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Antonio Papangelo's picture

Critical thresholds for mode-coupling instability in viscoelastic sliding contacts

Mode-coupling instabilities are known to trigger self-excited vibrations in sliding contacts. Here, the conditions for mode-coupling (or "flutter") instability in the contact between a spherical oscillator and a moving viscoelastic substrate are studied. The work extends the classical 2-Degrees-Of-Freedom conveyor belt model and accounts for viscoelastic dissipation in the substrate, adhesive friction at the interface and non-linear normal contact stiffness as derived from numerical simulations based on a boundary element method capable of accounting for linear viscoelastic effects.

giorgio_carta's picture

One Ring to Bind Them...Two Rings to Rule Them

In this paper, we discuss two problems concerning scattering and localisation of flexural waves in structured elastic plates. Firstly, we compare the scattering amplitudes of waves in a thin plate, generated by a point source, due to a single mass and to a large number of smaller masses, having the same equivalent mass and located around a circle. We show that in the second case, the scattering can be reduced, in particular in the medium- and high-frequency regimes.

Wenbin Yu's picture

Global Composites Experts Webinar by Dr. Nancy Sottos

dmHUB invites you to attend the Global Composites Experts Webinar Series. 

Title: Control of Reaction Fronts for Rapid Energy-Efficient Manufacturing of Multifunctional Polymers and Composites

Speaker: Dr.  Nancy R. Sottos

Time: 6/3, 11AM-12PM EST.

Parag Tandaiya's picture

Shear fracture in bulk metallic glass composites

In situ dendrite reinforced Bulk Metallic Glass matrix composites (BMGCs) are known to overcome poor ductility and fracture response exhibited by monolithic bulk metallic glasses (BMGs). In this paper (Shear fracture in bulk metallic glass composites) recently published by our group in Acta Materialia, we report mode I and mode II fracture experiments on the above in situ BMGCs containing transforming and non-transforming dendrites.

noyco's picture

Inversion and perversion in twist incompatible isotropic tubes

How can we induce twist in tubular structures without applying a torque?

In nature, such behavior is enabled by material anisotropy. In our new work, we show that isotropic bi-layer tubes with twist incompatible layers can twist upon inflation and extension.
Interestingly, the direction of twist can spontaneously reverse as the load increases!

Check out our new paper at EML:
https://www.sciencedirect.com/science/article/pii/S2352431621000766

matthew.grasinger's picture

Flexoelectricity in soft elastomers and the molecular mechanisms underpinning the design and emergence of giant flexoelectricity

Dear colleagues,
We invite you to see the preprint of our new paper "Flexoelectricity in soft elastomers and the molecular mechanisms underpinning the design and emergence of giant flexoelectricity" that will appear in PNAS. Here we present a molecular-to-continuum scale theory for the flexoelectric effect in elastomers. The theory unveils a mechanism for achieving giant flexoelectricity--which finds support in prior experimental results; it is then leveraged for designing elastomers for 1) piezoelectricity, 2) tuning the direction of flexoelectricity, and 3) flexoelectricity which is invariant with respect to spurious deformations (https://doi.org/10.1073/pnas.2102477118).

Nayebi's picture

Application of stress gradient plasticity model in different passivated problems

Choose a channel featured in the header of iMechanica: 

In classical plasticity models, the physical length scale is not considered to control the size effects. Strain gradient plasticity models include one or more length scales that control size effects. Stress gradient plasticity model is introduced with a specific physical length scale and does not include any additional parameters.

arash_yavari's picture

On Eshelby's Inclusion Problem in Nonlinear Anisotropic Elasticity

The recent literature of finite eignestrains in nonlinear elastic solids is reviewed, and Eshelby's inclusion problem at finite strains is revisited. The subtleties of the analysis of combinations of finite eigenstrains for the example of  combined finite radial, azimuthal, axial, and twist eigenstrains in a finite circular cylindrical bar are discussed. The stress field of a spherical inclusion with uniform pure dilatational eigenstrain in a radially-inhomogeneous spherical ball made of arbitrary incompressible isotropic solids is analyzed.

Fan Xu's picture

Curvature tunes wrinkling in shells

Transverse wrinkles usually emerge in a uniaxially stretched elastic film and can be suppressed upon further tension, which is an instability-restabilization behavior due to the nonlinear competition between stretching energy and bending energy. Here, we show that curvature can effectively and precisely tune the wrinkling localization and amplitude.

Shuolun Wang's picture

Multi-physics modeling and finite element formulation of corneal UV cross-linking

The UV cross-linking technique applied to the cornea is a popular and effective therapy for eye diseases such as keratoconus and ectatic disorders. The treatment strengthens the cornea by forming new cross-links via photochemical reactions and, in turn, prevents the disease from further developing.

xiangzhang's picture

Rapid synchronized fabrication of vascularized thermosets and composites

Dear colleagues,

We are happy to share a recent collaborative study on experimental and numerical investigation of  rapid synchronized fabrication of vascularized thermosets and composites. This study demonstrated that a thermoset polymer or polymer composites with embedded microvascular systems can be fabricated in a single step, using a self-propagating polymerization reaction front.  For more details, please see: https://www.nature.com/articles/s41467-021-23054-7

mohsenzaeem's picture

Nanotwin-induced strengthening in silicon: A molecular dynamics study

Mechanical performance of silicon nanopillars with homogeneous and gradient nanotwinned structures are investigated through a series of molecular dynamics simulations. The most observed Σ3 twin boundary (TB) with two preferable (lowest surface energy) planes of {111} and {001} are used to generate homogeneous and gradient nanotwinned structures. Simulations of compression and tension of nanotwinned pillars reveal an extra strengthening behavior due to the addition of Σ3 TBs when compared to the single crystalline nanopillar without any TBs.

Teng Li's picture

Keep EML Webinar going!

Keep EML Webinar going by donating at: 

https://www.gofundme.com/f/keep-eml-webinar-going

We gratefully acknowledge the financial support for Season 2 of EML Webinar by (as of 18 May 2021):

Denian Zhuang, Jimmy Hsia, Zhigang Suo, Ruobing Bai, Teng Li, Liqing Jiao, Shengqiang Cai, Grace Gu, Xin Wen, Jianyu Li, Jin Yang, Nitesh Arora, and anonymous donors. 

Teng Li's picture

EML Webinar (Season 2) by Eduard Arzt, on 19 May 2021: Designing with gaps – functional surfaces for sustainable gripping

EML Webinar (Season 2) on 19 May 2021 will be given by Eduard Arzt, Saarland University. Designing with gaps – functional surfaces for sustainable gripping. Discussion Leaders: Huajian Gao, Nanyang Technological University

Time: 10 am Boston, 3 pm London, 10 pm Beijing on 19 May 2021

What makes plant cell walls both strong and extensible?-----a collaborative study led by Prof. Sulin Zhang and Prof. Daniel Cosgrove in Science

The plant cell wall possesses an unusual combination of strength and ability to expand without weakening or breaking (a quality required for plant growth), but the molecular basis for these traits has long been unclear. In a collaborative study led by Prof. Sulin Zhang and Prof.

Hangbo Zhao's picture

PNAS: Compliant 3D frameworks instrumented with strain sensors for characterization of millimeter-scale engineered muscle tissues

In this work published in PNAS (https://www.pnas.org/content/118/19/e2100077118), we present compliant 3D frameworks that incorporate microscale strain sensors for high-sensitivity measurements of contractile forces of engineered optogenetic muscle tissue rings, supported by quantitative simulations.

Abstract: 

Phase field modelling in octave

Choose a channel featured in the header of iMechanica: 

Hi I tried to code a basic phase field model for fracture in octave.

It doesn't seem to converge to the correct load. It fails later.

Also mesh refinement did not improve the results.

The link to the GIT is here

https://github.com/dontcallmesuren/Phase-field-modelling.git

 

Any idea where I am wrong?

Ping me. Thanks in advance.

Pradeep Sharma's picture

Mechanics to explain tsunamis---Rosakis and co-workers in PNAS

Ares Rosakis and collaborators across three other institute have just published a fascinating account of a rather unexpected mechanism for generating  tsunamis. The paper, published in PNAS, is attached with this post.

The associated press-release provides a compelling lay-person summary: https://www.caltech.edu/about/news/contrary-to-previous-belief-strike-sl...

 

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