bluuebunny/crossref_metadata_2025 huggingface dataset:
Powerplant Lubricant Selection for Improved Efficiency and Environmental Impact Reduction
Authors: Simmons Gregory F. , Kuznetsov Evgeny A. , Glavatskih Sergei B.
Published: May 2012

Computational models were used to optimize bearing performance by adjusting a number of lubricant properties. This computational optimization showed that the most beneficial characteristics to hydrodynamic bearing operation were high viscosity index (VI) and high specific heat capacity. Four environmentally adapted synthetic lubricants were developed to provide these characteristics including: ISO VG32 with 259 VI, ISO VG22 with 245 VI, ISO VG22 with 336 VI, and ISO VG15 with 226 VI. A full scale bearing test machine was then operated with these lubricants in addition to mineral based turbine oils, ISO VG68 with 103 VI and ISO VG32 with 105 VI, to determine the effect on bearing performance and to validate the models. The new lubricants reduced bearing power loss by up to 20% and significantly reduced bearing temperatures with somewhat reduced film thickness. The machine was then operated to provide equivalent minimum viscosity with the new lubricants by varying inlet temperature, finding that changes in power loss were less substantial with equivalent minimum viscosity. Comparison of simulated and experimental results led to development of a simple, practical method to estimate benefits and operational parameters for lubricants based on viscosity grade, viscosity index and a simplified description of the machine’s bearings. Other, less tangible, factors considered are bio-degradeability and impact of power loss reduction.
An Innovative Design Methodology for Optimum Cavitating Inducer Performance
Authors: Pascu Maria , Millward Brian , Howat Gordon , Purdom Tom
Published: May 2012

The present paper addresses a design method for pump inducers which allows the full calculation of the optimum impeller configuration for improved cavitation performance. This method permits a tight control of the blade geometry since it computes inversely the required blade shape to attain the desired stream-wise angle distribution. The blade profile is fully resolved by implementing a meridional analysis into the design process, where the radial head gradient (RHGR) is the design variable. Additional variables are the outlet blade angle and the diffusion factor (DF). Essential for the proposed method is the parabolic angle distribution assumption made to fully resolve the blade profile. Several new designs are derived for different outlet angles using the fore-mentioned design method and comparative multi-phase CFD analysis was performed, which allowed the determination of the optimum RHGR and outlet blade angle. It was shown that the models characterized by the highest hub loading delivered the best performance under the cavitating regime, with the smallest values for the inception cavitation number and the critical cavitation number. Because the overall suction performance of the pump, especially the breakdown point, is a direct measure of the inducer performance, the presented design method proves very advantageous since it delivers inducers optimized for the cavitation regime.
Innovation is the Key to Sustaining Sustainability
Authors: Heshmat Hooshang
Published: May 2012

Economic survival and sustainability in the increasingly interconnected global community during the 21st century and beyond will require new and innovative technologies supported by subsequent continuous product improvements that minimize the negative impact to the earth’s environment, resources and inhabitants. In the past several years, worldwide consumption of energy, through consumer products, industrial processes and transportation systems, has increased rapidly and has even given a whiff or glimpse of things to come in the not too distant future. As scarce resources become reality and global climate change accelerates, technological innovation must occur at a pace never before seen if we are to extend a new and sustainable lifestyle to more of the world’s inhabitants while also protecting our environment. Sustaining sustainability (i.e., the cycle of continually improving and introducing environmentally conscientious products) will require that we radically alter our myriad of energy consuming and producing systems through technological innovation. While every branch of engineering has its own impact on and contribution to the environment, it is in the energy consuming and producing technologies that considerable effort is needed. This paper will present several innovative oil-free systems designed to minimize deleterious emissions to the environment through higher system efficiencies and elimination of hydrocarbon lubricants. The discussion will also identify possible directions to foster innovation.
Precision Control of Piezoelectric Actuators With an Inversion-Based Approach
Authors: Shih Hui-Ru , Walters Wilbur L.
Published: May 2012

The emphasis in this study is on the compensation of the uncertainties associated with piezoelectric actuators for precise nanomanipulation. A cascade model for creep, hysteresis, and vibrational dynamics of the piezoelectric actuator is proposed. The procedure for identifying the model parameters by experimental data is introduced. The identified model is employed to develop an inverse-based feedforward compensator. This study presents a comprehensive analysis and evaluation of the proposed method. As a result, this proposed approach can lead to a software-compensated platform for precise nanomanipulation.
Experiential Learning for Engineering Technology Students in 21st Century
Authors: Dong Janet , Dave Janak
Published: May 2012

Experiential Learning (EL) is a philosophy in which educators purposefully engage learners in direct experience and focused reflection in order to maximize learning, increase knowledge, and develop skills. Based on the learning cycle proposed by Lewin and the philosophy of Dewey, in that each experience builds upon previous experiences and influences the way future experiences will affect the learner, Kolb[1] developed the experiential learning model to describe the learning process. The four stages of the model are: Concrete Experience, Reflective Observation, Abstract Conceptualization and Active Experimentation. This model shows how theory, concrete experience, reflection and active experimentation can be brought together to produce richer learning than any of these elements can on its own. The College of Engineering and Applied Science did not implement the Kolb model fully due to insufficient resources. Therefore, only the first two of the four stages were used. Many avenues of concrete experiential learning exist for the students in the engineering technology programs at the University of Cincinnati, such as co-op, service learning, global study programs, field projects, academic research, etc. This paper gives a description of the experiential learning of students at the University of Cincinnati in the areas of global study, honors program and undergraduate research. Two faculty members in Mechanical Engineering Technology from the College of Engineering and Applied Science were involved in these experiences. Their experiences, along with student reflections, are discussed in the paper.
Deformation Kinetics in Cu/Ta Nanoscale Multilayers
Authors: Wang F. , Huang P. , Xu M. , Lu T. J.
Published: May 2012

Intensive research has been carried out on two key parameters important for interpreting the deformation kinetics of nanocrystalline metals, i.e., strain rate sensitivity and activation volume. Other than nanocrystalline metals, however, only a few recent studies focus on evaluating the two parameters for nanoscale multilayers that also possess nanoscale grain size. Using transmission electron microscope and nanoindentation test, we study the deformation behavior of nanoscale Cu/Ta multilayers having modulation period of 140 nm and 18 nm, respectively. The microstructure, grain size and strain rate sensitivity of the nanoscale multilayer subjected to nanoindentation are examined to explore its deformation mechanisms. It is established that the strain rate sensitivity of nanoscale Cu/Ta multilayers differ from those of nanocrystalline metals. The implications of these findings for the mechanical properties of nanoscale multilayers are discussed.
Active Damping Using Distributed Anisotropic Actuators
Authors: Schiller Noah H. , Cabell Randolph H. , Quinones Juan D. , Wier Nathan C.
Published: May 2012

A helicopter structure experiences substantial high-frequency mechanical excitation from powertrain components such as gearboxes and drive shafts. The resulting structure-borne vibration excites the windows which then radiate sound into the passenger cabin. In many cases the radiated sound power can be reduced by adding damping. This can be accomplished using passive or active approaches. Passive treatments such as constrained layer damping tend to reduce window transparency. Therefore this paper focuses on an active approach utilizing compact decentralized control units distributed around the perimeter of the window. Each control unit consists of a triangularly shaped piezoelectric actuator, a miniature accelerometer, and analog electronics. Earlier work has shown that this type of system can increase damping up to approximately 1 kHz. However at higher frequencies the mismatch between the distributed actuator and the point sensor caused control spillover. This paper describes new anisotropic actuators that can be used to improve the bandwidth of the control system. The anisotropic actuators are composed of piezoelectric material sandwiched between interdigitated electrodes, which enables the application of the electric field in a preferred in-plane direction. When shaped correctly the anisotropic actuators outperform traditional isotropic actuators by reducing the mismatch between the distributed actuator and point sensor at high frequencies. Testing performed on a Plexiglas panel, representative of a helicopter window, shows that the control units can increase damping at low frequencies. However high frequency performance was still limited due to the flexible boundary conditions present on the test structure.
A Vibration Study of a Hydraulically-Actuated Legged Machine
Authors: Guglielmino Emanuele , Cannella Ferdinando , Semini Claudio , Caldwell Darwin G. , Nava Rodri´guez Nestor Eduardo , Vidal Guillermo
Published: May 2012

This paper presents a study on the impact of the vibration on a hydraulically-actuated legged robot designed for outdoor operations. The choice of using hydraulic actuation in lieu of electric actuation as is common in robotics has been driven by the need to cope with heavy loads and respond swiftly to external inputs and disturbances. However in such machines hydraulically-induced vibration (fluid borne noise and structure borne noise) is a major issue. Volumetric pumpmotor assembly is a primary cause of vibration. These are transmitted to the robotic structure, which has been designed as light as possible to minimise the robot’s total weight and power consumption and make it more agile. Initially a multi-body analysis of the robot was carried out to select an appropriate vibration isolation system. Subsequently a numerical and experimental modal analysis was carried out on the structure. The latter was carried with modal hammer tests and pump running tests. This has allowed identifying the main modes of vibration of the structure. The pros and cons of this approach are described and areas of improvements identified.
Strength Evaluation and Failure Prediction of a Composite Wind Turbine Blade Using Finite Element Analysis
Authors: Poulose Prenil , Hu Zhong
Published: May 2012

Strength evaluation and failure prediction on a modern composite wind turbine blade have been conducted using finite element analysis. A 3-dimensional finite element model has been developed. Stresses and deflections in the blade under extreme storm conditions have been investigated for different materials. The conventional wood design turbine blade has been compared with the advanced E-glass fiber and Carbon epoxy composite blades. Strength has been analyzed and compared for blades with different laminated layer stacking sequences and fiber orientations for a composite material. Safety design and failure prediction have been conducted based on the different failure criteria. The simulation error estimation has been evaluated. Simulation results have shown that finite element analysis is crucial for designing and optimizing composite wind turbine blades.
Heat Transfer Enhancement for Flows in a Channel With Corona Wind Generator
Authors: Zhang J. , Lai F. C.
Published: May 2012

Heat transfer enhancement using corona wind generators in a square channel has been numerically examined in this study. Three configurations of the corona wind generators (separately with 4, 12, and 28 pins) are investigated for their effectiveness in the enhancement of heat transfer as well as the pumping power requirement. To achieve the maximum enhancement in heat transfer, the emitting electrodes of the corona wind generator are flush mounted on the channel walls so that the corona wind produced directly perturbs the boundary layer. The Reynolds number considered varies in a range between 200 and 2000. The influence of electric field on the flow and temperature fields is examined for a wind range of operating conditions. The results show that EHD technique has a great potential for many engineering applications.
Combustion Properties of Partially-Premixed Turbulent Flames of Soy Methyl Ester and Diesel Blends
Authors: Dhamale Nikhil S. , Parthasarathy Ramkumar N. , Gollahalli Subramanyam R.
Published: May 2012

Soy methyl ester (SME) is a biofuel that is a renewable alternative energy resource and is produced by the transesterification of soy oil; it is carbon-neutral and low in sulphur content. The objective of this study was to document the combustion characteristics of blends of SME and No 2 diesel fuel in a partially-premixed turbulent flame environment. The experiments were conducted at an initial equivalence ratio of 7 and three Reynolds numbers (based on the injector diameter and the bulk burner-exit velocity of the air/fuel mixture): 2700, 3600 and 4500. Three blends, B25, B50 and B75 corresponding to 25, 50 and 75% volume concentration of SME were studied. The liquid fuel was completely vaporized and mixed with air before exiting the burner. The radiative heat fraction measured in the SME flames was lower than the corresponding value in pure diesel flames and increased with Reynolds number. The global emission measurements indicated that the NOx emissions from the SME-diesel blend flames were lower than those from the pure diesel flame. At quarter and half flame height the temperature peaked at the edge of the flame where as for three quarters the temperature peaked at the centerline of the flame. In-flame NOx concentrations decreased with an increase in Reynolds number. The CO emission index decreased with the increase in the SME concentration in the fuel blend and decreased with the increase in Reynolds number.
The Effects of Optimized Nozzle-Substrate Distance on Cold Gas Dynamic Spray (CGDS) Process
Authors: Yen Yi-Hsin , Wong Sung-Cheng , Jen Tien-Chien , Chen Qinghua , Liao Quan
Published: May 2012

This paper presents research that is focused on the particle coating quality of Cold Gas Dynamic Spray (CGDS) process. The coating quality is affected by several different factors, namely the carrier gas species, nozzle-substrate distance, nozzle inlet pressure and the coating particle size. The intent of this research is to use numerical simulations to predict the coating quality and to find the optimized nozzle-substrate distance and particle size in CGDS process by tuning the factor of nozzle-substrate distance and the coating particle size. Air was chosen as the carrier gas to accelerate copper (Cu) particles, which have diameters ranging from 2–50μm.. There are two main target factors, the nozzle-substrate distance and particle size, which are going to affect the coating quality in this study. In the first part, 14 sets of nozzle-substrate distance models ranging from 2.5mm to 100 mm were setup to study the air velocity, density, temperature and pressure contour through the De-Laval nozzle to the aluminum substrate. In the second part, 49 sets of different particle sizes ranging from 2–50μm in diameter were computed. The particle’s impact velocities on the aluminum substrate were applied to 12 different nozzle-substrate distance models. The bow shock wave, a high pressure gradient region, formed in front of the aluminum substrate, makes the copper particles decelerate in front of the substrate. The results showed that the gas flow velocity contours was affected by different nozzle-substrate distances, which caused different particle accelerating characteristics.
Heat Conduction in a Rectangular Tube With Eccentric Hot Spots
Authors: Dan Bo , Geer James F. , Sammakia Bahgat G.
Published: May 2012

The current paper presents the results of an analytical study of steady state heat conduction in a rectangular tube with eccentric hot spots on both the top and the bottom surfaces. The rectangular domain is assumed to be adiabatic on the lateral surfaces and a single or multiple eccentric hot spots can be applied on the top and bottom surfaces. Isothermal, heat flux or convection boundary conditions can be applied on the hot spots. Because the hot spots are eccentric, the spreading resistance becomes a dominant factor in heat conduction in the tube. The multiple hot spots, multiple layer and combination problems are also studied in the current paper. The solutions can be applied to the thermal management of three-dimensional stacks of electronic devices, the interconnect layers and the thermoelectric devices.
Polarization Measurements of Molded Liquid Crystal Polymer/Titania Composites
Authors: Dantal B. R. , Saigal A. , Zimmerman M. A.
Published: May 2012

During the past decade, the preparation of inorganic/organic hybrid materials with high refractive index has attracted considerable attention. In particular, TiO2 (Titanium dioxide or Titania), as inorganic domains, have been incorporated into a polymer matrix to produce high refractive index hybrid materials [1–3]. Polarization of injection molded liquid crystal polymer/Titania composite parts have been investigated in the broad band millimeter wave frequency range. The measurements have been performed by using two different spectroscopy techniques. First, free space quasi optical millimeter wave spectrometer, equipped with a high power source coherent radiation tunable in the 40–90 GHz frequency range is used. Second, low power dispersive Fourier transform spectrometer has been used for higher frequencies in the range of 100–600 GHz. Dielectric properties of liquid crystal polymer/Titania composites have been determined in the broad band millimeter wave frequency range. A correlation between dielectric properties and dispersed Titania weight percent has been observed using the two spectroscopy techniques. It is found that the absorption coefficient and loss tangent is a strong function of the output power of the sources of the incident radiation. On the other hand, refractive index and real permittivity values measured from both spectroscopy techniques are similar. In addition, it has been found that transmittance level and absorption losses depend on the orientation of the samples with respect to the orientation of electric and magnetic fields in the incident electro-magnetic wave. Finally, the polarization of the parts varies with the direction of flow of the molten plastic into the cavity.
Equilibrium Molecular Dynamics and the Thermal Behavior of Small Systems
Authors: Guajardo-Cue´llar Alejandro , Go David B. , Sen Mihir
Published: May 2012

Equilibrium molecular dynamics can be used to investigate the heat transport due to conduction in small scale systems. The results from a molecular dynamics simulation can be used to extract the thermal behavior. In this study, an equilibrium molecular dynamics calculation of a model system using three interatomic potentials, a harmonic potential, an anharmonic potential, and the Tersoff interatomic potential, has been conducted. The characteristics of the transport are studied from the kinetic energies in the frequency domain. The power spectral density of the kinetic energy of the three different potentials is compared. This study helps to understand how heat is transported in a small system of atoms.
Comparison of Motion Characteristics of High Performance CNC Rotary Tables
Authors: Dassanayake Muditha K. M. , Tsutsumi Masaomi
Published: May 2012

In this paper, the motion performances of the two rotary tables which are driven by roller gear cam and direct drive motor are measured and compared. The table with roller gear cam was controlled in semi-closed loop and full-closed loop methods while the other was controlled only in full-closed loop method. In the measurements, the positioning accuracy and repeatability, rotational fluctuation, frequency response, step response and etc of the systems were measured. All these tests were carried out without any kind of compensation methods such as pitch error or cogging torque compensation etc. Three rotary encoders for rotary table with roller gear cam and one rotary encoder for rotary table with direct drive motor were used for measurements. Furthermore, the simulations were carried out by mathematical models and the results were compared with measured results. The comparison shows that the measured and simulated results have a good agreement. From the simulation results, the friction torque was identified and also compared. The results imply that though both the tables show high performances, the performances of the rotary table driven by roller gear cam are comparatively higher than that of rotary table driven by direct drive motor.
Mechanical Engineering Curriculum Review by QFD Methodology: A Case Study
Authors: Satter M. A. , Satter M. R. , Pumwa J.
Published: May 2012

The paper deals with the design and review of curriculum of a formal study program employing the Quality Function Deployment (QFD) methodology that can take into account of the requirements of various stakeholders such as, academics, students, sponsors, employers, and accreditation agencies. Starting with a simple model for teaching and learning, in which curriculum is one of the basic elements, the paper describes curriculum review procedure employing the QFD planning tool known as House of Quality. Then, it presents a case study on the review of mechanical engineering program of the PNG University of Technology.
An Improved Fourier Eight-Sensor (F8S) Method for Separating Straightness, Yawing and Rolling Errors of a Linear Slide
Authors: Fung Eric H. K. , Zhu M. , Zhang X. Z. , Wong W. O.
Published: May 2012

This paper proposes an improved Fourier eight-sensor (F8S) measurement method for separating the straightness, yawing and rolling motion errors as well as determining the profile of a linear slide. The previous F8S method [1] used the constant parameters C2 and C4 to estimate the profile function f1(θ) in different angle ranges and f2(θ) is also computed with the same fused sensor data. By constant parameters, the profile estimation and error separation are implemented via iterative method which is a time-consuming procedure and can not maintain the acceptable accuracy. Here, the improved F8S method applies the matrix technique instead of the iterative method to estimate the profile functions by three distinct sets of C2 and C4 parameters and different fused sensor data according to the linear slide motion within different angle ranges. Furthermore various errors can be separated through simple equations based on the calculated profile functions. In the second part of this paper the uncertainty induced by the sensor reading error is analyzed in both frequency and spatial domains, and the uncertainty for the profile function can also be obtained. The simulation results confirm that the improved F8S method provides better performance and effectiveness, and is more feasible than the previous F8S method [1].
Nonlinear Behavior of Metallic Material Under Constant Acceleration Loading
Authors: Takla Monir , Jazar Reza N.
Published: May 2012

There is frequent confusion in literature and in published data of material properties between the strain rate effect and the inertia effect on the behavior of metallic materials. While the measured changes of material behavior due to dynamic loading are frequently referred to as strain rate effects, little emphasis has been given to separating the effects of material inertia. In this work, inertia effects have been investigated during elastic deformations using transient dynamic finite element simulations. The work presents a case study in which a metallic bar is dynamically loaded by constant acceleration in simple tension. The material is assumed to be simple linear elastic. The material behavior is assumed to be time independent, strain rate effect was not considered in the simulations. Controlled axial displacement loading is applied at constant acceleration. When loading the material in the elastic range at high accelerations, the deformation becomes more concentrated towards the point of load application and a larger load is required to achieve a pre-defined displacement at this point, thus resulting in an apparent elasticity modulus higher than that measured at quasi-static conditions. Moreover, the material apparent response becomes non-linear. Keeping in mind that time independent properties have been adopted in the simulation and no strain rate effects have been considered, the resulting changes can be referred to pure inertia effects. In experimental testing, these changes would have been referred to strain-rate effects.
A Study on Cavitation Damage Reduction in Fuel Injection Pumps
Authors: Ryu Seung-Hyup , Kim Dong-Hun , Park Tae-Hyung , Kim Byung-Seok , Ghal Sang-Hak
Published: May 2012

Cavitation phenomena during the spill process of the Bosch type fuel injection pump for medium-speed diesel engine were investigated by optical observations. Typically, these phenomena can cause a surface damage with material removal or round-off at the plunger and barrel port etc., and may shorten their expected life time. The images, which were recorded with high speed CCD camera and borescope, show that the plunger damage is mainly affected by fountain-like cavitation generated before the end of delivery. And the damages of barrel port and deflector are caused by jet-type cavitation generated after end of delivery. Based on the results of optical investigation, 12 different type pumps varied in the geometry of components were designed to alter the direction, distribution, and intensity of cavitations. Finally, the effects of each countermeasure were evaluated by the durability test on actual diesel engine (HiMSEN H21/32).
Improvement of the Exhaust Valve Damping Unit for a 2-Stroke Large Diesel Engine
Authors: Kim Dong-Hun , Park Tae-Hyung , Kim Hoon-Suk , Kang Sang-Lip , Kim Ju-Tae
Published: May 2012

Hydraulic exhaust valve actuating system is generally applied on a 2-stroke large diesel engine for the purpose of structural stability and simplification. In this type of system, damping unit has the function of decreasing impact at the moment of valve closing and preventing damage of exhaust valve and valve seat. However, in the opening stage of exhaust valve, existing damping unit substantially increases maximum hydraulic pressure and causes the cavitation inside which lead to vibration, noise, and higher pressure fluctuation and cavitation damage. Design modification of damping unit was performed to solve existing problems. Hydraulic simulation of exhaust valve actuating system was carried out to verify the application possibility of design modification. Also the effect of design modification could be verified by the rig test of prototype. Finally, it was applied on actual engines and proved to give satisfactory results in solving the substantial problems of the existing damping unit.
Approach for Visualization of Uncertainty in CAD-Systems Based on Ontologies
Authors: Mosch Lucia , Sprenger Andre´ , Anderl Reiner
Published: May 2012

In this paper an approach for controlling uncertainties in load-carrying systems in virtual product development during the phase of product design will be presented. In design, manufacturing and usage of technical products uncertainties arise according to process properties and they influence products properties. Many of these properties impact each other. These facts lead to deviation of expected property values which are shown for example in the approximation of stress and strength. In cases of load carrying systems misjudgment can lead to disastrous consequences. In this paper an approach for the visualization of information about uncertainty in load-carrying systems in CAD (Computer Aided Design)-systems within the Collaborative Research Center (CRC) 805: “Control of Uncertainty in Load-Carrying Systems in Mechanical Engineering” funded by the DFG (Deutsche Forschungsgemeinschaft) will be described. The representation of the properties’ interdependency is to be expressed by an ontology based system. The visualization of the properties and the information about uncertainty is demonstrated in a CAD-system.
Developing Students as Higher-Order Thinkers: Analyzing Student Performance Against Levels of Cognitive Demand in a Material Science Course
Authors: Simpson Z. , Janse van Rensburg N. , van Ryneveld M.
Published: May 2012

Today’s increasingly complex engineering workplace demands skill in evaluation, reasoning and critical thinking; however, engineering curricula often test lower-order learning at the expense of higher-order reasoning. This paper analyzes the level of cognitive demand in a course on Material Science in the Department of Mechanical Engineering Science at the University of Johannesburg, South Africa. This is done by applying Biggs’ SOLO taxonomy to classify test and exam questions in the course and then analyzing student performance against this taxonomy of higher- and lower-order learning. The results demonstrate that many students battle with questions that require extended abstract reasoning (argument, evaluation, hypothesizing and generalization). Similarly, relational thinking (through comparison, contrast, application and so on) proves to be a significant problem for weaker students. The paper recommends that engineering lecturers build higher-order thinking into course outcomes, teaching and assessment and that engineering qualifications work systematically towards developing students as higher-order thinkers.
Contact Stress Analysis Around Elliptic Pin-Loaded Holes in Orthotropic Plates
Authors: Aluko O. , Whitworth H. A.
Published: May 2012

This analysis utilizes the complex stress function approach to obtain the stress distribution in pin loaded composite joints with elliptic openings. The stress functions were derived from assumed displacement expressions that satisfy the boundary conditions around the hole. In the method of solution Coulomb friction was used to determine the prescribed displacements at the boundary. The material properties of graphite/epoxy and carbon fiber reinforced plastics laminates were used in this investigation and the results also compared with available data for joints with circular openings. It was revealed that the stress distributions followed the same pattern in both geometries but with lower magnitude in elliptical shape and the reduction in stress distributions caused by changing the pin/hole shape from circular to elliptic depend on friction.
Analysis of Experimental Data From Ship Trajectories of Turning Circles in a Regular Seaway
Authors: Klamo Joseph T. , Lin Ray-Qing
Published: May 2012

The accurate prediction of the track of a ship maneuvering in a seaway is one of the most important tasks in seakeeping. Most ship maneuvering studies, both experimental and numerical, focus on maneuvering in calm water. Recently, Lin and Klamo (2010) used the Digital Self-consistent Ship Experimental Laboratory (DiSSEL) to study the ship track of a turning circle maneuver in a wave field. In that study, it was shown that their simulated ship trajectories had good agreement with experimentally measured tracks. This agreement motivated the following quantitative analysis of the experimental data to characterize the effects that wave impacts have on turning circle ship tracks. Our method involves describing the ship trajectories as sinusoids with time-varying means. We also estimate the uncertainty in the results from our analysis of the experimental measurements. The quantitative analysis shows overall agreement with Lin and Klamo (2010). New findings are also discussed such as changes in the distance and time to complete the maneuver as well as the speed and preferred directions of a drifting turning circle.
Input Shaping Vibration Control for Nonminimum Phase Systems
Authors: Tang Jiping , Parker Gordon
Published: May 2012

Many systems exist that contain coupled rigid body and flexible body dynamics. Rigid body repositioning of these systems can be problematic due to unwanted residual vibration of the flexible body degrees of freedom. Input shaping is a method for generating system commands creating desired rigid body motion where the flexible body motion being quiescent at the end of the maneuver. Either operator-in-the-loop or batch commands are convolved with a carefully designed input shaping filter to produce the eventual system input. Systems with minimum phase zeros are easily accommodated using input shaping filters designed for the system without zeros, and then using a secondary pole-zero cancellation filter. This approach cannot be practically applied to nonminimum phase systems since the resulting system input may become unbounded. This paper considers input shaping methods for generating residual vibration-free input time histories for non-minimum phase, oscillatory systems using bounded inputs. An example is presented where the system is an undamped oscillator with a single right plant zero.
A Reliability Study of a Novel Type of Solder-Less Interconnection
Authors: Lueg Raymond T. , Rose James W. , Simpson James E.
Published: May 2012

The reliability of a novel type of solder-less electrical interconnection has been investigated. The technique is known as Compressive Displacement (CD). CD is the mechanical bonding of flex to a printed circuit board (PCB) using an adhesive layer under specified temperature, pressure and time process parameters. Unlike the more commonly used anisotropic conductive film (ACF) attach process; CD does not require electrically conductive spheres dispersed in the adhesive. The metal features on the flex and the mating PCB pads are designed to displace the adhesive from between them during processing, resulting in a direct metal-to-metal electrical interconnection between the two and robust mechanical adhesion in the regions other than the metal features. Reliability experiments were performed on specially-designed test assemblies which incorporated a variety of component footprints, including 1206, 0805, 0603, 0402 and 0201 types from the IPC-SM-782 standard. Process parameters and adhesives were varied between test boards in order to evaluate the effect of these parameters on reliabilty. The assemblies were subjected to 3,700 temperature cycles of −45°C to +125°C and a 2,400 hr soak test at 85°C / 85% RH. Continuity tests were performed every 100 cycles / 100 hours. The resulting failure data indicated very few failures for many component footprint types under these conditions and indicated which process parameters had the most influence on life. Analysis of the reliability data also indicated that the CD connections for most component footprints greatly exceed the ten-year service life requirement of the intended application.
Rapid Spray Method for Improving Cu-Epoxy Interface Strength
Authors: Wetherhold Robert C. , Pisanova Elena , Alarifi Hani
Published: May 2012

A simple spray method using a plain orifice atomizer has been developed for depositing γ-aminopropyltriethoxysilane (APS) from solutions in water and in methanol onto copper surfaces. The peel strengths between copper foil and epoxy resin were measured with and without APS deposition. In all cases, a higher concentration of APS gives higher peel strength. APS applied from 1 wt% solution in methanol resulted in higher peel strength than when applied from a 1 wt% aqueous solution; the opposite was true with 0.2 wt% APS solutions, indicating a trade-off between deposited APS film thickness and surface coverage. APS was very effective when chemisorption occurred at the surface but much less effective when there was only physisorption. A study of the fracture surfaces showed that the failure is cohesive, inside the epoxy layer, and that the deposited APS on the copper surfaces had a long-range effect which was seen deep in the epoxy layer, well away from the copper surface.
Non-Destructive Thermal Barrier Coating Spallation Prediction by a Load-Based Micro-Indentation Technique
Authors: Tannenbaum J. M. , Lee K. , Kang B. S.-J. , Alvin M. A.
Published: May 2012

Currently, the durability and life cycle of thermal barrier coatings (TBC) applied to gas turbine blades and combustor components are limiting the maximum temperature and subsequent efficiency at which gas turbine engines operate. The development of new materials, coating technologies and evaluation techniques is required if enhanced efficiency is to be achieved. Of the current ceramic coating materials used in gas turbine engines, yttria stabilized zirconia (YSZ) is most prevalent, its low thermal conductivity, high thermal expansion coefficient and outstanding mechanical strength make it ideal for use in TBC systems. However, residual stresses caused by coefficients of thermal expansion mismatches within the TBC system and unstable thermally grown oxides are considered the primary causes for its premature and erratic spallation failure. Through finite element simulations, it is shown that the residual stresses generated within the thermally grown oxide (TGO), bond coat (BC), YSZ and their interfaces create slight variations in indentation unloading surface stiffness response prior to spallation failure. In this research, seven air plasma sprayed and one electron beam physical vapor deposition yttria partially stabilized zirconia TBCs were subjected to isothermal and cyclic loadings at 1100°C. The associated coating degradation was evaluated using a non-destructive multiple partial unloading micro-indentation procedure. The results show that the proposed non-destructive micro-indentation evaluation technique can be an effective and specimen-independent TBC failure prediction tool capable of determining the location of initial spallation failure prior to its actual occurrence.
Pumping Performance Increase Through the Addition of Turbulent Drag-Reducing Polymers to Pulp Fibre Suspensions
Authors: AbuYousef Imad A. , Olson James A. , Martinez D. Mark , Green Sheldon
Published: May 2012

The addition of a small amount of long chain polymers to a turbulent fluid is known to reduce the wall shear stress and drag. Similarly, the addition of pulp fibres to a turbulent suspension is also turbulent-drag reducing despite pulp fibres having a length scale that is 1000 times larger than polymer molecules. The mechanism of drag reduction and its impact on centrifugal pump performance is poorly understood, especially when there is a combination of polymer and fibres in suspension. Centrifugal (slurry) pump performance was measured as a function of pulp fibre and PAM polymer concentration. Both the pump best efficiency and maximum head rise were greater when pumping modest concentrations of polymer solutions and low consistency pulp fibre than pure water. We measured an efficiency increase of 22 percent and a maximum head increase of 4.3 percent with the addition of 150 ppm PAM polymer relative to pure water. We measured an increase of 8 percent and 2.3 percent in pump efficiency and maximum head coefficient, respectively, with 2 percent pulp fibres over that of water alone. With both 1 percent consistency pulp fibres and 100 ppm of PAM polymers, we measured a 12 percent increase in efficiency over that of pulp suspension alone. With both 2 percent consistency pulp fibres and 100 ppm of PAM polymers, we measured an 8 percent increase in efficiency over that of pulp fibre suspension alone. The reasons for the increased pump efficiency with addition of additives is not known but are thought to be due to the turbulent-drag-reducing properties associated with flow of these suspensions.
Flow and Heat Transfer Enhancement Characteristics of Impinging Jets in Transitional Time Periodic Flow Regimes
Authors: Gutierrez Julian P. , Ortega Alfonso , Guzman Amador M.
Published: May 2012

The flow and heat transfer characteristics of an impinging jet on a perpendicular flat surface are obtained by two dimensional numerical simulations of laminar and transitional flow regimes for the Reynolds number of Re = 300, 350, and 400 for a Prandtl number of Pr = 0.7. A fixed jet to plate spacing of H/W = 5 and a given heat flux on the plate surface are considered. Temporal evolution of velocity and temperature fields, Fourier spectra of the velocity temporal evolution and time average local and global Nusselt numbers are obtained for increasing Reynolds numbers for determining the time depending behavior and its effect on the heat transfer characteristics. Numerical simulation results demonstrate that self-sustained transitional periodic flow regimes arise from a laminar regime, when the Reynolds number is further increased to Re = 400 and that these regimes spread out to the whole domain with similar time dependent characteristics due to the flow incompressibility. Evaluations of time average local and global Nusselt numbers demonstrate the asymmetric Gaussian-type spatial distribution and the increase of both parameters when the flow evolves through the transitional periodic regime, with reasonable increases on the pumping power requirements.
Experimental and Finite Element Analysis of Tong Load Slip Versus Clamping Force
Authors: Verenski Douglas R. , Suchora Daniel H. , Allen Christoper W.
Published: May 2012

Tong type mechanisms have been used in industry to lift many types of loads where the clamping force generated in the tong mechanism along with friction and indentation prevent the load from slipping out of the tongs. There are several types of tong designs, lifted load geometries and levels of hardness resulting in numerous variations of clamping forces and grip/load geometries which makes the design of the tong mechanisms extremely challenging. The purpose of this work is to develop a Finite Element Analysis (FEA) simulation of the grip behavior under the multitude of variables that occur in the practical use of tongs to lift loads. Variables include tong mechanism geometry and load size resulting in different tong grip angles relative to the lifted load and resulting clamping force. Other variables include the hardness of the lifted load and the style of grips. With an FEA simulation methodology developed, a multitude of different variables affecting tong effectiveness can be evaluated. To verify the FEA simulation, a series of actual laboratory tests were conducted. These tests measured the load slip force as a function of clamping force, grip geometry, and load and grip hardness. Also measured was the grip indentation into the load and deflection versus slip force. A comparison of the results of the FEA simulation and the experimental tests is given. In some cases the correlation is good and in others more work is needed. A plan for further improvement of the FEA simulation technique is given.
Gas-Turbine-Cycle District Heating/Cooling-Power System With Refrigerating Exhaust
Authors: Stankovic Branko
Published: May 2012

A gas-turbine-cycle modification has been proposed, optimized primarily for (district) heating purposes, with a side-effect of obtaining gas-turbine exhaust gas at very low temperatures and potentially GHG-emission-free. Since its primary purpose is district heating without power generation, the associated gas-turbine-cycle equipment (compressors, turbines, heat exchangers) is typically arranged so that a maximum possible ratio of heat output and heat input is achieved. Whenever the heat ratio is greater than unity, that is, greater than 100% of the heat input, the exhaust gas temperature at the last gas-turbine exit is lower than atmospheric temperature. In other words, this means that it is possible to achieve greater heat output (or GT-cycle “waste heat”) than the heat input, at the “expense” of the cold GT exhaust gas (its internal energy). It is possible to arrange proposed GT-cycle modification in various configurations, such as: simple GT cycle, recuperated, intercooled, intercooled-recuperated, reheat-recuperated and intercooled-reheat-recuperated GT cycle. Maximum achievable ratio of heat output and heat input is estimated to about 1.15 (115%) and corresponding minimum GT exhaust gas temperature can be lower than the CO2 solidification temperature at atmospheric pressure (−78°C or 195 K or −108.4°F). This also means that the GT exhaust-gas stream could be entirely GHG-emission-free, without GHG-s like H2O and/or CO2, which could therefore be captured and sequestered in solid state, and in addition at very low refrigerating temperature. Such low-temperature GT exhaust gas could then be used for refrigeration purposes, or ultimately to refrigerate the Earth’s atmosphere and thus mitigate global-warming effects. The proposed GT-cycle heating system can operate also in the combined heating/cooling and power (CCHP) mode or in the stand-alone power generation mode using a combined-cycle configuration. In such operating modes/regimes, the heating part of the CHP system could still maintain its inherent advantages (achievement of the ratio of heat output and heat input greater than unity, potentially GHG-emission-free GT exhaust gas at refrigerating temperature levels), with CC thermal efficiencies only slightly lower than today’s typical values and with the CHP performance similar or better than modern GTCC or steam-turbine based CHP cycles.
Electronics Packaging to Isolate MEMS Sensors From Thermal Transients
Authors: Feng Michael Y. , Marinis Thomas F. , Giglio James , Sherman Peter G. , Elliott Richard D. , Magee Thomas C. , Warren Jeffrey W.
Published: May 2012

This paper describes a methodology for passive thermal management of a microelectromechanical system (MEMS) sensor. The MEMS sensor has a temperature rate dependence that must be minimized while the system containing the sensor experiences thermal transients from a cold power-up. A multi-step packaging concept has been developed to manage the thermal transient at the MEMS sensor. The strategy minimizes heat flow to the sensor through use of thin, high thermal resistance kovar leads and an insulating air gap between sensor and electronics. The thermal mass of the sensor assembly is increased with minimal increases in weight and volume by mounting the sensor on a high heat capacity beryllium block. Lastly, a commercial off-the-shelf (COTS) heat sink diverts as much of the heat dissipation into the ambient air as possible. This paper describes the practical implementation of these concepts. This includes the soldering of the leads to the board, the mounting of the component onto the block, and the positioning of the block relative to the frame. This paper also presents a lumped parameter thermal analysis of the packaging. The analysis predicted a maximum dT/dt of 0.4K/minute where dT/dt is the temporal derivative of the MEMS sensor temperature. Test data validating the model is also presented.