Download - Project # 12 – Multiscale modelling
1 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Project # 12 – Multiscale modelling
Denis Davydov (PhD student)
Milan Jirásek (supervisor)
Bruno Capra (industrial partner)
Henrik Stang (academic partner)
2 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Multiscale modelling
July 10th, 1983 Born in Perm city, Russia (USSR)
Sept. 1998 – June 2000 Lyceum of Perm State Technical University, Russia.
Sept. 2000 – June 2004 Bachelor degree in Applied Mathematics and Computer Science, Department of Mathematical Modeling of Systems and Processes, Perm State Technical University, Russia. Graduation thesis on “Model for superplasticity”. Distinction: cum laudae.
Sept. 2004 – June 2006 Master degree in Applied Mathematics and Computer Science, Department of Mathematical Modeling of Systems and Processes, Perm State Technical University, Russia. Graduation thesis on “Uniaxial strain stability study problem of the nonlinear viscous material”.
Distinction: cum laudae.
Feb. 2007 – present PhD research at Faculty of Civil Engineering, Czech Technical University, Prague. MC-RTN Project nr 12. “MULTISCALE MODELLING”
3 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Multiscale modelling
Objectives:• Analysis of the role of loading rate in nanoindentation test,
understanding and evaluation of the visco-elastic properties from nanoindentation.
• Extension of models for micromechanical properties of cement paste to time-dependent behavior. FEM approach as a homogenization technique at the scale of cement paste.
• Extension of multiscale model for concrete to time-dependent behavior. This includes analytical homogenization at the scale of mortar and concrete.
• Preliminary study on possible extension to inelastic phenomena such as cracking and plastic deformation.
4 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Multiscale modelling
Deliverables:•Procedures for evaluation of nanoindentation tests taking into account the influence of loading rate.•Numerical FEM simulation tool for viscoelastic properties of cement paste.•Multiscale model for viscoelastic properties of mortar and concrete. Extension of the homogenization analytical techniques for the visco-elastic deformation. •Recommendations for further investigation of inelastic properties of cement paste.
Date Placement Brief description
12.2007-04.2008 CTU Micromechanical creep simulations; homogenization at the level of cement paste. Methodology for determination of viscoelastic properties
05.2008-07.2008 Oxand Extension of multiscale model to viscoelastic behavior
08.2008-02.2009 CTU Comparison between analytical and numerical homogenization techniques. Verification of predicted viscoelastic properties
03.2009-07.2009 DTU Preliminary investigation of possible extension of micromechanical models to fracture analysis
08.2009-01.2010 CTU Preparation and defense of PhD dissertation
5 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Multiscale modelling
Accomplishment during the first reporting period is
Literature survey on:
• Chemistry, morphology, hydration kinetic
• Creep and shrinkage effects
• Models of the CSH structure and creep theories
• Creep modeling from engineering point of view
• Thermo-chemo-mechanical couplings
• Homogenization, Eshelbian approach, multiscale models
• Analytical solutions for indentation problem and dimensionless analysis
6 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Multiscale modelling
P
Force
E0
E1
R
What is the error of Oliver-Pharr procedure of extracting elastic propertiesinduced by experimental hypothesis of half-space homogeneous media?
Diff
ere
nce
be
twe
en
E
0 a
nd
E1
|E0-Eop|/E0 - error
h/R - dimensionless depthtang
Difference between E0 and E1
|E0-E1|/E0 -
7 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Kelvin-Maxwell-Voight visco-elastic model
time secP
enet
rati
on
dep
th n
ano
met
res
Multiscale modelling
Numerical modelling of the nanoindentation experiment
experiment
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
-0.005 0 0.005 0.01 0.015 0.02 0.025
10^(-4)m
N/2
PI (
appl
. loa
d in
axi
sym
met
ric c
ase)
experiment
experiment
0
0.0005
0.001
0.0015
0.002
0.0025
0.003
-0.002 0 0.002 0.004 0.006 0.008 0.01 0.012
10^(-4) m
N / 2
*PI
experiment
E=229.026 nu=0.2 yld=1.7816m=0.272606 K=19.3281 (Tc=6281.7174)
Norton’s visco-plastic model
Too deep!!! (1.5micron)homogenized respond ofsurrounding rather then somephase of interest
8 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Multiscale modelling
1) Perform nanoindentation experiments into specific places of cement paste to better capture intrinsic properties
2) Use different loading rates to distinguish better between viscous and plastic deformation and have several cycles
3) Try analytical and numerical fitting nanoindentation curves with visco-elastic creep and visco-plastic Norton model. Compare the results
4) Estimate a minimum area of the phase needed for reliable results
“matrix” approach tothe indentation measurements
9 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Multiscale modelling
Indent. Module M=E/(1-nu^2)
All products(matrix)
HD-CSH only(manual)
All products HD-CSH
mean 30.877 37.017
Std. dev. 5.252 2.074
time
force
Experimental programs to use:
C3S Alitegrain
Turned out to be Belite
Fit model on one experimentAnd check on another!
10 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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NEW IDEAS :
Deviatoric creep (same for LD and HD)
Porosity (different for LD and HD)
+Self-ConsistentUpscaling with Eshelby Solution
=Like a GranularMediaLD and HD CSH
11 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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NEW IDEAS :
Force
UPSCALING (Self-Consistent Scheme)
Deviatoric creep (same for LD and HD)
Porosity (different for LD and HD)
+Self-ConsistentUpscaling with Eshelby Solution
=Like a GranularMedia
Indentation experiment:
LD and HD CSH
12 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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NEW IDEAS :
Force
UPSCALING (Self-Consistent Scheme)
Deviatoric creep (same for LD and HD)
Porosity (different for LD and HD)
Volumetric & deviatoric creep
+Self-ConsistentUpscaling with Eshelby Solution
=Like a GranularMedia
Indentation experiment:
LD and HD CSH
13 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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NEW IDEAS :
Force
UPSCALING (Self-Consistent Scheme)
Deviatoric creep (same for LD and HD)
Porosity (different for LD and HD)
Volumetric & deviatoric creep
+Self-ConsistentUpscaling with Eshelby Solution
=Like a GranularMedia
Use of elaborated analyticalSolution based on one, published by Vandamme tofit Deviatoric creep propertiesFrom LD and HD CSH Indentation experiments
Indentation experiment:
LD and HD CSH
14 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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NEW PROBLEMS : machine precision
Before: After:
Hope to have HD CSH hereUnhydrated grain
Points to indentReal indents (with shift!)
15 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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NEW PROBLEMS : hard to identify/indent HD
16 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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NEW IDEAS (2):
Use another indentation machine with higher precision, with AFM, but with bad optics Find “good” grains in advance using BSE/electron microscope.
AFM gradient map
BSE
BSE
AFM
grainEnd of HD zone
indent
17 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Effect of the not straight surface:
3.70
Force
79.2tan
Contact square has changed,So the Oliver-Pharr procedureWill give inappropriate results.Is it possible at all to use that Procedure in such a case???
18 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Recent work:
19 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Recent work (2):
?
Is it good quality mix/clinker!?
20 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Recent work (3):
21 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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MATRIX vs MANUAL
Is it possible at all to access Properties of the phase of Interest by matrix method?
Success will probably depend on ratio between characteristicsize of the phase and distancebetween the indents.BUTin order to have indents close to each other one has to do small depths, which, from themorphological point of view for CSH, has to be greater then 100nm
Does it worth trying to chose right indents from big matrix?
22 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Multiscale modelling
Perspectives:
1. Have more reliable procedure for nanoindentation of cement phase (with manual method or with choosing indents from a “matrix” method)
2. Better understand viscous and plastic behaviour during loading phase of indentation using different indentation rates
3. Have reliable results for cyclic loading by manual choice of indentation points and maximum penetration depth
4. Come up with a reliable model to describe the indentation experiment
23 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Multiscale modelling
Questions (Chemistry and Sample preparation/mixing):1. What is the good C/S ratio for HD/LD CSH?2. It is necessary to have a fresh, very well mixed and vibrated cement in quite a
big amount (for good mixing) to provide “homogenous” hydrated paste without air bubbles, bunches of agglomerated aggregates. It is very important for good polishing.
3. Presence of Phosphor?? 4. Lots of Portlondite in paste??5. The best cement for that purpose?? (white/gray/…)
Questions (Mechanical/Mathematical):1. HD CSH zone and indents are often situated on the slope. Corrections to
Oliver-Pharr?2. Statistical lack of experimental curves in manual method to be representative,
very time consuming.3. Do properties of the CSH change in time?? What is right age to make
indents??? According to some experiments (??) after one year the creep is recoverable absolutely.
4. Problems with manual indentation, machine precision or HD CSH finding
24 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid
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Multiscale modelling
Thank you for you attention!