User login

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.

Virginia Tech shootings take away two mechanicians

During the shootings occurred on the campus of Virginia Tech, the department of engineering science and mechanics lost two fine professors. Dr. Liviu Librescu was teaching solid mechanics class when the gunman initiated a two-minute massacre next door. Most of the students in his class escaped from the windows while Dr. Librescu held the door and did not survive when the gunman broke in. Another professor is Dr. Kevin Granata.

ericmock's picture

Virginia Tech Tragedy

With a great many ties to VT, I have been following the tragic shootings there closely. While my former student (Nakhiah Goulbourne) and my former department head (Dick Benson) are both safe, I am afraid we may have lost one of our own this morning. From an AP report, a student stated that the instructor teaching a 9:05am mechanics class in 204 Norris Hall was killed. According to the timetable of classes at VT, this instructor would have been Liviu Librescu. I certainly hope the AP's report is wrong. As someone very interested in shell theories, I have spoken with Prof. Librescu many times and followed his work. His loss would be a great loss to our community.

Ken P. Chong's picture

NSF CMMI RECRUITING FOR PROGRAM DIRECTORS

NATIONAL SCIENCE FOUNDATION

4201 WILSON BOULEVARD ARLINGTON, VA 22230

 

Title: Division of Civil, Mechanical and Manufacturing Innovation (CMMI)

Fang Wang's picture

BIOMECHANICAL STUDY OF GOLF BALL IMPACT ON CHILD’S HEAD USING THE FINITE ELEMENT METHOD

Head traumatic injury due to the impact of a flying golf ball is one of the severest injuries sustained on a golf course. This paper presents numerical simulation results based on the finite element (FE) method to investigate head injuries in children due to impacts by flying golf balls.

Some weekend reading

Terence Tao (one of the Fields Medal winners this year) has started blogging. He has a detailed discussion on the Navier-Stokes equations here. It's long but definitely worth reading - particularly because of the wide range of ideas that he talks about.

Pradeep Sharma's picture

J-club Editor: Election versus Appointment?

Choose a channel featured in the header of iMechanica: 

As many of you know, last year we had a lively debate prior to the launch of the j-club regarding the rules and regulations governing the functioning of the j-club. This continued in a more low-key fashion this year. One of the more important topics under discussion has been the selection of the future editors (which is to be done each year). I, and perhaps a few other people, had reasoned that the editor should be elected by popular vote. It was proposed that candidates will either self-nominate themselves or be nominated by other mechanicians.

Vlado A. Lubarda's picture

The Leonhard Euler Tercentenary

Just a reminder that this Sunday, April 15 will be exactly 300 years since Leonhard Euler was born.

I am sure many mechanicians will toast this weekend on this extraordinnary anniversary to the person who laid down much of the foundations in mathematics and mechanics.

Some of the related links on the web are:

http://www.maa.org/Euler/

Srikar Vengallatore's picture

Symposium on Microelectromechanical Systems: Materials and Devices, MRS Fall 2007

From the Call for Papers: 

Microelectromechanical Systems (MEMS) represent the integration of miniaturized mechanical, chemical, fluidic, and optical devices with microelectronics. MEMS have a broad range of applications in optical- and radio-frequency communications, physical/chemical/biosensing, display technology, drug delivery, and the manipulation and isolation of cells.

MichelleLOyen's picture

Fundamentals of Nanoindentation and Nanotribology IV at MRS Fall 2007

First announcement and call for papers.

The symposium "Fundamentals of Nanoindentation and Nanotribology" will run for the fourth time at the Fall, 2007, Materials Research Society Meeting, Boston, MA, USA.   

Xiaodong Li's picture

On the uniqueness of measuring elastoplasticproperties from indentation

Indentation is widely used to measure material mechanical properties such as hardness, elastic modulus, and fracture toughness (for brittle materials). Can one use indentation to extract material elastoplastic properties directly from the measured force-displacement curves? Or simply, is it possible to obtain material stress-strain curves from the corresponding indentation load-displacement curves? In an upcoming paper in JMPS titled "On the uniqueness of measuring elastoplastic properties from indentation: The indistinguishable mystical materials," Xi Chen and colleagues at Columbia University and National Defense Academy, Japan show the existence of "mystical materials", which have distinct elastoplastic properties yet they yield almost identical indentation behaviors, even when the indenter angle is varied in a large range. These mystical materials are, therefore, indistinguishable by many existing indentation analyses unless extreme (and often impractical) indenter angles are used. The authors have established explicit procedures of deriving these mystical materials. In many cases, for a given indenter angle range, a material would have infinite numbers of mystical siblings, and the existence maps of the mystical materials are also obtained. Furthermore, they propose two alternative techniques to effectively distinguish these mystical materials. The study in this paper addresses the important question of the uniqueness of indentation test, as well as providing useful guidelines to properly use the indentation technique to measure material elastoplastic properties.

Ashkan Vaziri's picture

Flexible Probes for Characterizing Surface Topology: From Biology to Technology

In nature, several species use flexible probes to actively explore their environment, and acquire important sensory information, such as surface topology and texture, water/air flow velocity, etc. For example, rats and other rodents have an array of facial vibrissae (or whiskers) with which they gather tactile information about the external world.  The complex mechanisms, by which mechanical deformations of the probe lead to neuronal activity in the animal’s nervous system are still far from being understood. This is due to the intricacy of the deformation mechanics of the flexible sensors, the processes responsible for transforming the deformation to electrical activity, and the subsequent representation of the sensory information by the nervous system. Understanding how these mechanosensory signals are transduced and extracted by the nervous system promises great insight into biological function, and has novel technological applications. To understand the mechanical aspect of sensory transduction, here we monitored the deformation of a rat’s vibrissa as it strikes rigid objects with different topologies (surface features) during locomotion, using high-speed videography. Motivated by our observations, we developed detailed numerical models to study the mechanics of such flexible probes. Our findings elucidate how active sensation with vibrissae might provide sensory information and in addition have direct implications in several technological areas. To put this in perspective, we propose strategies in which flexible probes can be used to characterize surface topology at high speeds, which is a desirable feature in several technological applications such as memory storage and retrieval. (The full article is attached)

Amit Acharya's picture

Toward averaging nonlinear dynamics

Attached is a paper outlining ideas for averaging autonomous dynamics, based on a dynamical systems point of view.

People interested in computational multiscale modeling, especially of the sequential kind, as well as nonequilibrium statistical mechanics may find these ideas useful.

What is "randomness"?

Does the word "randomness" have antonym? If yes, what is it? Why? What view of randomness does that imply?

fengliu's picture

From self-bending of nanofilms to fabrication of nanotubes

We demonstrate, by theoretical analysis and molecular dynamics simulation, a mechanism for fabricating nanotubes by self-bending of nanofilms under intrinsic surface stress imbalance due to surface reconstruction. A freestanding Si nanofilm may spontaneously bend itself into a nanotube without external stress load, and a bilayer SiGe nanofilm may bend into a nanotube with Ge as the inner layer, opposite of the normal bending configuration defined by misfit strain.

N. Sukumar's picture

Epi-convergence (max-ent bases), crack growth

In the attached paper, we have used Variational Analysis techniques (in particular, the theory of epi-convergence) to prove the continuity of maximum-entropy basis functions. In general, for non-smooth functionals, moving objectives and/or constraints, the tools of Newton-Leibniz calculus (gradient, point-convergence) prove to be insufficient; notions of set-valued mappings, set-convergence, etc., are required. Epi-convergence bears close affinity to Gamma- or Mosco-convergence (widely used in the mathematical treatment of martensitic phase transformations). The introductory material on convex analysis and epi-convergence had to be omitted in the revised version; hence the material is by no means self-contained. Here are a few more pointers that would prove to be helpful. Our main point of reference is Variational Analysis by RTR and RJBW; the Princeton Classic Convex Analysis by RTR provides the important tools in convex analysis. For convex optimization, the text Convex Optimization by SB and LV (available online) is excellent. The lecture slides provide a very nice (and gentle) introduction to some of the important concepts in convex analysis. The epigraphical landscape is very rich, and many of the applications would resonate with mechanicians.

On a different topic (non-planar crack growth), we have coupled the x-fem to a new fast marching algorithm. Here are couple of animations on growth of an inclined penny crack in tension (unstructured tetrahedral mesh with just over 12K nodes): larger `time' increment and smaller `time' increment. This is joint-work with Chopp, Bechet and Moes (NSF-OISE project). I will update this page as and when more relevant links are available.

Pages

Subscribe to iMechanica RSS Subscribe to iMechanica - All comments

Recent comments

More comments

Syndicate

Subscribe to Syndicate