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Small Caliber Engraving Force Measurements Jeff Siewert Systems Engineer Arrow Tech Associates 1233 Shelburne Rd., Suite D-8 S. Burlington, Vt. 05403 802-865-3460 x19 [email protected] 1 Sponsor Contract: DAAE30-00-M-0236 Dr. Sheldon Cytron AMSTA-AR-PC-H 973-724-3368 [email protected]

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Small CaliberEngraving ForceMeasurementsJeff SiewertSystems EngineerArrow Tech Associates1233 Shelburne Rd., Suite D-8S. Burlington, Vt. 05403802-865-3460 [email protected]

1

sponsor
Sponsor

Contract: DAAE30-00-M-0236

Dr. Sheldon CytronAMSTA-AR-PC-H

973-724-3368

[email protected]

background
Medium Caliber Measurements

1972 GE ASD: Wolf & Cochran, 25mm

Large Caliber Experimental Data

1989, 1991 “Sticker” Testing, 155mm & 203mm

Small Caliber Interior Ballistic Simulations

Missing: Change in Pmax as F(n) Small Change in Dia.

No direct push force measurement until Feb 2003

Background
barrel sections for push force testing
Barrel Sections for Push Force Testing

Barrel Sections& Adapters

Instron Machine

Push Test In Progress

7 62mm barrel config con t
7.62mm Barrel Config. (con’t)

7.8225mm Dia.+ 0.0375

7.643mm Dia.+ 0.0325

4.365mm+ 0.175

0.0898mm

“Standard” Barrel Cross Section

mod 7 62mm reamer
Fabricated from Muzzle End of Original 7.62mm Bbl

Dimension

Key

Dimension, Inches

A:

0.4370

C:

0.474

D:

0.4570

E:

0.3460

F:

0.3440

G:

0.30850

H:

(TBD, est.0.2897”)

K:

2.0250

L:

1.3560

M:

0.3300

N:

0.1200

O:

0.2000

Q:

20 Degree

R:

2 1/2 Degree

Mod 7.62mm Reamer

2.5 Deg. Forcing ConeHalf Angle

polygonal barrel
Polygonal Barrel

5

6

7

8

4

3

Max Feature Depth

9

10

Barrel Radius

Torque Sidewall Angle

Angle (D)

x

Note: All Barrel Corners Have 3.9116mm Radius x 0.508mm Wide

Polygonal Barrels Attractive for Ceramic / Refractory Metals

m80 projectile resist press vs travel lube fc angle
Non-linear behavior

Differing Engraving Mechanism Assumed

Elastic in 1.2 Deg. Bbl, Plastic in 2.5 Deg. Bbl

M80 Projectile Resist Press vs. Travel, Lube & FC Angle
radial stiffness effect
Radial Stiffness Affects Engraving Forces

Bullet Construction Affects Radial Stiffness

Radial Stiffness Effect
relative stiffness effect on resistance pressure
Relative Stiffness Effect on Resistance Pressure

Multiplier on baseline engraving force prediction

effect on p t19
Changes to Peak Pressure within “normal” limits

FC Increase: Reduced Pmax, Lube: No Effect

Effect on P-T
observations
Non-linear Engraving Behavior

F(n) of Projectile Construction

F(n) of Projectile Lubrication

F(n) of Forcing Cone Half Angle

F(n) of Bullet: Diameter, Engraved Length

Reduced P-T Sensitivity

Due to Travel of Resistance wrt Pmax

>15 Shots Req’d to Attain SS Engraving

Observations
small caliber resistance pressure algorithm
Small Caliber Resistance Pressure Algorithm
  • Where:
    • Pr = Computed Resistance Pressure
    • PrN = Normalized Resistance Pressure
    • BD = Band Diameter, Calibers
    • BL= Band Length, Calibers
    • Mat’ FF = Material Code, 1.0 for Fe & Cu, 0.2 for Plastics
    • Stiffness FF = Stiffness Factor from chart
    • FC Len = Forcing Cone Length
    • K = Small Residual Constant
    • Q = Forcing cone angle (included angle)
predicted vs calc resistance pressure
Predicted vs. CalcResistance Pressure

Data Collection Length Limited by Column Buckling of Punch

conclusions
Small Caliber Engraving is a More Complex Relationship Than Expected

Closed Form Equation Can Be Used For Approximations

Detailed Knowledge Req’d of:

Barrel: Lands & Grooves, FC angle

Bullet: Construction, Lubrication

More Sophisticated Barrel Geometries (Polygonal) are under study

Conclusions
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