| Project/Area Number |
18560071
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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 | Tokyo University of Agriculture and Technology |
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Principal Investigator |
NAGAKI Shigeru Tokyo University of Agriculture and Technology, Institute of Symbiotic Science and Technology, Professor (30135959)
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| Co-Investigator(Kenkyū-buntansha) |
OHOSIHTA Kenichi Tokyo University of Agriculture and Technology, Institute of Symbiotic Science and Technology, Assistant Professor (60334471)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,860,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥360,000)
Fiscal Year 2007: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2006: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Keywords | phase transformation / transformation plasticity / thermo-elasto-plasticity / constitutive equation / stress induced transformation / multi-axial stress state / 応力誘起変態 / 熱処理 / 変態塑性 / 温度・伸び線図 |
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| Research Abstract |
In this project the response of phase-transforming steels under multi-axial stress state at elevated temperature is studied both theoretically and experimentally.
The new biaxial loading equipment is developed, where tensile and torsional loads can be applied to the specimen independently at elevated temperature and the specimen can be cooled rapidly so that martensite and bainite transformations are observed. The dilatation-temperature diagram is obtained experimentally for SCM440 steel and it is found that the transformation temperature depends on both applied stress state and cooling rate. It is also fount that transformation plasticity is observed to occur for both tensile and torsional stresses and depends on stress state.
The constitutive model for thermo-elastic-plastic behavior of some steels during phase transformation process is also proposed in terms of internal state variable theory, where the volume fraction of each phase is considered as an internal state variable. The explicit form of the evolutional equations for internal variables is derived. The coefficient of transformation plasticity is also identified within the proposed framework. Calculated results of the continuous cooling transformation (C-C-T) diagram and the isothermal time-temperature-transformation (T-T-T) diagram, together with the dilatation-temperature diagram show the stress dependency of phase transformation and are compared with experimental data for SCM440 steel.
Applications of the theory to the cases of bending of locally heated plate are also presented. Stress, displacement and temperature distributions are numerically calculated by a finite element technique and compared with corresponding experimental results.
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