17 April 02 - 1

Prepared by: Callista RodriguezPresented by: Jim TalleyGeneral Dynamics Armament SystemsBurlington, Vermont

17 April 2002

Prepared by: Callista RodriguezPresented by: Jim TalleyGeneral Dynamics Armament SystemsBurlington, Vermont

17 April 2002

Correlation of Analysis and FiringTest Results for a TurretedGatling Gun System

Correlation of Analysis and FiringTest Results for a TurretedGatling Gun System

17 April 02 - 2

l Objective: To Obtain a Correlated Model for systemdesign studies and requirements flowdownä Traditional Linear Finite Element Analysis (FEA) Approach

ä New Non-Linear Rigid and Flexible Body Dynamics (ADAMS)Approach

ä Integrate ADAMS non-linear model with control systemalgorithms

Analytic Modeling Process

17 April 02 - 3

Turret Configuration 33 Round Burst

17 April 02 - 4

l Three key elements are compared in the direction of largeMPI shiftä Targeting Point of Impact (PI) comparison (Hardstand and Turret)

n muzzle pitch anglen muzzle translational velocity effects

ä Barrel bending shape (Hardstand)ä Interface loads (Hardstand)

Correlation Parameters

Muzzle Pitch Angle

Muzzle Vertical Displacement derivative is Muzzle Vertical Velocity

17 April 02 - 5

l Small Deflections (No spinningbarrel cluster)

l Linear systemä Linear recoil adapterä No gapsä Fixed boundary conditions at motor

l Fixed temperaturel Mass of all components match

weight reports or measurementsl P-T curve applied at barrel breechl Turret is modeled as a lumped

mass spring system using stiffnessvalues from test

Linear Finite Element Models

Firing Barrel9 O’Clock

Firing Barrel12 O’Clock

Hardstand

Turret

17 April 02 - 6

Tests Performed in Support ofCorrelation

l Gun in Hardstandand TurretConfigurationsä Modal Testingä Fire Testing of Static

(non-rotating) SingleShots for muzzleangle and barrelshape measurements

ä Burst Fire Testing

l Turret StiffnessMeasurements

17 April 02 - 7

Hardstand Correlation forNormalized Predicted Impact Point

Comparison of Normalized Predicted Impact Point

Due to Muzzle Angle and Lateral Velocity

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

-3 -2.5 -2 -1.5 -1 -0.5 0 0.5

TIME (msec)

NO

RM

ALI

ZED

AN

GLE

OFF

BO

RE

SIG

HT

"Average of Test Data" "FEA Results"

l FEA results follow shapeof test measurements

l Key Metric is Slopel Projectile exit occurs

within +/- .05 msec of 0on the X axis

l Small differences infrequency between FEmodel and actualhardware make asignificant difference inpredicted target

17 April 02 - 8

-0.8-0.6

-0.4-0.2

00.2

0.40.6

0.81

1.2

0 5 10 15 20 25 30 35

DISTANCE FROM MUZZLE

NO

RM

ALI

ZED

DEF

LEC

TIO

N

Test Number 2 Test Number 3 Test Number 4

Test Number 5 Test Number 6 Test Number 7

Test Number 8 FEA Early Exit FEA Late Exit

Hardstand Barrel DeflectionCorrelation

l Predicted shape issimilar to measuredshape

MIDBARRELMUZZLE

17 April 02 - 9

l Close comparisonl Most predictions up to 200 Hz within 7%

Modal Correlation in Turret Configuration1st Elevation and Azimuth Modes

Elevation Azimuth

17 April 02 - 10

l Most Significant Barrel Bending Mode

High Frequency Barrel Bending Mode

This mode is excited by high frequency pitching/yawing excitation due to• Off center firing impulse which contains high frequency content• Muzzle axial fixity (firing barrel recoil imparts moment at muzzle)

l Barrel Deflected Shape at Projectile Exit

17 April 02 - 11

Normalized Predicted Vertical Impact Point Comparison of FEA Predictions to Test Calculations

-0.2

0

0.2

0.4

0.6

0.8

1

-2 -1.8 -1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6

Test SAR configuration

Test SAC configuration

FEA prediction

l Most significantbarrel bendingmode is evident

l FEA resultsfollow shape oftest data

l Projectile exitoccurs within +/-.05 msec of 0 onthe X axis.

Correlation of Predicted ImpactPoint in Turret Configuration

NO

RM

ALI

ZE

D D

EV

IAT

ION

FR

OM

BO

RE

SIG

HT

TIME AFTER ROTATING BAND EXIT

17 April 02 - 12

l Non-linear recoiladapter

l Spinning barrel clusterl Flexible barrel cluster

and housingl Does not include

modeling of friction orclearances

Non-linear ADAMS Model:Firing Animation

Barrel deflection is highly exaggerated

17 April 02 - 13

Normalized Muzzle X-Y Motion Plot

-1.25

-1.00

-0.75

-0.50

-0.25

0.00

0.25

0.50

0.75

1.00

1.25

-1.25 -1.00 -0.75 -0.50 -0.25 0.00 0.25 0.50 0.75 1.00 1.25

Non-linear ADAMS Model: Barrel X-Y Plot

l Traces position oftop barrel duringspinning (counterclockwise)

l (0,0) center ofmuzzle clusterbefore gravity

l Exhibits deflectionfrom gravity

l Exhibits barreldeflection wheneach barrel fires

Start of burst

End of burst

Response of Brl 1 to Brl 2 firing

Response of Brl 1 to Brl 3 firing

Firing Barrel Muzzle Swept Motion

LATERAL MOTION

VE

RT

ICA

L M

OT

ION

17 April 02 - 14

l Shape of muzzleangle prediction issimilar to test data

l High frequencycomponentsmissing

ADAMS Muzzle Pitch AngleComparison

Normalized Muzzle Pitch Angle

Normalized Pitch Muzzle Angle versus Rotating Band Exit Comparison of ADAMS Predictions to Test Calculations

-1.00

-0.75

-0.50

-0.25

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

-2 -1.9 -1.8 -1.7 -1.6 -1.5 -1.4 -1.3 -1.2 -1.1 -1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3

Time After Rotating Band Exit (ms)

Test SAR configurationADAMS predictionTest SAC configuration

;

TIME AFTER ROTATING BAND EXIT

NO

RM

ALI

ZE

D M

UZ

ZLE

AN

GLE

17 April 02 - 15

l Most Comprehensive and Successful Gun and Turret Correlationto Date

ä Correlation of linear FEM of gun in Hardstand and Turretconfigurations (traditional method)

ä Correlation of non-linear ADAMS model of gun in Turretconfiguration (New Approach)

l Both FEA and ADAMS models are excellent tools for designtrade studies

l ADAMS Non-linear model advances state of the art analysistechniques for:

ä Greater fidelity of interface load calculations

ä Spinning stability evaluation including gravity effects

ä System failure mode evaluation

Analytic Modeling