Ferrooil's dynamic viscosity changes significantly alter the tribological properties and thus its usefulness as a lubricant of the sliding journal bearings. Due to the fact that the ferrooil demonstrate strong magnetic polarity in the presence of an external magnetic field, it is possible to control the viscosity by means of an external magnetic field just by changing the intensity as well as by changing of the concentration of magnetic particles. There is presented an effect of the changes of the concentration of magnetic particles included in the ferrooil on the dynamic viscosity in the absence of external magnetic field in this paper. The study was conducted in the context of temperature's and shear rate's changes. In that way, it was also taken into account the influence of external physical conditions of ferrooil's employment. Tests were performed on HAAKE MARS III rheometer for the shear rate range from 0 to 100000 1/s and temperature of work to 120ºC and the tested ferrofluid was product of FerroTec of Unterensingen (Germany), which is a mixture of colloidal mineral motor oil Penzzoil's LongLife Gold's SAE 15W-40 with Fe 3 O 4 magnetic particles at a concentrations of: 8, 6, 4, 3, 2 and 1% and the surfactant. Addition of surfactant is to prevent clustering of magnetic particles in the oil. The paper presents, in the form of graphs, the changes of ferrooil's dynamic viscosity as a function of temperature, shear rate and concentration of magnetic particles. The results of research were also subjected to analysis. This work is part of a wider study on the analysis of changes in operating parameters of journal bearing ferrofluid's lubricated.

This paper presents the results of studies which characterize the dynamic viscosity changes of ferrofluid in terms of changes of selected physical conditions of its work. Knowledge of the variation of the ferrofluids density, lubricity, and especially viscosity depending on the concentration of Fe3O4 magnetic particles, temperature, deformation speed and impact direction, type and value of magnetic induction, it is necessary to analyze the changes of operating conditions of the slide journal bearing ferrofluids lubricated. This theme is the broader context of the authors interests and his research. In this article has been briefly characterized the viscous properties of the tested ferrofluid. There also has been shown an analysis of the impact of changes in temperature and velocity of deformation on the change of ferrofluids dynamic viscosity. The paper has been summarized the observations and conclusions reached on the basis of analysis results.

The purpose of this article is to determine, identify and describe the viscosity characteristics of the ferro-oil with different concentrations of magnetic particles at context of temperature changes. These characteristics were determined for the following test conditions: atmospheric pressure, constant shear rate and absent of an external magnetic field. Tests were performed for selected concentrations of magnetic particles in ferro-oil ranging: 1%, 2%, 4%, 6% and 8%. Tested ferro-oil was product from Unterensingen FerroTec Company (Germany) which is a mixture of colloidal mineral engine oil LongLife Gold Penzzoil class SAE 15W-40 with addition of Fe3O4 magnetic particles and a surfactant. Analysis of the results, identifying and fitting of characteristics has been made by means of software StatSoft STATISTICA ver.9.1. There has been also undertaken comparison of the accuracy of estimation of reached results by selected mathematical models as well as these results have been rated according to their compliance with theoretical assumptions. Moreover, the waveform parameters of functions have been determined and their assessed quality has been done also. The obtained characteristics going to be used by author in his future work to build mathematical models of viscosity changes of ferro-oils in the aspect of changes of parameters like temperature, pressure, shear rate and the value of the external magnetic field. The determined parameters of physical properties will be used in analytical and numerical studies of flow and operating parameters of slide journal bearings lubricated with ferro-oils.

In this article, the results of the experimental research of determining the dynamic viscosity of the ferro-oils with different concentration of the magnetic particles in terms of pressure change are presented. The research was conducted on the Thermo Scientific Haake Mars III rheometer in the configuration with a pressure chamber. The applied configuration allowed the author to conduct research on the change of viscosity for the selected pressure values p in range from 0 to 100 bars. The research was conducted for three selected temperature values, including t = 30°C, 60°C, and 90°C, as well as selected shear rates of 200 and 600s-1. The chosen concentration values of the magnetic particles were nCS = 1%, 2%, 4%, 6%, and 8%. The viscous characteristics gathered as a result of the research have been analysed with the aim of identifying the nature of the correlations and to create mathematical-physical models of changes in the dynamic viscosity of the ferrooils due to the change in pressure in terms of concentrations of the magnetic particles. Analysis, identification, and adaptation of the characteristics were conducted using the StatSoft STATISTICA ver. 9 software. Selected mathematical adaptations of the acquired results were submitted through the enhanced analysis. In addition, parameters of the course of functions were designated and their qualitative assessments were made.

The purpose of this article is to determine the effect of the concentration of magnetic particles in ferro-oil on the value of its magnetic su Determination of the flow and operating parameters of slide journal bearings lubricated with ferro-oils requires, inter alia, designation the first magnetization N and the magnetic induction B vector components, dependent on the lubricant. The fundamental problem lies in the inability to make direct accurate measurement of magnetic induction in the lubricating gap of slide bearing and its solution is to determine it on the analytical and numerical way. A key issue for the accuracy of such solutions is to obtain reasonably accurate values attempts to determine these values and estimate their relationship with the concentration of magnetic particles concentration in ferro-oil being potential lubricant above-mentioned bearings. In this paper, the authors present the characteristic of experimental test benches to determine the coefficients of the magnetic susceptibility. They present method of determining this value from obtained measurement data and analyse the impact of the magnetic particles concentration in ferro-oil on its magnetic susceptibility values. Tests were performed for selected concentrations of magnetic particles in ferro-oil ranging: 2%, 4%, 6% and 8% and the tested ferro-oil was product from Unterensingen FerroTec Company (Germany) which is a mixture of colloidal mineral engine oil LongLife Gold Penzzoil class SAE 15W-40 with addition of Fe 3 O 4 magnetic particles and a surfactant.