Showing papers on "Flexural rigidity published in 1998"

Influence of rigidity on laterally loaded pile groups in marine clay

Abstract: Pile-supported marine structures are designed for significant amounts of lateral load. In this paper, the influence of parameters like flexural rigidity of pile material, embedment length of pile, and arrangement of piles with respect to the direction of loading on the behavior of laterally loaded pile groups has been studied through an experimental program. The results obtained from lateral load tests carried out on model pile groups arranged at different spacings and embedded in a marine clayey bed are presented and discussed. The results indicate that the lateral load capacity of the pile group depends mainly on the rigidity of pile soil system for different arrangements of piles within a group. This is further substantiated by a simplified finite element analysis bringing in the differences in passive resistance. The group efficiencies under lateral loading obtained from the present investigation are found to be in good agreement with the predictions of earlier researchers.

Mechanical properties of thin films from the load deflection of long clamped plates

Abstract: A plane-strain load-deflection model for long plates clamped to a rigid support is developed. The analytical model describes the nonlinear deflection of plates with compressive or tensile residual stress and finite flexural rigidity under uniform load. It allows for the extraction of the residual stress and plane-strain modulus of single-layered thin films. Properties of compressively and weakly prestressed materials are extracted with an accuracy achieved previously only with tensile samples. Two approximations of the exact model are derived. The first reduces the plates to membranes by neglecting their flexural rigidity. Considerable errors result from this simplification. The second approximation provides an exact expression for the linear plate response. Using the model, mechanical properties were extracted from two plasma-enhanced chemical-vapor deposition (PECVD) silicon nitride films with weakly tensile and compressive prestress, respectively. Measured residual stresses are 1.3/spl plusmn/3.8 and -63/spl plusmn/12.4 MPa, respectively. Corresponding plane-strain moduli are 134.4/spl plusmn/3.9 and 142/spl plusmn/2.6 GPa, respectively.

Boundary layers and non-linear vibrations in an axially moving beam

Abstract: The non-linear oscillations of a one-dimensional axially moving beam with vanishing flexural stiffness and weak non-linearities are analysed. The solution of the initial-boundary value problem for the partial differential equation that describes the motion of the beam when two parameters related to the flexural stiffness and the non-linear terms vanish is expanded into a perturbative double series. Two singular perturbation effects due to the small flexural stiffness and to the weak non-linear terms arise: (i) a boundary layer effect when the flexural stiffness vanishes, (ii) a secular effect. Some tests are performed to compare the “first order” perturbative solution with an approximate solution obtained by a finite difference scheme. The effect of the oscillation amplitude combined with the presence of small bending stiffness and axial transport velocity is investigated enlighting some interesting aspects of axially moving systems. The value of the perturbative series as a computational tool is shown.

On the effect of the fiber orientation on the flexural stiffness of injection molded short fiber reinforced polycarbonate plates

Abstract: The through-thickness fiber orientation distribution of injection molded polycarbonate plates was experimentally determined by light reflection microscopy and manual digitization of polished cross sections. Fiber length distribution was determined by pyrolysis tests followed by image analysis. A statistical analysis was done to determine the confidence limits of the fiber orientation results. The fiber orientation distribution was described by using second-order orientation tensors. The through-thickness stiffness variations were determined by the orientation averaging approach. This layer stiffness distribution was used to simulate the behavior of beams subjected to three point bending with a FEM Ansys model. The results were compared with experimentally determined flexural stiffness both in the flow direction and in the transverse flow direction. The effect of flow rate and melt-temperature on stiffness and fiber orientation is discussed.

Mechanical properties of perforated and partially demineralized bone grafts.

Abstract: Changes in flexural rigidity and compression strength of 18 sheep tibias were investigated after laser perforation and partial demineralization. Test bones were divided into three groups: Group 1, no treatment; Group 2, laser hole grid; and Group 3, laser hole grid and partial demineralization. Starting in the anterior direction at the tibial tuberosity, the flexural rigidity was determined using a nondestructive four-point bending test. The elliptical distribution of the flexural rigidity before and after a specific treatment was compared. After the bending test, a cylindrical center section of each test bone was loaded axially to failure to determine subsequent changes in compression strength. Results showed that perforation alone produced minimal reduction of rigidity and insignificant changes in compression strength. However, additional partial demineralization resulted in larger reductions. In compression testing, perforated and partially demineralized bone specimen showed marked decrease of the ultimate failure stress. The observed increase in failure strain appeared to be related to compression of the laser holes. The findings of this study suggest that partial demineralization and perforation can be applied to diaphyseal bone grafts and that their decreased mechanical properties are a function of the bone volume reductions produced by both processes.

The bending to stretching transition of a pressurized blister test

Abstract: The mechanical behavior of a thin blistering film under a uniform pressure changes from a bending to a stretching membrane as the thickness and flexural rigidity decrease. An analytical solution is found for the elastic response and the strain energy release rate based on an average membrane stress approximation.

Integral equation methods in plane-strain elasticity with boundary reinforcement

Abstract: In this paper, a linear theory of elastic boundary reinforcement of an elastic solid is developed for plane–strain deformations. The reinforcement consists of a thin elastic coating bonded to part of the boundary of the solid. The elastic properties of the coating incorporate both extensibility and bending rigidity. Interior and exterior mixed–boundary problems are formulated and solved using integral equation methods. The boundary value problems are reduced to systems of singular integro–differential equations to which Noether–type theorems are shown to apply. The case corresponding to a coating which has only extensibility properties and no bending rigidity is particularly interesting from a mathematical point of view and is given special attention. Finally, existence and uniqueness results are presented for both interior and exterior reinforcement problems of plane–strain.

On-Line Measurement of Fabric Bending Behavior Part II: Effects of Fabric Nonlinear Bending Behavior

Abstract: A generalized fabric bending model is developed based on the nonlinear bending moment-curvature relationship of fabrics. This model makes it possible to theoretically investigate the effects of fabric nonlinear bending behavior on measured bending prop erty values. The dependence of measured parameters (e.g., bending length, bending rigidity) on the conditions for the cantilever and heart loop, loop 3, and loop 4 tests is determined theoretically. Calculated results show good agreement with experimental observations reported in the literature for the cantilever and heart loop. An important discovery in this investigation is that the bending length values calculated and measured from loop 3 and loop 4 are not influenced by fabric sample length if that length is beyond a certain critical value.

Colonoscope flexural rigidity measurement.

Abstract: A testing device is developed that determines the stiffness, or flexural rigidity, of an endoscope at specific locations down its length by subjecting it to a compressive axial force, a situation similar to the actual forces applied to the endoscope during a clinical procedure. The endoscope is made to deform in a similar fashion to a slender buckled column and the force causing this deformation is related to the flexural rigidity using column buckling theory. A direct relationship between the critical load needed to cause buckling and the square of column length L is demonstrated experimentally and is expected theoretically, giving confidence in the application of column buckling theory to endoscope testing. Additional confidence in the validity of the columnbuckling test results is obtained by their similarity to data obtained by subjecting the endoscope to a transverse load, determining deflection, and modelling the endoscope as a bent elastic beam. Several makes and models of endoscopes were tested, with flexural rigidity values typically ranging between 160 to 240 Ncm2. The effect of a metal stiffener inserted in an endoscope's accessory channel is quantified, as is the change in flexural rigidity down the insertion shaft of a graded-stiffness endoscope. Significant differences in flexural rigidity were obtained between identical endoscopes, each sharing similar usage histories, indicating the need for flexural rigidity measurements for each individual endoscope of a particular model line, though a more extensive study is required to reliably determine scope-to-scope stiffness variations for a particular model line.

A predictive model for the penetration force of a woven fabric by a needle

Abstract: Proposes an algorithm for the computation of maximum needle penetration force; it introduces the direct dependence of penetration force on fabric structural parameters and warp and weft geometrical and mechanical properties. Uses the approach to the simulation of local deformation of woven material which accounts for the thread resistance to crimp change and friction forces when the thread is shifted from its original position in the fabric structure as the result of its interaction with a needle. The resistance of threads to tension caused by a needle pushing them from their straight‐line paths is also accounted for. The resulting formulae give the dependence of needle penetration force for a plain‐woven fabric on the following parameters: needle diameter and surface angle; warp and weft spacing, dimensions, crimp height and bending rigidity; friction coefficients thread‐thread and thread‐needle. For a non‐plain‐woven fabric the linear dependence of penetration force on the fabric tightness is suggested. The comparison with the published and specially measured penetration force data proves the predictive ability of the model to be qualitatively accurate and quantitatively reasonable.

Analysis of plain-weave composites subjected to flexure

Abstract: Techniques were developed for analyzing plain-weave composites subjected to flexure. These techniques were based on the solutions for an infinite array of unit celts subjected to extension and flexure. Periodic boundary conditions were derived for flexure of the configuration. (Periodic boundary conditions for extension already have been documented in the literature.) The stress distributions and homogenized moduli from the infinite array can be used with simple formulas to predict the variation of flexural stiffness with thickness and the distribution of stresses in thick but finite specimens. For exterior mats, where the accuracy of the predictions was poor, an alternative procedure was developed that gives quite accurate predictions.

Flexural Rigidity of Laboratory and Surgical Substitutes for Human Fibular Bone Grafts

Abstract: The purpose of this study was to measure flexural rigidity of two new synthetic fibular graft substitutes, and compare these data to the flexural rigidity of natural human fibulas. These substitutes were composite fiberglass surrogate fibulas, to be used in laboratory experimental studies, and porous tantalum cylinders, being researched as a bone graft substitute. Ten fiberglass surrogate fibulas and 13 porous tantalum rods were tested in a 4-point bending fixture. Both types of fibular graft substitute had flexural rigidities comparable to natural human fibulas. The fiberglass surrogate fibulas had much less inter-specimen variability in flexural rigidity than did the natural human fibulas (6%/10% vs. 36%/52% for A-P/M-L directions). The surrogate fibula is therefore appropriate for use in laboratory experimental studies of fibular grafts which will undergo bending. The flexural rigidity of the porous tantalum rods increased with relative density to the 1.2 power, as suggested by theory and empirical data for porous solids; thus, porous tantalum density and rod diameter can be varied to obtain the desired flexural rigidity.

Composite steel beams using precast concrete hollow core floor slabs

Abstract: The main aim of this thesis is to develop an insight into the behaviour of composite floors that utilise steel beams acting in combination with precast concrete hollow core floor slabs and to produce design recommendations for use by industry for this type of construction. Full scale bending tests of proprietary precast prestressed concrete hollow core unit floor slabs attached through 19mm diameter headed shear studs to steel Universal Beams (UB) have been carried out to determine the increased strength and stiffness when composite action is considered. The results show the bending strength of the composite beam to be twice that of the bare steel beam, and its flexural stiffness to be more than trebled. In addition to the beam tests, isolated push-off tests and horizontal eccentric compression tests were used to study the horizontal interface shear resistance of the headed studs and the strength of the slab, respectively. Maximum resistances were compared with the predictions of the Eurcode EC4, and a reduction formula for the precast effect derived. In addition to the experimental investigations, finite element (FE) studies were also conducted using the FE package ABAQUS to extend the scope of the experimental work. Results show a 2-dimensional plane stress analysis to be sufficiently accurate, providing the correct material input data obtained from isolated push-off and compression tests are used. The FE model for the composite beam was designed and validated using the full scale beam tests. A parametric study, involving 45 analyses, was carried out to cover the full range of UB sizes and floor depths used in practice. From the finite element work, design charts are formulated which may be used to simplify the design rules. Given the results of this work, a full interaction composite beam design may be carried out using the proposed design equations. The results show that precast slabs may be used compositely with steel UB's in order to increase both flexural strength and stiffness at virtually no extra cost, except for the headed shear studs. The failure mode is ductile, and may be controlled by the correct use of small quantities of transverse reinforcement and insitu infill concrete.

Shaft for light-weight golf clubs

Abstract: A golf club shaft is 35-50 percent lighter than a conventional shaft while maintaining the outer diameter and structural characteristics of conventional shafts. The shaft has at least four layers of fiber reinforced material. The fiber reinforced layers are from innermost to outermost: a first angled layer; a first straight layer; a second angled layer; and a second straight layer. The angled layers are formed by bonding together two materials, each with fibers aligned in different directions. The second angled layer maintains the proper strength and rigidity of the shaft while keeping the shaft as light weight as possible. Aligning the second layer's fibers at an angle of 35-75 degrees with respect to the longitudinal direction of the shaft ensures proper weight and strength characteristics of the shaft. The resulting shaft is light-weight and exhibits the flexural rigidity, flexural strength, torsional rigidity, torsional strength, and crushing strength of conventional shafts.

Method and equipment for measuring flexural rigidity

Abstract: PROBLEM TO BE SOLVED: To calculate flexural rigidity from measurements according to a predetermined theoretical formula by measuring a bending reaction acting on one plane through a reaction measuring means when a wire is held by a wire holding means comprising a positioning means for holding the wire while bending the intermediate part thereof into a U-shape. SOLUTION: The wire holding means 3 comprises the positioning means 2(2a, 2b) mounted on two planes 1 and/or two parallel plans 1(1a, 1b) facing each other and holding a wire T at two intermediate parts thereof while bending into a U-shape. A bending reaction W acting on one plane 1b is measured through a reaction measuring means 4 when the wire T is held by the wire holding means 3. The gap between opposite parallel planes 1(1a, 1b) is decreased by moving an interplane gap setting means 5 downward and the wire T is bent in U-shape thus matching the distance between the centers of the wire T at the opposite ends thereof with a specified value. Finally, flexural rigidity is calculated from the reaction W.

Kawabata evaluation of enzyme-treated cotton knitted fabric

Abstract: Industrial trial of the enzymatic treatment of cotton knitted fabric widt cellulase enzyme Denifade has been carried out under optimised conditions and the various low-stress mechanical properties of the treated fabrics have been assessed in the Kawabata system. The results show an improvement in the surface smoothness and a decrease in the bending and shear rigidities. The improvement in handle is reflected by the decrease in tensile and compressional energies.

Parameters Back-Calculation for Concrete Pavement with Two Slab Layers

Abstract: This paper presents a new procedure for back-calculating the properties of a concrete pavement with two slab layers using deflection measurements from nondestructive deflection testing. The two slab layers are first represented by an equivalent single slab layer based on the principle of equivalent flexural rigidity. In the back-calculation analysis, the pavement deflection response under load is evaluated using an analytical model for a slab supported on an elastic foundation. Employing a closed-form back-calculation algorithm, it is shown that the back-calculated equivalent radius of relative stiffness and subgrade modulus are unique and independent of the characteristics of the two slab layers. It follows that the equivalent flexural rigidity for the two slab layers is also unique. The next step employs a trial-and-error algorithm to back-derive the moduli of the two slab layers by matching the equivalent flexural rigidity. An upper bound and a lower bound to the modulus can be established for the slab layer with the higher modulus. Similarly, an upper bound to the modulus can be found for the slab layer with the lower modulus. Four numerical examples are presented to demonstrate the use of the proposed back-calculation method.

Sheet metal forming analysis of planar anisotropic materials with a proper numerical scheme for the blank holding force

Abstract: A modified membrane finite element with a proper formulation for planar anisotropic materials is introduced to correctly enhance the flexural rigidity not only within an element but among elements. The strain energy term in the formulation is decomposed into the membrane energy term for mean stretching and the bending energy term for pure bending. This procedure needs careful evaluation for the orientation of the anisotropic axes. The formulation is then combined with an effective algorithm to deal with the contact between the material and the dies. Distribution of the blank holding force is calculated in each step according to the thickness in the flange region. The calculation employs a special relation between the thickness and the blank holding force. The simulation examples demonstrate the validity and versatility of the computer code by showing the earing phenomenon in circular cup drawing and the variation of the blank holding force in rectangular cup drawing. The results shows that the thickness variation in the flange region redistributes the blank holding force during the deformation. The present algorithm can predict more precise contour lines in the flange region and a more precise shape and strain distribution.

Sandwich-structured, polystyrene-cored surf board has fiberglass- and carbon-reinforced epoxy skin in design optimizing lightness, impact-resistance, responsiveness, damping and resilience

Abstract: The sandwich structure comprises a calibrated core (4) in soft foam, e.g. polystyrene, with a skin (3) especially in glass- and carbon fiber. This is initially adhesively-impregnated, especially with epoxy resin. It is then polymerized under vacuum, flattening it down. The sandwich structure comprises a calibrated core (4) in soft foam, e.g. polystyrene, with a skin (3) especially in glass- and carbon fiber. This is initially adhesively-impregnated, especially with epoxy resin. It is then polymerized under vacuum, flattening it down. For lightness and flexibility, a hull zone can be made more sensitive to point impacts (than in conventional practice), being only stressed by the water. This also avoids too much bouncing resulting from excessive rigidity in the assembly. Longitudinal reinforcement allows control of flexural rigidity when the board is used out of balance, to the front or to the rear. This reinforcement is especially made of unidirectionally-aligned carbon fiber. Polyurethane-based paint, or other protective finish is applied. An Independent claim is included for the corresponding method of manufacture.

Receiving device for paper sheet and the like

Abstract: PROBLEM TO BE SOLVED: To receive it easily and surely even if it is a sheet member having a way of bending or a sheet member of relatively weak elasticity by feeding the sheet member in a curved state for improving flexural rigidity of the sheet member cooperated with a first feed roller. SOLUTION: When a bank bill 122 carried in a carrying passage is pinchedly held between a carry roller 78 and a carry roller 114 so as to be carried, it is curved downward by guide rollers 106, 108. Consequently, even if it is a bank bill having a way of bending, it can be introduced while being corrected into a curved shape. Further, in case of a bank bill 122 of relatively weak elasticity, the flexural rigidity is enlarged by being corrected into a downward curved shape, and it is led onto the arm of a presser member so that the extreme end of the bank bill 122 is not slided on the surface of the already received bank bill 122 due to hanging down of the extreme end in a receiving chamber. As a result of this, without being affected by the loading state of bank bills 122 already loaded on the arm of the presser member, the bank bill 122 is smoothly introduced.

Support member for orthosis and orthosis using it

Abstract: PROBLEM TO BE SOLVED: To reduce the weight and thickness, and improve rigidity, durability and air permeability by making triaxial woven fabric reinforced plastic into a sheet shaped molding SOLUTION: For example, a triaxial woven fabric 1 with a weave density of about 182 is woven by a bundle of about 6000 carbon fibers with a tensile strength of about 3609 kgf/mm and a tensile elastic modulus of about 23500 kgf/mm The triaxial woven fabric 1 is impregnated with a resin component composed of an epoxy resin to form a pre-preg 2 The pre-preg 2 is fixed along the cylindrical wood pattern with a diameter of about 150 mm, bent and put in a hot blast stove to be hardened After cooling, the triaxial woven fabric reinforced plastic molding is formed by cutting By this arrangement, the molding having excellent bending rigidity, METSUKE, air permeability, application feeling, and indicating performance can be obtained

Body bending vibration reducer for rolling stock

Abstract: PROBLEM TO BE SOLVED: To reduce bending vibration which is impaired by the decrease of bending rigidity in accordance with the light weight of a body. SOLUTION: A movable mass unit 5 which is mounted under the floor at the center of a body 1 via a spring 4 is controlled to be moved by an actuator 7 after a gain and a phase at the central part of the body as a detection result by an up-and-down vibration detecting means 6 are compensated by a controller 8, to reduce the primary bending vibration of the body. The movable mass unit with a mass being 10-20% of conventional one is used to bring sufficient bending vibration reducing effect.

Rigidity reinforced iron golf head

Abstract: PROBLEM TO BE SOLVED: To provide high rigidity by reinforcing a part of a golf club head having a comparatively low elastic modulus manufactured by using a titanium alloy and metallic glass as a main material. SOLUTION: In a golf head having a face to constitute the ball hitting surface, average flexural rigidity of the face part is set not more than 16,000 kgf.mm 3 , and in the top blade part, rigidity is reinforced by a material having an elastic modulus not less than 15,000 kgf/mm 2 . Therefore, a carry can be improved by inexpensively/easily reinforcing/increasing rigidity. COPYRIGHT: (C)1999,JPO

Discrete Solid-On-Solid Model of Interface with Bending Rigidity: Restricted and Unrestricted Step Sizes

Abstract: We report the results of imposing a physically motivated restriction on the step sizes in a (d + 1)-dimensional discrete solid-on-solid (SOS) model, which we have proposed recently (Phys. Rev.E54, 2670 (1996)) for a d-dimensional interface with bending stiffness and interfacial tension. We clarify some features of this model in the absence of such restrictions. We also draw analogies between the relaxation to thermally roughened equilibrium states of these SOS models and nonequilibrium growth of some kinetically roughened model surfaces.

Composite laminated material

Abstract: PROBLEM TO BE SOLVED: To provide a composite laminated material light in weight and excellent in flexural rigidity. SOLUTION: A composite laminated material comprises outer layers and an inner layer. Each of the outer layers includes at least one layer consisting of a glass continuous long fiber and a polypropylene resin reinforced composite material. The inner layer includes at least one layer consisting of a polypropylene resin reinforced composite material and a glass short fiber having a diameter of 6-25μ and a length of 2mm or more. The composite laminated material has the following characteristics. (1) Density [ρ](g/cm ): 0.6 ): 900<=Eb.

Member for mounting bush

Abstract: PROBLEM TO BE SOLVED: To improve flexural rigidity, and reduce costs, in a bush mounting member provided with a bush mounting part for mounting a bush on a part on a member main body which is formed of a rod shaped metal extrusion member and which is bent in a nearly V-shape in a longitudinal direction around a bending part. SOLUTION: A member main body 10 is formed by bending a rod shaped aluminum extrusion member at an intermediate part of a longitudinal direction. In the bending part 11, plastic deformation work is carried out for increasing a geometrical moment of inertia. Change of curvature radius is inhibited with respect to a load of a direction where the curvature radius of the bending part 1 is changed, by the plastic deformation work. COPYRIGHT: (C)1999,JPO

Method of determination of bending rigidity of objects made of composition materials

Abstract: FIELD: testing technology. SUBSTANCE: series of identical objects to be examined is cut preliminarily into specimens in every rated section. Specimens are loaded with tensile force, modulus of their elasticity is determined, and dependence of distribution of modulus mean-statistic values for object length are found. They are used for calculation of rigidity of object being examined. This done, objects are subjected to identification by bending rigidity. For this purpose every object under test is secured as cantilever, loaded with static force in elastic deformation area, maximum deformations are measured in every rated section, and maximum deformations in the same sections are calculated. If difference of measured and calculated deformations exceeds preliminarily estimated maximum permissible error Δepsi of deformation measuring method selected, actual bending rigidity is determined in every section of construction being examined by multiplying rated rigidity by relation of calculated deformation to measured one. EFFECT: enhanced measurement accuracy. 4 dwge