Altair HyperWorks Newsletter February 2006 by AndyHobson


									  IN THIS ISSUE                                                             March 2006

     Free-Size: New
                           Altair Hosts New Grid and                 Support Tips
Optimization Technique for
                                 Grow Seminar                          & Tricks
     Shell Elements


Efficient Composite Design Optimization
Uses Free-Size Optimization Techniques
This article introduces the capabilities of HyperMesh and OptiStruct for composite
optimization, using a new optimization technique for shell elements called Free-Size. Free-
Size differs from traditional shell topology optimization by utilizing the thickness of each
element as the design variable, as opposed to the element density, in topology. The
advantages of using thickness instead of density include more accurate calculation of
bending stiffness for “intermediate density” elements and more efficient optimization
capabilities for obtaining “shear-web” designs. Furthermore, while shell topology
optimization methods typically find “truss-type” designs, Free-Size optimization methods
can find either “shear-web” or “truss-type” designs, whichever is optimal. Free-sizing is
available in 7.0 SP1 through the Free-Size utility and will be fully integrated into
OptiStruct 8.0 through the DSIZE card.

The concept of Free-Size optimization for homogeneous shell elements (PSHELL) has
been extended to that of layer-wise composite shell elements (PCOMP), and is called
composite Free-Size optimization. In composite Free-Size optimization, the thickness of
each ply within each element is a design variable. A schematic of Free-Size design
variables compared to composite Free-Size design variables is shown in Figure 1. The
primary benefit of composite Free-Size optimization is that effects due to both total
element thickness and ply angle percentages are accounted for in the calculation of the
element stiffness. For example, composite Free-Size optimization has the ability to
increase the thickness of a given element through one or multiple thickness design
variable changes, and each one is associated with a given ply angle. The selection of a
particular thickness design variable associated with a given ply not only increases the
element thickness, but also changes the ratio of the thickness of each ply angle to the
total thickness. It is this effect that makes composite Free-Size optimization technology
unique for concept design optimization of composite structures.

A laminate family is denoted by [%0’s, %+/-45’s, %90] and allows for complete
determination of the A-matrix for any given laminate thickness, as the A-matrix is
stacking-sequence independent. It is this fact that allows for the composite Free-Size
optimization to “grow” plys through the thickness design variable associated with a given
ply angle, without having to modify the PCOMP definition for the exact stacking
sequence. This approximation holds for structures dominated by in-plane (Nx, Ny, Nxy)
behavior, as they can be accurately represented through A-matrix behavior only. Most
structures that are modeled as shells behave this way, and, as such, the assumption of
in-plane dominated behavior is typically valid – at least at the conceptual design phase.
In addition, the user will see that ply angles are implicitly included in the optimization
through the ply thickness design variable. The user can include any number of plys in the
“initial” laminate definition, each one with its own thickness design variable. If a given ply
angle thickness design variable is driven to zero, that angle is not required. Conversely,
any ply angles with “thickness” are required. With this implicit approach, the user can
optimize for both laminate thickness and ply angles with only thickness design variables.
For example, the initial laminate in the composite Free-Size optimization definition could
be [15/30/45/90/-45/-30/-15/0]s instead of the more traditional [45/90/-45/0]s.

         Figure 1. Free-Size Compared to Composite Free-Size Design Variables

Free-Size optimization capabilities have been implemented in HyperMesh/OptiStruct v8.0
similar to topology set up in previous versions. However, Free-Size setup – composite or
otherwise – in v7.0SP1 is a two-step process involving the Free-Size utility and the Gage
panel. The Free-Size utility operates on a “baseline” model that has component
collectors with PCOMP (or PSHELL) definitions for each global region, as shown in Figure
2. The Free-Size utility creates a component collector for each element with the
properties from its “parents” component collector, also shown in Figure 2. Finally, to
create the required design variables, i.e. the thickness of each ply within each element,
the Gage panel is used, as shown in Figure 3. Typical parameters for the Gage panel are:
lower bound of 1 ply, upper bound of ~30plys, and type of PCOMP(Ti) with a separate
variable for each ply option selected, as shown.

      Figure 2. Free-Size Utility to Create Component Collectors for Each Element

     Figure 3. Optimization > Gage Panel for Setup of Ply Thickness Design Variables

The objective of the composite Free-Size optimization is to determine “where the
material wants to be” or for composites “where plys want to be dropped or added” for a
maximum stiffness part. This is the conceptual design phase, and the optimization results
need to be interpreted into constant thickness regions in order to develop a size-and-
shape optimization model. By plotting the total element thickness for the last iteration in
multiples of ~10 plys (user defined), the resulting color maps can be used to determine
where constant thickness regions should be defined. Figure 4 shows the resulting color
maps from a composite Free-Size optimization. Using these color maps, a size-and-shape
model of constant thickness regions can be developed, as shown in Figure 5.
                  Figure 4. Results of Composite Free-Size Optimization

    Figure 5. Interpretation of Free-Size Optimization Results – Size-and-Shape Model

Finally, a size-and-shape optimization should be performed to determine the constant
regional thickness (number of plys) and laminate families (number of plys of each angle)
that satisfy the design constrains. The setup of the design variables is equivalent to that
described in the composite Free-Size optimization section, except that the design
variables are now at the regional level instead of the element level. An initial laminate of
[45/90/-45/0]s can be utilized, as in the composite Free-Size optimization setup,
although alternative laminates could also be considered, as described earlier. In addition,
composite manufacturing constraints may be introduced at this stage, a step that will
not be discussed here. It is important to note, however, that these types of constraints
can also be easily applied.

The size-and-shape optimization run outputs the .prop file containing the PCOMP cards
updated with the results of the optimization run. When this file is read into HyperMesh
with FE overwrite option activated, the component collectors for each region are
updated with the results of the design variables from the last optimization iteration. An
additional utility called the Component Laminate Family Utility (CLFU) has been developed
to post-process these results within HyperMesh. This utility calculates from the final
design variable values, the total thickness of each region, truncates to the nearest
whole number of plys, and determines the number of plys required for each angle and,
consequently, for the laminate family. The utility outputs a .csv file that can be
automatically opened in MS Excel for review and additional formatting. The results from
the CLFU for a typical optimization problem is shown in Figure 6. It is this table that is
typically necessary for a designer to develop a candidate design for the composite
structure of interest and further develop a detailed model of the part with the actual
stacking sequence for final analysis.
Click here to download the Free-Size utility and the CLFU. It contains a Readme.txt file
that gives a brief description of the utilities and the procedure to install them.

If you have any problems downloading the utilities, please contact your local support
office or send an email to

  ALTAIR HOSTS GRID AND GROW                                   UPCOMING EVENTS

Altair to Host Grid and Grow                                 Altair is participating in the
                                                             following events:
Seminar in May
                                                             SAE World Congress &
On May 23, Altair will host a Grid and Grow seminar at its
Troy headquarters. The seminar will examine the
                                                             Detroit, Mich.
challenges of deploying an integrated solution to
                                                             April 3-6, 2006
leverage a grid environment to maximize CAE throughput
                                                             Click here for more info
within their product design process. The complimentary
event is sponsored by IBM and Intel.
                                                             Dimensions 06 –
                                                             Transport Packaging
Grid and Grow topics include how new concepts in CAE
                                                             San Antonio, Texas
product design drive hardware requirements; how to
                                                             April 18-21, 2006
accelerate business results and time to market; and how
                                                             Click here for more info
to manage growth while controlling costs.

To register for this complimentary event, please visit       17 t h Annual HP CAE                                           Symposium
                                                             Los Angeles, Calif.
                                                             April 25, 2006
  SUPPORT TIPS & TRICKS                                      Click here for more info

                                                             Altair Engineering Grid
KB#1: 694
                                                             and Grow
Creation of regional compliance response across multiple
                                                             Troy, Mich.
loadsteps using DRESP2 and DRESP1L - PDF
                                                             May 23, 2006
                                                             Click here for more info
KB#2: 692
Setting up environment variables for UG file import - PDF
                                                               NEWSLETTER FORMAT
                                                             Please view the PDF if you are
Macro name: mat_manager_70.tcl                               unable to see the pictures in
                                                             this e-mail. If you can't access
This macro helps the user create and manage a material       the PDF files or did not receive
database and manage the interaction between the              the attachments, please contact
database and HyperMesh model. In doing so, the user
can create his or her own database and add directories
with the new material; edit and rename materials; and
load these materials in the model. The user can also           REGISTER TODAY
check in materials from the HyperMesh model to the
database. This macro currently supports ABAQUS,              If you are new to this site or
ANSYS, LS-DYNA, NASTRAN and OptiStruct solvers. For          have not registered as an
more information, please see the attached zip file           Insider user, we invite you to
containing tcl files, the database and “Material Manager     complete a brief sign-up form.
Documentation.doc”. - Download ZIP                           As a registered user, you will
                                                             have access to other support
Macro name: mat_assembly.tcl                                 resources, including
                                                             documentation, tutorials,
This macro creates assemblies of the components based        software updates and macros.
on their material assigned. The assemblies are named         You will also have access to the
from the respective materials. The user needs to select      iExchange message board.
one or more materials. Then, the macro will create
assemblies with the material name containing the
respective components. - Download ZIP


Develop your skills
Here are our upcoming training sessions for HyperWorks.
Simply click on each title to view details of the course's

Michigan training classes

   q   Introductory FEA Modeling and Results
       Visualization, April 3-5
   q   Interfacing HyperWorks with ABAQUS, April 6
   q   Introductory Concept Design and Fine Tuning with
       OptiStruct, April 19-20
   q   Introductory DOE, Optimization and Stochastic
       Studies, April 21
                                                               ALTAIR IN THE NEWS
California training classes
   q   Introductory FEA Modeling and Results                          Aerospace Design Strategies
       Visualization, April 4-6                                       Headline Altair Engineering’s
                                                                      Product Innovation Magazine -
>> You can get more details on these courses, obtain a                Link
full schedule, or inquire about tailored, on-site training by
calling your local Altair office or emailing                          Altair Engineering Announces                                                   Establishment of Trans-
                                                                      National European and
                                                                      Asia/Pacific Operations - Link

             Support inquiry? Unable to access the web links above? Please email
         or call 248-614-2425 for assistance.

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