bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Response of Elastic Rods Under Parametric Excitations
Authors: Sankar T. S. , Rajan G.
Published: November 2010

The problem of dynamic behavior of parametrically excited mechanical elements, viz., elastic rods and linkages in mechanisms and boring bars, is presented using the WKB solutions of a general second-order partial differential equation. The differential equations are solved by using first a plane wave type solution leading to the “regular WKB” solution and then through the solutions of Airy integral type employing the “generalized WKB” method. The analytical techniques are illustrated by considering the lateral vibrations due to an exponentially decaying axial force on a pin-ended rod. It is shown that the regular and generalized WKB solutions are complementary, i.e., where the regular WKB method fails, the generalized WKB solution yields satisfactory results.
Properties of Reinforced Abrasive Disks in Flexure
Authors: Rajagopal S. , Kalpakjian S.
Published: November 2010

This paper deals with a study of the flexural behavior of thin, fiber-reinforced, resinoid abrasive disks. During use, these disks generally encounter a much higher ratio of flexural or bending stress to rotational stress than do straight grinding wheels. Material characteristics such as flexural modulus of elasticity, flexural strength, and flexural strain to fracture were evaluated for specimens machined from the disks at known orientations of each layer of fiber reinforcement. The effect of transverse loading on the abrasive disk was investigated by means of static flexural tests on randomly oriented disks. The failure load was predicted from considerations of beam theory and was found to agree well with experimental data.
A Determination of Contact-Loss at a Bearing of a Linkage Mechanism
Authors: Wu C. L. S. , Earles S. W. E.
Published: November 2010

A method is described for analyzing the kinematic and dynamic response of a linkage mechanism in which one bearing has a known clearance. Assuming the clearance to be represented by a massless link, the analysis predicts the occurrence of contact-loss. Part of an extensive experimental investigation is presented in which the impact accelerations resulting from contact-loss are measured. A good correlation is shown to exist between the predicted and measured times of contact-loss. Although the analysis may predict no contact-loss, it does not readily indicate, from a design point of view, how this condition could be produced.
Mixed Exact-Approximate Planar Mechanism Position Synthesis
Authors: Sutherland G. H.
Published: November 2010

Design equations are developed for rigid body guidance through K equals one, two, three, and four exact positions and N – K approximate positions. Both circle and straight-line points are considered. Algebraic solution techniques for use with a pocket scientific calculator and a digital computer are illustrated using numerical examples.
Tool-Life Distributions—Part 1: Single-Injury Tool-Life Model
Authors: Ramalingam S. , Watson J. D.
Published: November 2010

The statistical variability of tool life in production machining must be accounted for in any rational design of large-volume or automated manufacturing systems. The probabilistic approach needed for such a design is presently limited by lack of data on tool-life distributions and by lack of knowledge of the underlying causes giving rise to tool-life scatter. Given these circumstances, on the basis of relevant physical arguments one may construct probabilistic models that produce distribution functions germane to the problem of tool-life scatter. This paper is concerned with such a study. This first part presents the results obtained on the assumption that the useful life of a tool is terminated by a single, catastrophic injury. Cases where resistance to tool failure is time-independent and time-dependent are examined. The case of tool failure caused by multiple injuries will be presented in Part 2.
A New Approach to the Analysis of Machine-Tool System Stability Under Working Conditions
Authors: Burney F. A. , Pandit S. M. , Wu S. M.
Published: November 2010

A new stochastic approach is developed in this paper for analyzing the machine-tool system stability under working conditions. Mathematical models are fitted to the relative longitudinal cutter-workpiece displacement data recorded under different cutting conditions during the face-milling operation on a milling machine. The stability of the system is judged from the characteristic roots of these models. The variation in stability is examined versus both the cutting speed and the feed, and good results are obtained. It is shown that not only the dynamic but also the static stability can be ascertained. Furthermore, the stability of subsystems can also be determined. The significance of these results is discussed with special reference to on-line chatter control. The analysis of vibration signals produced by similar but evenly and unevenly spaced face milling cutters is presented as a vindication of the new approach.
Elastodynamic Analysis of a Completely Elastic System
Authors: Kohli D. , Hunter D. , Sandor G. N.
Published: November 2010

The completely elastic system considered for this vibration analysis consists of an offset slider-crank mechanism having (a) elastic supports and mountings of the mechanism permitting translational vibrations of the shafts and supports, (b) elastic shafts permitting torsional vibrations, (c) elastic links of the mechanism which deform due to external or internal body forces and allow flexural and axial vibrations. Both the effect of the deformations caused by the inertia forces in the mechanism links, shafts, and supports and the effect of change in the inertia forces due to these deformations are taken into account in constructing a general mathematical model for conducting elastodynamic analysis. The rigid displacements (finite and infinitesimal) of the mechanism links due to deformations in the support are evaluated using a truncated Taylor series approximation. Deformation in the links caused by the inertia forces is approximated by a finite number of terms in a Fourier series using the Raleigh-Ritz method. The Lagrange equations of motion are used to obtain coupled time varying linear ordinary differential equations of motion for the vibration analysis of the slider-crank mechanism. The method in general may be applied to any planar or spatial system consisting of elastic links, elastic shafts, and elastic supports. Numerical examples are presented for illustration.
On the Elastokinematics of the Involute Gear Pair
Authors: Crisp J. D. C. , Rebbechi B.
Published: November 2010

The planar motion of the spur-gear pair having unseparated teeth of involute and elastically deformable form is analyzed by reducing it to an elastically and inertially constrained five-bar chain of mobility three. Particular concern is in describing the movement of the material point of profile contact and so in establishing the displacement and velocity constraint equations that govern the four angular coordinates that describe the instantaneous state of the assemblage. An expression is developed for the elasticity-dependent sliding velocity at tooth contact. The concept of the virtual base circle is introduced to make explicit the irrelevance to deforming teeth of the pitch point and the invariance property of the common normal that are apt to rigid teeth.
A Numerical Method for the Dynamic Analysis of Mechanical Systems in Impact
Authors: Beckett R. E. , Pan K. C. , Chu S. C.
Published: November 2010

This paper develops a general procedure for solving mechanism problems where intermittent separations and impacts can occur between mating parts. The numerical technique employed to solve the problem identifies the onset of separation and gives the behavior of the mechanism during separation and impact. The Hertz law is used to find force displacement relationships in impact. Equations of motion are generated by using Hamilton’s principle. A key contribution of this paper is the development of a general approach to the handling of constraint conditions that occur during the separation and impact phase of the motion. Example problems are solved to illustrate the generality and breadth of the method of solution.
Hydroforming Process for Uniform Wall Thickness Products
Authors: Tirosh J. , Yosifon S. , Eshel R. , Betser A. A.
Published: November 2010

A fundamental new approach of deep drawing processes for uniform wall thickness is suggested and proved experimentally. It is based on imposition of a back-up fluid pressure which is prescheduled to vary with respect to the punch position during the drawing stroke in the hydroforming process. The formula for scheduling this fluid pressure path is generated via the plastic limit analysis and presented in terms of the geometry of the product, the work-hardening of the material, and the friction coefficient. It leads systematically to better results than empirical procedures reported in the current literature and industrial technical reports. Experiments in hydroforming sheets to cups and hemispheres performed on different materials (Al, Cu, and stainless steel) substantiate the improvement suggested. The associated overall punch load is overestimated (at most by 15 percent) with the unique feature of including Coulomb friction into the rigorous upper bound analysis.
Bunker Design—Part 3: Wall Pressures and Flow Patterns in Funnel Flow
Authors: Van Zanten D. C. , Richards P. C. , Mooij A.
Published: November 2010

A maximum of four zones have been found to exist within a funnel flow bunker. The wall pressures depend upon whether or not material is flowing along the wall. High pressures were found just above irregularities.
Wheel/Rail Vertical Forces in High-Speed Railway Operation
Authors: Radford R. W.
Published: November 2010

The nature and magnitude of the vertical forces between a railway vehicle wheel and the rail at a dipped rail joint is investigated using methods developed by British Rail. The dependence of these forces on the unsprung weight is determined and a procedure is given for the specification of new equipment to insure that the principal wheel/rail forces at higher speeds will not exceed those of a reference vehicle at conventional speeds.
Heterogeneity of Deformation in Cold-Rolled Brass
Authors: Thompson N. J. , Bradley W. L.
Published: November 2010

The heterogeneity of deformation produced in alpha brass during cold rolling for various deformation zone geometries has been studied. The strain variation through the thickness was measured indirectly using indentation hardness. The redundant strain factor Φ, which is the ratio of the average strain through the thickness to the geometric strain, was found to increase from 1.0 to 16.3 as the deformation zone height to width ratio (Δ) increased from 1.0 to 11.2. Slip line field predictions of the redundant strain factor for various Δ values were made assuming no friction and no strain hardening. The predictions were in surprisingly good agreement with the experimental observations.
Analytical Prediction of Three Dimensional Cutting Process—Part 1: Basic Cutting Model and Energy Approach
Authors: Usui E. , Hirota A. , Masuko M.
Published: November 2010

The paper proposes a new model of chip forming process in three dimensional cutting with single point tool, in which the process is interpreted as a piling up of orthogonal cuttings along the cutting edge. Based upon the proposed model, an energy method similar to the upper bound approach, which enables to predict the chip formation and the three components of cutting force by using only the orthogonal cutting data, is developed. The method is also applied to predict chip formation and cutting force in oblique cutting, plain milling, and groove cutting operations.
Flanged Acrylic Plastic Hemispherical Shells for Undersea Systems—Part 2: Static and Cyclic Fatigue Life Under Hydrostatic Loading
Authors: Stachiw J. D. , Sletten R.
Published: November 2010

Over 25 acrylic plastic windows with t/Ri = 0.364 in the shape of hemispherical domes with equatorial flanges have been thermoformed from flat sheets and tested under short term, long term, and cyclic pressure loading at 65–75°F ambient temperature. Two kinds of flanges with O-ring grooves on the bearing surfaces were experimented with: Type 1, a flat lip with a rounded heel and instep, and Type II, a conical lip with a rounded heel. The 14,500 psi short term critical pressure of hemispherical windows with t/Ri = 0.364 was found to be independent of the equatorial flange configuration. Both the static and cyclic fatigue lives of the windows were also found to be independent of equatorial flange configuration. In either case, the maximum acceptable working pressure for 65–75°F temperature range was found to be 1000 psi. Only by elimination of the O-ring groove in the bearing surface of the window flange and the use of a thin neoprene bearing gasket between the arylic flange and the steel is it possible to extend the working pressure to 2000 psi for 65–75°F temperature range. Operating the flanged windows at pressures in excess of the safe working pressures shown above will generate fatigue cracks in the bearing surface of the flange in less than 1000 pressure cycles; at 5000 psi pressure the cyclic fatigue life decreases to less than 100 cycles.
Limit Analysis of Hollow Disk Forging—Part 2: Lower Bound
Authors: Sauerwine F. , Avitzur B.
Published: November 2010

A lower bound for hollow disk forging is presented. The hollow disk is separated into several regions by permissible surfaces of stress discontinuity. The friction stress in each zone is assumed to be either variable or constant; the overall friction stress distribution has characteristics similar to experimentally determined distributions. A statically admissible stress field describes the stress distribution within each deforming zone. The dependence of the relative average pressure, the friction stress distribution and the neutral radius upon friction and ring geometry is given. It is found that only for thin rings is the friction stress constant over most of the interface. Finally, it is proposed that friction factors being measured by use of the mathematically calibrated ring compression test may be somewhat high.
Computerized Selection of Optimum Machining Conditions for a Job Requiring Multiple Operations
Authors: Rao S. S. , Hati S. K.
Published: November 2010

The problem of determining the optimum machining conditions for a job requiring multiple operations has been investigated. Three objectives, namely, the minimization of the cost of production per piece, the maximization of the production rate and, the maximization of the profit are considered in this work. In addition to the usual constraints that arise from the individual machine tools, some coupling constraints have been included in the formulation. The problems are formulated as standard mathematical programming problems, and nonlinear programming techniques are used to solve the problems.
High Energy Water Jet Cutting Equations for Wood
Authors: duPlessis M. P. , Hashish M.
Published: November 2010

To evaluate the potential of cutting wood with high velocity water jets containing polymer additives it is necessary to develop general cutting equations that relate the cutting depth and specific energy to the jet parameters (nozzle size and pressure), the cutting speed and the wood properties. Wood has a complex structure and there are about 14 different properties based on standard physical tests. An experimental investigation is carried out to determine the dominant properties that effect the depth of cut for three typical wood types: maple, elm and poplar. The dominant properties are found to be the wood densities, (wet and dry) and a root mean square value of the compressive and tensile strengths normal and parallel to the grain. Linear and exponential non-dimensional equations are developed that relate the depth of cut to these wood properties and to the cutting speed and jet parameters. The exponential equation with a threshold jet velocity below which no cutting occurs gives the best agreement with experimental results. The equation is transformed to a nondimensional form from which the specific energy of cutting can be determined directly for wood with known physical properties.
Ductile Fracture in Axisymmetric Extrusion and Drawing—Part 2: Workability in Extrusion and Drawing
Authors: Oh S. I. , Chen C. C. , Kobayashi S.
Published: November 2010

In this part of the present investigation, the validity of the theory on ductile fracture was examined by the experimental data found in the literature. Then, combining the formulation of fracture criterion with the deformation mechanics obtained in Part 1, the workability of materials in extrusion and drawing was determined.
An Analysis of Thermal Cracking of Carbide Tools in Intermittent Cutting
Authors: Wu H. , Mayer J. E.
Published: November 2010

This paper re-examines the problem of thermal cracking of carbide tools during intermittent cutting. In the paper a two-dimensional tool model is presented. A square-wave type of heat flux is assumed in the model to simulate the thermal loading of the tool during the cutting and non-cutting cycle. The transient temperature and thermal stress distributions of the tools are obtained by the finite element method. Two examples are considered in the paper to illustrate the procedures. It is found that tensile stress near the cutting edge and strong compressive thermal stress may exist in the tool respectively at different cutting cycles. Their magnitudes depend upon the tool material properties and the cutting conditions.
Static and Dynamic Analysis of Hydraulic Copying System Using Throttling Valve
Authors: Kato S. , Yamaguchi K. , Marui E.
Published: November 2010

The effect of dimension parameters of hydraulic copying control system using throttling valve on the copying accuracy is investigated from two points of view for good design of the system. One is the static characteristic in steady copying operation, and the other is the dynamic characteristics in machining a square shoulder and tapering. Some remarks which serve the design of the hydraulic copying system are clarified. The approximate equations, which are the functions of dimension parameters especially in dynamic operation, are proposed to estimate the dynamic characteristics of the copying system and to simplify the design of the system.
Prediction Equations Relating High Velocity Jet Cutting Performance to Stand Off Distance and Multipasses
Authors: Hashish M. , du Plessis M. P.
Published: November 2010

A previously derived equation for continuous jet penetration of solids (1) is combined with empirical equation for jet spreading and velocity decay in air. These equations are used to study the effects of stand off distance and multipasses on cutting depth, volume removal and specific energy. Predicted trends are compared with limited published experimental data for wood, limestone and coal. Predicted cutting depths for single and multipass cutting are in reasonable agreement with measurements. Volume removal predictions are lower than measured values because other mechanisms such as brittle fracture and reverse jet flow not included in the present penetration model contribute to total material removal by widening of the kerf beyond the effective jet width. The equations confirm the existence of optimum stand off distance and the benefits of multipasses for certain combinations of jet, material and cutting speed parameters. Numerical values of the governing nondimensional groups for optimum performance are identified for conditions encountered in typical industrial applications.
Factors Affecting Curling in Rolled Sheet
Authors: Heiple C. R.
Published: November 2010

The influence of several rolling parameters on curling during the rolling of sheet was investigated. The material studied was primarily 0.5 in. thick 2024 aluminum. The factors studied were different top and bottom roll diameters, differential strength through the thickness of the sheet, lubrication, roll-table height, reduction ratio, temperature, roll speed, and a beveled leading edge. The sheet curled toward the smaller roll, away from the better lubricated side, toward the strong side if one side was stronger than the other, and up when the entrance roll table was too high. Curling increased for greater reductions (under the conditions studied) and also increased slightly with increasing temperature. Curling was not sensitive to roll speed or a beveled leading edge. The curling observed can generally be explained on the basis of a shear in the roll gap because of different locations of the neutral points along the arcs of contact for the two rolls. Curling observed when one side of the sheet is significantly softer than the other appears to be due to greater elongation of the soft side during rolling.
Effect of Tensile Prestrain on Fatigue Strength of Aluminum Alloy in High Cycle Fatigue
Authors: Arora P. R. , Raghavan M. R.
Published: November 2010

The effect of tensile prestrain on rotating bending fatigue strength of B51-S aluminum alloy in the solution treated and precipitation hardened condition, has been studied at fatigue life in the range of 5 × 104 to 106 cycles. The fatigue strength decreases when the tensile prestrain is 1.5 percent. At a higher prestrain of 3 to 4 percent, fatigue strength is close to that of virgin material. The cyclic stress-strain curves for virgin and prestrained materials are linear. There is no perceptible strain hardening/strain softening of the material under fatigue loading. The cyclic Young’s modulus is about 4 percent lower than the static modulus irrespective of the material condition. The relative disposition of static bending stress-strain curves in the inelastic region for virgin and prestrained materials shows qualitatively the relative disposition of the corresponding S-N curves.
High Strain Rate Tensile Properties of AISI Type 304 Stainless Steel
Authors: Steichen J. M.
Published: November 2010

The high strain rate tensile properties of solution annealed Type 304 stainless steel have been determined experimentally. Tests were performed at strain rates ranging from 3 × 10−5 to 1 × 102 in./in./sec at temperatures from 600 to 1600 deg F. At temperatures to 1000 deg F, the strength and ductility are largely insensitive to variations in strain rate, whereas at temperatures from 1200 to 1600 deg F, significant increases in both strength and ductility are observed with increasing strain rate.
Tube-Bulging Under Internal Pressure and Axial Force
Authors: Woo D. M.
Published: November 2010

A numerical solution for analysis of the bulging process of a thin-walled tube under internal pressure and axial force is proposed. The solution is applied to a case in which the longitudinal stress resulted from internal pressure and external compressive load is tensile along the whole length of the bulged tube. To verify whether the solution is applicable, theoretical and experimental results on the bulging of copper tubes have been obtained and are compared in this paper.
The Beer Can as a Shock Absorber
Authors: Wirsching P. H. , Slater R. C.
Published: November 2010

Static and dynamic testing performed on steel beer and soda cans has indicated that the cans, when loaded along the longitudinal axis, possess mechanical properties ideal for shock absorption. The static and dynamic mechanical behavior of the 12 oz steel cans is presented. It was shown that the energy absorption capability of the cans is not strongly dependent upon impact velocity. Moreover it was shown that pneumatic forces caused by air entrapped in the cans contribute significantly to the total force in the can during impact.
Residual Stresses Due to Circumferential Welds
Authors: Vaidyanathan S. , Todaro A. F. , Finnie I.
Published: November 2010

The residual stress distribution produced by a circumferential weld between axisymmetric shells (cylinders, spheres, cones, etc.) is quite different from that due to a butt weld between two flat plates. The reason for this difference is pointed out and it is shown that the state of stress in thin-walled shells may be estimated from that in a plate. Since a simple approximate method for predicting residual stresses in a butt-welded flat plate is available, it is possible to estimate the stresses due to a circumferential weld from the welding conditions and certain material properties. Experimental results show good agreement with the predictions.
Failure of a Twistdrill
Authors: Smith C. O.
Published: November 2010

This is an account of the failure of a high-speed twistdrill which failed in use. A suit for damages was entered by the injured party against the manufacturer on the basis of the drill being defective. The substance of the evidence developed by the plaintiff’s expert is presented. The rebuttal evidence is also presented with the true cause of the accident being developed.
Application of a Forming Limit Concept to the Design of Powder Preforms for Forging
Authors: Downey C. L. , Kuhn H. A.
Published: November 2010

The soundness of the metallurgical structure and the associated strength of a forged powder preform material increase with increasing lateral flow during the forging process. Unconstrained lateral flow, however, enhances the possibility of fracture during deformation. In this paper, a preform design technique is presented that provides the preform shape and dimensions for forging a part to full density with a sound metallurgical structure but without fracture. The basis of the approach is a forming limit concept developed previously for cold forming processes. Application of the technique is demonstrated through design of the preform for forging a pulley blank consisting of a flange, rim and hub.
The Role of Lubrication in the Cold Heading of Mild Steel
Authors: Tevaarwerk J. L. , Plumtree A. , Sowerby R.
Published: November 2010

This work provides information leading to the evaluation of the coefficient of friction for various lubricants during the first blow of a double blow heading operation on AISI 1018 steel wire. A Waterbury-Farrel cold heading machine was instrumented so that the total force and frictional force could be evaluated during the first blow operation. The lubricants investigated fell into four main groups: 1) Lubricants, physically or chemically bonded to the wire; this group included zinc phosphate, 2) Lubricants listed in 1) used together with a petroleum based polar oil, SAE 30 [780 SUS at 80° F (167 × 10−6 m2/s at 27° C)], 3) Liquid lubricants of various viscosities employed with the bare wire, 4) Solid lubricants mixed with a non-polar mineral oil [65 SUS at 80° F (12 × 10−6 m2/s at 27° C)], again used with bare wire. The calculated coefficient of friction was used to indicate the efficiency of the respective lubricants. Liquid lubricants either alone on bare wire or with bonded lubricants proved to be the most successful in reducing the calculated μ value; additives appeared to play a minor role. The results indicate that a low cost liquid lubricant used on bare wire has both economic and operational advantages when cold heading mild steel wire.
Determination of Dewetting Criterion for Nonlinear Solid Propellant
Stress Analysis
Authors: Lindsey G. H. , Woods J. E.
Published: November 2010

A criterion for dewetting in solid propellant materials is developed from an application of Drucker’s postulate to an idealized model of stress-strain behavior. The criterion is evaluated experimentally via dewetting measurements in uniaxial and multiaxial stress states. Development of the method of data reduction for the triaxial tensile test has brought new insight to previous work reported with the test.
Failure Analysis of Cast Irons Under General Three-Dimensional Stress States
Authors: Frishmuth R. E. , McLaughlin P. V.
Published: November 2010

Observations of microscale behavior of cast irons indicate that considerable plastic flow occurs between microflaws prior to rupture. Therefore, the plastic limit load for small representative volume elements of material treated as structures should be a close approximation to the load at rupture. A representative volume element of cast iron is analyzed using limit analysis techniques to obtain bounds on the limit, or failure, surface under three dimensional average stress. Comparisons with other cast iron failure criteria and experimental data are made.
Laws for Work-Hardening and Low-Temperature Creep
Authors: Kocks U. F.
Published: November 2010

The true stress-strain curves of polycrystalline aluminum, copper, and stainless steel are shown to be adequately represented by an exponential approach to a saturation stress over a significant range. This empirical law, which was first proposed by Voce, is expanded to describe the temperature and strain-rate dependence, and is put on a physical foundation in the framework of dislocation storage and dynamic recovery rates. The formalism can be applied to the steady-state limit of creep in the same range of temperatures and strain rates; the stress exponent of the creep rate must, as a consequence, be strongly temperature dependent, the activation energy weakly stress dependent. Near half the melting temperature, where available work-hardening data and available creep data overlap, they match. Extrapolation of the proposed law to higher temperatures suggests that no new mechanisms may be necessary to describe high-temperature creep. A new differential equation for transient creep also follows from the empirical work-hardening law.
On Proportional Combined Loading Tests of an Aluminum Alloy and Its Analytical Formulation
Authors: Ohashi Y. , Kawashima K. , Mori N.
Published: November 2010

Proportional combined loading tests using axial load and torque were conducted on thin-walled tubular specimens of annealed isotropic aluminum alloy 5056. The experimental results showed that the third invariant of stress deviator affects considerably the plastic deformation of the material; that is, an equivalent stress-equivalent strain curve for simple tension or compression appears higher than that for pure torsion and the plastic strain vector is generally noncoaxial with the deviatoric stress vector. These results were formulated in the form of a nonlinear tensor relation between stress deviator and plastic strain on the basis of the general relation between coaxial tensors. The tensor equation derived was found to represent well the experimental results.
Estimation of Fatigue Limit of Steel Subjected to Bending Loads
Authors: Subramanyan S. , Janarthanan G.
Published: November 2010

A method of estimating the fatigue limit of polished steel specimens subjected to bending loads, in terms of brinell hardness number for values of stress ratios other than (−1) and mean stresses other than zero is proposed in this paper.
Continuous Extrusion by Viscous Drag
Authors: Tirosh J. , Grossman G.
Published: November 2010

A multistage continuous extrusion process based on a new concept is described and studied. The billet is driven through a series of dies by the viscous drag of a fluid flowing along its perimeter, allowing for an unlimited length of the extruded product. Design parameters are obtained from an analysis of the flow and of the stresses in the billet. The geometry of the dies, the extrusion chambers, and the optimal flow characteristics are determined. Technical problems such as buckling of the billet and temperature rise of the fluid are discussed. Experimental results with a one-stage unit are given and compared to the theoretical prediction.
Cyclic Plasticity for Nonproportional Paths: Part 1—Cyclic Hardening, Erasure of Memory, and Subsequent Strain Hardening Experiments
Authors: Lamba H. S. , Sidebottom O. M.
Published: November 2010

Extensive experiments were conducted on annealed copper under cyclic nonproportional strain histories. After cyclically stabilizing the material by uniaxial cycling, out-of-phase axial-shear strain cycling for the same effective strain range caused additional increases in stress amplitudes to restabilized levels. Following cyclic stabilization of the material under out-of-phase cycling, a cycle whose effective strain amplitude was comparable to those of previous cycles resulted in stress-strain behavior unique to that cycle and independent of prior stable deformation. The experimental verification of this material property, which has been the subject of much conjecture, allowed the design of a fundamental class of experiments that determined the subsequent yield surface and strain hardening behavior from only one specimen.
An Experimental Study of Progressive Strain Growth Due to Thermal-Stress Ratcheting
Authors: Uga Takeo
Published: November 2010

A special plate-shaped specimen with two symmetrical, straight air gaps in the center portion and a pair of holes for load chucks at the end portion is used for thermal-stress ratcheting experiments. Experimental results on strain growth due to thermal-stress ratcheting are presented for specimens made of types 304 and 316 austenitic stainless steel. The results cover cumulative and incremental strain growths under conditions of load variation and the effect of hot to cold bar area ratio.
The Determination of the J-Integral on Precracked Charpy Specimens by Instrumented Impact Testing and Slow-Bend Testing
Authors: Nguyen-Duy P. , Phelippeau G. , Simoneau R. , Begin G.
Published: November 2010

The fracture criterion JIC is determined on SA-516-70 steel using precracked CVN specimens. The addition of an appropriate side-groove results in a better plane-strain condition at the crack tip and removes a major part of the absorbed energy due to lateral deformation. The value of JIC static is calculated from a single three-point-bend experiment. The displacement of the cracked front is followed by the measurement of the electrical resistance. We have shown that a single specimen is sufficient for determining JIC. Experiments on an instrumented Charpy machine were used for the calculation of the value of JICD. We assumed, for elasto-plastic behavior, that the maximum point of the load-displacement curve corresponds to the instability threshold of the crack. The values of JIC and JICD obtained by these two methods are compared and discussed.
A Description of a Study for the Thermal Anneal of Neutron-Embrittled Reactor Vessel Materials
Authors: Mager T. R. , Marston T. U.
Published: November 2010

A number of early light water reactor plants were constructed from materials having low initial Charpy upper shelf values and high copper and phosphorus content. As these elements have been shown to contribute the most to the radiation sensitivity of reactor pressure vessel material, there is a possibility that thermal annealing of the bellline regions of the these vessels may become necessary to meet Nuclear Regulatory Commission requirements for continued operation. Recognizing the possibility that thermal annealing treatment of the reactor vessel may become a reality, a program was started to determine the kinetics and mechanisms of thermal annealing to restore preservice fracture toughness and to develop engineering procedures for ready application to large-scale nuclear pressure vessels. This paper presents the program scope required for establishing the feasibility of and methodology for an in situ thermal anneal of an embrittled reactor vessel.
A State Variable Interpretation of Some Rate-Dependent Inelastic Properties of Steel
Authors: Larsson B. , Stora˚kers B.
Published: November 2010

Based on a state variable theory proposed by Onat some discriminating creep tests of stainless steel have been designed and carried out at elevated temperature conditions. Quantitative correlations of the results are sought with predictions from a physical theory for recovery creep proposed by Lagneborg. The findings are utilized to interpret the behavior of creeping members when subjected to a rapid increase in the rate of straining. Different approaches toward generalization of physical one-dimensional creep laws to multiaxial stress states are discussed. A tentative constitutive equation applicable to the solution of general boundary value problems is proposed.
Applicability of Fracture Mechanics Parameters to Crack Propagation Under Creep Condition
Authors: Koterazawa R. , Mori T.
Published: November 2010

A critical examination was made of the applicability of fracture mechanics parameters to crack propagation under creep condition with 304 stainless steels for a variety of specimen geometries at relatively high stress levels. The creep crack propagation rate could not be described in terms of elastic stress intensity factor but it could be in terms of net section stress for all dimensions of thin plate specimen. The net section stress, however, could not explain the difference between crack propagation rates of thin plate specimens and those of notched round bar specimens. This difference could be ascribed to the plastic constraint around the crack tip. Applicability of the modified J-integral to creep crack propagation was also examined and the results showed that this parameter was better for predicting the creep crack propagation rate at a high stress level. In the case of speicmens of similar geometries, the net section stress could be used in place of the modified J-integral provided that crack propagation rate was divided by the characteristic length of the specimen.
Unsteady Flow Phenomena in Rotating Centrifugal Impeller Passages
Authors: Lennemann E. , Howard J. H. G.
Published: November 2010

The phenomena of unsteady relative flow observed in a centrifugal impeller passage running at part capacity and zero flow are discussed. The mechanisms of passage stall for a shrouded and unshrouded impeller are investigated and a qualitative correlation is developed for the influence of secondary flow and inducer flow on the passage stall. The hydrogen bubble flow visualization technique is extended to higher velocities and rotating systems and provides the method for obtaining the experimental results.
A Dynamic Model and Measurement Technique for Studying Induction Air Swirl in an Engine Cylinder
Authors: Huebner K. H. , McDonald A. T.
Published: November 2010

A dynamic engine model and measurement technique have been developed to study induction air swirl in the cylinder of a 4-stroke-cycle engine. Fabrication of the cylinder and piston crown of the model from transparent plastic permitted flow visualization. Local mean flow directions were determined qualitatively using a tuft grid. Paddle wheels were used to determine the gross swirl characteristics of the flow. A single sensor hot wire anemometer placed in three orientations was used to measure the three orthogonal components of local mean velocity. An error analysis indicated that the technique gives results accurate within ±20 percent. The methods developed allow measurements under actual dynamic conditions of the gross swirl characteristics of different flows, as well as the detailed velocity fields at any time during the intake stroke. Sample results are presented to illustrate the application of the methods.
Computation of Thermodynamic Properties of Carbon Dioxide in the Range 0–750 Deg C
Authors: Angelino G. , Macchi E.
Published: November 2010

The computation of power cycles employing carbon dioxide as working fluid and extending down to the critical region requires the knowledge of the thermodynamic properties of CO2 within a wide range of pressures and temperatures. Available data are recognized to be insufficient or insufficiently accurate chiefly in the vicinity of the critical dome. Newly published density and specific heat measurements are employed to compute thermodynamic functions at temperatures between 0 and 50 deg C, where the need of better data is more urgent. Methods for the computation of thermal properties from density measurement in the low and in the high temperature range are presented and discussed. Results are reported of the computation of entropy and enthalpy of CO2 in the range 150–750 deg C and 40–600 atm. The probable precision of the tables is inferred from an error analysis based on the generation, by means of a computer program of a set of pseudoexperimental points which, treated as actual measurements, yield useful information about the accuracy of the calculation procedure.
The Fluid Dynamics of a Shrouded Disk System With a Radial Outflow of Coolant
Authors: Bayley F. J. , Owen J. M.
Published: November 2010

This paper describes an experimental study of an air-cooled gas turbine disk using the model of a disk rotating near a shrouded stator. Measurements of pressure distribution, frictional moment, and the cooling air flow necessary to prevent the ingress of hot gases over the turbine disk are described for a range of rotational speeds, mass flow rates, and different geometries. The pressure distribution is shown to be calculable by the superposition of the pressure drop due to the shroud and the unshrouded distribution. Moment coefficients are shown to increase with increasing mass flow rate and decreasing shroud clearance, but are little affected by the rotor/stator gap. Applying Reynolds analogy to the moment coefficients, it is estimated that heat transfer from the rotor will be controlled primarily by rate of radial cooling flow at low rotational Reynolds numbers, and will be governed primarily by Reynolds number at large rotational speeds.
Nuclear Power Plants With Closed-Cycle Helium Turbine for Industrial Energy Supply
Authors: Bammert K. , Boehm E. , Buende R.
Published: November 2010

All the possible arrangements of closed-cycle helium turbines for combined power and steam generation can be reduced to three variations of one single arrangement. A method for the optimum layout of this arrangement is described. Optimum data are determined for the expansion ratio and the regenerative heat exchange as functions of general parameters—electric power output and quantity and quality of the steam produced—and as functions of special parameters of the gas turbine cycle—number of intercoolers, cooling and feedwater temperatures, turbine inlet temperature and pressure drop—to obtain the best possible efficiencies.
150 kwe Supercritical Closed Cycle System
Authors: Hoffmann John R. , Feher Ernest G.
Published: November 2010

This paper explores the potential applicability of the Supercritical (Feher) Thermodynamic Power Cycle to advanced ground nuclear power systems. The supercritical cycle is a closed cycle heat engine that operates entirely above the critical pressure of the working fluid. It is characterized by high thermal efficiency and compactness of the machinery. The cycle is highly regenerated and receives heat over a narrow temperature range. For the evaluation of the advantages of the power conversion concept, a 150-kwe power conversion module has been selected that employs a gas turbine driven high speed alternator, using carbon dioxide as the working fluid.
Effect of Dimensional Parameters of Impellers on Performance Characteristics of a Radial-Inflow Turbine
Authors: Watanabe I. , Ariga I. , Mashimo T.
Published: November 2010

An experimental radial-inflow turbine having a pressure ratio of 2:1 was constructed, and the effect of dimensional parameters of an impeller was examined by performance tests of the turbine using compressed air. A series of four impellers having different passage areas and another series of three impellers having different mean diameters of exducer exits but with the same exit annular areas were employed to examine the effect. In addition, the effects of side clearance between impeller shroud and casing as well as radial clearance between nozzle exit and impeller inlet were examined.
Computed Performance Characteristics of Electrofluid Dynamic Colloid Generators
Authors: Minardi J. E.
Published: November 2010

The effects of the electric breakdown limitation on the power output of an electrofluid dynamic generator operating with colloids are studied. The study is performed for both an axisymmetric cylinder of charge and a two-dimensional (Cartesian) slab of charge between infinite, plane, parallel electrodes. The ratio of radius to length or width to length varies from zero to infinity, thus both the so-called slender channels (reference [9]) and broad channels (reference [2]) as well as the intermediate geometries are studied. Normalized power (the value of which is basically limited by electric breakdown) is presented as a function of normalized gas velocity and normalized applied voltage. Also presented is a normalized power per unit mass flow rate as a function of the normalized velocity and voltage. A single chart is sufficient to cover all geometries because the normalized power includes a geometric factor which can be determined from an auxiliary curve to account for the particular geometry.
Corrosion of Heat-Exchange Tubes in a Simulated Coal-Fired MHD System
Authors: Bienstock D. , Demski R. J. , Corey R. C.
Published: November 2010

An experimental unit was built to burn 125 lb of coal an hour at 4000 deg F in a cyclone burner with oxygen-enriched air preheated to 1500 deg F to ascertain the fireside corrosion problems that might be encountered in the coal-fired MHD generation of power. Potassium carbonate was added to the coal at seed concentrations that would be expected in an MHD combustor. Tubes having a metal composition used in conventional steam generators, and also having a range of alloy compositions that might have potential use in an MHD system, were maintained at surface temperatures of 800–1500 deg F and exposed to products of combustion at 1800–2500 deg F. The seeded flue gas was generally more corrosive than the unseeded. In tests up to 100-hr duration, Haynes 25 was slightly attacked at a wall temperature of 1500 deg F in combustion gas at 2500 deg F; the stainless steels 310, 316, and 446 were resistant at a metal temperature of 1100 deg F in gas at 2100 deg F; carbon steel was attacked at 800 deg F wall temperature and 1800 deg F flue gas.
Development of Cryogenic Heat Pipes
Authors: Eggers Philip E. , Serkiz Aleck W.
Published: November 2010

The operation of a LN2 cryogenic heat pipe has been demonstrated experimentally in the range 78 K to 90 K. This heat pipe involves a totally new wick concept, viz., the “parallel capillary channel” wick, which affords a heat flux capability an order of magnitude higher than possible with the more conventional heat pipe wick structures. The experimental measurements were performed utilizing specially designed cryogenic heat pipe evaluation equipment which permitted heat flux measurements accurate to within 8 percent. The design and optimization of the cryogenic heat pipe is discussed including a description of the BCL generalized heat pipe computer program. A comparison of experimental data with analytical predictions is also provided.
The Role of Chloride in the Corrosion Caused by Flue Gases and Their Deposits
Authors: Cutler A. J. B. , Halstead W. D. , Laxton J. W. , Stevens C. G.
Published: November 2010

The role of chloride in the corrosion of oil- and coal-fired boilers and gas turbines, by flue gases and their deposits, is discussed, on the basis of both experimental and theoretical studies. It is concluded that in most boilers, the presence of chloride in the fuel will not result in any serious increase in the rate of corrosion of plant components. On the other hand, a number of situations are identified, which can arise in both boilers and gas turbines, in which high chloride levels in the fuel can be associated with enhanced rates of corrosion.