1995 Fiscal Year Final Research Report Summary
Establshment of theory on fracture of wood and its application to RBD (Reliability Based Design)
| Project/Area Number |
06302069
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| Research Category |
Grant-in-Aid for Co-operative Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
林産学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
MASUDA Minoru Kyoto Univ., Fac.of Agri.Professor, 農学部, 教授 (40027165)
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| Co-Investigator(Kenkyū-buntansha) |
SOBUE Nobuo Shizuoka Univ., Fac.of Agri.Professor, 農学部, 教授 (50023495)
SATOH Kiyoshi Mie Univ., Fac.of Educa.Professor, 教育学部, 教授 (80006444)
YOSIHARA Hirosi Tokyo Univ., Fac.of Agri.Assis.Professor, 農学部, 助手 (30210751)
OHTA Masamitu Tokyo Univ., Fac.of Agri.Professor, 農学部, 助教授 (20126006)
MIHASHI Hirozou Touhoku Univ., Fac.of Engi.Professor, 工学部, 教授 (90091751)
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| Project Period (FY) |
1994 – 1995
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| Keywords | fracture mechanics / fracture criterion / reliability based design / finite area fracture theory / bolted joint / image correlation method / wood / laminated lumber |
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| Research Abstract |
(1) Bending strength of timber beams including end notches was calculated using finite area fracture theory. Theoretical results coincide well with experimental ones. The optimum sizes of the finite small area are 1.5mm for grain direction, 0.2mm for radial or tangential direction. Bolted joints were also investigated theoretically and experimentally, and good correlation was observed between them. Stress-strain relationship in shear was observed by image correlation method, and it makes clear that constitutive equation of shear is non-linear or nearly elasto-plastic (M.MASUDA) . Introduction of linear fracture mechanics especially stress intensity factor K was attemmpted for simple practical method in estimation of failure or ultimate load of bolted joints, but more investigation was needed for accurate estimation (N.SOBUE) .
(2) Monte Carlo method was used to estimate decrease of variation with lamination of Sugi (Japanese cedar) laminae. Considering the reinforcement effect of adhesion and elastoplastic behavior in compression, better estimation of strength variation was observed (H.MIHASHI)
(3) Propagation of crack in wood after crack initiation was investigated theoretically by means of EDEM (Extended Distinct Element Method) . More improvement was necessary to analyze the fracture process of wood (M.OHTA) . Plastic behavior in shear was observed by torsioning wood. It makes clear that Hill type equation fits better than Jenkin type equation in yielding behavior under mixed modes stresses (H.YOSHUHARA) . Fracture under mixed modes of I and II were investigated experimentally. None of fracture criteria fit the experimental results (K.SATO) . It was obseved experimentally that there is a little difference between Ks measured by three different methods i.e.compact tension, three point bending and tension with one side crack (N.SUZUKI) .
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