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Cavitation is the dynamic process of gas cavity growth and collapse in a liquid. These cavities are due to the presence of dissolved gases or volatile liquids and they are formed at the point where the pressure is less than the saturation pressure of the gas (gaseous cavitation) or vapor pressure (vaporous cavitation). In this paper, an overview of fluid properties affecting the cavitation process and bubble collapse mechanism will be discussed. This discussion will provide an overview of the cavitation process including the most recent mechanistic studies which have measured the bubble collapse temperatures and sonoluminesence mechanism. Sonochemical processes which may be induced by the cavitation process will be summarized as well as recent sonochemical-induced tribological reactions from a material science perspective.

The heat treatment used in manufacturing process of automotive parts are very important, and among them, particularly the quenching of steels. In this heat treatment the quenchant capacity of heat extration is a very critic parameter, and once specified, its cooling features must be preserved to ensure the maintenance of the mechanical properties of components, which will determine the project functionality and durability. The best way to control the quenchant during quenching is through the continued control of the quenchant cooling curve of the and its respective cooling rate. In this work was utilised a computer controlled data acquisition system, which allow in actual time, to get values of temperature and time during the cooling phenomena. This data are processed to give immediately values of the cooling rate. This system is applied to different quenchants, such as: water, polymeric solutions and oils.