Showing papers on "Deflection (engineering) published in 1990"

The analysis of interlaminar fracture in uniaxial fibre-polymer composites

Abstract: One of the most important mechanical properties of a fibre-polymer composite is its resistance to delamination. The presence of delaminations may lead not only to complete fracture but even partial delaminations will lead to a loss of stiffness, which can be a very important design consideration. Because delamination may be regarded as crack propa­gation then an obvious scheme for characterizing this phenomenon has been via a fracture mechanics approach. There is, therefore, an extensive literature on the use of fracture mechanics to ascertain the interlaminar fracture energies, G c , for various fibre-polymer composites using different test geometries to yield mode I, mode II and mixed mode I/II values of G c . Nevertheless, problems of consistency and discussions on the accuracy of such results abound. This paper describes a detailed study of the methods of analysing the experimental data obtained from fracture mechanics tests using double-cantilever beam, end loaded split and end notched flexure specimens. It is shown that to get consistent and accurate values of G c it is necessary to consider aspects of the tests such as the end rotation and deflection of the crack tip, the effective shortening of the beam due to large displacements of the arms, and the stiffening of the beam due to the presence of the end blocks bonded to the specimens. Analytical methods for ascertaining the various correction constants and factors are described and are successfully applied to the results obtained from three different fibre-polymer composites. These composites exhibit different types of fracture behaviour and illustrate the wide range of effects that must be considered when values of the interlaminar fracture energies, free from artefacts from the test method and the analysis method, are required.

A general formulation for the sound radiation from rectangular, baffled plates with arbitrary boundary conditions

Abstract: The radiation of sound from a baffled, rectangular plate with edges elastically restrained against deflection and rotation is analyzed. The elastic constants along the contour can be varied to reproduce simply supported, clamped, free, or guided edges as limiting cases. The formulation is based on a variational method for the vibration of the plate, and assumes no fluid loading of the structure. The elastic boundary conditions appear in the Hamiltonian of the plate through a dynamic contribution, which is expressed in terms of nondimensional edge parameters. The extremalization of the Hamiltonian is achieved using a Rayleigh–Ritz method, and both the free vibrations and the forced vibrations of the plate are presented. The radiation of sound from the plate is analyzed in the far field, and is calculated from one‐dimensional Fourier transforms. Numerical results are presented for the radiation efficiency of modes of simply supported, clamped, free, and guided plates. The values found agree well with predic...

One trip window cutting tool method and apparatus

Abstract: The present invention pertains to a device and method for drilling a secondary or deflection hole from a cased drill hole in underground rock or geologic formations. The device disclosed herein includes a deflection wedge unit mountable via a packer in the drill hole and a pilot cutting tool, all mountable to a drill string. A deflection guide actuated by deflection ramp on the deflection wedge unit initiates the deflection drilling process.

Analysis of Simply-Supported Orthotropic Cylindrical Shells Subject to Lateral Impact Loads

Abstract: The analysis is based on an expansion of the loads, displacements, and rotations in a double Fourier series which satisfies the end boundary conditions of simple support. By neglecting in-plane and rotary inertia the problem becomes a second-order ordinary differential equation in time for the Fourier coefficients of the radial deflection

Device and method for control of flexible link robot manipulators

Abstract: A method and device for controlling and dampening undesirable vibrational movement within flexible linkage of a robot arm coupled to a movable, controlled joint and attached drive motor. The method includes the steps of providing position displacement and control in accordance with position and velocity feedback input. In addition, elastic deflection arising within the robot arm is detected and a time-dependent deflection signal proportional to the degree of elastic deflection is generated. A control algorithm develops deflection feedback signals for input to the robot arm which are approximately proportional to the deflection signal and its first two time derivatives, each multiplied by a gain whose value is selected to reduce further elastic deflection. This procedure is applied within flexible robot arm structure by incorporating elastic deflection detection components and by converting the detected deflection signal to deflection feedback signals for application to the drive system of the robot arm. Elastic deflections arising upon movement of the flexible arm structure are almost immediately nullified and the robot arm is allowed to reposition itself without interference from such undesirable forces and resultant robot arm movement.

Punching of flat plates : a question of concrete properties in biaxial compression and size effect

Abstract: The paper presents a design method to predict the punching strength and deflection of flat plates at interior columns. Failure is assumed to occur when the compression zone of the slab in the vicin ...

Modeling ballistic impact into flexible materials

Abstract: The dynamic problem is approximated by a time series of static analysis problems. An algorithm is described wherein in each time step the material properties of the target and the geometry of the deflection cone are derived.An experimental program was performed involving bullets fired at Kevlar 29 fabric targets.

Aggregate interlock: a pure-shear load transfer mechanism

Abstract: A finite element investigation was made of the behavior of jointed or cracked pavement systems equipped with a pure-shear load transfer mechanism, such as aggregate interlock. Dimensional analysis was used in the interpretation of the data, leading to a general definition of the relative joint stiffness of the pavement system in terms of its structural characteristics. Results obtained in this study were verified by comparisons with earlier published field, laboratory, and analytical information. The investigation demonstrated that deflection load transfer efficiency is related to stress load transfer efficiency and that this relationship is sensitive to the size of the applied loading (or to the gear configuration). A simple back calculation procedure is outlined to evaluate the in situ joint stiffness of such pavements. Pure-shear load transfer devices are shown to be particularly desirable under a combined externally applied and thermal loading condition, since they offer no additional restraint to longitudinal curling.

Nonlinear Analysis of Thin‐Walled Structures Using Least Element/Member

Abstract: The paper presents the derivation of a deformation stiffness matrix for an asymmetric thin-walled beam-column element. This matrix KD is a function of element deformation and incorporates the coupling between axial stretching and the lateral and torsional deformations. The stiffness matrix derived and the solution procedure proposed may be used together with the linear and geometric stiffness matrices for thin-walled beam-column elements to analyze large deflection behavior of space frames comprising members in which the influence of sectorial warping in the section can be neglected. These include members with solid, tubular hollow, or angle type sections. The formulation has been applied to a variety of sample problems involving arbitrarily large deflections. Results obtained from the approach using only one element per member in most cases agree very well with independent analytical and other published finite element solutions. The proposed method is suitable for analyzing the nonlinear behavior of large space frames, such as transmission towers.

Intrarenal Pressures Generated During Flexible Deflectable Ureterorenoscopy

Abstract: Refinements in ureteroscopic instrumentation have provided flexible ureterorenoscopes of small external diameter with the capacity for active tip deflection. Despite the many advantages offered by ...

Performance of shuffle-like switching networks with deflection

Abstract: Four packet-switched networks using shuffle-exchange interconnections and deflection routing are analyzed. The first two are well-known networks based solely on shuffle interconnections, and the other two are variations in which the negative effects of deflection are reduced. Approximate state equations are given under a uniform traffic assumption. The equations predict the distribution of packet delay and can be used in situations where packets are assigned priorities. The four networks are briefly compared to each other and to Batcher-Banyan sorting networks and hypercube deflection networks. >

Mechanical design issues in laterally-driven microstructures

Abstract: The mechanical issues influencing the design and performance of laterally-driven resonant-structure micromechanical systems are identified and quantified. Two forms of resonant-structure suspensions are presented and the performance of each is calculated and compared. One represents tension-generating flexure, while the second, a ‘crab-leg’ flexure, utilizes motion-generated bending of the suspension. This second device is an unusual case of lateral motion (parallel to the substrate) with suspension elements subjected to lateral bending. The limit of linear motion (magnitude of motion subject to a constant flexural spring rate) is determined and a stress analysis is performed. An optimal design theory for each flexure is developed in which the objective is to obtain the greatest deflection per unit of allowable material stress. Preliminary results indicate that the inclusion of special design details can generate a two-to-one decrease in stress for a given level of displacement. In accordance with this optimal design theory, a prototype ‘crab-leg’ flexure is fabricated with a stress-to-displacement ratio calculated to be as low as 65 MPa/μm.

Anatomical multilayer bicycle seat

Abstract: An anatomical multilayer seat for use on a bicycle or the like The seat comprises a formed substantially rigid shell covered by a flexible cover sheet and having a layer of soft encapsulated gel material provided between the cover sheet and the seat shell The encapsulated gel layer is constrained against any appreciable lateral movement while permitting only limited deflection of the gel during use by a lower formed foam layer provided between the shell and the cover sheet to produce a controlled graduated support for the rider If desired, a second upper layer of a resilient material can be advantageously provided between the gel layer and the cover sheet of the seat for encapsulating the gel layer The invention also includes a method for making the anatomical multilayer seat

Use of magnetic forces to control distance in a surface force apparatus

Abstract: A simple system that permits the surface separation to be varied smoothly and accurately in a surface force apparatus is described. It is based on the deflection of the force-measuring spring in a magnetic field gradient created by a current passing through two coils. The resulting displacement of the surface is highly linear with applied current and free of hysteresis over separations of 10 mu m or more. This allows the accurate measurement of the force between two surfaces by monitoring the difference between expected and observed spring deflection (using, for example, multiple-beam interferometry).

Ultimate Strength of R.C. Wall Panels in Two‐Way In‐Plane Action

Abstract: Test results of 24 reinforced concrete wall panels in two-way action (i.e., supported on all the four sides) and subjected to in-plane vertical load are presented. The load is applied at an eccentricity to represent possible accidental eccentricity that occurs in practice due to constructional imperfections. Influences of aspect ratio, thinness ratio, slendemess ratio, vertical steel, and horizontal steel on the ultimate load are studied. Two equations are proposed to predict the ultimate load carried by the panels. The first equation is empirical and is arrived at from trial and error fitting with test data. The second equation is semi-empirical and is developed from a modification of the buckling strength of thin rectangular plates. Both the equations are formulated so as to give a safe prediction of a large portion of ultimate strength test results. Also, ultimate load cracking load and lateral deflections of identical panels in two-way action (all four sides supported) and oneway action (top and bottom sides only supported) are compared.

Modulus: a microcomputer-based backcalculation system

Abstract: MODULUS is a microcomputer-based backcalculation system that can be used on 2-, 3-, or 4-layer pavement systems with or without rigid bedrock layers. It uses a linear elastic program to generate a data base of deflection bowls. Once generated, a pattern search routine is used to fit measured and calculated bowls; error minimization is rapid, less than 5 sec per bowl on a 386 type microcomputer. The system is general purpose and can process data from any nondestructive testing device. The user has several options when performing backcalculations, including specifying the depth to bedrock or using existing default data bases for common pavement structures. Outputs include a summary listing showing the mean and variances of moduli values and also a graphical output that plots moduli values along a project and automatically performs subsectioning according to the recommended AASHTO procedure. The MODULUS system is described together with discussion on continuing efforts to validate the moduli values. These validations include (a) comparison of laboratory and field moduli values, and (b) the use of multidepth deflectometers to monitor deflections within the pavement system. The results of monthly deflection measurements on experimental pavements around the state of Texas are also described. Finally, current efforts to improve the MODULUS system are described. These attempts include automatically estimating the depth to bedrock using either the error minimization or zero deflection approach.

Portable machine tool

Abstract: A machine tool comprises an elongated beam adapted to be supported in a horizontal orientation at two locations spaced apart therealong and adapted to support a machining head. Tensioning bars extend parallel to the beam and engage the beam at opposite ends thereof. At least one of the tensioning bars is below the medial plane of the beam, and the tensioning bars are selectively operable to eliminate deflection from the beam.

Shear reinforcement for deflection ductility of flat plates

Abstract: The deflection ductility of flat plates with different types of shear reinforcement is tested. Excellent performance is achieved with a combination of bent bars and stirrups, even at reinforcement ...