| Abstract: | A standard tensile test device is improved to accurately measure the
mechanical properties of stranded cables, ropes, and other composite
structures wherein a witness is attached to the top and bottom mounting
blocks holding the cable under test. The witness is comprised of two
parts: a top and a bottom rod of similar diameter with the bottom rod
having a smaller diameter stem on its upper end and the top rod having a
hollow opening in its lower end into which the stem fits forming a
witness joint. A small gap is present between the top rod and the larger
diameter portion of the bottom rod. A standard extensometer is attached
to the top and bottom rods of the witness spanning this small witness
gap. When a force is applied to separate the mounting blocks, the gap in
the witness expands the same length that the entire test specimen is
stretched. |