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Localization and instability in sheared granular materials: Role of friction and vibration

Submitted by Ahmed Elbanna on
research
granular material
shear bands
friction
vibration
stick-slip

Shear banding and stick-slip instabilities have been long observed in sheared granular materials. Yet, their microscopic underpinnings, interdependencies and variability under different loading conditions have not been fully explored. Here, we use a non-equilibrium thermodynamics model, the Shear Transformation Zone theory, to investigate the dynamics of strain localization and its connection to stability of sliding in sheared, dry, granular materials. We consider frictional and frictionless grains as well as presence and absence of acoustic vibrations.

Objective Fracture Parameters and a Paradox for Interface Cracks

Submitted by Bin Liu on
research
fracture mechanics

Due to the oscillatory singular stress field around a crack tip, interface fracture has some peculiar features. This paper is focused on two of them. One can be reflected by a proposed paradox that geometrically similar structures with interface cracks under similar loadings may have different failure behaviors. The other one is that the existing fracture parameters of the oscillatory singular stress field, such as a complex stress intensity factor, exhibit some nonobjectivity because their phase angle depends on an arbitrarily chosen length.

PhD scholarship in Ecole Polytechnique, Paris, France

Submitted by Kostas Danas on
job
instabilities
Magnetorheological elastomers
experiments
finite elements

One Ph.D. position is now available starting October 2017 on harnessing instabilities in magnetorheological elastomers. The PhD will be pursued in the Solid Mechanics Laboratory of Ecole Polytechnique, Paris, France. The potential student will work on the development of new experimental procedures and numerical models for the fabrication and testing of new magnetorheological elastomeric devices that operate in the postbifurcation regime by proper combination of mechanical and magnetic loadings.

Masonry modeling in Abaqus

Submitted by eng.femiran on

here we are to tell you how we can model masonry in abaqus cae.
there are 3 ways:
1-micro modeling
2- macro modeling
3- micro-macro modeling(HOMOGENIZATION)
micro modeling; 
in this method all parts should be modeled in abaqus separately.
but notice that don't use shell to modeling grout because of 3d properties of grout and cohesive characteristics.
this method is suitable for small masonry panels with 2-3 layers of brick.

A simple finding on variable amplitude (Gassner) fatigue SN curves obtained using Miner’s rule for unnotched or notched specimen

Submitted by Mike Ciavarella on
research
Fatigue
variable amplitude
notches
critical distance method

We provide a very simple result for a problem which has been often neglected (variable amplitude loading) in academia, but which is of paramount importance in real engineering situations, where fatigue is almost never "constant amplitude".

We found few cases where we could check this extremely simple result, but it worked very well.  We would welcome further verifications.

The paper is in press here.

deadline for financial aid for the CISM summer course on Mesoscale models

Submitted by mesarovic on
education
education
interface
capillary effect
granular materials
discrete dislocations
Crystal plasticity
multiphase flow problems

This is a reminder that the deadline to apply for the financial aid for the summer course in Udine is approaching:  March 22. 

 

Short course at Centre International de Sciences Mechanique (CISM), Udine.

May 22-26, 2017

Lecturers:  S Forest, I Groma, D McDowell, S Mesarovic, J-N Roux, H Zbib

The flyer is attached.  Register at:   http://www.cism.it/courses/C1703/ 

A phononic band gap model for long bridges. The ‘Brabau’ bridge case

Submitted by Giorgio Carta on
research
elastic wave propagation
bridges
structural dynamics
dispersion relation

In this paper, we study the dynamic flexural behaviour of a long bridge, modelled as an infinite periodic structure. The analysis is applied to the ‘Brabau’ bridge across the river Tirso in Italy. The approach reduces to a spectral problem leading to the analytical expression of the dispersion relation, which provides the ranges of frequencies for which waves do and do not propagate. The contributions of the bridge structural elements on the dispersive properties of the structure are investigated in detail.

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