It is well known that size effects are present in plasticity with the observation that smaller being the stronger. This effect is attributed to the presence of geometrically necessary dislocations (GNDs). The hardening associated to GNDs can be separated in two groups: energetic and dissipative. The fi rst is associated with defect energy and different defi nitions for it are possible. In all c...

In this acticle a semi-smooth Newton method for frictional two-body contact problems and a solution algorithm for the resulting sequence of linear systems is presented. It is based on a mixed variational formulation of the problem and a discretization by finite elements of higher-order. General friction laws depending on the normal stresses and elasto-plastic material behaviour with linear isot...

Generalized I lyushin ' s deviatoric stress and s t ra in spaces are introduced, which make it possible to apply directly the postulate of isotropy to initially isotropic materials with plastic properties influenced by the third deviatorie stress invariant and to a certain class of initially anisotropie materials. The generalizations proposed are connected with a new concept of description of p...

In this paper, an elastoplastic constitutive model is presented for predicting sandy soil behavior under monotonic and cyclic loadings. The model is based on the CJS3 model that takes into account deviatoric and isotropic mechanisms of plasticity. The flow rule in deviatoric mechanism is non-associated and a kinematic hardening law controls the evolution of the &#10yield surface. In the present...

An elastoviscoplastic three-dimensional model is proposed in order to predict the response of brake discs for a High Speed Train (T.G.V.), which are subjected simultaneously to mechanical and thermal loadings. This elastoviscoplastic law is based on the internal thermodynamic variables and takes into account the non-linear kinematic and isotropic hardening with plastic strain memory effect. A m...

A phenomenological theory is presented for describing the anisotropic plastic flow of orthotropic polycrystalline aluminum sheet metals under plane stress. The theory uses a stress exponent, a rate-dependent effective flow strength function, and five anisotropic material functions to specify a flowpotential, an associated flow rule of plastic strain rates, a flow rule of plastic spin, and an ev...

We analyze the stability of homogeneous simple tensile/compressive deformations of an isotropic heat-conducting thermoviscoplastic bar by studying the growth of infinitesimal perturbations superimposed upon a homogeneous deformation. The smallest axial strain at which the superimposed perturbation has a positive initial growth rate is called the instability strain. Two criteria are used to dete...

The objective of this study is to evaluate the effect of constitutive equations on the prediction accuracy for springback in cold stamping with various deformation modes. In this study, two types of yield functions—Hill’48 and Yld2000-2d—were considered to describe yield behavior. Isotropic and kinematic hardening models based on the Yoshida–Uemori model were also adopted to describe hardening ...

In this paper an algorithm for large strain elasto-plasticity with isotropic hyperelasticity based on the multiplicative decomposition is formulated. The algorithm includes a (possible) constitutive equation for the plastic spin and mixed hardening in which the principal stress and principal backstress directions are not necessarily preserved. It is shown that if the principal trial stress dire...

Stress–strain response under constant and variable strain-rate is studied for selected models of inelastic behavior. The derived closed-form solutions for uniaxial loading enable simple evaluation of the strain-rate effects on the material response. The effect of an abrupt change of strain-rate is also examined. Non-Newtonian viscosity which decreases with an increasing strain-rate is incorpora...