Macroscopic aspects of Lüders band deformation in mild steel

Details are given of experiments on the propagation of single Luders bands in mild steel. The results cover the effect of varying grain size on the appearance of the bands in specimens of differing cross-section, and concentrate on the macroscopic shape changes observed following the passage of the band. The results are generally consistent with a shear-flow concept [E. O. Hall, N. J. Carter and G. Vitullo, ICSMA 6, p. 393. Pergamon Press, Oxford (1983)], whereby the Luders strain arises from a shear which creates both the macroscopic shape changes and sufficient free dislocation for the flow to continue at the lower yield stress. The shear component is strongly dependent on grain size, and at large grain sizes the Luders band front becomes diffuse. The flow component is more nearly constant. However, the direction of shear is not in the line of greatest slope in the Luders front, and this points to some other component, such as grip constraints or the bending moment of the specimen, as factors which may influence the shear direction. The same factors may be responsible for influencing the orientation of the Luders band front.

[1]  Hsun Hu.  Effect of solutes on lüders strain in low-carbon sheet steels , 1983 .

[2]  H. D. McNiven,et al.  A theory for the formation and propagation of lüders bands in a plate subjected to uniaxial tension , 1975 .

[3]  G. T. Hahn,et al.  A model for yielding with special reference to the yield-point phenomena of iron and related bcc metals , 1962 .

[4]  D. Moon.  Considerations on the present state of lüders band studies , 1971 .

[5]  M. Fortes.  Constitutive equations for inhomogeneous plastic flow and application to Lüders band propagation , 1984 .

[6]  Application of continuum dislocation theory to geometry of Lüders front , 1972 .

[7]  K. Prewo,et al.  Lüders band motion in iron , 1972 .

[8]  T. Vreeland,et al.  Stress dependence of mobile dislocation density and dislocation velocity from Lüders band front propagation velocity , 1968 .

[9]  Eric Ogilvie Hall,et al.  Yield Point Phenomena in Metals and Alloys , 1970 .

[10]  W. Johnston,et al.  Dislocation Velocities, Dislocation Densities, and Plastic Flow in Lithium Fluoride Crystals , 1959 .

[11]  H. Fujita,et al.  Lüders deformation in polycrystalline iron , 1978 .

[12]  E. Hall,et al.  Shear and kink angles at the lüders band front , 1989 .

[13]  A. Cabo,et al.  On the lüders band front in mild steel—I , 1977 .

[14]  G. T. V. Rooyen.  The stress and strain distribution in a propagating Lüders front accompanying the yield-point phenomenon in iron , 1968 .

[15]  W. Lomer.  The yield phenomenon in polycrystalline mild steel , 1952 .

[16]  Alan Cottrell,et al.  Mechanical Properties of Matter , 1964 .

[17]  D. Moon,et al.  Orientation of Lüders band fronts , 1971 .

[18]  P. Haasen,et al.  Chalmers anniversary volume , 1981 .

[19]  R. Liss.  Luder's bands , 1957 .

[20]  J. C. Fisher,et al.  Propagation of lüder's bands in steel wires , 1956 .

[21]  Par B. Jaoul.  Consolidation des polycristaux de fer et hypothèses sur l'origine du palier des courbes de traction , 1961 .