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Fatigue damage evolution study with ...

Lee, Tae-Kyu.

Fatigue damage evolution study with non-destructive magnetic properties measurement method using scanning SQUID microscopy.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Fatigue damage evolution study with non-destructive magnetic properties measurement method using scanning SQUID microscopy.
Author:	Lee, Tae-Kyu.
Description:	164 p.
Notes:	Chair: John W. Morris, Jr.
Notes:	Source: Dissertation Abstracts International, Volume: 66-08, Section: B, page: 4433.
Contained By:	Dissertation Abstracts International66-08B.
Subject:	Engineering, Materials Science.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3187086
ISBN:	9780542289620

Fatigue damage evolution study with non-destructive magnetic properties measurement method using scanning SQUID microscopy.
Lee, Tae-Kyu.

Fatigue damage evolution study with non-destructive magnetic properties measurement method using scanning SQUID microscopy. - 164 p.

Chair: John W. Morris, Jr.

Thesis (Ph.D.)--University of California, Berkeley, 2005.

In this study, a non-destructive evaluation method is established by continuously measuring the magnetic properties, which interact with the developing fatigue damage during cyclic loading. Dislocations and microcracks which are initiated during the fatigue act as pinning sites which impede the motion of magnetic domain walls under the applied magnetic field, thereby influencing the bulk magnetic properties. The remanence field of various fatigued steel specimens are detected using a scanning microscope based on a high transition temperature Superconducting Quantum Interference Device (SQUID). The results show the development of localized peaks in remanent magnetization prior to the formation of visible fatigue cracks. Even in the second stage of fatigue, where the macroscopic state of the sample is relatively constant, the results show that a scanning SQUID microscope is capable of detecting regions of fatigue damage both on surface and in sub-surface regions.

ISBN: 9780542289620Subjects--Topical Terms:

226940
Engineering, Materials Science.

Fatigue damage evolution study with non-destructive magnetic properties measurement method using scanning SQUID microscopy.
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245 1 0 $a Fatigue damage evolution study with non-destructive magnetic properties measurement method using scanning SQUID microscopy.
300 $a 164 p.
500 $a Chair: John W. Morris, Jr.
500 $a Source: Dissertation Abstracts International, Volume: 66-08, Section: B, page: 4433.
502 $a Thesis (Ph.D.)--University of California, Berkeley, 2005.
520 # $a In this study, a non-destructive evaluation method is established by continuously measuring the magnetic properties, which interact with the developing fatigue damage during cyclic loading. Dislocations and microcracks which are initiated during the fatigue act as pinning sites which impede the motion of magnetic domain walls under the applied magnetic field, thereby influencing the bulk magnetic properties. The remanence field of various fatigued steel specimens are detected using a scanning microscope based on a high transition temperature Superconducting Quantum Interference Device (SQUID). The results show the development of localized peaks in remanent magnetization prior to the formation of visible fatigue cracks. Even in the second stage of fatigue, where the macroscopic state of the sample is relatively constant, the results show that a scanning SQUID microscope is capable of detecting regions of fatigue damage both on surface and in sub-surface regions.
520 # $a The fatigue process can be precisely defined in the crack propagation stage, where the fatigue damage can be evaluated by observed cracks and where an increase of the dislocation density occurs at the first 10% of the fatigue life. But for the stages between dislocation saturation and prior to nucleation, no definition can be given due to the relative difficulty in quantifying the damage. Especially, detecting a high-cycle fatigue damage is a particularly important yet an unsolved problem in non-destructive testing. There are no reliable techniques to measure the progress of fatigue in the intermediate fatigue regime, the second stage of fatigue, where the overall dislocation density is approximately constant and the microstructural changes are subtle include about 80% of the fatigue life in high-cycle fatigue.
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650 # 0 $a Physics, Condensed Matter. $3 226939
650 # 0 $a Engineering, Metallurgy. $3 227093
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