Ł. Madej

Multiscale modelling of microstructure evolution during laminar cooling of hot rolled DP steels

Accelerated cooling of DP steel strips after hot rolling is considered in the paper. The work is focused on the multi scale model based on the Cellular Automata method as well as on conventional models. Dilatometric tests were performed to identify the coefficients in the models for a DP steel. These models are implemented in the computer system, which simulates controlled cooling of products after hot rolling. This system is described briefly in the paper. Results of numerical tests, which show an influence of the cooling parameters on the structure of the DP steels, are presented in the paper, as well. Arbitrary laminar cooling system, composed of n1 boxes in the first section and n2 boxes in the second section, is considered. Such parameters as strip thickness and velocity, the number of active boxes in the first section of the laminar cooling, the time interval between the two sections and water flux in the sections were independent variables in the analysis. The optimal cooling schedule is the main result of the work.

Conventional and Multiscale Modeling of Microstructure Evolution During Laminar Cooling of DP Steel Strips

Physical and numerical simulations of the hot rolling and laminar cooling of DP steel strips are presented in the paper. The objectives of the paper were twofold. Physical simulations of hot plastic deformation were used to identify and validate numerical models. Validated models were applied to simulate the manufacturing of DP steel strips. Conventional flow stress model and microstructure evolution model were used in the hot deformation part. The approach to the complex systems analysis based on global thermodynamic characterization and detailed microstructure characterization was applied to determine equilibrium state at various temperatures. Finally, two numerical models were used to simulate kinetics of austenite decomposition at varying temperatures: the first, conventional model based on the Avrami equation, and the second, the discrete Cellular Automata approach. Plastometric tests and stress relaxation tests were used for identification of the hot rolling model for the DP steel. Dilatometric tests were performed to identify the phase transformation models. Verification confirmed good accuracy of all models. Validated models were applied to simulate the manufacturing of DP steel strips. Influence of technological parameters (e.g., strip thickness and velocity, active sections in the laminar cooling, and water flux in the sections) on the DP microstructure was analyzed. The cooling schedules, which give required microstructures were proposed. The numerical tool, which simulates manufacturing chain for DP steel strips is the main output of the paper.

Development of Dynamic Recrystallization Model Based on Cellular Automata Approach

Development of a numerical model for the dynamic recrystallization (DRX) on the basis of the Cellular Automata method and the Digital Material Representation (DMR) idea is the main goal of the present work. Basic assumptions (space definition, neighborhood type, state and internal variables) of the proposed model are presented and discussed. Particular attention is put on description of the developed transition rules used to replicate mechanisms leading to dynamic recrystallization. Finally, examples of obtained results of DRX morphology and kinetics are also presented within 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.

Validation of Cellular Automata Model of Dynamic Recrystallization

Development and validation of the micro scale cellular automata (CA) model of dynamic recrystallization (DRX) were the main goals of the present paper. Major assumptions of the developed CA DRX model, which is based on the Digital Material Representation (DMR) concept, are described. Parameters like neighborhood type, state and internal variables of the proposed model and their influence on final results are presented and discussed. Particular attention was put on description of the developed transition rules used to replicate mechanisms leading to dynamic recrystallization. Finally, obtained results in the form of flow stress curves are compared with the experimental predictions.

The Material Flow Analysis in the Modified Orbital Forging Technology

The main aim of this work is the computer aided design of the new orbital forging process. The finite element model was developed and used in research on possibility of modification of the classical orbital forging technology based on the Marciniak press to obtain more effective process. Obtained numerical results from simulations of the new orbital process are compared with the experimental analysis, performed on the orbital press with the developed device. However, due to the novelty of the developed approach the investigation on direction of material flow during deformation is of particular interest in this work. Direction of material flow and strain path change effect due to incremental character of deformation is analyzed. Obtained results confirm good predictive capability of the FE model and are the basis for the comparison of the two processes and discussion on the effectiveness of the modified incremental forming process.

Numerical Modelling of Fracture Based on Coupled Cellular Automata Finite Element Approach

Investigation of failure of Dual Phase steels on the basis of the developed concurrent cellular automata finite element model is the subject of the present paper. Physical background of phenomena responsible for failure in these steels is described first. Then details of the developed random cellular automata model are presented. Particular attention is put on proper definition of the transition rules describing initiation and propagation of fractures across the microstructure. Finally combined cellular automata finite element model is established. Examples of obtained results are also presented within the paper.

Employing an Adaptive Projection-based Interpolation to Prepare Discontinuous 3D Material Data for Finite Element Analysis☆

Abstract In this paper we propose an adaptive 3D image data pre-processing technique for generating a continuous approximation of an input image representing some material data, along with a finite element mesh aligned to the properties of the material, which can be used as the initial mesh for a further hp-adaptive finite element analysis. First, we introduce the projection-based interpolation operator, we explain some design considerations, useful for reproducing this work, then we present a benchmark problem used as a proof of concept and we conclude with numerical results for this exemplary problem, obtained with our implementation of the discussed method.

Parallelization of the Monte Carlo Static Recrystallization Model

Implementation of parallel version of the Monte Carlo MC static recrystallization algorithm for application in the PL-Grid Infrastructure is presented in this work. General assumptions of the algorithm are described first. This is followed by presentation of modifications that were introduced and are required for the parallel execution. Monte Carlo space division schemes between subsequent computing nodes are particularly addressed. Implementation details are also presented. Finally, influence of size and geometry of the MC space on calculations efficiency is discussed.

Cellular Automata Finite Element Approach for Modelling Microstructure Evolution under Thermo-Mechanical Processing Conditions

The concurrent cellular automata finite element (CAFE) approach for modelling microstructure evolution under thermo-mechanical processing conditions is the subject of the present work. Particular attention is put on modelling two phenomena, static recrystallization after deformation and phase transformation during heating. Details of the developed models are presented within the paper. Both models are implemented based on the CA Framework, which is also described in the work. Finally cellular automata approaches are combined with the finite element model based on the digital material representation idea. The numerical modelling of complex multistage hot deformation process was selected as a case study to show capabilities of the developed cellular automata finite element model.