Dear friends / distinguished imechanicians,

I am trying to use micromechanics in  foams to numerically compute the elastic constants using one unit cell. I see some literature available when simple unit cell shapes are assumed (like cubical or hexagonal). However there is nothing specific about modelling for tetrakaidecahedral foams. Assuming the right boundary conditions would be critical for computing the constants. I am not able to come up with a reapeating pattern for determining the places to apply the boundary conditions.

Have any of you done something similar to this and if yes, would you want to throw some light on the same.

 Thanking you

Prasanna 

The Computational Solid Mechanics group under the direction of Prof. Marisol Koslowski in the School of Mechanical Engineering at Purdue has an opening for a postdoctoral position in the area of multiscale modeling as part of the project “Plasticity in ultrafine grained materials” funded by DOE. A successful candidate is expected to have a strong background in computational solid mechanics and programming experience. While experience in plasticity using dislocation dynamics or phase field methods is a plus, all outstanding candidates will be considered.

The Materials Research Department at Risø National Laboratory for Sustainable Energy, Technical University of Denmark, is seeking a PhD student within the field of advanced fibre composites. The PhD position will aim at increasing the fundamental knowledge of wood fibres and their behaviour as reinforcements in composite materials studying e.g. wood fibre structure and mechanical and hygroscopic properties e.g. by micromechanical modelling and advanced testing.

For more details see: http://www.dtu.dk/English/About_DTU/vacancies.aspx?guid=22340178

Helix is a very interesting structure. There are many biopolymers that have a helical structure. 

• How can someone model the helix in mechanics?
• How can the helix reinforce a rod? 
• How does this structure reflect the mechanical properties of biopolymers?

We find a way of constructing special inclusions by solving variational inequalities. As a side result, the Eshelby conjectures, which asserts that uniform eigenstress induces uniform elastic strain if and only if the inclusion is an ellipsoid, are solved. In a periodic setting, we can construct optimal ordered structures in the sense of attaining the Hashin-Shtrikman bounds. These works have been submitted and preprints are available at http://www.its.caltech.edu/~liulp/. Examples of multiply-connected inclusion with Eshelby uniformity property are shown below, see the papers for more examples and description of numerical schemes.

Adelaide, Australia, August 24 - 29, 2008

Final Announcement and Call for Papers

http://ictam2008.adelaide.edu.au

Hi everybody, 

In fact, I encounter this problem in my research and I would be grateful if someone can help. In micro mechanics, there are many problems concerning Green functions, e.g: the displacement is calculated from the distributed force in the domain, etc. Consider the following integral to determine the displacement field.

u(x)=∫A(x,y)dVy where A(x,y) is singular of order r-2 (i.e r2=(x-y)(x-y)).

You are cordially invited to submit an abstract to the symposium on “Emerging Methods To Understand Mechanical Behavior” at 2008 TMS annual meeting, New Orleans, LA, March 9-13, 2008.  

Concrete is currently the most important material in the building industry. However, it is very weak in tension,  compared to its strength in compression. To overcome this problem, prestressed concrete is usually used.  Prestressed concrete is plain concrete with reinforcement of steel, polymers or, in this case, shape memory alloys. The prestressing is usually introduced by applying tension to the reinforcement in the concrete members. Consequently, initial compressive stresses are transmitted to the concrete matrix; the application of permanent  compressive stress increases the apparent tensile strength of the concrete, since upon tensile loading, the compressive stresses must first be nullified.

Computational Mesomechanics of Composites, by Leon Mishnaevsky Jr. (Risoe National Laboratory, Technical University of Denmark)

This message about a new book came over the PoroNet (poroelasticity network) mailing list:

Dear Colleagues:

      I would like to inform you that my book "Micromechanics of Heterogeneous Materials” (containing around 700 pages, 140 figures, 3000 formulae, and 1200 references) should be published by Springer on 07.06.07. [Details are on the web http://www.springer.com/west/home/engineering?SGWID=4-175-22-173670290-detailsPage=ppmmedia|toc ] .

      In the framework of a unique scheme of the proposed multiparticle effective field method, we have undertaken in this book an attempt to analyze the wide class of statical and dynamical, local and nonlocal, linear and nonlinear multiscale problems of composite materials with deterministic (periodic and nonperiodic), random (statistically homogeneous and inhomogeneous, so-called graded) and mixed (periodic structures with random imperfections) structures in bounded and unbounded domains, containing coated or uncoated inclusions of any shape and orientation and subjected to coupled or uncoupled, homogeneous or inhomogeneous external fields of different physical natures.

        Any the remarks and comments regarding the book will be fully appreciated.

The 28th Risø International Symposium on Materials Science addresses the whole range from fundamental understanding to industrial applications. Topics include:

• surface functionalising
• chemical and physical surface characterisation
• mechanical characterisation of interfaces
• micromechanical modelling
• fibre/matrix debonding
• sizings effects on composite processing
• interface aspects and their integration into manufacturing
• fibre bridging in composites
• fracture resistance of composite
• tensile and compressive strength of composite
• macroscale modelling
• hole and notch sensitivity

More information, including invited key-note speakers, see web site here.

This blog focuses on the micromechanics modeling of composite materials.

The discovery of a new material type, graphene and extremely thin platelets of graphite, was discussed in several articles from my research group published in 1999:

Lu XK, Huang H, Nemchuk N, and Ruoff RS, Patterning of highly oriented pyrolytic graphite by oxygen plasma etching, APPLIED PHYSICS LETTERS, 75, 193-195 (1999).

Smart materials have received much attention in recent years, especially due to their various applications in smart structures, medical devices, actuators, space and aeronautics. Among these
materials, shape memory alloys exhibit extremely large, inelastic, recoverable strains (of the order of 10%), resulting from transformation between austenitic and martensitic phases. This
transformation may be induced by a change, either in the applied stress, the temperature, or both.

We published this paper in APL on a study of the deformation near interfaces. It provides insight in the strain localization at the interface and its influence on the deformation in bulk metals. 

Abstract An optical full-field strain mapping technique has been used to provide direct evidence for the existence of a highly localized strain at the interface of stacked Nb/Nb bilayers during the compression tests loaded normal to the interface. No such strain localization is found in the bulk Nb away from the interface. The strain localization at the interfaces is due to a high void fraction resulting from the rough surfaces of Nb in contact, which prevents the extension of deformation bands in bulk Nb crossing the interface, while no distinguished feature from the stress-strain curve is detected.

Companion web site http://micro.stanford.edu ISBN:0-19-852614-8, Hard cover, 304 pages, Nov. 2006, US $74.50.

This book presents a broad collection of models and computational methods - from atomistic to continuum - applied to crystal dislocations. Its purpose is to help students and researchers in computational materials sciences to acquire practical knowledge of relevant simulation methods. Because their behavior spans multiple length and time scales, crystal dislocations present a common ground for an in-depth discussion of a variety of computational approaches, including their relative strengths, weaknesses and inter-connections. The details of the covered methods are presented in the form of "numerical recipes" and illustrated by case studies. A suite of simulation codes and data files is made available on the book's website to help the reader "to learn-by-doing" through solving the exercise problems offered in the book. This book is part of an Oxford Series on Materials Modelling.

Fundamentals of Micromechanics of Solids, Jianmin Qu, Mohammed Cherkaoui
ISBN: 0-471-46451-1, Hardcover, 400 pages, August 2006, US $120.00

PART I: LINEAR MICROMECHANICS AND BASIC CONCEPTS

Chapter 1 INTRODUCTION

• 1.1 Background and Motivation
• 1.2 Objectives
• 1.3 Organization of Book
• 1.4 Notation Conventions
• References

Applications are invited from suitably qualified candidates for three University Lectureships. They should have a proven record of scholarship in experimental and/or theoretical research involving Engineering Materials, Solid Mechanics, Mechanics of Biological Materials or Computational Mechanics. The lecturers will be expected to contribute directly to the research and teaching of the Mechanics, Materials and Design Division of the Engineering Department. This Division enjoys an international reputation for high-quality, innovative research in materials design and characterisation, including novel micro-architectured materials, bulk high-temperature superconducting materials, and increasingly in biological materials.

The posts will involve contributing to the teaching of the undergraduate course in Engineering, leading to the BA and MEng degrees. The successful candidates will take up the appointments 1 October 2006 or as soon as possible thereafter. The appointment will be for 5 years in the first instance with the possibility of reappointment to the retiring age subject to satisfactory performance. The current pensionable scale of stipends is in the range of £25,565-£39,303 per annum.

Further particulars and an application form may be obtained from the Personnel Office, Department of Engineering, Trumpington Street, Cambridge CB2 1PZ, UK (tel +44 (0) 1223 332615, fax +44 (0) 1223 766364, email personnel-appointments@eng.cam.ac.uk).

Applications should be sent to this address no later than by Friday 9 June 2006 and include a completed form, a curriculum vitae, a list of publications, and a one-page statement of research interests and future plans. Informal enquiries may be made to Professor Norman Fleck (telephone +44 (0)1223 332650 or email mj@eng.cam.ac.uk). The University is committed to equality of opportunity