preservation, maintanence and improvement of industrial organism.pptx
On the use of machine learning for investigating the toughness of ceramic nanocomposites
1. On the use of machine learning for investigating the
toughness of ceramic nanocomposites
Christos Athanasiou1, Xing Liu1, Nitin Padture1, Brian Sheldon1, Huajian Gao1,2
1 Brown University, USA
2 Nanyang Technological University, Singapore
5. σ0
#$% = Yσ ()
2α
geometry
crack length
fracture toughness
σ0
σ = 2σ+
,
-
./0ρ
fracture toughness, KIC: how easy or difficult for a crack to propagate
6. 3.5 – 5.0 MPa.m1/2
Conventional alumina:
N. Koratkar, RPI & E. Corral, University of Arizona
1 μm
7. 3.5 – 5.0 MPa.m1/2
Conventional alumina:
E. Zapata-Solvas, et al. J. Eur. Ceram. Soc, 32, 12 (2012)
Reinforce ceramics w/ nanomaterials for high fracture toughness
5.0 – 8.5 MPa.m1/2
Alumina with graphene:
N. Koratkar, RPI & E. Corral, University of Arizona
1 μm
8. Reinforce ceramics w/ nanomaterials for high fracture toughness
3.5 – 5.0 MPa.m1/2
Conventional alumina:
5.0 – 8.5 MPa.m1/2
Alumina with graphene:
E. Zapata-Solvas, et al. J. Eur. Ceram. Soc, 32, 12 (2012)N. Koratkar, RPI & E. Corral, University of Arizona
1 μm
9. Reinforce ceramics w/ nanomaterials for high fracture toughness?
3.5 – 5.0 MPa.m1/2
Conventional alumina:
5.0 – 8.5 MPa.m1/2
Alumina with graphene:
E. Zapata-Solvas, et al. J. Eur. Ceram. Soc, 32, 12 (2012)W. Curtin, J. Am. Ceram. Soc. 74 ,11 (1991)
What we know: Nanomaterials increase fracture
toughness of ceramic nanocomposites
10. Reinforce ceramics w/ nanomaterials for high fracture toughness?
3.5 – 5.0 MPa.m1/2
Conventional alumina:
5.0 – 8.5 MPa.m1/2
Alumina with graphene:
E. Zapata-Solvas, et al. J. Eur. Ceram. Soc, 32, 12 (2012)W. Curtin, J. Am. Ceram. Soc. 74 ,11 (1991)
What we do not know yet: Perform accurate
mechanical testing of nanocomposites
11. Measuring fracture toughness of coatings using
focused-ion-beam-machined microbeams
D. Di Maio and S.G. Roberts
Department of Materials, University of Oxford, Oxford OX1 3PH, United Kingdom
(Received 23 July 2004; accepted 10 November 2004)
Measuring the toughness of brittle coatings has always been a difficult task. Coatings
are often too thin to easily prepare a freestanding sample of a defined geometry to use
standard toughness measuring techniques. Using standard indentation techniques gives
results influenced by the effect of the substrate. A new technique for measuring the
toughness of coatings is described here. A precracked micro-beam was produced using
focused ion beam (FIB) machining, then imaged and loaded to fracture using a
nanoindenter.
Determining the mechanical properties of coatings can
be very difficult due to their thinness (typically a few
microns), effects of the substrate, effects of adhesion, and
residual stresses. Using a nanoindenter, it is possible to
determine some properties of coatings (hardness and the
elastic modulus).1
Some other properties, however, are
still very difficult to measure. One of them is the fracture
toughness. The classical method for measuring fracture
toughness is to fracture a pre-notched sample with well-
defined geometry. From the critical load it is then pos-
sible to determine the fracture toughness KIc. However,
in the case of thin coatings, it is difficult to manufacture
a sample of the coating material alone: normal fracture
toughness specimens are several tens of millimeters in
size or larger.In the case of brittle ceramic materials, toughness is
very often measured using indentation techniques. The
size of cracks around the indent is measured and then
related to fracture toughness using a specific model.2,3
This method is difficult to use for thin coatings because
typical indentation crack sizes are several tens of microns
to several hundreds of microns; the effect of the substrate
will dominate. If the substrate is not brittle it will be
difficult to obtain a well-defined fracture geometry. This
is also the case for fracture toughness testing using
Hertzian indentation.4Some other methods more spec
been proposed. Thedeterm
with those obtained with other techniques. Micro-beams
and similar micro-mechanical elements have been pre-
pared for many years in silicon, mostly by etching meth-
ods.8–11
These methods are not easily applicable to other
materials (though silicon-etching has been used to pre-
pare Al and Au beams by Son et al.12
). Variants on these
micro-beam testing methods have included focused ion
beam (FIB) machining of cantilevers of Al-coated Si
from material polished to 10 m thickness,13
and use of
FIB to put V-notches in Si specimens produced by etch-
ing methods.14
The technique used here involves the preparation and
testing of pre-cracked micro-beams from “bulk” speci-
mens, using FIB (FEI Company, Hillsboro, OR). The
method is first demonstrated using monolithic silicon and
then applied to produce beams of a thin (10 m) WC
coating on a bulk steel substrate. Specimens are imaged
and loaded to fracture using a nanoindenter.
The operating principle of a FIB system is similar to
that of a scanning electron microscope (SEM), the major
difference being the use of a rastered gallium ion (Ga+
)
beam instead of an electron beam. The
moves material from the su
ing).15
The secto
D. DiMaio, S. Roberts, J. Mater. Res, 20 (2005)
19. D. DiMaio, S. Roberts, J. Mater. Res, 20, (2005)
Measuring fracture toughness via finite elements
Empirical solutions
FEM
20. Using finite elements to prepare the dataset
KI/P
!/# = %. '~%. )
*/# = '. %~+. %
,'/# = %. '~%. -
,./# = .. %~/. %
Small P (Linear Elastic Fracture Mechanics)
Simulation #Finite element software input
Finite element software output
35
100
10
10
Total number of simulations: 439,956
16 CPUs: 120 sec per simulation