bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonaxisymmetric Waves of a Stratified Vertical Vortex
Authors: Fung Y. T.
Published: April 2008

The interfacial conditions for a cylindrical and an axial vortex sheet or thin fluid layer are obtained for a general class of vortex flows in a radius and gravity-stratified environment. The flow is assumed to be inviscid and incompressible. No Boussinesq approximation is required. In addition to the kinematic and dynamic conditions that the flow has to satisfy in the centrifugal and gravitational directions, a third condition, which restrains the interaction of the centrifugal and gravitational force fields, has to be imposed on those vortex sheets. This is consistent with the previous derived criteria for this type of vortex motions, in which a third condition based on pressure and force balance must be satisfied. Nonaxisymmetric instability for a special flow profile is examined and the stability boundary is obtained to show the behavior of this type of stratified vertical vortex. The results provide us with some information on the instability mechanism for the generation of the horizontal vortices in the ocean and for the spiral type of vortex breakdown in tornadoes and waterspouts in the atmosphere.
Symmetrizable Systems in Mechanics and Control Theory
Authors: Kliem W. R.
Published: April 2008

Stability investigations of nonconservative systems MX¨ + BX˙ + CX = 0 in mechanics and control theory become substantially easier if the coefficient matrices B and C are either both real symmetric or both complex symmetric. It is therefore of interest to give conditions under which, by means of a similarity transformation, a system may be converted into one of these forms. We discuss the following questions: Are such systems robust with respect to perturbations in the entries of the coefficient matrices? Do relevant applications exist?
The Response Spectrum of a Nonlinear Oscillator
Authors: Davies Huw G. , Liu Qiang
Published: April 2008

The response of a nonlinear oscillator excited by white noise is considered. A truncated Hermite polynomial series is used as an approximation to the probability density function. While this approach has been used before by many authors to obtain statistics such as the time-dependent mean or mean-square values, it has not been noted before that the approach can be extended to obtain the correlation function and spectrum. This series when substituted into the Fokker-Planck equation yields a set of time-dependent moment equations, which can be solved numerically for the correlation functions, or, after a Fourier transform, a set of complex algebraic equations which can be solved for the spectrum. Examples of spectra for the Duffing and van der Pol oscillators are shown.
Correction of Joint Stiffnesses and Constraints for Finite Element Models in Structural Dynamics
Authors: Mottershead John E. , Weixun Shao
Published: April 2008

Finite element models are based upon known physical characteristics. But there are two main sources of error, namely (i) ill-defined joints and boundary constraints, and (ii) overstiffening due to the application of shape function discretization. It is difficult to correct an ill-defined constraint without simultaneously compensating (to some unknown degree) for discretization overstiffening. A general approach is proposed whereby the measured eigendata from a physical system are altered to resemble the eigendata of a discrete system with identical (but unknown) constraints. With the effects of discretization overstiffening present in both the adjusted measurements and the model it is straightforward to obtain progressively improved estimates of the constraint stiffnesses by using the least-squares method. The proposed approach may be considered to be equivalent to a model reduction scheme. Specific methods are applied to the correction of a stiffness in the joint of a finite element framework model.
Random Vibrations of Externally Damped Viscoelastic Timoshenko Beams With General Boundary Conditions
Authors: Singh M. P. , Abdelnaser A. S.
Published: April 2008

A complex mode approach is presented to analyze an externally damped viscoelastic Timoshenko beam subjected to distributed loads. The eigenfunctions of the original and adjoint equations are used to decouple the equations. Any conventional or nonstandard boundary conditions at beam ends can be handled with equal ease. Numerical response results are presented for random loads with spatial and temporal correlations.
Axisymmetric Bending of Generally Laminated Cylindrical Shells
Authors: Birman Victor
Published: April 2008

Nonlinear bending deformations of generally laminated circular cylindrical shells subjected to an axisymmetric radial pressure, axial loading, and torsion are considered. Deformations of such shells are axisymmetric, i.e., while cross-sections can rotate about the shell axis, they remain circular and all derivatives with respect to the circumferential coordinate are equal to zero. In this case a nonlinear term is included into the axial strain only. Excluding this strain from the equilibrium equations, one can reduce the analysis to integration of a system of linear differential equations. In the first part of the paper the solution based on Love’s first approximation and Donnell’s theories is shown for thin shells. While out-of-surface boundary conditions can be arbitrary, several combinations of in-surface conditions are discussed. The second part of the paper outlines the approach to the solution for shear-deformable geometrically nonlinear shells. First-order shear-deformation theory is used in the analysis. The approach is based on exclusion of the nonlinear term (axial strain) and subsequent solution of linear differential equations of equilibrium by the operational method. This approach can be also used for an analysis of thin, generally laminated cylindrical shells.
Buckling of Thick Orthotropic Cylindrical Shells Under External Pressure
Authors: Kardomateas G. A.
Published: April 2008

An elasticity solution to the problem of buckling of orthotropic cylindrical shells subjected to external pressure is presented. In this context, the structure is considered a three-dimensional body. The results show that the shell theory predictions can produce nonconservative results on the critical load of composite shells with moderately thick construction. The solution provides a means of accurately assessing the limitations of shell theories in predicting stability loss.
Response of a Fiber Composite Laminate to a Time-Varying Surface Line Load
Authors: Green E. Rhian
Published: April 2008

A symmetric cross-ply laminated plate consisting of four layers of a fiber-reinforced composite material is subjected to a time varying line load on its upper surface. The response at points remote from the application of the line load on both upper and lower surfaces of the plate is determined. Two different pulses are considered, namely a square pulse and a half-sine pulse. The significant parameter governing the nature of the response is the duration of the pulse.
A Simple Representation of the J-Integral and Some Estimates of Elastic Stress Intensity Factors
Authors: Lubarda V. A.
Published: April 2008

Precise estimates of the elastic stress intensity factors for the Griffith and edge cracks are made by using one convenient representation of the J-integral and asymptotic crack-tip fields, without recourse to the solutions of corresponding boundary value problems.
Universal Relations in Piezoelectric Composites With Eigenstress and Polarization Fields, Part II: Multiphase Media—Effective Behavior
Authors: Benveniste Y.
Published: April 2008

We consider heterogeneous piezoelectric media in general and multiphase piezoelectric composites in particular. A distribution of statistically homogeneous eigenstress and spontaneous polarization fields is admitted in the solid which is itself statistically homogeneous, and the effective eigenstress and spontaneous polarization is sought. The method here is based on the use of virtual work theorems in piezoelectric media and therefore differs from the approach used in the companion paper (Benveniste, 1993). We show that the effective eigenstress and polarization follow from a knowledge of the influence functions related to an electromechanical loading of the composite aggregate in which no eigenstresses and polarizations are present. When applied to the special case of binary systems with constant eigenstress and polarization fields in the phases, the above result implies that the effective eigenstress and polarization can be determined in terms of the effective elastic, piezoelectric, dielectric tensors of the medium, the constituent properties, and the individual eigenstresses and polarizations.
The Eigenvalues for a Self-Equilibrated, Semi-Infinite, Anisotropic Elastic Strip
Authors: Crafter E. C. , Heise R. M. , Horgan C. O. , Simmonds J. G.
Published: April 2008

The linear theory of elasticity is used to study an homogeneous anisotropic seminfinite strip, free of tractions on its long sides and subject to edge loads or displacements that produce stresses that decay in the axial direction. If one seeks solutions for the (dimensionless) Airy stress function of the form φ = e−γxF(y), γ constant, then one is led to a fourth-order eigenvalue problem for F(y) with complex eigenvalues γ. This problem, considered previously by Choi and Horgan (1977), is the anisotropic analog of the eigenvalue problem for the Fadle-Papkovich eigenfunctions arising in the isotropic case. The decay rate for Saint-Venant end effects is given by the eigenvalue with smallest positive real part. For an isotropic strip, where the material is described by two elastic constants (Young’s modulus and Poisson’s ratio), the associated eigencondition is independent of these constants. For transversely isotropic (or specially orthotropic) materials, described by four elastic constants, the eigencondition depends only on one elastic parameter. Here, we treat the fully anisotropic strip described by six elastic constants and show that the eigencondition depends on only two elastic parameters. Tables and graphs for a scaled complex-valued eigenvalue are presented. These data allow one to determine the Saint-Venant decay length for the fully anisotropic strip, as we illustrate by a numerical example for an end-loaded off-axis graphite-epoxy strip.
On Axisymmetric Residual Stresses in Tubes With Longitudinally Nonuniform Stress Distribution
Authors: Nishimura T.
Published: April 2008

New equations for calculating residual stress distribution are derived from the theory of elasticity for tubes. The initial distribution of the stresses including the shearing stress is computed from longitudinal distributions of residual stresses measured by the X-ray methods at the surface after removal of successive concentric layers of material. For example, the residual stresses of a steel tube quenched in water were measured by the X-ray diffraction method. The new method was also applied to a short tube with hypothetical residual stress distribution. An alternative finite element analysis was made for a verification. The residual stresses computed by finite element modeling agreed well with the hypothetical residual stresses measured. This shows that good results can be expected from the new method. The equations can also be used for bars by simple modification.
Stress Analysis for Rolling Contact Between Two Viscoelastic Cylinders
Authors: Wang Guangqiu , Knothe K.
Published: April 2008

The two-dimensional viscoelastic rolling contact with Coulomb’s dry friction is considered for steady-state rolling. A so-called standard linear solid (three parameter model) is used to characterize the viscoelastic material behavior. Rolling contact stresses between two rolling cylinders are investigated by a boundary element method, based on the half-space theory. Numerical results are presented including the stress distribution at the contact surfaces and in viscoelastic bodies as well as rolling resistance.
A Study on Plastic Shakedown of Structures: Part I—Basic Properties
Authors: Polizzotto C.
Published: April 2008

For a continuous elastic-perfectly plastic solid body subjected to a combination of cyclic (mechanical and/or kinematical) load and of a steady (mechanical) load such as to produce plastic shakedown (i.e., alternating plasticity), a number of characterizing properties are established and discussed. The conditions for the body’s transition from plastic shakedown to ratchetting are also addressed.
Interfacial Fracture Mechanics for Anisotropic Bimaterials
Authors: Qu J. , Bassani J. L.
Published: April 2008

This paper focuses on aspects of fracture mechanics of interface cracks in anisotropic bimaterials. In this case there is a coupling of all three crack-tip fracture modes in the natural interface-crack coordinate system, whereas in the isotropic case, mode 3 is decoupled from modes 1 and 2. This paper intends to shed light on how to interpret the crack-tip fields which are given explicitly along the interface in terms of two (real 3x3) bimaterial matrices W and D. A matric function Y is defined in terms of W and D which determines the coupling and oscillations in the cracktip fields. Explicit expressions for the crack-tip fields and the associated stress intensity factors are given as well as for the energy release rate. The finite (Griffith) interface crack is considered in detail.
Perturbation Eigensolutions of Elastic Structures With Cracks
Authors: Shen I. Y.
Published: April 2008

The purpose of this paper is to determine approximate eigensolutions of a class of cracked mechanical systems governed by the two-dimensional Helmholtz equation through a perturbation approach. Shen (1993) shows that exact eigenvalues λm2, and their corresponding crack-opening shapes ΔΨm of such mechanical systems satisfy a Fredholm integral equation A(λm2)ΔΨm = 0. Following the integral equation approach, the approximation in this paper consists of formulating the Rayleigh quotient of the Fredholm operator A(λ2) and estimating eigenvalues μ(λ2) of the operator A(λ2) through perturbation and stationarity of the Rayleigh quotient. The zeros of μ(λ2) then approximate eigenvalues λm2 of the cracked systems. Finally, approximate λm2 are calculated for two-dimensional elastic solids under antiplane-strain vibration with an oblique internal crack and a boundary crack.
On the Flexural-Torsional Behavior of a Straight Elastic Beam Subject to Terminal Moments
Authors: Tan Z. , Witz J. A.
Published: April 2008

This paper discusses the large-displacement flexural-torsional behavior of a straight elastic beam with uniform circular cross-section subject to arbitrary terminal bending and twisting moments. The beam is assumed to be free from any kinematic constraints at both ends. The equilibrium equation is solved analytically with the full expression for curvature to obtain the deformed configuration in a three-dimensional Cartesian coordinate system. The results show the influence of the terminal moments on the beam’s deflected configuration.
Stability Loss in Thick Transversely Isotropic Cylindrical Shells Under Axial Compression
Authors: Kardomateas G. A.
Published: April 2008

The stability of equilibrium of a transversely isotropic thick cylindrical shell under axial compression is investigated. The problem is treated by making appropriate use of the three-dimensional theory of elasticity. The results are compared with the critical loads furnished by classical shell theories. For the isotropic material cases considered, the elasticity approach predicts a lower critical load than the shell theories, the percentage reduction being larger with increasing thickness. However, both the Flu¨gge and Danielson and Simmonds theories predict critical loads much closer to the elasticity value than the Donnell theory. Moreover, the values of n, m (number of circumferential waves and number of axial half-waves, respectively, at the critical point) for both the elasticity, and the Flu¨gge and the Danielson and Simmonds theories, show perfect agreement, unlike the Donnell shell theory.
An Inverse Problem in Elasticity With Partially Overprescribed Boundary Conditions, Part II: Numerical Details
Authors: Koya Tatsuhito , Yeih Weichung , Mura Toshio
Published: April 2008

In Part I we examined an alternative formulation to the one employed by Gao and Mura (1989). In this paper, we look into numerical details to facilitate computer implementation. This implementation is quite general in that it works for both Gao and Mura and us (Koya and Mura (1992)).
Response of Annular Plates to Circumferentially and Radially Moving Loads
Authors: Weisensel G. N. , Schlack A. L.
Published: April 2008

The forced dynamic response of annular plates to circumferentially and radially moving concentrated transverse loads is investigated utilizing classical plate theory, with damping included, and solved in integral form. The boundary conditions are that the inner boundary of the plate is clamped and the outer boundary is free. An analytical expression in Fourier-Bessel series form is obtained for the forced deflection response to an arbitrarily moving concentrated load. This study includes radially moving loads and is a significant extension of the understanding of circular and annular plate dynamics. This understanding of radially moving loads is used to examine the nature of resonance conditions and corresponding critical values of the load parameters. The shapes of deflection modes of plate vibration are also presented. Damping and loading parameter sensitivities are studied in detail.
Equations of Motion for Nonholonomic, Constrained Dynamical Systems via Gauss’s Principle
Authors: Kalaba R. E. , Udwadia F. E.
Published: April 2008

In this paper we develop an analytical set of equations to describe the motion of discrete dynamical systems subjected to holonomic and/or nonholonomic Pfaffian equality constraints. These equations are obtained by using Gauss’s Principle to recast the problem of the constrained motion of dynamical systems in the form of a quadratic programming problem. The closed-form solution to this programming problem then explicitly yields the equations that describe the time evolution of constrained linear and nonlinear mechanical systems. The direct approach used here does not require the use of any Lagrange multipliers, and the resulting equations are expressed in terms of two different classes of generalized inverses—the first class pertinent to the constraints, the second to the dynamics of the motion. These equations can be numerically solved using any of the standard numerical techniques for solving differential equations. A closed-form analytical expression for the constraint forces required for a given mechanical system to satisfy a specific set of nonholonomic constraints is also provided. An example dealing with the position tracking control of a nonlinear system shows the power of the analytical results and provides new insights into application areas such as robotics, and the control of structural and mechanical systems.
Superplastic Forming Formula for Aluminum Channel Panels
Authors: Lee Frank G. , Hanna M. David
Published: April 2008

A parametric study was conducted to determine how the design features and forming parameters affect part thinning and forming time in the Superplastic Forming Process (SPF). Explicit formulas, describing the maximum percent thinning and the forming time for channel parts formed by the SPF process as a function of eight designs and forming parameters, were derived. The formulas are good approximations of those obtained by finite element simulation analyses and physical experiments. Thinning of the channels was influenced most by the component aspect ratio (height versus width) and entry radius at top of the channel forming tool. The forming time was most influenced by strain rate, aspect ratio and tool bottom radius. A design domain can be established to avoid excessive thinning. The Taguchi design-of-experiment method was applied to select parameter combinations, and the MARC finite element code was used to conduct sectional analysis for various combinations.
A New Approach to Mechanics of Materials: An Introductory Course With Integration of Theory, Analysis, Verification and Design
Authors: Rencis J. J. , Grandin H. T.
Published: April 2008

This paper presents a description of a first undergraduate course in mechanics of materials. Although many of the features of this course have been used by other faculty and presented formally in textbooks, the authors believe they have united them in a way that produces a course that is unique and innovative. The paper is titled “A New Approach to Mechanics of Materials: an Introductory Course with Integration of Theory, Analysis, Verification and Design”. The subtitle has been included to emphasize the unification of four strategic elements: Theory, Analysis, Verification and Design. The course leads the student through a traditional exposure to theory, but a non-traditional progressive approach to analysis that uses a modern engineering tool. Introduction of verification develops the student’s discipline to question and test ‘answers’. If a problem solution can be formulated in general symbolic format, and if specific solutions can then be obtained and carefully verified, the extension from analysis for one set of variables to the design for different sets of specifications can be done quickly and easily with confidence. Three examples are included to demonstrate the approach and one example considers design.
Data Driven Feedforward Transient Fueling Controller Identification for Spark Ignition Engines
Authors: Franchek Matthew A. , Mohrfeld Jackie , Osburn Andy
Published: April 2008

Presented in this paper is a feedforward fueling controller identification methodology for the transient fueling control of spark ignition (SI) engines. The proposed transient feedforward controller is identified and executed in the crank angle domain, and operates in tandem with a steady state fueling controller. The hypothesis is that the feedforward fueling control of SI engines can be separated into steady state and transient phenomena, and that the majority of the nonlinear behavior associated with engine fueling can be captured with nonlinear steady state compensation. The proposed transient controller identification process is built from standard nonparametric identification techniques using spectral density functions where crank angle serves as the independent variable. Two separate system identification problems are solved to identify the air path dynamics and the fuel path dynamics. The transient feedforward controller is then calculated as the ratio of the air path-over-the fuel path dynamics so that the fuel path dynamics match the air path dynamics. Consequently fueling is coordinated with the fresh air charge during transient conditions. It will be shown that a linear transient feedforward-fueling controller operating in tandem with a nonlinear steady state fueling controller can achieve air-fuel ratio (AFR) regulation comparable to a production controller without the extensive controller calibration process. The engine used in this investigation is a 1999 Ford 4.6L V-8 fuel injected engine.
Simplified Design of Combustion Chamber for Small Gas Turbine Applications
Authors: Kulshreshtha Digvijay B. , Channiwala S. A.
Published: April 2008

The combustion chamber of gas turbine unit is one of the most critical components to be designed. Scanning through literature reveals that the design methodologies for combustion chamber are available in a discrete manner and there exist a need to compile this information and evolve a systematic design procedure for combustion chamber. The present paper is an attempt towards presenting such a complete design methodology of combustion chamber for small gas turbine applications. The combustion chamber for the 20 kW gas turbine engine has been designed and fabricated as per these summarized design guidelines then checked for the axial and radial temperature profiles as well as liner wall temperatures, experimentally. The liner wall temperatures achieved is in the vicinity of 300°C when centerline temperature is of the order of 1300°C. This adequately validates the design methodologies proposed in this paper.
A Comparative Finite Element Analysis of Residual Stresses in Active Fiber Composites With Embedded Metal-Core Piezoelectric Fibers and Macro Fiber Composites
Authors: Askari Davood , Asanuma Hiroshi , Ghasemi-Nejhad Mehrdad N.
Published: April 2008

Residual stresses are basically developed due to intrinsic and extrinsic strains that form during the processing of composite materials. The extrinsic strains can be determined using Coefficient of Thermal Expansion (CTE), material properties, geometry of the structure, and processing conditions. Finite Element Method (FEM) as an efficient alternative technique for stress and strain analysis of the micromechanical systems and structures, has been employed to numerically investigate the residual stresses developed in Metal-Core Piezoelectric Fibers (MPF) and Active Fiber Composites (AFC) (or Macro Fiber Composites (MFC)), during the processing. Here in this work, ANSYS Finite Element Analysis (FEA) software is used to develop three different 3-dimensional models for MPF and MFC structures and then each model is solved for strain and stress results. Next, the stress and strain components of these models are studied throughout the structures to identify the magnitude and type of the stresses and strains within the constituent materials and then compared.
Simulation and Correlation of Durability Test on an Automotive Rear Suspension
Authors: Liao Gene Y.
Published: April 2008

This paper documents the Finite Element (FE)–based durability simulations and correlation with rig test for an automotive rear suspension. The rig test is developed and conducted on the rear suspension subject to road load per durability schedule. Analytical simulations indicate that the upper weld beads of both left and right sleeves to T–beams are potential failure locations. The correlation shows that the predicted fatigue life is one order lesser than the tested fatigue life. However, the experiment shows that a crack appears at the upper weld bead on the right sleeve connected to the T-beam where is exactly as simulation predicted. It is observed that the rigid modeling of welds is feasible in the simulation. The validated rig fatigue life simulation reduces the development time and cost on the common rear suspensions.
Semi-Active Vibration Damping by Modulation of Joint Friction
Authors: Agarwal Sandeep
Published: April 2008

The semi-active concept for vibration suppression in a clamped-free structural configuration is investigated. A fixed-free beam with the semi-active joint, designed to modulate friction, and hence the clamping load level, is considered. The vibration of the beam resulting from assumed initial conditions is examined in the time domain for a range of clamping load levels. The results obtained are studied and a control strategy is proposed to dissipate the energy efficiently and in a controlled way.
Effect of Guard Ring Design and Properties of Inter-Layer Dielectric Film on Chip Reliability
Authors: Parhami Farnaz , Pan Stephen
Published: April 2008

One of the common reliability problems in semiconductor industry is delamination of dielectric films used in the integrated circuit manufacturing process. Although these films have demonstrated good reliability performance in wafer form, once placed in different packages and undergo stress testing (e.g. pressure cooker test) they tend to crack and delaminate and lead to eventual reliability failure of the chip. The die guard ring can impact propagation of cracks that are initiated at the edge of the die into the active circuitry of the die. We designed several guard ring structures and performed finite element analysis to compare the potential of crack propagation for different guard ring designs. It is found that some features of the design do not affect stress intensity factor KI (potential of crack propagation). For long crack (3.75 um), structure A may reduce KI. But, structure B will increase KI. From fracture mechanics point of view, structure A may stop crack propagation toward die center. However, with structure B, the crack may still penetrate into the die. For short crack (1.25 um), effect of guard ring structure design is negligible. We have made experimental wafers using our wafer manufacturing processes to create structure A and B around the dice. Some wafers were made with film AA as interlayer dielectric and some with film BB as interlayer dielectric. SEM inspections validate our FEM models that structure A captures more cracks at the edge of the die and prevents its propagation into the die while structure B is less effective. We have shown that even with incorporation of structure B guard ring, film BB looses adhesion to other layers and delaminates upon exposure to humidity in pressure cooker test while film AA never delaminates.
A Finite Element Model for Drop-on-Demand Printing of Designer Hybrid Cardiovascular Constructs
Authors: Xu Tao , Baicu Catalin , Manley Brian , Zile Michael , Boland Thomas
Published: April 2008

A Finite element model (FEM) was constructed and used to predict the mechanical properties of hybrid cardiovascular tissue engineering constructs. The model allows implementing 3D structures with desired porosities, mechanical and chemical properties. CAD models where designed using the FEM, with mechanical properties matching those of cardiac tissue. Contractile cardiac hybrids have been fabricated by arranging alternate layers of hydrogels and mammalian cardiovascular cells according to these CAD models using inkjet printers. Alginate hydrogels with controlled microshell structures were built by spraying cross-linkers onto ungelled alginic acid using inkjet printers. Cells were seen to attach to the inside of these microshells. The cells remained viable in constructs as thick as 1 cm due to the programmed porosity. Microscopic and macroscopic contractile function of cardiomyocytes sheets was observed in vitro. These results suggest that the printing method could be used for hierarchical design of functional cardiac patches, balanced with porosity for mass transport and structural support.
In-Plane and Out-of-Plane Dynamic Response Predictions of a Truck Tire Using Detailed Finite Element and Rigid Ring Models
Authors: Chae Seokyong , O¨ijer Fredrik , El-Gindy Mustafa , Trivedi Mukesh , Johansson Inge
Published: April 2008

A detailed nonlinear finite element analysis (FEA) model of a radial-ply truck tire, 295/75R22.5, has been developed using explicit FEA simulation software, PAM-SHOCK. For the validation of the model, the tire model predictions of contact patch area, vertical stiffness, and cornering characteristics, such as cornering force and aligning moment versus slip angle, at different vertical loads are in good agreement with available physical measurements. For complete vehicle simulations, a simplified rigid ring tire model is required for efficient analysis throughput. The behavior of such a tire model can be verified and improved by comparing responses with the developed FEA model. Moreover, the in-plane and out-of-plane tire parameters needed for the simplified rigid ring tire model could be virtually determined at various vertical loads by testing the FEA tire model instead of performing expensive tire parameters measurements. The in-plane and out-of-plane tire parameters are implemented into a simplified rigid ring tire model to perform durability tests. The durability tests are conducted to examine dynamic behaviors by using the FEA truck tire and the rigid ring tire models during running on a water drainage ditch at various vertical tire loads. The ditch is 12.0-cm (4.72-in) deep and lies in 45-degree angle against tire traveling direction. The dynamic responses such as vertical displacement, forces, and moments at tire center are predicted using both tire models. The results obtained from both models are in reasonable agreement.
A Simple Analytical Method for Teaching Force Analysis of Planar Frictionless Mechanisms
Authors: Abhary Kazem
Published: April 2008

A purely analytical method for teaching force analysis of one degree-of-freedom planar frictionless mechanisms has been developed herein. The method uses the vectorial illustration of mechanisms, which is widely used for kinematic analysis of mechanisms too. In this method, a joint-force is determined either via its decomposition into the direction of its adjacent links or from the equilibrium equations of one of these links. Unlike the conventional analytical method which leads to a system of simultaneous equations, this method leads to only one simple algebraic-equation or one simple vectorial-equation at a time. Force analysis of planar mechanisms has always been tedious and time consuming but this method has proved to be simple, straightforward and quick. It is therefore a most suitable tool for teaching mechanisms as it downgrades the project-type problems to the level of classroom tutorials.
Effects of Corner Frequency on Bandwidth and Resonance Amplitude in Designing PZT Thin-Film Actuators: An Experimental Demonstration
Authors: Wu Chia-Che , Lee Cheng-Chun , Cao G. Z. , Shen I. Y.
Published: April 2008

In the last decade, Lead Zirconate Titanate Oxide (PZT) thin-film actuators have received increasing attention because of their high frequency bandwidth, large actuation strength, fast response, and small size. The PZT film thickness is usually less than several microns as opposed to hundreds of microns for bulk PZT patches that are commercially available. As a result, PZT thin-film actuators pose unique vibration issues that do not appear in actuators with bulk PZT. Two major issues affecting actuator performance are the frequency bandwidth and the resonance amplitude. As an electromechanical device, a PZT thin-film actuator’s bandwidth and resonance amplitude depend not only on the lowest natural frequency ωn of the actuator’s mechanical structure but also on the corner frequency ωc of the actuator’s RC-circuit. For PZT thin-film actuators, the small film thickness implies large film capacitance C and small ωc. When the size of the actuator decreases, frequency ωn increases dramatically. As a result, improper design of PZT thin-film actuators could lead to ωc ≪ ωn substantially reducing the actuator bandwidth and the resonance amplitude. This paper is to demonstrate this phenomenon through calibrated experiments. In the experiments, frequency response functions of a fixed-fixed silicon beam with a 1-μm thick PZT film are measured through use of a laser Doppler vibrometer and a spectrum analyzer. The silicon beam has multiple electrodes with a wide range of resistance R and corner frequency ωc. The experimental results confirm that the actuator bandwidth and resonance amplitude are substantially reduced when ωc ≪ ωn.
An Example Performance Trade-Off Evaluation Using the Integration Framework for Architecture Development (IFAD) for Conceptual Vehicle Design
Authors: Gu Xiaoyu , Fenyes Peter A.
Published: April 2008

The Integration Framework for Architecture Development (IFAD) is an integrated framework that provides fast and consistent discipline analysis results and identifies discipline consequences corresponding to vehicle design changes. This information is valuable for balancing and integration in the early design phase. In this paper, the IFAD framework is utilized to conduct an example multi-objective multi-disciplinary optimization to evaluate vehicle performance trade-offs for a hypothetical vehicle. We consider design changes on high-level geometrical dimensions including front overhang, rear overhang and vehicle width at rocker. We also study vehicle configurations including choice of materials and tires and choice of powertrains. A commonly used multi-objective genetic algorithm (MOGA) technique, Non-dominated Sorting Genetic Algorithm (NSGAII [1]) is chosen because of the mixed types of design variables involved (i.e., continuous design variables representing high-level geometrical dimensions and discrete design variables representing vehicle configurations such as powertrain selection and material choice). Vehicle performance analyses in a range of disciplines such as geometry, aerodynamics and energy are carried out automatically through IFAD. The use of response surface modeling (RSM) is desired due to the large number of evaluations typical for a MOGA application. A comparison of the engineering performance trade-offs based on two different sets of performance objectives is presented.
An Intelligent Robotic System Platform for Autonomous Mapping and Sensor Data Gathering of Non-GPS Friendly Environments
Authors: Crassidis Agamemnon , Walter Wayne W. , Carr Douglas A. , Long Erin
Published: April 2008

This paper presents results of a novel intelligent robotic system using a re-configurable platform for autonomous mapping and sensor data gathering of non-Global Positioning System (GPS) friendly, unknown and hazardous enclosed environments such as caves, underground and underwater tunnel networks, building floors, and spaces within a collapsed building rubble field. The work developed here forms a basis for a swarm of mini/micro robotic vehicles capable of autonomous routing and control with a self-contained navigation system that does not rely on GPS information. A robotic prototype capable of autonomously mapping a floor plan (such as hallways within a building) has been developed. The robot navigates autonomously without the use of GPS and gathers absolute position information developing a 2-dimensional map of the hallway network using a novel Mini Inertial Measurement/Navigation System (MIMNS) developed at RIT. Also, enhancements to the MIMNS unit are presented for estimating attitude orientation of the robot using an accelerometer based device allowing for non-flat plane mapping using the MIMNS unit. The paper presents the concepts of the robot hardware and software, results of a 2-dimensional mapping of a flat plane, and introduces simulation results of an accelerometer based attitude orientation device.
A Torque Based Sliding Mode Control of an Eddy Current Braking System for Automotive Applications
Authors: Anwar Sohel
Published: April 2008

A sliding mode controller based on a polynomial-based eddy current machine model is presented in this paper. The controller provides a novel torque tracking control strategy that does not require any torque measurement. The enhanced parametric model captures the steady state torque-speed-current characteristics of the eddy current machine. The model parameters are experimentally estimated using a two stage least square type algorithm. Simulation of the proposed controller using a SIMULINK model incorporating the controller model, the eddy current brake model and a 14 degree of freedom vehicle model is performed. Simulation results are presented for the proposed controller in the context of an automobile braking application. The simulation results show good torque tracking performance of the proposed controller.
Anti-Lock Braking Control of an Electromagnetic Brake-by-Wire System
Authors: Anwar Sohel
Published: April 2008

This paper presents a nonlinear sliding mode type controller for slip regulation in a braking event for an electromagnetic brake-by-wire system equipped automobile. The electromagnetic brake -by-wire system under consideration consists of a set of eddy current brakes attached to the automobile wheels. The anti-lock braking controller modifies the brake torque command generated by a supervisory controller which, in turn, is based on the driver’s command sensed via brake pedal sensors. The modified brake torque command is then generated by a closed loop actuator control algorithm to control the eddy current brake (ECB) system. It is shown in this paper that the proposed anti-lock braking control system is stable in the sense of Lyapunov. Experimental results are presented for a test vehicle equipped with an electromagnetic brake-by-wire system. Experimental results show that the proposed anti-lock brake control algorithm provides very good slip regulation in a braking event on low friction coefficient surfaces (wet Jennite) when compared with that of a non anti-lock braking event. Experimental results also indicate that the proposed anti-lock braking control system provided a very smooth stop for the vehicle.
Design Optimization of Networks of Cooling Passages
Authors: Jelisavcic Nenad , Martin Thomas J. , Moral Ramon J. , Sahoo Debasis , Dulikravich George S. , Gonzalez Maickel
Published: April 2008

A one-dimensional thermo-fluid flow network analysis program COOLNET was developed to predict coolant flow rates, total coolant pressures, bulk coolant total temperatures, and internal heat transfer coefficient distributions, inside internally cooled objects. The coolant passages were allowed to be an arbitrary network of one-dimensional fluid elements or tubes. Geometric parameters of each passage were optimized using a hybrid multi-objective optimization algorithm. For the chosen Pratt & Whitney gas turbine the cross-sectional areas, hydraulic diameters, ribs’ heights and angles in each passage were optimized in order to minimize coolant flow rate, coolant total pressure loss, and total heat removed by coolant from the system. Validation of the hybrid multi-objective optimizer was performed with various test functions. Also, validation of the COOLNET was done with existing Pratt & Whitney gas turbine blade. Program OBJ was written to connect hybrid multi-objective optimizer and COOLNET. Optimization process was visualized using Tecplot (commercial software). Program PLOT was written to write input file for Tecplot, purpose of PLOT was to visualize initial and optimized results. Analysis for the best optimal result is given. The resulting COOLNET analysis provided coolant flow rates, total and static pressures and temperatures, and the heat transfer coefficient of each fluid element. The COOLNET analysis algorithm would typically converge in 50 iterations requiring about 5 seconds of CPU time on a 3.0 GHz processor. Results demonstrated that in case of an internally cooled gas turbine blade an improvement in overall performance is possible. A typical design optimization required between 500-1,000 iterations with a population of 30 designs. Thus, total number of configurations analyzed was approximately 15,000-30,000.
Child Resistant Packaging: Regulations and Effectiveness, 1980–2002
Authors: Pattin Cheryl A.
Published: April 2008

Poisoning from household substances has been and continues to be a hazard to children under 5 years of age. In an effort to address this problem, the Poison Prevention Packaging Act (PPPA) of 1970 was enacted as of December 30, 1970. This act is a federally preemptive piece of legislation covering an ever expanding group of substances. The test methods used to establish compliance with the PPPA do not address the range of substances covered (e.g. liquids); the changing patterns of use of household substances such as increased use of liquid medications for children; or repeated access to and multiple reclosures of containers, as seen in the home situation. To examine the effectiveness of the PPPA in addressing actual poisonings in children under 5, national databases from 1980 through March 13, 2002 were examined. Reports mentioning the use of a CRC (child resistant container) were then analyzed. Assisted Access incidents involved an older child gaining access to the contents of a CRC and giving those contents to the younger victim. Transfer of Contents incidents involved ingestion of a substance that was originally packaged in a CRC and was transferred to a non-CRC The average age of children seen in hospitals is under 2, and fatalities due to Assisted Access and Transfer of Contents incidents were seen in children averaging under one year of age. These age ranges are below those of children used in CRC testing (3.5 to 4.25 years). More importantly, the average body weights — directly related to the susceptibility to poisoning injury — of children seen in hospitals is less than the 25 pound weight used to set toxicity thresholds by the PPPA. Training for children, the elderly, and parents would help increase awareness of Transfer of Contents and Assisted Access poisonings, which are disproportionately represented in fatal poisoning incidents of young children.
A Numerical Study of the Global Performance of Two Static Mixers
Authors: Rahmani Ramin K. , Ayasoufi Anahita , Keith Theo G.
Published: April 2008

Viscous liquids have to be homogenized in continuous operations in many branches of processing industries; and therefore, fluid mixing plays a critical role in the success or failure of many industrial processes. The use of static mixers has been utilized over a wide range of applications from simple blending to complex chemical reactions. Generally, a static mixer consists of a number of equal stationary units, placed on the inside of a pipe or channel in order to promote mixing of flowing fluid streams. These mixers have low maintenance and operating costs, low space requirements and no moving parts. A range of designs exists for a wide range of specific applications. The shape of the elements determines the character of the fluid motion and thus determines the effectiveness of the mixer. There are several key parameters in the design procedure of a static mixer. Some of the most important ones are: the degree of mixing of working fluids, pressure drop across the mixer, and residence time distribution of fluid elements. An ideal static mixer provides a highly mixed material with low pressure drop and similar traveling history for all fluid elements. To choose a static mixer for a given application or in order to design a new static mixer, besides experimentation, it is possible to use powerful computational fluid dynamics (CFD) tools to study the performance of static mixers. This paper extends previous studies by the authors on industrial static mixers and illustrates how static mixing processes of single-phase viscous liquids can be simulated numerically. Using different measuring tools, the global performance and costs of two static mixers are studied.
Strain-Based Shape Estimation for Annular Plates
Authors: Sekouri El Mostafa , Hu Yan-Ru , Ngo Ahn Dung
Published: April 2008

Large flexible structures are used in many space applications, for example, satellite communication antennae, space robotic systems, and space station, etc. The flexibility of these large space structures results in problems of structure shape deformation and vibration, etc. In recent years, active shape control is developed to improve the performance of these flexible space structures. However, it is difficult to measure the surface shape of large flexible space structures in space environment. In this paper, a shape estimation method was developed to determine deflection of annular structures under arbitrary loading and boundary conditions. The shape estimation method utilizes strain information from strain gage sensors mounted on the structure. The strain field is calculated using polar components of stress in terms of Airy’s stress function. The coefficients of each function are determined based on the relationship of strain, displacement, and strain compatibility. The strain field is constructed by least squares smoothing procedure. This shape estimation method was verified by the numerical method, finite element and the experimental results. The results show that the shape estimation method can be used to determine deformation shape of the annular plate for active shape control of flexible structures.