• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.3-6
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• 1996

The Ultra-high molecular weight polyethylene (UHMWPE) is exclusivity used as the articulation component with metal or ceramic materials in artificial joint prosthesis because of its good mechanical properties. In the long term however, wear of UHMWPE causes complex problems and hence causes loosening of He prosthesis. In this study, we tried to enhance the wear property of UHMWPE by attaching a hydrophilic graft on the UHMWPE surface and by improving surface hardness without deteriorating the mechanical properties of UHMWPE. This was achieved by ion implantation and by ${\gamma}$-irradiation to the surface in acrylic acid solution and by photo-polymerization in divinylbenzen (DVB), diallysophthalate (DAIP) solution. The wear test was performed by a wear testing machine of ball-on-disk type devised by the authors. The UHMWPE with hydrophlic surface and increased surface hardness developed by above treatments showed less volumetric wear.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.404-410
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• 1989

Friction and wear tests were conducted with several different ceramics sliding against ceramic and metal couples with and without lubricant in a two disk type sliding machine. The purpose was to know the tribological properties of ceramics. With very different physical and chemical properties of ceramics compared to metal, the tribological properties of ceramics should be defined in detail. Among them, the wear and friction with same or different couple is very important. Also the lubrication of ceramic is one of the major area to be studied. From this research, SiC, SI$_{3}$N$_{4}$ and ZrO$_{2}$ were slid against SiC, AISI 4340 and bronze under various sliding condition. It was found that the friction and wear of ceramics are strongly dependent on the sliding condition. For unlubricated sliding against SiC, ZrO$_{2}$ shows low wear and friction coefficient over wide lange of load, but with lubricated sliding, SiC shows better performance whatever lubricants were used. Also the effect of lubricant depended upon the material properties of sliding pairs. The general tribological properties of ceramics were not correlated with chattering and noise at low load but it could be reduced or avoided effectively by using lubricants. SiC and Si$_{3}$N$_{4}$ slid against SiC have transition from mild to severe wear at high load but ZrO$_{2}$-SiC and SiC-steel have not. Wear debris formed on the contact area of SiC couples was main cause of the initiation of transition. At high speed, only ZrO$_{2}$ sliding against SiC has transition of wear by low thermal conductivity.

• The Journal of Advanced Prosthodontics
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• v.2 no.3
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• pp.111-115
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• 2010

PURPOSE. This study was conducted to evaluate clinical validity of a zirconia full-coverage crown by comparing zirconia's wear capacity over antagonistic teeth with that of feldspathic dental porcelain. MATERIALS AND METHODS. The subject groups were divided into three groups: the polished feldspathic dental porcelain group (Group 1), the polished zirconia group (Group 2), and the polished zirconia with glazing group (Group 3). Twenty specimens were prepared from each group. Each procedure such as plasticity, condensation, and glazing was conducted according to the manufacturer's manual. A wear test was conducted with 240,000 chewing cycles using a dual-axis chewing simulator. The degree of wear of the antagonistic teeth was calculated by measuring the volume loss using a three-dimensional profiling system and ANSUR 3D software. The statistical significance of the measured degree of wear was tested with a significant level of 5% using one-way ANOVA and the Tukey test. RESULTS. The degrees of wear of the antagonistic teeth were $0.119{\pm}0.059\;mm^3$ in Group 1, $0.078{\pm}0.063\;mm^3$ in Group 3, and $0.031{\pm}0.033\;mm^3$ in Group 2. Statistical significance was found between Group 1 and Groups 2 and between Group 2 and 3, whereas no statistical significance was found between Group 1 and Group 3. CONCLUSION. Despite the limitations of this study on the evaluation of antagonistic teeth wear, the degree of antagonistic tooth wear was less in zirconia than feldspathic dental porcelain, representing that the zirconia may be more beneficial in terms of antagonistic tooth wear.

• Journal of Biomedical Engineering Research
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• v.31 no.6
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• pp.449-455
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• 2010

A ceramic articulating system in total hip replacement thought to be superior to metal-on-polyethylene due to its extremely low coefficient of friction and potential for high resistance to wear. But ceramic is brittle, which makes it mechanically and theoretically susceptible to fracture under certain mechanical conditions. In the current study, nine different models of ceramic ball heads were mechanically evaluated using 3D finite element(FE) analyses. It was found that the maximum stress in all ceramic models was lower than ceramic flexural strength, and it satisfied the requirements of the FDA Gaudience for artificial hip implant. Thus, ceramic ball head models introduced in the current study could be mechanically safe for clinical applications.

• The Journal of the Korean dental association
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• v.56 no.3
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• pp.167-174
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• 2018

The development of dental materials has widened the scope of materials by changes in processing methods. CAD/CAM processing enables the use of zirconia as a dental material. Recent esthetic materials development has been made. For aesthetic purposes, a block for CAD/CAM processing by mixing polymer and ceramic materials are fabricated. However there is no guideline of how these materials should be used in actual clinical practice. Mechanical properties, wear and clinical studies were reviewed.

• Journal of the Korean Ceramic Society
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• v.39 no.1
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• pp.79-85
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• 2002

Plasma-sprayed Cr$_2$O$_3$-based coatings containing MoO$_3$were studied to gain a better understanding of the influence of MoO$_3$composition in the coatings on their tribological behaviour. A reciprocal type tribo-tester was employed to examine friction and wear behavior of the specimens at room temperature. The physical characteristics of worn surfaces were investigated by scanning electron microscopy and chemical composition of the coating surfaces was analyzed using a X-ray photoelectron spectrometer. The results showed that friction coefficient of the MoO$_3$-added coatings were lower than those without MoO$_3$addition. However pure Cr$_2$O$_3$coating showed the lowest wear loss at the self-mated test. The larger protecting layers were observed at the worn surface of plasma spray coated specimens with MoO$_3$addition. XPS analysis of the protecting layer indicated that MoO$_3$composition was dominantly formed at the surface. MoO$_3$composition in the protecting layer appears to be more favorable in reducing the friction.

• Korean Journal of Materials Research
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• v.10 no.10
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• pp.703-708
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• 2000

As the engine design changes to get high efficiency and performance of commercial diesel engine, surface w wear of the earn follower becomes an important issue as applied load increasing at the contact face between cam follower and cam. We developed the ceramic cam follower made of sili$\infty$n nitride ceramic which was more wear resistant than the cast iron or sintered metal cam follower. Ceramic cam follower was made by direct brazing of thin ceramic disk to steel body using an active brazing alloy without the interlayer. In-situ crowning(R), resulted from the difference of thermal expansion coefficient between ceramic and carbon steel after direct brazing without any stress-relieving inter]ayer, could be controlled. When a earbon steel was heated above $A_{c1}$ point and then c$\infty$led, the expansion curve represented a hysteresis. Appropriate crowning was achieved below the $A_{c1}$ point(about $723^{\circ}C$) and crowning increased with brazing temperature exponentially above the $A_{c1}$ point. Optimum brazing temperature range was from 700 to $720^{\circ}C$. We developed successfully the ceramic cam follower having appropriate crowning and being inexpensive. Also we could successfully control the crowning of ceramic earn follower by hysteresis behavior of thermal expansion of earbon steel during direct brazing process.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.24 no.2
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• pp.78-85
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• 2015

Although the finishing of ceramic restorations affects overall results of prosthetic procedures, the importance of finishing procedures has been underestimated. Finishing procedures have influence on the esthetics, and strength of ceramic restorations, and attrition of opposite tooth. For achieving the appropriate results of these factors, the overall understanding related to the finishing procedures of ceramic restoration is necessary.

• Journal of Korea Foundry Society
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• v.25 no.2
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• pp.88-94
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• 2005

The microstructure and mechanical property of the ceramic reinforced AC4C matrix composites processed by squeeze casting were investigated. In this study Kaowool and Saffil fiber which are ceramic reinforcements are used as preform materials. As a matrix material, Al-7wt.%Si-0.3wt.%Mg(AC4C) has been used. In case of Kaowool and Saffil/AC4C composites, 7.5 MPa squeezing pressure and minimum 7.0% binder amount are needed to produce sound composite materials. The tensile strength of Kaowool/ AC4C composite is lower than the matrix metal and this can be explained by the melt unfilling due to formed cluster of Kaowool reinforcements. But the mechanical properties of hardness, wear resistance and thermal expansion are better than the matrix materials due to the strengthening effect of ceramic reinforcements.

• Design & Manufacturing
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• v.6 no.1
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• pp.24-28
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• 2012

Friction and wear affect all processes involved in the extraction of materials and their conversion into finished products in the die applications such as drawing, extrusion etc. Originating phenomenon from the contact surface between the tool and workpiece, they are usually a hindrance to materials process operations which usually result in damaging the tools, increasing energy consumption, the contamination of processed material by wear particles and also some problems associated with technologies to control friction and wear. The most well established method to control friction and wear is by the application of lubricant such as fluorocarbon. Besides, a surface technique so-called surface modification can be applied to solve the tribology problems of the die applications for both the economical and ecological reasons. In this article, we applied DLC(diamond-like carbon) thin film on alumina ceramic for HT test using the PIID(plasma ion immersion deposition), 4 groups of test specimens were tested up to $200^{\circ}C$ which is a little higher than the normal working temperature of die application. Pin-on-disc tribo-tester was used to test the friction and surfaces were characterized by SEM and EDS and else, the morphology changes of DLC coatings were studied. The present work indicated that the DLC had a great potential to reduce the friction and wear in the alumina die application without lubricants.