Effect of inhomogeneous tensile deformation of plastic anisotropy

There are several methods leading to precise determination of plastic anisotropy of materials; all are based on the strain ratio r versus strain epsilon relationship. The present authors propose the description of the variation of plastic strain ratio during the macroinhomogeneous deformation by the sequence of processes of homogeneous strain in which stable, unchanging deformation mechanism is operating. Two groups of procedures should be displayed: the first consisting in the determination of strain ratio at several levels of deformation in the tensile test, and the second one when partial strains (due to the change of width and thickness of a sample) are related to the longitudinal strain, The effect of large experimental scatter around the r(epsilon) relationship may be minimized when calculating the fitting function based on maximal error procedure and describing the variation of r with epsilon by the hyperbolic relation. The method makes possible the determination of both, the r(o) = r(0) value which describes the plastic anisotropy of material with a well defined physical meaning, and the r (strain ratio at a freely chosen strain, e.g. at the limit of uniform elongation: r(a)) which is important for the plastic working technology.