Direct and Indirect Approaches at the Plasto-Hydrodynamic Lubrication Problem. Application to an Industrial Ironing Process

1999 ◽  
Vol 121 (3) ◽  
pp. 523-528 ◽  
Author(s):  
V. Cahouet ◽  
L. Baillet ◽  
M. H. Meurisse ◽  
B. Bou-Sai¨d
Keyword(s):  
Optimal Control Theory ◽  
Indirect Method ◽  
Classical Method ◽  
Hydrodynamic Lubrication ◽  
Direct Solution ◽  
Hydrodynamic Problem ◽  
Forming Process ◽  
Contact Conditions ◽  
Friction Forces ◽  
Tangential Contact

A finite element fluid-structure coupling is developed in order to simulate a lubricated forming process, A dynamic explicit code is used for elasto-plastic deformation calculations and normal and tangential contact conditions are handled using a dynamic projection method. Two complementary approaches to the hydrodynamic lubrication problem are proposed: a classical method using the direct solution of the inverse hydrodynamic problem and an original indirect method based on the so called “optimal control theory.” The applicability of the code developed is proved by the numerical simulation of an industrial ironing process. Results of the two methods are compared in terms of friction forces and film thickness profiles. The distribution of local friction coefficients is also obtained.

scholarly journals Micromechanism of the Breakage of Two Spherical Gypsum Particles under Normal–Tangential Contact Conditions

2021 ◽  
Vol 11 (9) ◽  
pp. 4039
Author(s):  
Yiran Niu ◽  
Lin Li ◽  
Yanwei Zhang ◽  
Shicai Yu ◽  
Jian Zhou
Keyword(s):  
Tangential Force ◽  
Coarse Grained ◽  
Spherical Particles ◽  
Contact Conditions ◽  
Normal Contact ◽  
Tangential Contact ◽  
Theoretical Predictions ◽  
Tangential Forces ◽  
Predicted Values ◽  
The Relationship

Contact breakage of particles makes a large difference in the strength of coarse-grained soils, and exploring the characteristics within the process of the breakage is of great significance. Ignoring the influence of particle shape, the micromechanism of two spherical particles breaking under normal–tangential contact conditions was investigated theoretically and experimentally. Through theoretical analysis, the breakage form, the shape and size of the conical core, and the relationship between the normal and tangential forces at crushing were predicted. Particle contact tests of two gypsum spheres were carried out, in which the breakage forms, features of the conical cores and the normal and tangential forces at crushing were recorded for comparison with the predicted values. The test results and the theoretical predictions showed good agreement. Both the analysis and test demonstrate that the presence of tangential forces causes the conical core to assume the shape of an oblique cone, and the breakage form to change. Moreover, with increasing normal contact force, the tangential force needed for crushing increases gradually first and then decreases suddenly.

Design Optimization of Ultra-Low Flying Head-Disk Interfaces Using an Improved Elastic-Plastic Rough Surface Model

2006 ◽  
Vol 128 (4) ◽  
pp. 801-810 ◽  
Author(s):  
Allison Y. Suh ◽  
Sung-Chang Lee ◽  
Andreas A. Polycarpou
Keyword(s):  
Rough Surface ◽  
Contact Pressure ◽  
Surface Model ◽  
Successful Implementation ◽  
Contact Conditions ◽  
Friction Forces ◽  
Interfacial Forces ◽  
Elastic Plastic ◽  
The Mean ◽  
Improved Model

Sub-5nm flying head-disk interfaces (HDIs) designed to attain extremely high areal recording densities of the order of Tbit∕in2 are susceptible to strong adhesive forces, which can lead to subsequent contact, bouncing vibration, and high friction. Accurate prediction of the relevant interfacial forces can help ensure successful implementation of ultra-low flying HDIs. In this study, an improved rough surface model is developed to estimate the adhesive, contact, and friction forces as well as the mean contact pressure relevant to sub-5nm HDIs. The improved model was applied to four different HDIs of varying roughness and contact conditions, and was compared to the sub-boundary lubrication rough surface model. It was found that the interfacial forces in HDIs undergoing primarily elastic-plastic and plastic contact are more accurately predicted with the improved model, while under predominantly elastic contact conditions, the two models give similar results. The improved model was then used to systematically investigate the effect of roughness parameters on the interfacial forces and mean contact pressure (response). The trends in the responses were investigated via a series of regression models using a full 33 factorial design. It was found that the adhesive and net normal interfacial forces increase with increasing mean radius R of asperities when the mean separation is small (≈0.5nm), i.e., pseudo-contacting interface, but it increases primarily with increasing root-mean-square (rms) surface height roughness between 2 and 4nm, i.e., pseudo-flying interface. Also, increasing rms roughness and decreasing R, increases the contact force and mean contact pressure, while the same design decreases the friction force. As the directions of optimization for minimizing the individual interfacial forces are not the same, simultaneous optimization is required for a successful ultra-low flying HDI design.

Deformations Limits Analysis of Sheet Metal Manufatured through the Incremental Forming Process

2017 ◽  
Vol 899 ◽  
pp. 272-277
Author(s):  
Hugo Dutra Gomes ◽  
Maria Carolina dos Santos Freitas ◽  
Luciano Pessanha Moreira ◽  
Flavia de Paula Vitoretti ◽  
Jose Adilson de Castro
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
Finite Element ◽  
Tool Path ◽  
Incremental Forming ◽  
Numerical Control ◽  
Tool Geometry ◽  
The Finite Element Method ◽  
Forming Process ◽  
Contact Conditions

The present study is primarily engaged in the implementation of the incremental stamping process in a computerized numeric control This paper presents two different approaches to this forming process, an experimental and other numerical. Experimental used by the computer numerical control to perform the printing process and performs numerical simulations of the process using the finite element method. Some parameters are analyzed in both approaches, such as product geometry effects, tool geometry, tool speed, tool path, contact conditions and mechanical properties of the materials.

Changes in Three Dimensional Magnetic Fields of Carbon Tool Steel (JIS-SKS93) under Single Spherical Hertzian Contact

2012 ◽  
Vol 457-458 ◽  
pp. 578-585 ◽  
Author(s):  
Katsuyuki Kida ◽  
Megumi Uryu ◽  
Takashi Honda ◽  
Edson Costa Santos ◽  
Kenichi Saruwatari
Keyword(s):  
Magnetic Fields ◽  
Tool Steel ◽  
Three Dimensional ◽  
Initial Distribution ◽  
Steel Plates ◽  
Hertzian Contact ◽  
Hall Probe ◽  
Forming Process ◽  
Film Sensor ◽  
Contact Conditions

Failure of dies and molds is caused by wear and deformation during the metal sheet forming process. Die wear takes various forms, and the contact conditions in die-parts affect the strength of the components. Non-destructive methods that can be related to contact conditions are necessary to study and understand the phenomena caused by the contact stresses. In the present work, a newly developed scanning Hall probe microscope (SHPM) equipped with a GaAs film sensor was used to observe the three-dimensional magnetic fields in tool steel plates before and after contact tests at room temperature in air. It was found that the intensity of three-dimensional magnetic fields is only slightly affected by the spherical Hertzian contact. However, all of the three-dimensional components of the magnetic fields change significantly. The extent of the changes depends not on the distribution of stress under spherical Hertzian contact but on the initial distribution of the magnetic fields.

Partial Hydrodynamic Lubrication With Large Fractional Contact Areas

1998 ◽  
Vol 120 (1) ◽  
pp. 16-20 ◽  
Author(s):  
W. R. D. Wilson ◽  
N. Marsault
Keyword(s):  
Metal Forming ◽  
Reynolds Equation ◽  
Hydrodynamic Lubrication ◽  
Full Range ◽  
Surface Pattern ◽  
Empirical Equations ◽  
Height Distribution ◽  
Contact Conditions ◽  
Initial Height ◽  
Semi Empirical

An alternative average Reynolds equation for use under conditions of large fractional contact area is proposed. The flow factors for this form of the equation are calculated for a variety of longitudinal surfaces and the results are shown to be relatively insensitive to the initial height distribution. Pressure and shear flow factors for the Christensen height distribution and a variety of Peklenik surface pattern parameters are also derived from the work of Patir and Cheng, Lo and Tripp. These are represented by semi-empirical equations over the full range of contact conditions. The implications of the results, with respect to the lubrication of metal forming processes, is discussed.

Friction Forces Within the Cylinder Bores of Swash-Plate Type Axial-Piston Pumps and Motors

1999 ◽  
Vol 121 (3) ◽  
pp. 531-537 ◽  
Author(s):  
Noah D. Manring
Keyword(s):  
Mathematical Model ◽  
High Speed ◽  
Hydrodynamic Lubrication ◽  
Stribeck Curve ◽  
Friction Forces ◽  
Swash Plate ◽  
Axial Piston Machine ◽  
Cylinder Bore ◽  
Axial Piston ◽  
Plate Type

In this research, the friction within the cylinder bore of a swash-plate type axial-piston machine is examined. Unlike previous research, this work develops a mathematical model for the friction based upon lubricating conditions which are described by the well-known Stribeck curve. Furthermore, a test device is built for measuring the frictional characteristics during low pressure and low speed operation and these results are compared with the mathematical model. For high pressure and high speed considerations, a numerical investigation based upon the model is conducted and it is shown that the friction associated with a pumping piston is greater than the friction associated with a motoring piston. It is also shown that increased piston speeds usually reduce the friction within the cylinder bore; however, a “cross-over” condition may exist where the increased speed will actually increase the friction as a result of increased fluid shear. Furthermore, it is shown that speed changes have a more significant impact on motoring pistons as opposed to pumping pistons due to a difference in the location of hydrodynamic lubrication within the cylinder bore. It is noted that this difference exits due to the bore geometry and the direction of piston travel.

Numerical and Experimental Investigation of Bump Foil Forming Process for Foil Air Bearings

2011 ◽  
Vol 204-210 ◽  
pp. 2103-2108
Author(s):  
Wen Bo Duan ◽  
Hai Peng Geng ◽  
Bai Song Yang ◽  
Yan Hua Sun ◽  
Lie Yu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Deformable Body ◽  
Friction Model ◽  
Nonlinear Finite Element ◽  
Air Bearings ◽  
Forming Process ◽  
Rigid Plastic ◽  
Friction Forces ◽  
Simulation Results

In this paper, a simplified nonlinear finite element for bump foil forming process of foil air bearings is developed. The bump foil is dealt with as flexible deformable body, the upper die and lower die are considered as the rigid body without deformation. The friction model between bump foil and dies with velocity-dependent friction forces is described by arctan function. The forming process of SS304 Stainless Steel bump foil under different loads is investigated with rigid-plastic finite element method. The simulation results are compared with theoretical values and experimental results. Therefore more feasible process parameters are obtained to fabricate the bump foils.

A Direct Solution of the Elasto-Hydrodynamic Lubrication Problem

1962 ◽  
Vol 5 (2) ◽  
pp. 365-374 ◽  
Author(s):  
R. Rhoads Stephenson ◽  
J. Fletcher Osterle
Keyword(s):  
Hydrodynamic Lubrication ◽  
Direct Solution

On a Simplified Model for the Tool and the Sheet Contact Conditions for the SPIF Process Simulation

2009 ◽  
Vol 410-411 ◽  
pp. 373-379 ◽  
Author(s):  
Camille Robert ◽  
Lanouar Ben Ayed ◽  
Arnaud Delamézière ◽  
Phillippe dal Santo ◽  
J.L. Batoz
Keyword(s):  
Incremental Forming ◽  
Large Strain ◽  
Single Point ◽  
Contact Interface ◽  
Forming Process ◽  
Contact Conditions ◽  
Simplified Approach ◽  
Contact Algorithm ◽  
Local Stresses ◽  
Good Agreement

The numerical simulation of the Single Point Incremental Forming process (SPIF) is time consuming due to the necessity to take into account various non-linearity such as the material behaviour, large strain deformation and the evolution of the tool-flange contact. Classical contact algorithms give good agreement with experimental results, but are time consuming. In this paper, we investigate the development of a procedure to simplify the management of the contact interface between the tool and the sheet. Nodes with imposed displacements are determined by a geometrical approximation of the deformed sheet. In order to have a better approximation of the local stresses in the flange, a pressure is applied on the tool side of the elements in the contact zone. The pressure value is obtained by an analytical model. A classical contact algorithm and the present simplified approach are compared in terms of an incremental forming benchmark. It has been shown that, for the benchmark problem studied here, a CPU time reduction of approximately 65% can be achieved while at the same time have good simulation results.

scholarly journals A New Progress in Random Hydrodynamic Lubrication for Movable Non-Rotational Curvilinear Biosurfaces with Phospholipid Bilayers

2020 ◽  
Vol 03 (02) ◽  
pp. 1-1
Author(s):  
Krzysztof Wierzcholski ◽  
Keyword(s):  
Dynamic Viscosity ◽  
Hydrodynamic Lubrication ◽  
Wrist Joint ◽  
Biological Fluid ◽  
Hydrodynamic Pressure ◽  
Superficial Layer ◽  
Estimation Methods ◽  
Friction Forces ◽  
Biological Surfaces ◽  
Gap Height

This paper aims to highlight the result of a new progression of mathematical estimation methods of stochastic bio-hydrodynamic lubrication parameters for arbitrary, curvilinear, non-rotational, co-operating, living biological surfaces coated with phospholipid bi-layers. Movable, non-rotational, co-operating surfaces occur in various biological friction nods like the collar bone, the blade bone, the jump joint, and the wrist joint. Specifically, the author presents a synthetic and comprehensive estimation of stochastic bio-hydrodynamic lubrication parameters for co-operating, rotational cartilage bio-surfaces with phospholipid bi-layers occurring in human spherical hip joints and cylindrical elbow joints. The method of research discussed in this paper focuses on a review of stochastic analytical considerations performed by the author. This research is based on the measurements of the gap height between two movable, non-rotational bio-surfaces. The gap is restricted between two co-operating biological surfaces. After several experiments, it could be inferred that there are symmetric as well as asymmetric random increments and decrements in the gap height. Such changes are applicable to the hydrodynamic pressure, load-carrying capacity, friction forces, and wear of the co-operating biological surfaces in human friction nods and contacts. The prime purpose of this paper is to demonstrate the influence of variations in the expected values and standard deviation of the gap height on the hydrodynamic lubrication parameters that occur during the friction process. It can thus be concluded that the apparent dynamic viscosity of biological lubricant varies in the ultra-thin gap height direction, depending on the susceptibility of the superficial layer of the lubricated bio-surface. The results presented in this paper are obtained considering the 3D variations in the dynamic viscosity of the biological fluid, particularly the random variations crosswise the film thickness in non-Newtonian biological fluid properties.

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