STP753: Upsetting Test for Determining Stress-Strain Curves in the Range of Very High Strains

    Pöhlandt, K
    Institut für Umformtechnik, Universität Stuttgart, Stuttgart,

    Roll, K
    Institut für Umformtechnik, Universität Stuttgart, Stuttgart,

    Pages: 18    Published: Jan 1982


    Abstract

    In the upsetting test, stress-strain curves can be determined up to very high strains. However, two sources of error make the result increasingly inaccurate with growing strain: friction, and the error of measurement of the instantaneous specimen height.

    Two methods are described by which these errors—or at least one of them—can be suppressed. The first method consists in the use of specimens according to Rastegaev. These specimens give excellent lubrication conditions and remain almost exactly cylindrical during testing, but the measurement of the instantaneous specimen height is even more inaccurate than for conventional specimens.

    In the second method, both errors are suppressed by using a new kind of specimen, the diameter of which is larger at the ends than in the middle section. As a result, the work required for friction is suppressed, and in addition the error of height measurement propagates only weakly into the calculated values of strain and stress. This is demonstrated both by experiments and by calculations based on the finite-element method.

    Keywords:

    stress-strain curve, upsetting test, friction, lubrication, finite-element method, specimen geometry, formability


    Paper ID: STP28396S

    Committee/Subcommittee: E28.02

    DOI: 10.1520/STP28396S


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