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.
Passing a vehicle over bumps generates sudden variations in acceleration with effects on passenger comfort. In this paper we aim to model the movement of a vehicle, considering only vertical movements, neglecting the movement of roll and pitch. Based on differential equations that govern dynamic behavior, a simulation model of motion is built in MATLAB, the Simulink® module. Suspensions of the vehicle will be considered as passive and semi-active. Passive and semi-active are still the most common suspensions, although active suspensions have been used lately, with mechanical parameters thatcharacterize suspensions, stiffness and dampers being controlled. The paper analyzes the responses given by the suspensions to the passage over bumps, and how they can be mitigated.
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