Showing papers on "Torsion (mechanics) published in 1977"

Mechanics of materials: An introduction to the mechanics of elastic and plastic deformation of solids and structural components

Abstract: Introduction Notation Unsymmetrical bending Struts Strains beyond the elastic limit Rings, discs and cylinders subjected to rotation and thermal gradients Torsion of non-circular and thin-walled sections Experimental stress analysis Circular plates and diaphragms Introduction to advanced elasticity theory Introduction to the Finite Element Method Contact stress, residual stress and stress concentrations Fatigue, creep and fracture Miscellaneous topics Appendices Index.

Creep of Nimonic 80A in torsion and tension

Abstract: With the object of observing the influence of stress system, the creep of Nimonic 80A has been studied in torsion and tension over the range of effective stress σ from 100 to 500 MPa and at the temperature 750°C For a given σ, tertiary creep and fracture occur sooner in tension than in torsion, while nucleation of cavities is faster The cavities evidently accelerate creep strain and, since creep strain produces cavities, the behaviour as regards both strain and cavitation is autocatalytic The results are expressed and explained in terms of (σ1/σ), where σ1 is the maximum principal stress, and a predictive law for fracture life is derived from constitutive relations connecting strain, cavity volume, and stress

Stress Analysis of the Double‐Torsion Specimen

Abstract: The double-torsion specimen was analyzed with a 3-dimensional elastic finite-element stress analysis. A crack-front configuration where the stress intensity is constant over ≅ 1/2 of the specimen thickness was determined. That value of the stress intensity is nearly equal to the “strength-of-materials” value. The stress intensity is nearly constant for crack lengths > 0.55 × specimen width (W) and ligament lengths > 0.65W.

A Servo-Controlled Hydraulic Hot-Torsion Machine for Hot Working Studies

Abstract: A closed loop servo-controlled hydraulic hot-torsion testing machine is described that is capable of applying a maximum of 100 revolutions of twist at velocities up to 15 revolutions/s with a maximum torque of 110 N·m. When a test specimen measuring 25 by 6 mm is used, these factors correspond to a maximum surface strain of 80, a shear strain rate of 12 s−1, and a shear stress of 1800 MPa. The motor displacement is programmed with the aid of a digital function generator and either torque or rotary displacement may be used for feedback control. The test pieces are held between a hydraulic motor and a fixed torque cell by superalloy loading members mounted in self-aligning chucks. They are heated by a radiant furnace and are enclosed in a transparent quartz tube that is flushed with argon during testing. By flooding the tube with water at the completion of a test, the specimen may be quenched to permit the study of the microstructures developed during hot deformation as well as the effect of various holding times on the deformation structures. The capability of the machine is illustrated by results obtained on specimens of Waspaloy® tested at temperatures between 20 and 1093°C at strain rates in the range 0.03 to 7 s−1. The flow curves generated during these tests and the relationship between stress, strain rate, and temperature are discussed.

Frame Analysis of Shear Wall Cores

Abstract: Existing methods for analysis of shear wall cores tend to involve techniques somewhat unfamiliar to designers. The frame method does not reequire the use of mathematics by the user and is applicable to a wide range of core shapes under arbitrary loading conditions. In particular torsional loading can be applied. Two elements are introduced to facilitate the use of the frame model. These are termed “the solid wall element” which is a bending and axial force element with rigid ends having two vertical degrees of freedom and a “tracing element” which is an axial force element used to preserve the cross-sectional shape of the core. The validity of the frame model is checked against three different core shapes under torsional loading.

Torsional Vibrations of Pile Foundations

Abstract: Figures are presented to facilitate this application and the response of various representative footings to torsional excitation is also shown. For a pile group the contribution of pile twisting to the total response in torsion is usually small. For a single pile or pier torsion can be important and the inclusion of material damping is essential. The following dimensionless parameters govern the soil-pile interaction in torsion: Shear wave velocity ratio, slenderness ratio, mass ratio, dimensionless frequency, and material damping ratio. With increasing shear wave velocity ratio, both pile stiffness and damping increase. For soft soils and pile slenderness ratio greater than 25, the response is independent of the slenderness ratio and the tip condition. Pile foundations can have higher resonant frequencies but smaller resonant amplitudes than shallow foundations. The analysis presented compares favourably with the static solution of Poulos.

Non-linear mechanical response of various metals. I. Dynamic and static response to simple compression, tension and torsion in the as-received and annealed states

Abstract: The mechanical behaviour of some metals has been investigated experimentally for compressive, tensile and torsional loading cycles of about 120 and 370 mu s duration and for steady-state loading in each of the three modes of deformation. For the dynamic measurements the split Hopkinson bar technique has been used in the three modes between two rods and deformed under the action of a transient stress wave induced by dynamically loading the free end of one of the rods. The experimental results show that for the range of high strain rates investigated, the dynamic stress-strain curve is independent of strain rate in all three modes of deformation. For compression and tension, the dynamic stress levels for a given value of the strain exceed the corresponding effectively static stress levels. In marked contrast, only a comparatively small difference has been detected between the corresponding dynamic and static stress levels in torsion over a range of strain rates from approximately 10-3 to approximately 103 s-1.

Torsion bar adjusting device

Abstract: The torsion bar adjusting device comprises a frame structure defining a collar with a slot in its lateral wall. Within the collar are first and second torsion bar end receiving sockets each having integrally radially outwardly extending arms passing through the slot in the collar. These arms may be individually moved to impart a rotation to the socket portion within the collar over a given number of degrees within the confines of the width of the slot. The arrangement is such that a center section of the housing for the torsion bars associated with the left and right rear wheels respectively in an automobile suspension system can be cut out and the adjusting device substituted for the section with the inner ends of the torsion bars being received in opposite ends of the collar to be secured to the respective torsion bar end receiving sockets. Individual movement of the radially extending arms will then impart a further twist to the associated torsion bars and thereby enable quick adjustment of the "stiffness" of the suspension system.

Dynamic Analysis of Horizontally Curved I-Girder Bridges

Abstract: The finite element displacement method is used with annular plate, thin-walled curved beam, straight prismatic beam, and frame-type diaphragm elements for the dynamic analysis of horizontally curved I-girder highway bridges. The stiffness and inertia properties of the finite elements are obtained within the bounds of linear elasticity and small displacement theories. Warping of the girder cross section due to torsion is included in the analysis. The moving vehicle on the bridge is idealized as a sprung mass supported on two unsprung masses. The centrifugal forces arising due to the motion of the vehicle in a circular path are included in the analysis. The inclusion of the vehicle inertia in the bridge-vehicle interaction results in a set of differential equations, the coefficients of which depend on the speed of the vehicle and thus are not constant. These equations of motion are solved by the linear-acceleration method of numerical integration.

Investigations on the self-loosening of threaded fasteners under transverse vibration

Abstract: This paper presents a solution for self-loosening mechanism of bolt-nut joints under transverse vibration. At the first stage of relative transverse displacement between fastened plates, a bolt-thread inclines in a mating nut-thread with slip on the screw-surface of the nut-thread, producing elastic torsion of the bolt-shank. At the next stage of the transverse displacement, the washer face of the nut slips on the surface of the vibrating plate, accompanying loosening rotation of the nut caused by spring back of the elastic torsion of the bolt-shank. Repetition of these behaviours in each cycle of the vibration, advances the self-loosening of the bolt-nut joint. Above mentioned self-loosening mechanism is analyzed theoretically, considering loci of slip on the screw surface and washer face. The theory is compared with the experiment, resulting that they show fairly good agreement, except small difference which is seemed to be caused by the fluctuation of the frictional coefficients on the screw surface and the washer face.

Ductile Fracture of Cabin Steel under Cold Metal Forming Conditions : 1st Report, Tension and Torsion Tests under Pressure

Abstract: Tensile and torsional machines were developed fro testing under high hydrostatic pressures of up to 4 kbars; experiments were carried out using these machines to investigate the mechanics of ductile fracture of 0.25 % carbon steel. The strain at which fracture-nuclei (voids or cracks) begin to grow is determined by a method in which the hydrostatic pressure is changed during deformation, and it is shown that the strain at which growth of nuclei begins increases with pressure. The rate of nuclei-growth is suggested to depend on pressure and strain. Based on these results, a criterion for ductile-fracture strain in torsion tests is proposed taking the pressure history into account, and it is found to agree with the experimental results of various pressure histories.

Molecular Mechanism for the Initial Process of Visual Excitation. II. Theoretical Analysis of Optical Activity in Rhodopsin and Bathorhodopsin

Abstract: The circular dichroism spectra in rhodopsin and bathorhodopsin are theoretically analysed in terms of intrinsic optical activity of the retinal chromophore according to a torsion model proposed in paper I. The self-consistent HMO method is used to treat the π-electron system of the chromophore. From the analysis of the α- and β-bands of optical absorption and circular dichroism spectra, the plausible conformation of the chromophore is predicted as follows. In rho-dopsin, 6s- cis , 11- cis protonated retinal Schiff-base 12s- trans form and the bonds 6C-7C, 11C-12C and 12C-13C are twisted in -, + and - directions, respectively, when torsional angles θ's are measured clockwise from planar cis conformation. Although we cannot determine the values of θ's definitely, the ranges of them are θ 6-7 =-40^°∼-120^°, θ 11-12 =30^°∼40^° and θ 12-13 =-130^°∼-150^°. In bathorhodopsin, the bond 11C-12C is isomerized to a trans form by the rotation of about 100∼120 around it in the plus direction.

Torsional vibration on pile foundations

Abstract: Figures are presented to facilitate this application and the response of various representative footings to torsional excitation is also shown. For a pile group the contribution of pile twisting to the total response in torsion is usually small. For a single pile or pier torsion can be important and the inclusion of material damping is essential. The following dimensionless parameters govern the soil-pile interaction in torsion: Shear wave velocity ratio, slenderness ratio, mass rati, dimensionless frequency, and material damping ratio. With increasing shear wave velocity ratio, both pile stiffness and damping increase. For soft soils and pile slenderness ratio greater than 25, the response is independent of the slenderness ratio and the tip condition. Pile foundations can have higher resonant frequencies but smaller resonant amplitudes than shallow foundations. The analysis presented compares favourably with the static solution of Poulos. /ASCE/

Analysis for torsion employing provisions of NZRS 4203:1974

Abstract: This paper is the result of deliberations of the Society's discussion group on seismic design of ductile moment resisting reinforced concrete frames.

Experimental investigation of the collapse of renforced concrete curved beams

Abstract: Synopsis The applicability of methods of plastic analysis to reinforced concrete curved beams is investigated and the results of experiments on seven straight and eight curved beams are presented. The straight beams were tested under different combinations of bending, torsion and shear, and the results are used to determine the intersection points of two yield surfaces (proposed in an earlier investigation) with the bending, torsion and shear axes and to check the validity of the surfaces. Of the curved beams tested, four were reinforced identically but were tested under different end conditions. In the other four, both the transverse reinforcement and the end conditions were varied so as to study changes in the mode of failure and the ultimate load. Comparison of the test results with the results predicted by the plastic analysis shows good agreement.

Dynamic mechanical behavior of polyethylene during creep to failure in uniaxial extension

Abstract: Dynamic mechanical measurements in torsion superposed on large uniaxial creep strains have been obtained on two types of polyethylene resins. At creep strains of about 10% it is observed that tanδ goes through a minimum and rises sharply thereafter.

Theory of the Ke, inverted and Collette torsion pendulums

Abstract: The equation of motion for torsion pendulums is solved to yield expressions for the internal friction and frequency of the specimen. They enable one to estimate explicitly the effect of the torsion wires on measurements for the inverted or Collette type. Drawbacks are found in the analysis for internal friction which Collette et al. (1961) made. Correct formulae for internal friction and frequency are presented.

Effect of chordwise forces and deformations and deformations due to steady lift on wing flutter

Abstract: This investigation explores the effects of chordwise forces and deformations and steady-state deformation due to lift on the static and dynamic aeroelastic stability of a uniform cantilever wing. Results of this analysis are believed to have practical applications for high-performance sailplanes and certain RPV's. The airfoil cross section is assumed to be symmetric and camber bending is neglected. Motions in vertical bending, fore-and-aft bending, and torsion are considered. A differential equation model is developed, which included the nonlinear elastic bending-torsion coupling that accompanies even moderate deflections. A linearized expansion in small time-dependent deflections is made about a steady flight condition. The stability determinant of the linearized system then contains coefficients that depend on steady displacements. Loads derived from two-dimensional incompressible aerodynamic theory are used to obtain the majority of the results, but cases using three-dimensional subsonic compressible theory are also studied. The stability analysis is carried out in terms of the dynamically uncoupled natural modes of vibration of the uniform cantilever.

Buckling of Imperfect Stiffened Cylinders under Destabilizing Loads including Torsion

Abstract: This paper deals with the buckling of imperfect, thin, circular, cylindric, stiffened shells under the application of destabilizing loads, including uniform axial compression, lateral pressure, and torsion. The analysis includes individual load application as well as the case of combined loads. The methodology presented is based on the smeared technique, the Yon Karman-Donnell nonlinear kinematic relations, linear constitutive relations, and it considers the most general shape of a geometric imperfection. Numerical results for various configurations are presented. From the limited cases considered, one may conclude that stiffened configurations are not as sensitive as unstiffened ones, when loaded in torsion.

Torsion in Concrete Beams Containing an Opening

Abstract: An analysis is presented for predicting the strength of reinforced concrete beams that are subjected to torsion and have openings cast in them in order to provide for the passage of service ducts. The equations proposed are based on addition of stresses due to torsion and flexure in the longitudinal reinforcement and the addition of stresses due to torsion and transverse shear in the stirrups. Test results of 14 beams with openings are also presented. Correlation between the test results and the strength predicted by the analysis indicates that the equations conservatively but adequately predict the strength of the beams.

Electrostatic corrections to extended Hückel theory

Abstract: An electrostatic correction to the energy of the EH method is deduced from the Hartree energy. A recent correction, due to Anderson and Hoffmann, is easily deduced as a particular case. Some calculations show how the correction can improve the description of stretching problems by EH calculations but poor results are obtained in bending and torsion problems.

Plastic Behaviour in the Combined Loading along Straight Stress Paths with a Bend : Investigation on the Stress-Strain Relation by an Anisotropic Hardening Plastic Potential

Abstract: The stress-strain relations of metals in loading along straight stress paths (or straight strain paths) with a bend are investigated experimentally as well as theoretically in the deviatoric stress (or strain) space. Equations of the equi-plastic strain surfaces of various metals after preloadings are given on the basis of the experimental results obtained by subjecting this-walled tubular specimens to combined axial load and torsion. Stress-strain relations for various loading paths are calculated using the equi-plastic strain functions. There is a good agreement between the calculation and the experiment.

Experiments on steel-concrete composite beams subjected to torsion and combined flexure and torsion

Abstract: The results of tests on eight composite beams, four under simple torsion and four under combined flexure and torsion have been discussed with reference to shear connection, ultimate strength in torsion and interaction between torsion and flexure. The results support the view that there is an increase in torsional capacity in the presence of flexure. Increase in flexural capacity beyond the theoretical ultimate strength, in the presence of torsional moment, was also observed. /TRRL/