Femap Topology Optimization

FEMAP

Topology Optimization

Version 10.3

MUF1000-GS-102

Proprietary and Restricted Rights Notice © 2011 Siemens Product Lifecycle Management Software Inc. All Rights Reserved. This software and related documentation are proprietary to Siemens Product Lifecycle Management Software Inc. All trademarks belong to their respective holders.

Siemens PLM Web:

http://www.femap.com

Customer Support Phone: Web:

(714) 952-5444, (800) 955-0000 (In US & Canada) http://support.ugs.com

The following copyright refers only to the “bmp2raster.exe” executable distributed with FEMAP: NeuQuant Neural-Net Quantization Algorithm Copyright (c) 1994 Anthony Dekker NEUQUANT Neural-Net quantization algorithm by Anthony Dekker, 1994. See "Kohonen neural networks for optimal colour quantization" in "Network: Computation in Neural Systems" Vol. 5 (1994) pp 351-367 for a discussion of the algorithm. See also http://members.ozemail.com.au/~dekker/NEUQUANT.HTML Any party obtaining a copy of these files from the author, directly or indirectly, is granted, free of charge, a full and unrestricted irrevocable, world-wide, paid up, royalty-free, nonexclusive right and license to deal in this software and documentation files (the "Software"), including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons who receive copies from any such party to do so, with the only requirement being that this copyright notice remain intact.

Conventions This manual uses different fonts to highlight command names or input that you must type.

a:setup

Shows text that you should type.

OK, Cancel

Shows a command name or text that you will see in a dialog box.

Throughout this manual, you will see references to Windows. Windows refers to Microsoft® Windows XP, Windows Vista, and Windows 7 (32-bit and 64-bit versions). You will need one of these operating environments to run FEMAP for the PC. This manual assumes that you are familiar with the general use of the operating environment. If you are not, you can refer to the Windows User’s Guide for additional assistance. Similarly, throughout the manual all references to FEMAP, refer to the latest version of our software.

FEMAP Topology Optimization Proprietary and Restricted Rights Notice 1. Introduction Introduction to Topology Optimization in FEMAP • Set up the Topology Optimization parameters • Analyze Your Model . . . . . • Post-process Results . . . . . Overview of Topological Optimization Module . • Results . . . . . . . .

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1. Topology Optimization Interface

FEMAP Analysis Set Manager - Gateway to Topology Optimization 1. Topology Optimization Definition . . . . . • Quick Groups icon Button . . . . . . . • Optimization Options and Manufacturing Constraints . • Optimization Post Processing . . . . . . • Optimization Analysis Monitor . . . . . . Using the Examples . . . . . . . . . • Working through the Examples . . . . . . • Using the Examples . . . . . . . .

2. Optimizing a Dome Structure

Importing the FEMAP Neutral File . . . Creating an Analysis Set with Topology Optimization • Analyzing the Model . . . . . Viewing the Optimized Shape . . . . Using a Freeze Group . . . . . . Using Planar Symmetry options . . . .

3. Optimizing a Solid Wheel

Importing the FEMAP Neutral File . . . Creating an Analysis Set with Topology Optimization • Analyzing the Model . . . . . Viewing the Optimized Shape . . . . Using Rotational Symmetry options . . .

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TOC-2

1.

Introduction

This section introduces Topology Optimization in FEMAP.

Introduction to Topology Optimization in FEMAP FEMAP can preform Topology Optimization in Static and Modal Analysis by using TOSCA Structure by FE DESIGN, Germany, along with a licensed copy of NX Nastran. In general, Topology Optimization determines the optimized distribution of material within a given space to create an optimized design, based on the applied loads and boundary conditions. Typically, this type of optimization removes material from the original design by creating holes, cutouts, or indentations, and/or dramatically altering the overall shape of the part. An existing finite element model must be created to determine the allowable design space before any type of topology optimization may be attempted. Typically, smaller design features should be removed before the optimization process begins. As with any finite element process, the proper definition and application of materials, properties, loads, boundary conditions, and other analysis paramaters will greatly impact the accuracy and usefulness of the results. For Topology Optimization, FEMAP with NX Nastran and the Design Optimization Module can: •

Set up the Topology Optimization paramaters.

•

Analyze Your Model

•

Post-process Results

Set up the Topology Optimization parameters Setting up the Topology Optimization paramaters in FEMAP is much like setting up any other type of analysis. This is done using the Analysis Set Manager. This control displays a series of dialog boxes which guide you through the inputs needed and options available for the specified Analysis Type. For Topology Optimization, setting the Analysis Type to Static or Normal Modes/Eignevalue will display the dialog boxes needed to enter the parameters. Also, the Topology Optimization options will only appear when a license exists for Topology Optimization.

Analyze Your Model When your model is complete, FEMAP provides an automatic way to launch the topological optimization solver and track the process of the optimization process.

Post-process Results After your topological optimization analysis is complete, FEMAP will allow the viewing of the optimized shape using groups and/or output data generated by the optimization process for the original model.

1-2

Introduction

Overview of Topological Optimization Module Inputs The topology optimization module used by Femap is based on TOSCA Structure by FE DESIGN, Germany. Its capabilities include optimization for Statics and Modes using NX Nastran solver. Parameters that may be optimized are weight (mass), Eigenfrequency, and stiffness. Constraints may be applied in the form of target volume reduction or limiting displacement. There are three optimization goal types: •

Maximize Stiffness & Reduce Volume

•

Maximize Eigenfrequency & Reduce Volume

•

Minimize Volume & Constrain Displacement

The topology optimization module uses NX Nastran results to drive an iterative material distribution process. After conducting an initial analysis step (step 0), the optimization algorithm analyzes the results for all loadcases and elements. It then determines which elements may have their material properties “softened” to simulate structural discontinuities and still satisfy required goals and constraints. The module then continues to iterate using NX Nastran solver to test model changes until convergence is achieved or it reaches a set maximum limit of 50 iterations. The topology optimization module does not add elements or reshape outer boundaries of the model in any way. Linear, parabolic and rigid elements are supported, as well as contact conditions. Manufacturing constraints may also be applied as needed. These include: Symmetry, structural member size ( max or min ), as well as various casting constraints. Areas may also be designated as not to be changed (frozen). Loaded and constrained elements may be auto-frozen.

Results Results produced include a smoothed optimized shape and various output set data vectors. Shape data is stored as industry standard STL file. Optimized shape is automatically or directly imported into Femap as a mesh consisting of triangular plot-only plate elements. When imported, creates a new group or will be placed into a selected group. The data vectors, which are placed into a new output set, are: E_CTRL: The envelope maximum average Von Mises stress for each element. MASS_PROP: Modifed element density (actual) MASS_PROP_NORMALIZED: Modified element density (normalized) Final Nastran .dat and .op2 files are retained and may be imported into femap.

1.

Topology Optimization Interface

This section discusses the Topology Optimization interface in FEMAP.

FEMAP Analysis Set Manager - Gateway to Topology Optimization All available options for Topology Optimization are set by using the Analysis Set Manger in FEMAP. To access the Analysis Set Manager, use the Model, Analysis command or “right-click” the Analyses heading in the Model Info tree and choose Manage from the context-sensitive menu. The following window will appear:

By default, no “Analysis Sets” exist. Click New to create a new Analysis Set. The Analysis Set dialog box will be displayed which allows you to enter a Title, choose an Analysis Program, and choose an Analysis Type. Currently in FEMAP, the only supported Analysis Program for Topology Optimization is “36..NX Nastran” and the only supported Analysis Types are “1..Static” and “2..Normal Modes/Eigenvalue”. If you simply click OK after choosing a program and type, a new “Analysis Set” will appear in the window to the left. You will notice that each Analysis Set contatins a tree structure which displays some general information, plus allows you to specify Options and/or set Master Requests and Condtions. Typically the Options contain solver specific information for the type of analsyis being performed, while Master Requests and Conditions allow you to specify Boundary Conditions (using

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Topology Optimization Interface

pre-defined Load or Constraint sets) and select Output Requests. For Topology Optimization, we will focus on the Options section, specifically, the Topolpgy Optimization “branch”. All the available parameters for Topology Optimization may be accessed by highlighting the Topology Optimization heading, then clicking the Edit button:

There are 3 dialog boxes for Topology Optimization, Topology Optimization Definition, Optimization Options and Manufacturing Constraints, and Optimization Post Processing. Use the Prev and Next buttons in each dialog box to navigate between the different Topology Optimization options. The dialog boxes for Topology Optimization will now be discussed in detail.

Topology Optimization Definition

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Topology Optimization Definition

First and foremost, the Topology Optimization Definition dialog box is used to “activate” the Topology Optimization capabilities when the model is solved. Only when the Active box is checked, will FEMAP attempt to optimize the part. The directory path to the right of the Active check box is where the model is currently located. This is where all additional files related to Topology Optimization will also be stored. File Name (.par) - Allows to specify a name for a parameter file. By default, this name will match the name of the FEMAP model file, but may be changed to anything else with a .par extension. Design Goal - Allows you to choose a design goal for the topological optimization (i.e., what the optimization is trying to accomplish). There are 3 different options: •

1..Maximize Stiffness & Reduce Volume - Reduces the volume of the “design area” as much as possible while maximizing the overall stiffness of the part for the applied boundary conditions. Uses the Percent Volume Reduct. field as an input for the target volume reduction.

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2..Maximize Eigenfrequency & Reduce Volume - Reduces the volume of the “design area” as much as possible while maximizing the value of the first eigenfrequency using applied boundary conditions. Uses the Percent Volume Reduct. field as an input for the target volume reduction.

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3..Minimize Volume & Constrain Displacement - Reduces the volume of the “design area” as much as possible while allowing a specified Displacement Node to displace only to a specified Displacement Limit value by the final iteration.

Design Group (Elements) - Either use the “0..Include All Elements” option or select a group currently in the model to indicate to Topology Optimization which elements may be removed from the “design area”. Volume Group (Elements) - Either use the “0..Include All Elements” option or select a group currently in the model to indicate to Topology Optimization which elements may be removed to reduce volume. Percent Volume Reduct. - Option is used to specify the volume reduction value when Design Goal is set to “1..Maximize Stiffness & Reduce Volume” or “2..Maximize Eigenfrequency & Reduce Volume”. Value is how much volume should be removed from the model, so if set to “30”, the model would retain “70” percent of original volume of the “Volume Group”. Default value is 30. Displacement Limit and Displacement Node - Options are only used when Design Goal is set to “3..Minimize Volume & Constrain Displacement”. Displacement Limit should be a real number representing a “max displacement” for the Displacement Node, which must be a node ID which currently exists in the model. Default value for Displacement Limit is “model diagonal/5000”.

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Topology Optimization Interface

Quick Groups icon Button Available in each of the dialog Topology Optimization dialog boxes, this button accesses the Quick Group dialog box. Allows you to make a group (elements only) on-the-fly. The Quick Group dialog box contains several buttons which allow you to perform different functions:

List of groups - Highlight a single group in the list, then click the buttons to edit, rename, or show the highlighted group. New Group - Creates a new group and allows the user to enter a title. Edit Group - Allows you to Add, Remove, or Exclude elements from the highlighted group. Rename - Renames the highlighted group. Show - Shows the highlighted group in the graphics window using the settings currently selected in the “Window, Show Entities” command or specified the Show When Selected icon menu in the Model Info tree or the Data Table.

Optimization Options and Manufacturing Constraints Optimization Options include choosing a Freeze Group, “auto-freezing” the Loaded and Constained Elements, and setting up Symmetry. The Manufacturing Constraints are Wall Thickness and Casting, which each can use a group or the whole model.

Optimization Options and Manufacturing Constraints

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Options Freeze Group - When on, allows you to choose a group of elements that must not be modified during optimization. Automatically Freeze - Automatically prevents modification of elements based on the selected option. There are 4 options: •

0..None - All elements NOT in the Freeze Group may be modified during optimization..

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1..Both - All loaded elements or elements with loaded or constrained nodes will NOT be modified during optimization.

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2..Loads - All loaded elements or elements with loaded nodes will NOT be modified during optimization..

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3.. Constraints - All elements with constrained nodes will NOT be modified during optimization.

Symmetry Symmetry Group - When on, allows you to choose a group of elements that will retain specified symmetry after optimization. There is an option to include all elements. Type - Choose between: •

0..Plane Symmetry - Symmetry is maintained on both side of a plane which is perpindicular to the specified Vector. The specified Vector is the X, Y, or Z axis of the selected Coordinate System (Coord Sys).

•

1.. Rotation Symmetry - Symmetry is maintained around the specified Vector (X, Y, or Z) of the selected Coordinate System (“Axis of symmetry”). The number of “symmetry sections” is defined by the Rotation Angle (Rot. Angle). For instance, if the Rot. Angle is set to 60, then there would be 6 “symmetry sections” (360/60 = 6) around the “axis of symmetry”.

Coord Sys - Choose an existing coordinate system for plane or roatation symmetry Coordinate System icon button - Create a new coordinate system without having to leave the analysis set manager. Follows the same procedure as the Model, Coord Sys command. Show icon button - Shows the highlighted group in the graphics window using the settings currently selected in the “Window, Show Entities” command or specified the Show When Selected icon menu in the Model Info tree or the Data Table. Wall Thickness Wall Thickness Group - When on, allows you to choose a group of elements that will retain specified wall thickness (gauge) after optimization. There is an option to include all elements. Min or Max - use radio button to select either Min or Max. Used to specify the thinnest (Min) or thickest (Max) wall thickness (gauge) which can exist after optimization. Default for Min value is Displacement Limit*30. Casting Casting Group - When on, allows you to choose a group of elements that need to have walls parallel to extract vector without undercuts. There is an option to include all elements. Midplane - Choose between: •

0..None - No central plane defined. Shape can be extracted from mold in the direction of Extract Vector

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1..Auto - Central plane automatically determined. Shape can be extracted from mold in the +/- Extract Vector direction

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2..Auto Tight - Same as 1..Auto, except optimization assures no holes are generated in central plane of optimized shape

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3.. Stamp - Optimized shape will be “stamp-able” in Extract Vector direction.

Extract Vector button - Allows you to specify a “vector” to use as the “Extract Vector”. “Vector” is normal to a plane defined using the standard Plane Locate dialog box in FEMAP. Check Group - When on, allows you to choose a group of elements guiding or hindering extraction from the mold.

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Topology Optimization Interface

Optimization Post Processing Allows you to select if you would like to import the Shape Data and/or the Results Data from the Topology Optimization run. Also, allows you to choose if you would like to see the Shape Data and/or Results Data from the final iteration (data placed in your choice of a new group or a selected existing group) or all iterations of the optimization process.

Shape Data Import Shape Data into Group - On by default. When on, imports the STL file containing the shape data into FEMAP. This STL file will create triangular plot-only plate elements representing the optimized shape. Iterations - 0..Final Iteration is the default and will only import the shape from the final iteration into either a new group or a group selected using the Import Into: option. When set to 1..All Iterations, the shape data from each optimization iteration will be imported and placed into a new group. Smoothing - Determines the positions on the element edges where the new nodes are created. Larger values lead to models with smaller volume. Value between 0 and 1. Default value is 0.3. Import Into - Only used when Iterations is set to 0..Final Iteration. Allows you to import Shape Data into a New Group or select and existing group. Results Data Import Results as Femap Output - Off by default. When on, imports results for “element density” in both actual and “normalized” format. Results are always placed into a new output set or sets. Iterations - 0..Final Iteration is the default and will only import the results data from the final optimization step into a new output set. When set to 1..All Iterations, the results data from each optimization iteration will be imported and placed into a new output set.

Optimization Analysis Monitor When the Topology Optimization is running, the Optimization Analysis Monitor will open. This monitor will update as the analysis progresses. There are for options which can be viewed, 2 which show text and 2 which show graphs of the progress. log - simply shows the log file being generated by Topology Optimization. par - simply shows the Topology Optimization parameters file (*.par) being used for the current Topology Optimization analysis. Design Objective - graphs the progress of the optimization process towards the Design Objective. VOLUME_CONSTRAINT or DISPLACEMENT_CONSTRA - Tranks of the constraint (volume or displacement) as the optimization process progresses.

Optimization Analysis Monitor

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Topology Optimization Interface

Using the Examples The FEMAP Topology Optimization guide is designed to teach new users the basics of using Topology Optimization. It contains a number of examples that take you step-by-step through the processes using the Topology Optimization module.

Working through the Examples As there are many different types of real analysis problems, there are different types of example problems shown here. Generally, you should start with the first example in chapter 3 and work through the examples sequentially. •

Optimizing a Dome Structure

•

Optimizing a Solid Wheel

Using the Examples

2-9

Using the Examples In general, italicized text identifies items in the user interface. For example: File, Preferences tells you to pick the File menu, then the Preferences command. The Examples also include some graphics to help you identify user interface (UI) items. They include: UI Graphic

Meaning Pick an option from a cascading menu.

Menu

Pick an item from a pull-down menu on a dialog box.

Pick an item from a list.

Pick an icon.

Enter a value into a field on a dialog box.

Pick a button.

Pick a radio button.

Check an item on or off in a dialog box.

Pick with the left mouse button.

Pick with the right mouse button.

Pick with middle mouse button if you have a three button mouse. Also can be the wheel of a wheel mouse.

Ctrl-A

Hold the Control key, then pick the letter key.

F5 key

Pick the function key.

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Topology Optimization Interface

2.

Optimizing a Dome Structure

In this first example, you will optimize a dome structure made of shell elements several times using some of the different topology optimization options available within FEMAP. Please remember, you will need a Topology Optimization license to set-up and run the analysis. Also, the sole purpose of these examples is to demonstrate the Topology Optimization capabilities. If you are looking for examples which cover other aspects (model building, meshing, post-processing, etc.), please see the FEMAP Examples manual.

You will work through the entire FEMAP analysis process, which includes: •

importing a FEMAP Neutral file of the Dome

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setting up the topology optimization parameters

•

analyzing the model using the NX Nastran solver with the Topology Optimization add-on

•

post-processing the results by viewing optimized shapes

Importing the FEMAP Neutral File What Import a FEMAP neutral file containing the geometry of the dome.

How Step

UI

Command/Display

1.

File, New Menu

2.

File, Import, FEMAP Neutral Menu

3-2 Step

UI

Optimizing a Dome Structure

Command/Display

3.

Read Model from FEMAP Neutral dialog box: Go to: FEMAP_INSTALL_FOLDER\fnxtopol\Examples directory

4.

File name: static dome.neu Open Neutral File Read Options dialog box: OK

5.

File, Save Menu

Give the model a name and save it into a directory. A directory which exists for the sole purpose of storing the models and data of Topology Optimization is recommended.

Creating an Analysis Set with Topology Optimization Analyzing the Model The analysis sets are stored with the FEMAP model file, and can also be stored in a FEMAP library that can be accessed from different model files.

What Create the analysis set, specify topology optimization parameters, and solve the model.

Analyzing the Model

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How Step

UI

Command/Display

1.

Model, Analysis Menu

2.

Analysis Set Manager dialog box: New

3.

Analysis Set dialog box: Title: Dome Optimization

4.

Analysis Program: 36..NX Nastran Analysis Type: 1..Static

5.

Click Next 5 times

6.

In the Topology Optimization Definition dialog box: CHECK the Active box. The File Name (.par) should be the model name with a .par extension. This may be changed to a different name if you like, but the default will work.

7.

Design Goal: 1..Maximize Stiffness & Reduce Volume Design Group (Elements): 0..Include All Elements Volume Group (Elements): 0..Include All Elements

8.

Percent Volume Reduct.: 30

9.

Click Next

10.

In the Optimization Options and Manufacturing Constraints dialog box: Set Automatically Freeze: 2..Loads

3-4 Step 11.

UI

Optimizing a Dome Structure

Command/Display Click Next In the Optimization Post Processing dialog box: Make sure: Import Shape Data into Group is checked Iterations is set to “0..Final Iteration” Smoothing Value = 0.3 Import Into is set to “0..New Group”

12.

Click OK, then Click Analyze Notice: The Optimization Analysis Monitor will display the status of the solve. You’ll know that the solve is done when the Load Results button becomes active. Also, the triangular plotonly plates used to represent the optimized shape will be shown highlighted in the graphics window.

Viewing the Optimized Shape Typically, the reason to do topology optimization is to get an optimized shape which may then be viewed and compared to the original part.

What Display the optimized shape. Because we chose to store the shape results in a new group, the best way to view the optimized shape will be to display only that group.

Using a Freeze Group

3-5

How Step 1.

UI

Command/Display Click View Visibility icon (on View Toolbar) OR Press Crtl+Q. Visibility dialog box: Choose the Group tab.

2.

In the Group tab Click Show Active Group

3.

Select “3..Optimized Shape” from the Show Active Group drop-down.

4.

Click Done

This is the optimized shape for a 30 percent volume reduction where only the loaded and constrained elements are “frozen” based on the Auto-freeze Loaded Elements option.

Using a Freeze Group What Choose an existing group as a Freeze Group, then run the topology optimization again.

3-6

Optimizing a Dome Structure

How Step

UI

Command/Display

1.

Click View Visibility icon (on View Toolbar) OR Press Crtl+Q. Visibility dialog box: Choose the Group tab.

2.

In the Group tab Click Show Active Group

3.

Select “2..Frozen” from the Show Active Group drop-down.

4.

Click Done

This is agroup which has been pre-defined for this example. It consists of the bottom 2 rows of shell elements.

5.

Model, Analysis Menu

6.

Analysis Set Manager dialog box: Edit, then... Click Next 6 times

7.

In the Optimization Options and Manufacturing Constraints dialog box: CHECK the Freeze Group box.

Using a Freeze Group

Step

UI

3-7

Command/Display

8.

Freeze Group: 2..Frozen

9.

Click OK, then Click Analyze Notice: The Optimization Analysis Monitor will display the status of the solve. You’ll know that the solve is done when the Load Results button becomes active. Also, the triangular plotonly plates used to represent the optimized shape will be shown highlighted in the graphics window.

What Display the optimized shape. Because we chose to store the shape results in a new group, the best way to view the optimized shape will be to display only that group.

How Step 1.

UI

Command/Display Click View Visibility icon (on View Toolbar) OR Press Crtl+Q. Visibility dialog box: Choose the Group tab.

2.

In the Group tab Click Show Active Group

3-8 Step

UI

Optimizing a Dome Structure

Command/Display

3.

Select “4..Optimized Shape” from the Show Active Group drop-down.

4.

Click Done

This is the optimized shape for a 30 percent volume reduction where both the loaded and constrained elements and the “Freeze Group” are “frozen” based on the Auto-freeze Loaded Elements option. You can see how all the material representing the “Freeze Group” has been left intact.

If you rotate the model, you will see that different amounts of material have been removed from various areas in the model. Many times, a “symmetricl shape” is preferred, therefore we will set up symmetry on this model.

Using Planar Symmetry options What Set up Symmetry options. We will be using the X-axis of user-defined coordinate system to specify a plane of symmetry. In other words, the X-axis is a vector normal to the plane of symmetry.

How Step

UI

Command/Display

1.

Model, Analysis Menu

Using Planar Symmetry options

Step 2.

UI

3-9

Command/Display Analysis Set Manager dialog box: Edit, then... Click Next 6 times

3.

In the Optimization Options and Manufacturing Constraints dialog box: CHECK the Symmetry Group box.

4.

Coord Sys: 3..Rectangular Coordinate System Vector: 0..X

5.

Click the Show icon button to highlight the coordinate system in the model.

6.

Click OK, then Click Analyze Notice: The Optimization Analysis Monitor will display the status of the solve. You’ll know that the solve is done when the Load Results button becomes active. Also, the triangular plotonly plates used to represent the optimized shape will be shown highlighted in the graphics window.

What Display the optimized shape. Because we chose to store the shape results in a new group, the best way to view the optimized shape will be to display only that group.

3-10

Optimizing a Dome Structure

UI

Command/Display

How Step 1.

Click View Visibility icon (on View Toolbar) OR Press Crtl+Q. Visibility dialog box: Choose the Group tab.

2.

In the Group tab Click Show Active Group

3.

Select “5..Optimized Shape” from the Show Active Group drop-down.

4.

Click Done

This is the optimized shape for a 30 percent volume reduction where both the loaded and constrained elements and the “Freeze Group” are “frozen” based on the Auto-freeze Loaded Elements option. You can see how all the material representing the “Freeze Group” has been left intact Finally, the shape is symmetrical about the specified plane of symmetry.

This is the end of the example. Save the model with the 3 different optimized shapes.

3.

Optimizing a Solid Wheel

In this example, you be optimizing a model made with solid elements and take advantage of the rotational symmetry option. The “Pully Wheel” is constrained around the outside edge and a tourque load is applied at the hole in the center of the “wheel”.

The example includes the following steps: •

importing a FEMAP Neutral file of the Wheel

•

setting up the topology optimization parameters, including rotational symmetry

•

analyzing the model using the NX Nastran solver with the Topology Optimization add-on

•

post-processing the results by viewing optimized shapes

4-2

Optimizing a Solid Wheel

Importing the FEMAP Neutral File What Import a FEMAP neutral file containing the geometry of the wheel.

How Step

UI

Command/Display

1.

File, New Menu

2.

File, Import, FEMAP Neutral Menu

3.

Read Model from FEMAP Neutral dialog box: Go to: FEMAP_INSTALL_FOLDER\fnxtopol\Examples directory

4.

File name: wheel.neu Open Neutral File Read Options dialog box: OK

5.

File, Save Menu

Give the model a name and save it into a directory. A directory which exists for the sole purpose of storing the models and data of Topology Optimization is recommended.

Creating an Analysis Set with Topology Optimization

4-3

Creating an Analysis Set with Topology Optimization Analyzing the Model The analysis sets are stored with the FEMAP model file, and can also be stored in a FEMAP library that can be accessed from different model files.

What Create the analysis set, specify topology optimization parameters, and solve the model.

How Step

UI

Command/Display

1.

Model, Analysis Menu

2.

Analysis Set Manager dialog box: New

3.

Analysis Set dialog box: Title: Wheel Optimization

4.

Analysis Program: 36..NX Nastran Analysis Type: 1..Static

5.

Click Next 5 times

6.

In the Topology Optimization Definition dialog box: CHECK the Active box. The File Name (.par) should be the model name with a .par extension. This may be changed to a different name if you like, but the default will work.

7.

Design Goal: 1..Maximize Stiffness & Reduce Volume Design Group (Elements): 0..Include All Elements Volume Group (Elements): 0..Include All Elements

8.

Percent Volume Reduct.: 48

9.

Click Next

10.

In the Optimization Options and Manufacturing Constraints dialog box: Set Automatically Freeze: to 2..Loads

4-4 Step 11.

UI

Optimizing a Solid Wheel

Command/Display Click Next In the Optimization Post Processing dialog box: Make sure: Import Shape Data into Group is checked Iterations is set to “0..Final Iteration” Smoothing Value = 0.3 Import Into is set to “0..New Group”

12.

Click OK, then Click Analyze Notice: The Optimization Analysis Monitor will display the status of the solve. You’ll know that the solve is done when the Load Results button becomes active. Also, the triangular plotonly plates used to represent the optimized shape will be shown highlighted in the graphics window.

Viewing the Optimized Shape Typically, the reason to do topology optimization is to get an optimized shape which may then be viewed and compared to the original part.

What Display the optimized shape. Because we chose to store the shape results in a new group, the best way to view the optimized shape will be to display only that group.

Using Rotational Symmetry options

4-5

How Step 1.

UI

Command/Display Click View Visibility icon (on View Toolbar) OR Press Crtl+Q. Visibility dialog box: Choose the Group tab.

2.

In the Group tab Click Show Active Group

3.

Select “2..Optimized Shape” from the Show Active Group drop-down.

4.

Click Done

This is the optimized shape for a 48 percent volume reduction where only the loaded and constrained elements are “frozen” based on the Auto-freeze Loaded Elements option.

Using Rotational Symmetry options What Set up Symmetry options. We will be using the Z-axis of user-defined coordinate system as the axis of symmetry and choose to create a “symmetrical section”every 30 degrees.

4-6

Optimizing a Solid Wheel

How Step

UI

Command/Display

1.

Model, Analysis Menu

2.

Analysis Set Manager dialog box: Edit, then... Click Next 6 times

3.

In the Optimization Options and Manufacturing Constraints dialog box: CHECK the Symmetry Group box.

4.

Type: 1..Rotational Symmetry Coord Sys: 3..Rectangular Coordinate System Vector: 2..Z

5.

Rot. Angle: 30

6.

Click the Show icon button to highlight the coordinate system in the model.

7.

Click OK, then Click Analyze Notice: The Optimization Analysis Monitor will display the status of the solve. You’ll know that the solve is done when the Load Results button becomes active. Also, the triangular plotonly plates used to represent the optimized shape will be shown highlighted in the graphics window.

Using Rotational Symmetry options

4-7

What Display the optimized shape. Because we chose to store the shape results in a new group, the best way to view the optimized shape will be to display only that group.

How Step 1.

UI

Command/Display Click View Visibility icon (on View Toolbar) OR Press Crtl+Q. Visibility dialog box: Choose the Group tab.

2.

In the Group tab Click Show Active Group

3.

Select “3..Optimized Shape” from the Show Active Group drop-down.

4.

Click Done

This is the optimized shape for a 48 percent volume reduction where both the loaded and constrained elements are “frozen” based on the Auto-freeze Loaded Elements option. Also, the shape is symmetric about the sxis fo rotational symmetry.

What Change the Symmetry options. We will still be using the Z-axis of user-defined coordinate system as the axis of symmetry, only this time we will create a “symmetrical section”every 60 degrees.

4-8

Optimizing a Solid Wheel

How Step

UI

Command/Display

1.

Model, Analysis Menu

2.

Analysis Set Manager dialog box: Edit, then... Click Next 6 times

3.

In the Optimization Options and Manufacturing Constraints dialog box: Rot. Angle: 60

4.

Click OK, then Click Analyze Notice: The Optimization Analysis Monitor will display the status of the solve. You’ll know that the solve is done when the Load Results button becomes active. Also, the triangular plotonly plates used to represent the optimized shape will be shown highlighted in the graphics window.

What Display the optimized shape. Because we chose to store the shape results in a new group, the best way to view the optimized shape will be to display only that group.

Using Rotational Symmetry options

4-9

How Step 1.

UI

Command/Display Click View Visibility icon (on View Toolbar) OR Press Crtl+Q. Visibility dialog box: Choose the Group tab.

2.

In the Group tab Click Show Active Group

3.

Select “4..Optimized Shape” from the Show Active Group drop-down.

4.

Click Done

This is the optimized shape for a 48 percent volume reduction where both the loaded and constrained elements are “frozen” based on the Auto-freeze Loaded Elements option. Also, the shape is symmetric about the sxis fo rotational symmetry.

This is the end of the example. Save the model with the 3 different optimized shapes.