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Constitutive modelling for cyclic plasticity with consideration of yield-drop phenomen.

100%

Yoshida F.

Inżynieria Materiałowa

1998

tom R. XIX, nr 3

116-123

A constitutive model of cyclic plasticity for annealed steel, which exhibits a sharp yield-point and the subsequent abrupt yield-drop in its stress-strain curve of uniaxial tension, is proposed. The model has been derived on the premise that the yield-drop phenomenon is a consequence of rapid dislocation multiplication and the stress-dependence of dislocation velocity. Cyclic deformation characteristics such as the Bauschinger effect, cyclic softening and rate-dependent ratchetting are described in the model by the rule of combined kinematic and isotropic hardening of the yield surface. The stress-strain responses for a mild steel during cyclic straining and stressing (ratchetting) calculated with the model agree well with the corresponding experimental observations on a mild steel.

Plasticity models describing the Bauschinger effect and yield-point phenomena.

51%

Yoshida F. , Uemori T. , Sun H. B. , Itoh M.

Inżynieria Materiałowa

2001

tom R. XXII, nr 5

974-980

This paper presents a plasticity model (rate-independent model) which has a high capability of describing the deformation behavior at large-strain and also the stress-strain responses at small-scale re-yielding after large prestrain. A new equation of backstress evolution is proposed for an accurate simulation of the transient Bauschinger effect. An original idea of a non-isotropic-hardening surface defined in the stress space is presented for the description of the workhardening stagnation appearing under reverse deformation. Furthermore, in order to describe the yield-point phenomena characterized by a sharp yield point and the subsequent abrupt yield drop, this model is extended to a model of viscoplasticity (rate-dependent model) on the premise that the phenomena of sharp yield point and the subsequent abrupt yield drop result from rapid dislocation multiplication and the stress-dependence of dislocation velocity. Based on this viscoplasticity model, the description of strain-ageing , i.e., the Cottrell locking and the precipitation hardening, is discussed.