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# Gap Axial Force

Builder

Dear Femap users,

A simple question. I perform a non linear analysis with gap element. This element is subject to an axial tensile force, but I don't understand why the Gap axial force results is negative.

Gap axial forcePlease, can anyone clarify me this point?

Best regards

Stefano

2 REPLIES 2

# Re: Gap Axial Force

Siemens Phenom

The Nastran documentation lists that a positive force shows compression. See number 5 in the CGAP bulk data entry of the Nastran Quick Reference Guide.

Here's a model showing one GAP element in tension and one in compression.

# Re: Gap Axial Force

Pioneer

Team,

I'm trying to use gap element in compression just liek this model? I'm running NLStatic and have have the gap elements working however when ever I add the tension (negative tension) the model fails to solve.

I'm wondering if anyone knows what I have incorrectly set-up.

INIT MASTER(S)
NASTRAN SYSTEM(442)=-1,SYSTEM(319)=1
ID Femap,Femap
SOL NLSTATIC
CEND
TITLE = NX Nastran NL Static Analysis Set
ECHO = NONE
DISPLACEMENT(PLOT) = ALL
SPCFORCE(PLOT) = ALL
FORCE(PLOT,CORNER) = ALL
NLSTRESS(PLOT) = ALL
STRESS(PLOT,CORNER) = ALL
SPC = 1
NLPARM = 1
BEGIN BULK
\$ ***************************************************************************
\$ Written by : Femap with NX Nastran
\$ Version : 11.4.2
\$ Translator : NX Nastran
\$ From Model :
\$ Date : Sun Jun 02 13:12:11 2019
\$ Output To : D:\Scratch\
\$ ***************************************************************************
\$
NLPARM 1 5 5 PW YES+
+ .001 .001 1.-7 3 25 4 .2 .5+
+ 5 20.
PARAM,PRGPST,YES
PARAM,LGDISP,1
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 : Untitled
FORCE 1 2 0 1. 5. 0. 0.
\$ Femap with NX Nastran Constraint Set 1 : Untitled
SPC1 1 123456 1
SPC1 1 23456 2
\$ Femap with NX Nastran Property 1 : GAP Property
PGAP 1 0. -5. 0. 100. 0. 0. 0.+
+ -1.
GRID 1 0 0. 0. 0. 0
GRID 2 0 5. 0. 0. 0
CGAP 1 1 1 2 0. 0. 1.
ENDDATA

If anyone has any ideas let me know thank you.

JP