Using the Femap API to Streamline Geometry … 07, 2014 · FEMAP SYMPOSIUM 2014 ... May 14-16,...

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FEMAP SYMPOSIUM 2014

Discover New Insights Femap Symposium 2014

May 14-16, Atlanta, GA, USA

Using the Femap API to Streamline Geometry Preparation

and Meshing for the Shipbuilding Industry

Victoria Harris, Project Engineer, ATA Engineering, Inc

11995 El Camino Real, Suite 200 | San Diego, CA 92130 | T 858.480.2000 | F 858.792.8932 | www.ata-e.com

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

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Reduce the time it takes to go from this: to this:


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

Analyst

delivers report

Unneeded

features are

removed from 3D

CAD (fillets, etc.)

2D “midsurface”

model is created

from 3D model

2D Geometry is prepared

for meshing (holes

removed, surfaces

partitioned, etc.)

2D Geometry is

meshed

Loads and boundary

conditions are

applied

Model is solved and

results are post-

processed


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

API Provides Ability to Combine

Existing Femap Tools in New Ways

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Program


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


Femap Help Has Full Documentation

of Objects and Functions



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

– Model checks

– Loads/constraints on un-meshed

surfaces

– Sliver surfaces

– List associated entities

– Expanded coincident element

check

– Meshing

– Get nodes attached to mesh points

– Add mesh to group

– Orient beams to shell normals

– Miscellaneous

– NEI Nastran log file parsing

– Gravity load combinations

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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.

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Mold-line

Mid-surface


“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 mid-

surfaceable solids

– Group tools to collect everything in one place



“Problem” Surfaces Needed to Be

Identified Before Meshing

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• 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


CheckSlivers Provides Additional Methods

for Finding Problem Surfaces

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• 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.


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


“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


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!

Using the Femap API to Streamline Geometry … 07, 2014 · FEMAP SYMPOSIUM 2014 ... May 14-16,...

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