bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Properties of a Metal Sandwich Panel Manufactured Using Longitudinally Laminated Forming Tools
Authors: Järvenpää Antti , Lämsä Janne , Hietala Mikko , Mäntyjärvi Kari
Published: May 2014

Sandwich panel structures are increasingly used in applications where the most important demands are the weight saving and long service life. Utilizing sandwich panels, extremely light-weight, stiff and robust structures can be manufactured. In this study, sandwich panels were produced by specially designed cost-effective forming tools. Various kind of test materials were used for corrugated cores and skin plates: conventional low-carbon steel grade EN 10130 and ferritic stainless steel grade 1.4509 with plate thicknesses of 0.6 and 0.75 mm. A common S355 structural steel was used as a reference for bending strength comparison.For measuring the stiffness, MTS tensile and fatigue testing machine was selected to determine the bending resistance of the sandwich panels. The bending force, needed for yielding and fracture, related to the bending length and intensity was compared with the results from bending of the reference plates. Results showed that the bending force of the panels is significantly higher than that of a plate having similar intensity. The best results were obtained with the stainless steel (SS) panel that had 27% higher bending force at the yield point than 5 mm thick S355 plate having 3 times larger intensity. The carbon steel panel was approximately 40% weaker than the SS-panel and both panel types lost strength when loading direction was changed from transverse to 45 degree and further to 90 degree load (longitudinal).
Improvement in Ductility in Commercially Pure Titanium Alloys by Stress Relaxation at Room Temperature
Authors: Eipert Irena , Sivaswamy Giribaskar , Bhattacharya Rahul , Amir Muhammad , Blackwell Paul
Published: May 2014

Present work focusses on the effect of stress relaxation on the tensile behaviour of two commercially pure titanium alloys of different strength levels (Grade 1 and Grade 4) subjected to tensile tests at room temperature. The stress relaxation tests were performed by interrupting the tensile tests at regular strain intervals of 5% in the plastic region of the tensile curve and compared to the monotonic tensile tests at different strain rates ranging from 10-4 to 10-1s-1. To understand the effect of anisotropy, samples were taken along 0° and 90° to rolling direction (RD) for both the alloys. Improvement in ductility of different levels at all the strain rates was observed in both the alloys when stress relaxation steps were introduced as compared to monotonic tests. However there is not much change in the flow stress as well as in strain hardening behaviour of the alloys. The true stress-true strain curves of Grade 4 samples taken in 90° to RD exhibited discontinuous yielding phenomenon after the yield point, which is termed as a yield-point elongation (YPE). The improvement in ductility of the Cp-Ti alloys can be linked to recovery process occurring during the stress relaxation steps which resulted in the improvement in ductility after repeated interrupted tensile tests. The paper presents and summarise the results based on the stress relaxation for the two different alloys.
High Stability of Temperature Control Using Vacuum Insulated Wall for Gauge Block Measurement
Authors: Ranusawud Monludee , Limsuwan Pichet , Vatcharanukul Ketsaya , Somthong Thammarat
Published: May 2014

The temperature has a critical effect on long gauge block measurement by interferometry. To reduce this effect, we developed a vacuum insulated wall for long gauge block measurement system. The long gauge block chamber has the dimension of 1.2 m x 2 m. The vacuum insulating walls are mainly composed of 8-mm and 10-mm thick Aluminum plates as the chamber walls and a rotary pump. Using this technique, the vacuum insulator is treated to have the pressure of 0.9 mbar. This technique can reduce heat transfer from outside environment to the chamber due to low heat conductivity of the system. The temperature stability of the chamber had been continuously investigated using 5 Pt100 probes and their temperature stability are below 15 mK at 17 OC, 20 OC and 23 OC
Revision of the SI: The Determination of the Avogadro Constant as the Base for the Kilogram
Authors: Nicolaus Arnold , Bettin Horst , Borys Michael , Kuetgens Ulrich , Pramann Axel
Published: May 2014

At least four units of the International System of Units (SI) are on the way to a new definition. Especially for the unit of mass, the kilogram, a rigorous change is considered. Instead of the current definition, a 1kg-artifact in form of a Pt-Ir-cylinder, the intended formulation relates the unit of mass to a fundamental constant. In detail this requires in a first step a measurement of the chosen fundamental constant with contemporary lowest uncertainty and best reproducibility. The constant will then be fixed to that value. As an example the metre is related to the fixed constant speed of light.For the kg there are considered two ways: one is a watt balance, which determines the mass in units of the Planck constant, h. While at present the watt balances show a heterogeneous appearance, the second class of experiment the determination of the Avogadro constant, NA, which measures the mass in terms of the number of elementary entities has reached a considerable level of uncertainty and reproducibility. The fundament of the new determination of the Avogadro constant is a highly enriched 28Si crystal. The different working groups of the Avogadro team determine molar mass and lattice parameter of the crystal, and mass and volume of two precision spheres made from different positions, but of the same crystal. All measurements are carried out for both spheres and all measurement quantities are determined at least from two independent working groups, usually of different countries.
Multi-Agent Based Chaotic Traffic Simulation for Cairo Ring Road
Authors: Hussein Sherif E. , Zahwi Sarwat
Published: May 2014

Transportation simulations are an important part of today’s decision making process for transport infrastructure and management. While proposed changes are getting more and more complex, tools supporting the decision making process are struggling to keep up. Traditional, flow-based traffic assignment tools are limited in the number of different person groups that can be distinguished and do in most cases not offer fully time-dynamic results. Newer technologies like agent-based simulations overcome those problems. This paper presents a novel traffic simulation scheme capable of modeling chaotic motorway traffic. Different from other lane-based or following-based approaches, the proposed approach models traffic as a large navigational problem in an agent based simulation context. In addition, the approach is efficiently able to handle hard cases like overtaking, behavior at turning and aggressive driving behavior. The simulation was demonstrated at real-time rates using MATSim applied to Cairo Ring Road. It has been described as well how MATSim simulation was extended to incorporate aggressive and careless drivers' behavior.
Orthogonality Measurement of Cross-Grating Based on Image Processing of Multi-Order Diffraction Patterns
Authors: Hu Yao , Wang Nan Fen
Published: May 2014

Cross-gratings or two-dimensional gratings have found applications in precision displacement measurement for nanoscale machine tools or mask-wafer alignment in photo-lithography. The orthogonality of displacement measurement or alignment in two perpendicular directions is assured by the orthogonality of the grating grooves. Once the grooves are not exactly normal to each other, it should be calibrated before measurement or alignment to guarantee the accuracy. Scanning probe microscopy (SPM) and optical diffractometry (OD) are commonly used for highly accurate calibration of cross-grating orthogonality. In this paper, two methods based on diffraction are proposed for middle accuracy measurement at relative higher speed. At first, we briefly explain the configuration of each method. The calibration results of cross-gratings are shown. We also discuss the results of uncertainty analysis and the cause of main uncertainty sources.
Impact Toughness of 0.3 Mass% Carbon Tempered Martensitic Steels Evaluated by Instrumented Charpy Test
Authors: Takebayashi Shigeto , Ushioda Kohsaku , Yoshinaga Naoki , Ogata Shigenobu
Published: May 2014

The effect of tempering temperature on the impact toughness of 0.3 mass% carbon martensitic steels with prior austenite grain (PAG) size of about 6 μm and 30 μm were investigated. Instrumented Charpy impact test (ICIT) method was used to evaluate the impact toughness. The tempering temperature of 723K gives the largest difference in the Charpy impact energy at room temperature (RT) between the specimens with two different PAG sizes. Investigation of the test temperature dependence of Charpy impact energy in the 723K tempered steels shows a steep transition at around 200 K for the 6 μm PAG specimen, while it shows a continuous slow transition in a wide range of temperature for the 60 μm PAG specimen. ICIT waveform analysis shows that the fracture propagation energy in stead of the fracture initiation energy mainly controls the temperature dependence of the impact energy. The carbide size distribution in these two specimens was investigated by SEM and TEM. The 60 μm PAG specimen shows the distribution of coarser carbides than does the 6 μm PAG specimen, which seems to be the main reason for the observed difference between them in the Charpy impact energy and the other properties of impact fracture.
Experimental Study on the Formation of Non-Metallic Inclusions Acting as Nuclei for Acicular Ferrite in HSLA Steels through Specific Deoxidation Practice and Defined Cooling Conditions
Authors: Michelic Susanne K. , Loder Denise , Arth Gregor , Bernhard Christian
Published: May 2014

Specific types of non-metallic inclusions are known to act as heterogeneous nuclei for the formation of acicular ferrite, which provides excellent toughness. By increasing the amount of acicular ferrite in the microstructure, the properties of HSLA steels can be optimized significantly.Although the formation of acicular ferrite caused by heat treatments (thermomechanical treatments or welding) is quite well described in literature, there is less information to find about the formation of acicular ferrite immediately out of the liquid melt. Within the present study experiments on laboratory scale are carried out simulating the influence of cooling conditions and Ti-content on size, chemical composition and morphology of non-metallic inclusions and consequently on the amount of acicular ferrite. All experiments were carried out with a dipping test simulator enabling very well controllable cooling conditions. Optical microscopy in combination with special etching methods as well as SEM/EDS-analysis was used for microstructure and inclusion characterization.
Investigation of Plastic Instability in TWIP Steels by In Situ Diffraction of High Energy X-Rays
Authors: Chateau-Cornu Jean Philippe , Jacques Alain , Tinnes Jean Philippe , Schenk Thomas
Published: May 2014

We investigate the non uniform plastic deformation of a TWIP FeMnC steel by diffraction of high energy synchrotron X-rays. In particular, we observe the propagation of bands of plastic strain localisation. Debye-Scherrer rings are recorded in situ during tensile tests at two different strain rates. Discontinuous initial rings characteristic of unstrained polycristals with no texture become rapidly continuous after several percents of plastic strain due to strain gradients within the grains and a strong texture develops. The crystallographic dependence of the Young’s modulus is estimated and is consistent with the elastic anisotropy of a cubic crystal. A delay between the serrations on the macroscopic tensile curve and the stepwise variations of the diffracted peak’s position and width are consistent with propagating bands nucleating outside the X-ray beam. Slower and thinner bands are observed at the lowest strain rate. A tensile test interrupted to perform a few minute relaxation leads to a displacement of the nucleation site of the bands from one end to the middle of the gauge part.
Microstructure and Mechanical Properties of NbSi2/MoSi2 Crystals with Lamellar Structure
Authors: Hagihara Koji , Hama Yoichiro , Fushiki Tatsuya , Yuge Koretaka , Nakano Takayoshi
Published: May 2014

NbSi2/MoSi2 duplex silicide crystals are potentially a new-class of ultra-high temperature structural materials. Improvement in the thermal stability of their lamellar microstructure was accomplished by the addition of a minute amount of either Cr or Zr. The mechanical properties of the duplex silicide, such as fracture toughness and high temperature strength, show strong orientation dependence, thereby suggesting the importance of the control of microstructure to improve their properties.
High Temperature Compression Properties of Ni3(Si,Ti) Based Intermetallic Compounds
Authors: Hagisawa Takehito , Madarame Hirokazu , Tanaka Shinji , Kaneno Yasuyuki , Takasugi Takayuki
Published: May 2014

High temperature compression properties of Al-, Cr-or Nb-added Ni3(Si,Ti) based intermetallic compounds were investigated by uni-axial compression test and microstructural observation. The Al-or Cr-added Ni3(Si,Ti) alloys after homogenization heat treatment exhibited a two-phase microstructure consisting of L12 and Ni-solid solution phases. The Nb-added Ni3(Si,Ti) alloy after homogenization heat treatment exhibited a triple-phase microstructure consisting of G-phase with D8a structure and Ni-solid solution phase in the L12 matrix. The volume fraction of Ni-solid solution phase increased in order of Cr-, Nb-and Al-added Ni3(Si,Ti) alloys. The Cr-added Ni3(Si,Ti) alloy was deformable at high strain rate, while the Nb-added one was deformable at low strain rate. It can be considered that the deformability of Ni3(Si,Ti) at high temperature is closely correlated with volume fraction of Ni-solid solution phase and recrystallization behavior.
Phase Equilibrium between B2 Aluminide NiAl and Nb-Mo bcc Solid Solution Phase
Authors: Miura Seiji , Sekito Yoshihito , Okawa Takuya , Yamanouchi Takuya , Mohri Tetsuo
Published: May 2014

In order to understand the composition of the Nb-Mo bcc phase suitable to introduce B2-NiAl phase for the improvement of oxidation resistance as an Al reservoir layer for maintaining Al2O3 surface layer, a NiAl-Nb-Mo section of the quaternary Al-Nb-Ni-Mo phase diagram is studied. It is found that the ternary τ2 phase appears in wide composition range of alloys, both the hardness and cracking tendency decreases with increasing the Mo concentration of the alloys.
Effects of Alloying Elements on Physical and Mechanical Properties of Co-Al-W-Based L12/fcc Two-Phase Alloys
Authors: Tanaka Katsushi , Inui Haruyuki
Published: May 2014

The changes in the γ’ solvus temperature and the volume fraction of Co-Al-W based alloys with fcc / L12 two-phase microstructures upon alloying with quaternary elements have been investigated. All investigated quaternary elements, except for Fe and Re, increase the γ’ solvus temperatures of Co-Al-W based alloys with varying efficiencies depending on quaternary element. On the other hand, the variation of the γ’ volume fraction with alloying depends on the alloying element. Of the investigated quaternary elements, Ta is found to be the most effective in increasing the γ’ solvus temperature of Co-Al-W based alloys. The lattice mismatch significantly increase upon alloying with Ta of 4at.%, which destroys the coherent cuboidal structure.
A Material Genomic Design of Advanced High Performance, Non-Corroding Steels for Ambient and High Temperature Applications
Authors: Lu Qi , Xu Wei , van der Zwaag Sybrand
Published: May 2014

This work presents an artificial intelligence based design of a series of novel advanced high performance steels for ambient and high temperature applications, following the principle of the materials genome initiative, using an integrated thermodynamics/kinetics based model in combination with a genetic algorithm optimization routine. Novel steel compositions and associated key heat treatment parameters are designed both for applications at the room temperature (ultra-high strength maraging stainless steel) and at high temperatures (ferritic, martensitic and austenitic creep resistant steels). The strength of existing high end alloys of aforementioned four types are calculated according to the corresponding design criteria. The model validation studies suggest that the newly designed alloys have great potential in outperforming existing grades.
Mechanical and Biological Biocompatibilityof Novel β-Type Ti-Mn Alloys for Biomedical Applications
Authors: Cho Ken , Niinomi Mitsuo , Nakai Masaaki , Hieda Junko , Santos Pedro Fernandes , Itoh Yoshinori , Hattori Tomokazu , Ikeda Masahiko
Published: May 2014

Mechanical biocompatibility, including tensile properties and Young’s modulus, of -type Ti-Mn alloys,namely, Ti-10Mn and Ti-14Mn, fabricated by the metal injection molding method were investigated. Thebone formability (biological biocompatibility) of a Ti-Mn alloy, namely, Ti-12Mn, fabricated by thearc-melting method was evaluated by means of an animal test. The tensile strength of sintered Ti-10Mn andTi-14Mn achieve a maximum value of 860 and 886 MPa, respectively. The Ti-14Mn specimen sintered at1273 K shows the lowest Young’s modulus (76 GPa) among all sintered Ti-10Mn and Ti-14Mn specimens.The tensile strength of Ti-Mn alloys is almost equal to that of Ti64 ELI; further, their Young’s modulus islower than that of Ti-6Al-4V ELI. The relative bone contact ratio of Ti-12Mn increases from 11% to 29%with increasing implantation time from 12 weeks to 52 weeks. Moreover, the relative bone contact ratio ofTi-12Mn and CP-Ti is almost constant for all implantation times.
Finite Element Simulation of Diffusion and Precipitation with Application to Internal Oxidation of Ni-Xwt%Cr Alloys at 950°C
Authors: Feulvarch Eric
Published: May 2014

For the simulation of internal oxidation phenomena, different numerical approaches are proposed in the literature based on 1D finite differences or on explicit time integration schemes which need small time-steps leading to very long computation times. The aim of this paper is to detail a multi-dimentional finite element approach which is coupled with an efficient implicit time integration algorithm. The thermodynamic activities and the total mass fractions are both used as principal nodal variables. The use of finite elements rather than finite differences greatly facilitates the meshing of 2D and 3D bodies. Its implicit time-integration allows using much larger time-steps without any degradation of the results. An application is proposed for the modeling of internal oxidation of chromia for Ni-Xwt%Cr alloys at 950°C by considering the barrier effect of precipitates.
Analysis of Osteocyte Morphology in Terms of Sensation of In Vivo Stress Applied on Bone
Authors: Ishimoto Takuya , Kawahara Keita , Matsugaki Aira , Wang Jun , Kamioka Hiroshi , Nakano Takayoshi
Published: May 2014

Most bones are anisotropically loaded and seem to be adapted to the anisotropic stress or strain field by changing the anisotropy in their microstructure. Osteocyte (OCY) is believed to play an important role as a mechanosensor and regulator of modeling and/or remodeling orchestrating osteoblast and osteoclast activity to make bone suitable to resist the mechanical environment. In general, osteocytes sense magnitude of stress (strain) applied upon the bone and then work as a trigger to change bone mass to adjust bone’s mechanical function to the stress field. This structural optimization is an important aspect of the bone functional adaptation; another inevitable optimization might be achieved through the change in intrinsic material anisotropy including the preferential c-axis orientation of biological apatite (BAp) crystal. To achieve this adaptation through material anisotropy, osteocyte needs to be a mechanosensor which can detect anisotropic stress field. In the present study, osteocyte lacunae and canaliculi in the mid-diaphysis and the distal part of the rat femur were stained by a fluorescein dye for visualization and analysis. The mid-diaphysis shows greater degree of the preferential c-axis orientation of BAp crystal than the distal part in relation to the magnitude of uni-axial stress field. It was found that the osteocytes in long bone preferentially align along the bone long axis and the degree of alignment is greater in the mid-diaphysis than in the distal region, which seems to be effective for the sensation of the site-dependent specific stress field applied on the long bone.
Challenges and Opportunities in Electrochemically Coating Calcium Phosphate on Magnesium Alloys for Biodegradable Implant Applications
Authors: Kannan Mathan Bobby
Published: May 2014

Magnesium alloys are attractive for use as biodegradable materials for temporary implant applications. However, the high localized degradation of magnesium alloys in physiological conditions is a major concern, which can affect the mechanical integrity of the implant during service. Calcium phosphate (CaP) coating is a suitable method to delay the initiation of localized attack in magnesium alloys. This paper will discuss the challenges and opportunities in electrochemically coating CaP on magnesium and its magnesium alloys for biodegradable implant applications.
Effect of Phase Stability on Some Physical and Mechanical Properties in β-Ti Single Crystal for Biomedical Applications
Authors: Todai Mitsuharu , Wang Pan , Fukunaga Keisuke , Nakano Takayoshi
Published: May 2014

The electron-atom ratio (e/a) dependence of the appearance of the lattice modulation and physical properties in β-phase Ti-xNb alloys (x = 28, 30, 34 and 40) were investigated by using some physical properties measurements, compressive test and transmission electron microscope observations (TEM observations), focusing on the β-phase stability. The microstructure, physical properties, deformation mode depend on the e/a ratio which is closely related to the β-phase stability in Ti-Nb alloys. The e/a ratio is defined by the average electrons per atom in free atom configuration. Athermal ω-phase is suppressed in Ti-30Nb alloy single crystal with low e/a ratio. The Ti-30Nb alloy single crystal also exhibits a lattice modulation and low Debye temperature. These results imply that the β-phase stability in β-phase Ti alloys decreases with decreasing the e/a ratio and are related to the softening of elastic stiffness, c′. Consequently, a decrease in the e/a ratio leads to the softening of c′ and a significant reduction in modulus along the [100] direction in β-phase Ti alloys single crystal. In fact, the Young’s modulus along [100] of the Ti-15Mo-5Zr-3Al alloy (wt.%) single crystal with low e/a ratio exhibits as low as 45 GPa, which is comparable to that the human cortical bone. That is, controlling the e/a ratio is an ultimate strategy to develop the future superior biocompatible implant materials with extremely low Young’s modulus and good deformability.
Comparison of Various Electroless Nickel Coatings on Steel: Structure, Hardness and Abrasion Resistance
Authors: Vitry Véronique , Sens Adeline , Delaunois Fabienne
Published: May 2014

Several electroless nickel deposits, on steel substrate, of varying chemistry were investigated in the as-plated and heat-treated condition: 3 nickel-phosphorous (low, mid and high P) and 2 nickel-boron (nickel-boron (lead) and nickel-boron (thallium)). Samples were characterized by SEM and X-ray diffraction. They were then submitted to Knoops microhardness testing and Taber abrasion tests, with abrasive CS-10 wheels, as well as scratch testing to investigate their mechanical properties and wear resistance. Hardness and wear resistance of all deposits were improved by heat treatment, but the best candidate was the Nickel-boron (lead), with a hardness over 1100 hk50 after heat treatment and a Taber Wear Index of 6. Scratch testing allowed identifying the damage mechanisms of the coated systems.
An Investigation into Double Oxide Film Defects in Aluminium Alloys
Authors: Griffiths William D. , Caden A.J. , El-Sayed M.A.
Published: May 2014

When the oxidised surface of a liquid metal is folded over onto itself and entrained double oxide film defects are formed, which form crevices or cracks in the solidified casting, of varying sizes and orientations. These defects not only reduce mechanical properties, but also increase the scatter of properties. This paper reports an analog experiment to study the behavior of the interior atmosphere of double oxide film defects in Al alloy melts of varying Mg content. Air bubbles were trapped in melts of liquid Al alloy which were then solidified after holding for varying periods of time. The composition of the bubbles was subsequently measured using mass spectroscopy. This showed the reaction of oxygen from the bubble atmosphere to form oxides, followed by the consumption of nitrogen to form AlN. Simultaneously, hydrogen from the melt diffused into the air bubble. The changes in composition were used to estimate the rate of change in composition of the interior atmosphere of a typical double oxide film defect of an estimated size. This suggested that double oxide film defects may quickly achieve an interior atmosphere that would consist of a mixture of mainly nitrogen and hydrogen, and that this atmosphere could exist for periods of time greater than the typical solidification times of light alloy castings. In other words, oxide film defects created during mould filling should persist into the solidified casting. In addition, SEM analysis of oxide film defects also suggested the presence of oxide whiskers, which seem to have formed during holding in the melt.
Silica-Containing Hybrid Nanocomposite "Melting Gels"
Authors: Klein Lisa C. , McClarren B. , Jitianu Andrei
Published: May 2014

Hybrid organic-inorganic nanocomposites can be prepared by the sol-gel process. An attribute of the sol-gel process is that organic and inorganic components can be linked together on the nanoscale through chemical reactions at room temperature. Functionalized siloxanes can be mixed and reacted to form nanocomposites with a wide range of mechanical, optical and dielectric properties.
Development of Microtextured Photocatalytic Surface by Vibration-Assisted Scratching
Authors: Shimizu Jun , Yamamoto Takeyuki , Zhou Li Bo , Onuki Teppei , Ojima Hirotaka
Published: May 2014

It is known that the TiO2 has some photocatalytic functions, even though they are relatively weak and their further enhancements are necessary for wider practical usages. On the other hand, improving materials surface functions by introducing microtextures is of great interest in various fields. Under such circumstances, the present study is aiming at developing a high-functional photocatalytic surface by earning the real surface area and reducing the light reflection and so on with the support of microtexturing technique. In this work, a pure Ti plate surface, which was covered with numerous micro impressions and micro pile-ups formed by the vibration-assisted microscratching, was anodized in order to obtain a regularly microtextured TiO2 film on the uppermost surface of Ti plate, and its wettabilty was evaluated in order to investigate its potential as the photocatalyst. As a result, it was found that the wettability of the TiO2 film surface regularly microtextured by the vibration-assisted microscratching was superior to those of the mirror finished one under the irradiation environment by the ultraviolet rays.
Development Status, Applications and Perspectives of Advanced Intermetallic Titanium Aluminides
Authors: Clemens Helmut , Mayer Svea
Published: May 2014

After almost three decades of intensive fundamental research and development activities, intermetallic titanium aluminides based on the ordered γ-TiAl phase have found applications in aircraft and automotive engine industry. The advantages of this class of innovative high-temperature materials are their low density and their good strength and creep properties up to 750°C as well as their good oxidation and burn resistance. Advanced TiAl alloys are complex multi-phase alloys which can be processed by ingot or powder metallurgy as well as precision casting methods. Each process leads to specific microstructures which can be altered and optimized by thermo-mechanical processing and/or subsequent heat treatments. The background of these heat treatments is at least twofold, i.e. concurrent increase of ductility at room temperature and creep strength at elevated temperature.
Influence of Laser Process on Mechanical Behavior during Cutting of Carbon Fiber Reinforced Plastic Composites
Authors: Harada Yoshihisa , Muramatsu Mayu , Suzuki Takayuki , Nishino Michiteru , Niino Hiroyuki
Published: May 2014

Carbon fiber-reinforced plastics (CFRP) composite is most attractive materials to reduce the weight of transportations. To increase the production volume and the efficiency in the field of CFRP component, fast, highly precise and cost-efficient technologies are required. Although laser cutting meets these requirements, it is not used because of insufficient knowledge about the effect of thermal damage on the material behavior. In this study, the effect of several cutting processes on the static tensile strength and the fatigue strength was evaluated for CFRP consisting of thermoset resin matrix and carbon fibers. The CFRP was cut using two different-type of lasers; a CO2 gas laser and single-mode fiber lasers, and a conventional mechanical tool. The mechanical cutting specimen produced a cut of high quality. While, the laser cutting specimens clearly showed a heat-affected zone (HAZ). The static tensile strength and the fatigue strength by laser cutting specimens clearly decreased in comparison with mechanical cutting specimen. The laser cutting specimen exhibited a linear dependency of the tensile strength on the HAZ, indicating that the main effect resulted from thermal destruction of CFRP within the HAZ.
Ultrasonic Degassing of Aluminum Alloys
Authors: Han Qin You
Published: May 2014

This article discusses research on using power ultrasound for degassing of molten aluminum alloys. At least three types of technique have been developed for ultrasonic degassing. The type deals with degassing using power ultrasound alone. Degassing in a small melt can be achieved within a few minutes of ultrasonic vibration. The second type is ultrasound assisted vacuum degassing. A combination of vacuum and power ultrasound makes degassing much complete and fast. The third type is ultrasound assisted lance degassing. Ultrasonic vibration is used to break up the large argon or nitrogen bubbles into much smaller ones, resulting in an increased efficiency of degassing of aluminum melt. The benefits of ultrasonic degassing include: no moving/rotation part in the degassing system; less use of argon and no use of chlorine; and less amount of dross formation during degassing. Furthermore, trace elements such as Na and Li can be removed using ultrasonic degassing.
Keywords: Aluminum alloys, degassing, porosity, and power ultrasound
Fabrication of Self-Lubricating Cu-Based Composite Containing Graphite Particle by Centrifugal Mixed-Powder Casting
Authors: Sato Hisashi , Wei Wei , Oguri Kazuaki , Yamada Motoko , Watanabe Yoshimi
Published: May 2014

Reduction of frictional coefficient at sliding position can improve wear resistance of material. In previous studies, Cu-based composites containing graphite particles have been reported. Since graphite is better lubrication material, the Cu-based composites containing graphite particles have better wear property comparing with the pure Cu. However, these composites are mainly fabricated by sintering method and its strength is relatively low. In this study, Cu-based composites containing graphite particles are fabricated by centrifugal mixed-powder casting. The centrifugal mixed-powder casting is novel centrifugal casting method combined with powder metallurgy. Using this casting method, the Cu-based composites containing graphite particles are successfully obtained. The graphite particles are distributed in the Cu matrix and no casting defects are observed. Moreover, wear resistance of these Cu-based composites are much better than pure Cu, and the frictional coefficient between these composites and bearing steel as the counter part is reduced by dispersion of the graphite particles. Furthermore, it is found that the optimum area fraction of the graphite particles to improve the wear resistance of the present Cu-based composite is from 15% to 21%.
Positron Lifetime Studies of Irradiated Ultra-High Molecular Weight Polyethylene and Composites Made of Martian Regolith
Authors: Seetala Naidu , Tull-Walker Naeem , Baburaj Abhijit , Zhou Jian Ren , Wilkins Richard , Barnett Milan
Published: May 2014

Positron Annihilation Lifetime Spectroscopy (PALS) is used to study the nanoporosity and fractional free volume in Ultra High Molecular Weight Polyethylene (UHMWPE) and composites with the addition of Martian Regolith (UHMWPE-MR) as-made and irradiated with 56Fe heavy ions at an energy of 600 MeV/u to three different doses (10, 32, 64 Gy). The positron lifetime spectra were obtained using 22Na positron source and the spectra were analyzed to two lifetime components using POSFIT program. First short lifetime component around 0.28 ns is related to positron annihilation in material including vacancy defects and the second long lived component around 1.7 ns is due to Positronium formation in free volume pores. UHMWPE-MR composites were shown to be less porous with much lower nanopores concentration compared to the UHMWPE polymer. The average size of the nanopores is around 0.5 nm (obtained from a simple model). Larger variations in positron lifetime parameters are observed with increasing irradiation dose for UHMWPE polymer compared to UHMWPE+MR composites. The 3-point bend test results also showed larger variations with increasing irradiation dose for the UHMWPE polymer. The variations in PALS parameters may indicate an increasing competition between two processes at higher irradiation doses: 1) vacancy defects aggregation and 2) escape of vacancy defects as the local temperature increases at higher doses resulting in increased vacancy defects mobility. Present results clearly indicate a qualitative inverse relationship between nanoscale porosity measured by positron life time and mechanical properties of UHMWPE and its composite with MR.
Fatigue and Fracture Behavior of MMC in the HCF- and VHCF-Regime
Authors: Wolf Matthias , Wagner Guntram , Eifler Dietmar
Published: May 2014

Aluminum matrix composites (AMCs) are characterized by improved mechanical properties in comparison to their unreinforced matrix alloys. But the knowledge about the fatigue behavior of AMCs in the HCF-and in the VHCF-regime is limited until now. Due to this AMC225xe and AMC xfine225 with an average SiC particle content of 25 vol.-% and particle sizes of 2.5 μm and 0.7 μm, respectively, as well as the base alloy AA2124 were fatigued up to 1010 cycles using the ultrasonic testing facility of the type "UltraFast-WKK-Kaiserslautern".To describe the fatigue behavior of the specimens several measuring devices were used to monitor and record the central process parameters. A very sensitive value to detect specimen failure at an early stage is the dissipated energy which can be determined as the integral of the generator power depending on the ultrasonic pulse time.In comparison to AA2124 the investigated AMCs have shown a considerably enhanced fatigue performance for stress amplitudes higher than 140 MPa. But below this stress amplitude for the matrix alloy run outs at 1010 cycles were realized whereas the AMCs failed at lower number of cycles still at lower stress amplitudes. Moreover, while crack initiation of the matrix alloy in all cases started at the surface for the AMCs the crack initiation point changes from surface to subsurface for more than 107 cycles. The subsurface failures of the composites were caused by microstructural inhomogeneities which could be identified with EDX and micro-CT as particle clusters and copper-iron-rich inclusions.
Morphology of Si Phase in Al-Mg-Si-Cu Alloys with Excess Si Addition
Authors: Han Yi , Wang Chu Yan , Zhai Tong Guang , Nagaumi Hiromi
Published: May 2014

The morphology of Si phase and its growth manner in the Al-Mg-Si-Cu alloys with amounts of excess silicon were investigated using by a combination of the higher magnification microstructure and DSC measurements. Solidification characteristics of the alloys were predicted by thermodynamic calculation and compared to the experimental results. It was found that addition of higher amount of excess silicon led to the formation of the evidently morphological Si phase, especially when the silicon content was beyond 1.35 wt.%. The Si phase was one of the dominant phases in the alloys and its reaction peak was identified with the onset temperature of 550.43oC in the DSC curves. These experimental results were in good agreement with the thermodynamic calculations by the Gulliver-Scheil model.
Keywords: Al-Mg-Si-Cu alloy; morphology; thermodynamic calculation; excess Si
Interfacial Magnetoelectric Switching in Multiferroic Heterostructures
Authors: Kleemann Wolfgang , Borisov Pavel , Chen Xi , Schmitz-Antoniak Carolin
Published: May 2014

Novel methods of switching magnetism with electric fields and vice versa, and aiming at magnetoelectric (ME) data processing are reported. First, the patented MERAM@ uses the electric field control of exchange bias via an epitaxial Cr2O3 layer and exchange coupling to a Pt/Co/Pt trilayer. It promises to crucially reduce Joule energy losses in RAM devices. Second, magnetic switching of the electric polarization by a transverse magnetic field in a 3-1 composite of a vertically poled BaTiO3 thick film embedding CoFe2O4 nanopillars produces a regular surface polarization pattern with rectangular symmetry. Its possible use for data processing is discussed.
Properties of GaN-Related Epitaxial Thin Films Grown on Sapphire Substrates as Transparent Conducting Electrodes
Authors: Sato Yuichi , Matsunaga Tatsuya
Published: May 2014

Thin films of gallium nitride (GaN) and related nitride materials were prepared, and their properties as transparent conducting electrodes were investigated. GaN thin films were directly grown on sapphire single crystal substrates by the molecular beam epitaxy. Heavy doping of germanium was employed to reduce resistivity of the films, with sufficient reduction found to be possible while maintaining their epitaxial growth state. Optical transmission spectra of the films in the short wavelength region were slightly deteriorated by the heavy doping; however, this was successfully improved by growing GaN films under metal-rich conditions to increase the electron mobility and suppress unwanted increase of the carrier densities. In addition, the optical transmission spectra in the short wavelength region was improved also by alloying GaN with aluminum nitride, though the resistivities of these films were relatively higher than those of the unmodified GaN films. The prepared nitride thin films exhibited sufficiently suitable properties as transparent conducting electrodes for use in applications such as full-spectrum nitride-based solar cells.
On the Role of the Crystallographic Grain Characteristics in the Corrosion Behavior of Polycrystalline Copper
Authors: Lapeire Linsey , Martinez Lombardia Esther , Verbeken Kim , de Graeve Iris , Kestens Leo A.I. , Terryn Herman
Published: May 2014

In order to increase the sustainability of metals, a more detailed understanding of the corrosion phenomenon is of crucial importance. In current literature, corrosion is often considered as a purely chemical interaction with nearly exclusive dependence on compositional effects, whilst ignoring the microstructural features of the metal surface. In the present work, results are presented which illustrate both the role of grain orientation and grain boundaries in the corrosion process.
To evaluate the grain orientation dependent electrochemical behavior, polycrystalline Cu, was brought into contact with a corrosive electrolyte. Subsequently, the attack was evaluated by measuring the surface with both Atomic Force Microscopy (AFM) and Electron Backscatter Diffraction (EBSD). It was demonstrated that the grain orientation itself did not significantly influence the corrosion kinetics, but, alternatively, that the orientation of the neighboring grains seemed to play a decisive role in the grain dissolution rate.
To increase understanding on the role of grain boundaries, a method was developed based on the electrochemical (galvanic) displacement of gold, which is deposited from an aqueous solution on a pure copper substrate. This technique demonstrated its sensitivity to the grain boundary characteristics as far less gold was deposited on special boundaries, such as coincidence site lattice boundaries, as compared to the random high angle grain boundaries.
Friction Stir Welding of Carbon Steel for Application in Used Fuel Containers
Authors: Mahoney Murray , Sanderson Sam , Maak Peter , Steel Russell , Babb Jon , Fleck Dale
Published: May 2014

Friction Stir Welding (FSW) is being investigated as a method to fabricate a partial penetration closure weld of the steel vessel of a copper-coated used fuel container. The hemi-head is made of A516 Grade 70 steel and the cylinder body is made of A106 Grade C steel. In this initial feasibility study, the objective is to use FSW to demonstrate the merits of FSW using flat steel plate in concert with a closure weld joint designed specifically for a cylindrical container. To complete this objective, there are two initial feasibility demonstrations. First, demonstrate the capability of FSW to create defect free welds in a corner joint design with specific dimensions (10 mm deep weld nugget). Subsequently, verify the weld quality by ultrasonic inspection and metallography. Further, characterize weld zone properties by establishing mechanical properties and hardness at room temperature, and impact toughness at-5°C. Second, demonstrate the ability to use FSW to repair defects that might occur in the initial friction stir weld. Weld repair was accomplished by intentionally creating tunnel defects by FSW, performing metallography and ultrasonic inspection to characterize the morphology of the defects, performing a second friction stir weld repair over the defects, and verifying the subsequent weld integrity by repeating the metallography and ultrasonic inspections. Results on these initial two phases of this program are presented herein.
Numerical Analysis of Multi-Field Coupled Phenomena in Friction Stir Welding and Applications
Authors: Shi Qing Yu , Chen Gao Qiang , Wang Xi Bo , Kang Xu
Published: May 2014

Friction stir welding (FSW) is an advanced solid state joining technology, which was invented by TWI in 1991. During the process, large amount of heat is generated due to the friction between the tool and the material. As a result, the metal around the tool is softened as the temperature rises, and significant plastic flow occurs. So FSW is a complex process with multi-field coupled phenomena. Material flow plays a central role in FSW. But it is still difficult to reveal the material flow regime and joining mechanism during FSW process. Numerical simulation is a powerful tool for investigating the metal-flow-related complex phenomena during FSW. Meanwhile, numerical simulation could also help to optimize FSW tool design and FSW parameters. In this paper, we review the recent development in simulation of material flow during FSW. Then, the important issues in modeling multi field coupled phenomena during FSW are summarized, which include the heat generation mechanism, the temperature and strain rate dependent material’s behavior, and the interaction between tool and material. Finally, a comprehensive simulation model is presented, which enables advanced study on the coupled phenomena of heat generation, temperature distribution, material flow, and defects formation. This model has shown potential applications in simulating the relation between the transport of material and the macrostructure formation or defects formation. In spite of these progresses, simulation of material flow during FSW still need quite a lot of researches to fulfill industry requirement.
Effect of Heat Treatment Conditions and Small Addition of Cu on Occurrence of Serration in Al-Si Alloys
Authors: Kanadani Teruto , Nagata Norihito , Nakagawa Keiyu , Murakami Koji , Hino Makoto
Published: May 2014

In this study, the effect of heat treatment conditions and small addition of Cu on occurrence of serration in Al-Si alloys was investigated. Specimens were aged for various times up to 87ks at 273K or 473K after quenching from 853K, and tensile-tested at room temperature. In the binary alloy, serration was observed even after aging for 87ks at 273K, while in the case of aging at 473K, serration did not occur under aging conditions at aging time, tA≧20s. On the other hand, serration was observed even after aging for 72ks at 473K in the Cu-added alloy. In both alloys, serration was also recognized when the specimens were furnace-cooled from 853K to room temperature. Thus, for aging at 473K of the binary alloy serration was observed only when the aging period was short enough, but addition of Cu to the binary alloy prolonged the aging period where serration could be recognized. Aging rate of both alloys measured by tensile strength was almost the same. The size of precipitates in the Cu-added alloy was smaller than that in binary alloy. Moreover, the number of the precipitates at the grain boundary in the Cu-added alloy was smaller than that in the binary alloy. It is considered that serration occurs for Al-Si alloys when the specimen is heat-treated so that small precipitates may be formed. Now the details of the effect of Cu addition are not clear.
Anomalous X-Ray Scattering Investigations on Metallic Glasses
Authors: Hosokawa Shinya
Published: May 2014

In this article, we show principles and advantages of anomalous x-ray scattering in combination with neutron scattering and reverse Monte Carlo modeling to characterize structures of non-crystalline materials, in particular, metallic glasses. Then, we briefly introduce examples of our recent applications to Pd40Ni40P20 and Zr63Ni25Al12 bulk metallic glasses having good glass-forming abilities.
Onset of the Portevin-Le Chatelier Effect: Role of Synchronization of Dislocations
Authors: Lebedkina Tatiana , Kobelev Nikolay P. , Lebyodkin Mikhail
Published: May 2014

The problem of the onset of the Portevin-Le Chatelier (PLC) effect is revised by combining a study of the kinetics of the flow stress evolution upon abrupt changes in the applied strain rate and acoustic emission (AE) accompanying plastic deformation of an AlMg alloy. The kinetic measurements allow evaluating the strain-rate sensitivity of the flow stress and the time characteristics of transient processes as functions of plastic strain. Using known criteria of plastic instability, domains of instability are constructed in the (strain, strain rate) plane. A particular accent is put on the strain-rate range corresponding to the so-called “inverse” behavior. The comparison of such maps with experimental data on the critical strain testifies to the insufficiency of these criteria for explaining the onset of the PLC effect. Moreover, the slow transient kinetics contradicts observations of the fast development of stress drops. The AE measurements bear witness that the stress serrations are associated with bursts in duration of acoustic events generated by the collective motion of dislocations. The possible role of synchronization of dislocation dynamics on the onset of plastic instability is discussed.