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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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.