bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of Rotating Losses in Heteropolar Radial Magnetic Bearings
Authors: Meeker David C. , Maslen Eric H.
Published: February 2008

Previously, thin plate assumptions have been used to obtain a one-dimensional eddy current model for predicting the stationary, transformer-type losses in magnetic bearings built out of laminated material. Using similar assumptions, as in the 1-D eddy current model, rotating losses can be predicted for a laminated heteropolar radial magnetic bearing. The thin plate model of rotating losses yields a hybrid analytical-boundary element model that is computationally inexpensive to implement. Predictions from this model compare favorably to losses experimentally measured in rotor run-down tests.
Tribochemical Applications of High-Intensity Ultrasound: Sonochemical Production of Intermetallic Coatings in Heterogeneous Media
Authors: Casadonte D. J. , Sweet J. D.
Published: February 2008

An energy-dispersive X-ray (EDX) study of binary mixtures of mixed composition metal powders exposed to high-intensity ultrasound in decane indicates that metal particles are fused by the action of ultrasound and develop intermetallic coatings. The principal mechanism behind both processes is interparticle collision caused by the rapid movement of particles propelled by shockwaves generated at cavitation sites. By examination of systems with differing metallurgical compatibilities (Ni/Co, Cu/Cr, and Cu/Mo), it has been determined that the intermetallic coatings are generated by both adhesive wear and direct impact. The mechanisms of ultrasound-induced coatings are discussed.
Pipeline Leak Detection System for Oil and Gas Flowlines
Authors: Rajtar J. M. , Muthiah R.
Published: February 2008

Petroleum fluids in production systems are frequently transported by surface steel pipelines of low diameter working at low pressures and under a two-phase flow regime. These pipelines operate without permanent, continuous supervision for leaks. The leaked volume is usually high before the leak is noticed and stopped. High leak volumes pollute the environment and increase production costs. This paper describes the expected performance of the acoustic emission leak detection system for low pressure flowlines in oil and gas gathering installations. The developed system detects acoustic emission signals generated by leaks. Specific features of the system are discussed. The system was tested in a closed field scale two-phase flowloop. Example results of tests are reported. The paper is completed with conclusions and discussion of potential applications of the system.
Milling Cutter Wear Monitoring Using Spindle Shaft Vibration
Authors: Kim Seoggwan , Klamecki B. E.
Published: February 2008

With the intent of continuously monitoring cutting tool condition in intermittent machining operations in a benign manner, a noncontacting measurement system was assembled to measure spindle shaft torsional vibration. Spindle vibration was measured using an optical system and analysis of it in the frequency domain resulted in a measure of spectral power which corresponded to amount of cutter wear.
Vibration Control of Redundant Flexible-Joint Manipulators
Authors: Xi Fengfeng
Published: February 2008

Presented in this paper is a method for controlling vibrations of a redundant flexible-joint manipulator. The main idea behind this method is to utilize joint redundancy to minimize the change in the manipulator inertia, so that a simple gain-fixed control law can be used to control joint vibrations. For this purpose, two optimal joint trajectory generators are proposed; one is based on the extended Jacobian method and the other is based on an optimization technique. Numerical simulations are provided to demonstrate the effectiveness of the proposed control method.
Assessment of Plasma Enhanced Machining for Improved Machinability of Inconel 718
Authors: Novak J. W. , Shin Y. C. , Incropera F. P.
Published: February 2008

An experimental study has been performed to assess the feasibility of using a hybrid machining system to improve the machinability of Inconel 718. An assembled plasma enhanced machining (PEM) system is described, and experimental results obtained from both conventional and plasma enhanced machining of Inconel 718 are compared. Several advantages of PEM over conventional machining are demonstrated, including improvement of surface roughness, lower cutting forces and extended tool life.
Macro-level Optimization of Cutting Tool Geometry
Authors: Kaldor S. , Venuvinod P. K.
Published: February 2008

A new approach to the macro-level optimization of tool geometro in machining is proposed. Methods for characterizing the tool material, the work material and the optimum tool geometry are proposed and a model describing the interactions between them is developed. Empirical evidence drawn from published literature is presented in support of the new approach. In this approach, the optimum tool geometry is characterized by a geometric entity number which can be explicity calculated in terms of cutting tool angles. Practical benefits derivable from the approach are discussed along with the issues requiring further research.
A Connection Design Methodology for Automated Assembly and the Framing of Buildings
Authors: Perreira N. Duke , Nguyen Viet X.
Published: February 2008

The erection of structural building frames, like that of other mechanical assemblies, involves the use of handling systems and connection technologies. A new “chamfered” connection, now known as the ATLSS Connection, has been developed to both facilitate the framing assembly task and provide adequate connection strength through the life of the building. This paper outlines the methodology and technical details used in developing the connection geometry from an insertion mechanics point of view. Although framing of buildings is explicitly addressed here, the approach is just as viable for other mechanical assemblies. Parameters associated with the connection geometry are defined and used in simulations of possible insertion trajectories. The insertion forces and moments are used to determine the fine details of the trajectory. It was found that the geometric parameters greatly affect the maximum allowable amount of initial misalignment between the beam and the two mating columns as well as the stiffness of the connection and its ability to be easily inserted.
Development of a Prototype Laser Processing System for Shaping Advanced Ceramic Materials
Authors: Todd J. A. , Copley S. M.
Published: February 2008

Laser machining has been shown to offer an increasingly attractive alternative to net shape forming processes and/or diamond grinding for producing components of advanced ceramic and ceramic composite materials. The control of machine parameters (incident power, feed, beam polarization, position of the focal plane and orientation of the beam relative to the surface) necessary for the optimization of process parameters (material removal rate and arithmetic average surface roughness) and of mechanical properties will be discussed. It will then be shown how these parameters can be incorporated into the operation of a prototype, fully automated, five axis, closed loop controlled laser shaping system (comprising a beam conditioner, high power laser scanner and noncontacting position sensor) to accurately and cost effectively produce complex shapes in advanced ceramic materials.
Structural Component Development of Three-Layer Cylinders for Superconducting Generators, Part 1: Selection of Layer-Bonding Method and Development of Long Large-Gauge Three-Layer Cylindrical Structure
Authors: Suzuki Nobuhisa , Murakami Toshiaki , Shibuya Junichi , Ohshima Shizuo
Published: February 2008

The warm damper, a component located outermost in a rotor of the superconducting generator, is intended to shut off magnetic fields of the armature and bear large bending stresses due to electromagnetic force. So it is required to have both high conductivity and sufficient strength against bending stresses. Meeting these requirements is a promising three-layer cylindrical structure composed of a highly conductive cylinder sandwiched between cylindrical high-strength nonmagnetic stiffeners, so that only middle cylinder bear high conductivity and outer and inner ones bear most of the bending stresses. Candidate materials for the middle is Cu-Cr, and for the outer and inner is A286, a iron-base superalloy. To realize this three-layer cylindrical structure, the first step is to select a method of bonding the three layers and the second step is to research and develop large structures. Using test rings (300 mm in O.D. × 500 mm in axial length) made to a reduced scale, layer bonding tests were carried out in the present study to investigate three bonding methods: explosion bonding, brazing, and diffusion bonding. The two methods other than brazing were selected because they involved few defects and provided high bonding strength. When manufacturing long large-gauge warm dampers, deformations due to bonding must be uniform and bonding strength must be thermally stable so as to join them axially by three-layer welding. The two methods were compared for these requirements and finally diffusion bonding was chosen. As the last step, diffusion bonding tests were carried out with a mock-up warm damper model, which was the largest diffusion-bonded cylinders that ever made. The size of the model was 885 mm in O.D. and 2800 mm in axial length, and the layer bonding strength was evaluated, proving that sufficient layer bonding strength could be obtained together with uniform deformations.
Machining Process Modeling: A Review
Authors: Ehmann K. F. , Kapoor S. G. , DeVor R. E. , Lazoglu I.
Published: February 2008

In this paper, a summary of work performed in the area of modeling of the dynamic metal cutting process is presented. A general view of evolution of the dynamic cutting process models is depicted. Specifically four modeling approaches including analytical, experimental, mechanistic and numerical methods are critically reviewed. A brief assessment of future research needs is also given.
Material Damage-Based Model for Predicting Chip-Breakability
Authors: Athavale S. M. , Strenkowski J. S.
Published: February 2008

A model for predicting the chip breakability potential of groove and obstruction-type tools is described. The potential for a tool to break chips is evaluated in terms of the chip geometry and the damage sustained by the chip as it is formed in the shear zone. The chip geometry is characterized by its thickness-to-radius ratio, and the material damage is evaluated in terms of a normalized accumulated damage factor that is based on a hole growth and coalescence model. The chip thickness-to-radius ratio and the normalized accumulated damage factor are evaluated using a finite element cutting model. A total of 210 cutting tests were conducted to verify the model. Different tools including flat, obstruction, and groove, were tested for cutting of AISI 1020 steel and SS 304 steel. Each of these tool geometries exhibited significantly different chip thickness-to-radius ratios and normalized accumulated damage. Threshold criteria for breaking chips were determined for AISI 1020 and SS 304. For difficult-to-break materials such as stainless, a lower normalized accumulated damage was needed and a higher chip thickness-to-radius ratio was required to break chips. Although the model presented in the paper was developed for orthogonal cutting, it can be readily extended to three dimensional machining processes. Using this approach, a new tool design can be evaluated for its chip breakability potential with much less reliance on prototype building and testing.
A Partially Constrained Eulerian Orthogonal Cutting Model for Chip Control Tools
Authors: Strenkowski J. S. , Athavale S. M.
Published: February 2008

A partially constrained Eulerian finite element model for orthogonal machining with chip control tools is described. A new constrained free surface algorithm was developed in which the chip thickness was constrained to be uniform along the length of the chip. Using the model, the deformed chip shape and thickness, chip-tool contact, and the velocity, strain, stress, and temperature distributions can be determined. Simulations for machining of stainless steel 304 (SS 304) with obstruction and groove tools are presented. Good agreement was found, between measured and predicted tool forces and chip thicknesses.
Temperature Measurement of Workpiece in Surface Grinding by PVD Film Method
Authors: Kato T. , Fujii H.
Published: February 2008

The near-surface temperature in the workpiece in surface grinding is measured by applying the PVD film method developed recently for measurement of cutting tool temperature. The boundary, identified clearly, between the melted film zone and unmelted film zone is regarded as the isotherm of the melting point of the film material deposited on the inner surface of the workpiece. The temperature for two kinds of workpieces, plain carbon steel and 18-8 stainless steel, was measured under conventional surface grinding conditions. It was found that the technique is useful in estimating the temperature in the workpiece.
Metal Cutting Machine Tool Design—A Review
Authors: Rao S. B.
Published: February 2008

This paper reviews the key developments in the area of metal cutting machine tool design over the last three decades, from a very practical perspective. While defining the drivers of machine tool design as higher productivity and higher accuracy, this paper examines the advances in design from the needs of these two drivers.
CNC Machine Accuracy Enhancement Through Real-Time Error Compensation
Authors: Ni Jun
Published: February 2008

Improving CNC machine tool accuracy has received significant attention recently. This paper intends to provide an introduction of the real-time error compensation methods as applied to reduce both geometric and thermally induced quasistatic machine tool errors. An illustrative example is used to demonstrate the use of error compensation systems for a horizontal machining center. Although several industrial applications of these error compensation systems have achieved significant results, a few major barriers have prevented this promising technology from being applied widely in manufacturing. Several ongoing research activities aimed at overcoming the barriers are also presented.
Control of Machine Tools
Authors: Koren Yoram
Published: February 2008

This paper reviews the progress in machine tool control during the last three decades. Three types of controls are discussed: (i) Servocontrol loops that control the individual axes of the machine, (ii) interpolators that coordinate the motion of several axes, and (iii) adaptive control that adjusts the cutting variables in real time to maximize system performance. We cover a selection of the most advanced techniques utilized in each of these types, and draw conclusions based on experimental results.
Laser Assisted Machining: An Overview
Authors: Chryssolouris G. , Anifantis N. , Karagiannis S.
Published: February 2008

Since laser technology has considerable synergy with machining technologies, Laser Machining (LM) and Laser Assisted Machining (LAM) are relevant research topics. This paper attempts to give an overview of recent developments and research trends. Although scientific work on this area has contributed to the understanding of the process, there are still unresolved problems regarding the limitations of the techniques, optimum machining conditions, etc. The outcome of experimental investigations on LAM shows potential applications for this process but there are several issues to be resolved.
State of the Art of Research and Development in Abrasive Waterjet Machining
Authors: Kovacevic R. , Hashish M. , Mohan R. , Ramulu M. , Kim T. J. , Geskin E. S.
Published: February 2008

Thermodynamic analysis of material removal mechanisms indicates that an ideal tool for shaping of materials is a high energy beam, having infinitely small cross-section, precisely controlled depth, and direction of penetration, and does not cause any detrimental effects on the generated surface. The production of the beam should be relatively inexpensive and environmentally sound while the material removal rate should be reasonably high for the process to be viable. A narrow stream of high energy water mixed with abrasive particles comes close to meeting these requirements because abrasive waterjet machining has become one of the leading manufacturing technologies in a relatively short period of time. This paper gives an overview of the basic research and development activities in the area of abrasive waterjet machining in the 1990s in the United States.
Rapid Prototyping and Solid Free Form Fabrication
Authors: Conley J. G. , Marcus H. L.
Published: February 2008

This article will give a brief review of the start-of-the-art in commercial practice and advanced research in the field of Rapid Prototyping with special attention to the additive methods of Solid Free Form Fabrication. Recent applications of this technology in computer integrated manufacturing environments will be outlined. Future applications and research in new materials will also be addressed.
Recent Advances in the Design and Analysis of Material Handling Systems
Authors: Manda B. S. , Palekar U. S.
Published: February 2008

We present an overview of recent research in the design and control of material handling systems. Research in both shopfloor transportation systems and storage systems is covered. The issues studied range from the integrated design of manufacturing facilities and material handling systems to the performance analysis of operating policies in these systems. In general, the design and control problems in material handling systems are very hard, but analytical results can be obtained for specific configurations and relaxations of the problem.
The Additive Ep-Condition and the Critical Scuffing Limit for
Rolling-Sliding
Authors: Escobar-Jaramillo Enrique F.
Published: February 2008

This paper introduces a new model for the scuffing load capacity in heavily loaded contacts, concerned specifically with the effects of EP-additive oils. The scuffing limit for the additive condition will be closely related to the initial additive-free case, using the calculation method of Blok, solely on a referential level. The process thermodynamics involved at a friction contact will be related to a phenomenological integral relation, containing the necessary internal coordinate to describe the implicit dependence of the friction coefficient with time. The experimental response of the friction contact depends on a relaxant friction coefficient due to the additive effect. The simple calculation method requires only three input parameters for the prediction of the scuffing limit, and these can be obtained from a few experimental scuffing tests. All the tribology of the present scuffing model can be considered to be contained in a simple linear relationship, with the sliding speed as the dominant variable. The calculation criterion has shown to have predictive capability which agrees well with experiments.
Experimental Study of Long-Term Static Friction and Magnetic
Slider/Disk Interplanar Separation
Authors: Gerber C. T. , Bhushan B. , Gitis N. V.
Published: February 2008

Capacitance between a slider and disk was measured to relate slider/disk interplanar separation to static friction. The parallel plate capacitance formula was used to convert the capacitance into separation with a resolution of less than 1 nm. Separation and coefficient of static friction (stiction) were measured using assorted lubricant thicknesses with and without bonding on polished and textured disks. Separation was measured during contact start/stop (CSS) and long term slider dwell times, after which static friction was measured. Polished disks had high stiction events with smaller separations during and after the stiction event, unlike textured disks. Long-term dwell studies showed the coefficient of static friction and slider micro descent (decrease in interplanar separation) to be greatest with greater lubricant thickness and polished disks. Static friction and separation with bonded and unlubricated disks were time independent.
Internal Stresses in Contact of a Rough Body and a Viscoelastic Layered Semi-Infinite Plane
Authors: Goryacheva Irina , Sadeghi Farshid , Nickel David A.
Published: February 2008

A model has been developed to investigate the effects of a rough elastic indenter in sliding contact with a viscoelastic layer bonded to an elastic semi-infinite plane. The viscoelastic layer is modeled as a one-dimensional Maxwell solid (small strain) while the substrate of the semi-infinite plane is modeled as a two-dimensional elastic half plane. The Fredholm integral equation of the second kind was obtained to determine the contact stresses. The results indicate that the viscoelastic properties of the layer and the velocity of the indenter significantly affect the contact pressure and internal stress distributions. The viscoelastic layer causes the pressure and internal stresses to become nonsymmetrical. High asperity densities reduce the amplitude of maximum shear stress at a fixed depth below the surface. Results are also presented for various coefficients of friction.
The Behavior of an Elastohydrodynamic Lubricant at Moderate Pressures
and High Shear Rates
Authors: Zhang Y. , Ramesh K. T.
Published: February 2008

Knowledge of the behavior of lubricants over a wide range of pressures and shear rates is fundamental to an understanding of elastohydrodynamic (EHD) lubrication. The mechanical properties of elastohydrodynamic lubricants have been measured by a number of researchers under the conditions of low pressures and low shear rates, as well as under high pressures and high shear rates. This paper presents experimental results for the synthetic lubricant 5P4E subjected to moderate pressures (60 MPa to 700 MPa) and high shear rates (105 s−1) using the technique of pressure-shear plate impact. Thin layers (25 μm thick) of the lubricant are confined between two hard elastic plates; the assembly is subjected to impact by a parallel plate in a manner designed to induce both compression and shear loading. For approximately 1 μs the compressed lubricant is subjected to a simple shearing motion; during that time, continuous records of the shear stress and shear rate are obtained using laser interferometry. Three test configurations were used in order to cover the pressure range, and special techniques were developed for preparing the specimen sandwich. The pressure range covered includes both the liquid and glassy states of the lubricant. The results show that a limiting shear stress model is an appropriate model for lubricant behavior under these conditions. The experimental results also show little change in the lubricant shearing behavior across the glass transition.
Roughness Influence on Turbulent Flow Through Annular Seals Including
Inertia Effects
Authors: Lucas Victor , Bonneau Olivier , Frêne Jean
Published: February 2008

An analysis is developed to calculate the static and dynamic characteristics for a rough seal that includes inertia effects. The method is detailed for a seal made up of a rough stator and a smooth rotor, a configuration which presents some peculiarities modifying the pattern of the model of turbulence where roughness effects and flow equations are included. A geometry with two identically roughened surfaces can be considered as a special case of the first one. In an earlier study, we developed a model of turbulence built from Prandtl's relation and Van Driest's mixing length method including roughness effects. This model is used to calculate the zeroth-order coefficients of turbulence kx, kz, the Couette velocity ucr for a roughened stator as well as the inertia coefficients. These coefficients derive from the numerical solution of the Generalized Couette Flow. The effects of inertia forces in the film are taken into account in an integrated way according to the film height and are expressed versus the mean velocity. Flow equations are derived from Navier-Stokes’ equations and from the continuity equation for incompressible flows. An analytical perturbation of the flow parameters leads to a set of zeroth-order and first-order equations. The integration of nonlinear zeroth-order equations leads to the steady state solution which permits the calculation of the seal leakage and static load. Dynamic stiffness, damping and added mass coefficients are obtained from the integration of the linear first-order equations. Comparisons are made with the results of the Bulk-flow theory applied to rough seals.
Ultra-Thin Gas Squeeze Film Characteristics for Finite Squeeze Numbers
Authors: Matsuda R. , Fukui S.
Published: February 2008

Ultra-thin gas squeeze film characteristics for finite squeeze numbers are examined by solving the molecular gas film lubrication (MGL) equation, which has a similar form to the conventional Reynolds-type lubrication equation but contains a flow rate coefficient and is valid for arbitrarily small spacings or for arbitrary Knudsen number. We quantitatively clarify by numerical computations that at thin film conditions below several micrometers, pressures generated by squeeze motions are lower than those of continuum flow case and therefore load-carrying capacities are smaller and depend upon film thickness because of the molecular gas effect. For example when the squeeze number is 10 and excursion ratio is 0.5, the load-carrying capacity at 0.1 μm is about one tenth of that at 1 μm.
The Rotor Dynamic Coefficients of Eccentric Mechanical Face
Seals
Authors: Wileman J. , Green I.
Published: February 2008

The Reynolds equation is extended to include the effects of radial deflection in a seal with two flexibly mounted rotors. The resulting pressures are used to obtain the forces and moments introduced in the axial and angular modes by the inclusion of eccentricity in the analysis. The rotor dynamic coefficients relating the forces and moments in these modes to the axial and angular deflection are shown to be the same as those presented in the literature for the concentric case. Additional coefficients are obtained to express the dependence of these forces and moments upon the radial deflections and velocities. The axial force is shown to be decoupled from both the angular and radial modes, but the angular and radial modes are coupled to one another by the dependence of the tilting moments upon the radial deflections. The shear stresses acting upon the element faces are derived and used to obtain the radial forces acting upon the rotors. These forces are used to obtain rotor dynamic coefficients for the two radial degrees of freedom of each rotor. The additional rotor dynamic coefficients can be used to obtain the additional equations of motion necessary to include the radial degrees of freedom in the dynamic analysis. These coefficients introduce additional coupling between the angular and radial degrees of freedom, but the axial degrees of freedom remain decoupled.
Friction and Wear of Metal Particle, Barium Ferrite and Metal
Evaporated Tapes in Rotary Head Recorders
Authors: Patton Steven T. , Bhushan Bharat
Published: February 2008

The friction and wear mechanisms of particulate (metal particle and barium ferrite) and metal evaporated (ME) magnetic tapes were investigated. We conducted tests on these tapes in contact with metal-in-gap (MIG) video heads, using a rotary head recorder in the still (pause) mode. We measured signal degradation and friction during the tests. We conducted chemical and surface analyses of the interface components after the tests. We found discernible differences between the tribological behavior of particulate tapes, and that of the ME tape. The particulate tapes exhibited a more stable friction and head output than the ME tape. We attributed this to a cleaner contact region, due to effective action of the head cleaning agents (HCAs) found in the particulate tapes. The particulate tapes exhibited wear lifetime longer by an order of magnitude, than that of the ME tape. Mild continuous adhesive wear occurred on particulate tapes followed by catastrophic failure. Tape fatigue possibly led to the catastrophic failure. On the ME tape surface, damage initiated at high points or bumps, which resulted in localized delaminations of the tape coating. This led to a catastrophic removal of the entire magnetic coating over the rubbing track. The major difference between the particulate and ME tapes was that signal dropouts concurrent with increases in friction, which resulted from debris accumulation on the video head, preceded the catastrophic failure in the case of ME tapes. We investigated the running-in process of the video head. We found that the durability of a tape and the initial head output increased, and the initial friction force on a tape decreased, as the head ran-in with the tape. We attributed this result to the tape forming a favorable contour on the head rubbing surface. Deposits on the head surface consisted of binder for the particulate tapes, and lubricant and the magnetic coating for ME tape. Tape materials transferred preferentially to the recessed metal core and the recessed glass of the MIG head.
Thermal Analysis of Noncircular Bearings
Authors: Hussain A. , Mistry K. , Biswas S. , Athre K.
Published: February 2008

The present work is on prediction of temperature distribution in noncircular journal bearings and the surrounding solids. Three forms are studied, viz. two-lobe, elliptical and orthogonally displaced bearings. For comparison purposes, a circular bearing with two different groove locations is analyzed. The investigation includes the effects of recirculation and oil mixing at the grooves. The cavitation zone has also been investigated. The work is based on a two-dimensional treatment following McCallion’s approach. The results are presented for various geometries of journal bearing configuration, including the conventional circular bearing.
A Numerical Three-Dimensional Model for the Contact of Rough Surfaces
by Variational Principle
Authors: Tian Xuefeng , Bhushan Bharat
Published: February 2008

A new numerical method for the analysis of elastic and elastic-plastic contacts of two rough surfaces has been developed. The method is based on a variational principle in which the real area of contact and contact pressure distribution are those which minimize the total complementary potential energy. The present variational approach guarantees the uniqueness of the solution of the contact problem and significantly reduces the computation time as compared with the conventional matrix inversion method, and thus, makes it feasible to solve 3-D contact problem with large number of contact points. The model is extended to elastic-perfectly plastic contacts. The model is used to predict contact statistics for computer generated surfaces.
A Generalized Non-Newtonian Fluid Model Incorporated Into
Elastohydrodynamic Lubrication
Authors: Wolff R. , Kubo A.
Published: February 2008

A generalized Reynolds equation for the non-Newtonian fluid, which can incorporate most of the published rheological models, is proposed. The solution of the isothermal EHL line contact lubricated by a non-Newtonian fluid is obtained by applying the Newton-Raphson method. The results of an isothermal non-Newtonian EHL line contact model with different rheological laws and the results of a thermal Newtonian EHL model are presented. Under low load and high rolling velocity conditions, the thermal effects caused by slip have a greater influence on the film shape and pressure distribution than the non-Newtonian effects. For low slip and under heavy load conditions the non-Newtonian behavior of fluid significantly influences the traction coefficient, while thermal effects have a great influence on the traction in case of high slip. The comparison between numerical and experimental results shows that the nonlinear viscous Eyring model overestimates the traction coefficient when high viscosity oil is subjected to a heavy load and low slip conditions. In this case, only the visco-plastic models can predict the traction value. The visco-elastic behavior of the fluid is important at very low slip conditions and it can slightly reduce the traction value.
Low Speed Mixed Lubrication of Bulk Metal Forming
Processes
Authors: Wilson W. R. D. , Chang Der-form
Published: February 2008

A simple analysis for the lubrication of saw-tooth surfaces with longitudinal lay under conditions of high fractional contact area is developed. This is then coupled with Wilson and Sheu’s asperity flattening model to treat the mixed lubrication of a bulk metal forming process (rolling). It is shown that, even under low speed conditions where the inlet zone does not generate significant hydrodynamic pressures, relatively high hydrodynamic pressures can be generated in the work zone. This explains the persistence of hydrodynamic effects noted in low speed experiments.
Design of Vehicle Power Transmission Systems
Authors: Freeman J. S. , Velinsky S. A.
Published: February 2008

The power transmission system is a critical component of any machine. Accordingly, the detailed analysis of this system is essential for both design purposes and the detailed assessment of machine performance. Due to the large number of possible power transmission system components and the nature of these systems, general power transmission system analysis methods have been difficult to develop. However, such analysis methods could meet a wide variety of needs for system design. This paper discusses the general power transmission system analysis approach developed by the authors over the last several years based on their study of vehicle powertrains. The formulation and solution of the governing equations are discussed, and the ability of the approach in addressing critical design related issues is demonstrated through an example system simulation.
Design of Passive Damping Systems
Authors: Johnson C. D.
Published: February 2008

This paper presents a brief review of techniques for designed-in passive damping for vibration control. Designed-in passive damping for structures is usually based on one of four damping technologies: viscoelastic materials, viscous fluids, magnetics, or passive piezoelectrics. These methods are discussed and compared. The technology of using viscoelastic materials for passive damping is discussed in more detail than the other methods since it is presently the most widely used type of damping technology. Testing and characterization of viscoelastic materials and design methods for passive damping are discussed. An example showing the benefits of a passive damping treatment applied to a stiffened panel under an acoustic load is presented.
Passive, Adaptive and Active Tuned Vibration Absorbers—A Survey
Authors: Sun J. Q. , Jolly M. R. , Norris M. A.
Published: February 2008

An overview of the recent development of tuned vibration absorbers (TVAs) for vibration and noise suppression is presented. The paper summarizes some popular theory for analysis and optimal tuning of these devices, discusses various design configurations, and presents some contemporary applications of passive TVAs. Furthermore, the paper also presents a brief discussion on the recent progress of adaptive and semi-active TVAs along with their on-line tuning strategies, and active and hybrid fail-safe TVAs.
A Design Method for Minimizing the Sound Power Radiated from Plates by Adding Optimally Sized, Discrete Masses
Authors: St. Pierre R. L. , Koopmann G. H.
Published: February 2008

In this paper, a novel method for minimizing the sound power radiated from a structure is presented. The method involves placing strategically sized masses at specific locations on the structure’s surface. The minimization procedure modifies the shapes of the resonant modes of the structure in the frequency range of interest such that they are forced to radiate sound inefficiently. Because of this, they are referred to as “weak radiator” mode shapes. The method uses an optimization procedure that directly minimizes the radiated sound power from the surface of a plate in an infinite baffle. The procedure can be carried out for a single frequency or over a range of frequencies. Analytical sensitivities of sound power with respect to the design variables are developed and used in the optimization algorithm. Results on various test cases show sound power reductions of 10 dB or more even when several resonances are included in the frequency band. An acoustic intensity probe is used to experimentally verify the results for one test case. The experiment confirms the sound power reductions predicted by the optimization program.
Concepts on an Integrated Design Approach to the Active Control of Structurally Radiated Noise (ASAC)
Authors: Silcox R. J. , Fuller C. R. , Burdisso R. A.
Published: February 2008

This work describes a range of issues relating to the implementation of active control for noise and vibration problems. It is important in the commercialization of this technology to consider these and many other factors relating to design of these systems. Many of the concepts required for efficient implementation have not been considered and it is important to begin giving design consideration to these aspects. A design technique based upon the eigenbehavior of feedforward controlled systems is developed and applied to control radiation from structures. Integration of the control system with the physical system dynamics allows the eigenproperties to be defined to meet a prescribed design criteria. Here the technique is demonstrated to implement a structural system that inefficiently couples vibration energy to acoustic energy. In addition, an approach to integrate “knowledge” about actuator configurations into an active control system that reduces spillover effects into structural vibrations is demonstrated. This approach has the advantages that no additional hardware is required while also reducing the order of the control system in terms of degrees of freedom. Finally, some design trade-offs between the passive material properties of an active trim panel and control system performance are examined. Improved performance can be attained but at the cost of additional weight.
Robust Mechanical Design Using Engineering Models
Authors: Parkinson A.
Published: February 2008

This paper examines how engineering models can be used to develop robust designs—designs that can tolerate variation. Variation is defined in terms of tolerances which bracket the expected deviation of model variables and/or parameters. Several methods for robust design are discussed. The method of transmitted variation is explained in detail and illustrated on a linkage design problem and a check valve design problem.
Optimal Design of Mechanical Engineering Systems
Authors: Papalambros P. Y.
Published: February 2008

The capability of mathematical optimization to support the mechanical design process is finally reaching wide recognition, as evidenced by significant applications in industry. The article reviews key issues and challenges for design optimization theorists and practitioners. Large scale system design and topology or configuration design are identified as the most important areas of future design optimization research. Some new approaches for partitioning large design problems and for topology optimization of multi-component structural systems are introduced.
Virtual Prototyping Simulation for Design of Mechanical Systems
Authors: Haug E. J. , Choi K. K. , Kuhl J. G. , Wargo J. D.
Published: February 2008

Developments in simulation technology that enable a qualitatively new virtual prototyping approach to design of mechanical systems are summarized and their integration into an engineering design environment is illustrated. Simulation tools and their enabling technologies are presented in the context of vehicle design, with references to the literature provided. Their implementation for design representation, real-time driver-in-the-loop simulation, dynamic performance simulation, dynamic stress and life prediction, maintainability analysis, design sensitivity analysis, and design optimization is outlined. A testbed comprised of computer aided engineering tools and a design level of fidelity driving simulator that has been developed to demonstrate the feasibility of virtual prototyping simulation for mechanical system design is presented. Two 1994 demonstrations of this capability for vehicle design are presented, to illustrate the state of the technology and to identify challenges that remain in making virtual prototyping simulation an integral part of mechanical system design in US industry.
Solving Polynomial Systems for the Kinematic Analysis and Synthesis of Mechanisms and Robot Manipulators
Authors: Raghavan M. , Roth B.
Published: February 2008

Problems in mechanisms analysis and synthesis and robotics lead naturally to systems of polynomial equations. This paper reviews the state of the art in the solution of such systems of equations. Three well-known methods for solving systems of polynomial equations, viz., Dialytic Elimination, Polynomial Continuation, and Grobner bases are reviewed. The methods are illustrated by means of simple examples. We also review important kinematic analysis and synthesis problems and their solutions using these mathematical procedures.
Optimal Robot Design and Differential Geometry
Authors: Park F. C.
Published: February 2008

In this article we survey some recent developments in optimal robot design, and collect some of the differential geometric approaches into a general mathematical framework for robot design. The geometric framework permits a set of coordinate-free definitions of robot performance that can be optimized for designing both open- and closed-chain robotic mechanisms. In particular, workspace volume is precisely defined by regarding the rigid body motions as a Riemannian manifold, and various features of actuators, as well as inertial characteristics of the robot, can be captured by the suitable selection of a Riemannian metric in configuration space. The integral functional of harmonic mapping theory also provides a simple and elegant global description of dexterity.
Computer-Aided Mechanism Design: Now and the Future
Authors: Erdman A. G.
Published: February 2008

The current status of computer-aided design of mechanisms is reviewed. The available software is described and several industrial examples are presented to illustrate current trends in the field of linkage design and analysis. Future strategies and CAD environments are also discussed.
Fatigue Growth Prediction of Internal Surface Cracks in Pressure Vessels
Authors: Lin X. B. , Smith R. A.
Published: February 2008

Fatigue crack growth was numerically simulated for various internal surface cracks with initially either semi-elliptical or irregular crack fronts. The simulation was directly based on a series of three-dimensional finite element analyses from which the stress intensity factors along the front of growing cracks were estimated. The fatigue crack growth law obtained from small laboratory specimens was incrementally integrated at a set of points along the crack front, and a new crack front was then re-established according to the local advances at this set of points by using a cubic spline curve. This method enabled the crack shape to be predicted without having to make the usual assumption of semi-elliptical shape. Fatigue analysis results are presented and discussed for fatigue shape developments and deviations from the semi-elliptical shape, aspect ratio changes, stress intensity factor variations during crack growth, and fatigue life predictions. Some of the results were also compared with those obtained by two simplified methods based on one and two degree-of-freedom models, respectively.
Statistical Analysis of the ASME KIc Database
Authors: Sokolov M. A.
Published: February 2008

The American Society of Mechanical Engineers (ASME) KIc curve is a function of test temperature (T) normalized to a reference nil-ductility temperature, RTNDT, namely, T – RTNDT. It was constructed as the lower boundary to the available KIc database. Being a lower bound to the unique but limited database, the ASME KIc curve concept does not discuss probability matters. However, a continuing evolution of fracture mechanics advances has led to employment of the Weibull distribution function to model the scatter of fracture toughness values in the transition range. The Weibull statistic/master curve approach was applied to analyze the current ASME KIc database. It is shown that the Weibull distribution function models the scatter in KIc data from different materials very well, while the temperature dependence is described by the master curve. Probabilistic-based tolerance-bound curves are suggested to describe lower-bound KIc values.
On Generation of Ultra-High Pressure by Converging of Underwater Shock Waves
Authors: Itoh S. , Kubota S. , Nagano S. , Fujita M.
Published: February 2008

The characteristics of a new assembly for the shock consolidation of difficult-to-consolidate powders, such as inter-metallic compounds or ceramic materials, were investigated by both the experimental method and numerical simulation method. The assembly consists of an explosive container, a water chamber, and a powder container. Once the explosive is detonated, a detonation wave occurs and propagates, and then impinges on the water surface of the water chamber. After that, there occurs immediately an underwater shock wave in the water chamber. The underwater shock wave interacts with the wall of the chamber during its propagation so that its strength is increased by the converging effect. We used the usual shadow graph system to photograph the interaction process between detonation wave and water. We also used a Manganin piezoresistance gage to measure the converged pressure of the conical water chamber. Finally, we numerically investigated, in detail, the converging effects of the various conical water chambers on the underwater shock waves. The experimental results and the correspondingly numerical results agree quite well with each other.
Analysis of Liquid Slug Motion in a Voided Line
Authors: Yang J. , Wiggert D. C.
Published: February 2008

A quasi-two-dimensional two-phase flow cylindrical model of slug motion in a voided line is developed that can reasonably predict the change of flow pattern of the slug, air entrainment, “holdup” and the distribution of axial velocity. However, when using the theory of incompressible momentum transfer to estimate the pressure-time history of slug at the elbow, the calculated results are not in good agreement with those of the experiments. Further analysis of the experimental results indicate that an acoustic, or waterhammerlike response may occur immediately upon impact of the high-speed slug with the elbow, and subsequently, the waveform exhibits momentum transfer due to the acceleration of the slug at the elbow.
Collapse Strength of Complex Metal Shell Intersections by the Effective Area Method
Authors: Teng J. G.
Published: February 2008

Cone-cone intersections and cone-cylinder intersections with or without ring stiffeners are common features in silos, tanks, pressure vessels, piping components, and other industrial shell structures. Under internal or external pressure, these intersections are subject to high circumferential membrane stresses as well as high bending stresses due to the presence of a slope discontinuity. As a result, they are susceptible to local plastic collapse. This paper first provides a summary of the effective area method initially proposed by Rotter for the plastic limit loads of cone-cylinder intersections in silos. The method is then generalized for complex intersections of cones and cylinders under uniform pressure and improved by including the local pressure effect. Results from the effective area method are compared with rigorous finite element results for a number of cases to demonstrate its accuracy. It is shown that the method is not only elegant and accurate, but also leads to a single simple formula for different types of intersections which is particularly suitable for codification purposes.