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  • 1
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    Investigation of Adhesive Bond Cure Conditions using Nonlinear Ultrasonic Methods (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The objective of this presentation is to investigate various cure conditions of adhesive bonds using nonlinear ultrasonic methods with water coupling. Several samples were used to obtain normal incidence, oblique incidence, and wave mixing.
    Keywords: Quality Assurance and Reliability
    Type: Proceedings of the Second Annual Symposium for Nondestructive Evaluation of Bond Strength; 90-108; NASA/CP-1999-209140
    Format: text
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  • 2
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    Nondestructive Determination of Bond Strength (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Current projects include loading adhesive bond in shear in MTS machine, ultrasonic tests with shear waves, shear-fatigue adhesive bonding, and use of ultrasound to detect onset of nonlinearity.
    Keywords: Quality Assurance and Reliability
    Type: Proceedings of the First Annual Symposium for Nondestructive Evaluation of Bond Strength; 90-108; NASA/CP-1999-209137
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  • 3
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    Performance of thermal barrier coatings in high heat flux environments (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Thermal barrier coatings were exposed to the high temperature and high heat flux produced by a 30 kW plasma torch. Analysis of the specimen heating rates indicates that the temperature drop across the thickness of the 0.038 cm ceramic layer was about 1100 C after 0.5 sec in the flame. An as-sprayed ZrO2-8 percent Y203 specimens survived 3000 of the 0.5 sec cycles with failing. Surface spalling was observed when 2.5 sec cycles were employed but this was attributed to uneven heating caused by surface roughness. This surface spalling was prevented by smoothing the surface with silicon carbide paper or by laser glazing. A coated specimen with no surface modification but which was heat treated in argon also did not surface spall. Heat treatment in air led to spalling in as early as 2 cycle from heating stresses. Failures at edges were investigated and shown to be a minor source of concern. Ceramic coatings formed from ZrO2-12 percent Y2O3 or ZrO2-20 percent Y2O3 were shown to be unsuited for use under the high heat flux conditions of this study.
    Keywords: METALLIC MATERIALS
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  • 4
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    Failure analysis of plasma-sprayed thermal barrier coatings (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Thermally induced failure processes of plasma-sprayed thermal barrier coatings are examined. Cracking processes give rise to noise which was monitored by acoustic emission (AE) techniques. The sequential failure of coatings was examined from samples which were thermally cycled. Coatings of yttria-stabilized zirconia with and without a NiCrAlZr bond coat were plasma-sprayed onto U700 alloy rod. In some cases the substrate was intentionally overheated during deposition of the thermal protection system to check how this process variable influenced the AE response of the specimen. In this way a qualitative appraisal of how process variables affect coating integrity could be discerned in terms of cracking behavior. Results from up to seven consecutive thermal cycles are reported here. Coating failure was observed in all cases. Failure of the thermal protection system is progressive, since cracking and crack growth were observed prior to ultimate failure. Thus castastrophic failure occurs at some stage when there is a transformation from the microcrack to a macrocrack network.
    Keywords: METALLIC MATERIALS
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  • 5
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    Failure analysis of plasma-sprayed thermal barrier coatings (1984)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Thermally induced failure processes of plasma-sprayed thermal barrier coatings are examined. Cracking processes give rise to noise which was monitored by acoustic emission (AE) techniques. The sequential failure of coatings was examined from samples which were thermally cycled. Coatings of yttria-stabilized zirconia with and without a NiCrAlZr bond coat were plasma-sprayed onto U700 alloy rod. In some cases the substrate was intentionally overheated during deposition of the thermal protection system to check how this process variable influenced the AE response of the specimen. In this way a qualitative appraisal of how process variables affect coating integrity could be discerned in terms of cracking behavior. Results from up to seven consecutive thermal cycles are reported here. Coating failure was observed in all cases. Failure of the thermal protection system is progressive, since cracking and crack growth were observed prior to ultimate failure. Thus castastrophic failure occurs at some stage when there is a transformation from the microcrack to a macrocrack network.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83777 , E-2269 , NAS 1.15:83777 , Intern. Conf. on Met. Coatings; Apr 09, 1984 - Apr 13, 1984; San Diego, CA; United States
    Format: application/pdf
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  • 6
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    Performance of thermal barrier coatings in high heat flux environments (1984)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Thermal barrier coatings were exposed to the high temperature and high heat flux produced by a 30 kW plasma torch. Analysis of the specimen heating rates indicates that the temperature drop across the thickness of the 0.038 cm ceramic layer was about 1100 C after 0.5 sec in the flame. An as-sprayed ZrO2-8%Y2O3 specimens survived 3000 of the 0.5 sec cycles with failing. Surface spalling was observed when 2.5 sec cycles were employed but this was attributed to uneven heating caused by surface roughness. This surface spalling was prevented by smoothing the surface with silicon carbide paper or by laser glazing. A coated specimen with no surface modification but which was heat treated in argon also did not surface spall. Heat treatment in air led to spalling in as early as 2 cycle from heating stresses. Failures at edges were investigated and shown to be a minor source of concern. Ceramic coatings formed from ZrO2-12%Y2O3 or ZrO2-20%Y2O3 were shown to be unsuited for use under the high heat flux conditions of this study.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-83663 , E-2010 , NAS 1.15:83663 , Intern. Conf. on Metallurgical Coatings; Apr 09, 1984 - Apr 13, 1984; San Diego, CA; United States
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  • 7
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    Instrumented adhesion tests on plasma sprayed thermal barrier coatings (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The failure mechanisms of plasma-sprayed two-layer coatings consisting of an NiCrAlY or NiCrAlZr bond coat with an yttria-stabilized zirconia overlay are presently examined by tensile adhesion tests. It has been found that adhesive failure within the bond coat exhibits greater failure strain than the cohesive failure of the ceramic overlay, supporting the view of the intermediate coatings being highly compliant. The absolute extension exhibited by failures occurring only through the ceramic coating is greater than that of adhesive failure, since the ceramic coating is much thicker than the bond coat.
    Keywords: METALLIC MATERIALS
    Type: Journal of Materials Engineering (ISSN 0931-7058); 11; 275-282
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  • 8
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    Radiation Damage In Advanced Bipolar Transistors (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Report describes measurements of common-emitter current gains (hFE) of advanced bipolar silicon transistors before, during, and after irradiation with 275-MeV bromine ions, 2.5-MeV electrons, and conductivity rays from cobalt-60 atoms.
    Keywords: ELECTRONIC COMPONENTS AND CIRCUITS
    Type: NPO-17570 , NASA Tech Briefs (ISSN 0145-319X); 13; 9; P. 32
    Format: text
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  • 9
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    SEU In An Advanced Bipolar Integrated Circuit (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Report summarizes investigation of single-event upsets (SEU) in bipolar integrated-circuit set of flip-flops (memory cells). Device tested made by advanced digital bipolar silicon process of Honeywell, Inc. Circuit chip contained 4 cells. Construction enabled study of effect of size on SEU behavior. Each cell externally biased so effect of bias current on SEU behavior. Results of study provides important information for optimal design of devices fabricated using buried-layer bipolar process operating in heavy-ion SEU environments. Designers use information to provide required levels of suppression of SEU in specific applications via combinations of size and/or cell-current scaling.
    Keywords: ELECTRONIC COMPONENTS AND CIRCUITS
    Type: NPO-17553 , NASA Tech Briefs (ISSN 0145-319X); 13; 10; P. 26
    Format: text
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