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Showing papers on "Deflection (engineering) published in 2003"


Journal ArticleDOI
TL;DR: In this paper, a nonlinear model of the actuator relates the resonant frequency and the maximum stable deflection to the actuators dimensions, and a suite of experiments that were carried out on deep reactive ion etched (DRIE), singlecrystal silicon, comb-drive actuators confirm the validity of the model.
Abstract: Electrostatic, comb-drive actuators have been designed for applications requiring displacements of up to 150 /spl mu/m in less than 1 ms. A nonlinear model of the actuator relates the resonant frequency and the maximum stable deflection to the actuator dimensions. A suite of experiments that were carried out on deep reactive ion etched (DRIE), single-crystal silicon, comb-drive actuators confirm the validity of the model. Four actuator design improvements were implemented. First, a folded-flexure suspension consisting of two folded beams rather than four and a U-shaped shuttle allowed the actuator area to be cut in half without degrading its performance. Second, the comb teeth were designed with linearly increasing lengths to reduce side instability by a factor of two. Third, the folded-flexure suspensions were fabricated in an initially bent configuration, improving the suspension stiffness ratio and reducing side instability by an additional factor of 30. Finally, additional actuation range was achieved using a launch and capture actuation scheme in which the actuator was allowed to swing backward after full forward deflection; the shuttle was captured and held using the backs of the comb banks as high-force, parallel-plate actuators.

228 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of shear slip on the deformation of steel-concrete composite beams were investigated, and it was found that including slip effects has significantly improved the accuracy of prediction.
Abstract: The present study investigated the effects of shear slip on the deformation of steel-concrete composite beams. The equivalent rigidity of composite beams considering three different loading types was first derived based on equilibrium and curvature compatibility, from which a general formula to account for slip effects was then developed. The predicted results were compared with measurements of six specimens tested in the present study and other available test results for both simply supported and continuous beams. It was found that including slip effects has significantly improved the accuracy of prediction. For typical beams used in practice, shear slip in partial composite beams has a significant contribution to beam deformation. Even for full composite beams, slip effects may result in stiffness reduction up to 17% for short span beams. However, slip effects are ignored in many design specifications that use transformed section method except that American Institute of Steel Construction ~AISC! specifications recommend a calculation procedure in the commentary. In the AISC procedure, stress and deflection calculations of partially composite girders are based on effective section modulus and moment of inertia to account for slip, while ignoring slip effects in full composite sections. For full composite sections, the effective section modulus and moment of inertia calculated with the AISC specifications are larger than that of present study, meaning that the specifications are not on the conservative side. For partial composite sections, the AISC predictions are more conservative than the present study.

211 citations


Journal ArticleDOI
TL;DR: In this article, the results from a study of vertical deflection measurement of bridges using digital close-range terrestrial photogrammetry (DCRTP) were reported, which consisted of a laboratory and two field exercises.
Abstract: This paper reports on the results from a study of vertical deflection measurement of bridges using digital close-range terrestrial photogrammetry (DCRTP). The study consisted of a laboratory and two field exercises. In the laboratory exercise, photogrammetric measurements of a 11.6 m (38 ft) steel beam loaded at midspan were made and compared with dial gauge readings and elastic beam theory. In the first field exercise, the initial camber and dead load deflection of 31.1 m (102 ft) prestressed concrete bridge girders were measured photogrammetrically and compared with level rod and total station readings. A comparison of the photogrammetric measurements with the dead load deflection diagram is also made. In the second field exercise, the vertical deflection of a 14.9 m (49 ft) noncomposite steel girder bridge loaded with two dump trucks was measured. Photogrammetric results are compared with deflections estimated using elastic finite-element analysis, level rod readings, and curvature-based deflection measurements. The paper is concluded with a discussion of work in progress to further improve the accuracy of DCRTP in the field.

153 citations



Journal ArticleDOI
TL;DR: In this paper, a method to analyze the 3D form error of a ball-end milled surface due to the elastic compliance of the cutting tool is presented. But the method is limited to the case where the holder is assumed to be a cantilever beam.
Abstract: This paper presents a method to analyze the 3-dimensional form error of a ball-end milled surface due to the elastic compliance of the cutting tool. In order to estimate the form error in various cutting modes, the cutting force and the cutter deflection models including the effect of the surface inclination were established. The cutting forces were calculated by using the cutter contact area determined from the Z-map of the surface geometry and the current cutter location. The tool deflection responding to the cutting force was then calculated by considering the cutter and the holder stiffness. The cutter was modeled as a cantilever beam consisting of the shank and the flute. The stiffness of the holder was measured experimentally. Various experimental works have been performed to verify the validity of the proposed model. It is shown that the proposed method is capable of accurate prediction of cutting forces and the surface form error.

134 citations


Journal ArticleDOI
TL;DR: In this paper, a model for the railway track consists of two beams on periodically positioned supports that are mounted on a visco-elastic 3D layer to model the rails, sleepers and soil, respectively.

134 citations


Journal ArticleDOI
TL;DR: In this article, the authors present an experimental critique of the current test methods used to assess the effects of reinforcement corrosion on the serviceability deflections of reinforced concrete beams, and highlight the weakness of tests aimed at assessing the deflection behaviour of beams in which the corrosion of the steel and the application of the service loads are undertaken as two separate and sequential processes.
Abstract: This paper presents an experimental critique of the current test methods used to assess the effects of reinforcement corrosion on the serviceability deflections of reinforced concrete beams. Importantly, the work reported here highlights the weakness of tests aimed at assessing the deflection behaviour of beams in which the corrosion of the steel and the application of the service loads are undertaken as two separate and sequential processes. In the present series of tests, the central deflections of beams subjected to 23% and 34% of the design ultimate load, under 4-point loading subjected to simultaneous accelerated corrosion, were monitored over a period of approximately 30 days. Uncorroded beams were used as control samples and tested in parallel with the corroded samples. The results show the importance of assessing the structural effects of reinforcement corrosion under simultaneous load and corrosion conditions, as would occur in situ. In this situation, when 6% of the mass of steel is corroded, beam deflections are increased by 40–70% relative to the deflection of the control samples.

129 citations


Journal Article
TL;DR: In this article, the revised contents of composite steel concrete beams in China Code for Design of Steel Structures (GB50017-2002), including the designing method and basic theory of negative bending regions in continuous beam, partial shear connection, composite beams with profiled sheeting, and the reduced stiffness method for calculating the deflection of the composite beam.
Abstract: This paper briefly introduces the revised contents of composite steel concrete beams in China Code for Design of Steel Structures (GB50017-2002), including the designing method and basic theory of negative bending regions in continuous beam, partial shear connection, composite beams with profiled sheeting, and the reduced stiffness method for calculating the deflection of the composite beam. The issues that need to be further done are also presented.

120 citations


Journal ArticleDOI
TL;DR: In this article, a closed form solution based on three asymptotic cases with deformation purely by indentation, bending or shear is presented for a Hertzian contact law, suitable for monolithic plates, and for a linear contact law suitable for sandwich panels.

118 citations


Journal ArticleDOI
TL;DR: In this article, the authors examined the deflection/penetration behavior of dynamic mode-I cracks propagating at various speeds towards inclined weak planes/interfaces of various strengths in otherwise homogeneous isotropic plates.
Abstract: We examine the deflection/penetration behavior of dynamic mode-I cracks propagating at various speeds towards inclined weak planes/interfaces of various strengths in otherwise homogeneous isotropic plates. A dynamic wedge-loading mechanism is used to control the incoming crack speeds, and high-speed photography and dynamic photoelasticity are used to observe, in real-time, the failure mode transition mechanism at the interfaces. Simple dynamic fracture mechanics concepts used in conjunction with a postulated energy criterion are applied to examine the crack deflection/penetration behavior and, for the case of interfacial deflection, to predict the crack tip speed of the deflected crack. It is found that if the interfacial angle and strength are such as to trap an incident dynamic mode-I crack within the interface, a failure mode transition occurs. This transition is characterized by a distinct, observable and predicted speed jump as well as a dramatic crack speed increase as the crack transitions from a purely mode-I crack to an unstable mixed-mode interfacial crack.

118 citations


Journal ArticleDOI
TL;DR: In this paper, a modular model consisting of three sub-models is presented to predict railway traffic induced vibrations if a new railway line is to be built in densely populated areas such as the Netherlands.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the deflection behavior of concrete flexural members reinforced with glass fiber-reinforced polymer (GFRP) reinforcing bars and found that the ACI 440.1R model overestimates the effective moment of inertia and an appropriate modification is presented.
Abstract: This paper investigates deflection behavior of concrete flexural members reinforced with glass fiber-reinforced polymer (GFRP) reinforcing bars. It is recognized that serviceability plays a major role in the design of GFRP-reinforced concrete beams. Therefore, accurate modeling of flexural stiffness is critical and the effect of influencing parameters must be considered. This study accounts for variations in concrete strength, reinforcement density, and shear span-depth ratio. Experimental results from 48 simply supported concrete beams reinforced with GFRP are compared with ACI Committee 440's published deflection model. The ACI 440.1R model is found to overestimate the effective moment of inertia, and an appropriate modification is presented.

Journal ArticleDOI
TL;DR: In this paper, a mathematical dynamic model is derived for compliant, constant-force compression mechanisms, based on the pseudo-rigid-body model simplification of the device, which allows every configuration to be represented by the same model, so a separate treatment is not required for each configuration.

Journal ArticleDOI
01 Aug 2003
TL;DR: In this paper, a transient analysis technique for point contact elastohydrodynamic (EHL) lubrication problems using coupled elastic and hydrodynamic equations is presented, which is validated under transient conditions by a detailed comparison with published work produced using a different, independent method incorporating a moving roughness feature.
Abstract: The paper presents a transient analysis technique for point contact elastohydrodynamic (EHL) lubrication problems using coupled elastic and hydrodynamic equations. Full coupling is made possible by use of a novel differential deflection formulation. The way in which the differential deflection is incorporated into the overall solution method for a point contact is discussed. A range of spatial and temporal discretization methods are incorporated and compared. The method is validated under transient conditions by a detailed comparison with published work produced using a different, independent method incorporating a moving roughness feature. A comparison of the results with different discretization methods leads to the conclusion that spatial central differencing with a Crank-Nicolson temporal discretization is the most effective finite difference scheme, and this is generally equivalent to the finite element discretization given in detail in the paper. A comparison of the results produced for moving rough surfaces suggests that the finite element formulation is preferred.

Journal ArticleDOI
TL;DR: In this article, the authors used ACI 440.1R-01 to predict deflections in concrete beams reinforced with fiber reinforced polymer (FRP) bars and crack width in beams with one-layer FRP bars.

Journal ArticleDOI
TL;DR: In this article, the dynamic stability of simply supported, circular cylindrical shells subjected to dynamic axial loads is analyzed by using the Donnell's nonlinear shallow-shell theory.

Journal ArticleDOI
TL;DR: Analysis of variance revealed that, irrespective of the test set up and wire type, wire size had a significant effect on the forces produced, and each of the thermally active wires produced less force that the non-thermally active wire.
Abstract: The objective of the study was to investigate the load/deflection characteristics of three commercially available thermally active nickel-titanium orthodontic archwires using a standard nickel-titanium archwire as a control. The thermally active wires were Regency Thermal, Orthoform, and Eurotherm and the control was Memory. Round 0.4 mm and rectangular 0.4 x 0.56 mm wires were subjected to 2 and 4 mm of deflection in a water bath at temperatures of 20, 30, and 40 degrees C and forces were measured in three-point bend and phantom head situations. Analysis of variance revealed that, irrespective of the test set up and wire type, wire size had a significant effect (P < 0.001) on the forces produced. An increase in size from 0.4 mm round to 0.4 x 0.56 mm rectangular wire approximately doubled the force values for a given deflection. The effect of wire deflection on the force values varied according to the test system, forces being much higher in the phantom head tests than in the beam tests. In the beam tests, an increase in wire deflection from 2 to 4 mm had no significant effect on the forces exerted, but in the phantom head tests the forces produced by each wire at 4 mm deflection were four to five times greater than those at 2 mm deflection. Each of the thermally active wires produced less force that the non-thermally active wire. However, there was a large variation between the three types of thermally active wire. In the beam tests each 10 degrees C rise in temperature from 20 to 40 degrees C had a highly significant effect on the force produced by each thermoelastic wire (P < 0.001). In the phantom head tests there were significant force increases between 20 and 30 degrees C (P < 0.001), but between 30 and 40 degrees C the forces did not change significantly.

Journal ArticleDOI
TL;DR: In this paper, the authors applied the moving least squares differential quadrature (MLSDQ) method to the bending and buckling analyses of symmetric laminates based on the first-order shear deformation theory (FSDT).

Journal ArticleDOI
TL;DR: In this paper, the dynamic displacement and stress responses of a plate of infinite extent on a viscous Winkler foundation subjected to moving tandem-axle loads with amplitude variation have been investigated.

Journal ArticleDOI
TL;DR: In this paper, the mechanical properties of ultrananocrystalline diamond (UNCD) thin films were measured using microcantilever deflection and membrane deflection techniques.
Abstract: The mechanical properties of ultrananocrystalline diamond (UNCD) thin films were measured using microcantilever deflection and membrane deflection techniques. Bending tests on several free-standing UNCD cantilevers, 0.5 μm thick, 20 μm wide and 80 μm long, yielded elastic modulus values of 916–959 GPa. The tests showed good reproducibility by repeated testing on the same cantilever and by testing several cantilevers of different lengths. The largest source of error in the method was accurate measurement of film thickness. Elastic modulus measurements performed with the novel membrane deflection experiment (MDE), developed by Espinosa and co-workers, gave results similar to those from the microcantilever-based tests. Tests were performed on UNCD specimens grown by both micro and nano wafer-seeding techniques. The elastic modulus was measured to be between 930–970 GPa for the microseeding and between 945–963 GPa for the nanoseeding technique. The MDE test also provided the fracture strength, which for UNCD was found to vary from 0.89 to 2.42 GPa for the microseeded samples and from 3.95 to 5.03 for the nanoseeded samples. The narrowing of the elastic modulus variation and major increase in fracture strength is believed to result from a reduction in surface roughness, less stress concentration, when employing the nanoseeding technique. Although both methods yielded reliable values of elastic modulus, the MDE was found to be more versatile since it yielded additional information about the structure and material properties, such as strength and initial stress state.

Journal ArticleDOI
TL;DR: An optical sensing system consisting of a laser diode and a position sensitive detector is introduced for the real-time measurement of the dynamic deflection and a Lyapunov-type controller based on the deflection feedback is proposed to damp out the tip oscillations and regulate the endpoint of the flexible robot.
Abstract: The use of flexible links in a robot inevitably causes the elastic deflection and vibration of the endpoint of the robot during high-speed operations. The deflection and vibration will tend to degrade the positioning performance of the robot. In this paper, an optical sensing system consisting of a laser diode and a position sensitive detector is introduced for the real-time measurement of the dynamic deflection. Utilising a non-linear, coupled and measurement-based dynamic system model, a Lyapunov-type controller based on the deflection feedback is then proposed to damp out the tip oscillations and regulate the endpoint of the flexible robot. Experimental tests are conducted for a flexible one-link robot arm with a payload mass at the tip. The results demonstrate the effectiveness of the proposed measuring and control schemes.

Journal ArticleDOI
TL;DR: In this article, an adaptive machining planning environment for modeling, prediction, and selection of process and tool path parameters for rapid machining of complex low-rigidity high-accuracy parts is presented.

Journal ArticleDOI
TL;DR: In this article, the seismic response of moment resisting (MR) steel frames enhanced with low-yield steel shear panels is analyzed. And the authors present a parametric analysis of the structural properties of these panels, namely strength, stiffness, ductility and hysteretic behaviour, aiming at determining those factors having the major impact on the seismic responses of the frame.

Proceedings ArticleDOI
18 Aug 2003
TL;DR: In this paper, the self-restoration capacity of a mortar beam with shape memory alloys (SMA) reinforcements was evaluated. And the results were compared with those for a beam containing steel wires, showing that after maximum deflection, the mortar beam can return to an about one-tenth deflection compared with the maximum.
Abstract: Shape Memory Alloys (SMA) exhibit stable superelasticity between a reverse transformation finish temperature (Af) and approximately 30°C above Af, and therefore can sufficiently work as a superelastic material for structural use in building under the temperature in a construction environment. In order to verify the potential self-restoration capacity of mortar beams containing superelastic SMA reinforcements, static loading tests were conducted, and the results were then compared with those for a beam containing steel wires. The comparison indicates that (1) after maximum deflection, the mortar beam with SMA can return to an about one-tenth deflection compared with the maximum, (2) the range of deflection of the mortar beam with SMA is more than seven times that of the beam with steel, and (3) wide single crack can occur at the critical section due to a weaker bond force between SMA and mortar.

Journal ArticleDOI
TL;DR: In this paper, a new deformability index for prestressed concrete beams is proposed, which is defined in terms of both a deflection factor and a strength factor, where deflection is defined as the ratio of the deflection at failure to the defect at first cracking, while strength factor is the ratio between the ultimate moment or load to the cracking moment (or load).
Abstract: After a brief review of the ductility and deformability indices currently used in the design of concrete beams reinforced or prestressed with steel or fiber reinforced polymer (FRP) tendons, a new definition of a deformability index (factor) for prestressed concrete beams is proposed. The new factor is defined in terms of both a deflection factor and a strength factor. The deflection factor is the ratio of the deflection at failure to the deflection at first cracking, while the strength factor is the ratio of the ultimate moment (or load) to the cracking moment (or load). The proposed deformability factor is verified not only by test results obtained by the writer, but also by other test results available in the literature and it appears to be a suitable measurement of the deformability of concrete beams prestressed with either FRP tendons or steel tendons.

Book
07 Apr 2003
TL;DR: In this paper, the authors present a finite element analysis of the stress cubic equation in the context of design of shafts and associated parts, and propose a solution to the stress Cubic equation.
Abstract: Part I Fundamentals 1 Introduction to Design 2 Materials 3 Stress and Strain 4 Deflection and Stiffness 5 Energy Methods in Design 6 Buckling Design of Members 7 Static Failure Criteria and Reliability 8 Fatigue Part II Applications 9 Shafts and Associated Parts 10 Bearings and Lubrication 11 Spur Gears 12 Helical, Worm, and Bevel Gears 13 Belts, Chain, Clutches, and Brakes 14 Springs 15 Power Screws, Fasteners, and Connections 16 Axisymmetric Problems in Design 17 Finite Element Analysis in Design Appendix A Units, Properties of Shapes, and Beam Deflections Appendix B Material Properties Appendix C Stress Concentration Factors Appendix D Solution of the Stress Cubic Equation

Journal ArticleDOI
TL;DR: In this article, a series of innovative cold-formed steel columns of intermediate length under axial compression were evaluated using finite element analyses (ABAQUS) and finite strip analysis program THINWALL.

Journal ArticleDOI
TL;DR: In this paper, the effect of cantilever width on the stress-induced bending of micromachined bilayer cantilevers was demonstrated and a finite element model has been established to analyze such a deformation.
Abstract: In this paper, the effect of cantilever width is demonstrated on the stress-induced bending of micromachined bilayer cantilevers. In previous literature, the bilayer cantilever has been modeled as a two-dimensional structure; consequently, the stress-induced bending of micromachined bilayer cantilever was considered to be independent upon the width. In this study, the fabrication and characterization of various widths of micromachined bilayer cantilever have been performed to observe the out-of-plane deformation caused by residual stresses. A finite element model has been established to analyze such a deformation. With the support of experimental and numerical results, width dependence in the stress-induced bending of micromachined bilayer cantilever has been discussed. As a result, the tip deflection of the bilayer cantilever gradually increases as the width increases until the width-to-length ratio reaches a critical value, in which the micromachined bilayer cantilever can be regarded as an infinitely wide cantilever, and any cross section along the length is in plane strain state. Furthermore, width-independent design, which exists among very wide cantilevers with various widths, has also been reported. Thus a more reliable design can be achieved.

Journal ArticleDOI
TL;DR: In this paper, a finite-element procedure considering nonlinear load-slip relationship for shear connectors is presented, which accounts for the concrete slab cracking and the resulting tension stiffening effect.
Abstract: In steel and concrete composite beams, the incomplete interaction between steel profile and concrete slab leads to an appreciable increase of the beam deflections with respect to full interaction behavior. Moreover, the concrete cracking in hogging moment regions of continuous beams needs to be considered. In this paper, a finite-element procedure considering nonlinear load–slip relationship for shear connectors is presented. Such a procedure accounts for the concrete slab cracking and the resulting tension stiffening effect; it also assumes different load–slip relationships for shear connectors in cracked slab. Some experimental comparisons show the accuracy of the proposed procedure. A wide parametric analysis is performed with reference to the evaluation of deflections for simply supported composite beams. Finally, a simplified method which is able to evaluate deflections for beams with nonlinear behaving shear connection is presented.

Proceedings ArticleDOI
01 Jan 2003
TL;DR: In this article, structural finite element models of the baseline design and carbon hybrid designs with and without twist-bend coupling were evaluated for a unit load condition and two extreme wind conditions.
Abstract: This study presents results obtained for four hybrid designs of the Northern Power Systems (NPS) 9.2-meter prototype version of the ERS-100 wind turbine rotor blade. The ERS-100 wind turbine rotor blade was designed and developed by TPI composites. The baseline design uses e-glass unidirectional fibers in combination with {+-}45-degree and random mat layers for the skin and spar cap. This project involves developing structural finite element models of the baseline design and carbon hybrid designs with and without twist-bend coupling. All designs were evaluated for a unit load condition and two extreme wind conditions. The unit load condition was used to evaluate the static deflection, twist and twist-coupling parameter. Maximum deflections and strains were determined for the extreme wind conditions. Linear and nonlinear buckling loads were determined for a tip load condition. The results indicate that carbon fibers can be used to produce twist-coupled designs with comparable deflections, strains and buckling loads to the e-glass baseline.