TM 1-1500-204-23-7
(c)
Cracks. Cracks and other crack-like discontinuities are found in numerous parts and structures and are
very dangerous discontinuities. This is particularly true where structures are subjected to vibration or fatigue loading, due
to propagation of these crack-like discontinuities. Crack-like discontinuities will appear in a radiograph as very straight
and sharply outlined dark or black lines. Cracks may also appear as diffused jagged lines. in some cases they have a
tree-like pattern. Scatter radiation from the sides of a crack can act as an amplifier of the crack image in a radiograph.
This is the most difficult service type failure to detect by radiography since these crack separations are usually not
associated with other detectable conditions which give clues to their presence.
(d)
Water in honeycomb. A typical condition that occurs in honeycomb structures is the formation of water
in the cores. This entrapped water freezes and expands at high altitudes. The expansion distorts the cells and can break
the bonds between core and facing sheets. When this condition exists, vibration of the face sheet can occur, causing
failure of adjacent bonds and propagation of bond failure. Entrapped water causes corrosion of both face sheet and core
structure. Radiographic inspection is conducted to evaluate core damage and water contents as a maintenance
inspection.
(e)
Foreign objects. Radiography is an excellent method to locate and evaluate foreign objects. Foreign
objects may be free rivets, bolts, or other objects that could be detrimental to the function of the part or assembly.
(f)
Assemblies. Radiography has found wide use in the evaluation of various assemblies to determine
status or condition. If the use of the assemblies produces changes in it which are recordable by an X-ray beam, then
radiography may be useful in supplying confirming evidence of the suspected condition.
(g)
Workmanship. On occasion, components are misassembled. In some areas it is not possible to check
dimensions by physical or visual means. Radiography may be used if precautions are taken to assure proper
geometrical relation to determine dimension of internal spacings.
(h)
Human error. There is continually the possibility of human error in servicing equipment. This type of
error can also be detected by radiography.
b.
Misinterpretation. The mistakes in radiographic interpretation most often are a result of misreading film artifacts.
There are a number of density patterns which resemble welding and casting defects which are often unjustified causes
for rejects. Refer to TM 551500-335-23 for common misinterpretations.
5-10. Filing Radiographs. The final radiographs should be placed In film filing envelopes for final storage. These
envelopes are constructed of heavy kraft paper to protect the films. The envelope should be identified as to the
radiographs it may contain and filed in a systematic manner to facilitate retrieval If and when necessary. Envelopes
should be marked prior to insertion of the film to prevent pressure marks. Films should not be stored in high humidity
areas. Film filing cabinets are available for film storage. Ordinary filing cabinets are not sufficiently strong to withstand
the heavy loads of filed film.
5-11. Radiography Safety Precautions and Equipment. The following paragraphs explain safety precautions and
equipment to be followed by personnel working with radiography.
WARNING
Women SHALL NOT perform radiographic procedures or be subjected to industrial ionizing
radiation during their term of medically confirmed pregnancy without specific approval. For
further guidance consult the Base Bioenvironmenta/Radiological Engineer.
Persons in the general population at any age. Such individuals should not receive an exposure
exceeding 0.5 rem per year in addition to natural background and medical exposures (This limit
applies to those persons who are not occupationally exposed. This rate equates to 10 percent of
that allowable for occupationally exposed/monitored personnel. NCRP Report No. 32, July
1,1966.)
a.
General. Safety is of paramount importance in radiography. Exposure to radiation results in the cumulative
buildup of radiation in the body. This buildup must be monitored and controlled.
5-6
