The Effect of Stress on Internal Friction in Polycrystalline Copper

Abstract

The internal friction of polycrystalline specimens of oxygen-free copper, subjected to compressive stress, increases and then decreases with continuously increasing stress. A complementary behavior of Young's modulus is found. Thus, while the internal friction increases 100 percent, Young's modulus decreases about 6 percent for a stress of 90 kg/${\mathrm{cm}}^2$. An increase of stress to 160 kg/${\mathrm{cm}}^2$ leaves a remnant increase of only 40 percent in the internal friction and a remnant decrease in Young's modulus of 4 percent. This effect is nearly independent of the temperature at which the stress is applied. Although the Taylor dislocation of plasticity is capable of explaining qualitatively the data obtained at any one temperature, no simple explanation of the temperature independence of the effect is available at the present time.