Volume 27, Issue 4 (July 1999)
Evaluating the Quality of a Mechanical Testing System Using Displacement Field Contours
A technique using displacement field data to qualify mechanical tests for in-plane deformation is proposed. Contour lines of the displacement fields that result from applied forces in mechanical tests are used for quantitative analysis and graphical representation of quality of the mechanical testing system in the tests. This method can visually, directly, and sensitively detect loading problems, such as misalignment, existing in the tests. A theoretical analysis using a displacement contour map to describe quantitatively the effect of the misalignment in a uniaxial tension test is described in detail. A technique to obtain the displacement contour map from the displacement field data and on-line inspection of some test system misalignment is presented. Several examples, including an eccentric tension test, a tension test with inhomogeneous fixing of a specimen in the grips, and an Iosipescu composite shear test with various degrees and sources of misalignment are analyzed with this contour method.