bluuebunny/crossref_metadata_2025 huggingface dataset:
Inclusion of a Support Friction Into a Computerized Solution of a Self-Compensating Pipeline
Authors: Sobieszczanski J.
Published: November 2010

Thermal elongations of a pipeline are compensated in many cases by bending of pipeline branches. If the pipeline lies on a horizontal rough and flat foundation that bending is influenced by friction forces. Analysis of that influence is given in the paper. A nonlinear, fourth order differential equation with variable coefficients governing the phenomenon is derived and solved numerically as a two-point boundary problem. A version of the solution suitable for a pipeline on discrete supports has been developed. It may be used in conjunction with any existing computer program for pipeline stress analysis. The results demonstrate existence of a very significant additional bending moment due to friction. It may exceed several times the one computed for a pipeline on frictionless foundation.
Effects of Crack Size on the Gross-Strain Crack Tolerance of A-533-B Steel
Authors: Randall P. N. , Merkle J. G.
Published: November 2010

Gross-strain crack tolerance is a measure of fracture toughness that is useful where yielding precedes fracture yet flaw size must be treated quantitatively. In these tests, rectangular bars containing surface fatigue cracks were pulled in tension at several temperatures. Strains were measured at the edges of the specimen on a gage length spanning the plane of the crack, and also in the gross section above and below the crack. Gross-strain crack tolerance is the strain at maximum load on the gage length designated. It is shown to be a function of crack size, constraint, and temperature.
Exhaust Vent Silencer Design
Authors: Meador C. L. , Allan J. J.
Published: November 2010

Noise control problems exist where high pressure, high temperature gasses are vented to the atmosphere. An example is used to illustrate an approach to the design of an acoustically treated expansion chamber for a typical noise problem caused by superheated steam vented to the atmosphere. An analysis is developed to aid in the design of the acoustically treated expansion chamber type muffler for broadband frequency application. The algorithm as well as the supporting theory are sufficiently general so as to be applicable to a number of high velocity gas-generated noise conditions. An Appendix of terminology definitions is included.
Multicomponent Calibration of Machine-Tool Dynamometers
Authors: Levi R.
Published: November 2010

Service loads of machine-tool dynamometers are usually reduced to a system of three mutually orthogonal force components through a fixed reference point. Three additional components (moments) result if the resultant cutting force does not pass through the reference point. At least some of these six components reach finite values under machining operations; sometimes all six must be considered. It follows that the response surface of the output signal of each channel to all six components must be known in order to evaluate the measurement process. Six component calibration of multi-component dynamometers, such as, e.g., wind tunnel balances, is known to be a rather expensive and time-consuming operation. It will be shown that, under some rather general limiting conditions, useful estimates of the response surface parameters may be obtained with a reasonable number of straightforward tests. Expensive special purpose calibration stands are dispensed with, simple jigs and general purpose equipment being all that is needed for most applications. The performance of machine-tool dynamometers may, therefore, be analyzed in detail, and a good understanding of their measurement capabilities may be obtained, even when operating under a light budget. Details are given concerning the application of the proposed method to a tool-post-type lathe dynamometer.
A Solution of the Free Oblique Continuous Cutting Problem in Conditions of Light Friction at Chip-Tool Interface
Authors: Morcos W. A.
Published: November 2010

A model for free oblique continuous cutting is proposed. In addition to the hypotheses used in Merchant’s model for free oblique continuous cutting, coincidence of chip-tool friction force with the direction of chip flow on the tool face is assumed; moreover, the deformation process in the primary deformation zone is considered as a case of plane strain. The direction of chip flow is predicted and is found to be function of the cutting conditions. The theoretical predictions compare favorably—less than 10 percent discrepancies—with experimental data published in literature for conditions of low friction at chip tool interface.
A Transient Elastic-Plastic Thermal Stress Analysis of Flame Forming
Authors: Iwamura Y. , Rybicki E. F.
Published: November 2010

The work described here is part of a larger experimental and theoretical program directed at obtaining a better understanding of the mechanics of flame bending. A capability for predicting the transient behavior of a line heated plate during heating and cooling is presented. Material properties are temperature dependent. Elastic-plastic stress-strain relations are used. Material unloading from the plastic range is treated. Deformations of a plate are predicted at various times during heating and cooling and compared with experimental results. The analysis is also carried out for consecutive heating and cooling cycles.
Motion of a Ball in a Ball Bearing
Authors: Portig H. , Rylander H. G.
Published: November 2010

A method is developed which allows the digital simulation of the unsteady motion of a single ball constrained only by two moving bearing races. Any desired motion of the races can be simulated. Normal forces acting on the ball are calculated by Hertzian contact deformation theory. If there is slippage between ball and races, Coulomb friction is assumed to occur. Solutions to the differential equations of motion were obtained on a computer with the digital simulation language MIMIC. The phenomenon of ball control as well as the behavior of the ball as it reached a controlled state from rest were observed. This analysis can produce more realistic results than methods that assume that the ball is controlled at all times, especially when the races are radially or angularly displaced with respect to each other.
Radial Displacements of a Hollow Shaft Subjected to a Uniform Band of External Pressure
Authors: Wilson E. A. , Parsons B.
Published: November 2010

The principle of superposition is used to combine the results of separate stiffness analyses of (a) a solid shaft loaded by a band of external pressure, using classical elasticity methods and (b) a hollow shaft loaded by bore surface tractions, using finite-element methods. The combined results provide solutions to the case of hollow shafts of infinite length loaded on their outer surface by a uniform band of external pressure; these results are presented in tabular form for a range of hollow shafts of different thicknesses.
Analytical Sensitivity Studies of the Optimum Machining Conditions for Milling, Drilling, Reaming, and Tapping
Authors: Ermer D. S. , Shah B. V.
Published: November 2010

An analytical method for sensitivity studies in the determination of the optimum machining conditions for the single point turning process was previously presented by Ermer and Faria [4]. In the present paper, an analytical method for sensitivity studies in the determination of the optimum machining conditions for milling, drilling, reaming and tapping is presented, assuming that the optimizing criterion is minimum cost or maximum production rate. A nomogram is given which provides a simple and efficient way to carry out quantitative sensitivity analyses.
Aeration Apparatus Converts Bin From Funnel-Flow to Mass-Flow Characteristics
Authors: Emery R. B.
Published: November 2010

A properly designed hopper provides cost control through increased unloading reliability, improved storage space utilization, steadier discharge rates, and improved blending of discharged materials. Hoppers have been designed to provide these advantages by providing mass-flow characteristics without application of auxiliary flow promoting devices. Many hoppers are not designed for proper flow. In some cases, limitations on head room, flow rate requirements, or bulk solid characteristics present barriers to design goals of proper flow. Application of aeration can alleviate flow problems in existing hoppers without major changes in hopper configuration and, in addition, it can be helpful in reducing required head room, promoting flow control, and handling some very fine powders. An application of such an aerating device to improve the flow characteristics of fine powders from funnel-flow to mass-flow is discussed in this paper.
The Relative Angular Velocity Between Links
Authors: Moustafa Mahmoud A.
Published: November 2010

The magnitude of the relative angular velocity between two links is equal to the component of the relative velocity between any two points, one on each link, along the line joining them divided by the normal to this line from the instantaneous center of the two links. Its direction is the same as the moment of this component about the instantaneous center.
Minimizing Segregation in Bunkers
Authors: Clague K. , Wright H.
Published: November 2010

Bunkers used in steelworks sinter plants and other applications need to be designed and operated so that the feed emerging is unsegregated. A series of model tests has been carried out to discover which bunker shape, flow regime, and filling method give the least segregation for raw materials of different particle size and density. Results are compared with results from larger bunkers. The main conclusions are that an evenly-filled wedge-shaped mass-flow bunker is best at preventing segregation and that material density has little effect.
The Mechanism of Gyroscopic Tracking: Part 1
Authors: Mansour W. M. , Pavlov D.
Published: November 2010

The tracking property of the free gyro is investigated using analytical and digital approaches. A strategy of analysis is developed which can be used to assess the quality of tracking for different geometrical configurations of the template. This property has a practical potential to be implemented into instruments for sensing and identification.
Synthesis of Seven-Link Mechanisms
Authors: Kohli D. , Soni A. H.
Published: November 2010

The mechanisms derived from the seven-link chains with five links in their two loops and having two degrees of freedom are examined for six synthesis problems. Using displacement matrices, closed form synthesis equations are derived. It is shown that three synthesis problems may be solved using the principle of linear superposition, and closed form solutions may be obtained. The other three synthesis problems involve highly nonlinear equations and must be solved numerically.
Deflection and Stress Analysis in High Speed Planar Mechanisms With Elastic Links
Authors: Imam Imdad , Sandor George N. , Kramer Steven N.
Published: November 2010

In the design of high speed machinery the solution of the kinematics problem alone may in certain cases not be sufficient due to the elastic nature of the mechanism parameters. A method of deflection analysis, suitable for computer programming, is presented here which is general for all planar linkages including multi-loop mechanisms. This generality is accomplished by the extension of the permutation vector method of structural analysis to the kineto-elastodynamic analysis of mechanisms and by the introduction of the rate of change of the eigenvalues with respect to the motion of mechanisms. Both of these methods are believed to be applied here for the first time in the area of linkage design. With these methods an eigenvalue problem of high order is solved whereby the required computation time is decreased by a factor of three with respect to conventional numerical methods in most cases. Furthermore a method of dynamic stress analysis is presented to indicate the relationship between the dynamic stresses and the mechanism design parameters. Several numerical examples illustrate the concepts developed in this paper.
Dynamic Synthesis of Constraint Paths
Authors: Starr P. J.
Published: November 2010

A class of dynamic synthesis problems is introduced which treats the determination of the constraint paths between specified positions for problems involving rigid body transfer. These paths are so determined as to optimize some quality of the dynamic behavior as the device moves under the action of external forces. A solution technique is presented which transforms the problem into an optimal control problem with the basic ideas being developed using a single link device with one unknown path. It is assumed that the resulting optimal paths could then be realized using existing methods of kinematic synthesis.
Balancing of Machines
Authors: Stevensen E. N.
Published: November 2010

A general method is presented for the complete balancing of a harmonic unbalance of any machine, including inertia forces, moments of the inertia forces, and inertia torques, utilizing six weights on three shafts in the machine parallel to the coordinate axes and rotating at the speed of the harmonic. For those cases where a full set of three shafts is not available, a method for optimizing unbalance is also presented, and illustrated by an example. In such cases the criterion for “best balance” must be carefully selected. This should be done to minimize some response to the unbalance.
On the Distribution of the RMS Shaking Moment of Unbalanced Planar Mechanisms: Theory of Isomomental Ellipses
Authors: Tepper F. R. , Lowen G. G.
Published: November 2010

It is shown that the RMS shaking moment of unbalanced planar mechanisms is constant with respect to all points along certain concentric ellipses (isomomental ellipses) in the mechanism plane. The RMS shaking moment decreases for reference points located on ellipses of decreasing size, and the center of this family of ellipses represents the point about which the RMS shaking moment of the mechanism is a minimum. This theory provides a useful tool for evaluating the effect of full force balancing on the RMS shaking moment of a given planar mechanism.
Stability and Kinematic Accuracy of Hydraulic Copying Mechanisms in Metal Cutting
Authors: Mansour W. M. , Osman M. O. M. , Gladwell G. M. L.
Published: November 2010

The nature and the size of the cutting forces were investigated to develop a model that accounts for their fluctuation. Due to the interaction between the velocity of the power cylinder and the cutting forces, the governing equations contained periodic coefficients. Stability analysis showed that the fluctuations of the cutting forces and their averages played important roles. Dimensionless plots were developed to be used as a guide for the design and operation of copying mechanisms. The kinematic accuracy of copying was found to be influenced most by the coefficient of leakage, and the degree of under lap of the spool valve. Digital and analog approaches were used in this study.
Design Considerations for Space Mission Washwater Processing by Reverse Osmosis
Authors: Wells G. W. , Wong W. , Putnam D. F.
Published: November 2010

Reverse osmosis (RO) is shown to be a promising method of reclaiming wash water. The amounts of wash water and cleansing agent required for showering, personal hygiene, housekeeping, dish washing, laundry, and experiment purposes are presented and the impact of clothing types and laundry schedule are discussed. A theoretical estimate of the contaminants found in wash water is made based on published data for sebum, sweat, and other body excretions. An analytical method for calculating mass balances in a reverse osmosis recycle system is presented and concentrations of the major chemical constituents expected in the RO feed, product and brine streams are projected.
The Effects of Fluid and Mechanical Compliance on the Performance of Hydraulic Shock Absorbers
Authors: Mayne R. W.
Published: November 2010

Dimensionless differential equations are developed which model a hydraulic shock absorber. These equations are solved numerically to determine quantitatively the effects of fluid compressibility and series and parallel springs on the shock absorber operation. Both variable and constant orifice area are considered for a system protecting a mass during impact against a rigid wall. The results show that a finely tuned variable area shock absorber is degraded by the considered forms of compliance. Performance of the constant area shock absorber can be improved by including compliance and, with an appropriate parallel spring, the ideal flat deceleration profile can be obtained without variable orifice area.
Optimum Design of an Impact Absorber
Authors: Afimiwala K. A. , Mayne R. W.
Published: November 2010

A shock absorber with nth order stiffness and mth order damping is designed for optimum response to a step change in base velocity (an acceleration impulse). The objective of the design is to minimize the maximum acceleration level occurring during the transient response. A single constraint is used to limit relative motion between the base and the isolated mass and another constraint is added to limit the oscillatory nature of the system response. Results of the study are presented on dimensionless curves showing the optimum stiffness and damping coefficients and the expected system performance as functions of m and n. Optimization methods used in the problem involve nonlinear programming and numerical solution of the governing differential equations. Effectiveness of the approximate parameter optimization scheme suggested by Sevin and Pilkey is also considered.
Mathematical Programming Procedures for Mixed Discrete-Continuous Design Problems
Authors: Pappas M. , Allentuch A.
Published: November 2010

Two mathematical programming procedures for treating nonlinear problems involving mixed variables are presented. One involves a relatively simple concept. First an optimum is located treating all variables as continuous. Adjacent discrete points are then evaluated in order of increasing distance from the all-continuous optimum, each evaluation requiring an optimization of the continuous variables, if any, until a satisfactory design is found. The other method utilizes an optimal discrete search to locate the optimum. These procedures are applied to the minimum weight design of stiffened, cylindrical shells where they prove to be effective.
Noise and Vibration Analysis of an Impact Forming Machine
Authors: Osman A. E. M. , Sadek M. M. , Knight W. A.
Published: November 2010

The mechanism of noise and vibration generation in an impact forming machine is investigated using Fourier Transform methods. Noise, vibration, and load measurements have been correlated for a fixed input energy and the sound field around the machine investigated. The measured results are compared with those predicted by a lumped parameter computer model for determining the normal modes of vibration of the machine structure and the moving platen. It is found that the major proportion of the noise energy is generated in the impact area and the dominant source of noise is the free vibration of the structure. Further contributions are observed due to the excitation of the structure by the impact force. For a constant input energy the noise and vibration levels increase as the billet height for simple upsetting is reduced.
Assessment of Ultimate Fidelity of an Eccentric Circular Disk Cam With Translating Flatfaced Follower as a Function Generator
Authors: Mischke C.
Published: November 2010

It is generally known that an eccentric circular disk cam actuating a flatfaced translating follower is an economical approximate function generator. The designer’s question is “Just how well can it approximate the function I have in mind?” The methodology presented herein will answer the question, “What is the best fidelity of which the concept is capable?” The methodology will enable the designer to assess whether he has the option of utilizing the concept or whether he must seek a different conceptual course of action.
Dynamic Response of Pipes Transporting Fluids
Authors: Liu Hong-Sun , Mote C. D.
Published: November 2010

The natural frequency-mass transport velocity relationship was experimentally determined on aluminum tubes throughout a broad mass transport velocity range. Simply-supported, clamped-clamped, and clamped-free conditions were examined. The results are compared with available theoretical developments in each case. Results indicate the theories examined have a range of application limited to the lower transport velocities and even there their application requires knowledge of the no transport reference frequency and the transport dependent axial tension. Process modelling in the higher transport regime is unsatisfactory, and use of the examined theoretical results there should be carefully considered. Since most conditions of instability are associated with high flow velocity, the application of the examined theories to the prediction of response near instability should be done with the clear understanding that large error is possible.
An Extension of the Holzer Method for Redundant Drive Trains
Authors: Hundal M. S.
Published: November 2010

A method is described for the determination of natural frequencies and mode shapes of closed drive trains. It is an extension of the Holzer method to a redundant system. The “error” for a given value of frequency is computed by the solution of a tridiagonal system of equations.
Heat Induced Vibration of a Rectangular Plate
Authors: Jadeja N. D. , Loo Ta-Cheng
Published: November 2010

The purpose of this paper is to investigate thermally induced vibration of a rectangular plate with one edge fixed and other three edges simply supported. The plate was subjected to a sinusoidal heat input, which varied with respect to time, on one face while the other face of the plate was insulated. An approximate solution to the governing differential equation of motion of the plate was assumed in the form of a double trigonometric series which satisfied all the boundary conditions. Galerkin’s method was then used to obtain the deflection curve for the plate and corresponding stresses at various points in the plate. Certain interesting phenomena indicate the possibility of predicting early fatigue failure. Results are presented in graph forms and discussed.
Clamshell Unloader Reeving Systems
Authors: Coulter S. M. , Fenton E. A.
Published: November 2010

Recent increases in bulk material tonnage being transported throughout the world are requiring the planning of many new ship and barge unloading installations, as well as the renovation and updating of a number of existing facilities. For many years, the clamshell unloader has been the heart of the typical unloading facility, and in spite of new unloading techniques, it will continue to play a major role in years to come. Since today’s high performance, high capacity unloader can represent an investment of several million dollars, it is important that the operation of this machine be well understood and appreciated by all those involved. The purpose of this presentation is to discuss the various types of reeving systems that are available, their major advantages and limitations, and the features that are essential to any system to insure smooth and trouble free operation.
Some Stability and Control Aspects of Airframe/Propulsion System Interactions on the YF-12 Airplane
Authors: Berry D. T. , Gilyard G. B.
Published: November 2010

Airframe/propulsion system interactions can strongly affect the stability and control of supersonic cruise aircraft. These interactions generate forces and moments similar in magnitude to those produced by the aerodynamic controls, and can cause significant changes in vehicle damping and static stability. This in turn can lead to large aircraft excursions or high pilot workload, or both. For optimum integration of an airframe and its jet propulsion system, these phenomena may have to be taken into account.
Void Behavior as Influenced by Pressure and Plastic Deformation
Authors: Kahlow K. J. , Avitzur B.
Published: November 2010

Void behavior has a pronounced effect on the properties and soundness of most materials, and is strongly influenced by the magnitude of hydrostatic pressure during plastic deformation. Using the upper bound theorem approach with a model of idealized geometry to simulate a void-material composite, an analytical criterion for the minimum effective pressure necessary to initiate a permanent void volume change is developed. This pressure is called critical pressure, and its absolute value is the same whether for compression and void closure or tension and void opening. A deviation parameter is also defined, and it indicates that voids of a given geometry will start to open faster under tension than they will start to close under compression of the same magnitude. To compare the aforementioned analytical predictions with real material behavior, copper split billets with artificially introduced voids of predetermined geometries were deformed under different magnitudes of hydrostatic pressure: the process of wire drawing for low pressure deformation, and the fluid environment of hydrostatic extrusion for higher pressure deformation. Those characteristics found to lead to significant void volume change are: (a) high void volume fraction, (b) large relative void size, and (c) voids of unity or greater aspect ratio. Experimental data compared well with the analytical curves; thus, the analytical expressions should be useful in explaining and predicting the behavior of voids in some real materials.
Machine Tool Chatter: Effect of Surface Slope on Machining Forces During Wave Removing
Authors: Sarnicola J. F. , Boothroyd G.
Published: November 2010

The effect of work surface slope (rate of change of undeformed chip thickness) on machining forces has been measured. The results of these experiments are used to develop equations for the cutting and thrust components of the resultant tool force during wave removing. It is found that the work surface slope effect gives rise to a significant out-of-phase component of the oscillating tool force which should not be neglected in stability analyses.
Analysis of Thermal Expansion in Face-Cutting Operations
Authors: Ichimiya R. , Usuzaka Y.
Published: November 2010

Theoretical and experimental analyses are developed for the thermal expansion of a tool and a cylindrical work during face-cutting with a lathe. Theoretical investigation considers temperature distributions in the tool and the work at the cutting position, and these temperature distributions relate to the elongations of the work and the tool. The experimental investigation was conducted on a lathe turning at the end face of a solid cylindrical work. The results of sample calculations for thermal expansion coincide significantly with the experimental results. When the end face of the work is machined from the center point to the circular surface, the end face deforms to become convex; when it is machined from the circular surface to the center point, the end face deforms to become concave.
Shear Angle Relationship With Variable Undeformed Chip Thickness
Authors: Kainth G. S. , Gupta R. C.
Published: November 2010

Effect of surface slope of the workpiece on shear angle has been considered by applying Hill’s [1] deformation criteria to the triangular shear zone in orthogonal metal-cutting process with variable undeformed chip thickness. It is shown that the variation of the shear angle with the surface slope δ can be written in the form φ = φ0 + Cδ where “C” is not a constant but depends upon steady state shear angle φ0, surface slope δ, and rake angle α. It is also shown that the present theory is in good agreement with the experimental results of Boothroyd [2].
The Mechanism of Conveyance With Bristled Tracks
Authors: Mansour W. , Massoud M. , Morcos W. , Lauzier C.
Published: November 2010

Material handling using bristly tracks is investigated. The dynamic equations of the transported mass are developed and digitally simulated. The investigation shows that appreciable gains can be achieved by using one sinusoidal cycle which is imparted normal to the trough. Parametric studies and design recommendations are included.
On the Motion of a Set of Spheres Between Two Parallel Planes
Authors: Freudenstein F. , So¨ylemez E.
Published: November 2010

The motion is investigated of the centers of a set of identical spheres in rolling contact with two plane, parallel surfaces having general, coplanar motions. This motion is shown to be a rigid-body motion (which we call cage-plane motion). General properties of the motion are derived. Next the nature of the cage-plane motion is investigated in the case of input-plane motions, which are generated mechanically. The results reduce to the known special cases and indicate that the element (cage) usually regarded only as a spacer in ball bearings has a general motion, which is both versatile and potentially useful.
Effects of Tensioning on Buckling and Vibration of Circular Saw Blades
Authors: Carlin J. F. , Appl F. C. , Bridwell H. C. , DuBois R. P.
Published: November 2010

A circular saw blade subjected to a concentrated radial in-plane load and initial tensioning stresses is theoretically investigated by energy methods. The buckling and vibrational properties of the blade are determined for various amounts of initial stress and extensive nondimensional results are presented. An optimum tensioning configuration for improving both the buckling and vibrational properties of the blade is proposed. The procedure is repeated for nine different combinations of blade thickness and clamping ratio.
Flow Stress Determination for Metals at Forging Rates and Temperatures
Authors: Douglas J. R. , Altan T.
Published: November 2010

In this study, the uniform compression test is used to determine the flow stress of 403 stainless steel, Waspaloy, Ti-6Al-2Sn-4Zr-2Mo, Inconel 718, Ti-8Mo-8V-2Fe-3Al, and, AISI 4340 at various forging temperatures. The ring-compression test is used to determine the flow stress of 6061 aluminum, Ti-7Al-4Mo, 403 stainless steel, Waspaloy, 17-7 PH stainless steel, Ti-6Al-4V, Inconel 718, Ti-8Al-1Mo-V, 7075 aluminum, and Udimet 700 alloy at forging temperatures. All the tests were conducted, at practical deformation rates encountered in forging, on an instrumented high-speed forging press. For the same material and at similar temperature and deformation-rate conditions, the data obtained from the uniform-compression and ring-compression tests were compared. It was found that the results obtained with rings 3-in. O.D., 1.5-in. ID and 1 in. high were practically identical to those obtained from the isothermal uniform-compression tests conducted with samples 1-in. dia and 1.5 in. high.
Platelike Dynamic Vibration Absorbers
Authors: Snowdon J. C.
Published: November 2010

Platelike dynamic vibration absorbers of novel design are described, and optimum values of their tuning and damping parameters are specified in graphical form. The dynamic absorbers are assumed to comprise either a circular or an annular damped plate that is loaded at its outer perimeter by a rigid annular mass. The plates, which act as combined “spring-and-damper” components for the absorber systems considered, are attached either at their midpoint or around their inner perimeter to the vibrating item or structure of concern. The platelike absorbers are shown to be very effective in suppressing the transmissibility at resonance (1) across a mass-spring vibrator, and (2) across circular and rectangular plates that have small internal damping and that are used to simulate bulkheads and panels. The platelike absorbers have the advantages of mechanical simplicity and planar geometry for compact flush-mounted application.
An Automated Method for Dynamic Analysis of Spatial Linkages for Biomechanical Applications
Authors: Langrana N. A. , Bartel D. L.
Published: November 2010

A computer-aided analysis procedure is developed to obtain biomechanical information for unassisted and assisted upper extremity systems. An automated assembly procedure is derived which determines the equations of motion for a linkage consisting of N links connected by ball and socket joints and/or pin joints. Springs may be attached between the links or between the links and ground. The major advantage of this procedure is that the lengthy and time-consuming derivations required to obtain the equations of motions using other methods are eliminated. The procedure automatically writes the equations of motion based on the input data alone. Changes in the linkage being analyzed require changes in input data; the basic program does not have to be modified. In particular the basic program does not depend upon the nature of the links or the types of joints.
Two Jeffcott-Based Modal Simulation Models for Flexible Rotating Equipment
Authors: Childs Dara W.
Published: November 2010

Two transient modal simulation models are presented based on the Jeffcott-Green flexible-rotor formulation. One of the models is based on the conventional “non-spinning” formulation, while the second employs a rotor fixed formulation. Numerical results are presented for these two basic models for the SSME (Space Shuttle Main Engine) turbopumps. The results presented demonstrate that either of the basic formulations is a computationally efficient simulation approach for a flexible rotor, which is to be modeled by a large number of rigid bodies. They also demonstrate that the models can readily account for an arbitrary number of bearings having nonlinear or speed-dependent characteristics, and for the motion of the bearing support structure. The results presented demonstrate that the rotor-fixed formulation generally requires less computer time than does the conventional formulation. Moreover, the modal cordinate solutions in the rotor-fixed formulation provide a significantly clearer picture of potential flexible-rotor-instability problems.
System Identification of the Machining Process
Authors: Milner D. A.
Published: November 2010

This paper describes an identification method for determining the transfer function of a system by the use of a computer program. Frequency response data is obtained by the use of a Digital Transfer Function Analyzer and, by on- or off-line computing, the transfer function of the desired system is obtained.
Some Properties of Mechanically-Traceable Algebraic Loci
Authors: Fichter E. F. , Hunt K. H.
Published: November 2010

A number of theorems interrelating certain properties of the algebraic loci traced by some mechanisms are presented. The properties discussed are the algebraic-geometric concepts of order, class, and rank, which are here shown to be related to one another by some new theorems based entirely on the kinematic geometry of the mechanisms. These theorems lead to a better understanding of the geometric relationships both within a mechanism and between different mechanisms. The theorems are also useful in some cases for determining these algebraic-geometric properties.
On the Application of Response Limiting to Finite Element Structural Analysis Programs
Authors: Curtis A. J.
Published: November 2010

The inclusion of response limiting or “notching” in random vibration design and test requirements for larger equipments such as spacecraft is becoming more commmon. This type of requirement states that the specified input excitation, usually motion, may be reduced in narrow frequency bands to the degree necessary to limit the response at any of a number of specified locations to a specified maximum response. Laboratory test procedures to implement such requirements have been developed and described in the literature. Clearly it is also desirable to include such notching during the design analysis stage when using finite element structural analysis programs typified by NASTRAN. Exact computation of the notched input excitation and associated system responses is quite complicated and therefore costly. This paper describes a simple, economical method of computing the notched spectrum using an approximation which relies only on reasonably separated peak responses at any response control node and a not unusually small difference in level between the maximum input and maximum response spectral density levels. The method accounts for the modal damping, the specified averaging bandwidth for response control, and any desired number of response control nodes, i.e., locations. An interesting by-product of the analysis was the determination that only 50 percent of the mean square response of a single d.o.f. system to white noise is due to the excitation within the resonant or 3 db bandwidth of the system. Some of the implications of this result with respect to spectral analysis procedures and popular methods of estimating the response of systems to shaped random vibration spectra are discussed.
An Improved Direct Search Mathematical Programming Algorithm
Authors: Pappas M. , Moradi J. Y.
Published: November 2010

An improved, nonlinear, constrained algorithm is presented, coupling a rotating coordinate pattern search with a feasible direction finding procedure used at points of pattern search termination. The procedure is compared with eighteen algorithms, including most of the popular methods, on ten test problems. These problems are such that the majority of codes failed to solve more than half of them. The new method proved superior to all others in the overall generality and efficiency rating, being the only one solving all problems.
Active Synchronization Control of the Gyroscopic Vibration Absorber
Authors: Sneckenberger J. E. , Clise R. A.
Published: November 2010

Active synchronization control of the gyroscopic vibration absorber is experimentally investigated to provide efficient transition between steady-state synchronization conditions. One open loop and two feedback loop synchronization control systems were designed, developed, and experimentally tested for their ability to quickly and smoothly maintain a nulled condition for an experimental structure-GVA system during transient synchronization. Maximum structural amplitude and resynchronization time were descriptive parameters of structure-GVA behavior used to compare the effectiveness of the three active synchronization control systems.
Design of Semiautomatic Standardizing Machines for Load Cells Testing
Authors: Morecki Adam , Narkiewicz Wiktor , Townsend M. A.
Published: November 2010

The paper deals with the systematic synthesis of semiautomatic standardizing machines used for load cells testing. The principal requirements are formulated and an evolutionary (such as followed in optimal design) is given. Of special note is the extreme accuracy required (0.01 percent) and acheived in a relatively large mechanical system. The paper includes some results of analyses made for two types of machines and data obtained from tests and long-term utilization of these machines.
Initial Curvature and Lateral Load Effects on Thin Struts With Large Elastic Displacements
Authors: Na T. Y. , Kurajian G. M.
Published: November 2010

Employing perturbation techniques, the problem of a thin strut experiencing large deflections which is treated in two previous papers by the authors, [1] and [2], is further examined for the effects of initial curvature and mid-span lateral load. Representative design tables and typical curves, embracing a selected range of realistic parameters for the complex cases, are included. Example problems are presented for demonstration and clarification.
Design Coefficients for Rings Loaded Out-of-Plane
Authors: Houtman J. L.
Published: November 2010

This article provides the solution to twelve cases of a ring loaded out of its plane. Each solution may be combined with the others so that many different loading cases may be solved from these twelve. Three sets of nondimensional coefficients are presented in the tables to permit the rapid calculation of forces and deflections as a function of the angle α around the ring circumference. Each set of coefficients is for a different value of the parameter ρ, the ratio of bending stiffness EI to torsional rigidity KG. Therefore, any ring with a value of ρ other than 1.3, 10, and 100 can be analyzed by simply interpolating between the tabular values at any angle α. Two cases (cases 9 and 11) involving sinusoidal torsional moment distributions, several combinations of simpler cases, and some classical out-of-plane cases are included in these tables.
On the Behavior of Statistical Models Used for Design
Authors: Wirsching P. H.
Published: November 2010

In probabilistic design, it is common practice to use two parameter statistical models (e.g., normal, lognormal) to describe random design factors. However, given a random sample of data, it is often difficult to distinguish which of several competing models provides the best description. It is demonstrated herein that the choice of model has a profound effect on probability estimates, particularly in the tails of the distributions. Given only the mean and standard deviation of a random variable, the Tchebycheff or Camp-Meidell inequalities can be used to provide upper-bound estimates of probabilities. However, these inequalities are usually too weak for design purposes. Probability models which yield more reasonable results are proposed. The two parameter exponential and power models are proposed for quasi-upper bounds of right and left tail probabilities, respectively. The exponential and power models are used for stress and strength, respectively, to derive, from inference theory, quasi-upper bounds for probability of failure of a structural element.
The Effect of Certain Machine Parameters and Fiber Preparation on the Properties of Open-End Cotton Yarns
Authors: Vaughn E. A. , Hiranprueck T.
Published: November 2010

Cotton yarns of 32.81 tex with a twist multiplier of 4.0 were spun using six different drafts ranging from 86.54 to 140.63 on a Suesson Open-End Spintester from slivers that had been carded with and without crushrolls. The static pressure in the spinning chamber was held at two levels equivalent to 7.9 × 10−5 and 5.8 × 10−5 Pa. The spinning was performed at turbine speeds of 30,000, 45,000, and 60,000 rpm. Trash extracted by the machine was weighed after each spinning condition. Statistical analyses of data collected from yarn physical tests were performed. Analyses of variance results and graphical presentations are given. The results of the investigation indicate that increasing turbine speed deteriorates yarn physical properties significantly, but also results in more trash extracted; lower drafts yield better yarn evenness and fewer imperfections, but result in less waste extracted than the higher drafts; static pressure in the spinning chamber equivalent to 7.9 × 10−5 Pa results in better yarn evenness and fewer imperfections, but also decreases the trash removal efficiency; and the use of crushrolls at carding slightly lowers the tensile properites of the spun yarn. With respect to trash extraction, the visible foreign matter content of the slivers was lowered by the use of crushrolls; the data normalized to the foreign matter content show only a small effect due to the use of crushrolls at carding on the trash extraction efficiency of the system.
Nonlinear Stresses and Deflections of Beams Subjected to Random Time Dependent Uniform Pressure
Authors: Seide P.
Published: November 2010

The nonlinear mean-square multimode response of beams subjected to uniform pressure uncorrelated in time is investigated. The method of equivalent linearization is used to obtain mean-square stresses and displacements in beams with arbitrary end conditions. Calculations are carried out for beams with both ends either simply-supported or clamped, for the case of white noise excitation. Although the maximum displacement can be obtained with the use of only a single-degree-of-freedom model, it is necessary to consider as many as 100 modal functions for accurate determination of the stresses. The maximum mean-square deflection of the clamped beam is found to be somewhat less than the simply-supported beam, whereas the maximum mean-square stresses are as much as twice as large.
Eccentric Limit Load on Fasteners
Authors: Fazekas G. A.
Published: November 2010

In eccentrically loaded joints, both the friction grip and the plastic yield strength can be found by the Pole Concept. Neither yield nor the full friction grip need to develop simultaneously in all fasteners, and this can lead to some singularities.
Modal Truncation of Substructures Used in Free Vibration Analysis
Authors: Tolani S. K. , Rocke R. D.
Published: November 2010

A unified approach to a group of structural dynamics analyses using the substructures technique and a consistent basis for the selection of substructure principal modes as required by this method are provided. Substructure frequency roots and strain energy in the principal modes are two criteria evaluated for the selection of substructure principal modes. Based on a simple example of a cantilever beam, it is noted that the substructure principal mode strain energy criterion provides slightly better results in terms of system eigenvalues and system strain energy in the principal modes. Errors in system eigenvalues and principal mode strain energy converge nonmonotonically as the number of substructure modes retained is increased. Since in actuality, these errors are not known, expressions for their estimates are presented. It is seen that modal truncation errors in system strain energy can be better estimated in comparison to the system eigenvalue errors. The substructure approach applied to solve an initial conditions problem indicates that the process of modal truncation depends to some extent on the type of initial conditions prescribed for the structure.
Surface Integrity in Machining AISI 4340 Steel
Authors: Bailey J. A. , Jeelani S. , Becker S. E.
Published: November 2010

The effect of cutting speed and tool wear land length on the surface integrity of quenched and tempered AISI 4340 steel machined under dry, unlubricated orthogonal conditions is determined. The surface region of machined test pieces is examined using optical microscopy, scanning electron microscopy, X-ray microprobe analysis, microhardness measurements, and profilometry. In addition, tool forces are measured and tool temperatures calculated. The results of the investigation show that during machining a damaged surface region is produced which is quite different from the bulk of the material. It is found when cutting at low speeds with sharp cutting tools that the damage is restricted to a variety of geometrical defects associated with the surface. It is found when cutting at high speeds or with tools having large artificially controlled wear lands that considerable subsurface damage involving changes in metallurgical structure and hardness is produced. The results are interpreted in terms of the type of chip produced during machining, the temperatures generated during machining, and the interaction between the tool nose region and workpiece. It is suggested that observations based on scanning electron microscopy are more indicative of the true surface condition than surface roughness measurements.