Advertisement

Analysis of the central cavity of axisymmetric forward extrusion by the upper bound approach

  • S. Wu
  • M. Li
Processing(Continued)

Abstract

In this paper, the use of a kinematically admissible velocity field to predict the presence of a central cavity in the final stage of axisymmetric forward extrusion is advanced, in accordance with the results of Moire experiments. On the basis of the velocity field, the critical condition for central cavity formation is obtained by the upper bound approach. Furthermore, the quantitative relationships between central cavity formation and process parameters (reduction in area, frictional factors on the ram and chamber wall, relative residual thickness of the of the billet) are studied. The results show that (1) the critical relative residual thickness of the billet used for the central cavity formation is affected primarily by the reduction in area and the frictional factors on the ram, and slightly by the frictional factor on the chamber wall; (2) the relative dimensions of the central cavity increase with a decrease in the relative residual thickness of the billet; (3) the growth rate of the central cavity decreases with an increase in the frictional factors on the ram, but is affected by the frictional factors on the chamber wall only slightly. Good correlation is found between the analytical and experimental results.

Keywords

Relative Dimension Chamber Wall Central Cavity Flow Velocity Field Admissible Velocity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    H. Kudo,Handbook of Cold Forging, Margunel Press Limited, (1973) in Japanese.Google Scholar
  2. 2.
    A.H. Hingwe,Quality Control Source Book: Application of QC to Ferrous Metalforming, Americal Society for Metals, Metals Park, 349–357 (1982).Google Scholar
  3. 3.
    B. Avitzur,Metal Forming: The Application of Limit Analysis, Marcel Dekker, New York and Basel (1980).Google Scholar
  4. 4.
    H. Kudo, Some Analytical and Experimental Studies of Axisym- metric Cold Forging and Extrusion (II),Int. J. Mech. Sci., 3(2), 91–117(1961).CrossRefGoogle Scholar
  5. 5.
    W. Johnson and H. Kudo,The Mechanics of Metal Extrusion, Manchester University Press, London(1952).Google Scholar
  6. 6.
    B. Avitzur, Analysis of Central Bursting Defects in Drawing, Ex- trusion and Rolling,Trans. ASMEB, 90(1), 79–91 (1968).Google Scholar
  7. 7.
    Z. Zimmerman and B. Avitzur, Analysis of The Effect of Strain Hardening on Central Bursting Defects in Drawing and Extru- sion,Trans. ASMEB, 92(1), 135–145 (1970).Google Scholar
  8. 8.
    C. Xiuquan, Simulation of Axisymmetric Forward Extrusion by Rigid-Plastic Finite Element Method, M.S. thesis, Northwestern Poly technical University, (1988) in Chinese.Google Scholar
  9. 9.
    W. Shichun and Z. Zhiwen, The Cavity Defect During Cup-Bar Combined Extrusion,Proc. Japan-China Joint Symp. on Cold Forging, Tokyo, 50–53 (1987).Google Scholar
  10. 10.
    W. Shichun and L. Miaoquan, A Study of The Cup-Cup Axisym- metric Combined Extrusion by The Upper-Bound Approach (II). Prediction of Defects,J. Mech. Working Technol., 19(1), 129–149 (1989).CrossRefGoogle Scholar
  11. 11.
    R.L. Fox,Optimization Methods for Engineering Design, Ad- dison-Wesley, New York(1971).Google Scholar
  12. 12.
    A.T. Male and M.G. Cockcroft, A Method for The Determination of The Coefficient of Friction of Metals Under Conditions of Bulk Plastic Deformation,J. Inst. Metals, 93(3), 38–55 (1964).Google Scholar

Copyright information

© ASM International 1992

Authors and Affiliations

  • S. Wu
    • 1
  • M. Li
    • 1
  1. 1.Department of Materials Science and EngineeringNorthwestern Polytechnical UniversityShaanxiPeople’s Republic of China

Personalised recommendations