scholarly journals Discussion: “A Theory of Hydrodynamic Friction Forces in Starved Point Contact Considering Cavitation” (Chiu, Y. P., 1974, ASME J. Lubr. Technol., 96, pp. 237–245)

1974 ◽  
Vol 96 (2) ◽  
pp. 245-245
Author(s):  
C. W. Allen
Keyword(s):  
Point Contact ◽  
Hydrodynamic Friction ◽  
Friction Forces

A Theory of Hydrodynamic Friction Forces in Starved Point Contact Considering Cavitation

1974 ◽  
Vol 96 (2) ◽  
pp. 237-245 ◽  
Author(s):  
Y. P. Chiu
Keyword(s):  
Fluid Layer ◽  
Point Contact ◽  
Rolling Friction ◽  
Rigid Bodies ◽  
Variable Degree ◽  
Hydrodynamic Friction ◽  
Friction Forces ◽  
Viscosity Parameter

Expressions for the hydrodynamic friction forces between two rigid bodies each having two principal radii of curvature have been found using an exponential pressure-viscosity assumptions. The rolling friction forces are presented graphically in terms of a dimensionless meniscus distance. These formulas are applicable to the computation of the rolling friction in a ball-race contact and in a ball-cage contact with a variable degree of starvation. In particular, the rolling friction forces can be predicted as a function of the usual speed-viscosity parameter and the thickness of the inlet fluid layer far upstream of the inlet.

CHAIN ROTATIONAL DYNAMICS IN MR SUSPENSIONS

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2293-2299 ◽  
Author(s):  
SONIA MELLE ◽  
OSCAR G. CALDERÓN ◽  
MIGUEL A. RUBIO ◽  
GERALD G. FULLER
Keyword(s):  
Power Law ◽  
Rotating Magnetic Fields ◽  
Hydrodynamic Friction ◽  
Friction Forces ◽  
Number Ratio ◽  
Mason Number ◽  
Dynamics Simulations ◽  
Average Size ◽  
The Magnetic Field ◽  
Good Agreement

The dynamics of induced dipolar chains in magnetorhelogical suspensions subject to rotating magnetic fields has been experimentally studied combining scattering dichroism and video microscopy experiments. When a rotating field is imposed the chainlike aggregates rotate synchronously with the magnetic field. We found that the average size of the aggregates decreases with Mason number (ratio of viscous to magnetic forces) following a power law with exponent -0.5 being the hydrodynamic friction forces the cause of the chains break up. However the total number of aggregated particles shows two different behaviors depending on Mason number. For low Mason numbers, the total number of aggregated particles remains almost constant and above a critical Mason number, the rotation of the field prevents the particle aggregation process from taking place so the number of aggregated particles decreases with Mason number following a power law behavior with exponent -1. Athermal molecular dynamics simulations are also reported, showing good agreement with the experiments.

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.

Friction Forces between Sheet Molding Compound Charge and Mold Cavity Surface in Compression Molding

2011 ◽  
Vol 471-472 ◽  
pp. 733-738 ◽  
Author(s):  
Mahmood M. Shokrieh ◽  
Reza Mosalmani
Keyword(s):  
Friction Force ◽  
Compression Molding ◽  
Molding Pressure ◽  
Cavity Surface ◽  
Hydrodynamic Friction ◽  
Friction Forces ◽  
Molding Compound ◽  
Sheet Molding Compound ◽  
Constant Friction ◽  
Proposed Model

In this study, three relevant friction ‎forces: constant friction force, hydrodynamic friction force and coulomb friction force are ‎considered between sheet molding compound (SMC) charge and contact surface of the mold. The power ‎law model is implemented to propose a model for prediction of hydrodynamic friction as the dominant friction of the SMC compression molding. The proposed model ‎is simple and does not need any extra experimental parameters. Finally, a model has been developed to predict the molding pressure under non-isothermal conditions. The obtained results of the model are in a very good agreement with the experimental data.

POTENTIAL FOR EXPANDING THE RANGE OF FLUID FRICTION WHILE MINIMISING FRICTION RESISTANCES AND IMPROVING AN OIL FILM ’S LOAD BEARING CAPACITY

Tribologia ◽  
2020 ◽  
Vol 291 (3) ◽  
pp. 33-38
Author(s):  
Krzysztof Krawczyk ◽  
Emil Nowiński ◽  
Grzegorz Wronka ◽  
Wojciech Żurowski ◽  
Wiktoria Edwardowna Burłakowa
Keyword(s):  
Friction Pair ◽  
Hydrodynamic Friction ◽  
Fluid Friction ◽  
Friction Forces ◽  
Friction Process ◽  
Oil Film ◽  
The Third ◽  
Third Stage ◽  
Three Stages ◽  
Selection Of

Traces of mechanical wear appear on co-working surfaces in the operation of precision fluid bearings. This should not be the case, since fluid friction and uninterrupted oil film should be present in a friction pair, which is a concept that this paper attempts to outline. The way friction forces, resistance, and oil film vary as unit pressure rises linearly is discussed. Three stages of the variations are distinguished. At the first stage, the oil film thickness and force of friction remain steady while the resistance declines. Stage two is temporary: Triboelectrical phenomena already escalate considerably and begin to decide effects of the friction process while a lubricant loses rheological properties of the Newtonian fluid. Hydrodynamic friction continues at the third stage, yet the triboelectrical effects are decided by stabilised triboelectrical phenomena. The third range can be identified as boundary friction where the layer separating surfaces is thicker than in the area of Newtonian rheology. This is very good in respect to wear, but higher-energy (not electrically neutral) particles cause increases in friction resistances. This range seems to exhibit a very high potential for being controlled with an adequate selection of oil based additions.

Featuring Pig Movement in Two-Phase Gas Pipelines

2012 ◽  
Author(s):  
David E. G. P. Bueno ◽  
Aline Barbosa Figueiredo ◽  
Renan Martins Baptista ◽  
Felipe B. F. Rachid ◽  
Gustavo C. R. Bodstein
Keyword(s):  
Numerical Scheme ◽  
Initial Boundary ◽  
Initial Boundary Value Problem ◽  
General Purpose ◽  
Gas Pipelines ◽  
Two Phase ◽  
Hydrodynamic Friction ◽  
Friction Forces ◽  
Different Types ◽  
Initial Boundary Value

This paper presents a mechanical model, along with a numerical scheme for obtaining approximating solutions for the resulting initial-boundary-value problem, for describing the pig movement in transient two-phase gas pipelines. By taking advantage of the best features of the existing models presented in the literature so far, an idealized general purpose pig model is proposed, contemplating the possibility of representing, within a same context, different types of pigs or pig functions. Both mechanical and hydrodynamic friction forces at the interface of the pig and the pipe wall, as well as by-pass flow rates for the liquid and gaseous phases, are naturally incorporated in the modeling in a coherent mechanical context. The governing equations of the two-phase flow model are intentionally written in a general form, so that different existing models can be used within the framework presented herein. Following this same strategy, a detailed numerical scheme is presented in which the discretization of the flux terms are left open, so that different numerical strategies of first or higher orders can be accommodated without any additional difficulties.

scholarly journals Influence of Humidity on Friction Forces in Point-Contact under Small Loads

2017 ◽  
Vol 58 (2) ◽  
pp. 236-242 ◽  
Author(s):  
Rongguang Wang ◽  
Shoma Furukawa ◽  
Masanobu Imakawa
Keyword(s):  
Point Contact ◽  
Friction Forces

Identification of Friction Coefficient for Constrained Robotic Tasks

2002 ◽  
Vol 124 (4) ◽  
pp. 529-538 ◽  
Author(s):  
I. Sharf ◽  
G. Gilardi ◽  
C. Crawford
Keyword(s):  
Coefficient Of Friction ◽  
Normal Load ◽  
Point Contact ◽  
Contact Dynamics ◽  
Dynamics Simulation ◽  
Identification Algorithm ◽  
Test Bed ◽  
Accurate Identification ◽  
Friction Forces ◽  
The Coefficient Of Friction

Correct modeling of friction forces during constrained robotic operations is critical to high-fidelity contact dynamics simulation. Such simulations are particularly important for the development, mission planning and operations analysis of space robotic systems. Most existing friction models employ the coefficient of friction to capture the relationship between the friction force and the normal load. Hence, accurate identification of this parameter is prerequisite to accurate simulation. This issue is particularly important for space robotic operations since friction characteristics of materials are very different in space. In this manuscript, the problem of identification of the coefficient of friction is investigated experimentally and numerically. The motivating application being space manipulator systems, our principal objective is to develop a practical off-line identification algorithm, requiring minimum number of measurements from sensors available on space robots. To this end, a strategy is proposed to determine the coefficient of friction by using only the measured end-effector forces. The key idea behind the method is that during one-point contact, these forces represent the contact force and hence, can be directly used to calculate the coefficient of friction. The proposed approach is tested with the experimental data from peg insertion experiments conducted on a planar robotics test-bed with a specially designed contact interface. The algorithm is generalized to arbitrary complex geometries and applied to identify the coefficient of friction for a simulated battery drop test.

Sign in / Sign up

Export Citation Format

Share Document