bluuebunny/crossref_metadata_2025 huggingface dataset:
NEMO Type Acrylic Plastic Spherical Hull for Manned Operation to 3000 ft Depth
Authors: Stachiw J. D.
Published: November 2010

NEMO Mod 2000 acrylic plastic pressure hull assembly represents the latest addition to the NEMO hull series represented by NEMO Mod 600 and 1000 hull assemblies. The 66 in. OD × 58 in. ID spherical acrylic hull with aluminum hatches has successfully withstood 24 hr long external hydrostatic pressurizations to 450, 900, 1350, and 1800 psi. Pressure cycling and short term destructive testing of 15 in. OD × 13 in. ID scale models has shown that the crackfree fatigue life is in excess of 1000 pressure cycles to 1500 psi and the short term implosion pressure is in the range of 4750–5000 psi. Stress wave emissions have been found to be a good indicator of incipient failure. NEMO Mod 2000 spherical pressure hulls with panoramic visibility are considered to be acceptable for manned submersibles with 3000 ft operational depth capability. The cyclic fatigue life of such hulls is conservatively predicted to be at least 12 × 106 ft hr.
Stability and Transient Motion of a Plain Journal Mounted in Flexible Damped Supports
Authors: Kirk R. G. , Gunter E. J.
Published: November 2010

This paper treats the effect of support damping and flexibility on the response characteristics of a symmetric rotor mounted in journal bearings. The successful operation of turbomachinery utilizing fluid-film bearings is shown to be very dependent upon the bearing support structure for high-speed applications. A stability analysis is discussed based upon the application of both the Routh criteria and the calculation of damped eigenvalues. Results are plotted for typical rotor support properties. The analysis also discusses the influence of rotor imbalance on the stability of rotor systems, and time transient orbits of shaft and support motions clearly indicate their dynamic behavior for both the stable and unstable operating speeds. Simplified design criteria are given for the selection of the support stiffness and damping based upon rotor weight and journal clearance to promote optimum stability. The stability analysis shows that the stability threshold with a damper support may increase the stability level over four times the value of a journal bearing on a rigid support. A nonlinear transient analysis is presented to show the size the journal limit cycles and forces transmitted with and without a damper support.
Removal of Water Base Mud From Well Bores in Permafrost Zones
Authors: Ng F. W.
Published: November 2010

In completing an Arctic oil or gas well, it is sometimes desirable to remove water-base drilling mud from a casing-casing or casing-tubing annulus to minimize the possibility of casing damage resulting from freezing and thus expansion of the fluid. The proposed field procedure involves an initial water wash step, where the mud is washed from the annulus by water, followed by the pack placement step where the water is displaced by an oil-base gelled and weighted casing pack. The casing pack fills the entire annulus and also acts as a thermal insulator by suppressing convection currents with its high gel strength. The study was performed to examine the fluid displacement mechanics involved in the field operations and to determine the methods of operation which should be adopted. The operations were studied in 10-ft long model annuli of various sizes in the laboratory and then in a 900-ft test hole in the back yard. Findings from these studies were then applied to the displacement procedures in a number of field operations at Prudhoe Bay, Alaska. Data gathered from these field operations were analyzed, and they compared satisfactorily with predictions from laboratory data. It was found that, for the water-wash step, two system volumes of water was sufficient to remove virtually all the drilling mud from the annulus. For the pack placement step, two system volumes of pack was sufficient to remove virtually all the water. Both displacements should be carried out with the water in turbulent flow. A system of commercially available electronic instruments was developed for monitoring water contamination of the pack returns. It provides instant indication of excessive contamination in case of displacement failure due to equipment breakdown or other unforeseen circumstances, so that remedial actions may be taken immediately.
Optimal Design of a Class of Welded Structures Using Geometric Programming
Authors: Ragsdell K. M. , Phillips D. T.
Published: November 2010

Geometric Programming is a new technique developed to solve nonlinear engineering design problems including linear or nonlinear constraints. This paper illustrates the use of Geometric Programming in obtaining optimal design parameters for a class of welded beam structures. The procedure is illustrated through the solution of a particular welded beam design formulation. In G/P format the problem solved consists of 9 nonlinear constraints, 24 terms, 7 variables, with 16 degrees of difficulty and a nonlinear objective function. Geometric Programming is compared to several other solution techniques, and found to be very efficient. Computational experience suggests that other problems of this class may be solved with similar efficiency. The welded beam problem given is a real world design situation typical of many encountered in actual practice. The solution is given for the first time in this paper.
Parameter Optimization of the Steel Grinding Process
Authors: Mayne R. W. , Malkin S.
Published: November 2010

This paper is concerned with the application of nonlinear programming methods to the surface grinding of steels and considers the specific case of plunge grinding. Performance equations based on a model of the process are presented and then optimized. Trade-off curves are established showing the best metal removal rate possible for given constraints on surface quality and at specified conditions of grinding wheel wear. Optimum values for the various parameters in the grinding process are also included. In addition, the sensitivity of steel grinding performance to nonoptimum choices of grinding wheel velocity and diameter is considered.
Prediction of Failure in Ductile Machine Elements Operating at Elevated Temperatures
Authors: Kurajian G. M. , Na T. Y.
Published: November 2010

This paper provides the designer with formulations and data so that he can more confidently design a ductile machine element, operating at elevated temperatures, by employing obtainable strength data at those temperatures. The paper begins by taking a panoramic view of the state of the art regarding a procedure for designing such elements, under such conditions, on the basis of stress vs. strength. Then, the paper combines the basic principle of the distortion-energy theory of failure, long recognized as the best theory of failure for ductile materials by well documented experiments, with thermodynamic behavioral and mechanical properties. This combination and accompanying study result in formulation, information and data so that the validity of the aforementioned design practice is given a sound theoretical basis. Specific applications are taken for various categories of steel with very good agreement between the theory and experimental data. However, with necessary data, the procedure can be applied to other ductile metals as well.
Optimum Reliability at Minimum Cost
Authors: Fenton R. G.
Published: November 2010

An analytical expression is derived for the total cost of equipments, including initial capital cost and the present value of the inflation escalated cost of the expected failures throughout the service life of the equipment. This total cost is a function of the reliability of the equipment, therefore, using numerical optimization the most suitable equipment can be selected for which the total cost is minimum.
Design Problem Solving by Functional Analysis and Creativity
Authors: Chohan S. M.
Published: November 2010

Most hardware design failures can be attributed to either functional incompatibility within the immediate hardware system or functional conditions imposed on the hardware from sources external to the system, exceeding its design capability. The failure cause-function can be a Primary, a Secondary, or an Application function. It can be systematically identified; however, by analyzing the interactions of failure-functions, namely the functions of the failed hardware with all other functions within the failed hardware system. If the cause-function does not emerge, the system boundary is expanded and the analysis repeated. Once the cause function is identified the problem can be solved either by removing the cause-function or modifying the failure-function. Innovation by creative thinking and brainstorming can be highly effective in finding a functional solution to the problem. The solution thus developed will tend to be of a superior quality compared to that of a hardware orientated approach.
Forced Vibrations of Viscoelastic Timoshenko Beams
Authors: Huang C. C. , Huang T. C.
Published: November 2010

In a previous paper, the correspondence principle has been applied to derive the differential equations of motion of viscoelastic Timoshenko beams with or without external viscous damping. To study free vibrations these equations are solved by Laplace transform and boundary conditions are applied to obtain the attenuation factor and the frequency of the damped free vibrations and mode shapes. The present paper continues to analyze this subject and deals with the responses in deflection, bending slope, bending moment and shear for forced vibrations. Laplace transform and appropriate boundary conditions have been applied. Examples are given and results are plotted. The solution of forced vibrations of elastic Timoshenko beams obtained as a result of reduction from viscoelastic case and by eigenfunction expansion method concludes the paper.
Hydrogen-Induced Cracking of Steels Under Wet Hydrogen Sulfide Environment
Authors: Miyoshi E. , Tanaka T. , Terasaki F. , Ikeda A.
Published: November 2010

The hydrogen induced cracking (HIC) of as-rolled steels has been investigated. The specimens were immersed into the synthetic sea water saturated with H2S. Since the cracks initiated at the elongated MnS particles, the HIC susceptibility decreased with decreasing sulfur content. It was, however, often observed that the HIC occurred even in the steels containing extremely low sulfur. These cracks propagated along an anomalous structure, which consisted of low temperature transformation products. Such an anomalous structure arose from the segregation of manganese and phosphorus during the solidification of steels. As to the controlled-rolled steels, the effects of texture, residual strain, and the shape of inclusions on the HIC were examined. It was revealed that the rolling at lower temperature did affect the HIC susceptibility with elongating the sulfide inclusions, while little effect of controlled rolling was recognized in the extremely low sulfur steels. It was also demonstrated that the addition of small amount of copper markedly reduced the amount of hydrogen absorbed. This could be due to the interface reaction between steel and wet H2S environment. As the application of the foregoing results, the steel highly resistant to the HIC under the present experimental environment has been developed.
Mechanical Joints With Clearance: A Three-Mode Model
Authors: Miedema B. , Mansour W. M.
Published: November 2010

A momentum exchange model is developed to describe the dynamic performance of mechanisms with clearance. A following mode is incorporated in the model to account for the case when contact is maintained between the pin and the socket while they move relative to each other. The regions of occurrence of the three modes for a crank-slider mechanism are discussed. This study is a first step in correlating noise-to-impact spectra for preventive maintenance.
Technology Transfer in the Vibration Analysis of Linearly Tapered Cantilever Beams
Authors: Mabie H. H. , Rogers C. B.
Published: November 2010

Curves are presented for determining the fundamental frequency and several higher harmonics for cantilever beams linearly tapered in the vertical or the horizontal plane or tapered in both planes simultaneously (double taper); both the single-tapered and the double-tapered beams are treated with free end, end mass, and end support. These curves have been selected from papers previously published by the authors in order to provide data in a form suitable for design application. They are reproduced with permission from Sandia Corporation, Albuquerque, N. M., and from the Acoustical Society of America.
Synthesis of a Spherical Cycloidal Mechanism
Authors: Mayo R. , Soni A. H.
Published: November 2010

Using rotational displacement matrices to describe spherical motions, closed-form synthesis equations are derived for two rotation matrix mechanisms. These equations are used to calculate the linkage parameters of a spherical cycloidal crank mechanism so that it will guide a rigid body through five finitely separated positions lying on the surface of a unit sphere. It is shown that the synthesis equation for calculating the coordinates of the fixed and moving points lying on the unit sphere is of fourth degree. This indicates that a maximum of four unique solutions of the mechanism are possible when five finitely separated positions are specified. A synthesis example is presented illustrating the proposed synthesis technique using a spherical cycloidal crank mechanism to guide a rigid body.
On Bidirectionally Snapping Linkages
Authors: Fazekas G. A.
Published: November 2010

A new criterion for bidirectional snap-buckling has been exploited for the design of two-way snapping linkages that can find many uses.
Assessment of Deep-Drawability and Stretchability by Bulge Test of Concentrically Grooved Metal Disks
Authors: Kawai N. , Kurosaki Y.
Published: November 2010

In order to obtain new parameters available for assessing deep-drawability and pure-stretchability of sheet metals, a bulge test employing concentrically grooved disks is investigated. Both the limiting polar height and the thickness strain measured at a designated point near the groove in a burst specimen are useful for the assessment of pure-stretchability. Moreover, the foregoing two formabilities can be assessed relatively well in terms of the oil pressure and the geometry of specimens at burst initiation. These three parameters can be obtained by a single-blank test.
On the Doubly Regenerative Stability of a Grinder: the Combined Effect of Wheel and Workpiece Speed
Authors: Thompson R. A.
Published: November 2010

The conditional stability of a plunge cylindrical grinder is worked out in explicit terms of wheel and workpiece speed. The analysis is an extension of the theory developed in the paper “On the Doubly Regenerative Stability of a Grinder.” This paper was published in JOURNAL OF ENGINEERING FOR INDUSTRY, TRANS. ASME, Series B, Vol. 96, No. 1, Feb. 1974, pp. 275–280. An example problem is solved. The machine and cutting parameters used by Hahn in his original analysis are employed. The results are plotted as a graph of wheel versus workpiece speed with unstable areas cross-hatched. It is shown that (1) improved stability accompanies high-speed grinding; (2) below given speeds of the wheel and/or workpiece all grinding is unstable; (3) although the difference is small, the destabilizing effect of the workpiece is greater than that of the wheel; (4) grinding frequency can be used to predict the onset of chatter.
Comparative Analysis of Trash Contamination in Cotton by Optical Scanning
Authors: Lyons D. W. , Barker R. L.
Published: November 2010

Successful utilization of an automated optical scanning system for the purpose of assessing the trash factor included in the grade classification of cotton was demonstrated in a study that featured analysis of cottons representing a broad range of trash levels and lint colors. The utility of image analysis as an absolute indication of grade-related differences in cotton was statistically confirmed. Sources contributing to the variability of nonlint assessment by optical imaging were defined and analyzed, as was the influence of interrelated grade factors such as lint coloration on optically measured contaminant levels. In a direct comparison with the Shirley Analyzer, computerized optical scanning was shown to be at least as reliable as this standard method for determining nonlint waste.
Stochastic Characterization of Macro- and Microerrors of Journal Bearing Roundness
Authors: Velsher B. , Osman M. O. M. , Sankar T. S.
Published: November 2010

A new approach for the characterization of form error and surface roughness of round bearings is presented. The method employs the theory of random function excursions to describe the macro- and microerrors of the round surface in both radial and circumferential directions. The mathematical principle of the measuring technique is given, and it is shown that an accurate description of the roundness can be obtained from the knowledge of the intercept probabilities of the crest and valley excursions of the surface trace about a given reference circle. Based on the mathematical model, new indices for the characterization of journal bearing roundness are proposed. These indices are computed directly from data obtained from commercially available roundness measuring devices. A number of experiments were performed to justify the validity of the proposed roundness indices. Roundness measurements were carried out on a number of differently machined cylinders using a specially equipped measuring device (Talyrond 51) with a link to a hybrid computer EAI-690. The theoretically computed indices compared favorably with the measurements made on the actual round surfaces.
Instantaneous Kinematics of a Special Two-Parameter Motion
Authors: Tsai Lung-wen
Published: November 2010

In this paper, the author studies the instantaneous kinematics of a rigid body when it is guided by a revolute-revolute crank. It is shown that the locus of the instantaneous screw axes is a cylindroid and the locus of all the parabolic points is a plane and a fifth order surface.
Pseudo-Cylindrical Shells: A New Concept for Undersea Structures
Authors: Knapp R. H.
Published: November 2010

A new structural concept is proposed which offers promising new alternatives to the design of undersea pressure-resisting structures. This novel geometrical configuration consists of a concave polyhedral cylinder which exhibits stress distributions similar to those in “true” cylinders, but exhibits markedly higher elastic buckling resistance. Several undersea applications of this concept are suggested. Geometrical, stress, and stability properties have been examined by experimental and finite-element analysis.
On the Solution of Three-Dimensional Metal-Forming Processes
Authors: Nagpal V.
Published: November 2010

The use of “dual-stream functions” in analyzing some three-dimensional metal-forming processes is demonstrated in this paper. The problems discussed are open-die forging of blocks, rolling of a rectangular bar with spread, piercing by elliptic and rectangular punches, and extrusion of a rectangular shape. For these forming processes, kinematically admissible velocity fields are selected using characteristics of the two stream functions. Approximate upper-bound solutions of the forming processes can be obtained from the proposed velocity fields.
Group Scheduling Technique for Multiproduct, Multistage Manufacturing Systems
Authors: Hitomi K. , Ham I.
Published: November 2010

“Group Scheduling,” which is operations scheduling based on the Group Technology concept, was analyzed in a multistage manufacturing system. In the case of fabricating multiple parts (jobs) grouped into several group cells, both optimal group and optimal job sequences were determined such that the total flow time (makespan) was minimized, by means of the branch-and-bound method. In addition, optimal machining speeds to be utilized on multiple stages (machines) for each job were determined to reduce the total production cost as much as possible. Optimizing algorithms for this Group Scheduling Technique were also presented with numerical examples.
Dynamic Stability of a Two-Stage Gear Train Under the Influence of Variable Meshing Stiffnesses
Authors: Tordion G. V. , Gauvin R.
Published: November 2010

In a two-stage gear train, the two meshing stiffnesses acting on the intermediate shaft produce parametric vibrations. Equations to find the principal and secondary regions of instability are given. Results showing the influence of the phase angle between both meshing stiffnesses are presented. An easy way to determine whether a certain operating condition lies in a stability or instability region is also suggested.
On the Thermal Effects in a Warp Beam (A Wound-Yarn-Package)
Authors: Batra S. K. , Lee D. S. , Backer S.
Published: November 2010

The development of the stress field in a cylindrically-wound-yarn-package with side flanges (warp beams), during winding, can be predicted [6] using Beddoe’s [4] cylindrically anisotropic continuum model. This model is extended to account for the temperature effects observed during prolonged storage of the beams. The results predicted by the new model compare well with the experimental observations.
Bunker Design—Part 2: Wall Pressures in Mass Flow
Authors: Van Zanten D. C. , Mooij A.
Published: November 2010

Measurements of wall pressures have been carried out in a 1.5-m-dia mass flow bunker with three materials. The high flow pressures generated at the top of the cone fluctuate and are unevenly distributed. High pressures occur in the cylinder above irregularities. The results are compared with those found with various prediction methods.
Matrix Representation and Prediction of Three-Dimensional Cutting Forces
Authors: Kirk J. A. , Anand D. K. , McKindra C.
Published: November 2010

Matrix geometry techniques are applied to predicting three-dimensional cutting forces. In the present model a specific cutting plane is located and two-dimensional metal cutting theory is applied. Force predictions in this plane are then matrix transformed to three orthogonal forces acting on the cutting tool. Experimental results show the matrix model accurately predicts three-dimensional cutting forces in turning of long slender workpieces. Experimental results are also compared to other analytical models described in the literature.
Computer-Aided Analysis of the Deformations and Temperatures in Strip Rolling
Authors: Lahoti G. D. , Shah S. N. , Altan T.
Published: November 2010

This paper describes the principles and the application of two mathematical models, developed for predicting the significant variables of the strip rolling process. The first model and the associated computer program ROLING can estimate the roll-separating force and the roll torque. This model includes the most up-to-date analyses of (a) the plastic deformation in the strip, (b) the elastic compression and recovery of the strip before and after rolling, and (c) the elastic deformation of the rolls. The second model and the associated computer program ROLTEM have been developed to simulate the metal flow and temperatures in strip rolling. They consider simultaneous heat generation, heat transport, and heat transfer during rolling using a finite-difference algorithm. The predictions made by the computer programs ROLING and ROLTEM have been compared with existing experimental data. The results indicate that the agreement of theoretical predictions with experimental results is well within acceptable engineering accuracy.
Data Dependent Systems Approach to Stochastic Tool Life and Reliability
Authors: Pandit S. M.
Published: November 2010

A Data Dependent Systems approach is outlined for obtaining tool life distribution and reliability models directly from shop floor and/or laboratory failure data. The approach does not require any a-priori knowledge of the distribution and can be used with a limited amount of data. Estimation of the first order model is illustrated by application to HSS tools in turning. The tool life signatures at three different speeds are exhibited in the form of plots of hazard rate, reliability and failure time probability density functions. Formulation of simple tool replacement strategies from these plots by the shop personnel is illustrated; the mathematical expressions given for these functions can be used to develop more elaborate optimal strategies in computerized adaptive control. It is shown that most of the commonly used tool life distributions are well approximated by special cases of the first order model and hence are included in the approach.
Ductile Fracture in Axisymmetric Extrusion and Drawing—Part 1: Deformation Mechanics of Extrusion and Drawing
Authors: Chen C. C. , Oh S. I. , Kobayashi S.
Published: November 2010

The present investigation is concerned with the application of theories on flow and fracture to the prediction of workability of materials in axisymmetric bar extrusion and drawing, with special reference to center bursting. Part 1 of the investigation deals with the determination of deformation mechanics by the rigid-plastic finite element method. The steady-state deformation characteristic were obtained as functions of material property, die-workpiece interface friction, die angle, and reduction.
Reverse Plastic Flow Associated With Plastic Indentation
Authors: Shaw M. C. , Hoshi T. , Henry D.
Published: November 2010

When an indenter is pressed into a surface as in a hardness test, the material beneath the indenter undergoes plastic flow. When the load is removed from the indenter, a second plastic flow occurs in the opposite direction. This paper presents experimental evidence for this reverse plastic flow and mentions a number of practical implications of this behavior.
Cold Pressure Welding—The Mechanisms Governing Bonding
Authors: Bay N.
Published: November 2010

Investigations of the bonding surface in scanning electron microscope after fracture confirm the mechanisms of bond formation in cold pressure welding to be: fracture of work-hardened surface layer, surface expansion increasing the area of virgin surface, extrusion of virgin material through cracks of the original surface layer, and establishment of real contact and bonding between virgin material. This implies that normal pressure as well as surface expansion are basic parameters governing the bond strength. Experimental investigations of pressure welding Al-Al under plane strain compression in a specially developed equipment allowing independent variation of normal pressure and surface expansion confirm this. Based upon a slip-line analysis of the extrusion through cracks of the surface layer and upon the establishment of real contact between virgin material, a theory for the bond strength as a function of surface expansion and normal pressure is developed. The theory is in good agreement with the experimental results.
Experimental Investigations of Prebuckled Cylinders Under External Pressure
Authors: Knapp R. H. , Dumlao C.
Published: November 2010

The prebuckled cylinder is a geometrical idealization of the actual buckled surface of an axially compressed circular cylinder. It is a polyhedral representation of the cylinder in which flat triangular surfaces are joined to form an undulated (corrugated) surface. Such surfaces have been generally regarded as failed forms of the cylinder; however, recent experimental investigations show that the prebuckled cylinder is remarkably more resistant to buckling failure under external pressure than the true cylinder. The prebuckled cylindrical (PC) shell can now be regarded as a new, unfailed structural form to resist external pressure.
Reliability Analysis of Cutting Tools
Authors: Hitomi K. , Nakamura N. , Inoue S.
Published: November 2010

This paper is concerned with the reliability analysis of tool life based on the tool-wear values obtained from metal cutting experiments. From experimental results, a statistical distribution of tool wear was decided, and the distribution of tool life and the reliability function of cutting tools were derived. Further, it was shown that the reliability of cutting tools at a certain time was easily calculated from machining parameters and tool-wear limits by the use of reliability function.
An Investigation of Local Heat Transfer during Grinding Process—Effects of Porosity of Grinding Wheel
Authors: Saito Y. , Nishiwaki N. , Ito Y.
Published: November 2010

The thermal boundary condition around the workpiece surface is one of important factors to analyze the thermal deformation of a workpiece, which is in close relation to the machining, accuracy of grinding. The heat dissipation from the workpiece surface which is influenced by the flow pattern, may govern this thermal boundary condition. In consequence, it is necessary to clarify the convection heat transfer coefficient and the flow pattern of air and/or grinding fluid around surroundings of a rotating grinding wheel and of a workpiece. Here experiments were carried out in a surface grinding process to measure the flow velocity, wall pressure and local heat transfer by changing the porosity of the grinding wheel. The air blowing out from the grinding wheel which is effected by the porosity may be considered to have large influences on the local heat transfer coefficient, which is found to be neither symmetric nor uniform over the workpiece surface.
Similitude Law for the Creep-Adhesion Function in Dry Contact
Authors: Sciammarella C. A. , Kumar S. , Nailescu L. , Seth B. B.
Published: November 2010

This paper describes an experimental study on the dry friction-creep phenomenon. The study has been carried out on a test-rig. The simulated wheel has an elliptical area of contact similar to the actual locomotive wheel and is made of a 1070 plain carbon steel. The testing was conducted with variable contact stresses up to approximately 200,000 psi and equivalent speeds of approximately 5 miles per hour. The results of the test show that all the different creep-adhesion curves obtained by changing the normal loads can be reduced to one single dimensionless curve. This can be achieved if the actual nominal area of contact experimentally measured, is introduced in the corresponding expressions. A law of constancy of the product of the creep times the area of contact for dry, clean contact surfaces and a constant value of adhesion and normal load is presented.
Flow Stress Model in Metal Cutting
Authors: Black J. T.
Published: November 2010

A model for the plastic deformation that occurs in metal cutting, based on dislocation mechanics, is presented. The model explains the fundamental deformation structure that develops during machining and is based on the well known Cottrell-Stokes Law, wherein the flow stress is partitioned into two parts; an athermal part which occurs in the shear fronts (or shear bands); and a thermal part which occurs in the lamella regions. The deformation envokes the presence of a cellular dislocation distribution which always exists in the material ahead of the shear process. This “alien” dislocation distribution either exists in the metal prior to cutting or is produced by the compressive stress field which operates in front of the shear process. The magnitude of the flow stress and direction of the shear are shown to be correlated to the stacking fault energy of the metal being cut. The model is tested with respect to energy consumption rates and found to be consistent with observed values.
Economic Sizing of Steam Piping and Insulation
Authors: Wepfer W. J. , Gaggioli R. A. , Obert E. F.
Published: November 2010

This paper presents a simple method for the optimal economic selection of pipe size and insulation thickness for steam piping systems. The primary operating costs inherent in any such system are consequences of fluid-flow friction and heat transfer losses. Striving to conserve energy, the engineer is motivated to select large pipe diameters and insulation thicknesses. But how large should the pipe diameter be and how much insulation is necessary? The answer is simply to make that investment in piping and insulation which minimizes the sum of the capital and operating costs (friction and heat transfer). Thus it is imperative that the operating expenses be precisely evaluated. The key is the recognition that it is available energy which is the commodity of value—that it is necessary to assign an economic value (cost) to the steam based on its available energy content. Because friction and heat transfer destroy available energy, their respective costs can then be accurately assessed. As an example a bleeder steam line that delivers 55,300 lbm/hr (7 kg/s) at 93.8 psia (0.65 MPa) and 603 F (317 C) to a feedwater heater is analyzed to show the optimal nominal pipe diameter and insulation thickness to be 12 in. (30.48 cm) and 3.5 in. (8.89 cm), respectively.
The Dependence of the Notch Sensitivity of Waspaloy at 1000–1400 Deg F on the Gamma Prime Phase
Authors: Wilson D. J.
Published: November 2010

The morphology of the gamma prime phase was correlated with the mechanical behavior of Waspaloy sheet at 1000–1400 deg F. “Overaging” eliminated time-dependent edge-notch sensitivity and produced a change in the dislocation motion mechanism from shearing to bypassing the gamma prime particles.
Material Behavior in Powder Preform Forging
Authors: Kuhn H. A. , Downey C. L.
Published: November 2010

The basic deformation and fracture behavior of sintered powder materials was determined through simple compression tests for application to powder forging processes. Tests were carried out on an aluminum alloy powder at hot working temperatures. A well-defined relationship exists between the level of porosity and the lateral spread behavior of the material (as expressed by the plastic Poisson ratio). This information is utilized along with a plasticity theory previously developed by the authors to predict the densification and stresses in some simple forging operations. A comparison between theoretical and experimental values is given for compression of cylinders under frictional conditions. The limiting strains at fracture in the compression test reflect the influence of friction and geometry and fit a relation similiar to that found in cold forming processes. These results can be used to predict the limiting deformations to fracture in forging processes.
Stress Distribution in a Bonded Anisotropic Lap Joint
Authors: Wah Thein
Published: November 2010

A theoretical analysis of a bonded single lap joint is presented. The adherends are considered anisotropic whereas the cement is treated as an isotropic material. The analysis is confined to the elastic range. Numerical results are given.
Stability Conditions in Quasi-Static Crack Propagation for Constant Strain Energy Release Rate
Authors: Chow C. L. , Lam P. M.
Published: November 2010

Measurement of valid fracture toughness of engineering materials and design assurance of quasi-static crack growth in structures before the onset of fracture instability are the important factors in the study of fracture mechanics. Generalized equations of the stability conditions are presented not only for linear but also for nonlinear load-displacement relationships at constant crack area. Examples are used to illustrate the applications of the proposed equations, and stability conditions of different crack geometries and loadings commonly observed in engineering structures are discussed. Experiments conducted to verify the stability conditions are described and found to be satisfactory.
Cells on Porous Substrates In Vitro and In Vivo
Authors: Ansevin K. D. , Welgus H. G. , Homsy C. A. , Lipps B. V.
Published: November 2010

Disaggregated cells of kidney, lung and liver of 14-day-old chick embryos were cultivated in vitro on several open-pore, organic-polymer sponges and on one gelatin sponge; in some cases this was followed by short-term, subcutaneous implantation into rats. In order to study invasion of connective tissue cells into the porous matrix, the same organic-polymer materials were implanted into rats, and in one experimental series this was followed by in vitro cultivation after they had been retrieved from the animals. The results showed that: 1) epithelial cells have different requirements for invasion and histogenesis from those of connective tissue cells; 2) the type of porous substrate influences morphology of connective tissue that forms within it.
Effect of Salt Water Temperature on the Crack Growth Characteristics of 12 Chrome Steel
Authors: Eisenstadt R. , Rajan K. M.
Published: November 2010

The corrosion fatigue crack growth rates on 12 chrome steels of typical composition, 12Cr, 0.2C, 1Mo, 1W, of 150,000-ksi yield is relatively unaffected by 4.5 percent NaCl salt water solution at room temperature. There is a significant rise in the crack growth rates of 12 chrome steels with increasing temperature for salt water corrosion fatigue of about 4 to 1 for 160 deg F—4.5 percent solution. In correlating rotating beam understressing data on average crack growth rate versus stress intensity factor with 0-maximum data generated by other techniques, the value 1−R Kmax equivalent to n = 0.5 in the expression Keff = Kmax (1 − R)n correlates the rotating beam data adequately with the 0-Max data for other techniques. A correction factor for eccentric crack fronts on solid round specimens for rotating beam crack growth data to calculate stress intensity factors for solid notched round bars has been developed. The correction term is 4rd2 for the following stress intensity expression. K1=2.257Mr3+4rd20.80t+7.12r−1/2
Large Deflection of a Different Modulus Circular Plate
Authors: Kamiya N.
Published: November 2010

It is known that some composite materials or high-polymers behave differently in simple tension and compression. The present paper is concerned with a bending analysis of a different modulus elastic plate subjected to a uniform lateral load. Employing the istoropic different modulus material model developed by Ambartsumyan and Khachatryan, the basic governing equations of an axisymmetric large deflection of a thin circular plate are derived under the usual assumption of Kirchhoff-Love. The differential equations are written approximately in finite-difference forms and solved numerically by an iteration method. Discussion and comparison of results are made with respect to different values of the ratio of tensile to compressive elastic moduli, Et/Ec.
Ductility Indices at Elevated Temperature
Authors: Manjoine M. J.
Published: November 2010

Ductility is a property of a material which has been defined by many investigators who have employed a variety of measurements or indices. The purposes of this paper are to describe some of these indices with emphasis on those employed at elevated temperature and to discuss some of the correlations with particular material applications. The influencing factors of strain rate and state of stress on ductility are characterized through phenomenological descriptions and proposed theories of damage.
Fatigue Crack Propagation Rates for Duralumin in Simple Bending
Authors: Cain P. J. , Plunkett R. , Hutchinson T. E.
Published: November 2010

Flat sheet stock of 2024-T3 Duralumin was tested for fatigue crack propagation in simple bending. Transcrystalline cracking was observed at a rate proportional to stress intensity factor squared at low levels where the plastic zone is less than grain size. A mixture of trans-and-intercrystalline cracking was observed at a rate proportional to stress intensity factor to the fourth power at high levels where the plastic zone is larger than grain size. A strain redistribution mechanism giving constant stress intensity factor through the thickness is postulated. The combination of strain redistribution in bending and change of mechanism with plastic zone size leads to a macroscopic behavior which is different from that previously reported for simple tension, particularly in mild steel.
A Description of Crack Growth From Defects Under Creep
Conditions
Authors: Williams J. A. , Price A. T.
Published: November 2010

Methods previously used to describe crack growth under creep conditions are reviewed. Under some conditions, materials can be notch insensitive and a model is developed based on engineering analyses of creeping structures using reference or skeletal point stresses. This stress, dependent on crack length and geometry, is derived for conventional test pieces. Examination of the relaxed stress distributions around stress concentrations suggests that the behavior of cracked structures is dependent on the total creep strain/stress index, p. Two categories of materials behavior are distinguished: when p>5, the reference stress description should be applicable and when p→1, the stress intensity factor description appears appropriate. Finally, the general applicability of the model is discussed with respect to the metallurgical aspects of creep damage accumulation, suggesting that crack initiation may dominate life when p>5 and crack growth when p→1. A comparison is then made with previous experimental data.
The Development of Fatigue Crack Propagation Models for Engineering Applications at Elevated Temperatures
Authors: Tomkins B.
Published: November 2010

The value of modelling the fatigue crack propagation process is discussed and current models are examined in the light of increasing knowledge of crack tip deformation. Elevated temperature fatigue is examined in detail as an area in which models could contribute significantly to engineering design. A model is developed which examines the role of time-dependent creep cavitation on the failure process in an interactive creep-fatigue situation.
Elevated Temperature Tensile Properties of Weld-Deposited Austenitic Stainless Steels
Authors: Ward A. L. , Blackburn L. D.
Published: November 2010

Trend curves describing the temperature dependence of tensile properties have been formulated for several weld-deposited austenitic stainless steels and also for wrought Type 304. Ratios of elevated-temperature properties to room-temperature properties were fitted to polynomial expressions in temperature by regression analysis. Represented in the study were eleven weldments, four weld processes, and five weld metal alloys. Trend curves were established for 308/308L, CRE 308, and 16-8-2 compositions as well as for all the weld metal data. The results showed that the degree of correlation between predicted and observed properties was dependent upon variations in weld process and parameters but that the ratio trend curve approach yielded a useful degree of correlation of the elevated-temperature properties even without considering all the complex features of the weld-deposited materials.
Thermal Ratcheting With Kinematic Hardening in a Two-Bar Assembly With Unequal Areas and Properties
Authors: Brunsvold A. R. , Ahmed H. U. , Stone C. C.
Published: November 2010

An analytical model based on a two-bar assembly with unequal areas and material properties is used to determine inelastic stress-strain behavior under a steady mean load and cyclic thermal loads. The study with the model extends previous study on thermal ratcheting with kinematic hardening. The model exhibits much of the behavior of interest in design of pressure vessels subject to thermal loads: elastic behavior, shakedown, ratcheting, captive plastic behavior (a special case of elastic followup), and plastic cycling. The expressions for cyclic changes in stress and cyclic inelastic strains are developed, and the mean-load and thermal-load bounds for the behavior modes are mapped.
Metal Flow and Fracture in an Extrusion-Forging Process
Authors: Suh S. K. , Kuhn H. A. , Downey C. L.
Published: November 2010

A study was conducted of the metal flow and fracture in a forging process involving both extrusion flow into a hub and lateral flow into a flange. In the initial stage of deformation, depending on the die angle and friction, either the extrusion mode of flow or the upsetting mode occurs, but never both. If the upsetting mode acts initially, tensile strains occur on the hub surface, which lead to fracture. The extrusion mode results in compressive strains and fracture does not occur. Slip-line field analysis is utilized to predict the combinations of die angle and friction coefficient that delineate between the initial extrusion and upsetting modes of deformation. In addition, an experimental study was performed using sintered powder billets of 601 AB aluminum alloy as the workpiece material. Measurements of the surface strains and workpiece deformation profiles confirm the slip-line field analytical predictions of initial deformation mode, even though the material properties do not match those required for slip-line analysis. After the initial stage of deformation, both extrusion and upsetting flow occur. Surface strain states on the hub surface that were compressive in the initial stage of deformation now become tensile and lead to fracture in the later stages of deformation. The strains at fracture obey a fracture criterion established previously by the authors. Results of this study can be utilized to aid preform and die design in extrusion-forging processes. In addition, the experimental techniques may aid the analysis of other deformation processes.
Finite Elastic Deformation of an Annular Rotating Disk
Authors: Haddow J. B. , Faulkner M. G.
Published: November 2010

An accurate approximate method for the solution of the generalized plane stress problem of finite elastic deformation of a rotating annular disk is given. The method is applicable to both compressible and incompressible materials. Use of the nonlinear governing differential equation is avoided by considering the disk to be an aggregate of discrete coaxial rings, equations of motion, force balance and compatibility relations being formulated for the rings. Results are given for neo-Hookean disks and disks of a compressible material which has a strain energy function proposed by Blatz and Ko [7].
Microstructural Effects in the Low-Cycle Fatigue of Fe-Ni-Cr Austenite
Authors: Fiore N. F. , Diercks D. R.
Published: November 2010

A series of low-cycle fatigue tests was performed at 593 deg C on Fe-20 Cr-10 Ni and Fe-20 Cr-20 Ni (in weight percent) austenitic alloys in both the cast and wrought conditions. The as-cast alloys exhibited substantially longer cyclic lives than the wrought alloys or wrought Type 304 stainless steel. An effect of Ni content on fatigue life was noted for the cast alloys, but not for the wrought. Striation, measurements indicated that the majority of the cyclic life was spent in crack initiation and early growth in all cases, and the superiority of the cast alloys was almost entirely due to a greater resistance to crack initiation. Macroscopic crack-growth rates were found to be essentially independent of composition and microstructure. A 1-min tension hold time per cycle produced a significant reduction in cyclic life in all cases except for the as-cast high Ni alloy. The decrease in life appeared to be associated with the initiation of cracks from localized deformation at grain boundaries.