Static and Clinging Friction of Pivot Bearings

1944 ◽  
Vol 151 (1) ◽  
pp. 274-284
Author(s):  
M. C. Hunter
Keyword(s):  
Stainless Steel ◽  
Coefficient Of Friction ◽  
Rapid Growth ◽  
Static Friction ◽  
Clear Distinction ◽  
Special Apparatus ◽  
The Coefficient Of Friction

The author points out the clear distinction which has to be drawn between kinetic and static friction, and describes the special apparatus used in the investigation carried out to determine the static friction of various combinations of metals, including stainless steel and duralumin, under several conditions of dry and viscous lubrication. The paper stresses the effect of time, and gives data showing the rapid growth of the coefficient of friction during the first twenty-four hours at rest, and the subsequent increases over a period of five days. A series of long-term tests of thirty, sixty, and ninety days, on a selected number of specimens, provides a direct comparison from which the relative merits of the various combinations of materials is drawn. Evidence is provided suggesting advantages to be derived from the use of graphite as a preventative of clinging friction. In conclusion, an explanation is put forward as to the possible causes responsible for the building up of friction with the passage of time.

scholarly journals Wax-oil lubricants to reduce the shear between skin and PPE

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kian Kun Yap ◽  
Manoj Murali ◽  
Zhengchu Tan ◽  
Xue Zhou ◽  
Luli Li ◽  
...  
Keyword(s):  
Olive Oil ◽  
Coefficient Of Friction ◽  
Static Friction ◽  
Mineral Oil ◽  
The Coefficient Of Friction ◽  
Friction Measurements ◽  
Lubricant Application ◽  
Static Coefficient Of Friction

AbstractProlonged use of tight-fitting PPE, e.g., by COVID-19 healthcare workers leads to skin injuries. An important contributor is the shear exerted on the skin due to static friction at the skin-PPE interface. This study aims to develop an optimised wax-oil lubricant that reduces the friction, or shear, in the skin-PPE contact for up to four hours. Lubricants with different wax-oil combinations were prepared using beeswax, paraffin wax, olive oil, and mineral oil. In-vivo friction measurements involving seven participants were conducted by sliding a polydimethylsiloxane ball against the volar forearms to simulate the skin-PPE interface. The maximum static coefficient of friction was measured immediately and four hours after lubricant application. It was found that the coefficient of friction of wax-oil lubricants is mainly governed by the ratio of wax to oil and the thermal stability and morphology of the wax. To maintain long-term lubricity, it is crucial to consider the absorption of oil into the PPE material. The best performing lubricant is a mixture of 20 wt% beeswax, 40 wt% olive oil, and 40 wt% mineral oil, which compared to unlubricated skin, provides 87% (P = 0.0006) and 59% (P = 0.0015) reduction in instantaneous and 4-h coefficient of friction, respectively.

scholarly journals Wax-Oil Lubricants to Reduce the Shear Between Skin and PPE

2021 ◽  
Author(s):  
Kian Kun Yap ◽  
Manoj Murali ◽  
Zhengchu Tan ◽  
Xue Zhou ◽  
Luli Li ◽  
...  
Keyword(s):  
Olive Oil ◽  
Coefficient Of Friction ◽  
Static Friction ◽  
Mineral Oil ◽  
The Coefficient Of Friction ◽  
Friction Measurements ◽  
Lubricant Application ◽  
Static Coefficient Of Friction

Abstract Prolonged use of tight-fitting PPE, e.g., by COVID-19 healthcare workers leads to skin injuries. An important contributor is the shear exerted on the skin due to static friction at the skin-PPE interface. This study aims to develop an optimised wax-oil lubricant that reduces the friction, or shear, in the skin-PPE contact for up to four hours. Lubricants with different wax-oil combinations were prepared using beeswax, paraffin wax, olive oil, and mineral oil. In-vivo friction measurements involving seven participants were conducted by sliding a polydimethylsiloxane ball against the volar forearms to simulate the skin-PPE interface. The maximum static coefficient of friction was measured immediately and four hours after lubricant application. It was found that the coefficient of friction of wax-oil lubricants is mainly governed by the ratio of wax to oil and the thermal stability and morphology of the wax. To maintain long-term lubricity, it is crucial to consider the absorption of oil into the PPE material. The best performing lubricant is a mixture of 20 wt% beeswax, 40 wt% olive oil, and 40 wt% mineral oil, which compared to unlubricated skin, provides 87% (P = 0.0006) and 59% (P = 0.0015) reduction in instantaneous and 4-hour coefficient of friction, respectively.

Frictional Vibrations

1955 ◽  
Vol 22 (2) ◽  
pp. 207-214
Author(s):  
David Sinclair
Keyword(s):  
Coefficient Of Friction ◽  
Equations Of Motion ◽  
Static Friction ◽  
Uniform Motion ◽  
Friction Characteristic ◽  
Stick Slip ◽  
The Coefficient Of Friction ◽  
Brake Lining ◽  
Solid Bodies ◽  
Frictional Vibrations

Abstract Frictional vibrations, such as stick-slip motion and automobile-brake squeal, which occur when two solid bodies are rubbed together, are analyzed mathematically and observed experimentally. The conditions studied are slow uniform motion and relatively rapid simple harmonic motion of brake lining over a cast-iron base. The equations of motion show and the observations confirm that frictional vibrations are caused primarily by an inverse variation of coefficient of friction with sliding velocity, but their form and occurrence are greatly dependent upon the dynamical constants of the mechanical system. With a constant coefficient of friction, the vibration initiated whenever sliding begins is rapidly damped out, not by the friction but by the “natural” damping of all mechanical systems. The coefficient of friction of most brake linings and other organic materials was essentially invariant with velocity, except that the static coefficient was usually greater than the sliding coefficient. Most such materials usually showed a small decrease in coefficient with increasing temperature. The persistent vibrations resulting from the excess static friction were reduced or eliminated by treating the rubbing surfaces with polar organic compounds which produced a rising friction characteristic.

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.

The Calculation of Roll Pressure in Hot and Cold Flat Rolling

1943 ◽  
Vol 150 (1) ◽  
pp. 140-167 ◽  
Author(s):  
E. Orowan
Keyword(s):  
Pressure Distribution ◽  
Yield Stress ◽  
Coefficient Of Friction ◽  
Static Friction ◽  
Rolled Stock ◽  
Theoretical Treatment ◽  
Frictional Drag ◽  
Roll Pressure ◽  
Plate Rolling ◽  
The Coefficient Of Friction

A numerical or graphical method is given for computing, in strip or plate rolling, the distribution of roll pressure over the arc of contact and the quantities derived from this (e.g. the vertical roll force, the torque, and the power consumption). The method avoids all mathematical approximations previously used in the theoretical treatment of rolling, and permits any given variation of the yield stress and of the coefficient of friction along the arc of contact to be taken into account. It can be used, therefore, in both hot and cold rolling, provided that the basic physical quantities (yield stress and coefficient of friction) are known. The usual assumption that the deformation could be regarded as a locally homogeneous compression has not been made, and the inhomogeneity of stress distribution has been taken into account approximately by using results derived by Prandtl and Nádai from the Hencky treatment of two-dimensional plastic deformation. It is found that the discrepancy between the roll pressure distribution curves calculated from the Kármán theory and those measured by Siebel and Lueg is due to the assumption in the theory that the frictional drag between the rolls and the rolled stock is equal to the product of the roll pressure and the coefficient of friction. If frictional effects are dominant, as in hot rolling, this product may easily exceed the yield stress in shear which is the natural upper limit to the frictional drag, and then static friction, instead of slipping, occurs. This has been taken into account in the present method, and the calculated curves of roll pressure distribution show good agreement with the curves measured by Siebel and Lueg.

scholarly journals Friction Behavior of Pre-Damaged Wet-Running Multi-Plate Clutches in an Endurance Test

Lubricants ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 68
Author(s):  
Thomas Schneider ◽  
Katharina Voelkel ◽  
Hermann Pflaum ◽  
Karsten Stahl
Keyword(s):  
Coefficient Of Friction ◽  
Later Life ◽  
Second Step ◽  
Experimental Investigations ◽  
Endurance Test ◽  
Friction Behavior ◽  
Speed Range ◽  
The Coefficient Of Friction ◽  
Endurance Tests

Wet-running multi-plate clutches should be prevented from failing due to the often safety-relevant functions they fulfill in the drive train. In addition to long-term damage, spontaneous damage is of particular relevance for failures. This paper focuses on the influence of spontaneous damage on frictional behavior in the later life cycle. The aim of the experimental investigations is to initially cause spontaneous damage in wet-running multi-plate clutches with sintered friction linings. For this purpose, three clutches are first pre-damaged in stage tests with different intensities, so that the first spontaneous damage (local discoloration, sinter transfer) occurs. In the second step, an endurance test is carried out with the pre-damaged clutch packs and a non-pre-damaged reference clutch. The friction behavior of the clutches during the endurance test is compared and evaluated. It shows that local discoloration and sinter transfer are no longer visible after the endurance tests. At the beginning of the endurance test, the values of coefficient of friction are higher over the entire speed range of the heavily pre-damaged clutches than with the slightly pre-damaged clutch and the non-pre-damaged reference clutch. At the end of the endurance test, it can be observed that the greater the pre-damage to the clutches is, the greater the coefficient of friction increases with decreasing sliding speed.

scholarly journals Experimental and Theoretical Analysis of Zircaloy-4 and AISI 304 Stainless Steel Material Pair in Water Sliding Conditions

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Neelima Khare ◽  
Praveen Kumar Limaye ◽  
Kulwant Singh ◽  
Dhananjay Tatyasaheb Jadhav ◽  
Arundhati Bute ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Coefficient Of Friction ◽  
Great Influence ◽  
304 Stainless Steel ◽  
Load Factor ◽  
Volume Loss ◽  
Aisi 304 Stainless Steel ◽  
Aisi 304 ◽  
Lubricating Film ◽  
The Coefficient Of Friction

Current work was simulated for sliding wear interaction of materials of fuel bundle bearing pad (zircaloy-4) and magazine rotor tube (AISI 304 stainless steel) of Indian Pressurised Heavy Water Reactors (PHWRs). A plan of experiments, based on the techniques of Taguchi, was performed. The objective was to establish a correlation between load and sliding speed with the volume loss and coefficient of friction (COF). These correlations were obtained by multiple linear regressions. The treatment of the experimental results is based on the analysis average and the analysis of variance (ANOVA). Worn surface analyses carried out using SEM and wear mechanisms were identified. ANOVA analysis indicated that load factor has a great influence on the coefficient of friction (~73%). COF suddenly increases to high value after a particular contact pressure due to absence of lubricating film and increase in metal to metal contact. Volume loss of AISI 304 stainless steel and zircaloy-4 is highly affected due to load (~90%) and speed (~65%), respectively. Worn surfaces exhibited deformation, adherence, and compaction of material at all PV conditions. Contact pressures above 475 MPa indicated formation of ratcheting mechanisms and formation of fatigue striation marks. Due to low yield strength of AISI 304 SS, volume loss was on higher side than that of Zr-4.

Friction studies of metal surfaces with various 3D printed patterns tested in dry sliding conditions

2017 ◽  
Vol 232 (1) ◽  
pp. 43-53 ◽  
Author(s):  
Y Holovenko ◽  
M Antonov ◽  
L Kollo ◽  
I Hussainova
Keyword(s):  
Stainless Steel ◽  
Coefficient Of Friction ◽  
Wide Range ◽  
The Coefficient Of Friction ◽  
Steel Aisi ◽  
3D Printed ◽  
Surface Patterns ◽  
Aisi 316 ◽  
Aisi 316 L ◽  
Stainless Steel Aisi

In recent years, 3D scanning and printing of plastics has rapidly matured while printing of metallic parts is only gaining popularity due to required refinements of technology combined with cost- and resources effectiveness for the main components of printers and consumables. The 3D printing allows producing complicated shapes that can be hardly produced by conventional mechanical tools and can provide the functionalization of surfaces. In this work, several different stainless steel (AISI 316 L) surface patterns (flat, gecko’s fibrils, dimples, pyramids, mushrooms, mesh, brush, inclined brush) intended for controlling the coefficient of friction were printed with the help of a 3D metal printer by selective laser melting technique. Unidirectional sliding tests were performed with pin-on-disc configuration. Sliding velocity of 5 × 10−3 m/s and continuously increasing load ranged from 5 to 103 N has been applied in the course of “scanning” mode and accompanied by simultaneous recording of the coefficient of friction. A stainless steel (AISI 316) disc counterbody was used in this series of the tests. It was found that the 3D printed structures allow to control the value and stability of the coefficient of friction in a wide range of loads. Microstructural analysis of the worn samples was performed to support the conclusions regarding wear mechanism.

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.

Tribological properties of structural alloys for the heat exchange equipment parts subjected to fretting

2020 ◽  
pp. 401-407
Author(s):  
E.A. Marchenko ◽  
M.M. Khrushchov ◽  
S.M. Kaplunov ◽  
V.A. Panov
Keyword(s):  
Stainless Steel ◽  
Heat Exchange ◽  
Titanium Alloys ◽  
Fatigue Fracture ◽  
Coefficient Of Friction ◽  
Wear Mechanism ◽  
Sliding Friction ◽  
Adhesive Interaction ◽  
Heat Exchange Equipment ◽  
The Coefficient Of Friction

Trobological characteristics of sliding friction in stainless steel and titanium alloys in dry and water lubricated conditions have been determined. The character of the coefficient of friction variation with load and the duration of tests have confi rmed the prevailing wear mechanism in these materials to be frictional fatigue fracture that in the case of titanium alloys is accompanied with adhesive interaction and plastic plowing. The frictional fatigue curves built in a result of this investigation make possible to estimate the materials tribological longevity.

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