bluuebunny/crossref_metadata_2025 huggingface dataset:
Natural Bovine Anorganic Apatite and Collagen Presents Osteoconductivity and Contribute to Bone Repair of Rat Calvaria Critical Size Defect
Authors: Silva I.I.C. , Pimentel-Soares S. , Bittencourt Rafael C. , Granjeiro José Mauro
Published: March 2009

The aim of this study was verify the biological efficacy of the use of a xenograft for bone loss therapy. Blood clot, particulate autogenous bone or anorganic bovine xenograft filled critical size defects (CSD) in rat calvaria (8mm diameter). After 0, 7, 30 and 90 days the animals were killed and macroscopic, radiographic and histopathological analysis were conducted. Although no treatment promoted the total closure of bone defect, autogenous bone group had better bone repair after 90 days, followed by xenograft group that exhibited direct bone neoformation onto, and around, the particles confirming its osteoconductivity. In conclusion, the xenograft tested in vivo showed biocompatibility, biodegradability and osteoconductive properties in rat calvaria CSD.
Porous Gradient Implant for Mandible and Craniofacial Surgery
Authors: Antunes E.S. , Sousa T. H. S. , Fortulan C.A. , Carvalho Jonas , de M. Purquerio B.
Published: March 2009

Non metallic materials like polyurethane has been successfully used for bone reconstruction in general and specifically in craniofacial and in mandible surgeries as an implantable material. However, any polymer alone cannot be universally successful as a medical device or structural implant because the eventual lack of well defined porous geometry, inherent interconnected porosity, the non dispensable need for a combined mechanical behavior with biological interaction and manufacturing feasibility. In this work, a bioactive material composite with high mechanical strength was designed using a castor oil polyurethane (PU) structure with a functional gradient having a dense core and a porous bioactive surface. The models and replicas for the implants were processed with Rapid Prototyping (RP) techniques and their application (case studies) were fulfilled according to the SUS (Brazilian Health Service) with the support of Santa Tereza Hospital, Petropolis, RJ.
Biocompatibility of Bovine Anorganic Xenograft
Authors: Jardelino C.L. , Takamori Esther R. , Santos Silvia R. A. , Rossi Antonella M. , Granjeiro José Mauro
Published: March 2009

Porous granules without organic residues were produced from bovine medular anorganic bone. Sample showed carbonate content and crystalline order similar to natural bone. The cytotoxicity of anorganic bovine xenograft (Ossĕus®) was valuated from fibroblasts (1.5x104/cm2) cultured in serial diluted extract (0 – 100%) of Ossĕus plus 10% of fetal bovine serum (FBS). Pure extract (100%) reduced in 15% the number of viable cells (p<0.05, ANOVA, Tukey test) indicating very low cytotoxicity. Samples were implanted in the subcutaneous tissue of mice in order to evaluate tissue reaction. An organized connective tissue in contact to the granules was observed nine weeks after implantation. The anorganic bovine xenograft (Ossĕus®) was biocompatible and its behavior and osteoconduction potential should be evaluated in bony defects.
Long-Term Study of Osteoconductivity of Bioactive Porous Titanium Metals: Effect of Sodium Removal by Dilute HCl Treatment
Authors: Tanaka Kojiro , Takemoto Mitsuru , Fujibayashi Shunsuke , Kawanabe Keiichi , Matsushita Tomiharu , Kokubo Tadashi , Nakamura Takashi
Published: March 2009

In a previous study, we have reported that sodium removal by dilute hydrochloric acid (HCl) converted the sodium titanate layer on the surface of an alkali-treated porous titanium into titania with a specific structure that has better bioactivity than sodium titanate. We have shown that a porous titanium with this treatment have good osteoinductivity in soft tissue of canines. In the present study, we investigated the effect of this treatment on the osteoconductive abilities of porous bioactive titanium implant in the long term. Three types of surface treatments were applied: (a) no treatment , (b) alkali, hot water, and heat treatment ( conventional treatment: W-AH treatment), and (c) alkali, dilute HCl, hot water, and heat treatment (Na-free treatment: HCl-AH treatment). We then examined the osteoconductivity of the materials implanted in the femoral condyles of Japanese white rabbits at 6, 12, 26, and 52 weeks. The results showed that the bone ingrowth in HCl-AH porous bioactive titanium was significantly higher than in W-AH porous bioactive titanium at 52 weeks. Therefore, sodium removal has a positive effect on the osteoconductivity of the porous bioactive titanium implant in the long term.
Nanomechanical Properties of Titanium Coated with Octacalcium Phosphate by Immersion in a Simplified Simulated Body Fluid
Authors: Gemelli E. , Resende Christiane Xavier , Lepienski Carlos M. , de Almeida Soares Gloria Dulce
Published: March 2009

In this study we report on the microstructure and its mechanical behavior of a Ca-P
coating produced on bioactive titanium by immersion in a simplified simulated body fluid (S-SBF).
The coating was probed by nanoindentation in several point times up to the formation of
octacalcium phosphate (OCP). Amorphous calcium phosphate, formed after 1h of immersion in SSBF,
presented the highest values of hardness (H) and elastic modulus (E). Nucleation of OCP was
observed after 2-2,5h of immersion in S-SBF. From this stage on, lower values of H and E were
obtained, probably due to the low dense structure of the coating.
Nanometer Coatings of Hydroxyapatite Characterized by Glancing-Incidence X- Ray Diffraction
Authors: Mello Alexandre , Mavropoulos Elena , Hong Zhen , Ketterson J.B. , Rossi Antonella M.
Published: March 2009

Hydroxyapatite (HAP) crystalline thin-coatings have been grown using a right angle RF magnetron sputtering approach at room temperature. The surface structural information of these biocompatible coatings at nanometer scales was obtained by glancing-incidence X-ray diffraction (GIXRD) with synchrotron radiation. The GIXRD spectra were obtained by fixed incidence theta angles at 0.5 and 1 degree. Structural profile analyses were performed over these nano-coating layers with reduced substrate interference. The coating thickness was calibrated by specular X-ray reflectivity (XRR) curves. Experiments have been performed on thin-coatings of HAP sputtered on silicon wafers and acid etched titanium discs at room temperature. GIXRD analysis has shown that all the principal peaks are attributed to a crystalline HAP. Previous tests of biocompatibility with osteoblasts cells have been encouraging studies on the surface of hydroxyapatite thin coatings prepared by opposing RF magnetron sputtering approach, as a promising candidate for bioimplant materials.
New Injectable Bone Substitute Using Reversible Thermosensitive Hydrogel and BCP Granules: In Vivo Rabbit Experiments
Authors: Daculsi G. , Uzel P.A. , Bourgeois N. , Le François T. , Rouvillain Jean Louis , Bourges Xavier , Baroth Serge
Published: March 2009

We have developed a new injectable bone substitute combining specific granules of BCP with or without radiopaque elements with a reversible thermo sensitive resorbable carrier such as Pluronic F-127. The composite is liquid at ambient temperature and set as hydrogel at 37°C. Rabbit experiment demonstrates high biocompatibility and bone ingrowth at the expense of the injectable bioceramic composite.
Whisker-Like Silicon Doped Hydroxyapatite Synthesis by Hydrolysis of Silicon Doped α-TCP
Authors: Ramos S.L.F. , Motisuke M. , Zavaglia Cecília A.C.
Published: March 2009

Biocompatible fibers has been studied and synthesized in order to improve the mechanical and general properties of bone cements. In order to do so, this work presents the synthesis of Whisker-like fibers of Silicon doped Hydroxyapatite by alkaline hydrolysis of Silicon doped α-TCP. The main fibers analyzed by SEM showed an aspect ratio of about 18 (l = 3.9 µm, d = 0.22 µm), well defined superficial aspect and hexagonal structure. XRD and EDX characterization presented Calcium Deficient Hydroxyapatite peaks and Ca/P ratio of 1.47.
Comparative Effect of the Ionic Products from Bioactive Glass Dissolution on the Behavior of Cementoblasts, Osteoblasts, and Fibroblasts
Authors: Carvalho Sandhra , Oliveira Agda , Andrade Vanessa , de Fatima Leite Maria , Goes Alfredo , Pereira Marivalda
Published: March 2009

The cementum, a mineralized tissue lining the tooth root surface, is required for development of a functional periodontal ligament. The presence of healthy cementum is considered to be an important criterion for predictable restoration of periodontal tissues lost as a consequence of disease. Despite the importance of cementum to general oral health, very little is known about the cells responsible for the formation of cementum, cementoblasts. The aim of this study was to examine the effect of the ionic products from the dissolution of bioactive glass with 60% of silica ( BG60S ) on the behavior of cementoblasts, osteoblasts and fibroblasts. The cell viability was tested by MTT assay based on mitochondria activity of the cell and Trypan Blue assay based on membrane cell viability. The membrane cell viability measured by Trypan Blue assay showed the beneficial effect on all the cell types tested. It was observed a higher proliferation in the presence of ionic products from dissolution of BG60S when compared to control. In the MTT assay we also observed increased cell viability on all the cell types, but proliferation of cementoblasts was higher (107%) than observed for the other cells (104%) compared to control. The results from this study suggest that Cementoblasts, osteoblasts and fibroblasts are important cells on events that control the development of mineralizing and not mineralizing tissues and the investigation of the comparative behavior of these cells can be a useful experimental model. The observed effect of the bioactive glass particles on cementoblasts shows that this material is an interesting alternative to be used in composite membranes for cementum tissue engineering.
Sol-Gel Synthesis of FHA Nanoparticles and CDHA Agglomerates from a Mixture with a Nonstochiometric Ca/P Ratio
Authors: Jahandideh R. , Behnamghader Aliasghar , Rangie M. , Youzbashi A. , Joughehdoust S. , Tolouei R.
Published: March 2009

The aim of this study was to investigate the sol gel synthesis of HA/FA nanoparticles and the possible formation of TCP phase or unstoichiometric calcium deficient hydroxyapatite (CDHA) from the precursors with a Ca/P ratio of 1.62. In order to prepare the sol, the solutions of Triethyl phosphite, ammonium fluoride and calcium nitrate in ethanol were used respectively as P, F and Ca precursors. The crystallinity, particle and crystallite size, powder morphology, chemical structure and phase analysis were investigated by SEM, XRD, FT-IR and Zeta sizer experiment. A multiphase compound containing hydroxyapatite (HA) and fluoroapatite (FA) nanoparticles and calcium deficient hudroxyapatite (CDHA) agglomerates was obtained. The size of the crystallites estimated from XRD patterns using Scherrer equation and the crystallinity of HA phase were about 5 nm and 66% respectively. The zeta sizer experiments for the dispersed particles in its own conditions showed an average size of 98 nm.
Structural Properties of Nanostructured Carbonate Apatites
Authors: Ramirez C.A.O. , Costa Andrea Machado , Bettini J. , Ramirez Antonio J. , Prado da Silva Marcelo Henrique , Rossi Antonella M.
Published: March 2009

B-type carbonate apatite samples were synthesized by wet chemical method and characterized by X-ray Fluorescence Spectrometry, X-ray Diffraction, Fourier Transformed Infrared Spectroscopy and High Resolution Transmission Electron Microscopy. The XRD and FTIR analysis confirmed the presence of one B-type carbonate apatite phase and the HRTEM images revealed the coexistence of amorphous and polycrystalline regions in the order of 2nm with the carbonate apatite structure. Second phases or precursors were not discovered.
Assessing In Vitro Degradation of β-Tricalcium Phosphate Ceramics via Micro-Computed Tomography
Authors: Diggs A.B. , Bae C.J. , Tseng Wei Ju , Flanagan C.L. , Halloran J.W. , Hollister S.J.
Published: March 2009

This paper describes the use of micro-computed tomography for determining in vitro degradation of calcium-phosphate ceramic materials. Samples were immersed in a simulated body fluid and scanned at the initial and final timepoints. Analysis indicates degradation of material density as well as changes in mineral content and mineral density. Findings are confirmed with known methods of materials characterization (SEM, mass analysis, and Archimedes’s density calculations), indicating changes in surface morphology, mass, and pore volume.
Effect of Hydroxyapatite on Biodegradable Scaffolds Fabricated by SLS
Authors: Eosoly Szilvia , Lohfeld Stefan , Brabazon Dermot
Published: March 2009

Selective laser sintering (SLS) has the potential to fabricate bioresorbable polymer / ceramic composite scaffolds with pre-designed external and internal architecture that can be used for bone tissue engineering applications. Scaffolds were fabricated using poly-ε-caprolactone as the base material. The effect of 15 and 30 wt% of hydroxyapatite (HA) addition was investigated in terms of compressive properties, accuracy, surface topology, and wettability. Fabricated dimensions of PCL microstructures showed great deviations from their nominal values. Average surface roughness was found to be Ra=25±4 µm. Increased HA content had no statistically significant effect on accuracy and surface roughness. However the addition of HA had a significant influence on compressive properties, hydrophobicity and wettability of the samples. Addition of 30 wt% HA improved initial compressive modulus of pure PCL scaffolds from 1.31±0.08 MPa to 1.58±0.18 MPa. Yield strength values increased from 0.14±0.07 MPa to 0.17±0.01 MPa by adding 15 wt% of HA, but decreased with further HA addition. Yield strain for all compositions was over ε=0.06. Increased HA content decreased hydrophobicity and increased wettability of scaffold surfaces. The study demonstrated the ability of SLS to fabricate tissue engineering scaffolds, and the positive effect of HA particle reinforcement in terms of compressive mechanical properties and surface characteristics
Application of Complete Gurson Model for Prediction of Ductile Fracture in Welded Steel Joints
Authors: Međo Bojan , Rakin Marko , Gubeljak Nenad , Sedmak Aleksandar
Published: March 2009

Ductile fracture process includes three stages: void nucleation, their growth and coalescence. The voids nucleate due to the fracture or separation of non-metallic inclusions and secondary-phase particles from the material matrix. Micromechanical models based on the Gurson plastic flow criterion are often used for analysis of ductile fracture. They consider the material as a porous medium in which the effect of voids on the stress-strain state and plastic flow cannot be neglected. Another important property of the Gurson criterion is that the hydrostatic stress component influences the plastic flow of the material.
Investigation of Implant Bone Interface with Non-Invasive Methods: Numerical Simulation, Strain Gauges and Optical Coherence Tomography
Authors: Antonie Sergiu , Sinescu Cosmin , Negrutiu Meda , Sticlaru Carmen , Negru Radu , Laissue Philippe L. , Rominu Mihai , Podoleanu Adrian Gh.
Published: March 2009

The quality of the evaluation of implant insertion could be investigated by implant bone interface analysis. In this study the numerical simulation, tensional stamps and optical coherence tomography as a noninvasive method were used in order to evaluate these interfaces. The system contains two interferometers and one scanner. For each incident analysis a stuck made of 61 slices was obtain. These slices were used in order to obtain a 3D model of the implant bone interface. The results obtained point out the existence of gaps between the implant and the bone. In conclusion the optical coherence tomography could be used for implant bone interface investigation.
Fracture Mechanics and Non-Destructive Testing for Structural Integrity Assessment
Authors: Sedmak Stojan , Sedmak Aleksandar
Published: March 2009

Fracture mechanics parameters can be applied for the analysis of failures of structures, and also for prevention of failures when defects in a structure are detected and defined. The approach is presented through stages: detection of defects, stress-strain analysis of loaded component, characterization of material properties required for structural integrity assessment and application of convenient procedure. In this way the decision about next use of defective component can be made (to continue the operation, increased care by inspection, exclusion the component from next service, with eventual repair, if possible). Special attention is paid to the most popular testing procedures for crack resistance parameters.
Damage Analysis of Waterproof Layer in Composite Tunnel Lining Based on Theory of Plate with Large Deflection
Authors: Jin Xian Yu , Jin Nan Guo , Gu Xiang Lin
Published: March 2009

: In order to analyze the cause of water leakage in highway tunnels, the damage property of waterproof board in composite tunnel lining with concrete matrix defects under hydraulic pressure was studied using Galerkin method for plates with large deflection. The deflection, stress and strain of waterproof boards were calculated in the conditions of rectangular and elliptic boundary due to concrete matrix defects. First strength theory was used to determine the critical load of the board and the critical depth of the defect. Investigation results showed that the maximum principal stress generates in the middle of longer side in the rectangular boundary condition and in the center in the elliptic boundary condition, the failure of the waterproof board under certain hydraulic pressure is related with the dimensions of concrete matrix defects and the dimension of the concrete matrix defect needs to be controlled in the design and construction of waterproof layer for tunnels.
Performance of Polypropylene Fiber and Rubber Powder Improved High Strength Concrete
Authors: Liu Feng , Zhu Jiang , Wen Zhou Li , Li Li Juan
Published: March 2009

Based on high strength concrete (HSC), the improved HSC concrete was produced by adding different contents of fine grain rubber particles and polypropylene fibers. The grain size of the rubber particle is 420 m and the rubber content is 1%, 2%, and 3% of the mass of cementitious material respectively. The volume fraction of polypropylene fiber is 0.1%.The performance of HSC, rubber particle improved high strength concrete (RHSC), polypropylene fiber improved high strength concrete (PHSC) and polypropylene fiber hybrid rubber particle improved high strength concrete (PRHSC) before and after high temperature are studied. The investigation methods used are the external surface inspection, weight loss and residual strength testing. The experimental results show that rubber particles can improve the workability of HSC and PHSC under normal temperature. Polypropylene fiber can significantly improve the spalling failure resistance property of HSC and RHSC.
Study on Impermeability and Resistance to Sulfate Attack of Polymeric Sulphoaluminate Cement
Authors: Li Yun Chao , Lu Ling Chao , Wang Shou De , Ye Zheng Mao , Cheng Xin
Published: March 2009

The polymer sulphoaluminate cement is composed of styrene-acrylic emulsion and sulphoaluminate cement. The resistance to sulfate attack, impermeability and mechanical performance are studied in the paper. The hardened paste microstructure of the polymer sulphoaluminate cement is studied by means of SEM. The experiment shows that the impermeability of the cement is improved with the increase of styrene-acrylic emulsion. When the ratio of polymer to cement increases from 0% to 15%, the permeate height of the hardened cement paste decreases by 70%. The resistance to sulfate attack of the cement is also improved with the increase of styrene-acrylic emulsion. Styrene-acrylic emulsion has little effect on the flexural strength of sulphoaluminate cement. When the ratio of polymer to cement is less than 15%, the flexural strength of the cement at 28d curing ages are all above 7.1MPa. As shown from SEM photographs, the cement becomes more close-grained when the ratio of polymer to cement increases.
Elastic Bending Theory of Composite Bridge with Corrugated Steel Web Considering Shear Deformation
Authors: He Jun , Liu Yu Qing , Chen Ai Rong
Published: March 2009

The classical Euler-Bernoulli girder theory is not applicable due to shear deformation of corrugated steel web, elastic bending theory considering shear deformation is presented to analyze deflection and mechanical property. Differential equation is derived based on displacement field assumption, internal force equilibrium equations, deformation compatibility condition and relation of deformation and internal force, and solutions are obtained according to boundary and load condition. Simply supported I and box girder bridges with corrugated steel web are analyzed with elastic bending theory considering shear deformation, their predicted results are found in good agreement with those by 3D finite element analysis and test. A limit value of depth-span ratio is suggested for considering influence of shear deformation or not, the simplified formula of deflection in middle span is presented to guide deflection design. Corrugated web accounts for more than 80% of total shear force in the whole span under uniform load while one third apart from bearing under concentrated load in mid-span. The elastic bending theory considering shear deformation makes a reference for designing composite bridge with corrugated steel web.
Dynamic Characteristic and Aseismatic Analysis of Tall Structures with Outriggers
Authors: Chen Yu , Shen Pu Sheng
Published: March 2009

Based on the finite element software ETABS, the effect of outriggers on the seismic response of a 50-story steel frame-reinforced concrete core tube structure was analyzed in this paper. Periods of free-vibrations were obtained from mode analysis. Response spectrum on the seismic properties was discussed. Elastic time history method was used to get complete analysis of the structure adopting four seismic waves. Structural horizontal displacement, drift angle, internal force of components and the distribution of internal forces between inner tube and outer frame under earthquake were studied. The rational quantity and locations of outriggers were considered. Further research in elastic time history was presented considering the influence of quantity of outriggers when outriggers were all set in “reasonable locations”. Some suggestions about steel frame-reinforced concrete core tube structures with outriggers in earthquake areas were given.
Seismic Behaviors of Concrete-Filled T-Shaped Steel Tube Columns
Authors: Wang Yu Yin , Yang Yuan Long , Zhang Su Mei , Liu Jie Peng
Published: March 2009

Concrete-filled special-shaped (L-shaped, T-shaped, and cross-shaped, and etc.) steel tube column is a type of member in which concrete is poured into special-shaped steel tube so that steel and concrete support loads together. It improves the seismic behaviors of reinforced concrete special-shaped columns due to the better confining effects provided by the steel tube. A test research on the seismic behaviors of one concrete-filled T-shaped steel tube column with pseudo static method is presented and the load-displacement curve and skeleton curve are provided. Series of steel bar stiffeners were welded onto the steel tube in order to postpone the buckling of steel tube and to enhance confining effects. A numerical analysis program was developed using a fiber-based method. The constitutive model of concrete employed the modified Mander model, and that of steel employed a bi-linear model considering the Bausinger effect. The numerical analysis program was verified by the test results and parametric analysis was carried out, in which the influences of the ratio of axial compression stress to strength, steel tube thickness and concrete strength were mainly discussed. The following conclusions are obtained: with the increase of the ratio of axial compression stress to strength, the bearing capacity of member increases and the energy dissipation capacity improve, while the ductility deteriorates. With the increase of steel tube thickness, the initial rigidity, bearing capacity, ductility and energy dissipation capacity improves simultaneously. With the increase of concrete strength, the bearing capacity increases, the energy dissipation capacity improves, while the ductility deteriorates.
The Seismic Response of 1/4-Scale Frame — Supported Reinforced Masonry Shear Wall
Authors: Huang Liang , Gao Xiang , Shi Chu Xian , Chen Sheng Yun
Published: March 2009

The study of this paper focuses on the seismic performance of a new complex tall building-FSRMW (frame-supported-reinforced-masonry-shear-wall).The new structure combines the advantages of RMW (reinforced-masonry-shear-wall) and FSRCW (frame-supported- reinforced- concrete-shear-wall) and have good economic value and extensive use value.Big space can be gained by using the structure, which provide a new appropriate selection for the design of hotel, multifunctional office building and dwelling house with shop at bottom. Substructure pseudodynamic testing were adopted to carrying out the seismic testing of 1:4 Reduced-scale models of FSRMW.Seismic evaluation of this structure has been carried out by substructure pseudodynamic testing of 1/4-scale specimen.The dynamic response of the tested structure under the influence of earthquake excitation is analyzed.The horizontal bearing capacity and the damage degree of the test model are investigated. The testing are cited to illustrate that the seismic performance of the structure(frame-shear-wall-supported reinforced masonry shear wall) is better than that structure(frame- supported reinforced masonry shear wall) and can be satisfied with the design request of 6-8 degree seismic zone.
Size Effect of Concrete Compressive Strength with Different Aggregate Composition
Authors: Su Jie , Yang Zuan , Fang Zhi
Published: March 2009

81 concrete prism specimens under axial compression were tested to invesgigate the size effect on the axial load stength. Three different kinds of specimens with the dimension 100×100×300mm, 150×150×300mm, 200×200×400mm were tested. The parameters including compressive strength of concrete and aggregate composition are taken into consideration. Three different strength grades of concrete and three different aggregate composition are included in those specimens. The test method are undertaken according to ASTM C 39/C 39M-2005. Based on the test results, a new size effect law for different kinds of concrete in prismatical compressive strength is suggested and those relative parameters on the size effect are discussed.
Size Effect of Concrete Compressive Strength with Different Reinforcement Ratio
Authors: Su Jie , Fang Zhi
Published: March 2009

An experimental investigation is reported into the size effect for compressive strength from 36 concrete prism specimens under axial loading and with three different kinds of dimensions of 100×100×300mm, 150×150×300mm, 200×200×400mm. Such parameters as strength grade of concrete and reinforcement ratio are taken into consideration. Three different strength grades of concrete and two different reinforcement ratio are included in those specimens, all tests are undertaken according to ASTM C 39/C 39M-2005. Based on the results obtained, a new size effect law for different kinds of concrete in prismatical compressive strength is suggested and those relative parameters on the size effect are discussed.
Load-Deflection Analysis of Pretensioned Inverted T-Beam with Web Openings
Authors: Cheng Hock Tian , Bashar S. Mohammed , Mustapha Kamal Nasharuddin
Published: March 2009

A precast, prestressed concrete girder with circular web openings allows building service systems (mechanical, electrical, communications, and plumbing) to cross the girder line within the member’s depth, reducing a building’s floor-to-floor height and the overall height of the structure. These height reductions have the potential to improve the competitiveness of total precast concrete structures versus other types of building systems. The experimental program reported in this paper tested five full-scale inverted-tee girders with circular web openings to failure, to evaluate the openings’ effect on girder behavior. The girders failed in a ductile manner due to diagonal cracking above the openings. The tested girders were designed using available recommendations in the existing literatures. It was observed that concrete fractured from tension zones around an opening, with cracks developing vetically towards the beam flanges. A beam would collapse when the cracks reached the flanges. In the present work, an analytical solution is developed for the load-deflection calculation of prestressed beam with web openings at any load stage. The solution assumes a trilinear deflection response characterized by the flexural cracking initiation, steel yielding, and ultimate capacity. Closed form expressions are presented for the case of simple beams subjected to four-points loading. These expressions are modified from present ACI code equations by incorporating appropriate laboratory determined coefficients in order to predict more precisely with some degree of conservativeness on flexural load-point deflection with any extent of uncracked, postcracked, and postyielded region along their spans. Accordingly, a simplified analysis procedure is developed by adopting a trilinear load-deflection response. The effectiveness of the simplified procedure is demonstrated by comparing its results to those of the analytical solution and the experimental values.
SiAlON B-Phase Glass-Ceramic Microstructures
Authors: Falk L.K.L. , Menke Yvonne , Hampshire Stuart
Published: March 2009

This paper is focussed on the development of microstructure during crystallisation heat treatment of B-phase parent glasses with composition (e/o) 35R:45Si:20Al:83O:17N, where R = Er, Yb, Y or a mixture of Y and Yb. Extensive high resolution analytical transmission electron microscopy has shown that the lenticular B-phase crystals take up a substantial range of composition. The element R is always clearly anti-correlated with the Si, and a larger R3+ cation radius moves the composition range to lower R contents. It is suggested that a locally increased density in the bi-dimensional network of randomly oriented (Si,Al)(O,N)4 tetrahedra is associated with an increased density of vacancies in the R3+ cation lattice.
New Green Phosphor Ba3Si6O12N2:Eu for White LED: Crystal Structure and Optical Properties
Authors: Mikami Masayoshi , Shimooka Satoshi , Uheda Kyota , Imura Hiroyuki , Kijima Naoto
Published: March 2009

A new oxynitride, Ba3Si6O12N2, has been synthesized. The crystal structure has been successfully determined by close collaboration between experiment and first-principles calculation. This compound doped with Eu exhibits intense green photoluminescence with high color purity under near-ultraviolet to blue light excitation; in particular, it has much less thermal quenching than (Ba,Sr,Eu)2SiO4. Thus (Ba,Eu)3Si6O12N2 appears promising green phosphor for white LED backlight for display. The atomic/electronic structure is discussed in comparison with Ba3Si6O9N4, which could not become efficient phosphor by doping Eu due to strong thermal quenching at room temperature.
Corrosion of β-SiAlON in Molten Aluminium, Cryolite and NaCl-KCl Mixture
Authors: Plachký T. , Křesťan J. , Korenko M. , Lenčéš Zoltán , Šajgalík Pavol
Published: March 2009

β-sialons prepared from pyrophyllite resp. kaoline were used for investigation of corrosion resistance in aluminium, NaF-AlF3 and NaCl-KCl mixture. The results were compared with β-sialon of similar composition, prepared from commercial powders. The differences in corrosion process of β-sialon prepared from natural hydrosilicates and synthetic powders are discussed.
Gelcasting of Carbide Ceramics
Authors: Jiang Dong Liang
Published: March 2009

In this paper, the aqueous gelcasting of carbide ceramics (SiC, TiC, and B4C) were studied systematically. N, N-dimethyl acrylamide (DMAA) and N, N’-methylenebisacrylamide (MBAM) are used as organic monomer and cross-linker respectively. The initiator was selected from ammonium persulfate (APS) and 2, 2’-azobis[2-(imidazolin-2-yl) propane]dihydrochloride (AZIP2HCl) in accordance with the dispersant used. After gelcasting and drying, SiC samples can be densified by pressureless sintered at 2000°C. The gelcasted TiC green samples can be densified at 1530°C in vacuum with the strength as high as 1062.7749.81. The gelcasted B4C samples can be easily densified at 2250°C by pressureless sintering with the relative density around 96.2%. Results showed that it was possible to prepare carbide ceramics with complex shape and satisfied mechanical properties by gelcasting.
A Novel Approach for Preparing Electrically Conductive SiAlON-TiN Composites by Spark Plasma Sintering
Authors: Ayas E. , Kara Alpagut , Kara Ferhat
Published: March 2009

An effective approach for preparing electrically conductive SiAlON-TiN composites was developed. Granules of a designed composition of α- SiAlON was obtained by spray drying and coated with varying amounts of TiO2 powder homogenously by mechanical mixing. Fully dense composites were obtained by spark plasma sintering (SPS) under a pressure of 50 MPa at 1650°C for 5min. According to the SEM analysis, unique microstructures containing continuously segregated in-situ formed TiN phase in 3-D were achieved. Additionally, XRD studies revealed that all TiO2 was successfully converted to TiN. The resistivity of the α-β SiAlON
(1x1011 .m) was drastically reduced with the addition of only 5 vol. % TiO2 (2x10-4 .m).
Sintering Shrinkage Behavior and Mechanical Properties of HfO2-Added Si3N4 Ceramics
Authors: Horikawa Daisuke , Tatami Junichi , Wakihara Toru , Komeya Katsutoshi , Meguro Takeshi
Published: March 2009

HfO2-added Si3N4 ceramics are known to exhibit excellent high-temperature strength and excellent damage characteristics because HfO2 assists the crystallization of the grain boundary phase. However, the sintering shrinkage behavior and mechanical properties of HfO2-added Si3N4 have not been well clarified so far, although it has been reported that TiO2, in which Ti is from the same group as Hf in the periodic table, enhances the densification of the Si3N4-Y2O3-Al2O3-AlN system and wear resistance due to TiN formed from TiO2 and AlN in the grain boundary. In the present study, we focus on HfO2 as the sintering aid to investigate the sintering shrinkage behavior and mechanical properties of HfO2-added Si3N4. The powder mixtures are prepared by the addition of HfO2 to the Si3N4-Y2O3-Al2O3 or Si3N4-Y2O3-Al2O3-AlN system. The sintering shrinkage curves of HfO2-added Si3N4 ceramics show rapid shrinkage at 1600°C as compared with those of the Si3N4 ceramics without HfO2.The shrinkage can be explained by the formation of SiO2-Y2O3-HfO2 derived liquid phases. Furthermore, the mechanical properties of HfO2-added Si3N4 were as excellent as those of the Si3N4 ceramics without HfO2.
First Principles Calculations of Advanced Nitrides, Oxides and Alloys
Authors: Tanaka Isao , Kuwabara Akihide , Yuge Koretaka , Seko Atsuto , Oba Fumiyasu , Matsunaga Katsuyuki
Published: March 2009

The phase stability of silicon nitride is examined using a series of first principles phonon calculations. -phase shows slightly higher free energy than  in the temperature range from 0 to 2000K. The difference between  and is only 0.02 eV/Si3N4 or 2 kJ/mol at 300 K. The result is consistent with the experimental report by high-temperature oxide-melt-drop solution-calorimetry. Similar calculations are made for ZrO2, Ga2O3, BN and some perovskites. Using cluster expansion technique combined with a large set of first principles calculations, the cation disordering of II-III spinel oxides and the phase diagram of diamond vs. c-BN are theoretically investigated. Theoretical results on the atomic structures of  and  sialons are also shown.
Efficient Super-Smooth Finishing Characteristics of SiC Materials through the Use of Fine-Grinding
Authors: Kasuga H. , Ohmori Hitoshi , Lin Wei Min , Watanabe Y. , Mishima T. , Doi Toshiro K.
Published: March 2009

Silicon carbide (SiC) materials have increasingly been needed in the wide range of industries, such as for structural components, automobile parts, space telescope, X-ray mirror, and next-generation semiconductors. However, SiC materials have difficulties in super-smooth finishing because of their hard and brittle characteristics. The authors have been investigating appropriate conditions on their finishing by fine-grinding with the unique grinding process called ELID (Electrolytic In-process Dressing) grinding method. The ELID grinding method has a stable grinding ability, so very detailed characteristics of their material-remove mechanisms were to be investigated. Surface analysis of each material has been discussed through the ELID, and this study proposes good finishing conditions for SiC. In this paper, the advantages of the applied fine-grinding are shown, and unique features on grinding characteristics of SiC through various grinding experimental parameters are described.
Performance of a Slow-Release Type Carboxylic Polymer and its Application
Authors: Li Chong Zhi , Niu Quan Lin , He Guang Ming , Feng Nai Qian
Published: March 2009

A slow-release type carboxylic polymer(SLPC) is synthesized with the monomer mixture at a certain Molecule ratio of methacrylic acid, methoxy polyethylene glycol methacrylate and polyethylene glycol di-methacrylate. Test results of the fluidity, Zeta potential and adsorption in cement paste show that the polymer SLPC has the remarkable anti-adsorbing and high fluid-retaining ability for enhancing fluidity of cement paste as time elapsed, concrete experimental results indicated that it could be used to substitute 30～50% polycarboxylic type water-reducer in the same quality for preparing high workability concrete and controlling its slump loss.
Research on Some Properties of Fly Ash Concrete with Nano-CaCO3 Middle Slurry
Authors: Qian Kuang Liang , Meng Tao , Qian Xiao Qian , Zhan Shu Lin
Published: March 2009

Some long-term properties such as anti-carbonation properties, shrinkage, penetrability of chloride ion of fly ash concrete with nano-CaCO3 middle slurry were studied. Test results showed that the properties of anti-carbonation and impenetrability for chloride of fly ash concrete increased by adding nano-CaCO3 middle slurry because the tiny hole was filled by nano-CaCO3 and the density of concrete increased. But at the same time, the shrinkage of fly ash concrete with and without nano-CaCO3 was the same. Results of SEM also implied the hydration degree of fly ash could be increased by nano-CaCO3.
C60 High Performance Concrete Prepared from Manufactured Sand with a High Content of Microfines
Authors: Li Bei Xing , Wang Ji Liang , Zhou Ming Kai
Published: March 2009

The workability, strength and modulus of elasticity, drying shrinkage and creep, and chloride ion permeability as well as freeze-thaw resistance of the C60 high Performance concretes (HPCs) with manufactured sand (MS) containing crushed limestone dust in percents ranging from 3.5% to 14% were experimentally investigated. The results were compared with those of river sand (RS) concrete. In addition, the effect of clay amounts at 3% and 5% in MS on properties of C60 HPCs was also investigated. The results showed that expect for the creep, the other performances of C60 MS-HPCs with crushed limestone dust content of 7% to 10.5% were excellent or compared favorably with those of C60 RS-HPCs. The increment of clay content in MS obviously decreased workability, increased dry shrinkage and accelerated freeze-thaw destruction of C60 MS-HPCs, but didn’t affecting compressive strength and chloride ion permeability of the concrete. It was concluded that C60 HPC can be made with MS with a high content of crushed limestone dust but the amount of clay in MS should be controlled to a low limit.
Tensile Properties of Low Shrinkage Engineered Cementitious Composite
Authors: Zhang Jun , Gong Cheng Xu
Published: March 2009

This paper reports the tensile properties of a new class of engineered cementitious composite with characteristic of low drying shrinkage. Experimental results show that drying shrinkage of the composite is greatly reduced as using the low shrinkage cementitious material in matrix, while the composite remains strain-hardening and multiple cracking characteristics. The measured drying shrinkage strain at 28 days is only 10910-6 to 24210-6 for low shrinkage ECCs. For traditional ECC, the shrinkage strain at 28 days is nearly 120010-6. The average tensile strain capacity after 28 days curing is 2.5% of the low shrinkage ECC with tensile strength of 4-5MPa.
Tool Path Generation for Free Form Surfaces in Robot-Based Incremental Sheet Metal Forming
Authors: Meier Horst , Brüninghaus Jan , Buff B. , Hypki Alfred , Schyja Adrian , Smukala V.
Published: March 2009

This paper describes a new development in incremental, robot-based sheet metal forming (Roboforming). Roboforming is a dieless sheet metal forming process which ensures cost-effective manufacturing of prototype parts and small batches. Its principle is based on flexible shaping by means of a freely programmable path synchronous movement of two industrial robots driving work-piece independent forming tools. The final shape is produced by the incremental inward motion of the forming tool in depth direction and its movement along the contour in lateral direction on a heli-cal path. The supporting tool, with its simple geometry, holds the sheet on the backside by moving syn¬chronously along the outer contour, at constant depth. In this way no special dies are needed. For mil¬ling machines, which are used in numerous incremental forming approaches, CAD/CAM inter¬faces exist for generating necessary tool paths. For industrial robots only a few simple solutions emerge, which do not have the potential of classical CAD/CAM interfaces and are unusable for co-operating robot systems. While the two coupled robot programs can be programmed manually for simple geometries, this approach does not work for complex geometries. In this paper a further de-velopment in robot programming systems is presented that is now able to derive helical tool paths from any CAD file and generate two cooperating programs for the forming and the sup¬porting tools. The helixes pitch is variable and dependent on the geometry’s wall angle. To increase the part accu¬racy a process database is used, that stores relevant information about the process pa¬rameters, sensor data and used equipment. Based on this information strategies for increasing the part accuracy can be applied.
Prevention of Oxidation in Hot Stamping of Ultra High Strength Steel Sheets
Authors: Mori Kenichiro , Maki Seijiro , Saito Shouichi
Published: March 2009

Oxidation in hot stamping of ultra high strength steel sheets was prevented by coating the sheets with an oxidation preventive oil. For four types of oxidation preventive oil, the degree of oxidation under natural cooling of the heated sheets without forming was first evaluated. The oil that forms a liquefied film at elevated temperatures exhibited high oxidation prevention, and this oil was chosen for a hot bending experiment. Hot hat-shaped bending of the coated sheets using resistance heating was carried out to examine the properties of the products. The bending load was markedly decreased, the shape accuracy of bent products was very high, the surface roughness was similar to that of the sheet, and the hardness was about 1.5 times larger than that of the sheet before the bending due the die quenching. In addition, the layer remaining on the surface of the formed product could be removed using phosphoric acid. It was found that the hot stamping operation using the oxidation preventive oil is effective in the precision forming of ultra high strength steel sheets.
Investigation Mechanism of V-Ring Indenter Geometry in Fine-Blanking Process
Authors: Thipprakmas Sutasn , Jin Masahiko
Published: March 2009

The V-ring indenter geometry (angle, height and position) was investigated by using the finite element method (FEM) to theoretically clarify the mechanism and its action in the fine-blanking process. The FEM simulation results indicate that very small or very large V-ring indenter angles, heights, and positions cause difficulty in the rotation of the material-flow and that the hydrostatic pressure is generated with great difficulty in the blanked material; therefore, crack formation occurs easily. The application of a suitable V-ring indenter angle, height, and position significantly suppresses the formation of rotating flow, which results in increased hydrostatic pressure, and crack formation is consequently prevented.
Multifunctional Lightweight Structures from Tailored Cladded Blanks
Authors: Homberg W. , Tekkaya A. Erman , Beerwald Charlotte , Brosius Alexander , Dau J. , Trompeter Michael
Published: March 2009

In this paper, the use of partially or tailored cladded blanks is proposed for the production of multifunctional lightweight components. Therefore, the non-joined sheet areas will be formed to hollow structures by hydroforming subsequent to the partial cladding operation. The paper presents results of research work on the production processes and potential applications of partially cladded blanks in the field of thermal engineering and automotive engineering. Furthermore, it is focused on possible developments regarding the use of multiple materials and process combinations for sophisticated applications e.g. in the field of lightweight constructions.
On a Simplified Model for the Tool and the Sheet Contact Conditions for the SPIF Process Simulation
Authors: Robert Camille , Ayed Lanouar Ben , Delamézière Arnaud , dal Santo Phillippe , Batoz J.L.
Published: March 2009

The numerical simulation of the Single Point Incremental Forming process (SPIF) is time consuming due to the necessity to take into account various non-linearity such as the material behaviour, large strain deformation and the evolution of the tool-flange contact. Classical contact algorithms give good agreement with experimental results, but are time consuming. In this paper, we investigate the development of a procedure to simplify the management of the contact interface between the tool and the sheet. Nodes with imposed displacements are determined by a geometrical approximation of the deformed sheet. In order to have a better approximation of the local stresses in the flange, a pressure is applied on the tool side of the elements in the contact zone. The pressure value is obtained by an analytical model. A classical contact algorithm and the present simplified approach are compared in terms of an incremental forming benchmark. It has been shown that, for the benchmark problem studied here, a CPU time reduction of approximately 65% can be achieved while at the same time have good simulation results.