Abstract: An apparatus and method for testing viscoelastic solids, such as tire cord. The apparatus includes: a holding means, a pretension means, a displacement generator, and a mechanical-electrical transforming means. The holding means holds the material in a predetermined position. The pretension means applies tension during testing. The displacement generator has an eccentric means for applying cyclic displacement. The mechanical-electrical transforming means transforms mechanical motion into electrical signals, such as a stress signal, a strain signal and a differentiated strain signal. There is a phase lag between the stress signal and the strain signal and the phase lag may vary in amount and direction as a function of time. The apparatus may also include: an integrating means for integration of a stress-strain hysteresis loop; and a display means for displaying an output of the integrating means to measure the area of the hysteresis loop and thereby determine energy loss.