Self-Excited Oscillations of a Finite-Thickness Elastic Layer Sliding Against a Rigid Surface With a Constant Coefficient of Friction

2017 ◽  
Vol 85 (2) ◽  
Author(s):  
Neda Karami Mohammadi ◽  
George G. Adams
Keyword(s):  
Friction Coefficient ◽  
Coefficient Of Friction ◽  
Elastic Layer ◽  
Sliding Friction ◽  
Finite Thickness ◽  
Elastic Solid ◽  
Constant Speed ◽  
Bottom Surface ◽  
Rigid Surface ◽  
Positive Real

This investigation considers the dynamic stability of the steady-state frictional sliding of a finite-thickness elastic layer pressed against a moving rigid and flat surface of infinite extent. The elastic layer is fixed on its bottom surface; on its entire top surface, the rigid surface slides with constant speed and with a constant friction coefficient. The plane-strain equations of motion for a linear isotropic elastic solid are solved analytically for small dynamic disturbances. The analysis shows that even with a constant (speed-independent) friction coefficient, the steady solution is dynamically unstable for any finite friction coefficient. Eigenvalues with positive real parts lead to self-excited vibrations which occur for any sliding speed and which increase with increasing coefficient of friction. This is in contrast to the behavior of an elastic half-space sliding against a rigid surface in which the instability only occurs if the coefficient of friction is greater than unity. This work and its extensions are expected to be relevant in the theoretical aspects of sliding friction as well as in a variety of areas such as earthquake motion and brake dynamics.

scholarly journals Anisotropic Vibration Tactile Model and Human Factor Analysis for a Piezoelectric Tactile Feedback Device

Micromachines ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 448 ◽  
Author(s):  
Jichun Xing ◽  
Huajun Li ◽  
Dechun Liu
Keyword(s):  
Friction Coefficient ◽  
Coefficient Of Friction ◽  
Ciliary Body ◽  
Human Factor ◽  
Sliding Friction ◽  
Excitation Frequency ◽  
Tactile Feedback ◽  
Body Structure ◽  
Full Coverage ◽  
The Coefficient Of Friction

Tactile feedback technology has important development prospects in interactive technology. In order to enrich the tactile sense of haptic devices under simple control, a piezoelectric haptic feedback device is proposed. The piezoelectric tactile feedback device can realize tactile changes in different excitation voltage amplitudes, different excitation frequencies, and different directions through the ciliary body structure. The principle of the anisotropic vibration of the ciliary body structure was analyzed here, and a tactile model was established. The equivalent friction coefficient under full-coverage and local-coverage of the skin of the touch beam was deduced and solved. The effect of system parameters on the friction coefficient was analyzed. The results showed that in the full-coverage, the tactile effect is mainly affected by the proportion of the same directional ciliary bodies and the excitation frequency. The larger the proportion of the same direction ciliary body is, the smaller the coefficient of friction is. The larger the excitation frequency is, the greater the coefficient of friction is. In the local-coverage, the tactile effect is mainly affected by the touch position and voltage amplitude. When changing the touch pressure, it has a certain effect on the change of touch, but it is relatively weak. The experiment on the sliding friction of a cantilever touch beam and the experiment of human factor were conducted. The experimental results of the sliding friction experiment are basically consistent with the theoretical calculations. In the human factor experiment, the effects of haptic regulation are mainly affected by voltage or structure of the ciliary bodies.

Radiation of Body Waves Induced by the Sliding of an Elastic Half-Space Against a Rigid Surface

1999 ◽  
Vol 67 (1) ◽  
pp. 1-5 ◽  
Author(s):  
G. G. Adams
Keyword(s):  
Friction Coefficient ◽  
Half Space ◽  
Coefficient Of Friction ◽  
Wave Train ◽  
Tangential Velocity ◽  
Body Waves ◽  
Rigid Surface ◽  
Plane Shear ◽  
Interface Friction ◽  
The Coefficient Of Friction

The steady sliding of a flat half-space against a rigid surface with a constant interfacial coefficient of friction is investigated. It is shown here that steady sliding is compatible with the formation of a pair of body waves (a plane dilatational wave and a plane shear wave) radiated from the sliding interface. Each wave propagates at a different angle such that the trace velocities along the interface are equal and supersonic with respect to the elastic medium. The angles of wave propagation are determined by the Poisson’s ratio and by the coefficient of friction. The amplitude of the waves are indeterminant, subject only to the restriction that the perturbations in interface contact pressure and tangential velocity satisfy the inequality constraints for unilateral sliding contact. It is also found that a rectangular wave train, or a rectangular pulse, can allow for motion of the two bodies with a ratio of remote shear to normal stress which is less than the coefficient of friction. Thus the apparent coefficient of friction is less than the interface coefficient of friction. Furthermore it is shown that the apparent friction coefficient decreases with increasing speed even if the interface friction coefficient is speed-independent. This result supports the interpretation of certain friction behavior as being a consequence of the dynamics of the system, rather than strictly as an interface property. In fact no distinction is made between the static and kinetic interface friction coefficients. [S0021-8936(00)02101-2]

Analysis of sliding friction of WC-Co composite on particleboard

2020 ◽  
Vol 111 ◽  
pp. 60-67
Author(s):  
Jacek Wilkowski ◽  
Marek Barlak ◽  
Radosław Jałocha ◽  
Zbigniew Werner ◽  
Alicja Auriga
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Coefficient Of Friction ◽  
Sliding Friction ◽  
Roughness Parameter ◽  
Average Increase ◽  
Average Coefficient ◽  
Before And After ◽  
The Coefficient Of Friction ◽  
Nano Size

Analysis of sliding friction of WC-Co composite on particleboard. The paper presents the analysis of the coefficient of friction at the contact area between WC-Co composite and particleboard. The four types of WC-Co composite in the form of milling indexable knives for wood materials machining were tested. The tests were carried out on a linear reciprocating tribotester (pin-on-flat), where the sample was the clearance surface of WC-Co indexable knives and the counter-sample was made of three-layer particleboard. Before and after tribological tests, the surface roughness of tested knives was measured. The highest values of friction coefficient were obtained for the type UMG04 of cemented carbide - with nano size of WC grains and the lowest content of cobalt. The average coefficient of friction for selected types of WC-Co correlated with the average increase in surface roughness (the roughness parameter Ry).

Experimental study on the relationship between the friction coefficient and interference in locomotive axle press-fitting

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ting Wang ◽  
Hanfei Guo ◽  
Jianjun Qiao ◽  
Xiaoxue Liu ◽  
Zhixin Fan
Keyword(s):  
Friction Coefficient ◽  
Coefficient Of Friction ◽  
Friction Pair ◽  
Rolling Stock ◽  
Content Type ◽  
Press Fitting ◽  
The Press ◽  
The Coefficient Of Friction ◽  
The Relationship ◽  
Locomotive Wheels

PurposeTo address the lack of data in this field and determine the relationship between the coefficient of friction and the interference between locomotive wheels and axles, this study evaluates the theoretical relationship between the coefficient of friction and the interference under elastic deformation.Design/methodology/approachWhen using numerical analyses to study the mechanical state of the contacting components of the wheels and axle, the interference between the axle parts and the coefficient of friction between the axle parts are two important influencing factors. Currently, as the range of the coefficient of friction between the wheel and axle in interference remains unknown, it is generally considered that the coefficient of friction is only related to the materials of the friction pair; the relationship between the interference and the coefficient of friction is often neglected.FindingsA total of 520 press-fitting experiments were conducted for 130 sets of wheels and axles of the HXD2 locomotive with 4 types of interferences, in order to obtain the relationship between the coefficient of friction between the locomotive wheel and axle and the amount of interference. These results are expected to serve as a reference for selecting the coefficient of friction when designing axle structures with the rolling stock, research on the press-fitting process and evaluations of the fatigue life.Originality/valueThe study provides a basis for the selection of friction coefficient and interference amount in the design of locomotive wheels and axles.

scholarly journals Rotation and Magnetic Field Effect on Surface Waves Propagation in an Elastic Layer Lying over a Generalized Thermoelastic Diffusive Half-Space with Imperfect Boundary

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
S. M. Abo-Dahab ◽  
Kh. Lotfy ◽  
A. Gohaly
Keyword(s):  
Magnetic Field ◽  
Surface Waves ◽  
Half Space ◽  
Attenuation Coefficient ◽  
Elastic Layer ◽  
Finite Thickness ◽  
Relaxation Times ◽  
Magnetic Field Effect ◽  
Plane Boundary ◽  
Special Cases

The aim of the present investigation is to study the effects of magnetic field, relaxation times, and rotation on the propagation of surface waves with imperfect boundary. The propagation between an isotropic elastic layer of finite thickness and a homogenous isotropic thermodiffusive elastic half-space with rotation in the context of Green-Lindsay (GL) model is studied. The secular equation for surface waves in compact form is derived after developing the mathematical model. The phase velocity and attenuation coefficient are obtained for stiffness, and then deduced for normal stiffness, tangential stiffness and welded contact. The amplitudes of displacements, temperature, and concentration are computed analytically at the free plane boundary. Some special cases are illustrated and compared with previous results obtained by other authors. The effects of rotation, magnetic field, and relaxation times on the speed, attenuation coefficient, and the amplitudes of displacements, temperature, and concentration are displayed graphically.

scholarly journals Solid Lubrication by Multiwalled Carbon Nanotubes in Air and in Vacuum for Space and Aeronautics Applications

2005 ◽  
Author(s):  
K. Miyoshi ◽  
K. W. Street ◽  
R. L. Vander Wal ◽  
R. Andrews ◽  
David Jacques ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Multiwalled Carbon Nanotubes ◽  
Coefficient Of Friction ◽  
Sliding Friction ◽  
Solid Lubrication ◽  
Multiwalled Carbon ◽  
Solid Lubrication Friction ◽  
The Coefficient Of Friction ◽  
Dry Conditions ◽  
Steel Balls

To evaluate recently developed aligned multiwalled carbon nanotubes (MWNTs) and dispersed MWNTs for solid lubrication applications, unidirectional sliding friction experiments were conducted with 440C stainless steel balls and hemispherical alumina-yttria stabilized zirconia pins in sliding contact with the MWNTs deposited on quartz disks in air and in vacuum. The results indicate that MWNTs have superior solid lubrication friction properties and endurance lives in air and vacuum under dry conditions. The coefficient of friction of the dispersed MWNTs is close to 0.05 and 0.009 in air and in vacuum, respectively, showing good dry lubricating ability. The wear life of MWNTs exceeds 1 million passes in both air and vacuum showing good durability. In general, the low coefficient of friction can be attributed to the combination of the transferred, agglomerated patches of MWNTs on the counterpart ball or pin surfaces and the presence of tubular MWNTs at interfaces.

Hydrodynamic Model for Cold Strip Rolling

1967 ◽  
Vol 182 (1) ◽  
pp. 153-162 ◽  
Author(s):  
D. S. Bedi ◽  
M. J. Hillier
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Entropy Production ◽  
Coefficient Of Friction ◽  
Hydrodynamic Model ◽  
Reynolds Equation ◽  
Viscous Friction ◽  
Strip Rolling ◽  
Roll Pressure ◽  
Cold Strip Rolling

The theory of rolling is modified to allow calculation of a hydrodynamic film thickness and viscous friction coefficient using Reynolds equation for the lubricant. Calculations are made for the case where the fluid film covers the arc of contact. The film thickness is assumed uniform and is determined by the principle of minimum rate of entropy production. It is shown that the apparent coefficient of friction varies significantly over the arc of contact. At small reductions the roll load tends to decrease with speed of rolling, while at high reductions the load tends to increase. The point of maximum roll pressure does not coincide with the neutral plane; and under certain rolling conditions there may be no maximum in the pressure over the arc of contact.

Stresses Due to Tangential and Normal Loads on an Elastic Solid With Application to Some Contact Stress Problems

1953 ◽  
Vol 20 (2) ◽  
pp. 157-166
Author(s):  
J. O. Smith ◽  
Chang Keng Liu
Keyword(s):  
Plane Strain ◽  
Coefficient Of Friction ◽  
Contact Area ◽  
Normal Load ◽  
Elastic Solid ◽  
Real Variable ◽  
The Body ◽  
Shearing Stress ◽  
Tangential Load ◽  
The Coefficient Of Friction

Abstract The results of two-dimensional approach using real variable method to Hertz’s problem of contact of elastic bodies are presented. Both normal and tangential loads are assumed to be distributed in Hertzian fashion over the area of contact. The magnitude of the intensity of the tangential load is assumed to be linearly proportional to that of the normal load when sliding motion of the body is impending. The stresses in the elastic body due to the application of these loads on its boundary are presented in closed form for both plane-stress and plane-strain cases. A numerical value of f = 1/3 is assumed for the linear proportionality (coefficient of friction) between the tangential and normal loads in order that the distribution of stresses may be illustrated. The significance of the stress distribution, across the contact area and in the body, is also discussed. It is shown that when the combination of loads considered in the paper are applied at the contact area of bodies in contact the maximum shearing stress may be at the surface instead of beneath the surface. For example, for plane strain, if the coefficient of friction is f = 1/3, the maximum shearing stress is at the surface and is 43 per cent larger than the maximum shearing stress, which would be below the surface, that occurs when the normal force acts alone. The effect of range of normal stress and of shearing stress on the plane of maximum shear and on the plane of maximum octahedral shear on failure by progressive fracture (fatigue) is discussed.

Influence of Third Element of TiNi Alloy on Tribological Behavior in Dry and Wet Conditions for Orthodontic Applications

2019 ◽  
Vol 803 ◽  
pp. 167-171
Author(s):  
Aphinan Phukaoluan ◽  
Anak Khantachawana ◽  
Pongpan Kaewtatip ◽  
Surachai Dechkunakorn
Keyword(s):  
Surface Roughness ◽  
Surface Area ◽  
Coefficient Of Friction ◽  
Sliding Friction ◽  
Tribological Behavior ◽  
Artificial Saliva ◽  
Tini Alloy ◽  
Oral Temperature ◽  
Wet Condition ◽  
Dry And Wet Conditions

The tribological behavior of Ti49.4Ni50.6, Ti49Ni46Cu5 and Ti50Ni47Co3 (at%) alloy in dry and wet conditions was studied. The alloy was prepared in a Vacuum Arc Re-melting (VAR), homogenized at 800°C for 3600 s and quenched in water. The phase transformation temperatures were measured by differential scanning calorimetry. Before a tribology test, it is necessary to determine surface roughness, because high surface roughness affects friction. The hardness behavior, based on the load over residual indent area, was determined by a Vickers hardness tester. The sliding friction tests were performed using a ball-on-disk tribometer in dry condition at room temperature and wet condition in artificial saliva (pH 5.35) at 37°C (Oral temperature). The results showed that transformation temperature (Af) lowered oral temperature (37°C), this was mainly attributed to the superelastic properties that can be taken into orthodontic applications. The studies showed significant influences in dry condition of coefficient of friction. Caused by the force between the ball and the disk, contact pressure of surface area effect in wear occurred. The debris could not be removed from the surface area tested. TiNiCu and TiNiCo generated significantly lower average coefficient of friction when tested under dry condition, which may have been due to the addition of Cu and Co. Wet condition decreased coefficient of friction more than dry condition, owing to the lubricating effects of artificial saliva.

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