The Influence of Temperature and Rate of Strain on the Properties of Metals in Torsion

Abstract

Abstract : The mechanical properties of 7 structural metals in pure torsion were studied for the effects of temperature (room to 1200 deg F) and the rate of strain (0.0001 to 12.5 in./in./sec). The experimental data were analyzed in terms of the basic mechanisms controlling the behavior. An increase in the strain rate generally caused an increase in strength. The properties of Ti were the most sensitive to strain-rate changes. A temperature increase reduced the strength of all of the metals except steel in the blue-brittle range. Some metals exhibited great ductility at the highest temperatures, particularly at low straining rates. Two Al alloys displayed a ductility of 800% of 600 deg F and 0.25-in./in./sec strain rate. A 200-hr aging pretreatment did not appreciably affect the properties of most metals; significant changes were evidenced only by Al alloys at 400 deg and 600 deg F and by alloy steel at 1200 deg F. A comparison was made of the data and the effects predicted by several mathematical theories. Equations are presented in terms of the flow stress and parameters of a temperature-modified strain rate and a velocity-modified temperature; the equations approximately express the observed variations in mechanical properties.