# Design and Testing of a Measurement Device for High-Speed Bearing Evaluation
## 1 Introduction
Nanoparticles can help to increase wear resistance, reduce friction, and improve lubricity. A current trend in the industrial processing of oil and lubricant manufacturing is the shift towards the development and utilization of alternative fuels from renewable sources and the creation of environmentally friendly and easily degradable lubricants and additives [11; 12]. Organic and organometallic compounds, such as zinc dialkyl (diaryl) dithiophosphate (ZDDP), tricresyl phosphate (TCP), trixylyl phosphate (TXP), and dilauryl phosphate, are used due to their excellent properties as extreme-pressure/anti-wear (EP/AW) additives in motor and industrial oils. Typically, these compounds incorporate one or more polar groups into their molecular structure, with heteroatoms such as sulfur, phosphorus, or chlorine. However, due to environmental considerations, the use of these effective additives is becoming increasingly restricted, mainly due to the presence of the aforementioned heteroatoms. Attention in the development of new additives for lubricants is currently focused on the development and utilization of new environmentally friendly compounds. A promising and novel area in the development of EP/AW additives involves the use of inorganic nanoparticles. With the discovery of the unique properties of fullerenes and nanotubes, scientists' interest in researching nanoparticles and nanocomposite materials has rapidly increased. Nanoparticles and nanotechnologies find applications in almost all scientific fields, including tribology and tribochemistry [13]. While research on the use of nanoparticles has experienced significant growth in recent years, the use of nanoparticles in industrial lubricants has been practiced for over 50 years [14]. Surface-modified CaCO\({}_{3}\) nanoparticles are used as detergent additives in oils and are a common component of what is known as an additive package. In oils, they primarily serve a detergent function and are carriers of what's called alkaline reserve. Research on nanoparticles in tribology is mainly focused on testing their high-pressure and anti-wear properties. More than 50 different types of inorganic compounds and elements have been experimentally tested so far [15], and some of them have proven to be excellent EP/AW additives in these experiments. The results of some studies [16; 17] have even demonstrated better EP/AW properties for inorganic nanoparticles than the standard ZDDP-based additives used today. However, the disadvantage of most inorganic substances can be their insolubility and inability to form a stable dispersion in the base oil. Therefore, it is usually necessary to modify the nanoparticles' surfaces before use. Surface modifications of nanoparticles are achieved using suitable coatings or the addition of appropriate dispersing agents. Several diagnostic methods can be employed to assess the impact of nanoparticle additives on the functional and operational characteristics of rolling bearings. Vibration measurement is a common method for diagnosing rotating machinery and is also the primary method for bearing diagnostics [18]. Vibrations are typically measured in the range of 1 Hz to 25 kHz. Frequencies lower than 1 Hz or higher than 25 kHz are also used for diagnostics. For measuring vibrations higher than 1 kHz, piezoelectric accelerometers are the most suitable. They typically have a sensing frequency range from approximately 1 Hz to 10 kHz. Velocity sensors and position sensors are also used for vibration measurement. Position sensors are based on eddy current sensing and are primarily used for lower-frequency vibrations [19]. Vibrations in bearings can have several causes. They can be induced by external forces, such as the centrifugal force caused by an unbalanced rotating shaft. Bearing vibrations can also be caused by inherent vibrations, which are determined by the bearing's geometry and material properties, defined in terms of stiffness and damping. Elastic deformations of components also contribute to the generation of vibrations.