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  • 1
    Publication Date: 2004-10-30
    Keywords: STRUCTURAL MECHANICS
    Type: NDE at NASA Langley. Advancing the State-of-the-Art and Providing a Quantitative Science Base for Materials Characterization; 7 p
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  • 2
    Publication Date: 2011-08-24
    Description: Low-frequency resonant model analysis, a technique for the detection and characterization of fatigue cracks in thin metal plates, which could be adapted to rapid scan or large area testing, is considered. Experimental data displaying a direct correlation between fatigue crack geometry and resonance frequency for the second vibrational plate mode are presented. FEM is used to calculate the mechanical behavior of the plates, and provides a comparison basis for the experimentally determined resonance frequency values. The waveform of the acoustic emission generated at the resonant frequency is examined; it provides the basis for a model of the interaction of fatigue crack faces during plate vibration.
    Keywords: STRUCTURAL MECHANICS
    Type: In: Review of progress in quantitative nondestructive evaluation. Vol. 11B; Proceedings of the 18th Annual Review, Brunswick, ME, July 28-Aug. 2, 1991 (A93-19582 06-38); p. 2085-2092.
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  • 3
    Publication Date: 2019-07-13
    Description: As the basic physical principles behind the low-field magnetoacoustic interactions have been unfolded, a new step in the present research had to be taken. First, the stress measurements began in samples obtained in real railroad wheel and rail materials. Second, the effect of texture, which is the prime obstacle of conventional NDE techniques, has been investigated. The first stage shows experimental results on these subjects again confirmed that the present technique is most suited for nondestructive stress characterization in steel components. The stress effects on the magnetoacoustic interaction obtained in a sample made from railroad rail which were very similar to those obtained previously in 1045 steel. These results being somewhat different from the results with low (1020) and high (1095) carbon steels, there seemed to be certain range of medium carbon steels having the same characteristics. Also, as expected from the model, the stress information obtained by this technique has been confirmed to be least affected by the presence of texture.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-176236 , NAS 1.26:176236
    Format: application/pdf
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  • 4
    Publication Date: 2019-07-13
    Description: Detailed experimental investigation and numerical analysis were performed on the characterization of fatigue cracks in thin aluminum alloys by a low frequency resonant modal analysis technique. The resonance frequency of plate modes is altered by the presence of fatigue cracks. This frequency shift was analyzed using a finite element approach and the results were compared to experimental data. Acoustic sensors were used to detect the fatigue cracks which were stimulated by standing waves in 0.1 cm aluminum alloy plates. The response of several different sensors to the crack noise was studied, as was the response at higher order modes. It was found that critical crack information can be obtained from the amplitude and phase of the emitted signal with respect to that of the external driving force.
    Keywords: STRUCTURAL MECHANICS
    Type: ; 5 p.|IEEE, Ultrasonic Symposium; Dec 08, 1991 - Dec 11, 1991; Lake Buena Vista, FL; United States
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