BESO3D

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Centre for Innovative Structures and Materials, RMIT University

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BESO3D Manual Getting started with BESO3D

Zhihao Zuo

Centre for Innovative Structures and Materials

RMIT University, Australia

Two sections are included in this manual: Step-by-step Instruction of using BESO3Dand Cautions.

An example is demonstrated in the first section showing a straightforward guide and the second

section is dedicated to a brief description of cautions of using BESO3D.

STEP-BY-STEP INSTRUCTION OF USING BESO3D:

In this section, we will demonstrate, step by step, the procedure of optimizing a structure using

BESO3D as a post-processor of ABAQUS1, from creating a model in ABAQUS/CAE, to optimize

the structure using BESO3D package, to inspecting the final solution. The whole procedure

includes the following steps:

1. Creating an ABAQUS input file for the initial design of the structure.

2. Optimizing the structure using BESO3D.

3. Inspecting the final solution.

4. Continuing optimization from the obtained solution.

To illustrate these steps, a 3D cantilever shown in Figure 1 is used as an example. As length and

force in ABAQUS are dimensionless, no unit is specified in Figure 1 and in the example. Yet the

user can still have prescribed units for default.

20

40100

Figure 1Design domain of a 3D cantilever.

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Furthermore, we assume that the user has a working folder D:\BESO3D\ where the user has full

control, i.e. file reading, writing and deleting.

1. Creating an ABAQUS input file for the initial design of the structure

First we need to build up the 3D cantilever model and store it in an ABAQUS input file using

ABAQUS/CAE. As introducing ABAQUS is not the main task of this manual, we assume the user

has the preliminary knowledge for ABAQUS/CAE and ABAQUS/Standard and only describe this

step briefly. The version of ABAQUS used in this example is 6.7.1, the same actions/steps apply to

versions 6.4 and above as well.

This step is described as the following actions:

Start ABAQUS/CAE. In order to write the later INP file into the working folder, we would

like to start ABAQUS/CAE from the working folder. Command line is as in Figure 2.

Figure 2Starting ABAQUS/CAE from the command line.

In the Partmodule, create a part named Part-1 using the following configurations (which

are specified in the Create Part dialogue): Modelling Space = 3D, Type = Deformable,

Shape = Solid and Type (within Base Feature) = Extrude. After sketching a 2020 square as

the section for the solid extrusion, in the Edit Base Extrusiondialogue input 40 for the depth

of extrusion and click on OK. The created part will look as in Figure 3.

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Figure 3A part of solid extrusion has been created.

In the Propertymodule, create a linear elastic material with Youngs modulus = 2E11 and

Poissons ratio = 0.3. Create a solid section of type homogeneous using the just-created

material. Then assign this solid section to Part-1. The ABAQUS/CAE window will now be as

Figure 4.

Figure 4The part has been assigned a solid section.

In the Assemblymodule, instance the previously created Part-1. Now the created assembly

will be as shown in Figure 5.

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Figure 5Part-1 has been instanced.

In the Stepmodule, create a step after the initial step and with the procedure type of Linear

perturbation Static, Linear perturbation.

In the Loadmodule, create a boundary condition of the type of Displacement/Rotation with

all three translational DOF fixed (U1 = 0, U2 = 0, U3 = 0) and apply the boundary condition

to one end face of the cantilever. Create a load of the type of Concentrated force with the

CF2 component of -100 and apply the load to the centre of another end face (the user needs topartition the face using menu Tool->Partition to get the centre as in Figure 6) opposite to

the fixed end face. The boundary and loading conditions are applied as shown in Figure 6.

Figure 6Fix one end and apply a downward concentrated force at the centre of the opposite end.

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In the Meshmodule, assign the part instance with the mesh control of Element shape = Hex

and Technique = Structured. Assign the part instance with element type of C3D8. Seed the

part instance with global size of 1. Then mesh the part instance. The part instance will now

look as shown in Figure 7.

Figure 7The part instance after being meshed.

In the Jobmodule, create a job and name it Test. Write the model in an input file (select the

created job in the Job Manager dialogue and click on Write Input). Now an ABAQUS

input file named Test.inp will be written to the working folder. Close ABAQUS/CAE.

2. Optimizing the structure using BESO3D

Start BESO3D (the user can do so through the BESO3D shortcut under BESO3D menu in the

Windows Start Menu or double-click the BESO3D.BAT in the install folder). Note that an

accompanying command line window starts to run in order to communicate information for

the user.

In the BESO3D 1.4dialogue shown in Figure 8, input the complete path of the ABAQUS

executable in the Path of ABAQUS Engine, input D:\BESO3D in Path of Working

Folder and the name of the just created ABAQUS input file Test in the ABAQUS Model

File Name (without the extension .inp). Click on OK to accept the inputs.

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3. if there are more than one parts/instances to be optimized, for each part/instance you

need to set up individual parameters and click on Save to active the part, tips are

also found in the field above the button;

4. when more than one load cases are considered, the weighting factors for the load

cases are specified in Weights and they should be split by ,;

5. the named numbers of parts/instances and load cases should not exceed the number

of existing numbers of parts/instances/steps defined in the ABAQUS model file.

Figure 9Parameter settings for the BESO optimization of the 3D cantilever.

During the optimization run, messages from ABAQUS/Standard and BESO3D are seen to roll

in the accompanying command line window. After a while, a message pops up notifying the

end of the optimization run as in Figure 10 with filled information, where a brief report and

suggestions for further actions are given. Then the user is ready to inspecting the final

solution.

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Figure 10Message pops up after optimization is finished.

3. Inspecting the final solution

The final solution include the final design of the 3D cantilever that can be viewed by opening the

ABAQUS output database file .odb and the result file Result.txt that stores the evolutionary

history of the volume fraction and the mean compliance.

Open ABAQUS/CAE by typing ABAQUS CAE under the prompt D:\BESO3D> in the

previous command line window in Figure 2.

Open the output database of the final design (note that the intermediate and final designs are

named after the initial ABAQUS model input file with a three-digit number indicating theiteration number): in the Open Databasedialogue of ABAQUS/CAE, select the database file

with the largest number in the file name and open it. As shown in Figure 11, the final design

that is stored in Test043.odb is displayed in the ABAQUS/CAE window. Note that due to

the convergence of the solution, the designs of the last few (say 10) iterations are very similar

and they can all regarded as the final optimal design in most of the circumstances.

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Figure 11The final design that is stored in Test043.odb.

Double click Result.txt in the working folder, a text file containing the evolutionary history

can be viewed. The result file will as shown in Figure 12 and contains four columns of data:

iteration number, volume fraction, the mean compliance and the time. Note that the volume

fraction data are between 0 and 1, e.g. 0.5 means 50.0% volume fraction.

Figure 12Result.txt recording the evolutionary history.

4. Continuing optimization from the obtained solution

Sometimes the optimization run stops before the solution converges due to reasons such as that themaximum iteration number has been set too small. BESO3D offers the user an option to continue

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CAUTIONS:

1. The parts/instances for which optimization parameters have been set will be designable. Other

following instances are regarded as non-designable.

2. Following element types can be identified by BESO3D: S4, CPS4, CPE4, C3D8, C3D4, S3,

CPS3 and CPE3.

3. The ABAQUS input file and the ABAQUS output database file for every iteration are named

NNN.inp and NNN.odb respectively. The designs can be

viewed by opening either one in ABAQUS/CAE.

4. The program is designed for both problems of mean compliance minimization and volume

minimization, input MIN for either and a constraint value for the other to define the

optimization problem.

5. Be sure to click on Save button to save parameters set for each part/instance, for both cases

of starting a new optimization run and continuing the previous optimization run.

6. Be sure that you have enough parts/instances/steps defined in your ABAQUS model file,

otherwise you will get an error.

1ABAQUS is the trademark of SIMULIA.

If the user has any difficulties in obtaining or using BESO3D, or has queries about updates of the

program, please contact us by email at the following address:

[email protected] (Y.M. Xie)

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