Detailed Three-Dimensional Modeling of the C-130 Center Wing ...

Center for Aircraft Structural Life Extension 

Providing Structural Integrity Technology to the Aerospace Community 

Detailed Three-Dimensional 

Modeling of the C-130 

Center Wing Box for 

Damage Tolerance Analyses 

12 May 2010 

We would like to thank AFRL/RX for funding this work 

Mr. Matthew Hammond, USAFA/CAStLE 

Dr. James Greer, USAFA/CAStLE 

Dr. Scott Fawaz*, USAFA/CAStLE 

Mr. Börje Andersson, Swedish Defense Res. Agency 

Dr. Robert Rainsberger, XYZ Scientific Inc. 

Ms. Monica Poelking (Sponsor), AFRL/RX 

*Gulfstream Aerospace Corporation

Presentation Outline 

• Background / Purpose of project 

• Solid model generation 

• Finite element mesh generation 

• Fastener modeling / locations / insertion 

• Simple Example 

• Remaining Effort 

NOTE: All CAStLE work was performed under USAFA Contracts Vehicles. 

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BACKGROUND / 

PURPOSE OF PROJECT 

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Background / Purpose 

• Transport airframe since late 1950s 

• ≈ $40-60 million per airframe 

• ≈ $6-7 million per CWB 

• 6-7 figures ($) per PDM inspection 

• Develop a robust high fidelity 3D finite element model 

of the C-130 CWB with discretely modeled fasteners 

• Residual life / residual strength calculations 

• Anticipate cracking scenarios 

• Quickly analyze new cracking scenarios (Battle Damage) 

• SHM system design & sensor placement 

• Fleet management (i.e. Inspection Int., Retirement, etc.) 

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CWB SOLID MODEL 

GENERATION 

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CWB Solid Model 

• Highly detailed solid model necessary for accurate FE 

Model. 

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C-130 JEDMICS Database 

Drawing 390619-5 Wing Joint 

Fitting 


C-130 SolidWorks 390619-5 

Wing Joint Fitting Solid model 

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• Problem: Orthogonal part geometry fit to curved airfoil 

loft profile (must mate flush) 

• Solution: Use curved part geometry while maintaining 

part tolerances 

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• ≈ 1000 Critical structural components 

• Primary / Secondary / Tertiary structural components 

• Some Tertiary components are necessary to properly interface 

higher level parts 

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FINITE ELEMENT MESH 

GENERATION 

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FE Analysis Software 

• C-130 CWB FE Model ~10 GDoFs 

• Commercial FE solvers 

• NASTRAN, ANSYS, ABAQUS 

• Scalable to 16 processors 

• Max. 100-200 MDoFs 

• Research Codes 

• FRANC3D/NG 

• STRIPE 

• No known size limitations (except hardware) 

• 2.4 GDoFs successfully solved 

• Separate DoD HPC Challenge Project 

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• Mesh topology: 

FE Mesh Topology 

• Tet elements have poorer results (automatic generation) 

• Hex elements have much better results (harder to 

generate mesh) 

• STRIPE requires Hexahedral elements 

• (15-node Wedge elements are also allowed) 

Hex-20 

Tet-10 

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FE Mesh Design 

• Typical FE mesh design software requires part 

division into 5 or 6 sided components for Hex mesh 

• Highly time consuming 

• Unique FE mesh software to expedite Hex mesh 

generation (TrueGrid®) 

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FE Mesh Example 

Solid Model 

FE Mesh 

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FASTENER MODELING / 

LOCATIONS / INSERTION 

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Fasteners 

• Discretely model fasteners 

• High fidelity stress distributions (concentrations) 

• Accurate fatigue crack propagations (Residual Life) 

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• Manual extraction from blueprints 

• Extremely tedious process 

Fastener Database 

≈ 50,000 fasteners 

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Mesh Drilling 

• New feature developed specifically for this project by 

XYZ Scientific, Inc. for the TrueGrid® software 

• Uses data from Fastener Database for command line 

code input for TrueGrid® 

• “Drills” holes through structured mesh. This creates a 

uniform hole with nodal alignment b/w parts for 

automatic fastener insertion 

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Mesh Drilling 

Pre-Drill Mesh Topology 

Post-Drill Mesh Topology 

Transition elements dictated by: Parent mesh, fastener axis 

location and orientation, shank diameter, head type and diameter 

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Automatic Fastener Insertion 

1 2 

3 

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• Three types of fasteners 

• Universal head rivet 

• Round head rivet 

• Countersunk rivet 

• Generates Patran neutral file 

Current Status 

• Generates list of element faces in contact with 

existing structure 

• Head faying , tail faying, shank faying, mated material 

faying surfaces 

• Approximately 3000 lines of FORTRAN code in 16 

routines 

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Current Assumptions 

• Holes are straight 

• All elements 20-noded hex 

• Assumes exactly 2 rings of 

elements outside of hole 

(shank diameter) 

• Assumes outer edge of 2 nd 

ring is same diameter as 

outer-most head diameter 

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Approach 

• Find duplicate nodes in the structure and delete them 

• These nodes occur at faying surfaces of pieces to be joined 

• Build a cylindrical coordinate system centered on the 

hole bore 

• Find structure nodes along hole bore 

• Make duplicate nodes of those and make the fastener 

elements out of those nodes 

• Add heads and tails 

• Transform all the nodal coordinates back into global 

coordinates and write to output 

• Make elements out of the nodes 

• Go to the next hole and repeat… 

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Building Fasteners 

make nodes for shank make elements for shank make nodes/elements 

for head center 

make nodes/elements 

for head periphery 


for tail center 


for tail periphery 

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Fastener Code Input File 

3.966819500D+2 2.203318200D+2 1.446636200D+2 0.975897130D+0 -0.097595818D+0 -0.195191640D+0 

0.125000000D+0 2.500000000D+0 3, 0.110944000D3, 0.500000000D0 

3.966306800D+2 2.210986600D+2 1.440238500D+2 0.975891110D+0 -0.097595215D+0 -0.195190430D+0 

0.125000000D+0 2.500000000D+0 2, 0.000000000D0, 0.000000000D0 

3.965794100D+2 2.218655200D+2 1.433840600D+2 0.975891110D+0 -0.097595215D+0 -0.195190430D+0 

0.125000000D+0 2.500000000D+0 1, 0.000000000D0, 0.000000000D0 

3.965281400D+2 2.226323700D+2 1.427442900D+2 0.975891110D+0 -0.097595215D+0 -0.195190430D+0 

0.125000000D+0 2.500000000D+0 2, 0.000000000D0, 0.000000000D0 

3.964768700D+2 2.233992200D+2 1.421045200D+2 0.975891110D+0 -0.097595215D+0 -0.195190430D+0 

0.125000000D+0 2.500000000D+0 1, 0.000000000D0, 0.000000000D0 

3.964256000D+2 2.241660800D+2 1.414647500D+2 0.975891110D+0 -0.097595215D+0 -0.195190430D+0 

0.125000000D+0 2.500000000D+0 1, 0.000000000D0, 0.000000000D0 

x,y,z origin; x,y,z vector components; hole radii; search depth (from vector origin); head type; head angle for CS; 

head diam for CS 

• Other inputs 

• Node and element number offsets 

• Search tolerances 

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Fastener Code Output Files 

Nodes 

25 0 0 1 0 0 0 0 0 

P3/PATRAN Neutral File from fastener creation program 

1 5000001 0 2 0 0 0 0 0 

0.397755981E+03 0.220349686E+03 0.144460815E+03 

1G 6 0 0 000000 

1 5000002 0 2 0 0 0 0 0 

0.397761536E+03 0.220342438E+03 0.144492142E+03 

1G 6 0 0 000000 

… 

Elements 

2 6000505 8 3 0 0 0 0 0 

20 0 0 0 0.000000000E+00 0.000000000E+00 0.000000000E+00 

5002265 5002267 5002294 5002290 5002793 5002795 5002822 5002818 5002266 5002293 

5002291 5002289 5002769 5002770 5002782 5002781 5002794 5002821 5002819 5002817 

2 6000506 8 3 0 0 0 0 0 

20 0 0 0 0.000000000E+00 0.000000000E+00 0.000000000E+00 

5002267 5002269 5002296 5002294 5002795 5002797 5002824 5002822 5002268 5002295 

5002322 5002293 5002770 5002771 5002783 5002782 5002796 5002823 5002850 5002821 

2 6000507 8 3 0 0 0 0 0 

… 

Surfaces 

6000001, 5, shank surface 










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Simple Example 

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• Complete Fastener Database 

Remaining Effort 

• “Drill” holes in meshed components 

• Assemble structure with automatic fastener insertion 

routine 

• Run Analysis 

• Validate Model with load/strain survey 

• Currently working with Lockheed Engineers 

• Increase available fastener types 

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One more thing… 

Happy Birthday Greg Shoales! 

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Questions 

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