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Friction Characteristics of CNx Coated Dimple Pattern with Hexagonal Array
wonsik Choi(최원식),Noritsugu Umehara 한국트라이볼로지학회 2011 한국윤활학회지(윤활학회지) Vol.27 No.5
In this study, we examined the friction characteristics of a dimple pattern on a carbon nitride coating. The study was conducted with a hexagonal array 40 ㎛ dimple pattern on a steel bearing containing a CNx coating. The area density of the dimple patterns were varied between 5% and 25%, the speed was varied from 0.06-0.26 ㎧, and the load was varied between 20-100N. In general, we found that as the velocity increased, the friction coefficient increased. Furthermore, the friction coefficient was lowest at a load of 40N. The friction coefficient of the non-coated specimen was 0.025-0.15; on the other hand, the friction coefficient of the coated specimen was 0.002-0.02. Thus, we determined that the coated materials could reduce the friction coefficient by a factor of 7.5.
Wonsik Choi(최원식),Pandu Sandi Pratama(프라타마 판두 산디),Destiani Supeno(수페노 데스티아니),Jaeyoung Byun(변재영),Ensuk Lee(이은숙),Jihee Woo(우지희),Jiung Yang(양지웅),Dimas Harris Sean Keefe(키프 디마스 하리스 신),Maynanda Brigita Chry 한국산업융합학회 2018 한국산업융합학회 논문집 Vol.21 No.5
In this research, the effect of normal load, sliding velocity, and texture density on thefriction coefficient of surfaces micro-textured on AISI 4140 under paraffin oil lubrication were investigated. The predicted tribological behavior by numerical calculation can be serves as guidance for the designer during the machine development stage. Therefore, in this research friction coefficient prediction model based on response surface methodology (RSM), support vector machine (SVM), and artificial neural network (ANN) were developed. The experimental result shows that the variation of load, speed and texture density were influence the friction coefficient. The RSM, ANN and SVM model was successfully developed based on the experimental data. The ANN model can effectively predict the tribological characteristics of micro-textured AISI 4140 in paraffin oil lubrication condition compare to RSM and SVM.
Wonsik Choi(최원식),Pandu Sandi Pratama(프라타마 판두 산디),Destiani Supeno(수페노 데스티아니),Jaeyoung Byun(변재영),Ensuk Lee(이은숙),Jiung Yang(양지웅),Dimas Harris Sean Keefe(키프 디마스 하리스 신),Yeonho Jeon(전연호),Sungwon Chung(정성원) 한국산업융합학회 2018 한국산업융합학회 논문집 Vol.21 No.5
In this research, tricycle vehicle simulation based on multi-body environment has been introduced. Mathematical model of tricycle vehicle was developed. In this research the left and right wheel speed are calculated based on the rear steering angle and velocity. The kinematic model for the three - wheel drive system was completed and the results were analyzed using the actual vehicle drawings. Through simulink vehicle performance on linear and rotation movement were simulated. Using the mathematical model the control system can be applied directly to the tricycle vehicle. The simulation result shows that the proposed vehicle model is successfully represent the movement characteristics of the real vehicle. This model assists the vehicle developer to create the controller and understand the vehicle during the development process.
Choi, Wonsik,Ranasinghe, Dilhara,DeShazo, J.R.,Kim, Jae-Jin,Paulson, Suzanne E. Elsevier 2018 Environmental pollution Vol.233 No.-
<P><B>Abstract</B></P> <P>Epidemiological studies have shown that exposure to traffic-related pollutants increases incidence of adverse health outcomes. Transit users in cities across the globe commonly spend 15–45 min or more waiting at transit stops each day, often at locations with high levels of pollution from traffic. Here, we investigate the characteristics of concentration profiles of ultrafine particles (UFP) with 5 m spatial resolution across intersections, to determine the best place to site transit stops to minimize exposures. Cross-intersection UFP profiles were derived from 1744 profiles covering 90 m before and after each intersection center with a mobile monitoring platform. Measurements were made at 10 signalized intersections located at six urban sites, each with a distinct built environment, during both mornings and afternoons. Measurements were made within 1.5 m of the sidewalk and approximately at breathing height (1.5 m above ground level) to approximate sidewalk exposures. UFP profiles were strongly influenced by high emissions from vehicle stops and accelerations, and peaked within 30 m of intersection centers; from there concentrations decreased sharply with distance. Peak concentrations averaged about 90% higher than the minima along the block. They were accompanied by more frequent and larger transient concentration spikes, increasing the chance of people near the intersection being exposed to both short-term extremely high concentration spikes and higher average concentrations. The decays are somewhat larger before the intersection than after the intersection, however as siting transit stops after intersections is preferred for smooth traffic flow, we focus on after the intersection. Simple time-duration exposure calculations combined with breathing rates suggest moving a bus stop from 20 to 40–50 m after the intersection can reduce transit-users' exposure levels to total UFP substantially, in proportion to the reciprocal of the magnitude of elevation at the intersection.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Roadway pollutant concentrations generally peak within ±30 m from the intersection. </LI> <LI> Pollutant concentrations decrease sharply with distance to local minima at ∼45 m. </LI> <LI> Placing bus stops 40–50 m from intersections significantly reduces UFP Exposure. </LI> <LI> UFP enhancement is correlated queue lengths in the intersections. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Choi, Wonsik,Pratama, Pandu Sandi,Byun, Jaeyoung,Kwon, Soonhong,Kwon, Soongu,Park, Jongmin,Kim, Jongsoon,Chung, Songwon The Korean Society of Industry Convergence 2019 한국산업융합학회 논문집 Vol.22 No.1
An experimental study was conducted on the wear and friction responses in sliding tests of a micro-textured surface on laser pattern (LP) steel as reduction gear material in electric guided vehicle. In this research, the friction characteristics of laser pattern steel under different micro texture density conditions were investigated. The friction tests were carried out at sliding speeds of 0.06 m/s to 0.34 m/s and at normal loads of 2 to 10 N. Photolithography method was used to create the dimples for surface texturing purpose. Four different specimens having different dimple densities of 10%, 12.5%, 15%, and 20% were observed respectively. In this research, friction conditions as shown in Stribeck curve were investigated. Furthermore, the microscopic surface was observed using scanning electron microscope. It was found that the dimple density had a significant role on the friction characteristics of laser pattern steel conditioned as reduction gear material in an agricultural vehicle. The duty number showed that the friction condition was hydrodynamic regime. The best performance was obtained from 12.5% dimple density with lowest friction coefficient achieved at 0.018771 under the velocity of 0.34 m/s and 10N load.
최원식(Wonsik Choi),김원구(Wongu Kim),권주리(Jury Kwon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Our teeth was one of the most important internal organ, Whenever we chewing the food and drink something our teeth undergo various influences on the wearing. In this study we tested the gold alloy dental prosthesis in several lubricant- cola, soju, coffee, toothpaste and milk of the various speed and load conditions. In case of the toothpaste the friction coefficient was very lower and the coffee was the worst in the wearing.