Shell Edge Contact

[DVJones]

Greetings again! I have another NX Nastran shell element quandary.

I have a question about contacts on the edges of shell elements. I have 2 sheets, perpendicular to each other forming a 'T'. I would like to be able to have non-glued contact between the horizontal sheets face and the vertical sheets edge. The surface-to-surface contact functionality does not work because there is no surface on the shell element edge.

Would a CGAP element be useful in this situation?

Any thoughts on the topic would be greatly appreciated.

Thanks!
Dan

 

[BlasMolero]

Dear Dan,
Yes, in fact, CGAP node-to-node contact element is the only resource left if you want to consider the "no-penetration" contact between edge & surface. Please note that you need to activate the flag "GAPs as contact", if not the CGAP will act like a spring.

Also, surely next version of NX NASTRAN will feature the contact EDGE-TO-SURFACE, then meanwhile you need to use CGAP elements.

In the attached nastran input file I have setup a T-type contact using CGAP "compression-only" with GAP distance = 0.0 and compression stiffness = 1e6

NOTES:
======
• When a BCSET case control command exists, CGAP elements are treated as linear contact elements, if not the CGAP element will be considered as a spring.
• You can use CGAP elements in linear static analysis (SOL101) together with surface-to-surface contact defined (BCTSET bulk entries exist), or without (no BCTSET bulk entries exist). In the case where no surface-to-surface contact is defined, "n" on the BCSET case control command can point to a BCTPARM bulk entry which optionally defines PENN, PENT or PENTYP for the CGAP/linear contact elements, or to nothing if a BCTPARM bulk entry does not exist (an integer value for "n" is still required in this case).

• If you need to increase the numbr of contact iterations, then the contact control parameters on the BCTPARM bulk entry (optional) can help you adjust the contact algorithm when you are having problems getting a solution to converge and complete, or when the contact results are not as expected.

Here the example:

INIT MASTER(S)
NASTRAN SYSTEM(442)=-1, SYSTEM(319)=1
ID cgap,Femap
SOL SESTATIC
TIME 10000
CEND
TITLE = NX Nastran Static Analysis Set
ECHO = NONE
DISPLACEMENT(PLOT) = ALL
SPCFORCE(PLOT) = ALL
OLOAD(PLOT) = ALL
MPCFORCE(PLOT) = ALL
GPFORCE(PLOT) = ALL
FORCE(PLOT,CORNER) = ALL
STRESS(PLOT,CORNER) = ALL
BCRESULTS(TRACTION,FORCE,SEPDIS,PLOT) = ALL
SPC = 1
BCSET = 108
LOAD = 1
BEGIN BULK
BCTPARM,108,MAXS,50
$ ***************************************************************************
$ Written by : Femap with NX Nastran
$ Version : 10.3.1
$ Translator : NX Nastran
$ From Model : D:\MODELOS\test\cgap_edge2face.modfem
$ Date : Thu Mar 08 20:18:50 2012
$ Output To : D:\Scratch
$ ***************************************************************************
$
PARAM,POST,-1
PARAM,OGEOM,NO
PARAM,AUTOSPC,YES
PARAM,K6ROT,100.
PARAM,GRDPNT,0
CORD2C 1 0 0. 0. 0. 0. 0. 1.+FEMAPC1
+FEMAPC1 1. 0. 1.
CORD2S 2 0 0. 0. 0. 0. 0. 1.+FEMAPC2
+FEMAPC2 1. 0. 1.
$ Femap with NX Nastran Load Set 1 : Caso de Carga#1: Pressure
PLOAD4 1 9 -.1
PLOAD4 1 10 -.1
PLOAD4 1 11 -.1
PLOAD4 1 12 -.1
PLOAD4 1 13 -.1
PLOAD4 1 14 -.1
PLOAD4 1 15 -.1
PLOAD4 1 16 -.1
PLOAD4 1 17 -.1
PLOAD4 1 18 -.1
PLOAD4 1 1 -.1
PLOAD4 1 2 -.1
PLOAD4 1 3 -.1
PLOAD4 1 4 -.1
$ Femap with NX Nastran Constraint Set 1 : Restricciones
SPC1 1 123456 14
SPC1 1 123456 15
SPC1 1 123456 16
SPC1 1 123456 19
SPC1 1 123456 28
SPC1 1 123456 29
$ Femap with NX Nastran Property 1 : Mid-Surface t=2.
PSHELL 1 1 2. 1 1 0.
$ Femap with NX Nastran Property 2 : Mid-Surface t=2.
PSHELL 2 1 2. 1 1 0.
$ Femap with NX Nastran Property 4 : GAP Property
PGAP 4 0. 0.1000000. 0. 0. 0. 0.+
+
$ Femap with NX Nastran Material 1 : Acero (MPa)
MAT1 1 205000. .3 7.85-9 0. 0. +
+ 260. 260.
GRID 1 0 24. 1. -15. 0
GRID 2 0 24. 1. 0. 0
GRID 3 0 24. 1. 15. 0
GRID 4 0 37. 1. 15. 0
GRID 5 0 50. 1. 15. 0
GRID 6 0 50. 1. 0. 0
GRID 7 0 50. 1. -15. 0
GRID 8 0 37. 1. -15. 0
GRID 9 0 37. 1. 0. 0
GRID 10 0 24. 0. 15. 0
GRID 11 0 24. 0. 0. 0
GRID 12 0 24. 0. -15. 0
GRID 13 0 24. -12.5 -15. 0
GRID 14 0 24. -25. -15. 0
GRID 15 0 24. -25. 0. 0
GRID 16 0 24. -25. 15. 0
GRID 17 0 24. -12.5 15. 0
GRID 18 0 24. -12.5 0. 0
GRID 19 0 -50. 1. 15. 0
GRID 20 0 -35.2 1. 15. 0
GRID 21 0 -20.4 1. 15. 0
GRID 22 0 -5.6 1. 15. 0
GRID 23 0 9.2 1. 15. 0
GRID 24 0 9.2 1. -15. 0
GRID 25 0 -5.6 1. -15. 0
GRID 26 0 -20.4 1. -15. 0
GRID 27 0 -35.2 1. -15. 0
GRID 28 0 -50. 1. -15. 0
GRID 29 0 -50. 1. 0. 0
GRID 30 0 -35.2 1. 0. 0
GRID 31 0 -20.4 1. 0. 0
GRID 32 0 -5.6 1. 0. 0
GRID 33 0 9.2 1. 0. 0
CQUAD4 1 1 1 2 9 8
CQUAD4 2 1 2 3 4 9
CQUAD4 3 1 8 9 6 7
CQUAD4 4 1 9 4 5 6
CQUAD4 5 2 10 11 18 17
CQUAD4 6 2 11 12 13 18
CQUAD4 7 2 17 18 15 16
CQUAD4 8 2 18 13 14 15
CQUAD4 9 1 19 20 30 29
CQUAD4 10 1 20 21 31 30
CQUAD4 11 1 21 22 32 31
CQUAD4 12 1 22 23 33 32
CQUAD4 13 1 23 3 2 33
CQUAD4 14 1 29 30 27 28
CQUAD4 15 1 30 31 26 27
CQUAD4 16 1 31 32 25 26
CQUAD4 17 1 32 33 24 25
CQUAD4 18 1 33 2 1 24
CGAP 19 4 1 12 1. 0. 0.
CGAP 20 4 2 11 1. 0. 0.
CGAP 21 4 3 10 1. 0. 0.
ENDDATA f56f64f1

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

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48011 BILBAO (SPAIN)
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[DVJones]

Wow. Thank you for the detailed explanation and a script.