Showing papers on "Torsion (mechanics) published in 1988"

Softened truss model theory for shear and torsion

Abstract: The softened truss model theory, which has recently been developed for shear and torsion of reinforced concrete members, is summarized in a systematic and unified manner. Eleven equations involving fourteen variables are derived from equilibrium, compatibility, and materials conditions to solve the shear problem. An additional six equations involving six more variables are required to treat the torsion problem. The theory was successfully applied to structures where shear behavior predominates, such as low-rise shearwalls, framed wall panels, deep beams, and shear transfer strengths. It also worked very well for members subjected to torsion. Efficient algorithms are proposed to solve the simultaneous equations for different types of structures. The theoretical predictions are in good agreement with the test results in all cases. The prediction includes not only the shear and torsional strengths, but also the deformations of structures throughout their post-cracking loading history.

The importance of torsion in the design of insect wings

Abstract: A model insect wing is described in which spars of corrugated membrane which incorporate stiffening veins branch serially from a V-section leading edge spar The mechanical behaviour of this model is analysed The open, corrugated spars possess great resistance to bending, but are compliant in torsion Torsion of the leading edge spar will result in torsion and relative movement of the rear spars As a result camber will automatically be set up in the wing as it twists Aerodynamic forces produced during the wing strokes will result in torsion and camber of the wing which should improve its aerodynamic efficiency The effects of varying parameters of the wing model are examined For given wing torsion, higher camber is given by spars branching from the leading edge at a lower angle, by spars which curve posteriorly, and by spars which diverge from each other Wings of three species of flies were each subjected to two series of mechanical tests Application of a force behind the torsional axis caused the wings to twist and to develop camber Immobilizing basal regions of the leading edge greatly reduced compliance to torsion and camber, as predicted by the theoretical model Aerodynamic forces produced during a half-stroke are sufficient to produce observed values of torsion and camber, and to maintain changes in pitch caused by inertial effects at stroke reversal

Electric power steering system

Abstract: An electric power steering system has a torsion torque sensor provided for detecting torsion torque generating in a steering system of a motor vehicle, for providing an assist signal for driving a motor to turn a steering wheel A steering angle sensor is provided for detecting steering angle of the steering wheel and for producing a steering angle signal In response to the steering angle signal, a return torque signal is produced for steering wheel A vehicle speed sensor is provided for producing a vehicle speed signal dependent on speed of the vehicle, and a calculator is provided calculating lateral acceleration impared to the vehicle and for producing a lateral-acceleration-dependent-return torque signal In accordance with the vehicle speed signal, the lateral-acceleration-dependent-return torque signal is corrected to produce return torque correcting signal, the absolute value of which reduces with increase of vehicle speed The return torque correcting signal is added to the return torque signal for correcting the latter signal

The sliding of robot fingers under combined torsion and shear loading

Abstract: The authors are concerned with finding the magnitudes of applied moment and force which will cause a robot finger to slip on the surface of a grasped object. Friction and contact models used in previous grasp analyses are reviewed, and an improved model which includes torsion-shear interaction is described. Experimental measurements of the initiation of sliding as a function of loading are reported. These measurements suggest that a simple linear function of torsion and shear magnitudes will adequately predict the onset of the slip in many tasks. The use of this function is illustrated in two measures of slip susceptibility for grasp planning. >

Torque detecting apparatus

Abstract: A device for detecting a load torque using angle detectors fitted with a certain spacing on a shaft which is rotated by a drive source and on the basis of a relative angular difference of angles detected by the angle detectors. The device includes two rotary drums or discs fitted with a certain spacing on the drive side and load side of the shaft, with a plurality of magnetic poles for generating magnetic signals being formed on the surface thereof, and a magnetic sensor disposed to confront the surface of the rotary drums or discs, with magnetic resistance effect elements which vary in internal resistance in response to the magnetism of the magnetic poles being provided thereon. The amount of torsion created by the load on the load side of the rotary shaft is measured as a phase difference of outputs of the magnetic sensor, and the torque is detected in terms of the angular difference between the magnetic drums or discs. The device is operative to detect a torque in both storage and rotation, and capable of detection within a period of magnetic signal, whereby high-accuracy, high-resolution torque detection is made possible.

Elastic buckling of tapered monosymmetric I-beams

Abstract: A finite‐element method of analysis is presented for the elastic flexural‐torsional buckling of non‐prismatic I‐section beam‐columns. The formulation presents a general approach to the problem, in which the coupling of torsion and bending is simplified by adopting the web mid‐height as an arbitrary axis of twist. By making this simplification, the formulation does not sutler from the restrictions of other solutions, such as the use of uniform elements and finite differences. Buckling stiffness and stability matrices are developed, and these may be readily included in existing finite‐element programs. The method is shown to be in good agreement with the more complex finite‐integral treatment, and its scope is demonstrated by application to the buckling of tapered cantilevers.

Is there really a problem with the teleparallel theory

Abstract: The problem of non-predictable behaviour of the torsion in the experimentally viable one-parameter teleparallel theory of gravity, first pointed out by Kopczynski (1982), is found to be non-generic, occurring only for very special solutions.

Stresses and rate of twist in single-cell thin-walled beams with anisotropic walls

Abstract: The classical theory of elastic thin-walled beams of (assumedly) nondeformable cross section, familiar to aerospace structures engineers, is generalized to the case in which the walls are anisotropic. The assumed anisotropy is such as to allow coupling between cross-sectional shear flow and longitudinal strain and, reciprocally, between shear strain and longitudinal stress. The theory and several illustrative applications show that anisotropy of the walls can, as expected, lead to coupling phenomena not present in the classical theory, e.g., twist due to bending mements, bending due to torque, twist due to tension, and extension due to torque, thus confirming the well-known possibility of "tailoring" elastic behavior through the use of laminated composites. It is also shown that anisotropy of the walls can lead to a nonconstant rate of twist in uniform beams even if the cross-sectional torque and shears are constant. Another interesting outcome of the present theory is its prediction that the shear flows are independent of the coupling constant in the constitutive equations, i.e., the constant that defines the longitudinal strain due to shear flow and the shear strain due to longitudinal stress, and also independent of the elastic constant relating shear strain to shear flow.

Observations of cracking behavior in tension and torsion low cycle fatigue

Abstract: A series of tension and torsion low-cycle fatigue tests were conducted on several engineering materials. Detailed observations of nucleation and early crack growth were made. Cracking behavior is shown to depend upon loading mode (tension or torsion), strain amplitude, and material type. Multiaxial models developed for shear sensitive materials did not correlate multiaxial test results of a tension sensitive material. Differences in cracking behavior for different materials and loading conditions need to be considered in successful life predictions for components subjected to multiaxial fatigue.

A revision of the double-torsion technique for brittle materials

Abstract: Serious doubts about the constant-K characteristics of double-torsion specimens have been expressed in recent years. However, compliance calibration shows that the energy release rate and hence the stress intensity factor are independent of the crack length in this technique. Relatively large scattering in the results obtained by the load-relaxation method makes the data unreliable. The load-relaxation experiments should be carried out in combination with other methods. A theoretical calculation of the load-deformation curve under a constant displacement rate gives a rough estimation of the stress corrosion index. The subcritical crack growth data can be given, in principle, by only one experimental run of the constant displacement rate method of double-torsion testing.

Dilatometric study of deformation induced volume increase and recovery in rigid PVC

Abstract: A new torsion dilatometer is presented which allows simultaneous measurement of shear deformation, twisting moment, volume variation and axial deformation (or normal force). It is intended to be utilized principally for studies of volume changes during torsion and recovery behavior of amorphous polymers in their glassy state. Preliminary results on unplasticized PVC are presented which show rather complex volume changes. With increasing torsional strain, a volume decrease at low strains was found, followed by a volume increase for higher strains. In the latter case, after coming back to zero torsion angle, shear induced relative volume increase and subsequent recovery were observed.

Torsion vibration damping by mass acceleration or mass deceleration

Abstract: The invention relates to an arrangement of a supplementary mass within a torsion vibration damper which mass can be driven by means of a gear system - preferably a planetary gear system, and in the case of relative movement between the input components and the output components of the torsion vibration damper the supplementary mass is accelerated or decelerated via the gear system.

On non-proportional infinitesimal plastic deformation after finite plastic prestraining and partial unloading

Abstract: E xperimental data from combined tension-torsion loading of thin-walled tubes of annealed polycrystalline copper subjected to loading, partial unloading, and then loading in a different direction are presented. Special attention is focused on the direction of the plastic strain increment, experimental values of which are compared with predicted values from the Ziegler and Mroz kinematic hardening models, and endochronic theory. The back stress terms in the above mentioned three constitutive models are calculated using the entire deformation history of more than 10% strain in extension (or 15% in shear), followed by partial unloading, and then loading in torsion (or tension). Thus, the main objective of the study is to investigate the effect of finite deformation on subsequent infinitesimal deformation due to 180° and 90° changes in loading paths in the tension-torsion loading space. Among the three constitutive equations used for comparison, the Mroz model is shown to predict the direction of the plastic strain increment closest to the experimental results.

On the torsion of a cylinder with several cracks

Abstract: In this paper, based on paper [1], the analytic expression of the torsion function for a cylinder containing arbitrary oriented cracks is obtained. The problem is reduced to solve a system of singular integral equations for the unknown dislocation density functions. Using the numerical method of the singular integral equations[2,7] the torsional rigidities and stress intensity factors are evaluated for several multicracked cylinders. Next, the creak-cutting method[5] is firstly extended to lve the torsion problem for a rectangular prism. The numerical results show that the method presented here is successful.

Steering torque detecting device

Abstract: A steering torque detecting device comprises a steering shaft consisting of an input shaft and an output shaft, a torsion bar provided between the input shaft and the output shaft, a torque detecting unit for converting a quantity of torsion produced in the torsion bar into an electric output, an electricity collecting unit comprising slip rings and brushes which takes the electric output and supplies an electric power from an outer power source, bearings for supporting the input and output shaft on the same axial line, and a housing supporting the bearings, a printed wiring board in a circular plate form which is provided at its one surface with a resistance layer and an output electrode radially spaced apart from the resistance layer, the resistance layer and the output electrode constituting a potentiometer, and a slider having a portion extending in the radial direction of the circular printed wiring board so as to have contacting areas with a small width to the resistance layer and the output electrode.

Torsion damping device with a centring ring member

Abstract: A torsion damper, especially for a friction disc clutch for an automotive vehicle, comprising a hub, a main damper plate, at least one guide ring, and a ring member which is resiliently deformable. The ring member comprises at least one first part which is resiliently deformable and a second part comprising pins for centring with respect to the damping plate.