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Mogadalai Gururajan's picture

Going beyond 2D Neumann-Mullins (or, what is popularly known as, solving the beer froth structure)


The blogosphere is abuzz with the latest report of the generalisation of the von Neumann-Mullins grain growth relation to 3 (and N) dimensions by MacPherson and Srolovitz (As an interesting aside, almost all the reports say mathematical structure of beer foam structure resolved, or words to that effect --hence, I also decided to join the bandwagon on that one). I heard Prof. Srolovitz describe the work in a seminar nearly six months ago. Based on my notes of the talk, I would like the explain their work in this post. Curvature in the following refers to mean curvature (and not Gaussian).

Microcantilever operated in liquid environment for in-vitro biomolecular detection

We have recently reported the piezoelectric thick film microcantilever, which enables the in-situ real-time detection of the protein related to disease (e.g. C reactive protein) in liquid environment. This work was published at APL (click here).

"In-situ real-time monitoring of biomolecular interactions based on resonating microcantilevers immersed in a viscous fluid"

Mogadalai Gururajan's picture

Sample issue of Journal of Materials, a TMS publication

JOM is a monthly publication of TMS--The minerals, metals, and materials society. It covers a wide range of materials topics. I expecially like the overview articles, which, in four or five pages pack lots of information. Further, the historical articles about metallurgy and materials in ancient civilizations will interest those of you who like to read about history in general, and science history, in particular.

Chip-package interaction and interfacial delamination

In flip-chip package, the mismatch of thermal expansion coefficients between the silicon die and packaging substrate induces concentrated stress field around the edges and corners of silicon die during assembly, testing and services. The concentrated stresses result in delamination on many interfaces on several levels of structures, in various length scales from tens of nanometers to hundreds of micrometers. A major challenge to model flip-chip packages is the huge variation of length scales, the complexity of microstructures, and diverse materials properties. In this paper, we simplify the structure to be silicon/substrate with wedge configuration, and neglect the small local features of integrated circuits. This macroscopic analysis on package level is generic with whatever small local features, as long as the physical processes of interest occur in the region where the concentrated stress field due to chip-packaging interaction dominates. Because it is the same driving force that motivates all of the flaws. Therefore, the different interface cracks with same size and same orientation but on different interfaces should have similar energy release rates provided that the cracks are much smaller than the macroscopic length. We calculate the energy release rate and the mode angle of crack on the chip-package interface based on the asymptotic linear elastic stress field. In a large range of crack length, the asymptotic solution agrees with finite element calculation very well. We discuss the simplified model and results in context of real applications. In addition, we find that the relation of energy release rate G and crack length a is not power-law since local mode mixity is dependent of crack length a. Therefore, the curve of G~a can be wavy and hardly goes to zero even if crack length a goes to atomically small. The local mode mixity plays an important role in crack behavior.

Robert Paynter's picture

iMechanica needs a logo

I agree with Michelle, we need to get beyond the default Drupal water drop.

How about my little offering, that came to mind:


It's overall shape approximates that of the letter i

At a glance it can look like a Mass on a Spring - major components of mechanics.

It has a globe because this is international

and it says iMechanica at the bottom.

Sure, it need some polishing, but perhaps offers a start.


Oxford, UK

Taxonomy upgrade extras: 
zhan-sheng guo's picture

ICNM 2007

The International Conferences on Nonlinear Mechanics (ICNM-x) have been regarded as important series conferences in mechanics circles. The previous four meetings in the series were successfully held in Shanghai and Beijing in 1985, 1993, 1998 and 2002, respectively. In recent years, new achievements in this field have been made. Therefore, it is appropriate to organize a new conference on this vitally important area of applied mathematics and mechanics. The Fifth International Conference on Nonlinear Mechanics (ICNM-V) will be held in Shanghai. The Conference aims to provide an international forum for presenting the latest results and stimulating wider academic exchange for experts in the related fields all over the world.

Marek-Jerzy Pindera's picture

In Memory of Professor Liviu Librescu

I had known Liviu since his early days in the Engineering Science and Mechanics Department at Virginia Tech when I was just beginning my own academic career. I had received my PhD from this department in 1981 in an area (composite materials) that at the time was at the cutting edge of high technology. In 1985 I had come back to VA Tech from the industry to continue working in this exciting area in which the ESM Department excelled world-wide. Liviu had arrived shortly thereafter with an already established reputation as a top-notch scientist.

Xuanhe Zhao's picture

Electromechanical hysteresis and coexistent states in dielectric elastomers

Active polymers are being developed to mimic a salient feature of life: movement in response to stimuli. Large deformation can lead to intriguing phenomena; for example, recent experiments have shown that a voltage can deform a layer of a dielectric elastomer into two coexistent states, one being flat and the other wrinkled. This observation, as well as the needs to analyze large deformation under diverse stimuli, has led us to reexamine the theory of electromechanics.

Simulating explosions

Recently Henry talked about software that could be used to simulate explosions and introduced CartaBlanca. Luming asked whether anyone had used the software, how good it was, and whether one needed Java to implement models into CartaBlanca.

Ying Li's picture



Mogadalai Gururajan's picture

Computer simulations and visualization: Seed video

Here is a video from the Seed magazine called Science in Silico. The video shows results from large scale simulations (and visualization) of fractals, microscopic dynamic processes in ribosomes, structure of viruses, bacterial flagellum, turbulence, explosions, and the modelling of cosmological events.

Teng Li's picture

iMechanica now has 2000+ registered users

iMechanica was lunched on 9 September 2006. It took about five months for iMechanica to see its 1000th registered user. Today we are welcoming the 2000th registered user after only another two and half months.

MichelleLOyen's picture

New Micromechanics Book

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|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.

Fang Wang's picture


The present paper studies the effect of intracranial temperature (ICT) change on intracranial pressure (ICP). Thermal and mechanical effects were analyzed using a 3D finite element model of the human head.

Xuejun Fan's picture

Fracture at corners or edges in bi-material systems

Dr. Suo's group is recently studying the sharp features such as corners or edges. It becomes important to characterize fracture behaviors at corners and edges in microelectronics.

I have two questions,

MichelleLOyen's picture

Dr. Kevin Granata

Kevin P. Granata, 45, of Blacksburg, beloved husband and father, loving son and brother, passed away Monday, April 16, 2007. Kevin was born and raised in Toledo, Ohio. He began his bachelor's studies at John Carroll University in Cleveland, Ohio and then transferred to Ohio State University where he received degrees in electrical engineering and physics. He later earned a Master's degree in physics from Purdue University and was employed by the Applied Physics Lab in Maryland where he did classified research. He returned to Ohio State University and completed his Ph. D. in Biomedical Engineering, continuing his research until he transferred to the Department of Orthopedics at the University of Virginia, where he was the director the Gait Lab In 2002, Kevin came to Virginia Tech in Blacksburg, Va. to continue his teaching and research interests. He had numerous publications and research grants and lectured both nationally and internationally. Kevin's greatest passion and pride was his family, especially his wife and children. He was also an athlete. He rowed crew at Purdue, participated in biathlons and triathlons and was an avid runner and cyclist. He loved coaching his sons' Lacrosse teams, reading and doing construction around his home and was a member of St. Mary's Roman Catholic Church. Kevin believed in being a well-rounded person and he successfully used his talents to the utmost, academically, physically and spiritually. He will be greatly missed. He is survived by wife, Linda (nee Ankenman); sons, Alex and Eric; and daughter, Ellen; parents, Mildred and Joseph Granata (Toledo); brother, Paul; sisters, Eileen and Anne; and numerous nieces and nephews, aunts and uncles. A public memorial service will be held at the Blacksburg Presbyterian Church at 2 p.m. Friday, April 20, 2007. A private funeral will be held. In lieu of flowers, memorials can be made to the Kevin P. Granata Memorial Trust, 1872 Pratt Drive, Blacksburg, Va, 24068. Arrangements by McCoy Funeral Home, 150 Country Club Drive, Blacksburg, Va.

Zhigang Suo's picture

Leaping Shampoo

Choose a channel featured in the header of iMechanica: 

I came across this video of a fluid phenomenon today. I have no clue what caused it. If you know something about it, please explain to us.

Kyung-Suk Kim's picture

Sharing sadness for loss of dear friends and students

Upon hearing the painful news of VPI tragedy, I am deeply saddened that we lost our young students and fellow faculty, in particular, Liviu Librescu, G. V. Loganathan and Kevin Granata. I would like to share the sorrow with the family and friends of the victims who lost their lives in the senseless crime. I am deeply compelled to write this message, since I am a faculty teaching young students applied mechanics/engineering like professors Librescu, Loganathan and Granata, and belong to a small community of Korean Americans. I feel helpless and guilty that I could not mentor our young people and hear such incomprehensible tragic news.

JDI's picture

Science, 6, April, 2007 Direct-Current Nanogenerator Driven by Ultrasonic Waves

Choose a channel featured in the header of iMechanica: 

What can we do in this discovery and creation?

By Xudong Wang, Jinhui Song, Jin Liu, Zhong Lin Wang*

Dr. Liviu Librescu (1930-2007)

Professor Dr. Liviu Librescu was murdered while teaching a solid mechanics course at Virginia Tech on April 16, 2007.

The great works he left behind are, including, but not limited to, the following books (which are the ones in English):

Seungtae Choi's picture

Scale bridging mechanics: Nanoscale planar field projection of atomic decohesion and slip in crystalline solids

I would like to introduce my recent paper on field projection method with Prof. K.-S. Kim at Brown University. When atomistic simulations or atomic resolution experiments are carried out to analyze deformation energetics of atomic lattices near a crack tip, the results of the atomic positions and the total energy of the system have not been systematically converted to field quantities such as stresses or tractions near the crack tip. In this study, we introduce a mathematically consistent way of defining and measuring the cohesive tractions, separations and surface stresses in an atomic decohesion process zone using the atomic displacement data at some distance away from the crack tip. The method is called “nano-scale planar field projection method.” This is a generalization of the method developed for isotropic homogeneous solids by Hong and Kim (2003). The formulation introduced here is applicable to interface cracks between anisotropic solids as well as to cracks in homogeneous solids whether they are anisotropic or isotropic. The field projection method is then applied to a crack tip field in gold, simulated atomistically. The atomistic simulation is made with an embedded atom method (EAM) potential for a crystal decohesion along [112] direction in a (111) plane. Then, the details of energy partition in various modes of nano-scale separation processes are analyzed with the field projection method.


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