Applied Mechanics and Materials Vols. 592-594

Abstract: This work presents an experimental study of tribological performance of electroless Ni-P coating under lubricated condition. Mild steel specimens are used as the substrate material for the deposition of Ni-P coating. Tribological tests are carried out based on L₂₇ orthogonal array (OA) varying three test parameters viz. normal load, sliding speed and sliding time in a multi-tribotester using block-on-roller configuration in lubricated condition. The experimental results for friction coefficient and wear are analysed using weighted principal components analysis (WPCA). An optimal test parameter combination is found out for minimum wear and friction coefficient. It is seen that the optimum combination of parameters are found at higher level of normal load, sliding speed and sliding time at 99% confidence level. Finally, a confirmation test is carried out to validate the analysis.

Abstract: Present work aimed at investigating the friction and wear of martensitic stainless steel of grade 410. This steel is used in nuclear industry for various moving components due to its high strength and moderate corrosion resistance. Properties of this material depend upon the heat treatment to which subjected to. The wear tests by sliding were performed on a pin on disk apparatus whose pin is in normalized and tempered condition. The counter face disc was machined from EN24 steel of high hardness in nature. The AISI 410 stainless steel wear rates were evaluated using Pin-on Disc Tribometer at various load and sliding speed. The worn pins were investigated by using scanning electron microscopy and surface profilometer.

Abstract: In thepresent study, preparation and characterization of LM6 (A413) aluminum alloy reinforced with nanoalumina powder (Al₂O₃) is investigated. Al₂O₃ nanopowder reinforced LM6 (A413) aluminum alloy Metal Matrix nanoComposites (MMNCs) were prepared by stir casting method. The distribution of reinforcement of alumina nanoparticles in LM6 (A413) aluminum alloy were observed with a scanning electron microscopy (SEM). The effect of Al₂O₃ nanoparticles on mechanical properties of MMNCs were investigated. The wear behavior of MMNCs against hardened steel under dry sliding condition was evaluated on friction wear tester. The results revealed that the inclusion of 2.5% weight fraction alumina nanopowders into LM6 (A413) aluminum alloy enhanced the hardness, impact strength and wear resistance compared with reinforcement of 1, 1.5, 2.5, 5% weight fraction alumina nanopowders. However, the better tensile strength is achieved with 1.5% weight fraction reinforcement in the composites.

Abstract: The wear behavior of aluminium alloy (A356) reinforced with 5 wt. % of quarry dust particles composite disc was sliding against automobile brake friction lining pin was investigated. Dry sliding wear studies were investigated in pin-on-disc apparatus. The wear tests were carried out range of applied load 20 to 60 N and constant sliding velocity (0.5 m/s) under sliding distance of 500 m. The wear behavior of aluminium metal matrix composite (AMC) has been compared with the commercially used 25 grade Gray Cast Iron disc (GCI).The results showed that the wear rate of AMC disc decreased with increasing the applied load. However the wear rate of AMC disc with respective pin decreased with increasing the applied load. The coefficient friction increased with increasing the applied load. The scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDAX) used to investigate the disc and pin. The wear debris was analyzed by SEM image.

Abstract: Monitoring the condition of the engine through oil analysis will help operators to get the most value from their equipment and their lubricant. This is just one part of an overall Preventive Maintenance (PM) Program. Engine lubricant condition reflects the state of health of engine through its properties. Recognition and analysis of the correlation between engine lubricant system based on the lubricant properties and engine performance is crucial to provide insight into engine health. Aim of this paper is an investigation for prior failure of engine component through oil analysis. Engine is the heart of automobile vehicles. Engine performances are directly dependent upon the health of its components like piston, cylinder, cylinder head, crankshaft, cam shaft, connecting rod etc. Metals in lubricating oil can come from various sources, such as wear, contamination and additives. Wear metals result from friction or corrosion of the engine components; for example pistons, bushing, piston ring and bearings, during operation. Contamination can come from dirt, leaks or residual metal pieces. Additives used as detergents, anti-oxidants and anti-wear agents, are added in order to reduce engine wear. Wear of a specific component is heralded by an increase in the concentration of a particular metal, or the sudden appearance of a metal. Since different engine components are composed of different alloys, the increase of a particular metal can be used to identify impending failure of a specific component. An analysis of trace metals in engine oil has permitted the identification of wearing components before severe failure, without dismantling of the engine. Spectrometric Oil Analysis Program (SOAP). The determination of Al, Cd, Cr, Cu, Fe, Mg, Ni, Pb, Sn and Zn impurities using flame atomic absorption spectroscopy method. The used engine oil samples were digested with HCL

Abstract: Elastohydrodynamic line contact simulations have been carried out in the present study. A practical situation of transient EHL film collapse has been analyzed. The aim is to observe the effect of variation of maximum Hertzian pressure (P_H) on transient behavior of EHL film thickness (H).The analysis is based upon classical Reynolds equation considering time variation. The simulation results pertaining to EHL film thickness calculated using linear pressure-viscosity relationship have been compared for different values of load. It has been observed that film thickness reduces with increase in load. Similar results are obtained using exponential pressure-viscosity relationship and compared with those for linear pressure-viscosity. The EHL equations are solved by discretizing Reynolds equation and load equilibrium equation along with other equations using Newton-Raphson technique with the help of a computer code.

Abstract: Consideration of surface roughness in steady state EHL line contact is the first step towards understanding the lubrication of rough surface problem. Current paper investigates the use of sinusoidal waviness in the contact; more precisely it gives performance of real fluid in EHL line contact. The effect of various parameters like rolling velocity (U) and maximum Hertzian pressure (p_h) on surface roughness by using properties of linear and exponential piezo-viscosity is taken into consideration to evaluate behavior of pressure distribution of load carrying fluid film and film thickness. Full isothermal, Newtonian simulation of EHL problem gives described effects. Spiking or fluctuation of pressure and film thickness curves is expected to show presence of irregularities on the surface chosen and amount of fluctuation depends on certain parameters and intensity of irregularities present. Rolling side domain of-4.5 ≤ X ≤ 1.5 with grid size ∆X=0.01375 is selected. A computer code is developed to solve Reynolds equation, which governs the generation of pressure in the lubricated contact zone is discritized and solved along with load balance equation using Newton-Raphson technique.

Abstract: The present paper theoretically investigates the influence of partial and full texture on the performance of the hybrid thrust pad bearing operating with non-Newtonian lubricant. The presented results show that the dilatant lubricant with partial textured surface has the maximum load carrying capacity. The effect of full texture on hybrid thrust bearing is positive. In the present paper, Finite element method with Reynolds boundary conditions is implemented. The comparative study shows that partial texturing in the bearing significantly works better than the full texturing and the friction coefficient in the bearing can be reduce upto 60% as shown in the results.

Abstract: This paper describes the stability analysis of a flexible rotor supported by two horizontal identical plain circular bearings lubricated with Non-Newtonian fluid as micropolar fluid. The basic principles of hydrodynamic lubrication are also discussed here to study the dynamics of rotor bearing system. The mechanisms of hydrodynamic film generation and the effects of operating variables such as velocity, load, design parameters etc., on the performance of such films are outlined. The effects in hydrodynamic lubrication of rotor system using Non-Newtonian lubricant found some undesirable vibrations, undergoes periodic and quasi-periodic motion is described and their influence on bearing performance assessed. The numerical solution of modified Reynolds equation under micropolar lubrication with the usual lubrication assumptions is considered which yield the pressure distribution to find the couple of resulting forces in radial as well as in tangential direction.

Abstract: This paper presents the complex dynamic analysis of a flexible rotor–bearing system supported by two turbulent micropolar fluid film journal bearings under nonlinear suspension. The Modified Reynolds equation based on the assumptions of turbulent flow and the micropolar parameters has been considered. The system considers Short bearing approximation to simplify the numerical computations. The pressure distribution thus obtained is used to find out the resulting forces about the journal center in the radial and tangential directions. The Non-dimensional dynamic equations are derived considering appropriate non dimensional parameters and solved using MATLAB for a wide range of non-dimensional speed ratios. Plots of the journal center trajectories and rotor center trajectories are obtained. The results show that the system undergoes undesirable nonsynchronous vibrations due to bearing center displacement. Micropolar fluid is found to stabilize the system even when the flow of the system becomes turbulent. The study presented enhances the understanding of the nonlinear dynamics of turbulent journal bearings with respect to dimensionless parameters.