• The korean journal of orthodontics
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• v.20 no.2
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• pp.409-417
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• 1990

Tooth movement would be impeded by frictional force arised between archwire and tube, bracket or elastics in the fixed orthodontic appliances, which could be changed variably by such several factors as the contact area, normal (perpendicular) force and the condition of contact surface. There were many literatures about frictional force in the orthodontic region, but different results were obtained from little controlled research so that was very difficult in clinical application. Therefore we have reviewed comprehensively previous literatures about frictional force and thus several results were obtained as follows: 1. For use species of the orthodontic wire, frictional force was influenced mainly by surface roughness of wire in the absence of binding, while that was influenced mainly by normal force in high binding angulation. 2. For the cross-section and diameter of the wire, the contact area influenced mainly on frictional force in the absence of binding, while wire stiffness influenced mainly on frictional force in high binding angulation. 3. The greater the bracket width, the greater frictional force, and frictional force of the plastic bracket was larger than that of the metal bracket. 4. For ligation type, frictional force of the stainless steel ligation was larger than that of the elastic ligation, and frictional force was directly proportional to ligation force. 5. Variable frictional force were occured from the saliva combined with such another factors as normal force and mode of surface oxide et al.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.4
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• pp.78-87
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• 1997

In machine tools, frictional force exists between the table and the guideways, and in ballscrews. In this paper, feed motor current measured by a hall sensor is used to calculate the motor torque. Some frictional phenomena are studied in feed drive systems, such as the relationship between feedrate and frictional torque, and chip cover effects on frictional torque. Considering frictional phenomena, the relation- ship between the feed froce and the feed motor current id obtained. Feed force can be well estimated by feed motor current measurement considering frictional behavior. The relationship between the cutting force and the feed motor current is slightly different between up milling and down milling due to the effect of y direc- tional cutting force on frictional torque.

• The korean journal of orthodontics
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• v.18 no.1 s.25
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• pp.55-63
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• 1988

It has been suggested that the frictional force between bracket and arch wire may impede the tooth movement. The present study was aimed to compare and analyze the effect of wire size, type of ligation, and duration of ligation on the magnitude of frictional force between cobalt chromium wire and stainless steel bracket under the artificial saliva. The results were as follows: 1. Type of ligation and size of wire were the main influencing factor on the level of friction. 2. Stainless steel ligature generated higher frictional forces than elastomeric module. 3. The rectangular wire consistently exhibited more frictional force values than round wires, while there was no significant difference between frictional forces of round wires. 4. In elastic ligature, frictional force decreased with time. 5. Artificial saliva had no significant influence on the frictional force between cobalt chromium wire and bracket.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.249-253
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• 1994

In machine tools, frictional force exists between the table and the bed, and in ballscrews. In this paper, feed motor current is used to measure the motor torque and frictional force. A hall sensor is used to measure the feed motor current. Some frictional pheonomina in feed drice systems, such as, the relationship between feedrate and frictional force, lubrication conditions and frictional force, and feed direction and frictional force, are obtained. Generally, the friction behavior is in good agreement with Stribeck's curve. However, the data shows significant scatter when feedrate is high.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.14 no.3
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• pp.16-22
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• 2006

The friction and wear of tire determined by frictional behavior of tire tread that translate driving force, cornering force and braking force between automobile and road as a result of frictional behavior of each tread block. The tire tread block is representative case of rubber block doing frictional behavior. In this paper, frictional behavior of rubber block under compressive force and shear force was analytically obtained by using slip starting position parameter instead of friction coefficient which is uncertain to express exact value between rubber and other surfaces yet. And local coefficients of friction were calculated as a function of compressive force, shear force, shear modulus of rubber, shape factor and slip starting position.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.6
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• pp.216-222
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• 2001

The paper presents the dynamic stability of a flexible shoe in drum brake systems subjected to a frictional force. The frictional force between the drum and the shoe is assumed as a distributed frictional force, while the shute is modeled as an elastic beam supported by two translational springs at both ends and elastic foundations. Governing equations of motion are derived by energy expressions, and their numerical results are obtained by employing the finite element method. The critical distributed frictional force and the instability regions are demonstrated by changing the stiffness of two translational springs and elastic foundation parameters. It is also shown that the beam loses its stability by flutter and divergence depending on the stiffness of elastic supports and elastic foundation parameters. Time responses of beams corresponding to their instability types are also demonstrated.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.11
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• pp.890-896
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• 2002

This paper deals with the dynamic stability of a brake shoe under pulsating frictional forces. A lining part of brake systems is assumed as a distributed spring, and the supported elements of a shoe are assumed as translational springs for a constant distributed frictional force and a pulsating frictional force. Governing equations are derived by the use of the extended Hamilton's principle, and numerical results are calculated by finite element method. The critical distributed frictional force and instability regions were investigated for the change of distributed spring constants and translational spring constants.

• The korean journal of orthodontics
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• v.18 no.1 s.25
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• pp.155-163
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• 1988

The purpose of this study was to evaluate and compare frictional forces generated between orthodontic brackets and arch wires. Independent variables were chosen for study: arch wire size and shape, arch wire material, bracket width, and second-order angulation between bracket and arch wire. Kinetic frictional forces of stainless steel (0.014', 0.016', 0.018', 0.016' ${\times}$ 0.022', 0.018' ${\times}$ 0.022'), $\beta-titanium$ (0.016' ${\times}}$ 0.022') arch wires were measured on wide and junior edgewise twin brackets (0.018' ${\times}$ 0.022' slot). Instron was used to pull arch wires while $0^{\circ},\;3^{\circ},\;6^{\circ},\;or\;9^{\circ}$ angulation between and wire and bracket was given. The results were as follows: 1. The frictional force of $\beta-titanium$ wire was larger than that of stainless steel wire. 2. The frictional force was generally increased as the size of wire is increased. 3. The frictional force of rectangular wire was larger than that of round wire. 4. As second order angulation was increased, the frictional force was also increased. 5. The frictional force was larger on a wide bracket than on a junior bracket.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.6
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• pp.487-494
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• 2013

In this study, solutions for a liquid pool spreading model with continuous and instantaneous release are discussed based on the model used in the FERC's report. The effects of the release time on the liquid pool volume and radius are investigated for the continuous release. For the continuous release with the frictional resistance force in the liquid pool spreading model, the vaporization time decreases as the release time increases. On the other hand, for the continuous release without the frictional resistance force in the liquid pool spreading model, the vaporization time increases as the release time increases. These phenomena are deeply related to the pool radius. In addition, the effects of the initial pool radius for the instantaneous release in the liquid pool spreading model are discussed. For the case with the frictional resistance force in the liquid pool spreading model, as reducing release time in the model with the frictional resistance force for the continuous release, the solution for a continuous release approaches to that for an instantaneous release. On the contrary to this, the pool volume and radius for the instantaneous release without the frictional resistance force are totally different from those for the continuous release without the frictional resistance force.

• The korean journal of orthodontics
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• v.23 no.2 s.41
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• pp.283-294
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• 1993

The friction of orthodontic appliances is recogonized to be detrimental to tooth movement. The purpose of this study was to determine the magnitude of frictional force changes between bracket$(018'\times025'\;solt)$ and orthodontic wires(stainless steel, cobalt-chromium, and $\beta-titanium$, $017'\times0.25'$ rectangular) with time. The wire was secured in the bracket slot with a elastomeric ligature. Frictional forces were measured by universal testing machine. The following conclusions were obtained. 1. The frictional forces under dry condition were greater than those in saliva. 2. The frictional forces produced by cobalt-chromium wire were less than those generated by stainless steel and $\beta-titanium$ wire. 3. The frictional forces increased progressively with time, and the amount of increase on first two weeks was greater than on last two weeks. 4. The change of frictional force under dry condition was greater than in artificial saliva.