The Design of a Press for Use in the Hydrostatic Extrusion Process

Friction at die/billet interface is a complex phenomenon affected by various operating and process parameters in metal forming industries. In presence of lubricating layer at the interfacial contact friction effect is reduced and enhances tool life and surface quality of product. The lubricant viscosity is strongly dependent on pressure and temperature during deformation of hard material and an accurate prediction of lubricants viscosity leads to realistic results in the work zone. Therefore, the paper incorporates numerical simulation of friction at the die/billet interface in hydrostatic extrusion of tungsten alloy 93W for three different lubricants whose rheology is represented by a Non-Newtonian friction model. The billet heating effect is incorporated in the investigation and results show that the co-efficient of friction varies in a range (0.058 to 0.062) along the work zone for various lubricating conditions in hydrostatic extrusion process.

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A Thermal Hydrodynamic Lubrication Theory for Hydrostatic Extrusion of Low Strength Materials

Journal of Lubrication Technology ◽

10.1115/1.3452842 ◽

1976 ◽

Vol 98 (2) ◽

pp. 335-342 ◽

Cited By ~ 17

Author(s):

R. W. Snidle ◽

B. Parsons ◽

D. Dowson

Keyword(s):

Plastic Deformation ◽

Theoretical Analysis ◽

Thermal Effects ◽

Hydrodynamic Lubrication ◽

Extrusion Process ◽

Lubrication Theory ◽

Lubricant Film ◽

Hydrostatic Extrusion ◽

Solid Friction ◽

Hydrodynamic Lubrication Theory

The paper presents a theoretical analysis of hydrodynamic lubrication in the hydrostatic extrusion process which includes a consideration of thermal effects in the lubricant film arising from the work of plastic deformation. A Newtonian lubricant with an exponential pressure-temperature-viscosity relationship has been assumed and allowance has been made for the effects of redundant deformation of the worked material. The results of the theory are compared with those from previous isothermal and solid friction theories.

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An Elasto-Plasto-Hydrodynamic Lubrication Analysis of the Hydrostatic Extrusion Process

Journal of Lubrication Technology ◽

10.1115/1.3451743 ◽

1973 ◽

Vol 95 (2) ◽

pp. 113-122 ◽

Cited By ~ 14

Author(s):

R. W. Snidle ◽

D. Dowson ◽

B. Parsons

Keyword(s):

Plastic Deformation ◽

Thermal Effects ◽

Preliminary Analysis ◽

Hydrodynamic Lubrication ◽

Numerical Procedure ◽

Extrusion Process ◽

Lubricant Film ◽

Hydrostatic Extrusion ◽

Small Influence ◽

Theoretical Results

The authors describe a numerical procedure for the solution of the problem of hydro-dynamic lubrication in the hydrostatic extrusion process. The lubricant is assumed to be a Newtonian fluid and in this preliminary analysis it is assumed that the yield strength of the worked material remains constant. Elastic deformation of the billet as it enters and leaves the die is considered but this effect is found to have only a small influence upon the thickness of the lubricant film which is generated. Thermal effects arising from plastic deformation of the billet and viscous dissipation in the lubricant film are also considered. Theoretical results are presented showing the influence of die angle and reduction ratio upon values of film thickness and extrusion pressure for two materials.

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Evaluation of New Hypothetical Concept (LHSIR) for Die Profile Design for Hydrostatic Extrusion Of AL/MG Compound

Diyala Journal of Engineering Sciences ◽

10.24237/djes.2014.07104 ◽

2014 ◽

Vol 7 (1) ◽

pp. 40-60

Author(s):

Muhsin J. Jweeg ◽

Moneer H. Tolephih Al-Saady ◽

Abdullah Dhayea Assi

Keyword(s):

Extrusion Process ◽

Strain Increment ◽

Hydrostatic Extrusion ◽

Die Design ◽

Relative Pressure ◽

Major Conclusion ◽

Validity Assessment ◽

Heat Treated ◽

Die Profile ◽

First Time

This paper presents, for the first time, a new developed concept for design of Die pass profile used in hydrostatic-extrusion of Al/Mg compound. The new design criteria proposes a "Linearity" of the Homogeneous Successive Strain Increment Ratios (LHSIR) of the deformed material, instead of the "Constancy" concept (CHSIR) found in literature, as the tool base to generate the profile. The developed profiles were evaluated numerically to assess their relative pressure ratios as the main parameter for performance checking adopting the well-known Upper Bound Approach (UBA). A further developed aspect for the velocity field proposition is successfully made to carry out the necessary tedious computations. 12 different samples of commercial tool steel were CNC-manufactured, heat treated and tested to Al/Mg compound, from lead alloy, for sake of comparison and validity assessment. The major conclusion comes out of this work claims that a small variance in the classical constancy criteria of the Die design is very sensitive to change the expected levels of the relative pressure ratios of the extrusion process.

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