Measurements of Grain Kernel Friction Coefficients Using a Reciprocating-Pin Tribometer

2020 ◽  
Vol 63 (3) ◽  
pp. 675-685 ◽  
Author(s):  
Zhengpu Chen ◽  
Carl Wassgren ◽  
Kingsly Ambrose
Keyword(s):  
Coefficient Of Friction ◽  
Particle Interaction ◽  
List Type ◽  
Dynamic Friction ◽  
Friction Coefficients ◽  
Particle Level ◽  
The Coefficient Of Friction ◽  
Wall Materials ◽  
Wall Interaction ◽  
Wheat Kernels

Highlights A tribometer was used to measure the friction coefficients of corn and wheat kernels. Both static and dynamic friction coefficients were measured for particle-wall interaction. Data analysis processes were developed to calculate dynamic friction coefficients for inter-particle interaction. Abstract. Various devices have been developed to measure the coefficient of friction (COF) of grain kernels; however, the majority of these tests measure the particle-wall COF at a bulk level. A method that can accurately measure both particle-wall and inter-particle COFs at a single-particle level remains to be developed. The objective of this study was to explore the feasibility of using a reciprocating-pin tribometer to measure static and dynamic COFs between grain kernels and between grain kernels and wall materials. In this study, the methodology of the test was developed, and representative data from the particle-wall and inter-particle friction tests were reported. It was found that the static COFs of corn-steel, corn-acrylic, wheat-steel, and wheat-acrylic are 0.24 ±0.05, 0.22 ±0.03, 0.32 ±0.02, and 0.29 ±0.03, respectively. The dynamic COFs of corn-steel, corn-acrylic, corn-corn, wheat-steel, wheat-acrylic, and wheat-wheat are 0.22 ±0.06, 0.16 ±0.01, 0.09 ±0.02, 0.30 ±0.02, 0.20 ±0.02, and 0.18 ±0.04, respectively. The current study demonstrates that the reciprocating-pin tribometer is suitable for measuring the particle-wall and inter-particle COFs of grain kernels. Keywords: Coefficient of friction, Grain kernel, Reciprocating-pin tribometer

Single Particle Interaction Properties: Investigations on the Coefficient of Restitution and Coefficient of Friction

2012 ◽  
Author(s):  
Martin C. Marinack ◽  
Patrick S. M. Dougherty ◽  
C. Fred Higgs
Keyword(s):  
Coefficient Of Friction ◽  
Particle Interaction ◽  
Low Carbon Steel ◽  
Granular Flows ◽  
Coefficient Of Restitution ◽  
Natural Phenomena ◽  
Low Carbon ◽  
Solids Processing ◽  
Particle Level ◽  
The Individual

Understanding granular flows has always been important for predicting natural phenomena such as rockslides and soil erosion, as well as industrial processes such as coal-based fossil fuel systems and solids processing. As such, it becomes important to understand granular flows from both a classical granular flow and tribological perspective. Inherently important in the study of granular flows is the study of the individual particle level interactions, which define the global behavior of the flow. The current work examines both the coefficient of restitution (COR) and coefficient of friction (COF) for various material combinations. COR and tribological experiments are performed on various sphere and plate (disk) materials, such as low carbon steel, tungsten carbide (WC), and NITINOL 60.

Coefficients of Friction: Static Versus Dynamic

2020 ◽  
Author(s):  
Jack Youqin Huang
Keyword(s):  
Coefficient Of Friction ◽  
Frictional Force ◽  
Inertial Force ◽  
Static Friction ◽  
Theory And Practice ◽  
Dynamic Friction ◽  
Kinetic Friction ◽  
The Coefficient Of Friction ◽  
Static Versus Dynamic ◽  
New Discovery

Abstract This paper deals with the problem of static and dynamic (or kinetic) friction, namely the coefficients of friction for the two states. The coefficient of static friction is well known, and its theory and practice are commonly accepted by the academia and the industry. The coefficient of kinetic friction, however, has not fully been understood. The popular theory for the kinetic friction is that the coefficient of dynamic friction is smaller than the coefficient of static friction, by comparison of the forces applied in the two states. After studying the characteristics of the coefficient of friction, it is found that the comparison is not appropriate, because the inertial force was excluded. The new discovery in the paper is that coefficients of static friction and dynamic friction are identical. Wheel “locked” in wheel braking is further used to prove the conclusion. The key to cause confusions between the two coefficients of friction is the inertial force. In the measurement of the coefficient of static friction, the inertial force is initiated as soon as the testing object starts to move. Therefore, there are two forces acting against the movement of the object, the frictional force and the inertial force. But in the measurement of the coefficient of kinetic friction, no inertial force is involved because velocity must be kept constant.

A Theory of Dynamic Rubber Friction

1966 ◽  
Vol 39 (2) ◽  
pp. 320-327 ◽  
Author(s):  
A. Schallamach
Keyword(s):  
Coefficient Of Friction ◽  
Time Lag ◽  
Quantitative Agreement ◽  
Dynamic Friction ◽  
Average Life ◽  
Thermally Activated ◽  
Molecular Adhesion ◽  
Rubber Friction ◽  
The Coefficient Of Friction ◽  
Rate Processes

Abstract Assuming dynamic friction to arise from the shearing and subsequent breaking of distinct bonds between the rubbing members, a general equation is derived for the frictional force which involves the number and average life of the bonds as well as the average time lag between breaking and re-making of a bond at a given site. In the case of friction between rubber and smooth, hard surfaces, the bonds are attributed to local molecular adhesion between rubber and track, both formation and breaking of the bonds being thermally activated rate processes. A theory developed on this basis reproduces the experimental results obtained by Grosch in that the coefficient of friction as function of the velocity has a pronounced maximum. The height of the maximum and the velocity at which it occurs are in semi-quantitative agreement with Grosch's findings.

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.

The Coefficients of Friction between Rubber and Other Materials. Frictional Grip of Rubber-Tired Wheels

1930 ◽  
Vol 3 (1) ◽  
pp. 67-73
Author(s):  
R. Ariano
Keyword(s):  
Coefficient Of Friction ◽  
Static Friction ◽  
Systematic Difference ◽  
Road Surface ◽  
Dynamic Friction ◽  
Simple Relationship ◽  
Inflation Pressure ◽  
The Coefficient Of Friction ◽  
Individual Design ◽  
Increasing Load

Abstract (i) The coefficients of friction (ƒI and ƒnI) of rubber tires on dry non-dusty surfaces are practically independent of the load on the wheel, and (with pneumatics) of the inflation pressure; on muddy surfaces the coefficients (especially ƒnI tend to decrease with increasing load. (ii) Dust, mud, or water reduces the friction with rubber tires, but not with iron tires. (iii) The tread pattern reduces the friction on dry surfaces, but increases it on muddy surfaces. (iv) There is no systematic difference between pneumatic, semi-pneumatic (cushion) and solid tires as regarda coefficient of friction; the details of individual design and material are the deciding factors; this is in agreement with the results of Bredtscheiner (Verkehrstechnik, 1922; see Schaar, “Die Beanspruchung der Strassen durch die Kraftfahrzeuge,” Zementverlag, 1925). (v) There is no simple relationship between the coefficient of friction and the compressibility or area of contact of the tire. (vi) The static friction perpendicular to the direction of travel is greater than in this direction. (vii) The coefficient of friction depends on the type of road surface, its de-formability, and especially on the presence or absence of dust, mud, or water. (viii) Rubber tires have a much higher coefficient of friction than iron tires, especially on dry hard surfaces. (ix) The static friction is 10 to 20 per cent higher than the dynamic friction.

scholarly journals Effect of Stick - Slip Phenomena between Human Skin and UHMW Polyethylene

2021 ◽  
Vol 29 (3) ◽  
Author(s):  
Emad Kamil Hussein ◽  
Kussay Ahmed Subhi ◽  
Tayser Sumer Gaaz
Keyword(s):  
Friction Coefficient ◽  
Human Skin ◽  
Coefficient Of Friction ◽  
Normal Load ◽  
Static Friction ◽  
Time Interval ◽  
Dynamic Friction ◽  
Sliding Velocity ◽  
Stick Slip ◽  
The Coefficient Of Friction

The present paper investigates experimentally effect of applied load and different velocity on the coefficient of friction between two interacting surfaces (human skin and Ultra-high-molecular-weight polyethylene (UHMW- polyethylene) at static and dynamic friction. It is possible to conclude specific point based on the above practical part and frictional analysis of this investigation as the most important mechanical phenomenon was creep has been observed a stick time interval where the static friction force is significantly increased during this stroke. The analytical model for stick-slip of skin and UHMWPE is proposed. The difference between static and kinetic friction defines the amplitude of stick-slip phenomena. The contact pressure, the sliding velocity, and rigidity of system determine the stability conditions of the movement between skin and UHMWPE. Experiments were carried out by developing a device (friction measurement). Variations of friction coefficient during the time at different normal load 4.6 and 9.2 N and low sliding velocity 4, 5, 6 and 7 mm/min were experimentally investigated. The results showed that the friction coefficient varied with the normal load and low sliding velocity. At static friction, the coefficient of friction decreased when the time increases, whereas, at dynamic friction, the coefficient of friction decreased when the time increased at normal load 4.6 and 9.2 N.

The Correlation of the Characteristics of Rough Surfaces with Their Friction Coefficients

1987 ◽  
Vol 201 (5) ◽  
pp. 321-329 ◽  
Author(s):  
H Moalic ◽  
J A Fitzpatrick ◽  
A A Torrance
Keyword(s):  
Experimental Evidence ◽  
Coefficient Of Friction ◽  
Unbiased Estimate ◽  
Rough Surfaces ◽  
New Method ◽  
Friction Coefficients ◽  
Probe Size ◽  
The Coefficient Of Friction ◽  
Profile Characteristics

Although a number of models have been suggested for relating the coefficient of friction of a surface with its profile characteristics, no firm experimental evidence to support a specific theory has been reported. In this work, the methods commonly used to calculate the characteristics of slope and curvature of a surface are investigated. The limitations of these methods are discussed and a new method for calculating the slopes and curvatures of a surface is recommended and shown to provide the most unbiased estimate for data limited by probe size. Finally, the results from preliminary tests show that the slope characteristics calculated using this technique are related to the friction coefficients of a surface as suggested by Challen et al. (1).

scholarly journals Influence of the Structure of Seersucker Woven Fabrics on their Friction Properties

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Łukasz Frącczak ◽  
Małgorzata Matusiak
Keyword(s):  
Friction Coefficient ◽  
Coefficient Of Friction ◽  
Relative Motion ◽  
Woven Fabrics ◽  
Friction Coefficients ◽  
Frictional Properties ◽  
Measuring Element ◽  
The Coefficient Of Friction ◽  
Two Bodies

AbstractFriction is defined as a force resisting a relative motion between two bodies in contact. The friction of a fabric on itself or on another fabric influences significantly a fabric’s performance and user’s utility comfort, especially the so-called sensorial comfort. Generally, the coefficient of friction is determined for a given pair of materials. The aim of the present work was to investigate the influence of the structure of the seersucker woven fabrics on their frictional properties. Three variants of the seersucker woven fabrics of different repeat of the seersucker effect were the objects of the investigations. Three measuring elements were applied: made of aluminum and steel and covered with silicone. The obtained results confirmed the influence of the pattern of the seersucker effect on the values of friction coefficient. It was also stated that there are differences between the friction coefficients measured in the warp and weft directions of the seersucker woven fabrics. Values of friction coefficient between the seersucker woven fabrics and measuring elements were the highest for the measuring element covered by silicone. These values were several times higher than the values of friction coefficient measured using the measuring elements made of aluminum and steel.

Research Note: Average Friction Coefficients in Gears

1975 ◽  
Vol 17 (6) ◽  
pp. 360-362 ◽  
Author(s):  
A. C. Rao
Keyword(s):  
Coefficient Of Friction ◽  
Mathematical Analysis ◽  
Load Distribution ◽  
Power Loss ◽  
Experimental Results ◽  
Sliding Velocity ◽  
Friction Coefficients ◽  
Oil Film ◽  
Gear Teeth ◽  
The Coefficient Of Friction

Variation in sliding velocity—both in magnitude and direction—during a meshing cycle, the load distribution among the pairs of teeth, and the accuracy with which teeth are cut are some of the factors that make the mathematical analysis of friction in gear teeth extremely difficult. Of these, sliding velocity, which is responsible for the formation of an oil film between the teeth, plays an important role, and any attempt to determine the friction coefficients must take account of changes in sliding velocity. In this note an expression has been developed, considering the variation in sliding velocity, for power loss in terms of the coefficient of friction and gear parameters. The experimental results are compared with those obtained by other methods.

Effect of Load and Temperature on the Tribological Characteristics of a Steel Pin on Polyoxymethylene Disk Interface

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Matthew G. Larson ◽  
Shannon J. Timpe
Keyword(s):  
Coefficient Of Friction ◽  
Thermal Energy ◽  
Skin Layer ◽  
Dynamic Friction ◽  
Injection Mold ◽  
Friction Mechanism ◽  
Disk Interface ◽  
Load Dependence ◽  
The Coefficient Of Friction ◽  
Initial Drop

The static and dynamic friction properties of a steel pin on polyoxymethelyne homopolymer disk were studied at temperatures ranging from 22 to 160 °C. Samples were tested at externally applied normal loads ranging from 20 to 80 N. Under this range of temperatures, the friction coefficients displayed a linearly increasing dependence on the load. The load dependence is attributed to an enhanced contribution of the plowing friction mechanism at higher loads. As load increases, the pin asperities penetrate into the hard, injection mold-induced skin layer, causing an increase in the frictional plowing. The coefficient of friction was observed to decrease from 0.08 at 22 °C to 0.05 at 50 °C, and subsequently rise to 0.07 at 160 °C. The initial drop was caused by a decrease in the modulus of elasticity attributed to the rise in molecular mobility with increased available thermal energy. As the temperature increased to 160 °C, however, the further decrease in modulus allowed the penetration of the pin asperities to increase significantly, requiring increased material displacement to initiate frictional motion.

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