bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence Coefficients and Pressure Vessel Analysis
Authors: Galletly G. D.
Published: December 2011

A description is given of the utility of influence coefficients for analyzing pressure vessels. To illustrate their advantages two relatively complex problems were selected and their final stress distributions calculated. The problems were (i) a cylinder closed by a torispherical head and (ii) a cylinder joined to a smaller cylinder by an ellipsoidal-toroidal shell. Two vessels were analyzed using influence coefficients which have recently become available. It is shown that accurate stress distributions can be obtained quickly and that a specialized knowledge of shell theory is not required. The method also shows the distribution of bending stresses throughout the shells. These latter, which can be important, are usually ignored by the various codes.
Mechanical Vibration Filters With Nonlinear Characteristics
Authors: Worley Will J.
Published: December 2011

The behavior of a single degree of freedom system consisting of a single mass mounted on a spring and damper attached to an oscillating base is investigated. Steady-state and transient sinusoidal oscillations are applied to the base to which the suspension is attached. The response of the mass is recorded for various combinations of linear and nonlinear springs and dampers. Solutions are obtained with a differential analyzer.
Dimensionless Parameters for Helical Compression Springs
Authors: Erisman R. J.
Published: December 2011

Spring design, in many instances, is still a trial-and-error process. The underlying reason is the large number of complex variables which must be related to the allotted space which the spring will occupy and to the desired loads throughout the working range. This paper presents a system of parameters which enables the spring designer to graphically portray these variables for a given problem. Derivations are based on the total number of coils as well as the outside diameter which accurately defines the entire space required for the spring. Charts are presented for springs with two dead coils and a torsion modulus of 11,500,000 psi.
An Analysis of the Yielded Compound Cylinder
Authors: Becker S. J.
Published: December 2011

An analysis is made of the partially plastic range, restricted to plane strain, of the compound cylinder, made by shrinking together many concentric cylinders. An example is given using, for ease of illustration, a cylinder designed to yield simultaneously in all its components. A comparison is made between a structure with a compressible elastic material and one with an incompressible elastic material. Finally, an important auto-frettage formula, Equation (10), is developed.
Analysis and Design of Tangent Elasticity Vibration Isolators
Authors: Ruzicka Jerome E.
Published: December 2011

General solutions are obtained for the natural frequency and deflection of hardening vibration isolators that fall into the “tangent elasticity” class of nonlinearity for the case of small harmonic motions about the static equilibrium position. A procedure is developed for the minimization of the natural frequency and the determination of certain properties of an isolator for which a load-deflection curve is available. This procedure is applied to the design of conical compression springs as well as rubber compression isolators.
Stresses in a Pipe Bent Into a Circular Arc
Authors: Weil N. A. , Brock J. E. , Cooper W. E.
Published: December 2011

The stress distribution in circular bends formed from straight pipe and subjected to internal pressure is presented. The analysis determines first the thickness distribution after forming, followed by an examination of the validity of membrane solutions for a complete torus. The predicted thickness distribution is in excellent agreement with experimental results as well as with three previous empirical formulations. The analysis shows that stresses in curved bends will always exceed the governing hoop stress in a comparable straight pipe, the deviation becoming greater with increased corrosion allowance. The authors recommend that, for purposes of acceptance by the ASA B31 Code, an excess stress level of the order of 5 per cent be allowed to develop in pipe bends. The resulting bend radius to pipe diameter limitations are listed in Table 3 and shown in Fig. 5. The last section of the paper deals with the major assumptions made in the derivation, and finds all of them to be acceptable for purposes of this analysis.
Forces on a Worn Cutting Tool
Authors: McAdams H. T. , Rosenthal Paul
Published: December 2011

The forces on a single-point cutting tool under conditions of progressive flank wear are analyzed under the assumptions of constant rake, friction, and shear angle. Relations between wear land area and stock removal rate are derived for the case of constant feed force. For the case of constant depth of cut, the relation between wear land area and feed force is developed.
Measurement of Four-Pole Parameters of Complex Structures
Authors: Safford F. B.
Published: December 2011

A method of measurement of the four-pole parameters of a system as a function of frequency is presented. This procedure consists of no-load dynamic measurements followed by measurements under a known load. From the foregoing measurements, the four-pole parameters of a system are derived. Application is made to an electrodynamic motion exciter with graphical presentation of the parameters with respect to amplitude, phase angle, real, and imaginary parts.
Tensions in Straight and Curvilinear Belt Conveyers
Authors: Winkler W. A.
Published: December 2011

This paper presents a simplified method of tension calculations in belt conveyers, suggesting the same approach regardless of whether belts are straight or curvilinear. A Key Diagram is introduced for the quick identification of critical tensions for all basic conditions. It is common practice to use an analytical method for the calculation of tensions and horsepower of more complicated belt conveyers, especially curvilinear belt conveyers. The big advantage of this method is that it permits the establishment of tension values for the design of concave and convex curves and also for the design of drive and take-up when not located at conveyer ends. However, the so-called analytical method has a distinct disadvantage in practical engineering—it is tedious and time-consuming. The purpose of this paper is to present a faster way to find all belt tensions necessary for the proper design or selection of conveyer components.
The Use of Derivative Pressure Feedback in High Performance Hydraulic Servomechanisms
Authors: Welch T. R.
Published: December 2011

Hydraulic servomechanisms are sometimes used to drive a load member which is predominantly inertia. The usual overriding requirements for output disturbance discrimination and high power efficiency dictate a simple closed center, flow type, servo valve, and a positive displacement actuator. The resulting transfer function relating output velocity to servo valve input current invariably includes an underdamped quadratic lag due to fluid compliance. In simple hydraulic servo systems, the corner frequency of this quadratic lag represents the absolute limit to system bandwidth. Pressure feedback systems have been devised to damp the fluid resonance so effectively that bandwidth extension beyond the quadratic corner frequency is entirely feasible. Unfortunately, such a scheme destroys the natural output disturbance discrimination inherent in the closed center hydraulic systems. A hybrid method of compensation is proposed whereby pressure feedback occurs only in the region of the resonant frequency, effectively preserving the natural output disturbance discrimination characteristics at the lower frequencies. The pressure drop across positive displacement type hydraulic actuators is a good measure of acceleration. Therefore, the technique involves feeding back this load differential pressure, sensed by electromechanical transducers, through a simple RC high pass (derivative) filter. The effectiveness of the damping is determined by the filter time constant and loop gain. Experimental results verify linear predictions of the possibility of extending the closed loop bandwidth beyond the uncompensated resonant frequency.
Forming, Trimming, and Edge Finishing of Molybdenum-0.5 Per Cent Ti Sheet Material
Authors: Pickrell A. L.
Published: December 2011

This paper is a summary of recent manufacturing experience with molybdenum-0.5 per cent Ti sheet material. This refractory metal is new to industry, it is needed for high temperature vehicle application, and its fabrication characteristics differ significantly from other common airframe metals. The paper presents manufacturing development test data and production experience from forming, trimming, and edge finishing of moly-0.5 per cent Ti material. It describes techniques, equipment, and procedures for “hot” forming moly-0.5 Ti. It provides recommendations for trimming moly and it suggests suitable methods for edge finishing production parts.
Shrink Fits of Moderately Long Bands on Thin-Walled Cylinders
Authors: Paul Burton
Published: December 2011

It is shown that lateral pressure, axial force, and radial interference all may be treated by a uniform procedure, when a moderately narrow ring is shrunk onto a uniformly loaded thin-walled cylinder which may be made of a second material. The generalized problem is then solved for stresses and deformations in both cylinder and ring. The present solution, unlike previous solutions, takes into account the finite axial length of the ring.
An Exploratory Study of Stress Concentrations in Thermal Shock Fields
Authors: Becker Herbert
Published: December 2011

Exploratory investigations were performed on the effect of stress concentrations upon the stresses generated in a free elastic plane space by thermal shock applied to the boundary. The emphasis was on a search for a general upper bound to the stresses induced in a plane space of arbitrary shape by a temperature change T0 applied to the boundary of the space. Theory indicates that, when a thermal shock penetrates into a plane elastic space a distance less than half the local boundary radius of curvature, then αET0 would be the magnitude of the upper bound and the stress field would be confined to a boundary layer. In order to obtain the reported results it was necessary to obtain temperature and fringe pattern data within 10 sec from initiation of thermal shock. The experimental program to accomplish this result is reported in detail.
Equilibrium Shapes for Pressurized Fiberglas Domes
Authors: Read W. S.
Published: December 2011

The netting concept is used to analyse filament wound shells of revolution. First the fiber tensions are resolved parallel and perpendicular to the meridian. These components of the fiber tensions give the meridional and hoop forces in the dome. A comparison of these forces is made with the forces calculated from membrane theory. It is shown that the shell will be unstable unless the forces calculated from the fiber tensions are equal to the membrane forces computed from membrane theory. A dome with a polar opening is examined to see if a shape can be found which will make the dome stable. It is shown that for stability, two separate differential equations must be satisfied by the dome curve. The two equations are found to be dependent, and thus both are satisfied by the same curve. The equation for a stable dome is presented in terms of a nondimensional integral.
Study on Wear of Grinding Wheels: 1—Bond Fracture in Grinding Wheels
Authors: Yoshikawa Hiroyuki , Sata Toshio
Published: December 2011

Fracturing of bond bridges in grinding wheels is explained from the standpoint of brittle-fracture. It is shown that the wear rate of grinding wheels can be expressed as the single exponential function of the grinding speed and as the double exponential function of the grinding force. Experimental results are shown to confirm the theoretical interpretation.
Rate of Strain Effect in Metal Cutting
Authors: Oxley P. L. B.
Published: December 2011

An analysis of the cutting process is presented which in conjunction with experimental cutting data enables the initial shear yield stress and the mean slope of the corresponding plastic stress-strain curve to be calculated for different rates of strain. It is found that for an increase in the strain rate the initial yield stress increases and the slope of the plastic stress-strain curve decreases.
Chip Formation in High-Speed Cutting of Copper and Aluminum
Authors: Trigger K. J. , von Turkovich B. F.
Published: December 2011

This paper presents metal-cutting data for the high-speed machining of copper and aluminum, each at two levels of purity, and over a range of workpiece temperatures from −326 deg F (80 deg K) to 550 deg F (560 deg K). It has been found that cutting behavior is influenced by purity of work material, its initial temperature, and extent of tool-chip contact. The influence of plastic deformation on chip hardness has been found to be intimately associated with the purity of the work material.
An Investigation of Electrolytic Jet Polishing at High Current Densities
Authors: Cole Reno R. , Hopenfeld Yoram
Published: December 2011

A method of polishing metals by means of an electrolytic jet at extremely high current densities (to 1750 amps per sq in.) is described. Data are presented on the relation of polishing effect on various metals to current density and electrolyte flow rate for several electrolytes. An experimental method is described whereby the relationship of the above factors can be determined. It was found that all metals investigated could be polished at high enough current densities. Previous theories of electrolytic polishing are discussed and shown to not fully account for the process investigated. A modified theory to account for polishing at the high current densities observed is presented and is supported by mathematical analysis based on fundamental mass transfer considerations.
1962 Review of Metal Processing Literature
Authors: Wennberg J. L. , von Turkovich B. F. , Weller E. J. , Boulger Francis W. , Hahn R. S. , Smith P. A. , Yang C. T. , Kobayashi S. , Galimberti J. M. , Roubik J. R. , Crawford J. H. , Pickrell A. L. , Tarasov L. P. , Cook N. H. , Krabacher E. J. , Backer W. R. , Sluhan C. A. , Downing C. E. , Shaw M. C. , Dorman F. S.
Published: December 2011

The purpose of this review is to appraise the important contributions to the knowledge of metalworking appearing in the published literature and to present a digest of this new knowledge through the Society as a contribution to the improvement of metalworking practices throughout industry.
High-Strength Tool Geometry—A Result of Research in Tool Geometry
Authors: Albrecht P.
Published: December 2011

A high-strength tool geometry has been developed as a result of research conducted in the Physical Research Department of the Cincinnati Milling Machine Company. This research was carried out with the purpose of overcoming difficulties in the machining of high-strength metals. Milling was chosen in the development of the high-strength tool geometry because it presents the most severe condition for the cutting tool, initial impact with each revolution. This tool geometry has been developed for the work-hardness range of 400 Bhn and over.
A Microscopic Study of Chip Formation
Authors: Datsko Joseph , DeVries M. F.
Published: December 2011

This paper is a report on an improved technique to study the formation of chips while observing them through a metallurgical microscope. By using polished and etched specimens it is possible to see the formation of slip lines in front of the tool as plastic deformation initiates. The mechanism of the chip-formation process is clearly shown on a 16-mm motion-picture film that is presented with this paper.
Tool-Life Testing by Response Surface Methodology—Part 1
Authors: Wu S. M.
Published: December 2011

This paper presents a study of tool-life testing by a statistical approach, referred to as response surface methodology, instead of the conventional one-variable-at-a-time method. With this new technique the number of tests required to develop a tool-life predicting equation can be substantially reduced. The reliability of such an equation can also be estimated. Three independent variables, speed, feed, and depth of cut, were investigated in this project. A simple first order equation is “graduated” in Part 1 and a more general second-order equation will be presented in Part 2 of this study.
Some Observations on the Mechanics of Orthogonal Cutting of Delrin and Zytel Plastics
Authors: Rao U. M. , Cumming J. D. , Thomsen E. G.
Published: December 2011

An investigation of the mechanics of orthogonal cutting on an acetal resin (Delrin 150x) plastic and a nylon resin (Zytel 101) plastic was carried out. The specimens were in the form of tubes and the rake angles and feeds were varied from −10 to +40 deg and 0.003 to 0.0115 ipr, respectively. It was found that a shear-plane type of analysis and the minimum-energy principle at low tool chip contact friction are applicable. It was found further that some of the reasons for the formation of discontinuous chips for Delrin 150x were excessive strains and induction of tensile stresses into the zone ahead of the tool. By the use of the minimum-energy principle and a constant dynamic shear stress, which appears to correlate with static properties, it was possible to predict the tool forces for Zytel 101 to a satisfactory degree of accuracy.
Investigations on the Nature of Surface Finish and Its Variation With Cutting Speed
Authors: Chandiramani K. L. , Cook N. H.
Published: December 2011

An attempt has been made to investigate the nature and cause of the variation of surface finish with cutting speed during orthogonal cutting operations. It is found that the variation of cutting speed alone is sufficient to give rise to the three different mechanisms of chip formation, conventionally known as discontinuous, continuous without “bue” (built-up-edge) and continuous with bue. The transition from low-speed, nonbue cutting to high-speed, bue cutting is found to greatly influence the surface finish and in fact the entire cutting mechanism. Photomicrographs of the cutting zones, the chips, and the profiles of the finished surfaces have been taken to observe these changes closely. Tests have also been carried out to determine the relative importance of cutting speed and cutting temperature in affecting the surface finish of the workpiece being machined.
Bolt Force to Flatten Warped Flanges
Authors: Levy Samuel
Published: December 2011

Initial lack of flatness of the flanges of pipe connectors can result in leakage if the bolt loads are not sufficient to achieve positive gasket compression at all points on the circumference. Equations are presented for computing the magnitude of the bolt load necessary to flatten the flange. Account is taken of the bending and twisting resistance of the flange itself, the membrane and hoop bending restraint afforded by the pipe, and the fact that the bolt circle is displaced from the gasket circle. The analysis applies to flanges whose warping can be adequately described by considering it to vary as cos 2θ. Numerical examples are considered for several typical flanges.
Chip Formation With Varying Undeformed Chip Thickness at Very Slow Speed
Authors: Kobayashi Shiro , Shabaik A.
Published: December 2011

Steel S.A.E. 1112 cold rolled specimen was cut orthogonally at slow speed of 0.625 ipm, and the shear plane formation was examined from a series of photographs taken during a cut for cutting triangular wavy surface and for the case where the straight surface is cut by the tool moving along the triangular wavy path. It was found that the shear angle variation is approximately given by equation (3) of the text. An explanation for this shear angle variation is provided by the consideration of the state of stress around the singular point at the free surface.
Deformation During Chip Formation
Authors: Russell J. K. , Brown R. H.
Published: December 2011

Expressions are derived for the deformed orientation of an initially rectangular grid and the direction of maximum elongation with respect to the rake face of the tool in orthogonal machining.
Drawing of Tubes Filled With Particulate Solids
Authors: Polakowski N. H. , Mayfield R. M.
Published: December 2011

The principal parameters involved in drawing of metal tubes containing metallic, mineral, and organic powders were investigated on small copper, mild steel, and 304 stainless tubing. The type of filler controlled the change of the ratio of diameter to wall thickness which decreased at first but became constant after a certain reduction. The above decrease could be held to a minimum by employing a center rod of ductile metal separated from the tube by a powder barrier. The particulate core or barrier need not form an integral part of the product but can be used as a “deformable mandrel” being eventually removed from the reduced tube by reeling, melting, dissolving, or washing the powder out. Such a drawing procedure should prove useful in bulk reducing hard to draw (e.g., refractory) tubing. If warm drawing is called for, the operation is facilitated by the substantial heat capacity of the quasi-solid cross section. The danger of local interwelding (galling) between tube and inside tool is eliminated because of the absence of relative slippage between tube and inside tool.
High-Temperature, Cobalt-Tungsten Alloys for Aerospace Applications
Authors: Freche J. C. , Ashbrook R. L. , Sandrock G. D.
Published: December 2011

The high-temperature capability and workability of cobalt-tungsten alloys for aerospace applications is discussed. The average life at 1850 F and 15,000 psi of the strongest previously reported alloy, Co-25 W-1Ti-1Zr-0.4C, was doubled from 92 to 185 hr by small additions of chromium and rhenium. At 2200 F and 5000 psi, the strongest alloy, Co-25W-1Ti-1Zr-3Cr-2Re-0.4C, had a rupture life of 23 hr; the elevated-temperature rupture strength compared favorably with the strongest available conventional (high-chromium) cobalt-base alloys. Above approximately 2035 F and at reasonably high stress levels (10,000 and 15,000 psi), its stress-rupture life also exceeded those of the strongest known nickel-base alloys, including the NASA tantalum-modified alloy and SM-200. It is particularly significant that even the strongest alloys of this series were readily hot-rolled. Ingots 1/2 in. thick were reduced to 0.065-in. sheet and subsequently cold-rolled to 0.0125-in. sheet. Elongations as high as 31 percent were obtained at room temperature with annealed sheet specimens. The good ductility obtained suggests that these alloys could be fabricated into complex shapes required for various aerospace and other applications. Although the strongest alloys had a chromium content of only 3 percent, they did not oxidize catastrophically in air.
Continuity of Cylindrical Shells Subjected to the Uniformly Distributed Longitudinal Surface Loads
Authors: Shang Jeng C.
Published: December 2011

The continuity problems in the cylindrical shells due to abrupt change in geometry, plate thickness, or loading condition are discussed. In order to illustrate the method of determining the membrane stresses and the secondary stresses caused by the discontinuity in geometry, plate thickness, or loading, a numerical example is also presented for a cylindrical shell subjected to (a) constant pressure; (b) hydrostatic pressure; and (c) partial loading.
Hesitation
Authors: Harding B. L.
Published: December 2011

Exact dwells can exist only in synthetic motion such as that of cams. Generated motion such as that of linkages can only produce approximate dwells. This paper defines such approximate dwells as “hesitations,” reduces them to theory, then proceeds to develop techniques for designing mechanisms to produce approximate dwells of various degrees. The discussion involves properties of path curvature and mechanisms connected in series; it also introduces “chain derivatives”—a useful concept in the analysis of compound motions.
Stresses and Deflections of Thick, Curved Plates
Authors: Griffin D. S.
Published: December 2011

A solution is obtained using the linear theory of elasticity for the stresses in a long, thick, uniformly curved plate due to pressures on the curved surfaces and forces or deflections specified on the straight edges. The maximum stresses are compared with those obtained by the elementary thin beam theory, showing the range of applicability of the simpler theory. In general, the accuracy of the elementary theory depends on the total plate angle (α) as well as the mean radius-to-thickness ratio (rm/t).
Performance of Tungsten Carbide, Titanium Carbide, and Oxide Tools in Finish Turning of C-30 Gray Iron
Authors: Ham I. , Hoshi T. , Thuering G. L.
Published: December 2011

Performance data were obtained for tungsten carbide, titanium carbide, and oxide tools in the finish turning of C-30 gray iron. Characteristics of typical wear patterns were examined in relation to their effects on cutting force and surface finish. Using both surface finish and tool wear as tool life criteria, the comparative performance of these tools was evaluated. The oxide tool was superior to the carbide tools except at low cutting speeds. The influence of depth of cut and of a prehoned land on the cutting edge was also studied.
Strip-Drawing Experiments With a Sigmoidal Die Profile
Authors: Devenpeck M. L. , Richmond O.
Published: December 2011

Strip-drawing experiments were conducted to evaluate a sigmoidal die profile which, according to slip-line theory, can achieve perfect work efficiency and uniform deformation. The performance of this die profile was compared with that of a straight, a convex circular, and a concave circular die profile, each designed for a similar reduction and axial length. The sigmoidal profile proved best in all criteria examined: Efficiency, uniformity of deformation, and product strength, ductility and fatigue life. The concave circular profile, which is similar to a rolling profile, proved worst in all of these same criteria. The improvement of the sigmoidal profile over the straight profile in fatigue life and ductility was of the order of 20 and 30 percent, respectively, but in efficiency, uniformity of deformation and tensile strength was less than 4 percent. When fabrication of the sigmoidal die is unwarranted by these improvements, the analysis for the sigmoidal profile may yet be useful for approximating the best die angle for a straight profile.
Structural Dynamics in Machine-Tool Chatter: Contribution to Machine-Tool Chatter Research—2
Authors: Long G. W. , Lemon J. R.
Published: December 2011

This paper is one of four being presented simultaneously on the subject of self-excited machine-tool chatter. Transfer-function theory is applied to obtain a representation of the dynamics of a machine-tool structure. The stability theory developed to investigate self-excited machine-tool chatter requires such a representation. Transfer functions of simple symmetric systems are derived and compared with measurements. When measured frequency-response data of more complex structures are obtained, it provides a very convenient means of data interpretation and enables one to develop the significant equations of motion that define the structure response throughout a specified frequency range. The transfer function presents the phase relationship between structure response and exciting force at all frequencies in the specified range. This knowledge of phase is essential to the proper application of the stability theory and explains the “digging-in” type of instability that is often encountered in machine-tool operation. The instrumentation used throughout these tests is discussed and evaluated. The concept of developing dynamic expressions for machine-tool components and joining these together through properly defined boundary conditions, thereby building up the transfer function of the complete machine-tool structure, is suggested as an area for further study.
Cryogenic Temperature Dependence of the Yield Strength of High-Strength Alloys
Authors: Yang C. T.
Published: December 2011

The effect of cryogenic temperatures (from 78 F to −423 F) on the yield strength of twenty alloys was studied. Experimental results prove that they do not conform to any of the following theories: Hollomon and Zener’s, Cottrell and Bilby’s, or Fisher’s. However, all the plottings in loge-loge scale of yield strength versus absolute cryogenic temperatures of these alloys fall on straight lines which are governed by one single general equation, σy = bT−m. From the Cottrell’s dislocation theory on yielding and Fisher’s equation of activation energy in forming a dislocation loop, the same type of equation of yield strength versus temperature as expressed by the empirical ones can be derived theoretically. The empirical equations are very useful in predicting yield strengths at any cryogenic temperature within or slightly out of the test range for which data were available. Some limited yield strength data at elevated temperatures for a few alloys were studied for comparison. It was observed the general equation for yield strength versus cryogenic temperatures holds valid for stainless steels but not so well for titanium, nickel, and aluminum alloys at elevated temperatures. However, no conclusion can be drawn until further detailed studies at elevated temperatures are made.
Passive-Element Analog Circuits for Three-Dimensional Elasticity
Authors: Barnoski R. L. , Freberg C. R.
Published: December 2011

This paper considers the derivation of passive-element electrical analogs for three-dimensional elasticity in rectangular, cylindrical, and spherical polar coordinates. The analogs represent, in finite-difference format, the elastic behavior of differential volumes of material defined by the partial differential equations of linearized elasticity theory. Basically, the circuits are derived by equating the elastic strain energy to the power dissipation in the analog circuit. The analogs discussed here are force-current, displacement-voltage circuits. As compared to the more widely known operational amplifier or “active” electrical analog, these analogs simulate the appropriate equations of the elastic system by “passive” electrical components; i.e., by some combination of resistors, inductors, capacitors, and transformers. Strictly speaking, the circuits shown in this discussion are for static elasticity problems. However, as referenced in the text, these analogs can be converted readily into dynamics circuits by visual inspection of the static analogs.
Radioisotope Power-Generating System for a Manned Space Laboratory
Authors: Tonelli A. Duane , Regnier Edward P.
Published: December 2011

The results of a Douglas sponsored study of radioisotope secondary power-generating systems for space applications are presented. The study results are applicable to various space vehicles and missions requiring 4 kw or more of electrical power. The first generation of manned vehicles where a radioisotope power system is potentially applicable include the Extended Apollo and MOL type earth-orbiting laboratories. For this reason, the study results were applied to selecting a radioisotope power system for a small manned orbiting laboratory. The laboratory considered is capable of being launched in the post-1968 time period by a Titan 3C booster. An argon Brayton cycle, Dowtherm A Rankine cycle, and thermoelectric systems were investigated as possible secondary power systems capable of generating 4 kw of electrical power for the vehicle subsystem. Tradeoffs in weight, radiator-area requirement, development risk and isotope availability and cost were performed for the various systems. On the basis of the tradeoffs and the 4-kw design load, the argon Brayton cycle system was recommended.
Stress Concentrations in Thin Spherical Shells
Authors: Popov Egor P. , Penzien Joseph , Rajan Mandayam K. S.
Published: December 2011

Stress distributions occurring in the proximity of rigid circular inserts attached to thin spherical shells are reported in this paper. The solutions are achieved by employing conical coordinates tangent to the sphere at its intersection with the insert. A small-deflection theory is used and results are stated in terms of readily available functions. For convenience in practical applications, solutions for several loading conditions are carried through to completion. Specifically, the paper gives formulas for stress distributions occurring in a spherical shell when provided with a rigid insert and when subjected to (a) internal pressurization in the shell; (b) axial load on the insert; (c) external moment on the insert; and (d) tangential shear load on the insert. The necessary constants of integration are given in tables and the procedure developed is illustrated by a comprehensive example.
Computer-Designed Vacuum Vessels
Authors: Restivo C. A.
Published: December 2011

Today a wide variety of chemical and petrochemical processes require equipment that operates under partial vacuum. The ASME Code for Unfired Pressure Vessels, Section VIII, sets forth a method for designing these vessels by trial and error, leaving any consideration for economics up to the designer, who quite often neglects this because he is pressed for time. For this reason it became apparent that a computerized design was the only solution since the computer can perform this time-consuming, tedious, and repetitive calculation quickly and systematically. The computer cannot make use of the vacuum charts in their present form; thus the IBM program “STUFF,” Sixteen Twenty Universal Function Filter, was used to obtain formulas that replace the charts. With this program an optimum design is obtained each time, thus realizing a savings for each vessel processed through it, both in material and time. The following paper describes some of the problems encountered in trying to program the charts and how they were solved. A specific formula is set up showing the method used, and a hand-calculated problem is compared with the same problem processed through the program.
A Modified Gibbs Experiment
Authors: Babina F. , Levy M. J. , Potter J. H.
Published: December 2011

Experiments were conducted on the effects of the shift of the gas mass from the high-pressure to the low-pressure sides of a divided vessel, with communication by (a) bursting diaphragm and (b) bypass valve. Analytical solutions indicate the true complexity of the problem and the need for transient force and pressure information.
The Study of Spatial Mechanisms by Electronic Analog Computer
Authors: Keller R. E.
Published: December 2011

A simulation technique, applicable to any spatial mechanism having lower pairs, is presented. A detailed description of the required electronic analog-computer circuitry is given. The geometrical relationships imposed by a mechanism are satisfied in the simulation by contactor feedback-control systems, thereby minimizing the need for nonlinear computing components such as squarers and multipliers. Several example simulations are presented.
An Analytical Study of the Dynamics of an Elastic Linkage
Authors: Neubauer A. H. , Cohen R. , Hall A. S.
Published: December 2011

The transverse vibrational characteristics of the connecting rod in a slider-crank mechanism are investigated. The equations of motion are derived, simplified, and solved. For the solution, two different numerical techniques are employed and correlation is achieved. Two dimensionless parameters, S the speed parameter and Z the physical parameter, arise during the derivation of the equations of motion. These parameters can be used by the designer as an indication of the vibrational activity of the mechanism.
Mechanics of Punching Circular Holes in Materials for Data Handling
Authors: Queener C. A. , Smith T. C. , Gilkey H. E.
Published: December 2011

A theoretical model is developed in an effort to predict the effect of various design and operating parameters on the mechanics of punching circular holes in relatively ductile, nonmetallic materials which are commonly used in data-handling equipment. Solutions are obtained for the various punch geometries most frequently used. Experimental results for punching force versus punch displacement, maximum punching force, and total energy expended during punching are in good agreement with the theoretical solutions. Although this work is primarily concerned with circular holes, the theoretical approach used is equally applicable to the punching of other hole geometries, such as rectangular holes. The possibility of extending the theoretical treatment to metal punching is also discussed briefly.
Effects of Nonsymmetry in Strip Rolling on Single-Roll Drive Mills
Authors: Holbrook Richard L. , Zorowski Carl F.
Published: December 2011

An investigation of unsymmetrical deformation effects in hot strip rolling on single-roll drive mills is performed analytically. The model developed permits prediction of the rolling load, torque, and exit strip curvature as a function of mill geometry and strip reduction, through a formulation of the appropriate equilibrium equations and a realistic approximate yield criterion. Inclusion of the unsymmetric effects is achieved by assuming a reasonable distribution for the pressure difference between the rolls. Numerical results for rolling load, rolling torque, and strip curvature are presented and compared with earlier theories, with conclusions drawn relative to the importance of the effects of the nonsymmetry of the deformation state.
Ultrasonic Grinding Economics
Authors: Kaczmarek J. , Kops L. , Shaw M. C.
Published: December 2011

In ultrasonic grinding the abrasive gradually loses its effectiveness, and must be replaced after a given period of use (T). The rate of material removal (Q in mm3/min) is related to the time of use of the abrasive charge (τ) as follows: Qτm = constant, which resembles the Taylor tool life (T) equation for a single point tool VTn = constant, where V is the cutting speed and m and n are constants. Economic analyses for the optimum abrasive use time, optimum size of abrasive change, and best choice of abrasive may be made following the technique commonly used for single point cutting tools. In these analyses the volume rate of material removal (Q) plays the same role as cutting speed (V) does in conventional machining. This paper first discusses the wear of the abrasive in ultrasonic grinding and then considers the aforementioned economic problems.
Densification of Plasma Sprayed SOFC Electrolyte Layer Through Infiltration With Aqueous Nitrate Solution
Authors: Mirahmadi A. , Valefi K.
Published: December 2011

Electrolyte of the solid oxide fuel cells deposited by atmospheric plasma spraying of 8 mol.% yttria (8YSZ), is not applicable in as sprayed condition. Optimization of the plasma spraying process parameters or application of feedstock powder, consisting of 8YSZ and 5wt.% alumina improves the problem of gas leakage through electrolyte layer, whereas provides no solution to the problem of electrodes short-circuiting. Infiltration of deposited electrolyte layer with a thin aqueous solution of nitrate precursors of 8YSZ for one time is a solution to high gas permeability; however three infiltration cycles are required to omit the risk of electrodes short circuiting thoroughly.
A Review on Critical Heat Flux Enhancement With Nanofluids and Surface Modification
Authors: Seon Ahn Ho , Hwan Kim Moo
Published: December 2011

Recently, there has been increasing interest in boiling nanofluids and their applications. Among the many articles that have been published, the critical heat flux (CHF) of nanofluids has drawn special attention because of its dramatic enhancement. This article includes recent studies on CHF increasing during the past decade by various researchers for both pool boiling and convective flow boiling applications using nanofluids as the working fluid. It presents a review of nanofluid critical heat flux research with the aim of identifying the reasons for its enhancement and the limitations of nanofluid applications based on various published reports. In addition, further research required to make use of the CHF enhancement caused by nanofluids for practical applications is discussed. Finally, the surface modification method with micro/nanostructures to increase the CHF is introduced and recommended as a useful way.
Transient Model Validation of a Desulfurizer and a Syngas Generator for High Temperature Fuel Cells
Authors: Ferretti Andrea , Traverso Alberto , Saunders Gary J. , Perna Mark A. , Massardo Aristide F.
Published: December 2011

This paper presents the steady state and transient model of a natural gas fuel processing system of a solid oxide fuel cell (SOFC) hybrid system, and its validation using data obtained through the use of a real plant. The model was developed by the Thermochemical Power Group of the University of Genoa, Italy, using the in-house tool TRANSEO working in the Matlab/Simulink environment, whereas the real plant was designed and built by Rolls-Royce Fuel Cell Systems Limited (RRFCS) to feed a 250 kWe SOFC hybrid system with a methane stream undergoing requirements about composition, pressure, and temperature. The paper presents in detail the fuel processing system and, with particular emphasis, the selective catalytic sulphur oxidation (SCSO) and the catalytic partial oxidation (CPOx) subsystems. Thanks to the collaboration between the University and RRFCS, in the model the real physical properties of the different materials and geometry of the components have been carefully used. The transient model has been fully validated against experimental data obtained from long duration tests, which included the warm-up, part and full load operation, and cool-down phases of the external fuel processing system. In the validation process both gas and wall temperatures have been taken into account. The transient model has shown the ability to predict satisfactorily the plant behavior both at steady-state and transient conditions. The validated model is now under further development to be used for dynamic control system applications.
Serum vitamin D levels among patients in a clinical oncology practice compared to primary care patients in the same community: a case–control study
Authors: Churilla Thomas M , Lesko Samuel L , Brereton Harmar D , Klem Mary , Donnelly Patrick E , Peters Christopher A
Published: December 2011

Objectives

Low serum vitamin D levels have been associated with risk for certain malignancies, but studies have not directly analysed levels between community oncology and primary care practices. The purpose of this study was to compare serum vitamin D levels in patients at a community oncology practice with non-cancer patients at a primary care practice.

Design

Retrospective case–control study. 25-Hydroxyvitamin D levels were ordered for screening in both cancer and non-cancer patients. Levels were compared in univariate and multivariate analyses adjusted for age, body mass index and season of blood draw.

Setting

A community-based radiation oncology centre and a community-based primary care practice: both located in Northeastern Pennsylvania, USA.

Participants

170 newly diagnosed cancer patients referred for initial consultation at the community oncology centre from 21 November 2008 to 18 May 2010, and 170 non-cancer patients of the primary care practice who underwent screening for hypovitaminosis D for the first time from 1 January 2009 to 31 December 2009.

Primary and secondary outcome measures

The primary outcome measure was mean serum vitamin D level, and the secondary outcome measures were frequencies of patients with vitamin D levels <20 ng/ml and levels <30 ng/ml.

Results

The oncology patients had a significantly lower mean serum vitamin D level (24.9 ng/ml) relative to a cohort of non-cancer primary care patients (30.6 ng/ml, p<0.001) from the same geographical region. The relationship retained significance after adjustment for age, body mass index and season of blood draw in multivariate analysis (p=0.001). Levels <20 and <30 ng/ml were more frequent in the oncology patients (OR (95% CI)=2.59 (1.44 to 4.67) and 2.04 (1.20 to 3.46), respectively) in multivariate analysis.

Conclusions

Cancer patients were found to have low vitamin D levels relative to a similar cohort of non-cancer primary care patients from the same geographical region.
What do patients and relatives know about problems and failures in care?
Authors: Iedema Rick , Allen Suellen , Britton Katherine , Gallagher Thomas H
Published: December 2011

Objective

To understand what patients and family members know about problems and failures in healthcare.

Design

Qualitative, semistructured open-ended interviews were conducted with 39 patients and 80 family members about their experiences of incidents in tertiary healthcare. Nineteen interviews involved more than one respondent, yielding 100 interviews in total. Participants were recruited through advertisements in the national broadsheet and tabloid print media (43%), with the help of the health services where the incidents occurred (28%), through invitations sent out by two internet marketing companies (27%) and by consumer organisations (2%).

Setting

Interviews were conducted in the homes of the respondents or over the phone. One participant emailed her responses to the questionnaire.

Results

Analysis of the interview data revealed: (1) considerable knowledge on the part of patients and relatives about health service risks, problems and incidents; (2) the insight of interviewees into care improvement opportunities; and (3) challenges faced by patients and relatives when trying to negotiate their knowledge and insights with health service staff.

Conclusion

Patients (and family members) need access to structured processes ensuring dialogue with health service personnel about perceived risks, problems and incidents. Such dialogue would reveal patients' and family members' questions and knowledge about improvement opportunities, and minimise the risk that their questions and knowledge are ignored.
Bayesian spatial methods for small-area injury analysis: a study of geographical variation of falls in older people in the Wellington–Dufferin–Guelph health region of Ontario, Canada
Authors: Chan Wing C , Law Jane , Seliske Patrick
Published: December 2011

Objectives

To examine falls in older people in the Wellington–Dufferin–Guelph (WDG) health region of Ontario, Canada, and to identify areas with excess RR and associated risk factors, particularly those related to private dwellings.

Methods

Cases of hospitalisation following falls among older people in the WDG health region between 2002 and 2006 were geocoded to the dissemination area level and used in the spatial analysis. The falls data and covariates from the 2006 Canadian census were analysed using Poisson log-linear models with (spatial and non-spatial) random effects at the dissemination area level. A Bayesian approach with Markov chain Monte Carlo simulation allowed the spatial random effects models to be fitted. Map decomposition was used to visualise the results.

Results

The percentage of occupied private dwellings requiring repairs and median income were significantly associated with falls in older people in the WDG health region. Twenty-six dissemination areas with high RR of falls in older people in the WDG health region were identified. Map decomposition revealed that RR were also driven by unknown factors that have spatial patterns.

Conclusions

This research identified an association between falls in older people and housing conditions; the higher the percentage of dwellings requiring repairs in an area, the higher its risk of falls in older people. Bayesian spatial modelling accounts for measurement errors and unobserved or unknown risk factors that have spatial patterns. The findings have the potential to contribute to future research in reducing falls in older people and generate more interest in using Bayesian spatial modelling approaches in injury and public health research.