bluuebunny/crossref_metadata_2025 huggingface dataset:
Axial Crushing Behavior and Energy Absorption Capability of Al/CFRP Square Tubes for Light-Weights
Authors: Yang In Young , Lee Kil Sung , Kim Young Nam , Chung Jin Oh , Cha Cheon Seok
Published: March 2009

An aluminum or CFRP (Carbon Fiber Reinforced Plastics) tube is representative
light-weight materials but its axial collapse mechamism is different from each other. The aluminum tube absorbs energy by stable plastic deformation, while the CFRP tube absorbs energy by unstable brittle failure with higher specific strength and stiffness than those in the aluminum tube. In an attempt to achieve a synergy effect by combining the two members, aluminum/CFRP square tubes were manufactured, which are composed of aluminum tubes wrapped with CFRP outside aluminum square tubes with different fiber orientation angle and thickness of CFRP, and axial collapse tests were performed for the tubes. The crushing behavior and energy absorption capability of the tubes were analyzed and compared with those of the respective aluminum square tubes and CFRP square tubes. Test results showed that the collapse of the aluminum/CFRP square tube complemented unstable brittle failure of the CFRP square tube due to ductile characteristics of the inner aluminum
square tube. The collapse modes were categorized into four modes under the influence of the fiber orientation angle and thickness of CFRP. The absorbed energy per unit mass, which is in the light-weight aspect, was higher in the aluminum/CFRP square tube than that in the aluminum square tube or the CFRP square tube alone.
Roof Bolts Broken Mechanism and Their Reasonable Construction Structures
Authors: Zhang Zhi Jie , Han Qun-Liang , Liu Shao Wei , Li Ying Ming
Published: March 2009

Since the broken phenomenon is always appeared in the roof of mine roadway, it largely affects the roadway’s roof stability. With Material Mechanics theory, the authors expound bolt tail subjected to no center load action and roof bolt broken mechanism while roadway is supported with bolts. By theoretical analysis and Lab test, the paper puts forward a kind of new type bolts which may prevent bolt tails from being broken, bolt construction structure’s pattern, and bolt made technology. It is illustrated that the reasonable grading relationship between bolt body’s iameter
and bolt tail’s screw diameter. At same time, the authors compare disturbed values of the thick tail metal bolt and common bolt under the load action. It is verified that roof bolt broken problem may be solved with new type’s thick tail bolt. Therefore, the new type bolts have a wide application in the future.
Hybrid Finite-Discrete Element Simulation of Crack Propagation under Mixed Mode Loading Condition
Authors: Ariffin Ahmad Kamal , Huzni Syifaul , Nor Mohd Jailani Mohd , Mohamed Nik Abdullah Nik
Published: March 2009

This paper describes the numerical modeling based on combination of finite element method (FEM) and discrete element method (DEM) has been employed to simulate crack propagation under mixed mode loading. The work demonstrates the ability of combination finitediscrete element method to simulate the crack propagation that is usually performed through, what is termed, transition from continua to discontinua process. Crack propagation trajectory under selected loading angles (30o & 60o) are presented. The result obtained using the proposed model compare well with experimental result.
Interplay between Fracture and Domain Switching of Ferroelectrics
Authors: Cui Y.Q. , Yang Wei
Published: March 2009

Applications of above-coercive electric fields lead to domain switching of a large or global scale. Large scale switching model is proposed to deal with load-induced domains witching in experiment. Both a discussion of crack initiation via the stress intensity factor and a discussion of crack path stability via T-stress are presented. The theoretical predictions and the experimental data roughly coincide for crack initiation, propagation and stability phenomena. Attention is also extended to consider the effect of non-uniform ferro-elastic domain switching in the vicinity of a crack. The domain switching zone is divided into a saturated inner core and an active surrounding annulus. Toughening for ferroelectrics with different poling states is estimated via Reuss type approximation. Solutions obtained according to spherical and cylindrical inclusions cover the range of experimental data.
Fracture Characteristic of Single Crystalline Silicon Using Nano-Indentation and Finite Element Analysis
Authors: Baek Seung , Koo Jae Mean , Seok Chang Sung
Published: March 2009

Nano-indentation test is used widely to determine the fracture toughness of brittle
materials and to provide information on important material properties such as the Young’s modulus and hardness. In this study, using nano-indentation testing, atomic force microscope (AFM), and finite element method (FEM), we performed the indentation fracture toughness and fracture strength measurement for a (100) single crystalline silicon at different load states. In addition, the loads of the phase transformation events during unloading were estimated by the load-depth curves. The phase transformation load and micro-crack propagation events at pop-out during the unloading process depended on the maximum applied indentation load.
Application of Grid-Based Approach for Auto Mesh Generation of Vacuum Chamber
Authors: Park Young Jae , Kim H.K. , Chang Yoon Suk , Choi Jae Boong , Kim Young Jin
Published: March 2009

A seamless analysis of complex geometry is one of greatly interesting topic. However, there are still gaps between the industrial applications and fundamental academic studies owing to time consuming modeling process. To resolve this problem, an auto mesh generation program based on grid-based approach has been developed for IT-product in the present study. At first, base mesh and skin mesh are generated using the information of entities which extracted from IGES file.
Secondly the provisional core mesh with rugged boundary geometry is constructed by superimposing the skin mesh as well as the base mesh generated from the CAD model. Finally, the positions of boundary nodes are adjusted to make a qualified mesh by adapting node modification and smoothing techniques. Also, for the sake of verification of mesh quality, the hexahedral auto mesh constructed by the program is compared with the corresponding tetrahedral free mesh and hexahedral mapped
mesh through static finite element analyses. Thereby, it is anticipated that the grid-based approach can be used as a promising pre-processor for integrity evaluation of various IT-products.
Nonlinear Analysis of Cracked Plates
Authors: Purbolaksono J. , Dirgantara T. , Aliabadi M.H.
Published: March 2009

This paper presents the geometrically nonlinear analysis of cracked plates by the
dual boundary element method. Extrapolation of displacements on the crack surfaces is used to compute the stress intensity factors. The normalized stress intensity factors for the cracked square plate with fully clamped and simply supported boundary conditions are presented.
Dynamic Fracture Analysis of Aluminum Honeycomb Sandwich Panel
Authors: Kim Byung Il , Noh Byeong Wook , Choi Young Woo , Bae Sung In , Song Jung I.
Published: March 2009

Impact behaviors of Aluminum Honeycombs Sandwich Panel (AHSP) by drop weight test were investigated in this study. Two types of specimens with l/2" and l/4" cell size were tested by two impactors with the weight of 5.25kgf and 11.9kgf respectively. Transient, contact and elastic-plastic analyses were performed by finite element method. Impact behavior of AHSP about impact sites appeared nearly the same in low impact energy, but it was different in high impact energy. Face was the strongest about impact and short-edge was the weakest. The damaged area of AHSP was enlarged with the increase of impactor weight that is corresponding to impact energy. After 3-point bending test, fracture modes of AHSP were analyzed with AE counts, lower face sheet was fractured in the long-edge direction first, and then separation between face sheet and core happened. In the short-edge direction
after core wrinkled, lower face sheet was torn, impact behavior by FE analysis were increased localized damage in high velocity because the faster velocity of the impact was, the smaller the stress of core was. Consequently, impactor weight had an effect on widely damaged area, while the impact velocity gave rise to localized damaged area.
Parameter Optimization of Surface Grinding Process Based on Taguchi and Response Surface Methods
Authors: Kwak Jae Seob , Kim In Kwan
Published: March 2009

To minimize the geometric error made in ground surface, the optimization of grinding
parameters is essential. This paper focused on the parameter optimization of the surface grinding process based on Taguchi and response surface methods for minimizing the geometric error. Firstly, the effect of grinding parameters on the geometric error was evaluated and optimum grinding conditions were determined. Then, a second-order response model for predicting the geometric error was developed and the validation of the response surface model was examined with industrial constraints such as the surface roughness and the material removal rate. Finally, experimental verification was conducted at an optimal condition and two selected conditions to see accuracy of the developed response surface model.
Prediction of Elastic Properties of Honeycomb Core Materials and Analysis of Interlaminar Stress of Honeycomb Sandwich Composite Plate
Authors: Kim Hyoung Gu , Yoon Hoong Soo , Choi Nak Sam
Published: March 2009

Theoretical formulas for effective elastic modulus and Poisson's ratio of honeycomb core materials were proposed considering the bending, axial and shear deformations of cell walls. Theoretical results obtained by the formulas showed orthotropic elasticity and large Poisson’s ratio, which were comparable to results by finite element analysis(FEA). Tensile test of honeycomb sandwich composite(HSC) plates was performed for analysis of their deformation behaviors and
interlaminar stresses. Equivalent plate model using the theoretical results of honeycomb core layer show that interlaminar shear stress occurring due to large difference of Poisson’s ratio between skin and honeycomb core layers led to the delamination in HSC plate under tensile loading. Load-displacement behavior of HSC specimen simulated by equivalent plate model coincided fairly with that of detailed FEA model similar to experimental results.
An Analysis of Fracture Problems of Orthotropic Composite Plate under Bending and Twisting
Authors: Li Jun Lin , Zhang Xue Xia , Yang Wei Yang
Published: March 2009

An analysis of fracture problems near crack tip for linear elastic orthotropic composite plate under bending and twisting is carried out. By solving the boundary value problem of partial differential equations and applying the method of undetermined coefficients, the two group expressions for bending moment, twisting moment and displacement near crack tip are derived. The formulae have certain practical and referential value in related fracture analysis.
Spot Weldability Assessment of Similar and Dissimilar Steel Sheets for Light Weight Automobile Body
Authors: Bae Dong Ho , Jung Won Seok , Heo J.B.
Published: March 2009

An effective way to reduce the weight of vehicle body seems to be application of new
materials, and such trend is remarkable. Among the various materials for automobile body, stainless steel sheets and cold rolled steel sheets are under the interests. However, in order to guarantee reliability of new material and to establish the long life fatigue design criteria for body structure, it is necessary to assess spot weldability and fatigue strength of spot welded lap joints fabricated under optimized spot welding condition. In this paper, spot weldability of stainless steel sheets, STS301L and STS304L, and cold rolled steel sheets, SPCC and SPCD. Fatigue strength of lap joints spot welded between similar and dissimilar materials were also assessed.
An Experimental Study of the Displacement and Strain Fields across Interphases in Thermoplastic Composites
Authors: Chen Jin Long , Wang He Min , Qin Yu Wen , Ji Xin Hua
Published: March 2009

The main purpose of this paper is to develop a set of improved micro-metrology system, which consists of a digital image-measuring device and a microscope with a long focal length, for the study of displacement fields, strain fields in the area across the interphases, and also the effect of temperature on the micro-mechanics properties of interphases in thermoplastic composites. Meanwhile, the precision of the micro-metrology system is assessed by using an extra solution within of the framework of infinitesimal strain in particular, the choice of the size of subset in the correlation technique is discussed when the displacements are not infinitesimal. Experimental results show that, under practical service conditions of thermo-mechanical coupled loads, a significant residual thermal stress mismatch due to the difference in coefficients of thermal expansion between the fiber and the matrix is balanced out.
Hydroxyapatite Formation on Cellular Alumina Coated with Bioactive Glasses
Authors: Kim Cheol Y. , Kim Dong Hyun
Published: March 2009

Various works have been done to produce a cellular form of bioactive ceramics for a
scaffold. However, the most of these cellular implants have low compressive strength. In this study, therefore, glass-infiltrated cellular alumina with compressive strength of 7.3MPa was first prepared. Bioactive glass was then coated on the cellular alumina. When the specimen was reacted in simulate
body fluid, hydroxyapatite developed on the bioactive glass coat in 18 hours.
Effect of Cooling Rate and Particle Size on Compressive Strength of Macroporous Hydroxyapatite
Authors: Kim Yeon Ung , Lee Byung Hyun , Kim Min Chul , Kim Kyoung Nam , Kim Kwang Mahn , Choi Seong Ho , Kim Chong Kwan , LeGeros Racquel Z. , Lee Yong Keun
Published: March 2009

The objective of this study was to produce a macroporous hydroxyapatite(HA) scaffold with high strength by controlling the size of HA particles as well as cooling rate from the sintering temperature. Macroporous polyurethane sponge was employed as template to manufacture the macroporous HA scaffolds. Particle sizes of HA powders selected in this study were 4 µm and 7 µm.
They were dispersed in distilled water with organic additives and infiltrated into polyurethane sponge. After drying and sintering at 1300oC, cooled down to room temperature slowly to prevent microcracking either 1oC/min or 3oC/min. Density, porosity and compressive strength were measured with different particle size and cooling rate. Both density and compressive strength were increased
with decreasing particle size or cooling rate, while porosity was not related to.
Preparation and Characterization of Porous Hydroxyapatite Block Using a HHP Method
Authors: Song Hee , Kim Soo Ryong , Kim Hae Jung , Hwang Jong Hee , Kwon Woo Teck , Kim Y.
Published: March 2009

Porous hydroxyapatite has been prepared using a hydrothermal hot pressing method from calcium carbonate as a starting material. SEM result shows porous hydroxyapatite block is formed of three dimensionally inter-connected pores of 100-400µm in size, similar to human cancellous bone. At the ~ 70% porosity, the compressive strength was about 4MPa, which is similar to that of the commercially available porous hydroxyapatite derived from natural coral.
Evaluation of Pore Architecture in Hydroxyapatite/Collagen Scaffold Using Micro Computed Tomography
Authors: Yunoki Shunji , Ikoma Toshiyuki , Monkawa Akira , Ohta Kazushi , Kikuchi Masanori , Tanaka M.
Published: March 2009

Hydroxyapatite/collagen (HAp/Col) composite scaffold with unidirectionally elongated pores (scaffold-U) was fabricated by the unidirectional solidification with ice growth and subsequent freeze-dry process. The pore architecture in the composite was evaluated by using scanning electron microscopy (SEM) and micro computed tomography (micro-CT) with a high resolution. The SEM observation showed that the scaffold-U had unidirectional pores elongated
along the vertical direction (i.e. ice growth direction), however the horizontal cross-section showed quite different pore morphology: spindle-shaped pores with random direction. The 3-D micro-CT image of the scaffold-U simultaneously showed the microstructure of the unidirectionally elongated pore and the cross-sectional pore, indicating that the interconnected micropores were successfully
fabricated along the ice growth direction. The micro-CT is a powerful tool for the visualization of 3-D pore structure.
Phase Stability and Residual Stress Field in Nano-Structured 3Y-TZP
Authors: Ikeda Junji , Pezzotti Giuseppe , Kondo Makoto
Published: March 2009

Phase stability of 3Y-TZP was evaluated by acceleration test in water vapor environment and Raman spectroscopy. We found that the phase stability was affected not only by grain size but also by residual stress field, which could be quantitatively measured by Raman piezo-spectroscopy and controlled by sintering temperature. This study shows that Raman spectroscopy is a very useful technique for non-destructive analysis of 3Y-TZP.
Comparison of the Results of a Simulator Study and Retrieval Implants in Ceramic THA
Authors: Shishido Takaaki , Yamamoto Kengo , Clarke Ian C. , Masaoka T. , Manaka M. , Tateiwa Toshiyuki
Published: March 2009

In simulator studies, the Biolox-forte hip prosthesis were run for 5 million cycles (Mc) using 50% new born calf serum for both the standard test (STD) mode and the micro-separation test (MSX) mode. Wear measurements were carried out every 0.5 Mc. The wear patterns were mapped and observed by SEM. In a clinical study, the OstealTM hip prostheses which were implanted for 15
to 19 years and 17 year BioloxTM hip prostheses were analyzed. According to the same technique as the simulator study, the wear patterns were analyzed using SEM. The steady-state wear rates for alumina THR ranged from 0.16 to 0.65 mm3/Mc in the MSX mode and 0.011 mm3/Mc in the STD mode. The MSX simulator mode produced two narrow wear scars (stripes) of dull appearance on
the ball. In the SEM analysis, the stripe scars showed mild wear after 5 Mc duration. In the Biolox and the Osteal retrieval alumina ball, the stripe scars showed severe wear. The Osteal retrievals had one grade lower wear in the main worn area than the Biolox retrievals on SEM analysis. The stripe wear and its location in the retrieval balls were seen in the simulator study. The area and wear severity of the stripe wear were influenced by the quality of alumina, design of THA and various
actual motions in patients.
Enhancement of Differentiation and Homeostasis of Human Osteoblasts by Interaction with Hydroxyapatite in Microsphere Form
Authors: Nakaoka Ryusuke , Tsuchiya Toshie
Published: March 2009

The aseptic loosening of artificial joints with associated periprosthetic bone resorption may be partly due to the suppression of osteoblast function to form new bone by wear debris derived from the joint. To assess the effect of wear debris on osteoblasts, we cultured normal human osteoblasts (NHOst) in contact with several kinds of microspheres as models of wear debris. The NHOst in contact with polystyrene, polyethylene, and alumina microspheres showed a lower differentiation level than NHOst alone as estimated from the amounts of deposited calcium. On the other hand, hydroxyapatite particles enhanced the differentiation of NHOst. In addition, sintered hydroxyapatite enhanced expression of osteocalcin mRNA and gap junctional communication of NHOst. This study suggests that polystyrene, polyethylene, and alumina microspheres have the potential to disorder not only the differentiation but also the homeostasis of NHOst in contact with them. However, hydroxyapatite enhanced the differentiation as well as the homeostasis of NHOst, even in microsphere form, suggesting its good biocompatibility as biomaterials for bone tissues.
Carbonate Substituted Hydroxyapatite; Development and Function of Osteoclasts
Authors: Spence Gavin M. , Patel Nelesh , Brooks Roger A. , Ireland D.C. , Bonfield William , Rushton Neil
Published: March 2009

Human osteoclasts derived from CD14+ precursors were cultured on discs of
stoichiometric hydroxyapatite (HA) and carbonate substituted hydroxyapatite (CHA) of varying carbonate contents. Resorption of the ceramic increased with increasing carbonate content up to 2.35 wt. %. Development of osteoclasts is qualitatively different on ceramics compared to dentine, occurring in discrete, confluent subpopulations, which suggests local cell signalling may be
important in the process. Resorption appears to drive further development of osteoclasts. Controlling carbonate content may be one way of controlling the rate of resorption of synthetic HA ceramics.
Effects of pH on the Transformation of Gypsum to Carbonate Apatite in the Presence of Ammonium Hydrogen Phosphate
Authors: Kunio Ishikawa , Suzuki Yumiko , Matsuya Shigeki , Nakagawa Masaharu , Koyano Kiyoshi
Published: March 2009

Effects of pH on the transformation of gypsum to apatite in the presence of ammonium hydrogen phosphate was studied using NH4H2PO4, (NH4)2HPO4 and (NH4)3PO4. When set gypsum was immersed to ammonium hydrogen phosphate, pH of the solution decreased regardless of the
solution. Although pH of the solution decreased, no significant compositional change was observed when gypsum was immersed in NH4H2PO4. On the other hand, apatite and small amount of dicalcium phosphate anhydrous (CaHPO4) was formed when gypsum was immersed in (NH4)2HPO4 solution. Only apatite was formed when gypsum was immersed in (NH4)3PO4 solution. Although the
detailed mechanism for the pH dependent products has not been clarified, one of the causes may be the different thermodynamical difference between gypsum and apatite. We would like to recommend the use of (NH4)3PO4 solution since this provides higher pH and thus larger thermodynamical difference between apatite and gypsum and resulting pure apatite block.
Solubility of Magnesium-Containing β-Tricalcium Phosphate: Comparison with that of Zinc-Containing β-Tricalcium Phosphate
Authors: Ito Atsuo , Hida Tomomi , Sogo Yu , Ichinose Noboru , LeGeros Racquel Z.
Published: March 2009

The purpose of this study was to determine the solubility of magnesium-containing
tricalcium phosphate (MgTCP) over a magnesium content range from 0 to 10 mol%, and to compare it with that of zinc-containing tricalcium phosphate (ZnTCP). MgTCP powders with various Mg contents were immersed in 0.08M acetic acid and sodium acetate buffer solution of pH 5.5 at 25±2
°C. Solubility product, Ksp = (Ca2+)3-x(Mg2+)x(PO4
3-)2, was calculated. From the Ksp data, the solubility of MgTCP in the pH range from 5 to 7.5 was inversely calculated. The solubility of MgTCP
decreased with increasing Mg content. The negative logarithm of solubility product (Ksp) was regressed as pKsp = 29.041+0.90467C-0.18069C2+0.025962C3-0.00192C4-0.000055199C5 , where C is the Mg content of MgTCP in mol%. In the magnesium content range from 0 to 10 mol%, the solubility of MgTCP is higher than that of ZnTCP containing the same amount of zinc.
Effects of Polyethylene Glycol and Methacryloxypropyltrimethoxysilane on Morphology and Bioactivity of CaO-SiO2 Gel Prepared by Sol-Gel Method
Authors: Kim Ill Yong , Ohtsuki Chikara , Kamitakahara Masanobu , Tanihara Masao , Cho S.B.
Published: March 2009

CaO-SiO2 gels for bioactive organic-inorganic composites were prepared from
tetraethoxysilane (TEOS) and calcium nitrate tetrahydrate (Ca(NO3)2⋅4H2O) by a sol-gel method with the addition of polyethylene glycol (PEG) and methacryloxypropyltrimethoxysilane (MPS). The effects of PEG and MPS on morphology and bioactivity of the gel were investigated. The samples with the nominal compositions of Ca(NO3)2:TEOS:MPS = 30:70:0 and 30:63:7 (in molar
ratio) were prepared with or without coexistence of PEG at a molar ratio of (TEOS+MPS):PEG = 70:0.16. Spherical powders were obtained regardless of the addition of MPS after removal of PEG by washing, whereas the samples prepared without PEG gave crack-free bulk bodies. Incorporation of MPS was confirmed form the results of Fourier transform infrared spectroscopy (FT-IR). All the
samples, regardless of addition of PEG and MPS, formed apatite on their surfaces in simulated body fluid (SBF), when washing time was 3 h during the preparation. These results show that the bioactive spherical powder of CaO-SiO2 gel modified with MPS can be obtained by the present method. It is expected to induce the increase of the chemical bonding with surrounding organic matrix when it was used as fillers for composite materials.
Effects of Electrical Wave Form on Pore Size of Micro-Arc Oxidized TiO2 Film
Authors: Han In Ho , Choi Jai Hyuk , Zhao Bao Hong , Baik Hong Koo , Lee In Seop
Published: March 2009

The surface morphology of commercially pure titanium was investigated with varying electrical waveform. Controlling of electrical pulse width is effective to change pore sizes. Longer electrical pulse width was induced, larger size of pores were generated.
TiO2-HDPE Composite: Bone Bonding Ability and Biocompatibility
Authors: Nasu Tomonori , Fujibayashi Shunsuke , Neo Masashi , Nakamura Takashi
Published: March 2009

A novel material, namely, TiO2-HDPE (TiO2/high density polyethylene) composite was developed by our research group. Its mechanical properties are similar to those of the human cortical bone; hence, we examined the possibility of using it as a bone substitute. We prepared two groups of TiO2-HDPE; one was subjected to ultraviolet irradiation for 0.1 h and the other for 9 h. In bone bonding ability test, the former indicated a lower ability than the latter, which showed approximately 7 to 8 N of failure load. The bone bonding ability of the latter group alone is not sufficient for clinical application; on the other hand, the biocompatibility test was carried out. In the
biocompatibility test, the group that was irradiated for 9 h revealed neither a major inflammatory response nor formation of neoplasm. We have to further examine alternate types of polyethylene or TiO2 particles in order to improve the bone bonding ability.
In Vitro Bioactivity Assessment of Metallic Magnesium
Authors: López Haydée Y. , Cortés-Hernández Dora A. , Escobedo Sergio , Mantovani D.
Published: March 2009

In the aim to decrease the degradation rate of magnesium in simulated body fluid, pure magnesium was treated by two different routes, i) by soaking specimens in an HF aqueous solution at 30oC for 30 min and ii) by heating specimens at 345oC for 15 min. The treated samples were immersed in simulated body fluid (SBF) at 37oC for different periods of time. Samples with no treatment were also immersed in SBF. The magnesium released into the SBF, the weight loss of the specimens and the pH of SBF increased with time of immersion in all the cases. The heat treated samples showed a lower degradation rate and lower pH values. A substantial decrease of magnesium concentration in the SBF corresponding to the heat treated samples was also observed. However, the degradation rate of the heat treated samples remains being extremely high. On the other hand, a bonelike apatite layer was observed after only 3 days of immersion in SBF in all the cases. The thickness of this layer increased with time of immersion. Further research needs to be performed to decrease the degradation rate. However, these results indicate that magnesium is a highly potential bioactive material for biomedical applications.
Sintering Effect on Mechanical Properties of Composites of Bovine Hydroxyapatite (BHA) and Li2O
Authors: Oktar Faik N. , Demirer M.R. , Gunduz Oguzhan , Genc Yasin , Agathopoulos Simeon , Peker Ismail , Ozyegin L.S. , Salman S.
Published: March 2009

In this study, hydroxyapatite (HA) material, obtained from calcinated bovine bone
(BHA), was mixed with 0.25, 0.50, 1.00, and 2.00 wt% Li2CO3. The pressed pellets were sintered at various sintering temperatures between 900°C and 1300°C. Measurements of compression strength, microhardness, and density, along with SEM observation and X-ray diffraction analysis were performed. The experimental results showed that the samples with 0.25 and 0.50% Li2CO3 reached
a maximum of densification and the highest values of compression strength and microhardness were achieved after sintering at 1300°C. The wetting effect of a Li2O-associated glassy phase was observed even from 900°C.
RF Induction Plasma Synthesized Calcium Phosphate Nanoparticles
Authors: Xu J.L. , Khor Khiam Aik , Kumar R. , Cheang P.
Published: March 2009

It was a normal phenomena that hydroxyapatite (HA) decomposes into tricalcium
phosphate (TCP), tetracalcium phosphate (TTCP), calcium oxide (CaO) and amorphous calcium phosphate (ACP) during the plasma processing step. The present study characterized the phase evolution of calcium phosphates (CaPs) in the nanoparticles synthesized using a radio frequency
(RF) induction plasma processing technique. The morphology and microstructure of the CaP nanoparticles were investigated by XRD, SEM, TEM, Raman spectroscopy, FTIR spectroscopy and thermal analysis. It was found that ACP, α-TCP, TTCP and CaO were the main decomposed phases
in the nanoparticle. After heat treatment at dicalcium pyrophosphate (β-Ca2P2O7) due to the extreme decomposition of the starting HA during
the RF plasma processing step which rapidly solidified into amorphous phase.
Formation of c-Axis Aligned Hydroxyapatite Sheet by Simultaneous Imposition of High Magnetic Field and Mold Rotation During Slip Casting Process
Authors: Akiyama Jun , Hashimoto Masami , Takadama Hiroaki , Nagata Fukue , Yokogawa Yoshiyuki , Sassa Kensuke , Iwai Kazuhiko , Asai Shigeo
Published: March 2009

A high magnetic field is a useful tool to control the crystal alignment of non-magnetic
materials such as ceramics and polymers. In the case of Hydroxyapatite crystal, the a,b-axis is aligned parallel to the direction of an imposed magnetic field. This fact implies that the alignment of the c-axis is not controllable only using a high static magnetic field due to the freedom of the c-axis in a plane perpendicular to a magnetic field direction. In this study, a high static magnetic field and mold rotation was simultaneously so applied during a slip casting process as to align the
c-axis of HAp poly crystals.
Chemicovector Effect of Nano-Size-Hydroxyapatite Doped YSZ Ceramics on Apatite Formability in SBF
Authors: Kishi Shigeki , Okimoto Norikazu , Nakamura Satoshi , Nishio Keishi , Hashimoto Kazuaki , Toda Yoshitomo , Yamashita Kimihiro
Published: March 2009

To produce ceramics with high mechanical strength and bioactivity, we developed the little amount of nano-sized hydroxyapatite (HA)-doped zirconia composite ceramics (nanoHA-Z). The bioactivity of the nanoHA-Z was studied by in vitro estimation with simulated body fluid (SBF). Scanning electron microscopy observation showed deposited bone-like apatite layer entire covering the surface of nanoHA-Z ceramics in SBF. The enhanced apatite formability was attributed to higher Ca and PO4 concentrations in the vicinities of the nanoHA-Z surfaces due to the dissolution of the β-tricalcium phosphate decomposed from the added HA. Utilization of Chemicovector effect was proved to be one of the powerful approaches for improvement method of biomaterials.
Highly Oriented Hydroxyapatite Coating Using rf Plasma Spraying
Authors: Inagaki Masahiko , Yokogawa Yoshiyuki , Kameyama Tetsuya
Published: March 2009

Highly oriented hydroxyapatite (HA) coatings were prepared on titanium (Ti) substrates through a radio-frequency thermal plasma spraying method. XRD patterns showed that the HA coating layer had an structure with (00l) preferred crystal orientation. TEM observation showed that 200-800 nm-width prismatic crystals were formed in HA splats and the longitudinal axis of such prismatic crystals oriented vertical to the coating's surface. TEM images also indicate that the interface between prismatic crystals became compacted. SAD pattern show that the longitudinal axis of prismatic crystals corresponds to the <001> axis of HA.
Plasma Sprayed Zirconia-Hydroxyapatite Composite Coatings
Authors: Aydın Murat , Ozyegin L.S. , Oktar Faik N. , Erkmen E.Z. , Anzabi O. , Gross Kārlis A.
Published: March 2009

In order to overcome the fragility and to improve the physical stability of hydroxyapatite (HA) on the implant, 5, 10, and 15 % yttria stabilized zirconia (YTZP) was added to the starting plasma spraying HA powder Metco XPT-D-703. From the recent literature it is already known that HA coatings tend to dissolve in body fluid environment. To decrease the dissolution effect many additives like zirconia (Zr) could be added to HA powder. In this study, prepared HA composite powders were sprayed onto titanium (Ti) surfaces with a Metco plasma gun. As a control group, pure HA powder was sprayed onto other Ti samples. All samples were subjected to tensile tests according to the ASTM C-633-79. SEM images were taken using back-scattering from prepared cross-sections. X-ray diffraction images were taken from the surface. It was seen that with the increase of the Zr content, the tensile test values increased. Pure HA showed also that the addition of Zr had improved the tensile bond strenght (TBS) values.
Incorporation of Proteins with Different Isoelectric Points into Biomimetic Ca-P Coatings: A New Approach to Produce Hybrid Coatings with Tailored Properties
Authors: Azevedo H.S. , Leonor Isabel B. , Reis Rui L.
Published: March 2009

This work aims to study the effect of incorporating proteins with different isoelectric points (pI) on the structure, composition and morphology of biomimetic calcium-phosphate (Ca-P) coatings. For that, bovine serum albumin (BSA) and lysozyme, having respectively acidic and basic pIs, were used as model proteins. It was observed that the incorporation of positively charged proteins, such as lysozyme, was able to significantly change the structure of the coatings, possibly due to the preferential interactions between the protein and negatively charged phosphate ions. These results indicated that proteins with different characteristics can be incorporated into biomimetic Ca-P coatings in order to obtain a hybrid coating and at the same tailoring their properties.
New Characterization of Setting Times of Alkali Containing Calcium Phosphate Cements by Using an Automatically Working Device According to Gillmore Needle Test
Authors: Berger Georg , Ullner Christian , Neumann Gerhard , Marx Heidi
Published: March 2009

This paper presents equipment for the measurement of initial as well as final setting times of calcium phosphate cements containing alkali to achieve higher solubility. Until now, the selfsetting process of cements also if alkali is integrated has been tested by using the “standard test method for time of setting of hydraulic-cement paste by Gillmore needles” in accordance to ASTM C 266 – 99. This procedure needs high man power and, furthermore, the results have been markedly influenced by individual experiences that are incorporated in the criterion “without appreciable
indentation”.
MCM-41 /PCL Coated Hydroxyapatite and its Application to Drug Delivery System
Authors: Kim Y. , Kim Kyung Ja , Kim Soo Ryong , Lee Hyo Won
Published: March 2009

Porous hydroxyapatite coated with MCM-41/PCL has been utilized as the matrix for
controlled drug delivery. SEM result shows porous hydroxyapatite block is formed of three dimensionally inter-connected pores of 250 –300 *m in size, similar to human cancellous bone. TEM observation confirms the pore size of MCM-41 scatters about 50 Å. Ibuprofen was loaded into the pores of MCM-41 and hybridized with polycaprolactone to coat on the surface of hydroxyapatite block and controlled release profiles were studied by soaking the samples in a simulated body fluid using a UV-VIS spectrophotometer.
Local Delivery of Antibiotics Using Hydroxyapatite with Bi-modal Pore Size Distribution
Authors: Hasegawa Masahiro , Sudo Akihiro , Komlev Vladimir S. , Barinov Sergej M. , Uchida Atsumasa
Published: March 2009

A novel hydroxyapatite (HA-A) was developed and we evaluated the slow release of antibiotic in vitro as well as osteoconduction of the material in vivo. HA-A (4 x 4 mm) was synthesized by mixing HA powder, gelatin, and vegetable oil. The material had a bi-modal pore size distribution, with intragranular (10 nm to 10 µm) and intergranular (100 µm) pores, and porosity of 40 vol%, while a control HA had pore sizes ranging from 50 to 300 µm and identical porosity. In vitro drug release was tested using antibiotics soaked on the HA cylinders using a vacuum system. The mean adsorption efficiency was higher for HA-A than for control and higher levels of antibiotic were released from HA-A. Bone ingrowth into the pores was observed for both materials. Since the novel HA showed both the slower release of antibiotic (nanosize pores) and supported excellent osteoconduction (microsize pores), it could be useful for the treatment of osteomyelitis.
BMP-2 Dose-Response and Release Studies in Functionally Graded HAp
Authors: Tazaki Junichi , Akazawa Toshiyuki , Murata Masaru , Yamamoto Masaya , Tabata Yasuhiko , Yoshimoto Ryota , Arisue Makoto
Published: March 2009

Hydroxyapatite (HAp) has been used as a biomaterial for hard tissues. Critical characteristics of biomaterials will include surface geometry, hydrophobicity and hydrophilicity, crystallinity, biodegradation rates, and release pharmacokinetics (PK) of incorporated molecules such as BMP-2. Optimizing BMP-2 for clinical application may be dependent on localized sustained release from biomaterials. We forcused on in vivo local BMP-2 PK and bone induction in two ceramics systems, based on different surface structures. The functionally graded apatites (fg-HAp) was designed by the step-wise calcinations and partial dissolution-precipitation methods. We estimated the in vivo release profile of 125I-labeled BMP-2 from fg-HAp and the dose response of bone induction by BMP-2 in the back subcutis histologically. Bulk-HAp (b-HAp) by only the step-wise calcinations was prepared as a control. The amount of BMP-2 remaining in the fg-HAp at 1 day after implantation was 83.8%, while that was 34.6% in the b-HAp. Moreover, ectopic bone formation were found surely in the fg-HAp/BMP-2 (0.5μg) system at 3 weeks, not in the b-HAp/BMP-2 system. By using fg-HAp, it is likely that an extremely low dose of BMP-2 is enough to enhance bone induction if BMP-2 is appropriately delivered to the site of action.
A Preliminary Study on Cryogenic Mechanical Properties of Epoxy Blend Matrices and SiO2/Epoxy Nanocomposites
Authors: Fu Shao Yun , Pan Qin-Yan , Huang Chuan Jun , Yang Guo , Liu Xin-Hou , Ye Lin , Mai Yiu Wing
Published: March 2009

Epoxy blend matrices were prepared by incorporating polyurethane-epoxy into diglycidyl ether of bisphenol-F (DGEBF) type epoxy while SiO2/epoxy nanocomposites were made using DGEBF type epoxy and tetraethylorthosilicate (TEOS) via a sol-gel process. The mechanical properties including tensile and impact properties at 77 K of the matrices and nanocomposites were studied. The mechanical properties at room temperature were also given for the purpose of comparison with the cryogenic mechanical properties. The results showed that the incorporation of polyurethane-epoxy with a proper content into DGEBF type epoxy enhanced the mechanical properties at both room and cryogenic temperatures. Addition of SiO2 nanoparticles to DGEBF type epoxy led to significant increase in tensile strength at cryogenic temperature (77 K) while no evident change in tensile strength at room temperature. In addition, a slight enhancement by the addition of 2 wt % silica while a slight reduction by the addition of 4 wt % silica were observed in impact energy.
Fracture Behaviours of Nano-Silica Modified Epoxies at Elevated Temperatures
Authors: Deng Shi Qiang , Ye Lin
Published: March 2009

An experimental investigation was conducted to characterize the mechanical properties of nano-silica modified epoxies at room temperature and elevated temperatures. A commercial nano-silica dispersed epoxy product was used as modifiers to toughen a DGEBA epoxy resin. Fracture toughness and other material properties of the cured epoxies were measured using the standard compact tension (CT), tensile and flexural test methods to investigate the effects of the
nano-silica on fracture behaviours of the cured epoxies at 23oC, 50oC and 70oC. It has been found that the fracture toughness of the nano-silica modified epoxies have been significantly increased at 23oC and 50oC, while the strength and modulus of the materials remain unchanged or slightly higher. The increases in KIC at room temperature and 50oC are up to 50% and 70% respectively, compared to the unmodified epoxies. At 70oC, the effect of nano-silica on the fracture behaviour
diminished because of the change of failure mechanisms from the brittle fracture to the plastic deformation. It is also very encouraging that the nano-silica modified epoxies did not show reduction in glass transition temperature (Tg).
Advances in Three-Dimensional Fracture Mechanics
Authors: Guo Wan Lin , She Chongmin , Zhao Jun Hua , Zhang Bin
Published: March 2009

The historical developments of the fracture mechanics from planar theory to threedimensional (3D) theory are reviewed. The two-dimensional (2D) theories of fracture mechanics have been developed perfectly in the past 80 years, and are suitable for some specific cases of engineering applications. However, in the complicated 3D world, the limitation of the 2D fracture theory has become evident with development of the structure toward complication and micromation. In the 1990’s, Guo has proposed the 3D fracture theory with a 3D constraint factor based on the deformation theory and energy theory. The proposed 3D theory can predict accurately the fracture problems for practical and complicated engineering structures with defects, by integrating the 3D theory of fatigue, which has been developed to unify fatigue and fracture. Our efforts to develop the 3D fracture mechanics and the unified theory of 3D fatigue and fracture are summarized, and perspectives for future efforts are outlined.
Finite Element Analysis on the Stress and Fracture in the Second Metatarsal
Authors: Wang B. , Lu Guo Xing
Published: March 2009

Footwear has direct impact on the stress level in the metatarsal bones of human feet. In particular, stress fractures at the neck of the second metatarsal are the most common injuries. A finite element analysis was carried out to study the load and stress level in the second metatarsal of a 50-kg female wearing flat and high-heel shoes. It found that the bending of metatarsal due to the flat-footed posture increases the chance of fracture, and the stiletto (high-heeled) posture leads to
large compressive stress.
Contact Damage in Brittle Curved Coatings: The Influence of Indenter/Coating Modulus Mismatches
Authors: Qasim Tarek , Ford Chris , Bush Mark , Hu Xiao Zhi
Published: March 2009

The effects of indenter/coating modulus mismatch on contact damage in bilayer systems composed of brittle coating layers on compliant polymeric underlayers is investigated. Convex specimens having curvature of 12 mm inner coating diameter are produced, and loaded using flat indenters of four different moduli. Glass plates of d = 1 mm thick are used as representative of the brittle coating, and soft epoxy filler is used as an underlayer. Specimens are loaded along the convex axis of symmetry. In this fashion the influence of indenter modulus on radial crack initiation and damage evolution is examined. Previous studies utilised hard spherical indenters of various sizes, and did not consider the effect of a compliant indenter on radial crack evolution and subsequent damage patterns. It is demonstrated that critical loads for initiation of radial cracks and subsequent damage patterns especially at specimen margins are sensitive to indenter modulus (indenter/coating modulus mismatch).
Electrical and Mechanical Properties of Metal-Particle-Dispersed PZT-Matrix Composites
Authors: Li Jing Feng , Zhang Hai Long , Zhen Yu Hua
Published: March 2009

Pt- or Ag-particle-dispersed Pb(Zr,Ti)O3-based ceramic composites were fabricated by using powder processing for the purpose to investigate their ferroelectric and piezoelectric properties that are essential for the optimal design of piezoceramic/metal bending actuators with Functionally Graded Microstructure (FGM). The ferroelectric and piezoelectric constants as well as mechanical properties of the Pt/PZT and Ag/PZT composites as a function of metal content are
discussed in relation with the composite microstructures.
Alumina/Glass Composites Fabricated by Melt-Infiltration of Glass into Porous Alumina
Authors: Lin Yung Jen , Chang Li Bin
Published: March 2009

Alumina/glass composites were successfully fabricated by melt-infiltration of glass into porous alumina pellets. Alumina powder was first pressed uniaxially at 100MPa to form disc-shaped pellets, then, heated up to 1200°C for 2 h to form porous pellets with moderate strength for subsequent infiltration. A mixture of calcium aluminosilicate and magnesium borosilicate glass powders were melt-infiltrated into porous alumina at 1200°C ~1250°C by capillary pressure to form composites. The infiltration depths varied with the square root of infiltration time. And the activation energy of the infiltration process was estimated to be 621 KJ/mole. After complete
infiltration, the composite had bulk density approaching 3.3 g/cm3 (~ 96% of theoretical density) and open porosity reaching zero, with slight expansion of 0.5% in diameter. Its flexural strength was 150MPa and its Vickers microhardness was about 1000 Kg/mm2.
Wettability at Al-Mg/Ceramic Interfaces
Authors: Ouyang Qiu Bao , Zhou Wei Min , Zhang Guo Ding , Zhang Di
Published: March 2009

The objective of the present paper is to study the wetting phenomenon of metal-ceramic interfaces. Two composite systems, i.e., SiCox/Al+xMg and Al2O3/Al+xMg were selected for calculation. The effects of alloy elements such as Mg and the processing temperature on wettability were investigated theoretically. The calculated wetting contact angles from the physicochemical model are approximately in agreement with experimental values.
Discontinuously Reinforced Aluminum Composite and Its Application in Brake Discs
Authors: Ouyang Qiu Bao , Wang Wen Long , Zhang Di , Zhang Guo Ding
Published: March 2009

Discontinuously reinforced aluminum (DRA) composites are attractive for a large range of engineering applications because of its excellent wear-resistance, high thermal conductivity and light weight etc. In this paper, DRA composites were designed and fabricated especially for automotive application, and their properties were measured. Brake discs of DRA composites were manufactured and their braking performances were investigated, including brake velocity, brake
pressure, brake torque, brake deceleration, brake time and surface temperature etc. The test results show DRA composites exhibit an excellent braking performance.