• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 추계학술대회 논문집
• /
• pp.1012-1015
• /
• 2005

This paper is designed to estimate friction and powdering characteristic of coating layer on galvannealed sheet steel with different annealing temperature, which is 465, 505, 515 and $540^{\circ}C$. Estimations of powdering and friction were done using a $60^{\circ}$ bending test and one side friction test, respectively. In order to obviously understand the effect of coatings on friction cross-section of coatings before and after friction test was also observed by SEM. The results show that powdering of coatings is increased with increasing of annealing temperature and that friction characteristic greatly depends on powdering which leads to increase of real contact area between tools and coatings.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2000년도 추계학술대회 논문집
• /
• pp.60-63
• /
• 2000

In this study, efficient force reflection algorithm is developed for the Haptic Display by using a proxy concept and friction model. When there are not any contacted obstacles the proxy is following human operator's command trajectory in the 3D virtual space. But when the operator's command trajectory is locating inside of the object, the proxy is constrained by the surface of the object. Here only with the information of the proxy position and operator's command trajectory at every time step, we can calculate the reflection force and its orientation. To display the friction force between two virtual stiff material which are sliding against each other, modified Karnopp's friction model is used. In the friction model, a damping term and a Stribeck effect term are included to display the relative velocity effect and stick-slip effect at the very low relative velocity region respectively.

• Journal of Welding and Joining
• /
• 제15권4호
• /
• pp.90-98
• /
• 1997

A copper-tungsten sintered alloy(Cu-W) has been friction welded to a tough pitch copper in order to investigate the effect of friction pressure on bonding strength and a charicteristic of fracture. The tensile strength of the friction welded joint was increased up to 90% of the Cu base metal under the condition of friction time 1.2 sec, friction pressure 4.5kgf/$\textrm{mm}^2$ and upset pressure 10kgf/$\textrm{mm}^2$. From the results of fracture surface analysis, the increase of friction pressure could remarkably decrease the force and the time to be normally acted on weld interface. The W particles which were included in the plastic zone of Cu side could induce fracture adjacent to the weld interface because their existance in Cu induces a decrease in available section area and an increase in notch effect. Therefore, the tensile strength was decreased at high friction pressure (6kgf/$\textrm{mm}^2$) because the destruction of W was increased by an increase in mechanical force and crack was formed at weld interface.

• 대한기계학회논문집A
• /
• 제29권7호
• /
• pp.938-946
• /
• 2005

Friction is a dominant nonlinear factor in servomechanisms, which seriously deteriorates system accuracy. A friction compensator is indispensable to fabricate high-performance servomechanisms. In order to compensate for the friction in the servomechanism, identification of the friction elements is required. To estimate the friction of the servomechanism, an accurate linear element model of the system is required first. Tn this paper, a nonlinear friction model, in which static, coulomb and viscous frictions as well as Stribeck effect are included, is identified through the describing function approximation of the nonlinear element. A nonlinear element composed of two relays is intentionally devised to induce various limit cycle conditions in the velocity control loop of the servomechanism. The friction coefficients are estimated from the intersection points of the linear and nonlinear elements in the complex plane. A Butterworth filter is added to the velocity control loop not only to meet the assumption of the harmonic balance method but also to improve the accuracy of the friction identification process. Validity of the proposed method is confirmed through numerical simulations and experiments. In addition, a model-based friction compensator is applied as a feedforward controller to compensate fur the nonlinear characteristics of the servomechanism and to verify the effectiveness of the proposed identification method.

• 한국분무공학회지
• /
• 제27권3호
• /
• pp.161-166
• /
• 2022

To measure the change in friction loss due to the control of fuel mass and oil temperature in a gasoline engine, the floating liner method was used to measure the friction generated by the piston of a single-cylinder engine. First, to check the effect of combustion pressure on friction, the friction loss was measured by adjusting the fuel mass. It was confirmed that the friction loss increased as the fuel mass increased under the same lubrication conditions. In addition, it was confirmed that the mechanical efficiency decreased as the fuel mass increased. Next, to check the effect of lubrication conditions on friction, the friction loss was measured by controlling the oil temperature. It was confirmed that friction loss increased as the oil temperature decreased at the same fuel mass. As the oil temperature decreases, the viscosity increases, resulting in decreased mechanical efficiency and increased friction loss.

• 동력기계공학회지
• /
• 제9권2호
• /
• pp.57-64
• /
• 2005

This paper is the study on dry sliding wear behavior of carbon fiber reinforced epoxy matrix composites against lay-up orientation. Tests were investigated on the effect of the lay-up orientation, fiber sliding direction, load and sliding velocity when circumstance keep continuously at $21^{\circ}C$, 60%RH. Pin-on-disk dry sliding wear tests for each experimental condition were carried out with a carbon fiber reinforced plastic pin on stainless steel disk in order to search the friction and wear characteristics. The wear rates and friction coefficients against the stainless steel counterpart were experimentally determined and the wear mechanisms were microscopically observed. The effect on friction and wear behavior are observed differently, according to various conditions. When sliding took place against counterpart, the highest wear resistance and the lowest friction coefficient were observed in the $[0]_{24s}$ lay-up orientation at anti-parallel direction.

• Tribology and Lubricants
• /
• 제17권6호
• /
• pp.459-466
• /
• 2001

In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk on friction characteristics in various sliding conditions were investigated. AISI52100 steel ball was used for the substrate of coated ball specimens, which were prepared by depositing TiN coating with 1(m in coating thickness. AISI1045 steel was used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of two materials, the tests were performed both in air for forming oxide layer on the contact parts and in nitrogen environment to avoid oxidation. From the test results, the frictional characteristic between the two materials was predominated by iron oxide layer that formed on wear tract of counter-body and this layer caused friction transition and high friction. And the adhesive wear occurred from steel disk to TiN coated ball caused the formation of oxide layer on counter parts between the two materials.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2006년도 춘계학술대회 논문집
• /
• pp.165-166
• /
• 2006

Surface pattern of tribological applications is an attractive technology of engineered surface. Therefore, friction reduction is considered to be necessary for improved efficiency of machines. This study investigated the effect of friction property fur angles of micro-scale crosshatch grooved surface pattern on bearing steel flat mated with pin-on-disk. We obtain sample which can be fabricated by photolithography process. We discuss friction property depend on an angle of cross-hatch grooved pattern. We can verify the lubrication mechanism as a Stribeck curve, which has a relationship between the friction coefficient and a dimensionless parameter under the lubrication condition. It was found that the friction coefficient was related to angle of crosshatch on surface, even when surface pattern was the same density.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 1996년도 제24회 춘계학술대회
• /
• pp.45-54
• /
• 1996

The effect of graphite on the frictional characteristics of Cu-based sintered friction materials was studied by pin-on-disk type wear test. A study has been carried out concerning the optimum concentration of graphite in sintered friction material to obtain the minimum wear rate and low friction coefficient . Friction coefficient and wear rate were increased as increasing the content of graphite in the matrix. In the study the optimum concentration of graphite was 19vol % to get the minimum wear rate and optimal frick'ion coefficient.

• 대한기계학회논문집A
• /
• 제26권4호
• /
• pp.660-666
• /
• 2002

It has many variables and factors to design the friction materials for automotive brake pads. The purpose of this study is to develop the proper method for design of low-cost and to know friction characteristics of each raw materials. For the purpose of examining the effect of each major raw materials, we used the Taguchi L9(3$^4$)orthogonal matrix and 1/5 scale dynamo machine for evaluation of the friction characteristics of composite brake pads. By adapting the Taguchi method, it is easy to investigate the influence of each component in complicated composites friction materials. After analyzing the testing results by the Taguchi method, the effect of factors and levels influenced friction behavior was studied.