1994 Fiscal Year Final Research Report Summary
STUDY ON MICRO MECHANISM OF DUCTILE FRACTURE
| Project/Area Number |
03402026
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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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 Tadasi Univ.of TOKYO Faculty of eng.Professor, 工学部, 教授 (30013733)
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| Co-Investigator(Kenkyū-buntansha) |
SATOH Katsuhiko Univ.of TOKYO Faculty of eng.Assistant, 工学部, 助手 (30010911)
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| Project Period (FY) |
1991 – 1994
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| Keywords | Ductile Fracture / Void / Tensile Test / Ultrasonic Method / Stress Triaxiality / Constitutive Equation / Effect of Size / Dimple |
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| Research Abstract |
Microscopic procedure of ductile fracture of material consists of three processes ; 1) Voids nucleation at the second phase particles and/or the triple points of grain boundaries, 2) The voids growth under multi-axial stress states, and 3) The voids coalescences to lead final fracture.
In the project, experimental studies are prosecuted on the ductile fracture of mild steel and aluminum specimens under multi-axial stress states. The ultrasonic wave transmission tests are performed measuring the attenuation of the wave during the fracture process in real time to evaluate the voids growth process. The fracture surfaces are observed by scanning electron microscope and optical microscope. The dimples appeared on the fracture surfaces are statistically processed to correlate the stress states and material composition.
In the analysis, numerical calculations are carried out to simulate the voids nucleation and growth processes with proposed criteria of nucleation condition and growth rule. The growth process of an isolated void is also analyzed with time-dependent constitutive relation of material. The elongation of the void shape in relation with the initial shape and the applied stress state is examined.
The experimental results and the analysis are compared to explain the microscopic process of the ductile fracture qualitatively and quantitatively.
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Research Products
(14 results)
