Automotive industries made a paradigm shift in selection of viscometrics of engine lubricant, from higher to lower viscosity grade, for improving fuel economy of vehicles. Engine fuel consumption is influenced by friction between the various engine components. Engine friction power (FP) of a direct injection diesel engine is calculated from the measured value of in-cylinder pressure signals at various operating conditions. For predicting FP, as a function of speed, load, and lubricant viscosity, a full factorial design of experiments (DOE) was formulated and an empirical correlation was developed. Response surface methodology (RSM) was used for analyzing the dominant parameters and their interactions, which influence engine friction power significantly. Predicted results of engine FP are in good agreement with measured values at all operating points. ANOVA and RSM analysis revealed that the significant parameters influencing engine FP are speed, load, viscosity, speed-load, and speed-viscosity. The effect of engine lubricant viscosity on friction power of a diesel engine was insignificant at low speed, whereas, at high speed, it played a vital role. The empirical relation developed for predicting FP is very useful in estimating engine friction power for various combinations of engine speeds, loads, and lubricant viscosity without running the engine.

Devendra Singh

Fengshou Gu

John D. Fieldhouse

Nishan Singh

S. K. Singal

Prediction and Analysis of Engine Friction Power of a Diesel Engine Influenced by Engine Speed, Load, and Lubricant Viscosity

Various amounts of short fibers (glass and carbon) and particulate fillers like polytetrafluoroethylene (PTFE), silicon carbide (SiC), and alumina (Al2O3) were systematically introduced into the thermoplastic copolyester elastomer (TCE) matrix for reinforcement purpose. The mechanical properties such as storage modulus, loss modulus, and Tan &#x3b4; by dynamic mechanical analysis (DMA) and three-body abrasive wear performance on a dry sand rubber wheel abrasion tester have been investigated. For abrasive wear study, the experiments were planned according to <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.427751pt" id="M1" height="12.4257pt" version="1.1" viewBox="-0.0498162 -8.99795 18.5456 12.4257" width="18.5456pt"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path id="g113-77" d="M541 160L512 170C485 116 462 88 439 67C411 41 376 35 318 35C272 35 238 37 224 48C207 61 205 85 212 121L290 533C305 611 308 615 391 622L397 650H139L133 622C217 615 221 612 206 533L126 118C111 41 103 34 23 26L17 0H474C489 31 528 124 541 160Z"/></g><g transform="matrix(.0095,0,0,-0.0095,8.644,3.264)"><path id="g50-51" d="M414 144C384 79 371 75 317 75H135L276 221C367 316 408 376 408 465C408 570 327 635 237 635C179 635 131 609 100 575L42 494L67 471C94 510 138 565 205 565C277 565 321 517 321 435C321 348 258 270 195 195C146 137 88 81 33 26V0H411C423 44 433 88 446 135L414 144Z"/></g><g transform="matrix(.0095,0,0,-0.0095,13.262,3.264)"><path id="g50-56" d="M453 623H65C60 580 56 530 46 472H80C103 538 110 548 175 548H389C310 380 195 168 90 0L98 -12L175 -2C273 206 366 408 462 610L453 623Z"/></g></svg> orthogonal array by considering three factors and three levels. The complex moduli for TCE hybrid composites were pushed to a higher level relative to the TCE filled PTFE composite. At lower temperatures (in the glassy region), the storage modulus increases with increase in wt.&#x25; of reinforcement (fiber + fillers) and the value is maximum for the composite with 40&#x2009;wt.&#x25; reinforcement. The loss modulus and damping peaks were also found to be higher by the incorporation of SiC and Al2O3 microfillers. The routine abrasive wear test results indicated that TCE filled PTFE composite exhibited better abrasion resistance. Improvements in the abrasion resistance, however, have not been achieved by short-fiber and particlaute filler reinforcements. From the Taguchi&#x2019;s experimental findings, optimal combination of control factors were obtained for minimum wear volume and also predictive correlations were proposed. Further, the worn surface morphology of the samples was discussed.

Hemanth Rajashekaraiah

Sekar Mohan

Pramoda Kumari Pallathadka

Suresha Bhimappa

Dynamic Mechanical Analysis and Three-Body Abrasive Wear Behaviour of Thermoplastic Copolyester Elastomer Composites

Nanofluids are nanosize-powder suspensions that are of interest for their enhanced thermal transport properties. They are studied as promising alternatives to ordinary cooling fluids, but the tribiological effects of nanofluids on cooling-system materials are largely unknown. The authors have developed methodology that uses jet impingement on typical cooling-system materials to test such effects. The work is presented of the authors&#x2019; research on the interactions of a typical nanofluid (2&#x25; volume of alumina nanopowders in a solution of ethylene glycol in water) which is impinged on aluminum and copper specimens for tests as long as 112 hours. The surface changes were assessed by roughness measurements and optical-microscope studies. Comparative roughness indicate that both the reference cooling fluid of ethylene glycol and water and its nanofluid with 2&#x25; alumina produce roughness changes in aluminum (even for the shortest 3-hour test), but no significant roughness differences were observed between them. No significant roughness changes were observed for copper. Microscopy observations, however, show different surface modifications in both aluminum and copper by both the nanofluid and its base fluid. The possible mechanisms of early erosion are discussed. These investigations demonstrate suitable methods for the testing of nanofluid effects on cooling system-materials.

Gustavo J. Molina

Fnu Aktaruzzaman

Whitney Stregles

Valentin Soloiu

Mosfequr Rahman

Jet-Impingement Effects of Alumina-Nanofluid on Aluminum and Copper

The aim of the study is to evaluate the friction and wear behavior of high-strength alloys Ti-6Al-7Nb used in femoral stem and compare it with a Ti-6Al-4V alloy cylindrical bar corresponding to ISO 5832-3 part 3/01-07-199 standard. The tribological behavior was investigated by wear tests, using ball-on-disc and pin-on-disc tribometers. These tests consisted of measuring the weight loss and the friction coefficient of samples. The oscillating friction and wear tests have been carried out in ambient with oscillating tribotester in accordance with standards ISO 7148, ASTM G99-95a, and ASTM G133-95 under different conditions of normal loads (3, 6, and 10&#x2009;N) and sliding speeds (1, 15, and 25&#x2009;mm&#x000B7;s&#x2212;1). As counter pairs, a 100Cr6 steel ball with 10 mm in diameter was used. Results show that the two alloys had similar friction and wear performance, although their grain structures and compositions are different. Occurrence of large frictional occurred, is probably caused by formation and periodic, localized fracture of a transfer layer. Higher friction with larger fluctuation and higher wear rate was observed at the higher siding speed. The Ti-6Al-4V wear mechanism transforms from ploughing and peeling off wear at low sliding speed to plastic deformation and adhesive wear.

Mamoun Fellah

Mohamed Laba&#xef;z

Omar Assala

Leila Dekhil

Ahlem Taleb

Hadda Rezag

Alain Iost

Tribological behavior of Ti-6Al-4V and Ti-6Al-7Nb Alloys for Total Hip Prosthesis

Combined effects of surface roughness and viscosity-pressure dependency on the couple stress squeeze film characteristics of parallel circular plates are presented. On the basis of Christensen&#x2019;s stochastic theory, two types of one-dimensional roughness structures, namely, the radial roughness and azimuthal roughness patterns, are considered and the stochastic modified Reynolds equation for these two types of roughness patterns is derived for Stokes couple stress fluid by taking into account variation of viscosity with pressure. The standard perturbation technique is employed to solve the averaged Reynolds equation and closed form expressions for the mean fluid film pressure, load carrying capacity, and squeeze film time are obtained. It is found that the effects of couple stresses and viscosity-pressure dependency are to increase the load carrying capacity, and squeeze film time for both types of roughness patterns. The effect of azimuthal (radial) roughness pattern is to increase (decrease) these squeeze film characteristics as compared to the corresponding smooth case.

Neminath Bhujappa Naduvinamani

Siddangouda Apparao

Ayyappa G. Hiremath

Effect of Surface Roughness and Viscosity-Pressure Dependency on the Couple Stress Squeeze Film Characteristics of Parallel Circular Plates

Solid particle erosion (SPE) tests are carried out to evaluate the performance of plasma sprayed coatings of borosilicate glass microspheres (BGM) premixed with Al2O3 particles on metallic substrates. For this purpose, an Air Jet Erosion test rig confirming to ASTM G 76 test standards is used. Relative influence of different operating parameters on erosion rate is assessed by statistical analysis of the experimental findings that are based on Taguchi&#x2019;s L16 orthogonal array. This analysis helps to identify the most significant factor affecting the erosion wear rate of the coating. The study reveals that the impact velocity, impingement angle, erodent size, and Al2O3 content in the feed stock, in the declining sequence, are the significant factors influencing the wear rate of these coatings. An Artificial Neural Network (ANN) approach is then implemented taking into account training and test procedure to predict the triboperformance of these coatings under wear conditions beyond the experimental range. Further, the microstructural features of the eroded samples are studied from SEM images to identify possible wear mechanisms.

Gaurav Gupta

Alok Satapathy

Studies on Erosion Behavior of Plasma Sprayed Coatings of Glass Microspheres Premixed with Al2O3 Particles

Aluminium-graphite composites were synthesized using powder metallurgy route. Graphite was added as reinforcement in the range of  0, 3, and 6 weight &#x25; and composites were prepared by P/M. Microstructural analysis of the newly synthesized composites was carried out using SEM. The hardness of the composites was studied using Vickers microhardness tester, by applying a load of 1&#x2009;kg for 5&#x2009;sec. Also the amount of porosity was determined. Further the wear test was conducted on the sintered specimens using pin-on-disc wear apparatus according to ASTM-G99 standards. A regression model was developed to predict the wear rate of the specimen. Then the worn images were studied using SEM based on response surface methodology in order to understand the various wear mechanisms involved. The study revealed that mild wear, oxidational wear, plowing, cutting, and plastic deformation are the main mechanisms responsible for causing the wear.

Amrishraj Doraisamy

Senthilvelan Thiagarajan

Characterization and Empirical Modelling of Sliding Wear on Sintered Aluminium-Graphite Composites

The paper investigates the exceptional antiwear and extreme pressure properties of multiwalled carbon nanotube based mineral oil. Different samples of oil containing varying proportions of MWNT (MWNT) and graphite were prepared. The samples were tested for their antiwear and load bearing capacity according to ASTM G99 and ASTM D-2783 standards. After pass load test in four ball tester the rubbed surfaces were investigated with Scanning Electron Microscope (SEM) images. The wear test results show a decrease wear by 70&#x2013;75&#x25; in case of multiwalled nanotube based mineral oil as compared with pure mineral oil. Furthermore, it has been observed that the load bearing capacity in case of multiwalled carbon nanotube based mineral oil increases by 20&#x25; as compared to pure mineral oil. A comparison in the antiwear and load bearing capacity properties of graphite and nanotube based mineral oil was studied which showed the inefficiency of graphite based lubricant over MWNT based oil. Thus, the finding would be helpful in developing new nanoparticle based lubricants.

Shubrajit Bhaumik

S. Prabhu

Kingsly Jeba Singh

Analysis of Tribological Behavior of Carbon Nanotube Based Industrial Mineral Gear Oil 250 cSt Viscosity

Solid particle erosion behavior of short date palm leaf (DPL) fiber reinforced polyvinyl alcohol (PVA) composite has been studied using silica sand particles (200 &#xb1; 50&#x2009;&#x3bc;m) as an erodent at different impingement angles (15&#x2013;90&#xB0;) and impact velocities (48&#x2013;109&#x2009;m/s). The influence of fiber content (wt&#x25; of DPL fiber) on erosion rate of PVA/DPL composite has also been investigated. The neat PVA shows maximum erosion rate at 30&#xB0; impingement angle whereas PVA/DPL composites exhibit maximum erosion rate at 45&#xB0; impingement angle irrespective of fiber loading showing semiductile behavior. The erosion efficiency of PVA and its composites varies from 0.735 to 16.289&#x25; for different impact velocities studied. The eroded surfaces were observed under scanning electron microscope (SEM) to understand the erosion mechanism.

Jyoti R. Mohanty

Sankar N. Das

Harish C. Das

Tapan K. Mahanta

Sataya B. Ghadei

Solid Particle Erosion of Date Palm Leaf Fiber Reinforced Polyvinyl Alcohol Composites

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Advances in Tribology publishes papers on the science of friction, wear, and lubrication. Topics covered include investigations into contact mechanics, wear and damage processes, surface and coating engineering, and lubrication technology.

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Advances in Tribology - Table of contents 2014

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Advances in Tribology publishes papers on the science of friction, wear, and lubrication. Topics covered include investigations into contact mechanics, wear and damage processes, surface and coating engineering, and lubrication technology.

Advances in Tribology