Showing papers on "Deflection (engineering) published in 1973"

Flexible roughness in open channels

Abstract: The logarithmic flow formula for open channels is valid for flow over a roughness cover made up of flexible plastic strips. The deflection of such roughness is an important parameter as the deflection directly influences the relative roughness. Dimensionless parameters which relate the amount of bending to the stiffness of the roughness and the boundary shear are defined. Three regimes of boundary behavior are observed for flexible plastic roughness, leading to two resistance functions. The flexible plastic roughness is produced by affixing thin plastic strips of various thickness to the bed of a flume. The flow of water over flexible plastic strips simulates flow over a vegetative channel lining.

Vehicular safety device

Abstract: An improved vehicle door is provided which is resistant to impact at high deflection Such a door is provided by incorporating within the door in a region most likely to be subject to impact, a plurality of horizontally extending resilient members supported generally adjacent opposing portions of the door frame Beneficially, the resilient members are a composite material such as a hardened synthetic resin and a plurality of longitudinally extending resilient fibers such as fibers of glass

Dynamic buckling of a rectangular orthotropic plate

Abstract: The elastic buckling of a simply-supported rectangular orthotropic plate, with initial imperfections, under a rapidly applied compressive load is analyzed. The large deflection plate equations are used to study inertial effects in the postbulkling phase. Numerical results for a controlled rate of load application show that the critical load is increased over the corresponding static case. The load-deflection relation is oscillatory in the postbuckling phase, thereby increasing the stresses in the plate over those in the static case. Initial imperfections decrease the critical load as well as increase the frequency and decrease the amplitude of the oscillations.

Post-Buckling Behaviour of Rectangular Orthotropic Plates

Abstract: An analysis is presented for the post-buckling behaviour of a simply supported, rectangular, orthotropic plate subjected to biaxial compression. The solution of von Karman-type large deflection equations of the plate satisfying the prescribed boundary conditions is expressed in the form of a double Fourier series for the transverse deflection and a double series for the stress function consisting of the appropriate beam functions. The effect of plate properties on stresses and deflections has been studied for three fibre-reinforced materials. Numerical results indicate good convergence of the present series solution and are compared with the available data.

Steel Column Failure Under Thermal Gradients

Abstract: An analytical study of the behavior of axially loaded steel columns subject to thermal gradients across the cross section of the member is presented. The influence of residual stress, thermal stress, and the change in material properties at elevated temperature is considered. Moment-load-curvature-temperature, M-P-φ-T, relationships and a numerical integration method are used to determine the deflection of the column. The results indicate that the bowing produced by the thermal gradients has a significant effect on the ultimate strength of the member.

Charge detection for ink jet printers

Abstract: Circuits are described involving a method of detecting charges on drops in an ink jet stream without contacting the stream. This permits a determination of proper synchronization and charging of the drops, the velocity of the ink stream, the extent of deflection of the drops, and whether or not the stream is in operation, or has stopped.

Error compensating deflection coils in a conducting magnetic tube

Abstract: This invention relates to an error compensating arrangement for use with the deflection system in a conducting magnetic tube such as that of an electron microscope or the like. More particularly, compensating coils are provided to correct time lag errors due to eddy currents set up in permeable magnetic enclosures which surround the principal deflection coils and act essentially as pole-pieces.

Synthesis of two discrete vibratory systems using eigenvalue modification.

Abstract: without an axial force. If the force P in each segment is specified, the analysis of either static or dynamic problems is straightforward. This is the case, for example, for beam-columns and for rotating beams. Problems in the elastic stability of columns can be handled by applying an arbitrary lateral force (or moment) and calculating the deflection with a series of successively greater axial forces. Southwell's method4 can then be applied to determine the buckling load. Incidentally, for a uniform column with any combination of end conditions, the exact expression for the elastic buckling load can be found directly from the stiffness matrix of the single beam segment. If the ends of the beam are restrained so as to prevent axial displacements, the axial force P is a nonlinear function of the lateral displacements. The customary assumption3 is that the deflection curve is a cubic. In this case, the axial force due to the stretching of the neutral axis of the beam segment shown in Fig. 3 is

Electronmagnetic deflection display system including dual mode deflection amplifiers and output power limited power supplies

Abstract: An electromagnetic deflection display system for both random stroke and raster displays provides larger, faster and brighter displays with reduced power consumption and physical size. Dual mode deflection amplifiers having independent linear and slew characteristics provide reduced slewing time without any significant increase in power consumption and system power is limited to a predetermined average value to reduce system size and weight.

High Speed Beam Deflection and Blanking for Electron Lithography

Abstract: A fast magnetic deflection system and beam blanking unit have been incorporated into the electron optical column of a commercial SEM for application to electron lithography. The achieved response-time of the deflection system is about 1 μsec. Double deflection coils are located outside of a glass tube enclosing the electron beam. A thin silver film deposited on the inside surface of the tube serves to conduct charge to ground but does not significantly impede high-frequency deflection fields. A ferrite magnetic shield is placed between the deflection coils and the surrounding iron pole-piece of the objective lens. The function of the shield is to minimize the undesirable eddy currents induced in the iron by the deflection field. The response time of the beam blanking unit is about 10 nsec. The unit employs a pair of electrostatic plates which blank the beam by deflecting the latter against an aperture-stop. The center of deflection of the plates coincides with the crossover point produced by the first con...

Nonlinear analysis of orthotropic skew plates.

Abstract: The nonlinear analysis of clamped orthotropic skew plates of constant thickness subjected to a uniformlydistributed transverse load has been presented. The recently developed numerical technique of dynamic relaxation which is specially suited for nonlinear problems has been used in the present analysis. A detailed study of the large deflection behavior of rhombic-ortho tropic skew plates has been made by varying the skew angle and load. Numerical results have been obtained for a particular case of orthotropy. These results have been specialized for the case of a square plate and compared with available solutions. Representative nondimensional solutions are presented in the form of graphs to elucidate the nonlinear effect due to large deflection at higher loads. The effect of skew on the deflection and stress resultants are also discussed. Suggestions have been made for arriving at an approximate estimate of the time increment At suitable for orthotropic skew-plate analysis, which assures stability of numerical calculations.

Stationary device sensitive to torque in rotating shafts

Abstract: This disclosure relates to a stationary device for measuring stresses particularly in a rotating shaft comprising a housing, a bore in the housing, a ring-like member in the bore, a bearing assembly within the ring-like member, the bearing assembly having inner and outer races and anti-friction elements therebetween, a shaft mounted for rotation within the bearing assembly, transducer means between the bearing assembly and the housing for detecting forces caused by deflection of the shaft, and means for translating the detected deflection forces into the output torque of the shaft.

Performance of precast prestressed hollow core slab with composite concrete topping

Abstract: This load test of a machine-made hollow-core slab with composite topping verified a number of accepted industry design and fabrication practices, specifically the following: 1. Impact test hammer data taken on the side of the member provided an accurate assessment of concrete strength as determined by uncracked deflection behavior and ultimate moment capacity. 2. The observed ultimate moment was about 10 percent greater than calculations based on Eq.(18-3) in ACI 318-71 but nearly identical to calculations based on strain compatibility by Fig. 5.2.5 in the PCI Design Handbook. 3. The bilinear concept for predicting the deflection of cracked prestressed members was conservative well beyond a nominal bottom fiber tensile stress of 12i,/ f'c. 4. Composite action between the precast and cast-in place portions was evident up to ultimate load. The top surface of the precast slab was a smooth, even, machine cast finish and did not comply with Section 17.7 of ACI 318-71. There was no reinforcing steel projecting from the precast slab into the topping concrete. 5. A shear failure did not occur even though the ultimate shear stress vu was 1.75 times vc as computed in accordance with ACI 318-71.

Time dependent deflection control for ink jet printer

Abstract: An ink jet printer in which ink droplets issuing from a source serially pass through an electrically energizable deflection field which is activated at regularly recurring intervals Deflection of the drops occurs along different trajectories toward a recording medium because of the variable time each droplet is subjected to the energized deflection field The droplets which are deflected have the same physical or electrical characteristics and are not given differing charges, for example, before entry into the deflection field Both electrically chargeable droplets and magnetic droplets may be used as the marking fluid when directed according to time dependent deflection Generally, the deflection field is of sufficient length to include simultaneously all droplets which will comprise a full character stroke on the recording medium and the deflection signal is a square wave selectively applied However, deflection fields may be shortened and the applied signal may either increase or decrease with time during the energizing interval In addition, apparatus may be included to produce deflection along either of two coordinate axes and means are disclosed to select droplets required for printing while discarding others during issuance of the droplets from the source at a fixed generation rate

Failure criteria developed from aasho road test data

Abstract: Theoretical models of pavement deformation behavior such as elastic-layered theory can only be used for design purposes when failure criteria are specified. Although such models can be used to predict stress and strain states, they in no way indicate whether the material in the pavement can withstand the predicted deformations. For elastic-layered theory, limiting values of strain or stress need to be defined before the theory can be used to assist practicing engineers in the design of asphalt pavements. There is general agreement in the literature that horizontal tensile stress or strain at the bottom of a thick asphalt layer is the controlling criterion for design to prevent retetitive load cracking. Although such strains were not measured at the bottom of the asphalt layer at the AASHO Road Test, they can be inferred from a knowledge of the material characteristics mechanism of initial failure at the Road Test. Since the bituminous base sections provided a complete range of performance, from failures to survivors of over 1 million load repetitions it was possible to describe the strain history of these test sections in terms of performance. The bituminous base sections fell into three performance classifications, depending upon whether they failed the first spring of testing, survived the testing period with a low serviceability rating or survived the testing without any change in serviceability. The horizontal tensile strain, horizontal tensile stress and vertical strain on top of the subgrade data were computed for each test section in each performance classification. Asphalt moduli for a wide spectrum of deflection measurements were input into the stress and strain computations. Moduli values were determined from dynamic loading in compression. Subgrade moduli were inferred from the deflection measurements. The results of the elastic-layer computations showed that there were indeed large differences in horizontal tensile strain, horizontal tensile stress and vertical strain in the subgrade, depending upon the performance classification. Secondly, the level of strain or stress for each performance classification was a function of the asphalt base stiffness at the asphalt layer bottom. From the horizontal strain results it was apparent that asphalt pavements can tolerate higher strains at lower stiffnesses. The horizontal tensile strain and stress relationships with asphalt stiffness were converted into "load repetition to failure" relationships by relating two performance classifications to the number of load repetitions to failure. A log-log relationship was assumed. The resulting family of "fatigue-like" curves for a range of asphalt stiffnesses has been used by Witczak and is the subject of another paper to this conference. /Author/

Image enhancement apparatus utilizing variable velocity scan

Abstract: An electron beam tube with internal deflection plates to modulate the scanning velocity of an electron beam in response to a control signal. The control signal is produced in response to at least transient parts included in a video signal and supplied to the beam deflection means through condenser means fabricated by conductive films coated on the inner and outer surfaces of a neck portion of the tube.

Failure criteria developed from aasho road test data

Abstract: Theoretical models of pavement deformation behavior such as elastic-layered theory can only be used for design purposes when failure criteria are specified. Although such models can be used to predict stress and strain states, they in no way indicate whether the material in the pavement can withstand the predicted deformations. For elastic-layered theory, limiting values of strain or stress need to be defined before the theory can be used to assist practicing engineers in the design of asphalt pavements. There is general agreement in the literature that horizontal tensile stress or strain at the bottom of a thick asphalt layer is the controlling criterion for design to prevent retetitive load cracking. Although such strains were not measured at the bottom of the asphalt layer at the AASHO Road Test, they can be inferred from a knowledge of the material characteristics mechanism of initial failure at the Road Test. Since the bituminous base sections provided a complete range of performance, from failures to survivors of over 1 million load repetitions it was possible to describe the strain history of these test sections in terms of performance. The bituminous base sections fell into three performance classifications, depending upon whether they failed the first spring of testing, survived the testing period with a low serviceability rating or survived the testing without any change in serviceability. The horizontal tensile strain, horizontal tensile stress and vertical strain on top of the subgrade data were computed for each test section in each performance classification. Asphalt moduli for a wide spectrum of deflection measurements were input into the stress and strain computations. Moduli values were determined from dynamic loading in compression. Subgrade moduli were inferred from the deflection measurements. The results of the elastic-layer computations showed that there were indeed large differences in horizontal tensile strain, horizontal tensile stress and vertical strain in the subgrade, depending upon the performance classification. Secondly, the level of strain or stress for each performance classification was a function of the asphalt base stiffness at the asphalt layer bottom. From the horizontal strain results it was apparent that asphalt pavements can tolerate higher strains at lower stiffnesses. The horizontal tensile strain and stress relationships with asphalt stiffness were converted into "load repetition to failure" relationships by relating two performance classifications to the number of load repetitions to failure. A log-log relationship was assumed. The resulting family of "fatigue-like" curves for a range of asphalt stiffnesses has been used by Witczak and is the subject of another paper to this conference. /Author/