Now showing 1 - 7 of 7
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    Damage characterization of unmodified and surface modified medical grade titanium alloys under fretting fatigue condition
    (25-01-2006)
    Vadiraj, Aravind
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    Fretting 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.
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    Publication
    Fretting fatigue behavior of surface modified biomedical titanium alloys
    (01-01-2010)
    Vadiraj, Aravind
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    Fretting 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.
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    Publication
    Fretting fatigue studies of titanium nitride-coated biomedical titanium alloys
    (01-10-2006)
    Vadiraj, Aravind
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    Fretting 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.
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    Publication
    Effect of surface treatments on fretting fatigue damage of biomedical titanium alloys
    (01-01-2007)
    Vadiraj, Aravind
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    Fretting fatigue is an adhesive wear damage caused by tangential micromotion under normal force at contact areas. It is observed along the contact points of hip implants and bone plates. Surface-modified biomedical titanium alloys offer better resistance against fretting damage. PVD TiN coatings and plasma nitriding have proved effective in minimizing friction and delaying the failure of materials. In the present study, attempt has been made to explain the fretting fatigue failure mechanism sequence of PVD TiN-coated and plasma-nitrided Ti-6Al-4V and Ti-6Al-4V couple through friction measurement and microscopic examination. © 2006.
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    Publication
    Effect of surface modified layers on fretting fatigue damage of biomedical titanium alloys
    (01-09-2006)
    Vadiraj, A.
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    Kamachi Mudali, U.
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    Nath, A. K.
    Fretting fatigue is a typical wear phenomena effecting from conjoint action of fretting and cyclic load under fixed contact pressure. The aim of the present work is to investigate the effect of surface modification processes such as plasma nitriding, ion implantation and laser nitriding in preventing fretting fatigue failures of Ti-6Al-4V and Ti-6Al-7Nb contact pairs. Surface modified contact pads and calibrated proof ring was used to apply contact pressure normal to the fatigue specimen. The surface modified layers and fretting fatigue damage is shown with optical and SEM micrographs. Friction coefficient between fretting contacts is continuously recorded to explain the sequence of damage during fretting process. Plasma nitrided pairs have performed better than all other processes with minimal damage and low friction (0-1). The facture of ion implanted pairs was similar to that of unmodified alloys. Laser nitrided pairs have shown premature failure owing to higher case depth. © 2006 Institute of Materials, Minerals and Mining.
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    Publication
    Fretting wear studies on PVD TiN coated, ion implanted and thermally oxidised biomedical titanium alloys
    (01-05-2007)
    Vadiraj, A.
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    Fretting damage is normally expected in biomedical implants due to body movements. Titanium alloys are most commonly used for biomedical devices and surface modified alloys have superior tribological properties to virgin materials. In the present study, the fretting wear resistance of physical vapour deposition (PVD) TiN coated, ion implanted and thermally oxidised biomedical alloys have been investigated and compared. PVD TiN coating has shown the best fretting wear resistance with minimum friction coefficient, less wear scar depth and diameter, and minimum wear rate compared to other coatings. The ion implanted specimen has undergone fretting assisted electrochemical dissolution to give higher wear loss after the modified layer has eroded away. Thermal oxidation has shown intermediate response to fretting. Fretting resistance can be improved with layers of high hardness and thickness. © 2007 Institute of Materials, Minerals and Mining.
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    Publication
    Fretting fatigue studies of surface modified biomedical titanium alloys
    (01-01-2007)
    Vadiraj, Aravind
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    Fretting fatigue is a form of adhesive wear damage caused due to tangential micro motion ol two contact bodies under normal pressure and cyclic load. Biomedical implants such as hip joints and bone plates undergo fretting fatigue damage leading to premature in-vivo failure and revisior surgeries. Surface modification of implants delays the process of fretting and thereby improves the life of these medical devices. This work involves investigation of fretting fatigue damage of surface treated titanium alloys couple. The surface treatment involves PVD TiN coating, Plasma nitriding, Ion Implantation, Laser nitriding and thermal oxidation. Fretting of all surface treated alloys have shown both adhesive and abrasive mode of contact damage. Friction coefficient of all the surface treated pairs is less compared to uncoated alloys. Plasma nitrided pairs have shown the best performance in terms of fretting fatigue life and friction coefficient compared to all other coatings Ion implanted pairs have shown little improvement in fretting fatigue lives due to shallow modified layer. PVD TiN coated pairs have irregular friction pattern due to abrasive particles at contact Thermal oxidation and Laser nitriding have shown poor fretting fatigue performance due to high case thickness.