2007 Fiscal Year Final Research Report Summary
Fatigue Life Evaluation of Ultra High Strength Notched Member using New Digital Image Correlation Method
| Project/Area Number |
18560092
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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 | Osaka Institute of Technology |
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Principal Investigator |
NIHSIKAWA Izuru Osaka Institute of Technology, Faculty of Engineering, Professor (90189267)
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| Co-Investigator(Kenkyū-buntansha) |
WAKI Hiroyuki Osaka Electro-Communication University, Faculty of Engineering, Associate professor (30324825)
UEDA Sei Osaka Institute of Technology, Faculty of Engineering, Professor (10176589)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Digital Correlation Method / Strain / Displacement / Notch / Fatigue Strength / Crack / Crack Closure / Notch Sensitivity |
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| Research Abstract |
A new digital image correlation (DIC) method for analyzing the fracture problem of notched member was developed. At first, the application of the fast Fourier transform method is primarily employed for reduction of the analysis time. Meanwhile, a misunderstanding on the identical point searching can be avoided by using a new DIC method with the FFT treatment. Furthermore, a successful technique for the strain singular field near the crack tip was newly developed for the application of a DIC method to crack problems.
On the other hand, the additional technique on measurement of multi-axial strains was also developed to measure the complex strain fields near the notch root. In this case, 3-dimensional measurement technique was needed to be applicable to monitor the transformation/strain at notch root. Multi-axial strains can be measured by using this developed system.
For researching the notch sensitivity of ultra high strength steels, two types of ultra high strength steels were used in this study. Conventional fatigue tests were conducted to obtain the data on the fatigue life (fatigue strength). These data were investigated through the Kikukawa theory on fatigue strength. It was found that these strength data on the ultra high strength steel were fitted on the master curve of the Kikukawa theory.
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