Uniformity of Axial Displacement in Element Testing

    Volume 31, Issue 3 (May 2008)

    ISSN: 0149-6115

    CODEN: GTJOAD

    Published Online: 5 November 2007

    Page Count: 5


    Kim, Woosung
    University of Minnesota, Minneapolis, MN

    Labuz, Joseph
    University of Minnesota, Minneapolis, MN

    Chadbourn, Bruce
    Minnesota Department of Transportation, Maplewood, MN

    Loken, Marc
    Barr Engineering Company, Minneapolis, MN

    (Received 12 July 2006; accepted 6 September 2007)

    Abstract

    Uniform axial deformation is a basic assumption in element testing, where axial strain typically is determined from displacement measurements. In applying force through rigid platens, however, some rotation may occur such that the fundamental stress field is perturbed. Thus, nonuniformity among measures of axial displacement may be present, and the response may consist of a component due to uniform deformation and a component due to rotation. To estimate this nonuniformity for cylindrical specimens, at least three sensors are needed, and in general, the axial strain cannot be estimated without error from only two sensors. For equiangular placement of three sensors, it is shown that the mean of the displacement readings is equal to the displacement from the uniform component. The rotation does not affect the average value, but the rotation must be calculated to estimate the nonuniformity. The ratio of the measured maximum and minimum displacement does not provide an objective evaluation.


    Paper ID: GTJ100722

    DOI: 10.1520/GTJ100722

    ASTM International is a member of CrossRef.

    Author
    Title Uniformity of Axial Displacement in Element Testing
    Symposium , 0000-00-00
    Committee D18