Showing papers on "Flexural rigidity published in 1993"

Flexural rigidity of microtubules and actin filaments measured from thermal fluctuations in shape.

Abstract: Microtubules are long, proteinaceous filaments that perform structural functions in eukaryotic cells by defining cellular shape and serving as tracks for intracellular motor proteins. We report the first accurate measurements of the flexural rigidity of microtubules. By analyzing the thermally driven fluctuations in their shape, we estimated the mean flexural rigidity of taxol-stabilized microtubules to be 2.2 x 10(-23) Nm2 (with 6.4% uncertainty) for seven unlabeled microtubules and 2.1 x 10(-23) Nm2 (with 4.7% uncertainty) for eight rhodamine-labeled microtubules. These values are similar to earlier, less precise estimates of microtubule bending stiffness obtained by modeling flagellar motion. A similar analysis on seven rhodamine-phalloidin-labeled actin filaments gave a flexural rigidity of 7.3 x 10(-26) Nm2 (with 6% uncertainty), consistent with previously reported results. The flexural rigidity of these microtubules corresponds to a persistence length of 5,200 microns showing that a microtubule is rigid over cellular dimensions. By contrast, the persistence length of an actin filament is only approximately 17.7 microns, perhaps explaining why actin filaments within cells are usually cross-linked into bundles. The greater flexural rigidity of a microtubule compared to an actin filament mainly derives from the former's larger cross-section. If tubulin were homogeneous and isotropic, then the microtubule's Young's modulus would be approximately 1.2 GPa, similar to Plexiglas and rigid plastics. Microtubules are expected to be almost inextensible: the compliance of cells is due primarily to filament bending or sliding between filaments rather than the stretching of the filaments themselves.

Elastic moduli of a composite of hollow spheres in a matrix

Abstract: L ow density foams deform primarily by bending of the cell edges. Their mechanical properties could be improved by increasing the flexural rigidity of the wall. The introduction of a high volume fraction of thin walled hollow spheres into a foamed matrix produces a composite cellular solid with a sandwich cell wall: the walls of the spheres act as the faces of the sandwich while the foamed matrix acts as the core. As a first step to producing cellular solids with sandwich cell walls, in this paper we describe the elastic moduli of a composite cellular solid made by introducing thin walled hollow spheres into a solid matrix.

Flexural behavior of high-strength fiber reinforced concrete beams

Abstract: Eight high-strength concrete beams with different fiber contents and shear span-depth ratios were tested to study the influence of fiber addition on ultimate load, crack propagation, flexural rigidity, and ductility. The addition of steel fibers enhanced the strength and increased the ductility and flexural stiffness of the tested beams. A semi-empirical equation is proposed to estimate the effective moment of inertia of simply supported high-strength fiber reinforced concrete beams. The estimated deflections using this equation agree well with the experimental values. At ultimate conditions, the length of the plastic hinge developed was found to be proportional to the fiber content.

Water waves on flexible and porous breakwaters

Abstract: This is a theoretical study of the reflection and transmission of small‐amplitude waves by a flexible, porous, and thin beam‐like breakwater held fixed in the seabed. The fluid motion is idealized as a linearized, two‐dimensional potential flow and the breakwater is idealized as a one‐dimensional beam of uniform flexural rigidity and uniform mass per unit length. The velocity potentials of the wave motion are coupled with the equation of motion of the breakwater. Analytical solutions in closed forms are obtained for the reflected and transmitted velocity potentials together with the displacement of the breakwater. The free‐surface elevation, hydrodynamic force acting on the breakwater, and the overturning moment are determined. The dynamic response of the breakwater in terms of bending moment and shear force are also evaluated. It is found in general that hydrodynamic force increases as structural rigidity increases. The magnitude of the force is reduced dramatically for a stiffer porous breakwater. It is...

Sedimentary loading, lithospheric flexure, and subduction initiation at passive margins

Abstract: Investigation of lithospheric flexure at continental margins by sedimentary loading has been carried out using elastic-plate theory. The geometry of mature marginal basins fits the deflection produced by loading of an infinite plate in which the flexural rigidity of the continental lithosphere is larger than that of oceanic lithosphere. Decoupling of a previously locked passive margin by reactivation of margin faults may cause the lithospheric bending behavior of the margin to change from that of an infinite plate to that of a semi-infinite plate, with a resultant increase in deflection of the marginal basin and possible subduction initiation.

The Effect of Fibre Cross-sectional Shape on Fabric Mechanical Properties and Handle

Abstract: In order to clarify the effects of different fibre cross-sectional shapes on fabric mechanical properties and handle, polyester ‘Shingosen’ fabrics of different fibre cross-sections were investigated using the KES-FB system. The results were discussed by comparing them with typical women's fine dress fabrics and the following conclusions were obtained. Polyester fabric becomes soft and deformable with an increase in the space ratio in the fibre cross-section, however, it does become inelastic and unrecoverable. FUKURAMI (fullness and softness) and SHINAYAKASA (flexibility with a soft feel) of polyester fabrics is greater with higher space ratios, but, KOSHI (stiffness) and HARI (and-drape stiffness), however, is lowered. Fabric bending rigidity is in proportion to fibre bending rigidity if all other conditions such as yarn density, count and finishing conditions remain the same. However, in general, the fabric mechanical properties and handle are controlled by the fibre assembly structure rather than fibr...

The Initial Bending Behaviour of Plain-woven Fabrics

Abstract: The relation between the flexural rigidity of a plain-woven fabric and the fabric and yarn parameters, such as thread spacing and crimp, yarn flexural rigidity, etc., is discussed. Some experimental data to test the theory are presented.

Enhancing Induced Strain Actuator Authority Through Discrete Attachment to Structural Elements

Abstract: In structural control, induced strain actuators are used by bonding them or embedding them in a structure. With bonded or embedded actuators used for inducing flexure, the developed in-plane force contributes indirectly through a locally generated moment. Control authority in this configuration is thus limited by actuator offset distance. In this paper, a new concept of flexural or shape control is presented, whereby induced strain actuators such as piezoelectric ceramic patches or shape memory alloys are attached to a structure at discrete points (as opposed to being bonded). This paper specifically addresses discretely attached induced strain actuators like piezoceramic and electrostrictive actuators which are available in the form of plates or patches, and includes actuator flexural stiffness considerations. This configuration is different from the bonded actuator configuration in two ways. One, because the actuator and the structure are free to deform independently, the in-plane force of the actuator can result in an additional moment on the structure and enhanced control. Second, the actuator can be offset from the structure without an increase in the flexural stiffness of the basic structure. This allows for the optimization of the offset distance to maximize control. Enhanced control is demonstrated by comparing the static response of a discretely attached actuator beam system with its bonded counterpart system. The advantage of this configuration over the bonded configuration is also verified experimentally.

Bending tensions and the bending rigidity of fluid membranes

Abstract: It is shown theoretically that the lateral tension associated with bending may in erect reduce the elastic resistance to curvature of fluid membranes. In particular, the spontaneous curvature of surfactant monolayers gives rise to a reduction of the bending rigidity

Factors affecting tooth movement in sliding mechanics.

Abstract: The force system operating between bracket and wire in sliding mechanics has been examined analytically using simple beam theory with the object of providing further information on the cause of bracket binding. The results were checked on an enlarged model system, and satisfactory agreement between experiment and theory was obtained. It is shown that for a given bracket tip the restoring couple varies not only with the flexural rigidity (El) of the wire, the bracket width and span length, but also with the position of the bracket along the span. In addition, as tipping occurs a net vertical force is brought into play which is initially intrusive, but becomes extrusive as retraction proceeds.

Healing of plated femoral osteotomies in dogs. A mechanical study using a new test method.

Abstract: We investigated changes in whole bone flexural rigidity during healing of plated osteotomized beagle femora. Using a recently developed mechanical method, healing femora and their intact contralateral controls were tested in non-destructive bending in 24 planes at 15 degree angular increments. The elliptical distributions of flexural rigidity were used to define 4 parameters which describe the mechanical status of a healing bone relative to its control. Plates of 3 different rigidities were used in 21 beagles; 6 for 2 months and 15 for 6 months. 2 healing efficiency parameters, describing bone rigidity, indicated that plated femora may never reach the rigidity of their controls. One of the parameters, describing bone asymmetry, showed that changes in bone asymmetry occurred early in the healing process. Results at 6 months showed no differences in rigidity and asymmetry of bones plated with the different plates. This is attributed to antagonistic effects of axial and flexural rigidities of the plates on b...

Stiffness of reinforced concrete walls resisting in-plane shear. Final report

Abstract: Reinforced concrete walls, with height to length ratios of approximately two and less, are commonly used in power-plant structures to resist earthquake effects. Determination of wall stiffness is of particular importance for establishing design forces on attached equipment. Available experimental data indicate differences between the measured initial stiffness and the stiffness calculated by assuming the wall to be uncracked. The work reported was undertaken to investigate the causes of the observed differences. Force-displacement data from three experimental investigations were analyzed in detail. It was determined that the difference between measured and calculated initial stiffness was due to volume-change cracking, often too small to be observed, occurring at the junctures of the wall with the massive slabs or griders attached to it. This phenomenon affected only the initial flexural stiffness of the wall. Initial shear stiffness was found to be unaffected. The availability of detailed experimental information enabled studies of the effect on stiffness of flexural and shear cracks in the concrete and yielding of the flexural reinforcement. A procedure is presented for constructing the force-displacement relationship for walls resisting in-plane shear. Effects on floor response spectra of the observed changes in stiffness are discussed. Possible increases with time of themore » strength and stiffness characteristics of concrete used in nuclear plant structures are estimated with the help of experimental data obtained over a duration of approximately 20 years.« less

Steel cord for reinforcing belt part of pneumatic tire for middle or heavy load

Abstract: PURPOSE:To improve penetration of rubber material and flexural strength into the face of belt layer by respectively specifying the diameter, twisting pitch, the minor axis and flatness ratio of elliptical shape and rigidity ratio of yarn stock of steel cord of single layer twisted open structure. CONSTITUTION:The diameter (d) of a yarn stock 1 of steel cord 2 of single layer twisted open structure comprising 6-8 yarn stocks, having an approximately elliptical shape is 0.23-0.38mm, twisting pitch is 40 d-50dmm and the minor axis A of elliptical shape is 2 d-3dmm. Further, the flatness ratio of the elliptical shape (the major axis B/the minor axis A) is 1.2-2.5 and rigidity ratio (flexural rigidity in the direction of the major axis/flexural rigidity in the direction of the minor axis) is 1.05-1.2.

Direct Analysis of Slender Columns with P‐Delta Effects

Abstract: A numerical method is introduced for direct analysis of nonlinear behavior of slender beam‐columns. A strain control technique in conjunction with the quasi‐Newton's method was developed to obtain the updated flexural stiffness directly for lateral deflection estimation. Numerical difficulties such as singular problems or softening behavior could be detected beforehand and overcome. This algorithm may also be formulated to trace the M‐P‐Φ curve and to calculate the current flexural stiffness for sections from very small strain to extremely large strain. Details about the principles and the formulations are given in this paper. Examples include step‐by‐step calculation results for biaxially loaded sections and analyses of slender reinforced concrete and steel columns including uniform or nonuniform cross sections. Further applications can be made to uniaxially or biaxially loaded columns constructed with most engineering materials or to enhance the performance of nonlinear frame analyses.

Free flexural vibration analysis of one-way stiffened plates by the free interface modal synthesis method

Abstract: A numerical model is presented for predicting the natural frequencies of one-way stiffened plates with ribs having high ratios of flexural to shear rigidity. The model is based on the free interface modal synthesis method. Experimental validation using floors with wood I-joists and wood-based sheathing showed that the model has good numerical accuracy in the predictions of natural frequencies and mode shapes if analyses include shear deformation and rotatory inertia effects in ribs. Neglect of these effects can lead to large errors in the predicted natural frequencies for plates with ribs having high ratios of flexural to shear rigidity. Large errors can also be encountered in natural frequency prediction for plates with fairly low ratios of flexural to shear rigidity. This occurs with mode shapes that have multiple curvature along ribs if shear deformation and rotatory inertia effects are neglected. Key words: free flexural vibration, natural frequencies, ribbed plates, flexural rigidity, shear rigidity,...

Studies on Bending at Small Hole Drilling of Printed Wiring Boards.

Abstract: In recent years, needs for drilling small diameter holes (φ0.2-0.4 mm) are increasing, accompanying the development of higher wiring density of printed wiring boards. However, the drilling of small diameter holes includes many technically difficult problems which must be solved. In contrast to drilling of normal diameter (φ0.5-1.2 mm) where epoxy smear, surface roughness of the hole wall, tool life, etc. are important, small diameter drilling has a different set of performance criteria : drill breakage, initial positional accuracy and hole bending. This investigation was conducted to examine hole positional accuracy and hole bending in relation with tool wear using φ0.4 mm drill to several kinds of glass epoxy circuit board. Furthermore, to limit initial slippage and then bending, vibrant drilling and drilling with a cross-thinned drill were carried out. A numerical analysis was executed to obtain accurate flexural rigidity of the drill which has an effect on the slippage before the drill point has stayed at a certain position and on hole bending even more. Conclusions are summarized as follows : (1) Amount of hole bending is generally affected by that of tool wear, but initial positional accuracy is less affected. (2) Hole bending develops with drilled depth without hole wondering (Burnhum, 1980). (3) Vibrant drilling is effective for minimizing hole bending but less for limiting initial slippage. (4) The effect of cross-thinning on hole bending is as evident as of vibrant drilling, but not on initial slippage.

Transverse shear effects on buckling and postbuckling of laminated and delaminated plates

Abstract: The one-dimensional buckling and postbuckling solutions of unsymmetric laminates with clamped edges subjected to constant membrane strain loads are obtained based on the large deflection shear deformation theory. Closed-form expressions of the critical buckling load and postbuckling deflection have been derived. It is found that both effects of bending-exten sion coupling and transverse shear deformation will reduce the equivalent bending rigidity and buckling load and increase the postbuckling deformation. These solutions are used to study the behavior of a thin-film strip delamination in a base laminate. The analytic form of energy release rate is obtained by a variational energy principle that shows that the slope of the energy release rate with load parameter will be decreased due to effects of both bending-extension coupling and transverse shear deformation.

Rigidity variable car body

Abstract: PURPOSE:To contribute to the ensuring of a satisfactory riding feeling without improving the rigidity of a vehicle when the satisfactory riding feeling of the vehicle under the travelling condition is prior to others and further provide an input vibration frequency from the road surface which is a frequency equal or approximate to a resonance frequency and set to the resonance condition or one approximate thereto to prevent the occurrence of uncomfortable vibrations having relatively large amplitude. CONSTITUTION:There are provided mechanisms 30-37 for adjusting the rigidity of a door part, engine hood part and rear gate part to change the bending rigidity and torsional rigidity of a car body 11 accompanied by left and right doors, engine hood and rear gates 3, 4, 7 and 9, a vibration sensor 55 for detecting the input vibration frequency from the road surface to a car body part 11 and a circuit composing part 57 for set the adjusting mechanisms 30, 37 to conditions of improving the bending rigidity and torsional rigidity of the car body part 11 when the input vibration frequency obtained on the basis of the output of vibration sensor 55 is less than a predetermined value.

Highly rigid bumper reinforcing material

Abstract: PURPOSE: To provide a highly rigid bumper reinforcing material by preventing cross-sectional deformation. CONSTITUTION: A highly rigid bumper reinforcing material is characterized in that a cross section is formed in a truss structure or a quasi-truss shape. Thereby, since the cross section is formed in a truss shape, rigidity of the cross section to flatening - shearing deformation can be heightened, and the whole rigidity can be improved. Since cross-sectional deformation is restrained, deterioration of flexural rigidity can be prevented, so that contribution to the whole rigidity becomes large. In this way, since the rigidity is improved, weight of a reinforcing material can be reduced. COPYRIGHT: (C)1994,JPO&Japio

Ground reinforcing construction method

Abstract: PURPOSE:To form a sandy layer of large flexural rigidity or a sandy layer of large strength in both the flexural rigidity and the tensile strength on a surface layer of the poor subsoil. CONSTITUTION:In the case that a soil structure 10 of banking or the like is constructed on the poor subsoil 20, a cubic structure 50, in which plastic sheets 51 of hollow structure are built in a lattice shape, is set up on the poor subsoil 20. Next, the inside of lattices 60 of the cubic structure 50 is filled with sandy soil 70 to form a sandy layer 30 of large flexural rigidity on a surface layer of the poor subsoil 20.

Spherical joint for exhaust pipe

Abstract: PURPOSE:To reconcile reduction of flexural rigidity and downsizing, and lengthen the service life of durability by preventing the occurrence of a crack of a bellows pipe. CONSTITUTION:A bellows valley part diameter D' set smaller than a pipe general part diameter D of the connecting parts 11a and 11b can reduce flexural rigidity of a joint. Radiuses of curvature Rh and Rm of the respective parts 11h and 11m are set larger than radiuses of curvature Ri and Rj of the respective parts 11i and 11j, and bending time stress concentration is prevented, and the service life of durability is lenghtened.

Slenderness of Columns in Braced Frames

Abstract: Moment-magnification factors for columns in braced frames are dependent upon column slenderness and the flexural stiffness of restraining beams. A column bent in single curvature has a flexural stiffness that can be as little as one-third that of the same column bent in reverse curvature. Column slenderness ratios (\IL\N/\IR\N) above which reverse curvature moments must be magnified are significantly higher than those for which single-curvature moments would require magnification. This paper shows that when loading conditions are considered together with framing restraints, magnified moments from the single-curvature condition rarely generate moment values as high as moments unmagnified from the reverse-curvature loading condition. Thus, without need for moment magnification, column slenderness ratios can be significantly higher than the limit ratios traditionally derived for single-curvature bending conditions of columns.

Rodlike reinforcing elastic body

Abstract: PURPOSE:To obtain the subject elastic body, having a high, flexural rigidity, excellent in corrosion, weather and water resistance and useful as a crawl frame, a pier, etc., by embedding plural core materials composed of fiber- reinforced plastic rods in a bonded state in the axial direction in a rodlike rubber. CONSTITUTION:The objective elastic body is obtained by embedding plural core materials composed of fiber-reinforced plastic (FRP) rods 2 in a mutually bonded state in the axial direction in a rubber rod 1 which is a base material.