This research project deals with nonlinear evolution problems that arise in the study of the inelastic behaviour of solids, in particular in plasticity and fracture. The project will focus on selected problems, grouped into three main topics, namely: 1. Plasticity with hardening and softening, 2. Quasistatic crack growth, 3. Dynamic fracture mechanics. The analysis of the models of these mechan...

This article deals with a viscoplastic material model of overstress type. The model is based on a multiplicative decomposition of the deformation gradient into elastic and inelastic part. An additional multiplicative decomposition of inelastic part is used to describe a nonlinear kinematic hardening of Armstrong-Frederick type. Two implicit time-stepping methods are adopted for numerical integr...

While the expenses for computational power decrease, iterative reconstruction methods for x-ray computed tomography (CT) that allow the use of improved model assumptions, become more attractive. In applications for non-destructive testing one of the most common degradations of image quality with standard x-ray CT reconstruction methods is beam hardening. Techniques for beam hardening correction...

Stress and deformation analysis of the simple shear at finite strain of a strainhardening elastoplastic hollow circular cylinder is given. Both isotropic and anisotropic hardening models are considered. In the case of isotropic hardening, there is a closed form analytical solution. No normal stresses exist in this case. Purely kinematic hardening with a Mises-type yield condition is utilized as...

Dynamic recrystallization (DRX) processes are widely used in industrial hot working operations, not only to keep the forming forces low but also to control the microstructure and final properties of the workpiece. According to the second derivative criterion (SDC) by Poliak and Jonas, the onset of DRX can be detected from an inflection point in the strain-hardening rate as a function of flow st...

A Fe-34.5 wt % Mn-0.04 wt % C ultra-high Mn steel with a fully recrystallised fine-grained structure was produced by cold rolling and subsequent annealing. The steel exhibited excellent cryogenic temperature properties with enhanced work hardening rate, high tensile strength, and high uniform elongation. In order to capture the unique mechanical behaviour, a constitutive model within finite str...

The rigorous derivation of lower dimensional models for thin structures is a question of great interest in mechanics and its applications. In the early 90’s a rigorous approach to dimension reduction has emerged in the stationary framework and in the context of nonlinear elasticity. This approach is based on Γ-convergence and, starting from the seminal paper [3, 4], has led to establish a hiera...

A single crystal plasticity theory for insertion into finite element simulation is formulated using sequential laminates to model subgrain dislocation structures. It is known that local models do not adequately account for latent hardening, as latent hardening is not only a material property, but a nonlocal property (e.g. grain size and shape). The addition of the nonlocal energy from the forma...

Abstract: Methods of fault-hardening software implementations of the numerical Model Predictive Control (MPC) algorithms are discussed in the paper. In particular, Generalized Predictive Control (GPC) algorithms are considered. The robustness of these algorithms with respect to faults is crucial for process safety and economic efficiency, as faults may result in major control performance degrad...

Sinter-hardening is an emerging powder metallurgy process by which the consolidation of and hardening dense bulk samples are integrated into one step. In this study, to understand complex effects sinter-hardening parameters on properties Fe-Cr-Ni (Cu)-C alloy, artificial neural network (ANN) with topology a nonlinear multi-layered perceptron was designed predict ultimate tensile strength elonga...