• Title, Summary, Keyword: Rough surface

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Study on the Fatigue Crack Initiation Life uncle]r 3-Dimensional Rough Contact (3차원 거친 접촉하에서의 피로균열 시작수명에 관한 연구)

  • 김태완;구영필;조용주
    • Tribology and Lubricants
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    • v.18 no.2
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    • pp.160-166
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    • 2002
  • In case of rough contact fatigue, the accurate calculation of surface tractions is essential to the prediction of crack initiation life. Accurate Surface tractions influencing shear stress amplitude can be obtained by contact analysis based on the morphology of contact surfaces. In this study, to simulate rough contact under sliding condition, gaussian rough surface generated numerically in the previous study was used and to calculate clack initiation life in the substrate, dislocation pileup theory was used.

The Fatigue Crack Initiation Life under the Rolling Contact of Rough Surfaces using Critical Plane Approach (임계평면법을 이용한 거친 표면의 구름접촉시 피로균열 시작수명)

  • 설광조;김태완;조용주
    • Tribology and Lubricants
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    • v.19 no.1
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    • pp.26-30
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    • 2003
  • The stresses of surface and substrate under the rough surface contact are irregular. Using rainflow counting method for irregular stresses, the fatigue surface crack initiation lift was calculated. With the surface generated by computer, this paper figures out the random load generated by contacting to the rough surface, analyzes the stress of its subsurface, and calculates the fatigue crack initiation life of the rough surface fatigue theory.

A study for improve MCPs product surface about injection process (MCPs 사출 제품의 Gate 부근에 발생하는 Gas Flow Mark 개선을 위한 사출성형 공정 연구)

  • Hyun C.H.;Cha S.W.;Lee D.W.;Park Y.W.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.1710-1714
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    • 2005
  • Micro Cellular Plastics create a sensation at polymer industrial for lowering product cost & overcoming a lowering of mechanical intensity. This research is surface quality research of MCPs product Through surface rough measurement. This experiment is carried out according to injection speed control with the surface rough & Product surface quality are searched

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A study on Rough machining path generation of sculptured surface by bisection method (이분법에 의한 자유곡면 황삭가공 경로산출에 관한 연구)

  • 신동혁;주종남
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.157-163
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    • 1995
  • This paper presents an algorithm to deternine the tool path height for rough machining of sculptured surface. To minimize rough machining of sculptured surface, it is necessary to determine the tool path heights of contour planes. the proposed algorithm searches for the height at which maximum metal removal rate is obtained. This bisection method is accomplished until all shoulder heights are within roughing tolerance. The machining experiment demonstrates the superiority of the algorithm presented in this thesis.

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Analysis of Surface Forces in Micro Contacts between Rough Surfaces (거친 표면간의 미세 접촉에서의 표면력 해석)

  • Kim, Doo-In;Ahn, Hyo-Sok;Choi, Dong-Hoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.10
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    • pp.2180-2186
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    • 2002
  • In a micro-scale contact, capillary force and van der Waals interaction significantly influence the contact between asperities of rough surfaces. Little is, however, known about the variation of these surface forces as a function of chemical property of the surface (wet angle), relative humidity and deformation of asperities in the real area of contact. A better understanding of these surface forces is of great necessity in order to find a solution for reducing friction and adhesion of micro surfaces. The objective of this study is to investigate the surface forces in micro-scale rough surface contact. We proposed an effective method to analyze capillary and van der Waals forces in micro-scale contact. In this method, Winkler spring model was employed to analyze the contact of rough surfaces that were obtained from atomic force microscopy (AFM) height images. Self-mated contact of DLC(diamond like carbon) coatings was analyzed, as an example, by the proposed model. It was shown that the capillary force was significantly influenced by relative humidity and wet angle of the DLC surface. The deformation of asperities to a critical magnitude by external loading led to a considerable increase of both capillary and van der Waals forces.

Analysis of Electromagnetic Wave Propagation from 2 Dimensional Random Rough Surfaces (2차원 불규칙 조면에서의 전자파 전파 해석)

  • Yoon, Kwang-Yeol
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.6
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    • pp.1114-1119
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    • 2010
  • This paper is concerned with an numerical analysis of electromagnetic wave propagation from randomly rough surfaces as a desert, sea surface and so on. We propose discrete ray tracing method (DRTM) for analysis of characteristics of wave propagation along one dimensional (1D) and two dimensional (2D) random rough surfaces. The point of the present method is to discretize not only rough surface but also ray tracing. This technique helps saving computer memories and does simplifying ray searching algorithm resulting in saving computation time. Numerical calculations are carried out for 1D and 2D random rough surfaces and electric field distributions are shown to check the effectiveness of the proposed DRTM.

Transition of Turbulent Boundary Layer with a Step Change from Smooth to Rough Surface (표면 형상 변화에 따른 난류경계층 유동장 분석)

  • Lee, Jae Hwa
    • Journal of the Korean Society of Visualization
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    • v.12 no.3
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    • pp.15-20
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    • 2014
  • Direct numerical simulation (DNS) dataset of a turbulent boundary layer (TBL) with a step change from smooth to rough surface is analyzed to examine spatially developing flow characteristics. The roughness elements are periodically arranged two-dimensional (2-D) spanwise rods with a streamwise pitch of ${\lambda}=8k$ ($=12{\theta}_{in}$), and the roughness height is $k=15{\theta}_{in}$, where ${\theta}_{in}$ is the inlet momentum thickness. The step change is introduced $80{\theta}_{in}$ downstream from the inlet. For the first time, full images from the DNS data with the step change from the smooth to rough walls is present to get some idea of the geometry of turbulent coherent structures over rough wall, especially focusing on their existence and partial dynamics over the rough wall. The results show predominance of hairpin vortices over the rough wall and their spanwise scale growth mechanism by merging.

Study on the Fatigue Crack Initiation Life under 3-Dimensional Rough Contact (3차원 거친 접촉하에서의 피로균열 시작수명에 관한 연구)

  • 이문주;구영필;조용주
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.72-79
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    • 2000
  • In case of rough contact fatigue, the accurate calculation of surface tractions is essential to the prediction of crack initiation life. Accurate Surface tractions influencing shear stress amplitude can be obtained by contact analysis based on tile morphology of contact surfaces. In this study, to simulate rough contact under sliding condition, gaussian rough surface generated numerically in the previous study was used and to calculate crack initiation life in the substrate, dislocation pileup theory was used.

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Electromagnetic Wave Propagation Characteristics from Large Scale Random Rough Surfaces (큰 규모의 불규칙 조면에 의한 전자파 전파 특성)

  • Yoon Kwang-Yeol;Chai Yong-Yoong
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.4
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    • pp.393-399
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    • 2006
  • In this paper we applied a ray tracing method to estimate the scattering characteristics from large scale random rough surfaces. For the electromagnetic field evaluation, we have used the diffracted coefficient of the knife edge diffraction for the diffracted rays and Fresnel's reflection coefficients in connection with reflected rays. In addition, we examine to search for the traced rays using the imaging method which can be obtained all rays to arrived at receivers accurately and the diffracted field from rough surfaces is considered. Numerical examples have been carried out for the scattering characteristics of an ocean wave-like rough surface and delay spread characteristics of a building-like surface. In the present work we have demonstrated that the ray tracing method is effective to numerical analysis of a rough surface scattering.

Comparison of the Numerical, Theoretical, and Empirical Scattering Models for Randomly Rough Surfaces

  • Hong Jin-Young;Oh Yisok
    • Proceedings of the KSRS Conference
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    • pp.725-728
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    • 2005
  • The scattering problem of the randomly rough surface is examined by the method of moments(MoM), small perturbation method (SPM), integral equation method (IEM) and the semi-empirical polarimetic model. To apply the numerical technique of the MoM to microwave scattering from a rough surface, at first, many independent randomly rough surfaces with a rms height and a correlation length are generated with Gaussian random deviate. Then, an efficient Monte Carlo simulation technique is applied to estimate the scattering coefficients of the surfaces.

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