bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Processing Variables on Mechanical Properties and Sulfide Stress Cracking Resistance of SAE 4135 Steel Modified With 0.75 Percent Mo and 0.035 Percent Cb
Authors: Grobner P. J. , Sponseller D. L. , Diesburg D. E.
Published: November 2010

Laboratory heats of SAE 4135 steel modified with 0.75 percent Mo and 0.035 percent Cb were tested for the effect of rolling temperature, cooling rate after austenitizing and after tempering, and tempering time and temperature on mechanical properties and sulfide stress cracking (SSC) resistance. The SSC resistance of unworked heat-treated material was also determined. Tests were performed on bent beam specimens and double cantilever beam specimens. Hot working temperature in the range of 815 – 1205°C (1500–2200° F) has practically no effect on SSC resistance. Cast modified SAE 4135 steel in the quenched-and-tempered conditon has lower SSC resistance than wrought material, but the SSC resistance of the unworked material is nevertheless about equal to that of wrought SAE 4130 steel in the quenched-and-tempered condition having the same yield strength. Optimum SSC resistance of modified SAE 4135 steel is obtained in quenched-and-tempered material with a uniform structure of tempered martensite. The SSC resistance is reduced with increasing amounts of bainite in the microstructure. SSC resistance increases with increasing tempering time and temperature. Rapid cooling after tempering reduces SSC resistance only insofar as it increases the hardness of the steels. SSC resistance of the modified steel is distinctly higher than that of unmodified SAE 4130 steel. This advantage increases with increasing strength level of the steel.
Liquid Container Filling and Charging
Authors: Nunn R. H. , Gibson E. J.
Published: November 2010

A simple analytical model has been developed to describe the dynamic behavior of a liquid slug as it is rapidly and suddenly rammed into a receiving chamber. Useful closed-form solutions are obtained from approximate versions of the governing relationships. Experimental results indicate the essential correctness of the analytical formulation.
Regenerative Drive for Subway Trains—Part 3: System Evaluation
Authors: Flanagan R. C. , Suokas L. A.
Published: November 2010

The most efficient hybrid drive philosophy eliminates high-acceleration power peaking and operates as a fully regenerative system (little or no accumulator top-off during station stop). The optimal accumulator control concept is designed as vehicle velocity dependent and is shown to vary only slightly with vehicle load and station distance. Furthermore, accumulator sizing is numerically determined subject to this control concept. The effect of large coast (5 percent) or cruise periods opposes the justification of any regenerative system and is herein questioned as an integral part of the drive cycle. Conversely, short coast (2 percent) or cruise has little effect on the hybrid drive performance. As a basis of comparison (with other drive systems), the ideal vehicle concept is postulated.
The Future of Safety and Health: A Challenge to Engineering Managers
Authors: Stanton George B.
Published: November 2010

Engineers always have considered safety in their decisions on design concepts and design criteria. But the values of our society are changing, and so different emphases are necessary in these decisions. This paper reviews three approaches to safety, the multiple values which our society uses when evaluating the work of engineers, and the principles of engineering design. The interaction of these factors is discussed, resulting in suggestions to guide engineers and managers in making design decisions for the future.
Mechanical Separation Phenomena in Picking Mechanisms of Fly-Shuttle Looms
Authors: Hart F. D. , Patel B. M. , Bailey J. R.
Published: November 2010

Mechanical separation between cam and pick ball in fly-shuttle looms gives rise to impact and vibration which causes significant noise emission. Elimination of separation is analyzed using a mathematical model which simulates the dynamic response characteristics of the system. Parameters considered in the study include equivalent stiffness, mass, and damping of the system, amplitude of excitation, effect of preload provided by a retaining spring, and operating frequency. Combinations of system parameters and operating conditions which give rise to separation are predicted by examining the contact force developed between cam and cam-follower. Equations and graphs are presented that specify the preload required to eliminate separation as a function of the system parameters.
On the Theory of the Calculation of the Constant Velocity Ball Transmission Joints
Authors: Bellomo N.
Published: November 2010

In this work a general method for the calculation of constant velocity ball transmission joint with straight grooves is studied. Numerical calculations concerning the forces transmitted by each driving ball and the torque capacity have been realized with reference to known and manufactured types of joint. The study allows one to deduce some important and experimentally confirmed designing rules and gives a precise picture of the load distribution in the joint as well as the limits of safe working conditions.
Semiactive Control of Multimode Vibratory Systems Using the ILSM Concept
Authors: Karnopp D. , Allen Ross R.
Published: November 2010

The Identically Located Sensor and Manipulator concept involves deriving a control force from measurements of motion at the force generator mounting point. A semiactive force generator may be made from a damper whose force-velocity law can be varied in response to a signal. These two ideas are discussed and the advantages from combining the two ideas for controlling several normal modes for distributed parameter structures are presented. Computer simulation results comparing active, semiactive, and passive suspensions for a beam-like structure subjected to broadband noise excitation are given to illustrate the performance capability of each system.
Application of the Deformation Theory of Plasticity for Determining Elastoplastic Stress and Strain Concentration Factors
Authors: Eimermacher J. P. , Wang I.-Chih , Brown M. L.
Published: November 2010

The deformation theory of plasticity is considered as a means for obtaining a solution to the problem of calculating stress and strain concentration factors at geometric discontinuities where the local stress state exceeds the yield strength of the material. Through the use of the Hencky-Nadai constitutive law and the Von Mises failure criteria, the elastoplastic element stiffness matrix is derived for a plane stress triangular plate element. An elastoplastic solution is arrived at by considering direct-iterative and finite element techniques. Verification of the analytical results is obtained by considering a numerical example and comparing the calculated results with published experimental and analytical data.
The Mechanical State of the Sublayer of a Surface Generated by Chip-Removal Process—Part 1: Cutting With a Sharp Tool
Authors: Liu C. R. , Barash M. M.
Published: November 2010

The mechanical state of a machined component surface was studied and three quantitative measures, namely, apparent strain energy density, strain hardening index, and residual stress distribution in a semi-infinite model, were established as parameters defining it. The surface generated by a sharp tool is discussed in the first paper of a two-paper sequence. Phase change was isolated by machining low-carbon steel in selected conditions, so as to reveal the basic mechanism controlling the surface mechanical state. The length of the shear plane (or cutting ratio) was found to be a unique parameter which determines the mechanical state of the surface layer. Mechanical state of the surface due to temperature effect cannot be separately considered from the chip-removal mechanism. The size effect appears to be significant in both removing the chip and deforming the surface. The cutting force obtained by extrapolating to zero depth of cut does not represent the force deforming the surface.
The Mechanical State of the Sublayer of a Surface Generated by Chip-Removal Process—Part 2: Cutting With a Tool With Flank Wear
Authors: Liu C. R. , Barash M. M.
Published: November 2010

The mechanical state of a surface machined with a tool having flank wear is discussed in this paper, which is the second in a sequence of two papers, the first dealing with sharp tools. A technique is developed to ensure proper contact between artificially produced flank wear land and the workpiece. Mechanical state indices developed earlier, viz., apparent strain energy density, strain hardening index, and residual stress distribution in a semi-infinite model, were found to be governed and characterized by shear plane length, depth of cut, and the flank wear length. Thermal effects due to flank wear were also observed. Depending upon the cutting speed and thus upon the temperature generated, the residual stress pattern is lightly or severely modified. It is established that the thermal effect is primarily the result of yield strength change rather than of thermally induced strain.
Analytical and Experimental Investigation of Elastic Slider-Crank Mechanisms
Authors: Golebiewski E. P. , Sadler J. P.
Published: November 2010

Analytical and experimental dynamic bending stresses are determined for a slider-crank mechanism with a rigid crank and an elastic connecting rod. The mathematical model is derived by way of the lumped-parameter approach using d’Alembert’s principle and the Euler-Bernoulli beam equation. Viscous damping is included, and the resulting differential equations are solved numerically. Experimental data are obtained by means of strain gauge bridges mounted on the connecting rod. The effects on the elastic response of various parameters, including the crank speed, crank length, and slider offset, are examined. Comparison of the analytical and experimental results shows good agreement.
Heuristic Combinatorial Optimization in the Kinematic Design of Mechanisms—Part 2: Applications
Authors: Lee T. W. , Freudenstein F.
Published: November 2010

The heuristic algorithm, developed in Part 1, is applied here to solve certain realistic mechanisms synthesis problems. These include dimensional synthesis of a rotary-to-linear recording mechanisms for minimum structural error, torque minimization of a variable-speed drive, and kinematic synthesis of the printing-bed drive of a printing-press mechanism with optimization of displacement-time function of working stroke. The solution of these problems represents a confirmation of the effectiveness of the algorithm, and at the same time the problems we have selected are believed to be significant representatives of unsolved or partially solved problems in the mechanisms design field.
Reduction of the Contact Stress in Internal Gear Pumps
Authors: Colbourne J. R.
Published: November 2010

A method is described for calculating the tooth contact stresses in internal gear pumps, and it is shown that a considerable reduction can be achieved in the maximum contact stress by altering the proportions commonly used in existing pumps.
Electromechanical Dynamics of a Four-Link Mechanism Operating in a Magnetic Field
Authors: Smith W. D. , Reed W. S.
Published: November 2010

The electromechanical dynamics of a four-link mechanism moving in a magnetic field perpendicular to the plane of motion is considered. As the linkage moves, a voltage is generated around the closed conducting path formed by the mechanism links, causing current to flow through these links. As a result of the magnetic field and this induced current, time varying, distributed magnetic forces act on each link. The equations of motion of the mechanism and the generated current are derived for a torque input on the driving link. These equations are then integrated numerically in an example design.
Mechanisms as Components of Dynamic Systems: A Bond Graph Approach
Authors: Allen R. R. , Dubowsky S.
Published: November 2010

In recent years, bond graphs have been used to analyze complex dynamic systems. In this paper a bond graph study is made of the kinematics and dynamics of a general mechanism treated as a component of a dynamic system. The method is applicable to multiple-loop, multiple degree-of-freedom mechanisms for which the displacement and velocity loop equations are known. A bond graph multiport representing the kinematic relations forms a power-conserving core to which dissipative, inertial, and compliance effects may be added to form a dynamic mechanism model. A constitutive relation suitable for automatic computation is derived in terms of system variables. A numerical example is presented illustrating an application of the technique.
On the Mechanics of Tapping by Cutting
Authors: Henderer W. E.
Published: November 2010

The mechanics of the tapping process by cutting have been investigated by means of a mathematical model that predicts the magnitude of torque and the parameters that influence torque variation. The analysis is based on an extension of the plane deformation model developed by Armarego for triangular groove cutting. Experimental analysis shows that additional contributions to torque exist that are not required for material removal alone. When these contributions are accounted for or are eliminated, the model provides an adequate torque prediction and responds properly to pertinent tapping parameters.
Particle Size Analysis of Cotton Dust Using Scanning Electron Microscopy
Authors: Fornes R. E. , Kleinfelter M. M. , Hersh S. P.
Published: November 2010

Particle size distributions of dusts generated in a model card room and collected on filter media by a vertical elutriator having a particle size cut-off of 15 μm dia have been determined using scanning electron microscopy. Photomicrographs, usually at 3000×, were made of the samples and the particle diameters were estimated by the Martin method. It was found that the average particle size of cotton dust samples measured by this technique was smaller than that reported in the literature obtained by light microscopy. It was also found that the distribution of particle sizes does not follow a simple log-normal distribution unless the smallest particles observed in this study are omitted. A bimodal or perhaps a multimodal distribution yields a better representation of the data. It is concluded that scanning electron microscopy is a practical and accurate method for sizing cotton dust particles on filter surfaces.
Tool-Life Distributions—Part 2: Multiple-Injury Tool-Life Model
Authors: Ramalingam S.
Published: November 2010

The single-injury tool-life model developed in Part 1 of this paper is extended to the case of tool failure due to a multitude of injuries. The expected tool-life distribution in the case of tool failure from multiple injuries due to constant, time-independent stochastic hazards is shown to be a gamma distribution. The result obtained is based on a linear wear-rate assumption. The model is further extended to ensure applicability in the nonlinear wear region. It is shown that the expectation of a log-normal tool-life distribution when tool failure is due to crater wear is not unrealistic. No specific mechanism of tool wear is used to develop the model. The nature of the hazards and the wear mechanisms that are consistent with the multiple-injury tool-life model will be discussed in a subsequent work.
Optimization of Helium Refrigerators for Superconducting Power Transmission Lines in Terms of Cost and Reliability
Authors: Kadi F. J. , Longsworth R. C.
Published: November 2010

Helium refrigerators for superconducting power transmission lines are optimized in terms of the minimum cost required to achieve a specified level of reliability. This paper summarizes the cost and reliability of large helium refrigerator components as determined from a survey of existing refrigerators, compressor and expander studies, and an analysis of Air Products unattended standard nitrogen plants. These data are used to analyze the cost and reliability of several alternate refrigerator designs.
A Method for Optimal Tolerance Selection
Authors: Ostwald P. F. , Huang J.
Published: November 2010

This paper introduces and formalizes a method for specifying independent functional tolerances in an optimal least-cost manner. Previous methods have been thwarted by formulation and computational difficulties presented by nontrivial designs. This method is versatile, submits to a diversity of mechanical problems, and relates the production process and cost to process tolerance in the optimization. This tolerance-specification scheme follows Balas’ zero-one algorithm. Generality and efficiency of the method are discussed. Effects of tolerance relaxation on costs are given. Small and large design problems, constructed to satisfy the requirements of the algorithm, show the practical ramifications. The problem is treated with limit, sensitivity, and probability analysis. Widespread adoption of the method throughout industry is encouraged.
Graphical Solution of the Branch and Order Problems of Linkage Synthesis for Multiply Separated Positions
Authors: Waldron K. J.
Published: November 2010

The graphical solutions to the order and branch problems previously developed for the P-P-P-P case are extended to cover all finitely separated, infinitesimally separated, and multiply separated four-bar Burmester synthesis problems. Two examples are given in detail: a P-P-P-P-P problem and a PP-P-P problem.
Design of a Viscoelastic Dynamic Absorber for Machine Tool Applications
Authors: Nessler G. L. , Brown D. L. , Stouffer D. C. , Maddox K. C.
Published: November 2010

The design equations are developed for a viscoelastic dynamic absorber in uniaxial compression. The dependence of mechanical properties of the absorber on frequency, temperature, and preload are developed through an extension of the thermorheologically simple theory of linear viscoelasticity. An approximation of the exact boundary value problem is made in order to develop practical design criteria for the size and shape of the absorber element. The results of the experimental program for the constitutive equation are included. A dynamic absorber is designed to control a self-excited lathe chatter problem and a significant improvement is demonstrated.
A Regenerative Compressor
Authors: Sixsmith H. , Altmann H.
Published: November 2010

A regenerative or peripheral compressor has been developed with aerodynamic blading in place of the usual straight radial vanes on the rotor. The blades are shrouded by a core, around which a helical toroidal flow path is established. Two compressors have been constructed, the first with a single row of blades and the second with two rows side by side to provide parallel counterrotating flow paths. The diameter of the impellers is 0.30 m. The characteristics of the compressor resemble those of a Rootes blower, with a steep variation of pressure with respect to flow rate. At a speed of 4000 rpm the isothermal efficiency reaches a maximum of 57 percent when the pressure ratio is 1.17 and the flow rate is 0.2 m3/s. When the flow rate is reduced by throttling to 0.165 m3/s the pressure ratio is raised to 1.50, but the isothermal efficiency is reduced to 44 percent. The theory, design, and development of the compressor are discussed.
Optimum Design of Ribbon and Wire Wound Cylinders for Metal Forming Dies
Authors: Gro̸nbaek J. , Wanheim T.
Published: November 2010

The ribbon winding process enables the manufacture of metal forming dies with higher allowable internal working pressure than is possible by conventional shrink-fit constructions. Varying the tensile stress in the ribbon in the winding process, the stress distribution in the die can be given a predetermined shape. Based on the assumption that all ribbon layers carry the same shear stress when the internal working pressure is acting, a new winding theory is derived. This method permits the internal working pressure to be increased about 30 percent compared to that of the previously known winding theories and about 60 percent compared to that of shrink-fit constructions.
Thermal Stresses From a Moving Band Source of Heat on the Surface of a Semi-Infinite Solid
Authors: Mercier R. J. , Malkin S. , Mollendorf J. C.
Published: November 2010

Thermoelastic stresses arising from a moving band source of heat on the surface of a semi-infinite solid have been calculated using well-known temperature solutions and a finite element stress analysis. Results are presented in nondimensional form for a wide range of conditions for both quasi-steady state and transient regimes. The effect of convective cooling at the surface has also been investigated. Peak stresses, which occur at the surface, have been related to a modified source Peclet number for instances in which surface cooling is not employed. Reduction in stress levels due to convective cooling at the surface has also been determined. For all cases considered, the greatest stress levels were found to occur at the surface of the constrained direction. Using results obtained in this study, thermoelastic stresses in sliding and machining processes may be calculated in order to predict the onset of yielding which can result in residual tensile stresses and cracking.
Analytical Prediction of Three Dimensional Cutting Process—Part 2: Chip Formation and Cutting Force with Conventional Single-Point Tool
Authors: Usui E. , Hirota A.
Published: November 2010

The cutting model and the energy method to predict chip formation and cutting force, which were proposed in the previous part of this study, are extended to machining with conventional single-point tool. The prediction is always possible in the practical range of cutting conditions regardless of size of cutting and tool geometry, if only orthogonal cutting data under equivalent cutting conditions are in hand. The predicted results are verified to be in good agreement with the experimental results in a wide variety of depth of cut, side and back rake angles, side cutting edge angle, and nose radius.
The Conflicting Roles of Carbontetrachloride as a Boundary Lubricant
Authors: Shirakashi T. , Komanduri R. , Shaw M. C.
Published: November 2010

Under certain conditions, carbontetrachloride is found to be a negative boundary lubricant (gives a higher coefficient of friction than that of dry surfaces in air), while under other conditions, it lowers friction and gives a beneficial effect. Both of these situations are illustrated for heavily loaded sliding surfaces where the subsurface is undergoing gross plastic flow and an explanation is presented which appears to be consistent with all experimental facts. Carbontetrachloride is found to be more reactive chemically when the sliding surfaces are heavily strained or galled under high normal and shear stresses and containing microcracks, a situation that arises when cutting at low speed.
Investigation of the Cutting Process Dynamics in Turning Operations
Authors: Srinivasan K. , Nachtigal C. L.
Published: November 2010

There exist a great number of variational cutting force models for the case of plunge cutting but the analytical prediction of the parameters in these models is still elusive at best. The case of traverse cutting is even more intractable from an analytical point of view. A knowledge of the coefficients in the variational cutting force model is necessary to predict the borderline of chatter stability in machining operations. This paper describes the application of a sequential equation error minimization technique to determine empirically the optimum parameter values in a predetermined set of force component models from dynamic cutting data. The identification technique was verified on an analog computer simulation of the dynamic behavior of a machine tool system. The identified parameter values were compared with the actual simulated values. Even in the presence of noise inputs, the identification was accurate to within two to three percent. Experimental plunge cutting tests were performed on an aluminum workpiece. The results of the identification technique applied to these tests were analyzed against the backdrop of the simulation results. Conclusions drawn from the cutting tests were for the most part consistent with other researchers’ results and with intuition. The important contributions of this work are not the conclusions drawn from the cutting tests but the methodologies developed for obtaining results such as these. Specifically, no special inputs are required as in frequency response testing. Identification for both wave generating cuts and wave removing cuts is carried out in the same test. This situation is more indicative of a real cutting situation than either wave generating cuts or wave removing cuts considered separately.
Development of a Prototype Regenerable Carbon Dioxide Absorber for Portable Life Support Systems
Authors: Onischak M. , Baker B.
Published: November 2010

The design and development of a prototype carbon dioxide absorber using potassium carbonate (K2CO3) is described. Absorbers are constructed of thin, porous sheets of supported K2CO3 that are spirally wound to form a cylindrical reactor. Axial gas passages are formed between the porous sheets by corrugated screen material. Carbon dioxide and water in an enclosed life support system atmosphere react with potassium carbonate to form potassium bicarbonate. The potassium carbonate is regenerated by heating the potassium bicarbonate to 150° C at ambient pressure. The extravehicular mission design conditions are for one man for 8 h. Results are shown for a subunit test module investigating the effects of heat release, length-to-diameter ratio, and active cooling upon performance. The most important effect upon carbon dioxide removal is the temperature of the potassium carbonate.
Reducing the Temperature at Tool-Chip-Work Contact by Changing the Effective Thermal Conductivity of the Tool
Authors: Kotval C. J. , Barash M. M.
Published: November 2010

A method for cooling carbide tools by increasing their effective thermal conductivity was investigated. Its essence is in coating the tool with a layer of high thermal conductivity material, specifically copper or silver. Reduction in cutting temperature near the cutting edge was verified by the embedded thermocouple and tool-work thermocouple measurement techniques. Theoretical models of the tool further support the experimental results and demonstrate a greatly altered temperature gradient at the cutting edge and its vicinity.
Disk and Strip Forging with Side-surface Foldover—Part 1: Velocity Field and Upper-Bound Analysis
Authors: Avitzur B. , Kohser R. A.
Published: November 2010

With the assumptions of a Mises’ rigid, perfectly-plastic material and constant shear stress friction prevailing between the forge platens and deforming solid, the upper-bound analysis technique was applied to the upset forging of rectangular strip and solid cylindrical disks in an effort to incorporate the combined phenomena of bluge and fold. A two-zone velocity field was proposed for each geometry with Zone I occupying the interior volume and Zone II, the region near the free-surface periphery. The velocity field in Zone I was chosen as the exponential cusp-type used successfully in several previous analyses. Zone II was represented by a velocity field compatible with a foldover phenomenon and kinematically admissible with respect to boundary conditions and compatibility with Zone I. Solutions based on the above assumptions provide the forging pressure as a function of specimen geometry, interface friction, material strength, rate of bulge formation and relative size of Zone II. Minimization with respect to the last two variables provides the optimum rate of barreling or bulging and determines the degree of foldover expected.
Characterization and Analysis of Grinding Wheel Topography as a Stochastic Isotropic Surface
Authors: Nassirpour F. , Wu S. M.
Published: November 2010

The grinding wheel topography is characterized and analyzed as a stochastic isotropic surface. An explicit procedure is given to check the assumption of surface isotropy. Geometric statistical properties such as the number of active cutting points per unit area, the ratio of real to apparent area of contact, and the mean and root-mean-square rake angle of ten grinding wheels are calculated. Using the characteristic parameters as responses, the relative contribution of the wheel grit size, hardness, and structure to the total wheel topography is quantified by factorial design analysis. The procedure of characterization is also applicable to other homogeneous stochastic isotropic surface.
Atmospheric Cloud Physics Laboratory Thermal Control
Authors: Moses J. L. , Fogal G. L. , Scollon T. R.
Published: November 2010

This paper presents the development background and the present status of the Atmospheric Cloud Physics Laboratory (ACPL) thermal control capability. The ACPL, a Spacelab Payload, is currently in the initial flight hardware development phase for a first flight scheduled in June 1981. The ACPL is intended as a facility for conducting a wide variety of cloud microphysics experimentation under zero gravity conditions. The cloud chambers, which are key elements of the ACPL, have stringent thermal requirements. Thus the Expansion Chamber inner walls must be uniform to within ±0.1°C during both steady state and transient operation over a temperature range of +30 to −25°C. Design progression of the Expansion Chamber, from early inhouse NASA-MSFC concepts (including test results of a prototype chamber) to the thermal control concept currently under development at General Electric, is discussed.
Determination of True Cutting Signal by Separation of Instrumentation Dynamics From Measured Response
Authors: Garcia-Gardea E. , Burney F. A. , Wu S. M.
Published: November 2010

The Dynamic Data System (DDS) methodology is used for the separation of the cutting signal from the dynamics of a dynamometer. A sixth order continuous Autoregressive Moving Average model is fitted to a milling machine’s cutting force signals. The dynamics of the dynamometer are separated as a second order model and the true milling signals are constructed using the resultant parameters of a fourth order model. It is shown that with the constructed signal, an explanation of the pertinent characteristics such as the location errors in the cutter insert may be obtained. The technique to separate the dynamics of the instrument from the cutting signal can be used for the dynamic calibration of the instrumentation.
Development of a Hydraulic Chambered, Actively Controlled Boring Bar
Authors: Glaser D. J. , Nachtigal C. L.
Published: November 2010

A major problem in the active control of the boring process is developing a practical method of providing small-amplitude tool-tip positioning. The main thrust of the underlying research work is the design, development and evaluation of a new actuation concept for active control of the boring operation. The actuation concept was implemented using a special boring bar with two internal longitudinal hydraulic chambers. A pressure difference between these two chambers provides the driving force to create the desired tool-tip motion. Using a measure of the dynamic cutting force, the controlled boring bar system was successful in making improvements over the uncontrolled boring bar’s cutting performance in terms of regenerative chatter control. The cutting tests used in this thesis were plunge cuts in mild steel. The controlled level of improvement was smaller than was anticipated. The problem was considered not a fault of the actuation scheme, but a result of a non-optimal combination of the servovalve, measurement system and controller. Further work in these areas should yield considerably improved results using the new actuation concept.
Application of the Finite Element Method in the Development of Improved Railroad Car Wheel Designs
Authors: Rusin T. M. , Kleeschulte D. G. , Coughlin J. M.
Published: November 2010

This paper discusses the use of the finite element method in the development of an improved 33-inch (.838 m) railroad wheel that has been introduced into service. Calculated elastic stresses resulting from the thermal and mechanical loads are presented for an existing wheel design and for the new wheel design. Validation of the calculated stresses is by experimental data developed on a railroad dynamometer. Drag test data for the new wheel design is compared to historical data.
Kinetics of Subcritical Crack Growth and Deformation in a High Strength Steel
Authors: Landes J. D. , Wei R. P.
Published: November 2010

The kinetics of subcritical crack growth under sustained loading in a chemically inert environment (dehumidified argon) and the companion deformation kinetics were determined to examine the possible relationship between the crack growth and deformation processes in an AISI 4340 steel tempered at 400 deg F (∼205 degC). Crack growth experiments were carried out over a range of temperatures from 20 to 140 deg C, using the crack tip stress intensity factor K to chacterize the mechanical crack driving force. Deformation kinetics were determined as a function of deformed structure either at constant load or by a strain rate cycling procedure over the same range of temperatures. Detectable crack growth (with rates above 10−5 ipm) in dehumidified argon occurred at K levels exceeding about 70 percent of Kc at room temperature and 50 percent of Kc at the higher temperatures. Crack growth exhibited transient, steady-state and tertiary stages of growth, akin to creep, in agreement with the results of Li, et al. Experimental data indicate that subcritical crack growth in dehumidified argon is controlled by thermally activated processes, with apparent activation energies in the range of 11,000 to 18,000 cal/mole. This range of apparent activation energies is in general agreement with an observed range of 12,000 to 28,000 cal/mole for steady-state creep in this material. The apparent activation energies for steady-state creep were found to be dependent on flow stress and structure. Based on the similarity between the observed crack growth and deformation behaviors and on the order of magnitude agreement between the apparent activation energies, it is reasonable to consider that subcritical crack growth in inert environments is controlled by the time dependent deformation processes occurring at the crack tip. A model for relating steady-state crack growth and steady-state creep is suggested, and is shown to correlate well with experimental data.
The Super Flywheel: A Second Look
Authors: Brunelle E. J.
Published: November 2010

The potentialities of the super flywheel are re-examined by two analysis techniques. The first technique utilizes a highly idealized model that permits one to easily see the basic physics of the problem; the second technique employs a more realistic model that provides detailed information about the super flywheel behavior. Both techniques demonstrate that the kinetic energy and the stresses are higher, at a given rotational speed, than classical analyses predict and that an inertio-elastic instability provides a theoretical upper limit to the rotational speed attainable by the super flywheel.
Rotating Band Pressures and Engraving Forces in 155mm Artillery Shells
Authors: Hartman W. F. , Stirbis P. P.
Published: November 2010

The forces retarding the motion of 155mm artillery shells during quasi-static engraving of the rotating band were investigated both experimentally and analytically. The analytic method was based on a determination of the pressures existing between the projectile and the gun tube and the use of this information in a frictional model of the process. The retardation forces predicted in this manner are shown to be in good agreement with the hydrostatic pressures required to engrave the projectile in quasi-static push tests. This model leads to some interesting conclusions regarding alteration of engraving forces. In particular, the model suggests that, for shells similar to those used in this study, the rotating band pressure is more dependent upon the form and mechanical properties of the band than upon the mechanical stiffness of the projectile.
Computerized Materials Selection
Authors: Hanley D. P. , Hobson E.
Published: November 2010

Two analytical approaches are described for computer-aided selection of engineering materials. With given design or selection properties in mind, various materials within a given class may be rated by means of minimization procedures in conjunction with assignable engineering judgment factors. The first approach uses a geometric analogy in which two encompassing material parameters—“mean weighted characteristic” and “balance factor”—are used as a measure of the closeness of fit to a shape defined by desired material properties. The second approach is a variation on a familiar algebraic aid to decision making. In the latter approach materials are selected with the least total sum of property deviations from those desired. A number of examples dealing with plastics are given. Comparisons are made between the two approaches. Both approaches offer advantages over “hit and miss” procedures. By segmenting material classes and by limiting the number of material properties, an iterative and useful program has been proven on a minicomputer.
A Fracture Criterion for Cold Forming
Authors: Kuhn H. A. , Lee P. W. , Erturk T.
Published: November 2010

Fracture under combined stresses has been studied with the objective of evaluating existing fracture criteria and providing data for the formulation of new criteria. Upsetting, bending, rolling, and plane strain tests were used for the fracture study. By utilizing various combinations of test specimen height-to-diameter ratio and die contact surface friction conditions, a wide range of stress and strain ratios can be developed in the test specimens. The procedure involves measurement of the tensile and compressive strains at the fracture site. Two grades of carbon steel and one grade of stainless steel were tested in upsetting, bending, rolling, and plane strain deformation. The results are expressed as a forming limit in a total compressive strain versus total tensile strain diagram. The data are also consistent with the Cockcroft fracture criterion.
Subsequent Yield Surfaces for Annealed Mild Steel Under Dead-Weight Loading: Aging, Normality, Convexity, Corners, Bauschinger, and Cross Effects
Authors: Michno M. J. , Findley W. N.
Published: November 2010

After initial yielding of one to five percent small-offset multiple-probe yield curves were determined under combined axial-torsion loading for six tubular specimens. Subsequent yield curves were obtained following either strain aging or loading into the plastic range. Aging and plastic straining usually resulted in smooth, convex yield curves. Occasionally well-rounded blunt corners were formed under combined tension and torsion. Subsequent curves underwent translation and changes in shape. Plastic strain increment vectors from zigzag loadings supported well-rounded blunt (not sharp) corners. Normality of plastic strain increment vectors was observed.
Displacement Consideration for a Ductile Propagating Fracture in Line Pipe
Authors: Shoemaker A. K. , McCartney R. F.
Published: November 2010

To date, the technically complex problem of arriving at an analysis for a running shear fracture in a gas-transmission line pipe has been primarily viewed by investigators in terms of an energy balance that involves empirical correlations of data. In contrast, in the present paper, the problem is reviewed in terms of the forces, masses, and time involved in the fracturing event and the resultant accelerations, velocities, and displacements with respect to (1) the forces driving the crack, (2) the pipe-wall ductility resisting the driving forces, and (3) the manner in which the crack arrests. Special attention is given to the effects of backfill on these events. On the bases of the data available, it is proposed that the displacements developed by the driving force are the result of the acceleration developed by the pressure acting on the flaps behind the crack. The driving force developed by the flaps results in forces which open the crack. For a constant velocity of propagation, the time for this flap displacement corresponds to the time for the pipe-wall thinning at the crack tip, which is controlled by the pipe-wall ductility. Thus, pipe-wall ductility can limit the speed of the crack. At a low crack speed, sufficient radial displacement of the flaps behind the crack occurs to cause the crack to turn in a helical path and arrest. Finally, the backfill significantly decreases the driving force and thus reduces the pipe-wall ductility necessary for arrest. Therefore, considerations of the displacements which occur during a propagating shear fracture indicate that the time and forces required for thinning the material at the crack tip, which is essentially governed by the ductility of the pipe wall, limit the speed of the crack.
The Design and Application of Shear Fracture Propagation Studies
Authors: Poynton W. A. , Shannon R. W. E. , Fearnehough G. D.
Published: November 2010

Shear fracture propagation is studied using an analysis based upon the thermodynamic equilibrium of a constant velocity fracture. This equation is shown to describe the behavior of all full scale tests which exhibit constant velocity propagation. This equation is developed to identify the conditions for fracture arrest; the resulting formulation is again consistent with full scale test behavior. The paper also discusses the application of the theory to existing and new pipelines.
Analysis of Thermal Stresses and Metal Movement During Welding—Part II: Comparison of Experimental Data and Analytical Results
Authors: Muraki T. , Bryan J. J. , Masubuchi K.
Published: November 2010

This is the second part of a study of thermal stresses and metal movement during welding. Part I described the finite-element analysis of two-dimensional thermal stresses and metal movement during bead-on-plate and butt welding. Part II presents results of experiments on bead-on-plate and butt welds in 6061-T6 aluminum alloy. Measurements were made of changes of temperature, thermal strains, and metal movement during welding. The paper then compares experimental data with analytical results. Good agreements were obtained between experimental and analytical results.
The Double Ligament Tensile Test: Its Development and Application
Authors: Oppenheimer E. D. , Kumble R. G. , Berry J. T.
Published: November 2010

Determination of yield and ultimate strengths and elongation in three orthogonal directions by means of the double ligament tensile test permits detailed exploration of anisotropy in rolled plate, extrusions, forgings and castings of relatively small size. Values obtained at low average strain rates can be compared with impact energy values obtained from tensile impact tests using identical specimens. Data are presented from tests of a number of medium strength, low carbon, rolled steel plates which reveal dramatic differences in properties in various directions. The total strain energies from these tests are correlated with impact energy values and confirm the expected relationship. The test may have special application to the exploration of problems in lamellar tearing.
Flexural Stiffness of Sandwich Beams
Authors: Adams R. D. , Weinstein A. S.
Published: November 2010

Two new theories have been developed for predicting the bending stiffness of sandwich beams. The first theory applies to the general case of any combination of skin and core while the second, but simpler, treatment may be used for shear-soft cores. The general theory also gives the shear stress between the skin and the core, together with the direct stress induced in the facings. Experimental results are given for a range of core materials and sandwich geometry including fiber reinforced plastics cross-ply laminates: excellent correlation is obtained with the predicted values.
Fracture Toughness Phenomena in an Unaged Beta Titanium Alloy
Authors: Rack H. J.
Published: November 2010

The fracture toughness behavior of a commercial beta titanium alloy, Ti-3Al-8V-6Cr-4Zr-4Mo, has been examined between −196°C and 380°C, The observed tough-brittle transition results from increasing amounts of intergranular and cleavage fracture with decreasing temperature. Crack initiation is associated with particle/matrix interface parting, while cleavage crack propagation at low temperature requires the attainment of a critical stress over a characteristic distance. Micromechanical modeling of the principal fracture event associated with critical stress cleavage crack propagation does appear to accurately predict the magnitude of this distance, although it is limited to initiation controlled cleavage fracture events.
Mechanical Properties of Several Products From a Single Heat of Type 304 Stainless Steel
Authors: McCoy H. E. , Waddell R. D.
Published: November 2010

Tensile and stress-rupture tests were run on several products from a 90-ton (8.2 × 104 Kg) heat of type 304 stainless steel. The yield stress of the products in the as-received condition varied from 26,500, to 57,200 psi (183 to 395 MPa) at 75 deg F (24 deg C). There were significant differences between the strengths of various products and considerable variation for a single product due to nonuniform residual cold work. Reannealing 0.5 hr (1.8 × 103 sec) at 2000 deg F (1093 deg C) resulted in yield stresses in the 25,000 to 27,000 psi, (172 to 186 MPa) range; only the properties of the hot-reduced tubing fell below this range. At a test temperature of 1100 deg F (593 deg C), the as-received products had yield stresses from 14,800 to 35,500 psi (102 to 245 MPa). Reannealing caused the yield stresses to fall in the range 9,440 to 11,700 psi (65.1 to 80.7 MPa). Stress-rupture tests at 1100 deg F (593 deg C) on the reannealed products did not reveal significant variation in properties.
Fatigue Crack Tip Plasticity Associated With Overloads and Subsequent Cycling
Authors: Lankford J. , Davidson D. L.
Published: November 2010

The plastic zones associated with single overloads of cyclically loaded specimens have been mapped using electron channeling patterns. The zones are asymmetric with respect to the crack tip, and are complex in shape. Crack retardation subsequent to an overload is closely related to the size and shape of the overload zone, but has no apparent relationship to the maximum zone dimension. Following an overload, cracks try to exit from the monotonic zone by moving toward the nearest elastic-plastic boundary. The size of the overload zone is predicted by a plane strain rather than plane stress relationship. The minimum retarded growth rate corresponds to an effective stress intensity factor no greater than the threshold value for Stage II growth. This is caused by crack closure, with minimal crack tip shear strains and an absence of crack tip opening and blunting. Since the crack growth rate quickly approaches the preoverload rate once the crack crosses the overload boundary, it appears that residual stress within the overload plastic zone is the key factor in governing crack retardation.
Plastic Strain Distribution at the Tips of Propagating Fatigue Cracks
Authors: Davidson D. L. , Lankford J.
Published: November 2010

The techniques of selected area electron channeling and positive replica examination have been used to study the plastic zones attending fatigue crack propagation in 304 SS, 6061-T6 aluminum alloy, and Fe-3Si steel. These observations allowed the strain distribution at the crack tip to be determined. The results indicate that the concepts of a monotonic and a cyclic plastic zone are essentially correct, with the strains at demarcation between these two zones being 3 to 6 percent. Strain distribution varies as r−1/2 in the cyclic zone and as ln r in the monotonic plastic zone. The strain distributions for all materials studied may be made approximately coincident by using a dimensionless parameter related to distance from the crack tip.