"Internal friction is defined as the ability of a vibrating solid to convert its mechanical energy of vibration into heat, even when completely isolated from its surroundings. (1) The most familiar manifestation of internal friction is the damping of a freely vibrating body, such as a torsional pendulum. Another example would be the increased width of the resonance peak observed when a nonelastic body is forced to vibrate over a spectrum of frequencies.(2) Internal friction manifests itself in numerous ways, and we will here be concerned with the first example cited and the potency of data gained in studying the decay of torsional vibration.
During the past ten years internal friction has become an increasingly prominent research topic among physicists, metallurgists, and engineers. To the engineer internal friction manifests itself as high damping in alloys, which he can machine into mechanical components having the ability to abate unwanted and destructive modes of vibration. In turn, the metallurgist endeavors to selectively heat treat, age, or alloy various metallic elements and thus produce alloys bearing efficient damping mechanisms. In conjunction with this vast research program, the physicist looks to internal friction for information about the basic structure of solid matter and the laws that govern its dynamic behavior.
Interest in internal friction has been shown at the Bureau of Mines in Rolla with regard to the damping capacity of manganese-copper alloys. Extensive investigations by the Bureau of Mines have brought to light the valuable qualities of this alloy as an engineering material, and at the same time have presented data revealing the structural nature of the alloy in various states. A need was felt for information that could be obtained by a study of the behavior of manganese-copper alloys in torsional vibration at very low stress levels. Emphasis was placed on the variation of internal friction and dynamic rigidity with temperature. Thus an investigation was proposed which entailed the following:
- Design and construction of a Ke type pendulum for measurements under vacuum or inert atmospheres and elevated temperatures. Adaptation of that instrument to the measurement of internal friction and dynamic rigidity of manganese-copper alloys under conditions of varying temperature and reduced pressure.
- Design and construction of equipment for heat treating manganese-copper wires in the solid solution range, and the development of a technique for rapidly quenching the wire specimens without bending them. Use of this equipment to prepare straight and unoxidized wire specimens (1.3 inches long by 1/32-inch in diameter) of two compositions (85 per cent manganese-15 per cent copper and 75 per cent manganese-25 per cent copper), as quenched from the α -solid solution region, in an attempt to retain the solid solution structure at room temperature.
- Measurement of the internal friction and dynamic rigidity of these specimens as a function of temperature, at low stress levels and low frequencies.
- Development of aging techniques for annealing these specimens to produce α -manganese precipitation.
- Investigation of the effect of the precipitated α -manganese on the internal friction and dynamic rigidity of these alloys.
- Correlation of the data thus obtained to establish a mechanism for the vibration damping encountered in these alloys"--Abstract, pages 1-3.
Fuller, Harold Q., 1907-1996
M.S. in Physics
Missouri School of Mines and Metallurgy
v, 46 pages
© 1956 Ed. N. Sickafus, All rights reserved.
Thesis - Open Access
Internal friction -- Measurement
Damping (Mechanics) -- Mathematical models
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Link to Catalog Record
Sickafus, Ed. (Edward), "An investigation of the internal friction of manganese-copper alloys" (1956). Masters Theses. 2581.