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Your search keyword '"Zalameda, Joseph N"' showing total 291 results
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291 results on '"Zalameda, Joseph N"'

252. Thermographic imaging of the space shuttle during re-entry using a near-infrared sensor

Author

Zalameda, Joseph N., Horvath, Thomas J., Kerns, Robbie V., Burke, Eric R., Taylor, Jeff C., Spisz, Tom, Gibson, David M., Shea, Edward J., Mercer, C. David, Schwartz, Richard J., Tack, Steve, Bush, Brett C., Dantowitz, Ronald F., and Kozubal, Marek J.

Abstract

High resolution calibrated near infrared (NIR) imagery of the Space Shuttle Orbiter was obtained during hypervelocity atmospheric re-entry of the STS-119, STS-125, STS-128, STS-131, STS-132, STS-133, and STS-134 missions. This data has provided information on the distribution of surface temperature and the state of the airflow over the windward surface of the Orbiter during descent. The thermal imagery complemented data collected with onboard surface thermocouple instrumentation. The spatially resolved global thermal measurements made during the Orbiter's hypersonic re-entry will provide critical flight data for reducing the uncertainty associated with present day ground-to-flight extrapolation techniques and current state-of-the-art empirical boundary-layer transition or turbulent heating prediction methods. Laminar and turbulent flight data is critical for the validation of physics-based, semi-empirical boundary-layer transition prediction methods as well as stimulating the validation of laminar numerical chemistry models and the development of turbulence models supporting NASA's next-generation spacecraft. In this paper we provide details of the NIR imaging system used on both air and land-based imaging assets. The paper will discuss calibrations performed on the NIR imaging systems that permitted conversion of captured radiant intensity (counts) to temperature values. Image processing techniques are presented to analyze the NIR data for vignetting distortion, best resolution, and image sharpness.

Published
2012
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253. Improved flaw detection and characterization with difference thermography

Author

Winfree, William P., Zalameda, Joseph N., and Howell, Patricia A.

Abstract

Flaw detection and characterization with thermographic techniques in graphite polymer composites is often limited by localized variations in the thermographic response. Variations in properties such as acceptable porosity, variations in fiber volume content and surface polymer thickness result in variations in the thermal response that in general cause significant variations in the initial thermal response. These variations result in a noise floor that increases the difficulty of detecting and characterizing deeper flaws. The paper investigates comparing thermographic responses taken before and after a change in state in a composite to improve the detection of subsurface flaws. A method is presented for registration of the responses before finding the difference. A significant improvement in the detectability is achieved by comparing the differences in response. Examples of changes in state due to application of a load and impact are presented.

Published
2011
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289. Numerical Simulations of Thermographic Responses in Composites.

Author

Winfree, William P., Cramer, K. Elliott, Zalameda, Joseph N., and Howell, Patricia A.

Subjects
*MICROFABRICATION, *FINITE element method, *COMPUTER simulation, *THERMOGRAPHY, *COMPOSITE materials
Abstract

Numerical simulations of thermographic responses in composite materials have been useful for evaluating and optimizing thermographic analysis techniques. Numerical solutions are particularly beneficial for thermographic techniques, since the fabrication of specimens with realistic flaws is difficult. A quadrupole method for performing the simulations in two dimensions is presented. The results are compared to a finite element simulation of the same geometry. The technique is shown to be in good agreement with a finite element simulation of the same geometry, however, it requires about one hundredth of the computational time. [ABSTRACT FROM AUTHOR]

Published
2016
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290. Determination of Flaw Size from Thermographic Data.

Author

Winfree, William P., Howell, Patricia A., and Zalameda, Joseph N.

Subjects
*DELAMINATION of composite materials, *THERMOGRAPHY, *CONSTRAINT algorithms, *THERMAL properties, *DIFFUSION, *HEAT exchangers
Abstract

Conventional methods for reducing the pulsed thermographic responses of delaminations tend to overestimate the size of the flaw. Since the heat diffuses in the plane parallel to the surface, the resulting temperature profile over the flaw is larger than the flaw. A variational method is presented for reducing the thermographic data to produce an estimated size for the flaw that is much closer to the true size of the flaw. The size is determined from the spatial thermal response of the exterior surface above the flaw and a constraint on the length of the contour surrounding the flaw. The technique is applied to experimental data acquired on a flat bottom hole composite specimen. [ABSTRACT FROM AUTHOR]

Published
2015
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291. Thermography inspection for early detection of composite damage in structures during fatigue loading

Author

Zalameda, Joseph N., Burke, Eric R., Parker, F. Raymond, Seebo, Jeff P., Wright, Christopher W., and Bly, James B.

Abstract

Advanced composite structures are commonly tested under controlled loading. Understanding the initiation and progression of composite damage under load is critical for validating design concepts and structural analysis tools. Thermal nondestructive evaluation (NDE) is used to detect and characterize damage in composite structures during fatigue loading. A difference image processing algorithm is demonstrated to enhance damage detection and characterization by removing thermal variations not associated with defects. In addition, a one-dimensional multilayered thermal model is used to characterize damage. Lastly, the thermography results are compared to other inspections such as non-immersion ultrasonic inspections and computed tomography X-ray.

Published
2012
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