STP808

    Stress and Deformation States Associated with Upset Tests in Metals

    Published: Jan 1983


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    Abstract

    The objective of this research is to provide quantitative information on the stress and deformation states induced in the compression of metallic cylinders. Of particular interest are the conditions prevailing after barreling occurs and when large reductions in height are induced, including the onset of fracture. Interior as well as surface states of stress, strain, and displacement are needed to formulate a reliable fracture criterion, since it has been shown in a companion paper that there are competitive fracture modes at several sites within the specimen.

    The analysis was conducted by employing the HEMP code, a finite difference program that solves the equations of motion in two spatial dimensions and time. Independently obtained constitutive data were used and included the effects of workhardening materials. Large strain behavior is accounted for as well as finite rotations, two effects that become critical as the deformation proceeds. The role of friction between specimen and end platens was accounted for.

    Theoretical results are in the form of distributions of stress, strain, and deformation within the specimen. Comparisons were made whenever possible with companion experimental observations, such as dimensions of the deformed specimen, appearance of heavily deformed zones versus the lightly deformed ones that appear in sectioned specimens, and finally details of the deformation involved in the roll-over process occurring near the specimen-platen interface. Such comparisons help establish confidence in the validity of the theoretical results and thus in the predictions of the stress/strain states prevailing at the onset of experimentally observed fracture. Such data are vital in establishing valid fracture criteria under nominally compressive loads. We do not propose such a criterion in this paper, since we believe it necessary to obtain more experimental and analytical data before such a model can be considered both general and reliable. We do discuss some elements that such a model should encompass.

    Keywords:

    upset test, compressive fracture, computer simulation


    Author Information:

    Mescall, J
    Army Materials and Mechanics Research Center, Watertown, Mass.

    Papirno, R
    Army Materials and Mechanics Research Center, Watertown, Mass.

    McLaughlin, J
    Army Materials and Mechanics Research Center, Watertown, Mass.


    Paper ID: STP36193S

    Committee/Subcommittee: E28.02

    DOI: 10.1520/STP36193S


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