bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser-Based Measurement of Temperature or Concentration Change at Liquid Surfaces
Authors: Fan C. H. , Longtin J. P.
Published: July 2002

This work presents a noncontact laser-based thermoreflectance technique to measure changes in temperature or concentration at a liquid surface. Changes in temperature and, for multi-component liquid mixtures, concentration result in a change in the liquid index of refraction, which alters the reflectivity of the liquid surface. An intensity-stabilized diode laser and silicon photodiode are used to monitor the surface reflectivity. Temperature variations in 1-propanol, methanol, ethanol, and water are measured with uncertainties of 0.5, 0.7, 0.7, and 3.7°C, respectively. For binary mixtures, the concentration of a methanol-propanol mixture is measured with an uncertainty of 0.3 percent. The experimental configuration is noninvasive, simple in design, and inexpensive. The technique can be used over a wide range of time scales, ranging from micro-seconds to minutes, and can achieve high spatial resolution by focusing the probe laser beam to a small spot size on the liquid surface. [S0022-1481(00)02803-6]
Solder Joint Reliability of Wafer Level Chip Scale Packages (WLCSP): A Time-Temperature-Dependent Creep Analysis
Authors: Lau John H. , Lee S.-W. Ricky , Chang Chris
Published: July 2002

A novel and reliable wafer level chip scale package (WLCSP) is investigated in this paper. It consists of a copper conductor layer and two low cost dielectric layers. The bump geometry consists of the eutectic solder, the copper core, and the under bump metallurgy. Nonlinear time-temperature-dependent finite element analyses are performed to determine the shear stress, shear creep strain, shear stress and shear creep strain hysteresis loops, and creep strain energy density of the corner solder joint. The thermal-fatigue life of the corner solder joint is then predicted by the averaged creep strain energy density range per cycle and a linear fatigue crack growth rate theory. The WLCSP solder bumps are also subjected to shear test. Finally, the WLCSP solder joints are subjected to both mechanical shear and thermal cycling tests. [S1043-7398(00)01004-5]
Fretting Stresses in Single Crystal Superalloy Turbine Blade Attachments
Authors: Arakere Nagaraj K. , Swanson Gregory
Published: July 2002

Single crystal nickel base superalloy turbine blades are being utilized in rocket engine turbopumps and turbine engines because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. High cycle fatigue induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Blade attachment regions are prone to fretting fatigue failures. Single crystal nickel base superalloy turbine blades are especially prone to fretting damage because the subsurface shear stresses induced by fretting action at the attachment regions can result in crystallographic initiation and crack growth along octahedral planes. This paper presents contact stress evaluation in the attachment region for single crystal turbine blades used in the NASA alternate advanced high pressure fuel turbo pump for the space shuttle main engine. Single crystal materials have highly anisotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. Blades and the attachment region are modeled using a large-scale three-dimensional finite element model capable of accounting for contact friction, material anisotropy, and variation in primary and secondary crystal orientation. Contact stress analysis in the blade attachment regions is presented as a function of coefficient of friction and primary and secondary crystal orientation. Fretting stresses at the attachment region are seen to vary significantly as a function of crystal orientation. The stress variation as a function of crystal orientation is a direct consequence of the elastic anisotropy of the material. Fatigue life calculations and fatigue failures are discussed for the airfoil and the blade attachment regions.
3-D Stress Intensity Factors for Internal Cracks in an Overstrained Cylindrical Pressure Vessel—Part I: The Effect of Autofrettage Level
Authors: Perl M. , Nachum A.
Published: July 2002

Three-dimensional, mode I, stress intensity factor (SIF) distributions for arrays of internal surface cracks emanating from the bore of an autofrettaged thick-walled cylinder are evaluated in Part I of this paper. The 3-D analysis is performed via the finite element (FE) method and the submodeling technique, employing singular elements along the crack front. The autofrettage residual stress field is simulated using an equivalent temperature field. More than 200 different crack configurations were analyzed. SIFs for numerous crack arrays (n=1–180 cracks), a wide range of crack-depth-to-wall-thickness ratios a/t=0.05-0.6, various ellipticities a/c=0.2-1.5, and different levels of autofrettage (e=10–100 percent) were evaluated. The results clearly indicate the importance of autofrettage in reducing the effective stress intensity factor, and thus, slowing the crack growth rate. The sensitivity of this favorable effect to the number of cracks in the array as well as to the level of autofrettage are also discussed. The combined effect of pressure and autofrettage is discussed in detail in Part II of this paper. [S0094-9930(00)00604-1]
Arbitrary Load Distribution on a Layered Half Space
Authors: Schwarzer N.
Published: July 2002

This paper develops a method which allows one to calculate the complete elastic field (stress field and displacements) of layered materials of transverse and complete isotropy under given load conditions. It is assumed that the layered body consists of an infinite half-space and various infinite planes which are all ideally bonded to each other. Thus, the interfaces are parallel to the surface of the resulting “coated half space.” The approach is based on the method of images in classical electrostatics. The final solution for an arbitrary load problem can be presented as a series of potential functions, where corresponding functions may be interpreted as “image loads” the analogous to “image charges.” The solution for the elastic field for any arbitrary stress distribution on the surface of the coated half space can be obtained in a relatively straightforward manner by using the method described here as long as the corresponding solution for the homogeneous half space is known. Further, if this solution of the homogeneous case may be expressed in terms of elementary functions, then the solution for the coated half space is elementary, too. Explicit formulas for the stress fields for some particular examples are given. [S0742-4787(00)01204-2]
Geometric Parameters Influencing Flow in an Axisymmetric IC Engine Inlet Port Assembly: Part II—Parametric Variation of Valve Geometry
Authors: Maier Andreas , Sheldrake Terry H. , Wilcock Dennis
Published: July 2002

The influence of inlet valve geometry on IC engine port flow characteristics was investigated systematically by varying the key valve geometric parameters of fillet radius, cone angle, and seat angle. The analysis of flow through the port was measured for 36 valves having geometries determined by R/D=0.20-0.30, cone angle 0–20 deg and seat angle 30–45 deg. Discharge coefficients were measured to gain an understanding of the general flow performance. These were used in conjunction with heat transfer data to gain a clear understanding of the state of the boundary layer on the valve and port seats for varying lifts and pressure drops. This established the presence or otherwise of the four flow regimes within the valve passage. The results demonstrate that the cone and seat angle have major effects on valve flow performance and enable engine designers to choose more readily the valve characteristics they desire. [S0098-2202(00)00404-1]
Models for Estimating Solar Radiation and Illuminance From Meteorological Parameters
Authors: Muneer T. , Gul M. S. , Kubie J.
Published: July 2002

Sunshine fraction, cloud amount, temperature, and global irradiation are the most commonly measured meteorological parameters. In this article five models based mainly on the abovementioned variables for the determination of irradiation and illuminance components are presented. These models are divided into three categories. Category 1 includes three solar radiation models: a Meteorological Radiation Model (MRM), developed by present authors based on sunshine fraction and temperature data, b Cloud-Cover Radiation Model (CRM)—modification of an earlier model for the UK by the present authors based on cloud-cover in oktas, and c Page Radiation Model (PRM), developed by Page based on simultaneous sunshine and cloud data. Category 2 comprises of a new Diffuse Ratio Model (DRM), developed by authors, for estimating diffuse irradiation when global irradiation is provided as the input parameter. The third category includes luminous efficacy models that enable estimation of diffuse and global illuminance once the respective irradiation components have been obtained from category 1 models. [S0199-6231(00)02003-7]
PIV Technique for the Simultaneous Measurement of Dilute Two-Phase Flows
Authors: Kiger K. T. , Pan C.
Published: July 2002

A Particle Image Velocimetry (PIV) image processing technique has been developed which can be applied to solid-liquid two-phase turbulent flows. The main principle of the technique is to utilize a two-dimensional median filter to generate separate images of the two phases, thus eliminating the errors induced by the distinct motion of the dispersed component. The accuracy and validity of the technique have been studied in the present research for different filter widths, f, and for 4 groups of different sized dispersed particles ranging from an effective image diameter of dp=2.9 pixels to 13 pixels in combination with tracer particles with an effective image size of dt∼2.4 pixels. The results have shown that the errors introduced by the filter are negligible, and mainly arise in regions of large velocity gradients that are sensitive to the slight loss of information incurred by the processing. The filter width f also affects the algorithm’s ability to correctly separate and identify the dispersed phase particles from the two-phase images, with the main result that above a critical particle image size ratio, dp/dt≈3.0, the particle size had no significant influence on the number of particles identified, or the accuracy of the displacement calculation. Sample results of particle-fluid interaction and cross-correlation terms which can be obtained from the method are also presented. [S0098-2202(00)01104-4]
Chattering Elimination With Second-Order Sliding Modes Robust to Coulomb Friction
Authors: Bartolini G. , Punta E.
Published: July 2002

In this paper, a solution to the regulation problem of mechanical systems in presence of Coulomb friction is proposed. The control objective is attained by means of continuous control signals designed according to a second-order sliding mode algorithm. The proposed solution avoids the main drawback presented by the standard first-order sliding mode control, that is the chattering phenomenon which is due to the unavoidable presence of non idealities and to the discontinuous nature of the control signals. The proposed algorithm is proved to be efficient in counteracting discontinuous disturbances such as friction. [S0022-0434(00)00704-8]
Extremum Control for Optimal Operating Point Determination and Set Point Optimization Via Sliding Modes
Authors: Haskara I˙brahim , O¨zgu¨ner U¨mit , Winkelman Jim
Published: July 2002

In the design of a control system, it is often desirable to operate at the peak of an appropriate performance surface which characterizes the performance of the closed-loop operation. However, in many cases, only limited information might be available on the plant and the desired performance criterion which makes a priori determination of such an optimal operation mode difficult in the first place. The online identification of an optimal operating point and the development of a controller structure which enables the system to robustly operate at such a point constitute a remarkable research problem with this motivation. In this paper, a two-time scale sliding mode optimization method is studied for this purpose. The adopted scheme assumes a regulative controller which produces an equilibria for the closed-loop system parametrized by a free control parameter and employs a sliding mode optimization method to adapt this parameter in a slower time scale to increase the performance of the overall system. A simulation study is summarized to illustrate the approach. [S0022-0434(00)01004-2]
A General Sliding Mode Controller for Nonlinear Chemical Processes
Authors: Camacho Oscar , Rojas Rube´n
Published: July 2002

This paper summarizes an approach of Sliding Mode Control, which can be used for a width class of nonlinear chemical processes. The controller was synthesized from an empirical model of the process. The designed controller was developed for minimum phase systems and presents a fixed structure and can be tuned based on the characteristic parameters of the model. A proposed implementation scheme is shown. The designed controller was tested for minimum and nonminimum phase systems, as well as for integrating and MIMO systems in different experimental conditions (i.e., disturbances, noise, modeling errors). The designed controller had shown good performance for the different kind of systems and conditions. [S0022-0434(00)01504-5]
Sliding Mode Control of a Three Degrees of Freedom Anthropoid Robot by Driving the Controller Parameters to an Equivalent Regime
Authors: Efe M. Onder , Kaynak Okyay , Yu Xinghuo
Published: July 2002

Noise rejection, handling the difficulties coming from the mathematical representation of the system under investigation and alleviation of structural or unstructural uncertainties constitute prime challenges that are frequently encountered in the practice of systems and control engineering. Designing a controller has primarily the aim of achieving the tracking precision as well as a degree of robustness against the difficulties stated. From this point of view, variable structure systems theory offer well formulated solutions to such ill-posed problems containing uncertainty and imprecision. In this paper, a simple controller structure is discussed. The architecture is known as Adaptive Linear Element (ADALINE) in the framework of neural computing. The parameters of the controller evolve dynamically in time such that a sliding motion is obtained. The inner sliding motion concerns the establishment of a sliding mode in controller parameters, which aims to minimize the error on the controller outputs. The outer sliding motion is designed for the plant. The algorithm discussed drives the error on the output of the controller toward zero learning error level, and the state tracking error vector of the plant is driven toward the origin of the phase space simultaneously. The paper gives the analysis of the equivalence between the two sliding motions and demonstrates the performance of the algorithm on a three degrees of freedom, anthropoid robotic manipulator. In order to clarify the performance of the scheme, together with the dynamic complexity of the plant, the adverse effects of observation noise and nonzero initial conditions are studied. [S0022-0434(00)01704-4]
Sliding Mode Control of Discrete-Time Systems
Authors: Koshkouei A. Jafari , Zinober A. S. I.
Published: July 2002

In discrete-time systems, instead of having a hyperplane as in the continuous case, there is a countable set of points comprising a so-called lattice; and the surface on which these sliding points lie is the latticewise hyperplane. In this paper the concept of multivariable discrete-time sliding mode is clarified and new sufficient conditions for the existence of the sliding mode are presented. A new control design using the properties of discrete sliding is proposed, and the behavior of the system in the sliding mode is studied. Furthermore, the stabilization of discrete-time systems and an optimal sliding lattice are considered. [S0022-0434(00)02804-5]
Analysis of Rigid-Body Dynamic Models for Simulation of Systems With Frictional Contacts
Authors: Song P. , Kraus P. , Kumar V. , Dupont P.
Published: July 2002

The use of Coulomb’s friction law with the principles of classical rigid-body dynamics introduces mathematical inconsistencies. Specifically, the forward dynamics problem can have no solutions or multiple solutions. In these situations, compliant contact models, while increasing the dimensionality of the state vector, can resolve these problems. The simplicity and efficiency of rigid-body models, however, provide strong motivation for their use during those portions of a simulation when the rigid-body solution is unique and stable. In this paper, we use singular perturbation analysis in conjunction with linear complementarity theory to establish conditions under which the solution predicted by the rigid-body dynamic model is stable. We employ a general model of contact compliance to derive stability criteria for planar mechanical systems. In particular, we show that for cases with one sliding contact, there is always at most one stable solution. Our approach is not directly applicable to transitions between rolling and sliding where the Coulomb friction law is discontinuous. To overcome this difficulty, we introduce a smooth nonlinear friction law, which approximates Coulomb friction. Such a friction model can also increase the efficiency of both rigid-body and compliant contact simulation. Numerical simulations for the different models and comparison with experimental results are also presented.
Penetration Experiments With Limestone Targets and Ogive-Nose Steel Projectiles
Authors: Frew D. J. , Forrestal M. J. , Hanchak S. J.
Published: July 2002

We conducted three sets of depth-of-penetration experiments with limestone targets and 3.0 caliber-radius-head (CRH), ogive-nose steel rod projectiles. The ogive-nose rod projectiles with length-to-diameter ratios of ten were machined from 4340Rc45 and Aer Met 100Rc53 steel, round stock and had diameters and masses of 7.1 mm, 0.020 kg; 12.7 mm, 0.117 kg; and 25.4 mm, 0.931 kg. Powder guns or a two-stage, light-gas gun launched the projectiles at normal impacts to striking velocities between 0.4 and 1.9 km/s. In addition, we present an analytical penetration equation that described the target resistance by its density and a strength parameter determined from depth of penetration versus striking velocity data. [S0021-8936(01)00201-X]
Adapting an Articulated Vehicle to its Drivers
Authors: Yang Xiaobo , Rakheja Subhash , Stiharu Ion
Published: July 2002

A yaw plane model with limited roll-DOF of a five-axle tractor semitrailer is developed to study the open-loop directional dynamics of the vehicle. A driver model incorporating path preview, low and high frequency compensatory gains and time delays, and prediction of the vehicle state, is developed and integrated with the vehicle model. The coupled model is analyzed to investigate the vehicle design, which could be best adapted in view of the control limits of different driver, which are identified in terms of preview distance, reaction time and compensatory gain. A performance index based upon the vehicle path tracking, directional response characteristics and the driver’s steering effort is formulated and minimized using Gauss-Newton method to derive the desirable ranges of vehicle parameters, that could be adapted for drivers with varying skills. It is concluded that the adaptability and thus the directional performance of the vehicle can be enhanced through variations in the weights and dimensions, and compliant properties of the suspension, tire and the fifth wheel. The results of the study suggest that a driver with superior driving skill can easily adapt a vehicle with relatively large size, soft suspension and higher degree of oversteer. The results further show that the driver-adapted vehicle yields up to 33 percent reduction in the steering effort demand posed on the driver, while the roll angle and yaw rate response decrease by up to 40 percent.
Simulation of Thermal Plasma Spraying of Partially Molten Ceramics: Effect of Carrier Gas on Particle Deposition and Phase Change Phenomena
Authors: Ahmed I. , Bergman T. L.
Published: July 2002

A three-dimensional simulation of the thermal plasma spraying process is reported. In particular, the effect of the radial injection of a carrier gas is taken into account for a dilute spray. The thermal history of powder particles of different sizes is predicted. It is shown that introduction of a carrier gas can lead to a significant modification of the plasma jet, and can have an effect on the thermal histories of the injected particles. The study is motivated by the processing of non-traditional materials, specifically nanostructured ceramics.
South Arne-Nybro Offshore Pipeline—The Subsea Installations
Authors: Gjerso̸e Fog Nils , Krogh Michael
Published: July 2002

A summary is given for the design and construction of the South Arne-Nybro 24-in. gas pipeline. The main design requirements for the subsea installations are presented: subsea Wye piece configuration to enable gas export from both South Arne and Harald, use of subsea safety valves close to platforms, platform-based control systems for opening of subsea check valves, subsea ball valves and small bore ports for precommissioning, pipeline isolation and contingency purpose, strong protection structures to avoid damage by fishing gear, and, finally, design to avoid scour problems. The design work to achieve these objectives as well as simple installation methods for the subsea assemblies by use of a medium-sized diving support vessel is described. An outline for the offshore construction work is finally given.
Quantitative Feedback Design Using Forward Path Decoupling1
Authors: Boje Edward , Nwokah Osita D. I.
Published: July 2002

The Perron-Frobenius root is used to measure the level of interaction in MIMO quantitative feedback design (QFT). A design approach to reduce interaction in uncertain plants via a precompensator is presented. A decentralized stability result applies if the interaction index can be made less than unity by design.
Dynamic Behavior of Complex Fluid-Filled Tubing Systems—Part 1: Tubing Analysis
Authors: Brown Forbes T. , Tentarelli Stephen C.
Published: July 2002

A general transmission-matrix approach is given for finding the frequency response of linearized long-wavelength models for the vibration in systems with straight and curved fluid-filled tubes. Couplings between the fluid and wall motions include the Bourdon effect, frequency-dependent wall shear, the Poisson coupling and the effect of discontinuities. The introduction of a global transmission matrix allows nonplanar tubing systems of virtually any complexity to be analyzed, overcoming the round-off error problem that plagues the basic transmission-matrix approach for this and analogous system models. Corroborating experiments focus on the Poisson and Bourdon effects.
Warpage of Plastic IC Packages as a Function of Processing Conditions
Authors: Yeung Dickson T. S. , Yuen Matthew M. F.
Published: July 2002

Variation of processing conditions on warpage prediction of a plastic quad flat package (PQFP) is examined. Thermal mismatch between package constituent materials is the major cause of IC package warpage. To minimize the warpage problem, a thorough understanding of epoxy molding compound (EMC) properties with molding parameters is necessary as EMC is epoxy-based with time and temperature dependent viscoelastic properties. This paper first addressed the thermal characterization of encapsulating material. Degree-of-cure (DOC or β), coefficient of thermal expansion (CTE or α), glass transition temperature Tg, and shear modulus G′ and G of the molded specimens were measured by various thermal analysis techniques. The glass transition temperature was shown to be a good and direct measure of the degree-of-cure. The CTEs (α1 and α2),G′ and G″ were found to be decreasing functions of degree-of-cure. Viscoelastic EMC material models with DOC (i.e., Tg) dependent were formulated. Package warpage predictions against different processing conditions were performed via finite element analyses. Out-of-plane displacement measurements were performed on plastic quad flat package (PQFP) to validate the numerical results. Warpage prediction by the viscoelastic material model was found to agree with the measured data better than the thermoelastic one. For a given cured content, less warpage was found in packages molded at low temperature and longer molding time OR high temperature and shorter molding time.
Assessment of Corner Failure Depths in the Deep Drawing of 3D Panels Using Simplified 2D Numerical and Analytical Models
Authors: Yao Hong , Cao Jian
Published: July 2002

Methodologies of rapidly assessing maximum possible forming heights are needed for three-dimensional 3D sheet metal forming processes at the preliminary design stage. In our previous work, we proposed to use an axisymmetric finite element model with an enlarged tooling and blank size to calculate the corner failure height in a 3D part forming. The amount of enlargement is called center offset, which provides a powerful means using 2D models for the prediction of 3D forming behaviors. In this work, an analytical beam model to calculate the center offset is developed. Starting from the study of a square cup forming, a simple analytical model is proposed and later generalized to problems with corners of an arbitrary geometry. The 2D axisymmetric models incorporated with calculated center offsets were compared to 3D finite element simulations for various cases. Good assessments of failure height were obtained.
A Power Flow Model for High Speed Motorized Spindles—Heat Generation Characterization
Authors: Bossmanns Bernd , Tu Jay F.
Published: July 2002

Lack of a more complete understanding of system characteristics, particularly thermal effects, severely limits the reliability of high speed spindles to support manufacturing. High speed spindles are notorious for their sudden catastrophic failures without alarming signs at high speeds due to thermal problems. In this paper, a qualitative power flow model is presented to characterize the power distribution of a high speed motorized spindle. Quantitative heat source models of the built-in motor and the bearings are then developed. These models are verified with a custom-built high performance motorized spindle of 32 KW and a maximum speed of 25,000 rpm (1.5 million DN). Several systematic test procedures are also developed to validate the models.
Extinction and Scattering Properties of Soot Emitted From Buoyant Turbulent Diffusion Flames
Authors: Krishnan S. S. , Lin K.-C. , Faeth G. M.
Published: July 2002

Extinction and scattering properties at wavelengths of 250–5200 nm were studied for soot emitted from buoyant turbulent diffusion flames in the long residence time regime where soot properties are independent of position in the overfire region and characteristic flame residence times. Flames burning in still air and fueled with gas (acetylene, ethylene, propane, and propylene) and liquid (benzene, toluene, cyclohexane, and n-heptane) hydrocarbon fuels were considered. Measured scattering patterns and ratios of total scattering/absorption cross sections were in good agreement with predictions based on the Rayleigh-Debye-Gans (RDG) scattering approximation in the visible. Measured depolarization ratios were roughly correlated by primary particle size parameter, suggesting potential for completing RDG methodology needed to make soot scattering predictions as well as providing a nonintrusive way to measure primary soot particle diameters. Measurements of dimensionless extinction coefficients were in good agreement with earlier measurements for similar soot populations and were independent of fuel type and wavelength except for reduced values as the near ultraviolet was approached. The ratios of the scattering/absorption refractive index functions were independent of fuel type within experimental uncertainties and were in good agreement with earlier measurements. The refractive index function for absorption was similarly independent of fuel type but was larger than earlier reflectometry measurements in the infrared. Ratios of total scattering/absorption cross sections were relatively large in the visible and near infrared, with maximum values as large as 0.9 and with values as large as 0.2 at 2000 nm, suggesting greater potential for scattering from soot particles to affect flame radiation properties than previously thought.
An Efficient Method for Modeling Radiative Transfer in Multicomponent Gas Mixtures With Soot
Authors: Solovjov Vladimir P. , Webb Brent W.
Published: July 2002

An efficient approach for predicting radiative transfer in high temperature multicomponent gas mixtures with soot particles is presented. The method draws on the previously published multiplication approach for handling gas mixtures in the spectral line weighted-sum-of-gray-gases (SLW) model. In this method, the gas mixture is treated as a single gas whose absorption blackbody distribution function is calculated through the distribution functions of the individual species in the mixture. The soot is, in effect, treated as another gas in the mixture. Validation of the method is performed by comparison with line-by-line solutions for radiative transfer with mixtures of water vapor, carbon dioxide, and carbon monoxide with a range of soot loadings (volume fractions). Comparison is performed also with previously published statistical narrow band and classical weighted-sum-of-gray-gases solutions.
Experimental Study of Tangential Micro Deflection of Interface of Machined Surfaces
Authors: Ni Jun , Zhu Zhenqi
Published: July 2002

This paper studies the characteristics of micro tangential deflection of the interface of mating machined surfaces subjected to normal and tangential forces. Experimental results show that contact interface subjected to a tangential force experiences elastic deformation, plastic deformation and micro slip before macro-breakaway occurs. The linearity of tangential stiffness is only valid in the stage of elastic deformation. The nonlinear tangential stiffness of the interface should be considered in the stages of elastic and plastic deformation before micro-breakaway occurs.
Plasticity in the Thickness Direction of Paperboard Under Combined Shear and Normal Loading
Authors: Stenberg N. , Fellers C. , O¨stlund S.
Published: July 2002

Creasing and offset printing are both examples of paperboard converting operations where the stress state is multiaxial, and where elastic-plastic deformation occurs in the thickness direction. Optimization of paperboard for such operations requires both advanced modeling and a better understanding of the mechanical behavior of the material. Today, our understanding and modeling of the out-of-plane properties are not as well established as our knowledge of the in-plane behavior. In order to bridge this gap, a modification of the Arcan device, which is well known in other fields, was developed for the experimental characterization of the out-of-plane mechanical behavior of paperboard. A fixture attached to the Arcan device was used to control the deformation in the test piece during loading. The test piece was glued to the device with a high viscosity adhesive and left stress-free during curing to achieve an initial state free of stresses. The apparatus proved to work well and to produce reliable results. Measurements of the mechanical behavior in combined normal and shear loading generated data points for the determination of the yield surface in the stress space. The elastic-plastic behavior in the thickness direction of paperboard was modeled assuming small-strain orthotropic linear elasticity and a quadratic yield function. Simulations using this yield function and an associative flow law showed good agreement with the test results.
Creep Crack Growth in X20CrMoV 12 1 Steel and Its Weld Joint
Authors: Park Y. K. , Kim K. S. , Chung Y. K. , Park J. J.
Published: July 2002

A combined experimental and computational study is carried out on creep crack growth in X20CrMoV 12 1 steel and its weld joint. Crack growth tests are conducted on compact specimens at 545°C. For weld specimens, the crack propagates in the heat-affected zone parallel to the fusion line. It is found that C*t correlates crack growth rates satisfactorily under the loads used in the test not only for base metal specimens but also for weld specimens. An elastic-plastic-steady-state creep analysis of crack growth is performed using a finite element code. Calculated load point displacement rates agree with experimental measurements during steady-state crack growth. The creep zone is asymmetric, and it becomes more so in weld specimens as the crack propagates. Yet the mode II effect appears to be insignificant.
Detailed Chemical Kinetic Simulation of Natural Gas HCCI Combustion: Gas Composition Effects and Investigation of Control Strategies
Authors: Flowers D. , Aceves S. , Westbrook C. K. , Smith J. R. , Dibble R.
Published: July 2002

This paper uses the HCT (hydrodynamics, chemistry and transport) chemical kinetics code to analyze natural gas combustion in an HCCI engine. The HCT code has been modified to better represent the conditions existing inside an engine, including a wall heat transfer correlation. Combustion control and low power output per displacement remain as two of the biggest challenges to obtaining satisfactory performance out of an HCCI engine, and these challenges are addressed in this paper. The paper considers the effect of natural gas composition on HCCI combustion, and then explores three control strategies for HCCI engines: DME (dimethyl ether) addition, intake heating and hot EGR addition. The results show that HCCI combustion is sensitive to natural gas composition, and an active control may be required to compensate for possible changes in composition. Each control strategy has been evaluated for its influence on the performance of an HCCI engine.
Robust Feedrate Selection for 3-Axis NC Machining Using Discrete Models
Authors: Fussell B. K. , Jerard R. B. , Hemmett J. G.
Published: July 2002

This research effort is focused on improving the efficiency of CNC machining by automatic computer selection of feedrate for 3-axis sculptured surface machining. A feedrate process planner for complex sculptured end milling cuts is developed from mechanistic and geometric end milling models. The selection program uses tool deflection, surface finish, tool failure and machine power to set constraints on the cutting force and the feed-per-tooth for rough, semi-finish, and finish passes. A NC part program is processed one tool move at a time by the planner. For each tool move a geometric model calculates the cut geometry, and an inverse mechanistic model uses this information along with the constraint force to calculate a desired feedrate. The feedrate is written into the part program resulting in a file that contains a feedrate for each tool move. Experimental results for a sculptured surface show the accuracy of the algorithms in maintaining a desired force.
System Identification of a MEMS Gyroscope
Authors: M’Closkey Robert T. , Gibson Steve , Hui Jason
Published: July 2002

This paper reports the experimental system identification of the Jet Propulsion Laboratory MEMS vibratory rate gyroscope. A primary objective is to estimate the orientation of the stiffness matrix principal axes for important sensor dynamic modes with respect to the electrode pick-offs in the sensor. An adaptive lattice filter is initially used to identify a high-order two-input/two-output transfer function describing the input/output dynamics of the sensor. A three-mode model is then developed from the identified input/output model to determine the axes’ orientation. The identified model, which is extracted from only two seconds of input/output data, also yields the frequency split between the sensor’s modes that are exploited in detecting the rotation rate. The principal axes’ orientation and frequency split give direct insight into the source of quadrature measurement error that corrupts detection of the sensor’s angular rate.
Viscous-Flow Two-Dimensional Analysis Including Secondary Flow Effects
Authors: Mo¨nig Reinhard , Mildner Frank , Ro¨per Ralf
Published: July 2002

During the last few decades extremely powerful Quasi-three-dimensional (3D) codes and fully 3D Navier-Stokes solvers have been developed and successfully utilized in the design process and optimization of multistage axial-flow compressors. However, most of these methods proved to be difficult in handling and extremely time consuming. Due to these disadvantages, the primary stage design and stage matching as well as the off-design analysis is nowadays still based on fast 2D methods incorporating loss-, deviation- and end wall modeling. Only the detailed 3D optimization is normally performed by means of advanced 3D methods. In this paper a fast and efficient 2D calculation method is presented, which already in the initial design phase of multistage axial flow compressors, considers the influence of hub leakage flows, tip clearance effects, and other end wall flow phenomena. The method is generally based on the fundamental approach by Howard and Gallimore (1992). In order to allow a more accurate prediction of skewed and nondeveloped boundary layers in turbomachines, an improved theoretical approach was implemented. Particularly the splitting of the boundary layers into an axial and tangential component proved to be necessary in order to account for the change between rotating and stationary end walls. Additionally, a new approach is used for the prediction of the viscous end wall zones including hub leakage effects and strongly skewed boundary layers. As a result, empirical correlations for secondary flow effects are no longer required. The results of the improved method are compared with conventional 2D results including 3D loss- and deviation-models, with experimental data of a three-stage research compressor of the Institute for Jet Propulsion and Turbomachinery of the Technical University of Aachen and with 3D Navier-Stokes solutions of the V84.3A compressor and of a multistage Siemens research compressor. The results obtained using the new method show a remarkable improvement in comparison with conventional 2D methods. Due to the high quality and the extremely short computation time, the new method allows an overall viscous design of multistage compressors for heavy duty gas turbines and aeroengine applications.
Fully Coupled Rigid Internal Combustion Engine Dynamics and Vibration—Part II: Model-Experiment Comparisons
Authors: Hoffman D. M. W. , Dowling D. R.
Published: July 2002

In internal combustion engine vibration modeling, it is typically assumed that the vibratory state of the engine does not influence the loads transmitted to the engine block from its moving internal components. This one-way-coupling assumption leads to energy conservation problems and does not account for Coriolis and gyroscopic interactions between the engine block and its rotating and reciprocating internal components. A new seven-degree-of-freedom engine vibration model has been developed that does not utilize this assumption and properly conserves energy. This paper presents time and frequency-domain comparisons of this model to experimental measurements made on an inline six-cylinder heavy-duty Diesel engine running at full load at peak-torque (1200 rpm) and rated (2100 rpm) speeds. The model successfully predicts the overall features of the engine’s vibratory output with model-experiment correlation coefficients as high as 70 percent for vibration frequencies up through third engine order. The results are robust to variations in the model parameters. Predictions are less successful at the detail level and at higher frequencies because of uncertainties in the actual imperfections of the test engine, and because of the influence of unmodeled engine components.
An Experimental Investigation of Bending Fatigue Initiation and Propagation Lives
Authors: Singh Avinash
Published: July 2002

It has long been recognized that the fatigue life of a component can be divided into a crack initiation phase and a crack propagation phase, but researchers have typically ignored one phase or the other in their analytical models. Even in the stress-life method of life prediction, which implicitly includes both phases, no distinction is made between the initiation and propagation phases. In this paper a methodology for generating initiation and propagation S-N curves will be outlined. It will be shown that for components like gears, both phases represent significant portions of total life. It will also be shown that gear bending fatigue lives for variable amplitude load tests are better predicted by a two-stage linear damage theory compared to the commonly used Miner’s total life linear damage theory.
Linearized Unsteady Viscous Turbomachinery Flows Using Hybrid Grids
Authors: Sbardella L. , Imregun M.
Published: July 2002

The paper describes the theory and the numerical implementation of a three-dimensional finite volume scheme for the solution of the linearized, unsteady Favre-averaged Navier–Stokes equations for turbomachinery applications. A further feature is the use of mixed element grids, consisting of triangles and quadrilaterals in two dimensions, and of tetrahedra, triangular prisms, and hexahedra in three dimensions. The linearized unsteady viscous flow equations are derived by assuming small harmonic perturbations from a steady-state flow and the resulting equations are solved using a pseudo-time marching technique. Such an approach enables the same numerical algorithm to be used for both the nonlinear steady and the linearized unsteady flow computations. The important features of the work are the discretization of the flow domain via a single, unified edge-data structure for mixed element meshes, the use of a Laplacian operator, which results in a nearest neighbor stencil, and the full linearization of the Spalart–Allmaras turbulence model. Four different test cases are presented for the validation of the proposed method. The first one is a comparison against the classical subsonic flat plate cascade theory, the so-called LINSUB benchmark. The aim of the second test case is to check the computational results against the asymptotic analytical solution derived by Lighthill for an unsteady laminar flow. The third test case examines the implications of using inviscid, frozen-turbulence, and fully turbulent models when linearizing the unsteady flow over a transonic turbine blade, the so-called 11th International Standard Configuration. The final test case is a rotor/stator interaction, which not only checks the validity of the formulation for a three-dimensional example, but also highlights other issues, such as the need to linearize the wall functions. Detailed comparisons were carried out against measured steady and unsteady flow data for the last two cases and good overall agreement was obtained.
A Recursive Multibody Dynamics and Sensitivity Algorithm for Branched Kinematic Chains
Authors: Sohl Garett A. , Bobrow James E.
Published: July 2002

In this work an efficient dynamics algorithm is developed, which is applicable to a wide range of multibody systems, including underactuated systems, branched or tree-topology systems, robots, and walking machines. The dynamics algorithm is differentiated with respect to the input parameters in order to form sensitivity equations. The algorithm makes use of techniques and notation from the theory of Lie groups and Lie algebras, which is reviewed briefly. One of the strengths of our formulation is the ability to easily differentiate the dynamics algorithm with respect to parameters of interest. We demonstrate one important use of our dynamics and sensitivity algorithms by using them to solve difficult optimal control problems for underactuated systems. The algorithms in this paper have been implemented in a software package named Cstorm (Computer simulation tool for the optimization of robot manipulators), which runs from within Matlab and Simulink. It can be downloaded from the website http://www.eng.uci.edu/∼bobrow/
On the Nonlinear Response of Piping to Seismic Loads
Authors: Lazzeri Luciano
Published: July 2002

The response of a piping system to extreme seismic conditions may be controlled and limited by yielding of the structure. The effect of yielding has been found to be decisive for individual components, but for complex systems, the effect of yielding may be either important or negligible, depending on the specific geometry. Analytical and experimental tests are reviewed. The L test is devised to give an indication of the response characteristics of the system. It has been found that a parameter related to the frequency shift is capable of reasonably predicting the effect of yielding.
Experimental and Numerical Investigation of a Planar Combustor Sector at Realistic Operating Conditions
Authors: Carl M. , Behrendt T. , Fleing C. , Frodermann M. , Heinze J. , Hassa C. , Meier U. , Wolff-Gassmann D. , Hohmann S. , Zarzalis N.
Published: July 2002

Results of an ongoing collaboration between the engine manufacturer MTU and the German aerospace research center DLR on the NOx reduction potential of conventional combustors are reported. A program comprising optical sector combustor measurements at 1, 6, and 15 bars and CFD calculations is carried out. The aims are to gather information in the combustor at realistic operating conditions, to understand the differences between the sector flow field and data from tubular combustors, to verify the used CFD, and to discover the benefits and limitations of the applied optical diagnostics. Selected results of measurements and calculations of the isothermal flow and of measurements at 6 bars and 700 K at a rich-lean and overall lean AFR are reported. The used measurement techniques were LDA, PDA, Mie scattering on kerosene, quantitative light scattering, OH* chemiluminescence, and LIF on OH. The measurements were able to confirm the intended quick and homogeneous mixing of the three staggered rows of secondary air jets.
Prediction of the Hydrodynamic Parameters in the Coupled Heave and Pitch Motion Equations for Underwater Robotic Vehicles Using Measured Responses at Sea
Authors: Mahfouz Ayman B. , Haddara Mahmoud R. , Williams Christopher D.
Published: July 2002

A method for the identification of the damping, restoring, and coupling parameters in the equations describing the coupled heave and pitch motions for an underwater robotic vehicle (URV) sailing near sea surface in random waves using only its measured responses at sea is presented. The random decrement equations are derived for the URV performing coupled heave and pitch motions in random waves. The hydrodynamic parameters in these equations are identified using a new identification technique called RDLRNNT, which uses a combination of a multiple linear regression algorithm and a neural networks technique. The combination of the classical parametric identification techniques and the neural networks technique provides robust results and does not require a large amount of computer time. The developed identification technique would be particularly useful in identifying the parameters for both moderately and lightly damped motions under the action of unknown excitations effected by a realistic sea. Numerically generated data for the coupled heave and pitch motion of a URV are used initially to test the accuracy of the technique. Experimental data are also used to validate the identification technique. It is shown that the developed technique is reliable in the identification of the parameters in the equations describing the coupled heave and pitch motions for an URV.