Papers by Author: Hiroyuki Saiki

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Authors: Yasuo Marumo, Hiroyuki Saiki
353
Authors: Hiroyuki Saiki, Yasuo Marumo, Hiroshi Nishitake, Masahiro Hazama, Fuminori Sakata
Abstract: Tensile tests of epoxy molding compounds were carried out using specimens composed of epoxy molding compounds which are transfer molded and post cured. The mechanical characteristics of the epoxy molding compounds change significantly due to changes in temperature and strain rate. In addition, the effect of nonlinear viscosity is large in both elastic and plastic regions. The characteristics of the visco-elastic-plastic behaviors of the epoxy molding compounds were examined. The behavior characteristics of the epoxy molding compounds during loading and unloading were shown in detail.
599
Authors: Akihiro Minami, Yoshihiro Tabaru, Yasuo Marumo, Li Qun Ruan, Hiroyuki Saiki
Abstract: Tool damages including plastic deformation and wear are affected by forging load, thermal load and frictional slide applied to tool surface. Plastic deformation of forging tools proceeds in the tool corer owing to elevated temperature, high contact pressure and severe frictional slide. Hard layers on the tool surface increase plastic deformation resistance and thermal resistance. The optimal design of hard layer structure reduces the tool damage and improves tool life. Temperature and equivalent strain of forging tools are influenced by friction shear factor, contact thermal conductance and contact time between the tool and the workpiece. At the friction shear factor of less than 0.4, equivalent strain of the tool is reduced. At the friction shear factor of approximately 0.4 or greater, equivalent strain increases sharply and concentrates in the vicinity of the surface hard layer. This tendency becomes more significant when the contact time between the tool and the workpiece increases. Equivalent strain is reduced by low workpiece temperature.
2540
Authors: Hiroyuki Saiki, Yasuo Marumo, Li Qun Ruan, Junpei Kozasa
Abstract: The effect of the flow stress of solid lubricant for cold forging on the tribological conditions was investigated using a rigid-plastic finite element method. The thickness of lubricant film decreases with decreasing flow stress of the solid lubricant and then decreases rapidly. The apparent friction coefficient also decreases with the decrease in the flow stress of the solid lubricant. The thickness of lubricant film tends to decrease with decreasing friction shear factor. When flow stress of solid lubricant is low, the thickness of lubricant film decreases remarkably with increasing tool stroke. We can observe a good correlation between the flow stress of solid lubricant, friction shear factor, minimum film thickness and apparent friction coefficient.
2275
Authors: Yasuo Marumo, Hiroyuki Saiki, Li Qun Ruan, Kazuyuki Hokamoto, Shigeru Itoh, Hirofumi Iyama
337
Authors: Akihiro Minami, Yasuo Marumo, Hiroyuki Saiki
Abstract: A model hot forging test was carried out using tools of matrix high-speed steel. Dynamic thermal loads were applied to tools subjected to ion nitriding on the surface layer of the tool, and the conditions of deterioration and thermal softening were examined by measuring Vickers hardness in the vicinity of the tool surface after the thermal load test. In addition, static tempering softening tests were carried out, and thermal softening equations are obtained using tempering parameter on the basis of the obtained master tempering curves. When the thermal load was applied under the same conditions to nitrided and heat-treated tools, the degree of surface deterioration and thermal softening was small for nitrided tools. Equations of softening for two cases, i.e., specimen subjected only to heat treatment and specimen subjected to both heat treatment and nitriding, were expressed using tempering parameter.
1242
Authors: Hiroyuki Saiki, Yasuo Marumo, Li Qun Ruan, Ryuuta Haraguchi, Mitsuhiro Moriyama
295
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