This study experimentally investigates the subsequent yield surfaces of thin-walled tubular ductile cast iron (QT600-7) specimens under various pre-deformation histories and elucidates their evolution patterns. The effects of pre-deformation level, unloading position, and loading path on the subsequent yield surfaces are examined, with particular attention to the concave phenomenon observed in the measured yield surfaces. The results show that the subsequent yield surfaces of QT600-7 translate towards the pre-loading direction. Translation and distortion are more pronounced at smaller offset strains and gradually diminish with increasing offset strains. Under different pre-loading paths, a sharp corner appears in the pre-loading direction and a concave or flattened shape forms in the opposite direction when the offset strain is small; this concave phenomenon tends to disappear under larger offset strains. A higher pre-deformation level leads to more noticeable distortion of the yield surface corresponding to small strains. After pre-tension and unloading, if reverse compression occurs, the subsequent yield surface under small offset strains exhibits a complex shape in the opposite direction.
Huang et al. (Sat,) studied this question.