bluuebunny/crossref_metadata_2025 huggingface dataset:
Incorporation of Magnesium Ions into Synthetic Hydroxyapatite: Synthesis and Characterization
Authors: Salma-Ancane Kristine , Stipniece Liga , Borodajenko Natalija , Jakovlevs Dmitrijs , Berzina-Cimdina Liga
Published: November 2012

The objective of this work is to synthesize pure and Mg-substituted hydroxyapatite (HAp) powders with different MgO content in synthesis media (in the wide range of 0.1-10.0 wt% in respect to Ca), and to study the influence of Mg2+ ions substitution on the physicochemical properties of HAp materials. In this work HAp and magnesium-substituted hydroxyapatite (Mg-HAp) were synthesized by modified wet chemical precipitation of homogenous suspension of Mg(OH)2/Ca(OH)2 and H3PO4 solution. Systematic investigation on as-synthesized and sintered Mg-HAp and HAp samples shows that the incorporation of MgO promotes decomposition of HAp to β-tricalcium phosphate (β-TCP) and significantly modified its microstructure. The effect and evidence of incorporation of Mg2+ ions into HAp structure is discussed.
The Production of High Density Cast Iron Tubes by Horizontally Continuous Casting
Authors: Bockus Stasys
Published: November 2012

In this paper, a new technique to produce cast iron tubes used for liners of auto engines has been developed and examined. The tubes with an outer diameter of 90 mm and a wall thickness of 14 mm were produced massively by horizontally continuous casting. There are the values of casting parameters and constructions of crystallizers recommended for the continuous casting process of cast iron tubes in our paper. The metallographic microstructure, chemical composition and the mechanical properties of the tubes were investigated. The results of our investigations were successfully used for producing cast iron tubes suitable for liners of auto engines.
Preparation of TiB2-TiN and TiN-B Powders and their Processing
Authors: Grabis J. , Šteins Ints , Rašmane Dz.
Published: November 2012

TiN and TiN/TiBSubscript text2 nanoparticles with crystallite size of TiN in the range of 27–38 nm and TiBSubscript text2 in the range of 55–90 nm have been prepared by thermal plasma technique. The prepared nanoparticles and mechanical mixture of TiN with amorphous boron have been densified using spark plasma sintering and the microstructure and density of the samples were compared. The relative density of the samples with content of TiBSubscript text2 about 36 wt.% is in the range of 95.9–97.1% in dependence on the precursors. The higher relative density of the samples provided reactive sintering of TiN/B powder. The grain size of the composites in the range of 0.5–3 µm testified that spark plasma sintering intensified the grain growth in despite of the short sintering time.
Structure and Properties of Recycled Aromatic Thermoplastic Polyester Nanocomposites
Authors: Merijs Meri Remo , Zicans Janis , Ivanova Tatjana , Berzina Rita , Japins Guntis , Locs Janis
Published: November 2012

Structure as well as mechanical and thermal properties of the nanocomposites based on recycled polyethylene terephthalate (RPET) are investigated. 1, 2 and 5 wt. % of unmodified montmorillonite nanoclay (MMT) were introduced in the RPET matrix by melt compounding in a twin screw extruder. Results of the investigations testify that optimum content of MMT for modification of RPET is between 1 and 2 wt. %. Up to this nanofiller weight content, the most rapid increase of stiffness, strength and impact toughness is observed. Besides it, at this nanofiller weight content the investigated composite have somewhat improved thermal resistance. It is demonstrated that the improvement of these properties is due to better distribution of MMT in the polymer matrix. At higher nanofiller content, the undesirable effects of the nanofiller agglomeration becomes more important.
Densification and Microstructure Development in Zirconia Toughened Hardmetals
Authors: Voltsihhin Nikolai , Hussainova Irina , Cura M. Erkin , Hannula Simo Pekka , Traksmaa Rainer
Published: November 2012

Different process methods and parameters together with different amount of additives were used to fabricate WC-Ni-ZrO2 hardmetals with mechanical properties aiming at improved performance under erosive wear. XRD observation showed the presence of tetragonal zirconia in the cermet matrix after processing. The best erosion resistance with erosion rate of about 0.7 mm3/kg was demonstrated by the specimen produced either by vacuum sintering or SPS and added by 0.2 wt% of free carbon. This cermet has also demonstrated the highest hardness of 17.7 GPa.
Influence of Pressurized Sintering on Performance of TiC-Based Cermets
Authors: Kübarsepp Jakob , Klaasen Heinrich , Tšinjan Aleksei , Juhani Kristjan , Kollo Lauri , Viljus Mart
Published: November 2012

This paper discusses the effect of advanced sintering technologies – sinter + hot isostatic pressing (HIP) and sinter/HIP on the performance of TiC-based cermets. The performance was evaluated by strength (transverse rupture strength), adhesive wear resistance and durability. Adhesive wear was performed by a turning method (turning of mild steel at low speed) while durability was evaluated by functional testing – wear of tools during blanking of sheet metal. It was found that sinter/HIP ensures a higher positive effect than sinter + HIP in different cycles.
Critical Radius in the Effect of Transformation Toughening of Zirconia Doped Ceramics and Cermets
Authors: Freidin Alexander B. , Filippov Roman A. , Hussainova Irina , Vilchevskaya Elena N.
Published: November 2012

Possible increase in fracture toughness of ceramics can be derived from stress induced martensite transformation from tetragonal to monoclinic polymorph of ZrO2particles embedded into a bulk ceramic material. The incidence of transformations depends on zirconia particle size: too small particles remain overstabilized and do not experience transformation while too large particle may spontaneously transform at the technological stage of cooling. The critical particle size is, therefore, of primary concern for toughening of intrinsically brittle materials. We give a brief review of the previous results obtained. Then basing on the Gibbs energy expression and taking into account interface surface energy as well as thermal stresses, external loading and elastic interaction of the inclusions we estimate the proper range of particle sizes needed for considerable increase in fracture toughness. We specify general results obtained for the case of yttria stabilized ZrO2particles in Al2O3- and WC-based ceramics.
The Rolling Contact Fatigue of PVD Coated Spur Gears
Authors: Michalczewski Remigiusz , Piekoszewski Witold , Szczerek Marian , Tuszynski Waldemar , Antonov Maksim
Published: November 2012

The aim of the study was to investigate the resistance to rolling contact fatigue of a C:H:W and MoS2/Ti coated gears. The investigation of rolling contact fatigue was realised by means of a gear test rig using FZG PT C/10/90 pitting test. Four material combinations of gears were tested: wheel and pinion uncoated, wheel and pinion coated, wheel coated and pinion uncoated as well as wheel uncoated and pinion coated. The tests were performed using for lubrication mineral gear oil of API GL-5 performance level and 80W/90 viscosity grade. The results indicate that for the coated/coated pair (pinion and wheel coated) and coated pinion/steel wheel pair a significant decrease in the fatigue life compared to the uncoated gears was obtained. The best results were obtained in the case of the uncoated pinion / a-C:H:W coated wheel – even fourfold increase in the fatigue life was observed. This shows a very high potential of application of PVD coatings for gears.
Influence of Surface Morphology on the Tribological Behavior of Diamond-Like Carbon Coating
Authors: Podgursky Vitali , Bogatov Andrei , Freund Martin , Kulu Priit
Published: November 2012

Diamond-like carbon (DLC) films were prepared in-situ on top of hard coatings, namely, prior to the DLC deposition, CrN, TiCN and nanocomposite nACo (nc-AlTiN/(a-Si3N4) layers were deposited on WC-Co substrates. The Ra roughness of WC-Co substrates was 0.05 and 0.2 µm. Surface morphology of DLC coatings was investigated by means of profilometry and geometrical parameters Ra, Rsk, Rku and Rz were evaluated. Fretting tests were conducted with 3 mm in diameter alumina balls under 1 and 2 N load, at slip distance of 2 mm and frequency of 2 Hz. Statistical analysis shows significant correlation between Ra and Rz parameters corresponding to initial DLC surface and wear scar surfaces produced by fretting tests after 2400 and 4800 cycles, respectively. This finding indicates a relationship between friction (wear) and Ra and Rz parameters. Positive correlation between the coefficient of friction (COF) and kurtosis Rku indicates that surface flatness is an important factor for optimal friction of an alumina ball against DLC coating.
Development of TiB2-Based Cermets with Fe-Mo Binder
Authors: Panasuk A. , Umanskyi A. , Storozhenko M. , Akopyan V.
Published: November 2012

In this study, the wettability and interaction of TiB2with melted iron and iron-molybdenum alloys have been investigated. The wetting contact angles were determined, the structure and phase composition of the drops have been investigated by the methods of energy dispersive X-ray microanalysis. The results showed that TiB2–(Fe-13%Mo) system prove to be an optimum one for the new cermets production because of good wetting and minimal interaction between components. The TiB2-(Fe-13wt.%Mo) cermets were produced by sintering in vacuum. The influence of initial TiB2particles size on the structure formation of the cermets above has been established.
Ductile Fracture in Metal Forming: A Review of Selected Issues
Authors: Alexandrov Sergei , Lyamina Elena
Published: November 2012

The paper reviews several theoretical and experimental methods for the assessment of ductile fracture criteria and for their application to the fracture prediction in metal forming processes. In particular, distinguished features of two widely used ductile fracture criteria are demonstrated in the case of free surface fracture. Conventional empirical ductile fracture criteria are not compatible with behaviour of plastic solutions in the vicinity of maximum friction surfaces. An approach to overcome this difficulty is discussed. Finally, a theoretical/experimental method to reveal a possible effect of geometric singularities on the applicability of ductile fracture criteria is reviewed.
Identification of Defects in an Elastic Body by Means of the Boundary Measurements
Authors: Shifrin E.I. , Shushpannikov Pavel S.
Published: November 2012

A problem of identification of a single defect (a crack, a cavity or an inclusion) in an anisotropic, linear elastic body using boundary measurements is considered. An analytical solution of the problem of ellipsoidal defect identification in an infinite elastic solid is presented in the conditions when arbitrary constant stresses are applied at the infinity and the loads and displacements are known on a closed surface, containing the defect inside. The problem is solved using reciprocity gap functional method. The obtained analytical solution is used for solving the problem of ellipsoidal defect identification in a bounded elastic body by means of the results of one static test. It is assumed that the loads and displacements are measured on the external boundary of the body. Numerical examples illustrating efficiency of the developed method are considered. Stability of the results relative to the noise in the data and variation of the defect shape is studied.
Investigation of the Asymptotic Behavior of Stresses at the Tip of Wedge- and Cone-Shaped Cracks
Authors: Korepanova T. , Matveenko V.P. , Sevodina N.
Published: November 2012

Numerical method is proposed for construction of singular solutions for spatial crossing wedge-and cone-shaped cracks. The results of numerical simulations made in the study allowed us to estimate the stress singularity indices at the tip of wedge-shaped cracks for different boundary conditions on the crack faces and at the tip of crossing cone cracks. The stress singularity at the tips of cone-shaped cracks is investigated.
Grain Refinement of AZ61/SiCp Magnesium Matrix Composites for Tubes Extruded by Hot Extrusion Processes
Authors: Huang Song Jeng , Hwang Yeong-Maw , Huang Y.S.
Published: November 2012

Magnesium (Mg) alloys are gaining more recognition as a lightest structural material for light-weight applications, due to their low density and high stiffness-to-weight ratio. Nevertheless, their ductility is still not good for further metal forming and their strength is not large enough for real structure applications. The aim of this paper is to develop new magnesium metal matrix composites (Mg MMCs) reinforced with SiC particles by the stir-casting method for the hot extrusion processes to produce tubes. AZ61/SiCp MMCs ingots reinforced with 1, 2, and 5 wt% SiC particles are fabricated by the melt-stirring technique. AZ61/SiCp MMCs tubes are manufactured by hot extrusion using a specially designed die-set for obtaining uniform thickness distribution tubes. Finally, the mechanical properties of the reinforced AZ61/SiCp MMCs and Mg alloy AZ61 tubes are compared with those of the billets to manifest the advantages of extrusion processes and addition of SiC particles. The microstructures of the billet and extruded tubes are also observed. Obvious grain size refinement both by addition of particles and extrusion process are discovered.
Fluid Flow Control in Micro- and Nanochannels
Authors: Indeitsev Dmitry A. , Abramyan Andrey K.
Published: November 2012

In the present paper, we propose new equations describing the fluid behavior in nanochannels with its molecular structure. We consider the Poiseuille flow and the flow throw the channel with vibrating walls. The obtained results show that it is possible to describe the structural transformations in thin layers by using the continuum mechanics methods. We introduce new degrees of freedom of the material by introducing the second continuum, which plays the role of the arising new phase of state. In the models considered here, the properties of the new phase are determined by the influence of rigid boundaries with a different structure.
Accumulation and Healing of Damage during Plastic Metal Forming Simulation and Experiment
Authors: Smirnov S.V.
Published: November 2012

Based on the analysis of experimental data on measuring metal density under plastic deformation, an adaptive model of damage accumulation, which takes into account the transient processes of damage variation with changes in loading conditions, has been formulated. The analysis of damage in the process of cold closed-die forging of a lid-type steel blank being taken as an example, the applicability of the model to the prediction of fracture in the optimization of industrial metal forming technologies has been demonstrated.
Modes of Stability Loss of Materials
Authors: Kashtanova Stanislava , Morozov N.F. , Tovstik P.E.
Published: November 2012

Three problems of stability loss are investigated and corresponded buckling modes are discussed. The first one is the stability loss of a compressed transversely isotropic linearly elastic medium. The standard analysis based on the Hadamard condition is conducted to solve this problem. The critical compression could be uniquely defined from the bifurcation equations but not a wave length. So, the buckling mode remains generally indefinite. The second considered problem is the stability loss of a compressed half-space with a free surface. It could be shown that the waviness is localized near the free plane surface but as for an entire space the wave length and the buckling mode are indefinite. These problems are treated in linear and nonlinear statement. In linear approach the pre-buckling deformations are ignored. It is shown that for some values of parameters the linear approach leads not only to the numerical error but also to qualitatively incorrect results. The thisrd problem under investifation is the stability loss of an uniformly compressed plate lying on a soft elastic half-space. In this problem the wave length is uniquely defined. Using the nonlinear post-critical analysis it is shown that the buckling mode could be fully defined and is has a chessboard-like character.
Development of a Novel Pvt Measuring Technique
Authors: Szabó Ferenc , Kovács József Gábor
Published: November 2012

The pressure-temperature-specific volume relation of polymers is important not only for physical chemistry, but they are very significant input data for injection molding simulation software. Todays methods for measuring pvT data are slow, measurements can take days to be carried out, and in many cases the accuracy of the measurement is unsatisfactory. In our work, a new measuring method has been developed which makes the determination of the pvT relation faster compared to conventional processes within injection molding processing conditions. For the measurements a special injection mould was developed, in which the pvT relation of the material can be determined from the shrinkage in the mold. The data measured by the new method using polypropylene at a mold temperature of 23°C were compared to the data given in the database of the simulation software.
Loading Simulations of Carbon Nanotube Junctions
Authors: Pataki T. , Zsoldos I.
Published: November 2012

Weakest points of carbon nanotube junctions have been determined by molecular mechanical algorithms. This algorithm is based on the application of the so-called Brenner potential function, atomic forces are calculated from the derivatives of the potential function describing the energetics. Behavior of various types of symmetric Y-junctions is studied with respect to axial tensile load.
In Situ Synthesis of a Wear Resistant Layer on the Surface of Low Carbon Steel Produced by Laser Melt Injection Technology
Authors: Mertinger Valéria , Buza Gábor , Major Balázs
Published: November 2012

Titanium and its compounds are one of the most frequently used reinforcing particles in iron ceramic composite materials. These materials have special characteristics because they are quenchable, their hardness can be increased by heat treatment and they can be quite easily machined. The point of the technology developed in the Bay Zoltán Institute of Materials Sciences and Technology is to form the reinforcing layer on the surface of the sample in an in situ way by melting the surface of the low carbon steel and the laminar carbon felt using laser beam while the titanium metal powder is simultaneously added to the melt. Several methods (metallographic examinations, selective area hardness measurements, SEM, and XRD) were applied to answer the questions about the optimal conditions for the in situ synthesis of a wear resistant layer.
On the Fabrication Parameters of Buried Microchannels Integrated in In-Plane Silicon Microprobes
Authors: Fekete Z. , Pongrácz A. , Márton G. , Fürjes P.
Published: November 2012

This paper aims the characterization of buried microchannels in silicon realized by deep reactive ion etching. The effects of dry etching parameters on the integrability into hollow microprobes are thoroughly investigated from both technological and functional aspects. Results are supposed to give physiology related probe designers a deeper insight into microfabrication-related issues.
Microstructure and Thermal Stability of Copper - Carbon Nanotube Composites Consolidated by High Pressure Torsion
Authors: Jenei P. , Yoon E.Y. , Gubicza Jenő , Kim Hyoung Seop , Lábár J.L. , Ungár Tamás
Published: November 2012

Blends of Cu powders and 3 vol. % carbon nanotubes (CNTs), and an additional sample from pure Cu powder were consolidated by High Pressure Torsion (HPT) at room temperature (RT) and 373 K. The grain size, the lattice defect densities as well as the hardness of the pure and composite materials were determined. Due to the pinning effect of CNTs, the dislocation density is about three times larger, while the grain size is about half of that obtained in the sample consolidated from the pure Cu powder. The increase of the HPT-processing temperature from RT to 373 K resulted in only a slight increase of the grain size in the Cu-CNT composite while the dislocation density and the twin boundary frequency were reduced significantly. The flow stress obtained experimentally agrees well with the value calculated by the Taylor-formula indicating that the strength in both pure Cu and Cu-CNT composites is determined mainly by the interaction between dislocations. The addition of CNTs to Cu yields a significantly better thermal stability of the UFG matrix processed by HPT.
Development of Nitinol Stents: Etching Experiments
Authors: Katona Bálint , Nagy Péter , Bognár Eszter , Hirschberg Kristóf
Published: November 2012

The present study focus on the chemical etching of shape memory nickel-titanium (nitinol) alloy stents made by laser cutting. Application of nitinol stents widely spread in case of atherosclerosis of peripheral vessels. This type of stent has to have appropriate surface quality, flexibility and strength. The aim of chemical etching is removing the burr, which arises during the laser cutting. Etching is one step of the production of stents. The appropriate parameters allow the laser burned surface and most of protruding material removing without significant damage of stent shape. During these experiments etching time was changed. After etching the cross section area was determined by metallographic examinations. The results of the examinations show the relationship between the etching time and the cross-section area. The analysis of measurement data revealed the change of etching velocity. Before and after etching the samples was examined by scanning electron microscopy (SEM). The different surfaces also were compared and the findings were discussed.
Bone Formation with Nano-Hydroxyapatite from Eggshell
Authors: Balázsi Csaba , Gergely Gréta , Balázsi Katalin , Chae Chang Hoon , Sim Hye Young , Choi Je Yong , Kim Seong Gon
Published: November 2012

Hydroxyapatite, (Ca10(PO4)6(OH)2 is chemically similar to the mineral component of bones and teeth. HAp is among of the few materials that are classified as bioactive, meaning that it will support bone ingrowth and osseointegration when used in orthopaedic, dental and maxillofacial applications. Hydroxyapatite may be employed in forms such as powders, porous blocks and hybrid composites to fill bone defects or voids. These may arise when large sections of bone have had to be removed or when bone augmentations are required (e.g. dental applications). In this work, nanohydroxyapatite (nanoHAp) was successfully produced by using recycled eggshell and phosphoric acid by mechanochemical activation method (e.g. attrition milling). nanoHAp bioactivity was evaluated in animal (rabbit) models. Sixteen 4-month-old New Zealand white rabbits with an average weight of 2.8kg were used in experiments. After bilateral parietal bony defects formation (diameter: 8.0mm), nanoHAp was grafted. The control was unfilled defect. The bone regeneration was evaluated by micro-computerized tomograms (μCT) and histomorphometric analysis at 4 and 8 weeks. In conclusion, nanoHAp from eggshell showed much more bone formation compared to unfilled control group in both μCT analysis and histomorphometric analysis. Considering that the eggshell is easily available and cheap, nanoHAp from the eggshell can be good calcium source in tissue engineering.
Nanostructure Layer Formation on Cu-Zr-Al Alloy during Laser Remelting
Authors: Svéda Mária , Janovszky Dóra , Tomolya K. , Sólyom J. , Buza G. , Roósz A.
Published: November 2012

This paper reports laser remelting of crystalline Cu based alloys in order to produce amorphous layer on the surface. The as prepared Cu based master alloy ingots were imbedded in a metallic sinking with Wood metal to assure the good thermal conductivity during the laser treatment. The laser remelting of a thin surface layer and a subsequent rapid cooling of it was performed using impulse and continuous mode of Nd:YAG laser. In respectively the impulse mode the laser power and the interaction time were 1.5; 2 kW and 20÷100 ms. In the continuous mode the laser power was 2 kW, and the laser scan speed was 80÷120 mm/s. The characterization of the microstructure of surface layer was performed by XRD, scanning electron microscopy and microhardness measurements.
Calculation of Elastic Energy Contributions in Single Crystalline Cu-11.5wt%Al-5.0wt%Ni Shape Memory Alloy
Authors: Elrasasi Tarek Y. , Daróczi Lajos , Beke Dezső L.
Published: November 2012

Using our local equilibrium model of the martensitic transformation [ the elastic energy contributions, as the function of martensite volume fraction, ξ, in the phase transformation of single crystalline Cu-11.5wt%Al-5.0wt%Ni shape memory alloy were calculated from our measurements published earlier [. The derivative of the elastic energy δE/δξ=e (E is the total elastic energy stored/released during the austenite to martensite (AM) as well as MA transformation) could be calculated only irrespectively of the ST0 term (T0 is the equilibrium transformation temperature and S is the entropy change of phase transformation). But, since ST0 is independent of ξ, the functions obtained reflect the ξ dependence of e as well as E quantities. From the DSC curves measured at zero uniaxial stress (σ = 0) [, the ξ-T hysteric loop was constructed. Then the e (ξ) curves at fix σ as well as fix T were calculated. The E values obtained from the integral of e (ξ), fit well to the E(σ) as well as E(T) curves calculated from the strain-temperature and stress-temperature curves measured in [.
Development of Ferritic-Pearlitic, Pearlitic and Spheroidite Initial Structures for Simulating the Austenitization in Unalloyed Steels
Authors: Karacs Gábor , Roósz András
Published: November 2012

Our aim was to develop initial structures similar to the real structures of unalloyed steels that could later be used for simulating austenitization. Both simple models and models that can be compared to the real structures were developed. In our paper, it is described how the initial structures were developed by using digitalized microscopic images.
Correlation between Milling Parameters, Structural and Mechanical Properties of Nanostructured Austenitic Y2O3 Strengthened Steels
Authors: Koncz Péter , Horváth Ákos , Balázsi Katalin , Şahin Filiz Çinar , Göller G. , Onüralp Yücel , Balázsi Csaba
Published: November 2012

In this paper, the correlation between structural and mechanical properties of nanostructured austenitic oxide dispersion strengthened (ODS) steel prepared by powder metallurgy were studied. High efficient milling process was applied to achive an optimal dispersion of ceramic oxide particles in the steel matrix. The austenitic powder with or without Y2O3 addition was milled by two different milling process (wet and dry). Spark plasma sintering as a fast and effective compaction method was used as sintering equipment. The morphology and structural properties of ODS were studied by X-ray diffraction and scanning electron microscopy. Mechanical properties, such as microhardness, bending strength and modulus of nanostructured ODS were also determined.
The Hardness Control in the Coated Surface Layer
Authors: Kovács Tünde Anna , Bitay Enikő
Published: November 2012

This paper wants to find one of the solutions to control the coated surface properties. The surface layers control is not easy. We have a very simple test like hardness test to get some important information of the surface, but in case of the coatings we need to do this test very circumspectly. The hardness test results always depend on the surface roughness, the coating microstructure, the layer thickness and the type and load of the hardness test. The chose method was the nanohardness test which gave the penetration depth us function of the very small load.
Development of Nitinol Stents: Electropolishing Experiments
Authors: Lengyel Ákos , Nagy Péter , Bognár Eszter , Hirschberg Kristóf
Published: November 2012

As a result of the collective efforts of engineers and physicians modern medicine is one of the most developed discipline nowadays. The invention of stents is one of the most important result of these works. With development of stents artery narrowing, which can often lead to death, can be efficiently treated. The stent is a biocompatible mesh, which is inserted into the narrowed section of the artery to dilate and prop up its wall hereby it ensures continuous blood flow. The bio-and haemocompatibility of stents have to be sufficient to avoid significant recurrent stenosis (restenosis). Better biocompatibility can be achieved using surface treatments such as chemical etching, electropolishing and coatings. In our research we developed self-expandable stents made of shape memory Ni-Ti alloy called nitinol. In this article the present stage of our work, the electropolishing experiments are summarized. A new electropolishing cell was worked out by using special stent holder to lead the current to the stent, which made possible the even electropolishing of the stent surface. The electrolyte, which was applied, contains less than 5% of perchloric acid. A current interval was determined which will be sufficient to determine the optimal polishing parameters, such as polishing time and current density with further researches.
The Effect of Multiple Forging and Cold Rolling on Bending and Tensile Behavior of Al 7075 Alloy
Authors: Naser Tareg S. Ben , Krallics György
Published: November 2012

This work studies the effect of multiple forging (MF), followed by cold rolling, on the tensile and bending behavior of Al 7075 alloy. The raw material was received as a rod shape. The specimens were subsequently cut and annealed at 450 °C for 30 minutes. The cylindrical specimens were subjected to MF at 250°C for three passes, then the bulk of multiple forging specimens were faced rolling at room temperature. Three different base materials were tested, raw material (as received then annealed), MF material, and rolled sheet. Hardness test, tensile test, and bending test were carried out in order to measure the mechanical properties, which are affected by the MF and cold rolling. It has been proved that the MF base specimens have higher tensile strength and better maximum elongation comparing with the raw material specimens. Rolled sheets specimens have got the highest tensile strength and lowest ductility. The result of bending test was similar to the tensile test results, beside these mechanical tests some metallographic samples were performed to help finding an explanation of this properties change.
Kinking Resistance of Guidewires
Authors: Pelyhe Liza , Bán Melinda , Bognár Eszter
Published: November 2012

The guidewire is a small diameter, steerable wire which facilitates the navigation of the interventional devices such as stent, balloon, or coil in endovascular intervention. The guidewire has an elongated flexible body and a relatively more flexible ribbon tip. The elongated body (shaft) is tapered to the ribbon tip. The composition of the helical coil formed ribbon tip is different than the elongated body. In this article we demonstrate the correlation between the material composition and the kinking resistance of guidewire. The identified metal composition of the core wire was 18-8 stainless steel and the helical coil composed of platinum-nickel alloy and the material of tip bond was tin. The kink angle which caused permanent deformation were significantly higher on the helical coil (=68,3o) due to the higher flexibility of the helical coil than that was found on the shaft portion (=55o) (p=0,00032). The remnant angel induced by 90o kinking on the helical coil was significantly lower (=15o) than that was observed on the shaft portion (=23,9o) (p=0,00046). The deformation of the helical coil was smaller due to the higher flexible properties of the platinum-nickel alloy material against the stainless steel.
In Vivo Failure Phenomena of Ultra-High Molecular Weight Polyethylene Acetabular Cups
Authors: Zsoldos Gabriella , Bárczy Pál , Szabó Tamás József
Published: November 2012

During this study the distortion phenomenon was investigated on selected UHMWPE cups removed from patients, using 3dimensional measurement method. The cups investigated were machined by Metrimed Ltd. from ram extruded Chirulen 1020 type UHMWPE rods. The samples were measured with a 3D touch coordinate measurement device with an accuracy of 3 microns.
Development of Thermally Conductive Polymer Materials and their Investigation
Authors: Suplicz András , Kovács József Gábor
Published: November 2012

In the recent years a remarkable development can be observed in the electronics. New products of electronic industry generate more and more heat. To dissipate this heat, thermally conductive polymers offer new possibilities. The goal of this work was to develop a novel polymer based material, which has a good thermal conduction. The main purpose during the development was that this material can be processed easily with injection molding. To eliminate the weaknesses of the traditional conductive composites low-melting-point alloy was applied as filler. Furthermore in this work the effect of the filler content on thermal conductivity, on structure and on mechanical properties was investigated.
Influence of the Cohesive Law Parameters on the Strength Prediction of Adhesively-Bonded Joints
Authors: Campilho Raul D.S.G. , Chaves Filipe J.P. , Pinto Arnaldo M.G. , Banea Mariana D. , da Silva Lucas F.M.
Published: November 2012

Adhesive joints are largely employed nowadays as a fast and effective joining process. The respective techniques for strength prediction have also improved over the years. Cohesive Zone Models (CZM’s) coupled to Finite Element Method (FEM) analyses surpass the limitations of stress and fracture criteria and allow modelling damage. CZM’s require the energy release rates in tension (Gn) and shear (Gs) and respective fracture energies in tension (Gnc) and shear (Gsc). Additionally, the cohesive strengths (tn0 for tension and ts0 for shear) must also be defined. In this work, the influence of the CZM parameters of a triangular CZM used to model a thin adhesive layer is studied, to estimate their effect on the predictions. Some conclusions were drawn for the accuracy of the simulation results by variations of each one of these parameters.
Mechanical Behavior of the Lamellar Structure in Semi-Crystalline Polymers
Authors: Simões Ricardo , Viana Julio , Dias Gustavo R. , Cunha António M.
Published: November 2012

We have employed molecular dynamics simulations to study the behavior of virtual polymeric materials under an applied uniaxial tensile load. Through computer simulations, one can obtain experimentally inaccessible information about phenomena taking place at the molecular and microscopic levels. Not only can the global material response be monitored and characterized along time, but the response of macromolecular chains can be followed independently if desired. The computer-generated materials were created by emulating the step-wise polymerization, resulting in self-avoiding chains in 3D with controlled degree of orientation along a certain axis. These materials represent a simplified model of the lamellar structure of semi-crystalline polymers, being comprised of an amorphous region surrounded by two crystalline lamellar regions. For the simulations, a series of materials were created, varying i) the lamella thickness, ii) the amorphous region thickness, iii) the preferential chain orientation, and iv) the degree of packing of the amorphous region. Simulation results indicate that the lamella thickness has the strongest influence on the mechanical properties of the lamella-amorphous structure, which is in agreement with experimental data. The other morphological parameters also affect the mechanical response, but to a smaller degree. This research follows previous simulation work on the crack formation and propagation phenomena, deformation mechanisms at the nanoscale, and the influence of the loading conditions on the material response. Computer simulations can improve the fundamental understanding about the phenomena responsible for the behavior of polymeric materials, and will eventually lead to the design of knowledge-based materials with improved properties.
Numerical and Experimental Study of Tensile Strength of Single and Double-Strap Repairs
Authors: Pinto Arnaldo M.G. , Campilho Raul D.S.G. , Mendes Isabel R. , Magalhães A.G. , Baptista A.P.M.
Published: November 2012

Adhesive bonding as a joining or repair method has a wide application in many industries. Repairs with bonded patches are often carried out to re-establish the stiffness at critical regions or spots of corrosion and/or fatigue cracks. Single and double-strap repairs (SS and DS, respectively) are a viable option for repairing. For the SS repairs, a patch is adhesively-bonded on one of the structure faces. SS repairs are easy to execute, but the load eccentricity leads to peel peak stresses at the overlap edges. DS repairs involve the use of two patches, one on each face of the structure. These are more efficient than SS repairs, due to the doubling of the bonding area and suppression of the transverse deflection of the adherends. Shear stresses also become more uniform as a result of smaller differential straining. The experimental and Finite Element (FE) study presented here for strength prediction and design optimization of bonded repairs includes SS and DS solutions with different values of overlap length (LO). The examined values of LO include 10, 20 and 30 mm. The failure strengths of the SS and DS repairs were compared with FE results by using the Abaqus® FE software. A Cohesive Zone Model (CZM) with a triangular shape in pure tensile and shear modes, including the mixed-mode possibility for crack growth, was used to simulate fracture of the adhesive layer. A good agreement was found between the experiments and the FE simulations on the failure modes, elastic stiffness and strength of the repairs, showing the effectiveness and applicability of the proposed FE technique in predicting strength of bonded repairs. Furthermore, some optimization principles were proposed to repair structures with adhesively-bonded patches that will allow repair designers to effectively design bonded repairs.
Enhancing the Response of Chemocapacitors with Electrospun Nanofiber Films
Authors: Igreja Rui , Domingos H. , Borges João Paulo , Dias C.J.
Published: November 2012

Chemocapacitors are polymer coated Interdigital electrodes (IDE) where the transducer mechanism relies on the permittivity changes and swelling of the coating polymer (sensitive layer), usually in a form of a thin film, when exposed to an volatile organic compound (VOC). Despite several synthetic and natural polymers have already been produced by electrospinning, there have been fewer studies on rubbery polymers with low glass transition temperature (e.g. Poly(dimethyl siloxane) – PDMS). In this work we produce PDMS:PMMA 3:1 nanofiber (NF) layers by electrospinnig to be used as chemical sensitive layers on IDE chemocapacitors. The results show an enhanced response from the sensors with NFs with respect with sensors prepared with the same sensitive layers in the form of a homogeneous film.
Fractal Analysis of Coated Papers
Authors: Velho J. , Santos N.F.
Published: November 2012

The main goal of this research is to apply AFM to the analysis of coated paper topography in order to find out relationships between sheet gloss and some parameters obtained from AFM, such as roughness and fractal dimension (D). Flooding technique was also developed using appropriated software. Number of hills/flooding volume for 25%, 50% and 75% flooded volume was applied in this research. Ground calcium carbonate and precipitated calcium carbonate were applied in coating colour formulations, alone and blended in three formulations, 75:25, 50:50 and 25:75. The results obtained showed high correlations between sheet gloss with fractal dimension (D) parameter. Finally, flooding technique showed to be very interesting, all of them gave useful information in interpreting the influence of topography on sheet gloss.
Cementitious Composites Reinforced with Polypropylene, Nylon and Polyacrylonitile Fibres
Authors: Pakravan H.R. , Jamshidi M. , Latifi M. , Pacheco-Torgal F.
Published: November 2012

This paper compares the adhesion strength between three polymeric fibres (polypropylene (PP), nylon66 (N66) and polyacrylonitrile (PAN)) embedded in a cement paste. The specimens were prepared at a water to cement ratio (w/c) of 0.5 and tested after 7, 14 and 28 curing days. It was found that although the adhesion between the polymeric fibres to the cement matrix is an important factor, the energy absorption capacity or energy dissipation ability of the fibres, plays a more important role in the improvement of the cementitious composites fracture toughness. Scanning electron micrographs were used to characterize the fibres surface before and after the Pull-out tests.
Composite Material Sensitive to Volatile Organic Compounds
Authors: Lima Roberto R. , Hernandez Leonardo F. , Pecoraro Edsion , Rosim-Fachini Estevão , da Silva Maria L.P.
Published: November 2012

This work evaluates fluorinated thin films and their composites for sensor development. Composites were produced using 5 µm starch particles and plasma films obtained from organic fluorinated and silicon compounds reactants. Silicon wafers and aluminum trenches were used as substrates. Film thickness, refractive index and chemical structure were also determined. Scanning electron microscopy shows conformal deposition on aluminum trenches. Films deposited on silicon were exposed to vapor of volatile organic compounds and CV curves were obtained. A qualitative model (FemLab 3.2® program) was proposed for the electronic behavior. These environmentally correct films can be used in electronic devices and preferentially reacted to polar compounds. Nonetheless, due to the difficulty in signal recovery, these films are more effective in one-way sensors, in sub-ppm range.
Effect of Sintering Isothermal Time on Mechanical Properties of Metal Matrix Composite
Authors: de Oliveira Leiliane Alves , Silva Jr José F. , Umbelino Gomes Uilame , de Souza Carlson P. , Mello Murillo M.B. , Santos Alessandra A.A.
Published: November 2012

Mechanical properties of ferritic-marensitic steels can be improved through dispersion of fine particles with large industrial applications like nuclear, military and aeronautic areas. Steels used at nuclear reactors suffer some damage when exposure to various kinds of radiation such as gamma, plasma, neutrons among others. Special steels have been studied to resist these processes in which cause a significant degradation of these materials. Reduced activation ferritic/martensitic steels (RAFM) are used for fusion structural materials with the substitution of some alloying elements such as Mo, Nb and Ni present in the commercial martensitic steels by other elements which exhibit faster decay of induced radioactivity, such as Ta, W and V. This present work study the development of EUROFER97 steel reinforced with 3wt% of tantalum carbide (TaC).
Study of Mechanical Behavior of a Sand Soil Reinforced with Curaua Treated Fibers with Asphalt
Authors: Santiago Gislene A. , Franco Camila , Consoli Nilo C. , Botaro Vagner R.
Published: November 2012

This paper discusses the behaviour of the granular soil reinforced with the random inclusion of the short and superficially treated curaua fibers with asphalt. These fibers are extracted from the leaves of Ananas erectifolius plants, which are a natural occurring bromeliacea from Amazon region, Brazil. The curaua treated fibers were mixed in the granular soil in order to evaluation their influence on the mechanical properties improvements of the soil. In order to characterize the performance of these fibers, scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA) were employed. Also a series laboratory triaxial compression tests were performed to determine the static stress–strain response of the composites. Through the obtained results, it was observed that the addition of vegetal fibers randomly distributed presented significant improvements on the mechanical properties of this soil. The results show the potential of the curaua fibers used as soil reinforcement.
Thermal and Dynamic Investigations on Brake Pad Composites Produced with Lignin-Phenol-Formaldehyde Resin
Authors: Silveira Joao V.W. , Bittencourt Edison , Águila Zaida J.
Published: November 2012

Brake pads are composite materials which have been constantly improved by new materials that increase the quality and reduce the non-renewable raw materials. The goal of this work is to study the behavior of brake pads produced with replacement of phenol-formaldehyde resin by lignin up to 40% weight ratio. The Krauss method of characterization and SEM analysis were employed. The results showed an average friction coefficient approximately to μm=0.4 and a heterogeneous surface morphology. The satisfactory results are compatible with the current friction materials.
Adherence Evaluation in Tile-Mortar Interface
Authors: Botas Sandro , Veiga Rosário , Velosa Ana Luísa
Published: November 2012

This article deals with some of preliminary tests to study the adherence mechanism of lime mortars to late XIXth Century tiles. The bond between them is mainly physical. A water absorption by capillary test and a suction test were performed to study the parameters of mortar penetration in tiles porosity. The old tiles seem to have a higher porosity than new ones. Some of the new specimens can be used to simulate the old tiles in future tests without applying partially destructive tests to historical objects.
Computer Aided Design of Extrusion Dies for Complex Geometry Profiles
Authors: Gonçalves Nelson D. , Ribau Ângela M. , Carneiro Olga S. , Nóbrega João M.
Published: November 2012

The inherent design freedom promoted by the employment of thermoplastic profiles is one of the major reasons for their attractiveness. Theoretically, thermoplastic profiles can be produced with any cross section suited for a specific application. The design of the corresponding extrusion dies usually employ a methodology based on experimental trial-and-error approaches, being highly dependent on the experience of the designer and highly demanding in terms of resources. These difficulties are obviously more evident when the plastic profile has a complex geometry. This research team is involved since the mid-nineties on the development of computational tools to aid the design of thermoplastic profile extrusion dies. Initially, the numerical code employed was based on structured meshes that limited its use to simple geometries. In this work, a numerical modelling code developed to work with unstructured meshes is described and employed in a case study involving the design of a extrusion die for the production of complex cross section profile. The results obtained show that the developed code can be a useful tool to aid the design of complex profile extrusion dies.
Contrast of a Probabilistic Design Model for Laminated Glass Plates
Authors: Lamela María Jesús , Fernández Canteli Alfonso , Przybilla Constanze , Menéndez Mónica
Published: November 2012

As other ceramic materials, glass presents a brittle behaviour and a broad scatter of strength results, due to the random distribution of micro-cracks on its surface. On the other hand, the specific properties of glass and Polyvinyl Butyral (PVB) are combined in laminated glass, resulting in a viscoelastic behaviour for the whole assembly. In this paper, a probabilistic design model is proposed for laminated glass plates of annealed and tempered glass, taking into account the time-dependent properties of the PVB interlayer and the glass characterization by means of a three-parameter Weibull cumulative distribution function of critical stresses. To validate the model proposed, an experimental programme was carried out using laminated glazing of 1.4 m x 1.4 m, varying the kind of glass, thickness and boundary conditions.