Showing papers on "Deflection (engineering) published in 1976"

The measurement of magnetostriction in ferromagnetic thin films

Abstract: The application of a magnetic field parallel to a ferromagnetic film deposited on one side of a cantilevered substrate causes a small deflection of the free end. This deflection can be measured and the magnetostriction determined since the magnetostriction is proportional to the deflection. An instrument has been devised which can measure the deflection as a function of the applied field. This is accomplished as follows: the cantilevered substrate with the film on the upper side forms one plate of a capacitor which is part of the tuning capacitance of an oscillator operating at l0 MHz. The deflection of the free end causes a change in frequency of about 10 to 100 Hz. which is easily measured. The sign of the magnetostriction is immediately discernible from the increase or decrease in oscillator frequency. The instrument is calibrated by hanging a known weight from the free end of the substrate. Magnetostriction constants as small as 3 \times 10^{-7} and as large as 40 \times 10^{-6} have been measured.

Tests of Circular Steel Tubes in Bending

Abstract: A series of tests on 10-3/4in. (270-mm) tubes was conducted to determine the plastic rotation capacity of tubular beams. Six different D/t values ranging from 18-102 were used in the tests. Cantilever and fixed-ended beams, with moment gradients (shears) and restraints against ovalizing at the end, are compared with the behavior of the constant moment region of simple beams. Tubes with D/t greater than about 50 do not have sufficient plastic hinge rotation capacity to develop the classical ultimate strength. In the absence of a small moment gradient or stiffening, the plastic moment is not quite reached in tubes with D/t of 35. For inelastic buckling in the range of D/t of 18-80, critical strains appear to be proportional to (t/D)², as opposed to the conventionallinear relationship. Information concerning the complex post-buckling behavior is also presented.

Bridge deck behaviour

Abstract: Preface. Structural forms and calculation methods. Beam decks and frames. Slab decks. Beam-and-slab decks. Multicellular decks. Box-girder decks. Space frame methods and slab membrane action. Shear lag and edge stiffening. Skew, tapered and curved decks. Distribution coefficients. Temperature and prestress loading. Harmonic analysis and folded plate theory. Finite element method. Stiffnesses of supports and foundations. Appendices. A: Product integrals. Functions of load on a single span. Harmonic components. B: Calculation of torsion constants for solid beams. Author index. Subject index.

Geometry effects and the J-integral approach to elastic-plastic fatigue crack growth

Abstract: Fatigue crack growth rate data are obtained for center cracked specimens of A533B steel subjected to elastic-plastic cyclic loading. Cyclic J-integral values estimated from load versus deflection hysteresis loops are correlated with these growth rate data. The relationship obtained is in agreement with previous elastic-plastic data on compact specimens and also with linear elastic data on large size compact specimens. These experimental data suggest that the fracture mechanics approach to fatigue crack growth may be extended by the use of the J-integral concept, so that large scale plasticity effects are included.

The finite strip method

Abstract: The finite strip method consists in breaking down the field studied into rectangular elements called: "strip" linked together by means of "nodal" lines The deflection is transformed into series with a limited number of terms On each nodal line are two unknown factors: the deflection and the rotation, instead of three as in the finite element method The width of the half-strip of the stiffness matrix in the finite strip method does not depend on the mesh but on the number of terms in the series This method was shown to be more economical than the finite element method It seems to be more efficient and easier for analyzing plates and beams such as in bridges, in particular orthotropic slab bridges, including cantilevered beams /TRRL/

Device for the measurement of mechanical work and power

Abstract: Mechanical work and power transmitted through transmission elements such as chain drives is determined by deflecting a transmission element and measuring the distance and/or speed of deflection and the deflection force while the transmission continues its operation.

Inelastic Cycles of Axially Loaded Steel Members

Abstract: Sixteen fixed-ended steel bars of rectangular cross section 1/2 in. x 1 (12.7 x 25.4-mm) and (12.7-mmand of various lengths were tested under 25.4-mm) nder static and dynamic loads to determine the cyclic hysteretic response of steel columns. The specimens were subjected to tensile yielding, post-buckling deflection cycles. Column slenderness ratios ranged from 85 to 210. This research complemented a corresponding elasto-plastic theoretical development; the experimental results generally agreed with theoretical predictions, yet significant deviations were noted. Principal findings were that the buckling load decreased with number of cycles, the columns exhibited net tensile or compressive plastic deformation in a cycle depending on deflection level, and the static and dynamic responses were similar.

Finite Element Analysis of Wood-Stud Walls

Abstract: A theoretical procedure based on the finite element model and linear step-by-step analysis for evaluating the behavior of wood-stud walls under combined bending and compression loads was developed and verified. The procedure accounts for the variations in material properties, nonlinear material behavior of studs, partial composite action and slip among the components, and the load sharing among the studs of various strengths and stiffnesses. I-beam wall sections and full-size walls are tested to verify the procedure. Theoretical and experimental deflections and slips at service loads and overloads, and the ultimate load of the tested wall panels showed good agreement. Parameter study investigating the effect of the joint and wall covering stiffness on the ultimate load is included. The developed procedure can be used to obtain the information necessary for improved structural and economic design of wood-stud walls for residential and commercial buildings.

Bumper having pivotal load spreader plate for deflecting energy absorbing medium

Abstract: Bumper assembly having resilient energy absorbing media supported on a substantially rigid beam and adapted to absorb impact energy in response to deflection by impact load. A load spreader plate outwardly of the media is supported for pivotal movement about one end thereof for transferring impact forces and increasing deflection of the media thereby improving its performance in absorbing impact energy.

Wind turbine with automatic pitch and yaw control

Abstract: A wind turbine having a flexible central beam member supporting aerodynamic blades at opposite ends thereof and fabricated of uni-directional high tensile strength material bonded together into beam form so that the beam is lightweight, and has high tensile strength to carry the blade centrifugal loads, low shear modulus to permit torsional twisting thereof for turbine speed control purposes, and adequate bending stiffness to permit out-of-plane deflection thereof for turbine yard control purposes. A selectively off-set weighted pendulum member is pivotally connected to the turbine and connected to the beam or blade so as to cause torsional twisting thereof in response to centrifugal loading of the pendulum member for turbine speed control purposes.

System for damping vibrations in a deflectable transducer

Abstract: Electronic damping of a deflectable videotape transducer is effected by apparatus including a deflectable support arm for supporting the transducer and deflecting it in response to an electrical deflection signal. A signal transducer generates a deflection velocity signal representative of instantaneous deflection velocity of the transducer. A feedback loop receives the deflected velocity signal, converts it to a damping signal, and applies the damping signal to the deflectable support arm to dampen vibrations therein.

Drive circuitry for controlling movable video head

Abstract: Improved deflection of a bimorph having a pair of electrically poled piezo-ceramic elements bonded to opposite sides of a common substrate is achieved by applying to each element a deflection voltage whose polarity is always in the poling direction of the element to which it is applied. By maintaining the polarity of the deflection voltages in the poling direction of the piezo-ceramic elements, large amplitude deflection voltages can be used without de-polarizing the piezo-ceramic elements.

Stress Analysis of Large Deflection of Glass Plates by the Finite-Element Method

Abstract: A computer program is used in analyzing stress and deflection characteristics of plates undergoing large deflection. Experimental data were obtained for glass plates with different area, aspect ratio, and thickness subjected to simulated windload. The theoretical predictions and test data are correlated herein and show excellent agreement.

Creep deflection of metal beams in transient heating processes, with particular reference to fire

Abstract: A new numerical technique is described by which the process of creep bending under transient heating conditions can be predicted. It utilizes a convenient creep model, proposed by Dorn and expanded...

Post-Buckling Behaviour of Simply-Supported Cross-Ply Rectangular Plates

Abstract: An analysis is presented for the post-buckling behaviour of simply-supported, laminated cross-ply rectangular plates subjected to biaxial compression. The solution to von Karman-type large deflection equations of the plate is expressed as a double sine series for the transverse deflection and a double series of clamped-clamped beam functions for the force function. All the boundary conditions, including those involving the normal bending moment at the edges, are satisfied exactly. The series solution is found to converge rapidly. Using only the first few terms in the series, numerical results for square graphite-epoxy unsymmetric laminates under uniaxial compression is presented graphically.

Deflection-restrained load cell for on-board vehicle weighing systems

Abstract: A problem that is often encountered under uneven terrain conditions with on-board load weighing systems for vehicles, such as logging trucks, having a frame member and a load support member to which a load which is to be measured is applied, is that structural failures occur in the load cell assemblies included in the on-board load weighing system. The cause of these structural failures is traced to rotation of the load cell assemblies resulting in undue tensive forces in the load cells thereof. Various restraining devices are discussed for limiting the upward deflection of an upper, load concentrating portion of the load cell to maintain the tensive forces within acceptable levels.

Nonlinear effects of initial bending on the vibrations of crystal plates

Abstract: The changes in the resonance frequencies of circular crystal plates subject to initial bending stresses are studied. The plate is flexed as a cantilever clamped near the edge and stressed by a transverse, concentrated force applied at a point diametrically opposite the support. A system of plate equations which takes into account the nonlinear effects due to the large, initial deflection and to the third‐order elastic stiffness coefficients in the stress–strain relations is employed. In obtaining the initial fields caused by bending, strain components are assumed to be small, but large gradient of plate deflection and large rotations of the plate element about x1 and x3 axes are permissble by retaining their quadratic terms in the strain‐displacement relations. The changes of resonance frequencies of fundamental thickness‐shear vibrations are calculated for rotated Y cuts of quartz. The calculated frequency changes are compared with experimental values as a function of the force position, the azimuth angl...

Large Deflection of Unsymmetric Cross-Ply and Angle-Ply Plates

Abstract: An approximate solution to the von Karman-type large-deflection equations of unsymmetrically laminated, anisotropic, rectangular plates under uniform transverse load is formulated by the perturbation technique. The membrane boundary conditions are the zero normal and shear boundary forces. By expressing the load, force function and transverse deflection in the form of series, the governing equations and boundary conditions are reduced to a series of linear partial differential equations and boundary conditions. In each approximation a solution is assumed in the form of polynomials which satisfy the associated boundary conditions and physical requirements for deflection and and three membrane forces in unsymmetric cross-ply and angle-ply plates. Taking the first three terms in the truncated series, numerical results are graphically presented for the load-deflection relations, bending moments and membrane forces in unsymmetric cross-ply and angle-ply plates with various values of aspect ratio and total numb...

Field testing of a reinforced concrete highway bridge to collapse

Abstract: A three-span reinforced concrete slab bridge was loaded to collapse. The slab was 9.75 m (32 ft) wide and 30.5 cm (12 in) thick, and on each edge was cast a 92 by 25.4-cm (34 by 10-in) curb. Loading was produced by hydraulic rams that were reacted to by overhead steel beams attached to the piers by tension rods through the slabs. the load was increased at intervals, and at each interval deflection and strain on the concrete surface were measured. The strength of the concrete and steel materials was more than the design minimum values; average cylinder strength was 47.33 MPa (6865 lbf/in square) compared with a design value of 20.68 MPa (3000 lbf/in square), and average steel coupon yield strength was 365.77 MPa (53 050 lbf/in square) compared with a design value of 275.79 MPa (40 000 lbf/in square). The results indicate that (a) the measured concrete stresses were lower than the calculated values; (b) the load causing first permanent set was accurately predicted by calculaing the yield moment in the slab; (c) the collapse load was accurately predicted by considering the formation of yield moments along the centerline and over the piers of the bridge for a channel section loaded around its weak axis; and (d) based on the line load for the center span, it would take 8 HS20-44 trucks placed in the center of the bridge to cause any permanent deflection and 20 HS20-44 trucks to cause collapse. /Author/

Vibration damper with variable spring rate and damping friction

Abstract: A torsional vibration dampener assembly having resilient means to provide a variable torque output in conjunction with variable damping friction torque. The assembly utilizes a first set of torsion springs to provide a low deflection or displacement rate for a first stage of travel between the input and output members and a second set of springs providing an increased deflection rate for a second stage of travel, and a cooperating cam construction which can be arranged to provide an increase or decrease in damping friction as required in relation to the transmitted torque.

Influence of the interface condition on stress distribution in a layered system (abridgement)

Abstract: The behavior of a system containing a number of homogeneous, isotropic linear-elastic layers is analyzed using a linear fictional model to simulate the real behavior at the interfaces. The results of the computations emphasize the influence of the interface condition on the stress distribution and hence on the design of pavements. In flexible pavements, the radial stress is strongly affected by the interface condition. The vertical stress and the deflection bowl are also affected, but to a smaller extent. Since the rational design of flexible pavements is based on the radial stress or strain at the bottom of the asphalt-concrete layer and on the vertical stress or strain at the top of the subgrade, the determination and use in design of the modulus of resistance to displacement between different layers should improve the design system and make it more realistic. In rigid pavement overlays also, the condition of the interface between the existing and the new surface is important. In the case analyzed, the partial bond (as defined by the Corps of Engineers) corresponds to a large value of the modulus of resistance to displacement. Since the existence of such a large value is questionable, the determination of realistic values will make the design of overlays more rational.