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An application of a polarization-maintaining photonic crystal fiber (PM-PCF) for torsion sensing is proposed and experimentally demonstrated. The response of the sensor is theoretically validated using the Jones matrix. High normalized sensitivity of ~0.014/[degrees] was measured within a linear twist angle range from 30[degrees] to 70[degrees]. The sensor response was observed to be highly repeatable over a 90[degrees] twist in both the clockwise and counterclockwise directions. The proposed sensor exhibits reduced temperature sensitivity due to the low thermal coefficient of PM-PCF, making it an ideal candidate for torsion sensing. OCIS codes: 060.2370, 060.3735.

The article explains the development of a new longitudinal-torsional hybrid-type ultrasonic motor, which is shown to exhibit large torque and low revolution speed. The motor is shown to be small, light and noiseless with a hollow and short cylindrical structure.

A theoretical analysis, associated simulations and tests of the coupling between the torsional waves in a semi-infinite cylindrical wave guide and a viscous fluid on the interface boundary for two viscometer configurations are presented. It is concluded that the product of the viscosity and the density of the fluid can be measured from the end reflection coefficient of the torsional wave in the wave guide.

High resolution by microwave Fourier transform spectroscopy (FTMW) is used to study the ground state rotational spectrum of B[F.sub.2]OH. The small torsional splitting is analysed using a phenomenological model developed for HN[O.sub.3].

Nonlinear torsional motions in a long circular rod with relatively large shear deformation are studied. Results prove useful in the understanding and design of devices operating with torsional modes.

The study explains the effects of the bending and torsion strains on the values of the critical current in various YBCO coated conductors. The bend of the coil is shown to be extremely sensitive to the sample-tape thickness, as well as the sample-tape width.

The study describes the critical current degradation behavior in the long length YBCO coated conductors that are subjected to torsional strain. The critical current is found to degrade gradually and slowly in these films.

Stability of a cemented implant, once the stem-cement interface has debonded, is reliant upon stem geometry and surface finish. There are relatively few studies addressing the effect of cross-sectional stem shape on cemented implant fixation. The purpose of this investigation was to compare the torsional stability of five different stem cross-sectional shapes--circular, oval, triangular, rectangular with rounded edges, and rectangular with sharp edges--under monotonically increasing and cyclic loading conditions. Seven samples of each stem geometry were tested. Stems were potted in bone cement and loaded to 5 deg of rotation. For monotonic loading, torque was applied at a constant rate of 2.5 deg/min. For cyclic loading, a sine wave torque pattern was applied, with a maximum magnitude that began at 4.5 Nm for 1500 cycles and then increased by 2.25 Nm every 1500 cycles until 5 deg of rotation. The rectangular stem with the sharp edges always provided the greatest resistance to torque, followed by the rectangular with rounded edges, triangular, oval, and circular. These results, including the effects of sharp corners, may differ for modes of loading other than torsion. These experimental results support the findings of earlier finite element models, indicating stem shape has a significant effect on resistance to torsional loading. [DOI: 10.1115/1.2720907] Keywords: implant fixation, implant design, cemented implant failure, torsional stability, arthroplasty

This paper deals with the application of neural networks (NNs) to the mechanical state estimation of the drive system with elastic joint. The torsional vibrations of the two-mass system are damped using the control structure with additional feedbacks from the torsional torque and the load-side speed. These feedbacks signals are obtained using NN estimators. The learning procedure of the NNs is described, and the influence of the input vector size to the accuracy of the state-variable estimation is investigated. The neural estimators of the torsional torque and the load machine speed are tested with open-loop and closed-loop control structures. The simulation results are confirmed by laboratory experiments. Index Terms--Neural networks (NNs), state variable estimation, torsional vibration, two-mass system.

In this paper, consideration is given to the dynamic response of a rotating cantilever twisted and inclined airfoil blade subjected to contact loads at the free end. Starting with the basic geometrical relations and energy formulation for a rotating Timoshenko beam constrained at the hub in a centrifugal force field, a system of coupled partial differential equations are derived for the combined axial, lateral and twisting motions which includes the transverse shear, rotary inertia, and Coriolis effects, as well. In the mathematical formulation, the torsion of the thin airfoil also considers a very general case of shear center not being coincident with the CG (center of gravity) of the cross section, which allows the equations to be used also for analyzing eccentric tip-rub loading of the blade. Equations are presented in terms of axial load along the longitudinal direction of the beam which enables us to solve the dynamic pulse buckling due to the tip being loaded in the longitudinal as well as transverse directions of the beam column. The Rayleigh-Ritz method is used to convert the set off our coupled-partial differential equations into equivalent classical mass, stiffness, damping, and gyroscopic matrices. Natural frequencies are computed for beams with varying 'slenderness ratio' and 'aspect ratio' as well as 'twist angles.' Dynamical equations account for the full coupling effect of the transverse flexural motion of the beam with the torsional and axial motions due to pretwist in the airfoil. Some transient dynamic responses of a rotating beam repeatedly rubbing against the outer casing is shown for a typical airfoil with and without a pretwist. [DOI: 10.1115/1.2423035]

Classical molecular dynamics simulations are used to examine the mechanical responses of several different carbon nanotube systems to applied torsional loading at various temperatures. The simulations have shown that the critical buckling moment can be modified by adjusting the system temperature and through chemical functionalization of the carbon nanotube walls.

A number of common fallacies regarding various theories of relativity and methods of falsification thereof are considered in this paper. A 'weak' principle of relativity implicitly applied in theories of [...]

To investigate the flutter characteristics of cascading blades in multiple blade rows, the computation program to calculate the unsteady blade loading based on the unsteady lifting surface theory for contra-rotating annular cascades was formulated and coded. Then a computation program to solve the coupled bending-torsion flutter equation for the contra-rotating annular cascades was also developed. Some results of the flutter analysis are presented. It is shown that the presence of the neighboring blade row gives rise to substantial change in the critical flutter condition irrespective of the blade row gap when the main acoustic duct mode is of cut-on state. The effect of the neighboring blade row is also significant irrespective of the state of the main acoustic duct mode when the blade rows are very closely placed. DOI: 10.2514/1.22561

This paper investigates the shear buckling of flat, stiffened panels of specially orthotropic skin material, for which the stiffeners are assumed to possess both flexural and torsional rigidity. It is shown that the shear buckling behavior can be captured by four generic, nondimensional panel parameters, two of which relate to the skin orthotropy, the other ones representing the flexural and torsional stiffness of the stiffeners. Several design curves, showing the nondimensional shear buckling load as a function of these four panel parameters, are generated using the STAGS FEM code. The validity of the FEM method is demonstrated through comparison with an analytical procedure based on the Rayleigh-Ritz and Lagrangian multiplier methods. Furthermore, to assess the accuracy of the design curves a number of Glare panels containing stiffeners of different shapes and attachment methods typically applied in aerospace structures are analyzed as well. These particular FEM analyses are more realistic than the ones used to generate the design curves in the sense that the exact shape of the stiffeners is modeled and the attachment method is explicitly accounted for. It is shown that the predictions from the design curves are in reasonable agreement with the detailed FEM results.

The torsional buckling analysis of multiwalled carbon nanotubes subjected to thermal load is studied and numerical results of the general case are presented for thermal effect. It is concluded that at room or lower temperature the critical torsional load of a multiwalled carbon nanotube increases as the value of temperature change increases, while at higher temperature than room temperature the critical torsional load decreases as the value of the temperature change increases.

A dynamic analysis is performed for torsional resonance (TR) and lateral excitation (LE) modes of atomic force microscopy (AFM) by considering the coupling between the cantilever torsion and lateral bending. Parametric analyses show that in TR and LE modes, the pure torsional approximation can provide accurate cantilever responses if the lateral tip-sample interaction is weak when compared to the cantilever torsional stiffness.

In structural design of steel structures in fire, the failure criterion needs to be checked for all members under individual design actions or a combination of them. For space frames, combined design actions usually include forces due to bending, axial, shear, and torsion. An increase in temperature will result in changes to these forces as well as the diminution of the failure criterion due to reduced member capacities as a result of these combined design actions. This paper presents an elastic method for the prediction of limiting temperature of members in space steel frames. Since the critical temperature of the structure corresponds to the ultimate failure of the member with the lowest limiting temperature, this elastic method is equivalent to finding the location of the first plastic hinge in a general plastic analysis. By considering the degradation of the mechanical properties of steel in fire, a formulation based on the failure criterion of combined design actions including torsion is presented for limiting temperature calculation. The fundamentals of the solution strategy are also explained. CE Database subject headings: Torsion; Temperature; Steel structures; Fire hazards; Fire resistance.

This paper introduces a small-signal dynamic model of a fixed-frequency (induction machine based) wind farm connected to an electrical power system. The model represents the system small-signal dynamics in the frequency range of a fraction of Hz to 50/60 Hz. The model includes the dynamics of the wind energy capturing mechanism, the rotating shaft system, the generator electrical system of each wind energy unit, the wind farm collector system, and the utility grid. Based on the proposed model, two performance indices are introduced to i) investigate sensitivity of the system modes, e.g., torsional modes, to the system parameters, and ii) evaluate the system capability to reject electrical and mechanical disturbances, e.g., a wind gust. The application of the model to the analysis of a system with two wind units is presented and the study results are validated based on comparison with the time-domain simulation results obtained in the PSCAD/EMTDC environment. Index Terms--Fixed-speed wind farm, sensitivity analysis, small-signal dynamics, torsional phenomenon.

Abstract: Through out this paper an experimental study was carried out to study the static torsion capability of hybrid aluminum glass fiber composite shaft. A hybrid shaft was fabricated using [...]

Ab initio calculations for determining the relative stabilities and the sizes of the torsional barriers that hinder the internal rotation are discussed. This method produces observable parameters and represents an improvement of the usual way consisting in the direct determination of the parameters from ab initio force fields.

A torsional dependence of electron spin-spin exchange coupling in trimethylenemethane (TMM)-type dinitroxide biradicals is described. This torsional dependence is compared with an analogous series of TMM-type bis(semiquinone) biradicals.

This paper presents a study developed on a three-phase 11-MW synchronous motor with a solid salient-pole rotor of a blower drive system of a blast furnace at the Companhia Siderurgica Belgo-Mineira, Joao Monlevade, Brazil. A mechanical model including motor, gears, couplings, and blower is used in a simulation study to evaluate the torsional dynamics and stresses during motor startup and voltage sag conditions. In addition, the operation of the synchronous motor under voltage sag is analyzed with a comparative study between complete and approximated models of the motor. The utilization of a dynamic voltage restorer to protect the drive system under this abnormal situation is also evaluated. Index Terms--Power quality, simulation models, synchronous motors.

A Ch stretching methyl torsional model is used to simulate the methyl band overtone profiles. This model is applied to a series of molecules with torsional barriers ranging from 5 to about 500 cm(super -1), and the methyl CH-stretching overtone band structure for most barrier heights is explained.

The active twist rotor investigated in this research is a derivative of the previously developed smart-active-blade-tip (SABT) rotor. On the SABT rotor, the blade tips are independently pitched, with respect to the main blade. A novel piezo-induced bending-torsion coupled actuator beam, located spanwise in the hollow midcell of the main rotor blade, is used to actuate the blade tip. When the blade tip is locked to the main blade, the actuator beam twists the entire blade. A Mach scale rotor with a 1.542 m diameter was hover tested, open loop, to evaluate the control authority for vibration reduction. A nonrotating tip-twist amplitude of 0.78 deg was achieved (below resonance, 150 V rms). Analysis indicates that no significant twist actuation degradation is expected at full rotor speed. In 2000-rpm hover (tip Mach 0.47), at 8-deg collective, and for a single blade actuation of 150 V rms at 1, 2, and 3 per revolution, respectively, the measured oscillatory thrust coefficients are 1.4 x [10.sup.-3], 0.55 x [10.sup.-3], and 0.7 x [10.sup.-3]. The corresponding finite element model estimated blade twist amplitudes are 0.8, 1,0, and 1.9 deg. Good correlation of the predicted and measured rotor thrust was achieved up to 3 per revolution. The hover test demonstrates the potential of the active twist rotor system using an internal actuation beam and warrants further research for a dedicated next-generation model-scale design and full-scale feasibility study.

Density functional theory (DFT) calculations are employed at the Becke-3-Lee-Yang-Parr (B3LYP) level using the 6-31+G(d,p) basis set to explain geometrical optimizations on the ground and triplet states of the cis- and trans-stilbenes and of 2,3-diphenylnorbornene. Results on theoretical calculations support that in 2,3-diphenylnorbornene and in cis- and trans-stilbenes torsional motion about the CC double bonds offers more stabilization in the triplet state, instead of phenyl-vinyl torsion.

Byline: Y.G. Smeyers (1), M. Villa (2,3) Keywords: large amplitude motions in trimethylamine; classes and character table for torsion--inversion in trimethylamine Abstract: The non-rigid molecule group theory (NRG) in which the dynamical symmetry operations are defined as physical operations is applied to determine the character table for the triple equivalent methyl rotation and pyramidal inversion in trimethylamine. The restricted NRG of this molecule is seen to be a group of order 648, formed as a product of two subgroups: the G .sub.324 subgroup corresponding to planar trimethylamine and the pyramidal inversion. For this purpose the structure of the r-NRG of planar trimethylamine is first deduced, i.e., the number of classes, irreducible representations, as well as their dimensions. Finally, guidelines are given to deduce systematically the symmetry eigenvectors developed on the basis of quadruple products of trigronometric functions. The r-NRG molecule group theory is seen to be used advantageously to study the internal dynamics of such small organic molecules. Author Affiliation: (1) Instituto de Estructura de la Materia, C.S.I.C, Serrano, 123, 28006, Madrid, Spain (2) Instituto de Estructura de la Materia, C.S.I.C, Serrano, 123, 28006, Madrid, Spain (3) Departamento de Quimica, Universidad Autonoma Metropolitana, Iztapalapa, 09340, Mexico, D.F., Mexico Article History: Registration Date: 08/10/2004

Abstract: Issuing from a geometry with nonmetricity and torsion we build up a generalized classical electrodynamics. This geometrically founded theory is coordinate covariant, as well as gauge covariant in the Weyl sense. Photons having arbitrary mass, intrinsic magnetic currents, (magnetic monopoles), and electric currents exist in this framework. The field equations, and the equations of motion of charged (either electrically or magnetically) particles are derived from an action principle. It is shown that the interaction between magnetic monopoles is transmitted by massive photons. On the other hand, the photon is massive only in the presence of magnetic currents. We obtained a static spherically symmetric solution, describing either the Reissner-Nordstrom metric of an electric monopole, or the metric and field of a magnetic monopole. The latter must be massive. In the absence of torsion and in the Einstein gauge one obtains the Einstein-Maxwell theory. Article History: Registration Date: 03/10/2004

The relationship of torque versus angle of rotation stabilizes after only a few cycles so that the alternating stress will become a constant as long as the maximum shear stress is less than the shear yield strength of the material. Using this information in Findley's fatigue criterion, it is demonstrated that the mean shear stress has very little influence on the fatigue limit of a notch-free ductile material under cyclic torsional loading. [DOI: 10.1115/1.2349582]

Byline: Gianni Caligiana A research method has been developed for prediction of life endurance of large shafts bearing variable torsional loadings like those of the electric utility industries. Several programs are proposed to calculate damage for complex loading histories and component geometries. Torsion and push-pull fatigue tests were conducted in strain control at constant strain amplitude as a local strain approach was used in the numerical programs arrangement. Torsion tests were made on both solid and hollow specimens. Cyclic and fatigue (strain-life) curves are drawn for torsion and push-pull tests. An attempt to give an alternative correlation of results was made on the basis of Novozilov and Romanov's theory. During tests, the bending strain on the specimen was controlled in both torsion and push-pull tests.

Byline: Meinhard Schwaiger, Franz Schuch Although bonding as a jointing method for metals has quite a number of advantages, this method so far has had only modest significance in the field of vehicle construction. This rather sceptical view of bonding can be attributed to the lack of appropriate empirical values and calculating standards. Starting from this viewpoint, experimental results are described, which have been elaborated on bonded cylindrical joints under static and dynamic loading as a joint project with Loctite Ireland. Subsequently the practical applicability of these experiments is discussed. The paper describes the following items: reaction to deformation of adhesive coat under axial and torsional loading respectively; dependence of nominal shear strength on load direction; computed interpretation of press fit joints and shrink fit joints with bonding; finite fatigue life and endurance limit of bonded joints in dependence on various influential parameters failing mechanisms of dynamically loaded bonded joints; cyclic softening and hardening effects.

Byline: S. Curioni The use of low cycle fatigue methodology to evaluate the life expectancy of a structure is on the increase in the last years. This is connected also to the use of computer programs that permit evaluation of stress and strain concentration factors in the plastic field. In this paper the principal procedures used to predict the life expectancy of a mechanical component subject to a biaxial stress state are presented and discussed. The experimental work is connected with torsional loadings on large turbine-generator shafts due to electrical disturbances.

Byline: S.H. Lim, J. Niisawa, N. Tomioka, A. Kosio Box members formed by spot welding two thin-walled members of hat selection are widley employed in motor car frame structures. In particular, those members subjected to large bending loads are reinforced by sandwiching a longitudinal partition between the two hat members and spot welding to connect. This clarifies that although the partition increases the bending strength on the one hand, it tends to reduce the torsional rigidity.

Byline: S.H. Lim, J. Niisawa, N. Tomioka, A. Koiso Box members formed by spot welding two thin-walled members of hat section are widely employed in motor vehicle frame structures. In particular, the members subjected to large bending loads are reinforced by sandwiching a longitudinal partition between the two hat members and spot welding to connect. This paper explains that although the partition increases the bending strength, it tends to increase the stress in the nugget end and to reduce the fatigue strength.