Congressional Serial Set Volume 3252 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1895 Excerpt: ...without stress the said change may result from secular subsidence. Moreover it is conceivable that molecular disintegration may occur in such a way as to elude detection. Now I have since been able to prove experimentally that in glasshard steel a change of the viscous quality may be obtained as the result of at least two distinct kinds of structural change, probably as the result of the two kinds of break up in question. The present chapter purposes to show this by aid of the phenomena of accommodation, or motional annealing, as they may be called more uniformly in keeping with the following work. MOTIONAL ANNEALING DEFINED. 7. The term annealing or tempering, in its most general sense, refers to a process by which strained solid structure, whether maintained by mechanical or chemical causes, is changed to isotropic structure. In viscosity, inasmuch as strained structure is ultimately accompanied by molecular instability, annealing is a process by which viscosity is increased; and from this point of view annealing need have no direct reference to exposure to temperature. Hence I have designated by the term motional annealing all such forced molecular motion to and fro, in virtue of which the molecules of a thoroughly soft solid are brought into new relations to each other, to the effect that viscosity is increased at Phil. Mag., November, 1888. the expense of the motionally less stable configurations of the soft solid. There may appear to be some incongruity in tbe term, inasmuch as the solid motionally acted on always experiences strain; it is not the strain, however, but the increment of viscosity of the solid, to which the term refers.1 Again, in order that a solid may be motionally annealed the mechanical treatment (torsion, traction, etc.) must be app...