Uniaxial Ratcheting is a phenomenon that occurs in metallic materials submitted to unbalanced cyclic uniaxial loads controlled by stress, that is, in which the mean stress is not zero. In this case, the material suffers successive accumulation of plastic deformations at each cycle, with a sign equal to the average applied component (usually an accumulation of deformations in tensile for mean tension in tensile). Another phenomenon present in unbalanced uniaxial histories is mean-stress relaxation, in which the inverse problem of uniaxial ratcheting occurs: in this case, the material is subjected to unbalanced cyclic uniaxial loadings controlled by strain, that is, with non-zero mean strain, which causes a successive reduction of the resulting mean stress to zero. The study of these two complementary phenomena is important, as the fatigue lives of metallic materials are affected by the effects of average stresses that can relax, and can be abbreviated by premature failure of the material if accumulated plastic deformations from ratcheting reach the material s ductility. For the study of these phenomena, uniaxial fatigue tests under stress or strain control will be performed on metallic specimens, both with non-zero mean components. From the experiments, it is expected to adjust mathematical models or to propose new models to adjust the rates of ratcheting or relaxation of the mean stress, and eventually establish a correlation between these two phenomena.