| 研究課題/領域番号 |
16F16809
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| 研究機関 | 九州大学 |
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研究代表者 |
陳 強 九州大学, 工学研究院, 教授 (30264451)
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| 研究分担者 |
HE CHAO 九州大学, 工学研究院, 外国人特別研究員
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| 研究期間 (年度) |
2016-11-07 – 2019-03-31
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| キーワード | Ultrasonic Fatigue / Magnesium Alloy / LPSO Phase / Crack Initiation / Crack Propagation / Very High Cycle Fatigue |
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| 研究実績の概要 |
Magnesium alloys containing long period stacking ordered (LPSO) structure received considerable concerns in the last decade due to their good combined properties of mechanical strength and corrosion resistance. This research work aims to investigate high cycle fatigue (HCF) and very high cycle fatigue (VHCF) behaviors of LPSO phase containing Mg alloys, including (1)HCF and VHCF strength of Mg alloys with LPSO phase; (2)cyclic deformation mechanisms of matrix Mg and LPSO phase; (3)fatigue crack initiation mechanisms and the effect of LPSO phase on the fatigue behaviors.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
1. Carried out pre-experiments on a commercial magnesium alloy (ZK60) using ultrasonic fatigue system.
2. Designed three different ultrasonic fatigue specimens for fatigue crack initiation, propagation and strength investigations, respectively.
3. Submitted a manuscript to the 70th General Meeting held by Japan Society of Mechanical Engineers Kyushu Branch and gave a presentation entitled "Very high cycle fatigue strength and failure mechanisms of welded joints" in Saga University.
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| 今後の研究の推進方策 |
1. Observation on the fatigue crack initiation process. Fatigue damage mechanism at a stress well below the bulk yield strength will be investigated in LPSO containing Mg alloys with different microstructures using scanning electron microscopy, electron back-scattering diffraction (EBSD) and transmission electron microscopy (TEM). Changes in surface microstructure at different stages of fatigue life will be measured with an in-situ optical microscope (OM) in order to determine the fatigue damage mechanisms that govern the cyclic deformation and fatigue failure.
2. The interaction between crack growth and microstructure. Using plate specimen with a small notch, the fatigue crack propagation rate and the effect of LPSO on the crack growth rate and crack path will be investigated.
3. VHCF strength and failure mechanism. Samples taken from the gauge sections of fatigued specimens as well as from materials unaffected by cyclic loading will be used for TEM investigation in order to characterize the morphology of basal dislocation arrangements. The deformation kink band and the deformation twin caused by cyclic loading will be discussed, and their effect on the fatigue crack initiation will be addressed.
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