A simple new machine and procedure far fatigue testing of metallic wire

A simple and inexpensive machines has been designed and built for fatigue tests an metallic wires. A loop of the wire to be tested is wound around a needle bearing with the external ring (outer race) removed. One of the ends is fixed to the frame and a Ioad is applied, for instance with a deadweight, on the other end. Each of the wire spans between the contacts with two adjacent needles is loaded in traction and variable bending by the applied Ioad and the wire-needle reactions. When the bearing cage is put in rotation through the internal ring (inner race) fitted on a rotating spindle, the contact points are displaced along the standing wire so that each section is subjected to the same stress variations, and, at the inner diameter, to the same contact (Hertzian) loads. The number of fatigue cycles is proportional to cage speed and number of needles in the bearing, so the machines may be very fast. The device is designed to improve the estimate of the behaviour of a wire rope which will be subjected to variable bending loads while being acted upon by surrounding wires and pulley. Corresponding advances for the knowledge of the behaviour of the wires in a tyre are also possible.

Author(s): Ciuffi, R.