scholarly journals Strain localisation and dynamic recrystallisation in the ice-air aggregate: A numerical study

2016 ◽  
Author(s):  
Florian Steinbach ◽  
Paul D. Bons ◽  
Albert Griera ◽  
Daniela Jansen ◽  
Maria-Gema Llorens ◽  
...  
Keyword(s):  
Numerical Study ◽  
Numerical Approach ◽  
Second Phase ◽  
Strain Localisation ◽  
Time Resolved ◽  
Full Field ◽  
First Results ◽  
Dynamic Recrystallisation ◽  
Heterogeneous Microstructures ◽  
Heterogeneous Deformation

Abstract. We performed numerical simulations on the micro-dynamics of ice with air inclusions as a second phase. This provides first results of a numerical approach to model dynamic recrystallisation in polyphase crystalline aggregates. Our aim was to investigate the rheological effects of air inclusions and explain the onset of dynamic recrystallisation in the permeable firn. The simulations employ a full field theory crystal plasticity code coupled to codes simulating dynamic recrystallisation processes and predict time-resolved microstructure evolution in terms of lattice orientations, strain distribution, grain sizes and grain boundary network. Results show heterogeneous deformation throughout the simulations and indicate the importance of strain localisation controlled by air inclusions. This strain localisation gives rise to locally increased energies that drive dynamic recrystallisation and induce heterogeneous microstructures that are coherent with natural firn microstructures from EPICA Dronning Maud Land ice coring site in Antarctica. We conclude that although overall strains and stresses in firn are low, strain localisation associated with locally increased strain energies can explain the occurrence of dynamic recrystallisation.

scholarly journals Strain localization and dynamic recrystallization in the ice–air aggregate: a numerical study

2016 ◽  
Vol 10 (6) ◽  
pp. 3071-3089 ◽  
Author(s):  
Florian Steinbach ◽  
Paul D. Bons ◽  
Albert Griera ◽  
Daniela Jansen ◽  
Maria-Gema Llorens ◽  
...  
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Localization ◽  
Numerical Study ◽  
Second Phase ◽  
Time Resolved ◽  
Full Field ◽  
Grain Sizes ◽  
Dronning Maud Land ◽  
Heterogeneous Microstructures ◽  
Heterogeneous Deformation

Abstract. We performed numerical simulations on the microdynamics of ice with air inclusions as a second phase. Our aim was to investigate the rheological effects of air inclusions and explain the onset of dynamic recrystallization in the permeable firn. The simulations employ a full-field theory crystal plasticity code coupled to codes simulating dynamic recrystallization processes and predict time-resolved microstructure evolution in terms of lattice orientations, strain distribution, grain sizes and grain-boundary network. Results show heterogeneous deformation throughout the simulations and indicate the importance of strain localization controlled by air inclusions. This strain localization gives rise to locally increased energies that drive dynamic recrystallization and induce heterogeneous microstructures that are coherent with natural firn microstructures from EPICA Dronning Maud Land ice coring site in Antarctica. We conclude that although overall strains and stresses in firn are low, strain localization associated with locally increased strain energies can explain the occurrence of dynamic recrystallization.

scholarly journals Cellular Automata-based computational library for development of digital material representation models of heterogenous microstructures

2021 ◽  
Vol 21 (2) ◽  
Author(s):  
Konrad Boguń ◽  
Mateusz Sitko ◽  
Mateusz Mojżeszko ◽  
Łukasz Madej
Keyword(s):  
Cellular Automata ◽  
Numerical Approach ◽  
Dynamic Link Library ◽  
Full Field ◽  
Practical Applications ◽  
C Programming Language ◽  
Wide Range ◽  
C Programming ◽  
Digital Material ◽  
Heterogeneous Microstructures

AbstractThe development of an efficient numerical approach for the generation of a wide range of heterogeneous microstructures models with the application of the lean workflow concept is presented in the paper. First, the idea and implementation details of the developed cellular automata-based computational library allowing the development of digital material representation models within a workflow are presented in the paper. Such an approach provides the desired flexibility in the generation of various digital models of heterogenous microstructures. Therefore, the proposed library is mostly implemented within the object-oriented C + + programming language with the assumption of modularity. In this case, the main part of the application consists of classes and methods, which can be treated like base elements to be inherited and extended in other libraries. Each additional dynamic link library implements particular algorithms for the generation of specific microstructure features in the digital model within the unified data structures that allow the application of the workflow concept. The set of developed libraries and their assumptions are described as case studies to show the capabilities of the presented solution. Finally, examples of practical applications of the developed library in the full-field numerical simulations of complex material deformation are presented at the end of the paper.

scholarly journals Microscopic strain localisation in WAAM Ti-6Al-4V during uniaxial tensile loading

2020 ◽  
Vol 321 ◽  
pp. 03008
Author(s):  
David Lunt ◽  
Alistair Ho ◽  
Alec Davis ◽  
Filomeno Martina ◽  
Jan Hönnige ◽  
...  
Keyword(s):  
Grain Refinement ◽  
Large Scale ◽  
Image Correlation ◽  
Grain Structure ◽  
Uniaxial Tensile ◽  
High Deposition Rate ◽  
Strain Localisation ◽  
Full Field ◽  
Columnar Grain ◽  
Heterogeneous Deformation

Wire Arc-Based Additive manufacturing is a high deposition rate process suitable for building large-scale aerospace components. However, the larger heat source can cause greater microstructural heterogeneity and, in particular, a coarse columnar ß grain structure. The effect of the subsequent related transformation microstructure heterogeneity on the mechanical behaviour is investigated, in both standard WAAM materials and samples subjected to inter-pass rolling, which leads to substantial ß grain refinement and texture randomisation. Full-field strain maps were produced by digital image correlation, using tensile samples loaded in different orientations. When loaded normal to the columnar grain structure, it is shown that the coarse ß grains lead to a highly heterogeneous deformation distribution, which is linked the presence of dominant hard and soft α variants in texture colonies within each parent ß grain. ß grain refinement through the application of inter-pass rolling was found to be very effective at homogenising the strain localisation for all test orientations.

scholarly journals The light/dark cycle of microalgae in a thin-layer photobioreactor

2020 ◽  
Author(s):  
Alessandro Chiarini ◽  
Maurizio Quadrio
Keyword(s):  
Thin Layer ◽  
Time Scale ◽  
Stokes Equations ◽  
Numerical Study ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Dark Cycle ◽  
Navier Stokes Equations ◽  
Time Resolved ◽  
Typical Time

AbstractA numerical study of the motion of algal cells in a representative thin-layer-cascade (TLC) photobioreactor is presented. The goal is to determine the time scale associated with the light/dark (L/D) cycle seen by the cells during their turbulent motion in the liquid culture. Owing to the limited reliability of the available numerical results which deal with time-averaged quantities and thus lack time-resolved information, the present study is based upon the Direct Numerical Simulation of the Navier-Stokes equations, a reliable but consequently expensive numerical approach which does not incur in turbulence modelling errors. Indeed, the simulation is successfully validated in terms of averaged velocity with experimental data. The availability of full temporal information allows algae cells to be followed in time along their trajectories. A large number (up to a million) of tracers is placed in the flow to mimic the algae cell. Their trajectories are statistically studied and linked to the turbulent mixing. Results indicate that, in a typical TLC reactor designed to mimic an experimental setup, cells undergo an L/D cycle with a time scale in the range 0.1–2 s. Such time scale, albeit much longer than the typical time scale of the photosynthesis, significantly benefits the productivity of the algae compared to a steady illumination.

scholarly journals Dynamic recrystallisation of ice aggregates during co-axial viscoplastic deformation: a numerical approach

2016 ◽  
Vol 62 (232) ◽  
pp. 359-377 ◽  
Author(s):  
MARIA-GEMA LLORENS ◽  
ALBERT GRIERA ◽  
PAUL D. BONS ◽  
JENS ROESSIGER ◽  
RICARDO LEBENSOHN ◽  
...  
Keyword(s):  
Grain Size ◽  
Pure Shear ◽  
Numerical Approach ◽  
Major Effect ◽  
Preferred Orientation ◽  
Minor Effect ◽  
Axial Deformation ◽  
Full Field ◽  
Dynamic Recrystallisation ◽  
Individual Grains

ABSTRACTResults of numerical simulations of co-axial deformation of pure ice up to high-strain, combining full-field modelling with recrystallisation are presented. Grain size and lattice preferred orientation analysis and comparisons between simulations at different strain-rates show how recrystallisation has a major effect on the microstructure, developing larger and equi-dimensional grains, but a relatively minor effect on the development of a preferred orientation of c-axes. Although c-axis distributions do not vary much, recrystallisation appears to have a distinct effect on the relative activities of slip systems, activating the pyramidal slip system and affecting the distribution of a-axes. The simulations reveal that the survival probability of individual grains is strongly related to the initial grain size, but only weakly dependent on hard or soft orientations with respect to the flow field. Dynamic recrystallisation reduces initial hardening, which is followed by a steady state characteristic of pure-shear deformation.

PARALLEL SOLVER FOR THE SIMULATIONS OF DETONATION WAVES ON UNSTRUCTURED GRIDS

2020 ◽  
Author(s):  
A. I. Lopato ◽  
◽  
A. G. Eremenko ◽  
Keyword(s):  
Chemical Kinetics ◽  
Numerical Scheme ◽  
Unstructured Grids ◽  
Numerical Study ◽  
Numerical Approach ◽  
Detonation Waves ◽  
Detailed Chemical Kinetics ◽  
Parallel Solver ◽  
Further Development ◽  
Detailed Chemical

Recently, we developed a numerical approach for the simulation of detonation waves on fully unstructured grids and applied it to the numerical study of the mechanisms of detonation initiation in multifocusing systems. Current work is devoted to further development of our numerical approach, namely, parallelization of the numerical scheme and introduction of more comprehensive detailed chemical kinetics scheme.

scholarly journals Experimental and Numerical Study of the Effects of the Reversal Hot Rolling Conditions on the Recrystallization Behavior of Austenite Model Alloys

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 26
Author(s):  
Krzysztof Muszka ◽  
Mateusz Sitko ◽  
Paulina Lisiecka-Graca ◽  
Thomas Simm ◽  
Eric Palmiere ◽  
...  
Keyword(s):  
Microstructure Evolution ◽  
Hot Rolling ◽  
Strain Path ◽  
Physical Simulation ◽  
Numerical Study ◽  
Kinematic Hardening ◽  
Process Window ◽  
Recrystallization Behavior ◽  
Full Field ◽  
Strain Reversal

The experimental and numerical study of the effects of the recrystallization behavior of austenite model alloys during hot plate rolling on reverse rolling is the main goal of the paper. The computer models that are currently applied for simulation of reverse rolling are not strain-path-sensitive, thus leading to overestimation of the processing parameters outside the accepted process window (e.g., deformation in the partial austenite recrystallization region). Therefore, in this work, a particular focus is put on the investigation of strain path effects that occur during hot rolling and their influence on the microstructure evolution and mechanical properties of microalloyed austenite. Both experimental and numerical techniques are employed in this study, taking advantage of the integrated computational material engineering concept. The combined isotropic–kinematic hardening model is used for the macroscale predictions to take into account softening effects due to strain reversal. The macroscale model is additionally enriched with the full-field microstructure evolution model within the cellular automata framework. Examples of obtained results, highlighting the role of the strain reversal on the microstructural response, are presented within the paper. The combination of the physical simulation of austenitic model alloys and computer modeling provided new insights into optimization of the processing routes of advanced high-strength steels (AHSS).

Nonlinear dynamic behaviour of guy cables in turbulent winds

2001 ◽  
Vol 28 (1) ◽  
pp. 98-110 ◽  
Author(s):  
Bruce F Sparling ◽  
Alan G Davenport
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Aerodynamic Drag ◽  
Numerical Study ◽  
Horizontal Displacement ◽  
Wind Loading ◽  
Second Phase ◽  
Nonlinear Coupling ◽  
Wide Range ◽  
Cable Vibrations

Large amplitude cable vibrations are difficult to predict using linear theory due to the presence of sag in the suspended profile. A numerical study was therefore undertaken to investigate the dynamic behaviour of inclined cables excited by imposed displacements. To model the nonlinear nature of cable response, a time domain finite element approach was adopted using nonlinear catenary cable elements. Two types of horizontal displacement patterns were enforced at the upper end of the guy. In the first phase of the study, harmonic displacement histories with a wide range of forcing frequencies were considered. In the second phase, random enforced displacements were used to simulate the motion of a guyed mast in gusty winds. The influence of aerodynamic drag and damping forces was investigated by performing analyses under still air, steady wind, and turbulent wind conditions. It was found that nonlinear coupling of related harmonic response components was significant at certain critical frequencies, particular when the excitation was harmonic and acted in the plane of the guy. Positive aerodynamic damping was shown to effectively suppress resonant and nonlinear coupling response.Key words: cables, structural dynamics, wind loading, finite element method, nonlinear analysis, guyed towers.

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