thermal desktop advanced modeling guide in various formats (creo®, solidworks®, step, iges, etc.)....

Thermal Desktop®

Advanced Modeling Guide

Guidelines for working with geometry

and imported models

17 May 2017

C&R Thermal Desktop® is a registered trademark of Cullimore and Ring Technologies, Inc.

SpaceClaim® is a registered trademark of SpaceClaim Corporation.

This manual, as well as the software described in it, is furnished under license and may be used or copied only in accordance with the terms of such license. The content of this manual is furnished for informational use only, is

subject to change without notice, and should not be construed as a commitment by Cullimore & Ring Technologies. Cullimore & Ring Technologies assumes no responsibility or liability for any errors or inaccuracies that may appear

in this book.

Prepared, distributed, and supported by:

Cullimore and Ring Technologies, Inc.

(303) [email protected]

Authors:

Douglas P. Bell

Timothy D. Panczak

Brent A. Cullimore

Table of Contents

Table of Contents ................................................................................. 1-2

1 Introduction .......................................................................................... 1-1

1.1 Purpose.............................................................................................................. 1-1

1.2 Important Concepts........................................................................................... 1-2

1.3 Software Modules ............................................................................................. 1-4

1.4 Process .............................................................................................................. 1-4

1.5 Guidance ........................................................................................................... 1-6

2 Creating CAD Geometry..................................................................... 2-1

2.1 AutoCAD .......................................................................................................... 2-2

2.1.1 Capabilities ........................................................................................... 2-2

2.1.2 AutoCAD Training Resources.............................................................. 2-5

2.2 SpaceClaim ....................................................................................................... 2-5

2.2.1 Capabilities ........................................................................................... 2-5

2.2.2 SpaceClaim Training Resources ........................................................... 2-6

2.3 Summary of AutoCAD vs. SpaceClaim ........................................................... 2-6

2.4 Example Cases .................................................................................................. 2-7

3 Importing CAD Geometry .................................................................. 3-1

3.1 Importing Directly into AutoCAD.................................................................... 3-1

3.2 Importing into SpaceClaim............................................................................... 3-2

3.3 SpaceClaim Importer ........................................................................................ 3-3

3.3.1 Creating a New Importer ...................................................................... 3-3

3.3.2 Synchronize .......................................................................................... 3-8

4 Working with CAD Geometry ............................................................ 4-1

4.1 Simplifying CAD Geometry ............................................................................. 4-1

4.1.1 AutoCAD .............................................................................................. 4-1

4.1.2 SpaceClaim ........................................................................................... 4-2

2

4.1.3 Other Geometry Preparation Tools .......................................................4-3

4.2 Snapping TD Objects to CAD Geometry..........................................................4-5

5 Third Party Finite Element Models ................................................... 5-1

5.1 Importing FE Model as Nodes and Elements....................................................5-1

5.2 Importing FE Model as Graphics ......................................................................5-2

5.3 Mapping Results................................................................................................5-2

3

1 Introduction

This document provides guidance for working with CAD geometry within C&R Ther-

mal Desktop® (TD) and the companion tool CRTech TD Direct™, an add-in to Space-

Claim®.

Model geometry can come from many sources (customers, co-workers, suppliers) and

also in various formats (Creo®, SolidWorks®, STEP, IGES, etc.). Conversion or incorpo-ration of this data into a thermal/fluid model must often be repeated as designs are revised.

Advances in CAD technology are making it easier for non-specialists to use these pro-grams, even if their use is sporadic: ease-of-use is flattening the learning curve. Increasingly,the thermal engineer is not just the passive recipient of model geometry, but also the activegenerator of geometric models. Even if thermal engineers don’t originate the design, knowl-edge of how to adjust and change it, or make quick models of simplified equivalent parts,ground planes, test chambers, etc. is necessary.

Therefore, this manual doesn’t just focus on what to do with incoming geometry ofvarious forms and formats, it also provides higher-level guidance on how to work within

AutoCAD® and SpaceClaim. The tools presented here allow the user to quickly generate,modify, defeature, and simplify CAD geometry imported from a variety of formats, andthen use that CAD geometry for mesh generation. The advanced features of these tools alongwith a dynamic, real-time coupling of TD Direct with Thermal Desktop allow thermalmodels to be automatically updated when changes to the design geometry occur.

1.1 Purpose

Advanced modeling techniques should be used when:

• The geometry is complex and cannot be easily modeled with Thermal Desktop (TD) finite difference surfaces and solids. This includes complexity of contacting surfaces between objects.

• Frequent or major updates to the geometry are expected, such that the useful-ness of grip point stretching and shrinking of TD finite different entities would be compromised.

• The geometry has been developed in other CAD tools.

• The geometry has been developed in other analysis tools.

Of course, a system-level model in TD can be composed of many parts and assemblies,so some portions may use one type of modeling (such as native FD surfaces and solids)while other portions use imported objects.

Introduction 1-1

This manual assumes that the user is already very familiar with basic Thermal Desktopmodeling, as covered in the separate Thermal Desktop User’s Manual. The user should referto the TD Direct User’s Manual for the usage of TD Direct for marking and meshinggeometry directly.

1.2 Important Concepts

This section represents a brief summary for reference only. Explaining these conceptsis a primary purpose of the rest of this document.

Geometric Model vs. Thermal Model. The earlier generation of computer tools dividedthe world up into two parts: a radiation tool (e.g., TRASYS), and a tool to compute temper-atures (e.g., SINDA). The radiation tool computed radiation exchange factors and orbitalheating loads. These were the boundary and matrix terms for the temperature solver. Theinput to the radiation tool consisted of an input file that described surfaces such as rectangles,discs, and spheres. This was often called the “Geometric Math Model,” or GMM, or just“geometric model.” The set of conduction terms, radiation terms, and boundary conditionsthat was input to the temperature solver was called the “Thermal Math Model,” or TMM,or just “thermal model.” The term “geometry” became synonymous with radiation, sincethe rest of the thermal model was generated by hand. Although such a division is an anach-ronism, the terminology still persists and can be a source of confusion.

The situation is much more complex today, since the term “geometry” can have manymeanings. Geometry is not just used to calculate radiation, it is also used to generate con-duction and capacitance terms, and to represent even higher level objects like pipes thatcompute fluid flow, convective ties, radiation, conduction, and capacitance terms.

With the advent of Thermal Desktop and its integration with AutoCAD, geometry usedfor design and manufacturing was also made available for use in thermal analysis. Thisapproach is taken a step further with the integration of TD Direct. Now, design geometryfrom many different sources can be imported, manipulated, and used for generating thermalmodels. Thus, there is design geometry created by CAD systems, construction geometryused to facilitate the generation of other geometry, and geometry used to perform thermalanalysis, both radiation and conduction.

The concepts related to geometry and thermal models will be expanded in later sections,but it is wise to abandon the traditional definitions of “thermal model” and “geometry.” Thethermal model consists of many components, including geometry. Geometry has manysources, and where ambiguous, will be prefaced with a description. For example, “designgeometry” is used to denote geometry constructed by a CAD system for the purpose ofdesign and manufacture, and “analysis geometry” refers to geometric entities that are di-rectly a part of the thermal model, such as a finite element.

TD Direct Domains. Any edge, face, or solid in SpaceClaim can be assigned to one ormore “domains.” (For 2D surfaces, each side can be separately assigned.) Domains are ageneral-purpose identification technique. What is really being named is the collection of

1-2 Introduction

finite element vertices (nodes), surfaces, edges, and solids that will result from that designgeometry object. Those thermal modeling elements don’t yet exist (or might be changedlater), so domains provide a way to refer to them indirectly.

Each domain will generate appropriate Domain Tag Sets (see below) when the objectis meshed (or is remeshed) and the mesh is sent to Thermal Desktop. For example, placingthe top square of a cube in the domain “upmost” will result in domain tag sets“upmost_nodes” and “upmost_surfaces,” which can be used for contact, conductance, ties,and automating post-mesh editing operations.

TD Direct Tags. “Domains” are one type of “Tag,” which is a TD Direct mark-up ofan edge, surface, or solid. These design geometry objects might also be assigned materialproperties, submodel designations, insulation specifications, and localized mesh controls.Any such application of a piece of information to an edge, surface, or solid is genericallyreferred to as a “tag.” The current set of tags may be viewed in the SpaceClaim Tag Tree.

All of these Tags (domains, thermal properties, mesh controls etc.) are rememberedwhen the geometry is reshaped.

Thermal Desktop Domain Tag Sets. Domain Tag Sets are like AutoCAD groups: aplaceholder for referring to underlying members of a set. Nodes, surfaces, etc. can be placedin domain tag sets and referenced by other TD objects. The set of objects acted upon by aTD object (e.g., a heat load), is called the object’s domain. This domain is more preciselycalled the “applied domain,” since it is the domain of objects to which the heat load is applied.

The applied domain can consist of either directly specified objects, or a Domain TagSet by name, or to both. When a Domain Tag Set is named (e.g., “top_side_nodes” of acube), the heat load does not refer to a particular entity, rather to whatever relevant entitiesthat the domain currently contains as members (nodes, in the case of a heat load).

Conductors, contactors, ties, heat loads, etc. can be established using directly specifiedobjects by selecting those objects in the TD graphics area. But those same modeling toolscan also apply to indirect objects as named by domain tag sets. The primary advantage ofthis indirect method is that the conductor, contactor, tie, or heat load does not change (orget deleted) if the members of each domain tag set are changed, deleted, etc. Whatever isdefined in the domain tag set at the time an analysis is performed is what is used.

For example, if the TD surfaces (whether FDM or FEM) on the bottom of a box areplaced in a domain tag set named “mount_side” and the TD surfaces on the facesheet of ahoneycomb panel are placed in a domain tag set named “top_face,” then a contactor can beestablished between mount_side and top_face. The box can be reshaped, renodalized, oreven deleted and the contactor will persist, and contact will be re-established based onwhatever the current members of the domain tag set are at run time.

A primary purpose of TD Direct Domains (see above) is to automatically generate TDdomain tag sets. If the box and the honeycomb panel in the above example had been gen-erated in SpaceClaim, then the appropriate sides of those objects could have been taggedwith the domain names, resulting (as a minimum) in the creation of the domain tag setsMOUNT_SIDE_SURFACES and TOP_FACE_SURFACES, which could have been usedas the basis for a contactor. If the dimensions or mesh of the box or panel are changed,contact is re-established automatically.

Introduction 1-3

1.3 Software Modules

The following software modules are referenced in this document.

SINDA/FLUINT. CRTech’s core batch-style solver of thermal/fluid design or simulationproblems posed as networks, where “networks” can represent finite element models (FEM),finite difference models (FDM), or both. The focus in this manual is on the SINDA (thermalnetwork) side of SINDA/FLUINT.

Thermal Desktop. Thermal Desktop (“TD”) is CRTech’s geometry-based model develop-ment tool for SINDA/FLUINT modeling. The Thermal Desktop core module can be ex-tended with either or both of the RadCAD module (for thermal radiation heat transfer) orthe FloCAD module (for thermohydraulics and heat pipes). In this manual, FloCAD willonly be rarely mentioned, and the distinction between Thermal Desktop and RadCAD willnot be emphasized

TD Mesher (“TDMesh”). Thermal Desktop features a basic surface or solid meshing ca-pability called the TD Mesher, which will often just be abbreviated as “TDMesh.”

Autodesk AutoCAD. Thermal Desktop is based in Autodesk’s AutoCAD product. As such,any capability of AutoCAD is also available to the TD user. The user is assumed to be usingAutoCAD 2012 or later.

Autodesk Fusion®. Fusion is a direct (vs. parametric or history-based) modeling CAD toolthat, while normally part of Autodesk Inventor, also has functionality that can be accesseddirectly from AutoCAD.

SpaceClaim. SpaceClaim refers to SpaceClaim Corporation’s popular direct modelingCAD program, SpaceClaim Engineer. SpaceClaim is specifically designed for geometricmodel preparation (including import, healing, and defeaturing). In this manual, this productmay simply be called “SpaceClaim.” The user is assumed to be using CRTech SpaceClaim2012 or later.

TD Direct. TD Direct is an extension to SpaceClaim that assists in thermal model prepara-tion including advanced meshing, referred to as “SCMesh”. This extension allows for mark-ing up the geometry with thermal data, setting meshing controls and allowing a link betweenThermal Desktop and SpaceClaim.

1.4 Process

The advanced modeling techniques consist of two basic steps: defining the geometryand building the thermal model.

1-4 Introduction

One (fortunately rare) exception is when an FEA mesh produced by another program isimported and used as the thermal model itself. This, of course, limits the analyst’s abilityto control the resolution of the model or make adjustments to the geometry. While covered

in this manual, this usage is not emphasized since better alternatives are available.1

The Advanced Modeling Process Map (Figure 1-1) provides an overview of the pathsfrom design geometry to the thermal model. To use this map, start from the block describingwhere the geometry has been or will be created, and follow the possible paths for transferringthe data to Thermal Desktop, where the final thermal model will reside. Note that any oneportion of a system-level model may follow a different path, different approaches can beused for different portions of the thermal model.

1 It is not necessary for a thermal model to use the same mesh as a structural model, nor even the exact samegeometric basis for the mesh... even if thermoelastic load cases are needed.

Figure 1-1 Advanced Modeling Process Map

Raw Geometry

Creo®, SolidWorks®, NX® CAD, CATIA®, Autodesk

Inventor®, STEP, IGES, ACIS, etc.

GeometryPreparation

SpaceClaim®

Thermal Modeling

C&R Thermal Desktop®

TD Direct™

Import Import

Link

Introduction 1-5

1.5 Guidance

The key to using the advanced modeling techniques described in this manual and ob-taining a usable thermal model is planning. As with any analytical task, the analyst mustunderstand the goal of the analysis; understand the necessary detail of the model; plan theappropriate path through the process; and have a preliminary, simple analysis completed.

The quickest way to have troubles with a model is to over-build from the start. Includingunnecessary detail (i.e. small features which lead to too many nodes) can slow or stall thesolution, obscure important results, or make troubleshooting impossible.

1-6 Introduction

Table 1-1 Recommendations

ModuleGeometry Creation

Geometry Import

Clean/heal/defeature

Thermal Model Prep.

Thermal Model Update

Thermal Desktop, AutoCAD, Fusion, & TDMesh

OK for simple sur-face and solids, especially if indepen-dent

Good OK Best for FDM, OK for FEM.

OK

Space-Claim

Best Best Best N/A N/A

TD Direct N/A N/A N/A Best for FEM. No FDM

Best

Table 1-2 Comparison of Modeling Methods

Basis Native TD TDMesh SCMesh

Type Finite Difference Finite Element Finite Element

Surface types rectangles, triangles, conic sections, etc.

triangles (quadri-lateral on sides of extrusions)

triangles & quad-rilateral

Curvature accuracy

perfect function of resolution

function ofresolution

Nodal density usually low, no mini-mum

any (subject to surface accuracy), with a minimum

any (subject to surface accuracy), with a minimum

Applicability basic geometry shapes any single sur-face or solid

any (including assemblies and nonmanifold bod-ies)

Controls Customizable per body axis

Global (per body) Customizable per edge, surface, or body

Extrusions yes (into FEM solids) yes yes

Introduction 1-7

Merging of con-tacting geometry

not unless manually aligned

no yes

Matching of con-tacting geometry

not unless manually aligned

no yes

Domain Tag Set generation for automating updates, ease of selection

no no yes

Mesh Action Script for auto-mating updates

not required in order to reshape or to change resolution

no yes

Tags for local optical and ther-mophysical prop-erties, radiation analysis groups, insulation

not required in order to reshape or to change resolution

no yes

Global (per body) setting of sub-model, optical properties, insula-tion, radiation analysis groups

yes yes yes

Table 1-2 Comparison of Modeling Methods

Basis Native TD TDMesh SCMesh

1-8 Introduction

2 Creating CAD Geometry

Tools that create geometry for design and manufacturing purposes (but more and morenow for analysis as well) have been traditionally referred to as Computer Aided Design(CAD) tools. Geometry created by these tools is called CAD geometry, or dropping “Com-puter Aided”, is referred to as just “Design” geometry.

This section provides an overview of how to create design geometry in AutoCAD andSpaceClaim. Design geometry is defined as graphical entities that visually represent theitem desired to be thermally analyzed, but it is a visual representation only, it will notcontribute to the thermal model. Design geometry requires additional steps to produce athermal model.

“Thermal model geometry”, or just “thermal geometry”, on the other hand, is a visualrepresentation that is used directly by Thermal Desktop to perform thermal analysis. Ther-mal geometry, such as Thermal Desktop’s custom conic primitives and finite elements,visually represent the item desired to be analyzed as well as contribute to heat loads, radiationexchange factors, conduction terms, thermal mass, etc., for the thermal model.

Design geometry does not participate in the thermal model as is, and must be eitherconverted or used in a meshing operation. For example, a solid geometric body is not useddirectly by Thermal Desktop, but may be meshed with finite elements using either TDMeshin Thermal Desktop or SCMesh in TD Direct. As another example, certain types of 2Ddesign surfaces generated in AutoCAD are represented by a collection of flat facets. Thesetypes of surfaces may be converted into either finite difference or finite element ThermalDesktop analysis objects.

Design geometry may need two separate processes before it is included in the thermalanalysis process. The first may be a healing, simplification, or defeaturing step. Often ge-ometry imported from CAD systems contains defects. For analysis, geometry must be to-pologically precise. A solid body must be completely bound by faces. Those faces must becompletely bound by curves that share common start and end vertices. The faces that bounda solid body must share their boundary curves where they adjoin. Many protocols for exportand import are only concerned with an acceptable visual representation, and may have manyhidden flaws. Healing operations attempt to correct these topological defects.

Often imported design geometry is more complex than desired for thermal analysis.Meshing the part as is could produce an intractably large model. In this case, the part mightbe simplified by mid-planing operations, or removing inconsequential features, such as boltholes. Design geometry can be a visual representation created by a designer to completelyspecify an item for manufacture, or it can be “thermal analysis ready” design geometry,which is appropriately simplified (or created with an appropriate level of detail) and readyfor conversion or meshing to produce a thermal model.

This section covers the generation of thermal analysis ready design geometry using thefeatures of AutoCAD and SpaceClaim. If the thermal analyst has been supplied with a CADdrawing, please refer instead to Section 3 "Importing CAD Geometry" on how to import

Creating CAD Geometry 2-1

such data, and Section 4 "Working with CAD Geometry" on how to prepare it for thermalmodeling tasks.

With the advent of easier to use CAD systems, many engineers are creating analysisready design geometry from scratch themselves, rather than simplifying complex designgeometry created by a designer and intended as a complete specification for manufacture.Such geometry created by the thermal analyst is still referred to as “design” geometry, todenote that it is not used directly for thermal analysis. To avoid confusion, the terms “thermalgeometry”, “thermal analysis geometry”, “thermal model geometry” and contractions there-of (“analysis geometry” and “model geometry”) all refer to the built-in visual ThermalDesktop objects used to directly represent the thermal model.

Thermal Desktop contains a built-in suite of “primitives” that may be used to represent2D conic surfaces trimmed on regular parametric boundaries (discs, paraboloids, cones,etc.) as well as a collection of regular 3D solid primitives (cylinders, spheres, etc.). Thissection presumes that no CAD drawing of the geometry is already available, and that oneor more parts must be modeled in 2D and/or 3D, and that the complexity of these partsexceeds the applicability of the native suite of Thermal Desktop surface and solid primitives.This section describes how design geometry is converted into thermal geometry.

This section is an introduction to the 2D and 3D modeling capabilities provided by toolssupplied by CRTech. Further detailed instructions on 2D and 3D modeling capabilities areavailable from Autodesk, SpaceClaim, and other sources (see Section 2.1.2 "AutoCADTraining Resources" and Section 2.2.2 "SpaceClaim Training Resources"). Rather, thischapter seeks to provide initial guidance to the thermal modeler whose CAD experience islimited.

2.1 AutoCAD

2.1.1 Capabilities

AutoCAD can be used to generate wireframes, surfaces, regions or graphical meshes(not to be confused with finite element meshes), and solids. The following sections providemore information on these categories of design geometry.

2.1.1.1 Wireframes

AutoCAD can be used to create various wireframe objects (lines, polylines, arcs, rect-angles, polygons, circles, etc.). Most of the wireframe objects are accessible under the Drawmenu.

Using the Draw > Modeling menu, these wireframes can be extruded, revolved, lofted,

or swept. If a closed wireframe is used, a solid1 will be created; if an open wireframe is useda surface will be created.

1 In some cases, it would be better to leave them as wireframes, convert them into regions, then use the TD op-tions for extruding or revolving a mesh, as explained in the Thermal Desktop manual.

2-2 Creating CAD Geometry

Closed, co-planar wireframes (including a set of co-planar wireframes sharing end-points) may also be converted to “regions” using the region command in the text window(or the Draw > Region menu option) before either being meshed or performing booleanoperations. Regions are two-dimensional so wireframes must be coplanar.

Similar to regions are planar surfaces. A planar surface may be created using the Draw> Modeling > Planar Surface menu selection. The user is then queried for two points defininga rectangle's origin and diagonal or a closed-loop, planar wireframe.

2.1.1.2 Surfaces, Regions, and Meshes

AutoCAD has three main types of topologically two dimensional objects: surfaces,

regions, and meshes2 (not finite element meshes). Surfaces may exist in three dimensionalspace with curvature. Regions must be planar, but may be used in boolean operation. Meshesare comprised of planar faces and, therefore, can only approximate curved surfaces.

As described in the previous section, surfaces may be created by extruding, revolving,lofting or sweeping open wireframes. Surfaces may also be extracted from solids by usingthe EXPLODE command on the solid. Wireframe curves can be extracted from surfaces byexploding the surface.

Regions are created either by using the REGION command and selecting a planar, closedwireframe or using the BOUNDARY command and selecting an interior point of the region.The BOUNDARY command will determine all boundaries using any coplanar lines andcurves (including wireframes, surfaces and other regions). The term “region” survives fromwhen AutoCAD was just a 2D drafting program. Regions were areas of the drawing thatwere to be cross-hatched. Regions are now general purpose planar surfaces bound by a setof coplanar curves. Regions may have holes by subtracting one region from another in aboolean operation.

AutoCAD can also be used to create meshed surfaces from multiple lines. Using theDraw > Modeling > Meshes menu, lines can be used to create revolved meshes, ruled,meshes, edge meshes, and tabulated meshes. The meshes are described by a matrix of Mby N points that define the vertices of the planar faces. The values of M and N are definedby the AutoCAD variables SURFTAB1 and SURFTAB2.

Boolean operations can be performed on regions. As an example, the process of makinga plate with a hole in it will be described. First, create a rectangle and a coplanar circle(coplanar will be the default if the UCS is not changed in between creation of the twoobjects). Use the region command to convert both the rectangle and the circle into regions.Then, type subtract or Modify > Solids Editing > Subtract, choosing the rectangle first asthe “object to subtract from,” and then the circle as the “object to be subtracted.” Thiscomplex region can now be meshed (in 2D), or extruded, lofted, etc. then meshed (in 3D).Figure 2-1 depicts the region after having been extruded.

2 “Meshes” in this instance refers to the method used by AutoCAD to create the surface. Nodes and elements donot exist at this point.


Other boolean operations include union (encompass all surfaces or volumes of all se-lected objects as the new region or solid), and intersect (consider only the common area orvolume as the new region or solid). For example, to make a race-track shape, union arectangular region with two circular regions. Figure 2-2 depicts such a race-track, afterhaving been revolved 20 degrees around an axis parallel to the straight sides.

Figure 2-1 Plate with Hole (subtracted circle), Extruded

Figure 2-2 Rectangle with End Circles, Unioned and Revolved 20 Degrees


2.1.1.3 Solids

Section 2.1.1.1 described how to create a solid by starting with a wireframe. Solids canalso be created directly using various options under Draw > Modeling, including toroids,cones, and polysolids (a solid version of a polyline).

Once created by whatever means, solids can be unioned, intersected, or subtracted with

other solids to create unusual shapes.3

One particularly useful command, once a solid is finished, is explode (Modify > Ex-plode). This command replaces the solid with all the surfaces that it contains. The explodecommand can be used to create unusual surfaces (for example, the curved edge of the soliddepicted in Figure 2-2).

Organic shapes can be created from fundamental solid primitives by using mesh-smooth-ing. This feature is available in AutoCAD 2010 and later. For example, if a cube is smoothed,the edges and corners become rounded. Any solid model may be smoothed. Creases andother features can be added to prevent smoothing in certain areas. The smoothed mesh maybe converted directly into a Thermal Desktop finite element mesh.

2.1.2 AutoCAD Training Resources

Help Menu. Extensive resources are accessible via the Help menu in AutoCAD, includingmanuals, tutorials, “showme” features, and access to various online resources.

Autodesk University. (www.autodesk.com/au). An annual user conference is hosted withextensive training opportunities.

CADTutor Website. (www.cadtutor.net). A tutorial site with an extensive user forum.

2.2 SpaceClaim

2.2.1 Capabilities

SpaceClaim (www.spaceclaim.com) represents an exciting advance in tools for geom-etry creation and modification. It is an easy to use, full featured CAD program that allowsgeometry to be created from scratch, as well as importing from virtually any other CADsystem. Imported geometry can be quickly simplified, defeatured, and healed as necessary.

SpaceClaim is a direct modeling tool. This means that the software recognizes the to-pology of the geometry and does not rely on a history tree of features. This allows on-the-fly modification of complex geometry without having to decipher a complicated construc-tion sequence. Most modifications involve a simple selection and “pull” operation.

3 Caution: If not done carefully, and sometimes even with suitable care, slivers and other defects can arise. Fortruly complex solids, consider using SpaceClaim instead.


http://www.crtech.com/spaceclaim.html

www.crtech.com/spaceclaim.html

www.crtech.com/spaceclaim.html

SpaceClaim can create solids and surfaces, parts and assemblies. The geometry can thenbe parameterized through the use of driving dimensions. Even existing geometry created inanother CAD system can be imported and parameterized. This is finally a CAD systemdedicated to the engineer. Complex geometry can be created quickly, without the engineerhaving to become a CAD expert.

With TD Direct, CRTech has further extended the functionality of this powerful tool byproviding a dynamic link with Thermal Desktop. Both design geometry and a finite elementmodel are automatically maintained congruent with the design geometry. An existing ther-mal model stays synchronized when inevitable changes to the design occur.

Because of the quantity and quality of the training resources available to the new Space-Claim user, and because of the ease-of-use of the program, it is recommended that the userreview the excellent training videos and resources provided at the web sites listed below.

2.2.2 SpaceClaim Training Resources

Online Help. By clicking the question mark (?) in the tab bar or pressing the F1 key, theuser has access to help within SpaceClaim. The online help provides step-by-step instruc-tions, animations, and examples. Within the online help are also a printable quick-referencecard for keyboard shortcuts and another for mouse and touch gestures (movements with amouse or on a touchpad or touchscreen to issues commands).

SpaceClaim Website. (www.spaceclaim.com). Under the support section of the Space-Claim website are tutorials and downloads that can be used to learn the features providedby SpaceClaim. A good place to start is the Basic Tutorials, http://www.spaceclaim.com/en/Support/Tutorials/Essentials/SpaceClaim_Basics_Tutorials.aspx.

CRTech Website. (www.crtech.com). An overview of SpaceClaim and TD Direct for ge-ometry preparation, and a follow-on for an overview of SCMesh are available at http://www.crtech.com/spaceclaim.html.

2.3 Summary of AutoCAD vs. SpaceClaim

AutoCAD’s heritage as a drafting tool means that it focuses on 2D objects and repre-sentations, although the most recent releases have expanded its 3D capabilities. SpaceClaimis meant to be an easy-to-learn, easy-to-use fully featured CAD system, with an emphasison 3D modeling (but with extensive sheet metal capabilities as well). SpaceClaim alsocontains dedicated tools for healing, simplification, and defeaturing complex design geom-etry.

This distinction leads to top-level recommendations:

1. If the desired object is a surface, use either AutoCAD or SpaceClaim.

Surfaces suffice in many cases for thin objects, and are in many ways superior to sol-ids since they are computationally more efficient. Recall that a virtual thickness, insu-


http://www.spaceclaim.com

http://www.spaceclaim.com

http://www.crtech.com


lation, etc. can be added to Thermal Desktop surfaces, and that surfaces can be extruded, rotated, etc. into 3D objects or meshes, and symmetry options might then be exploited to further reduce model size.

However, if the surface is in contact with other surfaces, or if it is an extension of a solid, or if it is expected to undergo dimensional changes, then TD Direct should be used. It is sometimes simpler to create a solid and then extract the surfaces with an explode or detach operation than creating the surfaces using strictly 2D techniques.

2. If the desired object is a complex solid, use SpaceClaim.

If TD Direct is not available, then each time dimensions change, the CAD part must be reimported or regenerated. This means that mesh controls and thermal properties and boundary conditions must also be reapplied.

By using TD Direct, the update process is automated. Tags assigned to the design geometry in SpaceClaim are used to define materials, surfaces properties, analysis groups, and general purpose domains. As geometry changes, the thermal model can be automatically updated with the only action required by the analyst is to request the update.

In summary, if TD Direct is available, then use SpaceClaim for anything other thana simple surface or solid that is not expected to change, or that does not share contactregions with other objects.

2.4 Example Cases

Please visit the CRTech website, www.crtech.com, to check for the latest example cases,and information posted in the CRTech Users Forum.



3 Importing CAD Geometry

Starting with AutoCAD 2012, just about any CAD format can be imported into Auto-CAD. The import capability is accessed from the AutoCAD File > Import menu. The Fusionprogram can also be used to perform basic defeaturing, and the resulting geometry can bemeshed using TDMesh.

However, the direct-to-AutoCAD route (Section 3.1) is very limited, and should onlybe used for simple “one-time” tasks, or as a work-around if SpaceClaim with TD Direct areunavailable. These fully featured tools are documented in Section 3.2.

Section 3.3 documents how to link SpaceClaim with Thermal Desktop. SpaceClaimwith TD Direct is licensed separately from Thermal Desktop, but provides the ability toupdate geometry and/or a finite element mesh from changes made in SpaceClaim.

3.1 Importing Directly into AutoCAD

CAD geometry can be directly imported into AutoCAD using the File > Import menu.

Surfaces and solids that have been imported can be used to create thermal models usingone of two methods, which can be combined as needed within one TD model:

1. Use the geometry as scaffolding for snap-on finite difference modeling.

Once FDM objects (plates, bricks, cylinders, etc.) have been snapped onto a CAD object(using it as reference geometry, as described in Section 4.2), the imported CAD objects canbe either deleted or rendered invisible.

If design changes are made, the new CAD model should be re-imported, and the existingFDM objects should be stretched, moved, or reshaped to fit the new dimensions.

The advantages of this method are simplicity and the improved accuracy of “analytic”(versus faceted) geometry. The work required to perform updates is modest.

The primary disadvantage is that basic FD shapes cannot be used as substitutes forcomplex geometry.

2. Mesh the geometry using TDMesh, either meshing it directly, or using it as the basis for extruding a mesh.

Before using TDMesh, the built-in tri/tet object-level mesher inside of Thermal Desktop,the CAD geometry will often need to be prepared for meshing: CAD objects are rarelymeshed immediately after import.

Importing CAD Geometry 3-1

Once inside of AutoCAD, the Fusion utility can be optionally used to restore geometricrelationships (e.g., turn IGES surfaces back into solids) and to perform modest defeaturingoperations (e.g., remove bolt holes). The mesher itself can be used to “jump over” certaindefects and small features when coarse resolution is specified, but it is always best to elim-inate such problems before meshing.

TDMesh is documented in the Thermal Desktop User’s Manual. The meshing processallows assignment of surface and solid properties to the generated finite elements.

Nonetheless, once meshed, the user will often want to create connections (contact, con-duction, ties, etc.) or assign heat loads, or customize radiation or insulation on subsets ofthe surfaces. The use of Thermal Desktop Domain Tag Sets is highly recommended whenselecting these subsets, such that the amount of re-work is decreased if the geometry ormesh changes. SCMesh supports automatic generation of tag sets, TDMesh does not.

The primary advantage of using TDMesh and importing CAD geometry directly intoAutoCAD is that it is a simple interface designed for simple tasks. It is therefore easy tolearn, but is limited in functionality. If the analysis process will be iterative as the systemdesign evolves, SCMesh should be considered instead.

3.2 Importing into SpaceClaim

This section briefly describes the strategy behind using SpaceClaim with TD Direct asan intermediate for incoming geometry: a preparation tool before adding the resulting ther-mal model generated from one or more such CAD objects (including an assembly) to aThermal Desktop model.

At first, it might seem counterintuitive that inserting yet another tool between the ulti-mate source of the CAD files and Thermal Desktop could simplify the process. SpaceClaimtakes advantage of powerful importers and geometry analysis to make any source of geom-etry (whether IGES or Solidworks) nearly equally useful. Like Autodesk Fusion, it usesdirect modeling technology to recover the intent of the designer. However, it transcends thattool in its ease of use, and in its ability to heal, clean, defeature, and adjust.

If the geometry changes, its intuitive “push/pull” techniques can be used to quicklyreshape the prior version to fit the new dimensions. This is similar in philosophy to the wayexisting FDM objects are reshaped to snap onto the newly imported dimensions using grippoint editing (Section 4.2), but unlike that technique, SpaceClaim editing operations can beused on much more complex shapes.

With the TD Direct (“SCMesh”) add-on, the geometry can be further prepared for Ther-mal Desktop modeling by assigning properties, insulation, radiation analysis groups, initialconditions, contact conduction, local mesh controls, etc. as described in the TD Direct UsersManual. All of these preparation steps are designed such that if modest geometry changesare made, or if any mesh refinements are requested, then the entire model can be updatedwithout any rework.

3-2 Importing CAD Geometry

Thus, there are few disadvantages to this method. If available, it should be used inpreference to other techniques described above, with one exception: FDM methods shouldstill be used for certain simple geometry shapes, especially when radiation is involved. Whilecoarse meshes can be specified, approaching the low nodal resolution of FD models, thesurfaces are still faceted and therefore approximate. FD methods would therefore be supe-rior, when applicable, to objects such as parabolic solar troughs, dishes, or reflectors.

3.3 SpaceClaim Importer

TD Direct allows the user to dynamically link SpaceClaim and Thermal Desktop. Withthe two products installed, the geometry can be generated and modified in SpaceClaim andthe changes updated in Thermal Desktop. TD Direct also contains meshign capabilitiesknown as “SCMesh” (to distinguish it from TDMesh).

A SpaceClaim importer is a Thermal Desktop object that controls the geometry importedfrom SpaceClaim. The importer can be repositioned within Thermal Desktop to orient thegeometry within the thermal model without having to reposition in SpaceClaim. A ThermalDesktop model can have multiple SpaceClaim importers. Each SpaceClaim importer shouldreference a unique SpaceClaim document. If multiple copies of a part are desired in thethermal model, copies can be made by constructing an assembly in SpaceClaim.

The sections below provide instructions for accessing CAD (or “design”) geometrycreated in SpaceClaim from within Thermal Desktop. The meshing operations availablewith SCMesh are covered in the TD Direct Users Manual.

3.3.1 Creating a New Importer

In Thermal Desktop, select Thermal > SpaceClaim > Create SpaceClaim Link tocreate a SpaceClaim importer. When this is done, a file open window will appear with thefilenames filtered to *.scdoc files (the SpaceClaim file extension). After selecting the Space-Claim document, the SpaceClaim Importer window will open (Figure 3-1). The followingsections will cover options and the other tabs on this form.

The two primary options for the SpaceClaim importer are Import CAD Geometry andGenerate Finite Element Mesh. The two options can be chosen at the same time, individ-ually, or not at all.

The SpaceClaim importer (the bounding box around the imported geometry or generatedmesh as seen in Figure 3-2) can be selected and edited (Thermal > Edit) to access theSpaceClaim importer form to make changes to the options or to simply update the geometryor mesh based on changes made within the SpaceClaim document.


Figure 3-1 SpaceClaim Importer window Options Tab

Figure 3-2 CRTech SpaceClaim importer


3.3.1.1 Import CAD Geometry

With TD Direct, the geometry in a SpaceClaim document can be linked into a ThermalDesktop drawing. By selecting the Import CAD Geometry checkbox, the geometry inSpaceClaim will be imported into Thermal Desktop using the selected format. The importedgeometry can be used for scaffolding (Section 4.2) or meshing using TDMesh (ThermalDesktop Users Manual). With the link, if the geometry in SpaceClaim changes, then theupdated geometry can be brought into Thermal Desktop by synchronizing the SpaceClaimlink (Section 3.3.2). Importing geometry converts the geometry dimensions from Space-Claim length units to the current Thermal Desktop units.

3.3.1.2 Generate Finite Element Mesh

This option is available with TD Direct, which is described in the TD Direct UsersManual. Checking the Generate Finite Element Mesh checkbox will generate a new finiteelement mesh in Thermal Desktop based on the mesh controls and thermal tags defined inSpaceClaim (see the TD Direct Users Manual).

3.3.1.3 Dimension Overrides

Note: To set up Dimension Overrides, the SpaceClaim importermust be fully created. After making selections on the Optionstab the first time, the Synchronize button must be selected. Whenthe SpaceClaim importer is subsequently edited the DimensionOverrides can be set.

SpaceClaim allows parameterizing geometry using “Driving Dimensions.” Driving di-mensions are created by creating a group on the Group tab of SpaceClaim while a dimensionis highlighted within an operation, like Pull (Figure 3-3). Once the group is created thename can be changed and the dimension edited by selecting the value and typing a newvalue while in SpaceClaim. With the SpaceClaim importer, any driving dimension can bechanged on the Dimension Overrides tab (Figure 3-4).

To control the driving dimension from Thermal Desktop, select the driving dimensiongroup name from the SC Group Name pull-down menu and select Add. The Edit DrivingDimension form will open (Figure 3-5) with the current value of the driving dimension inthe field in Thermal Desktop units. Changing the value and selecting OK will update theSpaceClaim driving dimension on the next synchronize operation. The updated geometrywill then be reimported into Thermal Desktop.

The value in the Edit Driving Dimension form can be provided by a Thermal Desktopsymbol by double-clicking on the field to access the expression editor. See the ThermalDesktop User’s Manual for more information on symbols and the expression editor.


Important: It is the user’s responsibility to ensure changes tothe driving dimensions are reasonable and valid. If a mistakeis made, perform an Undo is SpaceClaim and then change theEdit Driving Dimension value in Thermal Desktop back toavalid value and synchronize.

Figure 3-3 Creating driving dimensions in SpaceClaim


3.3.1.4 Mesh Editor Action Script

Note: To set up Mesh Editor Action Scripts, the SpaceClaimimporter must be fully created. After making selections on theOptions tab the first time, the Synchronize button must be se-lected. When the SpaceClaim importer is subsequently edited theMesh Editor Action Scripts can be defined.

Figure 3-4 Dimension override tab in SpaceClaim Importer

Figure 3-5 Edit Driving Dimension form


The Mesh Editor Action Script form allows the user to define actions based on domaintags defined in SpaceClaim. The full functionality of this option is documented in the TDDirect Users Manual.

3.3.2 Synchronize

When all desired options have been set for the SpaceClaim importer, the Synchronizebutton executes those options. Upon synchronization the following steps are taken in order:

• The referenced SpaceClaim document is opened, if it is not already open. Space-Claim will be launched if necessary.

• Driving dimensions from Thermal Desktop are updated in SpaceClaim and thegeometry in SpaceClaim is updated

• The updated geometry is imported from SpaceClaim and/or a finite element meshis generated based on the updated geometry

• The mesh editor action scripts are performed on the specified domains

Synchronization can be performed on a single importer by selecting and editing (Ther-mal > Edit) the importer bounding box. All SpaceClaim importers can be synchronizedsimultaneously by selecting Thermal > SpaceClaim > Synchronize SpaceClaim Links.Note that the Create New Importer and Synchronize All Importers buttons are next toeach other on the tool bar, use care to select the desired operation.


4 Working with CAD Geometry

4.1 Simplifying CAD Geometry

Simplifying geometry is probably the most important step of advanced modeling. With-out simplification, an automated mesher, such as TDMesh or SCMesh, can focus or fail ona section of the model that has no bearing on the thermal results. An extreme example, butnot uncommon, would be a part with threads included in a bolt hole: it can be argued thatthe bolt hole (or at least its location) may be necessary for a thermal analysis, but the threadswould have no effect. The mesh that would be required to capture each thread face wouldbe extreme (if meshing were even successful) and would unduly complicate the model.

4.1.1 AutoCAD

AutoCAD has some basic capabilities for modifying geometry for simplification. Ifsolids are present, opening the Solid Editing toolbar will help, otherwise most commandsare found under the Modify and Modify > Solid Editing menus. For simplifying the modelthe following sections will describe some of the more common editing tools.

4.1.1.1 Explode

The Modify > Explode menu option will break a solid into its faces. The primary benefitof this is simplifying a solid to just the face so that the extrude or revolve mesher can be used.

Treating thin objects as solids instead of surfaces can cause undesirable mesh densitieswhen the part is meshed. A 2D mesh can be assigned a virtual thickness within the TDMeshedit form, but if a geometrically faithful thickness is required (perhaps for radiation), thenthe 2D mesh can be extruded (Non-planar surfaces can also be extruded along local surfacenormals.). If the thickness is large enough (or if the conductivity low enough), several 2Dmesh layers can be used. If, instead, the thickness is small enough (or conductivity highenough), these layers can contain the same node numbers when the TDMesh Extrude optionis used, resulting in a model which is geometrically faithful but thermally approximate.

4.1.1.2 Select and Modify Sub-objects

By holding the <CRTL> key and clicking on edges and faces, the edge or face of a solidcan be individually selected. This same method allows selecting the original objects of asolid created by boolean operations. Once selected, the grip points of a sub-object willbecome available and the sub-object can be edited (e.g. - the radius of a cylinder used tocreate a hole in a block).

Working with CAD Geometry 4-1

4.1.1.3 Delete Face

The Modify > Solid Editing > Delete Face command allows the user to remove a facefrom the solid. The faces can be selected using the method described in the previous section.AutoCAD will attempt to heal the solid (fill the gap) by extending existing faces to re-enclose the solid object. Examples where this command would be useful would be unnec-essary bolt holes, fillets, or chamfers. In some instances, an object may not be healable.When this happens, AutoCAD will not delete the selected face and note that the objectscould not be healed. Certain faces may need to be deleted in a specific order for healing totake place.

Figure 4-6 shows an electronics cover with some unnecessary details which are high-lighted in red and some potentially unnecessary details highlighted in yellow. These are allfaces that may be deleted, but the chamfer around the edge of the base cannot be deleted inone step since it is not one face Along each straight edge is a face and along each curvededge is a face. If any one of these faces is deleted, a discontinuity will occur at the next face,causing AutoCAD to fail the healing process. The solution to this is to remove the roundedcorners of the base, followed by the chamfer faces at each corner, and then the chamfersalong the straight edges can be removed (as seen on the left of Figure 4-6). The otherhighlighted surfaces could be deleted directly.

4.1.2 SpaceClaim

SpaceClaim is a program designed specifically for the engineer to repair and prepareCAD geometry for thermal analysis. It represents a new level in ease of use and modelingpower. Most operations are performed with a simple selection and button click. CRTech hasfurther extended the functionality of this revolutionary tool by providing dynamic integra-tion with Thermal Desktop. Both tools work simultaneously with bi-directional associativity

Figure 4-6 Simplifying a solid

4-2 Working with CAD Geometry

to automatically maintain congruence between design geometry and the thermal model.Changes to the design in SpaceClaim automatically propagate into the thermal model inThermal Desktop with a one-button update.

More information, including sample models and tutorials, can be found atwww.crtech.com/spaceclaim.html and www.spaceclaim.com.

4.1.3 Other Geometry Preparation Tools

Table 4-1 on page 4-3 is a partial list of tools that could be used upstream of ThermalDesktop for simplifying geometry or simply translating from one format into another. Thislist is based on datasheets and not experience. This section is not comprehensive. Rather, itcan serve as an introduction to some tools that may be useful for simplifying geometry orpossibly translating into formats suitable for importing into Thermal Desktop. This list innot an endorsement of any tools or products. The product names used in this table are foridentification purposes only. All trademarks and registered trademarks are the property oftheir respective owners. In the list, the user will find some capabilities of the software andone or more suggested paths or supported file formats to move the data from the tool toThermal Desktop.

Table 4-1 Other Upstream Tools

Tool Vendor Capabilities

Pro/ENGINEER®

(Creo®)

PTC • Simplified representations

• Mid-planing

Suggested paths to Thermal Desktop

• Pro/ENGINEER > SpaceClaim

• Pro/ENGINEER > Inventor > ACIS

• Pro/ENGINEER > AutoCAD 2012 or higher

SolidWorks® Dassault Systémes SolidWorks Corp.


• ACIS v7

• Parasolid® > SpaceClaim

• Parasolid > Inventor > ACIS

• Parasolid > AutoCAD 2012 or higher


Femap™ Siemens • Meshing

• Mid-plane meshing


• Femap Neutral

• NASTRAN mesh

• ACIS v7

• Parasolid > SpaceClaim



PATRAN™ MSC • Meshing


• NASTRAN mesh

ANSYS™/Struc-tural

ANSYS • Meshing


• ANSYS structural mesh

KeyCreator™ Kubotek • History-free model manipulations


• ACIS v7

IronCAD™ IronCAD • History-free model manipulations


• ACIS v7

NX™ Siemens Suggested paths to Thermal Desktop

• Parasolid > SpaceClaim



Table 4-1 Other Upstream Tools

Tool Vendor Capabilities


4.2 Snapping TD Objects to CAD Geometry

Each custom Thermal Desktop surface has a collection of grips (please refer to theAutoCAD User’s Guide for more information about editing with grips) that are used tographically modify the shape of the surface. For example, the cylinder has grips to changeits location, orientation, height, radius, and start and end angles. Using grips in combinationwith snap modes and the geometry calculator (AutoCAD ‘cal command) enables easy andpowerful geometry construction. Any grip may be used to move a surface by toggling thegrip mode to move mode by pressing the space bar or entering the letters mo at the commandprompt.

Graphical objects in AutoCAD, including Thermal Desktop objects, define snap pointsfor various locations on the objects. Examples of object snaps are: end point, mid point,center point, intersection, extension, and node point. Setting the running object snapmode to end, mid, center, and node will automatically select these points during pickingoperations. Holding down the <Shift> key and then holding down the right mouse buttonmay be used to bring up a pop-up menu to select a snap mode during picking operations.

Using the grip points with object snaps allows the user to match the Thermal Desktopobjects to the underlying geometry, thus providing the benefits of the Thermal Desktopsurfaces (true curvature for radiation calculations, parameterization, etc.) while verifyingan accurate representation of the geometry.


5 Third Party Finite Element Models

Many times thermal analysts must work with structural analysts in order to allow tem-perature-dependent stress calculations to be made (e.g., for thermoelastic load case gener-ation).

This does not mean that the structural mesh must be used as the basis for the thermalmodel, and in fact that method is not recommended. As long as the geometric basis is thesame, a results of a thermal model can be mapped to a (usually more detailed) structuralmesh (Section 5.3).

However, if the user lacks geometry or mesh preparation tools, or if no other CADrepresentation is available, then this chapter becomes relevant.

Finite elements models may be imported in one of two ways: as graphics or as nodesand elements. Both methods are available using the Thermal > Import > Create FE MeshImporter menu option. If temperature results will be mapped back to the structural model,the structural model can be imported as graphics and the mapping option set by using thePost Processing Data Mapper. Detailed instructions for importing models are providedin the Thermal Desktop User’s Manual.

5.1 Importing FE Model as Nodes and Elements

If the user wishes to simply import the thermal model from a finite element preprocessor, the finite element model should be imported as a thermal model (nodes and elements). This may be the process if a third-party preprocessor, such as Femap or ANSYS, were used to generate the thermal model. The implications of this choice are:

• The thermal model is already built.

• The thermal model resolution is determined upstream of Thermal Desktop.

• Curved surfaces are faceted and radiation will not account for actual curvature.

• 1:1 node association between thermal and structural model (this typically resultsin an overly defined and complex thermal model and is not necessary for mappingresults).

• The analyst must verify that elements and boundary conditions have been im-ported correctly.

• Nodes and elements that are included in groups (SET1 or SET3 cards in NAS-TRAN) will be added to tag sets. Tag sets can be used to define conductors,contactors, heat loads, ties and other network elements. If a mesh is updated and

Third Party Finite Element Models 5-1

includes the same group names, the network elements are updated to include theappropriate elements.

Thermal Desktop will conduct tests on the imported elements for quality. Any elementswhich are degenerate (multiple nodes of the same element in the same location) or of poorquality will be added to an AutoCAD group named BADELEMS. Additionally, if multipleelements are co-located (elements share the same node set), two groups will be created: oneof the co-located elements will be placed into DUPELEMS2 and all other co-located ele-ments will be placed in DUPELEMS. The DUPELEMS group can be deleted to ensure onlyone element per node set. The Model Browser can be used to list out AutoCAD groups sothe user can check to see if these groups exist and to see what elements have been placedin them.

5.2 Importing FE Model as Graphics

If the user wishes to generate the thermal model using Thermal Desktop surfaces, the finite element model should be imported as graphics. The implications of this choice are:

• The analyst must build the thermal model.

• The analyst maintains control over model resolution.

• The analyst can choose between finite element and finite difference objects.

• The analyst must apply all boundary conditions.

When the finite element file is imported, the mesh appears as a graphical object. Byediting the graphical object (select the mesh and choose Thermal > Edit), the user maychoose the display options for the mesh displayer, such as wireframe outline, wireframeexterior faces, etc. This graphical object can be used for object snapping for either ThermalDesktop objects or AutoCAD wireframes, surfaces, or solids to be used for generatinggeometry that can be meshed using TD Mesher.

If the results of the thermal model will be mapped back to the structural model, then thepost processing data mapper is recommended as described in the following section.

5.3 Mapping Results

Using the Post Processing Data Mapper is described in the Thermal Desktop User’sManual, but for purposes of advanced modeling, the data mapper object can be used similarto importing a finite element model as graphics (as described in Section 5.2). The benefitsof using the data mapper are:

• a graphical representation of the finite element mesh will be displayed;

• the mesh graphics may be relocated (translated and/or rotated);

5-2 Third Party Finite Element Models

• the thermal model can be verified to represent the same geometry represented bythe structural model;

• the mesh may be reimported;

• the thermal model results may be mapped back to the structural analysis mesh inits own format accounting for all translations and rotations;

• the mapped results can be verified on the mapper.

In addition to these benefits, the analyst also maintains control of the resolution of thethermal model and the types of objects used for the thermal analysis.

Third Party Finite Element Models 5-3

5-4 Third Party Finite Element Models

Index

AACIS 4-3AutoCAD commands

BOUNDARY 2-3delete face 4-2explode 2-3, 2-5, 4-1region 2-3subtract 2-3

AutoCAD geometrycreating 2-2curves 2-3mesh 2-3region 2-3–2-4surfaces 2-3, 2-6

Bboolean operations 2-3–2-4

Ccommands

AutoCADBOUNDARY 2-3delete face 4-2explode 2-3, 2-5, 4-1region 2-3subtract 2-3

curve 2-3See wireframe

Ddomains 1-2

Eexplode 2-3, 2-5, 4-1

FFusion 1-4

Ggeometry

AutoCAD wireframes 2-2creating 2-1simplifying 4-1

snapping Thermal Desktop object to 4-5

Iimport

FE modelas graphics 5-2as nodes and elements 5-1

geometry 4-3STEP AP203 3-1

Mmapping results to FE model 5-2mesh

AutoCAD geometry 2-3mesh editor action script 3-7Mesh Generation for SpaceClaim 1-4mesher

extrude 4-1model, thermal 1-4, 5-1

Rregion

AutoCAD 2-3–2-4command 2-3

SSCmesh 1-4, 1-7, 3-5, 3-8SpaceClaim 1-4SpaceClaim Importer 3-3subtract 2-3surface

AutoCAD 2-3, 2-6Thermal Desktop 4-5

synchronize 3-8

Ttag sets 1-3tags 1-3TDMesh

extrude 4-1TDmesh 1-4, 1-7thermal model 1-4, 5-1

Uupstream tools 4-3

Wwireframe

AutoCAD 2-2

thermal desktop advanced modeling guide in various formats (creo®, solidworks®, step, iges, etc.)....

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