bluuebunny/crossref_metadata_2025 huggingface dataset:
Residual Stresses Induced by Robotized Hammer-Peening
Authors: Thibault Denis , Simoneau Raynald , Lanteigne Jacques , Fihey Jean-Luc
Published: March 2009

The strains induced by hammer-peening were measured by strain gauges on a mild steel plate during the hammer-peening operation. This process has recently been robotized by the research institute of Hydro-Québec (IREQ), so the hammer-peening performed for this study was done with the help of a Scompi robot. The resulting stresses calculated from the strain measurements were compared with residual stress measurements made with the hole drilling technique. The comparison
shows a very good correlation of the two sets of measurements. Residual stress measurements were also made in the hammer-peened zone: as expected we found a highly biaxial compressive state of stress in this zone. An unexpected region of transverse tension was found at the end of the hammerpeened zone. This region can be very critical if hammer-peening is made with the objective of improving fatigue behaviour.
Compressive Residual Stress Evolution Process by Laser Peening
Authors: Akita Koichi , Tanaka Hirotomo , Sano Yuji , Ohya Shin Ichi
Published: March 2009

Microscopic residual stress distribution on laser-irradiated materials was measured using a synchrotron radiation source. Intense laser pulses were irradiated in water to high tensile strength steel and austenitic stainless steel without any surface coating. Residual stress was measured in a laser-irradiated spot (0D), line (1D) and area (2D) on the materials in order to clarify the evolution process of residual stress. Tensile residual stresses were observed in the laser single pulse irradiated spot (0D). In the line (1D) and area (2D) irradiation, however, the tensile residual stress gradually changed into compressive side as the density of irradiated laser pulses increased. In case of laser irradiation in water, resulting residual stress is considered to be the sum of a tensile stress component by thermal effect and a compressive one by plastic deformation due to shock wave. The tensile stress component remains constant even if the laser pulse density increases, because the thermal effect may be reset every pulse, whereas the compressive stress component increases with laser pulse density, until the saturation of plastic deformation. As a result, the surface residual stress changes into compression with increasing the laser pulse density.
An Investigation into Work Hardening of Shot Peening Affected Layer Using X-Ray Stress Analysis Technique
Authors: Li J.B. , Gai X.Y. , Wang D.L. , Ma S.Y. , Ji Vincent
Published: March 2009

The work hardening effect of the shot peening affected layer of hardened and low
temperature tempered spring steel was investigated using the method for determining the yield strength of a metallic surface with biaxial residual stress. The results show that for the surface layer of the specimens, the microhardness and half-width values of X-ray diffraction lines is decreased, whereas the yield strength is increased during shot peening. Thus, shot peening leads the surface layer of steel in hard state to work hardening instead of work softening.
Calculation of Relaxation of Residual Stress and Change of Yield Strength in Shot Peened Layer
Authors: Li Yan Huai , Lu Jian , Xu Ke Wei
Published: March 2009

Residual stresses distribution after shot peening and its relaxation during uni-axial loading were investigated experimentally and theoretically on stainless steel of AISI304. An analytical model was proposed based upon continuum plasticity theory and elasto-plasticity finite element (FE) analysis, in which both relaxation of shot peening induced residual stress and variation of yield strength in the surface layer were taken into consideration. The results show that the value of yield strength in surface layer is altered after shot peening, and the relaxation of residual stress takes
place at the point where the combination of applied strain and residual strain exceeds the true value of yield strength. A fundamental agreement was proved between measurements and predictions in simple tension and compression.
Residual Stresses around an Expanded Hole in an Aluminum Clad Sheet
Authors: Matos P. , Moreira Pedro Miguel Guimarães Pires , Pina J.C.P. , Dias A. Morão , de Castro Paulo Manuel Salgado Tavares
Published: March 2009

Cold working introduces a compressive stress field around rivet holes, reducing the
tendency for fatigue cracks to initiate and grow under cyclic mechanical loading. As it is well known, for the accurate assessment of fatigue lifetimes a detailed knowledge of the residual stress profile is required. Powerful experimental and numerical tools are nowadays available for that purpose. In the present work both types of tools, X-ray diffraction and 3D Finite Element Analysis (FEA), were used
in order to evaluate the residual stress profile. A comparison of experimental and numerical data is presented and discussed.
Effect of Applied and Residual Stresses on the Analysis of Mechanical Properties by Means of Instrumented Indentation Techniques
Authors: Gibmeier Jens , Hartmann Stefan , Scholtes Berthold
Published: March 2009

Various methods have been proposed in recent years for the determination of mechanical properties of a material by using instrumented indentation testing. These load and depth sensing indentation techniques imply the measurement of a characteristic load-indentation depth curve by the aid of which numerous materials properties can be extracted. On the other hand in many publications the effect of applied or residual stresses on the results of hardness readings is investigated. Methods are proposed to estimate applied or residual stresses by means of instrumented indentation testing. Based on this obvious inconsistency between these procedures on the use of information of instrumented hardness testing the influence of residual stresses as well as applied stresses on continuous microhardness readings is systematically investigated for steel samples. Experimental investigations were supplemented by finite element simulations of ball
indentation tests on equi-biaxially prestressed materials states. These simulations show that the registered force-indentation depth curves as well as the geometry of the indentations are affected by loading and residual stresses in a characteristic way. For hardness values changes of up to 35% are determined with reference to the unstressed initial state.
Residual Stress Profiles of the Laser Surface Remelted Nodular Irons
Authors: Grum Janez , Šturm Roman
Published: March 2009

Laser remelting process is a very promising hardening method for ferrous and nonferrous alloys, which do not show a homogeneous microstructural state after having been heattreated in a traditional way. Consequently, the alloys concerned do not achieve the required hardness of the surface layer and do not provide the required wear resistance either. The paper deals with residual stresses of thin flat specimens of nodular cast iron 500-7 in the laser remelting process. In the process of gradual remelting of the specimen surface, that is during its heating and cooling, volume changes of the specimen occur due to thermal and microstructural changes. For a better knowledge of volume changes in the thin surface layer of the specimen, the latter were evaluated by residual-stress measurement in the thin modified surface layer after the remelting process. In laser remelting of a workpiece such remelting conditions should be ensured that a uniform thickness of the modified layer could be obtained in spite of several laser-beam passages across the workpiece surface. Because of a multiple laser-beam passage across the workpiece
surface, the state of internal stress in the workpiece changes. Optimal laser surface remelting conditions on the basis of knowing the residual stresses were chosen, while the way of guiding the laser beam over the surface of flat samples and degree of overlapping were varied.
Analysis of Residual Stresses and Distortions in Brazed Joints of Cemented Carbide and Steel
Authors: Ottlik A. , Schulze Volker , Pintschovius L. , Müller Hermann , Löhe Detlef
Published: March 2009

Brazing of cemented carbides to steel bodies gives rise to the development of complex stress states and distortions which influence the fatigue behaviour of the parts. It is quite important to estimate the residual stresses with numerical methods whose agreement is to be guaranteed with experimental characterization of the brazed parts. In this work FEM simulations and X-ray as well as neutron stress analysis were used to examine the residual stresses of brazed samples. Joints with
different geometries and dimensions made of cemented carbide and different steels showing different phase transformation behaviours were investigated.
Analysis of Residual Stresses in Micro Powder Injection Moulded Micro Bending Specimens Made of Zirconia
Authors: Kasanická B. , Wroblewski Thomas , Schulze Volker , Löhe Detlef
Published: March 2009

Analysis of the residual stress state, the microstructure and surface topography of
ceramic microcomponents made of Y2O3-stabilized ZrO2 produced by micro powder injection moulding were performed. During the production of the microspecimens sintering conditions were varied. The measurement of residual stresses has been carried out using the MAXIM (MAterials XRay IMaging) diffractometer at HASYLAB beamline G3 at DESY in Hamburg (Germany). The
microstructure and surface topography of differently moulded specimens were examined using a scanning electron microscope (SEM) and a confocal white light microscope type NANOFOCUS. The findings are used to establish correlations between process parameters and characteristics of the microcomponents. These will allow to improve the production process with respect to the mechanical properties of the microcomponents.
The Connection between Micro-Residual Stress and Thermo-Mechanical Treatments in 6061Al-15vol%SiCw Composites
Authors: Bruno Giovanni , Fernández R. , González-Doncel G.
Published: March 2009

In this work it is shown how the microscopic residual stress state in 6061Al-15vol%SiCw composites can be modified by plastic strain and by isothermal annealing (the latter, affecting also the precipitation state). The composites were obtained by a powder metallurgical route, which involves extrusion of Al-SiCw powder blends. Neutron diffraction measurements were carried out to determine the RS state.
Several degrees of plastic strain, from 1% up to 15% in compression, have been applied ex-situ to the same specimen on several composite materials. Furthermore, the m-RS was also investigated in one of the composites at several precipitation states as resulting from isothermal annealing at 300°C during different times. Investigations were carried out from a fully hardened state, T6 up to an overannealed
condition, OV (obtained after annealing during 100 h). The results show that quenching from solid solution treatment temperature prior to annealing at 146°C to achieve the T6 condition provokes a RS state, which does not relax during this treatment. No decrease of the deviatoric component and partial relaxation of the hydrostatic term of the micro- RS developed in the composite occur when treating from the T6 to the OV condition. Instead, only 1% plastic strain is sufficient to produce total relaxation of the hydrostatic term of the m-RS. Even inversion of the radial component occurs on higher straining. Again, no relaxation of the deviatoric
component occurs. This may be explained bearing in mind that the deviatoric component is linked to the geometry of the reinforcing particles (whiskers degree of orientation). The hydrostatic term does not relax totally after heat treatment because is partially re-generated on cooling, while the plastic deformation is ‘locked’ in the microstructure via dislocation activity.
Effect of Thermal Mismatch Stress on Thermal Expansion Behaviors of Al18B4O33w/Al Composite Containing Fe3O4 Particle
Authors: Li Gang , Fei Wei Dong
Published: March 2009

The thermal expansion behaviors of aluminum borate whisker and Fe3O4 reinforced pure aluminum matrix composite with different thermal treatments were studied. Using transmission electron microscopy (TEM) the microstructures of the composite were investigated. The results indicated that the thermal expansion coefficient of the new composite was low. It can be found that the thermal expansion coefficient of as-cast composite is much lower than that of quenched and annealed composites. On the basis of phase transformation analysis of Fe3O4 particles in the
composite, the mechanism of low CTE of the composite was discussed.
Measurements of the Residual Stresses due to Cement Polymerization for Cemented Hip Implants
Authors: Nuño Natalia , Plamondon Dominic
Published: March 2009

The initial fixation of the cemented hip prosthesis relies on the resistance of the
interface between the metallic stem of the implant, the PMMA, and the adjacent bone. During the operation, the bone cement still in a liquid form is inserted between the implant and the bone. During polymerisation of the cement, residual stresses are generated in the bulk cement. An experiment has been devised to reproduce the in vivo behaviour of a cemented hip prosthesis, and to develop a technique to measure the residual stresses of the bone cement at the stem-cement interface. An idealized prosthesis (19-mm diameter) was placed inside a synthetic bone (outer diameter of 40 mm, inside diameter of 30 mm). The bone cement was poured between the stem and the bone. A sub-miniature load cell was inserted inside the idealized stem
to measure directly the radial stresses generated by the cement curing on the hip stem. The tests are conducted at body temperature of 37°C to simulate the in-vivo conditions.
Residual Stress Effects on Raman Spectra of RuO2 Thin Films
Authors: Meng Li-Jian , Silva Rui A. , Cui Hai Ning , Teixeira Vasco , dos Santos M.P.
Published: March 2009

The RuO2 thin films have been deposited onto glass substrates by rf reactive magnetron sputtering at different deposition conditions, such as different substrate temperatures, different sputtering pressures and different reactive gas pressures, using a metallic target. The deposited films have been characterized by the X-ray diffraction and Raman scattering. By analysis of data of the X-ray diffraction, it has been found that all the films are subject to a compressive stress. The residual stress in these films can be released by increasing the substrate temperature. In addition,
the films, which have been prepared at the oxygen partial pressure higher than 1 x 10-3 mbar and at the total pressure lower than 6 x 10-3 mbar, show a quite high residual stress because the films peeled off automatically from the substrates when they were moved out from the vacuum chamber. Three Raman models (Eg, A1g and B2g) have been observed in all the Raman spectra. These Raman spectra have shown a strong relation with the residual stress in the films. As the residual
stress increases, the Raman peaks move toward to the low wavenumber comparing to the standard value. In addition, the residual stress also results in the disappearance of the A1g Raman mode. In this work, these phenomena will be discussed.
Microstresses in Molybdenum Nitride Thin Films Deposited by Reactive DC Magnetron Sputtering
Authors: Shen Yao Gen
Published: March 2009

Thin films of molybdenum nitride (MoNx with 0≤x≤0.35) were deposited on Si(100) at room temperature using reactive DC magnetron sputtering. The residual stress of films was measured as a function of sputtering pressure, nitrogen incorporation, and annealing temperature by wafer curvature-based technique. It was found that the stress of the films was strongly related to their microstructure, which depended mainly on the incorporation of nitrogen in the films. The film stresses without nitrogen addition strongly depended on the argon pressure and changed from highly compressive to highly tensile in a relatively narrow pressure range of 0.8-1.6 Pa. For pressures exceeding ~5.3 Pa, the stress in the film was nearly zero. Cross-sectional transmission electron microscopy indicated that the compressively stressed films contained a dense microstructure without any columns, while the films having tensile stress had a very columnar microstructure. High sputtering-gas pressure conditions yielded dendritic-like film growth, resulting in complete relaxation of the residual tensile stresses. It was also found that the asdeposited film was poorly ordered in structure. When the film was heated at ~775 K, crystallization occurred and the stress of the film drastically changed from –0.75 to 1.65 GPa.
The stress development mechanism may be due to volumetric shrinkage of the film during crystallization.
Influence of Interfacial Neighborhood on Residual Stress due to Deposition of TiN Thin Films Made by PVD
Authors: Hirose Hajime , Suzuki Shinya , Gotoh Masahide , Sasaki Toshihiko
Published: March 2009

In depositing the TiN thin films to the substrate by Physical Vapor Deposition (PVD), it influences the substrate interface. Change of the residual stress and the full-width at half maximum (FWHM) in each process of the TiN deposition of thin film was measured by the X-ray stress measurement. As a result of the X-ray stress measurement, there are no changes in the residual stress and the FWHM. It is thought that there is a difference in the penetration depth to the substrate of X-rays and Ti ion.
Effect of Substrate Temperature on Crystal Orientation and Residual Stress in RF Sputtered Gallium Nitride Films
Authors: Kusaka Kazuya , Takao Hanabusa , Tominaga Kikuo , Yamauchi Noriyoshi
Published: March 2009

The crystal orientation and residual stress in gallium nitride (GaN) films deposited on a single-crystal (0001) sapphire substrate using a new sputtering system are examined through x-ray diffraction measurements as part of a study of low-temperature sputtering techniques for GaN. The new rf sputtering system has an isolated deposition chamber to prevent contamination with impurities, and is expected to produce high-purity nitride films. GaN films are deposited at various substrate temperatures and constant gas pressure and input power. This new system is found to produce GaN films with good crystal orientation, with the c-axes of GaN crystals oriented normal to the substrate surface. The crystal size of films deposited at high temperature is larger than that deposited at low Ts. All films except that deposited at 700oC exhibit compressive residual stress, and this residual stress is found to decrease with increasing temperature. Finally, the film deposited at 700 oC was tinged with white, and the surface contained numerous micro-cracks.
Residual Stress and Wear Characteristics of Ni3Al Coating Layer
Authors: Murotani Takayuki , Wang Zhou , Ikenaga Akira , Hirose Yukio
Published: March 2009

The Ni3Al intermetallic compound is of great interest because of its oxidation,
corrosion-resistance, and high melting point. The low-temperature hot press + thermal diffusion process method is a technique that uses the thermal reactive diffusions between the elements that compose the intermetallic compound. In this method the powder mixture is heated and be able to generate the diffusions of the powder elements by keeping the heating temperature comparatively lower temperature with other technique. The authors evaluated the preparation conditions and joining quality in Ni3Al coating layer of particular interest is the residual stress due to the different mechanical properties of the coating and the substrate and its effect on the interface joining quality. It is known that residual stresses were generated by the difference in the coefficient of thermal expansion (CTE) of coating and substrate during cooling process. Such a residual stress caused by the
differences of mechanical properties has strong influence on composite material strength. X-ray stress measurement techniques has been developed for experimental determination of residual stresses. In this paper, the Ni3Al intermetallic compound was coated on spheroidal graphite cast iron and austenite stainless steel using the reactive sintering method. Wear characteristics and residual stress on these intermetallic compound layers were investigated to evaluate the effect of substrate materials on coating layer properties.
Testing and Analysis of the Inner Stress in Adhesive Coating Layer Using Strain Gauges and Finite Element Method
Authors: Zheng Xiao Ling , You Min , Zheng Yong , Yu Hai Zhou , Yang Chun Mei
Published: March 2009

The residual stress in epoxy adhesive layer deposited on metal and other substrate at room temperature is studied. With embedded strain gauges in arranged depth of epoxy layer, the strain changes in the adhesive layer induced by the curing procedure and the changes of ambient temperature were measured to evaluate the changes of residual stress in place during a period after the curing procedure finished. The actual strain in epoxy adhesive layer from curing is used to estimate the residual stresses in it. While taking the strain obtained from the surface of the adhesive layer as free strain, the residual stress can be calculated and presented a strongly cyclic variation with a period of 24 h. The inner stress is also analyzed using the finite element method.
Effect of Graphite Inclusions on Mechanical Properties of Austempered Ductile Iron
Authors: Serban Florin , Baczmanski Andrzej , Labbe E. , Wierzbanowski Krzysztof , Lodini Alain
Published: March 2009

Recently, austempered ductile iron (ADI) has emerged as a new class of ferrous materials and represents a major achievement in cast iron technology [1]. The mechanical strength and impact toughness of nodular iron are provided by the precipitation of the graphite phase as spheroids surrounded by ferrite (bull’s-eye structure) in a continuous pearlite matrix. The quality of ductile iron increases with the number of the graphite spheroids. A high spheroids volume fraction, which is mainly controlled by the inoculation process, limits the chemical segregation during solidification and ensures the structural homogeneity of the component. In this work, a lower value of Young modulus was obtained when the graphite phase was taken
into account in the self-consistent modelling. For 12% of graphite the theoretical Young modulus agrees with the measured one (mechanical tensile test). The volume fraction of graphite was confirmed independently by micrographic observation (14%). It can be concluded that the macroscopic behaviour of ADI steel can be modelled by the self-consistent approach in which the austeno-ferritic aggregate is represented by an effective matrix, while instead of the graphite spherical empty spaces are introduced. Using such an approach it was shown that in the elasto-plastic range of deformation, presence of graphite phase caused stress relaxation.
Determination of Residual Stress Distribution in Autofrettaged Tube Based on Modified Yielding Criterion and Tensile-Compressive Curve of Material
Authors: Huang Xiao Ping , Cui Weicheng
Published: March 2009

An autofrettage model considering the material strain-hardening behavior and the
Bauschinger effect, based on the actual tensile–compressive curve of material and modified yield criterion, has been proposed. The analytic expressions of residual stress distribution and the autofrettage pressure have been obtained. This model has stronger curve fitting ability, nearly all of the strain-stress curves of materials used in making autoefrettage tubes can be fitted well by this model, and each of those models based on the simplified strain hardening relationship of material is a
special case of the model. It was used to predict the residual stress distributions of an autofrettaged tube. The results show that the residual stress distributions predicted by the present model are in good agreement with the experimental data.
Electrophoretic Deposition as a Novel Near Net Shaping Technique for Functionally Graded Biomaterials
Authors: Anné Guy , Vanmeensel Kim , Vleugels Jef , Van der Biest Omer
Published: March 2009

Complex shaped functionally graded alumina and zirconia based femoral ball-heads for biomedical applications were shaped by electrophoretic deposition (EPD). A composition gradient in alumina and zirconia was engineered to obtain a pure alumina surface region and a homogeneous alumina/zirconia core with intermediate continuously graded regions to generate appropriate thermal residual stresses after sintering. The gradient profiles were designed to obtain maximum compressive surface stresses and minimal tensile stresses in the core of the component to increase the strength and wear properties when compared to pure alumina components.
Full Form of the Near Tip Field for the Interface Crack between a Piezoelectric Material and a Thin Electrode
Authors: Häusler Christoph , Balke Herbert
Published: March 2009

The Hilbert problems and their solutions of the near tip field for the permeable and the
impermeable electrode-ceramic interfacial cracks are derived with the aid of the modified Stroh formalism. In addition, a linear extrapolation method for numerical calculation of field intensity factors is given. This extrapolation method is based on a special combination of the field quantities.
Stacking of Bi2Te3 and FeSi2 for Thermoelectric Applications
Authors: Drasar Cestmir , Müller Eckhard
Published: March 2009

Recently, there is a strong interest in developing superior thermoelectric materials with the aim to improve the performance of a thermoelectric device. However, the performance of a thermoelectric generator (TEG) can be considerably improved also by applying a graded composition along the temperature gradient inside the thermoelectric device so that at each position the respective material achieves its maximum thermoelectric performance (TE FGM principle). Combining the high efficiency of Bi2Te3 (used at low temperatures) and general durability of FeSi2 (applied up to high temperatures) will result in a thermoelectric device with enhanced efficiency operating in air at a wide temperature range. The challenge is to contact these dissimilar materials without any negative impact on the performance of TEG. Besides providing a good electrical and thermal contact between Bi2Te3 and FeSi2 the junctions have to remain mechanically and chemically stable over long term. A Bi2Te3-SiO2 composite interlayer was used to adjust the different coefficient of thermal expansion (CTE) of FeSi2 (≈ 7·10-6 K-1) and Bi2Te3 (≈ 19·10-6 K-1). Due to low chemical stability of the Bi2Te3/FeSi2 contact at elevated temperatures (1000 h @ 300°C) a contacting material (diffusion barrier) based on Ni, Zn, Ti, and ZnTe was tested. Some contacts show excellent chemical and mechanical stability, though the electrical properties of the contacts do not meet the requirements (e.g. ZnTe is a wide gap semiconductor with high electrical resistivity). According to very recent studies at the Zn-based diffusion barriers a very thin layer of undoped ZnTe growing at the Bi2Te3/Zn interface causes the deterioration of the contact resistance. Ideas solving this problem are outlined and discussed.
Interaction between an Embedded Crack and an Interface Crack in Nonhomogeneous Coating System
Authors: Theotokoglou E.E. , Paulino Glaucio H.
Published: March 2009

A general methodology is constructed for the fundamental solution of a crack in the
homogeneous half-plane interacting with a crack at the interface between the homogeneous elastic half-plane and the nonhomogeneous elastic coating in which the shear modulus varies exponentially with one coordinate. The problem is solved under plane strain or generalized plane stress condition using the Fourier integral transform method. The stress field in the homogeneous half plane is evaluated by the superposition of two states of stresses, one is associated with a local coordinate
system in the infinite fractured plate, while the other in the infinite half plane defined in a structural coordinate system.
Computer-Integrated Safe Design of FGM Component for Hip Replacement Prosthesis
Authors: Zhang Bao Sheng , Gasik Michael M. , Facchini A. , Pressacco M. , DallaPria P. , Posocco S.
Published: March 2009

Computer-integrated safe design of FGM component for hip replacement prosthesis was presented based on principle of optimal stresses distribution in the FGM component. The goals were to create an FGM structure with reasonable compressive stresses on the surfaces (subjected to wear) and to keep them during the entire manufacturing cycle (sintering, machining, assembling and application). The residual stresses developed in the different parts of the composite were implemented into the subsequent process of the surface grinding and assembly to simulate properly the whole processing route to ensure optimal combination of the processing parameters.
Creep Response of Ceramic/Metal Functionally Graded Thermal Barrier Coating
Authors: Wang Jian Ping , Yang Shu Yong , Liu Li Sheng
Published: March 2009

The functionally graded thermal barrier coating (TBC) serves in high temperature and/or high temperature gradient environment for a long time. According to the experimental and theoretical research, in the metal substrate and the metal-rich interlayer creep deformation will appear under high temperature environment. In order to design and optimize the compositional distribution of FGM, it is necessary to analyze the stress and strain responses taking into account the creep phenomenon of the materials. In this article, the thermo-mechanical responses of ceramic/metal functionally graded TBC in work environment are analyzed by a finite element method. The creep phenomenon of the metal and the interlayers are taken into account. The numerical results indicate that the creep behavior of all interlayers, even for the ceramic-rich interlayer, cannot be neglected in analysis. It is suggested that the creep phenomenon of the material is important in the functionally graded TBC systems.
Creep Property of Functionally Graded Materials
Authors: Zhai Peng Cheng , Chen Gang , Zhang Qing Jie
Published: March 2009

The present paper investigates the creep phenomenon of the functionally graded
materials under high temperature environment by the computational micromechanical method (CMM). Based on the real microstructure of the functionally graded interlayer with different component volume fractions, the emulation experiment is implemented for the creep test numerically and the creep parameters are obtained. A further series of simulation works are carried out to investigate the creep phenomenon of FGM interlayers in more detail. Numerical results show that the creep phenomenon is obvious not only for the metal-rich interlayers but also for the
ceramic-rich interlayers. The creep property of ceramic/metal interlayer depends on the material’s properties of the ceramic obviously. It is remarkable that the creep strain rate of the ceramic/metal interlayer is larger than the corresponding one of pure metal under the same load when the modulus of the ceramic component is lower than the one of the metal component.
Steel Parts with Tailored Material Gradients by 3D-Printing Using Nano-Particulate Ink
Authors: Godlinski Dirk , Morvan Stéphane
Published: March 2009

It is difficult to generate any user-defined three dimensional gradient to tailor the functional properties of a component. Problems are not only the lack of local material design tools, but also a suitable manufacturing process. The implementation of the concept of local composition control into the Solid Freeform Fabrication (SFF) process 3D-Printing is described, which leads to geometrical complex parts out of tailored materials. Suspensions of different functional inks containing a binder and carbon black nano-particles are dispensed into droplets through multiple jets – like inkjet printing a halftone image on a paper – but into a metal powder bed to generate layer by layer graded green parts. In this case the tailored preforms are then sintered, while the nano-particle additions from the functional ink act locally as alloying elements in the steel matrix to combine e.g. both, toughness and hardness in the part. This work concentrates on the realisation of the new process and shows first results taking the generation of carbon-graded steel parts as an example.
Phase Transformation of Hexacelsians Doped with Li, Na and Ca
Authors: Dondur V. , Dimitrijević R. , Kremenović A. , Damjanović Lj. , Kićanović M. , Cheong H.M. , Macura S.
Published: March 2009

A series of hexacelsians with different compositions were synthesized by thermally
induced transformation of a LTA zeolite. Various forms of hexacelsians have been characterized by XRPD, IR, Raman and 29Si MAS NMR method. The phase transformation ab hexacelsian was investigated by DSC method. This phase transformation is sensitive to synthesis conditions, doping and thermal treatment. The peak maximum temperature, Tm, varies from 302 up to 353 oC. Heat of transformation changes from 0.42 to 1.77 kJ/mol.
Synthesis of Lanthanum-Strontium Manganites by a Hydroxide-Precursor Co-Precipitation Method in Solution and in Reverse Micellar Microemulsion
Authors: Uskoković V. , Makovec Darko , Drofenik Miha
Published: March 2009

Nanostructured lanthanum-strontium manganites have been synthesized using two different co-precipitation approaches, one in bulk solution, and the other in reverse micelles of CTAB/1-hexanol/1-butanol/water microemulsion. In both cases, precursor cations were precipitated by alkali precipitating agents. The properties of the material synthesized by using these two methods were compared in order to reveal potential advantages of microemulsion-assisted approach. The influence of the annealing conditions on the properties of synthesized manganites was investigated by using X-ray diffraction, transmission electron microscopy, differential thermal analysis, thermogravimetric analysis and magnetic measurements.
Microstructural and Mechanical Properties of Ti3Al-Based Intermetallics Produced by Powder Metallurgy
Authors: Dimčić B. , Vilotijević M. , Božić D. , Rajnović D. , Jovanović M.T.
Published: March 2009

The structural and compression mechanical properties of Ti3Al-based intermetallics
produced by powder metallurgy techniques have been studied. The as-milled powders were compacted by hot pressing to non-porous homogenous compacts. Prior to compression tests, all compacts were homogenized by a solution treatment at 1050°C (a+β region) for 1h, followed by water quenching. The compression tests were performed from room temperature to 500°C in vacuum at a strain rate of 1 3 10 4 . 2 − − × s . Detailed microstructural characterization was evaluated by
scanning electron microscopy (SEM), followed by energy dispersive spectroscopy (EDS) and X-ray diffraction analysis.
Computer Simulation of Grain Coarsening during Liquid Phase Sintering
Authors: Nikolić Z.S.
Published: March 2009

The microstructure during liquid phase sintering may change either by larger particles growing during the Ostwald ripening process or by shape accommodation. In this study, simulation of liquid phase sintering based on sub-models for solution-precipitation and grain coarsening will be considered. This paper describes a two-dimensional computer-based simulation method for determination of a qualitative and a quantitative effect of the moving grain boundary on the solid/liquid interface during liquid phase sintering of porous structure.
Mechanical and Fracture Behaviour of a SiC-Particle-Reinforced Aluminum Alloy at High Temperature
Authors: Božić D. , Vilotijević M. , Rajković V. , Gnjidić Ž.
Published: March 2009

The compressive characteristics and fracture behavior of CW67 aluminum alloy and of a composite based on CW67 alloy were studied under unaxial compressive loading in the temperature range 25-400°C, at a constant strain rate of 1 - 3 10 4 . 2 s × . The yield strength values of the composite were higher than those of the monolithic alloy at all temperatures. The ultimate strength values of the composite were lower at room temperature, but higher at elevated temperatures when compared with those of the monolithic alloy. The composite exhibited lower ductility than the monolithic alloy in the entire temperature range. High concentration of SiC particles in the structure of CW67 composite affected its compressive properties. At higher temperatures, it behaved like a typical precipitation hardened alloy, in other words, with temperature increase the main influence on the mechanical properties occurred in its matrix. When temperature rises, the fracture process changes from particle cracking and particle agglomerate decohesion (at room temperature) to particle matrix debonding (at high temperature).
Alginate Microbeads as Potential Support for Cultivation of Bone Marrow Stromal Cells
Authors: Bugarski D. , Obradović B. , Petakov M. , Jovčić G. , Stojanović N. , Bugarski B.
Published: March 2009

Alginate is currently being employed and explored for a broad range of biomedical and biotechnology applications, due to its biodegradability and simple procedure for cell immobilization. However, cell immobilization was mostly aimed for immunoisolatory and biochemical processing applications and far less is known about potentials of alginate as a substrate for tissue formation. In the present work, isolation, immobilization and cultivation procedures of murine bone marrow stromal cells (BMSC) were studied and standardized in order to establish the alginate-bioreactor culture system for chondrogenic and/or hematopoiesis-supportive tissue progression. Two techniques for cell immobilization based on alginate were investigated: entrapment within gel matrix using electrostatic droplet generation and simple cell adsorption onto gel surfaces. Alginate gels in forms of microbeads and discs with immobilized culture expanded BMSC were cultivated for up to 30 days and analyzed for surface properties, cell concentration, viability, and differentiation.
Magnetic Field Effect on the Microstructure of Low Silicon Steel
Authors: Bacaltchuk C.M.B. , Castello-Branco G.A. , Garmestani Hamid
Published: March 2009

Magnetic annealing at five different magnitudes of field was conducted to evaluate the effect of the field on the recrystallized microstructure of Fe-0.75%Si samples. At higher fields the retardation during recrystallization is compensated by the magnetic filed driving force that causes an increase in the grain boundary mobility of grains that have a certain relationship with the direction of the field
Simulation of Recrystallization Textures in fcc Materials Starting from Self-Consistent Modelling Results
Authors: Roatta A. , Fourty A.L. , Signorelli Javier , Bertinetti M.A. , Bolmaro R.E.
Published: March 2009

Recrystallization (RX) textures in FCC materials have defied modelling for quite a long time despite the major micro-mechanisms influencing the texture development are currently considered understood. FCC materials are coarsely classified in high and low stacking fault energy materials with a rather continuous transition between them. Both extreme kinds will give rise, after rolling deformation and later RX, to what are called Cube and Brass texture patterns. Besides long discussions, not still settled, about the influence of twinning on deformation textures, attempts of simulating RX textures have been unsuccessful. The current contribution will show SelfConsistent (SC) plus RX modelling taking into account accumulated deformation energy and misorientation angles between neighbouring crystals. Starting from grains characterized by previous SelfConsistent simulations, nucleation is probabilistically allowed on each crystal whenever the accumulated energy is larger than certain threshold. Grain boundary mobility is commanded by a probability function of the misorientation angles also calculated by the SC model. The modelling is able to predict the right trend for many of the literature experimental data without resorting to other more sophisticated variables.
Simulation of Cup-Drawing Based on Crystal Plasticity Applied to Reduced Grain Samplings
Authors: Delannay Laurent , Béringhier M. , Chastel Yvan , Logé Roland E.
Published: March 2009

This paper presents a means of reducing the computational cost of finite element (FE) simulations coupled to polycrystal plasticity theory. One typically assumes that a polycrystal with a large number of grains underlies every integration point of the FE mesh. Instead, it is suggested here using reduced samplings of grains which differ from one integration point to another. On average, every set of 5 to 25 finite elements contains a variety of lattice orientations that is representative of the macroscopic texture. The model is applied to deep-drawing of a cylindrical cup made of steel. In a first set of simulations, grains are assigned orientations representative of a cold rolling texture and the “earing” profile is compared to experiment. In a second set of simulations, lattice orientations are random and an isotropic deep-drawing result is expected. It is demonstrated that using a minimum of 20 grains per integration point allows properly predicting the final shape of the cup and the texture development.
Effect of Local Texture on the Orange Peel Defect in St14 Steel Sheet
Authors: Cao Sheng Quan , Zhang Jin Xu , Wu Jian Sheng , Chen Jia Guang
Published: March 2009

In this paper, the ‘orange peel’ defect in the surface range of the st14 steel sheet has been investigated using the electron backscatter diffraction (EBSD) technique. It has been found that the ‘orange peel’ defect in the st14 steel sheet was resulted from the local coarse grains which were produced during hot-rolling due to the critical deformation in dual-phase zone; During deep drawing, the coarse grains with {100}<001> microtexture can slip on the {112}<111> slip system to form bulging and yields orange peel defects, while the coarse grains with {112}<110> orientation do not form the defect as the Schmid factor of {112}<111> slip system in it equals zero.
ECAE of Al-4%Cu Alloys: Experimental Study Assisted by Polycrystalline-FEM Simulations
Authors: Signorelli Javier , Logé R. , Turner P.A. , Sordi V. , Vieira E.A. , Ferrante M. , Bolmaro R.E.
Published: March 2009

The present work reports on the results obtained on equal channel angular extrusion
experiments (ECAE) done on a laboratory-cast Al-4%Cu alloy, in the T4 condition, and the use of Polycrystalline-FEM simulations to assist in the interpretation of the experiments. The experimental setup consists on a die of approximately 15 x 15 mm2 sections intersecting at 120o. Deformation at room temperature consisted of up to 5 passes with no rotation between passes. After each extrusion pass, the samples were cut from the deformed billet along planes parallel to the extrusion direction and the preferential orientations were measured on surface and middle layers. Three pole figures, (111), (200) and (220) were measured by conventional x-ray diffraction techniques and used for Orientation Distribution Function calculation and analysis. In addition tensile tests and optical
microscopy have been performed in each sample to provide a good estimation of the parameters that enter in the modeling process. A finite element code specially developed to model large deformation processes (Forge3Ò) was used with tetrahedral elements and an elastic-viscoplastic material model to investigate the
influence of the different strain paths sustained by different areas of the samples. The calculated distribution of deformations agrees well with the theoretical result. The simulation was used to assist in the selection of sample-cutting procedures for texture measurements and to provide the strain paths needed for self-consistent polycrystal modeling of texture development.
Deformation and Recrystallization Texture of Heavily Drawn OFHC Copper
Authors: Waryoba Daudi R. , Kalu Peter N.
Published: March 2009

Deformation and recrystallization texture has been investigated in Oxygen free high conducting (OFHC) copper wires drawn at room temperature to true strain of 2.31, and isothermally annealed at various temperatures between 150°C and 750°C. Local orientations of the microstructures were measured by means of electron backscattered diffraction (EBSD) technique. While the drawn wire was characterized by a major<111> + minor<100> duplex fiber texture, recrystallization occurred at annealing temperatures between 250°C and 400°C and resulted into a major<100>+minor<111> recrystallization texture. At temperatures above 500°C, the <100> dominated recrystallization texture changed to the <111> dominated growth texture due to secondary recrystallization, which favored the <111> orientation at the expense of the <100> component.
Effect of Calcination Conditions on the Magnetic Properties of MnZn Ferrites Powders Produced by Co Precipitation
Authors: Janasi S.R. , Rodrigues Daniel , Landgraf Fernando José Gomes
Published: March 2009

MnZn ferrites are conventionally produced by the ceramic method that involves the solid state reaction of metallic oxides or carbonates at high temperatures. The particles obtained by this method are rather large and non-uniform in size. In order to overcome the difficulties arising out of the ceramic process, the coprecipitation method has been used as an alternative route to produce chemically homogeneous powders with fine particle size. In this work MnZn ferrites powders were produced by the coprecipitation method. The calcination conditions, such as temperature (900oC to 1100oC) and atmosphere (air and nitrogen), were investigated. X ray diffractometry, scanning electron microscopy, thermomagnetic analysis and vibration sample magnetometry were used to characterize the obtained samples. The results indicated that when the samples were calcined in nitrogen atmosphere, the ferrite formation occurred at low calcination temperatures and presented better magnetic properties than those calcined in air.
Influence of NbC-Addition on Mechanical Properties of WC-Co
Authors: Acchar Wilson , Macedo Harim Revoredo de
Published: March 2009

Cemented carbides have been intensively used as cutting tool through their high hardness, high fracture toughness and high wear resistance. A considerable amount of works has been developed in order to improve the mechanical properties of alternate cemented carbide systems.
This work has the purpose to reports the first results obtained to WC-Co reinforced with 5 wt.% NbC. The mixture of powders was hot-pressed at 1250 °C in a inert atmosphere. Hardness and fracture toughness were carried out in a Vickers hardness testing machine. The results have showed that the addition of niobium carbide improves the hardness of tungsten carbide and inhibits the WCgrain growth.
Dimension Stone Cutting with AWJ Methods
Authors: Cortés Guillermo Ruperto Martín , Hennies Wildor Theodoro , Lauand Carlos Tadeu , Valenzuela-Díaz Francisco Rolando
Published: March 2009

The application of high-pressure abrasive water jets (AWJ) has evolved quickly in some fields of engineering. At Polytechnic School, University of São Paulo, one application has particular interest that is the cutting of friable materials, as rock and ceramics. The main aspect in this field is the cut at the beneficiation process of end product in dimension stone plates. How much the cut of plates, by different kind of AWJ methods, was the research of a PhD work of one of the authors. The abrasive water jet equipment, installed in the Laboratory of Rock Mechanics of the Mining and Petroleum Engineering Department, was used. Some fundamentals considerations regarding, the employed single and multiple passes methods of AWJ to cut rocks, are discussed.