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Subject: Re: [STRUC] MPCs on contacts with pilot node
Author: Krishna Raichur
Date: 2008-04-11 13:25:13

Below is a sample problem that shows the correct reaction moment for a cylindrical pipe model. No need for any FSUM and SPOINT commands. The input builds three parallel models -- a Pipe16 model, a Solid185 model with MPC contact elements, and another Solid185 model with MPC184 rigid links. The moment reaction from all three models is as expected.

Regards,
Krishna
------------------------------------------
Krishna S. Raichur
SimuTech Group - Chicago
kraichur_at_simutechgroup.com


!! CHECK MOMENT REACTIONS WITH PILOT NODES
fini
/clear
OD=24 ! pipe outer diameter, in
TK=0.25 ! thickness
LEN=40 ! length
FF=10000 ! force value
ANGDV=10 ! no. of elem's in 90-degree arc
ANGSIZ=90/ANGDV ! angle size in degrees
ELSIZ=4 ! elem size along axis

! Geometry
/prep7
wpoff,-OD*3
rect,OD-TK,OD,,LEN
k,50,-OD*3
k,51,-OD*3,LEN

! 2-D Mesh
et,200,200,6
esize,ELSIZ
mshk,1
amesh,1
eplot

! 3-D Geom & Mesh
et,1,185
mpread,Stl_AISI-C1020,BIN_MPL,,lib
type,1 $mat,1 $real,1
extopt,esize,ANGDV
vrot,all,,,,,,50,51,360,4
aclear,1
/view,,1,1,1
eplot

! Constraints
! (use pilot node _at_ bottom center)
CID=11 ! contact element type ID
TID=12 ! target element type ID
et,CID,174 ! contact element type
keyo,CID,12,5 ! bonded contact
keyo,CID,4,1 ! force-distributed surface constraint
keyo,CID,2,2 ! MPC formulation
et,TID,170 ! target element type
keyo,TID,2,1 ! user-specified constraints
R,CID ! real constant set
mp,mu,CID,0
asel,,loc,y,0
nsla,,1 ! select bottom nodes
nplot
real,CID $mat,CID
type,CID
esurf ! contact elements
type,TID
nsel,none
kmesh,50 ! pilot node at bottom center
dk,50,all ! fix pilot node
allsel

! Loading
! (use pilot node _at_ top center)
CID=13 ! contact element type ID
TID=14 ! target element type ID
et,CID,174 ! contact element type
keyo,CID,12,5 ! bonded contact
keyo,CID,4,1 ! force-distributed surface constraint
keyo,CID,2,2 ! MPC formulation
et,TID,170 ! target element type
keyo,TID,2,1 ! user-specified constraints ***IMPORTANT!
R,CID ! real constant set
mp,mu,CID,0
asel,,loc,y,LEN
nsla,,1 ! select top nodes
nplot
real,CID $mat,CID
type,CID
esurf ! contact elements
type,TID
kmesh,51 ! pilot node at top center
!fk,51,fx,FF ! force _at_ pilot node
fk,51,my,FF*LEN ! moment _at_ pilot node
allsel
/pnum,type,1
/num,1
/pbc,all,1
eplot

! Parallel pipe element model
et,2,16
r,2,24,0.25
k,100,OD*3
k,101,OD*3,LEN
lsel,none
l,100,101
type,2 $mat,1 $real,2
lmesh,all
dk,100,all
!fk,101,fx,FF
fk,101,my,FF*LEN
allsel
eplot

! Parallel solid model with MPC184 elements
csys,0
vgen,2,all,,,OD*3
et,3,184,1 ! rigid beam
n,20000
n,20001,,LEN
csys,5
esel,none
*do,I,0,360,ANGSIZ
nsel,,loc,z,0
nsel,r,loc,x,0,OD
nsel,r,loc,y,I
type,3 $mat,3 $real,3
e,20000,node(OD-TK,I,0)
e,node(OD-TK,I,0),node(OD,I,0)
*enddo
*do,I,0,360,ANGSIZ
nsel,,loc,z,LEN
nsel,r,loc,x,0,OD
nsel,r,loc,y,I
type,3 $mat,3 $real,3
e,20001,node(OD-TK,I,0)
e,node(OD-TK,I,0),node(OD,I,0)
*enddo
allsel
eplot
d,20000,all
!f,20001,fx,FF
f,20001,my,FF*LEN
sbctran
eplot

! Solution
/solu
anty,static
nlgeom,off
nsub,1
solve

:p1
/post1
/pbc,f,,2
/pbc,rmom,,2
plns,u,sum

! Verify reaction moments
nsel,,,,20000,20001
ksel,,,,100,101
ksel,a,,,50,51
nslk,a
nplot
prrf



________________________________________
From: xansys-bounces_at_xansys.org [xansys-bounces_at_xansys.org] On Behalf Of brahmaji.vasantharao_at_rolls-royce.com [brahmaji.vasantharao_at_rolls-royce.com]
Sent: Thursday, April 10, 2008 4:08 PM
To: xansys_at_xansys.org
Subject: RE: [Xansys] [STRUC] MPCs on contacts with pilot node

>> Be sure to set Keyopt(2)=1 for the Target170 (pilot) element type, then
manually specify the appropriate constraints for the pilot node. The default
is automatic constraints.


>>Regards,
>>Krishna





Krishna,



Thanks for the reply. I did the analysis with Keyopt(2) set to 1, and a
moment load applied to the pilot node. I get the appropriate stress and
displacements, but am surprised to see that the reaction moment shows up as
zero. I am unable to understand this behavior. If one of you knowledgeable
guys can tell me why this is the case, I would appreciate it.



Regards,

Brahmaji



Rolls-Royce Energy Systems

PT Design - Mechanical Engineer

Mount Vernon, OH



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Posts possibly associated with message #92818AuthorDateScore
92794[STRUC] MPCs on contacts with pilot nodebrahmaji.vasantharao_at_rolls-royce.com2008/04/10 
92795Re: [STRUC] MPCs on contacts with pilot nodeCharles Bhaskaran2008/04/10 
92799Re: [STRUC] MPCs on contacts with pilot nodeKrishna Raichur 2008/04/10 
92800Re: [STRUC] MPCs on contacts with pilot nodebrahmaji.vasantharao_at_rolls-royce.com2008/04/10 
92806Re: [STRUC] MPCs on contacts with pilot nodeArne Löhn2008/04/11 
92807Re: [STRUC] MPCs on contacts with pilot nodeRiccardo Testi2008/04/11 
92818Re: [STRUC] MPCs on contacts with pilot nodeKrishna Raichur 2008/04/11 
92824Re: [STRUC] MPCs on contacts with pilot nodebrahmaji.vasantharao_at_rolls-royce.com2008/04/11 
92826Re: [STRUC] MPCs on contacts with pilot nodeKrishna Raichur 2008/04/11 
92827Re: [STRUC] MPCs on contacts with pilot nodeChristopher Wright2008/04/12