An Isoviscous Model for the Hydrodynamic Lubrication of Plane Strain Forging Processes With Flat Dies

1974 ◽  
Vol 96 (4) ◽  
pp. 539-546 ◽  
Author(s):  
W. R. D. Wilson
Keyword(s):  
Plane Strain ◽  
Hydrodynamic Lubrication ◽  
Hydrodynamic Theory ◽  
Experimental Measurements ◽  
Maximum Thickness ◽  
Good Agreement

Transient isoviscous hydrodynamic theory is used to investigate the lubrication of plane strain forging processes with flat dies. It is shown that during yielding a film which decreases from a maximum thickness at the center of the contact to zero at the edges is formed. As the deformation continues, the film is transported outwards at half the surface speed of the workpiece. In the case where the dies extend beyond the workpiece, an unlubricated region is formed. The variation in width of this region with reduction predicted by the model is in good agreement with experimental measurements.

Complementary Approaches for the Numerical Simulation of the Micro-Plasto-Hydrodynamic Lubrication Regime

2015 ◽  
Vol 651-653 ◽  
pp. 492-497 ◽  
Author(s):  
Cédric Hubert ◽  
André Dubois ◽  
Laurent Dubar ◽  
Maxime Laugier ◽  
Nicolas Legrand ◽  
...  
Keyword(s):  
Sheet Metal Forming ◽  
Metal Forming ◽  
Hydrodynamic Lubrication ◽  
Central Element ◽  
Experimental Measurements ◽  
Finite Element Models ◽  
Lubrication Regime ◽  
Lubricant Flow ◽  
Strip Drawing ◽  
Good Agreement

This paper presents recent investigations in the field of lubricant escapes from asperities. This phenomenon, named Micro Plasto Hydrodynamic Lubrication (MPHL), induces friction variation during metal forming processes. A better understanding of MPH lubrication would lead to a better management of friction, which is a central element in most sheet metal forming processes. To fulfil that goal, experiments were conducted in plane strip drawing using a transparent upper tool in order to observe lubricant flow around macroscopic pyramidal cavities. These experiments were then numerically reproduced with two complementary Finite Element models. The numerical results are discussed in this paper and show good agreement with experimental measurements.

The Behaviour of Multiple Loops in Torsion

1988 ◽  
Vol 15 (3) ◽  
pp. 149-156 ◽  
Author(s):  
R. A. Cavina ◽  
N. E. Waters
Keyword(s):  
Energy Method ◽  
Strain Energy ◽  
Vertical Axis ◽  
Experimental Measurements ◽  
Complementary Strain ◽  
Radial Axis ◽  
Strain Energy Method ◽  
Good Agreement

The angular stiffness of a multiple looped span, subject to rotation about a vertical axis (torsion) and also to rotation about a horizontal or radial axis (mesio-distal tilt), have been derived using the complementary (strain) energy method. Experimental measurements on enlarged models were in good agreement with the values calculated from the theoretical relationships obtained. The variations in angular stiffness resulting from changes in the loop height, width, and position of clinical sized loops are discussed.

Application of Potential Flow Theory to Plane-Strain Extrusion

1967 ◽  
Vol 89 (3) ◽  
pp. 503-511 ◽  
Author(s):  
A. Shabaik ◽  
S. Kobayashi ◽  
E. G. Thomsen
Keyword(s):  
Plane Strain ◽  
Potential Flow ◽  
Flow Line ◽  
Flow Theory ◽  
Flow Fields ◽  
Potential Flow Theory ◽  
Good Agreement

Theoretical and experimental flow fields of several extrusion ratios of lead in plane strain were compared. It was found that, for extrusion ratios where dead metal exists, the agreement between the potential and experimental flow nets was better for small reductions when a modified boundary approaching a flow line was used. It was also found that when the flow changed direction gradually, the potential flow net was in good agreement with the experimental one. The solution obtained is unique and complete.

ELECTRONIC STRUCTURE AND OPTICAL PROPERTIES OF CRYSTALLINE C60

1992 ◽  
Vol 06 (06) ◽  
pp. 309-321 ◽  
Author(s):  
W.Y. CHING ◽  
MING-ZHU HUANG ◽  
YONG-NIAN XU ◽  
FANQI GAN
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
First Principles ◽  
Optical Spectrum ◽  
Local Density ◽  
Low Dielectric Constant ◽  
Experimental Measurements ◽  
Absorption Bands ◽  
Low Dielectric ◽  
Good Agreement

The electronic structure and optical properties of crystalline C 60 and their pressure dependence have been studied by first-principles local density calculations. It is shown that fcc C 60 has a low dielectric constant and an optical spectrum rich in structures. The spectrum shows five disconnected absorption bands in the 1.4 to 7.0 eV region with sharp structures in each band that can be attributed to critical point transitions. This is a manifestation of the localized molecular structure coupled with long range crystalline order unique to the C 60 crystal. At a sufficient high pressure, the structures in the optical spectrum start to merge due to the merging of the bands. These results are in good agreement with some recent experimental measurements.

A new look at filter backwash hydraulics

2001 ◽  
Vol 1 (2) ◽  
pp. 65-72 ◽  
Author(s):  
Ömer Akgiray ◽  
Ahmet M. Saatçı
Keyword(s):  
Experimental Measurements ◽  
New Approach ◽  
Ergun Equation ◽  
Mathematical Formulas ◽  
Good Agreement ◽  
New Look

A new approach to model media expansion during filter backwash is presented. The proposed approach is based on the assumption that the Ergun equation remains valid after fluidization. Mathematical formulas are derived for predicting expanded porosity for a given backwash velocity or backwash velocity for a given expanded porosity. These formulas can be easily used by the engineer. Values predicted using the proposed approach are in good agreement with experimental measurements.

Adhesion Force Between High Energy Surfaces in Vapor Atmosphere

1994 ◽  
Vol 366 ◽  
Author(s):  
Jerome Crassous ◽  
Jean-Luc Loubet ◽  
Elisabeth Charlaix
Keyword(s):  
Liquid Bridge ◽  
Adhesion Force ◽  
Van Der Waals ◽  
Surface Force ◽  
High Energy ◽  
Attractive Force ◽  
Experimental Measurements ◽  
Metallic Substrates ◽  
Energy Surfaces ◽  
Good Agreement

ABSTRACTWe report experimental measurements of the adhesion force between metallic substrates in undersaturated heptane vapor atmosphere, with a surface force apparatus. The attractive force between the substrates is strongly dependant of the condensation of a liquid bridge connecting the surfaces. The results show the importance of wetting phenomena for the maximum attractive force: we find that this maximum attraction varies as the power two-third of the curvature of the meniscus connecting the surfaces, in good agreement with the theory of Van der Waals wetting.

Predicting Thermal Mixing and Fatigue Inside Control Rod Guide Tubes

2013 ◽  
Author(s):  
Eric Lillberg
Keyword(s):  
Thermal Fatigue ◽  
Turbulent Mixing ◽  
Low Frequency ◽  
Experimental Measurements ◽  
Guide Tube ◽  
Control Rod ◽  
Thermal Mixing ◽  
Purge Flow ◽  
Control Rods ◽  
Good Agreement

The cracked control rods shafts found in two Swedish NPPs were subjected to thermal fatigue due to mixing of cold purge flow with hot bypass water in the upper part of the top tube on which the control rod guide tubes rests. The interaction between the jets formed at the bypass water inlets is the main source of oscillation resulting in low frequency downward motion of hot bypass water into the cold purge flow. This ultimately causes thermal fatigue in the control rod shaft in the region below the four lower bypass water inlets. The transient analyses shown in this report were done to further investigate this oscillating phenomenon and compare to experimental measurements of water temperatures inside the control rod guide tube. The simulated results show good agreement with experimental data regarding all important variables for the estimation of thermal fatigue such as peak-to-peak temperature range, frequency of oscillation and duration of the temperature peaks. The results presented in this report show that CFD using LES methodology and the open source toolbox OpenFOAM is a viable tool for predicting complex turbulent mixing flows and thermal loads.

Disordering of MgAl2O4 spinel from first principles

2000 ◽  
Vol 64 (2) ◽  
pp. 311-317 ◽  
Author(s):  
M. C. Warren ◽  
M. T. Dove ◽  
S. A. T. Redfern
Keyword(s):  
Free Energy ◽  
Electronic Structure ◽  
First Principles ◽  
Large Scale ◽  
Experimental Measurements ◽  
Zero Temperature ◽  
Macroscopic Models ◽  
Tetrahedral Sites ◽  
Degree Of Order ◽  
Good Agreement

AbstractAt high temperature, MgAl2O4 spinel is stabilized by disorder of Mg and Al between octahedral and tetrahedral sites. This behaviour has been measured up to 1700 K in recent neutron experiments, but the extrapolation of subsequently fitted thermodynamic models is not reliable. First principles simulation of the electronic structure of such minerals can in principle accurately predict disorder, but would require unfeasibly large computing resources. We have instead parameterized on-site and short-ranged cluster potentials using a small number of electronic structure simulations at zero temperature. These potentials were then used in large-scale statistical simulations at finite temperatures to predict disordering thermodynamics beyond the range of experimental measurements. Within the temperature range of the experiment, good agreement is obtained for the degree of order. The entropy and free energy are calculated and compared to those from macroscopic models.

Non-Linear Lubricant Behavior in Concentrated Contacts

2001 ◽  
Author(s):  
Andras Z. Szeri
Keyword(s):  
Elastic Deformation ◽  
Hydrodynamic Lubrication ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Contact ◽  
Material Behavior ◽  
Solid Surfaces ◽  
Hydrodynamic Theory ◽  
Shear Rates ◽  
Liquid Lubricant ◽  
Temperature And Pressure

Abstract Elastohydrodynamic lubrication (EHL) is the name given to hydrodynamic lubrication when it is applied to solid surfaces of low geometric conformity (counterformal contacts) that are capable of, and are subject to, elastic deformation. In bearings relying on EHL principles, the residence time of the fluid is less than 1 ms, the pressures are up to 4 GP, the film is thin, down to 0.1 μm, and shear rates are up to 108 s−1 — under such conditions lubricants exhibit material behavior that is distinctly different from their behavior in bulk at normal temperature and pressure. In fact, without taking into account the viscosity-pressure characteristics of the liquid lubricant and the elastic deformation of the bounding solids, hydrodynamic theory is unable to explain the existence of continuous lubricant films in highly loaded gears and rolling contact bearings.

Application of Various Combustion Models to a Generic Combustor

2003 ◽  
Author(s):  
Lei-Yong Jiang ◽  
Ian Campbell
Keyword(s):  
Experimental Tests ◽  
Combustion Model ◽  
Discrete Ordinates ◽  
Experimental Measurements ◽  
Finite Rate ◽  
Zone Length ◽  
Combustion Models ◽  
The Mean ◽  
Heat Transfers ◽  
Good Agreement

The flow-field of a generic gas combustor with interior and exterior conjugate heat transfers was numerically studied. Results obtained from three combustion models, combined with the re-normalization group (RNG) k-ε turbulence model, discrete ordinates radiation model, and partial equilibrium NOx model are presented and discussed. The numerical results are compared with a comprehensive database obtained from a series of experimental tests. The flow patterns and the recirculation zone length are excellently predicted, and the mean axial velocities are in fairly good agreement with the experimental measurements, particularly at downstream sections for all three combustion models. The mean temperature profiles are also fairly well captured by the probability density function (PDF) and eddy dissipation (EDS) combustion models. The EDS-finite-rate combustion model fails to provide acceptable temperature field. In general, the PDF shows some superiority over the EDS and EDS-finite-rate models. NOx levels predicted by the EDS model are in reasonable agreement with the experimental measurements.

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