• Elastomers and Composites
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• 제56권4호
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• pp.223-233
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• 2021

In this study, epoxidized liquid isoprene rubber (E-LqIR) was used as a processing aid in a silica-filled natural rubber compound to improve the fuel efficiency, abrasion resistance, and oil migration problems of truck and bus radial tire tread. The wear resistance, fuel efficiency, and extraction resistance of the compound were evaluated according to the molecular weight of E-LqIR. Results of the evaluation showed that the E-LqIR compound had a lower chemical crosslink density than that of a treated distillate aromatic extract (TDAE) oil compound because of the sulfur consumption of E-LqIR. However, the filler-rubber interaction improved because of the reaction of E-LqIR with silica and crosslink with the base rubber by sulfur. As the molecular weight of E-LqIR increased, crosslink with sulfur was facilitated, and the filler-rubber interaction improved, resulting in improved abrasion resistance. The fuel efficiency performance of the E-LqIR compound was poorer than that of the TDAE oil compound because of the low chemical crosslink density and hysteresis loss at the free chain end of E-LqIR. However, the fuel efficiency performance improved as the molecular weight of E-LqIR increased.

• Elastomers and Composites
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• 제59권1호
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• pp.8-16
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• 2024

As regulations on greenhouse gas emission have strengthened globally, the demand for improved fuel efficiency in automobiles continues to rise. In response, the tire industry is actively conducting research to improve fuel efficiency by enhancing tire performance. In this study, silica-filled epoxidized natural rubber (ENR)/butadiene rubber (BR) blend compounds were manufactured according to ENR types and silica contents, and their physical properties and vulcanizate structure were evaluated. ENR-50, which has a higher epoxide content than ENR-25, exhibited stronger filler-rubber interaction, resulting in superior abrasion resistance. In addition, because of its high glass transition temperature (T_g), the wet grip performance of ENR-50 improved, even though the rolling resistance increased. Increasing the amount of silica had little effect on the abrasion resistance due to the increase in filler-rubber interaction and decrease in toughness. In addition, ENR-50 exhibited better wet grip performance; however, the rolling resistance increased. The results indicated that truck bus radial (TBR) tire tread compounds can be designed by applying ENR-50 to improve wear resistance and wet grip performance. In addition, by applying ENR-25 and reducing the silica contents improve fuel efficiency.

• Journal of Korea Foundry Society
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• 제38권1호
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• pp.16-26
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• 2018

In this study, the effects of the pouring temperature, preheating temperature, surface condition and fraction of the wear resistant part on the production of duo-castings were investigated using a high Cr white cast iron with excellent abrasion resistance and a low Cr alloy steel with good toughness. The constituent materials of the duo-castings were designed to have high hardness, fracture toughness and abrasive wear resistance for the replacement of high Mn alloy steels with low abrasive wear resistance. In particular, the amount of abrasive wear of 17% Cr white cast iron was about 1/20 of that of high Mn alloy steel. There was an intermediate area of about 3mm due to local melting at the bonding interface of the duo-castings. These intermediate regions were different from those of the constituent materials in chemical composition and microstructure. This region led to fracture within the wear resistant part rather than at the bonding interface in the bending strength test. The bending fracture strengths were 516-824 MPa, which were equivalent to the bending proof strength of high Mn steel. The effects of various casting conditions on the duo-cast behavior were studied by simple pouring of low Cr alloy steel melt, but the results proved practically impossible to manufacture duo-castings with a sound bonding interface. However, the external heating method was suitable for the production of duo-castings with a sound bonding interface.

• Elastomers and Composites
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• 제57권3호
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• pp.92-99
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• 2022

A large amount of particles on the roads is produced by friction between the vehicles and the road surface and by inflow from outside. The type of these particles affects the abrasion behavior of tire tread. In this study, road dust collected at a bus stop was separated by size, and the particles with sizes of 106-212 mm were analyzed. The particles were separated by density using NaI and NaBr aqueous solutions with densities in the range of 1.10-1.80 g/cm³ with the 0.10 g/cm³ interval. In the road dust sample, the following particle types were found: tire-road wear particles (TRWPs), asphalt pavement wear particles (APWPs), plant-related particles (PRPs), road paint wear particles (RPWPs), and plastic particles (PPs). The densities of TRWPs, APWPs, PRPs, and RPWPs were 1.20-1.80, >1.60, >1.10, and >1.40 g/cm³, respectively, while PPs were found in all density ranges. Additionally, many small mineral particles were observed on the particles. Order of the relative content of the particles was PRP > TRWP > APWP ~ RPWP > PP. APWPs that were stuck to TRWP could be removed by chloroform treatment. The shapes of the particles were characterized using their magnified images.

• The Journal of Korean Academy of Prosthodontics
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• 제34권3호
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• pp.464-474
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• 1996

A principal advantage of a plastic tooth over a porcelain tooth should be its ability to bond to the denture base material. But plastic teeth could craze and wear easily, so more abrasion resistant plastic denture teeth have been developed. To resist abrasion, the degree of cross-linking was increased, but bonding to denture base meterial became more difficult. The purpose of this study was to evaluate the bond strength of plastic teeth and abrasion resistant teeth bonded to heat-curing, self-curing and light-curing denture base material. Denture tooth molds were chosen that had a>8mm diameter. The denture teeth was bonded to three denture base materials and then machined to the same dimensions. Three denture base materials were used as control groups. Prior to tensile testing, the specimens were thermocycled between $5^{\circ}C\;and\;55^{\circ}C$ for 1000cycles. Tensile testing was performed on an Instron Universal testing mechine. Experimental group ; plastic teeth(Justi Imperial)+heat-curing resin(Lucitone 199) plastic teeth(Justi Imperial)+light-curing resin(Triad) plastic teeth(Justi Imperial)+self-curing resin(Vertex SC) abrasion resistant teeth(IPN)+heat-curing resin(Lucitone 199) abrasion resistant teeth(IPN)+light-curing resin(Triad) abrasion resistant teeth(IPN)+self-curing resin(Vertex SC) Control group ; heat-curing resin(Lucitone 199) light-curing resin (Triad) self-curing resin(Vertex SC). The results were as follows : 1. The denture teeth bonded to heat-curing resin showed the cohesive failure and those bonded to the other resins showed adhesive failure. 2. Tensile bond strength of the plastic teeth bonded to self-curing resin was not significantly greater than bonded to light-curing resin(p>0.05). 3. Tensile bond strength of the abrasion resistant teeth bonded to self-curing resin was not significantly greater than bonded to light-curing resin(p>0.05). 4. Tensile bond strength of the plastic teeth to self-curing resin was not significantly different from that of the abrasion-resistant teeth(p>0.05). 5. Tensile bond strength of the plastic teeth to light-curing resin was significantly greater than that of the abrasion resistant teeth(p<0.01).

• Journal of the korean academy of Pediatric Dentistry
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• 제33권4호
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• pp.633-642
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• 2006

This study evaluated the surface changes such as surface average roughness(RA), surface free energy(SFE) and wear depth among groups treated with surface penetrating sealant(Fortify, Biscover), non treated polishing group before and after tooth-brushing, analyzing the influence of the sealants in filling of surface microdefects formed during the finishing and polishing procedures of composite resin. Results were as follow(p= 0.05) : 1. Ra was increased Biscover. Fortify and Polishing group. Before abrasion and in 6 months, all groups were statistically significant. In 1 month, 2 months and 3 months no statistical difference was noticed between Fortify and Biscover 2. SFE of Polishig and Biscover group. Fortify and Biscover group were statistically significant before abrasion. SFE of Polishing and Fortify group was statistically significant in 1 month. No statistical difference was noticed among groups in 2 months. SFE of Fortify and Biscover group was statistically significant in 3 months. Polishing and Fortify group, Fortify and Biscover group were statistically significant in 6 months. 3, Wear rate between Polishing and Fortify group was statistically significant in only 1 month. Wear rate between Polishing and Biscover group was statistically different in each month except for 2 month and so it was between Fortify and Biscover group. Considering film thickness of Fortify and Biscover, Fortify almost discappeared after 2 months and Biscover did after 6 months.

• Tribology and Lubricants
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• 제15권1호
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• pp.29-38
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• 1999

In recent years, the tribological behavior of coated ceramic material has been the issue of much interest. Particularly, the understanding of the tribological performance of thin film under light load is important for its potential in applications of MEMS. The friction and wear behavior of ceramic material that occur at light load depends on several factors such as surface roughness, contact area and material properties. In this work, the tribological behavior of coated silicon under light load and low speed was investigated. Particularly, the effects of coated materials, humidity and undulated surface were also studied. The results show that the effect of humidity on fiction was influenced by the apparent area of contact between the two surfaces. Also both adhesive and abrasive wear occurred depending on the sliding condition. Finally, undulations on the silicon wafer were found to be effective in trapping wear particles and resulted in the reduction of friction.

• Journal of Korean Tunnelling and Underground Space Association
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• 제20권2호
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• pp.453-467
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• 2018

The excavation performance and the cutting tool wear prediction of shield TBM are very important issues for design and construction in TBM tunneling. For hard-rock TBMs, CSM and NTNU model have been widely used for prediction of disc cutter wear and penetration rate. But in case of soft-ground TBMs, the wear evaluation and the excavation performance have not been studied in details due to the complexity of the ground behavior and therefore few testing methods have been proposed. In this study, a new soil abrasion and penetration tester (SAPT) that simulates EPB TBM excavation process is introduced which overcomes the drawbacks of the previously developed soil abrasivity testers. Parametric tests for penetration rate, foam mixing ratio, foam concentration were conducted to evaluate influential parameters affecting TBM excavation and also ripper wear was measured in laboratory. The results of artificial soil specimen composed of 70% illite and 30% silica sand showed TBM additives such as foam play a key role in terms of excavation and tool wear.

• Journal of Biomedical Engineering Research
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• 제22권6호
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• pp.519-526
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• 2001

At present. about 0.3 million and more THRs (Total Hip Replacement) in a rear are being done worldwide. The increase in mechanical failure with the increase in THR, required more revisions. Revisions compensate mainly the wear of the artificial joint frictional surface and the loosening of the cup and stem. According to recent researches, loosening is mainly due to wear debris UHMWPE (Ultra High Molecular Weight Polyethylene) from frictional surfaces . To overcome the wear problems associated with artificial joint materials , new surface structures with regular Patterns were designed and fabricated The lubrication Properties were examined to evaluate the wear of the frictional surfaces. The surface structure manifested a Pattern of "dents" with a 0.2-1.0 mm of diameter and 0.6-2.0 mm of Pitch. From the friction test of the SUS316L vs UHMWPE using the frictional tester, we found that the lubrication Performance was improved due to of drastically reduced amount of abrasion. There were optimum sizes for the diameter and the pitch of the Pattern. The results demonstrated that the lubrication properties could be improved by Patterning of the frictional surfaces. The surface Patterning was effective in preventing wear of the frictional surfaces, and the life of an artificial joint could be extended with such Patterning.

• Tribology and Lubricants
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• 제30권4호
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• pp.199-204
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• 2014

Various heat-treated and surface coating methods are used to mitigate abrasion in sliding machine parts. The most cost effective of these methods involves hard coatings such as diamond-like carbon (DLC). DLC has various advantages, including a high level of hardness, low coefficient of friction, and low wear rate. In practice, a supporting layer is generally inserted between the DLC layer and the steel substrate to improve the load carrying capacity. In this study, an indentation and sliding contact problem involving a small, hard, spherical particle and a DLC-coated steel surface is modeled and analyzed using a nonlinear finite element code, MARC, to investigate the influence of the supporting layer thickness on the coating characteristics and the related coating failure mechanisms. The results show that the amount of plastic deformation and the maximum principal stress decrease with an increase in the supporting layer thickness. However, the probability of the high tensile stress within the coating layer causing a crack is greatly increased. Therefore, in the case of DLC coating with a supporting layer, fatigue wear can be another important cause of coating layer failure, together with the generally well-known abrasive wear.