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.

An Experimental Investigation of Surface Pit Evolution During Cold-Rolling or Drawing of Stainless Steel Strip

2000 ◽  
Vol 123 (1) ◽  
pp. 1-7 ◽  
Author(s):  
R. Ahmed ◽  
M. P. F. Sutcliffe
Keyword(s):  
Experimental Investigation ◽  
Stainless Steel ◽  
Hydrodynamic Lubrication ◽  
Steel Strip ◽  
Similar Rate ◽  
Steel Strips ◽  
Strip Drawing ◽  
Hot Band ◽  
Cold Rolled

This paper presents an experimental investigation of the mechanisms of pit elimination in strip drawing and rolling of stainless steel strips. Strip drawing tests with artificial indents confirm the role of micro-plasto-hydrodynamic lubrication (MPHL) in allowing pits to be reduced in size and depth. The similarity of results for two oils, which differ in viscosity by a factor of 10, is attributed to the fact that oil is drawn out of the pits rather easily, so that the behavior tends to the unlubricated case. Similar behavior is observed for strip drawing of shot blast white hot band. For much smoother bright anneal strip, it is suggested that the presence of an oil film in the unpitted region prevents generation of pressure differences between the pits and the unpitted regions. A comparison of strip-drawn and cold-rolled stainless steel samples show that the change in pit area and Rq roughness varies with overall reduction in a remarkably similar way. The reason for such similar behavior is attributed to the absence of hydrodynamic action in preventing pit elimination, albeit for opposite reasons. The similar rate of pit evolution in both cases confirms the usefulness of the strip drawing rig as a tool to model the change of surface topography during rolling, as long as care is taken in matching the regimes of lubrication.

Heating Effects in the Drawing of Wire and Strip Under Hydrodynamic Lubrication Conditions

1996 ◽  
Vol 118 (4) ◽  
pp. 628-638 ◽  
Author(s):  
D. A. Lucca ◽  
R. N. Wright
Keyword(s):  
High Speed ◽  
Hydrodynamic Lubrication ◽  
Lubricant Film ◽  
Strip Surface ◽  
Heating Effects ◽  
Strip Drawing ◽  
Dimensional Parameters ◽  
Lubrication Conditions ◽  
Lubricant Viscosity

The use of high metal processing speeds to meet the demands for increased productivity has focused attention on the pronounced heating of tooling and workpiece which occurs under these conditions. In the present study, heating under hydrodynamic conditions in wire and strip drawing is addressed by considering a two-dimensional representation of the tool-lubricant-workpiece interface. An analytical formulation is presented for prediction of the resultant temperatures. The model considers deformation heating in the strip, lubricant viscosity to be a function of temperature and pressure, and matches the heat flux at the strip-lubricant boundary. Convection of heat in the lubricant film is considered. The model is constructed in terms of the governing non-dimensional parameters and solved by a Crank-Nicolson finite difference technique. By comparison with solutions which do not consider convection, it is found that convection only begins to play a role in the resulting temperatures when the Graetz number U0h02/αLl is greater than 0.4. For the high speed drawing of aluminum with mineral oil used as a lubricant, the model predicts a monotonic increase in mean lubricant temperatures from 366 K to 404 K over a range of initial strip velocities of 20.3 m/s to 50.8 m/s. The maximum strip surface temperature is predicted to monotonically decrease from 345 K to 335 K over this range of strip velocities. The ratio (kLρLcpL/ksρscpS)1/2 is shown to be important in determining the relative temperatures of lubricant and strip. Results are compared to those metalworking analyses which do not consider the role of the lubricant film.

Evolution of Surface Pits on Stainless Steel Strip in Cold Rolling and Strip Drawing

2003 ◽  
Vol 125 (2) ◽  
pp. 384-390 ◽  
Author(s):  
H. R. Le ◽  
M. P. F. Sutcliffe
Keyword(s):  
Stainless Steel ◽  
Cold Rolling ◽  
Hydrodynamic Lubrication ◽  
Steel Strip ◽  
Theoretical Models ◽  
Finite Depth ◽  
Work Zone ◽  
Oil Film ◽  
Strip Drawing ◽  
Inlet Zone

Theoretical models are presented for describing the evolution of pits in the inlet and work zone during cold rolling and strip drawing of shot-blast stainless steel under ‘mixed’ lubrication. Results shows that the rough shot-blast surface is flattened rapidly in a short inlet zone, thereby entrapping the lubricant in surface pits. The subsequent evolution of these surface pits in the work zone can be explained by micro-plasto-hydrodynamic-lubrication (MPHL) models described previously. A development of these models is presented which takes into account the effects of the oil film entrained in the inlet, an oil film penetrating from adjacent pits and the finite depth of the pits. The role of an inlet oil film and penetrating MPHL oil film is to limit the potential reduction of pit size. Lubrication regime maps are constructed which describe the evolution of the surface pits for a range of pit geometries. Results explain the experimental observation that some pits survive even after a multi-pass schedule. Predictions of the pit area show good agreement with measurements on samples obtained in strip drawing or rolled under industrial conditions.

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.

Rolling and Recrystallization Textures in High Purity Al Cold Rolled to Very High Rolling Reductions

2005 ◽  
Vol 495-497 ◽  
pp. 603-608 ◽  
Author(s):  
Atsushi Todayama ◽  
Hirosuke Inagaki
Keyword(s):  
Cold Rolling ◽  
High Purity ◽  
Work Hardening ◽  
Dynamic Recovery ◽  
The Other ◽  
Rolling Reduction ◽  
Theoretical Investigations ◽  
Theoretical Predictions ◽  
Cold Rolled ◽  
Very High

On the basis of Taylor-Bishop-Hill’s theory, many previous theoretical investigations have predicted that, at high rolling reductions, most of orientations should rotate along theβfiber from {110}<112> to {123}<634> and finally into the {112}<111> stable end orientations. Although some exceptions exist, experimental observations have shown, on the other hand, that the maximum on the β fiber is located still at about {123}<634> even after 97 % cold rolling. In the present paper, high purity Al containing 50 ppm Cu was cold rolled up to 99.4 % reduction in thickness and examined whether {112}<111> stable end orientation could be achieved experimentally. It was found that, with increasing rolling reduction above 98 %, {110}<112> decreased, while orientations in the range between {123}<634> and {112}<111> increased, suggesting that crystal rotation along the βfiber from {110}<112> toward {123}<634> and {112}<111> in fact took place. At higher rolling reductions, however, further rotation of this peak toward {112}<111> was extremely sluggish, and even at the highest rolling reduction, it could not arrive at {112}<111>. Such discrepancies between theoretical predictions and experimental observations should be ascribed to the development of dislocation substructures, which were formed by concurrent work hardening and dynamic recovery. Since such development of dislocation substructures are not taken into account in Taylor-Bishop-Hill’s theory, it seems that they can not correctly predict the development of rolling textures at very high rolling reductions, i. e. stable end orientations. On annealing specimens rolled above 98 % reduction in thickness, cube textures were very weak, suggesting that cube bands were almost completely rotated into other orientations during cold rolling. {325}<496>, which lay at an intermediate position between {123}<634> and {112}<111> along theβfiber, developed strongly in the recrystallization textures.

The propagation of gravity currents in a V-shaped triangular cross-section channel: experiments and theory

2014 ◽  
Vol 754 ◽  
pp. 232-249 ◽  
Author(s):  
Marius Ungarish ◽  
Catherine A. Mériaux ◽  
Cathy B. Kurz-Besson
Keyword(s):  
Reynolds Number ◽  
Cross Section ◽  
Viscosity Coefficient ◽  
Gravity Currents ◽  
Quantitative Agreement ◽  
Flat Bottom ◽  
Special Configuration ◽  
Theoretical Predictions ◽  
Speed Of Propagation ◽  
High Reynolds

AbstractWe investigate the motion of high-Reynolds-number gravity currents (GCs) in a horizontal channel of V-shaped cross-section combining lock-exchange experiments and a theoretical model. While all previously published experiments in V-shaped channels were performed with the special configuration of the full-depth lock, we present the first part-depth experiment results. A fixed volume of saline, that was initially of length $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}x_0$ and height $h_0$ in a lock and embedded in water of height $H_0$ in a long tank, was released from rest and the propagation was recorded over a distance of typically $ 30 x_0$. In all of the tested cases the current displays a slumping stage of constant speed $u_N$ over a significant distance $x_S$, followed by a self-similar stage up to the distance $x_V$, where transition to the viscous regime occurs. The new data and insights of this study elucidate the influence of the height ratio $H = H_0/h_0$ and of the initial Reynolds number ${\mathit{Re}}_0 = (g^{\prime }h_0)^{{{1/2}}} h_0/ \nu $, on the motion of the triangular GC; $g^{\prime }$ and $\nu $ are the reduced gravity and kinematic viscosity coefficient, respectively. We demonstrate that the speed of propagation $u_N$ scaled with $(g^{\prime } h_0)^{{{1/2}}}$ increases with $H$, while $x_S$ decreases with $H$, and $x_V \sim [{\mathit{Re}}_0(h_0/x_0)]^{{4/9}}$. The initial propagation in the triangle is 50 % more rapid than in a standard flat-bottom channel under similar conditions. Comparisons with theoretical predictions show good qualitative agreements and fair quantitative agreement; the major discrepancy is an overpredicted $u_N$, similar to that observed in the standard flat bottom case.

Prediction of Springback in Metal Forming of Diaphragm of Automotive Horn Based on BPANN

2010 ◽  
Vol 139-141 ◽  
pp. 594-599
Author(s):  
Yan Qiu Zhang ◽  
Shu Yong Jiang ◽  
Yu Feng Zheng
Keyword(s):  
Young’S Modulus ◽  
Metal Forming ◽  
Young's Modulus ◽  
Steel Strip ◽  
Back Propagation ◽  
Spring Steel ◽  
Yield Ratio ◽  
Punch Radius ◽  
Cold Rolled ◽  
The Relationship

The spring steel strip 50CrVA which is cold rolled was applied to manufacture the diaphragm of the automotive horn by means of sheet metal forming. The combination of the experiments with back-propagation artificial neural network (BPANN) is used to solve the springback problem of the diaphragm. Experiments have shown that a 4-8-1 BPANN is able to predict the springback of the diaphragm successfully, and the network is able to model the relationship between the springback of the diaphragm and the process parameters rationally. BPANN simulation results and experimental ones have shown that the springback of the diaphragm is particularly influenced by such parameters as blank thickness, Young’s modulus, punch radius and yield ratio. Furthermore, the springback of the diaphragm decreases with the increase of blank thickness and Young’s modulus, but increases with the increase of punch radius and yield ratio.

Effect of Hot-Rolled Microstructure on the Recrystallization Texture of Cold-Rolled Non-Oriented Electrical Steel

2011 ◽  
Vol 298 ◽  
pp. 203-208 ◽  
Author(s):  
Zi Li Jin ◽  
Wei Li ◽  
Yi Ming Li
Keyword(s):  
Cold Rolling ◽  
Electrical Steel ◽  
Texture Evolution ◽  
Steel Strip ◽  
Silicon Steel ◽  
Grain Structure ◽  
Recrystallization Annealing ◽  
Rolled Sheet ◽  
Cold Rolled ◽  
Hot Rolled

With the help of orientation distribution function (ODF) analysis, experiments of different hot band grain microstructure 0.33% silicon steel were cold-rolled and annealed in the laboratory，to study the effect of the microstructure hot-rolled steel strip for cold rolled non-oriented silicon steel microstructure and texture of recrystallization annealing. The results show that hot rolled microstructure on cold rolled Non-Oriented Electrical Steel cold-rolled sheet evolution of texture and recrystallization have important influence, the quiaxed grain structure of steel by cold rolling and recrystallization annealing, the recrystallization speed than the fiber grain-based mixed crystals recrystallization fast , With the equiaxed grains made of cold rolled silicon steel after annealing the {110}<UVW> texture components was enhanced and {100}<uwv> texture components weakened. Different microstructure condition prior to cold rolling in the recrystallization annealing process the texture evolution has the obvious difference, the equiaxial grain steel belt cold rolling and annealing, has the strong crystal orientation. This shows that the equiaxed grain when hot microstructure is detrimental to the magnetic properties of cold-rolled non-oriented silicon steel to improve and increase.

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