ask the experts mpc contact

8/13/2019 Ask the Experts MPC Contact

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WEBINAR onMulti-pointConstraint (MPC)Technology


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AgendaMultipoint Constraint (MPC)

What are Multipoint Constraints or MPCs?

Where do we use MPCs?

Advantages of MPC over traditional contact

What is new at 12.0 for MPC


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Multi-point constraints enforce compatibility atan interface using internally generated

constraint equations. For example, the constraint equation that would transfer action

between ROTZ at node 2 and UY at nodes 1 and 3 has this form:

0 = UY3 - UY1 - 10*ROTZ2

What is MPC?


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MPC can be used to bond different element typesat interfaces with incompatible mesh regions:

Where do we use MPC?

Two solid element surfaces

Solid/Shells surfaces or edges

Beam to Shells/Solids

I am happy to share the lecturing duties with you. Let me know what chapters you would like to teach.


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MPC is the surface based constraint technologybehind:

Remote forces and displacements

Remote points

Structural and Thermal Point Mass

Joints and Springs



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x-axis Revolute joint

z-axis Revolute joint

Universal joint

Slot joint

Point-in-plane joint

Translational joint

x-axis Cylindrical joint

z-axis Cylindrical joint

x-axis Planar joint

z-axis Planar joint

Weld joint

Orient joint

Spherical joint

General joint

Screw joint

MPC is the technology behind the joint optionsavailable in workbench

A Joint between flexible bodies typically consists of

two surface based constraints tied together at the

respective pilot nodes with an MPC184 element

http://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184revo.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184revo.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184univ.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184slot.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184poin.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184tran.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184cyl.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184cyl.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184plan.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184plan.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184weld.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184orie.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184sphe.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184gen.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184scr.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184scr.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184gen.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184sphe.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184orie.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184weld.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184plan.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184plan.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184plan.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184plan.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184plan.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184plan.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184cyl.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184cyl.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184cyl.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184cyl.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184cyl.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184cyl.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184tran.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184poin.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184poin.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184poin.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184poin.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184poin.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184slot.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184univ.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184revo.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184revo.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184revo.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184revo.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184revo.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Hlp_E_MPC184revo.html


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Flexible Usual 3D meshed models

Nonlinear material options

Rigid Point mass representation of

3D geometry

Force-distributedconstraint Connect flexible bodies to

joints

MPC is also the technology behind connectingrigid bodies to flex bodies in workbench




Lumped mass of rigid body is representedby MASS21 element tied to the pilot node of

flex body surface based constraints via a

TARGE170 line element




Limitations of traditional bonded or no-separation contact:

Only translational DOFs apply.

Results depend on specified contact stiffness.

Multiple iterations are required to adjustpenetration in order to satisfy equilibrium evenfor small deformation problems.

Occasionally spurious natural frequencies canoccur in modal analysis.

How does MPC differ from

traditional contact ?



Limitations of manual constraint tools (CERIGand RBE3)

Only suitable for small strain.

RBE3 only supports force constraints applied on

the master node, not displacements.RBE3 requires manual definition of weighing

factors. MPC surface constraints calculate weighing factors

automatically.

How does MPC differ from manually

generated constraints?



Improved solution efficiency over traditionalbonded contact:

For a large assemblies with MPC bonded (or

no-separation) contact, the CPU run time is

faster than the same analysis using defaultalgorithm.

ContactAlgorithm

Iterations CPU Time(seconds)

Aug-Lagrange 4 2710

MPC 1 880

Advantages of MPC



Advantages of MPC(contd): Ease of use:

No contact stiffness is required as an input.

Internal Multi-Point Constraints will be generated

automatically at the execution of a Solve

For large deformation problems, the MPC

equations are updated during each iteration.

Shape functions are taken into accountautomatically for RBE3-type of surface constraint

(force distributed); no weight factor is needed

Advantages of MPC



Overconstraint detection and elimination When a degree of freedom is subjected to multiple

constraints, overconstraint occurs

results in solver-failure convergence difficulties or inaccurate

solutions.

The program automatically eliminates a limited set of

overconstraints detected during solution and issues

appropriate warning messages.

For troubleshooting purposes, you can display certain

eliminated constraints in the POST1 postprocessor

New at 12 0



The assembly is connected with MPC contacts

In these regions, Parts are

not correctly connected

Contact status

Solution in R12:

2 elements in sweep

direction

Contact status

New at 12.0


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Advanced tools to improve shell and beamconnections

New at 12.0

At 12.0 Constraint equations

always built as long ascontact node(s) and target

segments are inside the

pinball region.

At 11.0,constraint

equations only built at

nodes whose target and

contact normals

intersection

ask the experts mpc contact

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