Digirad or Digital Radiography of Body Armour Inserts.
Digirad is a fairly new technology available to the NDT community for improved radiography.
Simple Theory.
As with conventional Radiography, a collimated beam of ionising radiation is passed through the
component under inspection. Where a radiographed material is homogeneous, of uniform thickness
and contains no cracks, voids or other defects the radiation that penetrates the component will largely
be of equal intensity.
Where a void, crack or other defect type is present the amount of radiation penetrating the imperfection
will tend to be a little higher. With conventional (film) radiography, a radiation sensitive film is placed on
the far side of the component, which records the amount of radiation that impinges on the plate over each
individual grain of medium.
Digital radiography is set-up in a very similar manner, except that the plate used to detect the radiation
can be re-used and requires no chemicals. Instead a special laser scanner scans the plate and detects
the latent image that has been generated by the radiation.
A few of the advantages of Digital Radiography over conventional film radiography are:
ü less energy is used posing a smaller radiation hazard
ü the plate is re-useable
ü processing is by scanner and requires no chemicals to be used or disposed of
ü the images can be stored on CD, hard disk or similar, thus reducing storage space
ü the images can be readily copied and can be transmitted electronically
ü the image can be digitally enhanced, thereby permitting much more subtle changes
in density to be detected
Body Armour Plates.
With body armour plates there exists an assembly which would typically consist of a ceramic plate
bonded with adhesive onto a composite backing plate (possibly Aramid or similar). All of this would
then be enveloped inside an outer coat of a ballistic nylon held in place with yet another adhesive.
Digirad.
ArmourTest’s DIGIRAD testing service offers the maximum level of assurance in the integrity of their body
armour plates.
Our laboratory in the heart of the UK is fully equipped with devices to offer a full inspectionand sentencing service using DIGIRAD, thereby ensuring that users “in theatre" have safe equipment to
use.
By combining the RFID and DIGIRAD technologies with the additional archiving and traceability services
offered by ArmourTest the end user will be able to assure the quality and track logistically the whole
fleet of ceramic armour plates throughout their operational life.
For small quantity users of Body Armour Plates, ArmourTest is able to offer a mobile “on-site" service
using a motorised exposure and evaluation unit, staffed by skilled personnel.
Other Inspections.
DIGIRAD is a definitive test on existing plates, but is inappropriate for “in theatre" applications by unskilled
or semi-skilled personnel. The radiation hazard must be respected and in the hands of unskilled personnel
a greater health hazard exists. As well as DIGIRAD, ArmourTest is able to offer a Resonant Inspection
testing service and also sales of a Resonant Inspection test machine which can be operated “in theatre"
by semi-skilled personnel. This equipment is not a definitive test technology, but will serve to identify those
body armour plates that present a significant risk to the users.
Inspection using Air Coupled Ultrasonics (or Airscan) to evaluate the integrity of the bonding between
Kevlar
and Ceramic has been investigated. It has been concluded that for used body armour plates,differences in bonding characteristics of the Ballistic Nylon coatings has a significantly greater effect on
the airscan result that bonding problems between Kevlar and Ceramic. This is only a feasible test to
perform during total refurbishment when the covers are not present.