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Xiao-Yan Gong's picture

Nitinol, stent fracture and related issues

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Stent and Nitinol have revolutionized the medicine.  In past decades, guidewires, stents, filters and many minimumly invasive devices and implants are made of Nitinol and they proved to be very successful.

However, the fatigue behavior of Nitinol has not been well understood.  As a consequences, many stent fractures have been observed in-vivo.  Below is a list of misconcepts that may contribute to the widely observed in-vivo fractures on Nitinol stents:

Zhigang Suo's picture

A field of material particles vs. a field of markers

In continuum mechanics, it is a common practice to view a body as a field of material particles, so that the continuum mechanics is phrased as an algorithm to determine the function x(X, t), where X is the name of a particle, and x is the place of the particle at time t.

MichelleLOyen's picture

Second International Conference on Mechanics of Biomaterials and Tissues

Abstracts are due April 27, 2007 for the Second International Conference on Mechanics of Biomaterials and Tissues, to take place on the Hawai’ian island of Kaua’i. Full call for papers is at the conference website. The conference is hosted by Elsevier and the launch of a new Elsevier journal on biomechanics will coincide with the timing of the meeting. (The official journal website is here.)

Harold S. Park's picture

Deformation of FCC Nanowires by Twinning and Slip

We present atomistic simulations of the tensile and compressive loading of single crystal FCC nanowires with <100> and <110> orientations to study the propensity of the nanowires to deform via twinning or slip.  By studying the deformation characteristics of three FCC materials with disparate stacking fault energies (gold, copper and nickel), we find that the deformation mechanisms in

Notes on Nonlinear Fracture Mechanics

These are the notes I wrote at the Technical University of Denmark in 1979. Zhigang Suo and I will be using these in the course on fracture and thin film mechanics (ES 242r) this spring (2007). This is a joint course with the University of Nebraska.

Engineering Sciences 242r: Fracture Mechanics of Thin Films and Composite Materials

Time. Thursday and Tuesday. 1:30-3:00 pm (Harvard University), 12:30-2:2:00 pm (University of Nebraska). First meeting: 1 February 2007

Place. Harvard University: Fairchild 102 (map). University of Nebraska: 111 Walter Scott Engineering Center

Course website (this page): node/754

Zhigang Suo's picture

Flip test: imagine continuum mechanics as a revolutionary idea

Let's say the world has only e-books, then someone introduces this technology called 'paper.' It's cheap, portable, lasts essentially forever, and requires no batteries. You can't write over it once it's been written on, but you buy more very cheaply. Wouldn't that technology come to dominate the market?

Yanfei Gao's picture

Symposium on "Mechanics of Nanofabrication and Nanostructure Growth" at the 2007 IMECE (ASME Meeting)

(Please also refer to node/711 for the introduction of this ASME meeting and some important changes. )

Mechanics has been playing a critical role in understanding the fabrication and reliability of nanostructured material systems, such as the self-assembly of quantum dots during heteroepitaxial thin film growth. Sponsored by the Elasticity Committee of Applied Mechanics Division, this symposium will identify opportunities and challenges in mechanics of materials that are motivated from a variety of novel and emerging nanofabrication and nanostructure growth methods. Presentations in experimental, theoretical, and computational studies are solicited in the following areas (but not limited to):

Jinxiong Zhou's picture

A subdomain collocation method based on Voronoi domain partition and reproducing kernel approximation

A subdomain collocation method based on Voronoi diagrams and reproducing kernel approximation is presented. The unkonwn field variables are approximated via reproducing kernel approximation. The body integration arising from the numerical evaluation of Galerkin weak form is converted into much cheaper contour integration along the boundary of each Voronoi cell. The Voronoi cells also provide an natural structure to perform h-adaptivity.

Interfacial Thermal Stresses in a Bi-Material Assembly with a Low-Yield-Stress Bonding Layer

An approximate predictive model is developed for the evaluation of the interfacial thermal stresses in a soldered bi-material assembly with a low-yield-stress bonding material. This material is considered linearly elastic at the strain level below the yield point and ideally plastic at the higher strains. The results of the analysis can be used for the assessment of the thermally induced stresses

On the thermomechanical coupling of shape memory alloys and shape memory alloys composites

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.

Zhigang Suo's picture

Texas Instruments will extend outsourcing model. Will more people lose jobs?

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News of Texas Instruments are intriguing. The world's largest maker of chips for mobile phones has just posted good fourth-quarter earnings. Despite the gains, the company said it will further increase efficiency and profitability by extending the model of outsourcing. This time it will include development of certain chips. The news on the Internet is rather terse. Will the company drastically reduce its research and development activities? Will many people lose jobs?

Mechanics Symposium in Beijing 2007

Some of you may be interested in attending this conference, and the post-conference tour. Details are described in the two attached files.

Xin-Lin Gao's picture

Symposium on Nanoscale, Biological, Cellular and Nonlinear Materials at the 2007 IMECE

The 2007 International Mechanical Engineering Congress and Exposition
November 11-16, 2007, Seattle, Washington, Sponsored by the Composites and Elasticity Committees, Applied Mechanics Division
Track 18-7 Nanoscale, Biological, Cellular and Nonlinear Materials

HCHan's picture

Adaptation of arteries to pressure changes

Arteries are living organs that can remodel themself in response to stress changes. Arterial remodeling is a big topic and this paper shows only a tip of the iceberg.

Harold S. Park's picture

Modeling Surface Stress Effects on Nanomaterials

We present a surface Cauchy-Born approach to modeling FCC metals with nanometer scale dimensions for which surface stresses contribute significantly to the overall mechanical response. The model is based on an extension of the traditional Cauchy-Born theory in which a surface energy term that is obtained from the underlying crystal structure and governing interatomic potential is used to augment the bulk energy.

Ken P. Chong's picture

2007 VISUALIZATION CHALLENGE NOW ACCEPTING ENTRIES

If you understand the power of visual communication to explain, explore, and extend our knowledge of the world around us, then you are invited to enter the 2007 Science & Engineering Visualization Challenge, co-sponsored by the National Science Foundation (NSF) and Science, published by the American Association for the Advancement of Science (AAAS). Entry deadline: 31 May 2007.

L. Roy Xu's picture

Faculty Position of Structures/ Mechanics/Materials at Vanderbilt University

Vanderbilt University, Department of Civil and Environmental Engineering is seeking candidates to fill a tenure-track faculty position commencing Fall 2007.  Appointment at the assistant professor level is anticipated but higher ranks will be considered for truly outstanding candidates.  The successful candidate will have research and teaching expertise in structures with a research focus in one or more of the following areas:  structural health monitoring, systems-scale failure analysis, dynamic control, computational mechanics and micromechanics, advanced mat

Blood Clot Mechanics at the Molecular Level

Cross-posted to Biocurious a blog about biology through the eyes of physicists.

The function and dysfunction of blood clots are often directly related to their mechanical properties: clots stop blood from flowing through wounds but can also break away (embolize) and block blood vessels causing stroke. Strength and plasticity are both important for ensuring the former is more common than the latter and so people have been studying the mechanics of clots for over 50 years. 

MichelleLOyen's picture

Introductory Biomechanics Courses

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In the early days of biomechanics, there probably were not many dedicated biomechanics courses and instead a regular mechanics curriculum was studied by people interested in tissues and biosystems. However, now that there are so many dedicated bioengineering programs at Universities throughout the world, it seems as though it is more likely that much of students' basic mechanics knowledge comes through dedicated biomechanics courses. This then in turn raises the interesting question of what is taught in these courses?

Jie Wang's picture

Phase field simulations of polarization switching-induced toughening in ferroelectric ceramics

Polarization switching-induced shielding or anti-shielding of an electrically permeable crack in a mono-domain ferroelectric material with the original polarization direction perpendicular to the crack is simulated by a phase field model based on the time-dependent Ginzburg-Landau equation. The domain wall energy and the long-range mechanical and electrical interactions between polarizations are taken into account. The phase field simulations exhibit a wing-shape- switched zone backwards the crack tip.

Ashkan Vaziri's picture

"Wrinkled hard skins on polymers created by Focused Ion Beam", PNAS , January 2007

A stiff skin forms on surface areas of a flat polydimethylsiloxane (PDMS) upon exposure to focused ion beam (FIB) leading to ordered surface wrinkles. By controlling the FIB fluence and area of exposure of the PDMS, one can create a variety of patterns in the wavelengths in the micrometer to submicrometer range, from simple one-dimensional wrinkles to peculiar and complex hierarchical nested wrinkles. Examination of the chemical composition of the exposed PDMS reveals that the stiff skin resembles amorphous silica. Moreover, upon formation, the stiff skin tends to expand in the direction perpendicular to the direction of ion beam irradiation. The consequent mismatch strain between the stiff skin and the PDMS substrate buckles the skin, forming the wrinkle patterns. The induced strains in the stiff skin are estimated by measuring the surface length in the buckled state. Estimates of the thickness and stiffness of the stiffened surface layer are estimated by using the theory for buckled films on compliant substrates. The method provides an effective and inexpensive technique to create wrinkled hard skin patterns on surfaces of polymers for various applications. Click here for access to the full article. See also the press release: Applied scientists create wrinkled 'skin' on polymers

Jonathan Zimmerman's picture

Summer Internship at Sandia National Labs, Livermore, CA

Sandia National Laboratories, California has established the Engineering Sciences Summer Institute (ESSI) program, in which applied mechanics, structural analysis and mechanical engineering graduate students are invited to spend a summer at SNL/CA performing research that would jointly benefit the students and Sandia. The program is nine years old and a description of the program is attached. Because of the funding base for this program, we can only consider students having U.S.

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