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New Method for Predicting and Describing How Materials Break

tlaverne's picture

I saw this on Science Daily, anyone knows ?

www.sciencedaily.com/releases/2010/03/100329135101.htm

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Mike Ciavarella's picture

Helical crack-front instability in mixed-mode
fracture

The addition of shear orthogonal to
the tension-loading plane of crack propagation generates an instability
that results in three-dimensional helical crack propagation, atomically
rough surfaces and a fracture pattern resembling a series of lance
shapes. Here numerical simulations reveal a new law that governs crack
propagation in space for materials subject to general stress conditions.

Antonio J. Pons
&
Alain Karma

Nature
464, 85-89 (4 March 2010) | doi:10.1038/nature08862

 

 

Michele Ciavarella, Politecnico di BARI - Italy, Rector's delegate.
http://poliba.academia.edu/micheleciavarella
Editor, Italian Science Debate, www.sciencedebate.it
Associate Editor, Ferrari Millechili Journal, http://imechanica.org/node/7878

Mike Ciavarella's picture

Planar crack propagation under pure tension loading (mode I) is generally stable.However, it becomes universally unstablewith the superposition of a shear stress parallel to the crack front (mode III). Under thismixed-mode (I1III) loading configuration, an initially flat parent crack segments into an array of daughter cracks that rotate towards a direction of maximum tensile stress. This segmentation produces stepped fracture surfaces with characteristic ‘lance-shaped’markings observed in a wide range of engineering and geological materials


The origin of this instability remains poorly understood and a theory with which to predict the surface roughness scale is lacking.Herewe performlarge-scale simulations of mixed-mode I-III brittle fracture using a continuum phase-field method that describes the complete three-dimensional crack-front evolution. The simulations reveal that planar crack propagation is linearly unstable against helical deformations of the crack front, which evolve nonlinearly into a segmented array of finger-shaped daughter cracks. Furthermore, during their evolution, facets gradually coarsen owing to the growth competition of daughter cracks in striking analogy with the coarsening of finger patterns observed in nonequilibrium growth phenomena.

We show that the dynamically preferred unstable wavelength is governed by the balance of the destabilizing effect of far-field stresses and the stabilizing effect of cohesive forces on the process zone scale, andwe derive a theoretical estimate for this scale using a new propagation law for curved cracks in three dimensions. The rotation angles of coarsened facets are also compared to theoretical predictions and available experimental data.

 

Michele Ciavarella, Politecnico di BARI - Italy, Rector's delegate.
http://poliba.academia.edu/micheleciavarella
Editor, Italian Science Debate, www.sciencedebate.it
Associate Editor, Ferrari Millechili Journal, http://imechanica.org/node/7878

Mike Ciavarella's picture

It would seem many interesting people are working on this problem at the moment.  For example, Jim Rice indicated me 

Bisen Lin, M.E. Mear, and K. Ravi-Chandar
Center for Mechanics of Solids, Structures and Materials
The University of Texas at Austin
Austin, TX 78712-0235 

Maybe they can share more recent news if they like...

 

Michele Ciavarella, Politecnico di BARI - Italy, Rector's delegate.
http://poliba.academia.edu/micheleciavarella
Editor, Italian Science Debate, www.sciencedebate.it
Associate Editor, Ferrari Millechili Journal, http://imechanica.org/node/7878

Mike Ciavarella's picture

Materials
science: Mind the helical crack.

Nature 464, 42-43 (4 March 2010) | doi:10.1038/464042a;
Published online 3 March 2010

Materials science: Mind the helical crack

Markus
J. Buehler1
&
Zhiping Xu1

Top
Abstract

Catastrophic breakage of
brittle materials such as ceramics is usually triggered by the rapid
spreading of cracks. Computer simulations have now cracked the
three-dimensional details of this process.

Earthquakes, the damage to biological tissues caused by
disease, and the wear of materials in aeroplanes share an underlying
feature — all eventually reach a point at which the breakdown of
material constituents leads to the failure of a functional system. In
brittle materials such as ceramics, rocks and glass, a fundamental
mechanism of failure is the spreading of cracks, a phenomenon also seen
in the shearing of tectonic plates in earthquakes1.

  1. Markus J. Buehler and Zhiping Xu are at
    the Laboratory for Atomistic and Molecular Mechanics, Department of
    Civil and Environmental Engineering, and the Center for Materials
    Science and Engineering, Massachusetts Institute of Technology,
    Cambridge, Massachusetts 02139, USA.

    Email: mbuehler@mit.edu

 

 

Michele Ciavarella, Politecnico di BARI - Italy, Rector's delegate.
http://poliba.academia.edu/micheleciavarella
Editor, Italian Science Debate, www.sciencedebate.it
Associate Editor, Ferrari Millechili Journal, http://imechanica.org/node/7878

Mike Ciavarella's picture

8.
You are<br />
						not entitled to access the full text of this document

Crack front rotation and segmentation in
mixed mode I + III or I + II + III. Part I: Calculation of stress
intensity factors

Journal of the Mechanics and Physics
of Solids
, Volume 49, Issue 7, July 2001, Pages
1399-1420

Véronique Lazarus, Jean-Baptiste Leblond, Salah-Eddine
Mouchrif

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9.
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Crack front rotation and segmentation in
mixed mode I+III or I+II+III. Part II: Comparison with experiments

Journal
of the Mechanics and Physics of Solids
, Volume 49, Issue 7, July
2001
, Pages 1421-1443
Véronique Lazarus, Jean-Baptiste Leblond,
Salah-Eddine Mouchrif

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10.
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						not entitled to access the full text of this document

Propagation de fissures en mode mixte (I +
III) ou (I + II + III)

Comptes Rendus de l'Académie des
Sciences - Series IIB - Mechanics-Physics-Chemistry-Astronomy
, Volume
326, Issue 3
, March 1998, Pages 171-177
Véronique Lazarus,
Jean-Baptiste
Leblond

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Michele Ciavarella, Politecnico di BARI - Italy, Rector's delegate.
http://poliba.academia.edu/micheleciavarella
Editor, Italian Science Debate, www.sciencedebate.it
Associate Editor, Ferrari Millechili Journal, http://imechanica.org/node/7878

Mike Ciavarella's picture


Interesting the remark in the Nature paper that "extending thermal fracture experiments" should produce highly regular stepped surfaces in a fracture context.   I wonder if it has something in this fros weathering....

Frost weathering

A rock in Abisko,
Sweden
fractured along existing joints possibly by frost weathering or thermal stress

This article needs attention from an
expert on the subject
. See the talk page for details. Consider associating this request with a WikiProject.

Main article: Frost weathering

Frost weathering or cryofracturing is the collective name for
serveral processes where ice is present. This processes include frost
shattering, frost-wedging and freeze-thaw weathering. This type of
weathering is common in mountain areas where the temperature is around
the freezing point of water. Certain frost-susceptible soils expand or heave
upon freezing as a result of water migrating via capillary action to grow ice lenses
near the freezing front.[2]
This same phenomena occurs within pore spaces of rocks. The ice
accumulations grow larger as they attract liquid water from the
surrounding pores. The ice crystal growth weakens the rocks which, in
time, break up.[3]
It is caused by the expansion of ice when water
freezes, so putting considerable stress on the walls of containment.

Freeze induced weathering action occurs mainly in environments where
there is a lot of moisture, and temperatures frequently fluctuate above
and below freezing point—that is, mainly alpine and periglacial
areas. An example of rocks susceptible to frost action is chalk, which
has many pore spaces for the growth of ice crystals. This process can
be seen in Dartmoor where it results in the formation of tors. When water
that has entered the joints freezes, the ice formed strains the walls
of the joints and causes the joints to deepen and widen. When the ice
thaws, water can flow further into the rock. Repeated freeze-thaw cycles
weaken the rocks which, over time, break up along the joints into
angular pieces. The angular rock fragments gather at the foot of the
slope to form a talus slope (or scree
slope). The splitting of rocks along the joints into blocks is called
block disintegration. The blocks of rocks that are detached are of
various shapes depending on rock structure.

 

Michele Ciavarella, Politecnico di BARI - Italy, Rector's delegate.
http://poliba.academia.edu/micheleciavarella
Editor, Italian Science Debate, www.sciencedebate.it
Associate Editor, Ferrari Millechili Journal, http://imechanica.org/node/7878

andrea_vita's picture

The following movie highlights the helical nature of the crack-front instability. It shows that the front deforms into a “helix” that subsequently evolves nonlinearly into a more complex sawtooth wave shape as the crack-front segments into partial fronts to produce the observed stepped surfaces.
http://www.youtube.com/watch?v=ujKzI6nBruI
When a material is both under tension and sheared parallel to the crack front, those two fracture modes produces stepped fracture surfaces with characteristic lance-shaped markings.Those markings are ubiquitous in both engineering and geological materials including glasses, polymers, ceramics, metals, and rocks. Although it is known that stepped surfaces result from a complex segmentation of the crack front into partial fronts, the mechanism of this segmentation has remained elusive. Besides these crack-front evolutions are hard to track during the material failing, especially in three dimensions.The accompanying movie of phase-field simulations reveals for the first time the complex path followed by a crack-front in mixed mode fracture. This movie was obtained by numerical simulations of crack propagation using the "phase-field method".This method has the advantage that it tracks automatically the crack-front evolution by the introduction of a scalar “phase field”, which distinguishes between broken and unbroken states of the material.

Mike Ciavarella's picture

I wonder if there can be any simpler explanation of model....  This is not easy to include in undergraduate courses, for example!  

If you understood it, it means that you are above average :)

 

Michele Ciavarella, Politecnico di BARI - Italy, Rector's delegate.
http://poliba.academia.edu/micheleciavarella
Editor, Italian Science Debate, www.sciencedebate.it
Associate Editor, Ferrari Millechili Journal, http://imechanica.org/node/7878

marjan.oboudi's picture

Hello Mike

 I read your comment about "frost heave". I'm working on modelling the freezing process in frost susceptible soils using ABAQUS. I read the article named " Simulation of jeat transfer in freezing soils using ABAQUS" in which the numerical preceedure of the soil freezing process is developed. 

 would you please let me know if you have any information related to this sort of problems,  

 

Regards

Marjan 

kawaminaii's picture

Hello everybody

I am working on freeze-thaw in concrete.I want to simulate it in abaqus.

If anyone has done a work similar to this please help me to start my project.

thanks.

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