bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on Nondestructive Tomographic Visualization of Plane-Woven Fiber-Reinforced Rubber Using Optical Coherence Straingraphy
Authors: Sakata Yoshitaro , Saeki Souichi , Saito Takashi , Ohgi Junji
Published: May 2012

Authors proposed Optical Coherence Straingraphy (OCS), which could visualize micromechanical information, e.g. strain, tomographically and non-destructively. This method can execute the speckle deformation analysis based on cross-correlation technique of synthetic images obtained before and after loading by Optical Coherence Tomography. In this study, applying OCS to composite materials, e.g. plain-woven fiber-reinforced rubber, the experimental feasibility study was carried out, compared with numerical simulated results by image-based FEM. Consequently, OCS could discover the strain concentration in the vicinity of the intersection of orthogonally oriented fiber bundles. It was confirmed that tomographic strain distribution had qualitative agreement with the simulated one. Therefore, OCS was verified to provide mechanical properties non-destructively as internal strain distribution at the micro scale resolution.
Power Stack Die Package Design, Simulation and Reliability Analysis
Authors: Liu Yong , Allen Howard , Martin Stephen
Published: May 2012

This paper presents a power stack die package design for a point of load buck converter. The buck converter system in package (SiP) consists of a lower side Mosfet and a high side Mosfet together with an IC controller. Its structure includes a premolded leadframe with an IC controller. The two Mosfets (both low side and higher side) are stacked on the premolded leadfrrame (LF) and IC controller. Solder balls are placed on the leadframe’s exposed lands, and together with the two drains of Mosfets, to form the stacked die power package. The thermal cycling simulations for the solder balls to connect the PCB and solder joints of the two Mosfet die to the leadframe pads are studied. The failure mechanism and reliability analysis of the power package in TMCL test are discussed.
Carbon Nanotubes Swine Influenza (H1N1) Virus Sensors
Authors: Lee Dongjin , Chander Yogesh , Goyal Sagar M. , Cui Tianhong
Published: May 2012

We present a label-free detection of swine influenza virus (SIV) H1N1 by means of the excellent electrical properties of single-walled carbon nanotubes (SWCNTs). The electrical resistance of SWCNT resistor tends to increase upon the surface adsorption of macromolecules such as poly-L-lysine, anti-SIV antibodies, and SIVs in the process of immunoassay. The SWCNT network resistor was successfully able to detect as low as 180 TCID50/ml of SIV using the resistance shifts upon immunobinding of SIVs. The sensor specificity was demonstrated against transmissible gastroenteritis virus (TGEV) and feline calicivirus (FCV). This facile CNT-based immnoassay has potential applications as a rapid point-of-care detection or a sensing platform for lab-on-a-chip systems.
Fly Ear Inspired Miniature Sound Source Localization Sensor: Localization in Two Dimensions
Authors: Lisiewski Andrew P. , Liu Haijun , Yu Miao
Published: May 2012

Miniature directional microphones are desirable and attractive in many applications including micro air vehicles, hearing aid devices, and anti-sniper systems. To overcome the size constraint, the natural world can serve as a source of inspiration. One striking example is found in the parasitoid fly Ormia Ochracea. Although the interaural distance of the fly ears is only 520μm, it can localize its cricket host with a resolution of as small as 2° [1]. The key to this remarkable directional hearing capability has been linked to a mechanical coupling between the fly’s two eardrums [1–3]. By mimicking the fly-ear design, two-membrane devices have been developed in our previous work [4] which can localize sound in one dimension. This work is intended to develop a three-membrane sound localization sensor, with a coupling beam connected between each of the two adjacent membranes. By utilizing the responses from all three membranes, this device can pinpoint a sound source based on the obtained bearing and elevation angles. A reduced-order model with three degrees of freedom has been developed, and parametric studies have been carried out to study the performance of the system. In experiment, the membrane responses have been detected by using a fiber optic interferometric system. The experimental results have demonstrated an improved directional sensitivity compared with that obtained from a conventional microphone array with uncoupled membranes. This work offers an entirely new approach for sensor design and development practice via the seamless integration of bio-inspired solutions, mechanics modeling, micro-fabrication techniques, and optical detection strategies.
Considerations on the Numerical Implementation of the Lattice Boltzmann Method for Phonon Transport Modelling
Authors: Nabovati Aydin , Sellan Daniel P. , Amon Cristina H.
Published: May 2012

The current miniaturization trend of engineering systems and ever increasing appearance of nano-devices urge for the development of new computational techniques capable of modelling sub-continuum physical phenomena. Among different methods available in the literature, the lattice Boltzmann method has received a lot of attention in recent years because of its versatility and ease of use. The present work describes the lattice Boltzmann methodology and implementation techniques for the phonon transport modelling with an emphasis on the heat transfer modelling in nano-structured semiconductor devices. Numerical methodology and lattice structure selection are discussed in detail; numerical examples are presented to demonstrate the method implementation.
Determination of Damage Criteria in Medial Collateral Ligaments
Authors: Guo Zheying , De Vita Raffaella , Barrett Jennifer G. , Freeman Joseph G.
Published: May 2012

The effect of consecutive and gradually increasing strain on the mechanical behavior of rat medial collateral ligaments (MCLs) was studied to characterize and understand the damage evolution process. Displacement-controlled tensile tests were conducted on femur-MCL-tibia complexes (FMTCs) harvested from 9 Sprague Dawley rats. Each FMTC was loaded to a given displacement, unloaded, and re-loaded to another increasing displacement several times until complete failure occurred. From the recorded tensile stress-strain data, two different phenomena indicative of initiation and propagation of damage were observed: an elongation of the toe region and a decrease in stiffness of the linear region. The threshold strain at which the elongation of the toe region first appeared was found to be (2.59±1.37)% while the threshold strain at which the decrease in stiffness first occurred was determined to be (5.11 ± 1.25)%. These results suggest that there are two different mechanisms that control the damage process in ligaments and further investigation is needed to elucidate their micro-structural origin.
Transient Analysis of Thermal Transport During Start-Up of a Solid Oxide Fuel Cell in a Hybrid Arrangement
Authors: Hughes Dimitri O. , Wepfer William J. , Haynes Comas L.
Published: May 2012

A one-dimensional, distributed solid oxide fuel cell (SOFC) model, capable of operating in real time, has been developed for integration into a direct-fired SOFC/gas turbine pilot scale hybrid facility using hardware-in-the-loop simulation (HiLS). Preliminary studies of the impact of the initial start-up of the hybrid system on transient thermal response in the SOFCs have been conducted. Further investigation of the impact of process parameters upon the fuel cells is also presented in this paper. Specifically, the influence of cathode airflow rate and inlet temperature upon thermal response during inert preheating is studied and analyzed in both the spatial and temporal regimes. Particular emphasis is placed upon the evolution of spatial and temporal temperature derivatives (possibly leading to undesirable thermally induced stresses) in the ceramic SOFC material.
UNAM’s University-Industry PhD Engineering Program
Authors: Lopez-Parra Marcelo , Olivares Gustavo , Rami´rez-Reivich Alejandro , Gonzalez-Villela Victor J. , Borja Vicente
Published: May 2012

This article presents UNAM’s University-Industry PhD Engineering Program that has been implemented over the last six years to help in the training of young researchers. The program expands along 8 semesters and is strengthened by the Mexican Science and Techology’s (CONACYT’s) funding schemes. Specifically, CONACYT’s new “Funds for Innovation Scheme”, which is intended for corporations that wish to design and develop new products, processes or services. The paper reports on the activities typically carried out by a research student (RS) in each of the 8 semesters and presents the results obtained in the PhD research work titled “Design and Development of a PVC Ampoule Filler-Sealer Machine System”.
A Study of Dynamical Model on the Competitive Relationship Between Soil Erosion and Vegetation Growth in Humid Regions
Authors: Huang Tousheng , Zhang Huayong , Zhu Xinqiang , Zhao Lei , Han Lu
Published: May 2012

In this study, a new dynamical model is established based on Thornes’ model. Then a detailed competitive and interactive relationship between soil erosion process and vegetation growth process is detected in humid regions. By employing the nonlinear dynamical analyses, a globally asymptotically stable equilibrium point is obtained under given parameters. This stable state indicates the vegetation growth process can coexist with soil erosion process. Furthermore, the transitions among different equilibrium states caused by the variation describe the competitive process in diverse environment. The results show that the soil erosion has effect on the formations of vegetation patterns in humid regions.
The Change of Relative Turbulence Intensity Within the Reed Population
Authors: Jing Yu , Zhang Huayong , Wang Zhongyu , Xu Weigang , Ji Changming , Zhang Hua
Published: May 2012

The relative turbulence intensity within the natural reed population is studied in this paper. We analyze the changes of turbulence intensity under three conditions corresponding to the different densities of 54, 108, 202 stems per square meter. Results reveal that the flow state in sparse reed population approximates to that in control experiment (no reeds), and the relative turbulence intensity increases with the reed density. Furthermore, the relative turbulence intensity of a measure point is affected by both the longitudinal location of its cross-section and the horizontal distance to the channel wall. Therefore, the relative turbulence intensity becomes more stable when the flow passes through the reed population.
Parametric Numerical Study of Flow and Heat Transfer in Microchannels With Wavy Walls
Authors: Gong Liang , Kota Krishna , Tao Wenquan , Joshi Yogendra
Published: May 2012

Wavy channels are investigated in this paper as a passive scheme to improve the heat transfer performance of laminar fluid flow as applied to microchannel heat sinks. Parametric study of three-dimensional laminar fluid flow and heat transfer characteristics in micro-sized wavy channels was performed by varying the wavy feature amplitude and wavelength at different Reynolds numbers between 50 and 150. Two different types of wavy channels were considered and their thermal performance for a constant heat flux of 47 W/cm2 was compared. Based on the comparison with straight channels, it was found that wavy channels can provide improved overall thermal performance. In addition, it was observed that wavy channels with a configuration in which crests and troughs face each other alternately (serpentine channels) were found to show an edge in thermal performance over the configuration where crests and troughs face each other. The best configuration considered in this paper was found to provide an improvement of up to 55% in the overall performance compared to microchannels with straight walls and hence are attractive candidates for cooling of future high heat flux electronics.
Trajectory Planning for a Wheeled Mobile Robot and its Robotic Arm
Authors: Fotouhi Reza , Salmasi Hamid , Waheed Imran , Vakil Mohammad
Published: May 2012

A temporal planning algorithm that is implemented on a wheeled mobile robot is presented. This algorithm has two parts: the first part is developed to control the motion of the mobile robot, and the second part is designed to control a 6-degrees-of-freedom (DOF) arm attached to the robot. In most robotic applications, it is necessary for the mobile robot to plan and follow a desired path. It may also be necessary for the robot to follow a given velocity profile, which is known as temporal planning. The advantage of temporal planning method in this paper is in its simplicity and its computational efficiency. A rudimentary trajectory is first created by assigning an arbitrary time to each segment of the path. This trajectory is made feasible by applying a number of constraints and using a linear scaling technique. When a velocity profile is given, a nonlinear time scaling technique is used to fit the mobile robot’s linear velocity to the given velocity profile. A method for avoiding moving obstacles is also implemented. Simulation and experimental results showed good agreement with each other. A novelty of this paper is in developing and implementing a new method for control of a 6-DOF arm attached to the mobile robot. Two methods have been proposed and tested for position control of the robot arm; i) linear end-effector increment (LEI), and ii) linear joints increment (LJI). It is shown that LEI is more precise than LJI in trajectory tracking of robot arm; however, the singularity of Denavit-Hartenberg (DH) transformations matrix limits the application of this method for specific trajectories. The LJI is developed to avoid the singularity in DH transformation matrix. The experimental results for four different paths show the effectiveness of the LJI approach. The successful experimental results of path and temporal planning of a wheeled mobile robot and motion control of its industrial arm is reported.
Coupled Thermal and Structural Parametric Analysis of TSVs in 3D Electronics
Authors: Mirza Fahad , Muralidharan Bharathkrishnan , Mynampati Poornima , Karajgikar Saket , Agonafer Dereje
Published: May 2012

The convergence and miniaturization of the consumer electronic products such as cell phones and digital cameras has led to the vertical integration of packages i.e., 3-D packaging. Chip-stacking (3-D) is emerging as a powerful tool that satisfies such Integrated Circuit (IC) package requirements. 3-D technology looks to be the future of hand-held electronics; hence, making it an important research area. Stacked chips are peripherally interconnected through wires; this increases the package size and usually requires an extra “interposer” layer between the chips, causing substantial delays. Due to high package density and chip-stacking on top of each other, heat dissipation from the die becomes a concern. To overcome these thermal challenges and provide better inter-chip and chip-substrate electrical connection, Through Silicon Via (TSV) technology is being implemented in 3-D electronics. Electrical interconnection and heat dissipation improves with the number of TSVs. But, there is a trade-off; TSVs occupy the chip real estate, resulting in reduced silicon efficiency when compared to the baseline (no-TSV) scenario. Coefficient of thermal expansion (CTE) mismatch and reduced chip area causes thermal stresses and may lead to premature chip failures. This can be a major reliability issue. In this paper, a parametric study of the number of TSVs in a test vehicle (TV) consisting of 2 vertically stacked dies and TSVs (between the die and the substrate) has been performed using ANSYS WORKBENCH. A quarter symmetry model has been formulated to study the various cases as a function of number of TSVs. Each die has an area of 5.7mm2 with 0.1-mm thickness and 0.5W power rating. The TSV diameter is 50-μm each with a SiO2 insulation film of 25-μm thickness. Junction temperature and thermal resistance is determined to obtain the best case in terms of temperature distribution on the die. Furthermore, thermo-mechanical analysis is performed for all the TSV configurations and a guideline is proposed based on thermal and structural response.
Design of Z Axis Actuator and Quick Tool Change Assembly for an Endodontic Micro Robot
Authors: Dong Janet , Hong Shane Y.
Published: May 2012

Although the technology of endodontic therapy (root canal treatment) had developed for many years, it is still operated by hands. A typical treatment procedure includes access preparation (opening crown with drills), root canal shaping and cleaning, and then root canal filling. This treatment is expensive, time-consuming, and prone to human error. The outcome relies on the clinician’s skill, which is gained through years of training and practice. The success quotient of this treatment is 60–65% for general dentists and 90% for specialists (endodontists). Therefore, an Advanced Endodontic Technology Development project was initiated. The goal of this project is to develop an intelligent micro robot and a computer aided treatment system to execute the endodontic treatment automatically. It is expected that this intelligent micro robot system will overcome the problems encountered in current treatment practice and increase the treatment accuracy and efficiency. This paper briefly describes the Advanced Endodontic Technology Development project followed by the design of the micro robot for the root canal treatment. The paper focuses on the design of the Z axis actuator to control the treatment tool’s motion and quick tool change assembly in the micro robot.
Analysis Tools for Thermally Driven Microfluidics
Authors: Sigurdson M. , Meinhart C. D.
Published: May 2012

Thermally driven microfluidics, that is, flow that is driven by a temperature gradient, has applications from lab-on-a-chip to electronics cooling. Development of such devices requires tools to predict and probe temperature and velocity fields. We have developed analytical, numerical, and experimental analysis tools for design and characterization of thermally driven microfluidic systems. We demonstrate these tools through the analysis of two different systems: an electrothermal microstirring biochip, and a high aspect heat pipe for cooling. First, a numerical model is developed for temperature and velocity fields, in a hybrid electrothermal-buoyancy microstirring device. An analytical tool, the electrothermal Rayleigh number, is used to further explore the relative importance of electrothermal and buoyancy driven flow. Finally, two experimental thermometry techniques are described: fluorescence thermometry and infrared thermometry. These analytical, numerical, and experimental tools are useful in the design of thermally driven microfluidic systems, as demonstrated here through the development and analysis of microstirring and heat pipe systems.
CFD Investigation of a Hydrogen Reformer Furnace for Improved Flow Distribution
Authors: Zheng Dezhi , Zhang Song , Wu Bin , Fleitz Jeff , Trajkovski Robert , Zhou Chenn Q.
Published: May 2012

A hydrogen reformer furnace is a combustion chamber used to supply heat for the catalytic process that converts natural gas into hydrogen. The reforming reaction that happens inside the catalyst tubes is endothermic and requiring high levels of heat input. The combustion process in the hydrogen reformer furnace provides the heat to maintain the chemical reaction inside the tubes. Consequently, heat control in the hydrogen reformer furnace is one of the most important factors for the catalytic reforming process. The previous investigation indicates the uneven heat distribution inside the furnace has caused the aging issue of catalyst tubes. Hence, optimization of heat distribution inside the furnace is a vital step of the catalytic reforming process. Utilizing the multiphase and non-premixed model of CFD (Computational Fluid Dynamic), the thermal behavior inside the furnace has been investigated. Results revealed that both the gaps on the sidewall of the tunnel and the location of air distribution wall have impact on the temperature distribution of catalyst tubes. The performance of each configuration with different parameters is carried out to provide a great deal of insight for industry field.
Tape Peel Testing as a Simple Method to Evaluate Interfacial Adhesion of Sputtered Thin Layers of Various Metals
Authors: Scholz Bernd , Pekmic Ismir , Ahmad Syed S. , Reinholz Aaron
Published: May 2012

The quality and reliability of electronic systems depend on the integrity of interfacial adhesion. Adhesion is critical at all electronics assembly levels. Material layers on a chip, package and system need to have excellent adhesion to each other. Thin films are an integral part of chip devices and also are necessary at other levels of electronic systems. The quality and reliability of their interfacial adhesion defines the quality and reliability of the finished product. To assure interfacial adhesion integrity, numerous measurement techniques are employed. Most of these measurement techniques require the use of sophisticated and expensive equipment. Of the simpler techniques, one is tape peel testing which usually is used as a go no-go screening test. This paper outlines its application as a valid quantifiable evaluation tool. In this narrative, testing setup and measurement procedure is outlined for tape peel testing. The procedure was used successfully to evaluate and choose pretreatments to enhance interfacial adhesion of sputtered thin layers of various metals. It is shown that the procedure provided results which could be validated through subsequent thick film peel testing. Thin films are used industry-wide in applications other than electronic systems, therefore, this study is applicable industry-wide providing a quantifiable method to measure thin film adhesion.
Simulation of Thrombus Formation Process Using Lattice Boltzmann Method With Consideration of Adhesion Force to Wall
Authors: Tamagawa Masaaki
Published: May 2012

Recently artificial organs, especially rotary blood pumps, have been developed in the worldwide, but in this development, thrombus occurs in the pumps. In general, the main physical factors of thrombus formation are considered to be shear rate, wall properties for blood’s adhesion. But, there are no proper CFD codes for predicting thrombus formations using physical parameters in shear flows. In this paper, new model for predicting thrombus formation by considering aggregation and adhesion force to the wall by lattice Boltzmann method is proposed, and the trend of thrombus’s adhesion to the wall can be simulated more adequately than that of previous one.
Phase Field Modeling for Domain Characterization of Ferroelectric Materials
Authors: Su Yu
Published: May 2012

In this study we adopted a recently developed continuum mechanics-based non-equilibrium thermodynamics framework to investigate domain wall evolutions and interactions within ferroelectric materials. Furthermore, based on such framework, a finite element computing program is implemented to investigate the domain patterns of polarization within low dimensional ferroelectric nanostructures. It is observed from the computational results that the distribution of polarization in low-dimensional ferroelectric nanostructures appears to form vortex structures under open-circuit boundary conditions. The domain characterizations and the minimum geometric limits for existence of such single-vortex structure in ferroelectric nanodots and nanodisks have been numerically evaluated. The effect of intrinsic surface stress has been considered during the analysis.
Water Permeation Through Gas Diffusion Layers of Proton Exchange Membrane Fuel Cells
Authors: Tamayol A. , Bahrami M.
Published: May 2012

Water transport through gas diffusion layer of proton exchange membrane fuels cells is investigated experimentally. A filtration cell is designed and the permeation threshold and the apparent water permeability of several carbon papers are investigated. Similar carbon paper with different thicknesses and different Teflon loadings are tested to study the effects of geometrical and surface properties on the water transport. Permeation threshold increases with both GDL thickness and Teflon loading. In addition, a hysteresis effect exists in GDLs and the permeation threshold reduces as the samples are retested. Moreover, several compressed GDL are tested and the results show that compression does not affect the breakthrough pressure significantly. The measured values of apparent permeability indicate that the majority of pores in GDLs are not filled with water and the reactant access to the catalyst layer is not hindered.
Tolerance Analysis of Mechanical Assemblies Based on Fuzzy - Small Degrees of Freedom (F-SDOF) Model
Authors: Khodaygan S. , Movahhedy M. R.
Published: May 2012

Tolerances naturally generate an uncertain environment for design and manufacturing. In this paper, a novel fuzzy based tolerance representation approach for modeling the variations of geometric features due to dimensional tolerances is presented. The two concepts of fuzzy theory and small degrees of freedom are combined to introduce the fuzzy-small degrees of freedom model (F-SDOF). This model is suitable for tolerance analysis of mechanical assemblies with linear and angular tolerances. The presented method is compatible with the current dimensioning and tolerancing standards. The application of the proposed methodology is illustrated through presenting an example problem.
System Identification and Vibration Control of a Piezo-Driven Flexure-Based XYZ Parallel Micropositioning Stage
Authors: Li Yangmin , Xu Qingsong
Published: May 2012

This paper presents experimental investigations on vibration control of a piezo-driven micropositioning stage aiming at a submicron-accuracy motion tracking. The stage has decoupled XYZ translational motions and is featured with flexure hinges and parallel kinematics. The flexure structure renders the stage a lightly damped resonant mode, and the stack piezoelectric actuator (PZT) introduces hysteresis behavior into the system. The obtained frequency responses of the system confirm the decoupled property of the stage, which allows the adoption of single-input-single-output (SISO) control strategy for each of the three axes. A low-pass filter is employed to reduce the noise level and an integral resonant control (IRC) scheme is adopted to damp the resonant mode. An additional high-gain integral feedback control is implemented to alleviate the hysteresis effects and to achieve a suitable bandwidth with sufficient stability margin. The effectiveness of the combined controller is verified by extensive simulation and experimental studies. Results show that the adverse vibration, hysteresis and noise of the piezo-driven stage are well attenuated, which validates the effectiveness of the presented control scheme.
Resistance Spot Welding Evaluation of 1.4 mm Electro Galvanized (EG) Dual Phase 780 (DP780) and 1.6 mm Electro Galvanized Transformation Induced Plasticity 780 (TRIP780) Steel for Automotive Body Structural Applications
Authors: Koganti Ramakrishna , Elliott Adrian , Orsette Charles
Published: May 2012

The usage of advanced high strength steel (AHSS) in automotive body structures is projected to grow significantly in the next 5–10 years with the introduction of new safety and fuel economy regulations. This is due to their superior mechanical properties and weight savings potential. These new materials pose significant manufacturing challenges, particularly for welding and stamping. Due to the high strength nature of AHSS materials, higher weld forces and longer weld times are often needed to weld these advanced steels. In this paper, the weldability of 1.4 mm electro galvanized (EG) Dual Phase 780 (DP780) welded to a 1.6 mm Electro Galvanized (EG) Transformation Induced Plasticity 780 (TRIP780) is discussed. Also, weld current lobes, mechanical properties (shear and cross tension), metallographic cross-section and micro-hardness profile in a two-metal stack-up are discussed. Weld Lobes and a full factorial Design of Experiment (DOE) was conducted. Weld current and hold time are the chosen factors for the DOE. Based on the DOE data analysis, weld current was the significant factor for tensile load and hold time was the significant factor for the cross tension load. There were no interaction effects observed between weld current and hold time o for tensile and cross tensions loads.
Resistance Spot Welding (RSW) Evaluation of 1.0 mm Usibor® 1500 P to 2.0 mm Usibor® 1500 P Steel for Automotive Body Structure Applications
Authors: Koganti Ramakrishna , Elliott Adrian , Maatz Donald F.
Published: May 2012

There has been a substantial increase in the use of advanced high strength steel (AHSS) in automotive structures in the last few years. The usage of these materials is projected to grow significantly in the next 5–10 years with the introduction of new safety and fuel economy regulations. AHSS are gaining popularity due to their superior mechanical properties and use in parts for weight savings potential, as compared to mild steels. These new materials pose significant manufacturing challenges, particularly for welding and stamping. Proper understanding of the weldability of these materials is critical for successful application on future vehicle programs. Due to the high strength nature of AHSS materials, higher weld forces and longer weld times are often needed to weld these advanced strength steels. In this paper, the weld current lobes, mechanical properties (shear tension and cross tension), metallographic cross-section and microhardness profile of 1.0 mm Usibor® 1500 P and 2.0 mm Usibor® 1500 P joint in a two-metal stackup are discussed. Weld lobes were developed with Medium Frequency Direct Current (MFDC) equipment, ISO-type B16 tips, weld force of 3.42 kN and hold time of 5 cycles. The weld times were varied at 12, 15 and 18 cycles, with each producing current ranges at or below 3.0 kA. Tensile shear and cross tension samples were made at weld time of 15 cycles, with samples showing average loads of 15.73 kN and 4.41 kN, respectively. Also, microhardness assessment using metallographic cross-sections were analyzed at three different weld cycles (12, 15, and 18 cycles). Voids were observed at 12 and 15 weld cycles, however there was no void at 18 cycles. Similar heat affected zones (HAZ) and weld zones were observed for three different weld cycles.
Formulation of Seawater Flow Exergy Using Accurate Thermodynamic Data
Authors: Sharqawy Mostafa H. , Lienhard John H. , Zubair Syed M.
Published: May 2012

Seawater is a complex electrolyte solution of water and salts with sodium chloride as the major constituent. However, the thermodynamic properties of seawater are considerably different from those of aqueous sodium chloride solution. In the literature, exergy analyses of seawater desalination systems have sometimes modeled seawater by sodium chloride solutions of equivalent salt content or salinity; however, such matching does not bring all important properties of the two solutions into agreement. Furthermore, some published studies attempt to represent sodium chloride solutions as a specific model for an ideal mixture of liquid water and solid sodium chloride, which is shown to have serious shortcomings. In this paper, the most up-to-date thermodynamic properties of seawater are compared with those of aqueous sodium chloride solution as well as the ideal mixture model. The flow exergy is calculated using various models and the results are compared. In addition, the minimum work required to desalinate a unit mass of fresh water from seawater of varying salinity is calculated using these models. The flow exergy calculated using the ideal mixture model in question is about 50% less than that of seawater. Accordingly, the minimum desalination work is underpredicted by about 50% when calculating it using that ideal mixture model. This consequently shows that exergy analysis and the second law efficiency calculations performed using the ideal mixture model is comparatively far from the actual values.
A Numerical Study of Traumatic Brain Injury Due to Ground Impact in an SUV-Pedestrian Crash Using Full-Scale Finite Element Models
Authors: Tamura Atsutaka
Published: May 2012

A number of studies have worked on traffic injuries or traumas related to pedestrian impacts. However, most of them placed more focuses on traumatic injuries due to primary impact with a striking vehicle rather than those involved in secondary impact with the ground. In this study, a validated, human whole-body, pedestrian finite element model was utilized to investigate the potential risk of traumatic brain injury (TBI) relevant to the ground impact as well as primary head strike in an SUV-to-pedestrian collision. By conducting a set of numerical experiments at impact speed of 25 and 40 km/h with pedestrian’s pre-impact, transverse, traveling speed of 1.3 m/s, it was found that ground impact is likely to cause serious TBI even in a low impact speed level. Although the post-impact kinematics and subsequent kinetics were considerably unpredictable due to the intrinsic complexity of pedestrian impact, this finding also suggests that impact speed does not necessarily contribute to the severity of pedestrian TBI involving vehicle with a higher profile. In the future, an effective countermeasure for ground impact should be taken into account to reduce the risk of sustaining serious TBIs in pedestrian crashes.
Heat-Pipe Assisted Thermoelectric Generators for Exhaust Gas Applications
Authors: Goncalves L. M. , Martins Jorge , Antunes Joaquim , Rocha Romeu , Brito Francisco P.
Published: May 2012

Millions of hybrid cars are already running on our roads with the purpose of reducing fossil fuel dependence. One of their main advantages is the recovery of wasted energy, namely by brake recovery. However, there are other sources of wasted energy in a car powered by an internal combustion engine, such as the heat lost through the cooling system, lubrication system (oil coolers) and in the exhaust system. These energies can be recuperated by the use of thermoelectric generators (TEG) based on the Seebeck effect, which transform heat directly into electricity. To recover the energy from the hot (up to more than 700 °C) exhaust gases it is possible to use controlled heat transfer, but this would limit the heat transfer potential at partial loads, as commercialy available TEG are limited by their maximum allowable temperature (∼250°C). Therefore Heat Pipes were used as an alternative heat transfer mean, so it would be possible to retain the heat transfer potential, while controlling the maximum temperature at a reasonable level. This is the method to recover the exhaust heat presented in this work. Numerical simulations were performed to assess the potential for this design, involving internal combustion engine simulation, thermoelectric generators simulation and heat transfer modelling. Additionally, the use of variable conductance heat pipes (VCHP) is discussed, as a means of achieving TEG module maximum temperature limitation.
Effects of Impeller Blade Loading on Industrial Centrifugal Compressor Performance and Stability
Authors: Ji Min , Cave Michael , Zhang Donghui
Published: May 2012

Multistage centrifugal compressors are widely used in the oil and gas industry for various applications. As energy demand increases, the compressor has been challenged to have both high efficiency and broad operating range in order to minimize the life-cycle operation cost. Therefore much effort has been devoted to improve performance of the centrifugal impeller through various design methods. This paper highlights experiences gained in the development of three-dimensional impeller design in an effort combining different design methodologies and experimental investigations. In the present paper, a radial impeller in a medium specific speed range was designed through the conventional direct approach as the baseline. Then, it was redesigned with a different loading profile and a challenged loading magnitude by means of the inverse design method. To assess the two design approaches, the resulting two impellers were manufactured and tested in a closed-loop compressor test rig. The experimental investigation consists of both the performance test and detailed traverse test measuring the flow field downstream of the impeller. The paper presents the comparison of impeller performance and time-averaged data of the downstream flow field between the two impellers. Analysis of the test data illustrates the critical impact of the blade loading on the overall compressor performance and stability.
Design Consideration of a Centrifugal Compressor Impeller With High Mach Number and High Swirl Angle at Exit
Authors: Im Kangsoo
Published: May 2012

A centrifugal compressor impeller with high exit Mach number (M = 0.8–1.1) & high outlet flow angle (ALPHA 2 = 78–85 degrees) was designed. The objective of this work is to create a real condition for the better understanding of the behavior of the fluid flow in transonic and high swirl flow vaned diffusers. Particular attention was given to the flows located at the rotor–stator interface. The unsteady interaction between impeller and diffuser plays an important role in the compression process, especially in high loaded impellers. Actually, the vaned diffuser has to tolerate the distorted upstream flow due to the jet-wake structure coming from the impeller. Following the impeller design, numerical investigations were conducted for the transonic centrifugal compressor impeller composed of backswept unshrouded blades. The characteristic plots of the impeller resulting from the simulations show a good stable operation.
Advanced Polytropic Calculation Method of Centrifugal Compressor
Authors: Oldrich Jiri
Published: May 2012

The contribution deals with a new method for calculation of the polytropic change of real gas or gaseous mixture. This method can be used for high accurate polytropic analysis of centrifugal compressors compressing real gases. In the course of design and test evaluation of the compressor the most important is to decrease energy consumption. Advantage of the polytropic analysis is the fact that the polytropic change is very close to the actual process which is in progress in the centrifugal compressor. Several various methods for calculation of polytropic process have been developed till now. The new method is based on numerical solution of basic definition equation of polytropic change in form edH = Vdp where “polytropic efficiency” e has constant value along the whole polytropic path. This method enables to calculate arbitrary unknown parameters from set of quantities (polytropic efficiency, initial pressure and temperature and final pressure and temperature) if the remaining parameters and gas composition are known. Suitable real gas equation of state can be used to calculation of real gas thermodynamic properties. Presented method is independent of equation of state. Accuracy of this method depends only on chosen equation of state. Computer procedure based on above mentioned method can be incorporated into computer programs for calculation of compressors, refrigerating cycles, expansion turbines, gas or steam turbines etc.
Design and Performance Evaluation of a 10:1 Pressure Ratio Centrifugal Compressor Impeller
Authors: Vagani Marco , Bolin Christopher D.
Published: May 2012

Small gas turbine engines for advanced helicopter application and for auxiliary power have strong interest in centrifugal compressors, where high pressure ratios are required in a single stage. But there are few single stage centrifugal compressors capable of pressure-ratios around 10:1, due to stress considerations which severely limit the compressor’s safety, durability and life expectancy. In this work, design considerations are carried out for single stage centrifugal impeller with a pressure ratio of 10:1 and mass flow of 3 kg/s. One-D design procedure is used to compute the skeletal geometry of the impeller and to set a rough description of the flow at inlet and outlet. The theoretical head will be evaluated from Euler’s equation using slip factor. Determining the pressure ratio and efficiency of the impeller are achieved through evaluation of the slip factor and the internal and external losses. The losses evaluated in the impeller are those due to incidence, transonic inlet, skin friction, blade loading, shroud clearance, and recirculation. The design procedure adopted will be verified and compared with the well-documented Eckardt impellers and data. After one-D design, three-D geometry of the impeller is developed, and CFD flow simulation of the impeller flow is carried out to determine the performance of the impeller.
Stress Approximation Technique for Helical Compression Springs Subjected to Lateral Loading
Authors: Keller Scott G. , Gordon Ali P.
Published: May 2012

Helical compression springs are commonly used devices capable of storing kinetic energy. Typical applications vary in simplicity, ranging from low stress amplitudes and in favorable environments, e.g. ball point pen spring at room temperature, to millions of cycles in elevated temperatures, e.g. valve train spring in IC engines. Regardless of the load or environment, springs are able to use the intrinsic elasticity of the material and the initial geometry to resist plastic deformation, all while allowing for the transfer of load over various distances. Generally, these loads are parallel to the axis of the spring; however, as more complex designs arise, these uniaxial springs are gaining popularity in a variety of off-axis loading situations, e.g. flexible shaft couplings, invalidating traditional stress/strain equations. As such, equivalent stress and strain equations have been developed capable of fast, real-time calculations based upon visual inspection of the bent helix. Coupled with the initial dimensions and material of the spring, the state of equivalent stress/strain can be resolved at any position within the wire. Experiments were conducted on several off-the-shelf steel springs (conforming to ASTM A229), then compared to FEA and analytical solutions. Ultimately, it was observed that through an approximation of the bent helix, the equivalent stress and strain can be determined at any location within the wire, allowing for the approximation of life and crack initiation locations of the spring.
Thermally Based Design Optimization of Telecommunication Shelter
Authors: Mynampati Venkata Naga Poornima , Mariam Feroz Ahamed Iqbal , Muralidharan Bharathkrishnan , Menon Abhilash Ramachandran , Agonafer Dereje , Hendrix Mark
Published: May 2012

Telecommunication shelters are generally used for housing the electronic equipments and are an integral component at various levels of wireless access networks. The electronics which dissipate heat needs to be cooled for proper functioning of the equipment. Telecom shelters are generally stand-alone, modular structures with their own electrical HVAC systems. The effect of cabinet’s location in the shelter on temperature is studied. The outline of the paper is to validate the shelter model with the test data available by using CFD tool and perform thermal analysis for different location of 2G cabinets and then, to study the effect of isolation in the shelter. It is observed that the isolation in the shelter attributes to lowering the temperature of the cabinets.
Topological Design Optimization of Nested Channels for Squeeze Flow of Thermal Interface Materials
Authors: Bajaj Nikhil , Subbarayan Ganesh , Garimella Suresh V.
Published: May 2012

Thermal interface resistance remains a bottleneck for thermal transport in electronic systems, comprising a significant portion of overall system thermal resistance. Performance of thermal interface materials (TIMs) is largely dependent on the bulk thermal conductivity of the TIM but also on the bond-line thickness (BLT) of the applied material as well as interfacial contact resistances. Recently, Hierarchically Nested Channels (HNCs), created by modifying the surface topology with hierarchical arrangements of microchannels in order to improve flow, were proposed to reduce both required squeezing force and final BLTs in interfaces. In this paper, a topological optimization framework that enables the design of channel arrangements is developed. The framework is based on a resistance network approximation to Newtonian squeeze flow. The approximation, validated against finite element method (FEM)-based solutions, allows efficient, design-oriented solutions for squeeze flow in complex geometries. A comprehensive design sensitivity analysis exploiting the resistance network approximation is also developed and implemented. The resistance approximation and the sensitivity analysis is used to build an automated optimal channel design framework. A Pareto optimal problem formulation for the design of channels is posed and the optimal solution is demonstrated using the framework.
Developing Innovative Teaching Materials That Use Molecular Simulations in Engineering Thermodynamics
Authors: Dartnall W. John , Reizes John
Published: May 2012

Traditionally, Engineering Thermodynamics is presented to undergraduate mechanical engineering students from a classical viewpoint. The emphasis in the courses is on analyzing processes involving bulk thermodynamic properties of materials to ascertain the performance of systems of significant size such as internal combustion engines, steam boiler power plants, vapour compression refrigeration systems, gas compressors etc. This emphasis may need to change so that mechanical engineers gain a better understanding of areas such as nanotechnology, fuel cells, photovoltaic cells and solid state electronics. A further need for change, is because thermodynamics, as a subject, has a reputation that many students apply formulae in a rote-like manner and struggle to understand the underlying physics and practicalities. One of our innovations is to use simple one and two dimensional hard sphere simulations to demonstrate the validity of such basic constants as Avogadro’s Number and the Boltzman constant, and then visually demonstrate the ideal gas equation explaining concepts such as temperature and pressure and the way in which they relate to the volume containing a specified number of molecules. The underlying mechanical/physical reasons for the idealizations and processes of thermodynamics can be visually demonstrated by simple hard sphere models in ways that are related to mechanics. We outline some examples of simple simulations and innovative teaching materials that model the molecular (microscopic) behaviour on which macroscopic thermodynamic behaviour depends. Initial trials of some of the ideas that have appeared in past congress papers have been or are currently being trialed. These trials have revealed how students tend to follow the “rote learning of formulae and procedure approach” rather than the “physical understanding” approach.
The Role of the Mechanical Engineer in the Present Energetic Context
Authors: Duran M. D. , Rinco´n E. A.
Published: May 2012

This paper shows how the economic, technological, and environmental contexts of today influence the conceptualizations and role of Mechanical Engineering as a discipline. Special attention is given to the environmental and energetic scope in order to define the current responsibility of this science, which specializes in energy consumption at both national and international levels, and to define its role in designing systems that let us use energy more efficiently and with less pollution. Based on this, at the end of this paper some abilities are listed that the Mechanical Engineer in today’s Mexico must develop during his or training.