bluuebunny/crossref_metadata_2025 huggingface dataset:
Bonding and Separation Behaviors between Ti-Sn Alloys and High Carbon Steel
Authors: Morizono Yasuhiro , Nakatsukasa Seiichiro , Nishida Minoru
Published: January 2010

Ti-Sn binary alloys (Ti-5 to 20 mol% Sn) were diffusion-bonded to high carbon steel between 1073 and 1273 K for 3.6 ks in a vacuum to investigate the influence of the alloy composition on the interfacial microstructures. Ti-5 and 10 mol% Sn alloys were attached firmly to the steel at a bonding temperature of 1273 K. A continuous TiC layer was formed along the interface, while voids were observed between the TiC layer and the steel. Although the joints with Ti-15 and 20 mol% Sn alloys were also prepared at 1273 K, these joints separated near the interface after the bonding treatment. The TiC layer was formed in the separated surface of Ti-Sn alloy, and Fe in the steel diffused into the Ti-Sn alloy. This indicates that the Ti-15 and 20 mol% Sn alloys established contact with the steel at elevated temperatures until just before the separation. The specimens bonded at 1173 K also denoted the same tendency. However, the Ti-15 mol% Sn/steel joint bonded at 1073 K showed a shear strength of more than 50 MPa. The mechanism and the application of the interface separation are discussed on the basis of the microstructural observations.
Experimental Setup for the Determination of Mechanical Solder Materials Properties at Elevated Temperatures
Authors: Müller Wolfgang H. , Worrack Holger , Sterthaus Jens
Published: January 2010

The fabrication of microelectronic and micromechanical devices leads to the use of only very small amounts of matter, which can behave quite differently than the corresponding bulk. Clearly, the materials will age and it is important to gather information on the (changing) material characteristics. In particular, Young’s modulus, yield stress, and hardness are of great interest. Moreover, a complete stress-strain curve is desirable for a detailed material characterization and simulation of a component, e.g., by Finite Elements (FE). However, since the amount of matter is so small and it is the intention to describe its behavior as realistic as possible, miniature tests are used for measuring the mechanical properties. In this paper two miniature tests are presented for this purpose, a mini-uniaxial-tension-test and a nanoindenter experiment. In the tensile test the axial load is prescribed and the corresponding extension of the specimen length is recorded, both of which determines the stress-strain- curve directly. The stress-strain curves are analyzed by assuming a non-linear relationship between stress and strain of the Ramberg-Osgood type and by fitting the corresponding parameters to the experimental data (obtained for various microelectronic solders) by means of a non-linear optimization routine. For a detailed analysis of very local mechanical properties nanoindentation is used, resulting primarily in load vs. indentation-depth data. According to the procedure of Oliver and Pharr this data can be used to obtain hardness and Young’s modulus but not a complete stress-strain curve, at least not directly. In order to obtain such a stress-strain-curve, the nanoindentation experiment is combined with FE and the coefficients involved in the corresponding constitutive equations for stress and strain are obtained by means of the inverse method. The stress-strain curves from nanoindentation and tensile tests are compared for two mate-rials (aluminum and steel). Differences are explained in terms of the locality of the measurement. Finally, material properties at elevated temperature are of particular interest in order to characterize the materials even more completely. We describe the setup for hot stage nanoindentation tests in context with first results for selected materials.
Weldability Study of Aluminum Alloys Using Weld Simulation and Complimentary Variable Restraint Testing
Authors: Walsh D.W. , Gibbs D.B.
Published: January 2010

Aluminum alloys containing lithium are attractive to the aerospace industry. The high specific strength and stiffness of these alloys improves lift efficiency, fuel economy and performance and increases payload capability. The objective of this study was to compare the fabricability of six different aluminum base alloys. Three were Li containing alloys, two variants of AL 2195 (Al-4Cu-1Li) and a lithium enhanced analog of AL 5083 (Al-4Mg-2Li). Three were materials in common usage, Al 2219, Al 2014 and Al 5083. Fabricability was assessed using Gleeble thermomechanical testing, Varestraint testing and differential scanning calorimetry (DSC). Results indicate that Alloy 2195 is more susceptible to hot cracking than both Al 2219 and Al 2014. Cracking sensitivity is a strong function of chemical composition within specification ranges for Al 2195. Results also indicate that the lithium containing analog of Al 5083 is more hot crack susceptible than its parent material. Fabricability was correlated to material microstructure using optical microscopy, scanning electron microscopy and microprobe analysis. Hot cracking in all materials was associated with persistent, continuous liquid films produced by weld thermal cycling, aggravated by base material structure. Measures of several characteristic temperatures using the Gleeble simulator were fully consistent with Varestraint results. The maximum crack length in the Varestraint test correlates well to the liquidus temperature for the alloy less the nil ductility temperature. The temperature difference is equivalent to the thermal gradient associated with welding times the maximum crack length.
Incompatibility Stresses and Elastic Energy Stored in Polycrystalline Materials
Authors: Baczmanski Andrzej , Wawszczak Roman , Seiler Wilfrid , Braham Chedly , Wroński S. , Wróbel Mirosław , Wierzbanowski Krzysztof
Published: January 2010

ray diffraction method is used to determine the stress field in polycrystalline materials. The measurement of peak shifts enables the determination of the macrostresses and the plastic incompatibility stresses (intergranular stresses). In the interpretation of the experimental results self-consistent model of elatoplastic deformation is used. In the present work, the plastic incompatibility stresses and the elastic energy stored in cold rolled brass and ferritic steel were determinate. The results are discussed and presented in Euler space.
TEM In Situ Investigation on Non-Equilibrium Eutectics in Semicontinuous Casting Ingot of Al-6.2Zn-2.3Mg-2.3Cu Super-High Strength Aluminum Alloy
Authors: Gao Feng Hua , Zhao Gang , Bian Wei Min , Tian Ni
Published: January 2010

The in-situ investigation on morphology, chemical contents and crystal structure of non-equilibrium eutectics in semicontinuous casting ingot of Al-6.2Zn-2.3Mg-2.3Cu super-high strength aluminum alloy have been carried out by transmission electron microscopy equipped with energy dispersive X-ray spectroscopy (TEM-EDX). The results show that a large amount of lamellar non-equilibrium eutectics exists in semicontinuous casting ingot of this alloy; the non-matrix phase of this eutectics is a secondary phase which contains Al, Zn, Mg and Cu elements, with the atom ratio of approximately 1:1:1:1, and this non-matrix phase of non-equilibrium eutectics owns the same crystal structure as that of η phase (MgZn2).
Fracture Toughness of a Silica-Doped Cubic Zirconia (8Y-CSZ)
Authors: Hiraga Keijiro , Morita Koji , Kim Byung Nam , Yoshida Hidehiro
Published: January 2010

In a high-purity 8Y-CSZ, the doping of 0.15 - 5 mass% pure silica introduces a glass phase dispersing uniformly along grain-boundary facets and at multiple junctions. For materials with grain sizes of 0.75 - 2.4 m, the dispersion of the glass phase decreases the elastic modulus, the Vickers hardness and the elastic modulus-to-hardness ratio, whereas it affects little in the fracture toughness measured by a Vickers-indentation method and a single-crack-precracked-beam method. Inspection of crack propagation paths shows that the glass phase with sizes smaller than those of the matrix grains is not a site for easy crack-propagation, but provides a site for a crack-deflection mechanism.
Effect of Parameters of Notch on Fatigue Life of Shaft Based on Product Lifecycle Management
Authors: Li You Tang , Chen Bo , Yan Chang Feng
Published: January 2010

For designing the fatigue life of shaft with a circumferential notch exactly, the influencing factors have been analyzed completely. The modified mechanics model to estimate the fatigue life of shaft with a circumferential notch is set up. The assessment method of fatigue life for shaft with a circumferential notch is put forward. The effects of notch on stress concentration factor and fatigue life of shaft with a circumferential notch are discussed and the influencing parameters are obtained. The results show that the tip radius of notch has a great effect on fatigue life of shaft; on the other hand, the open angle of notch has a little effect on it. The results will establish the base of anti-fatigue design of shaft.
Predication of Fatigue Life of Notched Torus under Random Scan Vibration
Authors: Li You Tang , Yan Chang Feng , Jin Wu Yin
Published: January 2010

The fatigue life of notched torus under random scan vibration is discussed in this paper. The stress function and stress field intensity of the materials under composted cyclic stress are analyzed. The experiments of vibration of the notched torus under random load are made in the digital vibration equipment. The fatigue life of notched torus is predicted by use the local stress-strain field method and three parameters formula. The elasto-plastic properties of the material are described by Von Mises yield criterion and stress-strain of uniaxial cyclic loading. The field of local fatigue damage of notched torus under random vibration is determined by using the method of local stress-strain field intensity, and the cycle stress-strain response near the tip of notch is obtained. The revised factor of fatigue life of LY12-CZ material is determined, the relationship between high-frequency cycle of stress and fatigue life is set up by use three parameters formula, and the fatigue life of the notched torus is obtained.
Thermomechanical Process Innovation via Computer Modeling and Simulation
Authors: Manohar Priya A.
Published: January 2010

A new approach is proposed in this paper that describes the development of flexible rolling technology in industrial processing of C – Mn and Low C - microalloyed steels. Scientific knowledge of industrially-significant processes for these materials is presently fragmented and scattered in published literature, which causes impediment to process innovation and optimization. In the current work, it is demonstrated that new process sequences could be developed by breaking down existing process routes in to key elements and then by recombining them to generate novel alternative and more efficient hot processing sequences. The proposed methodology establishes a platform for a more realistic assessment of existing process routes and the development of new hybrid process routes that combine ideas from alternative processes. This enables the identification of an optimal process sequence for specified steel compositions that also satisfies simultaneous design criteria such as process feasibility and property maximization. Application of the proposed algorithm in industrial-scale rod rolling of a medium C-Mn steel is demonstrated and discussed.
Fracture Process of Aluminum/Aluminum Nitride Interfaces during Thermal Cycling
Authors: Nagatomo Yoshiyuki , Muranaka Ryo , Hayashi Hiromasa , Kuromitsu Yoshirou , Kuwano Noriyuki
Published: January 2010

Al circuit substrates, which are composed of a sintered AlN plate and pure Al plate joined to both sides of the AlN plate, are used for semiconductor power devices. It is important to prevent fracture of the Al/AlN interface to ensure normal and stable device operation. In this study, the fracture process of Al/AlN interface during thermal cycling was investigated using advanced scanning electron microscopy (SEM). Al circuits joined to an AlN plate were plastically deformed with thermal cycling. Al grains were divided with the formation of sub-boundaries due to the plastic deformation. After 2000 thermal cycles, a crack was generated at edges of the Al/AlN interface and propagated gradually to the center of the substrate. Cross-sectional observation, using an angle selective backscattered electron detector (AsB), revealed that the Al grain size near the Al/AlN interface decreased to 3 m or less, and the crack proceeded along the Al grain boundaries.
To clarify the temperature dependence of the fracture process, a repeated bending test was performed at various temperatures. Shear strains were induced at the Al/AlN interface by the repeated bending. The rate of crack propagation tends to be higher at higher temperatures for bending test. In substrates bent at 373 K or higher, the crack proceeded after the Al grains had been refined. These results indicate that fine-grained Al resulting from thermal cycling is formed by creep deformation and recrystallization at higher temperatures. Thus, improving the creep strength of the Al plate is thought to be effective for prevent cracking during thermal cycling. The effect of additive elements in the Al plate was also discussed in this study.
Metallurgical Investigation on Low Ductility Failures of Cu-ETP Components
Authors: Pantazopoulos George , Vazdirvanidis Athanasios , Papamantellos D.C.
Published: January 2010

In the present paper, the investigation on low ductility failures occurred to ETP copper strips and connectors manufactured from cold stamping of copper tubes is presented. Optical microscopy, SEM/EDS for macro- and microfractography and local elemental analysis along with tensile testing were employed as the principal analytical techniques in the context of the present investigation. Casting defects and microstructural abnormalities associated to hydrogen induced cracking (H.I.C.) are the principal contributors of the examined failures.
Tools and Technologies for Hot Forming with Local Adjustment of Part Properties
Authors: Kolleck Ralf , Veit Robert
Published: January 2010

In general hot stamped car body parts show a uniform strength distribution. Especially for safety relevant parts with high requirements concerning crash performance, this uniform strength distribution can cause problems. During a crash a B-pillar e. g. can absorb more energy when the lower part is relatively flexible while the middle and upper part has to be high-tensile to prevent the intrusion into the passenger compartment. Also during the production of hot stamped parts, the high strength causes trouble. When the trimming takes place after the hardening process, the durability of the tool is limited. Thus at the moment the only economic process for trimming of ultra-high-strength steels is laser cutting.
This paper presents different approaches to reach local different strength distributions in hot stamped components. In particular the results of a research project of the Institute Tools & Forming, Graz University of Technology are shown where precisely defined areas of different strengths could be obtained in one part. This was achieved by the use of simple and cheap ceramic inserts in conventional press hardening tools.
Simulating Phase Coarsening of Ultra-High Volume Fractions
Authors: Wang Ke Gang , Ding X.
Published: January 2010

The dynamics of phase coarsening at ultra-high volume fractions is studied based on two-dimensional phase-field simulations by numerically solving the time-dependent Ginzburg-Landau and Cahn-Hilliard equations. The kinetics of phase coarsening at ultra-high volume fractions is discovered. The microstructural evolutions for different ultra-high volume fractions are shown. The scaled particle size distribution as functions of the dispersoid volume fraction is presented. The particle size distribution derived from our simulation at ultra-high volume fractions is close to Wagner's particle size distribution due to interface-controlled ripening rather than Hillert's grain size distribution in grain growth. The changes of shapes of particles are carefully studied with increase of volume fraction. It is found that more liquid-filled triple junctions are formed as a result of particle shape accommodation with increase of volume fraction at the regime of ultra-high volume fraction.
Method of Constraint Loss Correction for CTOD Fracture Toughness under Welding Residual Stress Field
Authors: Yamashita Yoichi , Minami Fumiyoshi
Published: January 2010

This paper studied the assessment method for welding residual stress effects and constraint loss effects on brittle fracture of structural component subjected to membrane stress. The methodology of CTOD fracture toughness correction for welded joints is proposed from lower to upper ductile-brittle transition temperature region. The methodology is based on the tensile plastic zone size criterion and the equivalent CTOD ratio derived from the Weibull stress criterion. It has been found that the proposed methodology has given the reasonable fracture assessment results.
Evaluation of High Temperature Fatigue Behaviour of P22 by Miniature Specimen Testing
Authors: Callaghan Mark D. , Humphries S.R. , Law M. , Li Hui Jun , Yeung Wing Y.
Published: January 2010

Miniature specimen testing to evaluate mechanical properties, presents a novel opportunity to undertake structural integrity assessments of in-service power generation components, by removing only a very small volume of material. In this study, high temperature fatigue testing of P22 steel was undertaken and a number of fatigue properties determined using a miniature specimen testing methodology. Good comparisons were observed between fatigue properties determined by miniature specimens and the more established standard-sized specimen testing reported in literature.
Roping Phenomena in Aluminium Alloy 6016: A Microtextural Investigation
Authors: Bennett Tricia A. , Sidor Jurij J. , Petrov Roumen H. , Kestens Leo A.I.
Published: January 2010

Roping was investigated in two 6016 aluminium alloys that exhibit different levels of susceptibility to its occurrence. The level of roping is lower, as manifested by the less pronounced (roping) lines on the surface, in the GR material compared to the BR case. Through-process characterization of GR and BR materials by means of electron backscatter diffraction (EBSD) reveals similarities in the grain size, (grain) orientation texture and the spatial distribution of {100} <001> Cube grains up to, but not including the T4 state. Cube grains in the T4 state are spatially banded in the BR material but more uniformly distributed in the GR case. It was found that the thermo-mechanical treatments prior to the T4 state account for the difference in spatial distributions of Cube grains and hence, the different roping behaviours exhibited by these materials.
The Effect of Ultrasonic Injection on the Microstructure and Mechanical Properties of A356 Alloy
Authors: Kang Byoung Il , Ko Dae Gyun , Youn Jeong Il , Kim Young Jig
Published: January 2010

A356 alloy is one of the wide used casting aluminum alloys and intense research activities of worldwide on casting process or refinement agent and procedure. In this study, we attempted refinement on Al primary phase and eutectic phase of A356 alloy by ultrasonic injection into the melts. The effect of ultrasonic injection into the melts could be summarized as follows: the morphology of the Al primary phase was refined and changed shape from dendritic to nondendritic and the eutectic phase of A356 was also refined and changed morphology from dendritic to plate shape.
On the Plastic Flow Behavior of Ti-6Al-4V Alloy during Multi-Stand Tandem Hot Rolling
Authors: Chen Li Qing , Liang Shuang , Liu Xianghua
Published: January 2010

Titanium alloys are usually used as structural parts in forged and subsequent heat treated state. Up to now, there have been rare researches appeared on their shaping or forming by multi-stand tandem hot rolling. In this article, we choose Ti-6Al-4V as experimental material and a simulated research has been carried out in a thermo-mechanical simulator MMS-300 to model its hot-rolling process. The plastic flow behavior for Ti-6Al-4V alloy during hot-working has been determined at various deformation temperatures and deformation rates by considering its hot-rolling in single or two phase region. The deformation mechanisms at elevated temperatures are also analyzed in correlation with its deformation activation energy. This research can provide guidance in designing processing parameters for hot-rolling of Ti-6Al-4V alloy.
Reliability Evaluation for Aerospace Anodizing Process of Aluminum
Authors: Torng Chau Chen , Huang Chi Kong , Chang Hsien Ming
Published: January 2010

Detail parts of airframe should have higher precision and lightweight to satisfy the requirements of safety, payload, and controllability. Due to requirement of lightweight, aluminum alloy is widely used in airframe parts. Anodizing process is an important surface treatment process uses to prevent corrosion in aluminum parts. Salt spray is the critical test to verify the anodizing process of aluminum alloy and ensure the corrosion resistance can meet the requirement of specification. This study collects the failure time of salt spray and uses statistical method to construct the suitable probability distribution of those failure data. Furthermore, analyzes the failure time of salt spray and evaluate the reliability of anodizing process. Thereby the process control engineer can use the concept of reliability to monitor the anodizing process.
Phase Constitution and Heat Treatment Behavior of Titanium-Manganese Alloys
Authors: Ikeda Masahiko , Ueda Masato , Matsunaga Ryuichi , Ogawa Michiharu , Niinomi Mitsuo
Published: January 2010

Although titanium is considered to be a ubiquitous element since it has the tenth highest Clarke number of all elements, it is classified as a rare metal because the current refinement process is more environmentally damaging than the processes used to refine iron and aluminum. Furthermore, the beta stabilizing elements of titanium alloys (e.g., V, Mo, Nb, and Ta) are very expensive due to their low crustal abundances. Manganese is also considered to be a ubiquitous element, since it has the 12th highest Clarke number of all elements. Therefore, manganese is a promising alloying element for titanium, especially as a beta-stabilizer. In order to develop beta titanium alloys as ubiquitous metallic materials, it is very important to investigate the properties of Ti-Mn alloys. In this study, the phase constitution of and the effect of heat treatment on Ti-3.3 to 8.7 mass% Mn alloys were investigated by electrical resistivity and Vickers hardness (HV) measurements and by X-ray diffraction (XRD) analysis and optical microscopy. In 3.3, 5.1, and 6.0 mass% Mn alloys quenched from 1173 K, ’ martensite and  phase were identified by XRD, whereas in the 8.7 mass% alloy, only the  phase was detected. The resistivities at both temperatures increased with increasing Mn content up to 6.0 mass% Mn and the positive temperature dependence of resistivity became negative at 6.0 mass% Mn. LN increased gradually with increasing Mn content up to 8.7 mass% Mn, whereasRT decreased considerably at a Mn content of 8.7 mass% Mn. HV increased with increasing Mn content up to 5.1 mass%, after which it began to decrease. In Ti-3.3 mass%Mn and 5.1 mass%Mn alloys, the resistivity and the resistivity ratio decreased with increasing temperature of isochronal heat treatment because of decomposition of ’ martensite. In 6.0Mn and 8.7Mn alloys, the resistivity and the resistivity ratio decreased, while Vickers hardness increased with increasing temperature of isochronal heat treatment because of isothermal  precipitation. Furthermore, the temperature for the onset of precipitation increased with higher Mn content.
New Multi-Material Design Concepts and High Integration Light Metal Applications for Lightweight Body Structures
Authors: Kopp Gundolf , Beeh Elmar
Published: January 2010

A major motivation for the development of new vehicle structures is, apart from the reduction of fuel consumption, is to decrease emissions which affect the climate.
Therefore we also have to look at the reduction of vehicle weight and consequently at various strategies for lightweight construction. In the future steel structure concepts still show lightweight potential. But even more attractive potential for lightweight body in white structures could be realised by new multi-material design concepts and highly integrated light metal applications.
Today’s research activities are focussed on the area of multi-material design, with the objective of placing the material with the best properties for the given requirements in the right position. Based on various methods of lightweight construction, techniques and tools, it is possible to find an optimum between lightweight design and costs.
These activities will be illustrated by several research examples. One example will be the lightweight concept of the front module developed by the Institute of Vehicle Concepts (DLR) in the European research project -‘Super Light Car’ (SLC). By using aluminium in the front structure and the high pressure die casting strut tower the concept has a weight benefit of 32% compared to a steel reference structure. The methodology for reaching targets and requirements like weight reduction, crash performance and cost targets will be explained. Another example is a concept which is developed in the DLR project ‘Novel Vehicle Structures’. This concept shows the combination of different materials and a new construction method to increase front impact crash performance.
Effect of ECAP on Al 6061 – FEA Approach
Authors: Nagaraj Shanmukha , Mamtha V. , Vinod M.S.
Published: January 2010

Equal Channel Angular Pressing (ECAP) is currently being widely investigated because of its potential to produce ultra-fine grained microstructures in metals and alloys. The objective of this work is to study the effect of ECAP on Al 6061 alloy. ECAP is processed using die channel angles of 90º, 120º and 140º. The stress and the deformation behavior of the ECAP processed material were investigated by hardness tests. The finite element analysis (FEA) is carried out for ECAP using PAM-CRASH software for different channel angles, which are prescribed in the experiment. The inputs such as material properties, loads, boundary conditions, contacts and controls were provided to the software and the results were visualized. The Von Mises Stress values obtained by FEA were found to be in good consistence with the experimental stress values.
Evaluation of the Heat Treatment Role for Light Aluminum Alloys Subjected to Creep and Low Cycle Fatigue
Authors: Rutecka A. , Dietrich L. , Kowalewski Zbigniew L.
Published: January 2010

The AlSi8Cu3 and AlSi7MgCu0.5 cast aluminium alloys of different composition and heat treatment were investigated to verify their applicability as cylinder heads in the car engines [1]. Creep tests under the step-increased stresses at different temperatures, and low cycle fatigue (LCF) tests for a range of strain amplitudes and temperatures were carried out. The results exhibit a significant influence of the heat treatment on the mechanical properties of the AlSi8Cu3 and AlSi7MgCu0.5. An interesting fact is that the properties strongly depend on the type of quenching. Lower creep resistance (higher strain rates) and lower stress response during fatigue tests were observed for the air quenched materials in comparison to those in the water quenched. Cyclic hardening/softening were also observed during the LCF tests due to the heat treatment applied. The mechanical properties determined during the tests can be used to identify new constitutive equations and to verify existing numerical models.
Effect of Cr and Zr Dopes on Hydrogen Behaviour in Rapidly Solidified Aluminium Foils
Authors: Tashlykova-Bushkevich Iya I. , Shikagawa Takahiro , Suzuki Takayoshi , Shepelevich Vasiliy G. , Itoh Goroh
Published: January 2010

Hydrogen (H) behaviour in materials was investigated in rapidly solidified (RS) foils of pure aluminium (Al), Al-0.4 Cr and Al-0.25 Zr alloys (at %) by means of thermal desorption spectroscopy (TDS). In addition, Al-0.25; 0.3 Zr alloys were examined with respect to microstructure and its instability during the thermal process using SEM and microhardness measurements. The effect of dopes and heating rate on H desorption was summarized. The lowest energy desorption is attributed with significant thermal desorption peak which temperature was found is correlated with sample composition.
Creep Strain Behavior in Transient Region and Minimum Creep Rate of Tempered Martensitic 9%Cr Steel
Authors: Abe Fujio
Published: January 2010

The effect of fine precipitates, excess dislocations and sub-boundary hardening on creep strain behavior in the transient region has been investigated for tempered martensitic 9%Cr steel at 600 and 650oC. The fine precipitates that form during tempering or during creep decrease the creep rate in the transient region, while excess dislocations produced by cold rolling promote the recovery of dislocations during creep, resulting in higher creep rates. The sub-boundary hardening is enhanced by fine precipitates along lath and block boundaries, which retards the onset of acceleration creep. The movement and annihilation process of dislocations in the transient region is controlled by not only the movement of dislocations in the matrix but also the absorption of dislocations at boundaries. The minimum creep rate is basically determined by the time to minimum creep rate.
Precipitate Behavior and Microstructure Characterization of An Al-Zn-Mg-Cu Alloy Prepared by Spray Forming Process
Authors: Zhu Bao Hong , Xiong Bai Qing , Zhang Yong An , Fritsching Udo , Zhang Ji Shan , Wang Feng , Li Zhi Hui , Liu Hong Wei
Published: January 2010

A high Zn content Al-Zn-Mg-Cu alloy was prepared by spray forming process and the precipitate behavior and microstructure of the extruded alloy were also investigated. The precipitate sequence of the spray-formed alloy could be described as “α-solid solution → GPI zone → GPII zone (also called Metastable ′ )→ Stable  (MgZn2)” during artificial ageing treatment. In the early stage of artificial ageing treatment, the GPI zone was the main strengthening phase and kept coherent relationship with the matrix. With the increasing of ageing time, ′ phase dominate strengthening phase and kept semi-coherent relationship with the matrix. With the further increasing of ageing time,  phase took the place of ′ phase, and dominated the strengthening phase in the alloy. The grain size of the spray deposit is finer than that of cast alloys. The ultimate tensile strength of the alloy is over 810MPa in peak ageing condition.
Mechanical Performance of Newly Developed Titanium and Zirconium System Alloys for Biomedical Applications
Authors: Akahori Toshikazu , Niinomi Mitsuo , Nakai Masaaki , Tsutsumi Harumi , Hattori Tomokazu , Fukui Hisao
Published: January 2010

A new -type Ti alloy composed of non-toxic and allergy-free elements like Nb, Ta, and Zr, Ti-29Nb-13Ta-4.6Zr alloy (TNTZ) proposed by present authors, has been developed in order to achieve relatively low Young’s modulus and excellent mechanical performance. On the other hand, Zr has been also paid attention as metallic biomaterial for the next generation because of good biocompatibility nearly equal to Ti or a few GPa smaller Young’s modulus as compared to one. In this study, mechanical performances such as tensile properties and Young's modulus of TNTZ subjected to thermo-mechanical treatments or severe deformation, and the mechanical properties and biocompatibility of Zr-Nb system alloys were investigated in order to judge their potential for biomedical applications.
Young’s modulus of as-solutionized TNTZ, which is around 63 GPa, is pretty similar to that of as-cold-rolled TNTZ. The Young’s moduli of hot-rolled Ti-6Al-4V ELI alloy are respective around 110 GPa. The Young’s moduli of as-solutionized and as-cold-rolled TNTZ are around a half of those, and are twice as large as that of the cortical bone. The tensile strengths of TNTZ aged after solution treatment and those aged after cold rolling decrease with an increase in the aging temperature, although the elongation shows the reverse trend. The tensile strength of as-cold-rolled TNTZ is improved drastically through severe deformation such as high pressure torsion and shows more than 1000 MPa.
Zr-XNb system alloy (X: 5-30mass%) shows the smallest value of Young’s modulus (around 58 GPa) at Nb content of 20mass%. In the case of implantation of the bars made of Zr-XNb system alloys into the lateral femoral condyles of Japanese white rabbits, the tendency of contact between the cancellous bone and the bar becomes remarkably at 24 weeks after the implantation according to increasing with Nb content.
Lamellar Surface Structures on Stainless Steel 316 LVM and their Influence on Osteoblastic Cells
Authors: Beck Ulrich , Elter Patrick , Lange Regina , Ewald Andrea
Published: January 2010

In this study, nanoscaled lamellar surface structures were prepared on medical stainless steel by chemical etching of the decomposed phases and their effect on the morphology of osteoblastic cells was investigated using Field Emission Scanning Electron Microscopy. Long filopodia were grown from the cells perpendicular to the lamellar structure while almost no or only short filopodia are formed parallel to the lamellae. The results are explained by a different surface roughness parallel and perpendicular to the lamellae: During the growth process of the filopodia a nearly flat surface is recognized parallel to the lamellae while a topographical change is sensed perpendicular to the structure, which is preferred by the cells.
Proliferation and Migration of Human Osteoblasts on Porous Three Dimensional Scaffolds
Authors: Bergemann Claudia , Klinkenberg Ernst Dieter , Lüthen Frank , Weidmann Arne , Lange Regina , Beck Ulrich , Bader Rainer , Schröder Karsten , Nebe Barbara
Published: January 2010

Porous tantalum (Ta) biomaterial is designed to function as a scaffold for osseous ingrowths and has found applications in orthopedics. Integration of this Ta foam into the neighboring bone requires that osteoprogenitor cells attach to the implant, grow into the scaffold, proliferate and differentiate to osteoblasts. The aim of the present study was to create an in vitro 3D model system to investigate the interaction of human osteoblasts with porous Ta in the depth of the corpus. To explore active migration of osteoblasts into the Ta scaffold two porous Ta discs (Zimmer, Poland) were horizontally fixed within a clamping ring. Thereby a 3D Ta module with 4 levels is generated, which is placed into a cell culture well with the appropriate medium. Osteoblast-like cells were seeded apical onto the Ta module and cultured for 7 days in humidified atmosphere. Active migration of cells into the scaffold was monitored by field emission scanning electron microscopy (FESEM) imaging of the apical, medial and basal layers. A problem in 3D cell culture is the nutrition of cells inside of the scaffold. Therefore morphological changes and differentiation of the cells in distinct layers were analyzed.
Haematological Performances of Carbon Coated PTFE by Plasma-Based Deposition
Authors: Boccafoschi Francesca , Chevallier P. , Sarkissian A. , Mantovani Diego
Published: January 2010

Materials in contact with tissue and biological fluids affect cell reaction that could eventually lead to clinical complications (i.e. thrombosis, restenosis). Improving the biological performances of the materials used for biomedical applications is the main goal of this study. In particular, cardiovascular devices require excellent haemo- and biocompatibility properties. PTFE is currently the main material used for vascular prostheses. After long contact periods with blood, clinical complications leading to thrombosis and restenosis are often reported. Improving the haematological performances of PTFE could significantly increase its life-time and decrease long-term complications. However, inadequately engineered surfaces could trigger the coagulation cascade with the formation of a clot, the first step towards a thrombosis. Plasma carbon-based coatings with varying nitrogen contents deposited on PTFE have been studied as promising coating to improve the haematological performances of PTFE implants. In this work, several techniques were applied to study the viscoelastic properties of blood after contact with virgin and treated PTFE as well as the presence and the clot morphology eventually formed onto the surfaces. The chemical composition of the surfaces was analysed with XPS and FTIR.
Numerical Simulations of the Global Behaviour of Implant Supported or Retained Dental Prostheses
Authors: Bonnet Anne Sophie , Daas Marwan , Postaire Michel , Lipiński Paul
Published: January 2010

In spite of the recent efforts concerning prevention and treatment of dental diseases, total edentulism remains an important world health problem, even in industrialized countries. Different solutions to mandibular total edentulism are available from the classical removable denture to the implant supported prostheses. The aim of the present work is to compare, through finite element simulations, two distinct types of prosthetic solutions. The first one is an implant-supported prosthesis (ISP) using a “All-On-Four” base and the second one is a mandibular implant-retained overdenture (IRO) using two implants. A foodstuff situated on molar is modelled to simulate the mastication force. An orthotropic behaviour is assumed inside the symphyseal area. The results of the simulations show a strong influence of the prosthetic solution type on the stress and strain repartition in the implant and peri-implant bone. This can be explained by the difference of load transfer to bone between those two configurations. Indeed, in the implant-supported prosthesis, the totality of the mastication force is directly transmitted to peri-implant bone whereas the implant-retained solution benefits from a large participation of mucosa to the global load transfer from overdenture to bone.
Polymer Surface Processing by Atmospheric Pressure DBD for Post-Discharge Grafting of Washing-Resistant Functional Coatings
Authors: Borra Jean Pascal , Valt A. , Arefi-Khonsari Farzaneh , Tatoulian Michael
Published: January 2010

We present a process for rapid post-discharge deposition of liquid monomer to form functional coatings at atmospheric pressure. The post-discharge polymerization of dense polyacid and polyether coatings is first depicted versus the energy density deposited by the preliminary surface treatment of polyethylene and polystyrene substrates in air Dielectric Barrier Discharge (DBD) with respect to SEM, to XPS and FTIR-ATR analysis and to polymerization yield determined by mass measurements. The paper focuses on the effect of the filamentary air DBD on surface of the polymer substrates and on post-discharge polymerization mechanism. Indeed, the grafting yield is shown to depend on the energy density deposited by DBD and on the time exposure to air between DBD and monomer deposition, controlling respectively the surface density of radicals and labile peroxides, both triggering the polymerization of vinyl precursors. Then, the effect of deposition conditions on the polymerization yield and related thickness of the functional polymer coatings is shown and special attention is paid to the stability of the coating upon washing.
Crack Detection by Wavelet-Based Acoustic Emission Test In Vitro Cemented Implant
Authors: Dias Gueiral Nuno Eduardo , da Silva Marques Nogueira Elisabete Maria , Ramos António Manuel
Published: January 2010

One the mechanisms of failure in total hip arthroplasty in cemented prosthesis is cement fatigue. The main objective of this work is to use Acoustic Emission (AE) as a non-destructive and non-intrusive monitoring test in a cemented prosthesis. The femoral component was sinusoidally loading in a fatigue machine. Experimental data collected during acoustic emission test was treated and analysed by Wavelet Transform and allowed to locate a crack in cement mantle of femoral component.
Other complementary diagnostic tests were used to confirm the existence of a fault (crack). One of them was penetrating liquids in different cut sections of femoral component. The other one was microscopic analysis that allowed observing the existence of a crack which location is pointed out by the results of AE answer.
The AE sources locations are situated inside the crack observed in the optical microscope.
The Wavelet Transform (WT) AE signals demonstrated the accuracy of damage location in bone cement and thus becoming useful in other orthopedics studies.
Development of Titanium-Calcium Alloy Resistant to Aqueous Fluoride Solutions
Authors: Haruna Takumi , Shinohara Itsuki
Published: January 2010

It has been tried to develop Ti-Ca alloys which demonstrates corrosion resistance in an aqueous fluoride solutions. The Ti-Ca alloys were produced by diffusion-metallizing method. A Ti plate and Ca grains were put in a sealed container of stainless steel. As the container was heated at 1000 oC, Ca was melted and partially vaporized in the inner space. Ca then contacts and permeats into the Ti plate to metallize. In a holding time of 450 h, the alloy surface consisted of two layers, the first was oxide layer and the second was metal layer of about 200 m thick. A Vickers micro hardness of the second layer was quite large, upto about 600 Hv. Evaluation of corrosion resistance for the second layer and the inner part was carried out by electrochemical potentiokinetic method. Test solutions were aqueous fluoride solutions produced with HF and NaF. A concentration of fluoride ion was fixed to 0.024 kmol m-3, and pH of the solution was varied from 3.4 to 4.7. As a result, both Ti and Ti-Ca alloy were passivated under natural immersion condition in the solution of pH 4.7. At pH 3.4, on the other hand, Ti was actively dissolved, but Ti-Ca alloy was still passivated, that means Ti-Ca alloy performs much better corrosion resistance than Ti.
Bone Regeneration Based on Orientation of Biological Apatite (BAp) C-Axis in Osteopetrotic (op/op) Mice
Authors: Lee Jee Wook , Kawahara Keita , Nakano Takayoshi
Published: January 2010

The diagnosis of hard tissues is generally carried out by bone mineral density (BMD) measurement as a bone quantity parameter. BMD, however, does not necessarily explain bone fracture risks in some clinical cases. Recently, various parameters relating to bone strength have been investigated. These additional parameters, so-called bone quality, reflect intrinsic bone conditions. We have been studying the preferential alignment of the biological apatite (BAp) c-axis among various bone quality parameters. BAp, a dominant component of hard tissue, is an ionic crystal that crystallizes in a hexagonal lattice accompanied with the anisotropic property.
In this article, we investigated the osteoclast role in the recovery process of BAp orientation during bone regeneration using osteopetrotic (op/op) mice in which the number of osteoclasts decreases. A surgically drilled, 500-μm diameter hole on each tibia of both control and op/op 8-week-old mice was introduced from the medial surface into the medullary cavity located at a 30% length from the proximal tibia end. After surgery, tibiae injuries were regularly observed by in situ micro-CT, and then the mice were sacrificed four to eight weeks after surgery. BAp orientation was analyzed in and near the regenerated portion by the microbeam X-ray diffraction system. As a result, we found the insufficient recovery of BAp orientation in spite of the apparent repair of bone appearance and quantity from CT images, even eight weeks after surgery in both cases of control and op/op mice. We conclude that this defective animal model can be used to evaluate bone quantity and quality at the cortical portion during bone regeneration in gene-defect mice in which the expression of bone cells is controlled, for example.
Neutron Diffraction Residual Stress Evaluation and Numerical Modeling of Coating Obtained by PTA Process
Authors: Nady Abdeljalil , Bonnefoy Herve , Klosek Vincent , Mathon Marie Helene , Lodini Alain
Published: January 2010

The Stellite 6 hardfacing alloys have been deposited on steel substrate using a Plasma Transferred Arc (PTA) with complex geometry. The residual strain of the PTA technology at the surface of coating layer and the interface were determined by neutron diffraction method. In the present work, a numerical model for the residual stresses formed during the PTA process with physical conditions and mechanical properties using the Abaqus code is analysed. The result reveals that the residual stresses obtained by the numerical simulation are in very good agreement with experimental results by the neutron diffraction.
Methods for Filling Hollow Structures with Aluminium Foam
Authors: Baumeister Joachim
Published: January 2010

Aluminium foams produced according to the powder metallurgical/foaming agent process are currently being used in several industrial sectors, such as automotive, rail transport or machine tools. Nevertheless there still is a high further application potential to be exploited. Especially in hybrid structures, e.g. in automotive structures that are locally filled with aluminium foam, great improvements regarding the energy absorption capacity and the sound absorption behaviour can be obtained.
In the present paper several methods that allow for filling or local filling of hollow structures are investigated and presented. The effect of the foam filling on the energy absorption behaviour of the hybrid structure is discussed. Similar effects were also observed in compression tests on foam filled hollow profiles. The results of these investigations are presented.
Coarse Grain Modeling for Microtubule Mechanics
Authors: Deriu Marco A. , Soncini Monica , Bidone Tamara C. , Redaelli Alberto , Montevecchi Franco Maria
Published: January 2010

Microtubules (MTs) are cellular supramolecular structures that, in combination with actin and intermediate filaments, form the cell cytoskeleton. Within cytoskeleton filaments, MTs exhibit the highest bending stiffness. Up today, experimental techniques have not been able to investigate the origin of MTs flexural rigidity, despite the many experimental efforts done to estimate MT mechanical properties. Molecular Dynamic (MD) and Normal mode Analysis (NMA) show the potentiality for getting insight into this topic. However, these standard molecular modelling techniques are not yet able to simulate large molecular structures as MTs. In this work we developed a multiscale Coarse Grain (CG) model of an entire MT up to 180 nm long, by integrating information from MD and NMA molecular modelling. In particular, MD models were used to obtain information about the molecular conformation and arrangement of the tubulin dimers inside the MT lattice structure and Normal Mode Analysis (NMA) was used in order to study the mechanical behaviour of a MT modelled as an elastic network. MT macroscopic properties, such as bending stiffness (kf), bending modulus (Yf), stretching modulus (Ys), and persistence length (lp) were calculated on the basis of the bending and stretching modes, and results were directly compared to experimental data. Starting from the stretching modes calculated for MTs with lengths up to 180 nm, we found a non-length dependent Ys of about 0.5 GPa, which is in the range of the experimental values (Ys~0.1-2.5 GPa), and a Yb in the range of 0.13-0.35 GPa depending on MT length. These results strongly confirm the anisotropy of the MT mechanical properties.