M. Arad, D. Touati, A. Pila and I. LatovitzM. Arad, D. Touati, A. Pila and I. Latovitz

PERFORMANCE OF KINETIC ENERGY PROJECTILE -

NUMERICAL AND EXPERIMENTAL STUDY

IMI, P.O. Box 1104, IMI, P.O. Box 1104, RamatRamat Hasharon 47100, Israel Hasharon 47100, Israel

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Effect of Yaw and Obliquity on Penetration

n High velocity kinetic energy long rods are one

of the most important munitions of the main

battle tank.

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Passive armor

n One way to protect a tank against a kinetic

energy long rod is to configure a series of thin

plates as passive armor.

n These plates are generally oblique.

n This target is capable of breaking the rod.

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Effect of Yaw and Obliquity on Penetration

n The penetration process of a rod while penetrating a

thin and oblique target is characterized by the

following factors:

n erosion at the nose of the rod (large plastic strain)

n rotation and bending of the rod

n long rod breakage

n interaction between the broken parts and the target

n Yaw worsens the above phenomena

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The goals of the present work

n To build a numerical simulation of the penetrationprocess.

n Validation of the numerical model withexperimental results.

n Using the model to study the influence of the initialyaw on projectile penetrability.

n Using the numerical model to design an improvedprojectile.

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Obliquity is the angle between the velocity vector

of the rod and the normal to the target.

V

Obliquity

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Yaw is the angle between the velocity vector

direction of the rod and it's axis of symmetry.

V YawV Yaw

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Initial Yaw Sign

Negative initial yaw angle

Zero initial yaw angle

Positive initial yaw angle

VVVV

VV

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n The tungsten-alloy long rod penetrates the thin

steel target

Schematic of the Experimental Set-up

50 mm ≈700 mm

V=1600 m/s 65o

L/D=30

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X-Ray image of the rod after penetration

1600 /V m s=

simulation

Initial yaw ≈ 0°

Experimental Results

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simulation

Initial yaw ≈ 1°

X-Ray image of the rod after penetration

1600 /V m s=

Experimental Results

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simulation X-Ray image of the rod after penetration

Initial yaw ≈ -1° 1600 /V m s=

Experimental Results

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It is apparent that:

n the rod was bent and its nose was broken

n for a negative initial yaw angle the rod bends up

n for a positive initial yaw the rod bends down

n for a zero initial yaw the bending is minimal

Experimental Results

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A three-dimensional time-dependent finite

element numerical simulation (MSC/DYTRAN)

was performed in order to emulate the

penetration process of the rod during and after

target penetration .

Numerical Simulation

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n Lagrangian explicit model.n adaptive contacts to model the rod - target interactionn a nonlinear, plastic material description with isotropic

hardening:

n a polynomial equation of state: ε

σhE

E0σ0

hy p

h

E EE E

σ σ ε= +−

( )( )

2 3 2 31 2 3 0 1 2 3 0

01 0 1 0

0, 1

0

a a a b b b b ep

a b b e

µ µ µ µ µ µ ρ µ ρµ

ρµ µ ρ µ

+ + + + + + >= = −+ + ≤

Numerical Simulation

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A failure criterion model in the form of a user written

subroutine was added to the MSC/DYTRAN code:

n it depends upon the state of the material in the element

(stress, strain, pressure …)

n it is based on two types of material failure:n erosion failuren static maximum plastic strain failure

Numerical Simulation

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Experiment

Numerical Simulation

1600 /V m s= Initial yaw = 0°

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Experiment

Numerical Simulation

Initial yaw = 1° 1600 /V m s=

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Experiment

Numerical Simulation

Initial yaw = -1° 1600 /V m s=

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The bending process:

n enlarges the hole crater in the target

n decreases the rod velocity

n diverts the direction of the penetrator

In addition, for none zero initial yaw values:

n the side of the rod pointing in the direction of its velocity

is damaged. (This side is in greater contact with the

target because of the velocity direction).

Numerical Simulation

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n The overall results are a weakening of the rod and

a decrease in its ability to penetrate a series of

plates following the original thin plate target.

n For large yaw angles the bending of the long rod

will cause it to break into several pieces.

Numerical Simulation