bluuebunny/crossref_metadata_2025 huggingface dataset:
A Review of Researches on Cache Coherence Protocols for Multi-Core Processor
Authors: Tian Yong Hong , Chen Guang Jian
Published: May 2014

Multi-core processor parallels two or more computing core in a single processor to enhance computational capability. Plenty of former researches are focused on CMP (Chip multi-processor), the most typical structure of multi-core processor. Thus deign of cache coherence, in particular, is one of the primary problems beyond other researches about CMP. In this paper, cache coherence protocol of CMP is fully presented, along with its advantages and disadvantages. Finally, some edging issues of cache coherence protocols are addressed in this paper.
Mould Running System Design to Achieve the Minimum Waste
Authors: Monkova Katarina , Monka Peter , Cizikova Andrea , Hric Slavomir
Published: May 2014

The article deals with the mould running system design. The goal of design presented in the article was to propose the mould form so to be achieved the minimum waste for selected component. Studied component is intended to serve as a stopper in the automotive spotlight. The waste is considered the material that solidifies in the volume of plastic inside the running system. 3D model of the mould was created in Autodesk Inventor Proffesional software and then solidification of material was simulated in Autodesk Moldflow Insight software. There were designed three alternatives of running system at which the waste amount was evaluated. On the basis of the best solution, the real form was manufactured and placed into the injection moulding machine Arburg Allrounder 320 C.
Fabrication and Characterization of CeO2-NiO/SiC Membranes for Hydrogen Permeation
Authors: Park Ji Hye , Jung Mie Won
Published: May 2014

In order to enhance the hydrogen permeation, Silicon carbide (SiC) was prepared with CeO2-NiO mixed oxides via sol-gel process and the SiC membranes with various contents of χ wt% mixed oxides (χ = 20, 40, 60 and 80) were fabricated by hot-press sintering (HPS) at 1173 K under vacuum condition. The effect of the CeO2-NiO mixed oxides was studied in terms of properties on hydrogen permeation. All the membranes were characterized by XRD, FE-SEM and BET instrument. The hydrogen permeation test was carried out at various temperatures under 0.1 MPa. Hydrogen permeation flux of the 80 wt% CeO2-NiO/SiC membrane, which has the highest value, was obtained at 2.92×10-6mol/m2sPa, 323 K. The reaction enthalpy (ΔH°) was calculated as - 4.95 J/mol by Arrhenius’s plot.
Physical Chemistry of Integrated High-Magnesia Siderites Processing
Authors: Kolokoltsev V. , Klochkovskii S. , Smirnov A.
Published: May 2014

In the article the results of research are considered, that can be the basis for the modernization of the technology used at present time and can be applied for development of the fundamental principles of the complex processing technology of high-magnesian siderite satisfying the modern environmental requirements.
Keywords: siderite ores, magnesium oxide, technology, leaching, carbonic acid
A Mechano-Chemical Coupling for Hydrogen Diffusion in Metals Based on a Thermodynamic Approach
Authors: Creton Nicolas , Dejardin Steeve , Grysakowski B. , Optasanu Virgil , Montesin Tony
Published: May 2014

Hydrogen diffusion in metals is still an ongoing topic of research due to its technical relevance (hydrogen embrittlement, hydrogen storage...). In the last decades, significant progress in understanding the time evolution of the hydrogen concentration in solids was completed. This paper presents a modeling of hydrogen diffusion with a general and thermodynamically based diffusion concept coupled with mechanical and chemical aspects. This model was previously used to simulate the oxidation of a metal [1][2]. This concept has been upgraded to offer a thoroughly macroscopic behavior law used to simulate hydrogen diffusion in metal parts under mechanical loadings. The thermodynamic approach of the stress-diffusion coupling was implemented in a finite element code in order to study the hydrogen diffusion mode into a strained metal. Simulations were performed on a cylindrical austenitic steel tank under important internal pressure. The results of this study allow us to understand how hydrogen diffusion and mechanical stresses are mutually induced and modified.
Rising Damp: Optimization of the Wall Base Ventilation System
Authors: Guimarães A.S. , Delgado João M.P.Q. , de Freitas V.P.
Published: May 2014

Rising damp constitutes one of the main causes of monumental heritage and old buildings degradation, especially, its thick walls with heterogeneous composition. The LFC-FEUP has been developed important research in rising damp domain. In recent years, was validated and experimentally characterized the operation principle of a technique called "wall base ventilation system" for the treatment of rising damp in monumental heritage and ancient buildings consisting of circulating air at the base of the buildings walls with high thickness and heterogeneity in its constitution, with a saturation distant relative humidity. The studies previously developed allowed the interest and viability of the proposed system, taking time to develop a methodology for optimizes it. In this paper it is presented the optimization of the wall base ventilation system based on some important physical parameters. To optimize the system, it was developed a 2D evaporation model that describes the moisture transfer between the system and the wall as well as the water vapour transport throughout the system (Evaporation and Transport Model – ETM). It was also used and adapted another 2D model, to describe the rising damp phenomenon in buildings walls, considering the wall base ventilation system (Rising Damp and Evaporation Model – RDEM). Finally, the design model was developed, using both models(ETMandRDEM) and some experimental validation was done, which allowed the comparison between the levels archived by the wet front analytically and experimentally.
Studies on the Treatment of Wastewaters Containing Cr6+ with Iron Oxide-Silica Composite Materials Prepared by Different Methods
Authors: Ullah Rafique , Deb Biplob Kumer , Mollah Mohammad Yousuf Ali
Published: May 2014

Chromium (VI) is known to be carcinogenic to humans and thus it is important to ensure the removal of Chromium (VI) from aqueous solutions and industrial effluents. The present study introduces a good alternative method for Cr (VI) removal from aqueous solutions at ambient temperature by adsorption, allowing the development of newer, lower operational cost, and more efficient technology than other processes already in use. Adsorption was found to be dependent on pH and initial concentration of Cr (VI) solution. Results of adsorption studies suggest that pristine iron oxide and silicon (IV) oxide removes 72.10% and 24.73%, respectively. The iron oxide – silicon (IV) oxide composite, prepared in this work, removes 93.88% Cr (VI) in 20 minutes from aqueous solution at an initial concentration of 50 mgL-1at pH 4.8 ± 0.2. The effect of concentration, contact time, adsorbent dose and solution pH on the adsorption of Cr (VI) were studied in detail in batch experiments. Studies of the sorption kinetics shows that equilibrium adsorption was attained in 20 minutes depending on other experimental conditions. The kinetic data justified Lagergren’s first-order kinetic equation. Adsorption isotherm study showed that the results fulfilled the Langmuir Model of adsorption isotherm. The maximum adsorption (98.28%) was recorded at pH 3 in 90 minutes for the initial Cr (VI) concentration of 50 mg L-1. Therefore, it can be concluded that iron oxide – silicon (IV) oxide composite is a potential adsorbent for adsorption of Cr (VI) from aqueous solution.
A Study on Processing and Chemical Composition of Date Pit Powder for Application in Enhanced Oil Recovery
Authors: Adewole Jimoh K. , Sultan A.S.
Published: May 2014

Studies were conducted on method of processing and chemical compositions of date pit for possible applications in enhanced oil recovery. Date seed from the eastern province of Saudi Arabia were washed by sonication and sun dried. The dried seeds were ground, de-oiled and made into solutions using alkaline. Physicochemical properties and chemical compositions of the de-oiled date seed powder were investigated using SEM and FTIR. The properties of the powder solutions were investigated by evaluating their viscosifying properties. Results of elemental analysis showed that the powder contains 57.41 - 65.84% carbon and 34.16 - 41.35% oxygen. The peak values in the range 3369.6 - 3417.3cm-1obtained from FTIR are indicative of the presence of OH functional groups. The results obtained from viscosity measurement revealed that date seed be utilized as viscosity modifier to alter the mobility ratio in enhanced oil recovery processes. In addition, the multiple hydroxyl functional groups contained in date pit powder can be made available for organic reactions to produce surfactants and polymeric polyols that can be used for wettability and interfacial tension (IFT) alteration as employed in enhanced oil recovery operations. Furthermore, more studies need to be done to investigate and improve other relevant properties of the powder solution so that it can be used in near reservoir conditions. Accordingly, future work will be focused on detailed investigation on the use of the powder to alter mobility ratio, wettability and IFT.
The Influence of Temperature on Zinc Abrasion in Deep Drawing Processes
Authors: Sachnik Peter , Volk Wolfram , Golle Roland , Hoffmann Hartmut
Published: May 2014

Due to the development of corrosion-resistant lightweight, todays automotive manufacturers typically use zinc coated sheet metals in the forming process. However, zinc abrasion in industrial presses decreases the process stability and often causes interruption of the whole process. The application of high strength steels leads to a significant increase of the temperature due to the plastic work. So far a detailed, quantitative analysis of the relation between temperature and zinc abrasion is not available. Therefore, this paper examines the impact of the temperature on abrasion behaviour in sheet metal processes. To achieve this, a progressive die was built. The deep drawing stage of this tool is connected to a cooling / heating system in order to obtain a constant temperature during the forming process. A variety of different galvanized sheet metals compared to commonly used tool materials has been tested. For each combination of materials five experiments at different temperatures were performed to determine the effect of the temperature on the zinc abrasion. Applying the method of total reflection x-ray fluorescence (TXRF) the quantity of zinc abrasion was measured.
A relation between low temperatures and reduced zinc abrasion can be clearly observed. Industrial experiments revealed that temperature exerts a high influence on the zinc abrasion. The new insights into the impact of the temperature show a significant way to lower the zinc abrasion and therefore increase the process stability in deep drawing processes.
Numerical Simulation of Workpiece Thermal Field in Drilling CFRP/Aluminum Alloy
Authors: Montoya Maxime , Calamaz Madalina , Gehin Daniel , Girot Franck
Published: May 2014

Machining is a process implying extremely high coupled thermo-mechanical stresses. The workpiece mechanical properties decrease with the temperature generated during the process and that temperature has a direct influence on wear intensity undergone by the tool. In the case of a drilling operation, the temperature generated by the cutting process can lead to metal burr formation and/or composite matrix degradation by burning. When these two materials are used in the form of a sandwich-type stacking, the temperature attained in the metallic part can cause new defects such as: i) a difference between the diameters measured in each material and ii) organic matrix damages due to heat diffusion from the metal towards the CFRP layer. Temperature reached at the tool/workpiece interface is difficult to measure during drilling operation, due to its enclosed configuration; numerical simulation is therefore a good alternative to access to this information. The purpose of this study is to develop and carry out numerical simulations in order to estimate the workpiece thermal field generated during drilling. The simulations are validated by comparing simulated and measured temperatures at 4 mm from the holes wall. This method is applied to evaluate thermal field generated during drilling (with chip removing cycles) of CFRP/Aluminum alloy stacks. The influence of the drilling kinematics on the workpiece thermal field is also investigated.
Fast Plastic Integration Algorithms for Forming Process Simulations
Authors: Halouani Ali , Li Yu Ming , Abbès Boussad , Guo Ying Qiao
Published: May 2014

This paper presents a fast plastic integration algorithm and compares it with other algorithms for forming process simulations. The iterative Return Mapping Algorithm (RMA) is widely used owing to its accuracy and efficiency, but it is still time consuming and may cause divergence problems. Another algorithm based on the Incremental Deformation Theory (IDT) was proposed, using the deformation theory of plasticity by piecewise; it is very fast but could not well consider the loading history, leading to notable errors.
The new Direct Scalar Algorithm (DSA) based on the flow theory of plasticity is proposed in this paper. The basic idea is to transform the constitutive equations in terms of the unknown stress vectors into a scalar equation in terms of the equivalent stresses which can be determined by using the experimental tensile curve; thus, the plastic multiplier λ can be directly calculated without iterative solution. The DSA is a fast and robust plastic integration algorithm. The comparison of the results obtained by using the three algorithms shows the accuracy and efficiency of the DSA.
A Study of the Effects of Reversal Cycles in the Gear Rolling Process by Using Finite Element Simulations
Authors: Khodaee Alireza , Melander Arne
Published: May 2014

The manufacturing of machine components with sustainable and innovative methods is an interesting topic for research. Gears are some components which have complexity in both design and production technology. Therefore applying innovative methods on gear manufacturing can be of interest to industry. One of the most promising production methods for gear wheels is Gear Rolling. The gear wheel is formed during a certain rolling process from a cylindrical blank into the final designed shape. The process of gear rolling with rotational gears is progressing by running several rolling cycles with one, or two dies in contact with a work-piece. A specified rotational speed and radial feed speed is applied to the dies in order to form the required geometry on the blank. In this paper, the authors have simulated the process with the finite element code, DEFORM 3D. Especially the effects of reversal cycles on final gear wheel geometry have been evaluated from the simulations. Different settings for the rotation direction of the dies have been used and the effects are evaluated with specific quality criteria.
A Fast Approach to Shape Optimization Using the Inverse FEM
Authors: Landkammer Philipp , Steinmann Paul
Published: May 2014

Inverse form finding aims to determine the optimum blank design of a workpiece whereby the desired spatial configuration that shall be obtained after a forming process, the boundary conditions and the applied loads are known. As a verification of the optimal material configuration a subsequent direct FEM computation has to result in the desired shape of the deformed workpiece. In this contribution the inverse FEM, which formulates the mechanical weak form in the spatial configuration and solves it with respect tothe material configuration, is used to obtain an admissible blank configuration. An example of applying this inverse method to a contact forming simulation is presented.To this end a FE-code applicable to use the inverse mechanical formulation is coupled with the commercial software MSC.Mentat. In the inverse computation the contact problem is approximated by displacement control.
Unerring Planning of Clinching Processes through the Use of Mathematical Methods
Authors: Drossel Welf Guntram , Falk Tobias , Israel Markus , Jesche Fred
Published: May 2014

Mechanical joining technologies are becoming increasingly important with the trend towards light and multi-material designs in the automotive industry. Providing robust connection techniques will be of particular importance. Thus, rejection rates are reduced and costs are cut in the parts production. This paper discusses the example of clinching and its potentials and limits concerning FEM based sensitivity analysis and optimization for the joining by forming technology. By determining the sensitivity of the design for relevant connection parameters, the most important values for the optimization of the forming die are derived. On this basis, both, appropriate tools for a particular material combination and other tools for the joining of different thicknesses and sheet materials are designed. Furthermore, a sensitivity analysis of uncertain variables allows to evaluate the robustness of the clinching process in production. Based on these results, methods to increase process robustness or process monitoring in terms of quality assurance can be derived.
Galvanic Corrosion Related to Steel/Aluminum Dissimilar Joining Tailored Blank
Authors: Takehisa Shoki , Iizuka Takashi
Published: May 2014

In order to use a steel/aluminum tailored blank in actual practice, galvanic corrosion due to the contact of dissimilar metals should be examined. However, few studies have reported the influence of galvanic corrosion on a steel/aluminum laser butt-welded joint. In this study, the effect of galvanic corrosion on the strength of SPCC/A1100-O laser butt-welded joints was investigated by immersion tests in air, distilled water, and salt water. The appearance was observed and tensile tests were conducted. In addition, the joint interface and the surface near the joint interface were observed and analyzed by FE-SEM and EDS. During the immersions in distilled water and in salt water, specimens were covered with an oxide film and the joint strength decreased. In the salt water immersions, the strength of the SPCC base materials decreased. And a large reduction of the cross-sectional area of the A1100-O side of the joints was seen in the salt water immersions. From the results of the observations and analyses by FE-SEM and EDS, a layer of brittle intermetallic compounds formed in the joint interface during the immersion test, and corrosion progressed as the oxide film sloughed off.
Profile Strip Casting with Inline Hot Rolling: Numerical Simulations for the Process Chain Design
Authors: Vidoni Michele , Mendel Arne , Hirt Gerhard
Published: May 2014

A process to produce thin steel strips with an optimized cross-section has been recently developed at the Institute of Metal Forming (IBF) as possible alternative to tailor welding and cold profile rolling for the production of tailored flat products. This process was named profile strip casting and combines the advantages of twin-roll strip casting, such as energy efficiency and compact production route, with the attractiveness of tailored products for lightweight applications. A finite difference model for the thermal description of the complete process chain including solidification, air cooling, and rolling is presented in this work. The developed simulation tool is calibrated on the temperature measurements obtained with profile casting experiments and targets the investigation of thicknesses not achievable with the available equipment. The measured surface temperature difference between the thick and thin zone of the profile for a strip with a thickness of 1.5 mm in the thin and 2.2 mm in the thick section cast using selectively coated rolls was ΔT = Tthick - Tthin = 82 K after the casting gap and 109 K at the mill exit. The simulation indicates that increasing the thickness to 3.5 mm in the thin and to 5.1 mm in the thick profile zone the surface temperature difference results 26 K after the casting gap and 126 K at the mill exit.
Friction Stir Processing Multi-Run Modification of Cast Aluminum Alloy
Authors: Weglowski Marek S. , Kopyściański Mateusz , Dymek Stanisław
Published: May 2014

The effect of multi-run FSP modification of cast aluminum alloy AlSi9Mg are presented. The relationship between the number of trials and microstructures are shown. FSP process was performed on the typical milling machine specifically adopted for the processing trials. The microstructure was examined by light as well as scanning and transmission electron microscopy. The studies have shown that the multi-run FSP process causes decrease of the grain size and increase of the homogeneity of the microstructure. In contrast to the cast condition, the microstructure in the processed material was characterized by a relatively uniform distribution of the second phase particles. The size and aspect ratio of these particles decreased significantly. Application of FSP process resulted in a decrease of the porosity in the modified material. The modified materials achieved at perpendicular runs can be characterized by the higher dislocation density that obtained at parallel ones. The multi-run FSP process caused increase the elongation and ultimate tensile strength of modified material in comparison to properties of the cast aluminum alloy.
Warm-Forging Characteristics and Microstructural Response of Medium-Carbon High-Strength Steels for High-Duty Components
Authors: Skubisz Piotr , Lisiecki Łukasz
Published: May 2014

Paper presents deformation behaviour and microstructural response of selected medium-carbon high-strength steels commonly used for high-duty components deformed under high-strain-rate and warm work temperature range. The investigation of material behaviour is oriented at analysis of hot and warm workability of material and microstructure evolution resultant from deformation mechanisms, strain induced recrystallization and hardening at temperatures of lower forging regime and high strain rate deformation. The effect of these factors on microstructure after forging and subsequent direct-cooling was studied. Metallographic work aided with numerical methods of simulation of the metal flow and microstructure evolution during forging were used to correlate thermo-mechanical parameters observed with microstructure and mechanical properties after forging and cooling.
Experimental Chemo-Mechanical Characterization and Multiscale Modeling of the Alloys Al1050, Al2024 and Al5754
Authors: Kebriaei Reza , Vladimirov Ivaylo Nikolov , Reese Stefanie
Published: May 2014

In the last decades, manufacturing of layered composite materials has become an interesting topic in industrial development. Joining properties of adhesively bonded materials are characterized by a complex interaction of plastic deformation, thermo-mechano-chemical coupling effects, adhesion and diffusion. Additionally, the interactions between the microstructures involved in the process have to be taken into account. In this paper the microstructure of materials (as e.g. Al1050, Al2024 and Al5754), which have a wide range of applications in engineering structures, is numerically and experimentally investigated. The results are compared with experimental data.
Modelling Non-Quadratic Anisotropic Yield Criteria and Mixed Isotropic-Nonlinear Kinematic Hardening at Finite Strains
Authors: Grilo Tiago Jordao , Vladimirov Ivaylo Nikolov , Valente Robertt , Reese Stefanie
Published: May 2014

A constitutive model that accounts for mixed isotropic-nonlinear kinematic hardening, suitable for any non-quadratic yield criteria, is proposed. The finite strain model is derived from a thermodynamically consistent framework and relies on the multiplicative split of the deformation gradient in the context of hyperelasticity. The nonlinear kinematic hardening approach is introduced in the constitutive model by means of the multiplicative split of the plastic deformation gradient. The constitutive equations are consistently derived by exploiting the dissipation inequality, and expressed by symmetric tensor-valued internal variables only. The exponential map algorithm was employed in the integration of the evolution equations. This algorithmic strategy has the advantage of preserving both the plastic incompressibility and the symmetry of the internal variables. The model was implemented into a material user-subroutine of a commercial finite element code (ABAQUS), and some numerical results are presented to assess the performance of the present model.
Deformation Behavior of a Magnesium Alloy Sheet with Random Crystallographic Orientations
Authors: Hama Takayuki , Mayama Tsuyoshi , Takuda Hirohiko
Published: May 2014

In the present study, the deformation behavior of a cast Mg alloy sheet that had random crystallographic orientations was studied both experimentally and numerically. Although the crystallographic orientations were random, the stress-strain curve was asymmetric between tension and compression: the flow stress under tension was higher than that of compression. Moreover, the stress-strain curve exhibited a strain path dependency: a slightly sigmoidal curve occurred under tension following compression, while it did not occur under compression following tension. Clearly, such tendencies were similar to those observed in rolled Mg alloy sheets although the tendencies were less pronounced in the cast Mg alloy sheet. A crystal plasticity finite-element method was used to understand the mechanism of these results. Simulation results showed that the asymmetry and the strain path dependency in the stress-strain curves occurred in the cast Mg alloy sheet because of the asymmetry in the activity of twinning between tension and compression as in the case of rolled Mg alloy sheets.
Thermoforming Simulation of Multilayer Composites with Continuous Fibre and Thermoplastic Matrix
Authors: Guzman Maldonado Eduardo , Hamila Nahiene , Boisse Philippe , Chaudet Philippe
Published: May 2014

CFRTP prepreg laminates thermoforming (Continuous Fibre Reinforcements and Thermoplastic Resin) is a fast composite manufacturing process. Furthermore the thermoplastic matrix is favourable to recycling. The development of a thermoforming process is complex and expensive to achieve by trial/error. A simulation approach for thermoforming of multilayer thermoplastic is presented. Each prepreg layer is modelled by semi-discrete shell elements. These elements consider the tension, in-plane shear and bending behaviour of the ply at different temperatures around the fusion point. The contact/friction during the forming process is taken into account using forward increment Lagrange multipliers. A lubricated friction model is implemented between the layers and for ply/tool friction. Thermal and forming simulations are presented and compared to experimental results. The computed shear angles after forming and wrinkles are in good agreement with the thermoforming experiment.
Variable Forming Tool and Process for Thermoset Prepregs with Simulation Verified Part Quality
Authors: Hundt Tobias , Schmidt Carsten , Denkena Berend , Engel Kevin , Horst Peter
Published: May 2014

In this paper a new variable forming tool concept and associated numerical methods for calculating optimal actuator layout and estimating CFRP part quality are presented. The concept of the tool features a modular design and active control of the forming process to achieve the desired geometry. Initially the laminate is placed on the flat top layer of the forming tool. There it is fixed and compacted using vacuum bagging. After compacting, it is heated up to increase the performance of the forming process using water based tempering of the forming tools top layer. The heated laminate is then formed, pulling the tools top layer into the desired geometry using the actuators. Finally, the formed laminate is cooled and transferred into a mold for curing. The position of the forming tools actuators on the base plates is variable. Numerical optimization in combination with finite element (FE) technologies is utilized, to approximate the tool surface within given error margins, with as few actuators as possible. In addition, results of a numerical method for part quality estimation are shown. The influence of the forming process on mechanical properties due to fiber waviness is taking into account using a self-developed method that includes manufacturing characteristics in FE modeling of the part. The method is based on mathematical descriptions of fiber waviness, which are implemented into a FE model. Therefore a structure discretization assuming perfect fiber orientations is realized and the expected fiber waviness induced by the forming process is applied element-wise.
Friction Coefficient Identification in Roll Forming Processes
Authors: Galdos Lander , Ulibarri Unai , Gil Imanol , Ortubay Rafael , Sáenz de Argandoña Eneko
Published: May 2014

Roll forming process is an interesting process for the production of complex profiles because of its high production rate, low investment and efficient use of material. Furthermore, and due to their high yield strength, this technology is suitable for the forming of Advanced High Strength Steels which are being increasingly introduced in the automobile sector.
Novel Experimental Set-Up to Test Tubes Formability at Elevated Temperatures
Authors: Michieletto Francesco , Ghiotti Andrea , Bruschi Stefania
Published: May 2014

In the last ten years, the automotive sector presents large interest for light alloys tubes for structural and body car parts to reduce CO2 emissions. Tubes hydroforming is one of the most popular processes to obtain complex parts by using liquids as active part of the dies (i.e. water-or oil-based emulsions) with reduced costs of equipment and machines. However, when elevated temperatures should be used to increase the material formability, hydroforming processes are strongly limited due to the boiling point of liquids. The use of gas at elevated temperature in the so-called Hot Metal Gas Forming process (HMGF) has shown promising capabilities thanks to the increased formability and the possibility to form parts with lower pressures. The paper focuses on a novel experimental set-up to evaluate the tubes formability at high temperatures. Tubes are heated by electric current and air in pressure is used to form the material. Aluminium alloy AA6060 tubes specimens were used to test the experimental equipment and evaluate temperature and pressure ranges able to shape the material.
Acetaldehyde Generation in Processing PET by Means of Hot Runner Systems
Authors: Lucchetta Giovanni , Chirico Serafina
Published: May 2014

Polyethylene terephthalate (PET) is a polyester widely used as packaging material in drink-bottling application. PET is rather sensitive to heat and oxidation and during processing it may undergo degradation reaction with generation of acetaldehyde. In this work the generation of acetaldehyde in a hot runner system has been measured. A special test apparatus was developed to separate the contributions due to the action of the extruder screw from those due to the melt residence at high temperature. Results showed that the acetaldehyde content non-linearly increases with temperature and residence time. A model has been proposed to provide for the generation of acetaldehyde as a function of temperature and residence time regardless of the geometry and other specific conditions of the process.
Cold Forging with Lubricated Tools
Authors: Müller Christoph , Rudel Lena , Yalcin Deniz , Groche Peter
Published: May 2014

Cold forging processes require high-capability tribological systems in order to ensure sound forming results. Due to a rising ecological awareness, alternatives to the established and reliable conversion coatings are necessary. Single bath systems like polymers and salt wax coatings with integrated lubrication appear to be the most promising approach to prevent galling. For an optimization and investigation of the tribological system a definition of the tribological loads is necessary. However, only insufficient values are available in literature. Especially, long sliding distances, which occur in multistage operations, can cause a breakdown of the lubricant. Therefore, approaches are necessary to enable long sliding distances. This paper presents the results obtained with a cold forging tribometer, the Sliding Compression Test, which reveal the high impact of remaining lubricant on the friction coefficient. Also, tests with prelubricated tools show the ability to reduce the friction and the results of investigations with rough tool surfaces are presented.
Studies on Ductile Damage and Flow Instabilities during Hot Deformation of a Multiphase γ-TiAl Alloy
Authors: Halici Dilek , Zamani Hassan Adrian , Prodinger Daniel , Poletti Cecilia , Huber Daniel , Stockinger Martin , Sommitsch Christof
Published: May 2014

Gamma titanium aluminides are promising alloys for low-pressure turbine blades. A significant disadvantage of such intermetallic alloys is failure induced during forming processes due to ductile damage and flow instabilities. Previous investigations on a gamma titanium aluminide alloy (TNM), have shown ductile damage due to tensile stress components and instabilities such as shear bands, pores and micro-cracks at low temperatures and high strain rates. The main part of the current work is to delineate damage and unstable regions in the low temperature region. Hot deformation experiments are conducted on a Gleeble®3800 thermomechanical treatment simulator to obtain flow curves to be implemented in a finite element method (FEM) code. Instabilities in the material are described by existing instability criteria as proposed by Semiatin and Jonas and implemented into FEM code DEFORMTM 2D. Predictions of ductile damage models and the instability parameter are validated through detailed microstructural studies of deformed specimens analysed by light optical- and scanning electron microscopy.
Innovation and Processing of Novel Tough Ductile Ultra-High Strength Steels through TMR-DQP Processing Route
Authors: Somani Mahesh C. , Porter David A. , Karjalainen L. Pentti , Suikkanen Pasi , Misra R.D.K.
Published: May 2014

Based on the recent concept of quenching and partitioning (Q&P), a novel TMR-DQP (thermomechanical rolling followed by direct quenching and partitioning) processing route has been established for the development of ultra-high strength structural steels with yield strengths ≈1100 MPa combined with good uniform and total elongations and impact toughness. Suitable compositions were designed based on high silicon and/or aluminium contents with or without small additions of Nb, Mo or Ni. The DQP parameters were established with the aid of physical simulation on a Gleeble simulator. Finally, the TMR-DQP processing route was designed for trials on a laboratory rolling mill. Metallographic studies showed that the desired martensite-austenite microstructures were achieved thus providing the targeted mechanical properties. The advantage of strained austenite in refining the martensite packets/blocks was clearly evident. No adverse effect of prolonged partitioning simulating the coiling stage has been noticed suggesting new possibilities for strip and plate products. Promising results in respect of microstructures and mechanical properties indicate that there are possibilities for developing tough ductile structural steels through the TMR-DQP route.
The Effects of Cooling Rate on Retained Austenite Characteristics of a 0.2C-1.5Si-1.5Mn-1.0Cr-0.05Nb TRIP-Aided Martensitic Steel
Authors: Sugimoto Koh Ichi , Kobayashi Junya , Nakajima Yuji , Kochi Takuya
Published: May 2014

With the aim of increasing the volume fraction and stability of the retained austenite characteristics in a transformation-induced plasticity (TRIP)-aided steel with wider lath-martensite structure matrix, the effects of varying the post-hot-working cooling rate of a 0.2%C-1.5%Si-1.5%Mn-1.0%Cr-0.05%Nb (mass%) steel on the retained austenite characteristics were investigated. When, after hot-working at 950°C, the steel was cooled to room temperature from 430°C above the martensite-start temperature using cooling rates lower than 3°C/s, the steel attained a higher volume fraction of metastable retained austenite and lower volume fractions of a finely dispersed martensite-austenite complex phase, carbide, and pro-eutectoid ferrite, although the volume fraction of bainitic ferrite increased. This was associated with a marked carbon-enrichment in the untransformed austenite, which was mainly due to the promoted bainitic ferrite, the initial lath martensite, and the refined prior austenitic grain.
Effective Fluorine Treatment for Improved High Temperature Oxidation Behavior of Novel Cu, Mo and Si Containing TiAl-Alloys
Authors: Donchev Alexander , Galetz M. , Schütze M.
Published: May 2014

Intermetallic light weight TiAl-alloys are expected to replace the heavy Ni-based super alloys in several high temperature applications. However until now they cannot be used at temperatures above 700°C for longer times due to their insufficient oxidation resistance. The high temperature oxidation behavior can be improved drastically for the use at temperatures up to at least 1050°C by small amounts of fluorine in the surface region of TiAl-components. A thin protective alumina layer is formed after an optimized fluorine treatment during exposure in oxidizing high temperature environments. Results of isothermal and thermocyclic high temperature oxidation tests of untreated and halogen treated TiAl-samples of new types of TiAl-alloys containing Mo, Cu and Si will be presented in this paper. These results will be compared and discussed considering the beneficial effect of fluorine for a later use as e.g. turbine blades in jet engines.
Key words: Titanium aluminides, high temperature oxidation, halogen effect,
Evaluation of Tool Performance of Recycle-Type Fe3Al Based Alloy for Pure Cu
Authors: Itoi Takaomi , Sudo Tomoaki , Yoshimi Kyosuke
Published: May 2014

Recycle-type Fe3Al (hereinafter designated as Re-Fe3Al) based alloys reinforced by the carbides of TiC or ZrC were processed by the high frequency induction melting method using a high-carbon Cr steel sludge, Al can scraps and the transition metals of Ti or Zr. The carbides were synthesized by in-situ reaction between the transition metal and carbon in the molten iron aluminum alloy. Vickers hardness values are 309HV0.5 for Re-Fe3Al/TiC alloy, and 473HV0.5 for Re-Fe3Al/ZrC alloy, which are higher than that of P-Fe3Al (preprared from pure-Fe and-Al). The cutting performance of the Re-Fe3Al baed alloys was compared with a High-Speed-Steel (HSS) by cutting tests for pure-Cu extruded bar (C1020) using a lathe under a dry condition. Tool life limit was estimated from frank wear length after the cutting tests of C1020 by finish-machining. Tool life limit of Re-Fe3Al/TiC alloy is more than16 min; P-Fe3Al was 12 min; HSS was 8 min, Re-Fe3Al/ZrC alloy was 7 min at the cutting speed of 100m/min. Also, tool life limit of the Re-Fe3Al/TiC alloy was more than twice times as long as that of the HSS at the cutting speed of 300/min. The relationship between cutting speed and tool life limit clearly indicated that the Re-Fe3Al/TiC alloy was better than the HSS at a higher cutting speed. Therefore, it was concluded that Re-Fe3Al/TiC alloy has excellent cutting tool performance.
Layer-by-Layer Thin Films of Alginate/Chitosan and Hyaluronic Acid/Chitosan with Tunable Thickness and Surface Roughness
Authors: Taketa Thiago Bezerra , Beppu Marisa Masumi
Published: May 2014

Layer-by-layer (LbL) is a bottom-up technique used for construction of films with self-assembly and self-organizing properties. In most cases, the fundamental driving force for the formation of these films is originated from the electrostatic interaction between oppositely charged species. The charged segments of polyelectrolytes behave as small building units and their orientation and position can be designed to target structures of great complexity. Furthermore, the technique enables the use of various materials, including natural polymers. In this work, we chose the cationic biopolymer chitosan (CHI) and the negative polyelectrolytes sodium alginate (ALG) and hyaluronic acid (HA). The aim of this study was to evaluate the effect of ionic strength (0 versus 200 mM) and pH (3 versus 5) on ALG/CHI and HA/CHI nanostructured multilayered thin films properties. From profilometry and atomic force microscopy (AFM) analyses, changes in thickness and roughness of the coatings were monitored. The presence of salt in polyelectrolyte solutions induced the polymer chains to adopt conformations with more loops and tails and this arrangement in solution was transmitted to films, resulting in rougher surfaces. Furthermore, the film thickness can be precisely controlled by adjusting the pH of the polyelectrolyte solution. The variation of these parameters shows that it is possible to molecularly control chemical and structural properties of nanostructured coatings, thus opening up new possibilities of application (e.g. cell adhesion).
Additive Manufacturing for Medical and Biomedical Applications: Advances and Challenges
Authors: Koptioug Andrey , Rännar Lars Erik , Bäckström Mikael , Cronskär Marie
Published: May 2014

Additive Manufacturing (AM) has solidly established itself not only in rapid prototyping but also in industrial manufacturing. Its success is mainly determined by a possibility of manufacturing components with extremely complex shapes with minimal material waste. Rapid development of AM technologies includes processes using unique new materials, which in some cases is very hard or impossible to process any other way. Along with traditional industrial applications AM methods are becoming quite successful in biomedical applications, in particular in implant and special tools manufacturing. Here the capacity of AM technologies in producing components with complex geometric shapes is often brought to extreme.
Certain issues today are preventing the AM methods taking its deserved place in medical and biomedical applications. Present work reports on the advances in further developing of AM technology, as well as in related post-processing, necessary to address the challenges presented by biomedical applications. Particular examples used are from Electron Beam Melting (EBM), one of the methods from the AM family.
Osteoblast Ingrowth into Titanium Scaffolds Made by Electron Beam Melting
Authors: Koptioug Andrey , Bergemann Claudia , Lange Regina , Jaggi Victor Emanuel , Rännar Lars Erik , Nebe J. Barbara
Published: May 2014

Present paper describes early findings from the study of Ti-6Al-4V scaffolds additively manufactured using electron beam melting (EBM®) technology and the influence of surface topography on the initial stages of cell acceptance. The surface topography of the components made by additive manufacturing (AM) processes including EBM® are often hard to control within the desired feature size range without post-processing. Two groups of experiments studying the behavior of human osteoblast-like cells (MG63) on samples with different surface roughness were carried out in vitro: Ti-6Al-4V samples only powder-blasted, and Ti-6Al-4V samples additionally electrochemically polished. The cell migration into powder-blasted Ti-6Al-4V 3D scaffolds with different shapes and dimensions of the lattice structures were studied.
Optimization of Mo Content in Beta-Type Ti-Mo Alloys for Obtaining Larger Changeable Young’s Modulus during Deformation for Use in Spinal Fixation Applications
Authors: Nakai Masaaki , Niinomi Mitsuo , Hieda Junko , Cho Ken , Narita Kengo , Zhao Xing Feng
Published: May 2014

In order to meet the requirements of the patients and surgeons simultaneously for spinal fixation applications, beta (β) -type Ti-Mo alloys with self-tunable Young’s modulus due to deformation have been developed to prevent the stress-shielding effect for patients and to suppress springback for surgeons. In this study, the effects of Mo on the deformation-induced omega-phase transformation were investigated and then the Mo content in binary Ti-Mo alloys was optimized in order to achieve a large increase in Young’s modulus via deformation-induced omega-phase transformation, leading to suppression of springback.
Microstructure of Co-Cr Alloy Products with Three-Dimensional Geometry Fabricated by Laser Beam Sintering
Authors: Serizawa Ai , Tanaka Tomoki , Nakano Takayoshi
Published: May 2014

The development of the implant material which works much like bone must be an intrinsic approach to reduce the mechanical mismatch. Bone expresses the anisotropy of the mechanical characteristics based on the microstructual adaptation attributed to the apatite c-axis orientation corresponding to in vivo stress distribution. Therefore, the control of microstructure of implant material was performed by laser beam sintering technique aiming at the modification of mechanical property. The Co-Cr alloy products with three-dimensional geometry were successfully fabricated by laser beam sintering based on the design model. The grain showed an elongated dendritic morphology and aligned along the build direction during laser beam sintering. The crystallographic texture was developed responsible for the macroscopic heat flow along the build direction rather than the macroscopic one through the structures. Thus, the microstructure involving the grain morphology and crystallographic texture formation was anisotropically controlled by laser beam sintering technique. The mechanical properties could be modified anisotropically by the oriented microstructure in the Co-Cr alloy structures with three-dimensional geometry for the biomedical applications.
Octacalcium Phosphate: A Potential Scaffold Material for Controlling Activity of Bone-Related Cells In Vitro
Authors: Suzuki Osamu , Anada Takahisa
Published: May 2014

We have previously established a wet synthesis method of octacalcium phosphate (OCP) in a relatively large scale and found that OCP enhances bone formation more than synthetic hydroxyapatite (HA) if implanted onto bone surface and various bone defects. The present paper reviews, based on our studies, as to how OCP controls in vitro cellular activities of bone-related cells, such as bone marrow stromal cells, and how OCP enhances bone repair in critical sized bone defect experimentally created in animal models. OCP tends to progressively convert to HA in culture media and in rat calvaria defects. OCP is capable of enhancing in vitro osteoblast differentiation and osteoclast formation in the presence of osteoblasts. Recent our studies also indicated that OCP enhances odontoblast differentiation while suppresses chondrogenic differentiation. The physicochemical properties, such as chemical composition and adsorption affinity of serum proteins, vary depending on the advancement of conversion from OCP to HA, which suggests that the change on the surface property during the conversion of OCP may affect the cellular responses in vitro and tissue reaction in vivo. OCP could be used as a scaffold material that can control the activity of bone-related cells.