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Multiscale modeling of engineering materials VTT ProperTune
Anssi Laukkanen, Tom Andersson, Kenneth Holmberg, Kim Wallin VTT Technical Research Centre of Finland 5.2.2013
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VTT ProperTune
• multiscale modeling of materials
Modeling solution
• process-structure-properties-performance (PSPP)
Concept for material design
• metallic materials, powder metallurgical materials, composites (metallic, ceramic, polymer)
Material structure at mesoscale (structure → properties)
• crack initiation, propagation, crack fields, wear
Defects and material damage at mesoscale (properties → performance)
framework & concept for modeling assisted design and tailoring of materials, 4 main elements of this presentation:
Multiphysical, emphasis of this presentation in deformation, failure and wear of materials, but the framework can be applied to a range of phenomena, behavior and mechanisms.
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MULTISCALE MODELING & PROCESS-STRUCTURE-PROPERTIES-PERFORMANCE
VTT ProperTune
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2/6/2013 4
Multiscale modeling
multiscale modeling = means of quantifying the material structure & behavior critical for desired & tailored performance
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processing
structure
properties
performance
The “PSPP” Approach
goals, means, requirements, constraints
solutions, cause and effect
Integrate required disciplines for a specific problem
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MATERIAL STRUCTURE AT MESOSCALE
VTT ProperTune
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Focal areas of modeling at mesoscale: material structure and defects
simple synthetic models synthetic models
mesoscopic synthetic models image based models
principal properties and trends statistics of structure and resulting properties
defects, material failure uncompromised realistic structures
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Example on generation of microstructures for multiscale analysis using VTT ProperTune
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Metallic materials - Synthetic aggregates by 3D voxel manipulation
Introduction of twins (or laths etc.) to a primary structure
Use of 3D discrete voxel volumes for complete freedom in manipulating nano- and microstructures, to obtain 3D images of structure. Emphasis in metallic and composite structures, but no morphological limitations with respect to the method itself.
Isosurfaces (grain boundaries) after stochastic Monte-Carlo sampling of grain boundaries (to generate more realistically shaped grains and structures)
Introduction of 2nd phase structures (precipitates, carbides etc) to a primary structure
Synthetic microstructure by
tesselation and “filling”
Also, mixing of synthetic and imaging features (i.e. “pluck” features of imaging data)
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Metallic materials – Synthetic aggregates with simplistic lath like features Emphasis on “lath like” structures, both in terms of aggregate geometry and constitutive model
development (=RPV materials)
tesselation for primary grains, “partitioning” for laths like features
tesselation for primary grains, “partitioning” for laths followed by further geometry
operations (essentially
repartitioning of the 3D image
grains in whatever form seen
appropriate)
do a “somewhat of a fair job” in meeting up with general statistics of grain morphology (packet size and such)
~ 80 grains
~ 110 grains
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Metallic materials – Synthetic aggregates with lath like features
~ 110 grains
~ 400 grains
~ 300 grains
tesselation + laths tesselation + laths + substructure laths
tesselation
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Metallic materials – Aggregate crystal plasticity at ductile to brittle transition region (T = -20°C)
equivalent stress axial strain
contours of equivalent stress in an aggregate undergoing uniaxial tension
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Metallic materials – Synthetic dispersion strengthened microstructures
Synthetic microstructure by tesselation and Monte-
Carlo filling & erosion
Distribution of parent
microstructure and secondary
dispersion phase
Parent microstructure grains & grain orientations
Dispersion phase
morphology
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Powder metallurgical materials – WC-CoCr thermal spray metal matrix composite, synthetic model
Tesselation of particle (“splat”)
boundaries (TS PM particles)
Introduction of a WC carbide structure & network by “space filling”
Detail of WC carbide structure
Amorphous metal binder of a single particle, “splat”
Aggregate internal splat structure
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Powder metallurgical materials – Image based analysis without synthetic structures
SEM image detail
Segmentation for phases and defects
Meshing or use of discrete
methods
Simulated material test –
indentation stress and
strain distribution
local material
distribution
stress contours strain contours
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Powder metallurgical materials – Image based analysis without synthetic structures
Comparing the behavior (defect initiation probability plot) of a composite consolidated with three different powder metallurgical particle distributions (nominally nano, micron, conventional) undergoing indentation.
Nanoscale powder
Microscale powder Conventional powder
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Composites – Multi-phase microstructures
Fillers, inclusions, spheroids, sinters…
Platelets, flakes,…. Porous materials, cells, foams,….
Generation of numerical models of composite microstructures using the very same tools contained within the VTT ProperTune package, commonly applying various stochastic space filling methods.
Examples of finite element meshes of constituents of various multi-phase composite microstructures.
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DEFECTS AT MESOSCALE VTT ProperTune
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Generation of defect structures – Ceramic single phase Cr2O3
tesselate a block with single phase material perform Monte-Carlo sampling
to remove a statistical fraction of the material
designate the material fraction as “damaged”, and create a “2 phase” material
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Generation of defect structures – Ceramic single phase Cr2O3
perform an “imperfect botched up repair job” using again Monte-Carlo stochastics, the imperfections being controlled by imaging based defect statistics (size, geometry, number density,….)
and voxel mesh the resulting material volume:
pores & porosity, spherical like defects
particle boundary defects, wall like defects (decohesion)
cracks
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Defects and their evolution within microstructure –(+components), the extended finite element method
Adaptive & enriched XFEM analysis of fatigue crack propagation initiating from a semi-elliptical surface crack under combined tension & bending (Paris’ law for FCP).
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Defects and their evolution within microstructure – cracking of a powder metallurgical thermal spray coating
Stress state in a ~ 20 by 40 by 10 micron “block” of WC-CoCr coating during scratch testing for “XFEM” analysis, pertinent region identified via a non-cracked body analysis
branched crack initiation, WC carbide throat and “excess” amorphous phase
crack tips grow together immediately and
link
crack arrest at binder to carbide
interface
further propagation to adjacent carbide with increasing load
crack path across a “soft” binder region
crack propagates to adjacent WC carbide via a throat
between 2 carbides
crack penetrates coating surface through binder-WC carbide interface when scratch tip
tensile stress region approaches Section of microstructure
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Multiple interacting defects & crack fields – discrete methods (CGMD)
Dynamic fracture analysis of a SEN(T) [single-edge notched tension] fracture mechanics specimen with a part-through initial crack
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Multiple interacting defects – compression of a SEN(T) specimen & holed plate structure
Throw to a rigid wall at 200 m/s – linear-elastic, elastic-plastic, cohesive zone fracture material model (parameters from fracture toughness of a
“fairly brittle” material).
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Multiple interacting defects – compression of a SEN(T) specimen & holed plate structure
Resolution of dynamic propagating cracks within the “structure”. The plate consists of ~80M discrete cells.
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Multiple interacting defects – Ballistic impact of a toughened ceramic ball to a steel plate
Projective with a velocity of 600 m/s – linear-elastic, elastic-plastic, cohesive zone fracture material model (parameters from fracture
toughness of a “fairly brittle” material).
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Multiple interacting defects – Ballistic impact of a toughened ceramic ball to a steel plate
Projective with a velocity of 600 m/s – linear-elastic, elastic-plastic, cohesive zone fracture material model (parameters from fracture toughness of a “fairly brittle” material).
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Multiple interacting defects – Erosion wear of a 140 micron thick coating on a steel substrate
Erosive wear arising from impact of wearing particles, the particle properties and impact conditions being controlled by via simple stochastics. Substrate exposure and significant damage to coating.
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Summary
• VTT ProperTune is a holistic framework for performance driven modeling assisted design and tailoring of material solutions.
• Brief outline of the VTT ProperTune method was presented, emphasizing the Process-Structure-Properties-Performance concept and multiscale modeling methods.
• Two areas paramount for multiscale modeling were addressed – i) description of material structure and ii) modeling of mechanisms critical to performance. Mechanisms typically problematic for numerical solutions were addressed, those involving solution dependent domains, which is often the case for failure and wear problems.
• VTT ProperTune is highly transferable and customizable for different materials, and can be applied in a multiphysical context.