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ReseaRch PRogRammes
This programme concentrates on the lower length scales
of materials, from the atomic up to micrometre scale.
Thus, it will provide experimental and calculated input to
the multiscale framework from the lower scale. This will
provide constitutive models for microstructure evolution,
strength and work hardening for metallic materials, such
as aluminium and steels. It will also provide a foundation
for the development of physically based models for crystal
plasticity, continuum plasticity, damage and fracture.
The overall goal is to connect and coordinate the atomic
and microscale frameworks connecting the models and
the experiments at the different scales. The results will
provide increased basic understanding of mechanical
properties and deformation of metal structures in a
multiscale framework (from the nano-scale to the
complete structure). This will work as a basis for
achieving improved models and will be used in both
model developments and validations, Figure 4.
Four PhD students are working in the lower scale
programme:
• PhD research by Emil Christiansen (Dept. of Physics,
2015-2019) is focused on the micro- and nanostructure
characterization of deformed aluminium alloys using
transmission electron microscopy (TEM). The objective
is to investigate the underlying physical mechanisms of
ductile fracture in age hardening aluminium alloys. In
short, this PhD work is concerned with the interaction
between dislocations and precipitation free zones (PFZs)
and the evolvement of the microstructure as a function
of strain. So far, he has studied how the microstructure
in the PFZ of the AA6060 alloy changes as a function of
deformation. His results will act as input to the different
models used to describe deformation response and will
be applied to verify and develop numerical models in the
related SFI CASA projects.
• PhD student Christian Oen Paulsen (Dept. of Materials
Science and Engineering, 2015–2019) is focusing
his research on combining experimental work and
modelling activities to describe the correlation between
microstructure and mechanical properties in multiphase
steel. He is performing a systematic, experimental study
of local mechanical properties and in-situ testing using
scanning electron microscopy (SEM), with the possibility
of cooling the material to sub-zero temperatures.
This gives input data for mathematical models for
understanding and describing the performance of
heterogeneous materials based on microstructure
information. The experimental tests are combined with
digital image correlation to obtain detailed information
about the local deformation.
• The PhD project of Jonas Frafjord (Dept. of Physics,
2016-2020) will couple atomistic simulations, e.g.
density functional theory, and meso-scale methods,
e.g. dislocation dynamics. The goal is to provide a more
fundamental understanding of mechanical properties
and use this to improve and calibrate models on a
continuum scale. He will study the effect of solute
atoms and hardening precipitates, and how these
affect initial yielding and hardening under different
conditions. Initially, Jonas has started to study how
solute-dislocation interactions affect the yield stress
and he is developing a method that predicts from first
principle the influence of hydrostatic pressure on the
solute strengthening of various alloying elements (such
as Mg, Si, Fe and Mn) in aluminium.
• PhD student Jianbin Xu (Dept. of Materials Science
and Engineering, 2016-2019) is studying the Portevin–
Le Chatelier (PLC) effect, which describes the serrated
yielding some materials exhibit as they undergo plastic
deformation, resulting in early shear failure and thus
reduced formability. The effect is associated with
dynamic strain aging or interaction between solute
atoms and matrix dislocations in strained metallic
alloys. Initially, Jianbin has started to familiarize himself
with existing modelling approaches for work hardening
and flow stress to describe solid solution strengthening
and the PLC effect in aluminium alloys. He will continue
with experimental characterization to provide a basis for
testing, validation and further improvement of existing
modelling tools.
Lower Scale
Head of Programme: Randi Holmestad
Figure 4: In a multiscale framework, the lower scale
programme covers the micrometre and nanometre
scales for modelling and experiments.
RESEARCH PROGRAMMES