機械構造の結合部における摩擦減衰の解明と定量的予測(ねじり振動が作用する場合)
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概要
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The purpose of this study is to clarify the phenomenon of friction damping on contact surfaces of mechanical structures and to realize its quantitative prediction. Damping has been a crucial problem for many years for conducting simulations, predictions and optimizations of mechanical structures. Damping in the mechanical structures mainly depends on friction on the contact surfaces. Thus, there have been many attempts to estimate the friction loss energy dissipated on the contact surfaces to analytically predict machine dynamics. However, all of those attempts required experimentally identified parameters, i.e. they were not successful to achieve analytical prediction of friction damping. This may be because of difficulty in time-history non-linear analysis of sticking/sliding contact, whose areas and displacements change as a result of force equilibrium. As an example, two mechanical parts are connected with a bolt, and a torsional vibration is applied between those parts in this study. The sticking/sliding contact is a non-linear problem, but it contains linear phenomena such as contact pressure and torsional deformation. This research presents a fully analytical model of the friction damping, where those linear phenomena are extracted and analyzed preliminarily by FEM, and then the non-linear contact problem is iteratively solved by simple linear combination of the FEM results. An experimental vibration device with some measuring instruments is developed, and it is confirmed that the measured friction loss energy (friction damping) agrees well with the results predicted by the proposed model, which is fully analytical unlike the conventional models.