bluuebunny/crossref_metadata_2025 huggingface dataset:
Aircraft Power System Evaluations for a Solid State Laser Power Conversion Application
Authors: Shanmugasundaram V. , Ramalingam M. L. , Donovan B. D. , Fellner J. P. , Miller C.
Published: April 2008

General thermodynamic analytical evaluations were performed to investigate the impact of technological improvements on mission effectiveness, weapon power generation and size of an aircraft based high-energy laser power system. The Aircraft Electrical Laser (AEL) power system essentially consists of six major components, the prime power source, the power generator, the power conditioner, the laser system including the gain medium, the beam processor and the thermal management system (TMS). The prime power source was essentially a 180 kW power stream provided by the cargo aircraft, which served as the platform for the AEL power system. The analysis was based on a 100 kW power output solid state laser power system and a notional mission profile with an engagement period of 680 seconds during which several duty cycle scenarios were considered. The entire mission consisted of the potential prosecution of four clusters with four targets in each cluster. Two primary power system architectures were evaluated, a baseline AEL power system architecture with current state-of-the-art technologies for all components and an advanced power system architecture based on future technological improvements to each of the six components. The investigations were extended to determine the effects of diode operating temperature, temperature gradients within the diode, duty cycle variations and environmental considerations such as the type of day, on the the mass and volume of the overall power system. Preliminary analysis based on current technologies and anticipated advanced technologies in a decade revealed that the overall mass of the power system could be brought down by 35% from the baseline near-term architecture to the conceptual far-term architecture. The impacts of diode operating temperature, diode temperature gradient, duty cycle (DC) and environmental conditions on the overall mass of the AEL power system for near-term operation, were evaluated. The general trend observed in most cases, was an increase in the mass of the TMS with a subsequent increase in the overall power system mass. There were several situations where the Ram Air Heat Exchanger (RAHX) could not handle the entire heat load and so thermal energy storage cells were designed to augment the RAHX to accommodate the total heat loads.
Smart Electromagnetic Sensors for Damage Identification
Authors: Ray Laura E. , Fisher Reginald P.
Published: April 2008

This paper investigates sensitivity issues for eddy current sensors in order to enhance the ability to use these simple, inexpensive sensors to determine flaw geometry. Using a parameterized two-dimensional flaw, scalar metrics are developed to relate the forward solution of the electromagnetic dynamics to the inverse problem of damage geometry reconstruction. The sensitivity or limitations of these metrics are identified. Then, the concept of sensitivity enhancing control is applied to enrich the data set in order to improve damage geometry reconstruction.
Evaluation of a Thermal Management System With Energy Storage for an Airborne Laser Power System
Authors: Shanmugasundaram V. , Ramalingam M. L. , Donovan B. D. , Fellner J. P. , Miller C.
Published: April 2008

In order to determine the impact of thermal management related conceptual improvements on the overall performance of an aircraft based high-energy laser power system, a general thermodynamic analytical investigation was conducted for several power system architectural variations. The Thermal Management System (TMS) is one of six primary components of the Aircraft Electrical Laser (AEL) power system that is mounted on a cargo aircraft and operated at a fixed altitude. Air properties at this altitude and a designated aircraft speed were used in the thermal management of the various components of the power system architectures. Data for a layered plate-fin type of heat exchanger configuration was generated based on liquid-air heat transfer with the liquid providing the bulk of the heat absorption from each component by single-phase forced convection. Thermal energy storage was also involved in the TMS design and analysis depending on the ambient conditions for any given architectural variation. When there is a restriction on the payload mass and volume in an aircraft at a high altitude, it becomes imperative to look for a TMS that would suitably accommodate a wide spectrum of heat loads. A closed-loop cooling scheme was selected with water as the coolant that carries the heat loads from the various components and either dissipates it to the ambient conditions through a ram air heat exchanger (RAHX) or stores it in a thermal energy storage (TES) cell. The impacts of varying technologies, diode operational parameters, duty cycles and environmental conditions on the size of the TMS were evaluated based on a laser system output of 100 kW with a corresponding total heat load of 787 kWt in the near-term. The introduction of advanced technologies for the far-term architectural evaluations resulted in a decrease of the TMS mass from 1870 kg for the near-term architecture to 1190 kg While the TMS system mass came down by 200 kg when the diode operating temperature was increased from 298 K to 318 K, there was a negligible decrease in mass at higher temperatures. Increasing the temperature gradient in the diode did not yield any significant changes in TMS mass. Environmental conditions resulted in a 50% increase in TMS mass going from the coldest day to the hottest day.
Design and Characterization of a Variable High Temperature/Low Pressure Facility for Evaluating Thermal Protection Systems in Reentry Environments
Authors: Ferguson Timothy P. , Cain Andrew W. , Bell David C. , Starrett H. Stuart , Koenig John R.
Published: April 2008

A variable high temperature / low pressure facility has been developed to characterize the thermal response of candidate thermal protection materials in reentry environments. Transient, non-linear finite element models were developed to optimize the design of the test facility. All models used temperature dependent material properties and time dependent boundary conditions based on thermocouple data obtained during checkout runs. These experimental runs were based on simulated reentry profiles. A one-dimensional model was developed considering only the axial heat flow through the thickness of the test stack. It was used as a benchmark when considering multi-dimensional heating effects. Axisymmetric and three-dimensional models were developed to minimize transverse heating and edge effects through a unique combination of material selection and geometry. The final, optimized configuration is capable of temperatures as high as 4500 °F with pressures as low as 100 mTorr in inert atmosphere. Heating rates that produce surface temperature changes of 300 °F / min are attainable. Pyrometers are used to measure the element temperature and the specimen hot face temperature. Up to thirty-five thermocouples are used to measure internal specimen, cold-face, and insulation temperatures within the stack. A PID algorithm is used to control the furnace, while a data acquisition system is used to log all data.
Self-Powered Wireless Corrosion Detection System
Authors: Pen˜a Gerardo , Hunziker Kenneth , Davis Christopher , Malkin Matthew
Published: April 2008

Corrosion affects the maintenance of metal aircraft. Because the onset of corrosion is unpredictable, sensing corrosion is a challenge and scheduled inspections are mandated by corrosion prevention and control programs. Visual inspection is the most common method of corrosion detection. Visual inspections of aircraft structures that are difficult to access are costly and invasive. Beyond visual inspection, several non-destructive corrosion detection methods exist, such as ultrasonic scanners and pulsed eddy current systems. The functionality of these systems, however, does not minimize the invasiveness of inspections. Access to the structure under inspection is required to use these systems or to perform visual inspections. This paper describes a self-powered, wireless corrosion detection system which could enable modification of existing inspection schemes in difficult-to-access areas where corrosion is expected to develop, for example, on structure beneath an aircraft galley or lavatory. The system consists of an energy harvester, an energy storage and conditioning circuit, a corrosion sensing element, and a wireless transceiver network. Advances in energy harvesting and low-power wireless transceivers have enabled the design. The system allows users to download corrosion data from a sensor through a wireless connection, without the need for costly structural disassembly. Because the device is self-powered and wireless, it operates indefinitely without battery replacement, and does not require power or data wiring from the aircraft.
A New Method for Analyzing of Process in Catalytic Converters
Authors: Zhapbasbayev U. K. , Rakhmetova K. B.
Published: April 2008

The transfer phenomenon in catalytic converter was numerically investigated by taking into account the influence of heat effects and aerodynamics. The problem is solved using 3-D model in entire region of laminar flow of viscous gas. The influence of near-wall non-uniformity of porosity on formation of aerodynamics, temperature and concentration pictures of process was studied. The possibility of existence of different regimes of heterogeneous catalytic reactions across reactor depending on gasdynamic and thermophysical parameters is shown.
Thermodynamic Analysis of the First Stage of Heavy Water Production
Authors: Cha´vez R. Hilda , de J. Guadarrama Javier , Herna´ndez-Guerrero Abel
Published: April 2008

The present paper describes the thermodynamic analysis of the first stage of enrichment of heavy water production by the Girdler Sulfide (GS) process. A very useful procedure for analyzing a proces is by means of the Second Law of Thermodynamics. Thermodynamic analyses based on the concept of irreversible entropy increase have frequently been suggested as pointers to sources of inefficiency in chemical processes. Furthermore, this study points out where the irreversibilities of the process are located, and provides a generalized discussion from the successful application of the technique.
CFD Results of Cavity Flows With and Without Regularly Spaced Slats
Authors: Zoccola Paul J. , Slomski Joseph F. , Farabee Theodore M.
Published: April 2008

In flow over cavity-backed openings, instability in the shear flow can result in self-excited oscillations of the flow. These can become coupled to a resonant response of the cavity, resulting in high amplitude pressure fluctuations in the cavity. Recent studies have shown that these self-excited oscillations can persist even in the presence of a perforated plate or a series of regularly spaced slats in the opening. In this study, various flow-field quantities of a self-excited cavity flow at different speeds and with and without regularly spaced slats in the opening are examined and compared. Unstructured hybrid RANS/LES methods are used to simulate shear driven cavity flows with and without slats at a resonant-coupled speed, as well as without slats at a lower, nonresonant-coupled speed. The results are compared to experimental data for corresponding conditions to validate the numerical results. Various flow field quantites, including the energy production term and the energy flow vector, are calculated from the data and compared for the different conditions in order to understand the features of the flow associated with self-excited oscillations with slats in the opening.
Transient Simulations of Electrokinetic Nanowire Transport in Bounded Microfluidic Channels
Authors: Davison Scott M. , Sharp Kendra V.
Published: April 2008

The motion of a cylindrical nanowire is transiently modeled for two different boundary cases to determine whether or not steady motion is observed. The first case is a nanowire located concentrically at the center of a relatively narrow channel and angled at 45° with respect to the horizontal. The second case is a nanowire located eccentrically in a large channel and aligned with the horizontal. In both cases, the main particle motion is horizontal translation through the channel. In the concentric case, the nanowire translates horizontally while translating vertically and rotating in an oscillatory manner. The eccentric particle translates vertically upward and rotates away from the wall throughout it horizontal translation.
Prediction of Mechanical Behavior of Equivalent Adhesive-Layer Using Theory of Duality of Famage
Authors: Liu Jiemin , Sun Yazhen , Liu Jintang
Published: April 2008

Concepts of equivalent adhesive-layer and Theory of Duality of Damage (TDD) are presented. Basic idea of the TDD is to assume that material damaged consists of two parts, i.e., Relative Non-Damaged Part (RNDP) and Complete Damaged Part (CDP). The mechanical behaviors of the material damaged can be simulated simultaneously by both mechanical behaviors of the RNDP and the CDP. The RNDP can be simulated by linear-elasticity and non-linear elasticity, respectively. The CDP can be approximately determined in engineering significant. Observed stress-strain relation of the equivalent adhesive layer of a steel/steel butt joint is measured. Evolution equation of damage of the equivalent adhesive-layer is established, and increment equation of stress-strain including effect of damage is given. The observed stress-strain relation is predicted through four damage parameters, i.e., plastic strain trajectory, plastic strain energy density, total strain trajectory, and total strain energy density. As a result, it is shown that the stress-strain curves predicted are of consistence with the observed stress-strain curve. The result predicted using total strain trajectory is better than others. It should be pointed out that the method presented in this paper could be applied to a variety of damaged structures not only to the equivalent adhesive-layer.
Developing an Algorithm for SI Engine Diagnosis Using Parity Relations
Authors: Mostofi M. , Shamekhi A. H. , Ziabasharhagh M.
Published: April 2008

Diagnosis is an algorithm for finding and isolating faults in a dynamic system. In 1994, California designated some regulations which were called OBD II. According to these regulations, there is a system installed in an automobile which can analyze the function of the automobile continuously. The decrease of pollution for the expansion of diagnostic system is necessary in the future. To reach the aims of diagnosis, some redundancies are required in the system, either hardware or soft ware. In the hardware redundancy methods, the installation of additional sensors or actuators on the system is required which is costly and takes up a lot of space, whereas in software redundancy methods, this is done with no expense. In this article, one of the software redundancy methods or analytical methods is implied for solving the problem. At first a discussion on literature survey is mentioned, and then a modified mathematical model for SI engine is acquired. The usage of this method and parity space relations, which is a model based method, accomplished the process of diagnosis. Developing a modified SI engine model and diagnosis of MAT sensor which less has been considered besides other components are this article contributions.
Development and Performance Validation of a Heat Pump Water Heater
Authors: Abu-Mulaweh H. I.
Published: April 2008

Heat pump water heater was designed and a prototype was developed and constructed. The performance of the heat pump water heater prototype is described by presenting some experimental test data. The experimental measurements include temperature, flow rates, and power consumption. The testing procedure consisted of evaluating the recovery rate and the coefficient of performance (COP) of the system. The results strongly indicate that heat pump water heater system design is very practical and it provides the consumer with a more efficient hot water heater alternative.
Mathematical Modeling of Direct Flame Impingement Heat Transfer
Authors: Malikov German , Lisienko Vladimir , Malikov Yuri , Wagner John , Kurek Harry , Chudnovsky Yaroslav , Viskanta Raymond
Published: April 2008

Direct flame impingement (DFI) furnaces consist of large arrays of high velocity combusting jets with temperatures up to 1700 K and impinging on complex configuration surfaces of the work pieces. This results in serious convergence problems DFI modeling and computational efforts. A new method of modeling convective-diffusion transfer (CDT) and zone radiation transfer (RT) employing different calculation schemes with a multi-scale grid is presented. Relatively coarse grid calculation domain allows use of conservative and accurate zone radiation transfer method with only modest computational efforts. A fine grid calculation domain is used to predict convective -diffusion transfer for a representative furnace section, containing a small number of jets that allows to significantly decrease the computer time. The main difficulty of coupling between convective-diffusion transfer (CDT) and radiation heat transfer numerical computations is successfully overcome using a relatively simple algorithm. The method allows one to model the physicochemical process taking place in the DFI and reveals as well as explains many features that are difficult to evaluate from experiments. The results were obtained for high velocities (up to 400 m/s) and high firing rates. Maximum (available for natural gas-air firing) total heat fluxes up to 500 kW/m2 and convective heat fluxes of up to 300 kW/m2 were obtained with relatively 'cold' refractory wall temperatures not exceeding 1300 K. The combustion gas temperature range was 1400-1700 K. A simplified analysis for NOx emissions has been developed as post-processing and shows extremely low NOx emissions (under 15 ppm volume) in DFI systems. Good agreement between measurements and calculations has been obtained. The model developed may be regarded as an efficient tool to compute and optimize industrial furnaces designs in limited time.
Energy-Efficient Servo Control of Pneumatic Systems via Direct Cross Flow
Authors: Shen Xiangrong , Goldfarb Michael
Published: April 2008

This paper proposes a structure and control approach for the energy saving servo control of a pneumatic servo system. The energy saving approach is enabled by supplementing a standard four-way spool valve controlled pneumatic actuator with an additional two-way valve that enables flow between the cylinder chambers. The "crossflow" valve enables recirculation of pressurized air, and thus enables the extraction of stored energy that would otherwise be exhausted to atmosphere. A control approach is formulated that supplements, to the extent possible, the mass flow required by a sliding mode controller with the recirculated mass flow provided by the crossflow valve. Following the control formulation, experimental results are presented that indicate energy savings of 25% to 52%, with essentially no compromise in tracking performance relative to the standard sliding mode control approach (i.e., relative to control via a standard four-way spool valve, without the supplemental flow provided by the crossflow valve).
Numerical Study of Dynamic Behavior of Dielectric Fluid Bubbles Within Diverging, External Electric Fields
Authors: Pearson Matthew R. , Seyed-Yagoobi Jamal
Published: April 2008

Past research in the area of pool boiling within the presence of electric fields has generally focused on the case of uniform field intensity. Any numerical or analytical studies of the effect of non-uniform fields on the motion of bubbles within a dielectric liquid medium have assumed that the bubbles will retain their spherical shape rather than deform. These studies also ignore changes to the electrical field caused by the presence of the bubbles. However, these assumptions are not necessarily accurate as, even in the case of a nominally uniform electric field distribution, bubbles can exhibit considerable physical deformation and the field can become noticeably affected in the vicinity of the bubble. This study explores the effect that a non-uniform electric field can have on vapor bubbles of a dielectric fluid by modeling the physical deformation of the bubble and the alteration of the surrounding field. Numerical results show that the imbalance of electrical stresses at the bubble surface exerts a net dielectrophoretic force on the bubble, propelling the bubble to the vicinity of weakest electric field, thereby enhancing the separation of liquid and vapor phases during pool boiling. However, the proximity of the bubble to one of the electrodes can considerably alter the bubble trajectory due to an attractive force that arises from local distortions of the potential and electric fields. This phenomenon cannot be predicted if bubble deformation and field distortion effects are neglected.
Design of Nitrous Oxide-Referencing Fuel Pressure Regulator
Authors: Terry Jonathan , Rousseau Tony , Amano R. S.
Published: April 2008

Nitrous oxide can be used for internal combustion engines as a supplemental oxidizer. In a nitrous oxide system the nitrous is stored in a pressurized container or bottle. Under dynamic use, as the nitrous oxide is being spent the mass in the bottle decreases. This decrease in mass leads to a decrease in pressure. The pressure is the source of delivery of the nitrous oxide to the system. Typically nitrous oxide systems do not have a way to maintain a constant oxidizer deliver flow that can adjust to the pressure drop in the bottle as the nitrous oxide is spent. By not having a way to maintain the oxidizer deliver as the bottle pressure drops it becomes hard to stay consistent interms of the Air (Oxidizer) to Fuel ratio (A/F). The net effect of this pressure drop is that the A/F changes. When this happens the performance of the engine may be compromised as well as the health of the engine. One way to maintain the A/F by regulating the pressure the fuel pressure with respect to the nitrous oxide bottle pressure. This regulator is the focus of this project. A pressure regulator would insure that a constant pressure after the regulator could be maintained. The theory behind the regulator has been previously established but the want of a design of a regulator for a certain application has been brought to the design teams attention. A dynamometer test lab based in Milwaukee has offered testing support for the design of a pressure regulator that would maintain a constant A/F mixture delivery. Motorcycles, due to the need for small components, need to have small nitrous oxide bottles when they are set up with nitrous oxide systems. This small bottle empties faster than a large bottle so the need to maintain the A/F is even more applicable for use on a motorcycle.
A Prototype of Hybrid Solar Power Generation System
Authors: Huang H. H. , Yu N. W.
Published: April 2008

The objectives of this research are to design a photovoltaic/thermal hybrid solar power generation system and to develop a prototype. The design factor of consideration is the fan speed which transfers heat from the solar cells to water within storage tanks and controls operational temperature of the solar cell to obtain higher efficiency of power. Therefore the system identification, simulation, and series of tests of the temperature controller are also present in this research to evaluate the performance of the design system. The results show that if operational temperature of the solar cell is set under 50°C, which the temperature error is between ± 0.1°C and we can obtain the highest heat collection efficiency ηth (0.28), the performance of the heat collection system with this well designed temperature controller is better.
An Electrolysis-Bubble-Actuated Micropump Based on the Roughness Gradient Design of Hydrophobic Surface
Authors: Cheng Chih-Ming , Liu Cheng-Hsien
Published: April 2008

A novel electrolysis-bubble-actuated micropump with a specific design on the hydrophobic surface of the lateral breather which could achieve a net pumping flow has been successfully developed. The micropump is implemented by means of electrolysis, surface tension effect and the periodic electrolysis-bubble generation. The advantages of this proposed micropump design not only achieve a net pumping flow but also resolve the main problem existing in most electrolytic bubble actuators for the issue of degassing the insoluble gases out of microchannels. This micropump with a simple circuit control and without moving parts is suitable for the development of low power-consumption and compact micropumps. Experimental results successfully demonstrate the pumping function of our micropump to continuously push liquid forward based on our gradient roughness design of hydrophobic surface and the periodic generation of an electrolytic bubble in a microchannel. Furthermore, experimental results also show that the liquid displacement and pumping rate could be easily and accurately controlled by adjusting the applied voltage with specific operating frequency. Under the applied voltage of 15 volts at 4.5 Hz, a maximum pumping rate of 114 nl/min is achieved for our micropump#1 with a microchannel cross section of 100 μm × 20 μm. In this paper, we describe the theoretical analysis, design, micromachining process, and operating principles, as well as the experimental demonstration of this micropump.
From Traditional to Virtual Design of Machine-Tools: A Long Way to Go ... Part 2 — The Talk Between Two Worlds
Authors: Bedini Raffaele , Tani Giovanni , Fortunato Alessandro , Goti Gabriele , Mantega Claudio
Published: April 2008

To allow easy and fast interaction between the simulation modules developed by the authors in a Virtual Design environment and the data bases set up in the past by an Italian manufacturer for the traditional design of Machining Centers for High Speed Milling, a graphic interface was created. The work was done utilising advanced features of Matlab suitable, through Microsoft Windows assisted procedures, to extract from Microsoft Excel sheets all sensitive data regarding the machine-tool components, feeding the input module of the simulation package. In this way it is now possible to perform intensive simulation campaigns quickly and easily avoiding the very burdensome procedures demanded for the input to the simulation language. This graphic module also makes it possible to quickly present and compare the results of experimental tests with the outputs of simulation runs.
3-D Modelling of Laser Ablation of Metals in Mould Manufacturing
Authors: Tani Giovanni , Orazi Leonardo , Fortunato Alessandro , Cuccolini Gabriele
Published: April 2008

An original model for laser milling characterization is presented in this paper. A 3-D numerical model able to simulate the physical phenomena involved in laser ablation of metals was developed where the heat distribution in the work piece, the prediction of velocity of the vapour/liquid front and the physical state of the plasma plume were taken into account. The numerical model was implemented in C++ and an overview of the code capacities is presented.
Departure and Lift-Off Point of Bubbles at Heating Wall in Vertical Channel
Authors: Pan Liang-Ming , Chen De-Qi , Yuan De-Wen , He Ying-Qing , Zhang Li
Published: April 2008

This paper proposed a theoretical model involving in conditions of bubble departure point and lift-off point, the principle and estimating method of individual forces have been proposed as well. The forces acted on growing bubble are, namely, surface tension force Fs, growth force of bubbles Fdu, shear lift force FsL, drag force of flow Fqs, hydrodynamic pressure force Fh, contact pressure force Fcp, buoyancy force Fb and bubble acceleration inertia force d(mvc)/dt as well. Horizontal and vertical momentum equations are presented according to forces balance of bubble, meanwhile, the estimating method of lean angle of bubble before departure also has been discussed.
Numerical Simulations of Gas-Liquid Flow Dynamics in Bubble Columns
Authors: Law Deify , Battaglia Francine , Heindel Theodore J.
Published: April 2008

There is great potential for using computational fluid dynamics (CFD) as a tool in scale-up and design of bubble columns. Full-scale experimentation in bubble columns is expensive and CFD is an alternative approach to study bubble column hydrodynamics. However, CFD can be computationally intensive as a predictive tool for a full three-dimensional geometry. In this paper, a 0.2 m diameter semi-batch bubble column is numerically simulated and the results are compared to experimental measurements performed by Rampure et al. [1]. The objectives are to examine and determine an appropriate set of numerical parameters and to determine if two-dimensional simulations are able to accurately predict observed bubble phenomena so that the computational cost can be reduced. A two-fluid Eulerian-Eulerian model is employed to represent each phase as interpenetrating continua and the conservation equations for mass and momentum for each phase are ensemble-averaged. Time-averaged gas holdup is mainly examined due to its significant role in gas-liquid mass transfer and to compare to available data. Numerical predictions are presented for gas holdup at various axial heights as a function of radial position for a superficial gas velocity of 0.1 m/s. The numerical predictions exhibit the axial development of the gas holdup profile phenomena; that is, the gas holdup at the center of the column increases with increasing axial height. The effects of grid resolution and convergence criteria on the numerical predictions are also demonstrated.
Responses of Hybrid-III 50th and Thor-NT 50th in Sled Tests With Different Seat Belt Pretensioner Configurations
Authors: Paek Chang In , Shaw Greg , Crandall Jeff , Baek Yoon Ho , Ko Ol Suk
Published: April 2008

This study quantifies the effectiveness of the various seat belt pretensioner configurations relative to the no pretensioner condition and defines the relative sensitivity of the Hybrid-III 50th and THOR-NT 50th percentile male anthropomorphic test devices to pretensioner effects. The results of this study indicate that pretensioners reduced the chest accelerations and Head Injury Criteria (HIC) of both Hybrid-III and THOR-NT dummies. In addition, the pretensioners reduced the chest forward movement by providing restraint earlier in the event. The dual pretensioners and the retractor pretensioners were more effective than the buckle pretensioner and the no pretensioner conditions. Although the Hybrid-III and THOR-NT were different in construction and sitting depth, the Hybrid-III and THOR-NT's responses to the pretensioner conditions were similar. Test-to-test repeatability was acceptable for both dummies.
Efficiency of Surface Heat Transfer Intensifiers for Laminar and Turbulent Flows in Heat Exchanger Channels
Authors: Leontiev A. I. , Popov I. A. , Gortyshov Yu. F. , Olympiev V. V. , Kas'kov S. I.
Published: April 2008

The present work presents the comparison of efficiency of surface-type intensifiers in a wide range of geometric parameters and in the range of Reynolds numbers corresponding to rated laminar and turbulent flow regimes in a channel on the basis of a single general criterion. It is also aimed to clarify objective thermal and hydraulic properties of intensifiers, to present a table of intensifier optimal parameters for the further theory and practice development, to formulate practical recommendations for selecting intensifier types and parameters in the design of promising energy-saving heat transfer equipment. The comparison of intensifiers efficiency was carried out under identical conditions for constricted and unobstructed channels containing intensifiers of various shapes. It is shown that intensifiers in the form of transverse annular ridges and systems of spherical holes show high thermal and hydraulic efficiency at specific flow operating parameters and design parameters of both, a channel and intensifier. The acquired results and recommendations on optimal parameters of surface-type intensifiers make it possible to calculate and design heat exchangers with intensifier optimal configurations and sizes. To confirm the obtained fundamental knowledge in the field of surface heat transfer augmentation based on a system of spherical holes/ridges several heat exchanger prototypes were developed.
Vibration Durability Comparison of Sn37Pb vs SnAgCu Solders
Authors: Zhou Yuxun , Scanff Estelle , Dasgupta Abhijit
Published: April 2008

In this paper, the vibration durability of SnAgCu (SAC) solders is compared to that of SnPb solder, using selected surface mount technology (SMT) interconnects. A time-domain approach, reported in the literature [1], was adopted for this study. Vibration durability tests under random excitation (between 10 Hz & 500 Hz) were conducted for both SAC and SnPb SMT boards. The test assembly consists of daisy-chained components, to facilitate real-time failure monitoring. Step-stress tests were conducted by increasing the RMS excitation levels from 7G to 14G in out of plane direction. The test was continued until most of the components on the board failed. In general, the SAC solders were found to have lower fatigue durability than the SnPb solder, under the vibration excitation levels applied in this study. This result is consistent with results in the literature from mechanical cycling studies, repetitive mechanical shock studies [2] and vibration studies [3] [4]. Destructive failure analysis (cross-sectioning, polishing and microscopy) was used to confirm that the failure was by solder fatigue. Durability model constants were estimated for a generalized Coffin-Manson strain-life fatigue model [5], for both SnPb and SAC solders
Optimal Choice of the Shaft Angle for Involute Gear Hobbing
Authors: Innocenti Carlo
Published: April 2008

With reference to the machining of an involute spur or helical gear by the hobbing process, the paper suggests a new criterion for selecting the position of the hob axis relative to the gear axis. By adhering to the proposed criterion, the hob axis is set at the minimum distance from the gear axis, thus maximizing the depth of the tooth spaces of the gear. The new criterion is operatively implemented by solving a univariate equation, which stems from a new, synthetic analysis of the meshing of crossed-axis involute gears. A numerical example shows application of the suggested procedure to a case study and compares the optimal hob setting to the customary one.
Engineering Ethics: Improving Pedagogical Methods
Authors: Bertha Carlos E.
Published: April 2008

Engineers like to solve problems. But they tend to like to solve problems that have discrete solutions. As long as they know which formulae apply, the rest is a matter of calculation. When philosophers teach ethics, they often take an approach that seems antithetical to the engineer's methods of solving problems: ethicists teach in terms of "ill-defined problems." For the purposes of this essay, I will assume that it has been fairly well established that engineering students should take an ethics course as part of their curriculum. Having said that, should engineers suffer through an ethics course taught by a philosopher? Or should engineers teach engineering ethics? Should engineering students get a tailored version of the course offered by the philosophy department?
A Qualitative Understanding of Interfacial Failure During Flexural Loading of Printed Wiring Assemblies
Authors: Varghese Joseph , Dasgupta Abhijit
Published: April 2008

A global-local approach is used to qualitatively understand the dependence of intermetallic failure on specimen geometry, interconnect material property and interfacial morphology. The structure of interest is an area array package that is subjected to flexural loading. The interconnect is modeled as a thin continuous layer, sandwiched between the component and the board. The global model uses a closed-form low-order analytical solution to estimate the shear and peeling stresses in the interconnect. A parametric analysis is conducted to characterize the variation of the stresses with specimen geometry and material properties. The local model uses fracture mechanics to relate the strain energy release rate at the interface to the morphology of the intermetallic layer. It is shown that for a given Printed Wiring Assembly (PWA) and loading condition, the strain energy release rate at the interface increases with decreasing interfacial roughness. This could explain why one observes failure site transition from the solder to the intermetallic layer during flexural loading of aged specimens.
Molecular Dynamics Prediction of the Thermal Resistance of Solid-Solid Interfaces in Superlattices
Authors: McGaughey A. J. H. , Li J.
Published: April 2008

Molecular dynamics simulations are used to predict the thermal resistance of solid-solid interfaces in crystalline superlattices using a new Green-Kubo formula. The materials on both sides of the interfaces studied are modeled with the Lennard-Jones potential and are only differentiated by their masses. To obtain the interface thermal resistance, a correlation length in the bulk materials is first predicted, which approaches a system-size independent value for larger systems. The interface thermal resistance is found to initially increase as the layer length is increased, and then to decrease as the phonon transport shifts from a regime dominated by ballistic transport to one dominated by diffusive transport.
Designing for Vehicle Stability During Rear Tire Tread Separation Events
Authors: Renfroe David A. , Roberts Alex
Published: April 2008

Rear tire separation or delamination events affect the rear wheel adhesion and thus the vehicle stability. Maintenance of the lateral force of the tires on the rear axle of a vehicle is paramount to vehicle control. Tire tread separation events are, unfortunately, a foreseeable event for which allowance in the design of the vehicle must be made. Testing of vehicles illustrates how loss of control of a vehicle can occur if, during the process of delamination, the excitation of the rear wheel due to the delaminating tread causes tramp on the rear axle of the vehicle. This tramp occurs if the excitation is at the natural frequency of the rear axle. For solid rear axle vehicles, this natural frequency coincides with the rotational frequency of the wheel when traveling at highway speed. The tramp motion can be so severe to cause the tires to alternately leave the ground. Testing of the vehicle with excitation within the natural frequency of the axle/tire combination during an SAE J266 circle test, showed an oversteer gradient of 12 to 19 degrees per g, resulting in a critical speed of approximately 28 mph (45 kph), a highly unstable situation while traveling at highway speed. This paper reports from testing results how the vehicle may, be designed to eliminate the dangerous tramp mode by proper installation of the shock absorbers and proper shock damping characteristics. The test results show that the vehicle can maintain a continuous understeer characteristic during the rear wheel excitation at the natural frequency.
Design of an Anthropomorphic Upper Extremity Prosthesis
Authors: Fite Kevin B. , Wait Keith W. , Withrow Thomas J. , Goldfarb Michael
Published: April 2008

This paper describes the design of a 21 degree-of-freedom, nine degree-of-actuation, gas-actuated arm prosthesis for transhumeral amputees. The arm incorporates a direct-drive elbow and three degree-of-freedom wrist, in addition to a 17 degree-of-freedom underactuated hand effected by five actuators. The anthropomorphic device includes full position and force sensing capability for each actuated degree of freedom and integrates a monopropellant-powered gas generator to provide on-board power for untethered operation. Design considerations addressed in this paper include the sizing of pneumatic actuators based on the requisite output energy at each joint; the development of small low-power servovalves for use with hot/cold gases; the design of compact joints with integrated position sensing; and the packaging of the actuators, on-board power, and skeletal structure within the volumetric envelope of a normal human forearm and elbow. The resulting arm prototype is intended to approach the dexterous manipulation capabilities of its anatomical counterpart while delivering approximately 50% of the force and power output of an average human arm.
Modal Analysis of an Axial Flow Fan and the Formula to Estimate Blade Swing Induced Tonal Noise
Authors: Qi Yuan-Sheng , Wu Xian-Jun , Zhu Shi-Jian
Published: April 2008

Modal analysis is performed on an axial flow fan of air-conditioner. Modal test is performed for verification. Results indicate that in the low frequency ranges the vibrating shape is dominantly the blades swing around the hub because the rigidity is very small at this position. The low frequency vibrations contribute greatly on turbine noise. A formula to estimate the blade swing induced noise is deduced for reference.
Gripping Efficiency of Gripping Mechanism Using Buckling Phenomenon of Long Column
Authors: Muramatsu N. , Ando H. , Takaki M. , Matsumoto H. , Kubouchi Y.
Published: April 2008

In the development of miniature opening and closing mechanism, piezoelectric element has been used as its actuator. This mechanism, however, tends to become larger and complicated as it needs a mechanism for displacement enlargement because of the infinitesimal output displacement. Therefore, an attempt applying buckling phenomenon of long column to the opening and closing mechanism of finger has been made. An elastic member with a long strip shape was bent in the shape of M character, both ends fixed and reciprocating translational drive was imparted to the V-shaped common portion at the center. As a result, a simple miniature gripper with large rate of bending displacement at the finger tip to a translational displacement at the center, namely the enlargement rate of the displacement, has been developed. In this study, in addition to the element technology development for product, such improvements as increasing of the rate of gripping force to driving tensile force on the finger, that is, gripping efficiency were aimed. The results obtained are as follows. (1) Hinge joints on supporting portions at both ends or the mid common portion of the fingers decrease the driving tensile force beginning to grip. They, however, little contribute to the improvement of the gripping efficiency. (2) Crossing an operating member at the center in the shape of × character so as to enlarge an angle of the operating members to the finger increases the gripping efficiency. The enlargement rate of the displacement, however, decreases, so that the angle should be decided based on the object. (3) Free support of an intermediate portion on a lateral surface of the finger allows the change of the gripping efficiency. When bending deformation outside at the center in length of the finger is restrained, the gripping efficiency increases by about 2 times.
Direct Touch and Manipulation of Native 3D Models With Haptic Interface in the Mainstream CAD Systems
Authors: Zhu Weihang , Lee Yuan-Shin
Published: April 2008

This paper presents new techniques for integrating haptic interface with mainstream CAD systems. Haptic interface, by providing force feedback in human-computer interaction, can improve the working efficiency of CAD/CAM (Computer-aided Design and Manufacturing) systems in a unique way. Compared to the test beds and prototypes in the past research, the new techniques would allow the user to directly touch and manipulate native 3D CAD models in mainstream CAD/CAM systems with force/touch feedback. Contrary to the common thoughts among the research community, the presented techniques eliminate time- and resource-consuming pre-processing or duplication of the CAD models data, such as conversion to volumetric models or triangulated mesh models. It would allow the CAD/CAM user to evaluate or assembly the CAD models with force/touch feedback, and meanwhile modify the design without having to resort to other geometry representation method or systems. By integrating haptic interface directly with mainstream CAD systems, the powerful built-in functions of CAD systems can be leveraged and enhanced to realize more agile 3D CAD design and evaluation, which will eventually lead to a more competitive design and manufacturing industry. This research would open up a new direction of haptic application research in CAD/CAM area. The presented techniques can be used in tasks such as digital mockup, virtual assembly, virtual prototyping, computer-aided product design and manufacturing.
Finite Element Analysis of Compound Acoustic Horn for Portable Ultrasonic Cleaning Machine
Authors: Zhang Yundian , Wang Qifang
Published: April 2008

Now, ultrasonic cleaning has been widely used in industry, however its applications in our lives are very few. It is theoretically possible that ultrasonic cleaning could be applied in civil. The author studies a kind of portable ultrasonic cleaning machine which is suitable for various fields. In consideration of the portable ultrasonic cleaning machine characteristics such as small, convenient, high frequency and high intensity focus, the author presents a model of compound acoustic horn which is composed of a conic horn of varying section and a horn of uniform section. Because this compound acoustic horn which has complicated shape is not traditional horn, and it is difficult to analyze it with traditional method. This situation is able to influence on the design of the acoustic horn, especially the confirmation of the vibration node, even the whole system matching. So in this paper the finite-element method (FEM) is used to analyze the dynamic performance of the compound acoustic horn. By the finite-element analysis, the natural frequency and the natural vibration mode of the compound acoustic horn are ascertained, furthermore, from the graph results we can find the stress and the displacement in the end of the acoustic horn are the biggest, but the displacement in the Flange is about zero. So the reliability performance and the reasonable design of the compound acoustic horn are proved in theory. In addition, the tests indicate the result of the finite-element analysis tallies with that of actual use after processing the compound acoustic horn.
Web-Based Product Data Management and Design Automation
Authors: Wang Zhonghui , Fu Qinrong , Dong Hongzhi , Zhang Liping , Xiang Wei
Published: April 2008

Product data management (PDM) systems have been successfully applied to maintain product-related information as well as to integrate different applications for design, process and manufacturing throughout the product life cycle. However, the issues on how to use the PDM system to enable design automation have not been adequately addressed. This paper proposed a framework to enable product design automation by employing the web-based PDM system and the Computer-aided Design (CAD) platform. The components of the framework include a feature-based parametric template module, 3D and 2D auto-generation modules, a web-based PDM system, and the data communication protocol between PDM and CAD platform. The features and relations for product families can be defined with the parametric module. 3D and 2D modules help to auto generate the solid and 2D drawings based on the features and relations of the product. The web-based PDM system provides the easy access for designer to create or edit or store the product feature information, and manage the workflow process. The illustrating example demonstrates the feasibility and effectiveness of this proposed framework for design automation.