In 1860, Sir W. Fairbairn, using a riveted girder, carried out a series of experiments, which seem to be the first recorded experiments on Repeated Stress. From 1860 to 1870, Wöhler carried out his laborious and valuable researches on the Fatigue of Wrought Iron and Steel. From his results published in the ‘Zeitschrift fur Bauwesen,’ Berlin, the following important points may be deduced:— (1) That these materials (wrought iron and steel) will rupture with stresses much
below
the statical breaking stress, if such stress be repeated a sufficient number of times. (2) That within certain limits, the
range
of stress, and not the maximum stress, determines the number of reversals necessary for rupture. (3) That as the range of stress is diminished, the number of repetitions for rupture increases. (4) That there is a
limiting range
of stress for which the number of repetitions of stress for rupture becomes infinite. (5) That this limiting range of stress diminishes as the maximum stress increases.
IV. On a throw-testing machine for reversals of mean stress