"Every structure has a fundamental frequency which is sometimes referred to as its first natural frequency. If a periodic force acts on the structure whose frequency is equal to that of the natural frequency of the structure, a vibration is set up whose amplitude would approach infinity if it were not for the presence of damping. Since damping is always present, steady state conditions will finally be reached provided that the applied force is not so great that it will cause the structure to fail. The amplitude of the vibration will be a function of the applied force and the damping capacity of the structure. Steady state conditions will also be finally obtained if a periodic force acts on a structure whose frequency is not equal to the natural frequency of the structure. In this case, the amplitude of the vibration will be a function of the magnitude of the applied force, the damping capacity of the structure, and the ratio of the frequency of the applied force to the natural frequency. The maximum amplitude is obtained when the ratio is equal to 1.
An impulse will excite vibrations also, but no steady state harmonic conditions will be obtained. Either the structure will fail or it will return back to the initial state on account of the presence of damping. The mining engineer is interested in the impact loading of structures, because this is the type of force supplied by the action of explosives.
This is a preliminary investigation of the strain time history in a small hydro-stone beam due to a suddenly applied force. The impact loading was obtained by dropping steel balls from various heights on the beam. The purpose of the first part of this project was to determine the influence of a number of variables on the strain. The factors which were studied are: a variation in the height of drop and in the weight of the balls; and the effect of the size of the variable resistance wire strain gage on the dynamic strain record. The object of the second part of this project was to investigate the strains present in a small hydro-stone beam when it is subjected to an impact loading which is sufficiently large to cause the beam to fail"--Introduction, pages 1-2.
Caudle, Rodney D.
M.S. in Mining Engineering
National Science Foundation (U.S.)
Missouri School of Mines and Metallurgy
v, 27 pages
© 1958 Niels B. Haubold, All rights reserved.
Thesis - Open Access
Strains and stresses
Cement -- Fracture
Strength of materials -- Testing
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Haubold, Niels B., "A preliminary investigation of strains and fracturing in small hydro-stone beams due to impact loading" (1958). Masters Theses. 5527.