bluuebunny/crossref_metadata_2025 huggingface dataset:
On a New Approach to Mechanism Topology Identification
Authors: Zhang W. J. , Li Q.
Published: February 2008

This paper argues that different levels of mechanism topology should be considered in order to make the activity or tool of the computer comparison of mechanism topology more useful to support a whole design process of mechanisms. In this connection, four abstraction levels are identified to relate the different types of mechanism topology with reference to mechanism design tasks, processes or objectives. A new approach is developed to compare mechanism topology for all these levels. One of the ideas of this approach is to extend the existing incident degree code approach by identifying more features of mechanism topology and to define them into an extended code. This is further enhanced by an algorithm to perform permutation (without a need of exhaustive enumeration) within a group of vertices that have the same features. Examples are given to show how the approach works. Compared with some existing methods for mechanism topology identification, this approach is shown to be more effective and efficient.
On the General Evaluation of Customer Requirements During Conceptual Design
Authors: Huang Y. M.
Published: February 2008

Customer requirements must be satisfied for a product to succeed in the market. Evaluation of customer requirements plays an important role during the conceptual design phase of various design methodologies. However, since customer requirements are continuously revised during design processes, much effort, time, and money are required. Twenty items are recommended to organize customer requirements and enhance efficiency. The relative importance of these recommended items, without regard to the product, is evaluated by using the pairs comparison method. The weighting factors for all recommended items are then calculated. The relative importance of the items shows that safety, quality, environment and performance are the most important. The relative importance and the weighting factors of the items from this study suggest that their use in the process during preliminary or lead time conceptual design of various design methods can assist with cost and time reductions.
A New Approach to Solving the Inverse Problem for Compound Gear Trains
Authors: Mathis R. , Re´mond Y.
Published: February 2008

The calculation of a gear train, if the concept is given (resolution of the direct problem) never poses fundamental problems, but is no help in its invention. The inverse problem (i.e., conception of a gear train if the kinematics are fixed) having never been approached in an analytical way, we propose, from the general formula of the ratios, one equation which allows us to resolve the inverse problem for every elementary or two-set nested gear train.
Quality Utility—A Compromise Programming Approach to Robust Design
Authors: Chen W. , Wiecek M. M. , Zhang J.
Published: February 2008

In robust design, associated with each quality characteristic, the design objective often involves multiple aspects such as “bringing the mean of performance on target” and “minimizing the variations.” Current ways of handling these multiple aspects using either the Taguchi’s signal-to-noise ratio or the weighted-sum method are not adequate. In this paper, we solve bi-objective robust design problems from a utility perspective by following upon the recent developments on relating utility function optimization to a Compromise Programming (CP) method. A robust design procedure is developed to allow a designer to express his/her preference structure of multiple aspects of robust design. The CP approach, i.e., the Tchebycheff method, is then used to determine the robust design solution which is guaranteed to belong to the set of efficient solutions (Pareto points). The quality utility at the candidate solution is represented by means of a quadratic function in a certain sense equivalent to the weighted Tchebycheff metric. The obtained utility function can be used to explore the set of efficient solutions in a neighborhood of the candidate solution. The iterative nature of our proposed procedure will assist decision making in quality engineering and the applications of robust design.
Optimization for Vibration Problems: Junction Layout of a Combined Structure Under Oscillation
Authors: Kawabe Y. , Yoshida S. , Saegusa S. , Kajiwara I. , Nagamatsu A.
Published: February 2008

We proposed a method for optimizing the layout of junctions between two structures so as to minimize the relative displacement between them when one of them is oscillated by noise disturbances. Layout optimization yields the minimum number of junctions, which means fewer joint components or fewer spot-welding operations leading to higher production efficiency.
Variable-Geometry Motion Control of an Aircraft Door
Authors: Beiner L.
Published: February 2008

The paper deals with the motion control of an aircraft door hinged at its lower edge. The door opens under the influence of weight, restrained by cross-mounted air springs and dampers. The goal is to mechanically control the motion so as to bring the door in a specified time from rest at a specified initial position to rest at a specified final position, while minimizing the peak force in the dampers. It is shown that such a velocity profile requires to engage the dampers at an optimized position and simultaneously start to modulate the spring moment so that it equals the weight moment at the final position. A variable-geometry solution is proposed consisting of a mechanical feedback in which the door rotation drives an elongation of the spring levers via bevel gears and screw leads. The associated double two point boundary value problem is solved by casting it into a constrained optimization form, yielding the required damper engagement position, the amount of spring lever extension and the damper lever length. The approach is illustrated by a design example.
Solving the Input/Output Problem for Planar Mechanisms
Authors: Nielsen J. , Roth B.
Published: February 2008

This paper presents a method for solving the input/output problem for all planar mechanisms composed of revolute and slider joints. The solution procedure is a modification of the Dixon resultant method, which was developed to solve sets of polynomial equations; in this paper the method is applied to sets of equations which are linear in the sines and cosines of unknown angles. A particular planar multicircuit mechanism is analyzed to illustrate the solution procedure, and implementation details are discussed.
An Energy Formulation for Parametric Size and Shape Optimization of Compliant Mechanisms
Authors: Hetrick J. A. , Kota S.
Published: February 2008

Compliant mechanisms are jointless mechanical devices that take advantage of elastic deformation to achieve a force or motion transformation. An important step toward automated design of compliant mechanisms has been the development of topology optimization techniques. The next logical step is to incorporate size and shape optimization to perform dimensional synthesis of the mechanism while simultaneously considering practical design specifications such as kinematic and stress constraints. An improved objective formulation based on maximizing the energy throughput of a linear static compliant mechanism is developed considering specific force and displacement operational requirements. Parametric finite element beam models are used to perform the size and shape optimization. This technique allows stress constraints to limit the maximum stress in the mechanism. In addition, constraints which restrict the kinematics of the mechanism are successfully applied to the optimization problem. Resulting optimized mechanisms exhibit efficient mechanical transmission and meet kinematic and stress requirements. Several examples are given to demonstrate the effectiveness of the optimization procedure.
Geometric Criteria for Gouge-Free Three-Axis Milling of Sculptured Surfaces
Authors: Pottmann H. , Wallner J. , Glaeser G. , Ravani B.
Published: February 2008

The paper presents a geometric investigation of collision-free 3-axis milling of surfaces. We consider surfaces with a global shape condition: they shall be interpretable as the graphs of bivariate functions or shall be star-shaped with respect to a point. If those surfaces satisfy a local millability criterion involving curvature information, it is proved that this implies globally gouge-free milling. The proofs are based on general offset surfaces. The results can be applied to tool-motion planning and the computation of optimal cutter shapes.
Curve and Surface Modeling with Uncertainties Using Dual Kriging
Authors: Limaiem A. , ElMaraghy H. A.
Published: February 2008

This paper presents a new technique based on dual Kriging interpolation for modeling curves and surfaces in the presence of uncertainties in data points. Uncertainties result from measurement errors; therefore, a direct application of this method is found in curve/surface modeling using discrete sets of digitized points. It focuses on a common problem in geometric modeling, the trade-off between curve/surface smoothness and the approximation errors. The Kriging model filters the noise in the data while controlling the deviation locally at each point. However, the classical least-squares technique minimizes the average deviation, hence allowing only a global control of the model. The presented method generates smoother and more accurate representation of the actual curve or surface. It has potential applications in reverse engineering, NC machining, computer-aided inspection and tolerance analysis and verification. Examples of a computer mouse and a portion of the hood of a scaled-down car are presented for illustration.
Computerized Design, Generation and Simulation of Meshing of a Spiroid Worm-Gear Drive with a Ground Double-Crowned Worm
Authors: De Donno M. , Litvin F. L.
Published: February 2008

The authors propose methods of computerized design and analysis of a spiroid worm-gear drive with ground worm based on the following considerations: (1) The theoretical thread surface of the hob is generated by a cone surface. (2) The worm surface is crowned in profile and longitudinal directions in comparison with the hob thread surface. (3) The double crowning of the worm enables to localize the bearing contact and obtain a predesigned parabolic function of transmission errors of an assigned level. Computerized design of the worm-gear drive enables to discover and avoid singularities of the generated worm face-gear surface and pointing of teeth. The meshing and contact of the double-crowned worm and the worm face-gear is simulated to determine the influence of misalignment on the shift of bearing contact and transmission errors. Computer program for numerical solution is developed and applied. A numerical example that illustrates the developed theory is provided.
Noise and Life of Helical Timing Belt Drives
Authors: Ueda H. , Kagotani M. , Koyama T. , Nishioka M.
Published: February 2008

A new helical timing belt has been developed to reduce noise. In the present study, three belts, each having a curvilinear tooth profile and helix angles of 3 deg, 5 deg and 10 deg, respectively, were designed. The noise and life of the helical timing belt under a constant transmission force are compared with those of a conventional timing belt, in which the helix angle is zero. The noise level of the new helical belts having helix angles of 5 deg or 10 deg was found to be around 5 dB(A) lower than the conventional belt. The belt life was found to be almost identical for each type when the installation tension was set while the slack side tension for the transmission force was lowest. The results of the present study showed that helical belts should be selected for applications in which noise is a crucial factor.
Correlation Procedures for Fatigue Life Determination
Authors: Kouta R. , Play D.
Published: February 2008

Fatigue life determination of vehicle parts requires fine definition of load spectra applied. Significant load spectra must be defined from experimental data. Then, using Gram-Charlier-Edgeworth mathematical developments, global shapes of loading distribution curves are obtained. In addition to considering the physical aspect of material fatigue behaviour, a local definition of extreme loading is introduced. Frequency analyses are linked to the distribution of amplitudes. 200 practical recordings are analysed. Equivalent load spectra are compared to S-N curves and correlations between real loading of vehicle parts in service and laboratory test loading are obtained.
Variation Risk Management Using Modeling and Simulation
Authors: Thornton A. C.
Published: February 2008

Design and manufacturing firms are under significant pressure to simultaneously increase product complexity, reduce design cycles, decrease cost, and improve quality. A key enabler to reduce cost without sacrificing quality is the control of variation during both design and manufacturing. The best time to reduce the impact of variation is in the early stages of design. This paper presents a tool set used to identify, early in the design process, where variation will have significant impact on the final cost and quality of a product. It presents the design team with a graphical view of variation risk, enabling them to quickly identify high-risk areas. The uncertainty about process capability and risk is also quantified and presented to the user.
Mechanical Alignment Using Duplicate Circular Wedges
Authors: Ca´rdenas-Garci´a J. F. , Suryanarayan K. P. , Ingalls W. E.
Published: February 2008

There is a need for the repeatable, accurate, precise and versatile alignment of mechanical components. A flexible and inexpensive approach to this problem is the use of a duplicate pair of wedged discs. This paper uses kinematic transformation matrices to examine in detail the design of such a wedge pair. The accuracy, precision and versatility of the circular wedges are shown to be functions of wedge angle, the number of positions or increments along the circumference of the circular wedge, and changes in the offset angle, which defines the asymmetry of the discs.
Prediction of the First Modal Frequency of Compliant Mechanisms Using the Pseudo-Rigid-Body Model
Authors: Lyon S. M. , Erickson P. A. , Evans M. S. , Howell L. L.
Published: February 2008

The pseudo-rigid-body modeling technique is used to simplify the nonlinear analysis of compliant mechanisms. This paper presents the first work that investigates the possibility of using the pseudo-rigid-body model to predict the first modal response of compliant mechanisms. Four different configurations of the parallel-guiding mechanism are modeled and tested, as well as two configurations of compliant straight-line mechanisms. The model predictions of the first natural frequencies were compared with experimental results for all six mechanism configurations. The model predictions are within 9 percent of the experimental results for all cases.
A New Method of Torque Compensation for High Speed Indexing Cam Mechanism
Authors: Guilan Teng , Haibo Fu , Weiyi Zhou
Published: February 2008

Severe vibration and poor positioning accuracy may occur in an indexing cam mechanism operating at a high speed. Torque fluctuation of the input shaft and the resulting fluctuation of kinetic energy of the mechanism may be the major cause of the vibration. In this paper a method is proposed to minimize the fluctuation by using a so-called “speed-varying flywheel” that produces an opposite kinetic energy fluctuation that can counteract the effect of the energy fluctuation. The flywheel is installed on the output shaft of an additional cam-linkage mechanism. The parameter of the cam-linkage mechanism is optimized. An example is given to demonstrate the effectiveness of this method.
A Triangular Nomogram for Spherical Symmetric Coupler Curves and its Application to Mechanism Design
Authors: Lu D.-M.
Published: February 2008

This paper presents a triangular nomogram for spherical symmetric coupler curves generated by a spherical crank-rocker with special dimensions. The paper also illustrates the application of this nomogram for spherical mechanism design. The expression of symmetric coupler curves traced by the spherical crank-rocker is derived. A computer program is developed to calculate the coordinates of the coupler curve points for the prescribed dimensions of the mechanism. According to the classified properties of coupler curves obtained, a triangular nomogram for spherical symmetric coupler curves can then be constructed by using three design parameters, i.e., length of crank, length of fixed link, and coupler angle. The triangular nomogram provides an alternative selection for dimensional synthesis of spherical path generators. The synthesized mechanisms can also be used to provide initial estimates for optimal synthesis of spherical path generators. A design example is presented.
On the Role and Use of Mathematical Models in Engineering Design
Authors: Hazelrigg G. A.
Published: February 2008

Mathematical models encompassing virtually all aspects of engineered products are in widespread use. Indeed, entire industries exist in support of some models: finite element models, computational fluid dynamics models, electric power grid load-flow models, process models, simulation models, and so on. Nonetheless, the purpose, construction, and use of models is not adequately understood. One major issue is that no model perfectly represents reality. Therefore models always diverge from reality somewhere, and they are always inaccurate by some amount. Estimation of model error and the use of model-generated results in support of engineering design decision making are key to the successful use of models.
An Axiomatic Framework for Engineering Design
Authors: Hazelrigg G. A.
Published: February 2008

In order to ensure that engineering design is conducted as a rational process producing the best possible results given the context of the activity, a mathematics of design is needed. It is possible to develop such a mathematics based on the recognition that engineering design is a decision-making intensive process and adapting theories from other fields, such as economics and decision theory. We present here eight axioms and derive from them two theorems, which underlie the mathematics of design. Then we present a third theorem that, in the context of the axioms presented, imposes severe conditions upon design methodologies. Together, the axioms and theorems provide a framework that enables the development of a normative theory of design. This theory is applied to a simple example. The results, while intuitively obvious, are substantially different from the results of a “conventional” engineering design analysis.
Finding All Solutions to Unconstrained Nonlinear Optimization for Approximate Synthesis of Planar Linkages Using Continuation Method
Authors: Liu A.-X. , Yang T.-L.
Published: February 2008

Generally, approximate kinematic synthesis of planar linkage is studied using optimization method. But this method has two defects: i) the suitable initial guesses are hard to determine and ii) the global optimum solution is difficult to find. In this paper, a new method which can find all solutions to approximate kinematic synthesis of planar linkage is proposed. Firstly, we reduce the approximate synthesis problem to finding all solutions to polynomial equations. Polynomial continuation method is then used to find all solutions. Finally, all possible linkages can be obtained. Approximate syntheses of planar four-bar linkage for function generation, rigid-body guidance and path generation are studied in detail and three examples are given to illustrate the advantages of the proposed method.
Mobility in Metamorphic Mechanisms of Foldable/Erectable Kinds
Authors: Dai J. S. , Rees Jones J.
Published: February 2008

This paper looks at a class of mechanisms that change structure when erected or folded. The class includes a variety of artefacts and decorative gifts and boxes comprised of flat card creased to enable the folding or unfolding of a structure. Such a structure admits kinematic study in keeping with theory of mechanisms when the creases are treated as hinges joining card and paper panels treated as links. New horizons have been brought up in the use and mechanised manufacture of mechanisms of this kind. Here typical types are described in terms of their fundamental parts and their equivalent mechanisms. Screw system theory is brought into the analysis of mechanisms of these kinds, particularly those containing multiple loops. Different geometry and system combinations are used for the study of mobility and kinematics making use of the result from the equivalent screw systems.
Modeling the Plane Joint
Authors: Fischer I. S.
Published: February 2008

The plane joint, often referred to as the “E” joint is modeled using dual-number coordinate-transformation matrices. The joint consists of two flat surfaces held in contact so that three degrees of freedom are allowed, two translations and a rotation. The swash-plate mechanism is used as an example of a mechanism featuring the plane joint.
Solving the Kinematics of Planar Mechanisms
Authors: Wampler C. W.
Published: February 2008

This paper presents a general method for the analysis of planar mechanisms consisting of rigid links connected by rotational and/or translational joints. After describing the links as vectors in the complex plane, a simple recipe is outlined for formulating a set of polynomial equations which determine the locations of the links when the mechanism is assembled. It is then shown how to reduce this system of equations to a generalized eigenvalue problem, or in some cases, a single resultant polynomial. Both input/output problems and tracing-curve equations are treated.
A Method to Determine the Static Load Distribution in a Chain Drive
Authors: Troedsson I. , Vedmar L.
Published: February 2008

A model of how to calculate the load distribution for a chain drive is presented. In the model the complete standard geometry is used without any assumptions. The rollers which are in contact with the sprockets can move freely along the tooth flanks and their positions are given by force equilibrium. Since the positions of the rollers and thereby also the load distribution are dependent on the two connecting spans, these necessary tight and slack spans have been included in the model. The elastic deformation in the chain is included as well as the gravitational force.
Sensitivity Analysis and Surface-Deviation Minimization of ZK-Type Dual-Lead Worm Gear Drives
Authors: Bair Biing-Wen , Tsay Chung-Biau
Published: February 2008

This work uses the mathematical model of ZK-type dual-lead worm gear drive proposed in our recent work (1998). Based on the proposed mathematical model, coordinates and unit normals of the worm gear surface grid points can be determined and a data file subsequently formed. The data file is considered as the theoretical tooth surface data and then input into the computer of a three-dimensional coordinate measurement machine (3-D CMM) to numerically calculate the surface deviations of a real-cut worm gear. In addition, a computerized tooth surface measurement model compatible with the 3-D CMM is developed. Sensitivity analysis is also performed on machine-tool settings and tool-profile errors to the generated gear tooth surface variations. Minimization on gear tooth surface variations can be determined by applying the proposed measurement and calculation methods. In addition, optimum machine tool settings and tool-profile modifications are obtained by applying the developed computer simulation softwares. Moreover, the singular value decomposition (SVD) and sequential quadratic programming (SQP) methods are compared to establish the optimum machine-tool settings and resolve the minimum surface deviation problems.
A Well-Behaved Revolute Flexure Joint for Compliant Mechanism Design
Authors: Goldfarb M. , Speich J. E.
Published: February 2008

This paper describes the design of a unique revolute flexure joint, called a split-tube flexure, that enables (lumped compliance) compliant mechanism design with a considerably larger range-of-motion than a conventional thin beam flexure, and additionally provides significantly better multi-axis revolute joint characteristics. Conventional flexure joints utilize bending as the primary mechanism of deformation. In contrast, the split-tube flexure joint incorporates torsion as the primary mode of deformation, and contrasts the torsional properties of a thin-walled open-section member with the bending properties of that member to obtain desirable joint behavior. The development of this joint enables the development of compliant mechanisms that are quite compliant along kinematic axes, extremely stiff along structural axes, and are capable of kinematically well-behaved large motions.
Analytical Dynamics of Unrooted Multibody Systems with Symmetries
Authors: Pfister F. M. J. , Agrawal S. K.
Published: February 2008

This paper is concerned with the theory of differential equations of motion for a class of unrooted (i.e., without kinematical constraints to a Galilean frame) mechanisms called orthotropic multibody-systems and the application of this theory to the solution of three mechanisms: the Hoberman-sphere, the Wohlhart Octoid and the Fulleroid. Dedicated to O. Univ.-Prof. Dipl.-Ing. Dr. Techn. Karl Wohlhart on his 70th birthday
A Mechanism for Dexterous End-Effector Placement During Minimally Invasive Surgery
Authors: Minor M. , Mukherjee R.
Published: February 2008

Presented here is the design of a mechanism for dexterous placement of an end-effector during minimally invasive surgery. A literature review is presented to show that capabilities of the mechanism are unavailable in current instrumentation. Apart from actuation of the end-effector, our mechanism provides 180° bi-directional articulation relative to the support tube and rotation of the end-effector about the articulated axis. These are accomplished via a compact multi-link structure comprised of gears and gear-links that provide excellent stiffness, load capacity and durability. The structure is optimized to have a large and dexterous workspace, low backlash, and small force magnification. Maximization of load capacity and durability of the complete mechanism is achieved by the use of high strength stainless steels, gears with 25° pressure angles to accommodate larger sized teeth, optimized gear pack thicknesses to distribute stresses evenly, and a compact forceps design to reduce tip length. Resistance to pitting is improved by alternating materials and/or hardness of materials between mating parts. The instrument is capable of supporting 4.5 N needle tip loads with infinite life expectancy and loads up to 8.7 N intermittently.
Design and Implementation of a Lightweight, Large Workspace, Non-Anthropomorphic Dexterous Hand
Authors: van Varseveld R. B. , Bone G. M.
Published: February 2008

The design and implementation of a novel dexterous robotic hand is described. To Provide flexibility of application the design features three fingers, each position or force controllable in X-Y-Z, and a large workspace (400 mm dia. × 75 mm deep). These requirements plus the need for adequate strength (i.e. force and stiffness) are in conflict with the need to keep the mass within the payload capacity of common robots. These contrary objectives are met by designing a novel hybrid parallel-serial finger mechanism, a lightweight frame and pneumatic servos for finger actuation. The implemented design is verified experimentally, and may be scaled for other applications.
Computer Aided Geometric Design of Two-Parameter Freeform Motions
Authors: Ge Q. J. , Sirchia M.
Published: February 2008

This paper brings together the notion of analytically defined two-parameter motion in Theoretical Kinematics and the notion of freeform surfaces in Computer Aided Geometric Design (CAGD) to develop methods for computer aided design of two-parameter freeform motions. In particular, a rational Be´zier representation for two-parameter freeform motions is developed. It has been shown that the trajectory surface of such a motion is a tensor-product rational Be´zier surface and that such a kinematically generated surface has a geometric as well as a kinematic control structure. The results have not only theoretical interest in CAGD and kinematics but also applications in CAD/CAM and Robotics.
The Synthesis of Planar Parallel Manipulators with a Genetic Algorithm
Authors: Boudreau R. , Gosselin C. M.
Published: February 2008

This paper presents a genetic algorithm approach for the synthesis of planar three-degree-of-freedom parallel manipulators. A genetic algorithm is an optimization method inspired by natural evolution. As in nature, the fittest members of a population are given better chances of reproducing and transmitting part of their genetic heritage to the next generation. This leads to stronger and stronger generations which evolve towards the solution of the problem. For the applications studied here, the individuals in the population consist of the architectural parameters of the manipulators. The algorithm optimizes these parameters to obtain a workspace as close as possible to a prescribed working area. For each individual of the population, the geometric description of the workspace can be obtained. The algorithm then determines the intersection between the prescribed workspace and the actual workspace, and minimizes the area of the regions that do not intersect. The method is applied to two planar three-degree-of-freedom parallel manipulators, one with prismatic joints and one with revolute joints.
The Use of Trust Region Algorithms to Exploit Discrepancies in Function Computation Time Within Optimization Models
Authors: Nelson S. A. , Papalambros P. Y.
Published: February 2008

Computational models in engineering often use a range of analysis functions within the same optimization problem, from finite element models to analytical expressions. The computational expense of these models often differs by orders of magnitude, and practical optimization algorithms should address this discrepancy. In this article, in an effort to reduce the number of expensive analyses, a technique is discussed for modifying trust region algorithms to utilize the inexpensive functions directly when calculating iterates. The technique is implemented with a trust region algorithm of Yuan and applied to valve event optimization of an internal combustion engine.
Detecting Gear Tooth Breakage Using Acoustic Emission: a Feasibility and Sensor Placement Study
Authors: Singh A. , Houser D. R. , Vijayakar S.
Published: February 2008

Vibration and debris monitoring methods are being increasingly used to detect gear tooth breakage. In this paper an alternate method of detecting gear tooth cracking is investigated. It is based on the phenomenon of acoustic emission (AE). The detectability of growing cracks using AE is established. Before this method can be used to detect crack growth in real systems, the transmissibility of these waves has to be studied. These waves have to propagate across a number of mechanical interfaces as they travel from the source to the sensor. The loss in strength of these waves at various interfaces commonly encountered in mechanical systems is studied in this paper.
Analytical Method for the Prediction of Reliability and Maintainability Based Life-Cycle Labor Costs
Authors: Fitzpatrick M. , Paasch R.
Published: February 2008

An analytical method for predicting life-cycle maintainability labor costs is developed. The purpose of the analytical method is to allow the evaluation of products, based on life-cycle labor costs, early in the design process. The Boeing 737-300/400/500 Bleed Air Control System is used as a test model, and the results of the analysis are compared with historical data for this system. Four prospective design changes to the Bleed Air Control system are analyzed to demonstrate the ability of the analytical method to evaluate and compare differing designs or design changes.
Steady-State Reliability Analysis of Repairable Systems Subject to System Modifications
Authors: Jiang Z. H. , Shu L. H. , Benhabib B.
Published: February 2008

Environmentally conscious design is approached through analysis and further development of a reliability model that facilitates design for reuse of products. Many reliability models may not he suitable for describing systems that undergo repairs performed during remanufacture and maintenance since they do not allow for the possibility of system reconfiguration. In this paper, expressions of reliability indices of a model that allows system modifications during repair are derived. These reliability indices that describe a population of repairable systems are theoretically proven to reach steady state, supporting the simulation results of the model. This model can be used to estimate life-cycle replacement requirements for systems that are remanufactured, thereby facilitating decisions during system design and use. An example illustrates the application of the model to a relevant industry.
The Effect of the Longitudinal to Transverse Moduli Ratio on the Natural Frequencies of Symmetric Cross-Ply Laminated Cylindrical Helical Springs
Authors: Yildirim Vebil , Sancaktar Erol , Kiral Erhan
Published: February 2008

The first six free vibration frequencies of symmetric cross-ply laminated cylindrical helical springs with fixed-fixed ends are theoretically computed based on the transfer matrix method. The rotary inertia, shear and axial deformation effects are taken into account in the solution. Considering different values for the helix pitch angles and the number of active turns, a parametric study is performed to analyze the effects of the ratio of the longitudinal Young’s modulus to the transverse Young’s modulus on the natural frequencies of such springs with square section. The results are given in dimensionless graphical forms.
Design of a Roller Coaster System Through Graphical Simulation
Authors: Tenaglia C. A. , Orin D. E.
Published: February 2008

This paper presents a roller coaster system model for the purpose of developing a graphical simulation of a roller coaster system. A foundational set of track elements with constant curvature and constant bank angle is developed. For these elements, a general parameterization scheme is proposed and equations are developed to generate the spatial location of the track and train. Kinematic equations of train motion are also developed, and results are presented for a test track which features many of the elements presented in this paper. Speed and acceleration data which are generated provide important information concerning the ride performance of the roller coaster system.
Design of a Tele-Operated Robot for the Maintenance of Boiler Hoppers in Electric Power Plants
Authors: Saidi K. S. , Seo J. , Sreenivasan S. V. , Haas C. T. , Traver A. E.
Published: February 2008

The design of a novel tele-robotic device for clearing undesirable residues from boiler hoppers in electric power plants is presented. A key aspect of the problem that drives the design process is the fact that the environment inside the hopper is harsh and unstructured. This has led to a robot design which has all its sophisticated mechanical and control hardware located outside the hopper access port. Results from experimental testing of a prototype are included.
A Two-Fluid Model of Mixing in a Two-Dimensional Enclosure
Authors: Ilegbusi O. J. , Mat M. D.
Published: February 2008

Mixing of fluids in a cavity under isothermal and nonisothermal conditions is studied with a two-fluid model. This model involves the solution of separate transport equations for zone-averaged variables of each fluid with allowance for interface transport of momentum and energy. The effects of thermal and potential energy driven convection as well as Prandtl number are investigated. The material interface is represented by the contour of the volume fraction separating the fluids. The effect of the buoyancy force due to the initial potential energy of the fluids is found to predominate over thermal buoyancy for comparable Grashof numbers.
Flow Boiling in Horizontal Tubes: Part 1—Development of a Diabatic Two-Phase Flow Pattern Map
Authors: Kattan N. , Thome J. R. , Favrat D.
Published: February 2008

An improved two-phase flow pattern map is proposed for evaporation in horizontal tubes. The new map was developed based on flow pattern data for five different refrigerants covering a wide range of mass velocities and vapor qualities. The new map is valid for both adiabatic and diabatic (evaporating) flows and accurately identifies about 96 percent of the 702 data points. In addition, the new flow pattern map includes the prediction of the onset of dryout at the top of the tube during evaporation inside horizontal tubes as a function of heat flux and flow parameters.
Flow Boiling in Horizontal Tubes: Part 3—Development of a New Heat Transfer Model Based on Flow Pattern
Authors: Kattan N. , Thome J. R. , Favrat D.
Published: February 2008

A new heat transfer model for intube flow boiling in horizontal plain tubes is proposed that incorporates the effects of local two-phase flow patterns, flow stratification, and partial dryout in annular flow. Significantly, the local peak in the heat transfer coefficient versus vapor quality can now be determined from the prediction of the location of onset of partial dryout in annular flow. The new method accurately predicts a large, new database of flow boiling data, and is particularly better than existing methods at high vapor qualities (x > 85 percent) and for stratified types of flows.
The Origin of the Dynamic Growth of Vapor Bubbles Related to Vapor Explosions
Authors: Lee H. S. , Merte H.
Published: February 2008

An explosive type of vapor bubble growth was observed during pool boiling experiments in microgravity using R-113. Photographs reveal that the liquid-vapor interface of the explosive bubbles are wrinkled and corrugated, leading to the conclusion that some type of instability mechanism is acting. The classical hydrodynamic instability theories of Landau and Rayleigh-Taylor do not consider the effect of heat transfer, at the interface, which is believed to be responsible for the observed instability of the evaporating surface. This was confirmed by the mechanisms proposed by Prosperetti and Plesset, combined with a model of the early growth of spherical vapor bubbles.
Numerical Simulation of Film Boiling Near Critical Pressures With a Level Set Method
Authors: Son G. , Dhir V. K.
Published: February 2008

Attempts have recently been made to numerically simulate film boiling on a horizontal surface. It has been observed from experiments and numerical simulations that during film boiling the bubbles are released alternatively at the nodes and antinodes of a Taylor wave. Near the critical state, however, hydrodynamic transition in bubble release pattern has been reported in the literature. The purpose of this work is to understand the mechanism of the transition in bubble release pattern through complete numerical simulation of the evolution of the vapor-liquid interface. The interface is captured by a level set method which is modified to include the liquid-vapor phase change effect. It is found from the numerical simulation that at low wall superheats the interface moves upwards, bubbles break off, and the interface drops down alternatively at the nodes and antinodes. However, with an increase in wall superheat, stable vapor jets are formed on both the nodes and antinodes and bubbles are released from the top of the vapor columns. The numerical results are compared with the experimental data, and visual observations reported in the literature are found to be in good agreement with the data.
The Minimum Meniscus Radius and Capillary Heat Transport Limit in Micro Heat Pipes
Authors: Ma H. B. , Peterson G. P.
Published: February 2008

Based on the momentum conservation and Laplace-Young equations, an analytical expression for the minimum meniscus radius was derived and an expression for the maximum capillary heat transport limit in micro/small heat pipes was obtained. These expressions incorporated the shear stresses at the liquid/solid and liquid/vapor interfaces, contact angle effects, vapor pressure drop, tilt angle, groove dimensions, and channel angle effects. In order to verify the expressions derived herein, comparisons with experimental data from triangular grooves and micro heat pipes were made; they demonstrated that these equations can be used to predict the maximum capillary heat transport in the micro/small triangular grooves or micro heat pipes with a higher degree of accuracy, and they can explain the behavior better than previously developed models.
Double Diffusive Natural Convection in a Composite Fluid-Porous Layer
Authors: Gobin D. , Goyeau B. , Songbe J.-P.
Published: February 2008

This study deals with natural convection driven by combined thermal and solutal buoyancy forces in a binary fluid. The consequence of thermosolutal convection on heat and mass transfer is examined in a confined enclosure partially filled with a porous medium. The mathematical description of the problem makes use of a one-domain formulation of the conservation equations. The presented numerical results quantitatively show the significant influence of the presence of a relatively thin porous layer on the flow structure and on heat and species transfer in the enclosure. The paper is dedicated to the analysis of the influence of the thickness and permeability of the porous layer in a range of governing parameters. For a low permeability porous layer, the numerical results are compared to an analysis based on simple scaling laws, which provide a good interpretation in terms of the wall transfer decrease with the porous layer thickness. The effect of permeability is investigated and it is shown that flow penetration in the porous layer induces a specific behavior of the flow structure and average heat transfer in the enclosure.
Far-Infrared Radiation Modulators Using High-Tc Superconductors
Authors: Zhang Z. M.
Published: February 2008

The potential of using high-Tc superconductors as intensity modulators for far-infrared radiation is investigated in this work. Reflectance and transmittance for several design structures are computed using the published optical constants of the superconductor YBa2Cu3O7 and substrate materials. Notable differences in the reflectance and transmittance between the superconducting state and the normal state are illustrated. The best results are obtained based on the reflectance of thin films (10 nm–50 nm thick) on thin substrates (less than 100 μm thick) and for radiation incident on the substrate. This study demonstrates that high-Tc superconductive thin films can be used to build far-infrared radiation modulators. Future experimental study is recommended in order to materialize this promising thermo-optical device.
Yield Limits of Plates at Extremely High Heat Flux
Authors: Lienhard J. H. , Napolitano D. S.
Published: February 2008

For heat fluxes ranging above 10 MW/m2 or so, solid surfaces usually experience large thermal stresses and degradation of mechanical properties. The resulting mechanical failure of such surfaces is a primary limitation to the design of thermal systems at extremely high heat flux. This investigation considers the elastic stresses in circular plates subjected to extremely high heat fluxes. A gaussian distributed heat load is applied to one surface of the plate and the heat flux at which yielding occurs is identified. Several candidate materials are examined, accounting for the temperature dependence of yield strength and other properties. The mechanical boundary conditions on the plate are varied. Figures of merit are given for the high flux performance of a number of materials.
An Investigation of Key Factors Affecting Solder Microdroplet Deposition
Authors: Xiong B. , Megaridis C. M. , Poulikakos D. , Hoang H.
Published: February 2008

This paper combines a theoretical model with experimental measurements to elucidate the role of key operating parameters affecting solder microdroplet deposition in the electronics manufacturing industry. The experimental investigation is used to evaluate the final deposit (bump) shapes and trends predicted by the model. The effects of substrate temperature, material composition, layer thickness, and thermal contact resistance (including surface oxidation) are delineated. Solder-deposit shape comparisons between experiments and modeling suggest that the value of thermal contact resistance may change with process parameters, and is probably dependent on the solder phase. It is established that inferences regarding the overall shape or solidification times of solder bumps using limited modeling trends should be made only after careful consideration of the substrate composition, accurate representation of the thermal contact resistance, and adequate resolution of the fluid dynamical oscillatory motion and its effects on solidification rates. It is shown that modeling tools can be used in conjunction with experiments to promote our fundamental understanding of the transport processes in the complex solder jetting technology.
Stokes’ First and Second Problems for Rivlin-Ericksen Fluids With Nonclassical Heat Conduction
Authors: Puri P. , Kythe P. K.
Published: February 2008

The nonclassical heat conduction equation based on the Maxwell-Cattaneo-Fox (MCF) model is used to study the Stokes’ first and second problems for the Rivlin-Ericksen fluids. The discontinuities in velocity gradients in fluid flows induced by impulsive or sudden heating of a plate and the influence of the thermal relaxation time and elastic parameter of the fluid on the velocity field are investigated. The structure of the waves in the temperature and velocity fields is presented. An anomalous behavior of the medium is characterized by infinite or negative values of the group velocity for the wave packets as the frequency attains or exceeds a critical value. The displacement thickness and the rate of heat transfer at the plate are determined.
Numerical Study of Shear-Induced Heating in High-Speed Nozzle Flow of Liquid Monopropellant
Authors: Shi X. , Knio O. M. , Katz J.
Published: February 2008

A numerical study is performed which focuses on peak temperatures experienced by a liquid monopropellant during high-speed injection in a small-diameter nozzle. Attention is focused on short-duration injection during which the nozzle wall boundary layer is predominantly laminar. An unsteady ID analysis of the temperature distribution associated with sudden fluid acceleration over a flat insulated boundary is first conducted. Expressions are provided which relate the normalized peak wall temperature to the prevailing Eckert and Prandtl numbers. Results reveal a quadratic dependence of the normalized wall temperature on impulse velocity, and a nonlinear variation with Prandtl number. Next, simulation of high-speed flow in an axisymmetric nozzle is performed. The numerical schemes are based on finite-difference discretization of a vorticity-based formulation of the mass, momentum, and energy conservation equations. Implementation of the numerical schemes to flow of LP 1846 in a 4 mm diameter nozzle indicates that preignition is likely to occur for velocities higher than 200 m/s. The effects of wall heat transfer and temperature-dependent properties are also discussed.
Low Dean Number Convective Heat Transfer in Helical Ducts of Rectangular Cross Section
Authors: Thomson D. L. , Bayazitoglu Y. , Meade A. J.
Published: February 2008

Flow in a torroidal duct is characterized by increased convective heat transfer and friction compared to a straight duct of the same cross section. In this paper the importance of the nonplanarity (torsion) of a helical duct with rectangular cross section is investigated. A previously determined low Dean number velocity solution is used in the decoupled energy equation for the hydrodynamically fully developed, thermally developing case. Torsion, known to increase the friction factor, is found to cause a decrease in the fully developed Nusselt number compared to pure torroidal flow. Therefore, it is recommended that torsion be minimized to enhance heat transfer.