STRAIN-DEPENDENCE OFPLASTIC STRAIN RATIO OF DEEP-DRAWING ALUMINIUM-KILLED STEEL SHEET
(Department of Materials Science and Engineering，Central South University of Technolog，Changsha 410083)
Abstract: The change of width and length of an aluminium-killed(AK) steel sheet was measured in detail at various tensile strain levels. The effects of tensile strain on the conventional strain ratio. rc-value，and the instantaneous strain ratio，ri-value，were analyzed. It was shown that the strain ratio of the AK steel sheet had obvious strain-dependency. The individual rc -values for all tested directions tended to unity with increasing strain so that the planar anisotropy decreased with increasing strain. The ri-value had overall strain-denpendency similar to that of rc-value，though it was overly sensitive to the experimental errors and showed significant variation with strain . In the representation of average strain ratio. the linear regression strain ratio，rr-value，which was obtained by fitting a straight line to the εW VS εT curve，is preferable to the rc -value measured at some specfic extension
Key words: plastic strain ratio anisotropy tension