1990 Fiscal Year Final Research Report Summary
A Mechanical Study on Fracture Sstength of Material with Composite Structure Taking Special Consideration on Inelastic Interfacial Instability
| Project/Area Number |
63460078
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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 | Osaka University |
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Principal Investigator |
KITAGAWA Hiroshi Osaka University, Mechanical Eng. Dept,. Professor, 工学部, 教授 (30029095)
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| Co-Investigator(Kenkyū-buntansha) |
INOUE Yutaka Osaka University, Mechanical Eng. Dept., Research Associate, 工学部, 助手 (90029033)
SHIBUTANI Youji Osaka University, Mechanical Eng. Dept., Research Associate, 工学部, 助手 (70206150)
NAKAMACHI Eiji Osaka University, Mechanical Eng. Dept., Associate Prof., 工学部, 助教授 (60099893)
KUBO Shiro Osaka University, Mechanical Eng. Dept., Professor, 工学部, 教授 (20107139)
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| Project Period (FY) |
1988 – 1990
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| Keywords | Laminated Thin Plate / Inelastic Instability / Interfacial Instability / Propagation of Delamination / Deformation Limit / Localized Necking / Elasto / Visco-Plastic Material / Interfacial Roughness |
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| Research Abstract |
The aim of this project is to acquire the estimation principle for fracture strength of the material with composite structure. Special Consideraion is taken on inelastic interfacial instability. The main results obtained are summarized as follows :
1) Through the analytical and numerical investigations of bifurcation appearing in a plane strain block with laminated structure under tension, the following facts are brought to light : Conditions for the governing equation being elliptic or hyperbolic, are definitely determined, under the latter of which shear-band type localized straining is predicted to appear. In the elliptic region, bifurcations of interfacial mode with various wave length exist, including the infinitesimal one. This bifurーcation corresponds to appearance of localized straining on the interface, and then we can use it as the criterion of interfacial delamination. Dependence of the bifurcation condition with the material properties are studied in detail.
2) Experimental o
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bservation of growth of interfacial roughness appearing in the laminated thin plate composed by aluminum foil and polymer gives valuable information for the reality of the surface and interfacial instability. This composite material is known to have the extreme deformability. Not the simple, but the biaxial tension test is suitable for estimate the true ability of deformation of the thin material, because the effect of free edge instability is excluded. The interfacial roughness increases with nearly proportional rate to the applied at the early stage, and after the period of the roughness held to be nearly constant, rapid growth to the final fracture is observed. During this plateau period, the polymer laminate seems to suppress the interfacial instability which leads to the ultimate deformation state.
3) The interfacial unevenness energy to be composed of two geometrical structures with different fractional dimensions. The origin of the one is the initial unevenness and the grain size and the other is localized ship of the crystal in microscopic level. Although the magnitude of roughness (unevenness) increase with the applied strain, each fractional dimension is held to be nearly constant.
4) Numerical simulation of delamination and its propagation gives details of mutual interaction between the defect of materials and adhesive layer and the mechanical properties of the materials composed. Less
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