Skip to main content

Trond Aukrust

Followers

4

Following

0

Public Views

IIT Kanpur

Daniel Flórez-Orrego

Ecole Polytechnique Federale de Lausanne

Harijono Djojodihardjo

Institut Teknologi Bandung

Sravankumar Kota

Institute Of Aeronautical Engineering

Apostolos Papanikolaou

National Technical University of Athens

Akwa Ibom State University

Christos N Markides

Imperial College London

Illinois Institute of Technology

University of East London

Gwen Robbins Schug

University of North Carolina at Greensboro

Interests

Uploads

Papers by Trond Aukrust

Modelling of texture development in aluminium extrusions

Texture prediction and aluminium extrusion

Coupled FEM and texture modelling for aluminium extrusion

Coupled FEM and texture modelling of plane strain extrusion of an aluminium alloy

International Journal of Plasticity, 1997

An extrusion experiment of a flat section of the aluminium alloy AA6082 has been performed. The m... more An extrusion experiment of a flat section of the aluminium alloy AA6082 has been performed. The material showed only a small degree of recrystallization. A careful texture characterization has been carried out in order to study the texture evolution during the extrusion process. The extrusion process has been simulated with an Eulerian finite element model in order to predict the texture development. The deformation history has been extracted from the results of finite element simulations for selected particle paths. This was subsequently transferred to the polycrystalline Taylor model for simulation of the texture evolution. The qualitative features of the simulated texture were found to correspond well with experimental measurements.

A Viscoplastic Simulation of Texture Evolution during Extrusion of an Aluminium Alloy

Materials Science Forum, Feb 1, 1998

ABSTRACT Numerical simulations of texture development have been carried out for hot plane strain ... more ABSTRACT Numerical simulations of texture development have been carried out for hot plane strain extrusion of an aluminium alloy using both finite element calculations and a polycrystal plasticity model. The latter is based on the Taylor localisation hypothesis (relaxed constraints) and a viscoplastic constitutive law. We have considered the {111}&lt;110&gt; slip systems and the {100}, {110} and {112} &lt;110&gt; non-octahedral systems. The finite element code first simulates the local extrusion strain paths of the material flow through the die. Secondly, for the different deformation paths between the centre section and the surface the polycrystalline model is used to calculate the local deformation texture evolution. The results are compared with experimentally measured deformation textures at different depths of an extruded bar of a 6082 aluminium alloy. Near the centre section both the numerical simulations and the experimental textures are in good agreement, with typical β-fibre hot rolling texture components as a consequence of the essentially plane strain compression deformation mode. Texture simulations using the non-compact slip systems give significantly better agreement than for slip restricted to the {111} planes. However, very near the surface where there is a very high shear component, none of the models gives good quantitative predictions although there is a reasonable qualitative agreement assuming non-octahedral slip.

Study of Flow Balance and Temperature Evolution over Multiple Aluminum Extrusion Press Cycles with HyperXtrude 9.0

Key Engineering Materials, Dec 1, 2009

In this research, transient finite element simulations of the aluminum extrusion process have bee... more In this research, transient finite element simulations of the aluminum extrusion process have been performed in order to study how process parameters influence flow balance and exit temperature. This has been achieved by investigating the influence of billet taper, front billet temperature and ram speed on the run-out velocity and temperature of two separate outlets. Analysis of variance (ANOVA) has been employed to study the effect of each parameter on the velocity and temperature variation of the extruded section. Results show that increasing each of these three parameters results in an undesired increase in exit velocity and temperature. The front billet temperature is found to be the most significant factor affecting the variation. The finite elements software used was Altair HyperXtrude 9.0.

<title>Vector and scalar field interpretation</title>

Proceedings of SPIE, Jun 1, 1991

ABSTRACT Complex computations and simulations often produce multiple scalar and vector 3D fields ... more ABSTRACT Complex computations and simulations often produce multiple scalar and vector 3D fields which require display and interpretation. This paper presents an approach to imaging scalar fields based on an optical model with several interactive options. Vector fields are imaged with flow line and moving comets, and related to the scalar field using color coded 2D images. The D structure bounding the computed fields is imaged as a solid, and is a spatial reference for the data. The utility of the methods are illustrated with data from a large scale simulation of ocean circulation in the Norwegian-Greenland seas.

Microstructure Control during Extrusion with Respect to Surface Quality

Materials Science Forum, May 1, 1996

Study of isothermal extrusion of aluminum using finite element simulations

International Journal of Material Forming, Apr 1, 2010

The focus in this work is isothermal extrusion of aluminum. Transient finite element simulations ... more The focus in this work is isothermal extrusion of aluminum. Transient finite element simulations of the extrusion process have been performed over 20 press cycles using the 3D finite element software Altair HyperXtrude 9.0 and the 2D finite element software ALMA2π. The process parameters considered are front billet temperature, initial billet temperature gradient (taper), ram speed and container cooling rate. The press cycle has been divided into three phases: start, middle and the end of the ram stroke. The best combinations of process parameters for isothermal extrusion has been found and represented as so called "isothermal maps" for each phase of the press cycle.

Optimisation of flow balance and isothermal extrusion of aluminium using finite-element simulations

Journal of Materials Processing Technology, Apr 1, 2011

There is significant demand to reduce variations in the shape and mechanical properties of the al... more There is significant demand to reduce variations in the shape and mechanical properties of the aluminium extrusion process to meet tighter tolerance requirements. To reduce variations, the flow and temperature evolution in the container and die must be controlled. To study how the process parameters influence the temperature evolution and the material flow, the effects of ram speed, initial temperature distribution in the billet and container cooling rate have been studied. This work is divided into three parts which examine the different aspects of the extrusion process. (1) To minimize the radial variations of temperature and velocity fields over multiple press cycles. (2) To obtain isothermal extrusion of aluminium. (3) To understand and formulate the effect of an undesired lateral temperature gradient in the billet on the exit velocity of the aluminium sections. In each part, the effect of different process parameters on the flow balance and temperature evolution of the extruded sections is shown and discussed.

Studies of the mechanisms for buckling and waving in aluminum extrusion by use of a Lagrangian FEM software

International Journal of Plasticity, 2006

... the highly non-linear behavior of hot aluminium, the coupled thermo-mechanical nature of the ... more

Effect of Heat Treatment on the Ductility of Inconel 718 Processed by Laser Powder Bed Fusion

Lecture notes in electrical engineering, 2020

Inconel 718 is a precipitation-hardening alloy, with a typical heat treatment consisting of solut... more Inconel 718 is a precipitation-hardening alloy, with a typical heat treatment consisting of solution annealing before a two-stage ageing process. Depending on the heat treatment procedure, strength or ductility can be enhanced, typically at the cost of the other. This study aims to determine a heat treatment procedure suitable for applications that require high ductility. Tensile tests of Inconel 718 processed by laser powder bed fusion additive manufacturing has been carried out on specimens subjected to different heat treatment procedures. The results show that solution annealing above 1010°C followed by a two-stage ageing at 720°C/8 h with furnace cooling to 620°C/2 h and final holding at 620°C/10 h, produce elongation at break of above 30% tested at room temperature and above 24% tested at 650°C.

Evolution in texture and its through-thickness variations in Al-Mg-Si-extrusions: experiments and modelling

The visual appearance and mechanical properties of aluminium alloy extrusions are strongly depend... more The visual appearance and mechanical properties of aluminium alloy extrusions are strongly dependent on the microstructure and texture of the extruded profiles, where the desired microstructure and texture may depend on the specific applications. In the present work, the evolution of deformation, as well as recrystallization textures during extrusion of AA6xxx aluminium alloys, have been experimentally and numerically investigated. Extrusion trials were performed in a laboratory extrusion setup , which enabled immediate water-quenching of the profiles at the exit of the die, and thus the possibility to capture the deformation texture prior to post-extrusion recrystallization. The textures and their through-thickness variations were experimentally measured by the electron back-scatter diffraction technique (EBSD, and the deformation textures numerically modelled by coupling FEM flow simulations and crystal plasticity (CP) simulations. Different CP models as well as different choices of model parameters were employed and evaluated for texture predictions. With an appropriate choice of crystal plasticity model and model parameters, the deformation texture can mainly be predicted, although the accurate intensities are hard to reproduce. The corresponding recrystallization textures, either generated through spontaneous recrystallization of the extruded profiles or through post-extrusion annealing, are far more challenging to reproduce with available recrystallization models.

Adaptive exponential finite elements for the shear boundary layer in the bearing channel during extrusion

Computer Methods in Applied Mechanics and Engineering, 2002

ABSTRACT This paper presents the application of new special finite elements for modelling the flo... more ABSTRACT This paper presents the application of new special finite elements for modelling the flow shear boundary layer in the bearing channel during extrusion processes. The shape functions in the special elements account for an exponential nature of the velocity field in the boundary layer and are directly controlled by both process and material parameters. They are also functions of the element&#39;s characteristic height. This makes the new special elements adaptive to both process and mesh style. The special elements are implemented and used to treat the case of a 2-dimensional extrusion problem. The special elements show superior performance without the substantial refinement otherwise needed when standard elements are used.

Thin shear boundary layers in flow of hot aluminium

International Journal of Plasticity, 2000

The¯ow of hot aluminium in channels is investigated. The constitutive relation considered for the... more The¯ow of hot aluminium in channels is investigated. The constitutive relation considered for the¯ow stress is the inverse hyperbolic sine function of the Zener±Hollomon parameter. Analytical solutions for the¯ow are derived. At high strain rates, an exponential velocity pro®le close to the channel walls is predicted indicating the existence of a thin shear boundary layer characterized by strong shear. The characteristic length scale for the exponential velocity pro®le is a function of material parameters in the constitutive relation and the inverse of the local pressure gradient. The analytical prediction of a thin shear boundary layer close to the channel walls for large strain rates is consistent with the observed microstructure in an extruded section.

Kinetic Phase Transition in a One-Component Irreversible Reaction Model

Europhysics Letters (EPL), 1989

ABSTRACT Irreversible many particle dynamical systems are relevant to a broad scope of phenomena ... more ABSTRACT Irreversible many particle dynamical systems are relevant to a broad scope of phenomena in physics, chemistry and biology. We present a study of an irreversible kinetic reaction model for a one component autocatalytic reaction A + A → A2. The system is updated as follows: if an atom adsorbed on a lattice has any neighbors it reacts with one of them with a probability (1 - p), and the two atoms leave the lattice, else the atom remains adsorbed. As p is varied, the adsorbed atoms undergo a second order kinetic phase transition from a chemically active partially covered state to a completely covered state which corresponds to the &quot;poisoning&quot; phenomenon seen on catalysts. The transition is studied both numerically and theoretically to gain more understanding of kinetic phase transitions and to find new methods to describe them. Finite size scaling analysis of the critical behavior has been carried out, and critical and dynamical exponents are found. The critical exponents are found to be consistent with the critical exponents in the Reggeon field theory/directed percolation universality class.

Coupled FEM and texture modelling for aluminium extrusion

Modelling of texture development in aluminium extrusions

Evolution in texture and its through-thickness variations in Al-Mg-Si-extrusions: experiments and modelling

The visual appearance and mechanical properties of aluminium alloy extrusions are strongly depend... more The visual appearance and mechanical properties of aluminium alloy extrusions are strongly dependent on the microstructure and texture of the extruded profiles, where the desired microstructure and texture may depend on the specific applications. In the present work, the evolution of deformation, as well as recrystallization textures during extrusion of AA6xxx aluminium alloys, have been experimentally and numerically investigated. Extrusion trials were performed in a laboratory extrusion set-up, which enabled immediate water-quenching of the profiles at the exit of the die, and thus the possibility to capture the deformation texture prior to post-extrusion recrystallization. The textures and their through-thickness variations were experimentally measured by the electron back-scatter diffraction technique (EBSD, and the deformation textures numerically modelled by coupling FEM flow simulations and crystal plasticity (CP) simulations. Different CP models as well as different choices ...

Effect of Heat Treatment on the Ductility of Inconel 718 Processed by Laser Powder Bed Fusion

Lecture Notes in Electrical Engineering, 2020

Inconel 718 is a precipitation-hardening alloy, with a typical heat treatment consisting of solut... more Inconel 718 is a precipitation-hardening alloy, with a typical heat treatment consisting of solution annealing before a two-stage ageing process. Depending on the heat treatment procedure, strength or ductility can be enhanced, typically at the cost of the other. This study aims to determine a heat treatment procedure suitable for applications that require high ductility. Tensile tests of Inconel 718 processed by laser powder bed fusion additive manufacturing has been carried out on specimens subjected to different heat treatment procedures. The results show that solution annealing above 1010°C followed by a two-stage ageing at 720°C/8 h with furnace cooling to 620°C/2 h and final holding at 620°C/10 h, produce elongation at break of above 30% tested at room temperature and above 24% tested at 650°C.

Modelling of texture development in aluminium extrusions

Texture prediction and aluminium extrusion

Coupled FEM and texture modelling for aluminium extrusion

Coupled FEM and texture modelling of plane strain extrusion of an aluminium alloy

International Journal of Plasticity, 1997

An extrusion experiment of a flat section of the aluminium alloy AA6082 has been performed. The m... more An extrusion experiment of a flat section of the aluminium alloy AA6082 has been performed. The material showed only a small degree of recrystallization. A careful texture characterization has been carried out in order to study the texture evolution during the extrusion process. The extrusion process has been simulated with an Eulerian finite element model in order to predict the texture development. The deformation history has been extracted from the results of finite element simulations for selected particle paths. This was subsequently transferred to the polycrystalline Taylor model for simulation of the texture evolution. The qualitative features of the simulated texture were found to correspond well with experimental measurements.

A Viscoplastic Simulation of Texture Evolution during Extrusion of an Aluminium Alloy

Materials Science Forum, Feb 1, 1998

ABSTRACT Numerical simulations of texture development have been carried out for hot plane strain ... more ABSTRACT Numerical simulations of texture development have been carried out for hot plane strain extrusion of an aluminium alloy using both finite element calculations and a polycrystal plasticity model. The latter is based on the Taylor localisation hypothesis (relaxed constraints) and a viscoplastic constitutive law. We have considered the {111}&lt;110&gt; slip systems and the {100}, {110} and {112} &lt;110&gt; non-octahedral systems. The finite element code first simulates the local extrusion strain paths of the material flow through the die. Secondly, for the different deformation paths between the centre section and the surface the polycrystalline model is used to calculate the local deformation texture evolution. The results are compared with experimentally measured deformation textures at different depths of an extruded bar of a 6082 aluminium alloy. Near the centre section both the numerical simulations and the experimental textures are in good agreement, with typical β-fibre hot rolling texture components as a consequence of the essentially plane strain compression deformation mode. Texture simulations using the non-compact slip systems give significantly better agreement than for slip restricted to the {111} planes. However, very near the surface where there is a very high shear component, none of the models gives good quantitative predictions although there is a reasonable qualitative agreement assuming non-octahedral slip.

Study of Flow Balance and Temperature Evolution over Multiple Aluminum Extrusion Press Cycles with HyperXtrude 9.0

Key Engineering Materials, Dec 1, 2009

In this research, transient finite element simulations of the aluminum extrusion process have bee... more In this research, transient finite element simulations of the aluminum extrusion process have been performed in order to study how process parameters influence flow balance and exit temperature. This has been achieved by investigating the influence of billet taper, front billet temperature and ram speed on the run-out velocity and temperature of two separate outlets. Analysis of variance (ANOVA) has been employed to study the effect of each parameter on the velocity and temperature variation of the extruded section. Results show that increasing each of these three parameters results in an undesired increase in exit velocity and temperature. The front billet temperature is found to be the most significant factor affecting the variation. The finite elements software used was Altair HyperXtrude 9.0.

<title>Vector and scalar field interpretation</title>

Proceedings of SPIE, Jun 1, 1991

ABSTRACT Complex computations and simulations often produce multiple scalar and vector 3D fields ... more ABSTRACT Complex computations and simulations often produce multiple scalar and vector 3D fields which require display and interpretation. This paper presents an approach to imaging scalar fields based on an optical model with several interactive options. Vector fields are imaged with flow line and moving comets, and related to the scalar field using color coded 2D images. The D structure bounding the computed fields is imaged as a solid, and is a spatial reference for the data. The utility of the methods are illustrated with data from a large scale simulation of ocean circulation in the Norwegian-Greenland seas.

Microstructure Control during Extrusion with Respect to Surface Quality

Materials Science Forum, May 1, 1996

Study of isothermal extrusion of aluminum using finite element simulations

International Journal of Material Forming, Apr 1, 2010

The focus in this work is isothermal extrusion of aluminum. Transient finite element simulations ... more The focus in this work is isothermal extrusion of aluminum. Transient finite element simulations of the extrusion process have been performed over 20 press cycles using the 3D finite element software Altair HyperXtrude 9.0 and the 2D finite element software ALMA2π. The process parameters considered are front billet temperature, initial billet temperature gradient (taper), ram speed and container cooling rate. The press cycle has been divided into three phases: start, middle and the end of the ram stroke. The best combinations of process parameters for isothermal extrusion has been found and represented as so called "isothermal maps" for each phase of the press cycle.

Optimisation of flow balance and isothermal extrusion of aluminium using finite-element simulations

Journal of Materials Processing Technology, Apr 1, 2011

There is significant demand to reduce variations in the shape and mechanical properties of the al... more There is significant demand to reduce variations in the shape and mechanical properties of the aluminium extrusion process to meet tighter tolerance requirements. To reduce variations, the flow and temperature evolution in the container and die must be controlled. To study how the process parameters influence the temperature evolution and the material flow, the effects of ram speed, initial temperature distribution in the billet and container cooling rate have been studied. This work is divided into three parts which examine the different aspects of the extrusion process. (1) To minimize the radial variations of temperature and velocity fields over multiple press cycles. (2) To obtain isothermal extrusion of aluminium. (3) To understand and formulate the effect of an undesired lateral temperature gradient in the billet on the exit velocity of the aluminium sections. In each part, the effect of different process parameters on the flow balance and temperature evolution of the extruded sections is shown and discussed.

Studies of the mechanisms for buckling and waving in aluminum extrusion by use of a Lagrangian FEM software

International Journal of Plasticity, 2006

... the highly non-linear behavior of hot aluminium, the coupled thermo-mechanical nature of the ... more

Effect of Heat Treatment on the Ductility of Inconel 718 Processed by Laser Powder Bed Fusion

Lecture notes in electrical engineering, 2020

Inconel 718 is a precipitation-hardening alloy, with a typical heat treatment consisting of solut... more Inconel 718 is a precipitation-hardening alloy, with a typical heat treatment consisting of solution annealing before a two-stage ageing process. Depending on the heat treatment procedure, strength or ductility can be enhanced, typically at the cost of the other. This study aims to determine a heat treatment procedure suitable for applications that require high ductility. Tensile tests of Inconel 718 processed by laser powder bed fusion additive manufacturing has been carried out on specimens subjected to different heat treatment procedures. The results show that solution annealing above 1010°C followed by a two-stage ageing at 720°C/8 h with furnace cooling to 620°C/2 h and final holding at 620°C/10 h, produce elongation at break of above 30% tested at room temperature and above 24% tested at 650°C.

Evolution in texture and its through-thickness variations in Al-Mg-Si-extrusions: experiments and modelling

The visual appearance and mechanical properties of aluminium alloy extrusions are strongly depend... more The visual appearance and mechanical properties of aluminium alloy extrusions are strongly dependent on the microstructure and texture of the extruded profiles, where the desired microstructure and texture may depend on the specific applications. In the present work, the evolution of deformation, as well as recrystallization textures during extrusion of AA6xxx aluminium alloys, have been experimentally and numerically investigated. Extrusion trials were performed in a laboratory extrusion setup , which enabled immediate water-quenching of the profiles at the exit of the die, and thus the possibility to capture the deformation texture prior to post-extrusion recrystallization. The textures and their through-thickness variations were experimentally measured by the electron back-scatter diffraction technique (EBSD, and the deformation textures numerically modelled by coupling FEM flow simulations and crystal plasticity (CP) simulations. Different CP models as well as different choices of model parameters were employed and evaluated for texture predictions. With an appropriate choice of crystal plasticity model and model parameters, the deformation texture can mainly be predicted, although the accurate intensities are hard to reproduce. The corresponding recrystallization textures, either generated through spontaneous recrystallization of the extruded profiles or through post-extrusion annealing, are far more challenging to reproduce with available recrystallization models.

Adaptive exponential finite elements for the shear boundary layer in the bearing channel during extrusion

Computer Methods in Applied Mechanics and Engineering, 2002

ABSTRACT This paper presents the application of new special finite elements for modelling the flo... more ABSTRACT This paper presents the application of new special finite elements for modelling the flow shear boundary layer in the bearing channel during extrusion processes. The shape functions in the special elements account for an exponential nature of the velocity field in the boundary layer and are directly controlled by both process and material parameters. They are also functions of the element&#39;s characteristic height. This makes the new special elements adaptive to both process and mesh style. The special elements are implemented and used to treat the case of a 2-dimensional extrusion problem. The special elements show superior performance without the substantial refinement otherwise needed when standard elements are used.

Thin shear boundary layers in flow of hot aluminium

International Journal of Plasticity, 2000

The¯ow of hot aluminium in channels is investigated. The constitutive relation considered for the... more The¯ow of hot aluminium in channels is investigated. The constitutive relation considered for the¯ow stress is the inverse hyperbolic sine function of the Zener±Hollomon parameter. Analytical solutions for the¯ow are derived. At high strain rates, an exponential velocity pro®le close to the channel walls is predicted indicating the existence of a thin shear boundary layer characterized by strong shear. The characteristic length scale for the exponential velocity pro®le is a function of material parameters in the constitutive relation and the inverse of the local pressure gradient. The analytical prediction of a thin shear boundary layer close to the channel walls for large strain rates is consistent with the observed microstructure in an extruded section.

Kinetic Phase Transition in a One-Component Irreversible Reaction Model

Europhysics Letters (EPL), 1989

ABSTRACT Irreversible many particle dynamical systems are relevant to a broad scope of phenomena ... more ABSTRACT Irreversible many particle dynamical systems are relevant to a broad scope of phenomena in physics, chemistry and biology. We present a study of an irreversible kinetic reaction model for a one component autocatalytic reaction A + A → A2. The system is updated as follows: if an atom adsorbed on a lattice has any neighbors it reacts with one of them with a probability (1 - p), and the two atoms leave the lattice, else the atom remains adsorbed. As p is varied, the adsorbed atoms undergo a second order kinetic phase transition from a chemically active partially covered state to a completely covered state which corresponds to the &quot;poisoning&quot; phenomenon seen on catalysts. The transition is studied both numerically and theoretically to gain more understanding of kinetic phase transitions and to find new methods to describe them. Finite size scaling analysis of the critical behavior has been carried out, and critical and dynamical exponents are found. The critical exponents are found to be consistent with the critical exponents in the Reggeon field theory/directed percolation universality class.

Coupled FEM and texture modelling for aluminium extrusion

Modelling of texture development in aluminium extrusions

Evolution in texture and its through-thickness variations in Al-Mg-Si-extrusions: experiments and modelling

The visual appearance and mechanical properties of aluminium alloy extrusions are strongly depend... more The visual appearance and mechanical properties of aluminium alloy extrusions are strongly dependent on the microstructure and texture of the extruded profiles, where the desired microstructure and texture may depend on the specific applications. In the present work, the evolution of deformation, as well as recrystallization textures during extrusion of AA6xxx aluminium alloys, have been experimentally and numerically investigated. Extrusion trials were performed in a laboratory extrusion set-up, which enabled immediate water-quenching of the profiles at the exit of the die, and thus the possibility to capture the deformation texture prior to post-extrusion recrystallization. The textures and their through-thickness variations were experimentally measured by the electron back-scatter diffraction technique (EBSD, and the deformation textures numerically modelled by coupling FEM flow simulations and crystal plasticity (CP) simulations. Different CP models as well as different choices ...

Effect of Heat Treatment on the Ductility of Inconel 718 Processed by Laser Powder Bed Fusion

Lecture Notes in Electrical Engineering, 2020

Inconel 718 is a precipitation-hardening alloy, with a typical heat treatment consisting of solut... more Inconel 718 is a precipitation-hardening alloy, with a typical heat treatment consisting of solution annealing before a two-stage ageing process. Depending on the heat treatment procedure, strength or ductility can be enhanced, typically at the cost of the other. This study aims to determine a heat treatment procedure suitable for applications that require high ductility. Tensile tests of Inconel 718 processed by laser powder bed fusion additive manufacturing has been carried out on specimens subjected to different heat treatment procedures. The results show that solution annealing above 1010°C followed by a two-stage ageing at 720°C/8 h with furnace cooling to 620°C/2 h and final holding at 620°C/10 h, produce elongation at break of above 30% tested at room temperature and above 24% tested at 650°C.