bluuebunny/crossref_metadata_2025 huggingface dataset:
Fracture of Oxide Matrix Composites with Different Phase Arrangement
Authors: Pędzich Zbigniew
Published: September 2009

The paper presents the analysis of the fracture path in composites with the alumina or zirconia matrix containing inclusions of another oxide or tungsten carbide. The description concerns the fracture of composite systems with 10 vol.% of inclusions (particulate composites), other three-systems with 33 vol.% of inclusions of each phase and the two phase composite with the equal phase content (50 : 50 vol.%). The different phase proportion and diversified content of inclusions cause significant differences in the microstructure of composites. The main difference between particulate composites and composites with continuous phases depends on a possibility of occurrence of toughening mechanisms connected with crack – inclusions interactions. In connection with a different interphase boundary strength, this phenomenon leads to significant differences in the way of composite fracture. The presented results of mechanical properties of composites were analyzed in the aspect of their way of fracture.
Influence of Internal Architectures on the Fracture Response of LTCC Components
Authors: Bermejo Raúl , Kraleva I. , Antoni Mathieu , Supancic Peter , Morrell Roger
Published: September 2009

Low Temperature Co-fired Ceramics (LTCCs) are layered ceramic based components, which – in recent years - are increasingly used as high precision electronic devices (e.g. mobile and automotive technologies) in highly loaded (temperatures, inertia forces, etc.) environments. They consist of a complex three-dimensional micro-network of metal structures embedded within a glass-ceramic substrate. Even though LTCCs have been used for more than 20 years, there is insufficient understanding of the mechanical loads during processing. In this regard, different types of failure of the end component during service have been reported, coming from different parts within the part. In this work, the influence of the internal architectures in the fracture response of LTCC components during bending has been investigated. Strength has been determined in 10 × 10 mm2 specimens using the ball-on-three-balls test (biaxial loading) and evaluated using Weibull statistics. Fractography of broken specimens has been performed to determine the mode of fracture of the components and the role of the internal architecture in the crack path. Results show strength dependence as a function of the testing position within the part. The influence of the internal architecture and residual stresses is also discussed.
Fractography of Dense Metal-Like Carbides Sintered with Carbon
Authors: Gubernat Agnieszka , Stobierski Ludosław
Published: September 2009

Metals belonging to groups 4-6 of periodic table of elements form with carbon compounds named metal-like carbides (WC, TiC1-x, NbC, TaC, CryCz). It was established that is possible to achieve dense sintered bodies of this carbides at temperatures near 2000oC using only carbon powder as an additive. Its role consists in reduction of oxide impurities.
Presented paper summarized investigations on sintering of metal-like carbides with carbon. Dense WC, TiC1-x, NbC, TaC and CryCz bodies were characterized by KIc factor value. A special care was taken on microstructure and the way of fracture description in relation to the critical stress intensity factor (KIc). It was established that the way of fracture and the finally fracture toughness depend on type of microstructure and degree of nonstoichiometry.
Crack Profile under Vickers Indents
Authors: Jonšta Zdenĕk , Olejníčková Lucie , Mazanec Karel
Published: September 2009

The present work is focused on complex evaluation of crack profiles, created around Vickers indents in two types of cutting tool ceramics, namely in the Al2O3 + ZrO2 ceramics and -Si3N4. The geometry of Vickers indents is investigated using two different evaluation methods. The first one is based on the application of serial sectioning from the indented specimen surface. The second method consists in the layer removing from plane perpendicular to the indented surface. These evaluation methods are convenient for determine the shape of created cracks and profiles of deformed area developed around the investigated indents. The mentioned methods contribute to the understanding of physical engineering principles resulting from the radial/median and lateral crack formation as the important characteristics influencing the reliable technical application of investigated ceramic materials.
Effect of Sintering Time on the Phase Composition in PFN Ceramics Prepared by Sol-Gel Process
Authors: Bruncková Helena , Medvecký Ľubomír , Mihalik Ján
Published: September 2009

Lead iron niobate Pb(Fe0.5Nb0.5)O3 (PFN) ceramics were prepared using sol-gel synthesis by mixing acetates Pb and Fe with Nb-ethylene glycol-tartarate (Pechini) complex at 80°C, calcination of gels at 600°C and sintering at 1150°C for various times. The metastable pyrochlore phase Pb3Nb4O13 in stoichiometric precursor was partially decomposed to perovskite phase Pb(Fe0.5Nb0.5)O3 in ceramics sintered at temperature of 1150°C for 2, 4 and 6 hours. Excess of Pb in molar ratio (Pb:Fe:Nb = 1.2:0.5:0.5) caused the increase of the content of the perovskite phase (~50 vol.%) in nonstoichiometric PFN ceramics sintered at 1150°C for 6 hours while the decrease in perovskite phase content was found in stoichiometric PFN ceramics (~16 vol.%). In microstructures of PFN ceramics sintered at 1150°C for different times, the bimodal grain size distribution was observed with small spherical grains of perovskite phase and larger octahedral grains of pyrochlore phase. EDX analysis confirm that complex types of pyrochlore phases that differ in iron content were present in ceramics.
Effect of Cerium and Lanthanum Addition on Mechanical Properties of Bismuth Titanate Ceramics
Authors: Pavlovic Nina , Rajnovic Dragan , Sidjanin L. , Srdic Vladimir V.
Published: September 2009

Cerium- and lanthanum- substituted bismuth titanate (Bi4-xAxTi3O12; where A=La or Ce, and x=0, 0.5 and 1) ceramics were prepared from nanopowders synthesized by coprecipitation method. The as-synthesized powders were calcined, uniaxially pressed and finally sintered at 1050°C. It was shown that sintering behaviour, phase composition and grain morphology of the obtained ceramics were influenced by the presence of lanthanum and especially cerium ions in the titanate structure. Mechanical properties (hardness and fracture toughness) were measured at room temperature on polished sample surfaces using a Vickers microhardness tester. The hardness values for of bismuth titanate based ceramics were in the range for some other important perovskite titanate, whereas their fracture toughness was somewhat higher.
Mechanical and Fractographic Analyses of Monolithic Si3N4 Ceramics during Impact Testing
Authors: Maros Maria Berkes , Helmeczi Nikoletta Kaulics , Arató Péter , Balázsi Csaba
Published: September 2009

A comprehensive experimental and theoretical work aiming at studying the dynamic failure process of silicon nitride ceramics has been recently started. The main goal of this research programme consists in characterizing the mechanical behaviour of the material under dynamic loading as well as investigating the dynamic failure process using micro- and macro-fractography. The current paper deals with the phenomenon of special rate dependence of KId dynamic fracture toughness of Si3N4 based ceramics. The KId values have been determined during instrumented impact test on the one hand based on the dynamic key curve method using notched specimens, on the other hand based on fractographic analyses of fracture surface of impacted unnotched samples.
The Fabrication and Properties of Biscuit-Sintered Y-TZP Ceramics for Dental Applications
Authors: Kosmač Tomaž , Andrejczuk Mariusz , Perko Sebastjan
Published: September 2009

Moderately porous Y-TZP dental ceramics were designed to combine the high strength and fracture toughness of densely sintered Y-TZP and the relatively low elastic modulus of porous Y-TZP ceramics. The materials were produced by biscuit-sintering dry-pressed pellets at different temperatures in an ambient air atmosphere. The flexural strength progressively increased with the fractional density, starting from 150–200 MPa at 55–60 % of theoretical density (TD), and exceeding 500 MPa at >80 % TD. The elastic modulus of the early-stage sintered material was matched with that of dentine, but the flexural strength was too low for a practical application. Strength values equal to or higher than those of the existing dental glass-ceramics and glass-infiltrated ceramic materials were achieved with specimens sintered to 8085 % TD, but the elastic modulus of these ceramics (100130 GPa) was about two times higher than that of dentine. Soft grinding of the biscuit-sintered samples resulted in a noticeable increase in the surface roughness, also leading to a significant strength reduction.
Strength Degradation Flaws in the Liquid-Phase-Sintered SiC Based Ceramics
Authors: Kovalčíková Alexandra , Dusza Ján , Šajgalík Pavol
Published: September 2009

The effect of the heat treatment on the fracture toughness and flexural strength of the silicon carbide – silicon nitride composites prepared by liquid-phase-sintering was investigated. The results were compared to those obtained for a reference silicon carbide material, prepared by the same fabrication route. The fracture toughness increased from 3.19 to 5.15 MPa.m1/2 due to the toughening mechanisms (crack deflection, mechanical interlocking, crack branching) occurring in the heat treated materials during the crack propagation. However, the flexural strength decreased after the heat treatment of the experimental materials. The strength of the investigated materials was degraded by the presence of processing flaws mainly in the form of pores, clusters of pores, and SiC agglomerates.
Impedance Changes and Carbon Stability during the Heat Treatment of Si3N4–Carbon Composites
Authors: Fényi Balazs , Hegman Norbert , Szemmelveisz K. , Balázsi Csaba
Published: September 2009

Electrical properties of the insulator silicon nitride ceramics may be improved by addition of electrical conductive parts. The conductive carbon parts were mixed with the base ceramic matrix to form a percolation network. Electrical current can flow through the ceramic by using the connected carbon channels. In air atmosphere however, the carbon can oxidize and burn out. Heat treatments were performed to observe the carbon degradation in composites in atmosphere. As resulted, the carbon exhaust started at 400°C from surface and finished above 750°C. Electrical measurements showed the conductor-insulator transformation. Thermo-gravimetric measurements suggested that some carbon inclusion still remained in isolated closed porosities.
The Milling Time Effect on Sintering Kinetics of Silicon Nitride Based Composites
Authors: Koszor Orsolya , Balázsi Csaba
Published: September 2009

We have investigated the influence of the milling time on the structure and mechanical properties of the nanocomposite, as well as the effect of grain size on the sintering kinetics (α to β silicon nitride phase transformation). As we observed, by increasing the milling time the mechanical properties of the ceramics may be improved. The reason of this improvement is partly due to the α-Si3N4 to β-Si3N4 transformation facilitated by the smaller grain size, on the other hand it is due to the better dispersion of the carbon nanotubes. The X-ray measurements confirmed that in the case of samples milled for 5 hours, even when sintered at 1700°C, low nitrogen pressure (2MPa) and without holding time, a faster phase transformation occurs, resulting in improved mechanical properties.
Chemical Methods for Scanning Electron Microscope Characterization of Non-Oxide Ceramics and Composites
Authors: Pfeifer Judit , Horváth Enikõ , Vértesy Zófia , Arató Péter , Balázsi Csaba
Published: September 2009

The deformation of ceramic matrix composites (CMC) is controlled by several processes occurring in the matrix, in the enforcing phase, at the interfaces between different phases and at the surface of the body. The main tool to study morphology features of CMC-s is high resolution scanning electron microscopy (SEM). In this study destructive chemical methods such as chemical etching and burning of combustible phases were used to prepare samples for SEM investigations from three types of materials. I. SiC skeletons of C/C-SiC structures prepared of 2D woven fabric and chopped fiber bodies were produced by chemical elimination of the constituents: Si, reinforcing C- fibers and amorphous carbon. II. Silicon-nitride reaction bonded silicon-carbide samples with finishing surface oxide films – as produced and aged - were handled by HF etchants. Etching revealed cristobalite crystallites at the interface between ceramics and oxide film, and cracks in the glassy surface layer. III. Microstructure and pore structure of Si3N4 ceramics, carbon nanotube reinforced Si3N4 (CNT/Si3N4), and C/Si3N4 with graphite and carbon black addition were examined by HF etching.
Brittle Intergranular Failure in Grain Aggregates - A Computer Simulation by Means of the Graphics Processing Unit
Authors: Kupková Miriam , Kupka Samuel
Published: September 2009

Within a model considered, each of bonds between contacting grains is treated as a two-state system and represented by a binary variable. Its two values refer to the two possible states of bond – intact or broken. A Monte Carlo simulation of fracture is carried out on a set of binary variables arranged to a cubic lattice. The transition from one configuration of broken bonds to another is governed by a Griffith-like energy associated with each of configurations. The results demonstrate i) the capability of the model to provide a useful information (e.g. the increase in roughness of fracture surface with increasing temperature, that is the transition from “brittle” to “plastic” failure), and ii) the advantage of simulation by using the graphics processing unit (saving of a computational time).
Porosity Measurement Method by X-Ray Computed Tomography
Authors: Prokop Josef , Švéda Libor , Jančárek Alexandr , Pína Ladislav
Published: September 2009

This paper describes a new nondestructive approach for porosity measurement developed in response to a need for a more accurate porosity measuring method for solid samples. The conventional methods in X-ray CT imaging are based on image segmentation where a threshold is applied at a user-defined value. As a result, the uncertainty in the porosity measurement is introduced. Therefore, the new method, called the grey level method, which reflects the phenomenon of image processing and computation of ration between the volume of voids and the total volume of the entire sample, was considered and improved in term of image noise and artifacts. The volumes of 2D CT image as a surface are achieved by means of integrating the surface with operations relating to image histogram. The porosity value is given from the curve of a porosity distribution. Subsequently, the properties of individual pores were measured and comparison with conventional destructive method of porosity computation was carried out. Also limitations of industrial X-ray CT as well as their accuracy are discussed.
Cracked bi-Material Plates under Thermomechanical Loading
Authors: Nikolova Gergana , Ivanova Jordanka
Published: September 2009

A bimaterial structure composed of two elastic plates bonded together by an interface with a normal (transverse) crack in the first plate and subjected to monotonically temperature and tension loading is considered. The interface is assumed to exhibit brittle failure at critical shear stress value or progressive damage in a cohesive zone preceding delamination. Using modified Shear lag model, the analytical solution is provided specifying the length of debonding. The critical lengths of a partial debonding along the interface are calculated and the limit value of temperature at full debonding is obtained. The analytical predictions are compared with experimental data and numerical results of Lemaitre and Song. The comparison shows a good agreement and proves the validity of the model used.
Silicon Nitride Tools for Hot Rolling of High-Alloyed Steel and Superalloy Wires
Authors: Danzer Robert , Lengauer Markus , Rubeša Domagoj , Harrer Walter
Published: September 2009

For hot rolling wires of high-alloyed steels or superalloys tools are nowadays made of ce¬mented carbides. In service they suffer from roughening of the surfaces and severe wear, which de¬teriorates the surface quality of the wires and restricts the lifetime of the tool. Due to their high hard¬ness and good high-temperature properties, improvements in tool behaviour can be expected by the use of silicon nitride tools. Experiments with several types of rollers were performed in commercial rolling mills. At modest and medium severe loaded positions (e.g. in the case of guidance rolls) silicon nitride rolls show superior performance to conventional steel or cemented carbide rolls. At the most severe loaded positions silicon nitride rolls were also superior to conventional rolls when rolling high strength steel wires. But for rolling superalloy wires, cracks, which limited further applications of the rolls, appeared in the roll surface profile (calibre). Cracks in the surface of the rollers are in general caused by Hertzian contact stresses, which can reach several hundred MPa. These cracks come into existence if a limiting load is exceeded. Then small flaws can quickly extend to a length of more then one millimetre, and then they stop again (pop in behaviour). Popped in cracks can slowly extend by cyclic fatigue up to a length where breaking out of large fragments of the rollers occurs. The critical load depends on the flow curve of the rolled materials and on the design of the rolls. For the analysed design it is exceeded when rolling superalloy wires, but it is not exceeded when rolling materials having a lower flow curve.
Brittle Fracture Studies of Solid Oxide Fuel Cells
Authors: Malzbender Jürgen , Steinbrech Rolf W. , Wessel Egbert
Published: September 2009

Solid Oxide Fuel Cells (SOFCs) with electrical efficiencies above 50 % are considered as very promising option for future decentralized energy conversion. At the Forschungszentrum Juelich (FZJ) planar SOFC stacks are currently being developed and tested at 800°C and up to 10000 h using H2 and methane as fuel. Stacks in the kW class routinely reach power densities of 700 W/cm². Typically the layered material composite of the FZJ-stack consists of cells with yttria stabilized zirconia (YSZ) electrolyte, Ni-YSZ anode and a cathode of lanthanum strontium manganite. The cells are mounted between ferritic steel interconnects. The fuel and air compartment are sealed by glass-ceramics and more recently also by metal brazes. Significant progress in reliable stack operation has been achieved over the past decade. However, problems with thermo-chemical and thermo-mechanical compatibility still remain a major challenge. To illustrate the complexity of material interactions in SOFCs, selected problems related to mechanical failure processes are presented. The role of residual stresses is addressed and fracture phenomena of cell and sealant are described in greater detail.
Electrophoretic Deposition Mechanism of Mesoporous Silica Powder in Acetone
Authors: Miyamoto Ai , Negishi Hideyuki , Endo Akira , Lu Bao Wang , Sakaki Keiji , Ohmori Takao , Yanagishita Hiroshi , Watanabe Kunihiro
Published: September 2009

The preparation of a thick coating of mesoporous silica (MPS) on metal substrates by electrophoretic deposition (EPD) has been studied for application to an advanced desiccant cooling system. In this study, we investigated the EPD mechanism of MPS in acetone under a constant applied voltage for the fabrication of a thick MPS coating. We consider that the main contributors to the resistance between the deposition electrode and the counter electrode are the deposited MPS layer and the EPD bath. The current density was measured during EPD under a constant applied DC voltage. The current density decreased as the EPD progressed, and the resistance increased between the electrodes. The AC impedance between the deposition substrate and the counter electrode was measured in the range of 10 Hz-80 kHz. We observed a single semicircle in the impedance plots.　 We investigated the influence of the MPS powder concentration of the EPD bath and the amount of deposition layer on the total resistance. We found that the resistance caused by forming the MPS layer increased as EPD progressed whereas the resistance of EPD bath was almost constant through the EPD process. Moreover, we determined the EPD mechanism of MPS powder in acetone.
Distribution of the Local Electric Field during Electrophoretic Deposition of an Alumina Suspension on a Membrane
Authors: Elsenheimer Hendrik C. , Tabellion Jan , Paul Florian , Haußelt Jürgen
Published: September 2009

The spatially distributed local electric field strength during the electrophoretic deposition (EPD) of alumina suspensions on a membrane is within the scope of the present article. The water-based alumina suspensions were optimized in order to achieve stable suspensions, high deposition rates and maximum green densities of the deposited bodies. In-situ measurements of the local potential drop inside the EPD-cell were carried out using a computer assisted process control set-up with electronic data acquisition. The behaviour of the spatial- and time-dependent electric field distribution was calculated from measured potential drops. The influence of varrying input voltages on the output parameters, such as deposition rate and green density for EPD on membranes was investigated and is discussed. It is shown that the distribution of the local electric field depends on the applied voltage and on time for the case of higher voltages. A dependance of the local electrical fields on the deposition rate is suggested as well.
Ceramic Coating on Metal Substrate by Electrophoretic Deposition Assisted by Sweeping Flow in Aqueous Suspension
Authors: Mori Takamasa , Hirasawa Naoya , Ito Ryuta , Tsubaki Jun Ichiro
Published: September 2009

Silica coatings were fabricated on stainless steel substrates by electrophoretic deposition (EPD) of aqueous slurries. An cationic surfactant, polyethylenimine (PEI) was used for obtaining positively charged silica particles and coatings on the cathode in order to prevent the anode elution. In addition, in order to prevent formation of cracks in coatings on metal substrates after drying, polyvinyl alcohol (PVA) was added in slurries as a binder. Furthermore, we could obtain crack free coatings after drying by aqueous EPD assisted by sweeping flow.
Control of Residual Stress in Multilayered Alumina Composites Prepared Using EPD in a Strong Magnetic Field
Authors: Suzuki Tohru , Uchikoshi Tetsuo , Sakka Yoshio
Published: September 2009

The mechanical properties of ceramics materials can be tailored by designing their microstructures. Residual stress is one of the important factors for controlling the crack propagation and consequently improving the mechanical properties. On the other hand, development of the crystallographic orientation even in a diamagnetic ceramic can be controlled by colloidal processing in a strong magnetic field. In this study, alumina/alumina laminar composites with different crystalline-oriented layers were fabricated by EPD in a strong magnetic field in order to control the residual stress using the difference in the thermal expansion of each layer.
Electrophoretically Deposited Porous Ceramics and their Characterisation by X-Ray Computer Tomography
Authors: Moritz Kirsten , Moritz Tassilo
Published: September 2009

Planar zirconia green bodies with unidirectionally aligned pore channels were prepared by an electrophoretic deposition method using an effect which is usually disadvantageous for the EPD from aqueous suspensions: the formation of gas bubbles by electrolysis.
Aqueous ZrO2 suspensions containing acetic acid to enable a sufficient gas generation were used for the EPD experiments. The influence of selected parameters – electrolyte content, applied voltage, and kind of deposition electrode – on the pore structure has been investigated. The green bodies were sintered at 1450 °C in air.
Optical microscopy and X-ray computer tomography (CT) were used for characterising the porous structures. CT-investigations have the advantage of a three-dimensional characterisation of the samples by a non-destructive method.
The resulting pore structure depended to a high degree on the experimental conditions of the EPD. The kind of the deposition electrode – platinum foil or platinum gauze on foil – had a strong influence on the arrangement of the pores. The EPD on Pt-foil led to randomly arranged pores, whereas very regular pore structures were obtained by the use of Pt-gauze.
Application of Ionic Liquids in the Electrophoretic Deposition of Oxide Layers
Authors: Grosse-Brauckmann Jana , Lair Virginie , Argirusis Christos
Published: September 2009

Ionic Liquids (IL) are novel materials with a wide range of applications. The variable combination of organic cation and inorganic anion offers the possibility of tuning their properties. In the present investigation we test the application of different ionic liquids as charging agents for the preparation of stable oxide suspensions for direct use in electrophoretic deposition to produce oxide layers on different substrates. Main objective of these investigations was to prove that this substance class constitutes suitable additives for successful electrophoretic deposition (EPD). As one key parameter for the EPD process is the particle charge, a big part of our investigations involved the measurement of the zeta-potential of in alcoholic suspension under the influence of phosphonium and imidazolium based ionic liquids using a micro-electrophoresis measurement
Fabrication of Multi-Layered Thermoelectric Thick Films and their Thermoelectric Performance
Authors: Horii Shigeru , Sakurai Masayuki , Uchikoshi Tetsuo , Funahashi Ryoji , Suzuki Tohru , Sakka Yoshio , Ogino Hiraku , Shimoyama Jun Ichi , Kishio Kohji
Published: September 2009

We report the fabrication of p- and n-type thermoelectric oxide thick films laminated by insulating alumina using electrophoretic deposition and their thermoelectric performance. From the experimental studies performed for optimization of the thermoelectric performance in the p- and n-type mono-layers, the control of sintering temperature for densification and the usage of fine powder were effective for reducing the electrical resistivity of thermoelectric layers. These findings could be applicable also to the triple-layered thick films. When one assumes that two triple-layered films of p- and n-type thermoelectric materials are combined as unicouple of thermoelectric module, an estimated maximum output power was 20 times higher than a measured maximum output power of a previously reported multi-layered thermoelectric module. It was found that precise control of the microstructure in the thermoelectric layers is indispensable for development of the thermoelectric modules based on the electrophoretic deposition.
Electrophoretic Deposition of Liquid Templates
Authors: Neirinck Bram , Fransaer Jan , Van der Biest Omer , Vleugels Jef
Published: September 2009

Recent developments demonstrated that liquid templates in the form of solid particles stabilized emulsions can be used to produce porous materials. The use of such emulsions offers the possibility to control the porous properties over a wide range of pore sizes and porosities for a variety of materials. In addition, the liquid nature of the template enables the formed products to be sintered without a low temperature debinding step. In this work, the electrophoretic deposition (EPD) of these liquid templates for the production of porous alumina is reported. The experimental parameters needed to obtain stable emulsions, their influence on the final porous properties, as well as the influence of the deposition parameters are discussed.
Local Electrophoretic Deposition with Coaxial Electrodes
Authors: Nold Alexander , Assion Thomas , Zeiner Johannes , Clasen Rolf
Published: September 2009

Shaping of structures is of growing importance so that innovative processes of fabrication are needed. In this sense, electrophoretic deposition (EPD) of local structures from aqueous suspensions on a membrane has proved to be a suitable process. In this work, the electrical field between two point electrodes was simulated employing the finite element method. Different electrode configurations were studied, seeking to attain a strong focusing of the electric field in order to achieve a local deposition. Aqueous suspensions are preferred for industrial application due to the high polarity of water enabling high solid loadings and also for environmental reasons. Nevertheless, the bubbles generating at the point electrodes surface (due to water electrolysis) disturb the electric field. It is therefore very important to minimize the bubbles size. In this respect, we applied a measuring technique to detect and monitor the bubbles formation and first results are presented.
Electrophoretic Deposition on Anodes from Aqueous Titania Suspensions with Titanate Solution
Authors: Sakurada Osamu , Komaba Mizuki , Obata Seizo , Hashiba Minoru , Takahashi Yasutaka
Published: September 2009

Titanate aqueous solution (TTIP-Lac) prepared by direct reaction of titanium tetraisopropoxide (TTIP) with lactic acid (Lac) in water shows characteristics of a polyanion and acts as a dispersant for preparing titanate suspension. Electrophoretic deposition (EPD) of aqueous titania suspensions was investigated with TTIP-Lac as a dispersant and hydroquinone (HQ) as an effective additive for bubble-free EPD of the aqueous system. The oxygen produced electrolytically by the EPD process at basic pH would be consumed by the chemical oxidation of HQ to quinone (Q). Bubble-free titania depositions were fabricated on anodes by EPD. A fired density with 99% theoretical density was obtained.
Aqueous Electrophoretic Deposition at High Electric Fields
Authors: Neirinck Bram , Fransaer Jan , Vleugels Jef , Van der Biest Omer
Published: September 2009

From an environmental, safety and economic perspective water should be the solvent of choice for electrophoretic deposition under industrial circumstances. However, because of the electrolytic decomposition of water under the influence of direct current, the majority of EPD is carried out in non-aqueous solvents. In this work, experiments prove that deposits can be obtained from aqueous alumina suspensions while avoiding electrolysis of the medium by using unbalanced alternating current fields [1]. In addition it is shown that the formed deposits have a green density which is intrinsically higher than those formed by traditional DC EPD from ethanol based suspensions. A theoretical basis for both electrophoretic deposition by means of unbalanced alternating fields and the higher density of deposits formed by application of such fields is provided.
Electrophoretic Deposition and Photocatalytic Activity of Titanate Nanosheets
Authors: Kambayashi Tomohisa , Daiko Yusuke , Muto Hiroyuki , Sakai Mototsugu , Matsuda Atsunori
Published: September 2009

Titanate nanosheet thick films were prepared on indium-tin oxide (ITO)-coated glass substrates by electrophoretic deposition. Three types of sols with different preparation procedures and pH values were prepared. In the case of titanate nanosheet films prepared from a sol with pH=7.0, surface of the films was flat and nanosheets which deposited on substrates were uniformly dense. Titanate nanosheet thick film deposited from the sol using dimethyl ethanol amine for the exfoliation showed a high photocatalytic activity due to the high crystallinity
Electrophoretic Deposition of Titania Nanopowders
Authors: Ghorbani Mohammad , Roushanafshar Milad
Published: September 2009

Titania Nanopowders were successfully deposited on stainless steel sheet by means of electrophoretic deposition method from titania suspension in which isopropanol was employed as a solvent and Triethanolamine as a dispersant. The effect of TEA addition on the stability of nanopowders in suspensions was examined by sedimentation test; in addition, Malvern zeta sizer was employed for determination their particle size. Electrophoretic Deposition was done at different deposition conditions of voltage (5-20 volts) and time (5-60 sec) and the scanning electron microscopy (SEM) was used to investigate the effect of suspension composition and deposition parameters on the microstructure of coatings. Furthermore, the effect of deposition parameters on the consistencies of different coatings was analyzed by Scanning Probe Microscope (SPM).
Deposition of Multiwall Carbon Nanotubes Using Low Frequency Alternating Electrophoretic Deposition
Authors: Gardeshzadeh Amir Reza , Raissi Babak , Marzbanrad Ehsan
Published: September 2009

In this paper, electrophoretic deposition of multiwall carbon nanotubes (MWNTs) using low frequency (0.01-1000 Hz) AC electric fields, is reported. The effect of depositing parameters such as frequency and waveform on deposit yield is investigated. Results show that the deposit yield decreases with frequency. The rectangular waveform yields more deposit yield than sinusoidal and triangular waveforms. The deposition pattern is also different in AC and DC electric fields. This technique may be used for deposition of MWNTs thick films.
Nickel Electrodeposition on Electrophoretically Deposited Carbon Nanotube Films
Authors: De Riccardis Maria Federica , Carbone Daniela , Martina Virginia , Re Marilena , Meng De Cheng , Roether Judith A. , Boccaccini Aldo Roberto
Published: September 2009

Multi-walled carbon nanotubes (CNTs) were deposited by electrophoretic deposition on stainless steel substrates forming homogeneous porous CNT deposits. These CNT structures were then coated with a thin layer of Ni by electrodeposition. SEM and TEM observations confirmed that the Ni layer covered uniformly the CNT surfaces. This Ni coating treatment could facilitate the dispersion of CNTs in metal matrix composites leading to improved mechanical and thermal properties.
Semi-Quantitative Analysis of Defect in Pipelines through the Use of Technique of Ultrasonic Guided Waves
Authors: Tse Peter W. , Wang Xiao Juan
Published: September 2009

Modernized cities must have adequate infrastructures to support the daily needs from her citizens. The continuity in pipeline services that supply water, gas and oil to citizens and deliver wastes to designated collectors are in prime concern to any modernized city. However, in-service pipeline is prone to defects due to aging, external impacts, or hazardous operating environment. It is of prime importance to apply an efficient inspection method to characterize the potential defect in pipeline so that the information of damage caused can be determined prior to the fatal rupture of pipeline. An early warning generated from an accurate characterization of defect can encourage the performance of proper remedy and maintenance for minimizing the scope of damage to pipelines. In this paper, a presentation is given to an advanced inspection technique based on ultrasonic guided waves. This technique has already shown great potentials in non-destructive testing of material and structures in many fields. The advantages and difficulties involved in the pipeline inspection using ultrasonic guided waves have been identified. For the quantitative characterization of defect in pipeline inspection based on advanced guided waves, we propose the method through considering the reflected signal since it provides useful information related to defect. The method analyzes the captured signals reflected from the potential defect, decomposes the embedded dimensional information of defect and then accordingly identifies its severity. Although the experiments were conducted on artificial defects, the results proved that qualitative characterization of defect is feasible. Combined with guided waves, our method can provide comprehensive information related to the existence, location, severity of defect etc., through the analysis of reflected signal from the interactions of excited guided waves with pipeline defect.
Structural Damage Detection Accounting for Loss of Data in Wireless Network Sensors
Authors: Quek Ser Tong , Tran Viet Anh , Hou Xiao Yan
Published: September 2009

For detection of damage in frame and truss structures, the normalized cumulative energy is proposed as the identification parameter within the framework of the damage locating vector (DLV) method. Due to the limited number of sensors used, it is necessary to filter out the actual damaged elements from the identified set of potential damaged elements. An intersection scheme using only the measured signals is proposed for the filtering and verified using a warehouse frame comprising truss, beam and column elements. As wireless sensors are introduced into structural health monitoring systems, loss of data during transmission is one significant issue which needs to be addressed. An algorithm to patch the loss data is proposed and when integrated with the proposed damage detection method is experimentally shown to be feasible using a cantilever truss.
Crack Detection in Pipe Structures by Lifting Wavelet Finite Element Method
Authors: Chen Xue Feng , Li Bing , He Zheng Jia
Published: September 2009

Due to the fact that near a crack singularity, gradients of the solution are large and are also subject to abrupt changes, so that the solution cannot locally be accurately approximated by a piecewise polynomial function on a quasi-uniform mesh. Lifting wavelet finite element has good ability in modal analysis for singularity problems like a cracked pipe. The first three natural frequencies of the cracked pipe were solved with lifting wavelet finite element, and the database for crack diagnosis was obtained. The first three measured natural frequencies were employed as inputs and the intersection of the three frequencies contour lines predicted the normalized crack location and size. The experimental examples denote the method is of higher identification precision.
Feature Extraction from Spectral Data Using the Bayesian Evidence Framework
Authors: Hensman James J. , Barthorpe Rob J.
Published: September 2009

The optimal selection of discriminatory features from large datasets remains a pressing
problem in damage identification. In this paper, a Bayesian approach to classification and feature
selection is introduced and applied to a challenging experimental problem.
Ensemble Empirical Mode Decomposition for Machine Health Diagnosis
Authors: Zhang Jian , Yan Ru Qiang , Gao Robert X.
Published: September 2009

Ensemble Empirical Mode Decomposition (EEMD) is a new signal processing technique
aimed at solving the problem of mode mixing present in the original Empirical Mode
Decomposition (EMD) algorithm. This paper investigates its utility for machine health monitoring
and defect diagnosis. The mechanism of EEMD is first introduced. Parameters that affect
effectiveness of the EEMD are then discussed with the assistance of a simulated signal in which the
mode mixing exists. Experimental study on bearing vibration signal analysis verified its
effectiveness of EEMD for machine health monitoring and defect diagnosis.
Gearbox Fault Diagnosis Based on Vibration Signals Measured Remotely
Authors: Al-Arbi Salem , Gu Feng Shou , Guan Lu Yang , Ball Andrew , Naid Abdelhamid
Published: September 2009

In many cases, it is impractical to measure the vibrations directly at or close to their source. It is a common practice to measure the vibration at a location far from the source for condition monitoring purposes. The vibration measured in this way inevitably has high distortions from the vibrations due to the effect of the attenuation of signal paths and the interference from other sources. The suppression of the distortions is a key issue for the remote measurements based condition monitoring. In this paper, the influences of transducer locations are investigated on a typical gearbox transmission system for the detection of the faults induced to the gearbox. Several signal processing techniques’ analysis results show that the attenuation and interference cause high influences on the gear transmission signals. However, time synchronous average (TSA) is very effective to detect the local faults induced to the gear system.
Application of Rotational Measurements in Stiffness Reconstruction of Beams and Frames
Authors: Zembaty Zbigniew , Kokot Seweryn
Published: September 2009

A stiffness reconstruction method is tested when rotational degrees of freedom are added to the dynamic model of the structure. The inverse problem is formulated as a minimization problem in terms of harmonic vibrations of the structure and its finite element model. An example of frame structure is analyzed by numerical simulations. The results of these numerical analyses show that the damage detection appeared to be much more effective when the angular amplitudes of harmonic vibrations are acquired. This makes very good prospects for the future applications of angular sensors in damage detection of structures.
Statistical Analysis of Frequency Estimation Methods of Vibration Signal
Authors: Xuan Jian Ping , Shi Tie Lin , Liao Guang Lan , Liu Shi Yuan
Published: September 2009

In the fault diagnosis of a machine, frequencies of its vibration are important indicators to show conditions of the machine. There are two main categories of methods to estimate frequency. One is based on the fast Fourier transform, and the other is on the signal subspace decomposition. Using FFT directly to estimate frequency may introduce larger estimation error, several approaches are proposed to correct or decrease the error, which comprise phase difference, energy centrobaric, interpolation and search method. The signal subspace decomposition method (SSDM) consists of Pisarenko harmonic decomposition, multiple signal classification. In order to assess the performance of these methods, the Cramer-Rao bound is used to compare with the error variance of difference frequency estimation methods, and simulations are based on Monte Carlo experiments for various record sizes and signal-to-noise ratios (SNR’s). The results show that there is a turning point about 25 dB for FFT based methods, above which FFT based methods are less sensitive to the noise, and SSDM achieves higher precision estimation at higher SNR and for the short time series, but produces poor accuracy at lower SNR’s.
The Research of the Effective Moduli of Particle Reinforced Polymer Composites Based on Interface Debonding
Authors: Chang Xin Long , Jian Bin , Ouyang Chang
Published: September 2009

This paper is devoted to studying influences of matrix/particle interface debonding and particulate size in micromechanical predictions of the effective moduli of particulate reinforced polymer composites (PRPC). The PRPC is regarded as a three-phase composite that includes the matrix, particle and interphase. The formulation for the effective moduli of the interphase is derived by the cohesive zone model, and combined with the Mori-Tanaka method, the micromechanical model for the effective moduli of the PRPC is formulated with emphasis on the effects of the matrix/particle interface, particulate size and volume fraction. The numerical example shows that the interface debonding, the particulate size and volume fraction have significant influences on the effective moduli of PRPC. The effective moduli of the PRPC can be used to characterize its damage degree.
Residual Life Assessment of Electricity Pylons – A Case Study
Authors: Maguire John R.
Published: September 2009

This case study describes a structural integrity assessment of a 220 kV overhead power line. The line comprises 70 pylons over a distance of approximately 30 km, predominantly in a valley location. The pylons are spaced at intervals of approximately 400 m and each pylon is approximately 32 m in height. The line was originally constructed in the 1950’s, approximately 50 years prior to the requested structural integrity assessment. This paper describes the independent assessment that was carried out. The review established site-specific safety factors at the time of original design and construction; at the time of the review (2007), accounting for the possible presence of the “Thomasstahl” steel; and in the future, at the anticipated end of pylon life (in 2012).
Development of Delamination in Cross-Ply Laminates: Effect of Microstructure
Authors: Khokhar Zahid R. , Ashcroft Ian A. , Silberschmidt Vadim V.
Published: September 2009

Various aspects of the effect of microstructural randomness exhibited by carbon fibre-reinforced cross-ply laminates on the delamination damage mechanism is investigated in this paper. In the first part, the matrix cracks with different spacings measured in experiments are simulated using finite elements in order to obtain the levels of degradation and effective properties for a composite beam loaded in bending. The results show significant levels of degradation of obtained effective properties depicting the importance of accounting for the inherent stochasticity in these laminates. In the second part of the paper, initiation of delamination at an interface between 0° and 90° layers due to stress concentrations at tips matrix cracks is simulated for a beam under tension. Stochastic cohesive zone elements with fracture parameters presented as random fields are used to model this interface in a composite. Different values of the axial stress are obtained for initiation of damage for a number of realisations based on this approach. The results emphasize the need to take into consideration the microstructural randomness in fibre-reinforced laminates for adequate predictions of damage and load carrying capacities.
Damage Assessment of a Cracked Bar: Effect of Material Nonlinearity on Vibro-Impact Response
Authors: Hiwarkar Vikrant , Babitsky Vladimir I. , Silberschmidt Vadim V.
Published: September 2009

Structural health monitoring is receiving much attention as a means to prevent catastrophic failure in structures in operating conditions. In most cases fracture is caused by the growth of crack, which cannot be precluded in many engineering structures. Moreover, to have an accurate quantitative estimate of crack tolerance of a structure to prevent fracture of load bearing components, an effective non-destructive evaluation procedure becomes necessary to monitor the structure under working conditions.
Statistical Damage Detection in a Smart Structure under Different Temperatures via Vibration Testing: A Global Model Based Approach
Authors: Hios John D. , Fassois Spilios D.
Published: September 2009

Statistical damage detection in a structure operating under different temperatures via vibration
testing is addressed by means of a stochastic global model based approach. The approach relies
upon novel global models of the Functionally Pooled (FP) form, which are capable of describing the
dynamics under any temperature, and statistical decision making. In its present form the approach
utilizes response (output–only) vibration data, although excitation–response data may be also used.
Its effectiveness is confirmed via a large number of experiments performed on a smart composite
beam under different temperatures within the [¡20; +20]oC range.
Assessment of the Condition of a Beam Using a Static Loading Test
Authors: Walsh Brian J. , González Arturo
Published: September 2009

This paper presents a novel approach for structural damage detection. The cross-entropy method is used to estimate the structural parameters of a simply supported beam from its response to a static load consisting of a heavy vehicle. Various states of beam damage are modelled through local reductions in flexural rigidity. The proposed method estimates the distribution of stiffness throughout the beam using the deflections due to a heavy load located on the beam. Parameters such as initial distribution values, structural model, number of readings and sample size are varied to assess their influence on the prediction of the damage severity and its location.