Steel can fail prematurely under repeated cyclic loading below its proportional limit (or yielding point). Provided that a certain threshold... Show moreSteel can fail prematurely under repeated cyclic loading below its proportional limit (or yielding point). Provided that a certain threshold in the loading magnitude, known as the endurance limit, is not exceeded, the material can sustain an infinite number of cycles (N 107). Recent interests in the piezo-magnetic behavior of ferromagnetic steels have been successfully providing reliable and physical indicators of fatigue properties of the material. Cyclic mechanical strain applied to ferromagnetic steels produce abrupt variations in the magnetization of the material referred to as piezo-Barkhausen pulses. Among the many variables influencing fatigue characteristics, the influence of the frequency of loading upon the piezo-Barkhausen response of steel is investigated herein. While the amplitude of the pulses varies, the cumulative piezo-Barkhausen indicator of damage is independent of the frequency and provides a specific measure of damage for a given level of applied strain and may be a way to evaluate service life. The distribution of the dominant frequency of the observed pulses also permits one to separate the stable states of loading from those leading to fatigue failure. Further observations on the piezo-Barkhausen signals particularities have also been made to provide a greater insight on the micro mechanisms of fatigue and damage accumulation in steel. M.S. in Civil Engineering, July 2014 Show less
