bluuebunny/crossref_metadata_2025 huggingface dataset:
Two Approaches for Greenization of Fixture Design and Corresponding Technology Innovation
Authors: Zhong Kang Min , Guo P.Q. , Chi Q.
Published: March 2009

The research on greenization of fixture technology is next to nothing nearly now.
Approaches for greenization of fixture technology were discussed based on the analysis of energy forms and medium of fluid transmission. The feasibility that using manual fixture with multiple series supper-force-amplified device instead of power driven fixture was presented in the point of view for greenization of energy type. The working principle of manual fixture with four-step series force-amplified device, which we have invented independently, was introduced. According to the thought for greenization of medium of fluid transmission, the feasibility that employing pneumatic fixture with force-amplified device or pneumatic-hydraulic pressure-amplified device instead of hydraulic fixture. The innovated pneumatic fixture with sphere-coin two-step force-amplified device and the two-action pneumatic-hydraulic pressure-amplified device with two steps of pressure output were illustrated briefly by means of diagram.
Development of Endless Diamond Wire Saw and Sawing Experiments
Authors: Ge Pei Qi , Zhang L. , Gao W. , Liu Zhen Chang
Published: March 2009

The endless diamond wire saw was developed using complex electroplating method. The sawing process on granite was experimented. The effects of diamond grain size, feed load, wire speed, and granite properties on sawing process were investigated. It is proved that the edges of sawing slot of granite were regulative and the cutting surfaces were smooth. The cutting efficiency could be improved by increasing the diamond grain size, wire speed, and feed load. However the increase of the feed load would induce higher tangential cutting force, and the case of the effect of wire speed was reversed.
A Study on Computer Simulation of Plastic Lens Molding Process
Authors: Li W. , Jin Yang Fu , Lv Xun , Kua C.H.
Published: March 2009

In this paper, some molding process parameters such as injection time, packing time,
packing pressure and process temperature etc. were optimized by the Computer Aided Engineering (CAE) simulation (Moldex 3D) for injection molding of a plastic lens. Some experimental trials were carried out for verifying of the CAE simulation results with checking of the lens shrinkage and birefringence etc. as well. The results showed that, the recommended molding process parameters from CAE simulation and the actual experiments were almost the same, hence the CAE is a
established tool based on the scientific approach to reduce experimental works, to identify critical parameters and to save substantial costs. Lately, a perfect plastic lens was gained by the Injection–Compression Molding process with the optimized process parameters by a CAE simulation.
Investigational Advances in Residual Stresses by Hard Turning
Authors: Zhang Xue Ping , Liu C.Richard , Yao Zheng Qiang
Published: March 2009

Hard turning has been recognized as a substitute for abrasive-based processes not only due to its flexibility, economic benefit and environmental consciousness, but also its determinate surface integrity (surface roughness, micro hardness and residual stress), which is superior and more consistent than ground surfaces. Residual stress is of considerable industrial importance because they can affect failure by fatigue, creep or cracking. It is believed that compressive residual stresses are more favorable for fatigue life than tensile residual stresses. Hard turning generally generates compressive residual stress, which is the dominant role in determining both the variance and average value of fatigue life. This paper focus on the published data, especially C.R.Liu’s research, which address the residual stresses by hard turning in terms of experimental approaches， theoretical modeling，numerical simulation by Finite Element Analysis (FEA) and the correlation with its fatigue life and performance. The potential trends and key technologies for residual stresses are predicated and discussed so as to capture the most effective approach to investigate residual stress by hard turning.
Numeric Investigation of the Cutting Temperature Fields on the Rake Face in Orthogonal Machining
Authors: Wang Su Yu , Zhao Jun , Meng Hui , Ai Xing , Li Z.L.
Published: March 2009

This paper proposes a numerical cutting model with the FEM to simulate the temperature field at the contact zone on the tool rake face. The analysis of the tool rake face temperature in orthogonal machining is studied based on heat transfer theory and calculus of variation. Then, the FEM simulation results of the temperature field on the rake face in various cutting speeds and the cutting speeds vs peak temperature curves are given. The results show that the highest temperature of the tool surface is located at a distance nearby the tool tip, and the higher cutting speeds can increase the tool rake face temperature obviously. In addition, the workpiece materials have a great effect on the peak temperatures at the rake face. Therefore, this study is helpful to investigate tool wear mechanism and optimize the machining parameters for the metal cutting processes.
The Application of Product Variant Design Based on Case-Based Design in the Development of Stone Equipments
Authors: Wang Jing Kun , Ai Xing , Zhang Jin Sheng , Wang Zhenya
Published: March 2009

As the actual design process and CBD process have collateral corresponding relation, CBD accords with the actual design process of deviser. This paper studies the application of CBD technology in product variant design. The basic resolution model of variant design is established, and the instance of products variant design is presented. With the application of variant design principle, the design intensity will be lightened, and the design time will be shortened. Therefore the variant design could accommodate the requirement of product diversification and client orientation.
Application of Wavelet Digital Filter of Fourier Transform Profilometry in 3-D Measurement
Authors: Wang Yun Shan , Fu S. , Xu Jin Quan , Zhou Can Lin , Si S.C. , Gao C.Y.
Published: March 2009

Fourier transform profilometry in 3-D measurement based on wavelet digital filter is
presented in this paper. Before phase demodulation, original modulated grating image is handled with wavelet transform in order to remove the background components and high frequency. This method resolves spectrum overlapping at some extent and reduces the requirement of low-pass filter.
Finite Element Analysis of Effects of Ball Burnishing Parameters on Residual Stresses
Authors: Deng Wen Jun , Xia Wei , Zhou Zhao Yao , Chen Wei Ping , Li Yuan Yuan
Published: March 2009

A three-dimensional coupled thermal-mechanical model of ball burnishing process is
developed using commercial explicit finite element code MSC. Marc. The workpiece is modeled as being elastic-plastic, while its flowstress is taken as a function of strain, strain-rate, and temperature. Temperature-dependent material properties are also considered in this analysis. The burnishing ball is considered as rigid and only heat transfer analysis is carried out for it. In the zone of the workpiece and tool contact, the Coulomb friction is taken into account. Effects of ball burnishing parameters (burnishing force, feed rate, speed, ball diameter and number of tool passes) on residual stresses are analyzed. The results show that burnishing force, ball diameter, number of passes and burnishing feed have the most significant effect on the residual stresses. However, burnishing speed seems to just produce little effect on those. Larger burnishing force, larger number of passes, smaller ball diameter and small feed rate seem to be more effective in increasing in the maximum compressive residual stress and the depth of the layer at the compressive stress state.
Method of Product Development Process Analysis and Reengineering for Concurrent Engineering
Authors: Liu D.Z. , Liu M. , Zhong Pei Si
Published: March 2009

Product development process analysis and reengineering are the basic for enterprise to put CE into practice. The characteristics of concurrent PDP are analyzed and compared with the traditional PDP. The basic requirements, methods and steps of PDP analysis, improvement and reengineering for CE are presented. The process model for PDP analysis and reengineering is built. According to the actual PDP in Qiqihar Railway Rolling Stock Company in China, the process for the
grain rolling stock development is analyzed and improved, and the result is satisfactory.
Research on the Sintering Process and Performance of Large-Scale Alumina Matrix Ceramic Products
Authors: Zhang Xing Hong , Liu Chun Xiao , Zhang Jian Hua
Published: March 2009

With the virtue of high Young's modulus, fine thermal stability, low density, low price, resourceful and easy to be industrialized, alumina matrix ceramics are widely applied in the environments of high temperature, high pressure, radiation, impact, abrasion and corrosion, etc. The sintering process of large-scale alumina matrix ceramic products is researched in this paper. The conception of temperature gradient is introduced to the sintering process, and corresponding mathematics model is established to get the cellular girder made of alumina, in which the microstructure is distributed evenly. Meanwhile, the material structure and the mechanics performance of the products are discussed. All the study will theoretically guide the development of large-scale fine alumina products.
Research and Application on High Efficiency Reversible Cutting Technique
Authors: Wu Wen Ge , Pang Si Qin , Yu Qi Xun
Published: March 2009

Reversible cutting method is a research thesis proposed to shorten processing route, decrease tool number and handling time, increase machining efficiency. There are three movement ways, i.e. reversible feed motion, reversible primary motion and reversible composite motion. Primary motion is done by workpiece, conventional or reversible feed motion is done by cutting tool in the way of reversible feed motion, e.g. turning. Cutting velocity is passed to cutting tool, clockwise or anti-clockwise cutting movement is done by cutting tool in the way of reversible primary motion,
e.g. milling, shaping, drilling (spade drill), reaming. Primary and feed motions are all reversible in composite motion, e.g. turn-milling. Chip deformation and machined surface with reversible finishing is discussed. A mechanical analysis is carried out to the workpiece deformation of slender shaft turning in normal direction and reversible direction. The result has been verified by experiments. Experimental data for the range of cutting parameters tested showed that the reversible fine
machining produce the compressive residual stresses at the surface, which are critical in the performance of the machined components. Experimental research indicted that the results of micro-hardness of reversible fine machining technique are smaller than that of general fine machining show that decreased plastic deformation of the surface layer and work-hardening. It can be adopted such planning which rough machining during advance stroke and fine machining during return stroke in machining process.
Direct Joining between Ethylene Propylene Rubber and Cast Iron with Functional Polymeric Nanofilm
Authors: Kang Zhi Xin , Chen Wei Ping , Long Yan , Mori Kunio , Li Yuan Yuan
Published: March 2009

A novel technique was developed for direct joining between ethylene propylene rubber and high ductile spheroidal-graphite cast iron using functional polymeric nanofilm without any adhesive. The functional polymeric nanofilm was created on the surface of cast iron by means of polymer plating with a synthesized organic compound of 6-diallylamino-1,3,5-triazine-2,4-dithiol monosodium salt. High peel strength joints of the rubber to polymer-plated cast iron were achieved by adding an accelerating agent of perhexane 3M under crosslinking condition of 418 K for 7 min. As the thickness of polymeric nanofilm was around 8.5 nm, peel strength of the joints was high to 8.9 kN/m and its broken-out section was rubber cohesive failure with 100% rubber coverage. Rubber/cast iron joints possessed good heat-resistant property. The film thickness and perhexane content had large effects on water resistance of joints. It is considered that high joining property results from chemical
bond at interface between polymer-plated cast iron and rubber chain.
Complex Magnetic Investigation of Ferritic Stainless Steel
Authors: Mészáros István
Published: March 2009

Magnetic Barkhausen noise measurement (MBN) is a relatively new non-destructive detection technique. Its working principle is based on Barkhausen discontinuities or noise when a ferromagnetic material is subjected to a varying magnetic field. MBN is being used to characterise the stress state of a ferritic stainless steel (AISI 430). Other magnetic parameters such as saturation induction (BMax), remnant induction (BR), coercive field (HC) and maximal relative permeability (PMax) derived from the hysteresis loop have also been used to support the results achieved using MBN. Microstructural changes due to cold working and heat treatments were characterized by the applied magnetic measurements. The MBN technique was proved to be a useful non-destructive and quantitative method for microstuctural investigation of the investigated ferritic stainless steel.
Processing and Properties of Polymer Composites Reinforced by Functionalized SWNTs
Authors: Zhu Jiang , Khabashesku Valery , Imam M. Ashraf , Crane Roger , Lozano Karen , Barrera Enrique V.
Published: March 2009

Carbon nanotube is seen to be an excellent reinforcement candidate to produce
multifunctional composites with improved mechanical, thermal and electrical properties. Strong interfacial bonding and homogenous dispersion are necessary conditions to obtain effective load transfer for mechanical enhancement. This paper addresses the processing of polymer composites reinforced by functionalized single wall carbon nanotubes. FTIR, SEM/EDX and DMA analysis are presented. The results demonstrated that the chemical functionalization of nanotubes helps to improve both dispersion and interaction in polymer matrix. Mechanical property improvement for the epoxy polymer composites has been shown with a small amount of carbon nanotube addition.
Synthesis and Properties of Ti3SiC2/SiC Ceramic Composites
Authors: Lin Tong Wei , Cao Wen Bin , Li Jiang Tao , Ge Chang Chun
Published: March 2009

Ti3SiC2/SiC ceramic composites with different content of SiC were synthesized through in-situ solid displacement reaction by hot pressing from starting mixture powders of TiC, Si and active carbon. The densities of the specimens were measured, the phase composition of the specimens was identified by XRD, and the microstructures were observed by SEM.
Microstructural Evolution and Micro-Texture in Zr-2.5Nb Tubes
Authors: Zhao P. , Holt R.A.
Published: March 2009

Both small experimental extruded tubes and full-size pressure tubes were examined using scanning electron microscope/electron backscattered diffraction (SEM/EBSD) and transmission electron microscope/selected area diffraction (TEM/SAD). The final microstructures and textures vary with billet microstructure, extrusion temperature and extrusion ratio. Three components in {0002} pole figures were determined. The first component (radial) is produced by a and c+a slip in a-grains during extrusion. The second component (transverse) is associated with the elongated a- grains with their c-axes parallel to their long dimension. The third component (axial) is produced by b-a phase transformation after extrusion with a preferred variant of the Burgers relationship.
Application of Creep Ductility Model for Evaluation Creep Crack Growth Rate of Type 316SS Series
Authors: Kim Woo Gon , Kim Hyun Hie , Yoon Kee Bong , Ryu Woo Seog
Published: March 2009

This paper is to evaluate the creep crack growth rate (CCGR) of the type 316SS series: 316SS, 316FR and 316LN, and to apply a creep ductility model. A number of the data are collected through wide literature surveys and experiment, and evaluated by the C* parameter. The results of the CCGR data were nearly matched with a small scattering band regardless of the different applied stresses, temperatures and test specimens configuration. In the CCGR, type 316FR and 316LN steels were slower than type 316SS. Type 316SS showed a better agreement in the application of the creep ductility model than the type 316FR and 316LN steels.
Damage Localization on Two-Dimensional Structure Based on Wavelet Transform and Active Lamb Wave-Based Method
Authors: Peng Ge , Yuan Shen Fang
Published: March 2009

Damage characterization was carried out by comparing single mode sensor signals
collected before and after the damage event. By subtracting the signals of both conditions from each other, a scatter signal is produced which can be used for damage localization. By using Gabor wavelet to analyze single mode Lamb wave recorded before damage and scatter signal, the difference of time-of-flight can be obtained. Combining with the ellipse technique, the localization experiment on fiberglass plate of dimension 100×100×2mm is completed.
Rheology and Foaming Characteristics of Melt for Metal Foam
Authors: Park Soo Han , Hur Bo Young , Song Kwang-Ho
Published: March 2009

Metal foam was produced by the Melt Foaming Method. In this foaming process, the
surface tension and the viscosity of molten Al (recycled waste Al) and Mg alloy (Az91) that were measured respectively by the ring method and the rotational method are the most important two factors. They surface tension and the viscosity were investigated in the temperature range of about 600-900°C and the effects of the additional surface-active elements were investigated at the about 640°C. The measured surface tension of the molten recycled Al and Az91 decreased linearly with the increasing temperature of Ar gas (99.999%) and SF6+CO2 (1:100) atmosphere. The effect of surface-active elements is a decrease of the surface tension and an increase of the viscosity. The optimal conditions for the foam metal manufacturing are needed the low surface tension and the high viscosity. It is possible that the optimal conditions of the surface tension and the viscosity can be
obtained through controlling the amount of adding surface-active elements.
High Temperature Deformation Behavior of AZ31 Mg Alloy
Authors: Lee B.H. , Shin Kwang Seon , Lee Chong Soo
Published: March 2009

High temperature deformation behavior of AZ31 Mg alloy was investigated in this study on the basis of a processing map (e » 0.6). To construct a processing map, compression tests were carried out at various temperatures and strain rates. Two regions of high deformation efficiency (h) were identified as: (1) a dynamic recrystalization (DRX) domain at 250°C and 1/s and (2) a superplasticity domain at 450°C and 10-4/s. The average grain size observed in the DRX region was considerably smaller (2.9µm) than in any other region. In the superplastic condition, tensile elongation to failure approached to 1040%. At the high Z regions, flow softening occurred resulting from the dynamic recrystallization but below 1010 of Z value, flow hardening occurred due to the grain growth. Possible deformation mechanisms operating at high temperature were discussed in relation to the activation energy. A two-stage deformation method was found to be effective in
enhancing the superplasticity of AZ31 Mg alloy.
Fabrication and Property of Amorphous/Nano Crystalline Al84Ni10Ce6 Bulk Alloy by a Powder Forging
Authors: Noh Si Joon , Jung Taek Kyun , Kim Mok Soon
Published: March 2009

The bulk Al84Ni10Ce6 alloy was fabricated by a powder forging process. The process involved pre-compaction of amorphous powder by cold pressing and subsequent isothermal forging at temperatures from 523 to 823K with the strain rate of 10-2 s-1. The porosity decreased rapidly with increasing forging temperature up to 648K, and a fully dense bulk specimen with the porosity less than 1% was achieved when the forging was carried out at and above 648K. TEM observation on the fully dense bulk alloys revealed a mixed structure consisting of nano-scaled crystalline particles and amorphous matrix. It was also revealed that the size and volume fraction of the crystalline phases increased with increasing forging temperature. Noticeably high compressive fracture strength of 1355MPa and Vickers hardness number of 530 were obtained at room temperature for the fully dense bulk specimen forged at 648K, which contains the refined crystalline particles (average size: 28nm, volume fraction: 44%) in an amorphous matrix.
Nano-Scale Clusters Formed in the Early Stage of Phase Decomposition of Al-Mg-Si Alloys
Authors: Shoichi Hirosawa , Sato Tatsuo
Published: March 2009

The formation of nano-scale clusters (nanoclusters) prior to the precipitation of the strengthening b” phase significantly influences two-step aging behavior of Al-Mg-Si alloys. In this work, the existence of two kinds of nanoclusters has been verified in the early stage of phase decomposition by differential scanning calorimetry (DSC) and three-dimensional atom probe (3DAP). Pre-aging treatment at 373K before natural aging was also found to form preferentially one
of the two nanoclusters, resulting in the remarkable restoration of age-hardenability at paint-bake temperatures. Such microstructural control by means of optimized heat-treatments; i.e. nanocluster assist processing (NCAP), possesses great potential for enabling Al-Mg-Si alloys to be used more widely as a body-sheet material of automobiles.
Laser Doping and Recrystallization for Amorphous Silicon Films by Plasma-Enhanced Chemical Vapor Deposition
Authors: Wuu Dong Sing , Lien Shui Yang , Wang Jui Hao , Mao Hsin-Yuan , Hsieh In-Cha , Wu Bing-Rui , Yao Pin Chuan
Published: March 2009

One of the most challenging problems to develop polycrystalline silicon thin-film solar
cells is the growth of crystalline silicon on foreign, low-cost and low-temperature substrates. In this paper, a laser doping technique was developed for the plasma-deposited amorphous silicon film. A process combination of recrystallization and dopant diffusion (phosphorous or boron) was achieved simultaneously by the laser annealing process. The doping precursor was synthesized by a sol-gel
method and was spin-coated on the sample. After laser irradiation, the grain size of the doped polycrystalline silicon was examined to be about 0.5~1.0 µm. The concentrations of 2×1019 and 5× 1018 cm-3 with Hall mobilities of 92.6 and 37.5 cm²/V-s were achieved for the laser-diffused phosphorous- and boron-type polysilicon films, respectively.
Study of Erbium Oxidation by XPS and UPS
Authors: Guerfi N. , Bourbia O. , Achour S.
Published: March 2009

X-ray and UV photoelectron spectroscopy (XPS and UPS were used for studying the oxidation of Er films deposited on Ta substrate under ultra-high vacuum.Oxidation has been carried out at room temperatue with an oxygen pressure of 2x10-5 mbar.Erbium exposition to oxygen produces ; Er2O3 and a hydoxide.Subjecting the sample to a post annealing treatment at 750 °C dissociates the hydroxide and produces additional Er2O3.UPS and XPS valence band gives evidence that the formed oxide is Er2O3.
Control of the Weak Phosphorus Doping in Polysilicon
Authors: Zaghdoudi M. , Abdelkrim M.M. , Fathallah M. , Mohammed-Brahim T. , Le Bihan F.
Published: March 2009

The optical and electrical properties of undoped and low doped polycrystalline silicon
films deposited by LPCVD technique are analysed. Photothermal deflexion spectroscopy, and electrical conductivity in the temperature range 50- 475 K are used. The effect of low phosphorus doping on the density of defects, electrical parameters and hopping conduction are examined and interpreted in conjunction with the passivation of defects by the introduction of phosphorus atoms.
The density of states at the Fermi level is also calculated.
Effect of Heat Treatments in the Silicon Eutectic Crystal Evolution in Al-Si Alloys
Authors: Forn Antonio , Baile Maite T. , Martín Enric , Rupérez Elisa
Published: March 2009

This paper describes the heat treatment effect on the eutectic silicon evolution in the
A357 alloy, obtained by semisolid forming process (SSM). The coarsening rate of the silicon was determined by Image Analysis Technique in specimens from rheocasting ingots and thixocasting components. The study was realized in the temperature range from 450 to 550°C by applying heating times between 1 and 24 hours. The results show that during the heat treatment the coarsening and sphereodization of the silicon particles is produced and the fragmentation stages,
which are observed in conventional alloys, do not appear. Kinetic silicon growth has been adjusted to the Oswald’s ripening equation.
High Performance Photocathodes with 50% Quantum Efficiency
Authors: Townsend P.D. , Downey R.J. , Harmer S.W. , Cormack A.N. , Mcalpine R.
Published: March 2009

Multialkali photocathodes are used from 200 to 850 nm, but high transparency at longer wavelengths reduces the quantum efficiencies. Theoretically, routes to enhance absorption could achieve high efficiency over most of this spectral range. Realisations of some of the concepts have been successfully attempted leading to quantum efficiencies of ~50%, with examples from 200 to 750 nm. Improvement factors of up to 50 times occur by ~900 nm, giving an extension of the useful wavelength operating range.
Effect of Structural Disordering on the Magnetic, Magneto-Optical and Optical Properties of the Ni2MnIn Heusler Alloy Films
Authors: Kudryavtsev Yuri V. , Lee Young Pak , Lee Ni Na , Huang Mei Dong
Published: March 2009

The magnetic, the magneto-optical and the optical properties of Ni2MnIn alloy films
with significantly different atomic orders (from nearly single-crystalline to amorphous) were investigated. The crystalline Ni2MnIn alloy films are a ferromagnetic with a Curie temperature of 325 - 330 K, while the amorphous phase is not ferromagnetically-ordered (at least, above 293 K). The diagonal and the off-diagonal components of the dielectric function for the crystalline alloy were experimentally determined for the first time. The nature of interband excitations in the optical spectra of the ordered phase is discussed in terms of the band structures of Ni2MnSn. The analyses of changes in the electron energy structure of Ni2MnIn alloy, caused by the structural disordering, are performed using the results of optical study. An annealing at 750 K for 2 hrs of the amorphous film restores its crystallinity (B2 phase) and also the ferromagnetic order.
Critical Planes in Multiaxial Fatigue
Authors: Karolczuk Aleksander , Macha Ewald
Published: March 2009

The paper includes a review of literature on the multiaxial fatigue failure criteria based on the critical plane concept. The criteria were divided into three groups according to the distinguished fatigue damage parameter used in the criterion, i.e. (i) stress, (ii) strain and (iii) strain energy density criteria. Each criterion was described mainly by the applied the critical plane position. The multiaxial fatigue criteria based on two critical planes seem to be the most promising. These two
critical planes are determined by different fatigue damage mechanisms (shear and tensile mechanisms).
Studies of SCC and Hydrogen Embrittlement of High Strength Alloys Using Fracture Mechanics Methods
Authors: Dietzel Wolfgang , Pfuff Michael , Juilfs Guido G.
Published: March 2009

Fracture mechanics based test and evaluation techniques are used to gain insight into the phenomenon of stress corrosion cracking (SCC) and to develop guidance for avoiding or controlling SCC. Complementary to well known constant load and constant deflection test methods experiments that are based on rising load or rising displacement situations and are specified in the new ISO standard 7539 – Part 9 may be applied to achieve these goals. These are particularly suitable to study cases of SCC and hydrogen embrittlement of high strength steels, aluminium and titanium alloys and to characterise the susceptibility of these materials to environmentally assisted cracking. In addition, the data generated in such R-curve tests can be used to model the degradation of the material caused by the uptake of atomic hydrogen from the environment. This is shown for the case of a high strength structural steel (FeE 690T) where in fracture mechanics SCC tests on pre-cracked C(T) specimens a correlation between the rate of change in plastic deformation and the crack extension rate due to hydrogen embrittlement was established. The influence of plastic strain on the hydrogen diffusion was additionally studied by electrochemical permeation experiments. By modelling this diffusion based on the assumption that trapping of the hydrogen atoms takes place at trap sites which are generated by the plastic deformation, a good agreement was achieved between experimentally obtained data and model predictions.
Modelling Cleavage Fracture in High Strength Steels and Their Welds
Authors: Rodriguez Rodolfo-Martín , Ocaña-Arizcorreta I. , Martín-Meizoso A.
Published: March 2009

High strength steels are characterized by their high yield strength, but to guarantee a safe design, a sufficiently large fracture toughness value is also required. In this paper, the fracture toughness of three high strength steels (sy= 460-890 MPa) and their welds has been studied at low temperatures. Experimental results have been used to validate a statistical “weakest link” fracture model. The model takes into account the possibility of fracture nucleation in different types of particles and brittle phases, as well as the crack-arrest factors at the different microstructural barriers (particle-matrix interface and grain boundaries).
Microstructure and Thermal Stability of Ultra Fine Grained Mg and Mg-Gd Alloys Prepared by High-Pressure Torsion
Authors: Čížek Jakub , Procházka Ivan , Smola Bohumil , Stulíková Ivana , Kužel Radomír , Matěj Z. , Cherkaska V. , Islamgaliev Rinat K. , Kulyasova Olya B.
Published: March 2009

Bulk samples of pure Mg and Mg-Gd alloys were prepared by high-pressure torsion
(HPT). The HPT made samples exhibit ultra fine grained (UFG) structure with grain size around 100 nm. Results of microstructure investigations of the UFG samples obtained by positron lifetime (PL) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) are presented. In particular, lattice defects introduced by HPT were characterized. The data obtained at
atomistic level are compared with macroscopic properties given by microhardness measurements.
Experimental Investigation of the Local Deformation Behaviour of MMCs
Authors: Unterweger Klaus , Kolednik Otmar
Published: March 2009

Particle reinforced MMCs with a particle size of 100µm and an aluminium matrix
(Al6061) are analyzed by the means of automatic local deformation analysis. Two different heat treatment conditions (under- and over-aged) are investigated. It is found that the local deformation behaviour is strongly determined by particle damage. While the under-aged material shows only particle fracture, the over-aged MMC shows also particle debonding as a relevant damage mechanism.
The Formation and Destruction of the Boundary Layer in Polymer Composite Fiber Shells during Their Ageing
Authors: Senchurov S.P. , Zabashta Yu.F.
Published: March 2009

This paper considers the composite "core-shell" fibers ageing. A physical model of
ageing is proposed. The stress state due to the structural relaxation processes in the shell results from the ageing. The ageing model was verified experimentally. The agreement between the model and experiment is found. A weak periodical boundary layer between the core and the shell is formed as a result of the composite fiber ageing process. The values characterizing the boundary layer (thickness and shear modulus) were obtained.
On Crack Path in Fibres-Reinforced Ceramic Composites
Authors: Profant Tomáš , Kotoul Michal
Published: March 2009

A micromechanics study is presented of the matrix cracking of fibres-reinforced ceramic composites when subject to tensile stressing normal to fibres. Stability and/or instability of the straight micro-crack paths is investigated for a periodic array of originally collinear, slowly growing microcracks with fibres located in between the neighbouring micro-cracks tips. The relevant application e.g. refers to matrix cracking in 90° plies of cross-ply ceramic composites. The problem is solved using the technique of distributed dislocations and an approximate fundamental solution
for a single edge dislocation lying in a general point between inclusion centres. The Muschelishvili complex potentials and the Galerkin method for a numerical evaluation of coefficients of suitable chosen bas functions are employed. Numerical results are presented showing an influence of mutual microcracks-fibres geometry and the mismatch of elastic properties on micro-crack path stability/instability.
A Method for the Analysis of the Growth of Short Fatigue Cracks
Authors: McEvily A.J.
Published: March 2009

The behavior of short fatigue cracks is a matter of importance not only because much of the fatigue lifetime is spent in propagating these cracks, but also because the boundary between propagation and non-propagation separates the safe from the potentially unsafe fatigue regimes. The method of analysis is based upon the following equation:
The Role of the Constraint in the Case of Short Cracks
Authors: Hutař Pavel , Seitl Stanislav , Knésl Zdeněk
Published: March 2009

A two-parameter constraint-based fracture mechanics approach is used to explain the effect of the constraint on the apparently anomalous behavior of short fatigue cracks. The different levels of stress constraint are quantified by the T-stress, and microstructurally as well as mechanically short cracks are discussed. Short cracks generally behave more sensitively to the constraint than the long ones. It is shown that in most cases, the existence of short cracks goes hand in hand with an intrinsic loss of the constraint, which contributes to a decrease of their fatigue threshold values and accelerates their growth. In this paper, the above effect is quantified and
conclusions concerning the applicability of the fracture mechanics parameters and approaches to the estimation of the residual fatigue life of structures are discussed.
Crack Growth Anomalies in Base Steel P91 and in HAZ
Authors: Balík Jaroslav , Janeček Miloš , Pešička Josef
Published: March 2009

The growth of cracks in base steel P91 of 9Cr-1Mo class and in intercritical layer of HAZ is measured under creep coditions. For long term tests, a material degradation was detected consisting in an increase of crack growth rate and in a decrease of crack initiation time. An attempt is made to connect these effects with drop in ductility during thermomechanicalexposition.
On a Testing of Mechanical Properties of Material Surfaces
Authors: Berka L. , Murafa N.V.
Published: March 2009

Hardness testing is a method frequently used for evaluating the resistance of body
surfaces to the influence of contact loading. The Vickers hardness test is applied for this purpose in a case when the material is sufficiently ductile and no cracks occur in the corners of the indents. Testing of the surface hardness of such materials as glass and ceramics on the basis of the Vickers testing method must take into account the energy that is spent on crack spreading. This paper
describes a more exact and accurate method for evaluating resistance to microcrack formation on the surface of a material. To evaluate the conditions for crack spreading, it is necessary to test a specimen under loading in bulk. The suggested procedure involves a bent strip. As bending stresses are known, from them and from the differences in crack length along and across the strip, the
resistance of the material surface to crack propagation is determined.
Relation between Uniaxial and Equi-Biaxial Creep and Creep Fracture Behaviour in P91 Steel
Authors: Milička Karel , Dobeš Ferdinand
Published: March 2009

Conventional uniaxial creep tests on massive specimens and small punch creep tests on thin discs were performed on P91 steel at temperatures from 823 to 873 K. The shapes of corresponding time dependences, i. e., creep curves and time dependence of the disc deflection, are very similar. A simple linear relationship between the applied stress in creep tests and the acting force in small punch tests leading to identical times to rupture was empirically derived. The proportionality factor reaches a value close to values observed in other creep-resistant ferritic steels.
Effect of Processing Route on Microstructure and Mechanical Behaviour of Ultrafine Grained Metals Processed by Severe Plastic Deformation
Authors: Sklenička Václav , Dvořák Jiří , Svoboda Milan , Král Petr , Vlach B.
Published: March 2009

Aluminum-based alloys containing quasicrystalline particles of 50 – 600 nm in diameter as a reinforcing phase were produced in the form of powder or ribbons by water atomization or melt spinning techniques, respectively. Rods were compacted from powders and some ribbons by severe plastic deformation without sintering. Structure and mechanical behavior of alloys are discussed.
The Significance of Plastic Zone Growth under Cyclic Loading and Crack Opening/Closing Model in Fatigue Crack Propagation
Authors: Toyosada Masahiro , Gotoh Koji
Published: March 2009

Fatigue cracks remain closed at lower loading level during a part of load cycle even though a tension-to-tension loading is applied. The crack closure plays a role to obstruct the generation and growth of compressive plastic zone during unloading. Cyclic plastic work, which corresponds to an irreversible energy consumed in a cracked body is generated ahead of a crack, is required as a fatigue crack driving force. The amout of cyclic plasticity is reduced by a crack closure. The crack
opening/closing model based on the Dugdale model under arbitrary stress distributions for a through thickness straight crack is proposed and the fatigue crack growth under various loadings is investigated.
Is the Al Solubility Limit in SiC Temperature Dependent or not?
Authors: Jacquier Christophe , Ferro Gabriel , Zielinski Marcin , Polychroniadis Efstathios K. , Andreadou A. , Camassel Jean , Monteil Yves
Published: March 2009

The so-called VLS (Vapour-Liquid-Solid) mechanism in an Al-Si melt has recently
demonstrated the capability to grow at low temperature single crystalline 4H-SiC layers, with a high Al content. Using the newly developed VLS technique, we have deposited several 4H-SiC layers and determined the incorporated Al level by SIMS (Secondary Ion Mass Spectroscopy). Depending on the sample, we have found that the SIMS doping level ranges from 5x1019 to 1x1021 at.cm-3. This last value is the highest one reported so far for in-situ doped SiC:Al. From TEM (Transmission
Electron Microscopy) analyses we show that the layers are single crystals, with a high density of defects located only at the lower interface and no foreign phase inclusion. These results compare well with the ones obtained in previous works using alternative doping techniques, like ion implantation, chemical vapour deposition or sublimation. It thus suggests that Al solubility limit in SiC is rather temperature independent.
Epitaxial Growth of n-Type 4H-SiC on 3" Wafers for Power Devices
Authors: Thomas Bernd , Hecht Christian
Published: March 2009

In this paper we present recent results of epitaxial growth of 4H-SiC on 3” (0001) 8° and 4° off-oriented wafers using a multi-wafer hot-wall CVD system. This equipment exhibits a capacity of 5x3” or 7x2” wafers per run. By optimizing the process conditions epitaxial layers with excellent crystal quality, purity and homogeneity in doping and thickness were grown. The intra-wafer as
well as the wafer-to-wafer homogeneity will be illustrated by doping and thickness mappings of a full-loaded run. Surface morphology of epitaxial layers on 8° and 4° off-oriented wafers was investigated by atomic force microscopy.
Suppression Mechanism of Double Positioning Growth in 3C-SiC(111) Crystal by Using an Off-Axis Si(110) Substrate
Authors: Nakamura Mitsutaka , Isshiki Toshiyuki , Nishiguchi Taro , Nishio Koji , Ohshima Satoru , Nishino Shigehiro
Published: March 2009

Hetero-epitaxial CVD growth of 3C-SiC on a Si(110) substrate gives a (111) crystal with low defects density. However, double positioning growth often disturbs growth of a single crystal. The growth on an off-axis Si(110) substrate suppressed propagation of the double positioning defects in the grown layer effectively. Cross-sectional transmission electron microscopy revealed
the details of the suppression process on the off-axis substrate. The suppression mechanism and the origin of the defects formation at double positioning boundaries were interpreted by the growth model based on an anisotropic growth rate on (111) plane of 3C-SiC.
Influence of Substrate Roughness on the Formation of Defects in 3C-SiC Grown on Si(110) Substrate by Hetero-Epitaxial CVD Method
Authors: Isshiki Toshiyuki , Nakamura Mitsutaka , Nishiguchi Taro , Nishio Koji , Ohshima Satoru , Nishino Shigehiro
Published: March 2009

Interfaces between a Si(110) substrate and 3C-SiC crystals grown hetero-epitaxially by CVD were investigated by cross-sectional transmission electron microscopy. Gas flow condition during the carbonization process affects the roughness of the substrate surface and there is an optimum condition to preserve the flat surface. High quality 3C-SiC crystals grew only on the flat substrate, with crystallographic relationship of Si[1-10]//SiC[1-10] and Si[001]//SiC[1-1 - 2], because the well-lattice-match relationship was limited in a two-dimensional region at the SiC(111)/Si(110) interface. Using the optimum condition, some kinds of roughness at an atomic scale remained on the surface of the substrate. Nanoscopic observation of the crystals grown on an off-axis substrate revealed the influence of the roughness on the epitaxial growth and the defects generation at the interface.
Key Radicals for Hetero-Epitaxial Growth of 3C-SiC on Silicon Substrates
Authors: Shimizu Hideki , Hisada Kensaku , Aoyama Yosuke
Published: March 2009

Effects of the flow rate of C3H8 passed through hydrogen plasma on deposition rates and^microstructures of 3C-SiC films on Si (100) substrate were investigated by a reflection electron diffraction, an X-ray diffraction and an ellipsometric measurement. The deposition rate of the films increased independently of the flow rate of C3H8 with increasing the flow rate of SiH4. The films grown with increasing the flow rate of C3H8 kept single crystalline structure even at high flow rate of SiH4. Hydrogen radicals generated from C3H8 decomposition by plasma increase with increasing the flow rate of C3H8, and play important rolls to keep epitaxial growth.
Nucleation Control in FLASIC Assisted Short Time Liquid Phase Epitaxy by Melt Modification
Authors: Pezoldt Joerg , Polychroniadis Efstathios K. , Stauden Thomas , Ecke Gernot , Chassagne Thierry , Vennéguès P. , Leycuras André , Panknin D. , Stoemenos J. , Skorupa Wolfgang
Published: March 2009

The influence of the different additions to the melt on the nucleation behavior during
short time flash lamp processing was investigated. It was observed that germanium and carbon additions to the silicone melt led to an increase of the mass transport to the growing surface and to an increase of the nuclei size. In the case of germanium additions to the silicon melt an incorporation of germanium in the silicon substrate was observed.
Microstructures in the Pendeo Epitaxial Layer of 3C-SiC on Si Substrate
Authors: Shoji A. , Nakamura Mitsutaka , Mitikami K. , Isshiki Toshiyuki , Ohshima Satoru , Nishino Shigehiro
Published: March 2009

The pendeo epitaxial growth has been applied for the growth of 3C-SiC on (001) Si substrates. This growth was performed by VPE using hexamethyldisilane (HMDS) as a source gas. To characterize the crystallinity of the seed 3C-SiC and the pendeo epitaxial layer, the high resolution transmission electron microscopic (HRTEM) analysis was carried out. In the vertically grown layer on the seed 3C-SiC, the high-defect-density regions were observed. On the contrary, the
low-defect-density regions were observed in the laterally grown layer. It was revealed from the TEM observations that lattice information can be transferred through the seed 3C-SiC while defects can be prevented from propagating into the epitaxial layer due to the presence of the air gap.
Interface Defects in n-Type 3C-SiC/SiO2: An EPR Study of Oxidized Porous Silicon Carbide Single Crystals
Authors: von Bardeleben Hans Jürgen , Cantin J.L. , Ke L. , Shishkin Y. , Devaty Robert P. , Choyke Wolfgang J.
Published: March 2009

The defects at the 3C-SiC/SiO2 interface have been studied by X-band EPR spectroscopy in oxidized porous 3C-SiC. One interface defect is detected; its spin Hamiltonian parameters, spin S=1/2, C3V symmetry, g//=2.00238 and g⊥=2.00317, central hyperfine interaction (CHF) with one carbon atom and AB//[001]=48G and superhyperfine (SHF) interaction with three equivalent Si neighbour atoms and TB//[001]=12.4G, allow us to attribute the center to a sp3 coordinated carbon
dangling bond center, PbC.
Modification of the Oxide/Semiconductor Interface by High Temperature NO Treatments: A Combined EPR, NRA and XPS Study on Oxidized Porous and Bulk n-Type 4H-SiC
Authors: von Bardeleben Hans Jürgen , Cantin J.L. , Vickridge I. , Song Yong Wei , Dhar S. , Feldman Leonard C. , Williams John R. , Ke L. , Shishkin Y. , Devaty Robert P. , Choyke Wolfgang J.
Published: March 2009

The effect of thermal treatments in nitric oxide (NO) on the paramagnetic defects at the 4H-SiC/SiO2 interface are analyzed by EPR in oxidized porous samples. The results on ultrathin thermal oxides show that the NO treatment at 1000°C is insufficient for an efficient reduction of the two dominant paramagnetic interface defects: PbC centers and carbon clusters. From the NRA and XPS analysis of bulk samples treated under the same conditions we attribute the weak effect to
the low nitrogen concentration of only 1% at the interface.
Hyperfine Interaction of Nitrogen Donor in 4H-SiC Studied by Pulsed-ENDOR
Authors: Son Nguyen Tien , Isoya Junichi , Yamasaki Satoshi , Janzén Erik
Published: March 2009

Shallow N donors in n-type 4H-SiC were studied by electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR). For the N donor at the cubic site (Nk) in 4H-SiC, the hyperfine (hf) constants of the interaction with the nearest neighbour (NN) 29Si atom along the c axis were determined as A = 41.07 MHz and A^ = 41.31 MHz. For other three NN Si
atoms in the basal plane, the hf tensor has C1h symmetry and the principal values Axx = 5.94 MHz, Ayy = 5.06 MHz and Azz = 14.25 MHz. Our EPR and ENDOR observations unambiguously confirm that the N donor occupies the C site in 4H-SiC lattice and also reveal a considerable amount of the spin density of Nk (~23.9%) which was not obtained in previous studies.
Optical Studies of Nonequilibrium Carrier Dynamics in Highly Excited 4H-SiC Epitaxial Layers
Authors: Neimontas K. , Aleksiejūnas R. , Sūdžius M. , Jarašiūnas Kęstutis , Bergman Peder
Published: March 2009

We applied picosecond four-wave mixing technique to investigate carrier diffusion and recombination in n-type 4H-SiC epilayers. The dependence of bipolar diffusion coefficient D on photocarrier density was measured in range from ~ 1017 to ~ 1020 cm-3. We determined a decrease of D value from 3.4 to 2.2 cm2/s with increase of the photoexcitation level in range from ~ 1017 to ~ 1019 cm-3, and found its increase up to 3.8 cm2/s at carrier density above 1020 cm-3. Auger recombination governed decrease of carrier lifetime from 11 ns at ~ 1017 cm-3 to 1.8 ns at ~ 1020 cm- 3 has also been observed.