Showing papers on "Deflection (engineering) published in 1991"
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413 citations
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TL;DR: In this paper, a brief review of applications of piezoelectric bimorphs is presented, and the constituent equations which describe the behavior of bimomorphs for various mechanical boundary conditions are derived.
Abstract: A brief review of applications of piezoelectric bimorphs is presented. The constituent equations which describe the behavior of piezoelectric bimorphs for various mechanical boundary conditions are derived. The internal energy density of infinitesimally small volume elements in thermodynamic equilibrium is calculated in the presence of a voltage on the electrodes, a clamped cantilever beam condition on one side of the beam and a set of three different classical boundary conditions on the other side of the beam. These are a mechanical moment M at the end of the beam, a force F perpendicular to the beam, applied at its tip, and a uniformly distributed body force p.
The total internal energy content is calculated by integrating over the entire volume of the beam. Two different beam configurations are considered: parallel polarizations of the two adjoining elements of the beam with an internal electrode; and antiparallel orientation without an internal electrode.
The canonical conjugate of the moment is calculated as the angular deflection at the tip of the beam α, while that of the force at the tip is the local vertical deflection δ. The canonical conjugate of the uniform load on the beam is found to be the volume displacement V of the beam. The canonical conjugate of the voltage across the electrodes is the charge on the electrodes. The equations are given in the direct form, with external parameters (M, V), (F, V), and (p, V) as independent variables and also in a linear combination with (M, F, p, V) as variables.
These constituent equations can be used to calculate the behavior of the bimorph under any condition that can be described as a linear combination of forces at the tip, moments at the tip and uniform loads on the entire beam. This allows us to use the bimorph as a black box, without having to consider its internal movement or charges.
401 citations
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TL;DR: In this article, an error analysis for the recently introduced mixed-interpolated finite element methods for Reissner-Mindlin plates is given, which are valid uniformly with respect to the thickness of the plate.
Abstract: We give an error analysis for the recently introduced mixed-interpolated finite element methods for Reissner-Mindlin plates. Optimal error estimates, which are valid uniformly with respect to the thickness of the plate, are proven for the deflection, rotation and the shear force. In addition, the earlier families are augmented with a new method with linear approximations for the deflection and the rotation. We also introduce a simple postprocessing method by which an improved approximation for the deflection can be obtained.
216 citations
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01 Jan 1991
TL;DR: In this paper, the concept of stress, strain and material relations analysis of axially loaded members torsion stresses in beams combined with integration deflection of beams by special methods energy methods inelastic behaviour buckling of columns moments of areas.
Abstract: Fundamental principles concept of stress, strain and material relations analysis of stress and strain axially loaded members torsion stresses in beams combined stresses deflection of beams by integration deflection of beams by special methods energy methods inelastic behaviour buckling of columns moments of areas.
211 citations
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TL;DR: In this article, the authors extended the cohesive crack model to mixed mode propagation and an experimental confirmation is provided by testing four-point shear specimens of concrete, where a constant crack mouth sliding displacement rate is imposed, so that is is possible to control and detect the snapback load vs deflection branches.
197 citations
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TL;DR: In this paper, a higher-order plate theory is used in each individual layer to determine the natural frequencies and the relative stress and deflection distributions through the thickness of simply supported rectangular plates.
193 citations
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21 Jun 1991
TL;DR: In this paper, a play or clearance is formed between the outer roll shell and the inner roll shell part of a controlled deflection roll, which enables dismantling and exchange of the outer part of the roll shell without the need to dismantle the entire roll shell or remove such from the machine.
Abstract: In a controlled deflection roll having a roll shell rotatable about a stationary carrier and braced by one or more support elements against the stationary carrier, the roll shell comprises an inner roll shell part and an outer roll shell part which, during operation of the controlled deflection roll, form a press or force fit with respect to one another, for instance, due to excess pressure in the interior of the controlled deflection roll or due to elastic pre-biasing of the parts of the roll shell. Upon pressure relief or the existence of negative pressure within the controlled deflection roll a play or clearance is formed between the outer roll shell part and the inner roll shell part of the roll shell which enables dismantling and exchange of the outer roll shell part of the roll shell without the need to dismantle the controlled deflection roll or to remove such from the machine.
181 citations
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TL;DR: In this paper, the authors used computer-based machanics of cutting models and software modules for the prediction of the average and fluctuating force components and torque in end milling.
153 citations
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24 Jun 1991TL;DR: In this paper, the authors describe the fabrication of a silicon cantilever beam with an integrated piezoresistor for sensing its deflection and an image of a grating was obtained with this technique.
Abstract: An atomic force microscope (AFM) is an instrument which measures the topography of a surface by bringing a cantilever beam into contact with a sample and measuring the deflection of the cantilever as it is scanned across the surface. The complexity of an AFM is predominantly governed by the detector used for measuring the deflection of the cantilever probe. The authors describe the fabrication of a silicon cantilever beam with an integrated piezoresistor for sensing its deflection. A silicon-on-insulator material is used for the fabrication. A p-type resistor is fabricated at the surface of the cantilever along a direction so that the piezoresistive effect of silicon causes its resistance to vary linearly with its deflection. The cantilevers considered typically have spring constants from 1 to 10 N/m and minimum detectable deflections from 1 to 10 AA over a 10-Hz-1-kHz frequency range. The cantilevers were successfully used in an AFM, and an image of a grating was obtained with this technique. >
150 citations
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TL;DR: In this paper, nonlinear vibrations at a Hertzian contact are studied by the perturbation technique known as the method of multiple scales, and the average normal contact deflection during oscillations is smaller than the static deflection under the same average load.
Abstract: Nonlinear vibrations at a Hertzian contact are studied by the perturbation technique known as the method of multiple scales. As a result of the nonlinear Hertzian stiffness, the average normal contact deflection during oscillations is smaller than the static deflection under the same average load
140 citations
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TL;DR: In this article, an experimental and theoretical investigation on the behavior of single-screw helical anchors in sand is presented, which includes 56 tests conducted on five model anchors installed in dense, medium, and loose dry sands.
Abstract: Experimental and theoretical investigations on the behavior of single‐screw helical anchors in sand are presented. A testing program included 56 tests conducted on five model anchors installed in dense, medium, and loose dry sands. A sand‐placing technique was developed and utilized over the testing program in order to achieve the predetermined unit weight. The experimental setup was instrumented to allow the measurement of the pullout load, the upward displacement of the anchor, and the deflection of the sand surface. It was observed that the failure mechanism as well as the pullout load varied with the installation depth of the anchor and the angle of shearing resistance of the sand. A mathematical model is developed using the limit‐equilibrium method of analysis and the observed failure mechanism of the anchor from the present experimental work. Based on experimental results, a simple equation is proposed to introduce the degree of shear mobilization on the coefficient of passive earth pressure. Compar...
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TL;DR: In this paper, a method for calculating the non-linear mode shapes and natural frequencies of fully clamped beams at large vibration amplitudes is presented, and results are compared with those of previous studies and of experimental measurements.
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TL;DR: In this article, a moment curvature relationship is used to describe the girder behavior and a load model is developed for a single unit truck, a semitrailer, and combinations of these trucks.
Abstract: Reliability procedures are developed for girder bridges. Load models are based on the available statistical data. The derivation of load models is described in other papers. Resistance models are developed by simulations using the available test results for materials and components. The girder behavior is described by a moment curvature relationships. Bridge capacity is determined in terms of the maximum truck load before failure. The analysis is performed for a single unit truck, a semitrailer, and combinations of these trucks. For a given truck position, the load is gradually increased until the deformation (maximum deflection) exceeds the critical level. The developed resistance models are used in the reliability analysis. Reliability indices are calculated for noncomposite and composite steel girders, reinforced concrete T-beams, and prestressed concrete girders. The calculations are performed for girders and structural systems. Reliability indices for the system are higher than for girders. The effect of correlation between girder strengths is analyzed. Girder bridges behave as parallel systems. Sensitivity functions are developed for various parameters related to the considered girders. The developed approach is demonstrated on typical girder bridges.
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TL;DR: In this paper, a relationship between the risk of significant thoracic injury (AIS is greater than or equal to 3) and Hybrid III dummy sternal deflection for shoulder belt loading is developed.
Abstract: A relationship between the risk of significant thoracic injury (AIS is greater than or equal to 3) and Hybrid III dummy sternal deflection for shoulder belt loading is developed. This relationship is based on an analysis of the Association Peugeot-Renault accident data of 386 occupants who were restrained by three-point belt systems that used a shoulder belt with a force-limiting element. For 342 of these occupants, the magnitude of the shoulder belt force could be estimated with various degrees of certainty from the amount of force-limiting band ripping. Hyge sled tests were conducted with a Hybrid III dummy to reproduce the various degrees of band rearing. The resulting Hybrid III sternal deflections were correlated to the frequencies of AIS greater than or equal to 3 thoracic injury observed for similar and tearing in the field accident data. This analysis indicates that for shoulder belt loading a Hybrid III sternal deflection of 50 mm corresponds to a 40 to 50 percent risk of an AIS greater than or equal to 3 thoracic injury.
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Abstract: A comparison is made of the experimental and theoretical values of bending moment, shear force, deflection, and pressure for a reinforced concrete box culvert measuring 1,200 by 1,200 mm (inside dimensions) by 9-m long and 75 mm (uniform) thick. Dry sand is used to backfill the culvert. Both the numerical and experimental results compare favorably, but the results differ appreciably from those considered for conventional analysis and design. Also, there is a substantial reduction in the midspan bending moments as compared with conventional analysis.
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24 Aug 1991
TL;DR: In this article, an elastic material is provided which is disposed around and between the plurality of coils, but either not bonded to or partially bonded to the coils, modifying the force exerted by the spring assembly in response to the deflection of the assembly along the loading direction.
Abstract: A spring assembly (10) includes a plurality of coils (12) interconnected with one another in a spaced-apart relationship for causing the spring assembly (10) to exert as force in a loading direction approximately normal to a tangent to a centerline (16) of the plurality of coils (12) in response to deflection of the spring assembly along the loading direction. An elastic material (18) is provided which is disposed around and between the plurality of coils, but either not bonded to or partially bonded to the coils, modifying the force exerted by the spring assembly in response to the deflection of the spring assembly along the loading direction.
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24 Jun 1991
TL;DR: In this article, a large deflection performance was measured and modeled for its dependence on diaphragm geometries and corrugation parameters using a surface micromachining technique.
Abstract: The large deflection performance was measured and modeled for its dependence on diaphragm geometries and corrugation parameters. Corrugated polyimide diaphragms of various diameters, corrugation frequencies, and thicknesses were fabricated using a surface micromachining technique. Current models correctly described the observed increase in deflection from corrugated diaphragms compared to deflections in flat diaphragms at equivalent loads. The models are extended with the definition of the transition deflection which delineates the transition between the small and large deflection regions. The range of corrugation quality factors available in surface micromachined diaphragms is determined, and predicted load-deflection curves are compared to measurements. >
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23 Sep 1991
TL;DR: In this paper, the residual strength of electricity poles is determined by the deflection of the poles under a pre-determined applied load, and the load is applied by an extensible ram which has a foot secured to the base of the pole by a chain and a head plate with teeth which engages the sides of poles.
Abstract: The residual strength of electricity poles is determined by the deflection of the poles under a pre-determined applied load. The load is applied by an extensible ram which has a foot secured to the base of the pole by a chain and a head plate with teeth which engages the sides of the poles. A preset hydraulic pressure is applied to the ram by a manual pump and the deflection if measured by strain gauges mounted on a support frame. The load deflection data are fed to a programmed computer which calculates the residual strength.
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TL;DR: In this article, the authors present an analytical part of an investigation of a type of double-layer tensegrity grids (DLTGs), where the bars are confined between two parallel layers of cables.
Abstract: Tensegrity structures are freestanding prestressed cable networks in which the cables are prestressed against a discontinuous system of bars. In double‐layer tensegrity grids (DLTGs), the bars are confined between two parallel layers of cables. This paper presents the analytical part of an investigation of a type of DLTG. A first‐order linear analytical model indicates that these structures possess low stiffness and low bar force efficiency. Under full prestress, determined by the condition that no cable is slack under the applied load, the model predicts deflections of approximately 1/20 of the span, and 20% of bar load‐bearing capacity is available for the applied load, the rest being required by prestress. Member forces and deflections are strongly affected by the span, structural depth and level of prestress. Enhancement techniques are discussed.
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TL;DR: In this paper, anomalous experimental results on fully clamped beams subjected to projectile impact at the mid-span are presented, showing that the permanent midpoint deflection of a thin beam may be in the direction opposite to the direction of impact.
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TL;DR: In this article, Symonds et al. describe tests made in an attempt to observe anomalous behavior that had been predicted in computations for the elastic-plastic response of fixed pin ended beams to short pulse loading.
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TL;DR: In this paper, the authors measured the damping of wakefield deflection modes in a slow-wave accelerating structure consisting of a dielectric-lined waveguide with segmented conducting boundaries wrapped with absorbing material.
Abstract: We have directly measured the damping of wake‐field deflection modes in a slow‐wave accelerating structure consisting of a dielectric‐lined waveguide with segmented conducting boundaries wrapped with rf absorbing material. Such damping of deflection modes is desired to prevent beam breakup instabilities. Attenuation e‐folding times of 246 ps were recorded for deflection modes at the Advanced Accelerator Test Facility while the quality of the desired accelerating mode remained unaffected.
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TL;DR: In this paper, the deflection of cracked reinforced concrete beams under various types of loading is investigated and the effect of the type of loading on their effective moment of inertia is discussed.
Abstract: The deflection of cracked reinforced concrete beams tested under various types of loading is investigated and the effect of the type of loading on their effective moment of inertia is discussed. Four type of loading were considered in this study, which include: midspan and third-point concentrated loads, uniformly distributed load, and a combination of a midspan concentrated and uniformly distributed load. The value of the effective moment of inertia was found to be significantly affected by the type of loading used. Therefore, to account for such an effect, a newly developed model for estimating the effective moment of inertia of cracked reinforced concrete beams under any type of symmetrical loading is proposed.
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TL;DR: In this paper, a large body of experimental evidence is available confirming that the creep coefficient of high-strength concrete under sustained axial compression is significantly less than that of ordinary concrete.
Abstract: A large body of experimental evidence is available confirming that the creep coefficient of high-strength concrete under sustained axial compression is significantly less than that of ordinary concrete. Thus, the ratio of time-dependent deflection to immediate elastic deflection of high-strength concrete beams under sustained loads should likewise be lower. However, long-term deflection multipliers of the 1989 ACI Building Code do not account for concrete strength as a variable. Experimental results are reported for 9 beams with nominal concrete compressive strengths over a reange to 123,000 psi, loaded over a 12 month period. These tests confirm the significant differences between beams using high-strength and normal strength concrete. Based on these and other tests, modifications to the present ACI Building Code method for predicting long-term deflections are suggested.
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TL;DR: In this article, a convergence method based on the use of nonlinear least squares is described, which is adapted to a layered elastic program (CHEVRON N-layer).
Abstract: In recent years the analysis of pavement structures has relied increasingly on characterizing material properties (such as resilient modulus) by use of nondestructive deflection testing and backcalculation procedures. An important element common to all backcalculation procedures--the technique used to achieve a "convergence" of the measured and calculated deflection basins--will be described. A convergence method based on the use of nonlinear least squares is described. The method was adapted to a layered elastic program (CHEVRON N-layer). This convergence approach improves moduli estimates over prior procedures; however, the most important element is the ability to efficiently backcalculate not only layer moduli but also layer thicknesses. This ability is illustrated by using hypothetical two- and three-layer pavement sections and by using real data for a three-layer section.
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TL;DR: In this paper, a boundary element method is developed for the large deflection analysis of thin elastic plates resting on elastic foundation, where the subgrade reaction may depend linearly (Winkler-type) or nonlinearly on the deflection as well as on the point coordinates (nonhomogeneous subgrade).
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22 Jan 1991
TL;DR: In this article, a deflection yoke device provided with a correction circuit in which horizontal and vertical misconvergences appearing on a screen of a color cathode-ray tube are corrected.
Abstract: This invention relates to a deflection yoke device provided with a correction circuit in which horizontal and vertical misconvergences appearing on a screen of a color cathode-ray tube are corrected.
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08 Apr 1991
TL;DR: In this article, the turning bars and the deflection rollers are retained in an essentially rectangular frame, with the position of the turning bar adjustable along the sides of the frame and the positioning of the rollers.
Abstract: To supply an arriving and delivered portion of a traveling web (1, 21, 31, 41, 81, 91, 101) to have the same side-orientation as the delivered portion, the web is passed about a first turning bar (2), then looped about a first deflection roller (3), and spanning the arriving portion of the web, about a second deflection roller (4) to be then turned again, selectively, by a second turning bar (5). Other web paths are possible, omitting the second deflection roller (4). Rather than using a single second deflection roller, smaller roller elements (FIG. 11: 16, 17) can be used, the second deflection roller, or the elements having effective diameters which are larger than the diameter of the first deflection roller. The turning bars and the deflection rollers are retained in an essentially rectangular frame, with the position of the turning bars adjustable along the sides of the frame and the position of the deflection rollers, likewise, preferably being longitudinally adjustable along the sides of the frame as well as height-adjustable perpendicular to the plane of the web traveling between the respective turning bars and deflection rollers.