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Kamaraj M
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Kamaraj M
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Kamaraj M
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Kamaraj, Muthusamy
Kamaraj, M.
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24 results
Now showing 1 - 10 of 24
- PublicationDamage characterization of unmodified and surface modified medical grade titanium alloys under fretting fatigue condition(25-01-2006)
;Vadiraj, AravindFretting is a form of adhesive wear normally occurring at the contact points gradually leading to premature of load bearing medical implants made of titanium alloys. The aim of this work is to characterize the fretting fatigue damage features of PVD TiN coated, plasma nitrided and thermally oxidized Ti-6Al-4V and Ti-6Al-7Nb contact pairs. Fretting damage is applied with calibrated proof ring and contact pad arrangement. The results are compared with fretting damage of uncoated alloys. The damage progression during fretting process is apparently explained with friction coefficient curves. Plasma nitrided pairs performed better in terms of fretting fatigue lives with low friction coefficient of friction. PVD TiN coated pairs have experienced early failures due to third body mode of contact interaction with irregular friction coefficient pattern. Thermally oxidized pairs have experienced early failures due to high case thickness as well as irregular development of modified layer. © 2005 Elsevier B.V. All rights reserved. - PublicationFretting wear studies on uncoated, plasma nitrided and laser nitrided biomedical titanium alloys(15-02-2007)
;Vadiraj, Aravind; Fretting wear resistance of uncoated and surface modified biomedical titanium alloys (Ti-6Al-7Nb) in air and Ringer fluid has been investigated in the present work. Laser nitrided specimen has shown superior performance with minimum surface damage and wear rate (<0.1 × 10-6 mm3/Nm) despite high friction coefficient in air (0.6) compared to uncoated and plasma nitrided (>12 × 10-6 mm3/Nm) specimens. This is due to presence of TiN dendrites (60-80%) in the laser nitrided layer. Plasma nitrided surface is relatively softer and hence wear rates and surface damage are comparable with uncoated alloys. Friction coefficient is high for uncoated (0.8) and plasma nitrided alloys (0.6) in air as well as Ringer fluid. Fretting induced electrochemical dissolution is responsible for higher wear rates in uncoated and plasma nitrided specimens. The fretting damage resistance is primarily governed by relative hardness and modified layer thickness of the mating components. © 2006 Elsevier B.V. All rights reserved. - PublicationMechanical and wear behavior of alloyed gray cast iron in the quenched and tempered and austempered conditions(01-08-2011)
;Balachandran, G. ;Vadiraj, Aravind; Kazuya, EkusaThree groups of hypereutectic cast irons alloyed with Cu, Ni and microalloying additive like Ti and Nb were examined for its hardness and wear resistance in the austempered (360 °C/3. h) and quenched and tempered conditions at varying tempering temperatures. It is observed that the cast irons in the quenched and tempered condition showed good wear resistance and moderate hardness at 400 °C. This was comparable with the wear resistance in austempered condition. The study also showed that in quenched and tempered condition, increasing Cu content in cast irons improved its wear resistance moderately while increasing Ni content has decreased its wear resistance. The presence of strong carbide formers (Nb, Ti) did not give significant improvement in wear resistance in quenched and tempered condition. Even in austempered alloys, higher Cu content increases its wear resistance and higher Ni content decreases their wear resistance. The austempered alloys showed ausferritic microstructure with 20% austenite phase which enhances wear resistance through transformation induced plasticity effect. On the other hand, the quenched and tempered alloys showed good wear resistance at 400. °C due to fine tempered carbides in the matrix. © 2011 Elsevier Ltd. - PublicationWear and friction behavior of alloyed gray cast iron with solid lubricants under boundary lubrication(01-09-2011)
;Vadiraj, Aravind; Sreenivasan, V. S.Friction and wear behavior of MoS2, boric acid, graphite and TiO2 has been compared under extreme boundary lubrication condition. Boundary lubrication was simulated for the study. Results show that MoS 2 and graphite were 3050% more effective than other two lubricants. Friction coefficient shows a decreasing trend with increase in sliding speed due to increasing temperature and higher shear force. High friction coefficient values were recorded for all the lubricants (0.20.5). This is due to predominating solid interactions during boundary lubrication condition. Boric acid and TiO2 were not much effective in lubrication. © 2011 Elsevier Ltd. All rights reserved. - PublicationFretting fatigue of biomaterials(01-10-2005)
;Vadiraj, Aravind; ;Kamachi Mudali, U.Raj, BaldevThe use of metals and materials for replacement and repair of human body parts are attracting more attention in recent times. Like any other components in service, biomaterials also undergo degradation due to fretting, wear and corrosion. Fretting wear, fretting fatigue and fretting corrosion are the three main areas of concern for the orthopedic surgeons. This paper reviews fretting fatigue along with various methodologies and mechanisms. Fretting of materials is controlled by several sets of variables working synergistically, making the process difficult to quantify. A fretting test rig for biomaterials has been developed simulating the conditions of the actual implants as close as possible. Fretting fatigue life is also controlled by contact geometries, which delay or accelerate the crack initiation. Several contact geometries have been mentioned which can influence the fretting life of the materials. Fretting conditions are also governed by normal pressure and slip amplitude regime in fretting maps. Physiological medium may aggravate or reduce the fretting failures depending on the nature of surface and the medium. Titanium alloys have been established as the most suitable materials for bio implants due to their attractive properties within the body environment. Some important aspects of the fretting damage of these alloys are mentioned in this paper. Fretting fatigue life of these alloys can be significantly improved by surface modification with specialized techniques such as plasma nitriding, ion implantation and Physical Vapour Deposited TiN coatings. The paper describes details of these methods as well. - PublicationCharacterization of fretting fatigue damage of PVD TiN coated biomedical titanium alloys(10-04-2006)
;Vadiraj, AravindFretting fatigue is a form of adhesive wear damage due to small oscillatory movement between two contacting bodies under the action of uniform or non-uniform cyclic loads. Cyclic loads may be experienced due to vibration of one or both the bodies eventually leading to failure at the contact area. Fretting damage is also experienced by load bearing implants within the body environment such as hip joints, knee joints, bone plates, etc. Damage characterization is important from the view of minimizing in-vivo failures. Titanium alloys are frequently used as bioimplants due to its excellent biocompatibility and low modulus of elasticity compared to stainless steel or Co-Cr-Mo alloys. Fretting wear damage of load bearing implants can be minimized through suitable surface modification process. Ti-6Al-4V and Ti-6Al-7Nb are commonly used for biomedical applications and PVD TiN coated alloys are used for our fretting fatigue studies. Fretting fatigue life of PVD TiN coated alloys improved compared to uncoated alloys. © 2005 Elsevier B.V. All rights reserved. - PublicationStructure-property correlation in austempered alloyed hypereutectic gray cast irons(15-01-2010)
;Vadiraj, Aravind ;Balachandran, G.; ;Gopalakrishna, B.Prabhakara Rao, K.The austempering behavior of a series of hypereutectic alloyed gray iron compositions with carbon equivalent from 4.37 to 5.14 was studied to understand the influence of microstructure on its mechanical and wear properties. The alloying elements in the alloys included Ni, Mo, Cr and inoculation by micro-constitution of Ti, Nb and Ce. The alloys were austempered at 360 °C and upper bainitic type feathery ferrite was observed in the matrix. While the graphite content determined by optical metallography varied between 16 and 24 vol%. The volume of austenite determined by XRD analysis showed values between 20 and 26%. The ferrite lath size was determined using XRD peak broadening. The tensile property varying between 188 and 270 MPa, showed no significant variation with volume percentage of carbon or austenite in the ausferrite. However the wear rate varying between 0.5 and 2.6 × 10-7 g/Nm, showed a decreasing trend with graphite content attributed to the higher lubricating effect of released carbon during sliding wear. The specific wear rate of hypereutectic alloys, increased with increasing ferrite lath size due to enhanced softer ferrite phase on the sliding surface. The wear rate was found to increase with volume of austenite, austenite carbon content and austenite lattice parameter, which is attributed to increased stability of austenite against strain induced martensite formation and the increased formation of bainitic carbides in the second stage tempering. The various technical aspects in correlating the microstructure with the mechanical and wear properties of hypereutectic austempered gray iron are described. © 2009 Elsevier B.V. All rights reserved. - PublicationFretting fatigue behavior of surface modified biomedical titanium alloys(01-01-2010)
;Vadiraj, AravindFretting is a form of adhesive wear normally occurring at the contact points gradually leading to premature failure of load bearing medical implants made of titanium alloys. The aim of this work is to characterize the fretting fatigue damage features of PVD TiN coated, plasma nitrided, ion implanted, laser nitrided and thermally oxidized Ti-6Al-4V and Ti-6Al-7Nb contact pairs. The surface layers were characterized. The damage progression during fretting process is apparently explained with tangential force coefficient curves. Plasma nitrided pairs showed highest fretting fatigue life compared to others. PVD TiN coated pairs have experienced early failures due to third body mode of contact interaction with irregular tangential force coefficient pattern. Ion implanted layers showed similar damage as unmodified alloys. Laser nitrided and thermally oxidized pairs experienced early failures due to brittle and irregular modified layers. © 2010 TIIM, India. - PublicationFretting fatigue studies of titanium nitride-coated biomedical titanium alloys(01-10-2006)
;Vadiraj, AravindFretting fatigue is an adhesive wear mechanism caused by repetitive tangential micro-oscillation between two contacting materials pressed together under cyclic load. Bioimplants, such as hip joints and bone plates, are prone to undergo fretting fatigue failures during their service within the body. This article presents the fretting fatigue damage characterization of physical vapor deposition (PVD) TiN-coated biomedical titanium alloys (Ti-6Al-4V and Ti-6Al-7Nb) subjected to cyclic loads. The PVD TiN layer delayed the damage because of superior tribological properties compared with uncoated alloys. Delamination and abrasive wear damage of TiN at contact caused failure of the alloy. Friction coefficient curves of the PVD TiN-coated pair showed an irregular pattern caused by the influence of wear particulates and Ringer fluid at the contact. © ASM International. - PublicationMechanical and wear behavior of quenched and tempered alloyed hypereutectic gray cast iron(01-04-2011)
;Vadiraj, Aravind ;Balachandran, G.; Kazuya, EkusaThe effect of tempering temperature (100-600 °C) on the hardness and wear resistance of a series of quenched and tempered hypereutectic alloyed gray cast irons has been studied in this work. Hardness was observed decreases with increase in tempering temperature and this trend is influenced by alloying additions and the volume of graphite flakes. Hardness of alloyed gray irons is also influenced by solid solution strengthening of tempered ferrite and carbide content and their distribution. The wear loss of alloyed cast irons was found to be lowest at a tempering temperature of 100 °C and 400 °C. The optimum tempering temperature is 400 °C with moderate hardness and low wear rate. This has been attributed to strengthening of the matrix at this temperature. Beyond 400 °C, the wear rate increases significantly due to carbide coagulation. © 2010 Elsevier Ltd.
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