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An active control of vibration for a mechanical system involves the introduction an external source to perform its function to reduce vibration and noise level, such as for example, use of hybrid absorbers with controlled force to reduce the influence of seismic waves or wind power on buildings or mechanical structures, noise reduction in the cabin of an aircraft by reducing vibration of the large panels and thin metal forming booth walls; reduction of vibrations level using piezoelectric or electromagnetic devices mounted on the trailing edge of helicopter blades, devices tuning cars, etc. In this paper we are presented main active vibration control techniques currently employed to control of natural frequency in aim to reduce the effects of vibration by changing damping, stiffness or inertia of the system. [ABSTRACT FROM AUTHOR]

The vibrations most often leads to undesirable effects such as mechanical failure, costly maintenance of machines, worsening positioning performance of machines tools and also human discomfort. Theoretically, the vibrations can sometimes be eliminated. However, due to the high manufacturing equipment cost that may be involved in eliminating or reduction of vibration, we need a compromise between an acceptable level of vibration and the supplementary manufacturing cost of devices. In this paper have been presented some classical techniques of passive and semi active vibration control in order to reduction the vibration level, the control of natural frequencies through damping modification, using of different isolators and absorbers systems. [ABSTRACT FROM AUTHOR]

Reliability is a feature that creates trust and confidence in a product design and gives a determining role in the constructive solutions. Due to the particular importance of reliability in recent years manufacturers have been obliged to specify information about the parameters of reliability and maintenance program when they deliver products to customers. If the manufacturing reliability may decrease due to technological deviations or exceptions to construction documentation, operational reliability can occur at the project level only if they respect relevant maintenance program design. The reliability may decrease if the operating instructions are not followed, adapted to the conditions of use, which may differ from one point in the life of the equipment of those originally considered basic or conceptual conditions. In this paper the concept of mentanance program designed to increase the reliability of mechanical energy and petrochemical industry is highlited. [ABSTRACT FROM AUTHOR]