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J.B. LojkoJ.B. LojkoEngineer IIEngineer II
H.F. SmithH.F. SmithSr. Structural Specialist Engr.Sr. Structural Specialist Engr.
Lockheed Martin Aeronautics Lockheed Martin Aeronautics Company - MariettaCompany - Marietta
Modeling and SimulationModeling and Simulationof the C-5 Aftof the C-5 Aft
Cargo Loading SystemCargo Loading System
Title
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AgendaAgenda
•System Description & BackgroundSystem Description & Background
•DADS ModelDADS Model
•EASY5 ModelEASY5 Model
•Solution DevelopmentSolution Development
•TestingTesting
•Solutions, Part 2Solutions, Part 2
-NASTRAN ModelNASTRAN Model
•Conclusions & Lessons LearnedConclusions & Lessons Learned
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System DescriptionSystem Description& Background& Background
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C-5 Aft Pressure DoorC-5 Aft Pressure Door
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Mechanical System Mechanical System DescriptionDescription
• Plug-type Door - Seals Aft Cargo EnvelopePlug-type Door - Seals Aft Cargo Envelope
- HeightHeight - 11.4 ft- 11.4 ft
- WidthWidth - 19.0 ft- 19.0 ft
- Door Weight 1845 lbDoor Weight 1845 lb
• Carries Cabin Pressure Loads in Flight & Cargo or Vehicle Carries Cabin Pressure Loads in Flight & Cargo or Vehicle Loads for Drive-in LoadingLoads for Drive-in Loading
• Pressure Door Opens Up for Aerial Delivery & Truck-bed or Pressure Door Opens Up for Aerial Delivery & Truck-bed or Down for Drive-in LoadingDown for Drive-in Loading
• 2 Sets of Hinges and Actuators, Upper and Lower, Left and 2 Sets of Hinges and Actuators, Upper and Lower, Left and RightRight
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Mechanical System Mechanical System DescriptionDescription
• Aerial Delivery SystemAerial Delivery System
- Aerial Delivery System (ADS) Requires Installation of a Aerial Delivery System (ADS) Requires Installation of a Pilot Parachute on the Lower Half of the DoorPilot Parachute on the Lower Half of the Door
- Pilot Parachute and Associated Hardware Weight 558 lbPilot Parachute and Associated Hardware Weight 558 lb
• Supporting Fuselage Structure Found to be Very FlexibleSupporting Fuselage Structure Found to be Very Flexible
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Hydraulic System Hydraulic System DescriptionDescription
• 3000 psi System3000 psi System
• OpeningOpening
- 2 gpm Split to 1 gpm at 2 gpm Split to 1 gpm at ActuatorsActuators
- Ramp Blocker ValveRamp Blocker Valve
- Balanced Relief ValveBalanced Relief Valve
• ClosingClosing
- Initial Lift - FuseInitial Lift - Fuse
- Slow Down - FuseSlow Down - Fuse
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First ContractFirst Contract
• Fatigue Problems with Upper Hinge Prompted USAF to Fatigue Problems with Upper Hinge Prompted USAF to Place LM Aero-Marietta Under Contract to Improve the Place LM Aero-Marietta Under Contract to Improve the Reliability of this SystemReliability of this System
• Initial Contract 1996 - Less Than Four Month ProjectInitial Contract 1996 - Less Than Four Month Project
- Geometry and Kinematics Created in CATIAGeometry and Kinematics Created in CATIA
- Ground Test Performed to Validate SimulationsGround Test Performed to Validate Simulations
- Analysis Performed in CATIA Using CAT/DADSAnalysis Performed in CATIA Using CAT/DADS
- Several Solutions ProposedSeveral Solutions Proposed
• Hydraulic Modifications - Slow Door OpeningHydraulic Modifications - Slow Door Opening
• Structural Modifications - Increase Strength in Selected Structural Modifications - Increase Strength in Selected AreasAreas
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First ContractFirst Contract
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First ContractFirst Contract
Actuator Load Comparison, Normal Actuator Load Comparison, Normal Operation, Test vs. DADSOperation, Test vs. DADS
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First ContractFirst Contract
Actuator Load Comparison, Slow Actuator Load Comparison, Slow Operation, Test vs. DADSOperation, Test vs. DADS
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Second ContractSecond Contract
• Follow On Contract 1999Follow On Contract 1999
- Incorporate Hydraulic Modifications to Reduce Door Incorporate Hydraulic Modifications to Reduce Door Opening SpeedOpening Speed
• First Attempt FailedFirst Attempt Failed
• Use DADS/Plant & EASY5 to Analyze All Proposed Use DADS/Plant & EASY5 to Analyze All Proposed Hydraulic Modifications Prior to TestingHydraulic Modifications Prior to Testing
• Using Analysis-Led Design the Second Attempt at Using Analysis-Led Design the Second Attempt at Modifying the Hydraulics was a SuccessModifying the Hydraulics was a Success
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DADS ModelDADS Model
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Model DefinitionModel Definition
• Model Simplified - Flexibility Greatly ReducedModel Simplified - Flexibility Greatly Reduced
• 16 Bodies 16 Bodies
• 6 Control Elements6 Control Elements
- Left & Right Actuator Distance, DistanceD, ForceLeft & Right Actuator Distance, DistanceD, Force
• ForcesForces
- 1 Contact Force - Door Stop1 Contact Force - Door Stop
- 2 TSDAs - Lower & Upper Fuselage Stops2 TSDAs - Lower & Upper Fuselage Stops
- 2 RSDAs - Flexibility in Torque Arm/Hook2 RSDAs - Flexibility in Torque Arm/Hook
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Model DefinitionModel Definition
• Approximately 20 JointsApproximately 20 Joints
• OtherOther
- Curves - Door Stop DriverCurves - Door Stop Driver
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EASY5 ModelEASY5 Model
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Model DefinitionModel Definition
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Model DefinitionModel Definition
• 62 Components62 Components
• Main Control ValveMain Control Valve
- Custom - HV LibraryCustom - HV Library
• Balanced Relief Valve (Simplification)Balanced Relief Valve (Simplification)
- Pilot-to-Open Check ValvePilot-to-Open Check Valve
• Fuses - Variable Orifice that Closes After Specified Fuses - Variable Orifice that Closes After Specified Volume of Flow is SensedVolume of Flow is Sensed
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Model Definition, cont.Model Definition, cont.
• Actuators - AP Component for use with DADS Model Actuators - AP Component for use with DADS Model Extension ComponentExtension Component
• Ramp Blocker Valve - Critical that Pressure was Ramp Blocker Valve - Critical that Pressure was MeasuredMeasured
- Simple Fixed OrificeSimple Fixed Orifice
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Solution DevelopmentSolution Development
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SimulationsSimulations
• Conduct Simulations to Determine the Best Combination Conduct Simulations to Determine the Best Combination of Flow Regulatorsof Flow Regulators
- Performance Criteria - Load Reduction vs. Opening Performance Criteria - Load Reduction vs. Opening TimeTime
- Constraint - Slowing Opening Time Could Impact Constraint - Slowing Opening Time Could Impact Aircraft OperationAircraft Operation
• Current Flight Profile Could Change for ADS Current Flight Profile Could Change for ADS PreparationPreparation
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EASY5 Results - EASY5 Results - Actuator Pressures & Actuator Pressures & PositionPosition
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EASY5 Results - Ramp EASY5 Results - Ramp Position Valve, Pilot Position Valve, Pilot LineLine
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DADS/Plant Results - DADS/Plant Results - Actuator LoadActuator Load
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TestingTesting
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Flow RegulatorsFlow Regulators
• Manifold, Cartridge Valve Flow RegulatorManifold, Cartridge Valve Flow Regulator
- Fluid RegulatorsFluid Regulators
- Modify Current 2.0 gpm Flow RegulatorsModify Current 2.0 gpm Flow Regulators
- .5 gpm & 1.0 gpm.5 gpm & 1.0 gpm
• MS-Type Flow RegulatorMS-Type Flow Regulator
- Parker HannifinParker Hannifin
- 1.5 gpm & 2.0 gpm1.5 gpm & 2.0 gpm
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Cartridge Valve Flow Cartridge Valve Flow RegulatorRegulator
Two-Way Flow Regulator Response
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 500 1000 1500 2000 2500 3000
Valve Differential Pressure (psi)
Flo
w (
gp
m)
1 gpm Valve
.5 gpm Valve
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TestsTests
• Baseline TestBaseline Test
- Verify Door Operates ProperlyVerify Door Operates Properly
• 1st Test1st Test
- 1.0/2.0 gpm Flow Regulators1.0/2.0 gpm Flow Regulators
- Regulators Delivered as SpecifiedRegulators Delivered as Specified
• 2nd Test2nd Test
- .5/1.5 gpm Flow Regulators.5/1.5 gpm Flow Regulators
- Modified 2.0 -> .5 gpm Could Not Perform as DesiredModified 2.0 -> .5 gpm Could Not Perform as Desired
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C-5 Aft Pressure DoorC-5 Aft Pressure Door
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C-5 Aft Pressure DoorC-5 Aft Pressure Door
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C-5 Aft Pressure DoorC-5 Aft Pressure Door
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Test ResultsTest Results
• BaselineBaseline
- Operated ProperlyOperated Properly
- Approximately 10 second OpeningApproximately 10 second Opening
• 1st Test1st Test
- Approximately 19 second OpeningApproximately 19 second Opening
- Predicted 21.29 second OpeningPredicted 21.29 second Opening
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Test Results, cont.Test Results, cont.
• 2nd Test2nd Test
- Approximately 22 second OpendingApproximately 22 second Opending
- Predicted 40 seconds with Constant .5 gpm FlowPredicted 40 seconds with Constant .5 gpm Flow
- 2nd Test - Better Performance2nd Test - Better Performance
• Re-Run Simulations with Variable Flow Rate Re-Run Simulations with Variable Flow Rate RegulatorRegulator
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SolutionsSolutionsPart 2Part 2
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Loads & PressuresLoads & Pressures
• Goal of First ModelGoal of First Model
- Hydraulic Modification Will It Work?Hydraulic Modification Will It Work?
- How Long to Open & Close DoorHow Long to Open & Close Door
- Not Concerned with LoadsNot Concerned with Loads
• After Test, Model Fidelity Improved to Assist Loads & After Test, Model Fidelity Improved to Assist Loads & Structural Analysis OrganizationsStructural Analysis Organizations
- Variable Flow Regulator SimulatedVariable Flow Regulator Simulated
- Balanced Relief Valves AddedBalanced Relief Valves Added
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Model DefinitionModel Definition
• Structural Flexibility in Fuselage ModeledStructural Flexibility in Fuselage Modeled
• DADS/Flex Used to Model Torque Arm/HookDADS/Flex Used to Model Torque Arm/Hook
• ForcesForces
- 10 Bushings10 Bushings
• MSC NASTRAN Model Used to Find Spring ConstantsMSC NASTRAN Model Used to Find Spring Constants
- 4 RSDAs - Damping Only - Friction, Any Uncertainties4 RSDAs - Damping Only - Friction, Any Uncertainties
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Model DefinitionModel Definition
• Flexible BodiesFlexible Bodies
- Left & Right Torque Arm & HookLeft & Right Torque Arm & Hook
- MSC NASTRANMSC NASTRAN
- 1st Simulation Craig-Bampton Modes not Defined 1st Simulation Craig-Bampton Modes not Defined ProperlyProperly
- Continue Work Upon Return to MariettaContinue Work Upon Return to Marietta
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DADS/FlexDADS/Flex
• Craig-Bampton Mode ErrorsCraig-Bampton Mode Errors
- Fixed ConstraintsFixed Constraints
- Free ConstraintsFree Constraints
• Axis OrientationAxis Orientation
- Local z-axis Parallel to Global y-axis for Revo & Cyli Local z-axis Parallel to Global y-axis for Revo & Cyli JointsJoints
- Several Axes Rotated about Global y-axis to Achieve Several Axes Rotated about Global y-axis to Achieve Correct Load PathCorrect Load Path
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NASTRAN ModelNASTRAN Model
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Torque Fitting Torque Fitting RepresentationRepresentation
• Torque Fitting and Arms IsolatedTorque Fitting and Arms Isolated
• Interface Points DefinedInterface Points Defined
- Shaft Inboard and Outboard BearingsShaft Inboard and Outboard Bearings
- Actuator AttachActuator Attach
- Door/Arm ContactDoor/Arm Contact
- Inboard RollerInboard Roller
- Restraint HookRestraint Hook
• Structure Idealized in NASTRANStructure Idealized in NASTRAN
• Mirrored for Right SideMirrored for Right Side
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Fitting Back-Up Fitting Back-Up RepresentationRepresentation
• Fuselage Plug from FS 1964 to 2178 Used. Detailed Fuselage Plug from FS 1964 to 2178 Used. Detailed Idealization of Back-up Frame Included.Idealization of Back-up Frame Included.
• Five Interface Points ChosenFive Interface Points Chosen
- Actuator PointActuator Point
- Inboard Upper Support PointInboard Upper Support Point
- Outboard Upper Support PointOutboard Upper Support Point
- Inboard Lower Support PointInboard Lower Support Point
- Outboard Lower Support PointOutboard Lower Support Point
• Mirrored for Right SideMirrored for Right Side
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NASTRAN Analysis RunNASTRAN Analysis Run
• Normal ModesNormal Modes
• Imposed Deflection Force Matrix GenerationImposed Deflection Force Matrix Generation
- Unit deflections imposed on interface point DOF’s one Unit deflections imposed on interface point DOF’s one at a time with remaining interface point DOF’s at a time with remaining interface point DOF’s constrained.constrained.
• Analyses performed for each side separately for each Analyses performed for each side separately for each substructure.substructure.
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Fitting IdealizationFitting Idealization
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Back-Up IdealizationBack-Up Idealization
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Conclusion &Conclusion &Lessons LearnedLessons Learned
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MethodologyMethodology
MECHANICALSYSTEM
PROTOTYPE
MONODETAILMODELS
KINEMATICS(CAT/DADS)
MECHANICALSYSTEMBUILDUP
DYNAMICS
HYDRAULICS& CONTROLS
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Integrated CAEIntegrated CAE
• CATIACATIA
- Work From One Geometry Model (CATIA)Work From One Geometry Model (CATIA)
• DADSDADS (CAT/DADS)(CAT/DADS)
- Define Load PathsDefine Load Paths
• NASTRANNASTRAN
• EASY5EASY5
• Clearly Define Requirements for InterfacesClearly Define Requirements for Interfaces
• INTEGRATED CAE WILL SAVE TIME & MONEYINTEGRATED CAE WILL SAVE TIME & MONEY