NDI General Safety Precautions

Figure 1-5. Bond Testing Reference Block Displays

TM-1-1520-265-23 H-60 Helicopter Series Manual
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TM 1-1520-265-23 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. 1.4.5 NDI General Safety Precautions. WARNING 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. 1.4.6 Bond Testing (BT) Method. NOTE 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. 1.4.6.1 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.

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