1999 Fiscal Year Final Research Report Summary
Measurements of Localized Ion Distribution and Nanoscopic AFM Observation of Crack Initiation and Propagation of Stress Corrosion Cracking
| Project/Area Number |
10650086
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
MINOSHIMA Kohji Kyoto University Graduate School of Eng., Dept. Mech. Eng., Associate Professor, 工学研究科, 助教授 (50174107)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Environmental Strength / Localized Ion Distribution / Atomic Force Microscopy / Localized Corrosion / Pitting Corrosion / Nanofractography / Crack Initiation / Crack Propagation |
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| Research Abstract |
In order to perform in situ observation of an initiation stage of corrosion damage including pitting corrosion and stress corrosion cracking, a so called chronoamperometric method was applied to localized corrosion damage, where a micron size Pt microelectrode (Diameter : 20 μm) is cyclically polarized by using a square waveform : local concentration of chloride ion and hydrogen ion, or pH values, can be respectively measured by using a current by an anodically and a cathodically polarized condition. By using this chronoamperometric method, distributions of chloride and hydrogen ion near a pitting corrosion was measured, at the bottom of which a stress corrosion crack sometimes initiates : the distributions of ions in and out of a corrosion pit was successfully measured, and the localization of ions around a pitting corrosion could be clearly visualized. In situ nanoscopic atomic force microscope (AFM) observation was also conducted to closely examine the growing process of stress corrosion cracking of a high-strength steel under a sustained loading : nanoscopic mechanism of stress corrosion cracking was discussed. Crack initiation and growth behavior was also investigated in a high-strength P/M Al-Zn-Mg alloy and a Ti-6Al-4V alloy under dynamic loading in order to clarify the environmental degradation behavior. Special attention was paid to the influence of combined loading on crack initiation and fracture behavior in a SiC whisker reinforced Al alloy.
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[Publications] K. Minoshima, I. Nagashima and K. Komai: "The Influence of NaCl Solution on Fatigue Fracture Behaviour of SiC Whisker/Aluminum Matrix Composite under Combined Tension/Torsion Loading"Proceedings of the Seventh International Fatigue Congress, Fatigue '99, X. R. Wu and Z. G. Wang, Eds., Vol. 4/4, Engineering Materials Advisory Service, Cradley Health, UK, Beijing, China. 2299-2304 (1999)
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