Cyclic behaviour concerning the response of material subjected to tension levelling

Tension levelling is employed in cold steel strip manufacturing to guarantee that flat material is provided for shape-critical applications. The loading system of the process leads to a corresponding [very] low cycle fatigue stress–strain history being applied to surface and sub-surface sections of the material. In this paper, results are presented from a series of low cycle fatigue tests (in the crack-free phase) under constant strain amplitude control for a number of strain amplitudes, typical of those found in levelling applications. The results for the tests reported here suggest that a mixed mode work hardening process is present, with the application of a Bauschinger effect resulting in a closed hysteresis loop on completion of the first cycle. All tests showed that the material gradually work softened under the cyclic loads imposed. Strain-amplitude dependent work hardening, however, was observed in some early cycles.