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The purpose of this study is to acquire design method of machine tools with higher dynamic stiffness and consequently higher chatter stability. This study focuses on stiffness of main structures and friction damping in guide of a machine tool, because stiffness and friction damping are considered to have major influence on the dynamic stiffness. A special testing machine with variable stiffness and friction was developed to clarify effects of the stiffness of main structures and the friction in guide on the dynamic stiffness and therefore the chatter stability. The stiffness of main structures and the friction in guide were changed experimentally, and it was clarified that the optimal friction force exists at every stiffness condition, and that higher stiffness does not always lead to higher stability.

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.

Abrasive flow machining (AFM) is one of the most promising technologies for internal finishing and de-burring for features with complex geometry. This study investigates the effect of media degradation on finishing characteristics achieved using the AFM process. A total of 50 experiments, using Inconel 718 cylindrical coupons machined by Wire-Electron Discharge Machining (WEDM), were conducted employing the same process conditions while using a single batch of AFM media. Experimental results indicate that media degradation has minor influence on surface roughness, but more significant influence on material removal and media flow rate. Material removal decreases exponentially with increasing cumulative media flow volume despite media flow rate increasing. There is a linear correlation between material removal and media flow rate. As a result, material removal can be estimated from media flow rate which can be monitored easily.