Tribology in Industry

142-153

Authors: I.A. Samotu, M. Dauda, F.O. Anafi, D.O. Obada

A recycling aimed research was carried out to produce a new composite material and proffer suggestion for the possible use of the newly developed composite material. The empty water sachet (commonly called pure water nylon in Nigeria), was used as a matrix, which was reinforced by carbonized palm kernel shell (CPKS) particulate and iron fillings. The percentage composition of iron fillings was maintained at 5 wt%, while that of palm kernel shell ash was varied from 5 wt% - 20 wt% at an interval of 5 %. The composites were compounded and compressively moulded. Physical and mechanical properties of the composites were tested for alongside three conventional car bumper samples, and the results obtained shows that the composite material could be used to produce a car bumper among other parts of automobile like dashboard due to their impact strength and low density. Impact strength - density ratio for the materials gave prime information on the possible application of the developed material. Scanning Electron Microscope (SEM) was used to examine the distribution of the reinforcement within the matrix. After results analysis, materials with 5 wt% of CPKS and that with 10 wt% of CPKS were recommended for the car bumper production following their high impact strength - density ratio of 0.26 and 0.19 respectively, which are higher as compared to that of a conventional bumper material measured alongside the composite materials.

161-169

Authors: J.V. Kumar, R.R. Rao

A generalized form of Reynolds equation for two surfaces is taken by considering surface roughness at the bearing surfaces. This equation is applied to study the effects of surface roughness for the lubrication of squeeze film of two parallel plates. Expressions for the load capacity and squeezing time are obtained and studied theoretically for various parameters. The load capacity and squeeze time increases with an increase in the value of which represent a ratio of the viscosity of the peripheral layer to the middle layer. In the case of transverse roughness the load capacity and squeezing time increases as the mean height of surface asperities increases and the load capacity and the squeezing time decreases as the mean height of surface asperities increases in the case of longitudinal roughness. Hence the effect of surface roughness is more pronounced in the case of transverse roughness.

176-185

Authors: V.V. Rao, Ch. Ratnam

This paper describes the comparison between Vibration Analysis (VA) and Acoustic Emission (AE) method to predict the defect severity in rolling element bearings with respect to the gradual increase of defect size. In bearing fault diagnosis vibration based methods are very popular, but the signals acquired by its transducers from the bearings are distorted by other faults and mechanical noise from the equipment. Vibration based methods are effective when the defect in the bearings has already become severe. AE is a non destructive testing (NDT) technique used in structural health monitoring and its application for bearing defect diagnosis is gaining momentum as an alternate diagnostic tool because of its inherent high signal-to-noise-ratio (SNR). A bearing test rig was designed and set up to study the various defects in rolling element bearings in real environment. In earlier cases, though the researchers studied on different types of seeded defects with random sizes, they could not ascertain the correlation between their defect sizes and the vibration amplitude. The experimental investigation reported in this paper is centered on seeded defect of same type with gradual increase of its size on outer race of radially loaded cylindrical roller bearings and running the defective bearing at different speeds and loads. Data acquired through AE & vibration probes simultaneously for better diagnosis. Comparisons between AE and VA over a range of speed and load conditions at gradual increase of defect size are presented and from them it is concluded that AE method is superior to identify the severity of defect.

196-203

Authors: S. Bhaumik, S.D. Pathak

The present work investigated the anti-wear properties of CuO nanoparticles based mineral oil using pin-on-disk apparatus. The pin material selected was EN 24(untreated) as it is used in gear manufacturing. Commonly used graphite macro particles (wt.%) and CuO nanoparticles(wt.%) were used as additives. It had been observed that the additives based mineral oil samples exhibited superior antiwear properties than pure mineral oil. Both CuO nanoparticles (0.2 wt.%) and graphite (0.2 wt.%) based lubricant showed significant decrease in coefficient of friction and specific wear rate. There was a reduction in both coefficient of friction (28.5 % approx.) and specific wear rate (70 % approx.) in case of CuO nanolubricants and graphite based mineral oil as compared with the pure mineral oil.Flash-fire point, viscosity and viscosity index also increased with the increase in additive concentration. The surface characteristics of the pin were studied using Scanning Electron Microscope (SEM) and surface roughness tester. The SEM images showed more rough surfaces in case of pure mineral oil samples as compared with graphite and CuO nanoparticles based samples. The surface roughness values of the pins in case of graphite (0.2 wt.%) and CuO nano particles (0.2 wt.%) based lubricant were much lesser than pure mineral oil. From the results predicted minimum 0.2 wt.% CuO nanoparticles were required to enhance the antiwear property of the lubricant. This work aimed in bringing a comparative experimental analysis using CuO nanoparticles and commonly used graphite macro particles as lubricant additives on various properties such as viscosity, flash point, fire point, surface roughness and anti-wear properties. Thus, the work would be useful in developing new nano lubricants with minimum additive concentration

215-224

Authors: D. Adamović, M. Stefanović, M. Živković, S. Mitrović, J. Živković, F. Živić

If it is needed to achieve a higher strain rate during the ironing process, which is possible without inter-stage annealing, the ironing is performed in succession through multiple dies. During that process, changes of friction conditions occur due to the change of contact conditions (dislodging of lubricants, changes of surface roughness, formation of friction junctions, etc.). In the multistage ironing, after each stage, the completely new conditions on the contact surfaces occur, which will significantly affect the quality of the workpiece surface. Lubricant has a very important role during the steel sheet metal ironing process; to separate the sheet metal surface from the tool and to reduce the friction between the contact surfaces. The influence of tribological conditions in ironing process is extremely important and it was a subject of study among researches in recent years, both in the real processes and on the tribo-models. Investigation of tribological conditions in the real processes is much longer and more expensive, so testing on the tribo-models is more frequent. Experimental research on the original tribo-model presented in this paper was aimed to indicate the changes that occur during multistage ironing, as well as to consider the impact of some factors (tool material, lubricant on die and punch) on increase or decrease of the sheet metal surface roughness in ironing stages.

236-243

Authors: M. Madić, M. Radovanović, D. Petković, B. Nedić

In this paper an approach for multi-criteria analysis of laser cut surface characteristics using multi-criteria decision making (MCDM) approach was presented. Laser cutting experiment was conducted based on Taguchi’s L27 experimental design by varying laser power, cutting speed, assist gas pressure and focus position at three levels. Multi-criteria analysis was performed by using the weighted aggregated sum product assessment (WASPAS) method while considering burr height, drag line separation, depth of separation line, surface roughness and perpendicularity of the cut as assessment criteria. Based on conducted experimental investigation the MCDM model with 27 alternatives (laser cuts) and five criteria was developed. The relative importance of criteria was determined by using pair-wise comparison matrix and geometric mean method of the analytic hierarchy process (AHP) method.

257-263

Authors: S.A. Bello, S.B. Hassan, J.O. Agunsoye, M.G. Zebase Kana, I.A. Raheem

The possibility of using mechanical milling for the synthesis of uncarbonised coconut shell nanoparticles (UCSNPs) has been investigated. UCSNPs were synthesized from discarded coconut shells (CSs) using top down approach. The sundried CSs were crushed, ground and then sieved using hammer crusher, a two disc grinder and set of sieves with shine shaker respectively. The CS powders retained in the pan below 37 µm sized sieve were milled for 70 hours to obtain UCSNPS. Samples for analysis were taken at 16 and 70 hours. UCSNPs were analyzed using transmission electron microscope (TEM), scanning electron microscope (SEM) with attached EDS and Gwyddion software. Samples of UCSNPs obtained at 16 and 70hours show that the deep brown colour of the initial CS powder became fading as the milling hour increased. The size determination from TEM image revealed spherical particles with an average size of 18.23 nm for UCSNPs obtained at 70 hour milling. The EDS spectrographs revealed an increase in the carbon counts with increased milling hours. This is attributable to dryness of the CS powders by the heat generated during the milling process due to absorption of kinetic energy by the CS powders from the milling balls. SEM micrographs revealed UCSNPs in agglomerated networks. The SEM micrograph/Gyweddion particles size determination showed average particles of 170.5 ±3 and 104.9 ±4.1 nm for UCSNPs obtained at 16 and 70 hours respectively. Therefore, production of UCSNPs through mechanical milling using mixture of ceramic balls of different sizes has been established especially when the particles of the sourced/initial CS powders falls below 37 µm.