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Corrosion is a natural process of degradation of the mechanical properties of some materials like: metals, ceramics or polymers. The metals and their alloys corrode only because of their presence in a damp environment, but the process is more powerful in some corrosive environments. Corrosion is a diffusion process by which some chemical bonds of the base material are broken, and therefore the oxides, bases, or salts are formed, resulting in a process of mass loss but also of weak interatomic bonding forces, that means a loss of stiffness. Mass distribution and stiffness in a mechanical structure determine the natural frequencies and shape of natural modes, that is, so-called modal parameters that characterize its dynamic behavior. The purpose of this paper is to determine the influence of simultaneous loss mass and loss stiffness on natural frequencies. Applying the Finite Element Method and the Modal Analysis Module of the ANSYS software, the natural frequencies are obtained in numerical approach, which compares with the obtained analytical values, to confirm the validity of the proposed method.

Today, reduction of industrial noise is a widely used concept for improving the life standard in vicinity of industrial and residential mixed areas. The human ear has a very poor auditory acuity in perceiving sounds produced by sound pressure variations in the very low frequencies or very high frequency range. Noise is, in general interpretation, disturbing sound, annoying or even dangerous, although this perception is subjective. There are at least two kinds of people, one that "adapted" psychological noise and learned to work with it and another which gradually became sensitive to noise. In the current situation of industrial development, and housing, many locations of manufacturing facilities are near residential areas, so it is very important to realize noise levels monitoring. Legislation provides for annual measurements of noise levels to limit industrial properties. This paper describes the monitoring, over a period of several years, the noise sources within a company at the limits of Timisoara.

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Metallic materials are subjected to degradation mechanisms when working in corrosive environments, such as those created by mineral oils and residues of a motor fuel. The camshaft is subjected to multiaxial stresses, creep, fatigue, corrosion and abrasion. As a result of the operation in special conditions of high temperature and high pressure can lead to forming cracks, damages or failure. In such cases it is necessary for these components to be repaired by welding, followed by a rectification process. This paper presents a method for determining the quality of welding repairs and rectification results from the analysis of vibration signals. A Fast Fourier Transform algorithm and an algorithm based on Prony's series method are used for processing the sampled signals.