Synchronous Observation With Friction Measurement Prior to and During Occurrence of Scuffing

2010 ◽  
Author(s):  
Kazuyuki Yagi ◽  
Joichi Sugimura ◽  
Seiji Kajita ◽  
Toshihide Ohmori ◽  
Atsushi Suzuki
Keyword(s):  
Friction Coefficient ◽  
Contact Area ◽  
Wear Debris ◽  
Point Contact ◽  
The Other ◽  
Test Rig ◽  
Friction Measurement ◽  
Inlet Zone ◽  
Sapphire Disc ◽  
Ball On Disc

In the current work, scuffing phenomenon was investigated by a direct observation of a contact area. A ball-on-disc test rig was used, which produced a point contact area between a rotating sapphire disc and a stationary steel ball. Sequence of the friction and photograph in the contact area was synchronously obtained prior to and during occurrences of scuffing. Experiments were conducted in a dry condition and a lubricated condition with hexadecane. In the lubricated condition, wear debris accumulated in the inlet zone entered suddenly into the contact area to sharply increase the friction coefficient. On the other hand, macro plastic flow occurred in the whole contact area in the dry condition during a rapid increase in friction coefficient.

The Effects of Grit Particle Size on Frictional Characteristics of Automotive Braking System

2011 ◽  
Vol 189-193 ◽  
pp. 3511-3516
Author(s):  
Mohd Kameil Abdul Hamid ◽  
Gwidon W. Stachowiak
Keyword(s):  
Particle Size ◽  
Friction Coefficient ◽  
Contact Area ◽  
Wear Debris ◽  
Silica Sand ◽  
Test Rig ◽  
Braking System ◽  
Hard Particles ◽  
Effective Contact

The effect of grit particle size on frictional characteristics was investigated using a vertically oriented brake test rig. Silica sand of grit sizes 50-180 µm, 180-355 µm and 355-500 µm were used in drag mode application. Results showed that the presence of hard particles from environment can influence the friction response significantly. Basically, once the hard particles enter the gap, the value and amplitude of friction coefficient tend to decrease. However, slight increase in friction with smaller particles was recorded due to more hard particles involved in mixing and changing the effective contact area. Better friction stability was related to the presence of smaller grit particles and compacted wear debris to form frictional film on the braking interface.

scholarly journals A thermal resistances-based approach for thermal-elastohydrodynamic calculations in point contacts

2017 ◽  
Vol 232 (11) ◽  
pp. 2088-2102 ◽  
Author(s):  
Eduardo de la Guerra Ochoa ◽  
Javier Echávarri Otero ◽  
Enrique Chacón Tanarro ◽  
Benito del Río López
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Thermal Effects ◽  
Good Accuracy ◽  
Computational Cost ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
New Approach ◽  
Ball On Disc

This article presents a thermal resistances-based approach for solving the thermal-elastohydrodynamic lubrication problem in point contact, taking the lubricant rheology into account. The friction coefficient in the contact is estimated, along with the distribution of both film thickness and temperature. A commercial tribometer is used in order to measure the friction coefficient at a ball-on-disc point contact lubricated with a polyalphaolefin base. These data and other experimental results available in the bibliography are compared to those obtained by using the proposed methodology, and thermal effects are analysed. The new approach shows good accuracy for predicting the friction coefficient and requires less computational cost than full thermal-elastohydrodynamic simulations.

Test Rig for Extraction of the Contact Parameters for Plane on Plane Contact

2012 ◽  
Author(s):  
D. Botto ◽  
M. Lavella ◽  
M. M. Gola
Keyword(s):  
Contact Area ◽  
Contact Stiffness ◽  
Point Contact ◽  
Real Plane ◽  
Operational Environment ◽  
Test Rig ◽  
Friction Forces ◽  
Plane Contact ◽  
Wide Range ◽  
Contact Parameters

The modelling of the friction interfaces has received much attention in recent years from the aerospace industry. In order to obtain reliable prediction of the nonlinear dynamic behaviour of the disc and blades in the aerospace engine the friction forces at interfaces, such as in under-platform dampers, blade and fir tree roots or shrouds, must be modelled accurately. Two contact parameters, namely the contact stiffness and the coefficient of friction, are sufficient to model, with good accuracy, the friction contact. The contact parameters are obtained experimentally, and are of interest for the designer only if representative of the operational environment of the engine. To pursue this aim a test rig has been designed to perform experiments in a wide range of temperatures, with different combinations of normal and tangential load, frequencies and mating materials, representative of the real operating condition of the engine. Most of the rigs found in literature perform most likely point contact even if the two bodies have plane mating surfaces. The design of a real plane-on-plane contact test rig is not an easy task but despite the difficulty a solution was found in the design shown in this work. The core of the rig is a tilting mechanism enabling one surface to lies down on the other so that the plane-on-plane contact is achieved, at least within the flatness geometrical tolerance of the surfaces. The results of the experiments are the hysteresis loops, namely the tangential contact force against the relative displacement, from which the contact parameters can be calculated. Measurements of displacements are taken very close to the actual contact area and are performed by means of two laser interferometers. Localized heating is achieved by means of an induction heating machine while a thermocouple measures the temperature at points close to the contact area.

Effect of two-body and three-body microcontacts under dry friction on contact characteristics

2017 ◽  
Vol 232 (4) ◽  
pp. 706-719 ◽  
Author(s):  
Horng-Wen Wu ◽  
Yang-Yuan Chen
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Contact Area ◽  
External Load ◽  
Wear Debris ◽  
Elastoplastic Deformation ◽  
Particle Diameter ◽  
Body Contact ◽  
Wide Range ◽  
Three Body

The wear debris generation is unavoidable between the contact interfaces of moving components. In three-body contact instances, friction and wear occur at these separate contact points. This paper discusses the characteristics of the three-body contact comprising the abrasive particle in the interface compared to the two-body contact. The results show that for the wear debris or foreign particles present in the interface of the three-body contact, as external load initially increases, the external load is fully borne by the contact characteristics of particle-to-surface. Until the external load rises to a particular critical external load, it enters the real three-body situation, and the critical external load thus increases with an increase in the ratio of particle diameter to surface roughness. For two contact surfaces, the summit deformation is the elastoplastic deformation in a wide range of external loads. As the external load is lower than the critical external load value of the three-body contact, the contact surface is under the particle-to-surface two-body contact, and the elastic deformation of surface peak has the largest proportion of contact area. When the external load is higher than the critical external load value, the elastoplastic deformation contact area quickly dominates, and the total contact area ratio approximates to the surface-to-surface two-body contact situation. In the range of engineering surface roughness (σ = 50–400 nm), at each external load and surface roughness, the total friction coefficient decreases with the increase in the ratio of particle diameter to surface roughness under the three-body contact, and this shows that the friction coefficient of surface-to-surface contact is larger than that of the sphere wear debris between the contact interface. At the same surface roughness, the friction coefficient may increase or decrease with an increase in the external load because it is determined by particle diameter. At the same ratio of particle diameter to surface roughness and external load, the friction coefficient increases with the decreasing surface roughness.

Friction and Wear Behaviors of WC-Co/WC-Co Pairs in Air

2007 ◽  
Vol 534-536 ◽  
pp. 1193-1196
Author(s):  
Hiroyuki Hosokawa ◽  
Takeshi Nakajima ◽  
Koji Shimojima
Keyword(s):  
Friction Coefficient ◽  
Diffraction Pattern ◽  
Wear Debris ◽  
Friction And Wear ◽  
Sliding Friction ◽  
Wear Test ◽  
Wear Volume ◽  
Grain Sizes ◽  
Ball On Disc

To investigate sliding friction and wear behaviors of WC–Co/WC–Co pairs containing different WC grain sizes, the ball-on-disc test in air were carried out for WC-Co containing WC grain sizes of 0.5 μm (F.G.) and 1.5 μm (C.G.). The results show that the wear volume of F.G. pin for F.G. pin/C.G. disc is larger than that of F.G. pin for F.G. pin/F.G. disc due to higher friction coefficient, and the surfaces after wear test are richer in oxygen compared to those before test. Furthermore, the wear debris, which is composed of nona-scale grains, after the wear test are remarkably richer in oxygen than to those before test. The diffraction pattern reveals sharp ring

scholarly journals The Effect of Addition of Nanoparticles, Especially ZrO2-Based, on Tribological Behavior of Lubricants

Lubricants ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 23 ◽  
Author(s):  
Adam Rylski ◽  
Krzysztof Siczek
Keyword(s):  
Friction Coefficient ◽  
Tribological Behavior ◽  
The Other ◽  
Zro2 Nanoparticles ◽  
Lubrication Mechanism ◽  
Lithium Grease ◽  
Frictional Properties ◽  
The Difference ◽  
Ball On Disc

The aim of the paper was to discuss different effects, such as, among others, agglomeration of selected nanoparticles, particularly those from zirconia, on the tribological behavior of lubricants. The explanation of the difference between the concepts of ‘aggregation’ and ‘agglomeration’ for ZrO2 nanoparticles is included. The factors that influence such an agglomeration are considered. Classification and thickeners of grease, the role of additives therein, and characteristics of the lithium grease with and without ZrO2 additive are discussed in the paper. The role of nanoparticles, including those from ZrO2 utilized as additives to lubricants, particularly to the lithium grease, is also discussed. The methods of preparation of ZrO2 nanoparticles are described in the paper. The agglomeration of ZrO2 nanoparticles and methods to prevent it and the lubrication mechanism of the lithium nanogrease and its tribological evaluation are also discussed. Sample preparation and a ball-on disc tester for investigating of spinning friction are described. The effect of ZrO2 nanoparticles agglomeration on the frictional properties of the lithium grease is shown. The addition of 1 wt.% ZrO2 nanoparticles to pure lithium grease can decrease the friction coefficient to 50%. On the other hand, the agglomeration of ZrO2 nanoparticles in the lithium grease can increase twice the friction coefficient relative to that for the pure grease.

scholarly journals True Stability of Lubricants Determined Using the Ball-on-Disk Test

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Angela Maria Tortora ◽  
Deepak Halenahally Veeregowda
Keyword(s):  
Contact Zone ◽  
Relative Motion ◽  
Contact Area ◽  
Wear Debris ◽  
Point Contact ◽  
High Viscosity ◽  
Contact Condition ◽  
Water Mixture ◽  
Glycerol Water ◽  
Low Viscosity

True stability of lubricants can be determined when there is minimum change in the contact area and also the intervention of wear debris in the contact zone. Here, we have used the ball-on-disk instrument with the migrating point contact, that is, relative motion between the ball and disk condition to fix the contact area and minimize the wear debris at the contact zone. The jump in the friction coefficient indicates the film failure, which appeared earlier for the motor oil 5W30 compared to 5W40. Such profile was not recorded in absence of relative motion. Therefore, 5W40 was considered to have a better lubricant stability than 5W30. Applying the same test condition to the natural lubricants shows that glycerol has better lubricant stability than glycerol-water mixture. Superior true lubricant stability by glycerol and 5W40 can be related to its high viscosity. However, they were less wear resistant compared to low viscosity lubricants like 5W30 and glycerol-water. We suspect the role of microscopic wear debris at the contact zone for this behavior although it should have been avoided in the migrating point contact condition. Overall, ball-on-disk instrument with a migrating point contact condition is an effective technique to determine the stability of lubricants.

scholarly journals Relationship between the real contact behavior and tribological characteristics of cotton fabric

Friction ◽  
2020 ◽  
Author(s):  
Rongxin Chen ◽  
Jiaxin Ye ◽  
Wei Zhang ◽  
Jiang Wei ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Contact Area ◽  
Dynamic Change ◽  
Tribological Characteristics ◽  
Real Contact Area ◽  
Cotton Fibers ◽  
Friction Behavior ◽  
Contact Behavior ◽  
The Real ◽  
Real Contact

Abstract The tribological characteristics of cotton fibers play an important role in engineering and materials science, and real contact behavior is a significant aspect in the friction behavior of cotton fibers. In this study, the tribological characteristics of cotton fibers and their relationship with the real contact behavior are investigated through reciprocating linear tribotesting and real contact analysis. Results show that the friction coefficient decreases with a general increase in load or velocity, and the load and velocity exhibit a co-influence on the friction coefficient. The dynamic change in the real contact area is recorded clearly during the experiments and corresponds to the fluctuations observed in the friction coefficient. Moreover, the friction coefficient is positively correlated with the real contact area based on a quantitative analysis of the evolution of friction behavior and the real contact area at different loads and velocities. This correlation is evident at low velocities and medium load.

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.

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