The United States of America As Represented by the Administrator of the

United States of America As Represented by the Administrator of Nasa

The United States of America As Represented by the United States

William P Winfree

Joseph S Heyman

Terry L St Clair

Anne K St Clair

K Elliott Cramer

Joseph N Zalameda

William E Miller

D Michele Heath

William T Yost

Christopher S Welch

Christopher Welch

Joseph N Zalamedia

Acoustic thermography uses a housing configured for thermal, acoustic and infrared radiation shielding. For in-situ applications, the housing has an open side adapted to be sealingly coupled to a surface region of a structure such that an enclosed chamber filled with air is defined. One or more acoustic sources are positioned to direct acoustic waves through the air in the enclosed chamber and towards the surface region. To activate and control each acoustic source, a pulsed signal is applied thereto. An infrared imager focused on the surface region detects a thermal image of the surface region. A data capture device records the thermal image in synchronicity with each pulse of the pulsed signal such that a time series of thermal images is generated. For enhanced sensitivity and/or repeatability, sound and/or vibrations at the surface region can be used in feedback control of the pulsed signal applied to the acoustic sources.

Air-coupled acoustic thermography for in-situ evaluation

The invention is a synchronized electronic shutter system (SESS) and method for same side and through transmission thermal analysis and inspection of a material for finding defects, corrosion, disbond defects, integrity of a weld and determination of paint thickness. The system comprises an infrared detector that acquires background images of the sample. A shutter then covers the detector and lamps rapidly heat the sample above ambient temperature. Shutters cover all lamps at the same time the shutter over the infrared detector is opened. The infrared detector acquires a series of temperature images over time radiated from the sample as the sample cools down. After collecting a series of temperature images taken by the SESS, a processed image is developed using one of the group comprising time derivative calculation, temperature normalization data reduction routine, thermal diffusivity curve fitting and averaging the series of temperature images.

Synchronized electronic shutter system and method for thermal nondestructive evaluation

A method and a portable apparatus for the nondestructive identification of defects in structures. The apparatus comprises a heat source (20) and a thermal imager (30) that move at a constant speed past a test surface (10) of a structure. The thermal imager (30) is off set at a predetermined distance from the heat source (10). The heat source (10) induces a constant surface temperature. The imager (20) follows the heat source (10) and produces a video image of the thermal characteristics of the test surface. Material defects produce deviations from the constant surface temperature that move at the inverse of the constant speed. Thermal noise produces deviations that move at random speed. Computer averaging of the digitized thermal image data with respect to the constant speed minimizes noise and improves the signal of valid defects. The motion of thermographic equipment coupled with the high signal to noise ratio render it suitable for portable, on site analysis.

Method and apparatus for the portable identification of material

A heat source such as a magnetic induction/eddy current generator remotely heats a region of a surface of a test structure to a desired depth. For example, the frequency of the heating source can be varied to heat to the desired depth. A thermal sensor senses temperature changes in the heated region as a function of time. A computer compares these sensed temperature changes with calibration standards of a similar sample having known disbond and/or inclusion geography(ies) to analyze the test structure. A plurality of sensors can be arranged linearly to sense vector heat flow.

Method and apparatus for thermographically and quantitatively analyzing

A series of polyimides based on the dianhydride of 1,4-bis(3,4-dicarboxyphenoxy)benzene (HQDEA) or on 2,2-bis[4(3-aminophenoxy)phenyl]hexafluoropropane (3-BDAF) are evolved from high molecular weight polyamic acid solutions yielding flexible free-standing films and coatings in the fully imidized form which have a dielectric constant in the range of 2.5 to 3.1 at 10 GHz.

Low dielectric polyimides

A structure which is effective as an electrical insulator or as a transmitter-receiver of electromagnetic energy is prepared by providing a suitable substrate and covering the substrate with an adhering layer of a low dielectric, high temperature, linear aromatic polyimide. This polyimide is prepared by:

Structures from low dielectric polyimides

A sample in a wind tunnel is radiated from a thermal energy source exteriorly of the wind tunnel. A thermal imager system, also located exteriorly of the wind tunnel, reads surface radiations from the sample as a function of time. The produced thermal images are characteristic of the heat transferred from the sample to the flow across the sample. In turn, the measured rates of heat loss of the sample are characteristic of the flow and the sample.

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Williamsburg, VA, United States of America

William P Winfree