STP753: Formability Testing for Precision and Accuracy

    Niemeier, BA
    Research scientist, Reynolds Metals Co., Richmond, Va.

    Pages: 19    Published: Jan 1982


    Abstract

    The author views the ability to shape press-formed parts with the logic and reason that are definitive of science. Materials which are in existence and those which are being developed for shape changeability are considered from intrinsic and extrinsic characteristics of force-deformation situations. Both mathematical modeling and statistics of precision and accuracy are introduced for direct measurements, such as depth to fracture. Elasticity and plasticity characteristics, which are both dimensionalized and nondimensionalized parametric relationships, are related to the fundamental physical variables of force and length.

    Precision and accuracy are first presented in a simplistic format. Common and not-so-common parametric terms, such as stress, strain, strain hardening, and texture hardness, are used to indicate significance of precision. While numbers, charts, graphs, and equations are provided to handle abstract variables, full insight into the complete phenomena of numerical precision and accuracy remains with each investigator.

    Levels of success and failure in correlating formability response are described from selected cooperative research. Included are encoded data from a large number of industrial and academic mechanical testing laboratories. Inter- and intralaboratory comparisons are related. There is the zone of uncertainty which may be deduced from a zone of confusion. Correlation or lack of the same is ascribed to an inadequately small zone of uncertainty. Statistical viewpoints of the author are offered through an in-depth level of references.

    Keywords:

    formability, precision, accuracy, metallic materials, mechanical tests, regression, standard deviation, coefficient of variation, Olsen test, tension test, strain hardening, texture hardness, elasticity


    Paper ID: STP28401S

    Committee/Subcommittee: E28.02

    DOI: 10.1520/STP28401S


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