Finite Element Modelling of contact phenomena in structural analysis · PDF fileFinite Element Modelling of contact phenomena in structural analysis Albert Konter Netherlands Institute

NIMR College NAFEMS Contact Workshop: 1
Netherlands Institute for Metals Research
Finite Element Modelling of contact phenomena in structural analysis
Albert Konter
Netherlands Institutefor Metals Research

NIMR College NAFEMS Contact Workshop: NIMR 2
www.nimr.nl

Welding
www.nimr.nlSysweld

Steel production
www.nimr.nlMSC.Marc

Aluminium production
www.nimr.nlMSC.Marc

Fundamentals of forming
cutting process
www.nimr.nl

A Benchmark on Hydro Mechanical forming shows that modelling contact/friction is still a critical issue
DiekA
Sheet metal forming

NIMR College NAFEMS Contact Workshop: Contents 8
Contents
Overview of contact analysis using FE Contact comparisons
MSC.MARC & Abaqus
Seminar themes FE contact benchmarks difficulties by FE users in modeling contact problems current limitations of commercial FE codes desirable contact features not currently offered by FE software need for further research in application of contact problems
Concluding remarks

NIMR College NAFEMS Contact Workshop: Some examples 9
Shock absorber
Rubber-steel assembly
Self contact rubber
Rigid steel insert
Large deformations

Bio medical
experimentFE simulation

Sheet metal forming
deformable body blank
rigid bodies blank holder
binder punch die
constraints friction drawbeads Optris

Bulk metal forming
thermal contact
rigid tools
remeshing
contact redefined during analysis

Ship collision experiment
Royal Schelde

NIMR College NAFEMS Contact Workshop: Contact methodology 14
Information for a contact analysis
what are the various contact bodies? can some bodies be considered as rigid? what is the outline of the body?
surface description nodes and segments
are the (undeformed) boundary contours curved or initially straight?
which bodies can contact each other during the analysis?
what are contact properties at the interface normal contact tangential contact

Information for a contact analysis (continued)
Can a body get in contact with itself ? Is there an initial overlap (shrink fit simulations) or a
discrete clearance? When are nodes considered to be in contact?
tolerance values If contact, how is this modelled?
node to node node to segment segment to segment
When are nodes considered to separate?

FEM contact phenomena
Contact description special action needed
non-linear springs contact elements contact procedures
method of contact node to curve/surface node to segment segment to segment
111 FuK =222 FuK =
=
2
1
2
1
2
1
00
FF
uu
KK
careful with rigid body modes if no contact

NIMR College NAFEMS Contact Workshop: Approaches 17
Approaches (1)
node to node contactnr
Only if limited sliding contact mesh generation requires opposite nodes specify normal direction
from position of nodes manually if nodes initially very close

Simplified beam model
collapse element
gap element springs mass distributions
Question:
How is characteristic of collapse element determined?
F
u

Approaches (2)
node to segment contactnr
nrnr
Frequently applied line or surface segment allows unequal number of elements at both sides of contact surface problem with normal definition near corners nodes sliding to a next segment: additional action needed

Example node to segment contact
top rigid surface is load controlled

Example node to segment contact
mesh test section
Royal Schelde
The Netherlands

Motion bulb: displacement controlledMotion bulb: displacement controlled

Approaches (3)
segment to segment contactnr
Beam to beam contact problems useful if large amount of sliding present specify normal direction cross-sections can be accounted for in
closure distance determination

Beam contact

Beam contact
frictional forces

NIMR College NAFEMS Contact Workshop: Contents 26
Surface to surface contact
surface penetrates
contact satisfied for node with segment

Normal contact methodology
visual inspection incremental displacements occurring during analysis of problem defined without contact methodology and adaptation of the boundary conditions
non-linear springs
contact elements Lagrange multipliers Penalty function
contact procedures
not practical
limited application
academic literature
often in finite element codes
MARC & Abaqus

Simple contact example
0.2
u = 0.3
ru
Contact:
stiffnessustiffnessnou
r
r
2.02.0
== rrr
Axr
lxr

Lagrangian multipliers
add constraint equation through Lagrangian multiplier accurate satisfaction of contact at the cost of extra degrees of freedom
often direct determination of contact stresses/forces potentially zeros on the diagonal matrix
Introduction of gap or contact elements
node to node contact
node to segment contact

Compression of circular segment
closure distance is function of position

Deformable rigid contact
normal direction to surface for each node different

Penalty stiffness
contact element with same technology as non-linear spring no extra degrees of freedom user defined or default penalty stiffness
high stiffness: convergence problemssometimes overcome through damping mechanisms
low stiffness: nodal penetration
forgiving for bad contact detection

Contact elements or contact procedures
Aspects node to node contact
slid

Documents

Finite Element Modelling of contact phenomena in structural analysis · PDF fileFinite Element Modelling of contact phenomena in structural analysis Albert Konter Netherlands Institute