Victoria Harris, Project Engineer, ATA Engineering, Inc
Using the Femap API to Streamline Geometry Preparation
and Meshing for the Shipbuilding Industry
Femap Symposium 2014
May 14-16, Atlanta, GA, USA
Unrestricted © Siemens AG 2014
FEMAP SYMPOSIUM 2014
Discover New Insights
ATA Used Femap’s API to Create New
Tools for Industry-Specific Workflows
Our shipbuilding customers were looking to develop Femap tools that
would make common shipbuilding-industry processes more efficient.
Femap’s Application Program Interface (API) allows users to
customize existing Femap tools for their specific needs.
In collaboration with Huntington Ingalls Industries, we used the API to
combine and extend existing Femap tools in new ways in order to
streamline the model-building process for shipbuilders.
The project was funded by NSRP.
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Shipbuilders Were Looking to Make
Geometry Preparation More Efficient
Reduce the time it takes to go from this:
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to this:
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Efficiency Improvements in Modeling
Result in Large Time Savings
• The design and manufacturing of a ship requires the creation of
thousands of analysis models of everything from the ship as a whole
down to individual equipment racks
• For each of these models, the analyst must create “meshable
geometry” for the object to be analyzed, from the CAD provided by
the designer
• Tens of thousands of man-hours are spent creating meshable
geometry models for many thousands of objects on each ship hull
• Even a modest reduction in the number of hours required to create a
single analysis model results in a large reduction in the total number
of man-hours per hull when the individual savings are multiplied by
the thousands of analysis models that are created
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Typical Shipbuilding Workflow
Analyst
receives CAD
geometry from
designer
Unneeded
features are
removed from 3D
CAD (fillets, etc.)
2D Geometry is prepared
for meshing (holes
removed, surfaces
partitioned, etc.)
2D “midsurface”
model is created
from 3D model
Loads and boundary
conditions are
applied
2D Geometry is
meshed
Analyst
delivers report
11995 El Camino Real, Suite 200 | San Diego, CA 92130 | T 858.480.2000 | F 858.792.8932 | www.ata-e.com
Model is solved and
results are postprocessed
API Provides Ability to Combine
Existing Femap Tools in New Ways
Femap Application Program Interface (API)
• Can automate any manual process in Femap
• Codes are written in programming languages such as Visual Basic or C++
• Can interact with other software such as Excel or Matlab
This toolbox was written for Femap 10.2.1
• Toolbox needed to be accessible for multiple shipbuilders
• API code is usually forward-compatible
Program
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Use the API Within Femap or
Through Visual Studio
API can be accessed as a
window within Femap – great for
writing programs quickly
You can also write programs in
Visual Studio – lots of debugging
tools and easy GUI construction
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Femap Help Has Full Documentation
of Objects and Functions
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Shipbuilding Toolbox Focused on
Preparing Geometry for Analysis
In the toolbox:
– Mid-surface tools
–
–
–
–
–
–
–
Mold-line surfaces
“Washer” boundaries
Extending surfaces
Surface “healing”
Hole removal
Defeaturing selection
Snipe creation
– Get nodes attached to mesh points
– Add mesh to group
– Orient beams to shell normals
– Miscellaneous
– NEI Nastran log file parsing
– Gravity load combinations
– Model checks
– Loads/constraints on un-meshed
surfaces
– Sliver surfaces
– List associated entities
– Expanded coincident element
check
– Meshing
11995 El Camino Real, Suite 200 | San Diego, CA 92130 | T 858.480.2000 | F 858.792.8932 | www.ata-e.com
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Shipbuilders Like Mold-Line
Surfaces
• When shipbuilders create 2D surfaces from 3D geometry, they like to use
a mix of mid-surfaces and “mold-line” surfaces.
• Ship models have a lot of adjacent panels with varying thicknesses.
Typically the faces on one side of the panels are coplanar – this is the
mold-line surface.
• Using a mid-surfacing tool on these panels creates sheet bodies that are
no longer coplanar.
Mold-line
Mid-surface
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“Moldline” Combines Mid-surfacing
Benefits with Mold-line Concept
• Shipbuilding analysts wanted a tool that uses
the mold-line instead of the mid-surface for
some solids while still mid-surfacing other
solids
• It was also desired that the mold-line
surfaces would have a thickness property
assigned to them (much like a mid-surface
would)
• The Moldline tool uses:
– Copy Surface command to grab mold-line
surfaces
– some vector math to get the solid thickness
– the built-in Mid-Surface command for midsurfaceable solids
– Group tools to collect everything in one place
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“Problem” Surfaces Needed to Be
Identified Before Meshing
• The Meshing Toolbox can identify
surfaces with an area smaller than the
specified tolerance so that those
surfaces can be suppressed before
meshing
• The analysts at HII reported that because
of the nature of their models, they often
get “sliver” surfaces that are fairly large in
area, but still need to be eliminated
before meshing can commence
Sliver surfaces
11995 El Camino Real, Suite 200 | San Diego, CA 92130 | T 858.480.2000 | F 858.792.8932 | www.ata-e.com
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CheckSlivers Provides Additional Methods
for Finding Problem Surfaces
• The CheckSlivers tool needed to have several
different options for identifying and grouping
surfaces
• The tool uses several properties and methods
associated with the point, edge, and surface
objects in the API.
• For example – to check the “aspect ratio” of a
surface, the program collects all of the edges
associated with the surface, then compares the
length of each edge to all the other edges. If any
ratio is greater than the user-selected tolerance,
the surface is added to an output group.
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Element Warnings in NEI Nastran Can
Be Imported Directly
• The API can be used to
interact with files outside of
Femap, too
• Analysts wanted to quickly
parse the element errors
and warnings that are listed
in an NEI Nastran log file
• The API was used to read
the entire log file into a
Visual Basic program, hunt
for keywords related to
element issues, and put
element IDs into a Femap
group
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“Snipe” Is An Example of Automated
Geometry Editing
• It can be useful to write a program “from scratch” to address a repetitive task
specific to your needs
• Shipbuilding analysts frequently cut “snipe” corners into their geometry; the
existing methodology involved either drawing a line on the geometry or
orienting a plane to make the cut
• The “Snipe” program automates the process by asking the user to define the
snipe dimensions
• The GUI options available in Visual Studio allow for an instructional pop-up
that appears when the program runs
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“BeamsNormaltoShells” Builds From the “Beams
Normal to Surface” Example Program
• The Femap installation comes with several example programs,
which are useful for learning how to use the API
• “BeamsNormalToShells” expands the concept of the example
“Beams Normal to Surface” program
• The program reads in the normals of any 2D elements attached to a
beam element and aligns the cross-section with the average of the
normal vectors
11995 El Camino Real, Suite 200 | San Diego, CA 92130 | T 858.480.2000 | F 858.792.8932 | www.ata-e.com
Final Thoughts About the API
• The easiest way to get started is to pick a simple task
and figure out the steps needed to recreate it in the API
• Everything you need is in the documentation
• External editors can provide extra debugging options
• Once your code is up and running, ask for examples from
other people to test it
• Enjoy!
11995 El Camino Real, Suite 200 | San Diego, CA 92130 | T 858.480.2000 | F 858.792.8932 | www.ata-e.com