The effect of serrated yielding on the determination of r-values in aluminium alloys and yield locus calibration

An Associated and Nonassociated Flow Rule Comparison for AISI 439-430TI Forming: Modeling and Experimental Analysis

“…The relation between the transverse and longitudinal true plastic strains is noted by the slope 𝑚𝑚(𝜃𝜃), which is obtained by the linear regression of the fitted curve. The technique utilized to calculate the Lankford parameter was based on the method outlined in the British Standard BS ISO 10113:2006 according to Kilpatrick et al (Kilpatrick et al, 2010). The obtained transverse versus longitudinal true plastic strain curves are plotted in Figure 11 for all seven specimens with different orientations.…”

The finite element implementation, validation and verification of a plane stress yield criterion for use in sheet metal forming analysis

“…Additionally the Portevin-Le Châtelier (PLC) effect negatively influences the Hill 1948 yield criterion when calibrated using the r-value (plastic strain ratio) method [10]. Subsequent yield criteria by Hill [11][12][13] were non-quadratic, incorporating the equibiaxial stress within the yield function.…”