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Arash_Yavari's picture

Applications of Algebraic Topology in Elasticity

In this book chapter we discuss some applications of algebraic topology in elasticity. This includes the necessary and sufficient compatibility equations of nonlinear elasticity for non-simply-connected bodies when the ambient space is Euclidean. Algebraic topology is the natural tool to understand the topological obstructions to compatibility for both the deformation gradient F and the right Cauchy-Green strain C. We will investigate the relevance of homology, cohomology, and homotopy groups in elasticity.

Zhaohe Dai's picture

Bending of Multilayer van der Waals Materials

Dear colleagues, I'd like to share our recent work on blister testing of multilayer 2D materials that gives a direct measurement of Young's modulus and bending rigidity of a multilayer (~10-70 layers). Materials involved include graphene, MoS2, and hBN.

D.Rittel's picture

About Mechanics-Materials and Dentistry of dental implants

Dental implants are increasingly being placed for edentulous patients worldwide. While the clinical aspects of the implants are extensively investigated, engineering considerations of the implant as a functional structure subjected to ill-defined boundary conditions are less considered. A recent trend is to consider all ceramic implants as an alternative to the classical titanium-based implants.

Shuozhi Xu's picture

Uniaxial deformation of tungsten nanopillars/nanowires/nanotubes: Atomistic and coarse-grained atomistic simulations

Dear Colleague,

In the last two years, we published six papers on uniaxial deformation of tungsten nanopillars/nanowires/nanotubes using atomistic and coarse-grained atomistic simulations:

Jinxiong Zhou's picture

Snap-back induced hysteresis in an elastic mechanical metamaterial under tension

We combine experiment and finite element simulation and come up with a design of a mechanical metamaterial which demonstrates snap-back induced hysteresis and energy dissipation. The resultant is an elastic system that can be used reversibly for many times. The underlying mechanism of existence of hysteresis and the physics of snap-back induced elastic instability is unveiled. Our results open an avenue for design and implementation of recoverable energy dissipation devices by harnessing mechanical instability.

Antonio Papangelo's picture

Citation metrics author database for many scientific fields

Citation metrics are widely used and misused.  Ioannidis and co-authors have created a publicly available database of 100,000 top scientists that provides standardized information on citations, h-index, coauthorship-adjusted hm-index, citations to papers in different authorship positions, and a composite indicator.

Arash_Yavari's picture

Compatible-Strain Mixed Finite Element Methods for 3D Compressible and Incompressible Nonlinear Elasticity

A new family of mixed finite element methods --- compatible-strain mixed finite element methods (CSFEMs) --- are introduced for three-dimensional compressible and incompressible nonlinear elasticity. A Hu-Washizu-type functional is extremized in order to obtain a mixed formulation for nonlinear elasticity. The independent fields of the mixed formulations are the displacement, the displacement gradient, and the first Piola-Kirchhoff stress. A pressure-like field is also introduced in the case of incompressible elasticity.

sairajatm's picture

Finite Element Approximation of Finite Deformation Dislocation Mechanics

We develop and demonstrate the first general computational tool for finite deformation static and dynamic dislocation mechanics. A finite element formulation of finite deformation (Mesoscale) Field Dislocation Mechanics theory is presented. The model is a minimal enhancement of classical crystal/J_2 plasticity that fundamentally accounts for polar/excess dislocations at the mesoscale. It has the ability to compute the static and dynamic finite deformation stress fields of arbitrary (evolving) dislocation distributions in finite bodies of arbitrary shape and elastic anisotropy under general boundary conditions. This capability is used to present a comparison of the static stress fields, at finite and small deformations, for screw and edge dislocations, revealing heretofore unexpected differences. The computational framework is verified against the sharply contrasting predictions of geometrically linear and nonlinear theories for the stress field of a spatially homogeneous dislocation distribution in the body, as well as against other exact results of the theory. Verification tests of the time-dependent numerics are also presented. Size effects in crystal and isotropic versions of the theory are shown to be a natural consequence of the model and are validated against available experimental data. With inertial effects incorporated, the development of an (asymmetric) propagating Mach cone is demonstrated in the finite deformation theory when a dislocation moves at speeds greater than the linear elastic shear wave speed of the material.

 

Paper can be found at link Finite_Deformation_Dislocation_Mechanics.

 

 

 

Opening for new Ph.D. students in the Design & Uncertainty Quantification group, The University of Iowa.

The Design & Uncertainty Quantification group at The University of Iowa, led by Professor Sharif Rahman, is looking for new Ph.D. students, who are capable of and interested in performing high-quality research on uncertainty quantification and stochastic design optimization. The research, supported by U.S. National Science Foundation, requires building a solid mathematical foundation, devising efficient numerical algorithms, and developing practical computational tools, all associated with stochastic analysis and design of complex materials and structures.

Mike Ciavarella's picture

Universal features in "stickiness" criteria for soft adhesion with rough surfaces

A very interesting recent paper by Dalvi et al. has demonstrated convincingly with adhesion experiments of a soft material with a hard rough material that the simple energy idea of Persson and Tosatti works reasonably well, namely the reduction in apparent work of adhesion is equal to the energy required to achieve conformal contact. We demonstrate here that, in terms of a stickiness criterion, this is extremely close to a criterion we derive from BAM (Bearing Area Model) of Ciavarella, and not very far from that of Violano et al.

Bin Liu's picture

Why are most 2D lattices hexagonal? The stability of 2D lattices predicted by a simple mechanics model

Published in Extreme Mechanics Letters: https://doi.org/10.1016/j.eml.2019.100507. For more than half a century, physicists rejected the existence of two-dimensional (2D) materials since they theoretically underestimated the stability. However, the discovery of one-atom-thick graphene proved the inapplicability of this theory.

Ramathasan Thevamaran's picture

Asymmetric acoustic energy transport in non-Hermitian metamaterials

One of our studies on linear and nonlinear non-Hermitian metamaterials has been published on the recent special issue of the Journal of the Acoustical Society of America: Non-Reciprocal and Topological Wave Phenomena in Acoustics.

Abstract

KevinGE's picture

Submission Invitation to Special Issue of Polymers

The special issue “Design and Manufacturing of Shape Memory Polymers and Active Structures” of Polymers is now inviting submission. If you have any suitable manuscript, please consider this special issue. Feel free to contact me through geq@sustech.edu, if you have any questions. Thank you all for your support!

 

 

Koffi Enakoutsa's picture

Habilitation Defense

After a decade of research, I am pleased to announce that I will defense my Habilitation on "Nonlocal Mechanics and Engineering Applications" at Sorbonne University in Paris (France) on September 3, 2019. The composition of the Jury Members of my defense is as follows: 

Prof. David Steigmann (UC-Berkeley, Reviewer)

Prof. Jean-Michel Bergheau (Saint Etienne School of Mine, Reviewer)

Prof. Veronique Lazarus (Paris Tech, Reviewer)

Antonio Papangelo's picture

Reconstruction of Governing Equations from Vibration Measurements for Geometrically Nonlinear Systems

Data-driven system identification procedures have recently enabled the reconstruction of governing differential equations from vibration signal recordings. In this contribution, the sparse identification of nonlinear dynamics is applied to structural dynamics of a geometrically nonlinear system. First, the methodology is validated against the forced Duffing oscillator to evaluate its robustness against noise and limited data.

Magneto-elastic composite

Dear all,

May I bring your attention to recent papers of our that deals with fibre-reinforced magneto elastic composite at large strain?

https://arxiv.org/pdf/1811.11536

https://authors.elsevier.com/a/1ZVv44jvR22kv

I think the content would be of much interest for the community.

marc53042's picture

Postdoctoral Research Opportunities at EPUSP

The Fracture Mechanics and Structural Integrity Research Laboratory (NAMEF) of the Polytechnic School of Engineering at the University of São Paulo (EPUSP) has openings for 2-year postdoctoral fellows (which may be extended to an additional year depending on funding availability) with a strong background in fracture mechanics, fatigue and computational modeling of materials starting from August/2019 or September/2019. Interested applicants can see details in the attached document.

marc53042's picture

PhD Research Opportunities at EPUSP

The Fracture Mechanics and Structural Integrity Research Laboratory (NAMEF) of the Polytechnic School of Engineering at the University of São Paulo (EPUSP) has openings for 3-year PhD positions (which may be extended to an additional year) to conduct research in the areas of fracture mechanics, fatigue and computational modeling of materials starting from August/2019 or September/2019.

Shengyou Yang's picture

Flexoelectricity as a universal mechanism for energy harvesting from crumpling of thin sheets

Can the mere crumpling of a paper produce electricity? An inhomogeneous strain can induce electrical response in all dielectrics and not just piezoelectric materials. This phenomenon of flexoelectricity is rather modest unless unusually large strain gradients are present. In this paper, we analyze the crumpling of thin elastic sheets and establish scaling laws for their electromechanical behavior to prove that an extremely strong flexoelectric response is achieved at submicron length scales.

marco.paggi's picture

New book on Modeling and Simulation of Tribological Problems in Technology, CISM series, Springer

The new book "Modeling and Simulation of Tribological Problems in Technology" (CISM book series, Springer) has been published: https://link.springer.com/book/10.1007/978-3-030-20377-1

Editors: Paggi, Marco (IMT School for Advanced Studies Lucca, Italy), Hills, David (University of Oxford)

Main contributing authors, lecturers of the CISM course http://www.cism.it/courses/C1805/: D.A. Hills, J.R. Barber, M. Paggi, D. Dini, A. Almqvist 

Antonio Papangelo's picture

Axisymmetric JKR-type adhesive contact under equibiaxial stretching

 Our research has just been published in Journal of Adhesion. It deals with axisymmetric frictionless adhesive contact problem for a spherical indenter pressed against an isotropic elastic incompressible half-space under equibiaxial stretching is studied in the framework of the generalized Johnson{Kendall{Roberts (JKR) theory, which accounts for the effect of weak coupling between fracture modes I and II by means of a phenomenological mode-mixity function. The model predicts that contact area can withstand a larger level of the substrate stretch under moderate pre-pulling force.

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