Asymmetry behavior between tension and compression in the cyclic deformation of copper single crystals and other ductile metals

Asymmetry behavior between tension and compression, i.e. stresses in compression are larger than those in tension, has been observed frequently in cyclic deformation. In order to investigate this behavior, a parameter, the asymmetry factor, has been defined to measure the degree of asymmetry in copper single crystals. It is found that the asymmetry factors “scatter” widely during rapid hardening and converge to the commonly accepted imbalance of about 5% between tension and compression after the crystals reach saturation. The causes of these behaviors are explored by studying crystals of different orientation and model experimental systems. The asymmetry is explained in terms of several factors, but the dominant one in saturation appears to be deformation constraint associated with strain localization. At long to medium life the strain localization takes the form of persistent slip bands, but other forms of localization can affect the asymmetry behavior at short life.