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Modeling of dynamic growth of a micro-scaled void based on strain gradient elasto-plasticity

Ma Xinbing, Liu Jinxing, Wang Jiadong, Pan Hao

Journal of Theoretical and Applied Mechanics

2020

Vol. 58 nr 4

927--941

Void initiation and growth serve as an important mechanism in ductile failures in metals. Particularly, on the micron-level, the extra hardening effect associated with strain gradient is accounted for by adopting strain gradient elasto-plasticity instead of the conventional plasticity. Effects of inertial, strain gradient hardening and thermal softening are formulated analytically for the case where a spherical void expands under external hydrostatic stress. As demonstrated by our results, the inertia effect firstly tends to hinder but then promotes the void growth. The threshold stress required for rapid void growth is lifted due to extra hardening of strain gradient so that the growth of a smaller void is delayed more remarkably. A considerable thermal softening phenomenon is observed here, which is caused by plastic work during the deformation process. The final void growth rate is mainly related to the maximum loading, which is consistent with the prediction based on the classical plastic theory.

Simulations of thermal softening in large strain thermoplasticity

Wcisło B.

Engineering Transactions

2016

Vol. 64, iss. 4

563--572

This paper deals with numerical simulations of the thermoplastic behaviour of isotropic materials undergoing large deformations. The attention is focused on the constitutive modelling of thermal softening understood here as a reduction of the plastic strength with increasing temperature. Different concepts of thermal softening embedded in the plasticity function are considered, in particular, the reduction of the total yield strength, its initial value or the hardening part. Moreover, apart from linear dependencies between temperature and the yield strength, the formulation involving function arc tangent is proposed. The analysed models are numerically tested in the finite element environment AceFEM using subroutines generated with the AceGen code generator. In particular, shear banding in an elongated rectangular plate with imperfection in plain strain conditions is investigated.