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![Page 1: Expeditionary Systems Evaluation Division · Expeditionary Systems Evaluation Division NSWC Crane Division Detachment Fallbrook ... • Evaluation of Operational Loading of M777 Magazine](https://reader031.vdocuments.site/reader031/viewer/2022020214/5afb124a7f8b9ad220900970/html5/thumbnails/1.jpg)
105/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Pyrotechnic Shock Loadingof the
M82 Percussion Primer in theM777 Light Weight Howitzer Magazine Assembly
Presented to theNDIA Joint Armaments Conference
May 2010
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205/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Co-Authors• Dr. Ryan Olsen, T&E Board Chairman, NSWC Crane, Detachment
Fallbrook, ESED• Kathryn Hunt, Chemical Engineer, USMC MARCORSYSCOM, PM
Ammo• Mr. Victor Hugo, Mechanical Engineer, NSWC Crane, Detachment
Fallbrook, ESED• Mr. Jon Conner, Senior Scientist, National Technical Systems,
Dana Point, CA• Mr. Caleb Bell, Program Manager, National Technical Systems,
Camden, AR
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305/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Pyrotechnic Shock Loading of the M82 Percussion Primer in the M777 Light Weight Howitzer Magazine Assembly
• Background– M82 Percussion Primer Description and Design– M777 Primer Feed Mechanism– Premature Primer Functioning Observations– Test Design and Objective
• Evaluation of Operational Loading of M777 Magazine Assembly– Instrumentation Description– Field Test Firing Schedule– Data Reduction/Signals Analysis
• Simulation of Operational Loading with Laboratory Shock Tests– Baseline Sensitivity Test– Pyrotechnic Shock– Sine Burst– Drop Shock
• FEA and Test Results• Summary and Conclusions
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405/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
M82 Percussion Primer Description
– US Army and Marine Corps standard primer for the initiation of all 155mm Howitzers
– During functioning, black powder output ignites propelling charge
– On earlier Howitzers the primer was hand loaded into breach– New Howitzer designs incorporate a mechanical loading
assembly
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505/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
M82 Percussion Primer Design
PLUNGER
PRIMER
BODY
PRIMER CHARGE (BLACK POWDER)
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605/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
M777 Howitzer Primer Feed Mechanism Description
PRIMER MAGAZINE AND TRAY ASSEMBLY
PRIMER FEED ATBREACH ASSEMBLY
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705/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Premature Primer Functioning
– During initial weapon testing, multiple primers functioned in the magazine during firing
– Field malfunctions associated with functioning of primers during chambering
– Primer is subjected to extreme forces associated to M777 firing
– Primer not designed to withstand these types of forces
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805/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Test Design and Objective
Understand the impact of M777 firing on the M82 primer– Measure forces associated with M777 firing– Simulate these forces – Condition M82 Primers to simulated forces– Verify their functional performance and sensitivity
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905/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Instrumentation Description
• 3 Each Endevco 2225M5A Piezoelectric Accelerometers (100,000 g’s)
• Installed on Tri-axial Mounting Block
• Mounting Block Bolted to Top of Primer Magazine Assembly
• Cables Tied Down and Routed to Side of Gun System
• Endevco 133 Charge Amplifier
• LDS Genesis Digital Data Recorder
– 125 kHz Sampling Rate
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1005/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Field Test Firing Schedule
Round Numbers
Projectile Fuze PropellingCharge
1-4 M795 HE M739A1 MACS at Increment 5
5-8 M795 HE M739A1 M203A1
9-12 M107 HE M739A1 M4A2 White Bag - Charge 7
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1105/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Data Reduction/Signals Analysis
Raw Accel Data – Z Axis
Band Pass FilterSmoothed
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1205/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Composite Acceleration Shock Response Spectra
X Axis Y Axis Z Axis
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1305/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Data Reduction/Signals Analysis Summary
• Forces compromised of 3 distinct phenomena– Shock associated with propellant combustion– Harmonics associated with projectile travelling down
barrel– Recoil force
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1405/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Data Reduction/Signals Analysis - Conclusions
• Laboratory simulation requires three techniques– Pyrotechnic Shock
– Simultaneous in all 3 axes – Based on Composite SRS
– Electro-Dynamic Shaker– 250 Hz, 200 g Sine Burst in Z axis
– Drop Test – 200 g, 10 msec Half Sine Pulse in Z axis
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1505/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Simulation of Operational Loads – Test Methodology
• Sensitivity Testing– Establish Baseline M82 Percussion Primer Lot Sensitivity– Evaluate Impact of Sequential Shock Testing on Sensitivity
• Shock Testing w/Test Fixtures to Replicate Tactical Magazine Interfaces
– 100 Primers Total– Replica Magazine Test Fixture Holds 10 Primers– 9 Shock Replications Applied to Each Group Sequentially
• Drop Shock• Pyrotechnic Shock Tests• Sine Burst Tests
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1605/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Drop Shock Testing
M82 Primers in Magazine Fixture Drop Shock Test SetupAccel Data – Z Axis
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1705/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Pyrotechnic Shock Testing
Magazine Fixture w/Accels Magazine Fixture Mounted to Resonating Plate
Det Cord Patters for Pyroshock
Example +/- SRS Response Curve
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1805/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Pyrotechnic Shock TestingPremature Function of M82 Primer
Group 5 Pre-Test Group 5 Post-Test
Group 5 SN 1 Premature Function(overstress of force)
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1905/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Sine Burst Shock Testing
Group 10 Pre-Test
Electro-Dynamic Shaker Test Setup
Example Response Accel Output
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2005/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Dynamic FEA Analysis Results
Plunger/Primer Only Model:Primer Cup Material Yield Strength Approx 17 ksi
Dynamic Shock Load Max Von Mises Stress in Primer Cup (ksi)
Z Axis Pyroshock SRS 19.8Z Axis Drop Shock 0.136Z Axis Sine Burst 0.235
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2105/04/10
Expeditionary Systems Evaluation DivisionNSWC Crane Division Detachment Fallbrook
Summary and Conclusions• Operational Loading of M82 Percussion Primers During
M777 Firings Evaluated for Various Maximum Charge Configurations
– Loading consists of three aspects: pyrotechnic shock, 250 Hz harmonic burst, and recoil shock
• Pyrotechnic Shock Loading is Most Severe Aspect of Operational Loads Based on Lab Tests and Dynamic FEA Analysis
– Overstress induced premature function of primers
• Sensitivity testing of conditioned primers in progress