WorldWideScience

Sample records for monotonic mechanical properties

  1. Interface failure modes explain non-monotonic size-dependent mechanical properties in bioinspired nanolaminates

    Science.gov (United States)

    Song, Z. Q.; Ni, Y.; Peng, L. M.; Liang, H. Y.; He, L. H.

    2016-03-01

    Bioinspired discontinuous nanolaminate design becomes an efficient way to mitigate the strength-ductility tradeoff in brittle materials via arresting the crack at the interface followed by controllable interface failure. The analytical solution and numerical simulation based on the nonlinear shear-lag model indicates that propagation of the interface failure can be unstable or stable when the interfacial shear stress between laminae is uniform or highly localized, respectively. A dimensionless key parameter defined by the ratio of two characteristic lengths governs the transition between the two interface-failure modes, which can explain the non-monotonic size-dependent mechanical properties observed in various laminate composites.

  2. Limit properties of monotone matrix functions

    NARCIS (Netherlands)

    Behrndt, Jussi; Hassi, Seppo; de Snoo, Henk; Wietsma, Rudi

    2012-01-01

    The basic objects in this paper are monotonically nondecreasing n x n matrix functions D(center dot) defined on some open interval l = (a, b) of R and their limit values D(a) and D(b) at the endpoints a and b which are, in general, selfadjoint relations in C-n. Certain space decompositions induced b

  3. Monotonic Property in Field Algebra of G-Spin Model

    Institute of Scientific and Technical Information of China (English)

    蒋立宁

    2003-01-01

    Let F be the field algebra of G-spin model, D(G) the double algebra of a finite group G and D(H) the sub-Hopf algerba of D(G) determined by the subgroup H of G. The paper builds a correspondence between D(H) and the D(H)-invariant sub-C*-algebra AH in F, and proves that the correspondence is strictly monotonic.

  4. Inhibitory properties underlying non-monotonic input-output relationship in low-frequency spherical bushy neurons of the gerbil.

    Science.gov (United States)

    Kuenzel, Thomas; Nerlich, Jana; Wagner, Hermann; Rübsamen, Rudolf; Milenkovic, Ivan

    2015-01-01

    Spherical bushy cells (SBCs) of the anteroventral cochlear nucleus (AVCN) receive input from large excitatory auditory nerve (AN) terminals, the endbulbs of Held, and mixed glycinergic/GABAergic inhibitory inputs. The latter have sufficient potency to block action potential firing in vivo and in slice recordings. However, it is not clear how well the data from slice recordings match the inhibition in the intact brain and how it contributes to complex phenomena such as non-monotonic rate-level functions (RLF). Therefore, we determined the input-output relationship of a model SBC with simulated endbulb inputs and a dynamic inhibitory conductance constrained by recordings in brain slice preparations of hearing gerbils. Event arrival times from in vivo single-unit recordings in gerbils, where 70% of SBC showed non-monotonic RLF, were used as input for the model. Model output RLFs systematically changed from monotonic to non-monotonic shape with increasing strength of tonic inhibition. A limited range of inhibitory synaptic properties consistent with the slice data generated a good match between the model and recorded RLF. Moreover, tonic inhibition elevated the action potentials (AP) threshold and improved the temporal precision of output functions in a SBC model with phase-dependent input conductance. We conclude that activity-dependent, summating inhibition contributes to high temporal precision of SBC spiking by filtering out weak and poorly timed EPSP. Moreover, inhibitory parameters determined in slice recordings provide a good estimate of inhibitory mechanisms apparently active in vivo.

  5. Comparison of boundedness and monotonicity properties of one-leg and linear multistep methods

    KAUST Repository

    Mozartova, A.

    2015-05-01

    © 2014 Elsevier B.V. All rights reserved. One-leg multistep methods have some advantage over linear multistep methods with respect to storage of the past results. In this paper boundedness and monotonicity properties with arbitrary (semi-)norms or convex functionals are analyzed for such multistep methods. The maximal stepsize coefficient for boundedness and monotonicity of a one-leg method is the same as for the associated linear multistep method when arbitrary starting values are considered. It will be shown, however, that combinations of one-leg methods and Runge-Kutta starting procedures may give very different stepsize coefficients for monotonicity than the linear multistep methods with the same starting procedures. Detailed results are presented for explicit two-step methods.

  6. Complete Monotonicity of a Difference Between the Exponential and Trigamma Functions and Properties Related to a Modified Bessel Function

    DEFF Research Database (Denmark)

    Qi, Feng; Berg, Christian

    2013-01-01

    In the paper, the authors find necessary and sufficient conditions for a difference between the exponential function αeβ/t, α, β > 0, and the trigamma function ψ (t) to be completely monotonic on (0,∞). While proving the complete onotonicity, the authors discover some properties related to the fi...... to the first order modified Bessel function of the first kind I1, including inequalities, monotonicity, unimodality, and convexity....

  7. Effects of temperature on monotonic and fatigue properties of carbon fibre epoxy cross ply laminates

    OpenAIRE

    Matsuhisa, Y.; King, J.

    1993-01-01

    The effects of test temperature on damage accumulation behaviour has been studied using "Torayca" T800H / #3631 in conditions of monotonic and fatigue loading. The damage accumulation behaviour was found to vary as a function of the test temperature, with the effect of temperature on the damage behaviour being different between monotonic and fatigue loading.

  8. Effects of temperature on monotonic and fatigue properties of carbon fibre epoxy cross ply laminates

    Energy Technology Data Exchange (ETDEWEB)

    Matsuhisa, Y. (Composite Materials Research Labs., Toray Industries Inc., Ehime (Japan)); King, J.E. (Composite Materials Research Labs., Toray Industries Inc., Ehime (Japan) Dept. of Materials Science and Metallurgy, Univ. of Cambridge (United Kingdom))

    1993-11-01

    The effects of test temperature on damage accumulation behaviour has been studied using ''Torayca'' T800H/[3631] in conditions of monotonic and fatigue loading. The damage accumulation behaviour was found to vary as a function of the test temperature, with the effect of temperature on the damage behaviour being different between monotonic and fatigue loading. (orig.).

  9. Monotone partitions and almost partitions

    NARCIS (Netherlands)

    Bonanzinga, M.; Cammaroto, F.; van Mill, J.; Pansera, B.A.

    2014-01-01

    In this paper we are interested in monotone versions of partitionability of topological spaces and weak versions thereof. We identify several classes of spaces with these properties by constructing trees of open sets with various properties.

  10. MONOTONIZATION IN GLOBAL OPTIMIZATION

    Institute of Scientific and Technical Information of China (English)

    WU ZHIYOU; BAI FUSHENG; ZHANG LIANSHENG

    2005-01-01

    A general monotonization method is proposed for converting a constrained programming problem with non-monotone objective function and monotone constraint functions into a monotone programming problem. An equivalent monotone programming problem with only inequality constraints is obtained via this monotonization method. Then the existingconvexification and concavefication methods can be used to convert the monotone programming problem into an equivalent better-structured optimization problem.

  11. Monotone Increasing Properties and Their Phase Transitions in Uniform Random Intersection Graphs

    CERN Document Server

    Zhao, Jun; Gligor, Virgil

    2015-01-01

    Uniform random intersection graphs have received much interest and been used in diverse applications. A uniform random intersection graph with $n$ nodes is constructed as follows: each node selects a set of $K_n$ different items uniformly at random from the same pool of $P_n$ distinct items, and two nodes establish an undirected edge in between if and only if they share at least one item. For such graph denoted by $G(n, K_n, P_n)$, we present the following results in this paper. First, we provide an exact analysis on the probabilities of $G(n, K_n, P_n)$ having a perfect matching and having a Hamilton cycle respectively, under $P_n = \\omega\\big(n (\\ln n)^5\\big)$ (all asymptotic notation are understood with $n \\to \\infty$). The analysis reveals that just like ($k$-)connectivity shown in prior work, for both properties of perfect matching containment and Hamilton cycle containment, $G(n, K_n, P_n)$ also exhibits phase transitions: for each property above, as $K_n$ increases, the limit of the probability that $G...

  12. Mechanical Behavior of AZ31B Mg Alloy Sheets under Monotonic and Cyclic Loadings at Room and Moderately Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Ngoc-Trung Nguyen

    2014-02-01

    Full Text Available Large-strain monotonic and cyclic loading tests of AZ31B magnesium alloy sheets were performed with a newly developed testing system, at different temperatures, ranging from room temperature to 250 °C. Behaviors showing significant twinning during initial in-plane compression and untwinning in subsequent tension at and slightly above room temperature were recorded. Strong yielding asymmetry and nonlinear hardening behavior were also revealed. Considerable Bauschinger effects, transient behavior, and variable permanent softening responses were observed near room temperature, but these were reduced and almost disappeared as the temperature increased. Different stress–strain responses were inherent to the activation of twinning at lower temperatures and non-basal slip systems at elevated temperatures. A critical temperature was identified to account for the transition between the twinning-dominant and slip-dominant deformation mechanisms. Accordingly, below the transition point, stress–strain curves of cyclic loading tests exhibited concave-up shapes for compression or compression following tension, and an unusual S-shape for tension following compression. This unusual shape disappeared when the temperature was above the transition point. Shrinkage of the elastic range and variation in Young’s modulus due to plastic strain deformation during stress reversals were also observed. The texture-induced anisotropy of both the elastic and plastic behaviors was characterized experimentally.

  13. Monotonicity-preserving linear multistep methods

    NARCIS (Netherlands)

    Hundsdorfer, W.; Ruuth, S.J.; Spiteri, R.J.

    2002-01-01

    In this paper we provide an analysis of monotonicity properties for linear multistep methods. These monotonicity properties include positivity and the diminishing of total variation. We also pay particular attention to related boundedness properties such as the total-variation-bounded (TVB) property

  14. Monotone Boolean approximation

    Energy Technology Data Exchange (ETDEWEB)

    Hulme, B.L.

    1982-12-01

    This report presents a theory of approximation of arbitrary Boolean functions by simpler, monotone functions. Monotone increasing functions can be expressed without the use of complements. Nonconstant monotone increasing functions are important in their own right since they model a special class of systems known as coherent systems. It is shown here that when Boolean expressions for noncoherent systems become too large to treat exactly, then monotone approximations are easily defined. The algorithms proposed here not only provide simpler formulas but also produce best possible upper and lower monotone bounds for any Boolean function. This theory has practical application for the analysis of noncoherent fault trees and event tree sequences.

  15. 单调q矩阵的Feller性质%The Feller Property for the Monotone q-Matrix

    Institute of Scientific and Technical Information of China (English)

    张秀珍; 李扬荣

    2011-01-01

    In this paper, a necessary and sufficient condition for a monotone q-matrix Q to be Feller is given in terms of (Q), where (Q) is the dual of 2. Then, the authors further point out that the minimal (Q)-function (P)(t) is the dual for the minimal Q-function P(t) if Q is monotone and zero-exit.%给出了单调q-矩阵Q是Feller的充分必要条件,进一步指出:若q-矩阵Q是单调零流出的且(Q)是Q的对偶,则最小(Q)-函数(Q)(t)是最小(Q)-函数P(t)的对偶.

  16. Mechanical properties of viruses.

    Science.gov (United States)

    de Pablo, Pedro J; Mateu, Mauricio G

    2013-01-01

    Structural biology techniques have greatly contributed to unveil the relationships between structure, properties and functions of viruses. In recent years, classic structural approaches are being complemented by single-molecule techniques such as atomic force microscopy and optical tweezers to study physical properties and functions of viral particles that are not accessible to classic structural techniques. Among these features are mechanical properties such as stiffness, intrinsic elasticity, tensile strength and material fatigue. The field of virus mechanics is contributing to materials science by investigating some physical parameters of "soft" biological matter and biological nano-objects. Virus mechanics studies are also starting to unveil the biological implications of physical properties of viruses. Growing evidence indicate that viruses are subjected to internal and external forces, and that they may have adapted to withstand and even use those forces. This chapter describes what is known on the mechanical properties of virus particles, their structural determinants, and possible biological implications, of which several examples are provided.

  17. Monotone Boolean functions

    Energy Technology Data Exchange (ETDEWEB)

    Korshunov, A D [S.L. Sobolev Institute for Mathematics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2003-10-31

    Monotone Boolean functions are an important object in discrete mathematics and mathematical cybernetics. Topics related to these functions have been actively studied for several decades. Many results have been obtained, and many papers published. However, until now there has been no sufficiently complete monograph or survey of results of investigations concerning monotone Boolean functions. The object of this survey is to present the main results on monotone Boolean functions obtained during the last 50 years.

  18. Version Spaces and Generalized Monotone Boolean Functions

    NARCIS (Netherlands)

    J.C. Bioch (Cor); T. Ibaraki

    2002-01-01

    textabstractWe consider generalized monotone functions f: X --> {0,1} defined for an arbitrary binary relation <= on X by the property x <= y implies f(x) <= f(y). These include the standard monotone (or positive) Boolean functions, regular Boolean functions and other interesting functions as speci

  19. Version Spaces and Generalized Monotone Boolean Functions

    NARCIS (Netherlands)

    J.C. Bioch (Cor); T. Ibaraki

    2002-01-01

    textabstractWe consider generalized monotone functions f: X --> {0,1} defined for an arbitrary binary relation <= on X by the property x <= y implies f(x) <= f(y). These include the standard monotone (or positive) Boolean functions, regular Boolean functions and other interesting functions as

  20. On the strong monotonicity of the CABARET scheme

    Science.gov (United States)

    Ostapenko, V. V.

    2012-03-01

    The strong monotonicity of the CABARET scheme with single flux correction is analyzed as applied to the linear advection equation. It is shown that the scheme is strongly monotone (has the NED property) at Courant numbers r ∈ (0,0,5), for which it is monotone. Test computations illustrating this property of the CABARET scheme are presented.

  1. Testing Monotonicity of Pricing Kernels

    OpenAIRE

    Timofeev, Roman

    2007-01-01

    In this master thesis a mechanism to test mononicity of empirical pricing kernels (EPK) is presented. By testing monotonicity of pricing kernel we can determine whether utility function is concave or not. Strictly decreasing pricing kernel corresponds to concave utility function while non-decreasing EPK means that utility function contains some non-concave regions. Risk averse behavior is usually described by concave utility function and considered to be a cornerstone of classical behavioral ...

  2. Mechanical Properties of Transcription

    Science.gov (United States)

    Sevier, Stuart A.; Levine, Herbert

    2017-06-01

    The mechanical properties of transcription have recently been shown to play a central role in gene expression. However, a full physical characterization of this central biological process is lacking. In this Letter, we introduce a simple description of the basic physical elements of transcription where RNA elongation, RNA polymerase rotation, and DNA supercoiling are coupled. The resulting framework describes the relative amount of RNA polymerase rotation and DNA supercoiling that occurs during RNA elongation. Asymptotic behavior is derived and can be used to experimentally extract unknown mechanical parameters of transcription. Mechanical limits to transcription are incorporated through the addition of a DNA supercoiling-dependent RNA polymerase velocity. This addition can lead to transcriptional stalling and resulting implications for gene expression, chromatin structure and genome organization are discussed.

  3. Concerns on Monotonic Imbalance Bounding Matching Methods

    OpenAIRE

    Yatracos, Yannis G.

    2013-01-01

    Concerns are expressed for the Monotonic Imbalance Bounding (MIB) property (Iacus et al. 2011) and for MIB matching because i) the definition of the MIB property leads to inconsistencies and the nature of the imbalance measure is not clearly defined, ii) MIB property does not generalize Equal Percent Bias Reducing (EPBR) property, iii) MIB matching does not provide statistical information available with EPBR matching.

  4. Mechanical Properties of Cells

    Science.gov (United States)

    Bradley, Robert; Becerril, Joseph; Jeevarajan, Anthony

    2007-01-01

    Many physiologic and pathologic processes alter the biomechanical properties of the tissue they affect, and these changes may be manifest at the single cell level. The normal and abnormal mechanical properties of a given cell type can be established with the aid of an atomic force microscope (AFM), nonetheless, consistency in the area of the tip has been a mayor limitation of using the AFM for quantitative measurements of mechanical properties. This project attempts to overcome this limitation by using materials with a known elastic modulus, which resembles the one of the cell, to create force-deformation curves to calculate the area of indentation by means of Hooke s Law (sigma = E(epsilon)), which states that stress (sigma) is proportional to the strain (epsilon) where the constant of proportionality, E, is called the Young s modulus, also referred as the elastic modulus. Hook s Law can be rearranged to find the area of indentation (Area= Force/ E(epsilon)), where the indentation force is defined by the means of the added mass spring calibration method.

  5. Mechanical Properties of Cells

    Science.gov (United States)

    Bradley, Robert; Becerril, Joseph; Jeevarajan, Anthony

    2007-01-01

    Many physiologic and pathologic processes alter the biomechanical properties of the tissue they affect, and these changes may be manifest at the single cell level. The normal and abnormal mechanical properties of a given cell type can be established with the aid of an atomic force microscope (AFM), nonetheless, consistency in the area of the tip has been a mayor limitation of using the AFM for quantitative measurements of mechanical properties. This project attempts to overcome this limitation by using materials with a known elastic modulus, which resembles the one of the cell, to create force-deformation curves to calculate the area of indentation by means of Hooke s Law (sigma = E(epsilon)), which states that stress (sigma) is proportional to the strain (epsilon) where the constant of proportionality, E, is called the Young s modulus, also referred as the elastic modulus. Hook s Law can be rearranged to find the area of indentation (Area= Force/ E(epsilon)), where the indentation force is defined by the means of the added mass spring calibration method.

  6. Viable harvest of monotone bioeconomic models

    CERN Document Server

    De Lara, Michel; Cabrera, Hector Ramirez

    2009-01-01

    Some monospecies age class models, as well as specific multi-species models (with so-called technical interactions), exhibit useful monotonicity properties. This paper deals with discrete time monotone bioeconomics dynamics in the presence of state and control constraints. In practice, these latter ``acceptable configurations'' represent production and preservation requirements to be satisfied for all time, and they also possess monotonicity properties. A state $\\state$ is said to belong to the viability kernel if there exists a trajectory, of states and controls, starting from $\\state$ and satisfying the constraints. Under monotonicity assumptions, we present upper and lower estimates of the viability kernel. This helps delineating domains where a viable management is possible. Numerical examples, in the context of fisheries management, for the Chilean sea bass (\\emph{Dissostichus eleginoides}) and Alfonsino (\\emph{Beryx splendens}) are given.

  7. 加权分支过程的单调性、对偶性和Feller性质%The Monotonicity, Duality and Feller Property of Weighted Markov Branching Process

    Institute of Scientific and Technical Information of China (English)

    丁水琴; 李扬荣

    2008-01-01

    In this paper, the monotonicity, duality and Feller property of weighted Markov branching processes are studied and some necessary and sufficient conditions for the minimal Q-function being an monotone or dual transition function are obtained, where Q is a weighted Markov branching q-matrix. Especially, Feller criteria are obtained when Q is neither dual nor monotone.%研究加权分支过程的单调性, 对偶性以及Feller性质, 并得到了加权分支q矩阵的最小Q函数成为单调或对偶时的充要条件, 特别是得到了当Q既不对偶也不单调时的Feller准则.

  8. Mechanical properties of ceramics

    CERN Document Server

    Pelleg, Joshua

    2014-01-01

    This book discusses the mechanical properties of ceramics and aims to provide both a solid background for undergraduate students, as well as serving as a text to bring practicing engineers up to date with the latest developments in this topic so they can use and apply these to their actual engineering work.  Generally, ceramics are made by moistening a mixture of clays, casting it into desired shapes and then firing it to a high temperature, a process known as 'vitrification'. The relatively late development of metallurgy was contingent on the availability of ceramics and the know-how to mold them into the appropriate forms. Because of the characteristics of ceramics, they offer great advantages over metals in specific applications in which hardness, wear resistance and chemical stability at high temperatures are essential. Clearly, modern ceramics manufacturing has come a long way from the early clay-processing fabrication method, and the last two decades have seen the development of sophisticated technique...

  9. Mechanical Property of Foamed Metal

    Institute of Scientific and Technical Information of China (English)

    LIU Pei-sheng; SANG Hai-bo

    2004-01-01

    A comprehensive study on the mechanical behavior of foamed metals was demonstrated. The relationship among their mechanical properties, preparation method, porosity and the structure was briefly studied as well.

  10. Free Monotone Transport

    CERN Document Server

    Guionnet, A

    2012-01-01

    By solving a free analog of the Monge-Amp\\`ere equation, we prove a non-commutative analog of Brenier's monotone transport theorem: if an $n$-tuple of self-adjoint non-commutative random variables $Z_{1},...,Z_{n}$ satisfies a regularity condition (its conjugate variables $\\xi_{1},...,\\xi_{n}$ should be analytic in $Z_{1},...,Z_{n}$ and $\\xi_{j}$ should be close to $Z_{j}$ in a certain analytic norm), then there exist invertible non-commutative functions $F_{j}$ of an $n$-tuple of semicircular variables $S_{1},...,S_{n}$, so that $Z_{j}=F_{j}(S_{1},...,S_{n})$. Moreover, $F_{j}$ can be chosen to be monotone, in the sense that $F_{j}=\\mathscr{D}_{j}g$ and $g$ is a non-commutative function with a positive definite Hessian. In particular, we can deduce that $C^{*}(Z_{1},...,Z_{n})\\cong C^{*}(S_{1},...,S_{n})$ and $W^{*}(Z_{1},...,Z_{n})\\cong L(\\mathbb{F}(n))$. Thus our condition is a useful way to recognize when an $n$-tuple of operators generate a free group factor. We obtain as a consequence that the q-deforme...

  11. Stepsize Restrictions for Boundedness and Monotonicity of Multistep Methods

    KAUST Repository

    Hundsdorfer, W.

    2011-04-29

    In this paper nonlinear monotonicity and boundedness properties are analyzed for linear multistep methods. We focus on methods which satisfy a weaker boundedness condition than strict monotonicity for arbitrary starting values. In this way, many linear multistep methods of practical interest are included in the theory. Moreover, it will be shown that for such methods monotonicity can still be valid with suitable Runge-Kutta starting procedures. Restrictions on the stepsizes are derived that are not only sufficient but also necessary for these boundedness and monotonicity properties. © 2011 Springer Science+Business Media, LLC.

  12. Electronic, mechanical and dielectric properties of silicane under tensile strain

    Energy Technology Data Exchange (ETDEWEB)

    Jamdagni, Pooja, E-mail: j.poojaa1228@gmail.com; Sharma, Munish; Ahluwalia, P. K. [Physics Department, Himachal Pradesh University, Shimla, Himachal Pradesh, India 171005 (India); Kumar, Ashok [Physics Department, Panjab University, Chandigarh, India, 160014 (India); Thakur, Anil [Physics Department, Govt. Collage Solan, Himachal Pradesh, India,173212 (India)

    2015-05-15

    The electronic, mechanical and dielectric properties of fully hydrogenated silicene i.e. silicane in stable configuration are studied by means of density functional theory based calculations. The band gap of silicane monolayer can be flexibly reduced to zero when subjected to bi-axial tensile strain, leading to semi-conducting to metallic transition, whereas the static dielectric constant for in-plane polarization increases monotonically with increasing strain. Also the EEL function show the red shift in resonance peak with tensile strain. Our results offer useful insight for the application of silicane monolayer in nano-optical and electronics devices.

  13. COMPUTER NUMERICAL SIMULATION OF MECHANICAL PROPERTIES OF TUNGSTEN HEAVY ALLOYS

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    A microstructure model of tungsten heavy alloys has been developed. On the basis of the model and several assumptions, the macro-mechanical properties of 90 W heavy alloy under quasi-static tensile deformation and the effects of microstructural parameters (mechanical properties of the matrix phase and tungsten content) on them have been analyzed by computer numerical simulation. The mechanical properties of the alloy have been found to be dependent on the mechanical parameters of the matrix phase. As the elastic modulus and yield strength of the matrix phase increase, the tensile strength of the alloy increases, while the elongation decreases. If the mechanical parameters except the tensile strength of the matrix phase are constant, both the tensile strength and the elongation of the alloy increase linearly with the increase of tensile strength of the matrix phase. The properties of the alloy are very sensitive to the hardening modulus of the matrix phase. As the hardening modulus increases, both the tensile strength and the elongation of the alloy exponentially decrease. The elongation of the alloys monotonically decreases with the increase of tungsten content, while the decrease of tensile strength is not monotonic. When the tungsten content < 85 %, the strength of tungsten heavy alloys increases with the increase of tungsten content, while decreases when the tungsten content >85 %. The maximum of tensile strength of the alloys appears at the tungsten content of 85 %. The results showed that the binder phase with a higher strength and a lower hardening modulus is advantageous to obtaining an optimum combination of mechanical properties of tungsten heavy alloys.

  14. Monotone Rank and Separations in Computational Complexity

    CERN Document Server

    Li, Yang D

    2011-01-01

    In the paper, we introduce the concept of monotone rank, and using it as a powerful tool, we obtain several important and strong separation results in computational complexity. We show a super-exponential separation between monotone and non-monotone computation in the non-commutative model, and thus give the answer to a longstanding open problem posed by Nisan \\cite{Nis1991} in algebraic complexity. More specifically, we exhibit a homogeneous algebraic function $f$ of degree $d$ ($d$ even) on $n$ variables with the monotone algebraic branching program (ABP) complexity $\\Omega(n^{d/2})$ and the non-monotone ABP complexity $O(d^2)$. We propose a relaxed version of the famous Bell's theorem\\cite{Bel1964}\\cite{CHSH1969}. Bell's theorem basically states that local hidden variable theory cannot predict the correlations produced by quantum mechanics, and therefore is an impossibility result. Bell's theorem heavily relies on the diversity of the measurements. We prove that even if we fix the measurement, infinite amo...

  15. Mechanical Properties of Materials

    CERN Document Server

    Pelleg, Joshua

    2013-01-01

    The subject of mechanical behavior has been in the front line of basic studies in engineering curricula for many years.  This textbook was written for engineering students with the aim of presenting, in a relatively simple manner, the basic concepts of mechanical behavior in solid materials. A second aim of the book is to guide students in their laboratory experiments by helping them to understand their observations in parallel with the lectures of their various courses; therefore the first chapter of the book is devoted to mechanical testing. Another aim of the book is to provide practicing engineers with basic help to bridge the gap of time that has passed from their graduation up to their actual involvement in engineering work. The book also serves as the basis for more advanced studies and seminars when pursuing courses on a graduate level. The content of this textbook and the topics discussed correspond to courses that are usually taught in universities and colleges all over the world, but with a differ...

  16. MECHANICAL PROPERTIES OF WROUGHT TUNGSTEN

    Science.gov (United States)

    Mechanical properties of wrought tungsten vol. II. Creep rupture test data from 1500 to 5000 F, and tensile test data from room temperature to 5000 F at various strain rates for tungsten sheet material.

  17. Monotone complete C*-algebras and generic dynamics

    CERN Document Server

    Saitô, Kazuyuki

    2015-01-01

    This monograph is about monotone complete C*-algebras, their properties and the new classification theory. A self-contained introduction to generic dynamics is also included because of its important connections to these algebras. Our knowledge and understanding of monotone complete C*-algebras has been transformed in recent years. This is a very exciting stage in their development, with much discovered but with many mysteries to unravel. This book is intended to encourage graduate students and working mathematicians to attack some of these difficult questions. Each bounded, upward directed net of real numbers has a limit. Monotone complete algebras of operators have a similar property. In particular, every von Neumann algebra is monotone complete but the converse is false. Written by major contributors to this field, Monotone Complete C*-algebras and Generic Dynamics takes readers from the basics to recent advances. The prerequisites are a grounding in functional analysis, some point set topology and an eleme...

  18. Mixed Monotonicity of Partial First-In-First-Out Traffic Flow Models

    OpenAIRE

    Coogan, Samuel; Arcak, Murat; Kurzhanskiy, Alexander A.

    2015-01-01

    In vehicle traffic networks, congestion on one outgoing link of a diverging junction often impedes flow to other outgoing links, a phenomenon known as the first-in-first-out (FIFO) property. Simplified traffic models that do not account for the FIFO property result in monotone dynamics for which powerful analysis techniques exist. FIFO models are in general not monotone, but have been shown to be mixed monotone - a generalization of monotonicity that enables similarly powerful analysis techni...

  19. The Number of Monotone and Self-Dual Boolean Functions

    Directory of Open Access Journals (Sweden)

    Haviarova L.

    2014-12-01

    Full Text Available In the present paper we study properties of pre-complete class of Boolean functions - monotone Boolean functions. We discuss interval graph, the abbreviated d.n.f., a minimal d.n.f. and a shortest d.n.f. of this function. Then we present a d.n.f. with the highest number of conjunctionsand we determinate the exact number of them. We count the number of monotone Boolean functions with some special properties. In the end we estimate the number of Boolean functionthat are monotone and self-dual at the same time.

  20. Ratio Monotonicity of Polynomials Derived from Nondecreasing Sequences

    CERN Document Server

    Chen, William Y C; Zhou, Elaine L F

    2010-01-01

    The ratio monotonicity of a polynomial is a stronger property than log-concavity. Let P(x) be a polynomial with nonnegative and nondecreasing coefficients. We prove the ratio monotone property of P(x+1), which leads to the log-concavity of P(x+c) for any $c\\geq 1$ due to Llamas and Mart\\'{\\i}nez-Bernal. As a consequence, we obtain the ratio monotonicity of the Boros-Moll polynomials obtained by Chen and Xia without resorting to the recurrence relations of the coefficients.

  1. Mechanical Properties of Picea sitchensis

    DEFF Research Database (Denmark)

    Bräuner, Lise; Hoffmeyer, Preben; Poulsson, Lise

    2000-01-01

    the requirements at the same level as Danish grown Norway spruce. The study shows that Sitka spruce and Norway spruce of the same origin exhibit highly comparable mechanical properties. Key words: annual ring width, bending strength, characteristic strength, dry density, EN 338, INSTA 142, modulus of elasticity...

  2. Mechanical Properties of Composite Materials

    Directory of Open Access Journals (Sweden)

    Mitsuhiro Okayasu

    2014-10-01

    Full Text Available An examination has been made of the mechanical and failure properties of several composite materials, such as a short and a long carbon fiber reinforced plastic (short- and long-CFRP and metal based composite material. The short CFRP materials were used for a recycled CFRP which fabricated by the following process: the CFRP, consisting of epoxy resin with carbon fiber, is injected to a rectangular plate cavity after mixing with acrylonitrile butadiene styrene resin with different weight fractions of CFRP. The fatigue and ultimate tensile strength (UTS increased with increasing CFRP content. These correlations, however, break down, especially for tensile strength, as the CFPR content becomes more than 70%. Influence of sample temperature on the bending strength of the long-CFRP was investigated, and it appears that the strength slightly decreases with increasing the temperature, due to the weakness in the matrix. Broken fiber and pull-out or debonding between the fiber and matrix were related to the main failure of the short- and long-CFRP samples. Mechanical properties of metal based composite materials have been also investigated, where fiber-like high hardness CuAl2 structure is formed in aluminum matrix. Excellent mechanical properties were obtained in this alloy, e.g., the higher strength and the higher ductility, compared tothe same alloy without the fiber-like structure. There are strong anisotropic effects on the mechanical properties due to the fiber-like metal composite in a soft Al based matrix.

  3. Monotone operators and "bigger conjugate" functions

    CERN Document Server

    Bauschke, Heinz H; Wang, Xianfu; Yao, Liangjin

    2011-01-01

    We study a question posed by Stephen Simons in his 2008 monograph involving "bigger conjugate" (BC) functions and the partial infimal convolution. As Simons demonstrated in his monograph, these function have been crucial to the understanding and advancement of the state-of-the-art of harder problems in monotone operator theory, especially the sum problem. In this paper, we provide some tools for further analysis of BC--functions which allow us to answer Simons' problem in the negative. We are also able to refute a similar but much harder conjecture which would have generalized a classical result of Br\\'ezis, Crandall and Pazy. Our work also reinforces the importance of understanding unbounded skew linear relations to construct monotone operators with unexpected properties.

  4. Convex functions, monotone operators and differentiability

    CERN Document Server

    Phelps, Robert R

    1993-01-01

    The improved and expanded second edition contains expositions of some major results which have been obtained in the years since the 1st edition. Theaffirmative answer by Preiss of the decades old question of whether a Banachspace with an equivalent Gateaux differentiable norm is a weak Asplund space. The startlingly simple proof by Simons of Rockafellar's fundamental maximal monotonicity theorem for subdifferentials of convex functions. The exciting new version of the useful Borwein-Preiss smooth variational principle due to Godefroy, Deville and Zizler. The material is accessible to students who have had a course in Functional Analysis; indeed, the first edition has been used in numerous graduate seminars. Starting with convex functions on the line, it leads to interconnected topics in convexity, differentiability and subdifferentiability of convex functions in Banach spaces, generic continuity of monotone operators, geometry of Banach spaces and the Radon-Nikodym property, convex analysis, variational princ...

  5. Mechanical properties of graphene nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Faccio, Ricardo; Pardo, Helena; Goyenola, Cecilia; Mombru, Alvaro W [Crystallography, Solid State and Materials Laboratory (Cryssmat-Lab), DETEMA, Facultad de Quimica, Universidad de la Republica, Avenida General Flores 2124, PO Box 1157, Montevideo (Uruguay); Denis, Pablo A [Computational Nanotechnology, DETEMA, Facultad de Quimica, Universidad de la Republica, Avenida General Flores 2124, CC 1157, 11800 Montevideo (Uruguay)], E-mail: rfaccio@fq.edu.uy

    2009-07-15

    Herein, we investigate the structural, electronic and mechanical properties of zigzag graphene nanoribbons in the presence of stress by applying density functional theory within the GGA-PBE (generalized gradient approximation-Perdew-Burke-Ernzerhof) approximation. The uniaxial stress is applied along the periodic direction, allowing a unitary deformation in the range of {+-} 0.02%. The mechanical properties show a linear response within that range while a nonlinear dependence is found for higher strain. The most relevant results indicate that Young's modulus is considerable higher than those determined for graphene and carbon nanotubes. The geometrical reconstruction of the C-C bonds at the edges hardens the nanostructure. The features of the electronic structure are not sensitive to strain in this linear elastic regime, suggesting the potential for using carbon nanostructures in nano-electronic devices in the near future.

  6. Mechanical properties of organic nanofibers

    DEFF Research Database (Denmark)

    Kjelstrup-Hansen, Jakob; Hansen, Ole; Rubahn, H.R.

    2006-01-01

    Intrinsic elastic and inelastic mechanical Properties of individual, self-assembled, quasi-single-crystalline para-hexaphenylene nanofibers supported on substrates with different hydrophobicities are investigated as well as the interplay between the fibers and the underlying substrates. We find f...... on a silicon substrate with a low-adhesion coating, whereas such motion on a noncoated substrate is limited to very short (sub-micrometer) nanofiber pieces due to strong adhesive forces....

  7. Mechanical properties of collagen fibrils

    OpenAIRE

    Wenger, M. P. E.; Bozec, L.; Horton, M. A.; Mesquida, P

    2007-01-01

    The formation of collagen fibers from staggered subfibrils still lacks a universally accepted model. Determining the mechanical properties of single collagen fibrils ( diameter 50 - 200 nm) provides new insights into collagen structure. In this work, the reduced modulus of collagen was measured by nanoindentation using atomic force microscopy. For individual type 1 collagen fibrils from rat tail, the modulus was found to be in the range from 5 GPa to 11.5 GPa ( in air and at room temperature)...

  8. Mechanical Properties of Flexographic Prints

    Directory of Open Access Journals (Sweden)

    Simona Grigaliūnienė

    2014-02-01

    Full Text Available Mechanical properties of paper and flexographic prints madewith different anilox rollers were investigated experimentally.Flexographic prints roughness, breaking force and folding resistancevalues were determined. The results showed that foldingresistance is bigger for machine direction prints than for crossmachine direction prints. Flexographic prints on cardboardsfolding resistance values are different for machine direction andcross machine direction. It was determined that roughness offlexographic prints increases with the amount of ink on aniloxroller. Results were explained by the ink water influence.

  9. Mechanical properties and stabilities of α-boron monolayers.

    Science.gov (United States)

    Peng, Qing; Han, Liang; Wen, Xiaodong; Liu, Sheng; Chen, Zhongfang; Lian, Jie; De, Suvranu

    2015-01-21

    We investigate the mechanical properties and stabilities of planar α-boron monolayers under various large strains using density functional theory (DFT). α-Boron has a high in-plane stiffness, about 2/3 of that of graphene, which suggests that α-boron is four times as strong as iron. Potential profiles and stress-strain curves indicate that a free standing α-boron monolayer can sustain large tensile strains, up to 0.12, 0.16, and 0.18 for armchair, zigzag, and biaxial deformations, respectively. Third, fourth, and fifth order elastic constants are indispensable for accurate modeling of the mechanical properties under strains larger than 0.02, 0.06, and 0.08 respectively. Second order elastic constants, including in-plane stiffness, are predicted to monotonically increase with pressure, while the trend of Poisson's ratio is reversed. The surface sound speeds of both the compressional and shear waves increase with pressure. The ratio of these two sound speeds increases with the increase of pressure and converges to a value of 2.5. Our results imply that α-boron monolayers are mechanically stable under various large strains and have advanced mechanical properties - high strength and high flexibility.

  10. Why Monotonous Repetition is Unsatisfying

    CERN Document Server

    Salingaros, Nikos A

    2011-01-01

    Human beings prefer ordered complexity and not randomness in their environment, a result of our perceptual system evolving to interpret natural forms. We also recognize monotonously repeating forms as unnatural. Although widespread in today's built environment, such forms generate reactions ranging from boredom to unease. Christopher Alexander has introduced rules for generating forms adapted to natural geometries, which show structured variation with multiple symmetries in a hierarchy of scales. It turns out to be impossible to generate monotonously repeating forms by following those rules. As it is highly probable that traditional artifacts, buildings, and cities were created instinctively using a version of the same rules, this is the reason we never find monotonously repeating forms in traditional cultures.

  11. Monotonicity of social welfare optima

    DEFF Research Database (Denmark)

    Hougaard, Jens Leth; Østerdal, Lars Peter Raahave

    2010-01-01

    This paper considers the problem of maximizing social welfare subject to participation constraints. It is shown that for an income allocation method that maximizes a social welfare function there is a monotonic relationship between the incomes allocated to individual agents in a given coalition...... (with at least three members) and its participation constraint if and only if the aggregate income to that coalition is always maximized. An impossibility result demonstrates that there is no welfare maximizing allocation method in which agents' individual incomes monotonically increase in society......'s income. Thus, for any such allocation method, there are situations where some agents have incentives to prevent society in becoming richer....

  12. Convergence for pseudo monotone semiflows on product ordered topological spaces

    Science.gov (United States)

    Yi, Taishan; Huang, Lihong

    In this paper, we consider a class of pseudo monotone semiflows, which only enjoy some weak monotonicity properties and are defined on product-ordered topological spaces. Under certain conditions, several convergence principles are established for each precompact orbit of such a class of semiflows to tend to an equilibrium, which improve and extend some corresponding results already known. Some applications to delay differential equations are presented.

  13. Effect of hydrogen on mechanical properties of -titanium alloys

    Indian Academy of Sciences (India)

    H-J Christ; A Senemmar; M Decker; K Prüßner

    2003-06-01

    Conflicting opinions exist in the literature on the manner in which hydrogen influences the mechanical properties of -titanium alloys. This can be attributed to the -stabilizing effect of hydrogen in these materials leading to major changes in the microstructure as a result of hydrogen charging. The resulting (extrinsic) effect of hydrogen on the mechanical properties can possibly cover up the direct (intrinsic) influences. On the basis of experimentally determined thermodynamic and kinetic data regarding the interaction of hydrogen with -titanium alloys, hydrogen concentrations of up to 8 at.% were established in three commercial alloys by means of hydrogen charging from the gas phase. In order to separate intrinsic and extrinsic effects the charging was carried out during one step of the two-step heat treatment typical of metastable -titanium alloys, while the other step was performed in vacuum. The results on the single-phase condition represent the intrinsic hydrogen effect. Monotonic and cyclic strength increase at the expense of ductility with increasing hydrogen concentration. The brittle to ductile transition temperature shifts to higher values and the fatigue crack propagation threshold value decreases. The microstructure of the metastable, usually two-phase -titanium alloys is strongly affected by hydrogen, although the extent of this effect depends not only on the hydrogen concentration but also on the temperature of charging. This microstructural influence (extrinsic effect) changes the mechanical properties in the opposite direction as compared to the intrinsic hydrogen effect.

  14. Mechanical Properties of Niobium Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Dhakal, Pashupati [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Matalevich, Joseph R. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Myneni, Ganapati Rao [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

    2015-09-01

    The mechanical stability of bulk Nb cavity is an important aspect to be considered in relation to cavity material, geometry and treatments. Mechanical properties of Nb are typically obtained from uniaxial tensile tests of small samples. In this contribution we report the results of measurements of the resonant frequency and local strain along the contour of single-cell cavities made of ingot and fine-grain Nb of different purity subjected to increasing uniform differential pressure, up to 6 atm. Measurements have been done on cavities subjected to different heat treatments. Good agreement between finite element analysis simulations and experimental data in the elastic regime was obtained with a single set of values of Young’s modulus and Poisson’s ratio. The experimental results indicate that the yield strength of medium-purity ingot Nb cavities is higher than that of fine-grain, high-purity Nb.

  15. Mechanical properties of metal dihydrides

    Science.gov (United States)

    Schultz, Peter A.; Snow, Clark S.

    2016-03-01

    First-principles calculations are used to characterize the bulk elastic properties of cubic and tetragonal phase metal dihydrides, \\text{M}{{\\text{H}}2} {\\text{M}   =  Sc, Y, Ti, Zr, Hf, lanthanides} to gain insight into the mechanical properties that govern the aging behavior of rare-earth di-tritides as the constituent 3H, tritium, decays into 3He. As tritium decays, helium is inserted in the lattice, the helium migrates and collects into bubbles, that then can ultimately create sufficient internal pressure to rupture the material. The elastic properties of the materials are needed to construct effective mesoscale models of the process of bubble growth and fracture. Dihydrides of the scandium column and most of the rare-earths crystalize into a cubic phase, while dihydrides from the next column, Ti, Zr, and Hf, distort instead into the tetragonal phase, indicating incipient instabilities in the phase and potentially significant changes in elastic properties. We report the computed elastic properties of these dihydrides, and also investigate the off-stoichiometric phases as He or vacancies accumulate. As helium builds up in the cubic phase, the shear moduli greatly soften, converting to the tetragonal phase. Conversely, the tetragonal phases convert very quickly to cubic with the removal of H from the lattice, while the cubic phases show little change with removal of H. The source and magnitude of the numerical and physical uncertainties in the modeling are analyzed and quantified to establish the level of confidence that can be placed in the computational results, and this quantified confidence is used to justify using the results to augment and even supplant experimental measurements.

  16. A Characterization of Generalized Monotone Normed Cones

    Institute of Scientific and Technical Information of China (English)

    S.ROMAGUERA; E.A.S(A)NCHEZ-P(E)REZ; O.VALERO

    2007-01-01

    Let C be a cone and consider a quasi-norm p defined on it. We study the structure of the couple (C, p) as a topological space in the case where the function p is also monotone. We characterize when the topology of a quasi-normed cone can be defined by means of a monotone norm. We also define and study the dual cone of a monotone normed cone and the monotone quotient of a general cone.We provide a decomposition theorem which allows us to write a cone as a direct sum of a monotone subcone that is isomorphic to the monotone quotient and other particular subcone.

  17. Mechanical Properties of Nanocrystal Supercrystals

    Energy Technology Data Exchange (ETDEWEB)

    Tam, Enrico; Podsiadlo, Paul; Shevchenko, Elena; Ogletree, D. Frank; Delplancke-Ogletree, Marie-Paule; Ashby, Paul D.

    2009-12-30

    Colloidal nanocrystals attract significant interest due to their potential applications in electronic, magnetic, and optical devices. Nanocrystal supercrystals (NCSCs) are particularly appealing for their well ordered structure and homogeneity. The interactions between organic ligands that passivate the inorganic nanocrystal cores critically influence their self-organization into supercrystals, By investigating the mechanical properties of supercrystals, we can directly characterize the particle-particle interactions in a well-defined geometry, and gain insight into both the self-assembly process and the potential applications of nanocrystal supercrystals. Here we report nanoindentation studies of well ordered lead-sulfide (Pbs) nanocrystal supercrystals. Their modulus and hardness were found to be similar to soft polymers at 1.7 GPa and 70 MPa respectively and the fractures toughness was 39 KPa/m1/2, revealing the extremely brittle nature of these materials.

  18. Mechanical properties of polyethylene foils

    Directory of Open Access Journals (Sweden)

    Ľubomír KUBÍK

    2014-03-01

    Full Text Available The paper deals with the evaluation of the mechanical properties of the polyethylene foils such as the stress, strain, modulus of elasticity and stress and strain in the moment of breaking. The thin foils (50 mm which contained 91 % of polyethylene Bralen RA 2–63 and 9 % colored concentrate Maxithen were studied. Four sorts of foils were examined: Maxithen HP 1510 – white, Maxithen HP 231111 – yellow, Maxithen HP 533031 – blue and Maxithen HP 533 041 – violet. Longitudinal and transversal tensile properties were studied. The tensile behavior was monitored on the motorized test stand ANDILOG STENTOR 1000. The moduli of elasticity of longitudinal samples of polyethylene Bralen RA 2—63 foils achieved the values in the range from 222.73 MPa to 298.24 MPa and the transversal samples in the range 179.61 MPa to 270.41 MPa. The stress of longitudinal samples of polyethylene Bralen RA 2–63 foils in the moment of the rupture achieved the values in the range from 9.46 MPa to 13.33 MPa at the strain from 1.51 mm*mm–1 to 1.54 mm*mm–1 and the transversal samples in the range from 12.38 MPa to 15.54 MPa at the strain from 1.48 mm*mm–1 to 1.58 mm*mm–1.

  19. Monotonic shear mechanical characteristics and affecting factors of interface layers between frozen soil and structure%冻黏土与结构接触界面层单剪力学特性试验

    Institute of Scientific and Technical Information of China (English)

    孙厚超; 杨平; 王国良

    2015-01-01

    With the increasing of the number of structures in permafrost regions or structures (such as urban underground and mine shaft engineering) using freezing method, the properties of interface layer between frozen soil and structure are receiving more attention. Under the action of loads, the mechanical responses of interface layer are different from frozen soil and structure material. The interface layer between frozen soil and structure is vulnerable to severe damage under the loads of gravity, construction and earthquake, and thus will affect the safety and durability of structures. The newly developed mechanical testing apparatus is used to test the mechanical characteristics of interface layers between frozen soil and structure. Based on the existing apparatus called large-scale frozen soil direct shear system (DDJ-1) in our laboratory, the shearing box of frozen soil is modified to highlight the interface layer of frozen soil, and the measuring system of tiny deformation is developed, which thus constitute the experimental system. Micro deformation measuring system is composed of digital imaging system (DIS) and digital image processing software system (DIPSS). DIS consists of high definition and resolution camera (JHSM1400) and 7.2 mm distortionless industry fixed-focus camera, and DIPSS has functions of calibration setting, measurement setting and data display. The data received from the system are accurate and the error is about only 1μm. The newly developed mechanical testing apparatus is used to test the mechanical characteristics of interface layers between frozen soil and rough steel plate under the monotonic load. The mechanism of basic forces and deformation of the interface layers is analyzed from the perspectives of macro mechanics and micro deformation. The results show that the peak shearing stress, stable shearing stress and initial shearing stiffness increase with normal stress, and shearing strength of the interface layer is correlated with

  20. Monotonicity of chi-square test statistics

    OpenAIRE

    Ryu, Keunkwan

    2003-01-01

    This paper establishes monotonicity of the chi-square test statistic. As the more efficient parameter estimator is plugged into the test statistic, the degrees of freedom of the resulting chi-square test statistic monotonically increase.

  1. Effect of fiber fabric orientation on the flexural monotonic and fatigue behavior of 2D woven ceramic matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Chawla, N., E-mail: nchawla@asu.edu [Materials Science and Engineering, Arizona State University Tempe, AZ 85287-6106 (United States); Liaw, P.K. [Department of Materials Science and Engineering, University of Tennessee-Knoxville, Knoxville, TN 37996 (United States); Lara-Curzio, E.; Ferber, M.K.; Lowden, R.A. [High Temperature Materials Laboratory, Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)

    2012-11-15

    The effect of fiber fabric orientation, i.e., parallel to loading and perpendicular to the loading axis, on the monotonic and fatigue behavior of plain-weave fiber reinforced SiC matrix laminated composites was investigated. Two composite systems were studied: Nextel 312 (3M Corp.) reinforced SiC and Nicalon (Nippon Carbon Corp.) reinforced SiC, both fabricated by Forced Chemical Vapor Infiltration (FCVI). The behavior of both materials was investigated under monotonic and fatigue loading. Interlaminar and in-plane shear tests were conducted to further correlate shear properties with the effect of fabric orientation, with respect to the loading axis, on the orientation effects in bending. The underlying mechanisms, in monotonic and fatigue loading, were investigated through post-fracture examination using scanning electron microscopy (SEM).

  2. Some Generalizations of Monotonicity Condition and Applications

    Institute of Scientific and Technical Information of China (English)

    虞旦盛; 周颂平

    2006-01-01

    @@ O Introduction It is well known that there are a great number of interesting results in Fourier analysis established by assuming monotonicity of coefficients, and many of them have been generalized by loosing the condition to quasi-monotonicity, O-regularly varying quasi-monotonicity, etc..

  3. A monotone framework for CCS

    DEFF Research Database (Denmark)

    Nielson, Hanne Riis; Nielson, Flemming

    2009-01-01

    The calculus of communicating systems, CCS, was introduced by Robin Milner as a calculus for modelling concurrent systems. Subsequently several techniques have been developed for analysing such models in order to get further insight into their dynamic behaviour. In this paper we present a static...... analysis for approximating the control structure embedded within the models. We formulate the analysis as an instance of a monotone framework and thus draw on techniques that often are associated with the efficient implementation of classical imperative programming languages. We show how to construct...

  4. Outstanding mechanical properties of monolayer MoS2 and its application in elastic energy storage.

    Science.gov (United States)

    Peng, Qing; De, Suvranu

    2013-11-28

    The structural and mechanical properties of graphene-like honeycomb monolayer structures of MoS2 (g-MoS2) under various large strains are investigated using density functional theory (DFT). g-MoS2 is mechanically stable and can sustain extra large strains: the ultimate strains are 0.24, 0.37, and 0.26 for armchair, zigzag, and biaxial deformation, respectively. The in-plane stiffness is as high as 120 N m(-1) (184 GPa equivalently). The third, fourth, and fifth order elastic constants are indispensable for accurate modeling of the mechanical properties under strains larger than 0.04, 0.07, and 0.13 respectively. The second order elastic constants, including in-plane stiffness, are predicted to monotonically increase with pressure while the Poisson ratio monotonically decreases with increasing pressure. With the prominent mechanical properties including large ultimate strains and in-plane stiffness, g-MoS2 is a promising candidate of elastic energy storage for clean energy. It possesses a theoretical energy storage capacity as high as 8.8 MJ L(-1) and 1.7 MJ kg(-1), or 476 W h kg(-1), larger than a Li-ion battery and is environmentally friendly.

  5. Properties of porous FeAlO/FeAl ceramic matrix composite influenced by mechanical activation of FeAl powder

    Indian Academy of Sciences (India)

    V Usoltsev; S Tikhov; A Salanov; V Sadykov; G Golubkova; O Lomovskii

    2013-12-01

    Porous ceramic matrix composites FeAlO/FeAl with incorporated metal inclusions (cermets) were synthesized by pressureless method, which includes hydrothermal treatment of mechanically alloyed FeAl powder followed by calcination. Their main structural, textural and mechanical features are described. Variation of FeAl powder alloying time results in non-monotonous changes of the porosity and mechanical strength. Details of the cermet microstructure and its relation to the mechanical properties are discussed.

  6. Research on mechanical properties of corn stalk

    Science.gov (United States)

    Zhang, Kaifei; He, Yujing; Zhang, Hongmei; Li, He

    2017-03-01

    Many domestic scholars have studied on straw utilization from lodging resistance, by breeding agricultural experts to optimization parameters, which selected by agricultural mechanical experts and efficient utilization after the harvest crush. Therefore, the study of the mechanical properties of corn stalks has great prospects. It can provide the basis for the design of agricultural machinery and comprehensive utilization of straw that study the relationship between the properties of the corn stalk and the mechanical properties. In this paper, the radial compression and bending mechanical properties of corn stalk was conducted by universal material testing machine, which contributes to the increase of corn crop and provides basis for the development of equipment.

  7. On the sample monotonization problem

    Science.gov (United States)

    Takhanov, R. S.

    2010-07-01

    The problem of finding a maximal subsample in a training sample consisting of the pairs “object-answer” that does not violate monotonicity constraints is considered. It is proved that this problem is NP-hard and that it is equivalent to the problem of finding a maximum independent set in special directed graphs. Practically important cases in which a partial order specified on the set of answers is a complete order or has dimension two are considered in detail. It is shown that the second case is reduced to the maximization of a quadratic convex function on a convex set. For this case, an approximate polynomial algorithm based on linear programming theory is proposed.

  8. Effects of annealing process on electrical conductivity and mechanical property of Cu-Te alloys

    Institute of Scientific and Technical Information of China (English)

    ZHU Da-chuan; TANG Ke; SONG Ming-zhao; TU Ming-jing

    2006-01-01

    The effects of annealing process on the electrical conductivity and mechanical properties of Cu-Te alloys were studied via AG-10TA electronic universal machine, SB2230 digital electric bridge, SEM and EDS. The results show that recrystallization and precipitation occur simultaneously during the annealing process of Cu-Te alloys. Tellurium precipitates as Cu2Te second phase. The grain size increases with the increasing of annealing temperature and time. The electrical conductivity increases monotonously. The tensile strength of Cu-Te alloy is higher than that of pure copper.

  9. Convex functions, monotone operators and differentiability

    CERN Document Server

    Phelps, Robert R

    1989-01-01

    These notes start with an introduction to the differentiability of convex functions on Banach spaces, leading to the study of Asplund spaces and their intriguing relationship to monotone operators (and more general set-values maps) and Banach spaces with the Radon-Nikodym property. While much of this is classical, some of it is presented using streamlined proofs which were not available until recently. Considerable attention is paid to contemporary results on variational principles and perturbed optimization in Banach spaces, exhibiting their close connections with Asplund spaces. An introductory course in functional analysis is adequate background for reading these notes which can serve as the basis for a seminar of a one-term graduate course. There are numerous excercises, many of which form an integral part of the exposition.

  10. Generalized convexity, generalized monotonicity recent results

    CERN Document Server

    Martinez-Legaz, Juan-Enrique; Volle, Michel

    1998-01-01

    A function is convex if its epigraph is convex. This geometrical structure has very strong implications in terms of continuity and differentiability. Separation theorems lead to optimality conditions and duality for convex problems. A function is quasiconvex if its lower level sets are convex. Here again, the geo­ metrical structure of the level sets implies some continuity and differentiability properties for quasiconvex functions. Optimality conditions and duality can be derived for optimization problems involving such functions as well. Over a period of about fifty years, quasiconvex and other generalized convex functions have been considered in a variety of fields including economies, man­ agement science, engineering, probability and applied sciences in accordance with the need of particular applications. During the last twenty-five years, an increase of research activities in this field has been witnessed. More recently generalized monotonicity of maps has been studied. It relates to generalized conve...

  11. Non-monotonic effect of growth temperature on carrier collection in SnS solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, R.; Steinmann, V.; Mangan, N. M.; Brandt, R. E.; Poindexter, J. R.; Jaramillo, R.; Mailoa, J. P.; Hartman, K.; Polizzotti, A.; Buonassisi, T. [Massachusetts Institute of Technology, Cambridge, Cambridge, Massachusetts 02139 (United States); Yang, C.; Gordon, R. G. [Harvard University, Cambridge, Massachusetts 02138 (United States)

    2015-05-18

    We quantify the effects of growth temperature on material and device properties of thermally evaporated SnS thin-films and test structures. Grain size, Hall mobility, and majority-carrier concentration monotonically increase with growth temperature. However, the charge collection as measured by the long-wavelength contribution to short-circuit current exhibits a non-monotonic behavior: the collection decreases with increased growth temperature from 150 °C to 240 °C and then recovers at 285 °C. Fits to the experimental internal quantum efficiency using an opto-electronic model indicate that the non-monotonic behavior of charge-carrier collection can be explained by a transition from drift- to diffusion-assisted components of carrier collection. The results show a promising increase in the extracted minority-carrier diffusion length at the highest growth temperature of 285 °C. These findings illustrate how coupled mechanisms can affect early stage device development, highlighting the critical role of direct materials property measurements and simulation.

  12. Vector optimization and monotone operators via convex duality recent advances

    CERN Document Server

    Grad, Sorin-Mihai

    2014-01-01

    This book investigates several duality approaches for vector optimization problems, while also comparing them. Special attention is paid to duality for linear vector optimization problems, for which a vector dual that avoids the shortcomings of the classical ones is proposed. Moreover, the book addresses different efficiency concepts for vector optimization problems. Among the problems that appear when the framework is generalized by considering set-valued functions, an increasing interest is generated by those involving monotone operators, especially now that new methods for approaching them by means of convex analysis have been developed. Following this path, the book provides several results on different properties of sums of monotone operators.

  13. Enhancement of mechanical properties of 123 superconductors

    Science.gov (United States)

    Balachandran, Uthamalingam

    1995-01-01

    A composition and method of preparing YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T.sub.c. About 5-20% additions give rise to substantially improved mechanical properties.

  14. Mechanical properties of C-5 epimerized alginates.

    Science.gov (United States)

    Mørch, Y A; Holtan, S; Donati, I; Strand, B L; Skjåk-Braek, G

    2008-09-01

    There is an increased need for alginate materials with both enhanced and controllable mechanical properties in the fields of food, pharmaceutical and specialty applications. In the present work, well-characterized algal polymers and mannuronan were enzymatically modified using C-5 epimerases converting mannuronic acid residues to guluronic acid in the polymer chain. Composition and sequential structure of controls and epimerized alginates were analyzed by (1)H NMR spectroscopy. Mechanical properties of Ca-alginate gels were further examined giving Young's modulus, syneresis, rupture strength, and elasticity of the gels. Both mechanical strength and elasticity of hydrogels could be improved and manipulated by epimerization. In particular, alternating sequences were found to play an important role for the final mechanical properties of alginate gels, and interestingly, a pure polyalternating sample resulted in gels with extremely high syneresis and rupture strength. In conclusion, enzymatic modification was shown to be a valuable tool in modifying the mechanical properties of alginates in a highly specific manner.

  15. Semiparametric approach for non-monotone missing covariates in a parametric regression model

    KAUST Repository

    Sinha, Samiran

    2014-02-26

    Missing covariate data often arise in biomedical studies, and analysis of such data that ignores subjects with incomplete information may lead to inefficient and possibly biased estimates. A great deal of attention has been paid to handling a single missing covariate or a monotone pattern of missing data when the missingness mechanism is missing at random. In this article, we propose a semiparametric method for handling non-monotone patterns of missing data. The proposed method relies on the assumption that the missingness mechanism of a variable does not depend on the missing variable itself but may depend on the other missing variables. This mechanism is somewhat less general than the completely non-ignorable mechanism but is sometimes more flexible than the missing at random mechanism where the missingness mechansim is allowed to depend only on the completely observed variables. The proposed approach is robust to misspecification of the distribution of the missing covariates, and the proposed mechanism helps to nullify (or reduce) the problems due to non-identifiability that result from the non-ignorable missingness mechanism. The asymptotic properties of the proposed estimator are derived. Finite sample performance is assessed through simulation studies. Finally, for the purpose of illustration we analyze an endometrial cancer dataset and a hip fracture dataset.

  16. Semiparametric approach for non-monotone missing covariates in a parametric regression model.

    Science.gov (United States)

    Sinha, Samiran; Saha, Krishna K; Wang, Suojin

    2014-06-01

    Missing covariate data often arise in biomedical studies, and analysis of such data that ignores subjects with incomplete information may lead to inefficient and possibly biased estimates. A great deal of attention has been paid to handling a single missing covariate or a monotone pattern of missing data when the missingness mechanism is missing at random. In this article, we propose a semiparametric method for handling non-monotone patterns of missing data. The proposed method relies on the assumption that the missingness mechanism of a variable does not depend on the missing variable itself but may depend on the other missing variables. This mechanism is somewhat less general than the completely non-ignorable mechanism but is sometimes more flexible than the missing at random mechanism where the missingness mechansim is allowed to depend only on the completely observed variables. The proposed approach is robust to misspecification of the distribution of the missing covariates, and the proposed mechanism helps to nullify (or reduce) the problems due to non-identifiability that result from the non-ignorable missingness mechanism. The asymptotic properties of the proposed estimator are derived. Finite sample performance is assessed through simulation studies. Finally, for the purpose of illustration we analyze an endometrial cancer dataset and a hip fracture dataset.

  17. The Bird Core for Minimum Cost Spanning Tree problems Revisited : Monotonicity and Additivity Aspects

    NARCIS (Netherlands)

    Tijs, S.H.; Moretti, S.; Brânzei, R.; Norde, H.W.

    2005-01-01

    A new way is presented to define for minimum cost spanning tree (mcst-) games the irreducible core, which is introduced by Bird in 1976.The Bird core correspondence turns out to have interesting monotonicity and additivity properties and each stable cost monotonic allocation rule for mcst-problems i

  18. The Bird Core for Minimum Cost Spanning Tree problems Revisited : Monotonicity and Additivity Aspects

    NARCIS (Netherlands)

    Tijs, S.H.; Moretti, S.; Brânzei, R.; Norde, H.W.

    2005-01-01

    A new way is presented to define for minimum cost spanning tree (mcst-) games the irreducible core, which is introduced by Bird in 1976.The Bird core correspondence turns out to have interesting monotonicity and additivity properties and each stable cost monotonic allocation rule for mcst-problems

  19. Monotonicity of the CABARET scheme approximating a hyperbolic equation with a sign-changing characteristic field

    Science.gov (United States)

    Kovyrkina, O. A.; Ostapenko, V. V.

    2016-05-01

    The monotonicity of the CABARET scheme approximating a hyperbolic differential equation with a sign-changing characteristic field is analyzed. Monotonicity conditions for this scheme are obtained in domains where the characteristics have a sign-definite propagation velocity and near sonic lines, on which the propagation velocity changes its sign. These properties of the CABARET scheme are illustrated by test computations.

  20. The Bird Core for Minimum Cost Spanning Tree problems Revisited : Monotonicity and Additivity Aspects

    NARCIS (Netherlands)

    Tijs, S.H.; Moretti, S.; Brânzei, R.; Norde, H.W.

    2005-01-01

    A new way is presented to define for minimum cost spanning tree (mcst-) games the irreducible core, which is introduced by Bird in 1976.The Bird core correspondence turns out to have interesting monotonicity and additivity properties and each stable cost monotonic allocation rule for mcst-problems i

  1. Heritability of lumbar trabecular bone mechanical properties in baboons.

    Science.gov (United States)

    Havill, L M; Allen, M R; Bredbenner, T L; Burr, D B; Nicolella, D P; Turner, C H; Warren, D M; Mahaney, M C

    2010-03-01

    Genetic effects on mechanical properties have been demonstrated in rodents, but not confirmed in primates. Our aim was to quantify the proportion of variation in vertebral trabecular bone mechanical properties that is due to the effects of genes. L3 vertebrae were collected from 110 females and 46 male baboons (6-32 years old) from a single extended pedigree. Cranio-caudally oriented trabecular bone cores were scanned with microCT then tested in monotonic compression to determine apparent ultimate stress, modulus, and toughness. Age and sex effects and heritability (h(2)) were assessed using maximum likelihood-based variance components methods. Additive effects of genes on residual trait variance were significant for ultimate stress (h(2)=0.58), toughness (h(2)=0.64), and BV/TV (h(2)=0.55). When BV/TV was accounted for, the residual variance in ultimate stress accounted for by the additive effects of genes was no longer significant. Toughness, however, showed evidence of a non-BV/TV-related genetic effect. Overall, maximum stress and modulus show strong genetic effects that are nearly entirely due to bone volume. Toughness shows strong genetic effects related to bone volume and shows additional genetic effects (accounting for 10% of the total trait variance) that are independent of bone volume. These results support continued use of bone volume as a focal trait to identify genes related to skeletal fragility, but also show that other focal traits related to toughness and variation in the organic component of bone matrix will enhance our ability to find additional genes that are particularly relevant to fatigue-related fractures.

  2. 具有突变率的广义生-灭过程——随机单调性、Feller性及可配称性%An Extended Birth-Death Processes with Catastrophes——Stochastically Monotone, Feller and Symmetric Properties

    Institute of Scientific and Technical Information of China (English)

    吴群英

    2002-01-01

    本文给出了具有突变率的广义生-灭过程的随机单调性、Feller性及可配称性的充要条件.%A new structure with the special property that catastrophes is imposed to ordinary Birth-Death processes is considered. The necessary and sufficient conditions of stochastically monotone, Feller and symmetric properties for the extended birth-death processes with catastrophes are obtained.

  3. Monotonic Allocation Schemes in Clan Games

    NARCIS (Netherlands)

    Voorneveld, M.; Tijs, S.H.; Grahn, S.

    2000-01-01

    Total clan games are characterized using monotonicity, veto power of the clan members, and a concavity condition reflecting the decreasing marginal contribution of non-clan members to growing coalitions.This decreasing marginal contribution is incorporated in the notion of a bi-monotonic allocation

  4. Monotone models for prediction in data mining

    NARCIS (Netherlands)

    Velikova, M.V.

    2006-01-01

    This dissertation studies the incorporation of monotonicity constraints as a type of domain knowledge into a data mining process. Monotonicity constraints are enforced at two stages¿data preparation and data modeling. The main contributions of the research are a novel procedure to test the degree of

  5. Monotonic Stable Solutions for Minimum Coloring Games

    NARCIS (Netherlands)

    Hamers, H.J.M.; Miquel, S.; Norde, H.W.

    2011-01-01

    For the class of minimum coloring games (introduced by Deng et al. (1999)) we investigate the existence of population monotonic allocation schemes (introduced by Sprumont (1990)). We show that a minimum coloring game on a graph G has a population monotonic allocation scheme if and only if G is (P4,

  6. Monotone Hurwitz numbers in genus zero

    CERN Document Server

    Goulden, I P; Novak, Jonathan

    2012-01-01

    Hurwitz numbers count branched covers of the Riemann sphere with specified ramification data, or equivalently, transitive permutation factorizations in the symmetric group with specified cycle types. Monotone Hurwitz numbers count a restricted subset of the branched covers counted by the Hurwitz numbers, and have arisen in recent work on the the asymptotic expansion of the Harish-Chandra-Itzykson-Zuber integral. In this paper we begin a detailed study of monotone Hurwitz numbers. We prove two results that are reminiscent of those for classical Hurwitz numbers. The first is the monotone join-cut equation, a partial differential equation with initial conditions that characterizes the generating function for monotone Hurwitz numbers in arbitrary genus. The second is our main result, in which we give an explicit formula for monotone Hurwitz numbers in genus zero.

  7. Mechanical property characterization of intraply hybrid composites

    Science.gov (United States)

    Chamis, C. C.; Lark, R. F.; Sinclair, J. H.

    1979-01-01

    An investigation of the mechanical properties of intraply hybrids made from graphite fiber/epoxy matrix hybridized with secondary S-glass or Kevlar 49 fiber composites is presented. The specimen stress-strain behavior was determined, showing that mechanical properties of intraply hybrid composites can be measured with available methods such as the ten-degree off-axis test for intralaminar shear, and conventional tests for tensile, flexure, and Izod impact properties. The results also showed that combinations of high modulus graphite/S-glass/epoxy matrix composites exist which yield intraply hybrid laminates with the best 'balanced' properties, and that the translation efficiency of mechanical properties from the constituent composites to intraply hybrids may be assessed with a simple equation.

  8. Dynamical zeta functions for piecewise monotone maps of the interval

    CERN Document Server

    Ruelle, David

    2004-01-01

    Consider a space M, a map f:M\\to M, and a function g:M \\to {\\mathbb C}. The formal power series \\zeta (z) = \\exp \\sum ^\\infty _{m=1} \\frac {z^m}{m} \\sum _{x \\in \\mathrm {Fix}\\,f^m} \\prod ^{m-1}_{k=0} g (f^kx) yields an example of a dynamical zeta function. Such functions have unexpected analytic properties and interesting relations to the theory of dynamical systems, statistical mechanics, and the spectral theory of certain operators (transfer operators). The first part of this monograph presents a general introduction to this subject. The second part is a detailed study of the zeta functions associated with piecewise monotone maps of the interval [0,1]. In particular, Ruelle gives a proof of a generalized form of the Baladi-Keller theorem relating the poles of \\zeta (z) and the eigenvalues of the transfer operator. He also proves a theorem expressing the largest eigenvalue of the transfer operator in terms of the ergodic properties of (M,f,g).

  9. Mechanical deformation mechanisms and properties of amyloid fibrils.

    Science.gov (United States)

    Choi, Bumjoon; Yoon, Gwonchan; Lee, Sang Woo; Eom, Kilho

    2015-01-14

    Amyloid fibrils have recently received attention due to their remarkable mechanical properties, which are highly correlated with their biological functions. We have studied the mechanical deformation mechanisms and properties of amyloid fibrils as a function of their length scales by using atomistic simulations. It is shown that the length of amyloid fibrils plays a role in their deformation and fracture mechanisms in such a way that the competition between shear and bending deformations is highly dependent on the fibril length, and that as the fibril length increases, so does the bending strength of the fibril while its shear strength decreases. The dependence of rupture force for amyloid fibrils on their length is elucidated using the Bell model, which suggests that the rupture force of the fibril is determined from the hydrogen bond rupture mechanism that critically depends on the fibril length. We have measured the toughness of amyloid fibrils, which is shown to depend on the fibril length. In particular, the toughness of the fibril with its length of ∼3 nm is estimated to be ∼30 kcal mol(-1) nm(-3), comparable to that of a spider silk crystal with its length of ∼2 nm. Moreover, we have shown the important effect of the pulling rate on the mechanical deformation mechanisms and properties of amyloid fibril. It is found that as the pulling rate increases, so does the contribution of the shear effect to the elastic deformation of the amyloid fibril with its length of deformation mechanism of the amyloid fibril with its length of >15 nm is almost independent of the pulling rate. Our study sheds light on the role of the length scale of amyloid fibrils and the pulling rate in their mechanical behaviors and properties, which may provide insights into how the excellent mechanical properties of protein fibrils can be determined.

  10. Some Mechanical Properties of Austempered Ductile Iron

    Science.gov (United States)

    Waanders, F. B.; Vorster, S. W.; Vorster, M. J.

    1998-12-01

    In the present investigation the influence of the microstructure, obtained after an austempering treatment in a "process window", on the mechanical properties of austempered ductile iron has been investigated. These properties include tensile strength, elongation and hardness. Conversion electron Mössbauer spectra (CEMS) were measured, after heat treatment.

  11. Some mechanical properties of austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Waanders, F.B.; Vorster, S.W.; Vorster, M.V. [Potchefstroom Univ. (South Africa). Dept. of Metall. Eng.

    1997-12-01

    In the present investigation the influence of the microstructure, obtained after an austempering treatment in a ``process window``, on the mechanical properties of austempered ductile iron has been investigated. These properties include tensile strength, elongation and hardness. Conversion electron Moessbauer spectra (CEMS) were measured, after heat treatment. (orig.). 7 refs.

  12. Some Mechanical Properties of Austempered Ductile Iron

    Energy Technology Data Exchange (ETDEWEB)

    Waanders, F.B.; Vorster, S.W.; Vorster, M.J. [Potchefstroom University, Department of Metallurgical Engineering (South Africa)

    1998-12-15

    In the present investigation the influence of the microstructure, obtained after an austempering treatment in a 'process window', on the mechanical properties of austempered ductile iron has been investigated. These properties include tensile strength, elongation and hardness. Conversion electron Moessbauer spectra (CEMS) were measured, after heat treatment.

  13. A Hybrid Approach to Proving Memory Reference Monotonicity

    KAUST Repository

    Oancea, Cosmin E.

    2013-01-01

    Array references indexed by non-linear expressions or subscript arrays represent a major obstacle to compiler analysis and to automatic parallelization. Most previous proposed solutions either enhance the static analysis repertoire to recognize more patterns, to infer array-value properties, and to refine the mathematical support, or apply expensive run time analysis of memory reference traces to disambiguate these accesses. This paper presents an automated solution based on static construction of access summaries, in which the reference non-linearity problem can be solved for a large number of reference patterns by extracting arbitrarily-shaped predicates that can (in)validate the reference monotonicity property and thus (dis)prove loop independence. Experiments on six benchmarks show that our general technique for dynamic validation of the monotonicity property can cover a large class of codes, incurs minimal run-time overhead and obtains good speedups. © 2013 Springer-Verlag.

  14. Remarks on a monotone Markov chain

    Directory of Open Access Journals (Sweden)

    P. Todorovic

    1987-01-01

    Full Text Available In applications, considerations on stochastic models often involve a Markov chain {ζn}0∞ with state space in R+, and a transition probability Q. For each x  R+ the support of Q(x,. is [0,x]. This implies that ζ0≥ζ1≥…. Under certain regularity assumptions on Q we show that Qn(x,Bu→1 as n→∞ for all u>0 and that 1−Qn(x,Bu≤[1−Q(x,Bu]n where Bu=[0,u. Set τ0=max{k;ζk=ζ0}, τn=max{k;ζk=ζτn−1+1} and write Xn=ζτn−1+1, Tn=τn−τn−1. We investigate some properties of the imbedded Markov chain {Xn}0∞ and of {Tn}0∞. We determine all the marginal distributions of {Tn}0∞ and show that it is asymptotically stationary and that it possesses a monotonicity property. We also prove that under some mild regularity assumptions on β(x=1−Q(x,Bx, ∑1n(Ti−a/bn→dZ∼N(0,1.

  15. Influence of harvest day on changes in mechanical properties of grape berries

    Directory of Open Access Journals (Sweden)

    Šárka Nedomová

    2016-05-01

    Full Text Available Changes in the composition, physical and mechanical properties occur in grape berries during the ripening process, but the heterogeneity of the grapes harvested at different ripening stages affects the reliability of the results obtained. The characterization of the mechanical properties of grape berries seems to be an important parameter for understanding grape ripening. In this work, these changes were studied in seven grapevine varieties (Riesling, Blaufränkisch, Pinot Noir, Cerason, Malverina, Laurot, and Hibernal harvested during six consecutive weeks. Mechanical behaviour was measured using compression and puncture tests using of TIRATEST 27025 testing machine. Skin mechanical properties were evaluated using a puncture test carried out on the equatorial side. The dependence of these properties on the chemical composition has been evaluated. These parameters of force/time curves were studied by puncture test: the berry skin break force, the needle displacement at the skin break and the berry skin break energy. The crushing force, the plate displacement at the crushing strength and the berry crushing energy were studied from force/time curves by compression test. Results of the puncture test shows that there the skin break strength and the acidity content are monotonic functions of the time. A comparison of different varieties from the point of the value of the crushing force was obtained by vertical and transversal loading. The crushing force is monotonically decreasing function of the harvesting time like the break force evaluated at the puncture test. The correlation between the skin break strength and the sugar content is significant namely for the varieties: Hibernal, Riesling, Malverina, and Cerason. 

  16. Mechanical Properties of Crystalline Silicon Carbide Nanowires.

    Science.gov (United States)

    Zhang, Huan; Ding, Weiqiang; Aidun, Daryush K

    2015-02-01

    In this paper, the mechanical properties of crystalline silicon carbide nanowires, synthesized with a catalyst-free chemical vapor deposition method, were characterized with nanoscale tensile testing and mechanical resonance testing methods inside a scanning electron microscope. Tensile testing of individual silicon carbide nanowire was performed to determine the tensile properties of the material including the tensile strength, failure strain and Young's modulus. The silicon carbide nanowires were also excited to mechanical resonance in the scanning electron microscope vacuum chamber using mechanical excitation and electrical excitation methods, and the corresponding resonance frequencies were used to determine the Young's modulus of the material according to the simple beam theory. The Young's modulus values from tensile tests were in good agreement with the ones obtained from the mechanical resonance tests.

  17. Experimental study on material properties of Q460 high strength steel under monotonic and cyclic loading%Q460高强钢单调与反复加载性能试验研究

    Institute of Scientific and Technical Information of China (English)

    孙飞飞; 谢黎明; 崔嵬; 李国强; 陈素文; 王彦博

    2013-01-01

    通过对Q460高强钢进行单向拉伸与反复加载下材料性能试验,得到了各试件单调拉伸和反复加载下的应力-应变关系曲线,以及反复加载下的骨架曲线,并将试验结果与文献研究结果进行了对比.试验结果表明:单向拉伸材性试验中,11 mm厚Q460C高强钢板的平均断后伸长率为23.7%,屈强比为0.847; 21 mm厚钢板的平均断后伸长率为30.4%,屈强比为0.792;Q460钢的循环硬化程度比Q345钢明显减弱,主要原因是随着钢材强度的提高,钢材的屈强比增大,钢材的应变强化效应减小.根据钢材反复加载的滞回曲线,提出了Q460高强钢材的应力-应变滞回模型,用该模型计算得到的关系曲线与试验曲线对比,两者吻合较好.%By experimental study on the material properties of Q460 HSS under both monotonic and cyclic loading, Monotonie compressive loading and hysteretic curves of Q460 steel were obtained. The cyclic skeleton curves were compared with the existing research work. Results of the test show that, under monotonie loading, the average elongation rate of Q460C HSS plate with the thickness 11mm is 23. 7% , and the average yield to tensile strength ratio is 0. 847, while the average elongation rate of Q460 HSS plate with the thickness 21mm is 30. 4% , and the average yield to tensile strength ratio is 0. 792. The cyclic hardening property of Q345 is more obvious than that of Q460, since the increase of the strength of steel results in increased yield ratio while reduced strain hardening effect. By the hysteresis curve of Q460 obtained under cyclic loading, the stress-strain hysteresis model of Q460 HSS was proposed, which matched very well with experimental curves.

  18. Hyperbolic monotonicity in the Hilbert ball

    Directory of Open Access Journals (Sweden)

    Reich Simeon

    2006-01-01

    Full Text Available We first characterize -monotone mappings on the Hilbert ball by using their resolvents and then study the asymptotic behavior of compositions and convex combinations of these resolvents.

  19. SWCNT Composites, Interfacial Strength and Mechanical Properties

    DEFF Research Database (Denmark)

    Ma, Jing; Larsen, Mikael

    2013-01-01

    Abstract: Single-Walled Carbon Nanotubes (SWCNT) have despite the superior mechanical properties not fully lived up to the promise as reinforcement in SWCNT composites. The strain transfer from matrix to carbon nanotubes (CNT) is poorly understood and is caused by both fewer localized strong bond...... is applied to the composite materials. The effect of polymer matrix, modification and concentration of the CNTs are discussed. The strain transfer i.e. 2D band shift under tension is compared to the mechanical properties of the SWCNT composite material.......Abstract: Single-Walled Carbon Nanotubes (SWCNT) have despite the superior mechanical properties not fully lived up to the promise as reinforcement in SWCNT composites. The strain transfer from matrix to carbon nanotubes (CNT) is poorly understood and is caused by both fewer localized strong...

  20. Mechanical properties of nanoparticles: basics and applications

    Science.gov (United States)

    Guo, Dan; Xie, Guoxin; Luo, Jianbin

    2014-01-01

    The special mechanical properties of nanoparticles allow for novel applications in many fields, e.g., surface engineering, tribology and nanomanufacturing/nanofabrication. In this review, the basic physics of the relevant interfacial forces to nanoparticles and the main measuring techniques are briefly introduced first. Then, the theories and important results of the mechanical properties between nanoparticles or the nanoparticles acting on a surface, e.g., hardness, elastic modulus, adhesion and friction, as well as movement laws are surveyed. Afterwards, several of the main applications of nanoparticles as a result of their special mechanical properties, including lubricant additives, nanoparticles in nanomanufacturing and nanoparticle reinforced composite coating, are introduced. A brief summary and the future outlook are also given in the final part.

  1. Stability and monotonicity of Lotka-Volterra type operators

    CERN Document Server

    Mukhamedov, Farrukh

    2009-01-01

    In the present paper, we study Lotka-Volterra (LV) type operators defined in finite dimensional simplex. We prove that any LV type operator is a surjection of the simplex. After, we introduce a new class of LV-type operators, called $M$LV type. We prove convergence of their trajectories and study certain its properties. Moreover, we show that such kind of operators have totaly different behavior than ${\\mathbf{f}}$-monotone LV type operators.

  2. Physical and mechanical properties of hemp seed

    Science.gov (United States)

    Taheri-Garavand, A.; Nassiri, A.; Gharibzahedi, S. M. T.

    2012-04-01

    The current study was conducted to investigate the effect of moisture content on the post-harvest physical and mechanical properties of hemp seed in the range of 5.39 to 27.12% d.b. Results showed that the effect of moisture content on the most physical properties of the grain was significant (Phemp seed was not significant. However, the moisture content effect on rupture force and energy was significant (Phemp seed were significant (P<0.05).

  3. Monotonicity in the Sample Size of the Length of Classical Confidence Intervals

    CERN Document Server

    Kagan, Abram M

    2012-01-01

    It is proved that the average length of standard confidence intervals for parameters of gamma and normal distributions monotonically decrease with the sample size. The proofs are based on fine properties of the classical gamma function.

  4. Stainless Steel Microstructure and Mechanical Properties Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Switzner, Nathan T

    2010-06-01

    A nitrogen strengthened 21-6-9 stainless steel plate was spinformed into hemispherical test shapes. A battery of laboratory tests was used to characterize the hemispheres. The laboratory tests show that near the pole (axis) of a spinformed hemisphere the yield strength is the lowest because this area endures the least “cold-work” strengthening, i.e., the least deformation. The characterization indicated that stress-relief annealing spinformed stainless steel hemispheres does not degrade mechanical properties. Stress-relief annealing reduces residual stresses while maintaining relatively high mechanical properties. Full annealing completely eliminates residual stresses, but reduces yield strength by about 30%.

  5. Mechanical Properties of Ingot Nb Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi; Dhakal, Pashupati; Kneisel, Peter; Mammosser, John; Matalevich, Joseph; Rao Myneni, Ganapati

    2014-07-01

    This contribution presents the results of measurements of the resonant frequency and of strain along the contour of a single-cell cavity made of ingot Nb subjected to increasing uniform differential pressure, up to 6 atm. The data were used to infer mechanical properties of this material after cavity fabrication, by comparison with the results from simulation calculations done with ANSYS. The objective is to provide useful information about the mechanical properties of ingot Nb cavities which can be used in the design phase of SRF cavities intended to be built with this material.

  6. Probing cell mechanical properties with microfluidic devices

    Science.gov (United States)

    Rowat, Amy

    2012-02-01

    Exploiting flow on the micron-scale is emerging as a method to probe cell mechanical properties with 10-1000x advances in throughput over existing technologies. The mechanical properties of cells and the cell nucleus are implicated in a wide range of biological contexts: for example, the ability of white blood cells to deform is central to immune response; and malignant cells show decreased stiffness compared to benign cells. We recently developed a microfluidic device to probe cell and nucleus mechanical properties: cells are forced to deform through a narrow constrictions in response to an applied pressure; flowing cells through a series of constrictions enables us to probe the ability of hundreds of cells to deform and relax during flow. By tuning the constriction width so it is narrower than the width of the cell nucleus, we can specifically probe the effects of nuclear physical properties on whole cell deformability. We show that the nucleus is the rate-limiting step in cell passage: inducing a change in its shape to a multilobed structure results in cells that transit more quickly; increased levels of lamin A, a nuclear protein that is key for nuclear shape and mechanical stability, impairs the passage of cells through constrictions. We are currently developing a new class of microfluidic devices to simultaneously probe the deformability of hundreds of cell samples in parallel. Using the same soft lithography techniques, membranes are fabricated to have well-defined pore distribution, width, length, and tortuosity. We design the membranes to interface with a multiwell plate, enabling simultaneous measurement of hundreds of different samples. Given the wide spectrum of diseases where altered cell and nucleus mechanical properties are implicated, such a platform has great potential, for example, to screen cells based on their mechanical phenotype against a library of drugs.

  7. Variations of Microstructure and Mechanical Properties of Si-B-O-N Ceramics with Sintering Temperatures

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Si-B-O-N powder without B-O bonds synthesized by polymeric precursor were hot-pressed into ceramics at different temperatures. The variations of microstructure and mechanical properties of Si-B-O-N ceramics have been investigated. Crystallization of Si-B-O-N ceramics occurred at about 1400°C. Density, elastic modulus, and flexural strength of the ceramics increased with the increasing sintering temperatures, and reached to their maximum values at 1600°C. By contrast, hardness and fracture toughness of the ceramics monotonically changed with increasing sintering temperatures. Hardness decreased, while the fracture toughness increased. The principal toughening mechanisms including crack deflection, crack bridging and plate grain pulling-out effects are discussed

  8. Mechanical properties of thermoelectric lanthanum telluride from quantum mechanics

    Science.gov (United States)

    Li, Guodong; Aydemir, Umut; Wood, Max; Goddard, William A., III; Zhai, Pengcheng; Zhang, Qingjie; Snyder, G. Jeffrey

    2017-07-01

    Lanthanum telluride (La3Te4) is an n-type high-performance thermoelectric material in the high temperature range, but its mechanical properties remain unknown. Since we want robust mechanical properties for their integration into industrial applications, we report here quantum mechanics (QM) simulations to determine the ideal strength and deformation mechanisms of La3Te4 under pure shear deformations. Among all plausible shear deformation paths, we find that shearing along the (0 0 1)/ slip system has the lowest ideal shear strength of 0.99 GPa, making it the most likely slip system to be activated under pressure. We find that the long range La-Te ionic interactions play the predominant role in resisting shear deformation. To enhance the mechanical strength, we suggest improving the long ionic La-Te bond stiffness to strengthen the ionic La-Te framework in La3Te4 by a defect-engineering strategy, such as partial substitution of La by Ce or Pr having isotypic crystal structures. This work provides the fundamental information to understand the intrinsic mechanics of La3Te4.

  9. Microstructure and mechanical properties of MTG YBCO

    Science.gov (United States)

    Li, L. F.; Zhang, Z.; Jin, D.; Li, Y. Y.; Meriani, S.

    1997-08-01

    MTG (melt-texture-growth) samples were prepared by passing teh YBa2Cu3O7-x pellets (solid state reaction products) through a furnace with a temperature gradient of 15 °C for 5, 10 and 15 min, respectively. The Jc value, Vickers hardness and fracture toughness of the above samples were measured. And the results indicated that 211 precipitates can influence not only the critical current density, but also the mechanical properties According to microstructure analysis and fracture mechanics theory, the effects of 211 precipatates which can act as a toughening agent on mechanical gains were discussed in this paper.

  10. Mechanical properties of wet granular materials

    Energy Technology Data Exchange (ETDEWEB)

    Fournier, Z; Geromichalos, D; Herminghaus, S; Kohonen, M M; Mugele, F; Scheel, M; Schulz, M; Schulz, B; Schier, Ch; Seemann, R; Skudelny, A

    2005-03-09

    We elaborate on the impact of liquids upon the mechanical properties of granular materials. We find that most of the experimental and simulation results may be accounted for by a simple model assuming frictionless, spherical grains, with a hysteretic attractive interaction between neighbouring grains due to capillary forces.

  11. Nanostructured thin films and coatings mechanical properties

    CERN Document Server

    2010-01-01

    The first volume in "The Handbook of Nanostructured Thin Films and Coatings" set, this book concentrates on the mechanical properties, such as hardness, toughness, and adhesion, of thin films and coatings. It discusses processing, properties, and performance and provides a detailed analysis of theories and size effects. The book presents the fundamentals of hard and superhard nanocomposites and heterostructures, assesses fracture toughness and interfacial adhesion strength of thin films and hard nanocomposite coatings, and covers the processing and mechanical properties of hybrid sol-gel-derived nanocomposite coatings. It also uses nanomechanics to optimize coatings for cutting tools and explores various other coatings, such as diamond, metal-containing amorphous carbon nanostructured, and transition metal nitride-based nanolayered multilayer coatings.

  12. Improvement of mechanical properties of glass substrates

    Science.gov (United States)

    Karbay, Ismail Hakki Cengizhan; Budakoglu, Refika; Zayim, Esra Ozkan

    2015-12-01

    This paper aims to enhance the mechanical and optical properties of glass substrates with thin films by the sol-gel method. TiO2-SiO2 binary system and Ta2O5 were deposited on glass substrates with high transparency. Ring-on-ring flexure and scratch tests were the main mechanical characterization tests. Herein, we report that the thin films can be used to enhance the mechanical properties of the glass substrates efficiently and effectively. TiO2-SiO2 binary system shows more than two times and Ta2O5 thin films show nearly three times better ultimate strength in the ring-on-ring flexure test. Besides, Ta2O5 thin film samples show superior scratch resistance. Additionally, the finite element method was also used to check the conformity in the application of mechanical properties of composite materials. It is also worth noting that, the finite element method can be used to accurately analyze the mechanical stability of composite materials. The use of the finite element method can reduce the total number of experimental trials without losing reliability.

  13. Mechanical properties of additively manufactured octagonal honeycombs.

    Science.gov (United States)

    Hedayati, R; Sadighi, M; Mohammadi-Aghdam, M; Zadpoor, A A

    2016-12-01

    Honeycomb structures have found numerous applications as structural and biomedical materials due to their favourable properties such as low weight, high stiffness, and porosity. Application of additive manufacturing and 3D printing techniques allows for manufacturing of honeycombs with arbitrary shape and wall thickness, opening the way for optimizing the mechanical and physical properties for specific applications. In this study, the mechanical properties of honeycomb structures with a new geometry, called octagonal honeycomb, were investigated using analytical, numerical, and experimental approaches. An additive manufacturing technique, namely fused deposition modelling, was used to fabricate the honeycomb from polylactic acid (PLA). The honeycombs structures were then mechanically tested under compression and the mechanical properties of the structures were determined. In addition, the Euler-Bernoulli and Timoshenko beam theories were used for deriving analytical relationships for elastic modulus, yield stress, Poisson's ratio, and buckling stress of this new design of honeycomb structures. Finite element models were also created to analyse the mechanical behaviour of the honeycombs computationally. The analytical solutions obtained using Timoshenko beam theory were close to computational results in terms of elastic modulus, Poisson's ratio and yield stress, especially for relative densities smaller than 25%. The analytical solutions based on the Timoshenko analytical solution and the computational results were in good agreement with experimental observations. Finally, the elastic properties of the proposed honeycomb structure were compared to those of other honeycomb structures such as square, triangular, hexagonal, mixed, diamond, and Kagome. The octagonal honeycomb showed yield stress and elastic modulus values very close to those of regular hexagonal honeycombs and lower than the other considered honeycombs.

  14. Mechanical Properties of Polymer Nano-composites

    Science.gov (United States)

    Srivastava, Iti

    Thermoset polymer composites are increasingly important in high-performance engineering industries due to their light-weight and high specific strength, finding cutting-edge applications such as aircraft fuselage material and automobile parts. Epoxy is the most widely employed thermoset polymer, but is brittle due to extensive cross-linking and notch sensitivity, necessitating mechanical property studies especially fracture toughness and fatigue resistance, to ameliorate the low crack resistance. Towards this end, various nano and micro fillers have been used with epoxy to form composite materials. Particularly for nano-fillers, the 1-100 nm scale dimensions lead to fascinating mechanical properties, oftentimes proving superior to the epoxy matrix. The chemical nature, topology, mechanical properties and geometry of the nano-fillers have a profound influence on nano-composite behavior and hence are studied in the context of enhancing properties and understanding reinforcement mechanisms in polymer matrix nano-composites. Using carbon nanotubes (CNTs) as polymer filler, uniquely results in both increased stiffness as well as toughness, leading to extensive research on their applications. Though CNTs-polymer nano-composites offer better mechanical properties, at high stress amplitude their fatigue resistance is lost. In this work covalent functionalization of CNTs has been found to have a profound impact on mechanical properties of the CNT-epoxy nano-composite. Amine treated CNTs were found to give rise to effective fatigue resistance throughout the whole range of stress intensity factor, in addition to significantly enhancing fracture toughness, ductility, Young's modulus and average hardness of the nano-composite by factors of 57%, 60%, 30% and 45% respectively over the matrix as a result of diminished localized cross-linking. Graphene, a one-atom-thick sheet of atoms is a carbon allotrope, which has garnered significant attention of the scientific community and is

  15. Food mechanical properties and dietary ecology.

    Science.gov (United States)

    Berthaume, Michael A

    2016-01-01

    Interdisciplinary research has benefitted the fields of anthropology and engineering for decades: a classic example being the application of material science to the field of feeding biomechanics. However, after decades of research, discordances have developed in how mechanical properties are defined, measured, calculated, and used due to disharmonies between and within fields. This is highlighted by "toughness," or energy release rate, the comparison of incomparable tests (i.e., the scissors and wedge tests), and the comparison of incomparable metrics (i.e., the stress and displacement-limited indices). Furthermore, while material scientists report on a myriad of mechanical properties, it is common for feeding biomechanics studies to report on just one (energy release rate) or two (energy release rate and Young's modulus), which may or may not be the most appropriate for understanding feeding mechanics. Here, I review portions of materials science important to feeding biomechanists, discussing some of the basic assumptions, tests, and measurements. Next, I provide an overview of what is mechanically important during feeding, and discuss the application of mechanical property tests to feeding biomechanics. I also explain how 1) toughness measures gathered with the scissors, wedge, razor, and/or punch and die tests on non-linearly elastic brittle materials are not mechanical properties, 2) scissors and wedge tests are not comparable and 3) the stress and displacement-limited indices are not comparable. Finally, I discuss what data gathered thus far can be best used for, and discuss the future of the field, urging researchers to challenge underlying assumptions in currently used methods to gain a better understanding between primate masticatory morphology and diet.

  16. Measurement of non-monotonic Casimir forces between silicon nanostructures

    Science.gov (United States)

    Tang, L.; Wang, M.; Ng, C. Y.; Nikolic, M.; Chan, C. T.; Rodriguez, A. W.; Chan, H. B.

    2017-01-01

    Casimir forces are of fundamental interest because they originate from quantum fluctuations of the electromagnetic field. Apart from controlling this force via the optical properties of materials, a number of novel geometries have been proposed to generate repulsive and/or non-monotonic Casimir forces between bodies separated by vacuum gaps. Experimental realization of these geometries, however, is hindered by the difficulties in alignment when the bodies are brought into close proximity. Here, using an on-chip platform with integrated force sensors and actuators, we circumvent the alignment problem and measure the Casimir force between two surfaces with nanoscale protrusions. We demonstrate that the force depends non-monotonically on the displacement. At some displacements, the Casimir force leads to an effective stiffening of the nanomechanical spring. Our findings pave the way for exploiting the Casimir force in nanomechanical systems using structures of complex and non-conventional shapes.

  17. Computation of Optimal Monotonicity Preserving General Linear Methods

    KAUST Repository

    Ketcheson, David I.

    2009-07-01

    Monotonicity preserving numerical methods for ordinary differential equations prevent the growth of propagated errors and preserve convex boundedness properties of the solution. We formulate the problem of finding optimal monotonicity preserving general linear methods for linear autonomous equations, and propose an efficient algorithm for its solution. This algorithm reliably finds optimal methods even among classes involving very high order accuracy and that use many steps and/or stages. The optimality of some recently proposed methods is verified, and many more efficient methods are found. We use similar algorithms to find optimal strong stability preserving linear multistep methods of both explicit and implicit type, including methods for hyperbolic PDEs that use downwind-biased operators.

  18. Rational functions with maximal radius of absolute monotonicity

    KAUST Repository

    Loczi, Lajos

    2014-05-19

    We study the radius of absolute monotonicity R of rational functions with numerator and denominator of degree s that approximate the exponential function to order p. Such functions arise in the application of implicit s-stage, order p Runge-Kutta methods for initial value problems and the radius of absolute monotonicity governs the numerical preservation of properties like positivity and maximum-norm contractivity. We construct a function with p=2 and R>2s, disproving a conjecture of van de Griend and Kraaijevanger. We determine the maximum attainable radius for functions in several one-parameter families of rational functions. Moreover, we prove earlier conjectured optimal radii in some families with 2 or 3 parameters via uniqueness arguments for systems of polynomial inequalities. Our results also prove the optimality of some strong stability preserving implicit and singly diagonally implicit Runge-Kutta methods. Whereas previous results in this area were primarily numerical, we give all constants as exact algebraic numbers.

  19. Mechanical Properties of Cellulose Microfiber Reinforced Polyolefin

    Science.gov (United States)

    Kobayashi, Satoshi; Yamada, Hiroyuki

    Cellulose microfiber (CeF) has been expected as a reinforcement of polymer because of its high modulus and strength and lower cost. In the present study, mechanical properties of CeF/polyolefin were investigated. Tensile modulus increased with increasing CeF content. On the other hand, tensile strength decreased. Fatigue properties were also investigated with acoustic emission measurement. Stiffness of the composites gradually decreased with loading. Drastic decrease in stiffness was observed just before the final fracture. Based on the Mori-Tanaka's theory, the method to calculate modulus of CeF were proposed to evaluate dispersion of CeF.

  20. The monotonic and fatigue behavior of CFCCs

    Energy Technology Data Exchange (ETDEWEB)

    Miriyala, N.; Liaw, P.K.; McHargue, C.J. [Univ. of Tennessee, Knoxville, TN (United States); Snead, L.L. [Oak Ridge National Laboratory, TN (United States)

    1996-04-01

    Flexure tests were performed to study the fabric orientation effects on the monotonic and fatigue behavior of two commercially available continuous fiber reinforced ceramic composites (CFCCs), namely (i) Nicalon fiber fabric reinforced alumina (Al{sub 2}O{sub 3}) matrix composite fabricated by a direct molten metal oxidation (DIMOX) process and, (ii) Nicalon fiber fabric reinforced silicon carbide (SiC) matrix composite fabricated by an isothermal chemical vapor infiltration (ICVI) process. The fabric orientation effects on the monotonic and fatigue behavior were strong in the Nicalon/Al{sub 2}O{sub 3} composite, while they were relatively weak in the Nicalon/SiC composite.

  1. Weighted monotonicity inequalities for unbounded operators

    CERN Document Server

    Hoa, Dinh Trung

    2011-01-01

    Let $\\tau$ be a faithful normal semifinite trace on a von Neumann algebra $\\mathcal{M}$. For a continuous nonnegative convex monotone nondecreasing function $f$ on convex subset $\\Omega$ of $\\mathbb{R}$ and weight nonnegative Borel function $w$ we consider weighted monotonicity inequalities of the form {equation*} \\tau(w(A)^{1/2}f(A)w(A)^{1/2}) \\le \\tau (w(A)^{1/2}f(B)w(A)^{1/2}), {equation*} where $A$ and $B$ are unbounded operators affiliated with respect to algebra $\\mathcal{M}$.

  2. Mechanical properties of intra-ocular lenses

    Science.gov (United States)

    Ehrmann, Klaus; Kim, Eon; Parel, Jean-Marie

    2008-02-01

    Cataract surgery usually involves the replacement of the natural crystalline lens with a rigid or foldable intraocular lens to restore clear vision for the patient. While great efforts have been placed on optimising the shape and optical characteristics of IOLs, little is know about the mechanical properties of these devices and how they interact with the capsular bag once implanted. Mechanical properties measurements were performed on 8 of the most commonly implanted IOLs using a custom build micro tensometer. Measurement data will be presented for the stiffness of the haptic elements, the buckling resistance of foldable IOLs, the dynamic behaviour of the different lens materials and the axial compressibility. The biggest difference between the lens types was found between one-piece and 3-piece lenses with respect to the flexibility of the haptic elements

  3. Mechanical properties of silicones for MEMS

    Science.gov (United States)

    Schneider, F.; Fellner, T.; Wilde, J.; Wallrabe, U.

    2008-06-01

    This paper focuses on the mechanical properties of polydimethylsiloxane (PDMS) relevant for microelectromechanical system (MEMS) applications. In view of the limited amount of published data, we analyzed the two products most commonly used in MEMS, namely RTV 615 from Bayer Silicones and Sylgard 184 from Dow Corning. With regard to mechanical properties, we focused on the dependence of the elastic modulus on the thinner concentration, temperature and strain rate. In addition, creep and thermal aging were analyzed. We conclude that the isotropic and constant elastic modulus has strong dependence on the hardening conditions. At high hardening temperatures and long hardening time, RTV 615 displays an elastic modulus of 1.91 MPa and Sylgard 184 of 2.60 MPa in a range up to 40% strain.

  4. Mechanical properties of functionalized carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z Q; Liu, B; Chen, Y L; Hwang, K C [FML, Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China); Jiang, H [Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, AZ 85287 (United States); Huang, Y [Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208 (United States)], E-mail: liubin@tsinghua.edu.cn, E-mail: y-huang@northwestern.edu

    2008-10-01

    Carbon nanotubes (CNTs) used to reinforce polymer matrix composites are functionalized to form covalent bonds with the polymer in order to enhance the CNT/polymer interfaces. These bonds destroy the perfect atomic structures of a CNT and degrade its mechanical properties. We use atomistic simulations to study the effect of hydrogenization on the mechanical properties of single-wall carbon nanotubes. The elastic modulus of CNTs gradually decreases with the increasing functionalization (percentage of C-H bonds). However, both the strength and ductility drop sharply at a small percentage of functionalization, reflecting their sensitivity to C-H bonds. The cluster C-H bonds forming two rings leads to a significant reduction in the strength and ductility. The effect of carbonization has essentially the same effect as hydrogenization.

  5. Mechanical Properties of Autoclaved Shell-aggregate

    Institute of Scientific and Technical Information of China (English)

    MA Hailong; CUI Chong; LI Xing; Pierre Chevrier; Vanessa Bouchart; TANG Feng

    2011-01-01

    Waste solid propylene oxide sludge(POS)and fly ash were used as main raw material to prepare propylene oxide sludge aggregate(POSA)under the condition of autoclaved(180 ℃,1.0 MPa)curing.Three different test methods namely cylinder compressive strength(CCS),individual aggregate compressive strength(IACS)and strength contribution rate(SCR)proposed were used to characterize the mechanical properties of the autoclaved POSA.POS shell-aggregate with SCR of 94% were prepared under the hydrothermal synthesis and autoclaved curing.The experimental results indicate that CCS and IACS have good consistency in characterizing mechanical properties of POSA.It is suggested that SCR not only can characterize the strength of POSA core,but also can reflect the effect of shell on the performance of POSA.By means of least square method,relationships between CCS and IACS,CCS and SCR,IACS and SCR were deduced.

  6. New approach of eggshell mechanical properties determinantion

    Directory of Open Access Journals (Sweden)

    Libor Severa

    2010-01-01

    Full Text Available The paper describes a new approach for determination of mechanical properties of hen’s eggshell. The suitability and applicability of a Berkovich indentation is discussed. The eggshells were tested in the area surrounding equator line. The deformation modes active during indentation have been examinined from the shape of load-displacement curves. According to measured dependencies, the eggshel shown an viscous-elastic deformation.The values of Young’s modulus E obtained from radial and tangential directions did not vary significantly. This fact shows on isotropic nature of eggshell structure. It was found that values of E do not significantly change neither around the cir­cum­fe­ren­ce of the equator. The values obtained within this research correspond to values reported in literature and obtained on macroscopic samples. Nanoindentation was found to be a precise and powerful tool, suitable for determining local variations of mechanical properties of eggshells.

  7. Non-monotonic effect of confinement on the glass transition

    Science.gov (United States)

    Varnik, Fathollah; Franosch, Thomas

    2016-04-01

    The relaxation dynamics of glass forming liquids and their structure are influenced in the vicinity of confining walls. This effect has mostly been observed to be a monotonic function of the slit width. Recently, a qualitatively new behaviour has been uncovered by Mittal and coworkers, who reported that the single particle dynamics in a hard-sphere fluid confined in a planar slit varies in a non-monotonic way as the slit width is decreased from five to roughly two particle diametres (Mittal et al 2008 Phys. Rev. Lett. 100 145901). In view of the great potential of this effect for applications in those fields of science and industry, where liquids occur under strong confinement (e.g. nano-technology), the number of researchers studying various aspects and consequences of this non-monotonic behaviour has been rapidly growing. This review aims at providing an overview of the research activity in this newly emerging field. We first briefly discuss how competing mechanisms such as packing effects and short-range attraction may lead to a non-monotonic glass transition scenario in the bulk. We then analyse confinement effects on the dynamics of fluids using a thermodynamic route which relates the single particle dynamics to the excess entropy. Moreover, relating the diffusive dynamics to the Widom’s insertion probability, the oscillations of the local dynamics with density at moderate densities are fairly well described. At high densities belonging to the supercooled regime, however, this approach breaks down signaling the onset of strongly collective effects. Indeed, confinement introduces a new length scale which in the limit of high densities and small pore sizes competes with the short-range local order of the fluid. This gives rise to a non-monotonic dependence of the packing structure on confinement, with a corresponding effect on the dynamics of structural relaxation. This non-monotonic effect occurs also in the case of a cone-plate type channel, where the degree

  8. Mechanical Properties of Infrared Transmitting Materials

    Science.gov (United States)

    1978-01-01

    Theory of the Elasticity," 4th Edition, Dover Publ. Co., New York, N.Y., 1944. Marriott, J. B., and G. Rowden, "The Erosion of a Cobalt - Chromium Alloy...alumina (A1203), spinel (magnesium aluminate ), magnesia (MgO), yttria (Y203), as well as chemical vapor deposition (CVD) silicon carbide, CVD...known to be a problem. Because of their thermal and mechanical properties, alumina and magnesium aluminate (spinel) show, or can show, erosion

  9. Improvement of mechanical properties of chitosan film

    OpenAIRE

    Krkić, Nevena; Lazić, Vera; Šuput, Danijela

    2012-01-01

    This paper investigates the intensity of the influence which poly (ethylene oxide) and poly(ethylene glycol) additions have on the mechanical and structural properties of chitosan films. The films based on highly viscous and medium viscous chitosan were produced under laboratory conditions. Poly(ethylene oxide), with the average molecular weight of 100 000, and poly (ethylene glycol), with the average molecular weight of 400, were added to the films. The infrared spectrums of produced films w...

  10. Mechanical Properties of Palm Fiber Mattress

    Science.gov (United States)

    Li, Yu-Qian; Wu, Jia-Yu; Gu, Hao-Wei; Chen, Zong-Yong; Shi, Xiao-Bing; Liao, Ting-Mao; An, Cheng; Yuan, Hong; Liu, Ren-Huai

    2016-05-01

    Palm fiber mattress is increasingly accepted by many families. This study aims at evaluating the mechanical properties of palm fiber mattress. Two experiments were conduct to investigate the Young's modulus of palm fiber mattress in three directions. In addition, finite element models were established to characterize palm fiber mattress under uniform distributed pressure. Finally, results from finite element analysis are presented to illustrate that the thick mattress will stick with human body curve perfectly, which can support vertebral column effectively.

  11. Criteria for Response Monotonicity Preserving in Approximation of Fractional Order Systems

    Institute of Scientific and Technical Information of China (English)

    Mohammad Saleh Tavazoei

    2016-01-01

    In approximation of fractional order systems,a significant objective is to preserve the important properties of the original system.The monotonicity of time/frequency responses is one of these properties whose preservation is of great importance in approximation process.Considering this importance,the issues of monotonicity preservation of the step response and monotonicity preservation of the magnitude-frequency response are independently investigated in this paper.In these investigations,some conditions on approximating filters of fractional operators are found to guarantee the preservation of step/magnitude-frequency response monotonicity in approximation process.These conditions are also simplified in some special cases.In addition,numerical simulation results are presented to show the usefulness of the obtained conditions.

  12. Electrical properties of mechanically activated zinc oxide

    Directory of Open Access Journals (Sweden)

    Vojisavljević K.

    2006-01-01

    Full Text Available Microstructural properties of a commercial zinc oxide powder were modified by mechanical activation in a high-energy vibro-mill. The obtained powders were dry pressed and sintered at 1100°C for 2 h. The electrical properties of grain boundaries of obtained ZnO ceramics were studied using an ac impedance analyzer. For that purpose, the ac electrical response was measured in the temperature range from 23 to 240°C in order to determine the resistance and capacitance of grain boundaries. The activation energies of conduction were obtained using an Arrhenius equation. Donor densities were calculated from Mott-Schottky measurements. The influence of microstructure, types and concentrations of defects on electrical properties was discussed.

  13. Mechanical Properties of Additively Manufactured Thick Honeycombs

    Directory of Open Access Journals (Sweden)

    Reza Hedayati

    2016-07-01

    Full Text Available Honeycombs resemble the structure of a number of natural and biological materials such as cancellous bone, wood, and cork. Thick honeycomb could be also used for energy absorption applications. Moreover, studying the mechanical behavior of honeycombs under in-plane loading could help understanding the mechanical behavior of more complex 3D tessellated structures such as porous biomaterials. In this paper, we study the mechanical behavior of thick honeycombs made using additive manufacturing techniques that allow for fabrication of honeycombs with arbitrary and precisely controlled thickness. Thick honeycombs with different wall thicknesses were produced from polylactic acid (PLA using fused deposition modelling, i.e., an additive manufacturing technique. The samples were mechanically tested in-plane under compression to determine their mechanical properties. We also obtained exact analytical solutions for the stiffness matrix of thick hexagonal honeycombs using both Euler-Bernoulli and Timoshenko beam theories. The stiffness matrix was then used to derive analytical relationships that describe the elastic modulus, yield stress, and Poisson’s ratio of thick honeycombs. Finite element models were also built for computational analysis of the mechanical behavior of thick honeycombs under compression. The mechanical properties obtained using our analytical relationships were compared with experimental observations and computational results as well as with analytical solutions available in the literature. It was found that the analytical solutions presented here are in good agreement with experimental and computational results even for very thick honeycombs, whereas the analytical solutions available in the literature show a large deviation from experimental observation, computational results, and our analytical solutions.

  14. Mechanical Properties of Nanofilled Polypropylene Composites

    Directory of Open Access Journals (Sweden)

    Cristina-Elisabeta PELIN

    2015-06-01

    Full Text Available The paper presents a study concerning mechanical performance of thermoplastic nanocomposites based on isotactic polypropylene matrix, nanofilled with montmorillonite modified with quaternary ammonium salt and carboxyl functionalized carbon nanotubes, respectively, added in the same concentration relative to the matrix. The nanofilled and single polymer materials were obtained by simple melt compounding through extrusion process followed by injection molding into specific shape specimens for mechanical testing of the samples. Mechanical properties were evaluated by tensile and 3 point bending tests. In terms of modulus of elasticity, the results showed overall positive effects concerning the effect of nanofiller addition to the thermoplastic polymer. The fracture cross section of the tested specimens was characterized by FT-IR spectroscopy and SEM microscopy.

  15. Thermal-mechanical Properties of Epoxy-impregnated Bi-2212/Ag Composite

    Energy Technology Data Exchange (ETDEWEB)

    Li, Pei [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Wang, Yang [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Godeke, Arno [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Ye, Liyang [North Carolina State Univ., Raleigh, NC (United States); Flanagan, Gene [Muons Inc., Batavia, IL (United States); Shen, Tengming [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)

    2014-11-26

    Knowledge of the thermal-mechanical properties of epoxy/superconductor/insulation composite is important for designing, fabricating, and operating epoxy impregnated high field superconducting magnets near their ultimate potentials. We report measurements of the modulus of elasticity, Poisson’s ratio, and the coefficient of thermal contraction of epoxy-impregnated composite made from the state-of-the-art powder-in-tube multifilamentary Ag/Bi2Sr2CaCu2Ox round wire at room temperature and cryogenic temperatures. Stress-strain curves of samples made from single-strand and Rutherford cables were tested under both monotonic and cyclic compressive loads, with single strands insulated using a thin TiO2 insulation coating and the Rutherford cable insulated with a braided ceramic sleeve.

  16. Monotone Comparative Statics for the Industry Composition

    DEFF Research Database (Denmark)

    Laugesen, Anders Rosenstand

    2015-01-01

    We let heterogeneous firms face decisions on a number of complementary activities in a monopolistically-competitive industry. The endogenous level of competition and selection regarding entry and exit of firms introduces a wedge between monotone comparative statics (MCS) at the firm level and MCS...

  17. On a Monotone Ill-posed Problem

    Institute of Scientific and Technical Information of China (English)

    Nguyen BUONG

    2005-01-01

    A class of a posteriori parameter choice strategies for the operator version of Tikhonovregularization (including variants of Morozov's and Arcangeli's methods) is proposed and used in investigating the rate of convergence of the regularized solution for ill-posed nonlinear equation involving a monotone operator in Banach space.

  18. Population Monotonic Path Schemes for Simple Games

    NARCIS (Netherlands)

    Ciftci, B.B.; Borm, P.E.M.; Hamers, H.J.M.

    2006-01-01

    A path scheme for a simple game is composed of a path, i.e., a sequence of coalitions that is formed during the coalition formation process and a scheme, i.e., a payoff vector for each coalition in the path.A path scheme is called population monotonic if a player's payoff does not decrease as the pa

  19. Monotone method for nonlinear nonlocal hyperbolic problems

    Directory of Open Access Journals (Sweden)

    Azmy S. Ackleh

    2003-02-01

    Full Text Available We present recent results concerning the application of the monotone method for studying existence and uniqueness of solutions to general first-order nonlinear nonlocal hyperbolic problems. The limitations of comparison principles for such nonlocal problems are discussed. To overcome these limitations, we introduce new definitions for upper and lower solutions.

  20. Limit points of the monotonic schemes

    CERN Document Server

    Salomon, J

    2005-01-01

    Many numerical simulations in quantum (bilinear) control use the monotonically convergent algorithms of Krotov (introduced by Tannor), Zhu & Rabitz or the general form of Maday & Turinici. This paper presents an analysis of the limit set of controls provided by these algorithms and a proof of convergence in a particular case.

  1. REGULAR RELATIONS AND MONOTONE NORMAL ORDERED SPACES

    Institute of Scientific and Technical Information of China (English)

    XU XIAOQUAN; LIU YINGMING

    2004-01-01

    In this paper the classical theorem of Zareckii about regular relations is generalized and an intrinsic characterization of regularity is obtained. Based on the generalized Zareckii theorem and the intrinsic characterization of regularity, the authors give a characterization of monotone normality of ordered spaces. A new proof of the UrysohnNachbin lemma is presented which is quite different from the classical one.

  2. Monotonicity and bounds on Bessel functions

    Directory of Open Access Journals (Sweden)

    Larry Landau

    2000-07-01

    Full Text Available survey my recent results on monotonicity with respect to order of general Bessel functions, which follow from a new identity and lead to best possible uniform bounds. Application may be made to the "spreading of the wave packet" for a free quantum particle on a lattice and to estimates for perturbative expansions.

  3. Strong monotonicity for analytic ordinary differential equations

    Directory of Open Access Journals (Sweden)

    Sebastian Walcher

    2009-09-01

    Full Text Available We present a necessary and sufficient criterion for the flow of an analytic ordinary differential equation to be strongly monotone; equivalently, strongly order-preserving. The criterion is given in terms of the reducibility set of the derivative of the right-hand side. Some applications to systems relevant in biology and ecology, including nonlinear compartmental systems, are discussed.

  4. A monotonic archive for pareto-coevolution.

    Science.gov (United States)

    de Jong, Edwin D

    2007-01-01

    Coevolution has already produced promising results, but its dynamic evaluation can lead to a variety of problems that prevent most algorithms from progressing monotonically. An important open question therefore is how progress towards a chosen solution concept can be achieved. A general solution concept for coevolution is obtained by viewing opponents or tests as objectives. In this setup known as Pareto-coevolution, the desired solution is the Pareto-optimal set. We present an archive that guarantees monotonicity for this solution concept. The algorithm is called the Incremental Pareto-Coevolution Archive (IPCA), and is based on Evolutionary Multi-Objective Optimization (EMOO). By virtue of its monotonicity, IPCA avoids regress even when combined with a highly explorative generator. This capacity is demonstrated on a challenging test problem requiring both exploration and reliability. IPCA maintains a highly specific selection of tests, but the size of the test archive nonetheless grows unboundedly. We therefore furthermore investigate how archive sizes may be limited while still providing approximate reliability. The LAyered Pareto-Coevolution Archive (LAPCA) maintains a limited number of layers of candidate solutions and tests, and thereby permits a trade-off between archive size and reliability. The algorithm is compared in experiments, and found to be more efficient than IPCA. The work demonstrates how the approximation of a monotonic algorithm can lead to algorithms that are sufficiently reliable in practice while offering better efficiency.

  5. Nonparametric confidence intervals for monotone functions

    NARCIS (Netherlands)

    Groeneboom, P.; Jongbloed, G.

    2015-01-01

    We study nonparametric isotonic confidence intervals for monotone functions. In [Ann. Statist. 29 (2001) 1699–1731], pointwise confidence intervals, based on likelihood ratio tests using the restricted and unrestricted MLE in the current status model, are introduced. We extend the method to the trea

  6. Competitive learning of monotone Boolean functions

    OpenAIRE

    2014-01-01

    We apply competitive analysis onto the problem of minimizing the number of queries to an oracle to completely reconstruct a given monotone Boolean function. Besides lower and upper bounds on the competitivity we determine optimal deterministic online algorithms for the smallest problem instances.

  7. Nonparametric confidence intervals for monotone functions

    NARCIS (Netherlands)

    Groeneboom, P.; Jongbloed, G.

    2015-01-01

    We study nonparametric isotonic confidence intervals for monotone functions. In [Ann. Statist. 29 (2001) 1699–1731], pointwise confidence intervals, based on likelihood ratio tests using the restricted and unrestricted MLE in the current status model, are introduced. We extend the method to the

  8. Edit Distance to Monotonicity in Sliding Windows

    DEFF Research Database (Denmark)

    Chan, Ho-Leung; Lam, Tak-Wah; Lee, Lap Kei

    2011-01-01

    of a data stream is becoming well-understood over the past few years. Motivated by applications on network quality monitoring, we extend the study to estimating the edit distance to monotonicity of a sliding window covering the w most recent items in the stream for any w ≥ 1. We give a deterministic...

  9. New concurrent iterative methods with monotonic convergence

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Qingchuan [Michigan State Univ., East Lansing, MI (United States)

    1996-12-31

    This paper proposes the new concurrent iterative methods without using any derivatives for finding all zeros of polynomials simultaneously. The new methods are of monotonic convergence for both simple and multiple real-zeros of polynomials and are quadratically convergent. The corresponding accelerated concurrent iterative methods are obtained too. The new methods are good candidates for the application in solving symmetric eigenproblems.

  10. Classification Trees for Problems with Monotonicity Constraints

    NARCIS (Netherlands)

    R. Potharst (Rob); A.J. Feelders

    2002-01-01

    textabstractFor classification problems with ordinal attributes very often the class attribute should increase with each or some of the explaining attributes. These are called classification problems with monotonicity constraints. Classical decision tree algorithms such as CART or C4.5 generally do

  11. Different mechanical properties in Seldinger guide wires

    Directory of Open Access Journals (Sweden)

    Wolfram Schummer

    2015-01-01

    Full Text Available Background and Aims: Most central venous catheters are placed using Seldinger guide wires. EN ISO 11070 is the guideline for testing guide wire flexing performance and tensile strength, and we can safely assume that guide wires in use meet these requirements. Unfortunately, EN ISO 11070 guidelines do not reflect the clinical requirements and we continue to see mechanical failures and their associated complications. Material and Methods: This in vitro study was performed in an accredited laboratory. With regard to flexing, we: (1 Established the minimum flexing performance needed to meet clinical requirements, (2 developed flexing performance tests which mimic clinical requirement, and (3 evaluated the mechanical properties of various guide wires relative to these requirements. With regard to tensile strength, we used the testing method prescribed in ISO 11070, but did not end the test at 5 Newton (N. We continued until the guide wire was damaged, or we reached maximum tractive force. We then did a wire-to-wire comparison. We examined two basic wire constructions, monofil and core and coil. Results: Tensile strength: All wires tested, except one, met EN ISO 11070 requirements for 5 N tensile strength. The mean of the wire types tested ranged from 15.06 N to 257.76 N. Flexing performance: None of the wires kinked. The monofil had no evidence of bending. Two core/coil wires displayed minor bending (angle 1.5°. All other wires displayed bending angles between 22.5° and 43.0°. Conclusion: We recommend that: (1 Clinicians use guide wires with high-end mechanical properties, (2 EN ISO 11070 incorporate our flexing test into their testing method, raise the flexing requirement to kink-proof, (3 and raise the tensile strength requirement to a minimum of 30 N, and (3 all manufacturers and suppliers be required to display mechanical properties of all guide wire, and guide wire kits sold.

  12. Microstructural evolution and mechanical properties of Inconel 718 after thermal exposure

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Z.S., E-mail: yuzaisong@tpri.com.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, No. 28, Xianning West Road, Xi’an 710049 (China); Xi' an Thermal Power Research Institute Co. Ltd., No. 136, Xingqing Road, Xi’an 710032 (China); Zhang, J.X. [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, No. 28, Xianning West Road, Xi’an 710049 (China); Yuan, Y.; Zhou, R.C.; Zhang, H.J.; Wang, H.Z. [Xi' an Thermal Power Research Institute Co. Ltd., No. 136, Xingqing Road, Xi’an 710032 (China)

    2015-05-14

    Inconel 718 was subjected to various heat treatments, i.e., solution heat treatment, standard ageing treatment and standard ageing plus 700 °C thermal exposure. The mechanical properties of the alloys were determined using tensile tests and Charpy pendulum impact tests at 650 °C and room temperature, respectively. The highest yield strength of 988 MPa was attained in the standard aged specimen, whereas a maximum impact toughness of 217 J cm{sup −2} was attained in the solution-treated specimen. After thermal exposure, the mechanical properties of the specimens degrade. Both the yield strength and impact toughness decreased monotonically with increasing thermal exposure time. Subjected to a 10000-h long-term thermal exposure, the yield strength dramatically decreased to 475 MPa (almost 50% of the maximum strength), and the impact toughness reduced to only 18 J cm{sup −2}. The microstructures of the specimens were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Coarsening of γ′ and γ″ and the transformation of γ″ to δ-Ni{sub 3}Nb was observed after thermal exposure. However, a complete transformation from metastable γ″ to δ-Ni{sub 3}Nb was never accomplished, even after the 10000-h long-term thermal exposure. Based on the obtained experimental results, the effects of the microstructural evolution on the mechanical properties are discussed.

  13. Aggregate of nanoparticles: rheological and mechanical properties

    Directory of Open Access Journals (Sweden)

    Wang Yu

    2011-01-01

    Full Text Available Abstract The understanding of the rheological and mechanical properties of nanoparticle aggregates is important for the application of nanofillers in nanocompoistes. In this work, we report a rheological study on the rheological and mechanical properties of nano-silica agglomerates in the form of gel network mainly constructed by hydrogen bonds. The elastic model for rubber is modified to analyze the elastic behavior of the agglomerates. By this modified elastic model, the size of the network mesh can be estimated by the elastic modulus of the network which can be easily obtained by rheology. The stress to destroy the aggregates, i.e., the yield stress (σy , and the elastic modulus (G' of the network are found to be depended on the concentration of nano-silica (ϕ, wt.% with the power of 4.02 and 3.83, respectively. Via this concentration dependent behavior, we can extrapolate two important mechanical parameters for the agglomerates in a dense packing state (ϕ = 1: the shear modulus and the yield stress. Under large deformation (continuous shear flow, the network structure of the aggregates will experience destruction and reconstruction, which gives rise to fluctuations in the viscosity and a shear-thinning behavior.

  14. Design of monoliths through their mechanical properties.

    Science.gov (United States)

    Podgornik, Aleš; Savnik, Aleš; Jančar, Janez; Krajnc, Nika Lendero

    2014-03-14

    Chromatographic monoliths have several interesting properties making them attractive supports for analytics but also for purification, especially of large biomolecules and bioassemblies. Although many of monolith features were thoroughly investigated, there is no data available to predict how monolith mechanical properties affect its chromatographic performance. In this work, we investigated the effect of porosity, pore size and chemical modification on methacrylate monolith compression modulus. While a linear correlation between pore size and compression modulus was found, the effect of porosity was highly exponential. Through these correlations it was concluded that chemical modification affects monolith porosity without changing the monolith skeleton integrity. Mathematical model to describe the change of monolith permeability as a function of monolith compression modulus was derived and successfully validated for monoliths of different geometries and pore sizes. It enables the prediction of pressure drop increase due to monolith compressibility for any monolith structural characteristics, such as geometry, porosity, pore size or mobile phase properties like viscosity or flow rate, based solely on the data of compression modulus and structural data of non-compressed monolith. Furthermore, it enables simple determination of monolith pore size at which monolith compressibility is the smallest and the most robust performance is expected. Data of monolith compression modulus in combination with developed mathematical model can therefore be used for the prediction of monolith permeability during its implementation but also to accelerate the design of novel chromatographic monoliths with desired hydrodynamic properties for particular application.

  15. PICA Variants with Improved Mechanical Properties

    Science.gov (United States)

    Thornton, Jeremy; Ghandehari, Ehson M.; Fan, Wenhong; Stackpoole, Margaret; Chavez-Garcia, Jose

    2011-01-01

    Phenolic Impregnated Carbon Ablator (PICA) is a member of the family of Lightweight Ceramic Ablators (LCAs) and was developed at NASA Ames Research Center as a thermal protection system (TPS) material for the Stardust mission probe that entered the Earth s atmosphere faster than any other probe or vehicle to date. PICA, carbon fiberform base and phenolic polymer, shows excellent thermal insulative properties at heating rates from about 250 W/sq cm to 1000 W/sq cm. The density of standard PICA - 0.26 g/cu cm to 0.28 g/cu cm - can be changed by changing the concentration of the phenolic resin. By adding polymers to the phenolic resin before curing it is possible to significantly improve the mechanical properties of PICA without significantly increasing the density.

  16. Design and mechanical properties of insect cuticle.

    Science.gov (United States)

    Vincent, Julian F V; Wegst, Ulrike G K

    2004-07-01

    Since nearly all adult insects fly, the cuticle has to provide a very efficient and lightweight skeleton. Information is available about the mechanical properties of cuticle-Young's modulus of resilin is about 1 MPa, of soft cuticles about 1 kPa to 50 MPa, of sclerotised cuticles 1-20 GPa; Vicker's Hardness of sclerotised cuticle ranges between 25 and 80 kgf mm(-2); density is 1-1.3 kg m(-3)-and one of its components, chitin nanofibres, the Young's modulus of which is more than 150 GPa. Experiments based on fracture mechanics have not been performed although the layered structure probably provides some toughening. The structural performance of wings and legs has been measured, but our understanding of the importance of buckling is lacking: it can stiffen the structure (by elastic postbuckling in wings, for example) or be a failure mode. We know nothing of fatigue properties (yet, for instance, the insect wing must undergo millions of cycles, flexing or buckling on each cycle). The remarkable mechanical performance and efficiency of cuticle can be analysed and compared with those of other materials using material property charts and material indices. Presented in this paper are four: Young's modulus-density (stiffness per unit weight), specific Young's modulus-specific strength (elastic hinges, elastic energy storage per unit weight), toughness-Young's modulus (fracture resistance under various loading conditions), and hardness (wear resistance). In conjunction with a structural analysis of cuticle these charts help to understand the relevance of microstructure (fibre orientation effects in tendons, joints and sense organs, for example) and shape (including surface structure) of this fibrous composite for a given function. With modern techniques for analysis of structure and material, and emphasis on nanocomposites and self-assembly, insect cuticle should be the archetype for composites at all levels of scale.

  17. Mechanical properties of crepe paper and chickpaper

    Directory of Open Access Journals (Sweden)

    Ľubomír KUBÍK

    2016-06-01

    Full Text Available The paper deals with the evaluation of the mechanical properties of the crepe paper and chickpaper. The thickness of crepe paper was 300 m with the surface mass 150 g*m-2 and chickpaper paper thickness was 100 m with the surface mass 40 g*m-2. Crepe paper and chickpaper are usually used for chicken breeding. Longitudinal and transversal tensile properties were studied. The tensile behavior was monitored on the motorized test stand ANDILOG STENTOR 1000 (Andilog Technologies, Vitrolles, France.There were measured the tensile properties as modulus of elasticity, maximal elongation, maximal tensile force, tensile strengths, tensile index and strain at break of the longitudinal and transversal samples by testing paper strips. Mean values of the maximal elongation b of longitudinal chickpaper samples were three times smaller than maximal elongation of transversal samples. Mean values of maximal tensile force Ft, tensile strength btensile indexwand maximal strain at break T of longitudinal chickpaper samples were two times smaller than maximal quantities of transversal samples. Mean values of the tensile modulus of elasticity of longitudinal and transversal chickpaper samples were almost equal. Chickpaper mechanical properties in tension were different in the longitudinal and transversal direction of the original paper surface. Mean values of the maximal elongation b and maximal strain at break T of longitudinal crepe paper samples were sixty times smaller than maximal elongation and maximal strain at break of transversal samples. Mean values of maximal tensile force Ft, tensile strength bandtensile indexwof longitudinal crepe paper samples were fourth times smaller than maximal quantities of transversal samples. Mean values of the tensile modulus of elasticity of longitudinal samples of crepe paper were thirty eight times smaller than values of transversal samples.

  18. Monotonic and cyclic responses of impact polypropylene and continuous glass fiber-reinforced impact polypropylene composites at different strain rates

    KAUST Repository

    Yudhanto, Arief

    2016-03-08

    Impact copolymer polypropylene (IPP), a blend of isotactic polypropylene and ethylene-propylene rubber, and its continuous glass fiber composite form (glass fiber-reinforced impact polypropylene, GFIPP) are promising materials for impact-prone automotive structures. However, basic mechanical properties and corresponding damage of IPP and GFIPP at different rates, which are of keen interest in the material development stage and numerical tool validation, have not been reported. Here, we applied monotonic and cyclic tensile loads to IPP and GFIPP at different strain rates (0.001/s, 0.01/s and 0.1/s) to study the mechanical properties, failure modes and the damage parameters. We used monotonic and cyclic tests to obtain mechanical properties and define damage parameters, respectively. We also used scanning electron microscopy (SEM) images to visualize the failure mode. We found that IPP generally exhibits brittle fracture (with relatively low failure strain of 2.69-3.74%) and viscoelastic-viscoplastic behavior. GFIPP [90]8 is generally insensitive to strain rate due to localized damage initiation mostly in the matrix phase leading to catastrophic transverse failure. In contrast, GFIPP [±45]s is sensitive to the strain rate as indicated by the change in shear modulus, shear strength and failure mode.

  19. Linking properties to microstructure through multiresolution mechanics

    Science.gov (United States)

    McVeigh, Cahal James

    The macroscale mechanical and physical properties of materials are inherently linked to the underlying microstructure. Traditional continuum mechanics theories have focused on approximating the heterogeneous microstructure as a continuum, which is conducive to a partial differential equation mathematical description. Although this makes large scale simulation of material much more efficient than modeling the detailed microstructure, the relationship between microstructure and macroscale properties becomes unclear. In order to perform computational materials design, material models must clearly relate the key underlying microstructural parameters (cause) to macroscale properties (effect). In this thesis, microstructure evolution and instability events are related to macroscale mechanical properties through a new multiresolution continuum analysis approach. The multiresolution nature of this theory allows prediction of the evolving magnitude and scale of deformation as a direct function of the changing microstructure. This is achieved via a two-pronged approach: (a) Constitutive models which track evolving microstructure are developed and calibrated to direct numerical simulations (DNS) of the microstructure. (b) The conventional homogenized continuum equations of motion are extended via a virtual power approach to include extra coupled microscale stresses and stress couples which are active at each characteristic length scale within the microstructure. The multiresolution approach is applied to model the fracture toughness of a cemented carbide, failure of a steel alloy under quasi-static loading conditions and the initiation and velocity of adiabatic shear bands under high speed dynamic loading. In each case the multiresolution analysis predicts the important scale effects which control the macroscale material response. The strain fields predicted in the multiresolution continuum analyses compare well to those observed in direct numerical simulations of the

  20. Analysis of Mechanical Properties for GEM Foil

    CERN Document Server

    Chin, Yuk Ming

    2016-01-01

    In view of new assembly technique of the GEM detector; in which three foils stack is stretched to get the uniform gaps among the foils. We studied the mechanical properties of the foil material. We conditioned the samples in different environments to make them extra dry and wet. As holes are the major source of the charge amplification their deformation can effect the detector performance. Therefore in our studies we also studied at which level of the stress the holes deformation is seen. These tensile and holes deformation studies can help to optimize the stress during detector assembly.

  1. Passive mechanical properties of ovine rumen tissue

    Science.gov (United States)

    Waite, Stephen J.; Cater, John E.; Walker, Cameron G.; Amirapu, Satya; Waghorn, Garry C.; Suresh, Vinod

    2016-05-01

    Mechanical and structural properties of ovine rumen tissue have been determined using uniaxial tensile testing of tissue from four animals at five rumen locations and two orientations. Animal and orientation did not have a significant effect on the stress-strain response, but there was a significant difference between rumen locations. Histological studies showed two orthogonal muscle layers in all regions except the reticulum, which has a more isotropic structure. A quasi-linear viscoelastic model was fitted to the relaxation stage for each region. Model predictions of the ramp stage had RMS errors of 13-24% and were within the range of the experimental data.

  2. Investigation on Mechanical Property of Seamless Pipe

    Institute of Scientific and Technical Information of China (English)

    ZHAO Li-ming; YANG Xiao-yong; LIU Ye

    2004-01-01

    The mechanical properties of the steel pipe rolled with continuously casting round billet after determining the chemical composition in steel were studied. The results show that the total reduction ratio should be higher than 5.2 when the line pipes of grade B, grade 20 and other general seamless pipe were rolled with continuously casting round billet. And the total reduction ratio should be higher than 10.2 and the grain size should be controlled more than grade 7 for casing of oil countryside tubular goods (OCTG).

  3. Mechanical properties of low dimensional materials

    Science.gov (United States)

    Saini, Deepika

    Recent advances in low dimensional materials (LDMs) have paved the way for unprecedented technological advancements. The drive to reduce the dimensions of electronics has compelled researchers to devise newer techniques to not only synthesize novel materials, but also tailor their properties. Although micro and nanomaterials have shown phenomenal electronic properties, their mechanical robustness and a thorough understanding of their structure-property relationship are critical for their use in practical applications. However, the challenges in probing these mechanical properties dramatically increase as their dimensions shrink, rendering the commonly used techniques inadequate. This dissertation focuses on developing techniques for accurate determination of elastic modulus of LDMs and their mechanical responses under tensile and shear stresses. Fibers with micron-sized diameters continuously undergo tensile and shear deformations through many phases of their processing and applications. Significant attention has been given to their tensile response and their structure-tensile properties relations are well understood, but the same cannot be said about their shear responses or the structure-shear properties. This is partly due to the lack of appropriate instruments that are capable of performing direct shear measurements. In an attempt to fill this void, this dissertation describes the design of an inexpensive tabletop instrument, referred to as the twister, which can measure the shear modulus (G) and other longitudinal shear properties of micron-sized individual fibers. An automated system applies a pre-determined twist to the fiber sample and measures the resulting torque using a sensitive optical detector. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers. Two industrially important fibers, IM7 carbon fiber and KevlarRTM 119, were found to have G = 17 and 2.4 GPa, respectively. In addition to measuring the shear

  4. Photochromic properties and reaction mechanism of naphthopyran

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The photochromic properties and reaction mechanism of title compounds have been examined with steady method on compounds 3-phenyl-3-[3-methylbenzothiophene-2-yl]-3H- naphtho[2,1-b]pyran (1) and 3-phenyl-3-[benzofuran-2-yl]-3H-naphtho[2,1-b]pyran (2) and nanosecond laser flash photolysis techniques on compound 3-phenyl-3-[1,2-dimethylindol-3-yl]- 3H-naphtho[2,1-b]pyran (3). The influence of oxygen on transient spectra and decay kinetics of compound 3 has been investigated. Both excited singlet state and triplet state are involved in the photochromic mechanism of compound 3. The influence of molecular structure on photochromic behavior has been studied also. Decay kinetics indicated that the lifetime of colored forms of 1 and 2 were several orders of magnitude longer than that of 3.

  5. Photochromic properties and reaction mechanism of naphthopyran

    Institute of Scientific and Technical Information of China (English)

    潘桂兰; 魏景强; 朱爱平; 明阳福; 樊美公; 姚思德

    2001-01-01

    The photochromic properties and reaction mechanism of title compounds have been examined with steady method on compounds 3-phenyl-3-[3-methylbenzothiophene-2-yl]-3H-naphtho[2,1-b]pyran (1) and 3-phenyl-3-[benzofuran-2-yl]-3H-naphtho[2,1-b]pyran (2) and nanosecond laser flash photolysis techniques on compound 3-phenyl-3-[1,2-dimethylindol-3-yl]-3H-naphtho[2,1-b]pyran (3). The influence of oxygen on transient spectra and decay kinetics of compound 3 has been investigated. Both excited singlet state and triplet state are involved in the photochromic mechanism of compound 3. The influence of molecular structure on photochromic behavior has been studied also. Decay kinetics indicated that the lifetime of colored forms of 1 and 2 were several orders of magnitude longer than that of 3.

  6. Stability of generalized monotonicity with respect to their characterizations

    CERN Document Server

    An, P T

    2002-01-01

    We show that known types of generalized monotone maps are not stable with respect to their characterizations (i.e., the characterizations are not maintained during an arbitrary map of this type is disturbed by an element with sufficiently small norm) then introduce s-quasimonotone maps, which are stable with respect to their characterization. For gradient maps, s-quasimonotonicity is related to s-quasiconvexity of the underlying function. A necessary and sufficient condition for a univariate polynomial to be s-quasimonotone is given. Furthermore, some stability properties of a-quasiconvex functions are presented.

  7. Coronal Jet Plasma Properties and Acceleration Mechanisms

    Science.gov (United States)

    Farid, Samaiyah; Reeves, Kathy; Savcheva, Antonia; Soto, Natalia

    2017-08-01

    Coronal jets are transient eruptions of plasma typically characterized by aprominent long spire and a bright base, and sometimes accompanied by a small filament. Jets are thought to be produced by magnetic reconnection when small-scale bipolar magnetic fields emerge into an overlying coronal field or move into a locally unipolar region. Coronal jets are commonly divided into two categories: standard jets and blowout jets, and are found in both quiet and active regions. The plasma properties of jets vary across type and location, therefore understanding the underlying acceleration mechanisms are difficult to pin down. In this work, we examine both blow-out and standard jets using high resolution multi-wavelength data. Although reconnection is commonly accepted as the primary acceleration mechanism, we also consider the contribution chromospheric evaporation to jet formation. We use seven coronal channels from SDO/AIA , Hinode/XRT Be-thin and IRIS slit-jaw data. In addition, we separate the Fe-XVIII line from the SDO/94Å channel. We calculate plasma properties including velocity, Alfven speed, and density as a function of wavelength and Differential Emission Measure (DEM). Finally, we explore the magnetic topology of the jets using Coronal Modeling System (CMS) to construct potential and non-linear force free models based on the flux rope insertion method.

  8. Mechanical properties of nanoporous graphene membrane

    Science.gov (United States)

    Liu, Yilun; Chen, Xi

    2014-01-01

    Nanoporous graphene holds great promise in the application of filtration such as seawater desalination, gas separation, and ionic channels. In this paper, we study the mechanical properties of nanoporous graphene with different size, shape, and density of nanopore. The strength decreases as the size and porosity of the nanopore increases. However, the rough edges of the nanopore has significant influence to the strength where the blunt tip perpendicular to the loading direction has higher strength. The effective tensile modulus is only determined by porosity of the nanopore as ΔE ˜ -p0.64, while the strength is determined by the size, shape, and porosity of the nanopore, for the same type of nanopore the strength scales with the porosity as Δσs ˜ -p. In contrast, the effective fracture strain increases as porosity increases for small and moderate porosities. The work is a first study of the relation between mechanical properties and porosity of nanoporous graphene and is helpful to the design of high performance nanoporous graphene membrane.

  9. Mechanical properties of 3D ceramic nanolattices

    Science.gov (United States)

    Meza, Lucas

    Developments in advanced nanoscale fabrication techniques have allowed for the creation of 3-dimensional hierarchical structural meta-materials that can be designed with arbitrary geometry. These structures can be made on length scales spanning multiple orders of magnitude, from tens of nanometers to hundreds of microns. The smallest features are controllable on length scales where materials have been shown to exhibit size effects in their mechanical properties. Combining novel nanoscale mechanical properties with a 3-dimensional architecture enables the creation of new classes of materials with tunable and unprecedented mechanical properties. We present the fabrication and mechanical deformation of hollow tube alumina nanolattices that were fabricated using two-photon lithography direct laser writing (DLW), atomic layer deposition (ALD), and oxygen plasma etching. Nanolattices were designed in a number of different geometries including octet-truss, octahedron, and 3D Kagome. Additionally, a number of structural parameters were varied including tube wall thickness (t) , tube major axis (a) , and unit cell size (L) . The resulting nanolattices had a range of densities from ρ = 4 to 250 mg/cm3. Uniaxial compression and cyclic loading tests were performed on the nanolattices to obtain the yield strength and modulus. In these tests, a marked change in the deformation response was observed when the wall thickness was reduced below 20nm; thick-walled nanolattices (t>20nm) underwent catastrophic, brittle failure, which transitioned to a gradual, ductile-like deformation as wall thickness was reduced. Thick-walled nanolattices also exhibited no recovery after compression, while thin-walled structures demonstrated notable recovery, with some recovering by 98% after compression to 50% strain and by 80% when compressed to 90% strain. Across all geometries, unit cell sizes, and wall thicknesses, we found a consistent power law relation between strength and modulus with

  10. Complexity of Non-Monotonic Logics

    CERN Document Server

    Thomas, Michael

    2010-01-01

    Over the past few decades, non-monotonic reasoning has developed to be one of the most important topics in computational logic and artificial intelligence. Different ways to introduce non-monotonic aspects to classical logic have been considered, e.g., extension with default rules, extension with modal belief operators, or modification of the semantics. In this survey we consider a logical formalism from each of the above possibilities, namely Reiter's default logic, Moore's autoepistemic logic and McCarthy's circumscription. Additionally, we consider abduction, where one is not interested in inferences from a given knowledge base but in computing possible explanations for an observation with respect to a given knowledge base. Complexity results for different reasoning tasks for propositional variants of these logics have been studied already in the nineties. In recent years, however, a renewed interest in complexity issues can be observed. One current focal approach is to consider parameterized problems and ...

  11. Linear Inviscid Damping for Monotone Shear Flows

    CERN Document Server

    Zillinger, Christian

    2014-01-01

    In this article we prove linear stability, inviscid damping and scattering of the 2D Euler equations around regular, strictly monotone shear flows $(U(y),0)$ in a periodic channel under Sobolev perturbations. We treat the settings of an infinite channel, $\\mathbb{T} \\times \\mathbb{R}$, as well as a finite channel, $\\mathbb{T} \\times [0,1]$, with impermeable boundary. We first prove inviscid damping with optimal algebraic rates for strictly monotone shear flows under the assumption of controlling the regularity of the scattered vorticity. Subsequently, we establish linear stability of the scattering equation in Sobolev spaces under perturbations which are of not too large wave-length with respect to $x$, depending on $U''$.

  12. Mechanical properties of the beetle elytron, a biological composite material

    Science.gov (United States)

    We determined the relationship between composition and mechanical properties of elytral (modified forewing) cuticle of the beetles Tribolium castaneum and Tenebrio molitor. Elytra of both species have similar mechanical properties at comparable stages of maturation (tanning). Shortly after adult ecl...

  13. Improved selection in totally monotone arrays

    Energy Technology Data Exchange (ETDEWEB)

    Mansour, Y. (Harvard Univ., Cambridge, MA (United States). Aiken Computation Lab.); Park, J.K. (Sandia National Labs., Albuquerque, NM (United States)); Schieber, B. (International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center); Sen, S. (AT and T Bell Labs., Murray Hill, NJ (United States))

    1991-01-01

    This paper's main result is an O(({radical}{bar m}lgm)(n lg n) + mlg n)-time algorithm for computing the kth smallest entry in each row of an m {times} n totally monotone array. (A two-dimensional A = a(i,j) is totally monotone if for all i{sub 1} < i{sub 2} and j{sub 1} < j{sup 2}, < a(i{sub 1},j{sub 2}) implies a(i{sub 2},j{sub 1})). For large values of k (in particular, for k=(n/2)), this algorithm is significantly faster than the O(k(m+n))-time algorithm for the same problem due to Kravets and Park. An immediate consequence of this result is an O(n{sup 3/2} lg{sup 2}n)-time algorithm for computing the kth nearest neighbor of each vertex of a convex n-gon. In addition to the main result, we also give an O(n lg m)-time algorithm for computing an approximate median in each row of an m {times} n totally monotone array; this approximate median is an entry whose rank in its row lies between (n/4) and (3n/4) {minus} 1. 20 refs., 3 figs.

  14. Edit Distance to Monotonicity in Sliding Windows

    CERN Document Server

    Chan, Ho-Leung; Lee, Lap-Kei; Pan, Jiangwei; Ting, Hing-Fung; Zhang, Qin

    2011-01-01

    Given a stream of items each associated with a numerical value, its edit distance to monotonicity is the minimum number of items to remove so that the remaining items are non-decreasing with respect to the numerical value. The space complexity of estimating the edit distance to monotonicity of a data stream is becoming well-understood over the past few years. Motivated by applications on network quality monitoring, we extend the study to estimating the edit distance to monotonicity of a sliding window covering the $w$ most recent items in the stream for any $w \\ge 1$. We give a deterministic algorithm which can return an estimate within a factor of $(4+\\eps)$ using $O(\\frac{1}{\\eps^2} \\log^2(\\eps w))$ space. We also extend the study in two directions. First, we consider a stream where each item is associated with a value from a partial ordered set. We give a randomized $(4+\\epsilon)$-approximate algorithm using $O(\\frac{1}{\\epsilon^2} \\log \\epsilon^2 w \\log w)$ space. Second, we consider an out-of-order strea...

  15. Joining of aluminum and stainless steel using AlSi10 brazing filler: Microstructure and mechanical properties

    Science.gov (United States)

    Fedorov, Vasilii; Uhlig, Thomas; Wagner, Guntram

    2017-07-01

    Joining of dissimilar materials like stainless steel and aluminum is of special interest for automotive applications. Due to the different properties of these materials, suitable joining techniques are required. Brazing offers the possibilities to manufacture high performance joints in one step and at low joining temperatures. However, these joints often need to withstand a high number of high cyclic loads during application. Therefore, in addition to the monotonic properties, the fatigue behavior of the produced joints must be considered and evaluated. In the present work, specimens are manufactured by induction brazing using an AlSi10 filler and a non-corrosive flux. The mechanical properties are determined by tensile shear tests as well as in fatigue tests at ambient and elevated temperatures. The microstructure of the brazed joints and the fracture surfaces of the tested samples are investigated by SEM.

  16. Mechanism Analyses of Pressure Non-Monotonic Effect on Flammability Limits%压力对可燃极限非单调作用的机理分析

    Institute of Scientific and Technical Information of China (English)

    田雪沁; 陶志强; 张海

    2011-01-01

    1D, laminar premixed CH4/Air flames at elevated pressures were numerically studied to assess pressure effect on flammability limits, with attention primarily paid to maximum flame temperature loss caused by radiation, dominant chain branching and termination reactions and species profiles at different pressures. It was found that radiation heat loss effect increases with decreasing equivalence ratio, especially at the turning point showing the non-monotonic pressure effect. As pressure increases, sensitivity coefficient of main chain termination reaction H+O2+M=HO2+M changes non-monotonously, firstly increases then decreases and this chain termination reaction is gradually substituted by reaction HO2+CH3=OH+CH3O. The main reason of such change is that the relative concentration of HO2 species becomes higher than that of other species as pressure increases.%采用CHEMKIN的PREMIX模块对非常压下贫燃侧的一维、层流CH4/Air预混火焰进行数值模拟,分析了不同的压力下辐射引起的最高火焰温度损失、主要反应的敏感性系数和主要自由基摩尔分数的变化。结果表明,辐射热损失随着当量比的下降而加强,在非单调变化的拐点附近,热辐射损失对最高火焰温度的相对变化作用明显加强。随着压力增大,近极限火焰的主要链终止反应H+O2+M=HO2+M的敏感性呈现先增大后减小的非单调变化,并逐渐被HO2+CH3=OH+CH30取代;引起以上变化的原因是,随着压力增大,HO2对其它主要基团(OH、O、H)的相对浓度明显增大。

  17. Environmental properties set cell mechanics and morphology

    Science.gov (United States)

    Janmey, Paul

    2012-02-01

    Many cell types are sensitive to mechanical signals that are produced either by application of exogenous force to their surfaces, or by the resistance that their surroundings place on forces generated by the cells themselves. Cell morphology, motility, proliferation, and protein expression all change in response to substrate stiffness. Changing the elastic moduli of substrates alters the formation of focal adhesions, the assembly of actin filaments into bundles, and the stability of intermediate filaments. The range of stiffness over which different primary cell types respond can vary over a wide range and generally reflects the elastic modulus of the tissue from which these cells were isolated. Mechanosensing depends on the type of adhesion receptor by which the cell binds, and therefore on both the molecular composition of the extracellular matrix and the nature of its link to the cytoskeleton. Many cell types can alter their own stiffness to match that of the substrate to which they adhere. The maximal elastic modulus that cells such as fibroblasts can attain is similar to that of crosslinked actin networks at the concentrations in the cell cortex. The precise mechanisms of mechanosensing are not well defined, but they presumably require an elastic connection between cell and substrate, mediated by transmembrane proteins. The viscoelastic properties of different extracellular matrices and cytoskeletal elements strongly influence the response of cells to mechanical signals, and the unusual non-linear elasticity of many biopolymer gels, characterized by strain-stiffening, leads to novel mechanisms by which cells alter their stiffness by engagement of molecular motors that produce internal stresses. Cell cortical elasticity is dominated by cytoskeletal polymer networks and can be modulated by internal tension. Simultaneous control of substrate stiffness and adhesive patterns suggests that stiffness sensing occurs on a length scale much larger than single molecular

  18. Weak monotonicity inequality and partial regularity for harmonic maps

    Institute of Scientific and Technical Information of China (English)

    沈尧天; 严树森

    1999-01-01

    The notion of locally weak monotonicity inequality for weakly harmonic maps is introduced and various results on this class of maps are obtained. For example, the locally weak monotonicity inequality is nearly equivalent to the ε-regularity.

  19. Monotonic Loading of Circular Surface Footings on Clay

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Barari, Amin

    2011-01-01

    Appropriate modeling of offshore foundations under monotonic loading is a significant challenge in geotechnical engineering. This paper reports experimental and numerical analyses, specifically investigating the response of circular surface footings during monotonic loading and elastoplastic beha...

  20. Mechanical properties of stabilized artificial organic soil

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In order to study the influence of organic matter on the mechanical properties of stabilized soil and the effect of XGL2005 on stabilizing organic soil,unconfined compressive strength tests were carried out.Test results indicated that the strength of stabilized soil decreased in the form of a logarithmic function as the organic matter content increased.In contrast,the strength increased in the form of a power function as the content of the stabilization agent increased.The strength of cement stabilized organic soil was reinforced greatly by adding the stabilizer XGL2005.Based on the law obtained from the test,a strength prediction model was established by regression analysis.The model included the influence of the curing time,the content of the cement,the organic matter content and the stabilization agent on the strength of stabilized soil.

  1. Mechanical Properties of Sheared Wet Granular Piles

    Science.gov (United States)

    Seemann, Ralf; Schaber, Marc; Karmakar, Somnath; Hippler, Anna-Lena; Scheel, Mario; di Michiel, Marco; Brinkmann, Martin

    2015-03-01

    The mechanical properties of dry and wet granulates are explored when being sheared with a parabolic profile at constant shear volume. The dissipated energy increase linearly with external pressure both for a wet and a dry granulate. However, the dissipated energy for wet a granulate has a finite value for the limiting case of vanishing external pressure and increases slower with external pressure compared to the dry granulate. Using a down sized version of the shear cell the reorganization of a granulate and liquid is additionally imaged in real time using x-ray micro-tomography. With the insight from x-ray tomography the contribution of the breaking capillary bridges to the dissipated energy can be analyzed. We could also shed light on the influence of dilatation effects on the dissipated energy upon inverting the shear direction.

  2. Mechanical properties of high-strength concrete

    Science.gov (United States)

    Mokhtarzadeh, Alireza

    This report summarizes an experimental program conducted to investigate production techniques and mechanical properties of high strength concrete in general and to provide recommendations for using these concretes in manufacturing precast/prestressed bridge girders. Test variables included total amount and composition of cementitious material (portland cement, fly ash, and silica fume), type and brand of cement, type of silica fume (dry densified and slurry), type and brand of high-range water-reducing admixture, type of aggregate, aggregate gradation, maximum aggregate size, and curing. Tests were conducted to determine the effects of these variables on changes in compressive strength and modulus of elasticity over time, splitting tensile strength, modulus of rupture, creep, shrinkage, and absorption potential (as an indirect indicator of permeability). Also investigated were the effects of test parameters such as mold size, mold material, and end condition. Over 6,300 specimens were cast from approximately 140 mixes over a period of 3 years.

  3. Mechanical properties of ceramic-polymer nanocomposites

    Directory of Open Access Journals (Sweden)

    2009-03-01

    Full Text Available Nano crystalline powders of Barium Sodium Niobate (BNN with the composition Ba3–2x Na4+x R Nb10 O30 with (R stands for rare earth = 0, x = 0 have been prepared by conventional ceramic technique. Barium Sodium Niobate can form a wide range of solid solutions, incorporating rare earth and alkali, alkaline earth elements with different compositions. The powder belonged to tungsten bronze type structure with tetragonal symmetry and lattice constants a = b = 1.2421 nm and c = 0.3903 nm. XRD (X-ray Diffraction SEM (Scanning Electron Microscope and AFM (Atomic Force Microscope studies revealed that the particle size is in the nanometer range. Composites are prepared by mixing powders of BNN with polystyrene at different volume fractions of the BNN. Melt mixing technique is carried out in a Brabender Plasticoder at a rotor speed of 60 rpm (rotations per minute for composite preparation. Mechanical properties such as stress-strain behavior, Young’s modulus, tensile strength, strain at break etc. are evaluated. Addition of filler enhances the mechanical properties of the polymer such as Young’s modulus and tensile strength. The composites showed the trend of perfect adhesion between the filler and the polymer. The filler particles are distributed relatively uniform fashion in all composites and the particles are almost spherical in shape with irregular boundaries. To explore more carefully the degree of interfacial adhesion between the two phases, the results are analyzed by using models featuring adhesion parameter. The experimental results are compared with theoretical predictions.

  4. Biodegradable compounds: Rheological, mechanical and thermal properties

    Science.gov (United States)

    Nobile, Maria Rossella; Lucia, G.; Santella, M.; Malinconico, M.; Cerruti, P.; Pantani, R.

    2015-12-01

    Recently great attention from industry has been focused on biodegradable polyesters derived from renewable resources. In particular, PLA has attracted great interest due to its high strength and high modulus and a good biocompatibility, however its brittleness and low heat distortion temperature (HDT) restrict its wide application. On the other hand, Poly(butylene succinate) (PBS) is a biodegradable polymer with a low tensile modulus but characterized by a high flexibility, excellent impact strength, good thermal and chemical resistance. In this work the two aliphatic biodegradable polyesters PBS and PLA were selected with the aim to obtain a biodegradable material for the industry of plastic cups and plates. PBS was also blended with a thermoplastic starch. Talc was also added to the compounds because of its low cost and its effectiveness in increasing the modulus and the HDT of polymers. The compounds were obtained by melt compounding in a single screw extruder and the rheological, mechanical and thermal properties were investigated. The properties of the two compounds were compared and it was found that the values of the tensile modulus and elongation at break measured for the PBS/PLA/Talc compound make it interesting for the production of disposable plates and cups. In terms of thermal resistance the compounds have HDTs high enough to contain hot food or beverages. The PLA/PBS/Talc compound can be, then, considered as biodegradable substitute for polystyrene for the production of disposable plates and cups for hot food and beverages.

  5. AFM PeakForce QNM mode: Evidencing nanometre-scale mechanical properties of chitin-silica hybrid nanocomposites.

    Science.gov (United States)

    Smolyakov, G; Pruvost, S; Cardoso, L; Alonso, B; Belamie, E; Duchet-Rumeau, J

    2016-10-20

    PeakForce Quantitative Nanomechanical Mapping (QNM) AFM mode was used to explore the mechanical properties of textured chitin-silica hybrid films at the nanoscale. The influence of the force applied by the tip on the sample surface was studied for standard homogeneous samples, for chitin nanorods and for chitin-silica hybrid nanocomposites. Thick films of superimposed chitin nanorods showed a monotonous increase of DMT modulus (based on the Derjaguin-Muller-Toporov model) owing to an increase in modulus at the interface between nanorods due to geometrical constraints of the AFM acquisition. A similar variation of DMT modulus was obtained for chitin-silica hybrid thick films related to mechanical strengthening induced by the presence of silica. This work revealed the role of the organic-inorganic interface, at the nanoscale, in the mechanical behaviour of textured materials using PeakForce QNM mode, with optimized analysis conditions.

  6. A-monotonicity and applications to nonlinear variational inclusion problems

    Directory of Open Access Journals (Sweden)

    Ram U. Verma

    2004-01-01

    Full Text Available A new notion of the A-monotonicity is introduced, which generalizes the H-monotonicity. Since the A-monotonicity originates from hemivariational inequalities, and hemivariational inequalities are connected with nonconvex energy functions, it turns out to be a useful tool proving the existence of solutions of nonconvex constrained problems as well.

  7. Testing Manifest Monotonicity Using Order-Constrained Statistical Inference

    Science.gov (United States)

    Tijmstra, Jesper; Hessen, David J.; van der Heijden, Peter G. M.; Sijtsma, Klaas

    2013-01-01

    Most dichotomous item response models share the assumption of latent monotonicity, which states that the probability of a positive response to an item is a nondecreasing function of a latent variable intended to be measured. Latent monotonicity cannot be evaluated directly, but it implies manifest monotonicity across a variety of observed scores,…

  8. Wehrl entropy, Lieb conjecture and entanglement monotones

    CERN Document Server

    Mintert, F; Mintert, Florian; Zyczkowski, Karol

    2004-01-01

    We propose to quantify the entanglement of pure states of $N \\times N$ bipartite quantum system by defining its Husimi distribution with respect to $SU(N)\\times SU(N)$ coherent states. The Wehrl entropy is minimal if and only if the pure state analyzed is separable. The excess of the Wehrl entropy is shown to be equal to the subentropy of the mixed state obtained by partial trace of the bipartite pure state. This quantity, as well as the generalized (R{\\'e}nyi) subentropies, are proved to be Schur--convex, so they are entanglement monotones and may be used as alternative measures of entanglement.

  9. Topological recursion and a quantum curve for monotone Hurwitz numbers

    Science.gov (United States)

    Do, Norman; Dyer, Alastair; Mathews, Daniel V.

    2017-10-01

    Classical Hurwitz numbers count branched covers of the Riemann sphere with prescribed ramification data, or equivalently, factorisations in the symmetric group with prescribed cycle structure data. Monotone Hurwitz numbers restrict the enumeration by imposing a further monotonicity condition on such factorisations. In this paper, we prove that monotone Hurwitz numbers arise from the topological recursion of Eynard and Orantin applied to a particular spectral curve. We furthermore derive a quantum curve for monotone Hurwitz numbers. These results extend the collection of enumerative problems known to be governed by the paradigm of topological recursion and quantum curves, as well as the list of analogues between monotone Hurwitz numbers and their classical counterparts.

  10. Payoff-monotonic game dynamics and the maximum clique problem.

    Science.gov (United States)

    Pelillo, Marcello; Torsello, Andrea

    2006-05-01

    Evolutionary game-theoretic models and, in particular, the so-called replicator equations have recently proven to be remarkably effective at approximately solving the maximum clique and related problems. The approach is centered around a classic result from graph theory that formulates the maximum clique problem as a standard (continuous) quadratic program and exploits the dynamical properties of these models, which, under a certain symmetry assumption, possess a Lyapunov function. In this letter, we generalize previous work along these lines in several respects. We introduce a wide family of game-dynamic equations known as payoff-monotonic dynamics, of which replicator dynamics are a special instance, and show that they enjoy precisely the same dynamical properties as standard replicator equations. These properties make any member of this family a potential heuristic for solving standard quadratic programs and, in particular, the maximum clique problem. Extensive simulations, performed on random as well as DIMACS benchmark graphs, show that this class contains dynamics that are considerably faster than and at least as accurate as replicator equations. One problem associated with these models, however, relates to their inability to escape from poor local solutions. To overcome this drawback, we focus on a particular subclass of payoff-monotonic dynamics used to model the evolution of behavior via imitation processes and study the stability of their equilibria when a regularization parameter is allowed to take on negative values. A detailed analysis of these properties suggests a whole class of annealed imitation heuristics for the maximum clique problem, which are based on the idea of varying the parameter during the imitation optimization process in a principled way, so as to avoid unwanted inefficient solutions. Experiments show that the proposed annealing procedure does help to avoid poor local optima by initially driving the dynamics toward promising regions in

  11. Extracting nanobelt mechanical properties from nanoindentation

    Science.gov (United States)

    Zhang, Yin

    2010-06-01

    A three-spring-in-series model is proposed for the nanobelt (NB) indentation test. Compared with the previous two-spring-in-series model, which considers the bending stiffness of atomic force microscope cantilever and the indenter/NB contact stiffness, this model adds a third spring of the NB/substrate contact stiffness. NB is highly flexural due to its large aspect ratio of length to thickness. The bending and lift-off of NB form a localized contact with substrate, which makes the Oliver-Pharr method [W. C. Oliver and G. M. Pharr, J. Mater. Res. 7, 1564 (1992)] and Sneddon method [I. N. Sneddon, Int. J. Eng. Sci. 3, 47 (1965)] inappropriate for NB indentation test. Because the NB/substrate deformation may have significant impact on the force-indentation depth data obtained in experiment, the two-spring-in-series model can lead to erroneous predictions on the NB mechanical properties. NB in indentation test can be susceptible to the adhesion influence because of its large surface area to volume ratio. NB/substrate contact and adhesion can have direct and significant impact on the interpretation of experimental data. Through the three-spring-in-series model, the influence of NB/substrate contact and adhesion is analyzed and methods of reducing such influence are also suggested.

  12. Mechanical properties of lattice grid composites

    Institute of Scientific and Technical Information of China (English)

    Hualin Fan; Daining Fang; Fengnian Jin

    2008-01-01

    An equivalent continuum method only considering the stretching deformation of struts was used to study the in-plane stiffness and strength of planar lattice grid composite materials. The initial yield equations of lattices were deduced. Initial yield surfaces were depicted separately in different 3D and 2D stress spaces. The failure envelope is a polyhedron in 3D spaces and a polygon in 2D spaces. Each plane or line of the failure envelope is corresponding to the yield or buckling of a typical bar row. For lattices with more than three bar rows, subsequent yield of the other bar rowafter initial yield made the lattice achieve greater limit strength. The importance of the buckling strength of the grids was strengthened while the grids were relative sparse. The integration model of the method was used to study the nonlinear mechanical properties of strain hardening grids. It was shown that the integration equation could accurately model the complete stress-strain curves of the grids within small deformations.

  13. The Monotonicity Puzzle: An Experimental Investigation of Incentive Structures

    Directory of Open Access Journals (Sweden)

    Jeannette Brosig

    2010-05-01

    Full Text Available Non-monotone incentive structures, which - according to theory - are able to induce optimal behavior, are often regarded as empirically less relevant for labor relationships. We compare the performance of a theoretically optimal non-monotone contract with a monotone one under controlled laboratory conditions. Implementing some features relevant to real-world employment relationships, our paper demonstrates that, in fact, the frequency of income-maximizing decisions made by agents is higher under the monotone contract. Although this observed behavior does not change the superiority of the non-monotone contract for principals, they do not choose this contract type in a significant way. This is what we call the monotonicity puzzle. Detailed investigations of decisions provide a clue for solving the puzzle and a possible explanation for the popularity of monotone contracts.

  14. Determination of Some Mechanical Properties of Almond Seed ...

    African Journals Online (AJOL)

    Determination of Some Mechanical Properties of Almond Seed Related to Design of Food ... Nigerian Journal of Technological Development ... The determined engineering properties are vital for the design of postharvest handling and ...

  15. Real-time observations of mechanical stimulus-induced enhancements of mechanical properties in osteoblast cells

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xu; Liu Xiaoli; Sun Jialun [State Key Laboratory of Bioactive Materials, School of Physics, Nankai University, Tianjin 300073 (China); He Shuojie [State Key Laboratory of Bioactive Materials, School of Physics, Nankai University, Tianjin 300073 (China); Department of Physics, Pusan National University, Pusan (Korea, Republic of); Lee, Imshik [State Key Laboratory of Bioactive Materials, School of Physics, Nankai University, Tianjin 300073 (China)], E-mail: ilee@nankai.edu.cn2; Pak, Hyuk Kyu [Department of Physics, Pusan National University, Pusan (Korea, Republic of)

    2008-09-15

    Osteoblast, playing a key role in the pathophysiology of osteoporosis, is one of the mechanical stress sensitive cells. The effects of mechanical load-induced changes of mechanical properties in osteoblast cells were studied at real-time. Osteoblasts obtained from young Wister rats were exposed to mechanical loads in different frequencies and resting intervals generated by atomic force microscopy (AFM) probe tip and simultaneously measured the changes of the mechanical properties by AFM. The enhancement of the mechanical properties was observed and quantified by the increment of the apparent Young's modulus, E{sup *}. The observed mechanical property depended on the frequency of applied tapping loads. For the resting interval is 50 s, the mechanical load-induced enhancement of E{sup *}-values disappears. It seems that the enhanced mechanical property was recover able under no additional mechanical stimulus.

  16. Convergence of the natural approximations of piecewise monotone interval maps.

    Science.gov (United States)

    Haydn, Nicolai

    2004-06-01

    We consider piecewise monotone interval mappings which are topologically mixing and satisfy the Markov property. It has previously been shown that the invariant densities of the natural approximations converge exponentially fast in uniform pointwise topology to the invariant density of the given map provided its derivative is piecewise Lipshitz continuous. We provide an example of a map which is Lipshitz continuous and for which the densities converge in the bounded variation norm at a logarithmic rate. This shows that in general one cannot expect exponential convergence in the bounded variation norm. Here we prove that if the derivative of the interval map is Holder continuous and its variation is well approximable (gamma-uniform variation for gamma>0), then the densities converge exponentially fast in the norm.

  17. A new non-monotone fitness scaling for genetic algorithm

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The properties of selection operators in the genetic algorithm (GA) are studied in detail. It is indicated that the selection of operations is significant for both improving the general fitness of a population and leading to the schema deceptiveness. The stochastic searching characteristics of GA are compared with those of heuristic methods. The influence of selection operators on the GA' s exploration and exploitation is discussed, and the performance of selection operators is evaluated with the premature convergence of the GA taken as an example based on One-Max function. In order to overcome the schema deceptiveness of the GA, a new type of fitness scaling, non monotone scaling, is advanced to enhance the evolutionary ability of a population. The effectiveness of the new scaling method is tested by a trap function and a needle-in-haystack (NiH) function.

  18. MINLIP for the Identification of Monotone Wiener Systems

    CERN Document Server

    Pelckmans, Kristiaan

    2010-01-01

    This paper studies the MINLIP estimator for the identification of Wiener systems consisting of a sequence of a linear FIR dynamical model, and a monotonically increasing (or decreasing) static function. Given $T$ observations, this algorithm boils down to solving a convex quadratic program with $O(T)$ variables and inequality constraints, implementing an inference technique which is based entirely on model complexity control. The resulting estimates of the linear submodel are found to be almost consistent when no noise is present in the data, under a condition of smoothness of the true nonlinearity and local Persistency of Excitation (local PE) of the data. This result is novel as it does not rely on classical tools as a 'linearization' using a Taylor decomposition, nor exploits stochastic properties of the data. It is indicated how to extend the method to cope with noisy data, and empirical evidence contrasts performance of the estimator against other recently proposed techniques.

  19. Non-Payoff Monotonic Dynamics in an Evolutionary Game of Courtship

    CERN Document Server

    Chacoma, Andrés; Zanette, Damián H

    2015-01-01

    We propose an evolutionary coordination game to formalize a simplified model of the evolution of strategies during human courtship. The dynamics, derived from the consideration of experimental observations on human social behavior driven by self-esteem, turns out to be non-payoff monotonic. This property gives rise to nontrivial evolution in the players' strategies, which we study both numerically and analytically.

  20. Mechanical properties of non-woven glass fiber geopolymer composites

    Science.gov (United States)

    Rieger, D.; Kadlec, J.; Pola, M.; Kovářík, T.; Franče, P.

    2017-02-01

    This experimental research focuses on mechanical properties of non-woven glass fabric composites bound by geopolymeric matrix. This study investigates the effect of different matrix composition and amount of granular filler on the mechanical properties of final composites. Matrix was selected as a metakaolin based geopolymer hardened by different amount of potassium silicate activator. The ceramic granular filler was added into the matrix for investigation of its impact on mechanical properties and workability. Prepared pastes were incorporated into the non-woven fabrics by hand roller and final composites were stacked layer by layer to final thickness. The early age hardening of prepared pastes were monitored by small amplitude dynamic rheology approach and after 28 days of hardening the mechanical properties were examined. The electron microscopy was used for detail description of microstructural properties. The imaging methods revealed good wettability of glass fibers by geopolymeric matrix and results of mechanical properties indicate usability of these materials for constructional applications.

  1. Experimental Analysis of Tensile Mechanical Properties of Sprayed FRP

    Directory of Open Access Journals (Sweden)

    Zhao Yang

    2016-01-01

    Full Text Available To study the tensile mechanical properties of sprayed FRP, 13 groups of specimens were tested through uniaxial tensile experiments, being analyzed about stress-strain curve, tensile strength, elastic modulus, breaking elongation, and other mechanical properties. Influencing factors on tensile mechanical properties of sprayed FRP such as fiber type, resin type, fiber volume ratio, fiber length, and composite thickness were studied in the paper too. The results show that both fiber type and resin type have an obvious influence on tensile mechanical properties of sprayed FRP. There will be a specific fiber volume ratio for sprayed FRP to obtain the best tensile mechanical property. The increase of fiber length can lead to better tensile performance, while that of composite thickness results in property degradation. The study can provide reference to popularization and application of sprayed FRP material used in structure reinforcement.

  2. Microstructure, mechanical properties, bio-corrosion properties and antibacterial properties of Ti–Ag sintered alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Mian [Key Lab. for Anisotropy and Texture of Materials, Education Ministry of China, Northeastern University, Shenyang 110819 (China); Zhang, Erlin, E-mail: zhangel@atm.neu.edu.cn [Key Lab. for Anisotropy and Texture of Materials, Education Ministry of China, Northeastern University, Shenyang 110819 (China); Zhang, Lan [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China)

    2016-05-01

    In this research, Ag element was selected as an antibacterial agent to develop an antibacterial Ti–Ag alloy by a powder metallurgy. The microstructure, phase constitution, mechanical properties, corrosion resistance and antibacterial properties of the Ti–Ag sintered alloys have been systematically studied by X-ray diffraction (XRD), scanning electron microscope (SEM), compressive test, electrochemical measurements and antibacterial test. The effects of the Ag powder size and the Ag content on the antibacterial property and mechanical property as well as the anticorrosion property have been investigated. The microstructure results have shown that Ti–Ag phase, residual pure Ag and Ti were the mainly phases in Ti–Ag(S75) sintered alloy while Ti{sub 2}Ag was synthesized in Ti–Ag(S10) sintered alloy. The mechanical test indicated that Ti–Ag sintered alloy showed a much higher hardness and the compressive yield strength than cp-Ti but the mechanical properties were slightly reduced with the increase of Ag content. Electrochemical results showed that Ag powder size had a significant effect on the corrosion resistance of Ti–Ag sintered alloy. Ag content increased the corrosion resistance in a dose dependent way under a homogeneous microstructure. Antibacterial tests have demonstrated that antibacterial Ti–Ag alloy was successfully prepared. It was also shown that the Ag powder particle size and the Ag content influenced the antibacterial activity seriously. The reduction in the Ag powder size was benefit to the improvement in the antibacterial property and the Ag content has to be at least 3 wt.% in order to obtain a strong and stable antibacterial activity against Staphylococcus aureus bacteria. The bacterial mechanism was thought to be related to the Ti{sub 2}Ag and its distribution. - Highlights: • Ti–Ag alloy with up to 99% antibacterial rate was developed by powder metallurgy. • The effects of the Ag powder size and the Ag content on the

  3. Convergence and regularization for monotonicity-based shape reconstruction in electrical impedance tomography

    DEFF Research Database (Denmark)

    Garde, Henrik; Staboulis, Stratos

    2016-01-01

    demonstrate that for admissible choices of regularization parameters the inhomogeneities are detected, and under reasonable assumptions, asymptotically exactly characterized. Moreover, we rigorously associate this result with the complete electrode model, and describe how a computationally cheap monotonicity......The inverse problem of electrical impedance tomography is severely ill-posed, meaning that, only limited information about the conductivity can in practice be recovered from boundary measurements of electric current and voltage. Recently it was shown that a simple monotonicity property...... of the related Neumann-to-Dirichlet map can be used to characterize shapes of inhomogeneities in a known background conductivity. In this paper we formulate a monotonicity-based shape reconstruction scheme that applies to approximative measurement models, and regularizes against noise and modelling error. We...

  4. Scaling Effect of Area-Averaged NDVI: Monotonicity along the Spatial Resolution

    Directory of Open Access Journals (Sweden)

    Hiroki Yoshioka

    2012-01-01

    Full Text Available Changes in the spatial distributions of vegetation across the globe are routinely monitored by satellite remote sensing, in which the reflectance spectra over land surface areas are measured with spatial and temporal resolutions that depend on the satellite instrumentation. The use of multiple synchronized satellite sensors permits long-term monitoring with high spatial and temporal resolutions. However, differences in the spatial resolution of images collected by different sensors can introduce systematic biases, called scaling effects, into the biophysical retrievals. This study investigates the mechanism by which the scaling effects distort normalized difference vegetation index (NDVI. This study focused on the monotonicity of the area-averaged NDVI as a function of the spatial resolution. A monotonic relationship was proved analytically by using the resolution transform model proposed in this study in combination with a two-endmember linear mixture model. The monotonicity allowed the inherent uncertainties introduced by the scaling effects (error bounds to be explicitly determined by averaging the retrievals at the extrema of theresolutions. Error bounds could not be estimated, on the other hand, for non-monotonic relationships. Numerical simulations were conducted to demonstrate the monotonicity of the averaged NDVI along spatial resolution. This study provides a theoretical basis for the scaling effects and develops techniques for rectifying the scaling effects in biophysical retrievals to facilitate cross-sensor calibration for the long-term monitoring of vegetation dynamics.

  5. Stability of dynamical systems on the role of monotonic and non-monotonic Lyapunov functions

    CERN Document Server

    Michel, Anthony N; Liu, Derong

    2015-01-01

    The second edition of this textbook provides a single source for the analysis of system models represented by continuous-time and discrete-time, finite-dimensional and infinite-dimensional, and continuous and discontinuous dynamical systems.  For these system models, it presents results which comprise the classical Lyapunov stability theory involving monotonic Lyapunov functions, as well as corresponding contemporary stability results involving non-monotonicLyapunov functions.Specific examples from several diverse areas are given to demonstrate the applicability of the developed theory to many important classes of systems, including digital control systems, nonlinear regulator systems, pulse-width-modulated feedback control systems, and artificial neural networks.   The authors cover the following four general topics:   -          Representation and modeling of dynamical systems of the types described above -          Presentation of Lyapunov and Lagrange stability theory for dynamical sy...

  6. On the monotonicity of multidimensional finite difference schemes

    Science.gov (United States)

    Kovyrkina, O.; Ostapenko, V.

    2016-10-01

    The classical concept of monotonicity, introduced by Godunov for linear one-dimensional difference schemes, is extended to multidimensional case. Necessary and sufficient conditions of monotonicity are obtained for linear multidimensional difference schemes of first order. The constraints on the numerical viscosity are given that ensure the monotonicity of a difference scheme in the multidimensional case. It is proposed a modification of the second order multidimensional CABARET scheme that preserves the monotonicity of one-dimensional discrete solutions and, as a result, ensures higher smoothness in the computation of multidimensional discontinuous solutions. The results of two-dimensional test computations illustrating the advantages of the modified CABARET scheme are presented.

  7. Determination of Mechanical Properties of Microcapsules

    NARCIS (Netherlands)

    Sagis, L.M.C.

    2015-01-01

    Mechanical characterization methods can be important tools in optimizing the design of an encapsulation system. Food microcapsules can be subjected to considerable shear and extensional forces during their life cycle, and the shell of the capsules needs to be designed with sufficient mechanical stre

  8. Mechanical properties of UV irradiated rat tail tendon (RTT) collagen.

    Science.gov (United States)

    Sionkowska, Alina; Wess, Tim

    2004-04-01

    The mechanical properties of RTT collagen tendon before and after UV irradiation have been investigated by mechanical testing (Instron). Air-dried tendon were submitted to treatment with UV irradiation (wavelength 254 nm) for different time intervals. The changes in such mechanical properties as breaking strength and percentage elongation have been investigated. The results have shown, that the mechanical properties of the tendon were greatly affected by time of UV irradiation. Ultimate tensile strength and ultimate percentage elongation decreased after UV irradiation of the tendon. Increasing UV irradiation leads to a decrease in Young's modulus of the tendon.

  9. Mechanical Properties of Degraded PMR-15 Resin

    Science.gov (United States)

    Tsuji, Luis C.

    2000-01-01

    Thermo-oxidative aging produces a nonuniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hr. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and coefficient of thermal expansion (CTE) of nitrogen aged specimens were measured directly. The nitrogen-aged specimens were assumed to have the same properties as the interior material in the air-aged specimens. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

  10. Phonon spectrum, mechanical and thermophysical properties of thorium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Pérez Daroca, D., E-mail: pdaroca@tandar.cnea.gov.ar [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica (Argentina); Consejo Nacional de Investigaciones Cientı´ficas y Técnicas (Argentina); Jaroszewicz, S. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica (Argentina); Instituto de Tecnología Jorge A. Sabato, UNSAM-CNEA (Argentina); Llois, A.M. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica (Argentina); Consejo Nacional de Investigaciones Cientı´ficas y Técnicas (Argentina); Mosca, H.O. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica (Argentina); Instituto de Tecnología Jorge A. Sabato, UNSAM-CNEA (Argentina)

    2013-06-15

    In this work, we study, by means of density functional perturbation theory and the pseudopotential method, mechanical and thermophysical properties of thorium carbide. These properties are derived from the lattice dynamics in the quasi-harmonic approximation. The phonon spectrum of ThC presented in this article, to the best authors’ knowledge, have not been studied, neither experimentally, nor theoretically. We compare mechanical properties, volume thermal expansion and molar specific capacities with previous results and find a very good agreement.

  11. Study of UV fiber's mechanical properties

    Institute of Scientific and Technical Information of China (English)

    Feng TU; Xinwei QIAN; Deming LIU; Shuqiang ZHANG; Jie LUO; Tao DENG; Chen YANG; Jiangtao GUO

    2009-01-01

    A number of spectroscopic techniques make use of ultra violet (UV) absorbance and luminescence measurements to characterize materials, for use in medical/pharmaceutical applications, for forensic and sensor applications, and for remote detection or monitoring,especially for hazardous environments.Furthermore, many high-power applications in medicine and industry are looking forward to using UV wavelengths.The UV fiber's mechanical reliability has become one of the most crucial performances with longer length fiber being used.This paper reviews the researched evolvement of the normal single mode fiber's mechanical reliability.Based on the standard measure method of the normal fiber, the mechanical reliability of the UV fiber has been researched.The measurement results show the difference of mechanical reliability between the different doping composition UV fibers.

  12. Improvement of mechanical properties of steel sheet

    Institute of Scientific and Technical Information of China (English)

    Bashchenko; A.; P.; Knokhin; V.; G.; Beliavsky; P.; B.; Traino; A.; I.

    2005-01-01

    Consideration was given to some peculiarities of the resource-saving IDT-production that implements metallophysical principles of hot deformation effect upon the formation of martensite and perlite structures of alloy steels as well as upon their functional properties by way of DTT-cycling.

  13. Mechanical properties of short carbon/glass fiber reinforced high mechanical performance epoxy resins

    Institute of Scientific and Technical Information of China (English)

    张竞; 黄培

    2009-01-01

    To research the relationship between epoxy and fiber inherent property and mechanical properties of composite,we prepared a series of composites using three kinds of high mechanical performance epoxy resins as matrices and reinforced by the same volume fraction(5%)of short carbon and glass fiber.Their mechanical properties were investigated from the perspective of chemical structure and volume shrinkage ratio of epoxy.We analyzed their tensile strength and modulus based on the mixing rule and Halpin-Tsai eq...

  14. Monotone measures of ergodicity for Markov chains

    Directory of Open Access Journals (Sweden)

    J. Keilson

    1998-01-01

    Full Text Available The following paper, first written in 1974, was never published other than as part of an internal research series. Its lack of publication is unrelated to the merits of the paper and the paper is of current importance by virtue of its relation to the relaxation time. A systematic discussion is provided of the approach of a finite Markov chain to ergodicity by proving the monotonicity of an important set of norms, each measures of egodicity, whether or not time reversibility is present. The paper is of particular interest because the discussion of the relaxation time of a finite Markov chain [2] has only been clean for time reversible chains, a small subset of the chains of interest. This restriction is not present here. Indeed, a new relaxation time quoted quantifies the relaxation time for all finite ergodic chains (cf. the discussion of Q1(t below Equation (1.7]. This relaxation time was developed by Keilson with A. Roy in his thesis [6], yet to be published.

  15. Non-monotonicity of trace distance under tensor products

    Energy Technology Data Exchange (ETDEWEB)

    Maziero, Jonas, E-mail: jonas.maziero@ufsm.br [Universidade Federal de Santa Maria (UFSM), RS (Brazil). Departamento de Fisica

    2015-10-15

    The trace distance (TD) possesses several of the good properties required for a faithful distance measure in the quantum state space. Despite its importance and ubiquitous use in quantum information science, one of its questionable features, its possible non-monotonicity under taking tensor products of its arguments (NMuTP), has been hitherto unexplored. In this article, we advance analytical and numerical investigations of this issue considering different classes of states living in a discrete and finite dimensional Hilbert space. Our results reveal that although this property of TD does not show up for pure states and for some particular classes of mixed states, it is present in a non-negligible fraction of the regarded density operators. Hence, even though the percentage of quartets of states leading to the NMuTP drawback of TD and its strength decrease as the system's dimension grows, this property of TD must be taken into account before using it as a figure of merit for distinguishing mixed quantum states. (author)

  16. Mechanical Properties of Four Human Longbones.

    Science.gov (United States)

    1981-11-30

    Ultimate Properties of Compact Bone Tissue," J. Biomechanics, 1975, pp. 393-405. 41. Bass, William M., Human Osteology: A Laboratory and Field Manual of...bone’s proximal and distal epiphyses. Most of the measurements used can be found in the antropological literature [1, 2, 4, 5, 61. Those that cannot...using strain sensing load cells connected to j a manual switch and balance unit and digital display. The torque applied was inferred by the tensile

  17. Robust Monotone Iterates for Nonlinear Singularly Perturbed Boundary Value Problems

    Directory of Open Access Journals (Sweden)

    Boglaev Igor

    2009-01-01

    Full Text Available This paper is concerned with solving nonlinear singularly perturbed boundary value problems. Robust monotone iterates for solving nonlinear difference scheme are constructed. Uniform convergence of the monotone methods is investigated, and convergence rates are estimated. Numerical experiments complement the theoretical results.

  18. Regularization and Iterative Methods for Monotone Variational Inequalities

    Directory of Open Access Journals (Sweden)

    Xiubin Xu

    2010-01-01

    Full Text Available We provide a general regularization method for monotone variational inequalities, where the regularizer is a Lipschitz continuous and strongly monotone operator. We also introduce an iterative method as discretization of the regularization method. We prove that both regularization and iterative methods converge in norm.

  19. LIMITED MEMORY BFGS METHOD FOR NONLINEAR MONOTONE EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    Weijun Zhou; Donghui Li

    2007-01-01

    In this paper, we propose an algorithm for solving nonlinear monotone equations by combining the limited memory BFGS method (L-BFGS) with a projection method. We show that the method is globally convergent if the equation involves a Lipschitz continuous monotone function. We also present some preliminary numerical results.

  20. Positivity and Monotonicity Preserving Biquartic Rational Interpolation Spline Surface

    Directory of Open Access Journals (Sweden)

    Xinru Liu

    2014-01-01

    Full Text Available A biquartic rational interpolation spline surface over rectangular domain is constructed in this paper, which includes the classical bicubic Coons surface as a special case. Sufficient conditions for generating shape preserving interpolation splines for positive or monotonic surface data are deduced. The given numeric experiments show our method can deal with surface construction from positive or monotonic data effectively.

  1. New techniques of the mechanical properties assessment for Advanced High Strength Steel (AHSS) in automobile

    Energy Technology Data Exchange (ETDEWEB)

    Fang Jian [Baoshan Iron and Steel Co., Ltd., Shanghai (China)

    2005-07-01

    Based on the mathematical polynomial and differentiate processing onto tensile stress-strain curve, the experimental technique to monitor the trace of working hardening exponent against strain was established, with the hope of linking the characterization of the mechanical properties to the insight into the microstructure behavior of AHSS. The features of a significant strain hardening peak with slow decaying followed was obtained existing on the n value trace of strain during uniform deformation, which may be the predominant contribution to the outstanding combination of strength and plasticity of AHSS. In comparison, for conventional high strength steel as quench and temper prepared, the form of n value trace was changed into the monotonous decreasing tendency within overall uniform extension. As regards the dynamic loading response of AHSS, the recorded impact force-displacement curve by instrumented impact testing with characteristic force points subdivided the absorbed impact energy into distinct components, corresponding to the crack initiation and propagation. Combined with the quasi static tensile, the concept of toughness parameters including J{sub d}, J-{delta}a and so-called ''local strain toughness, LST'' were proposed, which implies that the stable plastic deformation and pronounced energy consumption may lead to the excellent material response against cracking and rupture under various loading conditions. (orig.)

  2. On mechanical properties of planar flexure hinges of compliant mechanisms

    Directory of Open Access Journals (Sweden)

    F. Dirksen

    2011-06-01

    Full Text Available The synthesis of compliant mechanisms yield optimized topologies that combine several stiff parts with highly elastic flexure hinges. The hinges are often represented in finite element analysis by a single node (one-node hinge leaving doubts on the physical meaning as well as an uncertainty in the manufacturing process.

    To overcome this one-node hinge problem of optimized compliant mechanisms' topologies, one-node hinges need to be replaced by real flexure hinges providing desired deflection range and the ability to bear internal loads without failure. Therefore, several common types of planar flexure hinges with different geometries are characterized and categorized in this work providing a comprehensive guide with explicit analytical expressions to replace one-node hinges effectively.

    Analytical expressions on displacements, stresses, maximum elastic deformations, bending stiffness, center of rotation and first natural frequencies are derived in this work. Numerical simulations and experimental studies are performed validating the analytical results. More importance is given to practice-oriented flexure hinge types in terms of cost-saving manufacturability, i.e. circular notch type hinges and rectangular leaf type hinges.

  3. Mechanical Properties of Layered Hybrid Fiber Reinforced Concrete

    Institute of Scientific and Technical Information of China (English)

    YUAN Hai-qing; CHEN Jing-tao; ZHU Ji-dong

    2003-01-01

    To improve the mechanical properties of concrete,Layered Hybrid Fiber Reinforced Concrete (LHFRC) was developed in this paper.Through comparative tests,the effects of layered hybrid fibers on a series of mechanical properties of concrete were discussed.The mechanical properties include compressive strength,tensile strength,flexural strength,compressive stress-strain relationship,flexural toughness and cracking resistance of concrete.The testing results and analysis demonstrate that layered hybrid fibers can significantly improve the flexural strength,toughness and cracking resistance of concrete while the cost of concrete increases slightly.

  4. Mechanical and microwave absorbing properties of carbon-filled polyurethane.

    Science.gov (United States)

    Kucerová, Z; Zajícková, L; Bursíková, V; Kudrle, V; Eliás, M; Jasek, O; Synek, P; Matejková, J; Bursík, J

    2009-01-01

    Polyurethane (PU) matrix composites were prepared with various carbon fillers at different filler contents in order to investigate their structure, mechanical and microwave absorbing properties. As fillers, flat carbon microparticles, carbon microfibers and multiwalled carbon nanotubes (MWNT) were used. The microstructure of the composite was examined by scanning electron microscopy and transmission electron microscopy. Mechanical properties, namely universal hardness, plastic hardness, elastic modulus and creep were assessed by means of depth sensing indentation test. Mechanical properties of PU composite filled with different fillers were investigated and the composite always exhibited higher hardness, elastic modulus and creep resistance than un-filled PU. Influence of filler shape, content and dispersion was also investigated.

  5. Grain size dependent mechanical properties in nanophase materials

    Energy Technology Data Exchange (ETDEWEB)

    Siegel, R.W. [Argonne National Lab., IL (United States); Fougere, G.E. [Northwestern Univ., Evanston, IL (United States). Dept. of Materials Science and Engineering

    1995-02-01

    It has become possible in recent years to synthesize metals and ceramics under well controlled conditions with constituent grain structures on a manometer size scale (below 100 nm). These new materials have mechanical properties that are strongly grain-size dependent and often significantly different than those of their coarser grained counterparts. Nanophase metals tend to become stronger and ceramics are more easily deformed as grain size is reduced. The observed mechanical property changes appear to be related primarily to grain size limitations and the large percentage of atoms in grain boundary environments. A brief overview of our present knowledge about the grain-size dependent mechanical properties of nanophase materials is presented.

  6. Dependence of Glass Mechanical Properties on Thermal and Pressure History

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Bauchy, Mathieu

    -equilibrium material, the structure and properties of glass depend not only on its composition, but also on its thermal and pressure histories. Here we review our recent findings regarding the thermal and pressure history dependence of indentation-derived mechanical properties of oxide glasses.......Predicting the properties of new glasses prior to manufacturing is a topic attracting great industrial and scientific interest. Mechanical properties are currently of particular interest given the increasing demand for stronger, thinner, and more flexible glasses in recent years. However, as a non...

  7. Elastic properties and mechanical tension of graphene

    Science.gov (United States)

    Ramírez, R.; Herrero, C. P.

    2017-01-01

    Room-temperature simulations of graphene have been performed as a function of the mechanical tension of the layer. Finite-size effects are accurately reproduced by an acoustic dispersion law for the out-of-plane vibrations that, in the long-wave limit, behaves as ρ ω2=σ k2+κ k4 . The fluctuation tension σ is finite (˜0.1 N/m) even when the external mechanical tension vanishes. Transverse vibrations imply a duplicity in the definition of the elastic constants of the layer, as observables related to the real area of the surface may differ from those related to the in-plane projected area. This duplicity explains the variability of experimental data on the Young modulus of graphene based on electron spectroscopy, interferometric profilometry, and indentation experiments.

  8. Mechanical Properties of Heavy Duty Epoxy Coatings

    OpenAIRE

    Reinoso Rodríguez, Rosa

    2013-01-01

    In a first stage, the composition of epoxy coatings is discussed with special focus on the mechanism of curing and the chemistry of curing agents and their advantages and downturns in prospect to their use in the manufacture of epoxy resins. Then literature on the causes of increased brittleness, cracking and degradation of epoxy resins was studied, especially in relation to evolution of the resins in the glassy state, hydrothermal aging and also in relation to chemical aging. ...

  9. The mechanical and strength properties of diamond.

    Science.gov (United States)

    Field, J E

    2012-12-01

    Diamond is an exciting material with many outstanding properties; see, for example Field J E (ed) 1979 The Properties of Diamond (London: Academic) and Field J E (ed) 1992 The Properties of Natural and Synthetic Diamond (London: Academic). It is pre-eminent as a gemstone, an industrial tool and as a material for solid state research. Since natural diamonds grew deep below the Earth's surface before their ejection to mineable levels, they also contain valuable information for geologists. The key to many of diamond's properties is the rigidity of its structure which explains, for example, its exceptional hardness and its high thermal conductivity. Since 1953, it has been possible to grow synthetic diamond. Before then, it was effectively only possible to have natural diamond, with a small number of these found in the vicinity of meteorite impacts. Techniques are now available to grow gem quality synthetic diamonds greater than 1 carat (0.2 g) using high temperatures and pressures (HTHP) similar to those found in nature. However, the costs are high, and the largest commercially available industrial diamonds are about 0.01 carat in weight or about 1 mm in linear dimension. The bulk of synthetic diamonds used industrially are 600 µm or less. Over 75% of diamond used for industrial purposes today is synthetic material. In recent years, there have been two significant developments. The first is the production of composites based on diamond; these materials have a significantly greater toughness than diamond while still maintaining very high hardness and reasonable thermal conductivity. The second is the production at low pressures by metastable growth using chemical vapour deposition techniques. Deposition onto non-diamond substrates was first demonstrated by Spitsyn et al 1981 J. Cryst. Growth 52 219-26 and confirmed by Matsumoto et al 1982 Japan J. Appl. Phys. 21 L183-5. These developments have added further to the versatility of diamond. Two other groups of

  10. Mechanical Properties of Intermediate Filament Proteins.

    Science.gov (United States)

    Charrier, Elisabeth E; Janmey, Paul A

    2016-01-01

    Purified intermediate filament (IF) proteins can be reassembled in vitro to produce polymers closely resembling those found in cells, and these filaments form viscoelastic gels. The cross-links holding IFs together in the network include specific bonds between polypeptides extending from the filament surface and ionic interactions mediated by divalent cations. IF networks exhibit striking nonlinear elasticity with stiffness, as quantified by shear modulus, increasing an order of magnitude as the networks are deformed to large strains resembling those that soft tissues undergo in vivo. Individual IFs can be stretched to more than two or three times their resting length without breaking. At least 10 different rheometric methods have been used to quantify the viscoelasticity of IF networks over a wide range of timescales and strain magnitudes. The mechanical roles of different classes of cytoplasmic IFs on mesenchymal and epithelial cells in culture have also been studied by an even wider range of microrheological methods. These studies have documented the effects on cell mechanics when IFs are genetically or pharmacologically disrupted or when normal or mutant IF proteins are exogenously expressed in cells. Consistent with in vitro rheology, the mechanical role of IFs is more apparent as cells are subjected to larger and more frequent deformations.

  11. Mechanical properties of alumina porcelain during heating

    Science.gov (United States)

    Šín, Peter; Podoba, Rudolf; ŠtubÅa, Igor; Trník, Anton

    2014-11-01

    The mechanical strength and Young's modulus of green alumina porcelain (50 wt. % of kaolin, 25 wt. % of Al2O3, and 25 wt. % of feldspar) were measured during heating up to 900 °C and 1100 °C, respectively. To this end, we used the three point-bending method and modulated force thermomechanical analysis (mf-TMA). The loss liberation - of the physically bound water (20 - 250 °C) strengthens the sample and Young's modulus increases its values significantly. The dehydroxylation that takes place in the range of 400 - 650 °C causes a slight decrease in Young's modulus. On the other hand, the mechanical strength slightly increases in this temperature range, although it has a sudden drop at 420 °C. Beyond the dehydroxylation range, above 650 °C, both Young's modulus and mechanical strength increase. Above 950 °C, a sharp increase of Young's modulus is caused by the solid-state sintering and the new structure created by the high-temperature reactions in metakaolinite.

  12. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing.

    Science.gov (United States)

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands.

  13. Structural Properties and Mechanical Durability of Extruded Fish Feed

    DEFF Research Database (Denmark)

    Haubjerg, Anders Fjeldbo; Veje, Christian; Jørgensen, Bo Nørregaard;

    2015-01-01

    This article investigates the possible correlation between mechanical properties of fish feed pellets and their mechanical durability. Mechanical properties were obtained by texture profile analysis (TPA) and stress relaxation test (SRT) of different types of fish feed. The results were correlated...... against a conventional test of mechanical durability (DORIS, Durability On a Realistic, test). From SRT it was found that for achieving a high durability, pellets should be able to relax an applied force nonelastically. From TPA, it was found that a durable pellet should also be able to return its...

  14. Mechanical Properties of Semiconductors and Their Alloys

    Science.gov (United States)

    1992-02-01

    enough footing to warrant refereed publication. 14 3. FIRST-PRINCIPLES APPROACH TO THE PLASTIC PROPERTIES OF HIGH-TEMPERATURE ALLOYS 3.1 INTRODUCTION With...10.2 9.8 10.274 C" 8.036 8.3 3.5 8.013 drC =(a/4)[l+(l-) 2+P2]’. C11 11.1 11.30 C 0.54 0.51 0.53 0.51 A similar procedure can now be carried out to...In CP structure, the first values dAc and dRc are for those bonds along the (111)direction, and the second values are for those in the other three

  15. Thermobimetals Mechanical Properties Produced by Explosive Welding with Rolling

    OpenAIRE

    Gulbin, V.; Kobelev, A.; Borissov, D.

    1997-01-01

    We used explosive welding with rolling to produce thermobimetals on the basis of beryllium bronze and alloys of nickel. It gave us possibility to obtain magnetic and non-magnetic thermobimetals possessing high physical and mechanical properties.

  16. Densely crosslinked polycarbosiloxanes .2. Thermal and mechanical properties

    NARCIS (Netherlands)

    Flipsen, T.A C; Derks, R.; van der Vegt, H.A.; Stenekes, R.; Pennings, A.J; Hadziioannou, G

    1997-01-01

    The thermal and mechanical properties of two densely crosslinked polycarbosiloxane systems were investigated in relation to the molecular structure. The networks were prepared from functional branched prepolymers and crosslinked via a hydrosilylation curing reaction. The prepolymers having only viny

  17. Determination of Mechanical Properties of Micromembranes with Compressive Residual Stress

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A novel model of a load-deflection method to determine the mechanical properties of micromembranes with compressive residual stress is described. Since thin film structures are frequently used in micro devices, characterisation of mechanical properties of thin films is desired by the design and fabrication of micromachines. In this paper, the mechanical properties of thin micromembranes under compressive stress are characterised, which are fabricated by bulk micromachining. The relation between the center deflection and the load pressure on a square membrane is deduced by modelling the membrane as an elastic plate having large deflection with clamped boundaries. According to the model, whether the membrane has initial deflection or not has no effect on the measurement result. The Young's modulus and residual stress are simultaneously determined. The mechanical properties of siliconoxide, silicon nitride membranes and composite membranes of polysilicon with silicon nitride are measured.

  18. Mechanical Properties of Plug Welds after Micro-Jet Cooling

    Directory of Open Access Journals (Sweden)

    Hadryś D.

    2016-12-01

    Full Text Available New technology of micro-jet welding could be regarded as a new way to improve mechanical properties of plug welds. The main purpose of that paper was analyzing of mechanical properties of plug welds made by MIG welding method with micro-jet cooling. The main way for it was comparison of plug welds made by MIG welding method with micro-jet cooling and plug welds made by ordinary MIG welding method. It is interesting for steel because higher amount of acicular ferrite (AF in weld metal deposit (WMD is obtained in MIG welding method with micro-jet cooling in relation to ordinary MIG welding method. This article presents the influence of the cooling medium and the number of micro-jet streams on mechanical properties of the welded joint. Mechanical properties were described by force which is necessary to destroy weld joint.

  19. Investigation of Mechanical Properties of Cryogenically Treated Music Wire

    CERN Document Server

    Heptonstall, A; Robertson, N A

    2015-01-01

    It has been reported that treating music wire (high carbon steel wire) by cooling to cryogenic temperatures can enhance its mechanical properties with particular reference to those properties important for musical performance. We use such wire for suspending many of the optics in Advanced LIGO, the upgrade to LIGO - the Laser Interferometric Gravitational-Wave Observatory. Two properties that particularly interest us are mechanical loss and breaking strength. A decrease in mechanical loss would directly reduce the thermal noise associated with the suspension, thus enhancing the noise performance of mirror suspensions within the detector. An increase in strength could allow thinner wire to be safely used, which would enhance the dilution factor of the suspension, again leading to lower suspension thermal noise. In this article we describe the results of an investigation into some of the mechanical properties of music wire, comparing untreated wire with the same wire which has been cryogenically treated. For th...

  20. A Study in Physical and Mechanical Properties of Hemp Fibres

    Directory of Open Access Journals (Sweden)

    Asim Shahzad

    2013-01-01

    Full Text Available This paper presents the results of the experiments undertaken to evaluate various physical and mechanical properties of hemp fibres. The study of these properties is vital for comparison with similar properties of synthetic fibres and for assessing hemp fibres’ suitability for use as reinforcement in composite materials. The properties of hemp fibres were found to be good enough to be used as reinforcement in composite materials. However, the issues of relatively high moisture content of fibres, variability in fibre properties, and relatively poor fibre/matrix interfacial strength were identified as factors that can reduce the efficiency with which these fibres can be utilised.

  1. Primate dietary ecology in the context of food mechanical properties.

    Science.gov (United States)

    Coiner-Collier, Susan; Scott, Robert S; Chalk-Wilayto, Janine; Cheyne, Susan M; Constantino, Paul; Dominy, Nathaniel J; Elgart, Alison A; Glowacka, Halszka; Loyola, Laura C; Ossi-Lupo, Kerry; Raguet-Schofield, Melissa; Talebi, Mauricio G; Sala, Enrico A; Sieradzy, Pawel; Taylor, Andrea B; Vinyard, Christopher J; Wright, Barth W; Yamashita, Nayuta; Lucas, Peter W; Vogel, Erin R

    2016-09-01

    Substantial variation exists in the mechanical properties of foods consumed by primate species. This variation is known to influence food selection and ingestion among non-human primates, yet no large-scale comparative study has examined the relationships between food mechanical properties and feeding strategies. Here, we present comparative data on the Young's modulus and fracture toughness of natural foods in the diets of 31 primate species. We use these data to examine the relationships between food mechanical properties and dietary quality, body mass, and feeding time. We also examine the relationship between food mechanical properties and categorical concepts of diet that are often used to infer food mechanical properties. We found that traditional dietary categories, such as folivory and frugivory, did not faithfully track food mechanical properties. Additionally, our estimate of dietary quality was not significantly correlated with either toughness or Young's modulus. We found a complex relationship among food mechanical properties, body mass, and feeding time, with a potential interaction between median toughness and body mass. The relationship between mean toughness and feeding time is straightforward: feeding time increases as toughness increases. However, when considering median toughness, the relationship with feeding time may depend upon body mass, such that smaller primates increase their feeding time in response to an increase in median dietary toughness, whereas larger primates may feed for shorter periods of time as toughness increases. Our results emphasize the need for additional studies quantifying the mechanical and chemical properties of primate diets so that they may be meaningfully compared to research on feeding behavior and jaw morphology.

  2. Microstructure and mechanical properties of neoprene montmorillonite nanocomposites

    Science.gov (United States)

    Yeh, Meng-Heng; Hwang, Weng-Sing; Cheng, Lin-Ri

    2007-03-01

    To investigate the microstructure and mechanical properties of neoprene-montmorillonite nanocomposite, three modified montmorillonite are used. An X-ray diffractometer is used to measure the corresponding change in d-spacing. Scanning electron microscopy is employed to investigate the morphology of the various composites. Transmission electron microscopy is employed to investigate the composite of montmorillonite and neoprene. The results indicate that the addition of montmorillonite enhances the mechanical properties of neoprene significantly.

  3. Correlation between the mechanical and histological properties of liver tissue

    OpenAIRE

    Başdoğan, Çağatay; Yarpuzlu, Berkay; Ayyıldız, Mehmet; Tok, Olgu Enis; Aktaş, Ranan Gülhan

    2014-01-01

    In order to gain further insight into the mechanisms of tissue damage during the progression of liver diseases as well as the liver preservation for transplantation, an improved understanding of the relation between the mechanical and histological properties of liver is necessary. We suggest that this relation can only be established truly if the changes in the states of those properties are investigated dynamically as a function of post mortem time. In this regard, we first perform mechanica...

  4. Dynamic mechanical properties of an inlay composite.

    Science.gov (United States)

    Dionysopoulos, P; Watts, D C

    1989-06-01

    A visible light-cured composite resin (Brilliant DI) has been studied over a wide range of temperature and frequency by a dynamic mechanical flexural method. The derived data of logarithmic modulus and loss tangent (tan delta) show considerable changes following a secondary-cure process applied to the material. This involved the application of heat and intense light with temperatures rising to 120 degrees C in 7 min. Following this oven-cure the resin phase exhibited enhanced stiffness with the activation-energy barrier for molecular motion at the glass-transition rising from 220 to 291 kJ/mol. This study clarifies the nature and extent of the internal molecular changes which may be produced in the fabrication of a composite inlay.

  5. Measuring the mechanical properties of molecular conformers

    Science.gov (United States)

    Jarvis, S. P.; Taylor, S.; Baran, J. D.; Champness, N. R.; Larsson, J. A.; Moriarty, P.

    2015-09-01

    Scanning probe-actuated single molecule manipulation has proven to be an exceptionally powerful tool for the systematic atomic-scale interrogation of molecular adsorbates. To date, however, the extent to which molecular conformation affects the force required to push or pull a single molecule has not been explored. Here we probe the mechanochemical response of two tetra(4-bromophenyl)porphyrin conformers using non-contact atomic force microscopy where we find a large difference between the lateral forces required for manipulation. Remarkably, despite sharing very similar adsorption characteristics, variations in the potential energy surface are capable of prohibiting probe-induced positioning of one conformer, while simultaneously permitting manipulation of the alternative conformational form. Our results are interpreted in the context of dispersion-corrected density functional theory calculations which reveal significant differences in the diffusion barriers for each conformer. These results demonstrate that conformational variation significantly modifies the mechanical response of even simple porpyhrins, potentially affecting many other flexible molecules.

  6. Dynamical Mechanical Properties for AD90 Alumina

    Institute of Scientific and Technical Information of China (English)

    REN Hui-lan; NING Jian-guo; LI Ping

    2007-01-01

    The dynamic response of polycrystalline alumina was investigated in the pressure range of 0 -13 GPa by planar impact experiments.Velocity interferometer system for any reflector(VISAR) was used to obtain free surface velocity profile and determine the Hugoniot elastic limit,and manganin gauges were employed to obtain the stress-time histories and determine Hugoniot curve.Both the free surface particle velocity profiles and Hugoniot curves indicate the dispersion of the "plastic" wave for alumina.With the measured stress histories,the complete histories of strain,particle velocity,specific volume and specific internal energy are gained by using path line principle of Lagrange analysis.The dynamic mechanical behaviors for alumina under impact loading are analyzed,such as nonlinear characteristic,strain rate dependence,dispersion and declination of shock wave in the material.

  7. Mechanical and Morphological Properties of Nano Filler Polyester Composites

    Directory of Open Access Journals (Sweden)

    Bonnia Noor Najmi

    2016-01-01

    Full Text Available This research is focusing on mechanical and morphological properties of unsaturated polyester (UP reinforced with two different types of filler which is nano size clay Cloisite 30B (C30B and Carbon Black (CB. Samples were fabricated via hand lay-up and open molding technique. Percentages of Cloisite 30B & Carbon Black (CB used vary from 0, 2, 4, 6, 8 and 10 wt%. The mechanical properties were evaluated by impact, flexural and hardness testing. Result shows that the mechanical strength of C30B was better compare to CB filled composite. The combination of UP with C30B helps to improve the properties due to the high surface area of nanosize filler in the matrix. The result shows that increasing of filler content had increased mechanical properties of composites. Optimum percentage represent good mechanical properties are 4% for both fillers. SEM images showed that rough surface image indicate to agglomeration of filler in the matrix for CB sample and smooth surface image on C30B sample indicate to homogenous blending between filler and matrix polyester. SEM images proved that mechanical properties result indicate that C30B polyester composite is a good reinforcement compare to CB polyester composite.

  8. Ultrasonic investigation of mechanical properties of double base rocket propellants

    NARCIS (Netherlands)

    Schroeff, J.A. van der; Boer, R.S. de

    1976-01-01

    For a series of double base rocket propellants and for poly-methylmethacrylate (PMMA) the longitudinal and transverse sound wave velocities are measured at a frequency of 0.351 MHz in t h e temperature range of −40°C to +60°C. The relations between these acoustic properties and mechanical properties

  9. Mechanical properties of short-flax-fibre reinforced compounds

    NARCIS (Netherlands)

    Bos, H.L.; Müssig, J.; Oever, van den M.J.A.

    2006-01-01

    The mechanical properties of flax/polypropylene compounds, manufactured both with a batch kneading and an extrusion process were determined and compared with the properties of Natural fibre Mat Thermoplastic (NMT) composites. The fibre length and width distributions of the fibres from the compounds

  10. Surface modification, microstructure and mechanical properties of investment cast superalloy

    OpenAIRE

    M. Zielińska; Kubiak, K.; J. Sieniawski

    2009-01-01

    Purpose: The aim of this work is to determine physical and chemical properties of cobalt aluminate (CoAl2O4) modifiers produced by different companies and the influence of different types of modifiers on the grain size, the microstructure and mechanical properties of high temperature creep resisting superalloy René 77.Design/methodology/approach: The first stage of the research work took over the investigations of physical and chemical properties of cobalt aluminate manufactured by three diff...

  11. Prediction of mechanical properties for hexagonal boron nitride nanosheets using molecular mechanics model

    Energy Technology Data Exchange (ETDEWEB)

    Natsuki, Toshiaki [Shinshu University, Faculty of Textile Science and Technology, Ueda (Japan); Shinshu University, Institute of Carbon Science and Technology, Nagano (Japan); Natsuki, Jun [Shinshu University, Institute of Carbon Science and Technology, Nagano (Japan)

    2017-04-15

    Mechanical behaviors of nanomaterials are not easy to be evaluated in the laboratory because of their extremely small size and difficulty controlling. Thus, a suitable model for the estimation of the mechanical properties for nanomaterials becomes very important. In this study, the elastic properties of boron nitride (BN) nanosheets, including the elastic modulus, the shear modulus, and the Poisson's ratio, are predicted using a molecular mechanics model. The molecular mechanics force filed is established to directly incorporate the Morse potential function into the constitutive model of nanostructures. According to the molecular mechanics model, the chirality effect of hexagonal BN nanosheets on the elastic modulus is investigated through a closed-form solution. The simulated result shows that BN nanosheets exhibit an isotropic elastic property. The present analysis yields a set of very simple formulas and is able to be served as a good approximation on the mechanical properties for the BN nanosheets. (orig.)

  12. Mechanical and Thermophysical Properties of Cerium Monopnictides

    Science.gov (United States)

    Bhalla, Vyoma; Singh, Devraj; Jain, S. K.

    2016-03-01

    The ultrasonic attenuation due to phonon-phonon interaction, thermoelastic relaxation and dislocation damping mechanisms has been investigated in cerium monopnictides CeX (X: N, P, As, Sb and Bi) for longitudinal and shear waves along {third-order elastic constants of CeX have also been computed in the temperature range 0 K to 500 K using Coulomb and Born-Mayer potential upto second nearest neighbours. The computed values of these elastic constants have been applied to find out Young's moduli, bulk moduli, Breazeale's non-linearity parameters, Zener anisotropy, ultrasonic velocity, ultrasonic Grüneisen parameter, thermal relaxation time, acoustic coupling constants and ultrasonic attenuation. The fracture/toughness ratio is less than 1.75, which shows that the chosen materials are brittle in nature as found for other monopnictides. The drag coefficient acting on the motion of screw and edge dislocations due to shear and compressional phonon viscosities of the lattice have also been evaluated for both the longitudinal and shear waves. The thermoelastic loss and dislocation damping loss are negligible in comparison to loss due to Akhieser damping (phonon-phonon interaction). The obtained results for CeX are in qualitative agreement with other semi-metallic monopnictides.

  13. Porosity and mechanical properties of zirconium ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Buyakova, S., E-mail: sbuyakova@ispms.tsc.ru; Kulkov, S. [Tomsk State University (Russian Federation); Tomsk Polytechnic University (Russian Federation); Institute of Strength Physics and Materials Science RAS (Russian Federation); Sablina, T. [Institute of Strength Physics and Materials Science RAS (Russian Federation)

    2015-11-17

    Has been studied a porous ceramics obtained from ultra-fine powders. Porous ceramic ZrO{sub 2}(MgO), ZrO{sub 2}(Y{sub 2}O{sub 3}) powder was prepared by pressing and subsequent sintering of compacts homologous temperatures ranging from 0.63 to 0.56 during the isothermal holding duration of 1 to 5 hours. The porosity of ceramic samples was from 15 to 80%. The structure of the ceramic materials produced from plasma-sprayed ZrO{sub 2} powder was represented as a system of cell and rod structure elements. Cellular structure formed by stacking hollow powder particles can be easily seen at the images of fracture surfaces of obtained ceramics. There were three types of pores in ceramics: large cellular hollow spaces, small interparticle pores which are not filled with powder particles and the smallest pores in the shells of cells. The cells generally did not have regular shapes. The size of the interior of the cells many times exceeded the thickness of the walls which was a single-layer packing of ZrO{sub 2} grains. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformation on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.

  14. Mechanical Properties of Nanoscopic Lipid Domains.

    Science.gov (United States)

    Nickels, Jonathan D; Cheng, Xiaolin; Mostofian, Barmak; Stanley, Christopher; Lindner, Benjamin; Heberle, Frederick A; Perticaroli, Stefania; Feygenson, Mikhail; Egami, Takeshi; Standaert, Robert F; Smith, Jeremy C; Myles, Dean A A; Ohl, Michael; Katsaras, John

    2015-12-23

    The lipid raft hypothesis presents insights into how the cell membrane organizes proteins and lipids to accomplish its many vital functions. Yet basic questions remain about the physical mechanisms that lead to the formation, stability, and size of lipid rafts. As a result, much interest has been generated in the study of systems that contain similar lateral heterogeneities, or domains. In the current work we present an experimental approach that is capable of isolating the bending moduli of lipid domains. This is accomplished using neutron scattering and its unique sensitivity to the isotopes of hydrogen. Combining contrast matching approaches with inelastic neutron scattering, we isolate the bending modulus of ∼13 nm diameter domains residing in 60 nm unilamellar vesicles, whose lipid composition mimics the mammalian plasma membrane outer leaflet. Importantly, the bending modulus of the nanoscopic domains differs from the modulus of the continuous phase surrounding them. From additional structural measurements and all-atom simulations, we also determine that nanoscopic domains are in-register across the bilayer leaflets. Taken together, these results inform a number of theoretical models of domain/raft formation and highlight the fact that mismatches in bending modulus must be accounted for when explaining the emergence of lateral heterogeneities in lipid systems and biological membranes.

  15. Mechanical properties of lanthanum and yttrium chromites

    Energy Technology Data Exchange (ETDEWEB)

    Paulik, S.W.; Armstrong, T.R. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-12-31

    In an operating high-temperature (1000{degrees}C) solid oxide fuel cell (SOFC), the interconnect separates the fuel (P(O{sub 2}){approx}10{sup -16} atm) and the oxidant (P(O2){approx}10{sup 0.2} atm), while being electrically conductive and connecting the cells in series. Such severe atmospheric and thermal demands greatly reduce the number of viable candidate materials. Only two materials, acceptor substituted lanthanum chromite and yttrium chromite, meet these severe requirements. In acceptor substituted chromites (Sr{sup 2+} or Ca{sup 2+} for La{sup 3+}), charge compensation is primarily electronic in oxidizing conditions (through the formation of Cr{sup 4+}). Under reducing conditions, ionic charge compensation becomes significant as the lattice becomes oxygen deficient. The formation of oxygen vacancies is accompanied by the reduction of Cr{sup 4+} ions to Cr{sup 3+} and a resultant lattice expansion. The lattice expansion observed in large chemical potential gradients is not desirable and has been found to result in greatly reduced mechanical strength.

  16. Magnetic and mechanical properties of a finite-thickness superconducting strip with a cavity in oblique magnetic fields

    Science.gov (United States)

    Huang, Chen-Guang; Liu, Jun

    2017-01-01

    This paper presents an investigation of the mechanical response of a finite-thickness superconducting strip containing an elliptical cavity in oblique magnetic fields. After the Bean critical state model and the minimum magnetic energy variation procedure are employed, the dependency of the magnetic and mechanical properties on the aspect ratio of the strip and the tilt angles of the applied field and elliptical cavity is discussed. The results show that for a strip in an oblique magnetic field, the current front penetrates non-monotonically from the surface inwards in the initial stage. The magnetization of the strip and the applied field are not collinear, and the angle between them becomes smaller with increasing field. Simultaneously, the strip suffers from a torque produced by the electromagnetic force and then has a tendency to rotate. Compared with the defect-free case, the appearance of the elliptical cavity affects the magnetic property of the strip and further causes significant stress concentration. If the tilt angle of the elliptical cavity is small, a position of stable mechanical equilibrium will exist for the strip. It is interesting that due to the elliptical cavity effect, an oblique magnetization and a non-zero torque are generated even if the applied field is perpendicular or parallel to the strip.

  17. In vitro indentation to determine the mechanical properties of epidermis

    NARCIS (Netherlands)

    Geerligs, M.; Van Breemen, L.; Peters, G.W.M.; Ackermans, P.A.J.; Baaijens,F.P.T.; Oomens, C.

    2011-01-01

    The lack of understanding of the mechanical behavior of the human skin layers makes the development of drug delivery using microneedles or microjets a challenging task. In particular, the key mechanical properties of the epidermis composed of stratum corneum and viable epidermis, should be better

  18. High temperature mechanical properties of iron aluminides

    Directory of Open Access Journals (Sweden)

    Morris, D. G.

    2001-04-01

    Full Text Available Considerable attention has been given to the iron aluminide family of intermetallics over the past years since they offer considerable potential as engineering materials for intermediate to high temperature applications, particularly in cases where extreme oxidation or corrosion resistance is required. Despite efforts at alloy development, however, high temperature strength remains low and creep resistance poor. Reasons for the poor high-temperature strength of iron aluminides will be discussed, based on the ordered crystal structure, the dislocation structure found in the material, and the mechanisms of dislocation pinning operating. Alternative ways of improving high temperature strength by microstructural modification and the inclusion of second phase particles will also be considered.

    Durante los últimos años se ha prestado mucha atención a la familia de intermetálicos Fe-Al, puesto que estos constituyen un considerable potencial como materiales de ingeniería en aplicaciones a temperaturas intermedias o altas, sobre todo en casos donde se necesita alta resistencia a la oxidación o corrosión. A pesar del considerable esfuerzo desarrollado para obtener aleaciones con mejores propiedades, su resistencia mecánica a alta temperatura no es muy elevada. Se discutirán los aspectos que contribuyen a la baja resistencia mecánica a temperatura elevada en función de la estructura de dislocaciones y los mecanismos de anclaje que operan en este intermetálico. Se considerarán, también, maneras alternativas para mejorar la resistencia a temperatura elevada mediante la modificación de la microestructura y la incorporación de partículas de segunda fase.

  19. Mechanical and biological properties of keratose biomaterials.

    Science.gov (United States)

    de Guzman, Roche C; Merrill, Michelle R; Richter, Jillian R; Hamzi, Rawad I; Greengauz-Roberts, Olga K; Van Dyke, Mark E

    2011-11-01

    The oxidized form of extractable human hair keratin proteins, commonly referred to as keratose, is gaining interest as a biomaterial for multiple tissue engineering studies including those directed toward peripheral nerve, spinal cord, skin, and bone regeneration. Unlike its disulfide cross-linked counterpart, kerateine, keratose does not possess a covalently cross-linked network structure and consequently displays substantially different characteristics. In order to understand its mode(s) of action and potential for clinical translatability, detailed characterization of the composition, physical properties, and biological responses of keratose biomaterials are needed. Keratose was obtained from end-cut human hair fibers by peracetic acid treatment, followed by base extraction, and subsequent dialysis. Analysis of lyophilized keratose powder determined that it contains 99% proteins by mass with amino acid content similar to human hair cortex. Metallic elements were also found in minute quantities. Protein oxidation led to disulfide bond cleavage and drastic reduction of free thiols due to conversion of sulfhydryl to sulfonic acid, chain fragmentation, and amino acid modifications. Mass spectrometry identified the major protein constituents as a heterogeneous mixture of 15 hair keratins (type I: K31-35 and K37-39, and type II: K81-86) with small amounts of epithelial keratins which exist in monomeric, dimeric, multimeric, and even degraded forms. Re-hydration with PBS enabled molecular assembly into an elastic solid-like hydrogel. Highly-porous scaffolds formed by lyophilization of the gel had the compression behavior of a cellular foam material and reverted back to gel upon wetting. Cytotoxicity assays showed that the EC50 for various cell lines were attained at 8-10 mg/mL keratose, indicating the non-toxic nature of the material. Implantation in mouse subcutaneous tissue pockets demonstrated that keratose resorption follows a rectangular hyperbolic regression

  20. Mechanical Properties and Durability of "Waterless Concrete"

    Science.gov (United States)

    Toutanji, Houssam; Grugel, Richard N.

    2008-01-01

    Waterless concrete consists of molten elementary sulfur and aggregate. The aggregates in lunar environment will be lunar rocks and soil. Sulfur is present on the Moon in Troilite soil (FeS) and by oxidation soil iron and sulfur can be produced. Iron can be used to reinforce the sulfur concrete. Sulfur concrete specimens were cycled between liquid nitrogen (approximately 191 C) and room temperature (approximately 21 C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression at room temperatures (approximately 21 C) and approximately 101 C. Test results showed that due to temperature cycling, compressive strength of cycled specimens was 20% of those non-cycled. Microscopic examination of the fracture surfaces from the cycled samples showed clear de-bonding of the sulfur from the aggregate material whereas it was seen well bonded in those non-cycled. This reduction in strength can be attributed to the large differences in thermal coefficients of expansion of the materials constituting the concrete which promoted cracking. Similar sulfur concrete mixtures were strengthened with short and long glass fibers. The glass fibers from lunar regolith simulant was melted in a 25 cc Pt-Rh crucible in a Sybron Thermoline high temperature MoSi2 furnace at melting temperatures of 1450 to 1600 C for times of 30 min to 1 hour. Glass fibers were cast from the melt into graphite crucibles and were annealed for a couple of hours at 600 C. Glass fibers and small rods were pulled from the melt. The glass melt wets the ceramic rod and long continuous glass fibers were easily hand drawn. The glass fibers were immediately coated with a protective polymer to maintain the mechanical strength. The glass fibers were used to reinforce sulfur concrete plated to improve the flexural strength of the sulfur concrete. Prisms beams strengthened with glass fibers were tested in 4-point bending test. Beams strengthened with glass fiber showed to

  1. Mechanical Properties and Durability of "Waterless Concrete"

    Science.gov (United States)

    Toutanji, Houssam; Grugel, Richard N.

    2008-01-01

    Waterless concrete consists of molten elementary sulfur and aggregate. The aggregates in lunar environment will be lunar rocks and soil. Sulfur is present on the Moon in Troilite soil (FeS) and by oxidation soil iron and sulfur can be produced. Iron can be used to reinforce the sulfur concrete. Sulfur concrete specimens were cycled between liquid nitrogen (approximately 191 C) and room temperature (approximately 21 C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression at room temperatures (approximately 21 C) and approximately 101 C. Test results showed that due to temperature cycling, compressive strength of cycled specimens was 20% of those non-cycled. Microscopic examination of the fracture surfaces from the cycled samples showed clear de-bonding of the sulfur from the aggregate material whereas it was seen well bonded in those non-cycled. This reduction in strength can be attributed to the large differences in thermal coefficients of expansion of the materials constituting the concrete which promoted cracking. Similar sulfur concrete mixtures were strengthened with short and long glass fibers. The glass fibers from lunar regolith simulant was melted in a 25 cc Pt-Rh crucible in a Sybron Thermoline high temperature MoSi2 furnace at melting temperatures of 1450 to 1600 C for times of 30 min to 1 hour. Glass fibers were cast from the melt into graphite crucibles and were annealed for a couple of hours at 600 C. Glass fibers and small rods were pulled from the melt. The glass melt wets the ceramic rod and long continuous glass fibers were easily hand drawn. The glass fibers were immediately coated with a protective polymer to maintain the mechanical strength. The glass fibers were used to reinforce sulfur concrete plated to improve the flexural strength of the sulfur concrete. Prisms beams strengthened with glass fibers were tested in 4-point bending test. Beams strengthened with glass fiber showed to

  2. Lithophysal Rock Mass Mechanical Properties of the Repository Host Horizon

    Energy Technology Data Exchange (ETDEWEB)

    D. Rigby

    2004-11-10

    The purpose of this calculation is to develop estimates of key mechanical properties for the lithophysal rock masses of the Topopah Spring Tuff (Tpt) within the repository host horizon, including their uncertainties and spatial variability. The mechanical properties to be characterized include an elastic parameter, Young's modulus, and a strength parameter, uniaxial compressive strength. Since lithophysal porosity is used as a surrogate property to develop the distributions of the mechanical properties, an estimate of the distribution of lithophysal porosity is also developed. The resulting characterizations of rock parameters are important for supporting the subsurface design, developing the preclosure safety analysis, and assessing the postclosure performance of the repository (e.g., drift degradation and modeling of rockfall impacts on engineered barrier system components).

  3. COMPARISON,SYMMETRY AND MONOTONICITY RESULTS FOR SOME DEGENERATE ELLIPTIC OPERATORS IN CARNOT- C ARATHEO D O RY SPACES

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This paper studies the properties of solutions of quasilinear equations involving the plaplacian type operator in general Carnot-Carathéodory spaces.The authors show some comparison results for solutions of the relevant differential inequalities and use them to get some symmetry and monotonicity properties of solutions,in bounded or unbounded domains.

  4. Compressive and tensile mechanical properties of the porcine nasal septum

    OpenAIRE

    Al Dayeh, Ayman A.; HERRING, SUSAN W.

    2013-01-01

    The expanding nasal septal cartilage is believed to create a force that powers midfacial growth. In addition, the nasal septum is postulated to act as a mechanical strut that prevents the structural collapse of the face under masticatory loads. Both roles imply that the septum is subject to complex biomechanical loads during growth and mastication. The purpose of this study was to measure the mechanical properties of the nasal septum to determine (1) whether the cartilage is mechanically capa...

  5. Mechanical Properties of Isotactic Polypropylene Modified with Thermoplastic Potato Starch

    Science.gov (United States)

    Knitter, M.; Dobrzyńska-Mizera, M.

    2015-05-01

    In this paper selected mechanical properties of isotactic polypropylene (iPP) modified with potato starch have been presented. Thermoplastic starch (TPS) used as a modifier in the study was produced from potato starch modified with glycerol. Isotactic polypropylene/thermoplastic potato starch composites (iPP/TPS) that contained 10, 30, 50 wt.% of modified starch were examined using dynamic mechanical-thermal analysis, static tensile, Brinell hardness, and Charpy impact test. The studies indicated a distinct influence of a filler content on the mechanical properties of composites in comparison with non-modified polypropylene.

  6. Mechanical and Morphological Properties of Nano Filler Polyester Composites

    OpenAIRE

    Bonnia Noor Najmi; Redzuan Aein Afina; Shuhaimeen Nurul Shakirah

    2016-01-01

    This research is focusing on mechanical and morphological properties of unsaturated polyester (UP) reinforced with two different types of filler which is nano size clay Cloisite 30B (C30B) and Carbon Black (CB). Samples were fabricated via hand lay-up and open molding technique. Percentages of Cloisite 30B & Carbon Black (CB) used vary from 0, 2, 4, 6, 8 and 10 wt%. The mechanical properties were evaluated by impact, flexural and hardness testing. Result shows that the mechanical strength of ...

  7. Mechanical properties of cellulose in orthopaedic devices and related environments.

    Science.gov (United States)

    Poustis, J; Baquey, C; Chauveaux, D

    1994-01-01

    The authors have undertaken a series of mechanical tests in order to assess the performance of regenerated cellulose under either static or dynamic conditions, and to evaluate its long-term behaviour under mechanical stress. In this respect, bending stiffness, resistance to compression, creep under compressive stress, in vitro and in vivo ageing and fatigue resistance were studied. It appears that this material demonstrates mechanical properties which depend upon its density, which is itself related to its water content. Moreover, this material is very stable under dynamic stress. This could be an interesting property for use in orthopaedic devices.

  8. Effect of vitro preservation on mechanical properties of brain tissue

    Science.gov (United States)

    Zhang, Wei; Liu, Yi-fan; Liu, Li-fu; Niu, Ying; Ma, Jian-li; Wu, Cheng-wei

    2017-05-01

    To develop the protective devices for preventing traumatic brain injuries, it requires the accurate characterization of the mechanical properties of brain tissue. For this, it necessary to elucidate the effect of vitro preservation on the mechanical performance of brain tissue as usually the measurements are carried out in vitro. In this paper, the thermal behavior of brain tissue preserved for various period of time was first investigated and the mechanical properties were also measured. Both reveals the deterioration with prolonged preservation duration. The observations of brain tissue slices indicates the brain tissue experiences karyorrhexis and karyorrhexis in sequence, which accounts for the deterioration phenomena.

  9. Mechanical properties of canine patella-ligament-tibia segment.

    Science.gov (United States)

    Biskup, Jeffery; Freeman, Andy; Camisa, Will; Innes, John; Conzemius, Michael

    2014-02-01

    To test the ex vivo mechanical properties of canine patella-ligament-tibia (PLT) segment and establish the relationship between donor size and PLT dimensions to the mechanical properties of PLT grafts. Ex vivo mechanical testing study. Canine PLT segments (n = 21 dogs; 42 PLT). Morphometric measurements of PLT segments were taken from computed tomography (CT) images and compared with results obtained using calipers. PLT were tested to failure at a rate of 100% length/s. Mechanical properties and failure mode were recorded. PLT width and thickness (P 25 kg were similar to those reported for the cranial cruciate ligament (CCL) suggesting that the PLT may be a suitable allograft for CCL replacement. © Copyright 2013 by The American College of Veterinary Surgeons.

  10. Whisker-reinforced dental core buildup composites: effect of filler level on mechanical properties.

    Science.gov (United States)

    Xu, H H; Smith, D T; Schumacher, G E; Eichmiller, F C

    2000-12-15

    The strength and toughness of dental core buildup composites in large stress-bearing restorations need to be improved to reduce the incidence of fracture due to stresses from chewing and clenching. The aims of the present study were to develop novel core buildup composites reinforced with ceramic whiskers, to examine the effect of filler level, and to investigate the reinforcement mechanisms. Silica particles were fused onto the whiskers to facilitate silanization and to roughen the whisker surface for improved retention in the matrix. Filler level was varied from 0 to 70%. Flexural strength, compressive strength, and fracture toughness of the composites were measured. A nano-indentation system was used to measure elastic modulus and hardness. Scanning electron microscopy (SEM) was used to examine the fracture surfaces of specimens. Whisker filler level had significant effects on composite properties. The flexural strength in MPa (mean +/- SD; n = 6) increased from (95+/-15) for the unfilled resin to (193+/- 8) for the composite with 50% filler level, then slightly decreased to (176+/-12) at 70% filler level. The compressive strength increased from (149+/-33) for the unfilled resin to (282+/-48) at 10% filler level, and remained equivalent from 10 to 70% filler level. Both the modulus and hardness increased monotonically with filler level. In conclusion, silica particle-fused ceramic single-crystalline whiskers significantly reinforced dental core buildup composites. The reinforcement mechanisms appeared to be crack deflection and bridging by the whiskers. Whisker filler level had significant effects on the flexural strength, compressive strength, elastic modulus, and hardness of composites.

  11. An Extragradient Method and Proximal Point Algorithm for Inverse Strongly Monotone Operators and Maximal Monotone Operators in Banach Spaces

    Directory of Open Access Journals (Sweden)

    Plubtieng Somyot

    2009-01-01

    Full Text Available Abstract We introduce an iterative scheme for finding a common element of the solution set of a maximal monotone operator and the solution set of the variational inequality problem for an inverse strongly-monotone operator in a uniformly smooth and uniformly convex Banach space, and then we prove weak and strong convergence theorems by using the notion of generalized projection. The result presented in this paper extend and improve the corresponding results of Kamimura et al. (2004, and Iiduka and Takahashi (2008. Finally, we apply our convergence theorem to the convex minimization problem, the problem of finding a zero point of a maximal monotone operator and the complementary problem.

  12. An Extragradient Method and Proximal Point Algorithm for Inverse Strongly Monotone Operators and Maximal Monotone Operators in Banach Spaces

    Directory of Open Access Journals (Sweden)

    Somyot Plubtieng

    2009-01-01

    Full Text Available We introduce an iterative scheme for finding a common element of the solution set of a maximal monotone operator and the solution set of the variational inequality problem for an inverse strongly-monotone operator in a uniformly smooth and uniformly convex Banach space, and then we prove weak and strong convergence theorems by using the notion of generalized projection. The result presented in this paper extend and improve the corresponding results of Kamimura et al. (2004, and Iiduka and Takahashi (2008. Finally, we apply our convergence theorem to the convex minimization problem, the problem of finding a zero point of a maximal monotone operator and the complementary problem.

  13. On the Monotone Iterative Method for Set Valued Equation

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper deals with the monotone iterative method for set- valued operator equation in ordered normed space. Some results for the case of single valued operator are generalized here, as an application, a discontinuous nonlinear differential equation problem is discussed.

  14. Monotone method for initial value problem for fractional diffusion equation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shuqin

    2006-01-01

    Using the method of upper and lower solutions and its associated monotone iterative, consider the existence and uniqueness of solution of an initial value problem for the nonlinear fractional diffusion equation.

  15. Approximations for Monotone and Non-monotone Submodular Maximization with Knapsack Constraints

    CERN Document Server

    Kulik, Ariel; Tamir, Tami

    2011-01-01

    Submodular maximization generalizes many fundamental problems in discrete optimization, including Max-Cut in directed/undirected graphs, maximum coverage, maximum facility location and marketing over social networks. In this paper we consider the problem of maximizing any submodular function subject to $d$ knapsack constraints, where $d$ is a fixed constant. We establish a strong relation between the discrete problem and its continuous relaxation, obtained through {\\em extension by expectation} of the submodular function. Formally, we show that, for any non-negative submodular function, an $\\alpha$-approximation algorithm for the continuous relaxation implies a randomized $(\\alpha - \\eps)$-approximation algorithm for the discrete problem. We use this relation to improve the best known approximation ratio for the problem to $1/4- \\eps$, for any $\\eps > 0$, and to obtain a nearly optimal $(1-e^{-1}-\\eps)-$approximation ratio for the monotone case, for any $\\eps>0$. We further show that the probabilistic domain ...

  16. Action-Maslov Homomorphism for Monotone Symplectic Manifolds

    CERN Document Server

    Branson, Mark

    2009-01-01

    We explore conditions under which the action-Maslov homomorphism vanishes on monotone symplectic manifolds. Our strategy involves showing that the units in the quantum homology, and thus the Seidel element, have a very specific form. Then we use induction to show that other relevant Gromov-Witten invariants vanish. We prove that these conditions hold for monotone products of projective spaces and for the Grassmannian of 2-planes in $\\C^4$.

  17. Completely monotonic functions related to logarithmic derivatives of entire functions

    DEFF Research Database (Denmark)

    Pedersen, Henrik Laurberg

    2011-01-01

    The logarithmic derivative l(x) of an entire function of genus p and having only non-positive zeros is represented in terms of a Stieltjes function. As a consequence, (-1)p(xml(x))(m+p) is a completely monotonic function for all m ≥ 0. This generalizes earlier results on complete monotonicity...... of functions related to Euler's psi-function. Applications to Barnes' multiple gamma functions are given....

  18. Isotonicity of the projection onto the monotone cone

    CERN Document Server

    Németh, A B

    2012-01-01

    A wedge (i.e., a closed nonempty set in the Euclidean space stable under addition and multiplication with non-negative scalars) induces by a standard way a semi-order (a reflexive and transitive binary relation) in the space. The wedges admitting isotone metric projection with respect to the semi-order induced by them are characterized. The obtained result is used to show that the monotone wedge (called monotone cone in regression theory) admits isotone projection.

  19. Monotonic loading of circular surface footings on clay

    Energy Technology Data Exchange (ETDEWEB)

    Ibsen, Lars Bo; Barari, Amin [Aalborg University, Aalborg (Denmark)

    2011-12-15

    Appropriate modeling of offshore foundations under monotonic loading is a significant challenge in geotechnical engineering. This paper reports experimental and numerical analyses, specifically investigating the response of circular surface footings during monotonic loading and elastoplastic behavior during reloading. By using the findings presented in this paper, it is possible to extend the model to simulate the vertical-load displacement response of offshore bucket foundations.

  20. Metal Additive Manufacturing: A Review of Mechanical Properties

    Science.gov (United States)

    Lewandowski, John J.; Seifi, Mohsen

    2016-07-01

    This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and directed energy deposition (e.g., LENS, EBF3). Although only a limited number of metallic alloy systems are currently available for additive manufacturing (e.g., Ti-6Al-4V, TiAl, stainless steel, Inconel 625/718, and Al-Si-10Mg), the bulk of the published mechanical properties information has been generated on Ti-6Al-4V. However, summary tables for published mechanical properties and/or key figures are included for each of the alloys listed above, grouped by the additive technique used to generate the data. Published values for mechanical properties obtained from hardness, tension/compression, fracture toughness, fatigue crack growth, and high cycle fatigue are included for as-built, heat-treated, and/or HIP conditions, when available. The effects of test orientation/build direction on properties, when available, are also provided, along with discussion of the potential source(s) (e.g., texture, microstructure changes, defects) of anisotropy in properties. Recommendations for additional work are also provided.

  1. Measurements and Characterizations of Mechanical Properties of Human Skins

    Science.gov (United States)

    Song, Han Wook; Park, Yon Kyu

    A skin is an indispensible organ for humans because it contributes to metabolism using its own biochemical functions and protects the human body from external stimuli. Recently, mechanical properties such as a thickness, a friction and an elastic coefficient have been used as a decision index in the skin physiology and in the skin care market due to the increased awareness of wellbeing issues. In addition, the use of mechanical properties is known to have good discrimination ability in the classification of human constitutions, which are used in the field of an alternative medicine. In this study, a system that measures mechanical properties such as a friction and an elastic coefficient is designed. The equipment consists of a load cell type (manufactured by the authors) for the measurements of a friction coefficient, a decompression tube for the measurement of an elastic coefficient. Using the proposed system, the mechanical properties of human skins from different constitutions were compared, and the relative repeatability error for measurements of mechanical properties was determined to be less than 2%. Combining the inspection results of medical doctors in the field of an alternative medicine, we could conclude that the proposed system might be applicable to a quantitative constitutional diagnosis between human constitutions within an acceptable level of uncertainty.

  2. Layered neural networks with non-monotonic transfer functions

    Science.gov (United States)

    Katayama, Katsuki; Sakata, Yasuo; Horiguchi, Tsuyoshi

    2003-01-01

    We investigate storage capacity and generalization ability for two types of fully connected layered neural networks with non-monotonic transfer functions; random patterns are embedded into the networks by a Hebbian learning rule. One of them is a layered network in which a non-monotonic transfer function of even layers is different from that of odd layers. The other is a layered network with intra-layer connections, in which the non-monotonic transfer function of inter-layer is different from that of intra-layer, and inter-layered neurons and intra-layered neurons are updated alternately. We derive recursion relations for order parameters for those layered networks by the signal-to-noise ratio method. We clarify that the storage capacity and the generalization ability for those layered networks are enhanced in comparison with those with a conventional monotonic transfer function when non-monotonicity of the transfer functions is selected optimally. We also point out that some chaotic behavior appears in the order parameters for the layered networks when non-monotonicity of the transfer functions increases.

  3. Mechanical Properties of Densified Tectosilicate Calcium-Aluminosilicate Glasses

    DEFF Research Database (Denmark)

    Johnson, Nicole; Lamberson, Lisa; Smedskjær, Morten Mattrup;

    Aluminosilicate glasses are widely used in applications such as LCD glass, touchscreens for hand held devices and car windows. We have shown that the tectosilicate compositions exhibit an interesting non-monotonic variation in hardness with increasing SiO2 content. From 40% to 85 mol% SiO2...

  4. Mechanical, Thermal and Dynamic Mechanical Properties of PP/GF/xGnP Nanocomposites

    Science.gov (United States)

    Ashenai Ghasemi, F.; Ghorbani, A.; Ghasemi, I.

    2017-03-01

    The mechanical, thermal, and dynamic mechanical properties of ternary nanocomposites based on polypropylene, short glass fibers, and exfoliated graphene nanoplatelets were studied. To investigate the mechanical properties, uniaxial tensile and Charpy impact tests were carried out. To study the crystallinity of the compositions, a DSC test was performed. A dynamic mechanical analysis was used to characterize the storage modulus and loss factor (tan δ). The morphology of the composites was studied by a scanning electron microscope (SEM). The results obtained are presented in tables and graphics.

  5. Finite Element Simulation of the Mechanical Properties of Mineralized Biomaterials

    Science.gov (United States)

    Yuan, Fang

    Mineralized biomaterials are natural composite materials with both biomineral and biopolymer phases. They have attracted intense attention in the past decades, due to their outstanding mechanical properties and great potential as future materials. Such exceptional properties are believed to be attributed to their complex structures. Therefore, two different mineralized biomaterials (bone and sea urchin spine) were studied mainly by the finite element method and their structure-mechanical properties relationships were investigated. The research on bone was performed with a bottom-up approach. We focused on the nanoscale level structure-properties relationship first: the models of mineralized collagen fibril, consisting of hydroxyapatite platelets aligned within a collagen matrix, were created and the importance of the parameters defining its structure and constituent properties was evaluated. With the elastic model well established, the long-term mechanical behavior at nanoscale level was studied. The viscoelastic properties of undamaged collagen phase were deduced from low-irradiation-dosage creep measurements, then different damage scenarios were evaluated to explain the evolution of phase strains with larger irradiation dosage. The higher level structure-properties relationship of bone was simulated by two different approaches: 1) Assuming the macroscopic composite strain was comparable to nanoscale fibrillar strain, then based on nanoscale model, the macroscopic distributions of nanoscale phase strains were investigated; 2) Considering the structural complexity of bone at several length scales, the effective properties from lower scales were applied as the input properties at higher scales, and the elastic properties at each level were investigated. The computational results were validated by experimental data obtained by synchrotron X-ray diffraction and show the mechanical properties of bone are greatly influenced by its structure. The research on sea urchin

  6. A Novel Method of Mechanical Oxidation of CNT for Polymer Nanocomposite Application: Evaluation of Mechanical, Dynamic Mechanical, and Rheological Properties

    Directory of Open Access Journals (Sweden)

    Priyanka Pandey

    2014-01-01

    Full Text Available A new approach of oxidation of carbon nanotubes has been used to oxidize the CNTs. A comparative aspect of the mechanical oxidation and acid oxidation process has been established. FTIR analysis and titration method have shown the higher feasibility of the mechanical oxidation method to oxidize the CNTs. Comparatively less damage to the CNTs has been observed in case of mechanically oxidized as compared to acid oxidized CNTs. The mechanical properties of the nanocomposites reinforced with the acid oxidized CNT (ACNT and mechanically oxidized CNTs (McCNT were analyzed and relatively higher properties in the nanocomposites reinforced with McCNT were noticed. The less degree of entanglement in the McCNTs was noticed as compared to ACNTs. The dynamic mechanical analysis of the nanocomposites revealed much improved load transfer capability in the McCNT reinforced composites. Further, the rheological properties of the nanocomposites revealed the higher performance of McCNT reinforced composites.

  7. Characterisation of steel components under monotonic loading by means of image-based methods

    Science.gov (United States)

    Xavier, J.; Pereira, J. C. R.; de Jesus, A. M. P.

    2014-02-01

    Ductile damage behaviour of S185 structural steel is determined by coupling numerical and experimental analyses. Monotonic experimental tests are carried out in five different specimen configurations. These mechanical tests are coupled with image-based methods for assessing displacement and strain fields over the gauge section. Three different ductile damage models proposed in the literature for monotonic loading are analysed. Their governing parameters are determined by comparing experimental and numerical mechanical responses. Measurements provided by digital image correlation and feature-tracking methods are used for calibrating and validating non-linear finite element modelling. Numerical analyses built in ANSYS are carried out to compute the necessary parameters (stress-strain and triaxiality histories) to calibrate Johnson-Cook (JC) and Kanvinde-Deierlein (KD) fracture criteria. Also, a calibration of the Gurson-Tvergaard-Needleman (GTN) model is performed based on an explicit finite element analysis in ABAQUS.

  8. Monotonicity properties for multi-class queueing systems

    NARCIS (Netherlands)

    Verloop, I.M. (Maaike); Ayesta, U.; Borst, S.C.

    2008-01-01

    We study multi-dimensional stochastic processes that arise in queueing models used in the performance evaluation of wired and wireless networks. The evolution of the stochastic process is determined by the scheduling policy used in the associated queueing network. For general arrival and service pro

  9. Microfibrous silver-coated polymeric scaffolds with tunable mechanical properties

    KAUST Repository

    Kalakonda, Parvathalu.

    2017-07-07

    Electrospun scaffolds of poly(glycerol sebacate)/poly(ε-caprolactone) (PGS/PCL) have been used for engineered tissues due to their desirable thermal and mechanical properties as well as their tunable degradability. In this paper, we fabricated micro-fibrous scaffolds from a composite of PGS/PCL using a standard electrospinning method and coated them with silver (Ag). The low temperature coating method prevented substrate melting and the Ag coating decreases the pore size and increases the diameter of fibers which resulted in enhanced thermal and mechanical properties. We further compared the mechanical properties of the composite fibrous scaffolds with different thicknesses of Ag coated scaffolds. The composite fibrous scaffold with a 275 nm Ag coating showed higher tensile modulus (E) and ultimate tensile strength (UTS) without any post-processing treatment. Lastly, potential controlled release of the Ag coating from the composite fibrous scaffolds could present interesting biomedical applications.

  10. [Classification and several mechanical properties of core composite resins].

    Science.gov (United States)

    Yamada, T; Hosoda, H; Tsurugai, T

    1990-03-01

    According to the classification proposed by Hosoda, six core resins could be divided into two categories on the basis of the elemental composition and size distribution of filler particles by SEM observation and EDX analysis. Furthermore, several mechanical properties of the resins were determined. The following facts were found: Bell Feel Core, Clearfil Core, Clearfil PhotoCore, Core Max, and Core Max II resins were classified as a semihybrid resin, and Microrest Core resin as a hybrid type resin. The elements detected in the resins by the EDX were Si, Zr, Al, Ba and La. The mechanical properties of the resins were shown to be highly stable at one day or one week after curing. The mechanical properties of the resins suggest that the subsequent crown preparation and impression taking should be postponed until the next appointment.

  11. Mechanical properties of rice husk flour reinforced epoxy biocomposite

    Directory of Open Access Journals (Sweden)

    Neeraj Bisht

    2015-06-01

    Full Text Available A bio-composite reinforced with rice husk flour in epoxy resin has been developed. The effect of fibre treatment and weight percentage of rice husk on the mechanical properties was studied and compared with wood dust reinforced epoxy composite. It was observed that addition of rice husk as filler is detrimental to almost all the mechanical properties. About 51% and 26.8% decrease in ultimate strength and Young’s Modulus for 40 wt% untreated rice husk reinforcement was observed. The corresponding decrease in flexural strength and flexural modulus was 51%. Similar trend was also observed in hardness and impact strength. However the mechanical properties of rice husk reinforced biocomposites are found to be superior than wood dust reinforced epoxy composite. SEM microscopy was also done to corroborate the results.

  12. Mechanical Properties Of Calcium Carbonate Crystallization Of Chitin Reinforced Polymer

    Directory of Open Access Journals (Sweden)

    Michael Ikpi Ofem

    2015-08-01

    Full Text Available ABSTRACT Chitin whiskers and CaCO3 were reinforced with Polyacrylic acid. Mechanical and thermal properties were characterised. The effect of CaCO3 growth on the mechanical properties of chitin whiskers reinforced Polyacrylic acid indicated that better mechanical properties can be achieved at chitin content of 3 wt when compared with neat PAA. The growth of CaCO3 on CHWPAA composite increased the melting endotherm of CHWPAACaCO3 composite when compared with CHWPAA composite. As an indication of increase in thermal stability the final weight loss at the end of decomposition for all composites was between 20 and 37 far below the 78 for the CHWPAA composite and 84 for the pure PAA .

  13. Pressing Speed, Specific Pressure and Mechanical Properties of Aluminium Cast

    Directory of Open Access Journals (Sweden)

    Gaspar S.

    2016-06-01

    Full Text Available Recent research in the process of aluminum alloy die castings production, which is nowadays deeply implemented into the rapidly growing automobile, shipping and aircraft industries, is aimed at increasing the useful qualitative properties of the die casting in order to obtain its high mechanical properties at acceptable economic cost. Problem of technological factors of high pressure die casting has been a subject of worldwide research (EU, US, Japan, etc.. The final performance properties of die castings are subjected to a large number of technological factors. The main technological factors of high pressure die casting are as follows: plunger pressing speed, specific (increase pressure, mold temperature as well as alloy temperature. The contribution discusses the impact of the plunger pressing speed and specific (increase pressure on the mechanical properties of the casting aluminum alloy.

  14. Tribological properties and lubricating mechanisms of Cu nanoparticles in lubricant

    Institute of Scientific and Technical Information of China (English)

    YU He-long; XU Yi; SHI Pei-jing; XU Bin-shi; WANG Xiao-li; LIU Qian

    2008-01-01

    Wear and friction properties of surface modified Cu nanoparticles as 50CC oil additive were studied.The effect of temperature on tribological properties of Cu nanoparticles was investigated on a four-ball tester.The morphologies,typical element distribution and chemical states of the worn surfaces were characterized by SEM,EDS and XPS,respectively.In order to further investigate the tribological mechanism of Cu nanoparticles,a nano-indentation tester was utilized to measure the micro mechanical Properties of the worn surface.The results indicate that the higher me oil temperature applied,the better the tribological properties of Cu nanoparticles are.It can be inferred that a thin copper protective film with lower elastic modulus and hardness is formed on the wom surface,which results in the good tribological performances of Cu nanoparticles,especially when the Oil temperature is higher.

  15. Monotonicity Conditions for Multirate and Partitioned Explicit Runge-Kutta Schemes

    KAUST Repository

    Hundsdorfer, Willem

    2013-01-01

    Multirate schemes for conservation laws or convection-dominated problems seem to come in two flavors: schemes that are locally inconsistent, and schemes that lack mass-conservation. In this paper these two defects are discussed for one-dimensional conservation laws. Particular attention will be given to monotonicity properties of the multirate schemes, such as maximum principles and the total variation diminishing (TVD) property. The study of these properties will be done within the framework of partitioned Runge-Kutta methods. It will also be seen that the incompatibility of consistency and mass-conservation holds for ‘genuine’ multirate schemes, but not for general partitioned methods.

  16. Structure–mechanics property relationship of waste derived biochars

    Energy Technology Data Exchange (ETDEWEB)

    Das, Oisik, E-mail: odas566@aucklanduni.ac.nz [Department of Civil and Environmental Engineering, University of Auckland, Auckland 1142 (New Zealand); Sarmah, Ajit K., E-mail: a.sarmah@auckland.ac.nz [Department of Civil and Environmental Engineering, University of Auckland, Auckland 1142 (New Zealand); Bhattacharyya, Debes, E-mail: d.bhattacharyya@auckland.ac.nz [Department of Mechanical Engineering, Center for Advanced Composite Materials, University of Auckland, Auckland 1142 (New Zealand)

    2015-12-15

    The widespread applications of biochar in agriculture and environmental remediation made the scientific community ignore its mechanical properties. Hence, to examine the scope of biochar's structural applications, its mechanical properties have been investigated in this paper through nanoindentation technique. Seven waste derived biochars, made under different pyrolysis conditions and from diverse feedstocks, were studied via nanoindentation, infrared spectroscopy, X–ray crystallography, thermogravimetry, and electron microscopy. Following this, an attempt was made to correlate the biochars' hardness/modulus with reaction conditions and their chemical properties. The pine wood biochar made at 900 °C and 60 min residence time was found to have the highest hardness and elastic modulus of 4.29 and 25.01 GPa, respectively. It was shown that a combination of higher heat treatment (≥ 500 °C) temperature and longer residence time (~ 60 min) increases the values of hardness and modulus. It was further realized that pyrolysis temperature was a more dominant factor than residence time in determining the final mechanical properties of biochar particles. The degree of aromaticity and crystallinity of the biochar were also correlated with higher values of hardness and modulus. - Highlights: • Characterization was done on waste based biochars which included nanoindentation. • Pine saw dust biochar made at 900 °C for 60 min had highest hardness/modulus. • Combination of temperature/residence time affect biochar's mechanical propertie.s • Aromaticity and crystallinity positively affected biochar's mechanical properties.

  17. A Low Protein Diet Alters Bone Material Level Properties and the Response to In Vitro Repeated Mechanical Loading

    Directory of Open Access Journals (Sweden)

    Victor Dubois-Ferrière

    2014-01-01

    Full Text Available Low protein intake is associated with an alteration of bone microstructure and material level properties. However, it remains unknown whether these alterations of bone tissue could influence the response to repeated mechanical loading. The authors investigated the in vitro effect of repeated loading on bone strength in humeri collected from 20 6-month-old female rats pair-fed with a control (15% casein or an isocaloric low protein (2.5% casein diet for 10 weeks. Bone specimens were cyclically loaded in three-point bending under load control for 2000 cycles. Humeri were then monotonically loaded to failure. The load-displacement curve of the in vitro cyclically loaded humerus was compared to the contralateral noncyclically loaded humerus and the influence of both protein diets. Material level properties were also evaluated through a nanoindentation test. Cyclic loading decreased postyield load and plastic deflection in rats fed a low protein diet, but not in those on a regular diet. Bone material level properties were altered in rats fed a low protein diet. This suggests that bone biomechanical alterations consequent to cyclic loading are more likely to occur in rats fed a low protein diet than in control animals subjected to the same in vitro cyclic loading regimen.

  18. Physical and mechanical properties of nanoreinforced particleboard composites

    OpenAIRE

    Candan,Zeki; AKBULUT, Turgay

    2015-01-01

    Novel composite materials having desired performance properties can be developed by nanotechnology. The major objective of this research was to produce nanomaterial- reinforced particleboard composites with enhanced physical and mechanical performance. Urea formaldehyde adhesive used to produce particleboard composites was reinforced with nanoSiO2, nanoAl2O3, and nanoZnO at loading level of 0%, 1%, and 3%. To evaluate physical properties density, thickness swelling, water absorption, and equi...

  19. Mechanical properties of micron and nanodimentional metal films

    Directory of Open Access Journals (Sweden)

    I.Yu. Protsenko

    2010-01-01

    Full Text Available The mechanical and strain resistivity properties data for bulk condensates and nanodimentional films at the elastic and plastic deformation was analyzed. The experimental results of strain resistivity properties of one-layer (Fe, Cr, Pd and Pt and two-layer (Fe/Cr, Cu/Cr and Pd/Fe films, in particular, dependence of the deformation at the transition from elastic to plastic deformation from thickness was presented.

  20. Decompositions of Revised Monotone Signed Fuzzy Measures

    Institute of Scientific and Technical Information of China (English)

    张强; 刘克

    2003-01-01

    The concept of fuzzy measure was introduced by Sugeno in 1974. A notion of signed fuzzy measure is introduced in this paper, and its elementary properties are briefly discussed. An analogue of Hahn decomposition theorem is established under the null-null-additive condition. A version of the Jordan decomposition theorem is proved under the null-additive condition.

  1. The effect of composition on mechanical properties of brushite cements.

    Science.gov (United States)

    Engstrand, Johanna; Persson, Cecilia; Engqvist, Håkan

    2014-01-01

    Due to a fast setting reaction, good biological properties, and easily available starting materials, there has been extensive research within the field of brushite cements as bone replacing material. However, the fast setting of brushite cement gives them intrinsically low mechanical properties due to the poor crystal compaction during setting. To improve this, many additives such as citric acid, pyrophosphates, and glycolic acid have been added to the cement paste to retard the crystal growth. Furthermore, the incorporation of a filler material could improve the mechanical properties when used in the correct amounts. In this study, the effect of the addition of the two retardants, disodium dihydrogen pyrophosphate and citric acid, together with the addition of β-TCP filler particles, on the mechanical properties of a brushite cement was investigated. The results showed that the addition of low amounts of a filler (up to 10%) can have large effects on the mechanical properties. Furthermore, the addition of citric acid to the liquid phase makes it possible to use lower liquid-to-powder ratios (L/P), which strongly affects the strength of the cements. The maximal compressive strength (41.8MPa) was found for a composition with a molar ratio of 45:55 between monocalcium phosphate monohydrate and beta-tricalcium phosphate, an L/P of 0.25ml/g and a citric acid concentration of 0.5M in the liquid phase.

  2. Mechanical properties of natural fibre reinforced polymer composites

    Indian Academy of Sciences (India)

    A S Singha; Vijay Kumar Thakur

    2008-10-01

    During the last few years, natural fibres have received much more attention than ever before from the research community all over the world. These natural fibres offer a number of advantages over traditional synthetic fibres. In the present communication, a study on the synthesis and mechanical properties of new series of green composites involving Hibiscus sabdariffa fibre as a reinforcing material in urea–formaldehyde (UF) resin based polymer matrix has been reported. Static mechanical properties of randomly oriented intimately mixed Hibiscus sabdariffa fibre reinforced polymer composites such as tensile, compressive and wear properties were investigated as a function of fibre loading. Initially urea–formaldehyde resin prepared was subjected to evaluation of its optimum mechanical properties. Then reinforcing of the resin with Hibiscus sabdariffa fibre was accomplished in three different forms: particle size, short fibre and long fibre by employing optimized resin. Present work reveals that mechanical properties such as tensile strength, compressive strength and wear resistance etc of the urea–formaldehyde resin increases to considerable extent when reinforced with the fibre. Thermal (TGA/DTA/DTG) and morphological studies (SEM) of the resin and biocomposites have also been carried out.

  3. Investigation of mechanical properties of cryogenically treated music wire

    Science.gov (United States)

    Heptonstall, A.; Waller, M.; Robertson, N. A.

    2015-08-01

    It has been reported that treating music wire (high carbon steel wire) by cooling to cryogenic temperatures can enhance its mechanical properties with particular reference to those properties important for musical performance. We use such wire for suspending many of the optics in Advanced LIGO, the upgrade to LIGO—the Laser Interferometric Gravitational-Wave Observatory. Two properties that particularly interest us are mechanical loss and breaking strength. A decrease in mechanical loss would directly reduce the thermal noise associated with the suspension, thus enhancing the noise performance of mirror suspensions within the detector. An increase in strength could allow thinner wire to be safely used, which would enhance the dilution factor of the suspension, again leading to lower suspension thermal noise. In this article, we describe the results of an investigation into some of the mechanical properties of music wire, comparing untreated wire with the same wire which has been cryogenically treated. For the samples we studied, we conclude that there is no significant difference in the properties of interest for application in gravitational wave detectors.

  4. The relationships between deformation mechanisms and mechanical properties of additively manufactured porous biomaterials.

    Science.gov (United States)

    Kadkhodapour, J; Montazerian, H; Darabi, A Ch; Zargarian, A; Schmauder, S

    2016-09-16

    Modulating deformation mechanism through manipulating morphological parameters of scaffold internal pore architecture provides potential to tailor the overall mechanical properties under physiological loadings. Whereas cells sense local strains, cell differentiation is also impressed by the elastic deformations. In this paper, structure-property relations were developed for Ti6-Al-4V scaffolds designed based on triply periodic minimal surfaces. 10mm cubic scaffolds composed of 5×5×5 unit cells formed of F-RD (bending dominated) and I-WP (stretching dominated) architectures were additively manufactured at different volume fractions and subjected to compressive tests. The first stages of deformation for stretching dominated structure, was accompanied by bilateral layer-by-layer failure of unit cells owing to the buckling of micro-struts, while for bending dominated structure, namely F-RD, global shearing bands appeared since the shearing failure of struts in the internal architecture. Promoted mechanical properties were found for stretching dominated structure since the global orientation of struts were parallel to loading direction while inclination of struts diminished specific properties for bending dominated structure. Moreover, elastic-plastic deformation was computationally studied by applying Johnson-Cook damage model to the voxel-based models in FE analysis. Scaling analysis was performed for mechanical properties with respect to the relative density thereby failure mechanism was correlated to the constants of power law describing mechanical properties.

  5. The mechanism and properties of acid-coagulated milk gels

    Directory of Open Access Journals (Sweden)

    Chanokphat Phadungath

    2005-03-01

    Full Text Available Acid-coagulated milk products such as fresh acid-coagulated cheese varieties and yogurt areimportant dairy food products. However, little is known regarding the mechanisms involved in gel formation, physical properties of acid gels, and the effects of processing variables such as heat treatment and gelation temperature on the important physical properties of acid milk gels. This paper reviews the modern concepts of possible mechanisms involved in the formation of particle milk gel aggregation, along with recent developments including the use of techniques such as dynamic low amplitude oscillatory rheology to observe the gel formation process, and confocal laser scanning microscopy to monitor gel microstructure.

  6. Structures and Mechanical Properties of PVC/Na+- Montmorillonite Nanocomposites

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Poly (vinyl chloride)/Na+-montmorillonite (PVC/MMT) nanocomposites with different MMT contents were prepared via melt blending. Wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) were used to characterize the structures. Effects of MMT content on the mechanical properties were also studied. It is found that PVC molecular chains can intercalate into the gallery of MMT layers during melt blending process, the stiffness and toughness of the composites are improved simultaneously within 0.5~7wt% MMT content, and the transparency and mechanical properties decrease as MMT content further increases.

  7. Computer simulations of the mechanical properties of metals

    DEFF Research Database (Denmark)

    Schiøtz, Jakob; Vegge, Tejs

    1999-01-01

    Atomic-scale computer simulations can be used to gain a better understanding of the mechanical properties of materials. In this paper we demonstrate how this can be done in the case of nanocrystalline copper, and give a brief overview of how simulations may be extended to larger length scales....... Nanocrystline metals are metals with grain sizes in the nanometre range, they have a number of technologically interesting properties such as much increased hardness and yield strength. Our simulations show that the deformation mechanisms are different in these materials than in coarse-grained materials...

  8. The factors influencing microstructure and mechanical properties of ADI

    Directory of Open Access Journals (Sweden)

    A. Vaško

    2009-01-01

    Full Text Available The paper deals with the influence of different conditions of isothermal heat treatment on microstructure and mechanical properties of austempered ductile iron (ADI. Different temperature of isothermal transformation of austenite and different holding time at this temperature were used for heat treatment of specimens. The microstructure of specimens after casting and after heat treatment was evaluated by STN EN ISO 945 and by image analysis (using Lucia software. Mechanical properties were evaluated by the tensile test, the Rockwell hardness test and fatigue tests.

  9. Inelastic behavior of materials and structures under monotonic and cyclic loading

    CERN Document Server

    Brünig, Michael

    2015-01-01

    This book presents studies on the inelastic behavior of materials and structures under monotonic and cyclic loads. It focuses on the description of new effects like purely thermal cycles or cases of non-trivial damages. The various models are based on different approaches and methods and scaling aspects are taken into account. In addition to purely phenomenological models, the book also presents mechanisms-based approaches. It includes contributions written by leading authors from a host of different countries.

  10. Effect of coal tar pitch modified by sulfur as a binder on the mechanical and tribological properties of bronze-impregnated carbon-matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Yang Huijun [School of Physics and Nuclear Energy Engineering, Beijing University of Aeronautics and Astronautics, No. 37, Xue Yuan Road, Hai Dian District, Beijing 100191 (China); Luo Ruiying, E-mail: ryluo@buaa.edu.cn [School of Physics and Nuclear Energy Engineering, Beijing University of Aeronautics and Astronautics, No. 37, Xue Yuan Road, Hai Dian District, Beijing 100191 (China)

    2011-03-15

    Research highlights: {yields} Sulfur addition increased the softening point and carbon yield of coal tar pitch. {yields} The mechanical properties of the composites reached a maximum at 7 wt. % of sulfur. {yields} The friction coefficient rose monotonously with increasing the content of sulfur. {yields} The wear rate of the composites reached a minimum at 7 wt. % of sulfur. {yields} The wear mechanism of composites was adhesive wear, abrasive wear and oxidative wear. - Abstract: Bronze-impregnated carbon-matrix composites were prepared through compression molding, carbonization and impregnation. The mechanism of sulfuration was studied, and the effect of coal tar pitch modified by sulfur as a binder on the mechanical and tribological properties of composites was investigated by varying the content of sulfur. The results showed that the sulfur addition increased the softening point, carbon yield and C/H atomic ratio of coal tar pitch but decreased the toluene solubility and quinoline solubility due to the dehydrogenating polymerization of pitch molecules. The micro-hardness, bending strength and compressive strength of the composites were enhanced by increasing the mass percentage of sulfur and reached a maximum of 160 HV, 132.82 MPa and 293 MPa at 7 wt. % of sulfur, respectively. However, both the hardness and strength of the composites decreased as the content of sulfur increased beyond 7 wt. %. The friction coefficient value of composites increased monotonously, but the wear rate decreased with increasing sulfur content; subsequently, the wear rate reached a minimum of 3.045 x 10{sup -7} mm{sup 3}/Nm at 7 wt. % of sulfur and then ascended. The wear mechanisms of the composites were adhesive wear, abrasive wear and oxidative wear. However, adhesive wear and oxidative wear occurred slightly for the composites with the binder modified by sulfur.

  11. Characterization of High Temperature Mechanical Properties Using Laser Ultrasound

    Energy Technology Data Exchange (ETDEWEB)

    David Hurley; Stephen Reese; Farhad Farzbod; Rory Kennedy

    2012-05-01

    Mechanical properties are controlled to a large degree by defect structures such as dislocations and grain boundaries. These microstructural features involve a perturbation of the perfect crystal lattice (i.e. strain fields). Viewed in this context, high frequency strain waves (i.e. ultrasound) provide a natural choice to study microstructure mediated mechanical properties. In this presentation we use laser ultrasound to probe mechanical properties of materials. This approach utilizes lasers to excite and detect ultrasonic waves, and as a consequence has unique advantages over other methods—it is noncontacting, requires no couplant or invasive sample preparation (other than that used in metallurgical analysis), and has the demonstrated capability to probe microstructure on a micron scale. Laser techniques are highly reproducible enabling sophisticated, microstructurally informed data analysis. Since light is being used for generation and detection of the ultrasonic wave, the specimen being examined is not mechanically coupled to the transducer. As a result, laser ultrasound can be carried out remotely, an especially attractive characteristic for in situ measurements in severe environments. Several examples involving laser ultrasound to measure mechanical properties in high temperature environments will be presented. Emphasis will be place on understanding the role of grain microstructure.

  12. Mechanical properties of carbon fiber composites for applications in space

    Science.gov (United States)

    Hana, P.; Inneman, A.; Daniel, V.; Sieger, L.; Petru, M.

    2015-01-01

    This article describes method of measurement mechanical properties of carbon fiber composites in space. New material structures are specifically designed for use on space satellites. Composite structures will be exposed to cosmic radiation in Earth orbit on board of a '2U CubeSat' satellite. Piezoelectric ceramic sensors are used for detection mechanical vibrations of composite test strip. A great deal of attention is paid to signal processing using 8-bit microcontroler. Fast Fourier Transformation is used. Fundamental harmonic frequencies and damping from on-board measurements will serve as the input data for terrestrial data processing. The other step of elaboration data is creation of the physical model for evaluating mechanical properties of Carbon composite - Piezoelectric ceramic system. Evaluation of anisotropic mechanical properties of piezoelectric ceramics is an interesting secondary outcome of the investigation. Extreme changes in temperature and the effect of cosmic rays will affect the mechanical properties and durability of the material used for the external construction of satellites. Comparative terrestrial measurements will be performed.

  13. Physical and mechanical properties of Tunisian women hair.

    Science.gov (United States)

    Sayahi, E; Harizi, T; Msahli, S; Sakli, F

    2016-10-01

    Mechanical analysis of human hair may provide the dermatologists with several markers of considerable diagnostic importance. The aim of this study was to analyse the physical and mechanical properties of Tunisian women's hair. Surface characteristics were determined with scanning electron microscopy (SEM). Mechanical properties were studied using the Miniature Tensile Tester Model 675 (MTT675), and the Fibre Dimensional Analysis Unit Model 765 (FDAS765) of Dia-Stron, UK, was used to measure the cross-sectional area. The cross-sectional area, stress at break, strain at break, elastic modulus and total work were 4643.21 ± 817 μm(2) , 201 ± 11.26 MPa, 47.3 ± 3.6%, 3.1 ± 0.16 GPa, and 9 ± 2.2 mJ, respectively. The effects of the factors 'hair curliness' and 'age' on the physical and mechanical properties were studied. The cross-sectional area and the break load are influenced by the factors 'age' and 'curl type', whereas Young's modulus shows a significant dependency only on the age. Tunisian women hair presented good mechanical properties as shown by a greater breaking stress and higher breaking strain. Both curl type and age are important factors to consider when evaluating the behaviour of hair. © 2016 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  14. Influence of Moisture on Mechanical Properties of Cellulose Insulation Paper

    Science.gov (United States)

    Wang, Y. Y.; Tian, M.; Xu, H. X.; Fan, P.

    2014-01-01

    This paper aims to investigate the impact of moisture on mechanical properties of insulation paper. According to the molecular modeling approach proposed by Theodorou, the amorphous cellulose models of insulation paper with different moisture contents were built up to calculate mechanical parameters and hydrogen bond networks. And relevant conclusions could be drawn through further analysis on these calculation results: water molecules can destroy hydrogen bond network between the neighboring cellulose molecules, which might be responsible for the significant decrease of Young's modulus and other mechanical parameters, while no appreciable effect of intramolecular hydrogen bonds on mechanical properties was detected. Thus tensile tests were also carried out to study the moisture influence on the Young's modulus, by which the result of the simulation was approved.

  15. Role of mismatch in mechanical properties in cancer cell migration

    Science.gov (United States)

    Butcher, Julian; Das, Moumita

    2014-03-01

    Recent experiments suggest that the mechanical stiffness of cells and their interaction with their surroundings undergo remarkable changes during tumor progression. An intriguing experimental result in this area suggests that the mismatch in the elasticity and adhesive properties between cancer cells and cells that have not yet transformed may lead to enhanced cancer cell motility in a binary cell population. Motivated by this, we study the mechanical response and dynamics of a binary system of active and deformable particles using Langevin Dynamics simulations. We characterize their motility by studying particle trajectories, mean square displacements and correlation functions. Our study may provide an understanding of the interplay of mechanical and statistical mechanical properties underlying the enhanced motility of cancer cells during metastasis. This work was partially supported by a D-RIG grant from the College of Science at Rochester Institute of Technology.

  16. Laser welding of polymers, compatibility and mechanical properties

    DEFF Research Database (Denmark)

    Nielsen, Steen Erik; Strange, Marianne; Kristensen, Jens Klæstrup

    2013-01-01

    Laser welding of polymers is today a commonly used industrial technology. It has shown obvious advantages compared to e.g. adhesive bonding in terms of higher productivity, better quality and easiness for automation. The ongoing development of lasers tailored for polymer welding in coordination....... There is an increasing industrial interest in joining dissimilar polymers. To overcome the challenges involved increased focus is set on the understanding of joining mechanisms, morphology and molecular structure behavior. Also the understanding of resulting mechanical and thermal properties is presently subject...... for research and development. This paper presents some research results related to laser welding of various polymer materials, including weld compatibility investigations related to the joining of different polymers. Theory for bonding mechanisms, strength development, mechanical properties testing and other...

  17. Monotone Semiflows Generated by Functional Differential Equations,

    Science.gov (United States)

    1986-02-01

    These results have been applied to ordinary differential equations in Rn (see e.g. [10,23]) where the well-known Kamke theorem applies and to nonlinear...sufficient condition (H) Whenever 0 - 0 and ,i(0) = i( 0) it follows that fi(0) ( fi(O). For those familiar with the Kamke (quasimonotone) condition for...ordinary differential equations, (H) will seem quite natural, it reduces to the Kamke condition. The order preserving property of a semiflow is not

  18. Mechanical Properties Prediction of the Mechanical Clinching Joints Based on Genetic Algorithm and BP Neural Network

    Institute of Scientific and Technical Information of China (English)

    LONG Jiangqi; LAN Fengchong; CHEN Jiqing; YU Ping

    2009-01-01

    For optimal design of mechanical clinching steel-aluminum joints, the back propagation (BP) neural network is used to research the mapping relationship between joining technique parameters including sheet thickness, sheet hardness, joint bottom diameter etc., and mechanical properties of shearing and peeling in order to investigate joining technology between various material plates in the steel-aluminum hybrid structure car body. Genetic algorithm (GA) is adopted to optimize the back-propagation neural network connection weights. The training and validating samples are made by the BTM(R) Tog-L-Loc system with different technologic parameters. The training samples' parameters and the corresponding joints' mechanical properties are supplied to the artificial neural network (ANN) for training. The validating samples' experimental data is used for checking up the prediction outputs. The calculation results show that GA can improve the model's prediction precision and generalization ability of BP neural network. The comparative analysis between the experimental data and the prediction outputs shows that ANN prediction models after training can effectively predict the mechanical properties of mechanical clinching joints and prove the feasibility and reliability of the intelligent neural networks system when used in the mechanical properties prediction of mechanical clinching joints. The prediction results can be used for a reference in the design of mechanical clinching steel-aluminum joints.

  19. Mechanical Properties Comparing Composite Fiber Length to Amalgam

    Directory of Open Access Journals (Sweden)

    Richard C. Petersen

    2016-01-01

    Full Text Available Photocure fiber-reinforced composites (FRCs with varying chopped quartz-fiber lengths were incorporated into a dental photocure zirconia-silicate particulate-filled composite (PFC for mechanical test comparisons with a popular commercial spherical-particle amalgam. FRC lengths included 0.5-mm, 1.0 mm, 2.0 mm, and 3.0 mm all at a constant 28.2 volume percent. Four-point fully articulated fixtures were used according to American Standards Test Methods with sample dimensions of 2×2×50 mm3 across a 40 mm span to provide sufficient Euler flexural bending and prevent top-load compressive shear error. Mechanical properties for flexural strength, modulus, yield strength, resilience, work of fracture, critical strain energy release, critical stress intensity factor, and strain were obtained for comparison. Fiber length subsequently correlated with increasing all mechanical properties, p<1.1×10-5. Although the modulus was significantly statistically higher for amalgam than all composites, all FRCs and even the PFC had higher values than amalgam for all other mechanical properties. Because amalgams provide increased longevity during clinical use compared to the standard PFCs, modulus would appear to be a mechanical property that might sufficiently reduce margin interlaminar shear stress and strain-related microcracking that could reduce failure rates. Also, since FRCs were tested with all mechanical properties that statistically significantly increased over the PFC, new avenues for future development could be provided toward surpassing amalgam in clinical longevity.

  20. Monotonically increasing functions of any quantum correlation can make all multiparty states monogamous

    Energy Technology Data Exchange (ETDEWEB)

    Salini, K. [School of Physics, IISER TVM, CET Campus, Thiruvananthapuram, Kerala 695 016 (India); Prabhu, R.; Sen, Aditi [Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211 019 (India); Sen, Ujjwal, E-mail: ujjwal@hri.res.in [Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211 019 (India)

    2014-09-15

    Monogamy of quantum correlation measures puts restrictions on the sharability of quantum correlations in multiparty quantum states. Multiparty quantum states can satisfy or violate monogamy relations with respect to given quantum correlations. We show that all multiparty quantum states can be made monogamous with respect to all measures. More precisely, given any quantum correlation measure that is non-monogamic for a multiparty quantum state, it is always possible to find a monotonically increasing function of the measure that is monogamous for the same state. The statement holds for all quantum states, whether pure or mixed, in all finite dimensions and for an arbitrary number of parties. The monotonically increasing function of the quantum correlation measure satisfies all the properties that are expected for quantum correlations to follow. We illustrate the concepts by considering a thermodynamic measure of quantum correlation, called the quantum work deficit.

  1. Mechanical properties of tricalcium phosphate-alumina composites

    Science.gov (United States)

    Sakka, S.; Ben Ayed, F.; Bouaziz, J.

    2012-02-01

    Tricalcium phosphate and alumina powder were mixed in order to elaborate biphasic ceramics composites. This study deals to produce bioceramics composites sintered at various temperatures for differents times. The characterization of samples, before and after the sintering process was investigated, using X-Ray diffraction, scanning electronic microscopy, 31P and 27Al nuclear magnetic resonance and differential thermal analysis. Mechanical properties of biphasic composites were studied using Brazilian test. The tricalcium phosphate - 75 wt% alumina composites mechanical resistance increased with sintered temperature. The mechanical resistance reach it's optimum value (8.6 MPa) at 1550°C for two hours.

  2. Interspecific comparison of the mechanical properties of mussel byssus.

    Science.gov (United States)

    Brazee, Shanna L; Carrington, Emily

    2006-12-01

    Byssally tethered mussels are found in a variety of habitats, including rocky intertidal, salt marsh, subtidal, and hydrothermal vents. One key to the survival of mussels in these communities is a secure attachment, achieved by the production of byssal threads. Although many studies have detailed the unique biomechanical properties of byssal threads, only a few prevalent species have been examined. This study assesses the variation in the mechanical properties of byssus in a broad range of mussel species from diverse environments, including intertidal and subtidal Mytilus edulis, Modiolus modiolus, Geukensia demissa, Bathymodiolus thermophilus, and Dreissena polymorpha. A tensometer was used to measure quasi-static and dynamic mechanical properties of individual threads, and several aspects of morphology were quantified. The results indicate that thread mechanical properties vary among mussel species, and several novel properties were observed. For example, of the species examined, D. polymorpha threads were the strongest, stiffest, least resilient, and fastest to recover after partial deformation. Threads of M. modiolus were characterized by the presence of two distinct yield regions prior to tensile failure. This comparative study not only provides insight into the ecological limitations and evolution of mussels, but also suggests new models for the design of novel biomimetic polymers.

  3. Mechanical properties of titanium alloys with strengthened surface layers

    Directory of Open Access Journals (Sweden)

    I.M. Pohreliuk

    2011-12-01

    Full Text Available Influence of oxinitriding and boriding on the mechanical properties (ultimate strength to destruction at uniaxial tension, plasticity, tendency to delayed destruction, fatigue resistance at bending with rotation, fatigue life at lowcycle pure bending of titanium alloys is studied.

  4. THE RHEOLOGICAL PROPERTIES AND OUTBURST MECHANISM OF GASEOUS COAL

    Institute of Scientific and Technical Information of China (English)

    何学秋; 周世宁; 林柏泉

    1991-01-01

    Coal and methane outburst is one of the harmful disasters in coal mines. We have studied the rheological properties of gaseous coal in laboratory and obtained its rheological fracture principle. This principle can better explain and describe the outburst mechanism of gaseous coal. Thereby a rheological hypothesis of coal and methane outburst is put forward in this paper.

  5. assessment of some mechanical properties and microstructure of ...

    African Journals Online (AJOL)

    user

    the composites and those of the aluminium 6063 (AA6063) alloy. ... Key words: Composites, Periwinkle shell, Aluminum, Mechanical properties, Microstructure. 1. .... In this work, we evaluated the effect of particle size and ... Zr. V. Ca. Be. Average content. 0.0347. 0.0566. ... micro structural study. 3.

  6. Temperature dependence of poly(lactic acid) mechanical properties

    DEFF Research Database (Denmark)

    Zhou, Chengbo; Guo, Huilong; Li, Jingqing

    2016-01-01

    The mechanical properties of polymers are not only determined by their structures, but also related to the temperature field in which they are located. The yield behaviors, Young's modulus and structures of injection-molded poly(lactic acid) (PLA) samples after annealing at different temperatures...

  7. Mechanical Properties, Purifying Techniques and Processing Methods of Metal Yttrium

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The mechanical properties of metal yttrium such as strength, plasticity, hardness and elasticity were introduced. The purifying techniques of yttrium were discussed in detail. The processing methods for metal yttrium including extruding, forging, rolling, wiredrawing and welding were also introduced. Finally, the potential use of yttrium and its alloys were prospected.

  8. IMPACT OF OIL ON THE MECHANICAL PROPERTIES OF SOIL SUBSIDENCE

    Directory of Open Access Journals (Sweden)

    Алексей Алексеевич Бурцев

    2016-08-01

    Full Text Available The paper studied the effect of oil content on the mechanical properties of soil subsidence - Ek modulus and compressibility factor m0, obtained in the laboratory with the help of artificial impregnation oil soil samples. A comparison of the above parameters with samples of the same soil in the natural and water-saturated conditions has been perfomed.

  9. Mechanical properties of porous, electrosprayed calcium phosphate coatings

    NARCIS (Netherlands)

    Leeuwenburgh, S.C.G.; Wolke, J.G.C.; Lommen, L.; Pooters, T.; Schoonman, J.; Jansen, J.A.

    2006-01-01

    Mechanical properties of calcium phosphate coatings (CaP), deposited using the electrostatic spray deposition (ESD) technique, have been characterized using a range of analytical techniques, including tensile testing (ASTM C633), fatigue testing (ASTM E855), and scratch testing using blunt and sharp

  10. Mechanical properties of short doughs and their corresponding biscuits.

    NARCIS (Netherlands)

    Baltsavias, A.

    1996-01-01

    The mechanical properties of short doughs of various composition were determined in small amplitude oscillatory experiments and in uniaxial compression. Regardless of composition, the linear region was very limited; beyond that, pronounced yielding and flow occurred. Conductimetry was also used to e

  11. Mechanical properties of hyaline and repair cartilage studied by nanoindentation.

    Science.gov (United States)

    Franke, O; Durst, K; Maier, V; Göken, M; Birkholz, T; Schneider, H; Hennig, F; Gelse, K

    2007-11-01

    Articular cartilage is a highly organized tissue that is well adapted to the functional demands in joints but difficult to replicate via tissue engineering or regeneration. Its viscoelastic properties allow cartilage to adapt to both slow and rapid mechanical loading. Several cartilage repair strategies that aim to restore tissue and protect it from further degeneration have been introduced. The key to their success is the quality of the newly formed tissue. In this study, periosteal cells loaded on a scaffold were used to repair large partial-thickness cartilage defects in the knee joint of miniature pigs. The repair cartilage was analyzed 26 weeks after surgery and compared both morphologically and mechanically with healthy hyaline cartilage. Contact stiffness, reduced modulus and hardness as key mechanical properties were examined in vitro by nanoindentation in phosphate-buffered saline at room temperature. In addition, the influence of tissue fixation with paraformaldehyde on the biomechanical properties was investigated. Although the repair process resulted in the formation of a stable fibrocartilaginous tissue, its contact stiffness was lower than that of hyaline cartilage by a factor of 10. Fixation with paraformaldehyde significantly increased the stiffness of cartilaginous tissue by one order of magnitude, and therefore, should not be used when studying biomechanical properties of cartilage. Our study suggests a sensitive method for measuring the contact stiffness of articular cartilage and demonstrates the importance of mechanical analysis for proper evaluation of the success of cartilage repair strategies.

  12. effects of sulphur addition on addition on and mechanical properties ...

    African Journals Online (AJOL)

    User

    on the microstructure and mechanical properties of sand cast been investigated in this .... Cu. Zn. Mn. Mg. Cr. B. 99.71. 0.045. -. 0.230. 0.002. 0.006. 0.001. 0.001. 0.001. 0.004 ..... Iron & Steel Making, MIR Publishers, Moscow,. 39. 1983. 40. 41.

  13. Switchable antimicrobial and antifouling hydrogels with enhanced mechanical properties.

    Science.gov (United States)

    Cao, Bin; Tang, Qiong; Li, Linlin; Humble, Jayson; Wu, Haiyan; Liu, Lingyun; Cheng, Gang

    2013-08-01

    New switchable hydrogels are developed. Under acidic conditions, hydrogels undergo self-cyclization and can catch and kill bacteria. Under neutral/basic conditions, hydrogels undergo ring-opening and can release killed bacterial cells and resist protein adsorption and bacterial attachment. Smart hydrogels also show a dramatically improved mechanical property, which is highly desired for biomedical applications.

  14. Sterilizing elastomeric chains without losing mechanical properties. Is it possible?

    Science.gov (United States)

    Pithon, Matheus Melo; Ferraz, Caio Souza; Rosa, Francine Cristina Silva; Rosa, Luciano Pereira

    2015-01-01

    OBJECTIVE: To investigate the effects of different sterilization/disinfection methods on the mechanical properties of orthodontic elastomeric chains. METHODS: Segments of elastomeric chains with 5 links each were sent for sterilization by cobalt 60 (Co60) (20 KGy) gamma ray technology. After the procedure, the elastomeric chains were contaminated with clinical samples of Streptococcus mutans. Subsequently, the elastomeric chains were submitted to sterilization/disinfection tests carried out by means of different methods, forming six study groups, as follows: Group 1 (control - without contamination), Group 2 (70°GL alcohol), Group 3 (autoclave), Group 4 (ultraviolet), Group 5 (peracetic acid) and Group 6 (glutaraldehyde). After sterilization/disinfection, the effectiveness of these methods, by Colony forming units per mL (CFU/mL), and the mechanical properties of the material were assessed. Student's t-test was used to assess the number of CFUs while ANOVA and Tukey's test were used to assess elastic strength. RESULTS: Ultraviolet treatment was not completely effective for sterilization. No loss of mechanical properties occurred with the use of the different sterilization methods (p > 0.05). CONCLUSION: Biological control of elastomeric chains does not affect their mechanical properties. PMID:26154462

  15. Mechanical properties of ultra-fine grained zirconia ceramics

    NARCIS (Netherlands)

    Theunissen, G.S.A.M.; Bouma, J.S.; Winnubst, A.J.A.; Burggraaf, A.J.

    1992-01-01

    The mechanical properties of tetragonal zirconia (TZP) materials doped with Y, Ce or Ti were studied as a function of temperature and grain size. Fine grained Y-TZP (grain size < 0.3 mgrm) shows values for fracture toughness and strength at room temperature, which are comparable with the coarse grai

  16. Theoretical Modeling of Mechanical Behavior and Release Properties of Microcapsules

    NARCIS (Netherlands)

    Sagis, L.M.C.

    2015-01-01

    Microcapsules in food often have a shell with a complex microstructure; the mechanical and structural properties of these shells affect the response of the capsules to deforming forces and the release kinetics of encapsulated components. In this chapter we will discuss a number of models which are t

  17. Influence of tempering temperature on mechanical properties of cast steels

    Directory of Open Access Journals (Sweden)

    G. Golański

    2008-12-01

    Full Text Available The paper presents results of research on the influence of tempering temperature on structure and mechanical properties of bainite hardened cast steel: G21CrMoV4 – 6 (L21HMF and G17CrMoV5 – 10 (L17HMF. Investigated cast steels were taken out from internal frames of steam turbines serviced for long time at elevated temperatures. Tempering of the investigated cast steel was carried out within the temperature range of 690 ÷ 730 C (G21CrMoV4 – 6 and 700 ÷ 740 C (G17CrMoV5 – 10. After tempering the cast steels were characterized by a structure of tempered lower bainite with numerous precipitations of carbides. Performed research of mechanical properties has shown that high temperatures of tempering of bainitic structure do not cause decrease of mechanical properties beneath the required minimum.oo It has also been proved that high-temperature tempering (>720 oC ensures high impact energy at the 20% decrease of mechanical properties.

  18. Sterilizing elastomeric chains without losing mechanical properties. Is it possible?

    Directory of Open Access Journals (Sweden)

    Matheus Melo Pithon

    2015-06-01

    Full Text Available OBJECTIVE: To investigate the effects of different sterilization/disinfection methods on the mechanical properties of orthodontic elastomeric chains. METHODS: Segments of elastomeric chains with 5 links each were sent for sterilization by cobalt 60 (Co60 (20 KGy gamma ray technology. After the procedure, the elastomeric chains were contaminated with clinical samples of Streptococcus mutans. Subsequently, the elastomeric chains were submitted to sterilization/disinfection tests carried out by means of different methods, forming six study groups, as follows: Group 1 (control - without contamination, Group 2 (70°GL alcohol, Group 3 (autoclave, Group 4 (ultraviolet, Group 5 (peracetic acid and Group 6 (glutaraldehyde. After sterilization/disinfection, the effectiveness of these methods, by Colony forming units per mL (CFU/mL, and the mechanical properties of the material were assessed. Student's t-test was used to assess the number of CFUs while ANOVA and Tukey's test were used to assess elastic strength. RESULTS: Ultraviolet treatment was not completely effective for sterilization. No loss of mechanical properties occurred with the use of the different sterilization methods (p > 0.05. CONCLUSION: Biological control of elastomeric chains does not affect their mechanical properties.

  19. Exploration of mechanisms underlying the strain-rate-dependent mechanical property of single chondrocytes

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Trung Dung; Gu, YuanTong, E-mail: yuantong.gu@qut.edu.au [School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland (Australia)

    2014-05-05

    Based on the characterization by Atomic Force Microscopy, we report that the mechanical property of single chondrocytes has dependency on the strain-rates. By comparing the mechanical deformation responses and the Young's moduli of living and fixed chondrocytes at four different strain-rates, we explore the deformation mechanisms underlying this dependency property. We found that the strain-rate-dependent mechanical property of living cells is governed by both of the cellular cytoskeleton and the intracellular fluid when the fixed chondrocytes are mainly governed by their intracellular fluid, which is called the consolidation-dependent deformation behavior. Finally, we report that the porohyperelastic constitutive material model which can capture the consolidation-dependent behavior of both living and fixed chondrocytes is a potential candidature to study living cell biomechanics.

  20. Driving performance impairments due to hypovigilance on monotonous roads.

    Science.gov (United States)

    Larue, Grégoire S; Rakotonirainy, Andry; Pettitt, Anthony N

    2011-11-01

    Drivers' ability to react to unpredictable events deteriorates when exposed to highly predictable and uneventful driving tasks. Highway design reduces the driving task mainly to a lane-keeping manoeuvre. Such a task is monotonous, providing little stimulation and this contributes to crashes due to inattention. Research has shown that driver's hypovigilance can be assessed with EEG measurements and that driving performance is impaired during prolonged monotonous driving tasks. This paper aims to show that two dimensions of monotony - namely road design and road side variability - decrease vigilance and impair driving performance. This is the first study correlating hypovigilance and driver performance in varied monotonous conditions, particularly on a short time scale (a few seconds). We induced vigilance decrement as assessed with an EEG during a monotonous driving simulator experiment. Road monotony was varied through both road design and road side variability. The driver's decrease in vigilance occurred due to both road design and road scenery monotony and almost independently of the driver's sensation seeking level. Such impairment was also correlated to observable measurements from the driver, the car and the environment. During periods of hypovigilance, the driving performance impairment affected lane positioning, time to lane crossing, blink frequency, heart rate variability and non-specific electrodermal response rates. This work lays the foundation for the development of an in-vehicle device preventing hypovigilance crashes on monotonous roads.

  1. Custom impression trays: Part I--Mechanical properties.

    Science.gov (United States)

    Breeding, L C; Dixon, D L; Moseley, J P

    1994-01-01

    Dimensional stability of custom impression trays is an important factor in determining the degree of accuracy achieved in forming a master cast. Such trays must remain stable over time and must not exhibit permanent deformation when a completed impression is removed from the oral cavity. Measurement of the mechanical properties allows comparison between various tray materials and is useful in interpreting data on stresses incurred during removal of the completed impression. In Part I of this three-part series, the various mechanical properties of five tray resins: one autopolymerizing polymethyl methacrylate, one light-polymerizing, and three brands of thermoplastic resins were recorded and compared. The thermoplastic resins studied in this investigation exhibited lower measured values for the strength and elastic modulus properties than the light-polymerizing resin and the autopolymerizing polymethyl methacrylate resin studied.

  2. Mechanical property determination of high conductivity metals and alloys

    Science.gov (United States)

    Harrod, D. L.; Vandergrift, E.; France, L.

    1973-01-01

    Pertinent mechanical properties of three high conductivity metals and alloys; namely, vacuum hot pressed grade S-200E beryllium, OFHC copper and beryllium-copper alloy no. 10 were determined. These materials were selected based on their possible use in rocket thrust chamber and nozzle hardware. They were procured in a form and condition similar to that which might be ordered for actual hardware fabrication. The mechanical properties measured include (1) tension and compression stress strain curves at constant strain rate (2) tensile and compressive creep, (3) tensile and compressive stress-relaxation behavior and (4) elastic properties. Tests were conducted over the temperature range of from 75 F to 1600 F. The resulting data is presented in both graphical and tabular form.

  3. Effect of graphene on mechanical properties of cement mortars

    Institute of Scientific and Technical Information of China (English)

    曹明莉; 张会霞; 张聪

    2016-01-01

    Functionalized graphene nano-sheets (FGN) of 0.01%−0.05% (mass fraction) were added to produce FGN-cement composites in the form of mortars. Flow properties, mechanical properties and microstructure of the cementitious material were then investigated. The results indicate that the addition of FGN decreases the fluidity slightly and improves mechanical properties of cement-based composites significantly. The highest strength is obtained with FGN content of 0.02% where the flexural strength and compressive strength at 28 days are 12.917 MPa and 52.42 MPa, respectively. Besides, scanning electron micrographs show that FGN can regulate formation of massive compact cross-linking structures and thermo gravimetric analysis indicates that FGN can accelerate the hydration reaction to increase the function of the composite effectively.

  4. Effects of nano TiN addition on the microstructure and mechanical properties of TiC based steel bonded carbides

    Institute of Scientific and Technical Information of China (English)

    WANG Zhi'an; DAI Haiyang; ZOU Yu

    2008-01-01

    TiC based steel bonded carbides with the addition of nano TiN were prepared by vicuum sintering techniques.The microstructure was investigated using scanning electron microscopy(SEM)and transmission electron microscopy (TEM),and the mechanical properties,such as bending strength,impact toughness,hardness,and density,were measured.The results indicate that the grain size becomes small and there is uniformity in the steel bonded carbide with nano addition;several smaller carbide particles are also found to be inlaid in the rim of the larger carbide grains and prevent the coalescence of TiC grains.The smaller and larger carbide grains joint firmly,and then the reduction of the average size of the grains leads to the increase in the mechanical properties of the steel bonded carbides with nano addition.But the mechanical properties do not increase monotonously with an increase in nano addition.When the nano TiN addition accounts for 6-8 wt.% of the amount of steel bonded carbides.the mechanical properties reach the maximum values and then decrease with further increase in nano TiN addition.

  5. Porcine bladder acellular matrix (ACM): protein expression, mechanical properties.

    Science.gov (United States)

    Farhat, Walid A; Chen, Jun; Haig, Jennifer; Antoon, Roula; Litman, Jessica; Sherman, Christopher; Derwin, Kathleen; Yeger, Herman

    2008-06-01

    Experimentally, porcine bladder acellular matrix (ACM) that mimics extracellular matrix has excellent potential as a bladder substitute. Herein we investigated the spatial localization and expression of different key cellular and extracellular proteins in the ACM; furthermore, we evaluated the inherent mechanical properties of the resultant ACM prior to implantation. Using a proprietary decellularization method, the DNA contents in both ACM and normal bladder were measured; in addition we used immunohistochemistry and western blots to quantify and localize the different cellular and extracellular components, and finally the mechanical testing was performed using a uniaxial mechanical testing machine. The mean DNA content in the ACM was significantly lower in the ACM compared to the bladder. Furthermore, the immunohistochemical and western blot analyses showed that collagen I and IV were preserved in the ACM, but possibly denatured collagen III in the ACM. Furthermore, elastin, laminin and fibronectin were mildly reduced in the ACM. Although the ACM did not exhibit nucleated cells, residual cellular components (actin, myosin, vimentin and others) were still present. There was, on the other hand, no significant difference in the mean stiffness between the ACM and the bladder. Although our decellularization method is effective in removing nuclear material from the bladder while maintaining its inherent mechanical properties, further work is mandatory to determine whether these residual DNA and cellular remnants would lead to any immune reaction, or if the mechanical properties of the ACM are preserved upon implantation and cellularization.

  6. Short-range mechanical properties of skeletal and cardiac muscles.

    Science.gov (United States)

    Campbell, Kenneth S

    2010-01-01

    Striated muscles are disproportionately stiff for small movements. This facet of their behavior can be demonstrated by measuring the force produced when the muscle is stretched more than about 1% of its initial length. When this is done, it can be seen that force rises rapidly during the initial phases of the movement and much less rapidly during the latter stages of the stretch. Experiments performed using chemically permeabilized skeletal and cardiac muscles show that the initial stiffness of the preparations increases in proportion with isometric force as the free Ca²(+) concentration in the bathing solution is raised from a minimal to a saturating value. This is strong evidence that the short-range mechanical properties of activated muscle result from stretching myosin cross-bridges that are attached between the thick and thin filaments. Relaxed intact muscles also exhibit short-range mechanical properties but the molecular mechanisms underlying this behavior are less clear. This chapter summarizes some of the interesting features of short-range mechanical properties in different types of muscle preparation, describes some of the likely underlying mechanisms and discusses the potential physiological significance of the behavior.

  7. Porcine bladder acellular matrix (ACM): protein expression, mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Farhat, Walid A [Department of Surgery, Division of Urology, University of Toronto and Hospital for Sick Children, Toronto, ON M5G 1X8 (Canada); Chen Jun; Haig, Jennifer; Antoon, Roula; Litman, Jessica; Yeger, Herman [Department of Developmental and Stem Cell Biology, Research Institute, Hospital for Sick Children, Toronto, ON M5G 1X8 (Canada); Sherman, Christopher [Department of Anatomic Pathology, Sunnybrook and Women' s College Health Sciences Centre, Toronto, ON (Canada); Derwin, Kathleen [Department of Biomedical Engineering, Lerner Research Institute and Orthopaedic Research Center, Cleveland Clinic Foundation, Cleveland, OH (United States)], E-mail: walid.farhat@sickkids.ca

    2008-06-01

    Experimentally, porcine bladder acellular matrix (ACM) that mimics extracellular matrix has excellent potential as a bladder substitute. Herein we investigated the spatial localization and expression of different key cellular and extracellular proteins in the ACM; furthermore, we evaluated the inherent mechanical properties of the resultant ACM prior to implantation. Using a proprietary decellularization method, the DNA contents in both ACM and normal bladder were measured; in addition we used immunohistochemistry and western blots to quantify and localize the different cellular and extracellular components, and finally the mechanical testing was performed using a uniaxial mechanical testing machine. The mean DNA content in the ACM was significantly lower in the ACM compared to the bladder. Furthermore, the immunohistochemical and western blot analyses showed that collagen I and IV were preserved in the ACM, but possibly denatured collagen III in the ACM. Furthermore, elastin, laminin and fibronectin were mildly reduced in the ACM. Although the ACM did not exhibit nucleated cells, residual cellular components (actin, myosin, vimentin and others) were still present. There was, on the other hand, no significant difference in the mean stiffness between the ACM and the bladder. Although our decellularization method is effective in removing nuclear material from the bladder while maintaining its inherent mechanical properties, further work is mandatory to determine whether these residual DNA and cellular remnants would lead to any immune reaction, or if the mechanical properties of the ACM are preserved upon implantation and cellularization.

  8. Brillouin microspectroscopy of nanostructured biomaterials: photonics assisted tailoring mechanical properties

    Science.gov (United States)

    Meng, Zhaokai; Jaiswal, Manish K.; Chitrakar, Chandani; Thakur, Teena; Gaharwar, Akhilesh K.; Yakovlev, Vladislav V.

    2016-03-01

    Developing new biomaterials is essential for the next-generation of materials for bioenergy, bioelectronics, basic biology, medical diagnostics, cancer research, and regenerative medicine. Specifically, recent progress in nanotechnology has stimulated the development of multifunctional biomaterials for tissue engineering applications. The physical properties of nanocomposite biomaterials, including elasticity and viscosity, play key roles in controlling cell fate, which underlines therapeutic success. Conventional mechanical tests, including uniaxial compression and tension, dynamic mechanical analysis and shear rheology, require mechanical forces to be directly exerted onto the sample and therefore may not be suitable for in situ measurements or continuous monitoring of mechanical stiffness. In this study, we employ spontaneous Brillouin spectroscopy as a viscoelasticity-specific probing technique. We utilized a Brillouin spectrometer to characterize biomaterial's microscopic elasticity and correlated those with conventional mechanical tests (e.g., rheology).

  9. Altered mechanical properties of the nucleus in disease.

    Science.gov (United States)

    Lombardi, Maria Lucia; Lammerding, Jan

    2010-01-01

    In eukaryotic cells, the nucleus is the largest and most rigid organelle. Therefore, its physical properties contribute critically to the biomechanical behavior of cells, e.g., during amoeboid migration or perfusion through narrow capillaries. Furthermore, it has been speculated that nuclear deformations could directly allow cells to sense mechanical stress, e.g., by modulating the access of specific transcription factors to their binding sites. Defects in nuclear mechanics have also been reported in a variety of muscular dystrophies caused by mutations in nuclear envelope proteins, indicating an important role in the maintenance of cells in mechanically stressed tissue. These findings have prompted the growing field of nuclear mechanics to develop advanced experimental methods to study the physical properties of the nucleus as a function of nuclear structure and organization, and to understand its role in physiology and disease. These experimental techniques include micropipette aspiration, atomic force microscopy of isolated nuclei, cellular strain and compression experiments, and microneedle manipulation of intact cells. These experiments have provided important insights into the mechanical behavior of the nucleus under physiological conditions, the distinct mechanical contributions of the nuclear lamina and interior, and how mutations in nuclear envelope proteins associated with a variety of human diseases can cause distinct alterations in the physical properties of the nucleus and contribute to the disease mechanism. Here, we provide a brief overview of the most common experimental techniques and their application and discuss the implication of their results on our current understanding of nuclear mechanics. Copyright (c) 2010 Elsevier Inc. All rights reserved.

  10. The mechanical properties of the human hip capsule ligaments.

    Science.gov (United States)

    Hewitt, John D; Glisson, Richard R; Guilak, Farshid; Vail, T Parker

    2002-01-01

    The human hip capsule is adapted to facilitate upright posture, joint stability, and ambulation, yet it routinely is excised in hip surgery without a full understanding of its mechanical contributions. The objective of this study was to provide information about the mechanical properties of the ligaments that form the hip capsule. Cadaver bone-ligament-bone specimens of the iliofemoral, ischiofemoral, and femoral arcuate ligaments were tested to failure in tension. The hip capsule was found to be an inhomogeneous structure and should be recognized as being composed of discrete constituent ligaments. The anterior ligaments, consisting of the 2 arms of the iliofemoral ligament, were much stronger than the posterior ischiofemoral ligament, withstanding greater force at failure and exhibiting greater stiffness. Knowledge of the anatomy and mechanical properties of the capsule may help the hip surgeon choose an appropriate surgical approach or repair strategy.

  11. On the mechanical properties of sintered metallic fibre structures

    Energy Technology Data Exchange (ETDEWEB)

    Veyhl, C., E-mail: Christoph.Veyhl@uon.edu.au [The University of Newcastle, School of Engineering, Centre for Mass and Thermal Transport in Engineering Materials, Callaghan, NSW 2308 (Australia); Fiedler, T., E-mail: Thomas.Fiedler@newcastle.edu.au [The University of Newcastle, School of Engineering, Centre for Mass and Thermal Transport in Engineering Materials, Callaghan, NSW 2308 (Australia); Jehring, U., E-mail: Ulrike.Jehring@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials, Branch Lab Dresden, 01277 Dresden, Winterbergstr. 28 (Germany); Andersen, O., E-mail: Olaf.Andersen@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials, Branch Lab Dresden, 01277 Dresden, Winterbergstr. 28 (Germany); Bernthaler, T., E-mail: Timo.Bernthaler@htw-aalen.de [University of Applied Sciences Aalen, Department of Surface Engineering and Materials Science, Faculty of Mechanical and Material Engineering, Beethovenstr. 1, 73430 Aalen (Germany); Belova, I.V., E-mail: Irina.Belova@newcastle.edu.au [The University of Newcastle, School of Engineering, Centre for Mass and Thermal Transport in Engineering Materials, Callaghan, NSW 2308 (Australia); Murch, G.E., E-mail: Graeme.Murch@newcastle.edu.au [The University of Newcastle, School of Engineering, Centre for Mass and Thermal Transport in Engineering Materials, Callaghan, NSW 2308 (Australia)

    2013-02-01

    The present study investigates mechanical properties of a novel sintered metallic fibre structure with different relative densities (i.e. 0.19, 0.27, and 0.46). The compressive mechanical properties Young's modulus, Poisson's ratio and 0.2% offset yield stress are determined. For this purpose, state of the art simulations are performed based on the real material structure using micro-computed tomography images. Computed results are compared with experimental uni-axial compression tests and good agreement between both methods is observed. Numerical analysis allows the investigation of directional dependence and mechanical anisotropy is observed to be governed by the fibre orientation. In addition, Young's modulus and 0.2% offset yield stress increase with rising relative density.

  12. Mechanical Properties of Materials with Nanometer Scale Microstructures

    Energy Technology Data Exchange (ETDEWEB)

    William D. Nix

    2004-10-31

    We have been engaged in research on the mechanical properties of materials with nanometer-scale microstructural dimensions. Our attention has been focused on studying the mechanical properties of thin films and interfaces and very small volumes of material. Because the dimensions of thin film samples are small (typically 1 mm in thickness, or less), specialized mechanical testing techniques based on nanoindentation, microbeam bending and dynamic vibration of micromachined structures have been developed and used. Here we report briefly on some of the results we have obtained over the past three years. We also give a summary of all of the dissertations, talks and publications completed on this grant during the past 15 years.

  13. Mechanical Properties of the TiAl IRIS Alloy

    Science.gov (United States)

    Voisin, Thomas; Monchoux, Jean-Philippe; Thomas, Marc; Deshayes, Christophe; Couret, Alain

    2016-12-01

    This paper presents a study of the mechanical properties at room and high temperature of the boron and tungsten containing IRIS alloy (Ti-48Al-2W-0.08B at. pct). This alloy was densified by Spark Plasma Sintering (SPS). The resultant microstructure consists of small lamellar colonies surrounded by γ regions containing B2 precipitates. Tensile tests are performed from room temperature to 1273 K (1000 °C). Creep properties are determined at 973 K (700 °C)/300 MPa, 1023 K (750 °C)/120 MPa, and 1023 K (750 °C)/200 MPa. The tensile strength and the creep resistance at high temperature are found to be very high compared to the data reported in the current literature while a plastic elongation of 1.6 pct is preserved at room temperature. A grain size dependence of both ductility and strength is highlighted at room temperature. The deformation mechanisms are studied by post-mortem analyses on deformed samples and by in situ straining experiments, both performed in a transmission electron microscope. In particular, a low mobility of non-screw segments of dislocations at room temperature and the activation of a mixed-climb mechanism during creep have been identified. The mechanical properties of this IRIS alloy processed by SPS are compared to those of other TiAl alloys developed for high-temperature structural applications as well as to those of similar tungsten containing alloys obtained by more conventional processing techniques. Finally, the relationships between mechanical properties and microstructural features together with the elementary deformation mechanisms are discussed.

  14. Monotonic and Cyclic Behavior of DIN 34CrNiMo6 Tempered Alloy Steel

    Directory of Open Access Journals (Sweden)

    Ricardo Branco

    2016-04-01

    Full Text Available This paper aims at studying the monotonic and cyclic plastic deformation behavior of DIN 34CrNiMo6 high strength steel. Monotonic and low-cycle fatigue tests are conducted in ambient air, at room temperature, using standard 8-mm diameter specimens. The former tests are carried out under position control with constant displacement rate. The latter are performed under fully-reversed strain-controlled conditions, using the single-step test method, with strain amplitudes lying between ±0.4% and ±2.0%. After the tests, the fracture surfaces are examined by scanning electron microscopy in order to characterize the surface morphologies and identify the main failure mechanisms. Regardless of the strain amplitude, a softening behavior was observed throughout the entire life. Total strain energy density, defined as the sum of both tensile elastic and plastic strain energies, was revealed to be an adequate fatigue damage parameter for short and long lives.

  15. Fused Lasso Screening Rules via the Monotonicity of Subdifferentials.

    Science.gov (United States)

    Wang, Jie; Fan, Wei; Ye, Jieping

    2015-09-01

    Fused Lasso is a popular regression technique that encodes the smoothness of the data. It has been applied successfully to many applications with a smooth feature structure. However, the computational cost of the existing solvers for fused Lasso is prohibitive when the feature dimension is extremely large. In this paper, we propose novel screening rules that are able to quickly identity the adjacent features with the same coefficients. As a result, the number of variables to be estimated can be significantly reduced, leading to substantial savings in computational cost and memory usage. To the best of our knowledge, the proposed approach is the first attempt to develop screening methods for the fused Lasso problem with general data matrix. Our major contributions are: 1) we derive a new dual formulation of fused Lasso that comes with several desirable properties; 2) we show that the new dual formulation of fused Lasso is equivalent to that of the standard Lasso by two affine transformations; 3) we propose a novel framework for developing effective and efficient screening rules for fused Lasso via the monotonicity of the subdifferentials (FLAMS). Some appealing features of FLAMS are: 1) our methods are safe in the sense that the detected adjacent features are guaranteed to have the same coefficients; 2) the dataset needs to be scanned only once to run the screening, whose computational cost is negligible compared to that of solving the fused Lasso; (3) FLAMS is independent of the solvers and can be integrated with any existing solvers. We have evaluated the proposed FLAMS rules on both synthetic and real datasets. The experiments indicate that FLAMS is very effective in identifying the adjacent features with the same coefficients. The speedup gained by FLAMS can be orders of magnitude.

  16. Estimating monotonic rates from biological data using local linear regression.

    Science.gov (United States)

    Olito, Colin; White, Craig R; Marshall, Dustin J; Barneche, Diego R

    2017-03-01

    Accessing many fundamental questions in biology begins with empirical estimation of simple monotonic rates of underlying biological processes. Across a variety of disciplines, ranging from physiology to biogeochemistry, these rates are routinely estimated from non-linear and noisy time series data using linear regression and ad hoc manual truncation of non-linearities. Here, we introduce the R package LoLinR, a flexible toolkit to implement local linear regression techniques to objectively and reproducibly estimate monotonic biological rates from non-linear time series data, and demonstrate possible applications using metabolic rate data. LoLinR provides methods to easily and reliably estimate monotonic rates from time series data in a way that is statistically robust, facilitates reproducible research and is applicable to a wide variety of research disciplines in the biological sciences. © 2017. Published by The Company of Biologists Ltd.

  17. Monotone traveling wavefronts of the KPP-Fisher delayed equation

    CERN Document Server

    Gomez, Adrian

    2010-01-01

    In the early 2000's, Gourley (2000), Wu et al. (2001), Ashwin et al. (2002) initiated the study of the positive wavefronts in the delayed Kolmogorov-Petrovskii-Piskunov-Fisher equation. Since then, this model has become one of the most popular objects in the studies of traveling waves for the monostable delayed reaction-diffusion equations. In this paper, we give a complete solution to the problem of existence and uniqueness of monotone waves in the KPP-Fisher equation. We show that each monotone traveling wave can be found via an iteration procedure. The proposed approach is based on the use of special monotone integral operators (which are different from the usual Wu-Zou operator) and appropriate upper and lower solutions associated to them. The analysis of the asymptotic expansions of the eventual traveling fronts at infinity is another key ingredient of our approach.

  18. Conductive reduced graphene oxide/MnO2 carbonized cotton fabrics with enhanced electro -chemical, -heating, and -mechanical properties

    Science.gov (United States)

    Tian, Mingwei; Du, Minzhi; Qu, Lijun; Zhang, Kun; Li, Hongliang; Zhu, Shifeng; Liu, Dongdong

    2016-09-01

    Versatile and ductile conductive carbonized cotton fabrics decorated with reduced graphene oxide (rGO)/manganese dioxide (MnO2) are prepared in this paper. In order to endow multifunction to cotton fabric, graphene oxide (GO) is deposited on cotton fibers by simple dip-coating route. MnO2 nanoparticles are assembled on the surface of cotton fabric through in-situ chemical solution deposition. MnO2/GO@cotton fabrics are carbonized to achieve conductive fabric (MnO2/rGO@C). The morphologies and structures of obtained fabrics are characterized by SEM, XRD, ICP and element analysis, and their electro-properties including electro-chemical, electro-heating and electro-mechanical properties are evaluated. The MnO2/rGO@C yields remarkable specific capacitance of 329.4 mA h/g at the current density of 100 mA/g, which is more than 40% higher than that of the control carbonized cotton fabric (231 mA h/g). Regarding electro-heating properties, the temperature of MnO2/rGO@C fabric could be monotonically increased to the steady-state maximum temperatures (ΔTmax) of 36 °C within 5 min under the applied voltage 15 V while the ΔTmax = 17 °C of the control case. In addition, MnO2/rGO@C exhibits repeatable electro-mechanical properties and its normalized resistance (R-R0)/R0 could reach 0.78 at a constant strain (curvature = 0.6 cm-1). The MnO2/rGO@C fabric is versatile, scalable, and adaptable to a wide variety of smart textiles applications.

  19. Mechanical properties of Municipal Solid Waste by SDMT

    Energy Technology Data Exchange (ETDEWEB)

    Castelli, Francesco, E-mail: francesco.castelli@unikore.it [Geotechnical Engineering, Faculty of Engineering and Architecture, Kore University of Enna, 94100 Enna (Italy); Maugeri, Michele [Geotechnical Engineering, Department of Civil and Environmental Engineering, University of Catania, 95125 Catania (Italy)

    2014-02-15

    Highlights: • The adoption of the SDMT for the measurements of MSW properties is proposed. • A comparison between SDMT results and laboratory tests was carried out. • A good reliability has been found in deriving waste properties by SDMT. • Results seems to be promising for the friction angle and Young’s modulus evaluation. - Abstract: In the paper the results of a geotechnical investigation carried on Municipal Solid Waste (MSW) materials retrieved from the “Cozzo Vuturo” landfill in the Enna area (Sicily, Italy) are reported and analyzed. Mechanical properties were determined both by in situ and laboratory large-scale one dimensional compression tests. While among in situ tests, Dilatomer Marchetti Tests (DMT) is used widely in measuring soil properties, the adoption of the DMT for the measurements of MSW properties has not often been documented in literature. To validate its applicability for the estimation of MSW properties, a comparison between the seismic dilatometer (SDMT) results and the waste properties evaluated by laboratory tests was carried out. Parameters for “fresh” and “degraded waste” have been evaluated. These preliminary results seems to be promising as concerns the assessment of the friction angle of waste and the evaluation of the S-wave in terms of shear wave velocity. Further studies are certainly required to obtain more representative values of the elastic parameters according to the SDMT measurements.

  20. Correlations Between Mechanical Properties of Steel Fiber Reinforced Concrete

    Directory of Open Access Journals (Sweden)

    Carrillo Julián

    2013-06-01

    Full Text Available Tension strength and post-cracking deformation capacities that exhibits steel fiber reinforced concrete (SFRC stimulate its use in elements governed by shear deformations. Aimed at developing design aids that promote the use of SFRC as web shear reinforcement of concrete walls for low-rise economic housing (LEH, an experimental study for describing the mechanical properties of SFRC was carried out. The experimental program included testing of 128 cylinder- and beam-type specimens. According to requirements specified by ACI-318, to thickness of walls used in LEH, and to results of previous studies, three Dramix fibers with length-diameter ratios of 55, 64 and 80 were selected. Fiber dosage was expressed in terms of the minimum fiber dosage specified by ACI-318 for replacing the minimum area of conventional shear reinforcement in beams (60 kg/m3. Therefore, five dosages were used: 0, 40, 45, 60 and 75 kg/m3. Mechanical properties of SFRC under compressive, tensile and flexural stresses were evaluated in this study. Based on trends of experimental results, numerical correlations for estimating both basic mechanical properties and properties that describe flexural performance of SFRC are proposed.

  1. Structure-mechanics property relationship of waste derived biochars.

    Science.gov (United States)

    Das, Oisik; Sarmah, Ajit K; Bhattacharyya, Debes

    2015-12-15

    The widespread applications of biochar in agriculture and environmental remediation made the scientific community ignore its mechanical properties. Hence, to examine the scope of biochar's structural applications, its mechanical properties have been investigated in this paper through nanoindentation technique. Seven waste derived biochars, made under different pyrolysis conditions and from diverse feedstocks, were studied via nanoindentation, infrared spectroscopy, X-ray crystallography, thermogravimetry, and electron microscopy. Following this, an attempt was made to correlate the biochars' hardness/modulus with reaction conditions and their chemical properties. The pine wood biochar made at 900°C and 60min residence time was found to have the highest hardness and elastic modulus of 4.29 and 25.01GPa, respectively. It was shown that a combination of higher heat treatment (≥500°C) temperature and longer residence time (~60min) increases the values of hardness and modulus. It was further realized that pyrolysis temperature was a more dominant factor than residence time in determining the final mechanical properties of biochar particles. The degree of aromaticity and crystallinity of the biochar were also correlated with higher values of hardness and modulus.

  2. Mechanical properties of several iron-nickel meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Mulford, Roberta N [Los Alamos National Laboratory; El - Dasher, Bassem [LLNL

    2011-01-06

    Iron-nickel meteorites exhibit a unique lamellar microstructure, consisting of small regions with steep-iron-nickel composition gradients. The microstructure arises as a result of slow cooling in a planetary core or other large mass. The microstructure is further influenced by variable concentrations of other elements such as phosphorous which may have influenced cooling and phase separation. Mechanical properties of these composite structures have been investigated using Vickers and spherical indentation, x-ray fluorescence, and EBSD. Direct observation of mechanical properties in these highly structured materials provides a valuable supplement to bulk measurements, which frequently exhibit large variation in dynamic properties, even within a single sample. Previous studies of the mechanical properties of a typical iron-nickel meteorite, a Diablo Canyon specimen, indicated that the strength of the composite was higher by almost an order of magnitude than values obtained from laboratory-prepared specimens. This was ascribed to the extreme work-hardening evident in the EBSD measurements. Additional specimens from the Canyon Diablo fall (type IAB, coarse octahedrite) and several fine octahedrite meteorites, from the Muonionalusta meteorite (IVA) and Gibeon fall (IVA), have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon reentry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure.

  3. Unique microstructure and excellent mechanical properties of ADI

    Directory of Open Access Journals (Sweden)

    Jincheng Liu

    2006-11-01

    Full Text Available Amongst the cast iron family, ADI has a unique microstructure and an excellent, optimised combination of mechanical properties. The main microstructure of ADI is ausferrite, which is a mixture ofextremely fine acicular ferrite and stable, high carbon austenite. There are two types of austenite in ADI:(1 the coarser and more equiaxed blocks of austenite between non-parallel acicular structures, which exist mainly in the last solidified area, and (2 the thin films of ustenite between the individual ferriteplatelets in the acicular structure. It is this unique microstructure, which gives ADI its excellent static and dynamic properties, and good low temperature impact toughness. The effect of microstructure on the mechanical properties is explained in more detail by examining the microstructure at the atomic scale. Considering the nanometer grain sizes, the unique microstructure, the excellent mechanical properties,good castability, (which enables near net shape components to be produced economically and in large volumes, and the fact that it can be 100% recycled, it is not overemphasized to call ADI a high-tech,nanometer and “green” material. ADI still has the potential to be further improved and its production and the number of applications for ADI will continue to grow, driven by the resultant cost savings over alternative materials.

  4. Unique microstructure and excellent mechanical properties of ADI

    Institute of Scientific and Technical Information of China (English)

    Jincheng Liu

    2006-01-01

    Amongst the cast iron family, ADI has a unique microstructure and an excellent, optimised combination of mechanical properties. The main microstructure of ADI is ausferrite, which is a mixture of extremely fine acicular ferrite and stable, high carbon austenite. There are two types of austenite in ADI:(1) the coarser and more equiaxed blocks of austenite between non-parallel acicular structures, which exist mainly in the last solidified area, and (2) the thin films of austenite between the individual ferrite platelets in the acicular structure. It is this unique microstructure, which gives ADI its excellent static and dynamic properties, and good low temperature impact toughness. The effect of microstructure on the mechanical properties is explained in more detail by examining the microstructure at the atomic scale.Considering the nanometer grain sizes the unique microstructure, the excellent mechanical properties,good castability, (which enables near net shape components to be produced economically and in large volumes), and the fact that it can be 100% recycled, it is not overemphasized to call ADI a high-tech,nanometer and "green" material. ADI still has the potential to be further improved and its production and the number of applications for ADI will continue to grow, driven by the resultant cost savings over altemative materials.

  5. Monotone data visualization using rational trigonometric spline interpolation.

    Science.gov (United States)

    Ibraheem, Farheen; Hussain, Maria; Hussain, Malik Zawwar

    2014-01-01

    Rational cubic and bicubic trigonometric schemes are developed to conserve monotonicity of curve and surface data, respectively. The rational cubic function has four parameters in each subinterval, while the rational bicubic partially blended function has eight parameters in each rectangular patch. The monotonicity of curve and surface data is retained by developing constraints on some of these parameters in description of rational cubic and bicubic trigonometric functions. The remaining parameters are kept free to modify the shape of curve and surface if required. The developed algorithm is verified mathematically and demonstrated graphically.

  6. Monotone Data Visualization Using Rational Trigonometric Spline Interpolation

    Directory of Open Access Journals (Sweden)

    Farheen Ibraheem

    2014-01-01

    Full Text Available Rational cubic and bicubic trigonometric schemes are developed to conserve monotonicity of curve and surface data, respectively. The rational cubic function has four parameters in each subinterval, while the rational bicubic partially blended function has eight parameters in each rectangular patch. The monotonicity of curve and surface data is retained by developing constraints on some of these parameters in description of rational cubic and bicubic trigonometric functions. The remaining parameters are kept free to modify the shape of curve and surface if required. The developed algorithm is verified mathematically and demonstrated graphically.

  7. Ultimate generalization to monotonicity for uniform convergence of trigonometric series

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Chaundy and Jolliffe proved that if {a n } is a non-increasing (monotonic) real sequence with lim n →∞ a n = 0, then a necessary and sufficient condition for the uniform convergence of the series ∑∞ n=1 a n sin nx is lim n →∞ na n = 0. We generalize (or weaken) the monotonic condition on the coefficient sequence {a n } in this classical result to the so-called mean value bounded variation condition and prove that the generalized condition cannot be weakened further. We also establish an analogue to the generalized Chaundy-Jolliffe theorem in the complex space.

  8. Mechanical properties of fibroblasts depend on level of cancer transformation.

    Science.gov (United States)

    Efremov, Yu M; Lomakina, M E; Bagrov, D V; Makhnovskiy, P I; Alexandrova, A Y; Kirpichnikov, M P; Shaitan, K V

    2014-05-01

    Recently, it was revealed that tumor cells are significantly softer than normal cells. Although this phenomenon is well known, it is connected with many questions which are still unanswered. Among these questions are the molecular mechanisms which cause the change in stiffness and the correlation between cell mechanical properties and their metastatic potential. We studied mechanical properties of cells with different levels of cancer transformation. Transformed cells in three systems with different transformation types (monooncogenic N-RAS, viral and cells of tumor origin) were characterized according to their morphology, actin cytoskeleton and focal adhesion organization. Transformation led to reduction of cell spreading and thus decreasing the cell area, disorganization of actin cytoskeleton, lack of actin stress fibers and decline in the number and size of focal adhesions. These alterations manifested in a varying degree depending on type of transformation. Force spectroscopy by atomic force microscopy with spherical probes was carried out to measure the Young's modulus of cells. In all cases the Young's moduli were fitted well by log-normal distribution. All the transformed cell lines were found to be 40-80% softer than the corresponding normal ones. For the cell system with a low level of transformation the difference in stiffness was less pronounced than for the two other systems. This suggests that cell mechanical properties change upon transformation, and acquisition of invasive capabilities is accompanied by significant softening.

  9. Mechanical and tribological properties of ion beam-processed surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kodali, Padma [Univ. of Maryland, College Park, MD (United States)

    1998-01-01

    The intent of this work was to broaden the applications of well-established surface modification techniques and to elucidate the various wear mechanisms that occur in sliding contact of ion-beam processed surfaces. The investigation included characterization and evaluation of coatings and modified surfaces synthesized by three surface engineering methods; namely, beam-line ion implantation, plasma-source ion implantation, and DC magnetron sputtering. Correlation among measured properties such as surface hardness, fracture toughness, and wear behavior was also examined. This dissertation focused on the following areas of research: (1) investigating the mechanical and tribological properties of mixed implantation of carbon and nitrogen into single crystal silicon by beam-line implantation; (2) characterizing the mechanical and tribological properties of diamond-like carbon (DLC) coatings processed by plasma source ion implantation; and (3) developing and evaluating metastable boron-carbon-nitrogen (BCN) compound coatings for mechanical and tribological properties. The surface hardness of a mixed carbon-nitrogen implant sample improved significantly compared to the unimplanted sample. However, the enhancement in the wear factor of this sample was found to be less significant than carbon-implanted samples. The presence of nitrogen might be responsible for the degraded wear behavior since nitrogen-implantation alone resulted in no improvement in the wear factor. DLC coatings have low friction, low wear factor, and high hardness. The fracture toughness of DLC coatings has been estimated for the first time. The wear mechanism in DLC coatings investigated with a ruby slider under a contact stress of 1 GPa was determined to be plastic deformation. The preliminary data on metastable BCN compound coatings indicated high friction, low wear factor, and high hardness.

  10. Exterior difference systems and invariance properties of discrete mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Xie Zheng; Xie Duanqiang; Li Hongbo [Center of Mathematical Sciences, Zhejiang University, Zhejiang 310027 (China); Key Laboratory of Mathematics Mechanization, Chinese Academy of Sciences, Beijing 100080 (China)], E-mail: lenozhengxie@yahoo.com.cn

    2008-06-27

    Invariance properties describe the fundamental physical laws in discrete mechanics. Can those properties be described in a geometric way? We investigate an exterior difference system called the discrete Euler-Lagrange system, whose solution has one-to-one correspondence with solutions of discrete Euler-Lagrange equations, and use it to define the first integrals. The preservation of the discrete symplectic form along the discrete Hamilton phase flows and the discrete Noether's theorem is also described in the language of difference forms.

  11. Structural and Mechanical Properties of Fluorinated SWCNTs: a DFT Study

    Directory of Open Access Journals (Sweden)

    I.K. Petrushenko

    2015-03-01

    Full Text Available This paper presents a study on structural and mechanical properties of a series of fluorinated armchair single-walled carbon nanotubes (SWCNTs by using density functional theory. At the PBE / SVP level, the data obtained compare well with experimental and theoretical studies. The results show that fluorination, in general, distort SWNCTs framework, but there exists the difference between ‘axial’ and ‘circumferential’ functionalization. It turns out that elastic properties diminish with increasing concentration of adsorbents, however, the fluorinated SWCNTs remain strong enough to be suitable for reinforcement of composites.

  12. The Structure, Functions, and Mechanical Properties of Keratin

    Science.gov (United States)

    McKittrick, J.; Chen, P.-Y.; Bodde, S. G.; Yang, W.; Novitskaya, E. E.; Meyers, M. A.

    2012-04-01

    Keratin is one of the most important structural proteins in nature and is widely found in the integument in vertebrates. It is classified into two types: α-helices and β-pleated sheets. Keratinized materials can be considered as fiber-reinforced composites consisting of crystalline intermediate filaments embedded in an amorphous protein matrix. They have a wide variety of morphologies and properties depending on different functions. Here, we review selected keratin-based materials, such as skin, hair, wool, quill, horn, hoof, feather, and beak, focusing on the structure-mechanical property-function relationships and finally give some insights on bioinspired composite design based on keratinized materials.

  13. The mechanical and tribological properties of UHMWPE loaded ALN after mechanical activation for joint replacements.

    Science.gov (United States)

    Gong, Kemeng; Qu, Shuxin; Liu, Yumei; Wang, Jing; Zhang, Yongchao; Jiang, Chongxi; Shen, Ru

    2016-08-01

    Ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN) has tremendous potential as an orthopeadic biomaterial for joint replacements. However, poor mechanical and tribological properties of UHMWPE-ALN are still obstacle for further application. The purpose of this study was to investigate the effect and mechanism of mechanical activation on mechanical and tribological properties of 1wt% ALN-loaded UHMWPE (UHMWPE-ALN-ma). In this study, tensile test, small punch test and reciprocating sliding wear test were applied to characterize the mechanical and tribological properties of UHMWPE-ALN-ma. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) were employed to characterize UHMWPE-ALN-ma. Tensile test and small punch test showed that Young׳s modulus, tensile strength and work-to-failure (WTF) of UHMWPE-ALN-ma increased significantly compared to those of UHMWPE-ALN. The friction coefficients and wear factors of UHMWPE-ALN-ma both decreased significantly compared to those of UHMWPE-ALN. Mechanical activation obviously reduced type 1 (void) and type 2 (the disconnected and dislocated machining marks) fusion defects of UHMWPE-ALN-ma, which were revealed by SEM images of freeze fracture surfaces after etching and lateral surfaces of specimens after extension to fracture, respectively. It was attributed to peeled-off layers and chain scission of molecular chains of UHMWPE particles after mechanical activation, which were revealed by SEM images and FTIR spectra of UHMWPE-ALN-ma and UHMWPE-ALN, respectively. Moreover, EDS spectra revealed the more homogeneous distribution of ALN in UHMWPE-ALN-ma compared to that of UHMWPE-ALN. The present results showed that mechanical activation was a potential strategy to improve mechanical and tribological properties of UHMWPE-ALN-ma as an orthopeadic biomaterial for joint replacements.

  14. Remanence Properties and Magnetization Reversal Mechanism of Fe Nanowire Arrays

    Institute of Scientific and Technical Information of China (English)

    WANG Jian-Bo; LIU Qing-Fang; XUE De-Sheng; LI Fa-Shen

    2004-01-01

    @@ Remanence properties and magnetization reversal mechanism of Fe nanowire arrays with diameters 16 nm and130nm are studied. Isothermal remanent magnetization curves show that the contribution of irreversible magnetization decreases when the diameter changes from 16nm to 130nm. The remanence coercivities of these nanowires obtained in dc-demagnetization curve are about 2400 Oe and 800 Oe, respectively. The magnetization reversal mechanism is different in these two samples. For the nanowire array with diameter 16nm, both the nucleation and the pinning have effects on magnetization reversal mechanism, and the pinning field (about 2500Oe) is larger than the nucleation field (about 2200 Oe). However, for the nanowire array with diameter 130nm,the magnetization reversal mechanism is dominated by the pinning effect of domain walls.

  15. Structural and mechanical properties of mandibular condylar bone.

    Science.gov (United States)

    van Eijden, T M G J; van der Helm, P N; van Ruijven, L J; Mulder, L

    2006-01-01

    The trabecular bone of the mandibular condyle is structurally anisotropic and heterogeneous. We hypothesized that its apparent elastic moduli are also anisotropic and heterogeneous, and depend on trabecular density and orientation. Eleven condyles were scanned with a micro-CT system. Volumes of interest were selected for the construction of finite element models. We simulated compressive and shear tests to determine the principal mechanical directions and the apparent elastic moduli. Compressive moduli were relatively large in directions acting in the sagittal plane, and small in the mediolateral direction. The degree of mechanical anisotropy ranged from 4.7 to 10.8. Shear moduli were largest in the sagittal plane and smallest in the transverse plane. The magnitudes of the moduli varied with the condylar region and were proportional to the bone volume fraction. Furthermore, principal mechanical direction correlated significantly with principal structural direction. It was concluded that variation in trabecular structure coincides with variation in apparent mechanical properties.

  16. Bifurcation property and persistence of configurations for parallel mechanisms

    Institute of Scientific and Technical Information of China (English)

    王玉新; 王仪明; 刘学深

    2003-01-01

    The configuration of parallel mechanisms at the singularity position is uncertain. How to control the mechanism through the singularity position with a given configuration is one of the key problems of the robot controlling. In this paper the bifurcation property and persistence of configurations at the singularity position is investigated for 3-DOF parallel mechanisms. The dimension of the bifurcation equations is reduced by Liapunov-Schmidt reduction method. According to the strong equivalence condition, the normal form which is consistent with the bifurcation condition of the original equation is selected. Through universal unfolding of the bifurcation equation, the influences of the disturbance factors, such as the influence of length of the input component on the configuration persistence at the bifurcation position, are analyzed. Using this method we can obtain the bifurcation curve in which the configuration will be held when the mechanism passes through the singularity position. Therefore, the configuration is under control in this way.

  17. Evaluating mechanical properties and degradation of YTZP dental implants

    Energy Technology Data Exchange (ETDEWEB)

    Sevilla, Pablo, E-mail: pablo.sevilla@upc.edu [Biomaterials and Biomechanics Division, Department of Materials Science and Metallurgy, Technical University of Catalonia (Spain); Sandino, Clara; Arciniegas, Milena [Biomaterials and Biomechanics Division, Department of Materials Science and Metallurgy, Technical University of Catalonia (Spain); Martinez-Gomis, Jordi; Peraire, Maria [Department of Prosthodontics, Faculty of Odontology, University of Barcelona (Spain); Gil, Francisco Javier [Biomaterials and Biomechanics Division, Department of Materials Science and Metallurgy, Technical University of Catalonia (Spain)

    2010-01-01

    Lately new biomedical grade yttria stabilized zirconia (YTZP) dental implants have appeared in the implantology market. This material has better aesthetical properties than conventional titanium used for implants but long term behaviour of these new implants is not yet well known. The aim of this paper is to quantify the mechanical response of YTZP dental implants previously degraded under different time conditions and compare the toughness and fatigue strength with titanium implants. Mechanical response has been studied by means of mechanical testing following the ISO 14801 for Standards for dental implants and by finite element analysis. Accelerated hydrothermal degradation has been achieved by means of water vapour and studied by X-ray diffraction and nanoindentation tests. The results show that the degradation suffered by YTZP dental implants will not have a significant effect on the mechanical behaviour. Otherwise the fracture toughness of YTZP ceramics is still insufficient in certain implantation conditions.

  18. Monotonic and Cyclic Bond Behavior of Deformed CFRP Bars in High Strength Concrete

    Directory of Open Access Journals (Sweden)

    T. Tibet Akbas

    2016-05-01

    Full Text Available Composite reinforcing bars (rebars that are used in concrete members with high performance (strength and durability properties could have beneficial effects on the behavior of these members. This is especially vital when a building is constructed in an aggressive environment, for instance a corrosive environment. Although tension capacity/weight (or volume ratios in composite rebars (carbon fiber reinforced polymer (CFRP, glass fiber reinforced polymer (GFRP, etc. are very high when compared to steel rebars, major weaknesses in concrete members reinforced with these composite rebars may be the potential consequences of relatively poor bonding capacity. This may even be more crucial when the member is subjected to cyclic loading. Although monotonic bond tests are available in the literature, only limited experimental studies exist on bond characteristics under cyclic loading conditions. In order to fill this gap and propose preliminary design recommendations, 10 specimens of 10-mm-diameter ribbed CFRP rebars embedded in specially designed high strength concrete (f’c = 70 MPa blocks were subjected to monotonic and cyclic pullout tests. The experimental results showed that cyclically loaded CFRP rebars had less bond strength than those companion specimens loaded monotonically.

  19. Nanoclay reinforced thermoplastic toughened epoxy hybrid syntactic foam: Surface morphology, mechanical and thermo mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Asif, A. [Propellants and Special Chemicals Group, Propellants Polymers Chemicals and Materials Entity, Vikram Sarabhai Space Centre, Trivandrum 695022 (India); Rao, V. Lakshmana, E-mail: rao_vl@yahoo.co.in [Propellants and Special Chemicals Group, Propellants Polymers Chemicals and Materials Entity, Vikram Sarabhai Space Centre, Trivandrum 695022 (India); Ninan, K.N. [Propellants and Special Chemicals Group, Propellants Polymers Chemicals and Materials Entity, Vikram Sarabhai Space Centre, Trivandrum 695022 (India)

    2010-09-15

    Epoxy hybrid syntactic foams were prepared with diglycidyl ether of bisphenol A (DGEBA) epoxy resin, diamino diphenyl sulfone (DDS), hydroxyl terminated polyether ether ketone having pendant methyl group (PEEKMOH), microballoon and nanoclay. The density of the foam was maintained between 0.6 and 0.72 g/cc for all compositions. Fracture toughness, tensile, flexural and compressive properties of the foam were evaluated with respect to clay and PEEKMOH concentrations. Morphology by X-ray diffraction revealed that the clay particles within the epoxy resin were intercalated for all the compositions of the syntactic foam. Fracture toughness and mechanical properties of the syntactic foam were significantly improved by the addition of nanoclay. A further enhancement in fracture toughness and mechanical properties was observed by the addition of PEEKMOH. The hybrid epoxy syntactic foam thus prepared exhibited 58%, 77% and 38% improvement in compressive strength, percentage elongation and fracture toughness, respectively, compared to the neat epoxy syntactic foam. The specific mechanical properties were found to be higher for the epoxy hybrid syntactic foam containing 3 wt% nanoclay and 3 wt% of PEEKMOH combination. The storage and loss modulus of the syntactic foam were also increased by the addition of nanoclay and PEEKMOH. A marginal improvement in T{sub g} was observed with clay incorporated syntactic foam. SEM analysis revealed that increased microcracking, crack path deflection, matrix deformation, plastic deformation, rupture of microballoons and debonded microspheres influencing on fracture toughness and mechanical properties of epoxy hybrid syntactic foam.

  20. Mechanical properties of a collagen fibril under simulated degradation.

    Science.gov (United States)

    Malaspina, David C; Szleifer, Igal; Dhaher, Yasin

    2017-11-01

    Collagen fibrils are a very important component in most of the connective tissue in humans. An important process associated with several physiological and pathological states is the degradation of collagen. Collagen degradation is usually mediated by enzymatic and non-enzymatic processes. In this work we use molecular dynamics simulations to study the influence of simulated degradation on the mechanical properties of the collagen fibril. We applied tensile stress to the collagen fiber at different stages of degradation. We compared the difference in the fibril mechanical priorities due the removal of enzymatic crosslink, surface degradation and volumetric degradation. As anticipated, our results indicated that, regardless of the degradation scenario, fibril mechanical properties is reduced. The type of degradation mechanism (crosslink, surface or volumetric) expressed differential effect on the change in the fibril stiffness. Our simulation results showed dramatic change in the fibril stiffness with a small amount of degradation. This suggests that the hierarchical structure of the fibril is a key component for the toughness and is very sensitive to changes in the organization of the fibril. The overall results are intended to provide a theoretical framework for the understanding the mechanical behavior of collagen fibrils under degradation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Mechanical properties and thermal behaviour of LLDPE/MWNTs nanocomposites

    Directory of Open Access Journals (Sweden)

    Tai Jin-hua

    2012-12-01

    Full Text Available Multi-walled carbon nanotubes (MWNTs were incorporated into a linear low-density polyethylene (LLDPE matrix through using screw extrusion and injection technique. The effect of different weight percent loadings of MWNTs on the morphology, mechanical, and thermal of LLDPE/MWNTs nanocomposite had been investigated. It was found that, at low concentration of MWNTs, it could uniformly disperse into a linear low-density polyethylene matrix and provide LLDPE/MWNTs nanocomposites much improved mechanical properties. Thermal analysis showed that a clear improvement of thermal stability for LLDPE/MWNTs nanocomposites increased with increasing MWNTs content.

  2. On the Non-Monotonic Variation of the Opposition Surge Morphology with Albedo Exhibited by Satellites' Surface

    Science.gov (United States)

    Deau, E. A.; Spilker, L. J.; Flandes, A.

    2011-01-01

    We used well know phase functions of satellites and rings around the giant planets of our Solar System to study the morphology of the opposition effect (at phase angles alpha morphological model to retrieve the morphological parameters of the surge (A and HWHM). These parameters are found to have a non-monotonic variation with the single scattering albedo, similar to that observed in asteroids, which is unexplained so far. The non-monotonic variation is discussed in the framework of the coherent backscattering and shadow hiding mechanisms.

  3. Enhancing Microstructure and Mechanical Properties of AZ31-MWCNT Nanocomposites through Mechanical Alloying

    Directory of Open Access Journals (Sweden)

    J. Jayakumar

    2013-01-01

    Full Text Available Multiwall carbon nanotubes (MWCNTs reinforced Mg alloy AZ31 nanocomposites were fabricated by mechanical alloying and powder metallurgy technique. The reinforcement material MWCNTs were blended in three weight fractions (0.33%, 0.66%, and 1% with the matrix material AZ31 (Al-3%, zinc-1% rest Mg and blended through mechanical alloying using a high energy planetary ball mill. Specimens of monolithic AZ31 and AZ31-MWCNT composites were fabricated through powder metallurgy technique. The microstructure, density, hardness, porosity, ductility, and tensile properties of monolithic AZ31 and AZ31-MWCNT nano composites were characterized and compared. The characterization reveals significant reduction in CNT (carbon nanoTube agglomeration and enhancement in microstructure and mechanical properties due to mechanical alloying through ball milling.

  4. Response of mechanical properties of glasses to their chemical, thermal and mechanical histories

    DEFF Research Database (Denmark)

    Yue, Yuanzheng

    , surface, thermal history or excess entropy of the final glass state. Here I review recent progresses in understanding of the responses of mechanical properties of oxide glasses to the compositional variation, thermal history and mechanical deformation. The tensile strength, elastic modulus and hardness...... of glass fibers are dependent on the thermal history (measured as fictive temperature), tension, chemical composition and redox state. However, the fictive temperature affects the hardness of bulk glass in a complicated manner, i.e., the effect does not exhibit a clear regularity in the range...... and micro-cracks occurring during indentation of a glass is discussed briefly. Finally I describe the future perspectives and challenges in understanding responses of mechanical properties of oxide glasses to compositional variation, thermal history and mechanical deformation....

  5. A Review of the Mechanical Properties of Concrete Containing Biofillers

    Science.gov (United States)

    Ezdiani Mohamad, Mazizah; Mahmood, Ali A.; Min, Alicia Yik Yee; Khalid, Nur Hafizah A.

    2016-11-01

    Sustainable construction is a rapidly increasing research area. Investigators of all backgrounds are using industrial and agro wastes to replace Portland cement in concrete to reduce greenhouse emissions and the corresponding decline in general health. Many types of wastes have been used as cement replacements in concrete including: fly ash, slag and rice husk ash in addition to others. This study investigates the possibility of producing a sustainable approach to construction through the partial replacement of concrete using biofillers. This will be achieved by studying the physical and mechanical properties of two widely available biological wastes in Malaysia; eggshell and palm oil fuel ash (POFA). The mechanical properties tests that were studied and compared are the compression, tensile and flexural tests.

  6. Mechanical and Microstructural Properties of PTFE/Al/W System

    Science.gov (United States)

    Cai, Jing; Jiang, Fengchun; Vecchio, Kenneth S.; Meyers, Marc A.; Nesterenko, Vitali F.

    2007-12-01

    Mechanical and microstructural properties of high density PTFE/Al/W composites consisting of PTFE matrix, aluminum and tungsten particles were investigated. Three types of samples having different porosities and particle sizes of W with an identical weight ratio between PTFE, Al and W were fabricated by Cold Isostatic Pressing. The quasi-static and Hopkinson Bar compression tests were employed to investigate the mechanical properties of these materials. The results demonstrated that the porous PTFE/Al/W composite samples containing fine W particles have higher quasi-static and dynamic fracture stresses than higher density PTFE/Al/W samples containing coarse W particles. ESEM micrographs revealed that deformation occurred mainly in the PTFE matrix while metal particles remain undeformed. We observed nano-fibers of PTFE caused by high strain rate deformation.

  7. Effect of Natural Fillers on Mechanical Properties of GFRP Composites

    Directory of Open Access Journals (Sweden)

    Vikas Dhawan

    2013-01-01

    Full Text Available Fiber reinforced plastics (FRPs have replaced conventional engineering materials in many areas, especially in the field of automobiles and household applications. With the increasing demand, various modifications are being incorporated in the conventional FRPs for specific applications in order to reduce costs and achieve the quality standards. The present research endeavor is an attempt to study the effect of natural fillers on the mechanical characteristics of FRPs. Rice husk, wheat husk, and coconut coir have been used as natural fillers in glass fiber reinforced plastics (GFRPs. In order to study the effect of matrix on the properties of GFRPs, polyester and epoxy resins have been used. It has been found that natural fillers provide better results in polyester-based composites. Amongst the natural fillers, in general, the composites with coconut coir have better mechanical properties as compared to the other fillers in glass/epoxy composites.

  8. Mechanical properties of hot rolled 2519 aluminum alloy plate

    Institute of Scientific and Technical Information of China (English)

    彭大暑; 陈险峰; 林启权; 张辉

    2003-01-01

    The effects of differences of temper on mechanical properties of T6, T7 and T8 plates of aluminum alloy 2519 were studied. The stress corrosion cracking(SCC) sensitivity was evaluated with parameters such as Kσ and Kδ.Tensile tests were divided into two groups: one was performed on tensile specimens without pre-corrosion, the other was performed on tensile specimens which were pre-corroded in 3.5%NaCl+1%H2O2 solution at 25 ℃.The results show that SCC resistance of alloy 2519 ranks in the order of T8>T7>T6 and the mechanical properties rank in the order of T6>T8>T7. SEM fractographs of the failed specimen show that the SCC sensitivity can be determined by the distribution of the second phase particles and size and the shape of grains in the alloy.

  9. Microstructure characteristics and mechanical properties of rheocasting 7075 aluminum alloy

    Directory of Open Access Journals (Sweden)

    Yang Bin

    2013-09-01

    Full Text Available The microstructure characteristics and mechanical properties of 7075 aluminum alloy produced by a new rheoforming technique, under as-cast and optimized heat treatment conditions, were investigated. The present rheoforming combined the innovatively developed rheocasting process, named as ICSPC (inverted cone-shaped pouring channel process, and the existing HPDC (high pressure die casting process. The experimental results show that the ICSPC can be used to prepare high quality semi-solid slurry for the subsequent die casting. Compared with conventional HPDC process, the ICSPC process can improve the microstructures and mechanical properties of the cast tensile samples. An optimized heat treatment results in significant improvement in ultimate tensile strength. However, the ductility of the samples, both under as-cast and optimized heat treatment conditions, are relatively poor.

  10. Dynamic Mechanical Properties of Bio-Polymer Graphite Thin Films

    Science.gov (United States)

    Saddam Kamarudin, M.; Rus, Anika Zafiah M.; Munirah Abdullah, Nur; Abdullah, M. F. L.

    2017-08-01

    Waste cooking oil is used as the main substances in producing graphite biopolymer thin films. Biopolymer is produce from the reaction of bio-monomer and cross linker with the ratio of 2:1 and addition of graphite with an increment of 2% through a slip casting method. The morphological surface properties of the samples are observed by using Scanning Electron Microscope (SEM). It is shown that the graphite particle is well mixed and homogenously dispersed in biopolymer matrix. Meanwhile, the mechanical response of materials by monitoring the change in the material properties in terms of frequency and temperature of the samples were determined using Dynamic Mechanical Analysis (DMA). The calculated cross-linked density of biopolymer composites revealed the increment of graphite particle loading at 8% gives highest results with 260.012 x 103 M/m3.

  11. Mechanical Properties of Plant Cell Walls Probed by Relaxation Spectra

    DEFF Research Database (Denmark)

    Hansen, Steen Laugesen; Ray, Peter Martin; Karlsson, Anders Ola

    2011-01-01

    Transformants and mutants with altered cell wall composition are expected to display a biomechanical phenotype due to the structural role of the cell wall. It is often quite difficult, however, to distinguish the mechanical behavior of a mutant's or transformant's cell walls from that of the wild...... type. This may be due to the plant’s ability to compensate for the wall modification or because the biophysical method that is often employed, determination of simple elastic modulus and breakstrength, lacks the resolving power necessary for detecting subtle mechanical phenotypes. Here, we apply...... a method, determination of relaxation spectra, which probes, and can separate, the viscoelastic properties of different cell wall components (i.e. those properties that depend on the elastic behavior of load-bearing wall polymers combined with viscous interactions between them). A computer program, Bayes...

  12. Short-term Mechanical Properties of Glass Ionomer Cement

    Institute of Scientific and Technical Information of China (English)

    TANG Sanbao; XU Dongxuan

    2009-01-01

    The setting reaction of glass ionomer cement was studied by analyzing and comparing the short-tem mechanical properties of set cement stored in silicone oil,air and distilled water respectively at different temperatures.For the set cement stored at 37℃,the strength of the sample in the air reached the maximum value after 24 h,then decreased to about 210 MPa and kept steady.The strength of the sample in water increased continuously and slowly,however,the increasing rate of sample stored in silicone oil was higher than that in the water.At 20℃,the increasing rate of compressive strength for sample in air was higher than those in silicone oil and water.The diffusion speed and maintenance of water has significant effects on the mechanical properties of glass ionomer cements.

  13. Mechanical Properties of Plant Cell Walls Probed by Relaxation Spectra

    DEFF Research Database (Denmark)

    Hansen, Steen Laugesen; Ray, Peter Martin; Karlsson, Anders Ola

    2011-01-01

    Transformants and mutants with altered cell wall composition are expected to display a biomechanical phenotype due to the structural role of the cell wall. It is often quite difficult, however, to distinguish the mechanical behavior of a mutant's or transformant's cell walls from that of the wild...... type. This may be due to the plant’s ability to compensate for the wall modification or because the biophysical method that is often employed, determination of simple elastic modulus and breakstrength, lacks the resolving power necessary for detecting subtle mechanical phenotypes. Here, we apply...... a method, determination of relaxation spectra, which probes, and can separate, the viscoelastic properties of different cell wall components (i.e. those properties that depend on the elastic behavior of load-bearing wall polymers combined with viscous interactions between them). A computer program, Bayes...

  14. Mechanical properties of homogeneous nanofiber composites fabricated by electrospinning

    Science.gov (United States)

    Watanabe, Kentaro; Hotta, Atsushi

    2013-03-01

    A new composite that possesses uniformly dispersed polymeric nanofibers in different polymeric matrix was introduced by using electrospinning. Recently, nanofibers have been actively investigated for fillers for polymeric nano-composites to enhance the mechanical properties of the composites or to get highly functionalize polymer materials. Polyvinyl alcohol (PVA) nanofibers were selected as polymeric fillers and polydimethylsiloxane (PDMS) was used for polymeric matrix. Internally well-dispersed composites were fabricated by this new method, whereas rather anisotropic composites were also made by the traditional sandwich method. The morphology of the composites was analyzed by field emission scanning electron microscopy (FE-SEM). It was found that, in the new internally well-dispersed composites, PVA nanofibers existed from the both surfaces of the polymer matrix, uniformly dispersed in the composite. Isotropic mechanical properties were observed for internally well-dispersed composites, whereas relatively anisotropic characteristics could be observed for the traditionally-made composites.

  15. On the mechanical properties of selenite glass nanocomposites

    Science.gov (United States)

    Bar, Arun Kr.; Kundu, Ranadip; Roy, Debasish; Bhattacharya, Sanjib

    2016-05-01

    In this paper the room temperature micro-hardness of selenite glass-nanocomposites has been measured using a Vickers and Knoop micro hardness tester where the applied load varies from 0.01N to 0.98 N. A significant indentation size effect was observed for each sample at relatively low indentation test loads. The classical Meyer's law and the proportional specimen resistance model were used to analyze the micro-hardness behavior. It was found that the selenite glass-nanocomposite becomes harder with increasing CuI composition and the work hardening coefficient and mechanical properties like Young modulus, E, were also calculated. Our results open the way for the preparation, application and investigation of significant mechanical properties of new type of glass-nanocomposites.

  16. Mechanical properties of polymeric composites with carbon dioxide particles

    Science.gov (United States)

    Moskalyuk, O. A.; Samsonov, A. M.; Semenova, I. V.; Smirnova, V. E.; Yudin, V. E.

    2017-02-01

    Nanocomposites consisting of a polymethylmethacrylate or polystyrene matrix with embedded silicon dioxide nanoparticles surface-modified by silazanes have been prepared by melting technology. The influence of particles on viscoelastic properties of the nanocomposites has been studied using dynamic mechanical analysis. It has been revealed that the addition of 20 wt % of SiO2 raises the flexural modulus of the nanocomposites by 30%.

  17. Microstructure–mechanical property correlation of cryo rolled Zircaloy-4

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Apu, E-mail: asarkar5@ncsu.edu; Murty, Korukonda L.

    2015-01-15

    The evolution of microstructure and the mechanical properties of cryo-rolled Zircaloy-4 were both investigated to understand the origin of the alloy’s strength processed at a cryogenic temperature. The correlation of dislocation density, grain size and yield stress of the rolled product indicated that an increase in dislocation density due to the suppression of dynamic recovery is the primary source of strengthening.

  18. Simulative calculation of bromo-polystyrene mechanical properties

    CERN Document Server

    Wang Chao; Tang Yong Jian

    2002-01-01

    The non-crystal model of polystyrene and bromo-polystyrene was established with the help of simulative software in the computer. DREIDING was chosen as force field and its parameters is modified according to the published data. Based on the calculation results and other published data the mechanism properties of polystyrene and bromo-polystyrene, such as bulk module, Yong's module and Poisson's ratios, were discussed

  19. Nondestructive measurement of esophageal biaxial mechanical properties utilizing sonometry

    Science.gov (United States)

    Aho, Johnathon M.; Qiang, Bo; Wigle, Dennis A.; Tschumperlin, Daniel J.; Urban, Matthew W.

    2016-07-01

    Malignant esophageal pathology typically requires resection of the esophagus and reconstruction to restore foregut continuity. Reconstruction options are limited and morbid. The esophagus represents a useful target for tissue engineering strategies based on relative simplicity in comparison to other organs. The ideal tissue engineered conduit would have sufficient and ideally matched mechanical tolerances to native esophageal tissue. Current methods for mechanical testing of esophageal tissues both in vivo and ex vivo are typically destructive, alter tissue conformation, ignore anisotropy, or are not able to be performed in fluid media. The aim of this study was to investigate biomechanical properties of swine esophageal tissues through nondestructive testing utilizing sonometry ex vivo. This method allows for biomechanical determination of tissue properties, particularly longitudinal and circumferential moduli and strain energy functions. The relative contribution of mucosal-submucosal layers and muscular layers are compared to composite esophagi. Swine thoracic esophageal tissues (n  =  15) were tested by pressure loading using a continuous pressure pump system to generate stress. Preconditioning of tissue was performed by pressure loading with the pump system and pre-straining the tissue to in vivo length before data was recorded. Sonometry using piezocrystals was utilized to determine longitudinal and circumferential strain on five composite esophagi. Similarly, five mucosa-submucosal and five muscular layers from thoracic esophagi were tested independently. This work on esophageal tissues is consistent with reported uniaxial and biaxial mechanical testing and reported results using strain energy theory and also provides high resolution displacements, preserves native architectural structure and allows assessment of biomechanical properties in fluid media. This method may be of use to characterize mechanical properties of tissue engineered esophageal

  20. Mechanical properties of D0 Run IIB silicon detector staves

    Energy Technology Data Exchange (ETDEWEB)

    Lanfranco, Giobatta; Fast, James; /Fermilab

    2001-06-01

    A proposed stave design for the D0 Run IIb silicon tracker outer layers featuring central cooling channels and a composite shell mechanical structure is evaluated for self-deflection and deflection due to external loads. This paper contains an introduction to the stave structure, a section devoted to composite lamina and laminate properties and finally a section discussing the beam deflections expected for assembled staves using these laminates.

  1. Microstructure characteristics and mechanical properties of rheocasting 7075 aluminum alloy

    OpenAIRE

    Yang Bin; Mao Weimin; Song Xiaojun

    2013-01-01

    The microstructure characteristics and mechanical properties of 7075 aluminum alloy produced by a new rheoforming technique, under as-cast and optimized heat treatment conditions, were investigated. The present rheoforming combined the innovatively developed rheocasting process, named as ICSPC (inverted cone-shaped pouring channel) process, and the existing HPDC (high pressure die casting) process. The experimental results show that the ICSPC can be used to prepare high quality semi-solid slu...

  2. Characterization of Mechanical Properties of Porcelain Tile Using Ultrasonics

    OpenAIRE

    KURAMA, Semra; Eren, Elif

    2012-01-01

    Ultrasound affords a very useful and versatile non-destructive method, using a large application area, for evaluating the microstructure and mechanical properties of materials. In this study, porcelain tiles were sintered at different temperatures to change their porosity. Following this, the time of flight of both longitudinal and shear waves was measured through the tile. The time of flight of ultrasonic waves was measured using a contact ultrasonic transducer operating on a pulse-echo mode...

  3. ORMOSIL thin films: tuning mechanical properties via a nanochemistry approach.

    Science.gov (United States)

    Palmisano, Giovanni; Le Bourhis, Eric; Ciriminna, Rosaria; Tranchida, Davide; Pagliaro, Mario

    2006-12-19

    The mechanical properties (hardness and elastic modulus) of organically modified silicate thin films can be finely tuned by varying the degree of alkylation and thus the fraction of six- and four-membered siloxane rings in the organosilica matrix. This opens the way to large tunability of parameters that are of crucial practical importance for films that are finding increasing application in numerous fields ranging from microelectronics to chemical sensing.

  4. Structure and mechanical properties of austenitic steel after cold rolling

    Directory of Open Access Journals (Sweden)

    A. Kurc-Lisiecka

    2011-02-01

    Full Text Available Purpose: The aim of the paper is to determine the influence of the cold plastic deformation within the range 18-79% and heat treatment in a temperature range of 500 to 700°C on the microstructure and mechanical properties of austenitic stainless steel grade X5CrNi18-8.Design/methodology/approach: The investigations included observations of the microstructure on a light microscope, researches of mechanical properties in a static tensile test and hardness measurements made by Vickers’s method. The analysis of the phase composition was carried out on the basis of X-ray researches. Whereas, X-ray quantitative phase analysis was carried out by the Averbach Cohen method.Findings: Heat treatment of X5CrNi18-8 stainless steel in the range 500-700°C causes a significant decrease of the mechanical properties (Rm, Rp0.2 and increase of elongation (A. Hardness of investigated steel drops with decrease of cold working degree and increase of heat treatment temperature.Research limitations/implications: The analysis of the obtained results permits to state that the heat treatment causes an essential changes of the microstructure connected with fading of cold deformation. Heating of cold rolled austenitic stainless steels can cause a reverse transformation α’ → γ.Practical implications: Two-phase structure α’+γ of austenitic Cr-Ni steel in deformed state working at elevated temperature undergo a transformation. It significantly influences mechanical properties of steel. Austenite phase undergoes a recrystallization, while martensite α’ phase undergoes reverse transformation.Originality/value: The analytic dependence of the yield point of the investigated steel on the cold working degree in cold rolling process has been confirmed. Revealing this relation is of essential practical importance for the technology of sheetmetal forming of austenitic steel.

  5. The mechanical properties of density graded hemp/polyethylene composites

    Science.gov (United States)

    Dauvegis, Raphaël; Rodrigue, Denis

    2015-05-01

    In this work, the production and mechanical characterization of density graded biocomposites based on high density polyethylene and hemp fibres was performed. The effect of coupling agent addition (maleated polyethylene) and hemp content (0-30%) was studied to determine the effect of hemp distribution (graded content) inside the composite (uniform, linear, V and Λ). Tensile and flexural properties are reported to compare the structures, especially in terms of their stress-strain behaviors under tensile loading.

  6. Effect of Cr addition on the structural, magnetic and mechanical properties of magnetron sputtered Ni-Mn-In ferromagnetic shape memory alloy thin films

    Science.gov (United States)

    Akkera, Harish Sharma; Kaur, Davinder

    2016-12-01

    The effect of Cr substitution for In on the structural, martensitic phase transformation and mechanical properties of Ni-Mn-In ferromagnetic shape memory alloy (FSMA) thin films was systematically investigated. X-ray diffraction results revealed that the Ni-Mn-In-Cr thin films possessed purely austenitic cubic L21 structure at lower content of Cr, whereas higher Cr content, the Ni-Mn-In-Cr thin films exhibited martensitic structure at room temperature. The temperature-dependent magnetization ( M- T) and resistance ( R- T) results confirmed that the monotonous increase in martensitic transformation temperatures ( T M) with the addition of Cr content. Further, the room temperature nanoindentation studies revealed the mechanical properties such as hardness ( H), elastic modulus ( E), plasticity index ( H/ E) and resistance to plastic deformation ( H 3/ E 2) of all the samples. The addition of Cr content significantly enhanced the hardness (28.2 ± 2.4 GPa) and resistance to plastic deformation H 3/ E 2 (0.261) of Ni50.4Mn34.96In13.56Cr1.08 film as compared with pure Ni-Mn-In film. As a result, the appropriate addition of Cr significantly improved the mechanical properties with a decrease in grain size, which could be further attributed to the grain boundary strengthening mechanism. These findings indicate that the Cr-doped Ni-Mn-In FSMA thin films are potential candidates for microelectromechanical systems applications.

  7. Conductive magnetorheological elastomer: fatigue dependent impedance-mechanic coupling properties

    Science.gov (United States)

    Wang, Yu; Xuan, Shouhu; Ge, Lin; Wen, Qianqian; Gong, Xinglong

    2017-01-01

    This work investigated the relationship between the impedance properties and dynamic mechanical properties of magnetorheological elastomers (MREs) under fatigue loading. The storage modulus and the impedance properties of MREs were highly influenced by the pressure and magnetic field. Under the same experimental condition, the two characteristics exhibited similar fatigue dependent change trends. When pressure was smaller than 10 N, the capacitance of MRE could be divided into four sections with the increase of the cyclic numbers. The relative equivalent circuit model was established to fit the experimental results of the impedance spectra. Each parameter of circuit element reflected the change of fatigue loading, relative microstructure of MRE, MRE-electrode interface layer, respectively. Based on the above analysis, the real-time and nondestructive impedance method was demonstrated to be high potential on detecting the fatigue of the MRE device.

  8. Mechanical, elastic and thermodynamic properties of crystalline lithium silicides

    CERN Document Server

    Schwalbe, Sebastian; Trepte, Kai; Biedermann, Franziska; Mertens, Florian; Kortus, Jens

    2016-01-01

    We investigate crystalline thermodynamic stable lithium silicides phases (LixSiy) with density functional theory (DFT) and a force-field method based on modified embedded atoms (MEAM) and compare our results with experimental data. This work presents a fast and accurate framework to calculate thermodynamic properties of crystal structures with large unit cells with MEAM based on molecular dynamics (MD). Mechanical properties like the bulk modulus and the elastic constants are evaluated in addition to thermodynamic properties including the phonon density of states, the vibrational free energy and the isochoric/isobaric specific heat capacity for Li, Li12Si7, Li7Si3, Li13Si4, Li15Si4, Li21Si5, Li17Si4, Li22Si5 and Si. For a selected phase (Li13Si4) we study the effect of a temperature dependent phonon density of states and its effect on the isobaric heat capacity.

  9. Structure and mechanical properties of Octopus vulgaris suckers.

    Science.gov (United States)

    Tramacere, Francesca; Kovalev, Alexander; Kleinteich, Thomas; Gorb, Stanislav N; Mazzolai, Barbara

    2014-02-06

    In this study, we investigate the morphology and mechanical features of Octopus vulgaris suckers, which may serve as a model for the creation of a new generation of attachment devices. Octopus suckers attach to a wide range of substrates in wet conditions, including rough surfaces. This amazing feature is made possible by the sucker's tissues, which are pliable to the substrate profile. Previous studies have described a peculiar internal structure that plays a fundamental role in the attachment and detachment processes of the sucker. In this work, we present a mechanical characterization of the tissues involved in the attachment process, which was performed using microindentation tests. We evaluated the elasticity modulus and viscoelastic parameters of the natural tissues (E ∼ 10 kPa) and measured the mechanical properties of some artificial materials that have previously been used in soft robotics. Such a comparison of biological prototypes and artificial material that mimics octopus-sucker tissue is crucial for the design of innovative artificial suction cups for use in wet environments. We conclude that the properties of the common elastomers that are generally used in soft robotics are quite dissimilar to the properties of biological suckers.

  10. Mechanical Properties of Calcium Fluoride-Based Composite Materials

    Science.gov (United States)

    Kleczewska, Joanna; Pryliński, Mariusz; Podlewska, Magdalena; Sokołowski, Jerzy; Łapińska, Barbara

    2016-01-01

    Aim of the study was to evaluate mechanical properties of light-curing composite materials modified with the addition of calcium fluoride. The study used one experimental light-curing composite material (ECM) and one commercially available flowable light-curing composite material (FA) that were modified with 0.5–5.0 wt% anhydrous calcium fluoride. Morphology of the samples and uniformity of CaF2 distribution were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Mechanical properties were tested after 24-hour storage of specimens in dry or wet conditions. Stored dry ECM enriched with 0.5–1.0 wt% CaF2 showed higher tensile strength values, while water storage of all modified ECM specimens decreased their tensile strength. The highest Vickers hardness tested after dry storage was observed for 2.5 wt% CaF2 content in ECM. The addition of 2.0–5.0 wt% CaF2 to FA caused significant decrease in tensile strength after dry storage and overall tensile strength decrease of modified FA specimens after water storage. The content of 2.0 wt% CaF2 in FA resulted in the highest Vickers hardness tested after wet storage. Commercially available composite material (FA), unmodified with fluoride addition, demonstrated overall significantly higher mechanical properties. PMID:28004001

  11. Mechanical Properties of Calcium Fluoride-Based Composite Materials

    Directory of Open Access Journals (Sweden)

    Monika Łukomska-Szymańska

    2016-01-01

    Full Text Available Aim of the study was to evaluate mechanical properties of light-curing composite materials modified with the addition of calcium fluoride. The study used one experimental light-curing composite material (ECM and one commercially available flowable light-curing composite material (FA that were modified with 0.5–5.0 wt% anhydrous calcium fluoride. Morphology of the samples and uniformity of CaF2 distribution were analyzed using Scanning Electron Microscopy (SEM and Energy Dispersive Spectroscopy (EDS. Mechanical properties were tested after 24-hour storage of specimens in dry or wet conditions. Stored dry ECM enriched with 0.5–1.0 wt% CaF2 showed higher tensile strength values, while water storage of all modified ECM specimens decreased their tensile strength. The highest Vickers hardness tested after dry storage was observed for 2.5 wt% CaF2 content in ECM. The addition of 2.0–5.0 wt% CaF2 to FA caused significant decrease in tensile strength after dry storage and overall tensile strength decrease of modified FA specimens after water storage. The content of 2.0 wt% CaF2 in FA resulted in the highest Vickers hardness tested after wet storage. Commercially available composite material (FA, unmodified with fluoride addition, demonstrated overall significantly higher mechanical properties.

  12. [Mechanical properties of wiredrawn Ag-Pd-Cu alloys].

    Science.gov (United States)

    Hasegawa, T; Miyagawa, Y; Nakamura, K

    1989-01-01

    Nine experimental Ag-Pd-Cu ternary alloys, containing 20-30 wt% Pd and 10-20 wt% Cu, were cast into rods 4.5 mm in diameter using an original vacuum/argon-pressure oxide-free casting technique. Test samples 2.0 mm in diameter were made from the rods by wire-drawing. After softening and hardening heat treatments, mechanical properties (modulus of elasticity, elastic limit, proof stress, tensile strength, elongation, and Vickers hardness) of the samples were measured to analyze the effects of composition and fifteen sets of correlations between the mechanical properties on the condition that few internal casting defects existed. After softening heat treatment, values of hardness and strength increased with increasing Cu and Pd contents, while they increased approximately with increasing Pd content after hardening heat treatment. After softening and hardening heat treatments, tensile strength ranged from 44.4 to 60.7 and from 68.1 to 89.1 kgf/mm2, respectively. Values of elongation were more than 10% even after hardening heat treatment. Fourteen out of fifteen correlation coefficients (r) were statistically significant (p less than 0.01). One of the regression lines derived was as follows. Tensile strength (kgf/mm2) = 9.1 +/- 0.305 Hv (r = 0.990) Moreover, the mechanical properties observed in this investigation were compared with those of ordinarily cast samples with the same compositions.

  13. Mechanical Properties of a Primary Cilium Measured by Resonant Oscillation

    Science.gov (United States)

    Resnick, Andrew

    Primary cilia are ubiquitous mammalian cellular substructures implicated in an ever-increasing number of regulatory pathways. The well-established `ciliary hypothesis' states that physical bending of the cilium (for example, due to fluid flow) initiates signaling cascades, yet the mechanical properties of the cilium remain incompletely measured, resulting in confusion regarding the biological significance of flow-induced ciliary mechanotransduction. In this work we measure the mechanical properties of a primary cilium by using an optical trap to induce resonant oscillation of the structure. Our data indicate 1), the primary cilium is not a simple cantilevered beam, 2), the base of the cilium may be modeled as a nonlinear rotatory spring, the linear spring constant `k' of the cilium base calculated to be (4.6 +/- 0.62)*10-12 N/rad and nonlinear spring constant ` α' to be (-1 +/- 0.34) *10-10 N/rad2 , and 3) the ciliary base may be an essential regulator of mechanotransduction signalling. Our method is also particularly suited to measure mechanical properties of nodal cilia, stereocilia, and motile cilia, anatomically similar structures with very different physiological functions.

  14. Relationships between supercontraction and mechanical properties of spider silk

    Science.gov (United States)

    Liu, Yi; Shao, Zhengzhong; Vollrath, Fritz

    2005-12-01

    Typical spider dragline silk tends to outperform other natural fibres and most man-made filaments. However, even small changes in spinning conditions can have large effects on the mechanical properties of a silk fibre as well as on its water uptake. Absorbed water leads to significant shrinkage in an unrestrained dragline fibre and reversibly converts the material into a rubber. This process is known as supercontraction and may be a functional adaptation for the silk's role in the spider's web. Supercontraction is thought to be controlled by specific motifs in the silk proteins and to be induced by the entropy-driven recoiling of molecular chains. In analogy, in man-made fibres thermal shrinkage induces changes in mechanical properties attributable to the entropy-driven disorientation of `unfrozen' molecular chains (as in polyethylene terephthalate) or the `broken' intermolecular hydrogen bonds (as in nylons). Here we show for Nephila major-ampullate silk how in a biological fibre the spinning conditions affect the interplay between shrinkage and mechanical characteristics. This interaction reveals design principles linking the exceptional properties of silk to its molecular orientation.

  15. Composition, structure and mechanical properties of several natural cellular materials

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The stem piths of sunflower, kaoliang and corn are natural cellular materials. In this paper, the contents of the compositions of these piths are determined and their cell shapes and structures are examined through scanning electron microscope (SEM) and optical microscope. Further research is conducted in the effects of the compositions and structures of the piths on the mechanical properties after testing the partial mechanical properties. The results show that the total cellulose, hemicelluloses and lignin content of each sample approaches 75% of the dry mass of its primary cell walls. With the fall of R value, a parameter relative to the contents of the main compositions, the flexibilities of the cellular piths descend while their stresses and rigidities increase. The basic cell shape making up the sunflower pith is approximately a tetrakaidehedron. The stem piths of kaoliang and corn are made up of cells close to hexangular prisms and a few tubular ones which can observably reinforce their mechanical properties in the axial directions.

  16. Bulk Mechanical Properties of Single Walled Carbon Nanotube Electrodes

    Science.gov (United States)

    Giarra, Matthew; Landi, Brian; Cress, Cory; Raffaelle, Ryne

    2007-03-01

    The unique properties of single walled carbon nanotubes (SWNTs) make them especially well suited for use as electrodes in power devices such as lithium ion batteries, hydrogen fuel cells, solar cells, and supercapacitors. The performances of such devices are expected to be influenced, at least in part, by the mechanical properties of the SWNTs used in composites or in stand alone ``papers.'' Therefore, the elastic moduli and ultimate tensile strengths of SWNT papers were measured as functions of temperature, SWNT purity, SWNT length, and SWNT bundling. The SWNTs used to produce the papers were synthesized in an alexandrite laser vaporization reactor at 1100^oC and purified using conventional acid-reflux conditions. Characterization of the SWNTs was performed using SEM, BET, TGA, and optical and Raman spectroscopy. The purified material was filtered and dried to yield papers of bundled SWNTs which were analyzed using dynamic mechanical analysis (DMA). It was observed that the mechanical properties of acid-refluxed SWNT papers were significantly improved by controlled thermal oxidation and strain-hardening. Elastic moduli of SWNT papers were measured between 3 and 6 GPa. Ultimate (breaking) tensile stresses were measured between 45 and 90 MPa at 1-3% strain. These results and their implications in regard to potential applications in power devices will be discussed.

  17. MONOTONE ITERATION FOR ELLIPTIC PDEs WITH DISCONTINUOUS NONLINEAR TERMS

    Institute of Scientific and Technical Information of China (English)

    Zou Qingsong

    2005-01-01

    In this paper, we use monotone iterative techniques to show the existence of maximal or minimal solutions of some elliptic PDEs with nonlinear discontinuous terms. As the numerical analysis of this PDEs is concerned, we prove the convergence of discrete extremal solutions.

  18. Modeling non-monotone risk aversion using SAHARA utility functions

    NARCIS (Netherlands)

    A. Chen; A. Pelsser; M. Vellekoop

    2011-01-01

    We develop a new class of utility functions, SAHARA utility, with the distinguishing feature that it allows absolute risk aversion to be non-monotone and implements the assumption that agents may become less risk averse for very low values of wealth. The class contains the well-known exponential and

  19. On Uniqueness of Conjugacy of Continuous and Piecewise Monotone Functions

    Directory of Open Access Journals (Sweden)

    Ciepliński Krzysztof

    2009-01-01

    Full Text Available We investigate the existence and uniqueness of solutions of the functional equation , , where are closed intervals, and , are some continuous piecewise monotone functions. A fixed point principle plays a crucial role in the proof of our main result.

  20. L^p solutions of reflected BSDEs under monotonicity condition

    CERN Document Server

    Rozkosz, Andrzej

    2012-01-01

    We prove existence and uniqueness of L^p solutions of reflected backward stochastic differential equations with p-integrable data and generators satisfying the monotonicity condition. We also show that the solution may be approximated by the penalization method. Our results are new even in the classical case p=2.

  1. A monotonic method for solving nonlinear optimal control problems

    CERN Document Server

    Salomon, Julien

    2009-01-01

    Initially introduced in the framework of quantum control, the so-called monotonic algorithms have shown excellent numerical results when dealing with various bilinear optimal control problems. This paper aims at presenting a unified formulation of such procedures and the intrinsic assumptions they require. In this framework, we prove the feasibility of the general algorithm. Finally, we explain how these assumptions can be relaxed.

  2. On Some Conjectures on the Monotonicity of Some Arithmetical Sequences

    Science.gov (United States)

    2012-01-01

    THE MONOTONICITY OF SOME ARITHMETICAL SEQUENCES ∗ Florian Luca † Centro de Ciencias Matemáticas, Universidad Nacional Autonoma de México, C.P. 58089...visit of P. S. to the Centro de Ciencias Matemáticas de la UNAM in Morelia in August 2012. During the preparation of this paper, F. L. was supported in

  3. Interval Routing and Minor-Monotone Graph Parameters

    NARCIS (Netherlands)

    Bakker, E.M.; Bodlaender, H.L.; Tan, R.B.; Leeuwen, J. van

    2006-01-01

    We survey a number of minor-monotone graph parameters and their relationship to the complexity of routing on graphs. In particular we compare the interval routing parameters κslir(G) and κsir(G) with Colin de Verdi`ere’s graph invariant μ(G) and its variants λ(G) and κ(G). We show that for all the k

  4. Multivariate Regression with Monotone Missing Observation of the Dependent Variables

    NARCIS (Netherlands)

    Raats, V.M.; van der Genugten, B.B.; Moors, J.J.A.

    2002-01-01

    Multivariate regression is discussed, where the observations of the dependent variables are (monotone) missing completely at random; the explanatory variables are assumed to be completely observed.We discuss OLS-, GLS- and a certain form of E(stimated) GLS-estimation.It turns out that

  5. Minimum Cost Spanning Tree Games and Population Monotonic Allocation Schemes

    NARCIS (Netherlands)

    Norde, H.W.; Moretti, S.; Tijs, S.H.

    2001-01-01

    In this paper we present the Subtraction Algorithm that computes for every classical minimum cost spanning tree game a population monotonic allocation scheme.As a basis for this algorithm serves a decomposition theorem that shows that every minimum cost spanning tree game can be written as nonnegati

  6. Size monotonicity and stability of the core in hedonic games

    OpenAIRE

    Dimitrov, Dinko; Sung, Shao Chin

    2011-01-01

    We show that the core of each strongly size monotonic hedonic game is not empty and is externally stable. This is in sharp contrast to other sufficient conditions for core non-emptiness which do not even guarantee the existence of a stable set in such games.

  7. Monotone missing data and repeated controls of fallible authors

    NARCIS (Netherlands)

    Raats, V.M.

    2004-01-01

    Chapters 2 and 3 focus on repeated audit controls with categorical variables. Chapter 4 and 5 introduce and analyse a very general multivariate regression model for (monotone) missing data. In the final Chapter 6 the previous chapters are combined into a more realistic model for repeated audit contr

  8. A POTENTIAL REDUCTION ALGORITHM FOR MONOTONE VARIATIONAL INEQUALITY PROBLEMS

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A potential reduction algorithm is proposed for the solution of monotone variational inequality problems. At each step of the algorithm, a system of linear equations is solved to get the search direction and the Armijo's rule is used to determine the stepsize.It is proved that the algorithm is globally convergent. Computational results are reported.

  9. Relaxing monotonicity in the identification of local average treatment effects

    DEFF Research Database (Denmark)

    Huber, Martin; Mellace, Giovanni

    In heterogeneous treatment effect models with endogeneity, the identification of the local average treatment effect (LATE) typically relies on an instrument that satisfies two conditions: (i) joint independence of the potential post-instrument variables and the instrument and (ii) monotonicity...

  10. Incorporating "Unconscious Reanalysis" into an Incremental, Monotonic Parser

    CERN Document Server

    Sturt, P

    1995-01-01

    This paper describes an implementation based on a recent model in the psycholinguistic literature. We define a parsing operation which allows the reanalysis of dependencies within an incremental and monotonic processing architecture, and discuss search strategies for its application in a head-initial language (English) and a head-final language (Japanese).

  11. Interval Routing and Minor-Monotone Graph Parameters

    NARCIS (Netherlands)

    Bakker, E.M.; Bodlaender, H.L.; Tan, R.B.; Leeuwen, J. van

    2006-01-01

    We survey a number of minor-monotone graph parameters and their relationship to the complexity of routing on graphs. In particular we compare the interval routing parameters κslir(G) and κsir(G) with Colin de Verdi`ere’s graph invariant μ(G) and its variants λ(G) and κ(G). We show that for all the

  12. Reasoning Biases, Non-Monotonic Logics, and Belief Revision

    NARCIS (Netherlands)

    Dutilh Novaes, Catarina; Veluwenkamp, Herman

    2017-01-01

    A range of formal models of human reasoning have been proposed in a number of fields such as philosophy, logic, artificial intelligence, computer science, psychology, cognitive science etc.: various logics (epistemic logics; non-monotonic logics), probabilistic systems (most notably, but not exclusi

  13. Epoxy Resin Based Composites, Mechanical and Tribological Properties: A Review

    Directory of Open Access Journals (Sweden)

    S.A. Bello

    2015-12-01

    Full Text Available High fuel consumption by automobile and aerospace vehicles built from legacy alloys has been a great challenge to global design and material engineers. This has called for researches into material development for the production of lighter materials of the same or even superior mechanical properties to the existing materials in this area of applications. This forms a part of efforts to achieve the global vision 2025 i.e to reduce the fuel consumption by automobile and aerospace vehicles by at least 75 %. Many researchers have identified advanced composites as suitable materials in this regard. Among the common matrices used for the development of advanced composites, epoxy resin has attained a dominance among its counterparts because of its excellent properties including chemical, thermal and electrical resistance properties, mechanical properties and dimensional stability. This review is a reflection of the extensive study on the currently ongoing research aimed at development of epoxy resin hybrid nanocomposites for engineering applications. In this paper, brief explanation has been given to different terms related to the research work and also, some previous works (in accordance with materials within authors’ reach in the area of the ongoing research have been reported.

  14. Measurement of the Mechanical Properties of Intact Collagen Fibrils

    Science.gov (United States)

    Mercedes, H.; Heim, A.; Matthews, W. G.; Koob, T.

    2006-03-01

    Motivated by the genetic disorder Ehlers-Danlos syndrome (EDS), in which proper collagen synthesis is interrupted, we are investigating the structural and mechanical properties of collagen fibrils. The fibrous glycoprotein collagen is the most abundant protein found in the human body and plays a key role in the extracellular matrix of the connective tissue, the properties of which are altered in EDS. We have selected as our model system the collagen fibrils of the sea cucumber dermis, a naturally mutable tissue. This system allows us to work with native fibrils which have their proteoglycan complement intact, something that is not possible with reconstituted mammalian collagen fibrils. Using atomic force microscopy, we measure, as a function of the concentration of divalent cations, the fibril diameter, its response to force loading, and the changes in its rigidity. Through these experiments, we will shed light on the mechanisms which control the properties of the sea cucumber dermis and hope to help explain the altered connective tissue extracellular matrix properties associated with EDS.

  15. Length-dependent mechanical properties of gold nanowires.

    Science.gov (United States)

    Han, Jing; Fang, Liang; Sun, Jiapeng; Han, Ying; Sun, Kun

    2012-12-01

    The well-known "size effect" is not only related to the diameter but also to the length of the small volume materials. It is unfortunate that the length effect on the mechanical behavior of nanowires is rarely explored in contrast to the intensive studies of the diameter effect. The present paper pays attention to the length-dependent mechanical properties of 〈111〉-oriented single crystal gold nanowires employing the large-scale molecular dynamics simulation. It is discovered that the ultrashort Au nanowires exhibit a new deformation and failure regime-high elongation and high strength. The constrained dislocation nucleation and transient dislocation slipping are observed as the dominant mechanism for such unique combination of high strength and high elongation. A mechanical model based on image force theory is developed to provide an insight to dislocation nucleation and capture the yield strength and nucleation site of first partial dislocation indicated by simulation results. Increasing the length of the nanowires, the ductile-to-brittle transition is confirmed. And the new explanation is suggested in the predict model of this transition. Inspired by the superior properties, a new approach to strengthen and toughen nanowires-hard/soft/hard sandwich structured nanowires is suggested. A preliminary evidence from the molecular dynamics simulation corroborates the present opinion.

  16. Mechanical Properties of Nonwoven Reinforced Thermoplastic Polyurethane Composites.

    Science.gov (United States)

    Tausif, Muhammad; Pliakas, Achilles; O'Haire, Tom; Goswami, Parikshit; Russell, Stephen J

    2017-06-05

    Reinforcement of flexible fibre reinforced plastic (FRP) composites with standard textile fibres is a potential low cost solution to less critical loading applications. The mechanical behaviour of FRPs based on mechanically bonded nonwoven preforms composed of either low or high modulus fibres in a thermoplastic polyurethane (TPU) matrix were compared following compression moulding. Nonwoven preform fibre compositions were selected from lyocell, polyethylene terephthalate (PET), polyamide (PA) as well as para-aramid fibres (polyphenylene terephthalamide; PPTA). Reinforcement with standard fibres manifold improved the tensile modulus and strength of the reinforced composites and the relationship between fibre, fabric and composite's mechanical properties was studied. The linear density of fibres and the punch density, a key process variable used to consolidate the nonwoven preform, were varied to study the influence on resulting FRP mechanical properties. In summary, increasing the strength and degree of consolidation of nonwoven preforms did not translate to an increase in the strength of resulting fibre reinforced TPU-composites. The TPU composite strength was mainly dependent upon constituent fibre stress-strain behaviour and fibre segment orientation distribution.

  17. Mechanical properties and formation mechanisms of a wire of single gold atoms

    DEFF Research Database (Denmark)

    Rubio-Bollinger, G.; Bahn, Sune Rastad; Agrait, N.

    2001-01-01

    A scanning tunneling microscope supplemented with a force sensor is used to study the mechanical properties of a novel metallic nanostructure: a freely suspended chain of single gold atoms. We find that the bond strength of the nanowire is about twice that of a bulk metallic bond. We perform ab i...

  18. Mechanical properties testing and results for thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Cruse, T.A.; Johnsen, B.P.; Nagy, A.

    1995-10-01

    The paper reports on several years of mechanical testing of thermal barrier coatings. The test results were generated to support the development of durability models for the coatings in heat engine applications. The test data that are reviewed include modulus, static strength, and fatigue strength data. The test methods and results are discussed, along with the significant difficulties inherent in mechanical testing of thermal barrier coating materials. The materials include 7 percent wt. and 8 percent wt. yttria, partially stabilized zirconia as well as a cermet material. Both low pressure plasma spray and electron-beam physical vapor deposited coatings were tested. The data indicate the basic trends in the mechanical properties of the coatings over a wide range of isothermal conditions. Some of the trends are correlated with material density.

  19. Mechanical properties testing and results for thermal barrier coatings

    Science.gov (United States)

    Cruse, Thomas A.; Johnsen, B. P.; Nagy, Andrew

    1995-01-01

    The paper reports on several years of mechanical testing of thermal barrier coatings. The test results were generated to support the development of durability models for the coatings in heat engine applications. The test data that are reviewed include modulus, static strength, and fatigue strength data. The test methods and results are discussed, along with the significant difficulties inherent in mechanical testing of thermal barrier coating materials. The materials include 7 percent wt. and 8 percent wt. yttria, partially stabilized zirconia as well as a cermet material. Both low pressure plasma spray and electron-beam physical vapor deposited coatings were tested. The data indicate the basic trends in the mechanical properties of the coatings over a wide range of isothermal conditions. Some of the trends are correlated with material density.

  20. Mechanics of advanced materials analysis of properties and performance

    CERN Document Server

    Matveenko, Valery

    2015-01-01

    The last decades have seen a large extension of types of materials employed in various applications. In many cases these materials demonstrate mechanical properties and performance that vary significantly from those of their traditional counterparts. Such uniqueness is sought – or even specially manufactured – to meet increased requirements on modern components and structures related to their specific use. As a result, mechanical behaviors of these materials under different loading and environmental conditions are outside the boundaries of traditional mechanics of materials, presupposing development of new characterization techniques, theoretical descriptions and numerical tools. The book presents interesting examples of recent developments in this area. Among the studied materials are bulk metallic glasses, metamaterials, special composites, piezoelectric smart structures, nonwovens, etc.

  1. Characterisation of Dynamic Mechanical Properties of Resistance Welding Machines

    DEFF Research Database (Denmark)

    Wu, Pei; Zhang, Wenqi; Bay, Niels

    2005-01-01

    The dynamic mechanical properties of a resistance welding machine have significant influence on weld quality, which must be considered when simulating the welding process numerically. However, due to the complexity of the machine structure and the mutual coupling of components of the machine system...... characterizing the dynamic mechanical characteristics of resistance welding machines is suggested, and a test set-up is designed determining the basic, independent machine parameters required in the model. The model is verified by performing a series of mechanical tests as well as real projection welds......., it is very difficult to measure or calculate the basic, independent machine parameters required in a mathematical model of the machine dynamics, and no test method has so far been presented in literature, which can be applied directly in an industrial environment. In this paper, a mathematical model...

  2. Characterisation of Dynamic Mechanical Properties of Resistance Welding Machines

    DEFF Research Database (Denmark)

    Wu, Pei; Zhang, Wenqi; Bay, Niels

    2005-01-01

    The dynamic mechanical properties of a resistance welding machine have significant influence on weld quality, which must be considered when simulating the welding process numerically. However, due to the complexity of the machine structure and the mutual coupling of components of the machine system......, it is very difficult to measure or calculate the basic, independent machine parameters required in a mathematical model of the machine dynamics, and no test method has so far been presented in literature, which can be applied directly in an industrial environment. In this paper, a mathematical model...... characterizing the dynamic mechanical characteristics of resistance welding machines is suggested, and a test set-up is designed determining the basic, independent machine parameters required in the model. The model is verified by performing a series of mechanical tests as well as real projection welds....

  3. Spherical agglomerates of lactose with enhanced mechanical properties.

    Science.gov (United States)

    Lamešić, Dejan; Planinšek, Odon; Lavrič, Zoran; Ilić, Ilija

    2017-01-10

    The aim of this study was to prepare spherical agglomerates of lactose and to evaluate their physicochemical properties, flow properties, particle friability and compaction properties, and to compare them to commercially available types of lactose for direct compression (spray-dried, granulated and anhydrous β-lactose). Porous spherical agglomerates of α-lactose monohydrate with radially arranged prism-like primary particles were prepared exhibiting a high specific surface area. All types of lactose analysed had passable or better flow properties, except for anhydrous β-lactose, which had poor flowability. Particle friability was more pronounced in larger granulated lactose particles; however, particle structure was retained in all samples analysed. The mechanical properties of spherical agglomerates of lactose, in terms of compressibility, established with Walker analysis, and compactibility, established with a compactibility profile, were found to be superior to any commercially available types of lactose. Higher compactibility of spherical agglomerates of lactose is ascribed to significantly higher particle surface area due to a unique internal structure with higher susceptibility to fragmentation. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Mechanical and hydraulic properties of rocks related to induced seismicity

    Science.gov (United States)

    Witherspoon, P.A.; Gale, J.E.

    1977-01-01

    Witherspoon, P.A. and Gale, J.E., 1977. Mechanical and hydraulic properties of rocks related to induced seismicity. Eng. Geol., 11(1): 23-55. The mechanical and hydraulic properties of fractured rocks are considered with regard to the role they play in induced seismicity. In many cases, the mechanical properties of fractures determine the stability of a rock mass. The problems of sampling and testing these rock discontinuities and interpreting their non-linear behavior are reviewed. Stick slip has been proposed as the failure mechanism in earthquake events. Because of the complex interactions that are inherent in the mechanical behavior of fractured rocks, there seems to be no simple way to combine the deformation characteristics of several sets of fractures when there are significant perturbations of existing conditions. Thus, the more important fractures must be treated as individual components in the rock mass. In considering the hydraulic properties, it has been customary to treat a fracture as a parallel-plate conduit and a number of mathematical models of fracture systems have adopted this approach. Non-steady flow in fractured systems has usually been based on a two-porosity model, which assumes the primary (intergranular) porosity contributes only to storage and the secondary (fracture) porosity contributes only to the overall conductivity. Using such a model, it has been found that the time required to achieve quasi-steady state flow in a fractured reservoir is one or two orders of magnitude greater than it is in a homogeneous system. In essentially all of this work, the assumption has generally been made that the fractures are rigid. However, it is clear from a review of the mechanical and hydraulic properties that not only are fractures easily deformed but they constitute the main flow paths in many rock masses. This means that one must consider the interaction of mechanical and hydraulic effects. A considerable amount of laboratory and field data is now

  5. Non-monotonic wetting behavior of chitosan films induced by silver nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Praxedes, A.P.P.; Webler, G.D.; Souza, S.T. [Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió, AL (Brazil); Ribeiro, A.S. [Instituto de Química e Biotecnologia, Universidade Federal de Alagoas, 57072-970 Maceió, AL (Brazil); Fonseca, E.J.S. [Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió, AL (Brazil); Oliveira, I.N. de, E-mail: italo@fis.ufal.br [Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió, AL (Brazil)

    2016-05-01

    Highlights: • The addition of silver nanoparticles modifies the morphology of chitosan films. • Metallic nanoparticles can be used to control wetting properties of chitosan films. • The contact angle shows a non-monotonic dependence on the silver concentration. - Abstract: The present work is devoted to the study of structural and wetting properties of chitosan-based films containing silver nanoparticles. In particular, the effects of silver concentration on the morphology of chitosan films are characterized by different techniques, such as atomic force microscopy (AFM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). By means of dynamic contact angle measurements, we study the modification on surface properties of chitosan-based films due to the addition of silver nanoparticles. The results are analyzed in the light of molecular-kinetic theory which describes the wetting phenomena in terms of statistical dynamics for the displacement of liquid molecules in a solid substrate. Our results show that the wetting properties of chitosan-based films are high sensitive to the fraction of silver nanoparticles, with the equilibrium contact angle exhibiting a non-monotonic behavior.

  6. Estimation of mechanical properties of single wall carbon nanotubes using molecular mechanics approach

    Indian Academy of Sciences (India)

    P Subba Rao; Sunil Anandatheertha; G Narayana Naik; G Gopalakrishnan

    2015-06-01

    Molecular mechanics based finite element analysis is adopted in the current work to evaluate the mechanical properties of Zigzag, Armchair and Chiral Single wall Carbon Nanotubes (SWCNT) of different diameters and chiralities. Three different types of atomic bonds, that is Carbon–Carbon covalent bond and two types of Carbon–Carbon van der Waals bonds are considered in the carbon nanotube system. The stiffness values of these bonds are calculated using the molecular potentials, namely Morse potential function and Lennard-Jones interaction potential function respectively and these stiffness’s are assigned to spring elements in the finite element model of the CNT. The geometry of CNT is built using a macro that is developed for the finite element analysis software. The finite element model of the CNT is constructed, appropriate boundary conditions are applied and the behavior of mechanical properties of CNT is studied.

  7. Mechanical properties of lunar regolith and lunar soil simulant

    Science.gov (United States)

    Perkins, Steven W.

    1989-01-01

    Through the Surveyor 3 and 7, and Apollo 11-17 missions a knowledge of the mechanical properties of Lunar regolith were gained. These properties, including material cohesion, friction, in-situ density, grain-size distribution and shape, and porosity, were determined by indirect means of trenching, penetration, and vane shear testing. Several of these properties were shown to be significantly different from those of terrestrial soils, such as an interlocking cohesion and tensile strength formed in the absence of moisture and particle cementation. To characterize the strength and deformation properties of Lunar regolith experiments have been conducted on a lunar soil simulant at various initial densities, fabric arrangements, and composition. These experiments included conventional triaxial compression and extension, direct tension, and combined tension-shear. Experiments have been conducted at low levels of effective confining stress. External conditions such as membrane induced confining stresses, end platten friction and material self weight have been shown to have a dramatic effect on the strength properties at low levels of confining stress. The solution has been to treat these external conditions and the specimen as a full-fledged boundary value problem rather than the idealized elemental cube of mechanics. Centrifuge modeling allows for the study of Lunar soil-structure interaction problems. In recent years centrifuge modeling has become an important tool for modeling processes that are dominated by gravity and for verifying analysis procedures and studying deformation and failure modes. Centrifuge modeling is well established for terrestrial enginering and applies equally as well to Lunar engineering. A brief review of the experiments is presented in graphic and outline form.

  8. Experimental Investigation of the Influence of Joint Geometric Configurations on the Mechanical Properties of Intermittent Jointed Rock Models Under Cyclic Uniaxial Compression

    Science.gov (United States)

    Liu, Yi; Dai, Feng; Fan, Pengxian; Xu, Nuwen; Dong, Lu

    2017-06-01

    Intermittent joints in rock mass are quite sensitive to cyclic loading conditions. Understanding the fatigue mechanical properties of jointed rocks is beneficial for rational design and stability analysis of rock engineering projects. This study experimentally investigated the influences of joint geometry (i.e., dip angle, persistency, density and spacing) on the fatigue mechanism of synthetic jointed rock models. Our results revealed that the stress-strain curve of jointed rock under cyclic loadings is dominated by its curve under monotonic uniaxial loadings; the terminal strain in fatigue curve is equal to the post-peak strain corresponding to the maximum cyclic stress in the monotonic stress-strain curve. The four joint geometrical parameters studied significantly affect the fatigue properties of jointed rocks, including the irreversible strains, the fatigue deformation modulus, the energy evolution, the damage variable and the crack coalescence patterns. The higher the values of the geometrical parameters, the lower the elastic energy stores in this jointed rock, the higher the fatigue damage accumulates in the first few cycles, and the lower the fatigue life. The elastic energy has certain storage limitation, at which the fatigue failure occurs. Two basic micro-cracks, i.e., tensile wing crack and shear crack, are observed in cyclic loading and unloading tests, which are controlled principally by joint dip angle and persistency. In general, shear cracks only occur in the jointed rock with higher dip angle or higher persistency, and the jointed rock is characterized by lower fatigue strength, larger damage variable and lower fatigue life.

  9. A review of mechanical and electromechanical properties of piezoelectric nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Espinosa, Horacio D.; Bernal, Rodrigo A.; Minary-Jolandan, Majid [Department of Mechanical Engineering, Northwestern University, Evanston, IL (United States)

    2012-09-04

    Piezoelectric nanowires are promising building blocks in nanoelectronic, sensing, actuation and nanogenerator systems. In spite of great progress in synthesis methods, quantitative mechanical and electromechanical characterization of these nanostructures is still limited. In this article, the state-of-the art in experimental and computational studies of mechanical and electromechanical properties of piezoelectric nanowires is reviewed with an emphasis on size effects. The review covers existing characterization and analysis methods and summarizes data reported in the literature. It also provides an assessment of research needs and opportunities. Throughout the discussion, the importance of coupling experimental and computational studies is highlighted. This is crucial for obtaining unambiguous size effects of nanowire properties, which truly reflect the effect of scaling rather than a particular synthesis route. We show that such a combined approach is critical to establish synthesis-structure-property relations that will pave the way for optimal usage of piezoelectric nanowires. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Mechanical properties of the porcine bile duct wall

    Directory of Open Access Journals (Sweden)

    Andersen Helle

    2004-07-01

    Full Text Available Abstract Background and Aim The function of the common bile duct is to transport bile from the liver and the gall bladder to the duodenum. Since the bile duct is a distensible tube consisting mainly of connective tissue, it is important to obtain data on the passive mechanical wall properties. The aims of this study were to study morphometric and biomechanical wall properties during distension of the bile duct. Methods Ten normal porcine common bile ducts were examined in vitro. A computer-controlled volume ramp infusion system with concomitant pressure recordings was constructed. A video camera provided simultaneous measurement of outer dimensions of the common bile duct. Wall stresses and strains were computed. Results The common bile duct length increased by 25% from 24.4 ± 1.8 mm at zero pressure to 30.5 ± 2.0 mm at 5 kPa (p (βε - 1. The circumferential stress-strain curve was shifted to the left when compared to the longitudinal stress-strain curve, i.e. the linear constants (α values were different (p 0.5. Conclusion The porcine bile duct exhibited nonlinear anisotropic mechanical properties.

  11. Mechanical properties of thermoplastic composites reinforced with Entada Mannii fibre

    Directory of Open Access Journals (Sweden)

    Oluwayomi BALOGUN

    2017-06-01

    Full Text Available The mechanical properties and fracture mechanisms of thermoplastic composites reinforced with Entada mannii fibres was investigated. Polypropylene reinforced with 1, 3, 5, and 7 wt% KOH treated and untreated Entada mannii fibres were processed using a compression moulding machine. The tensile properties, impact strength, and flexural properties of the composites were evaluated while the tensile fracture surface morphology was examined using scanning electron microscopy. The results show that reinforcing polypropylene with Entada mannii fibres resulted in improvement of the tensile strength and elastic modulus. This improvement is remarkable for 5 wt% KOH treated Entada mannii fibre reinforced composites by 28 % increase as compared with the unreinforced polypropylene. The composites reinforced with Entada mannii fibres also had impact strength values of 70 % higher than the unreinforced polypropylene. However, the polypropylene reinforced with 5 and 7wt% KOH treated fibres exhibited significantly higher flexural strength and Young’s modulus by 53% and 52% increase as compared with the unreinforced polypropylene. The fracture surface of the polypropylene composites reinforced with untreated Entada mannii fibres were characterized by fibre debonding, fibre pull-out and matrix yielding while less voids and fibre pull-outs are observed in the composites reinforced with KOH treated Entada mannii fibres. v

  12. Measurement of Mechanical Properties of Cantilever Shaped Materials

    Directory of Open Access Journals (Sweden)

    Thomas Thundat

    2008-05-01

    Full Text Available Microcantilevers were first introduced as imaging probes in Atomic Force Microscopy (AFM due to their extremely high sensitivity in measuring surface forces. The versatility of these probes, however, allows the sensing and measurement of a host of mechanical properties of various materials. Sensor parameters such as resonance frequency, quality factor, amplitude of vibration and bending due to a differential stress can all be simultaneously determined for a cantilever. When measuring the mechanical properties of materials, identifying and discerning the most influential parameters responsible for the observed changes in the cantilever response are important. We will, therefore, discuss the effects of various force fields such as those induced by mass loading, residual stress, internal friction of the material, and other changes in the mechanical properties of the microcantilevers. Methods to measure variations in temperature, pressure, or molecular adsorption of water molecules are also discussed. Often these effects occur simultaneously, increasing the number of parameters that need to be concurrently measured to ensure the reliability of the sensors. We therefore systematically investigate the geometric and environmental effects on cantilever measurements including the chemical nature of the underlying interactions. To address the geometric effects we have considered cantilevers with a rectangular or circular cross section. The chemical nature is addressed by using cantilevers fabricated with metals and/or dielectrics. Selective chemical etching, swelling or changes in Young’s modulus of the surface were investigated by means of polymeric and inorganic coatings. Finally to address the effect of the environment in which the cantilever operates, the Knudsen number was determined to characterize the molecule-cantilever collisions. Also bimaterial cantilevers with high thermal sensitivity were used to discern the effect of temperature

  13. Investigation on mechanical properties of basalt composite fabrics (experiment study

    Directory of Open Access Journals (Sweden)

    Talebi Mazraehshahi H.

    2010-06-01

    Full Text Available To fully appreciate the role and application of composite materials to structures, correct understanding of mechanical behaviors required for selection of optimum material. Fabric reinforced composites are composed of a matrix that is reinforced with pliable fabric, glass fabric is most popular reinforcement for different application specially in aircraft structure, although other fabric material are also used. At this study new fabric material called basalt with epoxy resin introduced and mechanical behaviors of this material investigated from view point of testing. For this study two type of fabric with different thickness used. Comparison between this composite reinforcement with popular reinforcement as carbon, glass, kevlar performed. To determine mechanical properties of epoxy based basalt fabric following test procedure performed : 1. Tensile testing according to ASTM D3039 in 0° and 90° direction to find ultimate strength in tension and shear, modulus of elasticity, elangation and ultimate strain. 2. Compression testing according to EN 2850 ultimate compression strength and maximum deformation under compression loading. 3. Shear testing according to ASTM D3518-94 to find in plane shear response of polymer matrix composites materials. 4. Predict flexural properties of sandwich construction which manufactured from basalt facing with PVC foam core according to ASTM C393-94. Material strength properties must be based on enough tests of material to meet the test procedure specifications [1]. For this reason six specimens were manufactured for testing and the tests were performed on them using an INSTRON machine model 5582. In the study, the effect of percent of resin in basalt reinforced composite was investigated. Also the weights of the ballast based composites with different percent of resin were measured with conventional composites. As the weight is an important parameter in aerospace industry when the designer wants to replace one

  14. Bioprinting of hybrid tissue constructs with tailorable mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Schuurman, W; Khristov, V; Pot, M W; Dhert, W J A; Malda, J [Department of Orthopaedics, University Medical Center Utrecht (Netherlands); Van Weeren, P R, E-mail: j.malda@umcutrecht.nl [Faculty of Veterinary Sciences, Department of Equine Sciences, Utrecht University (Netherlands)

    2011-06-15

    Tissue/organ printing aims to recapitulate the intrinsic complexity of native tissues. For a number of tissues, in particular those of musculoskeletal origin, adequate mechanical characteristics are an important prerequisite for their initial handling and stability, as well as long-lasting functioning. Hence, organized implants, possessing mechanical characteristics similar to the native tissue, may result in improved clinical outcomes of regenerative approaches. Using a bioprinter, grafts were constructed by alternate deposition of thermoplastic fibers and (cell-laden) hydrogels. Constructs of different shapes and sizes were manufactured and mechanical properties, as well as cell viability, were assessed. This approach yields novel organized viable hybrid constructs, which possess favorable mechanical characteristics, within the same range as those of native tissues. Moreover, the approach allows the use of multiple hydrogels and can thus produce constructs containing multiple cell types or bioactive factors. Furthermore, since the hydrogel is supported by the thermoplastic material, a broader range of hydrogel types can be used compared to bioprinting of hydrogels alone. In conclusion, we present an innovative and versatile approach for bioprinting, yielding constructs of which the mechanical stiffness provided by thermoplastic polymers can potentially be tailored, and combined specific cell placement patterns of multiple cell types embedded in a wide range of hydrogels. (communication)

  15. Compressive and tensile mechanical properties of the porcine nasal septum.

    Science.gov (United States)

    Al Dayeh, Ayman A; Herring, Susan W

    2014-01-03

    The expanding nasal septal cartilage is believed to create a force that powers midfacial growth. In addition, the nasal septum is postulated to act as a mechanical strut that prevents the structural collapse of the face under masticatory loads. Both roles imply that the septum is subject to complex biomechanical loads during growth and mastication. The purpose of this study was to measure the mechanical properties of the nasal septum to determine (1) whether the cartilage is mechanically capable of playing an active role in midfacial growth and in maintaining facial structural integrity and (2) if regional variation in mechanical properties is present that could support any of the postulated loading regimens. Porcine septal samples were loaded along the horizontal or vertical axes in compression and tension, using different loading rates that approximate the in vivo situation. Samples were loaded in random order to predefined strain points (2-10%) and strain was held for 30 or 120 seconds while relaxation stress was measured. Subsequently, samples were loaded until failure. Stiffness, relaxation stress and ultimate stress and strain were recorded. Results showed that the septum was stiffer, stronger and displayed a greater drop in relaxation stress in compression compared to tension. Under compression, the septum displayed non-linear behavior with greater stiffness and stress relaxation under faster loading rates and higher strain levels. Under tension, stiffness was not affected by strain level. Although regional variation was present, it did not strongly support any of the suggested loading patterns. Overall, results suggest that the septum might be mechanically capable of playing an active role in midfacial growth as evidenced by increased compressive residual stress with decreased loading rates. However, the low stiffness of the septum compared to surrounding bone does not support a strut role. The relatively low stiffness combined with high stress relaxation

  16. Short Time Uniqueness Results for Solutions of Nonlocal and Non-monotone Geometric Equations

    CERN Document Server

    Barles, Guy; Mitake, Hiroyoshi

    2010-01-01

    We describe a method to show short time uniqueness results for viscosity solutions of general nonlocal and non-monotone second-order geometric equations arising in front propagation problems. Our method is based on some lower gradient bounds for the solution. These estimates are crucial to obtain regularity properties of the front, which allow to deal with nonlocal terms in the equations. Applications to short time uniqueness results for the initial value problems for dislocation type equations, asymptotic equations of a FitzHugh-Nagumo type system and equations depending on the Lebesgue measure of the fronts are presented.

  17. Positive and monotone solutions of an m-point boundary-value problem

    Directory of Open Access Journals (Sweden)

    Panos K. Palamides

    2002-02-01

    Full Text Available We study the second-order ordinary differential equation $$ y''(t=-f(t,y(t,y'(t,quad 0leq tleq 1, $$ subject to the multi-point boundary conditions $$ alpha y(0pm eta y'(0=0,quad y(1=sum_{i=1}^{m-2}alpha_iy(xi_i,. $$ We prove the existence of a positive solution (and monotone in some cases under superlinear and/or sublinear growth rate in $f$. Our approach is based on an analysis of the corresponding vector field on the $(y,y'$ face-plane and on Kneser's property for the solution's funnel.

  18. A weakly monotonic backward induction algorithm on finite bounded subsets of vector lattices

    Science.gov (United States)

    Dragut, A. B.

    2004-03-01

    We present a new efficient and robust backward induction algorithm, which is weakly monotonic, working on bounded subsets without holes of lattices. We prove all its properties, give examples of applications, and illustrate its behavior, comparing it with the natural extension of the unidimensional algorithm presented in Puterman (Markov Decision Processes: Discrete Stochastic Dynamic Programming, Wiley, New York, 1994), in the sense of Topkis (Frontiers of Economic Research Series, Princeton University Press, Princeton, NJ, 1998) and White (Recent Developments in Markov Decision Processes, Academic Press, New York, 1980, 261) and showing, also experimentally, that it is much more efficient.

  19. Microstructural and Mechanical Properties of Alkali Activated Colombian Raw Materials

    Directory of Open Access Journals (Sweden)

    Maria Criado

    2016-03-01

    Full Text Available Microstructural and mechanical properties of alkali activated binders based on blends of Colombian granulated blast furnace slag (GBFS and fly ash (FA were investigated. The synthesis of alkali activated binders was conducted at 85 °C for 24 h with different slag/fly ash ratios (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100. Mineralogical and microstructural characterization was carried out by means of X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR, Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX and Nuclear magnetic resonance (NMR. Mechanical properties were evaluated through the compressive strength, modulus of elasticity and Poisson’s ratio. The results show that two different reaction products were detected in the slag/fly ash mixtures, a calcium silicate hydrate with Al in its structure (C-A-S-H gel and a sodium aluminosilicate hydrate (N-A-S-H gel with higher number of polymerized species and low content in Ca. It was found that with the increase of the amount of added slag, the amount of C-A-S-H gel increased and the amount of N-A-S-H gel decreased. The matrix was more dense and compact with almost absence of pores. The predominance of slag affected positively the compressive strength, Young’s modulus and Poisson’s ratio, with 80% slag and 20% fly ash concrete being the best mechanical performance blend.

  20. Atomic vacancies significantly degrade the mechanical properties of phosphorene

    Science.gov (United States)

    Sha, Zhen-Dong; Pei, Qing-Xiang; Zhang, Ying-Yan; Zhang, Yong-Wei

    2016-08-01

    Due to low formation energies, it is very easy to create atomic defects in phosphorene during its fabrication process. How these atomic defects affect its mechanical behavior, however, remain unknown. Here, we report on a systematic study of the effect of atomic vacancies on the mechanical properties and failure behavior of phosphorene using molecular dynamics simulations. It is found that atomic vacancies induce local stress concentration and cause early bond-breaking, leading to a significant degradation of the mechanical properties of the material. More specifically, a 2% concentration of randomly distributed mono-vacancies is able to reduce the fracture strength by ∼40%. An increase in temperature from 10 to 400 K can further deteriorate the fracture strength by ∼60%. The fracture strength of defective phosphorene is also found to be affected by defect distribution. When the defects are patterned in a line, the reduction in fracture strength greatly depends on the tilt angle and the loading direction. Furthermore, we find that di-vacancies cause an even larger reduction in fracture strength than mono-vacancies when the loading is in an armchair direction. These findings provide important guidelines for the structural design of phosphorene in future applications.

  1. Study on Thermal and Mechanical Properties of EPDM Insulation

    Science.gov (United States)

    Zhang, Zhong-Shui; Xu, Jin-Sheng; Chen, Xiong; Jiang, Jing

    As the most common insulation material of solid rocket motors, thermal and mechanical properties of ethylene propylene diene monomer (EPDM) composite are inspected in the study. Referring to the results of thermogravimetric analysis (TGA), composition and morphology of EPDM composite in different thermal degradation degree are investigated by scanning electron microscope (SEM) to inspect the mechanism of thermal insulation. Mechanical properties of EPDM composite in the state of pyrolysis are investigated by uniaxial tensile tests. At the state of initial pyrolysis, composite belongs to the category of hyperelastic-viscoelastic material. The tendency of tensile strength increased and elongation decreased with increasing of heating temperature. Composite behaves as the linear rule at the state of late pyrolysis, which belongs to the category of bittle. The elasticity modulus of curves are almost the same while the heating temperature ranges from 200°C to 300°C, and then gradually go down. The tensile strength of pyrolytic material reach the highest at the heating temperature of 300°C, and the virgin material has the largest elongation.

  2. Dynamic viscoelastic properties of collagen gels with high mechanical strength.

    Science.gov (United States)

    Mori, Hideki; Shimizu, Kousuke; Hara, Masayuki

    2013-08-01

    We developed a new method for the preparation of mechanically strong collagen gels by combining successively basic gel formation, followed by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) cross-linking and lyophilization. Gels cross-linked three times with this method showed stronger mechanical properties (G': 3730±2060 Pa, G″: 288±35 Pa) than a conventional gel that was sequentially cross-linked with EDC once (G': 226±70 Pa, G″: 21±4.4 Pa), but not as strong as the same gel with heating for 30 min at 80°C (G': 7010±830 Pa, G″: 288±35 Pa) reported in our previous paper. The conventional collagen gel was cross-linked with EDC once, heated once, and then subjected twice to a lyophilization-gel formation-cross-linking cycle to give three-cycled gel 2. This gel had the strongest mechanical properties (G': 40,200±18,000 Pa, G″: 3090±1400 Pa, Young's modulus: 0.197±0.069 MPa) of the gels tested. These promising results suggest possible applications of the gels as scaffolds in tissue engineering research.

  3. Mechanical properties of metallic nanowires using tight-binding model

    Science.gov (United States)

    Aish, Mohammed; Starostenkov, Mikhail

    2016-01-01

    The mechanical properties of Nickel nanowires have been studied at different temperatures using molecular dynamics simulations. Molecular Dynamics (MD) simulations have been carried out on pure Nickel (Ni) crystal with face-centered cubic (FCC) lattice upon application of uniaxial tension at nanolevel with a speed of 20 m/s. The deformation corresponds to the direction . To the calculated block of crystal, free boundary conditions are applied in the directions , . A many body interatomic potential for Ni within the second moment approximation of the tight binding model (the Cleri-Rosato potentials) was employed to carry out three dimensional molecular dynamics simulations. MD simulation used to investigate the effect of temperature of Ni nanowire on the nature of deformation and fracture. Temperature effect on the extension property of metal nanowire is discussed in detail. The mechanical strengths and the mechanical strain of the nanowires decrease linearly with the increasing temperature. The feature of deformation energy can be divided into four regions: quasi-elastic, plastic, flow and failure. Experiments have shown that when the temperature increases the yielding stress decreases, the first stage of deformation was narrowed, and the second stage was widened. The results showed that breaking position depended on temperature.

  4. Mechanical properties for irradiated face-centred cubic nanocrystalline metals

    Science.gov (United States)

    Xiao, X. Z.; Song, D. K.; Chu, H. J.; Xue, J. M.; Duan, H. L.

    2015-01-01

    In this paper, a self-consistent plasticity theory is proposed to model the mechanical behaviours of irradiated face-centred cubic nanocrystalline metals. At the grain level, a tensorial crystal model with both irradiation and grain size effects is applied for the grain interior (GI), whereas both grain boundary (GB) sliding with irradiation effect and GB diffusion are considered in modelling the behaviours of GBs. The elastic-viscoplastic self-consistent method with considering grain size distribution is developed to transit the microscopic behaviour of individual grains to the macroscopic properties of nanocrystals (NCs). The proposed theory is applied to model the mechanical properties of irradiated NC copper, and the feasibility and efficiency have been validated by comparing with experimental data. Numerical results show that: (i) irradiation-induced defects can lead to irradiation hardening in the GIs, but the hardening effect decreases with the grain size due to the increasing absorption of defects by GBs. Meanwhile, the absorbed defects would make the GBs softer than the unirradiated case. (ii) There exists a critical grain size for irradiated NC metals, which separates the grain size into the irradiation hardening dominant region (above the critical size) and irradiation softening dominant region (below the critical size). (iii) The distribution of grain size has a significant influence on the mechanical behaviours of both irradiated and unirradiated NCs. The proposed model can offer a valid theoretical foundation to study the irradiation effect on NC materials. PMID:27547091

  5. On the Mechanical Properties of Chiral Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Mahnaz Zakeri

    2013-12-01

    Full Text Available Carbon nanotubes (CNTs are specific structures with valuable characteristics. In general, the structure of each nanotube is defined by a unique chiral vector. In this paper, different structures of short single-walled CNTs are simulated and their mechanical properties are determined using finite element method. For this aim, a simple algorithm is presented which is able to model the geometry of single-walled CNTs with any desired structure based on nano-scale continuum mechanics approach. By changing the chiral angle from 0 to 30 degree for constant length to radius ratio, the effect of nanotube chirality on its mechanical properties is evaluated. It is observed that the tensile modulus of CNTs changes between 0.93-1.02 TPa for different structures, and it can be higher for chiral structures than zigzag and armchair ones. Also, for different chiral angles, the bending modulus changes between 0.76-0.82 TPa, while the torsional modulus varies in the range of 0.283-0.301TPa.

  6. A theoretical analysis of the effect of the hydrogenation of graphene to graphane on its mechanical properties.

    Science.gov (United States)

    Peng, Qing; Liang, Chao; Ji, Wei; De, Suvranu

    2013-02-14

    We investigated the effect of the hydrogenation of graphene to graphane on its mechanical properties using first-principles calculations based on density-functional theory. The hydrogenation reduces the ultimate strengths in all three tested deformation modes--armchair, zigzag, and biaxial--and the in-plane stiffness by 1/3. The Poisson ratio was reduced from 0.178 to 0.078, a 56% decrease. However, the ultimate strain in zigzag deformation was increased by 8.7%. The shear mode elastic constants are more sensitive than longitudinal ones to hydrogenation. The fourth and fifth order longitudinal mode elastic constants are inert to the hydrogenation, in contrast to a large decrease of those in second and third order. The hydrogenation does not change the monotonic decrement of the Poisson ratio with increasing pressure, but the rate is tripled. Our results indicate that graphene-graphane systems could be used for hydrogen storage with high speed of charge-discharge of hydrogen.

  7. Injectability and mechanical properties of magnesium phosphate cements.

    Science.gov (United States)

    Moseke, Claus; Saratsis, Vasileios; Gbureck, Uwe

    2011-12-01

    Up to now magnesium phosphate cements are mainly being utilized in wastewater treatment due to their adsorptive properties. Recently they also have been shown to have a high potential as degradable biocements for application as replacement materials for bone defects. In comparison to degradable calcium phosphate cements they have the advantage of setting at neutral pH, which is favorable in biological environment. In this study two parameters of the cement composition, namely powder-to-liquid ratio (PLR) and citrate content, were varied in order to optimize the injectability properties of the cement paste and the mechanical properties of the reaction product. These properties were determined by means of testing setting time and temperature, paste viscosity, and injectability as well as phase composition and compressive strength of the set cements. Best results were obtained, when the cements were prepared with a PLR of 2.5 and a binder liquid consisting of an aqueous solution of 3 mol/l diammonium hydrogen phosphate and 0.5 mol/l diammonium citrate.

  8. Glass Fiber Reinforced Polypropylene Mechanical Properties Enhancement by Adhesion Improvement

    Directory of Open Access Journals (Sweden)

    Mariana Etcheverry

    2012-06-01

    Full Text Available Glass fibers (GF are the reinforcement agent most used in polypropylene (PP based composites, as they have good balance between properties and costs. However, their final properties are mainly determined by the strength and stability of the polymer-fiber interphase. Fibers do not act as an effective reinforcing material when the adhesion is weak. Also, the adhesion between phases can be easily degraded in aggressive environmental conditions such as high temperatures and/or elevated moisture, and by the stress fields to which the material may be exposed. Many efforts have been done to improve polymer-glass fiber adhesion by compatibility enhancement. The most used techniques include modifications in glass surface, polymer matrix and/or both. However, the results obtained do not show a good costs/properties improvement relationship. The aim of this work is to perform an accurate analysis regarding methods for GF/PP adhesion improvement and to propose a new route based on PP in-situ polymerization onto fibers. This route involves the modification of fibers with an aluminum alkyl and hydroxy-α-olefin and from there to enable the growth of the PP chains using direct metallocenic copolymerization. The adhesion improvements were further proved by fragmentation test, as well as by mechanical properties measurements. The strength and toughness increases three times and the interfacial strength duplicates in PP/GF composites prepared with in-situ polymerized fibers.

  9. Mechanical Properties of non-accreting Neutron Star Crusts

    CERN Document Server

    Hoffman, Kelsey

    2012-01-01

    The mechanical properties of a neutron star crust, such as breaking strain and shear modulus, have implications for the detection of gravitational waves from a neutron star as well as bursts from Soft Gamma-ray Repeaters (SGRs). These properties are calculated here for three different crustal compositions for a non-accreting neutron star that results from three different cooling histories, as well as for a pure iron crust. A simple shear is simulated using molecular dynamics to the crustal compositions by deforming the simulation box. The breaking strain and shear modulus are found to be similar in the four cases, with a breaking strain of ~0.1 and a shear modulus of ~10^{30} dyne cm^{-2} at a density of \\rho = 10^{14} g cm^{-3} for simulations with an initially perfect BCC lattice. With these crustal properties and the observed properties of {PSR J2124-3358} the predicted strain amplitude of gravitational waves for a maximally deformed crust is found to be greater than the observational upper limits from LIG...

  10. Mechanical Properties of Fiber Reinforced Lightweight Concrete Containing Surfactant

    Directory of Open Access Journals (Sweden)

    Yoo-Jae Kim

    2010-01-01

    Full Text Available Fiber reinforced aerated lightweight concrete (FALC was developed to reduce concrete's density and to improve its fire resistance, thermal conductivity, and energy absorption. Compression tests were performed to determine basic properties of FALC. The primary independent variables were the types and volume fraction of fibers, and the amount of air in the concrete. Polypropylene and carbon fibers were investigated at 0, 1, 2, 3, and 4% volume ratios. The lightweight aggregate used was made of expanded clay. A self-compaction agent was used to reduce the water-cement ratio and keep good workability. A surfactant was also added to introduce air into the concrete. This study provides basic information regarding the mechanical properties of FALC and compares FALC with fiber reinforced lightweight concrete. The properties investigated include the unit weight, uniaxial compressive strength, modulus of elasticity, and toughness index. Based on the properties, a stress-strain prediction model was proposed. It was demonstrated that the proposed model accurately predicts the stress-strain behavior of FALC.

  11. Investigation of tribological and mechanical properties of metal bearings

    Indian Academy of Sciences (India)

    Bekir Sadik Ünlü

    2009-08-01

    Copper, aluminum and tin–lead based alloys are widely used as journal bearing materials in tribological applications. Bronze and brass are widely used as journal bearing materials for copper based alloys. Zamacs find applications as journal bearing materials for zinc based alloys, while duralumines are chosen as journal bearing materials for aluminum based alloys. In addition, white metals are widely used as journal bearing materials for tin–lead based alloys. These alloys ensure properties expected from journal bearings. In this study, tribological and mechanical properties of these journal bearings manufactured by metals were investigated. SAE 1050 steel shaft was used as counter abrader. Experiments were carried out in every 30 min for a total of 150 min by using radial journal bearing wear test rig.

  12. Mechanical and Tribological Properties of Carbon-Based Graded Coatings

    Directory of Open Access Journals (Sweden)

    M. Kot

    2016-01-01

    Full Text Available The paper presents research on coatings with advanced architecture, composed of a Cr/Cr2N ceramic/metal multilayer and graded carbon layers with varying properties from Cr/a-C:H to a-C:N. The microstructure of the coatings was analysed using transmission electron microscopy and Energy Dispersive Spectroscopy, the mechanical properties were tested by nanoindentation, spherical indentation, and scratch testing, and tribological tests were also conducted. The proper selection of subsequent layers in graded coatings allowed high hardness and fracture resistance to be obtained as well as good adhesion to multilayers. Moreover, these coatings have higher wear resistance than single coatings and a friction coefficient equal to 0.25.

  13. Thermodynamics and statistical mechanics. [thermodynamic properties of gases

    Science.gov (United States)

    1976-01-01

    The basic thermodynamic properties of gases are reviewed and the relations between them are derived from the first and second laws. The elements of statistical mechanics are then formulated and the partition function is derived. The classical form of the partition function is used to obtain the Maxwell-Boltzmann distribution of kinetic energies in the gas phase and the equipartition of energy theorem is given in its most general form. The thermodynamic properties are all derived as functions of the partition function. Quantum statistics are reviewed briefly and the differences between the Boltzmann distribution function for classical particles and the Fermi-Dirac and Bose-Einstein distributions for quantum particles are discussed.

  14. Ferrosilt (Red Mud): Geotechnical Properties and Soil Mechanical Considerations

    Science.gov (United States)

    Jenny, F. C.

    The disposal of ferrosilt tailings creates problems because of the rather unusual geotechnical properties. Ferrosilt samples from three different bauxites were tested in connection with the alumina plant project in Wilhelmshaven (West Germany). The results of these laboratory tests explain various ferrosilt slides experienced during the past. Should ferrosilt be utilized for application where better physical qualities of the material are required it is possible to separate the coarser fraction from the finer fractions by using cyclons. The soil mechanical properties of the coarser fraction — called ferrosilt-sand — is of much better quality than the ferrosilt proper. On the other hand the quality of the finder fractions is not much inferior to the ferrosilt.

  15. Estimation of mechanical properties of nanomaterials using artificial intelligence methods

    Science.gov (United States)

    Vijayaraghavan, V.; Garg, A.; Wong, C. H.; Tai, K.

    2014-09-01

    Computational modeling tools such as molecular dynamics (MD), ab initio, finite element modeling or continuum mechanics models have been extensively applied to study the properties of carbon nanotubes (CNTs) based on given input variables such as temperature, geometry and defects. Artificial intelligence techniques can be used to further complement the application of numerical methods in characterizing the properties of CNTs. In this paper, we have introduced the application of multi-gene genetic programming (MGGP) and support vector regression to formulate the mathematical relationship between the compressive strength of CNTs and input variables such as temperature and diameter. The predictions of compressive strength of CNTs made by these models are compared to those generated using MD simulations. The results indicate that MGGP method can be deployed as a powerful method for predicting the compressive strength of the carbon nanotubes.

  16. Low-temperature mechanical properties of glass/epoxy laminates

    Science.gov (United States)

    Reed, R. P.; Madhukar, M.; Thaicharoenporn, B.; Martovetsky, N. N.

    2014-01-01

    Selected mechanical properties of glass/epoxy laminate candidates for use in the electrical turn and ground insulation of the ITER Central solenoid (CS) modules were measured. Short-beam shear and flexural tests have been conducted on various E-glass cloth weaves/epoxy laminates at 295 and 77 K. Types of glass weave include 1581, 7500, 7781, and 38050, which represent both satin and plain weaves. The epoxy, planned for use for vacuum-pressure impregnation of the CS module, consists of an anhydride-cured bisphenol F resin system. Inter-laminar shear strength, flexural elastic modulus, and flexural strength have been measured. The data indicate that these properties are dependent on the volume percent of glass. Short-beam shear strength was measured as a function of the span-to-thickness ratio for all laminates at 77 K. Comprehensive fractography was conducted to obtain the failure mode of each short-beam shear test sample.

  17. Mechanical properties of several Fe-Ni meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Mulford, Roberta N [Los Alamos National Laboratory; El - Dasher, Bassem [LLNL

    2010-10-28

    The strength and elastic constants of meteorites are of increasing interest as predictions of meteorite impacts on earth come within the realm of possibility. In addition, meteorite impacts on extraterrestrial bodies provide an excellent sampling tool for evaluation of planetary compositions and properties. Fe-Ni meteorites provide a well-defined group of materials of fairly uniform composition. Iron-nickel meteorites exhibit a unique lamellar microstructure, a Widmanstatten structure, consisting of small regions with steep-iron-nickel composition gradients. This microstructure is found in the Fe-Ni system only in meteorites, and is believed to arise as a result of slow cooling in a planetary core or other large mass. Meteorites with compositions consisting of between 5 and 17% nickel in iron are termed 'octahedrite,' and further characterized according to the width of the Ni-poor kamacite bands; 'fine,' (0.2-0.5 mm) 'medium,' (0.5-1.3 mm) and 'coarse,' (1.5-3.3 mm). Many meteorites have inclusions and structures indicating that the material has been shocked at some point early in its evolution. Several Iron-nickel meteorites have been examined using Vickers and spherical indentation, x-ray fluorescence, and EBSD. Direct observation of mechanical properties in these highly structured materials provides a valuable supplement to bulk measurements, which frequently exhibit large variation in dynamic properties, even within a single sample. Previous studies of the mechanical properties of a typical iron-nickel meteorite, a Diablo Canyon specimen, indicated that the strength of the composite was higher by almost an order of magnitude than values obtained from laboratory-prepared specimens. Additional meteorite specimens have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon re-entry contributes to yield, and to establish the degree to which the strength

  18. Scanning Probe Evaluation of Electronic, Mechanical and Structural Material Properties

    Science.gov (United States)

    Virwani, Kumar

    2011-03-01

    We present atomic force microscopy (AFM) studies of a range of properties from three different classes of materials: mixed ionic electronic conductors, low-k dielectrics, and polymer-coated magnetic nanoparticles. (1) Mixed ionic electronic conductors are being investigated as novel diodes to drive phase-change memory elements. Their current-voltage characteristics are measured with direct-current and pulsed-mode conductive AFM (C-AFM). The challenges to reliability of the C-AFM method include the electrical integrity of the probe, the sample and the contacts, and the minimization of path capacitance. The role of C-AFM in the optimization of these electro-active materials will be presented. (2) Low dielectric constant (low-k) materials are used in microprocessors as interlayer insulators, a role directly affected by their mechanical performance. The mechanical properties of nanoporous silicate low-k thin films are investigated in a comparative study of nanomechanics measured by AFM and by traditional nanoindentation. Both methods are still undergoing refinement as reliable analytical tools for determining nanomechanical properties. We will focus on AFM, the faster of the two methods, and its developmental challenges of probe shape, cantilever force constant, machine compliance and calibration standards. (3) Magnetic nanoparticles are being explored for their use in patterned media for magnetic storage. Current methods for visualizing the core-shell structure of polymer-coated magnetic nanoparticles include dye-staining the polymer shell to provide contrast in transmission electron microscopy. AFM-based fast force-volume measurements provide direct visualization of the hard metal oxide core within the soft polymer shell based on structural property differences. In particular, the monitoring of adhesion and deformation between the AFM tip and the nanoparticle, particle-by-particle, provides a reliable qualitative tool to visualize core-shell contrast without the use

  19. Genetic and environmental modification of the mechanical properties of wood

    Science.gov (United States)

    Sederoff, R.; Allona, I.; Whetten, R.

    1996-02-01

    Wood is one of the nation's leading raw materials and is used for a wide variety of products, either directly as wood, or as derived materials in pulp and paper. Wood is a biological material and evolved to provide mechanical support and water transport to the early plants that conquered the land. Wood is a tissue that results from the differentiation and programmed cell death of cells that derive from a tissue known as the vascular cambium. The vascular cambium is a thin cylinder of undifferentiated tissue in plant stems and roots that gives rise to several different cell types. Cells that differentiate on the internal side of the cambium form xylem, a tissue composed in major part, of long thin cells that die leaving a network of interconnected cell walls that serve to transport water and to provide mechanical support for the woody plant. The shape and chemical composition of the cells in xylem are well suited for these functions. The structure of cells in xylem determines the mechanical properties of the wood because of the strength derived from the reinforced matrix of the wall. The hydrophobic phenolic surface of the inside of the cell walls is essential to maintain surface tension upon which water transport is based and to resist decay caused by microorganisms. The properties of wood derived from the function of xylem also determine its structural and chemical properties as wood and paper products. Therefore, the physical and chemical properties of wood and paper products also depend on the morphology and composition of the cells from which they are derived. Wood (xylem cell walls) is an anisotropic material, a composite of lignocellulose. It is a matrix of cellulose microfibrils, complexed with hemicelluloses, (carbohydrate polymers which contain sugars other than glucose, both pentoses and hexoses), embedded together in a phenolic matrix of lignin. The high tensile strength of wood in the longitudinal direction, is due to the structure of cellulose and the

  20. Porosity and mechanical properties of porous titanium fabricated by gelcasting

    Institute of Scientific and Technical Information of China (English)

    LI Yan; GUO Zhimeng; HAO Junjie; REN Shubin

    2008-01-01

    Porous Ti compacts with large size and complex shape for biomedical applications were fabricated in the porosity range from 40.5% to 53.8% by controlling gelcasting parameters and sintering conditions. The experimental results show that the total porosity and open porosity of porous titanium compacts gelcast from the Ti slurry with 34 vol.% solid loading and sintered at 1100℃ for 1.5h are 46.5% and 40.7%, respectively, and the mechanical properties are as follows: compressive strength 158.6MPa and Young's modulus 8.5GPa, which are similar to those of human cortical bone and appropriate for implanting purpose.

  1. Microstructure and mechanical properties of neutron irradiated beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Ishitsuka, E.; Kawamura, H. [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Terai, T.; Tanaka, S.

    1998-01-01

    Microstructure and mechanical properties of the neutron irradiated beryllium with total fast neutron fluences of 1.3 - 4.3 x 10{sup 21} n/cm{sup 2} (E>1 MeV) at 327 - 616degC were studied. Swelling increased by high irradiation temperature, high fluence, and by the small grain size and high impurity. Obvious decreasing of the fracture stress was observed in the bending test and in small grain specimens which had many helium bubbles on the grain boundary. Decreasing of the fracture stress for small grain specimens was presumably caused by crack propagation on the grain boundaries which weekend by helium bubbles. (author)

  2. Mechanical properties of timber from wind damaged Norway spruce

    DEFF Research Database (Denmark)

    Hoffmeyer, Preben

    2003-01-01

    . The paper reports on a investigation of the relation between degree of damage and mechanical proper-ties of sawn timber from wind damaged Norway spruce. The project included about 250 bolts from wind damaged trees. The majority of bolts were cut to deliver a full-diameter plank containing the pith...... taken to bending failure and the relations between compression damage and bending strength and stiffness were established. The results showed that significant reductions of bending strength of dry timber are only caused by such wind induced compression damages that are easily recognised at a planed...

  3. Mechanical Properties of Heat Exchanger Tube Materials at Elevated Temperatures

    Science.gov (United States)

    Kahl, Sören; Zajac, Jozefa; Ekström, Hans-Erik

    Since automotive heat exchangers are operated at elevated temperatures and under varying pressures, both static and dynamic mechanical properties should be known at the relevant temperatures. We have collected elevated-temperature tensile test data, elevated-temperature stress amplitude-fatigue life data, and creep-rupture data in a systematic fashion over the past years. For thin, soft, and braze-simulated heat exchanger tube materials tested inside closed furnaces, none of the well-established methods for crack detection and observation can be applied. In our contribution, we present a simple statistical method to estimate the time required for crack initiation.

  4. Mechanical and electrical properties of polycarbonate nanotube buckypaper composite sheets

    Energy Technology Data Exchange (ETDEWEB)

    Pham, Giang T; Park, Young-Bin; Wang Shiren; Liang Zhiyong; Wang Ben; Zhang, Chuck [High-Performance Materials Institute (HPMI), Department of Industrial and Manufacturing Engineering, Florida A and M University, Florida State University College of Engineering, 2525 Pottsdamer Street, Tallahassee, FL 32310-6046 (United States); Funchess, Percy; Kramer, Leslie [Lockheed Martin Missiles and Fire Control-Orlando, Orlando, FL 32819-8907 (United States)], E-mail: gte640q@yahoo.com

    2008-08-13

    The thermogravimetric, mechanical, and electrical properties of composite sheets produced by infiltrating single-wall carbon nanotube films (also known as 'buckypapers') with polycarbonate solution were characterized. The composite sheets showed improved stiffness and toughness, while the electrical conductivity decreased, as compared to a neat buckypaper. In addition, polycarbonate/buckypaper composite sheets showed higher resistance to handling and processing damages. Experimental results suggest the viability of the infiltration process as a means to toughen buckypapers and to fabricate polymer/carbon nanotube composites having high nanotube concentration and controlled nanotube structure.

  5. Mechanical and structural properties of sputtered Ni/Ti multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Senthil Kumar, M.; Boeni, P.; Tixier, S.; Clemens, D.; Horisberger, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    Ni/Ti bilayers have been prepared by dc-magnetron sputtering in order to study their mechanical and structural properties. A remarkable reduction of stress is observed when the Ni layers are sputtered reactively in argon with a high partial pressure of air. The high angle x-ray diffraction studies show a tendency towards amorphisation of the Ni layers with increasing air flow. The low angle measurements indicate a substantial reduction of interdiffusion resulting in smoother interfaces with increasing air content. (author) 2 figs., 2 refs.

  6. MICROSTRUCTURE AND MECHANICAL PROPERTIES OF NOVEL 718 SUPERALLOY

    Institute of Scientific and Technical Information of China (English)

    J.H. Du; X.D. Lü; J.L. Qu; Q. Deng; J.Y. Zhuang; Z.Y. Zhong

    2006-01-01

    Recently, a novel 718 superalloy with remarkable structural stability at 680℃ has been designed and fabricated by CISRI (Central Iron and Steel Research Institute) etc. Phase identification of novel 718 alloy under the above-mentioned heat-treatment condition was performed using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Results show that the novel 718 alloy has outstanding structural stability at 680℃. The novel 718alloy possess excellent structural stability and good mechanical properties, which is attributed to y-phase strengthening and also to the specific sandwich structure of the γ′ + γ" strengthening phase.

  7. Mechanical Properties Optimization of Fiber Reinforced Foam Concrete

    Directory of Open Access Journals (Sweden)

    Yu Lei

    2016-01-01

    Full Text Available 3 factors including fiber kind, fiber content and fiber mix-ability are selected to optimizing mechanical properties of foam concrete. By orthogonal experiment design, compression and flexural stress and strain of specimens from different fiber added ways were test. Range analysis and factor levels analysis show the best fiber added way. Test shows that fiber content is the most important factor to flexural stress. Next one is fiber kind and the third is fiber mix-ability. Fiber kind is the most important factor to stress curves. Fiber is not good for compression strength but good for flexural strength.

  8. Physical and Mechanical Properties of Sorghum Grains (Sorghum Vulgare)

    OpenAIRE

    2016-01-01

    The physical and mechanical properties of sorghum grains (sorghum vulgare) were studied at varying moisture contents of 13%, 20% and 30% (w.b). The four varieties of sorghum grains studied include; Dura, Guinea, Faterita and Kafir. Results indicate that the size ranges were 3.94mm - 4.83mm for Dura variety; 3.75mm - 4.54mm for Guinea variety; 3.21mm - 4.42mm for Kafir variety and 2.70mm - 4.14mm for Faterita variety. Irregularities in the shapes of the grains were observed but all approximate...

  9. Mechanical Properties of Oil Palm Empty Fruit Bunch Fiber

    Science.gov (United States)

    Gunawan, Fergyanto E.; Homma, Hiroomi; Brodjonegoro, Satryo S.; Hudin, Afzer Bin Baseri; Zainuddin, Aryanti Binti

    In tropical countries such as Indonesia and Malaysia, the empty fruit bunches are wastes of the oil palm industry. The wastes are abundantly available and has reached a level that severely threats the environment. Therefore, it is a great need to find useful applications of those waste materials; but firstly, the mechanical properties of the EFB fiber should be quantified. In this work, a small tensile test machine is manufactured, and the tensile test is performed on the EFB fibers. The results show that the strength of the EFB fiber is strongly affected by the fiber diameter; however, the fiber strength is relatively low in comparison to other natural fibers.

  10. Mechanical properties of timber from wind damaged Norway spruce

    DEFF Research Database (Denmark)

    Hoffmeyer, Preben

    2003-01-01

    A storm may subject a tree to such bending stresses that extensive compression damage develops in the lee side. The tree may survive the wind load or it may be thrown. However, the damage is inherent and it may be of a magnitude to influence the mechanical properties of boards sawn from the stem...... taken to bending failure and the relations between compression damage and bending strength and stiffness were established. The results showed that significant reductions of bending strength of dry timber are only caused by such wind induced compression damages that are easily recognised at a planed...

  11. Influence of Carbonation on Mechanical Properties of Concrete

    Institute of Scientific and Technical Information of China (English)

    梁发云; 陈龙珠; 李检保

    2003-01-01

    As one of the most important factors that determine the lifespan of a reinforced concrete structure, car-bonation not only corrodes the reinforcing steel, but also changes the mechanical properties of concrete. For betterunderstanding the performance of carbonated concrete structure, it is necessary to study the mechanical propertiesof carbonated concrete. The strees-strain relationship of carbonated concrete was analyzed on the basis of experi-ments. The specimens were made by means of accelerated carbonation and then compressed on the testing ma-chine. Some very important characteristics of carbonated concrete were revealed by the testing results. In addition,a useful constitutive model of carbonated concrete, which proved to be suitable for analyzing carbonated concretemembers, was established in this research.

  12. Hydrodynamic interaction induced mechanical properties of SGF reinforced polyethersulfone

    Science.gov (United States)

    Munirathnamma, L. M.; Ningaraju, S.; Kumar, K. V. Aneesh; Ravikumar, H. B.

    2016-05-01

    In order to explore the effect of short glass fiber (SGF) reinforcement on the mechanical properties of Polyethersulfone (PES), short glass fibers of different proportion (10 - 40 wt %) are reinforced into PES matrix. The free volume distribution of SGFR-PES composites derived from CONTIN-PALS2 program exhibits the narrow full width at half maximum (FWHM). This is attributed to the improved adhesion resulted by the hydrodynamic interaction between the polymeric chains of PES matrix and SGF. The hydrodynamic interaction parameter (h) decreases as a function of SGF wt% and becomes more negative for 40 wt% SGFR-PES composites suggest the generation of excess friction at the interface. This improves the adhesion between the polymeric chains of PES matrix and SGF and hence the mechanical strength of the SGFR-PES composites.

  13. Structural and mechanical properties of Laponite-PEG hybrid films.

    Science.gov (United States)

    Shikinaka, Kazuhiro; Aizawa, Kazuto; Murakami, Yoshihiko; Osada, Yoshihito; Tokita, Masatoshi; Watanabe, Junji; Shigehara, Kiyotaka

    2012-03-01

    Inorganic/organic hybrids were obtained by the sol-gel type organic modification reaction of Laponite sidewalls with poly(ethylene glycol) (PEG) bearing alkoxysiloxy terminal functionality. By casting an aqueous dispersion of the hybrid, the flexible and transparent hybrid films were obtained. Regardless of the inorganic/organic component ratio, the hybrid film had the ordered structure of Laponite in-plane flat arrays. The mechanical strength of hybrid films was drastically improved by the presence of cross-linking among alkoxysilyl functionalities of PEG terminals and the absence of PEG crystallines. Hybrid films, especially those that consisted of PEG with short chain, showed good mechanical properties that originate from quasi-homogeneous dispersion of components due to anchoring of PEG terminal to Laponite sidewall and interaction of PEG to Laponite surface.

  14. Mechanical properties of tannin-based rigid foams undergoing compression

    Energy Technology Data Exchange (ETDEWEB)

    Celzard, A., E-mail: Alain.Celzard@enstib.uhp-nancy.fr [Institut Jean Lamour - UMR CNRS 7198, CNRS - Nancy-Universite - UPV-Metz, Departement Chimie et Physique des Solides et des Surfaces, ENSTIB, 27 rue du Merle Blanc, BP 1041, 88051 Epinal cedex 9 (France); Zhao, W. [Institut Jean Lamour - UMR CNRS 7198, CNRS - Nancy-Universite - UPV-Metz, Departement Chimie et Physique des Solides et des Surfaces, ENSTIB, 27 rue du Merle Blanc, BP 1041, 88051 Epinal cedex 9 (France); Pizzi, A. [ENSTIB-LERMAB, Nancy-University, 27 rue du Merle Blanc, BP 1041, 88051 Epinal cedex 9 (France); Fierro, V. [Institut Jean Lamour - UMR CNRS 7198, CNRS - Nancy-Universite - UPV-Metz, Departement Chimie et Physique des Solides et des Surfaces, ENSTIB, 27 rue du Merle Blanc, BP 1041, 88051 Epinal cedex 9 (France)

    2010-06-25

    The mechanical properties of a new class of extremely lightweight tannin-based materials, namely organic foams and their carbonaceous counterparts are detailed. Scaling laws are shown to describe correctly the observed behaviour. Information about the mechanical characteristics of the elementary forces acting within these solids is derived. It is suggested that organic materials present a rather bending-dominated behaviour and are partly plastic. On the contrary, carbon foams obtained by pyrolysis of the former present a fracture-dominated behaviour and are purely brittle. These conclusions are supported by the differences in the exponent describing the change of Young's modulus as a function of relative density, while that describing compressive strength is unchanged. Features of the densification strain also support such conclusions. Carbon foams of very low density may absorb high energy when compressed, making them valuable materials for crash protection.

  15. Ab initio investigation of the mechanical properties of copper

    Institute of Scientific and Technical Information of China (English)

    Liu Yue-Lin; Gui Li-Jiang; Jin Shuo

    2012-01-01

    Employing the ab initio total energy method based on the density functional theory with the generalized gradient approximation,we have systematically investigated the theoretical mechanical properties of copper (Cu).The theoretical tensile strengths are calculated to be 25.3 GPa,5.9 GPa,and 37.6 GPa for the fcc Cu single crystal in the [001],[110],and [111] directions,respectively.Among the three directions,the [110] direction is the weakest one due to the occurrence of structure transition at the lower strain and the weakest interaction of atoms between the (110) planes,while the [111] direction is the strongest direction because of the strongest interaction of atoms between the (111) planes.In terms of the elastic constants of Cu single crystal,we also estimate some mechanical quantities of polycrystalline Cu,including bulk modulus B,shear modulus G,Young's modulus Ep,and Poisson's ratio v.

  16. Carbon nanotube heterojunctions: unusual deformations and mechanical vibration properties

    Science.gov (United States)

    Scarpa, F.; Narojczyk, J.; Wojciechowski, K. W.; Inman, D. J.

    2011-04-01

    The mechanical deformation and dynamics properties of single wall carbon nanotube heterojunctions (HJ) oscillators are investigated using an hybrid finite element atomistic-continuum approach. The nanotube HJs provide a peculiar deformation pattern, with combined bending and axial stretching of carbon nanotubes (CNTs), and a broad agreement of their axial stiffness with spring series continuum mechanics and existing molecular dynamics (MD) simulations. We show also peculiar distributions of the natural frequencies and modes of the hetero-junctions compared to classical single-wall nanotube configurations, and the mass-sensor capability of (5,5)-(10,10) SWCNT HJ structures, with frequency shifts highly depending on the heterojunction section subjected to the mass loading.

  17. Microstructure and Mechanical Properties of Graphene Oxide/Copper Composites

    Directory of Open Access Journals (Sweden)

    HONG Qi-hu

    2016-09-01

    Full Text Available Graphene oxide/copper (GO/Cu composites were successfully synthesized through the ball milling and vacuum hot press sintering process. The morphologies of the mixture powders, and the microstructure and mechanical properties of GO/Cu composites were investigated by OM, SEM, XRD, hardness tester and electronic universal testing machine, respectively. The results show that the GO/Cu composites are compact. Graphene oxide with flake morphology is uniformly dispersed and well consolidated with copper matrix. When the mass fraction of graphene oxide is 0.5%, the microhardness and compress strength at RT reach up to 63HV and 276MPa, increased by 8.6% and 28%, respectively. The strengthening mechanism is load transfer effect, dislocation strengthening and fine crystal reinforcing.

  18. Laser welding of polymers, compatibility and mechanical properties

    DEFF Research Database (Denmark)

    Nielsen, Steen Erik; Strange, Marianne; Kristensen, Jens Klæstrup

    2013-01-01

    with the development of related absorbers added to the polymer materials provide the possibility of joining transparent and non-transparent materials. The automotive industry, the medical device industry and the electronic industry are just some of the areas where the technology is widely implemented......Laser welding of polymers is today a commonly used industrial technology. It has shown obvious advantages compared to e.g. adhesive bonding in terms of higher productivity, better quality and easiness for automation. The ongoing development of lasers tailored for polymer welding in coordination....... There is an increasing industrial interest in joining dissimilar polymers. To overcome the challenges involved increased focus is set on the understanding of joining mechanisms, morphology and molecular structure behavior. Also the understanding of resulting mechanical and thermal properties is presently subject...

  19. The humidity sensing properties and mechanism of strontium-hexaferrite

    CERN Document Server

    Zhang, Hui-Feng; Shao, Gang-Qin; Gao, Zhen-Sheng; Liu, Jin-Hua; Girish, H -N

    2016-01-01

    The humidity sensing properties of n-type strontium-hexaferrite semiconductors are investigated at room temperature. The involved materials include hexaferrites of pure Z-type (Sr3Co2Fe24O41) and X-type (Sr2Co2Fe28O46) / W-type (SrCo2Fe16O27) mixture, in which Fe3+ / Fe2+ ions have different lattice sites. The contact and reactions between water and material surface are demonstrated considering the formation of oxide ion vacancy, singly-ionized / fully-ionized oxide ion vacancy, and the chemisorbed / physisorbed / condensed water. An impedance spectra model is proposed considering the material-electrode interface, interior material, grain boundary, absorbed water and Warburg response. The mechanism of electronic coupled with protonic conduction and humidity sensing mechanism are explained.

  20. Macroporous hydrogels with tailored morphology and mechanical properties

    Science.gov (United States)

    Bignotti, Fabio; Agnelli, Silvia; Baldi, Francesco; Sartore, Luciana; Peroni, Isabella

    2016-05-01

    In this work it is shown that hydroxyethylcellulose (HEC) can be employed for preparing macroporous polyacrylamide (PAAm) hydrogels with tailored morphology and mechanical properties. By changing the HEC content in the reaction mixture hydrogels with different pore sizes and degrees of interconnectivity can be synthesized. The equilibrium swelling ratio in 0.1 M NaCl increases with the amount of HEC employed. Tensile tests run on equilibrated hydrogels show that these materials behave as rubber-like materials. Their mechanical stiffness decreases regularly as the amount of HEC, and therefore their porosity, is increased. A more complex trend is observed for elongation and stress at break, which display a maximum at intermediate contents of HEC.