bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetoelastic Interactions at the Planar Interface of Two Ferromagnetic Solids: A Theoretical Study
Authors: Harutyunyan S. , Hasanyan D. J. , Davis R. B.
Published: May 2012

A model for the phenomena in which magnetic waves excite elastic waves and vice versa, is formulated and used to explore magnetic and anti-plane elastic interactions in piecewise homogeneous ferromagnetic media. The magnetization vectors in each medium are perpendicular to the wave propagation direction. The space is in an external homogeneous magnetic field, the direction of which coincides with direction of the initial magnetization vector. A joint contact on the interface of two ferromagnetic semi-spaces is considered. The existence of new type of waves is shown. These waves are localized on the interface of two ferromagnetic media and accompany to the reflection and transmission waves. These types of waves named as an accompanying surface magnetoelastic (ASM) waves. An analytical expression for the coefficients of reflection, transmission, and accompanying surface magnetoelastic waves is derived. Coefficients of mentioned waves are strongly dependent on applied magnetic field, material properties of each medium as well as the frequency and the angle of an incident elastic wave. Conclusions and directions for the design of magnetoelastic devises are outlined.
A Thermal Conductivity Measurement System for Fuel Compacts
Authors: Jensen Colby , Xing Changhu , Ban Heng , Barnes Charles , Phillips Jeffrey
Published: May 2012

A measurement system has been designed and built for the specific application of measuring thermal conductivity of a composite nuclear fuel over a temperature range of 400 K to 1100 K. Because the composite nature of the sample requires measurement of the whole compact, there is no existing method available for obtaining its thermal conductivity in a non-destructive manner. The designed apparatus is an adaptation of the guarded-comparative-longitudinal heat flow technique. Initial testing has been performed on stainless steel 304. The determinate uncertainty is presented and found to be 2.5% excluding the error associated with the reference samples. The prototype system is expected to be further tested and modified for the measurement of thermal conductivity of fresh fuel compacts at elevated temperatures in a radioactive environment.
Rheological Study of Algae Slurries for Minimizing Pumping Power
Authors: Bolhouse Angel , Ozkan Altan , Berberoglu Halil
Published: May 2012

This paper reports the rheological properties of algae slurries as a function of cell concentration. From both energy and economic perspectives, the algae slurry for producing biofuels should have rheological attributes that minimizes the pumping power requirements while delivering the maximum amount of biomass from the cultivation fields to the biorefinery. To achieve this, an accurate knowledge of the rheological properties of algae slurries as a function of cell concentration is necessary. This study measures the rheological properties of eight different concentrations of Nannochloris sp. in ASP-m nutrient media ranging from 0.5 to 80 kg dry biomass/m3. Strain controlled dynamic frequency sweep tests, transient step rate tests, and steady rate sweep tests were performed with an ARES-TA Rheometer using a double wall couette cup and bob attachment. Shear rates ranged from 5–270 s−1. The results show that the concentrations of 10 kg/m3 and below behaved as Newtonian fluids with a dynamic viscosity of 1.1×10−3 Pa-s while the concentrations of 20 kg/m3 and above behaved as shear thinning non-Newtonian fluids. Finally, an energy analysis was performed where a non-dimensional bioenergy transport efficiency was defined as the ratio of the energy content of transported algae biomass to the required pumping power. The results show that an optimal biomass concentration minimizing pumping requirements occurs at the highest dry biomass concentration.
Increased Photobioreactor Productivity Using Algae With Low Pigmentation: A Light Transfer Perspective
Authors: Murphy Thomas E. , Berberog˘lu Halil
Published: May 2012

This paper reports a numerical study on the photosynthetic productivity of algae photobioreactors using wild strains and genetically engineered strains with low chlorophyll pigment content. First, the specific photosynthetic rates of the wild strain algae Chlammydomonas reinhardtii CC125 and the truncated chlorophyll transformant tla1 were obtained from experiments as a function of the total available irradiation for each cell. This rate was modeled with a modified Monod function accounting for light saturation and light inhibition. The models were coupled with the radiative transport equation (RTE) to predict both the local and total photosynthetic rate of an open pond photobioreactor. The benefits and limitations of using truncated antenna transformants for increasing productivity of mass algae culturing are discussed.
A New Nonlinear Higher-Order Shear Deformation Theory for Nonlinear Vibrations of Laminated Shells
Authors: Amabili M. , Reddy J. N.
Published: May 2012

A consistent higher-order shear deformation nonlinear theory is developed for shells of generic shape; taking geometric imperfections into account. The geometrically nonlinear strain-displacement relationships are derived retaining full nonlinear terms in the in-plane displacements; they are presented in curvilinear coordinates in a formulation ready to be implemented. Then, large-amplitude forced vibrations of a simply supported, laminated circular cylindrical shell are studied (i) by using the developed theory, and (ii) keeping only nonlinear terms of the von Ka´rma´n type. Results show that inaccurate results are obtained by keeping only nonlinear terms of the von Ka´rma´n type for vibration amplitudes of about two times the shell thickness for the studied case.
Reynolds Number Effects on the Freewheeling Behavior of a High Solidity Vertical River Kinetic Turbine
Authors: Birjandi Amir Hossein , Bibeau Eric
Published: May 2012

A four-bladed, squirrel-cage, and scaled vertical kinetic turbine was designed, instrumented and tested in the water tunnel facilities at the University of Manitoba. With a solidity of 1.3 and NACA0021 blade profile, the turbine is classified as a high solidity model. Results were obtained for conditions during freewheeling at various Reynolds numbers. In this study, the freewheeling tip speed ratio, which relates the ratio of maximum blade speed to the free stream velocity at no load, was divided into three regions based on the Reynolds number. At low Reynolds numbers, the tip speed ratio was lower than unity and blades were in a stall condition. At the end of the first region, there was a sharp increase of the tip speed ratio so the second region has a tip speed ratio significantly higher than unity. In this region, the tip speed ratio increases almost linearly with Reynolds number. At high Reynolds numbers, the tip speed ratio is almost independent of Reynolds number in the third region. It should be noted that the transition between these three regions is a function of the blade profile and solidity. However, the three-region behavior is applicable to turbines with different profiles and solidities.
Adaptive Backstepping Stabilization of Uncertain Switched Nonlinear Systems in Parametric Strict-Feedback Form
Authors: Haghpanah Arash , Eghtesad Mohammad , Hematiyan Mohammad Rahim , Khayatian Alireza
Published: May 2012

This paper considers the stabilization problem for a class of parametric switched nonlinear systems under arbitrary switching and parameter uncertainty. A parametric strict-feedback form is adopted in order to represent the switched system. Using the adaptive backstepping approach a common control Lyapunov function under simultaneous domination assumption is constructed and then a control input is designed such that the system is globally asymptotically stable. The design method is developed in a recursive manner and results in an overparametrized adaptive controller. The procedure is illustrated by a descriptive example and the simulation results verify the effectiveness of the designed controller in the system performance.
Quantify Resonance Inspection With Finite-Element-Based Modal Analyses
Authors: Lai K. , Sun X. , Dasch C.
Published: May 2012

Resonance inspection uses the natural acoustic resonances of a part to identify anomalous parts. Modern instrumentation can measure the many resonant frequencies rapidly and accurately. Sophisticated sorting algorithms trained on sets of good and anomalous parts can rapidly and reliably inspect and sort parts. This paper aims at using finite-element-based modal analysis to put resonance inspection on a more quantitative basis. A production-level automotive steering knuckle is used as the example part for our study. First, the resonance frequency spectra for the knuckle are measured with two different experimental techniques. Next, scanning laser vibrometry is used to determine the mode shape corresponding to each resonance. The material properties including anisotropy are next measured to high accuracy using resonance spectroscopy on cuboids cut from the part. Then, finite element model (FEM) of the knuckle is generated by meshing the actual part geometry obtained with computed tomography (CT). The resonance frequencies and mode shapes are next predicted with a natural frequency extraction analysis after extensive mesh size sensitivity study. The good comparison between the predicted and the experimentally measured resonance spectra indicate that finite-element-based modal analyses have the potential to be a powerful tool in shortening the training process and improving the accuracy of the resonance inspection process for a complex, production level part. The finite element based analysis can also provide a means to computationally test the sensitivity of the frequencies to various possible defects such as porosity or oxide inclusions especially in the high stress regions that the part will experience in service.
Spiking and Humping Defects in Laser Welding
Authors: Wei P. S. , Chuang K. C. , Ku J. S.
Published: May 2012

Pitches of surface humps or coarse ripples and spikes affected by the focusing characteristics and scanning speed in high-intensity electron-beam welding or melting are quantitatively measured. Humping and coarse rippling are referred to surface roughness, which often accompanies with undercut, segregation, porosity and other defects. Spiking represents a sudden increase in penetration beyond the average penetration line. In this work, acceleration voltage and welding current of the electron beam welder used are 55 kV and 20 mA, whereas scanning speed is between 15–30 mm/s. Specimens are Al 6061, 1050, 1100 and 5083, and SS 304. This study found that humping and coarse rippling are enhanced by lowering the focal spot location. The measured amplitudes of humping are confirmed by successfully comparing with scale analysis.
Application of the Extended Kantorovich Method to the Static Deflection of Microplates Under Capillary Force
Authors: Moeenfard H. , Kahrobaiyan M. H. , Ahmadian M. T.
Published: May 2012

The aim of this paper is to apply an Extended Kantorovich method (EKM) to simulate the static deflection of microplates under capillary force. The model accounts for the capillary force nonlinearity of the excitation. Starting from a one term Galerkin approximation and following the Extended Kantorovich procedure, the equations governing the microplate deflection are obtained. These equations are then solved iteratively with a rapid convergence procedure to yield the desired solution. The effects of capillary force on the pull-in phenomenon of microplates are delineated in some figures. It is shown that rapid convergence, high precision and independency of initial guess function makes the EKM an effective and accurate design tool for design optimization.
INS-Assisted Monocular Robot Localization
Authors: Krys Dennis , Najjaran Homayoun
Published: May 2012

This paper describes a computationally viable localization technique for an autonomous underwater vehicle (AUV) that is used to carry visual inspection and nondestructive testing equipment inside large water conduits and tunnels without decommissioning the service. The localization technique is required to estimate the instantaneous location of the robot with sufficient accuracy for the control system of the robot in real time. The proposed technique features a sensor fusion framework that incorporates a monocular camera and an inertial navigation system (INS). Localization is carried out using a standard Lucas-Kanade algorithm which searches for a subset of matching pixels between two sequential images to estimate a motion vector for the time interval between the two images. The novelty of the proposed technique is in regards with the use of an INS to predict a rotation and translation vector between the two sequential images. This prediction is used to minimize the search region of the Lucas-Kanade algorithm and hence significantly reduce the computational load of the overall localization process. Experimental results on a special testbed verify that the proposed system not only reduces the computational load but also improves the accuracy since finding a false match in the minimized search region is unlikely.
Nanoscale Direct Patterning With a Combination of Micro Zone Plates and Pulsed Light Sources
Authors: Sundaram Vijay M. , Wen Sy-Bor
Published: May 2012

Micro Fresnel zone plate has showed a potential in the recent few years for precise nanoscale detection and fabrication. In this study, nano-patterns have been generated on photoresist and copper films through coupling a micro Fresnel zone plate with pulsed light sources. To understand the near field and far field optical energy transport from the zone plate to the target along with the resulting thermal energy transport, a series of experimental measurement of the size and shape of nano-patterns generated on targets under different experimental conditions was conducted. In addition, a theoretical optical analysis for the light focusing in the near field range to the target along with the heating process of the target is established.
Piezo-Actuated Active Decoupler Hydraulic Engine Mount
Authors: Khameneifar Farbod , Arzanpour Siamak , Moallem Mehrdad
Published: May 2012

Hydraulic mounts are widely used in the automotive industry to isolate the engine and chassis from each other. For these passive economic vibration isolators the parameter values and characteristics are fixed. As a result, they cannot properly attenuate the complicated vibration transmitted from the engine. In this paper development of a new active mount using piezoelectric materials is described. The typical decoupler of the mount has been replaced by a set of piezoelectric actuators. The actuator consists of two piezoelectric bimorph cantilevers and the beams are covered by a thin rubber layer. The actuator moves upon receiving the signal from the controller, and it changes the dynamic performance of the mount accordingly. Mathematical modeling of the active mount is derived and the simulated results are presented for different voltage signals. Simulations demonstrate the performance of the designed active engine mount to deal with complicated vibration patterns.
Vibration Energy Harvesting From a Hydraulic Engine Mount via PZT Decoupler
Authors: Khameneifar Farbod , Arzanpour Siamak , Moallem Mehrdad
Published: May 2012

Engine is one of the major sources of vibration in a vehicle. An engine mount is the device for isolating the body of vehicles from these vibrations. Harvesting the ambient energy of the vibrating fluid inside a hydraulic engine mount and converting it to the electricity is discussed in this paper. The energy harvester mechanism consists of two piezoelectric bimorph cantilevers with tuning tip masses with the beams covered by a thin layer of rubber. The deflections of the thin rubber layer induce vibrations in the beams which result in electrical power to be generated through the piezoelectric beams. The generated power can be used to recharge the battery for pressure sensors inside the engine mount. This novel harvester is tuned to work in the low frequency, high amplitude excitation environment of the engine. A mathematical model for this energy harvesting application is derived in this paper. Based on this model, the optimum load of the electrical circuit is also obtained. Simulation studies demonstrate performance of the energy harvester and predict the output voltage and maximum power which can be extracted from the energy scavenging device.
Modeling Strategy and Numerical Validation for a Darrieus Vertical Axis Micro-Wind Turbine
Authors: Raciti Castelli Marco , Ardizzon Guido , Battisti Lorenzo , Benini Ernesto , Pavesi Giorgio
Published: May 2012

This paper presents a model for the evaluation of optimal spatial grid node distribution in the CFD analysis of a Darrieus vertical axis micro wind turbine, by analyzing the trends over a 360° rotation of some indicators of near-blade mesh quality. To this purpose, a complete validation campaign has been conducted through a systematic comparison of numerical simulations with wind tunnel experimental data. Both two-dimensional and three-dimensional grids, characterized by average y+ values of 30 and 1, have been tested by applying some statistical techniques as a guidance in selecting the appropriate grid configuration and corresponding turbulence model. Finally, the tip downstream recirculation zone due to the finite blade extension and the influence of spokes have been analyzed, achieving a numerical quantification of the influence of induced drag and spokes drag on overall rotor performance.
Hydrodynamic Energy Harvesting Using an Ionic Polymer-Metal Composite Stack for Underwater Applications
Authors: Krishnaswamy Arvind , Roy Mahapatra D.
Published: May 2012

Ionic Polymer Metal Composites (IPMCs) are a class of Electro-Active Polymers (EAPs) consisting of a base polymer (usually Nafion), sandwiched between thin films of electrodes and an electrolyte. Apart from fuel cell like proton exchange process in Nafion, these IPMCs can act both as an actuator and a sensor. Typically, IPMCs have been known for their applications in fuel cell technology and in artificial muscles for robots. However, more recently, sensing properties of IPMC have opened up possibilities of mechanical energy harvesting. In this paper, we consider a bi-layer stack of IPMC membranes where fluid flow induced cyclic oscillation allows collection of electronic charge across a pair of functionalized electrode on the surface of IPMC layers/stacks. IPMCs work well in hydrated environment; more specifically, in presence of an electrolyte, and therefore, have great potential in underwater applications like hydrodynamic energy harvesting. Hydrodynamic forces produce bending deformation, which can induce transport of cations via polymer chains of the base polymer of Nafion or PTFE. In our experimental set-up, the deformation is induced into the array of IPMC membranes immersed in electrolyte by water waves caused by a plunger connected to a stepper motor. The frequency and amplitude of the water waves is controlled by the stepper motor through a micro-controller. The generated electric power is measured across a resistive load. Few orders of magnitude increase in the harvested power density is observed. Analytical modeling approach used for power and efficiency calculations are discussed. The observed electro-mechanical performance promises a host of underwater energy harvesting applications.
Study of Ultrasonic-Assisted High Light Seamless Injection Molding Process and Technology
Authors: Li Jibin , Xu Keke , Wang Haixiong , Liu Haijun
Published: May 2012

This paper rebuilt a set of melt flow rate instrument which is loaded a power adjustable ultrasonic device. The melt flow rate (viscosity curve) is studied on three kinds of plastic materials, PC, ABS, and PMMA, at different temperatures. The variation of melt flow rate is analyzed under the ultrasonic field. In addition, the practicability of ultrasonic-assisted high light seamless injection molding process and technology is tested and discussed.
Adapting Computer Game Technology to Support Engineering Laboratories
Authors: Aziz El-Sayed , Chang Yizhe , Tumkor Serdar , Esche Sven K. , Chassapis Constantin
Published: May 2012

Today’s youth has become accustomed to and skilled in computer gaming. The potential use of multi-player computer games as an educational tool has drawn significant attention. Computer games exhibit several features that could provide the students with an effective learning experience. This paper introduces different methodologies for adopting computer game technologies such as the “Source” game engine (used in “Half-Life 2”) and “Second Life” to develop game-based interactive student laboratory environments. A number of predefined scenarios can be scripted which exercise the students’ problem solving skills by mimicking typical problems that might occur when carrying out actual hands-on experiments in a traditional student laboratory. The suitability of several gaming platforms for implementing such laboratory environments is discussed. The article concludes with some observations on the most relevant aspects of game platforms that can help to create engaging and effective digital learning environments to support engineering laboratories.
Angular Dependence of Highly Nonlinear Pulse Splitting in a Two Dimensional Granular Network
Authors: Ngo D. , Fraternali F. , Daraio C.
Published: May 2012

We investigate experimentally and numerically the propagation of highly nonlinear signals in a branched two-dimensional granular system composed by chains of uniform spherical beads. The system consists of a Y-shaped guide with various branch angles in which stainless steel spheres are arranged. We study the dynamic behavior of a solitary pulse crossing the bifurcated interface, and splitting between the two branches. We report for the first time the dependence of the split pulses’ speed on the branch angles. Numerical simulations based on Hertzian interaction between the particles are found in agreement with the experimental data.
Novel Algae Biofilm Photobioreactor for Reduced Energy and Water Usage
Authors: Ozkan Altan , Kinney Kerry , Katz Lynn , Berberoglu Halil
Published: May 2012

This paper reports the design and performance of a novel photobioreactor that decreases the water requirements of algae cultivation and energy requirements of harvesting and downstream processing for biofuel production compared to conventional technologies. The photobioreactor cultivates algae as a biofilm, immobilized on carbonated concrete surface. In this study the well known lipid producer Botryococcus braunii was used. The nutrient solution was flown over the surface to enhance the mass transfer of nutrients in and metabolites out of the algae biofilm. The prototype featured a footprint area of 0.275 m2 and has been operated for 35 days. The algae concentration in the photobioreactor reached 30.73 kg/m3 with a maximum total lipid content of 12.3% by dry weight. The water requirement for cultivation was reduced up to by about 41.58 times and energy required for nutrient delivery was estimated to be reduced by about 230 times with respect to raceway ponds.
The Phonon Thermal Conductivity of a Single-Layer Graphene From Complete Phonon Dispersion Relations
Authors: Gu Yunfeng , Ni Zhonghua , Chen Minhua , Bi Kedong , Chen Yunfei
Published: May 2012

In this paper, the phonon scattering mechanisms of a single layer graphene are investigated based on the complete phonon dispersion relations. According to the selection rules that a phonon scattering process should obey the energy and momentum conservation conditions, the relaxation rates of combing and splitting Umklapp processes can be calculated by integrating the intersection lines between different phonon mode surfaces in the phonon dispersion relation space. The dependence of the relaxation rates on the wave vector directions is presented with a three dimensional surfaces over the first Brillion zone. It is found that the reason for the optical phonons contributing a little to heat transfer is attributed to the strong Umklapp processes but not to their low group velocities. The combing Umklapp scattering processes involved by the optical phonons mainly decrease the acoustic phonon thermal conductivity, while the splitting Umklapp scattering processes of the optical phonons mainly restrict heat conduction by the optical phonons themselves. Neglecting the splitting processes, the optical phonons can contribute more energy than that carried by the acoustic phonons. Based on the calculated phonon relaxation time, the thermal conductivities contributed from different mode phonons can be evaluated. At low temperatures, both longitudinal and in-plane transverse acoustic phonon thermal conductivities have T2 temperature dependence, and the out-of-plane transverse acoustic phonon thermal conductivity is proportion to T3/2. At room temperature, the calculated thermal conductivity is on the order of a few thousands W/m.K depending on the sample size and the edge roughness, which is in agreement with the recently measured data.
An Analytical Model for the Effective Dielectric Constant of a 0-3-0 Composite
Authors: Cook-Chennault K. A. , Banerjee S.
Published: May 2012

An analytical expression for prediction of the effective dielectric constant of a three phase 0-3-0 ferroelectric composite is presented. The analytical results are verified with the experimental results from Nan et al [1]. We extend the analytical model, so that the influence of the shape of the third phase inclusion, on the effective dielectric constant of the composite, can be investigated. The results indicate that the dielectric constant increases ∼7 times, when the aspect ratio of the conductive inclusion is increased from 1 (sphere) to 10 (spheroid). The analytical predictions compare favorably with the experimental values.
A Moving Zonal Method in the Time-Domain Simulation for Acoustic Propagation
Authors: Zheng Z. Charlie , Ke Guoyi
Published: May 2012

Conventional time-domain schemes have limited capability in modeling long-range acoustic propagation because of the vast computer resources needed to cover the entire region of interest with a computational domain. Many of the long-range acoustic propagation problems need to consider propagation distances of hundreds or thousands of meters. It is thus very difficult to maintain adequate grid resolution for such a large computational domain, even with the state-of-the-art capacity in computer memory and computing speed. In order to overcome this barrier, a moving zonal-domain approach is developed. This concept uses a moving computational domain that follows an acoustic wave. The size and interval of motion of the domain are problem dependent. In this paper, an Euler-type moving domain in a stationary coordinate frame is first tested. Size effects and boundary conditions for the moving domain are considered. The results are compared and verified with both analytical solutions and results from the non-zonal domain. Issues of using the moving zonal-domain with perfectly-matched layers for the free-space boundary are also discussed.
Numerical Analysis of Liquid Water Droplets Removal in Gas Channels of a PEM Fuel Cell
Authors: Cheng Chin-Hsiang , Han Wei-Shan , Lee Chun-I , Shiu Huan-Ruei , Lin Ssu-Tai
Published: May 2012

The present study is concerned with the dynamic behavior of the liquid water droplets in the water removal process in the serpentine channels of a PEM fuel cell based on computational fluid dynamic (CFD) simulation. The volume of fluid (VOF) model is adopted to trace the interface between the liquid and the gas phases such that the motion of the liquid droplets can be observed. Effects of the incoming velocity are evaluated. In addition, the surface hydrophobic properties are influential to the droplets motion; therefore, the contact angle of the liquid droplet attached on the channel wall has been varied. In addition, the orientation of the bipolar plate is regarded as another important parameter in the present study. Results show that among these parameters considered, the incoming flow velocity and the contact angle are two key parameters which greatly affect the dynamic behavior of the liquid droplets. The liquid droplets attached on the wall of the bipolar plate can be removed by the gas flow only when the contact angle or the incoming flow velocity is sufficiently high.
Effect of Interfacial Trellis Contact Forces in a Wire Rope
Authors: Gnanavel B. K. , Parthasarathy N. S.
Published: May 2012

Tension resisting elements like wire ropes are critical elements in countless engineering applications ranging from material handling, construction site applications, tethers in underwater platforms, apart from stay cables in cable stayed bridges. The main advantage of the wire rope lies in its capacity to support large axial loads with high flexibility in bending and torsional modes. These properties are useful for their own storage, transportation and also in engineering applications where frequent bending is encountered in pulleys/sheaves/drums. The source of such a peculiar mechanical property of the rope can be attributed to the local relative movements between adjacent wires of the rope. A wire rope is a cable assembly consisting of a central core strand surrounded by a number of strands wound helically in a single or multi layers. The wires making up the strand are of helix patterns and when such strand combine to form a rope it takes up invariably another helix pattern, involving many times, a double helix arrangement. Depending on the nature of the contact of the helical wires at their interfaces the rope behaviour can be examined. Point or line contact forces, may arise, resulting in localised stresses. When these strands are assembled to form a wire rope, the complexity of the interfacial contact arrangement generally lead to simplified assumptions for predicting the rope response. An attempt is made in this paper to model a wire rope strand and deduce its equations of equilibrium, considering the interfacial contact forces and studying the associated slip of the wires. A mathematical model is developed to estimate the axial and torsional response of the rope. The effect of the interfacial forces is studied and compared with earlier researchers, where such considerations are not or partially made.
A Robust Anti-Swing Trajectory Control of Overhead Cranes With High-Speed Load Hoisting: Experimental Study
Authors: Lee Ho-Hoon , Liang Yi
Published: May 2012

The objective of this study is to solve serious robustness problems in the anti-swing trajectory control of overhead cranes caused by unavoidable mechanical inaccuracies and installation errors such as locally sloped trolley rails. Based on the theoretical results in the preliminary study, this paper experimentally shows that the proposed anti-swing control solves this robustness problem due to the usual mechanical inaccuracies and installation errors in application.
Design and Analysis for Thermal Control System of Nanosatellite
Authors: Bulut Murat , Kahriman Adem , Sozbir Nedim
Published: May 2012

It is desirable to be able to turn-around thermal analysis results in a couple of minutes early phases of a satellite thermal design. Therefore, ThermXL-spreadsheet-based Thermal Analysis Tool is one of the very flexible and easy-to-use tool that is suited to preliminary design of a nanosatellite. This paper focuses on the thermal design and the results of an initial analysis of the nanosatellite by using ThermXL. The goal of this study is to take suitable measures to ensure all the components will operate in their safe range of temperatures and also a proper heat rejection. The nanosatellite such as Cube Satellite (CubeSat) is a miniaturized satellite that has dimensions of 10cm × 10cm × 10cm and weights of 1kg. The thermal model of CubeSat was modelled and the thermal analysis was performed. The thermal control analysis on this CubeSat with passive thermal control has been conducted by the ThermXL program that provided by ITP Engines. Temperature distribution of solutions was computed with ThermXL. Temperature data met the need of the mission. The results of the temperatures show that the thermal design of nanosatellite is feasible.
Comparison of Modeling Techniques for a Landing Gear
Authors: Margetts Rebecca , Ngwompo Roger F.
Published: May 2012

A wide range of modeling techniques is available to the engineer. The objective of this paper is to compare some typical modeling techniques for the simulation of a multi-domain mechatronic system. Usual dynamic modeling methods, such as block diagrams and iconic diagrams, can cause problems for the engineer. Differential algebraic equations (DAEs) and algebraic loops can significantly increase simulation times and cause numeric errors. Bond graphs are less common in industry, and are presented here as a method which allows the engineer to easily identify causal loops and elements in differential causality. These can indicate DAEs in the underlying equations. An aircraft landing gear is given as an example of a multi-domain system, and is modeled as a block diagram, an iconic diagram and as a bond graph. The time to construct the model, time to solve and problems faced by the analyst are presented. Bond graphs offer distinct advantages in terms of the ease of implementing algebraic equations and visibility of causality. The time taken to model a system can be significantly reduced and the results appear free from computational errors. Bond graphs are therefore recommended for this type of multi-domain systems analysis.
CFD Analysis of Drag Reduction Using External Devices on Pickup Trucks
Authors: Adem Feysal A. , Zhou Dongmei , Krishnani Pramod
Published: May 2012

The flows over a pickup truck with add-on devises were studied using computational fluid dynamics (CFD) with the objective of investigating the effect of these add-no devices on the flow structures around the vehicle, aerodynamic drag, and lift coefficient. All numerical simulations were performed using commercial CFD software Fluent [8]. A generic pickup model with extended cab was used as the base model and all the flow simulations were performed at zero degree yaw angle. The pickup configurations used in the present CFD simulation include Aerocap with different rear inclination angle α, Tonneau cover, Rear Roof Garnish, and Tail-plates. Results from numerical simulations indicated that Aerocap with inclination angle α = 12° and a reduced rear width has produced the minimum aerodynamic drag coefficient. It was also shown that the wake region decrease when the rear inclination angle increases.
Waves Simulation in an Excited Cylindrical Tank Using σ-Transformation
Authors: Eswaran M. , Saha Ujjwal K.
Published: May 2012

Free surface motions of the liquid in partially filled tanks under gravity are of practical significance particularly in marine and road transportation applications. For this reason, liquid sloshing has always been a research subject attracting great concern during the last several decades. Numerical experiments of sloshing wave motion are undertaken in a 2-D tank which is moved horizontally. Results of liquid sloshing induced by sinusoidal base excitations are presented for small to steep non-breaking waves. The numerical model is valid for any water depth except for small depth when viscous effects would become important. Solutions are limited to steep non-overturning waves. In this paper, the semi-circular domain with time-varying fluid surface was mapped onto a rectangular domain by the σ-transformation. Based on the inviscid flow equations, a fully non-linear finite difference model has been developed. The simulations are limited to a half-filled container. The liquid free surface elevation and wave phase-plane diagram have been plotted for different tank excitation frequency. It has been observed that while increasing the tank frequency, the liquid wave height in the tank changes according to the system natural frequency. Finally, the proposed computational scheme has been applied to a real engineering problem to capture the irregular behavior of liquid free surface inside the tank. For this, acceleration-time history of EW and NS components of the EL-Centro earthquake, California has been studied and analyzed.
Mechanical Design of Wound Composite Impeller Using FEM
Authors: Wang Jifeng , Patil Mohit , Olortegui-Yume Jorge , Mu¨ller Norbert
Published: May 2012

A low-cost, light-weight, high-performance, composite turbomachinery impeller with uniquely designed blade patterns is analyzed. Such impellers can economically enable refrigeration plants to use water as a refrigerant (R718). A stress and vibration analyses procedure is developed to assess the maximum stresses and natural frequencies of these wound composite axial impellers under operating loading conditions using Finite Element Method. A commercially available software ANSYS is used for the FE calculations. Analysis is done for two different blade geometries and then suggestions are made for optimum design parameters. The relationship between impeller natural frequency and rotating speed is also determined based on dynamic characteristics analysis.
An Evaluation of a Modified Iosipescu Specimen for Measurement of Elastic-Plastic Properties of Solder Materials
Authors: Mukherjee Subhasis , Dasgupta Abhijit
Published: May 2012

There are various specimen configurations available in the literature for characterizing the mechanical behavior of solder interconnect materials. An ideal test specimen should use a simple geometry to minimize the complexity of the stress analysis and which produces a uniform material response throughout the test material. In the thermo-mechanical micro scale (TMM) test used in this study, we use a simple, notched shear specimen, based on a concept originally proposed by Iosipescu [1967] [1], which produces a very uniform shear stress field in the solder joint volume [Reinikainen et al., 1998] [2]. Our modified Iosipescu specimen comprises of two oxygen free, high conductivity (OFHC) copper platens soldered together and loaded in simple shear. The solder joint in this specimen is only 180 microns wide to capture the length scale effects of functional solder interconnects. This study examines the effects of dimensional variabilities of this modified Iosipescu specimen on the shear stress distribution in the solder joint. Variabilities encountered in these specimens include: (i) fillets at the V-notches, caused by excess solder; (ii) offset between the two copper platens along the loading direction; (iii) taper of the solder joint due to lack of parallelism of the edges of the copper platens; and (iv) misalignment between the specimen centerline and loading axis of the TMM test frame due to mounting variability. Detailed parametric studies of these four dimensional variations in the TMM specimen are conducted using a simple two-dimensional elastic-plastic finite element model. The uniformity of the shear stress field in the specimen is investigated and the variation in the derived stress-strain curves is examined, as a function of the dimensional variabilities described above.
Thermal Transfiguration Analysis for the Large Aperture Optical Element of Switchyard in ICF Driver Target Area
Authors: Zhou Yi , Yang Ping , Zhang Junwei , Zhou Hai
Published: May 2012

Temperature gradient is one of the most important factors that cause large deformation of the large aperture optical element in an inertial confinement fusion (ICF) laser driver. In this study, we measured the ambient temperature around the laser switchyard and analyzed the temperature distribution and changing characteristics over time. The results indicated that variation trends of temperature inside the switchyard was almost the same, the temperature gradients of the uppermost part were higher than the bottom, and the temperatures in the centre were higher than both sides. Loading the temperature profile into the finite element model of the switchyard showed that the deformation of the optical element changed with time. The results indicate that temperature distribution has a great impact on the optical elements, and it attains the design objective of being smaller than 0.24urad and contents with the requirement of shooting practice when temperature difference is about 0.01°C or partial temperature difference inside the switchyard is about 0.1°C.
Thermochemical Energy Storage Using Salt Hydrates
Authors: Balasubramanian Ganesh , Ghommem Mehdi , Hajj Muhammad R. , Wong William P. , Tomlin Jennifer A. , Puri Ishwar K.
Published: May 2012

We investigate the capability of salt hydrates, using magnesium sulfate heptahydrate as a model salt, to store thermo-chemical energy as they dissociate into anhydrous salts or lower hydrates and water vapor upon heating. When salt hydrates are heated to the temperature required to activate the dehydration reaction, water desorption occurs from the compound. While thermal diffusion governs thermal transport below this reaction temperature, the heat transfer during the dehydration process is influenced by thermochemical kinetics. An anhydrous salt that has relatively higher energy content than its hydrated counterpart can be stably stored over long durations and transported at ambient temperatures. Thus, thermal energy can be released by allowing water vapor to flow across the anhydrous salt, which transforms its chemically stored heat into a sensible form. We model the thermochemical process based on the conservation of mass and energy and a relation describing the chemical kinetics, and employ finite difference technique to solve them. Different cases are considered to provide suggestions to improve the process performance. This storage application has potential for long-term thermal applications, e.g., for storing solar heat during summer months and releasing it in the winter to warm buildings.
Behaviour of Vacuum Casting Plastic Composites Under Different Treatments of Banana Fibres
Authors: Monzo´n M. D. , Ortega Z. , Beni´tez A. N. , Herna´ndez P. M. , Marrero M. D. , Angulo I.
Published: May 2012

Nowadays, the natural fibres market is having an important growth due to the commitment of contemporary society with the sustainable development that leads the natural resources preservation and the environment protection. Fibres from banana food wastes provide high mechanical properties related to other natural fibers such as flax, sisal, hemp, etc. The aim of the present research work is to compare different banana fibres processing in order to improve the matrix fibre adhesion and behavior of fibre under processing conditions. Simple Anova analysis has been implemented on four different formulations: 1. No fibre processing, 2. Alkaline processing with Caustic Soda (NaOH), 3 Maleic Anhydride, 4. Combination of Soda and Maleic Anhydride. Several samples of MTT 8040 resin, under vacuum casting, with silicone moulds, conditions, have been done. Mechanical properties and efficiency factors of adhesion fibre-matrix have been determined and compared.
Robust Adaptive Control of Nonlinear Systems With Input/Output Delays
Authors: Balas Mark J. , Gajendar Suraj
Published: May 2012

Many systems must operate in the presence of delays both internal to the system and in its inputs and outputs. In this paper we present a robustness result for mildly nonlinear systems. We use this result to show that for small unknown input delays, a simple adaptive controller can produce output regulation to a neighborhood with radius dependent upon the size of the delay. This regulation occurs in the presence of persistent disturbances and the convergence is exponential. We conclude with an example to illustrate the behavior of this adaptive control law.
Simultaneous Monitoring of Rolling-Element and Journal Bearings Using Analysis of Structure-Born Ultrasound Acoustic Emissions
Authors: Albers A. , Dickerhof M.
Published: May 2012

The application of Acoustic Emission technology for monitoring rolling element or hydrodynamic plain bearings has been addressed by several authors in former times. Most of these investigations took place under idealized conditions, to allow the concentration on one single source of emission, typically recorded by means of a piezoelectric sensor. This can be achieved by either eliminating other sources in advance or taking measures to shield them out (e. g. by placing the acoustic emission sensor very close to the source of interest), so that in consequence only one source of structure-born sound is present in the signal. With a practical orientation this is often not possible. In point of fact, a multitude of potential sources of emission can be worth considering, unfortunately superimposing one another. The investigations reported in this paper are therefore focused on the simultaneous monitoring of both bearing types mentioned above. Only one piezoelectric acoustic emission sensor is utilized, which is placed rather far away from the monitored bearings. By derivation of characteristic values from the sensor signal, different simulated defects can be detected reliably: seeded defects in the inner and outer race of rolling element bearings as well as the occurrence of mixed friction in the sliding surface bearing due to interrupted lubricant inflow.
Static, Dynamic and Failure Behavior of a Novel Axial Composite Impeller for Water Chiller
Authors: Li Qubo , Piechna Janusz , Mueller Norbert
Published: May 2012

Centrifugal forces applied to an impeller due to spinning generate large stresses. Aerodynamic forces are also imparted on the blade varying with time. These two forces play different roles during compressor events. Damage accumulated from these events results in the fatigue failure of impeller material and structure. Therefore, it is important to design the impeller against fatigue failure. The finite element method has been used in the study of impeller fracture mechanics and is regarded as an important tool in the design and analysis of impeller structures. A novel axial composite impeller manufactured through filament winding technology was invented by Michigan State University to compress water vapor as refrigerant. In this study dynamic and fatigue behavior of this composite impeller were analyzed using commercial code ANSYS. To begin with, load cases were identified, calculated and evaluated. Static analysis was performed using a full 3-D finite element model and the critical zone where fatigue failure begins was extracted to determine life assessment positions. Secondly, aerodynamic forces imparted on the blade were obtained from FLUENT; so that damage from dynamic stresses could be calculated. Finally, based on the FEM and FLUENT simulation results, a linear damage accumulation model was employed as a damage estimation rule to predict life of the composite impeller. A conservative life of 6498 h is given by this method.
Solar Gasification of Biomass: Kinetics of Pyrolysis and Steam Gasification in Molten Salt
Authors: Hathaway Brandon J. , Davidson Jane H. , Kittelson David B.
Published: May 2012

The use of concentrated solar energy for pyrolysis and gasification of biomass is an efficient means for production of hydrogen rich synthesis gas. Utilizing molten alkali-carbonate salts as a reaction and heat transfer media offers enhanced stability and higher reaction rates to these solar processes. To establish the reaction kinetics, experiments were carried out in an electrically heated molten salt reactor. Cellulose or activated charcoal were pyrolyzed or gasified with steam from 1124 K to 1235 K with and without salt. Arrhenius rate expressions are derived from the data supported by a numerical model of heat and mass transfer. The average rate of the reactions in molten salt, as measured by their reactivity index, is increased by 70% for pyrolysis and by an order of magnitude for steam gasification.