WorldWideScience

Sample records for cement-bone interface micromechanics

  1. Experimental micromechanics of the cement-bone interface.

    NARCIS (Netherlands)

    Mann, K.A.; Miller, M.A.; Cleary, R.J.; Janssen, D.; Verdonschot, N.J.J.

    2008-01-01

    Despite the widespread use of cement as a means of fixation of implants to bone, surprisingly little is known about the micromechanical behavior in terms of the local interfacial motion. In this work, we utilized digital image correlation techniques to quantify the micromechanics of the cement-bone

  2. Finite element simulation of cement-bone interface micromechanics: A comparison to experimental results

    NARCIS (Netherlands)

    Janssen, Dennis; Mann, Kenneth A.; Verdonschot, Nico

    2009-01-01

    Recently, experiments were performed to determine the micromechanical behavior of the cement-bone interface under tension-compression loading conditions. These experiments were simulated using finite element analysis (FEA) to test whether the micromechanical response of the interface could be captur

  3. The behavior of the micro-mechanical cement-bone interface affects the cement failure in total hip replacement

    NARCIS (Netherlands)

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.

    2011-01-01

    In the current study, the effects of different ways to implement the complex micro-mechanical behavior of the cement-bone interface on the fatigue failure of the cement mantle were investigated. In an FEA-model of a cemented hip reconstruction the cement-bone interface was modeled and numerically im

  4. The effect of cement creep and cement fatigue damage on the micromechanics of the cement-bone interface.

    NARCIS (Netherlands)

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.

    2010-01-01

    The cement-bone interface provides fixation for the cement mantle within the bone. The cement-bone interface is affected by fatigue loading in terms of fatigue damage or microcracks and creep, both mostly in the cement. This study investigates how fatigue damage and cement creep separately affect th

  5. The mechanical effects of different levels of cement penetration at the cement-bone interface.

    NARCIS (Netherlands)

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.

    2010-01-01

    The mechanical effects of varying the depth of cement penetration in the cement-bone interface were investigated using finite element analysis (FEA) and validated using companion experimental data. Two FEA models of the cement-bone interface were created from micro-computed tomography data and the p

  6. Nanostructured interfaces for enhancing mechanical properties of composites: Computational micromechanical studies

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon

    2015-01-01

    Computational micromechanical studies of the effect of nanostructuring and nanoengineering of interfaces, phase and grain boundaries of materials on the mechanical properties and strength of materials and the potential of interface nanostructuring to enhance the materials properties are reviewed....... Several groups of materials (composites, nanocomposites, nanocrystalline metals, wood) are considered with view on the effect of nanostructured interfaces on their properties. The structures of various nanostructured interfaces (protein structures and mineral bridges in biopolymers in nacre...

  7. Viscoelastic micromechanical model for dynamic modulus prediction of asphalt concrete with interface effects

    Institute of Scientific and Technical Information of China (English)

    董满生; 高仰明; 李凌林; 王利娜; 孙志彬

    2016-01-01

    A viscoelastic micromechanical model is presented to predict the dynamic modulus of asphalt concrete (AC) and investigate the effect of imperfect interface between asphalt mastic and aggregates on the overall viscoelastic characteristics of AC. The linear spring layer model is introduced to simulate the interface imperfection. Based on the effective medium theory, the viscoelastic micromechanical model is developed by two equivalence processes. The present prediction is compared with available experimental data to verify the developed framework. It is found that the proposed model has the capability to predict the dynamic modulus of AC. Interface effect on the dynamic modulus of AC is discussed using the developed model. It is shown that the interfacial bonding strength has a significant influence on the global mechanical performance of AC, and that continued improvement in surface functionalization is necessary to realize the full potential of aggregates reinforcement.

  8. Micromechanics of the Interface in Fibre-Reinforced Cement Materials

    DEFF Research Database (Denmark)

    Stang, Henrik; Shah, S.P.

    1996-01-01

    the strength and ductility of the brittlematrix material rather than changing the overall stiffness,the ability of the fibres to interact with cracking processes in thematrix material is essential. Furthermore, since matrix cracking in afibre reinforced material can only take place with simultaneousinterfacial......In fibre reinforced brittle matrix composites the mechanicalbehaviour of the interface between the fibres and the matrix has avery significant influence on the overall mechanical behaviour ofthe composite material. Since brittle matrix composites are designed primarilywith the aim of improving...... debonding of the fibre-matrix interface, it is clear thatspecial emphasis should be put on the mechanical and strengthproperties of the interface. The present paper gives an overview of the different modelsapplied in the literature in the description of interfaces incementitious composite materials...

  9. Foam Micromechanics

    Energy Technology Data Exchange (ETDEWEB)

    Kraynik, A.M.; Neilsen, M.K.; Reinelt, D.A.; Warren, W.E.

    1998-11-03

    Foam evokes many different images: waves breaking at the seashore, the head on a pint of Guinness, an elegant dessert, shaving, the comfortable cushion on which you may be seated... From the mundane to the high tech, foams, emulsions, and cellular solids encompass a broad range of materials and applications. Soap suds, mayonnaise, and foamed polymers provide practical motivation and only hint at the variety of materials at issue. Typical of mukiphase materiaIs, the rheoIogy or mechanical behavior of foams is more complicated than that of the constituent phases alone, which may be gas, liquid, or solid. For example, a soap froth exhibits a static shear modulus-a hallmark of an elastic solid-even though it is composed primarily of two Newtonian fluids (water and air), which have no shear modulus. This apparent paradox is easily resolved. Soap froth contains a small amount of surfactant that stabilizes the delicate network of thin liq- uid films against rupture. The soap-film network deforms in response to a macroscopic strain; this increases interracial area and the corresponding sur- face energy, and provides the strain energy of classical elasticity theory [1]. This physical mechanism is easily imagined but very challenging to quantify for a realistic three-dimensional soap froth in view of its complex geome- try. Foam micromechanics addresses the connection between constituent properties, cell-level structure, and macroscopic mechanical behavior. This article is a survey of micromechanics applied to gas-liquid foams, liquid-liquid emulsions, and cellular solids. We will focus on static response where the foam deformation is very slow and rate-dependent phenomena such as viscous flow can be neglected. This includes nonlinear elasticity when deformations are large but reversible. We will also discuss elastic- plastic behavior, which involves yield phenomena. Foam structures based on polyhedra packed to fill space provide a unify- ing geometrical theme. Because a two

  10. Compound floating pivot micromechanisms

    Science.gov (United States)

    Garcia, Ernest J.

    2001-04-24

    A new class of tilting micromechanical mechanisms have been developed. These new mechanisms use compound floating pivot structures to attain far greater tilt angles than are practical using other micromechanical techniques. The new mechanisms are also capable of bi-directional tilt about multiple axes.

  11. $\\mu$MECH Micromechanics Library

    CERN Document Server

    Svoboda, Ladislav; Janda, Tomáš; Vorel, Jan; Novák, Jan

    2016-01-01

    The paper presents the project of an open source C/C++ library of analytical solutions to micromechanical fields within media with ellipsoidal heterogeneities. The solutions are based on Eshelby's stress-free, in general polynomial, eigenstrains and equivalent inclusion method. To some extent, the interactions among inclusions in a non-dilute medium are taken into account by means of the self-compatibility algorithm. Moreover, the library is furnished with a powerful I/O interface and conventional homogenization tools. Advantages and limitations of the implemented strategies are addressed through comparisons with reference solutions by means of the Finite Element Method.

  12. Micromechanisms with floating pivot

    Science.gov (United States)

    Garcia, Ernest J.

    2001-03-06

    A new class of tilting micromechanical mechanisms have been developed. These new mechanisms use floating pivot structures to relieve some of the problems encountered in the use of solid flexible pivots.

  13. Biodegradable micromechanical sensors

    DEFF Research Database (Denmark)

    Keller, Stephan Sylvest; Greve, Anders; Schmid, Silvan;

    The development of biopolymers for food packaging, medical engineering or drug delivery is a growing field of research [1]. At the same time, the interest in methods for detailed analysis of biopolymers is increasing. Micromechanical sensors are versatile tools for the characterization of mechani......The development of biopolymers for food packaging, medical engineering or drug delivery is a growing field of research [1]. At the same time, the interest in methods for detailed analysis of biopolymers is increasing. Micromechanical sensors are versatile tools for the characterization...... of biopolymers to microfabrication is challenging, as these polymers are affected by common processes such as photolithography or wet etching. Here, we present two methods for fabrication of biodegradable micromechanical sensors. First, we fabricated bulk biopolymer microcantilevers using nanoimprint lithography...

  14. Micromechanics of hierarchical materials

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon, Jr.

    2012-01-01

    A short overview of micromechanical models of hierarchical materials (hybrid composites, biomaterials, fractal materials, etc.) is given. Several examples of the modeling of strength and damage in hierarchical materials are summarized, among them, 3D FE model of hybrid composites...... with nanoengineered matrix, fiber bundle model of UD composites with hierarchically clustered fibers and 3D multilevel model of wood considered as a gradient, cellular material with layered composite cell walls. The main areas of research in micromechanics of hierarchical materials are identified, among them......, the investigations of the effects of load redistribution between reinforcing elements at different scale levels, of the possibilities to control different material properties and to ensure synergy of strengthening effects at different scale levels and using the nanoreinforcement effects. The main future directions...

  15. A Micromechanical RF Channelizer

    OpenAIRE

    Akgul, Mehmet

    2014-01-01

    AbstractA Micromechanical RF ChannelizerbyMehmet AkgulDoctor of Philosophy in Engineering - Electrical Engineering and Computer SciencesUniversity of California, BerkeleyProfessor Clark T.-C. Nguyen, ChairThe power consumption of a radio generally goes as the number and strength of the RF signals it must process. In particular, a radio receiver would consume much less power if the signal presented to its electronics contained only the desired signal in a tiny percent bandwidth frequency chann...

  16. Micromechanics of hearing

    Science.gov (United States)

    Hudspeth, A. J.

    2015-12-01

    The following summarizes the key points addressed during a tutorial session on the Micromechanics of Hearing that took place at the 12th International Workshop on the Mechanics of Hearing held at Cape Sounio, Greece, in June 2014. The tutorial was intended to present an overview of basic ideas and to address topics of current interest relevant to the Workshop. The session was recorded, and the audio file and accompanying visual content of the presentation can be found in the Mechanics of Hearing Digital Library (www.mechanicsofhearing.org).

  17. A Micromechanical RF Channelizer

    Science.gov (United States)

    Akgul, Mehmet

    The power consumption of a radio generally goes as the number and strength of the RF signals it must process. In particular, a radio receiver would consume much less power if the signal presented to its electronics contained only the desired signal in a tiny percent bandwidth frequency channel, rather than the typical mix of signals containing unwanted energy outside the desired channel. Unfortunately, a lack of filters capable of selecting single channel bandwidths at RF forces the front-ends of contemporary receivers to accept unwanted signals, and thus, to operate with sub-optimal efficiency. This dissertation focuses on the degree to which capacitive-gap transduced micromechanical resonators can achieve the aforementioned RF channel-selecting filters. It aims to first show theoretically that with appropriate scaling capacitive-gap transducers are strong enough to meet the needed coupling requirements; and second, to fully detail an architecture and design procedure needed to realize said filters. Finally, this dissertation provides an actual experimentally demonstrated RF channel-select filter designed using the developed procedures and confirming theoretical predictions. Specifically, this dissertation introduces four methods that make possible the design and fabrication of RF channel-select filters. The first of these introduces a small-signal equivalent circuit for parallel-plate capacitive-gap transduced micromechanical resonators that employs negative capacitance to model the dependence of resonance frequency on electrical stiffness in a way that facilitates the analysis of micromechanical circuits loaded with arbitrary electrical impedances. The new circuit model not only correctly predicts the dependence of electrical stiffness on the impedances loading the input and output electrodes of parallel-plate capacitive-gap transduced micromechanical device, but does so in a visually intuitive way that identifies current drive as most appropriate for

  18. Micromechanism of Ferroelectrics

    Institute of Scientific and Technical Information of China (English)

    XiCHEN; Dai-NingFANG; 等

    1997-01-01

    As one of the most important advanced electronic materials,ferroelectric and its nonlinear behavior have always been an interesting subject of study in the field of physics and materials science.Recently ferroelectrics has been applied more widely with the rapid development of the Smart/Intelligent materials,As the elementary components of sensors and actuators,ferroelectrics may be subjected to high stresses and electric fields and performance failure may rasult due to the complexity of the environment where the Smart/Intelligent materials are used.Therefore,it is very important to describe the constitutive behavior of the feroelectrics,which can serve as important basis for the design and application of the Smart/Intelligent materials.The main attempt here is to establish the explicit form of constitutive laws of ferroelectric single crystal in the framework of the micromechanics internal variable theory[1],After the “soft” approximation.this model can also be used to exhibit the nonlinear properties of ferroelectric ceramics.

  19. Micromechanics of shear banding

    Energy Technology Data Exchange (ETDEWEB)

    Gilman, J.J.

    1992-08-01

    Shear-banding is one of many instabilities observed during the plastic flow of solids. It is a consequence of the dislocation mechanism which makes plastic flow fundamentally inhomogeneous, and is exacerbated by local adiabatic heating. Dislocation lines tend to be clustered on sets of neighboring glide planes because they are heterogeneously generated; especially through the Koehler multiple-cross-glide mechanism. Factors that influence their mobilities also play a role. Strain-hardening decreases the mobilities within shear bands thereby tending to spread (delocalize) them. Strain-softening has the inverse effect. This paper reviews the micro-mechanisms of these phenomena. It will be shown that heat production is also a consequence of the heterogeneous nature of the microscopic flow, and that dislocation dipoles play an important role. They are often not directly observable, but their presence may be inferred from changes in thermal conductivity. It is argued that after deformation at low temperatures dipoles are distributed a la Pareto so there are many more small than large ones. Instability at upper yield point, the shapes of shear-band fronts, and mechanism of heat generation are also considered. It is shown that strain-rate acceleration plays a more important role than strain-rate itself in adiabatic instability.

  20. Introduction to micromechanisms and microactuators

    CERN Document Server

    Ghosh, Amitabha

    2015-01-01

    This book presents a basic introduction to micromechanisms and microactuators, particularly to their basic configurations and design. This book fills the persisting gap in the published literature on the mechanical manipulative aspects of micromechanisms. It also helps in offering specialized introductory courses on micromechanisms and microactuators not as part of MEMS sensing devices, but as mechanical manipulative systems. The level of the book is suitable for use in both undergraduate and introductory graduate programmes. The book presents an overview of miniaturization and scaling laws, basic design principles of micro-sized mechanisms and actuators, micro-fabrication processes, and some futuristic issues. The volume contains a large number of figures and illustrations for easy understanding by the readers. It will also be useful to researchers and professionals looking for an introduction to the topic.

  1. Determining Micromechanical Strain in Nitinol

    Energy Technology Data Exchange (ETDEWEB)

    Strasberg, Matthew; /SLAC

    2006-09-27

    Nitinol is a superelastic alloy made of equal parts nickel and titanium. Due to its unique shape memory properties, nitinol is used to make medical stents, lifesaving devices used to allow blood flow in occluded arteries. Micromechanical models and even nitinol-specific finite element analysis (FEA) software are insufficient for unerringly predicting fatigue and resultant failure. Due to the sensitive nature of its application, a better understanding of nitinol on a granular scale is being pursued through X-ray diffraction techniques at the Stanford Synchrotron Radiation Laboratory (SSRL) at the Stanford Linear Accelerator Center (SLAC). Through analysis of powder diffraction patterns of nitinol under increasing tensile loads, localized strain can be calculated. We compare these results with micromechanical predictions in order to advance nitinol-relevant FEA tools. From this we hope to gain a greater understanding of how nitinol fatigues under multi-axial loads.

  2. Micro-Mechanical Temperature Sensors

    DEFF Research Database (Denmark)

    Larsen, Tom

    Temperature is the most frequently measured physical quantity in the world. The field of thermometry is therefore constantly evolving towards better temperature sensors and better temperature measurements. The aim of this Ph.D. project was to improve an existing type of micro-mechanical temperature...... sensor or to develop a new one. Two types of micro-mechanical temperature sensors have been studied: Bilayer cantilevers and string-like beam resonators. Both sensor types utilize thermally generated stress. Bilayer cantilevers are frequently used as temperature sensors at the micro-scale, and the goal....... The reduced sensitivity was due to initial bending of the cantilevers and poor adhesion between the two cantilever materials. No further attempts were made to improve the sensitivity of bilayer cantilevers. The concept of using string-like resonators as temperature sensors has, for the first time, been...

  3. Micromechanics and Piezo Enhancements of HyperSizer

    Science.gov (United States)

    Arnold, Steven M.; Bednarcyk, Brett A.; Yarrington, Phillip; Collier, Craig S.

    2006-01-01

    The commercial HyperSizer aerospace-composite-material-structure-sizing software has been enhanced by incorporating capabilities for representing coupled thermal, piezoelectric, and piezomagnetic effects on the levels of plies, laminates, and stiffened panels. This enhancement is based on a formulation similar to that of the pre-existing HyperSizer capability for representing thermal effects. As a result of this enhancement, the electric and/or magnetic response of a material or structure to a mechanical or thermal load, or its mechanical response to an applied electric or magnetic field can be predicted. In another major enhancement, a capability for representing micromechanical effects has been added by establishment of a linkage between HyperSizer and Glenn Research Center s Micromechanics Analysis Code With Generalized Method of Cells (MAC/GMC) computer program, which was described in several prior NASA Tech Briefs articles. The linkage enables Hyper- Sizer to localize to the fiber and matrix level rather than only to the ply level, making it possible to predict local failures and to predict properties of plies from those of the component fiber and matrix materials. Advanced graphical user interfaces and database structures have been developed to support the new HyperSizer micromechanics capabilities.

  4. interfaces

    Directory of Open Access Journals (Sweden)

    Dipayan Sanyal

    2005-01-01

    macroscopic conservation equations with an order parameter which can account for the solid, liquid, and the mushy zones with the help of a phase function defined on the basis of the liquid fraction, the Gibbs relation, and the phase diagram with local approximations. Using the above formalism for alloy solidification, the width of the diffuse interface (mushy zone was computed rather accurately for iron-carbon and ammonium chloride-water binary alloys and validated against experimental data from literature.

  5. Micromechanics-BEM Analysis for Piezoelectric Composites

    Institute of Scientific and Technical Information of China (English)

    QIN Qinghua

    2005-01-01

    The effective material properties of piezoelectric composites are predicted using micromechanics models of the composite structure combined with a boundary element method (BEM) solution of the governing equation. The composites consist of inclusion and matrix phases. The micromechanics method gives formulae for the overall material constants as functions of the concentration matrix, while the boundary element simulation gives numerical solutions of the boundary displacement and electric potential equations for inclusion or hole problems. Numerical results for a piezoelectric plate with circular inclusions are presented to illustrate applications of the proposed micromechanics-BEM formulation.

  6. Cantilever-like micromechanical sensors

    DEFF Research Database (Denmark)

    Boisen, Anja; Dohn, Søren; Keller, Stephan Sylvest;

    2011-01-01

    The field of cantilever-based sensing emerged in the mid-1990s and is today a well-known technology for label-free sensing which holds promise as a technique for cheap, portable, sensitive and highly parallel analysis systems. The research in sensor realization as well as sensor applications has...... increased significantly over the past 10 years. In this review we will present the basic modes of operation in cantilever-like micromechanical sensors and discuss optical and electrical means for signal transduction. The fundamental processes for realizing miniaturized cantilevers are described with focus...... on silicon-and polymer-based technologies. Examples of recent sensor applications are given covering such diverse fields as drug discovery, food diagnostics, material characterizations and explosives detection....

  7. 3rd Conference on Microactuators and Micromechanisms

    CERN Document Server

    Ananthasuresh, Gondi; Corves, Burkhard; Petuya, Victor

    2015-01-01

    This book contains applications of micromechanisms and microactuators in several very modern technical fields such as mechatronics, biomechanics, machines, micromachines, robotics and apparatuses. In connection with its topic, the work combines the theoretical results with experimental tests on micromechanisms and microactuators. The book presents the most recent research advances in Machine and Mechanisms Science. It includes the accepted reviewed papers of researchers specialized in the topics of the conference: microactuators and micro-assembly, micro sensors involving movable solids, micro-opto-mechanical devices, mechanical tools for cell and tissue studies, micromanipulation and micro-stages, micro-scale flight and swimming, micro-robotics and surgical tools, micron-scale power generation, miniature manufacturing machines, micromechatronics and micro-mechanisms, biomechanics micro and nano scales and control issues in microsystems.  The presented applications of micromechanisms and microactuators i...

  8. Variational Asymptotic Micromechanics Modeling of Composite Materials

    OpenAIRE

    Tang, Tian

    2008-01-01

    The issue of accurately determining the effective properties of composite materials has received the attention of numerous researchers in the last few decades and continues to be in the forefront of material research. Micromechanics models have been proven to be very useful tools for design and analysis of composite materials. In the present work, a versatile micromechanics modeling framework, namely, the Variational Asymptotic Method for Unit Cell Homogenization (VAMUCH), has been invented a...

  9. Modeling of multi-inclusion composites with interfacial imperfections:Micromechanical and numerical simulations

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A micromechanical approach based on a two-layer built-in model and a numerical simulation based on boundary element method are proposed to predict the effective properties of the multi-inclusion composite with imperfect interfaces.The spring model is introduced to simulate the interface imperfection.These two methods are compared with each other,and good agreement is achieved.The effects of interface spring stiffness,volume ratio and stiffness of inclusions on the micro-and macro-mechanical behaviors of fiber-reinforced composites are investigated.It is shown that the developed micromechanical method is very comprehensive and efficient for fast prediction of effective properties of composites,while the numerical method is very accurate in detailed modeling of the mechanical behavior of composites with multiple inclusions.

  10. Materials Research Society Proceedings: Interfaces in Composites, volume 170

    Science.gov (United States)

    Pantano, Carlo G.; Chen, Eric J. H.

    1990-11-01

    Reports on the following topics are presented: (1) micromechanics of interfaces; (2) characterization of interfaces; (3) interface reactions in ceramic and metal systems; (4) interface effects in ceramic and metal matrix composites; and (5) interface effects in polymer matrix composites. A list of the materials research society symposium proceedings is also presented.

  11. Micromechanics and poroelasticity of hydrated cellulose networks.

    Science.gov (United States)

    Lopez-Sanchez, P; Rincon, Mauricio; Wang, D; Brulhart, S; Stokes, J R; Gidley, M J

    2014-06-01

    The micromechanics of cellulose hydrogels have been investigated using a new rheological experimental approach, combined with simulation using a poroelastic constitutive model. A series of mechanical compression steps at different strain rates were performed as a function of cellulose hydrogel thickness, combined with small amplitude oscillatory shear after each step to monitor the viscoelasticity of the sample. During compression, bacterial cellulose hydrogels behaved as anisotropic materials with near zero Poisson's ratio. The micromechanics of the hydrogels altered with each compression as water was squeezed out of the structure, and microstructural changes were strain rate-dependent, with increased densification of the cellulose network and increased cellulose fiber aggregation observed for slower compressive strain rates. A transversely isotropic poroelastic model was used to explain the observed micromechanical behavior, showing that the mechanical properties of cellulose networks in aqueous environments are mainly controlled by the rate of water movement within the structure. PMID:24784575

  12. Micromechanical failure in fiber-reinforced composites

    DEFF Research Database (Denmark)

    Ashouri Vajari, Danial

    Micromechanical failure mechanisms occurring in unidirectional fiber-reinforced composites are studied by means of the finite element method as well as experimental testing. This study highlights the effect of micro-scale features such as fiber/matrix interfacial debonding, matrix cracking......, the failure locus of the composite lamina under different loading conditions is obtained by means of computational micromechanics and compared with the predictions of Puck’s model. The results are in very good agreement with the predictions of Puck’s model under different interfiber failure modes. In order...

  13. Mechanical properties of Composite Engineering Structures by Multivolume Micromechanical Modelling

    Directory of Open Access Journals (Sweden)

    B. Novotný

    2000-01-01

    Full Text Available Engineering structures often consist of elements having the character of a periodically repeated composite structure. A multivolume micromechanical model based on a representative cell division into r1 × r2 × r3 subcells with different elastic material properties has been used in this paper to derive macromechanical characteristics of the composite construction response to applied load and temperature changes. The multivolume method is based on ensuring the equilibrium of the considered volume on an average basis. In the same (average way, the continuity conditions of displacements and tractions at the interfaces between subcells and between neighboring representative elements are imposed, resulting in a homogenization procedure that eliminates the discrete nature of the composite model. The details of the method are shown for the case of a concrete block pavement. A parametric study is presented illustrating the influence of joint thickness, joint filling material properties and the quality of bonding between block and filler elements.

  14. Theoretical analysis and experiment of micromechanics and mechanics-optics coupling of distributed optic-fiber crack sensing

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The micromechanical behaviors and mechanics-optics coupling effects of optic-fiber-concrete complex in the distributed optic-fiber sensing concrete-crack technology,which was used in health monitoring of Wu Gorge Bridge on Yangtze River and a large dam successfully,have been investigated.A micromechanical theoretical analysis method and micromechanical frictional contact bi-interface model,as well as a modified optical theoretical analysis method of the mechanics-optics coupling effects are presented.A series of verification experiments,including mechanical experiments and mechanics-optics coupling experiments,have been preformed.The results of micromechanical theoretical analysis and the analysis of the modified theory of mechanics-optics coupling along with mechanical and optical experimental data are shown to be in close agreement.Both the micromechanical theory and the modified theory of mechanics-optics coupling with their analysis methods can not only enhance credibility of this novel distributed sensing technology but also provide a way to understand its sensing mechanism and optimize its technical details and system.

  15. Micromechanical photothermal analyser of microfluidic samples

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to a micromechanical photothermal analyser of microfluidic samples comprising an oblong micro-channel extending longitudinally from a support element, the micro-channel is made from at least two materials with different thermal expansion coefficients, wherein the...

  16. Micromechanical study of plasticity of granular materials

    NARCIS (Netherlands)

    Kruyt, N.P.

    2010-01-01

    Plastic deformation of granular materials is investigated from the micromechanical viewpoint, in which the assembly of particles and interparticle contacts is considered as a mechanical structure. This is done in three ways. Firstly, by investigating the degree of redundancy of the system by compari

  17. Concrete Failure Modeling Based on Micromechanical Approach Subjected to Static Loading

    Directory of Open Access Journals (Sweden)

    Endah Wahyuni

    2010-02-01

    Full Text Available In this paper, a micromechanical model based on the Mori-Tanaka method and the spring-layer model is developed to study the stress-strain behavior of concrete. The concrete is modeled as a two-phase composite. And the failure of concrete is categorized as mortar failure and interface failure. The research presents a method for estimating the modulus of concrete under its whole loading process. The proposed micromechanical model owns the good capabilities for predicting the entire response of concrete under uniaxial compression. It is suitable that tensile strain is as the criterion of concrete failure and the prediction of crack direction also fits with experimental phenomenon.

  18. PUBLISHER'S ANNOUNCEMENT: A revised scope for Journal of Micromechanics and Microengineering A revised scope for Journal of Micromechanics and Microengineering

    Science.gov (United States)

    Forbes, Ian

    2010-05-01

    Journal of Micromechanics and Microengineering is well known for publishing excellent work in highly competitive timescales. The journal's coverage has consistently evolved to reflect the current state of the field, and from May 2010 it will revisit its scope once again. The aims of the journal remain unchanged, however: to be the first choice of authors and readers in MEMS and micro-scale research. The new scope continues to focus on highlighting the link between fabrication technologies and their capacity to create novel devices. This link will be considered paramount in the journal, and both prospective authors and readers should let it serve as an inspiration to them. The burgeoning fields of NEMS and nano-scale engineering are more explicitly supported in the new scope. Research which ten years ago would have been considered science fiction has, through the tireless efforts of the community, become reality. The Editorial Board feel it is important to reflect the growing significance of this work in the scope. The new scope, drafted by Editor-in-Chief Professor Mark Allen, and approved by the Editorial Board, is as follows: Journal of Micromechanics and Microengineering covers all aspects of microelectromechanical structures, devices, and systems, as well as micromechanics and micromechatronics. The journal focuses on original work in fabrication and integration technologies, on the micro- and nano-scale. The journal aims to highlight the link between new fabrication technologies and their capacity to create novel devices. Original work in microengineering and nanoengineering is also reported. Such work is defined as applications of these fabrication and integration technologies to structures in which key attributes of the devices or systems depend on specific micro- or nano-scale features. Such applications span the physical, chemical, electrical and biological realms. New fabrication and integration techniques for both silicon and non-silicon materials are

  19. HPC in Computational Micromechanics of Composite Materials

    OpenAIRE

    Blaheta, R. (Radim); Kolcun, A. (Alexej); Jakl, O. (Ondřej); Souček, K; Starý, J. (Jiří); Georgiev, J.

    2015-01-01

    By micromechanics we understand analysis of the macroscale response of materials through investigation of processes in their microstructure. Here by the macroscale, we mean the scale of applications, where we solve engineering problems involving materials. Examples could be analysis of aircraft constructions with different composite materials and analysis of rock behaviour and concrete properties in geo- and civil engineering applications. Analysis of bio-materials with many medicine...

  20. Micromechanics and Microactuators : Proceedings of MAMM 2010

    CERN Document Server

    Corves, Burkhard; Petuya, Victor

    2012-01-01

    This book contains selected papers presented at MAMM 2010, the First Workshop on Microactuators and Micromechanisms. This workshop has brought together scientists, industry experts and students and has provided a special opportunity for know-how exchange and collaboration in various disciplines referring to microsystems technology. The conference was organized by the Technical Committees of Mechanical Transmissions and Micromachines under the patronage of IFToMM, the International Federation for the Promotion of Mechanism and Machine Science.

  1. Micromechanics-Based Structural Analysis (FEAMAC) and Multiscale Visualization within Abaqus/CAE Environment

    Science.gov (United States)

    Arnold, Steven M.; Bednarcyk, Brett A.; Hussain, Aquila; Katiyar, Vivek

    2010-01-01

    A unified framework is presented that enables coupled multiscale analysis of composite structures and associated graphical pre- and postprocessing within the Abaqus/CAE environment. The recently developed, free, Finite Element Analysis--Micromechanics Analysis Code (FEAMAC) software couples NASA's Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC) with Abaqus/Standard and Abaqus/Explicit to perform micromechanics based FEA such that the nonlinear composite material response at each integration point is modeled at each increment by MAC/GMC. The Graphical User Interfaces (FEAMAC-Pre and FEAMAC-Post), developed through collaboration between SIMULIA Erie and the NASA Glenn Research Center, enable users to employ a new FEAMAC module within Abaqus/CAE that provides access to the composite microscale. FEA IAC-Pre is used to define and store constituent material properties, set-up and store composite repeating unit cells, and assign composite materials as sections with all data being stored within the CAE database. Likewise FEAMAC-Post enables multiscale field quantity visualization (contour plots, X-Y plots), with point and click access to the microscale i.e., fiber and matrix fields).

  2. Wireless actuation of bulk acoustic modes in micromechanical resonators

    Science.gov (United States)

    Mateen, Farrukh; Brown, Benjamin; Erramilli, Shyamsunder; Mohanty, Pritiraj

    2016-08-01

    We report wireless actuation of a Lamb wave micromechanical resonator from a distance of over 1 m with an efficiency of over 15%. Wireless actuation of conventional micromechanical resonators can have broad impact in a number of applications from wireless communication and implantable biomedical devices to distributed sensor networks.

  3. Micromechanical Simulation of Thermal Cyclic Behavior of ZrO2/Ti Functionally Graded Thermal Barrier Coatings

    OpenAIRE

    Hideaki Tsukamoto

    2015-01-01

    This study numerically investigates cyclic thermal shock behavior of ZrO2/Ti functionally graded thermal barrier coatings (FG TBCs) based on a nonlinear mean-field micromechanical approach, which takes into account the time-independent and dependent inelastic deformation, such as plasticity of metals, creep of metals and ceramics, and diffusional mass flow at the ceramic/metal interface. The fabrication processes for the FG TBCs have been also considered in the simulation. The effect of creep...

  4. Cochlear Micromechanics (Part II): A moderated discussion

    Science.gov (United States)

    Gummer, Anthony W.; Mountain, David C.

    2015-12-01

    The following is an edited transcript of a recorded discussion session on the topic of "Cochlear Micromechanics". The discussion, moderated by the authors, took place at the 12th International Workshop on the Mechanics of Hearing held at Cape Sounio, Greece, in June 2014. All participants knew that the session was being recorded. In view of both the spontaneous nature of the discussion and the editing, however, this transcript may not represent the considered or final views of the participants, and may not represent a consensus of experts in the field. The reader is advised to consult additional independent publications.

  5. Cochlear Micromechanics (Part I): A moderated discussion

    Science.gov (United States)

    Neely, Stephen T.

    2015-12-01

    The following is an edited transcript of a recorded discussion session on the topic of "Cochlear Micromechanics". The discussion, moderated by the author, took place at the 12th International Workshop on the Mechanics of Hearing held at Cape Sounio, Greece, in June 2014. All participants knew that the session was being recorded. In view of both the spontaneous nature of the discussion and the editing, however, this transcript may not represent the considered or final views of the participants, and may not represent a consensus of experts in the field. The reader is advised to consult additional independent publications.

  6. Synchronization of Delay-coupled Micromechanical Oscillators

    CERN Document Server

    Shah, Shreyas Y; Rand, Richard; Lipson, Michal

    2015-01-01

    Delay-coupled oscillators exhibit unique phenomena that are not present in systems without delayed coupling. In this paper, we experimentally demonstrate mutual synchronisation of two free-running micromechanical oscillators, coupled via light with a total delay 139 ns which is approximately four and a half times the mechanical oscillation time period. This coupling delay, imposed by a finite speed of propagation of light, induces multiple stable states of synchronised oscillations, each with a different oscillation frequency. These states can be accessed by varying the coupling strengths. Our result could enable applications in reconfigurable radio-frequency networks, and novel computing concepts.

  7. A micromechanical proof-of-principle experiment for measuring the gravitational force of milligram masses

    Science.gov (United States)

    Schmöle, Jonas; Dragosits, Mathias; Hepach, Hans; Aspelmeyer, Markus

    2016-06-01

    This paper addresses a simple question: how small can one make a gravitational source mass and still detect its gravitational coupling to a nearby test mass? We describe an experimental scheme based on micromechanical sensing to observe gravity between milligram-scale source masses, thereby improving the current smallest source mass values by three orders of magnitude and possibly even more. We also discuss the implications of such measurements both for improved precision measurements of Newton’s constant and for a new generation of experiments at the interface between quantum physics and gravity.

  8. A micromechanical proof-of-principle experiment for measuring the gravitational force of milligram masses

    CERN Document Server

    Schmöle, Jonas; Hepach, Hans; Aspelmeyer, Markus

    2016-01-01

    This paper addresses a simple question: how small can one make a gravitational source mass and still detect its gravitational coupling to a nearby test mass? We describe an experimental scheme based on micromechanical sensing that should allow to observe gravity between milligram-scale source masses, thereby improving the current smallest source mass values by three orders of magnitude and possibly even more. We also discuss the implications of such measurements both for improved precision measurements of Newton's constant and for a new generation of experiments at the interface between quantum physics and gravity.

  9. Micromechanical and Nanoscratch Behavior of SiCp Dispersed Metal Matrix Composites

    Science.gov (United States)

    Chatterjee, Subhranshu; Chabri, Sumit; Chakraborty, Himel; Bhowmik, Nandagopal; Sinha, Arijit

    2015-09-01

    Micromechanical response of silicon carbide particle dispersed Al/Mg/Ti/Cu composite, synthesized by powder metallurgy technique was investigated. A correlation between their microhardness and nanomechanical properties at submicron length scale was established. Hardening effect of SiC particles on the hardness, elastic modulus, recovery index, and plastic energy of the matrices was prominent and may be due to the interactions between geometrically necessary and statistically stored dislocations along with their impediment with dispersoids-matrix interface. The elastic recovery obtained from nanoscratch measurement was also correlated with the recovery parameter, which was derived from the nanoindentation of the composite compacts.

  10. Experimental and numerical study of the micro-mechanical failure in composites

    DEFF Research Database (Denmark)

    Ashouri Vajari, Danial; Martyniuk, Karolina; Sørensen, Bent F.;

    2013-01-01

    The fibre/matrix interfacial debonding is found to be the first microscale failure mechanism leading to subsequent macroscale transverse cracks in composite materials under tensile load. In this paper, the micromechanical interface failure in fiber-reinforced composites is studied experimentally....... This study is based on the comparison between the results of numerical modeling and those corresponding to the experimental tests by employing two parameters: The angle from the load direction to the crack tip and the crack normal opening. This comparison aims to investigate the interfacial properties...

  11. Hybrid circuit cavity quantum electrodynamics with a micromechanical resonator.

    Science.gov (United States)

    Pirkkalainen, J-M; Cho, S U; Li, Jian; Paraoanu, G S; Hakonen, P J; Sillanpää, M A

    2013-02-14

    Hybrid quantum systems with inherently distinct degrees of freedom have a key role in many physical phenomena. Well-known examples include cavity quantum electrodynamics, trapped ions, and electrons and phonons in the solid state. In those systems, strong coupling makes the constituents lose their individual character and form dressed states, which represent a collective form of dynamics. As well as having fundamental importance, hybrid systems also have practical applications, notably in the emerging field of quantum information control. A promising approach is to combine long-lived atomic states with the accessible electrical degrees of freedom in superconducting cavities and quantum bits (qubits). Here we integrate circuit cavity quantum electrodynamics with phonons. Apart from coupling to a microwave cavity, our superconducting transmon qubit, consisting of tunnel junctions and a capacitor, interacts with a phonon mode in a micromechanical resonator, and thus acts like an atom coupled to two different cavities. We measure the phonon Stark shift, as well as the splitting of the qubit spectral line into motional sidebands, which feature transitions between the dressed electromechanical states. In the time domain, we observe coherent conversion of qubit excitation to phonons as sideband Rabi oscillations. This is a model system with potential for a quantum interface, which may allow for storage of quantum information in long-lived phonon states, coupling to optical photons or for investigations of strongly coupled quantum systems near the classical limit.

  12. Wear Micro-Mechanisms of Composite WC-Co/Cr - NiCrFeBSiC Coatings. Part II: Cavitation Erosion

    OpenAIRE

    D. Kekes; P. Psyllaki; M. Vardavoulias; Vekinis, G.

    2014-01-01

    Composite coatings with five different proportions of WC-Co/Cr and NiCrFeBSiC components were deposited on stainless steel by HVOF spraying. Cavitation erosion tests were performed and the material removal micro-mechanisms were identified by SEM of both the eroded areas and the specimens’ cross-sections. Waves’ propagation and deflection at the weak interfaces within the coatings resulted in local tensile stresses perpendicular to the interface direction that eventually led to material remova...

  13. Micromechanics and dislocation theory in anisotropic elasticity

    CERN Document Server

    Lazar, Markus

    2016-01-01

    In this work, dislocation master-equations valid for anisotropic materials are derived in terms of kernel functions using the framework of micromechanics. The second derivative of the anisotropic Green tensor is calculated in the sense of generalized functions and decomposed into a sum of a $1/R^3$-term plus a Dirac $\\delta$-term. The first term is the so-called "Barnett-term" and the latter is important for the definition of the Green tensor as fundamental solution of the Navier equation. In addition, all dislocation master-equations are specified for Somigliana dislocations with application to 3D crack modeling. Also the interior Eshelby tensor for a spherical inclusion in an anisotropic material is derived as line integral over the unit circle.

  14. Generation of Random Numbers by Micromechanism

    Science.gov (United States)

    Mita, Makoto; Toshiyoshi, Hiroshi; Ataka, Manabu; Fujita, Hiroyuki

    We have successfully developed a novel micromechanism of random number generator (RNG) by using the silicon micromachining technique. The MEM(Micro Electro Mechanical)RNG produce a series of random numbers by using the pull-in instability of electrostatic actuation operated with a typical dc 150 volt. The MEM RNG is made by the deep reactive ion etching of a silicon-on-insulator(SOI) wafer, and is very small compared with the conventional RNG hardware based on the randomness of thermal noise or isotope radiation. Quality of randomness has been experimentally confirmed by the self-correlation study of the generated series of numbers. The MEM RNG proposed here would be a true random number generation, which is needed for the highly secured encryption system of today’s information technology.

  15. Micromechanical damage and fracture in elastomeric polymers

    Science.gov (United States)

    Heyden, Stefanie

    This thesis aims at a simple one-parameter macroscopic model of distributed damage and fracture of polymers that is amenable to a straightforward and efficient numerical implementation. The failure model is motivated by post-mortem fractographic observations of void nucleation, growth and coalescence in polyurea stretched to failure, and accounts for the specific fracture energy per unit area attendant to rupture of the material. Furthermore, it is shown that the macroscopic model can be rigorously derived, in the sense of optimal scaling, from a micromechanical model of chain elasticity and failure regularized by means of fractional strain-gradient elasticity. Optimal scaling laws that supply a link between the single parameter of the macroscopic model, namely the critical energy-release rate of the material, and micromechanical parameters pertaining to the elasticity and strength of the polymer chains, and to the strain-gradient elasticity regularization, are derived. Based on optimal scaling laws, it is shown how the critical energy-release rate of specific materials can be determined from test data. In addition, the scope and fidelity of the model is demonstrated by means of an example of application, namely Taylor-impact experiments of polyurea rods. Hereby, optimal transportation meshfree approximation schemes using maximum-entropy interpolation functions are employed. Finally, a different crazing model using full derivatives of the deformation gradient and a core cut-off is presented, along with a numerical non-local regularization model. The numerical model takes into account higher-order deformation gradients in a finite element framework. It is shown how the introduction of non-locality into the model stabilizes the effect of strain localization to small volumes in materials undergoing softening. From an investigation of craze formation in the limit of large deformations, convergence studies verifying scaling properties of both local- and non-local energy

  16. Micromechanical modeling of strength and damage of fiber reinforced composites

    Energy Technology Data Exchange (ETDEWEB)

    Mishnaevsky, L. Jr.; Broendsted, P.

    2007-03-15

    The report for the first year of the EU UpWind project includes three parts: overview of concepts and methods of modelling of mechanical behavior, deformation and damage of unidirectional fiber reinforced composites, development of computational tools for the automatic generation of 3D micromechanical models of fiber reinforced composites, and micromechanical modelling of damage in FRC, and phenomenological analysis of the effect of frequency of cyclic loading on the lifetime and damage evolution in materials. (au)

  17. Experimental Characterization and Micromechanical Modelling of Anisotropic Slates

    Science.gov (United States)

    Chen, Yi-Feng; Wei, Kai; Liu, Wu; Hu, Shao-Hua; Hu, Ran; Zhou, Chuang-Bing

    2016-09-01

    Laboratory tests were performed in this study to examine the anisotropic physical and mechanical properties of the well-foliated Jiujiang slate. The P-wave velocity and the apparent Young's modulus were found to increase remarkably with the foliation angle θ, and the compressive strength at any confining pressure varies in a typical U-shaped trend, with the maximum strength consistently attained at θ = 90° and the minimum strength at θ = 45°. The slate samples failed in three typical patterns relevant to the foliation angle, i.e. shear failure across foliation planes for θ ≤ 15°, sliding along foliation planes for 30° ≤ θ ≤ 60° and axial splitting along foliation planes for θ = 90°. The stress-strain curves at any given foliation angle and confining pressure display an initial nonlinear phase, a linear elastic phase, a crack initiation and growth phase, as well as a rapid stress drop phase and a residual stress phase. Based on the experimental evidences, a micromechanical damage-friction model was proposed for the foliated slate by simply modelling the foliation planes as a family of elastic interfaces and by characterizing the interaction between the foliation planes and the rock matrix with a nonlinear damage evolution law associated with the inclination angle. The proposed model was applied to predict the deformational and strength behaviours of the foliated slate under triaxial compressive conditions using the material parameters calibrated with the uniaxial and/or triaxial test data, with good agreement between the model predictions and the laboratory measurements.

  18. Micro-mechanisms of residual oil mobilization by viscoelastic fluids

    Institute of Scientific and Technical Information of China (English)

    Zhang Lijuan; Yue Xiang'an; Guo Fenqiao

    2008-01-01

    Four typical types of residual oil, residual oil trapped in dead ends, oil ganglia in pore throats,oil at pore comers and oil film adhered to pore walls, were studied. According to main pore structure characteristics and the fundamental morphological features of residual oil, four displacement models for residual oil were proposed, in which pore-scale flow behavior of viscoelastic fluid was analyzed by a numerical method and micro-mechanisms for mobilization of residual oil were discussed. Calculated results indicate that the viscoelastic effect enhances micro displacement efficiency and increases swept volume. For residual oil trapped in dead ends, the flow field of viscoelastic fluid is developed in dead ends more deeply, resulting in more contact with oil by the displacing fluid, and consequently increasing swept volume. In addition, intense viscoelastic vortex has great stress, under which residual oil becomes small oil ganglia, and finally be carried into main channels. For residual oil at pore throats, its displacement mechanisms are similar to the oil trapped in dead ends. Vortices are developed in the depths of the throats and oil ganglia become smaller. Besides, viscoelastic fluid causes higher pressure drop on oil ganglia, as a driving force, which can overcome capillary force, consequently, flow direction can be changed and the displacing fluid enter smaller throats. For oil at pore comers, viscoelastic fluid can enhance displacement efficiency as a result of greater velocity and stress near the comers. For residual oil adhered to pore wall,viscoelastic fluid can provide a greater displacing force on the interface between viscoelastic fluid and oil,thus, making it easier to exceed the minimum interfacial tension for mobilizing the oil film.

  19. The Micromechanics of Biological and Biomimetic Staggered Composites

    Institute of Scientific and Technical Information of China (English)

    Sacheen Bekah; Reza Rabiei; Francois Barthelat

    2012-01-01

    Natural materials such as bone,tooth and nacre achieve attractive properties through the “staggered structure",which consists of stiff,parallel inclusions of large aspect ratio bonded together by a more ductile and tougher matrix.This seemingly simple structure displays sophisticated micromechanics which lead to unique combinations of stiffness,strength and toughness.In this article we modeled the staggered structure using finite elements and small Representative Volume Elements (RVEs) in order to explore microstructure-property relationships.Larger aspect ratio of inclusions results in greater stiffness and strength,and also significant amounts of energy dissipation provided the inclusions do not fracture in a brittle fashion.Interestingly the ends of the inclusions (the junctions) behave as crack-like features,generating theoretically infinite stresses in the adjacent inclusions.A fracture mechanics criterion was therefore used to predict the failure of the inclusions,w hich led to new insights into how the interfaces act as a "soft wrap" for the itclusions,completely shielding them from excessive stresses.The effect of statistics on the mechanics of the staggered structure was also assessed using larger scale RVEs.Variations in the microstructure did not change the modulus of the material,but slightly decreased the strength and significantly decreased the failure strain.This is explained by strain localization,which can in turn be delayed by incorporating vaviness to the inclusions.In addition,we show that the columnar and random arrangements,displaying different deformation mechanisms,lead to similar overall properties.The guidelines presented in this study can be used to optimize the design of staggered synthetic composites to achieve mechanical performances comparable to natural materials.

  20. Micromechanical design of hierarchical composites using global load sharing theory

    Science.gov (United States)

    Rajan, V. P.; Curtin, W. A.

    2016-05-01

    Hierarchical composites, embodied by natural materials ranging from bone to bamboo, may offer combinations of material properties inaccessible to conventional composites. Using global load sharing (GLS) theory, a well-established micromechanics model for composites, we develop accurate numerical and analytical predictions for the strength and toughness of hierarchical composites with arbitrary fiber geometries, fiber strengths, interface properties, and number of hierarchical levels, N. The model demonstrates that two key material properties at each hierarchical level-a characteristic strength and a characteristic fiber length-control the scalings of composite properties. One crucial finding is that short- and long-fiber composites behave radically differently. Long-fiber composites are significantly stronger than short-fiber composites, by a factor of 2N or more; they are also significantly tougher because their fiber breaks are bridged by smaller-scale fibers that dissipate additional energy. Indeed, an "infinite" fiber length appears to be optimal in hierarchical composites. However, at the highest level of the composite, long fibers localize on planes of pre-existing damage, and thus short fibers must be employed instead to achieve notch sensitivity and damage tolerance. We conclude by providing simple guidelines for microstructural design of hierarchical composites, including the selection of N, the fiber lengths, the ratio of length scales at successive hierarchical levels, the fiber volume fractions, and the desired properties of the smallest-scale reinforcement. Our model enables superior hierarchical composites to be designed in a rational way, without resorting either to numerical simulation or trial-and-error-based experimentation.

  1. A Micromechanical INS/GPS System for Small Satellites

    Science.gov (United States)

    Barbour, N.; Brand, T.; Haley, R.; Socha, M.; Stoll, J.; Ward, P.; Weinberg, M.

    1995-01-01

    The cost and complexity of large satellite space missions continue to escalate. To reduce costs, more attention is being directed toward small lightweight satellites where future demand is expected to grow dramatically. Specifically, micromechanical inertial systems and microstrip global positioning system (GPS) antennas incorporating flip-chip bonding, application specific integrated circuits (ASIC) and MCM technologies will be required. Traditional microsatellite pointing systems do not employ active control. Many systems allow the satellite to point coarsely using gravity gradient, then attempt to maintain the image on the focal plane with fast-steering mirrors. Draper's approach is to actively control the line of sight pointing by utilizing on-board attitude determination with micromechanical inertial sensors and reaction wheel control actuators. Draper has developed commercial and tactical-grade micromechanical inertial sensors, The small size, low weight, and low cost of these gyroscopes and accelerometers enable systems previously impractical because of size and cost. Evolving micromechanical inertial sensors can be applied to closed-loop, active control of small satellites for micro-radian precision-pointing missions. An inertial reference feedback control loop can be used to determine attitude and line of sight jitter to provide error information to the controller for correction. At low frequencies, the error signal is provided by GPS. At higher frequencies, feedback is provided by the micromechanical gyros. This blending of sensors provides wide-band sensing from dc to operational frequencies. First order simulation has shown that the performance of existing micromechanical gyros, with integrated GPS, is feasible for a pointing mission of 10 micro-radians of jitter stability and approximately 1 milli-radian absolute error, for a satellite with 1 meter antenna separation. Improved performance micromechanical sensors currently under development will be

  2. Bio-Inspired Micromechanical Directional Acoustic Sensor

    Science.gov (United States)

    Swan, William; Alves, Fabio; Karunasiri, Gamani

    Conventional directional sound sensors employ an array of spatially separated microphones and the direction is determined using arrival times and amplitudes. In nature, insects such as the Ormia ochracea fly can determine the direction of sound using a hearing organ much smaller than the wavelength of sound it detects. The fly's eardrums are mechanically coupled, only separated by about 1 mm, and have remarkable directional sensitivity. A micromechanical sensor based on the fly's hearing system was designed and fabricated on a silicon on insulator (SOI) substrate using MEMS technology. The sensor consists of two 1 mm2 wings connected using a bridge and to the substrate using two torsional legs. The dimensions of the sensor and material stiffness determine the frequency response of the sensor. The vibration of the wings in response to incident sound at the bending resonance was measured using a laser vibrometer and found to be about 1 μm/Pa. The electronic response of the sensor to sound was measured using integrated comb finger capacitors and found to be about 25 V/Pa. The fabricated sensors showed good directional sensitivity. In this talk, the design, fabrication and characteristics of the directional sound sensor will be described. Supported by ONR and TDSI.

  3. Contact micromechanics in granular media with clay

    Energy Technology Data Exchange (ETDEWEB)

    Ita, S.L.

    1994-08-01

    Many granular materials, including sedimentary rocks and soils, contain clay particles in the pores, grain contacts, or matrix. The amount and location of the clays and fluids can influence the mechanical and hydraulic properties of the granular material. This research investigated the mechanical effects of clay at grain-to-grain contacts in the presence of different fluids. Laboratory seismic wave propagation tests were conducted at ultrasonic frequencies using spherical glass beads coated with Montmorillonite clay (SWy-1) onto which different fluids were adsorbed. For all bead samples, seismic velocity increased and attenuation decreased as the contact stiffnesses increased with increasing stress demonstrating that grain contacts control seismic transmission in poorly consolidated and unconsolidated granular material. Coating the beads with clay added stiffness and introduced viscosity to the mechanical contact properties that increased the velocity and attenuation of the propagating seismic wave. Clay-fluid interactions were studied by allowing the clay coating to absorb water, ethyl alcohol, and hexadecane. Increasing water amounts initially increased seismic attenuation due to clay swelling at the contacts. Attenuation decreased for higher water amounts where the clay exceeded the plastic limit and was forced from the contact areas into the surrounding open pore space during sample consolidation. This work investigates how clay located at grain contacts affects the micromechanical, particularly seismic, behavior of granular materials. The need for this work is shown by a review of the effects of clays on seismic wave propagation, laboratory measurements of attenuation in granular media, and proposed mechanisms for attenuation in granular media.

  4. Micromechanics stress–strain behavior prediction of dual phase steel considering plasticity and grain boundaries debonding

    International Nuclear Information System (INIS)

    Highlights: • A simulation procedure is utilized to investigate mechanical behavior of DP steels. • Cohesive elements are used for consideration of debonding on the grain boundaries. • The finite element model was first constructed from the SEM images. • Pattern of voids formation is investigated using CZM and elastic–plastic analysis. - Abstract: Stress–strain response of multiphase materials similar to dual phase (DP) steel depends on the elastic–plastic and damage behavior of all ingredient phases. DP steels typically contains of ferrite and martensite phases, but the grain boundaries of martensite phase may act as important location with possible occurrence of damage or debonding under static loading. The focus of this paper is consideration of ferrite and martensite interface debonding in addition to the elastic–plastic behavior of ferrite and martensite to predict the stress–strain behavior of DP steel using a finite element (FE) micromechanical approach. For this purpose the micromechanics representative geometry is selected from scanning electron microscopy (SEM) images and the finite element mesh is generated based on the real shape of grains. Interface elements based on the cohesive zone modeling are also used for consideration of damage or debonding on the ferrite and martensite interfaces. Therefore, the developed micro mechanic finite element model is based on the real microstructure, uses cohesive elements between martensite islands and ferrite matrix and also considers the elastic–plastic behavior of ferrite and martensite phases. Handling of such simulation procedure with two source of material nonlinearity (plasticity and cohesive zone damage) is not an easy task. It is shown that the obtained stress–strain behaviors are in well agreement with the experimental results

  5. 2D micromechanical analysis of SiC/Al metal matrix composites under tensile, shear and combined tensile/shear loads

    DEFF Research Database (Denmark)

    Qing, Hai

    2013-01-01

    and aluminum alloy matrix, respectively. A series of computational experiments are performed to study the influence of particle arrangements, interface strengths and loading conditions of the representative volume element (RVE) on composite stiffness and strength properties. © 2013 Elsevier Ltd.......The influence of interface strength and loading conditions on the mechanical behavior of the metal-matrix composites is investigated in this paper. A program is developed to generate automatically 2D micromechanical Finite element (FE) models including interface, in which both the locations...

  6. Modeling Piezoelectric Interfacial Wave Near an Imperfect Interface

    Institute of Scientific and Technical Information of China (English)

    XU Li-mei; FAN Hui; CHEN Min; LI Hui

    2006-01-01

    The interface wave propagating along an imperfect interface between two piezoelectric half spaces is derived firstly. The wave equations based on the interface modeled, called "spring model", are presented. The micro-scale structures of the interface for connecting the spring constant with the interface micro-structures are examined. For some simple interface micro-structure, exact dynamic solution is available, and the spring constant is obtained by comparing solutions. For the complex micro structures, it remains as a challenge of micro-mechanics modeling to connect the "spring constant" and micro-structure.

  7. Micromechanisms of damage in unidirectional fiber reinforced composites

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon; Brøndsted, Povl

    2009-01-01

    Numerical micromechanical investigations of the mechanical behavior and damage evolution of glass fiber reinforced composites are presented. A program code for the automatic generation of 3D micromechanical unit cell models of composites with damageable elements is developed, and used in the...... strength of a composite at the pre-critical load, while the fibers with randomly distributed strengths lead to the higher strength of the composite at post-critical loads. In the case of randomly distributed fiber strengths, the damage growth in fibers seems to be almost independent from the crack length...

  8. A micromechanical bridge-shaped voltage-controlled oscillator

    Institute of Scientific and Technical Information of China (English)

    HAN; Jianqiang; ZHU; Changchun; ZHAO; Hongpo; LIU; Junhua

    2004-01-01

    A novel micromechanical bridge-shaped voltage-controlled oscillator with high Q value was fabricated. The core of this kind of oscillators is an electrothermally excited and piezoresistively detected micromechanical bridge resonator. Its resonance frequency can be adjusted by changing the DC voltage applied to the Wheatstone bridge. Theoretical analysis and experimental data show that its resonance frequency is linear with the square of the DC voltage. The linearity is better than 0.16% and the adjustable frequency range excels 17.15%.

  9. Micromechanical modelling of oil palm empty fruit bunch fibres containing silica bodies.

    Science.gov (United States)

    Omar, Farah Nadia; Hanipah, Suhaiza Hanim; Xiang, Loo Yu; Mohammed, Mohd Afandi P; Baharuddin, Azhari Samsu; Abdullah, Jaafar

    2016-09-01

    Experimental and numerical investigation was conducted to study the micromechanics of oil palm empty fruit bunch fibres containing silica bodies. The finite viscoelastic-plastic material model called Parallel Rheological Network model was proposed, that fitted well with cyclic and stress relaxation tensile tests of the fibres. Representative volume element and microstructure models were developed using finite element method, where the models information was obtained from microscopy and X-ray micro-tomography analyses. Simulation results showed that difference of the fibres model with silica bodies and those without ones is larger under shear than compression and tension. However, in comparison to geometrical effect (i.e. silica bodies), it is suggested that ultrastructure components of the fibres (modelled using finite viscoelastic-plastic model) is responsible for the complex mechanical behaviour of oil palm fibres. This can be due to cellulose, hemicellulose and lignin components and the interface behaviour, as reported on other lignocellulosic materials. PMID:27183430

  10. 3D multiscale micromechanical model of wood: From annual rings to microfibrils

    DEFF Research Database (Denmark)

    Qing, Hai; Mishnaevsky, Leon

    2010-01-01

    A 3D micromechanical analytical-computational model of softwood, which takes into account the wood microstructures at four scale levels, from microfibrils to annual rings, is developed. For the analysis of the effect of the annual rings structure on the properties of softwood, an improved rule......-of-mixture model, based on 3D orthotropic stress–strain relations and taking into account the compatibility of deformations at the interface of two phases and equilibrium of tractions at phase boundaries, is proposed. The improved rule of mixture model (IRoM) was compared with the classical rule-of-mixture (Ro......, 2009a) and (Qing and Mishnaevsky, 2009b). Using the combined four-level model, the effect of wood density, microfibril angle (MFA) and cell shape angle (CSA) on the Young’s moduli, Poisson’s ratios and shrinkage properties of softwood has been investigated in numerical experiments. The simulations were...

  11. Single Element Excitation and Detection of (Micro-)Mechanical Resonators

    NARCIS (Netherlands)

    Tilmans, Harrie A.C.; IJntema, Dominicus .J.; Fluitman, Jan H.J

    1991-01-01

    The authors describe a single-element approach for the excitation and detection of the vibrational motion of (micro-)mechanical resonators. An equivalent electrical one-port network is derived for an electrostatically and a piezoelectrically driven resonator. In this way, the effect of the mechanica

  12. Design and Implementation of a Micromechanical Silicon Resonant Accelerometer

    Directory of Open Access Journals (Sweden)

    Libin Huang

    2013-11-01

    Full Text Available The micromechanical silicon resonant accelerometer has attracted considerable attention in the research and development of high-precision MEMS accelerometers because of its output of quasi-digital signals, high sensitivity, high resolution, wide dynamic range, anti-interference capacity and good stability. Because of the mismatching thermal expansion coefficients of silicon and glass, the micromechanical silicon resonant accelerometer based on the Silicon on Glass (SOG technique is deeply affected by the temperature during the fabrication, packaging and use processes. The thermal stress caused by temperature changes directly affects the frequency output of the accelerometer. Based on the working principle of the micromechanical resonant accelerometer, a special accelerometer structure that reduces the temperature influence on the accelerometer is designed. The accelerometer can greatly reduce the thermal stress caused by high temperatures in the process of fabrication and packaging. Currently, the closed-loop drive circuit is devised based on a phase-locked loop. The unloaded resonant frequencies of the prototype of the micromechanical silicon resonant accelerometer are approximately 31.4 kHz and 31.5 kHz. The scale factor is 66.24003 Hz/g. The scale factor stability is 14.886 ppm, the scale factor repeatability is 23 ppm, the bias stability is 23 μg, the bias repeatability is 170 μg, and the bias temperature coefficient is 0.0734 Hz/°C.

  13. Micromechanics of diffusion-induced damage evolution in reinforced polymers

    DEFF Research Database (Denmark)

    Abhilash, A.S.; Joshi, Shailendra P.; Mukherjee, Abhijit;

    2011-01-01

    In this work we numerically investigate the nucleation and evolution of micromechanical damage in reinforced glassy polymers under transient hygro-mechanical loading. In particular, we demonstrate the role that fiber distribution plays in the evolution of overall damage due to fiber–matrix interf...

  14. Micromechanical study of elastic moduli of loose granular materials

    NARCIS (Netherlands)

    Kruyt, N.P.; Agnolin, I.; Luding, S.; Rothenburg, L.

    2010-01-01

    In micromechanics of the elastic behaviour of granular materials, the macro-scale continuum elastic moduli are expressed in terms of micro-scale parameters, such as coordination number (the average number of contacts per particle) and interparticle contact stiffnesses in normal and tangential direct

  15. Micromechanics of creep fracture : Simulation of intergranular crack growth

    NARCIS (Netherlands)

    Onck, Patrick; Giessen, Erik van der

    1998-01-01

    A computational model is presented to analyze intergranular creep crack growth in a polycrystalline aggregate in a discrete manner and based directly on the underlying physical micromechanisms. A crack tip process zone is used in which grains and their grain boundaries are represented discretely, wh

  16. Understanding the mechanisms that change the conductivity of damaged ITO-coated polymeric films: A micro-mechanical investigation

    KAUST Repository

    Nasr Saleh, Mohamed

    2014-11-01

    Degradation from mechanical loading of transparent electrodes made of indium tin oxide (ITO) endangers the integrity of any material based on these electrodes, including flexible organic solar cells. However, how different schemes of degradation change the conductivity of ITO devices remains unclear. We propose a systematic micro-mechanics-based approach to clarify the relationship between degradation and changes in electrical resistance. By comparing experimentally measured channel crack densities to changes in electrical resistance returned by the different micro-mechanical schemes, we highlight the key role played by the residual conductivity in the interface between the ITO electrode and its substrate after delamination. We demonstrate that channel cracking alone does not explain the experimental observations. Our results indicate that delamination has to take place between the ITO electrode and the substrate layers and that the residual conductivity of this delaminated interface plays a major role in changes in electrical resistance of the degraded device. © 2014 Elsevier B.V.

  17. Application of micromechanics to the characterization of mortar by ultrasound.

    Science.gov (United States)

    Hernández, M G; Anaya, J J; Izquierdo, M A G; Ullate, L G

    2002-05-01

    Mechanical properties of concrete and mortar structures can be estimated by ultrasonic non-destructive testing. When the ultrasonic velocity is known, there are standardized methods based on considering the concrete a homogeneous material. Cement composites, however, are heterogeneous and porous, and have a negative effect on the mechanical properties of structures. This work studies the impact of porosity on mechanical properties by considering concrete a multiphase material. A micromechanical model is applied in which the material is considered to consist of two phases: a solid matrix and pores. From this method, a set of expressions is obtained that relates the acoustic velocity and Young's modulus of mortar. Experimental work is based on non-destructive and destructive procedures over mortar samples whose porosity is varied. A comparison is drawn between micromechanical and standard methods, showing positive results for the method here proposed.

  18. Computational methods for coupling microstructural and micromechanical materials response simulations

    Energy Technology Data Exchange (ETDEWEB)

    HOLM,ELIZABETH A.; BATTAILE,CORBETT C.; BUCHHEIT,THOMAS E.; FANG,HUEI ELIOT; RINTOUL,MARK DANIEL; VEDULA,VENKATA R.; GLASS,S. JILL; KNOROVSKY,GERALD A.; NEILSEN,MICHAEL K.; WELLMAN,GERALD W.; SULSKY,DEBORAH; SHEN,YU-LIN; SCHREYER,H. BUCK

    2000-04-01

    Computational materials simulations have traditionally focused on individual phenomena: grain growth, crack propagation, plastic flow, etc. However, real materials behavior results from a complex interplay between phenomena. In this project, the authors explored methods for coupling mesoscale simulations of microstructural evolution and micromechanical response. In one case, massively parallel (MP) simulations for grain evolution and microcracking in alumina stronglink materials were dynamically coupled. In the other, codes for domain coarsening and plastic deformation in CuSi braze alloys were iteratively linked. this program provided the first comparison of two promising ways to integrate mesoscale computer codes. Coupled microstructural/micromechanical codes were applied to experimentally observed microstructures for the first time. In addition to the coupled codes, this project developed a suite of new computational capabilities (PARGRAIN, GLAD, OOF, MPM, polycrystal plasticity, front tracking). The problem of plasticity length scale in continuum calculations was recognized and a solution strategy was developed. The simulations were experimentally validated on stockpile materials.

  19. Micromechanical approach to nonlinear poroelasticity : Application to cracked rocks

    OpenAIRE

    DEUDE, V; DORMIEUX, L; Kondo, D; MAGHOUS, S

    2002-01-01

    This paper considers a saturated porous medium in which the matrix is a cracked solid. Progressive crack closure is responsible for an overall nonlinear poroelastic behavior. The state equations of nonlinear poroelasticity are derived in a differential form within a micromechanical framework. When a hydraulic connection exists between the cracks and the pores of the porous space, the tangent drained stiffness tensor as well as the tangent Biot tensor and modulus are shown to depend on Terzagh...

  20. Micromechanical sensors for the measurement of biopolymer degradation

    DEFF Research Database (Denmark)

    Keller, Stephan Sylvest; Gammelgaard, Lene; Jensen, M P;

    2011-01-01

    We present microcantilever-based sensors for the characterization of biopolymer degradation by enzymes. Thin films of Poly(L-lactide) (PLLA) were spray-coated onto SU-8 cantilevers with well-known material properties and dimensions. The micromechanical sensors were immersed in solutions of protei...... of proteinase K to investigate enzymatic degradation of PLLA. A decrease of the resonance frequency after immersion indicated degradation of the biopolymer coating and allowed the estimation of the degradation rate at a specific enzyme concentration....

  1. A micromechanical study of dilatancy of granular materials

    Science.gov (United States)

    Kruyt, N. P.; Rothenburg, L.

    2016-10-01

    In micromechanics of granular materials, relationships are investigated between micro-scale characteristics of particles and contacts and macro-scale, continuum characteristics. Dilatancy is an important property of granular materials, defined as volume changes (dilative or compressive) induced by shear deformation. To obtain detailed information at the micro-scale, two-dimensional Discrete Element Method simulations of isobaric tests with disk-shaped particles have been performed. The required information includes the fabric tensor which characterizes statistical properties of the contact network. The dependence of the dilatancy rate on the shear strength and the fabric tensor has been investigated, based on the results of the simulations employing a dense and a loose initial system. The dilatancy rate depends in a complex, non-unique way on the shear strength, while the dependence on the fabric tensor is more amenable to analytical description. Two micromechanical mechanisms of dilatancy have been identified: (i) dilatancy due to deformation of loops that are determined by the interparticle contact network and (ii) dilatancy due to topological changes in the interparticle contact network that correspond to the creation or disruption of contacts. For the first mechanism the anisotropy in the contact network is the primary parameter, while for the second mechanism the average number of contacts per particle is the primary parameter. A fabric-based micromechanical relation for the dilatancy rate has been formulated that describes these identified mechanisms. Parameters present in this relation are determined by fitting this relation to the results of the Discrete Element Method simulations, using combined data for the dense and the loose initial system. Employing these fitted coefficients, good agreement is obtained between the results of the simulations and the predictions of the micromechanical dilatancy relation.

  2. Single Element Excitation and Detection of (Micro-)Mechanical Resonators

    OpenAIRE

    Tilmans, Harrie A.C.; IJntema, Dominicus J.; Fluitman, Jan H.J

    1991-01-01

    The authors describe a single-element approach for the excitation and detection of the vibrational motion of (micro-)mechanical resonators. An equivalent electrical one-port network is derived for an electrostatically and a piezoelectrically driven resonator. In this way, the effect of the mechanical resonator is transformed into the electrical domain and can easily be accounted for in a circuit simulation. A detection circuit, based on an (on-chip) bridged design, is proposed as a way to com...

  3. Mathematical modelling of the behavior of granular material in a computational fluid dynamics framework using micro-mechanical models

    International Nuclear Information System (INIS)

    In recent years, many researchers have been employing continuum mechanics in their attempt to formulate numerical models for the description of granular flows. Although these models are partially successful in capturing some of the flow characteristics, they lack essential information on material properties and parameters, which are necessary in order to account for the interactions between different particles or particles and their surrounding solid boundaries at the micro-scale level. These models are thus incomplete and can not be used for the description of processes such as hopper filling/emptying, pneumatic conveying, where these particle-particle interactions might lead to phenomena such as segregation and degradation. In the present paper, a computational fluid dynamics, finite-volume, unstructured mesh framework is presented for the modeling of the behavior of granular material. Appropriate physical models have been incorporated and sophisticated interface tracking algorithms have been developed for the correct representation of the behavior of the different material components in a granular mixture. The various processes, which arise from the micro-mechanical properties of the different mixture species can be obtained and parameterized in the DEM framework. In this way, these processes may be employed in the form of constitutive models in order to enable the continuum theory to account for the micro-mechanical properties of a granular system. The present study sets the computational framework and establishes the link between the micro-mechanics and continuum theory. The capabilities of the numerical model to correctly represent the behavior of granular matter are then demonstrated in simulations of processes which are of great importance in the process engineering industry and involve granular materials in complex geometries (i.e. pneumatic conveying systems, hoppers). Refs. 3 (author)

  4. Micromechanisms of thermomechanical fatigue: A comparison with isothermal fatigue

    Science.gov (United States)

    Bill, R. C.

    1986-01-01

    Thermomechanical Fatigue (TMF) experiments were conducted on Mar-M 200, B-1900, and PWA-1480 (single crystals) over temperature ranges representative of gas turbine airfoil environments. The results were examined from both a phenomenological basis and a micromechanical basis. Depending on constituents present in the superalloy system, certain micromechanisms dominated the crack initiation process and significantly influenced the TMF lives as well as sensitivity of the material to the type TMF cycle imposed. For instance, high temperature cracking around grain boundary carbides in Mar-M 200 resulted in short in-phase TMF lives compared to either out-of-phase or isothermal lives. In single crystal PWA-1480, the type of coating applied was seen to be the controlling factor in determining sensitivity to the type of TMF cycle imposed. Micromechanisms of deformation were observed over the temperature range of interest to the TMF cycles, and provided some insight as to the differences between TMF damage mechanisms and isothermal damage mechanisms. Finally, the applicability of various life prediction models to TMF results was reviewed. Current life prediction models based on isothermal data must be modified before being generally applied to TMF.

  5. Dynamics of micromechanisms controlling the mechanical behaviour of industrial single crystal superalloys

    Indian Academy of Sciences (India)

    M Benyoucef; A Coujou; F Pettinari-Sturmel; S Raujol; B Boubker; N Clément

    2003-02-01

    When deforming bulk material, micromechanisms involving moving defects result in mechanical characteristics observed at a macroscopic scale. In situ straining of microsamples in a Transmission Electron Microscope. provides the unique advantage of observing the dislocation dynamics involved in such microdeformation processes under the combined effects of stress and temperature. Here the efficiency of this technique is illustrated by describing the different obstacles controlling the movement of dislocations in a two-phase industrial single crystal superalloy. At 25° and 850°C, different core structures of the moving dislocations as well as several ways of crossing obstacles are described, which concern the movement of dislocations in channels, at $\\gamma /\\gamma' $ interfaces and while shearing $\\gamma' $ precipitates. From these observations, a quantitative analysis is developed leading to the evaluation of the critical propagation stresses involved in the channels of the matrix and when crossing the interfaces. This allows to discuss the various sites of resistance opposed to the dislocation movements and controlling the macroscopic deformation.

  6. Analytical Solution of Interface Effect on the Strength of Combined Model Composed of Different Geologic Bodies

    OpenAIRE

    Zeng-hui Zhao; Wei-ming Wang; Li-hua Wang; Ji-xing Yan

    2014-01-01

    According to the special combined structure of surrounding rock in western mining area of China, a micromechanical model with variable parameters containing contact interface was proposed firstly. Then, the derived stresses in coal and rock near the interface were analyzed on the basis of the harmonized strain relation, and the analytical solutions with respect to stress states near the interface were drawn up. The triaxial compressive strength of coal and rock was further determined in case ...

  7. Electro-Mechanical Response and Engineering Properties of Piezocomposite with Imperfect Interface

    Directory of Open Access Journals (Sweden)

    Tippayaphalapholgul Rattanan

    2016-01-01

    Full Text Available Composites of piezoelectric materials are widely use in practical applications such as nondestructive testing devices, smart adaptive structures and medical devices. A thorough understanding of coupled electro-elastic response and properties of piezocomposite are crucial for the development and design of piezoelectric composite materials used in advanced applications. The micromechanics analysis is employed in this paper to determine the response and engineering properties of the piezocomposite. A mechanical imperfect interface bonding between piezoelectric inclusion and polymer matrix is taken into consideration in the analysis. The micromechanics analysis is based on the Boundary Element Method (BEM together with the periodic micro-field micromechanics theory. A selected set of numerical results is presented to investigate the influence of volume ratio and interface bonding condition on effective piezocomposite material coefficients and portray basic features of coupled electroelastic response within the domain of piezocomposite unit cell.

  8. On micromechanical characteristics of the critical state of two-dimensional granular materials

    NARCIS (Netherlands)

    Kruyt, N.P.; Rothenburg, L.

    2014-01-01

    In micromechanics of quasi-static deformation of granular materials, relationships are investigated between the macro-scale, continuum-mechanical characteristics, and the micro-scale characteristics at the particle and interparticle contact level. An important micromechanical quantity is the fabric

  9. Micromechanics, Fracture Mechanics and Gas Permeability of Composite Laminates for Cryogenic Storage Systems

    Science.gov (United States)

    Choi, Sukjoo; Sankar, Bhavani; Ebaugh, Newton C.

    2005-01-01

    A micromechanics method is developed to investigate microcrack propagation in a liquid hydrogen composite tank at cryogenic temperature. The unit cell is modeled using square and hexagonal shapes depends on fiber and matrix layout from microscopic images of composite laminates. Periodic boundary conditions are applied to the unit cell. The temperature dependent properties are taken into account in the analysis. The laminate properties estimated by the micromechanics method are compared with empirical solutions using constituent properties. The micro stresses in the fiber and matrix phases based on boundary conditions in laminate level are calculated to predict the formation of microcracks in the matrix. The method is applied to an actual liquid hydrogen storage system. The analysis predicts micro stresses in the matrix phase are large enough to cause microcracks in the composite. Stress singularity of a transverse crack normal to a ply-interface is investigated to predict the fracture behavior at cryogenic conditions using analytical and finite element analysis. When a transverse crack touches a ply-interface of a composite layer with same fiber orientation, the stress singularity is equal to 1/2. When the transverse crack propagates to a stiffer layer normal to the ply-direction, the singularity becomes less than 1/2 and vice versa. Finite element analysis is performed to predict the fracture toughness of a laminated beam subjected to fracture loads measured by four-point bending tests at room and cryogenic temperatures. As results, the fracture load at cryogenic temperature is significantly lower than that at room temperature. However, when thermal stresses are taken into consideration, for both cases of room and cryogenic temperatures, the difference of the fracture toughness becomes insignificant. The result indicates fracture toughness is a characteristic property, which is independent to temperature changes. The experimental analysis is performed to

  10. SOl-based radial-contour-mode micromechanical disk resonator

    Institute of Scientific and Technical Information of China (English)

    Jia Yingqian; Zhao Zhengping; Yang Yongjun; Hu Xiaodong; Li Qian

    2011-01-01

    This paper reports a radial-contour-mode micromechanical disk resonator for radio frequency applications.This disk resonator with a gold plated layer as the electrodes,was prepared on a silicon-on-insulator wafer,which is supported by an anchor on another silicon wafer through Au-Au thermo-compression bonding.The gap between the disk and the surrounding gold electrodes is 100 nm.The radius of the disk is 20 μm and the thickness is 4.5μm.In results,the resonator shows a resonant frequency of 143 MHz and a quality factor of 5600 in vacuum.

  11. Configuration space representation for micro-mechanism function

    Energy Technology Data Exchange (ETDEWEB)

    Sacks, E. [Purdue Univ., Lafayette, IN (United States). Computer Science Dept.; Allen, J. [Sandia National Labs., Albuquerque, NM (United States). Intelligent Micromachine Dept.

    1998-11-01

    This paper describes the configuration space representation of mechanical function and shows how it supports the design of micro-mechanisms. The domain characteristics of curved geometry, joint play, and custom joints render traditional design tools inappropriate, but configuration spaces can model these characteristics. They represent the quantitative and the qualitative aspects of kinematic function in a concise geometric format that helps designers visualize system function under a range of operating conditions, find and correct design flaws, study joint play, and optimize performance. The approach is demonstrated on a surface micromachined counter meshing gear discrimination device developed at Sandia National Laboratories.

  12. Detection of electromagnetic radiation using micromechanical multiple quantum wells structures

    Science.gov (United States)

    Datskos, Panagiotis G [Knoxville, TN; Rajic, Slobodan [Knoxville, TN; Datskou, Irene [Knoxville, TN

    2007-07-17

    An apparatus and method for detecting electromagnetic radiation employs a deflectable micromechanical apparatus incorporating multiple quantum wells structures. When photons strike the quantum-well structure, physical stresses are created within the sensor, similar to a "bimetallic effect." The stresses cause the sensor to bend. The extent of deflection of the sensor can be measured through any of a variety of conventional means to provide a measurement of the photons striking the sensor. A large number of such sensors can be arranged in a two-dimensional array to provide imaging capability.

  13. Micromechanics of intergranular creep failure under cyclic loading

    DEFF Research Database (Denmark)

    van der Giessen, Erik; Tvergaard, Viggo

    1996-01-01

    This paper is concerned with a micromechanical investigation of intergranular creep failure caused by grain boundary cavitation under strain-controlled cyclic loading conditions. Numerical unit cell analyses are carried out for a planar polycrystal model in which the grain material and the grain...... a relatively simple phenomenology under either balanced loading, slow-fast loading or balanced loading with a hold period at constant tensile stress. Next, a (non-dimensionalized) parametric study is carried out which focusses on the effect of the diffusive cavity growth rate relative to the overall creep rate...

  14. Micromechanical modeling of unidirectional composites with uneven interfacial strengths

    DEFF Research Database (Denmark)

    Ashouri Vajari, Danial; Legarth, Brian Nyvang; Niordson, Christian Frithiof

    2013-01-01

    Composite materials under loads normal to the fiber orientation often fail due to debonding between fibers and matrix. In this paper a micromechanical model is developed to study the interfacial and geometrical effects in fiber-reinforced composites using generalized plane strain by means......, a trapezoidal cohesive zone model is used. A parametric study is carried out to evaluate the influence of the interfacial properties, fiber position and fiber volume fraction on the overall stressestrain response as well as the end-crack opening displacement and the opening crack angle. All the results...

  15. Squeezing of Quantum Noise of Motion in a Micromechanical Resonator.

    Science.gov (United States)

    Pirkkalainen, J-M; Damskägg, E; Brandt, M; Massel, F; Sillanpää, M A

    2015-12-11

    A pair of conjugate observables, such as the quadrature amplitudes of harmonic motion, have fundamental fluctuations that are bound by the Heisenberg uncertainty relation. However, in a squeezed quantum state, fluctuations of a quantity can be reduced below the standard quantum limit, at the cost of increased fluctuations of the conjugate variable. Here we prepare a nearly macroscopic moving body, realized as a micromechanical resonator, in a squeezed quantum state. We obtain squeezing of one quadrature amplitude 1.1±0.4  dB below the standard quantum limit, thus achieving a long-standing goal of obtaining motional squeezing in a macroscopic object. PMID:26705631

  16. 铝基复合材料阻尼的微观机制分析%ANALYSIS OF MICROMECHANISM OF DAMPING FOR Al-MATRIX COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    裴政; 王进华; 郭洪光; 郝昱民

    2001-01-01

    通过透射电镜分析了铝基复合材料阻尼行为规律的微观机制,阐明了位错、界面和增强相内耗对复合材料阻尼的影响。%The micromechanism of damping of Al-matrix composites is analyzed by means of TEM photomicrograph. The influence of dislocations, interfaces and internal friction of reinforcements on the damping behavior of composites is discussed.

  17. Wear Micro-Mechanisms of Composite WC-Co/Cr - NiCrFeBSiC Coatings. Part II: Cavitation Erosion

    Directory of Open Access Journals (Sweden)

    D. Kekes

    2014-12-01

    Full Text Available Composite coatings with five different proportions of WC-Co/Cr and NiCrFeBSiC components were deposited on stainless steel by HVOF spraying. Cavitation erosion tests were performed and the material removal micro-mechanisms were identified by SEM of both the eroded areas and the specimens’ cross-sections. Waves’ propagation and deflection at the weak interfaces within the coatings resulted in local tensile stresses perpendicular to the interface direction that eventually led to material removal. Such weak interfaces are the boundaries of the carbide particles with the metal binder within the same splat, those between splats along the same layer and those between successively deposited layers.

  18. Micromechanics of TEMPO-oxidized fibrillated cellulose composites.

    Science.gov (United States)

    Bulota, Mindaugas; Tanpichai, Supachok; Hughes, Mark; Eichhorn, Stephen J

    2012-01-01

    Composites of poly(lactic) acid (PLA) reinforced with TEMPO-oxidized fibrillated cellulose (TOFC) were prepared to 15, 20, 25, and 30% fiber weight fractions. To aid dispersion and to improve stress transfer, we acetylated the TOFC prior to the fabrication of TOFC-PLA composite films. Raman spectroscopy was employed to study the deformation micromechanics in these systems. Microtensile specimens were prepared from the films and deformed in tension with Raman spectra being collected simultaneously during deformation. A shift in a Raman peak initially located at ~1095 cm(-1), assigned to C-O-C stretching of the cellulose backbone, was observed upon deformation, indicating stress transfer from the matrix to the TOFC reinforcement. The highest band shift rate, with respect to strain, was observed in composites having a 30% weight fraction of TOFC. These composites also displayed a significantly higher strain to failure compared to pure acetylated TOFC film, and to the composites having lower weight fractions of TOFC. The stress-transfer processes that occur in microfibrillated cellulose composites are discussed with reference to the micromechanical data presented. It is shown that these TOFC-based composite materials are progressively dominated by the mechanics of the networks, and a shear-lag type stress transfer between fibers.

  19. Micromechanics and constitutive modeling of connective soft tissues.

    Science.gov (United States)

    Fallah, A; Ahmadian, M T; Firozbakhsh, K; Aghdam, M M

    2016-07-01

    In this paper, a micromechanical model for connective soft tissues based on the available histological evidences is developed. The proposed model constituents i.e. collagen fibers and ground matrix are considered as hyperelastic materials. The matrix material is assumed to be isotropic Neo-Hookean while the collagen fibers are considered to be transversely isotropic hyperelastic. In order to take into account the effects of tissue structure in lower scales on the macroscopic behavior of tissue, a strain energy density function (SEDF) is developed for collagen fibers based on tissue hierarchical structure. Macroscopic response and properties of tissue are obtained using the numerical homogenization method with the help of ABAQUS software. The periodic boundary conditions and the proposed constitutive models are implemented into ABAQUS using the DISP and the UMAT subroutines, respectively. The existence of the solution and stable material behavior of proposed constitutive model for collagen fibers are investigated based on the poly-convexity condition. Results of the presented micromechanics model for connective tissues are compared and validated with available experimental data. Effects of geometrical and material parameters variation at microscale on macroscopic mechanical behavior of tissues are investigated. The results show that decrease in collagen content of the connective tissues like the tendon due to diseases leads 20% more stretch than healthy tissue under the same load which can results in connective tissue malfunction and hypermobility in joints. PMID:26807767

  20. Elongated Tetrakaidecahedron Micromechanics Model for Space Shuttle External Tank Foams

    Science.gov (United States)

    Sullivan, Roy M.; Ghosn, Louis J.; Lerch, Bradley A.; Baker, Eric H.

    2009-01-01

    The results of microstructural characterization studies and physical and mechanical testing of BX-265 and NCFI24-124 foams are reported. A micromechanics model developed previously by the authors is reviewed, and the resulting equations for the elastic constants, the relative density, and the strength of the foam in the principal material directions are presented. The micromechanics model is also used to derive equations to predict the effect of vacuum on the tensile strength and the strains induced by exposure to vacuum. Using a combination of microstructural dimensions and physical and mechanical measurements as input, the equations for the elastic constants and the relative density are applied and the remaining microstructural dimensions are predicted. The predicted microstructural dimensions are in close agreement with the average measured values for both BX-265 and NCFI24-124. With the microstructural dimensions, the model predicts the ratio of the strengths in the principal material directions for both foams. The model is also used to predict the Poisson s ratios, the vacuum-induced strains, and the effect of vacuum on the tensile strengths. However, the comparison of these predicted values with the measured values is not as favorable.

  1. Virtual mass effect in dynamic micromechanical mass sensing in liquids

    Science.gov (United States)

    Peiker, P.; Oesterschulze, E.

    2016-06-01

    Weighing individual micro- or nanoscale particles in solution using dynamic micromechanical sensors is quite challenging: viscous losses dramatically degrade the sensor's performance by both broadening the resonance peak and increasing the effective total mass of the resonator by the dragged liquid. While the virtual mass of the resonator was discussed frequently, little attention has been paid to the virtual mass of particles attached to the resonator's surface and its impact on the accuracy of mass sensing. By means of the in situ detection of a polystyrene microbead in water using a bridge-based microresonator, we demonstrate that the virtual mass of the bead significantly affects the observed frequency shift. In fact, 55 % of the frequency shift was caused by the virtual mass of the adsorbed bead, predicted by Stoke's theory. Based on the observed shift in the resonator's quality factor during particle adsorption, we confirm this significant effect of the virtual mass. Thus, a quantitative analysis of the mass of a single adsorbed particle is strongly diminished if dynamic micromechanical sensors are operated in a liquid environment.

  2. A micromechanical model for estimating alveolar wall strain in mechanically ventilated edematous lungs.

    Science.gov (United States)

    Chen, Zheng-long; Chen, Ya-zhu; Hu, Zhao-yan

    2014-09-15

    To elucidate the micromechanics of pulmonary edema has been a significant medical concern, which is beneficial to better guide ventilator settings in clinical practice. In this paper, we present an adjoining two-alveoli model to quantitatively estimate strain and stress of alveolar walls in mechanically ventilated edematous lungs. The model takes into account the geometry of the alveolus, the effect of surface tension, the length-tension properties of parenchyma tissue, and the change in thickness of the alveolar wall. On the one hand, our model supports experimental findings (Perlman CE, Lederer DJ, Bhattacharya J. Am J Respir Cell Mol Biol 44: 34-39, 2011) that the presence of a liquid-filled alveolus protrudes into the neighboring air-filled alveolus with the shared septal strain amounting to a maximum value of 1.374 (corresponding to the maximum stress of 5.12 kPa) even at functional residual capacity; on the other hand, it further shows that the pattern of alveolar expansion appears heterogeneous or homogeneous, strongly depending on differences in air-liquid interface tension on alveolar segments. The proposed model is a preliminary step toward picturing a global topographical distribution of stress and strain on the scale of the lung as a whole to prevent ventilator-induced lung injury. PMID:24947025

  3. Reversible optical-to-microwave quantum interface.

    Science.gov (United States)

    Barzanjeh, Sh; Abdi, M; Milburn, G J; Tombesi, P; Vitali, D

    2012-09-28

    We describe a reversible quantum interface between an optical and a microwave field using a hybrid device based on their common interaction with a micromechanical resonator in a superconducting circuit. We show that, by employing state-of-the-art optoelectromechanical devices, one can realize an effective source of (bright) two-mode squeezing with an optical idler (signal) and a microwave signal, which can be used for high-fidelity transfer of quantum states between optical and microwave fields by means of continuous variable teleportation. PMID:23030075

  4. EDITORIAL: 16th European Workshop on Micromechanics (MME 2005)

    Science.gov (United States)

    Enoksson, Professor Peter

    2006-06-01

    This special issue of Journal of Micromechanics and Microengineering is devoted to the 16th European Workshop on Micromechanics (MME 2005), which was held in Göteborg, Sweden, at the Chalmers Conference Centre on the premises of Chalmers University of Technology, 4-6 September 2005. Göteborg is the second largest city in Sweden and is situated on the beautiful south-west coast. With its relaxed and friendly atmosphere Göteborg proudly lives up to its reputation of having the charm of a small town with all the opportunities of a big city. The MME workshop is a well recognized and established European event for creating microsensors and microactuators in the field of micromachining, microengineering and technology. The very first workshop was held at Twente University, The Netherlands, in 1989. Scientists and people from industry who are interested in the field gather annually for this event. The goals are stimulation and improvement of know-how in the field, as well as establishing cooperation and friendship between delegates. Thus MME is arranged so that people can meet in a friendly and informal atmosphere. That is why the accent is on mutual discussions around poster presentations rather than on formal oral presentations. The contributions, which came from 21 countries, were presented in four sessions and five keynote presentations. I am proud to present 24 high-quality papers from MME 2005 selected for their novelty and relevance to Journal of Micromechanics and Microengineering. Each paper passed a rigorous peer review process. May I take this opportunity to thank those authors who contributed their research to this special issue, which I hope gives an excellent overview of topics discussed at the workshop. I would also like to express my gratitude to Professor Robert Puers for advising on the selection of papers and to Dr Anke Sanz-Velasco for helping to coordinate the special issue with the Institute of Physics Publishing office at the start. I hope you

  5. Squeezing of light via reflection from a silicon micromechanical resonator

    CERN Document Server

    Safavi-Naeini, Amir H; Hill, Jeff T; Chan, Jasper; Aspelmeyer, Markus; Painter, Oskar

    2013-01-01

    We present the measurement of squeezed light generation using an engineered optomechanical system fabricated from a silicon microchip and composed of a micromechanical resonator coupled to a nanophotonic cavity. Laser light is used to measure the fluctuations in the position of the mechanical resonator at a measurement rate comparable to the free dynamics of the mechanical resonator, and greater than its thermal decoherence rate. By approaching the strong continuous measurement regime we observe, through homodyne detection, non-trivial modifications of the reflected light's vacuum fluctuation spectrum. In spite of the mechanical resonator's highly excited thermal state ($10,000$ phonons), we observe squeezing at the level of $4.5 \\pm 0.5%$ below that of shot-noise over a few MHz bandwidth around the mechanical resonance frequency of 28 MHz. This squeezing is interpreted as an unambiguous quantum signature of radiation pressure shot-noise.

  6. INCREMENTAL MICRO-MECHANICAL MODEL OF PLAIN WOVEN FABRIC

    Institute of Scientific and Technical Information of China (English)

    ZhangYitong; HaoYongjiang; LiCuiyu

    2004-01-01

    Warp yarns and weft yarns of plain woven fabric are the principal axes of material of fabric. They are orthogonal in their original configuration, but are obliquely crisscross in deformed configuration in general. In this paper the expressions of incremental components of strain tensor are derived, the non-linear model of woven fabric is linearized physically and its geometric non-linearity survives. The convenience of determining the total deformation is shown by the choice of the coordinate system of the principal axes of the material, with the convergence of the incremental methods illustrated by examples. This incremental model furnishes a basis for numerical simulations of fabric draping and wrinkling based oll the micro-mechanical model of fabric.

  7. Porosity estimation of aged mortar using a micromechanical model.

    Science.gov (United States)

    Hernández, M G; Anaya, J J; Sanchez, T; Segura, I

    2006-12-22

    Degradation of concrete structures located in high humidity atmospheres or under flowing water is a very important problem. In this study, a method for ultrasonic non-destructive characterization in aged mortar is presented. The proposed method makes a prediction of the behaviour of aged mortar accomplished with a three phase micromechanical model using ultrasonic measurements. Aging mortar was accelerated by immersing the probes in ammonium nitrate solution. Both destructive and non-destructive characterization of mortar was performed. Destructive tests of porosity were performed using a vacuum saturation method and non-destructive characterization was carried out using ultrasonic velocities. Aging experiments show that mortar degradation not only involves a porosity increase, but also microstructural changes in the cement matrix. Experimental results show that the estimated porosity using the proposed non-destructive methodology had a comparable performance to classical destructive techniques.

  8. Noise suppression for micromechanical resonator via intrinsic dynamic feedback

    Institute of Scientific and Technical Information of China (English)

    Hou IAN; Zhi-rui GONG; Chang-pu SUN

    2008-01-01

    We study a dynamic mechanism to passively suppress the thermal noise of a micromechanical resonator through an intrinsic self-feedback that is genuinely non-Markovian.We use two coupled resonators,one as the target resonator and the other as an ancillary resonator,to illustrate the mechanism and its noise reduction effect.The intrinsic feedback is realized through the dynamics of coupling between the two resonators:the motions of the target resonator and the ancillary resonator mutually influence each other in a cyclic fashion.Specifically,the states that the target resonator has attained earlier will affect the state it attains later due to the presence of the ancillary resonator.We show that the feedback mechanism will bring forth the effect of noise suppression in the spectrum of displacement,but not in the spectrum of momentum.

  9. Micromechanical analysis of interaction enersy for SMA reinforced composite

    Institute of Scientific and Technical Information of China (English)

    ZHU YuPing; DUI GuanSuo; DUO Liu

    2009-01-01

    The energy of the interaction between the matrix and the inclusions in shape memory alloy (SMA) re-inforced composite is one of the most important and complicated parts in thermodynamic constitutive theory. In this paper, the interaction energy is derived based on the classical theory of micromechanics and the thermodynamic theory. The SMA composite is treated as three phases, namely the austenitic phase, the martensite phase and the matrix phase. The interaction among the three phases is analyzed in a way close to the fact. The present expression is used to calculate the interaction energy of a typical SMA composite with attentions paid to understand of the effects of the matrix material, the fiber ge-ometry, and the fiber/matrix volume ratio. It is shown that the method developed in this paper is credi-ble compared with the references. Some useful conclusions are obtained.

  10. Micromechanical analysis of interaction energy for SMA reinforced composite

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The energy of the interaction between the matrix and the inclusions in shape memory alloy (SMA) re- inforced composite is one of the most important and complicated parts in thermodynamic constitutive theory. In this paper, the interaction energy is derived based on the classical theory of micromechanics and the thermodynamic theory. The SMA composite is treated as three phases, namely the austenitic phase, the martensite phase and the matrix phase. The interaction among the three phases is analyzed in a way close to the fact. The present expression is used to calculate the interaction energy of a typical SMA composite with attentions paid to understand of the effects of the matrix material, the fiber ge- ometry, and the fiber/matrix volume ratio. It is shown that the method developed in this paper is credible compared with the references. Some useful conclusions are obtained.

  11. Micromechanical study of corrosion products layers. Part I: Experimental characterization

    Energy Technology Data Exchange (ETDEWEB)

    Dehoux, A., E-mail: dehoux@lmt.ens-cachan.fr [UPMC Univ., Paris 06, LMT-Cachan (ENS Cachan/UMR8535/UPMC) (France); Andra, Agence Nationale pour la gestion des Dechets RadioActifs, 1-7 rue Jean Monnet, parc de la croix blanche, 92298 Chatenay Malabry Cedex (France); Bouchelaghem, F.; Berthaud, Y. [UPMC Univ., Paris 06, LMT-Cachan (ENS Cachan/UMR8535/UPMC) (France); Neff, D. [SIS2M/LAPA-Laboratoire Pierre Suee, UMR 9956 CNRS, CEA, Bt. 637, CEA Saclay, 91191 Gif/Yvette (France); L' Hostis, V. [DEN, DANS, DPC, SCCME, Laboratoire d' Etude du Comportement des Betons et des Argiles, F-91191 Gif/Yvette (France)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer The mechanical characterization of oxide formed on ancient ferrous artefacts has been performed. Black-Right-Pointing-Pointer The main phases present are goethite, magnetite and maghemite. Black-Right-Pointing-Pointer Typical ranges of the local mechanical properties can be related with the main phases present. Black-Right-Pointing-Pointer The Young moduli at the micrometric scale vary between 50 and 200 GPa. Black-Right-Pointing-Pointer Time dependent effects are negligible. - Abstract: A micromechanical characterization had been performed on ancient artefacts corrosion products. The proposed experimental approach allies scanning electron microscopy observations, micro-indentation tests which allow the characterization of the local stiffness of elementary constituents, and finally Raman micro-spectroscopy tests which give access to the local crystallised phases of the samples. The experimental campaign contains a large series of tests, which give us the opportunity to interpret the dispersion of local stiffness measurements.

  12. Micromechanical tunable vertical-cavity surface-emitting lasers

    Institute of Scientific and Technical Information of China (English)

    Guan Bao-Lu; Guo Xia; Deng Jun; Qu Hong-Wei; Lian Peng; Dong Li-Min; Chen Min; Shen Guang-Di

    2006-01-01

    We report the study on a short wavelength-tunable vertical-cavity surface-emitting laser utilizing a monolithically integrated bridge tuning microelectromechanical system. A deformable-bridge top mirror suspended above an active region is utilized. Applied bridge-substrate bias produces an electrostatic force which reduces the spacing of air-gap and tunes the resonant wavelength toward a shorter wavelength (blue-shift). Good laser characteristics are obtained:such as continuous tuning ranges over 11 nm near 940 nm for 0-9 V tuning bias, the peak output power near 1 mW and the full-width-half-maximum limited to approximately 3.2-6.8 nm. A detailed simulation of the micromechanical and optical characteristics of these devices is performed, and the ratio of bridge displacement to wavelength shift has been found to be 3:1.

  13. Micromechanical modeling of tuffaceous rock for application in nuclear waste storage

    International Nuclear Information System (INIS)

    This paper describes the development of micromechanical models for tuffaceous rock. In particular, laboratory tests have been conducted on Topopah Spring tuff from Yucca Mountain, Nevada and Apache Leap tuff from Superior, Arizona. Topopah Spring tuff is the host rock for the proposed underground nuclear waste repository at Yucca Mountain, and Apache Leap tuff is an analog for the host rock. Based on SEM microscopy of the damaged rock specimens, the specific micro-mechanisms for deformation in tuffs have been determined. Micromechanical models based on fracture mechanics theory are then developed for these specific mechanisms. The micromechanical models are able to predict the nonlinear stress-strain behaviour of tuff, including strain-hardening, strain-softening, triaxial strength, and dilatation. (Author)

  14. Prion protein detection in serum using micromechanical resonator arrays.

    Science.gov (United States)

    Varshney, Madhukar; Waggoner, Philip S; Montagna, Richard A; Craighead, Harold G

    2009-12-15

    Prion proteins that have transformed from their normal cellular counterparts (PrP(c)) into infectious form (PrP(res)) are responsible for causing progressive neurodegenerative diseases in numerous species, such as bovine spongiform encephalopathy (BSE) in cattle (also known as mad cow disease), scrapie in sheep, and Creutzfeldt-Jakob disease (CJD) in humans. Due to a possible link between BSE and CJD it is highly desirable to develop non-invasive and ante mortem tests for the detection of prion proteins in bovine samples. Such ante mortem tests of all cows prior to slaughter will help to prevent the introduction of PrP(res) into the human food supply. Furthermore, detection of PrP(res) in donated blood will also help to prevent the transmission of CJD among humans through blood transfusion. In this study, we have continued development of a micromechanical resonator array that is capable of detecting PrP(c) in bovine blood serum. The sensitivity of the resonators for the detection of PrP(c) is further enhanced by the use of secondary mass labels. A pair of antibodies is used in a sandwich immunoassay format to immobilize PrP(c) on the surface of resonators and attach nanoparticles as secondary mass labels to PrP(c). Secondary mass labeling is optimized in terms of incubation time to maximize the frequency shifts that correspond to the presence of PrP(c) on the surface of resonators. Our results show that a minimum of 200 pg mL(-1) of PrP(c) in blood serum can be detected using micromechanical resonator arrays. PMID:19836525

  15. Concentration independent modulation of local micromechanics in a fibrin gel.

    Directory of Open Access Journals (Sweden)

    Maxwell A Kotlarchyk

    Full Text Available Methods for tuning extracellular matrix (ECM mechanics in 3D cell culture that rely on increasing the concentration of either protein or cross-linking molecules fail to control important parameters such as pore size, ligand density, and molecular diffusivity. Alternatively, ECM stiffness can be modulated independently from protein concentration by mechanically loading the ECM. We have developed a novel device for generating stiffness gradients in naturally derived ECMs, where stiffness is tuned by inducing strain, while local mechanical properties are directly determined by laser tweezers based active microrheology (AMR. Hydrogel substrates polymerized within 35 mm diameter Petri dishes are strained non-uniformly by the precise rotation of an embedded cylindrical post, and exhibit a position-dependent stiffness with little to no modulation of local mesh geometry. Here we present the device in the context of fibrin hydrogels. First AMR is used to directly measure local micromechanics in unstrained hydrogels of increasing fibrin concentration. Changes in stiffness are then mapped within our device, where fibrin concentration is held constant. Fluorescence confocal imaging and orbital particle tracking are used to quantify structural changes in fibrin on the micro and nano levels respectively. The micromechanical strain stiffening measured by microrheology is not accompanied by ECM microstructural changes under our applied loads, as measured by confocal microscopy. However, super-resolution orbital tracking reveals nanostructural straightening, lengthening, and reduced movement of fibrin fibers. Furthermore, we show that aortic smooth muscle cells cultured within our device are morphologically sensitive to the induced mechanical gradient. Our results demonstrate a powerful cell culture tool that can be used in the study of mechanical effects on cellular physiology in naturally derived 3D ECM tissues.

  16. Micromechanical Modeling of Grain Boundaries Damage in a Copper Alloy Under Creep

    International Nuclear Information System (INIS)

    In order to include the processes on the scale of the grain structure into the description of the creep behaviour of polycrystalline materials, the damage development of a single grain boundary has been initially investigated in the present work. For this purpose, a special simulationmethod has been used, whose resolution procedure based on holomorphic functions. The mechanisms taken into account for the simulations include nucleation, growth by grain boundary diffusion, coalescence and shrinkage until complete sintering of grain boundary cavities. These studies have then been used to develop a simplified cavitation model, which describes the grain boundary damage by two state variables and the time-dependent development by a mechanism-oriented rate formulation. To include the influence of grain boundaries within continuum mechanical considerations of polycrystals, an interface model has been developed, that incorporates both damage according to the simplified cavitation model and grain boundary sliding in dependence of a phenomenological grain boundary viscosity. Furthermore a micromechanical model of a polycrystal has been developed that allows to include a material's grain structure into the simulation of the creep behaviour by means of finite element simulations. Thereby, the deformations of individual grains are expressed by a viscoplastic single crystal model and the grain boundaries are described by the proposed interface model. The grain structure is represented by a finite element model, in which the grain boundaries are modelled by cohesive elements. From the evaluation of experimental creep data, the micromechanical model of a polycrystal has been calibrated for a copper-antimony alloy at a temperature of 823 K. Thereby, the adjustment of the single crystal model has been carried out on the basis of creep rates of pure copper single crystal specimens. The experimental determination of grain boundary sliding and grain boundary porosity for coarse

  17. Superelement methods applications to micromechanics of high temperature metal matrix composites

    Science.gov (United States)

    Caruso, J. J.; Chamis, C. C.

    1988-01-01

    Adaptation of the superelement finite-element method for micromechanics of continuous fiber high temperature metal matrix composites (HT-MMC) is described. The method is used to predict the thermomechanical behavior of P100-graphite/copper composites using MSC/NASTRAN and it is also used to validate those predicted by using an in-house computer program designed to perform micromechanics for HT-MMC. Typical results presented in the paper include unidirectional composite thermal properties, mechanical properties, and microstresses.

  18. micro-mechanical experimental investigation and modelling of strain and damage of argillaceous rocks under combined hydric and mechanical loads

    International Nuclear Information System (INIS)

    The hydro-mechanical behavior of argillaceous rocks, which are possible host rocks for underground radioactive nuclear waste storage, is investigated by means of micro-mechanical experimental investigations and modellings. Strain fields at the micrometric scale of the composite structure of this rock, are measured by the combination of environmental scanning electron microscopy, in situ testing and digital image correlation technique. The evolution of argillaceous rocks under pure hydric loading is first investigated. The strain field is strongly heterogeneous and manifests anisotropy. The observed nonlinear deformation at high relative humidity (RH) is related not only to damage, but also to the nonlinear swelling of the clay mineral itself, controlled by different local mechanisms depending on RH. Irreversible deformations are observed during hydric cycles, as well as a network of microcracks located in the bulk of the clay matrix and/or at the inclusion-matrix interface. Second, the local deformation field of the material under combined hydric and mechanical loadings is quantified. Three types of deformation bands are evidenced under mechanical loading, either normal to stress direction (compaction), parallel (microcracking) or inclined (shear). Moreover, they are strongly controlled by the water content of the material: shear bands are in particular prone to appear at high RH states. In view of understanding the mechanical interactions a local scale, the material is modeled as a composite made of non-swelling elastic inclusions embedded in an elastic swelling clay matrix. The internal stress field induced by swelling strain incompatibilities between inclusions and matrix, as well as the overall deformation, is numerically computed at equilibrium but also during the transient stage associated with a moisture gradient. An analytical micro-mechanical model based on Eshelby's solution is proposed. In addition, 2D finite element computations are performed. Results

  19. Kinetic Interface

    DEFF Research Database (Denmark)

    2009-01-01

    A kinetic interface for orientation detection in a video training system is disclosed. The interface includes a balance platform instrumented with inertial motion sensors. The interface engages a participant's sense of balance in training exercises.......A kinetic interface for orientation detection in a video training system is disclosed. The interface includes a balance platform instrumented with inertial motion sensors. The interface engages a participant's sense of balance in training exercises....

  20. Design strategies of sea urchin teeth: structure, composition and micromechanical relations to function.

    Science.gov (United States)

    Wang, R Z; Addadi, L; Weiner, S

    1997-01-01

    The teeth of sea urchins comprise a variety of different structural entities, all of which are composed of magnesium-bearing calcite together with a small amount of organic material. The teeth are worn down continuously, but in such a way that they remain sharp and functional. Here we describe aspects of the structural, compositional and micromechanical properties of the teeth of Paracentrotus lividus using scanning electron microscopy, infrared spectrometry, atomic absorption. X-ray diffraction and microindentation. The S-shaped single crystalline calcitic fibres are one of the main structural elements of the tooth. They extend from the stone part to the keel. The diameter of the fibres increases gradually from less than 1 micron at the stone tip to about 20 microns at the keel end, while their MgCO3 contents decrease from about 13 mol% to about 4.5 mol%. Each fibre is coated by a thin organic sheath and surrounded by polycrystalline calcitic discs containing as much as 35 mol% MgCO3. This structure constitutes a unique kind of gradient fibre-reinforced ceramic matrix composite, whose microhardness and toughness decrease gradually from the stone part to the keel. Primary plates are also important structural elements of the tooth. Each primary plate has a very unusual sandwich-like structure with a calcitic envelope surrounding a thin apparently amorphous CaCO3 layer. This central layer, together with the primary plate/disc interface, improves the toughness of this zone by stopping and blunting cracks. The self-sharpening function of the teeth is believed to result from the combination of the geometrical shape of the main structural elements and their spatial arrangement, the interfacial strength between structural elements, and the hardness gradient extending from the working stone part to the surrounding zones. The sea urchin tooth structure possesses an array of interesting functional design features, some of which may possibly be applicable to materials science

  1. Effect of fibre arrangement on the multiaxial fatigue of fibrous composites: a micromechanical computational model

    Directory of Open Access Journals (Sweden)

    Roberto Brighenti

    2015-10-01

    Full Text Available Structural components made of fibre-reinforced materials are frequently used in engineering applications. Fibre-reinforced composites are multiphase materials, and complex mechanical phenomena take place at limit conditions but also during normal service situations, especially under fatigue loading, causing a progressive deterioration and damage. Under repeated loading, the degradation mainly occurs in the matrix material and at the fibre-matrix interface, and such a degradation has to be quantified for design structural assessment purposes. To this end, damage mechanics and fracture mechanics theories can be suitably applied to examine such a problem. Damage concepts can be applied to the matrix mechanical characteristics and, by adopting a 3-D mixed mode fracture description of the fibre-matrix detachment, fatigue fracture mechanics concepts can be used to determine the progressive fibre debonding responsible for the loss of load bearing capacity of the reinforcing phase. In the present paper, a micromechanical model is used to evaluate the unixial or multiaxial fatigue behaviour of structures with equi-oriented or randomly distributed fibres. The spatial fibre arrangement is taken into account through a statistical description of their orientation angles for which a Gaussian-like distribution is assumed, whereas the mechanical effect of the fibres on the composite is accounted for by a homogenization approach aimed at obtaining the macroscopic elastic constants of the material. The composite material behaves as an isotropic one for randomly distributed fibres, while it is transversally isotropic for unidirectional fibres. The fibre arrangement in the structural component influences the fatigue life with respect to the biaxiality ratio for multiaxial constant amplitude fatigue loading. One representative parametric example is discussed.

  2. Resonantly driven micromechanical energy converters; Resonante mikromechanische Energiewandler

    Energy Technology Data Exchange (ETDEWEB)

    Kuehne, Ingo

    2009-07-01

    This work focuses on the investigation of resonantly driven micromechanical energy harvesters. They are based on electromechanically coupled spring-mass-systems, converting mechanical vibrations into electrical energy by employing appropriate physical transduction mechanisms, such as the inductive, the piezoelectric and the capacitive principle. These three approaches are compared to each other, especially with respect to electrical energy density, scaling behaviour and microtechnological fabricability. Theoretical considerations lead to the decision to implement both a capacitive and a piezoelectric micromechanical energy harvester. The capacitive energy transducer essentially consists of a mass suspended by silicon springs. This mass simultaneously serves as a movable electrode. A fixed counter electrode completes the variable capacitor. In order to function properly, the parallel-plate capacitor needs to be biased electrically. In contrast to existing state of the art a new approach is introduced, employing two different electrode materials with a large difference in their work functions. A periodical mechanical excitation leads to a variation of the electrical energy content within the biased capacitor, thus inducing a current flow, which can be used for driving an external electrical load. For the piezoelectric energy harvester, the concept of a piezoelectric diaphragm with a mass attached to the surface was used and devices were implemented. A mechanical excitation leads to a periodic deflection of the diaphragm caused by the stiffly coupled inertial mass and, thus, to a changing mechanical stress distribution within the diaphragm. This, in turn, induces a periodic charge separation within the piezoelectric diaphragm. The energy generated in this way can be consumed by an external electrical load with appropriate impedance matching. Theoretical model descriptions are established for both types of energy harvesters based on systems of state space equations. On

  3. An integrated micromechanical large particle in flow sorter (MILPIS)

    Science.gov (United States)

    Fuad, Nurul M.; Skommer, Joanna; Friedrich, Timo; Kaslin, Jan; Wlodkowic, Donald

    2015-06-01

    At present, the major hurdle to widespread deployment of zebrafish embryo and larvae in large-scale drug development projects is lack of enabling high-throughput analytical platforms. In order to spearhead drug discovery with the use of zebrafish as a model, platforms need to integrate automated pre-test sorting of organisms (to ensure quality control and standardization) and their in-test positioning (suitable for high-content imaging) with modules for flexible drug delivery. The major obstacle hampering sorting of millimetre sized particles such as zebrafish embryos on chip-based devices is their substantial diameter (above one millimetre), mass (above one milligram), which both lead to rapid gravitational-induced sedimentation and high inertial forces. Manual procedures associated with sorting hundreds of embryos are very monotonous and as such prone to significant analytical errors due to operator's fatigue. In this work, we present an innovative design of a micromechanical large particle in-flow sorter (MILPIS) capable of analysing, sorting and dispensing living zebrafish embryos for drug discovery applications. The system consisted of a microfluidic network, revolving micromechanical receptacle actuated by robotic servomotor and opto-electronic sensing module. The prototypes were fabricated in poly(methyl methacrylate) (PMMA) transparent thermoplastic using infrared laser micromachining. Elements of MILPIS were also fabricated in an optically transparent VisiJet resin using 3D stereolithography (SLA) processes (ProJet 7000HD, 3D Systems). The device operation was based on a rapidly revolving miniaturized mechanical receptacle. The latter function was to hold and position individual fish embryos for (i) interrogation, (ii) sorting decision-making and (iii) physical sorting..The system was designed to separate between fertilized (LIVE) and non-fertilized (DEAD) eggs, based on optical transparency using infrared (IR) emitters and receivers embedded in the system

  4. Micromechanical study of protein-DNA interactions and chromosomes

    Science.gov (United States)

    Marko, John

    I will discuss micromechanics experiments that our group has used to analyze protein-DNA interactions and chromosome organization. In single-DNA experiments we have found that a feature of protein-DNA complexes is that their dissociation rates can depend strikingly on bulk solution concentrations of other proteins and DNA segments; I will describe experiments which demonstrate this effect, which can involve tens-fold changes in off-rates with submicromolar changes in solution concentrations. Second, I will discuss experiments aimed at analyzing large-scale human chromosome structure; we isolate metaphase chromosomes, which in their native form behave as remarkably elastic networks of chromatin. Exposure to DNA-cutting restriction enzymes completely eliminates this elasticity, indicating that there is not a mechanically contiguous protein ''scaffold'' from which the chromosome gains its stability. I will show results of siRNA experiments indicating that depletion of condensin proteins leads to destabilization of chromosome mechanics, indicating condensin's role as the major chromatin ''cross-linker'' in metaphase chromosomes. Finally I will discuss similar experiments on human G1 nuclei, where we use genetic and chemical modifications to separate the contributions of the nuclear lamina and chromatin to the mechanical stiffness of the nucleus as a whole. Supported by the NSF (DMR-1206868, MCB-1022117) and the NIH (GM105847, CA193419).

  5. Micromechanical cohesion force measurements to determine cyclopentane hydrate interfacial properties.

    Science.gov (United States)

    Aman, Zachary M; Joshi, Sanjeev E; Sloan, E Dendy; Sum, Amadeu K; Koh, Carolyn A

    2012-06-15

    Hydrate aggregation and deposition are critical factors in determining where and when hydrates may plug a deepwater flowline. We present the first direct measurement of structure II (cyclopentane) hydrate cohesive forces in the water, liquid hydrocarbon and gas bulk phases. For fully annealed hydrate particles, gas phase cohesive forces were approximately twice that obtained in a liquid hydrocarbon phase, and approximately six times that obtained in the water phase. Direct measurements show that hydrate cohesion force in a water-continuous bulk may be only the product of solid-solid cohesion. When excess water was present on the hydrate surface, gas phase cohesive forces increased by a factor of three, suggesting the importance of the liquid or quasi-liquid layer (QLL) in determining cohesive force. Hydrate-steel adhesion force measurements show that, when the steel surface is coated with hydrophobic wax, forces decrease up to 96%. As the micromechanical force technique is uniquely capable of measuring hydrate-surface forces with variable contact time, the present work contains significant implications for hydrate applications in flow assurance. PMID:22484169

  6. High-Fidelity Micromechanics Model Enhanced for Multiphase Particulate Materials

    Science.gov (United States)

    Pindera, Marek-Jerzy; Arnold, Steven M.

    2003-01-01

    This 3-year effort involves the development of a comprehensive micromechanics model and a related computer code, capable of accurately estimating both the average response and the local stress and strain fields in the individual phases, assuming both elastic and inelastic behavior. During the first year (fiscal year 2001) of the investigation, a version of the model called the High-Fidelity Generalized Method of Cells (HFGMC) was successfully completed for the thermo-inelastic response of continuously reinforced multiphased materials with arbitrary periodic microstructures (refs. 1 and 2). The model s excellent predictive capability for both the macroscopic response and the microlevel stress and strain fields was demonstrated through comparison with exact analytical and finite element solutions. This year, HFGMC was further extended in two technologically significant ways. The first enhancement entailed the incorporation of fiber/matrix debonding capability into the two-dimensional version of HFGMC for modeling the response of unidirectionally reinforced composites such as titanium matrix composites, which exhibit poor fiber/matrix bond. Comparison with experimental data validated the model s predictive capability. The second enhancement entailed further generalization of HFGMC to three dimensions to enable modeling the response of particulate-reinforced (discontinuous) composites in the elastic material behavior domain. Next year, the three-dimensional version will be generalized to encompass inelastic effects due to plasticity, viscoplasticity, and damage, as well as coupled electromagnetothermomechanical (including piezoelectric) effects.

  7. Active microrheology of a model of the nuclear micromechanical environment

    Science.gov (United States)

    Byrd, Henry; Kilfoil, Maria

    2014-03-01

    In order to successfully complete the final stages of chromosome segregation, eukaryotic cells require the motor enzyme topoisomerase II, which can resolve topological constraints between entangled strands of duplex DNA. We created an in vitro model of a close approximation of the nuclear micromechanical environment in terms of DNA mass and entanglement density, and investigated the influence of this motor enzyme on the DNA mechanics. Topoisomerase II is a non-processive ATPase which we found significantly increases the motions of embedded microspheres in the DNA network. Because of this activity, we study the mechanical properties of our model system by active microrheology by optical trapping. We test the limits of fluctuation dissipation theorem (FDT) under this type of activity by comparing the active microrheology to passive measurements, where thermal motion alone drives the beads. We can relate any departure from FDT to the timescale of topoisomerase II activity in the DNA network. These experiments provide insight into the physical necessity of this motor enzyme in the cell.

  8. Micromechanical Characterization of Polysilicon Films through On-Chip Tests.

    Science.gov (United States)

    Mirzazadeh, Ramin; Eftekhar Azam, Saeed; Mariani, Stefano

    2016-07-28

    When the dimensions of polycrystalline structures become comparable to the average grain size, some reliability issues can be reported for the moving parts of inertial microelectromechanical systems (MEMS). Not only the overall behavior of the device turns out to be affected by a large scattering, but also the sensitivity to imperfections gets enhanced. In this work, through on-chip tests, we experimentally investigate the behavior of thin polysilicon samples using standard electrostatic actuation/sensing. The discrepancy between the target and actual responses of each sample has then been exploited to identify: (i) the overall stiffness of the film and, according to standard continuum elasticity, a morphology-based value of its Young's modulus; (ii) the relevant over-etch induced by the fabrication process. To properly account for the aforementioned stochastic features at the micro-scale, the identification procedure has been based on particle filtering. A simple analytical reduced-order model of the moving structure has been also developed to account for the nonlinearities in the electrical field, up to pull-in. Results are reported for a set of ten film samples of constant slenderness, and the effects of different actuation mechanisms on the identified micromechanical features are thoroughly discussed.

  9. Micromechanical Characterization of Polysilicon Films through On-Chip Tests

    Directory of Open Access Journals (Sweden)

    Ramin Mirzazadeh

    2016-07-01

    Full Text Available When the dimensions of polycrystalline structures become comparable to the average grain size, some reliability issues can be reported for the moving parts of inertial microelectromechanical systems (MEMS. Not only the overall behavior of the device turns out to be affected by a large scattering, but also the sensitivity to imperfections gets enhanced. In this work, through on-chip tests, we experimentally investigate the behavior of thin polysilicon samples using standard electrostatic actuation/sensing. The discrepancy between the target and actual responses of each sample has then been exploited to identify: (i the overall stiffness of the film and, according to standard continuum elasticity, a morphology-based value of its Young’s modulus; (ii the relevant over-etch induced by the fabrication process. To properly account for the aforementioned stochastic features at the micro-scale, the identification procedure has been based on particle filtering. A simple analytical reduced-order model of the moving structure has been also developed to account for the nonlinearities in the electrical field, up to pull-in. Results are reported for a set of ten film samples of constant slenderness, and the effects of different actuation mechanisms on the identified micromechanical features are thoroughly discussed.

  10. Micromechanics Based Inelastic and Damage Modeling of Composites

    Directory of Open Access Journals (Sweden)

    P. P. Procházka

    2004-01-01

    Full Text Available Micromechanics based models are considered for application to viscoelasticity and damage in metal matrix composites. The method proposes a continuation and development of Dvooák’s transformation field analysis, considering the piecewise uniform eigenstrains in each material phase. Standard applications of the method to a two-phase are considered in this study model, i.e., only one sub-volume per phase is considered. A continuous model is used, employing transformation field analysis with softening in order to prevent the tensile stress overstepping the tensile strength. At the same time shear cracking occurs in the tangential direction of the possible crack. This is considered in the principal shear stresses and they make disconnections in displacements. In this case, discontinuous models are more promising. Because discrete models, that can describe the situation more realistically have not been worked out in detail, we retain a continuous model and substitute the slip caused by overstepping the damage law by introducing eigenparameters from TFA. The various aspects of the proposed methods are systematically checked by comparing with finite element unit cell analyses, made through periodic homogenization assumptions, for SiC/Ti unidirectional lay-ups. 

  11. Computational micromechanical analysis of the representative volume element of bituminous composite materials

    Science.gov (United States)

    Ozer, Hasan; Ghauch, Ziad G.; Dhasmana, Heena; Al-Qadi, Imad L.

    2016-08-01

    Micromechanical computational modeling is used in this study to determine the smallest domain, or Representative Volume Element (RVE), that can be used to characterize the effective properties of composite materials such as Asphalt Concrete (AC). Computational Finite Element (FE) micromechanical modeling was coupled with digital image analysis of surface scans of AC specimens. Three mixtures with varying Nominal Maximum Aggregate Size (NMAS) of 4.75 mm, 12.5 mm, and 25 mm, were prepared for digital image analysis and computational micromechanical modeling. The effects of window size and phase modulus mismatch on the apparent viscoelastic response of the composite were numerically examined. A good agreement was observed in the RVE size predictions based on micromechanical computational modeling and image analysis. Micromechanical results indicated that a degradation in the matrix stiffness increases the corresponding RVE size. Statistical homogeneity was observed for window sizes equal to two to three times the NMAS. A model was presented for relating the degree of statistical homogeneity associated with each window size for materials with varying inclusion dimensions.

  12. Micromechanical Models of Mechanical Response of High Performance Fibre Reinforced Cement Composites

    DEFF Research Database (Denmark)

    Li, V. C.; Mihashi, H.; Alwan, J.;

    1996-01-01

    The state-of-the-art in micromechanical modeling of the mechanical response of HPFRCC is reviewed. Much advances in modeling has been made over the last decade to the point that certain properties of composites can be carefully designed using the models as analytic tools. As a result, a new...... generation of FRC with high performance and economical viability, is in sight. However, utilization of micromechanical models for a more comprehensive set of important HPFRCC properties awaits further investigations into fundamental mechanisms governing composite properties, as well as intergrative efforts...... across responses to different load types. Further, micromechanical models for HPFRCC behavior under complex loading histories, including those in fracture, fatigue and multuaxial loading are urgently needed in order to optimize HPFRCC microstrcuctures and enable predictions of such material in structures...

  13. Micromechanics-based prediction of thermoelastic properties of high energy materials

    CERN Document Server

    Banerjee, Biswajit

    2012-01-01

    High energy materials such as polymer bonded explosives are commonly used as propellants. These particulate composites contain explosive crystals suspended in a rubbery binder. However, the explosive nature of these materials limits the determination of their mechanical properties by experimental means. Therefore micromechanics-based methods for the determination of the effective thermoelastic properties of polymer bonded explosives are investigated in this research. Polymer bonded explosives are two-component particulate composites with high volume fractions of particles (volume fraction $>$ 90%) and high modulus contrast (ratio of Young's modulus of particles to binder of 5,000-10,000). Experimentally determined elastic moduli of one such material, PBX 9501, are used to validate the micromechanics methods examined in this research. The literature on micromechanics is reviewed; rigorous bounds on effective elastic properties and analytical methods for determining effective properties are investigated in the ...

  14. Interface models

    DEFF Research Database (Denmark)

    Ravn, Anders P.; Staunstrup, Jørgen

    1994-01-01

    This paper proposes a model for specifying interfaces between concurrently executing modules of a computing system. The model does not prescribe a particular type of communication protocol and is aimed at describing interfaces between both software and hardware modules or a combination of the two....... The model describes both functional and timing properties of an interface...

  15. A MICROMECHANICAL MODEL FOR γ-TiAl BASE PST CRYSTALS

    Institute of Scientific and Technical Information of China (English)

    J.L. Su; G.K. Hu

    2005-01-01

    An analytical micromechanical method is proposed to examine the dependence of plastic deformation on the microstructure for a PST crystal. The sub-domain rnicrostructure of the γ phase and the effect of the α2 phase are taken into account by a proper micromechanical formulation,the dislocation slip and twinning deformation mechanisms are considered in the context of crystal plasticity. The model can well predict the dependence of stress-strain relations on loading angle with respect to the microstructure. The influence of the twinning and lamellar spacing on the deformation behavior and biaxial yield surfaces for PST crystals are also examined.

  16. Using Micromechanical Resonators to Measure Rheological Properties and Alcohol Content of Model Solutions and Commercial Beverages

    Directory of Open Access Journals (Sweden)

    Bart W. Hoogenboom

    2012-05-01

    Full Text Available Micromechanic resonators provide a small-volume and potentially high-throughput method to determine rheological properties of fluids. Here we explore the accuracy in measuring mass density and viscosity of ethanol-water and glycerol-water model solutions, using a simple and easily implemented model to deduce the hydrodynamic effects on resonating cantilevers of various length-to-width aspect ratios. We next show that these measurements can be extended to determine the alcohol percentage of both model solutions and commercial beverages such as beer, wine and liquor. This demonstrates how micromechanical resonators can be used for quality control of every-day drinks.

  17. Micromechanical properties of beryllium and other instrument materials, end-of-year-report

    International Nuclear Information System (INIS)

    The objective of the program is to evaluate and understand the micromechanical properties of beryllium and other instrument materials for use in gyroscopes, so that dimensional instability can be improved. Improved dimensional stability is expected to lessen the need to periodically align gyroscopes in service. Drift in alignment has been attributed in part to mass shifts of 0.000001 inches in critical components of gyroscopes. This report consists of two major parts. Part A - Micromechanical properties of instrument grade beryllium. (description of the materials problem, instrumentation to make strain measurements in the range of 10 to the -7 power, and initial results.) Part B - 10 to the -8 power creep measurement system

  18. Micromechanical Simulation of Thermal Cyclic Behavior of ZrO2/Ti Functionally Graded Thermal Barrier Coatings

    Directory of Open Access Journals (Sweden)

    Hideaki Tsukamoto

    2015-03-01

    Full Text Available This study numerically investigates cyclic thermal shock behavior of ZrO2/Ti functionally graded thermal barrier coatings (FG TBCs based on a nonlinear mean-field micromechanical approach, which takes into account the time-independent and dependent inelastic deformation, such as plasticity of metals, creep of metals and ceramics, and diffusional mass flow at the ceramic/metal interface. The fabrication processes for the FG TBCs have been also considered in the simulation. The effect of creep and compositional gradation patterns on micro-stress states in the FG TBCs during thermal cycling has been examined in terms of the amplitudes, ratios, maximum and mean values of thermal stresses. The compositional gradation patterns highly affect thermal stress states in case of high creep rates of ZrO2. In comparison with experimental data, maximum thermal stresses, amplitudes and ratios of thermal stresses can be effective parameters for design of such FG TBCs subject to cyclic thermal shock loadings.

  19. Micromechanical modelling of partially molten and sand reinforced polycrystalline ice

    Science.gov (United States)

    Castelnau, O.; Duval, P.

    2009-12-01

    The viscoplastic behaviour of polycrystalline ice is strongly affected by the very strong anisotropy of ice crystals. Indeed, in the dislocations creep regime relevant for ice sheet flow, dislocation glide on the basal plane of ice single crystals leads to strain-rates ~6 order of magnitude larger than strain-rates that might be obtain if only non-basal glide is activated. At the polycrystal scale, this behaviour is responsible for a strong mechanical interaction between grains in the secondary (stationary) creep regime, and strain-rate is essentially partitioned between soft grains well-oriented for basal glide and hard grains exhibiting an unfavourable orientation for basal slip. As a consequence, the macroscopic flow stress at the polycrystal scale essentially depends on the resistance of the hardest slip systems or on the associated accommodation processes such as climb of basal dislocation on non-basal planes. Creep experiments performed on polycrystalline ices containing a small amount (less than 10% volume fraction) of liquid water show a dramatic increase of strain-rate, by more than one order of magnitude, compared to solid ice when deformed under similar thermo-mechanical conditions. Similarly, a strong hardening is observed when polycrystalline ice is reinforced by sand (which can be considered as a rigid phase here). This behaviour can be explained by micromechanical models, which aims at estimating the mechanical interactions between grains. For example, the presence of water releases stress concentrations at grain boundaries and therefore favours the inactivation of non-basal systems. To estimate such effect and to reach quantitative comparison with experimental data, we make use of the recent Second-Order homogenization mean-field approach of Ponte-Castaneda, based on self-consistent scheme. The advantage of this approach, which has been shown to provide excellent results when applied to many different non-linear composite materials, comes from the

  20. Design considerations for micromechanical sensors using encapsulated built-in resonant strain gauges

    NARCIS (Netherlands)

    Tilmans, Harrie A.C.; Bouwstra, Siebe; Fluitman, Jan H.J; Spence, Scott L.

    1990-01-01

    This paper describes the various design aspects for micromechanical sensors consisting of a structure with encapsulated built-in resonant strain gauges. Analytical models are used to investigate the effect of device parameters on the behaviour of a pressure sensor and a force sensor. The analyses in

  1. Entanglement and decoherence of a micromechanical resonator via coupling to a Cooper box

    OpenAIRE

    Armour, A. D.; Blencowe, M. P.; Schwab, K. C.

    2001-01-01

    We analyse the quantum dynamics of a micromechanical resonator capacitively coupled to a Cooper box. With appropriate quantum state control of the Cooper box, the resonator can be driven into a superposition of spatially separated states. The Cooper box can also be used to probe the environmentally-induced decoherence of the resonator superposition state.

  2. Nanomorphology of graphene and CNT reinforced polymer and its effect on damage: Micromechanical numerical study

    DEFF Research Database (Denmark)

    Pontefisso, Alessandro; Mishnaevsky, Leon

    2016-01-01

    The effect of morphology, shapes and distribution of nanoscale carbon reinforcement in polymers on their strength and damage resistance is studied using computational micromechanical modeling. A new software and approach were developed for the automatic generation of finite element unit cell mode...

  3. Composite materials for wind energy applications: micromechanical modeling and future directions

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon

    2012-01-01

    The strength and reliability of wind turbine blades depend on the properties, mechanical behavior and strengths of the material components (glass or carbon fibers and polymer matrix), and the interaction between them under loading. In this paper, ideas, methods and concepts of micromechanical mod...

  4. Design and Fabrication of Micromechanical Optical Switches Based on the Low Applied Voltage

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A micromechanical optical switch driven by electrostatic was fabricated with (100) silicon and tilted 2.5° (111) silicon. The pull-in voltage is 13.2V, the insertion loss is less than 1.4dB, the crosstalk is less than -50 dB.

  5. Micromechanical definition of an entropy for quasi-static deformation of granular materials

    NARCIS (Netherlands)

    Rothenburg, L.; Kruyt, N.P.

    2009-01-01

    A micromechanical theory is formulated for quasi-static deformation of granular materials, which is based on information theory. A reasoning is presented that leads to the definition of an information entropy that is appropriate for quasi-static deformation of granular materials. This definition is

  6. Ultrasensitive thermometer for atmospheric pressure operation based on a micromechanical resonator

    DEFF Research Database (Denmark)

    Cagliani, Alberto; Pini, V.; Tamayo, J.;

    2014-01-01

    For highly integrated systems for bio and chemical analysis a precise and integrated measurement of temperature is of fundamental importance. We have developed an ultrasensitive thermometer based on a micromechanical resonator for operation in air. The high quality factor and the strong temperatu...

  7. Cooling a micromechanical resonator to its ground state by measurement and feedback

    DEFF Research Database (Denmark)

    Bergenfeldt, Christian; Mølmer, Klaus

    2009-01-01

    We present an analysis of the cooling of a micromechanical resonator by means of measurement and feedback. The measurements are performed via the coupling to a Cooper-pair box, and although the coupling does not lead to net cooling, the extraction of information and hence entropy from the system...

  8. A micromechanical study of porous composites under longitudinal shear and transverse normal loading

    DEFF Research Database (Denmark)

    Ashouri Vajari, Danial

    2015-01-01

    The mechanical response of porous unidirectional composites under transverse normal and longitudinal shear loading is studied using the finite element analysis. The 3D model includes discrete and random distribution of fibers and voids. The micromechanical failure mechanisms are taken into accoun...

  9. Mini-Symposium on Micromechanics at the CSME Mechanical Engineering Forum

    CERN Document Server

    Muschik, W

    1991-01-01

    This volume contains the lectures presented at the mini-symposium on "Micromechanics" held in conjunction with the CSME Mechanical Engineer­ ing Forum 1990 between the 3rd and 8th June, 1990 at the University of Toronto, Canada. The expressed purpose of this symposium was to discuss some recent developments in the Micromechanics of Materials and how ad­ vances in this field now relate to the solution of practical engineer­ ing problems. Due to the time limit set for this section of the Engineer­ ing Forum as well as the restriction on the number of papers to be pre­ sented, it was not possible to cover a much wider range of topics. How­ ever, an attempt was made to include the most important advances asso­ ciated with the progress made in micromechanics in its application to material science and engineering over the past decade. Thus, the topics are concerned with: the fundamental aspects of the thermodynamics of structured solids (part I), - the micromechanical behaviour of alloys (part II), - the mod...

  10. Determination of fiber-matrix interface failure parameters from off-axis tests

    Science.gov (United States)

    Naik, Rajiv A.; Crews, John H., Jr.

    1993-01-01

    Critical fiber-matrix (FM) interface strength parameters were determined using a micromechanics-based approach together with failure data from off-axis tension (OAT) tests. The ply stresses at failure for a range of off-axis angles were used as input to a micromechanics analysis that was performed using the personal computer-based MICSTRAN code. FM interface stresses at the failure loads were calculated for both the square and the diamond array models. A simple procedure was developed to determine which array had the more severe FM interface stresses and the location of these critical stresses on the interface. For the cases analyzed, critical FM interface stresses were found to occur with the square array model and were located at a point where adjacent fibers were closest together. The critical FM interface stresses were used together with the Tsai-Wu failure theory to determine a failure criterion for the FM interface. This criterion was then used to predict the onset of ply cracking in angle-ply laminates for a range of laminate angles. Predictions for the onset of ply cracking in angle-ply laminates agreed with the test data trends.

  11. Three-dimensional micromechanical models for the nonlinear analysis of pultruded composite structures

    Science.gov (United States)

    Kilic, Mustafa Hakan

    This study presents a new three-dimensional (3D) micromechanics-based nonlinear framework for the analysis of pultruded composite structures. The proposed material modeling framework is a nested micromechanical approach that explicitly recognizes the different composite systems within the cross-section of a pultruded composite member. The 3D lamination theory is used to generate a homogenized nonlinear effective response using a through-thickness representative stacking sequence. Different 3D micromechanical models can be used to represent the composite layers within the repeating stacking sequence, e.g. roving layer, continuous filament mat (CFM), and woven fabrics. The proposed modeling framework is applied for pultruded composite material systems made from roving and CFM. The roving layer is idealized using an existing 3D nonlinear micromechanics model for a unidirectional fiber reinforced material. A simple nonlinear micromechanical model for the CFM layer is introduced and implemented. The overall modeling approach is able to predict both the elastic and nonlinear response of the composite material based on the in-situ properties and response of the fiber and matrix constituents. Experimental data, from off-axis tests of pultruded plates, is used to verify the proposed modeling approach. The 3D modeling framework shows good prediction capabilities for the overall effective elastic constants, as well as the nonlinear multi-axial stress-strain response. In addition, a simple degradation and damage modeling is coupled with the proposed analysis framework. Several applications are performed for the nonlinear analysis of pultruded composite structures, such as progressive failure analysis of notched plates, bending of short beams, and damage analysis of pultruded FRP bolted connections.

  12. Testing Interfaces

    DEFF Research Database (Denmark)

    Holbøll, Joachim T.; Henriksen, Mogens; Nilson, Jesper K.;

    1999-01-01

    The wide use of solid insulating materials combinations in combinations has introduced problems in the interfaces between components. The most common insulating materials are cross-linked polyethylene (XLPE), silicone rubber (SIR) and ethylene-propylene rubbers (EPR). Assemblies of these materials...... have caused major failures. In the Netherlands, a major black out was caused by interface problems in 150kV cable terminations, causing a cascade of breakdowns. There is a need to investigate the reasons for this and other similar breakdowns.The major problem is expected to lie in the interface between...... two different materials. Environmental influence, surface treatment, defects in materials and interface, design, pressure and rubbing are believed to have an effect on interface degradation. These factors are believed to increase the possibility of partial discharges (PD). PD will, with time, destroy...

  13. Testing Interfaces

    DEFF Research Database (Denmark)

    Holbøll, Joachim T.; Henriksen, Mogens; Nilson, Jesper K.;

    1999-01-01

    The wide use of solid insulating materials combinations in combinations has introduced problems in the interfaces between components. The most common insulating materials are cross-linked polyethylene (XLPE), silicone rubber (SIR) and ethylene-propylene rubbers (EPR). Assemblies of these materials...... have caused major failures. In the Netherlands, a major black out was caused by interface problems in 150kV cable terminations, causing a cascade of breakdowns. There is a need to investigate the reasons for this and other similar breakdowns. The major problem is expected to lie in the interface...... between two different materials. Environmental influence, surface treatment, defects in materials and interface, design, pressure and rubbing are believed to have an effect on interface degradation. These factors are believed to increase the possibility of partial discharges (PD). PD will, with time...

  14. In-Situ Micromechanical Testing in Extreme Environments

    Science.gov (United States)

    Lupinacci, Amanda Sofia

    In order to design engineering applications that can withstand extreme environments, we must first understand the underlying deformation mechanisms that can hinder material performance. It is not enough to characterize the mechanical properties alone, we must also characterize the microstructural changes as well so that we can understand the origin of material degradation. This dissertation focuses on two different extreme environments. The first environment is the cryogenic environment, where we focus on the deformation behavior of solder below the ductile to brittle transition temperature (DBTT). The second environment is the irradiated environment, where we focus on the effects that ion beam irradiation has on both the mechanical properties and microstructure of 304 stainless steel. Both classes of materials and testing environments utilize novel in situ micromechanical testing techniques inside a scanning electron microscope which enhances our ability to link the observed deformation behavior with its associated mechanical response. Characterizing plasticity mechanisms below the DBTT is traditionally difficult to accomplish in a systematic fashion. Here, we use a new experimental setup to perform in situ cryogenic mechanical testing of pure Sn micropillars at room temperature and at -142 °C. Subsequent electron microscopy characterization of the micropillars shows a clear difference in the deformation mechanisms at room temperature and at cryogenic temperatures. At room temperature, the Sn micropillars deformed through dislocation plasticity while at -142 °C they exhibited both higher strength and deformation twinning. Two different orientations were tested, a symmetric (100) orientation and a non-symmetric (45¯1) orientation. The deformation mechanisms were found to be the same for both orientations. This approach was also extended to a more complex solder alloy that is commonly used in industry, Sn96. In the case of the solder alloy more complex geometries

  15. Microprocessor interfacing

    CERN Document Server

    Vears, R E

    2014-01-01

    Microprocessor Interfacing provides the coverage of the Business and Technician Education Council level NIII unit in Microprocessor Interfacing (syllabus U86/335). Composed of seven chapters, the book explains the foundation in microprocessor interfacing techniques in hardware and software that can be used for problem identification and solving. The book focuses on the 6502, Z80, and 6800/02 microprocessor families. The technique starts with signal conditioning, filtering, and cleaning before the signal can be processed. The signal conversion, from analog to digital or vice versa, is expl

  16. Micromechanics approach to poroelastic behavior of a jointed rock

    OpenAIRE

    Maghous, Samir; Dormieux, Luc; Kondo, Djimédo; SHAO, Jian Fu

    2013-01-01

    The formulation of macroscopic poroelastic behavior of a jointed rock is investigated within the framework of a micro-macro approach. The joints are modeled as interfaces, and their behavior is modeled by means of generalized poroelastic state equations. Starting from Hill's lemma extended for a jointed medium and extending the concept of strain concentration to relate the joint displacement jump to macroscopic strain, the overall poroelastic constitutive equations for the jointed rock are fo...

  17. EDITORIAL: The 19th MicroMechanics Europe Workshop (MME 2008) The 19th MicroMechanics Europe Workshop (MME 2008)

    Science.gov (United States)

    Schnakenberg, Uwe

    2009-07-01

    This special issue of Journal of Micromechanics and Microengineering is devoted to the 19th MicroMechanics Europe Workshop (MME 08), which took place at the RWTH Aachen University, Aachen, Germany, from 28-30 September, 2008. The workshop is a well recognized and established European event in the field of micro system technology using thin-film technologies for creating micro components, micro sensors, micro actuators, and micro systems. The first MME Workshop was held 1989 in Enschede (The Netherlands) and continued 1990 in Berlin (Germany), 1992 in Leuven (Belgium), and then was held annually in Neuchâtel (Switzerland), Pisa (Italy), Copenhagen (Denmark), Barcelona (Spain), Southampton (UK), Ulvik in Hardanger (Norway), Gif-sur-Yvette (France), Uppsala (Sweden), Cork (Ireland), Sinaia (Romania), Delft (The Netherlands), Leuven (Belgium), Göteborg (Sweden), Southampton (UK), and in Guimarães (Portugal). The two day workshop was attended by 180 delegates from 26 countries all over Europe and from Armenia, Austria, Bulgaria, Canada, China, Cuba, Iran, Japan, Korea, Malaysia, Taiwan, Turkey, and the United States of America. A total of 97 papers were accepted for presentation and there were a further five keynote presentations. I am proud to present 22 high-quality papers from MME 2008 selected for their novelty and relevance to Journal of Micromechanics and Microengineering. All the papers went through the regular reviewing procedure of IOP Publishing. I am eternally grateful to all the referees for their excellent work. I would also like to extend my thanks to the members of the Programme Committee of MME 2008, Dr Reinoud Wolffenbuttel, Professor José Higino Correia, and Dr Patrick Pons for pre-selection of the papers as well as to Professor Robert Puers for advice on the final selection of papers. My thanks also go to Dr Ian Forbes of IOP Publishing for managing the entire process and to the editorial staff of Journal of Micromechanics and Microengineering. I

  18. Interface Strength in NiAl-Mo Composites from 3D X-ray Microdiffraction

    Energy Technology Data Exchange (ETDEWEB)

    Barabash, Rozaliya [ORNL; Bei, Hongbin [ORNL; Gao, Yanfei [ORNL; Ice, Gene E [ORNL

    2011-01-01

    The depth-dependent strain gradients near buried interfaces in a model system of NiAl-Mo composite were nondestructively probed with 3-D X-ray microdiffraction. Coupled with micromechanical analysis, our study shows that the relaxation of the residual thermal strains in the NiAl-Mo composites results in the formation of a near-surface 'slip zone' with large strain gradients in both the reinforcing Mo fibers and NiAl matrix. Based on these results an approach to calculate the fiber-matrix interface strength for composite materials is suggested.

  19. Analysis of metal-matrix composite structures. I - Micromechanics constitutive theory. II - Laminate analyses

    Science.gov (United States)

    Arenburg, R. T.; Reddy, J. N.

    1991-01-01

    The micromechanical constitutive theory is used to examine the nonlinear behavior of continuous-fiber-reinforced metal-matrix composite structures. Effective lamina constitutive relations based on the Abouli micromechanics theory are presented. The inelastic matrix behavior is modeled by the unified viscoplasticity theory of Bodner and Partom. The laminate constitutive relations are incorporated into a first-order deformation plate theory. The resulting boundary value problem is solved by utilizing the finite element method. Attention is also given to computational aspects of the numerical solution, including the temporal integration of the inelastic strains and the spatial integration of bending moments. Numerical results the nonlinear response of metal matrix composites subjected to extensional and bending loads are presented.

  20. An extended micromechanics method for probing interphase properties in polymer nanocomposites

    Science.gov (United States)

    Liu, Zeliang; Moore, John A.; Liu, Wing Kam

    2016-10-01

    Inclusions comprised on filler particles and interphase regions commonly form complex morphologies in polymer nanocomposites. Addressing these morphologies as systems of overlapping simple shapes allows for the study of dilute particles, clustered particles, and interacting interphases all in one general modeling framework. To account for the material properties in these overlapping geometries, weighted-mean and additive overlapping conditions are introduced and the corresponding inclusion-wise integral equations are formulated. An extended micromechanics method based on these overlapping conditions for linear elastic and viscoelastic heterogeneous material is then developed. An important feature of the proposed approach is that the effect of both the geometric overlapping (clustered particles) and physical overlapping (interacting interphases) on the effective properties can be distinguished. We apply the extended micromechanics method to a viscoelastic polymer nanocomposite with interphase regions, and estimate the properties and thickness of the interphase region based on experimental data for carbon-black filled styrene butadiene rubbers.

  1. Micromechanics-Based Progressive Failure Analysis of Composite Laminates Using Different Constituent Failure Theories

    Science.gov (United States)

    Moncada, Albert M.; Chattopadhyay, Aditi; Bednarcyk, Brett A.; Arnold, Steven M.

    2008-01-01

    Predicting failure in a composite can be done with ply level mechanisms and/or micro level mechanisms. This paper uses the Generalized Method of Cells and High-Fidelity Generalized Method of Cells micromechanics theories, coupled with classical lamination theory, as implemented within NASA's Micromechanics Analysis Code with Generalized Method of Cells. The code is able to implement different failure theories on the level of both the fiber and the matrix constituents within a laminate. A comparison is made among maximum stress, maximum strain, Tsai-Hill, and Tsai-Wu failure theories. To verify the failure theories the Worldwide Failure Exercise (WWFE) experiments have been used. The WWFE is a comprehensive study that covers a wide range of polymer matrix composite laminates. The numerical results indicate good correlation with the experimental results for most of the composite layups, but also point to the need for more accurate resin damage progression models.

  2. Cyclic deformation behavior of an {alpha}/{beta} titanium alloy. 2: Internal stresses and micromechanic modelling

    Energy Technology Data Exchange (ETDEWEB)

    Feaugas, X.; Clavel, M. [Univ. de Technologie de Compiegne (France); Pilvin, P. [Univ. Paris VI, Evry (France)]|[Ecole des Mines de Paris, Evry (France). Centre des Materiaux

    1997-07-01

    A micromechanic model was used to study the influence of the different microstructure heterogeneity levels of an {alpha}/{beta} titanium alloy during monotonic and cyclic loadings. In the micromechanic model two levels of heterogeneity were considered: the cell and the two phases ({alpha} and {beta}). The cell is defined as an {alpha} (h.c.p.) crystal surrounded by {beta}-phase (b.c.c.). A modified Kroener`s rule is used to describe the stress localization. This rule takes into account the elasto-plastic accommodation between cells and between phases. The main results are the following: the rate of reduction of the {alpha}/{beta} incompatibilities is greater than that associated with inter-cells and the cyclic softening depends not only on the reduction of the transgranular incompatibilities ({alpha}-phase), but also on inter-cell internal stress redistribution.

  3. Micromechanical exfoliation of two-dimensional materials by a polymeric stamp

    Science.gov (United States)

    Ferraz da Costa, M. C.; Ribeiro, H. B.; Kessler, F.; de Souza, E. A. T.; Fechine, G. J. M.

    2016-02-01

    In this work, an alternative technique to the traditional micromechanical exfoliation of two-dimensional materials is proposed, consisting of isolated flakes of graphite and molybdenum disulphide onto polymeric surfaces films. The set made up of polymer and flakes is fabricated by using a hot-press machine called polymeric stamp. The polymeric stamp was used to allocate flakes and also to allow the exfoliation process to take place just in one face of isolated flake. Optical microscopy, Raman spectroscopy and photoluminescence spectroscopy results showed that multilayers, bilayers and single layers of graphene and MoS2 were obtained by using a polymeric stamp as tool for micromechanical exfoliation. These crystals were more easily found because the exfoliation process concentrates them in well-defined locations. The results prove the effectiveness of the method by embedding two-dimensional materials into polymers to fabricate fewer layers crystals in a fast, economic and clean way.

  4. Reducing support loss in micromechanical ring resonators using phononic band-gap structures

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Feng-Chia; Huang, Tsun-Che; Wang, Chin-Hung; Chang, Pin [Industrial Technology Research Institute-South, Tainan 709, Taiwan (China); Hsu, Jin-Chen, E-mail: fengchiahsu@itri.org.t, E-mail: hsujc@yuntech.edu.t [Department of Mechanical Engineering, National Yunlin University of Science and Technology, Douliou, Yunlin 64002, Taiwan (China)

    2011-09-21

    In micromechanical resonators, energy loss via supports into the substrates may lead to a low quality factor. To eliminate the support loss, in this paper a phononic band-gap structure is employed. We demonstrate a design of phononic-crystal (PC) strips used to support extensional wine-glass mode ring resonators to increase the quality factor. The PC strips are introduced to stop elastic-wave propagation by the band-gap and deaf-band effects. Analyses of resonant characteristics of the ring resonators and the dispersion relations, eigenmodes, and transmission properties of the PC strips are presented. With the proposed resonator architecture, the finite-element simulations show that the leaky power is effectively reduced and the stored energy inside the resonators is enhanced simultaneously as the operating frequencies of the resonators are within the band gap or deaf bands. Realization of a high quality factor micromechanical ring resonator with minimized support loss is expected.

  5. Fatigue crack tip damaging micromechanisms in a ferritic-pearlitic ductile cast iron

    Directory of Open Access Journals (Sweden)

    Francesco Iacoviello

    2015-07-01

    Full Text Available Due to the peculiar graphite elements shape, obtained by means of a chemical composition control (mainly small addition of elements like Mg, Ca or Ce, Ductile Cast Irons (DCIs are able to offer the good castability of gray irons with the high mechanical properties of irons (first of all, toughness. This interesting properties combination can be improved both by means of the chemical composition control and by means of different heat treatments(e.g. annealing, normalizing, quenching, austempering etc. In this work, fatigue crack tip damaging micromechanisms in a ferritic-pearlitic DCI were investigated by means of scanning electron microscope observations performed on a lateral surface of Compact Type (CT specimens during the fatigue crack propagation test (step by step procedure, performed according to the “load shedding procedure”. On the basis of the experimental results, different fatigue damaging micromechanisms were identified, both in the graphite nodules and in the ferritic – pearlitic matrix.

  6. Ascertaining the micromechanical damage parameters using the small scale test specimens

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, N.N. (HBNI, RSD, BARC, Trombay (India)), e-mail: naveenm@barc.gov.in; Durgaprasad, P.V.; Dutta, B.K. (Reactor Safety Division, Bhabha Atomic Research Centre Trombay (India)); Dey, G.K. (Material Science Division, Bhabha Atomic Research Centre Trombay (India))

    2009-07-01

    Objective of the study is to ascertain the damage parameters and stress strain behaviour of material under irradiated condition. To achieve this goal, following methodology is employed; a) Elastic-plastic and micro-mechanical analysis of small punch test is carried out. From the elastic plastic analysis, friction factor between the ball and specimen is found. From micro mechanical analysis, Gurson damage parameters are calibrated by comparing simulation results with experimental result of unirradiated material; b) load-displacement behaviour of small punch tests are obtained by assuming the damage parameters are unchanged due to irradiation and with approximate shift in the stress strain curve; c) Comparing the above small punch results with experimental load displacement data of irradiated sample, the stress-strain data of irradiated samples is obtained. At the next stage, the fracture properties like J-R curve can be evaluated for standard CT specimens by employing the calibrated micromechanical damage parameters and stress strain data

  7. Micromechanical study of the effect of inclusions on fatigue failure in a roller bearing

    DEFF Research Database (Denmark)

    Cerullo, Michele; Tvergaard, Viggo

    2015-01-01

    Purpose - The purpose of this paper is to carry out a set of micromechanical analyses to study the effect of small inclusions on fatigue life of wind turbine bearings. Design/methodology/approach - The local stress concentrations around an inclusion are determined from a characteristic unit cell...... of the most commonly used bearing steels, AISI 52100, and two different types of inclusions are considered. The macroscopic stress histories applied correspond to either a Hertzian or an elastohydrodynamic (EHL) contact pressure distribution under the rollers. Findings - The paper shows that sub-surface...... to work in the very high cycle regime (N>109 cycles). This paper develops a micromechanical study that provides a deeper understanding on effect of inclusions on the fatigue life, according to one of the most used multiaxial fatigue criteria....

  8. Sediment Micromechanics in Sheet Flows Induced by Asymmetric Waves: A CFD-DEM Study

    CERN Document Server

    Sun, Rui

    2016-01-01

    Understanding the sediment transport in oscillatory flows is essential to the investigation of the overall sediment budget for coastal regions. This overall budget is crucial for the prediction of the morphological change of the coastline in engineering applications. Since the sediment transport in oscillatory flows is dense particle-laden flow, appropriate modeling of the particle interaction is critical. Although traditional two-fluid approaches have been applied to the study of sediment transport in oscillatory flows, the approaches do not resolve the interaction of the particles. Particle-resolved modeling of sediment transport in oscillatory flows and the study of micromechanics of sediment particles are still lacking. In this work, a parallel CFD-DEM solver SediFoam that can resolve the inter-particle collision is applied to study the granular micromechanics of sediment particles in oscillatory flows. The results obtained from SediFoam are validated by the experimental data of coarse and medium sands. T...

  9. In-Situ Micromechanical Testing in Extreme Environments

    Science.gov (United States)

    Lupinacci, Amanda Sofia

    In order to design engineering applications that can withstand extreme environments, we must first understand the underlying deformation mechanisms that can hinder material performance. It is not enough to characterize the mechanical properties alone, we must also characterize the microstructural changes as well so that we can understand the origin of material degradation. This dissertation focuses on two different extreme environments. The first environment is the cryogenic environment, where we focus on the deformation behavior of solder below the ductile to brittle transition temperature (DBTT). The second environment is the irradiated environment, where we focus on the effects that ion beam irradiation has on both the mechanical properties and microstructure of 304 stainless steel. Both classes of materials and testing environments utilize novel in situ micromechanical testing techniques inside a scanning electron microscope which enhances our ability to link the observed deformation behavior with its associated mechanical response. Characterizing plasticity mechanisms below the DBTT is traditionally difficult to accomplish in a systematic fashion. Here, we use a new experimental setup to perform in situ cryogenic mechanical testing of pure Sn micropillars at room temperature and at -142 °C. Subsequent electron microscopy characterization of the micropillars shows a clear difference in the deformation mechanisms at room temperature and at cryogenic temperatures. At room temperature, the Sn micropillars deformed through dislocation plasticity while at -142 °C they exhibited both higher strength and deformation twinning. Two different orientations were tested, a symmetric (100) orientation and a non-symmetric (45¯1) orientation. The deformation mechanisms were found to be the same for both orientations. This approach was also extended to a more complex solder alloy that is commonly used in industry, Sn96. In the case of the solder alloy more complex geometries

  10. Design considerations for micromechanical sensors using encapsulated built-in resonant strain gauges

    OpenAIRE

    Tilmans, Harrie A.C.; Bouwstra, Siebe; Fluitman, Jan H.J; Spence, Scott L.

    1990-01-01

    This paper describes the various design aspects for micromechanical sensors consisting of a structure with encapsulated built-in resonant strain gauges. Analytical models are used to investigate the effect of device parameters on the behaviour of a pressure sensor and a force sensor. The analyses indicate that the sealing cap can have a strong degrading effect on the device performance if the thicknesses of the cap and of the supporting structure are of the same order of magnitude. A novel de...

  11. Micromechanical modelling of nanocrystalline and ultrafine grained metals: A short overview

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon; Levashov, Evgeny

    2015-01-01

    An overview of micromechanical models of strength and deformation behaviour of nanostructured and ultrafine grained metallic materials is presented. Composite models of nanomaterials, polycrystal plasticity based models, grain boundary sliding, the effect of non-equilibrium grain boundaries...... and nanoscale properties are discussed and compared. The examples of incorporation of peculiar nanocrystalline effects (like large content of amorphous or semi-amorphous grain boundary phase, partial dislocation GB emission/glide/GB absorption based deformation mechanism, diffusion deformation, etc...

  12. Nano- and micromechanical properties of dentine: investigation of differences with tooth side

    OpenAIRE

    Brauer, Delia S.; Hilton, Joan F.; Marshall, Grayson W.; Marshall, Sally J.

    2011-01-01

    The soft zone in dentine beneath the dentino-enamel junction is thought to play an important role in tooth function, strain distribution and fracture resistance during mastication. Recently reported asymmetry in mechanical properties with tooth side may point at a basic property of tooth function. The aim of our study was to test if this asymmetry was reflected in the nano- and micromechanical properties of dentine.

  13. Micromechanical analysis of nanocomposites using 3D voxel based material model

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon

    2012-01-01

    A computational study on the effect of nanocomposite structures on the elastic properties is carried out with the use of the 3D voxel based model of materials and the combined Voigt–Reuss method. A hierarchical voxel based model of a material reinforced by an array of exfoliated and intercalated ...... of glass fibers in hybrid (hierarchical) composites, using the micromechanical voxel-based model of nanocomposites, it was observed that the nanoreinforcement in the matrix leads to slightly lower fiber failure probability....

  14. Pattern recognition characterizations of micromechanical and morphological materials states via analytical quantitative ultrasonics

    Science.gov (United States)

    Williams, J. H., Jr.; Lee, S. S.

    1986-01-01

    One potential approach to the quantitative acquisition of discriminatory information that can isolate a single structural state is pattern recognition. The pattern recognition characterizations of micromechanical and morphological materials states via analytical quantiative ultrasonics are outlined. The concepts, terminology, and techniques of statistical pattern recognition are reviewed. Feature extraction and classification and states of the structure can be determined via a program of ultrasonic data generation.

  15. Micromechanics Analysis Code With Generalized Method of Cells (MAC/GMC): User Guide. Version 3

    Science.gov (United States)

    Arnold, S. M.; Bednarcyk, B. A.; Wilt, T. E.; Trowbridge, D.

    1999-01-01

    The ability to accurately predict the thermomechanical deformation response of advanced composite materials continues to play an important role in the development of these strategic materials. Analytical models that predict the effective behavior of composites are used not only by engineers performing structural analysis of large-scale composite components but also by material scientists in developing new material systems. For an analytical model to fulfill these two distinct functions it must be based on a micromechanics approach which utilizes physically based deformation and life constitutive models and allows one to generate the average (macro) response of a composite material given the properties of the individual constituents and their geometric arrangement. Here the user guide for the recently developed, computationally efficient and comprehensive micromechanics analysis code, MAC, who's predictive capability rests entirely upon the fully analytical generalized method of cells, GMC, micromechanics model is described. MAC/ GMC is a versatile form of research software that "drives" the double or triply periodic micromechanics constitutive models based upon GMC. MAC/GMC enhances the basic capabilities of GMC by providing a modular framework wherein 1) various thermal, mechanical (stress or strain control) and thermomechanical load histories can be imposed, 2) different integration algorithms may be selected, 3) a variety of material constitutive models (both deformation and life) may be utilized and/or implemented, and 4) a variety of fiber architectures (both unidirectional, laminate and woven) may be easily accessed through their corresponding representative volume elements contained within the supplied library of RVEs or input directly by the user, and 5) graphical post processing of the macro and/or micro field quantities is made available.

  16. Mechanobiological regulation of bone remodeling -- Theoretical development of a coupled systems biology-micromechanical approach

    OpenAIRE

    Scheiner, Stefan; Pivonka, Peter; Hellmich, Christian; Smith, David W.

    2012-01-01

    Bone remodeling involves the coordinated removal of bone by osteoclasts and addition of bone by osteoblasts, a process that is modulated by the prevailing mechanical environment. In this paper a fully coupled model of bone remodeling is developed, based on coupling a bone cell population model with a micromechanical homogenization scheme of bone stiffness. While the former model considers biochemical regulatory mechanisms between bone cells such as the RANK-RANKL-OPG pathway and action of TGF...

  17. Micromechanical modeling of the elastic behavior of unidirectional CVI SiC/SiC composites

    OpenAIRE

    CHATEAU, Camille; GELEBART, Lionel; Bornert, Michel; CREPIN, Jérôme

    2015-01-01

    The elastic behavior of SiC/SiC composite is investigated at the scale of the tow through a micromechanical modeling taking into account the heterogeneous nature of the microstructure. The paper focuses on the sensitivity of transverse properties to the residual porosity resulting from the matrix infiltration process. The full analysis is presented stepwise, starting from the microstructural characterization to the study of the impact of pore shape and volume fraction. Various Volume Elements...

  18. Micromechanics model for predicting anisotropic electrical conductivity of carbon fiber composite materials

    Science.gov (United States)

    Haider, Mohammad Faisal; Haider, Md. Mushfique; Yasmeen, Farzana

    2016-07-01

    Heterogeneous materials, such as composites consist of clearly distinguishable constituents (or phases) that show different electrical properties. Multifunctional composites have anisotropic electrical properties that can be tailored for a particular application. The effective anisotropic electrical conductivity of composites is strongly affected by many parameters including volume fractions, distributions, and orientations of constituents. Given the electrical properties of the constituents, one important goal of micromechanics of materials consists of predicting electrical response of the heterogeneous material on the basis of the geometries and properties of the individual phases, a task known as homogenization. The benefit of homogenization is that the behavior of a heterogeneous material can be determined without resorting or testing it. Furthermore, continuum micromechanics can predict the full multi-axial properties and responses of inhomogeneous materials, which are anisotropic in nature. Effective electrical conductivity estimation is performed by using classical micromechanics techniques (composite cylinder assemblage method) that investigates the effect of the fiber/matrix electrical properties and their volume fractions on the micro scale composite response. The composite cylinder assemblage method (CCM) is an analytical theory that is based on the assumption that composites are in a state of periodic structure. The CCM was developed to extend capabilities variable fiber shape/array availability with same volume fraction, interphase analysis, etc. The CCM is a continuum-based micromechanics model that provides closed form expressions for upper level length scales such as macro-scale composite responses in terms of the properties, shapes, orientations and constituent distributions at lower length levels such as the micro-scale.

  19. Micromechanical Properties of Injection-Molded Starch–Wood Particle Composites

    OpenAIRE

    Ueberschaer, A.; Cagiao, M. E.; Bayer, R. K.; Henning, S; Baltá Calleja, F. J.

    2006-01-01

    The micromechanical properties of injection molded starch–wood particle composites were investigated as a function of particle content and humidity conditions. The composite materials were characterized by scanning electron microscopy and X-ray diffraction methods. The microhardness of the composites was shown to increase notably with the concentration of the wood particles. In addition,creep behavior under the indenter and temperature dependence were evaluated in terms of the indepe...

  20. Fatigue damage in short glass fiber reinforced PA66: Micromechanical modeling and multiscale identification approach

    OpenAIRE

    DESPRINGRE, Nicolas; CHEMISKY, Yves; Meraghni, Fodil; FITOUSSI, Joseph; Robert, Gilles

    2015-01-01

    The paper presents a new micromechanical high cycle fatigue visco-damage model for short glass fiber reinforced thermoplastic composites, namely: PA66/GF30. This material, extensively used for automotive applications, has a specific microstructure which is induced by the injection process. The multi-scale developed approach is a modified Mori-Tanaka method that includes coated reinforcements and the evolution of micro-scale damage processes. The description of the damage processes is based on...

  1. Activation barrier scaling and crossover for noise-induced switching in a micromechanical parametric oscillator

    OpenAIRE

    Chan, H. B.; Stambaugh, C.

    2006-01-01

    We explore fluctuation-induced switching in a parametrically-driven micromechanical torsional oscillator. The oscillator possesses one, two or three stable attractors depending on the modulation frequency. Noise induces transitions between the coexisting attractors. Near the bifurcation points, the activation barriers are found to have a power law dependence on frequency detuning with critical exponents that are in agreement with predicted universal scaling relationships. At large detuning, w...

  2. Micromechanical Study of Rock Fracture and Fragmentation under Dynamic Loads using Discrete Element Method

    OpenAIRE

    Kazerani, Tohid

    2011-01-01

    The study presented in this thesis aims to numerically explore the micro-mechanisms underlying rock fracture and fragmentation under dynamic loading. The approach adopted is based on the Discrete Element Method (DEM) coupled to the Cohesive Process Zone (CPZ) theory. It assumes rock material as assemblage of irregular-sized deformable fragments joining together at their cohesive boundaries. The simulation, which is referred to as Cohesive Fragment Mod...

  3. Micromechanical effective elastic moduli of continuous fiber-reinforced composites with near-field fiber interactions

    OpenAIRE

    Ju, J. W.; Yanase, K

    2011-01-01

    A higher-order micromechanical framework is presented to predict the overall elastic deformation behavior of continuous fiber-reinforced composites with high-volume fractions and random-fiber distributions. By taking advantage of the probabilistic pair-wise near-field interaction solution, the interacting eigenstrain is analytically derived. Subsequently, by making use of the Eshelby equivalence principle, the perturbed strain within a continuous circular fiber is accounted for. Further, base...

  4. Micromechanical investigation of soil plasticity using a discrete model of polygonal particles

    OpenAIRE

    Alonso-Marroquin Fernando; Muhlhaus Hans B.; Herrmann Hans J.

    2008-01-01

    The mechanical behavior of soils has been traditionally described using continuum-mechanics-based models. These are empirical relations based on laboratory tests of soil specimens. The investigation of the soils at the grain scale using discrete element models has become possible in recent years. These models have provided valuable understanding of many micromechanical aspects of soil deformation. The aim of this work is to draw together these two approaches in the investigation of the plasti...

  5. In situ study of granular micromechanics in semi-solid carbon steels

    OpenAIRE

    Fonseca, J.,; O'Sullivan, C.; NAGIRA, T; Yasuda, H.; Gourlay, C. M.

    2013-01-01

    The granular micromechanics of semi-solid steel at ∼80% solid are studied by synchrotron radiography. A particulate soil mechanics approach to image analysis shows that deformation occurs by the translation and rotation of quasi-rigid grains under the action of contact forces, and that the changes in directional fabric and grain–grain contacts occur by mechanisms similar to those of highly compacted soils including “locked sands”. Grain-scale phenomena are then linked to the macroscopic displ...

  6. Activation barrier scaling and crossover for noise-induced switching in micromechanical parametric oscillators.

    Science.gov (United States)

    Chan, H B; Stambaugh, C

    2007-08-10

    We explore fluctuation-induced switching in parametrically driven micromechanical torsional oscillators. The oscillators possess one, two, or three stable attractors depending on the modulation frequency. Noise induces transitions between the coexisting attractors. Near the bifurcation points, the activation barriers are found to have a power law dependence on frequency detuning with critical exponents that are in agreement with predicted universal scaling relationships. At large detuning, we observe a crossover to a different power law dependence with an exponent that is device specific.

  7. Polydimethylsiloxane, a photocurable rubberelastic polymer used as spring material in micromechanical sensors

    OpenAIRE

    Lotters, J.C.; Olthuis, W; Veltink, P.H.; Bergveld, P.

    1997-01-01

    Polydimethylsiloxane (PDMS) is a commercially available physically and chemically stable photocurable silicone rubber which has a unique flexibility (G≈250 kPa) at room temperature. Further properties of PDMS are a low elasticity change versus temperature (1.1 kPa/°C), no elasticity change versus frequency and a high compressibility. PDMS is an interesting polymer to be used as spring material in micromechanical sensors such as accelerometers. The spring constant of the PDMS structures was th...

  8. Relations between a micro-mechanical model and a damage model for ductile failure in shear

    DEFF Research Database (Denmark)

    Tvergaard, Viggo; Nielsen, Kim Lau

    2010-01-01

    Gurson type constitutive models that account for void growth to coalescence are not able to describe ductile fracture in simple shear, where there is no hydrostatic tension in the material. But recent micro-mechanical studies have shown that in shear the voids are flattened out to micro-cracks, w......Gurson type constitutive models that account for void growth to coalescence are not able to describe ductile fracture in simple shear, where there is no hydrostatic tension in the material. But recent micro-mechanical studies have shown that in shear the voids are flattened out to micro......-cracks, which rotate and elongate until interaction with neighbouring micro-cracks gives coalescence. Thus, the failure mechanism is very different from that under tensile loading. Also, the Gurson model has recently been extended to describe failure in shear, by adding a damage term to the expression...... for the growth of the void volume fraction, and it has been shown that this extended model can represent experimental observations. Here, numerical studies are carried out to compare predictions of the shear-extended Gurson model with the shear failures predicted by the micro-mechanical cell model. Both models...

  9. Research on failure criterion of composite based on unified macro-and micro-mechanical model

    Institute of Scientific and Technical Information of China (English)

    Sun Zhigang; Zhao Long; Chen Lei; Song Yingdong

    2013-01-01

    A new unified macro-and micro-mechanics failure analysis method for composite structures was developed in order to take the effects of composite micro structure into consideration.In this method,the macro stress distribution of composite structure was calculated by commercial finite element analysis software.According to the macro stress distribution,the damage point was searched and the micro-stress distribution was calculated by reformulated finite-volume direct averaging micromechanics (FVDAM),which was a multi-scale finite element method for composite.The micro structure failure modes were estimated with the failure strength of constituents.A unidirectional composite plate with a circular hole in the center under two kinds of loads was analyzed with the traditional macro-mechanical failure analysis method and the unified macro-and micro-mechanics failure analysis method.The results obtained by the two methods are consistent,which show this new method's accuracy and efficiency.

  10. Micro-mechanical properties of 2219 welded joints with twin wire welding

    Institute of Scientific and Technical Information of China (English)

    Xu Wenli; Li Qingfen; Meng Qingguo; Fang Hongyuan; Gao Na

    2006-01-01

    Nanoindentation method was adopted to investigate the distribution regularities of micro-mechanical properties of 2219 twin wire welded joints, thus providing the necessary theoretical basis and guidance for joint strengthening and improvement of welding procedure.Experimental results show that in weld zone, micro-mechanical properties are seriously uneven.Both hardness and elastic modulus distribute as uneven sandwich layers, while micro-mechanical properties in bond area are much more uniform than weld zone;In heat-affected zone of 2219 twin wire welded joint, distribution regularity of hardness is similar to elastic modulus.The average hardness in quenching zone is higher than softening zone, and the average elastic modulus in solid solution zone is slightly higher than softening zone.As far as the whole welded joint is concerned,metal in weld possesses the lowest hardness.For welded specimens without reinforcement, fracture position is the weld when tensioning.While for welded specimens with reinforcement, bond area is the poorest position with joint strength coefficient of 61%.So, it is necessary to strengthen the poor positions-weld and bond area of 2219 twin wire welded joint in order to solve joint weakening of welding this kind of alloy.

  11. Application of finite element substructuring to composite micromechanics. M.S. Thesis - Akron Univ., May 1984

    Science.gov (United States)

    Caruso, J. J.

    1984-01-01

    Finite element substructuring is used to predict unidirectional fiber composite hygral (moisture), thermal, and mechanical properties. COSMIC NASTRAN and MSC/NASTRAN are used to perform the finite element analysis. The results obtained from the finite element model are compared with those obtained from the simplified composite micromechanics equations. A unidirectional composite structure made of boron/HM-epoxy, S-glass/IMHS-epoxy and AS/IMHS-epoxy are studied. The finite element analysis is performed using three dimensional isoparametric brick elements and two distinct models. The first model consists of a single cell (one fiber surrounded by matrix) to form a square. The second model uses the single cell and substructuring to form a nine cell square array. To compare computer time and results with the nine cell superelement model, another nine cell model is constructed using conventional mesh generation techniques. An independent computer program consisting of the simplified micromechanics equation is developed to predict the hygral, thermal, and mechanical properties for this comparison. The results indicate that advanced techniques can be used advantageously for fiber composite micromechanics.

  12. Designing Interfaces

    CERN Document Server

    Tidwell, Jenifer

    2010-01-01

    Despite all of the UI toolkits available today, it's still not easy to design good application interfaces. This bestselling book is one of the few reliable sources to help you navigate through the maze of design options. By capturing UI best practices and reusable ideas as design patterns, Designing Interfaces provides solutions to common design problems that you can tailor to the situation at hand. This updated edition includes patterns for mobile apps and social media, as well as web applications and desktop software. Each pattern contains full-color examples and practical design advice th

  13. Analytic and computational micromechanics of clustering and interphase effects in carbon nanotube composites.

    Energy Technology Data Exchange (ETDEWEB)

    Seidel, Gary D.; Hammerand, Daniel Carl; Lagoudas, Dimitris C. (Texas A& M University, College Station, TX)

    2006-01-01

    Effective elastic properties for carbon nanotube reinforced composites are obtained through a variety of micromechanics techniques. Using the in-plane elastic properties of graphene, the effective properties of carbon nanotubes are calculated utilizing a composite cylinders micromechanics technique as a first step in a two-step process. These effective properties are then used in the self-consistent and Mori-Tanaka methods to obtain effective elastic properties of composites consisting of aligned single or multi-walled carbon nanotubes embedded in a polymer matrix. Effective composite properties from these averaging methods are compared to a direct composite cylinders approach extended from the work of Hashin and Rosen (1964) and Christensen and Lo (1979). Comparisons with finite element simulations are also performed. The effects of an interphase layer between the nanotubes and the polymer matrix as result of functionalization is also investigated using a multi-layer composite cylinders approach. Finally, the modeling of the clustering of nanotubes into bundles due to interatomic forces is accomplished herein using a tessellation method in conjunction with a multi-phase Mori-Tanaka technique. In addition to aligned nanotube composites, modeling of the effective elastic properties of randomly dispersed nanotubes into a matrix is performed using the Mori-Tanaka method, and comparisons with experimental data are made. Computational micromechanical analysis of high-stiffness hollow fiber nanocomposites is performed using the finite element method. The high-stiffness hollow fibers are modeled either directly as isotropic hollow tubes or equivalent transversely isotropic effective solid cylinders with properties computed using a micromechanics based composite cylinders method. Using a representative volume element for clustered high-stiffness hollow fibers embedded in a compliant matrix with the appropriate periodic boundary conditions, the effective elastic properties

  14. Improvement and Micro-mechanism of a Low Expansion Superalloy

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Chromium free low expansion superalloys Incoloy 900 series based on the system Fe-Ni-Co-Nb-Ti are precipitation-strengthen austenitic alloys with combination of very low thermal expansion coefficient and high tensile strength. The most important problem of these alloys is the susceptibility to stress accelerated grain boundary oxygen embrittlement (SAGBO) due to the absence of chromium. The oxidation resistance of the alloys after they were exposed for long time at high temperatures and the notch bar rupture strength have been improved with appropriate rare earth (RE) addition. With trace yttrium addition, the platelet precipitates become smaller and denser and the phase of precipitate transforms from ε phase to H phase. The crystal structures of the platelet phases in the conventional and Y-containing superalloys have been investigated and determined. The interface between the H phase and the matrix has also been demonstrated.

  15. Manufacturing Interfaces

    NARCIS (Netherlands)

    Houten, van F.J.A.M.

    1992-01-01

    The paper identifies the changing needs and requirements with respect to the interfacing of manufacturing functions. It considers the manufacturing system, its components and their relationships from the technological and logistic point of view, against the background of concurrent engineering. Desi

  16. Application of reference point indentation for micro-mechanical surface characterization of calcium silicate based dental materials.

    Science.gov (United States)

    Antonijević, Djordje; Milovanović, Petar; Riedel, Christoph; Hahn, Michael; Amling, Michael; Busse, Björn; Djurić, Marija

    2016-04-01

    The objective of this study was to elucidate micromechanical properties of Biodentine and two experimental calcium silicate cements (CSCs) using Reference Point Indentation (RPI). Biomechanical characteristics of the cement type and the effects of a radiopacifier, liquid components, acid etching treatment and bioactivation in simulated body fluid (SBF) were investigated by measuring the microhardness, average unloading slope (Avg US) and indentation distance increase (IDI). Biodentine had a greater microhardness than the experimental CSCs, while the Avg US and IDI values were not significantly different among investigated materials. There was a statistically significant difference in microhardness and IDI values between pure CSCs and radiopacified cements (p < 0.05). Micromechanical properties were not affected by different liquid components used. Acid-etching treatment reduced Biodentine's microhardness while cements' immersion in SBF resulted in greater microhardness and higher IDI values compared to the control group. Clearly, the physiological environment and the cements' composition affect their surface micromechanical properties. The addition of calcium chloride and CSCs' immersion in SBF are beneficial for CSCs' micromechanical performance, while the addition of radiopacifiers and acid etching treatment weaken the CSCs' surface. Application of RPI aids with the characterization of micromechanical properties of synthetic materials' surfaces. PMID:26888441

  17. EDITORIAL: Selected papers from the 22nd MicroMechanics and Microsystems Europe Workshop (MME 2011) Selected papers from the 22nd MicroMechanics and Microsystems Europe Workshop (MME 2011)

    Science.gov (United States)

    Ohlckers, Per

    2012-07-01

    This special section of Journal of Micromechanics and Microengineering is a selection of 13 of the best papers presented at the 22nd Micromechanics and Microsystems Europe Workshop, which was arranged in Toensberg, Norway, 19-22 June, 2011. 110 participants attended the 3 day workshop that had 5 invited keynote speakers and 80 submitted poster presentations. The MME Workshop is organized every year to gather mostly European scientists and people from industry to discuss topics related to research in micromechanics and microsystems in an informal manner. A distinct feature of this specialized workshop is to be an excellent venue for young scientists in the field, such as PhD students, to present their latest work. This workshop series was inaugurated in Enschede, the Netherlands in 1989, followed by: Berlin, Germany (1990), Leuven, Belgium (1992), Neuchatel, Switzerland (1993), Pisa, Italy (1994), Copenhagen, Denmark (1995), Barcelona, Spain (1996) [1], Southampton, UK (1997) [2], Ulvik, Norway (1998) [3], Gif-sur-Yvette, France (1999) [4], Uppsala, Sweden (2000), Cork, Ireland (2001) [5], Sinaia, Romania (2002) [6], Delft, The Netherlands (2003) [7], Leuven, Belgium (2004) [8], Goteborg, Sweden (2005) [9], Southampton, UK (2006) [10], Guimaraes, Portugal (2007) [11], Aachen, Germany (2008) [12], Toulouse, France (2009) [13] and Enschede, the Netherlands (2010) [14]. The workshop series has remained remarkably true to its original concept such as still having micromechanics as a priority topic while, at the same time, adapting to recent research topics such as microsystems integration. It is nice to observe that an earlier fragmented and mostly academic research field now has matured into a very strong industrial field being one of the fastest growing industries in the world, with successful applications on all levels from high end to low end, from space to consumer applications, with the inclusion of microsystems in smartphones such as three-axis accelerometers and

  18. Soft Interfaces

    Science.gov (United States)

    Gilles de Gennes, Pierre; Edwards, Introduction By Sam

    1997-04-01

    Paul Adrien Maurice Dirac, one of the greatest physicists of the twentieth century, died in 1984. Dirac's college, St. John's of Cambridge, generously endowed annual lectures to be held at Cambridge University in his memory. This volume contains a much expanded version of the 1994 Dirac Lecture by Nobel Laureate Pierre Gilles de Gennes. The book presents an impressionistic tour of the physics of soft interfaces. Full of insight and interesting asides, it not only provides an accessible introduction to this topic, but also lays down many markers and signposts that will be of interest to researchers in physics or chemistry. Features discussions of wetting and dewetting, the dynamics of different types of interface and adhesion and polymer/polymer welding.

  19. Interface learning

    DEFF Research Database (Denmark)

    Thorhauge, Sally

    2014-01-01

    "Interface learning - New goals for museum and upper secondary school collaboration" investigates and analyzes the learning that takes place when museums and upper secondary schools in Denmark work together in local partnerships to develop and carry out school-related, museum-based coursework...... for students. The research focuses on the learning that the students experience in the interface of the two learning environments: The formal learning environment of the upper secondary school and the informal learning environment of the museum. Focus is also on the learning that the teachers and museum...... professionals experience as a result of their collaboration. The dissertation demonstrates how a given partnership’s collaboration affects the students’ learning experiences when they are doing the coursework. The dissertation presents findings that museum-school partnerships can use in order to develop...

  20. Museets interface

    DEFF Research Database (Denmark)

    Pold, Søren

    2007-01-01

    Søren Pold gør sig overvejelser med udgangspunkt i museumsprojekterne Kongedragter.dk og Stigombord.dk. Han argumenterer for, at udviklingen af internettets interfaces skaber nye måder at se, forstå og interagere med kulturen på. Brugerne får nye medievaner og perceptionsmønstre, der må medtænkes...

  1. Modification of Baksi sloppy hinge elbow to minimize the stresses at the humeral bone cement interface- An early experience

    Directory of Open Access Journals (Sweden)

    Baksi D

    2005-01-01

    Full Text Available Background : Baksi sloppy hinge elbow is an all metal prosthesis having 7 0 - 10 0 varus - valgus inherent laxity at the hinge section with minimal motion bearing contact area. Due to the presence of laxity at it′s hinge section, any strain on the prosthesis dissipates primarily to the surrounding soft tissues thus protecting the cement bone interfaces. However, from our long term clinical experiences on the use of our sloppy hinge design since 1984 and the knowledge of literature review of the results of using other semi-constrained (sloppy or unconstrained designs, it was observed that radiolucency or loosening at the bone-cement interface occurred mainly around the humeral stem in the long run due to the continued effect of rotational torque of forearm and hand. Hence, an attempt in the improvement of the design concept is being made. Methods : In this respect one flange each of one cm height and breadth and three mm thickness has been incorporated on either sides of the shank of humeral stem of the sloppy hinge at medio-lateral (coronal plane which will be seated in the corresponding longitudinal groove cut on either side of humeral shaft extending from its transverse cut end to become single assembly during the rotation of humerus. Results : The preliminary results of clinical application of the modified sloppy hinge elbow in ten cases are found satisfactory. Conclusion : The cyclical compression and distraction forces during flexion and extension of the elbow will be distributed over the larger bony area of lower end of humerus where flanges of the humeral shank being seated. The rotational torque effect of forearm and hand particularly with the arm in abduction will be minimised at the humeral bone cement interface as the humerus and the prosthetic stem act as a single assembly by the snugly fitting of the prosthetic flange in the humural shaft

  2. Discrete Element Models of the Micromechanics of Sedimentary Rock: The Role of Organization vs. Friction

    Science.gov (United States)

    Boutt, D. F.; McPherson, B. J.

    2001-12-01

    The micromechanics of sedimentary rock deformation are a fundamental aspect of many research fields, ranging from geotechnical engineering to petroleum recovery and hazardous waste disposal. Laboratory triaxial tests yield information concerning macroscopic behaviors but are not capable of quantifying micromechanical processes such as microcracking and localization. Thus, to quantify micromechanical processes we employed the discrete element method (DEM) of rock deformation, calibrated with triaxial test results. This DEM simulates rock using rigid disc shaped particles bonded at contacts between particles. Previous studies demonstrated that this type of DEM can qualitatively and quantitatively mimic macroscopic behaviors of triaxial tests. An important conclusion of these studies is that a number of particles must be bonded together with higher bond strengths than the surrounding particles to achieve a steeper strength envelope of rocks. This process, termed clustering, is the focus of this study. We hypothesize that since clusters posses a more complicated geometry, they may increase failure strength at elevated confining pressures by interlocking and creating a higher apparent friction. An alternative hypothesis is that the clusters change force chain development by allowing chains to persist longer in specimens. This ultimately causes failure to occur at higher strengths compared to unclustered material. A systematic study comparing effects of cluster shape, particle friction, and force chain development was undertaken. Several model simulations with various cluster shapes and sizes were compared with each other as well as single particle models with high friction coefficients (>1). Preliminary results suggest that the organization of the particle clusters play a key role in increasing the strength envelope. Particle friction coefficients needed to increase slopes of the strength envelopes are well beyond those of geological materials measured in the laboratory

  3. Development, Implementation and Application of Micromechanical Analysis Tools for Advanced High Temperature Composites

    Science.gov (United States)

    2005-01-01

    This document contains the final report to the NASA Glenn Research Center (GRC) for the research project entitled Development, Implementation, and Application of Micromechanical Analysis Tools for Advanced High-Temperature Composites. The research supporting this initiative has been conducted by Dr. Brett A. Bednarcyk, a Senior Scientist at OM in Brookpark, Ohio from the period of August 1998 to March 2005. Most of the work summarized herein involved development, implementation, and application of enhancements and new capabilities for NASA GRC's Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC) software package. When the project began, this software was at a low TRL (3-4) and at release version 2.0. Due to this project, the TRL of MAC/GMC has been raised to 7 and two new versions (3.0 and 4.0) have been released. The most important accomplishments with respect to MAC/GMC are: (1) A multi-scale framework has been built around the software, enabling coupled design and analysis from the global structure scale down to the micro fiber-matrix scale; (2) The software has been expanded to analyze smart materials; (3) State-of-the-art micromechanics theories have been implemented and validated within the code; (4) The damage, failure, and lifing capabilities of the code have been expanded from a very limited state to a vast degree of functionality and utility; and (5) The user flexibility of the code has been significantly enhanced. MAC/GMC is now the premier code for design and analysis of advanced composite and smart materials. It is a candidate for the 2005 NASA Software of the Year Award. The work completed over the course of the project is summarized below on a year by year basis. All publications resulting from the project are listed at the end of this report.

  4. Micromechanics and constitutive models for soft active materials with phase evolution

    Science.gov (United States)

    Wang, Binglian

    Soft active materials, such as shape memory polymers, liquid crystal elastomers, soft tissues, gels etc., are materials that can deform largely in response to external stimuli. Micromechanics analysis of heterogeneous materials based on finite element method is a typically numerical way to study the thermal-mechanical behaviors of soft active materials with phase evolution. While the constitutive models that can precisely describe the stress and strain fields of materials in the process of phase evolution can not be found in the databases of some commercial finite element analysis (FEA) tools such as ANSYS or Abaqus, even the specific constitutive behavior for each individual phase either the new formed one or the original one has already been well-known. So developing a computationally efficient and general three dimensional (3D) thermal-mechanical constitutive model for soft active materials with phase evolution which can be implemented into FEA is eagerly demanded. This paper first solved this problem theoretically by recording the deformation history of each individual phase in the phase evolution process, and adopted the idea of effectiveness by regarding all the new formed phase as an effective phase with an effective deformation to make this theory computationally efficient. A user material subroutine (UMAT) code based on this theoretical constitutive model has been finished in this work which can be added into the material database in Abaqus or ANSYS and can be easily used for most soft active materials with phase evolution. Model validation also has been done through comparison between micromechanical FEA and experiments on a particular composite material, shape memory elastomeric composite (SMEC) which consisted of an elastomeric matrix and the crystallizable fibre. Results show that the micromechanics and the constitutive models developed in this paper for soft active materials with phase evolution are completely relied on.

  5. Micromechanism and Kinetic Formulation of Vertically Aligned ZnO Nanorods Grown on Catalytic Bilayers

    OpenAIRE

    Dong-Hau Kuo; Jheng-Yu He

    2012-01-01

    Vertically aligned ZnO nanorods were grown at for 2 h on sapphire substrates with catalysts in bilayer configurations of Sn (top)/Ni (bottom) and Sn/In, where the top layer is formed by sputtering and the bottom one is deposited by spin coating. The effects of bilayer catalysts on growth kinetics of nucleation and growth, growth micromechanism, and vertical alignment of growing ZnO nanorods have been investigated. The vertical alignment of the Sn/Ni-catalyzing ZnO nanorods is determined at th...

  6. Testing the permeability and corrosion resistance of micro-mechanically interlocked joints

    DEFF Research Database (Denmark)

    Byskov-Nielsen, Jeppe; Holm, Allan Hjarbæk; Højsholt, Rune;

    2011-01-01

    Micro-mechanical interlocking (MMI) can be applied to create new and interesting composite materials. We have employed laser structuring to achieve MMI between stainless steel and plastic with extremely high joint strength. However, the water permeability and corrosion resistance of the joint must...... is conducted. The permeability seems to be consistent with the Hagen–Poiseuille equation independent of the laser structuring technique and is orders of magnitudes larger than the diffusion rate through the plastic. Two different types of corrosion tests have been undertaken, and we show that care must...... be taken in order not to degrade the corrosion resistance of the sample to an unacceptable level....

  7. Cooling of a micro-mechanical oscillator using radiation pressure induced dynamical back-action

    CERN Document Server

    Schliesser, A; Kippenberg, T J; Nooshi, N; Vahala, K J

    2006-01-01

    Cooling of a 58 MHz micro-mechanical resonator from room temperature to 11 K is demonstrated using cavity enhanced radiation pressure. Detuned pumping of an optical resonance allows enhancement of the blue shifted motional sideband (caused by the oscillator's Brownian motion) with respect to the red-shifted sideband leading to cooling of the mechanical oscillator mode. The reported cooling mechanism is a manifestation of the effect of radiation pressure induced dynamical backaction. These results constitute an important step towards achieving ground state cooling of a mechanical oscillator.

  8. MICROMECHANICAL DAMAGE MODEL FOR ROCKS AND CONCRETES SUBJECTED TO COUPLED TENSILE AND SHEAR STRESSES

    Institute of Scientific and Technical Information of China (English)

    Zhongjun Ren; Xianghe Peng; Chunhe Yang

    2008-01-01

    Based on the analysis of the deformation in an infinite isotropic elastic matrix with an embedded elliptic crack under far field coupled tensile and shear stresses,the energy release rate and a mixed fracture criterion are obtained using an energy balance approach.The additional compliance tensor induced by a single opening elliptic microcrack in a representative volume element is derived,and the effect of microcracks with random orientations is analyzed with the Taylor's scheme by introducing an appropriate probability density function.A micromechanical damage model for rocks and concretes is obtained and is verified with experimental results.

  9. Micromechanical analysis of thermo-inelastic multiphase short-fiber composites

    Science.gov (United States)

    Aboudi, Jacob

    1994-01-01

    A micromechanical formulation is presented for the prediction of the overall thermo-inelastic behavior of multiphase composites which consist of short fibers. The analysis is an extension of the generalized method of cells that was previously derived for inelastic composites with continuous fibers, and the reliability of which was critically examined in several situations. The resulting three dimensional formulation is extremely general, wherein the analysis of thermo-inelastic composites with continuous fibers as well as particulate and porous inelastic materials are merely special cases.

  10. Initiation of Failure for Masonry Subject to In-Plane Loads through Micromechanics

    Directory of Open Access Journals (Sweden)

    V. P. Berardi

    2016-01-01

    Full Text Available A micromechanical procedure is used in order to evaluate the initiation of damage and failure of masonry with in-plane loads. Masonry material is viewed as a composite with periodic microstructure and, therefore, a unit cell with suitable boundary conditions is assumed as a representative volume element of the masonry. The finite element method is used to determine the average stress on the unit cell corresponding to a given average strain prescribed on the unit cell. Finally, critical curves representing the initiation of damage and failure in both clay brick masonry and adobe masonry are provided.

  11. Micro-mechanical modeling of alpha/beta two-phased titanium alloy behaviour

    International Nuclear Information System (INIS)

    In order to better describe the mechanical behaviour of the Ti-6246 alloy, a two-phase material where the alpha phase inelastic behaviour is strongly anisotropic, a micro-mechanical approach has been developed to consider the various heterogeneity levels and the role of the various internal stresses induced by its heterogenous character. Among the simulation results, it is shown that the cyclic softening (or over-softening) is not only the consequence of a reduction of transgranular internal stresses (multiplication of the number of slip bands in the alpha phase) but is also related to the inter-cellular-type internal stress redistribution. (A.B.)

  12. Micro-mechanical oscillator ground state cooling via intracavity optical atomic excitations

    OpenAIRE

    Genes, C.; Ritsch, H.; Vitali, D.

    2009-01-01

    We predict ground state cooling of a micro-mechanical oscillator, i.e. a vibrating end-mirror of an optical cavity, by resonant coupling of mirror vibrations to a narrow internal optical transition of an ensemble of two level systems. The particles represented by a collective mesoscopic spin model implement, together with the cavity, an efficient, frequency tailorable zero temperature loss channel which can be turned to a gain channel of pump. As opposed to the case of resolved-sideband cavit...

  13. On the Finite Element Implementation of the Generalized Method of Cells Micromechanics Constitutive Model

    Science.gov (United States)

    Wilt, T. E.

    1995-01-01

    The Generalized Method of Cells (GMC), a micromechanics based constitutive model, is implemented into the finite element code MARC using the user subroutine HYPELA. Comparisons in terms of transverse deformation response, micro stress and strain distributions, and required CPU time are presented for GMC and finite element models of fiber/matrix unit cell. GMC is shown to provide comparable predictions of the composite behavior and requires significantly less CPU time as compared to a finite element analysis of the unit cell. Details as to the organization of the HYPELA code are provided with the actual HYPELA code included in the appendix.

  14. Detection of micromechanical deformation under rigid body displacement using twin-pulsed 3D digital holography

    Science.gov (United States)

    Perez-Lopez, Carlos; Hernandez-Montes, Maria del Socorro; Mendoza-Santoyo, Fernando

    2005-02-01

    Twin-pulsed digital holography in its 3D set up is used to recover exclusively the micro-mechanical deformation of an object. The test object is allowed to have rigid body movements such as rotation and translation, with the result that the fringe patterns contain information of the latter and the object deformation, a feature that may significantly modify the interpretation of the results. Experimental results from a flat metal plate subject to micro stress and a displacement in the x-z plane are presented to demonstrate that using this optical method it is possible to recover exclusively the contribution of the micro stress.

  15. Cooling of a Micro-mechanical Resonator by the Back-action of Lorentz Force

    OpenAIRE

    Wang, Y.D.; Semba, K.; Yamaguchi, H

    2007-01-01

    Using a semi-classical approach, we describe an on-chip cooling protocol for a micro-mechanical resonator by employing a superconducting flux qubit. A Lorentz force, generated by the passive back-action of the resonator's displacement, can cool down the thermal motion of the mechanical resonator by applying an appropriate microwave drive to the qubit. We show that this onchip cooling protocol, with well-controlled cooling power and a tunable response time of passive back-action, can be highly...

  16. Cooling of a micro-mechanical resonator by the back-action of Lorentz force

    Science.gov (United States)

    Wang, Ying-Dan; Semba, K.; Yamaguchi, H.

    2008-04-01

    Using a semi-classical approach, we describe an on-chip cooling protocol for a micro-mechanical resonator by employing a superconducting flux qubit. A Lorentz force, generated by the passive back-action of the resonator's displacement, can cool down the thermal motion of the mechanical resonator by applying an appropriate microwave drive to the qubit. We show that this on-chip cooling protocol, with well-controlled cooling power and a tunable response time of passive back-action, can be highly efficient. With feasible experimental parameters, the effective mode temperature of a resonator could be cooled down by several orders of magnitude.

  17. Resonant coupling of a Bose-Einstein condensate to a micromechanical oscillator

    CERN Document Server

    Hunger, D; Haensch, T W; Koenig, D; Kotthaus, J P; Reichel, J; Treutlein, P

    2010-01-01

    We report experiments in which the vibrations of a micromechanical oscillator are coupled to the motion of Bose-condensed atoms in a trap. The interaction relies on surface forces experienced by the atoms at about one micrometer distance from the mechanical structure. We observe resonant coupling to several well-resolved mechanical modes of the condensate. Coupling via surface forces does not require magnets, electrodes, or mirrors on the oscillator and could thus be employed to couple atoms to molecular-scale oscillators such as carbon nanotubes.

  18. Material characterization of open-cell foams by finite element based micromechanics methods

    Science.gov (United States)

    Thiyagasundaram, Prasanna

    Finite element based micromechanics methods have been used for predicting elastic properties, failure strengths, mode-I, mode-II and mixed mode fracture toughness of open-cell foams. In predicting the orthotropic elastic properties, foams with both equisided and Kelvin-elongated tetrakaidecahedron unit cells are studied. Periodic Boundary Conditions (PBCs) exploiting the special repeating microstructural geometry for these materials have been derived and have been applied on the micromechanical model to calculate the elastic properties. It is shown that the results for the elastic constants from these finite element based models agree well with the available analytical models. Further studies such as effect of a varying strut cross-section over a uniform strut cross-section on the elastic properties are also done in the same context. Next, the procedures used for predicting the above elastic properties are extended to predict multi-axial failure strengths of these low density open cell foams with a microstructure made out of tetrakaidecahedral unit cells. Again, foams with both equisided tetrakaidecahedron and Kelvin-elongated tetrakaidecahedron as unit cells are studied. Failure strengths in different material directions are computed using direct Micromechanics based Methods (DMM). Further, the effect of a varying strut cross section over a uniform strut cross section on failure strengths is also presented. Bi-axial failure envelopes for foams with equisided tetrakaidecahedron unit cells are shown to take the shape of a regular hexagon in the hydrostatic plane. The tri-axial failure envelope for foams made out of equisided tetrakaidecahedron unit cells is shown to have a shape of a double hexagonal pyramid. The bi-axial and tri-axial failure envelopes of foams with elongated tetrakaidecahedron unit cells are also plotted and the effect of anisotropy in foams with these unit cells on the failure envelopes is also discussed. Next, global-local models are developed

  19. Micromechanics-Based Permeability Evolution in Brittle Materials at High Strain Rates

    Science.gov (United States)

    Perol, Thibaut; Bhat, Harsha S.

    2016-08-01

    We develop a micromechanics-based permeability evolution model for brittle materials at high strain rates (≥ 100 s^{-1}). Extending for undrained deformation the mechanical constitutive description of brittle solids, whose constitutive response is governed by micro-cracks, we now relate the damage-induced strains to micro-crack aperture. We then use an existing permeability model to evaluate the permeability evolution. This model predicts both the percolative and connected regime of permeability evolution of Westerly Granite during triaxial loading at high strain rate. This model can simulate pore pressure history during earthquake coseismic dynamic ruptures under undrained conditions.

  20. Two micro-mechanical techniques for studying the enzymatic maceration kinetics of apple parenchyma

    OpenAIRE

    Maingonnat, J.F.; Missang, C.E.; Baron, A; Renard, C.M.G.C.

    2014-01-01

    The enzymatic texture loss during apple maceration was studied by two micro-mechanical techniques. The first technique consisted of a 5% strain compression cycles at a strain rate of 4.5 x 10 4 s -1. The second technique consisted on micro-puncture of the apple parenchyma with a small needle. The first technique led to the peripheral tissues degradation modelling with a first order kinetic reaction or a more pertinent Weibull function. The second technique evidenced that the jagged part of t...

  1. Soft Interfaces

    International Nuclear Information System (INIS)

    This book presents an extended form of the 1994 Dirac Memorial Lecture delivered by Pierre Gilles de Gennes at Cambridge University. The main task of the presentation is to show the beauty and richness of structural forms and phenomena which are observed at soft interfaces between two media. They are much more complex than forms and phenomena existing in each phase separately. Problems are discussed including both traditional, classical techniques, such as the contact angle in static and dynamic partial wetting, as well as the latest research methodology, like 'environmental' scanning electron microscopes. The book is not a systematic lecture on phenomena but it can be considered as a compact set of essays on topics which particularly fascinate the author. The continuum theory widely used in the book is based on a deep molecular approach. The author is particularly interested in a broad-minded rheology of liquid systems at interfaces with specific emphasis on polymer melts. To study this, the author has developed a special methodology called anemometry near walls. The second main topic presented in the book is the problem of adhesion. Molecular processes, energy transformations and electrostatic interaction are included in an interesting discussion of the many aspects of the principles of adhesion. The third topic concerns welding between two polymer surfaces, such as A/A and A/B interfaces. Of great worth is the presentation of various unsolved, open problems. The kind of topics and brevity of description indicate that this book is intended for a well prepared reader. However, for any reader it will present an interesting picture of how many mysterious processes are acting in the surrounding world and how these phenomena are perceived by a Nobel Laureate, who won that prize mainly for his investigations in this field. (book review)

  2. Molecular modeling of cracks at interfaces in nanoceramic composites

    Science.gov (United States)

    Pavia, F.; Curtin, W. A.

    2013-10-01

    Toughness in Ceramic Matrix Composites (CMCs) is achieved if crack deflection can occur at the fiber/matrix interface, preventing crack penetration into the fiber and enabling energy-dissipating fiber pullout. To investigate toughening in nanoscale CMCs, direct atomistic models are used to study how matrix cracks behave as a function of the degree of interfacial bonding/sliding, as controlled by the density of C interstitial atoms, at the interface between carbon nanotubes (CNTs) and a diamond matrix. Under all interface conditions studied, incident matrix cracks do not penetrate into the nanotube. Under increased loading, weaker interfaces fail in shear while stronger interfaces do not fail and, instead, the CNT fails once the stress on the CNT reaches its tensile strength. An analytic shear lag model captures all of the micromechanical details as a function of loading and material parameters. Interface deflection versus fiber penetration is found to depend on the relative bond strengths of the interface and the CNT, with CNT failure occurring well below the prediction of the toughness-based continuum He-Hutchinson model. The shear lag model, in contrast, predicts the CNT failure point and shows that the nanoscale embrittlement transition occurs at an interface shear strength scaling as τs~ɛσ rather than τs~σ typically prevailing for micron scale composites, where ɛ and σ are the CNT failure strain and stress, respectively. Interface bonding also lowers the effective fracture strength in SWCNTs, due to formation of defects, but does not play a role in DWCNTs having interwall coupling, which are weaker than SWCNTs but less prone to damage in the outerwall.

  3. Interface Screenings

    DEFF Research Database (Denmark)

    Thomsen, Bodil Marie Stavning

    2015-01-01

    In Wim Wenders' film Until the End of the World (1991), three different diagrams for the visual integration of bodies are presented: 1) GPS tracking and mapping in a landscape, 2) video recordings layered with the memory perception of these recordings, and 3) data-created images from dreams...... and memories. From a transvisual perspective, the question is whether or not these (by now realized) diagrammatic modes involving the body in ubiquitous global media can be analysed in terms of the affects and events created in concrete interfaces. The examples used are filmic as felt sensations...

  4. Hygrothermal Ageing and Damage Characterization in Epoxies and in Epoxy-Glass Interfaces: a Micromechanical Approach Using Embedded Optical Sensors

    OpenAIRE

    Lai, Marco

    2011-01-01

    Nowadays, composite materials are increasingly used in high technology fields such as aerospace and automotive because of the combination of excellent mechanical performance and lightweight. For these characteristics, classical metal alloys are progressively replaced in primary structural components by reinforced polymer composites. The service life of such structural components is more and more increased thus raising questions on the composites' ...

  5. Fiber Temperature Sensor Based on Micro-mechanical Membranes and Optical Interference Structure

    Energy Technology Data Exchange (ETDEWEB)

    Liu Yueming; Tian Weijian; Hua Jing, E-mail: liuym@cjlu.edu.cn [College of Optical and Electronic Technology, China Jiliang University, Hangzhou 310018 (China)

    2011-02-01

    A novel fiber temperature sensor is presented theoretically and experimentally in this paper. Its working principle is based on Optical Fabry-Perot interference structure that is formed between a polished optical fiber end and micro-mechanical Bi-layered membranes. When ambient temperature is varying, Bi-layered membranes will be deflected and the length of Fabry-Perot cavity will be changed correspondingly. By detecting the reflecting optical intensity from the Fabry-Perot cavity, the ambient temperature can be measured. Using finite element software ANSYS, the sensor structure was optimized based on optical Interference theory and Bi-layered membranes thermal expansion theory, and theoretical characteristics was simulated by computer software. In the end, using optical fiber 2x2 coupler and photo-electrical detector, the fabricated sample sensor was tested successfully by experiment that demonstrating above theoretical analysis and simulation results. This sensor has some favorable features, such as: micro size owing to its micro-mechanical structure, high sensitivity owing to its working Fabry-Perot interference cavity structure, and optical integration character by using optical fiber techniques.

  6. Analysis of Fiber Clustering in Composite Materials Using High-Fidelity Multiscale Micromechanics

    Science.gov (United States)

    Bednarcyk, Brett A.; Aboudi, Jacob; Arnold, Steven M.

    2015-01-01

    A new multiscale micromechanical approach is developed for the prediction of the behavior of fiber reinforced composites in presence of fiber clustering. The developed method is based on a coupled two-scale implementation of the High-Fidelity Generalized Method of Cells theory, wherein both the local and global scales are represented using this micromechanical method. Concentration tensors and effective constitutive equations are established on both scales and linked to establish the required coupling, thus providing the local fields throughout the composite as well as the global properties and effective nonlinear response. Two nondimensional parameters, in conjunction with actual composite micrographs, are used to characterize the clustering of fibers in the composite. Based on the predicted local fields, initial yield and damage envelopes are generated for various clustering parameters for a polymer matrix composite with both carbon and glass fibers. Nonlinear epoxy matrix behavior is also considered, with results in the form of effective nonlinear response curves, with varying fiber clustering and for two sets of nonlinear matrix parameters.

  7. Micromechanical modeling of stress-induced strain in polycrystalline Ni–Mn–Ga by directional solidification

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Yuping, E-mail: zhuyuping@126.com [Seismic Observation and Geophysical Imaging Laboratory, Institute of Geophysics, China Earthquake Administration, Beijing 100081 (China); Shi, Tao; Teng, Yao [Faculty of Civil Engineering and Mechanics, Jiangsu University, Zhenjiang 212013 (China)

    2015-10-05

    Highlights: • A micromechanical model of directional solidification Ni–Mn–Ga is developed. • The stress–strain curves in different directions are tested. • The martensite Young’s moduli in different directions are predicted. • The macro reorientation strains in different directions are investigated. - Abstract: Polycrystalline ferromagnetic shape memory alloy Ni–Mn–Ga produced by directional solidification possess unique properties. Its compressive stress–strain behaviors in loading–unloading cycle show nonlinear and anisotropic. Based on the self-consistent theory and thermodynamics principle, a micromechanical constitutive model of polycrystalline Ni–Mn–Ga by directional solidification is developed considering the generating mechanism of the macroscopic strain and anisotropy. Then, the stress induced strains at different angles to solidification direction are calculated, and the results agree well with the experimental data. The predictive curves of martensite Young’s modulus and macro reorientation strain in different directions are investigated. It may provide theoretical guidance for the design and use of ferromagnetic shape memory alloy.

  8. Micromechanics of breakage in sharp-edge particles using combined DEM and FEM

    Institute of Scientific and Technical Information of China (English)

    Ahad Bagherzadeh-Khalkhali; Ali Asghar Mirghasemi; Soheil Mohammadi

    2008-01-01

    By combining DEM (Discrete Element Method) and FEM (Finite Element Method),a model is established to simulate the breakage of two-dimensional sharp-edge particles,in which the simulated particles are assumed to have no cracks.Particles can,however,crush during different stages of the numerical analysis,if stress-based breakage criteria are fulfilled inside the particles.With this model,it is possible to study the influence of particle breakage on macro- and micro-mechanical behavior of simulated angular materials.Two series of tests,with and without breakable particles,are simulated under different confining pressures based on conditions of biaxial tests.The results,presented in terms of micromechanical behavior for different confining pressures,are compared with macroparameters.The influence of particle breakage on microstructure of sharp-edge materials is discussed and the related confining pressure effects are investigated.Breakage of particles in rockfill materials are shown to reduce the anisotropy coefficients of the samples and therefore their strength and dilation behaviors.

  9. Micromechanical Behavior of Single-Crystal Superalloy with Different Crystal Orientations by Microindentation

    Directory of Open Access Journals (Sweden)

    Jinghui Li

    2015-01-01

    Full Text Available In order to investigate the anisotropic micromechanical properties of single-crystal nickel-based superalloy DD99 of four crystallographic orientations, (001, (215, (405, and (605, microindentation test (MIT was conducted with different loads and loading velocities by a sharp Berkovich indenter. Some material parameters reflecting the micromechanical behavior of DD99, such as microhardness H, Young’s modulus E, yield stress σy, strain hardening component n, and tensile strength σb, can be obtained from load-displacement relations. H and E of four different crystal planes evidently decrease with the increase of h. The reduction of H is due to dislocation hardening while E is related to interplanar spacing and crystal variable. σy of (215 is the largest among four crystal planes, followed by (605, and (001 has the lowest value. n of (215 is the lowest, followed by (605, and that of (001 is the largest. Subsequently, a simplified elastic-plastic material model was employed for 3D microindentation simulation of DD99 with various crystal orientations. The simulation results agreed well with experimental, which confirmed the accuracy of the simplified material model.

  10. Relations between a micro-mechanical model and a damage model for ductile failure in shear

    Science.gov (United States)

    Tvergaard, Viggo; Nielsen, Kim Lau

    2010-09-01

    Gurson type constitutive models that account for void growth to coalescence are not able to describe ductile fracture in simple shear, where there is no hydrostatic tension in the material. But recent micro-mechanical studies have shown that in shear the voids are flattened out to micro-cracks, which rotate and elongate until interaction with neighbouring micro-cracks gives coalescence. Thus, the failure mechanism is very different from that under tensile loading. Also, the Gurson model has recently been extended to describe failure in shear, by adding a damage term to the expression for the growth of the void volume fraction, and it has been shown that this extended model can represent experimental observations. Here, numerical studies are carried out to compare predictions of the shear-extended Gurson model with the shear failures predicted by the micro-mechanical cell model. Both models show a strong dependence on the level of hydrostatic tension. Even though the reason for this pressure dependence is different in the two models, as the shear-extended Gurson model does not describe voids flattening out and the associated failure mechanism by micro-cracks interacting with neighbouring micro-cracks, it is shown that the trends of the predictions are in good agreement.

  11. Linearity enhancement of scale factor in an optical interrogated micromechanical accelerometer.

    Science.gov (United States)

    Zhang, Yu; Feng, Lishuang; Wang, Xiao; Wang, Yang

    2016-08-01

    A method to reduce the residual stress of support arms in an optical interrogated micromechanical accelerometer is proposed in order to enhance the linearity of the scale factor of the accelerometer. First, the behavior of residual stress in support arms is analyzed in detail, and the simulation of shape curvature caused by residual stress in aluminum-made support arms is completed using finite element analysis. Then, by comparing two different materials of support arms (aluminum-made and silicon-made support arms), a modified fabrication is introduced in order to reduce the unexpected residual stress in support arms. Finally, based on contrast experiments, the linearity of the scale factor of accelerometers with aluminum-made and silicon-made support arms is measured using the force feedback test system, respectively. Results show that the linearity of the scale factor of the accelerometer with silicon-made support arms is 0.85%, which is reduced about an order of magnitude compared to that of the accelerometer with aluminum-made support arms with the linearity of scale factor of 7.48%; linearity enhancement of the scale factor is validated. This allows accuracy improvement of the optical interrogated micromechanical accelerometer in the application of inertial navigation and positioning. PMID:27505396

  12. A multilayer micromechanical model of the cuticle of Curculio longinasus Chittenden, 1927 (Coleoptera: Curculionidae).

    Science.gov (United States)

    Andrew Jansen, M; Singh, Sudhanshu S; Chawla, Nikhilesh; Franz, Nico M

    2016-08-01

    Curculio longinasus Chittenden, 1927 (Coleoptera: Curculionidae), is a weevil species common throughout the southwestern United States that uses its rostrum - a very slender, curved, beak-like projection of the head - to excavate tunnels in plant organs (such as acorns) for egg laying (oviposition). Once the apical portion of the rostrum has been inserted into the preferred substrate for oviposition, the female begins rotating around the perimeter of the hole, elevating her head by extending the fore-legs, and rotating the head in place in a drilling motion. This action causes significant elastic deformation of the rostrum, which will bend until it becomes completely straight. To better understand the mechanical behavior of the cuticle as it undergoes deformation during the preparation of oviposition sites, we develop a comprehensive micro/macro model of the micromechanical structure and properties of the cuticle, spanning across all cuticular regions, and reliably mirroring the resultant macroscale properties of the cuticle. Our modeling approach relies on the use of multi-scale, hierarchical biomaterial representation, and employs various micromechanical schemata - e.g., Mori-Tanaka, effective field, and Maxwell - to calculate the homogenized properties of representative volume elements at each level in the hierarchy. We describe the configuration and behavior of this model in detail, and discuss the theoretical implications and limitations of this approach with emphasis on future biomechanical and comparative evolutionary research. Our detailed account of this approach can thereby serve as a methodological template for exploring the biomechanical behavior of new insect structures. PMID:27189867

  13. A micromechanics constitutive model of transformation plasticity with shear and dilatation effect

    Science.gov (United States)

    Sun, Q. P.; Hwang, K. C.; Yu, S. W.

    B ASED on micromechanics, thermodynamics and microscale t → m transformation mechanism considerations a micromechanics constitutive model which takes into account both the dilatation and shear effects of the transformation is proposed to describe the plastic, pseudoelastic and shape memory behaviors of structural ceramics during transformation under different temperatures. In the derivation, a constitutive element (representative material sample) was used which contains many of the transformed m-ZrO 2 grains or precipitates as the second phase inclusions embedded in an elastic matrix. Under some basic assumptions, analytic expressions for the Helmholtz and complementary free energy of the constitutive element are derived in a self-consistent manner by using the Mori-Tanaka method which takes into account the interaction between the transformed inclusions. The derived free energy is a function of externally applied macroscopic stress (or strain), temperature, volume fraction of transformed phase and the averaged stressfree transformation strain (eigenstrain) of all the transformed inclusions in the constitutive element, the latter two quantities being considered to be the internal variables describing the micro-structural rearrangement in the constitutive element. In the framework of the Hill-Rice internal variable constitutive theory, the transformation yield function and incremental stress strain relations, in analogy to the theory of metal plasticity, for proportional and non-proportional loading histories are derived, respectively. The theoretical predictions are compared with the available experimental data of Mg-PSZ and Ce-TZP polycrystalline toughening ceramics.

  14. Micromechanical properties of intercalated compounds of graphite oxide with dodecahydro- closо-dodecaboric acid

    Science.gov (United States)

    Karpenko, A. A.; Saldin, V. I.

    2016-08-01

    The micromechanical properties (Young's modulus, deformation, and adhesion) of the intercalated compound of graphite oxide with dodecahydro- closo-dodecaboric acid were studied by atomic force microscopy, transmission electron microscopy, and Raman spectroscopy and compared with the same characteristics of the starting graphite oxide. The significant difference in the micromechanical properties of the materials under study is dictated by differences in the topography and properties of their film surface, which, in turn, can be determined by their chemical composition. The introduction of dodecahydro- closo-dodecaboric acid in the interplanar space of graphite oxide affects the structuring of the latter. A considerable increase in the adhesion of the intercalated compound relative to that of oxide graphite is explained by high adhesive properties of the introduced acid, the Young's modulus of graphite oxide being higher than that of the intercalated compound. This was attributed to the high hydrophilicity of dodecahydro- closo-dodecaboric acid and the difficulty of water removal from the interplanar space; water plasticizes the material, which becomes softer than graphite oxide. The difference in the structure of the coating of the intercalated compounds and the starting graphite oxide was found to be also reflected by their Raman spectra, namely, by the increased intensity of the D line with the preserved position of the G line, which points to the impurity nature of the intercalate and the unchanged hexagonal lattice of graphite.

  15. Micromechanical Studies of 4n Gold Wire for Fine Pitch Wirebonding

    Directory of Open Access Journals (Sweden)

    M.F. M. Yunoh

    2011-09-01

    Full Text Available This study focuses towards typical micromechanical properties such as strength, yield point, Young’s Modulus, strain, shapes of fracture end and element analysis, atomic percentage of Ca of 4N gold (Au wire using microstructures and composition observation, micro-tensile test and depth sensing indentation technique. A series of micro-tensile test were performed with different strain rate values of 10˚-10-4 min-1 on to a 25.4 μm diameter plain gold wire. The nanoindentation with 20 mN maximum load was indented on a near fracture end of a gold wire specimen, for which this test was carried out after the micro-tensile test. The stress-strain curves were used to characterize the 4N purity gold wire. The shapes of fracture end of gold wire after micro tensile test were carried out using Scanning Electron Microscopic (SEM. The finding showed that the mechanical properties of ultra-fine gold wire was in the proportional relationship with the increment of the strain rate value. It is suggested that micromechanical behaviour gave the effect for the wirebonding process in order to characterize the wire loop control and strengthen the wire loop to avoid the wire sweep.

  16. Micromechanics Fatigue Damage Analysis Modeling for Fabric Reinforced Ceramic Matrix Composites

    Science.gov (United States)

    Min, J. B.; Xue, D.; Shi, Y.

    2013-01-01

    A micromechanics analysis modeling method was developed to analyze the damage progression and fatigue failure of fabric reinforced composite structures, especially for the brittle ceramic matrix material composites. A repeating unit cell concept of fabric reinforced composites was used to represent the global composite structure. The thermal and mechanical properties of the repeating unit cell were considered as the same as those of the global composite structure. The three-phase micromechanics, the shear-lag, and the continuum fracture mechanics models were integrated with a statistical model in the repeating unit cell to predict the progressive damages and fatigue life of the composite structures. The global structure failure was defined as the loss of loading capability of the repeating unit cell, which depends on the stiffness reduction due to material slice failures and nonlinear material properties in the repeating unit cell. The present methodology is demonstrated with the analysis results evaluated through the experimental test performed with carbon fiber reinforced silicon carbide matrix plain weave composite specimens.

  17. Mechanical design and force calibration of dual-axis micromechanical probe for friction force microscopy

    Science.gov (United States)

    Fukuzawa, Kenji; Terada, Satoshi; Shikida, Mitsuhiro; Amakawa, Hiroaki; Zhang, Hedong; Mitsuya, Yasunaga

    2007-02-01

    A dual-axis micromechanical probe that combines a double cantilever and torsion beams is presented. This probe can reduce the mechanical cross-talk between the lateral and vertical force detections. In addition, dual-axis forces can be detected by measuring the dual-axis displacement of the probe end using the optical lever-based method used in conventional friction force microscopes (FFMs). In this paper, the mechanical design of the probe, the details of the fabrication method, FFM performance, and calibration of the friction force are discussed. The mechanical design and the microfabrication method for probes that can provide a force resolution of the order of 1nN without mechanical cross-talk are presented. Calibration of the lateral force signal is possible by using the relationship between the lateral force and the piezodisplacement at the onset of the probe scanning. The micromechanical probe enables simultaneous and independent detection of atomic and friction forces. This leads to accurate investigation of nanotribological phenomena and visualization of the distribution of the friction properties, which helps the identification of the material properties.

  18. Improvement of interfacial adhesion and nondestructive damage evaluation for plasma-treated PBO and Kevlar fibers/epoxy composites using micromechanical techniques and surface wettability.

    Science.gov (United States)

    Park, Joung-Man; Kim, Dae-Sik; Kim, Sung-Ryong

    2003-08-15

    Comparison of interfacial properties and microfailure mechanisms of oxygen-plasma treated poly(p-phenylene-2,6-benzobisoxazole (PBO, Zylon) and poly(p-phenylene terephthalamide) (PPTA, Kevlar) fibers/epoxy composites were investigated using a micromechanical technique and nondestructive acoustic emission (AE). The interfacial shear strength (IFSS) and work of adhesion, Wa, of PBO or Kevlar fiber/epoxy composites increased with oxygen-plasma treatment, due to induced hydrogen and covalent bondings at their interface. Plasma-treated Kevlar fiber showed the maximum critical surface tension and polar term, whereas the untreated PBO fiber showed the minimum values. The work of adhesion and the polar term were proportional to the IFSS directly for both PBO and Kevlar fibers. The microfibril fracture pattern of two plasma-treated fibers appeared obviously. Unlike in slow cooling, in rapid cooling, case kink band and kicking in PBO fiber appeared, whereas buckling in the Kevlar fiber was observed mainly due to compressive and residual stresses. Based on the propagation of microfibril failure toward the core region, the number of AE events for plasma-treated PBO and Kevlar fibers increased significantly compared to the untreated case. The results of nondestructive AE were consistent with microfailure modes.

  19. Improvement of interfacial adhesion and nondestructive damage evaluation for plasma-treated PBO and Kevlar fibers/epoxy composites using micromechanical techniques and surface wettability.

    Science.gov (United States)

    Park, Joung-Man; Kim, Dae-Sik; Kim, Sung-Ryong

    2003-08-15

    Comparison of interfacial properties and microfailure mechanisms of oxygen-plasma treated poly(p-phenylene-2,6-benzobisoxazole (PBO, Zylon) and poly(p-phenylene terephthalamide) (PPTA, Kevlar) fibers/epoxy composites were investigated using a micromechanical technique and nondestructive acoustic emission (AE). The interfacial shear strength (IFSS) and work of adhesion, Wa, of PBO or Kevlar fiber/epoxy composites increased with oxygen-plasma treatment, due to induced hydrogen and covalent bondings at their interface. Plasma-treated Kevlar fiber showed the maximum critical surface tension and polar term, whereas the untreated PBO fiber showed the minimum values. The work of adhesion and the polar term were proportional to the IFSS directly for both PBO and Kevlar fibers. The microfibril fracture pattern of two plasma-treated fibers appeared obviously. Unlike in slow cooling, in rapid cooling, case kink band and kicking in PBO fiber appeared, whereas buckling in the Kevlar fiber was observed mainly due to compressive and residual stresses. Based on the propagation of microfibril failure toward the core region, the number of AE events for plasma-treated PBO and Kevlar fibers increased significantly compared to the untreated case. The results of nondestructive AE were consistent with microfailure modes. PMID:16256662

  20. Micromechanical Time-Lapse X-ray CT Study of Fatigue Damage in Uni-Directional Fibre Composites

    DEFF Research Database (Denmark)

    Jespersen, Kristine Munk; Lowe, Tristan; Withers, Philip J.;

    2015-01-01

    . The geometry of the cut-out is similar to that which will be used in the time-lapse study. As the micro-mechanical damage mechanisms are small features, it is necessary to obtain a high scan resolution which sets a limit to how large the field of view can be. Therefore, it is necessary to perform several scans...

  1. Contact damage and fracture micromechanisms of multilayered TiN/CrN coatings at micro- and nano-length scales

    Energy Technology Data Exchange (ETDEWEB)

    Roa, J.J., E-mail: joan.josep.roa@upc.edu [CIEFMA — Departament de Ciència dels Materials i Eng. Metallúrgica, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); CRnE, Universitat Politècnica de Catalunya, C. Pasqual i Vila 15, 08028 Barcelona (Spain); Jiménez-Piqué, E. [CIEFMA — Departament de Ciència dels Materials i Eng. Metallúrgica, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); CRnE, Universitat Politècnica de Catalunya, C. Pasqual i Vila 15, 08028 Barcelona (Spain); Martínez, R. [Centro de Ingeniería Avanzada de Superfícies, Asociación de la Industria Navarra — AIN, Crta. Pamplona, 1, Edificio AIN, 31191 Cordovilla (Spain); Ramírez, G. [CIEFMA — Departament de Ciència dels Materials i Eng. Metallúrgica, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); Fundació CTM Centre Tecnològic, Avda. Bases de Manresa 1, 08243 Manresa (Spain); Tarragó, J.M. [CIEFMA — Departament de Ciència dels Materials i Eng. Metallúrgica, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); CRnE, Universitat Politècnica de Catalunya, C. Pasqual i Vila 15, 08028 Barcelona (Spain); and others

    2014-11-28

    In this study, systematic nanomechanical and micromechanical studies have been conducted in three multilayer TiN/CrN systems with different bilayer periods (8, 19 and 25 nm). Additionally, experimental work has been performed on corresponding TiN and CrN single layers, for comparison purposes. The investigation includes the use of different indenter tip geometries as well as contact loading conditions (i.e. indentation/scratch) such to induce different stress field and damage scenarios within the films. The surface and subsurface damage under the different indentation imprints and scratch tracks have been observed by atomic force microscopy, field emission scanning electron microscopy and focused ion beam. Multilayer TiN/CrN coated systems are found to exhibit higher adhesion strength (under sliding contact load) and cracking resistance (under spherical indentation) than those coated with reference TiN and CrN monolayers. The main reason behind these findings is the effective development of microstructurally-driven deformation and cracking resistant micromechanisms: rotation of columnar grains (and associated distortion of bilayer period) and crack deflection of interlayer thickness length scale, respectively. - Highlights: • Nanomechanical and micromechanical study in TiN/CrN systems • TiN/CrN coated systems exhibit higher adhesion strength and cracking resistance. • Main deformation and cracking micromechanisms: columnar grain rotation and crack deflection.

  2. Explicit modeling the progressive interface damage in fibrous composite: Analytical vs. numerical approach

    DEFF Research Database (Denmark)

    Kushch, V.I.; Shmegera, S.V.; Mishnaevsky, Leon

    2011-01-01

    Two micromechanical, representative unit cell type models of fiber reinforced composite (FRC) are applied to simulate explicitly onset and accumulation of scattered local damage in the form of interface debonding. The first model is based on the analytical, multipole expansion type solution...... of the multiple inclusion problem by means of complex potentials. The second, finite element model of FRC is based on the cohesive zone model of interface. Simulation of progressive debonding in FRC using the many-fiber models of composite has been performed. The advantageous features and applicability areas...... of both models are discussed. It has been shown that the developed models provide detailed analysis of the progressive debonding phenomena including the interface crack cluster formation, overall stiffness reduction and induced anisotropy of the effective elastic moduli of composite....

  3. Analytical Solution of Interface Effect on the Strength of Combined Model Composed of Different Geologic Bodies

    Directory of Open Access Journals (Sweden)

    Zeng-hui Zhao

    2014-01-01

    Full Text Available According to the special combined structure of surrounding rock in western mining area of China, a micromechanical model with variable parameters containing contact interface was proposed firstly. Then, the derived stresses in coal and rock near the interface were analyzed on the basis of the harmonized strain relation, and the analytical solutions with respect to stress states near the interface were drawn up. The triaxial compressive strength of coal and rock was further determined in case the contact interface was in the horizontal position. Moreover, effects of stiffness ratio, interface angle, and stress level on the strength of two bodies near the contact area were expounded in detail. Results indicate that additional stresses which have significant effect on the strength of combined model are derived due to the adhesive effect of contact interface and lithological differences between geologic bodies located on both sides. The interface effect on the strength of combined body is most associated with the stiffness, interface angle, and the stress level. These conclusions are also basically valid for three-body model and even for the multibody model and lay important theory foundation to guide the stability study of soft strata composed of different geologic bodies.

  4. Design and fabrication of compliant micromechanisms and structures with negative Poisson's ratio

    DEFF Research Database (Denmark)

    Larsen, Ulrik Darling; Sigmund, Ole; Bouwstra, Siebe

    1996-01-01

    This paper describes a new way to design and fabricate compliant micromechanisms and material structures with negative Poisson's ratio (NPR). The design of compliant mechanisms and material structures is accomplished in an automated way using a numerical topology optimization method. The procedure...... allows the user to specify the elastic properties of materials or the mechanical or geometrical advantages of compliant mechanisms and returns the optimal structures. The topologies obtained by the numerical procedure require practically no interaction by the engineer before they can be transferred to...... the fabrication unit. Fabrication is carried out by patterning a sputtered silicon on a PECVD-glass with a laser micromachining set-up. Subsequently the structures are etched into the underlying PECVD-glass and the glass are underetched, all in one two-step RIE process. The components are tested using...

  5. Design and fabrication of compliant micromechanisms and structures with negative Poisson's ratio

    DEFF Research Database (Denmark)

    Larsen, Ulrik Darling; Sigmund, Ole; Bouwstra, Siebe

    1997-01-01

    This paper describes a new way to design and fabricate compliant micromechanisms and material structures with negative Poisson's ratio (NPR). The design of compliant mechanisms and material structures is accomplished in an automated way using a numerical topology optimization method, The procedure...... allows the user to specify the elastic properties of materials or the mechanical advantages (MA's) or geometrical advantages (GA's) of compliant mechanisms and returns the optimal structures. The topologies obtained by the numerical procedure require practically no interaction by the engineer before they...... can be transferred to the fabrication unit. Fabrication is carried out by patterning a sputtered silicon on a plasma-enhanced chemical vapor deposition (PECVD) glass with a laser micromachining setup. Subsequently, the structures are etched into the underlying PECVD glass, and the glass is underetched...

  6. A micromechanics-based finite element model for the constitutive behavior of polycrystalline ferromagnets

    Institute of Scientific and Technical Information of China (English)

    Binglei Wang; Changqing Chen; Yapeng Shen

    2006-01-01

    A micromechanics-based finite element model for the constitutive behavior of polycrystalline ferromagnets is developed. In the model, the polycrystalline solid is assumed to comprise numerous single crystals with randomly distributed crystallographic orientations, and the single crystals, in turn, consist of ferromagnetic domains, each of which is represented by a cubic element. The dipole directions of the domains are randomly assigned to simulate the crystallographic nature of ferromagnetic polycrystals. A switching criterion for the domains is specified at the microscopic level. The macroscopic constitutive behavior is obtained by averaging the microscopic/local behavior of each domain. The developed model has been applied to the simulation of a ferromagnetic material. With appropriate material parameters adopted, hysteresis loops of the predicted magnetic induction versus magnetic field and those of the strain versus magnetic field are shown to agree well with experimental observations.

  7. Third-order thermo-mechanical properties for packs of Platonic solids using statistical micromechanics

    Science.gov (United States)

    Gillman, A.; Amadio, G.; Matouš, K.; Jackson, T. L.

    2015-01-01

    Obtaining an accurate higher order statistical description of heterogeneous materials and using this information to predict effective material behaviour with high fidelity has remained an outstanding problem for many years. In a recent letter, Gillman & Matouš (2014 Phys. Lett. A 378, 3070–3073. ()) accurately evaluated the three-point microstructural parameter that arises in third-order theories and predicted with high accuracy the effective thermal conductivity of highly packed material systems. Expanding this work here, we predict for the first time effective thermo-mechanical properties of granular Platonic solid packs using third-order statistical micromechanics. Systems of impenetrable and penetrable spheres are considered to verify adaptive methods for computing n-point probability functions directly from three-dimensional microstructures, and excellent agreement is shown with simulation. Moreover, a significant shape effect is discovered for the effective thermal conductivity of highly packed composites, whereas a moderate shape effect is exhibited for the elastic constants.

  8. Micromechanical Fast Quasi-Static Detection of α and β Relaxations with Nanograms of Polymer

    DEFF Research Database (Denmark)

    Bose, Sanjukta; Schmid, Silvan; Larsen, Tom;

    2015-01-01

    Micromechanical string resonators are used as a highly sensitive tool for the detection of glass transition (Tg or α relaxation) and sub-Tg (β relaxation) temperatures of polystyrene (PS) and poly (methyl methacrylate) (PMMA). The characterization technique allows for a fast detection of mechanical...... relaxations of polymers with only few nanograms of sample in a quasi-static condition. The polymers are spray coated on one side of silicon nitride (SiN) microstrings. These are pre-stressed suspended structures clamped on both ends to a silicon frame. The resonance frequency of the microstrings...... is then monitored as a function of increasing temperature. α and β relaxations in the polymer affect the net static tensile stress of the microstring and result in measureable local frequency slope maxima. Tg of PS and PMMA is detected at 91 ±2°C and 114 ±2°C, respectively. The results match well with the glass...

  9. Moisture-related mechanical properties of softwood: 3D micromechanical modeling

    DEFF Research Database (Denmark)

    Qing, Hai; Mishnaevsky, Leon

    2009-01-01

    Computational micromechanical analysis of the influence of moisture, density and microstructure of latewood on its hydroelastic and shrinkage properties is carried out. The elastic properties of cell sublayers have been determined using the unit cell models as for fiber reinforced composites (two...... covered cylinders representative volume element, for S1, S2 and S3 sublayers) and rectangular embedded unit cells (for isotropic M and P sublayers). 3D hierarchical finite element models of softwood cells as a hexagon-shape-tube with multilayered walls were generated using parametric techniques....... The results for elastic properties of cell sublayers obtained from the unit cell models, from the self-consistent method and Halpin-Tsai equations are compared, and good agreement between these methods was observed. A computational technique, based on the representation of moisture effect as equivalent...

  10. Laser Cooling of a Micromechanical Membrane to the Quantum Backaction Limit

    Science.gov (United States)

    Peterson, R. W.; Purdy, T. P.; Kampel, N. S.; Andrews, R. W.; Yu, P.-L.; Lehnert, K. W.; Regal, C. A.

    2016-02-01

    The radiation pressure of light can act to damp and cool the vibrational motion of a mechanical resonator, but even if the light field has no thermal component, shot noise still sets a limit on the minimum phonon occupation. In optomechanical sideband cooling in a cavity, the finite off-resonant Stokes scattering defined by the cavity linewidth combined with shot noise fluctuations dictates a quantum backaction limit, analogous to the Doppler limit of atomic laser cooling. In our work, we sideband cool a micromechanical membrane resonator to the quantum backaction limit. Monitoring the optical sidebands allows us to directly observe the mechanical object come to thermal equilibrium with the optical bath. This level of optomechanical coupling that overwhelms the intrinsic thermal decoherence was not reached in previous ground-state cooling demonstrations.

  11. Micromechanics model for static and dynamic strength of concrete under confinement

    Institute of Scientific and Technical Information of China (English)

    Dan ZHENG; Qingbin LI

    2008-01-01

    The process of propagation, kinking of micro-cracks in concrete and the interaction among cracks as well as the induced failure were analyzed using the model that describes the wing type crack from the point of view of micromechanics. The pseudo-force method is applied to calculate the compressive strength factor of kinky pro-pagated crack taking into account the effect of interaction among cracks. On the assumption that the micro fracture toughness of concrete does not vary with stain rate, the static and dynamic strength of concrete under different confinements can be calculated. The comparison of cal-culation result with experimental data indicates that a good agreement is achieved which implies that the model can be used to explain the rate-dependent properties of concrete in multi-axial stress state.

  12. Micromechanics analysis of space simulated thermal deformations and stresses in continuous fiber reinforced composites

    Science.gov (United States)

    Bowles, David E.

    1990-01-01

    Space simulated thermally induced deformations and stresses in continuous fiber reinforced composites were investigated with a micromechanics analysis. The investigation focused on two primary areas. First, available explicit expressions for predicting the effective coefficients of thermal expansion (CTEs) for a composite were compared with each other, and with a finite element (FE) analysis, developed specifically for this study. Analytical comparisons were made for a wide range of fiber/matrix systems, and predicted values were compared with experimental data. The second area of investigation focused on the determination of thermally induced stress fields in the individual constituents. Stresses predicted from the FE analysis were compared to those predicted from a closed-form solution to the composite cylinder (CC) model, for two carbon fiber/epoxy composites. A global-local formulation, combining laminated plate theory and FE analysis, was used to determine the stresses in multidirectional laminates. Thermally induced damage initiation predictions were also made.

  13. Laser cooling of a micromechanical membrane to the quantum backaction limit

    CERN Document Server

    Peterson, R W; Kampel, N S; Andrews, R W; Yu, P -L; Lehnert, K W; Regal, C A

    2015-01-01

    The radiation pressure of light can act to damp and cool the vibrational motion of a mechanical resonator. In understanding the quantum limits of this cooling, one must consider the effect of shot noise fluctuations on the final thermal occupation. In optomechanical sideband cooling in a cavity, the finite Stokes Raman scattering defined by the cavity linewidth combined with shot noise fluctuations dictates a quantum backaction limit, analogous to the Doppler limit of atomic laser cooling. In our work we sideband cool to the quantum backaction limit by using a micromechanical membrane precooled in a dilution refrigerator. Monitoring the optical sidebands allows us to directly observe the mechanical object come to thermal equilibrium with the optical bath.

  14. Micromechanical modeling of viscoelastic voided composites in the low-frequency approximation.

    Science.gov (United States)

    Haberman, Michael R; Berthelot, Yves H; Jarzynski, J; Cherkaoui, Mohammed

    2002-11-01

    The self-consistent model of Cherkaoui et al. [J. Eng. Mater. Technol. 116, 274-278 (1994)] is used to compute the effective material moduli of a viscoelastic material containing coated spherical inclusions. Losses are taken into account by introducing the frequency-dependent, complex shear modulus of the viscoelastic matrix. Mode conversion appears through the localization tensors that govern the micromechanical behavior near the inclusions. The results are compared with the scattering model and the data of Baird et al. [J. Acoust. Soc. Am. 105, 1527-1538 (1999)]. The two models are in good agreement. The advantage of the self-consistent model is that it is applicable to the case of nonspherical inclusions embedded in anisotropic materials. PMID:12430805

  15. Microstructural heterogeneity directs micromechanics and mechanobiology in native and engineered fibrocartilage

    Science.gov (United States)

    Han, Woojin M.; Heo, Su-Jin; Driscoll, Tristan P.; Delucca, John F.; McLeod, Claire M.; Smith, Lachlan J.; Duncan, Randall L.; Mauck, Robert L.; Elliott, Dawn M.

    2016-04-01

    Treatment strategies to address pathologies of fibrocartilaginous tissue are in part limited by an incomplete understanding of structure-function relationships in these load-bearing tissues. There is therefore a pressing need to develop micro-engineered tissue platforms that can recreate the highly inhomogeneous tissue microstructures that are known to influence mechanotransductive processes in normal and diseased tissue. Here, we report the quantification of proteoglycan-rich microdomains in developing, ageing and diseased fibrocartilaginous tissues, and the impact of these microdomains on endogenous cell responses to physiologic deformation within a native-tissue context. We also developed a method to generate heterogeneous tissue-engineered constructs (hetTECs) with non-fibrous proteoglycan-rich microdomains engineered into the fibrous structure, and show that these hetTECs match the microstructural, micromechanical and mechanobiological benchmarks of native tissue. Our tissue-engineered platform should facilitate the study of the mechanobiology of developing, homeostatic, degenerating and regenerating fibrous tissues.

  16. Micromechanical modeling of sulphate corrosion in concrete: Influence of ettringite forming reaction

    Directory of Open Access Journals (Sweden)

    Basista M.

    2008-01-01

    Full Text Available Two micromechanical models are developed to simulate the expansion of cementitious composites exposed to external sulphate attack. The difference between the two models lies in the form of chemical reaction of the ettringite formation (through-solution vs. topochemical. In both models the Fick's second law with reaction term is assumed to govern the transport of the sulphate ions. The Eshelby solution and the equivalent inclusion method are used to determine the eigenstrain of the expanding ettringite crystals in microcracked hardened cement paste. The degradation of transport properties is studied in the effective medium and the percolation regime. An initial-boundary value problem (2D of expansion of a mortar specimen immersed in a sodium sulphate solution is solved and compared with available test data. The obtained results indicate that the topochemical mechanism is the one capable of producing the experimentally observed amount of expansion.

  17. Laboratory Observation and Micromechanics-Based Modelling of Sandstone on Different Scales

    Science.gov (United States)

    Li, Liming; Larsen, Idar; Holt, Rune M.

    2015-07-01

    The mechanical properties of sandstone are, to a large extent, controlled by its microstructure. When sandstone is loaded, the stress conditions and stress history can influence the sandstone in terms of the deformation parameters, strength parameters, failure modes, as well as acoustic properties and other petrophysical parameters. In this paper, we show how we may use a discrete element model to compute the mechanical behaviour based on the microstructure of the rock, as obtained from micro-computed tomography. The model is calibrated with triaxial test data obtained with three different sandstones. The key element in the model is a contact law, attempting to capture deformation and failure at the level of the grain scale. A micromechanics-based core-scale model was also suggested using the same contact law but without explicitly mimicking the rock microstructure. The simulation results from both the microscale model and the macroscale model were in reasonably good agreement with the laboratory measurements on sandstone specimens.

  18. Contribution of Acoustic Losses in the Quality Factor of a Micromechanical Resonator

    CERN Document Server

    Vishwakarma, Santhosh D; Parpia, J M; Pratap, R

    2012-01-01

    A semi-analytical study of the acoustic radiation losses associated with various transverse vibration modes of a micromechanical (MEMS) annular resonator is presented. The quality factor, Q, of such resonators is of interest in many applications and depends on structural geometry, interaction with the external environment, and the encapsulation method. Resonators with at least one surface exposed to air can display losses through acoustic radiation even at micro meter dimensions. Published experimental results suggest the dominance of acoustic losses in the Q of a MEMS drum resonator. In this study, a well established mathematical techniques to analytically model resonator vibration modes and fluid-structure interaction are used, and a semi-analytical procedure for computing Q due to acoustic radiation losses, Qac, in any vibrational mode outlined. Present technique includes calculation of the exact mode shape and its utilization in computing Qac. The dependence of Qac on the first 15 mode shapes is computed....

  19. Micromechanical investigation of soil plasticity using a discrete model of polygonal particles

    Directory of Open Access Journals (Sweden)

    Alonso-Marroquin Fernando

    2008-01-01

    Full Text Available The mechanical behavior of soils has been traditionally described using continuum-mechanics-based models. These are empirical relations based on laboratory tests of soil specimens. The investigation of the soils at the grain scale using discrete element models has become possible in recent years. These models have provided valuable understanding of many micromechanical aspects of soil deformation. The aim of this work is to draw together these two approaches in the investigation of the plastic deformation of non-cohesive soils. A simple discrete element model has been used to evaluate the effect of anisotropy, force chains, and sliding contacts on different aspects of soil plasticity: dilatancy, shear bands, ratcheting etc. The discussion of these aspects raises important questions such as the width of shear bands, the origin of the stress-dilatancy relation, and the existence of a purely elastic regime in the deformation of granular materials.

  20. An analytic approach to piezoelectric fiber composites - from micromechanics modeling to beam behavior

    Energy Technology Data Exchange (ETDEWEB)

    Brockmann, T.; Lammering, R. [Universitaet der Bundeswehr, Hamburg (Germany). Inst. fuer Mechanik

    2001-07-01

    In the context of adaptive systems, the technology of piezoelectric fiber composites with its capabilities for high-speed actuation and the beneficial effects of tailorable anisotropy is of great interest for structurally integrated vibration suppression and acoustic control. In order to study the interaction between active and load carrying functionalities and to analyze the influence of the diverse parameters, an analytic model containing all major characteristics from the micromechanics to the structural mechanics level is described. The effective electroelastic properties of a lamina with embedded continuous piezoceramic fibers exposed to an electric field in fiber direction are examined in the close-up investigation of a representative volume. With the aid of the classical lamination theory, extended by the internal actuation loads, such plies can be combined for the respective purpose. Finally, the active and passive properties of a single-cell closed cross-section beam with walls made from these laminated composites are derived. (orig.)

  1. Geometrically tuned wettability of dynamic micromechanical sensors for an improved in-liquid operation

    Science.gov (United States)

    Peiker, P.; Oesterschulze, E.

    2015-09-01

    Partial wetting is a vital tool to improve the quality factor of dynamic micromechanical sensors operated in liquids owing to the reduced viscous damping. This technique employs meniscus formation which so far could only be stabilized for a hydrophobic sensory surface excluding biosensing applications. Here, we report on the geometrically tuned wettability of particular hybrid bridge resonators (HBR) with an integrated overhang structure. This allows low-loss operation irrespective of the sensory surface material. The impact of the overhang structure on wetting is explained in a simplified model. Experimental evidence is adduced operating the HBR coated with hydrophilic thin films in water. With an in-liquid quality factor Q of 91 and a small mass m ≈ 5 ng of the HBR, the m/Q-ratio, which is proportional to the limit of detection for mass sensing, was significantly improved in comparison to immersed resonators presented so far.

  2. Micromechanical Modeling for the Deformation of Sand with Non-coaxiality Between Stress and Material Axes

    Science.gov (United States)

    Bennett, K. C.; Chang, C. S.; Borja, R. I.

    2011-12-01

    This research project has taken the micromechanics approach to model the strength and deformation behavior of inherently anisotropic sand subjected to stresses non-coaxial with the material axes. Asymmetric sand grains, such as elongated sand grains, are likely to develop a preferred orientation when deposited during the process of alluvial sedimentation, creating an inherently anisotropic material fabric with horizontally oriented bedding planes. Sand thus exhibits different strength and stress-strain behavior dependent on the direction of loading with respect to the axes of the soil. Accounting for non-coaxiality between the stress and material axes is paramount for the accurate prediction of soil's response to applied loads; however, despite the numerous advancements in constitutive models and numerical methods for geotechnical analysis, the problem of accounting for the effect of non-coaxiality between stress and material axes on soil behavior has not been satisfactorily addressed. Drained hollow cylinder torsional shear (HCTS) compression tests on Toyoura sand were simulated, where the direction of the major principal stresses were applied at various angles to the material axes ranging from 0° to 90° from vertical (i.e., ranging from normal to parallel with the bedding plane). Anisotropic behavior has been attributed to interlocking of the sand particles, where the interlocking is least and sliding occurs most easily on the bedding plane. The degree of interlocking was taken as a material property which varies in three dimensions with respect to the material axes, and has been shown to account for observed anisotropy of material strength. Anisotropy of elastic and plastic strain was accounted for, as was the volumetric strain behavior. The developed micromechanics model has been shown to be capable of predicting anisotropy of strength and stress-strain behavior resulting from non-coaxiality of the stress and material axes.

  3. Phases Micromechanical Properties of Ni-base Superalloy Measured by Nanoindentation

    Directory of Open Access Journals (Sweden)

    Lembit KOMMEL

    2012-03-01

    Full Text Available This investigation describes the changes in the phase’s micromechanical properties as a result of alloying elements moving at interdiffusion. The induction of the interdiffusion between different phases of a Ni-based single crystal superalloy still is a challenging issue in this field of the materials science. For this we used novel technique - hard cyclic viscoplastic deformation at room temperature. The chemical compositions of the phases were determined by the cumulative bulk deformation. For detailed knowledge of this material behavior during life time the micromechanical properties of phases were investigated by nanoindentation and the results were analyzed by scanning electron microscope and the corresponding chemical content was investigated by X-ray microanalysis. It was established, that the calculated results values depend on indentation load stepwise increase from 5 to 10 and 20 mN, respectively. The hardness, contact compliance and elastic recovery parameters decrease, while indentation modulus, elastic- and plastic parts of indentation work increase with load increase. In initial material the hardness, indentation modulus and elastic recovery parameter for the γ/γ’-microstructure with coarse intermetallic γ’-precipitates were lower with compared to microstructure with fine γ’-precipitations. As a result of interdiffusion the chemical content was changed and these parameters for the coarse γ/γ’-microstructure increased as the γ’-Ni3Al content was increased, while these values in the γ-γ’-eutectic and Nb/Ta-rich phases decreased as the niobium and rhenium contents decreased, respectively. By this the lakes of γ-γ’-eutectic phase have maximal plastic part of indentation work with compare to other phases of superalloy. The cumulative bulk deformation increases lead to decrease of dendrites dimensions.DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1337

  4. Micromechanical Tests and Geochemical Modeling to Evaluate Evolution of Rock Alteration by CO2-Water Mixtures

    Science.gov (United States)

    Aman, M.; Sun, Y.; Ilgen, A.; Espinoza, N.

    2015-12-01

    Injection of large volumes of CO2 into geologic formations can help reduce the atmospheric CO2 concentration and lower the impact of burning fossil fuels. However, the injection of CO2 into the subsurface shifts the chemical equilibrium between the mineral assemblage and the pore fluid. This shift will situationally facilitate dissolution and reprecipitation of mineral phases, in particular intergranular cements, and can potentially affect the long term mechanical stability of the host formation. The study of these coupled chemical-mechanical reservoir rock responses can help identify and control unexpected emergent behavior associated with geological CO2 storage.Experiments show that micro-mechanical methods are useful in capturing a variety of mechanical parameters, including Young's modulus, hardness and fracture toughness. In particular, micro-mechanical measurements are well-suited for examining thin altered layers on the surfaces of rock specimens, as well as capturing variability on the scale of lithofacies. We performed indentation and scratching tests on sandstone and siltstone rocks altered in natural CO2-brine environments, as well as on analogous samples altered under high pressure, temperature, and dissolved CO2 conditions in a controlled laboratory experiment. We performed geochemical modeling to support the experimental observations, in particular to gain the insight into mineral dissolution/precipitation as a result of the rock-water-CO2reactions. The comparison of scratch measurements performed on specimens both unaltered and altered by CO2 over geologic time scales results in statistically different values for fracture toughness and scratch hardness, indicating that long term exposure to CO2 caused mechanical degradation of the reservoir rock. Geochemical modeling indicates that major geochemical change caused by CO2 invasion of Entrada sandstone is dissolution of hematite cement, and its replacement with siderite and dolomite during the

  5. Micromechanical Modeling of Grain Boundaries Damage in a Copper Alloy Under Creep; Mikromechanische Modellierung der Korngrenzenschaedigung in einer Kupferlegierung unter Kriechbeanspruchung

    Energy Technology Data Exchange (ETDEWEB)

    Voese, Markus

    2015-07-01

    In order to include the processes on the scale of the grain structure into the description of the creep behaviour of polycrystalline materials, the damage development of a single grain boundary has been initially investigated in the present work. For this purpose, a special simulationmethod has been used, whose resolution procedure based on holomorphic functions. The mechanisms taken into account for the simulations include nucleation, growth by grain boundary diffusion, coalescence and shrinkage until complete sintering of grain boundary cavities. These studies have then been used to develop a simplified cavitation model, which describes the grain boundary damage by two state variables and the time-dependent development by a mechanism-oriented rate formulation. To include the influence of grain boundaries within continuum mechanical considerations of polycrystals, an interface model has been developed, that incorporates both damage according to the simplified cavitation model and grain boundary sliding in dependence of a phenomenological grain boundary viscosity. Furthermore a micromechanical model of a polycrystal has been developed that allows to include a material's grain structure into the simulation of the creep behaviour by means of finite element simulations. Thereby, the deformations of individual grains are expressed by a viscoplastic single crystal model and the grain boundaries are described by the proposed interface model. The grain structure is represented by a finite element model, in which the grain boundaries are modelled by cohesive elements. From the evaluation of experimental creep data, the micromechanical model of a polycrystal has been calibrated for a copper-antimony alloy at a temperature of 823 K. Thereby, the adjustment of the single crystal model has been carried out on the basis of creep rates of pure copper single crystal specimens. The experimental determination of grain boundary sliding and grain boundary porosity for coarse

  6. Interface losses in multimaterial resonators

    DEFF Research Database (Denmark)

    Villanueva, L.G.; Amato, B.; Larsen, Tom;

    2014-01-01

    We present an extensive study shedding light on the role of surface and bulk losses in micromechanical resonators. We fabricate thin silicon nitride membranes of different sizes and we coat them with different thicknesses of metal. We later characterize the 81 lowest out-of-plane flexural vibrati...

  7. 颗粒增强镁基复合材料细观力学场的数值模拟分析%Numerical Simulation Analysis on Micro-mechanical Characteristics of Titanium Particle Reinfored Magnesium Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    郗雨林; 武创; 刘国元; 张新杰

    2012-01-01

    The micro-mechanical characteristics of a participate reinforced magnesium matrix composite was analyzed by FEM simulation. The results showed that such mechanical parameters as Mises equivalent stress, stress spherical tensor, deformation-energy consumption, maximum principal stress and maximum principal strain concentrated markedly in some local areas. The stress concentration might cause local yielding although the loaded force was smaller than the matrix yielding strength. Local interface debonding and matrix cracking are main failure modes in the composite. Moreover, micro-mechanics analysis revealed that the strengthening effect of paniculate reinforcements comes mainly from its effect on the stress and strain distribution in matrix , and secondarily from its consumption of the deformation work.%本文借助有限元数值模拟,研究了颗粒增强镁基复合材料的细观力学特征.结果表明,等效应力、应力球量、功耗、最大主应力和最大主应变存在明显的集中现象.尽管外力小于基体的屈服强度,但应力集中可使基体发生微区屈服.复合材料主要的失效形式为界面脱粘和基体开裂,同时,细观力学分析说明,增强体的强化作用主要来自于它对基体应力、应变状态的改变,而不是其本身对形变功的分担.

  8. Micromechanics analysis of space simulated thermal stresses in composites. I - Theory and unidirectional laminates. II - Multidirectional laminates and failure predictions

    Science.gov (United States)

    Bowles, David E.; Griffin, O. H., Jr.

    1991-01-01

    A micromechanics analysis is used to study the effects of constituent properties on thermally induced stresses in continuous fiber reinforced composites. A finite element formulation is described, and results are presented for unidirectional carbon/epoxy laminates. It is shown that significant stresses develop in composites exposed to thermal excursions typical of spacecraft operating environments and that the fiber thermoelastic properties have a minimal effect on the magnitude of these stresses. The finite element micromechanics analysis is then extended to the study of multidirectional laminates using a simple global/local formulation. Damage initiation predictions are compared with experimental data, and factors controlling the initiation of damage are identified. Ways of improving the durability of composites are discussed.

  9. Development of Low-cost Chemical and Micromechanical Sensors Based on Thick-film,Thin-film and Electroplated Films

    Institute of Scientific and Technical Information of China (English)

    Wenmin Qu; Kurt Drescher

    2000-01-01

    Various films could be used as sensing materials or as constructional materials for the fabrication of chemical and micromechanical sensors. To illustrate this potential, three sensors fabricated by very different film deposition technologies are given as examples. The sensors are a humidity sensor in thickfilm technology, a multi-functional gas sensor in thin-film technology and a three-dimensional acceleration sensor chip manufactured by electroplating techniques. Design, fabrication and characterisation of these sensors are described in this paper.

  10. Micro-mechanisms of fatigue in short glass fiber reinforced polyamide 66: A multi-scale experimental analysis

    OpenAIRE

    ESMAEILLOU, Bardia; Fitoussi, Joseph; Meraghni, Fodil; TCHARKHTCHI, Abbas

    2014-01-01

    The objective of this work is to identify and to analyze the main micro-mechanisms which govern the fatigue behavior of a short glass fiber reinforced polyamide 66 composite through a multi-scale experimental analysis. Tension-tension fatigue tests have been performed at different applied maximum stress and have been analyzed at both microscopic and macroscopic scale. Together with the progressive stiffness reduction, the temperature rise due to self-heating during cyclic loading has been mea...

  11. The Relationship Between Constraint and Ductile Fracture Initiation as Defined by Micromechanical Analyses

    Science.gov (United States)

    Panontin, Tina L.; Sheppard, Sheri D.

    1994-01-01

    The use of small laboratory specimens to predict the integrity of large, complex structures relies on the validity of single parameter fracture mechanics. Unfortunately, the constraint loss associated with large scale yielding, whether in a laboratory specimen because of its small size or in a structure because it contains shallow flaws loaded in tension, can cause the breakdown of classical fracture mechanics and the loss of transferability of critical, global fracture parameters. Although the issue of constraint loss can be eliminated by testing actual structural configurations, such an approach can be prohibitively costly. Hence, a methodology that can correct global fracture parameters for constraint effects is desirable. This research uses micromechanical analyses to define the relationship between global, ductile fracture initiation parameters and constraint in two specimen geometries (SECT and SECB with varying a/w ratios) and one structural geometry (circumferentially cracked pipe). Two local fracture criteria corresponding to ductile fracture micromechanisms are evaluated: a constraint-modified, critical strain criterion for void coalescence proposed by Hancock and Cowling and a critical void ratio criterion for void growth based on the Rice and Tracey model. Crack initiation is assumed to occur when the critical value in each case is reached over some critical length. The primary material of interest is A516-70, a high-hardening pressure vessel steel sensitive to constraint; however, a low-hardening structural steel that is less sensitive to constraint is also being studied. Critical values of local fracture parameters are obtained by numerical analysis and experimental testing of circumferentially notched tensile specimens of varying constraint (e.g., notch radius). These parameters are then used in conjunction with large strain, large deformation, two- and three-dimensional finite element analyses of the geometries listed above to predict crack

  12. Micromechanical behavior of eutectoid steel quantified by an analytical model calibrated by in situ synchrotron-based X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Chengsi [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China); Li, Longfei, E-mail: lilf@skl.ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China); The Collaborative Innovation Center of Steel Technology (CICST), University of Science and Technology Beijing, Beijing 100083 (China); Wang, Yandong [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China); The Collaborative Innovation Center of Steel Technology (CICST), University of Science and Technology Beijing, Beijing 100083 (China); Yang, Wangyue [School of Materials Science and Engineering, University of Science & Technology Beijing, Beijing 100083 (China); Sun, Zuqing [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China)

    2015-04-17

    A eutectoid steel with three types of ferrite (α)+cementite particle (θ) microstructures, i.e., a coarse-grained α+θ structure, a fine-grained α+θ structure and an ultrafine-grained α+θ structure, was fabricated to explore the effects of the microstructural features on the micromechanical behavior of hard particle-strengthened two-phase alloys. An analytical model based on the Kocks–Mecking model was established to elucidate the evolution of the geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs) in the hard particle-strengthened alloys and, hence, to predict the stress partitioning for each phase and the enhancement in the work hardening during uniform plastic deformation. In situ synchrotron-based X-ray diffraction was used to verify the stress partitioning and the important material parameters predicted by our analytical model. Our results showed that a decrease in the geometric slip distance leads to an appreciable increase in the GND density, whereas an increase in the grain size of the ferrite causes an increase in the SSD density under uniform plastic deformation for eutectoid steel with an α+θ structure. Both the stresses for the individual phase and the difference in stress between the two phases for eutectoid steel with various α+θ structures were closely related to the change in the GND density near the phase interfaces. The GND density also played an important role in determining the work-hardening rate for eutectoid steel with various α+θ structures.

  13. Advances in Micromechanics Modeling of Composites Structures for Structural Health Monitoring

    Science.gov (United States)

    Moncada, Albert

    Although high performance, light-weight composites are increasingly being used in applications ranging from aircraft, rotorcraft, weapon systems and ground vehicles, the assurance of structural reliability remains a critical issue. In composites, damage is absorbed through various fracture processes, including fiber failure, matrix cracking and delamination. An important element in achieving reliable composite systems is a strong capability of assessing and inspecting physical damage of critical structural components. Installation of a robust Structural Health Monitoring (SHM) system would be very valuable in detecting the onset of composite failure. A number of major issues still require serious attention in connection with the research and development aspects of sensor-integrated reliable SHM systems for composite structures. In particular, the sensitivity of currently available sensor systems does not allow detection of micro level damage; this limits the capability of data driven SHM systems. As a fundamental layer in SHM, modeling can provide in-depth information on material and structural behavior for sensing and detection, as well as data for learning algorithms. This dissertation focuses on the development of a multiscale analysis framework, which is used to detect various forms of damage in complex composite structures. A generalized method of cells based micromechanics analysis, as implemented in NASA's MAC/GMC code, is used for the micro-level analysis. First, a baseline study of MAC/GMC is performed to determine the governing failure theories that best capture the damage progression. The deficiencies associated with various layups and loading conditions are addressed. In most micromechanics analysis, a representative unit cell (RUC) with a common fiber packing arrangement is used. The effect of variation in this arrangement within the RUC has been studied and results indicate this variation influences the macro-scale effective material properties and

  14. A micromechanical four-phase model to predict the compressive failure surface of cement concrete

    Directory of Open Access Journals (Sweden)

    A. Caporale,

    2014-07-01

    Full Text Available In this work, a micromechanical model is used in order to predict the failure surface of cement concrete subject to multi-axial compression. In the adopted model, the concrete material is schematised as a composite with the following constituents: coarse aggregate (gravel, fine aggregate (sand and cement paste. The cement paste contains some voids which grow during the loading process. In fact, the non-linear behavior of the concrete is attributed to the creation of cracks in the cement paste; the effect of the cracks is taken into account by introducing equivalent voids (inclusions with zero stiffness in the cement paste. The three types of inclusions (namely gravel, sand and voids have different scales, so that the overall behavior of the concrete is obtained by the composition of three different homogenizations; in the sense that the concrete is regarded as the homogenized material of the two-phase composite constituted of the gravel and the mortar; in turn, the mortar is the homogenized material of the two-phase composite constituted of the sand inclusions and a (porous cement paste matrix; finally, the (porous cement paste is the homogenized material of the two-phase composite constituted of voids and the pure paste. The pure paste represents the cement paste before the loading process, so that it does not contain voids or other defects due to the loading process. The abovementioned three homogenizations are realized with the predictive scheme of Mori-Tanaka in conjunction with the Eshelby method. The adopted model can be considered an attempt to find micromechanical tools able to capture peculiar aspects of the cement concrete in load cases of uni-axial and multi-axial compression. Attributing the non-linear behavior of concrete to the creation of equivalent voids in the cement paste provides correspondence with many phenomenological aspects of concrete behavior. Trying to improve this correspondence, the influence of the parameters of the

  15. Interface Simulation Distances

    Directory of Open Access Journals (Sweden)

    Pavol Černý

    2012-10-01

    Full Text Available The classical (boolean notion of refinement for behavioral interfaces of system components is the alternating refinement preorder. In this paper, we define a distance for interfaces, called interface simulation distance. It makes the alternating refinement preorder quantitative by, intuitively, tolerating errors (while counting them in the alternating simulation game. We show that the interface simulation distance satisfies the triangle inequality, that the distance between two interfaces does not increase under parallel composition with a third interface, and that the distance between two interfaces can be bounded from above and below by distances between abstractions of the two interfaces. We illustrate the framework, and the properties of the distances under composition of interfaces, with two case studies.

  16. A Study of Failure Strength for Fiber-Reinforced Composite Laminates with Consideration of Interface

    Directory of Open Access Journals (Sweden)

    Junjie Ye

    2015-01-01

    Full Text Available Composite laminates can exhibit the nonlinear properties due to the fiber/matrix interface debonding and matrix plastic deformation. In this paper, by incorporating the interface stress-displacement relations between fibers and matrix, as well as the viscoplastic constitutive model for describing plastic behaviors of matrix materials, a micromechanical model is used to investigate the failure strength of the composites with imperfect interface bonding. Meanwhile, the classic laminate theory, which provides the relation between micro- and macroscale responses for composite laminates, is employed. Theory results show good consistency with the experimental data under unidirectional tensile conditions at both 23°C and 650°C. On this basis, the interface debonding influences on the failure strength of the [0/90]s and [0/±45/90]s composite laminates are studied. The numerical results show that all of the unidirectional (UD laminates with imperfect interface bonding provide a sharp decrease in failure strength in the σxx-σyy plane at 23°C. However, the decreasing is restricted in some specific region. In addition, for [0/90]s and [0/±45/90]s composite laminates, the debonding interface influences on the failure envelope can be ignored when the working temperature is increased to 650°C.

  17. Effect of chain conformation on micro-mechanical behaviour of MEH–PPV thin film

    Indian Academy of Sciences (India)

    P Wang; L L Wu; D Zhang; H Q Zhang

    2013-10-01

    The morphology, photoluminescent properties and micro-mechanical character of poly[2-methoxy-5-(2'-ethylhexyloxy)--phenylene vinylene] (MEH–PPV) thin films prepared from toluene (T film) and chloroform (C film) were studied by transmission electron microscopy (TEM), absorption, photoluminescence spectrophotometry and nanoindentation test. The morphological feature of worm-like entities which appeared in T film was ∼10–20 nm in length and 3–5 nm in width. The C film displayed the continuous cotton fibre-shaped morphology. In contrast with C film, the band-edge absorption and maximum emission for T film shifted to the longer wavelength. An analysis fromTEM photograph, absorption and photoluminescence spectra indicated that different chain conformation presented in these two kinds of films. The nanoindentation test showed that the elastic modulus and indentation hardness of T film under the same experimental parameter (load: 50–200 N, loading rate: 20 N/s and holding time: 20 s) decreased by 33.3 ± 0.3 and 8.9 ± 0.5%, respectively comparing with C film. In addition, critical bending radius of these two films based on the flexible base was also evaluated from the obtained experimental results.

  18. Micromechanism and Kinetic Formulation of Vertically Aligned ZnO Nanorods Grown on Catalytic Bilayers

    Directory of Open Access Journals (Sweden)

    Dong-Hau Kuo

    2012-01-01

    Full Text Available Vertically aligned ZnO nanorods were grown at for 2 h on sapphire substrates with catalysts in bilayer configurations of Sn (top/Ni (bottom and Sn/In, where the top layer is formed by sputtering and the bottom one is deposited by spin coating. The effects of bilayer catalysts on growth kinetics of nucleation and growth, growth micromechanism, and vertical alignment of growing ZnO nanorods have been investigated. The vertical alignment of the Sn/Ni-catalyzing ZnO nanorods is determined at the initial nucleation stage, where the nuclei are formed as regular candlestick-like platforms. The reason for the formation of the candlestick-like nuclei is due to the contribution of strain energy built in the underlying catalyst bilayers. The variations of axial and radial dimensions with growth duration for the growth of ZnO rods were explained and data fitting with the aids of kinetic growth equations, which are based upon the well-known ledge model for crystal growth from vapor and diffusion kinetics.

  19. Micro-mechanical oscillator ground state cooling via intracavity optical atomic excitations

    CERN Document Server

    Genes, C; Vitali, D

    2009-01-01

    We predict ground state cooling of a micro-mechanical oscillator, i.e. a vibrating end-mirror of an optical cavity, by resonant coupling of mirror vibrations to a narrow internal optical transition of an ensemble of two level systems. The particles represented by a collective mesoscopic spin model implement, together with the cavity, an efficient, frequency tailorable zero temperature loss channel which can be turned to a gain channel of pump. As opposed to the case of resolved-sideband cavity cooling requiring a small cavity linewidth, one can work here with low finesses and very small cavity volumes to enhance the light mirror and light atom coupling. The tailored loss and gain channels provide for efficient removal of vibrational quanta and suppress reheating. In a simple physical picture of sideband cooling, the atoms shape the cavity profile to enhance/inhibit scattering into higher/lower energy sidebands. The method should be applicable to other cavity based cooling schemes for atomic and molecular gase...

  20. Micro-mechanics based damage mechanics for 3D Orthogonal Woven Composites: Experiment and Numerical Modelling

    KAUST Repository

    Saleh, Mohamed Nasr

    2016-01-08

    Damage initiation and evolution of three-dimensional (3D) orthogonal woven carbon fibre composite (3DOWC) is investigated experimentally and numerically. Meso-scale homogenisation of the representative volume element (RVE) is utilised to predict the elastic properties, simulate damage initiation and evolution when loaded in tension. The effect of intra-yarns transverse cracking and shear diffused damage on the in-plane transverse modulus and shear modulus is investigated while one failure criterion is introduced to simulate the matrix damage. The proposed model is based on two major assumptions. First, the effect of the binder yarns, on the in-plane properties, is neglected, so the 3DOWC unit cell can be approximated as a (0o/90o) cross-ply laminate. Second, a micro-mechanics based damage approach is used at the meso-scale, so damage indicators can be correlated, explicitly, to the density of cracks within the material. Results from the simulated RVE are validated against experimental results along the warp (0o direction) and weft (90o direction). This approach paves the road for more predictive models as damage evolution laws are obtained from micro mechanical considerations and rely on few well-defined material parameters. This largely differs from classical damage mechanics approaches in which the evolution law is obtained by retrofitting experimental observations.

  1. Tensile and fracture behavior of AA6061-T6 aluminum alloys: micro-mechanical approach

    International Nuclear Information System (INIS)

    The AA6061-T6 aluminum alloy was chosen as the material for the core vessel of the future Jules Horowitz testing reactor (JHR). The objective of this thesis is to understand and model the tensile and fracture behavior of the material, as well as the origin of damage anisotropy. A micro-mechanical approach was used to link the microstructure and mechanical behavior. The microstructure of the alloy was characterized on the surface via Scanning Electron Microscopy and in the 3D volume via synchrotron X-ray tomography and laminography. The damage mechanism was identified by in-situ SEM tensile testing, ex-situ X-ray tomography and in-situ laminography on different levels of triaxiality. The observations have shown that damage nucleated at lower strains on Mg2Si coarse precipitates than on iron rich intermetallics. The identified scenario and the in-situ measurements were then used to develop a coupled GTN damage model incorporating nucleation, growth and coalescence of cavities formed by coarse precipitates. The relationship between the damage and the microstructure anisotropies was explained and simulated. (author)

  2. High quality factor nanocrystalline diamond micromechanical resonators limited by thermoelastic damping

    International Nuclear Information System (INIS)

    We demonstrate high quality factor thin-film nanocrystalline diamond micromechanical resonators with quality factors limited by thermoelastic damping. Cantilevers, single-anchored and double-anchored double-ended tuning forks, were fabricated from 2.5 μm thick in-situ boron doped nanocrystalline diamond films deposited using hot filament chemical vapor deposition. Thermal conductivity measured by time-domain thermoreflectance resulted in 24 ± 3 W m−1 K−1 for heat transport through the thickness of the diamond film. The resonant frequencies of the fabricated resonators were 46 kHz–8 MHz and showed a maximum measured Q ≈ 86 000 at fn = 46.849 kHz. The measured Q-factors are shown to be in good agreement with the limit imposed by thermoelastic dissipation calculated using the measured thermal conductivity. The mechanical properties extracted from resonant frequency measurements indicate a Young's elastic modulus of ≈788 GPa, close to that of microcrystalline diamond

  3. A micromechanics-based thermodynamic model for the domain switch in ferroelectric crystals

    Energy Technology Data Exchange (ETDEWEB)

    Li, W.F.; Weng, G.J

    2004-05-03

    In this work we take the view that domain switch in ferroelectric crystals is a thermodynamics-driven process. In this light we first consider the micromechanics of domain switch to derive the Gibbs free energy of the heterogeneous system and the corresponding thermodynamic driving force at a given level of switched domain concentration f{sub p}, applied stress {sigma}-bar{sub ij}, and applied electric field E-bar{sub i}. Then in conjunction with Miller and Weinreich's [Phys. Rev. 117 (1960) 1460] resistance force for the sidewise motion of 180 deg. domain walls, a kinetic equation is established to calculate the evolution of new domains under a reversed electric field for a BaTiO{sub 3} crystal. The calculated results show that, as the field increases, the switching process is initially rapid, and then becomes quite slow as it approaches the saturation state. The calculated polarization versus the electric field relation (P-E relation) is found to agree with the measured characteristics. The effect of porosity on the switching processes is also examined. It is found that, due to the lower level of Gibbs free energy in the presence of pores, a higher field is required to overcome the energy resistance of domain switch. On the other hand, due to the lower initial parent domain concentration, the level of electric field to cause a complete reversal of the domains decreases with porosity.

  4. A micromechanical approach for the micropolar modeling of heterogeneous periodic media

    Directory of Open Access Journals (Sweden)

    M.L. De Bellis,

    2014-07-01

    Full Text Available Computational homogenization is adopted to assess the homogenized two-dimensional response of periodic composite materials where the typical microstructural dimension is not negligible with respect to the structural sizes. A micropolar homogenization is, therefore, considered coupling a Cosserat medium at the macro-level with a Cauchy medium at the micro-level, where a repetitive Unit Cell (UC is selected. A third order polynomial map is used to apply deformation modes on the repetitive UC consistent with the macro-level strain components. Hence, the perturbation displacement field arising in the heterogeneous medium is characterized. Thus, a newly defined micromechanical approach, based on the decomposition of the perturbation fields in terms of functions which depend on the macroscopic strain components, is adopted. Then, to estimate the effective micropolar constitutive response, the well known identification procedure based on the Hill-Mandel macro-homogeneity condition is exploited. Numerical examples for a specific composite with cubic symmetry are shown. The influence of the selection of the UC is analyzed and some critical issues are outlined.

  5. Fracture Propagation Characteristic and Micromechanism of Rock-Like Specimens under Uniaxial and Biaxial Compression

    Directory of Open Access Journals (Sweden)

    Xue-wei Liu

    2016-01-01

    Full Text Available This paper presents a set of uniaxial and biaxial compression tests on the rock-like material specimens with different fracture geometries through a rock mechanics servo-controlled testing system (RMT-150C. On the basis of experimental results, the characteristics of fracture propagation under different fracture geometries and loading conditions are firstly obtained. The newly formed fractures are observed propagating from or near the preexisting crack tips for different specimens, while the propagation paths are affected by the loading condition obviously. Then, by adopting acoustic emission (AE location technique, AE event localization characteristics in the process of loading are investigated. The locations of AE events are in good agreement with the macroscopic fracture propagation path. Finally, the micromechanism of macroscopic fracture propagation under uniaxial and biaxial compression conditions is analyzed, and the fracture propagation can be concluded as a result of microdamage accumulation inside the material. The results of this paper are helpful for theory and engineering design of the fractured rock mass.

  6. Micromechanical and macroscopic models of ductile fracture in particle reinforced metallic materials

    Science.gov (United States)

    Hu, Chao; Bai, Jie; Ghosh, Somnath

    2007-06-01

    This paper is aimed at developing two modules contributing to the overall framework of multi-scale modelling of ductile fracture of particle reinforced metallic materials. The first module is for detailed micromechanical analysis of particle fragmentation and matrix cracking of heterogeneous microstructures. The Voronoi cell FEM for particle fragmentation is extended in this paper to incorporate ductile failure through matrix cracking in the form of void growth and coalescence using a non-local Gurson-Tvergaard-Needleman (GTN) model. In the resulting enriched Voronoi cell finite element model (VCFEM) or E-VCFEM, the assumed stress-based hybrid VCFEM formulation is overlaid with narrow bands of displacement based elements to accommodate strain softening in the constitutive behaviour. The second module develops an anisotropic plasticity-damage model in the form of the GTN model for macroscopic analysis in the multi-scale material model. Parameters in this model are calibrated from results of homogenization of microstructural variables obtained by E-VCFEM analysis of microstructural representative volume element. Numerical examples conducted yield satisfactory results.

  7. Self-induced parametric amplification arising from nonlinear elastic coupling in a micromechanical resonating disk gyroscope.

    Science.gov (United States)

    Nitzan, Sarah H; Zega, Valentina; Li, Mo; Ahn, Chae H; Corigliano, Alberto; Kenny, Thomas W; Horsley, David A

    2015-01-01

    Parametric amplification, resulting from intentionally varying a parameter in a resonator at twice its resonant frequency, has been successfully employed to increase the sensitivity of many micro- and nano-scale sensors. Here, we introduce the concept of self-induced parametric amplification, which arises naturally from nonlinear elastic coupling between the degenerate vibration modes in a micromechanical disk-resonator, and is not externally applied. The device functions as a gyroscope wherein angular rotation is detected from Coriolis coupling of elastic vibration energy from a driven vibration mode into a second degenerate sensing mode. While nonlinear elasticity in silicon resonators is extremely weak, in this high quality-factor device, ppm-level nonlinear elastic effects result in an order-of-magnitude increase in the observed sensitivity to Coriolis force relative to linear theory. Perfect degeneracy of the primary and secondary vibration modes is achieved through electrostatic frequency tuning, which also enables the phase and frequency of the parametric coupling to be varied, and we show that the resulting phase and frequency dependence of the amplification follow the theory of parametric resonance. We expect that this phenomenon will be useful for both fundamental studies of dynamic systems with low dissipation and for increasing signal-to-noise ratio in practical applications such as gyroscopes.

  8. MEMS resonant load cells for micro-mechanical test frames: feasibility study and optimal design

    International Nuclear Information System (INIS)

    This paper presents the design, optimization and manufacturing of a novel micro-fabricated load cell based on a double-ended tuning fork. The device geometry and operating voltages are optimized for maximum force resolution and range, subject to a number of manufacturing and electromechanical constraints. All optimizations are enabled by analytical modeling (verified by selected finite elements analyses) coupled with an efficient C++ code based on the particle swarm optimization algorithm. This assessment indicates that force resolutions of ∼0.5–10 nN are feasible in vacuum (∼1–50 mTorr), with force ranges as large as 1 N. Importantly, the optimal design for vacuum operation is independent of the desired range, ensuring versatility. Experimental verifications on a sub-optimal device fabricated using silicon-on-glass technology demonstrate a resolution of ∼23 nN at a vacuum level of ∼50 mTorr. The device demonstrated in this article will be integrated in a hybrid micro-mechanical test frame for unprecedented combinations of force resolution and range, displacement resolution and range, optical (or SEM) access to the sample, versatility and cost

  9. MICROMECHANICS OF THE DAMAGE-INDUCED CELLULAR MICROSTRUCTURE IN SINGLE CRYSTAL Ni-BASED SUPERALLOYS

    Institute of Scientific and Technical Information of China (English)

    M.Sakaguchi; M.Okazaki

    2004-01-01

    An analytical method to investigate the morphological evolution of the cellular microstructure is explored and proposed. The method is essentially based on the Eshelby's micromechanics theory, and it is extended so as to be applied for a material system containing inclusions with high volume fraction, by employing the average stress field approximation by Mori and Tanaka. The proposed method enables us to discuss a stable shape of precipitate in the material system, which must be influenced by many factors: e.g., volume fraction of precipitate; Young's modulus ratio and lattice misfit between matrix and precipitate; external stress field in multiaxial state; and heterogeneity of plastic strain between matrix and precipitate. A series of numerical calculations were summarized on stable shape maps. The application of the method to predict the γ' rafting in superalloys during creep showed that the heterogeneity of plastic strain between matrix and precipitates may play a significant role in the shape stability of the precipitate. Furthermore, it was shown that the method was successfully applied to estimate the morphology of the cellular microstructure formed in CMSX-4single crystal Ni-based superalloy.

  10. Micromechanical Modeling of Anisotropic Damage-Induced Permeability Variation in Crystalline Rocks

    Science.gov (United States)

    Chen, Yifeng; Hu, Shaohua; Zhou, Chuangbing; Jing, Lanru

    2014-09-01

    This paper presents a study on the initiation and progress of anisotropic damage and its impact on the permeability variation of crystalline rocks of low porosity. This work was based on an existing micromechanical model considering the frictional sliding and dilatancy behaviors of microcracks and the recovery of degraded stiffness when the microcracks are closed. By virtue of an analytical ellipsoidal inclusion solution, lower bound estimates were formulated through a rigorous homogenization procedure for the damage-induced effective permeability of the microcracks-matrix system, and their predictive limitations were discussed with superconducting penny-shaped microcracks, in which the greatest lower bounds were obtained for each homogenization scheme. On this basis, an empirical upper bound estimation model was suggested to account for the influences of anisotropic damage growth, connectivity, frictional sliding, dilatancy, and normal stiffness recovery of closed microcracks, as well as tensile stress-induced microcrack opening on the permeability variation, with a small number of material parameters. The developed model was calibrated and validated by a series of existing laboratory triaxial compression tests with permeability measurements on crystalline rocks, and applied for characterizing the excavation-induced damage zone and permeability variation in the surrounding granitic rock of the TSX tunnel at the Atomic Energy of Canada Limited's (AECL) Underground Research Laboratory (URL) in Canada, with an acceptable agreement between the predicted and measured data.

  11. Silicone-based elastic composites able to generate energy on micromechanical impulse

    Science.gov (United States)

    Racles, Carmen; Ignat, Mircea; Bele, Adrian; Dascalu, Mihaela; Lipcinski, Daniel; Cazacu, Maria

    2016-08-01

    Elastic composites were prepared based on a polydimethylsiloxane-α,ω-diol (M w = 139 000 g mol‑1), different α,ω-bis(trimethylsiloxy)poly(methylcyanopropyl-methylhexyl-methylhydro)siloxanes as the polar group component and TEOS as a cross-linking agent and silica generator. The resulting materials consisted of polar–nonpolar interconnected networks as matrices which had 7.4 or 9.5 wt% in situ generated silica and contained up to 2.74 wt% CN groups. The films formed were tested for electromechanical response to a micromechanical impulse. It was found that their performance was proportional to their electromechanical sensitivity (β = ε‧/Y, where ε‧ is the dielectric permittivity and Y is Young’s modulus); thus it can be adjusted by their composition, via tailoring the dielectric and mechanical properties. The generated voltage peak-to-peak measured was between 3.75 and 12.3 V mm‑1. The best result for the tested materials (i.e. harvested energy of 460 nJ or energy density of 4.6 μJ cm‑3, as a response to a micro-impulse of 0.017 kg m s‑1) was obtained for a film having ε‧ = 3.6 and Y = 0.19 MPa.

  12. High-Q micromechanical resonators for mass sensing in dissipative media

    International Nuclear Information System (INIS)

    Single crystal silicon-based micromechanical resonators are developed for mass sensing in dissipative media. The design aspects and preliminary characterization of the resonators are presented. For the suggested designs, quality factors of about 20 000 are typically measured in air at atmospheric pressure and 1000–2000 in contact with liquid. The performance is based on a wine-glass-type lateral bulk acoustic mode excited in a rectangular resonator plate. The mode essentially eliminates the radiation of acoustic energy into the sample media leaving viscous drag as the dominant fluid-based dissipation mechanism in the system. For a mass loading distributed over the central areas of the resonator a sensitivity of 27 ppm ng−1 is measured exhibiting good agreement with the results of the finite element method-based simulations. It is also shown that the mass sensitivity can be somewhat enhanced, not only by the proper distribution of the loaded mass, but also by introducing shallow barrier structures on the resonator

  13. Prediction of permeability of monodisperse granular materials with a micromechanics approach

    Science.gov (United States)

    Yang, Rongwei; Lemarchand, Eric; Fen-Chong, Teddy; Li, Kefei

    2016-04-01

    Prediction of the permeability of porous media is of vital importance to such fields as petroleum engineering, agricultural engineering and civil engineering. The liquid water within unsaturated granular materials is distinguished as the intergranular layer, the wetting layer and the water film. By means of the micromechanics approach, a physical conceptual model is developed to predict the permeability (intrinsic and relative permeabilities) of the monodisperse granular materials. The proposed model has been validated by comparing the available experimental data and the empirical models, and has been used to re-interpret the Kozeny-Carman's relation in particular. The results obtained with this model show that the intergranular water will dominate the flow transport when the saturation degree is higher than the residual saturation degree; when the saturation degree is below the residual saturation degree, the wetting layer will govern the flow transport and the relative permeability will decrease by 3 to 8 orders of magnitude depending on the connectivity of the wetting layer.

  14. Micromechanical analysis on tensile modulus of structured magneto-rheological elastomer

    Science.gov (United States)

    Chen, S. W.; Li, R.; Zhang, Z.; Wang, X. J.

    2016-03-01

    This paper proposed a micromechanical model to investigate the tensile modulus of structured magnetorheological elastomers (MRE) to understand its anisotropic properties. A three parameter representative volume element (RVE) model was presented to describe the microscopic structure, where particles could be organized in layer-like or chain-like structure. And the tensile modulus is defined as a ratio of stress to strain in the stretched direction. We then applied effective medium theory to derive a theoretical model for the modulus of MRE in the absence of magnetic field, considering the influence of particles configuration and volume fraction. In addition, the effect of magnetic field on magneto-induced stress inside MRE is evaluated to further establish a multi-scale model which explains the magneto-rheological effect of structured MRE. The proposed model was then compared with finite element analysis and ‘free energy’ model. It demonstrated that the proposed model match better with the finite element solutions than that of ‘free energy’ method. The advantage of the proposed model is that it couples the magnetic field and displacement field, and considers the influence of both particles spatial energy and the relative position on magneto-rheological effect. The stiffer or softer of MREs induced by an applied magnetic field under tensile stress is predicted that is conformed to previous studies.

  15. Preparation of polystyrene brush film by radical chain-transfer polymerization and micromechanical properties

    Science.gov (United States)

    Zhao, Jing; Chen, Miao; An, Yanqing; Liu, Jianxi; Yan, Fengyuan

    2008-12-01

    A radical chain-transfer polymerization technique has been applied to graft-polymerize brushes of polystyrene (PSt) on single-crystal silicon substrates. 3-Mercapto-propyltrimethoxysilane (MPTMS), as a chain-transfer agent for grafting, was immobilized on the silicon surface by a self-assembling process. The structure and morphology of the graft-functionalized silicon surfaces were characterized by the means of contact-angle measurement, ellipsometric thickness measurement, Fourier transformation infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). The nanotribological and micromechanical properties of the as-prepared polymer brush films were investigated by frictional force microscopy (FFM), force-volume analysis and scratch test. The results indicate that the friction properties of the grafted polymer films can be improved significantly by the treatment of toluene, and the chemically bonded polystyrene film exhibits superior scratch resistance behavior compared with the spin-coated polystyrene film. The resultant polystyrene brush film is expected to develop as a potential lubrication coating for microelectromechanical systems (MEMS).

  16. Contributions to micromechanical model of the non linear behavior of the Callovo-Oxfordian argillite

    International Nuclear Information System (INIS)

    This work is performed in the general context of the project of underground disposal of radioactive waste, undertaken by the French National Radioactive Waste Management Agency (ANDRA). Due to its strong density and weak permeability, the formation of Callovo-Oxfordian argillite is chosen as one of possible geological barriers to radionuclides. The objective of the study to develop and validate a non linear homogenization approach of the mechanical behavior of Callovo-Oxfordian argillites. The material is modelled as a composite constituted of an elasto(visco)plastic clay matrix and of linear elastic or elastic damage inclusions. The macroscopic constitutive law is obtained by adapting the incremental method proposed by Hill. The derived model is first compared to Finite Element calculations on unit cell. It is then validated and applied for the prediction of the macroscopic stress-strain responses of the argillite at different geological depths. Finally, the micromechanical model is implemented in a commercial finite element code (Abaqus) for the simulation of a vertical shaft of the underground laboratory. This allows predicting the distribution of damage state and plastic strains and characterizing the excavation damage zone (EDZ). (author)

  17. Effect of gamma radiation on micromechanical hardness of lead-free solder joint

    Energy Technology Data Exchange (ETDEWEB)

    Paulus, Wilfred [Universiti Kebangsaan Malaysia, Bangi, 43600 Kajang, Selangor (Malaysia); Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor (Malaysia); Rahman, Irman Abdul; Jalar, Azman; Kamil, Insan; Bakar, Maria Abu [Universiti Kebangsaan Malaysia, Bangi, 43600 Kajang, Selangor (Malaysia); Yusoff, Wan Yusmawati Wan [Universiti Pertahanan Nasional Malaysia, Kem Sg. Besi, 57000 Kuala Lumpur (Malaysia)

    2015-09-25

    Lead-free solders are important material in nano and microelectronic surface mounting technology for various applications in bio medicine, environmental monitoring, spacecraft and satellite instrumentation. Nevertheless solder joint in radiation environment needs higher reliability and resistance to any damage caused by ionizing radiations. In this study a lead-free 99.0Sn0.3Ag0.7Cu wt.% (SAC) solder joint was developed and subjected to various doses of gamma radiation to investigate the effects of the ionizing radiation to micromechanical hardness of the solder. Averaged hardness of the SAC joint was obtained from nanoindentation test. The results show a relationship between hardness values of indentations and the increment of radiation dose. Highest mean hardness, 0.2290 ± 0.0270 GPa was calculated on solder joint which was exposed to 5 Gray dose of gamma radiation. This value indicates possible radiation hardening effect on irradiated solder. The hardness gradually decreased to 0.1933 ± 0.0210 GPa and 0.1631 ± 0.0173 GPa when exposed to doses 50 and 500 gray respectively. These values are also lower than the hardness of non irradiated sample which was calculated as 0.2084 ± 0.0.3633 GPa indicating possible radiation damage and needs further related atomic dislocation study.

  18. Microcomputer interfacing and applications

    CERN Document Server

    Mustafa, M A

    1990-01-01

    This is the applications guide to interfacing microcomputers. It offers practical non-mathematical solutions to interfacing problems in many applications including data acquisition and control. Emphasis is given to the definition of the objectives of the interface, then comparing possible solutions and producing the best interface for every situation. Dr Mustafa A Mustafa is a senior designer of control equipment and has written many technical articles and papers on the subject of computers and their application to control engineering.

  19. Water at Interfaces

    DEFF Research Database (Denmark)

    Björneholm, Olle; Hansen, Martin Hangaard; Hodgson, Andrew;

    2016-01-01

    The interfaces of neat water and aqueous solutions play a prominent role in many technological processes and in the environment. Examples of aqueous interfaces are ultrathin water films that cover most hydrophilic surfaces under ambient relative humidities, the liquid/solid interface which drives...

  20. Complex Interfaces Under Change

    DEFF Research Database (Denmark)

    Rosbjerg, Dan

    and mechanical processes that develop within this structure. Water-related processes at the interfaces between the compartments are complex, depending both on the interface itself, and on the characteristics of the interfaced compartments. Various aspects of global change directly or indirectly impact...

  1. EDITORIAL: Selected papers from the 20th Micromechanics Europe Workshop (MME 09) (Toulouse, France, 20-22 September 2009) Selected papers from the 20th Micromechanics Europe Workshop (MME 09) (Toulouse, France, 20-22 September 2009)

    Science.gov (United States)

    Pons, Patrick

    2010-06-01

    This special section of the Journal of Micromechanics and Microengineering is devoted to the 20th European Workshop on Micromechanics (MME 2009), which was held in Toulouse, France, 20-22 September 2009. The MME workshop series started in 1989 in Twente and was the first European event created in the field of micro machining technology for developing micro components, micro sensors, micro actuators, and micro systems. Over the last two decades the MEMS community has grown considerably, and the MME workshops have sustained this progress through annual meetings all around Europe: Twente (The Netherlands, 1989), Berlin (Germany, 1990), Leuven (Belgium, 1992), Neuchatel (Switzerland, 1993), Pisa (Italy, 1994), Copenhagen (Denmark, 1995), Barcelona (Spain, 1996), Southampton (United Kingdom, 1997), Ulvik (Norway, 1998), Gif-sur-Yvette (France, 1999), Uppsala (Sweden, 2000), Cork (Ireland, 2001), Sinaia (Romania, 2002), Delft (The Netherlands, 2003), Leuven (Belgium, 2004), Goteborg (Sweden, 2005), Southampton (United Kingdom, 2006), Guimaraes (Portugal, 2007) and Aachen (Germany, 2008). For twenty years, MME conferences have provided an excellent opportunity to bring together many, predominantly European, scientists and engineers to present and discuss the latest developments in this field. For the 20th anniversary of the MicroMechanics Europe Workshop, 115 papers from 23 countries were submitted. Selected contributions were presented during four poster sessions, including short oral presentations. A very interesting feature of the MME workshops is their ability to promote young researchers. Six invited speakers from research centres and industry also gave an overview on advanced technological, characterization and simulation tools. The two day workshop was attended by 185 delegates from 22 countries all over Europe, and from Japan, Taiwan, USA and Mexico. On behalf of the MME 2009 Program Committee, I would like to express my sincere gratitude to all authors of

  2. Quantization of interface currents

    Energy Technology Data Exchange (ETDEWEB)

    Kotani, Motoko [AIMR, Tohoku University, Sendai (Japan); Schulz-Baldes, Hermann [Department Mathematik, Universität Erlangen-Nürnberg, Erlangen (Germany); Villegas-Blas, Carlos [Instituto de Matematicas, Cuernavaca, UNAM, Cuernavaca (Mexico)

    2014-12-15

    At the interface of two two-dimensional quantum systems, there may exist interface currents similar to edge currents in quantum Hall systems. It is proved that these interface currents are macroscopically quantized by an integer that is given by the difference of the Chern numbers of the two systems. It is also argued that at the interface between two time-reversal invariant systems with half-integer spin, one of which is trivial and the other non-trivial, there are dissipationless spin-polarized interface currents.

  3. Water at Interfaces.

    Science.gov (United States)

    Björneholm, Olle; Hansen, Martin H; Hodgson, Andrew; Liu, Li-Min; Limmer, David T; Michaelides, Angelos; Pedevilla, Philipp; Rossmeisl, Jan; Shen, Huaze; Tocci, Gabriele; Tyrode, Eric; Walz, Marie-Madeleine; Werner, Josephina; Bluhm, Hendrik

    2016-07-13

    The interfaces of neat water and aqueous solutions play a prominent role in many technological processes and in the environment. Examples of aqueous interfaces are ultrathin water films that cover most hydrophilic surfaces under ambient relative humidities, the liquid/solid interface which drives many electrochemical reactions, and the liquid/vapor interface, which governs the uptake and release of trace gases by the oceans and cloud droplets. In this article we review some of the recent experimental and theoretical advances in our knowledge of the properties of aqueous interfaces and discuss open questions and gaps in our understanding. PMID:27232062

  4. Data-driven stochastic models for spatial uncertainties in micromechanical systems

    International Nuclear Information System (INIS)

    Accurate uncertainty quantification in engineering systems requires the use of proper data-driven stochastic models that bear a good fidelity with respect to experimentally observed variations. This paper looks at a variety of modeling techniques to represent spatially varying uncertainties in a form that can be incorporated into numerical simulations. In the context of microelectromechanical systems, we consider spatial uncertainties at the device level in the form of surface roughness and at the wafer level in the form of non-uniformities that arise as a result of various microfabrication steps. We discuss methods to obtain roughness characterization data ranging from the use of a simple profilometer probe to imaging-based techniques for the extraction of digitized data from images. We model spatial uncertainties as second-order stochastic process and use Bayesian inference to estimate the model parameters from the input data. We apply the data-driven stochastic models generated from this process to micromechanical actuators and sensors in which these spatial uncertainties are likely to cause significant variation. These include an electrostatically-actuated torsion-spring micromirror, an electromechanical comb-drive actuator and a pressure sensor with a piezoresistive strain gauge. We show that the performance of these devices is sensitive to the presence of spatial uncertainties and a proper modeling of these uncertainties helps us make reliable predictions about the variation in device performance. Where data is available, we even show that the predicted variation can be validated against experimental observations, highlighting the significance of proper stochastic modeling in the analysis of such devices. (paper)

  5. Micromechanical measurements of the effect of surfactants on cyclopentane hydrate shell properties.

    Science.gov (United States)

    Brown, Erika P; Koh, Carolyn A

    2016-01-01

    Investigating the effect of surfactants on clathrate hydrate growth and morphology, especially particle shell strength and cohesion force, is critical to advancing new strategies to mitigate hydrate plug formation. In this study, dodecylbenzenesulfonic acid and polysorbate 80 surfactants were included during the growth of cyclopentane hydrates at several concentrations above and below the critical micelle concentration. A novel micromechanical method was applied to determine the force required to puncture the hydrate shell using a glass cantilever (with and without surfactants), with annealing times ranging from immediately after the hydrate nucleated to 90 minutes after formation. It was shown that the puncture force was decreased by the addition of both surfactants up to a maximum of 79%. Over the entire range of annealing times (0-90 minutes), the thickness of the hydrate shell was also measured. However, there was no clear change in shell thickness with the addition of surfactants. The growth rate of the hydrate shell was found to vary less than 15% with the addition of surfactants. The cohesive force between two hydrate particles was measured for each surfactant and found to be reduced by 28% to 78%. Interfacial tension measurements were also performed. Based on these results, microscopic changes to the hydrate shell morphology (due to the presence of surfactants) were proposed to cause the decrease in the force required to break the hydrate shell, since no macroscopic morphology changes were observed. Understanding the hydrate shell strength can be critical to reducing the capillary bridge interaction between hydrate particles or controlling the release of unconverted water from the interior of the hydrate particle, which can cause rapid hydrate conversion.

  6. Passive micromechanical tags. An investigation into writing information at nanometer resolution on micrometer size objects

    International Nuclear Information System (INIS)

    The authors have completed a 3-year study of the technology related to the development of micron-sized passive micromechanical tags. The project was motivated by the discovery in 1990 by the present authors that low energy, high charge state ions (e.g., Xe+44) can produce nanometer-size damage sites on solid surfaces, and the realization that a pattern of these sites represents information. It was envisioned that extremely small, chemically inert, mechanical tags carrying a large label could be fabricated for a variety of applications, including tracking of controlled substances, document verification, process control, research, and engineering. Potential applications exist in the data storage, chemical, food, security, and other industries. The goals of this project were fully accomplished, and they are fully documented here. The work was both experimental and developmental. Most of the experimental effort was a search for appropriate tag materials. Several good materials were found, and the upper limits of information density were determined (ca. 1012 bit/cm2). Most of the developmental work involved inventing systems and strategies for using these tags, and compiling available technologies for implementing them. The technology provided herein is application-specific: first, the application must be specified, then the tag can be developed for it. The project was not intended to develop a single tag for a single application or for all possible applications. Rather, it was meant to provide the enabling technology for fabricating tags for a range of applications. The results of this project provide sufficient information to proceed directly with such development

  7. Passive micromechanical tags. An investigation into writing information at nanometer resolution on micrometer size objects

    Energy Technology Data Exchange (ETDEWEB)

    Schmieder, R.W.; Bastasz, R.J.

    1995-01-01

    The authors have completed a 3-year study of the technology related to the development of micron-sized passive micromechanical tags. The project was motivated by the discovery in 1990 by the present authors that low energy, high charge state ions (e.g., Xe{sup +44}) can produce nanometer-size damage sites on solid surfaces, and the realization that a pattern of these sites represents information. It was envisioned that extremely small, chemically inert, mechanical tags carrying a large label could be fabricated for a variety of applications, including tracking of controlled substances, document verification, process control, research, and engineering. Potential applications exist in the data storage, chemical, food, security, and other industries. The goals of this project were fully accomplished, and they are fully documented here. The work was both experimental and developmental. Most of the experimental effort was a search for appropriate tag materials. Several good materials were found, and the upper limits of information density were determined (ca. 10{sup 12} bit/cm{sup 2}). Most of the developmental work involved inventing systems and strategies for using these tags, and compiling available technologies for implementing them. The technology provided herein is application-specific: first, the application must be specified, then the tag can be developed for it. The project was not intended to develop a single tag for a single application or for all possible applications. Rather, it was meant to provide the enabling technology for fabricating tags for a range of applications. The results of this project provide sufficient information to proceed directly with such development.

  8. Experimental Characterization and Micromechanical Modeling of Woven Carbon/Copper Composites

    Science.gov (United States)

    Bednarcyk, Brett A.; Pauly, Christopher C.; Pindera, Marek-Jerzy

    1997-01-01

    The results of an extensive experimental characterization and a preliminary analytical modeling effort for the elastoplastic mechanical behavior of 8-harness satin weave carbon/copper (C/Cu) composites are presented. Previous experimental and modeling investigations of woven composites are discussed, as is the evolution of, and motivation for, the continuing research on C/Cu composites. Experimental results of monotonic and cyclic tension, compression, and Iosipescu shear tests, and combined tension-compression tests, are presented. With regard to the test results, emphasis is placed on the effect of strain gauge size and placement, the effect of alloying the copper matrix to improve fiber-matrix bonding, yield surface characterization, and failure mechanisms. The analytical methodology used in this investigation consists of an extension of the three-dimensional generalized method of cells (GMC-3D) micromechanics model, developed by Aboudi (1994), to include inhomogeneity and plasticity effects on the subcell level. The extension of the model allows prediction of the elastoplastic mechanical response of woven composites, as represented by a true repeating unit cell for the woven composite. The model is used to examine the effects of refining the representative geometry of the composite, altering the composite overall fiber volume fraction, changing the size and placement of the strain gauge with respect to the composite's reinforcement weave, and including porosity within the infiltrated fiber yarns on the in-plane elastoplastic tensile, compressive, and shear response of 8-harness satin C/Cu. The model predictions are also compared with the appropriate monotonic experimental results.

  9. Experimental approach and micro-mechanical modeling of the creep behavior of irradiated zirconium alloys

    International Nuclear Information System (INIS)

    The fuel rod cladding, strongly affected by microstructural changes due to irradiation such as high density of dislocation loops, is strained by the end-of-life fuel rod internal pressure and the potential release of fission gases and helium during dry storage. Within the temperature range that is expected during dry interim storage, cladding undergoes long term creep under over-pressure. So, in order to have a predictive approach of the behavior of zirconium alloys cladding in dry storage conditions it is essential to take into account: initial dislocation loops, thermal annealing of loops and creep straining due to over pressure. Specific experiments and modelling for irradiated samples have been developed to improve our knowledge in that field. A Zr-1%Nb-O alloy was studied using fine microstructural investigations and mechanical testing. The observations conducted by transmission electron microscopy show that the high density of loops disappears during a heat treatment. The loop size becomes higher and higher while their density falls. The microhardness tests reveal that the fall of loop density leads to the softening of the irradiated material. During a creep test, both temperature and applied stress are responsible of the disappearance of loops. The loops could be swept by the activation of the basal slip system while the prism slip system is inhibited. Once deprived of loops, the creep properties of the irradiated materials are closed to the non irradiated state, a result whose consequence is a sudden acceleration of the creep rate. Finally, a micro-mechanical modeling based on microscopic deformation mechanisms taking into account experimental dislocation loop analyses and creep test, was used for a predictive approach by constructing a deformation mechanism map of the creep behavior of the irradiated material. (author)

  10. Consequences of Location-Dependent Organ of Corti Micro-Mechanics.

    Directory of Open Access Journals (Sweden)

    Yanju Liu

    Full Text Available The cochlea performs frequency analysis and amplification of sounds. The graded stiffness of the basilar membrane along the cochlear length underlies the frequency-location relationship of the mammalian cochlea. The somatic motility of outer hair cell is central for cochlear amplification. Despite two to three orders of magnitude change in the basilar membrane stiffness, the force capacity of the outer hair cell's somatic motility, is nearly invariant over the cochlear length. It is puzzling how actuators with a constant force capacity can operate under such a wide stiffness range. We hypothesize that the organ of Corti sets the mechanical conditions so that the outer hair cell's somatic motility effectively interacts with the media of traveling waves-the basilar membrane and the tectorial membrane. To test this hypothesis, a computational model of the gerbil cochlea was developed that incorporates organ of Corti structural mechanics, cochlear fluid dynamics, and hair cell electro-physiology. The model simulations showed that the micro-mechanical responses of the organ of Corti are different along the cochlear length. For example, the top surface of the organ of Corti vibrated more than the bottom surface at the basal (high frequency location, but the amplitude ratio was reversed at the apical (low frequency location. Unlike the basilar membrane stiffness varying by a factor of 1700 along the cochlear length, the stiffness of the organ of Corti complex felt by the outer hair cell remained between 1.5 and 0.4 times the outer hair cell stiffness. The Y-shaped structure in the organ of Corti formed by outer hair cell, Deiters cell and its phalange was the primary determinant of the elastic reactance imposed on the outer hair cells. The stiffness and geometry of the Deiters cell and its phalange affected cochlear amplification differently depending on the location.

  11. Creep of a C-S-H gel: a micromechanical approach

    Directory of Open Access Journals (Sweden)

    Julien Sanahuja

    2010-03-01

    Full Text Available Both clays and calcium silicate hydrates(the main hydration products of Portland cements exhibit a microstructure made up of lamellar particles. The microscopic mechanism responsible for the macroscopic creep of such materials is often described as the relative sliding of the sheets. This paper proposes a micromechanical approach to estimate the macroscopic creep behavior rising from this microscopic mechanism. The asymptotic evolution of creep at both short- and long-term is especially investigated. More precisely, a non-vanishing initial elastic strain is retrieved. At long-term, a threshold on porosity appears. At lower porosities, the creep evolution admits an asymptotic strain. At higher porosities, it admits an asymptotic strain rate.Argilas e hidratos de cálcio (principal produto de cimentos ambos exibem microestrutura composta por partículas em forma de lamelas. O principal mecanismo responsável pelo fenômeno de fluência macroscópico é frequentemente descrito pelo deslizamento entre as lamelas. O artigo propõe uma abordagem micromecânica para estimar a fluência macroscópica que surge a partir do mecanismo microscópico. A evolução assintótica da fluência para tempos curtos e longos é especialmente investigada. Mais precisamente uma tensão inicial não nula é derivada. Para tempos longos um limiar de porosidade surge da modelagem. Na faixa de porosidades mais baixas a evolução da fluência admite deformação assintótica. Para porosidades altas o problema admite taxa de deformação assintótica.

  12. Micromechanical measurements of the effect of surfactants on cyclopentane hydrate shell properties.

    Science.gov (United States)

    Brown, Erika P; Koh, Carolyn A

    2016-01-01

    Investigating the effect of surfactants on clathrate hydrate growth and morphology, especially particle shell strength and cohesion force, is critical to advancing new strategies to mitigate hydrate plug formation. In this study, dodecylbenzenesulfonic acid and polysorbate 80 surfactants were included during the growth of cyclopentane hydrates at several concentrations above and below the critical micelle concentration. A novel micromechanical method was applied to determine the force required to puncture the hydrate shell using a glass cantilever (with and without surfactants), with annealing times ranging from immediately after the hydrate nucleated to 90 minutes after formation. It was shown that the puncture force was decreased by the addition of both surfactants up to a maximum of 79%. Over the entire range of annealing times (0-90 minutes), the thickness of the hydrate shell was also measured. However, there was no clear change in shell thickness with the addition of surfactants. The growth rate of the hydrate shell was found to vary less than 15% with the addition of surfactants. The cohesive force between two hydrate particles was measured for each surfactant and found to be reduced by 28% to 78%. Interfacial tension measurements were also performed. Based on these results, microscopic changes to the hydrate shell morphology (due to the presence of surfactants) were proposed to cause the decrease in the force required to break the hydrate shell, since no macroscopic morphology changes were observed. Understanding the hydrate shell strength can be critical to reducing the capillary bridge interaction between hydrate particles or controlling the release of unconverted water from the interior of the hydrate particle, which can cause rapid hydrate conversion. PMID:26618773

  13. Computational analysis of linear friction welding process and micromechanical modeling of deformation behavior for medium carbon steel

    Institute of Scientific and Technical Information of China (English)

    杨夏炜; 李文亚; 马铁军

    2015-01-01

    Finite element simulation of linear friction welding (LFW) medium carbon steel was carried out using the ABAQUS software. A two-dimensional (2D) coupled thermo-mechanical model was established. First, the temperature fields of medium carbon steel during LFW process were investigated. And then, the Mises stress and the 1st, 2nd and 3rd principal stresses fields’ evolution of the steel during LFW process were studied. The deformation behavior of LFW carbon steel was analyzed by using micromechanics model based on ABAQUS with Python code. The Lode parameter was expressed using the Mohr stress circle and it was investigated in detail.

  14. Micromechanism of Decrease of Impact Toughness in Coarse-Grain Heat-Affected Zone of HSLA Steel with Increasing Welding Heat Input

    Science.gov (United States)

    Cao, R.; Li, J.; Liu, D. S.; Ma, J. Y.; Chen, J. H.

    2015-07-01

    This paper analyzes the micromechanism of decrease of impact toughness with increasing the welding heat input in coarse-grain heat-affected zone (CGHAZ) of a low-alloy high-strength ship-building steel plate. By comparing the microstructures, measuring the extending length of the fibrous crack, identifying the critical event of cleavage fracture, measuring the critical length, and calculating the local cleavage fracture stress σ f, and then using the basic principles of the micromechanism of cleavage fracture, this work reveals the essential causes of deteriorated toughness in the CGHAZ of high-strength steel welded joints.

  15. Universal computer interfaces

    CERN Document Server

    Dheere, RFBM

    1988-01-01

    Presents a survey of the latest developments in the field of the universal computer interface, resulting from a study of the world patent literature. Illustrating the state of the art today, the book ranges from basic interface structure, through parameters and common characteristics, to the most important industrial bus realizations. Recent technical enhancements are also included, with special emphasis devoted to the universal interface adapter circuit. Comprehensively indexed.

  16. Dynamically forced cantilever system: A piezo-polymer characterization tool with possible application for micromechanical HF resonator devices

    Science.gov (United States)

    Schwödiauer, Reinhard

    2005-04-01

    A cantilever system, driven to a dynamically forced oscillation by a small piezoelectric specimen is presented as a simple and accurate tool to determine the converse dynamic piezocoefficient up to several kHz. The piezoelectric sample is mounted on top of a reflective cantilever where it is free to oscillate without any mechanical constraint. A Nomarsky-interferometer detects the induced cantilever displacement. The presented technique is especially suited for a precise characterization of small and soft piezoelectric polymer-samples with rough surfaces. The capability of the dynamically forced cantilever principle is demonstrated with a LiNbO3 crystal and with a porous ferroelectretic polypropylene foam. Results from measurements between 400 Hz and 5 kHz were found to be in excellent agreement with published values. Additionally, the dynamically forced cantilever principle may possibly improve the sensitivity of some micromechanical cantilever-sensors and it could also be interesting for the design of enhanced micromechanical high frequency mixer filters. Some ideas about are briefly presented.

  17. Static compressive strength prediction of open-hole structure based on non-linear shear behavior and micro-mechanics

    Science.gov (United States)

    Li, Wangnan; Cai, Hongneng; Li, Chao

    2014-11-01

    This paper deals with the characterization of the strength of the constituents of carbon fiber reinforced plastic laminate (CFRP), and a prediction of the static compressive strength of open-hole structure of polymer composites. The approach combined with non-linear analysis in macro-level and a linear elastic micromechanical failure analysis in microlevel (non-linear MMF) is proposed to improve the prediction accuracy. A face-centered cubic micromechanics model is constructed to analyze the stresses in fiber and matrix in microlevel. Non-interactive failure criteria are proposed to characterize the strength of fiber and matrix. The non-linear shear behavior of the laminate is studied experimentally, and a novel approach of cubic spline interpolation is used to capture significant non-linear shear behavior of laminate. The user-defined material subroutine UMAT for the non-linear share behavior is developed and combined in the mechanics analysis in the macro-level using the Abaqus Python codes. The failure mechanism and static strength of open-hole compressive (OHC) structure of polymer composites is studied based on non-linear MMF. The UTS50/E51 CFRP is used to demonstrate the application of theory of non-linear MMF.

  18. An anisotropic micromechanical-based model for characterizing the magneto-mechanical behavior of NiMnGa alloys

    Science.gov (United States)

    Wang, Xingzhe; Li, Fang; Hu, Qiang

    2012-06-01

    As a typical ferromagnetic shape memory alloy (FSMA), NiMnGa alloy at room temperature is a heterogeneous material with martensitic variants and a high magnetic anisotropy property to produce a giant magnetic-induced strain and high frequency response. A theoretical model based on micromechanical and thermodynamic theory is proposed to describe the magneto-mechanical behavior of single-crystal FSMAs during the reorientation process of martensitic variants. It follows the well-established Eshelby equivalent inclusion method and the Mori-Tanaka scheme, and incorporates the influence of the material anisotropy and the variant inclusion morphology on the reorientation of the martensite variants. The modified micromechanical model is further applied to characterize the stress-strain behavior and magnetic-field-induced strain during the martensite variant rearrangement process in a single-crystal NiMnGa rod under applied magnetic field and/or mechanical loading. The simulation results show good agreement with the experimental data. The effects of the material anisotropy and inclusion morphology on the magnetoelastic constitutive behavior of FSMAs are discussed.

  19. The influence of sterilization processes on the micromechanical properties of carbon fiber-reinforced PEEK composites for bone implant applications.

    Science.gov (United States)

    Godara, A; Raabe, D; Green, S

    2007-03-01

    The effect of sterilization on the structural integrity of the thermoplastic matrix composite polyetheretherketone (PEEK) reinforced with carbon fibers (CF) is investigated by nanoindentation and nanoscratch tests. The use of the material as a medical implant grade requires a detailed understanding of the micromechanical properties which primarily define its in vivo behavior. Sterilization is a mandatory process for such materials used in medical applications like bone implants. The steam and gamma radiation sterilization processes employed in this study are at sufficient levels to affect the micromechanical properties of some polymer materials, particularly in the interphase region between the polymer matrix and the reinforcing fibers. Nanoindentation and nanoscratch tests are used in this work to reveal local gradients in the hardness and the elastic properties of the interphase regions. Both methods help to explore microscopic changes in the hardness, reduced stiffness and scratch resistance in the interphase region and in the bulk polymer matrix due to the different sterilization processes employed. The results reveal that neither steam nor gamma radiation sterilization entails significant changes of the reduced elastic modulus, hardness or coefficient of friction in the bulk polymer matrix. However, minor material changes of the PEEK matrix were observed in the interphase region. Of the two sterilization methods used, the steam treatment has a more significant influence on these small changes in this region and appears to increase slightly the thickness of the interphase zone.

  20. Effects of fabrication on the mechanics, microstructure and micromechanical environment of small intestinal submucosa scaffolds for vascular tissue engineering.

    Science.gov (United States)

    Sánchez-Palencia, Diana M; D'Amore, Antonio; González-Mancera, Andrés; Wagner, William R; Briceño, Juan C

    2014-08-22

    In small intestinal submucosa scaffolds for functional tissue engineering, the impact of scaffold fabrication parameters on success rate may be related to the mechanotransductory properties of the final microstructural organization of collagen fibers. We hypothesized that two fabrication parameters, 1) preservation (P) or removal (R) of a dense collagen layer present in SIS and 2) SIS in a final dehydrated (D) or hydrated (H) state, have an effect on scaffold void area, microstructural anisotropy (fiber alignment) and mechanical anisotropy (global mechanical compliance). We further integrated our experimental measurements in a constitutive model to explore final effects on the micromechanical environment inside the scaffold volume. Our results indicated that PH scaffolds might exhibit recurrent and large force fluctuations between layers (up to 195 pN), while fluctuations in RH scaffolds might be larger (up to 256 pN) but not as recurrent. In contrast, both PD and RD groups were estimated to produce scarcer and smaller fluctuations (not larger than 50 pN). We concluded that the hydration parameter strongly affects the micromechanics of SIS and that an adequate choice of fabrication parameters, assisted by the herein developed method, might leverage the use of SIS for functional tissue engineering applications, where forces at the cellular level are of concern in the guidance of new tissue formation.

  1. Micromechanics of failure in brittle geomaterials. Final technical report (for 7/1/1994 - 8/31/2000)

    International Nuclear Information System (INIS)

    The overall objective was to provide a fundamental understanding of brittle failure processes in porous and compact geomaterials. This information is central to energy-related programs such as oil and gas exploration/production, reservoir engineering, drilling technology, geothermal energy recovery, nuclear waste isolation, and environmental remediation. The effects of key parameters such as grain boundary structure and cementation, damage state, and load path on the deformation and failure model of brittle geomaterials are still largely unknown. The research methodology emphasized the integration of experimental rock mechanical testing, quantitative microscopy, and detailed analysis using fracture mechanics, continuum plasticity theory, and numerical methods. Significant progress was made in elucidating the micromechanics of brittle failure in compact crystalline rocks, as well as high-porosity siliciclastic and carbonate rocks. Substantial effort was expended toward applying a new quantitative three-dimensional imaging technique to geomaterials and for developing enhanced image analysis capabilities. The research is presented under the following topics: technique for imaging the 3-D pore structure of geomaterials; mechanics of compressive failure in sandstone; effect of water on compressive failure of sandstone; micromechanics of compressive failure: observation and model; and the brittle-ductile transition in porous carbonate rocks

  2. Characterization and Evaluation of Micro-mechanical Properties of Ultra High Strength Concrete by using Micro-indentation Test

    Science.gov (United States)

    Murthy, A. Ramachandra; Iyer, Nagesh R.; Raghu Prasad, B. K.

    2016-09-01

    This work presents the details of characterization and micro-mechanical properties of ultra high strength concrete. Characterization was carried out for High Strength Concrete (HSC, HSC1) and Ultra High Strength Concrete (UHSC). Various mechanical properties, namely, compressive strength, split tensile strength and modulus of elasticity have been estimated for HSC, HSC1 and UHSC. It was observed from characterization studies that the split tensile strength is high in the case of UHSC compared to HSC and HSC1. X-ray diffraction analysis has been performed for cement, silica fume and quartz powder to know the chemical composition. The amount of quantified phases has been estimated. Micro indentation technique has been employed to evaluate the micromechanical properties such as modulus of elasticity and hardness. Oliver and Pharr method has been used to compute modulus of elasticity and hardness. It is observed that the value of modulus of elasticity obtained from the micro indentation test is in very good agreement with that of the value obtained from uniaxial compression test data of a cylindrical specimen. Finally micro-structure of the specimen has been obtained for various magnifications to examine the voids/pores in the UHSC matrix.

  3. Shape-changing interfaces:

    DEFF Research Database (Denmark)

    Rasmussen, Majken Kirkegård; Pedersen, Esben Warming; Petersen, Marianne Graves;

    2015-01-01

    these shortcomings. We identify eight types of shape that are transformed in various ways to serve both functional and hedonic design purposes. Interaction with shape-changing interfaces is simple and rarely merges input and output. Three questions are discussed based on the review: (a) which design purposes may......Shape change is increasingly used in physical user interfaces, both as input and output. Yet, the progress made and the key research questions for shape-changing interfaces are rarely analyzed systematically. We review a sample of existing work on shape-changing interfaces to address...

  4. Electromagnetic Interface Testing Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Electromagnetic Interface Testing facilitysupports such testing asEmissions, Field Strength, Mode Stirring, EMP Pulser, 4 Probe Monitoring/Leveling System, and...

  5. Optical Measurement of Micromechanics and Structure in a 3D Fibrin Extracellular Matrix

    Science.gov (United States)

    Kotlarchyk, Maxwell Aaron

    2011-07-01

    In recent years, a significant number of studies have focused on linking substrate mechanics to cell function using standard methodologies to characterize the bulk properties of the hydrogel substrates. However, current understanding of the correlations between the microstructural mechanical properties of hydrogels and cell function in 3D is poor, in part because of a lack of appropriate techniques. Methods for tuning extracellular matrix (ECM) mechanics in 3D cell culture that rely on increasing the concentration of either protein or cross-linking molecules fail to control important parameters such as pore size, ligand density, and molecular diffusivity. Alternatively, ECM stiffness can be modulated independently from protein concentration by mechanically loading the ECM. We have developed an optical tweezers-based microrheology system to investigate the fundamental role of ECM mechanical properties in determining cellular behavior. Further, this thesis outlines the development of a novel device for generating stiffness gradients in naturally derived ECMs, where stiffness is tuned by inducing strain, while local structure and mechanical properties are directly determined by laser tweezers-based passive and active microrheology respectively. Hydrogel substrates polymerized within 35 mm diameter Petri dishes are strained non-uniformly by the precise rotation of an embedded cylindrical post, and exhibit a position-dependent stiffness with little to no modulation of local mesh geometry. Here we present microrheological studies in the context of fibrin hydrogels. Microrheology and confocal imaging were used to directly measure local changes in micromechanics and structure respectively in unstrained hydrogels of increasing fibrinogen concentration, as well as in our strain gradient device, in which the concentration of fibrinogen is held constant. Orbital particle tracking, and raster image correlation analysis are used to quantify changes in fibrin mechanics on the

  6. The User Interface.

    Science.gov (United States)

    Lindeman, Martha J.; And Others

    1989-01-01

    The first of three articles on the design of user interfaces for information retrieval systems discusses the need to examine types of display, prompting, and input as separate entities. The second examines the use of artificial intelligence in creating natural language interfaces, and the third outlines standards for case studies in human computer…

  7. Interface colloidal robotic manipulator

    Energy Technology Data Exchange (ETDEWEB)

    Aronson, Igor; Snezhko, Oleksiy

    2015-08-04

    A magnetic colloidal system confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters. The colloidal system exhibits locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, structures can capture, transport, and position target particles.

  8. Icinga Monitoring System Interface

    CERN Document Server

    Neculae, Alina Georgiana

    2014-01-01

    The aim of this project is to develop a web interface that would be used by the Icinga monitoring system to manage the CMS online cluster, in the experimental site. The interface would allow users to visualize the information in a compressed and intuitive way, as well as modify the information of each individual object and edit the relationships between classes.

  9. Interface or Interlace?

    DEFF Research Database (Denmark)

    Hansen, Lone Koefoed; Wamberg, Jacob

    2005-01-01

    Departing from an analysis of the computer's indeterminate location between medium and machine, this paper problematises the idea of a clear-cut interface in complex computing, especially Augmented Reality. The idea and pratice of the interface is derived from the medium as a representational...... art works, especially Phunsombatlert's Path of Illusion, Dobson's Blendie, the Canadian collective Whisper and Rinaldo's Augmented Fish Reality....

  10. User Interface History

    DEFF Research Database (Denmark)

    Jørgensen, Anker Helms; Myers, Brad A

    2008-01-01

    User Interfaces have been around as long as computers have existed, even well before the field of Human-Computer Interaction was established. Over the years, some papers on the history of Human-Computer Interaction and User Interfaces have appeared, primarily focusing on the graphical interface era...... and early visionaries such as Bush, Engelbart and Kay. With the User Interface being a decisive factor in the proliferation of computers in society and since it has become a cultural phenomenon, it is time to paint a more comprehensive picture of its history. This SIG will investigate the possibilities...... of  launching a concerted effort towards creating a History of User Interfaces. ...

  11. Entanglement and topological interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Brehm, E.; Brunner, I.; Jaud, D.; Schmidt-Colinet, C. [Arnold Sommerfeld Center, Ludwig-Maximilians-Universitaet, Theresienstrasse 37, 80333, Muenchen (Germany)

    2016-06-15

    In this paper we consider entanglement entropies in two-dimensional conformal field theories in the presence of topological interfaces. Tracing over one side of the interface, the leading term of the entropy remains unchanged. The interface however adds a subleading contribution, which can be interpreted as a relative (Kullback-Leibler) entropy with respect to the situation with no defect inserted. Reinterpreting boundaries as topological interfaces of a chiral half of the full theory, we rederive the left/right entanglement entropy in analogy with the interface case. We discuss WZW models and toroidal bosonic theories as examples. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Microscale resolution fracture toughness profiling at the zirconia-porcelain interface in dental prostheses

    Science.gov (United States)

    Lunt, Alexander J. G.; Mohanty, Gaurav; Neo, Tee K.; Michler, Johann; Korsunsky, Alexander M.

    2015-12-01

    The high failure rate of the Yttria Partially Stabilized Zirconia (YPSZ)-porcelain interface in dental prostheses is influenced by the micro-scale mechanical property variation in this region. To improve the understanding of this behavior, micro-scale fracture toughness profiling by nanoindentation micropillar splitting is reported for the first time. Sixty 5 μm diameter micropillars were machined within the first 100 μm of the interface. Berkovich nanoindentation provided estimates of the bulk fracture toughness of YPSZ and porcelain that matched the literature values closely. However, the large included tip angle prevented precise alignment of indenter with the pillar center. Cube corner indentation was performed on the remainder of the pillars and calibration between nanoindentation using different tip shapes was used to determine the associated conversion factors. YPSZ micropillars failed by gradual crack propagation and bulk values persisted to within 15 μm from the interface, beyond which scatter increased and a 10% increase in fracture toughness was observed that may be associated with grain size variation at this location. Micropillars straddling the interface displayed preferential fracture within porcelain parallel to the interface at a location where nano-voiding has previously been observed and reported. Pure porcelain micropillars exhibited highly brittle failure and a large reduction of fracture toughness (by up to ~90%) within the first 50 μm of the interface. These new insights constitute a major advance in understanding the structure-property relationship of this important bi-material interface at the micro-scale, and will improve micromechanical modelling needed to optimize current manufacturing routes and reduce failure.

  13. Micromechanical Analyses of Debonding and Matrix Cracking in Dual-Phase Materials

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang; Yang, Qingda

    2016-01-01

    Failure in elastic dual-phase materials under transverse tension is studied numerically. Cohesive zones represent failure along the interface and the augmented finite element method (A-FEM) is used for matrix cracking. Matrix cracks are formed at an angle of 55 deg - 60 deg relative to the loading...

  14. The Java Legacy Interface

    DEFF Research Database (Denmark)

    Korsholm, Stephan

    2007-01-01

    The Java Legacy Interface is designed to use Java for encapsulating native legacy code on small embedded platforms. We discuss why existing technologies for encapsulating legacy code (JNI) is not sufficient for an important range of small embedded platforms, and we show how the Java Legacy...... Interface offers this previously missing functionality. We describe an implementation of the Java Legacy Interface for a particular virtual machine, and how we have used this virtual machine to integrate Java with an existing, commercial, soft real-time, C/C++ legacy platform....

  15. The interface effect

    CERN Document Server

    Galloway, Alexander R

    2013-01-01

    Interfaces are back, or perhaps they never left. The familiar Socratic conceit from the Phaedrus, of communication as the process of writing directly on the soul of the other, has returned to center stage in today's discussions of culture and media. Indeed Western thought has long construed media as a grand choice between two kinds of interfaces. Following the optimistic path, media seamlessly interface self and other in a transparent and immediate connection. But, following the pessimistic path, media are the obstacles to direct communion, disintegrating self and other into misunderstanding

  16. The computer graphics interface

    CERN Document Server

    Steinbrugge Chauveau, Karla; Niles Reed, Theodore; Shepherd, B

    2014-01-01

    The Computer Graphics Interface provides a concise discussion of computer graphics interface (CGI) standards. The title is comprised of seven chapters that cover the concepts of the CGI standard. Figures and examples are also included. The first chapter provides a general overview of CGI; this chapter covers graphics standards, functional specifications, and syntactic interfaces. Next, the book discusses the basic concepts of CGI, such as inquiry, profiles, and registration. The third chapter covers the CGI concepts and functions, while the fourth chapter deals with the concept of graphic obje

  17. Probing the micro-mechanical behavior of bone via high-energy x-rays.

    Energy Technology Data Exchange (ETDEWEB)

    Almer, J.; Stock, S. R.; X-Ray Science Division; Northwestern Univ.

    2006-01-01

    Bone is a highly-adaptive, particulate-reinforced composite which, through a complex hierarchical structure, achieves excellent mechanical performance. The composite preserves, to a large degree, the desirable properties of the individual components: high toughness of the bone matrix, collagen fibrils stabilized by water, and high stiffness of the reinforcing phase, nano-sized crystallites of carbonated apatite. Understanding bone fragility (osteoporosis) requires quantifying mechanical input to bone and identifying 'weak-link' microstructures. This mechanical input has been quantified in vivo with strain gages attached to cortical bone, but attached strain gages do not probe subsurface mechanical response. We addressed this shortcoming recently by appling wide- and small-angle x-ray scattering to canine fibula sections, to study the micro-mechanical response of bone on different length scales. These data provide a unique view of load partition between the constituent phases of bone, and here we extend these measurements to an entire rat tibia, where strain gradients due to bending are anticipated. Tibiae of 14 week old Sprague-Dawley rats were studied. A 3D microCT rendering of the sample and definitions of the loading (y) and transverse (x) directions appear in Fig.1, with the y-axis approximately parallel to the bone's longitudinal axis. Due to the curved shape of the tibia, significant sample bending in the x-direction was anticipated even under uniaxial compression, similar to that expected in vivo (there was little curvature in the y-z plane). The sample cross-section at y=0 was determined by microCT to be approximately 4 mm{sup 2}. The sample was potted in epoxy and compressed in a load frame designed for in situ x-ray scattering studies. Loading was in displacement control, at a rate of 0.06 {micro}m/sec. The aggregate macroscopic response was followed using a load cell combined with strain gages located on both the 'convex' (-x

  18. Welcome to the 2014 volume of Journal of Micromechanics and Microengineering

    Science.gov (United States)

    Fang, Weileun

    2014-01-01

    It is my great honor to serve as the Editor-in-Chief of Journal of Micromechanics and Microengineering (JMM) starting from 2014, the 24th year of the journal. I would also like to take this opportunity to convey my sincere appreciation to (i) the past editors for their vision to bring this journal to be such a significant publication and research platform in MEMS and microsystems technology; (ii) the reviewers for their precious time and valuable comments that enhance the publication quality of this journal; and (iii) the authors for their choice to publish their best work in this journal and their contribution to our community; (iv) the readers who extend the journal's impact not only to their research fields but to industry and all human society; and finally (v) the publication team at IOP Publishing. As the sixth Editor-in-Chief, I will aim to continue my predecessors' leadership and guidance, and further extend the distinguished reputation of JMM. In the past year, the number of submissions to this journal neared 900, an increase on last year, with the acceptance number of 401 (an acceptance rate lower than 50%). I would also like to point out the articles published in 2013 has jumped up to 383, showing a healthy growth compared to 365 in year 2012. To achieve this progress, the average times of the receipt-first decision and the receipt-accept confirmations are 39 days and 104 days, respectively. Furthermore, the average time of the accept-web publication is within 26 days, which is a considerable improvement in this journal. All abovementioned numbers together become a very attractive feature of this journal. To deal with the rapid expansion of the incoming papers and associated reviewing process we have tremendous help from the members of the journal's Editorial Board and referees worldwide, whom I would like to acknowledge since their well-constructed evaluation is of great importance to continuously enhancing the quality of the journal. Of course it would

  19. Quantifying the Micromechanical Effects of Variable Cement in Granular Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Goodwin, Laurel B.; Boutt David F.

    2010-02-18

    The mechanical and hydrologic behavior of clastic rocks and sediments is fundamentally controlled by variables such as grain size and shape, sorting, grain and cement mineralogy, porosity, and %cement - parameters that are not used directly in field-scale models of coupled flow and deformation. To improve our understanding of the relationship between these micromechanical properties and bulk behavior we focused on (1) relating detailed, quantitative characterization of the grain-pore systems to both hydrologic and mechanical properties of a suite of variably quartz-cemented quartz arenite samples and (2) the use of a combination of discrete element method (DEM) and poroelastic models parameterized by data from the natural samples to isolate and compare the influence of changes in the mechanical and hydrologic properties of granular porous media due to changes in degree of cementation. Quartz overgrowths, the most common form of authigenic cements in sandstones, are responsible for significant porosity and permeability reduction. The distribution of quartz overgrowths is controlled by available pore space and the crystallographic orientations of individual quartz grains. Study of the St. Peter Sandstone allowed evaluation of the relative effects of quartz cementation and compaction on final grain and pore morphology, showing that progressive quartz cementation modifies the grain framework in consistent, predictable ways. Detailed microstructural characterization and multiple regression analyses show that with progressive diagenesis, the number and length of grain contacts increases as the number of pores increases, the number of large, well-connected pores decreases, and pores become rounder. These changes cause a decrease in pore size variability that leads to a decrease in bulk permeability and both stiffening and strengthening of the grain framework. The consistent nature of these changes allows us to predict variations in hydrologic and mechanical properties

  20. Controlled carbon nanotube synthesis for quantification of polymer-nanotube composite micromechanics

    Science.gov (United States)

    Bult, Justin Bernard

    Conventional experimental approaches to the understanding of nanotube-polymer micro-mechanics have struggled to produce reproducible data due to the inherent difficulty in physically manipulating the nanotube in-situ. To avoid the problems scale represents in nanotube-polymer composites a novel approach of using Polarized Raman spectroscopy was developed. The Raman spectroscopic technique has the advantage of using non-invasive analysis to compute the composite micro mechanical properties of interfacial shear stress and critical length. Composites with nanotubes of defined length were needed in order to use the Raman technique. To satisfy this requirement a new thermal Chemical Vapor Deposition (CVD) tool capable of reproducibly growing aligned length uniformity with large mass yield was designed and built. The course of developing these furnace capabilities led to the investigation of nanotube growth mechanics. It is shown herein that a stable passivation barrier is required for nanotube growth. Using X-Ray Photoelectron Spectroscopy (XPS) depth profiling of metal substrate growth conclusively shows the presence of a stable catalyst layer on the outer surface of stable oxides of greater than 100 nm. By analyzing the diffusion profile represented in the XPS data it is shown that a critical thickness for the passivation oxide can be calculated as a function of time and temperature. For the growth parameters used in this study the critical thickness was found to be between 10 nm and 30 nm depending on the diffusivity value used for iron in chromia. This value agrees well with experimental observation. Uniformly grown carbon nanotubes with lengths of 4, 14, 17, 22, 43, 74, and 116 mum were incorporated into a polycarbonate matrix polymer via solvent-antisolvent processing. The nanotube composites of varied length were tested in tensile strain while Raman spectra were taken concurrently to deduce the load transfer to the nanotube due to composite strain. It is found

  1. Association of macroscopic laboratory testing and micromechanics modelling for the evaluation of the poroelastic parameters of a hardened cement paste

    CERN Document Server

    Ghabezloo, Siavash

    2010-01-01

    The results of a macro-scale experimental study performed on a hardened class G cement paste [Ghabezloo et al. (2008) Cem. Con. Res. (38) 1424-1437] are used in association with the micromechanics modelling and homogenization technique for evaluation of the complete set of poroelastic parameters of the material. The experimental study consisted in drained, undrained and unjacketed isotropic compression tests. Analysis of the experimental results revealed that the active porosity of the studied cement paste is smaller than its total porosity. A multi-scale homogenization model, calibrated on the experimental results, is used to extrapolate the poroelastic parameters to cement pastes prepared with different water-to-cement ratio. The notion of cement paste active porosity is discussed and the poroelastic parameters of hardened cement paste for an ideal, perfectly drained condition are evaluated using the homogenization model.

  2. Analysis micro-mechanism of burrs formation in the case of nanometric cutting process using numerical simulation method

    Institute of Scientific and Technical Information of China (English)

    HAN XueSong; HU YuanZhong

    2007-01-01

    Burrs (exit failure), being one of the important factors influencing the final precision of workpiece, have been widely studied. Today, with the development of manufacturing technology, the depth of cut falls into the range of nanometer or subnanometer, there may be some different disciplines dominating the burrs generation process. Molecular dynamics (MD) method, which is different from continuous mechanics, plays an important role in describing microscopic world. Take the example of single crystal copper, this paper carries out MD analysis micro-mechanism of burrs generation process. The results show that the burrs geometry depends on the type of workpiece (ductile or brittle). The depth of cut is decreased in the case of positive burrs generation process while the depth of cut is increased in case of negative burrs generation process.

  3. Design and Analysis of a Micromechanical Three-Component Force Sensor for Characterizing and Quantifying Surface Roughness

    Directory of Open Access Journals (Sweden)

    Liang Q.

    2015-10-01

    Full Text Available Roughness, which can represent the trade-off between manufacturing cost and performance of mechanical components, is a critical predictor of cracks, corrosion and fatigue damage. In order to measure polished or super-finished surfaces, a novel touch probe based on three-component force sensor for characterizing and quantifying surface roughness is proposed by using silicon micromachining technology. The sensor design is based on a cross-beam structure, which ensures that the system possesses high sensitivity and low coupling. The results show that the proposed sensor possesses high sensitivity, low coupling error, and temperature compensation function. The proposed system can be used to investigate micromechanical structures with nanometer accuracy.

  4. Micromechanical modelling of short-term and long-term large-strain behaviour of polyethylene terephthalate

    International Nuclear Information System (INIS)

    A micromechanically based model is used to describe the mechanical behaviour of polyethylene terephthalate (PET) under uniaxial compression up to large strains and at different temperatures. The creep behaviour of isotropic PET is simulated and compared to experimental data to demonstrate the applicability of the model to describe the long-term response. The material is modelled as an aggregate of two-phase layered domains, where different constitutive laws are used for the phases. A hybrid interaction law between the domains is adopted. The crystalline phase is modelled with crystal plasticity and the amorphous phase with the Eindhoven Glassy Polymer model, taking into account material ageing effects. Model parameters for the selected constitutive laws of the phases are identified from uniaxial compression tests for fully amorphous material and semicrystalline material. Texture evolution during the deformation predicted by the model adequately matches previously observed texture evolution. (paper)

  5. The micro-mechanics of strength, durability and damage tolerance in composites: new insights from high resolution computed tomography

    Science.gov (United States)

    Spearing, S. Mark; Sinclair, Ian

    2016-07-01

    Recent work, led by the authors, on impact damage resistance, particle toughening and tensile fibre failure is reviewed in order to illustrate the use of high-resolution X-ray tomography to observe and quantify damage mechanisms in carbon fibre composite laminates. Using synchrotron and micro-focus X-ray sources resolutions of less than 1 μm have been routinely achieved. This enables individual broken fibres and the micromechanisms of particle toughening to be observed and quantified. The data for fibre failure, cluster formation and overall tensile strength are compared with model predictions. This allows strategies for future model development to be identified. The overall implications for using such high-resolution 3-D measurements to inform a “data-rich mechanics” approach to materials evaluation and modeling is discussed.

  6. Ultrasonic and micromechanical study of damage and elastic properties of SiC/RBSN ceramic composites. [Reaction Bonded Silicon Nitride

    Science.gov (United States)

    Chu, Y. C.; Hefetz, M.; Rokhlin, S. I.; Baaklini, G. Y.

    1992-01-01

    Ultrasonic techniques are employed to develop methods for nondestructive evaluation of elastic properties and damage in SiC/RBSN composites. To incorporate imperfect boundary conditions between fibers and matrix into a micromechanical model, a model of fibers having effective anisotropic properties is introduced. By inverting Hashin's (1979) microstructural model for a composite material with microscopic constituents the effective fiber properties were found from ultrasonic measurements. Ultrasonic measurements indicate that damage due to thermal shock is located near the surface, so the surface wave is most appropriate for estimation of the ultimate strength reduction and critical temperature of thermal shock. It is concluded that bonding between laminates of SiC/RBSN composites is severely weakened by thermal oxidation. Generally, nondestructive evaluation of thermal oxidation effects and thermal shock shows good correlation with measurements previously performed by destructive methods.

  7. Electrons at helium interfaces

    OpenAIRE

    Leiderer, Paul

    1984-01-01

    Two-dimensional layers of charges trapped at the boundaries between the various helium phases strongly interact with these interfaces at high electric fields. The coupling, which leads to an electrohydrodynamic instability, provides new methods for studying helium properties.

  8. Interface Anywhere Project

    Data.gov (United States)

    National Aeronautics and Space Administration — To illustrate the viability of this technology, a prototype Natural User Interface (NUI) was developed as a proof-of-concept for system control.  Gesture and...

  9. A micromechanical analysis of the coupled thermomechanical superelastic response of textured and untextured polycrystalline NiTi shape memory alloys

    International Nuclear Information System (INIS)

    In this paper a micromechanical model that incorporates single crystal constitutive relationships is used for studying the pseudoelastic response of polycrystalline shape memory alloys (SMAs). In the micromechanical framework, the stress-free transformation strains of the possible martensite twinned structures, correspondence variant pairs (CVPs), obtained from the crystallographic data of NiTi are used, and the overall transformation strain is obtained by defining a set of martensitic volume fractions corresponding to active CVPs during phase transformation. The local form of the first law of thermodynamics is used and the energy balance relation for the polycrystalline SMAs is obtained. Generalized coupled thermomechanical governing equations considering the phase transformation latent heat are derived for polycrystalline SMAs. A three-dimensional finite element framework is used and different polycrystalline samples are modeled based on Voronoi tessellations. By considering appropriate distributions of crystallographic orientations in the grains obtained from experimental texture measurements of NiTi samples, the effects of texture and the tension–compression asymmetry in polycrystalline SMAs are studied. The interaction between the stress state (tensile or compressive), the number of grains and the texture on the mechanical response of polycrystalline SMAs is studied. It is found that the number of grains (or size) affects both the stress–strain response and the phase transformation propagation in the material. In addition to tensile and compressive loadings, textured and untextured NiTi micropillars with different sizes are also studied in bending. The coupled thermomechanical framework is used for analyzing the effect of loading rate and the phase transformation latent heat on the response of both textured and untextured samples. It is shown that the temperature changes due to the heat generation during phase transformation can affect the propagation of

  10. Fabrication and characterization of a CNT forest integrated micromechanical resonator for a rarefied gas analyzer in a medium vacuum atmosphere

    Science.gov (United States)

    Sugano, Koji; Matsumoto, Ryu; Tsutsui, Ryota; Kishihara, Hiroyuki; Matsuzuka, Naoki; Yamashita, Ichiro; Uraoka, Yukiharu; Isono, Yoshitada

    2016-07-01

    This study focuses on the development of a multi-walled carbon nanotube (MWCNT) forest integrated micromechanical resonator working as a rarefied gas analyzer for nitrogen (N2) and hydrogen (H2) gases in a medium vacuum atmosphere. The resonant response is detected in the form of changes in the resonant frequency or damping effects, depending on the rarefied gas species. The carbon nanotube (CNT) forest on the resonator enhances the effective specific surface area of the resonator, such that the variation of the resonant frequency and the damping effect based on the gas species increase significantly. We developed the fabrication process for the proposed resonator, which consists of standard micro-electro-mechanical systems (MEMS) processes and high-density CNT synthesis on the resonator mass. The high-density CNT synthesis was realized using multistep alternate coating of two types of ferritin proteins that act as catalytic iron particles. Two devices with different CNT densities were fabricated and characterized to evaluate the effect of the surface area of the CNT forest on the resonant response as a function of gas pressures ranging from 0.011 to 1 Pa for N2 and H2. Considering the damping effect, we found that the device with higher density was able to distinguish N2 and H2 clearly, whereas the device with lower density showed no difference between N2 and H2. We confirmed that a larger surface area showed a higher damping effect. These results were explained based on the kinetic theory of gases. In the case of resonant frequency, the relative resonant frequency shift increased with gas pressure and surface area because of the adsorption of gas molecules on the resonator surfaces. Higher density CNT forest adsorbed more gas molecules on the surfaces. The developed CNT forest integrated micromechanical resonator could successfully detect N2 and H2 gases and distinguish between them under pressures of 1 Pa.

  11. Silent Speech Interfaces

    OpenAIRE

    Denby, B; Schultz, T.; Honda, K.; Hueber, T.; Gilbert, J.M.; Brumberg, J.S.

    2010-01-01

    Abstract The possibility of speech processing in the absence of an intelligible acoustic signal has given rise to the idea of a `silent speech? interface, to be used as an aid for the speech handicapped, or as part of a communications system operating in silence-required or high-background-noise environments. The article first outlines the emergence of the silent speech interface from the fields of speech production, automatic speech processing, speech pathology research, and telec...

  12. Interfaces: nanometric dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, T J [School of Informatics, University of Wales Bangor, Dean Street, Bangor, Gwynedd, LL70 9PX (United Kingdom)

    2005-01-21

    The incorporation of nanometric size particles in a matrix to form dielectric composites shows promise of materials (nanodielectrics) with new and improved properties. It is argued that the properties of the interfaces between the particles and the matrix, which will themselves be of nanometric dimensions, will have an increasingly dominant role in determining dielectric performance as the particle size decreases. The forces that determine the electrical and dielectric properties of interfaces are considered, with emphasis on the way in which they might influence composite behaviour. A number of examples are given in which interfaces at the nanometric level exercise both passive and active control over dielectric, optical and conductive properties. Electromechanical properties are also considered, and it is shown that interfaces have important electrostrictive and piezoelectric characteristics. It is demonstrated that the process of poling, namely subjecting macroscopic composite materials to electrical stress and raised temperatures to create piezoelectric materials, can be explained in terms of optimizing the collective response of the nanometric interfaces involved. If the electrical and electromechanical features are coupled to the long-established electrochemical properties, interfaces represent highly versatile active elements with considerable potential in nanotechnology.

  13. Interfaces: nanometric dielectrics

    Science.gov (United States)

    Lewis, T. J.

    2005-01-01

    The incorporation of nanometric size particles in a matrix to form dielectric composites shows promise of materials (nanodielectrics) with new and improved properties. It is argued that the properties of the interfaces between the particles and the matrix, which will themselves be of nanometric dimensions, will have an increasingly dominant role in determining dielectric performance as the particle size decreases. The forces that determine the electrical and dielectric properties of interfaces are considered, with emphasis on the way in which they might influence composite behaviour. A number of examples are given in which interfaces at the nanometric level exercise both passive and active control over dielectric, optical and conductive properties. Electromechanical properties are also considered, and it is shown that interfaces have important electrostrictive and piezoelectric characteristics. It is demonstrated that the process of poling, namely subjecting macroscopic composite materials to electrical stress and raised temperatures to create piezoelectric materials, can be explained in terms of optimizing the collective response of the nanometric interfaces involved. If the electrical and electromechanical features are coupled to the long-established electrochemical properties, interfaces represent highly versatile active elements with considerable potential in nanotechnology.

  14. Micromechanical modeling of damage in periodic composites using strain gradient plasticity

    DEFF Research Database (Denmark)

    Azizi, Reza

    2012-01-01

    model for the fiber–matrix interface. For the micro structure, free energy holds both elastic strains and plastic strain gradients. Due to the gradient theory, higher order boundary conditions must be considered. A unit cell with a circular elastic fiber is studied by the numerical finite element cell......Damage evolution at the fiber matrix interface in Metal Matrix Composites (MMCs) is studied using strain gradient theory of plasticity. The study includes the rate independent formulation of energetic strain gradient plasticity for the matrix, purely elastic model for the fiber and cohesive zone...... model under simple shear and transverse uniaxial tension using plane strain and periodic boundary conditions. The result of the overall response curve, effective plastic strain, effective stress and higher order stress distributions are shown. The effect of the material length scale, maximum stress...

  15. Micromechanical modeling of damage growth in titanium based metal-matrix composites

    Science.gov (United States)

    Sherwood, James A.; Quimby, Howard M.

    1994-01-01

    The thermomechanical behavior of continuous-fiber reinforced titanium based metal-matrix composites (MMC) is studied using the finite element method. A thermoviscoplastic unified state variable constitutive theory is employed to capture inelastic and strain-rate sensitive behavior in the Timetal-21s matrix. The SCS-6 fibers are modeled as thermoplastic. The effects of residual stresses generated during the consolidation process on the tensile response of the composites are investigated. Unidirectional and cross-ply geometries are considered. Differences between the tensile responses in composites with perfectly bonded and completely debonded fiber/matrix interfaces are discussed. Model simulations for the completely debonded-interface condition are shown to correlate well with experimental results.

  16. User interface description languages for next generation user interfaces

    OpenAIRE

    Shaer, Orit; Jacob, Robert; Green, Mark; LUYTEN, Kris

    2008-01-01

    In recent years HCI researchers have developed a broad range of new interfaces that diverge from the "window, icon, menu, pointing device" (WIMP) paradigm, employing a variety of novel interaction techniques and devices. Developers of these next generation user interfaces face challenges that are currently not addressed by state of the art user interface software tools. As part of the user interface software community’s effort to address these challenges, the concept of a User Interface Descr...

  17. Environmental materials and interfaces

    International Nuclear Information System (INIS)

    A workshop that explored materials and interfaces research needs relevant to national environmental concerns was conducted at Pacific Northwest Laboratory. The purposes of the workshop were to refine the scientific research directions being planned for the Materials and Interface Program in the Molecular Science Research Center (MSRC) and further define the research and user equipment to the included as part of the proposed Environmental and Molecular Science Laboratory (EMSL). Three plenary information sessions served to outline the background, objectives, and status of the MSRC and EMSL initiatives; selected specific areas with environmentally related materials; and the status of capabilities and facilities planned for the EMSL. Attention was directed to four areas where materials and interface science can have a significant impact on prevention and remediation of environmental problems: in situ detection and characterization of hazardous wastes (sensors), minimization of hazardous waste (separation membranes, ion exchange materials, catalysts), waste containment (encapsulation and barrier materials), and fundamental understanding of contaminant transport mechanisms. During all other sessions, the participants were divided into three working groups for detailed discussion and the preparation of a written report. The working groups focused on the areas of interface structure and chemistry, materials and interface stability, and materials synthesis. These recommendations and suggestions for needed research will be useful for other researchers in proposing projects and for suggesting collaborative work with MSRC researchers. 1 fig

  18. High temperature interface superconductivity

    Science.gov (United States)

    Gozar, A.; Bozovic, I.

    2016-02-01

    High-Tc superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-Tc Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both 'passive' hetero-structures as well as surface-induced effects by external gating are discussed. We conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.

  19. Portraying User Interface History

    DEFF Research Database (Denmark)

    Jørgensen, Anker Helms

    2008-01-01

    The user interface is coming of age. Papers adressing UI history have appeared in fair amounts in the last 25 years. Most of them address particular aspects such as an in­novative interface paradigm or the contribution of a visionary or a research lab. Contrasting this, papers addres­sing UI...... history at large have been sparse. However, a small spate of publications appeared recently, so a reasonable number of papers are available. Hence this work-in-progress paints a portrait of the current history of user interfaces at large. The paper first describes a theoretical framework recruited from...... history. Next the paper analyses a selected sample of papers on UI history at large. The analysis shows that the current state-of-art is featured by three aspects: Firstly internalism, in that the papers adress the tech­nologies in their own right with little con­text­ualization, secondly whiggism...

  20. Workshop on Interface Phenomena

    CERN Document Server

    Kreuzer, Hans

    1987-01-01

    This book contains the proceedings of the first Workshop on Interface Phenomena, organized jointly by the surface science groups at Dalhousie University and the University of Maine. It was our intention to concentrate on just three topics related to the kinetics of interface reactions which, in our opinion, were frequently obscured unnecessarily in the literature and whose fundamental nature warranted an extensive discussion to help clarify the issues, very much in the spirit of the Discussions of the Faraday Society. Each session (day) saw two principal speakers expounding the different views; the session chairmen were asked to summarize the ensuing discussions. To understand the complexity of interface reactions, paradigms must be formulated to provide a framework for the interpretation of experimen­ tal data and for the construction of theoretical models. Phenomenological approaches have been based on a small number of rate equations for the concentrations or mole numbers of the various species involved i...

  1. Automatic generation of 2D micromechanical finite element model of silicon–carbide/aluminum metal matrix composites: Effects of the boundary conditions

    DEFF Research Database (Denmark)

    Qing, Hai

    2013-01-01

    for the automatic generation of 2D micromechanical FE-models with randomly distributed SiC particles. In order to simulate the damage process in aluminum alloy matrix and SiC particles, a damage parameter based on the stress triaxial indicator and the maximum principal stress criterion based elastic brittle damage...... are performed to study the influence of boundary condition, particle number and volume fraction of the representative volume element (RVE) on composite stiffness and strength properties....

  2. Role of a Compatibilizer in the Structure and Micromechanical Properties of Recycled Poly(ethylene terephthalate)/Polyolefin Blends with Clay

    OpenAIRE

    Hellati, A.; Benachour, D.; Cagiao, M. E.; Boufassa, S.; Baltá Calleja, F. J.

    2010-01-01

    The comparison of the degree of crystallinity and the micromechanical properties in the blends of recycled amorphous poly(ethylene terephthalate) (PET)with isotactic polypropylene (iPP) and high-density polyethylene (HDPE) with a compatibilizer in different proportions is reported. The physical study of the composites of the compatibilized blends and clay is also discussed. The analysis, performed by means of wide-angle X-ray scattering and differential scanning calorimetry techniques, per...

  3. Atomistic simulations to micro-mechanisms of adhesion in automotive applications

    Science.gov (United States)

    Sen, Fatih Gurcag

    This study aimed at depicting atomistic and microstructural aspects of adhesion and friction that appear in different automotive applications and manufacturing processes using atomistic simulations coupled with tribological tests and surface characterization experiments. Thin films that form at the contact interfaces due to chemical reactions and coatings that are developed to mitigate or enhance adhesion were studied in detail. The adhesion and friction experiments conducted on diamond-like carbon (DLC) coatings against Al indicated that F incorporation into DLC decreased the coefficient of friction (COF) by 30% -with respect to H-DLC that is known to have low COF and anti-adhesion properties against Al- to 0.14 owing to formation of repulsive F-F interactions at the sliding interface as shown by density functional theory (DFT) calculations. F atoms transferred to the Al surface with an increase in the contact pressure, and this F transfer led to the formation of a stable AlF3 compound at the Al surface as confirmed by XPS and cross-sectional FIB-TEM. The incorporation of Si and O in a F-containing DLC resulted in humidity independent low COF of 0.08 due to the hydration effect of the Si-O-Si chains in the carbonaceous tribolayers that resulted in repulsive OH-OH interactions at the contact interface. At high temperatures, adhesion of Al was found to be enhanced as a result of superplastic oxide fibers on the Al surface. Molecular dynamics (MD) simulations of tensile deformation of Al nanowires in oxygen carried out with ReaxFF showed that native oxide of Al has an oxygen deficient, low density structure and in O2, the oxygen diffusion in amorphous oxide healed the broken Al-O bonds during applied strain and resulted in the superplasticity. The oxide shell also provided nucleation sites for dislocations in Al crystal. In fuel cell applications, where low Pt/carbon adhesion is causing durability problems, spin-polarized DFT showed that metals with unfilled d

  4. Urban water interfaces

    Science.gov (United States)

    Gessner, M. O.; Hinkelmann, R.; Nützmann, G.; Jekel, M.; Singer, G.; Lewandowski, J.; Nehls, T.; Barjenbruch, M.

    2014-06-01

    Urban water systems consist of large-scale technical systems and both natural and man-made water bodies. The technical systems are essential components of urban infrastructure for water collection, treatment, storage and distribution, as well as for wastewater and runoff collection and subsequent treatment. Urban aquatic ecosystems are typically subject to strong human influences, which impair the quality of surface and ground waters, often with far-reaching impacts on downstream aquatic ecosystems and water users. The various surface and subsurface water bodies in urban environments can be viewed as interconnected compartments that are also extensively intertwined with a range of technical compartments of the urban water system. As a result, urban water systems are characterized by fluxes of water, solutes, gases and energy between contrasting compartments of a technical, natural or hybrid nature. Referred to as urban water interfaces, boundaries between and within these compartments are often specific to urban water systems. Urban water interfaces are generally characterized by steep physical and biogeochemical gradients, which promote high reaction rates. We hypothesize that they act as key sites of processes and fluxes with notable effects on overall system behaviour. By their very nature, urban water interfaces are heterogeneous and dynamic. Therefore, they increase spatial heterogeneity in urban areas and are also expected to contribute notably to the temporal dynamics of urban water systems, which often involve non-linear interactions and feedback mechanisms. Processes at and fluxes across urban water interfaces are complex and less well understood than within well-defined, homogeneous compartments, requiring both empirical investigations and new modelling approaches at both the process and system level. We advocate an integrative conceptual framework of the urban water system that considers interfaces as a key component to improve our fundamental

  5. Modal Interfaces in Hawaii

    Science.gov (United States)

    Wright, E. Alvey

    1974-01-01

    Hawaii, an archipelago where transportation distances are short but the interfaces are many, seeks elimination of modal changes by totally-submerged hydrofoil craft operating at the water surface directly between tourist resort destinations, by dual mode rapid transit vehicles operating directly between the deplaning bridges at Honolulu International Airport and hotel porte-cochere at Waikiki, by demand responsive vehicles for collection and distribution operating on fixed guideways for line haul, and by roll-on/roll-off inter-island ferries for all models of manually operated ground vehicles. The paper also describes facilitation of unavoidable interfaces by innovative sub-systems.

  6. Distributed User Interfaces

    CERN Document Server

    Gallud, Jose A; Penichet, Victor M R

    2011-01-01

    The recent advances in display technologies and mobile devices is having an important effect on the way users interact with all kinds of devices (computers, mobile devices, laptops, tablets, and so on). These are opening up new possibilities for interaction, including the distribution of the UI (User Interface) amongst different devices, and implies that the UI can be split and composed, moved, copied or cloned among devices running the same or different operating systems. These new ways of manipulating the UI are considered under the emerging topic of Distributed User Interfaces (DUIs). DUIs

  7. CAMAC to GPIB interface

    International Nuclear Information System (INIS)

    A CAMAC module developed at the Los Alamos Scientific Laboratory allows any device conforming to the GPIB standard to be connected to a CAMAC system. This module incorporates a microprocessor to control up to 14 GPIB-compatible instruments using a restricted set of CAMAC F-N-A commands. The marriage of a device-independent bus (IEEE Standard 488-1975) to a computer-independent bus (IEEE Standard 583-1975) provides a general method for interfacing a system of programmable instruments to any computer. This module is being used to interface a variety of interactive devices on a control console to a control computer

  8. Urban Sound Interfaces

    DEFF Research Database (Denmark)

    Breinbjerg, Morten

    2012-01-01

    This paper draws on the theories of Michel de Certeau and Gaston Bachelard to discuss how media architecture, in the form of urban sound interfaces, can help us perceive the complexity of the spaces we inhabit, by exploring the history and the narratives of the places in which we live. In this pa......This paper draws on the theories of Michel de Certeau and Gaston Bachelard to discuss how media architecture, in the form of urban sound interfaces, can help us perceive the complexity of the spaces we inhabit, by exploring the history and the narratives of the places in which we live...

  9. Development of Micromechanical Technique and Application on Wood Science%微观力学表征技术的发展及其在木材科学领域中的应用

    Institute of Scientific and Technical Information of China (English)

    林兰英; 秦理哲; 傅峰

    2015-01-01

    determining the properties of wood and wood fiber materials. It is also the essential stressed structure of wood. The mechanical properties of wood cell are depended on the wall layer structure,distribution and combination of chemical compositions. Researching the nano mechanical properties,distribution and affection of cell walls is critical for effective designing of wood and modified wood. Since nanoindentation was first successfully applied in wood cells of nature wood by Wimmer and his colleagues,scholars at home and abroad had generally adopted quasi-static nanoindentation and dynamic nanoindentation to study the nano mechanical properties of cell walls,such as hardness,modulus,creep properties, viscoelasticity,etc. As an interfacial layer or an interfacial phase with nano-scale thickness,the interfaces of wood materials impact their strength,stiffness and fracture toughness. Interfacial mechanics are the key of the whole mechanical properties of wood-based composites. They are also major causes of deformation and strength descent. The researches of the attributes and characteristics of interface are of great value of property evaluating and design optimizing of wood-based composites. The main researches in wood science field included bonding interface,interface of fiber reinforced polymers and micromechanics of coating over the woodworks. Micromechanical characterization technique was tending to high resolution and quantitative evaluation with researching scale shrinking, and already can be performed mechanical information imaging with nano resolution. Development of micromechanical characterization technique can provide great convenience for wood science research. However,tremendous room is needed for improvement. In the future,we should focus on the following three topics: Firstly,to conduct micromechanical technique standardization research,specify testing process and to ensure testing results consistency and reliability. Secondly,to establish relatively

  10. Is the interface OK?

    Digital Repository Service at National Institute of Oceanography (India)

    Suresh, T.

    When a peripheral device fails, software methods can be initially resorted to before the usual hardware test procedures are used. A test program is presented here that allows various peripherals, inter-faced to a Norsk Data computer, to be tested...

  11. The Liquid Vapour Interface

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage

    1985-01-01

    In this short review we are concerned with the density variation across the liquid-vapour interface, i.e. from the bulk density of the liquid to the essentially zero density of the vapour phase. This density variation can in principle be determined from the deviation of the reflectivity from...

  12. Designing groundwater visualization interfaces

    OpenAIRE

    Médard De Chardon, Cyrille

    2009-01-01

    Groundwater systems are inherently complex owing to their three-dimensional nature. The impacts of land use activities on groundwater quality and quantity, groundwater pumping, and the interaction of groundwater with surface waters are fundamental hydrogeologic concepts that require effective communication strategies. Using interactive visual interfaces may improve upon current educational techniques and encourage increased public participation in groundwater protection, conservation, and man...

  13. Photochemistry at Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Eisenthal, Kenneth B

    2015-02-24

    We have advanced our capabilities to investigate ultrafast excited state dynamics at a liquid interface using a pump to excite molecules to higher electronic states and then probe the subsequent time evolution of the interfacial molecules with femtosecond time delayed vibrational SFG.

  14. A New and General Formulation of the Parametric HFGMC Micromechanical Method for Three-Dimensional Multi-Phase Composites

    Science.gov (United States)

    Haj-Ali, Rami; Aboudi, Jacob

    2012-01-01

    The recent two-dimensional (2-D) parametric formulation of the high fidelity generalized method of cells (HFGMC) reported by the authors is generalized for the micromechanical analysis of three-dimensional (3-D) multiphase composites with periodic microstructure. Arbitrary hexahedral subcell geometry is developed to discretize a triply periodic repeating unit-cell (RUC). Linear parametric-geometric mapping is employed to transform the arbitrary hexahedral subcell shapes from the physical space to an auxiliary orthogonal shape, where a complete quadratic displacement expansion is performed. Previously in the 2-D case, additional three equations are needed in the form of average moments of equilibrium as a result of the inclusion of the bilinear terms. However, the present 3-D parametric HFGMC formulation eliminates the need for such additional equations. This is achieved by expressing the coefficients of the full quadratic polynomial expansion of the subcell in terms of the side or face average-displacement vectors. The 2-D parametric and orthogonal HFGMC are special cases of the present 3-D formulation. The continuity of displacements and tractions, as well as the equilibrium equations, are imposed in the average (integral) sense as in the original HFGMC formulation. Each of the six sides (faces) of a subcell has an independent average displacement micro-variable vector which forms an energy-conjugate pair with the transformed average-traction vector. This allows generating symmetric stiffness matrices along with internal resisting vectors for the subcells which enhances the computational efficiency. The established new parametric 3-D HFGMC equations are formulated and solution implementations are addressed. Several applications for triply periodic 3-D composites are presented to demonstrate the general capability and varsity of the present parametric HFGMC method for refined micromechanical analysis by generating the spatial distributions of local stress fields

  15. Micromechanical Effects of Cement on Deformation of Porous Granular Media: Example from the San Gregorio Fault, California and Laboratory Studies

    Science.gov (United States)

    Cook, J.; Goodwin, L.; Boutt, D.; Bucheitt, T.; Cook, B.

    2006-12-01

    The San Gregorio fault, part of the San Andreas fault system, provides a structural record of transitions in deformation mechanisms with progressive lithification. The San Gregorio is an active, predominantly dextral strike-slip fault with cumulative offset of 90 - 150 km. Within the study area the fault cuts syntectonic mudstones, siltstones, and sandstones of the Purisma Formation. Detailed mapping documents a post- lithification damage zone that overprinted pre-lithification mixed zones that bracket a well-developed, exceptionally wide (greater than 15 m) fault core. Deformation within the mixed zone was distributed and characterized by increasing disorganization and boudinage of relatively competent sedimentary layers. Multiple sandstone dikes crosscut these structures, demonstrating that they formed prior to lithification. Deformation is inferred to have occurred largely through particulate flow. The brittle damage zone, which consists of discrete fractures, minor faults, and veins that crosscut both boudins and sandstone dikes, is less extensive than the mixed zone. The transition in macroscale deformation behavior that these structures record is inferred to reflect a transition in grain-scale mechanics with progressive consolidation, tectonic compaction, and cementation. To quantitatively assess the importance of intergranular cements we are conducting experimental investigations of the micromechanical behavior of cemented granular systems, using both synthetic and natural samples. Synthetic samples have been created with both calcite and amorphous silica cement. Natural samples are sandstones with variations in primary grain and cement composition, cement abundance and distribution, and porosity, including selected samples from the San Gregorio fault. Synthetic grain assemblages will be tested in tension, compression, and shear. Nanoindentation and mm-scale deformation experiments will be used to probe the mechanical properties, including modulus, hardness

  16. Effect of stress and temperature on the micromechanics of creep in highly irradiated bone and dentin

    International Nuclear Information System (INIS)

    Synchrotron X-ray diffraction is used to study in situ the evolution of phase strains during compressive creep deformation in bovine bone and dentin for a range of compressive stresses and irradiation rates, at ambient and body temperatures. In all cases, compressive strains in the collagen phase increase with increasing creep time (and concomitant irradiation), reflecting macroscopic deformation of the sample. By contrast, compressive elastic strains in the hydroxyapatite (HAP) phase, created upon initial application of compressive load on the sample, decrease with increasing time (and irradiation) for all conditions; this load shedding behavior is consistent with damage at the HAP–collagen interface due to the high irradiation doses (from ∼ 100 to ∼ 9,000 kGy). Both the HAP and fibril strain rates increase with applied compressive stress, temperature and irradiation rate, which is indicative of greater collagen molecular sliding at the HAP–collagen interface and greater intermolecular sliding (i.e., plastic deformation) within the collagen network. The temperature sensitivity confirms that testing at body temperature, rather than ambient temperature, is necessary to assess the in vivo behavior of bone and teeth. The characteristic pattern of HAP strain evolution with time differs quantitatively between bone and dentin, and may reflect their different structural organization. Highlights: ► First systematic study of varying creep stresses on bone and dentin at nanoscale. ► HAP in highly irradiated bone and dentin sheds load during creep at all stresses. ► This suggests HAP–collagen interfacial damage due to irradiation and applied stress. ► HAP and fibril strain rates increase with stress, temperature and irradiation. ► Temporal evolution of strains different in bone and dentin

  17. PREFACE: Water at interfaces Water at interfaces

    Science.gov (United States)

    Gallo, P.; Rovere, M.

    2010-07-01

    This special issue is devoted to illustrating important aspects and significant results in the field of modeling and simulation of water at interfaces with solutes or with confining substrates, focusing on a range of temperatures from ambient to supercooled. Understanding the behavior of water, in contact with different substrates and/or in solutions, is of pivotal importance for a wide range of applications in physics, chemistry and biochemistry. Simulations of confined and/or interfacial water are also relevant for testing how different its behavior is with respect to bulk water. Simulations and modeling in this field are of particular importance when studying supercooled regions where water shows anomalous properties. These considerations motivated the organization of a workshop at CECAM in the summer of 2009 which aimed to bring together scientists working with computer simulations on the properties of water in various environments with different methodologies. In this special issue, we collected a variety of interesting contributions from some of the speakers of the workshop. We have roughly classified the contributions into four groups. The papers of the first group address the properties of interfacial and confined water upon supercooling in an effort to understand the relation with anomalous behavior of supercooled bulk water. The second group deals with the specific problem of solvation. The next group deals with water in different environments by considering problems of great importance in technological and biological applications. Finally, the last group deals with quantum mechanical calculations related to the role of water in chemical processes. The first group of papers is introduced by the general paper of Stanley et al. The authors discuss recent progress in understanding the anomalies of water in bulk, nanoconfined, and biological environments. They present evidence that liquid water may display 'polymorphism', a property that can be present in

  18. Easy-to-use interface

    Energy Technology Data Exchange (ETDEWEB)

    Blattner, M M; Blattner, D O; Tong, Y

    1999-04-01

    Easy-to-use interfaces are a class of interfaces that fall between public access interfaces and graphical user interfaces in usability and cognitive difficulty. We describe characteristics of easy-to-use interfaces by the properties of four dimensions: selection, navigation, direct manipulation, and contextual metaphors. Another constraint we introduced was to include as little text as possible, and what text we have will be in at least four languages. Formative evaluations were conducted to identify and isolate these characteristics. Our application is a visual interface for a home automation system intended for a diverse set of users. The design will be expanded to accommodate the visually disabled in the near future.

  19. Easy-to-use interface

    International Nuclear Information System (INIS)

    Easy-to-use interfaces are a class of interfaces that fall between public access interfaces and graphical user interfaces in usability and cognitive difficulty. We describe characteristics of easy-to-use interfaces by the properties of four dimensions: selection, navigation, direct manipulation, and contextual metaphors. Another constraint we introduced was to include as little text as possible, and what text we have will be in at least four languages. Formative evaluations were conducted to identify and isolate these characteristics. Our application is a visual interface for a home automation system intended for a diverse set of users. The design will be expanded to accommodate the visually disabled in the near future

  20. Discrete Element Modeling of Asphalt Concrete Cracking Using a User-defined Tlree-dimensional Micromechanical Approach

    Institute of Scientific and Technical Information of China (English)

    CHEN Jun; PAN Tongyan; HUANG Xiaoming

    2011-01-01

    We established a user-defined micromechanical model using discrete element method (DEM) to investigate the cracking behavior of asphalt concrete (AC).Using the “Fish” language provided in the particle flow code in 3-Demensions (PFC3D),the air voids and mastics in asphalt concrete were realistically built as two distinct phases.With the irregular shape of individual aggregate particles modeled using a clump of spheres of different sizes,the three-dimensional (3D) discrete element model was able to account for aggregate gradation and fraction.Laboratory uniaxial complex modulus test and indirect tensile strength test were performed to obtain input material parameters for the numerical simulation.A set of the indirect tensile test were simulated to study the cracking behavior of AC at two levels of temperature,i e,-10 ℃ and 15 ℃.The predicted results of the numerical simulation were compared with laboratory experimental measurements.Results show that the 3D DEM model is able to predict accurately the fracture pattern of different asphalt mixtures.Based on the DEM model,the effects of air void content and aggregate volumetric fraction on the cracking behavior of asphalt concrete were evaluated.

  1. Microstructural Analysis and Micromechanical Modeling of Flow Behaviour of Dual Phase Steels Using a Representative Volume Element Method

    Science.gov (United States)

    Amirmaleki, Maedeh

    Micromechanical modeling of flow curves of DP500 and DP600 steels in uniaxial tension was carried out using the representative volume element (RVE) method. Digimat and ABAQUS software were coupled and used to provide the required RVE model parameters and to perform simulations. Modeling results were validated using the experimental flow curves of the steels. It was found that the flow curve of DP500 steel was accurately predicted from the onset of plastic deformation up to the onset of necking. In case of DP600 steel, the numerical flow curve accurately predicted the experimental flow curve of steel after 0.07 strain up to necking strain. The RVE size of 12.7x12.7x12.7 mum and 7.9x7.9x7.9 mum containing 26 martensite islands were found as the optimum RVE sizes for DP500 and DP600 steel, respectively. A mesh of C3D4 elements having a size of 0.050 mum was found to be the optimum element type and mesh size.

  2. A Micromechanical Unit Cell Model of 2 × 2 Twill Woven Fabric Textile Composite for Multi Scale Analysis

    Science.gov (United States)

    Dixit, A.; Mali, H. S.; Misra, R. K.

    2014-04-01

    Woven fabric based composite materials are being considered for potential structural applications in automotive and aircraft industries due to their better out of plane strength, stiffness and toughness properties than ordinary composite laminates. This paper presents the micromechanical unit cell model of 2 × 2 twill woven fabric textile composite for the estimation of in-plane elastic properties. Modelling of unit cell and its analysis for this new model is developed by using open source coded tool TexGen and finite element software, ABAQUS® respectively. The predicted values are in good agreement with the experimental results reported in literature. To ascertain the effectiveness of the developed model parametric studies have also been conducted on the predicted elastic properties in order to investigate the effects of various geometric parameters such as yarn spacing, fabric thickness, yarn width and fibre volume fraction. The scope of altering weave pattern and yarn characteristics is facilitated in this developed model. Further this model can be implemented for the multi-scale micro/macro-mechanical analysis for the calculation of strength and stiffness of laminates structure made of 2 × 2 twill composite.

  3. Lattice strain measurements using synchrotron diffraction to calibrate a micromechanical modeling in a ferrite-cementite steel

    Energy Technology Data Exchange (ETDEWEB)

    Taupin, V.; Pesci, R. [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux, LEM3, CNRS, University of Lorraine/Arts et Metiers ParisTech, Metz Cedex 57045 (France); Berbenni, S., E-mail: stephane.berbenni@univ-lorraine.fr [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux, LEM3, CNRS, University of Lorraine/Arts et Metiers ParisTech, Metz Cedex 57045 (France); Berveiller, S.; Ouahab, R. [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux, LEM3, CNRS, University of Lorraine/Arts et Metiers ParisTech, Metz Cedex 57045 (France); Bouaziz, O. [Arcelor Research, Arcelor Mittal, Maizieres-les-Metz 57210 (France)

    2013-01-20

    In situ tensile tests were performed at room temperature on a ferrite-cementite steel specifically designed for this study. The evolution of the average stress in ferrite during loading was analyzed by X-ray diffraction. Lattice strain measurements were performed with synchrotron ring diffraction in both ferrite and cementite. These in situ tests were complemented by macroscopic tensile and reversible tensile-compression tests to study the Bauschinger effect. In order to reproduce stresses in ferrite and cementite particles, a recently developed micromechanical Internal Length Mean Field (ILMF) model based on a generalized self-consistent scheme is applied. In this designed ferrite-cementite steel, the third 'phase' of the model represents finite intermediate 'layers' in ferrite due to large geometrically necessary dislocation (GND) densities around cementite particles. The assumed constant thickness of the layers is calibrated thanks to the obtained experimental data. The ILMF model is validated by realistic estimates of the Bauschinger stress and the large difference between mean stresses in ferrite and in cementite phases. This difference cannot be reproduced by classic two-phase homogenization schemes without intermediate GND layers.

  4. Automatically produced FRP beams with embedded FOS in complex geometry: process, material compatibility, micromechanical analysis, and performance tests

    Science.gov (United States)

    Gabler, Markus; Tkachenko, Viktoriya; Küppers, Simon; Kuka, Georg G.; Habel, Wolfgang R.; Milwich, Markus; Knippers, Jan

    2012-04-01

    The main goal of the presented work was to evolve a multifunctional beam composed out of fiber reinforced plastics (FRP) and an embedded optical fiber with various fiber Bragg grating sensors (FBG). These beams are developed for the use as structural member for bridges or industrial applications. It is now possible to realize large scale cross sections, the embedding is part of a fully automated process and jumpers can be omitted in order to not negatively influence the laminate. The development includes the smart placement and layout of the optical fibers in the cross section, reliable strain transfer, and finally the coupling of the embedded fibers after production. Micromechanical tests and analysis were carried out to evaluate the performance of the sensor. The work was funded by the German ministry of economics and technology (funding scheme ZIM). Next to the authors of this contribution, Melanie Book with Röchling Engineering Plastics KG (Haren/Germany; Katharina Frey with SAERTEX GmbH & Co. KG (Saerbeck/Germany) were part of the research group.

  5. Micro-mechanic modeling of the stress-strain curves of a TiNiCu shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Lue, A.H.Y.; Taya, M.; Inoue, K.; Mori, T. [Washington Univ., Seattle, WA (United States). Dept. of Mechanical Engineering; Tomota, Y. [Department of Materials Science, Ibaraki 310-8512, University (Japan)

    2000-06-15

    A micro-mechanic model based on Eshelby's method and the minimization of the Gibbs free energy criterion, is proposed and used to predict the orientation angles of martensite variants in a single crystal TiNiCu shape memory alloy, which are in a good agreement with the observations by Saburi et al. Then, the stress-strain curve of a single crystal TiNiCu is predicted and is found to be dependent on the mode of applied stress, i.e. tension and compression. The above model is extended to the case of polycrystal TiNiCu system which is assumed to be composed of finite number of grains with several martensite variants being embedded in each grain. It turns out that use of only small number of grains are needed to simulate the smooth stress-strain curve of TiNiCu system. The stress-strain curves in both loading and unloading modes are correctly predicted at an equilibrium temperature. Finally this polycrystal model is applied for other temperatures, indicating the correct temperature dependance of the stress-strain curves. (orig.)

  6. An Overview of Dual-Phase Steels: Advances in Microstructure-Oriented Processing and Micromechanically Guided Design

    Science.gov (United States)

    Tasan, C. C.; Diehl, M.; Yan, D.; Bechtold, M.; Roters, F.; Schemmann, L.; Zheng, C.; Peranio, N.; Ponge, D.; Koyama, M.; Tsuzaki, K.; Raabe, D.

    2015-07-01

    Dual-phase (DP) steel is the flagship of advanced high-strength steels, which were the first among various candidate alloy systems to find application in weight-reduced automotive components. On the one hand, this is a metallurgical success story: Lean alloying and simple thermomechanical treatment enable use of less material to accomplish more performance while complying with demanding environmental and economic constraints. On the other hand, the enormous literature on DP steels demonstrates the immense complexity of microstructure physics in multiphase alloys: Roughly 50 years after the first reports on ferrite-martensite steels, there are still various open scientific questions. Fortunately, the last decades witnessed enormous advances in the development of enabling experimental and simulation techniques, significantly improving the understanding of DP steels. This review provides a detailed account of these improvements, focusing specifically on (a) microstructure evolution during processing, (b) experimental characterization of micromechanical behavior, and (c) the simulation of mechanical behavior, to highlight the critical unresolved issues and to guide future research efforts.

  7. Micromechanical experimental analysis and modelling of elastic and damageable behaviour of unidirectional SiC/SiC composites

    International Nuclear Information System (INIS)

    Because of their potential use as a cladding material in future nuclear reactors, the complex mechanical behavior of SiC/SiC composites, which combines damage and anisotropy, must be understood and predictable. As part of a multi-scale approach, this work focuses on the first scale change: from the elementary constituents to the tow. Micromechanical approaches are implemented to describe the macroscopic behavior of the tow taking into account its microstructure heterogeneity and damage mechanisms occurring at the local scale. A representative virtual microstructure is generated based on a detailed microstructural investigation of the tow and its elastic response is studied by numerical homogenization. In addition to addressing the mechanical RVE issue, this study highlights the significant effects of residual porosity on the transverse behavior of the tow, due to the matrix infiltration process. The longitudinal damage is being studied through mini-composites, for which the evolution of microscopic damage mechanisms (matrix cracks and fiber breaks) is experimentally analyzed (in-situ SEM and tomography tensile tests). The identification of interfacial parameters of a 1D statistical damage model is based on the experimental characterization. Conventional assumptions of such models can adequately describe matrix cracking at macro and micro scale. However it is necessary to change them to get a proper prediction of ultimate failure. (author)

  8. Politics at the interface

    DEFF Research Database (Denmark)

    Kannabiran, Gobinaath; Petersen, Marianne Graves

    2010-01-01

    At the birth of participatory design, there was a strong political consciousness surrounding the design of new technology, the design process in particular, establishing a rich set of methods and tools for user-centered design. Today, the term design has extended its scope of concern beyond...... the process of design and into how users interact with the designed product on a day-to-day basis. This paper is an attempt to call to attention the need for a new set of methods, attitudes and approaches, along with the existing, to discuss, analyze and reflect upon the politics at the interface....... By presenting a critical analysis of two design cases, we elicit the importance of such an agenda and the implications for design in doing so. We use the Foucauldian notion of power to analyze the power relationships in these two cases and to articulate the politics at the interface. We conclude by emphasizing...

  9. Space as interface

    DEFF Research Database (Denmark)

    Lykke-Olesen, Andreas

    2006-01-01

    to conceptualize space as more than the physical container for human activity. I do this by investigating space as interface. Based on a theory of space and place set forth by Tuan (Tuan, 1977), and informed by an explorative research approach, I make the distinction between space and place as a Euclidian space...... with actual use (Hallnäs et al. 2006). The challenge thus becomes understanding space as the interface, and further how intentions can be induced into the design of space in ways that point towards the dimensions of place, when interpreted in actual use situations. By designing and exploring a range......This Ph.D. dissertation takes its offset in the migration of technology and computing power into our physical environment. The consequence of this movement, termed ubiquitous computing (Wieser, 1991), is a new relationship between humans, technology and spaces. In this new context, I seek...

  10. Computer Interfaced Gauss Meter

    OpenAIRE

    Lo, Steven; Lai, Alan; Dao, Christine; Hung Vu, Hung

    2013-01-01

    Goal: Gauss Meter Model X01.  Gauss meter model X01 is the hand-held device designed to meet the needs of magnetic industry to measure magnetic fields accurately, provided high-end functionality and performance in an affordable laptop instrument. Magnet testing and sorting have never been easier. Additional features including calculating magnetic field intensity versus time and displaying magnetic field direction on a Graphical User Interface on Computer.  Introduction/Background:  Magnetic f...

  11. User interface design considerations

    DEFF Research Database (Denmark)

    Andersen, Simon Engedal; Jakobsen, Arne; Rasmussen, Bjarne D.

    1999-01-01

    user interface of EESCoolTools these issues led to a series of simulation tools each with a specific purpose and a carefully selected set of input and output variables. To allow a more wide range of questions to be answered by the same model, the user can change between different sets of input and...... have a lot of flexibility in choosing input variables and in assigning values of parameters....

  12. Standard interface file handbook

    Energy Technology Data Exchange (ETDEWEB)

    Shapiro, A.; Huria, H.C. [Cincinnati Univ., OH (United States)

    1992-10-01

    This handbook documents many of the standard interface file formats that have been adopted by the US Department of Energy to facilitate communications between and portability of, various large reactor physics and radiation transport software packages. The emphasis is on those files needed for use of the VENTURE/PC diffusion-depletion code system. File structures, contents and some practical advice on use of the various files are provided.

  13. SNE Industrial Fieldbus Interface

    Science.gov (United States)

    Lucena, Angel; Raines, Matthew; Oostdyk, Rebecca; Mata, Carlos

    2011-01-01

    Programmable logic controllers (PLCs) have very limited diagnostic and no prognostic capabilities, while current smart sensor designs do not have the capability to communicate over Fieldbus networks. The aim is to interface smart sensors with PLCs so that health and status information, such as failure mode identification and measurement tolerance, can be communicated via an industrial Fieldbus such as ControlNet. The SNE Industrial Fieldbus Interface (SIFI) is an embedded device that acts as a communication module in a networked smart sensor. The purpose is to enable a smart sensor to communicate health and status information to other devices, such as PLCs, via an industrial Fieldbus networking protocol. The SNE (Smart Network Element) is attached to a commercial off-the-shelf Any bus-S interface module through the SIFI. Numerous Anybus-S modules are available, each one designed to interface with a specific Fieldbus. Development of the SIFI focused on communications using the ControlNet protocol, but any of the Anybus-S modules can be used. The SIFI communicates with the Any-bus module via a data buffer and mailbox system on the Anybus module, and supplies power to the module. The Anybus module transmits and receives data on the Fieldbus using the proper protocol. The SIFI is intended to be connected to other existing SNE modules in order to monitor the health and status of a transducer. The SIFI can also monitor aspects of its own health using an onboard watchdog timer and voltage monitors. The SIFI also has the hardware to drive a touchscreen LCD (liquid crystal display) unit for manual configuration and status monitoring.

  14. Standard interface file handbook

    International Nuclear Information System (INIS)

    This handbook documents many of the standard interface file formats that have been adopted by the US Department of Energy to facilitate communications between and portability of, various large reactor physics and radiation transport software packages. The emphasis is on those files needed for use of the VENTURE/PC diffusion-depletion code system. File structures, contents and some practical advice on use of the various files are provided

  15. Adaptive Brain Interfaces

    OpenAIRE

    Millán, José del R.

    2003-01-01

    Severely disabled people are largely excluded from the benefits information and communication technologies have brought to our industries, economies, appliances, and general quality of life. But what if that technology would allow them to communicate their wishes or control electronic devices directly through their thoughts alone? This is the goal and promise of the Adaptive Brain Interfaces (ABI) project, which aims to augment natural human capabilities by enabling people to interact with co...

  16. An Approach to Interface Synthesis

    DEFF Research Database (Denmark)

    Madsen, Jan; Hald, Bjarne

    1995-01-01

    may contain the re-use of existing modules). The interface synthesis approach describes the basic transformations needed to transform the server interface description into an interface description on the client side of the communication medium. The synthesis approach is illustrated through a point......Presents a novel interface synthesis approach based on a one-sided interface description. Whereas most other approaches consider interface synthesis as optimizing a channel to existing client/server modules, we consider the interface synthesis as part of the client/server module synthesis (which......-to-point communication, but is applicable to synthesis of a multiple client/server environment. The interface description is based on a formalization of communication events....

  17. Interface Microstructures in Concrete

    Directory of Open Access Journals (Sweden)

    Puertas, Francisca

    1991-03-01

    Full Text Available This paper constitutes a compilation as well as an interpretation of the present state of knowledge about the different microstructures developed in the interface areas of concrete, that is, the cement paste-aggregates, the cement paste-reinforcement, the cement paste-fiber, etc. The Chemical reactions taking place in interface areas, the development and morphology of such areas and their strength ^since interfaces are taken as the weakest points of concrete are the aspects dealt with in some detail in this work.

    El presente trabajo constituye un resumen y también una interpretación del estado actual del conocimiento respecto de las diferentes microestructuras que se desarrollan en las zonas interfaciales de los hormigones, es decir: pasta de cemento-áridos, pasta de cemento-armaduras, pasta de cemento-fibras, etc. Las reacciones químicas que tienen lugar en la zona interfacial, el desarrollo y morfología de dicha zona y su resistencia (las interfases se consideran como uno de los puntos débiles del hormigón son los aspectos que con cierto detalle se tratan en el trabajo.

  18. Assessing Electromyographic Interfaces

    Directory of Open Access Journals (Sweden)

    Joaquim Armando Pires Jorge

    2009-01-01

    Full Text Available Electronic apppliances are increasingly a part of our everyday lives. In particular, mobile devices, with their reduced dimensions with power rivaling desktop computers, have substantially augmented our communication abilities offering instant availability, anywhere, to everyone. These devices have become essential for human communication but also include a more comprehensive tool set to support productivity and leisure applications.However, the many applications commonly available are not adapted to people with special needs. Rather, most popular devices are targeted at teenagers or young adults with excellent eyesight and coordination. What is worse, most of the commonly used assistive control interfaces are not available in a mobile environment where user's position, accommodation and capacities can vary even widely.To try and address people with special needs new approaches and techniques are sorely needed. This paper presents a control interface to allow tetraplegic users to interact with electronic devices. Our method uses myographic information (Electromyography or EMG collected from residually controlled body areas. User evaluations validate electromyography as a daily wearable interface. In particular our results show that EMG can be used even in mobility contexts.

  19. Vibrational spectroscopy at electrified interfaces

    CERN Document Server

    Wieckowski, Andrzej; Braunschweig, Björn

    2013-01-01

    Reviews the latest theory, techniques, and applications Surface vibrational spectroscopy techniques probe the structure and composition of interfaces at the molecular level. Their versatility, coupled with their non-destructive nature, enables in-situ measurements of operating devices and the monitoring of interface-controlled processes under reactive conditions. Vibrational Spectroscopy at Electrified Interfaces explores new and emerging applications of Raman, infrared, and non-linear optical spectroscopy for the study of charged interfaces. The book draws from hu

  20. Interface Input/Output Automata

    DEFF Research Database (Denmark)

    Larsen, Kim Guldstrand; Nyman, Ulrik; Wasowski, Andrzej

    2006-01-01

    Building on the theory of interface automata by de Alfaro and Henzinger we design an interface language for Lynch’s I/O, a popular formalism used in the development of distributed asynchronous systems, not addressed by previous interface research. We introduce an explicit separation of assumption...

  1. Postmortem analysis of sand grain crushing from pile interface using X-ray tomography

    International Nuclear Information System (INIS)

    Pile foundations of offshore platforms, wind and water turbines are typically subjected to a variety of cyclic loading paths due to their complex environment. While many studies focus on global pile behaviour, the soil-pile interface is explored here by a micromechanical study of the soil layer in contact with the pile surface. This work is devoted to the analysis of frozen post-mortem silica sand samples recovered at the pile interface following installation and cyclic loading tests in a calibration chamber using x-ray tomography. An experimental procedure developed for three dimensional (3D) snow imaging was adapted for the recovery of the in-situ sand samples to preserve their structure during tomography scans. 3D images at a pixel size of 7 μm were then obtained using a cryogenic cell. Results confirm the presence of a shear band at the pile surface as well as void ratios changes in the direction of the pile’s radius.

  2. Conceptual Framework for Aquatic Interfaces

    Science.gov (United States)

    Lewandowski, J.; Krause, S.

    2015-12-01

    Aquatic interfaces are generally characterized by steep gradients of physical, chemical and biological properties due to the contrast between the two adjacent environments. Innovative measurement techniques are required to study the spatially heterogeneous and temporally variable processes. Especially the different spatial and temporal scales are a large challenge. Due to the steep biogeochemical gradients and the intensive structural and compositional heterogeneity, enhanced biogeochemical processing rates are inherent to aquatic interfaces. Nevertheless, the effective turnover depends strongly on the residence time distribution along the flow paths and in sections with particular biogeochemical milieus and reaction kinetics. Thus, identification and characterization of the highly complex flow patterns in and across aquatic interfaces are crucial to understand biogeochemical processing along exchange flow paths and to quantify transport across aquatic interfaces. Hydrodynamic and biogeochemical processes are closely coupled at aquatic interfaces. However, interface processing rates are not only enhanced compared to the adjacent compartments that they connect; also completely different reactions might occur if certain thresholds are exceeded or the biogeochemical milieu differs significantly from the adjacent environments. Single events, temporal variability and spatial heterogeneity might increase overall processing rates of aquatic interfaces and thus, should not be neglected when studying aquatic interfaces. Aquatic interfaces are key zones relevant for the ecological state of the entire ecosystem and thus, understanding interface functioning and controls is paramount for ecosystem management. The overall aim of this contribution is a general conceptual framework for aquatic interfaces that is applicable to a wide range of systems, scales and processes.

  3. Brain-computer interface

    DEFF Research Database (Denmark)

    2014-01-01

    A computer-implemented method of providing an interface between a user and a processing unit, the method comprising : presenting one or more stimuli to a user, each stimulus varying at a respective stimulation frequency, each stimulation frequency being associated with a respective user......-selectable input; receiving at least one signal indicative of brain activity of the user; and determining, from the received signal, which of the one or more stimuli the user attends to and selecting the user-selectable input associated with the stimulation frequency of the determined stimuli as being a user...

  4. Interfacing with the Night

    OpenAIRE

    McLean, Alex; Parkinson, Adam

    2014-01-01

    In  this  paper,  the  authors  consider  the  interfaces  between academia and dance music. Dance music and club culture are, we argue, important to computer music and the live performance of electronic music, but there are many different difficulties encountered when trying to present electronic dance music within academic contexts. The authors draw upon their experiences as promoters, performers, researchers and audience members to discuss these difficulties and how and why we might negoti...

  5. Sistema Brain Computer Interface

    OpenAIRE

    Martín Barraza, Juan Ignacio

    2015-01-01

    En este trabajo de final de grado se realizará una aplicación de un sistema Brain Computer Interface en el cual, a partir del dipositivo Mind Wave de la compañía Neurosky, se pretenderá controlar el prototipo de una mano humana. Esta será controlada a partir de las ondas cerebrales medidas por el sensor que el dispositivo dispone. A continuación, la información captada por nuestro medidor de señales de electroencefalográficas será enviada por radiofrecuencia a un stick USB que viene incorpora...

  6. REAL- ESTATE INTERFACE

    OpenAIRE

    Jawad, Mohamad

    2016-01-01

    The purpose of the thesis was to implement the most efficient user interface (UI) for Real-estate in Finland for client companies due to their desire of having this feature in their system. The prototype was supposed to show the clients how the feature works to get needed data for real-estate properties in Finland in their map system. National Land Survey MML of Finland was chosen for tracking the real-estate properties data in the system. The real-estate prototype was developed by Micros...

  7. User interface concerns

    Science.gov (United States)

    Redhed, D. D.

    1978-01-01

    Three possible goals for the Numerical Aerodynamic Simulation Facility (NASF) are: (1) a computational fluid dynamics (as opposed to aerodynamics) algorithm development tool; (2) a specialized research laboratory facility for nearly intractable aerodynamics problems that industry encounters; and (3) a facility for industry to use in its normal aerodynamics design work that requires high computing rates. The central system issue for industry use of such a computer is the quality of the user interface as implemented in some kind of a front end to the vector processor.

  8. Bubble and drop interfaces

    CERN Document Server

    Miller

    2011-01-01

    The book aims at describing the most important experimental methods for characterizing liquid interfaces, such as drop profile analysis, bubble pressure and drop volume tensiometry, capillary pressure technique, and oscillating drops and bubbles. Besides the details of experimental set ups, also the underlying theoretical basis is presented in detail. In addition, a number of applications based on drops and bubbles is discussed, such as rising bubbles and the very complex process of flotation. Also wetting, characterized by the dynamics of advancing contact angles is discussed critically. Spec

  9. MAN – MACHINE INTERFACE

    Directory of Open Access Journals (Sweden)

    S.Bhuvaneswari

    2012-02-01

    Full Text Available Agents trained by learning techniques provide a powerful approximation of state spaces in games that aretoo large for naive approaches. In the study Genetic Algorithms and Manual Interface was implementedand used to train agents for the board game LUDO. The state space of LUDO is generalized to a small setand encoded to suit the different techniques. The impact of variables and tactics applied in training aredetermined. Agents based on the techniques performed satisfactory against a baseline finite agent, and aGenetic Algorithm based agent performed satisfactory against competitors from the course. Better statespace representations will improve the success of learning based agents.

  10. Engineering graded tissue interfaces.

    Science.gov (United States)

    Phillips, Jennifer E; Burns, Kellie L; Le Doux, Joseph M; Guldberg, Robert E; García, Andrés J

    2008-08-26

    Interfacial zones between tissues provide specialized, transitional junctions central to normal tissue function. Regenerative medicine strategies focused on multiple cell types and/or bi/tri-layered scaffolds do not provide continuously graded interfaces, severely limiting the integration and biological performance of engineered tissue substitutes. Inspired by the bone-soft tissue interface, we describe a biomaterial-mediated gene transfer strategy for spatially regulated genetic modification and differentiation of primary dermal fibroblasts within tissue-engineered constructs. We demonstrate that zonal organization of osteoblastic and fibroblastic cellular phenotypes can be engineered by a simple, one-step seeding of fibroblasts onto scaffolds containing a spatial distribution of retrovirus encoding the osteogenic transcription factor Runx2/Cbfa1. Gradients of immobilized retrovirus, achieved via deposition of controlled poly(L-lysine) densities, resulted in spatial patterns of transcription factor expression, osteoblastic differentiation, and mineralized matrix deposition. Notably, this graded distribution of mineral deposition and mechanical properties was maintained when implanted in vivo in an ectopic site. Development of this facile and robust strategy is significant toward the regeneration of continuous interfacial zones that mimic the cellular and microstructural characteristics of native tissue.

  11. VHF-band biconvex AlN-on-silicon micromechanical resonators with enhanced quality factor and suppressed spurious modes

    Science.gov (United States)

    Tu, Cheng; E-Y Lee, Joshua

    2016-06-01

    This paper reports experimental results demonstrating the use of biconvex-edge designs to enhance the quality factor (Q) in aluminum nitride (AlN)-on-silicon micromechanical resonators. The proposed biconvex design serves to confine the acoustic energy to the center of the resonators, thus reducing out-of-plane bending on the supporting tethers that contribute to acoustic energy leakage, thereby enhancing Q. We here demonstrate that the biconvex design concept can be scaled and applied across a range of operating frequencies from 70 to 141 MHz with the notable effect of boosting Q relative to conventional flat-edge designs. Our measurements of several resonators have shown that the biconvex designs result in an increase in Q by 4–10 times compared to conventional flat-edge designs. In addition, we have also investigated the effect of using different lengths of supporting tethers on Q for both biconvex and flat-edge designs. From the measurement results of devices under test, we have found that the variation in Q as a function of tether length was insignificant compared to the increase in Q going from a flat-edge to biconvex design. As such, the level of enhancement for Q using the biconvex design is much more significant compared to varying the geometry of the support structures. Interestingly, the biconvex shape causes a modal split that gives rise to an additional anti-symmetric mode not found in the flat-edge design. We show experimentally that this spurious anti-symmetric mode can be suppressed by over 54 dB by applying a novel center-loaded electrode design that matches the strain field pattern of the desired symmetric mode. Close agreements between the 3D coupled-domain finite element simulations and the measured results of fabricated devices have been obtained for the resonant frequencies and motional capacitances.

  12. Direct micromechanics derivation and DEM confirmation of the elastic moduli of isotropic particulate materials: Part I No particle rotation

    Science.gov (United States)

    Fleischmann, J. A.; Drugan, W. J.; Plesha, M. E.

    2013-07-01

    We derive the macroscopic elastic moduli of a statistically isotropic particulate aggregate material via the homogenization methods of Voigt (1928) (kinematic hypothesis), Reuss (1929) (static hypothesis), and Hershey (1954) and Kröner (1958) (self-consistent hypothesis), originally developed to treat crystalline materials, from the directionally averaged elastic moduli of three regular cubic packings of uniform spheres. We determine analytical expressions for these macroscopic elastic moduli in terms of the (linearized) elastic inter-particle contact stiffnesses on the microscale under the three homogenization assumptions for the three cubic packings (simple, body-centered, and face-centered), assuming no particle rotation. To test these results and those in the literature, we perform numerical simulations using the discrete element method (DEM) to measure the overall elastic moduli of large samples of randomly packed uniform spheres with constant normal and tangential contact stiffnesses (linear spring model). The beauty of DEM is that simulations can be run with particle rotation either prohibited or unrestrained. In this first part of our two-part series of papers, we perform DEM simulations with particle rotation prohibited, and we compare these results with our theoretical results that assumed no particle rotation. We show that the self-consistent homogenization assumption applied to the locally body-centered cubic (BCC) packing most accurately predicts the measured values of the overall elastic moduli obtained from the DEM simulations, in particular Poisson's ratio. Our new analytical self-consistent results lead to significantly better predictions of Poisson's ratio than all prior published theoretical results. Moreover, our results are based on a direct micromechanics analysis of specific geometrical packings of uniform spheres, in contrast to all prior theoretical analyses, which were based on difficult-to-verify hypotheses involving overall inter

  13. On consistent micromechanical estimation of macroscopic elastic energy, coherence energy and phase transformation strains for SMA materials

    Science.gov (United States)

    Ziółkowski, Andrzej

    2016-09-01

    An apparatus of micromechanics is used to isolate the key ingredients entering macroscopic Gibbs free energy function of a shape memory alloy (SMA) material. A new self-equilibrated eigenstrains influence moduli (SEIM) method is developed for consistent estimation of effective (macroscopic) thermostatic properties of solid materials, which in microscale can be regarded as amalgams of n-phase linear thermoelastic component materials with eigenstrains. The SEIM satisfy the self-consistency conditions, following from elastic reciprocity (Betti) theorem. The method allowed expressing macroscopic coherency energy and elastic complementary energy terms present in the general form of macroscopic Gibbs free energy of SMA materials in the form of semilinear and semiquadratic functions of the phase composition. Consistent SEIM estimates of elastic complementary energy, coherency energy and phase transformation strains corresponding to classical Reuss and Voigt conjectures are explicitly specified. The Voigt explicit relations served as inspiration for working out an original engineering practice-oriented semiexperimental SEIM estimates. They are especially conveniently applicable for an isotropic aggregate (composite) composed of a mixture of n isotropic phases. Using experimental data for NiTi alloy and adopting conjecture that it can be treated as an isotropic aggregate of two isotropic phases, it is shown that the NiTi coherency energy and macroscopic phase strain are practically not influenced by the difference in values of austenite and martensite elastic constants. It is shown that existence of nonzero fluctuating part of phase microeigenstrains field is responsible for building up of so-called stored energy of coherency, which is accumulated in pure martensitic phase after full completion of phase transition. Experimental data for NiTi alloy show that the stored coherency energy cannot be neglected as it considerably influences the characteristic phase transition

  14. Automatised selection of load paths to construct reduced-order models in computational damage micromechanics: from dissipation-driven random selection to Bayesian optimization

    Science.gov (United States)

    Goury, Olivier; Amsallem, David; Bordas, Stéphane Pierre Alain; Liu, Wing Kam; Kerfriden, Pierre

    2016-08-01

    In this paper, we present new reliable model order reduction strategies for computational micromechanics. The difficulties rely mainly upon the high dimensionality of the parameter space represented by any load path applied onto the representative volume element. We take special care of the challenge of selecting an exhaustive snapshot set. This is treated by first using a random sampling of energy dissipating load paths and then in a more advanced way using Bayesian optimization associated with an interlocked division of the parameter space. Results show that we can insure the selection of an exhaustive snapshot set from which a reliable reduced-order model can be built.

  15. Micro-mechanical modeling of alpha/beta two-phased titanium alloy behaviour; Modelisation micromecanique du comportement d`un alliage de titane biphase {alpha}/{beta}

    Energy Technology Data Exchange (ETDEWEB)

    Feaugas, X.; Clavel, M. [Universite de Technologie de Compiegne, 60 (France); Pilvin, P. [Ecole Nationale Superieure des Mines, 91 - Evry (France). Centre des Materiaux

    1996-12-31

    In order to better describe the mechanical behaviour of the Ti-6246 alloy, a two-phase material where the alpha phase inelastic behaviour is strongly anisotropic, a micro-mechanical approach has been developed to consider the various heterogeneity levels and the role of the various internal stresses induced by its heterogenous character. Among the simulation results, it is shown that the cyclic softening (or over-softening) is not only the consequence of a reduction of transgranular internal stresses (multiplication of the number of slip bands in the alpha phase) but is also related to the inter-cellular-type internal stress redistribution. (A.B.). 24 refs.

  16. Flexible DCP interface. [environmental sensor and signal conditioning interface

    Science.gov (United States)

    Kanemasu, E. T.; Schimmelpfenning, H.

    1974-01-01

    The author has identified the following significant results. A user of an ERTS data collection system (DCS) must supply the sensors and signal-conditioning interface. The electronic interface must be compatible with the NASA-furnished data collection platform. A universal signal-conditioning system for use with a wide range of environmental sensors is described. The interface is environmentally and electronically compatible with the DCP and has operated satisfactorily for a complete winter wheat growing season in Kansas.

  17. Oscars and Interfaces

    Directory of Open Access Journals (Sweden)

    Antony Unwin

    2012-06-01

    Full Text Available Graphical user interfaces (GUIs are gradually becoming more powerful and more accepted. They are the standard way of interacting with the web and play an increasing role in many software applications. Nevertheless, they have not been generally adopted, and critics point to particular weaknesses and disadvantages. Many of these are due more to flaws in design and implementation than to the basic concepts of GUIs. More attention could be paid to what users want to do and how a GUI might be developed to support these goals. Using a dataset about Oscar nominees and winners, this paper considers what analyses statisticians might carry out and what kind of GUI would be appropriate for these tasks. (It also offers some insights into the Oscars dataset.

  18. Human-computer interface

    Science.gov (United States)

    Anderson, Thomas G.

    2004-12-21

    The present invention provides a method of human-computer interfacing. Force feedback allows intuitive navigation and control near a boundary between regions in a computer-represented space. For example, the method allows a user to interact with a virtual craft, then push through the windshield of the craft to interact with the virtual world surrounding the craft. As another example, the method allows a user to feel transitions between different control domains of a computer representation of a space. The method can provide for force feedback that increases as a user's locus of interaction moves near a boundary, then perceptibly changes (e.g., abruptly drops or changes direction) when the boundary is traversed.

  19. Porphyrins at interfaces

    Science.gov (United States)

    Auwärter, Willi; Écija, David; Klappenberger, Florian; Barth, Johannes V.

    2015-02-01

    Porphyrins and other tetrapyrrole macrocycles possess an impressive variety of functional properties that have been exploited in natural and artificial systems. Different metal centres incorporated within the tetradentate ligand are key for achieving and regulating vital processes, including reversible axial ligation of adducts, electron transfer, light-harvesting and catalytic transformations. Tailored substituents optimize their performance, dictating their arrangement in specific environments and mediating the assembly of molecular nanoarchitectures. Here we review the current understanding of these species at well-defined interfaces, disclosing exquisite insights into their structural and chemical properties, and also discussing methods by which to manipulate their intramolecular and organizational features. The distinct characteristics arising from the interfacial confinement offer intriguing prospects for molecular science and advanced materials. We assess the role of surface interactions with respect to electronic and physicochemical characteristics, and describe in situ metallation pathways, molecular magnetism, rotation and switching. The engineering of nanostructures, organized layers, interfacial hybrid and bio-inspired systems is also addressed.

  20. Ions at hydrophobic interfaces

    International Nuclear Information System (INIS)

    We review the present understanding of the behavior of ions at the air–water and oil–water interfaces. We argue that while the alkali metal cations remain strongly hydrated and are repelled from the hydrophobic surfaces, the anions must be classified into kosmotropes and chaotropes. The kosmotropes remain strongly hydrated in the vicinity of a hydrophobic surface, while the chaotropes lose their hydration shell and can become adsorbed to the interface. The mechanism of adsorption is still a subject of debate. Here, we argue that there are two driving forces for anionic adsorption: the hydrophobic cavitational energy and the interfacial electrostatic surface potential of water. While the cavitational contribution to ionic adsorption is now well accepted, the role of the electrostatic surface potential is much less clear. The difficulty is that even the sign of this potential is a subject of debate, with the ab initio and the classical force field simulations predicting electrostatic surface potentials of opposite sign. In this paper, we will argue that the strong anionic adsorption found in the polarizable force field simulations is the result of the artificial electrostatic surface potential present in the classical water models. We will show that if the adsorption of anions were as large as predicted by the polarizable force field simulations, the excess surface tension of the NaI solution would be strongly negative, contrary to the experimental measurements. While the large polarizability of heavy halides is a fundamental property and must be included in realistic modeling of the electrolyte solutions, we argue that the point charge water models, studied so far, are incompatible with the polarizable ionic force fields when the translational symmetry is broken. The goal for the future should be the development of water models with very low electrostatic surface potential. We believe that such water models will be compatible with the polarizable force fields

  1. Detonation interaction with an interface

    OpenAIRE

    Lieberman, D. H.; Shepherd, J. E.

    2007-01-01

    Detonation interaction with an interface was investigated, where the interface separated a combustible from an oxidizing or inert mixture. The ethylene-oxygen combustible mixture had a fuel-rich composition to promote secondary combustion with the oxidizer in the turbulent mixing zone (TMZ) that resulted from the interaction. Sharp interfaces were created by using a nitro-cellulose membrane to separate the two mixtures. The membrane was mounted on a wood frame and inserted in the experimental...

  2. Audio Interfaces for Improved Accessibility

    OpenAIRE

    Duarte, Carlos; Carrico, Lu&#;s

    2008-01-01

    This chapter focused on how endowing interfaces with audio interaction capabilities can improve their accessibility. To exemplify this outcome the development of several versions of a Digital Talking Book player was presented. This allowed us to show it is possible to maintain the same set of features while stripping the interface of visual components, and still keep it usable for the visually impaired population. The interface development concerns focused on both ends of the interaction spec...

  3. Intelligent interface design and evaluation

    Science.gov (United States)

    Greitzer, Frank L.

    1988-01-01

    Intelligent interface concepts and systematic approaches to assessing their functionality are discussed. Four general features of intelligent interfaces are described: interaction efficiency, subtask automation, context sensitivity, and use of an appropriate design metaphor. Three evaluation methods are discussed: Functional Analysis, Part-Task Evaluation, and Operational Testing. Design and evaluation concepts are illustrated with examples from a prototype expert system interface for environmental control and life support systems for manned space platforms.

  4. Capillary flows with forming interfaces

    CERN Document Server

    Shikhmurzaev, Yulii D

    2007-01-01

    PREFACEINTRODUCTION Free-surface flows in nature and industryScope of the bookFUNDAMENTALS OF FLUID MECHANICS Main concepts Governing equations Elements of thermodynamics Classical boundary conditions Physically meaningful solutions and paradoxes of modelingMOVING CONTACT LINES: AN OVERVIEW Essence of the problem Experimental observations Molecular dynamics simulations Review of theoriesThe key to the moving contact-line problemBOUNDARY CONDITIONS ON FORMING INTERFACES Modeling of interfacesConservation lawsLiquid-gas and liquid-solid interfacesLiquid-liquid interfaces SummaryOpen questions an

  5. Micro-mechanical analysis and modelling of the behavior and brittle fracture of a french 16MND5 steel: role of microstructural heterogeneities

    International Nuclear Information System (INIS)

    Reactor Pressure Vessel is the second containment barrier between nuclear fuel and the environment. Electricite de France's reactors are made with french 16MND5 low-alloyed steel (equ. ASTM A508 Cl.3). Various experimental techniques (scanning electron microscopy, X-ray diffraction...) are set up in order to characterize mechanical heterogeneities inside material microstructure during tensile testing at different low temperatures [-150 C;-60 C]. Heterogeneities can be seen as the effect of both 'polycrystalline' and 'composite' microstructural features. Interphase (until 150 MPa in average between ferritic and bainitic macroscopic stress state) and intra-phase (until 100 MPa in average between ferritic orientations) stress variations are highlighted. Modelling involves micro-mechanical description of plastic glide, mean fields models and realistic three-dimensional aggregates, all put together inside a multi-scale approach. Calibration is done on macroscopic stress-strain curves at different low temperatures, and modelling reproduces experimental stress heterogeneities. This modelling allows to apply a local micro-mechanical fracture criterion for crystallographic cleavage. Deterministic computations of time to fracture for different carbides random selection provide a way to express probability of fracture for the elementary volume. Results are in good agreement with hypothesis made by local approach to fracture. Hence, the main difference is that no dependence to loading nor microstructure features is supposed for probability of fracture on the representative volume: this dependence is naturally introduced by modelling. (author)

  6. GRAPHIC INTERFACES FOR ENGINEERING APPLICATIONS

    Directory of Open Access Journals (Sweden)

    Ion PANA,

    2012-05-01

    Full Text Available Using effective the method of calculating Fitness for Service requires the achievement of graphical interfaces. This paper presents an example of such interfaces, made with Visual Basic program and used in the evaluation of pipelines in a research contract [4

  7. Playful Interfaces: Introduction and History

    NARCIS (Netherlands)

    Nijholt, Anton; Nijholt, Anton

    2014-01-01

    In this short survey we have some historical notes about human-computer interface development with an emphasis on interface technology that has allowed us to design playful interactions with applications. The applications do not necessarily have to be entertainment applications. We can have playful

  8. A micromechanics-based nonlocal constitutive equation incorporating three-point statistics for random linear elastic composite materials

    Science.gov (United States)

    Drugan, W. J.; Willis, J. R.

    2016-06-01

    A variational formulation employing the minimum potential and complementary energy principles is used to derive a micromechanics-based nonlocal constitutive equation for random linear elastic composite materials, relating ensemble averages of stress and strain in the most general situation when mean fields vary spatially. All information contained in the energy principles is retained; we employ stress polarization trial fields utilizing one-point statistics so that the resulting nonlocal constitutive equation incorporates up through three-point statistics. The variational structure is developed first for arbitrary heterogeneous linear elastic materials, then for randomly inhomogeneous materials, then for general n-phase composite materials, and finally for two-phase composite materials, in which case explicit variational upper and lower bounds on the nonlocal effective modulus tensor operator are derived. For statistically uniform infinite-body composites, these bounds are determined even more explicitly in Fourier transform space. We evaluate these in detail in an example case: longitudinal shear of an aligned fiber or void composite. We determine the full permissible ranges of the terms involving two- and three-point statistics in these bounds, and thereby exhibit explicit results that encompass arbitrary isotropic in-plane phase distributions; we also develop a nonlocal "Milton parameter", the variation of whose eigenvalues throughout the interval [0, 1] describes the full permissible range of the three-point term. Example plots of the new bounds show them to provide substantial improvement over the (two-point) Hashin-Shtrikman bounds on the nonlocal operator tensor, for all permissible values of the two- and three-point parameters. We next discuss further applications of the general nonlocal operator bounds: to any three-dimensional scalar transport problem e.g. conductivity, for which explicit results are given encompassing the full permissible ranges of the

  9. Online Remote Sensing Interface

    Science.gov (United States)

    Lawhead, Joel

    2007-01-01

    BasinTools Module 1 processes remotely sensed raster data, including multi- and hyper-spectral data products, via a Web site with no downloads and no plug-ins required. The interface provides standardized algorithms designed so that a user with little or no remote-sensing experience can use the site. This Web-based approach reduces the amount of software, hardware, and computing power necessary to perform the specified analyses. Access to imagery and derived products is enterprise-level and controlled. Because the user never takes possession of the imagery, the licensing of the data is greatly simplified. BasinTools takes the "just-in-time" inventory control model from commercial manufacturing and applies it to remotely-sensed data. Products are created and delivered on-the-fly with no human intervention, even for casual users. Well-defined procedures can be combined in different ways to extend verified and validated methods in order to derive new remote-sensing products, which improves efficiency in any well-defined geospatial domain. Remote-sensing products produced in BasinTools are self-documenting, allowing procedures to be independently verified or peer-reviewed. The software can be used enterprise-wide to conduct low-level remote sensing, viewing, sharing, and manipulating of image data without the need for desktop applications.

  10. Reflectometry on curved interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Früh, Johannes, E-mail: johannes.frueh@hit.edu.cn [Harbin Institute of Technology, Key Laboratory of Microsystems and Microstructures Manufacturing, Ministry of Education, Micro/Nano Technology Research Centre, Yikuang Street 2, Harbin 150080 (China); Rühm, Adrian [Max-Planck Institute for Intelligent Systems (formerly Max-Planck Institute for Metals Research), ZWE FRM II, Heisenbergstr. 3, 70569 Stuttgart (Germany); Möhwald, Helmuth [Max-Planck Institute of Colloids and Interfaces, Department of Interfaces, Am Mühlenberg 1, 14424 Golm/Potsdam (Germany); Krastev, Rumen [Natural and Medical Sciences Institute at the University of Tuebingen, Marktwiesenstr. 55, 72770 Reutlingen (Germany); Köhler, Ralf, E-mail: ralf.koehler@helmholtz-berlin.de [University of Technology Berlin, Stranski-Laboratorium, Straße des 17. Juni 124, 10623 Berlin (Germany); Helmholtz-Centre Berlin for Materials and Energy, Institute for Soft Matter and Functional Materials, Hahn-Meitner Platz 1, 14109 Berlin (Germany)

    2015-01-15

    Reflectometry is known since long as an interferometric method which can be used to characterize surfaces and thin films regarding their structure and, to a certain degree, composition as well. Properties like layer structures, layer thickness, density, and interface roughness can be determined by fitting the obtained reflectivity data with an appropriate model using a recursive fitting routine. However, one major drawback of the reflectometric method is its restriction to planar surfaces. In this article we demonstrate an approach to apply X-ray and neutron reflectometry to curved surfaces by means of the example of bent bare and coated glass slides. We prove the possibility to observe all features like Fresnel decay, Kiessig fringes, Bragg peaks and off-specular scattering and are able to interpret the data using common fitting software and to derive quantitative results about roughness, layer thickness and internal structure. The proposed method has become practical due to the availability of high quality 2D-detectors. It opens up the option to explore many kinds and shapes of samples, which, due to their geometry, have not been in the focus of reflectometry techniques until now.

  11. Next Generation Search Interfaces

    Science.gov (United States)

    Roby, W.; Wu, X.; Ly, L.; Goldina, T.

    2015-09-01

    Astronomers are constantly looking for easier ways to access multiple data sets. While much effort is spent on VO, little thought is given to the types of User Interfaces we need to effectively search this sort of data. For instance, an astronomer might need to search Spitzer, WISE, and 2MASS catalogs and images then see the results presented together in one UI. Moving seamlessly between data sets is key to presenting integrated results. Results need to be viewed using first class, web based, integrated FITS viewers, XY Plots, and advanced table display tools. These components should be able to handle very large datasets. To make a powerful Web based UI that can manage and present multiple searches to the user requires taking advantage of many HTML5 features. AJAX is used to start searches and present results. Push notifications (Server Sent Events) monitor background jobs. Canvas is required for advanced result displays. Lesser known CSS3 technologies makes it all flow seamlessly together. At IPAC, we have been developing our Firefly toolkit for several years. We are now using it to solve this multiple data set, multiple queries, and integrated presentation problem to create a powerful research experience. Firefly was created in IRSA, the NASA/IPAC Infrared Science Archive (http://irsa.ipac.caltech.edu). Firefly is the core for applications serving many project archives, including Spitzer, Planck, WISE, PTF, LSST and others. It is also used in IRSA's new Finder Chart and catalog and image displays.

  12. ATLAS Detector Interface Group

    CERN Document Server

    Mapelli, L

    Originally organised as a sub-system in the DAQ/EF-1 Prototype Project, the Detector Interface Group (DIG) was an information exchange channel between the Detector systems and the Data Acquisition to provide critical detector information for prototype design and detector integration. After the reorganisation of the Trigger/DAQ Project and of Technical Coordination, the necessity to provide an adequate context for integration of detectors with the Trigger and DAQ lead to organisation of the DIG as one of the activities of Technical Coordination. Such an organisation emphasises the ATLAS wide coordination of the Trigger and DAQ exploitation aspects, which go beyond the domain of the Trigger/DAQ project itself. As part of Technical Coordination, the DIG provides the natural environment for the common work of Trigger/DAQ and detector experts. A DIG forum for a wide discussion of all the detector and Trigger/DAQ integration issues. A more restricted DIG group for the practical organisation and implementation o...

  13. Multimodal Neuroelectric Interface Development

    Science.gov (United States)

    Trejo, Leonard J.; Wheeler, Kevin R.; Jorgensen, Charles C.; Totah, Joseph (Technical Monitor)

    2001-01-01

    This project aims to improve performance of NASA missions by developing multimodal neuroelectric technologies for augmented human-system interaction. Neuroelectric technologies will add completely new modes of interaction that operate in parallel with keyboards, speech, or other manual controls, thereby increasing the bandwidth of human-system interaction. We recently demonstrated the feasibility of real-time electromyographic (EMG) pattern recognition for a direct neuroelectric human-computer interface. We recorded EMG signals from an elastic sleeve with dry electrodes, while a human subject performed a range of discrete gestures. A machine-teaming algorithm was trained to recognize the EMG patterns associated with the gestures and map them to control signals. Successful applications now include piloting two Class 4 aircraft simulations (F-15 and 757) and entering data with a "virtual" numeric keyboard. Current research focuses on on-line adaptation of EMG sensing and processing and recognition of continuous gestures. We are also extending this on-line pattern recognition methodology to electroencephalographic (EEG) signals. This will allow us to bypass muscle activity and draw control signals directly from the human brain. Our system can reliably detect P-rhythm (a periodic EEG signal from motor cortex in the 10 Hz range) with a lightweight headset containing saline-soaked sponge electrodes. The data show that EEG p-rhythm can be modulated by real and imaginary motions. Current research focuses on using biofeedback to train of human subjects to modulate EEG rhythms on demand, and to examine interactions of EEG-based control with EMG-based and manual control. Viewgraphs on these neuroelectric technologies are also included.

  14. Nanoparticle Assemblies at Fluid Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Russell, Thomas P.

    2015-03-10

    A systematic study of the structure and dynamics of nanoparticles (NP) and NP-surfactants was performed. The ligands attached to both the NPs and NP-surfactants dictate the manner in which the nanoscopic materials assemble at fluid interfaces. Studies have shown that a single layer of the nanoscpic materials form at the interface to reduce the interactions between the two immiscible fluids. The shape of the NP is, also, important, where for spherical particles, a disordered, liquid-like monolayer forms, and, for nanorods, ordered domains at the interface is found and, if the monolayers are compressed, the orientation of the nanorods with respect to the interface can change. By associating end-functionalized polymers to the NPs assembled at the interface, NP-surfactants are formed that increase the energetic gain in segregating each NP at the interface which allows the NP-surfactants to jam at the interface when compressed. This has opened the possibility of structuring the two liquids by freezing in shape changes of the liquids.

  15. Playful user interfaces interfaces that invite social and physical interaction

    CERN Document Server

    2014-01-01

    The book is about user interfaces to applications that have been designed for social and physical interaction. The interfaces are ‘playful’, that is, users feel challenged to engage in social and physical interaction because that will be fun. The topics that will be present in this book are interactive playgrounds, urban games using mobiles, sensor-equipped environments for playing, child-computer interaction, tangible game interfaces, interactive tabletop technology and applications, full-body interaction, exertion games, persuasion, engagement, evaluation, and user experience. Readers of the book will not only get a survey of state-of-the-art research in these areas, but the chapters in this book will also provide a vision of the future where playful interfaces will be ubiquitous, that is, present and integrated in home, office, recreational, sports and urban environments, emphasizing that in the future in these environments game elements will be integrated and welcomed.

  16. Search-User Interface Design

    CERN Document Server

    Wilson, Max

    2011-01-01

    Search User Interfaces (SUIs) represent the gateway between people who have a task to complete, and the repositories of information and data stored around the world. Not surprisingly, therefore, there are many communities who have a vested interest in the way SUIs are designed. There are people who study how humans search for information, and people who study how humans use computers. There are people who study good user interface design, and people who design aesthetically pleasing user interfaces. There are also people who curate and manage valuable information resources, and people who desi

  17. Practical speech user interface design

    CERN Document Server

    Lewis, James R

    2010-01-01

    Although speech is the most natural form of communication between humans, most people find using speech to communicate with machines anything but natural. Drawing from psychology, human-computer interaction, linguistics, and communication theory, Practical Speech User Interface Design provides a comprehensive yet concise survey of practical speech user interface (SUI) design. It offers practice-based and research-based guidance on how to design effective, efficient, and pleasant speech applications that people can really use. Focusing on the design of speech user interfaces for IVR application

  18. Designing end-user interfaces

    CERN Document Server

    Heaton, N

    1988-01-01

    Designing End-User Interfaces: State of the Art Report focuses on the field of human/computer interaction (HCI) that reviews the design of end-user interfaces.This compilation is divided into two parts. Part I examines specific aspects of the problem in HCI that range from basic definitions of the problem, evaluation of how to look at the problem domain, and fundamental work aimed at introducing human factors into all aspects of the design cycle. Part II consists of six main topics-definition of the problem, psychological and social factors, principles of interface design, computer intelligenc

  19. Interfaces and thin films physics

    International Nuclear Information System (INIS)

    The 1988 progress report of the Interfaces and Thin Film Physics laboratory (Polytechnic School France) is presented. The research program is focused on the thin films and on the interfaces of the amorphous semiconductor materials: silicon and silicon germanium, silicon-carbon and silicon-nitrogen alloys. In particular, the following topics are discussed: the basic processes and the kinetics of the reactive gas deposition, the amorphous materials manufacturing, the physico-chemical characterization of thin films and interfaces and the electron transport in amorphous semiconductors. The construction and optimization of experimental devices, as well as the activities concerning instrumentation, are also described

  20. Automated Fluid Interface System (AFIS)

    Science.gov (United States)

    1990-01-01

    Automated remote fluid servicing will be necessary for future space missions, as future satellites will be designed for on-orbit consumable replenishment. In order to develop an on-orbit remote servicing capability, a standard interface between a tanker and the receiving satellite is needed. The objective of the Automated Fluid Interface System (AFIS) program is to design, fabricate, and functionally demonstrate compliance with all design requirements for an automated fluid interface system. A description and documentation of the Fairchild AFIS design is provided.

  1. The molecule-metal interface

    CERN Document Server

    Koch, Norbert; Wee, Andrew Thye Shen

    2013-01-01

    Reviewing recent progress in the fundamental understanding of the molecule-metal interface, this useful addition to the literature focuses on experimental studies and introduces the latest analytical techniques as applied to this interface.The first part covers basic theory and initial principle studies, while the second part introduces readers to photoemission, STM, and synchrotron techniques to examine the atomic structure of the interfaces. The third part presents photoelectron spectroscopy, high-resolution UV photoelectron spectroscopy and electron spin resonance to study the electroni

  2. Dispersive transport across interfaces

    Science.gov (United States)

    Berkowitz, Brian; Adler, Pierre

    2015-04-01

    Experiments demonstrating asymmetrical dispersive transport of a conservative tracer across interfaces between different porous materials have recently been performed. Here, this phenomenon is studied numerically on the pore scale. The flow field is derived by solving the Stokes equation. The dispersive transport is simulated by a large number of particles undergoing random walks under the simultaneous action of convection and diffusion. Two main two-dimensional configurations are studied; each consists of two segments (called coarse and fine) with the same structure, porosity, and length along the main flow, but different characteristic solid/pore sizes. One structure consists of two channels containing cavities of different sizes, and the second of square "grains" of different sizes. At time t=0, a large number of particles is injected (as a pulse) around a given cross-section. The corresponding breakthrough curves (BTCs) are registered as functions of time at six different cross sections. Calculations are made twice; in the first case (CtoF), particles are injected in the coarse side and are transported towards the fine one; in the second one (FtoC), the opposite case is studied. These calculations are performed for various Péclet numbers (Pe). Comparison of the resulting BTCs shows features that are similar to experimental observations, but with qualitative and quantitative differences. The influences of the medium, of the injection and observation planes, and of Pe are detailed and discussed. A BTC for pulse injection can be characterized by its maximum M(t_M) and the time tM at which it occurs. The observed differences for channels bounded by cavities are very small. However for the granular structures, M(t_M) is always larger for FtoC than for CtoF ; tM depends on all the parameters, namely Pe, the size ratio between the large and small grains, the injection and the observation planes. The numerical results are systematically compared with solutions of one

  3. Surface/interface effects on the effective propagation constants of coherent waves in composites with random parallel nanofibers.

    Science.gov (United States)

    Kong, Zhi; Wei, Peijun; Jiao, Fengyu

    2016-07-01

    The effective propagation constants of elastic waves in an inhomogeneous medium with randomly distributed parallel cylindrical nanofibers are studied. First, the surface energy theory proposed by Huang and Wang (Handbook of Micromechanics and Nanomechanics, 2013) is used to derive the nontraditional boundary conditions on the surfaces of the nanoholes and the interfaces between the nanofibers and the host. Then, the scattering matrix of individual scatterer (cylindrical hole or nanofiber) is derived from the nontraditional boundary condition. The total wave field is obtained by considering the multiple scattering processes among the dispersive scatterers. The configuration average of the total wave field results in the coherent waves or the averaged waves. By using the corrected Linton-Martin formula, the effective propagation constants (effective speed and effective attenuation) of the coherent waves are estimated. The in-plane waves (P and SV waves) and the anti-plane waves (SH wave) are considered, respectively, and the numerical results are shown graphically. Apart from the effects of surface elasticity, the effects of inertia of surface/interface and the effects of residual surface tension (which are often ignored in the previous literature) are also considered. Moreover, the influences of the nonsymmetric parts of in-plane surface stress and the out-of-plane parts of the surface stress are both discussed first based on the numerical examples. These investigations show the underestimation and overestimation of effective propagation constants caused by various simplifications. PMID:27475172

  4. Interface engineering in organic transistors

    Directory of Open Access Journals (Sweden)

    Yeong Don Park

    2007-03-01

    Full Text Available Recent technological advances in organic field-effect transistors (OFETs have triggered intensive research into the molecular and mesoscale structures of organic semiconductor films that determine their charge-transport characteristics. Since the molecular structure and morphology of an organic semiconductor are largely determined by the properties of the interface between the organic film and the insulator, a great deal of research has focused on interface engineering. We review recent progress in interface engineering for the fabrication of high-performance OFETs and, in particular, engineering of the interfaces between semiconductors and insulators. The effects of interfacial characteristics on the molecular and mesoscale structures of π-conjugated molecules and the performance of OFET devices are discussed.

  5. REXIB: Remote Experiments Interface Builder

    Directory of Open Access Journals (Sweden)

    Jose M. Ferreira

    2006-08-01

    Full Text Available Remote Experimentation is an educational resource that allows teachers to strengthen the practical contents of science & engineering courses. However, building up the interfaces to remote experiments is not a trivial task. Although teachers normally master the practical contents addressed by a particular remote experiment they usually lack the programming skills required to quickly build up the corresponding web interface. This paper describes the automatic generation of experiment interfaces through a web-accessible Java application. The application displays a list of existent modules and once the requested modules have been selected, it generates the code that enables the browser to display the experiment interface. The tools’ main advantage is enabling non-tech teachers to create their own remote experiments.

  6. The Simple Publishing Interface (SPI)

    NARCIS (Netherlands)

    Ternier, Stefaan; Massart, David; Totschnig, Michael; Klerkx, Joris; Duval, Erik

    2010-01-01

    Ternier, S., Massart, D., Totschnig, M., Klerkx, J., & Duval, E. (2010). The Simple Publishing Interface (SPI). D-Lib Magazine, September/October 2010, Volume 16 Number 9/10, doi:10.1045/september2010-ternier

  7. MICROSOURCE INTERFACE FOR A MICROGRID

    OpenAIRE

    Binduhewa, Prabath Janaka

    2010-01-01

    A MicroGrid is typically a small power system, which consists of several microsources and energy storage units, providing heat and electricity to local loads. The MicroGrid has the capability to island and operate autonomously from the main utility network. MicroGrids potentially enable a greater integration of small-scale renewable energy sources. The objective of this thesis is to develop a single-phase microsource interface with energy storage unit embedded into the interface. An integrate...

  8. Coal-shale interface detection

    Science.gov (United States)

    Broussard, P. H.; Burch, J. L.; Drost, E. J.; Stein, R. J. (Inventor)

    1979-01-01

    A penetrometer for coal-shale interface detection is presented. It is used with coal cutting equipment consisting of a reciprocating hammer, having an accelerometer mounted thereon to measure the impact of the hammer as it penetrates the ceiling or floor surface of a mine. Additionally, a pair of reflectometers simultaneously view the same surface, and the outputs from the accelerometer and reflectometers are detected and jointly registered to determine when an interface between coal and shale is being cut through.

  9. Coal-shale interface detector

    Science.gov (United States)

    Reid, H., Jr. (Inventor)

    1980-01-01

    A coal-shale interface detector for use with coal cutting equipment is described. The detector consists of a reciprocating hammer with an accelerometer to measure the impact of the hammer as it penetrates the ceiling or floor surface of a mine. Additionally, a pair of reflectometers simultaneously view the same surface, and the outputs from the accelerometer and reflectometers are detected and jointly registered to determine when an interface between coal and shale is being cut through.

  10. Interfacing Coq + SSReflect with GAP

    OpenAIRE

    Komendantsky, Vladimir; Konovalov, Alexander; Linton, Stephen Alexander

    2012-01-01

    Presentation slides and preprint both provided by author. Preprint published in Electronic Notes in Theoretical Computer Science: Proceedings of the 9th International Workshop On User Interfaces for Theorem Provers (UITP10). We report on an extendable implementation of the communication interface connecting Coq proof assistant to the computational algebra system GAP using the Symbolic Computation Software Composability Protocol (SCSCP). It allows Coq to issue OpenMath requests to a local o...

  11. Micromechanics senses biomolecules

    Directory of Open Access Journals (Sweden)

    Roberto Raiteri

    2002-01-01

    Cantilever sensors rely on relatively well known and simple transduction principles, and have attracted the interest of many researchers. This is, at least in part, because of the merging of silicon microfabrication techniques and surface functionalization biochemistry, together with the development of multi-cantilever sensing methods offering new opportunities in physical and (biochemical sensing.

  12. Micromechanics of Composite Materials

    CERN Document Server

    Dvorak, George

    2013-01-01

    This book presents a broad exposition of analytical and numerical methods for modeling composite materials, laminates, polycrystals and other heterogeneous solids, with emphasis on connections between material properties and responses on several length scales, ranging from the nano and microscales to the macroscale. Many new results and methods developed by the author are incorporated into a rich fabric of the subject, which has been explored by several researchers over the last 40 years.   The first  part of the book reviews anisotropic elasticity theory, and then it describes the frequently used procedures and theorems for bounding and estimating overall properties, local fields and energy changes in elastic inhomogeneities, heterogeneous media, fiber composites and functionally graded materials.  Those are caused by mechanical loads and by phase eigenstrains, such as thermal, transformation and inelastic strains, and also by cavities and cracks.    Worked examples show that the eigendeformations may...

  13. Micromechanical modeling of microtubules

    OpenAIRE

    Arslan, Melis

    2010-01-01

    Microtubules serve as one of the structural components of the cell and take place in some of the important cellular functions such as mitosis and vesicular transport. Microtubules comprise of tubulin subunits tubulin dimers arranged in a cylindrical beta and formed by alpha hollow tube structure with a diameter of 20nm. They are typically comprised of 13 or 14 protofilaments arranged in spiral configurations. The longitudinal bonds between the tubulin dimers are much stiffer and stronger than...

  14. MICROMECHANICS OF MACROELECTRONICS

    Institute of Scientific and Technical Information of China (English)

    Zhigang Suo; Joost Vlassak; Sigurd Wagner

    2005-01-01

    The advent of flat-panel displays has opened the era of macroelectronics. Enthusiasm is gathering to develop macroelectronics as a platform for many technologies, ranging from paper-like displays to thin-film solar cells,technologies that aim to address the essential societal needs for easily accessible information, renewable energy, and sustainable environment. The widespread use of these large structures will depend on their ruggedness, portability and low cost, attributes that will come from new material choices and new manufacturing processes. For example, thin-film devices on thin polymer substrates lend themselves to roll-to-roll fabrication, and impart flexibility to the products. These large structures will have diverse architectures, hybrid materials, and small features; their mechanical behavior during manufacturing and use poses significant challenges to the creation of the new technologies. This paper describes ongoing work in the emerging field of research - the mechanics of macroelectronics, with emphasis on the mechanical behavior at the scale of individual features, and over a long time.

  15. Micromechanics of Alveolar Edema

    OpenAIRE

    Perlman, Carrie E.; Lederer, David J.; Bhattacharya, Jahar

    2010-01-01

    The decrease of lung compliance in pulmonary edema underlies ventilator-induced lung injury. However, the cause of the decrease in compliance is unknown. We tested the hypothesis that in pulmonary edema, the mechanical effects of liquid-filled alveoli increase tissue stress in adjacent air-filled alveoli. By micropuncture of isolated, perfused rat lungs, we established a single-alveolus model of pulmonary edema that we imaged using confocal microscopy. In this model, we viewed a liquid-filled...

  16. Active matter clusters at interfaces.

    Science.gov (United States)

    Copenhagen, Katherine; Gopinathan, Ajay

    2016-03-01

    Collective and directed motility or swarming is an emergent phenomenon displayed by many self-organized assemblies of active biological matter such as clusters of embryonic cells during tissue development, cancerous cells during tumor formation and metastasis, colonies of bacteria in a biofilm, or even flocks of birds and schools of fish at the macro-scale. Such clusters typically encounter very heterogeneous environments. What happens when a cluster encounters an interface between two different environments has implications for its function and fate. Here we study this problem by using a mathematical model of a cluster that treats it as a single cohesive unit that moves in two dimensions by exerting a force/torque per unit area whose magnitude depends on the nature of the local environment. We find that low speed (overdamped) clusters encountering an interface with a moderate difference in properties can lead to refraction or even total internal reflection of the cluster. For large speeds (underdamped), where inertia dominates, the clusters show more complex behaviors crossing the interface multiple times and deviating from the predictable refraction and reflection for the low velocity clusters. We then present an extreme limit of the model in the absence of rotational damping where clusters can become stuck spiraling along the interface or move in large circular trajectories after leaving the interface. Our results show a wide range of behaviors that occur when collectively moving active biological matter moves across interfaces and these insights can be used to control motion by patterning environments.

  17. Hydrophobic effect at aqueous interfaces

    Science.gov (United States)

    Pohorille, Andrew

    2005-01-01

    Conceptual basis for hydrophobic effects in bulk water and at aqueous interfaces have similar conceptual basis but often manifests itself differently. Using a wide range of computer simulations as the basis, I will review different forms of hydrophobic effects at a variety of interfaces starting from simple liquid-vapor and water-oil interfaces and progressing to water-membrane interfaces. I will start with discussing how water is organized at different interfaces, stressing both similarities and differences. The main thread is that, as in the bulk liquid, hydrophobic effects have profound influence on conformational equilibria and organization of both small molecules and macromolecules, but the result of this influence is quite different. Specifically, it will be shown that many small, but not necessarily amphiphilic molecules tend to accumulate at the interface and, and this tendency will be explained. Furthermore, I will show that many short peptides that are disordered in water spontaneously fold into well-defined structures in the interfacial environment. Biological implications of this self-organizing effect will be discussed.

  18. Active matter clusters at interfaces.

    Directory of Open Access Journals (Sweden)

    Katherine eCopenhagen

    2016-03-01

    Full Text Available Collective and directed motility or swarming is an emergent phenomenon displayed by many self-organized assemblies of active biological matter such as clusters of embryonic cells during tissue development, cancerous cells during tumor formation and metastasis, colonies of bacteria in a biofilm, or even flocks of birds and schools of fish at the macro-scale. Such clusters typically encounter very heterogeneous environments. What happens when a cluster encounters an interface between two different environments has implications for its function and fate. Here we study this problem by using a mathematical model of a cluster that treats it as a single cohesive unit that moves in two dimensions by exerting a force/torque per unit area whose magnitude depends on the nature of the local environment. We find that low speed (overdamped clusters encountering an interface with a moderate difference in properties can lead to refraction or even total internal reflection of the cluster. For large speeds (underdamped, where inertia dominates, the clusters show more complex behaviors crossing the interface multiple times and deviating from the predictable refraction and reflection for the low velocity clusters. We then present an extreme limit of the model in the absence of rotational damping where clusters can become stuck spiraling along the interface or move in large circular trajectories after leaving the interface. Our results show a wide range of behaviors that occur when collectively moving active biological matter moves across interfaces and these insights can be used to control motion by patterning environments.

  19. Micromechanical measurement of beating patterns in the quantum oscillatory chemical potential of InGaAs quantum wells due to spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Herzog, Florian, E-mail: Florian.Herzog@ph.tum.de; Wilde, Marc A., E-mail: mwilde@ph.tum.de [Lehrstuhl für Physik funktionaler Schichtsysteme, Physik Department, Technische Universität München, James-Franck-Strasse 1, D-85748 Garching b. München (Germany); Heyn, Christian [Institut für Nanostruktur- und Festkörperphysik, Universität Hamburg, Jungiusstr. 11, D-20355 Hamburg (Germany); Hardtdegen, Hilde; Schäpers, Thomas [Peter Grünberg Institut (PGI-9) and JARA-FIT Jülich-Aachen Research Alliance, Forschungszentrum Jülich, D-52425 Jülich (Germany); Grundler, Dirk [Lehrstuhl für Physik funktionaler Schichtsysteme, Physik Department, Technische Universität München, James-Franck-Strasse 1, D-85748 Garching b. München (Germany); Laboratory of Nanoscale Magnetic Materials and Magnonics (LMGN), Institute of Materials, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland)

    2015-08-31

    The quantum oscillatory magnetization M(B) and chemical potential μ(B) of a two-dimensional (2D) electron system provide important and complementary information about its ground state energy at low temperature T. We developed a technique that provides both quantities in the same cool-down process via a decoupled static operation and resonant excitation of a micromechanical cantilever. On InGaAs/InP heterostructures, we observed beating patterns in both M(B) and μ(B) attributed to spin-orbit interaction. A significantly enhanced sensitivity in μ enabled us to extract Rashba and Dresselhaus parameters with high accuracy. The technique is powerful for detailed investigations on the electronic properties of 2D materials.

  20. A Coupled Mean Field / Gurson-Tvergaard Micromechanical Model For Ductile Fracture In Multiphase Materials With Large Volume Fraction of Voids

    Science.gov (United States)

    Van Hoof, Thibaut; Piérard, Olivier; Lani, Frédéric

    2007-04-01

    In the framework of the European project PROHIPP (New design and manufacturing processes for high pressure fluid power product — NMP 2-CT-2004-50546), CENAERO develops a library of constitutive models used to predict the mechanical response of a family of cast iron. The present contribution focuses on one particular microstructure, corresponding to a ferrite matrix containing spheroidal graphite and isolated inclusions of pearlite. An incremental mean field homogenisation scheme such as the one developed by Doghri and Ouaar is used. In the present application, the ferrite matrix is described by a Gurson type constitutive law (porous plasticity) while the pearlite inclusions are assumed to obey the classical isotropic J2 plasticity. The predictions of the micromechanical model are compared to the results of Finite Element simulations performed on three-dimensional representative volume elements (RVEs).

  1. The influence of the graphite mechanical properties on the constitutive response of a ferritic ductile cast iron – A micromechanical FE analysis

    DEFF Research Database (Denmark)

    Andriollo, Tito; Thorborg, Jesper; Hattel, Jesper Henri

    2015-01-01

    In the present paper a micro-mechanical approach is used to investigate the influence of the graphite mechanical properties on the loading response in the early deformation range of ductile cast iron. A periodic unit cell composed by a single graphite nodule embedded in a uniform ferritic matrix...... is considered and elasto-plastic behavior of both constituents is assumed; damage evolution in the ductile matrix is taken into account via Lemaitre’s isotropic model. Full 3D and 2D plane-stress finite element analyses are performed to simulate the loading conditions experienced by nodules located in the bulk...... as well as on the material surface. The effects of residual stresses arising during the manufacturing process are also accounted for. It is shown that the constitutive response of the equivalent composite medium can match ductile cast iron only if the graphite Young’s modulus value lies within a certain...

  2. Science at the interface

    International Nuclear Information System (INIS)

    the stakes against those who might want to enter. Laboratory sciences interface nature in a peculiar way: by barring real natural objects from entering the lab and by substituting for them reconfigured versions of these objects to work with in research. These supplemental versions of natural objects do refer back to natural processes or conditions, but at the same time they are also autonomous new objects and processes with differential qualities and reproductive powers within laboratory contexts. Laboratory sciences have the disadvantage that their products must be freshly contextualized when they leave the lab to reenter natural environments. In the natural sciences, re-contextualization is often accomplished by transferring some of the conditions that obtained in the lab onto the natural environment. Re-contextualization in the natural sciences may also just be a metaphor for a long chain of processes, involving specialized disciplines, by which some natural scientific results are used to create technologies which are then used in practice - a process that often fails, involves political strategies of persuasion and other complications. Contextualization involves adaptation not only to new laboratory external physical environments but also to the social world. One direction of social science research maintains that a form of (re) contextualization of a much larger scope and impact is evident today in contemporary societies, affecting in tendency all sciences and technological fields. This assessment is encapsulated in the idea that we have progressed from Mode 1 science and technology to a Mode 2 situation where knowledge is generated in the context of application and implication. (author)

  3. Interface groups and financial transfer architectures

    CERN Document Server

    Bergstra, Jan A

    2007-01-01

    Analytic execution architectures have been proposed by the same authors as a means to conceptualize the cooperation between heterogeneous collectives of components such as programs, threads, states and services. Interface groups have been proposed as a means to formalize interface information concerning analytic execution architectures. These concepts are adapted to organization architectures with a focus on financial transfers. Interface groups (and monoids) now provide a technique to combine interface elements into interfaces with the flexibility to distinguish between directions of flow dependent on entity naming. The main principle exploiting interface groups is that when composing a closed system of a collection of interacting components, the sum of their interfaces must vanish in the interface group modulo reflection. This certainly matters for financial transfer interfaces. As an example of this, we specify an interface group and within it some specific interfaces concerning the financial transfer arch...

  4. Theory of Interface States at Silicon / Transition - - Silicide Interfaces.

    Science.gov (United States)

    Lim, Hunhwa

    The Si/NiSi(,2)(111) interface is of both fundamental and techno- logical interest: From the fundamental point of view, it is the best characterized of all semiconductor/metal interfaces, with two well-determined geometries (A and B) involving nearly perfect bonding. (This is because Si and NiSi(,2) have nearly the same lattice spacing.) Consequently, a theoretical treatment of this system makes sense--as it would not for messier systems--and one can have some confidence that the theoretical predictions are relevant to experimental observa- tions. From the technological point of view, Si/NiSi(,2) is representative of the class of semiconductor/metal interfaces that are currently of greatest interest in regard to electronic devices--Si/transition -metal-silicide interfaces. The calculations of this dissertation are for the intrinsic interface states of Si/NiSi(,2)-A geometry. These calculations also provide a foundation for later studies of defects at this interface, and for studies of other related systems, such as CoSi(,2). The calculations employ empirical tight-binding Hamiltonians for both Si and NiSi(,2) (with the parameters fitted to prior calculations of the bulk band structures, which appear to be in agreement with the available experimental data on bulk Si and NiSi(,2)). They also employ Green's function techniques--in particular, the subspace Hamiltonian technique. Our principal results are the following: (1) Interface state disper- sion curves are predicted along the symmetry lines (')(GAMMA)(')M, (')M(')K and (')K(')(GAMMA) of the surface Brillouin zone. (2) A prominent band of interface states is found which disperses downward from an energy within the Si band gap to an energy below the Si valence band edge E(,(upsilon)) as the planar wavevector (')k increases from (')(GAMMA) ((')k = 0) to (')M or (')K (symmetry points at boundary of the surface Brillouin zone). This band of inter- face states should be observable. It produces a peak in the surface

  5. Interface dynamics of competing tissues

    Science.gov (United States)

    Podewitz, Nils; Jülicher, Frank; Gompper, Gerhard; Elgeti, Jens

    2016-08-01

    Tissues can be characterized by their homeostatic stress, i.e. the value of stress for which cell division and cell death balance. When two different tissues grow in competition, a difference of their homeostatic stresses determines which tissue grows at the expense of the second. This then leads to the propagation of the interface separating the tissues. Here, we study structural and dynamical properties of this interface by combining continuum theory with mesoscopic simulations of a cell-based model. Using a simulation box that moves with the interface, we find that a stationary state exists in which the interface has a finite width and propagates with a constant velocity. The propagation velocity in the simulations depends linearly on the homeostatic stress difference, in excellent agreement with the analytical predictions. This agreement is also seen for the stress and velocity profiles. Finally, we analyzed the interface growth and roughness as a function of time and system size. We estimated growth and roughness exponents, which differ from those previously obtained for simple tissue growth.

  6. XML Translator for Interface Descriptions

    Science.gov (United States)

    Boroson, Elizabeth R.

    2009-01-01

    A computer program defines an XML schema for specifying the interface to a generic FPGA from the perspective of software that will interact with the device. This XML interface description is then translated into header files for C, Verilog, and VHDL. User interface definition input is checked via both the provided XML schema and the translator module to ensure consistency and accuracy. Currently, programming used on both sides of an interface is inconsistent. This makes it hard to find and fix errors. By using a common schema, both sides are forced to use the same structure by using the same framework and toolset. This makes for easy identification of problems, which leads to the ability to formulate a solution. The toolset contains constants that allow a programmer to use each register, and to access each field in the register. Once programming is complete, the translator is run as part of the make process, which ensures that whenever an interface is changed, all of the code that uses the header files describing it is recompiled.

  7. Flow in presence of interfaces

    Science.gov (United States)

    Lunati, I.

    2011-12-01

    Although most physical properties and empirical laws are well defined and experimentally tested only for homogeneous systems, being able to solve environmental problems requires dealing with systems that are inherently heterogeneous. This is particularly true for applications in hydrogeology, where properties (such as permeability) can vary over orders of magnitude. The most challenging cases are those of flow in presence of interfaces, i.e., region characterized by sharp and abrupt contrasts in properties or state. Interfaces require a special treatment, both conceptually and numerically (e.g., quantity such as pressure can become discontinuous), and must be accurately described because of the important phenomena that can take place (e.g., reaction or instability) and influence the behavior of the system at large scales. We discuss the problems related with an accurate description of the propagation of a fluid-fluid interface in a pore geometry, and with the evolution of an unstable front between two fluids of different densities.

  8. Multi-robot control interface

    Science.gov (United States)

    Bruemmer, David J.; Walton, Miles C.

    2011-12-06

    Methods and systems for controlling a plurality of robots through a single user interface include at least one robot display window for each of the plurality of robots with the at least one robot display window illustrating one or more conditions of a respective one of the plurality of robots. The user interface further includes at least one robot control window for each of the plurality of robots with the at least one robot control window configured to receive one or more commands for sending to the respective one of the plurality of robots. The user interface further includes a multi-robot common window comprised of information received from each of the plurality of robots.

  9. Physics of Surfaces and Interfaces

    CERN Document Server

    Ibach, Harald

    2006-01-01

    This graduate-level textbook covers the major developments in surface sciences of recent decades, from experimental tricks and basic techniques to the latest experimental methods and theoretical understanding. It is unique in its attempt to treat the physics of surfaces, thin films and interfaces, surface chemistry, thermodynamics, statistical physics and the physics of the solid/electrolyte interface in an integral manner, rather than in separate compartments. The Physics of Surfaces and Interfaces is designed as a handbook for the researcher as well as a study-text for graduate students in physics or chemistry with special interest in the surface sciences, material science, or the nanosciences. The experienced researcher, professional or academic teacher will appreciate the opportunity to share many insights and ideas that have grown out of the author's long experience. Readers will likewise appreciate the wide range of topics treated, each supported by extensive references. Graduate students will benefit f...

  10. PinBus Interface Design

    Energy Technology Data Exchange (ETDEWEB)

    Hammerstrom, Donald J.; Adgerson, Jewel D.; Sastry, Chellury; Pratt, Richard M.; Pratt, Robert G.

    2009-12-30

    On behalf of the U.S. Department of Energy, PNNL has explored and expanded upon a simple control interface that might have merit for the inexpensive communication of smart grid operational objectives (demand response, for example) to small electric end-use devices and appliances. The approach relies on bi-directional communication via the electrical voltage states of from one to eight shared interconnection pins. The name PinBus has been suggested and adopted for the proposed interface protocol. The protocol is defined through the presentation of state diagrams and the pins’ functional definitions. Both simulations and laboratory demonstrations are being conducted to demonstrate the elegance and power of the suggested approach. PinBus supports a very high degree of interoperability across its interfaces, allowing innumerable pairings of devices and communication protocols and supporting the practice of practically any smart grid use case.

  11. Artful interfaces within biological materials

    Directory of Open Access Journals (Sweden)

    John W.C. Dunlop

    2011-03-01

    Full Text Available Biological materials have a wide range of mechanical properties matching their biological function. This is achieved via complex structural hierarchies, spanning many length scales, arising from the assembly of different sized building blocks during growth. The interfaces between these building blocks can increase resistance to fracture, join materials of different character, make them deform more easily and provide motility. While they represent only a tiny fraction of the overall volume, interfaces are essential for the integrity and function of the overall tissue. Understanding their construction principles, often based on specialized molecular assemblies, may change our current thinking about composite materials.

  12. Interface-læring

    DEFF Research Database (Denmark)

    Thorhauge, Sally

    2015-01-01

    Interface-læring er den læringsoplevelse, der kan opstå i grænsefladen mellem to væsensforskellige læringsmiljøer, når de mødes og griber ind i hinanden. Et gymnasium og et museum er eksempler på to sådanne læringsmiljøer. Artiklen præsenterer nogle af de væsentligste resultater fra min ph.d. afh.......d. afhandling Interface Learning - New goals for museum and upper secondary school collaboration (2014)....

  13. Chemical reactions at aqueous interfaces

    Science.gov (United States)

    Vecitis, Chad David

    2009-12-01

    Interfaces or phase boundaries are a unique chemical environment relative to individual gas, liquid, or solid phases. Interfacial reaction mechanisms and kinetics are often at variance with homogeneous chemistry due to mass transfer, molecular orientation, and catalytic effects. Aqueous interfaces are a common subject of environmental science and engineering research, and three environmentally relevant aqueous interfaces are investigated in this thesis: 1) fluorochemical sonochemistry (bubble-water), 2) aqueous aerosol ozonation (gas-water droplet), and 3) electrolytic hydrogen production and simultaneous organic oxidation (water-metal/semiconductor). Direct interfacial analysis under environmentally relevant conditions is difficult, since most surface-specific techniques require relatively `extreme' conditions. Thus, the experimental investigations here focus on the development of chemical reactors and analytical techniques for the completion of time/concentration-dependent measurements of reactants and their products. Kinetic modeling, estimations, and/or correlations were used to extract information on interfacially relevant processes. We found that interfacial chemistry was determined to be the rate-limiting step to a subsequent series of relatively fast homogeneous reactions, for example: 1) Pyrolytic cleavage of the ionic headgroup of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) adsorbed to cavitating bubble-water interfaces during sonolysis was the rate-determining step in transformation to their inorganic constituents carbon monoxide, carbon dioxide, and fluoride; 2) ozone oxidation of aqueous iodide to hypoiodous acid at the aerosol-gas interface is the rate-determining step in the oxidation of bromide and chloride to dihalogens; 3) Electrolytic oxidation of anodic titanol surface groups is rate-limiting for the overall oxidation of organics by the dichloride radical. We also found chemistry unique to the interface, for example: 1

  14. Performance Metrics for Haptic Interfaces

    CERN Document Server

    Samur, Evren

    2012-01-01

    Haptics technology is being used more and more in different applications, such as in computer games for increased immersion, in surgical simulators to create a realistic environment for training of surgeons, in surgical robotics due to safety issues and in mobile phones to provide feedback from user action. The existence of these applications highlights a clear need to understand performance metrics for haptic interfaces and their implications on device design, use and application. Performance Metrics for Haptic Interfaces aims at meeting this need by establishing standard practices for the ev

  15. Usable Interface Design for Everyone

    OpenAIRE

    Castro, Carlos; García, Enrique; Sainz, Beatriz; Burón, Javier; Ramírez, José Miguel; Zato, José Gabriel; Sánchez, Rafael; Bell, John; Alcantud Marín, Francisco

    2010-01-01

    En el diseño de "interfaces para todo el mundo" para los sistemas interactivos, es importante tener en cuenta factores como el costo, el mercado de destino, el estado del medio ambiente,etc. Los interfaces de usuario son fundamentales para el proceso de desarrollo de cualquier aplicación, y su diseño debe estar contemplado desde el principio. De las distintas partes de un sistema (hardware y software), es la interfaz el sistema que permite al usuario el acceso a los recursos informáticos. Lo...

  16. Fluorescent fluid interface position sensor

    Science.gov (United States)

    Weiss, Jonathan D.

    2004-02-17

    A new fluid interface position sensor has been developed, which is capable of optically determining the location of an interface between an upper fluid and a lower fluid, the upper fluid having a larger refractive index than a lower fluid. The sensor functions by measurement, of fluorescence excited by an optical pump beam which is confined within a fluorescent waveguide where that waveguide is in optical contact with the lower fluid, but escapes from the fluorescent waveguide where that waveguide is in optical contact with the upper fluid.

  17. Magnetoelectric interfaces and spin transport.

    Science.gov (United States)

    Burton, J D; Tsymbal, E Y

    2012-10-28

    Engineered heterostructures designed for electric control of magnetic properties, the so-called magnetoelectric interfaces, present a novel route towards using the spin degree of freedom in electronic devices. Here, we review how a subset of such interfaces, namely ferromagnet-ferroelectric heterostructures, display electronically mediated control of magnetism and, in particular, emphasis is placed on how these effects manifest themselves as detectable spin-dependent transport phenomena. Examples of these effects are given for a variety of material systems on the basis of ferroelectric oxides, manganese and ruthenium magnetic complex oxides and elemental ferromagnetic metals. Results from both theory and experiment are discussed. PMID:22987031

  18. Coordinating user interfaces for consistency

    CERN Document Server

    Nielsen, Jakob

    2001-01-01

    In the years since Jakob Nielsen's classic collection on interface consistency first appeared, much has changed, and much has stayed the same. On the one hand, there's been exponential growth in the opportunities for following or disregarding the principles of interface consistency-more computers, more applications, more users, and of course the vast expanse of the Web. On the other, there are the principles themselves, as persistent and as valuable as ever. In these contributed chapters, you'll find details on many methods for seeking and enforcing consistency, along with bottom-line analys

  19. Interface solitons in thermal nonlinear media

    OpenAIRE

    Ma, Xuekai; Yang, Zhenjun; Lu, Daquan; Hu, Wei

    2011-01-01

    We demonstrate the existence of fundamental and dipole interface solitons in one-dimensional thermal nonlinear media with a step in linear refractive index. Fundamental interface solitons are found to be always stable and the stability of dipole interface solitons depends on the difference in linear refractive index. The mass center of interface solitons always locates in the side with higher index. Two intensity peaks of dipole interface solitons are unequal except some specific conditions, ...

  20. BASIN: Beowulf Analysis Symbolic INterface

    Science.gov (United States)

    Vesperini, Enrico; Goldberg, David M.; McMillan, Stephen L. W.; Dura, James; Jones, Douglas

    2013-08-01

    BASIN (Beowulf Analysis Symbolic INterface) is a flexible, integrated suite of tools for multiuser parallel data analysis and visualization that allows researchers to harness the power of Beowulf PC clusters and multi-processor machines without necessarily being experts in parallel programming. It also includes general tools for data distribution and parallel operations on distributed data for developing libraries for specific tasks.

  1. Web OPAC Interfaces: An Overview.

    Science.gov (United States)

    Babu, B. Ramesh; O'Brien, Ann

    2000-01-01

    Discussion of Web-based online public access catalogs (OPACs) focuses on a review of six Web OPAC interfaces in use in academic libraries in the United Kingdom. Presents a checklist and guidelines of important features and functions that are currently available, including search strategies, access points, display, links, and layout. (Author/LRW)

  2. Gluing Soft Interfaces by Nanoparticles

    Science.gov (United States)

    Cao, Zhen; Dobrynin, Andrey

    Using a combination of the molecular dynamics simulations and scaling analysis we studied reinforcement of interface between two soft gel-like materials by spherical nanoparticles. Analysis of the simulations shows that the depth of penetration of a nanoparticle into a gel is determined by a balance of the elastic energy of the gel and nanoparticle deformations and the surface energy of nanoparticle/gel interface. In order to evaluate work of adhesion of the reinforced interface, the potential of mean force for separation of two gels was calculated. These simulations showed that the gel separation proceeds through formation of necks connecting nanoparticle with two gels. The shapes of the necks are controlled by a fine interplay between nanoparticle/gel surface energies and elastic energy of the neck deformation. Our simulations showed that by introducing nanoparticles at soft interfaces, the work required for separation of two gels could be 10-100 times larger than the work of adhesion between two gels without nanoparticle reinforcement. These results provide insight in understanding the mechanism of gluing soft gels and biological tissues by nano- and micro-sized particles. NSF DMR-1409710.

  3. Wheel/rail interface optimisation

    NARCIS (Netherlands)

    Shevtsov, I.Y.

    2008-01-01

    In this thesis, wheel/rail interface optimisation, and particularly the problems of wheel and rail profile design are considered. The research task pursued by this thesis engenders investigation of a range of problems. First, geometric properties of contact between wheel and rail are investigated. T

  4. Surface Waves on Metamaterials Interfaces

    DEFF Research Database (Denmark)

    Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee;

    2016-01-01

    We analyze surface electromagnetic waves supported at the interface between isotropic medium and effective anisotropic material that can be realized by alternating conductive and dielectrics layers. This configuration can host various types of surface waves and therefore can serve as a rich platf...

  5. Human-computer interface design

    Energy Technology Data Exchange (ETDEWEB)

    Bowser, S.E.

    1995-04-01

    Modern military forces assume that computer-based information is reliable, timely, available, usable, and shared. The importance of computer-based information is based on the assumption that {open_quotes}shared situation awareness, coupled with the ability to conduct continuous operations, will allow information age armies to observe, decide, and act faster, more correctly and more precisely than their enemies.{close_quotes} (Sullivan and Dubik 1994). Human-Computer Interface (HCI) design standardization is critical to the realization of the previously stated assumptions. Given that a key factor of a high-performance, high-reliability system is an easy-to-use, effective design of the interface between the hardware, software, and the user, it follows logically that the interface between the computer and the military user is critical to the success of the information-age military. The proliferation of computer technology has resulted in the development of an extensive variety of computer-based systems and the implementation of varying HCI styles on these systems. To accommodate the continued growth in computer-based systems, minimize HCI diversity, and improve system performance and reliability, the U.S. Department of Defense (DoD) is continuing to adopt interface standards for developing computer-based systems.

  6. Embodied agents in de interface

    NARCIS (Netherlands)

    Evers, M.J.; Nijholt, A.

    2001-01-01

    Steeds meer zien we het gebruik van mensachtige, geanimeerde figuren in interfaces en andere software applicaties, niet alleen in onderzoeksprojecten maar ook in commerciële software. Een voorbeeld dat bijna iedereen wel kent (en waar velen wel wat op aan te merken hebben) is de ‘office assistant’ i

  7. Miniaturized neural interfaces and implants

    Science.gov (United States)

    Stieglitz, Thomas; Boretius, Tim; Ordonez, Juan; Hassler, Christina; Henle, Christian; Meier, Wolfgang; Plachta, Dennis T. T.; Schuettler, Martin

    2012-03-01

    Neural prostheses are technical systems that interface nerves to treat the symptoms of neurological diseases and to restore sensory of motor functions of the body. Success stories have been written with the cochlear implant to restore hearing, with spinal cord stimulators to treat chronic pain as well as urge incontinence, and with deep brain stimulators in patients suffering from Parkinson's disease. Highly complex neural implants for novel medical applications can be miniaturized either by means of precision mechanics technologies using known and established materials for electrodes, cables, and hermetic packages or by applying microsystems technologies. Examples for both approaches will be introduced and discussed. Electrode arrays for recording of electrocorticograms during presurgical epilepsy diagnosis have been manufactured using approved materials and a marking laser to achieve an integration density that is adequate in the context of brain machine interfaces, e.g. on the motor cortex. Microtechnologies have to be used for further miniaturization to develop polymer-based flexible and light weighted electrode arrays to interface the peripheral and central nervous system. Polyimide as substrate and insulation material will be discussed as well as several application examples for nerve interfaces like cuffs, filament like electrodes and large arrays for subdural implantation.

  8. Emotional brain-computer interfaces

    NARCIS (Netherlands)

    Garcia Molina, G.; Tsoneva, T.; Nijholt, A.; Nijholt, A.; Heylen, D.K.J.

    2013-01-01

    Research in brain-computer interface (BCI) has significantly increased during the last few years. Additionally to their initial role as assisting devices for the physically challenged, BCIs are now proposed for a wider range of applications. As any human-machine interaction system, BCIs can benefit

  9. Graphical fiber shaping control interface

    Science.gov (United States)

    Basso, Eric T.; Ninomiya, Yasuyuki

    2016-03-01

    In this paper, we present an improved graphical user interface for defining single-pass novel shaping techniques on glass processing machines that allows for streamlined process development. This approach offers unique modularity and debugging capability to researchers during the process development phase not usually afforded with similar scripting languages.

  10. Polymer matrix and graphite fiber interface study

    Science.gov (United States)

    Adams, D. F.; Zimmerman, R. S.; Odom, E. M.

    1985-01-01

    Hercules AS4 graphite fiber, unsized, or with EPON 828, PVA, or polysulfone sizing, was combined with three different polymer matrices. These included Hercules 3501-6 epoxy, Hercules 4001 bismaleimide, and Hexcel F155 rubber toughened epoxy. Unidirectional composites in all twelve combinations were fabricated and tested in transverse tension and axial compression. Quasi-isotropic laminates were tested in axial tension and compression, flexure, interlaminar shear, and tensile impact. All tests were conducted at both room temperature, dry and elevated temperature, and wet conditions. Single fiber pullout testing was also performed. Extensive scanning electron microphotographs of fracture surfaces are included, along with photographs of single fiber pullout failures. Analytical/experimental correlations are presented, based on the results of a finite element micromechanics analysis. Correlations between matrix type, fiber sizing, hygrothermal environment, and loading mode are presented. Results indicate that the various composite properties were only moderately influenced by the fiber sizings utilized.

  11. A sharp interface method for SPH

    Science.gov (United States)

    Zhang, Mingyu; Deng, Xiao-Long

    2015-12-01

    A sharp interface method (SIM) for smoothed particle hydrodynamics (SPH) has been developed to simulate two-phase flows with clear interfaces. The level set function is introduced to capture the interface implicitly. The interface velocity is used to evolve the level set function. The smoothness of the level set function helps to improve the accuracy of the interface curvature. Material discontinuity across the interface is dealt with by the ghost fluid method. The interface states are calculated by applying the jump conditions and are extended to the corresponding ghost fluid particles. The ghost fluid method helps to get smooth and stable calculation near the interface. The performance of the developed method is validated by benchmark tests. The developed SIM for SPH can be applied to simulate low speed two-phase flows of high density ratios with clear interface accurately and stably.

  12. MIB Galerkin method for elliptic interface problems.

    Science.gov (United States)

    Xia, Kelin; Zhan, Meng; Wei, Guo-Wei

    2014-12-15

    Material interfaces are omnipresent in the real-world structures and devices. Mathematical modeling of material interfaces often leads to elliptic partial differential equations (PDEs) with discontinuous coefficients and singular sources, which are commonly called elliptic interface problems. The development of high-order numerical schemes for elliptic interface problems has become a well defined field in applied and computational mathematics and attracted much attention in the past decades. Despite of significant advances, challenges remain in the construction of high-order schemes for nonsmooth interfaces, i.e., interfaces with geometric singularities, such as tips, cusps and sharp edges. The challenge of geometric singularities is amplified when they are associated with low solution regularities, e.g., tip-geometry effects in many fields. The present work introduces a matched interface and boundary (MIB) Galerkin method for solving two-dimensional (2D) elliptic PDEs with complex interfaces, geometric singularities and low solution regularities. The Cartesian grid based triangular elements are employed to avoid the time consuming mesh generation procedure. Consequently, the interface cuts through elements. To ensure the continuity of classic basis functions across the interface, two sets of overlapping elements, called MIB elements, are defined near the interface. As a result, differentiation can be computed near the interface as if there is no interface. Interpolation functions are constructed on MIB element spaces to smoothly extend function values across the interface. A set of lowest order interface jump conditions is enforced on the interface, which in turn, determines the interpolation functions. The performance of the proposed MIB Galerkin finite element method is validated by numerical experiments with a wide range of interface geometries, geometric singularities, low regularity solutions and grid resolutions. Extensive numerical studies confirm the

  13. Technique for converting non-conforming hexahedral-to-hexahedral interfaces into conforming interfaces

    Science.gov (United States)

    Staten, Matthew L.; Shepherd, Jason F.; Ledoux, Frank; Shimada, Kenji; Merkley, Karl G.; Carbonera, Carlos

    2013-03-05

    A technique for conforming an interface between a first mesh and a second mesh is disclosed. A first interface surface in the first mesh and a second interface surface in the second mesh residing along the interface are identified. The first and second interface surfaces are initially non-conforming along the interface. Chords within the first and second interface surfaces that fall within a threshold separation distance of each other are paired. Sheets having chords that reside within the first or second interface surfaces are recursively inserted into or extracted from one or both of the first and second meshes until all remaining chords within the first interface surface are paired with corresponding chords in the second interface surface and all remaining chords within the second interface surface are paired with corresponding chords in the first interface surface.

  14. Through the Interface - a human activity approach to user interfaces

    DEFF Research Database (Denmark)

    Bødker, Susanne

    In providing a theoretical framework for understanding human- computer interaction as well as design of user interfaces, this book combines elements of anthropology, psychology, cognitive science, software engineering, and computer science. The framework examines the everyday work practices...... of users when analyzing and designing computer applications. The text advocates the unique theory that computer application design is fundamentally a collective activity in which the various practices of the participants meet in a process of mutual learning....

  15. ACPYPE - AnteChamber PYthon Parser interfacE

    Directory of Open Access Journals (Sweden)

    Sousa da Silva Alan W

    2012-07-01

    Full Text Available Abstract Background ACPYPE (or AnteChamber PYthon Parser interfacE is a wrapper script around the ANTECHAMBER software that simplifies the generation of small molecule topologies and parameters for a variety of molecular dynamics programmes like GROMACS, CHARMM and CNS. It is written in the Python programming language and was developed as a tool for interfacing with other Python based applications such as the CCPN software suite (for NMR data analysis and ARIA (for structure calculations from NMR data. ACPYPE is open source code, under GNU GPL v3, and is available as a stand-alone application at http://www.ccpn.ac.uk/acpype and as a web portal application at http://webapps.ccpn.ac.uk/acpype. Findings We verified the topologies generated by ACPYPE in three ways: by comparing with default AMBER topologies for standard amino acids; by generating and verifying topologies for a large set of ligands from the PDB; and by recalculating the structures for 5 protein–ligand complexes from the PDB. Conclusions ACPYPE is a tool that simplifies the automatic generation of topology and parameters in different formats for different molecular mechanics programmes, including calculation of partial charges, while being object oriented for integration with other applications.

  16. The Integrated Mode Management Interface

    Science.gov (United States)

    Hutchins, Edwin

    1996-01-01

    Mode management is the processes of understanding the character and consequences of autoflight modes, planning and selecting the engagement, disengagement and transitions between modes, and anticipating automatic mode transitions made by the autoflight system itself. The state of the art is represented by the latest designs produced by each of the major airframe manufacturers, the Boeing 747-400, the Boeing 777, the McDonnell Douglas MD-11, and the Airbus A320/A340 family of airplanes. In these airplanes autoflight modes are selected by manipulating switches on the control panel. The state of the autoflight system is displayed on the flight mode annunciators. The integrated mode management interface (IMMI) is a graphical interface to autoflight mode management systems for aircraft equipped with flight management computer systems (FMCS). The interface consists of a vertical mode manager and a lateral mode manager. Autoflight modes are depicted by icons on a graphical display. Mode selection is accomplished by touching (or mousing) the appropriate icon. The IMMI provides flight crews with an integrated interface to autoflight systems for aircraft equipped with flight management computer systems (FMCS). The current version is modeled on the Boeing glass-cockpit airplanes (747-400, 757/767). It runs on the SGI Indigo workstation. A working prototype of this graphics-based crew interface to the autoflight mode management tasks of glass cockpit airplanes has been installed in the Advanced Concepts Flight Simulator of the CSSRF of NASA Ames Research Center. This IMMI replaces the devices in FMCS equipped airplanes currently known as mode control panel (Boeing), flight guidance control panel (McDonnell Douglas), and flight control unit (Airbus). It also augments the functions of the flight mode annunciators. All glass cockpit airplanes are sufficiently similar that the IMMI could be tailored to the mode management system of any modern cockpit. The IMMI does not replace the

  17. Interface

    DEFF Research Database (Denmark)

    kulturhistoriske udviklingsfaser. Den tegner også et billede af, hvordan interfacet forandrer vores musikkultur, og hvordan de digitale kunstværker udfordrer vores økonomi og jura. Interfacet er vor tids drøm om gennemsigtighed, om at nå ind bag formidlingen. Det er dog også andet og mere end funktionel teknologi...

  18. The interface at the skin

    DEFF Research Database (Denmark)

    Hansen, Lone Koefoed

    2011-01-01

    In the development of and discourses around interfaces there has always been a strong urge to bypass representation and ‘jack’ directly in to the human brain, consciousness, perceptions and feelings. In her article ”The interface at the skin” Lone Koefoed Hansen looks at how two contemporary...... experimental dresses made by Philips within the field of wearable computing subscribe to the concept of ‘ideal communication’. In her article, she explains how this particular type of communication is linked to the paranormal phenomena of mind reading and telepathy, and argues that sensor-based wearable...... computing is the newest example of a technological development implicitly or explicitly aiming at manifesting two utopian parameters of communication: immediacy and instantaneity. Though utopian, this manifestation has served as a way to brand Philips “as a highly innovative and remarkable company”....

  19. IVOA Recommendation: IVOA Support Interfaces

    CERN Document Server

    Graham, Matthew; Grid,

    2011-01-01

    This document describes the minimum interface that a (SOAP- or REST-based) web service requires to participate in the IVOA. Note that this is not required of standard VO services developed prior to this specification, although uptake is strongly encouraged on any subsequent revision. All new standard VO services, however, must feature a VOSI-compliant interface. This document has been produced by the Grid and Web Services Working Group. It has been reviewed by IVOA Members and other interested parties, and has been endorsed by the IVOA Executive Committee as an IVOA Recommendation. It is a stable document and may be used as reference material or cited as a normative reference from another document. IVOA's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability inside the Astronomical Community.

  20. Soft matter at aqueous interfaces

    CERN Document Server

    Liu, Yi

    2016-01-01

    This book covers the science of interfaces between an aqueous phase and a solid, another liquid or a gaseous phase, starting from the basic physical chemistry all the way to state-of-the-art research developments. Both experimental and theoretical methods are treated thanks to the contributions of a distinguished list of authors who are all active researchers in their respective fields. The properties of these interfaces are crucial for a wide variety of processes, products and biological systems and functions, such as the formulation of personal care and food products, paints and coatings, microfluidic and lab-on-a-chip applications, cell membranes, and lung surfactants. Accordingly, research and expertise on the subject are spread over a broad range of academic disciplines and industrial laboratories. This book brings together knowledge from these different places with the aim of fostering education, collaborations and research progress.