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Phenomenological Description of the Effect of Micro-Shear Banding in Micromechanical Modelling of Polycrystal Plasticity

Kowalczyk-Gajewska K., Pęcherski R. B.

Archives of Metallurgy and Materials

2009

Vol. 54, iss. 4

1145-1156

The rigid-plastic crystal plasticity model accounting for the effect of micro-shear banding mechanism on the reduction of the global strain hardening rate is presented. The instantaneous contribution of micro-shear bands in the rate of plastic deformation is described by means of the constitutive function fMS that depends on the type of strain path specified by the current direction of strain rate tensor. The capabilities of the model are explored by studying the strain-stress behavior of polycrystalline material together with the crystallographic texture evolution in the polycrystalline element.

Przedstawiono sztywno-plastyczny model plastyczności kryształów uwzględniający wpływ mikropasm ścinania na redukcje globalnego modułu umocnienia. Chwilowy udział mikro-pasm ścinania w prędkości deformacji plastycznej został opisany poprzez dodatkowa konstytutywna funkcje fMS, która zależy od schematu odkształcenia zdefiniowanego przez aktualny kierunek tensora prędkości odkształceń. Zbadano możliwości proponowanego modelu mikromechanicznego w ramach analizy odpowiedzi materiału polikrystalicznego z uwzględnieniem rozwoju tekstury krystalograficznej.

Stress-Strain Analysis of Ideally Plastic Material in Notches

Grudziński J., Buczyński A.

Machine Dynamics Problems

2008

Vol. 32, No. 3

20-33

Reliability and fatigue life estimations of structural and mechanical components exercising multiaxial loads need predictions of evolution of stress and strain fields. The solution of the problem demands high accuracy regarding stress-strain distribution especially in zones affected by stress concentrators such as cracks, geometrical or structural notches etc. The paper is addressed to numerical analysis of material plastic flow near the root of the U-type notch, located in a plate made of ST37 steel, under non-symmetric cyclic loads. The FEM will be applied to solve the problem, formulated in 2D space. The material behavior will be predicted by using the ideal plasticity cyclic model.

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

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

Inżynieria Materiałowa

2001

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.