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1
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Evaluating Frictional Temperature Rise in Sliding Surface of Artificial Hip Joint Materials with Different Loading Conditions

100%
Sagbas B., Durakbasa M.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
453-455
EN
Friction between articulating surfaces cause temperature rise in acetabular cup and femoral head. This heating may influence the rate of wear, fatigue, creep, oxidative degradation of bearing materials and may terminate surrounding tissue. The objective of this study is to determine temperature rise with different applied load for the articulating surfaces of conventional ultra high molecular weight polyethylene (UHMWPE) and vitamin E blended ultra high molecular weight polyethylene (VE-UHMWPE) acetabular components paired with a ceramic femoral component in bovine calf serum lubrication condition. Additionally frictional torque between the bearing surfaces was measured and friction coefficient was calculated. Frictional measurements of the joints were carried out on a custom made hip joint friction simulator. Various levels of static loads were applied on 28 mm diameter prostheses. In flexion-extension plane, a simple harmonic oscillatory motion between ± 24° was applied to the UHMWPE acetabular component. The period of motion was 1 Hz and the tests were run up to 12,000 cycles. Temperature rise in acetabular and femoral component was recorded with embedded thermocouples. The results were compared in terms of UHMWPE and vitamin E blended UHMWPE.
2
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Investigating Effects of Testing Parameters on Frictional Heating of UHMWPE by Taguchi Method

100%
Sagbas B., Durakbasa M.
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vol. 125
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issue 2
571-573
EN
Frictional heating makes detrimental effects on surrounding tissue and lubricant around the artificial hip joint. For reduction of this thermal damage, testing parameters and their effects were investigated by using the Taguchi method and analysis of variance. Ultra high molecular weight polyethylene (UHMWPE) acetabular liners and CoCrMo femoral head artificial hip joint components were used as samples. Frictional heating measurements of the joints were carried out on a custom made hip joint friction experimental setup. Surface dimples in different sizes were machined on the inner surface of acetabular insert samples. The tests were conducted under different loading conditions with different testing time. Bovine calf serum was used as lubricant with different amount of third body wear particles in it. Temperature rise in acetabular and femoral component was recorded with embedded thermocouples. The experimental results demonstrated that the surface dimples were the major parameter on frictional heating, followed by applied load, amount of third body particles and time. The optimal combination of the testing parameters was predicted and validated by doing experiments.
3
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Surface Texturing of Vitamin E Blended UHMWPE for Reduction of Wear

100%
Sagbas B., Durakbasa M.
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vol. 125
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issue 2
481-483
EN
Ultra high molecular weight polyethylene (UHMWPE) has been the most commonly used bearing material in artificial hip and knee replacements. But wear and wear debris of UHMWPE has been the most important problem which cause aseptic loosening and revision surgery of these replacements. For enhangement of wear resistance, new generation UHMWPE materials have been developed and different surface modification techniques have been tried. The objective of this study is to determine the effect of surface dimples on wear behavior of conventional UHMWPE and vitamin E blended UHMWPE (VE-UHMWPE) in ultra-pure water lubrication conditions. Pin-on-disc tribotester was used for measurement of friction coefficient and wear. 0.5 mm in diameter dimples were machined on the surfaces of UHMWPE and VE-UHMWPE discs. CoCrMo pins were used as counter surface. Results were evaluated in terms of materials and presence of dimples.
4
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Analysis of Surface Modification of GFRP and Influence on the Drilled Part Delamination

81%
Cavusoglu I., Durakbasa M., Cakir M.
Acta Physica Polonica A
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2017
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vol. 131
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issue 3
423-427
EN
Glass fibre reinforced plastics are especially used in aviation industry, marine applications, automobile industry and wind power plants. The shape of the products to be manufactured from glass fibre reinforced plastics materials can be easily produced by using different primary methods [J.-M. Bertholet, Composite Materials, Springer, New York 2012, p. 54]. Assembly is necessary to create the final products which have been fabricated from glass fibre reinforced plastics. Components manufactured from glass fibre reinforced plastics are drilled with CNC, during assembling process. Several kinds of defects occur around the hole after drilling the materials. Presence of defects influences the quality of holes and of the products. The aim of this study is to make comparison between modified and unmodified composite materials, both of which are formed of 30% of glass fibres and 70% of epoxy resin, in terms of delamination factor. Influence of surface modification is evaluated to identify optimum drilling parameters by using Taguchi orthogonal L18 matrix. Surface condition, drill diameter, spindle speed and feed rate are changed as process parameters in the experiments. According to the study, feed rate and spindle speed are the most influential parameters and the drill tool surface condition does not show any general change.
5
Content available remote

Importance of Measurement Parameters for the Dental Implant Surface Characterization

81%
Gunay A., Sagbas B., Durakbasa M.
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vol. 125
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issue 2
484-487
EN
Pure titanium and its alloys have been widely used in biomedical applications on account of their biological and mechanical properties. Although the mechanical properties of titanium provide acceptable responses under dynamic pressures, surface modifications are needed in order to improve osseointegration between bone-implant interfaces. There are many different surface modification techniques like sand blasting, acid etching, or coating with various materials. Surface characterization is as important as surface modification for dental implants. Although many researchers studied about measurement of surface characteristics of dental implants with similar techniques but with different measurement parameters, there is still no consensus about the optimal surface characteristics values of a successful dental implant. Among many other surface characteristics, surface roughness is one of the most important features for dental implants. In this study, the importance of surface roughness measurement of dental implants is discussed and the need of a standardized procedure for implant surface roughness measurement is emphasized. In our experimental study three different processed surfaces as sand blasted and hydrofluoric acid etched surfaces, sand blasted and nitric acid etched surfaces and blasted surfaces were investigated. Results are compared via each method and each processing technique. It is aimed to highlight the importance of a standardized method for measuring and describing surface characteristics. More definitive, standardized methods are needed to augment the rather existing varied combined measurement parameters which affect the results for the assessment of biomedical surfaces.
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