Showing papers on "Torsion (mechanics) published in 1989"

Laminated piezopolymer plates for torsion and bending sensors and actuators

Abstract: A set of piezopolymer devices has been developed based on a composite laminate theory for piezoelectric polymer materials. By using different combinations of ply angles and electrode patterns, a piezopolymer/metal shim plate structure was built that exhibited both bending and torsion deformation under an applied electric field. A set of torsion‐beam sensor structures was also built that could distinguish between bending and torsion or between different vibration modes. These devices were based on a general theory of piezoelectric laminates. The experimental results agreed quite closely with the theoretical predictions. These integrated sensor–actuator devices may find application in the control of microactuators or may be used for modal control of larger continuous structures.

The Dean equations extended to a helical pipe flow

Abstract: In this paper the Dean (1928) equations are extended to the case of a helical pipe flow, and it is shown that they depend not only on the Dean number K but also on a new parameter λ/[Rscr ] where λ is the ratio of the torsion τ to the curvature κ of the pipe axis and [Rscr ] the Reynolds number referred in the usual way to the pipe radius a and to the equivalent maximum speed in a straight pipe under the same axial pressure gradient. The fact that the torsion has no first-order effect on the flow is confirmed, but it is shown that this is peculiar to a circular cross-section. In the case of an elliptical cross-section there is a first-order effect of the torsion on the secondary flow, and in the limit λ/[Rscr ] → ∞ (twisted pipes, provided only with torsion), the first-order ‘displacement’ effect of the walls on the secondary flow, analysed in detail by Choi (1988), is recovered.Different systems of coordinates and different orders of approximations have recently been adopted in the study of the flow in a helical pipe. Thus comparisons between the equations and the results presented in different reports are in some cases difficult and uneasy. In this paper the extended Dean equations for a helical pipe flow recently derived by Kao (1987) are converted to a simpler form by introducing an appropriate modified stream function, and their equivalence with the present set of equations is recovered. Finally, the first-order equivalence of this set of equations with the equations obtained by Murata et al. (1981) is discussed.

Coupled bending–torsional dynamic stiffness matrix for beam elements

Abstract: Explicit expressions for the coupled bending–torsional dynamic stiffness matrix of a uniform beam element are derived in an exact sense by solving the governing differential equation of the beam. Implementation of the derived dynamic stiffness matrix in a space frame computer program is discussed with particular reference to an established algorithm to enable vibration analysis of coupled systems to be made. The application of the theory is demonstrated by an illustrative example wherein the results for a cantilever beam with a substantial amount of coupling between bending and torsion are highlighted. The correctness of the theory is confirmed to a high degree of accuracy by computed results and numerical checks.

Quantum Mechanics and Path Integrals in Spaces with Curvature and Torsion

Abstract: We point out that there is a natural geometric procedure for constructing the quantum theory of a particle in a general metric-affine space with curvature and torsion. Quantization rules are presented and expressed in the form of a simple path integral formula which specifies compactly a new combined equivalence and correspondence principle. The associated Schrodinger equation has no extra curvature nor torsion terms that have plagued earlier attempts. Several well-known physical systems are invoked to suggest the correctness of the proposed theory.

Apparatus for Determining the Viscoelastic Properties of Materials Over Ten Decades of Frequency and Time

Abstract: This article describes an experimental apparatus and analysis scheme for determining the viscoelastic properties of a material isothermally, with a single apparatus, over 10 decades of time and frequency. Torque was applied to the specimen electromagnetically and its deformation was determined by laser interferometry. Resonances were eliminated from the torque and angle measuring devices by this approach. Resonances remaining in the specimen itself were corrected by a numerical analysis scheme based on an analytical solution which is applicable to homogeneous cylindrical specimens of any degree of loss. The apparatus is capable of creep, constant load rate, subresonant dynamic, and resonant dynamic experiments in bending and torsion. The range of equivalent frequency for torsion is from less than 10−6 Hz to about 104 Hz. The capability of the apparatus is illustrated with measurements upon several viscoelastic elastomers and upon poly(methyl)methacrylate.

Torsional oscillator for internal friction data at 100 kHz

Abstract: We describe a method for measuring the internal friction of solids at low temperatures. Our design uses a composite oscillator vibrating in torsion at 100 kHz. The oscillator makes good thermal contact to the cryostat while maintaining a low background loss of Q−1≂2×10−6 at 2 K. The usefulness of the design is demonstrated by data for BaF2 and a‐SiO2 from 2 to 300 K.

Existence and characterization of higher-order terms in an asymptotic expansion method for linearized elastic beams

Abstract: This work is a continuation of an earlier work by Bermudez and Viano (1984) on the same subject. In fact, using the same asymptotic expansion in linear elastic beams we give a complete characterization of displacements, bending moments and shear forces of orders 0, 1 and 2. These results include a characterization of the stress field of order 0 and of the axial and shear stresses of order 1. An appropriate physical interpretation of these results, which is considered elsewhere, will allow us to derive and to justify, from a mathematical point of view, the most well-known classical extension, bending and torsion theories for linear elastic beams, including the Bernoulli-Navier, Saint Venant, Timoshenko and Vlasov models.

Roll damper device

Abstract: PURPOSE: To increase the rolling restricting effect by engaging a pair of rotation transmitting members at a torsion shaft part of a stabilizer bar disposed between a left and a right wheel to be relatively rotated by the torsion of the shaft part, and providing a damping force generating means for damping an input through a speed increasing means between both of them. CONSTITUTION: A front suspension device connects type A arms for supporting a left and a right front wheel respectively by a stabilizer bar 9 extended along the car width, and a roll damper device 10 is provided in the middle of the stabilizer bar 9. In this case, a pair of rotation transmitting members 13, 14 to be engaged with a torsion shaft part 9b and relatively rotated by the torsion of this shaft part 9b. A damping force generating mechanism 19 is also provided for restricting torsion of the shaft part 19b by relative rotation motion of a first and a second speed increasing mechanisms 15, 16 of a planetary gear type for increasing the rotation speed of the rotation transmitting members 13, 14 respectively, and three of a first and a second partition wall part 17, 18 speed increased and rotated by the speed increasing mechanisms 15, 16. COPYRIGHT: (C)1991,JPO&Japio

Electric power steering system for a motor vehicle

Abstract: An electric power steering system for an automobile which includes a steering shaft having a steering torque transmitting shaft. The electric power steering system includes a housing mounted on the steering torque transmitting shaft, a torsion torque sensor, in the housing, for detecting a torsion torque in the steering shaft during a steering operation to generate a torsion torque signal representing the detected torsion torque, and a controlling unit for providing a drive signal, in response to the torsion torque signal, to control an electric motor, mounted to the housing and operatively connected to the steering torque transmitting shaft, for reducing a steering effort. The controlling unit is integrally mounted to the housing.

Combined extension and torsion of a swollen cylinder within the context of mixture theory

Abstract: Summary The problem of a cylindrical mixture of a nonlinearly elastic solid and an ideal fluid subjected to combined finite axial extension and torsion is considered. In previous work, a 'universal relation' has been presented by assuming a small angle of twist. In this work, the general problem for the finite deformation of the swollen cylinder is discussed in the context of Mixture Theory. ComputationAl results for the variation of the radial and tangential streLeh ratios and the distribution of the fluid in the swollen deformed state are presented. The results demonstl'a~e that the swollen volume of a cylinder reduces wi~h twisting when the axial stretch ratio is held constant. Computational results for the reduction in the swollen volume predict the same qualitative and quantitative trends as observed in experimental results.

A Mechanism for Shear Band Formation in the High Strain-Rate Torsion Test

Abstract: A moving boundary of rigid unloading, starting from the ends of the thin-walled tubular specimen, is a plausible mechanism for adiabatic shear band formation during the test The mathematical model is based on a physical model of thermoelastic-plastic flow and a phenomenological Arrhenius model for the plastic flow surface

Multi-fuseable shaft

Abstract: A fuseable torsion shaft for use within an aircraft flight control surface actuation system. The fuseable torsion shaft includes a shear tube which exhibits high strength elastic characteristics during normal operation up to a predetermined shear torque level. Thereafter, a torsion shaft having lower strength plastic characteristics provides torque transmission capability for a limited deflection.

Stress distribution and deformation of adhesive-bonded laminated composite beams

Abstract: A study is reported of the 3-dimensional elasticity solution of flexure and torsion in adhesive-bonded multilayered beams of uniform cross section having one end fixed and the other end loaded by transverse forces. The study found that the elementary beam theory (Beer and Johnston 1981) based on the assumption that plane sections of the beam remain plane after deformation yields an exact elasticity solution for the normal stress for multilayered beams if certain conditions are satisfied. These and other findings are discussed.

Analytic Prediction of Texture and Length Changes During Free-End Torsion

Abstract: The free-end torsion length change measurements of Rose and Stuwe (1968), carried out on cube-textured Cu tubes, are reanalyzed. Ratios of length change rate to applied shear rate are calculated using a newly-developed rate sensitive approach and also by the CMTP method. The dependence of this ratio on the orientation of the cube axis is shown to be in good agreement with the measurements, particularly for lengthening. The analysis is extended to its rate insensitive limit for comparison with the equivalent predictions of Rose and Stuwe. The rate of lattice rotation is also predicted; this is shown to be independent of rate sensitivity and identical to the rigid body rotation rate. Through the lattice rotations, analytic expressions are derived which predict the dependence of sample length on shear strain. These are also in good agreement with the experimental observations.

Strain Increment and Stress Directions in Torsion Shear Tests

Abstract: The directions of the major principal strain increment, stress, and stress increment during rotation of the principal stress axes at any stress level are studied for \IK\N\do-consolidated clay using a torsion shear apparatus with individual control of the vertical normal stress, the confining pressure, and the shear stress on hollow cylinder specimens under undrained and drained conditions. The torsion shear tests are performed along predetermined stress-paths, which are chosen to cover the full range of rotation of principal stress axes from 0° to 90° relative to vertical. The test results indicate that the major principal strain increment directions coincide with the major principal stress directions at failure. The directions of major principal strain increment coincide with the directions of major principal stress increment at low stress levels and with the directions of major principal stress at higher stress levels. This indicates that the behavior of clay gradually changes from elastic to plastic as the stress level is increased. Elasto-plastic theory is therefore suitable for modeling the behavior of clay during rotation of principal stress axes.

Einstein-Maxwell theory from torsion

Abstract: The Einstein-Maxwell formulation of gravitation and electromagnetism is developed in U4 spacetime by using a Lagrangian which produces propagating torsion. The resulting equations turn out to be identical to the Einstein-Maxwell formulation except that here the torsion vector represents the electromagnetic potential.

The Influence of Texture on Strain Hardening

Abstract: It is well known that the strain hardening behavior of metals is not the same in tension, compression, torsion and rolling, for example. The comparison is usually made on a basis of vonMises equivalent stress and strain. One reason for this difference lies in the development of deformation textures, which depends on the straining path. We report on a new set of experiments, comprising wire-drawing interrupted by tensile tests, free compression, channel-die compression, and short-tube torsion in aluminum, an Al-Mg alloy, copper, silver, and 70:30 brass. The texture was measured before straining and at vonMises strain levels of roughly 1.0 and 2.0. Computer simulations of the deformation, starting from a set of random grains weighted by the observed initial texture, predicted deformation textures in qualitative agreement with the observed ones in most cases. Quantitatively the simulations yielded the Taylor factors as a function of strain for all paths and, with an assumed hardening law for the representative grain, the macroscopic stress/strain curves. The grain hardening rate as a function of resolved shear stress was described in tabular form such as to match one of the macroscopic curves, and then used to predict the others. The eventual fit was quite good; we will describe what judgments needed to be made to achieve this result. The conclusion is that the strain-path dependence of work hardening can be explained simply as a consequence of texture development.

Sensor for measurement of the torque acting on a rotating shaft

Abstract: A sensor for measuring the torque acting on a rotating shaft has two electrode structures which are respectively mechanically coupled to two axially spaced points on the shaft to be measured so that a relative movement between the two electrode structures occurs due to the torque. The electrode structures each have a number of parallel, spaced electrodes and are asymmetrically mounted in a plane so that a number of capacitors are formed by electrode pairs each having an electrode from each electrode structure. Because of the asymmetrical arrangement, the electrodes in a pair are spaced a relatively large distance away from the next closest electrode, so that a capacitive decoupling between the pairs is achieved. Changes in the spacing between the points on the shaft due to torsion of the shaft caused by the torque will change the spacing between the electrodes in each pair, thereby resulting in a total capacitance change which is proportional to the torque. To compensate for the influence of transverse forces or bending moments acting on the shaft, a further capacitor arrangement identical to the first arrangement is arranged at an angle of 180° with respect to the first arrangement, with the capacitance used for the purpose of measurement being the capacitances of the two capacitor arrangements in the series.

Apparatus for detecting rotation

Abstract: A rotation-detecting apparatus includes a U-shaped support member, a rod at least one end of which is held to the support member, a vibrating sheet mounted to the rod, piezoelectric ceramic sheets mounted on the vibrating sheet, a torsion detector for detecting the rotation of the vibrating member relative to the rod, and an oscillator circuit for activating the piezoelectric sheets to vibrate the vibrating sheet. The Coriolis force produced on the vibrating sheet is converted into a twist of the rod and detected.

Torsional oscillations of unequally-loaded parallel identical turbine-generators

Abstract: This paper provides a detailed analytical investigation of the torsional phenomenon of closely coupled parallel identical T-G sets, under unequal loading conditions. The impact of important factors, i.e., 1) load difference of generators, 2) mechanical damping torque components and 3) series capacitor compensation level on the torsional modes of unequally loaded parallel T-G set, are examined. The studies are conducted on a system composed of two parallel identical T-G sets. An eigenvalue method is used for the studies and the analytical results are verified by detailed digital computer simulation of the system, using the EMTP. The T-G sets also represented by the so called EGM, and whenever applicable, the study results are compared with those obtained from the EGM. The studies indicate that the corresponding torsional modes of the parallel T-G sets under unequal loading conditions, are not in-phase. The phase-deviation depends on: 1) the load-difference of the generators and 2) the mechanical damping torque components. Among the mechanical damping coefficients, i.e., mutual-damping coefficient, absolute-speed self-damping coefficient and speed-deviation, self-damping coefficient, the first two are constants and the third one is load dependent. The mechanical damping torque components corresponding to the speed-deviation self-damping coefficients have a noticeable impact on the phase-deviation. This paper also reports the results of an investigation in which an SVC system is used to mitigate the torsional oscillatory modes of the unequally loaded T-G sets.

Tensioning device for vehicle drive belts - consists of hexagonal sectioned torsion bar, with lever and roller or disc

Abstract: The belt-tensioning piece is used for adjusting and continuously maintaining the correct belt tension for a vehicle drive-belt. It consists of at least one tension-piece in the form of at least one hexagonal-sectioned torsion bar (4), a tension-lever on the free end of which is a tension roller or tension belt disc. The torsion bars are positioned in a guide-pipe mounted in at least one bearing sleeve. USE/ADVANTAGE - The belt tensioning device is preferably three hexagonal sectioned torsion bars.

Non-intrusive determination of time varying and steady state torsional load magnitudes and locations of a shaft or system of shafts

Abstract: A nonintrusive method for determining the magnitudes and spatial and temporal origins of individual dynamic (time varying) torsion loads acting in superposition on a rotating shaft or system of shafts includes combining the measurements of said shaft's inertial response to the dynamic torsion loads with the measurements of discrete relative angular displacement parameters at causally connected space-time points. Changes in the shaft's characteristics, such as those due to change in its temperature or degradation of its structural integrity, can be monitored to provide updated torque determinations that maintain accuracy by taking these changes into account and to provide information on the onset and location of shaft fractures. Apparatus based on the method of this invention is self calibrating.