bluuebunny/crossref_metadata_2025 huggingface dataset:
Spin Motion of a Levitated Magnet Caused by Vertical Excitation of a High-Tc Superconductor
Authors: Sugiura Toshihiko , Hayakawa Shuuichi , Tanaka Tsuyoshi , Yoshizawa Masatsugu
Published: May 2008

This research deals with nonlinear dynamics of a permanent magnet freely levitated above a high-Tc superconductor excited in the vertical direction, focusing on generation of spin torque acting on the magnet. Equations of 6 d.o.f motion, nonlinearly coupled by magnetic force and torque, were described on the assumption that a magnet has an eccentricity between the center of gravity and the magnetic center. Force and torque were evaluated analytically by the flux frozen method. Dynamic behavior of the magnet was examined numerically for different frequencies of excitation. A simplified 2 d.o.f. system with only essential terms was introduced in order to discuss the mechanism of nonlinear coupling which generates spinning from vertical oscillation. Spinning motion of the magnet was examined in detail analytically by the method of harmonic balance. Experiments of vertical excitation were also carried out. Experimental results were compared with numerical ones.
Application of the Empirical Mode Decomposition Method to the Identification of Disc Brake Squeal
Authors: Yang Fulun , Tan Chin An , Chen Frank
Published: May 2008

This paper investigates the identification of mechanisms of disc brake squeal by the application of a recently developed Empirical Mode Decomposition method (EMD). A known strength of the EMD is its adaptive nature in analyzing nonstationary data, with success in its original application to ocean mechanics. The EMD decomposes an original signal into a number of intrinsic mode functions (IMFs), with each IMF often containing distinct physical significance. Several sets of disc brake squeal data were obtained and processed by EMD. A typical set data is presented in this paper for discussion. Employing a sifting process in the EMD, four prominent squeal-related IMFs are identified in this set of data. The Hilbert transform is then used to analyze the frequency and amplitude contents of the four IMFs, and it is shown that the first IMF is dominant. The spectrogram method is applied to analyze the time-evolution of the frequency components of the IMFs in the squeal process. This analysis procedure confirms an important squeal mechanism, i.e., the squeal condition is governed by the coupling of in-plane and out-of-plane vibration modes of the rotor and the coalescence of their natural frequencies. The inverse approach outlined in this paper is shown to be useful for providing new insights and confirming established hypotheses of disc brake squeal.
Characterization of Dynamical Instability Using Instantaneous Frequency
Authors: Yang Baozhong , Fisher James , Suh C. Steve
Published: May 2008

Dynamical instability induced by the initiation and advancement of mechanical faults in rotary elements is detrimental to the reliability and operation safety of the entire system. The inherent nonlinearity associated with bifurcation presents itself as difficulties in identifying and isolating features indicative of the presence and progression of faults that could lead to eventual mechanical deterioration. The perturbed and deteriorated states of a bearing-shaft system subjected to the actions of two types of commonly seen mechanical faults, namely, rotor speed and imbalance, are investigated using the basic notion of instantaneous frequency. The presented approach realizes temporal events of both short and long time scales as instantaneous frequencies in the joint time-frequency domain and thus effectively uncouples the harmonic components resulted from the coupling of multitude faults. Examples are given to demonstrate the feasibility of applying the approach to the characterization of various deteriorating bearing states and the identification of parameters associated with various modes of instability and chaotic response.
Experimental Assessment of Speech Privacy and Intelligibility in Multi-Language Environments
Authors: Dai L. , Ma Y. , Caswell D. J.
Published: May 2008

In the current literature, most assessments for speech privacy and speech intelligibility are relying on the subjective measurements utilized with the test materials of English and other Western languages. Effects of different languages and accents in speech privacy and speech intelligibility are usually overseen. This study aims at the speech privacy assessment of closed offices in multicultural environments. Subjective measurements are conducted in this study for closed offices by using English and a tonal language. The evaluation differences in speech privacy between the two languages are evident and significant. It is also found in this study that the existing single word tests used in research and industrial practice for subjectively evaluating speech privacy should be modified when closed spaces are considered. The subjective measurement results of this study are also compared with the objective measurement indices AI.
Microelectronic Cooling Techniques Using Single and Dual Oscillatory Impinging Air Jets
Authors: Chiriac Victor Adrian , Lee Tien-Yu Tom , Rosales Jorge Luis
Published: May 2008

A numerical investigation was performed to compare the flow and heat transfer characteristics for microelectronics cooling scenarios. The first cooling method uses a single unsteady/oscillatory impinging air jet while the second method uses dual unsteady impinging air jets. The unsteady confined impinging jet flow has proven to enhance the heat transfer, thus reducing the prohibitive temperatures in high-powered chips. Past a specific Reynolds number range, the jet core becomes distorted and buckles, leading to a sweeping motion of the jet tip. Due to these combined motions, the effective cooled area is notably enhanced thereby reducing the power needed to cool the components placed on the PCB (Printed Circuit Board). A comparison between the unsteady laminar impinging jet and the dual unsteady impinging jets reveals that at the same flow rate, the heat transfer enhancement provided by the single unsteady jet is at least 5–8 times better than that for the dual jets. This cooling enhancement significantly reduces the temperature increase by almost 50 percent. The oscillatory impinging jet cooling technique does not require the incorporation of costly heat sinks and heat spreaders or the unnecessary increase of blower work. This technique provides effective cooling at significantly lower pumping powers with reduced manufacturing and operating costs.
Experimental Measurements of the Flow and Heat Transfer of a Square Jet Impinging on an Array of Square Pin Fins
Authors: Issa Johnny S. , Ortega Alfonso
Published: May 2008

An experimental investigation was conducted to explore the flow behavior, pressure drop, and heat transfer due to free air jet impingement on square in-line pin fin heat sinks (PFHS) mounted on a plane horizontal surface. A parametrically consistent set of aluminum heat sinks with fixed base dimension of 25 × 25 mm was used, with pin heights varying between 12.5 mm and 22.5 mm, and fin thickness between 1.5 mm and 2.5 mm. A 6:1 contracting nozzle having a square outlet cross sectional area of 25 × 25 mm was used to blow air at ambient temperature on the top of the heat sinks with velocities varying from 2 to 20 m/s. The ratio of the gap between the jet exit and the pin tips to the pin height, the so-called tip clearance ratio, was varied from 0 (no tip clearance) to 1. The stagnation pressure recovered at the center of the heat sink was higher for tall pins than short pins. The pressure loss coefficient showed a little dependence on Re, increased with increasing pin density, and pin diameter, and decreased with increasing pin height and clearance ratio. The overall base-to-ambient thermal resistance decreased with increasing Re number, pin density and pin diameter. Surprisingly, the dependence of the thermal resistance on the pin height and clearance ratio was shown to be mild at low Re, and to vanish at high Re number.
Experiments and Modeling of the Heat Transfer of In-Line Square Pin Fin Heat Sinks With Top By-Pass Flow
Authors: Dogruoz M. Baris , Urdaneta Mario , Ortega Alfonso
Published: May 2008

This paper presents experimental results on the heat transfer characteristics of in-line square pin fin heat sinks with and without top by-pass. A self-consistent set of aluminum heat sinks were utilized, where the pin height was varied from 12.5 mm to 22.5 mm, the pin pitch was varied from 3.4 mm to 5.8 mm and the base dimensions were kept fixed at 25 × 25 mm. The overall base to ambient thermal resistance was measured as a function of Reynolds number and bypass height. Experimental results were then compared with predictions based on a simple one-dimensional “two-branch by-pass model”. Comparisons were made with the data using heat transfer coefficients available in the literature for infinitely long tube bundles. It was shown that there is a good agreement between the temperature predictions based on the model and the experimental data at high approach velocities for tall heat sinks, however the discrepancy between the computations and experiments increases as the approach velocity and heat sink height decrease. The validated model was used to identify optimum pin spacing as a function of clearance ratio.
An Effective Specific Heat Model of the Heat Transfer in a Micro-PCM Suspension in Laminar Tube Flow
Authors: Mulligan James C. , Gould Richard D.
Published: May 2008

An “effective” specific heat model of the heat transfer in the thermal entry region of a laminar tube flow carrying a microPCM fluid is presented. The model is in an analytical format and intended to be easy to apply. It is based on classical Graetz theory, along with a computational analysis of entry region heat transfer that includes the latent effects contributed by a suspended microPCM. Generally, the Nusselt number of a microPCM fluid is shown to be of the following general form Nu = f(Gr, L, P), where Gr is the classical Graetz number, and L and P are Stefan-like parameters defined as: Fλ/Cp(Tl−Ts) and Cp(Ts−Tin)/(q/m)˙, respectively. Here F is the fraction of PCM in the suspension, λ the latent heat, and q/m˙ the ratio of the system heat rate to the system flow rate.
Performance of an Octacosane Based MicroPCM Fluid in Transitional Flow
Authors: Gould Richard D. , Jackson Willard B. , Mulligan James C.
Published: May 2008

Use of microencapsulated phase change material (microPCM) in a single phase carrier of fluid for enhanced cooling has been demonstrated by many researchers for the case of laminar flow. However, very little is known about the behavior of microPCM fluids for turbulent flows. Here we consider the flow of octacosane microPCMs in a 50/50 by volume ethylene glycol/water carrier fluid. This high temperature microPCM fluid, with Tmelt = 60°C, has a much lower viscosity than room temperature microPCM fluids. Room temperature microPCMs in 50/50 by weight ethylene glycol/water carrier fluid generally operate at Reynolds numbers much below the critical value due to their large viscosity and the unreasonably large pumping power required to produce turbulent flow. At 60°C, however, the flow can become transitional and perhaps fully turbulent with moderate pressure rise pumps. This paper presents the performance of an octacosane based microPCM fluid operating in the transitional region at Reynolds numbers up to 2900. Transitional flow convective heat transfer coefficients are shown to be as much as 50% higher than laminar flow values. In addition, surface temperatures are reduced with increasing Reynolds number.
Nested Optimization of an Elevator and Its Gain-Scheduled LQG Controller
Authors: Fathy Hosam K. , Bortoff Scott A. , Copeland G. Scott , Papalambros Panos Y. , Ulsoy A. Galip
Published: May 2008

This paper studies the combined optimization of an elevator’s design (plant) and LQG controller for ride comfort. Elevator dynamics and primary vibration sources (drive motor torque ripple and guide rail irregularity) are modeled using an object-oriented language. The resulting model is nonlinear. Elevator vibrations are minimized with respect to both the design and the LQG controller. LQG gains are scheduled versus cab mass and height for robustness. Sequential plant/control optimization produces an optimal ride only when the torque ripple is the dominant disturbance. Otherwise, passive vibration reduction decreases the controller’s authority over the vibrations, hence coupling the plant and control optimization problems. Combined plant/controller optimization, using a nested strategy, mitigates this coupling and finds the correct optimal system design.
Crises to Crises: A 30-Year Retrospective on the Electric Utility Industry and Energy Efficient Lighting Technology
Authors: Andersen Kenneth J.
Published: May 2008

This paper reviews the change in energy efficiency of lighting technology during the 30-year period between the energy crises of the 1970’s oil embargo and last year’s de-regulated wholesale market, electricity price spikes. Lighting power requirements have been cut in half for new commercial buildings, dropping from 3 to 1.5 watts or less per square foot of conditioned space. Fluorescent lighting technology has changed from four-foot T-12 lamps requiring 40 watts, to high-lumen, 32-watt T-8 lamps. Copper intensive and noisy magnetic ballasts have been replaced with lightweight, high frequency electronic ballasts lowering power from 10 to one watt per fixture. Today this trend continues with the movement away from Edison’s incandescent lamp to compact fluorescent lamps (CFL) that save 70% of the electrical energy. In response to the wholesale electricity prices spikes, the Northwest Energy Efficiency Alliance partnered with regional electric utilities and retail stores to offer CFL discount coupons. As a result, CFL sales rose from about 500,000 in 2000 to over 8 million in 2001. This is one more example of how energy efficiency programs sponsored by the nation’s electric utilities have driven both technology and the market to change.
The Internet Engineering Design Agent System: iEDA
Authors: Radcliffe Clark J. , Sticklen Jon , Gosciak Gary J.
Published: May 2008

Approaches to engineering design and manufacturing such as integrated design and manufacture and just in time fabrication depend on interaction with and among component supply companies which most often use very diverse technologies. The Internet Engineering Design Agents (iEDA) approach is a distributed, component-based, agent methodology that is realized following a strong black box approach to modeling. An individual Design Agent (DA) is a virtual product capable of encapsulating both descriptive and model based information about the product it represents. Hierarchically recursive agents for sub-systems and/or components are linked via a communications network to form larger integrated model systems. A crucial part of the iEDA architecture is a global ontology of questions; these questions in the ontology are standardized engineering domain queries that form a sufficient set of queries to allow compositional modeling methods; the global query ontology is itself realized as a networked agent. Most importantly, Design Agents interact without divulging the proprietary descriptive information or models contained within component or device represented. The iEDA architecture thus enables both proprietary security and compositional modeling of component parts/systems. The structure and function of the iEDA architecture and its current implementation is discussed. A two dimensional bridge system model is used as an example to illustrate the distributed nature of assemblies and components registered as DA’s on a communications network. iEDA forms a distributed modeling environment that enables communication and coordination required for effective and efficient global collaborative distributed design.
Variable Fidelity Modeling of Vehicle Ride Dynamics Using an Element Activity Metric
Authors: Kypuros Javier A. , Longoria Raul G.
Published: May 2008

The evolving ability of vehicle simulation packages continues to facilitate the use of complex models for virtual prototyping. In formulating a virtual proving ground for conducting vehicle mission studies, it can be helpful to devise ways to facilitate the synthesis of models optimized for repetitive study of specific missions or maneuvers. Because subsystem models may have inherently different bandwidth characteristics, complex vehicle simulations that incorporate such models may be numerically stiff. Furthermore, complexity generally makes it difficult to interpret results and identify key parameters that affect dominant dynamics. The intent of this study is to examine the feasibility of optimizing simulation efficiency and/or enhancing physical insight using a variable fidelity approach that switches between reduced sub models optimized for specific dynamic intervals of the mission study. Because of its established use for model reduction, element activity is tested as a metric to measure and vary model fidelity of a vehicle ride mode model.
Simulating Distributed-Parameter Multiphase Thermodynamic Systems Using Bond Graphs
Authors: Brown Forbes T.
Published: May 2008

The use of convection bond graphs with temperature, mass and volume as state variables allows the associated thermodynamic properties of a wide variety of single and multi-phase fluids to be found accurately without iteration, using available formulas. As a result, non-experts can simulate efficiently unsteady systems with compressible flow and heat transfer, as long as the system is modeled with discrete compartments. This paper addresses the discretization of a heat exchanger under changing phase conditions into a finite element model, assuming no slip between phases in thermodynamic equilibrium and neglecting coherent kinetic energy. The staggered grid approach used in conventional numerical analyses for flowing systems is accommodated naturally. Partial upwinding is used to control numerically induced oscillations. The wall shear and the heat transfer are keyed to standard models for laminar and turbulent flow in single-phase and two-phase regimes. A condenser of a refrigeration cycle is given to illustrate the procedure and its results.
Local Heat Transfer Coefficients and Pressure Drop During Evaporation in a Smooth Horizontal Tube
Authors: Aprea C. , Greco A. , Vanoli G. P.
Published: May 2008

R22 is the most widely employed HCFC working fluid in vapour compression plant. HCFCs must be replaced within 2020. Major problems arise with the substitution of the working fluids, related to the decrease in performance of the plant. Therefore, extremely accurate design procedures are needed. The relative sizing of each of the components of the plant is crucial for cycle performance. For this reason, the knowledge of the new fluids heat transfer characteristics in condensers and evaporators is required. The local heat transfer coefficients and pressure drop of pure R22 and of the azeotropic mixture R507 (R125-R143a 50%/50% in weight) have been measured during convective boiling. The test section is a smooth horizontal tube made of a with a 6 mm I.D. stainless steel tube, 6 m length, uniformly heated by Joule effect. The effects of heat flux, mass flux and evaporation pressure on the heat transfer coefficients are investigated. The evaporating pressure varies within the range 3 ÷10 bar, the refrigerant mass flux within the range 200 ÷ 1000 kg/m2s, the heat flux within 0 ÷ 44 kW/m2. A comparison have been carried out between the experimental data and those predicted by means of the most credited literature relationships.
Heat Transfer to Water-Oxygen Mixtures at High Pressure
Authors: Rogak S. N. , Boskovic S. , Faraji D.
Published: May 2008

The constant pressure heat capacity and forced convection heat transfer coefficient was measured in a horizontal, smooth, electrically-heated tube. For the supercritical pressures considered, flow rates and temperatures (330–430 °C), the flow in the 6.2 mm ID tube was fully turbulent. The fluid was distilled water and up to 9 wt% oxygen. This mixture and the experimental conditions are found in supercritical water oxidation systems. At subcritical temperatures, the oxygen and water are almost immiscible, but just below the critical temperature, the fluid becomes single-phase. By measuring bulk and surface temperatures, knowing the mass and heat flux, both the heat capacity and heat transfer coefficient could be measured. The water-oxygen system is a highly non-ideal mixture, and small amounts of oxygen significantly reduce the temperature at which maximum heat transfer occurs. The changes in heat capacity appear to dominate the effect of oxygen on heat transfer, however, the mixtures do exhibit heat transfer deterioration at slightly subcritical temperatures, at flows and heat fluxes for which pure water shows nothing similar.
A CFD Model for Devices Operating Under Extensive Cavitation Conditions
Authors: Gerber A. G.
Published: May 2008

A robust CFD model is described suitable for general three-dimensional flows with extensive cavitation at large density ratios. The model utilizes a multiphase approach based on volume-scalar-equations, a truncated Rayleigh-Plesset equation for bubble dynamics, and specific numerical modifications (in a finite-volume solution approach) to promote robust solutions when cavitation is present. The model is tested and validated using hydrofoil, orifice, and pump flow applications.
Distributed Parameter Dependent Modeling and Control of Flexible Structures
Authors: Wu Fen , Yildizoglu Suat E.
Published: May 2008

In this paper, distributed parameter-dependent modeling and control approaches are proposed for flexible structures. This modeling approach mainly relies on a central finite difference scheme to capture the distributed nature of the flexible system. The distributed model is motivated from distributed control design, which is advantageous for reduced control implementation cost and control system reliability. The displacements at each discretized node are assumed measurable in real-time for controller use. Based on the proposed distributed model, sufficient conditions for analysis and synthesis of a distributed output-feedback controller are presented using the induced L2 norm as the performance criterion. The controller synthesis condition is characterized in terms of linear matrix inequalities (LMIs), which are convex optimization problems and can be solved efficiently using available software. The distributed controller inherits the same structure as the plant, which results in a localized control architecture and a simple implementation. The simulation results of a distributed controller is provided.
Target Reduction and Balancing Using System Norms: Application to Vehicle Design
Authors: Mahmoud Haitham A. , Kabamba Pierre T. , Ulsoy A. Galip , Brusher Gerald A.
Published: May 2008

A new approach for cascading system-level design targets to performance targets for the different subsystems is proposed and applied to a vehicle example. The proposed approach aims at reducing the total number of targets needed to quantify the performance of an engineering system and at systematically balancing these targets among its constituent subsystems. The vehicle example consists of three subsystems that transfer suspension forces to the cab in a lightweight truck. The three vehicle subsystems are connected in a general feedback configuration. The proposed approach significantly reduces the number of targets used to quantify the vehicle system performance. In addition the cascaded targets are systematically balanced among the different subsystems to deliver the desired system performance.
Experimental Investigation on Swash Plate Axial Piston Pumps With Conical Cylinder Blocks Using Fuzzy Logic Control
Authors: Bahr Khalil M. K. , Svoboda J. , Bhat R. B.
Published: May 2008

Analytical studies on the dynamic performance of variable displacement swash plate axial piston pumps show that the pump performance can significantly improved by replacing the conventional PD process controller with fuzzy logic controller. Electrically controlled, constant power regulated, swash plate pumps with conical cylinder blocks have been recently extensively studied. Comparative study has been carried out to compare the pump dynamic performance when the conventional PD process controller is replaced by a proposed fuzzy logic one. The study reveals some superior performance characteristics when fuzzy logic controller is used. In the present study an experimental setup is built to measure the dynamic performance of a typical 9-piston pump that has conical shaped cylinder block. The pump is of 40 cc/rev geometrical size, type A4VSO, that is manufactured by Rexroth. The experimental setup consists of a hydraulic test bed interfaced with real time control and data acquisition system. The setup is used firstly for testing the pump static characteristics. Subsequently, the setup is used to measure the time response of the pump, which is equipped with the conventional PD controller, to the stepwise changes in the load pressure. Pump model verification is then discussed based on the comparison between the theoretical and experimental results. The pump is afterwards interfaced with real time control software for prototyping the proposed fuzzy logic controller that replaces the currently used PD one. With the fuzzy logic control, measuring the pump time response under the same loading conditions is repeated. Experimental results are presented, compared with the analytical findings and discussed.
Discrete-Event Sensor Fault Isolation With Application to an Electro-Mechanical Break System
Authors: Pisu Pierluigi , Rizzoni Giorgio
Published: May 2008

Fault detection and isolation has become one of the most important aspects in vehicle control system design. In this paper, a new method for single sensor fault detection and isolation for automotive on-board applications that combines model-based diagnostic and qualitative modeling approach is presented. A depth one algorithm for qualitative identification is given and applied to a electro-brake system.
The Theoretical Flow Ripple of an External Gear Pump
Authors: Manring Noah D. , Kasaragadda Suresh D.
Published: May 2008

In this paper, the theoretical flow ripple of an external gear pump is studied for pumps of similar size using different numbers of teeth on the driving and driven gears. In this work, the flow ripple equation is derived based upon the flow of incompressible fluid across the changing boundaries of a control volume. From this method, it is shown that the instantaneous length of action within the gear mesh determines the instantaneous flow ripple. Using a numerical solution for the instantaneous length of action, different pump designs are compared. In summary, the results of this study show that it may be advantageous to design an external gear pump with a large number of teeth on the driving gear and a fewer number of teeth on the driven gear. This design configuration will tend to reduce both the physical pump size (without reducing the volumetric displacement of the pump) and the amplitude of the flow pulsation, while increasing the natural harmonic frequencies of the machine.
Valve Manufacturer Specification Based Hydraulic Velocity Control
Authors: Kannisto Sirkku , Virvalo Tapio
Published: May 2008

In this paper a closed loop hydraulic cylinder velocity control is realized with a mobile valve. The velocity feedback is based on the valve specifications and the measurement of the pressure difference over the control notch of the valve. Offsets and other non-linearities are approximated based on the pressure rise in chambers and the specifications of the manufacturer. The flow gain curve is measured with a method that suits mobile applications. The cylinder velocity is calculated from the spool control signal, measured cylinder chamber and supply pressures. The calculated velocity is compared to the actual velocity over the 1–100% velocity range and behaviour under disturbances is studied. The pressure compensator function is realized based on calculated velocity.
Evolutionary Algorithm for the Placement of Fluid Power Valves
Authors: Kathara Pasupathy Trichy M. , Wilhelm Robert G.
Published: May 2008

Placement and routing of fluid power valves impact operational or manufacturing costs. Choosing the right placement that provides optimum routing configuration, and subsequently determining the optimum routing for a given placement, are both hard problems. Evolutionary algorithms, for two categories, are developed here to determine the placement of the valves, based on the optimal routing configuration that minimizes costs. The two categories we consider are a) the placement of conventional valves on a valve-stand and b) the placement of cartridge valves on a manifold block. Our results meet or exceed experienced designers’ solutions.
EASY5 Model of Two Position Solenoid Operated Cartridge Valve
Authors: Liu Song , Krutz Gary , Yao Bin
Published: May 2008

The two position solenoid operated cartridge valve is widely used in the applications, such as process control systems, pavers, agricultural machinery, where response and installed costs are more important than precise control through electronic position feedback. In recent years, the combination of multiple cartridge valves, so called ‘smart valve’ or ‘programmable valve’, which is able to break the mechanical linkage between the meter-in and meter-out orifices and enables high precision control as well as optimal usage of energy, is gaining engineering interests. But the control of such combination is far from trivial. It demands good knowledge of the valve dynamics and nonlinear flow properties. Unlike servo valve or proportional directional control valve, a mathematic model of solenoid operated cartridge valve, or even a thorough understanding of the dynamics and nonlinear performance, are not available. This paper presents an EASY 5 model for the two position solenoid operated cartridge valve. The model, which includes the solenoid force, spring force, damping force, flow force and nonlinear mass flow rate, can be used to analyze cartridge valve as well as simulate system or controller performance. It is also able to connect with Matlab for more complicated simulation.
Axial Piston Pump Slipper Balance With Multiple Lands
Authors: Bergada J. M. , Watton J.
Published: May 2008

An explicit approach is developed which results in general flow and pressure drop equations for a multiple land slipper. A particular, and common, case of one balancing groove is considered allowing more accurate assessment of the pressure balance and probable slipper clearance. A comparison with the no-groove case is also made.
The Effect of Parameter Uncertainty on the Reliability of Pressure Accumulator Simulations
Authors: Kajaste Jyrki T. , Kauranne Heikki O. J. , Ellman Asko U. , Pietola Matti T.
Published: May 2008

The aim of this study is to demonstrate how the various parameters and the uncertainty associated with them affect the simulation results of a pressure accumulator. The parameters to be studied are related mainly to the pre-charging procedure of a membrane accumulator and cover the constants for the pressure and temperature of the nitrogen gas and the efficient volume of accumulator. These parameters are included in the non-linear model which is suited especially for large amplitude and low frequency transients. The background of the work is related to the fact that simulation is already an important tool in product development work. To be able to design the control of the system and predict the performance of it an estimate of the accuracy of the calculations is needed. The usability of simulation is determined by the fact how reliable the information is. To gain full benefit of simulation more attention has to be paid to the validity of the models, the accuracy of the parameter values needed in the models and the sensitivity of these parameters. The most sensitive parameters have to be recognized and paid special attention to the accuracy of the values given to them. Also the changes of these values in time due to wear or other modification in the system have to be noticed. Numerous factors have an influence on the accumulator operation. The most important of these are the ratio of the operation pressure to the pre-charge pressure, the amplitude of the flow rate disturbances, the temperature of the hydraulic fluid and the gas, the viscosity of the hydraulic fluid, the thermodynamic process of the nitrogen gas in the accumulator and the changes in the speed of sound. Also the mounting of the accumulator, the fittings used and the connecting pipes may have a significant role in the dynamics of an accumulator. The methods used in the study include measurements in time domain, modeling, simulations, and analytical work. The accumulator dynamics may alter due to remarkable changes in operating points like pressure levels. These are possible because of large amplitudes of flow rates particularly at the low frequency area where the presented study is focused on. The results include model analysis and information of the importance of the most fundamental parameters of the models and suggestions for future research work.
Impact of Ageing on Tribological Properties of Environmentally Friendly Hydraulic Fluids
Authors: Schmidt Martin , Murrenhoff Hubertus
Published: May 2008

Hydraulic systems are used in many technical applications, e.g. in agricultural and forestry machines. Hydrostatic pumps and engines as well as hydraulic fluids are essential components of these systems. Thereof, the hydraulic fluids are of great importance since not only technical but also ecological requirements have to be fulfilled. Apart from fluid power transmission the most important technical function of hydraulic fluids is lubrication and the resulting reduction of friction and wear. In times when saving energy and resources have become environmental matters, lubricants are increasingly attracting public awareness. Important ecological aspects which need to be considered since they have a major impact on the application of technical products and decide about their success are biodegradability, water pollution and ecological toxicity. This is why ester based hydraulic fluids have started to substitute mineral oil based fluids. Additionally, ester based fluids have excellent tribological features due to the polarity of the ester molecules. However, ester based fluids change their physical and chemical properties due to usage. This paper will show that both the total acid number and the viscosity is increased by ageing while the level of additives and the viscosity index is decreased. Therefore, the impact of ageing on the tribological performance of an ester based hydraulic fluid will be analysed by friction and wear investigations. Exemplary, two tribological contacts are chosen: a mixed friction and an elasto-hydrodynamic contact. These are representative conditions for hydrostatic pumps and engines. Analysing the fluid’s behaviour being stressed by mixed friction is performed by using a tribometer. Investigating the ageing impact on elasto-hydrodynamic behaviour of the fluid, a bearing test facility is used. Finally, after having been dealing with tribological contacts used in hydrostatic machines the performance of a hydrostatic machine itself will be analysed. The impact of increased viscosity on friction which is generated within a hydrostatic gear unit at low speed will be discussed.
Analysis of Electromagnetic Nonlinearities in Stage Control of a Stepper Motor and Spool Valve
Authors: Burton R. , Ruan J. , Ukrainetz P. , Bitner D.
Published: May 2008

In digital valves, stepper motors are often used as the electro-to-mechanical interface. To sustain both high speed of response and good quantitative accuracy, a special algorithm has been designed to control the stepper motor to produce a continuous displacement. Unlike conventional proportional magnets or torque motors, the input current to the stepper motor is cyclic (stage control) which has been shown to reduce magnetic saturation and hysteresis. In this paper a special mathematical formulation is developed to simulate magnetic saturation and hysteresis which can be applied to a generic situation. The mathematical formulation derived is one in which hysteresis and saturation parameters are established; an error rate of both saturation and hysteresis is defined from this. Since the error rates are easily determined experimentally or through manufacturers’ specifications, the parameters can be found from these mathematical formulations. The parameters can then be used to predict the hysteresis and saturation characteristics. Special experiments are designed to obtain the input-output characteristics of a stepper motor/valve system under single and multi-stage control. The model follows the experimental results reasonably well and can be used with confidence to model any system with hysteresis and saturation. The model also predicts very well the effects of using stage control in reducing hysteresis and saturation in a practical valve.
Numerical Integration of Pressure Build-Up Volumes Using an L-Stable Rosenbrock Method
Authors: Esque´ Salvador , Ellman Asko , Piche´ Robert
Published: May 2008

Simulation of fluid power systems has become a tool widely used for testing, designing and virtual prototyping. The choice of a numerical integration method for solving stiff systems of ordinary differential equations is a key factor for achieving proper stability and computational efficiency during simulation. Whereas widely used A-stable methods require small integration step sizes in order to avoid numerical oscillations when solving numerically stiff problems, the L-stable Rosenbrock method presented in this paper can take large steps. The method is implemented with an estimator of the local truncation error and a predictor of the step size. Simulations results show the good performance of the integrator in terms of both stability and efficiency.
And The World Came To See: New Manufacturing System Designs and Industrial Revolutions
Authors: Black J. T. , Cochran David S.
Published: May 2008

AND THE WORLD CAME TO SEE. When a new manufacturing system design (MSD) is developed by a company or a group of companies, the rest of the world comes to those factories to learn about the new system. In the last 200 years, three new factory designs have evolved, called the job shop, the flow shop and the lean shop. Each is based on a new system design — a functional design, a product flow design and a linked cell design. New factory designs lead to new industrial leaders and even new industrial revolutions (IR’s). Two appendixes are included: One outlines the implementation strategy for the lean shop and the other is a discussion of lean manufacturing from the viewpoint of K. Hitomi, Japanese professor of manufacturing systems engineering.
Infinitely Variable Transmission (IVT) of John Deere 7000 TEN Series Tractors
Authors: Mistry Sanjay I. , Sparks Gregory E.
Published: May 2008

The John Deere 7000 TEN series tractors represent a significant change in the transmission system compared to previous John Deere tractor models in this category. John Deere 7710 and 7810 series tractors are the first of the 7000 TEN series tractors offering an infinitely variable transmission (IVT). These tractors provide infinite vehicle speeds in the forward mode from 50 meters/hr to 40 km/hr or an optional 50 km/hr. Reverse mode provides infinite vehicle speeds from 50 meters/hr to 17 km/hr. The IVT provides performance improvements in several areas for unmatched operator convenience and control. The new IVT uses an electric signal to control the electro-hydraulic hydrostatic system with mechanical power train. The IVT represents a hydro-mechanical transmission system using electronics, hydraulics and mechanical systems’ integration to achieve the required performance. This paper describes the IVT system configuration, components, operation, characteristics and some of the engineering considerations dealt with in the development process. The overall IVT system truly represents a “drive-by-wire” mechatronic design.
An E/H Control Design for Poppet Valves in Hydraulic Systems
Authors: Du Hongliu
Published: May 2008

In this paper, an E/H control design is proposed for flow control in hydraulic systems using poppet valves. With the pressures at the valve input and output ports being known, the proposed poppet valve flow control is formulated as tracking the desired poppet displacement xd(t) under the system disturbances. No pilot pressure is required. Using the control pressure at its equilibrium points, the proposed control law largely simplifies the real world implementation with bounded tracking error. Preliminary studies show that the proposed controller is capable of controlling the flow in both directions, with some limitations on the pressure difference between input and output ports while flow is reversed. Simulation results show the effectiveness of the presented control design and experimental validations are scheduled in near future.
Dynamical Modeling and Analysis of the Human Jumping Process
Authors: Meghdari A. , Aryanpour M.
Published: May 2008

A dynamical model was developed in order to study the jumping process in human, and the effect of factors like joint speeds and hand motion. An experiment was designed and setup to compare the theoretical model with the experimental observations. Time histories of vertical force, mass center velocity and driving torques were obtained too. Using dynamical equations, the effect of joint speeds on the maximum values of these quantities is discussed. It is shown that reducing the joint speeds of a body can lead to an unsuccessful jump in which the body does not enter the flight phase. An increase in speed reduces the take-off time (the time necessary for the body to leave the ground) and increases the body’s linear velocity at take-off, as well as, the maximum value of driving torques. Effect of hand motion is also investigated through suppressing motion of the Shoulder and Elbow. It is observed that hand motion has an improving effect on the body’s linear velocity. Although speed of joints did not show to have a great influence on most torques, those at the Shoulder and Elbow were observed to be more sensitive to it.
Die Life Prediction in Rapid Prototype Dies
Authors: Park Young-Bin , Colton Jonathan S.
Published: May 2008

To meet the growing demand for rapid, low-cost die fabrication technology in the sheet metal forming industry, easy-to-machine, polyurethane-based, composite board stock is used widely as a rapid tooling material. In practice, it is desirable to terminate die life by wear rather than by catastrophic fatigue. However, the failure mechanisms of the rapid prototyped tools are not clearly understood, thus making the prediction of tool life difficult. This paper presents a method to estimate the fatigue life of a sheet metal forming die fabricated from ATH (aluminum trihydrate)-filled polyurethane. A finite element model of 90° V-die bending process was developed, and the effects of process parameters on stress distribution in the punch and die were investigated through simulation. Mechanical testing was performed to characterize the fatigue properties of the tooling material. The computer-simulated results were verified through experiments using instrumented, laboratory-scale punch and die sets.
Large-Scale Laminated Dies for Sheet Metal Forming
Authors: Walczyk Daniel
Published: May 2008

As part of a 5-year NSF-sponsored project, a design and fabrication system is being developed for Profiled Edge Laminated (PEL) tooling. The PEL tooling method is a thick-layer Rapid Tooling (RT) approach that offers distinct advantages over both conventional CNC machining of billets and other RT processes. Furthermore, the method is ideally suited for developing large-scale sheet metal forming tools. To date, the following design, fabrication and analysis tools have been completed: details of the ‘front-end’ design and analysis process; valid structural and thermal FEL modeling methods for PEL tooling; and development of the ‘back-end’ PEL tool fabrication process consisting of a CAM software system to allow AWJ cutting of individual PELs based on a CAD model. The front end process has been demonstrated with matched die forming of a 2-dimensional steel part. The back-end process has also been demonstrated using a 3-dimensional hydroformed aluminum part. Future work will include incorporation of variable thickness and orientation algorithms that account for stock lamination thicknesses and part dimensional tolerances, more advanced structural and thermal models, the means to predict the cost and time required for fabrication of PEL tools, an investigation of different lamination bonding methods, and additional industrial case studies.
Processing and Properties of Nanostructured Magnetic Materials
Authors: Kumar D. , Yarmolenko S. , Sankar J. , Narayan J. , Tiwari A. , Zhou H. , Jin C. , Kvit A. V. , Pennycook S. J. , Lupini A.
Published: May 2008

We report here a novel thin film processing method based upon pulsed laser deposition to process nanocrystalline materials with accurate size and interface control with improved mechanical and magnetic properties. Using this method, single domain nanocrystalline Fe and Ni particles in 5–10 nm size range embedded in amorphous alumina as well as crystalline TiN have been produced. By controlling the size distribution in confined layers, it was possible to tune the magnetic properties from superparamagnetic to ferromagnetic behavior. Magnetic hysteresis characteristics below the blocking temperature are consistent with single-domain behavior. The paper also presents our results from investigations in which scanning transmission electron microscopy with atomic number contrast (STEM-Z) and energy loss spectroscopy (EELS) were used to understand the atomic structure of Ni nanoparticles and interface between the nanoparticles and the surrounding matrices. It was interesting to learn from EELS measurements at interfaces of individual grains that Ni in alumina matrix does not from an ionic bond indicating the absence of metal-oxygen bond at the interface. The absence of metal-oxygen bond, in turn, suggests the absence of any dead layer on Ni nanoparticles even in an oxide matrix.
Mechanical Response of Unsaturated Particulate Materials: A Stiffness Assessment Study Under Controlled Matric Suction
Authors: Silva C. H. C. , Porras Ortiz F. O. , Fratta D. , Macari E. J.
Published: May 2008

This paper describes issues related to stiffness of unsaturated particulate materials including the effects of time-varying processes during the formation and disruption of the menisci during loading and their effect in the matric suction. The phenomena are studied using a true triaxial device with matric suction control and equipped with bender elements for shear-wave velocity measurements. Evidence shows that the low-strain and high-strain stiffness of the particulate media are stress- and suction-controlled. However at high strains the stiffness that results from the effect of matric suction is lost and its re-stiffening rate depends on the moisture content.