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ABSTRACT

This final report documents the Shipbuilder Toolbox created by ATA Engineering, Inc. (ATA).

Huntington Ingalls Industries (HII) led a team that included ATA and Bath Iron Works (BIW), and this

team secured a panel project from the National Shipbuilding Research Program (NSRP). Based on

requirements defined by HII, BIW, and Gibbs & Cox (G&C), ATA created a Femap toolbox that would

improve the process of creating an analysis model from CAD geometry. The tools aim either to automate

manual tasks within Femap or provide a shortcut for tedious procedures. Since the most time-consuming

part of creating an analysis model is often the creation of meshable geometry, the toolbox contains several

programs for creating or editing mid-surface models. The toolbox also includes new methods for

checking the quality of a model as well as tools to aid with mesh grouping. The toolbox is available to all

members of NSRP at no cost.


TABLE OF CONTENTS

1. INTRODUCTION ........................................................................................................................... 1

2. ANALYSIS OF A SHIP MODEL USING FEMAP ....................................................................... 2

2.1. Current Analysis Methodology ............................................................................................ 2 2.2. Customization of Femap ...................................................................................................... 5 2.3. Installation of Shipbuilder Toolbox ...................................................................................... 5

3. MID-SURFACING TOOLS ............................................................................................................ 7

3.1. DefeaturingSelection ............................................................................................................ 7 3.2. Moldline ............................................................................................................................... 8 3.3. RemoveHoles ..................................................................................................................... 10 3.4. HealSurface ........................................................................................................................ 12 3.5. WasherBoundaries .............................................................................................................. 13 3.6. ExtendSurface .................................................................................................................... 14 3.7. Snipes ................................................................................................................................. 15

4. MODEL CHECKS ........................................................................................................................ 16

4.1. CheckSlivers ....................................................................................................................... 16 4.2. CheckLoadsConstraints ...................................................................................................... 17 4.3. ListAssocEntities ................................................................................................................ 17 4.4. CheckCoincElements ......................................................................................................... 18

5. MESHING TOOLS ....................................................................................................................... 20

5.1. GroupNodesByMeshPoint .................................................................................................. 20 5.2. AddMeshToGroup .............................................................................................................. 20 5.3. BeamsNormalToShells ....................................................................................................... 20

6. MISCELLANEOUS ...................................................................................................................... 22

6.1. ParseLog ............................................................................................................................. 22 6.2. BodyLoadCombinations ..................................................................................................... 22


LIST OF FIGURES

Figure 2-1. Typical workflow in Femap for HII analyst. The blue boxes show steps taken by the analyst; the black arrows list the toolbox programs that are useful for each step. .................. 2

Figure 2-2. Typical CAD geometry received from designer; inset shows fillets on a stiffener. ................... 3 Figure 2-3. The mid-surface tool produces surfaces quickly, but the model still needs work. ..................... 4 Figure 2-4. When added to the Tools Directory, the Shipbuilder toolbox shows up as a submenu in

the Custom Tools list. .............................................................................................................. 6 Figure 3-1. DefeaturingSelection dialog. ...................................................................................................... 7 Figure 3-2. Solid geometry. .......................................................................................................................... 8 Figure 3-3. Mold-line surfaces are selected (highlighted in yellow). ........................................................... 9 Figure 3-4. Solids are selected for mid-surfacing (highlighted in yellow). .................................................. 9 Figure 3-5. Mold-lines and mid-surfaces have been created. ..................................................................... 10 Figure 3-6. RemoveHoles dialog. ............................................................................................................... 11 Figure 3-7. Use the size filter to selectively remove holes in surfaces. ...................................................... 11 Figure 3-8. Surfaces with asterisks in top picture are combined using HealSurface to produce

bottom picture. ....................................................................................................................... 12 Figure 3-9. WasherBoundaries used to create a border on a surface. ......................................................... 13 Figure 3-10. Corner imprint. ....................................................................................................................... 13 Figure 3-11. ExtendSurface extends surfaces using small target surfaces to define planes. ...................... 14 Figure 3-12. Snipe parameters. ................................................................................................................... 15 Figure 4-1. CheckSlivers dialog.................................................................................................................. 16 Figure 4-2. CheckLoadsConstraints dialog. ................................................................................................ 17 Figure 4-3. ListAssocEntities dialog. .......................................................................................................... 18 Figure 4-4. CheckCoincElements looks for any element whose nodes are all coincident with

another element’s nodes. ........................................................................................................ 19 Figure 5-1. GroupNodesByMeshPoint dialog. ........................................................................................... 20 Figure 5-2. BeamNormalToShells aligns a beam’s orientation to the average normal vector of the

shell elements attached to the beam element. ........................................................................ 21 Figure 6-1. BodyLoadCombinations dialog. ............................................................................................... 22


Femap Shipbuilder's Toolbox User Guide 1

1. INTRODUCTION

ATA Engineering has created a “Shipbuilder’s Toolbox” for use with Femap, in collaboration with HII

and BIW. The purpose of the toolbox is to reduce the cost for shipbuilders to perform contractually

required analyses by improving the methods used to create the analysis models. The project was funded

by NSRP as a panel project.

Analysis of a ship can take tens of thousands of labor hours; there are many models that must be created,

and there are many steps in the creation of each model. This project aims to reduce the hours required to

create each model, either by automating tedious tasks or by creating shortcuts for difficult procedures.

Since creating “meshable” geometry is often the most time-consuming part of the process, many of the

tools focus on the creation and editing of mid-surfaces. The toolbox also provides programs that check

model quality in new ways, as well as a few tools that aid in the actual meshing process, with new

grouping methods and beam orientation tools. There are also programs for parsing log files and creating

load combinations.

The toolbox uses the Femap Application Program Interface (API); this is a programming tool that can be

used to automate almost any Femap manual process. The toolbox was written in Visual Basic and is

accessed from within Femap (see Section 2.3 for details on installation). The tools were all written in

conjunction with Femap 10.2.1; different versions of Femap may cause small differences in the behavior

of the tools.

ATA Engineering will provide the initial release version of the toolbox to any member of NSRP free of

charge.


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Femap Shipbuilder's Toolbox User Guide 5

2.2. Customization of Femap

For customization, Femap provides the Application Program Interface (API). The API can be used to

automate almost any Femap process, and multiple programming languages can be used with the interface,

including Visual Basic and C++. The resulting programs can interact with other software such as Excel

and Matlab. The custom programs can interact with Femap from within a session, or Femap can be

embedded within the program.

For this toolbox, all programs were written in Visual Basic and operate from within Femap. The

following section describes how to install and use the tools.

2.3. Installation of Shipbuilder Toolbox

The Shipbuilder toolbox is provided as a folder containing executable files. The tools can be added to

Femap in two ways:

First, tools can be added to Femap one at a time. In Femap, go to Custom Tools Add Tools… and then

navigate to the location of the executable for the tool of interest and select that .exe file. Femap will copy

the .exe file to its Tools Directory (in the Femap installation) and add the name of the program to the

Custom Tools list. The program can then be accessed from this list.

The entire toolbox can also be added to Femap. First, go to Custom Tools Tools Directory… and note

the Tools path (e.g., C:/Siemens/FEMAPv1031/api/). Then, using Windows Explorer (or similar), copy

the entire Shipbuilder folder provided by ATA into the Tools Directory. The name of the Shipbuilder

folder should show up in the Custom Tools list with a submenu containing all of the programs, as shown

in Figure 2-4.


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Documents

ATTA Project No. Customer PO No. 746641/1 , 2013 · Femap Shipbuilder's Toolbox User Guide 1 1. INTRODUCTION ATA Engineering has created a “Shipbuilder’s Toolbox” for use with