The flow in metals under large constant stresses

Abstract

§1. The object of this research was to examine the general laws of flow in metallic wires when extended in the region of large permanent set by stresses kept constant throughout the flow. Previously I have investigated in detail the flow for one metal, lead, and put forward some empirical laws; it was desired to see if these laws could be extended to other metals, and especially to investigate the effect of temperature on the nature of the flow. For lead, rise of temperature causes a very rapid increase in the rate of the viscous part of the flow ( loc. cit. ); hence it seemed likely that at very low temperatures the viscous part of the flow would case altogether, although large permanent extensions might be obtainable, and thus lead might behave in this respect as iron behaves at atmospheric temperatures. Similarly iron at a high temperature might behave like lead at atmospheric temperatures. It was also desired to see if very pure metals behaved in the same way as commercial metals, for it has been supposed that the nonviscous character of the initial part of the extension-time curve is due to impurities. Further, the properties of the viscous flow itself were to be investigated in greater detail. Investigation on these points are described in this paper; a summary of the results will be found in §10. Incidentally, in the case of alloys, a type of flow not hitherto observed has been found.