In the sound and vibration analysis, dynamic data acquisition plays important role. Dynamic data acquisition not only means acquire data but analyse it according to the complexity of the signals generating from the source of vibration. Accuracy of result depends upon the accuracy with which signal processing technique is selected. However present work, a comprehensive condition monitoring algorithm is proposed. This algorithm classify the signal according to its behavior with respect to frequency and time characteristics and then select the signal processing technique to acquire a meaningful results. This system not only selects the signal processing technique but also gives the type of bearing defect generating the vibration signals.
Wear rate and debris are key problems to implanted metal-on-metal hip joints. Surface texture on bearing surfaces is reported to increase tribological performances. Research on the translation of this technology to metal-on-metal hip joint for reduction of friction, wear rate and debris generation is limited. The aim of this study was to investigate, by theoretical predictions and experimental investigations, the tribological properties of simulated metal-on-metal hip joints with different surface textures. Three different honed surfaces were produced with emery paper at controlled load and speed. The experiments were carried out using a computer-controlled friction simulator. Theoretical prediction was carried out using an existing model for textured surfaces. Both experimental and theoretical results demonstrated that honed surfaces had lower friction coefficients during walking and stairs ascent and descent, demonstrating their potential use in metal on metal hip joints for increased implant longevity.
Sintered steel is used as a material for valve seat insert in automotive engines. During operation, a dynamic contact occurs between the valve and its seat. To investigate the wear behavior of sintered steel for this application, we have developed an impact-sliding tester using a ball on flat configuration. Impact-sliding experiments have been conducted at different impact angles (30°, 45°, 60°) with and without lubrication to investigate the surface damage of the sintered steel under this contact loading and to understand the effect of lubrication. Our results have shown an important variation of the wear rate in relation to impact-sliding angle. In dry condition, a low wear regime is observed for low angles; whereas maximum wear is observed at 60° angle for lubricated contacts. The wear scar in the dry contact is deeper than in the lubricated one. The damaged surface of sintered steel is examined by a Scanning Electron Microscopy (SEM). In dry conditions, the contact area wears out quickly due to an adhesive-abrasive process. Under lubricated conditions, a fatigue crack opening is associated to a lower wear rate. The lubricated impact-sliding condition modifies the main surface damage phenomena.
The estimation of cage slips and ball slips, i.e. skidding, in ball bearings used for the main shafts of jet engines, gas turbines, and turbo machines is necessary to clarify the phenomenon of wear and smearing in the bearings. Therefore, in this study, a new method for estimating skidding has been developed by taking lubricating oils to be non-Newtonian fluids, by considering oil temperature rises caused by slips occurring in the ball-to-raceway contacts, and by considering the equilibrium of forces acting between the cage and balls. These factors were not taken into consideration in Harris’ theory. To establish the adequacy of our analysis, analytical data of our study have been compared against experimental data published by Poplawski. Our analysis can also calculate oil film thicknesses and traction coefficients under skidding conditions.
In order to clarify the ultra low friction mechanism of Carbon Nitride (CNx) coatings under blowing dry Ar, thickness and area of transfer layers on mating surface were in-situ observed with an optical microscope during sliding against a sapphire hemisphere under blowing dry Ar. During sliding, thickness of transfer layer from CNx coating to a sapphire hemisphere increased and leaded to ultra low friction. When thickness and area of transfer layer was thick and small respectively, ultra low friction was observed. The result showed that the coefficient of friction decreased from 0.18 to 0.003 and remained constant throughout the friction test. It was confirmed the formation of a graphite-like transfer layer with Raman analysis and Auger Electron Spectroscopy (AES).
The kinematic viscosities in the undiluted solutions of propylene glycol and the polypropylene glycols were proportional to their molecular weights, but the friction coefficients and compressibilities in polypropylene glycols hardly depended on their molecular weights except for those in propylene glycol. In the friction coefficient measurement, the sliding metal surface was oxidized by strong mechanical shearing force and heat. The boundary lubricant film formation between the polypropylene glycols and the metal oxide layer on the sliding surface was investigated by the contact angle and infrared absorption measurements. The contact angle of the polypropylene glycol at 40°C decreased with an increase in the heat-treated temperature of the metal plate. The infrared absorbance of the polypropylene glycol at 3496 cm-1 was proportional to the lubricant film thickness, but the absorbance intercept in the plot of the absorbance vs. the film thickness was negative at zero film thickness. The negative intercept indicates that the hydroxyl group of the polypropylene glycol disappeared owing to the adsorption of the lubricant molecules to the metal oxide surface. The molecular weight dependence of the friction coefficient was explained by the boundary lubricant film formation of the polypropylene glycol on the metal oxide surface.
This paper presents the theoretical study of porous inclined stepped composite bearings with couple stress fluids. The generalized Reynolds type equation is derived for porous inclined stepped composite bearings with couple stress fluids. The closed form expressions are obtained for the fluid film pressure, load carrying capacity, frictional force and coefficient of friction. These expressions can be utilized to obtain the performance characteristic of four different types of bearing systems viz; porous plane slider, porous composite tapered land bearing, porous composite tapered concave bearing. It is observed that the effect of couple stress fluid lubricant provide an enhanced load carrying capacity and reduced coefficient of friction as compared to the corresponding Newtonian case for the bearings under consideration. Further, it is found that porous inclined stepped composite bearing has the largest load carrying capacity and lowest coefficient of friction as compared to other bearing geometries under consideration.
The theoretical analysis of rheological effects of Rabinowitsch fluid on the steady and dynamic characteristics of inclined stepped composite bearings is investigated. The Rabinowitsch fluid model is considered to account the pseudoplastic and dilatant nature of the lubricant due to the presence of additives. The perturbation technique is used to derive the modified Reynolds equation separately for both steady state and perturbed characteristics of the bearing. The closed form expressions for the bearing characteristics are obtained. By using these expressions, the performance characteristics of four different types of bearings such as stepped, plane inclined slider, composite tapered land and composite tapered concave bearings are determined. It is found that, the non-Newtonian behaviour of the Rabinowitsch fluid have a significant effect on bearing characteristics. Further, it is found that the existence of a critical value for profile parameter at which the dynamic stiffness coefficient attains maximum.
Slider-disk contact hysteresis is investigated as a function of the Zdol bonded fraction at constant film thickness. The contact hysteresis is found to increase with the Zdol bonded fraction. AFM force-distance curves also indicate increasing work of adhesion and hysteresis with increasing bonded fraction. The data is interpreted on the basis of surface energy parameters.