Skin-skin contact: The normal-force dependence of the coefficient of friction between a bare finger and artificial skin changes randomly

2021 ◽  
Author(s):  
Koki Inoue ◽  
Shogo Okamoto ◽  
Yasuhiro Akiyama ◽  
Yoji Yamada
Keyword(s):  
Experimental Study ◽  
Coefficient Of Friction ◽  
Normal Force ◽  
Skin Surface ◽  
Artificial Skin ◽  
Skin Changes ◽  
Root Cause ◽  
Skin Contact ◽  
The Coefficient Of Friction ◽  
Frictional Forces

Abstract This study investigates the dependence of the coefficients of friction on the normal force produced by sliding a bare finger over different artificial skins with seven levels of hardness. The coefficient of friction was modeled as a power function of the normal force. An experimental study that involved sliding a finger over artificial skin surfaces was carried out under two conditions: the fingertip being wiped by a dry cloth or a cloth soaked in ethanol. Although the exponential term was assumed to be nearly constant for identical tribological conditions, we observed that the exponent varied randomly and could be negative, zero, or positive. This probabilistic behavior has not been explicitly analyzed in previous studies on human fingertips. The probability density function of the exponent depended on the moisture content of the finger. The exponent was either nearly zero or positive when the finger sliding on the skin surface was wiped with an alcohol-soaked cloth and dried. These findings play an important role in analyzing the frictional forces produced during skin–skin contact in terms of determining the root cause behind the random variations in the dependence of the coefficient of friction on the normal force.

scholarly journals A Technique to Determine Friction at the Fingertips

2008 ◽  
Vol 24 (1) ◽  
pp. 43-50 ◽  
Author(s):  
Adriana V. Savescu ◽  
Mark L. Latash ◽  
Vladimir M. Zatsiorsky
Keyword(s):  
Coefficient Of Friction ◽  
Normal Force ◽  
Tangential Force ◽  
Vertical Direction ◽  
Force Sensor ◽  
Displacement Method ◽  
Significant Difference ◽  
The Coefficient Of Friction ◽  
Slip Method ◽  
Slip Force

This article proposes a technique to calculate the coefficient of friction for the fingertip– object interface. Twelve subjects (6 males and 6 females) participated in two experiments. During the first experiment (the imposed displacement method), a 3-D force sensor was moved horizontally while the subjects applied a specified normal force (4 N, 8 N, 12 N) on the surface of a sensor covered with different materials (sandpaper, cotton, rayon, polyester, and silk).Thenormal forceand thetangential force(i.e., the force due to the sensor motion) were recorded. Thecoefficient of friction(µd) was calculated as the ratio between the tangential force and the normal force. In the second experiment (the beginning slip method), a small instrumented object was gripped between the index finger and the thumb, held stationary in the air, and then allowed to drop. The weight (200 g, 500 g, and 1,000 g) and the surface (sandpaper, cotton, rayon, polyester, and silk) in contact with the digits varied across trials. The same sensor as in the first experiment was used to record thenormal force(in a horizontal direction) and thetangential force(in the vertical direction). Theslip force(i.e., the minimal normal force or grip force necessary to prevent slipping) was estimated as the force at the moment when the object just began to slip. The coefficient of friction was calculated as the ratio between the tangential force and the slip force. The results show that (1) the imposed displacement method is reliable; (2) except sandpaper, for all other materials the coefficient of friction did not depend on the normal force; (3) theskin–sandpapercoefficient of friction was the highest µd= 0.96 ± 0.09 (for 4-N normal force) and theskin–rayonrayon coefficient of friction was the smallest µd= 0.36 ± 0.10; (4) no significant difference between the coefficients of friction determined with the imposed displacement method and the beginning slip method was observed. We view the imposed displacement technique as having an advantage as compared with the beginning slip method, which is more cumbersome (e.g., dropped object should be protected from impacts) and prone to subjective errors owing to the uncertainty in determining the instance of the slip initiation (i.e., impeding sliding).

Determination of Tire-Road Friction Coefficients for Skid Mark Analysis

1985 ◽  
Vol 13 (1) ◽  
pp. 41-64
Author(s):  
W. R. Garrott ◽  
D. A. Guenther
Keyword(s):  
Experimental Study ◽  
Coefficient Of Friction ◽  
Friction Coefficients ◽  
Pickup Truck ◽  
The Road ◽  
Heavy Trucks ◽  
Road Friction ◽  
Brake Application ◽  
The Coefficient Of Friction

Abstract An experimental study was made to compare the validities of methods currently used by accident reconstructionists to determine the coefficient of friction between the road and the vehicle tires at the time of an incident. This value could then be used in conjunction with skid mark length and vehicle weight to calculate the prebraking speed of the vehicle. Three automobiles and three trucks with a variety of tires and loadings were used on a variety of pavements. The accuracy and area of applicability of each of four methods for obtaining friction coefficients were determined by relating the prebraking speed calculated from each to the actual speed at the time of brake application. All four methods were satisfactory for automobiles and the pickup truck used, but only two were acceptable for heavy trucks. The most valid coefficients are obtained from skid mark lengths obtained under conditions duplicating those in an incident.

Experimental Study on Powder Suppression Characteristics of Autoclaved Brick

2013 ◽  
Vol 773 ◽  
pp. 272-277
Author(s):  
Wei Zhang ◽  
Yan Yan Zhang ◽  
Fan Zhu
Keyword(s):  
Experimental Study ◽  
Coefficient Of Friction ◽  
Lateral Pressure ◽  
Powder Compaction ◽  
Compression Rate ◽  
The Coefficient Of Friction ◽  
Pressing Technology

The curves of cylinder displacement and pressure can be obtained through the wall brick press autoclaved brick experiment, which can determine the powder compaction equation, including suppression, friction and the characteristics of stripping, modify Kawakita equation, and improve the calculation precision, get the product of the coefficient of friction and lateral pressure and its variation law with compression rate; .in order to provide the basis for the design of pressure machine and mould and optimization of pressing technology

Experimental Study on Superlubricity of Ag Nanometer-Thick Layers by Sliding on a Macroscopic System

2005 ◽  
Author(s):  
Minoru Goto ◽  
F. Honda ◽  
T. Nakahara
Keyword(s):  
Experimental Study ◽  
Coefficient Of Friction ◽  
Network Structure ◽  
Scale Up ◽  
Film Morphology ◽  
Macroscopic System ◽  
The Coefficient Of Friction ◽  
Thick Layers ◽  
Plate Type ◽  
Ag Film

The experimental study on the Ag film was carried out using a diamond pin-on-plate type tribometer under ultrahigh vacuum (UHV) conditions. The coefficient of friction varied with the film morphology in nanometric scale up to 170 nm, and superlubricity as minimum coefficient of friction 0.007 was obtained on 5-nm Ag film with network structure. RHEED and STM observation of the film showed that the film morphologies changed drastically during rubbing, and that the superlubricity of this system is attributed to the lamella gliding of Ag (111) sheets.

Paper 4: An Experimental Study of the Frictional Behaviour of Steels at Elevated Temperatures

1966 ◽  
Vol 181 (15) ◽  
pp. 1-10
Author(s):  
L. A. Mitchell ◽  
T. S. Crawford
Keyword(s):  
Experimental Study ◽  
Coefficient Of Friction ◽  
Elevated Temperatures ◽  
Oxide Films ◽  
Hardened Steel ◽  
Material Combination ◽  
Severe Wear ◽  
Mild Wear ◽  
The Coefficient Of Friction ◽  
Frictional Behaviour

Many investigators, by the manner of presentation of results, have implied that for any given material combination and atmosphere, the coefficient of friction is a function of temperature alone. Experiments are described which were designed to evaluate the importance of the sliding and temperature histories on the unlubricated sliding performance of steels at temperatures up to 500°C. Only for a hardened steel, when mild wear prevailed, was the specimen history unimportant, and, in this case, μ was virtually independent of temperature. With materials exhibiting severe wear, sliding produced changes in friction which were attributed to hardening of the surfaces and when the thickness of oxide films became comparable with the size of transferred particles, exposure to temperature could modify subsequent frictional behaviour.

Experimental Investigation of Porous Bronze Bearings

1973 ◽  
Vol 95 (2) ◽  
pp. 173-179 ◽  
Author(s):  
C. Cusano ◽  
R. M. Phelan
Keyword(s):  
Experimental Study ◽  
Experimental Investigation ◽  
Coefficient Of Friction ◽  
Boundary Lubrication ◽  
Operating Conditions ◽  
The Coefficient Of Friction ◽  
Theoretical Analyses ◽  
Lubrication Conditions

An experimental study was made of the performance of porous bronze bearings under different operating conditions. A PV value of 50,000 psi ft/min was found to be too high for the assembly used when the bearings were lubricated only by the oil initially provided within their structure. Tests at a PV value of 33,000 psi ft/min gave satisfactory results. The coefficient of friction was found to vary with load and to be almost independent of speed for the bearings tested under boundary lubrication conditions. Except for relatively light loads and moderate and higher speeds, the bearings operate under boundary lubrication conditions. When pressurized oil was supplied to the bearings, it was found that, for the same operating conditions, porous bearings run at higher eccentricity ratios than solid bearings, as predicted by theoretical analyses.

Abrasion and Friction of Rubberlike Materials

1956 ◽  
Vol 29 (3) ◽  
pp. 774-780 ◽  
Author(s):  
B. B. S. T. Boonstra ◽  
E. M. Dannenberg
Keyword(s):  
Surface Layer ◽  
Carbon Black ◽  
Coefficient Of Friction ◽  
Abrasion Resistance ◽  
Normal Load ◽  
Efficiency Coefficient ◽  
Cohesive Forces ◽  
The Coefficient Of Friction ◽  
Frictional Forces ◽  
The One

Abstract The relationship between abrasion resistance and the coefficient of friction was observed in the early days of development of the modern synthetic rubbers. It has gained new interest in connection with the appearance on the market of polyester-isocyanate rubbers of the Vulcollan type. The abrasion of a rubber object in contact with a solid depends on the forces interacting at the surface of the two materials. These forces are again dependent on the forces pressing the two surfaces together, on the relative surface speed of the one object with respect to the other, and on the nature of the surfaces of the materials. Forces acting on the rubber surface and tending to pull the surface layer away from the bulk of the material deform the bulk rubber and excite counteracting cohesive forces. Abrasion of the rubber depends on the following two factors: 1) Development of frictional forces at the surface. 2) Counteraction of the force caused by the rubbing by cohesive force in the polymer adjacent to the surface layer. The question may be raised if it is possible to improve abrasion resistance by increasing the cohesive forces (1) without affecting the frictional forces and (2) if so, to what degree. With the help of the modified Cabot-Lambourn abrader, a number of experiments have been carried out that give some answers to the correlation of abrasion and friction. Abrasion is measured in terms of abrasion efficiency, i.e., weight loss per unit of energy. Correlations are established between: (a) Coefficient of friction and normal load. (b) Coefficient of friction and percentage loss of weight. (c) Coefficient of friction and carbon black loading. (d) Abrasion efficiency, coefficient of friction, and carbon black loading. (e) Abrasion efficiency and energy spent on abrasion. (f) Percentage of slip and torque obtained.

scholarly journals The Effect of Annealing Temperatures on Selected Properties of WC/C Coatings, Deposited Using Hexacarbonyl Wolfram in an N2-SiH4 Atmosphere

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4658
Author(s):  
Peter Horňák ◽  
Daniel Kottfer ◽  
Karol Kyzioł ◽  
Marianna Trebuňová ◽  
Mária Kaňuchová ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Chemical Vapor Deposition ◽  
Chemical Composition ◽  
Coefficient Of Friction ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Protective Atmosphere ◽  
Annealing Temperatures ◽  
The Coefficient Of Friction

In this paper, we present the results of an experimental study on WC/C coatings, deposited by using plasma-enhanced chemical vapor deposition in an N2-SiH4 atmosphere, annealed at temperatures of 200, 500 and 800 °C, in which the hexacarbonyl of W was used as a precursor. During the experiments, the topography, chemical composition, morphology, as well as selected mechanical properties, such as hardness, Young’s modulus, and coefficient of friction of the WC/C coatings were analyzed. Annealing without the protective atmosphere in the mentioned temperatures caused a decrease in hardness (up to 15 ± 2.7 GPa). In addition, the coefficient of friction value increased only to 0.37 ± 0.03.

scholarly journals The Coefficient of Friction of Soccer Balls

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 92
Author(s):  
Adin Ming Tan ◽  
Yehuda Weizman ◽  
Firoz Alam ◽  
Franz Konstantin Fuss
Keyword(s):  
Coefficient Of Friction ◽  
Average Velocity ◽  
Normal Force ◽  
Force Plate ◽  
Average Coefficient ◽  
The Coefficient Of Friction

Nine soccer balls were tested for their friction against a leather sheet, using a force plate. An average normal force of 63.6 N was applied and the movement of the ball had an average velocity of 15 mm/s. Each test was repeated 15 times and the average Coefficient of Friction (COF) was reported. The following results were obtained: Jabulani (COF: 0.62 ± 0.05); Fracas (COF: 0.41 ± 0.01); Ordem 3 (COF: 0.63 ± 0.02); Teamgeist (COF: 0.38 ± 0.01); Brazuca (COF: 0.45 ± 0.01); Kopanya (COF: 0.39 ± 0.01); React (COF: 0.37 ± 0.01); Finale 15 (COF: 0.39 ± 0.06); Vintage T-panel leather ball (COF: 0.41 ± 0.02). Overall, the COF of all balls tested ranged between 0.37 and 0.62. The Finale 15 ball showed a decreasing COF trend with repeated trials and the React ball produced pronounced slip-stick phenomenon.

Experimental Investigation of Coefficient of Friction During the Friction Stir Processing of Aluminum

2010 ◽  
Author(s):  
Scott Miller ◽  
Lee Arnold ◽  
Grant Kruger
Keyword(s):  
Coefficient Of Friction ◽  
Solidus Temperature ◽  
Friction Stir ◽  
Work Material ◽  
The Coefficient Of Friction ◽  
Frictional Forces ◽  
Set Up ◽  
Thermocouple Temperature ◽  
Increasing Temperature ◽  
Temperature Force

There is a lack in understanding of the frictional contact condition during friction stir processes. High temperature, force and work material adhesion to and from the tool make the coefficient of friction difficult to measure. In this study, an experiment was set up to simultaneously measure the temperature and normal and frictional forces between a rotating tool and a stationary workpiece at steady state conditions. The coefficient of friction was measured for increasing temperature. A simple model was created to convert the thermocouple temperature measurement to the temperature at the point of contact between the tool and workpiece. It was found that the coefficient of friction had a decreasing trend as temperature approached the solidus temperature of the work material. The results and analysis of the experiments are presented.

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