Dynamic Friction Characteristics of Bulk Seeds Against Flat Vertical Surfaces

1992 ◽  
Vol 35 (2) ◽  
pp. 665-669 ◽  
Author(s):  
D. A. Irvine ◽  
D. S. Jayas ◽  
M. G. Britton ◽  
N. D. G. White
Keyword(s):  
Dynamic Friction ◽  
Friction Characteristics

The dynamic friction characteristics of a rapidly sheared granular material applied to the motion of snow avalanches

1993 ◽  
Vol 18 ◽  
pp. 215-220 ◽  
Author(s):  
J.D. Dent
Keyword(s):  
Shear Layer ◽  
Slip Plane ◽  
Flat Surface ◽  
Dynamic Friction ◽  
Friction Characteristics ◽  
Dynamic Friction Coefficient ◽  
Dispersed Particles ◽  
Number Of Layers ◽  
Shear Speed ◽  
Shearing Motion

A numerical simulation of simple two-dimensional shear of round uniform grains is used to investigate the dynamic friction characteristics of the layer of snow at the base of an avalanche. For steady, uniform flow on a uniform flat surface, the dynamic friction coefficient transmitted through the shear array is found as it varies with the shear speed and normal force applied to the top of the shear layer, and the properties of the particles in the shear layer.For this simple model, the flow in the shear layer is found to be independent of the total number of layers in the shear flow. A slip plane is formed along which most of the shearing motion takes places, so that the shear is confined to just two layers of particles which slide over one another. In the absence of gravity this slip plane jumps up and down randomly within the shear layer, which is otherwise composed of agitated semi-dispersed particles.

Model-Based Investigation of Friction During Start-Up of Hydrodynamic Journal Bearings

1995 ◽  
Vol 117 (4) ◽  
pp. 667-673 ◽  
Author(s):  
A. Harnoy
Keyword(s):  
Friction Model ◽  
Journal Bearings ◽  
Time Variable ◽  
Stribeck Curve ◽  
Dynamic Friction ◽  
Stick Slip ◽  
Friction Characteristics ◽  
Start Up ◽  
Variable Friction ◽  
Steady Velocity

An analysis is developed for the time-variable friction during the start-up of a rotor system. The analysis is based on a dynamic friction model that has been developed from the theory of unsteady lubrication and can describe the observed friction characteristics. The model reduces to the Stribeck curve of friction versus steady velocity, and shows hysteresis curves in oscillating velocity. The “Dahl effect” of a presliding displacement before the breakaway is also included. The results indicate that the friction characteristics and energy friction losses, during the start-up, depend on a set of dimensionless parameters that represent the bearing as well as the dynamic system. The study shows that appropriate design and operation can prevent stick-slip friction and minimize wear during start-up.

Numerical Analysis of the Ultrasonic Honing Chatter Based on the Stribeck Model

2013 ◽  
Vol 690-693 ◽  
pp. 3231-3234
Author(s):  
Jian Qing Wang ◽  
Xi Jing Zhu
Keyword(s):  
Numerical Analysis ◽  
Nonlinear System ◽  
Ultrasonic Vibration ◽  
Theoretical Basis ◽  
Dynamic Friction ◽  
Dynamics Model ◽  
Describing Function ◽  
Friction Characteristics ◽  
Power Ultrasonic ◽  
The Stability

Chatter easily occurs in machining, which is influenced by many factors. The power ultrasonic vibration honing equipment is taken as the research object. The dynamic friction is studied and the dynamics model is established based on the Stribeck model. The describing function of the ultrasonic honing friction characteristics is calculated. The stability of ultrasonic honing nonlinear system is analyzed. The conditions are studied, on which chatter occurs. The expressions of chatter amplitude and frequency are given. The research provides the theoretical basis on which chatter can be effectively avoided when ultrasonic honing equipment is designed.

Study of the effects of relative humidity and velocity on the friction characteristics of pneumatic cylinders

2020 ◽  
Vol 34 (22n24) ◽  
pp. 2040139
Author(s):  
Thuy-Duong Nguyen ◽  
Van-Hung Pham
Keyword(s):  
Relative Humidity ◽  
Sliding Friction ◽  
Static Friction ◽  
Pneumatic Cylinder ◽  
Dynamic Friction ◽  
Friction Forces ◽  
Measuring Device ◽  
Friction Characteristics ◽  
Rod Seals ◽  
Pneumatic Cylinders

The movement of a piston rod in a pneumatic cylinder is directly affected by the air humidity in the atmosphere, especially in the case of piston rods without any means of protection or grease on their surfaces. In a pneumatic cylinder system, the friction between the piston rod and the rod seal is sliding friction, and it has a significant value that varies with the variation in the moisture on the piston rod’s surface. In this paper, an investigation of the friction characteristics of piston rods and rod seals in a pneumatic cylinder was carried out with different humidity and velocity values to understand the effect of lubricants on the moving parts of pneumatic systems in humid environments, where the friction characteristics of the displacements corresponding to the static and dynamic friction forces were displayed on a measuring device. The research results showed that the static friction forces tended to decrease by [Formula: see text] and that the dynamic friction forces tended to decrease by [Formula: see text] when the relative humidity increased from 51% to 99% at different velocities between 5 and 100 mm/s.

scholarly journals Effects of hydraulic oil and lubricant additives on dynamic friction properties under various reciprocating sliding conditions

Friction ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 471-480
Author(s):  
Shinji Kato ◽  
Shinya Sasaki
Keyword(s):  
Shock Absorber ◽  
Dynamic Friction ◽  
Additive Concentration ◽  
Reciprocating Motion ◽  
Friction Behavior ◽  
Friction Characteristics ◽  
Reciprocating Sliding ◽  
Hydraulic Oil ◽  
Additive Formulation ◽  
Zinc Dithiophosphate

Abstract The friction characteristics of a shock absorber are very complex because the reciprocating motion is not always identical. In this study a device was developed and used to analyze the dynamic friction characteristics under various reciprocating sliding conditions to determine the sliding materials and hydraulic oils that improve the shock absorber performance. This study describes the influence of hydraulic oil additive on the fine reciprocating friction characteristics of steel and copper alloy. Hydraulic oils were prepared by blending a paraffinic mineral oil with zinc dithiophosphate (ZnDTP) and polyhydric alcohol ester as additives. The results show that the dynamic frictional characteristics vary mainly depending on the additive concentration. A specific additive formulation induces a unique amplitude-dependent friction behavior. In addition, the influence of different additives on the lubrication mechanism is investigated based on the instrumental analysis of the friction surface.

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