Strain localization in beams under cyclic plastic straining at room and elevated temperature

Abstract

Deflection-controlled tests have been conducted on beams subjected to uniform bending and two forms of non-uniform bending in which strain localization occurs. The materials tested were mild steel to B.S. 1501–161 Grade 28A at room temperature and 350°C and stainless steel En 58J at room temperature and 650°C. For materials which show a settled cyclic stress-strain relation (the cyclic semi-range of strain and the corresponding cyclic semi-range of stress) estimates may be made of life in deflection cycling for beams under strain-localization conditions if the strains are calculated from the cyclic relations and the corresponding endurances are obtained from strain-cycling tests in uniform bending. On the basis of the present and previous results, it is believed that this procedure will give predictions which are on the side of safety. In the present work the predictions were often unduly safe. For materials which strain-harden severely, an elastic analysis may sometimes be adequate for an assessment of the strains involved. However, with such an analysis the predicted endurances may be unsafe and should be reduced by a suitable factor to allow for uncertainties.