introduce mesh

Copyright 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.

Basic Training

Introduction to HyperMesh

Ir. Dr. Muhammad Sabri


Getting Started

Opening and Saving Files

Working with Panels

Organizing a Model

Controlling the Display

Chapter 1: HyperMesh Introduction


Panels: General Layout

Panels often have sub-panels

Accessed by radio buttons on the left side of the panel

Panels generally work from left to right

Example: Project / to plane sub-panel

1) What to do:

Pick a sub-panel

for the function

to be used

2) What to do it to:

Select entities that

will be affected

3) How to do it:

Give parameters

that define how

the function will

be executed

4) Do the action:

Execute the

function


Panels: General Layout

Some sub-panels are organized in columns

Each column is a different method

Work from top to bottom in the relevant column

Example: surface edit : trim with surfs/plane sub-panel

1) What to do:

Pick a sub-panel

for the function

to be used

3) What to do

it to:

Select entities

that will be

affected

4) How to do it:

Give parameters

that define how

the function will

be executed

5) Do the

action:

Execute the

function

2) Method to

use:

Work in the

appropriate

column


Model Organization: HyperMesh Entity Types

Geometry

Points

Lines

Surfaces

Solids

Connectors (used for welding)

FE Model

Nodes

Temp Nodes (marks a node with a small circle)

Elements

Points

Lines Surfaces

Nodes Elements

Temp Nodes

Solids



FE Loading

Loads (constraints, forces, pressures, etc.)

Equations (mathematical link between nodes)

Contacts

Group (defines contact between entities)

Contact Surfs (defines a list of entities that can be used as master or slave in a group)

Constraints

Forces

Pressures

Contact

Surface



Multibodies

Ellipsoids (defines a shape for rigid bodies)

Mbplanes (defines a shape for rigid bodies)

Mbjoints (defines the connection of 2 rigid bodies)

Safety

Sensors (defines a trigger to start an event)

Control Volumes (defines airbags)



Coordinate Entities

Systems (coordinate axes)

Vectors

Reference Entities

Sets (a simple list of a particular type of entity)

Blocks (a list of entities contained within a box shape)

1D Element Cross Sections

Beam Sections (cross sectional properties for a property collector)

Systems

Beam Section

Vectors



Plotting

Curves (X-Y data)

Plots (a display of curves with axes)

Output Requests

Loadsteps (combinations of load collectors)

Output Blocks (request output from an analysis for certain entities)

Labels

Titles (label for a displayed item)

Tags (assigns a name to an entity) T a g s

T i t l e s

Plot with a Curve



Morphing

Handles controls model shape during morphing

Domains divides a model into regions (for domain based morphing)

Morph volume A cube shaped volume that morphs all entities that are located inside the shape (for volume based morphing)

Morph constraints Control the motion of nodes during morphing

Symmetries forces regions to be morphed symmetrically

Shapes model state during morphing saved for retrieval at a later point

Symmetries

Handles

Domains Morph Volume



Optimization

Designvars Variables that are changed during optimization (ex: thickness)

Optiresponses Values being measured (ex: von Mises stress)

Objectives Responses to maximize/minimize (ex: minimize weight)

Dobjrefs Objective reference response for minmax/maxmin optimization (ex: minimize maximum von Mises stress)

Opticonstraints Limitations (ex: von Mises stress < Yield stress)

Optidscreens Filters constraints to reduce computation time

Dvprels Relationships between design variables and properties

Desvarlinks Relationships between design variables

Dequations A calculated value to be measured

Optitableentrs Table of constants

Opticontrols Parameters to control the optimization algorithms

DDVals Sets a discreet range of values to be used in a Designvar


Model Organization: Collectors

The HyperMesh model is organized using collectors

There are many types of collectors

Most entities in HyperMesh must be placed in a collector

Each collector type holds a specific type of entity

Collector Types Can contain entity types:

Component Elements, Points, Lines, Surfaces, Connectors

Multibody Ellipsoids, Mbjoints, Mbplanes, Sensors

Assembly Components, Multibodies, Assemblies

Load Collector Loads, Equations

Material none (materials and properties dont contain other entities but are still treated as collectors) Property

System Collector Systems

Vector Collector Vectors

Beam Section Collector Beam Sections



An entity can usually only belong to 1 collector of a given type

Ex: an element can only be in 1 component collector

Can create many collectors of the same type

All entities in a collector are the same color

Organization can be however the user desires

1 component per part Multiple components per part

Component 1

Component 2

Component 3

Component 1 Component 2

Component 3

Component 4



Model browser

View collectors and assemblies in a hierarchical tree format

Create, delete, and rename collectors

Edit collector attributes

Organize collectors into assemblies

Drag and drop

Right-Click on

Collector for

advanced

options



New entities are created in the current collector

Creating a new collector automatically sets the current collector to that new collector

Model Browser or can be used to change the current collector.

Include Browser can be used to change the current include.

Organize panel can be used to move entities into a different collector

Bold Current Collector

Bold Current Include


Model Organization: Tools

Panels

Collectors Create new collectors

Model Browser Set the current collector for various entity types

Organize Move entities into a different collector than the one they are currently contained in

Rename Change the name of an existing collector

Reorder

Collectors appear in a certain order when presented in a list to pick from

Reorder allows the order the collectors appear in to be changed

Delete Delete entities or collectors


Do-it-yourself

Exercise: Reorganizing a Bumper Model Page 29


Display Control: Viewing: Toolbar

Pan

Center (C)

Rotate Left

Rotate Right

Rotate Up

Rotate Down

Rotate Clockwise

Rotate Counter Clockwise

Dynamic Rotate (A)

Dynamic Spin (R)

Manually rotate by grabbing a point and dragging

Rotate relative to the mouse cursor and screen center

Pan the model

Select and click on the screen to re-center model in graphics window

Incremental rotations in respective directions


Importing and Repairing CAD

Generating Midsurface

Simplifying Geometry

Refining Topology to Achieve a Quality

Mesh

Chapter 2: Geometry Cleanup


Topology Repair: Importing Geometry

Import geometry data via:

Files > Import > Geometry drop-down menu

Toolbar > > Geometry

Common types of geometry files supported: Unigraphics (NX2, NX3, NX4, NX5)

UG Part Browser Import of *.prt files Requires an installation of

Unigraphics to be available

CATIA (V4 & V5) import of *.model files CATIA V5 license required to import

V5 files

Pro/ENGINEER (Wildfire 2.0 & 3.0) import of *.prt and *.asm files

IGES Import of *.igs / *.iges files

STEP import of *.stp files


Topology Repair: Surface Definitions

Fixed point (Surface vertex)

Point associated with a surface

Cannot be moved off the surface

Can lie on a surface edge or the interior of a surface

Separates surface edges from each other

Forces a node to be placed at that location during meshing

Surface edge

Line associated with a surface

Defines a surfaces boundary

Cannot be moved off the surface

Has a fixed point on both ends

Surface


Automeshing: What is topology?

Topology is how surfaces connect to adjacent surfaces of a part

Surface connectivity is controlled by the associated surface edges

If a surface edge is associated with more than 1 surface, those surfaces are considered to be connected (equivalenced)

Surface edges are categorized, named, and colored according to the number of associated surfaces:

Free edge (red) Associated with only 1

surface

Surfaces with a free edge between them are NOT

equivalenced at that edge

Shared edge (green) Associated with 2 surfaces Surfaces are equivalenced

Suppressed edge (blue) Surfaces are treated as though

combined into 1 surface

T-junction edge (yellow) Associated with 3 or more

surfaces

Example: surfaces forming a T-connection

Surfaces are equivalenced


Topology Repair: Viewing Topology

Topology display mode is default for some panels (w/ Auto ON)

surface edit, quick edit, point edit, edge edit, autocleanup, and automesh

Can also be accessed via geometry visualization type

Auto Default (topology display in only default panels mentioned above)

By Comp Always in component color mode

By Topo Always in topology display mode

By 2D Topo Displays only 2D geometry in topology display mode

By 3D Topo Displays only 3D geometry in topology display mode

Mixed Displays 2D and 3D geometry in topology display mode


Topology Repair: Viewing Topology

Toolbar > > Topology tab controls display of:

Visibility of free, shared, t-junctions, and suppressed edges

Visibility of fixed points

Level of surface transparency


Topology Repair: What is it?

HyperMesh will attempt to properly clean up surfaces during import

Some types of geometry files have surface connectivity information which helps HyperMesh. Typically native geometry files like Catia, UG, ProE, etc.

Geometry usually imports cleanly

Topology Repair consists of correcting connectivity errors between

adjacent surfaces

Possible errors include:

Unconnected adjacent surfaces

Duplicate surfaces

Missing surfaces

The Goal of Topology Repair: Restore the surface data to a perfectly clean representation of the part


Topology Repair: Process

General process is to:

Figure out what the ideal surface connectivity of the part should be

Observe the current display of topology colors (free, shared, t-junction)

Figure out what is causing the topology to be displayed this way

Use the tools in HyperMesh that get the connectivity from what it is to what it should be as quickly and efficiently as possible

Missing surface

created

Example:

Free edge pair

equivalenced

Duplicate surface

deleted


Topology Repair: Tools

Edge Edit Panel Equivalence (multiple edges at a time)

Search surfaces for pairs of free edges and combine into shared edges

Toggle (1 edge / edge pair at a time) Select an edge; equivalences with other free edges found within a user specified

tolerance

Replace (1 edge pair at a time) Select 2 edges to equivalence together

Control which edge to retain and which to move

Point Edit Panel Replace (1 edge at a time)

Release Combine pairs of free edges with gaps between them into a shared edges

Defeature Panel Duplicates Identify and delete duplicate surfaces within a user specified

tolerance

Surfaces Panel Spline / filler Select lines / surface edges to recreate any missing surfaces


Topology Repair: Tools

Quick Edit Panel

Has a number of tools found in other panels

Focused on tools with minimal user input for rapid editing

Unsplit Removes / deletes an edge created by splitting a surface in HyperMesh

Toggle Same as edge edit panel; change edge type within tolerance

Filler surf Select a line on a free surface edge to recreate any missing surfaces

Delete surf Same as delete panel (surfaces only)

Replace point Same as point edit panel; move/retain point

Release point Same as point edit panel; must be associated with line


Topology Repair: Strategy

Understand model size & scale to determine an appropriate global element size

Set a cleanup tolerance based on the determined global element size

Set appropriate value in options, geom cleanup, and automesh : cleanup

Cleanup tolerance specifies the largest gap size to be closed by topology functions

Tolerances > 15-20% of global element size can cause mesh distortions

Can change value multiple times for work on various areas of the model

Use topology display tools to decide what needs to be cleaned

Use equivalence to combine as many free edge pairs as possible

Make sure surfaces are not collapsed in undesirable manner

Use toggle to combine any remaining free edge pairs, 1 by 1

use replace function if more control is needed

Use find duplicates to check for any duplicate surfaces and delete them

Use filler surface to recreate any missing surfaces


Demo + Do-it-yourself

Exercise: Importing and Repairing CAD

Geometry Page 59


Midsurfacing: Introduction

For many FE analyses, parts are represented by shell elements

Thickness is assigned mathematically, rather than geometrically

Mesh is usually placed on the midplane of the part

CAD geometry usually comes as a solid part, or a series of surfaces defining a volume.

Midsurfacing creates a layer of surfaces on the midplane which can be directly meshed


Midsurfacing: Tools

Midsurfaces can be created using midsurface panel on the geom page

Auto Midsurface Automatically extracts midsurfaces from surfaces that enclose a volume or a solid geometry

Can sometimes work if there are missing surfaces

The greater number of missing surfaces, the less reliable the result

Surface Pair creates a midsurface between 2 selected surfaces


Midsurfacing: Tools

Once a midsurface has been created, it can be modified using tools on the

midsurface panel

Quick Edit Repair a midsurface by correcting where the verticies of the surface were placed

Assign Target An extension to quick edit, and functions in a similar fashion

Replace Edge Fill in gaps and slivers by combining one surface edge with another

same as in the edge edit panel

Extend Surface Extends two surfaces (e.g., ribs) until they intersect

View Thickness Review of the thickness of a midsurface using white lines (probes) extending from each vertex of the surface


Midsurfacing: Process & Strategy

1. Obtain a closed volume of surfaces or solids

Midsurface : auto midsurface requires an enclosed volume

Use topology repair techniques if needed

2. For complex parts, try defeaturing the surface defining the volume

This simplifies the part and may give better results with create : solid

3. Generate the midsurface using midsurface : auto midsurface

Use surface pair for areas that need more control

Use midsurface : editing tools for midsurfaces that need fine tuning

4. View the midsurface and correct errors using the midsurface editing

functionalities

Can generally use quick edit


Do-it-yourself

Exercise: Generating a Midsurface Page 70


Defeaturing: What is it?

Depending on the analysis, certain details in the geometry may be ignored.

This may depend on:

Importance of the part in the overall assembly

Location of the feature relative to the area of interest in the analysis

Size of the feature vs. the average size of the mesh being used

Defeaturing is the removal of details in the geometry in order to make the shape of the part simpler

Surface fillet

Pinholes

Edge fillets


Defeaturing: Tools

Defeature panel on Geom page

Pinholes: Searches for closed loops of free edges (holes) within a surface

Fills in the holes

Leaves fixed point at the center

Surf Fillets: Searches for surfaces that act as fillet between other surfaces

Tangentially extends them to form a sharp corner

Edge fillets: Searches for rounded corners on a surface

Squares off the corner

Duplicates: Finds and deletes duplicate surfaces

Symmetry: Finds symmetric surfaces within a single component

Deletes or organizes the surfaces into different components


Do-it-yourself

Exercise: Removing details from a

Midsurface Model Page 75


Topology Refinement: What is it?

Topology refinement is modifying topology in order to obtain a quality mesh

Unlike defeaturing, this generally does not change the shape of the part

CAD geometry has topology details that interfere with mesh quality

Edges are created where ever there is a change in surface curvature

Even smooth areas can be split into several faces

The automesher will be forced to place nodes along the edges and fixed points

This may cause small element lengths, angles, aspect ratios, etc. depending on the shape of the model

CAD geometry can also have surfaces with a complex outline

Highly complex shapes can make it hard to get a quality mesh

Adding in edges splits the surfaces into smaller and simpler regions which can be meshed easier

Fixed points can be added in to force a node to be placed at that location, giving more control


Topology Refinement: Examples

Suppressing

edges

Adding

edges

Removing

fixed points

Adding

fixed points

Replacing

fixed points

Aft

er

Befo

re


Topology Refinement: Tools

Edge edit

Toggle Select a shared edge to suppress it

(Un)Suppress Select multiple edges to suppress all of them at once

Point edit

Add Add fixed points to help control mesh pattern

Especially helpful along edges to control node seeding

Suppress Removes unwanted fixed points

Replace Combines 2 fixed points together at a single location

Project Projects fixed points onto a nearby edge

Useful for aligning mesh between 2 edges

Surface edit All functions add edges by cutting surfaces

Adding edges can be useful for controlling mesh patterns in large areas

Trim with nodes Uses node locations to cut surfaces

Trim with lines Uses lines to cut surfaces

Trim with surfs/plane uses other surfaces or a defined plane to cut surfaces



Quick edit Has a number of tools found in other panels

Focused on tools with minimal user input for rapid editing

Split surf-node: Adds an edge to or divides a surface by cutting in a straight line between 2 selected nodes

Split surf-line: Adds an edge to or divides a surface by cutting a straight line between a node and perpendicular to the selected line.

Washer split Adds a circular edge around a hole in a surface

Mostly used for creating all quad mesh around a hole

Toggle Same as edge edit panel

Remove Point Deletes a selected fixed point



Quick edit, continued

Replace point Same as point edit panel

Add/remove point : point Creates a new fixed point at the selected locations

Add point: line Creates a user specified number of fixed points along the selected edge

Project point Same as edge edit panel


Topology Refinement: Tips

Mesh the part

Visually scan the part to look for poor mesh patterns

Use element checks in order to find areas of poor element quality

Check elems panel, QI Panel, etc.

Suppress edges with edge edit :(un)suppress

Use various settings for break angle to suppress many edges at once

Sometimes suppressing all edges and then unsuppressing desired edges can be a good method.

Suppress all the fixed points before add more in

Gets rid of as many fixed points as possible, leaving ones that are required

Experiment!

There is no set process, so experience is a key factor in refining topology


Do-it-yourself

Exercise: Refining Topology to Achieve a

Quality Mesh Page 84


Automeshing

Checking and Editing Mesh

Batch Meshing

Chapter 3: Shell Meshing


Automeshing: What is it?

The automesh panel creates shell mesh on existing surfaces

Allows rapid generation of mesh

Most parts from CAD software come in as surfaces

Automeshing allows all surfaces of a part to be meshed at the same time

Mesh on properly connected geometry assures proper connectivity of mesh


Automeshing: What is topology?

Topology is how surfaces connect to adjacent surfaces of a part

Surface connectivity is controlled by the associated surface edges

If a surface edge is associated with more than 1 surface, those surfaces are considered to be connected (equivalenced)

Surface edges are categorized, named, and colored according to the number of associated surfaces:

Free edge (red) Associated with only 1

surface

Surfaces with a free edge between them are NOT

equivalenced at that edge

Shared edge (green) Associated with 2 surfaces Surfaces are equivalenced

Suppressed edge (blue) Surfaces are treated as though

combined into 1 surface

T-junction edge (yellow) Associated with 3 or more

surfaces

Example: surfaces forming a T-connection

Surfaces are equivalenced


Automeshing: How topology affects the mesh

Surface edges control how mesh created on adjacent surfaces interact:

Free edge between

2 surfaces

Nodes are placed along

edge for meshing

Mesh is discontinuous;

nodes along the free edge

are not equivalenced

(Nodes only separated for

illustration)

5

5

5

2

2 3

3

Shared edge between

2 surfaces

Mesh has proper

connectivity; nodes along

the edge are equivalenced


edge for meshing

Free edges (red) Shared edges (green)

5

5

5

2

2 3

3

5


Automeshing: How topology affects the mesh

Surface edges control how mesh created on adjacent surfaces interact:

Suppressed edge

between 2 surfaces

Edge is ignored; nodes

are not placed along

the edge

Area is treated just like 1

surface; there is no line

of nodes along the edge

Non-manifold edge

between 3 surfaces

Mesh has proper

connectivity; nodes along

the edge are equivalenced


edge for meshing

5

5

5 5

5

5

5

5

4

4 3

3

3 3

Suppressed edges (blue) T-junction edges (yellow)


Automeshing: Process and Strategy

Use geometry cleanup tools to address surface connectivity

Automesh the surfaces

Set the approximate element size you want

Use type and algorithm to set the overall mesh style

Alter individual densities to find better mesh patterns

Change some biasing on problem surfaces (this can change mesh pattern as well)

Use HyperMeshs mesh editing tools to fix the 10-20% elements that have poor quality or bad mesh pattern

Dont delete a mesh that is 90% good. Keep it and fix the 10% that is bad

Experience is key: EXPERIMENT!

Goal: get the mesh to be approximately 80-90% good quality



Exercise: Meshing a Channel Bracket Page 101



Exercise: Mesh cleanup of a Plastic

Cover Page 113


Batch Meshing: Introduction

Performs geometry cleanup and automeshing in a batch mode

Can dramatically improve productivity since there is minimal user interaction (especially for large assemblies)

Uses criteria and parameter files to determine how the parts should be meshed

Can mesh multiple files in the same run


Batch Meshing: Process & Required Input

1. Create / specify Configurations

Combination of element criteria and geometric parameters

Element criteria are element quality requirements

Geometric parameters are other requirements (element

type, removal of pinholes,

removal of fillets, etc.)

Criteria and parameters can be edited with the Criteria and

Parameters Files Editor



2. Register and specify User Procedures (optional)

Custom TCL scripts (macros) created by the user

Performs additional operations on models during the batch run

Pre Run and Post Run options can specify procedures performed before or after the run

Can specify when the procedure should be performed during the run

Pre-geometry load as soon as batch mesher is invoked

Pre-batch mesh just before loaded geometry is meshed

Post-batch mesh after meshing is finished

3. Set up the Batch Mesh job

Specify a directory where geometry files are located

Select geometry files from the directory

Select a configuration to use for the mesh type for each file

Specify any user procedures to be performed on each part

Specify a directory where the meshed files will be located

Run the batch mesh job



4. Monitor the Run Status of the job

Use the Run Status tab to keep track of all your submitted jobs

Use Load Mesh to open a selected file in a new HyperMesh session to view the resulting mesh



Exercise: Batch Meshing a Shell Bracket Page 130

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