A Theoretical Model of Micro-Pool Lubrication in Metal Forming

1999 ◽  
Vol 121 (4) ◽  
pp. 731-738 ◽  
Author(s):  
Sy-Wei Lo ◽  
William R. D. Wilson
Keyword(s):  
Theoretical Model ◽  
Metal Forming ◽  
Strong Influence ◽  
Hydrodynamic Lubrication ◽  
High Viscosity ◽  
Asperity Contact ◽  
Sliding Velocity ◽  
Lubrication Mechanism ◽  
Sliding Speed ◽  
Lubricant Viscosity

A model of a secondary hydrodynamic lubrication mechanism, which is called micro-pool or micro-plasto hydrodynamic lubrication, has been developed. It shows that, with sufficiently high viscosity and sliding speed, the lubricant trapped in the micro-pools between the tool and workpiece can be drawn into the interface. The friction force is either increased or decreased, depending on the viscosity and sliding speed. Without bulk stretching, the product of the lubricant viscosity and sliding velocity can be used as an index to indicate whether or not micro-pool lubrication will occur. Stretching the workpiece may make a strong influence not only on the thickness of the permeating film but also on the asperity contact area.

First Paper: An Investigation into the Steady-State Characteristics of Plain Slideways

1969 ◽  
Vol 184 (1) ◽  
pp. 1075-1087 ◽  
Author(s):  
R. Bell ◽  
M. Burdekin
Keyword(s):  
Cast Iron ◽  
Steady State ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Sliding Velocity ◽  
Experimental Conditions ◽  
Friction Characteristics ◽  
Feed Drive ◽  
Lubricant Viscosity

This paper describes steady-state friction tests on a scraped-cup ground combination of cast iron surfaces. The experimental conditions were representative of the operating conditions on a machine tool feed drive employing plain slideways. The range of the relative sliding velocity investigated was 0 → 1 in s-1, and the influence of lubricant viscosity of both polar and non-polar additive lubricants is shown. An investigation into the effect of oil grooves is also reported. Data obtained from squeeze film measurements enabled the characteristics, normal to the sliding plane, to be specified. These characteristics, together with measurements of the separation of the surfaces, enabled the steady-state friction characteristics to be predicted over the range of mixed and hydrodynamic lubrication covered by the tests. This work formed a basis for the investigation into the mechanism of the friction characteristics under dynamic conditions.

Theoretical and Experimental Study of the Glass Lubricated Extrusion Process

1975 ◽  
Vol 97 (1) ◽  
pp. 18-23 ◽  
Author(s):  
P. Baque´ ◽  
J. Pantin ◽  
G. Jacob
Keyword(s):  
Experimental Study ◽  
Theoretical Model ◽  
Process Parameters ◽  
Glass Powder ◽  
Extrusion Process ◽  
High Viscosity ◽  
Experimental Measurements ◽  
Glass Film ◽  
Lubrication Mechanism ◽  
Influence Of Process Parameters

The Ugine-Se´journet patent for glass lubrication of metals extrusion made it possible to extrude steel in large quantities. A cold pad of glass powder inserted between the die and the billet head melts progressively, providing a high viscosity glass film between the die and the metal. The authors propose a theoretical model of the lubrication mechanism: progressive melting, hydrodynamic flow, and stability of the film. The influence of process parameters is discussed and results are compared with experimental measurements.

Hydrodynamic Lubrication in Axisymmetric Stretch Forming—Part 1: Theoretical Analysis

1991 ◽  
Vol 113 (4) ◽  
pp. 659-666 ◽  
Author(s):  
W. R. D. Wilson ◽  
L. G. Hector
Keyword(s):  
Theoretical Model ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Sheet Metal ◽  
Newtonian Fluid ◽  
Hydrodynamic Lubrication ◽  
Lubricant Film ◽  
Previous Model ◽  
Stretch Forming ◽  
Lubricant Viscosity

An improved theoretical model for the hydrodynamic lubrication of axisymmetric, sheet metal stretch forming is presented. The infinite initial film thickness problem, encountered in a previous model, is removed by accounting for the squeeze action occurring during the initial stages of the process. Both isoviscous and thermoviscous theories are developed assuming that the lubricant is a Newtonian fluid. In the thermoviscous model, the lubricant viscosity is assumed to vary exponentially with temperature. The influence of plastic heating of the sheet on the entrainment and transport of the lubricant film is examined. The effects of variable punch speed are also investigated.

A comprehensive mathematical model for an accurate calculation of the oil film thickness of strip cold rolling

2019 ◽  
Vol 234 (3) ◽  
pp. 350-361
Author(s):  
Xinxiao Bian ◽  
Quan Wang
Keyword(s):  
Mathematical Model ◽  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Rolling Force ◽  
Elastohydrodynamic Lubrication ◽  
Rolled Strip ◽  
Asperity Contact ◽  
Oil Film ◽  
Rolling Oil ◽  
Lubricant Viscosity

The surface quality of cold rolled strip is related to a greater extent on the rolling oil film thickness, and there are many factors that affect the oil film thickness. Considering the various factors comprehensively, an integrated mathematical model is established, such as roughness of rolls and strips, elastohydrodynamic lubrication, friction heat and plastic deformation heat in the rolling zone, viscosity varying with temperature and pressure, etc. A series of equations are developed, such as the Reynolds equation of partial membrane hydrodynamic lubrication based on average flow theory, equation of oil film thickness on rough elastic surface, the thermal interface equations between strip, oil film and roller surface, surface asperity contact pressure equation, lubricant viscosity and density equations, motion equation of the oil film, etc. This model is solved by finite difference method to get the film pressure, oil film thickness, and temperature distribution in the rolling zone. The average rolling pressure, the roll, and strip temperature calculated by the model are very close to the field test results. Comparing the minimum film thickness calculated by the model with the regression formula of other literature test, the error is less than 10%. The minimum oil film thickness is analyzed. It increases with the decrease of the rolling force and is approximately proportional to the rolling speed and lubricant viscosity.

scholarly journals Modeling of Micro-Pit Evolution in Rolling or Strip-Drawing

2000 ◽  
Vol 123 (4) ◽  
pp. 791-798 ◽  
Author(s):  
M. P. F. Sutcliffe ◽  
H. R. Le ◽  
R. Ahmed
Keyword(s):  
Hydrodynamic Lubrication ◽  
Steel Strip ◽  
Viscosity Coefficient ◽  
Sliding Speed ◽  
Dimensional Group ◽  
Theoretical Predictions ◽  
Strip Drawing ◽  
Measured Change ◽  
Cold Rolled ◽  
Lubricant Viscosity

The micro-plasto-hydrodynamic lubrication (MPHL) model of pit evolution is extended to account for the variation of sliding speed and strain rate in rolling and drawing processes. Results show that all of the following factors are important: pit angle, lubricant viscosity and pressure viscosity coefficient, material yield stress and sliding speed. Theoretical predictions for the change in pit area during the deformation process are well correlated by a non-dimensional group of these parameters. The model agrees reasonably with the measured change in pit volume and area from drawing experiments on cold rolled stainless steel strip containing both artificial and stochastic roughness.

Effect of shape/size and distribution of microgeometries of textures on tribo-performance of crankpin bearing

2021 ◽  
pp. 135065012110105
Author(s):  
Nguyen Van Liem ◽  
Wu Zhenpeng ◽  
Jiao Renqiang
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Contact Force ◽  
Distribution Density ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Combined Model ◽  
Obvious Effect ◽  
Area Density

The effect of the shape/size and distribution of microgeometries of textures on improving the tribo-performance of crankpin bearing is proposed. Based on a combined model of the slider-crank mechanism dynamic and hydrodynamic lubrication, the distribution density, area density, and shape of spherical textures, square-cylindrical textures, wedge-shaped textures, and a hybrid between spherical texture and square-cylindrical texture on the crankpin bearing's tribo-performance are investigated under different operating conditions of the engine. The tribological characteristic of the crankpin bearing is then evaluated via the indexes of the oil film pressure p, asperity contact force, friction force, and friction coefficient of the crankpin bearing. The research results show that the distribution density with n = 12 and m = 6, and area density with α = 30% of various microtextures have an obvious effect on ameliorating the crankpin bearings tribo-performance. Concurrently, at the mixed lubrication region, the shape of the square-cylindrical texture on improving the tribo-performance is better than the other shapes of the spherical texture, wedge-shaped texture, and spherical and square-cylindrical texture. Particularly, all the average values of the asperity contact force, friction force, and friction coefficient with a square-cylindrical texture are significantly reduced by 14.6%, 19.5%, and 34.5%, respectively, in comparison without microtextures. Therefore, the microtextures of the spherical texture applied on the bearing surface can contribute to enhance the durability and decrease the friction power loss of the engine.

Enhancing Tribological Conditions in Tube Hydroforming by Using Textured Tubes

2004 ◽  
Author(s):  
Gracious Ngaile ◽  
Mark Gariety ◽  
Taylan Altan
Keyword(s):  
Deformation Behavior ◽  
Hydrodynamic Lubrication ◽  
Tube Hydroforming ◽  
Great Influence ◽  
Tribological Performance ◽  
Tube Surface ◽  
Sliding Velocity ◽  
Textured Surfaces ◽  
Interface Pressure ◽  
Surface Textures

The effects of textured tubes on the tribological performance in Tube Hydroforming (THF) are discussed. Textured surfaces, namely sand blasted, knurled, and as rolled surfaces were tested under various interface pressure and sliding velocity conditions. Sand blasted textured tubes were found to have the best tribological performance. It was also found that the interface pressure has a great influence on the attainment of Micro-Plasto HydroDynamic Lubrication (MPHDL) and Micro-Plasto HydroStatic Lubrication (MPHSL) conditions at the tool-workpiece interface. Preliminary finite element simulations on the deformation behavior of tube surface shows that surface textures can be optimized to enhance tribological performance.

scholarly journals Influence of the Lubrication Oil Temperature on the Disengaging Dynamic Characteristics of a Cu-Based Wet Multi-Disc Clutch

2021 ◽  
Vol 11 (23) ◽  
pp. 11299
Author(s):  
Liangjie Zheng ◽  
Biao Ma ◽  
Man Chen ◽  
Liang Yu ◽  
Qian Wang
Keyword(s):  
Dynamic Characteristics ◽  
Hydrodynamic Lubrication ◽  
Friction Pair ◽  
Automatic Transmission ◽  
Friction Torque ◽  
Asperity Contact ◽  
Uniformity Coefficient ◽  
Lubrication Oil ◽  
The Impact ◽  
First Time

Clutch disengaging dynamic characteristics, including the disengaging duration and the variations of friction pair gaps and friction torque, are crucial to the shifting control of an automatic transmission. In the present paper, the influence of lubrication oil (ATF) temperature on disengaging dynamic characteristics is investigated through a comprehensive numerical model for the clutch disengaging process, which considers the hydrodynamic lubrication, the asperity contact, the heat transfer, the spline resistance, and the impact between the piston and clutch hub. Moreover, the non-uniformity coefficient (NUC) is proposed to characterize the disengaging uniformity of friction pairs. As the ATF temperature increases from 60 °C to 140 °C, the clutch disengaging duration shortens remarkably (shortened by 55.1%); besides, the NUC sees a decreasing trend before a slight increase. When the ATF temperature is 80 °C, the distribution of friction pair gaps is most uniform. During the disengaging process, the increase of ATF temperature not only accelerates the change of the lubrication status between friction pairs but also contributes to the decrease of contact torque and hydrodynamic torque. This research demonstrates for the first time, evidence for clutch disengaging dynamic characteristics with the consideration of ATF temperature.

Study of the Effect of Deformation on the Axes of Anisotropy

1991 ◽  
Vol 113 (2) ◽  
pp. 187-191 ◽  
Author(s):  
A. Kumar ◽  
Shyam K. Samanta ◽  
K. Mallick
Keyword(s):  
Theoretical Model ◽  
Metal Forming ◽  
Grain Shape ◽  
Reference State ◽  
Deformation Tensor ◽  
Yield Behavior ◽  
Experimental Scheme ◽  
Principal Stretches ◽  
Principal Directions ◽  
Subsequent Deformation

Many metal forming operations, such as rolling and tube drawing, are known to induce orthotropic anisotropy. The change of axes of orthotropy with subsequent deformation has been studied in this paper. The change in the orthotropy directions is of great importance for understanding and interpreting the subsequent yield behavior of metals. Based on Hill’s hypothesis that the orthotropy axes coincides with the principal directions of stretch, the change in orthotropy directions has been studied theoretically and experimentally. Since the grain shape and its direction of elongation is a good indicator of the principal stretches and its directions, it has been used as an experimental means of determining, not only the directions of principal stretches in an as received material, but also to determine approximately the deformation it has undergone so far from a reference state. A fully annealed isotropic state is chosen as the reference state. The directions of the axes of anisotropy, induced as a result of finite deformation applied to this reference state, are characterized in terms of the principal directions of the Cauchy’s deformation tensor. An experimental scheme has been developed to determine the varying directions of orthotropy for comparison with the theoretical model.

scholarly journals Analysis on micro-motion of cylinder block based on elasto-hydrodynamic lubrication

2019 ◽  
Vol 72 (5) ◽  
pp. 645-650 ◽  
Author(s):  
Jihai Jiang ◽  
Wei-Peng Yan ◽  
Ge-Qiang Li
Keyword(s):  
Numerical Model ◽  
Hydrodynamic Lubrication ◽  
Valve Plate ◽  
Cylinder Block ◽  
Asperity Contact ◽  
Plate Interface ◽  
Content Type ◽  
Micro Motion ◽  
Belt Width ◽  
Discharge Pressure

Purpose The purpose of this paper is to analyze the micro-motion of the cylinder block. Design/methodology/approach Based on the elasto-hydrodynamic lubrication, a numerical model for the cylinder block/valve plate interface is proposed, with consideration of the elastic deformations, the pressure-viscosity effect and asperity contacts. The influence-function method is applied to calculating the actual deformations of the cylinder block and the valve plate. The asperity contact model simplified from Greenwood assumption is introduced into the numerical model. Furthermore, the relationship between the micro-motion and the operating condition, the sealing belt width is discussed, respectively. Findings The results show an increase in the discharge pressure causes the tilt state and the vibrating motion getting worse, which can be eased by improving the rotational speed, the sealing belt width and the ratio of external and internal sealing belt width. Originality/value The proposed research can provide a theoretical reference for the optimizing design of cylinder block/valve plate pair.

Sign in / Sign up

Export Citation Format

Share Document