bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical and Experimental Study of Phase Effects on the Elastic Modulus of Air Plasma Sprayed Alumina Coatings Using Nanoindentation
Authors: Liu Ranran , Guo S. M.
Published: May 2012

Phase effects on the hardness and elastic modulus of atmospheric plasma sprayed (APS) alumina coatings were studied experimentally and analytically in this paper. For experimental work, the hardness and elastic modulus of APS alumina coatings were investigated by nanoindentation. Large scattering was observed in the results. For analytical work, the laminated APS alumina coating was taken to be consisted as alternating layers of α and γ alumina phases. This model was used to derive an approximate closed-form solution for nanoindentation on APS alumina coatings. The analytical solutions revealed that the phase combination played an important role in the material’s behavior under nanoindentation. The model verified the experimentally observed scattering in modulus distribution of APS alumina coating was mainly due to the phase composition. In addition, it is possible to determine the ratio of α and γ phases in APS alumina coatings by comparing the experimental nano-indentation results with the analytical solutions.
Preparation and Integration of Beta Amyloid Protein Nanofibers With Microfabricated Electrodes
Authors: Kissoon Nicola N. , Gutierrez Andre´s D. , Paravastu Anant K. , Englander Ongi
Published: May 2012

Micro and nano fabricated bio-systems and bio-devices can be produced once compatible processes for the integration of biomaterials and micro and nano systems are developed. Here, we demonstrate the integration of Alzheimer’s β-amyloid peptide nanofibers with metalized electrodes. The metalized electrodes and Alzheimer’s β-amyloid peptide nanofiber solutions are prepared separately. Metalized electrodes, composed of either chrome/gold or aluminum, with multiple electrodes are prepared using standard photolithography processes. Meanwhile, the Alzheimer’s β-amyloid peptide nanofiber solutions are prepared via the hydration of β-amyloid powder at various concentrations. The self-assembly of the β-amyloid nanofibers, to achieve well-dispersed networks, is optimized through periodic sonication and readdition of aliquots over timed intervals. The β-amyloid peptide solution can be successfully deposited onto the metalized electrodes to yield dense yet well-dispersed nanofiber arrays.
Tensile Behavior of Woven Hybrids Composites
Authors: Sevkat E. , Liaw B. M. , Delale F.
Published: May 2012

This paper presents an experimental study to investigate the tensile behavior of plain-weave hybrid S2 glass-IM7 graphite fibers/toughened SC-79 resin (cured at 177°C) composite strips. The tests were conducted on hybrid S2 glass-IM7 graphite fibers/toughened SC-79 resin and non-hybrid S2 glass-fiber/toughened SC-79 resin composites strips using a 22-kip MTS servo hydraulic universal testing machine. To use in Finite Element Modeling, the mechanical properties of these composite specimens with four lay-up sequences were determined. It was observed that the hybrid composites mechanical properties were somewhere between those of glass and graphite reinforced composites.
Design of Photon Beam Vibration Measurement System for the CLS HXMA Beamline
Authors: Li J. W. , Chen X. B. , Matias E. , Zhang W. J.
Published: May 2012

At synchrotron radiation facilities vibration is often a problem causing poor quality of photon beams. At the Canadian Light Source (CLS) Hard X-ray MicroAnalysis (HXMA) beamline, the MicroProbe endstation is particularly sensitive to vibrations since very small beam size (∼ 3μm × 5μm) is required. Thus, a measurement system is desired to investigate vibrations of the X-ray beam at HXMA beamline. This paper presents a design of such a X-ray beam vibration measurement system. The system consists of two sub-systems: (a) measurement system and (b) vibration-isolation platform. Mathematical models are developed and detailed design is conducted. The design is numerically investigated and it shows very promising results.
Nonlinear Oscillations at Critical Shimmy Parameters: Experiments and Numerics
Authors: Taka´cs De´nes , Ste´pan Ga´bor
Published: May 2012

Brief description of a low degree of freedom shimmying wheel model is presented where the time delay effect is in the focus of the corresponding stretched-string-like tyre model. The stability charts obtained by linear stability analysis present various bifurcation phenomena. These are checked by experiments on a test rig and also by numerical simulations that involve the partial sliding of the tyre contact region as a nonlinear effect. The sense of the Hopf bifurcations are compared to various shimmy models including the classical single-contact-point ones. Double Hopf bifurcations leading to quasi-periodic oscillations are also investigated. The applied numerical methods are optimized for convergence and also for possible application in real-time control strategies.
Vibration-Based Electromagnetic Energy Harvester
Authors: Khan Farid , Sassani Farrokh , Stoeber Boris
Published: May 2012

This paper presents the simulation, fabrication, and experimental results of a vibration-based electromagnetic power (EMPG) generator. A novel, low cost, one mask technique is used to fabricate the planar coils and the planar spring. This fabrication technique can provide an alternative for processes such as Lithographie Galvanoformung Abformung (LIGA) or SU-8 molding and MEMS electroplating. Commercially available copper foils of 20 μm and 350 μm thicknesses are used for the planar coils and planar spring, respectively. The design with planar coils on either side of the magnets provides enhanced power generation for the same footprint of the device. The device overall size is 1 cm3. Simulations of the modal analysis of the spring-mass system and the magnetostatic analysis of the magnetic field generated by the magnets are performed with COMSOL multiphysics®. Excitation of the EMPG at the fundamental frequency of 371 Hz and at 13.5 g base acceleration (base amplitude 24.4 μm) yields an open circuit voltage of 60.1 mV, as well as 46.3 mV load voltage and 10.7 μW power for a 100 Ω load resistance. At matching impedance of 7.5 Ω the device produced a maximum power of 23.56 μW and a power density of 23.56 μW/cm3.
An Analytical Investigation of Interfacial Dissipation in Piezoelectric Block Resonators
Authors: Schiferl Zachary , Gardner John , Deerfield Derek , Hao Zhili
Published: May 2012

This paper presents an analytical investigation of interfacial dissipation in piezoelectric block resonators. Interfacial dissipation is the loss of vibration energy at the interface between two successive layers in such devices. The physical mechanism of interfacial dissipation is examined within the framework of continuum mechanics. This dissipation is further mathematically formulated in terms of a stress jump across the interface and its accompanying interfacial slip. By assuming the block resonator is an ideal rectangular block, the expressions for interfacial dissipation in two typical types of piezoelectric block resonators are derived. The calculated results are validated by comparison with experimental data in the literature. For the first time, this analytical investigation not only sheds insight on how interfacial dissipation occurs but also provides design guidelines on reducing this dissipation.
An Experimental Study to Find the Acoustic Quality Indicators of Mulberry Wood
Authors: Mansour Hossein , Behzad Mehdi
Published: May 2012

Morus Alba or mulberry is a wood species that is broadly used in making musical instruments in Eastern countries. However, the mechanical and acoustical properties of this type of wood are not investigated properly. In this study a set of features, previously examined for other species, are applied to this wood and its acoustic quality is evaluated. Setar, a Persian musical instrument made of mulberry wood, is selected as the test case of this experiment. Different samples of wood are gathered and categorized based on their appropriateness for Setar construction. The quality of each sample is identified based on the Perceptual knowledge of professional Setar makers. The most effective features are then selected and their average values are calculated for high quality samples. The result of this study helps Setar makers to select proper raw material before making an instrument. In addition, this approach can be applied to other wood species used in music industry.
Voiding and Thermal Resistance Modeling and Characterization for a QFN Assembly
Authors: Gadepalli Harish , Dhanasekaran Rangaraj , Ramkumar S. Manian , Jensen Tim , Briggs Ed
Published: May 2012

Quad Flatpack No lead (QFN) packages have become a popular choice in electronics packaging due to its small form factor. They are also gaining rapid industry acceptance because of its excellent thermal and electrical performance. The bottom side of the QFN package has a large thermal pad. This exposed die attach pad effectively conducts heat to the PCB and also provides a stable ground connection. Effective soldering of this surface to the pad on the PCB is required for good thermal dissipation and component functionality. The exposed thermal pad presents various challenges during the surface mount assembly process. One major challenge is solder void formation. Voids are primarily formed due to the entrapment of volatiles in flux outgassing during the reflow process. The primary objective of this study is to determine optimal parameters to minimize void formation in QFN packages (QFN16, QFN20, QFN28, QFN32 and QFN44), specifically the reflow profile, lead-free solder paste and stencil aperture opening for the thermal pad. A systematic Design of Experiments (DOE) based approach was used to arrive at conclusions, using the ratio of void volume on the thermal pad to the actual volume of solder paste printed, as the response variable. A theoretical thermal resistance response variable was also modeled to analyze the DOE parameters and the conclusions were similar to the void model. Various graphs are presented to understand the impact of different parameters. Interaction graphs are used to determine optimal settings for each parameter. A regression equation for relationship between the factors and the void volume is identified to predict void volumes for any given component, paste volume and paste transfer efficiency.
A Technique for Embedding SPICE in a Simulink Environment for MEMS Simulations
Authors: Wilson Christopher G. , Dean Robert , Flowers George T. , Hung John Y.
Published: May 2012

Computer simulations are powerful tools in the designer’s toolbox, giving an estimate of what the device will actually do once realized. Two such tools, Simulink and SPICE are commonly used to design, simulate, and verify models in the mechanical and electronic domains, respectively. Challenges can arise, however, when attempting to simulate behaviors of hybrid systems that possies both electronic and mechancial subsystems. For example, in microelectromechanical systems (MEMS) designs, variable capacitors are frequent methods for sensing and actuating. While straightforward to model in Simulink, MEMS are not intuitive to model in SPICE, where the control electronics are simulated. On the other hand, SIMULINK is a less mature tool than SPICE for simulating electronic behaviors — SPICE already posseses large libraries of electronic device models. Thus, current MEMS designers lack a straightforward method to simulate and verify variable capacitors in a transient electronic circuit in SPICE, since the entire mechanical system must be converted from Simulink and verified. This paper presents a technique for embedding NGSPICE, an open-source SPICE implementation, inside a Simulink model via a S-function block, enabling a full system model for transient responses to be realized. A Level 2 M-file S-function block implements the calling and parsing of the associated electronic subsystem circuit file. The required modifications for the circuit file to the Simulink model are described. Validation testing using a low-pass filter type circuits with constant and variable capacitance are presented. Some examples are presented and discussed.
A Comparative Analysis of Wind Propulsion Systems for Ocean-Going Vessels
Authors: Gully Benjamin H. , Webber Michael E. , Seepersad Carolyn C.
Published: May 2012

Recent increases in fuel prices have spurred interest in energy efficiency and alternative energy technologies. These interests are especially relevant for the marine industry, which is responsible for transporting over 90% of the world’s freight. The present global fleet of commercial ships consumes approximately 200 million tonnes of diesel fuel each year — which is expected to rise to around 350 million tonnes a year by 2020 [5]. Studies have been conducted evaluating technologies to increase seagoing propulsion efficiency as well as harness available alternative energy sources. One renewable source, wind, is particularly interesting since 1) it presents a vast source of free energy that has been used throughout much of the history of marine transportation, and 2) novel technologies are available that might make it attractive for modern ships. The purpose of this analysis is to specifically evaluate and compare the ability of two modern wind-based technologies to produce thrust-reducing propulsion power for use in reducing the fuel consumption of a ship, namely a rigid wing sail and Flettner rotor. The analysis focuses on design specifications for each based on existing literature and compares the performance of the two technologies within a specified, but naturally varying wind environment. The force-producing capabilities of each technology are compared as a function of the ship operational parameters of heading and speed.
On-Chip Structures for the Determination of the Dopant-Dependent Young’s Modulus of Heavily Phosphorus Doped Polysilicon With Stress Compensation
Authors: Bassiachvili E. , Godin J. R. , Nieva P. , Khajepour A.
Published: May 2012

Accurate knowledge of thin-film material properties, such as Young’s modulus, is imperative in proper design and operation of MEMS devices. The use of on-chip devices allows direct access to the material properties as they are known to change with fabrication process, temperature as well as location within the wafer. Resonant and pull-in structures have been designed and modeled for the measurement of the Young’s modulus of heavily doped polysilicon thin films. The cantilever and clamped-clamped beams allow us to extract the Young’s modulus through observing the resonant frequency and pull-in voltage and cross-referencing the results. Mechanical actuation using a calibrated piezoelectric shaker for some devices and electrostatic actuation for others ensures that the structural effects, rather than the actuation technique, are responsible for the varying response at different temperatures. Optical readout will be used in order to reduce readout-associated errors, which can occur with purely electrical techniques at higher temperatures. However, electrical readout is also possible for some of the devices. The devices have been designed and fabricated using a customized 1-mask process. In this paper, we present the modeling and numerical simulations obtained for heavily doped polysilicon microstructures and will describe the method used for the determination of the Young’s modulus with stress compensation. Although the method described here has been used for heavily doped polysilicon thin films, it can be easily modified for the determination of Young’s modulus of other MEMS structural materials.
Tip Enrichment System for Rapid Screening of Mycobacterium Tuberculosis
Authors: Kim Jong-Hoon , Yeo Woon-Hong , Shu Zhiquan , Inoue Shinnosuke , Oh Kieseok , Gao Dayong , Chung Jae-Hyun , Lee Kyong-Hoon
Published: May 2012

Rapid detection of tuberculosis (TB) has been critically demanded over the last century. To detect TB, numerous methods screening Mycobacterium tuberculosis (MTB) have been developed. However, the methods still have challenges of rapid and specific enrichment of MTB. In this study, we present a novel specific enrichment method of MTB using a microfabricated tip. Through our simulation study, a wavy-shaped microtip is designed to enhance capturing efficiency of bacteria. Using an optimized tip, bacteria are attracted by dielectrophoresis and captured by affinity binding and capillary action. In experiment, a surrogate marker of MTB, Bacilli Calmette-Guerin (BCG), is enriched with the micromachined tip. When a microtip decorated with capturing antibodies is used, BCG cells spiked in saliva are detected at the concentration of 5×105 CFU/mL within 20 minutes. The tip enrichment system demonstrates the potential for rapid, culture-free detection of MTB in a raw sample.
Laboratory Experiences in Alternative Energy Systems and Their Integration in a Green Curriculum
Authors: Dini Said , Mindek Richard B. , Goodwin Daniel , Desmarais Adam
Published: May 2012

Alternative energy laboratory experiences in solar PV and wind energy have been developed to help support the “green” concentration recently offered for the first time in the mechanical engineering program at Western New England College. These laboratories, which give students hands-on experience and a better understanding of basic concepts in alternative energy systems, are conducted in a newly developed indoor/outdoor alternative energy laboratory facility. The alternative energy indoor/outdoor laboratory facility includes a fully operation geothermal system, which is used to heat and cool the engineering labs. It also includes six 195 Watt photovoltaic panels, a 30,000 Btu/clear day flat-plate solar collector, a Thermomax evacuated tubes solar collector, as well as a full scale 1 kW wind turbine, which allows for useful power and hot water to be provided to the engineering building. This facility is also fully instrumented for the collection of key performance data and allows for large scale demonstration of alternative energy systems to students. This paper describes the development, operation and capability of the indoor/outdoor alternative energy facilities, as well as a detailed description of solar and wind experiments, and how these are used in support of the “green” concentration within the mechanical engineering curriculum to give engineering graduates greater competency in the design, analysis and application of solar and wind energy systems.
Robust Gain-Scheduled Control of a UAV Based on a Polytopic Model Approximation
Authors: Ramirez Juan A. , Gutierrez Luis B. , Vasquez Rafael E.
Published: May 2012

This work addresses the design of a robust H∞ gain-scheduled controller for the Condor Andino UAV (Unmanned Aerial Vehicle). A polytopic approximation of the linearization family of the nonlinear model is used for the design. Because the linearization family in the operating region derives in a linear parameter varying (LPV) description with a nonlinear dependence of a set of parameters, a least squares approximation of the system matrices is used in order to obtain affine dependence. The polytopic description is obtained from the affine LPV model when the operating range is defined choosing the varying parameter inside a convex hull. The controller is synthesized using the Bounded Real Lemma in order to guarantee quadratic H∞ performance over the operating region. The simulation results show that the designed controller can be successfully applied to the nonlinear system over the operating range.
Water Tunnel Rotor Testing With Post Processing Based on PIV Measurements
Authors: Lartiga Catalina , Crawford Curran
Published: May 2012

Experimental investigation is required to obtain the non-dimensional coefficients that characterize the performance of new wind turbines and marine energy extracting devices, such as tidal turbines. However, data acquired from scaled models tested in tunnel facilities suffers from wall blockage and therefore, corrections must be applied to properly predict the performance of the full-sized rotor. Analytical expressions based on the axial momentum theory and correlating thrust coefficient to an equivalent free stream velocity have traditionally been used to correct power coefficients obtained experimentally. For small models, accurate force measurement is very difficult requiring a new post processing methodology when thrust data is not available. A methodology is presented in this paper that uses the velocity field data at the rotor plane, obtained from PIV measurements and CFD simulations, to account for blockage without the requirement for thrust data. A correction curve correlating axial induction factor and power coefficient is obtained and will be utilized for correction in future experiment testing.
Strategies for Optimization of Spot Welding Sequence With Respect to Geometrical Variation in Sheet Metal Assemblies
Authors: Wa¨rmefjord Kristina , So¨derberg Rikard , Lindkvist Lars
Published: May 2012

During the assembly process of sheet metal parts, a lot of factors affect the final geometrical quality. It is important to have knowledge about the characteristics of as many as possible of those factors, not only to be able to reduce their effect, but also to be able to include those factors in variation simulations. Those tolerance simulations are crucial tools in early stages in automotive industry in order to predict the outcome in critical dimensions and it is of course important to have as good accuracy as possible in the simulations. One of the factors affecting the final geometry is the spot welding sequence. In this paper it is shown how the spot welding sequence affects the amount of geometrical variation in a sheet metal assembly. A method for including the welding sequence in tolerance simulations is described. Of course, it is desirable to find an optimal sequence, i.e. a sequence that minimizes the geometrical variation in the final assembly. Since this is a fast growing problem — the number of possible sequences for N welding points is N!, it is not practicable to test all possible sequences. In this work some different strategies for finding an optimal sequence are tested on several industrial case studies. The tested strategies are based on general guidelines, on minimizing variation in each welding step respectively calculations of the movements in unwelded points in each step. The strategies based on general guidelines was not successful, neither was the one based on minimization of the variation in each step. The strategy based on movements in the unwelded points seems however promising. It resulted in the best or one of the better sequences for all of the eight tested industrial case studies.
Rheology and Rotational Rheometry of Concentrated Clay Based Ceramic Suspensions: Steps From Measured to Relevant Data
Authors: Andertova´ Jana , Rieger Frantisˇek
Published: May 2012

The rheological behavior of ceramic suspensions affects significantly wet ceramic processing. On the base of knowledge of rheological parameters the technological parameters of various processes (mixing, batching, spray drying, slip casting, of rheological parameters the selection of proper geometry and sensors must be done. From the data measured the flow curves must be designed and parameters of appropriate rheological models must be calculated. The power-law is the simplest model mostly used for description of rheological behavior of non-Newtonian fluids. Using this model, the dependence of shear stress on shear rate can be expressed. The aim of this paper is to show how the flow curves necessary for parameters of rheological model evaluation can be obtained from primary experimental data received from measurements on rotational viscometer. The two arrangements of rotational viscometer method were used in rheological measurements. The procedure of experimental data to obtain parameters K (coefficient of consistency) and n (flow behavior index) is presented.
Estimation of Road Surface Conditions From Tire Vibration
Authors: Suda Yoshihiro , Nakano Kimihiko , Sugiyama Hiroyuki , Hayashi Ryuzo , Yamabe Shigeyuki
Published: May 2012

This paper proposes the estimation algorithm of road conditions from tire vibration. The basic concept of estimation is that the tire vibration is determined by road irregularity and road friction condition. Because of difficulty of direct measurement of tire vibration, it is estimated from body acceleration using known tire model and vehicle properties between tire and body. To estimate the road irregularity, the Independent Component Analysis (ICA) method is used. The elastic deformation of the tire belt is modeled using the finite element absolute nodal coordinate formulation which allows for modeling large rotational motion and the nonlinear inertia effects. With comparison between estimated tire vibration from road irregularity with ICA and tire model and actual tire vibration from road irregularity and road surface condition with known vehicle properties, road surface condition could be estimated. So, tire vibration power spectral density (PSD) calculated by using the transmission characteristics becomes the function of the road surface, the road ruggedness, and the tire characteristic. These are clarified by the PSD ratio, ICA and the tire model, and road surface condition become able to estimate.
3D Monte Carlo Simulations of Aggregate Structures in a Magnetic Colloidal Suspension Composed of Plate-Like Particles With Magnetic Moment Normal to the Particle Axis
Authors: Sakuda Yasuhiro , Aoshima Masayuki , Satoh Akira
Published: May 2012

We have investigated the internal aggregate structures of a colloidal suspension composed of magnetic plate-like particles with a magnetic moment normal to the particle axis by means of three-dimensional Monte Carlo simulations. In concrete, we have attempted to clarify the influences of the magnetic field strength, magnetic interactions between particles, and volumetric fraction of particles, on particle aggregation phenomena. In order to discuss quantitatively the aggregate structures of particles, we have focused on the radial distribution and orientational pair correlation function. For no applied magnetic field cases, long column-like clusters are formed as magnetic particle-particle interactions increase. Characteristics of these clusters are that particles incline in a certain direction with their magnetic moments alternating in direction between the neighboring particles. For applied magnetic field cases, the magnetic moments of the particles incline in the magnetic field direction, so that the columnar clusters are not formed. The brick wall-like aggregates are formed as the influences of the magnetic field and magnetic particle-particle interactions become significantly dominant.
Preliminary Design of a Hybrid Propulsion System for High-Endurance UAV
Authors: Capata Roberto , Marino Luca , Sciubba Enrico
Published: May 2012

In recent years, a renewed interest in the development of unmanned air vehicles (UAV’s) led to a wide range of interesting applications in the fields of reconnaissance and surveillance. In these types of mission, the noise produced by propeller driven UAVs is a major drawback, which can be partially solved by installing an electric motor to drive the propeller. The evolution of high performance brushless motors makes electric propulsion particularly appealing, at least for small and medium size UAVs. All electric propulsion systems developed to date are though characterized by the limited range/endurance that can be obtained with a reasonably sized battery pack. In this paper we propose a hybrid propulsion system based on recently developed, high efficiency micro-turbines which can be used to power an electric generator. The UMGT is under evaluation in our department, to achieve the optimal configuration and performances. For this scope a new compact regenerative combustion chamber has been developed and several tests has been carried out, with the aim to reduce weight and dimension and increase vehicle payload. In a high range/endurance mission the ultra-micro-turbine can provide the energy required for the cruise phase (the so-called “transfer to target”), while in the final approach, in which a quiet flight attitude is a demanding item, the battery pack drives the motor. The mission requirements adopted in the preliminary aircraft design presented here consist mainly of a long endurance (> 12 hours) step, with a cruise speed of 33.3 m/s and a dash speed of 45 m/s at an altitude of 5000 meters. The maximum take-off weight is 500 N, with a payload of 80 N. Under the above assumptions, a flying wing configuration for the UAV was defined, with a length of 1.6 meters and a span of 2.5 meters. A system of elevons assures the pitch and roll motion while a double vertical tail, in which a pusher propeller is lodged, guarantees the yaw stability and control.
Virtual Configuration of Lower Limb Prosthesis
Authors: Colombo Giorgio , Facoetti Giancarlo , Gabbiadini Stella , Rizzi Caterina
Published: May 2012

This paper presents a new design framework to configure lower limb prostheses, both transfemoral and transtibial, where the key elements are the patient digital avatar and the domain knowledge. The technician is supported during the design process by the knowledge acquired from analysis of the traditional process and represented in the framework. The last one integrates virtual prototyping tools and knowledge management techniques. A specific software tool, named Socket Modelling Assistant, has been developed to design the socket, the custom-fit component of the prosthesis. A commercial CAD system is used to model the standard components (e.g., knee, foot and tubes) and to create the final assembly. Patient avatar and his/her data (e.g., anthropometric and physiological parameters) are the backbone of the whole product design process. They guide both the selection of standard components and the modelling of the socket digital model.
Static Load Carrying Capacity in Four Contact Point Slewing Bearings: Theoretical and Preliminary Finite Element Calculations
Authors: Aguirrebeitia Josu , Abasolo Mikel , Avile´s Rafael , Fernandez de Bustos Igor , Ansola Rube´n
Published: May 2012

This paper presents a theoretical model to calculate the general static load-carrying capacity of four-contact-point slewing bearings under axial, radial and tilting-moment loads, compared with preliminary results obtained from a detailed parametric finite element model of the bearing. The theoretical model is based on a generalization of Sjova¨ll and Rumbarger’s equations and provides an acceptance surface in the load space. The finite element model is based on the modelization of the balls via nonlinear traction-only equivalent spring concept. The aim is to validate the theoretical model to be used as an acceptance curve generator for slewing bearing design.
Analysis of Free Flexural Vibrations of Composite Mindlin Base Plates or Panels Reinforced by Three Bonded Plate Strips
Authors: Yuceoglu Umur , Javanshir Jaber , Amireghbali Aydin , Gu¨vendik O¨zen
Published: May 2012

The present study is about the theoretical analysis and the numerical solutions of the free vibrations of a certain type of the “Bonded and Stiffened System”. In other words, the “Free Bending Vibrations of Composite Mindlin Base Plates or Panels Reinforced by Three Bonded Stiffening Plate Strips” are investigated. The plate elements of the entire “System” are considered as the dissimilar “Orthotropic Mindlin Plates” with the transverse shear deformations and the transverse and the rotatory moments of inertia. The relatively very thin and linearly elastic adhesive layers between the “Stiffening Plate Strips” and the “Base Plate or Panel” are assumed to be subjected to transverse normal and shear stresses. Also, the dissimilar adhesive layers with unequal thicknesses and the different material characteristics are to be taken into account in the theoretical formulation. The dynamic equations, the stress resultant-displacement expressions and the adhesive layer equations of the “System” under study are combined together in each “Part” (or “Region”) of the “Bonded and Stiffened System”. Following some manipulations and combinations, they are, eventually, reduced to a set of the “Governing System of the First Order Ordinary Differential Equations” in “state vector” forms. The aforementioned system of equations are very suitable for the direct application of the present “Method of Solution” developed for the problem. This semi-analytical and the numerical solution technique is the “Modified Transfer Matrix Method (MTMM) (with Interpolation Polynomials)”. The system of equations in the “state vector” forms are numerically integrated and the mode shapes and the natural frequencies are presented for various sets of the “Boundary Conditions”. It was observed that, in the “Hard” (or relatively “Stiff) adhesive layers case, the regions with the “Bonded Stiffening Plate Strips” are “almost stationary” in all modes up to the sixth mode, while the rest of the “System” vibrates in a way dependent on the “Support Conditions” of the “Base Plate or Panel”. However, in the “Soft” (or relatively “Flexible”) adhesive layer cases, there is no “almost stationary” region anywhere in the “System”. Additionally, some important parameters such as “Thickness Ratio” on the natural frequencies are investigated and graphically presented for a set of the “Support Conditions”.
Experimental Investigations to Study the Effect of Solid Lubricant MOS2 on the Performance of Hard Turning
Authors: Singh Dilbag , Rao P. Venkateswara
Published: May 2012

In hard turning, lot of heat is generated due to plastic deformation of the work material, friction at the tool-chip interface and friction between tool and the workpiece. The heat produced in machining adversely affects the quality of the products produced. Cutting fluids have been the conventional choice to deal with this problem. However, due to the environmental restrictions, the use of cutting fluids is restricted. Machining with solid lubricants, cryogenic cooling by liquid nitrogen and minimum quantity lubrication are some of the alternative approaches in this direction. This research work deals with an investigation on using molybdenum disulphide as solid lubricant in order to reduce friction for improving the machining performance and for overcoming some of the limitations that arise due to the use of cutting fluids or while dry hard turning. An experimental setup has been designed and built, and experiments have been conducted to study the effect of using molybdenum disulphide as solid lubricant on surface finish and cutting forces. An improvement in surface finish was observed with molybdenum disulphide assisted hard turning. It was also observed that there was a considerable reduction of cutting forces, thereby reducing the specific energy needed and consequently improving the machining performance.
Advanced Exergoeconomic Analysis Applied to a Complex Energy Conversion System
Authors: Petrakopoulou F. , Tsatsaronis G. , Morosuk T. , Carassai A.
Published: May 2012

Exergy-based analyses are important tools for studying and evaluating energy conversion systems. While conventional exergy-based analyses provide us with important information, further insight on the potential for improving plant components and the overall plant as well as on the interactions among components of energy conversion systems are significant when optimizing a system. This necessity led to the development of advanced exergy-based analyses, in which the exergy destruction, as well as the associated costs and environmental impact are split into avoidable/unavoidable and endogenous/exogenous parts. Based on the avoidable parts of the exergy destruction, costs and environmental impact, the potential for improvement and related strategies are revealed. This paper presents the application of an advanced exergoeconomic analysis to a combined cycle power plant. The largest parts of the unavoidable cost rates are calculated for the components constituting the gas turbine system and the low-pressure steam turbine. The combustion chamber has the second highest avoidable investment cost, while it has the highest avoidable cost of exergy destruction. In general, most of the investment costs are unavoidable, with the exception of some heat exchangers of the plant. Similarly, most of the cost of exergy destruction is unavoidable with the exception of the expander in the gas turbine system and the high-pressure and intermediate-pressure steam turbines. In general, the advanced exergoeconomic analysis reveals high endogenous values, which suggest improvement of the total plant by improving the design of the components primarily in isolation, and lower exogenous values, which suggest that the component interactions are of lower significance for this plant.
Stabilization Effect of Surfactant and Functional Group on Highly Concentrated Carbon Nanotube Conductive Ink
Authors: Tantang H. , Wei J.
Published: May 2012

This study focuses on the analysis of conductivity of resulting carbon nanotube film and UV-vis spectra of carbon nanotube solution to investigate the dispersion and stability of carbon nanotube solution as well as the factors affecting it. The dispersion stability of hydrophilic functional group (-COOH) and surfactant (SDBS) were tested, and was found to behave differently. Hydrophilic functional group tends to increase dispersion stability with increasing concentration, however surfactants shows some optimum points at 0.5wt%. The combination of both stabilization groups has shown a significant improvement in carbon nanotube dispersion quality as well as its stability that is reflected through the observed improvement in the deposited thin film conductivity. Possible mechanism could be explained by ionic repulsive force of functional group ions (-COO−) and surfactants ions (SO4−).
The Effect of Micro Pin-Fin Shape on the Heat Transfer Performance of Micro Pin-Fin Heat Sinks
Authors: Koz Mustafa , Kosar Ali
Published: May 2012

Micro heat sinks currently find applications in many areas such as in aerospace engineering, micro reactors, electronics cooling, micro turbine cooling, and micro biological applications. Among different types of micro heat sinks, the ones with micro pin-fins are becoming more and more popular due to their high heat transfer performances. There is however not enough experimental data available in the literature to show the effect of pin-fin shape on heat transfer. To address to this lack of information, micro heat sinks with a pin-fin having the same chord thickness/diameter of various shapes (circular, cone shaped, diamond shaped, hydrofoil shaped, rectangular, square and triangular) are numerically modeled, and their heat transfer performances are assessed and compared. The Reynolds number is between 20 and 120 in this study. Applied heat flux to micro pin-fin bases is set to values between 1200 and 7240 W/cm2. In the current study, micro pin-fins of various shapes are three dimensionally modeled based on a one-to-one scale and evaluated based on their heat transfer performances with the use of commercially available software COMSOL 3.5a. Full Navier-Stokes equations are solved along with continuity and energy equations under steady state conditions for weakly compressible, single phase water flow. For having increased computational efficiency, half of the domain, which consists of a micro pin-fin located inside a micro channel, is modeled with the use of a symmetry plane. In order to validate the use of numerical models, parametric values from previous experimental data available in the literature are exactly taken and simulated. The numerical and experimental results show a good agreement.
An Approach to Investigate Mixed Lubricated Systems in the Micro Scale by Means of the Coupled-Eulerian-Lagrangian Method
Authors: Albers Albert , Lorentz Benoit
Published: May 2012

This article presents an approach on the numerical investigations of mixed friction systems. By means of the Finite Element Method, a three-dimensional model has been developed at the micro-scale to calculate the influence of selected parameters on the behavior of frictional contact systems. Composed of two sliding rough surfaces and one lubricating fluid, the model is taken into account adhesion effect taking place in the pseudo solid-solid contact. To simulate the interactions between the fluid and the solid structure, the Coupled-Eulerian-Lagrangian meshing process is utilized for its ability to keep good results despite of large contact domain topology changes observed in such complex friction systems. Based on a section of an axial floating bearing, the model calculates the contact pressure and temperature, the stress and also the friction coefficient between the two lubricated solids. This approach gives the opportunity to identify the influence parameters on the tribological behavior of mixed friction systems.
A Thermoacoustic Engine-Refrigerator System for a Space Exploration Mission
Authors: Sastry Sudeep , Kadambi Jaikrishnan R. , Wernet Mark P. , Sankovic John M. , Ercegovic David B.
Published: May 2012

Unique cooling systems have to be designed to cool the electronic components of space exploration rover, especially in places like Venus, which has harsh surface conditions. The atmospheric pressure and temperature at the surface of Venus are 92 bars and 450°C respectively which make operation of electronic devices and sensors very difficult. Conventional cooling methods are currently deemed unfeasible due to the short life span of moving parts of the refrigerator systems at high temperatures. Furthermore, alternate energy sources such as solar power is not an option on Venus, since the cloud layer consisting of concentrated sulfuric acid droplets is thick and the surface reduces the solar intensity at the surface to about 2% of the intensity above the atmosphere. Therefore developing alternate method of power and cooling system is essential for Venus operation of any robotic rover. The advantages of using thermoacoustic systems are that there are no moving parts and they have efficiency comparable to conventional systems. Additionally there is a dearth in literature at using thermoacoustic refrigeration at high temperatures. This work discusses the development and optimization of a standing wave thermoacoustic engine refrigerator system to be used as a cooling device for the electronic components. The effects of various parameters such as gas mixture ratio, pressure, stack material etc. are discussed. The system designed provides cooling from 443K to 323K providing 150W of cooling.
Crib Tent Safety Analysis
Authors: Brickman Dennis B. , Grzetic Joseph F.
Published: May 2012

A 23 month old child sustained a severe head injury when a crib tent inverted and collapsed, lodging the child’s head against the top rail of the crib. A testing program was conducted using anthropomorphic child dummies to analyze the inversion danger during a crib tent collapse event. The primary goal of this investigation is to make crib tent designers, retailers, and users more aware of the inversion danger and to identify a design alternative to help reduce the number of these types of injuries.
Study of a Thermal Barrier Coating in a Pulsed Detonation Engine
Authors: Anderson Eric K. , Hoke John L. , Schauer Fred R.
Published: May 2012

A pulse detonation engine (PDE) works by establishing regular purge-detonation cycles. During a cycle, a point inside the detonation tube downstream of the ignition source is exposed to extreme high temperature briefly as the detonation wave passes, followed by near room temperature purge gas. As is the case for many combustion systems, minimizing unwanted heat loss in a PDE is important to maximizing efficiency. For this reason, the effect of coating the inner wall of a detonation tube with a thin, low thermal conductivity coating was studied experimentally and computationally. A three inch diameter 304 stainless steel detonation tube with 1.65 mm wall thickness was coated on the inside with a 0.635 mm thick layer of 93% Zirconium Oxide and 7% Yttrium Oxide. Experimental results were obtained operating the PDE at a frequency of 10 Hz. Temperature was measured at four points on the exterior of the detonation tube between 33 and 45 inches downstream of the ignition source. At all locations measured, the exterior tube temperature would rise from an initial ambient temperature faster with the uncoated tube until a crossover point approximately 1000–1500 cycles after the start of the experiment. After this cross over point, outer wall temperature was higher for the coated tubes, which at this point was increasing faster for the tube with the thermal barrier. To better understand the physical reason why the insulated tube always reached a higher temperature after roughly 1000 cycles, a simplified computational model was created using a time-dependent, one-dimensional, implicit finite difference method to calculate the temperature at 20 evenly spaced nodes. The temperature profile of the tube was assumed to vary only radially, so the interior points were solved using the transient one-dimensional heat conduction equation. One dimensional convection boundaries were applied at the inner and outer walls of the tube. Boundary conditions of increasing complexity were applied, beginning with a constant temperature, natural convection condition at the outer wall and a forced convection boundary condition at the inner wall with a step change in temperature to simulate the detonation wave. Experimentally measured wall temperatures are presented and compared to computationally obtained temperature profiles. The focus is on understanding the physical reason for the behavior of the insulated tubes.
CFD Simulations of Flow and Heat Transfer in a Zigzag Channel With Flow Pulsation
Authors: Olayiwola Bolaji O. , Schaldach Gerhard , Walzel Peter
Published: May 2012

Heat transfer enhancement by pulsating flow in a zigzag channel has been numerically studied using a commercial CFD software for the ranges of laminar flow 0 < Re < 550. The influence of inclination angle α of the zigzag channel and oscillation parameters is investigated. The amplitude of the pulsatile flow was varied between 0.5 mm and 4 mm. The frequency f ranges between 0.5 Hz and 5.5 Hz. For steady flow, fluid mixing is promoted by self induced fluctuation due to the instability of the flow. The Reynolds number Re for the occurrence of significant eddy decreases with increase of the inclination angle of the channel. Superposition of oscillation additionally promotes further fluid mixing by the propagation of different scales of vortices. In comparison to straight channels, significant heat transfer in the laminar regime is possible using a zigzag channel with inclination angle greater than 15°. Further intensification of the heat transfer is possible with superposition of oscillation on the main flow through the channel. However, the heat transfer enhancement due to imposed oscillation is found to increase with decreasing Reynolds number. The effect of the imposed oscillation yields heat transfer enhancement E of up to 1.41 when compared with steady flow in zigzag channel at Reynolds number Re = 107, frequency f = 2.17 Hz and oscillation amplitude A = 1mm using a zigzag channel with an inclination angle α = 15°. Further heat transfer enhancement E of up to 1.80 at the same flow and oscillation conditions is possible with a zigzag channel having inclination angle α = 45°. The influence of oscillation frequency on the heat transfer enhancement E becomes significant as soon as the Womersley number W > 41.32. The effect of superposition of oscillation is not significant using a zigzag channel with inclination angle α = 60°. When the oscillation amplitude is increased up to 4 mm at Reynolds number Re = 107, frequency f = 2.17 Hz and inclination angle α = 45°, the heat transfer enhancement E of about 3.3 is obtained.