This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922 edition. Excerpt: ...Relative Efflux Of Metallic Lead Through A Small Orifice At Various Temperatures (after Werigen, Lewkojeff And Tammann) When a wire, which is stretched by a weight, is subjected to torsional vibrations, the amplitudes of the vibrations form a series in geometrical progression, and therefore the logarithmic decrement of the amplitude is a constant. A part of the energy of vibration is given to the surrounding atmosphere and a part is transmitted to the support, but a portion of the energy is dissipated within the wire itself. It is generally agreed that this loss is due to the lack of perfect elasticity in the wire. In other words, the wire when subjected to shearing stress suffers permanent deformation even though the stress is not equal to the elastic limit. This deformation causes a shift in the position of rest, so that as the pendulum passes from its new position of rest to its old position of rest, it does so at the expense of its own momentum and there is thus a loss of energy. This flow is entirely analogous to the flow of various plastic materials such as clay slip and paint, which we have already considered, when the shearing stress is less than the friction. Since the flow is of the nature of local slippage rather than true plastic flow, strains accumulate and they remain after the stress is removed. The result is the same as that observed by Trouton in pitch, in that the substance tends to creep slowly back toward its old position of rest during a period of time which in pitch is comparatively short but may be observed in metals for hours or even days. The elastic "after effect" has been the subject of exhaustive investigation by Weber (1835), Warburg (1869), Kohlrausch (1863-76), Boltzmann (1876), G. Wiedemann...

Contains results of investigations, researches, etc., pertaining to scientific, technical and manufacturing interests of the country.

Contains results of investigations, researches, etc., pertaining to scientific, technical and manufacturing interests of the country.