The development of new analytical techniques applicable to the powder forging process

  • T. J. Griffiths

    Student thesis: Doctoral Thesis


    Five publications 6, 18, 28, 68, 110 were produced and a 3 month study tour of powder metallurgy in Europe 6 was undertaken.

    Elemental iron powder/graphite mixes of "as supplied" and "coarse fraction" powders were used throughout, and these were characterized in the normal manner.

    Test specimen and preforms were produced by mechanical compaction, and generally sintered in accordance with standard industrial practice, followed by micro-examination of selected specimen.

    Specimen were subjected to hot torsion, hot tensile and dilatometer tests. Room temperature tests were performed to measure the lateral and longitudinal strain components arising from uniaxial tensile stress.

    A mathematical model 110 was devised to represent a porous material subjected to tensile testing to destruction. Tensile tests were conducted at room temperature, to characterize the preform material, and check the findings of the micro-examinations.

    A pilot study of preform design 28 was undertaken to provide firstĀ­ hand experience of some of the problems involved in powder forging. A mathematical technique 68 was devised to assist in the design of new preforms, and to analyse successful preform shapes obtained by trial and error methods.

    Some preliminary fatigue tests were performed on partly forged components. Use was made of the mathematical model 110, to help explain the consolidation process. The concept of a "coefficient of consolidation" was introduced and verified experimentally by a series of cold axisymmetric upset tests. The dependence of the apparent plastic Poisson's ratio on the initial density of the preform was demonstrated, and information provided regarding the plastic flow stress requirements for cold axisymmetric upsetting.

    Hot axisymmetric upset and closed die tests were performed on cylindrical preforms, and the densification rates obtained were compared with the theoretically predicted values 18. Apparent plastic Poisson's ratios were measured at various sections along the partly forged preforms. Finally, a general appreciation of the forging load requirements was ascertained.
    Date of AwardJun 1979
    Original languageEnglish
    Awarding Institution
    • Polytechnic of Wales

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