Papers by Author: Takehiko Makino

Abstract: Most forming oils have changed to chloride-free oil containing no chloride additives to protect environments regarding as the big issue of sustainable manufacturing. Several high-performance oil without chloride and die coating has been developed recently. In this study, the effect of micro-dimples on a die formed by a cutting machine or a laser device was tried to use chloride-free oil for ironing of stainless steel. The heavy galling occurred during ironing of stainless steel when the normal die without micro-dimples is used under a condition lubricated with chloride-free oil. The micro-dimples formed by the cutting machine only promoted galling because a large amount of burr remained around the dimples. The micro-dimples formed by the ultrashort pulse laser prevent from galling. The dimples have a smooth and mild profile on the die. The coverage area ratio of micro-dimples larger than 20% is needed for better ironing. A zigzag arrangement of the dimples uses the oil efficiently for well lubrication because galling occurs at the no dimples line between two rows of dimples if the dimples are neatly arranged parallel to the ironing direction.

Abstract: Micro/meso-scale (from 0.1 to 10mm) metal parts are required in electronics and medical field in recent years. Rotary forming is one of possible methods to manufacture micro axial-symmetry parts. In rotary forming, the materials are rotated and compressed in radial directions. In order to investigate the basic deformation mechanism, flat dies are used. The pins with diameters of 0.3 to 0.8mm are used to clarify the effect of size of pins on deformation behavior. Additionally, the effect of lubrication conditions on the forming process is examined. It is considered that size effects in friction behavior are recognized to be large in micro/meso-scale rotary forming.

Abstract: Wetting can be regarded as a kind of effective nanostructure-forming process. To control the structure, a study on the relationship between atomic interactions and the resultant wetting behaviors is required. To model the wetting system, two sets of interatomic potentials for Metal/MgO(100) systems are derived from first principles calculation results for the simple configurations. A molecular dynamics method is applied to simulate the system and shows that Al atoms wet better than Sn atoms on the MgO substrate. The tendency is consistent with the experimental contact angles. The interfacial structures are different between these two systems.

Abstract: Considering the uniqueness of wetting systems consisting of three components, namely, the surface, liquid and liquid/solid interface, it is desirable to construct interatomic potentials following a consistent policy. To investigate the physical meaning of the behavior in terms of the interatomic potentials, the wetting systems are modeled by simple two-body interatomic potentials derived using ab initio molecular orbital calculations for hypothetical clusters representing the above three components. For In and Sn liquid atoms, spreading occurs on a Cu (111) surface, while in contrast, liquid atoms penetrate the substrate and form a surface alloy in the case of a Pd (111) surface.