bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of Two-Phase Flow in a Heat Exchanger Distributor Application
Authors: Andersson Victor , Sunde´n Bengt , Holm Martin
Published: April 2008

In this work, computations of the air/water flow in a distributor were completed with the FLUENT two-phase VOF model and compared to experiments. The parameters of interest concerned the ratio between the deflected mass flow rate of the water phase to the mass flow rate of the water phase at the inlet called the deflection ratio as well as the recreation of the flow pattern of the different two-phase flows which involved slug, slug/annular and annular flows. Due to the time-consuming calculations, only 9 out of 27 experimental tests were simulated. In conclusion, it can be stated that it is possible, given the right conditions, to perform comparatively accurate simulations concerning two-phase flows in pipe applications with the FLUENT two-phase VOF model.
Infant Pull Strength: Ability to Dislodge Crib Sheets
Authors: Barnett Ralph L. , Brickman Dennis B.
Published: April 2008

The suffocation of infants caused by crib sheet entanglement appears to be a nonproblem which has nevertheless resulted in a brouhaha that has incited remediation activities by the Good Housekeeping Institute (GHI), American Society for Testing and Materials (ASTM), Consumer Product Safety Commission (CPSC), Juvenile Products Manufacturers Association (JPMA), crib sheet manufacturers, and product liability support professionals of different stripes. To show that the removal of crib sheets by infants is not a safety issue, one may establish that the problem is not reasonably foreseeable. Three approaches for doing this are described in this paper: anecdotal, simulation, and reliability. The reliability of a crib sheet is the probability that it will remain in situ when exposed to the community of infants. Application of the classical “load minus strength” analysis required new information on the pull strength of infants.
Accelerated Life Test and Field Test Performance Results for an Integral Heat Pump Water Heater
Authors: Murphy R. W. , Baxter V. D.
Published: April 2008

A residential heat pump water heater (HPWH) of integral-type design (heat pump unit mounted directly to tank with no water circulation pump) has undergone both durability and field performance testing. Results of two rounds of durability testing and evaluation of as-installed field efficiency vs ambient conditions at HPWH location are summarized in this paper. Ten of the HPWHs were run through an initial durability test designed to represent seven to ten years of normal compressor cycling to meet hot water needs of a residence. The first generation control system proved to be the least reliable component of the units with a 40% failure rate for its temperature input sensors and one complete system failure. After modification of the controls a second durability test was run with five units. There were essentially no operational failures during the second test. In parallel with the durability tests, HPWH units were installed in occupied residences at 18 US locations and field performance data were collected for 1–2 years. Results for two units with differing degrees of exposure to seasonal ambient air temperature and supply water temperature variations are presented and interpreted in this paper. For the first unit, installed in a conditioned space with well water supply, such seasonal temperature variations were small. The average field-measured coefficient of performance (COP) over a 75-week test period for this unit was 2.44 ±5% and weekly averages ranged from 9% below to 10% above the overall average. For the second unit, installed in an unconditioned space with city water supply, the seasonal temperature variations were substantial. Its average COP was 1.81 ±5% over a 104-week test period and weekly averages ranged from 38% below to 28% above that value.
FE Simulation of Spin Forming Process Based on Fuzzy Intelligent Method
Authors: Yoshihara Shoichiro , Ray Pinaki , MacDonald Bryan , Koyama Hiroshi , Kawahara Masanori
Published: April 2008

In recent years, Finite element (FE) analysis of manufacturing using not only metal forming but also other forming processes has contributed to the imporvement of these manufacturing techniques and increased knowledge regarding the deformation mechanisms that occur during forming. An analysis of spin forming using FE simulation was performed by authors. Moreover, a fuzzy algorithm to optimize spin forming was developed to decrease the processing time and the number of processing paths. The algorithm was validated as the processing time was shortened by around 15% less than in the case of the process without control. Furthermore, the forming velocity was increased by using the fuzzy control during the process. In this study, the fuzzy intelligent method for expanding the geometry of the blank in spin forming was investigated using the finite element method. It is shown that the flexibility of the fuzzy intelligent method investigated improves several experimental conditions and reduces the duration of the process.
Intellectual Property Licensing: A Profitable Business Tool for Disseminating Technology
Authors: Rader Dennis
Published: April 2008

In an era of intense global competition, technology-based companies need effective strategies to generate additional revenues and high profit margins. Increasingly such companies are addressing this challenge by establishing new programs, or augmenting existing programs, to market their technologies more widely by outlicensing selected portions of their intellectual property (IP) portfolios. The prospective benefits of such programs are accompanied by new, but manageable, business risks. These risks can include, among other things, jeopardy to a company’s competitive position even when its technology is protected by one or more patents or is in the form of trade secrets, or a combination of the two. We will examine the use of technology outlicensing as a business tool and discuss the issues that a company should consider in establishing and managing a successful outlicensing program.
Laser Micro-Machining Using Near-Field Nano-Optics
Authors: Chung Haseung , Kurabayashi Katsuo , Das Suman
Published: April 2008

Solid immersion lenses (SIL) facilitate high numerical aperture (NA) and consequent sub-wavelength diffraction limited focusing in near-field optics based systems. Such systems are in commercial and research use for various applications including near-field scanning optical microscopy, ultra-high density magneto-optic data storage and near-field nanolithography. Here, we present a novel nanomanufacturing method using SIL-based near-field optics for laser-induced sub-micron patterning on silicon wafers. The near-field effect of SILs was investigated by using hemispherical BK7 lenses (n=1.5196, NA=0.9237) to superfocus an incident Q-switched, 532nm Nd:YAG laser beam transmitted through a focusing objective. This optical arrangement achieved a laser-processed feature resolution near the diffraction limit in air. Results of experiments that were conducted at various processing conditions to investigate the effects of varying incident laser power (with average pulse power less than 1W), pulse repetition rate, pulse width, number of pulses and size of SIL on processed feature size and resolution are presented.
An Analysis of Fluid-Mechanically-Coupled, Non-Linear Rotational Vibration Sensitivity of Automotive Hydraulic Power Steering Systems
Authors: Yu Jinghong
Published: April 2008

This paper introduces an effective simulation tool for analyzing non-linear rotational steering vibration sensitivity. The analysis tool includes all the major components and the coupling vibration behavior of steering mechanical and hydraulic sub-systems, as well as non-linear force elements. The simulation model is validated with an actual steering system under different excitation conditions of force level and frequency within the actual range of steering vibrations caused by steering shimmy and brake judder. Comparison results show a very good agreement between simulation prediction and experimental measurement as well as the capability of the tool to predict the fluid-mechanical-coupled, non-linear vibration sensitivity within the frequency range of interest.
The Absorption of Sound in Cellular Foams
Authors: Dupe`re Iain D. J. , Dowling Ann P. , Lu Tian J.
Published: April 2008

Porous materials are often used as sound absorbers in a variety of situations including architectural and industrial applications. In many cases it is advantageous for the material to be both lightweight and rigid. Metal foams, originally developed for use in catalytic converters in car exhaust systems, offer an attractive mix of properties being both lightweight and rigid. In addition they have good sound absorbing properties and are good heat conductors giving rise to the possibility of enhanced sound absorption through heat transfer. In this paper, we review the use and acoustic modelling of these materials. We compare the predictions made by a number of viscous models developed by the authors for the propagation of sound through open-cell metal foams with an experiment both for the metal foams and for the polymer substrates used to manufacture the foam. All models are valid in the limit of low Reynold’s number which is valid for the typical ligament dimensions found in metal foams provided the amplitude of the waves is below 160dB. The first model considers the drag experienced by acoustic waves as they propagate passed rigid cylinders parallel to their axes, the second considers propagation normal to their axes, and the third considers the propagation passed the spherical joints. All three are combined together to give a general model of the acoustic behaviour of the foams. In particular, the sound absorption is found to be significant and well predicted by the combined model. In addition we describe a post-processing technique for the experiment used to extract the fundamental wave propagation characteristics of the material.
Hierarchical Modular Structures and Their Mechanical Characteristics
Authors: Kishimoto N. , Natori M. C.
Published: April 2008

Future structure systems need adapatability to various changes from the viewpoint of total cost for their missions. In order to introduce such adaptability into artificial structure systems, their future concepts with autonomous life cycles are discussed, which are typical features of things in nature. To realize such concepts hierarchical modular structures are proposed and studied. They consist of a number of basic modules, which are assembled with hierarchical assembly rules. A mathematical algorithm extended from the one for fractal formations is introduced, which keeps their basic property of geometrical symmetry. Some examples of hierarchical modular structures composed of basic modules with hexagonal shape are illustrated. Their mechanical characteristics such as characteristic frequencies and distributions of internal forces under some boundary conditions are also calculated. It is shown that the hierarchical modular structures are able to provide systematically various structures based on required mechanical properties and control strategies, which means they can easily construct various structure systems fitted to wide environments and their changes.
Zero Spillover Active Structural Acoustic Control
Authors: Al-Bassyiouni Moustafa , Balachandran B.
Published: April 2008

In this article, a combined analytical and experimental study conducted on the feasibility of implementing a relaxed zero spillover control (RZSC) scheme for active structural acoustic control (ASAC) is presented. The aim of this effort is to actively control sound fields inside a three-dimensional rectangular enclosure into which noise is transmitted through a flexible boundary. Piezoceramic patches, which are mounted on the flexible boundary, are used as actuators, and microphones, which are placed inside and outside the enclosure, are used as sensors. In the experiments, an attenuation of 5.56 dB is obtained for broadband excitation in the frequency range of 20 Hz ≤ f ≤ 220 Hz.
Three-Dimensional Flow of Silicon Melt in a Rotating Shallow Annular Pool
Authors: Li You-Rong , Peng Lan , Wu Shuang-Ying , Zeng Dan-Ling , Imaishi Nobuyuki
Published: April 2008

In order to understand the mechanism of the surface patterns on silicon melt in Czochralski furnaces, we conducted a series of unsteady three-dimensional numerical simulations of silicon melt flow in a rotating shallow annular pool in the counter-clockwise direction under micro-gravity. The pool is heated from the outer cylindrical wall and cooled at the bottom of an inner cylinder. The temperature differences between the vertical outer wall and the inner wall are 16 K, 21 K, 26 K and 32 K. Bottom and top surfaces of the melt pool are adiabatic. When the rotation rate is very slow, the hydrothermal waves are dominant in the pool and propagate in a direction opposite to the pool rotation. When the rotation rate exceeds the first critical value, the phase velocity of the hydrothermal waves increases rapidly and its propagating direction becomes same as that of the pool rotation. With much larger rotation rate, the flow becomes an axisymmetric steady flow. Details of the flow and temperature disturbances are discussed and the critical rotation rates are determined.
On the Application of Intelligent Systems to Active Flow Control
Authors: Lin Feng , Schoen Marco P. , Ji Lucheng
Published: April 2008

In the recent decade, a great deal of research has been devoted to active control of the unsteady flow in a wide variety of components and/or subsystems of aircraft, automobile and marine vehicles and industrial fluid machinery, because small improvements in component and/or subsystem performance often lead to large payoffs. The term active flow control is used to describe the methods to actively manipulate flow fields with auxiliary power introduced to the flow. In this paper, a brief survey of the recent progress in active flow control research is made. The possibilities of further performance improvement using the theories and technologies of intelligent systems are discussed. Intelligent systems can be applied to improve sensing and actuating, increase model accuracy, and optimize the control schemes. The active flow control systems, on the other hand, may also challenge intelligent systems researchers and stimulate new development of intelligent tools.
Sustainable Design Through Flexible Product Evolution
Authors: Van Wie Michael , Stone Robert B. , McAdams Daniel A.
Published: April 2008

Sustainable design defined broadly is the problem of designing environmentally benign products so that the environment can be maintained with minimal negative effects from the product throughout the product’s entire lifecycle. This research investigates how sustainable design can be achieved at the conceptual design stage. Although sustainability encompasses a vast number of issues ranging from energy efficient solutions, design for disassembly, recycling, proper material selection, and improved manufacturing choices, the research focus of this work is on the particular issue of product evolution as it relates to the flexibility of a product or concept. Product evolution, often powered by new technology, erases the market competitiveness of concepts over time and impacts flexibility on the design effort side. Specifically, how does the designer develop concepts that can at least partially be reused and adapted to the next product generation with minimal effort? One answer is to design flexible concepts that can incur unknown future changes with maximum concept reuse. Flexibility in this context implies the property of a concept, physical solution, component, or product, to be robust and tolerant to generally unavoidable evolutionary changes. The challenge is to know how to configure a product to satisfy this requirement. As part of this research, we perform empirical studies of product evolution to determine evolutionary trends. Product evolution is measured in the broad terms of product performance over time. The goal is to predict when a product should evolve by either 1) moving from the lower plateau of an S-curve to the higher plateau or 2) jumping to a new S-curve being prepared to do so in a sustainable manner. That is, the objective is to allow companies to be able to reuse components or platforms (including reconditioning and recycling), tooling as well as design and manufacturing staff. The key toward this goal is an understanding how products evolve and what conditions coincide with product change. The approach is to investigate the types of changes (evolutions) that lead to flexible (sustainable) designs. The results of this research can be used for a prescriptive approach in developing a sustainable design method that relies on this newly acquired knowledge of product evolution.
Pumped Liquid Multiphase Cooling
Authors: Hannemann Robert , Marsala Joseph , Pitasi Martin
Published: April 2008

The performance limits of conventional cooling technologies are being reached in both military and commercial electronics and electro-optical systems. Pumped Liquid Multiphase Cooling (PLMC) provides significantly enhanced thermal management capabilities for these systems using mostly-conventional components and working fluids. PLMC is highly scalable and reliable. Energy efficiency is very high, surpassing conventional techniques by up to two orders of magnitude. This paper describes the basic PLMC technology and presents experimental results from several prototype embodiments of the technology.
On the Elliptic-Parabolic Motion of a Simple Pendulum in Three Dimensions
Authors: Han Seon
Published: April 2008

The elliptic-parabolic motion of an elastic pendulum is the subject of current study. The elasticity is either provided by a single spring or an elastic cable. The motion is called elliptic-parabolic since the point mass takes the elliptical path when viewed from the top and the parabolic path when viewed from the side. Such motion can be initiated when an initial displacement and and an initial velocity are given in the perpendicular directions. The fully nonlinear analysis shows that the elliptical path precesses. In this paper, perturbation analysis is used to obtained the precession rate for the discrete and continuous pendulum.
A Numerical Study of Forest Fire Progression and Fire Suppression by Aerial Fire Fighting
Authors: Satoh Kohyu , Kuwahara Kunio , Yang K. T.
Published: April 2008

Forest fires are of common occurrence all over the world, which cause severe damages to valuable natural resources and human lives. In the recent California Fire, which burned 300,000 hectors of land, the disaster danger could reasonably be predicted, but early control of fires by means of aerial fire fighting might have been failed in that situation. Also in Japan, there are similar problems in the aerial fire fighting. Most forest fires occur in the daytime and the fires are freely in progress without any control during the nighttime. Therefore, it is important to attack the fires when there is daylight. The water dropped by helicopters is not always sufficient to control fires, since the quantity of water that can be carried aloft is a critical issue. Large amount of water can be dropped from aircrafts, but the high-speed flight of aircrafts may be dangerous in the mountain, where tall trees and steel towers with electric wires may exist. Therefore, those aircrafts have to fly at much higher altitudes than helicopters, while the water drop at high altitudes changes water into mist in the air. The objective of this study is to examine the methods to prevent the ignition by firebrands in the downwind area by applying water through the aerial fire fighting. However, tests by real aircrafts to obtain such information would be too costly. Therefore, the patterns of water drop from aircrafts were examined in CFD simulations, together with the investigation of needed water drop rate based on the forest fire statistics, the previous real aircraft tests and laboratory experiments. It has been found in the simulations that the water supply with the water density of 2 L/m2 is effective to control fires and the patterns of dropping water are reasonable.
Surface Tension Propelled Microboats
Authors: Lee Ki Bang , Sammoura Firas , Lin Liwei
Published: April 2008

The operation of autonomous, liquid-fueled microboats driven by surface tension effects has been demonstrated, including the possibility of controlled steering. Two types of microboat with surface area of 6 × 11 mm2 have been fabricated by a bulk micromachining process and powered by 0.5μl of isopropanol on top of a pool of water. The first microboat design uses a cellulose film to store liquid-fuel and has been able to operate for 10 minutes with a maximum cruising velocity of 7.5cm/sec. The second microboat design uses a direct fueling system by adding a fuel droplet directly and has been able to cruise for about 30 seconds with a maximum velocity of 15cm/sec. A first-order theoretical model was developed that captures the discharging trend of the liquid-fuel and the surface tension effects. Numerical techniques were employed to find out the velocity profile of the microboat and compared with experimental results. Moreover, an onboard steerer has been added and successfully restrained the motion of the microboat into a desired path. When integrated with other microsystems, microboats could be used for future applications such as marine life observations or military surveillance/reconnaissance missions.
Rapid Low Temperature Bonding of Silicon to Steel for MEMS Sensors
Authors: Cao Andrew , Sosnowchik Brian , Lin Liwei , Pisano Albert
Published: April 2008

We have developed a rapid silicon to steel bonding process used to attach silicon microsensors onto steel. The specific application is to bond silicon based strain sensors to steel structures for real time strain sensing. Steel samples are electroplated with eutectic Pb/Sn alloy (Mp 183°C) and are bonded to silicon dice coated with Cr/Au or Cr/Cu/Ni/PbSn layers. Bonding took place in the inert environment of a rapid thermal annealing (RTA) oven at 220°C for about 20 seconds, which caused minimal damage to the steel samples. The silicon to steel bond survived >1000με of static loading at the steel surface and 1000 cycles of >1000με cyclic strain at the steel surface without failure. Corrosion resistance of the silicon to steel bond was tested by immersion in various oils and salt solutions, and the bonding method thus far has been successful.
Statistical Analysis of Damper Seal Clearance Divergence and Impact Upon Rotordynamic Stability
Authors: Tecza Joseph , Soulas Thomas , Eldridge Thomas
Published: April 2008

Rotordynamic stability in a high-speed, high-pressure centrifugal compressor is achieved through introducing stabilizing forces and managing destabilizing forces. It becomes the original equipment manufacturer’s (OEM) responsibility to provide sufficient stabilizing influence to ensure acceptable operational behavior. A variety of mechanisms exist to provide stability: damper bearings, de-swirl elements on seals, shunt holes and damper seals are commonly provided by the compressor manufacturer to combat instability. The application of damper seals provides a significant increase in rotordynamic stability if designed properly. A previous case study (Camatti, et. al. [1]) presented the detrimental effect of damper seal clearance divergence and seal gas pre-swirl upon predicted stability. Accurate prediction of rotordynamic stability requires knowledge of the destabilizing influences, and evaluation of the variation possible in the stability promoting elements. In particular, the damper seal can be strongly influenced by the presence of divergence in the seal-to-rotor clearance and can result in unexpected at-load behavior. One approach to ensure stable operation is to perform a “worst case” evaluation. However, this often results in excessive compromise (large seal clearance and impact on aerodynamic performance) to “eliminate” the possibility of unstable operation. A different and new approach is to define an acceptable envelope of probability. This study presents a statistical evaluation of the impact of damper seal clearance divergence, along with other compressor design parameters, and provides a method for ensuring stable operation regardless of manufacturing or operational variation. The logarithmic decrement is evaluated as a function of compressor design values and a statistical response surface is created. From the response surface and defined variation in design values, a measure of probability for instability can be obtained. Allowable parameter variation can be restricted to ensure stable operation. Three case studies will be presented where the potential for instability exists and the risk quantified using this statistical technique. Additionally, in one of these cases, test results are presented to support the analytical work.
Analysis of Solder Joint Breakdown Life in Electronic Device Mounted in Vehicle
Authors: Yu Qiang , Shiratori Masaki , Murayama Kimimasa , Igarashi Kazuhiro , Nakanishi Takashi
Published: April 2008

In recent years many electric equipments have come to be used for cars. Solder joints in electric device utilizing car are exposed to harder environment and required higher reliability than that in electric household appliances. Because of this reason, thermal fatigue reliability of solder joints has become one of the most important issues in car electronics. Generally thermal fatigue reliability is estimated by thermal cycle examination, but it needs long time. Estimation by FEM enables it to improve reliability and to reduce time. Analysis of solder life generally can predict only initial crack. But it is important to predict crack propagation and solder joints break down, considering that a function of solder joints is electric connection. In this study, the authors proposed a method to predict break down life by analytical approach.
Study on the Turbine Flowmeters With Hollow Hub Rotor
Authors: Sun Lijun , Zhang Tao , Yin Min
Published: April 2008

The structure of the hollow hub rotor is put forward in this paper. The physical analysis and test of the performance of the turbine flow meter with it are shown. Compared with the hollow hub rotor, other two different types rotor are presented also. The principles of designing the hollow hub rotor and the methods for improving it are described in details. The emphasis is placed on the physical analysis and test of the performance of the turbine flowmeters with different structures rotor.
Three-Dimensional Numerical Simulations of Curved Edge-Curved Surface Hemming of Aluminum Alloy
Authors: Lin Guosong , Koc¸ Muammer , Hu S. Jack , Cai Wayne
Published: April 2008

Hemming is a manufacturing process to fold a sheet onto itself or another sheet. The dimensional defects (roll-in/rollout, warp/recoil, distortion due to springback, etc.) of hems critically impact the perceived quality of automotive exteriors. This paper summarizes the procedures and the results of three-dimensional (3D) numerical simulations on curved edge-curved surface hemming of aluminum alloy AA6111-T4PD. A solid-element model is built in ABAQUS using explicit quasi-static finite element (FE) procedure for flanging, pre-hemming and final hemming, and implicit procedure for the corresponding preloading and resulting springback at high simulation cost. Aiming at improving the computational efficiency, various approaches have been taken and tested including using shell elements as alternatives, developing simplified simulation procedure by combining pre- and final hemming in explicit scheme, and further simplification by neglecting intermediate springback analysis. The same conditions are analyzed using shell elements in LS-DYNA, but only final hemming springback is considered. The results of the simplified models are compared with the results of ABAQUS solid-element model with complete procedure. Both accuracy and efficiency of the models are presented and discussed.
Alteration of Postural Responses Due to Chronic Recurrent Low Back Pain
Authors: Henry Sharon M. , Hitt Juvena R. , Jones Stephanie L. , Bunn Janice Y.
Published: April 2008

This study characterized postural responses in subjects with (n=26, 39 ± 13 yrs) and without (n=24, 32 ± 10 yrs) chronic ( >6 months), recurrent low back pain (LBP) in response to support surface translations, randomly delivered in 12 different horizontal directions. Using kinematic, force plate and anthropometric data, the net center of pressure (CP), total body center of mass (CM), and net joint torques (sagittal and frontal planes) at the ankle, knee, hip and trunk were examined to characterize the neuromuscular responses in the two subject groups. LBP subjects exhibited larger anterior and posterior CM displacements compared to NLBP (p = 0.0267) and smaller anterior and posterior CP displacements (p <0.0001). Overall, torque responses in persons with LBP were smaller, delayed and developed more quickly compared to NLBP subjects and the responses were non-directionally specific. These data suggest the automatic postural control of subjects with LBP is altered such that there is an overall stiffening strategy for LBP subjects, which is reflected in the reduced CP displacement and the smaller and delayed torque responses.
The General Fracture Problem of a Functionally Graded Thermal Barrier Coating (TBC) Bonded to a Substrate
Authors: Delale F. , Long X.
Published: April 2008

In this paper we consider the general fracture problem of a functionally graded thermal barrier coating (TBC) bonded to a substrate. Functionally Graded Materials (FGMs) used in TBCs are usually made from ceramics and metals. Ceramics provide thermal and corrosion resistance while metals provide the necessary fracture toughness and heat conductivity. The volume fractions of the constituents will usually vary from 100% ceramic at the surface to 0% at the interface continuously providing seamless bonding with the metal substrate. To study the general fracture problem in the TBC we consider an arbitrarily oriented crack in an FGM layer bonded to a half plane. The elastic properties of the FGM layer are assumed to vary exponentially, while those of the half plane are homogeneous. The elastic properties are continuous at the interface. As shown in [1], then the governing elasticity equations become partial differential equations with constant coefficients. Using the transform technique, and defining the crack surface displacement derivatives as the unknown auxiliary functions, the mixed-mode crack problem is reduced to a system of Cauchy type singular integral equations. It is shown that at the crack tips the stresses still possess the regular square-root singularity, making it possible to use the classical definition of stress intensity factors. The singular integral equations are solved numerically using a Gaussian type quadrature and the mode I and mode II stress intensity factors are calculated for various crack lengths and crack orientations. Also the crack surface displacements are computed for different crack inclinations. It is observed that the crack orientation, crack length and the nonhomogeneity parameter affect the stress intensity factors significantly.
Unsteady Forced Convection in Packed Beds: Computational and Experimental Analysis
Authors: Meji´a-Alvarez Ricardo , Agudelo John R. , Nieto Ce´sar , Villa Laura C.
Published: April 2008

In this work, a process of unsteady forced convection in a packed bed of spheres was experimentally and computationally analyzed. A device was designed and constructed in order to run the experiments in packed beds. It was used to carry out an experimental run in a packing of ten aluminum spheres, which tube-to-particle diameter ratio was 2,4. Methane-air combustion products were kept flowing into the packed bed at constant inlet conditions, 2,8 m/s and 369°C. Packed spheres were heated from 25°C to gases temperature. While heating, temperature of spheres, tube wall and gases at different positions were measured to follow unsteady process. On the other hand, computational simulation was carried out by modeling the ten-spheres packing under the same flow conditions of the experimental run. Physical properties of gases were kept constant and fluid flow profile was solved before heating process. Results of unsteady temperature variation in different positions showed good agreement with the experimental measures. This result allowed inferring that flow field calculations were a satisfactory representation of the actual flow field, since temperature field variation depends strongly upon flow field. In conclusion, it was found that the Computational Fluid Dynamics (CFD) simulation is an accurate tool to analyze unsteady forced convection in packed beds. The device designed is a flexible and powerful tool to measure unsteady forced convection in packed beds. The behavior of the gas-to-solid heat transfer coefficient is a fundamental question to solve, and CFD supported on experimental measures is the way to solve it.
Serrated Chip Morphology and Comparison With Finite Element Simulations
Authors: Deshayes L. , Mabrouki T. , Ivester R. , Rigal J.-F.
Published: April 2008

The complexity of chip formation in machining processes stems from the confluence of several physical phenomena — mechanical, thermal, and chemical — occurring at very high strain rate. The prediction of chip morphology depends on a fundamental understanding of these phenomena and is of industrial importance for cutting force prediction and surface integrity control. Our paper focuses on characterizing the chip morphology of serrated-chip (saw-tooth shape chip) and discusses the physical phenomena accompanying the serrated-chip formation according to finite element modeling (FEM) simulations. The paper presents a bibliographic review and an experimental study of chip formation. The experimental study, based on metallographic analysis of chip morphology and hardness measurements, focuses on machining of American Iron and Steel Institute (AISI) 4340 steel alloy. Two finite element software packages were used to simulate chip formation under orthogonal cutting conditions. The FEM results are compared with the hardness measurements, and the chip morphology characterization method used to support the simulations is discussed.
Critical Fiber Length for Load Transfer in Carbon Nanotube (CNT) Reinforced Composites
Authors: Delale Feridun , Wan Huapei
Published: April 2008

In this paper the load transfer mechanism in a carbon nanotube (CNT) reinforced polymeric composite is considered. It is assumed that the polymer matrix is reinforced with single-walled carbon nanotubes and that the continuum model with adjustments is valid in estimating the effective properties of the composite. The existing studies contradict each other with respect to effective load transfer between the matrix and the nanotubes. In this study we show that there is a critical CNT length below which the load transfer is not effective. Thus for an effective load transfer the CNT length must exceed a critical length. To determine the critical length we consider a CNT embedded in a polymer matrix. The polymer/CNT interface is modeled as a distinct layer with elastic properties different than those of the CNT and the matrix. The strain energy change due to the inclusion of a CNT in a polymer matrix is then computed for various interphase stiffnesses using the finite element method. The variation of the strain energy per unit fiber length ΔU/L is plotted versus the aspect ratio of the CNT, L/D. It is observed that ΔU/L first increases steeply with L/D and then reaches a plateau. Since the region of constant ΔU/L is associated with uniform stress distribution, we define the critical CNT length as 90% of the asymptotic value of ΔU/L. It is shown that the load transfer is affected by the nature of the interphase. Next, using a dilute solution the effective moduli of the composite are derived for the cases of both hard and soft interphase. The results indicate that the nature of matrix/CNT interface affects the effective moduli of the composite only slightly.
Effects of Shock Waves on the Particle Acceleration for Cold Gas Dynamic Spray
Authors: Jen Tien-Chien , Li Longjian , Cui Wenzhi , Chen Qinghua , Zhang Xinming
Published: April 2008

The particle velocity in cold gas dynamic spraying (CGDS) is one of the most important factors that can determine the properties of the bonding to the substrate. In this paper, the acceleration process of micro-scale and sub micro-scale copper (Cu) and platinum (Pt) particles inside and outside De-Laval-Type nozzle is investigated. A numerical simulation is performed for the gas-particle two phase flow with particle diameter ranging from 100nm to 50μm, which are accelerated by carrier gas Nitrogen in a supersonic De-Laval-type nozzle. The carrier gas velocity and pressure distributions in the nozzle and outside the nozzle are illustrated. The center-line velocity for two types of particles, Pt and Cu, are demonstrated. It is observed that the existence of the bow shocks near the substrate prevents the smaller size particles (less than 0.5 μm) from penetrating, thus leads to poor coating in the actual practices.
Investigation of Heat Pipe Drilling Application
Authors: Jen Tien-Chien , Chen Yau Min , Tuchowski Fern
Published: April 2008

It’s widely known that hole making is, by a significant margin, the most frequently performed process among metalworking operations. It’s also among the most difficult operations to control from a thermal perspective. The most common cooling method is the use of cutting fluids flooding through the cutting zone. However, disposal of the used fluids is subject to federal, state and local laws and regulations. More stringent regulations in environmental pollution are expected in the future, we can expect the cost associated with coolants to continue to rise. Experimental studies implementing the use of a heat pipe to cool the drill and thus reduce the amount of cutting fluid required have been recently conducted. The heat pipe works with no moving parts or electronics and it also offers an effective alternative to removing heat without significant increases in operating temperatures. The operating mechanism of heat pipes have been extensively studied, however, rotating heat pipes with a wick structure has not received adequate attention in the past. In this study, a numerical analysis has been conducted to model the flow in an axially rotating heat pipe. The result shows the transport capacity is strongly affected by changes in the thermal physical properties of the working fluid with the temperature. The rotating speeds have strong effect in the vapor core but this effect is weak in the liquid flow of the wick structure.
Decentralized Vibration Control With Networked Embedded Systems
Authors: Tao Tao , Amundson Isaac , Frampton Kenneth D.
Published: April 2008

The early promise of centralized active control technologies to improve the performance of large scale, complex systems has not been realized largely due to the inability of centralized control systems to “scale up”; that is, the inability to continue to perform well when the number of sensors and actuators becomes large. Now, recent advances in Micro-electro-mechanical systems (MEMS), microprocessor developments and the breakthroughs in embedded systems technologies, decentralized control systems may see these promises through. A networked embedded system consists of many nodes that possess limited computational capability, sensors, actuators and the ability to communicate with each other over a network. The aim of this decentralized control system is to control the vibration of a structure by using such an embedded system backbone. The key attributes of such control architectures are that they be scalable and that they be effective within the constraints of embedded systems. Toward this end, the decentralized vibration control of a simply supported beam has been implemented experimentally. The experiments demonstrate that the reduction of the system vibration is realized with the decentralized control strategy while meeting the embedded system constraints, such as a minimum of internode sensor data communication, robustness to delays in sensor data and scalability.
A Decentralized Approach to Sound Source Localization With Sensor Networks
Authors: Amundson Isaac , Schmidt Peter L. , Frampton Kenneth D.
Published: April 2008

A sound source localization system has been developed based on a fully decentralized sensor network. Decentralization permits all nodes in a network to handle their own processing and decision-making, and as a result, reduce network congestion and the need for a centralized processor. The system consists of an array of battery operated COTS Ethernet-ready embedded systems with an attached microphone circuit. The localization solution requires groups of at least four nodes to be active within the array to return an acceptable two-dimensional result. Sensor nodes, positioned randomly over a 10 square meter area, recorded detection times of impulsive sources with microsecond resolution. In order to achieve a scalable system, nodes were organized in groups of from 4 to 10 nodes. Grouping was determined by the selecting the nodes farthest apart from each other. A designated leader of each group analyzed the sound source arrival times and calculated the sound source location based on time-differences of arrival. Experimental results show that this approach to sound source localization can achieve accuracies of about 30 centimeters. Perhaps more importantly though, it is accomplished in a decentralized manner, which can lead to a more flexible, scalable distributed sensor network.
Increasing Student Interest and Understanding in a First Mechanics Course Through Software Modules
Authors: Jenkins Hodge
Published: April 2008

Increasing student understanding of engineering mechanics, interest, and readiness for engineering practice are significant concerns of engineering faculty. As a part of an attempt to address these concerns, engineering application software was integrated into a first engineering mechanics course at the sophomore level, Statics and Mechanics of Materials. The course software component is part of an educational initiative across the Mercer University School of Engineering to infuse a common software thread within the curriculum, especially relating to mechanics and design areas. Two course modules using solid modeling and finite element analysis software were included via laboratory sessions and assignments emphasizing visualization and relationships between design and analysis. Descriptions of the modules and their learning objectives as well as results of student surveys taken after each module are presented and discussed.
An AI-Based Computer-Aided Reconfiguration Planning Framework for Reconfigurable Manufacturing Systems
Authors: Tang Li , Yip-Hoi Derek M. , Koren Yoram , Wang Wencai
Published: April 2008

The manufacturing industry today faces a highly volatile market in which manufacturing systems must be capable of responding rapidly to market changes while fully exploiting existing resources. Reconfigurable manufacturing systems (RMS) are designed for this purpose and are gradually being deployed by many mid-to-large volume manufacturers. The advent of RMS has given rise to a challenging problem, namely, how to economically and efficiently reconfigure a manufacturing system and the reconfigurable hardware within it so that the system can meet new requirements. This paper presents a solution to this problem that models the reconfigurability of a RMS as a network of potential activities and configurations to which a shortest path graph-searching strategy is applied. The A* algorithm is employed to perform this search for the reconfiguration plan and reconfigured system that best satisfies the new performance goals. This search engine is implemented within an AI-based Computer-Aided Reconfiguration Planning (CARP) framework, which is designed to assist manufacturing engineers in making reconfiguration planning decisions. Two planning problems serve as examples to prove the effectiveness of the CARP framework.
Acoustic Tailoring of Composite Cylindrical Shells: A Survey of Current Capability
Authors: Campbell Robert L. , Hambric Stephen A.
Published: April 2008

Composites are becoming the material of choice for many weight-critical applications because of their high specific stiffness and the ability to tailor their properties for special applications. In addition, the composite fabrication process is amenable to the inclusion of embedded treatments, which can be exploited to enhance the structural-acoustic performance. This paper provides a summary of the techniques currently used for acoustically tailoring composite structures with embedded, passive damping techniques. A summary of prediction methods for assessing the treatment performance is also provided. The focus of the paper is on cylindrical shell structures such as pipes.
A New Aluminum Honeycomb Constitutive Model for Impact Analyses
Authors: Hinnerichs Terry , Neilsen Michael , Lu Wei-Yang
Published: April 2008

A new constitutive model for large deformation of aluminum honeycomb has been developed. This model has six yield surfaces that are coupled to account for the orthotropic behavior of the cellular honeycomb being crushed on-axis and off-axis. Model parameters have been identified to fit uniaxial and biaxial crush test data for high density (38 lb/ft3) aluminum honeycomb. The honeycomb model was implemented in the transient dynamic Presto finite element code for dynamic impact simulations. In order to extract useful constitutive-parameter information from crush tests, each test configuration and process is simulated with a Presto finite element model to analyze the non-uniform strain/crush behavior within the test samples. Results from the suite of honeycomb crush tests that were used to calibrate the new honeycomb model are shown. Also, the honeycomb model’s predictions are compared with test data and with the older Orthotropic Crush Model predictions.
A Non-Continuum Model of Aligned, Long Fiber Composite Textile Preform Tensile Response
Authors: Burns James S. , Scheder Constantin
Published: April 2008

Stretch-broken fiber preforms provide composites with post-formable characteristics that may reduce the costs of manufacturing complex shapes. Research into fiber preform production methods provides a fiber length and dispersion predictor that is then used to predict forming inputs required to excite tensile elongation of the preform under the influence of various boundary conditions common to sheet-based forming. Fiber behavior is discussed separately from the influence of liquid-phase matrix material. A comparison is made between model results and tensile response measurements of performs for polyarylate-matrix composites.
A Numerical Study of Effect of Liquid Encapsulation on Thermocapillary Convection in Liquid Bridge
Authors: Peng Lan , Zeng Dan-Ling , Li You-Rong
Published: April 2008

The physical and mathematical models of the thermocapillary convection in liquid bridge with liquid encapsulation are established in the present paper. A numerical simulation of the thermocapillary convection in liquid bridge with liquid encapsulation is performed by employed vorticity-stream function method and the Alternative Direction Implicit scheme in finite difference. The distribution of temperature and flow in liquid columns is then obtained. It is verified that liquid encapsulation can reduce the thermocapillary convection in liquid bridge and can improve the quality of crystal growth in float zone. The influence law of the thickness of liquid encapsulation on the thermocapillary convection in liquid bridge is obtained, the more thickness of liquid encapsulation decreases, the more the thermocapillary convection in the inner liquid and the outer liquid diminishes. It is found that the flow profile of two liquid columns is much more complex than that of single liquid column.