bluuebunny/crossref_metadata_2025 huggingface dataset:
Six-Mode Interaction of Panel Flutter With Joint Relaxation Deterministic Analysis
Authors: Ibrahim Raouf A. , Beloiu Dumitru M. , Pettit Chris L.
Published: April 2008

The influence of boundary conditions relaxation on two-dimensional panel flutter is studied in the presence of in-plane loading. The boundary value problem of the panel involves time-dependent boundary conditions that are converted into autonomous form using a special coordinate transformation. Galerkin’s method is used to discretize the panel partial differential equation into six nonlinear ordinary differential equations representing the first six modes. The influence of boundary conditions relaxation on the panel modal frequencies and limit cycle amplitudes in the time and frequency domains is examined through the spectrogram of the generalized coordinate for each mode. The relaxation and system nonlinearity are found to have opposite effects on the time evolution of the panel frequency. Depending on the system damping and dynamic pressure, the panel flutter frequency can increase or decrease with time as the boundary conditions approach the state of simple supports. Bifurcation diagrams are generated by taking the dynamic pressure and relaxation parameter as control parameters. They reveal different regions of periodic, quasi-periodic, and chaotic motions. These regions take place only when the in-plane load exceeds the Euler buckling load.
Robust Observer Design for Systems With Deterministic and Stochastic Uncertainties
Authors: Jung Jongchul , Lee Tae Hee , Stein Jeffrey L. , Huh Kunsoo
Published: April 2008

An observer design method for stochastic and deterministic robustness is developed so that the observer is less sensitive to uncertainties in transient and in steady-state observer performance. The uncertainties include not only deterministic factors such as unknown initial estimation error, round-off error, modeling error and sensing bias, but also stochastic factors such as disturbance and sensor noise. From a stochastic perspective, a small value in estimation error variance represents robustness to the stochastic uncertainties. It is shown that the upper bound of the error variance can be minimized by reducing the observer gain and by increasing the decay rate of the observer. From a deterministic perspective, a small value in the L2 norm condition number of the observer eigenvector matrix guarantees robust estimation performance to the deterministic uncertainties. An optimization problem constrained by a linear matrix inequality condition is formulated for both the deterministic and the stochastic robustness. The observer gain can be selected as a trade-off solution and the estimation performance to stochastic and deterministic uncertainties is demonstrated on simulation examples.
An Application of Independent Component Analysis to Gas Metal Arc Welding
Authors: Song Zhu Mei , Li Di , Ye Feng
Published: April 2008

A novel method, independent component analysis (ICA), is introduced to gas metal arc welding (GMAW) process monitoring. ICA was applied to arc signals, i.e. welding current and arc voltage, to remove the correlation between them and extract an independent component (IC). Two series of robotic GMAW experiments were carried out to study the feasibility of ICA for online monitoring. It was found that IC put up an abnormity when there was a step disturbance in the welding process. Experimental results showed that the IC could be used as a state variable representing the process variation. By applying statistical process control (SPC) for the obtained IC, a burning-through defect was isolated from the normal operation. The comparison between ICA and PCA was also made for the processes, which led an interesting result and was in need for further study.
Experimental and Finite Element Investigation of Cementless Cup/Bone Interface After Total Hip Arthroplasty
Authors: Zivkovic Ivan , Amirouche Farid , Romero Francisco , Gonzalez Mark
Published: April 2008

Permanent fixation of a cementless total hip arthroplasty requires bone ingrowth into the femoral and acetabular components. Early micromotion at the acetabular cup/bone interface can preclude ingrowth threatening long term fixation. To better characterize micromotion of the interface under loading conditions, an experimental and finite element (FE) study was undertaken. In this study cadaver hemi-pelvises were implanted with cementless acetabular cups and subjected to cyclical axial load and torque. Detailed finite element model, validated with experimental results, was developed to further analyze the conditions affecting the initial stability and loosening of the interface for different loading conditions.
Analysis of Crack Induced Vibration Localization in Simplified Bladed-Disk Structures
Authors: Fang X. , Tang J.
Published: April 2008

In this paper, we study the effect of crack on the vibratory response of a simplified bladed-disk model. A mono-coupled cyclically periodic structure consisting of cantilevered beams coupled with springs is used to emulate the dynamic response of bladed-disk in aero-engines. A fracture mechanics based approach is employed to evaluate the stiffness loss due to the occurrence of crack on single beam. Then, by taking advantage of the unique property of periodic structures, using the U-transform approach we develop analytical solutions to the free and forced vibrations of the structure with a single crack. It is identified that, while the stiffness loss on a single beam could be small and may not cause significant frequency change, it could lead to free and forced vibration localization in a periodic structure. The intrinsic relation between the response amplitudes and various system parameters such as internal coupling, crack severity, and excitation patterns is explored.
Porohyperelastic-Transport Finite Element Models of the Eye Using ABAQUS
Authors: Rigby P. H. , Park R. I. , Simon B. R.
Published: April 2008

Glaucoma is related to damage to nerve ganglion cells in the optic nerve head (ONH) including the lamina cribrosa, (LC). This disease is associated with elevated intraocular pressure (IOP) and possibly reduced trabecular meshwork (TM) outflow. The ABAQUS program was used to develop axisymmetric porohyperelastic (PHE) pore fluid finite element models (FEMs) to determine deformations, stresses, tissue fluid pressures (pf), and mobile fluid flux in the eye. These FEMs simulated aqueous pressure-fluid flow fields in the anterior chamber via the TM and posterior pressure-flow fields in the vitreous body (VIT) and ONH. Constant inlet flow at the ciliary processes (CP) was applied. The anterior chamber was modeled as a highly porous material containing large amounts of fluid whereas the VIT was modeled as a gel with mobile fluid. All ocular soft tissues were considered to be linear, isotropic PHE materials. Posterior transport was regulated by varying the permeability of the LC, retina, choroid, and sclera material layers. Two FEMs, i.e. IOP=15 mm Hg (normal) and IOP=44 mm Hg (glaucoma) were developed by varying the permeability of the TM. Deformations and tissue fluid pressures, fluid flux (relative fluid velocities), and stresses were determined and agree well with experimental data and other numerical model results. The displacement of the LC was 21–62 μm; the LC pressure gradient was 25–73 mm Hg/mm; and the posterior outflow ranged from 5%–15% of the inflow at the CP. The PHE material law can be extended to include nonlinear permeability effects and mobile species transport using a porohyperelastic-transport-swelling (PHETS) theory in future FEMs.
Parametric Study of a Thermosyphon Loop Pressure Drop Model
Authors: Zhang Jinsong , Hugenroth Jason , Mudawar Issam , Fisher Timothy S.
Published: April 2008

A closed loop two-phase thermosyphon has been modeled based on earlier experimental and numerical studies by Mukherjee and Mudawar [1, 2]. Unlike conventional thermosyphons in which the heat dissipating device is submerged in a pool of liquid coolant, the current system uses a flow boiling arrangement. The advantage is that for a given boiling surface area, the critical heat flux (CHF) can be increased. Parametric studies with respect to adiabatic section flow areas, boiler section flow area, and system height were performed. The maximum practical heat flux that is attainable is predicted, as well as other flow parameters such as mass flow rate, flow velocities and fluid quality existing the boiler. Performance enhancements relative to the original system, may be possible by introducing a divergent cross sectional area in the boiler section that increases the system mass flow rate. It can also, however, reduce the flow velocity in certain sections of the boiler, tending to reduce the boiler CHF. Experimental studies are recommended to determine if an actual improvement can be realized.
Sliding Mode Motion Control of a Pneumatic Cylinder
Authors: Jalal Syed Shah , Batur Celal
Published: April 2008

This paper presents simulation and implementation of a sliding mode controller on a pneumatic servo system. Typical controllers for pneumatic systems are fixed gain linear controllers. This study incorporates the non-linear characteristics of the pneumatic actuator into the controller design. A detailed mathematical model of a single ended pneumatic cylinder driven by a servo valve is developed. Effects of non-linear air flow through the valve, compressibility in the cylinder chambers and the residual volume of the connecting pipes are carefully considered. Both viscous and Coulomb frictions within the cylinder have been taken into account. A position tracking sliding mode control strategy is developed and implemented. A series of experiments and simulations are performed to show that the control performance is satisfactory in both tracking and regulation.
Evaluation of Different Efficiency Concepts of an Integrated Energy System (IES)
Authors: Petrov Andrei Yu. , Zaltash Abdolreza , Labinov Solomon D. , Rizy D. Tom , Liao Xiaohong , Radermacher Reinhard
Published: April 2008

The Integrated Energy System (IES) market in the United States (US) and worldwide has been increasingly expanding over the last few years. But there is still a lot of disagreement in interpretation of one of the most important IES performance parameters — efficiency. Some organizations, for example, use higher heating value (HHV) of fuel in efficiency calculations while some use lower heating value (LHV). Some accounts for auxiliary and parasitic losses while others do not. Some adhere to the “first-law” of efficiency while some use other methods, i.e., calculations recommended by the Federal Energy Regulatory Commission or the US Combined Heat & Power Association. Different efficiency concepts based on actual performance testing from the IES Laboratory at Oak Ridge National Laboratory (ORNL) are evaluated in this paper. The equipment studied included: a 30-kW microturbine, an air-to-water heat recovery unit (HRU), a 10-ton (35 kW) hot water-fired (indirect-fired) single-effect absorption chiller, and a direct-fired desiccant dehumidification unit. Efficiencies of different configurations of the above-mentioned equipment based on various approaches are compared. In addition, IES efficiency gains due to the replacement of a 1st generation HRU (effectiveness of approximately 75%) with a 2nd generation HRU (effectiveness of approximately 92%) for the same IES arrangement are discussed. The results showed that the difference in HHV- and LHV-based efficiencies for different IES arrangements could reach 5–8%, and that the difference in efficiency values calculated with different methods for the same arrangement could reach 27%. Therefore, it is very important to develop standard guidelines for efficiency calculations that would be acceptable and used by the majority of IES manufacturers and end-users. At the very least, every manufacturer or user should clearly indicate the basis for their efficiency calculations.
The Development Stages of Rear Upright for Formula Car
Authors: Fidan Ismail , McGough Adam , Foote Jeff
Published: April 2008

Formula SAE (FSAE) is a design competition organized each year by the Society of Automotive Engineers (SAE). The objective of the competition is to bring the best and brightest future engineers from each participating school to present a small scale race car. Although this sounds like a relatively simple concept, the actual execution is rather challenging and rewarding for the team. For almost three years Tennessee Tech University (TTU) has had a FSAE team. The first year was a planning year, so Tennessee Tech University has participated in the competition for the last two years. Both years have been extreme learning experiences since TTU was not prepared for the level of competition brought by participating schools. However TTU FSAE team is beginning to implement modern design tools such as FEA, Virtual Manufacturing, and Rapid Prototyping to help streamline the design efforts so that one day Golden Eagle FSAE will be one of the top competing teams. In this publication, authors will report on one Golden Eagle FSAE component (the rear upright) development stages and its accomplishments.
A Study of Soil Remediation by Vapor Extraction System and Air Sparging
Authors: Roy T. , Amano R. S. , Jatkar J.
Published: April 2008

Soil remediation by heated soil vapor extraction system and air sparging is a new technology developed by Advanced Remedial Technology, Inc. The areas around chemical companies or waste disposal sites have been seriously contaminated from the chemicals and other polluting materials that are disposed off. The process developed by Advanced Remedial Technology, consists of a heater/boiler that pump and circulates hot oil through a one-inch pipeline that is enclosed in a six-inch pipe. This six-inch pipe is vertically installed within the contaminated soil up to a certain depth and is welded at the bottom and capped at the top. Pea gravel or fine sand fills the six-inch pipe and thus acts as a heat transfer medium. The number of heat source pipes and the extraction wells depends on the type of soil, the type of pollutants, moisture content of the soil and the size of the area to be cleaned. The heat source heats the soil, which is transported in the interior part of the soil by means of conduction and convection. This heating of soil results in vaporization of the gases, which are then driven out of the soil by the extraction well. The extraction well consists of the blower which would suck the vaporized gases out of the system. Soil vapor extraction cannot remove contaminants in the saturated zone of the soil that lies below the water table. In that case air sparging may be used. In air sparging system air is pumped into the saturated zone to help flush the contaminants up into the unsaturated zone where the contaminants is removed by SVE well. In our present study we concentrated on modeling one Heated Soil Vapor Extraction System with air sparging and predicting the behavior of different chemicals in the saturated and unsaturated zone of the soil. This analysis uses the species transport and discrete phase modeling to predict the behavior of different chemicals when it is heated and driven out by the sucking well.
Simulation of Magneto-Rheological Fluids Using Lattice Boltzmann Method
Authors: Yadav A. , Calhoun R. , Phelan P. E. , Vuppu A. K. , Garcia A. A. , Hayes M. A.
Published: April 2008

Lattice Boltzmann (LB) simulations of Magneto-rheological fluids under a rotating magnetic field are presented in this paper. The LB method gives a complete solution of Navier-Stokes equation based on the Boltzmann transport equation. A relatively good agreement of normalized number of aggregated particles in experiments and simulations is found. Results pertaining to variation of chain length vs. Mason number are also shown. A complete analysis and comparison of forces on the particles found from LB simulations and from simple Particle dynamics (PD) type approach is also shown. Another aim of this study was to determine under what conditions do we need to solve the complete Navier-Stokes equations and under what conditions a simplistic but very fast simulation method like particle dynamics will work for Magneto-rheological fluids.
Study on the Charging and Discharging Model of Ni/MH Battery Module for Electric Vehicle
Authors: Wang Junping , Chen Quanshi , Chen Hao
Published: April 2008

The parameters of the battery model are time varying because the influence of the State of Charge (SOC). It is difficult to determine the relation between the parameters of the battery model and the SOC. In this paper, the mended equivalent circuit model is adopted and the time-varying parameters of which are estimated based on the fuzzy inference according to the fuzzy input SOC. So the accuracy of the model is improved and the requirement of the estimation accuracy of SOC is reduced. The results of the simulation test show that the maximum absolute error of the loaded voltage of the Ni/MH battery module is 0.04V and the relative error is 0.28.
Predictive Model and Application of a Hybrid GSHP System for Space Conditioning, Water Heating and Deicing of a Seniors Independent Living Center
Authors: Wrobel Joseph R.
Published: April 2008

A parametric estimation algorithm is described for system design criteria selection in Ground Source Heat Pump (GSHP) Heating, Ventilation and Air Conditioning (HVAC) applications requiring dissipation of annual cycle excess thermal energy to the air, i.e., a hybrid mode. The model applies a combination of order-of-magnitude scaling (OMS) and classical non-dimensional flow and heat transfer methods. The objective is to develop a simplified parametric range display for selection of design values. Application requirements and constraints map into the solution space for specific design value selections. The annual thermal budget cycle is configured to time-phase the earth-stored excess energy from the cooling season for dissipation in the heating season using water to ambient forced-air (fan-coil) cooling. Estimators for an application are developed for the quantity, spacing and depth of well bores and the loop flow rate range based on Reynolds number and Nusselt number correlations for water and earth thermal properties. A case study application in two parts is described. The GSHP system uses a common working fluid (water) in a closed loop serving all 70 zones to furnish heating, cooling, domestic water heating, and exterior walkway deicing for an 80,000 sq. ft. area, 54 apartment, senior, center in Dallas Texas, USA. In 1999, the initial Phase I facility of 55,000 sq. ft. area was occupied using the full capacity flow system design without the dissipation coolers. In 2004 the coolers were included with the expansion to full occupancy. Design parameter values, operating experience, energy use, and the rationale for the demonstrated compatibility of the single solution for essentially two applications are described.
Intake Manifold Wave Dynamic Analysis and Its Effects on Volumetric Efficiency
Authors: Lee Seong-Beom , Kim Yong-Wha , Yang Woong-Chul
Published: April 2008

Accurate estimation/measurement of the air mass and recirculated exhaust gas (EGR) charged in each cylinder during spark ignited (SI) engine breathing process is the primary concern for proper control of air fuel (A/F) ratio. In many internal combustion engines, air meter is used to measure airflow in the upstream of the throttle body. The final cylinder air charge is estimated using this measurement being compensated to take care of the manifold first order dynamics. However, the pressure waves traveling in the manifold and runners introduce significant variation of the charged air in the individual cylinder with the engine speed and load variations affecting the engine volumetric efficiencies. In this paper, a detailed dynamic model of the intake manifold system is developed including wave dynamics. For wave dynamics, a modal approximation method is used to predict the detailed wave dynamic characteristics and to determine the effects on the volumetric efficiencies at various engine speeds and loads. Also, experimental data are presented validating the simulation results.
Performance of Fuel Cell and Engine Based Cogeneration Systems in Heating and Cooling Applications
Authors: Kowalski Gregory J. , Zenouzi Mansour
Published: April 2008

A generalized thermodynamic model is developed to describe cooling, heating and power generating systems. This model is based on reversible power generation and refrigeration devices with practical, irreversible heat exchanger processes provides valuable information on a system’s performance and allows easy comparisons among different systems at different loading conditions. Using both the first and second laws as well as the carbon dioxide production rate allows one to make a first order system assessment on its energy usage and environment impact. The use of the exergy destruction rate and insuring that its behavior be consistent with that of the first law performance is a important to insure that the thermodynamic system boundaries are correctly and completely defined. The importance of the total thermal load to required power ratio (HLRP) as a scaling parameter is demonstrated. While the reported results confirmed that generalized trends are not possible identify, a number of trends for limited conditions have been identified. The results have shown that a combined vapor compression/absorption refrigeration has higher first law utilization factors and lower carbon dioxide production rate for system with higher refrigeration to total thermal load ratios for all HLRP values. Fuel cell based subsystems outperform engine based subsystems for systems with large refrigeration loads.
A Rate-Independent Constitutive Model for Square Honeycomb Core
Authors: Xue Zhenyu
Published: April 2008

All-metal sandwich construction with square honeycomb core holds promise for significant improvements in stiffness, strength and blast resistance for built-up plate structures. Analysis of the performance of sandwich plates under various loads, static and dynamic, requires modeling of face sheets and core with some fidelity. While it is possible to model full geometric details of the core for a few selected problems, this is unnecessary and unrealistic for larger complex structures under general loadings. A continuum constitutive model is recently developed as alternative means of modeling the cores. The constitutive model falls within the framework of a compressible rate-independent, anisotropic elastic-plastic solid. A multi-scale computing approach based on it has been developed for modeling the sandwich structures. The validity of the approach is established by comparing numerical finite element simulations using the model with those obtained by a full three-dimensional meshing of the core geometry for a clamped sandwich plate with square honeycomb core subject to uniform pressure load. Limitations of the model are also discussed.
Analysis and Identification of Chaotic Dynamics in a Flying Vibratory System
Authors: Liang Jin-Wei , Chen Shy-Leh , Yen Ching-Ming
Published: April 2008

This paper aims at determining whether chaotic dynamics exist in a flying vibratory system. It is important to identify chaotic behavior in a flying system since it may jeopardize the structure of the flying object and cause instability subsequently. It can also cause uncomfortable experience for passengers in a passenger airplane or inaccurate targeting for a missile. Identification of chaotic dynamics from experimental time series is a nontrivial task, since the data is likely to be contaminated with random noise that possesses similar properties to chaos. In this work, acceleration signals were measured at nine different locations or orientations of the flying object during a test fly. Steady-state acceleration signals were extracted and analyzed. The analysis is based on the pseudo phase-space trajectories reconstructed from the experimental time series using the method of delays. Two indices, the correlation dimension and the maximum Lyapunov exponent, are employed to identify the chaotic behavior and to distinguish it from random noise. In general, the correlation dimension calculated from the pseudo trajectory depends on the embedding dimension. It is found in three of the nine-channel signals that the correlation dimension saturates when the embedding dimension is larger than a critical value. The critical embedding dimension is the minimum dimension required for fully un-stretching the phase-space trajectories. This phenomenon indicates a possible existence of chaotic dynamics. It is also found that the maximum Lyapunov exponents calculated from the same acceleration signals are all positive, which further verifies the possibility of the existence of chaotic motion. In addition, some computational issues regarding the embedding dimension, correlation dimension, and maximum Lyapunov exponent are discussed in this paper.
Energetic and Exergetic Evaluation of Double-Stage/Double-Effect Metal Hydride Heat Pumps
Authors: Kapadia R. G. , Jain S.
Published: April 2008

This paper presents the energetic and exergetic evaluation of double-stage/double-effect metal hydried heat pumps (MHHP) emloying three different alloys. The operating temperatures and pressures are chosen so that the MHHP operates in the double-effect mode, i.e delievers both heating and referigeration effects. Results are obtained for seven different cases in terms of coefficient of performance for cooling (COP), coefficient of performance for heating (COA) and exergy loss or entropy generation. The COP and COA for a realistic case is equal to 0.65 and 0.92 and exergy loss is equal to 44%.
Fatigue Assessment of Tubular Automotive Components in Presence of Inhomogeneities
Authors: Beretta Stefano , Desimone Herna´n Juan , Poli Andrea
Published: April 2008

Tubular automotive components, e.g. stabilizers and half shafts, are components subjected to fatigue. In order to assess fatigue behavior of such components, it is important to know both the real load conditions as well as the material strength against multi-axial fatigue. For the second point, a detrimental effect in the fatigue limit of high strength steels is given by the defects present in the component, coming from the material (such as microinclusions, microvoids, etc) or for the process (e.g. handling marks). An integral approach in order to assess fatigue limit of tubular components is proposed. The attention is focused onto planar inhomogeneities, which are the most common in tubular products, though the methodology can be extended to different defect-shapes. The method is applied together with a probabilistic model, in order to analyze the probability of failure. In particular, two different processes (in terms of inhomogeneities present in the final component) are compared, and the results allow to evaluate, for example, the admissible load for the desired (or design) level of failure probability for the component.
A Comparison of Generator Mode on the Performance of Finish EDM of AISI P20 Tool Steel
Authors: Amorim Fred L.
Published: April 2008

The AISI P20 steel is applied by the tooling industry as material for injection molding tools. It is known that the EDM process parameters technology installed at the majority of CNC EDM machines do not cover some of the necessities of the tooling industry. So, the customers are required to develop their own process parameters. In order to provide useful technical information to the industry an experimental investigation on the EDM of the AISI P20 tool steel under finish machining has been carried out. The material removal rate Vw, volumetric relative wear v and workpiece surface texture Ra, which are representative of EDM performance aspects, were analyzed against the variation of some of the most important EDM electrical variables using copper tool electrodes under positive and negative polarity. The EDM machine generator was also programmed to actuate under isoenergetic mode and relaxation mode. The results are discussed and some appropriate parameters for EDM of AISI P20 are suggested.
Mixed-Sensitivity H∞ Control and µ Analysis of Active Automobile Suspension
Authors: Porumamilla Hemanth , Kelkar Atul G.
Published: April 2008

This study presents an H∞-based robust control design for an active automobile suspension system and compares its performance with a previously designed robust LQG controller and a well tuned PI controller from contemporary literature. The robustness of the controller designs is assessed by performing μ analysis of the closed loop system. The H∞ problem is formulated as a stacked nominal performance problem. The weighting functions on complementary sensitivity, sensitivity, and controller transfer functions are chosen to obtain desirable trade-off in performance and robustness. The main objective of the controller design is to provide ride comfort for passengers. The controller design presented in this paper is shown to provide robust stability as well as desirable robust performance which is an improvement over the previously designed robust LQG controller and a PI controller chosen from contemporary literature.
Engineering Techniques for the Forensic Analysis of Visibility Conditions
Authors: Kimbrough Scott
Published: April 2008

Many times forensic engineers are asked to evaluate the visibility of objects involved in accidents. For example they might be asked to determine if a pedestrian should have been visible to the driver of an oncoming car. The visibility of an object depends on the relative size of the object in the visual field, the level of ambient lighting, the contrast between the object and its surroundings, and whether glare sources are present. Equations and results based upon empirical studies can be used to access visibility using these factors. This paper outlines the basic tools of visibility analysis and presents a case study to illustrate their application.
Accurate Rail Vehicle Dynamic Simulations by DynaRail
Authors: Sany Jalil R.
Published: April 2008

A general purpose rail vehicle dynamic simulation tool has been developed at CAM (Center for Automated Mechanics). This tool allows the user to start any rail vehicle dynamic simulation with measured wheel and rail profile data without a need for generating pre-cooked wheel/rail contact geometry tables. Using the constrained multibody methods, the tool robustly solves the three dimensional wheel/rail interaction problem and computes the longitudinal, lateral and vertical locations of 1st and 2nd contacts, the sizes of all Hertzian contact areas, rolling radii, contact angles, normal reactions, the creepages and their associated forces and moments online and makes all the details available as outputs to the user for subsequent analysis and validation of the solution. The purpose of this study is to demonstrate the ability of the tool for predicting the detailed responses of the rail vehicle systems. For all simulations, in addition to the detailed contact reactions, the precise positions of all contacts in three-dimensional space are readily solved for and available for further considerations. This is an application paper and intends to introduce the railroad engineers and consultants to a tool that is capable of fulfilling their simulation and modeling needs for complex rail/vehicle systems. Such needs are not commonly provided by the specialized codes and very hard for the railroad engineers to fulfill them using other general purpose codes. DynaRail is particularly useful to the wheel/rail profile designers who may be concerned with the continuous movement of the contact point at an unprecedented accuracy. The online prediction and imposition of the contacts makes it possible to systematically include and consider the effect of the contact movements on its associated contact geometry variables such as the size of contact ellipses, rolling radii, contact angles and, ultimately the effect of all these on the stability and/or the resulting motion of wheel on rail.
Dynamics of Contact Angle During Growth and Liftoff of Bubbles at a Single Nucleation Site in Flow Boiling
Authors: Jia Wangcun , Dhir Vijay K.
Published: April 2008

Contact angle is a critical parameter needed in the mechanistic models for the prediction of flow boiling heat transfer. In this paper, variations of upstream and downstream contact angles for a single vapor bubble in flow boiling on horizontal and vertical surfaces were investigated experimentally. The nucleation site is a well-characterized cavity, which was etched on a highly polished silicon wafer surface using micro-fabrication techniques. Water at one atmosphere pressure was used as the working fluid. Photographic images of the bubble were recorded during its inception, growth and liftoff by using high-speed video system and analyzed by an image-processing program. The results provide clean data on the dependence of upstream and downstream contact angles on surface orientation and flow velocity.
Adaptive Control and Monitoring Using the Spindle Integrated Force Sensor System
Authors: Park Simon S. , Altintas Yusuf
Published: April 2008

Applications of spindle integrated force sensors are examined where the cutting forces are reconstructed from the piezoelectric force sensors that are imbedded in the spindle housing. The reconstruction of the cutting forces using the disturbance Kalman filter effectively provides the high bandwidth sensor requirements. The three applications that are presented in this paper are Adaptive Control with Constraint (ACC), chatter detection, and tool breakage detection, all using the spindle integrated sensors. ACC provides effective means of increasing machining productivity through the adjustment of feed rates by constraining cutting forces. The detection of chatter vibration in machining operations is important in order to ensure quality surface finishes. The cutting forces measured from the spindle sensors provide sufficient information as to whether the cutting operations are stable or not. Tool breakage detection is performed using both a good tool and a damaged tool. Two residual indices based on the first order auto-regressive (AR) filter are examined to determine tool breakage. The experiments verify the successful monitoring strategies using the spindle integrated force sensors.
Forming Process of Taylor Vortex Flow of Polymer Solutions
Authors: Sumio Shu , Watanabe Keizo , Ogata Satoshi
Published: April 2008

The laser-induced fluorescence (LIF) technique carried out the flow visualization for the formation of Taylor vortex, which occurred in the gap between the two coaxial cylinders. The test fluids were tap water and glycerin 60wt% solution as Newtonian fluids. Polyacrilamide (SeparanAP-30) solutions in the concentration range of 10 ppm to 1000 ppm and polyethylene-oxide (PEO15) solutions in the range of 20 ppm to 1000 ppm were tested as non-Newtonian fluids, respectively. The Reynolds number range was 80 < Re < 4.0 × 103 in the experiment. The rotating inner cylinder was accelerated under the slow condition (dRe*/ dt ≤ 1 min−1) in order to obtain a Taylor vortex flow of the stable primary mode. Flow visualization results showed that the Go¨rtler vortices of half the number of Taylor cells occurred in the gap when Taylor vortex flow of the primary mode was formed. In addition, the critical Reynolds number of the polymer solutions case, which Taylor vortices occur, because the generation of the Go¨rtler vortices was retarded. At the higher concentration of the polymer solutions, this effect became remarkable. Measurements of steady-state Taylor cells showed that the upper and the lower cells of polymer solutions became larger in wavelength than that of the Newtonian fluids. The Taylor vortex flow of non-Newtonian fluids was analyzed and the result of the Giesekus model agreed with the experimental result.
Shape Memory Alloy Springs Used as Reduced Power/Weight Actuators
Authors: Knowles Gareth , Bird Ross , Birman Victor
Published: April 2008

The paper presents a concept and realization of using shape memory alloy (SMA) spring actuators for deployment of flight control surfaces of small air vehicles. These actuators replace heavy servomotors resulting in increased endurance of the vehicle as well as reduced power consumption. The actuator represents a spiral wound tubular SMA helical spring that is extended in its martensitic phase prior to actuation. The actuation can be achieved by directing exhaust gas from the onboard engine, i.e. providing an influx of heat. When activated, the spring returns to its original (compressed) shape generating a force in the range of 10 to 25 lbf. The advantage of using SMA springs is related to the enhanced stiffness after activation, as the material transforms from the martensitic to austenitic phase. Such added rigidity is useful to deploy telescoping wing surfaces and implement extensive geometric airframe changes. Numerical examples conducted with a typical spring material and geometry illustrated that the required stroke can be achieved with the spring index of about 10, coil diameter of 2.5 inches and SMA diameter in the range from 0.14 to 0.24 inches. Experimental data confirms these numerical predictions. The present study has proven the feasibility of using SMA actuators for the deployment of wing surfaces of small air vehicles.
Substructuring Dynamic Modeling and Active Vibration Control of a Smart Parallel Platform
Authors: Wang Xiaoyun , Mills James K.
Published: April 2008

A substructuring approach to derive dynamic models for closed-loop mechanisms is applied to model a flexible-link planar parallel platform with Lead Zirconate Titanate (PZT) transducers. The Lagrangian Finite Element (FE) formulation is used to model flexible linkages, in which translational and rotary degrees of freedom exist. Craig-Bampton mode sets are extracted from these FE models and then used to assemble the dynamic model of the planar parallel platform through the application of Lagrange’s equation and the Lagrange multiplier method. Electromechanical coupling models of surface-bonded PZT transducers with the host flexible linkages are introduced to the reduced order dynamic models of flexible linkages. The assembled system dynamic model with moderate model order can represent essential system dynamic behavior and maintain kinematic relationships of the planar parallel platform. A Proportional, Integral, and Derivative (PID) control law is used as the motion control law. Strain rate feedback (SRF) active vibration control is selected as the vibration control law. Motion control simulation results with active vibration control and simulation results without active vibration control are compared. The comparison shows the effectiveness of active vibration control.
A Modular Wing-Tail Airplane Configuration for the Educational Wind Tunnel Laboratory
Authors: Beck B. Terry
Published: April 2008

An innovative modular airplane configuration has been developed for use in small-scale educational wind tunnels. The “airplane” consists of an interchangeable wing and horizontal tail configuration that mounts on a conventional wind tunnel electronic balance (“sting”) to facilitate measurements of normal force, axial force and longitudinal pitching moment. From these basic parameters, the total lift, total drag, and resultant airplane pitching moment can be deduced, along with the location of the aerodynamic center of the total airplane. Using known wing planform and airfoil shapes facilitates comparison of the total airplane aerodynamic characteristics with those predicted from the known characteristics of the separate wing and horizontal tail. In particular, the aerodynamic center of the simplified airplane configuration can be determined, along with the effect that downwash on the tail has on longitudinal stability of the airplane. Included in the paper is a description of the calibration procedure for the modular “sting” mount. This procedure accounts for an offset “line of action” for aerodynamic forces, as well as offset center of gravity effects. In conjunction with this same test setup, an available Rapid Prototyping system has been used to manufacture the test sections (separate wing and tail) for use in the wind tunnel, and in particular, in the modular wing-tail assembly. This provides tremendous flexibility in the types of wing-tail assemblies that can be investigated experimentally using the same module. The relatively inexpensive prototyping procedure also provides the capability for students to design and test their own configurations. Furthermore, the precision manufacturing capability of the Rapid Prototyping system guarantees reliable reproduction of virtually any desired aerodynamic planform and airfoil shape.
Enhancing the Teaching and Practice of Finite Element Analysis Using Asynchronous Computer-Based Instruction
Authors: Fuentes Arturo A. , Crown Stephen
Published: April 2008

Most engineering educators face complex, dynamic, pedagogical/cultural issues while teaching students. These issues include student motivation for the subject and self-direction, retention of information, integration of knowledge and adaptive expertise, and performance in projects and evaluations. They can be addressed by introducing modern learning strategies, expanding both the disciplinary breadth and the range of problems and problem-solving techniques to which engineering students are exposed, incorporating research experiences in the classroom, and effectively integrating the powerful software tools used in engineering practice. However, class time is limited and is usually overfilled with theory and fundamentals. This paper describes finite element analysis (FEA) computer-based instruction, which requires a limited amount of class time, that is currently providing an ideal context for learning and building student confidence. It consists of an integrated website with links to FEA software tutorials, FEA study cases and research projects, supplemental lecture notes, homework assignments and solutions, and sample exams and exam solutions. The FEA software tutorials include instruction on Algor and Visual Nastran. Furthermore, a cross-linked taxonomy of the course content and computer-based instruction is presented along with delivery examples.
Effects of Endplate Curvature on Stresses in a Vertebral Motion Segment: Finite Element Analysis
Authors: Kale Shreedhar P. , Langrana Noshir A. , Edwards Thomas
Published: April 2008

The vertebral endplates of the lumbosacral spine have various degrees of concavity and/or convexity. Several investigators including Seenivasan G., Goel, V. K., 1994, Liebschner et al, 2003, etc have performed finite element analysis on the vertebral bones, but the endplate curvatures are not included. Therefore, the effect of morphological details of the endplate curvatures on the stress distribution is unknown. Differences in these curvatures will increase stress in some regions and decrease stress elsewhere as the spine is compressed. In our previous study [Kale et al, 2003], lumbar vertebral endplate curvatures in the anterior-posterior and medial-lateral directions on human cadaver lumbar vertebrae were measured. The measurements were carried out using a reverse engineering instrument, built at Rutgers University [Hsieh et al, 2002]. Six sets of measurements (on human male-female L4 lower to S1 upper endplates) were performed. The data was later used in a linear elastic cylindrical model containing cortical shell and trabecular core. The model then was modified to a more accurate model, with more realistic, characteristic kidney shaped cross section (obtained from equation by Mizrahi et al, 1993) and linearly varying height. The endplates were assigned curvatures extracted from our human cadaver data. FEA, done on both the models, showed that the endplate curvatures and their location had significant effect on the stress distribution in the vertebral bone. In the current study we have extended our bone model into a motion segment and have investigated the effects of the curvatures on the stresses in the motion segment.
Numerical Simulations of Heat Transfer Problems Using an Immersed Boundary Method on Non-Staggered Grids
Authors: Pacheco J. Rafael , Rodic Tamara , Pacheco-Vega Arturo , Peck Robert E.
Published: April 2008

This paper describes the use of the immersed boundary technique for simulating fluid flow and heat transfer problems over or inside complex geometries. The methodology is based on a fractional step method to integrate in time. The governing equations are discretized and solved on a regular mesh with a finite volume non-staggered grid technique. Several phenomenologically different fluid flow and heat transfer problems are simulated using the technique proposed in this study. The accuracy of the method is second-order, and the efficiency is verified by favorable comparison with previous numerical and experimental results.
Magnesium V-Process Casting: Part I — CFD Simulations and Experimental Casting
Authors: Bakhtiyarov Sayavur I. , Overfelt Ruel A. , Palomar Pardave Manuel Eduardo
Published: April 2008

Given the rapid projected growth of magnesium casting usage in the automotive parts marketplace, there is a critical need to develop casting technologies applicable for a wide variety of part shapes, sizes, and production rates. The application of magnesium components will allow reduction in vehicle weight, improvement of parts-consolidation and minimization of noise/vibration characteristics. Magnesium is considered the fastest-growing metal in cars. Many of the earliest applications are instrument panel components, valve covers, etc. These are produced by a reasonably mature diecasting technology. Many potential structural components for automobiles could be converted to magnesium if a high volume, cost effective manufacturing process were developed. In this paper we propose a modified vacuum-sealed molding process for magnesium casting. Some results of computer modeling and design of experimental research are presented.
Magnesium V-Process Casting: Part II — Electrochemical and SEM Analyses for Corrosion Testing
Authors: Palomar Pardave Manuel Eduardo , Bakhtiyarov Sayavur I. , Overfelt Ruel A.
Published: April 2008

The corrosion testing of precision sand and V-process cast magnesium specimens was carried out in a typical three-electrode electrochemical cell, where the working electrodes were made with each of the alloy samples. The reference electrode was the saturated calomel electrode (SCE). The counter electrode was a graphite rod, and the electrolyte was a 0.85 M NaCl aqueous solution (pH 7). Two electrochemical methods were used: potentiodynamic scan and Tafel plots. The working electrode potential was controlled with a potentiostatgalvanostat PAR EG&G 273 coupled to a PC running the SoftCorr II software, which allows the experimental control and data acquisition. The measurements demonstrated that the sand cast magnesium specimen is more susceptible to corrosion, in this medium, compared with the V-process cast sample.
Thermally Driven Mechanical Actuators by Using Absorption/Desorption of Metal Hydrides: A Comprehensive Simulation
Authors: Lloyd George M. , Kim Kwang J. , Xia K. , Razani A. , Shahinpoor M.
Published: April 2008

Metal hydrides have been investigated for use in a number of applications, such as heat regenerators, thermal compressors, and hydrogen storage. McKibben actuators are pneumatic actuators that have unique characteristics, such as biomimeticity (having force/deflection characteristics similar to natural muscles), compactness, high force-to-mass ratios, and moreover are lubricationless, noiseless, soft actuating, and environmentally benign. Actuators with these characteristics are ideal for many industrial, space, defense, robotic, and biomedical applications. The combination of metal hydride technology with McKibben actuators builds on the advantages of both technologies, while mitigating the deficiencies of each. In this paper, we report results from a comprehensive simulation strategy for a LaNi4.3Al0.7 based McKibben actuator. The simulations are able to predict and characterize the performance bounds of the actuator in terms of actuator time/thermal input, power/efficiency and force/displacement diagrams. The advantages and disadvantages of the design are discussed from these perspectives.