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Mike Ciavarella's picture

On stickiness criteria for multiscale random rough contacts

We have just submitted a paper which solves a problem that I have been struggling to solve for many years.

Any comments are welcome to improve, while the paper goes the standard review process in the journal we submitted it.

 

Mike Ciavarella's picture

fatigue: overstressing and understressing

 

While teaching some students from old textbooks, I found reference to "understressing and overstressing" as producing effects into fatigue limits.    Looking at classical papers like  W SCHUTZ, A HISTORY OF FATIGUE Engineering Fracture Mechanics Vol. 54, No. 2, pp. 263-300, 1996, he says that the theory of understressing was largely a mistake due to statistically poor testing.  However, I see some chinese papers still talk of understressing, see below.

 

Antonio Papangelo's picture

Multistability and localization in forced cyclic symmetric structures modelled by weakly-coupled Duffing oscillators

Many engineering structures are composed of weakly coupled sectors assembled in a cyclic and ideally symmetric configuration, which can be simplified as forced Duffing oscillators. In this paper, we study the emergence of localized states in the weakly nonlinear regime. We show that multiple spatially localized solutions may exist, and the resulting bifurcation diagram strongly resembles the snaking pattern observed in a variety of fields in physics, such as optics and fluid dynamics.

Post-Doctoral Position – Thermal Transport in Crystalline Solids

The Materials Theory Group at the School of Materials Engineering of Purdue University has a post-doctoral opening in the area of physics of thermal transport in crystalline solids. The postdoc will use Boltzmann Transport Equation (BTE) approach to investigate the phonon and electron thermal transport in crystalline solids with lattice defects. A solid state physics background is highly desired for this position but applicants with a strong, closely related theory background from materials science or other engineering disciplines will be considered. The ideal candidate is one who is strongly interested in the fundamental theoretical concepts related to thermal transport and related computational modeling, and must have excellent programming skills in Fortran and/or C++. For inquiry please send an email to Professor Anter El-Azab (aelazab@purdue.edu). The position will remain open until filled. Interested candidates can send a curriculum vita with list of publications, a one-page or less statement of research interests and the names of at least two references, with their email addresses and telephone numbers to the provided email. The Materials Theory Group performs theoretical and computational research in the areas of mesoscale plasticity and dislocation dynamics, radiation effects in materials, microstructure evolution, phase field method development, phonon and electron thermal transport in crystalline solids, and computational methods for materials science and mechanics. The group has over ten graduate students and postdocs, with a wide range of collaborations.
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Purdue University is an EOE/AA employer. All qualified individuals, including minorities, women, individuals with disabilities, and veterans are encouraged to apply.

Constraint on a beam bottom surface not on the neutral axis

Hi!

I have a question regarding the beam deflection. As shown in the pic, the roller constraint is applied on the bottom of the beam(Beam A) rather than neutral axis(Beam B). Could anybody help to provide some information about Beam A hand calculation?

Thanks!

https://files.fm/u/54jwqnru#sign_up

subroutine interface to visit nodal displacements in Abaqus

I wonder if there is any subroutine interface to have access to nodal ( not integral point ) displacement in abaqus DURING the analysis phase.  Suppose I have a field that is going to be used in UMAT and that is dependent on  displacements of all nodes (presumably stored in an array) from the last increment. Is this possible to be implemented within Abaqus?

Thank you all !

Alejandro Ortiz-Bernardin's picture

Release of VEMLab v2.2

VEMLab: a MATLAB library for the virtual element method

 

Release of VEMLab v2.2

 

>>  From VEMLab v2.1 to VEMLab v2.2:

elishako's picture

A Paper about J. Den Hartog's Views about S.P. Timoshenko

My paper about the views of J. Den Hartog about S.P. Timoshenko has been published.

Will be pleased to hear your comments.

Teng zhang's picture

Symplectic Analysis of Wrinkles in Elastic Layers with Graded Stiffnesses

Wrinkles in layered neo-Hookean structures were recently formulated as a Hamiltonian system by taking the thickness direction as a pseudo-time variable. This enabled an efficient and accurate numerical method to solve the eigenvalue problem for onset wrinkles. Here, we show that wrinkles in graded elastic layers can also be described as a time-varying Hamiltonian system. The connection between wrinkles and the Hamiltonian system is established through an energy method.

MNasr's picture

Elaborating the controversy on the contribution of the surface stress in silicon nanowires

A link between the local surface stress at the atomic scale to the overall behavior of the continuum system indicates a twist deformation at the free end of silicon nano-cantilever. The importance of size and crystal orientation is demonstrated (for more details of the project see:https://www.researchgate.net/publication/327768951_Surface_Stress_Effect...).

Shuozhi Xu's picture

Nanoindentation and nanoscratching at finite temperatures: Three reviews

Dear Colleague,

Dr. Saeed Zare Chavoshi and I have co-authored three review articles, concerning nanoindentation and nanoscratching at finite temperatures from the computational and experimental perspectives:

Refat_Islam's picture

Stochastic continuum model for mycelium-based bio-foam

Mycelium, the root structure of fungi, grows naturally as a biodegradable filamentous material. This unique material has highly heterogeneous microstructure with pronounced spatial variability in density and exhibits strongly non-linear mechanical behavior. In this work we explore the material response in compression, under cyclic deformation, and develop an experimentally-validated multiscale model for its mechanical behavior. The deformation localizes in stochastically distributed sub-domains which eventually percolate to form macroscopic bands of high density material.

Antonio Papangelo's picture

On mixed-mode fracture mechanics models for contact area reduction under shear load in soft materials

The fundamental problem of friction in the presence of macroscopic adhesion, as in soft bodies, is receiving interest from many experimentalists. Since the first fracture mechanics 'purely brittle' model of Savkoor and Briggs, models have been proposed where the mixed mode toughness is interpreted with phenomenological fitting coefficients introducing weaker coupling between modes than expected by the "purely brittle" model.

Flavio Stochino's picture

A refined assumed strain finite element model for statics and dynamics of laminated plates

This work discusses some alternate models of a mixed assumed strain finite element which has been developed for laminated plates. After a brief theoretical review about this kind of plates and their possible finite element formulation, specifically devised for predicting the mechanical behavior of such structures, we discuss four possible assumptions for strains generating four kinds of mixed assumed strain finite elements.

Emilio Martínez Pañeda's picture

A phase field formulation for hydrogen assisted cracking [code included]

I hope some of you may find this work interesting, the finite element code developed (Abaqus UEL subroutine) can be downloaded from www.empaneda.com/codes

 

A phase field formulation for hydrogen assisted cracking

 

Emilio Martínez-Pañeda, Alireza Golahmar, Christian F. Niordson

 

Computer Methods in Applied Mechanics and Engineering, 342, pp. 742-761 (2018)

 

Amit Acharya's picture

Plasticity implies the Volterra formulation: an example

 A demonstration through an example is given of how the Volterra dislocation formulation in linear elasticity can be viewed as a (formal) limit of a problem in plasticity theory. Interestingly, from this point of view the Volterra dislocation formulation with discontinuous displacement, and non-square-integrable energy appears as a large-length scale limit of a smoother microscopic problem. This is in contrast to other formulations using SBV functions as well as the theory of Structured deformations where the microscopic problem is viewed as discontinuous and the smoother plasticity formulation appears as a homogenized large length-scale limit.

Jingjie Yeo's picture

Silica Aerogels: A Review of Molecular Dynamics Modelling and Characterization of the Structural, Thermal, and Mechanical Properties

https://doi.org/10.1007/978-3-319-50257-1_83-1 The second volume of the Handbook of Materials Modeling is now online: We reviewed the development of new empirical molecular dynamics forcefields, novel methods of generating aerogels’ percolated backbones, and compelling algorithms for characterizing their structural, mechanical, and thermal

Mike Ciavarella's picture

are fractal surfaces adhesive? a new attempt on JMPS

In 2007 I wrote a question in Imechanica, IS THERE NO PULL-OFF FOR ADHESIVE FRACTAL SURFACES?

Clearly, in 2007 this question was too hard to answer.  I pointed there that Fuller and Tabor 1975 asperity theory predicted a weird limit for a true fractal surface, that of no stickiness for any fractal dimension or amplitude, in the limit.

Teng zhang's picture

Deriving a lattice model for neo-Hookean solids from finite element methods

Lattice models are popular methods for simulating deformation of solids by discretizing continuum structures into spring networks. Despite the simplicity and efficiency, most lattice models only rigorously converge to continuum models for lattices with regular shapes. Here, we derive a lattice model for neo-Hookean solids directly from finite element methods (FEM). The proposed lattice model can handle complicated geometries and tune the material compressibility without significantly increasing the complexity of the model.

Funded PhD positions at the University of Southampton (Marie-Curie Fellows)

Two PhD positions are available at the University of Southampton in the areas of:

(1) Computational modelling of complex structures and structured materials - especially those fabricated using additive manufacturing,

https://jobs.soton.ac.uk/Vacancy.aspx?ref=1037118AK

and 

(2) Elastic and acoustic metamaterials using additive manufacturing.

https://jobs.soton.ac.uk/Vacancy.aspx?ref=1037018AK

mmalekan's picture

What topics are still under development using phase-field modeling?

Dear colleagues,

I wonder to know what topics are still under development using phase field (PF) modeling?

The PF has already applied to 2D, 3D, and shell structures, incorporating homogeneous, inhomogeneous, and heterogeneous materials. It also applied to brittle, ductile, dynamic, cohesive, finite deformation, and multi-field fractures. What else we can model using PF method?

Regards,

Malekan

Harold S. Park's picture

Post-Doctoral Position in Computational Modeling of Topological Insulators

I am looking to recruit a highly motivated and independent postdoctoral researcher to study, via the development of new computational techniques, various scientific issues surrounding phononic topological insulators.  The position is available for a 1-year duration, with possible extension to future years depending on the availability of funding.  

Requirements for the position include:

1.  A strong background in computational solid mechanics, and in particular topology optimization techniques (i.e. level set-based)

Jingjie Yeo's picture

Effects of CNT size on the desalination performance of an outer-wall CNT slit membrane

https://doi.org/10.1039/C8CP01191E We investigate the effect of varying carbon nanotube (CNT) size on the desalination performance through slit confinements formed by horizontally aligned CNTs stacked on top of one another. By increasing the CNT size, the results obtained from this study indicate a corresponding increase in the water flow rate, accompanied by a slight reduction in salt rejection performance.

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