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Fig. 3. Velocity and yield strength impact on the VNZh-90 alloy elongated projectile
steel target penetration depth
obtained by varying the initial velocities of the projectiles are summarized
in Fig. 3 by the curves linking penetration depth
L
(a cavity depth inside
the target measured from initial position of its free surface) with the initial
velocity
v
0
of the projectile and its material yield strength
σ
Y
. Analysis of
the given data shows that projectile material strength properties (its yield
strength) produce relatively little effect on its penetration depth at the given
interaction velocities. So at velocity
v
0
= 1400
m/s the difference between
the maximal and minimal penetrations for a yield strength
σ
Y
ranging from
50 to 1500MPa is no more than 10% (the maximal penetration is 560 mm,
the minimal penetration is 510 mm). The higher the interaction velocity is
the less the effect from the yield strength becomes. The penetration depth
change, which is a function of the projectile material yield strength
σ
Y
at
v
0
= 2000
m/s, is about 7%.
It is of particular interest a “singular” effect of the projectile material
strength on the penetration depth which becomes especially evident at
a velocity
v
0
= 1400
m/s (see Fig. 3). This “singularity” implies the
existence of an extremum. It means that as the yield strength
σ
Y
rises,
the penetration depth increases at first, but then it starts decreasing.
The above-mentioned behavior of the penetration depth
L
being a
function of the projectile material yield strength remains unchanged at
the initial interaction velocities of 1600 and 1800 m/s. Moreover, as the
velocity increases a peak location shifts in the direction of higher
σ
Y
. At
v
0
= 2000
m/s a cavity depth within the given range from 50 to 1500MPa
increases monotonically as
σ
Y
rises. However, it is evident that if the
projectile material yield strength (above 1500MPa) continues increasing,
L
must start decreasing.
At the velocity
v
0
= 1400
m/s the penetration depth of the projectile
with the minimum strength (
σ
Y
= 50
MPa) turns out to be higher than in
74 ISSN 0236-3941. HERALD of the BMSTU Series “Mechanical Engineering”. 2015. No. 1