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CASE PS1 - Failure of Barbed Ribbon Tape, J. Cecilio
Failure of Barbed Ribbon Security Tape
Failure-breaking apart of barbed ribbon security tape.
Collection of Facts:  Specification MIL-B-52775 general purpose barbed tape
obstacle (GPBTO) specified 3 types of material for the manufacture of the
tape.  Of these, the Navy has been specifying Type III. This allowed the use
of 201 and 301 stainless steel.  The cold working of the ribbon by crimping
the edge to obtain a curve in the plain of the ribbon suffered stress
corrosion cracking in these crimps.  Fatigue propogated the cracks across the
ribbon, causing failure.
Solution:  Laboratory evaluation (NRL) showed that 316 stainless steel would
perform satisfactorily if manufactured by the same process. The laboratory at
Keyport, WA. (NUWFS) showed that proper care in installation would
satisfactorily extend the fatigue life.
Specification MIL-B-52775 has been revised adding a Type VI material 316SS for
Navy use when exposed to a marine or evergreen acid environment.
CASE PS2 - Vehicle Barriers, J. V. Tyrrell
Providing adequate vehicle barriers to prevent unauthorized entry.
Unsatisfactory performance, excessive costs.
Collection of Facts:  Terrorism and overt unauthorized entry are becoming an
increasingly common problem.  There are many patented and proprietary systems
being offered to capitalize on the sudden demand (5/85).
Solution:  In order to design an effective barrier, the size, weight, and
speed of the vehicle must be considered.  A simple trench or a berm can
sometimes be very effective.  Heavy blocks (concrete, etc.) or planters can be
used.  For new facilities, it may be possible to provide a grade separation by
means of a low retaining wall along the perimeter to be protected.  There is
no value in providing an expensive gate control if the adjacent perimeter is
not equally resistant.

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