CHAPTER 1

INTRODUCTION

1.1 INTRODUCTION

One of the turning points in the development of mankind was the discovery of metal and its uses. Man has been using some plastic deformation process or other for many centuries now to shape the metal to suit his needs. But metal craft remained an artisan’s forte and the final result depends on his judgment and expertise. Only in the last One Hundred Twenty years or so systematic study of metal deformation process has began and a vast amount of literature is now available on this subject. Various theoretical and experimental studies has been conducted to understand the mechanics of deformation process. These theories have been helpful in extending process capabilities and selecting equipment and process is so complicated and is governed by so many factors that theories cannot predict the process parameters accurately and a little judgment is still needed to produce a highly successful product.

The products of various metal forming process have high dimensional accuracy and surface finish to further improve the surface finish. Various lubricant such as lubricants based on vegetable and mineral oil.

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CHAPTER 2

LITERATURE SURVEY

2.1 LITERATURE SURVEY

The author has gone through a number of research papers relating to the drawing process with tribological study. Hydrodynamic lubrication prevails when film of lubricant fully seperates the die from the work piece. Summery of some papers are summarized as:

Madhavian and Wilson [7] has been discussed the lubricant flow in plastohydrodynamic work zone. This includes the effects of different surface temperatures and shear heating within the lubricant film. Thermal effects on the lubricant velocity and temperature profile traction and volume flow rate are described. The difference in surface temperature plays a dominate role in deciding the variation of lubricant film thickness with position and time in metal forming operations.

Avitzer [9] analyze the wire drawing and extrusion through conical dies of small cone angle. Analytical expressions are derived for the required front pull for wire drawing, as well as the back push for extrusion. The effect of each of the process variables on these forces is presented graphically. The process variables are the cons semi angle (α) initial (R i) and final (Rf) wire radius, material yield limit (σo) at uniaxial load, back pull (σxb) an front pull (σxf), coefficient of friction (μ) or shear factor (m), die land (L), exit velocity (vf) and entrance velocity (vi).

The power balanceis set for these powers: (1) internal power of deformation of wire, (2) Power involved with the back force on the wire,

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(3) Power involved with the front force on the wire, (4) Power losses due to friction between the wire and the die.

By Susan M. Bloor*, D. Dowson and B. Parsons [12] has been analyzed plasto-Hydrodynamic lubrication of the plane strain drawing process. In recent years there has been an accumulation of evidence of hydrodynamic lubrication in various metal forming processes. In the present paper the possibility of hydrodynamic action in the plane strain drawing process is explored in a theoretical analysis which takes account of the variation of lubricant viscosity with pressure and temperature and plastic deformation of the strip. The generation of heat within the lubricant is considered and linear heat flow in the rigid die is considered in the thermal analysis.

Wilson and Mohdavian [13] gave hydrodynamic Lubrication of Hydrostatic Extrusion. An analytical model for the hydrodynamic lubrication of hydrostatic extrusion is developed. This includes the effect of viscous heating on the film formation process and the effect of viscous and plastic heating on the friction and film thickness variation in the work zone. Theoretical prediction of film thickness and extrusion pressure show good agreement with experimental measurements for aluminium billets lubricated with castor oil.

Avitzur [16] has been analyzed the wire drawing and extrusion through conical dies of large cone angle. This work is a direct extension of reference [9].

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2.2 Problem Definition

This present work is an exploratory attempt to evaluate the effect of

different parameters such as yield strength of work piece material,

viscosity of lubricant, pressure coefficient of viscosity on lubricant film

thickness, shear stress, pressure developed in lubricant film and

temperature of the strip, lubricant film and die surface in strip drawing

process. For this author has taken different work materials and different

values of lubricant viscosity and pressure coefficient of viscosity and has

analyzed the effect by changing one parameter on other parameters

involved in strip drawing process.

Aim of Thesis

Main themes of thesis is a study of the theoretical film thickness which could be developed under representative practical drawing condition this quantity gives a good indication of the potential of the system for hydrodynamic lubrication action when compared with the surface quality of die and strip. We also include the effect of changing the work material, lubricant viscosity, pressure coefficient of viscosity on the pressure, shear stress and temperature of die, lubricant film and strip.

CHAPTER 3

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ANALYSIS OF HYDRODYNAMIC LUBRICATION IN STRIP

DRAWING PROCESS

3.1 Process Analysis

The process consists of strip passing through die of conical shape. The lubricant film introduced during the process completely separates the die from work piece material. The film can be divided into three regions.

(1) The inlet zone(2) The working zone (3) The outlet zone

In the inlet zone the lubricant is drawn into the space between strip and die by hydrodynamic wedge action. The lubricant pressure rises rapidly until the work piece yields at the inlet of working zone. In deformation zone the strip material yields plastically. In the outlet zone the strip again become rigid it provides stability in work piece and pressure almost remains constant in this zone. Process is shown in Fig.

CHAPTER - 4

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CONCLUSIONS AND SCOPE FOR FUTURE WORK

6.1 Conclusions

From this present work following conclusions are drawn:

1. Effective hydrodynamic pressure generation is restricted to a very small portion of the inlet region.

2. In the zone of plastic deformation the film thickness decreases steadily in proportion to the reduction in strip thickness.

3. Predicted film thickness suggests that hydrodynamic action might be important under many modern drawing conditions.

4. Film thickness is more for low yield stress work material in comparison to high yield stress work material.

5. Film thickness comes out to be more highly viscous lubricant in comparison to low viscous lubricant.

6. Viscous heating effect is more than heating due to strip deformation in case of highly viscous oil.

7. Film pressure decays relatively slowly through the plastic zones.

6.2 Suggestion for Future Work

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Some suggestions for future work are given below:

1. The analysis can be extended to include thermal effect in inlet region.

2. Thermal conductivity may be considered as a variable.3. Effect of work hardening characteristics of work piece

material in hydrodynamic lubricant can be considered.4. Lubricant may be considered as Non-Newtonian fluid.

REFERENCES

1. Day, L., “The validity of some approximate solution to the Renolds equation”, Journal of lubricant Technology Vol 101, P 365, July 1979.

2. Yang C.T., “On the mechanics of wore drawing”, Trans ASME, Ser. B, Vol. 83, P 523, 1961.

3. Ramackers, J.A.H. and Kals, J.A.G., “Mathematical representation of friction in metal forming analysis”, Annals of the CRIP Vol. 35/1/1986, Page 137, 1986.

4. Dow, T.A., “Kannel, J.W. and Bupara S.S., “A hydrodynamic lubrication theory for strip rolling including thermal effects@, Trans. ASME, Journal of lubrication technology, Page 4,1975.

5. Wilson,W.R.D., “The film thickness Variation in the work Zone of Hydro dynamically lubricant continuous deformation process”, Trans. ASME, Journal of lubrication technology P. 541, Oct. 1973.

6. Ghosh, A. and Mallik, A.K., “Manufacturing science”, Affiliated East West Press Private Limited, New Delhi, 1988.

7. Wilson, W.R.D. and Mahdavian, S.M., “Lubricant flow in a plasto hydrodynamic work zone” Trans. ASME Journal of lubrication technology, P.16, Jan 1976.

8. Raghavan, V., “Material Science and Engineering”, Hall of India Private Limited 1990.

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9. Betzalel Avitzur, “Analysis of wire drawing and Extrusion through conical dies of small cone angle” Trans. ASME, Journal of Engineering for Industry, P. 89, Feb., 1963.

10. Avitzer, B., “Metal forming process and analysis”, Mc. Graw Hill Book Co., 1968.

11. Pinkus Oskar “Theory of lubrication” Mc. Graw Hill Book Co. New York, 1961.

12. Suson M. Bloor, Dowson D. and parsons B., “An Elasto-plasto - hydrodynamic ” lubrication analysis of the plane strain drawing process” Journal of Mechanical Engineering Science Vol. 12, No. 3, P.178, 1970.

13. Wilson, W.R.D. and Mahdavian, S.M., “Hydrodynamic lubrication of hydrostatic lubrication analysis of the plane strain drawing process” Journal of Mechanical Engineering Science Vol. 12, No. 3, P. 178, 1970.

14. Gameron, A. “Basic lubricant theory” Second edition Halsted Press. John Wiley and Sons, New York, 1976.

15. Kudo, H., Isubouchi, M., Takada, H. and Okamura K., “An investigation into plasto – hydrodynamic lubrication with a cold sheet drawing test” Annals of the CIRP Vol. 31/1/1982 Page 175, 1982.

16. Avitzer, B., “Analysis of wire drawing and extrusion through conical dies of large cone angle”, Trans. ASME, Journal of Engineering for Industry, P. 305, Nov. 1964.

17. Sastry, S.S.,”Introduction methods of numerical analysis” Second edition Prentice Hall of India Private Limited, New Delhi 1994.

18. Holman, J.P. “Heat transfer” Fifth edition, Mc Graw Hill International book Co. 1985.

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