Showing papers on "Torsion (mechanics) published in 1996"
TL;DR: The predicted left ventricular torsion exhibits several experimentally observed features, including a peak near end systole, rapid untwisting during isovolumic relaxation, and increased twist near the apex.
232 citations
Book•
01 Dec 1996
TL;DR: In this article, the theory of plasticity has been applied to reinforced concrete, and it has been shown that it is possible to develop a 3D stress field for simple reinforced concrete structures.
Abstract: 1 Introduction and Theoretical Basis.- 1.1 Introductory Remarks.- 1.2 Fundamentals of the Theory of Plasticity.- 1.2.1 Material Behaviour.- 1.2.2 Limit State Theorems of the Theory of Plasticity.- (a) Static Solution.- (b) Kinematic Solution.- 1.3 Engineering Methods.- 2 Stress Fields for Simple Structures.- 2.1 Introduction.- 2.2 Beams with Rectangular Cross-Section Subjected to Bending and Shear.- 2.2.1 Deep Beams, Concentrated Loads.- 2.2.2 Deep Beams, Several Concentrated Loads.- 2.2.3 Deep Beams, Distributed Load.- 2.2.4 Beams with Medium Slenderness Ratio, Concentrated Loads.- 2.3 Beams with I-Cross-Section Subjected to Bending and Shear.- 2.3.1 Slender Beams, Concentrated Loads.- 2.3.2 Slender Beams, Distributed Load.- 2.3.3 General Case, Practical Design.- 2.3.4 Beams of Variable Depth.- 2.3.5 Compression Flange.- 2.3.6 Tension Flange.- 2.4 Members Subjected to Torsion and Combined Action.- 2.4.1 Introduction.- 2.4.2 Warping Torsion (Open Cross-Sections).- 2.4.3 Circulatory Torsion.- 2.4.4 Circulatory Torsion Combined with Bending and Shear.- 2.5 Brackets.- 2.6 Coupling Beams.- 2.7 Joints of Frames.- 2.7.1 Corner Joint, Compression on the Inside.- 2.7.2 Corner Joint, Tension on the Inside.- 2.7.3 Joints of Frames with Three Connecting Beams.- 2.7.4 Joints of Frames with Four Connecting Beams.- 2.8 Beams with Sudden Changes in Cross-Section.- 2.9 Walls.- 2.9.1 Shear Walls.- 2.9.2 Diaphragms.- 2.10 Three-Dimensional Example.- 3 Material Strengths and other Properties.- 3.1 Reinforcing Steel.- 3.2 Concrete.- 3.2.1 Uniaxial Stress State.- 3.2.2 Three-Dimensional Stress State.- 3.2.3 Concrete with Imposed Cracks.- 3.2.4 Cracks: Aggregate Interlock.- 3.3 Force Transfer Reinforcement - Concrete.- 3.3.1 Anchorage of Reinforcing Bars.- 3.3.2 Splices of Reinforcement.- 3.3.3 Force Deviations.- 4 Additional Considerations for the Development of Stress Fields.- 4.1 Remarks on Plastic Design Applied to Reinforced Concrete.- 4.1.1 Behavior of Statically Indeterminate Beams.- 4.1.2 Selection of the Inclination of the Compression Field in the Web of Beams.- 4.1.3 Redistribution of Internal Forces and Ductility Requirements.- 4.2 Procedure for Developing Stress Fields.- 4.2.1 Introduction.- 4.2.2 Spreading of Force in a Wall Element Loaded in Tension.- 4.2.3 Spreading of Force in a Wall Element Loaded in Compression.- 4.2.4 Further Cases.- 4.3 Impaired Strength through Wide Cracks.- 4.4 Stress Distribution in Highly Stressed Compression Zones.- 4.4.1 Introduction.- 4.4.2 Stress Fields for Beam-Columns.- 4.5 Prestressed Beams.- 4.5.1 Beam with straight cable.- 4.5.2 Beam with curved cable.- 4.5.3 Anchorage zone of pretensioned beams.- 4.5.4 Unbonded prestressed beams.- 5 Plane Stress, Plate and Shell Elements.- 5.1 Plane Stress Elements.- 5.2 Slab Elements.- 5.3 Shell Elements.- 6 Outlook: Computer Programs.- References.
150 citations
TL;DR: In this article, a procedure for the calibration of the lateral force applied to a triangular cantilever tip by means of a lateral force microscope is presented, where the force is measured as a voltage on a four-sector photodiode.
143 citations
TL;DR: In this article, the authors considered the problem of a penny-shaped crack in homogeneous dissimilar materials bonded through an interfacial region with graded mechanical properties, and the applied loads are assumed to be axisymmetric but otherwise arbitrary.
127 citations
TL;DR: In this article, a gradient dependent multiaxial high-cycle fatigue criterion function of the stress invariants is formulated based on these observations, and the results showed that although the fatigue endurance is strongly affected by the gradient of the normal stress in bending tests, it remains insensitive to variations of the shear stress in torsion tests.
127 citations
TL;DR: In this paper, the texture properties of interstitial free (IF) steels and high purity α-iron were determined after deformation in torsion over the temperature range 20-500°C.
106 citations
TL;DR: In this paper, a double-quantum solid-state NMR experiment for determining torsion angles in unoriented polymers which contain segments with pairs of 13C-labeled sites separated by only one site is presented.
Abstract: This paper introduces a double-quantum solid-state NMR experiment for determining torsion angles in unoriented polymers which contain segments with pairs of 13C-labeled sites separated by only one ...
105 citations
101 citations
TL;DR: In this article, Taylor-type polycrystal plasticity models with various single slip hardening laws are evaluated by studying the large strain behaviour of FCC polycrystals during reversed torsion.
96 citations
TL;DR: In this paper, the authors developed one-dimensional pure bending, coupled bending and extension, and combined bending, extension and torsion models of isotropic beams with induced-strain actuation.
Abstract: This paper develops one-dimensional pure bending, coupled bending and extension, and combined bending, extension and torsion models of isotropic beams with induced-strain actuation. A finite thickness adhesive layer between the crystal and beam is included to incorporate shear lag effects. Experimental tests evaluate the accuracy and limitations of the models. The bending and coupled bending and extension models show acceptable correlation with static test results whereas the combined extension, bearing, torsion model predicts the system behavior poorly and needs refinement.
77 citations
TL;DR: In this article, a review article on the problem of buckling of moderately thick, laminated, composite shells subjected to destabilizing loads is presented, which consists of uniform axial compression, uniform lateral pressure and torsion applied individually or in combination.
Abstract: The present paper is a review article on the problem of buckling of moderately thick, laminated, composite shells subjected to destabilizing loads. The loads consist of uniform axial compression, uniform lateral pressure and torsion applied individually or in combination. In all the works reported in the literature, the analysis is based on higher-order shear deformation (HOSD) shell theory and/or first-order shear deformation (FOSD) shell theory with or without a shear correction factor. Results obtained by these two shell theories and by employing classical thin shell theory are compared to determine the range of applicability of each in predicting critical conditions. The effect of stacking sequence, radius-to-thickness ratio and length-to-radius ratio is assessed. Typical numerical results are presented in tabular form. Moreover, some limited results, which are based on limit point analysis are also presented (imperfection sensitivity studies).
TL;DR: In this article, the authors considered the problem of a cylindrically anisotropic linear elastic material subjected to a uniform normal stress and shearing stresses at the inner and outer surfaces of the tube.
Abstract: One of the novel features of the present paper is that we have written the equation of equilibrium and the stress-strain law of an inhomogeneous anisotropic linear elastic material in a compact form for cylindrical coordinate system using matrix notation. For a two-dimensional deformation the result resembles Stroh’s sextic formalism in a rectangular coordinate system. We then consider the material to be cylindrically anisotropic. It means that the elastic stiffnesses referred to a cylindrical coordinate system are constants. The problem of a circular tube subjected to a uniform normal stress and shearing stresses at the inner and outer surfaces of the tube is studied. Also studied are the axial extension and torsion of the tube. Unlike isotropic materials for which the applied normal stress (or shear stress) induces only the normal (or shear) stress, all three displacement components and most of the six stress components are nonzero for general anisotropic materials. This is particularly interesting for the uniform axial extension of the tube. For an isotropic material the stress σ 33 is the only non-zero and uniform stress inside the tube. For a cylindrically anisotropic material the stresses σ rr , σ θθ , and σ θ3 are also non-zero. Moreover, they depend on r and are not uniform. A solid cylinder or a cylinder with a pin hole is a special case of a tube. It is shown that, for the loads mentioned above including the axial extension, the stress may be unbounded at the pinhole.
TL;DR: In this article, the origin of the lack of symmetry in the earlier models has been identified and a symmetric model developed, which brings forth the much needed agreement between the global (strand) and the local (wire) responses which should help simplify considerably the analysis of multi-layer strands and multi-strand wire ropes.
Abstract: Among several mathematical models for predicting the mechanical response of a helical wire strand to axisymmetric tension and torque derived in the literature over five decades, purely tensile wire linear elastic models have the symmetry of a stiffness matrix. Curiously, in those models where wire bending and torsion terms were included there was a lack of symmetry. In this paper the origin of the lack of symmetry in the earlier models has been identified and a symmetric model developed. The correct generalized strains for this purpose were derived using Wempner's theory and verified using Ramsey's theory. The validity of this model has been verified by comparing its results with that of earlier models and experiments available. This linear elastic symmetric model brings forth the much needed agreement between the global (strand) and the local (wire) responses which should help to simplify considerably the analysis of multi-layer strands and multi-strand wire ropes.
TL;DR: In this article, a macro-scale model framework is proposed which uses the third invariant of overstress, J 3 ∗, to delineate stress state effects, including morphological changes of both texture and deformation substructure.
TL;DR: In this paper, double torsion tests were performed to study subcritical crack growth of a 3Y-TZP ceramic and a significant variation of stress intensity factor K 1 with crack length was observed.
TL;DR: In this paper, a new set of formulae for derivatives of torsion angle energy terms was developed and introduced into the program CHARMM, which avoids the singularities introduced by use of the derivatives of the torsions angle cosine.
Abstract: A new set of formulae is developed for the derivatives of torsion angle energy terms and is introduced into the program CHARMM. These formulae, which are based on derivatives of the torsion angle itself, avoid the singularities introduced by use of the derivatives of the torsion angle cosine. The potential energy can include any differentiable function of the torsion angle and there is no need for a special treatment for cases where planar conformations are not extrema. The resulting code is simpler than the original version and yields correct derivatives in all practical situations. Because the minimum of the torsion energy can be at any angle, the functionality of the existing energy routines is generalized. © 1996 by John Wiley & Sons, Inc.
TL;DR: In this article, the authors measured particle−particle and particle−wall capillary interactions as a function of the separation distance, based on counterbalancing the moment of a couple of forces acting between two pairs of particles by the torsion moment of thin platinum wire.
Abstract: Particle−particle and particle−wall capillary interactions were measured as a function of the separation distance. The “particles” were vertical thin glass cylinders and/or small glass spheres, protruding from an air/liquid interface. The particles attract each other due to the overlapping of the menisci formed around each of them. The force of interaction is detected by a sensitive torsion microbalance. It is based on counterbalancing the moment of a couple of forces, acting between two pairs of particles, by the torsion moment of a thin platinum wire. By varying the wire diameter, we accessed forces differing by several orders of magnitude, from about 5 dyn at small separation between the particles down to 0.001 dyn at large separation. The smallest force was measured with two cylinders of diameters about 300 μm. For two spheres (diameters 1.2 mm) we obtained difference in the forces corresponding to different heights of protrusion from the liquid surface. For interacting sphere and glass cylinder the f...
TL;DR: In this paper, an analytical series solution employing effective moduli is derived to study the fracture behavior of edge-cracked multilayer laminates to characterize the critical strain energy release rates.
TL;DR: In this paper, a semicontinuous model is proposed for the analysis of multilayered wire strands under bending, tensile, and torsion loads, which is based on continuum mechanics and elasticity of orthotropic materials.
Abstract: Semicontinuous wire strand modeling is an approach by which each layer of a strand is mathematically represented by an orthotropic cylinder whose mechanical properties are chosen to match the behavior of its corresponding layer of wires. Such a semicontinuous model is herein proposed for the analysis of multilayered wire strands under bending, tensile, and torsion loads. It is based on continuum mechanics and elasticity of orthotropic materials. The model premits the evaluation of strand stiffness, contact stress, interlayer shear stress, and interlayer slip. Results are obtained and given for a seven-wire strand and for selected steel reinforced aluminum conductors (ACSRs). Comparisons are made with results from two existing models that use a more classical approach, from another model that uses a semicontinuous approach, and from published experimental works. Under tensile and torsion loads, it is shown that the present semicontinuous model gives very accurate results. Under bending load, validation is more difficult to establish, but this new model is very promising.
TL;DR: In this article, a one-dimensional model was developed to predict the coupled extension, bending and torsion response of a beam subject to piezoceramic strain actuation.
Abstract: This paper develops a one-dimensional model to predict the coupled extension, bending and torsion response of a beam subject to piezoceramic strain actuation. The effects of cross-sectional warping are shown to be negligible for thin rectangular isotropic beams. The impact of adhesive shear lag, on the other hand, is measurable, especially in the torsional response. Experimental test results show that the models are accurate up to a 45O actuator orientation with respect to the beam axis even though detailed strain data indicate that the local strain state is highly two-dimensional . Nomenclature
TL;DR: In this article, a new approach to analyze the dynamic coupling between shaft torsion and blade bending of a rotating shaft-disk-blender unit is introduced, which allows the shaft to vibrate freely around its rotation axis instead of assuming a periodic perturbation of the shaft speed that may accommodate the shaft flexibility only to a limited extent.
Abstract: A new approach to analyzing the dynamic coupling between shaft torsion and blade bending of a rotating shaft-disk-blade unit is introduced. The approach allows the shaft to vibrate freely around its rotation axis instead of assuming a periodic perturbation of the shaft speed that may accommodate the shaft flexibility only to a limited extent. A weighted residual method is applied, and the receptances at the connections of blades and shaft-disk are formulated. Numerical examples are given for cases with between two and six symmetrically arranged blades. The results show not only coupling between the shaft, disk, and blades, but also coupling between individual blades where the shaft acts as a rigid support and experiences no torsional vibration. The blade-coupling modes occurred only in repeated frequencies. Finally, the effect of shaft speed on the modal frequencies was investigated. Plots illustrating the occurrence of critical speeds and flutter instabilities are presented.
Patent•
17 Sep 1996
TL;DR: In this article, a spring hinge is used for generating torque in a shaft and a single helical element, which produces variable torque between the first and second ends of the shaft.
Abstract: The present invention is a spring hinge for generating torque. The spring hinge includes a shaft and a single helical element. The shaft has a surface with an outer diameter and is capable of rotation. The single helical element is wrapped about the shaft. The helical element includes a first end and a second end. The helical element produces a variable torque between the first and second ends.
TL;DR: In this article, the response of a beam coupled in bending and torsion to deterministic and random loads was investigated by using the normal mode method, where the loading on the beam may be either concentrated or distributed over its length.
TL;DR: In this paper, a theory for hollow composite beams with arbitrary crosssection and thick walls is presented, which efficiently accounts for transverse shear, primary and secondary torsional warping, and threedimensional (3D) elastic effects in laminated beam walls which are accentuated as the wall thickness increases.
TL;DR: In this paper, a constitutive model for large viscoplastic deformations of metals is presented, which combines distortional and orientational hardening, reflecting macroscopically texture development, with standard isotropic and kinematic hardening features.
Patent•
31 May 1996
TL;DR: An improved helical torsion spring with an integrally attached clip is described in this article, which can be used to carry a slim-bodied object such as pencils, pens, or other similar goods.
Abstract: An improved helical torsion spring is disclosed which contains an integrally attached clip The improved helical torsion contains: (a) a helical torsion spring having a coiled portion and front and end non-coiled portions; (b) a clip having a transverse opening for sleeving about the coiled portion of the helical torsion spring, and a concave slot for receiving a slim-bodied object The transverse opening of the clip has a section-section smaller than a length of either of the front or end non-coiled portion so as to retain the clip therebetween The improved helical torsion spring can be used in essentially the same a conventional torsion spring can be used; however, it provides the advantage of being able to carry a slim-bodied object such as pencils, pens, or other similar goods
TL;DR: In this article, a quantum particle is constrained to move within a tube of central radius d embedded in 3-space, subject to Dirichlet boundary conditions, and an exact expression for the effective potential introduced by the imposition of curvature and torsion is derived.
Abstract: We consider a quantum particle constrained to move within a tube of central radius d embedded in 3-space, subject to Dirichlet boundary conditions. Taking the central axis of the tube as a reference curve and setting up a locally cylindrical polar coordinate system around this curve, we derive an exact expression for the effective potential introduced by the imposition of curvature and torsion. We then employ a minimax method to ascertain a sufficient requirement for the curvature and torsion to guarantee the existence of a bound state.
TL;DR: In this article, an approximate analytical theory for the optical anisotropy of a circular weakly bending filament was constructed for planar planar circles, and a rigorous derivation was presented for the force arising from the torsion potential, which couples torsional strain to writhing and crankshaft motions.
Abstract: An approximate analytical theory is constructed for the optical anisotropy of a circular weakly bending filament. It is argued that such circles exhibit very nearly dynamical mean local cylindrical symmetry, despite their inherent curvature. This theory and the corresponding approximate analytical theory for weakly bending rods are tested by fitting each theory to the results of Brownian dynamics simulations, in which all of the relevant forces are included. A rigorous derivation is presented for the force arising from the torsion potential, which couples torsional strain to writhing and crankshaft motions, and a new more convenient expression is obtained. Simulations of equilibrium trajectories performed with and without this force show that it has no significant effect on the optical anisotropy of either circular or linear filaments with parameters appropriate for DNA. However, when large net torsional strains are introduced into planar circles, this force enormously enhances the rate at which twist is ...
TL;DR: In this paper, the authors investigated the large strain behavior of 304L stainless steel (SS 304L) subjected to compression, torsion, and sequences of compression followed by Torsion and torsions followed by tension.
Abstract: In metals, large strain inelastic deformation processes such as the formation of a preferred crystallographic orientation (crystallographic texture) and strain hardening processes such as the formation and evolution of dislocation substructures depend on stress-state. Much of the current large strain research has focused on texture. Crystallographic texture development and strain-hardening processes each contribute to the overall material behavior, and a complete description of large strain inelastic material response should reflect both. An investigation of the large strain behavior of 304L stainless steel (SS 304L) subjected to compression, torsion, and sequences of compression followed by torsion and torsion followed by tension is reported. This paper focuses on the stress-state dependence of strain-hardening processes as well as the relative effect such processes have on the overall material behavior. To characterize these processes, transmission electron microscopy (TEM) as well as magnetization investigations were conducted at different strain levels and under different deformation modes. The {gamma} {yields} {alpha}{prime} martensitic transformation which occurs in this material was found to be related to both the strain level and stress state. Dislocation substructures in the form of Taylor lattices, dense dislocation walls, and microbands were also present. The ramifications of using a thin-walled tubular torsion specimen weremore » also explored.« less
TL;DR: In this paper, the authors describe a laminated spatially distributed piezoelectric torsional vibration actuator for a clamped-free cantilever beam, which is derived as a function of actuator strain only and then used to calculate the induced strain in a substructure loaded in uniaxial extension/compression, bending and torsion.