Journal Club for April 2020: Curvature-Affected Instabilities in Membranes and Surfaces
Journal Club for April 2020: Curvature-Affected Instabilities in Membranes and Surfaces
Fan Xu, Fudan University
research
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.
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.
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
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.
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.
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. The Century Fracture Mechanics Summit (CFMS), was held in Singapore on Apr.
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
Stone–Wales Defect Induced Performance Improvement of BC3 Monolayer for High Capacity Lithium-Ion Rechargeable Battery Anode Applications
S. Thomas, A. Kulangara Madam, and M. Asle Zaeem. Stone-Wales defect induced performance improvement of BC3 monolayer for high capacity lithium-ion rechargeable battery anode applications. The Journal of Physical Chemistry C (2020) (10 pages).