Papers by Author: Kazunari Shinagawa

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Authors: Kazunari Shinagawa, Y. Hirashima
Authors: Kazunari Shinagawa
Abstract: Aiming at the modification of the sinterability of metal/ceramic powder mixtures, the influence of the homogeneity in microstructure on the sintering behavior is examined. Ni/Al2O3 specimens, with ratios ranging from 0/100 to 100/0, are prepared by compaction through two different procedures of mixing and granulating, to change the degree of particle dispersion. The sintering stress and the viscosity of the specimens are measured by sinter-compression tests to consider the sinterability from the viewpoint of both driving force and resistance. The sintering rate of the inhomogeneous compacts, with agglomeration of powder particles, is larger than that of the homogeneous compacts. This is because the viscosity becomes low, but the sintering stress does not change much by inhomogenizing the microstructure.
Authors: K. Takeda, T. Hiraba, Ryuichiro Ebara, Kazunari Shinagawa, M. Hirai, T. Nonomura, I. Morimoto
Abstract: Fattiigue and ttensiille properttiies of speciimens cutt from palllletts made from wastte pllasttiics by usiing of newlly develloped recyclliing apparattus are presentted.. Testted matteriialls are pollypropyllene fiillm,, pollypropyllene pelllletts,, pollyetthyllene,, pollyetthyllene-20wtt%flly ash composiitte and pollyetthyllene -20wtt% callciium carbonatte composiitte.. Itt can be conclluded tthatt tthe newlly develloped recyclliing apparattus make possiiblle tto proviide palllletts made from wastte pollypropyllene and pollyetthyllene wiitth ullttiimatte ttensiille sttrengtths of more tthan niinetty percentt of tthose made from fresh pollypropyllene and pollyetthyllene.. Itt has become cllear tthatt carefull ttreattmentt of composiitte process for wastte pllasttiics enablle tto iimprove fattiigue sttrengtth of pollyetthyllene composiittes by sttrengttheniing tthe iintterface bettween an addiittiive and base matteriiall..
Authors: Kazunari Shinagawa, Tsutommu Kaneko, M. Nakashima, Y. Hirashima
Authors: Takashi Mizuguchi, Rintaro Ueji, Hayato Miyagawa, Yasuhiro Tanaka, Kazunari Shinagawa
Abstract: The fracture behavior transition due to the change of strain rate in 5%Si magnetic steel with dislocation microstructures was studied. The Si steel was multi-passed rolled at 800°C to a various reductions up to 50%. The room temperature tensile deformation was conducted at various strain rates from 10-5/s to 100/s. All rolled steels were fractured in ductile manners with local elongation (necking) at slower strain rate. When strain rate was faster, the local elongation disappeared and the fracture manner was turned to brittle. The strain rate at which fracture mechanism changed from ductile to brittle increased with the increasing of the reduction. On the other hand, the almost fully recrystallized Si steel was fractured in the brittle manner at any strain rate and the transition strain rate was not found. The fractured tensile specimen with no local elongations contains deformation twins; whereas these deformation twins were not observed in the fractured specimen with local elongations. This result indicates that dislocation structure evolved during rolling suppressed the twinning and that the dislocation structure is effective for the enhancement of toughness in Si steel.
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