# gst: pulse-to-crack transition, unsteady slip pulses under spatially-varying prestress scenarios.

AA << study the effects of a spatially-varying prestress τb(x) on 2D slip pulses, initially generated under a uniform τb along a rate-and-state friction fault. (They) consider periodic and constant-gradient prestress τb(x) around the reference uniform τb. For a periodic τb(x), pulses either sustain and form quasi-limit cycles in the L−c plane or decay predominantly monotonically along the L(c) line, depending on the instability index of the initial pulse and the properties of the periodic τb(x).  >>️

<< For a constant-gradient τb(x), expanding/decaying pulses closely follow the L(c) line, with systematic shifts determined by the sign and magnitude of the gradient. (They) also find that a spatially-varying τb(x) can revert the expanding/decaying nature of the initial reference pulse.  >>

<< Finally, (AA) show that a constant-gradient τb(x), of sufficient magnitude and specific sign, can lead to the nucleation of a back-propagating rupture at the healing tail of the initial pulse, generating a bilateral crack-like rupture. This pulse-to-crack transition, along with the above-described effects, demonstrate that rich rupture dynamics merge from a simple, nonuniform prestress. >>️️

Anna Pomyalov, Eran Bouchbinder. Unsteady slip pulses under spatially-varying prestress. arXiv: 2407.21539v1 [cond-mat.mtrl-sci]. Jul 31, 2024.

https://arxiv.org/abs/2407.21539

Also: transition, instability, crack, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, transition, instability, crack 

# gst: monitoring of stable crack growth; crack tip behavior at the nanoscale (during ceramic fracture).

<< To understand fracture and make brittle materials more ductile, (AA) rely on modeling what happens at a crack tip. However, observing a crack tip in a brittle material is challenging: cracks propagate fast, and the events that (AA) are interested in observing occur at the nanoscale or below. Up to now, (They) were not able to observe what happens ahead of a moving crack tip. >>

<< In this work, (AA) show how by carefully performing fracture experiments inside a transmission electron microscope (They) can grow stable cracks while observing the nanoscale events happening at the crack tip. >>️

Oriol Gavalda-Diaz, Max Emmanuel, et al. Observing the crack tip behavior at the nanoscale during fracture of ceramics. PNAS. 121 (43) e2408292121. Oct 17, 2024.

https://www.pnas.org/doi/10.1073/pnas.2408292121 

Also: fracture, crack, behav in https://www.inkgmr.net/kwrds.html 

Keywords: gst, fracture, crack, behavior

# gst: apropos of breaking mechanisms, crack of a floating particle raft caused by waves.

<< When particles of a few tens of microns are spread on the surface of water, they aggregate under the action of capillary forces and form a thin floating membrane, a particle raft. >>

<< For a sufficiently strong wave amplitude, the raft breaks up progressively by developing cracks and producing fragments whose sizes decrease on a timescale long compared to the period of the wave. (AA)  characterize the breaking mechanisms.  >>️️

<< The visual appearance of the fragments distributed in size and surrounded by open water bears a notable resemblance to the floes produced by the fracturing of sea ice by waves in the polar oceans. Fragmentation concepts and morphological tools built for sea ice floes can be applied to (AA) macroscopic analog, on which the entire dynamic evolution is accessible. However, the mechanics of the two systems differ, as (AA) particle raft breaks due to the viscous stresses, whereas the sea ice fractures due to its bending by the waves. >>️

Louis Saddier, Ambre Palotai, et al. Breaking of a floating particle raft by water waves. Phys. Rev. Fluids 9, 094302. Sep 27, 2024.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.9.094302 

Also: 'crack', 'particle', in  https://www.inkgmr.net/kwrds.html 

Also: 'break' in  https://flashontrack.blogspot.com/search?q=break

Also: 'raft' in  https://flashontrack.blogspot.com/search?q=raft

Also: 'zattera' (quasi-stochastic poetry) in  https://inkpi.blogspot.com/search?q=zattera  'randa' (quasi-stochastic poetry) in https://inkpi.blogspot.com/search?q=randa

Keywords: gst, crack, break, particle, raft, particle raft

# gst: critical crack length during fracture.

AA << established an inverse correlation between the strength of the material and the cracks which grow inside it—both the maximum crack and the one that sets in instability within the system, defined to be the critical crack. >>

AA << found that the maximum and the critical crack often differ from each other unless the disorder strength is extremely low. A phase diagram on the plane of disorder vs system size demarcates between the regions where the largest crack is the most vulnerable one and where they differ from each other but still show moderate correlation. >>️

Viswakannan R.K., Subhadeep Roy. Critical crack length during fracture. Phys. Rev. E 110, 024134. Aug 26, 2024.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.110.024134

Also: crack, instability, fluctuations, noise, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, crack, instability, fluctuations, noise, criticality

# gst: elastomers fail from the edge.

<< The performance of soft devices is limited by the fracture resistance of elastomers. (..) A key observation is that thicker elastomers can be significantly tougher than thinner ones. (AA) show that this surprising toughness enhancement in thick samples emerges from the 3D geometry of the fracture process. In contrast to the classical picture of a 2D crack, failure is driven by the growth of two separate “edge” cracks that nucleate early on at a sample’s sides. As loading is increased, these cracks propagate in towards the sample midplane. When they merge, samples reach their ultimate failure strength. In thicker samples, edge cracks need to propagate farther before meeting, resulting in increased sample toughness. (AA) demonstrate that edge-crack growth is controlled by the elastomer’s strain-stiffening properties. >>

️

Nan Xue, Rong Long, Eric R. Dufresne, Robert W. Style. Elastomers Fail from the Edge. Phys. Rev. X 14, 011054. March 22, 2024. 

https://journals.aps.org/prx/abstract/10.1103/PhysRevX.14.011054

Also: elastic, crack, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, elastic, crack, elastomers, fracture

# gst: compression and fracture of ordered and disordered droplet rafts

AA << simulate a two-dimensional array of droplets being compressed between two walls. The droplets are adhesive due to an attractive depletion force. As one wall moves toward the other, the droplet array is compressed and eventually induced to rearrange. The rearrangement occurs via a fracture, where depletion bonds are quickly broken between a subset of droplets. >>

<< For monodisperse, hexagonally ordered droplet arrays, this fracture is preceded by a maximum force exerted on the walls, which drops rapidly after the fracture occurs. >>

<< In small droplet arrays a fracture is a single well-defined event, but for larger droplet arrays, competing fractures can be observed. These are fractures nucleated nearly simultaneously in different locations. >>

AA << also study the compression of bidisperse droplet arrays. The addition of a second droplet size further disrupts fracture events, showing differences between ideal crystalline arrays, crystalline arrays with a small number of defects, and fully amorphous arrays. >>

️

Pablo Eduardo Illing, Jean-Christophe Ono-dit-Biot, et al. Compression and fracture of ordered and disordered droplet rafts. Phys. Rev. E 109, 014610. Jan 17, 2024.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.109.014610

Also: drop, defect, fracture, crack, in https://www.inkgmr.net/kwrds.html

Also:  raft   https://flashontrack.blogspot.com/search?q=raft  

zattera (quasi-stochastic poetry) https://inkpi.blogspot.com/2005/04/1864-onda-di-liberazione.html  

randa (quasi-stochastic poetry) https://inkpi.blogspot.com/search?q=randa

Keywords: gst, drop, droplet, raft, defect, fracture, crack

# gst: when science meets poetry, an image of three-dimensional stepped cracks (bistability, and their transition to simple cracks)

<< Slow cracks may be simple, with no internal structure. The leading edge of a simple crack, the crack front, forms a single fracture plane in its wake. Slow cracks may also develop segmented crack fronts, each segment propagating along a separate fracture plane. These planes merge at locations that form steps along fracture surfaces. Steps are not stationary, but instead propagate within a crack front. Real-time measurements of crack front structure and energy flux reveal that step dynamics significantly increase energy dissipation and drastically alter crack dynamics. Simple and stepped cracks are each stable. By extending the use of energy balance to include 3D crack front structure, (AA) find that, while energy balance is obeyed, it is insufficient to select the energetically favorable crack growth mode. Transitions from stepped cracks to simple cracks occur only when their in-plane front lengths become equal and a perturbation momentarily changes step topology. Such 3D crack dynamics challenge our traditional understanding of fracture. >>

Meng Wang, Mokhtar Adda-Bedia, Jay Fineberg. Dynamics of three-dimensional stepped cracks, bistability, and their transition to simple cracks. Phys. Rev. Research 5, L012001. Jan 9, 2023. 

https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.5.L012001

Also

keyword 'crack' in FonT

https://flashontrack.blogspot.com/search?q=crack

keyword 'rottura' | 'crepa' | 'frattura' | 'rugosa' in Notes

(quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=rottura

https://inkpi.blogspot.com/search?q=crepa

https://inkpi.blogspot.com/search?q=frattura

https://inkpi.blogspot.com/search?q=rugosa

keywords 'meets poetry' in FonT

https://flashontrack.blogspot.com/search?q=meets+poetry

Keywords:  gst, transitions, dynamical phase transitions, crack, cracking,   fracture, roughness

# gst: apropos of (multitudes) of transitional droplets, when a liquid film collapses in a foam ...

<< Foams have unique properties that distinguish them from ordinary liquids and gases, and are ubiquitously observed in nature, both in biological systems and industrial products. >>

️

<< Once a crack appears near the border and a collapse front is formed, (AA) find that the curvature of the front reverses as it migrates, followed by the emergence and emission of droplets. (they) elucidate the origins of this behavior and discuss the stability of foams, establishing how the characteristic time scales of the process relate to each other. >>️

Naoya Yanagisawa, Marie Tani, Rei Kurita. Dynamics and mechanism of liquid film collapse in a foam. Soft Matter. 17, 1738-1745. Feb 17, 2021.

https://pubs.rsc.org/en/content/articlelanding/2021/SM/D0SM02153A#

Also

keyword 'foam' in FonT

 https://flashontrack.blogspot.com/search?q=foam

keyword 'collapse' in FonT

https://flashontrack.blogspot.com/search?q=collapse

keyword 'schiuma' in Notes

(quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=schiuma

# gst: an atomic imaging of a (slow) crack

AA << successfully imaged the snapping of individual atomic bonds in a one-atom-thick sheet of rhenium disulfide ( ReS2) using scanning transmission electron microscopy. (STEM) >>

<< Because of its unusual chemistry, Re forms a 2D lattice with "lanes" that guide cracks, allowing the cracks to propagate with ease. The heavy element also efficiently deflects electrons, providing the signal needed to gain clear images. The study is a remarkable example of how a specific material can provide insight into the universal behavior of matter. >>

<< Because of its strong scattering, ReS2 provides an ideal target for STEM. (Interestingly, tungsten, the periodic-table neighbor of Re, has just one fewer proton and is routinely used in electron microscopy to stain viruses and bacterial flagella.)  >>

<< By measuring the deformation of the lattice around the crack, the team showed that the tearing stresses were concentrated around the crack tip. The stresses then decayed as the inverse square root of the distance from the tip, a finding that matches predictions for macroscopic materials. Using these measurements, the team defined a stress intensity threshold for cracks to propagate. >>

<< The images taken by Huang and colleagues used seconds-long exposure times, meaning they could only follow the propagation of the slowest crack (those that moved at a few angstroms per second). There is much interest in how faster cracks behave, as these cracks are subject to instabilities, meaning they can deviate from a straight line or form branches, for example. To observe faster cracks, future experiments could use reduced exposure times. >>

Itamar Kolvin. Atomic Imaging of Cracks. Physics 13, 193. Dec 9, 2020. 

https://physics.aps.org/articles/v13/193

Lingli Huang, Fangyuan Zheng, et al. In Situ Scanning Transmission Electron Microscopy Observations of Fracture at the Atomic Scale. Phys. Rev. Lett. 125, 246102. Dec 9, 2020.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.246102

Also

(+)  the intriguing dynamics of a crack. Nov 7, 2017. 

https://flashontrack.blogspot.com/2017/11/gst-intriguing-dynamics-of-crack.html

(+) multiple cracks, simultaneously ... Oct 23, 2016.

https://flashontrack.blogspot.com/2016/10/s-gst-multiple-cracks-simultaneously.html

(+) onda criptica. May 22, 2005 (quasi-stochastic poetry)

https://inkpi.blogspot.com/2005/05/1641b-onda-criptica.html

(+) keyword "fracture" in FonT

https://flashontrack.blogspot.com/search?q=fracture