分子シミュレーションで解明されたトライボ現象

抄録

Nowadays, 500 PFLOPS super computer is launched, which is about 50 times faster than the previous flagship machine in Japan in 10 years before. This means that the simulation size for molecular simulation is extended 3.7 times larger in each 3 directions. Since the multi-scale nature of the phenomena is essential for the tribological phenomena, not only the machine power dependent but the efficient modeling to grab the phenomena is important. Here we describe the analyses using all-atom and coarse grained molecular simulation methods to reveal tribological phenomena. For the solid friction, the origin of layered materials is cleared using coarse-grained simulations and all-atom simulations. The heat escape motion on the commensurate surface between transfer layer and the base material is essential, and the environmental effect is also important. For the boundary lubrication, the simulation of very beginning physical adsorption of oiliness additive molecules revealed that the effect of base oil is different which is understood as “chain matching”. Molecular dynamics can treat not only physical but chemical adsorption process. The simulation of adsorption process for anti-copper-corrosion additives revealed that the selective adsorption of additives on newly formed surface is due to the charge transfer from the metal surface to additive molecules. The large-scale all-atom dynamics simulation for elastohydrodynamic lubrication oil film revealed the origin of boundary slip, and saturation of traction coefficient. Now the authors are extending multi-physics method to treat tribology of complex fluids such as viscosity index improver. At last we discuss about the micron-sale bottom up simulation for solid friction and wear. We show recent approach to attack multi-physics and large scale phenomena such as occurrence of wear from molecular level, using smoothed particle hydrodynamics simulator.