bluuebunny/crossref_metadata_2025 huggingface dataset:
Raman Analysis of Microscopic Residual Stresses Stored in the Secondary Phase of Sc2O3-Doped Si3N4
Authors: Tochino Shigemi , Pezzotti Giuseppe
Published: March 2009

Residual stress studies were performed on the intergranular phase of a Sc2O3-doped Si3N4 polycrystal. Sc2O3 additive represents an ideal substance for residual stress analysis because of the intense Raman spectrum of its related silicate (intergranular) phases, which form during sintering. Crystallization of Sc2O3 to Sc2SiO7 during the cooling process after sintering causes a negative volume change at triple pockets of polycrystalline Si3N4 which overlaps mismatches in thermal expansion coefficients between secondary phase and the Si3N4 matrix. Conventional piezo-spectroscopic (PS) stress analyses have usually been limited to measurements in the Si3N4 matrix. In this paper, we show for the first time measurements of residual stresses stored within the secondary phase of Si3N4, using the Raman spectrum of Sc2O3. A change in crack propagation mode from intergranular to transgranular was found after annealing the Sc2O3-doped Si3N4 material, such a difference leading to an embrittlement of the material. Residual stress analysis of the annealed sample revealed that the tensile residual stress stored within the secondary phase was removed, thus explaining why the rising R-curve behavior of the material was substantially suppressed as compared to the as-sintered sample.
Fabrication of Refractive Index Controllable Inorganic-Organic Hybrid Thick Film
Authors: Jeong Sun Ho , Moon Joo Ho
Published: March 2009

Inorganic-organic hybrid material was synthesized by the sol-gel process. The control of the refractive index was achieved by varying the amount of phenyltrimethoxysilane as a refractive index modifier. Thick layers of hybrid material with 22㎛ thickness were fabricated by a single spin-coating without producing any crack at lower temperature. However, the heat-treatment of the hybrid film above 200°C induced significant cracks on the surface. The refractive index variations
and structural changes as a function of heat-treatment condition were analyzed using Fourier transform infrared spectrometer.
Promoted Growth of Murine Hair Follicles by Controlled Release of Growth Factors from Biodegradable Hydrogel
Authors: Ozeki Makoto , Tabata Yasuhiko
Published: March 2009

This study is an investigation to evaluate how the controlled release of different growth factors affects the hair follicle growth of mice in the second anagen stage of hair cycle. For the controlled release of basic fibroblast growth factor (bFGF) and hepatocyte growth factor (HGF), they were incorporating into biodegradable gelatin hydrogels, while a biodegradable collagen hydrogel was used for incorporation of vascular endothelial growth factor (VEGF). After subcutaneous implantation of the different hydrogels incorporating each growth factor or injection of phosphate buffered saline (PBS) containing the same dose of growth factor into the back of mice, the hair follicle growth was evaluated photometrically and histologically based on four parameters: the skin color of reverse side of the implanted or injected site, the number of vessels newly formed, the area occupied by hair follicle tissue, and the hair length. The area in close proximity to the implanted site of hydrogels incorporating growth factor was still dark in color 10 days after application. The hydrogel incorporating any type of growth factor enabled the hair follicles to increase the size, leading significantly enhanced area occupied by hair follicles per unit area of tissue. Implantation of the hydrogels incorporating growth factor increased significantly the number of blood vessels newly formed. Moreover, the length of hair shaft was elongated by the hydrogel incorporating
growth factor to a significantly higher extent than the corresponding growth factor. Neither empty gelatin nor collagen hydrogels affected the hair follicle growth.
These results indicate that the hydrogel incorporating growth factor induced the anagen-preservable activity. We conclude that the controlled release enabled growth factors to positively act on the hair growth cycle of mice, irrespective of the factor type.
A Study on PELGE Nanoparticles as Controlled Drug Delivery Systems for Intravenous
Authors: Duan You Rong , Liu W.S. , Liu J. , Zhang Z.R.
Published: March 2009

The objective of this study was to evaluate the in vivo characteristics of poly (ethylene glycol)-poly (lacticacid-co-glycolicacid)-poly (ethylene- glycol) (PELGE) copolymers as drug carriers. In order to test this circulation time, mitoxantrone (DHAQ) was used as a model drug in this study. DHAQ
nanoparticles (DHAQ-NP) were prepared, subsequently the DHAQ-NP were evaluated by measuring the drug concentration in plasma after intravenous administration via the tail vein of mice. The circulation time of the DHAQ-NP were tested. The results showed prolonged mitoxantrone (DHAQ) residence in systemic blood circulation.
Preparation of Nano-Hydroxyapatite/Poly(D,L-Lactide) Composite and Its Degradation in Femora of Rabbits
Authors: Xiao Yu Mei , Fan Hong Song , Wang Xin Long , Xu Jin Rui , Cheng Jing Qiu , Li Xu Dong , Zhang Xing Dong
Published: March 2009

With the outstanding biocompatibility of hydroxyapatite (HA) and biodegradation of poly(D,L)lactide(PDLLA), and the expected good bio-mechanical compatibility, nano-HA / PDLLA (n-HA/PDLLA)composite has been paid great interests in hard tissue repair. One of the key factors affecting the potential of the composite is the degradation of the composite. That is what the mechanism of degradation in the composite is and if the degradation of the materials would induce the crack of the composite or a porous structure facile for tissue ingrowth would be formed. In this study, an n-HA/ PDLLA composite containing about 40% n-HA (wt%) was prepared and the degradation of the composite in bony tissue of rabbits and tissue response were studied by implanting composite rods and control HA rods into the femora of 16 New Zealand rabbits. After definite intervals, the histological analysis was completed by light microscopy and the degradation behavior was observed by scanning electron microscopy. The results suggested that a nano-HA/PDLLA composite was obtained and the materials showed good biocompatibility and osteoconductivity. The substantial degradation of the composite occurred at 8 weeks in vivo. After a longer period of implantation, the further degradation of the composite led to the formation of interconnected microporous and macroporous structure in the materials that might facilitate the tissue ingrowth in the composite.
Successful Osteoinduction by Cell-Macroporous Biphasic HA-TCP Ceramic Matrix
Authors: Shin Hong In , Kim K.H. , Kang Inn Kyu , Oh Kyung Sik
Published: March 2009

To improve the potential of osteogenic repair, we developed macroporous biphasic hydroxyapatite-tricalcium phosphate (HA-TCP) ceramic and evaluated its efficiency as a scaffold for tissue engineered bone regeneration, which allows for appropriate cellular attachment and proliferation with osteogenic differentiation by evaluating ectopic bone formation ability after the implantation of cell-matrix construct in the skid mice subcutaneous pouches for 3 weeks. The macroporous biphasic HA-TCP ceramic matrix, with an average porosity of 86% and 200 µm mean pore size, provided favorable conditions for the attachment of cultured bone marrow derived osteoblastic cells along its inner surfaces in a filed up pattern and the active proliferation of them. The implanted cell-matrix constructs in the subcutaneous pouches induced favorable ectopic bone formation without any remarkable inflammatory reactions. These findings suggest that the biphasic HA-TCP ceramic matrix with macroporous structure has excellent biocompatibility, and that it allows for favorable cellular attachment with the acceleration of cellular proliferation and osteogenic differentiation support as well. Thus, with the controlled biodegradability, the biphasic HA-TCP ceramic may be a promising scaffold for tissue engineered bone regeneration technology.
Effect of Fibrin/Collagen Matrix on Osteogenic Differentiation of Bone Marrow Stromal Cells
Authors: Yang Young Il , Seol Dong Lim , Jeong S.J. , Lee D.S. , Jang Won Hee , Seo S.S. , Lee Sung Jae
Published: March 2009

Fibrin is a natural polymer with excellent biocompatibility and widely used as a cell
delivery vehicle in tissue engineering. However, fibrin of low concentration is not able to promote cell growth and differentiation within a desired time because of contraction and biodegradation of cell-seeded matrices. In this study we investigated effects of combining fibrin with collagen on growth and osteogenic differentiation of bone marrow stromal cells (BMSCs). Rabbit BMSCs-populated fibrin hydrogels with or without collagen were fabricated and cultured by the free floating method for 4 weeks. The DNA content of fibrin/collagen matrix significantly increased the growth of BMSCs compared to the fibrin-only matrix at 2week. Alkaline phosphatase activity was significantly higher in the fibrin/collagen matrix (71.0 nmol of p-nitrophenol /min/disc) than the fibrin-only matrix (45.1 nmol of p-nitrophenol /min/disc). Deposition of calcium was not significantly different between two groups. Histological examination also revealed more matured organization and deposition of collagen fibers and more concentric calcium deposition in the
fibrin/collagen matrix compared to the fibrin-only matrix. These results indicated that
fibrin/collagen matrix could be more effective than fibrin alone in supporting growth and osteogenic differentiation of BMSCs.
Evaluation of Poly(Lactic-Co-Glycolic Acid) (65/35) Treated by Dielectric Barrier Discharge in Atmospheric Pressure
Authors: Han In Ho , Choi Jai Hyuk , Baik Hong Koo , Park Jong Chul , Kim Jeong Koo , Lee Kwon Yong , Chung S.-M. , Lee In Seop
Published: March 2009

The surface properties of scaffolds are important since cell affinity is the most crucial
factor to be concerned when the biodegradable polymeric material is utilized as a scaffold in tissue engineering. The surface of biodegradable non-porous poly (lactic-co-glycolic acid) (PLGA) scaffolds were treated by atmospheric pressure dielectric barrier discharge (APDBD). The wetting angle of APDBD treated PLGA were decreased from the untreated PLGA of 73° to 42°. FTIR-ATR analyses showed hydroxyl groups were not detected regardless of treated condition, but the intensities of both ether groups and carbonyl groups were increased with treatment time and oxygen flow rate. Treatment time and oxygen flux are equally effective to make the PLGA surface more hydrophilic.
Two-Dimensional Array Formation of Multi-Cellular Spheroids on Micro-Patterned Polymer Brush Surface
Authors: Otsuka H. , Satomi T. , Hirano A. , Nagasaki Y. , Kataoka Kazunori
Published: March 2009

Here, a two-dimensional microarray of ten thousand (100x100) hepatocyte hetero-spheroids, underlaid with endothelial cells, was successfully constructed with a 100 µm spacing in an active area of 20x20 mm on micro-fabricated glass substrates coated with poly(ethylene glycol) (PEG) brushes (Fig. 1). Co-cultivation of hepatocytes with endothelial cells was essential to stabilize hepatocyte viability and liver-specific functions, allowing us to obtain hepatocyte spheroids with a diameter of 100 µm, functioning as a miniaturized liver to secret albumin for at least three weeks. The spheroid array constructed here is highly useful as a platform of TBB and CBB to detect a wide variety of clinically, pharmacologically, and toxicologically active compounds through a cellular physiological response.
Functionalization of Biomaterials
Authors: Hildebrand H.F. , Blanchemain N. , Mayer G. , Zhang Y.M. , Melnyk O. , Morcellet M. , Martel B.
Published: March 2009

In order to improve the tissue integration and subsequently the long-term maintenance, the implant surface can be modified by mechanical, physical, chemical or biological functionalization. In this way, the surface becomes biologically active by further grafting of biomolecules. Two principal concepts are considered for materials functionalization. (i) The Drug Delivery Systems (DDS) where the bioactive molecules goes to the target. (ii) The grafting of the bioactive compounds on small strongly bound spacer molecules. In this system, the target goes to the bioactive molecules. These techniques provide promising outlooks for any polymeric or ceramic scaffold used in tissue engineering for the construction of whole artificial and functional organs.
Macroporous Hydroxyapatite Scaffold Fabricated by Foam Impregnation
Authors: Dong Y.S. , Liu B. , Lin Ping Hua , Zhang Q.G. , Pu Yong Ping
Published: March 2009

Submicron hydroxyapatite powder with particle size in the range of 80-250 nm was
fabricated by sol-gel process in our laboratory. To make ceramic slurry with good flowability, the powder was mixed with binder and distilled water. The binder was consisted of acid magnesium and aluminum phosphates. The polyurethane foam was impregnated in the slurry, squeezed out the excess slurry and the composite porous body gained. Green body was dried in room temperature naturally and then moved to electric furnace and sintered at high temperature. The sintered scaffolds possess interconnected open pore structure and with a porosity of 70-85% and compressive strength 10-20 MPa, and was consisted of doped HA and other phosphates. The scaffolds were co-cultured with osteoblasts in vitro. SEM analyses revealed that the cells adhere to the ceramic surface, proliferate and growth properly. Experimental results showed that the scaffold possesses good biocompatibility and could be used in bone tissue engineering.
Fabrication of Tissue Engineering Scaffolds via Multi-Jet and Component Alternate Electrospinning
Authors: Zhang Lu , Wang Lin Gang , Hu Ping
Published: March 2009

In this article, electrospinning of poly (ethylene oxide) (PEO) /egg white blend and that of poly (carbon dioxide-co-propylene oxide) were studied. Blend fibrous mats containing poly (carbon dioxide-co-propylene oxide) and PEO/egg white blend were obtained through multi-jet and component alternate eletrospinning, respectively. Component alternate electrospinning exhibits higher efficiency and produces better blended products than multi-jet electrospinning does because
the inter-influence between different jets during multi-jet electrospinning greatly affects electrospinning process while component alternate electrospinning avoids such kind of influence.
Poly-N-Acetyl Glucosamine as a Scaffold for Cartilage Tissue Engineering in Nude Mice
Authors: Hill Christopher M. , An Yuehuei H. , Kang Qian K. , Demcheva Marina V. , Whitson S.William , Vournakis John
Published: March 2009

Athymic nude mice were used as an animal model to evaluate the chondrogenic
effects of bovine fetal chondrocytes seeded onto a new poly-N-acetyl glucosamine sponge. Results show excellent hyaline-like cartilage formation with high glycosaminoglycan concentration after 6 weeks. At 4 weeks there is less cartilage formation and more fibrous tissue infiltrate. Although further studies are needed, these initial data support the use of poly-N-acetyl glucosamine sponge as a scaffold for cartilage tissue engineering.
Chitosan Derivatives as Gene Carriers
Authors: Kim Tae Hee , Park In Kyu , Kim Su Il , Jeong Hwan Jeong , Bom Hee Seung , Cho Chong Su
Published: March 2009

Chitosan has been considered to be a good candidate for gene delivery system, since it is already known as a biocompatible, biodegradable, and low toxic material with high cationic potential. However, low specificity and low transfection efficiency of chitosan need to be overcome prior to clinical trial. In this review paper, chemical modification of chitosan for enhancement of cell specificity and transfection efficiency was explained. Also, chemical modification of chitosan for the stability of chitosan/DNA complexes was reviewed.
Comparison of Silicon Nitrides with Carbon Additions Prepared by Two Different Sintering Methods
Authors: Balázsi Csaba , Dolekcekic E. , Kövér Zsuzsanna , Wéber Ferenc , Hampshire Stuart , Arató Péter
Published: March 2009

In this work partially and fully densified silicon nitride based composites have been prepared using carbon black and graphite additions. Alumina and yttria sintering additives were also added to silicon nitride starting powders. Sinter-HIP and pressure-less sintering (PLS) have been employed for composite processing. The effects of carbon nano- and micro-grains on the microstructure, bending strength and hardness have been investigated. Higher strengths could be achieved by HIP, whereas more homogeneous properties can be assured by PLS.
Nano-Indentation of SiC and Si3N4/SiC Ceramic Materials
Authors: Balog Miroslav , Šajgalík Pavol , Lenčéš Zoltán , Hnatko Miroslav , Kečkéš Jozef , Huang Jow Lay , Janega J. , Horváthová R.
Published: March 2009

The present paper deals with the nano-indentation of SiC-micro and Si3N4/SiCmicro/
nano ceramic materials. The investigated SiC-micro and Si3N4/SiC-micro/nano ceramics were prepared by liquid phase sintering. Liquid phase was formed from different sintering additives (Y2O3, Yb2O3, Sm2O3). In the case of Si3N4/SiC-micro/nano ceramics the SiC nano-grains were created from SiNC amorphous powder. SiNC precursor decomposed to SiC and Si3N4 particles during sintering. The comparison of nano- and macro-hardness of investigated ceramic materials
showed that nano-hardness is significantly higher. The indentation modulus correlated with the measured nano-hardness. Remarkable influence of grain boundaries and SiC nano-inclusions on hardness was observed.
Labeled Weibull Plot of a C-Derived Si3N4-SiC Nanocomposite
Authors: Kašiarová Monika , Dusza Ján , Hnatko Miroslav , Šajgalík Pavol
Published: March 2009

Four-point bending strength and Weibull distribution of the strength values of a carbon derived Si3N4-SiC nanocomposite have been investigated. The fracture origins were identified and characterized and a “labeled Weibull plot” was constructed. The fracture origins are surface, subsurface and volume located technological defects with a dimension from 10 µm to 180 µm, mainly in the form of cluster of pores and large SiC grains.
Residual Stress Profile Determined by Piezo-Spectroscopy in Alumina/Alumina-Zirconia Layers Separated by a Compositionally Graded Intermediate Layer
Authors: Popa Monica , Calderón Moreno José-Maria , Hvizdoš Pavol , Bermejo Raúl , Anné Guy
Published: March 2009

In order to understand the mechanical behavior of layered composites with compositional gradient, it is necessary to determine their state of residual stresses. Compositionally graded materials can offer the advantage of eliminating abrupt changes in composition between layers having different thermal expansion coefficients. The existence of a compositional gradient may reduce discontinuities in thermal residual stresses, something beneficial from the point of view of the mechanical properties. We present here a study of the state of the residual stresses in a layered material made of thicker (several mm) homogeneous layers of alumina and alumina-20%zirconia separated by a thinner (less than 300 µm) intermediate graded alumina-zirconia layer, obtained by controlled deposition of powders from a solution using an electrophoretic deposition method. The thermal residual stresses generated during cooling after sintering were measured in the
homogeneous layers at each side, and at steps of about 30 µm in the graded layer along the direction of the compositional gradient, by using fluorescence ruby luminescence piezo-spectroscopy. Results show that the hydrostatic stresses on alumina grains vary continuously, indicating the absence of discontinuities in thermal residual stresses along the compositionally graded layer and at the interfaces of the homogeneous layers.
Damage Growth in Porous Ceramics
Authors: Sadowski Tomasz , Samborski Sylwester , Librant Zdzislaw
Published: March 2009

The paper deals with the experimental method of the mechanical properties estimation at the beginning of deformation process (elastic behaviour) of the material as well as during the whole deformation stages. The idea of the method results from the observation of the loading and unloading process of the material and analysis of the strain stage.
Failure Analysis of Si3N4 Rolls for Wire Hot Rolling by Numerical Simulation of Thermal and Mechanical Stresses
Authors: Lengauer Markus , Danzer Robert , Rubeša Domagoj , Harrer Walter , Zleppnig W.
Published: March 2009

Silicon nitride rolls for wire hot rolling have been tested in the rolling mill. After short
employment for processing of ultra-high strength materials, cracks appeared in the roll calibre, which limited further application of the rolls. In order to find out possible causes for the damage, relevant mechanical properties of the roll have been determined and thermally and mechanically induced stresses were assessed by numerical simulation. It has been found that thermal stresses are of little relevance, whereas mechanically induced stresses are high enough to enhance subcritical crack growth resulting in the development of the macroscopic cracks, so that the observed damage of the rolls could have been adequately explained. One further result of the analysis was that flaws induced by grinding are decisive for the service time of ceramic rolls, so that special attention has to be paid to the machining of the roll calibre.
Kinematic Analysis of Face Grinding Process at Lapping Machines
Authors: Cao L.X. , Wu H.J. , Liu J.
Published: March 2009

The precise face grinding and lapping technology with abrasive or abrasive tool has been widely used in the field of the precise manufacture and ultraprecise manufacture. It has become an essential technology in the manufacture of many components. The planetary lapping machine is typical equipment for face grinding or lapping process. And the relative motions between the workpieces and grinding wheel will affect the formation of wear profiles of the tools, furthermore, the work result will be affected directly by the cutting path of this relative motions. In this paper, the kinematic principle of face grinding process on lapping machines has been analyzed. By means of the concept of pitch point and pitch circles, the complicated grinding process has been converted into two kinds of rotations with the fixed center distance. Two kinds of path curves, i.e. workpiece against grinding wheel and grinding wheel against workpiece, and their relations are analyzed. The geometrical analyses and the manufacture quality of the workpiece are linked with the aid of the cutting velocity, the range of the rotational angle of the cutting traces and the rate of the change of the rotational angle with time. The optimal path curve and kinematic parameters are achieved, and these results are corresponding to the experimental results.
Dressing of Vitreous Bonded Wheels for Continuous Generating Grinding of Gears
Authors: Denkena Berend , Reichstein M. , Catoni F.
Published: March 2009

Grinding is a final step in the production chain of gears and therefore determines the quality of the product. In the industrial practice gears are cut - generally by means of a hobbing process - and their surface is hardened through a heat treatment, which has the target of increasing the wear resistance of the tooth flanks. Grinding is therefore necessary to remove the material distortions originating during the heat treatment and to fulfill dimensional and quality requirements. Usually only gears with high quality requirements are ground. Otherwise grinding is not carried out to reduce the production costs. In the recent years however the percentage of ground gears has been growing continuously due to the rising demands on load capacity, quiet running and life time as well as the increasing performance offered by the grinding processes. Generating grinding by means of cylindrical grinding worms shows the highest potential among the existing processes for gear grinding due to the high material removal performance that can be achieved. In order to use dressable
worms efficiently the dressing technology has to be optimized. The present contribution describes the technology for dressing vitreous bonded grinding worms. This process is based on the use of form dressing rollers by means of which the grinding worm geometry and topography are generated. The investigations are aimed at analyzing the influence of the dressing parameters, in particular the speed
ratio between dressing and grinding tool, and the attainable gear quality and surface properties. The results show significant dependencies between the dressing strategy and the grinding results.
Effect of Ultrasonic Elliptic Vibration on Friction between Shoe and Workpiece in Ultrasonic Elliptic-Vibration Shoe Centerless Grinding
Authors: Wu Yong Bo , Fan Y. , Tachibana T. , Kato M.
Published: March 2009

This paper describes an experimental investigation of the effect of ultrasonic elliptic
vibration of the shoe on the friction between the shoe and the workpiece in ultrasonic
elliptic-vibration shoe centerless grinding, a new centerless grinding technique proposed previously by the present authors. In the new technique, an ultrasonic elliptic-vibration shoe is employed to control the workpiece rotational speed as a regulating wheel does in conventional centerless grinding. The grinding accuracy is affected significantly by the workpiece rotation stability, which is dependent on the frictional force between the workpiece and the ultrasonic elliptic-vibration shoe. The issue relating to the friction between the workpiece and the shoe is therefore very important in the complete establishment of the new centerless grinding technique. In the present work, in order to clarify the effect of ultrasonic elliptic vibration of the shoe on the frictional coefficient and to determine the appropriate ultrasonic elliptic vibration conditions, a measurement apparatus was built up in-house and used to measure the frictional coefficient under the presence and absence of the ultrasonic elliptic vibration. The measurement results indicated that the frictional coefficient decreases with increase in the size of the ultrasonic elliptic motion, and a shape of the elliptic motion, in which the frictional coefficient reaches maximum, exists.
Friction Characteristic of Wafer Surface in Chemical Mechanical Polishing
Authors: Jia Zhen Yuan , Su Jian Xiu , Jin Zhu Ji , Guo Dong Ming , Li L.P.
Published: March 2009

The friction force of wafer surface plays an important role in removing material of wafer surface and the friction force distribution on wafer surface has a direct influence on nonuniformity of material removal in wafer CMP process. In this paper, models of friction force distribution and friction force on wafer surface were built according to the CMP process. Then the relationships between friction force and CMP process variables, such as the motion variables and pressure, are obtained. Measuring data of friction force on wafer surface are accord with analytical results. The research of this paper is helpful to further understanding the material removal mechanism in wafer CMP.
Study on Surface Integrity of PTFE Finished by Ultra-Precision Cutting and Surface Performance
Authors: Okuda Koichi , Nunobiki Masayuki
Published: March 2009

This study aims at clarifying the relationship between the surface integrity of PTFE
finished by an ultra-precision diamond cutting and the adhesion strength of a metal thin film. As the first step of this study, the basic properties such as surface integrity in the diamond cutting of PTFE and the effect of the surface roughness on the textile water repellency are demonstrated in this report. The following remarks were found. The measured roughness of finished surface largely exceeded the theoretical roughness, while the cutting force was very small comparing with aluminum and the flow type chips were formed. The surface with a smaller roughness tended to repel water.
Research on Highly Efficient EDM Pulse Power Supply and Its Experiments
Authors: Wang Yu Kui , Song Bo Yan , Zhao Wan Sheng
Published: March 2009

Their efficiency and their power factor of conventional independent electrical discharge machining (EDM) pulse power supplies with the current-limiting-resistor circuit is so low that they do not meet the need of advanced EDM technologies. The design of highly efficient EDM pulse power supply based on switching circuit pulse width modulation current closed-loop principle has been initiated. It is composed of such three stages as a single-phase active power factor correction preregulator, a full-bridge phase shift resonant converter based on machining current closed-loop
control and a pulse generator based on machining sequence control. Therefore, the efficiency of the new system is considerably increased to about 70%, its weight and size is decreased much. Its power factor is a great deal increased to about 0.95. Experiment results have demonstrated that the highly efficient EDM pulse power supply is capable of low electrode wear, high speed, stable machining.
Application of Neural Network in Plasma-Arc Flexible Forming
Authors: Xu Wen Ji , Fang Jian Cheng , Liu F. , Wang Xu Yue , Zhao Zhi Yu
Published: March 2009

Flexible forming using plasma arc (FFUPA) is a newly developed method of sheet metal forming. It makes the forming by means of thermal stress and thermal strain without mould and die, and is recognized as a promising forming method in developing new products. But the forming effect of FFUPA is determined by many factors, which compose a highly nonlinear system due to their complicated interact. As a result, it is difficult to predict the forming results and choose the processing
parameters in FFUPA. In this paper, BP neural network is applied to solve this problem. After introducing the mechanism of FFUPA and analyzing the influence of processing parameters on the forming result, BP neural network is established, which include an input layer, an output layer and a hidden layer. When inputs and outputs are properly chosen, the BP neural network can be used to predict the forming results and to select the forming parameters. To verify the validity of this network, the results obtained by the BP neural network are compared to those obtained by experiments, and the results show that the former is close to the later, which indicates it is feasible to apply BP neural network in determining the processing parameters and forecasting the bending effects in FFUPA.
A Novel Automatic Feedrate Adjustment Method for Die-Cavity Roughing
Authors: Wang Min Jie , Cai Y.J. , Yan W.G.
Published: March 2009

Sculptured surface machining is a critical process commonly used in die and mold industries. Since there is a lack of scientific tools in practical process planning stages, feedrates of CNC machining are selected based on previous experiences. In the selection of feedrate, the feedrate is set an individual conservative constant value all along the die cavity roughing processes in order to avoid undesirable results such as chipping, cutter breakage or over-cut due to excessive cutter deflection. Usually, volumetric models or vector force models used for optimizaton of feedrates must be created to get the variable feedrates along the tool path. Considering the die cavity roughing being a 2.5D cutting, a novel cutting force surface model is created based on orthogonal cutting tests to adjust the feedrates. The model is tested by a typical die-cavity roughing, thinning down machining time and balanced cutting-load can be attained. The presented feedrate scheduling characterized by balancing the cutting-loads in die-cavity roughing will be more significative in high speed machining.
Wear of Metal-Bonded Diamond Tools in Different Abrasive Processes
Authors: Xu Xi Peng , Han Q.L. , Li Yuan
Published: March 2009

In this present work, an experimental study was carried out to investigate the wear of
metal-bonded diamond tools (specimens) in five abrasive processes – stirring diamond specimens in rock slurries and surface grinding the specimens with a vitrified alumina wheel as well as circular sawing of refractory bricks, vitrified silicon carbide wheels and natural granite with segmented diamond blades. Three diamond specimens of different hardness were fabricated by hot pressing. In addition to following the worn morphologies of the diamond tools, forces and power were also
monitored in four abrasive processes. During stirring and surface grinding, the wear of the diamond specimens decreased with increasing specimen hardness, whereas the vertical force in surface grinding increased with the specimen hardness. In sawing of granite, however, the wear of the blades was closely related to the vertical force generated in sawing rather than the hardness of the diamond segments. The trends of force changes in sawing of refractory bricks were comparable to those in
sawing of granite. But the force ratios in sawing of the SiC wheel were found to be much higher than those in sawing of other two materials.
Analysis of Grinding Temperature Considering Surface Generation Mechanism
Authors: Obikawa Toshiyuki , Shinozuka J.
Published: March 2009

Grinding temperature was analyzed considering heat generation by cutting with each
abrasive on the wheel working periphery. A geometrical analysis of interference between the abrasives and workpiece gave the instantaneous cutting cross section, and visualized the surface topography generated by the time. Using the specific grinding energy and the instantaneous cutting cross sections, the instantaneous distribution of heat generation on the wheel-workpiece contact area was obtained. Then grinding temperature was calculated for a given heat partition into the workpiece. Since a cutting with an abrasive generated an impulse of heat flux, temperature distribution calculated for grinding carbon tool steel varied drastically, and very high local temperature or temperature spikes appeared.
A Description of Damage Based on Nanoscale Modelling of Fracture
Authors: Kaczmarek Jarosław , Ostachowicz Wiesław M.
Published: March 2009

In this paper we introduce nanoscale description of fracture in a single crystal in order to obtain foundations for modelling damage at more averaged scale. Nanoscale model of fracture is discussed together with nanoscale model of slip plasticity. Fracture systems and slip systems are introduced consistently by means of free energy. They enable us to express critical conditions for initiation of both crack and slip. Evolution equations which describe evo- lution of crack, slip and boundary of slip surface are introduced. Furthermore, we also discuss crack initiation and propagation on active slip surface. With the aid of variables characterizing damage at nanoscale level we discuss the form of damage tensor for more averaged model. One discusses larger context of nanoscale modelling in which the nanoscale models are considered as a segment of multiscale description of behaviour of materials.
On Fracture of Restored Teeth
Authors: Kahler Bill , Kotousov Andrei G. , Borkowski Krzysztof
Published: March 2009

The ultimate success or failure of a restored tooth is dependent on clinical management such as material choice, cavity design, bonding techniques and others. The current paper adopts a fundamental result in the linear theory of elasticity on the singular stress distribution in bi-materials wedge to analyze the choice of different materials used for the restoration of a tooth. Based on the value of the strongest singularity, different restorative materials are evaluated in terms of the susceptibility to the tooth fracture. Comparable results are reported for amalgam, gold alloys, and ceramic materials. Due to a wide variety of mechanical properties the application of resin composites could lead to better or worse fracture resistance of the restored tooth. The theoretical findings are supported by current clinical reports on longevity of restored teeth.
Application of Degree of Cyclostationarity in Rolling Element Bearing Diagnosis
Authors: Bi Guo , Chen Jin , He Jun , Zhou Fuchang , Zhang Gui Cai
Published: March 2009

Minor and random slip between rolling elements and races in rolling element bearings makes vibration signals have periodically time-varying ensemble statistics, which is known as cyclostationarity. Two second-order cyclostationary methods, the spectral correlation density (SCD) and the degree of cyclostationarity (DCS), are talked about in this paper based on a statistical model of rolling element bearings. The SCD provides redundant information in bi-frequency plane and cyclic frequency domain embodies the majority of it, which is a series of non-zero discrete cyclic frequencies completely reflecting the fault characters of rolling element bearings. The DCS has virtues of less computation and clearer representation, at the same time keeps the same characters with SCD in cyclic frequency domain. And the DCS is also proved to be resistant to the additive and multiplicative stationary noise. Simulation and experiential results from three rolling element bearing faults: outer race defect, inner race defect and rolling element defect, indicate practicability of the DCS analysis in rolling element bearing condition monitoring and fault diagnosis.
Stability Analysis of a Flexible Bladed-Rotor
Authors: Lesaffre N. , Sinou Jean Jacques , Thouverez F.
Published: March 2009

In any high-performance turbo-machinery, instability and damage are commonly occurring problems. The aim of this paper is to present a stability analysis of a fully-bladed flexible rotor. The flexural vibrations of the blades as well as those of the shaft are considered; the energetic approach used includes the effect of the rotational inertia. A stability detection method, bringing loci separation phenomena and coalescence, in case of an asymmetric rotor, to the fore, is made in order to determine a parametric domain where turbomachinery cannot encounter damage. Moreover, extensive parametric studies including for instance the length and the stagger angle of the blades are presented in order to obtain robust criteria for stable and unstable areas prediction. Finally, rotor/stator contact is introduced and the effect of the radial load acting on the blades when rubbing against a casing is considered.
Diagnosis of Local Fault and Identification of Transient Fault Force in Rotating Machinery
Authors: Yao Hong Liang , Yu Tao , Li Xiao Peng , Han Qing Kai , Wen Bang Chun
Published: March 2009

Model based fault identification techniques can be used to diagnose local faults in rotating machinery; the equivalent loads that represent fault forces can be used to identify the fault location. But in some cases the equivalent loads smeared over many nodes, and make it hard to identify accurate fault location and transient fault force. In this paper, the fault location is identified using least squares fitting approach by the system’s vibration shape when the fault signal is periodic or quasi-periodic. And after the fault location is ascertained, the transient fault forces can be identified by transient residual vibration using simple matrix multiplications and additions. Numerical simulations and experiment on rotor to stator rub are used to test the method, which proved the efficiency of the method.
Detecting Damage in a Beam by Static Tests
Authors: Caddemi Salvatore , Morassi Antonino
Published: March 2009

This paper presents a constructive procedure for the identification of a single crack in a beam based on the knowledge of the damage-induced variations in the static deflection of the beam. The crack is simulated by an equivalent rotational spring connecting the two adjacent segments of the beam. The analysis is based on an explicit expression of the crack-induced variation in the deflection of the beam under a given load distribution. The theoretical results are confirmed by a comparison with static measurements on steel beams with a crack.
An Investigation into Scalpel Blade Sharpness Using Cutting Experiments and Finite Element Analysis
Authors: McCarthy C.T. , Hussey M. , Gilchrist Michael D.
Published: March 2009

This paper presents an investigation into the sharpness of a surgical scalpel blade. An experiment was carried out in which a surgical scalpel blade was pushed through an elastomeric substrate at a constant velocity. The force-displacement characteristics were examined by plotting the stiffness as a function of blade displacement and it was found that this curve could clearly identify the point where the material separates to form a cut. A blade sharpness measurement was defined as the energy required to initiate an opening or cut in the substrate. A finite element model was developed to examine the stress state in the substrate at the point where the opening initiates. The development of this model is described. The model was validated against the experiment and close agreement was obtained. The von-Mises stress distribution under the blade tip was plotted and it was shown that the peak stress actually occurs away from the blade tip, suggesting that material separation would initiate away from the substrate surface.
Detection of Stray Current Field Interference on Metal Constructions Using STFT
Authors: Żakowski Krzysztof , Darowicki Kazimierz
Published: March 2009

A method of detection of stray currents using the Short Time Fourier Transformation (STFT) is presented. This particular kind of signal analysis makes the determination of changes of the spectral power density of a signal (e.g. structure to electrolyte potential) in function of time possible. The results of joint time-frequency analysis of the potential in the field of stray currents generated by tram-line are presented. The spectrogram is a composition of spectral lines of defined frequency distribution. A good correlation of localization of spectral lines corresponding to rail potential and pipeline potential in time domain is visible. These peaks may be treated as a characteristic feature of tram passing. The comparison of time and frequency localization of peaks from spectrograms is unambiguous evidence that the electric field generated by passing trams interfered on the investigated pipeline. A presented result unambiguously shows the possibility of accurate identification of source of stray currents and its interference on the metal construction.
Gearbox Fault Detection Using Hilbert and TT-Transform
Authors: Fan Xianfeng , Zuo Ming J.
Published: March 2009

Machine vibration signal has been used in fault detection and diagnosis. Modulation and non-stationarity existing in the signal generated by a faulty gearbox present challenges to effective fault detection. Hilbert transform has the ability to address the modulation issue. This paper outlines a novel fault detection method called Hilbert & TT-transform (HTT-transform) which combines Hilbert transform and TT-transform obtained from the inverse Fourier transform of the S-transform. The principle of the proposed method is to analyze the modulating signal created by a faulty gear using a time-time representation. The method has the advantage of providing a new way of localizing the time features of the modulating signal around a particular point on the time axis through scaled windows. It is verified with simulated signals and real gearbox vibration signals. The results obtained by CWT, S-transform, TT- transform, and HTT-transform are compared. They show that utilizing the proposed method can improve the effectiveness of gearbox fault detection.
Innovative 3D Dental Measurement for Tooth Model Restoration
Authors: Chen Liang Chia , Xu Z.Q.
Published: March 2009

This research develops an innovative free-form surface scanning system using laser triangulation for 3D dental data required for crown reconstruction. This novel design employs double laser diodes to produce two 45° structured-light lines projecting onto the plaster tooth models and three CCD cameras to capture deformed fringes to achieve fast and accurate 3D surface measurement of plaster tooth models. Effective strategies were implemented to overcome problems such as potential measurement occlusion and data registration inaccuracy, commonly encountered by other data scanning methods. The developed system has distinctive features such as laser projecting angles for complete surface measurement coverage, digitizing accuracy, and compact scanner volume for potential applications on 3D surface digitization of tiny industrial components. Experimental results verified that the proposed system achieves a 20µm digitizing accuracy and possesses fast scanning capability. Maximum one minute is used for a single-tooth model and 30 minutes are used for scanning the whole jaw.
Laser Feedback Interferometers Based on Orthogonally Polarized He-Ne Lasers
Authors: Zhang Shu Lian , Ding Y.C.
Published: March 2009

A novel unattached laser feedback interferometer by combining the laser feedback effect with the frequency splitting technology is presented and demonstrated. Light source is the birefringence dual frequency He Ne laser which generates o-light and e-light with orthogonally polarized states. When the feedback mirror is moved along the laser axis, the intensity of both o-light and e-light is changed periodically. If a threshold intensity for the output light is appropriately given by the signal processing circuits, the remaining intensity curves in each period shows four different polarization states: e-light, e-light and o-light, o-light, and no-light. Each change of polarization state corresponds to λ/8 displacement of the feedback mirror. We determine the movement direction by the difference of the order of the polarization state appearance. The resolution of the system is 0.079µm. In the experiment, the reflectivity of feedback has no influence on waveform. The laser feedback interferometer is likely to become an instrument which has no real contact with a measured object.
Detection of Random Defects on Highly Reflective and Complex Surfaces
Authors: Qu Xing Hua , He Y. , Jia G.X. , Ding J.M. , Ye S.H.
Published: March 2009

This paper describes a system that detects and categorizes workpieces with random defects on electrodeposits glossy metal surface. The system is developed on the basis of combination CCD photoelectricity inspection technology, image processing and automatic control technology. In the system, a special illumination apparatus with a light source of diffused light is designed. Workpieces with defects are automatically selected through measurement with image enhancement retreatment, gray scale analysis, image binaryzation, feature extraction and image recognition. Hardware comprises sections of optics, image collection, and control circuits. Software is programmed in Visual C++ and assembly language. The system can resolve the difficulty of detecting random defects on surface under the conditions of high reflection and complex surfaces.