ABSTRACT Electrical capacitance method has been applied in measuring the elasto-hydrodynamic lubrication film thickness in rolling element bearings since 1970s, due to its feasibility of measuring film thickness directly in metallic components and its simple theory. In the current article, a summary on the evolution of the method and the corresponding issues relating to the film thickness measurements is given. The evolution of electrical capacitance method and other developed electrical capacitance methods in measuring the film thickness are discussed. Especially, the two existing methods of converting measured capacitance into film thickness are highlighted. One is to calculate the capacitance in the Hertzian contact area and the dielectric constant of the lubricant. The other is to apply calibration tests which are then used to transfer the measured capacitances into film thicknesses. The strengths and weaknesses of the two methods are also explored and discussed based on published researches.

ABSTRACTFouling is known to be a prominent industrial problem which is greatly affected by parameters like temperature, time and flowrate. The aim of this work was to simulate the fouling process in AA 6061 by developing a model through Minitab 16 and evaluate the models. Box Behnken design of Response surface methodology was applied for modelling and optimization of fouling propensity in artificial sea water. A response surface model was obtained and Analysis of Variance was performed to test the significance of the model. Fouling propensity was found in terms of weight gain. An experimental rig consisting of a recirculating loop mimicking the industrial conditions of fouling was used in the study. SEM analysis shows uneven deposits on the metal surface. Sharp, irregular deposits pressed deep into the metal was observed. The finding of this work would enable us to evaluate the individual and interactive effects of the parameters.

ABSTRACTIt is important to monitor the roll bite interface during metal rolling to maintain the product size and homogeneity so as to minimize the material wastage. However, the harsh nature of cold rolling makes installation of sensors in metal roll for industrial applications difficult. The present study used a novel ultrasonic measurement technique whereby an ultrasonic signal went through an external sensor layout arrangement to study the metal-roll interface. The reflection coefficient obtained from the roll-strip interface at 0° to the roll surface (normal ultrasonic measurement technique) and 19° (oblique ultrasonic measurement technique) were modelled and experimentally investigated on an instrumented pilot metal rolling mill. Variances of 6.4% and 8.8% were obtained in the reflection coefficient of the techniques from experimental and modelling approaches, respectively. This showed that both techniques could be used to study the effect of the angle of incidence wave on the reflection coefficient.

ABSTRACTThe paper aims to predict the cam and follower wear in direct acting valve train considering the effects of operating conditions. A numerical approach has been developed using frictional and lubrication analysis which is applied in the cam/follower wear study. Loading and motion parameters have been determined from dynamic and kinematic analysis whereas the wear profiles are obtained by linear wear relation. The wear of cam/follower is largely dependent on the lubrication film thickness, normal loading/contact pressure and sliding velocity. At low camshaft speeds, the wear depth of cam/follower pair is higher whereas it decreases at higher speeds due to relatively thicker oil film. It is an original research work and is strongly believed that it would help to further improve the performance of engine valve train and would also provide an opportunity to control the operating conditions promoting wear.

ABSTRACTThe microstructure and wear behavior of Friction Stir Processed (FSPed) AISI 430 ferritic stainless steel were analyzed in the present study. FSP was performed with a tool rotation and advancing speeds of 1400 rpm 16 mm/min respectively by employing a tungsten carbide tool. The FSPed microstructure consisted of a mixture of ferrite and martensite. After FSP, microhardness increased with respect to that of the as-received material. The wear resistance of the FS processed material was significantly enhanced if compared to that of the as-received substrate. According to the SEM analyses of the worn surfaces and wear debris, a combination of adhesive wear and delamination was observed in the case of the base metal. The wear mechanism shifted to mild adhesive wear after FSP. The superior wear resistance of the FS processed AISI 430 steel was attributed to the pronounced grain refinement and to martensite formation in the stir zone.

ABSTRACTAluminium (AA5083)-alumina surface composites are prepared by friction stir processing in two conditions of heat input. The low heat (LH) input conditions is achieved at a rotational speed of 710 rpm and a traverse speed of 100 mm/min, and high heat (HH) input conditions are achieved at a rotational speed of 1400 rpm and a traverse speed of 40 mm/min. The tribological characteristics of aluminium alloy, friction stir processed (FSPed) alloy and FSPed surface composites against steel ball are studied at 5, 10 and 20 N load. While no significant influence is found on frictional behaviour, wear resistance of FSPed composites is superior to FSPed alloys. FSPed composites fabricated at HH input conditions exhibited improved wear resistance as compared to LH input condition. Adhesion and delamination are dominant wear mechanisms at 20 N. Debris particles are reduced in size and hydroxidated in sliding of surface composites.

ABSTRACTThe relationship between the volume loss rate and the wear pattern along an abraded rubber surface has been confirmed. Experimentally, long and short pattern spacings are formed along the abraded direction that, respectively, represent the initial and final pattern spacings. By modelling the abrasion, or the sliding contact, as a vibration system, an analytical study to identify the pattern spacing is carried out. There are two proposed interaction models of the contact between the rubber surface and the abrader, i.e. separation and unification, thus, the interaction along the sliding contact is a combination of both. It is confirmed that the separation model is correlated to the initial pattern spacing. The results are obtained that the final pattern spacing not only depends on the static load of the abrader but also depends on the dynamic load due to the inertia effect of the moving parts of abrasion apparatus.

The sliding wear behaviour of microwave processed, SiCp and Al2O3p reinforced aluminium alloy 2900 and 2024 metal matrix composites prepared by powder metallurgy method was investigated in a pin on disc system. The objective is to determine the effects of novel alloying elements of AA 2900, ceramic addition and microwave aging process on the strength to tribological properties. This composite is evaluated to be an effective replacement for conventionally available AA 2024 composites in brake applications. Compared to conventional heat treating processes, microwave processing used for heat treating the samples is observed to be novel method in improving the strength–microstructural–tribological properties. AA 2900 with 6 wt-% Al2O3 exhibited good strength to microstructure relationship with excellent wear characteristics compared to AA 2024 composites which are governed by alloying elements in AA 2900. 2 H aged AA 2900 with 6 wt-% Al2O3 sample exhibited good frictional coefficient values with good density and strength characteristics. Hence, it is observed that alloying elements in AA 2900 and microwave processing have enhanced the strength to tribological behaviour where the property enhancement is achieved only through ceramic reinforcements.

Slurry erosion behaviour of HVOF (High Velocity Oxy Fuel) and plasma sprayed coatings on CA6NM hydraulic turbine steel has been investigated at different levels of various parameters. The Cr2O3–50%Al2O3 composite powder was prepared and deposited on CA6NM steel samples to get the uniform thickness coatings. The surface roughness, porosity and microhardness of as-coated samples were measured. The as-coated samples were subjected to SEM/EDS analysis to evaluate the surface microstructure of the developed coatings. Erosion tests were performed on self made erosion test rig under hydro accelerated conditions. The study reveals that the velocity, impact angle and slurry concentration were the most significant parameters, influencing the erosion rate of these coatings. The average particle size had least affect on the erosion rate. HVOF-coated samples showed better corrosion resistance as compared to plasma-coated samples due to high hardness of HVOF-coated CA6NM samples.

Plasma spraying is used to produce wear resistant coatings. However, the primary problem is the poor bonding strength between the coating and the substrate. The secondary problem is the high porosity in the as-sprayed coatings, which reduces the wear resistance of coating. In order to overcome these problems, the sealing of plasma-sprayed coating by electrodeposition has been used. The sealing of plasma-sprayed coatings alters the wear mechanism and wear resistance. The wear mechanism and wear resistance largely depends on the applied load, sliding speed and sliding distance. Hence, an effort has been made in the present work to study the effects of these parameters on wear volume loss using response surface methodology (RSM)-based mathematical models. The experiments were conducted as per Central Composite Design (CCD). It reveals that the applied load was the most predominant factor affecting the wear volume loss of the coating material. The sliding speed is the next most important parameter influencing the wear volume loss. The wear volume loss of the sealed plasma-sprayed molybdenum coating occurs mainly due to the formation of grooves, surface tribo films, fracture of splats and delamination of the coating.