Design of an optimal damper to minimize the vibration of machine tool structures subject to random excitation
The vibration of machine tools during machining adversely affects machining accuracy and tool life, and therefore must be minimized. The cutting forces for stable turning are generally known to be random, and hence excite all the resonance modes. Of all these modes, those that generate relative motions between a cutting tool and a workpiece are of concern.This paper presents a new approach for designing an optimal damper to minimize the relative vibration between the cutting tool and workpiece during stable machining. An approximate normal mode method is employed to calculate the response of a machine tool system with nonproportional damping subject to random excitation. The major advantage of this method is that it reduces the amount of computation greatly for higher-order systems when responses have to be calculated repeatedly in the process of optimization. An optimal design procedure is presented based on a representative lumped parameter model that can be constructed by using existing experimental or analytical techniques. The two-step optimization procedure based on the modified pattern search and univariate search effectively leads the numerical solution to the global minimun irrespectively of initial values even under the existence of many local minima.
THE VIBRATORY BEHAVIOUR OF A LATHE WITH CONTINIOUS VARIATOR OF HIGH SPEED AND DYNAMIC ABSORBER
In this paper, a lathe with continuous variator of high speed and dynamic absorber is studied. The machine, which is a complex system with a great number of freedom degrees, has a corresponding number of freedom degrees, which is why in the dynamic study, there will be taken into account only those vibratory modes that, according to the required precision and the main purpose, have a great influence in the development of the studied vibratory phenomenon. From this case, in this paper, a model with 7 degrees of freedom will be used.
Mechanism of Action of Antibacterial Agents
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