Flow localization induced by a change in strain path in mild steel

Abstract Samples of mild steel predeformed by rolling were tested in plane simple shear for various prestrain levels. For slightly predeformed material, the deformation is homogeneous. The associated flow law exhibits a transient behaviour characterized by inflection points. By contrast, for a high prestrain, strain gradients appear in the form of band propagation. Consequently, the determination of the constitutive law is no longer straightforward. An adapted version of the uniaxial plastic instability analysis is presented, which enables the shape of the flow law to be derived despite the localization of the deformation. It is shown that the previous transient behaviour is amplified with prestrain and leads to a temporary softening tendency of the predeformed metal. Some results given in the literature which also present strain gradients are shown to be in agreement with the transient behaviour of the flow law.

[1]  E. Aernoudt,et al.  Yield loci for polycrystalline metals without texture , 1985 .

[2]  U. F. Kocks,et al.  The development of strain-rate gradients , 1979 .

[3]  J. Jonas,et al.  Effect of stress triaxiality on neck propagation during the tensile stretching of solid polymers , 1983 .

[4]  C. G'sell,et al.  Plastic banding in glassy polycarbonate under plane simple shear , 1985 .

[5]  A. Korbel,et al.  Microstructural events of macroscopic strain localization in prestrained tensile specimens , 1988 .

[6]  P. Jackson,et al.  The Instability of the Work Hardened State. II. Slip in “Alien” Dislocation Distributions , 1965 .

[7]  E. Rauch,et al.  Shear of prestrained steel specimens , 1987 .

[8]  R. H. Wagoner,et al.  Effect of stress-strain-law transients on formability , 1986 .

[9]  S. R. MacEwen,et al.  Effect of stress reversals on the work hardening behaviour of polycrystalline copper , 1986 .

[10]  G. Iooss,et al.  Elementary stability and bifurcation theory , 1980 .

[11]  J. Jonas,et al.  An analysis of flow localization during torsion testing , 1985 .

[12]  Alan Needleman,et al.  A numerical study of necking in circular cylindrical bar , 1972 .

[13]  E. W. Hart.  Theory of the tensile test , 1967 .

[14]  J. Jonas,et al.  Flow localization and the determination of constitutive relations in highly drawn polymers: one-dimensional Eulerian formulation of the effect of stress triaxiality , 1985 .

[15]  E. Aernoudt,et al.  Directional strain softening in ferritic steel , 1987 .

[16]  R. H. Wagoner,et al.  Plastic behavior of aluminum-killed steel following plane-strain deformation , 1983 .

[17]  Christian G'Sell,et al.  Application of the plane simple shear test for determination of the plastic behaviour of solid polymers at large strains , 1983 .

[18]  John W. Hutchinson,et al.  Influence of strain-rate sensitivity on necking under uniaxial tension , 1977 .

[19]  J. Jonas,et al.  Plastic stability in tension and compression , 1976 .