bluuebunny/crossref_metadata_2025 huggingface dataset:
Cohesive Zone Model for Crack Propagation in a Viscoplastic Polycrystal Material at Elevated Temperature
Authors: Wu Yan Qing , Shi Hui Ji
Published: March 2009

This study looks at the crack propagation characteristics based on the cohesive zone model (CZM), which is implemented as a user defined element within FE system ABAQUS. A planar crystal model is applied to the polycrystalline material at elevated temperature in which grain boundary regions are included. From the point of energy, interactions between the cohesive fracture process zones and matrix material are studied. It’s shown that the material parameter such as strain rate sensitivity of grain interior and grain boundary strongly influences the plastic and cohesive energy dissipation mechanisms. The higher the strain rate sensitivity is, the larger amount of the external work will be transformed into plastic dissipation energy than into cohesive energy which could delay the rupturing of cohesive zone. By comparisons, when strain rate sensitivity decreases, plastic dissipation energy is reduced and the cohesive dissipation energy increases. In this case, the cohesive zones fracture more quickly. In addition to the matrix material parameter, influence of cohesive strength and critical displacement in CZM on stress triaxiality at grain interior and grain boundary regions are also investigated. It’s shown that enhancing cohesive zones ductility could improve matrix materials resistance to void damage.
Delamination Growth in Ball Grid Array Electronic Package
Authors: Yeh Meng Kao , Lee In Shung
Published: March 2009

The delamination problem in plastic ball grid array electronic package was investigated analytically and experimentally. The ANSYS code was used in the analysis to find the deformation and the stress distribution in electronic package due to the thermal mismatch between different materials at reflow temperature with saturated moisture pressure at the delaminated region. The stress intensity factor and the strain energy release rate at the tip of interfacial delamination were calculated using the fracture mechanics approach. The results show that the delaminaton occurs at the corner of the die pad and at the middle region of the die attach/die pad interface. The delaminaton grew from the middle region of the die attach/die pad interface, along the epoxy molding compoend/die pad interface, the epoxy molding compound/substrate interface to the exterior surface. Possible growth directions of the interfacial delamination in plastic ball grid array electronic package were identified and observed in the experimental results. In addition, the reflow temperature affected the stress distribution and the strain energy release rate at the tip of interfacial delaminaton.
Development of Surface Welding Method for Surface Temperature Measurement of an IC Engine's Combustion Chamber
Authors: Kim Hyung Man , Choi Kap Seung , Kim Chang Ho , Lee Dong Jae
Published: March 2009

In the recent development of internal combustion engine, considerable increase in speed and power has been accomplished. This achievement, however, brought up various problems due to the excessive temperature of engine parts, which becomes a crucial factor in engine durability. In the present paper, temperature measurement of a marine engine was investigated experimentally. The adapter is made to pull out a thermocouple through the safety valve hole of the engine. The thermocouple is welded on the surface of the cylinder cover to measure the average temperatures of
the engine cylinder cover. Ceramic adhesive was used for preventing the affect of high temperature combustion gas. The cylinder cover temperatures of the engine were measured by means of surface welding method. As a result, average temperatures of the engine cylinder cover were successfully in the range of 85~335oC. In the present study, the surface welding method was confirmed from the
temperature measurement of cylinder cover in an experimental engine, and can be applied to large-sized marine engine without damage.
Parameter Optimization of a Static Micro-Mixer Using a Sequential Approximate Optimization Method
Authors: Han Seok Yoon , Maeng J.S. , Kim S.H. , Park J.Y.
Published: March 2009

Parameter optimization of a static micro-mixer with a cantilever beam was accomplished for maximizing mixing efficiency using a sequential approximate optimization method. The objective function and design variables were chosen as mixing index, and the length and the angle measured from the horizontal of the cantilever beam, respectively. The Optimization problem of the mixer was considered as a series of sub-problems. Approximation to solve the sub-problems was performed by response surface methodology. To verify the reliability and the accuracy of the approximated objective function, ANOVA table and variable selection method were implemented, respectively. It was verified that the sequential approximate optimization method worked very well, and the mixing efficiency was significantly improved compared with the initial design.
Buckling Analysis of Cylindrical Shells Having a Longitudinal Crack
Authors: Dirgantara T. , Putra I.S. , Sucipto A.A. , Jusuf A.
Published: March 2009

The presence of cracks or similar imperfections can considerably reduce the buckling load of a shell structure. In this paper, buckling analysis of cylindrical shells with a longitudinal crack is presented. Numerical buckling analyses of cylindrical shells were performed using FEM, and verified by experiment. The numerical analyses and experiments were conducted for several crack lengths and radius of curvature, and two different boundary conditions were applied, i.e. simply support and clamp in all sides. The results show the effect of the presence of crack to the critical buckling load of the shells. There are good agreements between experimental and numerical results.
Grillage Optimization with Multiple Objectives
Authors: Kim Ki Sung , Kim Kyung Su , Hong Ki Sup
Published: March 2009

The structural design problems are acknowledged to be commonly multicriteria in nature. The various multicriteria optimization methods are reviewed and the most efficient and easy-to-use Pareto optimal solution methods are applied to structural optimization of grillages under lateral uniform load.
The result of the study shows that Pareto optimal solution methods can easily be applied to structural optimization with multiple objectives, and the designer can have a choice from those Pareto optimal solutions to meet an appropriate design environment.
Midship Section Optimization of Hatchcoverless Container Ship Based on Real-Coded Micro-Genetic Algorithm
Authors: Kim Yunyoung , Kim Ki Sung , Park Je Woong
Published: March 2009

The optimum midship section design of container ship belongs to the nonlinear constrained optimization problem. The determination of scantlings for the midship region is a very crucial matter out of whole structural design process of a ship. This determination may be a process of satisfying a lot of complicated design constraints empirically, rather than optimizing some objective function. However, in order to realize optimum or rational design for midship region with complicated design constraints, it is necessary to model the design problem as strictly as possible and to accomplish more highly numerical optimization. Real-coded micro-Genetic lgorithm (RμGA) is proposed to find the optimum midship section arrangement of an actual hatchcoverless container ship without handling any of penalty functions.
Study on Torque Analysis of Micro-Electromagnetic Clutch by Using the Finite Element Method
Authors: Park Chang Hao , Cho Chong Du , Kim Chang Boo , Beom Hyeon Gyu
Published: March 2009

This study tries to analyze the torque generated in a micro-electromagnetic clutch by using FEM. For the purpose of design change and optimization of the micro-electromagnetic clutch, the torque prediction is very important. We employ a mathematical approach of the process based on electromagnetic principle. Then real material properties are substituted in the FEM model to obtain the analytical torque. For a test, the predicted torque is compared with the experimental one to discuss the rationality of torque analysis process. The analytical result agrees well with experimental data and hence explaining the validity of the mathematical process and the FEM model.
Investigating Strain Rate Effect on Transverse Compressive Strength of Fiber Composites
Authors: Tsai Jia Lin , Kuo Jui Ching
Published: March 2009

This research aims to investigate strain rate effect on transverse compressive strength of unidirectional fiber composites. Both glass/epoxy and graphite/epoxy composites were taken into account in this study. To demonstrate strain rate effect, composite brick specimens were fabricated and tested to failure in the transverse direction at strain rate ranges from 10-4/s to 500/s. For strain rate less than 1/s, the experiments were conducted by a hydraulic MTS machine. However, the higher strain rate tests were performed using a Split Hopkinson Pressure Bar (SHPB). Experimental observations reveal that the transverse compressive strengths increase corresponding to the increment of the strain rates. A semi-logarithmic function was employed to describe the rate sensitivity of the transverse compressive strength. SEM photographic on the failure surfaces depicts that for
glass/epoxy composites, the failure mechanism is mainly due to the matrix shear failure, however, for the graphite/epoxy composites, it becomes the fiber and epoxy interfacial debonding which could dramatically reduce the transverse compressive strengths of the fiber composites.
Studies on the Dynamic Compressive Properties of Open-Celled Aluminum Alloy Foams
Authors: Wang Zhi Hua , Ma Hong Wei , Zhao Long Mao , Yang Gui Tong
Published: March 2009

The compressive deformation behavior of open-cell aluminum foams with different densities and morphologies was assessed under quasi-static and dynamic loading conditions. High strain rate experiments were conducted using a split Hopkinson pressure bar technique at strain rates ranging from 500 to 1 2000 − s . The experimental results shown that the compressive stress-strain curves of aluminum foams also have the “ three regions” character appeared in general foam materials, namely elastic region, collapse region and densification regions. It is found that density is the primary variable characterizing the modulus and yield strength of foams and the cell appears to have a negligible effect on the strength of foams. It also is found that yield strength and energy absorption is almost insensitive to strain rate and deformation is spatially uniform for the open-celled aluminum foams, over a wide range of strain rates.
Analytical and Numerical Modelling of Strain and Strain Rate in Equal Channel Angular Pressing (ECAP)
Authors: Kim Hyoung Seop
Published: March 2009

Equal channel angular pressing (ECAP) is a convenient forming procedure among various severe plastic deformation processes. It is based on extruding material through specially designed entry and exit channel dies to produce an ultrafine grained microstructure. The properties of the materials obtained depend on the plastic deformation behaviour during ECAP, which is governed mainly by the die geometry, the material itself and the processing conditions. As the mechanical
properties of the severely deformed material are directly related to the deformation history, understanding the phenomena associated with strain and strain rate development in the ECAP process is very important. In this study, the results of continuum modelling of ECAP are described in order to understand strain and strain developments. For this purpose, the results of modelling ECAP using the finite element method and analytical solution are presented for various geometric conditions. It was concluded that although deformation is nonuniform due to geometric effects, the strain and strain rate values obtained by the analytical solutions are not much different from the average results of the finite element method.
Porous Granules of β-Tricalcium Phosphate Composed of Rod-Shaped Particles
Authors: Ioku Koji , Kawachi Giichiro , Nakahara Kazuhiko , Ishida Emile Hideki , Minagi Hideyuki , Okuda Takatoshi , Yonezawa Ikuho , Kurosawa Hisashi , Ikeda Tohru
Published: March 2009

Porous granules of β-tricalcium phosphate (β-Ca3(PO4)2; β-TCP) were prepared from porous hydroxyapatite granules with calcium deficient composition synthesized by hydrothermal method. The β-TCP granules were composed of rod-shaped particles of about 10-20 µm in length. Rod-shaped particles were locked together to make micro-pores, and the size of micro-pores formed by tangling of rod-shaped particles was about 0.1-0.5 µm. The granule size, particle size, and micro-pore size could be controlled by our unique method. The porous granules of β-TCP must be suitable for the bone graft material and for scaffold of cultured bone.
Bone Growth in Porous Titanium Implants Made by Rapid Prototyping
Authors: Lopez-Heredia Marco A. , Goyenvalle Eric , Aguado Eric , Leroux C. , Dorget M. , Layrolle Pierre
Published: March 2009

Two porous titanium implants with interconnected pore size of 800 and 1200 m in
diameter, were fabricated by a rapid prototyping method. Their dimensions and structure accomplished the expected design with accuracy and reproducibility. The porosity of titanium was around 60%. The compressive strength and Young’s modulus were comparable to those of cortical bone with values around 80 MPa and 2.7 GPa, respectively. The implants were implanted bilaterally in the femoral epiphysis of 12 New Zealand Rabbits. After 3 and 8 weeks, abundant bone
formation was found in the titanium porous structure. This work demonstrates that macroporous titanium with controlled shape and porosity is a good candidate for orthopaedic and maxilofacial applications.
A Novel Preparation Method for Nano-HA/PLA Composite with Grafted PLA
Authors: Xiao Yu Mei , Li Xu Dong , Fan Hong Song , Zhu Xiang Dong , Teng Li Zhao , Gu Zhong Wei , Zhang Xing Dong
Published: March 2009

Good interfacial interaction is crucial for preparation of inorganic-organic materials at a nanometer level. Poly(α-methacrylic acid) (PMAA) was grafted on the PLA surfaces via photooxidization and subsequent UV induced polymerization in an attempt to synthesize nano-hydroxyapatite/poly(lactide) (n-HA/PLA) composites. Grafting of PMAA on the PLA surface was confirmed using FTIR analysis and the size distribution measurement of the grafted-PLA
(g-PLA) particles. n-HA/g-PLA composites were in situ synthesized via dropwise addition of Ca2+- and g-PLA containing solution to PO4
3-- solution. The prepared composites were characterized by
FTIR, XRD，SEM and TEM means. Analytical results indicated that the g-PLA acts as a template to manipulate the nucleation and growth of n-HA crystals and thereby to control the morphology, size and anisotropy of n-HA crystals and their distribution over the organic phase. Chemical linkages and/or interfacial interactions between the n-HA and the g-PLA in the n-HA/g-PLA composite were further discussed.
Sintering Effect on Mechanical Properties of Composites of Enamel Derived Hydroxyapatite (EHA) and Titanium
Authors: Gunduz Oguzhan , Oktar Faik N. , Oz B. , Altundal H. , Agathopoulos Simeon , Salman S. , Ovecoglu L.
Published: March 2009

Hydroxyapatite (HA) is one of the most promising biomaterials, which is on use since decades in biomedicine. Because of the known mechanical weakness of HA in load carrying situations, various dopants, like ceramic oxides and metallic particles, have been used to produce HA-composite materials. In this study, Ti powders were admixed with enamel derived HA at 5 and 10 wt %. After ball milling, the mixtures were uniaxially pressed into pellets of a cylindrical form. The composites were sintered at temperatures between 1000°C and 1300°C. Microhardness, compression strength, and density measurements together with X-ray diffraction analysis and SEM studies were performed. The best mechanical values were obtained for the samples sintered between 1100°C and 1300°C.
Development of Bioactive Organic Polymer Composite by Electrophoretic Deposition
Authors: Yabutsuka Takeshi , Yamaguchi Seiji , Hibino Mitsuhiro , Yao Takeshi
Published: March 2009

By electrophoretic deposition, wollastonite particles were deposited in pores of porous ultrahigh molecular weight polyethylene (UHMWPE). The UHMWPE-wollastonite composite thus fabricated was soaked in a simulated body fluid. As a result, apatite was formed inside the pores as well as on the surface of the UHMWPE-wollastonite composite. The formed apatite showed high adhesive strength to the composite.
Wettability Analysis of Orthopaedic Materials Using Optical Contact Angle Methods
Authors: Salehi Abraham , Tsai Stanley , Pawar Vivek , Sprague Jeff , Hunter Gordon , Varma S.K. , Namavar F.
Published: March 2009

The wettability behavior of orthopaedic materials influences the fluid film layer that affects both the friction and wear of the articulating surfaces in total joint arthroplasty. This study examined the wettability of various orthopaedic bearing materials such as alumina, zirconia, cobalt chrome (CoCr), and oxidized zirconium (OxZr). Diamond-like carbon (DLC) coating on CoCr was also
examined. Additionally, the effect of radius of curvature was examined using OxZr femoral heads of various diameters. The contact angle of the liquid droplet on the surface of the material was measured using a optical contact angle method. Both water and bovine serum with 20 g/L protein concentration were used during testing, with a droplet size of 0.25 -L. The droplet was dispensed from an automated syringe and brought into contact with the sample surface. The contact angle was
then measured by fitting polynomial curves to the sample surface and drop geometry. Ten individual drops were analyzed on each test component, with at least three test components for each material. There were no differences in contact angles with changing head size or when using serum compared to water. The alumina, OxZr, and zirconia femoral heads all exhibited a similar contact
angle, while CoCr and DLC showed significantly greater contact angles. The smaller contact angles for the oxide ceramic surfaces indicate that they tend to be more wettable than the metals, which may help explain their lower friction and superior adhesive wear performance.
Heat Generation and Dissipation Behavior of Various Orthopaedic Bearing Materials
Authors: Tsai Stanley , Salehi Abraham , Aldinger Patrick , Hunter Gordon
Published: March 2009

It has been shown that with high interfacial temperatures in hip bearings, it is possible to precipitate proteins, greatly reduce the compressive creep properties of ultrahigh molecular weight polyethylene (UHMWPE), and change the phase content of monolithic tetragonal zirconia. These induced features may alter the wear rate of UHMWPE. It was the objective of this study to examine the interfacial temperatures of oxidized zirconium (OxZr) heads as compared with metallic and ceramic heads coupled with polyethylene in a hip simulator. The interface temperatures were measured by placing thermocouples within 0.5 mm of the interface surface of both femoral heads and acetabular liners, and then articulating the surfaces using a 12-station AMTI anatomic hip simulator. The alumina femoral heads had the lowest average interfacial temperature, followed in increasing order by OxZr, CoCr, and zirconia. The ranking corresponds to the thermal conductivity of each material. A statistically significant difference (p<0.05) was found between all four materials for the femoral head temperature. No difference was seen in liner temperature between the alumina and OxZr groups, but statistical differences were found between all other combinations. Additionally, increasing head diameter, peak load, cyclic frequency, and serum concentration all resulted in statistically significant increases in both femoral head and liner temperatures.
The Ceramic Option in Ball Head Revision Surgery
Authors: Merkert Patricie , Preuss Roman , Dietrich Martin
Published: March 2009

A ceramic ball head design with metal sleeves was developed to be used in revision
surgery if the stem is well fixed in the bone.
Mid-Term Results of Ceramic-on-Ceramic Total Hip Arthroplasty with Sandwich Cup
Authors: Hasegawa Masahiro , Sudo Akihiro , Uchida Atsumasa
Published: March 2009

In ceramic-on-ceramic total hip arthroplasty (THA), modular acetabular component with a sandwich insertion was developed and evaluated mid-term clinical results. 35 hips had undergone cementless ceramic-on-ceramic THA with sandwich cup (Kyocera, Kyoto, Japan). The mean duration of follow-up was 5 years. 6 hips had undergone component revisions. The reasons for revision included infection in 1 hip, dislocation with loosening in 2 hips, alumina liner fractures in 2 hips, and cup dissociation in 1 hip. All femoral and acetabular components showed no loosening in the unrevised hips at the time of the last follow-up. None of the 29 unrevised hips had osteolysis.
Immediate Mechanism of the Osteoconductivity of the Polarized Hydroxyapatite
Authors: Nakamura Miho , Sekijima Yasutaka , Nakamura Satoshi , Niwa Kazuki , Kobayashi Takayuki , Yamashita Kimihiro
Published: March 2009

We investigated the immediate response in the vicinity of the implanted polarized hydroxyapatite (HA). One of the important immediate events was found to be the fibrin adsorption on the implanted HA. The activation of the fibrin adsorption on the polarized HA was confirmed by the observation by SEM observation and immunohistochemical detection. After the implantation, the coagulation cascade induced the wound healing. The adsorbed fibrin was formed network structure and worked for later cell responses as the scaffolds. The acceleration of fibrin scaffolds formation in the vicinity of the implanted polarized HA contributed to the stimulation and activation of plate ets and osseous cells. The platelets were activated from the results of the signal transduction and cytoskeleton changes and released growth factors. The growth factors released from platelets led to bone regeneration by stimulating migration and proliferation of the osseous cells. In the vicinity of the implanted HA samples, the coagulation cascade reaction to repair wound healing led to the new bone formation by mediation of the platelets and osseous cells. The mechanism of osteoconduction at earlier stage had close relationships to the electrostatic properties of the implant.
Densification Behavior of Calcium Phosphates on Spark Plasma Sintering
Authors: Kawagoe Daisuke , Koga Yoshihiro , Kotobuki Noriko , Ohgushi Hajime , Ishida Emile Hideki , Ioku Koji
Published: March 2009

Ceramics of hydroxyapatite (Ca10(PO4)6(OH)2: HA) and β-tricalcium phosphate (β-Ca3(PO4)2: β-TCP), were prepared by spark plasma sintering (SPS) at the temperatures from 800 °C to 1000 °C for 10 min with a heating rate of 25 °C·min-1. The HA ceramics prepared at 900 °C and 1000 °C showed transparency. On the other hands, transparent β-TCP ceramics was obtained by SPS at 1000 °C. In analysis of the densification behavior during sintering of HA and β-TCP by SPS, dominant sintering mechanism was plastic flow in the early stage of densification. Transparent ceramics should be the most suitable materilas to investigate the interface between human cells and ceramics.
Synthesis and Evaluation of Amorphous Calcium Phosphate (ACP) by Various Synthesis Methods
Authors: Ohta Mitsuhiko , Honma Tetsuo , Umesaki M. , Nakahira Atsushi
Published: March 2009

Amorphous calcium phosphate (ACP) was prepared by a sol-gel method from Ca alkoxide synthesized with Ca metal and ethanol in N2 atmosphere. As-prepared products by sol-gel method were spherical ACP particles of approximately 3 to 10 nm in diameter before heat-treatments. The results from Ca-K edge of as-synthesized ACP showed only one peak around 0.2 nm, suggesting the presence of the first neighbor of Ca in Ca-PO4 cluster.
Effects of Paste Type Calcium Sulfate on the Periodontal Healing of 3-Wall Intrabony Defects in Dogs
Authors: Kim Tae Gyun , Hyun S.J. , Jung Ui Won , Kim C.S. , Kim Chong Kwan , Choi Seong Ho
Published: March 2009

The purpose of this study is to evaluate the effect of paste type calcium sulfate on the epithelial migration, alveolar bone regeneration, cementum formation and gingival connective tissue attachment in intrabony defect in dogs. These results suggest that the use of paste type calcium sulfate in 3-wall intrabony defects has significant effect on new cementum formation , but doesn't have any significant effect on the prevention of junctional epithelium migration and new bone formation. As a
result, the paste type calcium sulfate that is used in this study is suggested to be the material that can have a significant effect on the periodontal healing, if its biocompatibility is improved.
A MAS-NMR and Combined Rietveldt Study of Mixed Calcium/Strontium Fluorapatite Glass-Ceramics
Authors: Hill Robert G. , Calver Adam , Skinner Stephen , Stamboulis Artemis , Law Robert V.
Published: March 2009

Strontium is one of the most common substituents in apatite crystals. The presence and behavior of Sr in apatite-group phases are of considerable significance in biology. The present paper investigates the substitution of strontium for calcium in a glass-ceramic of the following composition 4.5SiO23Al2O31.5P2O54CaO1CaF2. The glasses were characterized using Differential Thermal Analysis (DTA), X-ray powder diffraction (XRD), neutron diffraction (ND) and 19F Resonance Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR). The all calcium glass crystallized to calcium fluorapatite (Ca5(PO4)3F). Substituting strontium partially for calcium resulted in the formation of a mixed strontium/calcium fluorapatites. In contrast complete substitution resulted in the formation of strontium fluorapatite. MAS-NMR showed the the F to be present as F-Ca(3) representing a fluoride ion surrounded by three Ca2+ ions in the all calcium glass and was present as F-Sr(3) in the all strontium glass. In the mixed glasses fluorine was present as FCa( 3), F-Ca(2)Sr, F-CaSr(2) and F-Sr(3). Ca had a higher tendency to occupy the F-M(3) sites than Sr which may reflect the higher charge to size ratio of Ca2+ relative to Sr2+ and its greater affinity for F- ions.
Sintering Effects on Mechanical Properties of Hydroxyapatite-Titanium Dioxide (HA-TiO2) Composites
Authors: Oktar Faik N. , Meydanoglu Onur , Göller Gültekin , Agathopoulos Simeon , Rocha G. , Ozyegin L.S. , Eruslu Niyazi , Peker Ismail , Kayali E.S.
Published: March 2009

Composites of bovine bone derived HA with 5 wt% and 10 wt% of TiO2 were sintered at different temperatures. Their characterization comprised measurements of density, microhardness, and compression strength together with SEM observations and X-ray diffraction analysis. Better densification behaviour was achieved at higher sintering temperatures. The highest microhardness value was measured in the samples sintered at 1300°C. The best compressive strengths of the samples containing 5% and 10% TiO2 were obtained after sintering at 1300°C and 1200°C, respectively.
Development of Carbon Nanotube Reinforced Hydroxyapatite Bioceramics
Authors: Kealley Catherine , Ben-Nissan Besim , van Riessen A. , Elcombe M.
Published: March 2009

This paper reports development of a production method to produce a composite material that is biocompatible, with high mechanical strength and resilience. The chemical precipitation conditions necessary for the production of synthetic hydroxyapatite (HAp) were determined and include pH,
temperature and rate of reaction. A gas phase purification method was optimised to remove the soot impurity from the nanotubes, with transmission electron microscopy showing the preservation of the carbon nanotubes. Subsequent development of chemical and physical reinforcement techniques to produce a HAp + carbon nanotube composite material have been trialled. Hot isostatically
pressed samples showed excellent densification and strength.
Electrophoretic Deposition of Hydroxyapatite Nanocrystal
Authors: Monkawa Akira , Ikoma Toshiyuki , Yunoki Shunji , Ohta Kazushi , Tanaka M.
Published: March 2009

Homogeneous nano-thin layer of hydroxyapatite (HAp) nanocrystals on the gold surface was fabricated by an electrophoretic deposition method (EPD); the HAp nanocrystals were dispersed into ethanol and the applied voltage was varied. The HAp nanocrystals were prepared by a wet method at 4 °C and 80 °C, which were characterized by X-ray diffraction and Fourier-transform infrared spectroscopy. The micro-thin layer of HAp nanocrystals was initially formed, and the ultrasonic treatments can remove the surplus nanocrystals from the surface. The
nanostructure of the surface was investigated by atomic force microscopy and contact angle measurement. The thickness of coating layers was approximately 20nm and the root mean square (RMS) roughness was under 6.6 nm, which was clearly depended on the crystal sizes, applied voltages and applied times.
Consequences of Fluoride Incorporation on Properties of Apatites
Authors: LeGeros Racquel Z. , Mijares Dindo Q. , Yao Fang , LeGeros John P. , Bromage T. , La V. , Xi Q. , Tannous Samar , Kijkowska Regina
Published: March 2009

Fluoride, when incorporated in the apatite, stabilizes the structure. The purpose of this study was to determine the consequences of fluoride (F) substitution on the physico-chemical properties of apatites. F-containing apatites were prepared by precipitation or by hydrolysis of CaHPO4 in solutions containing different F concentrations and characterized using x-ray diffraction, FT-IR spectroscopy, scanning electron microscopy, thermogravimetry and chemical analyses.
Results showed that F incorporation have the following effects: (a) decrease in a-axis dimension, (b) increase in crystal size and thickness, (c) decrease in calcium deficiency, and (d) lower solubility.
Natural Nacre Coatings on Titanium Implant Grown by Fresh Water Bivalve Shell
Authors: Wang Xiao Xiang , Xie Lei , Luo Cheng , Wang Ri Zhi
Published: March 2009

Titanium dental implant screws were implanted into the pearl sacs of a fresh water
bivalve (hyriopsis cumingii Lea) by replacing the pearls. After 45 days of cultivation, the implant surfaces were deposited with a nacre coating with iridescent luster. The coating was about 200-600 µm in thickness and composed of a laminated nacreous layer and a transitional non-laminated layer that consisted mainly of vaterite and calcite polymorphs of calcium carbonate. The transitional layer
was around 2-10 µm thick in the convex and flat region of the implant surface and could form close contact with titanium surface; while the transitional layer was much thicker in the steep concave regions and could not form close contact with the titanium surface. The improvement to the design of the dental implant with respect to this coating method was suggested in the paper. The results suggest that it is possible to fabricate a biologically active and degradable, and mechanically tough
and strong nacre coating on titanium dental implant by this novel coating technology.
Preparation of β-Tricalcium Phosphate Containing Silica by CO2-Laser-Irradiation
Authors: Ghaith El-Sayed , Kasuga Toshihiro , Nogami Masayuki
Published: March 2009

Silicon is one of the essential ions with a stimulating effect on bone formation. β-
tricalcium phosphate ceramic (β-TCP) with a modified surface containing silica was prepared in order to accelerate the bone formation. Sintered β-TCP pellets were spin-coated with a prehydrolyzed silica sol, and subsequently laser-irradiated using CO2 laser at the power of 6.5W. Scanning electron microscopy attached with X-ray energy dispersive spectrometry (SEM-EDS) showed that the silica was doped into the β-TCP surface. The silicon ion was released into a trisbuffer
solution at pH 7.4 at 37 oC during one week of soaking.
Preparation of α-TCP Cements from Calcium Deficient Hydroxyapatite Obtained by Hydrothermal Method
Authors: Jokic B. , Jankovic-Castvan I. , Veljković Dj. , Petrović R. , Drmanic S. , Janaćković Dj.
Published: March 2009

In this paper the synthesis of bioactive cement based on α-Ca3(PO4)2 (α-TCP) and calcium deficient hydroxyapatite (CDHAp), obtained by hydrothermal method from CaCl2, EDTA, NaH2PO4·12H2O and urea at 160oC, was described. According to the results of DTA, SEM, X-ray and FTIR analyses performed in this investigation, it is shown that CDHAp is transformed to β- TCP at 780oC, and to α-TCP at 1400oC. The hardening of the samples, prepared from the mixture of
α-TCP and 2.5 % solution of Na2HPO4, in simulated body fluid at 37oC, was followed by the microstructure changes.
Incorporation of 2nd and 3rd Generation Bisphosphonates on Hydroxyfluorapatite
Authors: Rodríguez-Lorenzo Luis M. , Vázquez Blanca , San Román Julio , Gross Kārlis A.
Published: March 2009

Bisphosphonates (BPs) may play an important role in minimizing osteolysis. In this work two new bisphosphonates pertaining to second and third generations respectively, have been synthesized and incorporated onto a chemically enriched hydroxyapatite. BP synthesis has been performed by adding H3PO3, PCl3 and methanesulfonic acid over 4-aminophenyl acetic acid (APBP) and 1-H-indole-3-acetic acid (IBP) respectively at 65°C in a N2 atmosphere. These
compounds bear a primary amine group bonded to an aromatic ring, and a secondary amine group within a heterocyclic ring respectively. A chemically enriched hydroxyapatite with a chemical content corresponding to a 50% fluorided hydroxyapatite has been synthesized. Ceramic bodies manufactured by uniaxial pressure followed by cold isostatic press have a 97% density and
submicron grain size. The BP was adsorbed onto the surface by immersion in a stirred solution at 37°C for 48 hours. A 10-fold decrease of the surface energy was observed for bodies modified with the APBP whereas only a 25 % decrease is obtained for bodies loaded with the bisphosphonate loaded with the IBP.
Nano-Scaled Hydroxyapatite/Silk Fibroin Composites as Mesenchymal Cell Culture Scaffolds
Authors: Hirose Motohiro , Hamada Kazunori , Tanaka Toshimitsu , Kotobuki Noriko , Ohgushi Hajime , Yasuda Shoji , Furuzono Tsutomu
Published: March 2009

The objective of this study was to evaluate cell adhesion and proliferation on the hydroxyapatite (HAp)-coated silk fibroin (SF) fabric. Nano-scaled sintered HAp particles were covalently coated on SF chemically modified by graft polymerization. After the fabrication of the HAp/SF composite,
mesenchymal cells (MCs) derived from EGFP-expressing transgenic rat bone marrow were seeded on the composite and cultured for 10 days. Fluorescence and scanning electron microscopy (SEM) revealed that the cells adhered and actively proliferated on the composites comparable to those on tissue culture polystyrene (TCPS) dishes. The results suggest that the composites are suitable for
mesenchymal cell culture scaffolds and useful materials for regenerative medicine.
Innovative Technique for the Preparation of Porous Bilayer Hydroxyapatite/Chitosan Scaffolds for Osteochondral Applications
Authors: Oliveira J. Miguel , Silva S.S. , Mano João F. , Reis Rui L.
Published: March 2009

In this study, it is shown that it is possible to develop 3D-porous bilayer hydroxyapatite/chitosan scaffolds by means of combining a sintering and a freeze-drying technique. Scanning electron microscopy (SEM/EDS) studies revealed that the scaffolds possess a well-defined orientation and anisotropic porosity, with pore size ranging between 50-350 µm. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) patterns evidenced the formation of crystalline hydroxyapatite. Moreover, the compression tests revealed that these scaffolds have adequate mechanical properties for being used in tissue engineering of osteochondral defects.
In Vivo Evaluation of Porous Hydroxyapatite/Collagen Composite as a Carrier of OP-1 in a Rabbit PLF Model
Authors: Sotome Shinichi , Orii Hisaya , Kikuchi Masanori , Ikoma Toshiyuki , Ishida Akimasa , Tanaka M. , Shinomiya Kenichi
Published: March 2009

Transplantation surgeries of autologous bone require a second surgery with inherent risks. To avoid these risks, we developed a multi porous implant of hydroxyapatite/collagen composite with desirable biophysical properties (flexibility, elasticity and compression resistance) for use with OP-1 as a graft implant. In this study, we tested the efficacy of this multi porous implant as OP-1
carrier using rabbit posterolateral lumbar fusion model (PLF). PLFs were performed in the following 4 groups of 8 New Zealand white rabbits each: autograft, HAp/Col alone, HAp/Col plus 0.3 mg OP-1, and HAp/Col plus 1.2 mg OP-1. At 5 weeks, fusion masses were analyzed by radiographic and biomechanical tests. Implants consisting of HAp/Col plus OP-1 were more effective than autologous bone in promoting spinal fusion. Low dose and high dose OP-1 were
equally effective.
The Effect of Interphase on the Elastic Modulus of Polymer Based Nanocomposites
Authors: Saber-Samandari Saeed , Afaghi Khatibi Akbar
Published: March 2009

The elastic modulus of interphase in polymer based nanocomposites is investigated. A new three-dimensional unit cell model has been developed for modeling three constituent phases including particle, interphase and matrix. The elastic modulus of the interphase as a function of radius is then evaluated with the help of mathematical models. The average value of interphase elastic modulus is defined and the effect of interphase thickness and particle and matrix elastic modulus on interphase is investigated.
Critical Behaviour in Concrete Structures and Damage Localization by Acoustic Emission
Authors: Carpinteri Alberto , Lacidogna Giuseppe , Niccolini Gianni
Published: March 2009

Extensive research and studies on concrete fracture and failure have shown that concrete should be viewed as a quasi-brittle material having a size-dependent behaviour. Numerous experimental techniques have been employed to evaluate fracture processes, and a number of modelling approaches have been developed to predict fracture behaviour. The non-destructive method based on the Acoustic Emission (AE) technique has proved highly effective, especially to
check and measure the damage phenomena that take place inside a structure subjected to mechanical loading. In this paper an experimental investigation conducted on concrete and RC structures by means of the AE technique is described. The AE signals reflecting the release of energy taking place during the damage process were recorded and micro-cracking sources were
localised by measuring time delays by means of spatially distributed AE sensors.
Observation of Dislocation Microstructures and Simulation of Stress Field during Fatigue Crack Initiation in a Copper Single Crystal
Authors: Yang J.H. , Zhang Xiao Ping , Mai Yiu Wing , Yan W.
Published: March 2009

How a crack initiates from the smooth surface of single crystals subjected to uniaxial cyclic loading is unclear. Experiments were conducted to observe in detail the dislocation microstructures during the saturation stage of cyclic deformation in a copper single crystal using scanning electron microscopy and the electron channeling contrast (SEM–ECC) technique. Some dark zones were found in the dislocation microstructures, which were located either at the edge region of the specimen or within the persistent slip bands (PSBs) at the matrix/PSB interfaces. Hence, fatigue cracks will initiate at these sites with high stress concentrations, i.e., the dark zones. Also, dislocation dynamics (DD) simulation was adopted to calculate internal stress distributions induced by dislocations, and finite element analysis (FEA) used to obtain stress distribution at the matrix/PSB interfaces and neighboring micro-regions caused by an externally applied load. Simulation results show that the external shear stresses distribute uniformly in all specimens; while near the free-surface regions, the maximum value of internal stresses not only occurs at interfaces between PSBs and dislocation matrix, but also at locations where these interfaces cross the freesurface. Consequently, the interfaces are most probable sites for nucleated cracks. Finally, the simulation results agree well with experimental observations.
Solutions of Stress Intensity Factors of Subsurface Cracks
Authors: Feng Xi Qiao , Xu M.
Published: March 2009

In the present paper, an integral transform-based method is presented for calculating the stress intensity factors of subsurface cracks. Due to the interaction between the crack and the free surface, the crack tip fields are generally of I-II mixed mode. The solutions for two typical configurations, a Griffith crack and a circular crack beneath the free surface of a semi-infinite solid, are derived.
Fabrication by SPS and Thermophysical Properties of High Volume Fraction SiCp/Al Matrix Composites
Authors: Gu X.F. , Zhang Lian Meng , Yang Mei Jun , Zhang Dong Ming
Published: March 2009

SiCp/Al composites containing high volume fraction of SiC particles were fabricated by spark plasma sintering (SPS), and their thermophysical properties, such as thermal conductivity (TC) and coefficient of thermal expansion (CTE), were characterized. High relative density (R-D) of composites was successfully achieved through the optimization of sintering parameters, such as sintering temperature, sintering pressure and heating rate. The measured TCs of SiCp/Al composites fabricated by SPS are higher than 195W/m.k, no matter the volume fraction of SiC particles is high or low as long as the R-D is higher than 95%. The measured CTEs of SiCp/Al composites are in good agreement with the estimated values based on Kerner,s model. The high volume fraction of
SiCp/Al composites are a good candidate material to substitute for conventional thermal management materials in advanced electronic packages due to its tailorable thermophysical properties.
Environmental Performance Testing System for Thermostructure Materials Applied in Aeroengines
Authors: Zhang Li Tong , Cheng Lai Fei , Luan Xin Gang , Mei Hui , Xu Yong Dong
Published: March 2009

The conventional ultimate performance test by applying a component in its true application (i.e., in an engine) is often very expensive and impractical when dealing with developmental materials. Simpler, less expensive, and more practical test methods must be utilized. The present work aims toward the applications of an innovative methodology for testing environmental performance of advanced Ceramic Matrix Composites (CMCs) in the presence of combined mechanical, thermal, and environmental applied conditions. To obtain a comprehensive understanding of how a composite might perform in certain application environments, a newly developed environmental performance testing system, which is able to provide the fundamental damage information of the composites in simulating service environments including variables such as temperature, mechanical and thermal stresses, flowing oxidizing gases and high gas pressure, is proposed. The system comprises of two subsystems: (1) equivalent experimental simulating subsystem, and (2) wind tunnel experimental simulating subsystem. The evolution mechanisms of the composites properties and microstructures can be achieved by the former, and then be validated and modified by the latter. Various loading (e.g. fatigue, creep), various atmospheres (e.g. argon, oxygen, water vapor, wet oxygen and molten salt vapor) and various temperature conditions (e.g. constant or cyclic temperatures) can be conducted on the system. Some typical experimental results are presented in this paper. Large quantities of tests have demonstrated the extraordinary stability and reliability of the system.
An Overview of the Study on Morph-Genetic Materials in State Key Lab of Metal Matrix Composites, Shanghai Jiao Tong University
Authors: Zhang Di , Fan Tong Xiang , Gu Jia Jun , Sun Bing He , Wang Tian Chi , Zhang Guo Ding
Published: March 2009

Morph-genetic synthesis, a preparation method using bio-structures as templates for
fabricating micro-cellular materials, has attracted a considerable interest in recent years. In this report, we summarize our obtained results on synthesizing oxides and carbides based on wood templates (for TiC and SiC) and cotton templates (for Al2O3, SnO2 and SiC), respectively. The final products are observed to be faithfully retaining the micro-morphologies of their original natural counterparts, with the template bodies absolutely or partially replaced by the chemically synthesized compounds. These results suggest a new and handy way to fabricate materials with
various microstructures, with deliberately choosing desired bio-structures from billions of different species as templates. Moreover, results on Al infiltrated wood templates, as a composite system, are also presented.
A Resistivity Model for Electrophoretic Deposition
Authors: Ferrari Begoña , Moreno Rodrigo , Cuesta Jose A.
Published: March 2009

Electrophoretic deposition (EPD) is a powerful method for obtaining particulate layers in a broad range of thicknesses if an adequate control of the growing kinetics is reached. Existing models of EPD kinetics consider that the growth of the deposit increases linearly with deposition time and deviations are due to a reduction of powder concentration and/or a decrease of electric field when EPD is performed at constant voltage conditions. Experimental observations show that long time tests lead to a S-shaped growing kinetics. This work presents a resistivity model that predicts a S-shape variation of mass per unit area with deposition time, with a first step in which the deposition rate increases, as a consequence of resistivity changes, followed by a decreasing slope associated to the lose of powder concentration. Currently available EPD models, such as the Hamaker and Sarkar & Nicholson models are particular cases of the generalized resistivity model proposed in this work.
Progresses in the Electrophoretic Deposition Technique to Infiltrate Oxide Fibre Mats for Fabrication of Ceramic Matrix Composites
Authors: Stoll Erick , Mahr P. , Krüger Horst Günter , Kern H. , Boccaccini Aldo Roberto
Published: March 2009

The electrophoretic deposition (infiltration) method represents a convenient alternative technique to fabricate ceramic matrix composites (CMCs) with improved high matrix density. The focal point of the present work is to describe the basic principle of the EPD technique applied to fabricate CMCs with oxide matrix and oxide fibres. Optimisation of the suspension stability is emphasised as well as the operational determination of the parameters for EPD and the designed of a new EPD cell to warrant the improved infiltration of the particles into fibre mats used as reinforcement. The electrophoretic deposition (infiltration) technique was applied to fabricate composites with alumina matrix (α-Al2O3) reinforced with NextelTM 720 fibres. The fabricated composites demonstrate that EPD permits to achieve a high matrix density with an excellent high intra-tow infiltration of the matrix particles. Moreover a mechanism of the EPD infiltration of oxide fibres is proposed and consequently progress in understanding the fundamentals of the technique applied to oxide-oxide systems has been made.