Mechanical-Nonlin 13.0 App4A AdvContact (MAPDL)

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Customer Training Material

Appendix 4A

Accessing Advanced

Contact Features via

Structural Nonlinearities

A4A-1ANSYS, Inc. Proprietary

2010 ANSYS, Inc. All rights reserved.Release 13.0

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ANSYS Mechanical Advanced Contact with MAPDL

Customer Training MaterialChapter Overview

WB-Mechanical already exposes a rich library of options to meet the

many challenges associated with simulating contact behavior.

advanced features not directly exposed in the WB-Mechanical GUI.

For example, consider the following cases:

Setting up a dynamic friction coefficient that varies as a function of

relative velocity over a large displacement.

dictates status change from sticking to sliding.

Surface cohesion (limited frictional resistance with zero normal force).

Cohesive Zone Modeling (bonded contact with a limit).

Fluid Pressure Penetration (Surface pressure based on contact status)



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and more


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Customer Training MaterialChapter Overview

This appendix presents an optional lecture on how to access

these advanced contact features not directly available in the

WB-Mechanical GUI

This is not intended to be a comprehensive presentation on allthe advanced feature details, but rather a presentation on the

-successfully within contact regions in WB-Mechanical.

A. Background on Contact Pair

B. Contact Documentation

C. MAPDL Command Syntax

D. General Procedure



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E. Example Cases


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Customer Training MaterialA. Background on contact pair

Recall that Face-to-Face, Edge-to-Face and Edge-to-Edge contact

use the concept of a contact pair, which is composed of target

elements and contact elements

The contact elements overlie the underlying finite element model like

a skin.

Face-to-Face populate the contact surface with Gauss points

Others use the node(s) on contact side directly (no gauss pts)

Separate element types define the target and contact surfaces.

The contact pair is identified through a shared real constant set.

Contact elements (REAL = N )

Target elements (REAL = N )



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on the target surface


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Customer Training Material... Background on contact pair

All the parameters that control the contact pair behavior are

identified as either Key Option settings or as properties

associated with the Real Constant Set.

A Key Option is analogous to a switch that controls a particular

element behavior

Contact formulation, Type (bonded, frictionless, frictional), Interface

Treatment, Normal stiffness updating schemes,etc, are examples of

Key Option settings

A Real Constant Set is a list of properties of a particular contact

pair that influences behavior and/or convergence

Normal contact stiffness value, contact surface offset value, pinball

radius value,etc, are examples of Real Constant properties



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Customer Training MaterialB. Contact Documentation

The Element Reference Manual (available on-line) contains a

comprehensive list of all Key Options and Real Constants available for

each contact element type.



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Customer Training Material... Contact Documentation

Each Key Option and Real Constant listed in the Elements Manual also

has a link to different sections of the Contact Technology Guide

containing a comprehensive description of its use.



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Customer Training MaterialC. MAPDL Command Syntax

The commands most commonly used to implement advanced

contact technology features are:

KEYOPT for settin ke o tions

RMODIF to modify a real constant value

MP, MPDATA for defining friction coefficients

TB and TBDATA for cohesive zone modeling parameters

Refer to Command Manual Documentation for complete command



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Customer Training Material... MAPDL Command Syntax

The syntax for the KEYOPT command is as follows:

KEYOPT, ITYPE, KNUM, VALUE

Where ITYPEis the Element type number

KNU is the number o the KEY PT

VALUEis the value of this KEYOPT

or examp e, e emen ype s on a sur ace o ycontact pair, the shell thickness effect can be included with the

following command:, , ,

Key Option Number (for shell thickness effect)

(=1 to include)



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ement ype um er


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Customer Training Material... MAPDL Command Syntax

The syntax for the RMODIF command is as follows:

RMODIF, NSET, STLOC, V1,,,,

Where NSETis the Real Constant Set number

STLOC is Starting location in table for modifying data.

VALUEis the new value assigned to constant in location STLOC.

or examp e, rea cons an se represen s a r c ona con ac pa r,a maximum limit on allowable shear stress at the contact interface can

be defined with, , ,

Location for max shear stress

Value for allowable shear stresss

ea e um er From CONTA174 docu:



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Customer Training MaterialD. Procedure

To introduce advanced contact features

not directly available in WB-Mechanical

GUI, start by inserting a command

The expectation is that these commandsapply to that specific contact region

.

For convenience, WB-Mechanical automatically parameterizes the

attributes (element type number, real set number, material id number).



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Customer Training Material... Procedure

Hence, there is usually is no need to look up the actual type and real

set numbers to execute a command. Simply use the parameter names

directly.

Below is an example command line added to a frictional contact

region to define a limit on the max allowable shear stress

(TAUMAX) at the contact interface

Optional notes can be added to the right of ! for further

clarification.



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If you are unfamiliar with the element type being used for a particular

contact region and you need to research the documentation for proper

key option or real constant table references, it is possible to extract

.

For example:

From Contact tool:

From Solver Output:



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Element Type for

docu research


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If this is a new run and there is no Solver Output, add a command

object to the Environment branch to execute a partial solve with the

following commands:



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on PSOLVE and /EOF


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There are also a number of contact results not directly available in a

WB-Mechanical Tool that can be extracted via a Command Object

strategically placed in the Solution Branch.

e er to ontact ement ocumentat on as we as comman s manua

documentation on ETABLE, ESOL, PRESOL, and PRNSOL,,, commands



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Mechanical-Nonlin 13.0 App4A AdvContact (MAPDL)

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