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

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.

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.

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.

Point-contact spectroscopy of quasi-1D conductors with CDW

1999 ◽  
Vol 09 (PR10) ◽  
pp. Pr10-179-Pr10-181
Author(s):  
A. A. Sinchenko ◽  
Yu. I. Latyshev ◽  
S. G. Zybtsev ◽  
I. G. Gorllova
Keyword(s):  
Point Contact ◽  
Point Contact Spectroscopy

Structure and properties of compact articles from high-alloyed iron powder with adding of boron nitride

2020 ◽  
pp. 39-48
Author(s):  
B. O. Bolshakov ◽  
◽  
R. F. Galiakbarov ◽  
A. M. Smyslov ◽  
◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Boron Nitride ◽  
Grain Boundary ◽  
Bending Strength ◽  
Physical And Mechanical Properties ◽  
Operating Conditions ◽  
Structure And Properties ◽  
Steam Turbines ◽  
Friction Forces ◽  
Wide Range

The results of the research of structure and properties of a composite compact from 13 Cr – 2 Мо and BN powders depending on the concentration of boron nitride are provided. It is shown that adding boron nitride in an amount of more than 2% by weight of the charge mixture leads to the formation of extended grain boundary porosity and finely dispersed BN layers in the structure, which provides a high level of wearing properties of the material. The effect of boron nitride concentration on physical and mechanical properties is determined. It was found that the introduction of a small amount of BN (up to 2 % by weight) into the compacts leads to an increase in plasticity, bending strength, and toughness by reducing the friction forces between the metal powder particles during pressing and a more complete grain boundary diffusion process during sintering. The formation of a regulated structure-phase composition of powder compacts of 13 Cr – 2 Mо – BN when the content of boron nitride changes in them allows us to provide the specified physical and mechanical properties in a wide range. The obtained results of studies of the physical and mechanical characteristics of the developed material allow us to reasonably choose the necessary composition of the powder compact for sealing structures of the flow part of steam turbines, depending on their operating conditions.

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