• Title, Summary, Keyword: 미끄러짐 각도

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Lattice Boltzmann Study on Droplet Behavior (격자 볼츠만 방법을 이용한 액적거동 연구)

  • Kim, Kiduk;Byun, Kisang;Jang, Joonkyung
    • New Physics: Sae Mulli
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    • v.67 no.9
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    • pp.1124-1128
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    • 2017
  • The lattice Boltzmann method (LBM) allows various fluid behaviors such as phase separation, evaporation, condensation, heat transfer, and surface-liquid interactions to be modeled. LBM is useful in fluid computations because it can easily construct porous materials and complex structures to calculate the flow of a fluid in the system and has many other advantages. In this study, we investigated the contact angles and the sliding angle of water for varying surface energies on the substrate. We also investigated the formation of a water meniscus between the probe and the substrate, which is relevant to dip-pen nanolithography. In the contact angle and the sliding angle investigations, the contact angle depended on the surface energy, and a very low sliding angle was observed. We also observed that a water meniscus formed between the probe and the substrate.

Experimental Study on the Slip Coefficient with Member Type and Dimensions of High Tension Bolt Hole (부재 및 고장력볼트 구멍치수에 따른 미끄러짐계수의 실험적 연구)

  • Yang, Seung-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.9
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    • pp.4277-4283
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    • 2012
  • Slip coefficient, whose value is dependent on the condition of contact surface at the friction joint of high tension bolt, is determined by slip load. Because contact area affects slip load, contact area that varies with bolt hole size is also related to the slip coefficient. In this study, we manufactured 32 specimens and performed bending and tension tests in order to examine changes in slip coefficient and load with material type, bolt diameter, and size of bolt hole. Slip load of specimens with oversize bolt hole had strength that was more than 80% higher than the slip load of specimens with standard bolt hole, and it also exceeded the design slip strength. In addition, we observed significant correlation between net-section ratio and slip ratio of specimens with oversize and standard bolt hole. However, some differences between the specimens are thought to have been caused by reduction in initial axial force of high tension bolt, which is an important parameter of slip coefficient. It is self-evident that increased bolt hole size would lead to decrease in design strength as it reduces both slip coefficient and bolt axial force. Nevertheless, we suggest that some flexibility in regulation of bolt hole, as long as it does not threaten the structural stability, may be a positive factor in terms of workability and efficiency.

A Study on the Slip Behavior of Coated High Tension Bolted Joints (도장처리한 고장력볼트 연결부의 미끄러짐 특성에 관한 연구)

  • Kyung, Kab Soo;Lee, Seung Yong;Kim, Ki Hyun
    • Journal of The Korean Society of Civil Engineers
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    • v.28 no.5A
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    • pp.691-697
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    • 2008
  • Coating the high tension bolted frictional joint has been generally allowed for anti-corrosion purpose. However in case of painting on paying surface of the high tension bolt, the influence on a slip strength of the joint depending on precision of painting has remained controversial. The study thus was intended to identify the slip behavior on high tension bolted frictional joint when applying ceramic painting, which has been currently developed. A slip test was conducted on a high tension bolted frictional joint specimen on which ceramic painting has been applied and a slip load and slip coefficient were measured. Based on result, the safety and usability of ceramic painting-applied high tension bolted frictional joint was evaluated. As a result, a difference to some extent by specimen in terms of load-displacement when a slip occurred was observed but an average slip coefficient appeared to have exceeded 0.4, which is the design frictional coefficient set forth in the specification. To secure the safety and usability of ceramic painting-applied high tension bolted frictional joint, it's necessary to establish the standard for painting as well as to revise the relevant specification.

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Development and Evaluation of ESP Systems for Enhancement of Vehicle Stability during Cornering (II) (차량의 선회시 주행 안정성 강화를 위한 ESP 시스템 개발 및 성능 평가 (II))

  • Song, Jeong-Hoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.12
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    • pp.1551-1556
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    • 2006
  • Two yaw motion control systems that improve a vehicle lateral stability are proposed in this study: a rear wheel steering yaw motion controller (SESP) and an enhanced rear wheel steering yaw motion controller (ESESP). A SESP controls the rear wheels, while an ESESP steers the rear wheels and front outer wheel to allow the yaw rate to track the reference yaw rate. A 15 degree-of-freedom vehicle model, simplified steering system model, and driver model are used to evaluate the proposed SESP and ESESP. A robust anti-lock braking system (ABS) controller is also designed and developed. The performance of the SESP and ESESP are evaluated under various road conditions and driving inputs. They reduce the slip angle when braking and steering inputs are applied simultaneously, thereby increasing the controllability and stability of the vehicle on slippery roads.

Scenario Analysis of Injection Temperature and Injection Rate for Assessing the Geomechanical Stability of CCS (Carbon Capture and Sequestration) System (이산화탄소 격리저장시스템의 역학적 안정성 평가를 위한 주입온도 및 주입량 시나리오 해석)

  • Kim, A-Ram;Kim, Hyung-Mok
    • Tunnel and Underground Space
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    • v.26 no.1
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    • pp.12-23
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    • 2016
  • For a successful accomplishment of Carbon Capture Sequestration (CCS) projects, appropriate injection conditions should be designed and optimized for site specific geological conditions. In this study, we evaluated the effect of injection conditions such as injection temperature and injection rate on the geomechanical stability of CCS system in terms of TOUGH-FLAC simulator, which is one of the well-known T-H-M coupled analysis methods. The stability of the storage system was assessed by a shear slip potential of the pre-existing fractures both in a reservoir and caprock, expressed by mobilized friction angle and Mohr stress circle. We demonstrated that no tensile fracturing was induced even in the cold CO2 injection, where the injected CO2 temperature is much lower than that of the reservoir and tensile thermal stress is generated, but shear slip of the fractures in the reservoir may occur. We also conducted a scenario analysis by varying injected CO2 volume per unit time, and found out that it was when the injection rate was decreasing in a step-wise that showed the least potential of a shear slip.

Dynamic Interface Friction Behavior Between Soils and Construction Material(Steel) (조립토와 건설재료(steel)사이의 동마찰계수)

  • Kim, Dae-Sang
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.461-468
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    • 2001
  • 지진등에 의해 유발된 동 하중에 의한 지반-구조물 계의 응답은 지반-구조물사이의 경계에서의 마찰특성과 미끄러짐에 의해 크게 영향을 받게 된다 본 논문에서는 진동대(Shaking table)를 이용하여 조립토와 건설재료(Steel)의 경계에서 지반으로부터 지중구조물에 전달되는 전단응력 의 전달정도를 파악하기 위한 실험을 실시하였다. 본 실험에서 설정한 미끌어짐속도 범위내에서는 미끄러짐속도 변화에 따른 조립토와 건설재료(Steel)사이의 동마찰계수의 변화가 작다는 사실이 관찰되었다. 그리고 조립토의 평균유효입경의 변화가 동마찰계수에 미치는 영향도 함께 조사되었다. 또한 이 동마찰계수를 같은 조립토에 대한 평면변형률시험을 통해 얻어진 최대내부마찰각으로부터 구한 마찰계수와 비교하여 정량화하였다.

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Dynamic Friction Behavior of Interfaces Between Granular Materials and Steel (조립토와 건설재료(steel)사이의 동마찰계수)

  • 김대상
    • Journal of the Korean Geotechnical Society
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    • v.17 no.3
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    • pp.33-39
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    • 2001
  • 지진 등에 의해 유발된 동 하중에 의한 지반-구조물 계의 응답은 지반-구조물사이의 경계에서의 마찰특성과 미끄러짐에 의해 크게 영향을 받게 된다. 본 논문에서는 진동대(Shaking table)를 이용하여 조립토와 건설재료(steel)와의 경계에서 지반으로부터 지중구조물에 전달되는 전단응력의 전달정도를 파악하기 위한 실험을 실시하였다. 본 실험에서 설정한 미끄러짐속도 범위 내에서는 미끄러짐속도 변화에 따른 조립토와 건설재료(steel) 사이의 동마찰계수의 변화가 작다는 사실이 관찰되었다. 그리고 조립토의 평균유효입경의 변화가 동마찰계수에 미치는 영향도 함께 조사되었으며, 이 동마찰계수를 같은 조립토에 대한 평면변형률시험을 통해 얻어진 최대내부마찰각으로부터 구한 마찰계수와 비교하여 정량화하였다.

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Development of Vehicle Integrated Dynamics Control System with Brake System Control (제동 장치를 이용한 차량통합운동제어시스템 개발)

  • Song, Jeonghoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.7
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    • pp.591-597
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    • 2017
  • This study is to develop a vehicle Integrated Dynamics Control System(IDCB) that can stabilize the lateral dynamics and maintain steerability. To accomplish this task, an eight degree of freedom vehicle model and a nonlinear observer are designed. The IDCB independently controls the brake systems of four wheels with a fuzzy logic control and a sliding model control. The result shows that the nonlinear observer produced satisfactory results. IDCB tracked the reference yaw rate and reduced the body slip angle under all tested conditions. It indicates that the IDCB enhanced lateral stability and preserved steerability.

Effect of Bending Angle and Embedment Length on the Bond Characteristics of V-shaped Tie Reinforcement (절곡각 및 묻힘길이에 따른 V형 띠철근의 부착특성)

  • Kim, Won-Woo;Yang, Keun-Hyeok
    • Journal of the Korea Institute of Building Construction
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    • v.15 no.5
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    • pp.465-471
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    • 2015
  • This study proposed V-shaped tie bar method as an alternative of internal cross-tie for reinforced concrete columns in order to enhance the constructability and confinement effectiveness of the lateral tie bars. A total of 35 pull-out specimens were prepared with the parameters of concrete compressive strength and bending angle and embedment length of the V-shaped bar to examine the bond stress-slip relationship of the V-shaped tie bar. The bond strength of the V-shaped tie bars with the bending angle not exceeding $60^{\circ}$ was higher than the predictions obtained from the equations of CEB-FIP provision. Considering the constructability and bond behavior of the V-shpaed tie bar, the bending angle and embedment length of such bar can be optimally recommended as $45^{\circ}$ and 6db, respectively, where db is the diameter of the tie bar.

Stress Distribution Under Line Load in Transversely Isotropic Rock Mass (평면이방성 암반에서 선하중에 의한 응력분포 특성)

  • Lee Youn-Kyou
    • Tunnel and Underground Space
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    • v.15 no.4
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    • pp.288-295
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    • 2005
  • Many mechanical defects originated from various geological causes make rock mass exhibit anisotropic characteristics. Understanding how the stress distribution occurs in anisotropic rock mass is, therefore, very important for the design of footings on rock and rock structures. In this study, the patterns of elastic stress distribution, developed by acting line load on the surface, in transversely isotropic was investigated. The influence of joint stiffness, joint spacing, and dip angle on the stress distribution was examined. By assuming the Mohr-Coulomb criterion as joint slip condition, the development of joint slip zone was also discussed.