research

On stickiness of multiscale randomly rough surfaces

Submitted by Antonio Papangelo on Wed, 11/06/2019 - 10:59

Adhesion and fracture; adhesion; contact mechanics; friction;

A new stickiness criterion for solids having random fractal roughness is derived using Persson's theory with DMT-type adhesion. As expected, we find stickiness, i.e., the possibility to sustain macroscopic tensile pressures or else non-zero contact area without load, is not affected by the truncation of the PSD spectrum of roughness at short wavelengths and can persist up to roughness amplitudes orders of magnitude larger than the range of attractive forces.

Elastic behavior in porous materials

Submitted by Dr. Hanaor - D… on Mon, 11/04/2019 - 17:21

research

porous materials

mechanical properties

fluid mechanics

multi-scale

In the work shown here:

Multiscale modeling of effective elastic properties of fluid-filled porous materials

The elastic deformation and its dependence on fluid displacement is studied at two distinct scales, to address the multi-scale nature of porous structures in nature.

Electrical resistance at rough surfaces in contact

Submitted by Dr. Hanaor - D… on Tue, 10/29/2019 - 10:34

Electrical Contact Resistance of Fractal Rough Surfaces

The presence of roughness at electrical contacts tends to involve contacting asperities across multiple scales. Depending on the nature of the contact between asperities on opposing surfaces, different conduction mechanisms take place. This is shown in the figure here.

Journal Club: Stretchy Electronics for Soft Robotics

Submitted by Martin Kaltenbrunner on Mon, 10/28/2019 - 09:56

research

In essence, we are sensor-clad soft machines capable of myriad intricate tasks. Stripped from proprioceptive feedback, we can no longer walk despite intact locomotor system. Likewise, integration of sensors, complex control loops, or machine learning is crucial in “classical” robotics. This JClub entry discusses recent efforts and challenges of merging soft electronics with robotics.

Modelling the thermal oxidation of silicon

Submitted by Dr. Hanaor - D… on Fri, 10/25/2019 - 14:31

computational materials science

Two-dimensional modeling of the self-limiting oxidation in silicon and tungsten nanowires

https://doi.org/10.1016/j.taml.2016.08.002

Contact Angle Hysteresis

Submitted by Dr. Hanaor - D… on Mon, 10/21/2019 - 08:52

research

Contact angle hysteresis

Dynamic Contact Angle Hysteresis

https://doi.org/10.1016/j.colsurfa.2018.07.004

Analytical Models for Fatigue Life Prediction of Metals in the Stress-Life Approach -- phd thesis by Pietro D’Antuono

Submitted by Mike Ciavarella on Sat, 10/19/2019 - 18:49

dear collegues

I'd be very grateful if you could have a look, if not a deep reading, at the phd thesis of my last student, playing on classical results on uniaxial fatigue, but with a view of simple, unified perspective on constant and varying amplitude fatigue. We made large use of e-fatigue.com web site and the data in there.

Thanks in advance for any remark. The final thesis will be submitted in few weeks time.

Drastic swelling-induced softening of polymer networks with non-covalent cross-linking bonds

Submitted by noyco on Fri, 10/18/2019 - 13:16

research

Polymer networks

gels

transient cross-links

hydrogen bonds

Our recent work introduces a microscopically motivated model for the swelling response of polymer networks with non-covalent cross-linking bonds.

As opposed to the classical theories of rubber, we show that the uptake of water in polymer networks comprising hydrogen cross-linking bonds can lead to the dissociation of cross-links. This phenomenon leads to a reduction in the chain-density, an increase in entropy, and a decrease in the free energy. As a result, the network experiences significant softening and exhibits a different mechanical response.