During processing of age-hardenable AA 6xxx series alloys for automotive applications the sheets may experience significant time spans between solution heat treatment at the aluminium supplier and age hardening upon the final paint bake... more
During processing of age-hardenable AA 6xxx series alloys for automotive applications the sheets may experience significant time spans between solution heat treatment at the aluminium supplier and age hardening upon the final paint bake cycle at the carmaker. Natural ageing during these pause times is known to greatly affect materials properties of autobody sheet. In the present study we explore the impact of natural ageing on the tensile properties and the in-plane anisotropy of alloy AA 6005C. Materials properties at various degrees of natural ageing are modelled with the help of a nanoscale material model NaMo, which consists of a precipitation model simulating the formation of clusters and phases upon natural ageing as input to a mechanical model simulating the evolution of yield strength and work hardening. Plastic anisotropy is modelled from the materials crystallographic texture by a visco-plastic self-consistent polycrystal-plasticity code VPSC.
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The present paper describes a concept that introduces a new dimension in design of crash management components and structures in aluminium. By deposition of a confined amount of heat in short pulses it is possible to manipulate the... more
The present paper describes a concept that introduces a new dimension in design of crash management components and structures in aluminium. By deposition of a confined amount of heat in short pulses it is possible to manipulate the mechanical properties of aluminium alloys at accurate positions. The method enables local modifications of e.g. yield strength and ductility in order to guide plastic deformation. This type of hidden design features of the product can be implemented utilizing the interplay between crash simulation analysis on one hand and numerical simulations of physical material properties on the other. A few examples are shown in the present paper as well as experimental results for an energy absorbing crash box. (A) For the covering abstract see ITRD E121867.
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Research Interests: Materials Engineering, Mechanical Engineering, Materials Science, Microstructure, Kinetics, and 15 moreMetallurgy, Diffusion theory, Chaos Theory Evolution Equation, Dissolution, Mathematical Model, Precipitation, Aluminium, Heat Flow, Microstructures, Aluminium Alloy, Process Model, Magnesium Alloy, Heat affected zone, Microstructure evolution, and Evolution Equation
The present paper describes a novel methodology for optimization of product properties and production costs in fabrication of aluminium alloys. The main idea is to represent each operation along the process chain by predictive tools,... more
The present paper describes a novel methodology for optimization of product properties and production costs in fabrication of aluminium alloys. The main idea is to represent each operation along the process chain by predictive tools, which include material-, mechanical-, cost-and logistics models. An optimisation tool is used to collect the simulation models into a common software environment, which allows fully automatic simulations to be carried out. When this coupling is established, the models are run in sequence using different types of optimisation strategies. The methodology has been applied for optimisation of strength, grain structure and costs of 6xxx series aluminium extrusions. The results indicate that the present methodology is sufficiently relevant and comprehensive to be used as a tool in fabrication of various aluminium products, for instance in optimisation of end-user properties and production costs of extruded, rolled or foundry based alloys.
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ABSTRACT In the present article, a new two-internal-variable model for the work hardening behavior of commercial Al-Mg-Si alloys at room temperature is presented, which is linked to the previously developed precipitation and yield... more
ABSTRACT In the present article, a new two-internal-variable model for the work hardening behavior of commercial Al-Mg-Si alloys at room temperature is presented, which is linked to the previously developed precipitation and yield strength models for the same class of alloys. As a starting point, the total dislocation density is taken equal to the sum of the statistically stored and the geometrically necessary dislocations, using the latter parameters as the independent internal variables of the system. Classic dislocation theory is then used to capture the overall stress-strain response. In a calibrated form, the work hardening model relies solely on outputs from the precipitation model and thus exhibits a high degree of predictive power. In addition to the solute content, which determines the rate of dynamic recovery, the two other microstructure parameters that control the work hardening behavior are the geometric slip distance and the corresponding volume fraction of nonshearable Orowan particles in the base material. Both parameters are extracted from the predicted particle size distribution. The applicability of the combined model is illustrated by means of novel process diagrams, which show the interplay between the different variables that contribute to work hardening in commercial Al-Mg-Si alloys.
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Additivity and isokinetic behaviour in relation to transformations that involve coupled nucleation and growth have been examined. As a starting point, a numerical solution is presented which takes into account the independent variations... more
Additivity and isokinetic behaviour in relation to transformations that involve coupled nucleation and growth have been examined. As a starting point, a numerical solution is presented which takes into account the independent variations of the nucleation and growth rate with temperature and matrix solute content. This solution is later used to check the validity of two analytical models, based on
Research Interests: Materials Engineering, Mechanical Engineering, Materials Science, Thermodynamics, Statistical Physics, and 12 moreChaos Theory Evolution Equation, Growth, Diffusion, Process Simulation, Nucleation, Nucleation and Growth, Learning Theory and Modeling, Phase Transformation, Analytical Model, Microstructures, Numerical Solution, and Evolution Equation
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Research Interests: Materials Engineering, Mechanical Engineering, Materials Science, Thermodynamics, Microstructure, and 14 moreMetallurgy, Heat Treatment, Nucleation, Dislocations, Phase Transformation, Room Temperature, Precipitation Hardening, Microstructures, Transmission Electron Microscope, Aluminium Alloy, Yield Strength, Particle Size Distribution, Thermal Processing, and Mechanical Property
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Abstract In the present paper the general purpose finite element code WELDSIM, equipped with a new natural aging model, is used to calculate the minimum heat affected zone (HAZ) strength level σ min and the equivalent half width of the... more
Abstract In the present paper the general purpose finite element code WELDSIM, equipped with a new natural aging model, is used to calculate the minimum heat affected zone (HAZ) strength level σ min and the equivalent half width of the reduced strength zone Δyeq red of strength σ min during single pass butt welding of Al–Mg–Si alloys. In particular, it is illustrated how the resulting strength loss depends on the interplay between the base metal chemistry and the initial temper condition on the one hand and the net arc power q 0, the welding speed v, the plate thickness d and the effective heat transfer coefficient h between the Al plate and the steel backing on the other hand. Assuming one-dimensional heat flow and pseudosteady state, the former parameters can be combined in a single group variable q 0/vd, which uniquely defines the HAZ thermal programme when welding is performed without the use of steel backing. Taking this as the main variable controlling the strength loss, the simulation results can be condensed into two-dimensional process diagrams, showing the variation in the design parameters σ min and Δyeq red with q 0/vd for different combinations of h and d. The output data from WELDSIM are, in turn, used as inputs to mechanical models to predict the resulting design stress under different loading conditions. It is concluded that significant weight reductions and cost savings can be achieved by minimising the strength loss after welding, provided that the design parameters σ min and Δyeq red are calculated on the basis of the actual yield strength profile within the weld HAZ, as obtained from WELDSIM.
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Research Interests: Materials Engineering, Mechanical Engineering, Materials Science, Thermodynamics, Heat Treatment, and 15 moreKinetic Theory, Cooling Rate, Discrete Differential Forms, Thermal history, Precipitation, Spectrum, Theoretical Framework, Materials Processing, Boolean Satisfiability, Differential equation, Thermal Cycling, Aluminium Alloy, Process Model, Constitutive Equation, and Microstructure evolution
Research Interests: Engineering, Materials Science, Microstructure, Metallurgy, Welding, and 2 moreAlloy and Base Metal(Alloy and Base Metal)
(Alloy and Base Metal)
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Research Interests: Engineering, Materials Science, Microstructure, Metallurgy, Welding, and 2 moreAlloy and Base Metal(Alloy and Base Metal)
(Alloy and Base Metal)
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The production and use of aluminum alloys involves a wide range of processing and fabrication methods. For a number of reasons discussed in this article, process modeling has an increasingly important role in all areas of production. This... more
The production and use of aluminum alloys involves a wide range of processing and fabrication methods. For a number of reasons discussed in this article, process modeling has an increasingly important role in all areas of production. This article reviews some process modeling activities in aluminum processing. The aims of the review are to (1) describe the current state of research in two major processing areas, (2) establish the principal motivations in the aluminum industry for undertaking process modeling, and (3) to identify generic research issues most in need of attention. This review is not intended to be exhaustive, but considers only selected processes, based on work in Norwegian laboratories with which the authors are most familiar. There is considerable parallel modeling activity worldwide in industry and academia which will not be discussed here. The case studies selected are sufficient, however, to illustrate all the main points of the review.A recent review of material...
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Research Interests: Materials Engineering, Mechanical Engineering, Materials Science, Microstructure, Metallurgy, and 15 moreNucleation, Dislocation, Dislocations, Phase Transformation, Room Temperature, Microstructures, Simulation experiment, Materials Processing, Aluminium Alloy, Numerical Solution, Coalescence, Precipitates, Heat Treatments, Age hardening, and Post Weld Heat Treatment
This paper is part of ‘through process modelling of welded aluminium’ project. It describes experimental and numerical investigation on butt-welded specimens of aluminium alloy AA6060. In the experiments, tensile test was used with... more
This paper is part of ‘through process modelling of welded aluminium’ project. It describes experimental and numerical investigation on butt-welded specimens of aluminium alloy AA6060. In the experiments, tensile test was used with Digital image correlation (DIC) technique to obtain full field strain measurement on the transversely loaded specimens. The tensile properties of these specimens are presented in terms of response curves. A user defined material was implemented in the explicit finite element code for the numerical calculations. The concept of non-local approach for plane stress analyses and the Cockroft Latham fracture criterion were used respectively to reduce mesh dependence of strain localization and to predict ductile fracture. The numerical results were compared to the experimental data and the measured and predicted response was evaluated.
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Research Interests: Engineering, Materials Science, Microstructure, Metallurgy, Welding, and 2 moreAlloy and Base Metal(Alloy and Base Metal)
(Alloy and Base Metal)
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... 8). Figure 2 shows the main inputs and outputs from the pre-dictive model. Design Optimization The yield strength distribution across a butt joint weld in AA6082-T6 after com-plete natural aging is illustrated in Fig. ... 6 shows the... more
... 8). Figure 2 shows the main inputs and outputs from the pre-dictive model. Design Optimization The yield strength distribution across a butt joint weld in AA6082-T6 after com-plete natural aging is illustrated in Fig. ... 6 shows the results for AA6082-T6. From the graphs in Fig. ...
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Research Interests: Materials Engineering, Mechanical Engineering, Materials Science, Heat Treatment, Dislocations, and 9 morePhase Transformation, Room Temperature, Microstructures, Transmission Electron Microscope, Aluminium Alloy, Yield Strength, Particle Size Distribution, Thermal Processing, and Mechanical Property
ABSTRACT In the present article, a new two-internal-variable model for the work hardening behavior of commercial Al-Mg-Si alloys at room temperature is presented, which is linked to the previously developed precipitation and yield... more
ABSTRACT In the present article, a new two-internal-variable model for the work hardening behavior of commercial Al-Mg-Si alloys at room temperature is presented, which is linked to the previously developed precipitation and yield strength models for the same class of alloys. As a starting point, the total dislocation density is taken equal to the sum of the statistically stored and the geometrically necessary dislocations, using the latter parameters as the independent internal variables of the system. Classic dislocation theory is then used to capture the overall stress-strain response. In a calibrated form, the work hardening model relies solely on outputs from the precipitation model and thus exhibits a high degree of predictive power. In addition to the solute content, which determines the rate of dynamic recovery, the two other microstructure parameters that control the work hardening behavior are the geometric slip distance and the corresponding volume fraction of nonshearable Orowan particles in the base material. Both parameters are extracted from the predicted particle size distribution. The applicability of the combined model is illustrated by means of novel process diagrams, which show the interplay between the different variables that contribute to work hardening in commercial Al-Mg-Si alloys.
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Combining precipitation, yield strength, work-hardening, and mechanical models has proved useful to optimize the load-bearing capacity of welded automotive components made of age-hardening Al-Mg-Si alloys.