• Title/Summary/Keyword: surface roughness model

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다이아몬드 공구를 사용한 선삭 가공에서의 표면 형상 예측

  • 윤영식;이상조
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1993.04b
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    • pp.102-107
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    • 1993
  • The achievable machining accuracy depends upon the level of the micro-engineering, and the dimensional tolerances in the order of 10nm and surface roughness in the order of 1nm are the accuracytargets to be achieved today. Suchrequirements cannot be satisfiedby the conventional machining processes. Single point diamond turning is one of the new techniques which can produce the parts with such accuracy limits. The aims of this thesis are to get a better understanding of the complex cutting process with a diamond tool and, consequently, to develope a predicting modelof a turned surface profile. In order to predict the turned surface profile, a numerical model has been developed. By means of this model, the influences of the cutting conditions, the material properties of the workpiece, the geometry of the cutting tool and the dynamic behaviour of the lathe and their influences via the cutting forces upon the surface roughness have been estimated.

The Contact Fatigue Life Analysis of Rough Surfaces (거친 표면의 접촉피로 수명예측)

  • Chu Hyo-Jun;Lee San-Don;Cho Yong-Joo
    • Tribology and Lubricants
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    • v.21 no.3
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    • pp.136-141
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    • 2005
  • Analytical model to calculate the contact fatigue life of rough surface is presented in this paper. The effect of surface roughness can be calculated by this model. Computational method and the theoretical basis are also discussed. Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions; the subsurface stress field is obtained using rectangular patch solutions. Mesoscopic multiaxial fatigue criterion which can yield satisfactory results for non-proportional loading is then applied to predict fatigue damage. Suitable counting method and damage rule were used to calculate the fatigue life of random loading caused by rough surface. As a result of analysis the relationship between the life and the roughness as well as the most probable depth of the crack initiation is calculated.

Jewelry Model Cast Elements Evolution with Alignment Angle in DuraForm Rapid Prototyping (쾌속조형 듀라폼 성형체에서의 배치각 변화에 따른 주얼리주조모형의 형상요소변화)

  • Joo, Young-Cheol;Song, Oh-Sung
    • Journal of Korea Foundry Society
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    • v.21 no.5
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    • pp.290-295
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    • 2001
  • We fabricated test samples containing various shape elements and surface roughness checking points for the jewelry cast master patterns by employing the 3D computer aided design (CAD), selective laser sintering (SLS) rapid prototype (RP) with the DuraForm powders. We varied the alignment angle from 0 to 10 at a given layer thickness of 0.08 and 0.1mm, respectively, in RP operation. Dimensions of the shape elements as well as values of surface roughness are characterized by an optical microscope and a contact-scanning profilometer. Surface roughness values of the top and vertical face increased as the alignment angle increased, while the other roughness values and shape elements variation were not depending on the alignment angle. The resolution of the shape realization was enhanced as the layer thickness became smaller. The minimum diameter of the hole, common in jewelry design, was 1.2 mm, and the shrinkage became 12% at the 1.6 mm-diameter hole, Our results implied that we face down the proposed design elements with 0 alignment angle, and consider the shrinkage effect of each shape element in DuraForm RP jewelry modeling.

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Friction Model for Finite Element Analysis of Sheet Metal Forming Processes (박판 성형공정 유한요소 해석용 마찰모델)

  • Keum Y.T.;Lee B.H.
    • Transactions of Materials Processing
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    • v.13 no.6 s.70
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    • pp.528-534
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    • 2004
  • In order to find the effect of lubricant viscosity, tool geometry, forming speed, and sheet material properties on the friction in the sheet metal forming, friction tests were performed. Friction test results show that as the lubricant viscosity becomes lower, the friction coefficient is higher. When surface roughness is extremely low or high, the friction coefficient is high. The bigger die corner radii and punch speed are, the smaller is the friction coefficient. From the experimental observation, the friction model which is the mathematical expression of friction coefficient in terms of lubricant viscosity, roughness and hardness of sheet surface, punch corner radius, and punch speed is constructed. By comparing the punch load found by FEM using the proposed friction model with that obtained from the experiment in 2-D stretch forming, the validity and accuracy of the friction model are demonstrated.

Analysis of Contact Stiffness and Bending Stiffness according to Contact Angle of Curvic Coupling (곡률 커플링 접촉각에 따른 접촉 강성 및 굽힘 강성해석)

  • Yu, Yonghun;Cho, Yongjoo;Lee, Donghyun;Kim, Young-Cheol
    • Tribology and Lubricants
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    • v.34 no.1
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    • pp.23-32
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    • 2018
  • Coupling is a mechanical component that transmits rotational force by connecting two shafts. Curvic coupling is widely used in high-performance systems because of its excellent power transmission efficiency and easy machining. However, coupling applications change dynamic behavior by reducing the stiffness of an entire system. Contact surface stiffness is an important parameter that determines the dynamic behavior of a system. In addition, the roughness profile of a contact surface is the most important parameter for obtaining contact stiffness. In this study, we theoretically establish the process of contact and bending stiffness analysis by considering the rough surface contact at Curvic coupling. Surface roughness parameters are obtained from Nayak's random process, and the normal contact stiffness of a contact surface is calculated using the Greenwood and Williamson model in the elastic region and the Jackson and Green model in the elastic-plastic region. The shape of the Curvic coupling contact surface is obtained by modeling a machined shape through an actual machining tool. Based on this modeling, we find the maximum number of gear teeth that can be machined according to the contact angle. Curvic coupling stiffness is calculated by considering the contact angle, and the calculation process is divided into stick and slip conditions. Based on this process, we investigate the stiffness characteristics according to the contact angle.

Proposed surface modeling for slip resistance of the shoe-floor interface

  • Kim, In-Ju
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • 1995.04a
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    • pp.515-528
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    • 1995
  • Slips and falls are the major causes of the pedestrian injuries in the industry and the general community throughout the world. With the awareness of these problems, the friction coefficients of the interface between floorings and footwear have been measured for the evaluation of slip resistant properties. During this measurement process, the surface texture has been shown to be substantially effective to the friction mechanism between shoe heels and floor surfaces under various types of walking environment. Roughness, either of the floor surface or shoe heels, provides the necessary drainage spaces. This roughness can be designed into the shoe heel but this is inadequate in some cases, especially a wear. Therefore, it is essential that the proper roughness for the floor surface coverings should be provided. The phenomena that observed at the interface between a sliding elastomer and a rigid contaminated floor surface are very diverse and combined mechanisms. Besides, the real surface geometry is quite complicate and the characteristics of both mating surfaces are continuously changing in the process of running-in so that a finite number of surface parameters can not provide a proper description of the complex and peculiar shoe - floor contact sliding mechanism. It is hypothesised that the interface topography changes are mainly occurred in the shoe heel surfaces, because the general property of the shoe is soft in the face of hardness compared with the floor materials This point can be idealized as sliding of a soft shoe heel over an array of wedge-shaped hard asperities of floor surface. Therefore, it is considered that a modelling for shoe - floor contact sliding mechanism is mainly depended upon the surface topography of the floor counterforce. With the model development, several surface parameters were measured and tested to choose the best describing surface parameters. As the result, the asperity peak density (APD) of the floor surface was developed as one of the best describing parameters to explain the ambiguous shoe - floor interface friction mechanism. It is concluded that the floor surface should be continuously monitored with the suitable surface parameters and kept the proper level of roughness to maintain the footwear slip resistance. This result can be applied to the initial stage of design for the floor coverings.

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Precise Measurement Method and Error Analysis with Roughness Variables for Estimation of Scattering Coefficients (지표면 산란 계수 예측을 위한 정확한 지표면 거칠기 변수 측정 방법 및 오차 분석)

  • Kweon, Soon-Koo;Hwang, Ji-Hwan;Oh, Yisok;Hong, Sungwook
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.24 no.1
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    • pp.91-97
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    • 2013
  • The input parameters of scattering models for computing the backscattering coefficients of earth terrains are mainly soil moisture and surface roughness. The backscattering coefficients of soil surfaces are more sensitive to surface roughness than soil moisture. In this study, we propose a precise measurement method for roughness parameters and analyze measurement errors. We measured surface roughness using a pin-board profiler(1 m, 0.5 cm interval) and a laser profiler(1 m, 0.25 cm interval). The measurement differences between two profilers in an average sense are 0.097 cm for root-mean-square (RMS) height and 1.828 cm for correlation length. The analysis of the correlation functions and relative errors shows that the laser measurements are more stable than the pin-board measurements. The differences of the calculated backscattering coefficients using a surface scattering model between pin-board and laser profiler measurements are less than 1 dB.

Steady Simulations of Impeller-Diffuser Flow Fields in Turbocompressor Applications (터보 압축기 임펠러-디퓨저 운동장에 대한 정상상태 해석)

  • Nam, S.S.;Park, I.Y.;Lee, S.R.;Ju, B.S.;Hwang, Y.S.;In, B.S.
    • 유체기계공업학회:학술대회논문집
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    • 2005.12a
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    • pp.405-412
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    • 2005
  • Numerical and experimental investigations were conducted to assess the aerodynamic performance of several centrifugal compressors. In order to impose an appropriate physics at the interface between impeller and vaned diffuser numerically, two different techniques, frozen rotor and stage models, were applied and the simulation results were compared with the corresponding prototype test data. An equivalent sand-grain roughness height was utilized in the present computational study to consider a relative surface roughness effect on the stage performance simulated. From a series of investigations, it was found that the stage model is more suitable than the frozen rotor scheme for the steady interactions between impeller and diffuser in turbocompressor applications. It is supposed that the solution by frozen rotor scheme is inclined to overrate the non-uniformity of the flow fields. The predicted aerodynamic performance accounting for surface roughness effect shows favorable agreement with experimental data. Simulations based on the aerodynamically smooth surface assumption tend to overestimate the stage performance.

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Study on surface roughness by emanation and part angle changing at FDM (FDM 장치에서 주사량과 시제품의 경사가 표면거칠기에 미치는 영향)

  • 권광진;전재억;정진서;김광희;하만경
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2001.04a
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    • pp.300-305
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    • 2001
  • Competitive power is rapidly manufacture product required consumers. Therefore, modern industry have changed from small item many production to many item small production. rapid production is necessary thing at the product development. Thus, rapid prototyping is appeared. If the graphic model was made by CAD, the production can be made in short term. That provide what the part was directly tested by the worker. It provide believable data. This study is experiment on surface roughness of part at FDM

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Evaluation of Pre-estimation Model to the Inprocess Surface Roughness for Grinding Operations (연삭가동용 Inprocess 표면조도 예측모델의 평가)

  • 김건희
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1998.03a
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    • pp.11-18
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    • 1998
  • In grinding operations, one of the most important problems is to increase efficiency of process. In order to achive this purpose, it is necessary to administer the tool life of grinding wheel and to optimize grinding conditions. Frequently dressing result in lowering the process efficiency remarkably and makes production cost high. On the other hand, grinding with a worn wheel causes the workpiece surface roughness to increase and often results in the occurrence of such troubles as chatter vibration and burning.

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