bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of Hydroxyapatite Nanosized and other Apatites by Electrolysis Process
Authors: Montalbert-Smith Ricardo , Palma Carlos Andrés , Arias Juan Diego , Montero Mavis L.
Published: March 2009

We report how a simple electrolysis reaction of Ca/EDTA/PO43- homogeneous solutions, produces nanosized apatites of calcium, strontium, and doped calcium apatites as solid precipitates. Preliminary studies changing the current density and initial pH demonstrate the possibility of controlling crystallinity and sizes. All being in the nanosize range.
Preparation and Characterization of Nanoporous Alumina Membrane Made by Two-Step Anodization
Authors: Zhou Zhen Zhen , Li Zhen , Li Li
Published: March 2009

he preparation of different pore diameter and thickness nanoporous alumina membranes by two-step anodic oxidation, and the corrosion resistance and mechanical properties of the alumina membrane were investigated. In order to show the infection of pore diameter and thickness on these properties, the dynamic polarization and nano indentation method were mentioned, at the same time hemolytic test was performed for testing biocompatibility of the membrane.
Properties of Nanostructured 3Y-TZP Blocks Used for CAD/CAM Dental Restoration
Authors: dos Santos Claudinei , Santos Felipe Antunes , Elias Carlos Nelson
Published: March 2009

Several CAD/CAM systems are available to dental prosthesis laboratories which can be used to fabricate all-ceramic copings and frameworks. The use of these systems presents low demand, due principally the high blocks ceramics cost used for theses systems. Usually, these ceramic blocks are sintered at high temperatures, between 1450 and 15500C, resulting in micrometric ZrO2 microstructure. A considerable innovation in these ceramics systems used in CAD/CAM applications was introduced by the use of nanometric-tetragonal ZrO2 blocks, which are sintered at low sintering temperatures resulting in nanometric grains morphology and improved mechanical properties. The purpose of the present work is to characterize the mechanical properties of nanoparticled zirconium oxide blocks comparing with commercial micrometric ceramic parts. XRD patterns showed that the blocks have only the tetragonal-ZrO2 as crystalline phase. The tetragonal-monoclinic transformation phase was responsible for the excellent mechanical properties. Nanometric blocks presented hardness of 13GPa, fracture toughness of 11MPam1/2 , bending strength of 1020MPa and Weibull modulus, m=14, while micrometric ZrO2 blocks similar hardness, fracture toughness 8.5MPam1/2, bending strength of 850MPa and Weibull modulus of 10.
Plasma Spray of Free-Standing Components for Bone Tissue Engineering
Authors: García-Alonso D. , Levingstone T. , Parco M. , Stokes Joseph
Published: March 2009

This research work deals with the development of free-standing hydroxyapatite (HA) components produced using the Atmospheric Plasma Spraying Process. The spray parameters were based on the optimal values found in previous work for the HA powder used. The deposition time used to produce the free-standing coupons was varied between 70 and 150 seconds. The influence of spray time on the deposit thickness and the resulting crystallinity of the coupons were investigated. The surface of the samples was characterised by means of SEM and surface roughness was measured using a laser profiler. The crystallinity of the samples was analysed using XRD. The phase content of the coupons was investigated using XRD and Raman Spectroscopy. The crystallinity and thickness of the coupons was found to increase with increasing spray time. A maximum crystallinity of 89% and maximum average thickness of 2.45 mm were obtained.
Porous Hydroxyapatite Scaffolds by Polymer Sponge Method
Authors: Fook A.C.B.M. , Aparecida A.H. , Fideles Thiago Bizerra , Costa R.C. , Fook Marcus Vinícius Lia
Published: March 2009

This study aimed to develop porous hydroxyapatite scaffold for bone regeneration using the replica of the polymeric sponge technique. Polyurethane sponges were used with varying densities to obtain the scaffolds. The results indicate the porous HA scaffolds developed in this study as potential materials for application as bone substitutes to have high porosity (> 70%), chemical composition, interconnectivity and pore sizes appropriate to the bone regeneration.
Influence of the Acidity of the Titania Sol on the Structural and Chemical Properties of Sol-Gel Derived TiO2-SiO2 (30/70) Films
Authors: Ääritalo Virpi , Rosling Ari , Areva Sami
Published: March 2009

Series of TiO2-SiO2 films with a silica content of 70 mol% were prepared on glass slides by dip-coating method. The mixed sols were prepared via prehydrolyzing of the titania sol in different acidity. The surface chemistry was analyzed by XPS and the topography by AFM. Dissolution of silica was performed in TRIS buffer and the stability of the coatings was tested in simulated body fluid (SBF). The coatings remained crack-free after the TRIS and SBF tests. The formed nanostructure was practically same in all surfaces. The dissolution of silica was slightly increased with the increased acidity of the titania sol. Furthermore, the binding energies (BEs) of the Si(2p) and Ti(2p3/2) peaks obtained from XPS were both shifted upward with increased acidity of the sol. The sol-gel titania-silica materials made with prehydrolyzed titania formed heterogeneous structure where the TiO2 and SiO2 particles were partly interconnected and covered with soluble silica.
Sol-Gel Hydroxyapatite-CaO Composites: Fabrication and Bioactivity Studies
Authors: Hatzistavrou E. , Chatzistavrou Xanthippi , Papadopoulou Lambrini , Kantiranis Nikolaos , Chrissafis K. , Boccaccini Aldo Roberto , Paraskevopoulos Konstantinos M.
Published: March 2009

In this study the fabrication and characterization of a novel sol-gel derived HAp-CaO composite material is investigated. The bioactive behavior of the fabricated composite was assessed by immersion studies in SBF. A brittle and weakly crystalline carbonate hydroxyapatite (HCAp) layer was found to develop few hours after the immersion in SBF confirming high bioactivity. The presence of CaO accelerates the formation of HCAp phase.
Polyurethane Foams Behaviour. Experiments versus Modeling
Authors: Marsavina Liviu , Sadowski Tomasz , Constantinescu Dan Mihai , Negru Radu
Published: March 2009

. Polyurethane foam materials are widely used as cores in sandwich composites, for packing and cushioning. The main characteristics of foams are light weight, high porosity, high crushability and good energy absorption capacity. The paper presents the experimental results obtained for the mechanical properties of polyurethane foams in different loading conditions and the influence of impregnation on the mechanical properties. A 200 kg/m3 density polyurethane foam was investigated in the experimental program in three different Strength of Materials laboratories from Lublin, Bucharest and Timisoara.
The paper assesses the possibility to describe the polyurethane foam behaviour trough compression tests, micromechanical models and Finite Element Analysis (FEA). The micromechanical models and Finite Element Analysis could be used successfully for representing the engineering stress – strain behaviour if the compression tests provide reliable material parameters.
Influence of Cracks on the Service Life of Concrete Structures in a Marine Environment
Authors: Audenaert Katrien , Marsavina Liviu , de Schutter Geert
Published: March 2009

Chloride initiated reinforcement corrosion is the main durability problem for concrete structures in a marine environment. If the chlorides reach the reinforcement steel, it will depassivate and start to corrode in presence of air and water. Since the corrosion products have a larger volume than the initial products, concrete stresses are induced, leading to spalling and degradation of the concrete structures.
If cracks, caused by early drying, thermal effects, shrinkage movements or overstress, are present in the concrete, the penetration of chlorides is much faster compared to uncracked concrete. In this way, the corrosion process is initiated earlier and the service life is decreasing drastically.
In order to study the influence of existing cracks in concrete structures on the penetration of chlorides a test program was set up at the Magnel Laboratory for Concrete Research of Ghent University, Belgium in cooperation with the “Politehnica” University of Timisoara, Romania.
The first part of the test program consists of concrete specimens with artificial cracks. The chloride penetration into the concrete was realised with a non-steady state migration test and modelled with the finite element method COSMOS/FFE Thermal software.
Based on the experimental and numerical results, a crack influencing factor was determined. With this factor, the resulting service life of the cracked concrete construction is determined and compared with the original service life.
Micromechanical Material Model of Wooden Veneers for Numerical Simulations of Plywood Progressive Failure
Authors: Ivanov Ivelin V. , Sadowski Tomasz
Published: March 2009

The plywood material is widely used in civil engineering and furniture industry as cheap, strong, and lightweight material. The progressive failure of the plywood is difficult to be modeled and predicted because of the complexity of its structure and the interaction between different modes of orthogonal damages and interlayer failure. The microstructure of the wood determines the failure of the plies. A micromechanical material model of wooden veneers is developed, which is based on a representative volume cell (RVC) taken from the tubular microstructure of the wood and represented as a truss structure with longitudinal, transverse, and diagonal bar finite elements. The damage variables prescribed for each type of the bars determine the progressive degradation of the material stiffness. The 2-D damage material model of wooden veneers is utilized as user-defined material in continuum shell elements of ABAQUS™ finite element code. The parameters of the model are determined to simulate the behavior of single veneers in tension tests in different directions of loading. Together with cohesive elements representing the interface between the plies, the suggested model can be used to simulate and analyze the progressive failure and damage interaction in the plywood. The simulations could give us better understanding of the complex failure of the plywood, the succession of the damage development and reveal the weakest link in the material. The analysis can be used for optimization of the plywood layup.
Biomechanical 3D Analysis of Stress Induced by Orthodontic Implants
Authors: Szuhanek Camelia , Faur Nicolae , Cernescu Anghel
Published: March 2009

The objective of this numerical study was to evaluate the stress induced by orthodontic loading in anchorage implants and surrounding tissues. Orthodontic implants were included in this study. 3D geometrical models were constructed and material characteristics were taken from the literature. Finite element models were created based on the geometry and material characteristics of the screws. Orthodontic horizontal loads of 2 N were applied, and the biomechanical parameters were evaluated by colored scales. The highest von Mises values were recorded around the implant neck area and at the bone-implant interface.
In Vitro Experimental Testing of a Cervical Implanted Unit
Authors: Stoia Dan Ioan , Faur Nicolae , Toth-Taşcău Mirela , Culea Laurenţiu
Published: March 2009

The paper describes the biomechanical behavior of a cervical implanted unit (CIU) in two conditions: during the physiological and extreme loading. In order to reveal these behaviors, the anatomical structure composed by the C2 and C3 cervical vertebras was implanted using a plate-screws metal structure. The implant was design to perform dynamical, by allowing longitudinal, transversal and rotational movements. The physiological conditions were simulated by the pulsatory negative loading, while the extreme loading was simulated by the alternant symmetrical loading. The tests reveal two behaviors: the durability of the CIU in the physiological loading conditions and the failure of the structure under extreme load.
Constraint Parameter for a Longitudinal Surface Notch in a Pipe Submitted to Internal Pressure
Authors: Hadj Meliani Mohammed , Benarous M. , Azari Z. , Pluvinage G.
Published: March 2009

The use of two parameters fracture mechanics criterion as a tool for structural design and analysis has increased significantly in recent years. First, we discuse the elastic solution for the stress distribution at crack tip for two dimensional geometries and particularly constraint as T-stress under various loading conditions. Secondly, using notch fracture mechanics and particularly the Volumetric Method approach, we study the stress distribution at the tip of a notch in pipes submitted to internal pressure. The Notch Stress Intensity Factor Kρ and the effective T-stress are combined into a two-parameter fracture criterion (KIρ-Tef). This approach is then used to quantify the constraint of notch-tip fields for various pipe geometry and loading conditions.
Impact Fatigue of Adhesive Joints
Authors: Silberschmidt Vadim V. , Casas-Rodriguez Juan Pablo , Ashcroft Ian A.
Published: March 2009

The paper presents results of studies into the effect of repetitive low-energy impacting (known as impact fatigue) on reliability and crack growth in adhesively bonded joints. This type of loading is compared to the standard tensile fatigue in order to assess severity of such loading regime. Another loading type studied is a combination of a small portion of repetitive impacts with tensile fatigue. Crack propagation in a joint exposed to these types of loading is studied experimentally and numerically (with finite elements). This analysis is accompanied by microstructural studies of various damage processes, active at different stages of the crack growth process.
Multiscale Modelling of Damage Processes in Polycrystalline Ceramic Porous Composites
Authors: Sadowski Tomasz , Marsavina Liviu
Published: March 2009

Modelling of polycrystalline ceramics built up of different phases has been done within mesomechanical approach. Porous ceramics consists of matrix material and second phase – pores. Such material has non-linear and complex overall response to applied load. Modelling of porous polycrystalline material was performed by multiscale approach describing different phenomena occuring at different scales: micro- meso- and macro- with application of averaging procedure over the Representative Surface Element (RSE).
Preparation and Performance of Sulfate Resistance Cement-Based Material
Authors: Zhang Feng Chen , Ma Bao Guo , Yin Geng , Wu Yuan Yuan , Zhu Yan Chao
Published: March 2009

To discuss prevention of sulfate attack, especially thaumasite form of sulfate attack (TSA), sulfate resistance cement based material (SRM) were designed and prepared, and properties of which were investigated systematically. Micro-analytical techniques were introduced to identify erosion substances especially thaumasite, namely Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with X-ray energy dispersive spectrometer(EDS). Results show that SRM have better sulfate resistance, as well as TSA resistance, when exposed to aggressive environment with 33800 ppm mass concentration of SO42- in magnesium sulfate solution at 5°C±2°C. When immersed in magnesium sulfate solution for 40 weeks, compressive strength and tensile strength of SRM are still higher than their initial, and those of control specimen are lower by 33.7%, 36.5% compared to its initial. Surface erosion substances of SRM named S1 are ettringite and gypsum, while those of control specimen are ettringite, gypsum, thaumasite and brucite.
Fatigue Fracture Propagation Random Process Model for Reinforcing Steel Bar in Reinforcing Concrete Structure
Authors: Zhu Hong Bing , Yu Zhi Wu
Published: March 2009

Fatigue fracture is one kind of common destruction form in structure which bearing dynamic load frequently. Reinforce concrete structure’s fatigue fracture behaved commonly as the reinforcing steel bar’s fatigue fracture. The fatigue fracture destruction process of the reinforcing steel bar in the reinforced concrete is divided into three phases as follow: before the crack propagation stage; stable crack growth stage and instable propagation of crack phases, and the corresponding damage state for initial damage state; stable development state and structural damage fracture state. Describing every state using Markov stochastic process, and has carried out a probability analysis to the structural destruction process. The example analysis indicated that this method is accurate and convenient, while corresponding action for structural maintenance according to the above adopts can effectively avoids the accident occurrence.
Extrusion of MOC-Based Panel
Authors: Li Xiang Yu , Chen Hui Su , Chau Chung Kong , Li Zong Jin
Published: March 2009

Magnesium Oxychloride Cement (MOC) is an air-hardened material with chemical reaction between magnesium oxide and magnesium chloride solution. It has many properties superior to Portland cement. It does not need wet curing, has very good fire resistance, low thermal conductivity. In this study, wood composites were developed by using MOC as binder and wood powders as filler. It was demonstrated that MOC was suitable for binding wood particles in large quantities. In order to ensure smooth extrusion process, additives and rheological modifiers were used to modify the rheology behaviors and properties of the mixture and the rheology behaviors of fresh materials were also investigated with upsetting and relaxation tests simultaneously. Then MOC-based panels with different cross-sections were produced by using extrusion technology and mechanical properties of them were investigated.
Parametric Study of Reinforced Concrete Column Cross-Section for Strength and Ductility
Authors: Anwar Naveed , Qaasim Mohammad
Published: March 2009

Several parameters and corresponding performance of reinforced concrete column cross-sections of different shapes (square, rectangular, circular, T-shape, I-shape, cross-shape, L-shape and C-shape) under various loading conditions have been studied in order to determine the suitable and optimum cross-sections for strength and ductility. In each cross-section shape, parameters include compressive strength of concrete (f’c), tensile strength of steel (fy), steel ratio (As/Ag), and angle of bending. In order to demonstrate the behavior and performance of the sections in terms of strength and ductility, CSISectionBuilder software was used to define the stress-strain curve for concrete and steel and then compute the moment-curvature relationship for each section. Considering different sections, the number of parameters in every section and various loading conditions, a total of around 1,800 sections were analyzed. The comparison procedures started within each section shape, and then across different sections in order to determine the most suitable cross-section for strength and ductility. Results of the study are deemed very useful in the system selection and preliminary design of important structures such as buildings with complicated geometry and high architectural demand including bridge piers and hydraulic structures.
Performance on Steel Fiber Reinforced Self-Stressing Concrete
Authors: He Huan An , Wang Bo Xin , Lin Jian Ting
Published: March 2009

In this paper a new sort of high performance concrete is introduced which combines most advantages of prestressed concrete and steel fiber concrete, named steel fiber reinforced self-stressing concrete(SFFRSSC for short). Self-stressing concrete is actually a kind of expansive concrete which self-stresses, namely pre-compressive stresses, are induced by dint of some restrictions generally provided by steel bars to concrete expansion after hydration of expansive cement. As a result of chemical reaction, concrete archived prestresses by itself different from mechanical prestressed concrete, so called self-stressing concrete. By distributing short-cut steel fibers into self-stressing concrete at random, self-stresses are generated in concrete under combined restriction of steel bars as well as steel fibers. Thank to the pre-stresses tensile strength of concrete are significantly increased as well as cracking strength. In addition, on the one hand, expansive deformation of SFFRSSC can compensate the shrinkage of concrete to decrease non-loaded cracks resulting from shrinkage, and even when cracking, the steel fibers play an important role in resistance to crack development. On the other hand, self-stressing concrete can avoid the troubles of construction compared with conventional mechanical prestressed concrete. Therefore, above-mentioned advantages of SFFRSSC over ordinary concrete imply a better prospect in using SFFRSSC in civil engineering. For purpose of understanding the properties of SFFRSSC, in this paper some researches were carried out to investigate the special expansive behaviors with ages and tensile strength. The test results indicated that at early age the expansion of SFFRSSC developed rapidly but 14 day the 90% of overall expansive deformation basically fulfilled and subsequently expansion kept stable. Axial tensile test result showed that tensile strength were improved 2-3 times for self-stressing concrete specimens restrained by steel bars as well as steel fibers.
Structural Damage Detection Using Signal Pattern-Recognition
Authors: Qiao Long , Esmaeily Asad , Melhem Hani G.
Published: March 2009

Deterioration significantly affects the structure performance and safety. A signal-based pattern-recognition procedure is applied for structural damage detection with a limited number of input/output signals. The method is based on extracting and selecting the sensitive features of the structure response to form a unique pattern for any particular damage scenario, and recognizing the unknown damage pattern against the known database to identify the damage location and level (severity). In this study, two types of transformation algorithms are implemented separately for feature extraction: (1) Continuous Wavelet Transform (CWT); and (2) Wavelet Packet Transform (WPT). Three pattern-matching algorithms are also implemented separately for pattern recognition: (1) correlation, (2) least square distance, and (3) Cosh spectral distance. To demonstrate the validity and accuracy of the procedure, experimental studies are conducted on a simple three-story steel structure. The results show that the features of the signal for different damage scenarios can be uniquely identified by these transformations, and correlation algorithms can best perform pattern recognition to identify the unknown damage pattern. The proposed method can also be used to possibly detect the type of damage. It is suitable for structural health monitoring, especially for online monitoring applications.
Experimental Study on Non-Perpendicular Frame Structure of Tall Building
Authors: Shi Wei Xing , Liu Cheng Qing , Lu Xi Lin , Zhang Song , Zhou Ying
Published: March 2009

A shaking table model test is conducted for Guangzhou West Tower to study its seismic behavior in State Key Laboratory for Disaster Reduction in Civil Engineering at Tongji University. Guangzhou West Tower adopts a new structure system and the significant characteristic of this system is the non-perpendicular frame arranged around the building, acting both as columns and bracings. Based on the similarity theory and member equivalent principle，a 1/80 scale model of this building is made of polymethyl methacrylate(PMMA). The model’s dynamic characteristics, earthquake-resistant behavior, responses of acceleration and deformation under different wave peak values are investigated, then the seismic responses of the prototype structure are deduced and analyzed. The whiplash effect of the prototype structure is studied, and the weak position of the structure is found out. The experiment results demonstrate that it is feasible to apply this structural type to practical engineering. Finally, some suggestions for the engineering design of the prototype structure are put forward.
Nonlinear Analysis of Interaction of Superstructure-Pile-Raft-Soil System in Layered Soil — Part II: Characteristics of Reaction Force on Pile Head and Displacement of Raft
Authors: Chen Jun , Chang Yong Hong , Zou Yin Sheng
Published: March 2009

Using the nonlinear analysis method and program of the interaction of superstructure- pile-raft-soil system in layered soil in the state of the previous literature, the reaction force on the pile head and the displacement characteristics of raft of the piled-raft foundation are analysed when the thickness of the raft, the spacing of the piles, the length and the diameter of the pile are changed. Some quantitative data and qualitative conclusions are obtained in this paper.
Experimental Studies on Seismic Behavior of Concrete-Filled Steel Square Tubular Column-Steel Beam Connection
Authors: Fan Hong , Li Q.S. , Xu Li Hua
Published: March 2009

This paper introduces a new connection－inner and through-type diaphragm, which is recommended by Technical Specification for Structures with Concrete-filled Rectangular Steel Tube Members. It studies some factors including the additional plates installed on both sides of the flanges, the width-to-thickness ratio of the column and the length of the through diaphragm which have an influence to the seismic resistance behaviors of connection through cyclic test. The results show the hysteresis curves attained in the experiment are full and the rigidity deterioration is not obvious. The connection models have a good energy dissipation capacity. Meanwhile the stress distributing can be ameliorated and the ductility of the connections can also be improved through welding the additional plates to both sides of the flanges.
The Design Spectrum Curve of Seismic Performance for Reinforced Concrete Structure
Authors: Liang Xing Wen , Tong Yue Sheng , Xin Li
Published: March 2009

The performance-based seismic design of structure is in a research and development situation. A method is proposed in this paper to adapt the present demand. This method is based on the current Chinese code for seismic design of buildings. In design process, the earthquake action and lateral displacement are considered, and thus the design spectrum curve for equivalent single degree of freedom system is established. Thus the performances of structure at different earthquake levels are obtained and checked to satisfy the design requirements. After accomplishment of design, an elasto-plastic static analysis of structure may be conducted to fully examine its performance.
Seismic Response Analysis of Multi-Span Cable-Stayed Bridge
Authors: He Guo Jing , Zou Zhong Quan , Ni Yi Qing , Ko Jin Ming
Published: March 2009

Based on the dynamic characteristics analysis results of a precise three-dimensional finite element model, the earthquake responses of the bridge are analyzed in this paper. The influences of cable local modes and stabilizing cables on the seismic response are investigated by using different mode combinations and different models. It is found that the influence of cable local modes is negligible on the side towers while significant and not negligible on the main tower; the influence of the stabilizing cables is significant and not negligible on side towers, while minor and negligible on the main tower. As for the deck displacements, the influence of cable local modes is minor and negligible, while that of longitudinal stabilizing cables is significant and not negligible.
Effects of Sustained Pre-Load on Residual Strength and Stiffness of Concrete-Filled Steel Tube after Exposure to High Temperatures
Authors: Huo Jing Si , Huang Guo Wang , Xiao Yan
Published: March 2009

This paper experimentally investigated the effects of axial load level on the residual strength and stiffness of concrete-filled steel tubular (CFT) stub columns which were heated and cooled down to room temperature under sustained axial load. Eight stub columns were axially loaded and heated to specified high temperatures in a purpose-built electric furnace. After the specimens cooled down to room temperature while the axial load was kept constant, the stub columns were loaded to failure. The test results show that not only the axial load level and the high temperature exposure have significant effects on the residual strength and stiffness of stub column, but the residual strength index and stiffness index of the fire-damaged CFT stub columns with pre-load are remarkably different from those without pre-load. From the test results, it is recommended that the sustained axial load effects and the fire cooling phase should be taken into consideration in assessing the fire-damaged CFT columns.
Experimental Study on Deep Four-Pile Caps with Different Reinforcement Layouts Based on 3D Strut-and-Tie Analogy
Authors: Gu Qian , Sun Cheng Fang , Peng Shao Min
Published: March 2009

Based on 3D strut-and-tie analogy developed for analyzing the load-transferring mechanism of deep pile cap, this paper focuses on the effect of different longitudinal reinforcement layouts at the lower part of cap on the mechanical behaviors of deep four-pile cap. Besides a common layout of uniformly distributed reinforcement by the flexural theory, three different layouts of concentrated reinforcement over piles were designed by 3D strut-and-tie analogy. All specimens were limited in same reinforcement percentages, dimensions, materials and test procedures. Four specimens with the scale ratio of 1/5 were tested under the statically incremental gravity loading. The load capacity, deflection, strain of longitudinal reinforcement of specimens were measured, and the failure mode, crack propagation, deformation of specimens and stress distribution of reinforcement were analyzed. Through comparisons of the test results among all specimens, it was found that deep pile cap failed in shear and corner-pile punching whether with concentrated or uniform reinforcement, and the reinforcement concentrated over each two adjacent piles, similar to the tension bars in the strut-and-tie model, had considerable advantages than common uniform reinforcement layout. The ultimate strength of deep pile cap with concentrated reinforcement was significantly increased, while the improvement of deformation resistance and brittleness of deep pile cap was limited. According to above findings, the appropriate reinforcement layouts for deep pile cap were suggested in this paper.
Thermo-Hygral Model for of Shrinkage Induced Stresses in Concrete Structures
Authors: Baluch M.H. , Mahmoud Isam A. , Kalimur Rahman M.
Published: March 2009

Rapid moisture loss in concrete and the coupled shrinkage strain in concrete elements cause distress in structural members at early ages. The shrinkage stresses and the associated cracks can be reduced by controlling the rate of the moisture loss. However, under some circumstances, controlling the rate of the moisture rate is not practically possible which may add additional cost to the concrete construction.
A finite element based technique is suggested in this paper to predict the shrinkage stresses and consequently predict the possibility of having shrinkage cracks. The technique utilizes the analog between the heat transfer and moisture diffusion, thermal stresses and shrinkage stresses. The analysis was performed using thermal and structural modules in the commercial finite element software ANSYS. The process described in this work makes the determination of restrained shrinkage stresses in problems of concrete structures readily accessible to design, repair and construction engineers.
Mechanical Properties of α- and β-SiAlON Composite Ceramics Using β-SiAlON Powder
Authors: Asakoshi Kei , Tatami Junichi , Komeya Katsutoshi , Meguro Takeshi , Yokouchi Masahiro
Published: March 2009

β-SiAlON powder was used as a raw powder to fabricate α/β-SiAlON composite ceramics with different rare earth elements. The phases present in the sample fabricated from -SiAlON, α-Si3N4, AlN, and rare earth oxide powders were - and -SiAlONs. The composition was dependent on the chemical composition and firing profile. The sample obtained by adding Yb2O3 had a high -SiAlON content. The /-SiAlON composite ceramics had high densit. Their microstructures depended on the used metal oxides, namely, the addition of Nd2O3 and CaCO3 resulted in the elongation of the -SiAlON grains. The bending strength, fracture toughness, and hardness were influenced by the -SiAlON content, amount of elongated grains, and density of the sample.
Influence of Additives on Mechanical Properties in Liquid-Phase Sintered Silicon Carbide Ceramics
Authors: Kim Young Wook , Nishimura Toshiyuki , Mitomo Mamoru
Published: March 2009

The effect of sintering additives comprising AlN and RE2O3 (RE=Lu, Yb, Er and Y) in 2:3 and 3:2 molar ratios on mechanical properties of liquid-phase-sintered (LPS) and subsequently annealed SiC ceramics was investigated. The toughness vs cationic radius curve had a maximum in both 2:3 and 3:2 molar ratios; Yb-doped specimens showed maximal toughness of 5.8 and 6.6 MPa..m1/2 in 2:3 and 3:2 molar ratios, respectively. There was no correlation between room temperature (RT) strength and cationic radius. In contrast, the high temperature (HT) strength vs cationic radius curve had a minimum in both 2:3 and 3:2 molar ratios; Yb-doped specimens showed minimal strength of 520 MPa and 550 MPa in 2:3 and 3:2 molar ratios, respectively. The present results suggest that there is a trade-off in improving both RT toughness and HT strength in LPS-SiC ceramics.
First-Principles Study of Ceramic Interfaces: Structures and Electronic and Mechanical Properties
Authors: Kohyama Masanori , Tanaka Shingo
Published: March 2009

First-principles calculations based on density-functional theory are powerful tools to investigate the structure and properties of ceramic interfaces. The Schottky-barrier heights of SiC/metal and Al2O3/metal interfaces have been examined, and significant effects of the interface stoichiometry (termination species) and metallic species have been found. Ab initio tensile tests have been applied to Al2O3/Cu and Al2O3/Ni interfaces, where the strength and features of failure also greatly depend on the interface stoichiometry and metallic species.
Interactions between AlN and SiAlON Ceramics
Authors: Kalemtas A. , Acikbas Nurcan Calis , Kara Ferhat , Mandal Hasan , Krnel Kristoffer , Kosmač Tomaž
Published: March 2009

In the present study, interactions between AlN and SiAlON laminated couples were investigated after gas pressure (GPS) and spark plasma sintering (SPS) by scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX) with the aim to produce laminated composites. In the laminated couples sintered by GPS, a significant reaction zone (~100-150 μm), containing a high aspect ratio of elongated polytypoid grains, was observed at the interface. However, in the case of laminated couples sintered by SPS, a considerably thin reaction region
(~2-3 μm) was observed, elongated polytypoid grain formations were also detected.
Polishing of Ultra Smooth Surface with Nanoparticle Colloid Jet
Authors: Zhang Fei Hu , Song Xiao Zong , Zhang Yong , Luan Dian Rong
Published: March 2009

A nanoparticle colloid jet machining system has been developed for polishing ultra smooth surface of brittle materials. Interaction between nanoparticles and work surface in nanoparticle colloid jet machining has been given, and the theoretical dependence of the material removal rate with various important process parameters of the nanoparticle colloid jet machining have been investigated through material removal experiments. Some material removal results of nanoparticle colloid jet machining show that it is possible to obtain removal rates of one nanometer level per minute for glass surfaces with appropriate machining process parameters. A K9 glass surface was polished for obtaining ultra smooth surface. The surface roughness value of atomic force microscopy (AFM) observations is under 1nm Rms.
Effect of Slurry and Nozzle on Hole Machining of Glass by Micro Abrasive Suspension Jets
Authors: Wang Cheng Yong , Yang P.X. , Fan Jing Ming , Song Yue Xian
Published: March 2009

Micro drilling experiments of glass by Micro Abrasive Suspension Jets (MASJ) were carried out. The influence of the nozzle and compositions of slurry including the selection of abrasives, suspending agents and their concentrations on material removal, the depth and the diameter of the machined holes were investigated for glass drilling. Four processing stages are provided to describe the erosion profile characteristics. The suspension properties of slurry play an important role in MASJ machining. Five million molecular weight non-ionic polyacrylamide with concentration of 0.6% , white corundum abrasive and the longest length of the nozzle cylindercal zone can achieve lager material removal and better quality of hole in MASJ machining.
On the Coherent Length of Fluid Nozzles in Grinding
Authors: Morgan Michael N. , Baines-Jones V.
Published: March 2009

The delivery of grinding fluid to the contact zone is generally achieved via a nozzle. The nozzle geometry influences the fluid velocity and flow pattern on exit from the nozzle orifice. It is important to the efficiency of the process and to the performance of the operation that the fluid is delivered in a manner that ensures the desired jet velocity has adequate coverage of the contact zone. Often, assumptions about adequate coverage are based on visual inspections of the jet coherence. This paper provides new insight into the internal nozzle flows and the coherent length of a wide range of nozzle designs. The work presents a new analytical model to predict coherent length which is shown to correlate well with measured data from experiment. Recommendations are given to guide a user to optimal design of nozzles to ensure adequate fluid supply to the contact zone.
The Properties of Fresh Cement Paste with Self-Combustible Gangue Powder
Authors: Rao Qiu Hua , Ma Xiao
Published: March 2009

This paper presents an investigation on the effects of self-combustible gangue powder on the water requirement of normal consistency and setting time of blended cement paste. It was observed that the water requirement of paste increased, when self-combustible gangue powder were substituted partially for cement. It was found that self-combustible gangue powder have little effect on the setting time of blended cement paste with dosage from 10% to 30%,and this means the range of dosage is a appropriate mix content.
Effect of Adding Electrolyte in Cement Paste on the Dispersing Force of Polycarboxylate-Type Superplasticizer
Authors: Lai Jun Ying , Qian Xiao Qian , Zhan Shu Lin , Fang Min Hui
Published: March 2009

A series of water-soluble polycarboxylate-type superplasticizer (PCA) were synthesized by free-radical copolymerization of methyl acrylic acid and methoxy poly(ethylene glyco1) monoacrylate macromonomers in water solutions．Micelles were formed from the resultant PCA with predetermined hydrophobic and hydrophilic blocks in water. The hydrodynamic diameter and size distribution of micelles were determined by dynamic light scattering. The change of the concentration of the electrolyte results directly in the variation of the dispersing force of PCA in cement paste. The dispersing force degrades with increasing electrolyte concentration.
Hydration and Expansion Properties of Novel Concrete Expansive Agent
Authors: Gao Pei Wei , Geng Fei , Lu Xiao Lin
Published: March 2009

The hydration and expansive characterization of a novel concrete expansive agent were investigated in this paper. The results showed that the hydration activities of the novel agent depended on the calcining temperature, particle size and curing temperature. When the expansive agent was mixed in concrete, the early shrinkage of concrete was reduced. If the content and distribution of the expansive agent in concrete is appropriate and uniform, the expansion rate of concrete may be controlled, and the shrinkage of concrete could be compensated effectively by the gentle volume expansion.
Experimental Study on the Characteristics of GGBS Concrete Bending Specimens
Authors: Xia Jun Wu , Chang Hong Fei
Published: March 2009

This paper reports the experimental study on the mechanical characteristics of bending component with ground granulated blastfurnace slag (ggbs). A laboratory study has carried out to investigate the influence of replacement ratio of GGBS on the mechanics and deformation of concrete bending specimen; the harmonious working of concrete and reinforced bar is discussed as well. The results indicate that although the proportion of slag improve the strength of the concrete, the mechanical performance of GGBS concrete bending specimen is quite similar to that of common concrete, and the design expressions of common concrete girder is available to GGBS concrete girder. The specimen experiment also proves the existance of optimum slag proportion in GGBS concrete specimen, and the girder performs well when replace 20% cement with slag.
Advanced Joining Technologies for Aluminium Assembly for the Automotive Industry
Authors: Han Li , Young Ken W. , Hewitt R. , Blundel N. , Thornton Martin
Published: March 2009

The increased application of lightweight materials, such as aluminium has triggered many investigations into new joining techniques for aluminium alloys. The Resistance Spot Welding concept for aluminium has always attracted many researchers from different organizations. Self-piercing riveting is the major production process used to join aluminium sheet body structures for the automotive industry. Mean while, interest in laser welding and application as a candidate for joining aluminium is also growing. These key technologies for aluminium assembly are therefore being investigated by the research team at the University Of Warwick. The paper reported here looks at the feasibility of each process for joining thin gauge aluminium and compares the mechanical behavior for each joint type. The results suggested that all three joining technologies are feasible for joining aluminum and their mechanical behaviour is strongly dependent on the selection of process parameters
Subtle Cosmetic Defects in Automotive Skin Panels
Authors: Hazra Sumit , Williams David K. , Roy R. , Aylmore R. , Smith A.
Published: March 2009

Cosmetic defects such as ‘hollows’ are the result of deviations in a skin panel. These deviations are usually too small and local to be detected by discrete measurements of the panel but become visually apparent after the application of paint. As a result, the perceived quality of a panel may become unacceptable and considerable time may be dedicated to minimizing their occurrence through tool modifications. This paper proposes that there are three aspects to the problem: the springback or buckling of the panel, the optics of the painted panel and the ability of an observer to perceive the defect. In particular, it will be argued that hollows cause optical distortions that inform the human eye of the presence of a defect. The paper then suggests that signal processing techniques, in particular the wavelet transform, provide a simple way of locating and quantifying the severity of these defects. The transform was applied to two physical parts and a simulation model.
Investigation of the Mechanical Behavior of a PU-Based Coil-Coating System with the Help of Indentation and FE Analysis
Authors: Behrens Bernd-Arno , Gatzen Hans Heinrich , Peshekhodov Ilya , Pape Florian
Published: March 2009

One-component polyurethane coatings on galvanized sheet steel are widely used to suppress white rust of the car body. To fulfill the requirements of corrosion resistance and aesthetics, such coatings have to withstand sheet forming and assembling operations without being damaged. Damage - which in the wide sense encompasses pores, surface and interface microcracks - would mean an inacceptable reduction in corrosion resistance and aesthetics deterioration. Therefore, understanding of coating damage initiation due to sheet forming becomes a key issue for producers of coating materials and forming technologists. To study coating performance in a forming process, FE simulations can be employed. This requires, however, an appropriate constitutive model of the coating and accurately determined model parameters. The present work investigates a two-layer coil-coating system Coilprime C manufactured by the BASF Coatings AG. The system consists of a primer with a thickness of approximately 5 µm and an intercoat, which is about 20 µm thick, both being based on a polyurethane (PU) resin. Applicability of indentation for determination of mechanical properties of the intercoat is studied. The experiments were carried out with a Hysitron TriboindenterTM using a conospherical indenter. In the experiments, the intercoat exhibited viscoelastoplastic behaviour. In the FE simulations of the indentation test, the intercoat and the primer were assumed to be a single continuum with a constitutive behaviour described as a combination of hyperelasticity defined by the Arruda-Boyce strain energy potential and ideal plasticity defined by the rate-independent von Mises yield surface. The full deformation is modelled using a multiplicative split of the deformation gradient into hyperelastic and plastic components.
Investigation of Die Corner Filling in Hydroforming of Cylindrical Stepped Tubes Using Finite Element Simulation and Experiment
Authors: Bakhshi-Jooybari Mohammad , Elyasi Majid , Gorji A. , Mohammad-Alinejad G. , Hosseinipour S.J. , Nourouzi S.
Published: March 2009

Seamless tubular components, such as stepped tubes, conical tubes and box shape tubes, are mainly produced in tube hydroforming process. In forming the components in this process, complete filling the die corners is very difficult. In this paper, the mechanism of improvement of die corner filling in a proposed tube hydroforming die was investigated. The FEM simulation results showed that the material flow and stress distribution could theoretically clarify the die corner filling in the proposed die. Also, the comparison of the die corner filling between the new die and a conventional die was explained. In order to verify the simulation results, some experiments were performed.
Application of Neural Network Technique to Predict the Formability in Incremental Forming Process
Authors: Ambrogio Giuseppina , Filice Luigino
Published: March 2009

Nowadays, several researchers all over the world on Incremental Sheet Forming are focused on formability analysis and, in particular, on the development of a model able to predict material response also in the design phase.
Focalising the attention on this aspect and taking into account the literature review, it is possible to establish that both numerical and analytical approaches were utilised to justify the experimental evidences. Anyway, many efforts are spent in order to define new models to predict material breakage during incremental forming of simply shaped components.
On the contrary, the availability of a predictive model able to detect failure insurgence, based on the products geometry, is a relevant issue to improve industrial application of incremental forming process. At the same time, it still represents an open point of the current scientific research.
According to this aim, a preliminary analysis was executed to detect the factors that deeply impact on the process performance. In a subsequent analysis, a robust Neural Network was built in order to define a more reliable tool for calculating the allowable component height when a multi-slope trajectory is imposed. The reliability of the proposed approach was tested executing some experimental results. All the details are accurately discussed in the paper.