Showing papers on "Flexural rigidity published in 1995"

Rigidity of microtubules is increased by stabilizing agents.

Abstract: Microtubules are rigid polymers that contribute to the static mechanical properties of cells. Because microtubules are dynamic structures whose polymerization is regulated during changes in cell shape, we have asked whether the mechanical properties of microtubules might also be modulated. We measured the flexural rigidity, or bending stiffness, of individual microtubules under a number of different conditions that affect the stability of microtubules against depolymerization. The flexural rigidity of microtubules polymerized with the slowly hydrolyzable nucleotide analogue guanylyl-(alpha, beta)-methylene-diphosphonate was 62 +/- 9 x 10(-24) Nm2 (weighted mean +/- SEM); that of microtubules stabilized with tau protein was 34 +/- 3 x 10(-24) Nm2; and that of microtubules stabilized with the antimitotic drug taxol was 32 +/- 2 x 10(-24) Nm2. For comparison, microtubules that were capped to prevent depolymerization, but were not otherwise stabilized, had a flexural rigidity of 26 +/- 2 x 10(-24) Nm2. Decreasing the temperature from 37 degrees C to approximately 25 degrees C, a condition that makes microtubules less stable, decreased the stiffness of taxol-stabilized microtubules by one-third. We thus find that the more stable a microtubule, the higher its flexural rigidity. This raises the possibility that microtubule rigidity may be regulated in vivo. In addition, the high rigidity of an unstabilized, GDP-containing microtubule suggests that a large amount of energy could be stored as mechanical strain energy in the protein lattice for subsequent force generation during microtubule depolymerization.

Buckling of a single microtubule by optical trapping forces: direct measurement of microtubule rigidity.

Abstract: As major determinants of cell shape and polarity, microtubules are required to have suitable rigidity. However, our knowledge of the mechanical properties of microtubules is far from satisfactory. We report here a new method of measuring the flexural rigidity of a single microtubule by direct buckling using the optical trapping technique. Microtubule buckling was induced by applying a small longitudinal compressing force through an optically trapped microsphere that was firmly attached to the microtubule. Three ways of estimating the flexural rigidity of a continuous slender rod, one from the observed critical load of buckling and two from deflected lengths and angles of bending, yielded values which agreed well when applied to the analysis of buckling microtubules. Unexpectedly, we found that the rigidity was not constant as expected but was dependent on microtubule length. This length dependency explains the discrepancies among reported values of microtubule flexural rigidity measured by different methods. Comparing microtubules of identical lengths, microtubules assembled with brain-derived associated proteins (4 × 10−23 Nm2 at around 10 mm in length) were four times more rigid than those assembled from purified tubulin and stabilized with taxol (1 × 10−23 Nm2). © 1995 Wiley-Liss, Inc.

The Bending Rigidity of Phosphatidylcholine Bilayers: Dependences on Experimental Method, Sample Cell Sealing and Temperature

Abstract: The bilayer bending rigidities were measured for the same spherical vesicles with two methods, fluctuation mode analysis and electric deformation. In some of the sample cells the glue sealing the cell was in direct contact with the sample, in others the sample was shielded from the glue by a silicone grease. The values of the rigidity, while being lowest and practically equal for the unshielded samples, differed significantly between methods for the shielded ones. We also measured the temperature dependence of the bending rigidity. The dependence of the rigidity on method seems to suggest the existence of a membrane superstructure

Flexural Stiffness of Injection Molded Glass Fiber Reinforced Thermoplastics

Abstract: Using a simulated laminated-plate model, an analytical method is presented for predicting stiffness of fiber reinforced injection moldings including the effects of fiber orientation and fi...

FAST – Fabric Assurance by Simple Testing

Abstract: Describes the FAST system, developed by CSIRO for quality control and assurance of fabrics. FAST, or Fabric Assurance by Simple Testing, consists of a series of instruments and test methods which are inexpensive, robust and simple to use. It measures properties which are closely related to the ease of garment making‐up and the durability of worsted finishing. FAST‐1 gives a direct reading of fabric thickness over a range of loads with micrometre resolution. FAST‐2 measures the fabric bending length and its bending rigidity. FAST‐3 measures fabric extensibility at low loads as well as its shear rigidity. FAST‐4 is a quick test for measuring fabric dimensional stability, including both the relaxation shrinkage and the hygral expansion.

Stacks of Fluid Membranes under Pressure and Tension

Abstract: Stacks of non-intersecting fluid membranes which are governed by bending rigidity and lateral tension and hold together by an external pressure are studied theoretically using Monte Carlo simulations. Thermal shape fluctuations give rise to an effective repulsion between the individual membranes, which depends sensitively on the relative strength of bending rigidity and lateral tension. For tensionless stacks, the strength of this repulsion is by a factor of two smaller than previously estimated and does not depend on the number of membranes in the stack within the numerical accuracy. For a pair of two membranes, the universal scaling form of this repulsion is determined for varying ratios of the bending rigidity and the surface tension.

Twist-to-bend ratios of woody structures

Abstract: Flexural rigidity (Eη, or resistance to bending loads, and torsional rigidity (GJ), or resistance to twisting loads, were measured on a variety of woody structures-bamboo culms, three kinds of hardwood trunks, two softwood trunks, two vines, and pine roots. The ratios of these rigidities, EI/GJ, was highest and relatively constant for bamboo and hardwoods, slightly lower for softwoods, and lower still for vines and roots. All values were substantially above those for circular cylinders of ordinary isotropic materials; since all specimens were nearly circular in cross-section, the high values reflect the elastic moduli of wood rather than geometric factors. While all material showed substantial creep under torsional loading, only the vine, Wisteria, crept appreciably under flexural loading as well.

Prebuckling Deformations and Flexural-Torsional Buckling of Arches

Abstract: When the ratio of the minor axis flexural stiffness to the major axis flexural stiffness is not small, classical analysis may lead to an inaccurate prediction of the flexural-torsional buckling loads of an arch, because prebuckling in-plane deformations change the curvature of the arch. A systematic treatment of the effects of prebuckling in-plane deformations on the elastic buckling of monosymmetric arches is presented in this paper. Nonlinear relationships between the displacements and the strains are obtained using position vectors. Energy equations are formulated for the elastic flexural-torsional buckling of monosymmetric arches, which include the effects of prebuckling in-plane deformations, and closed-form solutions are obtained for arches in uniform bending. The effect of the arch slenderness on flexural-torsional buckling is investigated. Comparisons with the existing theoretical solutions are made.

Flexural rigidity in partially demineralized diaphyseal bone grafts.

Abstract: Control of biomechanical properties of demineralized diaphyseal bone allografts is required for their clinical application. Therefore, the changes in flexural rigidity in human fibulae were investigated as a function of the demineralization depth using a nondestructive bending test. Starting at the facies medialis, the flexural rigidity was determined in 24 planes at 15 degrees sequential angular increments, which allowed data collection around the circumference of the bone. Test bones included 4 pairs of left and right human fibulae and 15 single fibulae. The elliptical distribution of the flexural rigidity of left and right fibulae and single fibulae before and after demineralization was compared. The stiffness index and the area ratio were defined as parameters to describe the mechanical status of the test bones. Results show that the rigidity of diaphyseal bones is strongly dependent on the reduction of their cortical thickness by demineralization. A mathematical model allowing prediction of the reduction of the rigidity of diaphyseal bone grafts as a function of the demineralization depth is presented.

Structural Modeling of Double-Braided Synthetic Fiber Ropes

Abstract: This study is primarily concerned with the performance of double-braided ropes. widely used in marine applications. The mechanical properties of such ropes are ob tained by combining their structural features and the constitutive behavior of individual rope components. Emphasis in this study is on the tensile behavior of straight ropes as well as bent ropes, either an eye splice or in a continuous loop around a bollard- like pin. In the former case, precycling and water effects on the model predictions are discussed. For new small ropes, bending rigidity is negligible, so the bending effect is considered by modifying the geometry of the rope to allow for variation of helix periods and change of cross-sectional shapes from circular to elliptical ( flattened ) . For two extreme frictional conditions considered, i.e., infinite and zero friction, predictions of small nylon rope behavior agree well with experimental results for both simple tension and tension plus bending. There is less agreement for small PET...

Torsional buckling and vibrations of a flexible rolled-up solar array

Abstract: An analysis of torsional behavior in a flexible rolled-up solar array is presented. The study is in three parts: (1) buckling in torsion, (2) the effect of an initial imperfection during deployment, and (3) free vibration analysis. The effect of axial forces on torsional natural frequencies is established for varying blanket tension. Computations are based on data representative of the Hubble Telescope solar array design. Numerical results show that buckling loads and natural frequencies in torsion are significantly smaller than corresponding values in bending, and the first buckling load in torsion is near the load imparted by the pretensioned solar blanket. Also, an imperfection before deployment will grow as the BiSTEMS are deployed. Under normal operating conditions, the solar arrays may experience a static twist. Nomenclature Bi-STEM: P =torsional buckling eigenvalue 6 ,E =flexural eigenvalues O r =angle of twist I = flexural buckling eigenvalue S , C =torsional eigenvalues PA =mass per unit length 4 =flexural eigenfunction Jr = torsidnal eigenfunction o =solar array natural frequency A =cross-sectional area EI‘ =warping rigidity EI =flexural rigidity GJ =torsional rigidity IE =sum of area moments of inertia 4 =mass moment of inertia about centerline L =length M =bending moment "Research Assistant, currently pursuing graduate studies at University of Minnesota, Minneapolis, MN ?Professor and Director, Light Thermal Structures Center, Associate Fellow, AIAA. Copyright 1995 by Peter W. Chung. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission MI =torque about centerline P =compressive axial load vz =shear in z-direction w =deflection Solar Blanket: Om =blanket deflection and xy plane angle b ' =one half width F,, F, =tensions along x, y axes Mm =mass per unit area Wm =deflection S~reader Bar: em =deflection angle b =one half length I, =mass moment of inertia about midpoint W , =deflection

From monolayers to bilayers: Effective rigidity and compressibility in asymmetric ternary amphiphilic systems.

Abstract: Fluctuation effects in lamellar phases of ternary asymmetric amphiphilic systems are considered. These systems are characterized by two length scales corresponding to the thickness of the oil and water layers. For large separations between the amphiphilic layers, the dominant contribution to the free energy can be written in the Helfrich form if an effective bending rigidity is introduced that is allowed to depend on the water and oil layer thicknesses. The scaling form of this effective rigidity is determined from Monte Carlo simulations of an asymmetric three-layer system. An expression for the effective layer compressibility is derived, which can be expressed in terms of the effective bending rigidity. These effects lead to pronounced corrections of the scattering exponents ${\mathrm{\ensuremath{\eta}}}_{\mathit{m}}$, which can be measured in scattering experiments.

Heat foaming reinforcing filler and reinforcing structure for closed cross section structure material using the filler

Abstract: PURPOSE: To provide a light-weight, inexpensive reinforcing material for closed cross section structure material-reinforcing structure such as a car, which comprises an epoxy resin, a synthetic rubber and a thermoplastic resin in a specific proportion, thus is increased in flexural rigidity, torsional rigidity and energy absorption properties. CONSTITUTION: At least, 30-40wt.% of an epoxy resin, 5-15wt.% of a synthetic rubber such as styrene-butadiene rubber, 5-15wt.% of a thermoplastic resin such as poly(vinyl butyral) and 40-50wt.% of a filler such as calcium carbonate are formulated to give this new, light-weight and inexpensive heat-foaming reinforcing filler material l having markedly improved flexural rigidity and torsional rigidity, further improved energy-absorption properties, thus is useful as closed cross section structure materials 11-15 for cars, particularly pillars 11-13, roof rails 14, side sills 15 for the body 10 of a high class car.

Three-pieces solid golf ball

Abstract: PURPOSE:To provide a solid golf ball having excellent flying performance, stability of iron shots and good ball hitting feel. CONSTITUTION:This three-pieces golf ball is composed by coating a solid core 1 consisting of the inside layer core 1a and outside layer core 1b described below with a cover 2. The diameter of the inside layer core 1a is 30.7 to 39.5mm, the bending rigidity is 300 to 2,500kgf/cm and the Shore D hardness is 30 to 55. The thickness of the outside layer core 1b is 1.0 to 4.0mm, the bending rigidity is 2,500 to 6,500kgf/cm and the Shore D hardness is 55 to 75. Both are butadiene rubber. The thickness of the cover 2 is 0.6 to 2.0mm, the bending rigidity is 1,000 to 2,500kgf/cm and the Shore D hardness is 40 to 55. The cover is an ionomer resin or a mixture composed of the ionomer resin and a soft resin.

Method and apparatus for continuously balancing and reducing the flexural rigidity of a flexible rotor, particularly a roll or a cylinder

Abstract: The invention relates to a method for reducing the flexural rigidity fluctuation of a roll or a cylinder and for lessening the ellipticity caused by flexural rigidity fluctuation in machining and for diminishing a semi-critical disturbance occurring in operation. The reasons for flexural rigidity fluctuation include grooves, splines as well as structural fluctuations in a roll, such as variation of the coefficient of elasticity or wall thickness of material or the ellipticity of a roll. The roll comprises a load-bearing body and a possible coating element made of a paper fiber, a fabric or a synthetic material. The measured or calculated flexural rigidity fluctuation or imbalance of a roll is compensated for by making new groove(s) or pocket(s) or by changing the size of previously machined grooves or pockets. The grooves or pockets are disposed such that the combined effect thereof diminishes the imbalance or flexural rigidity fluctuation or both in a roll.

The Friction Couple in Yarn Bending

Abstract: Yarn bending can be characterised by a flexural rigidity B and a friction or coercive couple Mo. This paper describes an analysis of Mo in terms of filament properties, yarn twist and yarn tex. Some limited experimental data are presented in support of the result of the analysis.

Guard bar for automobile door

Abstract: PURPOSE:To absorb the impact energy during the deformation by simultansimultaneous generating the elastic deformation and the viscous flow through the relaxing phenomenon of the filler to be filled inside a tubular beam when the beam is deformed. CONSTITUTION:A guard bar can increase the plastic deformation load of a beam part 2 due to the addition of the impact strength based on the low compressibility and the visco-elastic characteristic of the filler 4 when the load is applied to the beam part 2 the outside in the vehicle parts direction, and at the same time, the impact energy during the deformation of the beam part 2 can be absorbed in thc process of the elastic deformation and the viscous flow to be caused by the relaxing phenomenon based on the visco-elastic characteristic of the filler 4 due to the deformation of the beam part 2. The guard bar 1 can improve the bending rigidity and the impact energy absorbing efficiency, and the diameter of a tubular body 21 as the component of the beam part 2 can be reduced corresponding thereto, and the plate thickness can also be reduced, achieving the weight reduction.

Bending rigidity of fluctuating membranes

Abstract: A lattice model of random surfaces is studied including configurations with arbitrary topologies, overhangs and bubbles. The Hamiltonian of the surface includes a term proportional to its area and a scale-invariant integral of the squared mean curvature. We propose a discretization of the curvature which ensures the scale-invariance of the bending energy on the lattice. Nonperturbative renormalization groups for the surface tension and the bending rigidity are applied, which are also valid at high temperatures and scales above the persistence length. We find at vanishing surface tensions a closed expression for the scale dependent rigidity including the usual logarithmic decay at low temperatures. Different scaling behaviours at non-vanishing tensions occur yielding characteristic length scales, which determine the structure of homogeneous droplet, lamellar, and microemulsion phases.

Flow Resistance on Flexible Vegetation-Covered Bed in Open Channels

Abstract: The deformation of plants under the flow with velocity distribution and the flow over vegetation layer with heterogeneous permeability constituted by deformed plants are analyzed, and they are coupled to evaluate the resistance of flow over flexible vegetation-covered bed. The property of plant representative to such an analysis is the flexural rigidity. The analytical results are compared with the flume data. Furthermore, the flexural rigidity of real plants in rivers are measured to evaluate the hydraulic resistance of grass in flood plain of rivers.

Shaft-like composite member and manufacture thereof

Abstract: PURPOSE: To enhance impact resistance and bending rigidity by providing an inner ply of such a structure as to provide the impact resistance and an intermediate ply of such a structure as to provide load supporting rigidity. CONSTITUTION: An inner ply 12 functions mainly as an impact-resistant layer. An intermediate ply 14 functions mainly as a load supporting layer for a composite member 10. An outer ply 16 functions mainly as an abrasion-resistant layer. That is, the bending rigidity 18 of the composite member 10 stems mostly from the intermediate ply 14, which is more highly rigid than the inner ply 12 and the outer ply 16. The total bending rigidity 18 is equivalent to the sum of a first, a second and a third fraction. Since most of the bending rigidity 18 is given by the intermediate ply 14, the second fraction is larger than the first and the third fraction. Typically, the second fraction is at least twice as much as the first and the third fraction.

Inserting resin pipe used for repair of existing pipeline, and repairing technique of existing pipeline used therewith

Abstract: PURPOSE:To provide an inserting-resin pipe in which passage resistance is small in even a curved pipeline when the inserting-resin pipe is fed into an existing pipeline. CONSTITUTION:An inserting-resin pipe 1 is formed into the structure of the internal and external two layers by using thermoplastic and crystalline polyethylene material. The internal layer 12 is formed of low density polyethylene material in which flexural rigidity is small and density is . The external layer 13 is formed of medium density and high density polyethylene material whose density is 0.930-0.965g/cm . The wall thickness ratio of the internal layer 12 is made larger than the wall thickness ratio of the external layer 13 to soften the flexural rigidity of a tubular body under the ordinary temperature. The external layer 13 is constituted of material capable of applying an electrofusion joint without changing its fusion bonding conditions. The electrofusion joint is formed of the same material as a polyethylene pipe used for a conventional gas pipe and developed for the gas pipe.

Film for adjusting bending rigidity of shaft of golf club

Abstract: PURPOSE:To adjust the shaft rigidity of a golf club so as to meet a golfer's requirement while suppressing an increase in the weight over the entire part of the shaft of the golf club. CONSTITUTION:This film for adjusting the bending rigidity of the shaft of the golf club is composed of an para-oriented arom. polyamide film layer 1 and an adhesive layer 2 formed on the surface on one side of the film layer 1. The film is used by sticking the film to a point where the adjustment of the bending rigidity of the shaft 3 of the golf club is required.