ISRN Tribology The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Effect of Surface Forces on Ultrathin Film Lubrication Tue, 27 May 2014 00:00:00 +0000 Lubricated contact with nanoscale oil film is modeled for friction. Effect of the van der Waals pressure and the solvation pressure forces on such ultrathin lubricating oil film is considered while finding the friction and other parameters. Hydrodynamic action is represented using transient thermoelastohydrodynamics. Net pressure due to hydrodynamic, solvation, and van der Waals’ action is integrated over the contact area to find contact load. Conjunctional friction due to thermal activation of such ultrathin film is derived using the Eyring model. Effect of molecular dimension on friction is studied. Prakash Chandra Mishra Copyright © 2014 Prakash Chandra Mishra. All rights reserved. Effect of Surface Roughness on the Squeeze Film Lubrication of Finite Poroelastic Partial Journal Bearings with Couple Stress Fluids: A Special Reference to Hip Joint Lubrication Tue, 15 Apr 2014 11:41:15 +0000 A simplified mathematical model has been developed for understanding the combined effects of surface roughness and couple stresses on the squeeze film behavior of poroelastic bearings in general and that of hip joints in particular. The cartilage is modeled as biphasic poroelastic matrix and synovial fluid is modeled as couple stress fluid. The modified form of averaged Reynolds equation which incorporates the randomized roughness structure as well as elastic nature of articular cartilage with couple stress fluid as lubricant is derived. For the study of rough surfaces, Christensen's stochastic theory is used to study the effect of two types of one-dimensional random roughness, namely, longitudinal roughness pattern and the transverse roughness pattern. The averaged film pressure distribution equations are solved numerically by using the conjugate gradient method. It is observed that the surface roughness effect is dominant and pattern dependent and the influence of couple stresses is to improve the joint performance. N. B. Naduvinamani and G. K. Savitramma Copyright © 2014 N. B. Naduvinamani and G. K. Savitramma. All rights reserved. Effect of Fiber Content on Abrasive Wear Behavior of Date Palm Leaf Reinforced Polyvinyl Pyrrolidone Composite Wed, 22 Jan 2014 09:03:57 +0000 The effect of fiber contents on wear behavior of date palm leaf reinforced polyvinyl pyrrolidone (PVP/DPL) composites has been experimentally investigated. The test samples with fillers in 10, 20, 30, and 40% based on weight of fibers were prepared using injection molding. The optimum fiber content (i.e., 26 wt%) for maximum mechanical strength of the composites was determined by regression analysis. The dry sliding wear tests were conducted for each composition at different sliding velocities (0.392, 0.471, and 0.549 m/s) and sliding distances (188, 254, and 376 m) by applying normal loads of 5, 10, 15, and 20 N using pin-on-disc wear testing machine. The specific wear rate, wear loss, and coefficient of friction were plotted against the normal load and sliding distance at all sliding velocities. The results reveal that incorporation of date palm leaf fibers leads to significant improvement in the wear resistance of composites up to optimum fiber content and then decreases as fiber content increases. Further, it is found that surface modification has significant effect on wear performance. Worn surfaces of some selected samples were studied by scanning electron microscopy to analyze the wear mechanism. Jyoti R. Mohanty, Sankar N. Das, and Harish C. Das Copyright © 2014 Jyoti R. Mohanty et al. All rights reserved. Effect of an Improved Yasutomi Pressure-Viscosity Relationship on the Elastohydrodynamic Line Contact Problem Mon, 09 Sep 2013 09:23:50 +0000 This paper presents the application of an improved Yasutomi correlation for lubricant viscosity at high pressure in a Newtonian elastohydrodynamic line contact simulation. According to recent experimental studies using high pressure viscometers, the Yasutomi pressure-viscosity relationship derived from the free-volume model closely represents the real lubricant piezoviscous behavior for the high pressure typically encountered in elastohydrodynamic applications. However, the original Yasutomi correlation suffers from the appearance of a zero in the function describing the pressure dependence of the relative free volume thermal expansivity. In order to overcome this drawback, a new formulation of the Yasutomi relation was recently developed by Bair et al. This new function removes these concerns and provides improved precision without the need for an equation of state. Numerical simulations have been performed using the improved Yasutomi model to predict the lubricant pressure-viscosity, the pressure distribution, and the film thickness behavior in a Newtonian EHL simulation of a squalane-lubricated line contact. This work also shows that this model yields a higher viscosity at the low-pressure area, which results in a larger central film thickness compared with the previous piezoviscous relations. Vincenzo Petrone, Adolfo Senatore, and Vincenzo D'Agostino Copyright © 2013 Vincenzo Petrone et al. All rights reserved. Mathematical Model and Experimental Evaluation of Drag Torque in Disengaged Wet Clutches Tue, 27 Aug 2013 08:58:15 +0000 When the clutch is in disengaged condition, ideally no torque should be transmitted. However, in reality, the relative motion between the disks causes viscous shearing of fluids in the gap. This results in a drag torque which is considered as a loss. The objective of the present study is to formulate a drag torque model as well as to experimentally evaluate the effect of several parameters on the drag torque. A model based on continuity and Navier-Stokes equations, considering laminar flow, is deduced. The drag torque estimated by the model is the sum of drag torque due to shearing of the automatic transmission fluid (ATF) and mist (suspension of ATF in air) film. In order to validate the model and characterize the drag torque, experiments are performed using an SAE no. 2 test setup under real conditions of variable ATF flow rate and disks' rotational states for higher clutch speed range. The drag torque predicted by the model is in good agreement with the experimental results obtained by varying the flow properties and disks' rotational states. By analyzing the experimental results, a factor by which, the variation in parameters such as ATF flow rate, ATF temperature, disk size, and disk rotational state influencing the drag torque is determined. Shoaib Iqbal, Farid Al-Bender, Bert Pluymers, and Wim Desmet Copyright © 2013 Shoaib Iqbal et al. All rights reserved. Effect of Surface Roughness and Couple Stresses on Squeeze Films between Curved Annular Plates Wed, 07 Aug 2013 09:48:09 +0000 The combined effects of couple stresses and surface roughness patterns on the squeeze film characteristics of curved annular plates are studied. The Stokes (1966) couple stress fluid model is included to account for the couple stresses arising due to the presence of microstructure additives in the lubricant. In the context of Christensen's (1969) stochastic theory for the lubrication of rough surfaces, two types of one-dimensional roughness patterns (circumferential and radial) are considered. The governing modified stochastic Reynolds type equations are derived for these roughness patterns. Expressions for the mean squeeze film characteristics are obtained. Numerical computations of the results show that the circumferential roughness pattern on the curved annular plate results in more pressure buildup whereas performance of the squeeze film suffers due to the radial roughness pattern for both concave and convex pads. Further the squeeze film time is longer (shorter) for the circumferential (radial) roughness patterns. Improved squeeze film characteristics are predicted for the couple stress lubricant. Dhanapal P. Basti Copyright © 2013 Dhanapal P. Basti. All rights reserved. A Comparative Elastohydrostatic Analysis of CFV- and Capillary-Compensated Multirecess Hydrostatic/Hybrid Journal Bearing Operating with Micropolar Lubricant Sun, 07 Apr 2013 14:39:43 +0000 A comparative study on the performance characteristics of the flexible multirecess hydrostatic journal bearing system with constant flow valve and capillary restrictors has been presented considering the effect of micropolar parameters. The modified Reynolds equation for the flow of micropolar lubricant through the bearing has been solved using finite element method, and the resulting elastic deformation in the bearing shell has been determined iteratively. The results indicate that the micropolar parameters of the lubricant affect the performance of the flexible multirecess hydrostatic journal bearing system quite significantly. Suresh Verma, Vijay Kumar, and K. D. Gupta Copyright © 2013 Suresh Verma et al. All rights reserved. Modeling and Analysis for Wear Performance in Dry Sliding of Epoxy/Glass/PTW Composites Using Full Factorial Techniques Thu, 14 Mar 2013 15:53:18 +0000 The dry sliding friction and wear behavior of epoxy hybrid composites reinforced with glass fibers and a varying amount of potassium titanate whiskers (PTWs) fabricated by vacuum hand layup method were studied. The influence of normal load, sliding velocity, and whisker content on both friction coefficient and specific wear rate was investigated on a pin-on-disc machine. The tests were conducted at ambient conditions based on the 3 × 3 (3 factors at 3 levels) full factorial design. Analysis of variance (ANOVA) was performed to obtain the contribution of control parameters on friction coefficient and wear rate. The density and hardness of the composites were found to be enhanced with the PTW loading. The friction coefficient and wear resistance of the hybrid composites were found to be improved with the whisker content and were also greatly influenced by normal load and sliding velocity. A correlation between dry sliding wear behaviors of composites with wear parameters was obtained by multiple regressions. The worn out surface of selected samples was observed under scanning electron microscope (SEM) to identify wear mechanisms. This study revealed that the addition of the ceramic microfillers such as PTW improves the wear performance of the epoxy/glass polymer composites significantly. M. Sudheer, Ravikantha Prabhu, K. Raju, and Thirumaleshwara Bhat Copyright © 2013 M. Sudheer et al. All rights reserved. Assessment of Thermomechanical Couplings in Tribological Surface Transformations: Application to the Irreversible Near-Surface Solid-Solid Phase Transformations Thu, 07 Mar 2013 09:52:50 +0000 Tribological Surface Transformations (TSTs), which are irreversible near-surface solid-solid phase transformations, tend to occur on railroads frequented by heavy freight trains. The present study is proposed to assess the contribution of thermomechanical coupling processes to the emergence and development of TSTs near the surface of the rails. Grégory Antoni Copyright © 2013 Grégory Antoni. All rights reserved. Graphene Oxide Nanosheets as Effective Friction Modifier for Oil Lubricant: Materials, Methods, and Tribological Results Mon, 25 Feb 2013 13:53:47 +0000 The tribological behaviour of graphene oxide nanosheets in mineral oil was investigated under a wide spectrum of conditions, from boundary and mixed lubrication to elastohydrodynamic regimes. A ball-on-disc setup tribometer has been used to verify the friction reduction due to nanosheets prepared by a modified Hummers method and dispersed in mineral oil. Their good friction and antiwear properties may possibly be attributed to their small structure and extremely thin laminated structure, which offer lower shear stress and prevent interaction between metal interfaces. Furthermore, the results clearly prove that graphene platelets in oil easily form protective film to prevent the direct contact between steel surfaces and, thereby, improve the frictional behaviour of the base oil. This evidence is also related to the frictional coefficient trend in boundary regime. Adolfo Senatore, Vincenzo D'Agostino, Vincenzo Petrone, Paolo Ciambelli, and Maria Sarno Copyright © 2013 Adolfo Senatore et al. All rights reserved. Numerical Solution of the MHD Reynolds Equation for Squeeze-Film Lubrication between Porous and Rough Rectangular Plates Sun, 24 Feb 2013 09:18:15 +0000 The present theoretical study investigates the effects of surface roughness and couple-stress fluid between two rectangular plates, of which an upper rough plate has a roughness structure and the lower plate has a porous material in the presence of transverse magnetic field. The lubricant in the gap is taken to be a viscous, incompressible, and electrically conducting couple-stress fluid. This gap is separated by a film thickness H which is made up of nominal smooth part and rough part. The modified Reynolds equation in the film region is derived for one-dimensional longitudinal roughness structure and solved numerically using multigrid method. The numerical results for various physical parameters are discussed in terms of pressure distribution, load capacity, and squeeze film time of the bearing surfaces. Our results show that, the pressure distribution, load capacity and squeeze film time are predominant for larger values of Hartman number and roughness parameter, and for smaller values of couple-stress parameters when compared to their corresponding classical cases. Ramesh B. Kudenatti, N. Murulidhara, and H. P. Patil Copyright © 2013 Ramesh B. Kudenatti et al. All rights reserved. Effect of Cryosoaking Time on Transition in Wear Mechanism of M2 Tool Steel Sun, 24 Feb 2013 08:32:40 +0000 Specimens of M2 were hardened (H) by quenching at 1200°C, triple tempered (TTT) at 400°C, and then cryogenically (C) treated at minus 185°C for varying lengths of time interval starting from 4 hours to 48 hours of cryosoaking followed by soft tempering at 100°C to relieve cold stresses (HTC). Underlying wear mechanism, hardness, and impact energy were studied and optimum cryosoaking time was established. It was felt that wear resistance of cryogenically treated material was influenced by the so-called tertiary carbides possibly produced as a result of cryogenic treatment. N. B. Dhokey, J. V. Dandawate, and R. Rawat Copyright © 2013 N. B. Dhokey et al. All rights reserved. Performance of Magnetic-Fluid-Based Squeeze Film between Longitudinally Rough Elliptical Plates Wed, 06 Feb 2013 08:48:17 +0000 An attempt has been made to analyze the performance of a magnetic fluid-based-squeeze film between longitudinally rough elliptical plates. A magnetic fluid is used as a lubricant while axially symmetric flow of the magnetic fluid between the elliptical plates is taken into consideration under an oblique magnetic field. Bearing surfaces are assumed to be longitudinally rough. The roughness of the bearing surface is characterized by stochastic random variable with nonzero mean, variance, and skewness. The associated averaged Reynolds’ equation is solved with appropriate boundary conditions in dimensionless form to obtain the pressure distribution leading to the calculation of the load-carrying capacity. The results are presented graphically. It is clearly seen that the magnetic fluid lubricant improves the performance of the bearing system. It is interesting to note that the increased load carrying capacity due to magnetic fluid lubricant gets considerably increased due to the combined effect of standard deviation and negatively skewed roughness. This performance is further enhanced especially when negative variance is involved. This paper makes it clear that the aspect ratio plays a prominent role in improving the performance of the bearing system. Besides, the bearing can support a load even when there is no flow. P. I. Andharia and G. M. Deheri Copyright © 2013 P. I. Andharia and G. M. Deheri. All rights reserved. On the Possibilities of Decreasing Power Loss in Large Tilting Pad Thrust Bearings Mon, 14 Jan 2013 13:06:09 +0000 Different systems of direct oil supply have been developed in order to facilitate efficient introduction of fresh lubricant to the oil gap and reduction of churning power loss in tilting pad thrust bearings. Up to now there is no documented application of the supply groove in large thrust bearings used in water power plants. The results of modeling lubricant flow in the lubricating groove of a thrust bearing pad will be presented in the paper. CFD software was used to carry out fluid film calculations. Such analysis makes it possible to modify groove geometry and other parameters and to study their influence on bearing performance. According to the results a remarkable decrease in total power loss due to avoiding churning losses can be observed in the bearing. Michal Wasilczuk and Grzegorz Rotta Copyright © 2013 Michal Wasilczuk and Grzegorz Rotta. All rights reserved. Influence of Adhesive Wear and Thermal Degradation on the Frictional Characteristics of Paper-Based Friction Materials: A Comparative Study Thu, 10 Jan 2013 09:56:03 +0000 This paper discusses the effects of adhesive wear and thermal degradation on the dry frictional characteristics of paper-based friction materials against steel material. Some commercial paper-based friction materials typically used for clutch applications were subjected to adhesive wear and thermal degradation and the dry frictional characteristics were then measured at different states on a rotational tribometer. The experimental results reveal that both adhesive wear and thermal degradation have opposite effects on the frictional characteristics, where the static and kinetic coefficients of friction increase due to adhesive wear but decrease due to thermal degradation. Agusmian Partogi Ompusunggu, Paul Sas, and Hendrik Van Brussel Copyright © 2013 Agusmian Partogi Ompusunggu et al. All rights reserved. Squeeze Film Lubrication between Rough Poroelastic Rectangular Plates with Micropolar Fluid: A Special Reference to the Study of Synovial Joint Lubrication Sun, 30 Dec 2012 18:17:08 +0000 The effects of surface roughness and poroelasticity on the micropolar squeeze film behavior between rectangular plates in general and that of synovial joints in particular are presented in this paper. The modified Reynolds equation, which incorporates the randomized surface roughness structure as well as elastic nature of articular cartilage with micropolar fluid as lubricant, is derived. The load-carrying capacity and time of approach as functions of film thickness during normal articulation of joints are obtained by using Christensen stochastic theory for rough surfaces with the assumption that the roughness asperity heights are to be small compared to the film thickness. It is observed that the effect of surface roughness has considerable effects on lubrication mechanism of synovial joints. N. B. Naduvinamani and G. K. Savitramma Copyright © 2013 N. B. Naduvinamani and G. K. Savitramma. All rights reserved. Development of Machining Processes for the Use of Multilayer High-Performance Coatings Sun, 30 Dec 2012 15:49:40 +0000 The development of corrosion- and wear-resistant high-performance coatings is important to improve components of mobile and stationary turbines, aerospace undercarriages, combustion engines, and hydraulic modules. New micro- and nanostructured coating materials and processes to machine these coatings are developed in order to increase the performance of workpieces and components, to enhance durability, and to reduce maintenance and manufacturing costs. At the Institute of Machining Technology (ISF), milling and grinding procedures have been developed for the preparation of the workpiece surface for the subsequent coating process. In contrast to conventional applications, the workpieces are not manufactured with the aim of achieving a minimized resulting surface roughness. Instead of this, a defined and adequate structure has to be generated, providing a good adhesion of the thermal sprayed coating on the workpiece surface. After first coating of the prepared substrates by a High-Velocity-Oxygen-Fuel (HVOF) coating process, the resulting surface topography does not have the required surface quality for a subsequent (Diamond Like Carbon) DLC coating process. In order to generate a more uniform surface structure, the deteriorated surface resulting from the HVOF coating process also has to be processed. Therefore, the application of an adapted grinding process with diamond wheels is used. Sebastian Goeke, Tobias Brüggemann, and Dirk Biermann Copyright © 2013 Sebastian Goeke et al. All rights reserved. Friction Behavior of a Wet Clutch Subjected to Accelerated Degradation Sun, 30 Dec 2012 12:04:07 +0000 This study aims at experimentally investigating the sliding friction characteristics of a wet clutch during its lifetime. More precisely, the objective is to understand how the Stribeck and the frictional lag (i.e, sliding hysteresis) parameters evolve as the clutch degradation progresses. For this purpose, a novel test procedure has been proposed and a set of experiments has been carried out on a fully assembled (commercial) clutch using a modified SAE#2 test setup. Furthermore, a systematic methodology for the Stribeck and the frictional lag parameters identification is developed. Regardless of the applied pressure, it appears that the first three identified Stribeck parameters tend to decrease with the progression of the degradation, while the last parameter tends to increase. In regard to the frictional lag parameter, the trend shows pressure dependency. Agusmian Partogi Ompusunggu, Thierry Janssens, and Paul Sas Copyright © 2013 Agusmian Partogi Ompusunggu et al. All rights reserved. Finite-Element-Based Multiple Normal Loading-Unloading of an Elastic-Plastic Spherical Stick Contact Mon, 24 Dec 2012 13:57:22 +0000 The repeated normal elastic plastic contact problem of a deformable sphere against a rigid flat under full stick contact condition is investigated with a commercial finite element software ANSYS. Emphasis is placed on the effect of strain hardening and hardening model with the maximum interference of load ranging from elastic to fully plastic, which has not yet been reported. Different values of tangent modulus coupled with isotropic and kinematic hardening models are considered to study their influence on contact parameters. Up to ten normal loading-unloading cycles are applied with a maximum interference of 200 times the interference required to initiate yielding. Results for the variation of mean contact pressure, contact load, residual interference, and contact area with the increasing number of loading unloading cycles at high hardening parameter as well as for low tangent modulus with two different hardening models are presented. Results are compared with available finite element simulations and in situ results reported in the literature. It is found that small variation of tangent modulus results in same shakedown behavior and similar interfacial parameters in repeated loading-unloading with both the hardening rules. However at high tangent modulus, the strain hardening and hardening rules have strong influence on contact parameters. Biplab Chatterjee and Prasanta Sahoo Copyright © 2013 Biplab Chatterjee and Prasanta Sahoo. All rights reserved. Effect of Addition of Fine SiC Particles on the Dry Sliding Wear Behaviour of Extruded 2014 Al-Alloy Sun, 16 Dec 2012 08:55:03 +0000 Composites of 2014 alloy made by dispersing 10 vol.% of fine (20–50 µm) SiC particles using vortex method ensuring uniform distribution of SiC particles in the matrix have shown uniform distribution of SiC particles. Mechanical properties of the composites have also registered an improvement over the alloy. In an attempt to further improve the properties, the composites were subjected to hot extrusion of cylindrical rods along with the alloys under similar experimental conditions. A temperature range of 300–350°C and an extrusion ratio of 10 : 1 were maintained during the process. The extruded samples were compared for their mechanical properties, and improvement was noted. The mechanism of material failure from fractographic studies showed difference in behaviour between the alloy and composite. Dry sliding wear studies carried out on extruded specimens exhibited improved wear behaviour in composites over alloys as measured by volume loss and wear rate. Wear mechanism was studied from the worn surface and correlated with the wear performance. It was observed that the presence of SiC particles reduces the tendency of delamination and thus material removal from the wear surface. Rupa Dasgupta, A. K. Jha, and S. Das Copyright © 2013 Rupa Dasgupta et al. All rights reserved. Pressure Distributions Generated along a Self-Acting Fluid-Lubricated Herringbone-Grooved Journal Bearing with Trapezoidal Groove Tue, 11 Dec 2012 09:32:20 +0000 Numerical studies are carried out to investigate pressure distributions of a fluid-lubricated herringbone-grooved journal bearing with trapezoidal grooves of various angles. Additionally, the optimal trapezoidal groove geometry is discussed in terms of the radial load capacity and friction torque. Jun Liu and Yoshihiro Mochimaru Copyright © 2013 Jun Liu and Yoshihiro Mochimaru. All rights reserved. High-Speed Ice Friction Experiments under Lab Conditions: On the Influence of Speed and Normal Force Sun, 02 Dec 2012 16:12:42 +0000 Using a high-speed tribometer, coefficients of friction for bobsled runners were measured over a wide range of loads and speeds. Between 2.8 m/s and 28 m/s (equal to 10 km/h and 100 km/h), the measured coefficients of friction showed a linear decrease with increasing speed. The experiments revealed ultra-low friction coefficients of less than 0.01 after exceeding a sliding speed of about 20 m/s. At maximum speed of 28 m/s, the average coefficient of friction was 0.007. The experiments help to bridge the gap between numerous low-speed friction tests by other groups and tests performed with bobsleds on real tracks. It was shown that the friction data obtained by other groups and our measurements can be approximated by a single master curve. This curve exhibits the largest decrease in friction up to a sliding speed of about 3 m/s. The further increase in speed generates only a small decrease in friction. In addition, friction decreases with increasing load. The decrease stops when ice wear becomes effective. The load point of constant friction depends on the cross-sectional radius of the runner. The larger the radius is, the higher the load is, before the ice shows signs of fracture. It turned out that besides aerodynamic drag (not considered in this work), ice friction is one of the main speed-limiting factors. In terms of runner geometry, a flat contact of runner and ice ensures the lowest friction. The rocker radius of the runner is of greater importance for a low coefficient of friction than the cross-sectional radius. Matthias Scherge, Roman Böttcher, Mike Richter, and Udo Gurgel Copyright © 2013 Matthias Scherge et al. All rights reserved. The Effects of Trapezoidal Groove on a Self-Acting Fluid-Lubricated Herringbone Grooves Journal Bearing Wed, 19 Sep 2012 10:11:33 +0000 As a self-acting fluid-lubricated herringbone grooves journal bearing, a trapezoidal cross-sectional shape of grooves is considered. Trapezoidal groove shape effects on its bearing characteristics such as variations of load capacity, attitude, and friction torque for various trapezoidal angle of groove are determined. Jun Liu and Yoshihiro Mochimaru Copyright © 2013 Jun Liu and Yoshihiro Mochimaru. All rights reserved. Friction Performance Optimization of Chemically Deposited Ni-P-W Coating Using Taguchi Method Wed, 29 Aug 2012 13:52:12 +0000 The present study considers the friction behavior of chemically deposited Ni-P-W coatings and optimization of the coating process parameters for minimum friction using Taguchi method. The study is carried out by varying the combination of four coating process parameters, namely, concentration of nickel source, concentration of reducing agent, concentration of tungsten source, and annealing temperature. The friction tests are conducted in a plate-on-roller configuration by keeping the coated sample fixed against a rotating steel roller. The optimum combination of process parameters for minimum friction coefficient is obtained from the analysis of S/N ratio. Furthermore, a statistical analysis of variance reveals that the concentration of nickel source solution has the most significant influence in controlling friction characteristics of Ni-P-W coating. The surface morphology and composition of coatings are also studied with the help of scanning electron microscopy, energy dispersed x-ray analysis, and x-ray diffraction analysis. Supriyo Roy and Prasanta Sahoo Copyright © 2013 Supriyo Roy and Prasanta Sahoo. All rights reserved. Contribution to the Modelling of the Tribological Surface Transformations Thu, 23 Aug 2012 11:00:57 +0000 When solids are subjected to tribological loads, structural changes can occur both at the surface and in depth, immediately below the loaded area; in the case of some materials, especially metals, these changes are known as solid-solid phase transformations or Tribological Surface Transformations (TSTs). A thermomechanical model is presented in the present study in order to describe these TSTs. The ability of the model to take account TSTs is assessed with a 2D finite element analysis. G. Antoni Copyright © 2013 G. Antoni. All rights reserved. Friction Performance of Al-10%SiCp Reinforced Metal Matrix Composites Using Taguchi Method Wed, 22 Aug 2012 08:55:55 +0000 The present paper considers the friction performance of Al-10%SiCp reinforced metal matrix composites against steel for varying tribological test parameters. The composite is prepared by stir-casting process using aluminium alloy LM6 being mixed with 10% silicon carbide by weight. The tribological tests are performed by varying applied load, sliding speed, and time. The friction performance is studied using plate-on-roller configuration in a multitribotester and optimized using Taguchi L27 orthogonal array. Analysis of variance (ANOVA) is performed to observe the significance of test parameters and their interactions on friction performance. It is observed that normal load and the interaction between normal load and speed influence the friction behaviour, significantly. The wear tracks are analyzed with the help of scanning electron microscopy. Shouvik Ghosh, Prasanta Sahoo, and Goutam Sutradhar Copyright © 2013 Shouvik Ghosh et al. All rights reserved. Effect of Austempering and Martempering on the Properties of AISI 52100 Steel Wed, 15 Aug 2012 09:07:37 +0000 The mechanical properties of steel decide its applicability for a particular condition. Heat treatment processes are commonly used to enhance the required properties of steel. The present work aims at experimentally investigating the effect of austempering and martempering on AISI 52100 steel. Different tests like microstructure analysis, hardness test, impact test, and wear test are carried out after heat treatment process. It was found that annealed steel was least hard and more wear prone, while martempered steel was hardest and least vulnerable to wear. Austempered steel had the highest impact strength and it is increased with soaking time up to certain level. Least wear rate is observed in martempered sample both in abrasion and dry sliding. However, least friction coefficient is shown by annealed samples. P. Vamsi Krishna, R. R. Srikant, Mustafa Iqbal, and N. Sriram Copyright © 2013 P. Vamsi Krishna et al. All rights reserved.