Abstract: A more close fit model of the static σ ε curve is given at first. Then a new cyclic plastic model,two tangent model, is proposed. This model can analyze and calculate the response of the material to asymmetrical loading quantitatively. In the meantime, the total strain energy density theory is used to estimate the fatigue life. From the results, the calculated fatigue lives agree very well with the experimental data.

Key words: cyclic asymmetrical loading, stress-strain curve, two tangent model, total strain energy density fatigue life