TM 1-1520-253-23
Mechanical vibration energy generated by resonance test equipment can be measured, analyzed
by the tester, then displayed on a screen. There are several ways this energy can be applied to
material and then be analyzed. Because bonded metallic and composite material properties differ
substantially, no one test method will detect flaws n all types of material. For this reason, current
bond testing equipment incorporates at least one or more of the aforementioned features.
contained in this manual and the Nondestructive Inspection Methods manual listed in Table 1-1.
WARNING
Electrical equipment shall not be operated in areas where combustible gases or
vapors may be present, unless the equipment is explosion-proof.
a. If instrument is operated using AC power, use a grounded power cord.
b. Turn power OFF before connecting or disconnecting probe cable or power cable.
NOTE
Fluorescent penetrant inspections shall be performed in accordance with the
general applications and techniques in TM 55-1500-335-23 (Nondestructive In-
spection Methods manual) and the specific requirements of this technical manual.
The basic purpose of fluorescent penetrant inspection is to increase the visible contrast between
a discontinuity and its background. This method is performed by applying a fluorescent penetrant
solution to the inspection area which enters the surface opening of the discontinuity. The area is
then wiped or rinsed and a developer is added to draw the fluorescent material from the discontinu-
ity. A flaw or crack in the part will then become visible under the influence of ultraviolet light (black
light). This method is effective for detecting surface flaws in forgings, castings, extrusions, formed
sections, webs, and skins of materials. The penetrant method of inspection requires that the surface
of the inspection area be thoroughly cleaned. Paint on the part must be removed before inspection.
CAUTION
Penetrant-Emulsifier/Remover Combinations (lipophilic/hydrophilic) from one
manufacturer may not be mixed or used in conjunction with materials from a
different manufacturer.
Four penetrant procedures are given in Tables 1-3, 1-4, 1-5, and 1-6. All four inspections shall be
conducted using fluorescent penetrant, AMS 2644, Type I, Method A, B, C, or D, sensitivity level
3 or 4. Parts requiring fluorescent penetrant inspection shall be cleaned prior to inspection with
n-propyl bromide (vapor degreasing only) (Table 1-8), DS-108 (Table 1-8), Electron (Table 1-8),
Positron (Table 1-8). DS-108, Electron, and Positron must be followed by an Acetone (Table 1-8)
or Isopropyl Alcohol (Table 1-8) rinse or wipe; or drying until there is no visible solvent residue left
on parts. Refer to the Nondestructive Inspection Methods manual listed in Table 1-1 for more
detailed instructions. Table 1-5 describes the procedure for using Type I, Method C, Level 3 or 4
on a removed part or parts attached either to a component or to the helicopter. This procedure
supports the accomplishment of fluorescent penetrant inspection at the AVUM and AVIM levels
regardless of geographic location. Therefore, the procedure in Table 1-5 will be one of the most
frequently referred to in this manual. Table 1-7 lists the equipment and Table 1-8 lists the fluorescent
penetrant materials to be used.
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