bluuebunny/crossref_metadata_2025 huggingface dataset:
Production and Characterization of Hydroxyapatite/Niobo Phosphate Glass Scaffold
Authors: Navarro da Rocha Daniel , de Oliveira Cruz Leila Rosa , do Prado Neto João Luiz , Ayad Nadia Mohammed Elmassalami , de Andrade Gobbo Luciano , Prado da Silva Marcelo Henrique
Published: November 2013

The present study concerns the production and characterization of porous hydroxyapatite/niobo-phosphate glass ceramics to be used for bone repair. The scaffolds were produced by hydrothermal deposition of monetite on polyurethane sponge substrates, further converted to hydroxyapatite in an alkali solution. After heat treatment, elimination of the organic sponge provides a three-dimensional (3D) structure. Niobo-phosphate glasses were added to the heat treated struts and the scaffolds were sintered. The porous bodies were characterized by field-emission gun scanning electron microscope (FEG-SEM) with energy-dispersive X-ray spectroscopy (EDS).
Biodegradability of some Collagen Sponges Reinforced with Different Bioceramics
Authors: Antoniac Iulian
Published: November 2013

Composite materials based on collagen matrix could have the different properties in the case of reinforcement with different bioceramics. Not just the chemical composition of bioceramics used as reinforcement component have an influence on the composite properties, but also the microstructural aspects of bioceramics such as morphology, grain size and shape, homogeneity and distribution. We present in this paper the effect of the bioceramics type (TCP, hydroxyapatite) and ratio on the composite material structure and the biodegradation properties of some collagen based composites obtaining using the freeze-drying process. Also, we measure the porosity before made the biodegradation test using collagenase as medium and immersion in simulated body fluid in order to see the bioactivity properties.
Novel Three-Component Composite Materials (Hydroxyapatite/Polymer Mixtures) for Bone Regeneration
Authors: Ion Rodica Mariana , Poinescu Aurora Anca , Doncea Sanda Maria
Published: November 2013

Biomaterial is a non-drug substance suitable for inclusion in systems which augment or replace the function of body tissues or organs. The nano-hydroxyapatite (HAp) is one of the most applied biomaterial, a popular bone substitute, for coatings and other filler materials due to their ability to promote mineralization. Hydroxyapatite [Ca10(PO4)6(OH)2] is one of the most stable forms of calcium phosphate and it occurs in bones as major component (60 to 65%), along with other materials including collagen, chondroitin sulfate, keratin sulfate and lipids.
In order to improve the bioactivity and mechanical properties of hydroxyapatite, some synthetic and natural polymers (e.g., cellulose, collagen, chitosan, chitine) have been used as excellent candidates for bone/cartilage tissue engineering applications.
In this paper we propose to synthesize novel three-component composite materials from HAp and cellulose (carboxymethyl cellulose, CMC) with one of the following natural polymers (chitosan (CS), chitine (CT), collagen (CLG), all of them named CX), biocompatible (from CMC) and with excellent antimicrobial activity (from HAp). Similarly to CS, CMC has an extensive network of intra- and inter-molecular hydrogen bonds which makes it insoluble in water or in common organic solvents. To prepare this new composite material, ionic liquids (ILs) have been used as potential green solvents for biopolymers, knowing that 1-butyl-3-methylimidazolium chloride [BMImCl] is able to dissolve up to 10% (w/w) of CMC, and other polysaccharides such as CS. In the studied systems, HAp particles were dispersed uniformly in organic phase, and are present strong chemical interactions between the three phases. In our case, a highly porous film was prepared and its bioactivity was investigated by in vitro tests in a simulated body fluid (SBF) for 6 months. By ICP-OES, was found a migration of analyzed metals (Fe, Mn, Cr and Ni) in simulated physiological fluids (SBF) analyzed after a period of 6 months, but only in the ppb concentrations range.
Different system (HAp/CX/CMC) composites with weight ratios of 70/10/20, 70/15/15 and 70/20/10 were prepared. The new composites were characterized by infrared spectroscopy Fourier transformed (FT-IR), scanning electron microscopy (SEM) and ICP-OES.
Their antimicrobial activity has been tested on Candida albicans, Candida parapsilosis and Staphylococcus aureus, proofing an excellent antimicrobial activity.
Biological Properties of Chitosan/Collagen Composites
Authors: Sionkowska Alina , Kaczmarek Beata , Stalinska J. , Osyczka A.M.
Published: November 2013

The properties of new materials based on the blends of collagen and chitosan were studied along with their biological compatibility. Mechanical properties, thermal analysis, FTIR spectra and SEM images were obtained for different blends of chitosan/collagen in weight ratios 75/25, 50/50, 25/75. The materials in the form of 2D sheets were then subjected to cultures of human mesenchymal stem cells (hMSC) directed toward osteogenesis with ascorbate-2-phosphate and dexamethasone. The results showed that specified amounts of components influence the mechanical properties of obtained materials. Proliferation of hMSC decreased with increasing amounts of chitosan in collagen/chitosan films. However, the cellular activity of alkaline phosphatase (ALP), a marker of preosteoblasts and active osteoblasts, for plain collagen films ALP was the highest, whereas different ratios of collagen in chitosan/collagen composites had no effect on overall good ALP activity of hMSC. Based on the presented data, we believe the obtained materials are suitable for bone tissue engineering strategies.
The Effect of Bioglass Addition on Mechanical and Physical Properties of Photoactive UDMA-TEGDMA Resin Composites
Authors: Nicolae Laura C. , Shelton Richard M. , Cooper Paul R. , Martin Richard A. , Palin William M.
Published: November 2013

The effect of Bioglass addition on mechanical and physical properties of photoactive UDMA-TEGDMA resin composites Laura Nicolae, William Palin, Richard Shelton, Paul Cooper Aim: To determine the effect of Bioglass incorporation on the polymerisation rate (Rp), degree of conversion (DC), flexural strength and modulus (FS/FM) of light-curable filled resin composites (FRCs). Methods: Experimental photoactive resins containing various UDMA-TEGDMAratios and filled with non-silanised irregular or spherical 45S5-Bioglass (50μm; 5-40mass%) and/or silanised silicate glass filler particulates (0.7μm; 50-70mass%) weretested. Rp and DC wereanalysed by real-time near-infrared spectroscopy. FS/FM of resins and FRCs were determined using three-point flexural strength tests. Results: Addition of up to 20mass%45S5-Bioglass filler significantly increased DC and FS(p<0.05), although >20mass% had deleterious effects on mechanical properties. The addition of spherical Bioglass particles resulted in an increased DC compared with that of irregular filler morphology although no significant differences mechanical properties were observed (p>0.05). Conclusion: Addition of 45S5-Bioglass with specific filler content, size and morphology resulted in enhanced mechanical and physical properties compared with conventional silicate glass FRCs.
Bioactive Ti Metal with Ca-Enriched Surface Layer Able to Release Sr Ions
Authors: Yamaguchi Seiji , Nath Shekhar , Matsushita Tomiharu , Kokubo Tadashi
Published: November 2013

Bioactive Ti metal able to release Sr ions was prepared by chemical and heat treatments of Ti metal. Ti metal was initially soaked in 5M NaOH solution to form sodium hydrogen titanate. It was soaked in a mixed solution of CaCl2 and SrCl2 to replace its Na ions with Ca and Sr ions at a given range from 0.18 to 1.62 in Sr/Ca ratio. When it was heat-treated at 600 oC, it formed Sr-containing calcium titanate (SrCT) and rutile. The apatite formation in SBF of the treated metal was low, but increased markedly by subsequently soaking the metal in 1 M SrCl2 solution at 80 oC. Thus, the treated metal gradually released Sr ions into phosphate-buffered saline up to 0.9 ppm. It is expected that the Ti metal formed with the bioactive SrCT layer could release Sr ions in a living body to promote bone formation, and bond to a living bone through an apatite.
Socket Preservation Procedure after Tooth Extraction
Authors: Dimova Cena
Published: November 2013

Jaw deformities from tooth removal can be prevented and repaired by a procedure called socket preservation. Socket preservation can greatly improve the smile’s appearance and increase the chances for successful dental implants for years to come. The procedure begins with atraumatic tooth extraction. Every attempt is made to preserve the surrounding bone and soft tissue, with an emphasis on being careful not to fracture the delicate buccal plate. There are a number of techniques and instruments that aid in this process. In general, one never wants to elevate so that force is directed toward the buccal plate. Once the tooth is extracted, all the granulation tissue is removed from the socket. It is important that good bleeding is established in the socket. Next, a bone graft material is placed into the socket.Various materials are used in modern dental and maxillofacial surgery for bone tissue substitution and reconstruction. All osteoplastic materials can be divided into four groups by origin: autogenic, allogenic, xenogenic and synthetic. The development of new medical technologies enables use of achievements in material science, biochemistry, molecular biology and genetic engineering while creating new combined synthetic materials for bone grafting. Mineralized cancellous bone is appropriate for most socket preservation cases.Synthetic resorbable materials were intended as an inexpensive substitute for natural hydroxyapatite. Synthetic graft materials include various types of calcium phosphate ceramics: tribasic calcium phosphate; bioglass; hydroxyapatite and its compositions with collagen, sulphated glycosaminoglycans such as keratan and chrondroitin sulphate as well as with sulphate and calcium phosphate.After the graft material is placed in the socket, it is then covered with a resorbable or non-resorbable membrane and sutured. Primary flap closure is not ideal. Most importantly, socket preservation helps to maintain the alveolar architecture. Socket preservation significantly reduces the loss of ridge width and height following tooth removal.
Ceramics and Orthodontics
Authors: Mesaros Anca , Mesaros Michaela , Dudea Diana , Muntean Alexandrina , Badea Mandra
Published: November 2013

Introduction: An orthodontist has two clinical situations in which he is confronted with ceramics: 1. Use of ceramic brackets 2. Applying brackets on teeth with ceramic restorations. Aim: The present study wishes to emphasize the advantages and the disadvantages that the use of ceramics has brought to the orthodontic profession. Material And Method: 75 consecutive adult orthodontic patients after being presented with their treatment plan were administered a questioner to motivate their choice in the type of braces and the cases with aesthetic braces or which had ceramic restorations prior to orthodontics received a special follow-up threw-out their treatment. Results: Ceramic braces are chosen for aesthetic reasons but sometimes they create other type of problems during treatment. Adhesion between braces and ceramic restorations rests problematic. Conclusions: The use of ceramics in orthodontics was indispensable but dental materials still need to be perfected.
Study of the Expansion Behaviour of Some Materials Used in the Dental Metal-Ceramic Technology
Authors: Manolea Horia Octavian , Antoniac Iulian , Florescu Nicolae , Mărășescu Petre , Miculescu Marian , Dascălu Ionela Teodora
Published: November 2013

In this paper we have focused on the study of the thermal expansion coefficient of a dental alloy, WBC, and its compatibility with a ceramic mass ,VITA VM 13, following thermal treatment according to the technological stages of production of a metal-ceramic prosthetic restoration.
The Adsorption of Cytochrome C on Mesoporous Silica Coated Hydroxyapatite Ceramics in PBS Solution
Authors: Yokogawa Yoshiyuki , Ito S. , Yamato Y. , Kishida I.
Published: November 2013

The preparation of mesoporous silica coated hydroxyapatite (HAp) ceramics is reported. The adsorption of proteins onto hydroxyapatite (HAp) is important in a variety of oral or osseous biological events. HAp has been used as bone filler, and the protein adsorption onto HAp materials is of importance for the bond formation. HAp has been also used as the material for column packing of liquid chromatography to separate and refine proteins due to the adsorptive capabilities with respect to the HAp. Mesoporous silica (MPS) materials have been extensively studied as carriers of bio-molecules due to their potential practical applications in medical materials. Pore diameters of 1.5 30 nm of the periodic mesoporous materials are close to the diameters of target molecules and enclosure of the protein in a well-defined space may help to prevent denaturation. Previously, we reported the MPS coating on the porous hydroxyapatite (HAp) ceramics obtained by dip-coating method. Protein adsorption on the porous HAp with the MPS coatings was evaluated using UV-VIS spectrometry, and the quantity of BSA adsorbed onto the HAp ceramics with the MPS coatings is around 1.5 times high compared to that on porous HAp ceramics. In this study, the vapor-phase synthesis of MPS film on HAP ceramics was carried out to improve the protein adsorptive property of HAp ceramics. The quantity of adsorbed protein onto the HAp ceramic disc with MPS coatings is around 5 times high compared to that on HAp ceramic disc.
CAD Method for Profiling Helical Surfaces of Parts Used in the Orthopaedic Reconstruction Surgery
Authors: Baroiu Nicuşor , Atudorei Mihai , Berbinschi Silviu , Teodor Virgil
Published: November 2013

In orthopedics are used a lot of specialized tools and reconstructive elements. Many of these are tools bounded by helical surfaces, significantly different from those used in similarly constructions with general character. There are analyzed, in a comparative way, two methods for profiling side mill tools for generation of specific threads used in the construction of the orthopaedic prosthetic screw. It is proposed an analytical method, based on the fundamental theorem of the surfaces enveloping versus a graphical method, developed in CATIA.
Comparative Critical Study of Commercial Calcium Phosphate Bone Substitutes in Terms of Physic-Chemical Properties
Authors: Miramond T. , Borget Pascal , Baroth Serge , Guy Daculsi
Published: November 2013

Physico-chemical characteristics impact directly or indirectly the bioactive properties of biomaterials, it is then essential to correlate it with their effect in vivo. A panel of biomaterials available on the market, based on Hydroxyapatite (HA) and Tricalcium phosphate (β-TCP) is studied in terms of surface area, hydrophilicity, porosity, zeta potential, crystalline phases and density. This study highlights the dispersity of commercial calcium phosphates (CaP) properties, and demonstrates how the quality criteria required for such bone substitute based on biomimicry concept, whose pores distribution is certainly the more relevant, are often incompletely or not respected according to literature.
Microporous ß-Tricalcium Phosphate (TCP) - A Delivery Vehicle of Growth Factors and Drugs
Authors: Bernstein Anke , Suedkamp Norbert , Mayr Hermann O. , Kißling Steffen , Seidenstuecker Michael
Published: November 2013

In this present work we could show that a microporous β-TCP ceramic with interconnected porosity and 5 μm median pore diameter is a useful delivery vehicle for drugs and growth factors. However, it is necessary to combine the ceramics with degradable biopolymers, like hydrogels for retarded release. So the drug release could be increased by the factor 7 from 3 up to 21 days with concentrations having an antimicrobial activity. Concerning the growth factor, the release period was prolonged significantly.
The Simulation of the Fatigue Fracture Process at Random Loading
Authors: Nikonov Valery V. , Shapkin Vasily S.
Published: November 2013

The general scheme of crack growth modeling and periodicity of aviation structure elements checks was developed. The major factors determined the scale of inaccuracy calculation ( εN*) based on calculations of crack growth duration (N*) and inspections intervals (τ0) were marked and estimated with the block diagram.
Thermodynamically Consistent Model of Damage in Laminated Rocks
Authors: Izvekov Oleg , Pavlov Vladimir
Published: November 2013

The phenomenological model of microcracks evolution in laminated rocks was developed under an isothermal approximation. The general form of the constitutive relations of porous media with microcracks was obtained. This form is necessary and sufficient for carrying out the principle of objectivity and the principle of thermodynamic consistency. The approximation of infinitesimal deformations of medium was investigated. The elastic potential of transversal isotropic brittle rocks was constructed. It involves latent energy of damage and terms which characterize elastic energy release due to damage evolution.
Micromechanics of Discontinuities and High Porosity Bands Formation in the Unconsolidated Sedimentary Rocks
Authors: Mukhamediev Shamil A. , Ul'kin D.A.
Published: November 2013

Formation of thin macrofractures and high porosity bands parallel to the compression axis in the unconsolidated sedimentary rocks is treated on the basis of unified approach by considering migration of microdefects (pores) with respect to particles of the medium. The migration of pores is driven by a common cause, namely, a trend of a system to lower its total energy. The mechanism of how discontinuities develop along the maximum compressive stress Tmax is discussed and quantitatively investigated. A single pore splits into two separate holes which move away along the Tmax axis. The trace left by moving hole is interpreted as a macro-discontinuity. Multiple pores migrate so that they form a system of chains extending along the Tmax axis. We associate these chains with observed high porosity bands.
Micromechanical Modelling of Advanced Ceramics with Statistically Representative Synthetic Microstructures
Authors: Alveen Patricia , McNamara Declan , Carolan Declan , Murphy Neal , Ivanković Alojz
Published: November 2013

Advanced ceramics are a class of material used in extreme conditions, such as high speed turning of aerospace alloys and rock drilling. Their high hardness makes them suitable for these uses, however their lower toughness means that failure due to fracture and chipping is a problem. They are composed of micron-sized particles of a primary hard phase together with either a ceramic or metallic matrix material. A combined experimental-numerical method was used to investigate the role of microstructure on the fracture of advanced ceramics. Two dimensional, statistically representative microstructures of the advanced ceramics are created using Voronoi tessellation. The synthetic microstructures are compared to real microstructures in terms of particle size distribution and particle aspect ratio. Simulation results indicate that the computed elastic parameters are within the Hashin-Shtrikman bounds and agree closely with analytical predictions made with the Eshelby-Mori-Tanaka method. It is found that the local stress and strain distribution within the model is significantly affected by the underlying microstructure, which in turn affects fracture properties. Hence, tailoring the microstructure can optimise the bulk strength parameters of the material.
Modelling of Thermal Fracture of Functionally Graded/Homogeneous Bimaterial Structures under Thermo-Mechanical Loading
Authors: Petrova Vera , Schmauder Siegfried
Published: November 2013

Mathematical modeling of thermal fracture of functionally graded/homogeneous bimaterial structures with a system of arbitrarily located cracks is performed and based on the previously suggested theoretical approach [1-which used the integral equation method. It is supposed that the structure is subjected to thermal loading (a thermal flux) and mechanical loading (a tension). The properties of the functionally graded material (FGM) are described by a continuous exponential function. The main fracture characteristics (stress intensity factors and fracture angles) are presented as functions of the geometry of the problem and special inhomogeneity parameters of FGMs. Some typical crack patterns for FGM/homogeneous bimaterial structures resulting from experiments available in literature are studied in detail. Thermal fracture of actual material combinations of FGMs such as: ceramic/ceramic, e.g., TiC/SiC, MoSi2/Al2O3 and MoSi2/SiC, and also ceramic/metal FGMs, e.g., zirconia/nickel and zirconia/steel, is investigated.
Identification of Structural Parameters of Metal Fibre Concrete Using Magnetic Approach
Authors: Vala Jiří , Hobst Leonard
Published: November 2013

Mechanical behaviour of concrete structures and their durability are conditioned by the reduction of cracking due to plastic and drying shrinkage and of permeability of concrete. This can be done using small metal particles, typically short steel fibres, randomly distributed in the concrete matrix. Since the technological requirements to the preparation and early-age treatment of such mixtures are rather demanding, some reliable a posteriori validation of expected solid material structure is needed. As alternatives to destructive testing, various low-invasive radiographic, electromagnetic, etc. approaches have been developed in the last decade. This paper demonstrates an original magnetic approach to the identification of volume fraction, macroscopic (in) homogeneity and orientation of particles in the matrix, using the Hall effect and the properties of solutions of the Laplace equation, as well as an advanced computational homogenization approach, coupled with the least-square based optimization technique.
Evaluation of Three-Point Bending Fracture Tests of Concrete Specimens with Polypropylene Fibres via Double-K Model
Authors: Havlíková Ivana , Majtánová Romana Viktória , Šimonová Hana , Láník Jaromír , Keršner Zbyněk
Published: November 2013

The fracture-mechanical parameter values of concrete, a quasi-brittle composite material, are determined via evaluation of records of experiments on specimens with stress concentrators. One of the fracture models applicable to concrete is the double-K model. This model combines the concept of cohesive forces acting on the effective crack increment with a criterion based on the stress intensity factor. The outputs of the model are critical crack tip opening displacement and fracture toughness values, including the initiation stress intensity factor value corresponding to the beginning of stable crack propagation. Outputs of three-point bending fracture tests of fibre reinforced concrete obtained using double-K fracture model are presented in this paper. The main aim is the determination and comparison of the above-mentioned parameter values of two types of the composite both without and with polypropylene fibres. Both types of tested composite had the same basic matrix consisting of cement, sand and water. In one case, gravel was used for normal weight concrete, in the other case lightweight aggregates were used for lightweight concrete. Both types of the testing matrix were designed with a similar value of compressive strength. Concretes were reinforced by spread polypropylene fibres of three lengths. There were made eight sets of testing concrete specimens: without fibres, and with fibres of 19 mm, 38 mm and 54 mm length. Dosage of fibres was 9 kg/m3 in all six cases.
Crack Growth Modelling in the Silicon Nitride Ceramics by Application of the Cohesive Zone Approach
Authors: Kozák Vladislav , Chlup Zdeněk
Published: November 2013

Specific silicon nitride based materials are considered according to certain practical requirements of process, the influence of the grain size and orientation on the bridging mechanisms was found. Crack-bridging mechanisms can provide substantial increases in toughness coupled with the strength in ceramics. The prediction of the crack propagation through interface elements based on the fracture mechanics approach and cohesive zone model is investigated and from the amount of damage models the cohesive models seem to be especially attractive for the practical applications. Using cohesive models the behaviour of materials is realized by two types of elements. The former is the element for classical continuum and the latter is the connecting cohesive element. Within the standard finite element package Abaqus a new finite element has been developed; it is written via the UEL (users element) procedure. Its shape can be very easily modified according to the experimental data for the set of ceramics and composites. The new element seems to be very stable from the numerical point a view. The shape of the traction separation law for three experimental materials is estimated from the macroscopic tests, JR curve is predicted and stability of the bridging law is tested.
Numerical Simulation of Damage to Fracture Transition in Metals Based on the Statistical Model of Mesodefect Evolution
Authors: Kostina Anastasia , Bayandin Yuriy , Naimark Oleg , Plekhov Oleg
Published: November 2013

A comprehensive approach, including statistical physics and thermodynamics is required in the modelling of phenomena underlying the processes of deformation and fracture of solids. This work is devoted to the description of the damage to fracture transition, using statistically based thermodynamic model of mesocracks and mesoshifts evolution. Numerical simulation of quasistatic tensile experiment of vanadium plate specimen illustrated the influence of bulk and shear defects on stress-strain state.
Influence of Microstructure, Environment and Temperature on Fatigue Crack Propagation in 2XXX Aluminium Alloys
Authors: Petit Jean , Sarrazin-Baudoux Christine , Gerland Michel
Published: November 2013

Aluminum alloys, widely used for constitutive parts of aircrafts are confronted to a wide range of temperature depending on altitude and climate, from room temperature on the ground down to some 223K at high altitude. The fatigue crack growth behavior of two new generation aluminum alloys, 2024A in T351 temper and 2022 in T351 and T851 tempers, have been investigated at both temperatures. It is shown that temperature and air humidity do not affect the crack growth resistance of the peak aged 2022 while these two parameters widely influence the crack growth in the under-aged alloys which exhibit in cold air a crystallographic retarded propagation similar to that in vacuum. The respective role of microstructure, temperature, atmosphere residual humidity and crack closure is discussed on the basis of a preexisting modeling framework for environmentally assisted fatigue.
Interrelation between Local and Global Characteristics of Cleavage Fracture
Authors: Grishchenko Vladimir , Kotrechko Sergiy , Mamedov Sergey , Zatsarna Oleksandra , Dlouhý Ivo
Published: November 2013

The complexity of calibration procedure for determination of Weibull distribution parameters as well as necessity to perform FEM calculations is one of the shortcomings of conventional versions of Local Approach (LA). This report presents an attempt to ascertain interrelation between local and global characteristics of fracture of pre-cracked and notched specimens of reactor pressure vessel steels, high-strength steels etc. Criterion of cleavage fracture initiation ahead of a crack (notch) is formulated. Dimensionless parameter characterizing the effect of embrittlement by the crack or notch is proposed on the basis of this criterion. Based on the findings of low-temperature tests of pre-cracked or notched specimens of structural steels, it is proved that this parameter may be determined by both local and global characteristics.
Fatigue Crack Propagation in Steels for Railway Axles
Authors: Náhlík Luboš , Pokorný Pavel , Hutař Pavel , Matušek Petr
Published: November 2013

The paper deals with the influence of order of cycles in the loading block on the fatigue crack growth rate in railway axle. The railway axle can include some cracks from manufacturing process or initiated fatigue cracks from previous operation. It is advantageous to know how the crack will behave during further service of the train to ensure its safe operation. The most common approaches describing the fatigue crack growth do not take into account the effects of overload cycles, which enlarge the plastic zone ahead of the crack tip. The enlarged plastic zone generates residual compressive stresses, which cause a retardation of the fatigue crack growth. Finite element numerical calculations were used together with the generalized Willenborg model to determine influence of overload cycles on the increment of fatigue crack growing in railway axles. Real geometry of the axle, the crack front shape and typical loading spectrum were taken into account.
Features of Shock-Wave Processes and Fracture in Anisotropic Materials
Authors: Radchenko Andrey , Radchenko Pavel , Batuev Stanislav
Published: November 2013

For the description of the behavior of anisotropic materials within the framework of the phenomenological approach the model which is taking into account distinctions in strength on compression and a stretching is offered. The model as allows carrying out researches with any orientation of properties of a material concerning system of coordinates. Numerical modeling is carried out in three-dimensional statement. The range of velocities of interaction up to 3000 m/sec is considered.
Analysis of Fatigue Damage Accumulation in TiAl Intermetallics
Authors: Beretta Stefano , Filippini Mauro , Patriarca Luca , Sabbadini Silvia
Published: November 2013

In this work, a Ti-48Al-2Cr-2Nb alloy obtained with a additive manufacturing technique by electron beam melting (EBM) has been examined by conducting high cycle fatigue tests both with plain specimens and with specimens with artificially introduced defects with the objective of studying the growth behavior of small cracks. A consistent model for predicting the fatigue endurance strength of specimens with artificial defects is proposed, based on the Kitagawa diagram and taking into account of the presence of inherent microstructural features of the studied intermetallic alloy. Thus, the origin of fatigue failures due to intermetallic phases and orientation of lamellar colonies was investigated by means of micromechanical analysis through the use of high-resolution Digital Image Correlation (DIC). The local strain heterogeneities were measured out of the load frame by means of an optical microscope at high magnifications. The strain maps were then overlaid with the images of the microstructure and detailed analyses were performed to investigate the features of the microstructure where high local strain heterogeneities arise. High local residual plastic strains were measured inside lamellar colonies, which are detected as the precursor to fatigue crack initiation. The measure of the residual strains also provides further information on the role of the intermetallic phases on the fatigue behaviour of γ-TiAl alloys.
Strength Hierarchy for Nano-Sized Crystals
Authors: Kotrechko Sergiy , Mikhailovskij Igor , Mazilova Tatiana , Ovsjannikov Oleksandr
Published: November 2013

A concept of atomic mechanisms governing strength of nanosized defect-free crystals is presented. It is exhibited that these mechanisms consist in local instability of the lattice. Two main reasons for localization of instability in three-dimension (3D) crystals are analyzed, namely, (i) fluctuation of local stresses induced by thermal vibrations of atoms, and (ii) non-uniform distribution of local stresses caused by a surface tension. Based on this conception, explanations of both the temperature dependence of strength of 3D nanocrystals and scale effect are given. Ideas on the reasons for and regularities of change in strength at transition from 3D to 2D (graphene) and 1D (monatomic chain) crystals are represented. It is shown that dimensionality of crystal is one of the main factors governing strength of defect-free crystals. Experimental values of the strength of carbon monatomic chains are given, which times exceeds the strength of graphene and is the highest attainable level of strength in the world.
Interface Influence on Dispersion Dynamic of Metal Nanowires under Electric Pulse Loading
Authors: Zolnikov Konstantin Petrovich , Kryzhevich Dmitrij Sergeevich , Abdrashitov Andreij Vladimirovich , Psakhye Sergei Grigorievich
Published: November 2013

The molecular dynamics simulation of nanoparticle synthesis under pulse electric dispersion of metal nanowires with interfaces was carried out. Atomic interactions were described using the potentials calculated within the framework of embedded method atom. Surface properties, defect structure energy, elastic characteristics and a number of other features, which are critical for the simulation of the electric pulse metal wire dispersion, can be described by these interatomic potentials with high accuracy. The nanowires simulated had a cylindrical shape. Along the cylinder axis use was made of periodic boundary conditions, while in the other directions, a free surface was simulated. Heating of the nanowires was performed by scaling of the atomic velocities following a linear law while maintaining a Maxwell distribution. In the course of high-rate heating the specimen experienced fracture followed by the formation of clusters. Influence of interfaces, heat rate, temperature distribution along sample profile on structure of generated nanoparticles was investigated. The atoms were assumed to belong to one cluster, given that the spacing between the nearest atoms was less than the threshold distance. The latter was assumed to be equal to the radius of the second coordination sphere in a perfect metal lattice.
Details of the Formation of Superstructures in the Process of Ordering in Cu-Pt Alloys
Authors: Starostenkov Mikhail D. , Chaplygina Alexandra , Romanenko Veronika
Published: November 2013

Alloys of Cu-Pt [1] are of interest for research, since the phase transitions "order - disorder" at different concentrations of components form several types of superstructures. In the alloy Cu3Pt the ordering L12 superstructure formed on the basis of fcc lattice. In the ordering of the fcc lattice of the disordered solid solution the equiatomic composition transformed into the L11 superstructure with an rhombohedral crystal lattice (a state with an L11, whose angles α, β, and γ are other than π/2). A CuPt3 in an ordered state has an L13 superstructure (a state with an L13, whose angles α, β, and γ are other than π/2). A possible existence of an ordered phase containing 20 at.% Pt was reported in the literature [2], which corresponds to the composition of Cu4Pt (type of superstructure was not defined). In other sources, an occurrence of an ordered compound, Cu7Pt, was predicted, containing 12.5 at.% Pt [3]. Computer experiments performed on the Monte Carlo method, showed that the alloys of the Cu - Pt different composition components undergo phase transformations "disorder - order" from the FCC to the structures of different symmetry [4,11]. This paper presents the results of a study of the structural transformations in the alloys Cu3Pt, CuPt, CuPt3 (superstructure L12, L11, L13), containing shear antiphase boundaries (APB) in the planes {111}.
Glass Surface Refining by Deposition of Nano-Particles
Authors: Drajewicz Marcin , Rokicki Paweł
Published: November 2013

In the paper a new surface refining technology which uses nano-particles to improve the soda – lime – silica glass surfaces is presented. The SEM-EDS (Energy Dispersive X-ray Spectrometry) analysis was carried out to determine modification of the glass surface. A very thin modification layer was observed on the glass surface. The surface modification leads to an improvement of physical and chemical properties of the investigated glass.
Quantum-Mechanical Study of Single-Crystalline and Polycrystalline Elastic Properties of Mg-Substituted Calcite Crystals
Authors: Friák Martin , Zhu Li Fang , Lymperakis Liverios , Titrian Hajjir , Aydin Ugur , Janus Anna Maria , Fabritius Helge Otto , Ziegler Andreas , Nikolov Svetoslav , Hemzalová Pavlina , Raabe Dierk , Neugebauer Joerg
Published: November 2013

We use quantum-mechanical calculations to study single-crystalline elastic properties of (Ca,Mg)CO3 crystals with concentrations ranging from calcite CaCO3 to magnesite MgCO3. By analyzing results for a dense set of distributions of Ca and Mg atoms within 30-atom supercells, our theoretical study shows that those atomic configurations, that minimize the total energy for a given concentration, are characterized by elastic constants that either increase with the Mg content or remain nearly constants. Employing these ab initio calculated single-crystalline elastic parameters, the polycrystalline elastic properties of (Ca,Mg)CO3 aggregates are determined using a mean-field self-consistent homogenization method. The computed integral elastic moduli (bulk and shear) show a significant stiffening impact of Mg atoms on calcite crystals. Our analysis also demonstrates that it is not advantageous to use a granular two-phase composite of stoichiometric calcite and magnesite instead of substituting individual Ca and Mg atoms. Such two-phase aggregates are not significantly thermodynamically favorable and do not offer any strong additional stiffening effect.
Analysis of Compressive Properties of Porcine Temporomandibular Joint Disc
Authors: Lamela María Jesús , Fernández Pelayo , Ramos Alberto , Canteli Alfonso Fernández , Tanaka Eiji
Published: November 2013

Since the temporomandibular joint (TMJ) disc material exhibits a non-homogenous and viscoelastic structure, the compressive properties in five different regions of eleven porcine TMJ discs were investigated over a wide range of loading frequencies. The results obtained suggest that the dynamic viscoelastic compressive modulus is region-specific and depends on the loading frequency, thus having important implications for the transmission of load in the TMJ. The dynamic storage and loss moduli increase with frequency, the highest values being attained at the posterior region, followed by the central and anterior regions. Loss tangent, tan δ, ranged from 0.20 to 0.35, which means that the disc is primarily elastic in nature and has a small but not negligible viscosity.
Experimental Studies of Elastic Properties of Dental Enamel and Photopolymer Used for early Caries Treatment
Authors: Beliaev Anton Yu. , Gileva Olga S. , Zuev Andrew L. , Muraveva Maria A.
Published: November 2013

The paper is concerned with the study of the elastic properties of dental enamel and its destruction by a microindentation technique. A series of experiments were performed to find differences in the mechanical properties of healthy and diseased dental enamel. It has been found that the times of dental enamel destruction in healthy and carious areas under a constant force are different. The effect of an infiltrated photopolymer on the hardness and elastic modulus of dental enamel was investigated by microindentation testing. A comparative analysis of the features of healthy, damaged by caries and treated by photopolymer enamel was carried out.
Solute Interaction in Grain Boundary Segregation and Cohesion
Authors: Lejček Pavel
Published: November 2013

Effect of solute interaction on interfacial segregation and grain boundary cohesion is modeled on basis of combined Guttmann and Rice-Wang approaches in binary and ternary systems. It is shown that attractive II binary interaction strengthens interfacial segregation and enhances intergranular embrittlement while repulsion exhibits an opposite effects. In a ternary system the segregation is suppressed by the IJ attraction while increased by the repulsion. The effect of the binary interaction is generally stronger compared to the ternary one.
Fibre-Matrix Interface Development during High Temperature Exposition of Long Fibre Reinforced SiOC Matrix
Authors: Chlup Zdeněk , Černý Martin , Strachota Adam , Halasová Martina , Dlouhý Ivo
Published: November 2013

The fracture behaviour of long fibre reinforced composites is predetermined mainly by properties of fibre-matrix interface. The matrix prepared by pyrolysis of polysiloxane resin possesses ability to resist high temperatures without significant damage under oxidising atmosphere. The application is therefore limited by fibres and possible changes in the fibre matrix interface. The study of development of interface during high temperature exposition is the main aim of this contribution. Application of various techniques as FIB, GIS, TEM, XRD allowed to monitor microstructural changes in the interface of selected places without additional damage caused by preparation. Additionally, it was possible to obtain information about damage, the crack formation, caused by the heat treatment from the fracture mechanics point of view.
Influence of Low Pressure Plasma Spraying Parameters on MCrAlY Bond Coat and its Microstructure
Authors: Góral Marek , Kotowski Slawomir , Dychtoń Kamil , Drajewicz Marcin , Kubaszek Tadeusz
Published: November 2013

Low pressure plasma spraying (LPPS) is one of the most advanced processes of an MCrAlY bond coat formation. It ensures the forming of metallic coatings free of oxides which can act as an bond coat for thermal barrier coatings used, among others, for protection of turbine blade surface. The paper presents results of tests into microstructure of coatings made from AMDRY 997 powder on the base of type Inconel 617 heat-resistant nickel alloy. The tests were carried out using light and scanning electron microscopy. Evaluated was the influence of spraying conditions on microstructure, porosity and thickness of the obtained coating. Test results show that the LPPS method allows to form coatings of low porosity and free of oxides which can be used as an bond coat in thermal barrier coatings.
The Changes of Fatigue Properties in Aluminium Cast Alloy during Solution Treatment
Authors: Hurtalová Lenka , Tillová Eva , Chalupová Mária
Published: November 2013

This paper describes the effect of solution treatment on the fatigue properties of AlSi9Cu3 cast alloy. The heat treatment consisted of a solution treatment at two different temperatures 515°C and 525°C, a holding time of 4 hours; water quenching at 40°C and natural aging at room temperature for 24 hours. Thus prepared samples were subjected to fatigue test with a rotating bending loading (testing machine ROTOFLEX operating at 30 Hz, load ratio R = -1). The fatigue fracture surfaces were observed using a scanning electron microscope (SEM) after the fatigue test. The results showed that the existence of casting defects (8.4 % of micro-shrinkage) has considerable influence on fatigue properties and can be considered as fatigue crack initiators in what leads to final fatigue damage. Apart from cast defects, the morphology of eutectic silicon and intermetallic phases (Fe- and Cu-rich phases) are also important factors which have an influence on the fatigue properties of Al-Si cast components. The solution treatment used (at 525°C/4hours) has increased fatigue properties (the fatigue lifetime increased from 49 to 76 MPa), thanks to Si particles, morphology changes, and cast defects area reduction as well as reduction Fe-rich phases.
Degradation of TBC Coating during Low-Cycle Fatigue Tests at High Temperature
Authors: Hutařová Simona , Obrtlík Karel , Juliš Martin , Čelko Ladislav , Hrčková Martina , Podrábský Tomáš
Published: November 2013

The work is focused on the study of degradation of ZrO2 stabilized by Y2O3 (YSZ) thermal barrier-coating system with CoNiCrAlY bond coat applied on cast polycrystalline nickel-based superalloy Inconel 713LC. Cylindrical specimens in as-coated conditions were cyclically strained under strain control with constant total strain amplitude in symmetrical cycle at high temperature (900 °C) in air. Coating system YSZ with CoNiCrAlY bond coat were prepared by APS method on blasted surface. The microstructure of TBC was characterized with scanning electron microscopy and energy dispersion X-ray analysis. The coating thickness and hardness profile was measured. Fracture surface, surface relief and polished sections parallel to the specimen axis were examined to study damage mechanisms in coatings under cyclic loading at high temperature. It was find that initiation of the fatigue crack usually occurs on interface YSZ-CoNiCrAlY and the trajectory of the further crack propagation was documented.
The Influence of Long-Term Heat Treatment on Microstructure of Zr-Modified Aluminide Coating Deposited by CVD Method on MAR M200+Hf Nickel Superalloy
Authors: Filip Ryszard , Góral Marek , Zawadzki Marcin , Nowotnik Andrzej , Pytel Maciej
Published: November 2013

The article presents the investigation of influence of long-term annealing of Zr modified aluminide coatings on its microstructure. The coatings were deposited by Chemical Vapour Deposition on MAR M200+Hf nickel superalloy. Annealing was carried out in a vacuum furnace at the temperature 1020°C within the period of 12, 16 and 20 hours respectively. The microstructral analysis was carried out using Hitachi S-3400 scanning electron microscope. Phase changes in the aluminide layer were observed, particularly the NiAl phase into Ni3Al. Changes in thickness of individual layers in the coating were observed. Conducted research showed that there is no influence of Zr on structure of the aluminide coating during annealing. The structure changes are similar to observed in simple aluminide coating. The maximum time of heat treatment without significant influence on structure of aluminide coating is 16 hours. After that time the main component of coating is NiAl phase.
Dynamic Stability of Ni FCC Crystal under Isotropic Tension
Authors: Řehák Petr , Černý Miroslav
Published: November 2013

Lattice dynamics and stability of fcc crystal of Ni under isotropic (hydrostatic) tensile loading are studied from first principles using supercell method and a harmonic approximation. According to the results, strength of the crystal is determined by occurrence of an instability related to soft phonons with finite wave vector. On the other hand, the critical strains and stresses associated with such instabilities are only slightly lower than those related to the volumetric instability.
The Effect of Long-Term Annealing on Microstructure of Aluminide Coatings Deposited on MAR M200 Superalloy by CVD Method
Authors: Nowotnik Andrzej , Sieniawski Jan , Zawadzki Marcin , Góral Marek
Published: November 2013

The paper presents the influence of long-term heat treatment on aluminide coating. The MAR M-200 nickel superalloy was use as base material. The aluminide coating was deposited in low-activity chemical vapour deposition process using Ion Bond BPX Pro 325s device with following parameters: temperature 1040°C, time 12 hours, pressure 150 mbar. The samples (14 mm diameter) were annealed at 1020°C in vacuum for 12, 16 and 20 hours respectively. The XRD phase analysis and SEM microstructural observation with EDS analysis were conducted. The phase composition analysis showed that after deposition the NiAl phase is a main component of the coating. After the 20-hour-long annealing presence of Ni3Al phase in the coating was observed. Changes in structure of coatings and Al content during heat treatment were detected as well. The maximum duration of heat treatment performed for Ni superalloy with aluminide coating without significant changes in coating phase composition and microstructure is 16 hours.