| Project/Area Number |
59460064
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Aerospace engineering
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| Research Institution | University of Tokyo |
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Principal Investigator |
SHIOYA Tadashi Faculty of Engineering, University of Tokyo, 工学部, 助教授 (30013733)
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| Co-Investigator(Kenkyū-buntansha) |
SHIOIRI Jumpei Faculty of Engineering, Hosei University, 工学部, 教授 (80010700)
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| Project Period (FY) |
1984 – 1986
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| Project Status |
Completed (Fiscal Year 1986)
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| Budget Amount *help |
¥8,100,000 (Direct Cost: ¥8,100,000)
Fiscal Year 1986: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1985: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1984: ¥6,400,000 (Direct Cost: ¥6,400,000)
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| Keywords | Elasto-Plasticity / Ductile Fracture / Steel / Void / Stress Triaxiality / Ductile-Brittle Transition / ディンプル |
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| Research Abstract |
The fracture of solid materials generally involves elastic and plastic deformations the magnitudes of which depend on the materials and the loading conditions. This project is aimed at the understanding in microscopic aspects of the fracture, mainly from the ductile side which accompanies large plastic deformation towards the ductile-brittle transition. The microscopic process of the ductile fracture consists of the stages of voids nucleation, growth and their coalescences. The void nucleation and growth process is considered to be affected by the population of the impurities or second phase particles which can be the void nucleation sites and the stress-strain state which influences the nucleation and growth conditions of the voids.
In this project, tensile fracture experiments of steel specimens were conducted changing the chemical components concentration and the stress-strain conditions. The void nucleation and growth process was indirectly examined through the dimple distributions on the fracture surface. The observation of the fracture surface was performed by the use of the electron microscope. The results were shown as the relation between the area portion of the main dimples on the fracture surface and the stress tri-axiality of the specimen at the fracture. It was cleared that the area portion of the main dimples generally increases with the stress-triaxiality and approaches to a constant value, however, in the high purity materials, this approach to a limited value has not been seen. In the materials with increased inpurity phase, the cleavage fracture patterns were also observed besides the dimple patterns indicating that the transition to the brittle fracture occurs. This has been supported by the fact that the scale effect exists macroscopically as well as microscopically.
Simple theoretical modellings are proposed in this project concerning the void nucleation and growth process, showing the qualitative coincidence with the experimental results.
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