Interactions Between Dynamic Normal and Frictional Forces During Unlubricated Sliding

1983 ◽  
Vol 105 (2) ◽  
pp. 221-229 ◽  
Author(s):  
A. Soom ◽  
C. Kim
Keyword(s):  
Friction Coefficient ◽  
Frictional Force ◽  
Contact Region ◽  
Contact Forces ◽  
Force Fluctuations ◽  
Surface Irregularities ◽  
Frictional Forces ◽  
Steel Surfaces ◽  
Pin On Disk ◽  
Inertia Forces

The results of measurements showing large normal and frictional force oscillations during unlubricated smooth sliding between steel surfaces are presented. The measurements were made on a pin-on-disk type apparatus instrumented with piezoelectric force and acceleration transducers. Spectral analysis of the contact forces (including inertia forces) up to frequencies of 2 kHz indicate that the fluctuations have their major components in this frequency range. The force oscillations are primarily associated with normal and tangential contact vibrations which are excited by surface irregularities being swept through the contact region during sliding. Transfer function analyses between the normal and frictional forces show the frictional force fluctuations to be in phase with the normal force fluctuations, but related in magnitude by a ratio larger than the concurrently-measured (average) kinetic friction coefficient. This larger oscillatory (or AC) friction coefficient is indicative of fluctuations in the instantaneous coefficient of friction which are shown to occur in synchronism with the contact force oscillations.

FRICTIONAL INDETERMINANCY OF FORCES IN HARD-DISK PACKINGS

2003 ◽  
Vol 17 (29) ◽  
pp. 5623-5630 ◽  
Author(s):  
TAMÁS UNGER ◽  
JÁNOS KERTÉSZ
Keyword(s):  
Random Walk ◽  
Friction Coefficient ◽  
Contact Forces ◽  
Contact Dynamics ◽  
Force Fluctuations ◽  
Packing Structure ◽  
Hard Particles ◽  
Rigid Disks ◽  
Dynamics Simulations ◽  
Disk Packings

We study the statical indeterminacy of contact forces in 2D random frictional packings of perfectly rigid disks. Based on contact dynamics simulations we perform a random walk in the force space in order to explore the equilibrium force-states for a fixed packing structure. Our measurement is in agreement with the isostaticity of frictionless hard particles, in that case forces are fully determined. For non-zero friction coefficient the problem gets undetermined, the possible force fluctuations are growing with increasing friction up to a maximum at friction coefficient around 0.1. Further increase of friction reduces the force fluctuations on the average.

Contact Force and Frictional Heating due to “Large” Particles in the Head Disk Interface

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Xinjiang Shen ◽  
David B. Bogy
Keyword(s):  
Friction Coefficient ◽  
Contact Force ◽  
Contact Region ◽  
Frictional Heating ◽  
Frictional Coefficient ◽  
Movement Pattern ◽  
Contact Forces ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Large Particles

Particles in the head disk interface may cause large contact forces acting on the slider as well as thermal asperities in the read/write signal. This is especially true for the close spacing required for 1Tbit∕in.2. In this paper, a three-body contact model is employed to study the effects of a particle entrapped between a slider and a disk. A criterion for determining a particle’s movement pattern is proposed. The study of particles in the head disk interface shows that large particles are likely to slide between the slider and disk interface, and the particles going through the trailing pad of an air bearing slider cause severe contact forces on the slider and generate large heat sources. The frictional heating study shows that the temperature around the magnetoresistive head increases to about 5°C for a single 200nm particle passing through the trailing pad of the slider. The effects of the particle size, disk material, and friction coefficient are also studied. It is found that the disk and slider materials and the frictional coefficient between the materials largely affect the contact force acting on the slider by an entrapped particle as well as the temperature rise at its contact region. It is also found that the friction coefficient largely affects a particle’s movement pattern in the head disk interface.

Predicting the wear coefficient and friction coefficient in dry point contact using continuum damage mechanics

2018 ◽  
Vol 233 (3) ◽  
pp. 447-455 ◽  
Author(s):  
Sahar Ghatrehsamani ◽  
Saleh Akbarzadeh
Keyword(s):  
Friction Coefficient ◽  
Damage Mechanics ◽  
Point Contact ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Wear Coefficient ◽  
Mechanics Model ◽  
Pin On Disk ◽  
Disk Test ◽  
The Continuum

Wear coefficient and friction coefficient are two of the key parameters in the performance of any tribo-system. The main purpose of the present research is to use continuum damage mechanics to predict wear coefficient. Thus, a contact model is utilized that can be used to obtain the friction coefficient between the contacting surfaces. By applying this model to the continuum damage mechanics model, the wear coefficient between dry surfaces is predicted. One of the advantages of using this model is that the wear coefficient can be numerically predicted unlike other methods which highly rely on experimental data. In order to verify the results predicted by this model, tests were performed using pin-on-disk test rig for several ST37 samples. The results indicated that the wear coefficient increases with increasing the friction coefficient.

Comparison in Tribological Properties of YBa2Cu3OX/Ag and Bi2Sr2CaCu2OX/Ag Self-Lubricating Composites

2011 ◽  
Vol 291-294 ◽  
pp. 34-40
Author(s):  
Hua Tang ◽  
Wen Jing Li ◽  
Chang Sheng Li
Keyword(s):  
Friction Coefficient ◽  
Tribological Properties ◽  
Room Temperature ◽  
Superconducting Transition ◽  
Friction Test ◽  
Average Value ◽  
Structure And Morphology ◽  
Disk Friction ◽  
Pin On Disk ◽  
Self Lubricating Composites

The YBa2Cu3Ox/Ag and Bi2Sr2CaCu2Ox/Ag self-lubricating composites were prepared using powder metallurgic method. The crystal structure and morphology of the as-synthesized samples were characterized by XRD and SEM. The YBa2Cu3Ox/Ag and Bi2Sr2CaCu2Ox/Ag self-lubricating composites were found to compose of superconductor phase and Ag phase. The tribological properties from ultra-low temperature to room temperature of the composites were studied by pin-on-disk friction test. It was found that the friction coefficients of pure YBa2Cu3Ox(YBCO) and Bi2Sr2CaCu2Ox(BSCCO) were both dropped abruptly when the temperature cooled below the superconducting transition temperature. At room temperature, the friction coefficient of pure YBa2Cu3Oxis 0.68~0.95, when mixing 15wt% Ag, the friction coefficient of the sample decreased to the lowest value 0.11. The friction coefficient of pure Bi2Sr2CaCu2Ox is 0.15~0.17, When Ag content reach 10wt%, the coefficient was lowest (average value is 0.13). The addition of appropriate amount of Ag obviously improve the tribological property of YBCO, while only slightly meliorate that of BSCO. On the other hand, the YBCO/Ag composites exhibit better tribological properties than BSCCO/Ag composites at higher load under the same experimental condition.

A Study of Frictional Forces between Orthodontic Brackets and Archwires

1994 ◽  
Vol 21 (4) ◽  
pp. 349-357 ◽  
Author(s):  
Alison Downing ◽  
John McCabe ◽  
Peter Gordon
Keyword(s):  
Stainless Steel ◽  
Frictional Force ◽  
Nickel Titanium ◽  
The Other ◽  
Friction Testing ◽  
Beta Titanium ◽  
Polycrystalline Ceramic ◽  
Ceramic Brackets ◽  
Frictional Forces ◽  
Testing Assembly

The differences in magnitude of static and kinetic frictional forces generated by 0·022 × 0·030-inch stainless steel (Dentaurum®) and polycrystalline ceramic (Transcend®) brackets in combinntion with archwires of different sizes (0·018 inch and 0·019 × 0·025 inch) and materials (stainless steel, nickel-titanium, and beta-titanium) at a constant ligature force were investigated. A friction-testing assembly using the Instron machine was used. In all cases, the static frictional force was greater than the kinetic frictional force. There were no significant differences in the frictional forces generated by stainless steel and polycrystalline ceramic brackets. Beta-titanium archwires produced greater frictinal forces than the other two materials. Increasing the archwire diameter increased the frictional force.

Modeling of a Finger-Follower Cam System With Verification in Contact Forces

1993 ◽  
Author(s):  
Wensyang Hsu ◽  
Albert P. Pisano
Keyword(s):  
Constraint Equation ◽  
Contact Forces ◽  
Valve Train ◽  
Dynamic Responses ◽  
Valve Lift ◽  
Distributed Parameter ◽  
Contact Points ◽  
Frictional Forces ◽  
Contact Position ◽  
Force Data

Abstract A lumped/distributed-parameter, dynamic model is developed to investigate the dynamic responses of a finger-follower valve train with the effects of an oscillating pivot, frictional forces between sliding surfaces, and a hydraulic lash adjuster. Based on the measured force data at low speed, an algorithm is derived to determine the dynamic Coulomb friction coefficients around maximum valve lift simultaneously at three contact points. A constraint equation is formulated to find the contact position between the cam and the follower kinematically. This makes it possible for the model to simulate the dynamic response of the cam system when the pivot is moving. A hydraulic lash adjuster acting as the pivot of the follower is also modeled with the effects of oil compressibility and oil refill mechanism. The model is numerically integrated and shown to have good agreement between simulation results and experimental data of contact forces at three different speeds. The maximum operating speed is limited by valve toss, loss contact between components. The model predicts toss between the hydraulic lash adjuster and the follower at 2535 rpm, and experiment indicates toss starting at 2520 rpm of camshaft speed.

Peristaltic Flow of a Jeffery Fluid with Heat Transfer in an Inclined Porous Tube under the Influence of Slip and Variable Viscosity

2019 ◽  
Vol 393 ◽  
pp. 16-30 ◽  
Author(s):  
Gudekote Manjunatha ◽  
Hanumesh Vaidya ◽  
Choudhari Rajashekhar ◽  
K.V. Prasad
Keyword(s):  
Heat Transfer ◽  
Frictional Force ◽  
Variable Viscosity ◽  
Pressure Rise ◽  
Velocity Slip ◽  
Slip Parameter ◽  
Porous Tube ◽  
Closed Form Solutions ◽  
Long Wavelength ◽  
Frictional Forces

The present paper investigates the role of heat transfer on peristaltic transport of Jeffery liquid in a porous tube. The effect of variable viscosity and slip impacts are taken into account. The closed-form solutions are obtained with the help of long wavelength and small Reynolds number. The results of physiological parameters on velocity, pressure rise, frictional force, trapped bolus, and temperature are plotted graphically. It is seen that the pressure rise and the frictional forces decline with an expansion in the viscosity parameter. The study further demonstrates that an increase in the value of the slip parameter significantly alters the pressure rise, frictional force, and temperature. Moreover, the volume of trapped bolus increases with an increase in the value of the velocity slip parameter.

scholarly journals A Comparison of Surface Characteristics, Coating Stability and Friction Coefficients of Esthetic Archwires: A Comparative Study

2020 ◽  
pp. 030157422095988
Author(s):  
Harshal Jejurikar ◽  
Taabish Contractor ◽  
Salil Nene ◽  
Ajit Kalia ◽  
Wasu Patil ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Frictional Resistance ◽  
Surface Characteristics ◽  
Group 4 ◽  
Oral Environment ◽  
Surface Irregularities ◽  
Group 3 ◽  
Bonferroni Test ◽  
Coating Stability ◽  
Group 2

Aim: The aim of this article is to evaluate coated orthodontic aligning archwires for surface characteristics, coating stability, and associated dynamic frictional resistance and to compare and relate these results to each other. Materials and Methods: The archwire investigated were (1) group 1: American orthodontics (0.016 NiTi) (AO); (2) group 2: G and H Wire Company, USA (0.016) (G and H); (3) group 3: Orthosystems (0.016) (OS); and (4) group 4: Forestadent, Bio Cosmetic (0.017) (BC) Surface roughness (ESEM), coating stability, and frictional resistance were tested. Analysis of variance and Bonferroni test were used for analysis. Results: Frictional resistance from low to high—BC, AO, OS, G, and H. Coating stability from low to high—BC, AO, G and H, and OS. Surface characteristics from low to high—BC, OS, AO, G, and H. Conclusions: The study showed that BC has least friction coefficient, best coating stability, and less surface irregularities. Surface characteristics, friction coefficient, and coating stability may have correlation but are not statistically significant because of multifactorial conditions in the oral environment.

Friction coefficient study of nanocomposite Al2O3–NbC obtained by spark plasma sintering-SPS

2020 ◽  
Vol 72 (9) ◽  
pp. 1087-1094
Author(s):  
Susan Meireles C. Dantas ◽  
Marcio G. Di Vernieri Cuppari ◽  
Vania Trombini Hernandes
Keyword(s):  
Friction Coefficient ◽  
Peer Review ◽  
Spark Plasma Sintering ◽  
Contact Region ◽  
Content Type ◽  
3D Profilometry ◽  
Plasma Sintering ◽  
Dry Conditions ◽  
Spark Plasma ◽  
Surface Changes

Purpose This study aims to investigate the friction coefficient of Al2O3–NbC nanocomposite obtained by spark plasma sintering sliding against a steel ball. Design/methodology/approach Tribological tests were carried out using a reciprocating nanotribometer in a ball on flat configuration with normal loads in the range from 10 to 100 mN under dry conditions. Surface changes were analyzed by confocal microscopy and 3D profilometry. Findings The values of the friction coefficient varied from 0.15 to 0.6 and are independent of the applied load. Originality/value The tribological behavior is attributed to fracture in the contact region and the effect of wear debris. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0356/

Numerical Prediction of Surface Wear and Roughness Parameters During Running-In for Line Contacts Under Mixed Lubrication

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Yazhao Zhang ◽  
Alexander Kovalev ◽  
Noriyuki Hayashi ◽  
Kensuke Nishiura ◽  
Yonggang Meng
Keyword(s):  
Friction Coefficient ◽  
Contact Region ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Wear Particles ◽  
Wear Model ◽  
Wear Process ◽  
Line Contacts ◽  
Lubrication Condition ◽  
Initial Line

A stochastic model for predicting the evolutions of wear profile and surface height probability density function (PDF) of initial line contacts during running-in under mixed lubrication condition is presented. A numerical approach was developed on the basis of stochastic solution of mixed lubrication, which combined the Patir and Cheng's average flow model for calculation of the hydrodynamic pressure and the Kogut and Etsion's (KE) rough surface contact model for calculation of the asperity contact pressure. The total friction force was assumed to be the sum of the boundary friction at the contact asperities and the integration of viscous shear stress in the hydrodynamic region. The wear depth on the contact region was estimated according to the modified Archard's wear model using the asperity contact pressure. Sugimura's wear model was modified and used to link the wear particle size distribution and the variation of surface height PDF during wear. In the wear process, the variations of profile and surface height PDF of initial line contacts were calculated step by step in time, and the pressure distribution, friction coefficient, and wear rate were updated consequently. The effect of size distribution of wear particles on the wear process was numerically investigated, and the simulation results showed that the lubrication condition in which small wear particles are generated from the asperity contact region is beneficial to reduce friction coefficient and wear rate, and leads to a better steady mixed lubrication condition.

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