Interface crack between two elastic layers

A semi-infinite interface crack between two infinite isotropic elastic layers under general edge loading conditions is considered. The problem can be solved analytically except for a single real scalar independent of loading, which is then extracted from the numerical solution for one particular loading combination. Two applications of the basic solution are made which illustrate its utility: interface cracking driven by residual stress in a thin film on a substrate, and an analysis of a test specimen proposed recently for measuring interface toughness.

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Résumé On considère une fissure d'interface semi-infinie entre deux couches infinies élastiques et isotropes soumises à des conditions générales de sollicitations sur leurs bords. Le problème peut être solutionné par voie analytique, à l'exception d'un scalaire réel simple, indépendant de la charge, qui est extrait de la solution numérique relative à une combinaison particulière des sollicitations.On procède à deux applications de la solution de base qui illustrent son utilité: l'une est relative à une fissure d'interface soumise aux tensions résiduelles dans un film mince déposé sur un substrat. L'autre est l'analyse d'une éprouvette d'essai proposée récemment pour mesurer la ténacité de l'interface.

     

Tools for implementing network protocols

This paper describes two software tools—a message manager and a map manager—used to implement network protocols. The tools are provided as part of the x-kernel, an operating system kernel designed to support the construction and composition of protocols. For each tool, we briefly motivate the network task that needs to be done, give a high-level specification of the tool, outline the algorithms and data structures used to implement the tool and give concrete examples of how the tool is used to implement real protocols. We also demonstrate how the tools, even though they are designed for general use, perform efficiently.     

External psychologists: Best solution for some agencies?

Discusses the effective use of external (outside the agency) psychologists, with emphasis on general problems of psychologist–institution interaction. Examples of how these problems have been managed within one large childcare institution are presented, suggestions regarding how other institutions might better employ their own external psychologists are made, and drawbacks to psychological services being offered by external psychologists on a contractual basis are identified. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coexpression of Bcl-2, c-Myc, and p53 oncoproteins as prognostic discriminants in patients with colorectal carcinoma

Lanepitant is a high-affinity, selective neurokinin-1 receptor (NK-1) and is effective in the dural inflammation model of acute migraine. Lanepitant 30, 80, and 240 mg given orally was evaluated in a double-blind, placebo-controlled crossover study to determine its effect in reducing migraine pain and severity of associated symptoms. Outpatients treated four migraine headaches of moderate or severe pain intensity with study drug according to a randomization schedule. They recorded their pain intensity and severity of migraine-associated symptoms at 30, 60, 90, and 120 min. Although 53 patients were randomly allocated to a treatment sequence, only 40 patients completed all treatments. There was no statistically significant difference in improvement in migraine pain at any time for any of the treatments. Additionally, there was no change in severity of migraine-associated symptoms associated with lanepitant therapy. No adverse events could be attributed to lanepitant. Lanepitant was ineffective orally in treating acute migraine in this trial. This may be due to poor bioavailability during a migraine attack. Alternatively, the neurogenic inflammation hypothesis may not apply to migraine.     

The Mechanics of Indentation Induced Lateral Cracking

The mechanics governing the lateral cracks that form when a hard object plastically penetrates a ceramic is presented. The roles of indentation load, penetration depth, and work of indentation are all highlighted, as are the influences of the mechanical properties of the material. A closed form solution for cracking induced by expansion of a two-dimensional cavity is used to bring out essential features related to parametric dependence and scaling. The three-dimensional axisymmetric problem for an annular crack driven by a rigid spherical or conical indenter is solved using numerical methods. The region of highest tensile stress is identified corresponding to the location where a crack is most likely to nucleate. This location coincides with the depth below the surface where the crack will expand parallel to the surface under mode I conditions. The solutions have been substantiated by comparison with measurements of the cracks that form upon Vickers indentation. The basic formula for the crack radius has been used to predict trends in cracking upon static penetration and impact by a projectile. In both cases, the extent of the cracking is substantially diminished by increasing the toughness of the material. The yield strength has a much smaller effect. The cracks caused by penetration and the volume removed per impact both decrease marginally at higher yield strength.     

Gas leakage rate through reinforced concrete shear walls: Numerical study

Unlined reinforced concrete shear walls are often used as ‘tertiary boundaries’ in the United States Department of Energy (DOE) to house dangerous gases. An unanticipated event, such as an earthquake, may cause gases stored inside the walls to disperse into the environment resulting in excess pollution. To address this concern, in this paper, a methodology to numerically predict the gas leakage rate through these shear walls under lateral loading conditions is proposed. This methodology involves finite element and flow rate analysis. Strain distributions are obtained from the finite element analysis, and then used to simulate the crack characteristics on the concrete specimen. The flow rate through the damaged concrete specimen is then estimated using flow rate formulas available from the literature. Results from an experimental specimen are used to evaluate the methodology, and particularly its robustness in the flow rate estimation.     

Annoucement of a Round Robin on the Analysis of the Peel Test

There is some controversy over the analysis of the peel test when there is significant plastic deformation. To resolve this controversy a round robin on its analysis is announced contributions to which are invited. Details are given of test cases to be analysed.