can cause odd behavior and F06 warning messages. Also generally means some nodes where unintentionally equivalenced or merged. S2S does not have this shared not problem.

When touch contact model does not run, glue everything and try again. Half the time contact isn’t the culprit. Can also run normal modes (SOL 103 (model needs mass)), which only allows glue contact, to catch stiffness/connection problems.

Glue contact has options to control if moment is included. If moment should be included has same arguments as bolts when represented by BAR/BEAM. Should the BAR/BEAM omit rotation/moment using pin flags or RBEs setup. No moment is conservative but technically not correct. Suggesting using IGLUE=4 and not =2 to include moment.

“Permanent Glue” is special case of general glue (Video overview). By default it is on, turned on with BCPARA NLGLUE=0. Intended for model assembly and linear analysis. Shouldn’t use if permanent glue location is subject to large displacement effects. Glue connections does not update with load. Solution does not iterate. Generally analysis is faster without contact iterations/updates.

o If any touch in the model (IGLUE=0) permanent glue will be ignored or deactivated. o All intended permanent glue bodies must be in initial contact. Nastran has no idea if all contact is valid,

that is your job. o You will get the following warning if no bodies are connected or IGLUE=0 indicating Permeant Glue isn’t

taking place.*** USER WARNING MESSAGE 8156 (MCN1GCK) GENERAL CONTACT JOB WITH THE GLUE OPTION WILL BE ACTIVATED INSTEAD OF PERMANENT GLUE. NLGLUE IN BCPARA (ID=0) WILL BE SET TO 1. User Information: The model has both of glue and non-glue contact definitions. SOL101 and SOL400 support the mixed glued contact and the permanent glue contact changes to the mixed glue contact.

o “Permanent Glue” does not report “contact force, Friction” or “contact force, Normal”. It does report “contact status” and write MPCs from NLOPRM MPCPCH=BEGN or STEP. If you need ‘force’ (not friction obviously) type data either:

Use freebody Write MPCs that represent contact (if N2S) with NLOPRM and option MPCPUCH. Second run

turn off contact and use the MPC in subsequent run. Then you can look at MPC forces.o MODEL_CHECK CHECKOUT in executive section (above CEND) with NLOPRM MPCPCH=BEGN will write

MPC to punch and with Master/DBALL attached to Patran you can see “contact status”. Very handy to figure if you have contact master-slave, COPT, etc. setup correctly. This should work for no-load initial contact if ‘iterative glue’ or ‘touch glue’ but I haven’t

checked.o Patran by default turns on “Permanent Glue”, NLGLUE = 0. If you have any touch contact, as mentioned

above, then analysis will turn off/ignore permanent glue. In Patran you can turn this off with NLGLUE=1 and use ‘regular’ glue. This is under Analysis

Solution Type/Solution Parameters/Contact Parameters… and uncheck “Enable Initial Contact”

GROUNDCHECK(SET=ALL,DATAREC=YES)=YES. Only valid with Permanent Glue. o Look for NAS-21539 below. This has to do with S2S SPCs on contacted element and grounding.

IBSEP=4 or =2 will get you past the follow FATAL (end of this video). Has to do with midside nodes. QRG misleading about LINQUAD=-1.

*** USER FATAL MESSAGE 5 (CNX_BOUDRY) Quadratic elements in contact can only be used in combination with BCPARA and IBSEP=1,2,3 or 4

Analytic contact (SPLINE) is required for better topology on coarse/jagged mesh sliding. As an example it will let bolts spin in holes. (Activation of this option in Patran)

Rigid Body enforced transform + rotation is possible. But arbitrary rotation must be applied to auxiliary node… very odd setup.

Touch or glue slow run time due to bad constraints or contact. o The USER INFORMATION MESSAGE 4158 is a nice way to say FATAL 9050 but let your job run anyway. If

you see this message you should try to fix it. Something is loose in the model.o In some cases, more likely with glue, this message could go away as parts get close enough to glue.o Fix could be increasing ERROR, changing BIAS, etc. Maybe just move parts closer together.

*** USER INFORMATION MESSAGE 4158 (DFMSA) ---- STATISTICS FOR SPARSE DECOMPOSITION OF DATA BLOCK SCRATCH FOLLOW NUMBER OF NEGATIVE TERMS ON FACTOR DIAGONAL = 97491 MAXIMUM RATIO OF MATRIX DIAGONAL TO FACTOR DIAGONAL = 4.5E+14 AT ROW NUMBER 2342287

o An extension of this problem may be many listed separation nodes as shown below. Again the problem could go away depending on nature of contact and model. It isn’t a hard rule if you see this your model is bad, just suspect.

*** USER INFORMATION MESSAGE 4158 (DFMSA) ---- STATISTICS FOR SPARSE DECOMPOSITION OF DATA BLOCK SCRATCH FOLLOW NUMBER OF NEGATIVE TERMS ON FACTOR DIAGONAL = 70180 MAXIMUM RATIO OF MATRIX DIAGONAL TO FACTOR DIAGONAL = 1.8E+16 AT ROW NUMBER 2342289 *** warning: node 255836 separated 2 times and will be skipped in separation check *** warning: node 69803 separated 2 times and will be skipped in separation check *** warning: node 78131 separated 2 times and will be skipped in separation check

SOL 101 with contact can use NLPARM or NLSTEP. But whatever is provided in the deck is converted back to NLPARM and only some input is used.

SOL 400 with NLSTEP has far more options and is what you should use.o NLSTEP CTRLDEF is keyword for ‘canned’ combination of error setting. Look at QRG NLSTEP for more

info.

o CTRLDEF: SOL 101 options are LCPERF, LCACCU and LCNT (default)

o CTRLDEF: SOL 400 the values "QLINEAR", "MILDLY", and "SEVERELY" are available along with the option of leaving blank.

CQUAD8 and CTRIA6 K6ROT is not effective. For slightly curved surfaces (not flat or highly curves) high pivot ratios can appear. With contact this may run but Nastran is chewing up resources dealing with it. Either drop the mid-side nodes, change to CQUAD4 and CTRIA3 and let K6ROT deal with it, or AUTOSPC increase EPSSING (SOL 400 RESIDUAL) to fix corner nodes of CQUAD8 and CTRIA6.

o CQUAD8 and CTRIA6 may come from skinning solid elements, often to get 1D element (BAR, BEAM, BUSH, etc.) rotations into a solid. As the GRIDs at 1D to 3D junction ‘could’ have rotation stiffness AUTOSPC will not fix/constrain them. Generally what you want, but there can be unintended consequences, namely large rotations you did not expect.

o K6ROT stiffness, if you switch to CQUAD4 and CTRIA3 is dependent on shell thickness. For getting 1D rotations into a solid the shell thickness is generally very small (to not add much stiffness/mass). You could play games with PSHELL T and 12I/T**3 to get high rotation stiffness but still thin. But this could become a complex game. Alternative is RBE or more 1D elements to turn rotations into translations.

INREL or inertia relief (SOL 101 only functionality) does not work with touch nor ‘regular’ iterative glue body to body contact. Permanent Glue is okay. Linear Gaps also can’t be mixed with INREL, as it uses INREL to function.

o SOL 400 with IRLOAD works. Basically the same as INREL -2 but it ‘wants’ SPC or model floats off a few units. But with statically determinant SPC you’ll find SPC force near zero. See SimCompanion KB8022589.

o Potential workaround is use Global-Local type approach. Get load from INREL but with permanent glue. Then using fields apply it to job with touch contact. That easy

o SOL 101 with touch and INREL -2 produces no error. INREL seems to be ignored.o SOL 101 with touch and INREL -1 gives error regarding SUPORT card:

*** USER FATAL MESSAGE 9008 (SUBDMAP PHASE0) A SUPORT BULK DATA ENTRY IS PRESENT. USER INFORMATION: THIS ENTRY IS NOT ALLOWED IN LINEAR CONTACT ANALYSIS.

Segment to Segment with SPC on grids connected to element in contact body AND those elements are touched or glued will ground the model. This is a problem up through Nastran 2014.1. Model will have a difficult time converging for touch or iterative/nonlinear glue. Nastran 2016.0 this was partially solved. The exception is if ICOORD (stress free initial contact) is used. Then SPCs on contacted elements will ground. But it isn’t as bad as pre-2016. You’ll see imbalance between OLOAD RESULTANT vs SPCFORCE RESULTANT. But all tested models seem to converge okay and results appear good.

o JIRA for this is NAS-19688 . This non-ICOORD issue and has been closed. Fixed in 2016.0o JIRA for SPC+ICOORD is NAS-21539 . This issue will remain through 2016.0. Workaround is isolate SPC

from element via BUSH or other element. RBE is not a good workaround for some reason.o Node to segment does not ground.o If SPC grids are not contacted but associated with contact body it is okay. No grounding.o GROUNDCHECK will not help you identify these issues with touch or nonlinear glue. Tests are done

before iteration. But test is effective for permanent glue, but fails in N-set which is a little odd.

Video overview of these slides; ISEARCH or Master-Slave settings, ERROR and BIAS, NLOPRM to get Nastran calculated ERROR.

Touch/Glue grid behavior explanation expanstion to N2S Primarry Contact Setting ERROR & BIAS slide.

Touch and non-ICOORD BCONTACTC=0, if grids are within ERROR & BIAS they are pulled or pushed elastically onto ‘Master segment’. BUT, whether it stays on the face is dependent on the separation force, FNTOL, IBSEP and ICSEP. With default or normal separation forces and settings it very likely the GRID can get pulled off when it’s just barely inside ERROR & BIAS zone. With high FNTOL, IBSEP, ICSEP the slave grid may not be able to get loose from the master segement. You will get high normal forces suggesting tension (apposed to expected compression only). The touch contact will become ‘sticky’. Not good, but it does make the job run much faster.

Glue, not permanent glue, needs to be checked. It seems to act like touch. But once slave grid is inside ERROR & BIAS zone it is sucked onto the patch and stuck there. Unless you have breaking glue, JGLUE >1.

Permanent Glue, since it doesn’t update, if a node/body is in ERROR & BIAS zone it’s fozen at that location. Hence BIAS = 0.0 and larger ERROR doesn’t make much as much a difference (as touch).

Contact Status is an important check. Image below is relatively standard way to post ‘contact dots’. This is more clear than using Fringe.

With touch contact you should get an intial or BCONTACT=0 contact status then also status at 100% of load. SOL 400 you can get status per load % that can be very enlightening.

Permanent glue you only get contact status at start of run. Note that the status is binary and by element. So even if contact is only at one corner all the nodes from that

element get a postive status. It is not very granular. Better to use Contact Force, Normal if you need to get an idea of per node contact interaction.

Video of result in 1st of 3 Tipsheet videos; Introduction of tipsheets intent and contact compatibility.

PARAM,POST,+1 or enhanced OP2 ‘Attched’ in Patran does not have a BOTH option, it will not generate nodes and elements for post processing. And so it will not allow you to see the effects of ICOORD, how nodes were moved for stress-free initial contact. The enhanced OP2 is platform independent.

Video overview of this slide; 2 nd Tipsheet video :