Showing papers on "Torsion (mechanics) published in 1973"

The effect of creep constitutive and damage relationships upon the rupture time of a solid circular torsion bar

Abstract: L ower bounds on the rupture times of steadily loaded solid circular torsion bars are shown to agree well with values of the rupture times computed using an iterative procedure for different constitutive and damage laws. Corresponding to the lower bound rupture time a single reference stress can be defined for the structure. Multi-axial rupture effects are included in determining a lower bound rupture time and simple statements are made regarding structural performance and different types of material behaviour. The mode of expression of the Kachanov damage parameter in the calculation method is shown to be unimportant. Good agreement is shown between the prediction method and the results of experiments conducted on bars prepared from different materials.

Large-deflexion torsion and flexure of initially curved strips

Abstract: General expressions are derived for the large-deflexion relations between bending moment, torque, longitudinal and twisting curvature for initially curved strips of lenticular and constant thickness section. Particular attention is paid to the behaviour under pure moment and pure torque and it is shown that the presence of initial curvatures can introduce some novel forms of instability.

Effect of Specimen Geometry on Hot Torsion Test Results for Solid and Tubular Specimens

Abstract: Hot torsion tests have been carried out on aluminum, stainless steel, and silicon steel specimens using a wide range of gage length: radius ratios and bore diameters. For stainless steel, which dynamically recrystallises, a higher strain to maximum stress was found for specimens with a gage length : radius ratio A new effective radius is proposed for calculation of strains, strain rates, and shear stresses from torque-twist data for solid and tubular specimens.

Precise measurement of plastic behaviour of mild steel tubular specimens subjected to combined torsion and axial force

Abstract: In the present paper, as an investigation for obtaining detailed information about the plastic behaviour of real materials, precise measurement of plastic deformation of thin-walled tubular specimens of initially-isotropic mild steel was performed under combined loading of torsion and axial force having trajectories consisting of two straight lines at a constant rate of the effective strain. From the experimental results, it is found that the effect of the third invariant of the strain tensor appeared even for proportional deformation consisting of torsion and axial force. Moreover, it may be seen that the effective stress drops suddenly with increasing effective strain, and coaxiality between the stress deviator and the plastic strain increment tensor is seriously disturbed just after the corner of the strain trajectory. However, these local disturbances are recovered along the second branch of the trajectory. The effect of the third invariant of the strain tensor was eliminated from the experimental results by the introduction of the modified local stress space for isolating the influence of anisotropy due to the deformation history. This permits a systematic evaluation of the influence of anisotropy for various types of combined loading.

Effect of Major Axis Curvature on I-Beam Stability

Abstract: In the flexural-torsional buckling of beams, it is common practice to assume that the major axis flexural rigidity, EI x , is very large compared with the minor axis rigidity, EI y , and the torsional rigidity, GJ . That is, the in-plane deflections prior to buckling are assumed small enough to be ignored in the derivation of a method is presented for accounting for major axis curvature in the calculation of the buckling loads of doubly-symmetric I-section cantilevers and simple beams. This method involves little more effort than the conventional treatment. Beams of two different steel sections are investigated, one a column section and the other a beam section, and the results are presented in graphical form.

The Dynamic Properties of Unidirectional Fibre Reinforced Composites in Flexure and Torsion

Abstract: Theoretical predictions of the damping of composites are presented. New results are given for the damping and dynamic modulus in flexure and longitudinal shear using very carefully prepared specimens and improved apparatus. Comparison of these results, and others taken from the literature, with the theory reveals that the measured damping in flexure is higher and in torsion lower than predicted. Reasons for this discrepancy are investigated in detail and it is suggested that although specimen defects and extraneous losses always increase the damping, fibre misalignment may either increase or decrease it, and hydrostatic stresses may decrease it.The measured flexural modulus is less than that predicted by the law of mixtures, while the longitudinal shear modulus agrees closely with the square array prediction of Adams and Doner.

Mechanics of Solids and Structures

Abstract: The first part of this book deals with fundamental principles of the theoretical analysis of stress and strain, and applies these principles to common engineering problems. The chapter headings of Part 1 are: (1) Statically determinate frames and beams; (2) Statically determinate stress systems; (3) Stress-strain relations; (4) Displacements in statically determinate structures; (5) Statically indeterminate stress systems; (6) bending: stresses; (7) Bending: slope and deflection; (8) Elastic strain energy; (9) Theory of torsion; (10) Statically indeterminate beams and frames; (11) Buckling instability; (12) Stress and strain transformation and relationships; (13) Analysis of variation of stress and strain; (14) Some applications of the equilibrium and strain-displacement relationships; (15) Theories of yielding; (16) Thin plates and shells; (17) Stress concentration; (18) Elementary plastic and viscoelastic analyses. Part 2 deals with mechanical properties and testing of materials, and consists of the following chapters: (19) Tension, compression and torsion; (20) Hardness and other tests; (21) Toughness and unstable fracture; (22) Fatigue; (23) Creep; (24) Non-metallic materials. Part 3 covers some of the most common methods used in experimental analysis of stress and strain, and is presented under the following chapter headings: (25) Resistance strain gauges; (26) Photoelasticity; (27) Other methods of strain measurement. /TRRL/

A biaxial split Hopkinson bar for simultaneous torsion and compression

Abstract: A biaxial split Hopkinson bar which operates in simultaneous compression and torsion is described. The device utilizes torsional stress waves generated by release of a stored torque and compressive waves generated by mechanical impact of a long rod onto a loading bar. The torque is released by capacitive discharge explosion of a thin foil in a holding adhesive joint. The two stress waves travel in opposite directions toward a specimen sandwiched between two rods, arriving at the specimen within 10 μsec of each other. The machine is used on specimens of compact bone, and it is found that plastic deformation without fracture can be achieved under the combined dynamic torsion and compression, whereas it seldom occurs under either of these loading modes alone.

Safety belt reel with torsion rod

Abstract: Energy converter for motor vehicle safety belts having a belt wind-up drum in the hollow interior of which a torsion rod is mounted, includes a rigid tube surrounding the torsion rod and having a peripheral wall disposed between the torsion rod and the inner surface of the belt wind-up drum for limiting bending of the torsion rod.

An approximate solution for the free vibrations of rotating uniform cantilever beams

Abstract: Approximate solutions are obtained for the uncoupled frequencies and modes of rotating uniform cantilever beams. The frequency approximations for flab bending, lead-lag bending, and torsion are simple expressions having errors of less than a few percent over the entire frequency range. These expressions provide a simple way of determining the relations between mass and stiffness parameters and the resultant frequencies and mode shapes of rotating uniform beams.

General Analysis of Nonplanar Coupled Shear Walls

Abstract: A theory to analyze nonplanar coupled shear walls subjected to lateral loading is presented. The theory is applicable to a pair of shear walls of arbitrary cross-sectional shapes connected by a band of evenly spaced connecting members. The lateral loadings can be completely general and are not restricted to act in certain planes. The theory gives the torsional deformation in addition to the flexural deformations of the structure. A test on a Plexiglas structural modal is carried out to verify the accuracy of the theory.

Stress bounds for bars in torsion

Abstract: Upper bounds for the maximum shear stress in the St. Venant torsion problem are derived with the aid of the theory of subharmonic functions. The main result is a bound that is determined in a simple manner by the magnitude of the applied twisting moment and two parameters peculiar to the cross section: the radius of the largest circle contained in it and the minimum curvature of the curve that bounds it.

Torsion of Nonhomogeneous Solid

Abstract: A solution is given for the Reissner-Sagoci problem for a nonhomogeneous half-space and semi-infinite cylinder in each of which the shear modulus is assumed to vary with the depth. The formulation is reduced to Fredholm integral equations of the second kind. Numerical results have been presented for the physical quantities of interest. Some of these results indicate a marked difference from the corresponding response of a homogeneous isotropic solid. The analysis also reveals that the classical square root singularity in the shear stresses retains this order in the nonhomogeneous solid under consideration in contrast with a material possessing a modulus, in which the singularity is a function of a constant.

Plastic Deformation of Metals at High Strain Rates. Part I. The Effects of Temperature on the Static and Dynamic Stress-Strain Characteristics in Torsion of 1100-0 Aluminum.

Abstract: : A series of tests is described in which tubular specimens of a commercially pure polycrystalline aluminum were loaded in torsion up to shear strains of about 2 and 4% respectively, over the temperature range -180C to 250C. The experimental results give the flow stress in shear, the strain and the strain rate against time. They also give stress-strain curves which are compared to the corrresponding static curves obtained by testing similar specimens in torsion at about 0.001/sec. A graph showing the dependence of flow stress on temperature indicates that there are three different temperature ranges for polycrystalline aluminum within each of which a different deformation mechanism presumably dominates the flow process. (Modified author abstract)

Vehicle torsion bar

Abstract: A vehicle torsion bar wheel mounting includes a square tubular member fixed to the body frame and centrally housing a coupling block. Rectangular torsion bars are pivoted at their inner ends to the coupling block and at their outer ends to outwardly projecting shafts provided at their ends with radially extending arms proximate the ends of which are mounted transverse wheel supporting axles. An anchoring block slidably engages each of the torsion bars and the inside faces of the tubular member and is releasably fixed at any preset position by set screws available through a slot in the tubular member to permit the adjustment of the effective lengths of the torsion bars and the springing of the respective wheels by adjusting the point at which each torsion bar is fixed against axial rotation.

Tests of Curved Steel-Concrete Composite Beams

Abstract: Four curved composite beams, each consisting of a steel beam with a reinforced concrete slab, were fabricated and tested. The tests were limited to single girders on a simple span. The concrete slab was attached to the top flange of the steel girders using 1/2-in. (12.7 mm) diam stud shear connectors. The main variables in the test program were the girder size, radius of curvature, loading, and the number of connectors at a section. All four beams were loaded to failure and the vertical deflection, strain, rotation, and slip (between the steel and concrete) were recorded at several locations along the length of the span. Two of the beams failed in torsion near the supports and two failed in combined bending and torsion near midspan. Observations concerning the agreement between theory and experiment are presented for the loads causing failure, and stresses and deflections at one-half the failure loads. The significance of the test results regarding the design of the shear connection is examined and a simplified method of design of headed shear connectors is presented.

Tensile creep modulus, creep lateral contraction ratio and torsional creep measurements on small nonrigid specimens

Abstract: A torsional creep apparatus incorporating a novel linear bearing to permit simultaneous application of axial and torsional creep stresses to small nonrigid specimens is described. The results of a detailed examination of the capabilities of this apparatus and a comparison of shear creep and recovery compliance data is made (as measured direct in torsion and calculated from the axial and lateral strain data in tension). The measurements were made on isotropic and oriented sheets of low-density polyethylene and the use of oriented, as well as the more usual isotropic, material in such trials is illustrated.