Change 2 1-19
readily removed. Effective masking shall be used to protect those components, such as bearings
and certain nonmetallics, that may be damaged by contact with the inspection solution or medium.
NDI General Safety Precautions.
Electrical equipment shall not be operated in areas where combustible gases or
vapors may be present, unless the equipment is explosion proof.
Prior to conducting an NDI inspection, survey the general area in advance. Eliminate possible
hazards created by loose structures, protruding work stands, and support equipment. Secure loose
electric cords and remove toxic fluids or fumes. If AC power is supplied to equipment, be sure that
equipment is well grounded to prevent electrical hazards. Specific safety instructions for each NDI
method used in this manual are contained in the paragraph immediately following the discussion
of that method.
Bond Testing (BT) Method.
Inspection of bonded structures shall be performed in accordance with the general
applications and techniques in TM 1-1500-335-23 (Nondestructive Inspection
Methods manual) and the specific requirements of this technical manual.
A number of different methods of NDI can be applied to the many configurations and types of bonded
structures that are in use. Variables such as skin materials and thickness, adhesive type and
thickness, underlying structure, and accessibility are all factors in the development of specific
inspection procedures. Because of the many inspection methods and structural configurations,
each application must be considered and reference standards representative of the structure must
be evaluated to verify proposed techniques.
18.104.22.168 Bond Testing Equipment. The bond testing equipment, Bondmaster, used in the procedures
in this manual, operates by generating a mechanical vibration into the material being tested. This
equipment is designed to detect flaws in bonded metallic and composite structures. The instrument
is capable of determining bad bonds, delaminations, unbonds, and crushed honeycomb core
defects. The Bondmaster has the following features:
a. Resonance. Detects unbonds and delaminations by changes in phase and amplitude at
probe resonance. Couplant is required.
b. Pitch Catch Swept. Measures amplitude and phase changes using a swept frequency
method to detect unbonds and deeper defects. Requires no couplant.
c. Pitch Catch Impulse. Measures amplitude and phase changes using a short burst of energy
to detect unbonds, Requires no couplant.
d. Mechanical Impedance Analysis (MIA). Measures the effect of generated sound waves and
the effect of loading as drive frequency is swept in the range of 2.5 KHz to 10 KHz. This
method can be used on unbonds, crushed core, and defects on the inside of composites.
Requires no couplant. See Figure 1-5, Bond Testing Reference Block Displays.