Cyclic behaviour concerning the response of material subjected to tension levelling

Tension levelling is employed in cold steel strip manufacturing to guarante e that Bat material is provided for shape-critical applications. The loadin g system of the process leads to a corresponding [very] low cycle fatigue s tress-strain history being applied to surface and sub-surface sections of t he material. In this paper, results are presented from a series of low cycl e fatigue tests (in the crack-free phase) under constant strain amplitude c ontrol for a number of strain amplitudes, typical of those found in levelli ng applications. The results for the tests reported here suggest that a mix ed mode work hardening process is present, with the application of a Bausch inger effect resulting in a closed hysteresis loop on completion of the fir st cycle. All tests showed that the material gradually work softened under the cyclic loads imposed. Strain-amplitude dependent work hardening, howeve r, was observed in some early cycles. (C) 2000 Elsevier Science Ltd. All ri ghts reserved.