bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-Step Process Identification With Correlation Analysis and Least-Squares Parameter Estimation
Authors: Isermann R. , Bauer U.
Published: November 2010

An identification method is described which first identifies a linear nonparametric model (crosscorrelation function, impulse response) by correlation analysis and then estimates the parameters of a parametric model (discrete transfer function) and also includes a method for the detection of the model order and the time delay. The performance, the computational expense and the overall reliability of this method is compared with five other identification methods. This two-step identification method, which can be applied off-line or on-line, is especially suited to identification by process computers, since it has the properties: Little a priori knowledge about the structure of the process model; very short computation time; small computer storage; no initial values of matrices and parameters are necessary and no divergence is possible for the on-line version. Results of an on-line identification of an industrial process with a process computer are shown.
Fidelity of Mechano-Electric Transduction by the Labyrinthine Receptor Systems
Authors: Trincker D. E. W.
Published: November 2010

The mechanosensitivity of the receptors in the nonacoustic part (vestibular end organs) of the guinea pig’s inner ear was studied by microelectrode recordings. These receptors are directionally sensitive displacement detectors. Shearing force, i.e., the component of mechanical force, acting tangentially on the surface of the sensory cell layer, was proven to be the effective stimulus. Its characteristic curve is a sinusoidal function representing the information input. This holds for the statolith apparatus (utricle and saccule as organs of equilibrium) when tilting of the head occurs in one or the other direction. An almost identically sinusoidal characteristic curve was obtained by measuring d-c potentials (receptor potentials) inside the sensory cell layer of the macula utriculi. The significant fact is the bidirectional response to tilting: inclination in one direction produces depolarization, and in the opposite direction gives hyperpolarization. Corresponding results were obtained from the macular nerve twigs. Most of the units show reasonably constant resting discharge; tilting in one direction increases, and in the opposite direction decreases, the nerve action-potential frequency. This impulse frequency represents the information flow to the central nervous system. In the other part of the vestibular organs, the semicircular canals, the mechanical behavior of the coupled system cupula-endolymph can be described in terms of a highly damped torsion pendulum. The time course of mechanical stimulus, and that of nervous excitation at the different levels of the peripheral and central systems, was studied, during deflexions of the cupula, by recording the potential changes inside the sensory cell layer of the cristae ampullares. When a sudden mechanical event acts as stimulus, the central systems get a very true image of its time course.
A Suboptimal Method for Feedback Control of the St. Louis Econometric Model
Authors: Healey A. J. , Summers S.
Published: November 2010

In this study, the econometric model used by the Federal Reserve Bank of St. Louis to provide information on the most likely movement of strategic economic variables in response to monetary and fiscal actions is viewed as a control system. Government expenditure is viewed as an uncontrolled disturbance, while change in the money stock is viewed as the input control variable. Quarterly change in the money stock is treated as a linear function of errors in economic variables from established target values. A numerical gradient scheme is then applied to the proportionality constants of the function so as to minimize a quadratic performance index. Throughout the study, the nonlinear system equations are retained. The results of this study indicate that automatic control of the money stock by this method would have improved the nation’s economy over the last fifteen years.
A Note on Matching of Electromagnetically Damped Galvanometers
Authors: Markho P. H.
Published: November 2010

To a new user of an ultraviolet recorder, the matching of the associated galvanometers presents an awkward problem mainly due to a general lack of adequate information on the subject. With this in mind, the author presents, in this note, easy-to-follow guidelines together with a worked example.
Bond Graph Junction Structures
Authors: Perelson A. S.
Published: November 2010

The relationship between the port constitutive equations of a bond graph junction structure and the constitutive equations of its individual junctions is investigated. By combining network, bond graph, and graph theoretic techniques, the roles of bond orientation and causal assignments in determining when internal bond variables may be eliminated are examined. Graphical criteria are proven for establishing when a junction structure is an n-port.
A Fluidic Bridge Gas Concentration Sensor Applicable to Respiratory Gases
Authors: Woods R. L. , Villarroel F.
Published: November 2010

This paper describes a flueric gas concentration sensor potentially suitable for determining the concentration of carbon dioxide in respiratory gases. The sensor consists of fluid resistors connected in a bridge circuit and generates a differential pressure signal proportional to the concentration of CO2. The sensor is capable of measuring from 0.07 to 100 percent CO2 in air. The system discussed in this report contains a high-gain laminar proportional amplifier to produce high-level output signals. The amplified sensitivity of the prototype system is 0.6 kPa/percent CO2 (0.09 psi/percent CO2). The experimental results are in agreement with the theoretical analysis and show good linearity and low noise.
On the Design of Adaptive Servosystems
Authors: Tomizuka M.
Published: November 2010

This paper deals with tracking problems in which the plant is single-input single-output and the desired trajectory (command signal) is regarded as the output of an unknown free dynamical system. Two procedures are presented for designing adaptive servosystems which enable the plant output to follow the command signal with zero ultimate tracking error. The first procedure uses a pole assignment method and the second utilizes a result of optimal control. An illustrative example is given, and the effectiveness of the adaptive servosystem is verified by computer simulation.
Generalization of Adaptive Observer and Method of Optimizing Its Convergence Properties
Authors: Kim C. H. , Lindorff D. P.
Published: November 2010

This paper concerns a generalization of the design of the adaptive observer, and an investigation of its convergence properties. By application of hyperstability theory the design freedom is enlarged to permit use of time variable adaptive gains. Based on the assumption of periodic excitation, and with the aid of Floquet Theory a new convergence criterion is defined. By this means the effects of adaptive gains and input frequencies upon convergence time are evaluated. Structural properties of the adaptive observer are compared with other adaptive schemes, in particular with regard to bias due to noise.
Predicting Response of a Proposed Hydraulic Control System Using Bond Graphs
Authors: Barnard B. W. , Dransfield P.
Published: November 2010

Dynamic response is an important criterion of quality for many hydraulic control systems. It is suggested that power flow modeling procedures, and in particular the recent development of power bond graph techniques, provide the designer-analyst of hydraulic control systems with a particularly relevant means for investigating dynamic performance as he designs a proposed system. The bond graph modeling technique followed by digital simulation of the model is applied to a hydraulic system proposed for a particular task. Predicted response and subsequently measured response are given, compared, and discussed. Only generally available data and parameter assessment procedures were used for the prediction.
On the Transition of a Shaft Through Critical Speeds
Authors: Naveh B. M. , Brach R. M.
Published: November 2010

The motion of an eccentric rotating shaft and disk is studied for an exponential transition of the angular velocity (spin rale) through a critical speed. An analytical solution is found for the response, and it is shown that this response can yield higher amplitudes when compared to previous work where the angular velocity is varied linearly.
Simulation of Bond Graphs on Minicomputers
Authors: Van Dixhoorn J. J.
Published: November 2010

A need exists for inexpensive interactive simulation of nonlinear bond graphs. It is shown how existing block diagram oriented simulation languages can easily be adapted to accept bond graphs freely mixed with block diagrams. Procedures are stated for writing the input structure table and for remedying some often occurring causal conflicts and algebraic loops. Examples are given of hands-on simulation using the THTSIM language, written for PDP-11 minicomputers.
Vehicle-Follower Longitudinal Control for Automated Transit Vehicles
Authors: Caudill R. J. , Garrard W. L.
Published: November 2010

This paper examines the effects of spacing policy and control system nonlinearities on the dynamic response of strings of automated transit vehicles operating under automatic velocity and spacing control. Both steady-state and transient responses are studied. Steady-state response is examined by a modification of the describing function technique and transient response is studied by Liapunov procedures. It is shown that a nonlinearity commonly encountered in automated transit vehicles, a limiter on acceleration and deceleration, can result in string instabilities even though a linearized analysis indicates that the string is stable. Although this paper is specifically focused on automated transit systems, some of the results obtained also appear to be applicable to strings of automobiles on freeways.
An Analytical and Experimental Study of Automobile Dynamics With Random Roadway Inputs
Authors: Healey A. J. , Nathman E. , Smith C. C.
Published: November 2010

This paper presents the results of an analytical and experimental study of ride vibrations in an automobile over roads of various degrees of roughness. Roadway roughness inputs were measured. Three different linear mathematical models were employed to predict the acceleration response of the vehicle body. The models used included two, four, and seven degrees of freedom, primarily for vertical direction motion. The results show that the prime source of errors in predicting responses of this type lies in the common assumptions made for roadway roughness spectra. With adequate description of the roadway inputs, the results showed that the seven degree of freedom model accurately predicted the low frequency response (up to 10 Hz). Using the seven degree of freedom model, predicted accelerations compare well with measured data for a wide range of roadways in the low frequency range. Higher frequency components in the measured acceleration response are significant and are illustrated here.
Conical Acrylic Windows Under Long Term Hydrostatic Pressure of 20,000 Psi
Authors: Stachiw J. D.
Published: November 2010

Conical acrylic windows with cone angles 30 deg ≤ α ≤ 150 deg have been subjected to sustained hydrostatic pressure of 20,000 psi for up to 1,000 hr duration. The thickness to minor diameter ratio (t/D) of the more than 200 windows varied from 0.750 to 2.000. Model scale windows served as the bulk of test specimens, and the majority of the tests were conducted at room temperature. Test findings indicate that only windows with t/D > 1 and cone angle α ≥ 60 deg will not fail in less than 1,000 hr of sustained hydrostatic loading although considerable cracking will take place. For optically acceptable service of 1000 hr duration under 20,000 psi hydrostatic pressure, the windows must have t/D ≥ 2 and a cone angle α ≥ 90 deg. The axial displacements of such windows after 1000 hr of hydrostatic loading at 20,000 psi, are approximately 0.1 times their minor diameter, with approximately 50 percent of this displacement taking place during the first hour of pressure application.
Effect of Residual Stresses on the Low Cycle Fatigue Life of Large Scale Weldments in High Strength Steel
Authors: Cordiano H. V.
Published: November 2010

A determination was made of the influence of various mechanical finishing procedures on residual stresses and the resulting effect on the low cycle fatigue life of tee-fillet welds in 1-1/2 in. thick rolled steel plate with a yield strength of 80,000 psi. Included in this work were tee-fillet welds in the as-welded, ground, shot-peened, ground and shot-peened, and mechanically peened condition. Residual stresses were measured by a hole drilling technique developed at the Naval Applied Science Laboratory for application to linearly varying biaxial stress fields. This method has been found suitable for determining residual stresses at any point over a limited area at the toe of the weld. Fatigue tests were conducted on plate type specimens, 32 in. by 29 in. by 1-1/2 in. which were simply supported at two edges, free at the other two edges, and uniformly loaded with compressed air to develop a zero to maximum tension range of stress at the toe of the fillet weld. It was found that tensile residual stresses do not have a significant effect on fatigue life for the type of pulsating load used. Compressive residual stresses have been found to have a beneficial effect on fatigue life. Welds with relatively high residual stresses which were ground smooth to eliminate “stress raisers” showed very good fatigue resistance.
A Method of Relating Factor of Safety and Reliability
Authors: Mischke C.
Published: November 2010

A formal relationship between factor of safety and reliability is presented. Inasmuch as most engineering application will not economically justify the necessary experimental work to successfully implement the formal approach, a method for making conservative decisions based upon Bienayme-Chebyshev and Camp-Meidell theorems is offered. This step-by-step procedure reminds the engineer of the influence of each piece of information relating to strength and loading upon his factor of safety decision. The potential gain (reduction of weight, cost, etc.) can be compared to the cost of the experimental program necessary to establish modality, skewness, or symmetry.
Unique Descriptions of All Spherical Four-Bar Linkages
Authors: Savage Michael , Hall A. S.
Published: November 2010

A notation is presented which produces a complete set of unique mathematical models for the spherical four-bar linkage. The completeness of the set and the uniqueness of the models are proven. Its significance is illustrated, by the direct application of Grashof’s gross-motion classification law to the spherical four-bar linkage. The validity of this application is proven.
Evaluation of the Effects of Design Variables on Drill Temperature Responses
Authors: DeVries M. F. , Wu S. M.
Published: November 2010

The effect of five design and three operating variables on three different drill temperature responses is investigated. A total of 512 observations was made using a replicated two-level factorial design. Problems associated with the selection of the temperature responses are studied including the transient nature of the response, the location of the thermocouple, and the interrelationship of the workpiece volume and drill wear. The five drill design variables are web thickness at point, margin width, relative lip height, helix angle, and surface condition, of which the helix angle and web thickness at point had the most significance within the experimental range. The effect of two-factor interactions was also discussed.
Determination of the Pressure Drop Optimum Pipe Size for a Two-Phase Slug Flow in an Inclined Pipe
Authors: Singh G. , Griffith P.
Published: November 2010

A simple model of two-phase slug flow in inclined pipes is proposed. The model parameters are determined experimentally using five different size copper pipes at 5, 10, 15 deg inclinations on an air-water mixture at one atmosphere with up flow. The model predicts the total pressure gradient due to the sum of gravity and wall shear stresses. An investigation of the relationship between pressure gradient and pipe size results in an optimum pipe size at which the pressure gradient is minimum. A comparison between the simplified model predictions and experimental measurements shows a good agreement in the total pressure drop.
Elastoplastic Collapse of Tubes Under External Pressure
Authors: Heise O. , Esztergar E. P.
Published: November 2010

The specific objective of this paper is to develop external pressure design safety factors that are consistent with theory, test results, and service experience for application in pressure vessel codes. The standard methods of collapse pressure predictions for the buckling of tubes in the elastic and the plastic ranges are briefly reviewed. Test results on tubes made of various materials were collected from the literature and are compared with the corresponding predictions. For thin tubes which buckle in the elastic range, the correlation between the theory and experimentally measured collapse pressure is shown to be poor, justifying the large safety factors used in current design practice. For intermediate and thick tubes which buckle in the plastic range, it is demonstrated that the correlation of test results and theory improves significantly with decreasing radius-to-thickness ratio of the tubes. The range of improved correlation is identified by a material dependent “characteristic ratio” of tube radius and wall thickness. Based on the experimental evidence, a variable safety factor is proposed for inclusion in the ASME Code design charts. A simple formula for the conversion of the present plastic range allowable pressure into the new increased allowable pressure is presented. The consequences of the variable safety factor are discussed with respect to the resulting actual margin of safety, the economic advantages, and the requirements for the development of design rules for the creep range.
Analysis of Shells of Revolution Formed of Closed Box Section
Authors: Zudans Zenons , Gregory Frederick H.
Published: November 2010

An exact analysis method is presented for shells of revolution formed of closed box sections. A consistent shell theory is used to develop the differential equations of the shell which in turn are solved by the use of numerical integration. A new method is introduced to generate a symmetrical stiffness matrix from the numerically obtained exact displacement functions. While the exact solution is generated at all times, the highly developed finite element numerical techniques are shown to be immediately applicable.
Closed-Form Displacement Relations of a Five-Link R-R-C-C-R Spatial Mechanism
Authors: Soni A. H. , Pamidi P. R.
Published: November 2010

Using (3 × 3) matrices with dual-number elements, closed form displacement relationships are derived for a spatial five-link R-R-C-C-R mechanism. The input-output closed form displacement relationship is an eighth degree polynomial equation. A numerical example is presented.
On the Use of the Undulating Elastica for the Analysis of Flexible Link Mechanisms
Authors: Shoup T. E. , McLarnan C. W.
Published: November 2010

The equations of the undulating elastica describing the static behavior of an end-loaded flexible strip include forces, elastic properties, dimensions, and some parameters which are not physically measurable. This paper presents techniques whereby the designer can determine reasonable first approximations to the parameters contained in the equations of the undulating elastica. These first approximations are particularly useful for the iterative solution of the equations for the force or motion analysis of flexible link mechanisms containing one or more members that undergo large elastic deflections. Examples of the application of these techniques are presented.
Elastic Link Mechanism Dynamics
Authors: Winfrey R. C.
Published: November 2010

An improved mathematical model of a mechanism is described whereby the elastic deformations of its links are determined. A method of solving for these deflections is presented along with examples of the elastic behavior of both plane and space mechanisms. Finally, the dynamic forces in a mechanism are discussed and one example given.
Determination of Force-Balanced Four-Bar Linkages With Optimum Shaking Moment Characteristics
Authors: Lowen G. G. , Berkof R. S.
Published: November 2010

A technique is developed for applying a previously derived shaking moment optimization theory for force-balanced four-bar linkages. To this end, a standard linkage configuration is introduced. In addition, the RMS dimensionless moment is formulated as a means of comparing the moment characteristics of different mechanism families.
Analyses of Axisymmetric Upsetting and Plane-Strain Side-Pressing of Solid Cylinders by the Finite Element Method
Authors: Lee C. H. , Kobayashi Shiro
Published: November 2010

Detailed studies of the deformation characteristics in axisymmetric upsetting and plane-strain side-pressing were attempted by the finite element method. Solutions were obtained up to a 33 percent reduction in height in axisymmetric upsetting and up to a 19 percent reduction in height in side-pressing, under conditions of complete sticking at the tool-workpiece interface. Load-displacement curves, plastic zone development, and strain and stress distributions were presented, and some of the computed solutions were compared with those found experimentally.
Frictional Characteristics of Oxide-Treated and Untreated Tungsten-Carbide Tools
Authors: Suh N. P. , Sanghvi B. J.
Published: November 2010

The role of surface oxide layers in the tungsten carbide tool wear was investigated by treating the tools with titanium dioxide and by performing friction tests. The friction tests were performed using both the oxide-treated and untreated tools at various temperatures, loads, and sliding speeds. The oxide-treated tools were prepared by coating tungsten-carbide tools with titanium dioxide and heating them to temperatures above 1525 deg F in a vacuum of 10−4 torr to induce mass diffusion. The oxide-treated tools which contained titanium, tantalum, and niobium in addition to tungsten carbide and cobalt have higher hardness and lower coefficient of friction, especially at high temperatures. Structural changes take place at the subsurface layer during the oxide treatment, which lower the coefficients of friction of the tool and enhance the steel cutting properties of tungsten-carbide tools.
Vibrations of Elastic Connecting Rod of a High-Speed Slider-Crank Mechanism
Authors: Jasinski Peter W. , Lee Ho Chong , Sandor George N.
Published: November 2010

The research involved in this paper falls into the area of analytical vibrations applied to planar mechanical linkages. Specifically, a study of the vibrations, associated with an elastic connecting-bar for a high-speed slider-crank mechanism, is made. To simplify the mathematical analysis, the vibrations of an externally viscously damped uniform elastic connecting bar is taken to be hinged at each end (i.e., the moment and displacement are assumed to vanish at each end). The equations governing the vibrations of the elastic bar are derived, a small parameter is found, and the solution is developed as an asymptotic expansion in terms of this small parameter with the aid of the Krylov-Bogoliubov method of averaging. The elastic stability is studied and the steady-state solutions for both the longitudinal and transverse vibrations are found.
The Damping Effects of Viscoelastic Materials: Part 1—Transverse Vibrations of Beams With Viscoelastic Coatings
Authors: Baumgarten Joseph R. , Pearce Britt K.
Published: November 2010

An energy method similar to Rayleigh’s method is employed to analyze a nonhomogeneous, damped beam composed of an elastic (metal) layer and an unconstrained viscoelastic layer. This analysis is limited to the case of thin free-free beams vibrating freely in the fundamental mode. The theory developed enables one to predict the damped natural frequency and the rate of decay (in terms of logarithmic decrement) of the transverse vibrations of a composite beam of given dimensions and composed of two particular materials. Experimental measurements bear out the fact that theoretical predictions are indeed accurate. Beams with two symmetric elastic coatings are also considered and their damping effects are compared to those of coating applied to one side only.
Time Domain Optimization of a Vibration Absorber
Authors: Bartel Donald L. , Krauter Allan I.
Published: November 2010

This paper considers two design problems involving the transient vibrations of a dynamic vibration absorber. The design objective of the first problem is to minimize the maximum force transmitted between masses in an absorber system. In the second problem the time required for energy dissipation is minimized. The design objectives and the associated constraints are formulated as mathematical programming problems. The solutions are obtained numerically using a method of constrained steepest descent with state equations. The design procedure presented is general and can be applied to optimization problems involving more complex systems.
Analysis of Radiation-Induced Embrittlement Gradients on Fracture Characteristics of Thick-Walled Pressure Vessel Steels
Authors: Loss F. J. , Hawthorne J. R. , Serpan C. Z. , Puzak P. P.
Published: November 2010

The fracture behavior of thick-walled nuclear vessels is considered for the case of a radiation-induced toughness gradient through the wall which characteristically results from neutron attenuation by the wall material itself. Fracture-safe design analyses based on linear elastic formulations or extrapolations of these formulations to the elastic-plastic regime are not sufficiently developed to characterize the integrated behavior of a wall whose toughness can range from brittle at the inner surface to highly ductile at the outer surface. Solutions to the problem in the foreseeable future will be obtained only by experimental means. The present approach uses the Fracture Analysis Diagram (FAD) together with a new interpretative method for fracture extension resistance based on modified dynamic tear specimens as the tools for gradient assessments. With these techniques the significance of the toughness gradient through the wall is assessed in terms of thick section mechanical constraint, and fracture characteristics of the complete wall are predicted. Characterization of a hypothetical 8-in. vessel wall is based on measured through-thickness fluence levels; this behavior is correlated with fracture toughness degradation for steels of varying sensitivity to irradiation using the FAD. This analysis indicates that major portions of the vessel wall remain above the FTE temperature, which dictates yield stress loading requirements for fracture, when the wall temperature is maintained at the limiting value, NDT + 60 deg F, for the inside surface as suggested by current AEC criteria. Fracture extension resistance measurements based on data from a 3-in. thick plate having a metallurgically induced toughness gradient suggest that nuclear vessels with analogous gradients will not fracture in an unstable fashion and will not generate missiles capable of breaching the containment system. Additional research is necessary to fully develop the approach for application to the individual reactor vessel.
Study of the Distribution of the Life of HSS Tools
Authors: Wager J. G. , Barash M. M.
Published: November 2010

Numerous life tests carried out with high speed steel tools in machining low carbon steel indicate that tool life values are subject to a statistical distribution which can be approximated by the normal distribution with a coefficient of variation of about 0.3. Accelerated and normal tests show similar distribution patterns, which indicates a possibility for a wider use of accelerated tests. The conventionally accepted concepts of tool life “constant” and “exponent” should be considered only as representing statistical mean values which are not sufficient for the prediction of the life of any individual tool put to work. It is recommended that tool life predictions be made on a probabilistic basis, and the desired direction of further studies is indicated.
Mechanics of Tool-Workpiece Engagement and Incipient Deformation in Machining of 70/30 Brass
Authors: Weinmann K. J. , Von Turkovich B. F.
Published: November 2010

In this paper, studies of incipient chip formation when cutting annealed 70/30 brass under orthogonal conditions are presented. Cutting forces were recorded and changes in deformation occurring in the workpiece were investigated for slow velocity transient cuts involving different rake angles. The deformation was observed by means of micro-hardness plots and recrystallization photomicrographs. Stresses on the apparent tool-work contact area were calculated.
The Wear of Grinding Wheels: Part 1—Attritious Wear
Authors: Malkin S. , Cook N. H.
Published: November 2010

An investigation of attritious and fracture wear of grinding wheels in precision grinding is described in a two paper sequence. Attritious wear, the subject of this first paper, refers to the dulling of the abrasive grain due to rubbing against the workpiece surface. The amount of dulling, measured by the area of the wear flats on the surface of the wheel, is found to be directly related to the grinding forces. In general, both the vertical and horizontal grinding force components increase linearly with the wear flat area. This is explained by considering the grinding force as the sum of a cutting force due to chip formation and a sliding force due to rubbing between the wear flats and workpiece. Related studies of wheel dressing, surface finish, and workpiece burn are also presented.
The Wear of Grinding Wheels: Part 2—Fracture Wear
Authors: Malkin S. , Cook N. H.
Published: November 2010

The nature and extent of grinding wheel wear in precision grinding were investigated directly from the wear particles removed from the wheel. A statistical analysis of the wear particle size distributions was developed to determine the relative amounts of bond fracture, grain fracture, and attritious wear. Most of the wear consists of grain and bond fracture particles with relatively more bond fracture occurring with softer wheels. The rate at which fracture wear occurs is directly related to the grinding forces and the amount of binder in the wheel. The attritious wear, although contributing insignificantly to the total, is the most important form of wear as it is directly related to the size of the wear flats, grinding forces, and workpiece burn, and therefore controls grain and bond fracture wear.
Friction-Instability: A New Design Parameter for Brakes
Authors: Starkey W. L. , Foster T. G. , Marco S. M.
Published: November 2010

A new design parameter, friction-instability, is defined in this paper. Friction-instability is a variation in the coefficient of friction which may occur at any time during the life of a brake lining. A friction-index is defined which measures this variation. A lining which has a high friction index may tend to cause an automobile to swerve either to the right or to the left. A unique experimental facility is described by means of which the friction-instability characteristics of brake linings can be measured. Test results using this facility are presented and interpreted. The friction-index is proposed as a new parameter which should be taken into consideration when brakes are designed and, developed. This index should be particularly useful as a quality control device to insure that machines which use mass-produced braking systems will perform in a safe and effective manner.
A New Method of Screw Strength Calculation
Authors: Popper J. B.
Published: November 2010

By considering several factors usually neglected, a more realistic picture of screw strength is obtained. These are: thread geometry, combined tensile and shear stresses, and uncertainty in the exact value of the friction coefficient. This uncertainty increases the tightening torque necessary to obtain a required tensile load, and reduces the effective screw strength considerably. Taking all these factors into account, the calculated screw strength is much smaller, but more realistic, so that smaller safety factors can be employed, yet more reliable designs obtained. The equations derived point the way towards two methods for increasing screw strength. These are: use of preload-indicating washers; and turning the screw back by a certain amount after the initial tightening. The first method alone can double the usable screw strength.
Thermal Buckling and Snapping of a Circular Ring
Authors: Burgreen David
Published: November 2010

An analysis is made of the thermal buckling of flat rings and of shallow conical rings which are subjected to an axisymmetric temperature distribution. It is found that flat rings can buckle when there is a radial temperature variation only. Conical rings are subject to instability and snapping in the presence of either an axial temperature variation alone, or a combined axial and radial temperature variation, of the proper magnitude. Expressions are developed which give the temperatures at which buckling and snapping take place, as well as the temperature over-lap in a full thermostatic cycle of increasing and decreasing temperatures. Bimetallic conical rings at uniform temperature are examined, and snapping temperatures are determined for this type element.
The Stress Analysis of Plates With Single and Clustered Nozzles by the Boundary Point Least Squares Method
Authors: Hulbert L. E. , Hopper A. T. , Rybicki E. F.
Published: November 2010

This paper describes a method for determining the stresses and displacements in structures consisting of a flat plate with one or two nozzles attached normal to the plane of the plate. The analysis procedure can be viewed as the solution of three interdependent subproblems: (a) the stress analysis of the nozzle, (b) the plane-stress analysis of the plate membrane problem, and (c) the analysis of the transverse bending deformation in the plate. The solutions of these three problems are interrelated in the total solution through continuity and equilibrium conditions at the nozzle-plate interface. The paper describes the numerical techniques employed, and discusses some typical results obtained.
The Coupled Bending—Bending Vibration of Pre-Twisted Tapered Blading
Authors: Carnegie W. , Thomas J.
Published: November 2010

The work of this paper deals with the coupled bending–bending vibration of pre-twisted tapered cantilever blades. The equations of motion are established for a beam tapered in width (or depth) only and for a blade tapered in both width and depth. The equations are solved to obtain the frequencies and modal shapes and the theoretical results are compared with corresponding experimental values. Close agreement is obtained between the calculated and measured results. It is shown that taper has a considerable influence on both the frequencies of vibration and the associated modal shapes.
Shear Front-Lamella Structure in Large Strain Plastic Deformation Processes
Authors: Black J. T.
Published: November 2010

The examination of the surface morphology of copper, aluminum, and steel chips produced by standard shop machining processes through the use of scanning electron microscopy has led to a more fundamental understanding of large strain plastic deformation processes. The interpretation of these findings is discussed in terms of well documented dislocation mechanisms typically associated with tensile and compression deformation of metal crystals. The effect that such investigations will have on the true understanding of the mechanisms involved in plastic deformation processes is noted.
Hydrodynamic Lubrication in Rolling of Thin Strips
Authors: Avitzur B. , Grossman G.
Published: November 2010

The process of thin strip rolling is analyzed considering the hydrodynamic lubrication effect. Hydrodynamic lubrication prevails when a film of lubricant fully separates the rolls from the strip. The conditions which produce hydrodynamic effects are the subject of this study. A dimensionless parameter, the Sommerfeld Number, is defined as a function of lubricant viscosity, roll velocity, strip thickness, and yield strength of the material. The critical Sommerfeld Number for occurrence of hydrodynamic lubrication is determined. Increasing lubricant viscosity and roll velocity or decreasing flow stress and strip thickness produce a larger Sommerfeld Number with an increased tendency for hydrodynamic effects. The thickness of the lubricant film and the velocity of the emerging strip are both determined as functions of the Sommerfeld Number, reduction in strip thickness, and of roll diameter. Graphical and numerical examples are presented.
An Investigation of Springback in Wire Products
Authors: Kruger J. B. , Palazotto A. N.
Published: November 2010

This paper attempts to develop a simple expression for springback in which material properties are considered through the use of the Ramberg–Osgood stress-strain equation. Since work has been carried out using wire specimens, two dimensional properties are assumed negligible. Comparison is made between theory and experimental results for various radii and angle of bends.
Optimum Design of a Four-Bar Linkage Whose Coupler Path Has Specified Extremes
Authors: Tranquilla M.
Published: November 2010

The synthesis problem of specifying the extremes of a coupler path of a four-bar linkage is presented. Equations are derived to specify that a precision point be an extreme of the coupler path. Other portions of the path are considered as well. Constraints are imposed which limit the width of the coupler path, the locations of the crankshaft and rockshaft, and which guarantee that the input crank will make a full revolution. This suggests using a mathematical programming technique (i.e., optimization) to solve the synthesis problem. A graphical method is developed to obtain an initial trial design for the mathematical programming technique. An example problem is then solved.
Transient Flexible-Rotor Dynamics Analysis: Part 1—Theory
Authors: Shen F. A.
Published: November 2010

A mathematical formulation for the analysis of the transient and steady-state flexible rotor dynamics has been developed. Newton’s Laws of Dynamics, as used here were found to be more direct and efficient than the alternate Lagrange energy approach. In addition, the influence coefficient technique, including both bending and shear flexibility of a rotor, is applied to correlate the load deflection effects between various rotor stations. The mathematical formulation considers the general nonaxisymmetric and nonsyn-chronous rotor motion which may result from the included in-phase and out-of-phase stiffness and damping functions at all bearing and rotor stations. Other rotor dynamic parameters considered are the rotor masses and mass moments of inertia and their eccentricities and misalignments. The effects of rotor drive and dissipative torque and the interaction between torsional and transverse motion are also included.
Should a Flexible Rotor Be Balanced in N or (N + 2) Planes?
Authors: Kellenberger W.
Published: November 2010

The problem of balancing flexible rotors consists mainly of eliminating rotating bearing forces. Analytical expressions are derived for the deformation and the rotating bearing forces of a rotor, using orthogonal functions. With this kind of representation it is possible to set up simple conditions for the vanishing rotating bearing forces. They lead to a linear system of equations giving the compensating unbalances in each of a set number of balancing planes. Two methods used in practice are theoretically explained and compared. The “N” method employs N planes for balancing a speed range up to, and including, the Nth critical speed and can be characterized by the condition A = 0, see equation (13). The “(N + 2)” method requires two more planes for the same speed range and is characterized by A = 0 and B = 0. It is proved that limlimN→∞B=0, so that in the limiting case of an infinite number of balancing planes (speed range from zero to infinity) both methods are of equal value. The two methods differ for finite N in their accuracy and the amount of calculation. Considering simple examples with known unbalance distribution it will be shown that the main error of the N method is the result of treating B as equal to 0, which it is not, thus accounting for the greater accuracy of the N + 2 method. The additional effort needed for the latter method is justified in those cases where greater accuracy is demanded.
On the Use of Balancing Machines for Flexible Rotors
Authors: Bishop R. E. D. , Parkinson A. G.
Published: November 2010

During the last decade or so a variety of methods has been devised and adopted for balancing flexible rotating shafts. These techniques fall into two distinct classes, depending upon whether or not the shaft is also balanced as a rigid body. The relative merits of the two approaches have been the subject of much discussion, and this paper is an attempt to clarify the points at issue.
Fluctuating Lift Forces of the Karman Vortex Streets on Single Circular Cylinders and in Tube Bundles: Part 1—The Vortex Street Geometry of the Single Circular Cylinder
Authors: Chen Y. N.
Published: November 2010

The geometry of the vortex street for single circular cylinders will be calculated from the measured values given by numerous investigators about the steady pressure drag coefficient and the Strouhal number, whereby the Kronauer minimum drag criterion comes into use. The calculated results will be compared with the experimentally determined ones. A good agreement can be achieved between both. The Bearman-Strouhal number SB = fh/Us will also be computed as a function of the Reynolds number. Furthermore a new wake number C = fh2/Γ will be introduced. It will be shown that this new number is universally much better than the Bearman one. It remains constant at 0.165 for an ideal flow over the whole Reynolds number range up to the highest value of 107 ever measured hitherto.
Stability and Transient Motion of a Vertical Three-Lobe Bearing System
Authors: Falkenhagen G. L. , Gunter E. J. , Schuller F. T.
Published: November 2010

The stability characteristics and general transient motion of the finite-width three-lobe bearing assuming an incompressible fluid with cavitation are presented. The hydro-dynamic bearing forces are evaluated by both a finite-difference analysis and an approximate method. The approximate method consists of the infinite bearing solution corrected for end leakage. The approximate method is compared to the finite-difference solution of Reynolds equation and yields acceptable accuracy while running 100 times faster. Linearized bearing stiffness and damping coefficients are determined numerically and used to calculate the threshold of instability for a rigid vertical rotor. The stability curves developed are compared to NASA experimental data as well as analytic work performed by Lund. The nonlinear transient orbits for a balanced rotor are computed and plotted for comparison to the linear stability curves and the NASA test data. The influence of rotor unbalance above and below the stability threshold is investigated. The stability of the three-lobe bearing is optimized with respect to minimum film thickness. It is found that the optimum preload factor varies from 0.59 to 0.47 and the corresponding offset factor ranges from 0.8 to 1.0 for an aspect ratio L/D = 1.0.
Analysis of Hydrostatic Extrusion by the Finite Element Method
Authors: Iwata K. , Osakada K. , Fujino S.
Published: November 2010

An elastoplastic analysis of hydrostatic extrusion is made using the finite element method. The effect of frictional coefficient on the spread of plastic zone, the pressure-displacement curve, and the stress and the strain distributions are studied for the non-steady state in plane-strain and axisymmetric extrusions. Comparisons of results between the finite element solution and slip-line solution and between plane-strain and axisymmetric extrusions are presented. Tensile stresses on the surface of the extruded part behind the die are found to exist. It is also found that the die pressure is high near the die entry and exit and that the surface of the billet in front of the die entry tends to contract.
Analysis of Stress Concentrations in Thick Cylinders With Sideholes and Crossholes
Authors: Gerdeen J. C.
Published: November 2010

An approximate theoretical analysis is presented for the determination of stress concentration factors in thick walled cylinders with sideholes and crossholes. The cylinders are subjected to both internal pressure and external shrink-fit pressure. Stress concentration factors are plotted as functions of the geometrical ratios of outside diameter-to-bore diameter, and bore diameter-to-sidehole diameter. Theoretical results are compared to experimental values available in the literature and results of experiments described in a separate paper.
Modular Analysis of Geometry and Stresses in Closed-Die Forging: Application to a Structural Part
Authors: Akgerman N. , Altan T.
Published: November 2010

A computerized modular method is developed for predicting shape complexity, material volume, load, stress distributions, and center of loading in forgings. The method consists of dividing a forging into standard components which can be assembled in a building-block manner to analyze a given forging. The method has been applied to a nonsymmetric rib-and-web-type aircraft part from 6061 aluminum. The flow stress during forging, in two distinct zones of the part, was calculated by estimating average forging temperatures. The predicted values of the forging variables are compared with experimental results. The predicted forging load, which varies with the tool-material interface friction, agreed well with the measured load for a friction factor of about 0.3.
On the Mechanics of Rectilinear Continuous Cutting With a Single Point Tool
Authors: Morcos W. A.
Published: November 2010

Assuming plane shear surfaces and chip tool friction force in the direction of the relative displacement between chip and tool, the direction of chip flow is determined. The condition of minimum energy determines the shear angle. The cutting ratio, the cross section of the chip, and the cutting forces are theoretically predicted. The solution for the case of cutting in a solid prismatic block whose free surface is parallel to the direction of cutting is worked out.
Conical Acrylic Windows Under Long-Term Hydrostatic Pressure of 10,000 psi
Authors: Stachiw J. D.
Published: November 2010

Over 150 conical frustum acrylic plastic windows were subjected to 10,000 psi hydrostatic loading of up to 1000-hr duration in deep ocean simulators maintained at 65–75 deg F ambient temperature. Axial displacements of the windows under hydrostatic loading through the conical cavity in the flange were recorded and plotted as a function of time, thickness to minor diameter ratio (t/D), and included conical angle α. Data indicate that only windows with α ≥ 90 deg and t/D ≥ 0.75 are satisfactory for sustained long-term hydrostatic loading of 1000-hr duration at 10,000 psi in ambient temperatures ≤80 deg F. For general service, which includes also cyclic pressurizations to 10,000 psi, an included angle α ≥ 90 deg and t/D ratio of ≥ 1.0 are recommended. The axial displacement of windows recommended for 10,000 psi service is approximately 0.04D after 1000 hr of sustained loading. Approximately 75 percent of this displacement takes place during the first hour of pressure application.