K. Perzyński

Digital Material Representation as an efficient tool for strain inhomogeneities analysis at the micro scale level

The summary of recent research towards development of a tool for detailed microstructure modelling is presented within the paper. The main focus is put on micro scale behaviour, where advantages of digital material representation can be taken into account. Digital Material Representation allows modelling of microstructures along with features such as crystallographic orientation, grain boundaries or phase boundaries represented in an explicit manner. Incorporation of these digital microstructures into the numerical simulation methods provides the possibility to improve the quality of numerical results. The developed method can be used to design specifically dedicated microstructures, which meet very strict requirements. The clear motivation and importance of the work is presented in the first part of the paper followed by a short description of the developed approaches for creation of the digital microstructures. Two approaches are considered that provide an exact and statistical representation of the real microstructure. The main focus is put on the application of image processing and cellular automata techniques. Afterwards, obtained digital microstructures are used as input data for the finite element analysis of the micro scale compression test. Examples of applications during multiscale simulation are also presented in the paper.

Numerical Investigation of Influence of the Martensite Volume Fraction on DP Steels Fracture Behavior on the Basis of Digital Material Representation Model

Development of the methodology for creating reliable digital material representation (DMR) models of dual-phase steels and investigation of influence of the martensite volume fraction on fracture behavior under tensile load are the main goals of the paper. First, an approach based on image processing algorithms for creating a DMR is described. Then, obtained digital microstructures are used as input for the numerical model of deformation, which takes into account mechanisms of ductile fracture. Ferrite and martensite material model parameters are evaluated on the basis of micropillar compression tests. Finally, the model is used to investigate the impact of the martensite volume fraction on the DP steel behavior under plastic deformation. Results of calculations are presented and discussed in the paper.

Fracture modeling in dual-phase steel grades based on the random cellular automata finite element approach

The development of a parallel version of the fracture model dedicated for multi-phase materials based on a combination of the finite element model and random cellular automata approach is the overall goal of this study. Dual-phase (DP) steel, commonly used in the automotive industry, is selected as a case study for the present investigation. Firstly, various fracture modes that can occur during deformation in DP steel grade microstructures are presented from an experimental point of view. To consider explicitly microstructure features that play a significant role during initiation and subsequent failure propagation, the digital material representation concept is used. Then, details of the developed random cellular automata model, fully embedded within the finite element framework, are discussed. The cellular automata space definition, internal variables, state variables and transition rules replicating investigated fracture modes are presented in detail and discussed. The concept of data transfer and parallelization based on the Message Passing Interface methodology in such an innovative hybrid numerical model is also clearly presented. The final section of the paper is devoted to examples of obtained results highlighting model predictive capabilities.

Crack Investigation of the Multilayer TiN/Ti Coatings during the Nanoindentation Test

Nanoindentation test is one of the most commonly used methods for the strength investigation of the nanomaterials. Information provided from such test gives the possibility to obtain a knowledge about fracture development under the spot hitting tool. However, nano dimensions of the coatings obtained by the deposition method creates problems with exact investigation of this test. Costs of experimental study are very often excessive due to very specialized laboratory equipment. The numerical simulations can be a support for mentioned experimental research as they give possibility of fast and efficient investigation on behavior of different nanolayers dimensions and alignments. The main aim of this work is focused on taking into account real morphology of microstructure of ceramic TiN layers deposited on the metallic Ti layers during nanoindentation test. This combination of layers is widely used in medicine for improvement mechanical properties and biocompatibility behavior of bio elements. Particular attention during numerical simulation is put on influence of columnar structure of these layers on fracture development. Results obtained from the extended finite element model (XFEM) for various nanolayers alignments is discussed according to the fracture initiation and propagation.

Development and evaluation of data transfer protocols in the fully coupled random cellular automata finite element model of dynamic recrystallization

Abstract Development and application of the hybrid fully coupled, random cellular automata finite element (RCAFE) approach to modelling dynamic recrystallization phenomenon, during a high temperature deformation is the overall goal of the paper. The finite element (FE) solver provides information on equivalent stress, equivalent strain, temperature fields as well as on geometry of deformed computational domain after each time step. These data are transferred to the developed random cellular automata (RCA) model, which is responsible for evaluation of corresponding microstructure morphology evolution and dislocation density changes under dynamic recrystallization (DRX) conditions. Finally, a set of data from the RCA part is send back to the FE solver and used as an input for the next time step. As a result, the fully coupled RCAFE model for simulation of a DRX progress is established. Crucial developments of the RCA model related to the space deformation and efficient neighbors selection are presented within the paper. However, particular attention is put on the development of efficient communication algorithms and methods for input/output data transfer between the FE and RCA modules. The communication protocols based on text files and sockets have different levels of complexity but both are based on the Abaqus VUMAT subroutine. Their capabilities and limitations are evaluated within the paper. Finally, an application of the proposed RCAFE method to simulation of a dynamic recrystallization progress at the level of single grains is presented and discussed to highlight capabilities of the model.

HYBRID FE/XFE FINITE ELEMENT MODEL FOR SIMULATION OF BRITTLE-DUCTILE FRACTURES IN DUAL-PHASE STEEL GRADES.

Development of hybrid finite element/eXtended finite element numerical solution combined with the digital material representation (DMR) approach to simulate brittle/ductile fracture is the overall subject of the realized research. This particular work is divided into three main parts. In the first, proposed procedures for development of DMR model of investigated two phase steel are described. Then, details on the procedure of creation of representative digital material representation model to simulate interrelations between ductile and brittle fractures occurring within particular phases are presented. Finally, based on evaluated model parameters examples of its application to numerical simulation of failure in DP steels are presented. The main outcome from this work is the hybrid FEM/XFEM model, which can be easily applied to various deformation processes. The approach fulfils industrial demand to create a computer aided design of processes were fracture is an issue. Presented model is designed for practical research and industrial applications. K. Perzyński and L. Madej

Numerical model of the nanoindentation test based on the digital material representation of the Ti/TiN multilayers

Abstract The developed numerical model of a local nanoindentation test, based on the digital material representation (DMR) concept, has been presented within the paper. First, an efficient algorithm describing the pulsed laser deposition (PLD) process was proposed to realistically recreate the specific morphology of a nanolayered material in an explicit manner. The nanolayered Ti/TiN composite was selected for the investigation. Details of the developed cellular automata model of the PLD process were presented and discussed. Then, the Ti/TiN DMR was incorporated into the finite element software and numerical model of the nanoindentation test was established. Finally, examples of obtained results presenting capabilities of the proposed approach were highlighted.

Numerical Modelling of Explosive Welding on the Basis of the Coupled Eulerian Lagrangian Approach

The main goal of the paper is development of a numerical model for explosive welding involving geometry and properties of major process components, i.e. base plate, flyer plate and explosive material. To properly replicate material behavior under these severe conditions the Coupled Eulerian Lagrangian (CEL) approach is used. Series of numerical simulations are realized based on the developed model in order to relate the process variables to the physical parameters. That will be used in further work to establish how these can be used to predict whether or not bonding will occur.