The velocity and instability of crack motion in 2D hexagonal lattice of graphene under pure opening loads
are investigated by atomistic molecular dynamics simulations. The brittle crack along zigzag direction
in a strip can propagate supersonically at even 8.82 km/s under uniform normal loading of edge
displacements. Crack moving straightly at low speeds produces atomically smooth edges, while kinking
occur beyond a critical speed around 8.20 km/s equivalent to 65% of Rayleigh-wave speed in graphene,
which validates previous theoretical predictions of rapid fracture instability in elastodynamics, and
rough and irregular edges with oscillatory overhangs are formed subsequently.
Happy New Year!
The 17th U. S. National Congress on Theoretical and Applied Mechanics that will be held June 15-20, 2014 at Michigan State University, East Lansing, Michigan. (http://www.usnctam2014.org/)
George Z. Voyiadjis inducted into the Polish Academy of Sciences (pictured with Michal Kleiber - September 2013)Submitted by Pawel Woelke on Thu, 2014-01-02 10:34.
Please join me in congratulating George Z. Voyiadjis, chair of LSU Department of Civil and Environmental Engineering, on his induction into the Polish Academy of Sciences.
I read with interest an excellent discussion about Linear Algebra in Mechanics. I am attaching Chapter I: Tensor Preliminaries from my book Elastoplasticity Theory, which includes Hill's analysis of induced tensors mentioned in the discussion.
Dielectric Elastomers (DE) are promising materials for developing soft machines (e.g., a human-made octopus). The principle of actuation has gained to DE the name "artificial muscles" since they can undergo large deformation when excited by an electric field. Another class of active materials that can be actuated by external field is Magnetoactive Elastomers (MAE). Although MAE and DE share mathematical similarities, the physics is different. Electric field can induce polarization in elastomers, and hence generate electrostatic stresses within the material. As a response to the electrically induced stresses, the material deforms. For MAE the situation is different: elastomers are magnetically inactive, and a similar to DE effect is achieved by mixing the elastomer with magnetically active particles (e.g., carbonyl iron, nickel or Terfenol-D). Thus, due to the magnetic interaction of the particles embedded in a soft matrix, the composite can deform and modify overall stiffness as a response to a magnetic field. The performance of these composites can be further enhanced by optimizing microstructures. Indeed, a similar idea applies for designing DE composites with enhanced properties. These composites, once manufactured can solve the bottle-neck problem of DE technology - the need in extremely high electric fields for meaningful actuations, and potentially lead to a breakthrough in the technology.
I was curious whether there are any
experimental information and / or results regarding the out of plane (anti-plane)
deformation of (very) thin films. For example an elastic thin film subjected to anti-plane loading on its surface. Any other suggestions regarding possible applications of anti-plane loading conditions in thin films would be appreciated.
Thanks a lot,
How to consider a pretwisted tapered propeller balde either as beam orplate
When I was updating my very brief notes on tensors, it occurred to me to post on iMechanica a request for recommendation of textbooks on linear algebra. I was delighted to see Arash respond. I then asked for his opinion about the definition of tensor. He responded again, and we seemed to agree. Then Amit joined the discussion, and then others. That thread has become very interesting and very long.
But I have another issue with the way we use linear algebra. I wish to get your opinion. The issue is about scalars.
For my project I need to learn nonlinear finite element method (FEM) and composite materials. I am familier with linear FEM. Please suggest me good book for nonlinear FEM which will have good explanation of the subject. Also, please suggest book on composite materials especially having lot of solved examples. I know there are lots of experts in this subject on imechanica, so please give me some suggestions. Thanks.
A RA (MS level) position is available in the Department of Engineering Technology, University of North Texas-Denton in the fields of piezoelectric sensor modeling and experiment. The position will start from Summer, 2014. Candidates should have a Bachelor/Master's degree in engineering mechanics, mechanical engineering or electrical engineering with good academic standing and should have some experiences in the following:
(1) Modeling of electromechanical devices such as sensors and energy harvesters,
(2) Proficient in LABVIEW or MATLAB- based experiment test,
(3) Fundamental knowledge in solid mechanics,
(4) Sensor circuit development.
I attach some class notes developed by the late Professor Donald Carlson from which many generations of students at the University of Illinois learnt Continuum Mechanics.
Linear algebra is significant to many aspects of mechanics. For some years I have been using the book by Shilov. But this book may or may not be a good one to recommend to a student, depending on his or her prior experience. On StackExchange Mathematics, there are several excellent threads discussing textbooks of linear algebra. A particular recommendation was made for textbooks of linear algebra at three levels. Do you have any recommendations?
I am looking for a closed form analytical solution for the critical bucking load of a timoshenko beam with clamped-free BC.
please help me i'm in rush!!!
Thanks in advance
As you may know, our research group has, with my leaving the UK, moved in part to Luxembourg, where I am now based. I am of course keeping close ties with Cardiff, where Pierre Kerfriden is now taking care of the group.
It has been a fun and productive year, and I thank you all for contributing to this through numerous discussions emanating from this blog. I wish you all the best for 2014, and hope that it will bring you joy in the work you do.
Best regards from Lausanne where we are enjoying a few days off.
PS : the group’s publications are available on this repository: http://orbilu.uni.lu/simple-search?query=bordas
Harnessing Localized Ridges for High-Aspect-Ratio Hierarchical Patterns with Dynamic Tunability and MultifunctionalitySubmitted by Changyong Cao on Wed, 2013-12-25 21:40.
Harnessing Localized Ridges for High-Aspect-Ratio Hierarchical Patterns with Dynamic Tunability and Multifunctionality, Advanced Materials, DOI: 10.1002/adma.201304589.
There is a SIAM conference on life science on August, 2014. See website http://www.siam.org/meetings/ls14/
I want to organize a minisymposium on topic of "soft tissue modeling
by bio-mechanics". The organizer is responsible for inviting three more
speakers. I would like to know if any of you have interest considering yourself as one of the speakers for a 25
minute talk. If the application of this minisymposium is successful,
most probably you can get the travel support from SIAM if you are a student or a postdoc.
If you are interested, please reply to email@example.com with the title of your talk (no abstract of your talk at this stage).
hi every body:
What's your idea? The virtual displacement is special case of hamilton's principle or the hamilton's principle come from virtual displacement? Or, Which is older?
I want to analyse the inspection interval for the crack propagation in a gusset plate of a truss joint subjected to dynamic loading. I have the dynamic stress time history acting on the plate. Since I am new to abaqus I dont have much idea how to model the crack in the plate.Please kindly help me with this.
Thanks and regards,
COURSE NL14: NONLINEAR COMPUTATIONAL SOLID & STRUCTURAL MECHANICS. Theoretical formulations, technologies and computations.Submitted by eli_compmech on Fri, 2013-12-20 11:00.
We are glad to announce the 2014 version of the course:
NONLINEAR COMPUTATIONAL SOLID & STRUCTURAL MECHANICS. Theoretical formulations, technologies and computations. Pavia, May 5-9, 2014
Applications are invited for one postdoctoral position in Experimental
Granular Physics with the Collective Interactions Unit at the Okinawa
Institute of Science and Technology (OIST). Our group is broadly
interested in experimental softmatter physics, continuum mechanics, and
applied mathematics, and their application to biologically inspired
questions. Our current emphasis is on interfacial fluid dynamics,
disordered granular solids, and biomechanics of the human foot. For
further details about our group, please visit https://groups.oist.jp/ciu/
I tried to solve the problem
that a rigid disc under harmonic moments resting on a porous half-space, the
porous medium is modeled using Biot's theory, when I consider the disc as
totally impervious, I found from the numerical results that negative damping
appears when the permeability of the porous medium is very low at a small
exciting frequency. I have no idea whether this is possible, can someone give
me some suggestions? Thanks very much.
I am trying to model the soil churning action of a rotary tiller trough soil structure interaction. Based on some published articles, DEM and SPH approach both have been used to model the tool interaction with the soil. I am little confused in the selection of the appraoch. Can somebody throw some light on advantages and disadvantages of one approach over another and which approach should be chosen for more realistic results.
Two PhD positions on experimental and computational multiscale mechanics at Eindhoven University of Technology, the NetherlandsSubmitted by jhoefnagels on Thu, 2013-12-19 07:13.
Our Mechanics of Materials Group at Eindhoven University of Technology, the Netherlands has two openings for talented PhD students in the field of multiscale mechanics of materials. They are part of a European Union funded project on multiscale methods for advanced materials. One opening is on the development of a fundamentally new multiscale approach towards material modelling and the other aims to integrate this approach with experimental methods.