1989 Fiscal Year Final Research Report Summary
An analysis of cyclic stress-strain response correlated with static mechanical properties and development of new method for assessing fatigue life
| Project/Area Number |
62460079
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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 |
材料力学
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| Research Institution | Yamaguchi University |
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Principal Investigator |
HATANAKA Kenji Yamaguchi Univ., Dept. Mech. Engng., Professor, 工学部, 教授 (60026193)
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| Co-Investigator(Kenkyū-buntansha) |
OGAWA Hisashi Ube Tech. College, Dept. Mech. Engng., Assoc. Professor, 助教授 (10043887)
FUJIMITSU Tatsuro Yamaguchi Univ., Dept. Mech. Engng., Assoc. Professor, 工学部, 助教授 (70035062)
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| Project Period (FY) |
1987 – 1989
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| Keywords | Cyclic Stress-Strain Response / Notch / Elastic-Plastic Finite Element Method / Fatigue Crack / J-integral Range / Numerical Simulation / Fatigue Life Prediction |
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| Research Abstract |
The cyclic stress-strain curve is necessitated to calculate a crack growth rate based on elastic-plastic fracture mechanics and to predict the fatigue life. In view of this, the purpose of the present study is to develop a new method for the numerical simulation of the cyclic stress-strain curve and for the fatigue life assessment based on it. The cyclic stress-strain response of copper was numerically simulated by introducing the dynamic dislocation mechanics. Then, this was applied to the cyclic stress-strain analysis of the circumferentially notched components and to the life estimation. The main results obtained are summarized as follows.
(1),The cyclic stress-strain response was successfully calculated by using the static mechanical properties through the proposed method.
(2) The stress-strain responses of the circumferentially notched components were calculated by means of elastic-plastic finite element method , where the constitutive equation stated in the item (1) was introduced into the F.E.M. calculations.
(3) The change in the shape of the surface crack originated at trie notch root was successfully analyzed in terms of the elastic-plastic fracture mechanics. The transition from the semielliptical to circumferential crack, which occurred at the notch root in the crack extension process under a given test condition, was satisfactorily predicted in the proposed analysis.
(4) The crack initiation life of the circumferentially notched components was evaluated on the basis of the finite element stress analysis. Consequently, it was revealed that the equivalent plastic strain generated at the notch root dominates the crack initiation life of the notched components where the multiaxial stress develops.
(5) The low-cycle fatigue lives of the dully and acutely notched cylinder components were satisfactorily evaluated through the analysis of the growth of the surface and circumferential cracks.
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