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By Doug OatisOne of the most popular questions I getasked as an ANSYS user, besides "Whyare you so awesome, Doug?" is aboutcontact in ANSYS. My answer to thatquestion (about contact, because I can'texplain the first), is "how much time doyou have?”

Contact has become increasingly easierto implement in both ANSYS Classicand Workbench. In ANSYS Classic,you can use the contact wizard to easilydefine surface to surface contact. InWorkbench, you can automatically de-fine it for an imported assembly. Afteryou've set it up (or had it setup byWorkbench), you then face the issue oftrying to decide which behavior, formu-lation, offset behavior, etc. to use. Ta-ble 1 is my quick explanation of whatall those options mean.

As you can see, thereare two basic motionsthat are described byvarious behaviors.The contact pair caneither open, close, orslide relative to eachother. Depending onwhich behavior youset, there are differentways that ANSYS en-forces these relation-ships. These areshown in Table 2.

The MPC method sim-ply writes constraintequations between thecontacting bodies.Pure Penalty enforcesa contact stiffness for a given penetra-tion. The Augmented Lagrange is sim- ilar to Pure Penalty, except that it

includes a factor for contact pressure toeliminate some chattering effect. TheNormal Lagrange adds a Contact Pres-sure DOF to the model. In terms of runtime, the formulations shown are listedin increasing run time.

June 22, 2007 A Publication for ANSYS Users Issue 58

Part 3: The Rest of WorkbenchAs we work our way through the significantamount of enhancements in the 11.0 releaseof ANSYS, we now come to the parts ofWorkbench that are underutilized and un-derappreciated: FE Modeler, Meshing,CFX-Mesh and DesignXplorer. All of

these are useful modules that work withoutside programs or Simulation to providegreater functionality. In our support work,we have found that if users knew thesemodules better, they would find many of thecapabilities that they want in Workbenchalready exposed.

FE ModelerThis module is where the developers putfunctionality that is required to deal withmesh-only models. Primarily used for lega-cy models or translating to/from other soft-ware, at Version 11 it really comes into itsown and offers some very useful new func-tionality. We hope to have some tutorials

on the key functionsbefore the summer isover.

GeometrySynthesisEvery once in a whilea feature gets addedthat changes every-

thing, and this is one of those features.Once you have read a mesh into FE Model-er from ANSYS, NASTRAN or ABAQUS,you can convert the outside surface of themesh into geometry. Don't get too excited,it is not NURBS geometry that you can thenedit in a CAD tool or DesignModeler. It is

This One Goes to 11

Table of ContentsThis one Goes to 11: The Rest of Workbench ----------------------------------1Getting in Touch with ANSYS Contact --------------------------------------------15 Cool Controls for the Result Contour -------------------------------------------3Awesome APDL: Finding Common Block Info-----------------------------------4SSH: Secure Remote Solve --------------------------------------------------------5

Getting in Touch with ANSYS Contact(Cont. on pg. 2)

(Cont. on pg. 4)

Table 1: Contact Names and BehaviorName Gap Open/Close? Sliding Allowed?

Bonded No NoRough Yes No, infinite μNo Separation No Yes, μ = 0Frictionless Yes Yes, μ = 0Frictional Yes Yes, if Fsliding > Ffriction

Table 2: Formulation OptionsName Equations

SolvedDefault

Contact DetectionMPC Generates

CE’s Nodes

Pure Penalty F = Kx GaussAugmentedLagrange F=Kx + λ Gauss

Normal Lagrange Nodal PressureDOF Node

(Cont. on pg. 4)

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a faceted surface representation that you caneither send directly to Simulation or Ad-vanced Meshing for remeshing, or that youcan modify in FE Modeler using mesh mor-phing.

To try this out I found an old turbine-engineaft bearing mount from ANSYS 5.3 on a 10year old archive CD. I read that into 11.0,wrote out a CDB, then read that into FEModeler. Figure 1 shows how the SkinDetection tool builds a surface model fromthe mesh, Figure 2 shows the original meshin FE Modeler and Figure 3 shows whathappens if the Mesh Morpher (what used tobe paramesh and is now in FE Modeler) isused to offset one of the surfaces. We havefound this tool to be useful on simple tomoderately complex geometry, and espe-cially good when the original mesh is rela-tively refined. Figure 4 shows the key part,remeshed in Simulation.

Mesh MetricsThe mesh metrics area has been enhanced toinclude a variety of checks and great graph-ics feedback. The checks include: Element

Quality, Jacobian Ratio, Aspect Ratio,Warping Factor, Parallel Deviation, Maxi-mum Corner Area, Volume/Area.

If you click on the bar in the histogram thenthe elements that fall in that range plotwithin a transparent view of your model, anice way to see where you have problems.Figures 5a and 5b show typical plots.

Better Import/Export SupportA general area of improvement for V11 isimproved support for more entities in theNASTRAN and ABAQUS translators. Theoutput also gives better feedback on entitiesthat are not read in. You can now also readANSYS CDB files directly in, a beta featureat 10.0. To learn what is and what is notsupported, read the online help.

MeshingThe Unified Meshing Initiative at ANSYS,Inc. has been working hard at pooling vari-ous meshing technologies inside work-bench, and you will see the biggest changesin the Meshing module. Most of the chang-es are minor, but they add up to a morepowerful and useful tool.

The first thing you will notice is that thelook-and-feel is much more like simulation.In fact, it is the same as Simulation exceptthere is no solving or boundary conditioninsertion capability. Now when you want tostart meshing, you choose meshing algo-rithms by inserting a meshing method underthe mesh branch. Here you can pick from 5methods: Tetrahedron (Patch Dependent),Tetrahedron (Patch Independent), HexDominant, Sweep and CFX Mesh. You can

(ANSYS 11.0, cont...)

(Cont. on pg. 3)

Fig. 6a,6b: Virtual Topology

Fig. 1: Extracted Geometry

Fig. 2: Original Mesh

Fig. 3: Modified Mesh

Fig. 4: Modified Geometry, Remeshed

Fig. 5a: Mesh Metrics

Fig. 5b: Histogram Selection of Quality

Thicker Wall

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then set nice options like global sizing,transition speeds, smoothing and muchmore. Your choices vary depending onwhich algorithm you choose. Look for thearea to evolve in future releases into a moregeneral high-end meshing tool for going be-yond what Simulation has to offer, with anew product name, or maybe not dependingon how usage drives development.

CFX-MeshThis CFD centric meshing tool has also seensome benefits from the unified meshing ini-tiative.

Full Virtual Topology SupportA major advantage in Simulation has madeits way into this module in the form of Virtu-al Topology Support. Now you can do virtualmerges of surfaces and curves inside themeshing module before you mesh. Figures6a and 6b show a model (the snowflake usedin our Christmas greetings) and the tiny littlesurfaces that make meshers go nuts. Usingthe Virtual Topology these can be mergedinto nice fat surfaces.

Edge SpacingThe edge spacing object now allows you tospecify all of the options you have for faces,plus the ability to specify a bias when usingpatch dependent meshing. Not very fancy,but again, a much needed feature. Figure 7shows an example.

OtherSome small changes include the addition of aMesh Generation Interrupt button to stoplengthy meshing sessions and support fornamed selections that come in from DesignModeler. Lastly, parallel meshing has beenadded for CFD style meshes as a beta featureat 11.0. See the help for how to set it up, it iscurrently really only for power users who cancontrol their compute environment. But lookfor this capability to improve over releases asusers demand larger meshes and shortermeshing time.

DesignXplorerThe last module we will cover this month isDesignXplorer. This area of Workbench iswhere all the parameter variation capabilitiespay off because it automates the process ofDOE studies, Optimization, and various oth-er probabilistic studies. A review of all of thechanges points to another case where usersare starting to really give development goodfeedback and we are seeing lots of small butimportant changes. If you are not familiarwith the module, take a look at the help tolearn more and see all of the changes, sincethe following are just the most significant.

Startup WizardFor the occasional user, all the options in DXcan be a little overwhelming. So at 11.0 thereis now a wizard that helps users jump into astudy by giving guidance as to what studytypes and options are most appropriate. Oncein the environment, the user interface hasbeen updated a little to make it more intuitiveand informative.

Excel SupportThe beginnings of a link to Excel are exposedin DX in the form of an import and exportcapability from and to Excel. Simply clickthe Import or Export buttons to use thisfeature. Although a little basic in this firstouting, look for more in this area in the future.

New Sampling OptionsUser input is best represented in the new andbetter ways to do statistical studies. Theseinclude: 1) Fault tolerant sample generationfor optimization, DFSS and Robust design,and 2) Weighted Latin Hypercube samplingfor random number generation.

Fig. 7: Edge Spacing

Fig. 8: DX Wizard

5 Cool Controls for theResult Contour

A lot has changedin the look andcontrol of the leg-end in Simula-tion. If you clickon it and fiddlearound, you'llsoon discovermost of thechanges. Here arethe five that wefind most useful:

1. Save LayoutMaking all the modifications doesn't doyou much good unless it is easy to saveand recall your settings. In the RMBmenu you can choose Named Legendsthen New, Manage or pick a pre-de-fined legend. Very, quick, very easy.

2. Click-and-Drag RelocateIf you find your legend needs to moveout of the way to better show your re-sults, simply click on the title text at thetop and drag it to wherever you want togo. One cool feature of this is that if youdrag to the right edge of your plot, ev-erything flips around so it looks correct.

3. On the Fly Add-and-Remove Con-toursEver want to quickly change the num-ber of contours from 9 to 10 or 9 to 4.Click on the contour area and +/- iconshows up. Click on + or - to add orsubtract contours.

4. Specify Number of DigitsAnother thing that we always seem towant to change is the number of digitsused to show result value. The RMBmenu under "Digits" lets you specifyfrom 2 to 8 digits. The program willswitch from fixed to scientific notationas needed when you change this value.

5. Reset AllThe down-side of being able to makeall these changes so quickly is that youcan screw your menu up really fast.The developers have been thoughtfuland put a "Reset All" pick on the bot-tom of the RMB menu. Choosing itputs everything back to its default.

(ANSYS 11.0, cont...)

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The final setting that is most commonlyused is the offset behavior. This optionis used for many reasons, ranging fromfixing a dirty assembly to modeling apress fit. For the sake of time, andFocus length, I'll only cover offset be-havior listed within Workbench.

If you have an assembly that should beinitially in contact, but isn't, you can usethe “adjust to touch” to close whatevergaps exist. If you want to analyze apress fit that is modeled (parts are inter-fering), you can specify an offset valueof 0 and have the solver slowly ramp upthe interference. On the other hand, ifyou model your parts as being initiallyin-contact, you can specify a manualoffset to simulate an actual press fit.This way you can simulate several dif-ferent press fits without having to create

multiple CAD models. If you don'twant to ramp the effects during thesolution, you can specify that with thelast option. No matter which behavioryou choose, the Contact surface is off-set from the body mesh, and a rigidregion is defined between to tie themeshes together.

Hopefully, this has helped clarify someof the settings available within ANSYS.For typical contact problems, I try to

stick with Augmented Lagrange withramped effects turned on. If I'm con-cerned about contact penetration, I maygo as far as using Normal Lagrange.There are still many other settings, suchas contact stiffness, stiffness update,and pinball radius. If you're looking atbecoming an expert, I would highlyrecommend the Advanced ContactCourse, which spends 2+ days coveringall of these topics. (link)

(Contact, cont...)

Table 3: Offset OptionsName Option Translation

Adjust to Touch None Moves contact surface to touch target sur-face

Add Offset, Ramped Effects Offset Value Move contact surface by offset value,ramps offset during solution

Add Offset, No Ramping Offset Value Move contact surface by offset value, noramping

The Focus is a periodic publication of Phoenix Analysis & Design Technologies (PADT). Its goal is to educate and entertain the worldwide AN-SYS user community. More information on this publication can be found at: http://www.padtinc.com/epubs/focus/about

Awesome APDL: Finding Common Block InfoOnce again the Focus was almost done andwe needed a macro for the Awesome AP-DL section. Searching on ANSYS.NET,we found a macro that looked really useful,and surprise, someone at PADT had writtenit a year ago and totally forgot about it. Sohere it is, resurrected for your coding plea-sure.

When you are trying to extract informationfrom ANSYS and there is no good *getcommand, you sometimes need to delveinto the common blocks. Common Blocksare the way you create global variables inFORTRAN. Since ANSYS is FORTRAN,the program stores info that it needs toshare with itself in common blocks.

To make things easier for us, and for userwritten routines, the include files for com-mon blocks are always stored in theansys/custom/include directory. The firststep on using a common block is to searchthe include files for a variable you arelooking for. However, the name is notwhat you need. The *get,,common com-mands require the name of the commonblock and the position in the block

So your next step is to find that offset. Youcan count in the include file, but if you havearrays and such it gets complicated. So we

wrote this macro to figure out the positionin the block by: 1) storing the settings in theblock you are looking in, 2) changing thevalue you are looking for, 3) comparing thecontents of the block to find any differenc-es, and 4) reporting back what the numberis on values that changed.

Want to know more about common blocks,buy PADT’s “Guide to ANSYS Customi-zation with APDL” (link)

An example would be if I wanted to knowwhat the global minimum and max numberof divisions per line was (DESIZE):desize,10,11cmndif,0,'cfprp7',0desize,20,21cmndif,1,'cfprp7',0

Yields:Found: 99 10 20.Found: 100 11 21.

So to get the value use:*get,_mnlnsz,common,,cfprp7,,int,99*get,_mxlnsz,common,,cfprp7,,int,100

Here is the macro: CMNDIF/nopr!cmndif,IPASS, ABLK, IRTYP! IPASS: Pass number,! 0 or blank for first pass! 1 for sedond pass

! ABLK: Name of common block, in''s!IRTYP: 1 = REAL! 0 or Blank = INT!imax = 5000ipass = arg1ablk = arg2*if,arg3,eq,1,then irtyp = 'REAL'*else irtyp = 'INT'*endif*if,ipass,eq,0,then v1= v2= *dim,v1,,imax *dim,v2,,imax *do,i,1,imax

*GET,v1(i),COMMON,,%ablk%,,%irtyp%,i *enddo*else *do,i,1,imax

*GET,v2(i),COMMON,,%ablk%,,%irtyp%,i *enddo *msg +++++++ Looking for Changes: *do,i,1,imax *if,v1(i),ne,v2(i),then *msg,,i,v1(i),v2(i) Found: %g %g %g *endif *enddo /gopr*endif

June 22, 2007 The Focus Issue 58

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By Jason Krantz"No way. Never. Are you crazy?"

This is the typical response of a Unix sys-tem administrator when told that users wantANSYS installed so they can use Work-bench to send jobs to the Unix machine. Therequest sounds simple, but it alarms adminsbecause it requires the Unix server to runsomething called Remote Shell, a notori-ously insecure protocol.

Remote Shell (RSH) sends usernames andpasswords as cleartext — unencrypted text— which means that anyone "listening" totraffic between the Workbench machineand the Unix machine acquires handyusername/password pairs — and thereforeaccess to the Unix computer.

Security for FEA is important for a coupleof reasons:

a) ANSYS is often used for classifiedwork for government agnecies;

b) Many models, while not actually clas-sified, are new products in develop-ment and therefore trade secrets; and

c) I.T. departments with otherwise securenetworks are faced with a great big holecreated by ANSYS users submittingsolutions to remote solvers.

It is now possible to close that security hole.Although Workbench users can still submitjobs over RSH, Secure Shell (SSH) is nowa viable option, and an infinitely more se-cure option at that. SSH uses a variety ofencryption schemes, but all of them aremuch better than RSH. If RSH were PeterSellers' Inspector Clouseau, SSH would beDaniel Craig's James Bond: same roughidea, much better execution.

So how do we switch over to this magicalSSH? Currently, it's not entirely straightfor-ward, but detailed instructions are availablehere: [how-to link] The configuration pro-cess promises to become easier with thenext Service Pack for ANSYS.

The key to Workbench 11.0's newfoundSSH goodness is its Remote Solve Manager(RSM). The RSM calls a Windows-based

SSH client called Putty, which can bedownloaded here:

www.chiark.greenend.org.uk/~sgtatham/putty/

The RSM uses Putty to create a securetunnel between the Windows machine andthe Unix machine. SSH is usually used withpasswords, but the RSM uses a particularlysecure (passwordless) login procedurecalled hostkey-based authentication.

The inherent security of hostkey-authenti-cated SSH raises interesting possibilitiessuch as submitting jobs from the internetover SSH (as opposed to submitting themover a local network). As intriguing as thisoption is, it's not practical because 11.0pulls entire results files from the remotemachine to the Workbench machine. Forlarge models, these files can be multiplegigabytes — so bandwidth is a limiting fac-tor.

For organizations motivated to send jobs toservers in a secure manner, configuring theRSM to use SSH is worthwhile. The pro-cess should get easier with progressive re-leases, and there's no reason that SSHcouldn't be incorporated directly into theRSM — the OpenSSH libraries are avail-able to developers for free. Until then, theinstallation process link above should dothe trick.

SSH: Secure Remote Solving

News - Links - Info· ANSYS, Inc. Was recently recognized as the big-

gest R&D spender in the CAE industry. (link)

· ANSYS does a 2-1 split on stock price based oncontinued industry beating growth. (link)

· Want to learn more about FLUENT products? Visittheir really well done web pages at:www.fluent.com/software

· The ANSYS, Inc. Virtual Demo Room is growingevery month with useful videos and PowerPoints ofproducts in action. Demos, tutorials, presentations,100’s of files ready for you to download and few. Avery good way to get to know other products better:www-harwell.ansys.com/demoroom

Upcoming Training ClassesMonth Start End # Title Location

June, ‘07 6/25 6/26 107 ANSYS WB DesignModeler Tempe, AZ

July ‘07 7/9 7/10 104 ANSYS WB Simulation - Intro. Albq, NM

7/12 7/13 105 ANSYS WB Sim Struct. Nonlin Albq, NM

7/19 7/20 801 ANSYS Customization w/ APDL Tempe, AZ

7/23 7/24 203 Dynamics Tempe, AZ

7/26 7/27 102 Intro. To ANSYS, Part II Tempe, AZ

Aug ‘07 8/1 8/2 104 ANSYS WB Simulation - Intro Tempe, AZ

8/6 8/7 152 ICEM CFD/AI*Environment Tempe, AZ

8/9 8/10 202 Adv. Structural Nonlinearities Tempe, AZ

8/13 8/14 501 ANSYS/LS-DYNA Tempe, AZ

8/16 8/17 604 Intro to CFX Tempe, AZ

8/22 8/24 402 ANSYS High Frequency Emag Tempe, AZ

8/30 8/31 701 Design Optimization and Prob. Tempe, AZ

Sep ‘07 9/6 9/7 301 Heat Transfer Tempe, AZ

9/10 9/12 101 Intro to ANSYS, Part I Albq, NM

9/13 9/14 102 Intro to ANSYS, Part II Albq, NM

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