bluuebunny/crossref_metadata_2025 huggingface dataset:
Free Vibration Analysis of Multilayered Functionally Graded Composite Cylinder
Authors: Kargarnovin M. H. , Hashemi M.
Published: May 2012

Free vibration of multilayered composite cylinder which volume fraction of fiber varies according to power law in longitudinal direction has been studied. Rule of mixture model and reverse of that are employed to represent elastic properties of this fibrous functionally graded composite. Strain-displacement relations employed are based on Reissner-Naghdi-Berry’s shell theory. The displacement finite element model of the governing equations of motion is derived by writing weak form of them. The Lagrangian shape functions for in-plane displacements and Hermitian shape functions for displacement in normal direction to the surface of mid-plane are utilized by defining a conformal quadrilateral element. The results show that by appropriate grading material properties of fiber in longitudinal direction the natural frequencies can be increased in comparison with traditional composite in which volume fraction of fiber does not vary.
Circulation Control Span-Wise Blowing Location Optimization for a Helicopter Rotor Blade
Authors: Didion Alan M. , Kweder Jonathan , Clarke Mary Ann , Smith James E.
Published: May 2012

Circulation control technology has proven itself useful in the area of short take-off and landing (STOL) fixed wing aircraft by decreasing landing and takeoff distances, increasing maneuverability and lift at lower speeds. The application of circulation control technology to vertical take-off and landing (VTOL) rotorcraft could also prove quite beneficial. Successful adaptation to helicopter rotor blades is currently believed to yield benefits such as increased lift, increased payload capacity, increased maneuverability, reduction in rotor diameter and a reduction in noise. Above all, the addition of circulation control to rotorcraft as controlled by an on-board computer could provide the helicopter with pitch control as well as compensate for asymmetrical lift profiles from forward flight without need for a swashplate. There are an infinite number of blowing slot configurations, each with separate benefits and drawbacks. This study has identified three specific types of these configurations. The high lift configuration would be beneficial in instances where such power is needed for crew and cargo, little stress reduction is offered over the base line configuration. The stress reduction configuration on the other hand, however, offers little extra lift but much in the way of increased rotor lifespan and shorter rotor length. Finally, the middle balanced configuration offers a middle ground between the two extremes. With this configuration, the helicopter benefits in all categories of lift, stress reduction and blade length reduction.
Effect of Leading Edge Blowing Slots on Stall Angles of a 10:1 Elliptical Airfoil
Authors: Kweder Jonathan , Clarke Mary Ann , Smith James E.
Published: May 2012

Traditional uses of circulation control have been studied since the early 1960’s and have been developed primarily using trailing edge slots over a rounded trailing edge in order to take advantage of the Coanda˘ effect. The leading edge activated slots allow jets of air to enter the freestream flowing around the airfoil thus enhancing the energy of the lift force. The main purpose of circulation control for fixed wing aircraft is to increase the lifting force when large lifting forces and/or slow speeds are required, such as at take-off and landing. While there is a significant increase in the lifting forces achievable through the use of circulation control, there is also an inherent increase in the drag force on the airfoil (Abramson, 2004, Loth, 1976, 1984). Current effects of circulation control on stall angles of airfoils are not well documented and thus needs to be studied. Stall occurs when a sudden reduction in lift occurs caused by a flow separation between the incoming air flow and the lifting surface. The angle at which this happens is commonly called the critical angle of attack, and is typically between eight and twenty degrees depending on the wing profile, aspect ratio, camber, and planform area. For this study, a 10:1 aspect ratio elliptical airfoil with a chord length of 11.8 inches and a span of 31.5 inches was inserted into the West Virginia University Closed Loop Wind Tunnel and was tested at varying wind speeds (80, 100, and 120 feet per second), angle of attack (zero to sixteen degrees), and blowing coefficients, ranging from 0.0006 to 0.0127 depending on internal plenum pressure. By comparing the non-circulation controlled wing with the active leading edge slot circulation control data, a trend was found as to the influence of the circulation control exit jet on the stall characteristics of the wing. For this specific case, when the circulation control is in use on the 10:1 elliptical airfoil, the stall angle decreases, from eight degrees to six degrees, while providing up to a 46% increase in lift coefficient.
Innovative Design of Lightweight on Board Hydrogen Storage Tank
Authors: Shoukry Samir N. , William Gergis W. , Prucz Jacky C. , Evans Thomas H.
Published: May 2012

The hydrogen economy envisioned in the future requires safe and efficient means of storing hydrogen fuel for either use onboard vehicles, delivery on mobile transportation systems or high-volume storage in stationary systems. The main emphasis of this work is placed on the high -pressure storing of gaseous hydrogen on-board vehicles. As a result of its very low density, hydrogen gas has to be stored under very high pressure, ranging from 350 to 700 bars for current systems, in order to achieve practical levels of energy density in terms of the amount of energy that can be stored in a tank of a given volume. This paper presents 3D finite element analysis performed for a composite cylindrical tank made of 6061-aluminum liner overwrapped with carbon fibers subjected to a burst internal pressure of 1610 bars. As the service pressure expected in these tanks is 700 bars, a factor of safety of 2.3 is kept the same for all designs. The results indicated that a stress reduction could be achieved by a geometry change only, which could increase the amount of pressure sustained inside the vessel and ultimately increase the amount of hydrogen stored per volume. Such reductions in the stresses will decrease the thickness dimension required to achieve a particular factor of safety in a direct comparison to a cylindrical design.
A New Electrothermal Microactuator With Z-Shaped Beams: Design and Operation
Authors: Zhu Yong
Published: May 2012

A new class of thermal microactuators, Z-shaped thermal actuator, is introduced in comparison with the well-established V-shaped thermal actuator. Though they share many features in common, Z-shaped thermal actuator offers several advantages: compatibility with anisotropic etching, smaller feature size, larger displacement, and larger variety of stiffness and output force. While the Z-shaped thermal actuator was modeled analytically and verified by multiphysics finite element analysis (FEA), the beam width and length of the central beam were identified as the major design parameters in tuning the device displacement, stiffness, stability and output force. Experimental measurements were taken on three arrays of Z-shaped thermal actuator with variable parameters. Results agreed well with the finite element analysis. The development of Z-shaped thermal actuator is applicable in simultaneous sensing and actuating applications. During the quasi-static test of individual Z-shaped thermal actuator, the average temperature in the device structure was estimated based on electric resistivity at each actuation voltage.
Lysing E. Coli Using Titanium Dioxide Particles for Lab-on-a-Chip Applications
Authors: Wan Weijie , Yeow John T. W.
Published: May 2012

A novel method is proposed and demonstrated to be able to lyse E. Coli bacteria cells for Lab-on-a-Chip applications. The proposed method uses titanium dioxide particles as a photocatalyst and a miniaturized UV LED array as an excitation light source on the microchip level to perform cell lysis. The experimental result demonstrates the feasibility of the proposed novel device. The working device suggests an inexpensive, easy to be fabricated and effective way for microchip cell lysis. The miniaturized UV LED array and the microchip with a reaction chamber can be easily integrated with other functional components to form a customized whole Lab-on-a-Chip system.
Computational Modeling of Lamination of Tape Casted Ceramics With a Fugitive Phase
Authors: Wimmer Stephanie A. , DeGiorgi Virginia G. , Pan Ming-Jen
Published: May 2012

The complex geometries required for new and novel ceramic parts require new fabrication methods such as the fugitive phase approach. This paper examines the lamination step of fugitive phase approach ceramic fabrication process. The lamination step integrates the fugitive phase with the green ceramic material. The pressing used along with the geometric layout of the fugitive phase during the lamination step creates an uneven pressure distribution in the green ceramic. This pressure distribution causes density gradients and warping in the final ceramic part. A preliminary computational model of the lamination process is modeled and the resulting stress, strain energy, and deformed shape are examined.
An Experimental Apparatus to Investigate Natural Convection Heat Transfer From a Vertical Array of Isothermal Horizontal Cylinders
Authors: Atayılmaz S¸evket O¨zgu¨r , Demir Hakan , Ag˘ra O¨zden , Teke I˙smail
Published: May 2012

Steady natural convection heat transfer from vertical array of equally-spaced isothermal horizontal cylinders has been investigated experimentally and numerically. Experimental study was carried out at different ambient temperatures in a conditioned room which can be maintained at a stable required value and inside a sufficiently designed test cabin. The ambient and cylinders’ surface temperatures varied 20°C to 30°C and 30°C to 60°C respectively. The experimental apparatus was designed to adjust different operating parameters such as number of cylinders, cylinders’ surface temperatures, distance between the cylinders and environmental temperature. Each cylinder surface temperature can be accurately adjusted to the desired temperature by means of specially designed measurement and control system. Copper test cylinders have length of 1 m and outer diameter of 4.8 mm. The uncertainty analysis method proposed by Kline and McClintock was used and explained elaborately. Detailed information and algorithm of numerical method are given to ease the understanding of the numerical part of the study. The problem was solved numerically by means of a CFD program in 2D. Average Nusselt numbers are given based on the experimental data for single and each two horizontal cylinders. Heat transfer rates obtained from experimental and numerical studies for upper and lower cylinders were compared with each other. The deviation of experimental and numerical heat transfer rates are in a good agreement and stay in the range ± 20%. It is seen that heat transfer from the lower cylinder is close to the single cylinder case. However, higher temperature of the passing air reduces the heat transfer from the upper cylinder for S/D = 2.
Modelling of T-Junction Droplet Generator in the Transition Regime
Authors: Glawdel Tomasz , Elbuken Caglar , Ren Carolyn
Published: May 2012

One of the most commonly used microfluidic droplet generator designs is the T-junction as shown in Figure 1. In this design, the dispersed phase microchannel, usually containing an aqueous solution, perpendicularly intersects the main channel, which contains the continuous phase (oil). The T-junction design has been widely adopted because of its simplicity and the superior control it offers over droplet size. Two primary operational regimes have been identified where breakup is dominated by confinement of the emerging droplet within the microchannel, known as the squeezing regime (Ca<0.002), or by the balance of shear and surface tension forces known as the dripping regime (Ca>0.02). The operational mode of the T-junction generator is primarily characterized by the Capillary number (Ca = μU / γ), which describes the competition between the aforementioned forces. In between the two regimes exists the transition regime where both confinement and shear forces are important.
Linear and Nonlinear Model of Cutting Forces in Peripheral Milling: A Comparison Between 2D and 3D Models
Authors: Moradi Hamed , Movahhedy Mohammad R. , Vossoughi Gholamreza
Published: May 2012

Peripheral milling is extensively used in manufacturing processes, especially in aerospace industry where end mills are used for milling of wing parts and engine components. Knowledge of the cutting forces is the first necessary stage in analysis of the milling process. In this paper, cutting forces are presented for both two and three dimensional models. Instead of the common linear dependency of cutting forces to the cut chip thickness, two nonlinear models are presented. In the first model, cutting forces are considered as a function of chip thickness with a complete third order polynomial. In the second one, the quadratic and constant terms of the third order polynomial are set to zero. Results show about 2–3% and 2–7% maximum error between the linear, first and second nonlinear models, for 2D and 3D models, respectively. According to the simulation results, both the 2D and 3D models with second type of nonlinearity can be effectively used in practice. The advantage of such modelling is its simplicity in nonlinear analysis of the problem based on perturbation techniques.
Efficient Design of Complex Mechatronic Products Using the Example of the Separation-Process in an ATM
Authors: Just Viktor , Illg Igor , Zeineldin Tarek , Tra¨chtler Ansgar
Published: May 2012

The substantial challenge with designing mechatronic systems is the fully inclusive consideration of the system already in the early development phases. On designing mechatronic systems the conception phase is directly followed by the “Mechatronic Composition” [1]. In this contribution the mechatronic composition is subdivided into three phases: “Basic-System Composition”, “Idealized Composition” and “Holistic Composition”. The model-based analysis and synthesis provide the basis for the mechatronic composition. Beside the general procedure at modelling mechatronic systems the contribution discusses the adequate depth of the modelling considering the model validation. In the second part of the contribution the application of the three-phase Mechatronic Composition is represented by the advancement of the separator module of an ATM.
Finite Element Simulation of an Automotive Brake Rotor With Metallic Damping Inserts
Authors: Sung Shung H. , Hanna M. David , Schroth James G.
Published: May 2012

A finite element method is developed for simulating the performance of an automotive brake rotor with metallic inserts that are used to dampen the vibration and radiated noise response. The metallic inserts are located in slots that are cast at the edge of the rotor circumference between the two rotor surfaces. Three different rotor configurations are evaluated: (a) an undamped solid rotor, (b) a damped rotor with an unconstrained press-fit metallic insert, and (c) a damped rotor with a constrained cast-in coated metallic insert. Comparisons of the predicted versus measured rotor surface vibration and radiated sound pressure are made to evaluate the effect of the insert and the accuracy of the finite element method. The comparisons show that significant modal damping of the rotor vibration and radiated noise can be achieved through the use of the coated metallic insert. A methodology is developed and applied to evaluate the damping of different metallic inserts and coatings from only the radiated sound pressure response.
Forensic Engineering Applications in Crime Scene Reconstruction
Authors: Knox Michael A.
Published: May 2012

Forensic engineers have traditionally engaged in the analysis of such events as traffic accidents, fires, industrial accidents, structural failures and product liability claims. The application of engineering science and design principles to these types of cases has been well established and has proven valuable to the legal and professional communities. Despite this extensive background in forensic issues, engineers have been reluctant to apply their training and education to the reconstruction of criminal events. Anecdotal experience shows that the common response by engineers to the field of crime scene reconstruction is: “We don’t do that”. Indeed, Internet research reveals very few cases in which forensic engineers have delved into the reconstruction of shooting incidents, and virtually no cases in which engineers have engaged in that analysis of homicidal beatings, bloodstain patterns or other such criminal events. This paper will explore the role of the forensic engineer in the field of crime scene reconstruction both as practitioner and researcher and will show that there is a growing role for engineers to play in the reconstruction of criminal events. Example cases will be explored, and the application of engineering science to those cases will be demonstrated. This paper will also look at ways for forensic engineers to bridge the experience gap that has perhaps been at the center of their reluctance to become involved in crime scene reconstruction.
Achievable Accuracy and Repeatability in On-Site Machining
Authors: Berry Jethro , Wagner Stefan , Kahlen Franz-Josef
Published: May 2012

On-site machining requirements are significantly different from machining in a factory or other semi-controlled environments. Depending on size, geometry, weight and simple practicality, it is not always possible to disassemble a defective part or component and to bring it into a factory for refurbishing or repair. Machining components of a wind tower at an altitude of close to 100 meters must happen on-site, while being exposed to the elements such as sleet and ice, rain or sand storms, or cloudless skies near the equator. Maintaining machining accuracy and repeatability in such conditions is then challenging. Design considerations for a machine to improve machining accuracy and repeatability for surface finishing of objects on-site are presented and comparisons to previously achievable accuracies and repeatabilities are drawn.
Mechanical Design Implications on Power Transfer Through Thick Metallic Barriers Using Piezoelectric Transducers
Authors: Wilt K. R. , Lawry T. J. , Scarton H. A. , Roa-Prada S. , Saulnier G. J. , Ashdown J. D. , Das P. K. , Pinezich J. D.
Published: May 2012

Traditionally, power transfer through thick metallic barriers has required physical penetrations and wire feed-throughs, which reduces structural integrity and limits the environmental isolation provided by the barrier. The Faraday shielding presented by these barriers, however, prevents efficient transfer of electromagnetic power, limiting many RF coupling techniques. More recently, the use of ultrasound has been shown as an effective non-destructive technique for transmitting large amounts of power (100s of watts) through solid metallic mediums. By using two coaxially aligned piezoelectric transducers loaded onto opposite sides of the barrier through an acoustic couplant, an ultrasonic channel is formed through which efficient power delivery is possible. This work presents finite element modeling and simulations that help characterize the impacts of many mechanical design factors on the power transfer efficiency of these ultrasonic channels, including: transducer-wall coupling effects, transducer and wall resonance modes, transducer dimensions, and barrier composition and dimensions. Physical channel measurements are also presented to show the strong correlation between the finite element simulations and the systems modeled.
Computational Modeling of Polymer Flow in Microcavities Through a Microscreen
Authors: Chen Jie , Pitchumani Ranga
Published: May 2012

This paper investigates a new technique for rapid replication of electroforming micromolds with integral microscreens. The process is based on injection molding or hot embossing of plastic replicates with integral metallic screens onto a LIGA-fabricated master microtool, to produce sacrificial electroforming molds in which the metallic screen acts as the conducting base and the plastic features provide insulating sidewalls for electrodeposition of the desired metallic micropart. A computational model is developed for the polymer flow during the fabrication of electroforming micromolds incorporating the temperature dependent, non-Newtonian rheology of the polymer melts. The model is used to analyze the effects of the process parameters and micro-feature geometry on the polymer flow patterns.
Computational Modeling of Latent Thermal Energy Storage System With Embedded Heat Pipes
Authors: Nithyanandam Karthik , Pitchumani Ranga
Published: May 2012

Due to the intermittent nature of solar energy availability, storing sun’s energy in the form of latent thermal energy of a phase change material (PCM) is an effective technique that is widely used in energy storage and load management applications. In a Latent Thermal Energy Storage System (LTES), a heat transfer fluid (HTF) exchanges energy with a PCM. The advantages of an LTES include its isothermal operation and high energy storage density. However, the low thermal conductivity of PCM poses a significant disadvantage due to reduction in the rate at which the PCM can be melted (charging) or solidified (discharging). This paper explores an approach to reducing the thermal resistance of PCM in a LTES through embedded heat pipes. A heat pipe is a passive heat transfer device that efficiently transfers large amount of energy between the PCM and HTF thus indirectly amplifying the effective thermal conductivity of PCM. A transient computational analysis of a shell and tube LTES embedded with heat pipes is performed for charging to determine the position of melt front and energy stored as a function of time. The influence of the number and orientation of heat pipes and design configuration of the system is analyzed to identify configurations that lead to improved effectiveness.
Coating and Characterization of Energetic Materials
Authors: Hunt Emily M. , Jackson Matt
Published: May 2012

This project develops a method of manufacturing Plastic Bonded Explosives by using use precision control of agglomeration and coating of energetic powders. The energetic material coating process entails suspending either wet or dry energetic powders in a stream of inert gas and contacting the energetic powder with atomized droplets of a lacquer composed of binder and organic solvent. By using a high velocity air stream to pneumatically convey the energetic powders and droplets of lacquer, the energetic powders are efficiently wetted while agglomerate drying begins almost immediately. The result is an energetic powder uniformly coated with binder; i.e., a PBX, with a high bulk density suitable for pressing. Experiments have been conducted using mock explosive materials to examine coating effectiveness and density. Energetic materials are now being coated and will be tested both mechanically and thermally. This allows for a comprehensive comparison of the morphology and reactivity of the newly coated materials to previously manufactured materials.
Biomechanical Model Representing Energy Storing Prosthetic Feet
Authors: Sinatra Francy L. , Carey Stephanie L. , Dubey Rajiv
Published: May 2012

Previous studies have been conducted to develop a biomechanical model for a human’s lower limb. Amongst them, there have been several studies trying to quantify the kinetics and kinematics of lower-limb amputees through motion analysis [5, 10, 11]. Currently, there are various designs for lower-limb prosthetic feet such as the Solid Ankle Cushion Heel (SACH) from Otto Bock (Minneapolis) or the Flex Foot from Ossur (California). The latter is a prosthetic foot that allows for flexibility while walking and running. Special interest has been placed in recording the capabilities of these energy-storing prosthetic feet. This has been done through the creation of biomechanical models with motion analysis. In these previous studies the foot has been modeled as a single rigid-body segment, creating difficulties when trying to calculate the power dissipated by the foot [5, 20, 21]. This project studies prosthetic feet with energy-storing capabilities. The purpose is to develop an effective way of calculating power by using a biomechanical model. This was accomplished by collecting biomechanical data using an eight camera VICON (Colorado) motion analysis system including two AMTI (BP-400600, Massachusetts) force plates. The marker set that was used, models the foot using several segments, hence mimicking the motion the foot undergoes and potentially leading to greater accuracy. By developing this new marker set, it will be possible to combine the kinematic and kinetic profile gathered from it with previous studies that determined metabolic information. This information will allow for the better quantification and comparison of the energy storage and return (ES AR) feet and perhaps the development of new designs.
Forced Convection Analysis in a Vertical Square Cavity With a Vortex Promoter
Authors: Damian-Ascencio Enrique A. , Hernandez-Guerrero Abel , Rubio-Arana Cuauhtemoc , Kowalski Gregory
Published: May 2012

This paper presents a 2-D numerical study of the effect on the heat transfer from a promoter of turbulence in a vertical square cavity. The transient, turbulent flow simulation is for a fluid with a Prandtl number of 0.7 and constant properties. The thermal boundary conditions considered are isothermal cavity walls. In the analysis various aspect ratios and blockage fractions (10%, 25% and 50%) were examined at a constant Reynolds number (Re = 5000). The governing equations are solved using the LES (Large Eddy Simulation) method. The results demonstrate that increasing the channel blockage makes it more difficult to generate turbulence but increases the channel residence time of the fluid.
Realtime Ultrasound Elastography Technique for Multifocal Breast Cancer Assessment
Authors: Shavakh Shadi , Fenster Aaron , Samani Abbas
Published: May 2012

Early diagnosis and classification of breast cancer is a critical step in choosing appropriate treatment plan. An ultrasound (US) elastography method for unifocal and multifocal breast cancer is presented. While this technique uses full inversion approach, it is cost-effective, fast, and expected to be more sensitive and specific than conventional US based elastography methods. This technique is capable of imaging absolute Young’s modulus (YM) of the tumour in real-time fashion, in contrast with other conventional elastography techniques that image relative elastic modulus off-line. To validate the proposed technique, numerical and tissue mimicking phantom studies were conducted. In the tissue mimicking study, a block shape gelatine-agar phantom was constructed with a cylindrical inclusion located deep inside the phantom. Results obtained from this study show accurate reconstruction of the YM with average error of less than 3%. The numerical phantom study has been extended for multifocal cases with average errors less than 6%.
Modeling and Simulation of Translocation Phenomenon in a Solid State Nanopore for Nanoparticle Separation
Authors: Jubery Talukder Zaki , Prabhu Anmiv S. , Kim Min Jun , Dutta Prashanta
Published: May 2012

Solid state nanopore is a potential candidate for separation of nanoparticles or biomolecules such as proteins, DNA, and RNA. However, efficient separation of particles through nanopores is a challenging task as a number of factors such as externally applied voltage, size and charge density of particle, size and charge density of membrane pore, and the concentration of bulk electrolyte influence the translocation behavior of nanoparticles through pores. This paper uses a mathematical model based on Poisson–Nernst–Plank equations along with Navier-Stokes equations to systematically study these factors. Membrane pore surface charge is found to be a vital parameter in this seperation process. Numerical results reveal that efficient separation of high density lipoprotein (HDL) from low density lipoprotein (LDL) in a 0.2 M KCL solution (resembling blood buffer) through a 150 nm pore is possible if the pore surface charge density is around −4.0 mC/m2.
Integrating Mechatronics Into an Engineering Technology Curriculum
Authors: Fuehne Joseph P.
Published: May 2012

Mechatronics can be defined as a science combining mechanical elements, electrical elements, fluid power, and computer programming in a complex system to accomplish a certain task, such as the assembly of a hydraulic directional control valve. In the Mechanical Engineering Technology curriculum at Purdue University in Columbus, Indiana, all of these topics are addressed in individual classes but rarely are they considered together in a complex system. Mechatronics has been the vehicle to allow students to investigate a complete system, rather than simply individual elements or topics. In particular, a system that utilizes seven different machines, each controlled by programmable logic controllers, to assemble a directional control valve is employed to present these topics to students. In the absence of a specific class that might be called Mechatronics (a new class is being considered), the operations of the directional control valve assembly are being integrated into several classes including a first-semester class as a way to demonstrate some real-world manufacturing activities to new students who might otherwise become disinterested due to the math, English, and other related courses in the first year. As such, the mechatronics equipment serves as a retention tool. Additionally, the mechatronics system is used in a basic electricity class, a fluid power class, a machine elements class and, finally, an instrumentation and process control class, where all the individual elements are considered in the system. All of these integrating elements are considered in this work.
A Numerical Investigation on Nanofluids Forced Convection in Channels With Transverse Ribs
Authors: Manca O. , Nardini S. , Ricci D.
Published: May 2012

Heat transfer enhancement technologies are adopted in several applications as heat exchangers for refrigeration, automotives, process industry, solar heaters. A possibility for increasing the convective heat transfer in a fluid is to employ rough surfaces or adopting additives. When a fluid flows in a channel, ribs break the laminar sub-layer and create local wall turbulence due to flow separation and reattachment between consecutive ribs, which reduce thermal resistance and greatly augment the heat transfer. This behaviour overcomes the effect linked to the increased heat transfer area due to the ribs. However, higher friction losses are expected. In this paper a numerical investigation is carried out on forced convection with nanofluids (water-Al2O3) in a ribbed channel with a constant heat flux applied on the external walls. Properties of fluid are considered constant and a single phase model is employed. Flow regime is turbulent; in fact, Reynolds numbers ranging from 20000 to 60000 are considered. Furthermore, different shapes, such as square, rectangular, triangular ones, and different dimensionless heights and pitches of elements are analyzed. Moreover, two volume particle concentrations are investigated. Results are presented in terms of temperature and velocity fields, average heat transfer coefficients and pressure drop profiles. The aim of this study is to find arrangement of ribs such to give high heat transfer coefficients and low pressure drops in presence of nanofluids.
Influence of Non-Functionalized and Functionalized MWCNTs on Mechanical and Thermal Properties of Epoxy Composites
Authors: Zainuddin Shaik , Hosur Mahesh , Rao Harish , Barua Rajib , Jeelani Shaik , Kumar Ashok , Trovillion Jonathan
Published: May 2012

In this work, SC-15 epoxy resin was modified using 0.1–0.3 wt. % of non-functionalized and functionalized multi-walled carbon nanotubes (MWCNTs) using conventional and solvent based methods. A high-intensity ultrasonic liquid processor was used to disperse MWCNTs in solvent and to obtain a homogeneous molecular mixture of epoxy resin and MWCNTs. Viscosity, dynamic mechanical analysis (DMA), thermo-gravimetric analysis (TGA), tensile and flexure tests were performed on unfilled and 0.1–0.3 wt. % MWCNTs filled SC-15 epoxy. Preliminary results indicate increase in viscosity with increase in MWCNTs wt. % loading and 0.2 wt. % MWCNTs epoxy samples showed the highest improvement in tensile and flexural properties as compared to the neat system. DMA studies also revealed that 0.2 wt. % doped system exhibit the highest storage modulus and Tg as compared to neat and other loading percentages. TGA results show that amino functionalized MWCNTs samples are more thermally stable.
Configuration Optimization of a Boat Simulation Platform for a Mobile User
Authors: Blanco Juan C. , Rodri´guez Carlos F.
Published: May 2012

Motion simulation platforms are mechanical devices designed to replicate the dynamics of a given vehicle. These devices are very attractive for training individuals as drivers, pilots or passengers. In the case of river boats, the simulator consists of a section of the boat (hull) mounted over a 3 DOF parallel robot with a passive mass compensator (3UPS + PU). If users have mobility in the hull, an uncertainty in the position of the upper platform’s center of mass is produced. This variation may generate excessive loads on the robot that can be prevented by an adequate placement of the hull over the robot. Dynamic calculations, based on measurements of the real boat in motion, are computed by numerical simulations in SimMechanics. Three methodologies are presented for optimizing the configuration of a boat simulation platform. First, a manual procedure is developed in which critical cases are intuitively detected and evaluated. Then, two multi-variable optimization algorithms are used to systematically obtain the best position and orientation (pose) of the boat section: Genetic Algorithms and low discrepancy sequences. The pose is the design variable; the average forces are the objective functions and the maximum difference between the average forces is the fitness function. The article describes the design problem, the proposed optimization methodologies and simulation results for the optimal configuration.
Compose-It: A Computer-Based Tool for the Design and Optimization of Composite Laminates
Authors: Hamade Ramsey F. , Ammouri Ali H.
Published: May 2012

Compose-it is a software tool developed to aid users in the design of composite materials. This tool allows the user to input functional requirements associated with the composite structure and its loading. The software tool has a user-friendly graphical user interface which leads the user through the various phases of design and optimization of composites. While the analysis is based on the classical laminated plate theory, several special boundary conditions are incorporated to allow for out-of-plane loading and mixed boundary condition scenarios. The tool accepts many input variables relating to materials (fiber and matrix), material anisotropy, ply thickness, orientation, staking sequence, and symmetry and special layups. Output includes stress, strains, stiffness, and deflections for optimized ply stack-ups. Simulated annealing optimization technique is incorporated so that the user can compare different ‘optimum’ solutions for desired criteria such as design for maximum in-plane stiffness or maximum in-plane strength.
Air Hybrid Engine Torque Control Using Adaptive Sliding Mode Control
Authors: Fazeli Amir , Zeinali Meysar , Khajepour Amir , Pournazeri Mohammad
Published: May 2012

In this work, a new air hybrid engine configuration is introduced in which two throttles are used to manage the engine load in three modes of operation i.e. braking, air motor, and conventional mode. A Mean Value Model (MVM) of the engine is developed at braking mode and a new Adaptive Sliding Mode Controller (ASMC), recently proposed in the literature, is applied to control the engine torque at this mode. The results show that the controller performs remarkably well in terms of the robustness, tracking error convergence and disturbance attenuation. Chattering effect is also removed by utilizing the ASMC scheme.
Computational Study of the Synthetic Jet on Separated Flow Over a Backward-Facing Step
Authors: Okada Koichi , Fujii Kozo , Miyaji Koji , Oyama Akira , Nonomura Taku , Asada Kengo
Published: May 2012

Frequency effects of the synthetic jet on the flow field over a backward facing step are investigated using numerical analysis. Three-dimensional Navier-Stokes equations are solved. Implicit large-eddy simulation using high-order compact difference scheme is conducted. The present analysis is addressed on the frequency characteristics of the synthetic jet for understanding frequency characteristics and flow filed. Three cases are analyzed; the case computing flow over backward facing step without control, the case computing flow with synthetic jet control at F+h = 0.2, and the case computing flow with synthetic jet control at F+h = 2.0, where non-dimensional frequency F+h is normalized with the height of backward-facing step and the freestream velocity. The present computation shows that separation length in the case of the flow controlled at F+h = 0.2 is 20 percent shorter than the case without control. Strong two-dimensional vortices generated from the synthetic jet interact with the shear layer, which results in the increase of the Reynolds stress in the shear layer region. These vortices are deformed into three-dimensional structures, which make Reynolds stress stronger in the recirculation region. Size of the separation length in the case of the flow controlled at F+h = 2.0 is almost the same as the case without control because the mixing between the synthetic jet and the shear layer is not enhanced. Weak and short periodic vortices induced from the synthetic jet do not interacts with the shear layer very much and diffuse in the recirculation region.
Applying Stochastic Method in Engineering Design Under Uncertainty
Authors: Amir Yosef
Published: May 2012

Very often design engineer uses a single-point or deterministic approach. The design modeling involves using a single “best-guess” estimate of each variable within a model to determine the model’s outcome(s). The deterministic approach often leads the engineer to make unjustified assumptions and inherent design risk decisions. To improve this design process, this paper proposes applying a stochastic method in engineering design particularly, designs under uncertainty. This paper presents three design cases of applying a stochastic method by using a Monte Carlo simulation. The first case presents a Bolted Joints (BJ) design; prediction of a bolt preload to prevent a joint of slipping investigated for a confidence of 99.97% certainty. This BJ design case demonstrates how to overcome the obstacles that exist in a deterministic Bolted Joints analysis. The variables included in this investigation are the variations of coefficient of friction, preload scatter, Bolt and the Joint geometry. The second design case investigates the angular position control of Four Bars Mechanism (FBM). In this case, the paper shows how to quantify the design risk of the real FBM angular position for a given resolution spec. Sensitivity analysis uses after each simulation to identify the driver parameters influencing the angular position of the FBM. The dominant parameters influencing the design analysis include: bars tolerance variations and an actuator driver backlash. The third case of engineering design demonstrates a stochastic optimization of a flat spring design. The goal of this stochastic optimization is to achieve the maximum spring Specific_Resilience. The optimal solution of this optimization is to select the best material of six given materials and spring geometry that fit within a given restricted envelope.
Modeling of a Planar Microrobot Using LuGre Friction Model
Authors: Khodabakhsh M. , Vossoughi G. R. , Kamali A.
Published: May 2012

Microrobots design and manufacturing has been one of interesting fields in robotics in recent years. Various legged designs have been proposed in the literature. All designs rely on friction for locomotion. In this paper the dynamic model of a planar two-legged microrobot is presented using LuGre friction model. LuGre friction model is more realistic model, reducing uncertainties of the microrobot dynamic model, providing a better prediction for both design and control applications. The proposed microrobot is driven by a piezoelectric actuator mounted between centers of two legs. One of important issues in modeling of microrobots is to determine the friction force between robot and environment. The LuGre friction model which is a more realistic and comprehensive model for friction is used to determine the friction force between legs and horizontal surface. The results of the LuGre friction based model are compared with those of the model which uses the Coulomb friction. This comparison shows effectiveness of using the LuGre friction model in predicting the dynamic behavior in these types of robots.
A Method for Bonding PDMS Without Using Plasma
Authors: Martin Cristina , Sofla Aarash Y. N.
Published: May 2012

The vapor-assisted treatment constitutes a simple and inexpensive method to increase the adhesion strength of polydimethylsiloxane and glass without using plasma. In this method, the targeted PDMS-glass sample is exposed to a vapor in an enclosed container for a certain time. Different chemicals were tested as possible vapor sources. No increase in the adhesion strength of PDMS-glass samples was observed when silanes without chloro functional groups were used. On the other hand, all alkyl trichlorosilanes tested in this study led to permanent bondings. In addition, an increase in the strength of the PDMS-glass adhesion was obtained with di- and monochlorosilanes as well as with hydrochloric acid solution. These results experimentally demonstrate that the hydrogen chlorine gas assists with the PDMS-glass bonding, making the vapor-assisted treatment a method with multiple applications in both small scale laboratory research and large scale manufacturing processes.
Time-Domain Dynamic Analysis of Piezoelectric MLA
Authors: Righettini Paolo , Forlani Mauro , Strada Roberto
Published: May 2012

Piezoelectric multilayer actuators (MLAs) are among the most suitable piezoelectric actuators to be integrated into fast mechanical systems, given their high force capabilities and high dynamic response. Overall dynamic behaviour though is influenced by load and driving electric circuit characteristics. The aim of the present work is to investigate the transient dynamics of mechanical systems actuated by MLAs. To this purpose, the system, including the driving electric circuit, is modelled employing finite difference techniques. Such methods are extremely flexible and allow modelling non-linear behaviour and transient phenomena. In particular the response to an input step voltage will be simulated and the influence of the system’s parameters on its response will be investigated. The results provide valuable information such as required currents that can help the engineer in the design process.
A Study of Nanoparticle-Enhanced Heat Transfer
Authors: Jones Lawrence M. , Sirk Timothy , Brown Eugene
Published: May 2012

The study of the heat transfer characteristics of nanofluids, i.e. fluids that are suspensions of nanometer size particles, has gained significant attention in the search for new coolants that can effectively service a variety of needs ranging from the increasing heat transfer demands of ever smaller microelectronic devices to mitigating the effects of loss of coolant accidents in nuclear power plants. Experimental data has shown large increases in thermal conductivity and associated increases in the level of critical heat flux in nuclear reactors; however, in some cases the range of the applicability of the experimental results is uncertain and there is a lack of a theory by which this can be resolved. Complicating the theoretical description of heat transfer in nanofluids is the fact that fluids in the vicinity of the nanoparticles are a complex combination of phase transition, interfacial, and transport phenomena. This paper describes a study in which molecular dynamics simulations were used to enhance the understanding of the effect of nanoparticles on heat transfer. The molecular dynamics (MD) simulations presented here model a Lennard-Jones fluid in a channel where the walls are maintained at different temperatures. The heat flux is calculated for a variety of nanoparticle sizes and concentrations. The results are compared to experimental data in order to provide information that will more confidently bound the data and provide information that will guide the development of more comprehensive theories. We also anticipate that this work could contribute to the design of biosensors where suspended molecules are transported through micro- and nano-channels in the presence of heat transfer.
Large-Scale Electrospray Ionization Methods for Nanocoating Application
Authors: Merrill Marriner H.
Published: May 2012

A scalable nano-coating process is needed that can be applied at atmospheric temperatures and pressures with low waste. This would enable the efficient production of advanced thin-film materials from solar cells to super-hydrophobic surfaces. Unfortunately, current methods for producing nanoparticle or nano-structured macromolecular coatings often require substrate immersion, specific atmospheres, and/or long growth times. One potential technique to overcome these challenges would be to use electrospray ionization (ESI) to first disperse large numbers of nanoparticles or polymers in air at standard conditions, and then deposit these on a substrate. ESI is a relatively mature technology, and although it has been developed largely for processing microliter volumes in mass spectrometry, it is believed that the fundamental science can be scaled up. This work presents a model for an ESI deposition method. It combines scaling laws for charged jets with spray and fission models to capture relevant charge, spray, fission, and evaporation phenomena. The developed model is shown to be very simple and efficient while still matching published experimental results. Using the model, current ESI techniques are compared such as NanoESI and Flow-Focusing ESI. A significant technological challenge to ESI deposition is discovered to be the trapping of the majority of the solute in a few primary droplets. Different solutions to this challenge are examined and used to define the direction for future work.
Investigation of Magnetic Abrasive Finishing for Internal Polishing of Aluminium Tubes Using DOE
Authors: Tehrani Alireza Fadaei , Givi Mehrdad , Afghan Ashkan Sepehr
Published: May 2012

Magnetic Abrasive Finishing (MAF) is one of the nontraditional machining methods with vast applications in high-tech industries such as medical, aerospace and semiconductor manufacturing areas. Several researches have been done in order to studying the influence of various parameters on magnetic abrasive finishing process and characteristics of finished surface. The present paper investigates the effects of some effective parameters such as mesh size of the abrasives, the weight of the abrasive powder and the number of cycles on internal surface roughness of Aluminum tube. The optimum percentage of oil should be added to the abrasive powder was attained and applied for the main tests. Then, design of experiments (DOE) methods and Analysis of Variance (ANOVA) have been applied to determine significant factors and also to obtain an equation based on data regression.