In a magnetic fatigue testing machine at U. S. Steel's Research and Development Laboratory in the Oakland District of Pittsburgh, Pennsylvania, a steel sample is subjected to controlled vibration to determine its resistance to fatigue failure. Vibrating at about 100 cycles per second, the ends of the sample appear blurred in the photograph. The laboratory technician is about to use a stroboscopic light. In this light the sample appears to be bending slowly and its surfaces can be examined for small cracks.

United States Steel Corporation · [ca. August 1954]

[Information from item housing] Machinery ... Large + Small