bluuebunny/crossref_metadata_2025 huggingface dataset:
The Gigantism of Public Works in China in the Twenty-First Century
Authors: Martín-Antón Mario , Negro Vicente , Del Campo José , López-Gutiérrez José-Santos , Esteban M.
Published: September 2017

Part of human beings’ relationship with the world around them includes constructing or building. They connect with the land and makes civil engineering an action of reflection with the environment, a use of material, and a function of construction work. This involves a combination of necessities and perfection in order to fulfil an aim. To build is essential on this earth. From a “mud hut” as the commencement of architecture up to water regulating with dams, conducting it via a channel, overcoming obstacles by use of a bridge, or finding shelter and sailing by using harbours, a public work requires the welfare of a community as its “raison d´être”. The aim of this investigation is to analyse the human condition in construction and how works of an enormous size that change the way of “being on earth” have been tackled for instrumental reasons by disassociating necessities, revitalizing noxious effects, destroying nature’s scenery and landscapes, disturbing the environment, and negatively affecting the urban development of our “poly-cities”. Referred to by the authors of this article as “gigantism of public works”, this concept is analysed using examples in Asia and works of a notable size in China.
Sulfide Precipitation in Wastewater at Short Timescales
Authors: Kiilerich Bruno , Van de Ven Wilbert , Nielsen Asbjørn , Vollertsen Jes
Published: September 2017

Abatement of sulfides in sewer systems using iron salts is a widely used strategy. When dosing at the end of a pumping main, the reaction kinetics of sulfide precipitation becomes important. Traditionally the reaction has been assumed to be rapid or even instantaneous. This work shows that this is not the case for sulfide precipitation by ferric iron. Instead, the reaction time was found to be on a timescale where it must be considered when performing end-of-pipe treatment. For real wastewaters at pH 7, a stoichiometric ratio around 14 mol Fe(II) (mol S(−II))−1 was obtained after 1.5 s, while the ratio dropped to about 5 mol Fe(II) (mol S(−II))−1 after 30 s. Equilibrium calculations yielded a theoretic ratio of 2 mol Fe(II) (mol S(−II))−1, indicating that the process had not equilibrated within the span of the experiment. Correspondingly, the highest sulfide conversion only reached 60%. These findings differed significantly from what has been demonstrated in previous studies and what is attained from theoretical equilibrium conditions.
PSYM-WIDE: A Survey for Large-separation Planetary-mass Companions to Late Spectral Type Members of Young Moving Groups
Authors: Naud Marie-Eve , Artigau Étienne , Doyon René , Malo Lison , Gagné Jonathan , Lafrenière David , Wolf Christian , Magnier Eugene A.
Published: September 2017

We present the results of a direct imaging survey for very large separation (>100 au), low-mass companions around 95 nearby young K5–L5 stars and brown dwarfs. They are high-likelihood candidates or confirmed members of the young (≲150 Myr) β Pictoris and AB Doradus moving groups (ABDMG) and the TW Hya, Tucana–Horologium, Columba, Carina, and Argus associations. Images in

and

filters were obtained with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South to search for companions down to an apparent magnitude of

 ∼ 22–24 at separations ≳20″ from the targets and in the remainder of the wide 5.′5 × 5.′5 GMOS field of view. This allowed us to probe the most distant region where planetary-mass companions could be gravitationally bound to the targets. This region was left largely unstudied by past high-contrast imaging surveys, which probed much closer-in separations. This survey led to the discovery of a planetary-mass (9–13

) companion at 2000 au from the M3V star GU Psc, a highly probable member of ABDMG. No other substellar companions were identified. These results allowed us to constrain the frequency of distant planetary-mass companions (5–13

) to

% (95% confidence) at semimajor axes between 500 and 5000 au around young K5–L5 stars and brown dwarfs. This is consistent with other studies suggesting that gravitationally bound planetary-mass companions at wide separations from low-mass stars are relatively rare.
Color Difference Makes a Difference: Four Planet Candidates around τ Ceti
Authors: Feng F. , Tuomi M. , Jones H. R. A. , Barnes J. , Anglada-Escudé G. , Vogt S. S. , Butler R. P.
Published: September 2017

The removal of noise typically correlated in time and wavelength is one of the main challenges for using the radial-velocity (RV) method to detect Earth analogues. We analyze τ Ceti RV data and find robust evidence for wavelength-dependent noise. We find that this noise can be modeled by a combination of moving average models and the so-called “differential radial velocities.” We apply this noise model to various RV data sets for τ Ceti, and find four periodic signals at 20.0, 49.3, 160, and 642 days, which we interpret as planets. We identify two new signals with orbital periods of 20.0 and 49.3 days while the other two previously suspected signals around 160 and 600 days are quantified to a higher precision. The 20.0 days candidate is independently detected in Keck data. All planets detected in this work have minimum masses less than

with the two long-period ones located around the inner and outer edges of the habitable zone, respectively. We find that the instrumental noise gives rise to a precision limit of the High Accuracy Radial Velocity Planet Searcher (HARPS) around 0.2 m s−1. We also find correlation between the HARPS data and the central moments of the spectral line profile at around 0.5 m s−1 level, although these central moments may contain both noise and signals. The signals detected in this work have semi-amplitudes as low as 0.3 m s−1, demonstrating the ability of the RV technique to detect relatively weak signals.
Comparison of Damping Mechanisms for Transverse Waves in Solar Coronal Loops
Authors: Montes-Solís María , Arregui Iñigo
Published: September 2017

We present a method to assess the plausibility of alternative mechanisms to explain the damping of magnetohydrodynamic transverse waves in solar coronal loops. The considered mechanisms are resonant absorption of kink waves in the Alfvén continuum, phase mixing of Alfvén waves, and wave leakage. Our methods make use of Bayesian inference and model comparison techniques. We first infer the values for the physical parameters that control the wave damping, under the assumption of a particular mechanism, for typically observed damping timescales. Then, the computation of marginal likelihoods and Bayes factors enable us to quantify the relative plausibility between the alternative mechanisms. We find that, in general, the evidence is not large enough to support a single particular damping mechanism as the most plausible one. Resonant absorption and wave leakage offer the most probable explanations in strong damping regimes, while phase mixing is the best candidate for weak/moderate damping. When applied to a selection of 89 observed transverse loop oscillations, with their corresponding measurements of damping timescales and taking into account data uncertainties, we find that positive evidence for a given damping mechanism is only available in a few cases.
LOFAR Discovery of the Fastest-spinning Millisecond Pulsar in the Galactic Field
Authors: Bassa C. G. , Pleunis Z. , Hessels J. W. T. , Ferrara E. C. , Breton R. P. , Gusinskaia N. V. , Kondratiev V. I. , Sanidas S. , Nieder L. , Clark C. J. , Li T. , Amesfoort A. S. van , Burnett T. H. , Camilo F. , Michelson P. F. , Ransom S. M. , Ray P. S. , Wood K.
Published: September 2017

We report the discovery of PSR J0952−0607, a 707 Hz binary millisecond pulsar that is now the fastest-spinning neutron star known in the Galactic field (i.e., outside of a globular cluster). PSR J0952−0607 was found using LOFAR at a central observing frequency of 135 MHz, well below the 300 MHz to 3 GHz frequencies typically used in pulsar searches. The discovery is part of an ongoing LOFAR survey targeting unassociated Fermi-Large Area Telescope γ-ray sources. PSR J0952−0607 is in a 6.42 hr orbit around a very low-mass companion (

), and we identify a strongly variable optical source, modulated at the orbital period of the pulsar, as the binary companion. The light curve of the companion varies by 1.6 mag from

at maximum to

, indicating that it is irradiated by the pulsar wind. Swift observations place a 3σ upper limit on the

X-ray luminosity of

erg s−1 (using the 0.97 kpc distance inferred from the dispersion measure). Though no eclipses of the radio pulsar are observed, the properties of the system classify it as a black widow binary. The radio pulsed spectrum of PSR J0952−0607, as determined through flux density measurements at 150 and 350 MHz, is extremely steep with

(where

). We discuss the growing evidence that the fastest-spinning radio pulsars have exceptionally steep radio spectra, as well as the prospects for finding more sources like PSR J0952−0607.
INTEGRAL Observations of GW170104
Authors: Savchenko V. , Ferrigno C. , Bozzo E. , Bazzano A. , Brandt S. , Chenevez J. , Courvoisier T. J.-L. , Diehl R. , Hanlon L. , von Kienlin A. , Kuulkers E. , Laurent P. , Lebrun F. , Lutovinov A. , Martin-Carillo A. , Mereghetti S. , Roques J. P. , Sunyaev R. , Ubertini P.
Published: September 2017

We used data from the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) to set upper limits on the γ-ray and hard X-ray prompt emission associated with the gravitational-wave event GW170104, discovered by the Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo collaboration. The unique omnidirectional viewing capability of the instruments on board INTEGRAL allowed us to examine the full 90% confidence level localization region of the LIGO trigger. Depending on the particular spectral model assumed and the specific position within this region, the upper limits inferred from the INTEGRAL observations range from F

γ
 = 1.9 × 10−7 erg cm−2 to F

γ
 = 10−6 erg cm−2 (75 keV–2 MeV energy range). This translates into a ratio between the prompt energy released in γ-rays along the direction to the observer and the gravitational-wave energy of E

γ
/E
GW < 2.6 × 10−5. Using the INTEGRAL results, we cannot confirm the γ-ray proposed counterpart to GW170104 by the Astro—Rivelatore Gamma a Immagini Leggero (AGILE) team with the mini-Calorimeter (MCAL) instrument. The reported flux of the AGILE/MCAL event, E2, is not compatible with the INTEGRAL upper limits within most of the 90% LIGO localization region. There is only a relatively limited portion of the sky where the sensitivity of the INTEGRAL instruments was not optimal and the lowest-allowed fluence estimated for E2 would still be compatible with the INTEGRAL results. This region was also observed independently by Fermi/Gamma-ray Burst Monitor and AstroSAT, from which, as far as we are aware, there are no reports of any significant detection of a prompt high-energy event.
Health Literacy Not Associated with Chronic Kidney Disease Awareness
Authors: Saunders Milda R. , Snyder Ashley , Chin Marshall H. , Meltzer David O. , Arora Vineet M. , Press Valerie G.
Published: September 2017

Background:

Patient awareness of their chronic kidney disease (CKD) and health literacy (HL) are both important for adherence to therapies that slow CKD progression and to reduce risk of complications. Little is known about the association between HL and CKD awareness.

Objective:

We sought to determine if patient HL is associated with CKD awareness.

Methods:

We conducted a cross-sectional study of general medicine inpatients at an urban academic medical center discharged between June 2011 and July 2013 with CKD, defined as having at least one CKD
International Classification of Diseases
, ninth revision code (585.0–585.9), among their first 20 admission diagnoses. Logistic regression was used to analyze the influence of HL, demographic, clinical, and health care use covariates on the likelihood of patients' CKD awareness. Our primary outcome was patient awareness of their CKD, defined as correct patient self-report of “kidney problems.” We used the Brief Health Literacy Screen, a three-item verbal questionnaire, to assess HL.

Key Results:

Among 1,308 patients with CKD, awareness of CKD was 33%, and 48% had adequate HL. However, CKD awareness was not associated with HL even among patients with stage 4 or 5 CKD. In multivariable logistic regression, greater awareness was associated with being a woman, younger than age 50 years, married, White, having hypertension, and having a higher CKD stage (all
p
< .05). In stratified analyses, patients with hypertension had greater CKD awareness, regardless of HL or diabetes status (
p
< .05).

Conclusions:

Among hospitalized patients with CKD, both CKD awareness and HL are low and inadequate. Surprisingly, patients' knowledge of their CKD diagnosis was not related to patients' HL. Patients with hypertension who young, white, or married may be receiving or retaining more education related to CKD. More work is needed on how to effectively communicate CKD diagnosis to prevent widening health disparities.

[
Health Literacy Research and Practice
. 2017;1(3):e117–e127.]

Plain Language Summary:

We studied whether patients with low health literacy also had low awareness of their chronic kidney disease (CKD). Hospitalized patients with CKD were asked three questions about their health literacy and whether they had “kidney problems.” Overall CKD awareness and health literacy were low, but a low score on one did not predict a low score on the other.
On the Tensile Behaviour of CF and CFRP Materials under High Strain Rates
Authors: de Luca A. , di Caprio F. , Milella E. , Lamanna Giuseppe , Ignarra M. , Caputo Francesco
Published: September 2017

The paper deals with dynamic tensile tests on Carbon Fibre Reinforced Polymer – CFRP laminates. As a result of their viscoelastic nature, plastics exhibit rate dependence in their stress-strain response. The need to develop failure criteria to determine the dynamic failure stress for composite material under dynamic loading conditions is a current challenge for the research community. The main goal of such paper is to assess the efficiency of the analytical models provided by literature to predict the strain-rate effects on composite coupons tensile strength. Moreover, experimental tests have been performed in order to evaluate the mechanical behaviour of different stacking sequences at different strain rate.
Analysis of the Three-Dimensional Zone around the Interfacial Crack Tip: The K-Influence Domain Range in the Plane Stress State
Authors: Djoković Jelena M. , Vulović Snežana D. , Nikolić Ružica R. , Živković Miroslav M. , Hadzima Branislav
Published: September 2017

The bimaterial sample was analyzed to determine the three-dimensional zone at the interface crack tip and the field in the plane stress state. The solutions for the complete 3D field in different zones around the crack tip were approximated by the plane stress and plane strain states' asymptotic solutions. The difference between the solutions for the plane stress and plane strain states is defined by the three variables. The established relationship between the far field and the field around the crack tip in the plane strain conditions, enables relating the measured experimental results of the stress intensity factor to results for the stress intensity factor for the field around the crack tip, which represent the more relevant parameter for formulating the fracture criterion.
Analysis of Residual Stress around Semi-Circular Surface Notches due to Excessive Pressure
Authors: Ino Takuichiro , Sonobe Yohei , Saimoto Akihide , Hashiguchi Tomokazu
Published: September 2017

Residual stresses due to excessive internal pressure applied to an array of semi-circular surface notches is analyzed by body force method. The treated problem corresponds to a simple model of the Stealth Dicing (SD) which is expected as an alternative splitting technology applicable to brittle materials. In SD, laser beam of specific wave length is focused and scanned inside of the material to produce a SD-process zone which includes an array of microvoids. Each microvoid is thought to be received an excessive internal pressure due to thermal expansion and then material is split along a plane which contains an array of microvoids. After the mechanical splitting process, there expected to present a considerable residual stresses in the vicinity of an array of microvoids exposed at the
splitting surface. In the present study, by analyzing the elastic-plastic stress fields near the array of surface microvoids, the mechanical characteristics of the SD induces surface is discussed.
Using Numerical Simulation in the Optimization of the Finishing Phases in Ceramic Tiles Manufacturing
Authors: Radovanovic A. , Mladenovic M. , Campana G. , Mele M.
Published: September 2017

The Grés Porcelain stoneware surely represents a remarkable material for building inside the large family of constructive ceramics. It is appreciated in consideration of its superior properties of resistance and functionality, especially when considered respect to a relatively low cost. Billions of square meters of Grés Porcelain are produced worldwide each year, primarily in form of tiles of every dimension, thinness, color, decoration, in the way that the ceramic tile industry represents a relevant economy. But the tile manufacturing is a complex process, made by different stages and productive plants to be deeply investigated and optimized. This paper describes the use of Finite Elements for modelling and optimizing the production of Grés Porcelain tiles with special attention to the ending phases of the process, just after the treatments in kiln and realized by tool machining. The case study, used to redesign a fundamental part of a finishing machine driven by a numerical approach, is also detailed.
Fiber Orientation Control by Stretching in Cellulose Nanofiber Green Composites
Authors: Takagi Hitoshi , Nakagaito Antonio Norio , Sakaguchi Yuya
Published: September 2017

The presence of nanoscale cellulosic fiber; namely cellulose nanofiber, increases year by year because the mechanical and physical properties are believed to be comparable to those of common glass fibers. On the other hand, most of the reported strength data for the cellulose nanofiber-reinforced polymeric composite materials was not as high as expected. In order to obtain high-strength cellulose nanofiber-reinforced polymer composites, we tried to optimize the fiber orientation of cellulose nanofibers in poly (vinyl alcohol)-based polymer matrix by using a repeated mechanical stretching treatment. The fiber orientation of cellulose nanofibers in the poly (vinyl alcohol) matrix can be modified by changing the total amount of stretching strain applied during the multiple stretching treatments. The degree of fiber alignment was directly evaluated by observing the cellulose nanofibers on the sample surface with a digital microscope. The efficacy of proposed nanofiber alignment control has been explored experimentally and theoretically. The tensile strength and modulus of the cellulosic nanocomposites after applying the multiple stretching treatments increased by approximately 80% and 40% respectively, as compared with those of the untreated nanocomposites.
Analysis of Cracks in Functionally Graded Piezoelectric Materials by a Frequency-Domain BEM
Authors: Wünsche Michael , Sladek Jan , Sladek Vladimir , Zhang Ch. , Repka M.
Published: September 2017

Time-harmonic crack analysis in two-dimensional piezoelectric functionally graded materials (FGMs) is presented in this paper. A frequency-domain boundary element method (BEM) is developed for this purpose. Since fundamental solutions for piezoelectric FGMs are not available, a boundary-domain integral formulation is derived. This requires only the frequency-domain fundamental solutions for homogeneous piezoelectric materials. The radial integration method is adopted to compute the resulting domain integrals. The collocation method is used for the spatial discretization of the frequency-domain boundary integral equations. Adjacent the crack-tips square-root elements are implemented to capture the local square-root-behavior of the generalized crack-opening-displacements properly. Special regularization techniques based on a suitable change of variables are used to deal with the singular boundary integrals. Numerical examples will be presented and discussed to show the influences of the material gradation and the dynamic loading on the intensity factors.
A Phase Field Approach to Fracture with Mass Transport Extension for the Simulation of Environmentally-Assisted Cracking
Authors: Falkenberg Rainer
Published: September 2017

The fracture mechanics assessment of materials exposed to harmful environments requires the understanding of the interaction between the soluted species and the affected mechanical behaviour. With the introduction of a mass transport mechanism the entire problem is subjected to a time frame that dictates the time-dependent action of soluted species on mechanical properties. A numerical framework within the phase field approach is presented with an embrittlement-based coupling mechanism showing the influence on crack patterns and fracture toughness. Within the phase field approach the modeling of sharp crack discontinuities is replaced by a diffusive crack model facilitating crack initiation and complex crack topologies such as curvilinear crack patterns, without the requirement of a predefined crack path. The isotropic hardening of the elasto-plastic deformation model and the local fracture criterion are affected by the species concentration. This allows for embrittlement and leads to accelerated crack propagation. An extended mass transport equation for hydrogen embrittlement, accounting for mechanical stresses and deformations, is implemented. For stabilisation purposes a staggered scheme is applied to solve the system of partial differential equations. The simulation of showcases demonstrates crack initiation and crack propagation aiming for the determination of stress-intensity factors and crack-resistance curves.
Analysis of Planar Crack Coalescence by Mesh-Free Body Force Method
Authors: Sonobe Yohei , Ino Takuichiro , Saimoto Akihide , Hasib Md. Abdul , Koyama Atsuhiro , Shatil Giora
Published: September 2017

In a standard body force method analysis, a mesh division is required to define the boundary of a problem and to solve a governing equation using discretization procedure. However, in the present study, a moving least square strategy is introduced to define a weight function for the density of body force doublet and therefore a crack analysis is carried out without providing a standard mesh-division. Hence, the standard crack face elements are not required at all. A variety of 3D crack problems can be analyzed simply by providing a data that only de nes a crack front. Besides the nodal points for crack front, several internal nodes are generated on the crack face to represent a distribution of unknown function. At the internal nodes, an unknown variable is assigned which uniquely de ne a distribution of the relative crack face displacement. In the present approach, a crack problem is formulated
as a singular integral equation whose unknown is a value of the weight function at the internal nodal points. A crack growth can be simulated directly by changing the shape of crack front, by means of adding a new nodal point in the vicinity of the current crack front. In the present paper, the proposed method is used to simulate a coalescence of interacting planar cracks.
Lightning Strike Simulation in Composite Structures
Authors: de Toro Espejel J. Fernandez , Sharif Khodaei Zahra
Published: September 2017

Lighting strike is one of the critical threats to the safety of composite aircrafts during flight. This work reports on numerical simulation of lightning strike in composite structures. Different modelling techniques using the commercial software ABAQUS, together with damage models are studied to find the most appropriate one in comparison to experimental results. Once the numerical model is validated, the effect of insertion of carbon nanotubes (CNTs) and metallic mesh in the composite is investigated. It is concluded that inserting CNTs in the top layer of the composite can improve its lightning strike protection noticeably.
Bone Remodeling Algorithm Incorporating Various Quantities as Mechanical Stimulus and Assuming Initial Microcrack in Bone
Authors: Borák Libor , Marcián Petr
Published: September 2017

It is widely accepted that bones have the ability to adapt to new biomechanical environment by changing their material properties, geometry and inner architecture. Bones have also an exceptional ability to self-repair, to remove microcracks and to prevent the bone damage caused by the fatigue failure. These abilities are enabled through coupled processes of bone resorption and bone formation, the processes collectively referred to as bone remodeling. Numerous studies have shown that bone remodeling is governed by combination of mechanical stimulus (strains) and its frequency, both sensed by sensor cells (osteocytes). Through mechanotransduction, the stimulus is transmitted to actor cells (osteoclasts, osteoblasts) that actually do the bone resorption or formation. Several theories have been proposed to predict bone remodeling and several finite-element-based algorithms have been introduced. The vast majority of them uses strain energy density as the mechanical stimulus. The purpose of this paper is to investigate and discuss the applicability of also other strain-based representations of the mechanical stimulus in simulations of remodeling of bone with an initial microcrack. The need for developing more reliable models is essential for both clinicians and engineers who are interested, for instance, in prediction of bone performance when various implants are involved.
Numerical Computation of Stress Intensity Factors in Ultrasonic Very-High-Cycle Fatigue Tests
Authors: Hasani Najafabadi S.H. , Zucca Stefano , Paolino D.S. , Chiandussi G. , Rossetto Massimo
Published: September 2017

The correct computation of the Stress Intensity Factor (SIF) in ultrasonic Very-High-Cycle Fatigue (VHCF) loading conditions is a key issue when investigating the crack growth rate curve with pre-cracked specimens or when evaluating critical SIF values from fracture surfaces of failed specimens. Dynamic conditions related to the resonance of the vibrating specimen, contact nonlinearity between crack faces and stress singularity at the crack tip make the SIF computation difficult and cumbersome. Generally, numerical computation through Finite Element Models (FEMs) under non-linear dynamic conditions makes use of direct integration methods (implicit or explicit). However, in the high frequency regime of ultrasonic VHCF tests, the procedure may lead to an unacceptable computational time. In order to reduce the computational time, a hybrid procedure based on the Harmonic Balance Method (HBM) and on the Virtual Crack Closure Technique (VCCT) is originally presented and applied in this paper. The dynamic field parameters calculated with the HBM are used as input data for the computation of the SIF through the VCCT.
Prediction of Elastic Properties of 3D4d Braided Composite Based on Hybrid Model
Authors: Zhang Di , Zheng Xi Tao , Wu Tian Chi
Published: September 2017

This paper presents a meso-scale hybrid model which is used to predict the elastic properties of three-dimensional (3D) four-directional (4d) braided composites. At first, based on meso-structural model of 3D4d braided composite and the assumptions of iso-strain and iso-stress, two analytical models are established. Secondly, a hybrid model used to predict the elastic modulus of the 3D4d braided composite is established which introduces a new factor called hybrid-coefficient Ψ, which incorporates the iso-strain and iso-stress models at the same time, the value of Ψ is dependant on the braiding angle. Comparison between theoretical and experimental results shows that the hybrid model is more accurate than the iso-strain and iso-stress models, and can be used to predict the elastic properties of 3D4d braided composites, with the relative errors around 10%.
On the Scale-Transition in Multiscale Modeling of Ductile Damage
Authors: Lesičar Tomislav , Sorić Jurica , Tonković Zdenko
Published: September 2017

The standard numerical methods cannot adequately capture damage response of ductile heterogeneous materials, since they are unable to encompass the governing microstructural mechanisms. This issue is resolved by the multiscale approach, where the coarse scale problem incorporates behavior at the lower scales. In this paper, a multiscale scheme is employed for scaling of ductile damage occurring at the microstructural level to the macrolevel. A nonlocal implicit damage model is applied on the RVE, while a scale transition is performed by means of the first-order homogenization scheme. The influence of the boundary conditions used at the microscale on the macroscale response, as well as physical consistency of the RVE mechanical behavior are tested. It has been shown that displacement boundary conditions inhibit development of the softening band inside of the RVE and induce artificial material stiffness. The derived algorithms are embedded into the finite element software ABAQUS.
Influence of Agitation Equipment on Reinforcing Effect and Dispersion State of Cellulose Nano-Fibers in Natural Rubber
Authors: Omori Sho , Morita Takayuki , Matsumoto Koki , Nagatani Asahiro , Tanaka Tatsuya
Published: September 2017

There are many rubber products like tires, and reinforcing agents derived from fossil resources such as carbon black (CB) are used for them. However, in recent years, conversion to biomass resources has been demanded due to problems such as depletion of fossil resources. Therefore, we have studied the composite of natural rubber (NR) reinforced with cellulose nano-fibers (CNF), which has attracted attention as a next-generation biomass resource. It is very difficult to uniformly disperse CNF in the conventional kneading process. Therefore, it is preferable to agitate CNF in NR latex. Then, it is necessary to study the optimum agitation equipment of CNF. In this study, the reinforcing effect by CNF was investigated when the agitation equipment was changed. Agitation of NR latex and CNF was carried out by a hand, a homogenizer, a dispersion mixer, and planetary centrifugal mixer. Thereafter, agitated materials were dried and masterbatches were made. Furthermore, the masterbatch and vulcanizing agents were kneaded using an internal mixer. Tensile test and X-ray CT observation of the prepared vulcanized rubber sheets were carried out to evaluate the reinforcing effect and dispersion state of CNF. As a result, the planetary centrifugal mixer was most useful to uniformly disperse CNF.
Fracture Resistance of Flash Welded and Laser Welded Butt Joints in a Microalloyed HSLA Steel
Authors: Baptista C.A.R.P. , Ribeiro H.V. , Lima Milton Sergio Fernandes , Torres Marcelo A.S. , Costa D.H.S.
Published: September 2017

High-strength, low-alloy (HSLA) steels are widely used in the automotive and oil industries due to their good mechanical properties and weldability. The selection of the welding process depends on several factors, including the quality of the weld bead and the production capacity. The knowledge of the mechanical performance of the welded joint is essential to ensure structural reliability. In the present work, butt joints were produced from 5 mm thick plates of a microalloyed HSLA steel by flash welding and by laser welding processes, the latter using two different heat input conditions. The microsctructure and hardness of the weld beads were evaluated. The fracture toughness of the welded joints was assessed by means of CTOD tests. The higher heat input laser welded joint presented critical CTOD comparable to that of the flash welded joint, whereas the lower heat input martensitic-bainitic laser welded joint tended to a brittle behavior.
Effect of Surface Morphologies of Interface on Adhesion Strength in a Metal/Epoxy Joint
Authors: Yamazaki Yasuhiro , Mizuno Takehito
Published: September 2017

Metal/polymer joints as well as metal/metal joints bonded by epoxy adhesive have been widely used for automotive, electrical device and others. In the present study, the adhesion strength of a stainless-steel/epoxy joint was evaluated by using of the shear test and the 4-point bending test. Three kind of the surface finishing condition of the stainless steel were selected, and the effect of the surface morphologies of the interface on the adhesion strength in the metal/epoxy joint was investigated. The relationship between the interface morphology and the loading mode in the metal/epoxy joint was discussed.
Influence of Manufacturing Defects on the Mechanical Behaviour of All-Composite Wing under Service Load Conditions
Authors: Riccio Aniello , Russo A. , Sellitto Andrea , Pezone G. , San Millan J. , Armendariz I.
Published: September 2017

In this paper, the damage behaviour of aerospace composite structures has been studied. The analysed structure is an all-composite wing with inter-laminar manufacturing induced damage. The manufacturing induced delaminations are located at the leading edge on the extrados and in the area near the fuselage. Different analyses have been performed to correctly predict the pre-existent damages evolution under service loading conditions. Preliminary linear buckling analyses have been performed to check for instability of the delaminations under service loads; then the risk of delaminations’ propagation has been evaluated by means of a Virtual Crack Closure Technique based approach.
Modelling of Modified Compact Tension Test of Fine-Grained Cement-Based Concrete Specimens Using FEM Software
Authors: Klon Jiří , Sobek Jakub , Keršner Zbyněk
Published: September 2017

The paper discusses creation of numerical models of the modified Compact Tension (CT) test configuration on specimens made of fine-grained cement composite. Numerical models of this test configuration are used for predictions of crack initiation and damage propagation and are important for the further evaluation of fracture parameters. To assemble the numerical models, ATENA FEM software was used. In this software, fracture of the structure/specimen caused by cracks, their initiation and progressive propagation throughout the loading process, can be modelled. In case of this study the material model for concrete based on cohesive law approach was used. The analysis is focused on evaluation of 2D and 3D numerical models created with real material properties obtained from experimental data.
New Insights into the Anchorage Zones of Precast Pretensioned Concrete Girders
Authors: van Meirvenne Kizzy , de Corte Wouter , Boel Veerle , Taerwe Luc
Published: September 2017

Pretensioned concrete girders are widely used in the construction sector. Nevertheless, optimisation is still possible considering the end zones. These end zones are subject to different types of stress due to the local transmission of the prestress force. In order to optimise these regions, a 3D non-linear finite element model was developed using the Abaqus software. Different from other attempts, a full scale girder with multiple strands is modelled. The accuracy of the FE model was verified by comparing the numerical results with experimental data. A full scale test in a precast concrete plant during normal production is carried out, and a good fit between the experimental and numerical results is obtained. Finally, the model was used to design a girder without end block. The calculation of the additional reinforcement was based on vector plots of the tensile stresses, extracted from the FEM.
Assessment of the Structural Condition of a Hospital-Type Building in Mexico City Damaged in the 1985 Earthquake
Authors: Avila Jorge A. , Avila-Haro Jorge Arturo
Published: September 2017

The seismic-resistant behaviour and the current structural condition against gravity loads of a hospital-type building is evaluated. The building fell into disuse due to the damages caused by the 1985 Mexico City earthquake. The structural assessment intends to ease the decision-making process regarding either to: 1) demolish the structure (including foundation) in order to build another tower-type structure in the same location; or 2) rehabilitate the structure (increase resistance and stiffness). The building consists in a reinforced concrete structure of the late 1960's, with five levels based on a rigid box foundation with friction piles, which was abandoned after the 1985 earthquake. It is located in a compressible seismic zone (site dominant vibration period, Ts ~ 2 seconds) and was designed according to the RCDF-66 [1] with seismic coefficients of 0.06 and 0.08 for the longitudinal (frames) and transverse (concrete walls of head axes) directions, respectively. Between 1971 and 1972 the foundation was reinforced with control piles. There are no reported damages of the main structural elements resistances but, because of the observed effects in the non-structural components within the building, important lateral movements can be induced, which are not recommended, nor desired, in hospital-type structures. Important deterioration problems can be observed in the non-structural elements and finishes as well as in the main structure (including foundation) after being abandoned for more than 30 years with scarce maintenance. The assessment was performed through spectral modal dynamic analyses, including three-dimensional models of the structure and foundation in conjunction in accordance with the current Code (RCDF-04) [2], as well as with a newer and stricter Regulation proposal of the Mexico City Building Code. Additionally, time-history analyses were performed with both site-representative ground motion records and 1985 earthquake records. The analytical results of the fundamental vibration periods were calibrated against the ambient vibration measured periods. Slump field measurements resulted under 1% with respect to height. In general, it complies with the failure limit state (resistances), but not with the lateral displacements and story drift limit.
Deterioration Behaviors of Overlapping Layers between Al-5Mg Alloy Thermal Spray Coating and Heavy-Duty Paint Coating
Authors: Kainuma Shigenobu , Du Jin Xuan , Yang Mu Ye , Muto Kazuyoshi , Miyata Hirokazu
Published: September 2017

The objective of this study is to clarify the deterioration behaviors of overlapping layers between Al-5Mg alloy thermal spray coating and heavy-duty paint coating. Combined cyclic corrosion tests were carried out on common carbon steel plates with overlapping layers. To evaluate the effective area of the sacrificial anode reaction caused by the thermal spray coating, machined straight-line defects with widths of 0.2, 6 and 12 mm were introduced in the overlapping layer. The experimental results indicated that the layers began to deteriorate from the lower part of the thermal spray coating along the defects. The deterioration of the thermal spray coating was accelerated by the sealing treatment. The blister area and height at the overlapping layer were significantly different depending on the sealing treatment.
The Strange Case of Compacted Graphite Iron: A Remarkable Option with Unique Material Properties or an Unusable Alloy?
Authors: Mitrovic Slobodna , Savini Emanuele , Dzunic Dragan
Published: September 2017

The Compacted Graphite Iron (CGI) represents an example of material with remarkable and unexplored properties, especially in terms of resistance and machinability. With better strength and stiffness than several cast irons, as Grey Iron, and better castability, machinability and thermal conductivity than others, as Ductile Irons, this alloy would be, at least theoretically, the perfect material choice for a wide range of practical applications. Nevertheless, discovered more than 50 years ago, it has failed to establish itself in a definitive way. This review intends to highlight benefits and limits in choosing CGI in casting.
Fracture Toughness Characterization of Carbon Bonded Alumina Using Chevron Notched Specimens
Authors: Zielke H. , Abendroth Martin , Kuna Meinhard
Published: September 2017

A new generation of multifunctional filters is made of carbon bonded alumina and is investigated within the collaborative research center 920 (CRC920). These filters are used during a casting process with the aim of reducing non-metallic inclusions in the cast product. The high thermal and mechanical loading of the filter requires a fracture mechanical characterization of the investigated ceramic material.
In order to determine the fracture toughness of the ceramic material, a chevron-notched beam method (CNB) is applied. A 4-point-bending test set-up was constructed and brought into service, at which the load-displacement curve of small chevron-notched specimens (5 x 6 x 25 mm3) can be measured. The set-up offers the possibility of testing specimens at temperatures up to 1000oC.
Preceding numerically work using the finite element method was performed to identify a suitable notch geometry. For this purpose a cohesive zone model was used. A parameter study is presented, which shows the influence of the notch parameter on the load-displacement curve.
Experimental Study of Fatigue Crack Initiation and Strain Evolution around a Micro-Void by In Situ SEM and Digital Image Correlation
Authors: Wang De Qiang , Zhu Ming-Liang , Xuan Fu Zhen
Published: September 2017

Fatigue crack initiation stage occupies a large proportion of total fatigue life in modern engineering materials and structures which are often designed under lower service loading conditions. In this paper, the fatigue crack initiation behavior from a micro-void in a small-scale specimen was studied in-situ in SEM. Surface morphologies were monitored in-situ and images were taken during interrupted tests at selected number of cycles, and displacement and strain map around the void was calculated based on digital image correlation (DIC) technique. The results indicated that the strain evolution near the micro-void could be divided into stages, before crack initiation. The strain increasing rate was fast in the early stage and slower in the second stage. A critical cyclic strain value for fatigue crack initiation from the micro-void was obtained around 9%, and was believed to be the dominant factor for early stage of fatigue damage.
Experimental Characterization of Competition of Surface and Internal Damage in Very High Cycle Fatigue Regime
Authors: Zhang Wei Chang , Zhu Ming-Liang , Xuan Fu Zhen
Published: September 2017

Axially push-pull cyclic tests of a low strength rotor steel were performed up to the very high cycle fatigue regime at ambient environment under ultrasonic frequency. Fatigue tests were interrupted at selected number of cycles for surface morphology observation and roughness measurement with the help of a 3D surface measurement system (Alicona InfiniteFocusSL). The fatigue extrusions and slip band developed on the specimen surface were recorded. The influence of stress level on the number and morphology of slip band was discussed. The surface roughness of fatigue specimens was found to be increased with the increasing of fatigue cycles. The fatigued specimens were finally cracked from surface or interior micro-defects after observation of fracture surface by scanning electron microscopy. The internal damage behavior consists of crack initiation and early propagation from micro-defect, crack growth within the fish eye, and fast crack growth. It is observed that there exists a competition between surface and internal fatigue damage in the very high cycle fatigue regime, i.e., surface damage is gradually developed with the increasing of fatigue cycles, while the critical interior micro-defect can be dominant for fatigue cracking.
Buckling and Post-Buckling Behaviour of Impacted Glass Reinforced Composite Plates under Compression after Impact Tests
Authors: Cristiano Roberta , Perillo Gaetano
Published: September 2017

The present work deals with the Compression After Impact numerical simulations on low velocity impacted glass fibre reinforced composite plates configurations characterised by three different stacking sequences. The damaged numerical FEM models, deriving from impact explicit analyses, have been used as an input to perform explicit analyses simulating the compressive test. The drop, in terms of compressive residual strength, is analysed and discussed. Considerations on the buckling and post-buckling behaviour of these plates under compression are then introduced.
Effect of Shrinkage Porosity and Degenerated Graphite on Fatigue Crack Initiation in Ductile Cast Iron
Authors: Foglio E. , Gelfi Marcello , Pola Annalisa , Lusuardi D.
Published: September 2017

Heavy-section ductile iron castings solidify under low cooling rates, giving the risk to form defects like non-metallic inclusions, microporosities and degenerated shapes of graphite that have a negative effect on fatigue resistance, favoring the crack nucleation. The aim of this work is to precisely identify the defects that most affect the fatigue behavior in heavy-section castings, in order to guide the foundry to take the proper countermeasures. For this purpose, fatigue rotating bending tests were carried out on specimens machined from small-scale samples opportunely cast to reproduce long solidification times. The fracture surface of broken samples were investigated by means of Scanning Electron Microscopy in order to identify crack initiation points and fracture mechanisms. Shrinkage porosities and spiky graphite were found to play the most important effect on crack nucleation, lowering the fatigue resistance of the castings, while chunky graphite just behaved as a preferential path for crack propagation.
Continuum mechanics at nanoscale: A tool to study trees’ watering and recovery
Authors: Gouin Henri
Published: September 2017

The cohesion-tension theory expounds the crude sap ascent thanks to the negative pressure generated by evaporation of water from leaves. Nevertheless, trees pose multiple challenges and seem to live in unphysical conditions: the negative pressure increases cavitation; it is possible to obtain a water equilibrium between connected parts where one is at a positive pressure and the other one is at negative pressure; no theory is able to satisfactorily account for the refilling of vessels after embolism events.

A theoretical form of our paper [49] in the
Journal of Theoretical Biology
is proposed together with new results: a continuum mechanics model of the disjoining pressure concept refers to the Derjaguin school of physical chemistry. A comparison between liquid behaviour both in tight-filled microtubes and in liquid thin-films is o¤ered when the pressure is negative in liquid bulks and is positive in liquid thin-films and vapour bulks. In embolized xylem microtubes, when the air-vapour pocket pressure is greater than the air-vapour bulk pressure, a refilling flow occurs between the air-vapour domains to empty the air-vapour pockets although the liquid-bulk pressure remains negative. The model has a limit of validity taking the maximal size of trees into account.

These results drop an inkling that the disjoining pressure is an efficient tool to study biological liquids in contact with substrates at a nanoscale range.