bluuebunny/crossref_metadata_2025 huggingface dataset:
Extension of Vlasov’s Semi-membrane Theory to Reinforced Composite Shells
Authors: Birman V.
Published: April 2008

Governing equations for the statics and dynamics of reinforced composite shells are developed based on Vlasov’s semi-membrane shell theory. These equations have closed-form solutions illustrated for buckling and free vibration problems. The buckling solution converges to the known result for unstiffened isotropic shells.
Identification of Nonlinear Dynamic Systems Using Neural Networks
Authors: Masri S. F. , Chassiakos A. G. , Caughey T. K.
Published: April 2008

A procedure based on the use of artificial neural networks for the identification of nonlinear dynamic systems is developed and applied to the damped Duffing oscillator under deterministic excitation. The “generalization” ability of neural networks is invoked to predict the response of the same nonlinear oscillator under stochastic excitations of differing magnitude. The analogy between the neural network approach and a qualitatively similar nonparametric identification technique previously developed by the authors is illustrated. Some of the computational aspects of identification by neural networks, as well as their fault-tolerant nature, are discussed. It is shown that neural networks provide high-fidelity mathematical models of structure-unknown nonlinear systems encountered in the applied mechanics field.
Application of Dressler Theory to Weir Flow
Authors: Ramamurthy Amruthur S. , Vo Ngoc-Diep
Published: April 2008

The curvilinear flow past a circular-crested weir is analyzed with the help of Dressier equations. Specifically, the lower range of the depth over the weir crest is considered in the analysis, so that the shallow depth model could be adopted. The weir discharge coefficient is determined as a function of the total head of the approach flow and the crest radius. The weir discharge coefficient obtained on the basis of Dressier theory is verified with the help of present and previous experimental data.
An Analysis of Crack Trapping by Residual Stresses in Brittle Solids
Authors: Bower A. F. , Ortiz M.
Published: April 2008

The residual stress distribution in a brittle polycrystalline solid may have a significant influence on its toughness. Grains in a state of residual compression are less likely to be fractured by a growing crack and may trap the crack front or be left behind as bridging particles (Evans et al., 1977). This paper estimates the toughness enhancement due to intergranular residual stresses, using a three-dimensional model. The residual stress is approximated as a doubly sinusoidal distribution acting perpendicular to the plane of an initially straight semi-infinite crack. An incremental perturbation method developed by Bower and Ortiz (1990) for solving three-dimensional crack problems is extended here to cracks loaded by nonuniform remote stresses. It is used to calculate the shape of the semi-infinite crack as it propagates through the doubly sinusoidal residual stress. It is shown that the local regions of compression may trap the crack front and give rise to some transient toughening. In addition, if the residual stress exceeds a critical magnitude, pinning particles may be left in the crack wake. However, for practical values of residual stress and grain size, the predicted toughness enhancement is insignificant. Furthermore, the analysis cannot account for the large bridging zones observed in experiments. It is concluded that the R-curve behavior and bridging particles observed in monolithic ceramics are caused by mechanisms other than residual stresses acting perpendicular to the crack plane.
A Simple Continuum Model of Creep in a Fiber Composite Beam
Authors: Evans J. T.
Published: April 2008

A simple linear model of creep of a fiber composite beam treated as a continuum is presented. The model predicts that the displacement of a tip-loaded cantilever is linear with time but that the surface tensile stress increases approximately with the square root of time. The increase in tensile stress is in line with the prediction of stress channelling in the theory of ideal fiber-reinforced materials. The results are discussed in relation to some previous experimental observations and a generalization of the model which might be of value in life-time prediction is suggested.
A Study of Combined Asymmetric and Cavitated Bifurcations in Neo-Hookean Material Under Symmetric Dead Loading
Authors: Hou Hang-sheng
Published: April 2008

A study is given of the deformations of an incompressible body composed of a neo-Hookean material subjected to a uniform, spherically symmetric, tensile dead load. It is based on the energy minimization method using a constructed kinematically admissible deformation field. It brings together the pure homogeneous asymmetric deformations explored by Rivlin (1948, 1974) and the spherically symmetric cavitated deformations analyzed by Ball (1982) in one setting, and, in addition, Hallows nonsymmetric cavitated deformations to compete for a minimum. Many solutions are found and their stabilities examined; especially, the stabilities of the aforementioned asymmetric and cavitated solutions are reassessed in this work, which shows that a cavitated deformation which is stable against the virtual displacements in the spherical form may lose its stability against a wider class of virtual displacements involving nonspherical forms.
Complex Modes and Solvability of Nonclassical Linear Systems
Authors: Caughey T. K. , Ma F.
Published: April 2008

The purpose of this article is to give necessary and sufficient conditions under which nonclassical linear systems can be decoupled or become solvable.
Scattering of Ultrasonic Wave by Cracks in a Plate
Authors: Liu S. W. , Datta S. K.
Published: April 2008

A hybrid numerical method combining finite elements and the boundary integral representation is used to investigate the transient scattering of ultrasonic waves by a crack in a plate. The incident wave models the guided waves generated by a steel ball impact on the plate. Two surface-breaking cracks and one subsurface crack are studied here. The results show that the location and depth of cracks have measurable effects on the surface responses in time and frequency domains. Also, the scattered fields have distinct differences in the three cases.
On Newton’s and Poisson’s Rules of Percussive Dynamics
Authors: Batlle J. A.
Published: April 2008

Newton’s and Poisson ’s rules are widely used in percussive dynamics because they lead to an “all linear” solution. However, they are in general energetically inconsistent in rough collisions. The equivalence between both rules and a broad condition for them to be energetically consistent is presented for single point collisions in multibody systems with perfect constraints. It is fulfilled in collisions described by equations of motion with constant coefficients—sliding in the same direction or no sliding—and in “balanced” collisions—sliding velocity would not change if friction were negligible—Coulomb’s friction and infinite tangential stiffness are assumed at the collision point.
Vibration Absorbers for a Class of Self-Excited Mechanical Systems
Authors: Natsiavas S.
Published: April 2008

An averaging methodology is employed in studying dynamics of a two-degree-of-freedom nonlinear oscillator. The main system is modeled as a van der Pol oscillator under harmonic forcing. The objective is to reduce its amplitude of oscillation near resonance, by attaching to it a damped vibration absorber with a Duffing spring. It is first shown that substantial reduction in the response amplitude can be achieved in this way. However, for some combinations of the parameters, the low-amplitude periodic motion of the system in the original resonance regime becomes unstable through a Hopf bifurcation of the averaged equations. Direct numerical integration shows that this gives rise to amplitude modulated or chaotic response of the oscillator, with much higher vibration amplitudes than the unstable periodic response, which coexists with these complex motions. Finally, it is shown that the present analysis can be employed in selecting the parameters in ways that exploit the significant practical advantages arising from the presence of the absorber, by predicting and avoiding these instabilities.
A Multiple-Scales Analysis of Nonlinear, Localized Modes in a Cyclic Periodic System
Authors: Vakakis A. , Nayfeh T. , King M.
Published: April 2008

In this work the nonlinear localized modes of an n-degree-of-freedom (DOF) nonlinear cyclic system are examined by the averaging method of multiple scales. The set of nonlinear algebraic equations describing the localized modes is derived and is subsequently solved for systems with various numbers of DOF. It is shown that nonlinear localized modes exist only for small values of the ratio (k/μ), where k is the linear coupling stiffness and μ is the coefficient of the grounding stiffness nonlinearity. As (k/μ) increases the branches of localized modes become nonlocalized and either bifurcate from “extended” antisymmetric modes in inverse, “multiple” Hamiltonian pitchfork bifurcations (for systems with even-DOF), or reach certain limiting values for large values of(k/μ) (for systems with odd-DOF). Motion confinement due to nonlinear mode localization is demonstrated by examining the responses of weakly coupled, perfectly periodic cyclic systems caused by external impulses. Finally, the implications of nonlinear mode localization on the active or passive vibration isolation of such structures are discussed.
The r−1/2 (ln r) Singularities at Interface Cracks in Monoclinic and Isotropic Bimaterials due to Heat Flow
Authors: Yan G. , Ting T. C. T.
Published: April 2008

It is known that the stress singularities at an interface crack tip of bimaterials with the effects of heat flow may have the form r−1/2 (ln r). The existence conditions of the higher order singularitiy r−1/2 (ln r) are studied for monoclinic bimaterials whose plane of symmetry is at x3 = 0. It is shown that the higher order singularity does not exist if the bimaterial is mismatched. If the bimaterial is non-mismatched, the higher order singularity does not exist when a certain condition is satisfied. This condition is given explicitly for monoclinic bimaterials with the plane of symmetry of x3 = 0 and in a simple form for isotropic bimaterials.
Buckling and Post-buckling of Composite Plates and Shells Subjected to Elevated Temperature
Authors: Birman V. , Bert C. W.
Published: April 2008

Effects of temperature on buckling and post-buckling behavior of reinforced and unstiffened composite plates or cylindrical shells are considered. First, equilibrium equations are formulated for a shell subjected to the simultaneous action of a thermal field and an axial loading. These equations are used to predict a general form of the algebraic equations describing the post-buckling response of a shell. Conditions for the snap-through of a shell subjected to thermomechanical loading are formulated. As an example, the theory is applied to prediction of post-buckling response of flat large-aspect-ratio panels reinforced in the direction of their short edges.
Viscoelastic Response of a Strand
Authors: Conway T. A. , Costello G. A.
Published: April 2008

A method is presented in which the axial viscoelastic response of a multiple filament strand, constrained by a no-end rotation boundary condition, may be predicted. This method is an initial attempt to describe the time-dependent response of the multilayer strand by incorporating the stress relaxation data for a linearly viscoelastic construction material. Specifically, a strand consisting of a core filament, six filaments in the second layer, and twelve filaments in the outer layer is analyzed. This analysis could, however, include any number of layers of filaments where each layer has a concentric helix radius. The particular material used in this paper is polymethyl methacrylate (PMMA). The stress relaxation for PMMA is modeled analytically using the Schapery collocation method which determines the constant coefficient values for the elements of a Wiechert response model. Since this is a first approximation model, the approach is limited to linear viscoelasticity. The geometric effects of the strand are then combined with the Wiechert response model to develop a system of convolution integrals which satisfy the equilibrium and imposed boundary conditions for the multiple filament strand construction. The solutions for these integrals are approximated numerically using a modified Newton’s iterative method combined with a numerical technique which takes into account the material’s stress-strain history.
On the Approximate Solution of Nonclassically Damped Linear Systems
Authors: Hwang J. H. , Ma F.
Published: April 2008

A common procedure in the solution of a nonclassically damped linear system is to neglect the off-diagonal elements of the associated modal damping matrix. For a large-scale system, substantial reduction in computational effort is achieved by this method of decoupling the system. In the present paper, the error introduced by disregarding the off-diagonal elements is evaluated, and a quadrature formula for the approximation error is derived. A tight error bound is then obtained. In addition, an effective scheme to improve the accuracy of the approximate solution is outlined.
Switchmode Hydraulic Power Supply Theory
Authors: Cao Jianwei , Gu Linyi , Wang Feng , Qiu Minxiu
Published: April 2008

Switchmode hydraulic power supply is a new kind of energy-saving pressure converting system, which is originally proposed by the authors. It is mainly applied in multiple-actuator hydraulic systems, and installed between hydraulic pump and actuators (one switchmode hydraulic power supply for one actuator). It can provide pressure or flow rate that is adapted to the consumption of each actuator in the system by boosting or bucking the pressure, with low power loss, and conveniently, through high-speed switch valves, just like a hydraulic pressure transformer. There are two basic types of switchmode hydraulic power supply: pressure boost and pressure buck. Their structures and working principles are introduced. The dynamic characteristics of two typical types of switchmode hydraulic power supply, the pressure boost type and the pressure buck type, were analyzed through simulations and experiments. The performances were evaluated, and improvements on the efficiency of switchmode hydraulic power supply were proposed.
On the Effect of Mechanical and Thermal Anisotropy on the Stability of Gravity Driven Convection in Rotating Porous Media
Authors: Govender Saneshan , Vadasz Peter
Published: April 2008

We investigate Rayleigh-Benard convection in a porous layer subjected to gravitational and Coriolis body forces, when the fluid and solid phases are not in local thermodynamic equilibrium. The Darcy model (extended to include Coriolis effects and anisotropic permeability) is used to describe the flow whilst the two-equation model is used for the energy equation (for the solid and fluid phases separately). The linear stability theory is used to evaluate the critical Rayleigh number for the onset of convection and the effect of both thermal and mechanical anisotropy on the critical Rayleigh number is discussed.
Driver Fatigue/Inattention Monitoring Device: An Integrated System for Heavy Trucks
Authors: Ferrone Christopher W. , Sinkovits Charles
Published: April 2008

The National Transportation Safety Board has reported statistics which indicate that 31% of all fatal-to-the-truck driver accidents occur due to fatigue/inattention [1] and 58% of all single-vehicle large truck crashes were also fatigue related [2]. If these numbers can be reduced, many lives can be saved. A Driver Fatigue Monitoring System has been designed and built to monitor whether a driver is sleeping or inattentive. This integrated system monitors the steering input behavior of the driver during a specified period of time. If the number of steering inputs is below the expected predetermined threshold, the system activates an audible alarm and light in the cab, waking the driver. Furthermore, this system can deactivate cruise control as well as activate various other preprogrammed truck systems or components to further aid in the control of the truck and to alert nearby motorists.
The Runaway Diesel: A Side by Side Mechanical Analysis
Authors: Ferrone Christopher W. , Sinkovits Charles
Published: April 2008

When a diesel engine is exposed to an external fuel source such as an airborne combustible hydrocarbon in the surrounding environment, it naturally ingests the mixture into the air intake system. Since diesel engines control fuel and not air, the engine can no longer maintain speed control (Fig. 1).
Performance of the Combustion Process Inside an Aluminum Melting Furnace With Natural Gas and Liquid Fuel
Authors: Nieckele Angela O. , Naccache Moˆnica F. , Gomes Marcos S. P. , Carneiro Joa˜o N. E. , Silva Bruno Goes e
Published: April 2008

The choice of the type of fuel used as energy source for the aluminum melting can be of extreme importance for a better performance as well as for a greater preservation of the equipments. The option of a liquid or gaseous fuel can significantly alter the combustion aspects inside the furnace, such as the shape of the flame and the distribution of temperature and heat flux. In the present work, numerical simulations were carried out using the commercial package FLUENT, analyzing different cases with two types of fuel: a spray of liquid oil and a natural gas jet, both reacting with pure oxygen. The results showed the possible damages caused by the process if long or too intense and concentrated flames are present, increasing very much the wall temperatures and compromising the heat flux on the aluminum surface.
Performance Testing of Centrifugal Compressors Within the Petroleum Industry: A User’s View
Authors: Taherimoghaddam Mahdi
Published: April 2008

The role of centrifugal compressors within the petroleum industry is critical since they are used in all aspects of gas processing such as gas lift, transmission and distribution, re-injection into reservoir for pressure maintenance, wellhead separator boosting, casing head gas collection, under ground gas storage and liquefaction for transport, [1]. Among those optional tests applicable to centrifugal compressors stressed in API STD 617, performance test demands a great attention, since it determines if equipment meets design or expected performance criteria and serve as a means to determine fulfillment of manufacturer’s guarantees. Having a working knowledge coupled with more rigorous testing prior to accepting delivery of centrifugal compressors can reveal a fairly large percentage of performance failures. The main purpose of writing this paper is to share the author’s experience of purchasing and testing centrifugal compressors within the petroleum industry. Furthermore, it attempts to address the potential pitfalls of a poor performance test procedure.
The Gas Turbine Hybrid Vehicle Prototype of the University of Roma 1: Status Review
Authors: Capata R. , Coccia A. , Lora M. , Sciubba E.
Published: April 2008

In 1999, the University of Roma 1 launched a project to study the theoretical and practical feasibility of a hybrid passenger car in which the thermal engine is a Gas Turbine unit. The feasibility was demonstrated on paper, and some experimental tests were conducted at the ENEACasaccia Laboratories on a small (45 kW) gas turbine set, to investigate the performance of the propulsive unit (turbine plus batteries and electrical motor) under the standard european ECE emission tests. After successful completion of these tests, a further analysis was carried out to identify an “optimal” hybridization ratio with respect both to driveability and to fuel consumption: the results indicate that an absolute “optimal” configuration does not exist, because not only the system performance, but also the absolute and relative sizes (i.e., nameplate power) of the turbine and of the battery pack depend substantially on the type of driving mission the car is called to perform. The present status report describes all the above activities in some detail, and constitutes an attempt to put into perspective the entire Project. Using commercially available data for the components, the preliminary design of a road prototype is described and briefly discussed. For practical reasons the first prototype is likely to be equipped with a sub-optimal propulsion system: the differences and their implications are discussed as well.
Cooling System for a Portable Bio-Industry Centrifuge
Authors: Vatannia Shahla , Barez Fred
Published: April 2008

A centrifuge is used in bio-industry to separate species in blood and other chemicals. Bio-industry requires a temperature of zero degree centigrade in the rotor compartment of a centrifuge where samples are placed. In general, the current portable centrifuge systems generate a temperature of about 22 °C in the rotor compartment when operating at 3000 RPM. The motor and the electronics are the primary sources of the heat generation in such centrifuge. The aim of this study is to develop an appropriate cooling system for a specific portable centrifuge used in separating bioparticles that generates a total heat of approximately 43 W. Experimental, analytical and computer simulation were employed to achieve the project objective of reducing and maintaining the rotor compartment temperature at zero degree C. The CFD code Simulation model predicted rotor compartment temperatures that were in good agreement with those of the experimental measurements within 3%. Having confidence in the CFD model, simulation was carried out to incorporate four TEC units that are embedded on the surface of the rotor compartment resulting in reduced temperature to zero degree C.
The Role of C-Black in Improvement of Tribological Properties of Industrial Rubber Materials: Deproteinised Natural Rubber and Polyisoprene
Authors: El-Tayeb N. S. M. , Nasir R. Md.
Published: April 2008

This is a part of collaborative project between Multimedia University, Melaka and Malaysia Rubber Board, Sg. Buloh, Selangor. In this work, the tribological properties of Deproteinised Natural Rubber (DPNR) was examined and compared with synthetic cis 1,4 polyisoprene rubber (IR) namely Natsyn 2200. The effect of adding carbon black (CB) (0, 25 and 50 phr) to both DPNR and IR on the friction and wear characteristics was investigated. Dry abrasion tests were carried out using pin-on-ring tribometer with abrasive paper (diamond-50) under different operating test conditions such as applied normal load (5-35N), sliding speed (0.3-1.5 m/s), and sliding distance (90-450m). Experimental results showed that the addition of CB has significantly affected the wear and friction characteristics of both DPNR and IR, i.e. reduces the abrasion weight loss by more than 70% compared to unfilled rubber, depending on the test conditions and the concentration of CB. The friction coefficient of DPNR was improved by about 12.5% upon the addition of 50phr CB, compared to unfilled DPNR. Meanwhile, adding (25-50phr) CB to IR drastically deteriorates the friction coefficient, i.e. an increase in the friction by about 200% at 25phr CB and 300% at 50phr CB compared to unfilled IR. Finally, SEM technique is employed to observe the abrasion pattern of rubber in order to correlate the experimental test results to the wear mechanisms.
Effect of Physical Nonlinearity on Vibrations of Piezoelectric Rods
Authors: Birman Victor
Published: April 2008

Nonlinear stress-strain relationships (physical nonlinearity) may have a large effect on the structural response of piezoelectric sensors and actuators. The paper addresses the subject concentrating on cylindrical piezoelectric rods that experience vibrations as a result of an alternating electric field applied in the axial direction. The problem considered in the paper is important in connection with design of piezoelectric transducers. It is shown that neglecting the non-linear stress-strain relationship of the piezoelectric material can result in a significant error in the predicted response of the transducer.
Extended Lagrangian Formalism and Invariants of Motion of Dynamical Systems: A Case Study of Electromechanical System
Authors: Rastogi Vikas , Mukherjee Amalendu , Dasgupta Anirvan
Published: April 2008

In this paper, an extended Lagrangian formalism for general class of dynamical systems with dissipative, non-potential fields is formulated with the aim to obtain invariants of motion for such systems. A new concept of umbra-time has been introduced for this extension. D’Alembert basic idea of allowing displacement, when the real time is frozen is conveniently expressed in the terms of umbra-time. This leads to a peculiar form of equations, which is termed as umbra-Lagrange’s equations. A variational or least action doctrine leading to the proposed form of equation is introduced, which is based on recursive minimization of functionals. The concept of umbra-time extends the classical manifold over which the system evolves. The extension of Noether’s theorem in this extended space has been presented. The idea of umbra time is then used to propose the concept of umbra-Hamiltonian, which is used along with the extended Noether’s theorem to get into the dynamics of the dynamical systems with symmetries. In the mathematical models of dynamical system, the equations for the system can be formulated in a systematic way from the bondgraph representation as bondgraph representation of a system may be constructed in a total abstraction from the mathematical models of the dynamical system. In present paper, bond graphs are conveniently used to arrive at umbra-Lagrangian of the system. As a case study, we present a dynamic analysis of an electro-mechanical system through the proposed extended Lagrangian Formulation. The major objective of this paper is an analysis of symmetries of an electro-mechanical system comprising of an externally and internally damped, symmetric, elastic rotor driven by a three-phase induction motor, for which the umbra-Lagrangian remains unchanged under two families of transformations. The behaviour of limiting dynamics is obtained and validated through simulation studies.
Analysis of Destabilizing Moments Due to Dynamic Fluid Slosh Within a Partly-Filled Vehicular Tank Under Braking and Turning Accelerations
Authors: Modaressi-Tehrani Korang , Rakheja Subhash , Sedaghati Ramin
Published: April 2008

A general three-dimensional nonlinear model is formulated to study the liquid slosh inside a partly filled cylindrical tank with and without baffles, while subjected to lateral and longitudinal acceleration fields arising from braking and turning maneuvers of a tank vehicle. The analyses are performed to investigate the significance of resulting destabilizing forces and moments caused by transient fluid slosh using the FLUENT software. The analyses are performed under varying magnitudes of maneuver-induced planar braking-in-a-turn accelerations and different fill volumes. The influence of baffles is further investigated under time varying longitudinal and lateral accelerations. The deviations in transient lateral and longitudinal forces, as well as the roll, pitch and yaw moments imposed on the tank structure, are obtained with respect to the corresponding quasi-static solutions. The results show that the magnitudes of transient forces and moments are significantly larger than those obtained from steady-state or kineto-static solutions. The addition of baffles tends to limit the magnitudes of slosh forces not only in the longitudinal direction but also along the lateral axis.
Chemistry Consistency Analysis of Tungsten-Doped Diamond-Like Carbon (DLC) Coatings
Authors: Abou-Hanna Jeries , Carlson John , Lozano Jose´
Published: April 2008

Tungsten-doped diamond-like carbon (DLC) coatings have been magnetron sputtered onto 52100 steel with chromium and chromium/tungsten carbide dual interlayers using a Hauzer Techno Coating HTC 1200 4 UBM unbalanced magnetron deposition system. Internal fixturing to the deposition chamber rotates parts to be coated with a two degree of freedom system. By design, at certain intervals during the deposition, the acetylene flow is linearly altered to change film characteristics throughout the film. AES sputter depth profiling analysis shows that the fixture rotational system, designed to uniformly coat parts, causes localized chemistry variations in the coating. For a given location, the AES depth profile also clearly documents the intervals when acetylene flow was constant and when the flow was ramped.
An Empirical Equation for Flow Through Porous Media
Authors: Ortega Vivas C. A. , Barraga´n Gonza´lez S. , Garibay Cisneros J. M.
Published: April 2008

This study analyses the macroscopic flow through a two dimensional porous medium model by numerical and experimental methods. The objective of this research is to develop an empirical model by which the pressure drop can be obtained. In order to construct the model, a series of blocks are used as an idealized pressure drop device, so that the pressure drop can be calculated. The range of porosities studied is between 28 and 75 per cent. It is found that the pressure drop is a combination of viscosity and inertial effects, the later being more important as the Reynolds number is increased. The empirical equation obtained in this investigation is compared with the Ergun equation.
The International BIPM/CIPM Key Comparison Reference Value for Natural Gas Flow at High Pressure and Its Metrological Meaning for Natural Gas Trading
Authors: Dopheide D. , Mickan B. , Kramer R. , van der Beek M. P. , Blom G. J. , Vallet J.-P.
Published: April 2008

The paper describes the background of the European Harmonized Reference Value for the cubic meter of Natural Gas at high pressure, which is in use in Germany, The Netherlands and France since May 4th, 2004. The harmonization process began on November 1st, 1999 between Germany and The Netherlands and has been finalized on May 4, 2004 due to the incorporation of the French LNE to the Harmonized Reference Value. The outcome was named: “Harmonized European Natural Gas Cubic Meter” as realized by three independent National Metrology Institutes. The prerequisites of the harmonization process, underlying procedures, results obtained so far and the mutual benefits will be pointed out as well as the economic consequences for the European market as well as for the international user. The paper shows the degree of equivalence between the three participating NMIs PTB, LNE and NMi-VSL. Under auspices of the BIPM (International Bureau for Weight and Measurers) as well as the CIPM (International Conference for Weight and Measures), which is the highest metrological authority worldwide, so called Key Comparisons (KC) have been conducted to get international reference values for all quantities of interest. Among these KCs, the flow area is of economic importance and Key Comparisons for natural gas flow at high pressure and larger flow rates have been conducted successfully. The outcome of such a KC is the international Key Comparisons Reference Value (KCRV), which is then considered to be the worldwide best available realization of Natural Gas Flow at high pressure. These KCs have been conducted among the National Primary Standards of all nations worldwide, represented by their National Metrology Institutes (NMIs) and have been finalized in December 2004 and the KCRV has been approved by the BIPM in April 2005. It turns out at last that the international recommended reference value is exactly the same as the above mentioned European Harmonized Reference Value.
Experimental and Numerical Investigation of Centrifugal Pump Performance When Handling Viscous Fluids
Authors: Shojaee Fard M. H. , Ehghaghi M. B. , Boyaghchi F. A.
Published: April 2008

On the test bed of centrifugal pump, the centrifugal pump performance has been investigated using water and viscous oil as Newtonian fluids, whose kinematic viscosities are 1 × 10−6, 43 × 10−6 and 62 × 10−6 m2/s, respectively. Also, the finite volume method is used to model the three dimensional viscous fluids for different operating conditions. For these numerical simulations the SIMPLEC algorithm is used for solving governing equations of incompressible viscous/turbulent flows through the pump. The κ-ε turbulence model is adopted to describe the turbulent flow process. These simulations have been made with a steady calculation and using the multiple reference frame (MRF) technique to take into account the impeller-volute interaction. Numerical results are compared with the experimental characteristic curve for each viscous fluid. The data obtained allow the analysis of the main phenomena existent in this pump, such as: head, efficiency, power and pressure field changes for different operating conditions. Also, the correction factors for oils are obtained from the experimental for part loading (PL), best efficiency point (BEP) and over loading (OL) and the results are compared with proposed factors by American Hydraulic Institute (HIS) and Soviet Union (USSR). The comparisons between the numerical and experimental results show a good agreement.
Stresses During Impacts on Horizontal Rods
Authors: Leishear Robert A.
Published: April 2008

The impact of an object striking the tip of a horizontally mounted bar provides some insight into the dynamics of structural impact in general. Modeling a cylindrical bar provides significant simplifications to enable comparison between experiment and theory. In particular, experimental results available in the literature are compared herein to both elastic wave theory and vibration theory. Relating these two theories is the focus of this paper. Vibrations can be directly related to the time of impact, the maximum stress at the tip of the bar, and the frequencies of the struck bar. Once these stresses and frequencies are found, elastic wave theory can then be used to describe the stresses throughout the bar.
Surface Roughness Prediction Model for Ceramic Grinding
Authors: Agarwal Sanjay , Venkateswara Rao P.
Published: April 2008

Surface quality of workpiece during ceramic grinding is an ever-increasing concern in industries now-a-days. Every industry cares to produce products with supposedly better surface finish. The importance of the surface finish of a product depends upon its functional requirements. Since surface finish is governed by many factors and its experimental determination is laborious and time consuming. So the establishment of a model for the reliable prediction of surface roughness is still a key issue for ceramic grinding. In this study, a new analytical surface roughness model is developed on the basis of stochastic nature of the grinding process, governed mainly by the random geometry and the random distribution of cutting edges. The new model proposed for evaluating the surface roughness during ceramic grinding appears to yield results, which agree reasonably well with the experimental results. This model is found to be more accurate in predicting the surface roughness when compared to the existing model.
Optimal Time-Varying ILC Design to Monotonically Minimize Converged Error
Authors: Tharayil Marina , Alleyne Andrew
Published: April 2008

This paper presents a design method for Iterative Learning Control (ILC) algorithms using time-varying Q-filters. The design of an optimal bandwidth profile for a given plant model is formulated as a constrained minimization problem. The resultant time-varying ILC algorithm generates the lowest converged error norm possible while guaranteeing monotonic convergence. The time-varying ILC background, problem setup to optimize the time-varying Q-filter bandwidth, as well as results obtained using computational methods are presented. A simulation example is used to demonstrate the potential benefits of the algorithm in comparison with LTI ILC. Lastly, experimental validation is provided by application of the ILC algorithm developed here on a Microscale Robotic Deposition system for precision motion control.
Influence of Geometric Features and Material Orientation in Piezoelectric Ceramic Materials
Authors: DeGiorgi Virginia G. , Wimmer Stephanie A.
Published: April 2008

Orientation between loading and material property directions is a concern for both polycrystalline and single crystal piezoelectric materials. The design of devices fabricated from piezoelectric materials emphasizes alignment between principal actuation direction and a specific coupling coefficient direction. However, loading and actuation directions may not always be aligned. Complex component geometry, multiple loading types, multiple loading paths and fabrication tolerances may result in misalignment between mechanical loading direction, principal actuation direction, electrical loading direction and material property orientation. In this work a computational study is presented that examines the effects of off-axis loading as well as geometric features for piezoelectric ceramics. An ASTM dog-bone shaped tensile specimen is modified by the addition of cut-out features to provide geometry stress concentrations at various angles to the primary mechanical loading direction. Polycrystalline PZT-5A material properties are used. Mechanical loading is applied as in a standard tensile strength test. Electrical loading direction is aligned with the mechanical loading direction. The tensile specimen is also subjected to sequential mechanical and electrical loadings. In the initial condition the d33 axis is aligned with the mechanical loading direction of the tensile specimen. Additional runs are made after rotating the material axes away from the principal mechanical loading axes of the tensile specimen. Stress patterns and location of maximum stress levels, indicating initial failure sites, are discussed in terms of the complex relationship between geometric features, material orientation and loading condition.
Modeling the Response of Surface Micromachined Thermal Actuators
Authors: Atre Amarendra P.
Published: April 2008

Thermal microactuators, devices that use the principle of thermal expansion to amplify motion, have several advantages in comparison with other actuators used to motivate surface micromachined components such as rotary microengines. They provide higher output forces and have simple geometries. Accurate steady-state and transient modeling of such thermal actuators provides a tool for design optimization to obtain better actuator performance. This paper describes the development, modeling issues and results of a three dimensional multiphysics non-linear finite element model of a surface micromachined thermal actuator. The simulation results are compared with experimentally measured data. Reasonable agreement is observed for static actuator deflection response. The measured transient response is observed to be significantly slower than that predicted by the finite element model.
Computer Aided System for Semiautomatic Injection Mould Design
Authors: Claveria I. , Javierre C. , Ferna´ndez A. , Castany J.
Published: April 2008

Injection molding field has become one of the most important polymer manufacturing areas. One of the elements that plays a very important role in the injection molding process is the mold from which plastic part is obtained. The quality of the final product, depends highly on the proper design of the mold. A software to design injection molds following a design methodology has been developed. It allows the user both, to follow a suitable design itinerary for the mold design including plates, guiding system, ejection system, sliding cores, etc, and to eliminate the repetitive tasks of drawing the different mold elements. The software has been implemented by using PRO/TOOLKIT functions and a Visual C++ environment, and it is supported by PRO/ENGINEER. The usage of the software saves design time at ante project stage and it can be also used as a tool to check the feasibility of the mold according to the part to be manufactured.
Application of Pressure and Temperature Sensitive Paints for Study of Heat Transfer to a Circular Impinging Air Jet
Authors: Liu Quan , Sleiti A. K. , Kapat J. S.
Published: April 2008

Experimental and computational studies are performed to study pressure and temperature distributions and flow patterns on impingement target surface subject to a single impinging air jet from a plenum. The experiments cover a range of jet-to- target plate distance, Z/D, from 1.5 to 12 for Reynolds number range from 5000 to 60000. The main objective is to investigate the optimal jet-to-target distance (Z/D) for stagnation point heat transfer and location of second peak of local heat transfer at small Z/D value of 1.5. Pressure and temperature sensitive paints measurements techniques are implemented to obtain the distribution of pressure and temperature on target surface. Flow visualization test has also been performed using surface oil and smoke technique to obtain the streamline distribution over the impinged surface and to qualitative study jet characteristics. The optimal (Z/D) is found to be 4.8 and second peak location for Z/D of 1.5 is at radial location (r/D) of 1.8. Comparison of average Nu with correlation from open literature, shows agreement to within experimental uncertainty for Z/D=5, while for Z/D=1.5 a 23% difference is found. Experimental results are compared to computational (CFD) prediction using Realizable κ-ε turbulence model.
Creep Void Growth Simulation for Reliable Maintenance of High Temperature Components
Authors: Ogata Takashi
Published: April 2008

To reduce maintenance cost of high temperature components in aged thermal power plants, it is necessary to improve accuracy of remaining life assessment methods. High temperature components such as steam turbine rotors are operated under creep loading where creep voids initiate and grow on grain boundaries. Development of a quantitative evaluation method of void growth is important for reliable maintenance of these components. Purposes of this study are to clarify void growth behavior of a turbine rotor material under creep loading condition, and to develop void growth simulation program that can predict damage extension process in the components under actual operating condition quantitatively. From the creep tests and observation of a steam turbine rotor material, spherical shape voids initiate and grow up to their length of 2mm on the grain boundary at initial stage of damage, and then these voids change their shape to crack-like to grow until their length reaches around 10mm. Finally, crack-like voids coalesce each other to form one micro crack along boundary. It can be concluded that void growth rates are controlled by diffusion and power law creep under constrained condition based on theoretical consideration of void growth mechanism. Through these discussions, a new void growth model was proposed by modifying conventional models. A void growth simulation program was developed by incorporating the void growth model in a personal computer. It was confirmed that void growth process under the creep condition in the experiment could be well predicted quantitatively by the simulation program. The simulation program was also applied to predict creep void growth behavior in an actual steam turbine rotor during operation.
Dislocation Dynamics Modeling for Yield Strength of Nanoscale Film Heterostructures
Authors: Tan E. H. , Sun L. Z.
Published: April 2008

A novel dislocation dynamics framework is developed to simulate dislocation evolutions in thin film heterostructures at nanoscale. It is based on 3-D dislocation motion together with its physical background by adding the solid viscous effect. As the numerical simulation results demonstrate, this new model completely solves a long-standing paradoxical phenomenon with which the simulation results were dependent on dislocation-segment lengths in the classical discrete dislocation dynamics theory. The proposed model is applied to simulate the effect of dislocations on the mechanical performance of thin films. The interactions among the dislocation loop, free surface and interface are rigorously computed by decomposing this complicated problem into two relatively simple sub-problems. This model is allowed to determine the critical thickness of thin films for a surface loop to nucleate and to simulate how a surface loop evolves into two threading dislocations. Furthermore, the relationship between the film thickness and yield strength is constructed and compared with the conventional Hall-Petch relation.
The Design and Performance of the European Freight Wagon Standard Suspensions
Authors: True Hans , Hoffmann Mark , Jo¨nsson Per-Anders
Published: April 2008

In the paper we present the three most common European standard freight wagon suspensions. It is characteristic for the European suspensions that they are all primary suspensions without a bolster. The design and the function of their single elements are described. New results on the nature of dry friction and its influence on the damping characteristics are presented. Finally a few theoretical investigations of the dynamics of European freight wagons are surveyed with emphasis on the calculations of the critical speed. The results are compared with corresponding results for American wagons.
Combined Approximation Reanalysis Coupled With Finite Element Stress Analysis for Multiple Geometric Changes in Early Design Stage
Authors: Terdalkar Sachin S. , Rencis Joseph J.
Published: April 2008

In this work a new graphically driven interactive stress reanalysis finite element technique has been developed so that an engineer can easily carry out manual geometric changes in a machine element during the early design stage. The interface allow an engineer to model a machine element in the commercial finite element code ANSYS® and then modify part geometry graphically to see instantaneous graphical changes in the stress and displacement contour plots. A reanalysis technique is used to enhance the computational performance for solving the modified problem; with the aim of obtaining results of acceptable accuracy in as short a period of time in order to emphasize the interactive nature of the design process. Two case studies are considered to demonstrate the effectiveness of the prototype graphically driven reanalysis finite element technique. The finite element type considered is a plane stress four-node quadrilateral based on a homogenous, isotropic, linear elastic material. Each case study considered multiple redesigns. A combined approximation reanalysis method is used to solve each redesigned problem. The first case study considers a plate with a hole with the goal to determine the hole shape that will minimize the stress concentration. The second case study considers a support bracket. The goal is to design the cantilever portion of the bracket to have uniform strength and to minimize the stress concentration at the fillet.
Finite Element Analysis of Ground Imitating Tank
Authors: Liu Jiemin , Ma Guangtao
Published: April 2008

A typical ground imitating tank is analyzed regarding it as the thin-walled structure composed of plates (skins) and beams (reinforcement) using finite element method (FEM). Through moving the location of reinforcements, make the skins close with the flanges of the reinforcements in order to imitate actually the connection of the skins and the reinforcements. The thickness of plates, the size and the geometry shape and the location of reinforcements are taken as parameters to be optimized. In calculation, not only consider effects of the oil-weight, the extra-pressure in tank and the dead weight of the tank on the stresses and displacements of the tank, but also analyze the effects of the inertia forces produced due to the rotation of the tank on the stresses and displacements. Displacement, stress and deformation distributions of the ground imitating tank under the three typical flying postures imitated are given.