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Ying Li's picture

Journal Club for March 2020: Molecular Simulation-Guided and Physics-Informed Multiscale Modeling of Polymer Viscoelasticity

Journal Club for March 2020: Molecular Simulation-Guided and Physics-Informed Multiscale Modeling of Polymer Viscoelasticity

Ying Li, Department of Mechanical Engineering, University of Connecticut

1.       Introduction

sairajatm's picture

A unification of finite deformation J2 Von-Mises plasticity and quantitative dislocation mechanics

Rajat Arora       Amit Acharya

We present a framework which unifies classical phenomenological J2 and crystal plasticity theories with quantitative dislocation mechanics. The theory allows the computation of stress fields of arbitrary dislocation distributions and, coupled with minimally modified classical (J2 and crystal plasticity) models for the plastic strain rate of statistical dislocations, results in a versatile model of finite deformation mesoscale plasticity. We demonstrate some capabilities of the framework by solving two outstanding challenge problems in mesoscale plasticity: 1) recover the experimentally observed power-law scaling of stress-strain behavior in constrained simple shear of thin metallic films inferred from micropillar experiments which all strain gradient plasticity models overestimate and fail to predict; 2) predict the finite deformation stress and energy density fields of a sequence of dislocation distributions representing a progressively dense dislocation wall in a finite body, as might arise in the process of polygonization when viewed macroscopically, with one consequence being the demonstration of the inapplicability of current mathematical results based on $\Gamma$-convergence for this physically relevant situation. Our calculations in this case expose a possible 'phase transition'-like behavior for further theoretical study. We also provide a quantitative solution to the fundamental question of the volume change induced by dislocations in a finite deformation theory, as well as show the massive non-uniqueness in the solution for the (inverse) deformation map of a body inherent in a model of finite strain dislocation mechanics, when approached as a problem in classical finite elasticity.

Paper can be found at link Finite_Deformation_Dislocation_Mechanics.

 

 

 

Lixiang Yang's picture

Theoretical and Numerical Analysis of Anterior Cruciate Ligament Injury and its Prevention

Theory of physical aging from polymer science is, for the first time, introduced to understand ACL injury and its prevention. By analogy to physical aging of amorphous polymer materials, we think physical aging of two bundles of ACL will largely increase risk of ACL injury. Besides, physical aging will also build a heterogeneous stress and strain in ACL due to its natural anatomic structure, which is a large risk for athletes. The specific designed prevention programs for ACL injury such as plyometrics, strengthening and other neuromuscular training exercises [1] are believed to erase physical aging of ACL. ACL with less physical aging is less likely to get injured in sport activities. In this article, a virtual physical aging simulation is built to validate current hypothesis. Erasing physical aging of ACL may provide an accurate and quantitative way to prevent ACL injury.

Two-dimensional finite element analysis of elastic adhesive contact of a rough surface

Adhesive contact of a rigid flat surface with an elastic substrate having Weierstrass surface profile is numerically analyzed using the finite element method. In this work, we investigate the relationship between load and contact area spanning the limits of non-adhesive normal contact to adhesive contact for various substrate material properties, surface energy and roughness parameters. In the limit of non-adhesive normal contact, our results are consistent with published work.

yuzhen's picture

Blueprinting Photothermal Shape‐Morphing of Liquid Crystal Elastomers

By Alexa S. Kuenstler, Yuzhen Chen, Phuong Bui, Hyunki Kim, Antonio DeSimone, Lihua Jin, Ryan C. Hayward

Nuwan Dewapriya's picture

Characterizing fracture stress of defective graphene samples using shallow and deep artificial neural networks

Abstract: Advanced machine learning methods could be useful to obtain novel insights into some challenging nanomechanical problems. In this work, we employed artificial neural networks to predict the fracture stress of defective graphene samples. First, shallow neural networks were used to predict the fracture stress, which depends on the temperature, vacancy concentration, strain rate, and loading direction.

Arash_Yavari's picture

Nonlinear Mechanics of Thermoelastic Accretion

In this paper, we formulate a theory for the coupling of accretion mechanics and thermoelasticity. We present an analytical formulation of the thermoelastic accretion of an infinite cylinder and of a two-dimensional block.

Pradeep Sharma's picture

Freely Downloadable Special Issue of Journal of Applied Mechanics/Century of Fracture Mechanics/John W. Hutchinson's 80th Birthday

Fracture mechanics is one of the key research topics in our field (of mechanics) and has a rather rich history of innovation and applications. From earth-quakes to air-planes---the mechanics underpinning the phenomenon of materials falling apart has been essential in the development of technology.  Griffith’s work on fracture was published about a 100 years ago and is often widely regarded as the start of modern fracture mechanics.

Interface engineering for nanocomposite toughness enhancements

Engineering ceramic/nanocomposite interfaces may lead to the development of ultra-tough ceramic nanocomposites. The novel processing method, as well as micromechanical interpretation of the above result, can be found here: https://doi.org/10.1016/j.carbon.2020.02.075

Christos E. Athanasiou

Emilio Martínez Pañeda's picture

Phase field fracture modelling using quasi-Newton methods and a new adaptive step scheme

Dear iMechanicians,

I hope this paper is of interest to you. We show that quasi-Newton methods make monolithic phase field fracture implementations very robust. Convergence and computations times orders of magnitude smaller than the usual staggered approaches are demonstrated in complex problems such as unstable cracking, fatigue or dynamic crack branching.

XiaoyaoPeng's picture

Effective Response of Heterogeneous Materials using the Recursive Projection Method

This is the preprint of an article that will appear in Computer Methods in Applied Mechanics and Engineering (https://doi.org/10.1016/j.cma.2020.112946).

Effective Response of Heterogeneous Materials using the Recursive Projection Method

Zheng Jia's picture

A constitutive model of microfiber reinforced anisotropic hydrogels: With applications to wood-based hydrogels

Jian Cheng, Zheng Jia*, Teng Li*, A constitutive model of microfiber reinforced anisotropic hydrogels: with applications to wood-based hydrogels, Journal of the Mechanics and Physics of Solids, 138 (2020) 103893 (DOI: https://doi.org/10.1016/j.jmps.2020.103893)


linst06's picture

Fatigue-resistant hydrogel adhesion

This is our recent work on the design of fatigue-resistant hydrogel adhesion. In this work, we show that fatigue-resistant hydrogel adhesion can be achieved by anchoring ordered nanocrystalline domains at the interface. This method is applicable to glass, ceramic, titanium, aluminum, stainless steel, and even elastomers including PU and PDMS. We also demonstrate its potential applications as endurant hydrogel coatings for versatile engineering materials with complex geometries.

Baoxing Xu's picture

Capillary transfer of soft films

Yue Zhang, Mengtian Yin, Yongmin Baek, Kyusang Kim, Giovnni Zangari, Liheng Cai, Baoxing Xu. Capillary Transfer of Soft Films. Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.2000340117

Amit Acharya's picture

Computing with non-orientable defects: nematics, smectics and natural patterns

Chiqun Zhang         Amit Acharya        Alan C Newell          Shankar C Venkataramani

 

Defects, a ubiquitous feature of ordered media, have certain universal features, independent of the underlying physical system, reflecting their topological, as opposed to energetic properties. We exploit this universality, in conjunction with smoothing defects by "spreading them out," to develop a modeling framework and associated numerical methods that are applicable to computing energy driven behaviors of defects across the amorphous-soft-crystalline materials spectrum. Motivated by ideas for dealing with elastic-plastic solids with line defects, our methods can handle order parameters that have a head-tail symmetry, i.e. director fields, in systems with a continuous translation symmetry, as in nematic liquid crystals, and in systems where the translation symmetry is broken, as in smectics and convection patterns. We illustrate our methods with explicit computations.

Preprint

Hector Fellow Academy's picture

Carry out your own PhD project in Deformation & Fracture Processes / Tribology / Interface in Metals & Ceramics supervised by Prof. Peter Gumbsch

 

The Hector Fellow Academy offers you the opportunity to realize a self-developed research project under supervision Prof. Peter Gumbsch. He is one of the Hector Fellows, a community of outstanding professors from different research institutions across Germany working in STEM-subjects, medicine, and psychology.

 

Yang Lu's picture

Elastic straining of free-standing monolayer graphene

The extraordinary mechanical properties of graphene were measured on very small or supported samples. In our new paper published in Nature Communications, by developing a protocol for sample transfer, shaping and straining, we report the outstanding elastic properties and stretchability of free-standing single-crystalline monolayer graphene under in situ tensile tests.

Jingjie Yeo's picture

Adverse effects of Alport syndrome-related Gly missense mutations on collagen type IV: Insights from molecular simulations and experiments

https://doi.org/10.1016/j.biomaterials.2020.119857 Our unified experimental and computational approach provided underlying insights needed to guide potential therapies for Alport syndrome (AS) that ameliorate the adverse effects from AS disease onset and progression. Patients with AS exhibit blood and elevated protein levels in their urine, inflamed kidneys, and many other abnormalities.

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