Effect of Large Changes in Strain Rate in the Experimental Deformation of Yule Marble

Abstract

A new adaptable deformation apparatus has been developed for constant strain-rate tests up to 5 kb. confining pressure and 500° C. at strain rates from 0.4 to $3\cdot 10^{-8}/sec$. In most of the sixty-four tests reported here, jacketed cylinders of Yule marble (oriented parallel, at 45° and normal to the foliation) were extended 10 per cent at temperatures from 25° to 500° C., 5 kb. confining pressure. Several samples were deformed 60-80 per cent at temperatures ranging from 350° to 500° C. at a strain rate of $3\cdot 10^{-7}/sec$ for fabric study. Stress-strain curves are plotted and compared for a wide range of temperature and strain rates. Stress-strain curves at 25° C. show only slight decrease in strength with decreasing strain rate; at 500° C. strengths at 10 per cent strain are decreased 80 per cent from the fastest (0.25-second duration) to the slowest (35 days) tests. Strong strain hardening, characteristic in tests at the lower temperatures and higher strain rates, changes gradually to steady s...