bluuebunny/crossref_metadata_2025 huggingface dataset:
Virtual Five-Axis Flank Milling of Jet Engine Impellers: Part 1 — Mechanics of Five-Axis Flank Milling
Authors: Ferry W. , Altintas Y.
Published: May 2009

Jet engine impeller blades are flank-milled with tapered, helical, ball-end mills on five-axis machining centers. The impellers are made from difficult-to-cut titanium or nickel alloys, and the blades must be machined within tight tolerances. As a consequence, deflections of the tool and flexible workpiece can jeopardize the precision of the impellers during milling. This work is the first of a two part paper on cutting force prediction and feed optimization for the five-axis flank milling of an impeller. In Part I, a mathematical model for predicting cutting forces is presented for five-axis machining with tapered, helical, ball-end mills with variable pitch and serrated flutes. The cutter is divided axially into a number of differential elements, each with its own feed coordinate system due to five-axis motion. At each element, the total velocity due to translation and rotation is split into horizontal and vertical feed components, which are used to calculate total chip thickness along the cutting edge. The cutting forces for each element are calculated by transforming friction angle, shear stress and shear angle from an orthogonal cutting database to the oblique cutting plane. The distributed cutting load is digitally summed to obtain the total forces acting on the cutter and blade. The model can be used for general five-axis flank milling processes, and supports a variety of cutting tools. Predicted cutting force measurements are shown to be in reasonable agreement with those collected during a roughing operation on a prototype integrally bladed rotor (IBR).
Application of an Intelligent Hybrid Optimization Technique for Parameter Estimation in the Presence of Colored Noise
Authors: Ramkumar Barathram , Schoen Marco P. , Lin Feng
Published: May 2009

Parameter estimation is an important concept in engineering where a mathematical model of a system is identified with the help of input and output signals. The Classical Least Squares (LS) algorithm gives an unbiased estimate of the parameters when the system noise is white. This property is lost when the system noise is colored — which is generally the case. In order to overcome the bias problem associated with the colored noise environment, one can use a whitening filter. The cost function in the case of a colored noise environment becomes multimodal when the signal to noise ratio is high and hence some intelligent optimization technique is required to find the global minimum. A new hybrid algorithm combining intelligent optimization techniques is proposed. This algorithm includes Enhanced Continuous Tabu Search (ECTS) and an elitism based Genetic Algorithm (GA) which is applied to the parameter estimation problem. ECTS is a modified version of Tabu Search (TS) applied to continuous functions and has an advantage of covering large search spaces. GA is an evolutionary algorithm that has a better convergence towards the optimum solution. The hybrid algorithm combines the respective strengths of ECTS and GA. Simulation results show that the parameters estimated using the proposed algorithm is unbiased in the presence of colored noise.
Fault Detection for a Class of Nonlinear Systems in Presence of Unmodeled Dynamics and Parametric Uncertainties Using Adaptive Robust Observers
Authors: Gayaka Shreekant , Yao Bin
Published: May 2009

The goal of this work is to present some theoretical results which can be used for increasing fault sensitivity of a detection scheme, without sacrificing robustness. Robustness against modeling uncertainties and fault sensitivity are two contradicting demands, and typically, one is achieved at the expense of the other. The main reason for this trade-off is the use of a worst case scenario bound for modeling uncertainties at the residual evaluation stage. Many robust fault detection algorithms have been proposed based on the assumption that an a priori known functional bound exists for modeling uncertainties. In the present work, we look into the two main sources of modeling uncertainties, parametric uncertainties and unmodeled dynamics, and carefully examine their effect on residual evaluation. Finally, based on our analysis, and certain assumptions about the unmodeled dynamics and parametric uncertainties, we propose a threshold for residual generation and evaluation, and analytically prove its superior robustness and sensitivity properties.
Forced Convection in a Uniformly Heated Enclosure: Effect of the Inlet and Two Outlet Port Locations
Authors: Botello-Arredondo A. I. , Hernandez-Guerrero A. , Rubio-Arana C. , Picon-Nun˜ez M.
Published: May 2009

In an earlier study, Saeidi and Khodadadi presented results on forced convection inside a square cavity with one inlet and one outlet ports. Their most effective design showed maximum heat transfer and minimum pressure drop for a particular location of the ports. In the present study a cavity with one inlet and two outlet ports is considered, and different conditions and geometric arrays for the position of the ports are analyzed. The cold incoming fluid is heated by the isothermal hot walls. The outlet ports are positioned at forty-five different locations on the walls. A Reynolds number range of 10 < Re < 500 is considered, clearly within the laminar regimen. The flow and temperature fields are obtained as part of the solution. As expected, an increment of vorticity brought a heat transfer enhancement. The effect of the outlet ports and their location is discussed.
A Study on Bearing Creep Mechanism With FEM Simulation
Authors: Zhan Jianjun , Takemura Hiromichi , Yukawa Kinji
Published: May 2009

Because of the continuous quests for high performance and compact structure of automobile and machine in recent years, rolling bearings are required to work under harder conditions of high speed and heavy load than before. The applications of hard condition may lead to a greater likelihood of happening of bearing malfunctions such as flaking, wear, creep, fracture etc. In this paper, the phenomenon called outer ring creep occurring in bearings subject to non-rotating load is discussed. Outer ring creep is referred to that bearing outer ring rotates relatively to the housing in certain applications. Outer ring creep may result in such problems as unusual noise and vibration and may cause wear of housing and outer ring. If abrasive particles caused by wear of the ring and housing enter the raceway, the bearing may be damaged and destroyed. Conventionally, the problem of outer ring creep was considered to be a result of rotating bearing load. However, even if the direction of radial load remained relatively unchanged, outer ring creep is observed in many cases. The generation mechanism of this kind of outer ring creep has not yet been made clear till now. With FEM simulation and test verification, we analyzed the phenomenon of outer ring creep under non-rotating load. We concluded that outer ring creep under non-rotating load is a result of localized strain and rippling deformation caused by rolling elements. In this paper, only outer ring creep is discussed below, but the similar result can be obtained for inner ring creep.
Model-Based Unbalance Estimation for Steam Turbine-Generators
Authors: Yang Tachung , Koai Kwang-Lu , Lin Chun-Yi , Xu Wen-Ming
Published: May 2009

As demanded for parameter estimation based on the measured signals, a model-based method to estimate the unbalance distribution of steam turbine-generators due to unbalance response was proposed in this paper. The equivalent modal damping ratios for each mode estimated by GA from the measured Bode plots are incorporated into the modal models. A finite number of the modes are used to calculate the influence coefficient matrix. Finally, the equivalent unbalance distribution on the selected correction planes is estimated based on the measured responses. The merit of this approach is that no test run of trial mass is required. The feasibility of this method is demonstrated using a steam turbine-generator. The method presented not only provides a useful means for balancing work, but also can be further developed into an identification and diagnosis tool.
A Fast Method for Conjugate Heat Transfer Analysis of Centrifugal Compressor
Authors: Lei Vai-Man , Kawakubo Tomoki
Published: May 2009

The capability to calculate impeller temperature distribution is important to the life estimation of a centrifugal compressor. Three dimensional conjugate heat transfer (3D CHT) analysis with a high fidelity flow solver has become an indispensable tool for this class of problem. However, the application of 3D CHT analysis in the preliminary design of centrifugal compressor, which may involve the rapid evaluation of a large number of different configurations, is limited by the computation resource and setup time requirement. This paper presents a method of conjugate heat transfer analysis for centrifugal compressor design that requires significantly less computation power and setup time. The method, which consists of a one-dimensional flow model of the gas path and an axisymmetric CHT/flow solver, has been evaluated with data from 3D CHT analysis and experiment. Good agreement in impeller temperature distribution, as well as in impeller temperature trends due to changes in operating condition are obtained. To demonstrate the application of this method, various strategies to lower the impeller temperature are evaluated and discussed.
The Performance Estimation of a Landing Gear With In-Service Variations
Authors: Kim Tae-Uk , Shin Jeong Woo , Hwang In Hee
Published: May 2009

The performance estimation of a landing gear with uncertain parameters is presented. In actual use, many parameters can have a certain amount of variations which affect the overall performance of impact energy absorption. For example, the shock strut gas pressure, oil volume, tire pressure and temperature can have deviations from their nominal values. The objective function in this research is the ground reaction during the aircraft’s touchdown which is a function of the above-mentioned parameters and time. To consider the uncertain properties, the convex modeling and interval analysis are used in calculating objective function. The numerical results show that the ground reaction characteristics are quite different from those of the deterministic method. The peak load, which affects the overall efficiency and the structural integrity, is considerably increased when the uncertainties considered. Therefore, it is important to consider the possible uncertainties and the proposed methodology can be an efficient way to estimate the effect of such uncertainty.
Swing Reduction of Ropeway Carriers by Means of Two-Ball Rolling Type Damping Equipment: 2nd Report — Way to Implement Desired Damping for Two-Ball System
Authors: Sato H. , Chishima M.
Published: May 2009

To enhance transport safety and reliability of ropeway systems, it is essential to reduce the swing of the carriers that results from wind, etc. In the previous report [1], we provided a practical damping equipment using two rolling balls (hereinafter described as “two-ball rolling type damping equipment”) to reduce the swing of ropeway carriers. A linearized dynamic model is proposed. Then, on the basis of relevant parameters, the frequency response and time domain response of the system is studied and discussed. In this report, we will study relationship between theoretical best damping coefficient ratio and friction coefficient of two-ball system. Then we will provide the way to implement the desired damping for the two-ball system. We will then provide the detail on how to estimate the inherent damping within the two-ball system. In addition, we will show and discuss two balls behavior when this equipment works experimentally.
Numerical Calculation of Shear Stress Distribution on the Inner Wall Surface of CANDU Reactor Feeder Pipe Conveying Two-Phase Coolant
Authors: Jo Jong Chull , Kang Dong Gu , Roh Kyung Wan
Published: May 2009

Two-phase flow fields inside feeder pipes of a CANDU reactor have been simulated numerically using a CFD (computational fluid dynamics) code to calculate the shear stress distribution which is the most important factor to be considered in predicting the local areas of feeder pipes highly susceptible to FAC (flow-accelerated corrosion)-induced wall thinning. The CFD approach with schemes used in this study to simulate the turbulent flow situations inside the CANDU feeder pipes had been verified by showing a good agreement between the investigation results for the failed feedwater pipe at Surry Unit 2 plant in U.S. and the CFD calculation. Sensitivity studies of the three geometrical parameters such as angle of the 1st and 2nd bends, length of the 1st span between the grayloc hub and the 1st bend, and length of the 2nd span between the 1st and the 2nd bends had already been performed. In this study, the effects of void fraction of the primary coolant coming out from the exit of pressure tubes containing nuclear fuels on the fluid shear stress distribution at the inner surface of feeder pipe wall have been investigated to find out the local areas of feeder pipes conveying two-phase coolant, where are highly susceptible to FAC (flow-accelerated corrosion)-induced wall thinning. As the results of CFD analysis, it is seen that the local regions of feeder pipes of the operating CANDU reactors in Korea, on which the wall thickness measurements have been performed so far, are not coincided with the worst regions predicted by the present CFD analysis where is the connection region of straight & bend pipe near the inlet part of the bend intrados. Finally, based on the results of the present CFD analysis a guide to the selection of the weakest local positions where the measurement of wall thickness should be performed with higher priority has been provided.
Reproducible Reliable AuSi Eutectic Wafer Bond Process With High Yield
Authors: Schwerdtner R. , Wiemer M. , Froemel J. , Gessner Th.
Published: May 2009

The AuSi eutectic bond process is a well known and important technique in the field of single chip packaging. When it comes to low-cost and hermetic sealed packages for MEMS/NEMS sensors and actuators this technology has its decisive merits. The AuSi bonding is a low-temperature process with an electric conductive alloy. To achieve a reliable bonding with 100% yield is quite difficult, especially for large areas. In our institute we made several analyses with different process parameters and surface properties variations. The results show that the surface condition of the silicon side of the wafer pair as well as the process parameters are very important factors in relation to the yield of the eutectic bond. We also did investigations on the thickness of the gold layer. Unlike conventional AuSi wafer bonding technologies [1] our technique does not need several μm thick gold layers. We were able to achieve 100% bond yield with 1500nm and even 150nm thin gold layers. Another result we found was that a good bonding process is not only depending on the value of applied temperature and time, there is also an important influence because of the heat flow and applied pressure. In the presentation we would like to introduce our results and experience, plus we will present the coherences of parameter variations for achieving 100% yield.
Influence of Pulse Repetition Rate on Cavitation at the Surface of an Object Targeted by Lithotripter Shock Waves
Authors: Pishchalnikov Yuri A. , Kaehr Mark M. , McAteer James A.
Published: May 2009

Stone breakage in shock wave lithotripsy is improved by slowing the rate of shock wave (SW) delivery. Previous studies have shown that increased cavitation at fast pulse repetition frequency (PRF) reduces the tensile phase of the SW, while the leading positive wave is virtually unaffected. Since the tensile component of the SW drives cavitation, and since cavitation at the stone contributes to breakage, it seems likely that increased cavitation along the path to the stone affects cavitation at the stone. Here we present preliminary data suggesting that PRF influences bubble dynamics at the stone. High-speed imaging showed that as PRF increased, bubble density of cavitation clouds increased, and the size of individual bubbles decreased. A new method to measure stresses generated by cavitation was used to show that locally induced stresses from bubble collapse can be greater than the incident SW, and were higher at 0.5Hz than at 2Hz PRF.
Natural Convection From a Buried Pipe With a Superimposed Fluid Layer
Authors: Ngo C. C. , Lai F. C.
Published: May 2009

Heat transfer induced by buoyancy from a pipe buried in a semi-infinite porous medium with a superimposed fluid layer has been numerically examined in this study. Due to the complexity involved, finite difference method along with body-fitted coordinate systems has been employed. The Brinkman-extended Darcy equations are used to model flow in the porous medium while Navier-Stokes equations are used for the fluid layer. The conditions applied at the interface between the fluid and porous layers are the continuity of temperature, heat flux, normal and tangential velocity, shear stress and pressure. A parametric study has been performed to investigate the effects of Rayleigh number, Prandtl number, Darcy number, and fluid layer thickness on the flow patterns and heat transfer rates. The results show that heat transfer increases with the Rayleigh number, but the convective strength decreases with the Darcy number. The heat transfer rate is smaller when the superimposed fluid is air instead of water. For a porous layer with Da ≤ 0.0005 and an overlaying fluid layer thickness of L/ri ≥ 1, convection is initiated in the fluid layer and it may develop into multiple recirculating cells at a moderate Rayleigh number (i.e., Ra ≤ 104), and may further develop into a single cell at a higher Rayleigh number of 105.
Rough Terrain Mobile Robot Localization Using Stereovision
Authors: Milella Annalisa , Reina Giulio
Published: May 2009

Mobile robots are increasingly being used in high-risk rough terrain situations, such as reconnaissance, planetary exploration, safety and rescue applications. Conventional localization algorithms are not well suited to rough terrain, since sensor drift and the dynamic effects occurring at wheel-terrain interface, such as slipping and sinkage, largely compromise their accuracy. In this paper, we follow a novel approach for 6-DoF ego-motion estimation, using stereovision. It integrates image intensity information and 3D stereo data within an Iterative Closest Point (ICP) scheme. Neither a-priori knowledge of the motion and the terrain properties nor inputs from other sensors are required, while the only assumption is that the scene always contains visually distinctive features, which can be tracked over subsequent stereo pairs. This generates what is usually referred to as visual odometry. The paper details the various steps of the algorithm and presents the results of experimental tests performed with an all-terrain rover, proving the method to be effective and robust.
Cascade Blade Loading Analysis With Application to Turbomachinery Design
Authors: Pampreen Ronald C.
Published: May 2009

The efficient performance of a compressor or pump over a desired stall-free operating range is related to the fluid mechanic loading on the rotating and stationary blades. This loading is a function of the suction and pressure surface velocities and is commonly referred to as aerodynamic (compressors) or hydraulic (pumps) loading. Overall values of maximum limits have been established in design practice as a result of development work. However, the distribution of loading has not been well established. One source of guidance is the database provided by cascade data. Velocity distributions are available, and from this data, blade loading coefficients can be calculated with the intent of applying the results to blade design. In this paper, the blade loading equation is derived to illustrate the principal factors that influence blade loading. These factors include blade number, blade wrap angle, blade length, and the magnitude of the average velocity between blades as determined by flow path contours and blade thickness. The equation gives the designer the ability to make design adjustments to achieve proper loading distribution within recommended values of maximum loading. The review of the cascade data provides the designer with a reference for allowable design distribution and maximum loading limits.
Flows in Rotating Cylinders With a Porous Lining
Authors: Subotic M. , Lai F. C.
Published: May 2009

Flow and temperature fields in an annulus between two rotating cylinders have been examined in this study. While the outer cylinder is stationary, the inner cylinder is rotating with a constant angular speed. A homogeneous and isotropic porous layer is press-fit to the inner surface of the outer cylinder. The porous sleeve is saturated with the fluid that fills the annulus. The Brinkman-extended Darcy equations are used to model the flow in the porous layer while Navier-Stokes equations are used for the fluid layer. The conditions applied at the interface between the porous and fluid layers are the continuity of temperature, heat flux, tangential velocity and shear stress. Analytical solutions have been attempted. Through these solutions, the effects of Darcy number, Brinkman number, and porous sleeve thickness on the velocity profile and temperature distribution are studied.
A Concept of a Knowledge-Based Assistance System for Servohydraulic Drive Design
Authors: Schlemmer Kristof , Murrenhoff Hubertus
Published: May 2009

Outsourcing of drive engineering is a tendency to be observed in many industrial enterprises today. As in-house expertise diminishes, competitiveness of hydraulic drive systems compared to electrical drives gains importance. Servohydraulic control systems, however, require very specific and complex approaches to circuit and control design. They are thus demanding on the designer’s knowledge and experience, which often leads to hydraulic solutions being implemented unsatisfactorily or not at all. The concept developed in this paper therefore aims at providing support in drive system design to inexperienced customers or sales people. In order to make the diversity of existing expertise accessible and utilizable, a knowledge-based approach is proposed. The objective is seen in an interactive software tool that guides the user through the iterative process of analyzing the problem, planning and designing the most appropriate drive solution. Requirements and selection criteria for a development environment are specified, and an expert system shell is selected as a means of implementation. A taxonomy of linear hydraulic servo drives is created that provides a frame for an object-oriented knowledge base. Knowledge extracted from text books and expert interviews is integrated into the system as a collection of rules and facts. Special attention is paid to the selection of a control strategy that delivers optimum performance beyond the capability of standard PID controllers. A comprehensive survey of hydraulic control technology is to ascertain that the developed expert system employs both approved and novel techniques to the benefit of overall system performance.
Modeling of Three-Dimensional Gas Metal Arc Welding With Groove
Authors: Hu J. , Tsai H. L.
Published: May 2009

This article analyzes the dynamic process of groove filling and the resulting weld pool fluid flow in gas metal arc welding of thick metals with V-groove. Filler droplets carrying mass, momentum, thermal energy, and sulfur species are periodically impinged onto the workpiece. The complex transport phenomena in the weld pool, caused by the combined effect of droplet impingement, gravity, electromagnetic force, surface tension, and plasma arc pressure, were investigated to determine the transient weld pool shape and distributions of velocity, temperature, and sulfur species in the weld pool. It was found that the groove provides a channel which can smooth the flow in the weld pool, leading to poor mixing between the filler metal and the base metal, as compared to the case without a groove.
FRTCOILS: A General Purpose Simulation Software for Design and Prediction of Thermal and Hydraulic Performance of Finned-Tube Compact Heat Exchangers
Authors: Tun Maung Naing Naing , Egrican Nilufer
Published: May 2009

This paper presents computer software developed for rating and optimum selection of finned circular tubes compact heat exchangers with various coil geometries. The software is developed to use as a computing tool for commercial and R&D purposes in FRITERM A.S, an original equipment manufacturer (OEM) of finned tube heat exchangers. Finned-tube heat exchangers are highly utilized in refrigeration and process industries and heat transfer and pressure drop calculations are very important to manufactures and design engineers. For this purpose, a simulation and design software to predict the performance of finned-tube heat exchangers is presented. In finned-tube coils fin side fluid is air and tube side fluid can be water, oil, glycol water solution mixture and refrigerants. The analysis and rating of coils at dry and wet operating conditions are presented. Design and the most suitable selections of coils at the given parameters and design constraints from many different coil geometries are also performed in the software. User-friendly object-oriented programming C# is applied in developing the software. The software is developed in modular basic. Six modules are developed: Heating Coils, Cooling Coils, Condenser Coils, Steam Coils, Heat Recovery Coils and Evaporator (DX) Coils. REFPROP is also integrated in the software and all fluids’ thermal and transport properties are obtained from REFPROP. Heat transfer and pressure drop correlations available from literature are evaluated with recommendations. Simulated results are verified against experimental results.
Coupled Reactor-Scale and Surface Chemistry Model for Chemical Vapor Deposition of Carbon Nanotubes
Authors: Lysaght Andrew C. , Chiu Wilson K. S.
Published: May 2009

Carbon vapor deposition (CVD) of carbon nanotubes (CNTs) has been modeled with a coupled gas-phase and surface chemistry model. The gas-phase flow model consisting of coupled conservation of mass, energy, and momentum equations was developed to describe the fluid flow of hydrocarbons and hydrogen as they undergo heating and chemical reactions in a horizontal tube-flow CVD reactor. The model outputs steady state velocity, temperature, and concentration fields for each species involved in the reaction mechanism. The fully coupled surface chemistry model, applied as a variable multidirectional flux boundary condition to the mass balance equation, determines steady-state surface coverage of each chemical species as well as the rate of growth of CNTs as a function of gas phase thermal and chemical conditions. The results of the modeling effort demonstrate a dependence on thermal conditions of optimal inlet molar ratios for efficient CNT production as well as the large effect specification of active sites can have on calculated deposition rates.
Transient Conjugated Conduction: External Convection With Front Face Imposed Wall Heat Flux
Authors: Naveira Carolina P. , Cotta Renato M. , Lachi Mohammed , Padet Jacques
Published: May 2009

This work presents hybrid numerical-analytical solutions for transient laminar forced convection over flat plates of non-negligible thickness, subjected to arbitrary time variations of applied wall heat flux at the interface fluid-solid wall. This conjugated conduction-convection problem is first simplified through the employment of the Coupled Integral Equations Approach (CIEA) to reformulate the heat conduction problem on the plate by averaging the related energy equation in the transversal direction. As a result, a partial differential formulation for the average wall temperature is obtained, while a third kind boundary condition is achieved for the fluid in the heat balance at the solid-fluid interface. From the available velocity distributions, the solution method is then proposed for the coupled partial differential equations, based on the Generalized Integral Transform Technique (GITT) under its partial transformation mode, combined with the method of lines implemented in the Mathematica 5.2 routine NDSolve.
Massively Parallel Computations of Damage to a Thin-Walled Structure From Blast
Authors: Luketa-Hanlin Anay , Attaway Stephen
Published: May 2009

The objective of this work is to determine initial structural response from a blast threat for the newer class of liquefied natural gas (LNG) vessels. Import of LNG by ship is expected to significantly increase in the coming decade and there is concern over vulnerability. Current vessels hold up to 160,000 m3 of LNG, while the new vessels will hold up to 266,000 m3. These vessels are double-hulled and have an insulating containment system which keeps the LNG at a temperature of 111 K. Calculations were performed to determine the structural response of these ships from blast using CTH, a shock-physics code, developed at Sandia National Laboratories. The calculations were performed on massively parallel computing platforms (∼1000 processors) due to the number of elements required (∼109). Detailed geometry of the stiffeners, framing, and changing hull thickness with elevation were included, as well as the insulation, LNG, and water. Thus, there is multiphase interaction with the structure. The geometry of these ships fall within a class of problems termed ‘thin-walled problems’ since they require resolution of length scales from ∼10 mm to ∼10 m. In order to capture the smallest length scales an adaptive mesh refinement (AMR) feature was used. This feature allows for cells to be concentrated in active regions as the calculation progresses. This paper will discuss the resolution challenges of simulating thin-walled problems, as well as regimes in which shock-physics codes, such as CTH, are appropriate for application. Results will be provided without disclosure of threats.
Dynamic and Vibration Analysis of a SAR Membrane Antenna
Authors: Shen Yu , Zheng Wanping , Wang Xiaoyun
Published: May 2009

Synthetic Aperture Radar (SAR) membrane antennas have attracted much attention for their low mass, small stowed volume, large gain and high resolution. To deploy a membrane antenna requires a deployable support structure providing deployment and rigid support after it is fully deployed. A membrane antenna’s vibration may be caused by the disturbance of the satellite attitude-control torque in spacecraft, and it is determined by the mechanical properties of the membrane and its in-plane tension loads. In this paper, the dynamic properties of the deployable structure are studied with ADAMS when the flexibility of the frames is considered. The mode shapes and the natural frequencies of the membrane are analyzed with ABAQUS when the pre-tension loads provided by the tension cable are changed. The random response of the membrane subjected to the base excitation is studied for different tension forces and damping ratios. This work provides a guideline for the vibration control of the membrane by controlling its tension force or damping ratio.
Adaptive Piezoelectric Vibration Control With Synchronized Switching
Authors: Collinger J. C. , Wickert J. A.
Published: May 2009

An autonomous vibration controller that adapts to variations in a system’s mass, stiffness, and excitation, and maximizes dissipation through synchronized switching, is described. In the model and laboratory measurements, a cantilever beam is driven through base excitation and two piezoelectric elements are attached to the beam for vibration control purposes. The distributed-parameter model for the beam-element system is discretized by using Galerkin’s method, and time histories of the system’s response describe the controller’s attenuation characteristics. The system is piecewise linear, and a state-to-state modal analysis method is developed to simulate the coupled dynamics of the beam and piezoelectric circuit by mapping the generalized coordinates between the sets of modes for the open-switch and closed-switch configurations. In synchronized switching control, the elements are periodically switched to an external resonant shunt, and the instants of optimal switching are identified through a filtered velocity signal. The controller adaptively aligns the center frequency of a bandpass filter to the beam’s fundamental frequency through a fuzzy logic algorithm in order to maximize attenuation even with minimal a priori knowledge of the excitation or the system’s mass and stiffness parameters. In implementation, the controller is compact owing to its low inductance and computational requirement. The adaptive controller attenuates vibration over a range of excitation frequencies, is robust to variations in system parameters, and can outperform traditional synchronized switching.
Finite Element Model for Hysteretic Friction Damping of Traveling Wave Vibration in Axisymmetric Structures
Authors: Tangpong X. W. , Wickert J. A. , Akay A.
Published: May 2009

A finite element method is developed to treat the steady-state vibration of two axisymmetric structures—a base substructure and an attached damper substructure—that are driven by traveling wave excitation, and that couple through a spatially-distributed hysteretic friction interface. The base substructure is representative of a rotating brake rotor or gear, and the damper is a ring affixed to the base under preload and intended to control vibration through friction along the interface. In the axisymmetric approximation, the equation of motion of each substructure is reduced in order to the number of nodal degrees of freedom through the use of a propagation constant phase shift. Despite nonlinearity and with contact occurring at an arbitrarily large number of nodal points, the response during sticking, or during a combination of sticking and slipping motions, can be determined from a low-order set of computationally tractable nonlinear algebraic equations. The method is applicable to element types for longitudinal and bending vibration, and to an arbitrary number of nodal degrees of freedom in each substructure. In two examples, friction damping of the coupled base and damper is examined in the context of in-plane circumferential vibration (in which case the system is modeled as two unwrapped rods), and of out-of-plane vibration (alternatively, two unwrapped beams). The damper performs most effectively when its natural frequency is well below the base’s natural frequency (in the absence of contact), and also when its natural frequency is well-separated from the excitation frequency.
Experimental and Computational Study of Droplet Growth and Detachment Near the Inception Point
Authors: Molki Majid , Abbasi Bahman
Published: May 2009

An experimental and computational investigation was conducted to study the growth and detachment of a single liquid droplet. High-speed photography was employed to capture the droplet evolution from the onset to the breakup time. Three-dimensional computations were carried out to predict the droplet behavior and flow dynamics inside the droplet. The droplet fluid was water immersed in the surrounding atmospheric air. The computations were performed using the finite volume and Volume of Fluid (VOF) techniques. The computations and high-speed photography of the droplet formation were carried out at 20°C. Diameter of the injection port was 2.4 mm and the flow rate for generation of droplets was 1.1 × 10−4 kg/s. These values together with the choice of liquid resulted in a Bond number of 0.19, Capillary number of 3.4 × 10−4, and liquid-to-gas viscosity ratio of 56.05. The results indicated that the shape and evolution of the droplet as predicted by the computations were in good agreement with those captured on the high-speed photographs. The computations revealed details of the flow inside the droplet such as pressure and velocity.
Cutter-Workpiece Engagement Calculations by Parallel Slicing for Five-Axis Flank Milling of Jet Engine Impellers
Authors: Ferry W. , Yip-Hoi D.
Published: May 2009

Cutter-workpiece engagement maps, or cutting flute entry/exit locations as a function of height, are a requirement for prediction of cutting-forces on the tool and workpiece in machining operations such as milling. This paper presents a new method of calculating tool-part intersection maps for five-axis flank milling of jet engine impellers with tapered ball-end mills. It is called the parallel slicing method (PSM) and is a semi-discrete solid modeling technique written in C++ using the ACIS B-rep solid modeling environment. Although it is tailored towards five-axis flank milling, it can also be applied to both planar and multi-axis milling processes. The tool swept envelope is generated and intersected with the workpiece to obtain the removal volume. The removal volume is then sliced into a number of parallel planes along a given axis and the intersection curves with the tool and each plane are determined analytically. The swept area between the intersection curves of successive tool moves is calculated by solving for the area enclosed by the tangent lines. This area is removed from the workpiece material, which deletes the material cut between tool moves. Finally, the intersection curves are compared with the planar slices of the updated part, which results in a series of arcs. The end points of these arcs are joined with linear segments to form the engagement polygon which is used to calculate the engagement maps. Using this method, cutter-workpiece engagement maps are generated for a five-axis flank milling toolpath on a prototype integrally bladed rotor (IBR) with a tapered ball-end mill. These maps are compared with those obtained from a benchmark cutter-workpiece engagement calculation method – the Manufacturing Automation Laboratory’s Virtual Machining Interface (MAL-VMI). The MAL-VMI uses an application programming interface (API) in a commercial NC verification software package to obtain cutter-part intersections through a fast, z-buffer technique. Overall, the parallel slicing method appears to obtain more accurate engagement zones than those given by the MAL-VMI, although the calculation time is longer.
An Elastic Micropolar Mixture Theory Approach for Predicting Elastic Properties of Open Cell Foams
Authors: Elangovan Shreehari , Altan Burhanettin S. , Odegard Gregory M.
Published: May 2009

A constitutive model has been developed to predict the elastic response of two dimensional balsa wood material with a distribution of cell geometries. Two planar triangular grids, each assumed to represent the structural network of an open cell foam material, are superimposed to model an overall cellular structure with a distribution of cell geometries. The elastic mixture theory is applied in conjunction with the micropolar elasticity theory to homogenize the cellular structure and to establish the overall constitutive relationship.
Synthesis and Dynamic Analysis of a Quick-Return Mechanism Using MATLAB and SIMULINK
Authors: Mohammadzadeh Ali , Barakat Nael , Haidar Salim
Published: May 2009

The approach adopted in this work is an attempt to introduce students, in kinematics and dynamics of machinery course, to a complete design and analysis of function generation mechanisms via analytical methods. Although the approach implemented in this work is for function generation type of mechanisms, the concept is indeed extendable to the other types of mechanisms as well. As a project in the kinematics and dynamics of machinery class, students designed, and analyzed a four bar quick-return mechanism using MATLAB and SIMULINK as the primary software tools. One of the aims of this project was to abandon the traditional graphical synthesis and graphical analysis, covered in all the mechanisms textbooks, and to use the powerful combination of MATLAB and SIMULINK to implement the entire design and analysis process. The project, given to an undergraduate class, serves also as a prologue to future advanced courses in mechanical engineering, such as multi-body dynamics. In implementing the dimensional synthesis portion of the project, students employed complex number arithmetic to realize the design specifications. Once the design specifications were met, a known motor torque was applied to the crank to drive the mechanism. With the known geometric and inertial properties of each link, Lagrange’s equations for constraint motion were then utilized to arrive at the second order differential equations of motion. SIMULINK, as a user friendly graphical interface, was used to carry out the integration to obtain angular position, velocity, and acceleration of the designed mechanism. The project also calculates the reaction loads on the mechanism using the concepts of Newtonian mechanics. The project, though rigorous, is an excellent way to force students to practice their knowledge of dynamics and numerical methods. The project, certainly, meets the ABET criteria for implementing design in mechanical engineering curriculum. The author received positive feedbacks from his students with regard to this project.
Sustainability Impacts of a Program of Decommissioning Older Automobiles for Replacement With Newer, More Efficient Vehicles
Authors: Fronk Brian M. , Burton Ludovic , Garimella Srinivas
Published: May 2009

This paper investigates a representative vehicle replacement scenario on a comprehensive basis, including energy for fabrication, operation and decommissioning, together with the associated environmental and economic impacts. It is postulated that to lessen the environmental impact of older, inefficient devices, legislation may be passed to require the decommissioning and purchase of newer equipment. However, the energy consumed, greenhouse gases emitted, and economic costs of building a new product and decommissioning the old product may outweigh the benefit of removing an inefficient device from service on a life-cycle basis. A representative case of retirement of automobiles from 1990 and earlier by comparable 2007 model internal combustion engine automobiles is considered. The energy use, greenhouse gas emissions, and economic cost to the consumer are compared for two cases, one that includes the production and operation of a new car and decommissioning of the older car, and a second case accounting for only the continued operation of the older car. It was found that from an energy and emissions standpoint, it is beneficial to require the decommissioning of older automobiles. However in the same time period, economic considerations from the customer’s perspective favor continued operation of the older automobile. Therefore, the study concludes that without such an economic basis, legislation and incentives would be required to enable the replacement of older automobiles with more efficient models.
Determination of Laser Absorption Coefficients of Gas Mixtures Using an Ab Initio MD Model
Authors: Liang Zhi , Tsai Hai-Lung , Jiang Lan
Published: May 2009

In an effort to study the laser induced dissociation of gas mixtures for an ongoing research project on diamond thin film coating using multiple lasers, it is necessary to determine the absorption coefficient of laser energy by CO2 gas. An ab initio molecular dynamics (AIMD) model is used to determine the laser absorption coefficient of CO2 gas as a function of laser wavelength and gas temperature. The translational, rotational, and vibration motions of molecules are all taken into account in our model. The intra-molecular potential energy is obtained by solving the Kohn-Sham equation. The Projector-Augmented Wave (PAW) exchange-correlation potential function is used in the ab initio calculation. Specific heat of the CO2 gas is also calculated. The calculated thermal properties of CO2 gas and the vibration spectrum of molecules are in good agreement with the experimental results. The calculated normalized absorption line shape CO2 gas is close to the experimental results.
Design-Build-Test: The Capstone Design Project
Authors: Dong J. , Dave J.
Published: May 2009

Students working toward baccalaureate degree in Mechanical Engineering Technology (MET) at University of Cincinnati (UC) are required to complete a “Design, Build, and Test” senior capstone design project. Two of these capstone design projects during the 2005–2006 academic year were to design and build vehicles. One is a Basic Utility Vehicle (BUV), which was geared to meet the needs of developing countries for an affordable transportation. The national competition was held in Indianapolis, IN. The other one is an Autocross racing vehicle, which was built to meet the Sports Car Club of America (SCCA) Autocross specifications, and raced in the regional/local events. The Institute for Affordable Transportation (IAT) hosts a competition of designing and building BUV each year in Indianapolis, IN. IAT is a not-for-profit organization devoted to improving the living standards and enable economic growth in the developing world by creating a simple vehicle that can be assembled almost anywhere, by almost anyone. The competition tests and judges all of the entries to identify best design and suitable vehicles for developing countries. IAT has donated several vehicles to needy countries in South America and Africa. The SCCA is a 60,000-member not-for-profit organization featuring the most active membership participation in motorsports today. The foundation of the SCCA is its Club Racing program with over 2,000 amateur and professional motor sports events each year. One team of MET students built a BUV, and another team of students built an Autocross racing car as their senior projects. From concept to a final working vehicle with meeting the IAT’s or SCCA’s specifications, there are many challenges. The expertise and knowledge acquired from student’s coursework and co-op were utilized. This paper will give the short description of the senior capstone design course sequence at University of Cincinnati: the list of pre-requisites of its sequence, and partially describes 2005–2006 BUV and Autocross projects and the team experiences of the projects from start to finish.
Fabrication of Fully Integrated Microfluidic Device With Carbon Sensing Electrode for the Detection of Forensic and Biomedical Targets
Authors: Dawoud Abdulilah A.
Published: May 2009

Fabrication of fully integrated capillary electrophoresis (CE)-based microfluidic device with integrated carbon sensing electrode is described in this paper. A combination of microfabrication protocols were employed for fabricating the hybrid PDMS/glass microfluidic device including chemical wet etching, soft lithography, and micromolding techniques. The microdevice is comprised of glass substrate with integrated gold electrodes and carbon sensing electrode, and polydimethyl siloxane (PDMS) slab that encompasses the microchannels network. The carbon sensing electrode was physically characterized via atomic force microscopy (AFM) and Raman spectrometry. In addition, its quality was evaluated electrochemically and compared to commercial glassy carbon electrodes upon performing cyclic voltammetric analysis of two illicit drugs, morphine and codeine. The analytical performance of the stand-alone microdevice was evaluated upon testing the injection, separation and amperometric detection on the carbon sensing electrode. The carbon sensing electrode provides stable background current during applying high sensing potential, which is of particular necessity for sensing molecules that can be only detected at high potentials including morphine and codeine.
Vocal Fold Dynamics During Phonations
Authors: Lan H. , Al-Jumaily A. M. , Mirnajafi A.
Published: May 2009

During phonation, the vocal folds collision in the glottal closure is considered as a risk factor for pathology development. Based on the finite element model using the software ABAQUS™, the impact stresses between the vocal folds are studied.