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Gap Axial Force

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.PNGGap axial forcePlease, can anyone clarify me this point?

Best regards

Stefano

2 REPLIES 2

Re: Gap Axial Force

Siemens Phenom Siemens Phenom
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.

CGAP Nastran Doc.JPG

 

Here's a model showing one GAP element in tension and one in compression.
Gap Axial Force.JPG

Re: Gap Axial Force

Pioneer
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
LOAD = 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