| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2004: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2003: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Research Abstract |
Friction is one of the most familiar physical phenomena and has been investigated from ancient age. The fundamental mechanism of friction is, however, not clear still now. This situation of the investigation of friction results from the fact that friction is complicated phenomena and shows various aspects by the property of each material, form, surface state, lubrication and etc. Recent development of various experimental technique, such as frictional force microscope and computer enable us to study of friction under well controlled condition, which is impossible before the last few decades. Stimulated by these experiments we investigated the friction between clean graphite substrate and clean graphite flake by molecular dynamics simulation. We succeeded to reproduce atomic scale periodic stick slip motion and low frictional coefficients, both of which are observed in experiments. We first clarified the mechanism of low frictional coefficient of graphite as the cancellation of interlay
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er interaction between two sublattices in the flake.
Pinning and depinning of magnetic vortex in type-II superconductors and density waves are typical frictional phenomena in solids and their investigation shed light on the study of friction at solid surface mentioned above. Newly discovered superconductor, MgB2, attract much attention recently due to highest Tc in metallic compounds and the existence of two superconducting gaps. We investigated flux flow resistivity of this system and made clear that its behavior observed in experiment is the manifestation of two superconducting gaps with different magnetic field dependence.
Many works investigated elastic manifold model with pinning as the theoretical and numerical model of frictional phenomena in solids. Unfortunately the effects of plasticity is, however, not taken into account in this model, but the plasticity can play an important effects in real systems. We studied numerically the model which allows plastic deformation in detail and made clear the dynamical phase transition between the plastic flow regime and dynamic solid regime. The critical external driving force of the transition increases with observation time and diverges at infinite observation time. So we can conclude that the dynamical solid phase is stable only within finite observation time. Less
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