bluuebunny/crossref_metadata_2025 huggingface dataset:
Shape Optimization of a Plate-Fin Type Heat Sink for High Performance
Authors: Park Kyoungwoo , Choi Dong-Hoon , Lee Kwan-Soo
Published: April 2008

Thermal performance of heat sink for a fixed volume is influenced by the design variables. Thus, in this study the optimal values of the design variables are obtained numerically by integrating the CFD and mathematical optimization for high performance of the plate-fin heat sink with vortex generator. The optimum solutions in the heat sink can be achieved when the temperature rise and the pressure drop, which are the objective functions, are minimized simultaneously. The flow and thermal fields are predicted to calculate the objective functions using the finite volume method. The optimization is carried out by means of sequential quadratic programming (SQP) method. The results show that when the temperature rise is less than 40 K, the optimal design variables are B1 = 2.584 mm, B2 = 1.741 mm, and t = 7.914 mm. Comparing with the initial design, the temperature rise is reduced by 4.2 K, while the pressure drop is increased by 9.43 Pa. The Pareto optimal solutions are also presented between the pressure drop and the temperature rise.
A Two-Step Methodology for the Generation of Accurate Finite Element Models of Nonlinear Mechanical Systems
Authors: Kerschen Gae¨tan , Golinval Jean-Claude
Published: April 2008

Model updating and validation is currently a central issue in the fields of computational structural mechanics and dynamics. The vast majority of applications however concerns linear structures. On the other hand, updating nonlinear models is something the structural dynamicist prefers to avoid mainly because tools such as modal analysis are no longer available. The objective of the present study is to propose a two-step methodology for dealing with nonlinear systems. Its most appealing feature is that it decouples the estimation of the linear and nonlinear parameters. A numerical application consisting of an aeroplane-like structure is used to assess the efficiency of the procedure.
Transonic Passage Turbine Blade Tip Clearance With Scalloped Shroud: Part II — Losses With and Without Scrubbing Effects in Engine Configuration
Authors: Strasser Wayne S. , Feldman Gregory M. , Wilkins F. Casey , Leylek James H.
Published: April 2008

Loss mechanisms in a scallop shrouded transonic power generation turbine blade passage at realistic engine conditions have been identified through a series of large-scale (typically 12 million finite volumes) simulations. All simulations are run with second-order discretization and viscous sublayer resolution, and they include the effects of viscous dissipation. The mesh (y+ near unity on all surfaces) is highly refined in the tip clearance region, casing recesses, and shroud region in order to fully capture complex interdependent flow physics and the associated losses. Aerodynamic losses, in order of their relative importance, are a result of the following: separation around the tip, recesses, and shroud; tip vortex creation; downstream mixing losses, localized shocks on the airfoil; and the passage vortex emanating from under the shroud. A number of helical lateral flows were established near the upper shroud surfaces as a result of lateral pressure gradients on the scalloped shroud. It was found that the tip leakage and passage losses increased approximately linearly with increasing tip clearance, both with and without the effect of the relative casing motion. For each tip clearance studied, scrubbing slightly reduced the tip leakage, but the overall production of entropy was increased by more than 50%. Also the overall passage mass flow rate, for a given inlet total pressure to exit static pressure ratio, increased almost linearly with increasing tip clearance. In addition, it was also found that there was slight positive and negative lift on the shroud, depending on the tip clearance. At the lowest tip clearance of 20 mils there was a negative lift on the shroud. In the 200-mil tip clearance case there was a positive lift on the shroud. The relative motion of the casing contributed positively to the lift at every tip clearance, affecting more at the lowest tip clearance where the casing is closest to the blade tip. Lastly, it was found that the computed entropy generation for the stationary 80-mils case using the SKE turbulence model was close to that of the 80-mils scrubbing case using the RKE turbulence model. In light of the proposed mechanisms and their relative contributions, suggested design considerations are posed.
Modelling of a Novel Gas Strut Using Neural Networks
Authors: Gao B. , Darling J. , Tilley D. G. , Williams R. A. , Bean A. , Donahue J.
Published: April 2008

The strut is one of the most important components in a vehicle suspension system. Since it is highly non-linear it is difficult to predict its performance characteristics using a physical mathematical model. However, neural networks have been successfully used as universal ‘black-box’ models in the identification and control of non-linear systems. This approach has been used to model a novel gas strut and the neural network was trained with experimental data obtained in the laboratory from simulated road profiles. The results obtained from the neural network demonstrated good agreement with the experimental results over a wide range of operation conditions. In contrast a linearised mathematical model using least square estimates of system parameters was shown to perform badly due to the highly non-linear nature of the system. A quarter car mathematical model was developed to predict strut behavior. It was shown that the two models produced different predictions of ride performance and it was argued that the neural network was preferable as it included the effects of non-linearities. Although the neural network model does not provide a good understanding of the physical behavior of the strut it is a useful tool for assessing vehicle ride and NVH performance due to its good computational efficiency and accuracy.
Railcar Wheel Flat Impact Analysis
Authors: Dick Matthew G. , Reid John D.
Published: April 2008

Wheel flats are common railcar wheel defects that cause bearing failures and train derailments. In an effort to better understand the impacts created by a wheel flat, a nonlinear finite element model using LS-DYNA was created of a single 914.4 mm (36 in) railcar wheel with a wheel flat and a 3.24 m (127.5 in) half track with one rail, six wood ties and tie plates. Discrete element springs and dampers simulated the ballast and subgrade. Goals of this model were to accurately simulate a wheel flat impact at varying speeds and to monitor the plastic deformation that occurs at the sharp edges of the wheel flat during rotation. Producing and validating this model then could be used to test modifications to the track and wheel to lower the severity of wheel impacts. Results indicated an accurate simulation; however, improvements with the material properties, suspension model and mesh sensitivity can be made.
Development of Automatic Assembly and Evaluation Systems for the Optical Add/Drop Module
Authors: Seo Young Ho , Choi Doo-Sun , Park Han Soo , Je Tae-Jin , Whang Kyung-Hyun
Published: April 2008

In this paper, we present a system and program of automatic assembly and measurement for the optical add/drop module of optical fiber and filter. The system consists of upper optical collimator stage, lower optical collimator stage, and optical filter stage. The characteristics of add/drop module with optical fibers and filter is measured in the optimum conditions. In the packaging process of fibers and filter on the optical bench, automatic alignment and measurement systems maintain minimized optical losses conditions until completion of packaging process. In experimental study, the measured Transmission Insertion Loss (TIL) of add/drop module (optical fiber and 1510nm-CWDM filter) based on automatic and manual operations shows the average value of 0.142dB±0.002dB and 0.166dB±0.03dB, respectively. We have confirmed that the standard deviation of TIL of automatic operation is 15 times lower than that of manual operation. Also, the present automatic assembly and evaluation system requires less than 1 minute for add/drop module, while conventional method requires more than 3 minute. Moreover, we have compared the specification of optical filters including 1510nm-CWDM filter and 1536.61nm-DWDM filter with the measured characteristics of them using automatic operation. The measured characteristics of CWDM and DWDM filter are well agreement with the specification of them within standard loss of 0.3dB.
Modeling of Metal Transfer in Short Circuiting Arc Welding
Authors: Xu Guo , Schultz William W. , Kannatey-Asibu Elijah , Hu S. Jack , Wang Pei-Chung
Published: April 2008

The short-circuiting metal transfer during gas metal arc welding (GMAW) is simulated by a numerical model. To the best of our knowledge, for the first time the energy equation and the Marangoni convection are considered in analyzing the short-circuiting time. A front-tracking free surface method is applied to explicitly track the bridge profile. To benchmark this method, effects of the density and viscosity ratios between different phases are investigated by simulating a drop driven by surface tension. The temporal profile of the drop is compared to that computed by a Volume of Fluid (VOF) model, and very good agreement is found. The model is then applied to simulate GMAW short-circuiting transfer. The velocity, pressure, temperature and electromagnetic fields are calculated. Effects of welding current and Marangoni shear stress on short-circuiting time are examined. It is shown that the Marangoni effect plays an important role in GMAW short-circuiting transfer.
Interface Effect on Lattice Thermal Conductivities of Superlattice Nanowires
Authors: Chena Yunfei , Li Deyu , Yang Juekuan , Ni Zhonghua , Lukes Jennifer R.
Published: April 2008

The nonequilibrium molecular dynamics (NEMD) method has been used to calculate the lattice thermal conductivities of Ar and Kr/Ar nanostructures in order to study the effects of interface scattering, boundary scattering, and elastic strain on lattice thermal conductivity. Results show that interface scattering poses significant resistance to phonon transport in superlattices and superlattice nanowires. The thermal conductivity of the Kr/Ar superlattice nanowire is only about 1/3 of that for pure Ar nanowires with the same cross sectional area and total length due to the additional interfacial thermal resistance. It is found that nanowire boundary scattering provides significant resistance to phonon transport. As the cross sectional area increases, the nanowire boundary scattering decreases, which leads to increased nanowire thermal conductivity. The ratio of the interfacial thermal resistance to the total effective thermal resistance increases from 30% for the superlattice nanowire to 42% for the superlattice film. Period length is another important factor affecting the effective thermal conductivity of the nanostructures. Increasing the period length will lead to increased acoustic mismatch between the adjacent layers, and hence increased interfacial thermal resistance. However, if the total length of the superlattice nanowire is fixed, reducing the period length will lead to decreased effective thermal conductivity due to the increased number of interfaces. Finally, it is found that the interfacial thermal resistance decreases as the reference temperature increases, which might be due to the inelastic interface scattering.
Stress Concentration in Laminated Composites With an Elliptical Hole Under Uniaxial Load
Authors: Hu Zhong , Friedman Brett A. , Delfanian Fereidoon
Published: April 2008

The anisotropic nature of the laminate composites creates a unique opportunity and also a great challenge for tailoring its properties according to the design requirements. In this work, investigating the strength of laminate composite, a nonlinear finite element analysis is used to simulate the stress concentration caused by a through elliptical hole with various shapes and size within a metallic material and a fiber-reinforced laminate with different orientations subjected to the uniaxial tensile stress. This evaluation provides a clear indication and a key step in understanding failures initiated by stress concentration which may lead to the growth of a crack. Comparison between the effects of the hole both on a metallic material and on a fiber-reinforced laminate exposes a totally different situation. In general, the stress concentration depends not only on the material properties, the layer stacking order, and the orientations, but also on the geometry of the hole.
Issues in Assembly Process of Fine Pitch Chip-on-Flex Packages for LCD Applications
Authors: Jang Changsoo , Han Seongyoung , Ryu Jay , Kim Hangyu
Published: April 2008

Some of the current assembly issues of fine pitch chip-on-flex (COF) packages for LCD applications are reviewed. Traditional underfill material, anisotropic conductive adhesive (ACA) and non-conductive adhesive (NCA) are considered in conjunction with two applicable bonding methods including thermal and laser bonding. Advantages and disadvantages of each material/process combination are identified. Their applicability is further investigated to identify a process most suitable to the fine pitch packages (less than 40 μm). Numerical results and subsequent testing results indicate that NCA/laser bonding process produces most reliable joint for the fine pitch packages.
Board Level Drop Tests Comparing Lead-Free and Eutectic Solder Interconnects on a BGA Package for Mobile ICT Applications
Authors: Heaslip Greg M. , Punch Jeff M. , Rodgers Bryan A. , Ryan Claire
Published: April 2008

There is considerable reported evidence that a large percentage of failures which afflict portable electronic products are due to impact or shock during use. Failures of the external housing, internal electronic components, package-to-board interconnects, and liquid crystal display panels may occur as the result of accidental drops. Moreover, the introduction of lead-free solder to the electronics industry will bring additional design implications for future generations of mobile information and communication technology (ICT) applications. In this paper, drop tests performed on printed circuit boards (PCBs) populated with ball grid arrays (BGAs) are reported. During testing, measurements from strain gages were recorded using a high-speed data acquisition system. Electrical continuity through each package was monitored during the impact event in order to detect failure of package-to-board interconnects. Life distributions were established for both lead-free and eutectic solders for various drop heights. Microsections of the failed interconnects were obtained to determine the failure mechanisms for a range of drop heights. The life test data presented in this paper suggests that for board level drop testing different failure mechanisms can occur at different stress levels and that there is a considerable difference between lead-free solder characteristic life and tin-lead (SAC) solder characteristic life.
Investigations on the Use of Damage Indicating Criteria in FE Simulations of Cold and Semi-Hot Bulk Forging Operations
Authors: Just Hendrik , Behrens Arno
Published: April 2008

Bulk forging operations play an important role in metal forming. A wide range of applications is possible from some ounces to several tons of steel in a high diversity of shapes. However economical constraints demand for further optimisation and cost-effective production. One severe problem arising not only in bulk forging is the susceptibility of steels to ductile damage during the production process. In case it reaches macroscopic proportions the workpiece might be destroyed. Otherwise it inhibits a potential threat to safety and lifetime of the product. Recent research concentrated on cold forging processes as their share in the market clearly outweighs semi-hot or hot forging. Nevertheless semi-hot forging processes are prone to ductile damage as well. It is the intention of this paper to propose the damage indicating Model of Effective Stresses by Lemaitre for an application in the design of bulk forging operations. The model is identified from several different approaches and verified by combined experiments and finite element simulations. Last an application to exemplary cold and semi-hot forging operations will show the suitability of this approach.
Variable Structure Control of an Underactuated Air Spindle Testbed
Authors: Ashrafiuon Hashem
Published: April 2008

A robust control algorithm is developed for attitude control of an air spindle testbed based on variable structure control. The variable structure control approach is formulated for underactuated systems with actuated accelerations as control inputs. First order sliding surfaces are defined per actuated degrees of freedom as a linear combination of the tracking position and velocity errors of both actuated and unactuated coordinates. The controller law is determined based on Lyapunov theory and is shown to be asymptotically stable for the tiled air spindle axis where gravitational effects are included but only marginally stable for the vertical axis. Multiple step sliding surfaces are proposed to achieve asymptotic stability in the latter case. Simulations of the controller performance verify its effectiveness and accuracy.
The Cluster Treatment of Characteristic Roots and the Neutral Type Time-Delayed Systems
Authors: Olgac Nejat , Sipahi Rifat
Published: April 2008

A new methodology is presented for assessing the stability posture of a general class of linear time-invariant – neutral time-delayed systems (LTI-NTDS). It is based on a “Cluster Treatment of Characteristic Roots CTCR” paradigm. The technique offers a number of unique features: It returns exact bounds of time delay for stability, furthermore it yields the number of unstable characteristic roots of the system in an explicit and non-sequentially evaluated function of time delay. As a direct consequence of the latter feature, the new methodology creates entirely, all existing stability intervals of delay, τ. It is shown that the CTCR inherently enforces an intriguing necessary condition for τ-stabilizability, which is the main contribution of this paper. This, so called “small delay” effect, was recognized earlier for NTDS, only through some cumbersome mathematics. In addition to the above listed characteristics, the CTCR is also unique in handling systems with unstable starting posture for τ = 0, which may be τ-stabilized for higher values of delay. Example cases are provided.
Product Platform Design and the Gate Model: Lessons From Industry Case Studies
Authors: Chao Lawrence P. , Ishii Kosuke
Published: April 2008

Organizations that seek long-term success no longer depend on just one product but rather a platform of products that target key markets. Time-to-market pressures and globally distributed engineering design environments demand support through life-cycle models, particularly in the early stages of product development, for an effective product platform. Product definition and structured processes such as gate models are necessary in platform design for organizations to focus their effort on developing families of products that share common components and technology. This paper discusses conventions and research directions in different industries, describes methods in use, and explains a roadmap for product platform development. Case studies of laser printer, industrial robot, and AC motor drive controller platform development further explore challenges in platform design and the role of gate models. The paper concludes with gate model lessons and proposed work to further this research including decision analytic and system approaches.
Online Multi-Channel Forging Tonnage Monitoring and Fault Pattern Discrimination Using Principal Curve
Authors: Kim Jihyun , Huang Qiang , Shi Jianjun , Chang Tzyy-Shuh
Published: April 2008

Due to late response to process condition changes, forging processes are normally exposed to large number of defective products. To achieve online process monitoring, multi-channel tonnage signals are often collected from the forging press. The tonnage signals contain significant amount of real time information regarding the product and the process conditions. In this paper, a methodology is developed to detect profile changes of multi-channel tonnage signals for forging process monitoring and to classify fault patterns. The changes include global or local profile deviations, which correspond to deviations of a whole process cycle or process segment(s) within a cycle respectively. Principal curve method is used to conduct feature extraction and discrimination of tonnage signals. The developed methodology is demonstrated with industry data from a crankshaft forging processes.
Optical Transmission Properties of Silicon Wafters: Theoretical Analysis
Authors: Zhang J. M. , Sun J. G. , Pei Z. J.
Published: April 2008

As a nondestructive measurement method, laser scattering has been preliminarily applied to detect subsurface damage in silicon wafers, but the quantitative correlation between scatter images and subsurface damage depth has not been established yet. In order to assess subsurface damage depth in silicon wafers, a systematic study has been carried out. In the authors’ another paper, a detailed experimental investigation on optical transmission percentage of silicon wafers was presented. As a follow up, this paper will describe a method to calculate the “skin depth” of silicon wafers from the experimental data of optical transmission percentage. And also, how to apply this “skin depth” on assessment of subsurface damage depth will be discussed.
A Course on Flow-System Configuration and Multi-Scale Design
Authors: Bejan Adrian , Lorente Sylvie
Published: April 2008

This paper brings to the attention of the AES community our experience with developing and trying out a new course that focuses on the generation of system configuration (geometry, architecture, and drawing) during the optimization of performance. The configuration is free to morph. Real systems are destined to remain imperfect because of finiteness constraints. They are plagued by resistances to the flow of fluid, heat, and electricity. Resistances are always finite because of constraints. The balancing and distributing of resistances (irreversibility) through the available volume is the mechanism that generates the architecture. Our approach to this key topic is evolutionary, and from simple to complex. In the 2004 format, the course covers several main topics: the relationship between optimization and the generation of configuration, multi-scale hierarchical structures for fluid flow and heat flow, and tree-shaped networks for collection and distribution. The paper relies on classroom-level examples to illustrate these topics. The paper also discusses the teaching method, and the applicability of this course concept to other domains (cost minimization, urban design, etc.).
Meniscus Dynamics in Material Processing
Authors: Yang B. , Rickers J. , Wong M. , Zheng L. L.
Published: April 2008

Wetting behavior of liquid and dynamics of the meniscus are important in many meniscus-controlled material processes such as Edge-defined Film-fed Growth (EFG), fiber pulling growth, micro/nano tube growth, etc. Understanding dynamic responses of meniscus to perturbations is essential to the improvement of the quality of products from these processes. In this paper, symmetric meniscus structure as well as asymmetric structure and the break-up of the steady-state meniscus are studied experimentally using the techniques of pulling from shaper (TPS). The break-up conditions for the steady-state meniscus are obtained. A theoretical model is also proposed to study the dynamic response of the meniscus shape with a given ribbon thickness to the change in pulling rate and meniscus height. This model is analyzed for symmetric meniscus structure and its transition to an asymmetric system.
On Testing and Modeling Automotive Spool-Type Hydraulic Valve With Circular Flow Ports
Authors: Cao M. , Wang K. W. , DeVries L. , Fujii Y. , Tobler W. E. , Pietron G. M.
Published: April 2008

This paper describes empirical investigations of the fluid field for a spool-type hydraulic valve with symmetrically distributed circular ports that is often found in an automotive VFS (Variable Force Solenoid) valve system. Through extensive data analysis, a general trend of fluid force and flow rate is derived as a function of pressure drop and valve opening. Aiming at further revealing the insights of the steady state spool valve fluid field, the equivalent jet angle and discharge coefficient are calculated from the measurements based on the lumped parameter models. New Non-Dimensional Artificial Neural Network (NDANN)-based hydraulic valve system models are also developed in this paper through the use of equivalent jet angle and discharge coefficient. By introducing the outputs of the new NDANN models into the lumped parameter model, fluid force and flow rate can be easily calculated. Therefore, the new approach calculates fluid force and flow rate as well as the intermediate variables (equivalent jet angle and discharge coefficient) with useful design implications. The network training and testing demonstrate that the NDANN fluid field estimators can accurately capture the relationship between the key geometry parameters and discharge coefficient/jet angle. The new approach also maintains the non-dimensional network configuration and possesses scalability with respect to the geometry parameters and key operating conditions. All these features make the new NDANN fluid field estimator a valuable tool for automotive hydraulic system design.
Milling Model With Variable Time Delay
Authors: Long X.-H. , Balachandran B.
Published: April 2008

Taking into account the effect of feed rate, a milling-process model with a variable time delay is presented in this article. Loss-of-contact effects are also considered. The development of this formulation is described and the efforts undertaken to examine the stability of periodic orbits of this system are discussed. A semi-discretization treatment is used for the stability analysis, and this analysis provides evidence for period-doubling bifurcations and secondary Hopf bifurcations. Good agreement is found between the numerical results obtained from this work and experimental results published in the literature.
Three-Dimensional Node Mapping Model for Toroidal Field Coils of Tokamak Physics Experiment System
Authors: Tong Wei
Published: April 2008

The toroidal field (TF) coils, along with the poloidal field (PF) coils, are used to produce the desirable magnetic field in a Tokamak Physics Experiment (TPX) system. To design a reliable and cryogenic stabilized system, heat generation and transport in these coils during normal TPX operation mush be carefully considered and analyzed. In order to accurately determine the temperature distribution in the TF coils, a three-dimensional node mapping model has been developed to deal with heat conduction between adjacent turns, pancakes, and case sidewalls. In such a way, the interactive heat transfer effect is taken into account in the design of TF magnets. The node mapping at the coil winding transitions is also integrated into the model.
Personal Watercraft: Action/Reaction Hazards
Authors: Tudor Andrew H.
Published: April 2008

Personal watercraft (PWC) are small, light, high-horsepower boats. They are quite capable of injuring their occupants. This condition is exacerbated by the levels of acceleration these machines achieve under normal operating conditions, their unique operating characteristics, the design of the controls, operator/passenger configurations, seat and handhold designs and regulations. This paper explores the ergonomic design package, machine and boat design, injury patterns, safety hazards, regulations and some other issues that surround the PWC.
A Compact Falling Film Absorber
Authors: Goel Nitin , Goswami D. Yogi
Published: April 2008

The paper presents a new design of a falling film absorber that could considerably reduce the absorber size without penalizing on the vapor and coolant side pressure drops. The proposed design is based on the fundamental characteristics of an efficient absorber design: large liquid-vapor interfacial area and good wetting characteristics. A finite difference scheme is developed to numerically investigate the performance of the design. The results indicate that the proposed design is more compact and efficient than the conventional falling film absorber.
Finite Element Modeling of GMAW Process: Evolution and Formation of Residual Stresses Upon Cooling
Authors: Davoud Mohammad S. , Deng Xiaomin
Published: April 2008

Fusion arc welding processes often generate substantial residual stresses, which may alter the performance of welded structures. Residual stresses are the results of incompatible elastic and plastic deformations in a body. Destructive techniques are generally used to experimentally determine residual stresses. Employment of these methods would not often be possible or practical in industry. In this study, three-dimensional (3D) and two-dimensional (2D) finite element simulations and experimental work have been performed to analyze the thermomechanical problem of GMAW and to obtain a full-field view of the residual stress field. One of the purposes of this study is to examine the formation of residual stresses upon cooling of a weldment. Comparisons of the results of 2D and 3D finite element models reveal many three-dimensional features in the thermomechanical problem of GMAW. The magnitude of longitudinal residual stresses obtained from the 2D model, however, compares well with the results obtained from the 3D model.
Non-Traditional Machining Using Pulsed Water Drops
Authors: Jackson M. J.
Published: April 2008

This paper discusses water jet machining of selected materials using a non-traditional way of delivering water jets in the form of a series of discrete pulses. The theory of water jet impact has been used to demonstrate the principle of removing material by exploiting the existence of a Rayleigh wave that excites the formation of surface cracks and the lateral outflow of water that extends the cracks and removes material. A mathematical model has been developed that predicts changes in the response characteristics of materials owing to an idealised representation of a finite jet of water impacting a plane surface. The analytical approach used is applicable to the first stages of impact where the compressibility of water in the droplet is significant. The predicted response characteristics are compared with experimental data generated using controlled water jet impacts produced by a specially constructed pulsed water jet machining centre. The predicted response of selected materials compare well with experimental data. The results presented in this paper illustrate the importance of using pulsed water jets as a way of machining materials in a non-traditional manner.
Spot Weld Failure Prediction and Simulation in Crash Analysis
Authors: Tang Xiaodong
Published: April 2008

Weld failure/separation in vehicle body structures subjected to impact condition may results in component instability and thus reduced energy absorption. A new finite element method has been developed for modeling the behavior of spot welds in elastic, plastic and separation stages. This method can be used to simulate weld failure in vehicle crash analysis using a failure formulation derived from coupon test results. It is a generalized method and is intended to be applicable to any combination of the weld design parameters such as thickness, materials, coating and impact speed. The method has been validated on the crash tests on straight and S-type rails with a hat section. The CAE prediction based on the modeling procedure correlates well with the test results for all the rail crush cases. The welds are modeled using the beam-type spring element with the newly developed weld damage parameters. The baseline curves for the spring element and the detailed projection equations developed are provided in this paper. The presented method and major effect curves from the testing can also benefit the spot weld design and specification development.
Integrating New Learner Outcomes to a Mechanical Engineering Technology Advanced Machining Course
Authors: Oncina Carlos A.
Published: April 2008

A description follows of the new subject material and assessment process introduced to an Advanced Machining & NC Programming course for the purpose of improving its manufacturing industry content, thereby meeting our accredited Mechanical Engineering Technology program learner outcomes. The new outcomes introduced to the course include the following concepts: 1. Quality and Statistical Process Control, 2. Teamwork, 3. Economics and Cycle Times, 4. Work Flow and Flexible Manufacturing, and 5. Integrated Design and Manufacturing. This new subject material was assessed by three means: 1. Team performance, 2. Project success and 3. Student post-course evaluations. These outcomes are also discussed in their relationship to criteria put forth in the proposed ABET/TAC 2004–2005 Criteria for Accrediting Engineering Technology Programs.
Determination of Discharge Coefficient for Ball Valves With Calibrated Inserts
Authors: Rouss Gino James , Janna William S.
Published: April 2008

The valve coefficient was measured for 1, 1-1/4, 1-1/2 and 2 nominal ball valves. A recently designed orifice insert was used with these valves to obtain smaller valve coefficients. Orifice inserts were threaded into the body of a ball valve just upstream of the ball itself. The valve coefficient was measured for every insert used with these valves, and an expression was determined to relate the orifice diameter to other pertinent flow parameters. Two dimensionless groups were chosen to correlate the collected data, and expressions were developed that can be used as aids in sizing the orifice insert needed to obtain the desired valve coefficient. The study has shown that a 2nd order polynomial equation as well as a power law equation can both be used to predict the desired results. Knowing pipe size and schedule, the diameter of the orifice insert needed to obtain the required valve coefficient can be approximated with minimum error. An error analysis performed on the collected data shows that the results are highly accurate, and that the experimental process is repeatable.
Mechanical Forces Involved in Cardiac C-Looping
Authors: Taber Larry A. , Voronov Dmitry A. , Re´mond Mathieu C. , Latacha Kimberly S. , Alford Patrick W.
Published: April 2008

Cardiac looping is a vital morphogenetic process that transforms the initially straight heart tube into a curved tube normally directed toward the right side of the embryo. We examined the role of biomechanical forces during the initial stages of looping, when the heart bends and rotates into a c-shaped tube (c-looping). C-looping consists of two primary deformation components: ventral bending and dextral (rightward) rotation (torsion). Embryonic chick hearts were subjected to mechanical and chemical perturbations, and the experiments were simulated using a computational model. The results suggest that bending is driven primarily by actin polymerization within the heart tube, while rotation is driven by external loads due to the splanchnopleure and omphalomesenteric veins. The results of this study may help investigators searching for the link between gene expression and the mechanical processes that drive looping.
Safety Testing of Consumer Oven Broiler Doors With Live Children
Authors: Brickman Dennis B.
Published: April 2008

A 10 month old boy sustained burn injuries from contact with the inside of a hot consumer gas range lower broiler door. A unique human factors test program was conducted with live children to determine if they could open alternative lower broiler door designs. Safety and functional analyses of alternative broiler door designs are also performed. Finally, techniques for supervising young children around ovens are explored in this paper.
Strain Dependent Variations in the Frictional Properties of Bovine Articular Cartilage
Authors: Krishnan Ramaswamy , Kopacz Monika , Carter Michael J. , Ateshian Gerard A.
Published: April 2008

This study investigates the hypothesis that the equilibrium friction coefficient of cartilage decreases with increasing compressive strain. Furthermore, when accounting for this strain-dependence, it is hypothesized that the temporal response of the friction coefficient correlates linearly with interstitial fluid load support, in the configuration of unconfined compression stress-relaxation. Both hypotheses were confirmed from theory and experiment.
Possibilities and Problems in Finite Element Simulations of High Speed Cutting Mechanics
Authors: Behrens Arno , Kalisch Karsten , Wulfsberg Jens P.
Published: April 2008

High speed cutting (HSC) has received growing attention in recent years due to its widespread applications in modern manufacturing. However, the theoretical understanding of the HSC process is considerably underdeveloped in comparison to the rapid progress of its practical application. To improve the state of knowledge of this topic, the German Research Association (DFG) has funded some research projects. One of them is the improvement of finite element simulation techniques of the HSC process. It covers the chip formation description, development of material laws for the description of HSC-conditions, the prediction of lamellar chips, the calculation of residual stresses, resulting temperature fields in the cutting tool and first descriptions of spatial chip formation. The paper will give an overview of the current progress in this project.
Testability of Erbium Doped Fiber Amplifiers: An Approach Towards Yield Improvement
Authors: Pradhan Salil , Arbulich John , Damodaran Purushothaman , Srihari K.
Published: April 2008

Erbium Doped Fiber Amplifiers (EDFAs) are extensively used in Dense Wavelength Division Multiplexing (DWDM) technology for long haul optical transmission networks. The manufacturing of optoelectronic products has been gradually transferred from Original Equipment Manufacturers (OEMs) to the Electronics Manufacturing Service (EMS) providers. Operator dependency and the lack of automation increase the cycle time in optoelectronics manufacturing. Manufacturing difficulties and lower yield reduce the throughput. Consequently, identifying and implementing activities to improve yield becomes crucial for an EMS provider to survive in a medium-to-high volume environment. During the manufacturing processes, several tests are conducted to calibrate the EDFA at room temperature and temperature extremes. Critical parameters such as gain, flatness, and the noise figure are monitored at multiple stages. Failures (or non-conformities) observed in any of these parameters at any stage results in a reduced first pass yield. In this paper, several aspects of testing an EDFA and the failure modes at various stages, which result in lower yields, have been discussed. Root cause analysis and the corrective actions taken to significantly improve the first pass yield are presented. Relationships between some of the critical parameters have been discussed. Finally, guidelines for yield improvement are delineated. The results are based upon studies conducted on an EDFA, which is manufactured by the facility where this research was conducted.
Comparison of Convective Transport of Drug Between Intravitreal Injection and Controlled Release Implant
Authors: Park Juyoung , Bungay Peter M. , Lutz Robert J. , Augsburger James J. , Millard Ronald W. , Roy Abhijit S. , Banerjee Rupak K.
Published: April 2008

It is important to know the drug distribution following administration of drug in order to properly treat with adequate dosage and thus, avoid damage to tissues due to excessive high concentrations. A computer model was developed to determine drug distribution by convective-diffusive transport processes in a rabbit eye. When compared with pure diffusion within vitreous, the ratio of the amount of a model compound, fluorescein, reaching the retina to that cleared by aqueous outflow increased by 93% and 84% for intravitreal injection and implant, respectively, with maximum vitreous outflow (glaucomatous eye). The result shows that the combined “convective” effect due to the vitreous outflow and “wash out” effect by aqueous outflow has significant impact on drug distribution for both intravitreal injection and implant. These two effects should be considered in the design of drug delivery strategies.
Nash Equilibrium Strategies in Day-Ahead Electricity Markets: Optimum Management of Hydro-Thermal Systems
Authors: Carraretto Cristian , Zigante Andrea
Published: April 2008

Robust optimization procedures for power plants production planning are the keypoint to profitably compete in the electricity deregulated market. The authors recently presented a market model useful to optimize the management of a group of thermal power plants belonging to a competitive producer. This model determines the Nash equilibrium among a set of competitors. In this paper, this model is extended to manage groups of thermal and hydro power plants together. Hydro plants part-load operation and technical constraints (feasible working range, feasible water storage range, water storage variation in time as a function of natural and artificial inflows, etc.) are thoroughly included in the market model. The model is applied to a large-scale power system for different market conditions and typical days of the year. Various combinations of power plants and number of producers are investigated. In particular, their effect on power plants management, market equilibrium and prices are discussed.
Legal Risk Criteria Versus Tunnel Safety Guidelines: Freight Railway Safety in the Netherlands
Authors: Rosmuller Nils , Ale Ben
Published: April 2008

In 2006, in the Netherlands the Betuweline will be realized between the port of Rotterdam and the German Hinterland. The Betuweline is a dedicated high-speed freight railway for all kinds of freight transport, including hazardous materials. The Betuweline crosses multiple built environments and comprises 5 tunnels. As a result, safety is a main issue for various stakeholders such as railway engineers, spatial planners and emergency responders. For this railway, however, the juridical character of the safety topics differs widely from (hard) legal risk criteria such as individual risk to (soft) safety guidelines such as accessibility by emergency responders. In this article, safety topics of the Betuweline are described and analyzed with regard to the available laws and guidelines in order to search for opportunities to reduce societal risk and society’s vulnerability.
Experimental and Analytical Investigation of Compact Liquid Cooled Heat Sinks
Authors: Zugic M. , Culham J. R. , Teertstra P. , Muzychka Y. , Horne K. , Knapp E. , de Palma J.-F.
Published: April 2008

Compact, liquid cooled heat sinks are used in applications where high heat fluxes and boundary resistance preclude the use of more traditional air cooling techniques. Four different liquid cooled heat sink designs, whose core geometry is formed by overlapped ribbed plates, are examined. The objective of this analysis is to develop models that can be used as design tools for the prediction of overall heat transfer and pressure drop of heat sinks. Models are validated for Reynolds numbers between 300 and 5000 using experimental tests. The agreement between the experiments and the models ranges from 2.35% to 15.3% RMS.
Gearbox Fault Detection Using Empirical Mode Decomposition
Authors: Fan Xianfeng , Zuo Ming J.
Published: April 2008

Local faults in a gearbox cause impacts and the collected vibration signal is often non-stationary. Identification of impulses within the non-stationary vibration signal is key to fault detection. Recently, the technique of Empirical Mode Decomposition (EMD) was proposed as a new tool for analysis of non-stationary signal. EMD is a time series analysis method that extracts a custom set of bases that reflects the characteristic response of a system. The Intrinsic Mode Functions (IMFs) within the original data can be obtained through EMD. We expect that the change in the amplitude of the special IMF’s envelope spectrum will become larger when fault impulses are present. Based on this idea, we propose a new fault detection method that combines EMD with Hilbert transform. The proposed method is compared with both the Hilbert-Huang transform and the wavelet transform using simulated signal and real signal collected from a gearbox. The results obtained show that the proposed method is effective in capturing the hidden fault impulses.
Programmable Compliance and Equilibrium Point Control of a 2-DOF Manipulator Performing Free-Space, Contact and Transition Tasks
Authors: Clapa Damien J. , Croft Elizabeth A. , Hodgson Anthony J.
Published: April 2008

Programmable mechanical compliance (PMC) in actuation is desirable for human interaction tasks and important for producing biomimetic motion. In this paper, the equilibrium point (EP) hypothesis is proposed and implemented as a strategy for controlling programmable compliance. A two-DOF planar manipulator activated by McKibben actuators was constructed for the purpose of demonstrating the application of the equilibrium point hypothesis on a robotic platform. The equilibrium angle and stiffness of each of the joints on the manipulator can be independently programmed. The results presented herein show stable behavior for free motion, interaction and transition tasks using the EP hypothesis implemented with a linear PI control strategy.
Combined Sensing and Actuation: A New Control Laboratory Experiment
Authors: Elahinia Mohammad H.
Published: April 2008

This paper describes a new control experiment developed for Mechanical Engineering undergraduate students. The experiment with a Shape Memory Alloy (SMA) actuated robotic arm is designed for the senior undergraduate laboratory (ME4006) in the Department of Mechanical Engineering at Virginia Tech. ME4006 is designed to provide the students with experience in experimental investigation of mechanical engineering systems. In designing this control experiment it was intended for the students to have a hands-on experiment with smart materials. Furthermore, students learn about control problems and limitations of theses materials along with sensing and actuation advantages of the SMAs. The experiment uses a problem solving approach; students are not given a procedure to follow for conducting the experiment. The problem is described in a memorandum to the students from a supervisor, who defines the purpose of the problem and defines the audience for the report.
Application of DSP for Precision Positioning System Controlling
Authors: Chen Jau-Liang , Li Tsang-Chou
Published: April 2008

The objective of this research was to use a DSP for controlling a nano-precision positioning system. The positioning system was constructed by a piezoelectric actuator, a flexural stage that composed by notch hinges and parallel springs; capacitor sensor was used instead of laser interferometer as displacement sensor. In order to increase the traveling range of the stage, a lever mechanism was used to enlarge the displacement of the piezoelectric actuator. In this study a Dmatek PICE-DSP 320C542 microcomputer developing system was used as the controller, which contained a TI TMS320C542 DSP chip. PI feedback control rule together with n-times feedforward control rule were used for the controlling of this system. Three different experiments were conducted: (1) fixed-point test; (2) continuous stepping test; and (3) ramp-tracking test. From the experiment results, it was shown that the bias Ess was within 2 nm and the standard deviation 1σ was around 30 nm, with settling time less than 0.02 sec, in the continuous stepping test. While, in the ramp-tracking test, the bias Ess was less than 1.25 nm and the standard deviation 1σ was around 35 nm.