bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite Element Analysis of Temperatures, Metal Flow, and Roll Pressure in Hot Strip Rolling
Authors: Hwang S. M. , Joun M. S. , Kang Y. H.
Published: March 2013

This paper presents a new approach for the analysis of hot strip rolling processes. The approach is based on the finite element method and capable of predicting velocity field in the strip, temperature field in the strip, temperature field in the roll, and roll pressure. Basic finite element formulations are described with emphasis on modeling roll pressure and friction at the roll-strip interface and on treating the numerical instability resulting from a standard Galerkin formulation. Comparison with the theoretical solutions found in the literature is made to evaluate the accuracy of the temperature solutions. An iterative scheme is developed for dealing with strong correlations between the metal flow characteristics and thermal behavior of the roll-strip system. A series of process simulations are carried out to investigate the effect of various process parameters including interface friction, interface heat transfer coefficient, roll speed, reduction in thickness, and spray zone. The results are shown and discussed.
Real-Time Control of Sheet Stability During Forming
Authors: Hardt D. E. , Fenn R. C.
Published: March 2013

During the stamping of complex three-dimensional sheet metal parts, the in-plane compressive stresses created often lead to failure by buckling. These are typically suppressed by binding the material at the periphery to provide a tensile bias. In practice, these biases are difficult to determine, and must be addressed with a combination of a priori analysis and die-making skill. Even then, in-process variations will cause parts to begin failing by tearing or buckling as friction, material, or geometric changes occur. In this paper two methods are presented for controlling the blankholder force in-process to ensure optimal forming conditions at all times. This is effectively a signature-following method based on replicating either a previously determined optimal forming-punch force trajectory or a normalized average thickness trajectory. The method is implemented using closed-loop control of these quantities, and subjected to experiments where various disturbances are presented. Previously reported results for axisymmetric shapes indicated the ability to eliminate the effect of uncertain initial blankholder force settings, friction variations, and blank placement errors. In this paper, the work is extended to include material property changes and thickness variations, both of which require a scaling of the optimal trajectory based on simple process mechanics. The work is then extended to include nonsymmetric parts, in particular a square dish-shaped part with corners of unequal radii. Results from these experiments are essentially identical to the axisymmetric case, with a virtually complete elimination of common process disturbances on forming stability.
A Shortcut Fatigue Analysis Method
Authors: Thompson H. M.
Published: March 2013

A shortcut fatigue analysis method is presented which can be used to provide fatigue life estimates during the preliminary design phase of deepwater fixed platforms. For this type of structure, the method is intended to provide order of magnitude fatigue life estimates only. For simpler structures, such as deepwater offshore caissons, the shortcut analysis can provide good agreement with a detailed spectral fatigue analysis. The fundamental assumption of the method is that the dynamic transfer function can be closely approximated by the product of the static transfer function and a single degree of freedom dynamic amplification factor, which has been adjusted to produce a “fit” to the true DAF at resonance. Only one dynamic analysis of the structure needs to be performed, i.e., to determine the true DAF at resonance.
Dynamic Response Statistics of Linear System Under Morison-Type Wave
Force
Authors: Hu S.-L. J. , Muin M.
Published: March 2013

The primary objective of this study is to establish the non-normal relationship between Morison-type random wave loading and structural response via repeated Monte Carlo simulations. A standardized equation of motion will be developed, such that the numerical results can apply to various structures and sea states, instead of a particular structure or sea state. The reliability of the Monte Carlo simulation technique will also be investigated, analytically and experimentally.
Motion Prediction of a Single-Point Moored Tanker Subjected to
Current, Wind and Waves
Authors: Jiang T. , Schellin T. E.
Published: March 2013

Horizontal motions of a tanker attached to a single-point mooring (SPM) terminal were predicted using digital simulation in the time domain. Excitations from steady current, gusting wind, and irregular seaway were included. Hydrodynamic forces generated by the ship’s motion and the action of its propeller and rudder were calculated in accordance with a previously validated, nonlinear quasi-steady four-quadrant maneuvering model, extended to include linear memory effects due to waves generated by the moving ship. Memory effects were approximated by a vectorial recursive state space model corresponding to a set of higher order differential equations. A nonlinear relationship of the force in the mooring hawser was assumed to represent restoring force characteristics of the SPM system. Wave excitation forces comprised first-order forces at wave frequencies and second-order drift forces at low frequencies. First-order wave forces were obtained by superposition of force components corresponding to regular wave components comprising the wave spectrum. Based on the low-frequency wave envelope, drift forces were calculated using mean drift force coefficients in regular waves. Selected sample simulations are presented to illustrate the use of this digital simulation method.
An Improved Joint Model and Equations for Flexibility of Tubular
Joints
Authors: Ueda Y. , Rashed S. M. H. , Nakacho K.
Published: March 2013

In tubular frames with simple joints, joints may show considerable flexibility in the elastic as well as the elastic-plastic ranges. Such flexibility may have large effects on the behavior of the structure as a whole. In a previous paper, an effective simple model of tubular joints is developed. The model takes account of joint flexibility in the elastic as well as the elastic-plastic ranges based on elastic-fully plastic load-displacement relatioships. In this paper an improved joint model is presented to provide better accuracy while maintaining simplicity. The accuracy of the model is confirmed through comparisons with results of finite element analysis. Equations to evaluate the initial stiffness of tubular T and Y-joints when braces are subjected to axial compression or in-plane bending moment are also presented. Such equations for different types of joints in different loading conditions are needed in order to avoid expensive calculations to evaluate the initial stiffness of joints.
Model Tests of Load Transmission Through Grounded Ice
Rubble
Authors: Timco G. W. , Sayed M. , Frederking R. M. W.
Published: March 2013

A model test series has been performed to look at the load distribution through newly formed grounded ice rubble. In the tests, a section of a vertical-sided Arctic structure was built above a submerged berm. Both the structure and the berm were instrumented independently of one another so that the load apportioning through the rubble to the berm and structure could be determined. The results have important implications in the design loads of Arctic structures built on submerged berms.
Second-Order Radiation Condition of Scattering Wave and Its
Application
Authors: Li J. , Huang H.
Published: March 2013

The first and second-order radiation conditions for scattering waves in two and three-dimensional problems have been derived by virtue of a sequence of linear differential operators. The wave forces on a large circular cylinder are computed by using finite element methods with first and second-order radiation conditions and the Sommerfeld condition, respectively. The results show that an improvement in accuracy is achieved by employing the second-order radiation condition. The interior region in which finite elements are employed can be restricted to a much smaller one, compared with that using the Sommerfeld condition and the computing efforts and required storage in the computer are reduced.
Flow Around and Forces on a Pipeline Near a Scoured Bed in Steady
Current
Authors: Jensen B. L. , Sumer B. M. , Jensen H. R. , Fredso̸e J.
Published: March 2013

Flow around a pipeline placed initially on a flat, erodible bed was investigated at five characteristic stages of the progressive scour process in currents. The velocities, both in the streamwise direction and in the direction normal to the bed, were measured. A two-color flow visualization technique was used to detect the time-dependent flow structures. The forces on the cylinder were recorded simultaneously with the flow visualization. In the theoretical part of the study, a discrete vortex model (namely, the cloud-in-cell model) is employed to predict the flow. The early results appear to reveal the gross features of the flow shown by the experiments.
Design Criteria for Upheaval Creep of Buried Sub-Sea Pipelines
Authors: Nielsen N. J. R. , Pedersen P. T. , Grundy A. K. , Lyngberg B. S.
Published: March 2013

A new criterion is presented for the design against upheaval creep of buried hot marine pipelines. Observations have substantiated that the gradual upheaval of an “imperfect” buried pipe can take place when subjected to variable temperature and pressure loading. The imperfection amplitudes can thus grow until at a certain stage the overburden is insufficient to prevent upheaval (snap) buckling of the pipe. This paper shows that the “classical” upheaval buckling analysis is not applicable when designing against upheaval creep failure of an “imperfect” pipe. A new design procedure is established which determines the uplift resistance required to keep the upward movement of the “imperfect” pipe below critical values, thus preventing a progressive upheaval failure. The various aspects to be considered during the design and installation of a pipeline are highlighted, resulting in requirements for acceptable out-of-straightness of the pipe.
The Structure and Tensile Behavior of First-Year Sea Ice and Laboratory-Grown Saline Ice
Authors: Kuehn G. A. , Lee R. W. , Nixon W. A. , Schulson E. M.
Published: March 2013

Tensile tests have been performed on first-year sea ice and on laboratory-grown saline ice at −10° C and at two strain rates, 10−3 s−1 and 10−7 s−1. The first-year sea ice was collected from the Beaufort Sea in April of 1983 and November of 1984. The laboratory-grown saline ice was grown unidirectionally downward by means of a cooling plate on an insulated tank. The ice was loaded both parallel (vertical orientation) and perpendicular (horizontal orientation) to its growth direction. The results showed brittle behavior at the higher rate for both orientations, but ductile behavior at the lower rate for the horizontally loaded ice. At both strain rates, both the tangent modulus and the tensile strength are significantly higher along the vertical direction. The structure and mechanical properties of the laboratory-grown ice were similar to those of the first-year sea ice, indicating that the laboratory ice is a covenient and economical material for studying the mechanical properties of columnar saline ice.
An Iceberg Collision Reliability Model Incorporating Hydrodynamic Effects
Authors: Isaacson M. , McTaggart K. A.
Published: March 2013

A probabilistic model is developed for the selection of a design iceberg collision event with a fixed offshore structure. The model has been formulated such that input parameters can be obtained from available iceberg surveillance and wave climate data. Once input data for a given site are obtained, probabilities of exceedance for various kinetic energy levels are estimated using a second-order reliability method. A key feature of the model is its incorporation of wave-induced motions and added mass in the evaluate of iceberg kinetic energy.
Application of the Singularity Expansion Method to Elastic Wave Scattering
Authors: U¨berall Herbert , Delsanto P. P. , Alemar J. D. , Rosario E. , Nagl Anton
Published: March 2013

The singularity expansion method (SEM), established originally for electromagnetic-wave scattering by Carl Baum (Proc. IEEE 64, 1976, 1598), has later been applied also to acoustic scattering (H U¨berall, G C Gaunaurd, and J D Murphy, J Acoust Soc Am 72, 1982, 1014). In the present paper, we describe further applications of this method of analysis to the scattering of elastic waves from cavities or inclusions in solids. We first analyze the resonances that appear in the elastic-wave scattering amplitude, when plotted vs frequency, for evacuated or fluid-filled cylindrical and spherical cavities or for solid inclusions. These resonances are interpreted as being due to the phase matching, ie, the formation of standing waves, of surface waves that encircle the obstacle. The resonances are then traced to the existence of poles of the scattering amplitude in the fourth quadrant of the complex frequency plane, thus establishing the relation with the SEM. The usefulness of these concepts lies in their applicability for solving the inverse scattering problem, which is the central problem of NDE. Since for the case of inclusions, or of cavities with fluid fillers, the scattering of elastic waves gives rise to very prominent resonances in the scattering amplitude, it will be of advantage to analyze these with the help of the resonance scattering theory or RST (first formulated by L Flax, L R Dragonette, and H U¨berall, J Acoust Soc Am 63, 1978, 723). These resonances are caused by the proximity of the SEM poles to the real frequency axis, on which the frequencies of physical measurements are located. A brief history of the establishment of the RST is included here immediately following the Introduction.
Predicting the Autonomous Behaviour of Simple Nonlinear Feedback Systems
Authors: Atherton D. P.
Published: March 2013

The paper examines in depth two approaches, namely the describing function and Tsypkin methods, for predicting the autonomous behaviour of simple nonlinear feedback systems. Both procedures are supported by software which, in the case of the describing function method, allows iteration to the exact limit cycle solution and, for both methods, enables display of resulting limit cycle waveforms. One advantage of the Tsypkin method, which is applicable primarily to relay systems, is that the exact stability of the limit cycle solution can be found. It is shown how this may be helpful in indicating the possibility of chaotic motion. Several examples are given to show the advantages and limitations of the software implementations of the methods.
Development and Application of Ill-Posed Problems in the USSR
Authors: Markovsky Alexander
Published: March 2013

This article describes the earlier stage of development of ill-posed problems in the Soviet Union where this area of mathematics originated. There are several types of the problems, such as Fredholm and Volterra integral equations of the first kind, algebraic systems with ill-conditioned matrix, optimal regulations, approximate Fourier summation, inverse heat conduction, etc, where ill-posed nature is a serious barrier to construct a stable solution. Different methods, in increasing order of generality, showing how to interpret and solve these types of problems are reviewed. The main point is to demonstrate that all approaches in solving the ill-posed problems can be based on common sense and intuition, though formalization is needed to explore the methodology in different fields of applied mathematics and engineering.
Hydrodynamic Aspects of Fatigue in Plain Journal Bearings
Authors: Martin F. A. , Garner D. R. , Adams D. R.
Published: March 2013

The fatigue resistance of different bearing materials is usually given an “order of merit” in terms of specific load on the bearing. The bearing material cannot directly sense the applied specific load, since it is the hydrodynamic oil film pressures which directly create the stresses in the lining; both pressures and stresses need to be examined to see if a more meaningful criterion for fatigue can be found. As a first step in this study the experimental fatigue work carried out by Gyde at the University of Denmark was examined and compared with trends in peak specific load, hydrodynamic characteristics, and bearing lining stresses. It has been shown that peak specific load and peak hydrodynamic pressure are not in themselves realistic parameters, but that pressure variation on a bearing element, perhaps including some rapidly forming negative pressures, could be a significant term. The study of the more fundamental material stresses has not yet been extended to allow for the influence of any nonpositive film pressures, but results so far follow similar trends to those obtained on the pressure variation criterion.
High Speed Testing of the Hollow Roller Bearing
Authors: Bowen W. L. , Murphy T. W.
Published: March 2013

This bearing with its preloaded, hollow rollers has the qualities required for high speed operation. Roller hollowness improves cooling ability and its lighter weight reduces the centrifugal force against the raceway. Preloading between inner and outer races for 360 deg insures good roller guidance and minimizes roller skidding. However, the problems of operating a full complement of rollers at very high speeds were unknown. Also, limitations caused by roller bending fatigue needed investigation. To answer these questions, a high speed test machine was constructed and a hollow roller test bearing was designed for operation at 3 million DN. This paper describes the construction of a high speed test cell and subsequent testing of a full complement, preloaded, 115 mm hollow roller bearing. Testing culminated in a successful endurance test of 1000 hours at 26,100 RPM (3 million DN). The results verified several advantages regarding roller stability and antiskidding qualities as well as demonstrating a unique fail-safe condition.
Line Contact Deformation: A Cylinder Between Two Flat Plates
Authors: Hoeprich M. R. , Zantopulos H.
Published: March 2013

Various line contact deformation equations used in roller bearing technology are analyzed. Many of these deformation equations, primarily involving plane strain, are shown to be special cases of a general equation derived in this paper. Experimental results are also presented to support the results of the analytical work.
The Wear Coefficient—Magnitude, Scatter, Uses
Authors: Rabinowicz E.
Published: March 2013

One of the key factors in the analysis of a wear problem is the computation of the wear coefficient for a comparison with the value to be anticipated for this application. Typical values of adhesive wear coefficients for a variety of materials and lubricants are presented, and the values compared with those arising in the wear modes of abrasion, corrosion and fretting. A major uncertainty arises from the fact that wear coefficients show considerable variation, both in repeat testing, and in the testing of different materials that presumably should have the same wear coefficient. Quantitative values for the scatter encountered in adhesive wear situations are given and discussed. Various uses of the wear coefficient in the analysis of sliding systems are illustrated.
The Wear of Polymers Sliding on Polymeric Films Deposited on Rough Surfaces
Authors: Eiss N. S. , Smyth K. A.
Published: March 2013

The single-pass, transfer wear of LDPE, PVC, and PCTFE was studied as a function of the roughness of the steel counterface, and the presence or absence of a polymeric coating. A 50 nm thick film of poly(chloro-p-xylylene) was formed on the steel in a pyrolytic-vapor-deposition process. The results showed that LDPE had lower friction and wear on the coated surface than on the uncoated surface. There was no significant difference in wear or friction as a function of surface coating for PVC and PCTFE. The results were explained by considering the deformation characteristics of the polymeric coating and the three polymer sliders and the modification of the topography by the polymeric coating.
Calculated and Experimental Data for a 118-mm Bore Roller Bearing to 3 Million DN
Authors: Coe H. H. , Schuller F. T.
Published: March 2013

Operating characteristics for a 118-mm bore cylindrical roller bearing were calculated using the computer program CYBEAN. The predicted results of inner and outer-race temperatures and heat transferred to the lubricant generally compared well with experimental data for shaft speeds to 3 million DN (25,500 rpm), radial loads to 8900 N (2000 lb), and total lubricant flow rates to 0.0102 m3/min (2.7 gal/min).
Rheological and Thermal Effects in Lubricated E.H.D. Contacts
Authors: Houpert L. , Flamand L. , Berthe D.
Published: March 2013

Traction in lubricated elliptical Hertzian contacts with colinear speeds is studied. A method is described to calculate the stresses, temperatures and shear strain rates distribution along and across the film. Visco elasto-plastic behavior of the lubricant, convection, and conduction effects and pressure distributions are taken into account in this method. Elastic energy release is discussed. Shear modulus and limiting shear stresses are determined from experiment by curve fitting. Correlation between theory and experiment is analyzed.
Inverse Solution of Reynolds’ Equation of Lubrication Under Point-Contact Elastohydrodynamic Conditions
Authors: Evans H. P. , Snidle R. W.
Published: March 2013

The paper describes a technique for solving the inverse lubrication problem under point contact elastohydrodynamic conditions, i.e. the calculation of a film thickness and shape corresponding to a given hydrodynamic pressure distribution by an inverse solution of Reynolds’ equation. The effect of compressibility and influence of pressure upon viscosity are included in the analysis. The technique will be of use in solving the point contact elastohydrodynamic lubrication problem at heavy loads.
A Layered Notch Filter for High-Frequency Dynamic
Isolation
Authors: Sackman J. L. , Kelly J. M. , Javid A. E.
Published: March 2013

An efficient method of isolation from high-frequency vibrations is the use of periodically layered composites acting as a mechanical filter. This device is a periodically layered stack of alternating materials with widely different densities and stiffnesses. The working principle of the device is wave reflection, and the device becomes increasingly effective when there is a large impedance mismatch which leads to rapid attenuation of an input wave for certain frequency ranges. This filter acts only in specific frequency bands. At other frequencies, it will transmit the vibratory energy unmodified, thus acting as a mechanical notch filter. The theoretical development of the mechanical notch filter is based on the theory of waves in periodically layered media. Floquet theory is used to solve the equations for the propagation of plane waves through a laminated system of parallel plates of different materials when the direction of propagation is normal to the plates. Several experiments were conducted to prove the validity of the mechanical notch filter concept. These experiments demonstrated that the theory is correct and that the results have practical application.
A Study of the Liquid Slosh Response in Horizontal Cylindrical
Tanks
Authors: Kobayashi N. , Mieda T. , Shibata H. , Shinozaki Y.
Published: March 2013

An experimental and analytical study was conducted to determine the liquid natural frequencies and the resultant slosh forces in horizontal cylindrical tanks. This paper presents a study of the liquid slosh response of the small and the large slosh wave heights. In the former case, an effective calculation method of the longitudinal slosh response is presented by substituting an equivalent rectangular tank for a horizontal cylindrical tank. The calculated natural frequencies, slosh wave heights and slosh forces are in good agreement with the experimental ones. The transverse slosh response is also discussed. In the latter case, impulsive slosh forces were observed for longitudinal excitation, when the slosh liquid hit the top of the tank. The measured slosh forces including the impulsive forces were larger than the calculated ones. In order to determine the maximum slosh force, the experiments were parametrically conducted with several tank aspect ratios, liquid levels and excitation amplitudes. The obtained maximum slosh forces for longitudinal and transverse direction were about 0.28 and 0.16 times the full liquid weight of the tank, respectively.
Buckling of Axially Loaded Beam-Plate With Multiple
Delaminations
Authors: Kapania R. K. , Wolfe D. R.
Published: March 2013

A finite element formulation is presented to study the buckling behavior of axially loaded beam plates with multiple delaminations. A simple 6 degree-of-freedom beam-column finite element is used to model the beam plate. The delaminations are assumed to be present throughout the width of the beam-plate. Results are obtained for two delaminations having equal lengths and located one above the other. Results are presented for beam-plates having both ends (i) simply supported, and (ii) clamped. For beams with two delaminations, the stability of the beam in compression is found to depend greatly on the thinner delaminated region, especially when one delaminated region is much thinner than the other two. The energy release rate is determined using numerical differentiation.
A Review on the Analysis of Laminated Shells
Authors: Kapania R. K.
Published: March 2013

Laminated shell structures are increasingly being used in chemical, mechanical, marine and aerospace applications. A significant amount of research has been conducted in the past on studying the structural response of these structures. A review of various investigations on the analysis of these shells is given here. Specifically, this review deals with the development of various theories for modeling the thick laminated shells, including shear effects; analytical studies, development of various finite elements to model these shells, including applications to tire modeling; buckling and post-buckling analysis of perfect and imperfect laminated shells; and vibration and dynamic response analysis of various laminated shells.
Evolution and Synthesis of the Effective Elastic Constants Concept
for the Design of Tubesheets
Authors: Osweiller F.
Published: March 2013

The simplest way to take into account the weakening effect of holes in a multiperforated plate is to replace it by an equivalent solid one with adjusted “effective elastic constants.” This paper intends to show how this concept has evolved since 1948 to the present by providing a thorough review and comparison of papers dealing with this subject. A special item is devoted to square pattern problem. Curves for calculating effective elastic constants E* and ν* are proposed which enable treatment of even perforated plates, circular or not, as solid ones for which the classical equations of elasticity apply. These curves have been adopted in the French Pressure Vessel Code (CODAP) for the design of tubesheets.
Cleavage and Ductile Thermal Shock Fractures of Corner-Cracked
Nozzles
Authors: Yagawa G. , Ishihara K.
Published: March 2013

In order to study the structural integrity of the reactor pressure vessel under pressurized thermal shock, both the cleavage and the ductile thermal shock fracture experiments using initially corner-cracked nozzle specimens made of Type A508 class 3 pressure vessel steel were performed. In both experiments, unstable fractures were realized, although the test conditions were very conservative compared to those of real plants. Finally, the three-dimensional and time-dependent fracture parameter obtained with the finite element method was successfully employed to discuss the fracture phenomenon.
Fatigue of Thick Steel Plates Bent to a Low
R/t Ratio
Authors: Vossoughi H. , Soudki K. , White R. N. , Ingraffea A. R. , Sansalone M.
Published: March 2013

The use of cold-bent plates, instead of welded corner joints, in the fabrication of pressure vessels can reduce production costs. The cold-bending operation is relatively easy, inexpensive, and requires minimum quality control. The attractiveness of using cold-bent plates as a potential substitute for plates with welded corner joints motivated the fatigue study described here. Fatigue test resutls are reported for nineteen 25-mm thick HY80 and HY100 steel plates, cold-bent to a nominal bend angle of 90 deg and an R/t (inner bend radius/thickness) of 1.5, and ten 25-mm thick HY80 welded corner joints. Testing was performed under zero-to-tension loading (stress ratio R = 0) at room temperature and at a frequency of 4 Hz on specimens that retained the actual cold-bending-induced residual stresses. These test results indicate that the cold-bent plates may be a good alternative to welded corner joints for cyclic loading histories.
Efficient Numerical Analysis for Dynamic Stability of Pipes Conveying
Fluids
Authors: Dang X. Q. , Liu W. M. , Zheng T. S.
Published: March 2013

Based on the Floquet-Liapunov theory, this paper proposes an efficient one-dimensional search approach for stability analysis of pipes conveying pulsatile flow. The instability boundaries of a clamped-clamped pipe analyzed in this paper. The numerical results are satisfactory compared with existing results. Moreover, an instability region which failed to appear in ordinary numerical analyses is detected by our computations.
Simplified Method for Predicting Impact Loads of Solid-Walled
Transportation Packagings for Radioactive Materials
Authors: Teper W. W. , Sauve´ R. G.
Published: March 2013

Transportation packagings for radioactive materials must withstand severe impact conditions without loss of integrity and without excessive permanent distortions in the seal regions. The compliance with the requirements may be shown either through extensive testing, elastic-plastic impact analysis, or a combination of both. Elastic-plastic finite element analysis, although less costly than testing, is usually expensive and time consuming. In this paper, simplified methods for determining the impact force are presented for the following impact cases of solid-walled casks: impact on a pin, impact on an edge, and impact on a corner. The results of the simplified methods are in good agreement with the results of elastic-plastic finite element analysis. It is shown that in each case almost the entire impact energy is dissipated by the plastic deformation of the material in the impact zone.
Asymptotic Stability Conditions for Asymmetric Linear Mechanical
Systems
Authors: Nicholson D. W.
Published: March 2013

There are inequalities matrix derived which, except for some special cases, are necessary and sufficient for asymptotic stability of asymmetric, time-invariant linear mechanical systems. The results are applicable to systems with gyroscopic and hysteresial effects. Two examples of asymmetric systems include flexural vibration of a pipe conveying a fluid and an actively controlled vibrating system with asymmetric gain matrices. Well-known conditions are recovered for conventional symmetric positive definite systems. The inequalities are then used to establish asymptotic stability, marginal stability and instability in various examples of asymmetric systems. As further applications, a Lyapunov function is derived, response bounds are presented using the one-sided Lipschitz constant, and bounds are derived on the real and imaginary parts of the system eigenvalues.
Flow-Induced Vibrations in Bellows
Authors: Weaver D. S. , Ainsworth P.
Published: March 2013

Flow-induced vibrations have caused fatigue failures in a number of bellows units carrying cooling water flows. The bellows are made from Inconel 600 and have a nominal inside diameter of 20 mm. This paper presents the results of a project undertaken to study these vibrations and to develop a method for vibration alleviation. The experiments were conducted on prototype bellows with vibration amplitudes and frequency spectra being observed as a function of flow velocity. The bellows exhibit flow-induced resonant peaks with successively higher modes being excited by increasing flow velocities. The upstream flow geometry used in service conditions was found to reduce the mean flow velocity required to produce resonance. A fine stainless steel wire mesh was found to be the most effective means of eliminating the vibrations.
Dynamic Stability of Liquid-Filled Cylindrical Shells Under Periodic
Shearing Forces
Authors: Chiba M. , Yamashida T. , Sugiyama H. , Tani J.
Published: March 2013

Theoretical analyses are presented for the dynamic stability of a cylindrical shell partially filled with liquid, under periodic shearing forces. In the analyses, the dynamic version of the Donnell equations and the velocity potential theory are used for the motions of the shell and the contained liquid, respectively. The problem was solved by using the Galerkin method and the equations of motions coupling the shell and the liquid were derived from a type of coupled Mathieu’s equation. The instability boundaries where parametric resonance occurs were determined by using Hsu’s method. Numerical calculations were carried out for cylinders with various dimensions, i.e., radius-thickness and length-radius ratios. The effects of the liquid-filling ratio and the static shearing forces on the instability boundaries were clarified. It is found that the instability regions enlarge with increasing liquid and that the principal instability regions appear under the simultaneous action of the static shearing force.
Some Issues Concerning Fluid-Elastic Instability of a Group of
Circular Cylinders in Cross-Flow
Authors: Chen S. S.
Published: March 2013

Since the early 1970s, extensive studies of fluid-elastic instability of circular cylinders in cross-flow have been reported. A significant understanding of the phenomena involved now exists. However, some confusion, misunderstanding, and misinterpretation still remain. The objective of this paper is to discuss, based on the current state of the art, a series of the most asked questions. Emphasis is placed on the determination of the critical flow velocity, nondimensional parameters, stability criteria, and instability mechanisms.
Status of Photovoltaic Power Technology
Authors: Smith Arvin
Published: March 2013

The status of photovoltaic power technology is reviewed primarily from the viewpoint of current and future applications of the technology to the exploration and utilization of space. The photovoltaic solar cell has been the electric power workhorse throughout the first decade of the space age. The technology has shown steady improvement in reliability, increased efficiency, reduced cost, increased power per unit of hardware weight and ability to withstand extremes of the space environment. New developments are underway to increase solar cell and array size, to reduce stowage volume during boosting into orbit and to improve resistance to space radiation and thermal cycling. Silicon cell electrical contacts and interconnections, low energy proton damage to small exposed cell areas and instability of CdS thin film solar cells are examples of problems receiving attention at this time. The ongoing development of large, 2500–3000 ft2, solar cell arrays to power the planned Apollo Applications Telescope/Workshop Cluster demonstrates the growing confidence in the ability of photovoltaic power to handle space missions of the future. As photovoltaic technology advances and economic conditions change, the solar cell may well find large scale terrestrial markets.
A Novel Low-Cost Diffuser for High-Performance Centrifugal Compressors
Authors: Kenny D. P.
Published: March 2013

A novel, low-cost diffuser based upon discrete pipe drillings has been developed for high-performance centrifugal compressors. These discrete drillings are arranged in symmetrical array to mutually intersect in a radial plane so that a gradual transition from the open vaneless space at rotor tip to the individual throats of each pipe is implicitly defined. To draw a comparison, alternate cambered-vane and flat-plate diffusers were defined using the best available yet practical thinking. With a nominal 5:1 stage pressure ratio, rotor, 81.8 percent efficiency was obtained with the “pipe” diffuser at 5.42 pressure ratio. This efficiency level exceeded the best cambered-vane and flat-plate performance by 6.8 and 8.8 percent, respectively. Further testing with a second rotor yielded 81.3 percent efficiency at 6:1 pressure ratio for the pipe diffuser and 73 percent efficiency at 6:1 for the cambered-vane diffuser.
A Resonant Beam Tuned Damping Device
Authors: Nashif A. D. , Jones D. I. G.
Published: March 2013

A resonant beam tuned damping device, comprising a flexible beam joined by way of visco-elastic links at the ends, to a vibrating structure, is described. This device has the advantage of relying on the interaction between the beam stiffness and the link stiffness for tuning, rather than on the link stiffness alone as for the conventional tuned damper, so that a weight-saving potential exists. An analysis is developed and verified experimentally.
Alkali Iron Trisulfate Formation Within Deposits in an Oil-Fired Laboratory Combustor
Authors: Barrett R. E.
Published: March 2013

Alkali iron trisulfates have been recognized as a major contributor to corrosion of super-heater lubes of boiler furnaces. Factors effecting formation of trisulfate were studied in an oil-fired laboratory combustor that simulates a boiler-furnace environment. Catalysis of SO2 to SO3 by fly ash to produce the high SO3 concentrations necessary for stability of trisulfates at superheater temperatures was investigated. Effects of deposit composition, deposit thickness, temperature, and SO3 concentration on formation of trisulfates were examined.
Vibration Amplitudes of Compressor Blades Resulting From Scatter in Blade Natural Frequencies
Authors: Dye R. C. F. , Henry T. A.
Published: March 2013

Intercoupling between blades mounted on a flexible disk is examined employing a lumped-parameter model incorporating damping. Tests carried out on a gas turbine compressor and blades provide frequency and mass parameters for the model. Analysis of the model shows that vibration, and hence stress, in one or more blades, can be magnified if the distribution of blade natural frequency around the disk is suitably chosen. Feasible distributions are examined, leading to stress increases of up to 180 percent.
A Study of Thermal Transpiration for the Development of a New Type of Gas Pump
Authors: Hopfinger E. J. , Altman M.
Published: March 2013

Thermal transpiration, the phenomenon of the flow of gases through porous media under the influence of a temperature gradient, can be utilized as a driving force in a new type of gas pump. A parametric study for determining conditions for the optimum performance of such a pump requires, in addition to the thermal transpiration measurements, appropriate independent measurements for determining the geometric properties of the porous media. Experiments were carried out on five porous ceramics and two Millipore fillers of different geometric properties. It was found that a maximum reduced efficiency of about 1 percent can be achieved with a thermal pump under optimum conditions. Equations based on the methods of nonequilibrium thermodynamics and the dusty-gas theory satisfactorily explain the experimental results and thus allow the prediction of pump performance for given conditions.
The Friction Clutch Reverse-Reduction Gears for the GTS Adm. Wm. M. Callaghan
Authors: Richardson W. S.
Published: March 2013

The design and performance of the 20,000-hp reverse-reduction gears and clutches installed in the GTS Adm. Wm. M. Callaghan, the first large high-speed cargo ship designed for gas-turbine propulsion, are reviewed. Details of design, component testing, and performance calculations and the results of sea trials and service experience are presented. The successful operation of the reverse gears indicates that similar applications for gas-turbine propulsion of large merchant vessels can be undertaken.
Acoustic Resonances and Multiple Pure Tone Noise in Turbomachinery Inlets
Authors: Ehrich F. F.
Published: March 2013

Applying the Campbell [4] criterion (for excitation of axisymmetric physical systems in proximity to turbomachinery) to an analytic model of an annular acoustic cavity, a detailed view of acoustic resonances in the cavity is derived. The perspective expands on the prior work of Tyler and Sofrin [1] and others by considering the entire spectrum of modes, and the effects of axial Mach number and swirl velocity in the inlet cavity, as well as the geometric proportions of the cavity. Noise data from an experimental turbomachinery vehicle are examined over a spectrum of rotative speeds by means of a narrow band filter tracking integer multiples of rotative speed. Many aspects of the predicted acoustic resonances at supersonic wheel speeds are substantially confirmed. Additionally, unexpected subsonic resonant peaks are observed and partially explained. Conclusions are drawn as to probable influence of the aerodynamic and geometric parameters in manipulating acoustic resonances out of the operating range of aircraft engines.
A Mathematical Model For Steady Operation of Stirling-Type Engines
Authors: Qvale E. B. , Smith J. L.
Published: March 2013

A mathematical model of Stirling-type engines has been developed. The complexity of the problem has been reduced by analyzing the various components of the engine (heat exchangers, regenerator, and cylinders) separately for cyclically steady conditions, and by selecting pressure, temperature, and mass as the independent variables. The required piston displacements are a computed result. Losses due to flow friction, piston blow-by, and finite heat transfer rates have been accounted for by applying correction factors to the basic performance which is computed without these effects. The theory has been carried out for engines, but it is equally valid for refrigerators with minor modification. The theory is in good agreement with available experimental data.
The Development of a Miniature, High Speed Telemetry System For Dynamic Stress Analysis
Authors: Krassick W. M.
Published: March 2013

Twenty years ago diesel engine manufacturers guaranteed and expected 50,000 to 100,000 miles of trouble-free engine operation. Today’s standards are set at 250,000 to 1/2 million miles operation without a major overhaul. These continually expanding requirements have created new problems for the design engineer. To be competitive and to develop an efficient, long life product the design engineer must have a more complete understanding of his product’s capabilities. He can not always rely on calculations or instinct but must confirm his theories and designs by conducting more comprehensive physical tests. Many months of field testing often was required to evaluate the effect of a single design modification on the durability of the part. If a means could be found to measure the stress levels in these components under actual operating conditions in the laboratory answers could be obtained in a matter of days rather than months. A lack of commercially available test equipment suitable for obtaining these measurements resulted in a decision by Schwitzer to develop such equipment. By the end of 1963 a high speed telemetry system was in operation that could accurately transmit dynamic strain signals from a gas turbine wheel rotating over 100,000 rpm in a 1400 deg F environment. This paper reviews the several phases of this project and describes the telemetry system that finally evolved.
Flat Face Flanges With Metal-to-Metal Contact Beyond the Bolt Circle
Authors: Schneider R. W.
Published: March 2013

A method of designing flat face flanges with metal-to-metal contact beyond the bolt circle is described. The design method takes into account the interaction between shell and flange and provides for continuity at the flange-shell junction. Weld neck flanges, where the hub is of uniform thickness, and flange rings welded directly to a shell are discussed in detail, however, the same analytical approach can be extended to include tapered, hubbed flanges. Although the approach is fundamentally rigorous, sophisticated analyses have been omitted in favor of making the method useful to most engineering design offices.
Estimating the Efficiency of Prototype Pumps From Model Tests
Authors: Kittredge C. P.
Published: March 2013

The general formula for estimating the efficiency of a prototype pump from tests of a geometrically similar model is derived. A selection of formulas for pumps is presented, and the more recent literature is discussed briefly.
A Mathematical Model for Deposition From Turbulent Flows
Authors: Broadway J. A. , Vachon R. I. , Dyer D. , Zallen H.
Published: March 2013

A mathematical model was developed to estimate the dispersion and deposition of a contaminated flow. The model, which is independent of the nature of the contaminate source, is based on an analogy between the kinetic theory of gases and real turbulent flows. The average contamination concentration and deposition rate to the flow boundary as a function of the distance downwind of a reference point are given by calculations based on the model. Assumptions and limitations of the model and their significance are discussed. The results of calculations using the model are qualitatively supported by available experimental data. The model is applicable to radioactive and nonradioactive air pollutants.
Offset Rectangular Plate-Fin Surfaces—Heat Transfer and Flow Friction Characteristics
Authors: London A. L. , Shah R. K.
Published: March 2013

Basic heat transfer and flow friction design data are presented for eight offset rectangular plate-fin surfaces. One of the configurations had a heat transfer area density ratio of 1772 sq ft/ cu ft, one of the most compact plate-fin surfaces ever tested at Stanford University.
Three-Dimensional Calculation of Flow in Turbomachines With the Aid of Singularities
Authors: Ribaut M.
Published: March 2013

An analysis is presented which applies to the flow through a three-dimensional cascade of arbitrary shape using potential theory. It is shown that without simplifying assumptions a calculation method can be developed, which avoids numerical calculation of derivatives and leads for incompressible and inviscid flow to a system of linear equations. The different possibilities for the boundary vortex vector are discussed and the most suitable form for the components of velocity derived.
Axial Turbine Performance Evaluation. Part A—Loss-Geometry Relationships
Authors: Balje´ O. E. , Binsley R. L.
Published: March 2013

Generalized loss correlations for full and partial admission turbines have been derived and critically compared with recently published data. Effects included are Reynolds number, blade angles, blade height, blade number, blade trailing edge thickness, tip clearance, and reaction. These generalized loss relationships are for use in optimization of turbines over a wide range of possible operating conditions.