Showing papers on "Torsion (mechanics) published in 1968"

Torsional Vibration of an Elastic Solid Containing a Penny‐Shaped Crack

Abstract: The axisymmetric wave equation is solved for the problem of torsional elastic waves impinging on a penny‐shaped crack the periphery of which is assumed to be infinitely sharp. Using Hankel transforms, the problem is reduced to the solution of two simultaneous integral equations of the Fredholm type. The proposed method of solution permits an examination of the complete scattered‐wave field at points both near to and far from the penny‐shaped plane of discontinuity. In elastodynamics, however, it is the nearfield stress solution that is of chief interest. To this end, the singular nature of the local dynamic stress field is determined in elementary closed form, while the magnitude of this stress field, which can be adequately described by a singularity parameter k3, is calculated numerically. The important results are that (1) the stresses are singular of the order r1−12 as r1 → 0 at the diffracting edge of the crack and (2) k3 is found to be proportional to the material constants, the crack radius, and th...

Studies on Dynamic Torsional Viscoelasticity of Wood

Abstract: The modulus of torsion and the mechanical damping has been investigated on test pieces of beech wood (Fagus sylvatica L.) with transverse fibre direction by means of a torsional pendulum. Both characteristics have been determined as a function of temperature (from 20 ... 100°C) and moisture content (from 5 percent to fibre saturation). At a frequency of about 1 cycle per second a transition region has been found characterized by a large decrease of the modulus of torsion and a distinct maximum of damping.

Some Experiments in Dynamic Plasticity under Combined Stress

Abstract: The deformation of aluminum at strain rates from 10−3 sec−1 to 103 sec−1 and temperatures from 300° K to 700° K is studied experimentally under a range of stress states including tension, compression, torsion, and combined tension and torsion. The results from these tests are compared with a generalized constitutive equation developed from the thermally-activated dislocation model of deformation. Predicted functional relationships between the stress, strain and strain-rate invariants and temperature are supported by the experimental data.

Ultimate Torque of Reinforced Rectangular Beams

Abstract: An extensive investigation of plain and reinforced concrete beams subjected to torsion is being reported in a series of papers. Presented is an ultimate torque theory for reinforced concrete rectangular members based on the observed behavior of 53 test specimens. A design equation for ultimate torque is derived and compared with the writer's 53 tests and 27 other tests available in literature. The design equation is in agreement with the experimental results.

Ultimate strength of reinforced concrete beams in combined torsion and shear

Abstract: CLASSICAL THEORY SHOWS THAT BOTH TORSION AND FLEXURAL SHEAR HAVE THE SAME POINT OF MAXIMUM STRESS FOR RECTANGULAR SECTIONS. HOWEVER, THE STRESS DISTRIBUTION THROUGHOUT THE REST OF THE CROSS SECTION VARIES SIGNIFICANTLY. A SERIES OF RECTANGULAR REINFORCED CONCRETE BEAMS WITH NORMAL PERCENTAGES OF BOTH LONGITUDINAL AND TRANSVERSE STEEL WAS TESTED AND THE INTERACTION OF THEIR TORSIONAL AND FLEXURAL SHEAR CAPACITIES WAS DEVELOPED. THE EFFECTS OF BENDING AND AMOUNT OF REINFORCEMENT ARE DISCUSSED. VARIOUS INTERACTION FORMULAS ARE COMPARED. /AUTHOR/

Torsion bar suspension systems for motor vehicles

Abstract: IN A VEHICLE SUSPENSION SYSTEM EACH WHEEL OF A PAIR IS ROTATABLY MOUNTED AT ONE END OF AN ARM, THE OTHER END OF WHICH IS PIVOTALLY MOUNTED ON THE END OF A TRANSVERSE TUBULAR MEMBER. THE ARMS ARE SECURED TO THE OUTER ENDS OF A TORSION BAR MEANS EXTENDING WITHIN THE TRANSVERSE MEMBER AND SECURED TO THE MIDDLE OF THE TRANSVERSE MEMBER. THE TRANSVERSE MEMBER ITSELF IS CONNECTED TO THE VEHICLE BODY THROUGH RESILIENT BLOCKS WHICH INSULATE THE VEHICLE BODY FROM VIBRATION FROM THE WHEELS AND ARMS AND ACT AS ADDITIONAL TORSION ELEMENTS.

Buckling of inhomogeneous anisotropic cylindrical shells by bending.

Abstract: A theoretical analysis of the buckling of inhomogeneous anisotropic cylindrical shells by bending combined with pressure, axial load, and torsion is presented. Numerical results are given for contemporary composite cylinders. These results show that the pure bending buckling stress is nearly equal to the uniform axial compression buckling stress and that the bending plus uniform axial compression interaction is almost linear. T HIS study is concerned with the stability of radially inhomogeneous, anisotropic, circular cylindrical shells under bending combined with uniform axial load, torsion, and pressure. The buckling of homogeneous isotropic cylindrical shells under bending was investigated by Fliigge.1 He calculated the critical bending stress for a particular longitudinal buckle wavelength parameter and found that it was 1.3 times the critical stress for pure axial compression. Seide and Weingarten2 calculated critical bending stresses for isotropic cylinders by means of Batdorfs modified DonnelFs equations and the Galerkin method. They minimized the buckling load with respect to the longitudinal buckle wavelength and found that the critical bending stress is, for all practical purposes, equal to the critical compressive stress. Hedgepeth and Hall3 studied the stability of stiffened cylinders. They found that the resistance to bending was 25% greater than the resistance to compression for a corrugated cylinder with internal rings. Mah, Almroth, and Pittner4 have investigated the buckling of orthotropic cylinders under combined bending, axial compression, and external pressure. They found that the critical bending stress is substantially higher than critical compression when they are interacting with external pressure. A combined analytical and experimental investigation of the buckling of filament-woun d cylinders under axial compression has been reported by Tasi, Feldman, and Stang.5 Their experimental buckling loads were from 65 to 85% of predicted values, and they found the differences between clamped end and simple support solutions to be negligible. Tasi6 studied the effect of heterogeneity on the stability of composite cylinders under axial compression. He considered composites whose in-plane, coupling, and bending stiffness matrices were orthotropic and found that heterogeneity generally reduced the axial buckling load. Experiments to determine the strength of filament-wound cylinders loaded in axial compression have been reported by Card. 7 In some of his tests, failures were induced by buckling and these buckling loads were from 65 to 90% of predicted values. Holston8 investigated the effects of a soft elastic core on the buckling of inhomogeneous anisotropic cylindrical shells. He showed numerical results for filament-wound cylinders under pressure, axial compression, and torsion. He found that the increment in buckling load associated with an increment in the core parameter is largest for pressure buckling and smallest for axial compression. An analytical and experimental investigation of the stability of filament wound cylinders under combined loads has been presented by Holston, Feldman, and Stang.9 Their experimental buckling loads were from 67 to 90% of theoretical values for loadings without torsion. Ugural and Cheng10 have presented an analysis of the buckling of composite cylinders under pure bending and numerical results for plywood cylinders. In this study an analysis of the buckling of radially inhomogeneous, anisotropic cylindrical shells by bending combined with pressure, uniform axial load, and torsion is presented. Linear anisotropic shell theory is used and the effects of end conditions are not considered. The Donnell type of approximation is included, and these equations reduce to those given by Seide and Weingarten2 for isotropic materials. Numerical results are given for contemporary filamentwound cylinders. The bending-buckling stresses of these cylinders are, for all practical purposes, equal to their uniform axial compression buckling stresses, and the bending plus axial compression interactions are nearly linear. II. Stability Analysis

Torsion of structural concrete--interaction surface for combined torsion, shear, and bending in beams without stirrups

Abstract: MEMBERS SUBJECTED TO COMBINED TORSION, SHEAR, AND BENDING CAN BE CONVENIENTLY STUDIED BY A NON-DIMENSIONAL INTERACTION SURFACE. USING THIS METHOD AND TESTS AVAILABLE IN THE LITERATURE FOR REINFORCED CONCRETE MEMBERS WITHOUT STIRRUPS WERE ANALYZED, AND A SIMPLE CONSERVATIVE DESIGN CRITERION IS DERIVED. AN EXAMPLE DESIGN PROBLEM IS PRESENTED. /AUTHOR/

Simulation of Hot Working Operations by Means of Torsion Testing.

Abstract: : The torsion apparatus was modified to improve specimen alignment. Control mechanisms have been devised to enable high strain rate tests to be interrupted in predetermined fractions of a second. Stress measuring mechanisms were improved by the use of a load cell with a fast action, three-channel chart recorder to record torque, temperature, and number of twists as a function of time. Torsion tests and extrusion tests were made to investigate the hot working characteristics of three materials: a titanium alloy, 'Ti-6Al-4V', a high strength steel, 'D6-ac', and a nickel base alloy, 'Udimet 700'. The following factors were investigated for each alloy by torsion tests made at several different temperatures and strain rates: (1) ductility, (2) stress-strain relations, (3) peak flow stress, (4) temperature increase during deformation. Extrusion tests at three temperatures and torsion tests under comparable conditions were made on each of the alloys. The microstructures of the resulting products were examined and photomicrographs are presented for comparisons. (Author)

Torsion apparatus for measuring shear properties of adhesive bonded joints

Abstract: A napkin-ring torsion apparatus for the study of the shear properties of adhesive bonded joints is described. A high sensitivity capacitance-type extensometer is used for measuring the load-deformation characteristics of the adhesives. Angle of twist sensitivities as high as 6 × 10−8 radians can reliably be achieved. Shear stress is determined by using an extensometer to measure the strain developed in the metal adherends. The technique has been used with a variety of adhesive materials, having several glue-line thicknesses. Experimental variables include test temperature, strain rate, time at load and time between load-unload cycles.

Numerical Solutions of Two-Dimensional Elastic, Plastic Problems by Conformal Mapping and Finite-Difference Method : 3rd Report, Elasto-Plastic Torsion of Circumferentially Grooved Shafts

Abstract: In this report, the problem of elasto-plastic torsion of circumferentially grooved shafts is solved by the same numerical method as presented in the 1st report. The solutions based on both flow and deformation type theories are obtained for the Ramberg-Osgood material. The numerical calculations are carried out for several characteristic parameters of material, then the stress and strain concentration factors, stress distributions, the angle of twist, etc. are presented. The results calculated by the flow theory are experimentally verified, and comparing them with the deformation theory, it is proved that both results coincide fairly well with each other about the angle of twist, but about other quantities, for example, the stress and strain concentration factors, the difference between both results becomes larger as torque increases.

Componets of Creep in Mature Concrete

Abstract: TESTS ARE REPORTED ON THE CREEP AND RECOVERY OF CONCRETE UNDER UNIAXIAL COMPRESSION AND TENSION, APPLIED AT ADVANCED AGES OF OVER A YEAR. THE CHARACTERISTICS OF THE CREEP COMPONENTS (IRRECOVERABLE OR FLOW, RECOVERABLE OR DELAYED ELASTIC) FOR YOUNG AND MATURE CONCRETE ARE COMPARED, AND FOUND TO BE IN REASONABLE AGREEMENT. THE RATE OF FLOW METHOD (BASED ON THE TWO COMPONENTS) FOR CALCULATING STRAIN UNDER VARIABLE STRESS IS DISCUSSED. IN PARTICULAR, IT IS COMPARED FAVORABLY WITH SUPERPOSITION. /AUTHOR/