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Hayabusa2 is a current sample return mission spacecraft developed by JAXA. One of the most important scientific objectives of Hayabusa2 is to investigate the chemical and physical properties of the internal materials and structures of the asteroid Ryugu. To achieve this goal, we developed a new device called the small carry-on impactor (SCI). The SCI is a kinetic impactor that is being used to create an artificial crater on the surface of Ryugu. It has no attitude or orbit control device. The helical spring in the separation mechanism provides both separation force and spin torque to the SCI. The impact accuracy of the SCI depends heavily on the separation accuracy. Repeating a large number of separation tests is a straightforward approach to evaluate the separation accuracy. However, that is not realistic. Hence, first we performed several element tests to understand the separation dynamics. Then, the final separation accuracy was evaluated through a small number of separation tests, and this was followed by simulations that used the results of the element tests. This paper provides an overview of the separation mechanism, the results of development testing analyzed in detail, and a summary of the separation performance. [ABSTRACT FROM AUTHOR]

Aim: The Forsus fatigue-resistant device spring is a 3-piece telescoping compression spring used for Class II correction. The aims of this study were: (1) to measure the mean force delivered at different amounts of deflection; (2) to determine and compare the mean stiffness between loading and unloading; and (3) to determine the resilience of the fatigue-resistant device springs. Material and methods: Twelve fatigue-resistant device springs were tested with a universal testing machine and Winrcon software, with the load cell of 100 N, crosshead speed at 0.5 mm/second. Force-deflection data during loading and unloading were recorded at 2-mm intervals up to 12 mm compression. Results: (1) The mean force-deflection loading and unloading curves generally were linear, with a small area of hysteresis; (2) the loading mean stiffness (19.4 g/mm) was significantly greater than the unloading mean stiffness (18 g/mm), although this is clinically insignificant; (3) fatigueresistant device springs exhibited good resiliency. A calibrated table of force-deflection of fatigue-resistant device springs is presented for clinicians to select the appropriate length of the device for the particular orthodontic force needed. [ABSTRACT FROM AUTHOR]

INCONEL X-750 specimens were manufactured into helical springs by drawing and coiling followed by aging. They were subsequently subjected to stress-relaxation tests. Stress relaxation is the important property of springs that are compressed at elevated temperatures. To understand stress relaxation, this study investigated the effect of the drawing ratio (DR) on the γ′ size and volume fraction, grain size, carbide volume fraction, and dislocation density. Small-angle neutron scattering was used to measure the size and volume fraction of γ′ phase, and X-ray diffraction was employed to analyze the dislocation density in the springs as a function of the DR. The smallest DR specimen (DR0) had a longer free length than the larger DR specimens (DR17 and DR42) after the stress-relaxation test was completed at 773 K (500 °C) for 300 hours. However, the size and volume fraction of γ′, along with the dislocation density, had no influence on the stress relaxation of the INCONEL X-750 springs. The decreased grain size ( d) due to an increase in the DR was the main factor in the increase in the stress relaxation of the springs. The decrease in grain size displayed a nonlinear relationship with the increase in stress relaxation. The stress-relaxation behavior relationship was d . Grain boundaries were determined to play a role in dislocation sink via transmission electron microscopy (TEM) observations. Grain boundary diffusion accommodated by slip was responsible for the stress-relaxation properties of the spring at an elevated temperature (773 K = 500 °C). Graphical Abstract: [ABSTRACT FROM AUTHOR]

A general formulation of the static deflection under an axial force is required for accurate static, buckling and dynamic analyses. Even today, however, the helical spring formulas derived in 1960s still continue to be used in the spring design. So designers maintain to design helical springs with limited options in making a change in both the helix pitch angles and cross-section types. In this study, in order to carry out such formulation and get closed-form solutions for the vertical tip deflection, Castigliano's first theorem is directly employed to the linear elastic problem of cylindrical helical springs with large pitch angles. Derivation takes into account for the whole effect of the stress resultants such as axial and shearing forces, bending and torsional moments on the deformations. Cylindrical helical springs having doubly symmetric cross-sections such as a solid/hollow circle, a square, a horizontal/vertical rectangle, and a horizontal/vertical ellipse made of isotropic and homogeneous linear elastic materials are all handled in this work. For each shape of cross-section considered in the study, a closed form global formula in a compact form is offered for users with the common notations and common design parameters as currently used. These formulas may be directly used without hesitation for both closed-coiled (CC), α ≤ 10 ° , and open-coiled (OC), α ≥ 10 ° , cylindrical helical springs. That is one may use those formulas without the need for any extra information than he already has and without involving any design chart and correction factor. Some of formulas derived in this study are compared to the commonly used formulas in the available literature. It is verified that those formulas may be obtained readily from the present formulas by considering their certain assumptions. Benefits of this study related to previous ones are also discussed. Present global formulas are also verified with available recent experiments and finite element solutions. The groundwork for the data to be used directly in Castigliano's first theorem was obtained by using differential geometry of a helical structure from a general spatial rod, and governing equations derived by using equilibrium equations, constitutive equations and geometrical compatibility relations in vector forms. As a result, the author expects that a designer is to be free to design more accurate springs by using the global analytical formulas presented in this study. [ABSTRACT FROM AUTHOR]

In this paper, finite element method is implemented to model stranded-wire helical springs under different loading conditions. Finite element results are coupled with multiaxial fatigue criteria such as Fatemi–Socie and Kandil–Brown–Miller together with a uniaxial fatigue criterion, Coffin–Manson, to predict fatigue life of the stranded-wire helical springs. It is shown that due to damping effects between wires, stranded-wire helical springs have longer fatigue life compared to their equivalent single-wire helical springs at a similar condition. It is also demonstrated that fatigue life is longer for loadings with higher initial displacement of spring head. As practical examples, fatigue life of stranded-wire helical springs with 9 and 15 wires are estimated and compared. It is shown that the spring with 15 wires gives longer fatigue life. It is also observed that Kandil–Brown–Miller and Fatemi–Socie criteria give the least and the highest fatigue life prediction, respectively. [ABSTRACT FROM AUTHOR]

Purpose -- The purpose of this paper is to address the practically important problem of the load dependence of transverse vibrations for helical springs. At the beginning, the author develops the equations for transverse vibrations of the axially loaded helical springs. The method is based on the concept of an equivalent column. Second, the author reveals the effect of axial load on the fundamental frequency of transverse vibrations and derive the explicit formulas for this frequency. The fundamental natural frequency of the transverse vibrations of the spring depends on the variable length of the spring. The reduction of frequency with the load is demonstrated. Finally, when the frequency nullifies, the side buckling spring occurs. Design/methodology/approach -- Helical springs constitute an integral part of many mechanical systems. A coil spring is a special form of spatially curved column. The center of each cross-section is located on a helix. The helix is a curve that winds around with a constant slope of the surface of a cylinder. An exact stability analysis based on the theory of spatially curved bars is complicated and difficult for further applications. Hence, in most engineering applications a concept of an equivalent column is introduced. The spring is substituted for the simplification of the basic equations by an equivalent column. Such a column must account for compressibility of axis and shear effects. The transverse vibration is represented by a differential equation of fourth order in place and second order in time. The solution of the undamped model equation could be obtained by separation of variables. The fundamental natural frequency of the transverse vibrations depends on the current length of the spring. Natural frequency is the function of the deflection and slenderness ratio. Is the fundamental natural frequency of transverse oscillations nullifies, the lateral buckling of the spring with the natural form occurs. The mode shape corresponds to the buckling of the spring with moment-free, simply supported ends. The mode corresponds to the buckling of the spring with clamped ends. The author finds the critical spring compression. Findings -- Buckling refers to the loss of stability up to the sudden and violent failure of seed straight bars or beams under the action of pressure forces, whose line of action is the column axis. The known results for the buckling of axially overloaded coil springs were found using the static stability criterion. The author uses an alternative approach method for studying the stability of the spring. This method is based on dynamic equations. In this paper, the author derives the equations for transverse vibrations of the pressure-loaded coil springs. The fundamental natural frequency of the transverse vibrations of the column is proved to be the certain function of the axial force, as well as the variable length of the spring. Is the fundamental natural frequency of transverse oscillations turns to be to zero, is the lateral buckling of the spring occurs. Research limitations/implications -- The spring is substituted for the simplification of the basic equations by an equivalent column. Such a column must account for compressibility of axis and shear effects. The more accurate model is based on the equations of motion of loaded helical Timoshenko beams. The dimensionless for beams of circular cross-section and the number of parameters governing the problem is reduced to four (helix angle, helix index, Poisson coefficient, and axial strain) is to be derived. Unfortunately, that for the spatial beam models only numerical results could be obtained. Practical implications -- The closed form analytical formulas for fundamental natural frequency of the transverse vibrations of the column as function of the axial force, as well as the variable length of the spring are derived. The practically important formulas for lateral buckling of the spring are obtained. Originality/value -- In this paper, the author derives the new equations for transverse vibrations of the pressure-loaded coil springs. The author demonstrates that the fundamental natural frequency of the transverse vibrations of the column is the function of the axial force. For study of the stability of the spring the author uses an alternative approach method. This method is based on dynamic equations. The new, original expressions for lateral buckling of the spring are also obtained. [ABSTRACT FROM AUTHOR]

Purpose -- The purpose of this paper is to derive the exact analytical expressions for torsion and bending creep of rods with the Norton-Bailey, Garofalo and Naumenko-Altenbach-Gorash constitutive models. These simple constitutive models, for example, the time- and strain-hardening constitutive equations, were based on adaptations for time-varying stress of equally simple models for the secondary creep stage from constant load/stress uniaxial tests where minimum creep rate is constant. The analytical solution is studied for Norton-Bailey and Garofalo laws in uniaxial states of stress. Design/methodology/approach -- The creep component of strain rate is defined by material-specific creep law. In this paper the authors adopt, following the common procedure Betten, an isotropic stress function. The paper derives the expressions for strain rate for uniaxial and shear stress states for the definite representations of stress function. First, in this paper the authors investigate the creep for the total deformation that remains constant in time. Findings -- The exact analytical expressions giving the torque and bending moment as a function of the time were derived. Research limitations/implications -- The material isotropy and homogeneity preimposed. The secondary creep phase is considered. Practical implications -- The results of creep simulation are applied to practically important problem of engineering, namely for simulation of creep and relaxation of helical and disk springs. Originality/value -- The new, closed form solutions with commonly accepted creep models allow a deeper understanding of such a constitutive model's effect on stress and deformation and the implications for high temperature design. The application of the original solutions allows accurate analytic description of creep and relaxation of practically important problems in mechanical engineering. Following the procedure the paper establishes closed form solutions for creep and relaxation in helical, leaf and disk springs. [ABSTRACT FROM AUTHOR]

Abstract: The bi-orthogomality conditions in terms of generalised forces and displacements are derived from the reciprocity relations for a hierarchy of elastic waveguides, which support several travelling and evanescent modes (free waves). In the simple cases of waves in a straight beam and axisymmetric waves in a thin elastic cylindrical shell, these conditions are formulated as identities in an explicit form via wavenumbers. The forced vibrations of these waveguides under localised excitation are also considered with these identities being employed. The bi-orthogonality conditions in more advanced cases, specifically, for non-axisymmetric waves in an elastic cylindrical shell and for waves in an elastic helical spring, are derived, but not presented in an explicit form via wavenumbers. The results obtained for the hierarchy of waveguides are discussed in view of the classical bi-orthogonality conditions for an elastic layer. The grouping of generalised forces and displacements in these conditions is explained by inspection of the response of a given waveguide to the localised excitation. [Copyright &y& Elsevier]

Abstract: In this study, the vibrations of a coil, excited axially, in helical compression springs such as tamping rammers are discussed. The mathematical formulation is comprised of a system of four partial differential equations of first-order hyperbolic type, as the unknown variables are angular and axial deformations and velocities. The numerical resolution is performed by the conservative finite difference scheme of Lax–Wendroff. The impedance method is applied to calculate the frequency spectrum. The results obtained with this method were used to analyze the evolution in time of deformations and velocities in different sections of the spring resulting from a sinusoidal excitation of the axial velocity applied at the end of the spring. These results clearly show the effect of the interaction between the slow axial waves and the fast angular waves, the resonance and other phenomena related to wave propagations such as wave reflections and beat. [Copyright &y& Elsevier]

The antiaircrafts cannons guns housing is endowed by a helical compression spring, which have the function to accumulate the recul energy, energy used to reposition a reculant part. In this case the helical compression spring loads are dynamic, a fatigue-stress situation exists in the spring. In this paper is presented an method to optimization designing for this helical compression springs. [ABSTRACT FROM AUTHOR]

The advanced design of springs with tailored transmission characteristics is proposed. The existence of frequency stop-bands in the transmission characteristics is theoretically predicted and experimentally validated. The underlying mechanism of generating stop-band behavior is the periodic discontinuity of the curvature. The theoretical analysis is performed in the framework of the Floquet theory for an infinitely long spring. Experimental results are obtained for the springs consisting of a small number of repeated periodicity cells. [ABSTRACT FROM AUTHOR]

Free vibration analysis of non-cylindrical (conical, barrel, and hyperboloidal types) helical springs with rectangular cross-section is performed. The effects of the warping deformation of wire cross-section on the natural frequencies are first studied in the differential equations of motion for the springs. Improved Riccati transfer matrix method is introduced to solve the first order ordinary differential equations with variable coefficients, which consist of 14 degrees of freedom. The natural frequencies of non-cylindrical helical springs with rectangular cross-section and clamped-clamped boundary condition are calculated to validate the proposed method, and the effects of various parameters on the natural frequencies of the clamped-clamped conical springs with rectangular cross-section are also investigated. Calculations show that the warping effect upon the natural frequencies is prominent, which should be considered in the free vibration analysis of the springs. [ABSTRACT FROM AUTHOR]

This paper proposes the use of artificial neural networks (ANN) to perfectly predict the critical buckling loads of cylindrical isotropic helical spring with fixed ends and with circular sections, and with large pitch angles. The buckling equations of cylindrical isotropic helical springs loaded axially consist of a set of twelve linear differential equations. As finding a solution in an analytical manner is too difficult, numerical solution in an exact manner based on the transfer-matrix method to collect consistent dimensionless numerical data for the training process is used. In this way almost perfect weight values are obtained to predict the non-dimensional buckling loads. A good agreement is observed with the data available in the literature. [ABSTRACT FROM AUTHOR]

Planar crack propagation under pure tension loading (mode I) is generally stable. However, it becomes universally unstable with the superposition of a shear stress parallel to the crack front (mode III). Under this mixed-mode (I + III) loading configuration, an initially flat parent crack segments into an array of daughter cracks that rotate towards a direction of maximum tensile stress. This segmentation produces stepped fracture surfaces with characteristic ‘lance-shaped’ markings observed in a wide range of engineering and geological materials. The origin of this instability remains poorly understood and a theory with which to predict the surface roughness scale is lacking. Here we perform large-scale simulations of mixed-mode I + III brittle fracture using a continuum phase-field method that describes the complete three-dimensional crack-front evolution. The simulations reveal that planar crack propagation is linearly unstable against helical deformations of the crack front, which evolve nonlinearly into a segmented array of finger-shaped daughter cracks. Furthermore, during their evolution, facets gradually coarsen owing to the growth competition of daughter cracks in striking analogy with the coarsening of finger patterns observed in nonequilibrium growth phenomena. We show that the dynamically preferred unstable wavelength is governed by the balance of the destabilizing effect of far-field stresses and the stabilizing effect of cohesive forces on the process zone scale, and we derive a theoretical estimate for this scale using a new propagation law for curved cracks in three dimensions. The rotation angles of coarsened facets are also compared to theoretical predictions and available experimental data. [ABSTRACT FROM AUTHOR]

An optimization study on helical compression springs has been performed in this paper. Two objectives are considered: the first objective is to minimize the spring weight, and the second is to maximize the spring stiffness. These two objectives are affected by many engineering design parameters, which can be categorized in three main groups: functional, composite material, and geometrical groups. The objective functions and constraints are mathematically formulated and written in a multi-criteria optimization problem with a non-linear non-equality constraints form. Optimum design parameters, minimum spring weight, and maximum stiffness pertinent to each type of composite material under investigation can then be selected from the results obtained. [ABSTRACT FROM AUTHOR]

Copyright of Construction Science is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An analytical procedure to design binary shape memory actuators is described. A generic actuator is considered where a cursor is moved against dissipative forces using an elastic system containing a primary shape memory spring and a bias (backup) element. Three typical cases are analysed and differentiated in the way the bias force is applied to the primary shape memory spring, using a constant force, a conventional spring, or a second shape memory spring. Dimensionless, closed-form relationships are developed, which form the basis of a step-by-step procedure for an optimal design of the whole actuator (primary active spring and bias element). Specific formulas regarding the detailed design of the shape memory elements of the actuator in the form of straight wires and wire helical springs are also presented. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: A bellows, or a closed thin-walled elastic tube with corrugated walls, undergoes longitudinal extension when subjected to internal fluid pressure. Investigated herein is the mechanical behavior of several pressurized bellows in clusters, which are designed to bend and twist as well as to extend and compress longitudinally. Bellows in clusters can be employed as robotic limbs, such as manipulator arms and legs for walking machines. For limb bending, analysis shows that there is an optimal geometry for satellite bellows, or a set of identical bellows clustered longitudinally about a central core. For limb torsion, the bellows are clustered in a cylindrical helix whose angle is chosen to produce the desired load–displacement relationships, for instance the highest rotation for a given torque. For both bending and torsional limbs, experimental results are included that exhibit the predicted mechanical behavior. [Copyright &y& Elsevier]

We present the crystal structure of the DNA duplex formed by d(ATATATCT). The crystals contain seven stacked antiparallel duplexes in the asymmetric unit with A·T Hoogsteen base pairs. The terminal CT sequences bend over so that the thymines enter the minor groove and form a hydrogen bond with thymine 2 of the complementary strand in the Hoogsteen duplex. Cytosines occupy extra-helical positions; they contribute to the crystal lattice through various kinds of interactions, including a unique CAA triplet. The presence of thymine in the minor groove apparently contributes to the stability of the DNA duplex in the Hoogsteen conformation. These observations open the way toward finding under what conditions the Hoogsteen duplex may be stabilized in vivo. The present crystal structure also confirms the tendency of A·T-rich oligonucleotides to crystallize as long helical stacks of duplexes. [ABSTRACT FROM AUTHOR]

This study is concerned with the establishment of the characteristic equation of a combined system consisting of a cantilever beam with a tip mass and an in-span visco-elastic helical spring-mass, considering the mass of the helical spring. After obtaining the "exact" characteristic equation of the combined system, by making use of a boundary value problem formulation, the characteristic equation is established via a transfer matrix method, as well. Further, the characteristic equation of a reduced system is obtained as a special case. Then, the characteristic equations are numerically solved for various combinations of the physical parameters. Further, comparison of the results with the massless spring case and the case in which the spring mass is partially considered, reveals the fact that neglecting or considering the mass of the spring partially can cause considerable errors for some combinations of the physical parameters of the system. [ABSTRACT FROM AUTHOR]

The parametric three-dimensional geometric model of twin-screw supercharger rotors of any aspect ratio was developed. For model validation through visualization, computer-aided design (CAD) rotor models with scalable data were generated in commercial CAD software and calibrated experimentally by laser Doppler velocimetry (LDV) tests. Calibrated rotor profile data can be transferred into CAD-CFD interface for flow simulation for performance optimization. [ABSTRACT FROM AUTHOR]

The elaboration concerns the products of medical purpose, namely to the compressive-type devices for treatment and prophylaxis of chronic venous insufficiency and lymphostasis. The aim of the study - to elaborate helical local strips by jersey interlacing, which go along the whole product, similar to the histological constitution of vein wall. To invent new knitted structures with additional local spiral ribbons, first the mathematical model of the leg must be studied, to approximate the real system for each patient. Building upon general provisions of deformable firm body mechanics there is a need of acquiring the analytical dependencies connecting physical-mechanical characteristics of a product's material with its geometrical parameters and biochemical characteristics of the patient's body, which the product comes in contact with. In order to do that, the following kinematical models are to be recorded: of the local spiral-like strip of a compressive knitted article and a human leg. When the kinematic model of leg is known the spiral ribbon of new knitted structures may be invented. Using the results of research the following may be calculated: additional normal reaction of ribbon, additional deformation of ribbon-like spring, massage effect of ribbon, energy dissipation along the ribbon. [ABSTRACT FROM AUTHOR]

This article presents a geometrical description of canted coil springs as a particular type of space curve. The influence of the canted angle on the geometrical curvature and torsion is investigated in order to characterize the three-dimensional geometry of the springs. Geometrical descriptions of helical spring rings generated by joining together the two ends of a rectilinear-axis spring as well as several types of spring rings, obtained from rectilinear-axis canted coil springs, are proposed. To create such ring geometries, conservation of length of wire is assumed and approximate relations are derived in order to simplify computations. These geometrical descriptions are then applied to generate appropriate three-dimensional models. Such models can be further imported to computer-aided design and finite-element analysis programmes in order to estimate the mechanical response of such springs. [ABSTRACT FROM AUTHOR]

Abstract: In the dynamic analysis of the classical absorber composed of a spring, a damper and a lumped mass, the mass of its helical spring (or spring mass) is usually neglected. The purpose of this paper is to present a modified absorber with inertia effect of the spring mass considered. In order to evaluate the vibration–reduction efficiency of the presented modified absorber, the forced vibration analyses of a single degree-of-freedom (dof) and a multiple dof structural systems are performed. The first analysis is to determine the dynamic magnification factor of a single dof spring–mass system, respectively, attached by a classical absorber and a modified absorber and subjected to a harmonic excitation. The second analysis is to determine the maximum dynamic responses of a multiple dof pinned–pinned beam, respectively, attached by the last two kinds of absorbers and subjected to a moving concentrated load. Because the second analysis is conducted using the conventional finite element method (FEM), in additional to the mass matrix, damping matrix and stiffness matrix of the classical and modified absorbers, the expressions for calculating the optimum parameters of the last two absorbers associated with any order of vibration mode of the pinned–pinned beam are also derived based on the modal data obtained from the mode superposition methodology and the orthogonal property between the normal mode shapes. Numerical results reveal that the spring mass of the absorber has the effect of suppressing the maximum dynamic responses of the main structural system and should be considered in the formulation to agree with the practical situation. [Copyright &y& Elsevier]

The results of numerous studies performed to date have shown that the performance of various hydraulic systems can be significantly improved by using curved conduit geometries instead of straight tubes. In particular, the formation of Dean vortices, which enhance the development of centrifugal instabilities, has been identified as a factor behind reducing the near-wall concentration buildup in particulate flow devices (e.g., in membrane filtration modules). Still, several issues regarding the effect of conduit curvature on local multidimensional phenomena governing fluid flow still remain open. A related issue is concerned with the impact that conduit geometry makes on the concentration distribution of a dispersed phase in two-phase flows in general, and in particulate flows (solid/liquid or solid/gas suspensions) in particular. It turns out that only very limited efforts have been made in the past to understand the fluid mechanics of such flows via advanced computer simulations. The purpose of this paper is to present the results of full three-dimensional (3D) theoretical and numerical analyses of single- and two-phase dilute particle/liquid flows in U-bend and helical curved conduits. The numerical analysis is based on computational fluid dynamics (CFD) simulations performed using a state-of-the-art multiphase flow computer code, NPHASE. The major issues discussed in the first part of the paper are concerned with the effect of curved/coiled geometry on the evolution of flow field and the associated wall shear. It has been demonstrated that the primary curvature (a common factor for both the U-bend and helix geometries) may cause a substantial asymmetry in the radial distribution of the main flow velocity. This, in turn, leads to a significant, albeit highly nonuniform, increase in the wall shear stress. Specifically, the wall shear around the outer half of tube circumference may become twice the corresponding value for a straight tube, and gradually decrease to the straight tube level when approaching the inner bend location. Another important issue is concerned with the effect of the length of the curved section and of the straight tube just upstream of the bend. Specifically, the discontinuity in curvature at the straight-to-curved transition location results in a localized change in the wall shear distribution around the tube circumference. On the other hand, if the curved tube is sufficiently long, such as in the case of a helix, the asymmetric velocity profile eventually reaches a fully developed pattern. The effect of nondimensional flow parameters, the Reynolds and Dean numbers, on the entry length along the curved helix geometry is also investigated in this paper. It is shown that the predicted developing length agrees well with the existing experimental data. The objective of the second part of the paper is to investigate the mutual interactions between the liquid flow and solid particles in particulate two-phase flows in both the U-bend and helical geometries. It is shown that particle inertia causes an increase in the wall shear. At the same time, two interesting aspects are shown of Dean vortices on particle concentration under the effect of gravity. One of them is the shift in the particle settling zone from the bottom of the horizontal (or nearly horizontal) tube toward the inner bend of the tube. The other, even more important, is a dramatic reduction in peak concentration with increasing Dean number. Both effects are important for equipment design and optimization in biotechnology and process industries. [ABSTRACT FROM AUTHOR]

The load relaxation behavior of small Elgiloy helical extension springs has been evaluated by a combined experimental and modeling approach. Isothermal, continuous heating, and interrupted heating relaxation tests of a specific spring design were conducted. Spring constants also were measured and compared with predictions using common spring formulas. For the constant heating rate relaxation tests, it was found that the springs retained their strength to higher temperatures at higher heating rates. A model, which describes the relaxation behavior, was developed and calibrated with the isothermal load relaxation tests. The model incorporates both time-independent deformation mechanisms, such as thermal expansion and shear modulus changes, as well as time-dependent mechanisms such as primary and steady state creep. The model was shown to accurately predict the load relaxation behavior for the continuous heating tests, as well as for a complex stepwise heating thermal cycle. The model can be used to determine the relaxation behavior for any arbitrary thermal cycle. An extension of the model to other spring designs is discussed. [ABSTRACT FROM AUTHOR]

A series of helical ceramic springs were manufactured from MgO partially stabilized zirconia to investigate their mechanical properties. Nine springs were machined from zirconia tubing, initially one inch in length, with a rectangular pitch of 16, 14, or 12 turns per inch. An experimental apparatus that both supports and equalizes the applied loads on springs was developed. The spring deflection versus applied load was measured using an optical sight mounted on a micrometer. Deflection data on each spring were collected, plotted and successfully modeled using Hooke's Law. A more extensive model was used to calculate the shear modulus of rigidity and shear stress. This model incorporates the spring dimensions, pitch, applied load, and deflection and provides insight into the effects of the materials of construction and manufacturing technique on the effective shear modulus of spring. A specific manufacturing effect was observed in the initial deflection resulting from the mass of the spring as the pitch was increased. [ABSTRACT FROM AUTHOR]

Numerical and analytical studies are performed for the free vibration analysis of non-cylindrical (conical, barrel and hyperboloidal types) helical springs. The stiffness matrix method is used in the numerical analysis. A total of 12 degrees of freedom (six displacements and six rotations) is described for an element. The exact element stiffness matrix and the exact concentrated element inertia matrix are used in the formulation. The rotary inertia, the shear and extensional deformation effects are considered in the analysis. Comparison of the numerical results with the reported results obtained numerically and experimentally gives satisfactory values. After verification of the numerical frequencies, the non-dimensional fundamental frequencies of fixed–fixed non-cylindrical helical springs with circular section are expressed in a simple formula with a maximum absolute relative error of 5% using those numerical values for the constant helix pitch angles (5°, 10°, and 15°). These expressions restricted to the fundamental frequencies are also verified with ANSYS results. [Copyright &y& Elsevier]

The development of plasma-sputter-type negative ion sources is underway for the heavy-ion-beam probe system as plasma diagnostic beams of the large helical device (LHD) for potential and fluctuation field measurements. Our purpose is to increase the doubly charged exchanged Au+ beam intensity to enhance the detection signal after passing through the plasmas of the LHD. For this purpose, the characterization of the Au- ion source and the beam optics has been carried out both experimentally and numerically. Based on these results, a new plasma-sputter-type negative ion source is designed and tested. [ABSTRACT FROM AUTHOR]

In methanol, the reaction of Cu(ClO4)2·6H2O and a sterically constrained piperazine imine phenol ligand (H2L), in the presence of NEt3, affords a novel tetranuclear copper(II) complex of formula [CuII4(μ3-L)2(μ-OH)2(H2O)2](ClO4)2·H2O (1). The X-ray structure of this complex shows an elongated Cu4 quasi-tetrahedron coordinated to two hexadentate chair-(e,a)-μ3-piperazine bridging ligands. Variable-temperature magnetic studies show an St = 0 spin ground state resulting from antiferromagnetic interactions between CuII ions within the complex. [ABSTRACT FROM AUTHOR]

Design of vertical cylindrical tube furnaces having radial coils is described, and technical data for furnaces having vertical and helical coils are given. [ABSTRACT FROM AUTHOR]

The article discusses on shear resistance which is caused by transverse reinforcement and that can also be applied to concrete beams and columns. The researchers also attempted to specify the effective section area of circular hoops and spirals traversing the crack plane that determine the shear strength . They also included studies on the effect of inclination in spirals from the horizontal line attributable to the helical nature.

The spring rates of a coiled helical spring under an axial force and an axially directed torque are derived by a consistent application of Castigliano’s second theorem, and it is shown that the coupling between the two loads may not always be neglected. The spring rate of an extensional spring is derived for the first time through the use of the displacement based principle of minimum total potential energy. The present results are also compared with available derivations of and expressions for the stiffness of a coiled spring. [ABSTRACT FROM AUTHOR]