Tribology in Industry

400-412

Authors: F. Beyer, F. Hauer, K. Willner

Friction has a considerable impact in metal forming. This is in particular true for sheet-bulk metal-forming (SBMF) in which local highly varying contact loads occur. A constitutive friction law suited to the needs of SBMF is necessary, if numerical investigations in SBMF are performed. The identification of the friction due to adhesion and ploughing is carried out with an elasto-plastic half-space model. The normal contact is verified for a broad range of normal loads. In addition, the model is used for the characterization of the occurring shear stress. Ploughing is determined by the work which is necessary to plastically deform the surface asperities of the new area that gets into contact during sliding. Furthermore, the surface patches of common half-space models are aligned orthogonally to the direction in which the surfaces approach when normal contact occurs. For a better reflection of the original surfaces, the element patches become inclined. This leads to a geometric share of lateral forces which also contribute to friction. Based on these effects, a friction law is derived which is able to predict the contact conditions especially for SBMF.

421-426

Authors: A. Todi-Eftimie, S. Bobancu, C. GavrilaL. Eftimie

The aim of this research is to analyze the behavior of the transition between static and dynamic friction coefficient in a cylindrical joint, in order to reach high reliability when loads are acting. The friction between cylindrical contact faces is analyzed both in dry and lubricated conditions up to the moment that the assembly starts moving while tilting the entire assembly. It means that it is analyzed a complex static friction developed along a chain and its sprocket.

434-439

Authors: V. Kočović, S. Mitrović, G. Mihajlović, M. Mijatović, B. Bogdanović, Đ. Vukelić, B. Tadić

Friction stir processing has extensive application in many technological operations. Application area of friction stir processing can be extended to the processing of non-metallic materials, such as wood. The paper examines the friction stir processing contact between a specially designed hard and temperature-resistant rotating tool and workpiece which is made of wood. Interval of speed slip and temperature level under which the combustion occurs and carbonization layer of soft material was determined. The results of the research can be applied in technological process of wood engraving operations which may have significant technological and aesthetic effects.

449-454

Authors: S. Baskar, G. Sriram, S. Arumugam

The present work describes the tribological behavior of CuO, WS2 and TiO2 nano particles as an antiwear additive to a chemically modified rapeseed oil (CMRO). The tribological tests were run on a four ball tribometer. The variation of viscosity of various nano based biolubricants with respect to temperature is also estimated in accordance with ASTM D 445. The test results were compared with petroleum based synthetic lubricant (SAE20W40). The test results exhibited that CMRO with nano CuO has better tribological characteristics, smoother wear scar and higher viscosity compared to synthetic lubricant and other nano based biolubricants.

464-472

Authors: E. Hristovska

The experimental measuring of working loads upon the parts of rotating excavator is a complicated procedure given the complexity of the construction of the excavator and the specificity of exploitation conditions. Therefore, there are no uniform solutions and methods for this purpose, and any proposed solution is of great benefit to excavator users, as well to science studying this issue. This paper presents a preset methodology for measuring working loads of the clamp dogs on the carrying structure of the working wheel at the excavator used in surface coal mining. This methodology uses the default settings implicit to the strain gage method, which records the stresses resulting from external loads occurring within the clamp dogs’ material using strain gages and measuring equipment. Within this concept, the paper shows the manner of determining the measuring points and setting up the strain gages on both clamp dogs, the connecting with the measuring installation and the equipment. Employing diagrams, the paper presents the measurement results of static and dynamic loads, as well as induced stress state by them.

482-490

Authors: M.C. Bignozzi, A. Saccani, C. Fragassa

This paper investigates the surface alteration of gasket samples commercialized by two alternative producers. These gaskets, in polymeric materials, are installed in process plants used for cleaning tires molds by a pioneering ultrasonic process. They are exposed to a combination of ultrasonic waves, temperature, humidity and acid attack causing several erosion phenomena. Their surface degradation under ordinary operative conditions was investigated using mechanical and tribological tests. The experimental characterization was performed by optical microscopy, scanning electron microscopy, thermograms, differential scanning calorimetry curves and infrared spectra aiming at defining the specific mechanics of wearing. As a conclusion, it was possible to state that even if samples exhibit similar chemical structures, their thermal and mechanical properties as well as their geometric dimensions are different. Such differences in the materials might cause various unexpected wear behaviors when gaskets are employed in the same working conditions.


500-524

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

High fuel consumption by automobile and aerospace vehicles built from legacy alloys has been a great challenge to global design and material engineers. This has called for researches into material development for the production of lighter materials of the same or even superior mechanical properties to the existing materials in this area of applications. This forms a part of efforts to achieve the global vision 2025 i.e to reduce the fuel consumption by automobile and aerospace vehicles by at least 75 %. Many researchers have identified advanced composites as suitable materials in this regard. Among the common matrices used for the development of advanced composites, epoxy resin has attained a dominance among its counterparts because of its excellent properties including chemical, thermal and electrical resistance properties, mechanical properties and dimensional stability. This review is a reflection of the extensive study on the currently ongoing research aimed at development of epoxy resin hybrid nanocomposites for engineering applications. In this paper, brief explanation has been given to different terms related to the research work and also, some previous works (in accordance with materials within authors’ reach) in the area of the ongoing research have been reported.

284-290

Authors: N.K. Myshkin, S.S. Pesetskii

Polymer tribology is based on the analysis of abrasion, adhesion, and fatigue of polymer materials in a friction contact. The structural features of polymers provide a variety of tribological applications of basic polymers mostly as matrices and fillers of composite materials. Recently polymer nanocomposites are used for making components of various tribosystems. A short review of polymer materials for tribosystems is presented. The main results of studies in friction and wear of polymers are given. Formation of the real area of contact is evaluated when taking account of polymer viscoelasticity and the effects of temperature and load in the contact. Adhesion of polymers and its part in friction transfer is considered. Various aspects of friction and wear tests of polymer materials for estimation of their characteristics, prediction of service life in different operational conditions are discussed. Practical examples of applications of polymer composites and nanocomposites in various branches of industry are given.

299-308

Authors: G. Pantazopoulos, P. Psyllaki

The present study is focused on elucidating the wear mechanisms taking place during sliding friction of five (5) steel grades subjected to Trufftriding. For this purpose, three sliding friction experimental configurations were used and the friction coefficients, real-time-recorded during testing, were correlated to the post-testing microscopic observations of the worn surfaces. Finally, the experimental findings were evaluated with respect to the initial microstructure of the tool steels in their as-received and/or heat-treated state. In the case of non-conformal point contact against ceramic counterbodies, the friction coefficient was found to depend only on the steel grade and the particular counterbody, tending to a constant value, regardless of the applied load and/or its heat- or surface treatment. In the case of conformal plane contact against hardened steel, each steel grade exhibited an applied pressure range within which the wear coefficient remains practically constant, whereas for higher pressure values, seizure occurred. Nitrocarburising “displaced” the constant wear coefficient range towards higher pressure values, resulting in seizure retardation.

320-329

Authors: A. Vencl, B. Katavić, D. Marković, M. Ristić, B. Gligorijević

During the coal pulverizing, the working parts of the ventilation mill are being worn by the sand particles. For this reason, the working parts are usually protected with materials resistant to wear (hardfaced/thermal sprayed coatings). The aim of this study was to evaluate the tribological performance of four different types of coatings as candidates for wear protection of the mill’s working parts. The coatings were produced by using the filler materials with the following nominal chemical composition: NiFeBSi-WC, NiCrBSiC, FeCrCTiSi, and FeCrNiCSiBMn, and by using the plasma arc welding and flame and electric arc spraying processes. The results showed that Ni-based coatings exhibited higher wear resistance than Fe-based coatings. The highest wear resistance showed coating produced by using the NiFeBSi-WC filler material and plasma transferred arc welding deposition process. The hardness was not the only characteristic that affected the wear resistance. In this context, the wear rate of NiFeBSi-WC coating was not in correlation with its hardness, in contrast to other coatings. The different wear performance of NiFeBSi-WC coating was attributed to the different type and morphological features of the reinforcing particles (WC).

336-339

Authors: M.F. VasilacheI. Muscă

The existence of a continuous film of lubricant increases the electrical resistance of the contact that can provide information on the quality of contact’s lubrication. This paper presents some experimental results obtained in the control of the lubricant film presence through the resistive method, in lubricated sliding contact between a spherical roller and a cylindrical disc, with the interpretation which gives indications about the time of scuffing.

346-353

Authors: D. Bulut, V. TemizZ. Parlar

The effects of radial force (interface) produced by interference on the static contact properties and frictional characteristics of a radial lip seal are investigated by experimentally. For this reason, a test system has been developed. In this test system, a cylinder is placed on four load cells in order to monitor the friction torque generated between seal and counter face. A group of experiments are carried out with thermoplastic polyurethane radial lip seals. Three different inner diameters (40, 39.80 and 39.60 mm) are selected and the seals are tested under 0.5 and 0.3 bar for a short period. The frictional torque was measured and compared for different inner diameters. As a result, it is observed that the amount of interference effects seal friction torques based on seal material and seal design in different ratios.

360-36

Authors: I.G. Levanov, E.A. Zadorozhnaya, A.L. Dudnikov

The purpose of the article is to develop a tool to assess the theoretical resource crankshaft bearings of internal combustion engine. As a result, two methods for evaluating of the theoretical resource crankshaft bearings have been developed on the basis of the calculation of hydro-mechanical characteristics of bearings: the minimum film thickness and the extent of the zone of boundary friction. Under the theoretical resource of crankshaft bearing it is understood that during his work an increase of the radial clearance in the area of potential exposure (boundary friction) is over the limit. The first technique is based on the bearing life dependence on the ratio between the minimum film thickness and its maximum allowable value. The second technique is based on the molecular-mechanical theory of friction and wear fatigue theory. Thus, these techniques may be used to estimate the resource of the crankshaft journal bearings at the design and finishing stage. However, some parameters of mathematical models have to be determined from the experimental test. The use of molecular-mechanical theory of friction and wear fatigue theory takes into account the influence of the physical and mechanical properties of a bearing material on his life.

374-379

Authors: N.A. Stoica, A. Tudor

The tribological aspects concerning the behaviour of friction materials in the range of low and very low sliding speeds (0.2 – 200 mm/min) are essentially different of those in the high sliding speeds range. This paper aims to study the stick-slip phenomenon which occurs in the range of low and very low speeds. Typically, for the stick-slip phenomenon to occur, the static friction coefficient between the two contact surfaces of the friction materials must be larger than the kinetic friction coefficient. For disc brakes, the stick-slip phenomenon is mentioned in many specialized scientific papers. The phenomenon is manifested through self-induced vibrations. The experimental results were obtained on a dedicated testing machine where the parasite stick-slip motion is reduced through the use of bearings.

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.

13-19

Authors: S. Milojević, R. Pešić, D. Taranović

Reducing vehicle weight contributes to reducing fuel consumption and exhaust emissions. In practice, this is achieved by application of lightweight materials and through optimization of tribo-systems on the vehicle. The benefit of using aluminium is evident due to the reduced mass of the parts, but in parallel there is a problem due to the low strength of this metal. This is especially evident during overheating when can form cracks. The wear resistance and tribo-properties of aluminium are the problem, too. To achieve the strength and tribo-properties of aluminium alloys similar to grey cast iron, we applied eco-tribological knowledge during construction of reciprocating machines. The result of researches is patented prototype of aluminium piston and cylinder whose contact surfaces are coated or modified with inserts based on the tribo-materials.

29-33

Authors: I. Popa, L.S. Stanciu

Portable masts are parts of mobile servicing rigs designed to work at drilling or extraction wells and are made of three sections: fixed section, lower section and upper section. During transportation, the mast is placed in a horizontal position on a truck chassis, with the upper section nested inside the lower section. Before putting into service the mobile servicing rig, the lower and upper sections are erected as a unit, in a slightly inclined position. In this paper, the authors present the results of a research regarding the safety in functioning for such a mast which is under the action of the wind with high velocities. The wind’s action direction with respect to the mast is analyzed in two cases: front-back and lateral, with stress and strain values that occur.

42-54

Authors: P.C. Mishra, S. Bhattacharya, P. Pandey

Piston Compression ring is the constituent part of ring-liner sliding pair that is subjected to high load and speed condition. Due to lubrication regime transition, there is the greater chance of wear and tear in the ring as well as in the liner. In order to reduce the wear and to enhance the ring and liner life, ceramic coatings are provided on the surface of such contact pairs. Current paper uses a finite element method to analyze the coating strength of a compression ring at compression and power stroke transition, where peak combustion pressure is higher than other crank positions. The deformation, von Misses stress and strain in the core and coating interface are discussed elaborately.

60-65

Authors: K. Bouzid, N.E. Beliardouh, C. Nouveau

A comparative study was conducted to evaluate the performances against wear and corrosion of CrN, CrMoN, CrZrN, CrVN single layer thin films. The latest are synthesized onto steel substrates (DIN 90CrMoV8), using R.F reactive magnetron co-sputtering. The experimental work was achieved using ball-on-disc configuration in dry conditions against WC balls. The main conclusions are: (i) electrochemical tests in 0.3 wt.% NaCl solution indicated that CrZrN are improved anticorrosion performance when compared to CrN, while CrMoN demonstrated a poor corrosion resistance;(ii) the CrN coating presents the better tribological properties when compared to the ternary nitride coatings.

72-80

Authors: G. Pantazopoulos, A. Tsolakis, P. Psyllaki, A. Vazdirvanidis

The wear and degradation mechanisms of two principle vehicle tribosystems are presented to elucidate the main causes of their premature failure. The first case study concerns the malfunction of an automotive cast iron pressure plate operated in an automobile clutch system. The second is related to the unexpected failure of a stainless steel brake disk of a high performance motorcycle. Both components are designed to function under sliding friction conditions that lead to the severe wear of consumable non-metallic parts of the tribosystems: the clutch disk and the brake pad, respectively. However, in both cases it was the unexpected failure of the conjugate metallic parts that resulted in terminal system damage. The experimental approach to identify the root cause of failure involved both microstructure characterization, as well as observations of the metallic contact surfaces by means of optical and scanning electron microscopy, in conjunction with microhardness and surface topography measurements. For the case of the stainless steel brake disk in particular, Finite Element Analysis was employed to simulate the operating tribosystem, identify the site(s) prone for crack initiation and validate the failure mechanisms hypotheses.

88-96

Authors: M.A.C. Besnea, D.C. Trufasu, G. Andrei, M. Bastiurea, M.S. Rodeanu

Wear behavior of polyphenylene sulphide composites was investigated according to load and test speed. Two types of materials were studied: first, with 40 wt% glass fiber, and second, with 10 wt% carbon fiber, 10 wt% graphite and 10 wt%. Tribological tests were performed on the universal tribometer UMT-2, using a pin-on-disc device. The friction coefficient and wear rate for the composites were analyzed. As a result of experimental tests, it was established that polymer composite with polyphenylene sulphide matrix, carbon fibers, graphite and polytetrafluorethylene exhibit good wear behavior under operating conditions.

107-116

Authors: J.O. Agunsoye, S.A. Bello, I.S. Talabi, A.A. Yekinni, I.A. Raheem, A.D. Oderinde, T.E. Idegbekwu

Aluminium based metal matrix composites have been produced from recycled aluminium cans and 150µm sized eggshell particles using a stir cast process. The mechanical properties of the control and aluminium can/eggshell composites produced have been investigated. The microstructures of the aluminium can/eggshell composites were examined with the aids of Scanning Electron Microscope (SEM) after the sample surfaces have been carefully prepared and etched with aqueous solution of 0.5 cm3 nitric acid. Micrographs revealed that there was a homogenous distribution of eggshell particles within the aluminium can matrix. An indication of effective stirring action during the melting process. The wear resistance was also investigated under different applied loads (6 to 14 N) on an abrasive surface emery paper of grade 220. The results revealed an increase in Young’s modulus of elasticity and yield stress from 1,206.45 and 50.23 Mpa respectively of the cast aluminium can with 0 % eggshell particle to the maximum of 3,258.87and 73.2 MPa of aluminium can/12 % eggshell composites. The hardness values increased from 66.23 to 75.13 VN. There was a gradual increase in wear rate of the tested samples as the applied load increased. However, the wear resistance of the aluminium can/6 % eggshell and aluminium can/12 % eggshell composites increased significantly. Hence, recycling of aluminium cans and eggshells can be harnessed into development of useful engineering metal matrix composite materials.

348-353

Authors: C. Nicolicescu, M. Miclău, V.H. Nicoară

The paper presents experimental research regarding the wear behavior of some composite materials based on Cu/Cr and Cu/Cr/W prepared by Powder Metallurgy (PM) route. Because of low solubility between Cu and Cr is very difficult to elaborate these types of materials by classical technologies and because of that, in this research was used Mechanical Alloying (MA) technique to prepare Cu/Cr materials. In order to obtain good refractory was introduced 5% of W in the mass of materials. There were made studies regarding the wear behavior of these materials function the Cr content.

361-374

Authors: D. Kekes, P. Psyllaki, M. Vardavoulias

The influence of the cermet fraction in cermet/ metal composite coatings developed by High-Velocity Oxyfuel Flame (HVOF) spraying on their tribological behaviour was studied. Five series of coatings, each one containing different proportion of cermet-metal components, prepared by premixing commercially available feedstocks of NiCrFeBSiC metallic and WC-Co/Cr cermet powders were deposited on AISI 304 stainless steel substrate. The microstructure of as-sprayed coatings was characterized by partial decomposition of the WC particles, lamellar morphology and micro-porosity among the solidified splats. Tribological behavior was studied under sliding friction conditions using a Si3N4 ball as counterbody and the friction coefficient and volume loss were determined as a function of the cermet fraction. Microscopic examinations of the wear tracks and relevant cross sections identified the wear mechanisms involved. Coatings containing only the metallic phase were worn out through a combination of ploughing, micro-cracking and splat exfoliation, whilst those containing only the cermet phase primarily by micro-cracking at the individual splat scale. The wear mechanisms of the composite coatings were strongly affected by their randomly stratified structure. In-depth cracks almost perpendicular to the coating/ substrate interface occurring at the wear track boundaries resulted in cermet trans-splat fracture.

384-393

Authors: S.V. Fedorov

The concepts developed by the thermodynamic theory of solid body strength and fracture are used to examine the conditions of lubricant film failure. We obtain a quantitative criterion that defines the lubricant film "defectness" - the critical value (constant for a given mineral oil) of the internal (thermal) energy density in the volume of the lubricant film. We propose analytic relations for evaluating scuffing in friction with lubrication and verify them experimentally on a full-scale stand for testing actual sliding bearings. We show the constancy of the critical value of the internal (thermal) energy density in the volume of the oil film at the moment of scuffing for an inactive mineral oil.

406-418

Authors: A. Belhocine, N.M. Ghazali, O.I. Abdullah

The motivation of this work is to identify thermal effects on the structural and contact behaviour of a disc-pad assembly using a finite element approach. The first analysis is performed on the disc-pad model without the presence of thermal properties. Structural performance of the disc-pad model such as deformation and Von Mises stress is predicted. Next, thermomechanical analysis is performed on the same disc-pad model with the inclusion of convection, adiabatic and heat flux elements. The prediction results of temperature distribution, deformation, stress and contact pressure are presented. Comparison of the structural performance between the two analyses (mechanical and thermomechanical) is also made. From this study, it can assist brake engineers to choose a suitable analysis in order to critically evaluate structural and contact behaviour of the disc brake assembly.

428-436

Authors: N. Radhika, P. Shivaram, K.T. Vijay Karthik

This paper involves the optimization of input process parameters in Electric Discharge Machining of Aluminium hybrid Metal Matrix Composite. Aluminium AlSi10Mg alloy reinforced with 9 %wt. alumina and 3 %wt. graphite particles fabricated through liquid metallurgy route was used for machining. Experiments were conducted in an Electric Discharge Machine and the influence of input process parameters such as Peak current, Pulse-on time and Flushing pressure during machining of aluminium composite was studied. The objective was to obtain a minimum surface roughness with minimum tool wear rate and maximum material removal rate. Multi-objective optimization of the input process parameters was performed by employing Artificial Neural Network and Genetic Algorithm hybrid optimization technique. The results obtained provide a pareto-optimal solution set that offers a set of non-dominated solutions that can be used in a practical situation by a decision maker.

451-464

Authors: O. Maršálek, P. Novotný, P. Raffai

A description of the set of software tools for detailed computational modelling of thin lubrication layers behaviour is presented in this paper. Individual chapters outline reasons for realization of its each part, explain the functionality of each software tool and the given mathematical definition or digital implementation of all important equations or formulae. The following are examples of partial results of the analysis carried out and the resulting flow factors databases for some kinds of rough surfaces, together with an example of the analysis result of the connecting rod sliding bearing of supercharged internal combustion engine.

475-487

Authors: C. Bhagat, L. Roy

Steady state thermo-hydrodynamic analysis of two axial groove and multi lobe oil journal bearings is performed in this paper. To study the steady state thermo-hydrodynamic characteristics Reynolds equation is solved simultaneously along with the energy equation and heat conduction equation in bush and shaft. The effect of groove geometry, cavitation in the fluid film, the recirculation of lubricant, shaft speed has also been taken into account. Film temperature in case of three-lobe bearing is found to be high as compared to other studied bearing configurations. The data obtained from this analysis can be used conveniently in the design of such bearings, which are presented in dimensionless form.