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    ASTM E517 - 19

    Método de prueba estándar para la determinación de la relación r de deformación plástica para láminas metálicas

    Active Standard ASTM E517 Developed by Subcommittee: E28.02

    Book of Standards Volume: 03.01


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    Significance and Use

    4.1 The plastic strain ratio r is a parameter that indicates the ability of a sheet metal to resist thinning or thickening when subjected to either tensile or compressive forces in the plane of the sheet. It is a measure of plastic anisotropy and is related to the preferred crystallographic orientations within a polycrystalline metal. This resistance to thinning or thickening contributes to the forming of shapes, such as cylindrical flat-bottom cups, by the deep-drawing process. The value of r , therefore, is considered a measure of sheet-metal drawability. It is particularly useful for evaluating materials intended for parts where a substantial portion of the blank is drawn from beneath the blank holder into the die opening.

    4.2 For many materials the plastic strain ratio remains essentially constant over a range of plastic strains up to maximum applied force in a tension test. For materials that give different values of r at various strain levels, a superscript is used to designate the percent strain at which the value of r was measured. For example, if a 20 % elongation is used, the report would show r20.

    4.3 Materials usually have different values of r when tested in different orientations relative to the rolling direction. The angle of sampling of the individual test specimen is noted by a subscript. Thus, for a test specimen whose length is aligned parallel to the rolling direction, plastic strain ratio, r , is reported as r0. If, in addition, the measurement was made at 20 % elongation and it was deemed necessary to note the percent strain at which the value was measured, the value would be reported as r020.

    4.4 A material that has an upper yield strength (yield point) point followed by discontinuous yielding stretches unevenly while this yielding is taking place. In steels, this is associated with the propagation of Lüders' bands on the surface. The accuracy and reproducibility of the determination of plastic strain ratio, r , will be reduced unless the test is continued beyond this yield-point elongation. Similarly, the discontinuous yielding associated with large grain size in a material decreases the accuracy and reproducibility of determinations of plastic strain ratio, r , made at low strains.

    1. Alcance

    1.1 Este método de prueba abarca análisis especiales de tensión para la medición de la relación de deformación plástica, r, para láminas metálicas destinadas a aplicaciones de estampado profundo.

    1.2 Los valores indicados en pulgadas-libra deben considerarse como el estándar. Los valores entre paréntesis son conversiones matemáticas a unidades del Sistema Internacional que se proporcionan solo para fines informativos y no se consideran estándar.

    1.3 Este estándar no pretende abordar todas las inquietudes de seguridad, en caso de existir alguna, relacionadas con su uso. Es responsabilidad del usuario de este estándar establecer las prácticas de salud, prácticas de seguridad y prácticas ambientales apropiadas, y determinar la aplicabilidad de las limitaciones normativas antes de su uso.

    1.4 Este estándar internacional fue desarrollado de conformidad con principios de estandarización reconocidos a nivel internacional y establecidos en la Decisión sobre Principios para el Desarrollo de Estándares, Guías y Recomendaciones Internacionales (Decision on Principles for the Development of International Standards, Guides and Recommendations) publicada por el Comité de Acuerdo sobre Obstáculos Técnicos al Comercio (Technical Barriers to Trade, TBT) de la Organización Mundial del Comercio.

    2. Documentos Citados