• 제목/요약/키워드: Rate dependent friction

검색결과 34건 처리시간 0.025초

A CONVERGENCE RESULTS FOR ANTIPLANE CONTACT PROBLEM WITH TOTAL SLIP RATE DEPENDENT FRICTION

  • AMMAR, DERBAZI
    • Journal of applied mathematics & informatics
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    • 제39권5_6호
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    • pp.813-823
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    • 2021
  • In this work, we present the classical formulation for the antiplane problem of a eletro-viscoelastic materialswith total sliprate dependent friction and write the corresponding variational formulation. In the second step, we prove that the solution converges to the solution of the corresponding electro-elastic problem as the viscosity converges to zero.

마찰해석모델에 따른 PVDF/MgO 마찰재 적용 면진 장치가 설치된 교량의 성능 비교 분석 (Performance Comparison Analysis of a Bridge Installed with Anti-seismic Devices using PVDF/MgO Friction Material According to Friction Analysis Models)

  • 박혜리;김성조;한동석
    • 한국전산구조공학회논문집
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    • 제36권2호
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    • pp.105-112
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    • 2023
  • 본 연구에서는 마찰모델에 따라 다른 마찰진자시스템(FPS)이 적용된 교량의 성능을 비교·분석하기 위해 구조해석을 수행하였다. 마찰해석모델 별 성능을 분석하기 위해 PVDF/MgO 마찰재의 마찰계수를 활용하여 쿨롱 마찰모델과 속도 의존 마찰모델을 구축했다. 쿨롱 마찰모델은 마찰속도와 관계없이 단일 마찰계수를 사용하며, 속도 의존 마찰모델은 마찰속도에 따른 마찰계수의 변화를 반영하는 마찰모델이다. 지진해석으로 비선형 시간 이력 해석과 지진 취약도 해석을 수행하여 구조물의 응답을 확인하였다. 마찰모델에 따른 바닥판과 교각의 지진 응답을 활용해 면진된 교량의 성능을 분석하였으며, 면진된 교량의 성능을 효과적으로 평가할 수 있는 마찰모델을 분석했다.

Friction of a Brownian Particle in a Lennard-Jones Solvent: A Molecular Dynamics Simulation Study

  • Lee, Song-Hi
    • Bulletin of the Korean Chemical Society
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    • 제31권4호
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    • pp.959-964
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    • 2010
  • In this work, equilibrium molecular dynamics (MD) simulations in a microcanonical ensemble are performed to evaluate the friction coefficient of a Brownian particle (BP) in a Lennard-Jones (LJ) solvent. The friction coefficients are determined from the time dependent friction coefficients and the momentum autocorrelation functions of the BP with its infinite mass at various ratios of LJ size parameters of the BP and solvent, ${\sigma}_B/{\sigma}_s$. The determination of the friction coefficients from the decay rates of the momentum autocorrelation functions and from the slopes of the time dependent friction coefficients is difficult due to the fast decay rates of the correlation functions in the momentum-conserved MD simulation and due to the scaling of the slope as 1/N (N: the number of the solvent particle), respectively. On the other hand, the friction coefficient can be determined correctly from the time dependent friction coefficient by measuring the extrapolation of its long time decay to t=0 and also from the decay rate of the momentum autocorrelation function, which is obtained by time integration of the time dependent friction coefficient. It is found that while the friction coefficient increases quadratically with the ratio of ${\sigma}_B/{\sigma}_s$ for all ${\sigma}_B$, for a given ${\sigma}_s$ the friction coefficient increases linearly with ${\sigma}_B$.

Rate-dependent shearing response of Toyoura sand addressing influence of initial density and confinement: A visco-plastic constitutive approach

  • Mousumi Mukherjee;Siddharth Pathaka
    • Geomechanics and Engineering
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    • 제34권2호
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    • pp.197-208
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    • 2023
  • Rate-dependent mechanical response of sand, subjected to loading of medium to high strain rate range, is of interest for several civilian and military applications. Such rate-dependent response can vary significantly based on the initial density state of the sand, applied confining pressure, considered strain rate range, drainage condition and sand morphology. A numerical study has been carried out employing a recently proposed visco-plastic constitutive model to explore the rate-dependent mechanical behaviour of Toyoura sand under drained triaxial loading condition. The model parameters have been calibrated using the experimental data on Toyoura sand available in published literature. Under strain rates higher than a reference strain rate, the simulation results are found to be in good agreement with the experimentally observed characteristic shearing behaviour of sand, which includes increased shear strength, pronounced post-peak softening and suppressed compression. The rate-dependent response, subjected to intermediate strain rate range, has further been assessed in terms of enhancement of peak shear strength and peak friction angle over varying initial density and confining pressure. The simulation results indicate that the rate-induced strength increase is highest for the dense state and such strength enhancements remain nearly independent of the applied confinement level.

Flow and Heat Transfer Analysis of Copper-water Nanofluid with Temperature Dependent Viscosity Past a Riga Plate

  • Ahmad, A.;Ahmed, S.;Abbasi, F.M.
    • Journal of Magnetics
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    • 제22권2호
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    • pp.181-187
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    • 2017
  • Flow of electrically conducting nanofluids is of pivotal importance in countless industrial and medical appliances. Fluctuations in thermophysical properties of such fluids due to variations in temperature have not received due attention in the available literature. Present investigation aims to fill this void by analyzing the flow of copper-water nanofluid with temperature dependent viscosity past a Riga plate. Strong wall suction and viscous dissipation have also been taken into account. Numerical solutions for the resulting nonlinear system have been obtained. Results are presented in the graphical and tabular format in order to facilitate the physical analysis. An estimated expression for skin friction coefficient and Nusselt number are obtained by performing linear regression on numerical data for embedded parameters. Results indicate that the temperature dependent viscosity alters the velocity as well as the temperature of the nanofluid and is of considerable importance in the processes where high accuracy is desired. Addition of copper nanoparticles makes the momentum boundary layer thinner whereas viscosity parameter does not affect the boundary layer thickness. Moreover, the regression expressions indicate that magnitude of rate of change in effective skin friction coefficient and Nusselt number with respect to nanoparticles volume fraction is prominent when compared with the rate of change with variable viscosity parameter and modified Hartmann number.

FRP 선박 외판재의 연삭마모 특성에 관한 연구 (A study on abrasive wear characteristics of side plate of FRP ship)

  • 김병탁;고성위
    • 수산해양기술연구
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    • 제44권3호
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    • pp.250-256
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    • 2008
  • Generally the side plate materials of FRP ship are composed of glass fiber and unsaturated polyester resin composites(GFRP composites). In this study, the effect of applied load and sliding speed on friction and wear characteristics of these materials were investigated at ambient temperature by pin-on-disc friction test. The cumulative wear volume, friction coefficient and wear rate of these materials for SiC abrasive paper were determined experimentally. The cumulative wear volume showed a tendency to increase nonlinearly with increase of sliding distance and was dependent on applied load and sliding speed for these composites. The friction coefficient of GFRP composites was increased as applied load increased at same sliding speed in wear test. It was verified by SEM photograph of worn surface that major failure mechanisms were microfracture, deformation of resin, cutting and cracking.

Al계 준결정 분말의 제조 및 응용

  • Kim, W. T.;Kim, D.H.;Lee, S.M.;E.Fleury;H.S. Ahn
    • 한국분말야금학회:학술대회논문집
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    • 한국분말야금학회 2002년도 제3회 최신 분말제품 응용기술 Workshop
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    • pp.133-155
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    • 2002
  • 1. Quasicrystalline powders shows exotic physical and mechanical p properties 2. Applications: structural application: strengthening particles for composites C Coating application: wear resistance, low friction coefficient 3. For thermal spaying: material loss during process should be c considered to control chemical composition of deposit 4. Friction coefficient is strongly dependent on contact geometry F Friction coefficient from pin on plate: 0.1-0.2 Friction coe야icient from flat on plate: about 0.46. 5. Quasicrystalline materials show lower friction coefficient but higher w wear rate than corresponding values of $Cr_20_3$ coated layer. 6. Amorphous coating seems to be promising

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건축용 막 재료의 트라이볼로지적 고찰 (Tribological Performace of Architectural Fabrics)

  • 최원식;이인;박강근
    • Tribology and Lubricants
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    • 제24권2호
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    • pp.72-76
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    • 2008
  • There are 5 kinds of architectural fabrics in our country recently. The test piece were made by attaching on the steel disk which has been tested of various range of the test conditions in pin-on-disk wear testing machine. The results show that the friction coefficient and wear rate of the architectural fabrics are heavily dependent on the load and materials. PVDF type was better than others in wear rate and friction coefficient.

유전 알고리듬을 이용한 매니퓰레이터 조인트의 마찰력 규명 및 실험적 검증 (Manipulator Joint Friction Identification using Genetic Algorithm and its Experimental Verification)

  • 김경호;박윤식
    • 대한기계학회논문집A
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    • 제24권6호
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    • pp.1633-1642
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    • 2000
  • Like many other mechanical dynamic systems, flexible manipulator systems experience stiction or sticking friction, which may cause input-dependent instabilities. Manipulator performance can be enha nced by identifying friction but it is hard and expensive to measure friction by direct and precise sensing of contact displacements and forces. This study addresses the problem of identifying flexible manipulator joint friction. A dynamic model of a two-link flexible manipulator based upon finite element and Lagrange's method is constructed. The dynamic model includes the effects of joint compliances and actuator dynamics. Friction is also incorporated in the dynamic model to account for stick-slip at the joints. Next, the friction parameters are to be determined. The identification problem is posed as an optimization problem to be solved using nonlinear programming methods. A genetic algorithm is used to increase the convergence rate and the chances of finding the global optimum. The identified friction parameters are experimentally verified and it is expected that the identification technique is applicable to a system parameter identification problem associated with a wide class of nonlinear systems.

동압축 하중을 받는 재료의 고변형도율에서의 마찰영향 (The friction effects at high strain rates of materials under dynamic compression loads)

  • 김문생
    • 대한기계학회논문집
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    • 제11권3호
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    • pp.454-464
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    • 1987
  • 본 연구에서는 충격하중하에서 고변형도 .epsilon.=ln(h/h$_{o}$ )>1.0, 고변형도율 (.epsilon.>$10^{3}$m/s/m)로 변형하는 재료에 대하여 응력, 변형도, 변형도율사이의 함수관 계를 유도하고, 다음과 같은 현상들을 규명하였다. (1) 고변형도율에서 응력, 변형 도, 변형도율사이의 함수관계식 유도. (2) 압축하중시 시편과 접촉부재사이의 접촉면 에서 발생하는 마찰영향의 조사. (3) 유동응력과 시편의 기하학적 형상사이의 관계식 유도. (4) 압축하중시 재료의 제동현상(lock-up phenomena)의 해석.