bluuebunny/crossref_metadata_2025 huggingface dataset:
High Content Screening for Bio-Medical Applications
Authors: Owen Cathy H. , Giffin Maile , Alley Ray K. , Chang Michael D. , Higashi Len K.
Published: October 2008

Near-field optics (NFO) overcomes the diffraction limit of light microscopes and permits single molecules to be imaged. Current NFO systems are designed to scan over the object being imaged and has found many applications in the physical sciences. However, there is a lack of tools that allow one to view intracellular processes, which would have many applications in the neurosciences, cancer studies and drug delivery fields. In this work, the authors have developed near-field optical probes, with nanometer apertures, that achieve much higher light throughput than conventional near-field fiber probes. The probes are designed to penetrate a living cell without destroying it. In parallel to this work, a microfluidic device has been designed and fabricated which is part of a high resolution imaging system the authors are developing. The microfluidic device or “CellTray” contains over 7000 individual wells that contain multiple cells. Together the optical probe and CellTray bring us a step closer to a lab-on-a-chip device for biomedical research.
Fabrication and Process Characterization of Piezoelectric Nano Fiber Composites
Authors: Shi Yong , Zhang Xiangyi , Xu Shiyou , Kim Sang-Gook
Published: October 2008

This paper studies the fabrication of nano piezoelectric fiber composites using an integrated nano/micro process. Previously, piezoelectric composites or Active Fiber Composites (AFCs) use large diameter piezo fibers (120 to 400 μm), which have limited their applications. Nano piezoelectric fiber composites provide much superior structural integrity and also enable the design and fabrication of nano active structures. In this paper, micro fabrication method was combined with electrospinning process to form the nano active fiber composites (Nano AFCs). Two polymer materials PDMS and Epon828 epoxy were studied as candidates for the matrix materials because of their compatibility with micro fabrication. Clamped-clamped Nano AFC beams were micro fabricated over a trench on a silicon substrate. The beams were studied with SEM and Atomic Force Microscope (AFM). More effort is needed to improve the uniformity of the nano fiber distribution and the process influence of the piezoelectric properties of the nano AFCs.
Synthesis Fe-Ni Alloy Magnetic Nanoparticles for Biomedical Applications
Authors: Tai Ming-Fong , Hsiao Jong-Kai , Liu Hon-Man , Lee Shio-Chao , Chen Shin-Tai
Published: October 2008

In this investigation, we synthesize FeNi alloy magnetic nanoparticles (MNPs) by using both chemical precipitation and combustion methods. The FeNi MNPs prepared by combustion method have a rather high saturation magnetization Ms of ∼180 emu/g and a coercivity field Hc of near zero. The functionalized FeNi MNPs which were coated with biocompatible polyethyleneimine (PEI) polymer have also been synthesized. We demonstrated that the PEI coated FeNi MNPs can enter the mammalian cells in vitro and can be used as a magnetic resonance imagine (MRI) contrast agent. The results demonstrated that FeNi MNPs potentially could be applied in the biomedical field. To prepare a higher quality and well controlled Fe-Ni MNPs, we also developed a thermal reflux chemical precipitation method to synthesize FeNi3 alloy MNPs. The precursor chemicals of Fe(acac)3 and Ni(acac)2 in a molecular ratio of 1:3 reacted in octyl ether solvent at the boiling point of solvent (∼300°C) by the thermal reflux process. The 1,2-hexadecandiol and tri-n-octylphosphine oxide (TOPO) were used as reducer and surfactant, respectively. The chemically precipitated FeNi3 MNPs are well dispensed and have well-controlled particle sizes around 10–20 nm with a very narrow size distribution (± 1.2 nm). The highly monodispersive FeNi3 NPs present good uniformity in particle shape and crystallinity on particle surfaces. The MNPs exhibit well soft magnetism with saturation magnetization of ∼61 emu/g and Hc ∼ 0. The functionalized magnetic beads with biocompatible polymer coated on MNPs are also generated completed for biomedical applications.
Mechanical Properties and Deformation Behavior of a Carbon Nanofiber Polymer Composite Material
Authors: Plaseied Atousa , Fatemi Ali
Published: October 2008

Tensile behavior of a carbon nanofiber reinforced vinyl ester polymer composite was studied using dog-bone shaped specimens to obtain its mechanical properties. Pyrograf III which is a very fine, highly graphitic and yet low cost carbon nanofiber was used as the fiber material. Vinyl ester with low molecular weight which was used as the matrix material is a thermoset with high tensile strength at room temperature. When small amounts of carbon nanofibers are combined with vinyl ester, the stiffness of the resulting composite can improve if the fiber-matrix adhesion is good. The mechanical properties can improve further after surface treatment (functionalization) of carbon nanofibers. This surface treatment adds some functional groups chemically to the nanofiber’s surface which increases the adhesion between nanofiber and matrix resin. Understanding the mechanical behavior of these composites is crucial to their effective application. In this research the stiffness, strength, and tensile deformation behavior of these nanocomposites were investigated. The effects of matrix curing systems and composition, strain rate, nanofiber concentration, nanofiber surface treatment and environment such as low and high temperatures and humidity were also characterized. Based on the mechanical properties simple models were used to represent tensile stress-strain and deformation behaviors of the nanocomposite. The experimental results were also applied to these models to examine their predictive capability.
The Role of Interface in Fabrication of Clay-Polyolefin (PO) Nanocomposites: Computation and Reality
Authors: Ton-That Minh-Tan , Li Jianming , Leelapornpisit Weawkamol
Published: October 2008

The effect of interfacial interaction between the nano-particles and the polymer matrix plays a determined role in the fabrication of polymer nanocomposites. For layered structure nano-particles like nanoclays, depending on the level of such interaction, the dispersion of the nanoclays can vary from micro-size (micro-composite) to nano-size (nano-composite, both intercalated and exfoliated structure). This article focuses on the effect of the interaction between the nanoclay and polypropylene matrix on the dispersion of the obtained nanocomposites. Both computation (molecular modeling) and experiments have been conducted on various systems (with different modifications of clay surface) in order to get a better understanding about this complex issue. The results have provided different useful highlights for the fabrication of polyolefin nanocomposites.
Fabrication, Thermal and Mechanical Characterization of Silicon Carbide-Expancel Nanocomposite
Authors: Rangari Vijaya , Watson Tiffianni , Jeelani Shaik
Published: October 2008

A novel sonochemical method is developed to infuse silicon carbide nanoparticles (SiC) into expandable thermoplastic micro-spheres (Expancel) containing acrylonitrile and methylacrylonitrile polymer. Expancel micro-spheres consists a drop of liquid hydrocarbon encapsulated by a gas proof thermoplastic polymeric shell. These micro spheres expand ∼4 to 5 times of their original size (10μm) and drastically decrease it’s density from ∼1000kg/m3 to ∼30kg/m3, when exposed to the heat. To fabricate nanocomposite foam the Expancel microspheres were first dispersed in hexane along with known percentage of SiC nanoparticles and irradiated with high intensity ultrasonic horn for about 30min at room temperature. The excess n-hexane is removed using a high vacuum for 12h and heating at 60°C for 1h successively. The dry powder is transferred into a rectangular stainless steel mold and the mold is heated to ∼190°C at a heating rate of 10°C for 30 min using a MTP-14 programmable compression molding under a pressure of ∼ 3000lbs. The test coupons were cut precisely from the panels to carry out thermal, morphological and mechanical characterizations. The as-prepared nanophased foam samples were characterized by scanning electron microscopy (SEM), thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The SEM studies have shown that the SiC are well dispersed over the entire volume of the matrix with minimal, agglomeration. The foam cells structures are well ordered and uniform in size and spherical in shapes. The TGA and DSC analyses indicate that the nanophased foam materials are thermally more stable than the corresponding neat systems. Compression tests have been carried out for both nanophased and neat foams systems. Test results show a significant increase in compressive strength and modulus of the nanophased foams over the neat system. This enhancement in compressive properties has been observed repeatedly for multiple batches. Details of the synthesis procedure, thermal and mechanical characterization are presented in this paper.
Nanocomposites and Hierarchical Nanocomposites Development at Hawaii Nanotechnology Laboratory
Authors: Ghasemi-Nejhad Mehrdad N. , Cao Anyuan , Veedu Vinod , Askari Davood , Gudapati Vamshi
Published: October 2008

This paper presents activities related to the development of nanocomposites and hierarchical nanocomposites; at the Hawaii Nanotechnology Laboratory of the Department of Mechanical Engineering of the University of Hawaii at Manoa. On nanocomposites, developments on toughening of polymeric materials employing nanoparticles and carbon nanotubes are reported. On hierarchical nanocomposites, first, mechanical properties improvements for continuous fiber ceramic composites using nanoparticles are discussed. Second, a multifunctional micro-brush using carbon nanotubes is discussed. Third, the structure of a micro-foam using carbon nanotubes is explained. Finally, the multifunctional properties improvement of a novel three-dimensional hierarchical nanocomposite employing carbon nanotubes is discussed. In closing, the effect of chirality of single-walled nanotubes on their thermomechanical properties evaluated analytically using asymptotic homogenization method and numerically employing finite element method will be explained, and analytical closed form solutions for matrix filled nanotube nanocomposites, also verified numerically, assuming generally cylindrical orthotropic properties will be reported.
Mechanical Properties of Matrix Filled Single-Walled Carbon Nanotube Reinforced Nanocomposites
Authors: Askari Davood , Ghasemi-Nejhad Mehrdad N.
Published: October 2008

It is frequently reported that carbon nanotubes can efficiently be used to reinforce composite materials and considerably improve their structural mechanical properties. Therefore, it is essential to investigate the effective properties of such nanocomposites. In this work, an analytical approach is employed to derive the analytical exact solutions for the effective Young’s modulus and major Poisson’s ratio of a three-phase composite cylinder model representing a matrix filled single-walled carbon nanotube (SWCNT) embedded in another host material. In this study, all three constituents are considered generally cylindrical orthotropic. For validation, results from finite element analysis of an identical 3-D model are compared to those obtained analytically. It is shown that both techniques are in excellent agreement and therefore analytical exact solutions for the prediction of effective axial Young’s modulus and major Poisson’s ratio of the filled SWCNT embedded in another host material and all having orthotropic properties are verified.
Active Nanocomposite Polymers: Enhancing Sensing and Actuation Performance
Authors: Ounaies Zoubeida , Almasri Atheer , Banda Sumanth , Kim Yeon Seok , Grunlan Jaime
Published: October 2008

The dispersion of nanoparticles, especially those with high aspect ratio, into polymers has been shown through numerous commercial and academic ventures to yield an array of impressive property enhancements for a surprisingly low volume fraction (<5 vol%) of nanoparticle addition, thus maintaining the inherent processibility of the polymer. In this work, we propose a new generation of sensors and actuators based on a piezoelectric polymer (PVDF) with embedded carbon nanotubes. Polyvinylidene fluoride (PVDF)-double walled carbon-nanotubes (DWNT) composite films are prepared with the goal to develop new polymeric materials with enhanced electrical and electromechanical properties. Electrical conductivity and dielectric properties of polyvinylidene fluoride- double-walled carbon nanotubes composites are investigated as a function of frequency (10 Hz–1 MHz), and as a function of weight fraction (0.01–2 wt%). DWNT and PVDF are mixed under mechanical stirring and sonication. The dispersion is assessed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), indicating a good dispersion. Differential Scanning Calorimetery (DSC) is used to study the effect of DWNTs inclusions on the glass transition temperature, Tg, and the crystallinity of the resulting PVDF composite. The percolation threshold is computed by using the bulk conductivity data and it is found that percolation occurs at about 0.19wt%. These investigations promise to increase our understanding of the mechanisms involved, particularly as related to nanoparticle/polymer interaction. This in turn would allow us to tailor the polymer nanocomposites to yield desired performance in terms of actuation voltage, electroactive strain, blocking stress and response time to name a few.
Molecular Dynamics Study of Carbon Nanotubes in Bundles
Authors: Jensen Lars R. , Pyrz Ryszard
Published: October 2008

Molecular mechanics and dynamics have applied to study the behavior of single wall carbon nanotube bundles. A geometrical transformation of the nanotube cross section was observed when the tube diameter exceeded 1,4 nm where the cross section changed from circular to hexagonal. The elastic properties of the bundles were examined and shown to depend on the tube diameter but not on the geometrical transition. The interfacial shear strength between the adjacent tubes was estimated and shown to depend both on the diameter and on the geometrical transition.
Solar Photocatalytic Degradation of Atrazine in Water by TiO2/Ag Nanocomposite
Authors: Ge Ming , Azouri Assaf , Xun Kun , Sattler Klaus , Lichwa Joe , Ray Chittaranjan
Published: October 2008

One of the most common herbicides in the world, Atrazine, was used as a model pollutant in this study. The photocatalytic activities of the nanocomposite of TiO2/Ag, with nanopaticles of TiO2 and Ag, were investigated by photodegradation of atrazine under the natural sun. It was found that the efficiency of solar-photocatalytic activity was increased significantly by using the nanocomposites of TiO2/Ag, compared to the use of TiO2 alone. The mechanism of the TiO2/Ag composite for enhancement of photocatalytic activity was elucidated in this work.
Assembly at the Nanoscale: Towards Functional Nanostructured Materials (Invited)
Authors: Ozkan Cengiz S.
Published: October 2008

This paper reports the self assembly of functional nanostructured materials including multi-walled Carbon Nanotube-Quantum Dot (CNT-QD) heterojunctions using the Ethylene Carbodiimide Coupling procedure (EDC). Thiol stabilized ZnS capped CdSe quantum dots containing amine terminal groups (QD-NH2) were conjugated with acid treated Multi-Walled Carbon Nanotubes (MWCNT) ranging from 400 nm to 4μm in length. SEM, TEM, EDS and FTIR were used to characterize the conjugation process.
Fabrication of Laminated Nanocomposites by Vacuum-Assisted Deposition of Clay Onto Glass/Epoxy Prepregs
Authors: Aktas Levent , Altan M. Cengiz
Published: October 2008

In this study we are presenting a novel method for introducing nanoclay in epoxy matrix composites. The method involves vacuum-assisted deposition of fine clay particles directly onto the surface of commercially available prepregs. A deposition chamber is developed that is capable of breaking down nanoclay particles by subjecting them to shear and depositing them uniformly onto prepregs at room temperature. By using the deposition chamber, a thin layer of nanoclay is deposited on 101.6mm×101.6mm woven glass/epoxy prepregs. Twelve of these prepregs are stacked and cured by an autoclave at a temperature of 121°C under a constant pressure of 0.2MPa (30psi) for 1 hour. After the curing is complete, the laminates are cut into 10.8mm×31.7mm samples for three-point bending tests, glass transition temperature measurements and microstructural characterization. The improvements in mechanical properties such as flexural strength, flexural stiffness, and glass transition temperature by the addition of nanoclay are presented. Nanocomposite morphology is studied by light microscopy and scanning electron microscopy. Marginal improvements in mechanical properties are observed with only 0.6% nanoclay content. The flexural stiffness improved by 4% while maintaining the flexural strength constant at around 400Wa. Glass transition temperature is measured as 128°C for samples with and without nanoclay. However, significant differences in microstructure are observed. Although both samples contain micro-voids, these voids are observed to be more extensive in samples involving nanoclay.
Structure and Properties of Nanocomposites With a Poly(Ethylene Terephthalate) Matrix
Authors: Gurmendi U. , Eguiazabal J. I. , Nazabal J.
Published: October 2008

Polymer nanocomposites based on poly(ethylene terephthalate) PET and with an intercalated and fairly dispersed nanostructure have been obtained in the melt state using a twin screw extruder. The intercalation and dispersion levels as well as the mechanical properties were studied varying the chemical nature and amount of the organic modification of the clay as well as the clay content. The intercalation level of PET into the organoclay galleries was measured by the increase in the interlayer distance upon mixing. The surfactant content did not influence the intercalation level but an interaction between the polymeric matrix and the surfactant, through a common polar character led to easier intercalation. The observed modulus increases and consequently the overall dispersion did not almost depend on either the amount or chemical nature of the used organic modification of the clay, suggesting that the parameters leading to high intercalation differ from those lead to a high modulus of elasticity and therefore to a high dispersion level. The obtained increases in the modulus of elasticity that reflect the dispersion level were large attaining a 41% increase with respect to that of the matrix after a 6wt% clay addition.
Inorganic-Polymer Nanocomposites for Optical Applications
Authors: Du H. , Ng S. H. , Neo K. T. , Ng M. , Altman I. S. , Chiruvolu S. , Kambe N. , Mosso R. , Drain K.
Published: October 2008

The combination of organic and inorganic materials forms unique composites with properties that neither of the two components provides. Such functional materials are considered innovative advanced materials that enable applications in many fields, including optics, electronics, separation membranes, protective coatings, catalysis, sensors, biotechnology, and others. The challenge of incorporating inorganic particles into an organic matrix still remains today, especially for nanoparticles, due to the difficulties in their dispersion, de-agglomeration and surface modification. NanoGram has pioneered a nanomaterials synthesis technology based on laser pyrolysis process to produce a wide range of crystalline nanomaterials including complex metal oxides, nitrides and sulfides and with precisely controlled compositions, crystal structure, particle size and size distributions. In this paper we will present some examples of nanocomposites prepared using different polymer host materials and phase-pure rutile TiO2. The inorganic component can be dispersed at higher 50 weight percent into the polymer matrix. We have demonstrated a 0.2–0.3 increase of refractive index in the composite over that of host polymer while maintaining high optical transparency. These nanocomposites can be used in a range of applications or optical devices, such as planar waveguides, flat panel displays, optical sensors, high-brightness LEDs, diffraction gratings and optical data storage. Experimental data on TiO2 nanoparticle characterization, dispersion technique, surface modification and will be presented and nanocomposite properties discussed.
Effect of Fluence on the Discoloration of Marble Cleaned With UV Lasers
Authors: Zhang Jie , Birnbaum Andrew J. , Yao Y. Lawrence
Published: October 2008

The effect of fluence level on the discoloration of marble surfaces after the removal of the encrustation by 355nm laser pulses is comparatively studied. Considering the thermochemical reaction possibly occurring in the encrustation during laser irradiation, the mechanism responsible for the discoloration of the cleaned marble surface is analyzed. The reduction of iron oxides by graphite plays a key role in determining the final color of the cleaned marble surface. A two-dimensional laser ablative cleaning model including the reaction heat is applied to calculate the temperature distribution during laser heating. The kinetics of the thermochemical reaction is estimated based on the simulated temperature field. The occurrence of the thermochemical reaction is also verified indirectly with experiments. The marble surfaces before and after laser irradiation are characterized in term of the chemical components through surface enhanced Raman spectroscopy. The surface color is measured with a chromameter using a 1976 CIE Lab color system. The proposed mechanism is also applied to numerically analyze the severer discoloration of marble cleaned with laser pulses at 1064nm.
Intelligent Energy Field Manufacturing (EFM)
Authors: Zhang Wenwu , Azer Magdi
Published: October 2008

The nature of manufacturing is using information to control energy field in order to convert material into useful configurations, products, and systems. One way to view manufacturing differently is to explore it from the perspective of energy fields. In this paper, the origination and the evolution of Energy Field Manufacturing (EFM) and the concept of a dynamic M-PIE (Material-Process-Information-Energy) model of manufacturing are reviewed. The generality of energy fields and the importance of re-thinking of traditional and non-traditional manufacturing are discussed. Giving a general definition to intelligence, this paper further broadens the methodology of EFM to Intelligent EFM, which incorporates the ability to gather, interpret and use the information in energy fields, materials and systems in a systematic way. This paper further discusses the meaning and tasks of Intelligent EFM research. A systematic approach of energy field integration and optimization is proposed. Finally, representative processes are reviewed to highlight some principles of Intelligent EFM.
From Incident Laser Pulse to Residual Stress: A Complete and Self-Closed Model for Laser Shock Peening
Authors: Wu Benxin , Shin Yung C.
Published: October 2008

Laser shock peening (LSP) is emerging as a competitive alternative technology to classical treatments to improve fatigue and corrosion properties of metals for a variety of important applications. LSP is often performed under a water confinement regime (WCR), which involves several complicated physical processes. A complete and self-closed LSP model is presented in this paper, which requires a sequential application of three sub models: a breakdown-plasma model, a confined-plasma model, and a finite element mechanics model. Simulation results are compared with experimental data in many aspects under a variety of typical LSP conditions, and good agreements are obtained.
Laser-Assisted Milling of Silicon Nitride Ceramics
Authors: Tian Yinggang , Wu Benxin , Shin Yung C.
Published: October 2008

Laser-assisted machining (LAM) has shown its potential to significantly reduce fabrication costs and improve product quality for advanced ceramic materials. While extensive studies have been conducted on laser-assisted turning (LAT) of various ceramics, few attempts have been made to extend LAM to milling operations. In this paper, a transient, three-dimensional thermal model is developed for laser-assisted milling (LAML) and verified by surface temperature measurements with an infrared camera. LAML experiments designed by the model are successfully conducted on silicon nitride ceramics using TiAIN coated carbide end mills. The promising experimental results, including good surface roughness and acceptable tool wear, show the validation of applying the thermal model to design LAML processes and the feasibility of employing LAML to advanced ceramics.
Non-Traditional Micromachining Using Pulsed Liquids
Authors: Jackson M. J.
Published: October 2008

Non-traditional machining using the energy afforded by pulsed liquid impacts is currently being applied to machining materials at the microscale. This paper discusses the theoretical modelling of liquid impact machining thresholds as a result of temporal and spatial distributions of transient stresses in elastically deformable materials. The model predicts changes in the response characteristics of materials due to an idealised representation of a liquid droplet impacting a plane surface. The analytical approach used does not include the secondary effects of liquid impact and is therefore only applicable to the first stages of impact where the compressibility of the liquid droplet is most significant. The predicted response characteristics are compared with experimental data generated using a specially constructed micromachining center. The predicted response of a model material compare well with the experimental results. The results presented in this paper illustrate the importance of the energy provided by pulsed liquid impacts to remove material at the microscale. The secondary effects of liquid droplet dispersion are also illustrated and the mechanism of material removal during liquid droplet dispersion is described in detail.
Regenerative Chatter in High-Speed Tandem Rolling Mills
Authors: Zhao Huyue , Ehmann Kornel F.
Published: October 2008

Third-octave-mode chatter, the most detrimental form of rolling chatter, is generated by means of negative damping, mode coupling, and regeneration. While mechanisms that include negative damping, and mode coupling have been thoroughly investigated, those associated with the regenerative effect remain elusive. In this paper, the mechanisms that may lead to regenerative chatter are studied through a state-space representation of a multi-stand mill that is constructed by coupling a homogenous dynamic rolling process model with a structural model for the mill stands in a high-speed tandem mill configuration. Stability analysis, by using the integral criterion for the stability of systems described by delay differential equations, is carried out for the regenerative mechanism in order to better understand the effects of rolling parameters on a single stand as well as the overall system. Preliminary simulation results, based on the proposed chatter model, are presented to demonstrate the feasibility and the accuracy of the chatter model, as well as to investigate chatter phenomena too complex to be studied analytically.
Fundamental Studies on Incremental Forming of Titanium Sheet-Metal
Authors: Hussain G. , Gao L.
Published: October 2008

Several aspects of Incremental Forming, an innovative sheet-metal-forming process, were studied. Firstly, an optimal combination of tool and lubricant was explored to form the TA1 (commercial Titanium) sheet-metal parts. Secondly, the effect of the tool diameter on the surface texture of a part was investigated. In addition to this, the influence of the tool diameter on in-plane strain distribution and thickness distribution along a part was also studied. Lastly, experiments were conducted in order to investigate the influence of half-apex angle on thickness distribution along a part to be formed. It has been concluded that the surface coating of sheet-blanks is essential to form the TA1 parts with good surface textures, and the dispersion of MoS2 powder in grease should be rubbed on the coated surface of the sheet-blank to provide lubrication between the tool tip (tip of a surface-hardened HSS tool) and the sheet-blank surface. Furthermore, the tool diameter has no effect on the texture of a formed surface, the deformation mode, and the in-plane strain distribution on a part. It has also been found that the tool diameter does not influence the thickness distribution along a part; rather this is governed by the Sine of half-apex angle of the part to be formed.
An Investigation of Drawbead Models for Springback Prediction
Authors: Ren F. , Xia Z. C.
Published: October 2008

Accurate prediction of springback for rail-type structures remains a significant challenge for automotive stamping. A major characteristic of forming such parts is that metals go through drawbeads and die-entry radii and often end up within part geometry (i.e., inside trimline). The bending-unbending stresses generated by drawbeads contribute significantly to the eventual springback. In production springback simulation, line drawbead models are generally used to represent the restraining forces provided by the real drawbeads for computational efficiency. While such models can be well correlated to match overall deformation of the part, the bending stresses could not be accurately captured. In the present study, a model of an aluminum U-channel is used to evaluate springback predictability of line drawbead model, which is then compared against simulations that employ detailed drawbead geometry. The results show that the line drawbead model largely under-predicts the springback and the bending moment. The accuracy of the prediction cannot be improved through different binder simulation strategies such as displacement-control or force-control. The study suggests that either real drawbeads be modeled, or the bending stress be incorporated into the line model to improve springback prediction.
Reconfigurable Tooling for Overhaul and Repair
Authors: Nardiello J. A. , Anagnostou E. L. , Christ R. , Hoitsma D. , Ogilvie P. , Papazian J. M.
Published: October 2008

This paper will describe our initial operational experience using a reconfigurable-tooling-based stretch-forming work cell for production of sheet metal parts. This facility was created in response to the need to rapidly reverse engineer and manufacture sheet metal components in an overhaul and repair environment. The system is expected to dramatically reduce part lead time and cost, and reduce the need for fixed dies. This is an integrated hardware/software system comprised of a reconfigurable computer-controlled die with 1120 discrete elements, a laser moire´ interferometry shape measurement system, an automated finite element forming process simulation system, and an overall Manufacturing Design Software System/Shape Control Loop. These capabilities are integrated with a modern stretch-forming press. This system is particularly useful where part data may not exist other than the physical part to be duplicated, and where short lead times and low production quantities are prevalent. The typically iterative tasks of designing and methodizing the manufacturing process are significantly reduced by the software system which allows for rapid capture of part geometric data, its subsequent use in simulating the forming process, and for setting the surface shape on the reconfigurable tool. Results will be shown indicating that part shape fidelity can be maintained within required tolerance, and often improved upon, while providing reduced lead time and cost.
Planar Flame Hydrolysis and Sintering of Silica Parts
Authors: Hawtof Daniel , Stone John , Rosettie John
Published: October 2008

An apparatus and process has been designed and developed to fabricate silica soot in a planar orientation to form preforms that are sintered to clear glass in the same process platform. Flame hydrolysis is used to combust and react silica precursors to create SiO2 particles. The silica particles are generated on the order of 100 nm in size and stick to the target through the mechanism of thermophoresis. The principle precursor used to produce the silica is an organometalic liquid, octamethylcyclotetra-siloxane. The flame is a methane/oxygen torch with additional oxygenprovided for chemical stoichiometry targets. The silica particles created are directed towards, and collected upon, a rotating circular target placed several inches downstream of the flame. Preforms of various diameters and thickness are fabricated over time.
Correlation Between Strain and Exfoliating Performance of Galvannealed DP Steels
Authors: Xu Chun , Li Shuhui
Published: October 2008

The galvannealed dual-phase steels are used in automotive applications. However, galvannealed coating is often exfoliated when it is in the pressing process. Galvannealed exfoliation is examined as a function of strain state using double reserve Olsen test to simulate forming process. Distances of punch in first and second reverse Olsen tests are changed to used to generate other strain state. The circle grids are etched on sheet to measure strain. Significant exfoliating is encountered in biaxial compress strain zone while no exfoliating occurred in biaxial tensile strain zone. Exfoliating is measured at specific locations and correlated with strains in those locations. An exfoliating map is generated in strain space.
New Evaluation Method for Lubricant in Forging Process
Authors: Ito Shigekazu , Yoshida Hiroaki , Isogawa Sachihiro , Doi Yoshihisa , Dohda Kuniaki
Published: October 2008

A lubricant plays a very important role in forging. It can reduce the forging load and make for smooth knockout. The tribo-simulator tests that have often been used as standard evaluation methods for metal forming lubricants includes the ring compression test and spike forging test. However, the forging of components such as flange bolt and constant velocity joint is more severe than a spike forging test or ring compression test. Thus, the development of an evaluation method for lubricants for use in more severe conditions is much awaited. We have developed a new evaluation tribometer using backward extrusion with a taper punch. The new device is called a “Taper Cup Tribometer.” The taper cup test can evaluate lubricity under large deformation conditions. In this test, the surface expansion ratio can be controlled by changing the punch stroke. The surface expansion ratio of the new taper cup tribometer is around 15 to 50, as calculated by fine element analysis. The results of lubricant evaluation in cold forging of carbon steel are as follows. Zinc phosphate has a lower forging load than other lubricants, making it clear that it is a superior lubricant. Oil, on the other hand, has a high forging load and poor lubrication characteristics. The taper cup Tribometer can evaluate the friction characteristics of lubricants. Furthermore, MoS2 shows a higher forging load than zinc phosphate in the region of higher surface area expansion ratio around 12. The forging load of oil is higher than zinc phosphate in the region of higher surface area expansion ratio around 4. In this way, the new taper cup tribometer can recognize the forging limit for the lubricant under the forging load.
Effects of Local Heating on Material Flow in Free Forming Process
Authors: Okman O. , O¨zmen M. , Huwiler H. , Tekkaya A. E.
Published: October 2008

A novel manufacturing method is investigated, in which a proper temperature gradient is created within workpiece in order to control local material flow during free forming. The main motivation is to produce complicated shapes by reducing the flow stress on the regions, where local deformation is desired to take place. A sufficient control of temperature within the material results in the required product shape even in the absence of complicated dies. Besides the lower tooling costs the process provides, the heat energy applied to the workpiece is less than that in conventional hot forming processes, which is currently a strong alternative for manufacturing of such products. In the study, heating is realized by means of induction heating and laser beam scanning. The process is investigated experimentally on circular cylinder specimens made of different materials, namely Ti6Al4V, X5CrNi18/9 and 16MnCr5. The effect of process parameters on the mode of deformation is analyzed by finite element method (FEM). The thermo-mechanical analysis of induction heating is supported by electromagnetic calculations. The two alternative heating methods are compared. Affects of heating on multiple locations is investigated for induction heating applications. A brief overview of the process is presented and conclusions are drawn on the effectiveness, limitations, failure modes and applicability of the process.
Effect of DC Current on the Formability of 6Al 4V Titanium
Authors: Ross Carl D. , Kronenberger Thomas J. , Roth John T.
Published: October 2008

Recent research has demonstrated that the mechanical properties of metallic materials are altered when an electrical current is passed through the material. These studies suggest that titanium, due to its low formability and potential for dramatic improvement, should be subjected to additional study. The research presented herein further investigates the use of electricity to aid in the bulk deformation of 6Al-4V titanium under tensile and compressive loads. Extensive testing is presented that documents the changes that occur in the formability of titanium due to the presence of an electron wind at varying current densities. Using carefully designed experiments, this study also characterizes and isolates the effect of resistive heating from the change due to the electrical flow alone. The results demonstrate that the presence of an electrical current within the material during deformation can greatly decrease the force needed to deform titanium while also dramatically enhancing the degree to which it can be worked without fracturing. Isothermal testing further demonstrates that the changes are significantly beyond that which can be accounted for due to increases in the titanium’s temperature. The results are also supported by data from tests using pulsed and discontinuously applied current. Furthermore, current densities are identified that cause an apparent superplastic behavior to occur. Overall, this work fully demonstrates that an electrical current can be used to significantly improve the formability of 6Al-4V titanium and that these improvements far exceed that which can be explained by resistive heating.
Experimental and Numerical Analysis of the Buckling and Post-Buckling Phenomenon in the Yoshida Test
Authors: Cheng Hang Shawn , Cao Jian , Wang Hui-Ping
Published: October 2008

Simulation-based Design and Manufacturing has shown its great effectiveness in shortening the design cycle. The objective of this work was to further increase the robustness of numerical prediction in capturing subtle wrinkling in sheet metal forming process. A stress-based wrinkling predictor is further developed to predict the initiation and wave mode of potential wrinkling in forming of flat sheet. The predictor is linked to the LS-DYNA commercial FEM package. Stress prediction from LS-DYNA was compared to the implicit code ABAQUS and satisfactory results were obtained. Hence, stress, nodal coordinates and connectivity information of the LS-DYNA simulation are fed into the predictor via an automatic interface program. A set of Yoshida buckling tests was used as a verification tool for the wrinkling predictor. 0.78mm thick 180B steel and 1.012mm thick 6111-T4P aluminum are tested. Through the comparison of the experiments and simulations, it shows that the wrinkling predictor is able to predict the initiation point and wave mode for the wrinkling accurately. In addition, post-buckling behavior in numerical simulations was captured through including initial imperfections following the wrinkling mode predicted. It was found that such a method provides more reliable results in terms of the post-buckling behavior than random imperfection.
Investigation of Size Effects on Process Models for Plane Strain Microbending
Authors: Onyancha Richard M. , Kinsey Brad L.
Published: October 2008

Accurate process models provide vital information in the design of manufacturing processes. To characterize bending operations, analytical models have been developed and shown to predict the peak bending forces fairly accurately for sheets in the macro or mesoscale (i.e. sheets with a large number of grains through the thickness). However, whether these models also accurately predict bending forces for sheets in the microscale (i.e. sheets with approximately ten grains or less through the thickness) has not been evaluated. The present study is aimed at investigating the use of two such models from previous work with microscale bending data. In addition, using these previous models as a foundation, additional bending force models were developed to predict the bending force specifically for microscale bending operations. Data analysis showed that the process models from past research, which provide accurate results for macroscale bending, over predict the peak force required for bending microscale sheets. These process models assume a non-linear strain distribution through the thickness and a curved formed wall. The two models developed in this research provide accurate results for the microscale bending tests, however, they under predict the peak force for the macroscale bending operation. These developed process models assume a linear strain distribution through the thickness and a straight formed wall. The linear strain distribution is more appropriate for the microscale bending process as there are few grains through the thickness and the strain in individual grains varies linearly across the grain. The straight formed wall is more appropriate for the microscale bending process as there is not sufficient distance to warrant a curved formed wall assumption. These differences represent size effects for assumptions in the process models. The material used for these investigations was Brass (CuZn15). The sheets had between 2 and 50 grains through the thickness with grain sizes of between 10 μm and 71 μm.
Formability of Steel Tubes in Corner Fill Hydroforming
Authors: Chen Kuo-Kuang
Published: October 2008

Corner fill is a benchmark test intended to gain knowledge of tube hydroforming and to evaluate hydroforming parameters. The tests are used to compare steel grades, tube thickness and lubricants in tube hydroforming in this paper. The performance of the above variables were assessed by the final corner radius, radial displacement, burst pressure, burst location and thickness variations attained at burst. The formability of the tubes were indicated by the final corner radius and radial displacement attained at burst. The tests were simulated by finite element analysis using the measured coefficients of friction and mechanical parameters of the steel tubes. It was found that the pressure-expansion relations can be accurately predicted. However, burst pressures predicted by forming limit diagram and plastic strain criterion are too low for the AKDQ steel tubes compared to the experimental results. The discrepancy is due to the fact that the burst criteria used are not developed for tube hydroforming in a die where the radial stress and shear deformation can not be neglected. The need of better prediction methods is addressed.
Deposition of Rare-Earth Doped Nanophosphors on Multi-Wall Carbon Nanotube Surfaces: A New Approach in Cancer Diagnosis
Authors: Shi Donglu , Guo Yan , Wang Wei , Cho Hoonsung , Lian Jie , Wang Lumin , Ewing Rodney C. , Liu Guokui , Dong Zhongyun
Published: October 2008

In biomedical science and nanotechnology, it often requires surface multi funcationalization of a nanoparticle or a nanotube. In cancer diagnosis for instance, not only does the nanoparticle need a cavity structure for storage and delivery of drugs, but also be luminescent for diagnosis. Europium doped Y2O3 were deposited on the multi wall carbon nanotube (MWCNTs) surface by a novel solution method. High resolution transmission electron microscopy (HRTEM) experiments were carried out to study the surface morphologies of the deposited rare-earth doped nanophosphors on MWCNTs. The crystal lattice structures of the surface deposits were identified by using selected area electron diffraction. The optical properties of the surface functionalized MWCNTs were characterized by using a fluorescent spectrometer.
Modeling and Assessment of Porosity Effects on Mechanical Properties of Tissue Scaffolds
Authors: Parks W. M. , Guo Y. B. , Woodbury K. A.
Published: October 2008

Mechanical properties of scaffolds are important for fabricating engineered tissues. However, localized mechanical properties of scaffold cannot be directly obtained from experiments. This study provides a solid modeling approach to simulate mechanical behaviors of alginate scaffolds with different porosity. A scaffold micro-domain has been modeled as made of sub-units, arranged in a sphere-based pore architecture. An expression to calculate porosity was also derived for the scaffold architecture. Finite element simulations of compressing alginate scaffolds were performed to evaluate the effect of porosity on quasi-static mechanical behavior. The developed FEA model is capable of computing scaffold strength and predicting localized mechanical behavior without destructive materials testing.
Engineering Homogeneous Micromagnetic Fields for Cell Patterning
Authors: Loh Jeremy , Schumacher Karl , Schumacher Annegret , Kan Shyi-Herng , Ying Jackie Y.
Published: October 2008

Micropatterning of cells was achieved by the application of micromagnetic fields using ferromagnetic field modulators. These modulators were made of low carbon steel, and micromachined using the wire-cut method. They were engineered to disrupt the regular pathways of magnetic flux lines, and create localized regions of micromagnetic fields. Uniform micromagnetic fields were achieved via design evaluation using Maxwell®2D magnetostatic simulations. Application of the micromagnetic field modulators on Madin-Darby canine kidney (MDCK) epithelial cells demonstrated good cell adhesion and uniform cell columns of 200 μm-wide, spaced 200 μm apart. This approach would be useful towards cell micropatterning for tissue engineering, artificial organ and implant applications.
Designing Body-Part Templates for Regeneration
Authors: Ma Peter X.
Published: October 2008

Tissue losses and organ failures result in more than 8 million surgical procedures each year in the United States. Current therapies for these disorders are seriously limited. Our laboratory takes a biomimetic approach to design polymers into body-part templates (scaffolds) to engineer tissues/organs. The scaffolds are designed to take the form of the missing/damaged body parts, to mimic certain advantageous aspects of natural extracellular matrix, and to contain certain designed structural features to enhance tissue regeneration. To mimic bone matrix, biodegradable polymer/nano-hydroxyapatite composite scaffolds have been developed. To mimic the nano-fibrous architecture of collagen, synthetic nano-fibrous scaffolds have been developed. To optimize scaffolding function, a variety of macropore networks have been designed in the nano-fibrous materials. These novel nano-structured scaffolds enhance cell adhesion and function. Surface engineering and biological delivery in the nano-fibrous scaffolds are shown to improve cellular interactions and tissue formation. These experimental results demonstrate that the biomimetic template design is a powerful approach for tissue regeneration.