• 대한치과교정학회지
• /
• 제21권3호
• /
• pp.543-560
• /
• 1991

Practitioners are aware of the presence of friction between bracket system and archwire during sliding movement of teeth. Clinically a mesiodistally applied force must exceed the frictional force to produce a tooth movement. The objective of this study were to determine, on a dry condition, changes in magnitude of friction with respect to load, 3rd order inclination (Torque), archwire materials and ligature type. Three wire alloys (Stainless Steel, TMA, NiTi) in two wire sizes (.016, .016x, .022 inch) were examined respect to two bracket system (Straight, Standard), and two ligature type (Metal, Plastic ligature) at three levels of load (100g, 150g, 200g). The results were as follows; 1. Frictional resistance was found to increase with increasing load for S.S., TMA, NiTi. 2. The straight bracket system was exhibited more frictional force than standard bracket system for .016x, .022 S.S. tightly ligated metal ligature. But, torque difference did not increase friction for loose metal ligature & plastic ligature. 3. Regardless of the ligature type, torque and load, stainless steel wire sliding against stainless steel exhibited the lowest friction, and TMA sliding against stainless steel exhibited the highest friction. 4. The loose stainless steel ligature generated lower frictional resistance than plastic ligature in all experimental groups. 5. The following factors affected friction in decreasing order; wire material ligature type, and load.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
• /
• pp.193-194
• /
• 2002

The frictional characteristics of natural rubber plates under various conditions including sliding speed, contacted ball size, and lubrication conditions were evaluated experimentally. The frictional force and the normal force were measured by a self-made tester pin and a load cell with strain gages. In the lubrication condition, the effect of sliding speed was not significant over tested speed range. But in the none-lubrication condition, according to increase the sliding speed, the friction coefficient was decreased. The coefficients of friction under various lubrication conditions were varied from 0.03 to 0.32 and under none-lubrication condition was varied from 2.54 to 4.74.

• Tribology and Lubricants
• /
• 제11권3호
• /
• pp.48-53
• /
• 1995

In this paper, the friction characteristics of contact region between vane tip and camring is studied using a modeled experimental device. The contact region is under the influence of variable loads with the amplitude of hundreds of Newton and frequency of tens of Hz. The condition of lubrication between vane and disk is modeled after the actual condition between vane and camring. The coefficient of friction is obtained by measuring the frictional forces in the contact region between camring and vane. The friction characteristics of the actual oil hydraulic vane pump is estimated on the basis of coefficient of friction. The analysis of frictional characteristics shows us that the lubrication condition of vane tip is that of transition regime between hydrodynamic lubrication and mixed lubrication.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1997년도 추계학술대회논문집
• /
• pp.24-27
• /
• 1997

In the present work, rigid-plastic continuum elements employing the shape change and anisotropic effects are derived for the purpose of applying more realistic blankholding force condition in three-dimensional finite element analysis of sheet metal forming process. In order to incorporate the effect of shape change effectively in the derivation of finite element equation using continuum element for sheet metal forming, the convected coordinate system is introduced, rendering the analysis more rigorous and accurate. The formulation is extended to cover the orthotropic material using Hill's quadratic yield function. For the purpose of applying more realistic blankholding force condition, distributed normal and associated frictional tangent forces are employed in the blankholder, which is pressed normal and associated frictional tangent forces are employed in the blankholder, which is pressed against the flange until the resultant contact force with the blank reaches the prescribed value. As an example of sheet metal forming process coupling the effect of planar anisotropy and that of blankholding boundary condition, circular cup deep drawing has been analyzed considering both effects together.

• 감성과학
• /
• 제8권4호
• /
• pp.385-391
• /
• 2005

화장품을 바를 때 피부와 손가락 사이에서 일어나는 마찰계수는 화장품의 주관적 평가에 많은 영향을 주는 요소이다. in-vivo상태에서 피부와 접촉자 간의 마찰계수는 접촉자의 모양이나 거칠기의 정도 그리고 누르는 하중에 따라 변할 수 있다. 본 실험에서는 리니어 모터와 다축 로드셀을 이용하여 여러 가지 접촉자를 in-vivo상태에서 직접 피부에 접촉시키고 실시간으로 마찰계수를 측정할 수 있는 장치를 개발하였다. 이 장치를 이용하여 피부와 접촉자 간의 마찰계수를 측정하고 그 데이터를 화장품을 바를 때의 전후와 비교$\cdot$분석하였다. 또한 화장품을 바를 때 주관적인 평가에서 이용되는 형용사를 조사하며 마찰계수와의 그 상관관계를 분석하였다. 그 결과, 피부와 접촉자 간의 마찰계수는 화장품의 종류와 접촉자의 성질에 따라 0.17-1.2사이에서 나타나며, 주관적인 평가 또한 화장품을 바른 후 시간의 경과함에 따라 변하며, 그것은 마찰계수와 관련이 있음을 확인할 수 있었다.

• 소성∙가공
• /
• 제12권1호
• /
• pp.34-42
• /
• 2003

This paper presents a rigid-plastic finite element method to handle the frictional contact problem between two deformable bodies experiencing large deformation. The variational formulation combined with incremental quasi-static model is employed for treating the contact boundary condition. The frictional behavior of the model obeys Coulomb's law of friction. The proposed contact algorithms are classified into two categories, one for searching contacting nodes and the other for calculating contact forces at the contact surface. A slave node and master contact segment are defined using the geometric condition of finite elements on the contact interface. The penalty parameter is used to limit the penetration between contacting bodies, and the finite elements are coupled with contact boundary elements.us gates and cavity thicknesses. Through this study we have observed that the jetting is related to the die swell of material. This means that the jotting is strongly affected by the elastic flow property rather than the viscous flow property in viscoelastic characteristics of molten polymer. Different resins have different elastic properties, and elastic flow behavior depends on the shear rate of flow, i.e. injection speed. Large die swell would eliminate jetting however, the retardation of die swell would stimulate jetting. In the point of mole design, reducing the thickness ratio of cavity to gate can reduce or eliminate jetting regardless of amount of elasticity of polymer melt.

• 한국해양공학회지
• /
• 제24권4호
• /
• pp.13-22
• /
• 2010

While a caisson used for breakwater is carried by a floating dock, accompanying stability problem by its existing motions in the dock is quite important and should be pre-checked against sea environmental condition. In the stability analysis, the acceleration, velocity, angle of roll and pitch motions are important to calculate frictional force and separation force. If separation force becomes bigger than frictional force, serious collision may be occurred between caisson and floating dock. In this study, stability evaluation during the transportation of a caisson on floating dock for breakwater was performed by using a commercial program, HydroD and CHARM3D/HARP.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집A
• /
• pp.151-156
• /
• 2001

Experimental frictional and wear characteristics of silicon graphite materials is studied in this paper. Those specimens are lubricated with high temperature and highly pressurized water to simulate the same operating condition for the journal bearing and the thrust bearing on the main coolant pump bearing in the newly developing nuclear reactor named SMART(System-integrated Modular Advanced ReacTor). Operating condition of the bearings is realized by the tribometer and the autoclave. Friction coefficient and wear loss are analyzed to choose the best silicon graphite material. Pin on plate test specimens are used and coned disk springs are used to control the applied force on the specimens. Wear loss ana wear width are measured by a precision balance and a micrometer. The friction force is measured by the strain gauge which can be used under high temperature and high pressure. Three kinds of silicon graphite materials are examined and compared with each other, and each material shows similar but different results on frictional and wear characteristics.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2000년도 제31회 춘계학술대회
• /
• pp.19-23
• /
• 2000

Stiction is an undesirable phenomenon that can be encountered often in Micro-Electro Mechanical Systems (MEMS) applications, In order to minimize this effect, Self-Assembled Monolayers (SAM) are commonly used. In this work the frictional characteristics of SAM are investigated using both micro-tribotester and SPM. It was found that the performance of SAM is quite sensitive to coating condition. The experimental results show promise for SAM to be used in sliding applications of micro systems.

• 한국정밀공학회지
• /
• 제20권4호
• /
• pp.143-150
• /
• 2003

Frictional properties of ultra-thin carbon coatings on silicon wafer were investigated based on Taguchi experimental design method. Sensitivity analysis was performed with normal load, relative humidity, deposition process, and coating thickness as the variables. It was found that despite low thickness, the carbon coating resulted in relatively low friction coefficient. Also, the frictional behavior was affected significantly by humidity and normal load.