Do you have any examples showing how to connect two parts with MPC contact?


Yes, please see the ANSYS 8.1 example below. In this example, the gap size
can be varied along with the contact (MPC vs. Lagrange) and analysis (modal
vs. static) types. For too large of a gap, the MPC contact is not established ...

Note: This input is attached to this record, as well ...

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =


fini
/clear


nflag=1 ! NFLAG= 1=modal analysis, anything else=static analysis

ntype=2 ! NTYPE= 1=force-based MPC, 2=rigid-based MPC, else=augmented Lagrange

gap=0.01! gap (inches) between bars ... (logic might fail for poor gap size)


/title, MPC Contact vs. Augmented Lagrange Contact

/plopts,info,1
/view,,1,2,3
/pnum,type,1
/num,1

/prep7
et,1,SOLID185 ! lower order brick
et,2,SOLID187 ! higher order tetrahedron
r,1
mp,ex,1,30.0e6 ! Young's modulus, psi
mp,nuxy,1,0.30 ! Poisson's ratio, unitless
mp,dens,1,0.283/386.4 ! mass density, lbf-sec^2/in^4
tb,biso,1 ! bilinear isotropic plasticity
tbdata,1,60.0e3 ! yield stress, psi
tbdata,2,30.0e4 ! tangent modulus, psi

et,3,TARGE170 ! targets on lower order SOLID185 elements
r,3mp,mu,3,0.0
et,4,CONTA174 ! contacts on higher order SOLID187 elements
keyopt,4,9,1 ! exclude initial penetration or gap and offset ...
keyopt,4,12,5 ! bonded (always) contact ...

*if,ntype,eq,1,then ! force-distributed surface constraint
keyopt,4,4,1 ! nodal detection - normal from contact surface
keyopt,4,2,2 ! MPC based approach
*elseif,ntype,eq,2,then ! rigid constraint surface
keyopt,4,4,2 ! nodal detection - normal from target surface
keyopt,4,2,2 ! MPC based approach
*elsekeyopt,4,4,0 ! Gauss point detection (default)
keyopt,4,2,0 ! augmented Lagrange approach (default)
*endif

block,0,3.000,0,1,0,1
block,3+gap,6,0,1,0,1

mat,1
type,1
real,1
esize,0.25
vmesh,1

type,2
esize,0.40
vmesh,2

nsel,s,loc,x,2.9995,3.0+(0.5*gap)
cm,ntarg,node
mat,3
type,3
real,3
esurf

nsel,s,loc,x,3.0+(0.5*gap),1.001*(3.0+gap) ! logic fails for unreasonable gaps
cm,ncont,node
type,4
esurf
nsel,all
eplot
fini

/solu
outres,all,all
nsel,s,loc,x,0
d,all,all,0.0
nsel,all

*if,nflag,eq,1,then
antype,modal
modopt,lanb,6
mxpand,6
*else
antype,static
nlgeom,on
time,1.0
nsubst,5,500,5
nsel,s,loc,x,6
d,all,ux,0.20
d,all,uy,0.0,,,,uz
nsel,all
*endif

save
solve
celist,,,,inte ! undocumented command to list internal CE's
save
fini

/post1
set,last
/edge,,1

*if,nflag,eq,1,then
set,list
*do,i,1,6
set,1,i
plnsol,u,sum,2
/wait,0.5
*enddo
*else
/dscale,,1
plnsol,eppl,eqv
*endif

/eof

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =


For gap=0.10"
=============

*** NOTE *** CP= 7.438 TIME= 16:17:38
Deformable-deformable contact pair identified by real constant set 3
and contact element type 4 has been set up.
Contact algorithm: MPC based approach

*** NOTE *** CP= 7.438 TIME= 16:17:38
Contact related post- process items (ETABLE, pressure ...) are not
available.
Contact detection at: nodal point (normal to target surface)
MPC will be built internally to handle bonded contact.
Average contact surface length 0.32091
Average contact pair depth 0.24288
Default pinball region factor PINB 0.25000
The resulting pinball region 0.60720E-01
Default target edge extension factor TOLS 10.000
Initial penetration/gap is excluded.
Bonded contact (always) is defined.

*** NOTE ***CP= 7.438 TIME= 16:17:38
Min. Initial gap 0.1 was detected between contact element 672 and
target element 665.
The gap is closed due to initial adjustment.

*** WARNING *** CP= 7.438 TIME= 16:17:38
The closed gap/penetration may be too large. Increase pinball if it is
a true closed gap/penetration. Decrease pinball if it is a false one.

*** WARNING *** CP= 7.438 TIME= 16:17:38
The initial penetration/gap is relatively large. Using bonded/no
separation option may cause an accuracy issue. You may use the
CNCHECK,ADJUST command to move the contact nodes towards the target
surface.
****************************************

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =


For gap=0.01"
=============

*** NOTE *** CP= 8.891 TIME= 16:20:36
Deformable-deformable contact pair identified by real constant set 3
and contact element type 4 has been set up.
Contact algorithm: MPC based approach

*** NOTE *** CP= 8.891 TIME= 16:20:36
Contact related post- process items (ETABLE, pressure ...) are not
available.
Contact detection at: nodal point (normal to target surface)
MPC willbe built internally to handle bonded contact.
Average contact surface length 0.31972
Average contact pair depth 0.24429
Default pinball region factor PINB 0.25000
The resulting pinball region 0.61072E-01
Default target edge extension factor TOLS 10.000
Initial penetration/gap is excluded.
Bonded contact (always) is defined.

*** NOTE *** CP= 8.891 TIME= 16:20:36
Min. Initial gap 1.E-02 was detected between contact element 688 and
target element 682.
The gap is closed due to initialadjustment.
****************************************

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =






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