The Use of Workability Test Results to Predict Processing Limits

  • A. L. Hoffmanner


The concept of workability testing was developed from accurate determinations of the states of stress under which a material is deformed during testing. These results provided a general relationship between stress and fracture strain from a variety of tests and materials over a wide range of stress, strain rate and temperature. It was found that the major stress parameter determining the fracture strain ε¯f was the average value of the normal stress σT perpendicular to the direction of alignment of grain boundaries and second phase particles. This definition of stress provided the ductile fracture criterion lnεi¯f = A + B σT/ σ¯ in which σ¯ is the flow stress and A and B are material parameters related to the mechanical behavior of the solid solution and mechanical texturing respectively. The workability concept subsequently was amplified by applying the test results to make accurate predictions of working limits during forging, extrusion and rolling. Good agreement was found between predictions and observations when the mechanics of the processes were defined by analytical and experimental-analytical procedures. These results will be extended to support qualitative procedures for process improvements by isolating the factors which are most prominent in determining the limiting reductions during deformation processing.


Flow Stress Strain Energy Density Gauge Section Fracture Strain Torsion Test 
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.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    R, Hill, “A Theory of Yielding and Plastic Flow of Anisotropie Metals,” Proc. Roy. Soc. London, Ser.A, 193, (1948), 281.CrossRefGoogle Scholar
  2. 2.
    H. C. Rogers, “The Effect of Material Variables on Ductility” Ductility, ASM, (1968), 31.Google Scholar
  3. 3.
    F. A. McClintock, “On the Mechanics of Fracture From Inclusions,” Ductility, ASM, (1968), 255.Google Scholar
  4. 4.
    R, Hill, “New Method for Determining the Yield Criterion and Plastic Potential of Ductile Metals,” J. Mech. and Phys. of Solids, 1, (1953), 271.CrossRefGoogle Scholar
  5. 5.
    J. P. Ellington, “An Investigation of Plastic Stress-Strain Relationships Using Grooved Tensile Specimens,” J. Mech. Phys. Solids, 6, (1958), 276.CrossRefGoogle Scholar
  6. 6.
    A. H. Shabiak and E. G. Thomsen, “Investigation of the Application of Visioplasticity Methods of Analysis to Metal Deformation Processes,” Final Report — Part II prepared on Contract No. N000019-67-C-0509, University of California, (January 1968).Google Scholar
  7. 7.
    F. R. Larson and J. Nunes, “The Low Temperature Plastic Flow and Fracture Tension Properties of Heat Treated SAE 4340 Steel,” TASM, 53(1961)663.Google Scholar
  8. 8.
    P. W. Bridgman, Studies in Large Plastic Flow and Fracture, McGraw-Hill, (1952).Google Scholar
  9. 9.
    D. Lee and W. A. Backofen, “Superplasticity in Some Titanium and Zirconium Alloys,” Trans.AIME, 239, (1967)1034.Google Scholar
  10. 10.
    C. M. Young and O. D. Sherby, “Simulation of Hot Forming Operations by Means of Torsion Testing,” Technical Report AFML-TR-69-294 (Feb. 1970).Google Scholar
  11. 11.
    A. L. Hoffmanner, “Workability Testing Techniques,” Final Engineering Report on Contract No. F33615-67-C-1466, (June 1969).Google Scholar
  12. 12.
    J. L. Robbins, H. Wagenaar, O. C. Shepard, and O. D. Sherby, “Torsion Testing as a Means of Assessing Ductility at High Temperatures,” J. of Materials,(June 1967), 271.Google Scholar
  13. 13.
    M. G. Cockcroft and D. J. Latham, “Ducti1ity and Workabi1ity of Metals,” J. Institute of Metals, 96, (1968), 33.Google Scholar
  14. 14.
    E. G. Thomsen, “Comparison of Slip-Line Solutions with Experiment,” TASME, J. Appl.Mech., 23(June 1956)225.Google Scholar
  15. 15.
    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. of Metals, 93, (1964-1965) 38.Google Scholar
  16. 16.
    B. Avitzur, “Analysis of Central Bursting Defects in Extrusion and Wire Drawing,” ASME Paper No. 67-Proc.-5, (1967).Google Scholar

Copyright information

© Springer Science+Business Media New York 1971

Authors and Affiliations

  • A. L. Hoffmanner
    • 1
  1. 1.TRW Inc.ClevelandUSA

Personalised recommendations