MIL-DTL-45225F(MR)
complete penetration velocity is equal to or above the minimum specified
ballistic limit velocity for the forged thickness, the ballistic limit will be
computed on the basis of 4-rounds or 6-rounds using the smallest possible
velocity spread. If the lowest complete penetration velocity is below the
minimum allowable ballistic limit velocity then testing will continue until a 10
round ballistic limit has been attained using the smallest possible velocity
spread. Ten round ballistic limits should be reported as such in a ballistic
test report as specified in MIL-STD-662.
6.4.2.3 Reduction of large velocity gap in borderline cases. If the ballistic
limit which has been attained is within + 10 fps of the minimum allowable
ballistic limit and a gap exists which is greater than 25 fps, then another
round, or rounds, will be fired to reduce the gap to 25 fps or less. The
ballistic limit will then be recomputed using the above criteria. The recomputed
BL(P) will be reported as the BL(P) of the plate (in borderline cases a reduction
of the gap between the high partial penetration velocity and the low complete
velocity should result in a better evaluation of the BL(P)).
6.5 Mechanical properties to ballistic requirements. The minimum mechanical
properties specified (see 3.3) may not assure that aluminum armor forgings meet
the specified ballistic requirements (see 3.4).
6.6 Stress Corrosion. To prevent failure in service due to stress corrosion,
care should be exercised in design and fabrication to minimize sustained surface
tensile stresses in the transverse direction. Any machining performed on the
forgings supplied according to this specification should be closely controlled
and the procuring activity should specify protective measures, when necessary,
such as shot peening, buttering, etc., to curtail any possibility of
stress-corrosion cracking. No alkaline etching should be permitted.
6.7
Definitions.
6.7.1 Complete penetration, (CP). A complete penetration occurs when the
impacting projectile, or any fragment thereof, or any fragment of the test
specimen perforates the witness plate, resulting in a crack or hole which permits
light passage when a 60 watt, 110 volt bulb is placed proximate to the witness
plate.
6.7.2 Contractor. The term "contractor" is defined as the organization having a
direct contract with the procuring activity.
6.7.3 Contracting officer. The term "contracting officer" means the person
executing a contract on behalf of the government, and any other officer or
civilian employee who is properly designated contracting officer; and the term
includes, except as otherwise provided, the authorized representative of a
contracting officer acting within the limits of his authority.
6.7.4 Fair impact. An impact may be considered fair when an unyawed fragment
simulator or test projectile strikes an unsupported area of the target material
at a specified obliquity at a distance of at least two projectile diameters from
any previous impact or disturbed area resulting from an impact, or from any
crack, or from any edge of the test specimen.
6.7.5 Gap A gap is the difference in fps between the high partial penetration
velocity and the low complete penetration velocity used to compute the ballistic
limit when the high partial penetration velocity is lower than the low complete
penetration velocity.
6.7.6 Manufacturer. The term "manufacturer" is defined as the organization
actually performing the operations covered by this specification.
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