bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Constitutive Parameters on Formation of a Spherical Void in a Compressible Nonlinear Elastic Material
Authors: Biwa Shiro , Matsumoto Eiji , Shibata Toshinobu
Published: April 2008

Void formation in materials under isotropic tension is considered within the theory of finite elasticity. This phenomenon is described as the bifurcation of the solution containing a spherical cavity from the state of homogeneous deformation of a solid hyperelastic sphere. The equation giving the bifurcation point is derived, and the critical stretch and stress are numerically calculated for a special class of compressible nonlinear elastic materials for which the strain energy function was proposed by Hill. The effects of constitutive parameters on the post-bifurcation behavior as well as on the critical stretch and stress are discussed.
Free-Edge Effects in Anisotropic Laminates Under Extension, Bending and Twisting, Part I: A Stress-Function-Based Variational Approach
Authors: Yin W.-L.
Published: April 2008

A variational method involving Lekhnitskii’s stress functions is used to determine the interlaminar stresses in a multilayered strip of laminate subjected to arbitrary combinations of axial extension, bending, and twisting loads. The stress functions in each layer are approximated by polynomial functions of the thickness coordinate. The equilibrium equations, the traction-free boundary conditions, and the continuity conditions of the interlaminar stresses are exactly satisfied in the present analysis, while the compatibility equations and the continuity of the displacements across the interfaces are enforced in an averaged sense by applying the principle of complementary virtual work. This yields an eigenvalue problem for the interfacial values of the stress functions and their normal derivatives. Interlaminar stresses for all three distinct loading cases may be obtained, in a single solution process, by combining the eigenfunctions with appropriate particular solutions (peculiar to each loading case) so as to ensure satisfaction of the traction-free boundary condition at the free edge.
Free-Edge Effects in Anisotropic Laminates Under Extension, Bending, and Twisting, Part II: Eigenfunction Analysis and the Results for Symmetric Laminates
Authors: Yin W.-L.
Published: April 2008

The eigenvalue problem associated with the determination of the interlaminar stresses in a laminated strip is examined and physical interpretations are given to the (constant) particular solutions and the complementary solutions of the problem. The case of symmetric laminates is considered in detail, and variational solutions are computed for four-layer, symmetric, cross-ply, and angle-ply laminates subjected to the three fundamental types of strain loads. Solutions based on two sets of stress functions with polynomial expansions of different degrees are compared with each other and with the existing solutions to assess the accuracy. The interfacial values of the stress functions and their derivatives are identified as the resultant peeling and shearing forces over end intervals of the interface.
Asymptotic Viscoelastic Rays in a Thick Plate
Authors: Weaver R. L. , Sachse W.
Published: April 2008

The high-frequency behavior of generalized ray arrivals is discussed with a view towards material characterization by means of measurements of the dispersion of ultrasonic pulses. The effect of beam spreading is treated exactly. Signal processing algorithms are developed. They are demonstrated with a synthetic signal obtained in an elastic material.
Generalized Reynolds Equation for Solid-Liquid Lubricated Bearings
Authors: Dai F. , Khonsari M. M.
Published: April 2008

The continuum theory of mixture was employed to derive a generalized form of the Reynolds equation for the lubrication problems involving lubricants that contain solid particles. The derivation of the governing equations and the boundary conditions are presented. The governing equations are two coupled partial differential equations that must be solved simultaneously for the solid volume fraction and the pressure distribution in a hydrodynamic bearing. The boundary conditions allow the particles to slip at the boundary surfaces. The formulation takes the interaction between the solid and the fluid constituents into consideration. Extensive numerical results are presented for the performance parameters in finite journal bearings lubricated with granular powder mixed with Newtonian oil.
On the Double Cantilever Beam Specimen for Mode-I Interface Delamination
Authors: Balendran B.
Published: April 2008

A compliance model is presented for a DCB specimen for mode-I interface delamination. The undelaminated part of the specimen is modeled by using Reissner’s mixed variational principle from which the rotation of the cross-section at the tip of the crack and the shear stress at the interface are evaluated. The results for a homogeneous beam with midplane crack are deduced and shown to be in better agreement with the experimental and finite element results than any of the existing models.
Plastic Spin and Related Issues in Phenomenological Plasticity
Authors: Lubarda V. A. , Shih C. F.
Published: April 2008

The role of plastic spin within the framework ofa phenomenological polycrystalline plasticity is examined. We show that if elastic and plastic strain rates are properly identified, partitioning of total spin and identification of its “plastic” part is not required in the elastoplastic constitutive analysis of elastically isotropic materials.
An Energy Criterion for the Onset of Shear Localization in Thermal Viscoplastic Materials, Part I: Necessary and Sufficient Initiation Conditions
Authors: Shawki T. G.
Published: April 2008

Necessary and/or sufficient conditions for the onset of shear flow localization in thermal viscoplastic materials are derived. Initiation of shear band formation is examined through the analysis of a one-dimensional model of dynamic simple shear with velocity-controlled boundaries. An exact energy estimate is derived for the fully nonlinear initial boundary value problem which illustrates the weak effect of elasticity as regards the onset of localization. The existence, uniqueness and well-posedness properties of a spatially homogeneous solution are also examined. A unique homogeneous solution is shown to exist for the dynamic simple shear problem with velocity controlled and thermally insulated boundaries. The former solution is also shown to be the unique static solution of the simple shear problem, with no elastic or heat conduction effects, consistent with the foregoing boundary conditions. A linear system of equations is derived for the perturbations superposed on the reference, time-dependent homogeneous (static) solution. A discussion regarding the notions of instability and localization motivates the introduction of a novel localization criterion, based on an appropriately selected energy norm, that takes full account of the time variation of the homogeneous solution. Taking advantage of the admissible spatial form of the perturbations together with the foregoing criterion allows for the association of the positive rate of change of the total kinetic energy of the absolute perturbations with the onset of shear strain localization.
Interactions Between Dislocations and Anisotropic Elastic Elliptical Inclusions
Authors: Yen Wen J. , Hwu Chyanbin
Published: April 2008

A general field solution for the stresses and displacements of the interactions between dislocations and inclusions has been derived in this paper by applying the Stroh’s formalism and the Muskhelishvili’s method of analytical continuation. The solutions are valid for general elastic anisotropic media under two-dimensional deformation. The interaction energy between dislocations and elastic inclusions is obtained explicitly. The solutions in general are expressed in series form for elastic inclusions. However, for the special cases when the elastic inclusions are replaced by a hole or rigid inclusion, simple closed-form solutions are derived. The general solutions are verified by considering the isotropic media since it is the only solution available in the literature. For the general anisotropic media, a series of contour diagrams for the glide component of the force on a dislocation are provided in this paper to study the effects of inclusion hardness, shape, and matrix anisotropy.
Hilbert Transform Generalization of a Classical Random Vibration Integral
Authors: Spanos P. D. , Miller S. M.
Published: April 2008

Integrals which represent the spectral moments of the stationary response of a linear and time-invariant system under random excitation are considered. It is shown that these integrals can be determined through the solution of linear algebraic equations. These equations are derived by considering differential equations for both the autocorrelation function of the system response and its Hilbert transform. The method can be applied to determine both even-order and odd-order spectral moments. Furthermore, it provides a potent generalization of a classical formula used in control engineering and applied mathematics. The applicability of the derived formula is demonstrated by considering random excitations with, among others, the white noise, “Gaussian,” and Kanai-Tajimi seismic spectra. The results for the classical problem of a randomly excited single-degree-of-freedom oscillator are given in a concise and readily applicable format.
A Circular Crack System in an Infinite Elastic Medium Under Arbitrary Normal Loads
Authors: Yong Zhou , Hanson M. T.
Published: April 2008

This analysis considers a circular crack system containing a penny-shaped crack and a concentric, coplanar external circular crack under arbitrary normal loading in a transversely isotropic body. The solution is obtained by transforming the governing two-dimensional integral equation to a set of algebraic equations which are easily solved numerically due to the special coefficient matrix. The normal stress component coplanar with the crack system is determined in power series form. The equations are solved and solutions for the stress intensity factors around the crack fronts are given for several different loading conditions. Including the rigid-body displacements at infinity allows the contact problem of an annular flat punch on an elastic half-space to be solved simultaneously.
Propagation of Surface Waves Across an Anisotropic Layer
Authors: Its E. N. , Lee J. S.
Published: April 2008

Propagation of elastic surface waves across a thin anisotropic interface layer between two vertically inhomogeneous isotropic quarter-spaces is considered. The relationship between the surface wave fields at the opposite sides of the layer is obtained in the form of matrix differential operators. Based on the Green’s function technique, an analytical method is developed to calculate reflection and transmission coefficients of Rayleigh waves at the layer. The reflection and transmission coefficients of Rayleigh waves at the interface layer are calculated as a function of the angle of incidence for various models of layers with hexagonal symmetry and results are discussed in some detail. Several isotropic layers of low or high velocity materials are also considered to examine the trade-off between anisotropy and inhomogeneity of the interface layer.
Swerve During Three-Dimensional Impact of Rough Rigid Bodies
Authors: Stronge W. J.
Published: April 2008

For collisions between rough bodies, dry friction can be represented by Coulomb’s law; this relates the normal and tangential components of contact force by a coefficient of limiting friction if the contact is sliding. The friction force acts in a direction opposed to sliding. For a collision with planar changes in velocity, sliding is in either one direction or the other; the direction can reverse before separation only if the impact configuration is eccentric or noncollinear and the initial velocity of sliding is small. In general, however, friction results in nonplanar changes in velocity; for free bodies the velocity changes are three-dimensional or nonplanar unless the initial sliding velocity lies in the same plane as two principal axes of inertia for each body. Nonplanar velocity changes give a direction of sliding that continually changes or swerves during an initial phase of contact in an eccentric impact configuration. The present paper obtains changes in relative velocity during “rigid” body collisions as a function of impulse Pn of the normal component of reaction force. The method of resolving changes in relative velocity as a function of impulse is demonstrated by obtaining the solution for a spherical pendulum colliding with a rough half-space. The solution depends on two independent material parameters—the coefficient of friction and an energetic coefficient of restitution.
Equivalent Nonlinear System Method for Stochastically Excited Hamiltonian Systems
Authors: Zhu W. Q. , Soong T. T. , Lei Y.
Published: April 2008

An equivalent nonlinear system method is presented to obtain the approximate probability density for the stationary response of multi-degree-of-freedom nonlinear Hamiltonian systems to Gaussian white noise parametric and/or external excitations. The equivalent nonlinear systems are obtained on the basis of one of the following three criteria: least mean-squared deficiency of damping forces, dissipation energy balancing, and least mean-squared deficiency of dissipation energies. An example is given to illustrate the application and validity of the method and the differences in the three equivalence criteria.
A Theory of Hydrodynamic Lubrication Involving the Mixture of Two Fluids
Authors: Dai F. , Khonsari M. M.
Published: April 2008

Based on the principles of continuum mechanics, we drive the governing equations for the hydrodynamic lubrication involving the mixture of two incompressible fluids. The governing equations are general in the sense that they can be applied to the mixture of any simple non-Newtonian fluid with a Newtonian fluid. A mixture thus formed is considered to be nonhomogeneous and non-Newtonian. In the theoretical development, the interaction between the constituents is taken into consideration. It is shown that a number of currently available models are special cases of the theory presented in this paper. As an example, results are presented for journal bearing performance lubricated with a mixture of a power-law fluid mixed with Newtonian oil.
Nondimensional Parameters and Equations for Buckling of Anisotropic Shallow Shells
Authors: Nemeth M. P.
Published: April 2008

A procedure for deriving nondimensional parameters and equations for bifurcation buckling of anisotropic shallow shells subjected to combined loads is presented. First, the Donnell-Mushtari-Vlasov equations governing buckling of symmetrically laminated doubly curved thin elastic shallow shells are presented. Then, the rationale used to perform the nondimensionalization of the buckling equations is presented, and fundamental parameters are identified that represent measures of the shell orthotropy and anisotropy. In addition, nondimensional curvature parameters are identified that are analogues of the well-known Batdorf Z parameter for isotropic shells, and analogues of Dunnell’s and Batdorf s shell buckling equations are presented. Selected results are presented for shear buckling of balanced symmetric laminated shells that illustrate the usefulness of the nondimensional parameters.
Thermodynamics of Duffing’s Oscillator
Authors: Berdichevsky V. , O¨zbek O. , Kim W. W.
Published: April 2008

We study the averaged characteristics of the response of Duffing’s oscillator to harmonic excitation. We show that, as in classical thermodynamics, response characteristics are potential functions of excitation characteristics.
On the Geometry of Nonholonomic Dynamics
Authors: Esse´n H.
Published: April 2008

The formulation and derivation of equations of motion for finite degree-of-freedom nonholonomic systems, is discussed. The starting point is Newton’s equation of motion in the 3K-dimensional unconstrained configuration space of K particles. Constraints represent knowledge that motion is only possible along some directions in the local tangent spaces. Only projections of the 3K-dimensional vector equation onto these allowed directions are of interest. The formalism is essentially that of Kane-Appell cast into an abstract form. It is shown to give the same equations as Hamel’s generalization of Lagrange’s method. The algorithmic advantage of the Kane-Appell projection approach is stressed.
Linear Flow and Deformation in a Poroelastic Disk With a Free Surface
Authors: Sachs J. R. , Glucksberg M. R. , Jensen O. E. , Grotberg J. B.
Published: April 2008

The equilibration of an axisymmetric, linearly poroelastic layer of finite thickness is determined given an immobile, impermeable base and an impermeable, stress-free top surface. Analytical and numerical studies show that there are eigenfunctions corresponding to sites of fluid injection and removal. Numerical studies also show that an increase in effective stiffness accelerates the equilibration of initial disturbances with longer wavelengths. A Gaussian initial displacement is shown to spread radially rather than simply decaying in amplitude.
Weakly Nonlinear Deformation of a Thin Poroelastic Layer With a Free Surface
Authors: Jensen O. E. , Glucksberg M. R. , Sachs J. R. , Grotberg J. B.
Published: April 2008

Using the biphasic theory of Biot (1941), we examine the evolution of deformations of a poroelastic layer, secured at its base to a rigid plane and having a stress-free, impermeable upper surface. By identifying a limit in which the layer is very thin but the wavelength of disturbances is very long, we show how nonlinear effects due to the finite slope of the free surface cause local elevations of the free surface to decay more slowly than depressions.
Localization and Propagation of Instabilities in Long Shallow Panels Under External Pressure
Authors: Power T. L. , Kyriakides S.
Published: April 2008

This paper discusses the response of long, shallow, elastic panels to uniform pressure loading. Under quasi-static conditions, the deformation of such panels is initially uniform along their length, and their response has the nonlinearity and instabilities characteristic of shallow arches. Shallower panels deform symmetrically about the midspan and exhibit a limit load instability. For less shallow panels, the response bifurcates into an unsymmetric mode before the limit load is achieved. A formulation and a solution procedure are developed and used to analyze the response of such panels beyond first instability. It is demonstrated in both cases that following the first instability the deformation ceases to be axially uniform and locqlizes to a region a few arch spans in length. A drop in pressure accompanies this localized collapse and causes unloading in the remainder of the panel. Subsequent deformation is confined to this region until membrane tension arrests the local collapse. Further deformation can occur at a constant pressure and takes the form of spreading of the collapsed region along the length of the panel. The lowest pressure at which this can take place (propagation pressure) can be significantly lower than the pressure associated with first instability.
Stability Analysis of a Spinning Elastic Disk Under a Stationary Concentrated Edge Load
Authors: Chen Jen-San
Published: April 2008

The natural frequencies and stability of a spinning elastic disk subjected to a stationary concentrated edge load are investigated both numerically and analytically. It is found that a stationary, conservative, compressive edge load decreases the natural frequencies of the forward and backward traveling waves, but increases the natural frequency of the so-called reflected wave. It is also found that the significance of the effect of the conservative edge load on the natural frequencies and stability of the spinning disk is solely through the transverse component of the edge load on the boundary, and not through the membrane stress field it produces inside the disk. In addition, the compressive edge load induces a stationary-type instability before the critical speed, and induces a merged-type instability after the critical speed when a reflected wave meets a forward or a backward wave. The expression for the derivative of the eigenvalues of the spinning disk with respect to the edge load is derived to verify the numerical results.
The Annular Taylor Column
Authors: Scott W. E.
Published: April 2008

A study is made of the time evolution of the flow generated by an annulus (a disk with a hole in it) of inner, outer radii a and b (a ≪ b), impulsively set into motion and rising at an infinitesimal Rossby number along the axis of rotation of a uniformly rotating, unbounded mass of inviscid, incompressible fluid. The result is that a Taylor column in the form of an annular cylinder of inner, outer radii a and b, does evolve, with all the properties a Taylor column should possess. As a consequence, possibly the first engineering application of the Taylor column is suggested.
External Circular Crack Under Normal Load: A Complete Solution
Authors: Fabrikant V. I. , Rubin B. S. , Karapetian E. N.
Published: April 2008

For the first time, a complete solution in terms of elementary functions is given to the problem of a transversely isotropic elastic space weakened by an external circular crack and subjected to arbitrary normal loading applied symmetrically to both crack faces. A complete field of displacements and stresses due to a concentrated loading is given for both transversely isotropic and purely isotropic cases. The method of solution is based on the results published earlier by the first author.
Switching Phenomenon of a Bathtub Vortex
Authors: Shiraishi M. , Sato T.
Published: April 2008

Switching phenomenon of the bathtub vortex in a double-orifice water tank is experimentally investigated. This alternation between “vortexflow” and “nonvortex flow” is caused by flow rate differences through the two orifices. The oscillation frequency is experimentally examined by changing the design parameters, such as the orifice size, the distance between two orifices, and the fluid level. A linear relationship is obtained between the frequency and the flow rate difference.
Equations of Motion of Two-Phase Variable Mass Systems With Solid Base
Authors: Eke F. O. , Wang Song-Min
Published: April 2008

This paper develops dynamical equations for variable mass systems that can be viewed, at any given instant, as comprising a solid phase and a fluid phase. The equations of translational and rotational motion are presented, and several versions of each are given. It is shown that some versions have major advantages over others because they involve parameters that are relatively easy to estimate in practical problems, and make close-form solutions possible without the usual penalty of drastic simplifying assumptions. A simple rocket example is presented, and shows that instability cannot be ruled out for such systems. It is shown that system and combustion chamber geometry play a crucial role in the attitude stability of such systems.
Geometrically Nonlinear Stress-Deflection Relations for Thin Film/Substrate Systems With a Finite Element Comparison
Authors: Masters C. B. , Salamon N. J.
Published: April 2008

A new higher order geometrically nonlinear relation is developed to relate the deflection of a thin film /substrate system to the intrinsic film stress when these deflections are larger than the thickness of the substrate. Using the Rayleigh-Ritz method, these nonlinear relations are developed by approximating the out-of-plane deflections by a second-order polynomial and midplane normal strains by sixthorder polynomials. Several plate deflection configurations arise in an isotropic system: at very low intrinsic film stresses, a single, stable, spherical plate configuration is predicted; as the intrinsic film stress increases, the solution bifurcates into one unstable spherical shape and two stable ellipsoidal shapes; in the limit as the intrinsic film stress approaches infinity, the ellipsoidal configurations develop into cylindrical plate curvatures about either one of the two axes. Curvatures predicted by this new relation are significantly more accurate than previous theories when compared to curvatures calculated from three-dimensional nonlinear finite element deflection results. Furthermore, the finite element results display significant transverse stresses in a small boundary region near the free edge.
Finite Element Analysis of Thermoelastic Contact Stability
Authors: Yeo Taein , Barber J. R.
Published: April 2008

When heat is conducted across an interface between two dissimilar materials, theimoelastic distortion affects the contact pressure distribution. The existence of a pressure-sensitive thermal contact resistance at the interface can cause such systems to be unstable in the steady-state. Stability analysis for thermoelastic contact has been conducted by linear perturbation methods for one-dimensional and simple two-dimensional geometries, but analytical solutions become very complicated for finite geometries. A method is therefore proposed in which the finite element method is used to reduce the stability problem to an eigenvalue problem. The linearity of the underlying perturbation problem enables us to conclude that solutions can be obtained in separated-variable form with exponential variation in time. This factor can therefore be removed from the governing equations and the finite element method is used to obtain a time-independent set of homogeneous equations in which the exponential growth rate appears as a linear parameter. We therefore obtain a linear eigenvalue problem and stability of the system requires that all the resulting eigenvalues should have negative real part. The method is discussed in application to the simple one-dimensional system of two contacting rods. The results show good agreement with previous analytical investigations and give additional information about the migration of eigenvalues in the complex plane as the steady-state heat flux is varied.
Bending Vibrations of Rotating Nonuniform Timoshenko Beams With an Elastically Restrained Root
Authors: Lee Sen Yung , Lin Shueei Muh
Published: April 2008

Without considering the Coriolis force, the governing differential equations for the pure bending vibrations of a rotating nonuniform Timoshenko beam are derived. The two coupled differential equations are reduced into two complete fourth-order differential equations with variable coefficients in the flexural displacement and in the angle of rotation due to bending, respectively. The explicit relation between the flexural displacement and the angle of rotation due to bending is established. The frequency equations of the beam with a general elastically restrained root are derived and expressed in terms of the four normalized fundamental solutions of the associated governing differential equations. Consequently, if the geometric and material properties of the beam are in polynomial forms, then the exact solution for the problem can be obtained. Finally, the limiting cases are examined. The influence of the coupling effect of the rotating speed and the mass moment of inertia, the setting angle, the rotating speed and taper ratio on the natural frequencies, and the phenomenon of divergence instability (tension buckling) are investigated.
Vibrations of Transversely Isotropic Finite Circular Cylinders
Authors: Chau K. T.
Published: April 2008

This paper investigates the exact frequency equations for all the possible natural vibrations in a transversely isotropic cylinder of finite length. Two wave potentials are used to uncouple the equations of motion; the resulting hyperbolic equations are solved analytically for the vibration frequencies of a finite cylinder with zero shear tractions and zero axial displacement on the end surfaces and with zero tractions on the curved surfaces. In general, the mode shapes and the frequency equations of vibrations depend on both the range of the frequency and the elastic properties of the material. The vibration frequencies for sapphire cylinders are studied as an example. Two limiting cases are also considered: the long bar limit equals the frequency equation for the longitudinal vibration of bars obtained by Morse (1954) and by Lord Rayleigh (1945); and the frequency equation for thin disks (small length/radius ratio) is also obtained. The frequency for the first axisymmetric mode agrees with the experimental observation by Lusher and Hardy (1988) to within one percent. Natural frequencies for the first three longitudinal and circumferential modes are plotted for all cylinder geometries. The lowest frequency always corresponds to the first nonsymmetric mode regardless of the dimension of the cylinder. For axisymmetric vibration modes, numerical plots show that double roots exist in the frequency equations; such doublets were observed experimentally by Booker and Sagar (1971).
Load Transfer From a Finite Cylindrical Fiber Into an Elastic Half-Space
Authors: Lee Ven-Gen , Mura Toshio
Published: April 2008

Based on the equivalent inclusion method, the load transfer problem of a finite cylindrical fiber embedded in an elastic half-space of different elastic properties is presented. The equivalent condition of inhomogeneity and inclusion problems simulates the fiber to an inclusion with chosen eigenstrains, and the problem is formulated to a set of integral equations with the unknown strength of eigenstrains. A numerical procedure is developed using a discretizing scheme by which the set of integral equations is reduced to a system of algebraic equations.
A Note on Interface Cracks With and Without Friction in Contact Zone
Authors: Deng X.
Published: April 2008

A complete set of Comninou’s bimaterial interface crack-tip fields with and without friction in the contact zone (Comninou, 1977a,b) is given in terms of several arbitrary analytic functions. When the bimaterial becomes homogeneous, the complex function representation fully describes the crack-tip field for a cracked body under conditions of crack surface contact and slip, which can occur when the body is subjected to combined compression and shear loadings.
Post-buckling Behavior of Stiffened Cross-Ply Cylindrical Shells
Authors: Savoia M. , Reddy J. N.
Published: April 2008

The post-buckling of stiffened, cross-ply laminated, circular determine the effects of shell lamination scheme and stiffeners on the reduced load-carrying capacity. The effect of geometric imperfection is also included. The analysis is based on the layerwise shell theory of Reddy, and the “smeared stiffener” technique is used to account for the stiffener stiffness. Nu cylinders under uniform axial compression is investigated to merical results for stiffened and unstiffened cylinders are presented, showing that imperfection-sensitivity is strictly related to the number of nearly simultaneous buckling modes.
Identifying and Processing Undesired Functions During Conceptual Design
Authors: Bruch Christine , Grabowski Hans
Published: April 2008

This paper addresses the problem of product fault anticipation and prevention during conceptual design of mechanical engineering products by introducing the concept of undesired functions as potential fault causes. The undesired functions considered in this paper are induced during solution principle synthesis and affect a product either by reducing the input of its intended functions or by producing undesired outputs, and can be processed either by determining and optimizing their distribution function, or by finding inverse, consecutive or compensation functions to them. The formal definition of the generic process of processing undesired functions bases on its subdivision into elementary steps, each step being described by its states and the according state transition. Object patterns and process patterns are adopted for the representation of the static and dynamic design knowledge respectively. The concept is verified with a product example from mechanical engineering.
Mitigating Crew Health Degradation During Long-Term Exposure to Microgravity Through Countermeasure System Implementation
Authors: Gernand Jeremy M.
Published: April 2008

Experience with the International Space Station (ISS) program demonstrates the degree to which engineering design and operational solutions must protect crewmembers from health risks due to long-term exposure to the microgravity environment. Risks to safety and health due to degradation in the microgravity environment include crew inability to complete emergency or nominal activities, increased risk of injury, and inability to complete safe return to the ground due to reduced strength or embrittled bones. These risks without controls slowly increase in probability for the length of the mission and become more significant for increasing mission durations. Countermeasures to microgravity include hardware systems that place a crewmember’s body under elevated stress to produce an effect similar to daily exposure to gravity. The ISS countermeasure system is predominately composed of customized exercise machines. Historical treatment of microgravity countermeasure systems as medical research experiments unintentionally reduced the foreseen importance and therefore the capability of the systems to function in a long-term operational role. Long-term hazardous effects and steadily increasing operational risks due to non-functional countermeasure equipment require a more rigorous design approach and incorporation of redundancy into seemingly nonmission-critical hardware systems. Variations in the rate of health degradation and responsiveness to countermeasures among the crew population drastically increase the challenge for design requirements development and verification of the appropriate risk control strategy. The long-term nature of the hazards and severe limits on logistical re-supply mass, volume and frequency complicates assessment of hardware availability and verification of an adequate maintenance and sparing plan. Design achievement of medically defined performance requirements by microgravity countermeasure systems and incorporation of adequate failure tolerance significantly reduces these risks. Future implementation of on-site monitoring hardware for critical health parameters such as bone mineral density would allow greater responsiveness, efficiency, and optimized design of the countermeasures system.
Influence of Proximity-Effect Loss on Surface Temperature Distribution of High-Frequency Inductors
Authors: Koizumi Katsuhiro , Ishizuka Masaru
Published: April 2008

This paper describes the development of a thermal modeling method for high-frequency inductors used in switch mode power supply (SMPS). In the proposed modeling method, the effect of proximity-effect loss occurring near the air gap on winding surface temperature was considered. In addition, the effect of anisotropic thermal conductivity in a winding block on the winding surface temperature was considered. As the key point in the numerical modeling, the significance of considering the influence of the proximity-effect loss and the anisotropic thermal conductivity on the winding surface temperature was demonstrated experimentally and numerically.
Dynamic Response of Surface Micromachined Horizontal Beam Flexure Actuators
Authors: Atre Amarendra P.
Published: April 2008

Surface micromachined electro-thermal beam flexure actuators are characterized by a number of desirable attributes including low response time, which encourages their use in sensing applications. This provides motivation for investigating the dynamic characteristics of these actuators in order to design more energy efficient electro-thermal actuators. To this end, this paper presents the development and implementation of a comprehensive finite element model to examine the transient response of the beam flexure actuator in air and vacuum environments. The predicted dynamic response of the actuator in air is compared with measured data and a previous analytical model. The effects of pulse width modulation are also investigated using model simulations, which might simplify implementation of the actuator in microsystems.
Coupled Oxygen Transport in the Avascular Region of a Coronary Artery for Basal to Hyperemic Flow
Authors: Vaidya Vinayak , Back Lloyd H. , Banerjee Rupak K.
Published: April 2008

The numerical investigation of coupled oxygen transport to the avascular region of the wall of coronary artery is carried out for varying wall thickness and flow rates from basal to hyperemic condition. The factors affecting the O2 transport, such as, consumption of oxygen in the avascular wall region, w, the avascular thickness, δ, supply of O2 from vasa vasorum, nonlinear O2 binding capacity of the hemoglobin and varying flow rates, are taken into account. The O2 concentration boundary layer, δb, is observed to be of ~80 μm thickness. The lowest medial partial pressure, Po2,min decreases by ~80% for a larger avascular thickness, δ, of 300 μm when compared with that for smaller δ of 200 μm.
Effect of Wheel Loading on the Occurrence of Vertical Split Rim Wheel Failures
Authors: Krisdtan Joseph , Stone Daniel , Elkins John
Published: April 2008

The recent appearance of vertical split rim (VSR) wheel failures has presented North American railroads with a new mode of wheel failure. These failures originate from tread shelling as a result of rolling contact fatigue (RCF). One or more of the shallow RCF cracks initiate a brittle fracture that causes the separation of a large portion of the front or back of the wheel rim as shown in Figures 1, 2, and 3. TTCI is leading a consortium made up of railroads, suppliers, car owners, and the Federal Railroad Administration (FRA) to investigate wheel defects. VSR research is at the forefront of that effort.
Simulating and Measuring Structural Intensity Fields in Plates Induced by Spatially and Temporally Random Excitation
Authors: Daley Michael J. , Hambric Stephen A.
Published: April 2008

The structure-borne power in bending waves is well understood, and has been studied by many investigators in ideal beam and plate structures. All studies to date, however, have considered only the structural intensity induced by deterministic, localized drives. Since many structures of practical interest are excited by spatially random pressure fields, such as diffuse and turbulent boundary layer pressure fluctuations, techniques for measuring and predicting the structural intensity patterns in plates excited by such fields are presented here. The structural intensity at various frequencies in a simply-supported, baffled, flat plate driven by a diffuse pressure field is simulated using analytical techniques and measured by post-processing data from a scanning laser Doppler vibrometer and reference accelerometer using finite differencing techniques. The measured and simulated fields are similar, and show intensity patterns different from those caused by deterministic point drives.
Anti-Swing Adaptive Fuzzy Controller for an Overhead Crane With Hoisting
Authors: Renno Jamil M. , Trabia Mohamed B. , Moustafa Kamal A. F.
Published: April 2008

This paper presents a novel method for adaptive anti-swing fuzzy logic control for overhead cranes with hoisting. The control action is distributed between three fuzzy logic controllers (FLC’s): trolley controller, hoist controller, and anti-swing controller. A method for varying the ranges of the variables of the three controllers as a function of the crane’s parameters and/or motion variables is presented. Simulation examples show that the proposed controller can successfully drive overhead cranes under various operating conditions.
Dynamic Stress Analysis and Correlated With Test for an Automotive Driveline
Authors: Liao Gene Y.
Published: April 2008

This paper documents the result of dynamic stress analysis correlated with bending test for an automotive rear-wheel-drive driveline system. Good correlation is achieved. The procedure developed in this paper consists of three steps. Step 1 is to generate Finite Element Analysis (FEA) models of the components and subsystems, and analyze the system’s natural frequencies, mode shapes and driving point frequency response functions using Nastran software. Step 2 is to develop the propshaft model that includes manufacturing variation and simulated dynamic balancing. Step 3 is to run the dynamic stress analysis in ADAMS software. The objective of developing the analytical procedure of driveline dynamic system is to reduce the number of tests required under driveline design stage. This project also serves as a case study to graduate students in predicting dynamic stress of a real industrial part.
A Study of the Running Accuracy of Re-Circulating, Linear Bearings
Authors: Myszka David H.
Published: April 2008

The demand for faster operation, higher quality output and increased efficiency in automation and machine control systems has led to increased demands on guidance systems. Innovation of re-circulating, linear bearing guide technology has launched that option as the preferred choice for most precision linear motion stages. As the use of re-circulating linear guides increases, many vendors have entered the market, producing nearly identical products. All vendors promote similar load capabilities, running speeds and accuracies. A machine designer has difficulty in selecting a specific brand. An extensive study was conducted to evaluate the running accuracy of several commercially available, re-circulating bearings and configurations. This paper will describe the results of the study and explain the reasons for various inaccuracies. These results will help understand the subtle details of the different styles.
On the Influence of Artificial Cavitation on Underwater Noise Radiation From a Ship Hull
Authors: Matveev Konstantin I.
Published: April 2008

With increasing speed and power of next-generation combat and transport surface ships, the reduction of the magnitude of the ship acoustic signature becomes a vital task of naval engineering. Another related problem is to decrease the self-noise affecting operations of the ship’s own sonar. Currently, sponsors of naval research are encouraging the investigation of new methods for noise reduction, alternative to the usual weight-increasing enhancement of damping and insulating structures. One of the advanced concepts for future marine transportation is the use of artificial cavitation on a hull to reduce hydrodynamic drag and associated power requirements. Since this concept involves the application of air layers and possibly bubbly mixtures at the hull surfaces, underwater sound radiation properties of this ship type can differ significantly from those of traditional vessels. This paper deals with some major components of ship noise originating inside a ship and on its hull surface. The effects of the presence of gaseous layers on underwater radiation of ship’s noise are considered. Estimated results are presented for typical parameters of ships with artificial cavitation.
The Effect of Gravity on Heat Transfer by Rayleigh Streaming in Pulse Tubes and Thermal Buffer Tubes
Authors: Matveev Konstantin I. , Backhaus Scott , Swift Gregory W.
Published: April 2008

Thermoacoustic engines and refrigerators use the interaction between heat and sound to produce acoustic energy or to transport thermal energy. Heat leaks in thermal buffer tubes and pulse tubes, components in thermoacoustic devices that separate heat exchangers at different temperatures, reduce the efficiency of these systems. At high acoustic amplitudes, Rayleigh mass streaming can become the dominat means for undesirable heat leak. Gravity affects the streaming flow patterns and influences streaming-induced heat convection. A simplified analytical model is constructed that shows gravity can reduce the streaming heat leak dramatically.
Image Based MEMS Dynamics Characterization System
Authors: Bai Jinpeng , Xie Yongjun , Shi Tielin , Liu Sheng
Published: April 2008

For MEMS with moveable parts, it is crucial for the designers and fabricators to conduct real time observation of dynamic behaviors of the device and the packaged system, especially when the nonlinear behavior is obvious. This article presents an image based characterization system in which phase shifting interferometry, microvision, and strobe illumination are integrated. Several measurement examples of MEMS devices carried out by this system are presented.
Controlling a Constant Pressure Breathing Mask: A Task of Multiple Disturbances
Authors: Chan H. , Al-Jumaily A. M. , D’Arcy A. E. , Makinson D.
Published: April 2008

Developing a control system for breathing devices to control the pressure mask is a task which involves the consideration of breath cycle fluctuations due to normal and/or abnormal conditions, variations in environmental conditions and the airflow time delays within the device. Using forward compensation an appropriate control scheme is developed to achieve this task. To investigate the dynamic response, the breathing device incorporating the control system is modeled using Simulink® in a Matlab® environment and some validation experiments are conducted. The proposed control scheme seems to meet the demand of the fluid flow time delay and compensate for system fluctuations and disturbances.
Effect of Surface Profile Structure on Stability of Friction and Wear
Authors: Titov A. , Dubrovsky R.
Published: April 2008

This paper describes the role of surface texture parameters of bodies in contact on friction coefficient and wear rate. Experiments are done on wear friction testing machine that allows dynamically tracking friction coefficient and wear rate of surfaces in contact under heavy-duty boundary lubrication conditions. Experiments based on conforming steel 4340 -bronze SAE 40 friction couple showed the role of profile characteristics of bodies in contact such as skewness and bearing length ratio. Experimental results demonstrated that for surfaces with similar roughness, waviness and profile parameters, a surface with skewness higher than −1.3 invokes instability in test parameters causing fast climb of friction coefficient and increased mass loss.
Lung Simulator for Breathers Assessment and Occlusion Identification
Authors: Ijpma G. , Al-Jumaily A. M. , White David
Published: April 2008

Many respiratory devices are used to help patients to overcome breathing difficulties. As a first step, these equipments are normally tested and calibrated using a lung simulator. Many of the available positive pressure lung simulators achieve the purpose of simulation; however, they neither resemble actual lung vacuum conditions nor can be used for assessing breathing disorders. In this research a special purpose negative pressure simulator is proposed, developed, instrumented and tested. In addition to the lung elasticity, resistance, and compliance, the simulator replicates the vacuum conditions in the lung cavity. It also can be used for occlusion and ailments identification and other disorder diagnostics.
State-Space Approach to Calculate Sensitivity of Dynamic Response
Authors: Law S. S. , Lu Z. R.
Published: April 2008

The dynamic responses of a prestressed Euler-Bernoulli beam due to sinusoidal excitation are calculated by the state space approach. The sensitivities of displacement and acceleration responses with respect to the prestressing force are then calculated in the time domain, and they are compared with those from using Newmark method [1]. Computation simulation with a simply supported prestressed beam illustrates that both the dynamic responses and sensitivities calculated from the state space method is more efficient and both methods have the same accuracy.