Showing papers on "Torsion (mechanics) published in 1992"

Strength of materials and structures

Abstract: Preface * Introduction * Tension and compression: direct stress * Pin-jointed frames or trusses * Shearing stress * Joints and connections * Analysis of stress and strain * Thin shells under internal pressure * Bending moments and shearing forces * Geometrical properties of cross-sections * Longitudinal stresses in beams * Shearing stresses in beams * Beams of two materials * Bending stresses and direct stresses combined * Deflections of beams * Built-in and continuous beams * Plastic bending of mild-steel beams * Torsion of circular shafts and thin-walled tubes * Energy methods * Buckling of columns and beams * Lateral deflections of circular plates * Torsion of non-circular sections * Thick circular cylinders, discs and spheres * Introduction to matrix algebra * Matrix methods of structural analysis * The finite element method * Structural vibrations.

Composite structure for thrust reverser torque box

Abstract: A one-piece composite material torque box for the thrust reverser assembly of a jet engine. The torque box is made up of three composite material subassemblies, a generally planar flange subassembly, a tubular torque tube subassembly, and a cap subassembly. The flange subassembly is configured to transmit tension loads from the cascades of the reverser assembly to the V-blade ring which engages the engine, and the fibers in the composite material are aligned with these load paths. The torque tube subassembly is mounted to the flange subassembly, and is configured to transmit torsion loads from the actuators of the reverser assembly to the upper and lower latch members of the engine assembly; the fibers of the composite material therein are aligned at 45° angles to the tube axis, so as to be in alignment with paths of the tension/compression components of the torsion loads. The cap subassembly extends over the torque tube subassembly and is bonded to the flange subassembly on either side thereof, so as to bond these three subassemblies together into a unitary structure.

Effects of Hydrostatic Pressure on In-Plane Shear Properties of Graphite/Epoxy Composites:

Abstract: In order to determine effects of the fiber orientation on the pressure de pendent in-plane shear properties of continuous graphite fiber reinforced composites, mandrel-wrapped tubes are tested in torsion in the specially designed high pressure torsion test apparatus that is capable of containing pressure up to 7 Kbar.The shear properties that are determined include the in-plane shear modulus, shear yield strength and fracture strengths (maximum stress), and the strain to fracture as a function of hydrostatic pressure and fiber orientation. These results are then compared with those of the epoxy resin matrix without fibers and (0°) composite samples also tested under hydrostatic pressure. In all cases, the shear properties increase with increasing pressure but in different rates depending on the fiber orientation. The increase in the strengths and the toughness is manifested in the change in the modes of fracture. Visual and SEM examination are made to study fracture surface morphology and possible frac tu...

Shear deformable theories for cylindrical laminates - Equilibrium and buckling with applications

Abstract: A higher order theory is developped, which includes initial geometric imperfections and transverse shear effects for a laminated cylindrical configuration under the actions of lateral pressure, axial compression, and eccentrically applied torsion

Analysis of Aircraft Structures: An Introduction

Abstract: Introduction to the second edition Introduction to the first edition Part I. The Fundamentals of Structural Analysis: 1. Stress in structures 2. Stresses and coordinate axis rotations 3. Displacements and strains 4. Strains in rotated coordinate systems 5. The mechanical behavior of engineering materials 6. Linearly elastic materials Part II. Introduction to the Theory of Elasticity: 7. The theory of elasticity 8. Plane stress theory of elasticity solutions Part I and Part II review questions Part III. The Engineering Theory for Straight, Long Beams: 9. Bending and extensional stresses in beams 10. Beam bending and extensional deflections 11. Additional beam bending topics 12. Uniform torsion of beams 13. Beam torsion approximate solutions Beam bending and torsion review questions 14. Beam shearing stresses due to shearing forces Part IV. Work and Energy Principles: 15. Work and potential energy principles Part V. Energy Based Numerical Solutions: 16. Precursor numerical analyses 17. Introduction to the finite element method 18. Finite element truss problems 19. Basic aspects of multidimensional finite elements 20. The unit load method for determinate structures 21. The unit load method for indeterminate structures Parts IV and V review Part VI. Extensions to Plate Theory and Finite Element Applications: 22. Thin plate theory 23. Elastic and aeroelastic instabilities Selected answers to Part I exercises Selected answers to Part II exercises Selected answers to Part III exercises Selected answers to Part IV and Part V exercises Selected answers to Part VI exercises References.

Effective modelling of spatial buckling of beam assemblages, accounting for warping constraints and rotation-dependency of moments

Abstract: A simple, two-noded, finite element model for the three-dimensional buckling analysis of beam assemblages is developed. The underlying generalized-beam theory employed accounts for all coupled significant modes of deformations, including stretching, bending, shear and torsion, as well as warping. Its mixed formulation is of the two-field type, utilizing linear and constant interpolants for displacements and strain fields. Due considerations are given to the effect off inite rotations in space on the non-linear kinematic descriptions as well as the configuration-dependent behaviour of externally applied moment vectors of the conservative and non-conservative types. The performance of the model, and particularly the accuracy of its geometric and load-correction stiffnesses, is assessed in a fairly complete set of numerical simulations.

Quantum Mechanics of a Particle Confined to a Twisted Ring

Abstract: We derive an effective Hamiltonian for a particle confined to a thin tube which is gently twisted and curved to form a closed loop. The Hamiltonian describes the effect of both the curvature and the torsion of the loop correctly to the second order. Applied to the case of a tube of circular cross section, it reveals complete analogy with the Aharonov-Bohm effect. We also discuss eigenmodes for Mobius-like rings formed by a tube of non-circular cross section

Motor vehicle drive line torsional vibration damper

Abstract: For damping torsion vibrations in the drive line of a motor vehicle which contains a torsion vibration damper (5) between its internal combustion engine (1) and its gearbox (11), there is coupled to the output of the torsion vibration damper (5) an electric motor driven torque buffer (23) which compensates for any fluctuations in torque still present at the output of the torsion vibration damper (5) and occasioned by the firing sequence of the internal combustion engine (1). The torque buffer (23) is constructed after the fashion of a polyphase synchronous motor, the number of pairs of poles and possibly the rotary speed at which the magnetic fields rotates being so chosen that the angular cycle of the torque fluctuation exerted by the magnetic field on the rotor (31) of the torque buffer is equal to the angular cycle of the torque fluctuation originating from the firing sequence of the internal combustion engine (1). A control circuit (37) regulates the phasing of the magnetic field and its intensity.

Analysis and experiment of dynamic deflection of a thin plate with a coupling effect

Abstract: The authors describe computational analyses and an experiment on thin plate deflection in a magnetic field. The authors show the governing equation for the eddy current and the deflection analyses of a thin plate, considering the coupling effect between the eddy current and the deflection under nonuniform magnetic field. A computer code that takes the effect into account was developed on the basis of a thin plate approximation. The code was applied to the FELIX cantilevered beam (without torsion) and the results (current density, deflection, and bending strain) agreed quite well with the experimental results. The authors performed a plate deflection experiment (with torsion) and the code was also applied to this experiment. The comparison between numerical and experimental results verified the analysis method and the code. >

Torsion spring vehicle suspension

Abstract: A torsion spring cartridge is provided for torsionally absorbing loads on a trailer frame or the like. The torsion spring cartridge is insertable into an axle tube and includes a counter torque hub, a bearing block spaced therefrom, and a torque shaft mounted for oscillating rotational movement in the bearing block with torsion rods operably interconnected between the counter torque hub and the torque shaft. The bearing block and the torque shaft each include over-rotation stops that cooperate to prevent over-rotation of the torque shaft during use. The bearing block supports the inside of the axle tube to prevent distortion of the axle tube profile during over-torquing of the torque shaft during use, and a frame bracket supports the outside of the axle tube and transmits forces from the bearing block and axle tube directly to the trailer frame. The torsion rods have ends with substantially circular cross-sections, and are held in place by brazing. Oven brazing is utilized to equalize stress and minimize stress risers in the brazed joint so that the resulting brazing bonds resist stress fractures and failure from cyclical loading of the torsion spring cartridge.

Method for Calculating the Interlaminar Stresses in Symmetric Laminates Containing a Circular Hole

Abstract: An efficient approximate solution for three-dimensional stress distributions around a circular hole in symmetric laminates under a set of far-field in-plane stresses is presented. Stress functions for each ply are assumed according to the boundary-layer equilibrium equations. In addition, all the boundary conditions for each ply and traction continuity at the ply interface are exactly satisfied. Eventually, the unknown parameters in stress functions are determined by the minimization of complementary energy of the whole laminate. Numerical examples are presented in comparison with given literature which shows that the present method is efficient. I. Introduction D UE to stiffness discontinuity between plies, it is easy to cause interlaminar stress concentrations near the freeedge region in composite laminates. Such stresses will commence delamination, matrix crackings, and failure of laminates, especially under fatigue loading. Since 1970, numerous investigations1"5 have used various methods to determine the interlaminar stresses at the straight free edge of composite laminates. Pipes and Pagano1 adopted the anisotropic elasticity theory in conjunction with the finite difference method to analyze a simple four-ply laminate. Wang and Crossman2 used a finite element approach to investigate this same problem. Wang and Choi3'4 derived an analytical solution based on Lekhnitskii's stress potentials and the theory of anisotropic elasticity to determine the exact order of stress singularity at the free edges of laminate. In an effort to develop an efficient method to deal with thick laminates (say 100 plies), Kassapoglou and Lagace5 used the force balance method in conjunction with the principle of minimum complementary energy to obtain an analytical solution for interlaminar stresses at straight free edges. Owing to the complicated geometry for the curved free edges as compared with the straight free edges, little work has been done for composite laminates with curved free edges. Basically, the analysis of straight free edge may be assumed as a problem with two-dimensional stress and strain variations. However, the curved free edge is a typical three-dimensional problem. This difference has rendered the analysis for the curved free edge more difficult than the straight free edge. A boundary-layer theory based on the perturbation technique for isotropic elastic plates with a circular hole developed by Reiss6 has been extended to composite laminates by Tang.7-8 This approach is based on identifying the boundary-layer problem as two equivalent problems, namely, a modified torsion problem and a modified plane strain problem. However, Tang's solution can only satisfy part of boundary conditions in an average sense, which may result in unreliable stress results near the free edges.9 In addition, Tang's solution will be very tedious for laminates with numerous plies. Zhang and Ueng10 proposed a simplified method to investigate the effect of the ratio of hole radius to laminate thickness on the interlaminar stress distributions around a hole in a (0/90 deg)s laminate under far-field tensile or shear stress; however, it is assumed that the order of stress singularity is prescribed and

Axially compact torque transducer

Abstract: A torque transducer capable of installation in the housing (100) of a rotating machine, having a limited axial space therefor, has a disk shaped first member (14) fixed to a fixed portion of the housing. A disk shaped second member (16) has splines on its inside diameter which provide a sliding coupling with the first member. Splines on the outside diameter of the second member provide sliding connection to a floating portion (18) of an output drive train which coupling transfers reaction torque back from the output shaft (21), through the drive train, and into the second member. Shear webs are formed between the inner and outer diameters of the second member by removing some material to form torsion concentrator voids. Strain gages mounted on the shear webs and bridged with appropriate resistors provide an output signal in response to torsional strains imposed on the second disk shaped member. The output signal is routed to a calibrated signal processor and relay control unit.

The characteristics of laminar flow in a helical circular pipe

Abstract: The fully developed laminar flow in a helical circular pipe under the influence of both curvature and torsion is studied analytically. The solutions are obtained by the double series expansion method which perturbs the exact solution derived in this work for a twisted circular pipe. The perturbed parameters selected are dimensionless curvature k and dimensionless torsion τ. Since the expanded governing equations and series solutions have been arranged in a compact form, the complete solutions can be computed by a systematic procedure on computer. In addition, the accuracy of the solutions is only confined by the natural limitation of the series expansion method because no approximation was made in the governing equations. The ‘torsion number’ Tn which can be considered as the measure of the torsion effect that swirls the flow is defined Tn = 2τ[Rscr ], where [Rscr ] is the Reynolds number. The characteristics of the flow in the helical circular pipe are thus controlled by three parameters: [Rscr ], Dean number K and Tn. The flow rate solution of the extended Dean equations of Germano (1989) is then found. The effects of finite curvature and torsion on the flow rate, axial velocity and secondary flow are also found. The inconsistency of torsion effect on the secondary flow between Wang (1981) and Germano (1982, 1989) is also quantitatively explained by the different coordinate systems used.

A nonlinear composite beam theory

Abstract: Presented here is a general theory for the three-dimensional nonlinear dynamics of elastic anisotropic initially straight beams undergoing moderate displacements and rotations. The theory fully accounts for geometric nonlinearities (large rotations and displacements) by using local stress and strain measures and an exact coordinate transformation, which result in nonlinear curvature and strain-displacement expressions that contain the von Karman strains as a special case. Extensionality is included in the formulation, and transverse shear deformations are accounted for by using a third-order theory. Six third-order nonlinear partial-differential equations are derived for describing one extension, two bending, one torsion, and two shearing vibrations of composite beams. They show that laminated beams display linear elastic and nonlinear geometric couplings among all motions. The theory contains, as special cases, the Euler-Bernoulli theory, Timoshenko's beam theory, the third-order shear theory, and the von Karman type nonlinear theory.

Overhead door pre-loaded and pre-assembled torsion spring counterbalance assembly

Abstract: A torsion spring counterbalance assembly having one end of a torsion spring attached to a center support bracket with the other end attached to a torsion shaft around which the torsion spring is pre-loaded with the torsion shaft releasably locked to the center support bracket for allowing the tension of the pre-loaded torsion spring to be released after installation with an overhead garage door to counterbalance the garage door between open and closed positions via lift bands wound about drums mounted at the ends of the torsion shaft and secured to the door bottom by wire brackets. The drums are selectively connected for rotation with the torsion shaft and disconnected from rotation with the torsion shaft to permit adjustment of the tension and resulting torque of the torsion spring. A safety interlock mechanism limits the rotation of the torsion shaft relative to the center support bracket in the event of a malfunction upon initial installation. A manually actuated eccentric cam selectively locks and unlocks the lift band drums for lateral adjustment of the drums on the torsion shaft to properly align the spacing of the drums relative to variations in door width. A sleeve inside the torsion spring maintains the length of the torsion spring at its fully wound position to prevent lateral thrust on torsion shaft end supports enabling a single spring to be used on garage doors of various sizes and weights.

Extension-bend-twist coupling behavior of nonhomogeneous anisotropic beams with initial twist

Abstract: An analytical model is developed for assessing the extension-bend-twist coupling behavior of nonhomogeneous anisotropic beams with initial twist. The model is formulated as a coupled two-dimensional boundary value problem, where the displacement solutions are defined with pretwist-dependent functions that represent the extension, bending, and torsion, and unknown functions that represent local in-plane deformations and out-of-plane cross-section warping. The unknown deformation functions are determined by applying the principle of minimum potential energy to a discretized representation of the cross section. Numerical results are presented that fully verify this approach and illustrate the strong extension-twist coupling behavior present in pretwisted beams with thin-wall laminated composite cross sections as a function of ply angle, initial twist level, and initial twist axis location. Cross sections analyzed include thin laminated rectangles with either asymmetric or symmetric ply stacking sequences and a thin-wall single cell D-section composed of a graphite/epoxy woven cloth.

Nut runner for clamping bolts with predetermined torque and bolt clamping method

Abstract: In order to prevent a looseness of bolts after main clamping, a nut runner of the present invention comprises a torque sensor for detecting a clamping torque T of a clamping unit, and a torque comparison means for comparing the clamping torque T with a clamping completion torque ST. The nut runner further includes a torque control means which gradually reduces a rotational torque of the motor until a resilience such as a torsion accumulated in the clamping unit is entirely nullified when the clamping torque T reaches the clamping completion torque ST. This ensures an effective cancellation of an inverse torque arising from the resilience and acting in the direction loosening the bolt, thus preventing the bolt from loosening.