bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Crack Length on Ductile Fracture Initiation in Welded Joints with one and Two Weld Metals
Authors: Medjo B. , Rakin Marko , Gubeljak Nenad , Predan Jožef , Arsić Miodrag , Sedmak Aleksandar
Published: January 2011

Among various micromechanical models for ductile fracture analysis using local approach, those based on the Gurson plastic flow criterion have been intensively developed in the past three decades. However, their application is still subject of many researches, with the aim to improve the assessment of ductile fracture in various, mainly metallic, materials. In this work, Gurson criterion is applied to welded joints produced with one or two different weld metals (one of these is overmatched, while the other is undermatched). Welded single-edge notched bend (SENB) specimens are examined, with an initial pre-crack located in the symmetry plane of each joint. Local approach is chosen for assessment of behaviour of the joints under the external loading, to capture the effect of material inhomogeneity and initial crack length on deformation and ductile fracture initiation in analysed specimens.
Modeling of (121) Twin Boundaries in 2H Martensite
Authors: Ostapovets Andriy , Paidar Vaclav
Published: January 2011

The structures of {121} twin boundary in orthorhombic 2H martensite are modeled using Finnis-Sinclair type many-body interatomic potentials. The boundary corresponds to type-I twinning in 2H martensite of Cu-Al-Ni, Cu-Zn-Al and Au-Cd alloys. Three possible configurations of the {121} boundary are found. The structure with the lowest energy possesses a non-corrugated central {121} plane.
Influence of Dislocations on the Spatial Variation of Microstructure in Martensites
Authors: Gröger Roman , Lookman Turab
Published: January 2011

The continuum theory of dislocations, as developed predominantly by Kröner and Kosevich, views each dislocation as a source of incompatibility of strains. We show that this concept can be employed efficiently in the Landau free energy functional to develop a mean-field mesoscopic model of materials with dislocations. The order parameters that represent the distortion of the parent phase (often of cubic symmetry) are written in terms of elastic strains which are themselves coupled by incompatibility constraints. Since the “strength” of the incompatibility depends on the local density of dislocations, the presence of dislocations affects the evolution of the microstructure and vice versa. An advantage of this formulation is that long range anisotropic interactions between dislocations appear naturally in the formulation of the free energy. Owing to the distortion of the crystal structure around dislocations, their presence in multiphase materials causes heterogeneous nucleation of the product phase and thus also shifts of the transformation temperature. This novel field-theoretical approach is very convenient as it allows to bridge the gap in studying the behavior of materials at the length and time scales that are not attainable by atomistic or macroscopic models.
Elastic Parameters of Various Rafted Structures of Model Ni-Base Alloys
Authors: Buršík Jiří
Published: January 2011

Two-phase microstructure of ordered cube-shaped precipitates in the disordered matrix is characteristic of Ni-base superalloys. This microstructure degrades under the applied stress: depending on the stress direction, lattice misfit and elastic parameters of both constituent phases, the precipitates coalesce and change their overall shape. Various atomic configurations were modeled in this work representing various morphologies of precipitates developed under applied stress. A model Ni-base alloy containing six alloying elements typical of advanced Ni-based superalloys was used. Generated configurations were further subject to study of elastic parameters by means of computer straining experiments. Relaxation of atomic positions in the strained crystal blocks was implemented using molecular dynamics calculations with phenomenological Lennard-Jones pair potentials and interactions involving three coordination spheres. Changes of elastic parameters due to varying precipitates morphology are discussed.
Investigation of Plasticity in Silicon Nanowires by Molecular Dynamics Simulations
Authors: Guénolé J. , Godet Julien , Brochard Sandrine
Published: January 2011

We have performed molecular dynamics simulations on silicon nanowires (Si-NW) with [001] axis and square section. The forces are modeled by well-tested semi-empirical potentials. First we investigated the edge reconstruction of Si nanowires. Then, we studied the behavior of the NW when submitted to compression stresses along its axis. At low temperature (300K), we observed the formation of dislocation loops with a Burgers vector 1/2 [10-1]. These dislocations slip in the unexpected {101} planes having the largest Schmid factor.
Microstructure, Fracture and Damage Mechanisms in Rare-Earth Doped Silicon Nitride Ceramics
Authors: Tatarko Peter , Chlup Zdeněk , Dusza Ján
Published: January 2011

Influence of rare-earth oxide additives on the strength, fracture toughness and tribological behaviour of hot-pressed Si3N4 and Si3N4/SiC micro/nano-composites has been investigated. Four-point bending mode and ball on disc methods have been used for strength and wear tests and Single-Edge V-Notched Beam, Chevron Notched Beam, Indentation Strength and Indentation Fracture techniques for fracture toughness measurement. Fractography has been used to characterize strength limiting defects, fracture micromechanisms and damage mechanisms during the wear test. The strength values were strongly influenced by the present processing flaws. Wear behavior is significantly influenced by the chemical composition and by the microstructure of the materials.
Mechanical Behaviour and Thermal Conductivity of Mortars with Waste Plastic Particles
Authors: Corinaldesi Valeria , Mazzoli Alida , Moriconi Giacomo
Published: January 2011

In the present paper an investigation of mechanical behaviour and thermal conductivity of a lightweight building material containing either styrene butadiene rubber (SBR) or polyurethane (PU) waste particles is presented. Several mortar mixtures were prepared by replacing quartz sand with 0, 10 and 30% of either SBR or PU post-consumer plastics particles. The influence of rubber particle addition on fresh mortar behaviour, compressive and flexural strength of mortar as well as on mortar thermal conductivity was investigated. An optimization of mortar mixture proportions was carried out by adding a limestone powder as filler. The experimental investigation showed that the addition of rubber particles reduces both the material unit weight and the thermal conductivity. The thermal insulating effect of rubber particles indicates a promising potential for future developments. On the other hand, the addition of limestone powder produced higher thermal conductivity as well as higher compressive and flexural strength.
Realization of TRC Façades with Impregnated AR-Glass Textiles
Authors: Hegger Josef , Kulas Christian , Horstmann Michael
Published: January 2011

In the last 30 years, façade-panels made of steel-reinforced concrete have become less attractive for architects and clients. Due to the metallic reinforcement, the insufficient concrete covers of former design code generations and hence the material-dependent corrosion, many cases of damage occurred. Using technical textiles for a new composite material, Textile Reinforced Concrete (TRC), it is possible to produce concrete structures which are not vulnerable to corrosion. The presented ventilated large-sized façade elements and self-supporting sandwich panels exemplify the capability of TRC. In the paper, applied materials are characterized and the production process of tailor-made textile reinforcements as well as the load-bearing behavior of the members is described.
Polymer-Modified Mortars for Surface Treatment with the Utilization of Waste Polystyrene
Authors: Žižková Nikol , Drochytka Rostislav , Nosek Karel
Published: January 2011

The article is focused on the observation of usable possibilities of waste polystyrene that is created during foundry production and that could be used for production of cellular construction material. Thanks to its granulometry this kind of waste polystyrene is very suitable for use in the fine-soft Polymer-Modified Mortars (PMM), for example in the paste and gluing materials determined for ETICS (External Thermal Insulation Composite Systems). The mixtures for waste polystyrene application feature the required cellular light property, they conform to the requirements on the solidity and adhesiveness and conform also to the tension tests for the reinforcing layer.
Advanced Coatings to Improve the Durability in Continuous Glass-Fibre Reinforced Concrete
Authors: Weichold Oliver
Published: January 2011

Glass rovings undergo a loss in tensile strength when aged in highly alkaline concrete. Based on the hypothesis that this loss is due to hydrolysis of the silicate network, binary polymer/pozzolan and ternary polymer/pozzolan/cement coating formulations have been developed in order to provide both corrosion protection and improved fibre-matrix adhesion. While the ternary mixtures were found to do either or, the best overall result was obtained with the binary mixture poly(vinyl acetate)/silica 20:80, showing a 1.8-fold increase in the pull-out load and a 1.6-fold increase in the residual tensile strength when compared to the as-received glass.
Effect of Concrete Hydrophobation against Chloride Penetration
Authors: Årskog V. , Borgund K. , Gjørv Odd E.
Published: January 2011

For concrete structures in chloride containing environments, hydrophobic surface treatments are often used as an additional protective measure for protecting the embedded steel against corrosion. In recent years, silane-based hydrophobic agents that can be used as concrete admixtures for making the whole concrete hydrophobic have also been introduced. In the present paper, the protective effectiveness of such an admixture against chloride penetration has been investigated. For comparison, some field investigations on the effectiveness of a traditional surface hydrophobation of two concrete harbor structures based on similar products are also briefly reported.
Composition of Concrete Surfaces after Demoulding and Coating: Comparative Study by XPS, FTIR and Raman Spectroscopies
Authors: Horgnies Matthieu , Chollet Mélanie
Published: January 2011

Hardened concretes were studied by several spectroscopic techniques (FTIR, Raman and XPS) to determine the surface composition after demoulding and after coating. After demoulding, most of the paste was constituted of calcite but some areas were identified by µRaman as portlandite, ettringite, belite, alite and ferrite phases. The FTIR (in ATR mode) allowed detecting portlandite and C-S-H but it highlighted also organic residues from the demoulding oil. XPS allowed recording interesting atomic ratios to study the extreme surface and the presence of contamination. After post-treatments, the main organic units were determined by FTIR and XPS at the concrete’ surface. Raman was also interesting: no vibration modes of organic species were detected but mineral/hydrated phases were clearly characterized under a thick organic layer. Due to their own specificities, these complementary techniques allowed identifying the mineral/hydrated phases and organic residues/coating at the concrete surfaces.
Shrinkage Properties of Polymer-Modified Cement Mortars (PCM)
Authors: Bode Kay Andre , Dimmig-Osburg Andrea
Published: January 2011

The main difference between normal mortar and polymer modified mortar is the microstructure. Whereas cement is the only binder in normal concrete, the binder of PCM contains cement and polymer. It is known, that these polymer modified cementious matrixes show a higher shrinkage than the non-modified ones. But it is also known, that the PCMs show fewer cracks due to shrinkage. A lot of different investigations have been carried out to find the reason for this con-tradiction. The measurement of shrinkage of PCMs and polymer modified cement stones will be presented in this paper. The prisms were stored under various climate conditions and show a varying shrinkage accordingly. Taking these results into account it becomes obvious that the shrinkage of PCMs depends considerably on the hydration shrinkage, to a lesser extent on the drying shrinkage. Furthermore, a model experiment as to the adhesive bond of cement stones compared to natural stones was introduced.
Effect of Epoxy Resin Addition on the Moisture Sensitivity of Macro Defect Free Polymer-Cement Composites
Authors: Ekincioglu Ozgur , Ozkul M. Hulusi , Ohama Yoshihiko , Patachia Silvia , Moise Georgeta
Published: January 2011

Macro-defect-free (MDF) cements are cement-polymer composites and were developed by Birchall et al. three decades ago. The composites are produced by mixing small amounts of polymer and water with cement. However, they have a different production method than that of cement pastes, which was inspired by rubber production. Mixtures of cement, polymer and water are processed by using a two-roll mill. The composites are known with their high flexural strengths. Unfortunately, there are not any known commercial products using MDF cements because of their poor durability under moisture. In this study, MDF cements were prepared by using poly(vinyl alcohol--vinyl acetate) PVA, calcium aluminate cements and two different types of epoxy resins. Epoxy resins were a diglycidyl ether of bisphenol A and a mixture of a diglycidyl ethers of bisphenol A and F. Durability performance was compared with respect to biaxial flexural strengths, contact angle and atomic force microscopy (AFM) for the specimens stored in water.
Characterization of Poly(vinyl Alcohol) Fiber Reinforced Organic Aggregate Cementitious Materials
Authors: Xu Bo , Toutanji Houssam A. , Lavin Thomas , Gilbert John A.
Published: January 2011

This study focuses on the development of a lightweight, high-performance cementitious composite material reinforced with Poly(vinyl alcohol) (PVA) fiber. The material which contains Poly(vinyl butyral) (PVB) as the sole aggregate has a low average density of 1548 kg/m3 and a compressive strength of about 40 MPa. The flexural strength, impact resistance, and fracture toughness are also evaluated and are found to be improved in comparison to those of lightweight concrete. The addition of PVA fiber further improves ductility, fracture toughness and impact resistance. The increase in fracture toughness was found to be linear with increasing fiber volume fraction. Comparisons are made with a lightweight concrete of equal density, and a normal-weight concrete. A model based on fiber bridging mechanics and the rule of mixtures is developed to characterize the fracture toughness, and a good correlation is obtained for the materials tested when experimental results are compared to those predicted by the model.
Thermoelectric Energy Conversion and Ceramic Thermoelectrics
Authors: Kajitani Tsuyoshi , Miyazaki Yuzuru , Hayashi Kei , Yubuta Kunio , Huang X.Y. , Koshibae W.
Published: January 2011

Oxide thermoelectrics are relatively new materials that are workable at temperatures in the range of 400K≤T≤1200K. There are several types of thermoelectric oxide, namely, cobalt oxides (p-type semi-conductors), manganese oxides (n-type) and zinc oxides (n-type semi-conductors) for high temperature energy harvesting. The Seebeck coefficient of 3d metal oxide thermoelectrics is relatively high due to either high density of states at Fermi surfaces or spin entropy flow associated with the carrier flow. The spin entropy part dominates the Seebeck coefficient of 3d-metal oxides at temperatures above 300K. Introduction of impurity particles or quantum-well structures to enhance thermionic emission and energy filtering effects for the oxide semiconductors may lead to a significant improvement of thermoelectric performance.
Synthesis and Electron Density Analysis of SnO2 Nano Particles
Authors: Saravanakumar S. , Jeya Priya M. , Saravanan R.
Published: January 2011

Tin oxide material (SnO2) is synthesized in nano scale range and is characterized. The refined X-ray intensity data was obtained from the Reitveld method. The electron density of nano SnO2 is determined using MEM (Maximum Entropy Method). Using one, two and three dimensional MEM maps, the bonding within the atoms is clearly understood. The particle size of SnO2 is also analyzed using XRD and SEM.
Influence of Silicon and Boron Doping on the Thermal Conductivity of N-GaAs Single Crystals
Authors: Prema Rani M. , Saravanan R.
Published: January 2011

Thermal conductivity of three different GaAs crystals, one grown by Liquid Encapsulated Czochralski technique and the other two samples grown by Vertical Bridgman technique have been experimentally measured at temperatures 310 K to 360 K. Two crystals are undoped and semi insulating and one crystal is conductive which is doped with Si and B(Silicon ≈ 4x1015 cm-3 and Boron ≈ 8x 1015cm-3). It has been experimentally observed that doping of silicon and boron gives rise to an increase in thermal conductivity.
Dynamic Study of Adsorption for the Removal of Bismark Brown – Using Activated Carbons
Authors: Xavier A. , Sathya R , Gandhi Rajan J. , Nagarathnam R.
Published: January 2011

Many industries use dyes and pigments to colorize their products. Large amount different types of dyes enter in to the environment. These dyes are invariably left in the industrial wastes. As a part of removal of Bismark Brown dye from textile and leather industrial wastes, using activated carbon as adsorbents namely, commercial activated carbon (CAC), rose apple carbon (RAC), coconut shell carbon (CSC) and saw dust carbon (SDC). The percentage removal of Bismark-Brown adsorbed increases with decrease in initial concentration and particle size of adsorbent and increased with increase in contact time, temperature and dose of adsorbent. The pH is highly sensitive for dye adsorption process. The adsorption process followed first order kinetics and the adsorption data with Freundlich and Langmuir isotherm models. The first kinetic equations like Natarajan Khalaf, Lagergren, Bhattacharya and Venkobhachar and intra-particle diffusion were found to be applicable. A comparative account of the adsorption capacity of various carbons has been made. These activated carbons are alternative to commercial AC for the removal dyes in General and Bismark-brown (BB) is particular. These results are reported highly efficient and effective and low cost adsorbent for the BB. The thermodynamics parameters are also studied and it obeys spontaneous process. The results are confirmed by before and after adsorption process with the help of the following instrumental techniques viz., FT-IR, UV-Visible Spectrophotometer and SEM analyze.
Research Regarding the Influence of the Compaction Pressure of the Iron Powder on the Processes that Take Place when Elaborating Steels Obtained through the Carburizing – Sintering Proceeding
Authors: Ghermec Christian , Ghermec Olimpia , Trotea Mario
Published: January 2011

The elaboration of carbon steels sintered through the enrichment of compactised iron powders in carbon in methane gas medium has allowed the development of an innovative technology that fort he first time is based upon the carburizing (the process of carbon enrichment, in different proportions) at the same time with sintering. The parts obtained through this proceeding have been analysed from the point of view of the physical and the mechanical characteristic in correlation with the compaction pressure of the iron powder.
Preliminary Studies and Researches on the Elaboration of Gradual Porous Sintered Structures by Powder Sedimentation
Authors: Vida-Simiti Ioan , Jumate Nicolaie , Moldovan Valentin , Sechel Niculina , Thalmaier György
Published: January 2011

Spherical bronze powders were used for studies the obtaining of gradual porous structures by sedimentation and sintering methods. The powder size classes above 100 μm were used for the manufacturing of the macroporous support by spreading the powder into the sintering die. Sintering was conducted in vacuum (10-4 Torr) at a temperature of 750 °C for 40 minutes. On the macroporous support a layer of fine powder fraction was deposited by gravitational sedimentation. The deposited layers were consolidated by sintering at 750 °C for 30 minutes. The analysis of the gradual porous layers was done using scanning electron microscopy and mercury porosimetry. The fluids viscosity influences the sedimentation velocity of particles. The height of the column directly affects the quality of porous structure. If the sedimentary column is short, the turbulences created by adding the suspension of the dispersed powder in the sedimentary tube are more harmful.
Synthesis of the Mümetal Magnetic Powders by Mechanical Alloying
Authors: Chicinaş Ionel , Pop Viorel , Popa Florin , Prică Virgiliu Călin , Marinca Traian Florin , Neamţu Bogdan Viorel , Sorcoi Lidia Adriana
Published: January 2011

The formation of quaternary 76Ni17Fe5Cu2Cr (wt. %) alloy by mechanical alloying is investigated. The elemental powders of Ni, Fe, Cu and Cr where milled in argon atmosphere in a planetary ball mill for time up to 20 h. Formation of the alloy was checked by X-ray diffraction studies. It is found that the rapid formation of the alloy lead to the rapid establishment of an equilibrium between the welding and fracture process during milling, leading to a constant particle size distribution over a big range of milling time. The morphology of the powders, studied by scanning electron microscopy (SEM) confirms the rapid increase in size. The particle size distribution and the flowability of the powders are also analyzed as a function of milling time. Enhanced magnetization was found for the milled samples, compared to a cast alloy.
Wear Characteristics of Vacuum Sintered Steels
Authors: Rosso Mario , Dudrová Eva , Grande Marco Actis , Bidulský Róbert
Published: January 2011

The present paper is focused on the wear characteristic of vacuum sintered Cr-Mo-[Mn]-[Cu] steels. The effect of chemical composition and the processing conditions in a vacuum furnace were evaluated. In such furnaces the cooling rate is generally determined by the pressure of the gas (N2) introduced into the chamber, the average cooling rates were calculated in the range of 1240°C to 400°C. The wear characteristics were analyzed as function of the processing and microstructures of the tested alloys through pin on disk test. Sintering of specimens in vacuum together with rapid cooling resulted in the formation of dominant martensitic microstructures with some small bainitic areas. The effect of both surface hardness and microstructure on the wear behaviour of the investigated steels shows the relation between the hardness and the wear rate. The influence of processing condition on the amount of martensite is also presented.
Mechanical, Thermal and Electrical Properties of Acrilonitril Butadiene Styrene (ABS) Composites Filled with Bronze Powder
Authors: Chifor Victoria , Orban Radu Liviu , Tekiner Zafer , Turker Mehmet
Published: January 2011

This article reports on an experimental study of the mechanical, thermal and electrical properties of bronze-ABS composites containing 5, 10, 20, 30 vol.% of bronze powder. The mechanical properties such as ultimate tensile strength, elongation at fracture, modulus of elasticity, melt flow rate (MFR), hardness, thermal conductivity, electrical conductivity of bronze powder filler embedded in a ABS matrix were experimentally investigated. Thermal and electrical conductivity measurements were performed up to a filler concentration of 30 vol.%. The tensile strength, elongation, MFR values continuously decreased with increasing the bronze powder content. However, modulus of elasticity and hardness increased with increasing the bronze content. Thermal and electrical conductivity of the composites was found to be higher for ABS-20 vol.% bronze composites than that of the other composites.
Thermal, Mechanical and Electrical Properties of High Density Polyethylene Composites Reinforced with Copper Powder
Authors: Chifor Victoria , Orban Radu Liviu , Tekiner Zafer , Turker Mehmet
Published: January 2011

The thermal conductivity, electrical conductivity and mechanical properties such as tensile strength, elongation, modulus of elasticity, were experimentally investigated. Thermal and electrical conductivity measurements were performed up to filler concentration of 30 vol.%. The mechanical properties of high density polyethylene filled with up to 30 vol.% Cu particles were investigated. The tensile strength, elongation and toughness decreased with increasing Cu powder content. This was attributed to the introduction of discontinuities in the polymer structure in which modulus of elasticity increased with increasing the copper content.
Chemical Reactions during Sintering of Mn and Mn-Cr Prealloyed Steels in Inert versus Reducing Atmospheres
Authors: Danninger Herbert , Jaliliziyaeian Maryam , Gierl Mayer Christian , Bengtsson Sven
Published: January 2011

In this work the reduction during sintering of Mn and/or Cr prealloyed steels has been studied. In inert atmospheres, the reduction of surface and especially of internal oxides in these steels is shifted to markedly higher temperatures than in Fe-C or conventionally alloyed PM steel grades, reduction being not yet completed at 1300°C. At least at higher alloy element contents, the main reduction starts about 1000°C compared to 700°C for Fe-C, in both cases removal of surface oxides being the first major process. Sintering in high purity H2 results in partial reduction in the 400°C range, H2O being formed as the product, but removal of the remaining oxides requires more or less the same high temperatures as in inert atmospheres, and the reaction product is mainly CO, which confirms that at temperatures >1000°C carbon is the reducing agent in any sintering atmosphere.
Influence of the Reinforcing Elements on the Wear Behavior of Al/(Sic+Graphite) Composites Elaborated by Spark Plasma Sintering Technology
Authors: Sima Gabriela , Mangra Mihail , Gîngu Oana , Criveanu Marius Catalin , Olei Bebe Adrian
Published: January 2011

The paper presents the experimental results regarding the influence of the reinforcing elements on the wear behavior of Al-matrix composites discontinuously reinforced by SiC and Graphite. This antifriction composite material is processed by Reactive Mechanically Alloyed and then by Spark Plasma Sintering technology. In order to optimize the processing technology, especially the sintering parameters, the Spark Plasma Sintering process was applied because of its advantageous aspects: lower sintering temperatures, shorter sintering time and higher properties values of the sintered material vs. the corresponding ones obtained by the classical sintering route. The authors realized a comparative analysis on the wear behavior of the researched composite materials.
New Composite Materials, Obtained from Ashes Wastes, with Potential Applications for Electromagnetic Shielding
Authors: Kappel Wilhelm , Codescu Mirela Maria , Manta Eugen , Pătroi Eros Alexandru , Morari Cristian , Erdei Remus
Published: January 2011

By an appropriate processing of the pyritic ashes (resulted as residue in the fabrication process of the sulphuric acid) can be valorised the metallic elements. The paper presents the magnetic characteristics of the powders before and after the thermal annealing, and also the flowability and the granulometric characteristics of these powders. Starting from a very low magnetization, σ = 3.65 emu/g, the Fe amount of the powders is dramatically increased, after an appropriate thermal treatment, to approx. 34 %, corresponding to σ=128 emu/g. The Fe-enriched powders, embedded in epoxy resin matrix, generate a composites material, which can be used as electromagnetic shields, based on their materials properties (permittivity, permeability and electrical conductivity) in the 1000 – 2500 MHz range.
Physical and Quantitative Microstructural Analysis of Sintered Al-Cu/SiCp Composites
Authors: Popescu Ileana Nicoleta , Zamfir Simona , Bojin Dionezie , Brânzei Mihai , Gheorghe Dan , Sorcoi Lidia Adriana
Published: January 2011

Al-Cu matrix composite materials with 5-20 wt. proportions of SiC hard particles and un-reinforced Al-Cu alloys obtained by powder metallurgy (P/M), in the same homogenization (20 r.p.m., about 7 hours)– pressing (450 MPa for composites) - presintering (300-420oC/30 min/H2) conditions but at different sintering temperatures (520-620oC/60min/H2, furnace cooling) were analyzed in terms of microstructural and physical characteristics. The existence of good bonding between metallic matrix and ceramic particles at interface and the morphology and distribution of pores and carbides in the matrix was evaluated by means of quantitative analysis. Using computer-assisted Optic Quantitative Microscopy on the samples, we determined the pore surface area for the studied materials and the surface area and grain size distribution of the SiC particles of sintered composites by analyzing the captured images in many fields. The hardness were correlated with quantity pore surface area and resulted that the lowest values of porosity were achieved at 620oC and at 10 and 15% silicon carbide in matrix.
Research on the Elaboration by Sintering in Steps of Carbon Steels Based on Iron and Pure Synthetic Cementite Nanopowders Obtained by Mechanical Alloy
Authors: Ciobanu Mariana , Popescu Traian , Bucse Ionela Gabriela , Nicolicescu Claudiu , Ştefan Iulian
Published: January 2011

In this paper are presented the experimental results about the elaboration using mechanical alloying of some Fe+Fe3C composites nanopowders and much more sintering in steps. Powder compaction was done by unilateral pressing into a mould of Φ10 mm, at pressing stress of 600, 700 and 800 MPa in a hydraulic press. Following the research was obtained sintered carbon steels with more homogeneous structures regarding the uniformity of carbon distribution and implicitly of constituents structural characteristics of use (mechanical) higher compared with carbon steels sintered by classical methods.
Magnetic Submicron Powder Preparation and Characterization
Authors: Axinte Ciprian , Nadejde Claudia , Ursache Manuela , Airinei Anton , Cirlescu Aurelian , Racuciu Mihaela , Creangă Dorina
Published: January 2011

The goal of this experimental study was to present a comparative analysis of iron oxides powders obtained by two alternative methods, i.e. the co-precipitation at high temperature from aqueous reaction medium of iron oxides and, respectively, the solvent free method for the preparation magnetite at room temperature. Vibrational absorption spectra evidenced the dominancy of magnetite in both samples, while the X-ray diffractograms revealed the submicron size as well as the presence of additional iron oxide, in the second sample prepared by solvent free method.
From Sintered Iron to High Performance PM Steels
Authors: Torralba José M. , De Oro Raquel , Campos Mónica
Published: January 2011

Since low alloyed sintered steels were introduced in the market of the structural parts, we have followed the evolution of a material with poor mechanical properties and any uniformity (in the sense of reproducibility) to materials that today are produced with high reliability and performance. The working efficiency could be equivalent in many cases with the best wrought steel, and maintaining a good margin in terms of cost and competitively. In this paper a complete review of the topic is accomplished, from the early times when the first parts were made by plain iron or iron-carbon, going through the different alloying systems: Fe-Cu, Fe-P, Fe-Cu-Ni-Mo, and more recently Fe-Cr-Mo and Fe-Mn. The development in processing routes has been considered too. The main milestones in the field of new alloying systems have been: 1) the introduction of Cu in 60-70’s, 2) the new complex systems with Cu-Ni-Mo in the 80’s and 3) the introduction of alloying elements with high oxygen affinity (in the late 90’s). Regarding the milestones in processing could be considered: 1) the development of new mixing procedures, 2) the warm compaction and high velocity compaction, 3) the improvements in sintering control and high temperature sintering. Several decades of research and innovation, acting on the processing system (mixing, pressing, sintering, post-sintering operations,…) and on the alloying system (from the earliest times with plain iron to complex systems used today), has allowed us to have a highly competitive materials, in terms of performance, and processes in terms of cost. The future is still open to new developments.
Liquid Phase Sintering of Fe-Cu-Sn-Pb System
Authors: Teișanu Cristina , Gheorghe Stefan
Published: January 2011

In this study the formation of the liquid phase during sintering process of Fe-Cu-Sn-Pb system was investigated. In order to reach this purpose a new material based on iron powder was developed using PM technologies. Additions like copper, tin and lead were added to iron powder and the mixture was sintered in dry hydrogen atmosphere at different temperatures and maintaining time. The liquid phase formed during sintering led to a considerable accurate process and swelling of the sintered compact was observed and studied.
Researches Regarding the Barium W Ferrite Pyrosynthesis by Microwave Heating
Authors: Nicoară Victor Horia , Ştefan Iulian
Published: January 2011

In this work there are presented the results of experimental researches which had the goal to establish the thermal effect of BaCO3 and α- Fe2O3 homogeneity mixture heated in microwave, used to processing barium ferrite W type by pyrosynthesis.There was used thermal-gravimetric analysis with a derivatograph reordered for microwave heating of samples containing iron oxides with different grain size.Experimental results emphasized that the microwave heating comparatively with resistor heating, lead to a lower synthesis temperature of hexaferrite of about 150 0 C , using oxides with grain size suitable to SBET= (7-10) m2/g.
The Minimum Wave Damping Selects the Most Favored Solution from Multiple Ones to Acoustic-Like Problems
Authors: Lee Hyoung In , Lee El Hang
Published: January 2011

Back in 1990, D. S. Stewart and the first author contributed significantly to understanding the one-dimensional stability of detonation waves [1]. For this purpose, the reactive Euler’s equation with the one-component reaction term was linearized around the steady state of the well-known ZND (Zeldovich-Doering-von Neumann) model. The key aspect of this paper was to derive the linearized radiation condition (named after A. Sommerfeld). They numerically found multiple eigenvalues for pairs of the temporal frequency and temporal attenuation rate (TAR). Of course, the propagating-wave mode having the least value of the TAR (in the sense of its absolute value) was selected. The successful numerical implementation of the far-field radiation condition is a must when it comes to incorporating a large surrounding space into a problem of finite extent. To one of the sure examples in this category belong the problems involving detonation waves, where high-energy-rate processes take place in spatially confined spaces while the surrounding space should be taken into account for reasons of energy loss (or leaky waves in the language of optics). In another fascinating area of science is nano-photonics, where energy transport should be handled in highly confined regions of space, yet being surrounded by unbounded (dielectric) media. The total energy release in nano-photonics is certainly much smaller than that involved in detonation. However, the energy per unit nanometer-scale volume is not negligibly small in nano-photonics. Over the years, the first author has been successful in implementing both theory and numerical methods to find a multitude of eigenvalues in optics [2]. In this case, the governing Maxwell’s equations are already in a linearized form, being in a sense similar to the linearized Euler equations. In addition, the noble metals such as gold and silver are instrumental in enhancing local electric-field intensities, for which the science of plasmonics is being vigorously investigated in nano-photonics. Even the Bloch’s hydrodynamic equation describing the collective motion of the electrons is akin to the Navier-Stokes equations [3]. Meanwhile, assuming a real-valued frequency has been an old tradition in optics, partly because the real-valued photon’s energy is proportional to frequency and normally the continuous-wave (cw) approximation holds true. In a radical departure from this optical scientists’ tradition, we have recently attempted to deal with complex-valued frequencies in examining the wave propagations around nanoparticles [4, 5]. In consequence, the stability of multiple propagating waves was successfully determined for selecting most realizable wave mode. Further interesting points of the interplay between the two seemingly disparate branches of science (fluid dynamics and photonics) will be expounded in this talk.
Numerical Simulation of Explosively Compacted Powder-in-Tube MgB2 Superconductor
Authors: Mamalis Athanasios G. , Theodorakopoulos Ioannis D. , Vortselas Achilleas K.
Published: January 2011

High Tc MgB2 superconductors were fabricated using the ex-situ and in-situ powder in tube (PIT) technique. During treatment, the precursor materials were shock consolidated under high strain-rates using PETN as the explosive medium. After compaction, the superconducting properties of the steel-sheathed MgB2 samples were examined by means of magnetization measurements using a SQUID magnetometer. Bean’s critical state model was applied to investigate the critical current density characteristics of the samples at fields up to 5T. The superconducting transition temperature of the specimens was determined by examining the material temperature dependence of magnetisation in zero field cooled (ZFC) and field cooled (FC) states. An assessment of the explosive compaction technique was carried out by simulating the procedure using the LS-DYNA explicit finite element code. The sample is modelled as a porous soil-like material with a customised yield surface. The numerically estimated final product dimensions, porosity and hardness are compared to the experimental results; furthermore, the numerically obtained pressure, temperature and strain rate profiles are used to assess the efficiency of the compaction process for different explosive quantities and powder compositions.
Explosively Driven Fragmentation Behavior for Structural Components and Shatterproof Effect of Wall Doubling
Authors: Hiroe Tetsuyuki , Fujiwara Kazuhito , Hata Hidehiro , Tsutsumi Kiyotaka , Igawa Takuya , Yamashita Wataru
Published: January 2011

One-dimensional symmetrical explosive loadings are applied to expand structural components: tubular cylinders, spherical shells and rings of 304 stainless steel and double and single walled cylinders of an aluminum alloy, A5052 to fragmentation, and the effects of wall thicknesses, explosive driver diameters and the constant proportionality of the in-plane biaxial stretching rates are investigated on the deformation and fracture behavior of three types of single walled structures and shatterproof behavior for double walled cylinders experimentally and numerically. In the cylinder tests, the driver is a column of high explosive PETN, inserted coaxially into the bore of a cylinder and initiated by exploding a fine wire bundle at the column axis using a discharge current. In case of the ring tests, ring specimens are placed onto a cylinder charged with the PETN as an expansion driver, and for sphere tests, a specimen filled with the PETN is also initiated by exploding a fine copper wire line with small length located at the central point. Observation results of deformation have shown the final maximum in-plane stretching rate order of , and fracture evaluations on recovered fragments are discussed indicating the need of modified fragmentation model for the structural components. In the double walled cylinder tests, only for lowermost amount of the explosive the outer cylinder has almost caught the fragments of inner cylinder, revealing that the damage phenomena are much different from those for single walled ones.
A Study on an Initiation Technique of Small Amount of Explosive
Authors: Aoki Yusuke , Fujiwara Kazuhito , Hiroe Tetsuyuki , Hata Hidehiro
Published: January 2011

High explosives are useful material to generate great amount of energy in short time.　Since controlling their releasing energy is hard, the use of explosive is limited to specific fields and industries. However, the reduction of the explosive powder mass uses at a time makes the handling safe. And use of explosives in a continuous producing process leads the new utility of the explosion. Based on this concept, we enclosed small mass explosives with a polyethylene sheet and initiate them by using metallic foil explosion. We have also developed the system that can generate small explosion continuously. Since it was not easy to initiate a small amount of explosive steady, we had initiated them by metallic foil explosion using a power-supply unit of capacitor bank with 2500J (20kV). In present study, we tested the initiation of a small amount of explosive using a comparatively small power-supply unit of capacitor bank with 4.5J (600V) and that of 2J (1kV) to apply to the general use. In this paper, result of experiments and the conclusions are shown. We observed the perfectness of explosion by using omnidirectional microphone. It is concluded that initiation of explosives enclosed with polyethylene sheet by small power supply unit at 2J (1kV) is possible, while the explosion was not perfect.
A New Processing of Ginger Using the Underwater Shock Wave
Authors: Maehara Hironori , Watanabe Toshiaki , Takemoto Ayumi , Itoh Shigeru
Published: January 2011

In this study, a new processing technique of ginger using underwater shock wave has been studied. The extraction efficiency of ginger using controlled and shock wave method has been compared. The shock wave shows good improvement in the extraction efficiency of ginger.
Properties of Nd-Fe-B Powder Explosively Compacted
Authors: Eskandari H. , Gholamipouri R.
Published: January 2011

Nd-Fe-B magnets are used in wide range of industrial applications. In this research we studied the possibility of producing bulk Nd-Fe-B magnetic compact by using the direct cylinder explosive compaction. After compaction the density of compact was measured by the Archimedes method. Highly dense compact (> 98% relative density) without cracks was obtained by this technique. A concentric hole was observed at center of some compacts. The magnetic properties of the compact are Br=7.95KG, iHc=10.5kOe, (BH)max= 14MOe, and these values are same as those before explosive compaction.
A Possible New C-N Phase Originated from Graphitic Carbon Nitride Loaded by Shock Wave
Authors: Liu Jian Jun , Gao Xiang , Chen Peng Wan
Published: January 2011

A possible new phase of carbon nitride was synthesized by shock wave using a precursor of mixture of graphitic carbon nitride (g-C3N4) with iron powder in a weight ratio of 10:90 at the flyer velocity of about 3.0 km/s driven by explosive detonation. The results of XRD and TEM indicate that the new phase possesses four weak diffraction peaks at 2=36.06 (d=2.489Å), 41.90(d=2.154Å), 60.88(d=1.520Å) and 72.98(d=1.295Å) besides a strong diffraction peak of graphitic carbon nitride at 2=27.70 (3.218 Å) and shows a few tube-like structures in a diameter of about 200300nm and in a length of about 10003000nm with the exclusive element composition of carbon and nitrogen identified by EDX characterization.
A Deburring Process Performed by Underwater Shock Wave
Authors: Shiramoto Kazumasa , Shimizu Junki , Kobayashi Akiyoshi , Fujita Masahiro
Published: January 2011

A burr is most commonly created after machining operations, such as drilling. Drilling burrs, for example, are common when drilling almost any material. When burrs are broken during the operation of a machine including the parts with the created burrs, the broken piece is in fear of disturbing normal operation or damaging the parts of the machine, so that the sufficient deburring is requested because it can affect equipment performance, reliability, and durability. Several deburring method have been developed up to date. In the present report, we proposed a deburring method by means of applying underwater shock wave. The method is as follows: after all entrance of holes is closed with seal tape, the equipment is submerged, so that all passages for running fluid are filled with air. The explosive is set under water near the entrance of the main hole. As soon as the explosive is detonated, the underwater shock wave generated at the detonation point arrives at the entrance of the hole and breaks through the tape. The water flows into the hole with a high speed. The burr is broken by water hummer action of high speed. In the present investigation, the experiments of deburring are performed under some setting conditions of explosive. It is found by experimental results, that the burr is sufficiently removed with the newly proposed method. When the shock pressure is sufficiently high at the entrance of hole, the burr is broken surface is smooth as polished one. When the shock pressure is not sufficiently high, the broken surface of the burr is notched.
Modification of BKW EOS Introducing Density-Dependent Molecular Covolumes Concept
Authors: Suceska M. , Ang H.G. , Chan H.Y.
Published: January 2011

One of the most important tasks of thermochemical codes for the calculation of detonation properties is the accurate description of the state of gaseous products within a rather wide range of pressures and temperatures – from several hundreds of kbar and several thousands of K to atmospheric pressure and temperature. Due to its simplicity and convenience, the Becker-Kistiakowski-Wilson (BKW) equation of state is used in many practical applications in the explosives field, despite its lack of rigorous theoretical background. The BKW EOS gives good agreement between calculated and experimentally obtained detonation parameters for many standard high explosives having densities in the range 1.2 – 2 g/cm3. However, it fails to predict accurately detonation properties at lower densities. To overcome this problem, we introduced the concept of density dependent molecular covolumes in the BKW EOS instead of invariant. The applicability of the approach is verified by comparing experimental and calculated values of detonation parameters for a series of explosives having different formulations and densities. It was found that by applying this approach the accuracy of the calculations for lower densities can be significantly improved.
Observation of High-Speed Fracture Phenomena of Glass Containers by Using Underwater Shockwave
Authors: Kawabe Shinjiro , Sakamoto Hidetoshi , Ohbuchi Yoshifumi , Itoh Shigeru
Published: January 2011

The glass containers crushing process for recycling by using underwater shockwave was observed and the new cullet generation technique by explosive energy was proposed. In this study, the high-speed fracture behaviors of glass containers were visualized by using the high-speed photography and FEM simulation.