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Millimeter Wave Doppler Sensor for Nondestructive Evaluation of Materials

A novel Nondestructive Evaluation (NDE) method based on millimeter wave vibrometry has been developed for non-contact examination of materials and components. The 94 GHz I-Q Doppler sensor monitors the mechanical vibration signature of the object under interrogation that is induced by continuous wave or by pulsed excitation. For proof-of-principle demonstrations, the test objects were mechanically excited by an electronically controlled shaker using different excitation patterns: sinusoidal wave of various frequencies and a pulse excitation. Alternatively, the excitation could be induced in a non-contact manner by using a source of compressive waves (e.g., a speaker). The sensor allows continuous monitoring of the vibration signature of an object at relatively long standoff distances. The vibration signature can in turn reveal information about the thickness, shape, presence of defects, and other characteristics of the object under test. We will present a limited number of laboratory test results and will discuss the method’s applicability to some practical NDE applications.

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