FEASIBILITY STUDY OF A NON-DESTRUCTIVE TESTING INFRARED INSPECTION SYSTEM FOR BONDING FLAW DETECTION
PERKIN-ELMER CORP NORWALK CONN
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An investigation was begun to establish the feasibility of IR measuring techniques for detecting bond failures flaws or voids between rocket casings and the insulating liner and between the liner and the solid propellant. The IR detection principles involve 1 the injection of heat into the rocket casing over a small area surrounding the point of measurement, 2 detection of variations in wall diffusivity by the time varying emission characteristic from the region of heat application, and 3 evaluation of fluctuations of the emission characteristic by comparison of the signal to that arising from a flawless bond. Preliminary measurements were made on flat plate samples with known flaw configurations. An intensive analysis of heat flow mechanisms in bonded structures has progressed from the formal solution of partial differential equations to the creation of an electric analog model of the 1 dimensional heat flow problem. Analog results indicate that a flaw between the case and liner about 0.1 cm separation and 0.78 sq cm nominal area is detectable with a maximum contrast ratio of 6.7 between 2 and 5 sec after heat injection. A similar defect between the liner and propellant gives a maximum surface contrast ratio of 16.5 about 10 sec after heat injection.