Showing papers on "Flexural rigidity published in 1990"

Premature Failure of Externally Plated Reinforced Concrete Beams

Abstract: Reinforced concrete beams can be strengthened and stiffened by gluing mild steel plates to the tension face of the beam. However, experimental tests show that these externally bonded plates have a tendency to peel away after the formation of shear diagonal cracks or when the curvature in the beam is increased. Fifty‐seven plated reinforced concrete beams are tested to study peeling induced by increasing curvature; in these tests, the geometry and material properties of the beams are varied, and the reinforced concrete beams are subjected to pre‐cracking and pre‐cambering, as might occur in an existing structure. A method is derived for determining the moment at which peeling starts (serviceability limit) and the moment that causes complete separation of the plate (ultimate limit). This method, which depends on the flexural rigidity of the plated beam, the thickness of the plate, and the tensile strength of the concrete, can be used to adjust the size and extent of plating so that flexural peeling does not...

Variations in effective elastic thickness of the North American lithosphere

Abstract: A technique for estimating flexural rigidity that is not limited to sedimentary basins is used here to map variations in the effective elastic thickness of the North American lithosphere. The effective elastic thickness ranges from a minimum of about 4 km in the Basin and Range Province to more than 100 km in the Precambrian core of the continent. This finding supports the idea that flexural rigidity has increased with time since the last thermal event.

Bending of sandwich beams with transversely flexible core

Abstract: The bending behavior of a sandwich beam with a foam core is analytically investigated. The beam consists of upper and lower skins, metallic or composite laminated, and a soft core. The loading pattern consists of concentrated as well as distributed loads exerted at the upper or the lower skin or a combination of the two. The analysis includes the effects of the flexibility of the core in the vertical direction on the overall bending behavior. The main parameters affecting the overall behavior and particularly the peeling and the shear stresses between the skins and the core are studied. ANDWICH beams have been used in various industries for many years. A typical beam consists of two skins made of metal or laminated composite and a core. The core is usually made of honeycomb, metallic or nonmetallic, which is stiff in the vertical direction and flexible in the horizontal one. In recent years, plastic foams are used for cores in sandwich structures. In this case, the effect of the transverse flexibility of the core on the mechanical behavior of the beam should be taken into account. This flexibility affects the transverse bend- ing behavior of the beam and leads to unequal deflections of the upper and lower symmetrical skins (see Fig. 1). Sandwich beams with honeycomb cores were considered by many researchers. Reissner1'2 included the shear strain effect on the bending, but only the average bending behavior of the composite beam is considered. Many researchers3'5 dealt with the analysis of beams with an antiplane core, i.e., a core with shear rigidity only. The Hexcel designer manual6 outlines the design procedures for beams with honeycomb cores only. An antiplane-cor e approach with anisotropic and composite skin appears in Refs. 7-9. Ojalvo10 assumed different deflec- tions to the two skins, but neglected the peeling stresses. Ogorkiewicz and Sayigh11 dealt with a foam core by replacing it with an ordinary beam with equivalent properties. In this paper, the proposed analysis includes the effects of the transverse flexibility of the core and the peeling stresses between the skin face and the core on the overall bending behavior. The analysis is general and applicable to metallic or com- posite laminated identical skins. The behavior is described in terms of the deflections, the peeling, and the shear stresses in the adhesive layers. The effect of the variables that govern the behavior is incorporated through a parametric study. The mathematical formulation and the boundary conditions are discussed. The analytical solution for the various types of loading with different boundary conditions is presented.

Bending elasticity and thermal excitations of lipid bilayer vesicles: Modulation by solutes

Abstract: We present high-precision measurements of the bending elastic moduli of bilayers of a variety of different lipids and of modifications of the flexural rigidity by solutes. The measurements are based on the Fourier analysis of thermally excited membrane undulations (vesicle shape fluctuations) using a recently developed dynamic image processing method. Measurements of the bending modulus as a function of the undulation wave vector provide information on the limitation of the excitations by the constraint of finite membrane area (surface tension effects) and by transient lateral tensions arising in each monolayer by restricted diffusion at high wave vectors. Measurements of the autocorrelation function of the undulation amplitudes provide a further test of the theoretical models. Studies of the effect of solutes show that cholesterol increases the bending modulus of dimyristoylphosphatidylcholine from Kc = 1. 1 × 10−12 erg to 4.2 × 10−12 erg (at 30 mol%). Incorporation of a short bipolar lipid reduces Kc to the order of kT. Finally we present a variety of shape changes of vesicle and provide evidence for the stabilization of metastable non-equilibrium shapes by lateral phase separation.

Thermal stresses, differential subsidence, and flexure at oceanic fracture zones

Abstract: Geosat geoid undulations over four Pacific fracture zones have been analyzed. After correcting for the isostatic thermal edge effect, the amplitudes of the residuals are shown to be proportional to the age offset. The shape of the residuals seems to broaden with increasing age. Both geoid anomalies and available ship bathymetry data suggest that slip must sometimes occur on the main fracture zone or secondary faults. Existing models for flexure at fracture zones cannot explain the observed anomalies. A combination model accounting for slip and including flexure from thermal stresses and differential subsidence is presented. This model accounts for lateral variations in flexural rigidity from brittle and ductile yielding due to both thermal and flexural stresses and explains both the amplitudes and the shape of the anomalies along each fracture zone. The best fitting models have mechanical plate thicknesses that are described by the depth to the 600-700 C isotherms.

Decreased pain with lower flexural rigidity of uncemented femoral prostheses.

Abstract: One hundred one consecutive uncemented hip arthroplasties (87 patients) were analyzed radiographically at 1-year follow up to relate mechanical factors to hip pain as determined by clinical pain scores. The average area moment of inertia and flexural rigidity were greater for the bone than the metal prosthesis for each type of prosthesis (AML, HG, PCA). Normalization of the flexural rigidity ratio (bone to prosthesis) for patient weight yielded a Spearman correlation coefficient of 0.232, significant at P = .02, suggesting that both applied stress and bending stiffness have an effect on pain. No relationship was seen between pain and AP, or average gap between prostheses and bone.

Dynamic bending rigidity of DNA.

Abstract: Rapidly relaxing components in the decay of the transient electric dichroism of DNA restriction fragments were reported by Diekmann et al. [(1982) Biophys. Chem. 15, 263-270] and Porschke et al. [(1987) Biopolymers 26, 1971-1974]. These are analyzed using a new normal mode theory for weakly bending rods and assigned to bending. The longest bending relaxation times for fragments with 95-250 base pairs coincide with the theoretical curve calculated for a dynamic bending rigidity corresponding to a dynamic persistence length Pd = 2100 A. Analysis of the relative amplitudes of fast and slow components following weak orienting pulses is also consistent with a rather large dynamic persistence length. The enhancement of the relative amplitude of the fast component in large electric fields is attributed to steady-state bending of initially perpendicular DNAs by the field. Several reasons are proposed why the dynamic bending rigidity is 4 times larger than the apparent static bending rigidity inferred from equilibrium persistence length measurements on the same fragments.

Theoretical analysis of flexural viration of car body

Abstract: It is important to make clear the appropriate value of flexural rigidity when designing the carbody structure. For this reason we investigated the vertical vibration of the car body excited by vertical track irregularities and studied the relationships between flexural rigidity and riding comfort. As a result it becomes clear that a lower flexural rigidity generally causes poor riding comfort and especially in the case of a high speed car a lower flexural rigidity is not desirable.

General non-dimensional equation for lateral buckling

Abstract: A new approximate non-dimensional equation for the elastic lateral buckling load of straight prismatic beams of monosymmetric cross-section with general boundary conditions and general loading, which includes the effects of initial bending curvature prior to buckling, is derived. For sections where the flexural rigidity about the axis of initial bending, EIzz, is smaller than the flexural rigidity about the other principal centroidal axis, EIyy, it is shown that lateral buckling is still a possibility

On the Quasi-Static Design of Machine Tool Spindles:

Abstract: The paper simplifies the analysis of the general multi-stepped spindle-bearing system model. Various design parameters are considered with the objective of attaining high static stiffness in the cutting zone. Parameters considered in the study include bearing spacing and stiffness, dimensionless flexural stiffness, number and length of the steps, effect of the driving force and the reaction moment exerted at the central front bearing. The calculations enable optimization (for maximum stiffness) at the chuck for short overhang spindles such as those of lathes.The most effective design parameter is the optimum bearing spacing, demonstrated in the study by evaluating the exact analytical solution of the derived equations.

Piezoelectric transducer and sound-generating device

Abstract: A piezoelectric transducer useful for example as a sound source or a strain detector includes a ferroelectric liquid crystal sealed between two baseplates with electrodes and alignment layers on the inner facing surfaces of the baseplates. One of the baseplates is thicker than the other, or is of a different material, so that the two baseplates have different flexural rigidity.

Carbide cutting tool

Abstract: PURPOSE:To improve processing accuracy of cutting and prevent thermal stress destruction and improve connection strength by forming a cutting blade part and a non-cutting blade part with different cemented carbide materials, and connecting respective parts metallurgically to form integrally CONSTITUTION:Since a cutting blade part 1 is re-polished when it in worn away, length of a cutting blade part is made minimum in consideration of a re-polishing quantity, and materials in P group or K group of JIS having a high hardness are used as a material which can stand against cutting resistance Materials in D group which hardness is a little low but having a fine longitudinal elastic coefficiency and climp resisting force are used for a non- cutting blade part 2 The parts 1, 2 are connected by molding the super alloy powder of both the parts 1, 2 in a connecting shape at the time of compressure molding and sintering it to unify metallurgically As a result, abrasion resistance of the cutting blade 1 part is raised, and flexural rigidity and torsional rigidity of the non-cutting blade part 2 are raised, and processing accuracy can be improved as high as possible without oscillation, bending, wrap and twisting in the non-cutting blade part 2

Ferroelectric liquid crystal device

Abstract: PURPOSE: To prevent the deflection and deformation of a liquid crystal panel even when an external pressure and the shock at the time of falling and colliding are applied on the liquid crystal panel and the stress in the direction normal to the surface is generated by supporting and fixing the liquid crystal together with a reinforcing member having high bending rigidity between supports. CONSTITUTION: A transparent glass plate 20 is superposed and installed as the reinforcing member having the sufficient bending rigidity atop the liquid crystal panel and both ends of this liquid crystal panel and the transparent glass plate 20 are supported by a zebra rubber connector 12 and an a frame 10 having an L shaped cross section and are caulked to a driving circuit substrate 8 by claw parts 10a provided at the bottom end of the frame 10, by which the transparent glass plate 20 and the liquid crystal panel are fixed to the driving circuit substrate 8. The transparent glass plate 20 is used as the plate having the high bending rigidity by adequately selecting the material and shape thereof. The deflection and deformation of the liquid crystal panel are suppressed in this way even when the external pressure and the shock at the time of falling and colliding are applied on the liquid crystal panel and the stress in the direction normal to the surface is generated. The deformation of the liquid crystal is thus prevented and the generation of the disturbance in orientation is obviated. COPYRIGHT: (C)1991,JPO&Japio

Flywheel device for engine

Abstract: PURPOSE:To improve the action for suppressing the surface vibration of a flywheel by setting each flural rigidity of a plate member higher in case of the plate member on the first direction side and lower in case of the plate member on the second direction side CONSTITUTION:The surface vibration of a flywheel 4 is the behavior in which the peripheral part on the second direction (B-B) side perpendicular to the first direction (A-A) oscillates largely, having the part along the first direction having the highest dynamic flural rigidity of a crankshaft 1 as center In this case, also in a damper mass 8, the part connected by the plate members 13 and 14 having the less flural rigidity (ie, elastically deformable easily in the bending direction) oscillates relatively to the flywheel 4, having the part which is connected by the plate members 11 and 12 having the higher flexural rigidity and is formed along the first direction side as center Therefore, the action for offsetting the vibration of the flywheel 4 by the vibration of the damper mass 8 can be obtained easily, and the action for reducing the vibration of the flywheel 4 is improved

Effect of Fiber Length, Fineness, and Twist on the Bending Behavior of Polyester and Viscose Staple Rotor Spun Yams:

Abstract: The effects of fiber length, fineness, and twist of polyester and viscose staple rotor spun yams have been examined for their bending behavior using a bending hysteresis tester. For the polyester staple rotor spun yarns, use of shorter and coarser fibers leads to a higher magnitude of bending hysteresis, yarn bending rigidity, and bending re covery ; the percent reduction in bending hysteresis and yarn bending rigidity is greater for coarser, shorter fibers with increasing twist. For the viscose staple rotor spun yarns, use of longer staple fibers leads to increased bending hysteresis and yarn bending rigidity; the percent reduction in bending hysteresis and yarn bending rigidity is greater for longer fibers with increasing twist. An increase in twist leads to a drop in the bending hysteresis and yam bending rigidity, regardless of the length or fineness. Wrapper fibers do contribute to the bending behavior of rotor spun yams.

Anisotropic continuous strand mats

Abstract: We have developed a new pattern for continuous strand fiberglass mat which gives improved torsional rigidity to the molded structure. The pattern is basically an elongated elliptical loop where the strands lay on the conveyor and look like lazy whirl formations or concentric circles with diameters dependent upon properties such as bending rigidity and torsional rigidity. The lay-down pattern looks cycloidal in nature. Elongated elliptical strand loops become further elongated until at some point they also contain "pigtails" or somewhat straight strands with small elliptical loops oriented in the cross-machine direction.

Thin-type electronic equipment

Abstract: PURPOSE:To enhance flexural rigidity without deteriorating electromagnetic coupling characteristics by a method wherein a metallic reinforcing member having an open part for preventing a closed magnetic circuit around a center axis of a secondary-side core is provided on the periphery of a planar thin-type electronic equipment incorporating a secondary-side element of an electromagnetic transformer. CONSTITUTION:A metallic reinforcing frame 4 made of an aluminum or other light metal is bonded on the periphery of an IC card case 3c with an adhesive. An open end 4a of the reinforcing frame 4 is connected by an insulating material 4b. Since the metal reinforcing frame 4 is magnetically opened by the insulating material 4b, it can prevent a one-turn short circuit and improve the flexural rigidity of a thin-type electronic equipment. As an alternative, metallic reinforcing plates 5 made of an aluminum or other light metal provided with holes 5a and slits 5b may be bonded on the upper and lower surfaces of the case 3c for enhancing the flexural rigidity. The holes 5a disposed just on and under secondary-side cores 3a, 30a prevent the deterioration of electromagnetic coupling characteristics, and the slits 5b prevent a one-turn short circuit.

Effect of butt joints on the flexural stiffness of laminated timber bridges

Abstract: Prestressed and nailed laminated timber bridge decks are made from laminates which, because of their being usually shorter in length than the deck span, are butt-jointed at regular intervals. In calculating deflections of such decks, it is usual to ignore the reduction in flexural rigidity of the deck caused by the presence of the butt joint. The effect of butt joints on the flexural rigidity of the laminated deck is studied analytically, and it is shown that the deflections of a deck having such joints may be significantly larger than those of a deck without them. A simple method is presented to account conservatively for the presence of butt joints in the calculation of the deflections of a prestressed laminated timber deck. Key words: timber bridge, laminated deck, butt joint, prestressed wood deck.

Strengthening reinforced concrete beams by bonding steel plates to their soffits

Abstract: A method is described of strengthening and repairing reinforced concrete beams by gluing mild steel plates to their soffits. This technique is often used to increase the flexural and shear strengths of existing beams and is also used to reduce the flexural crack widths and the deflections of the beams. However, plated beams have been found to be susceptible to premature failure due to two modes of debonding of the plate from the original reinforced concrete beam: that due to shear forces, and that due to flexural forces. Debonding due to flexural forces has been found to be a gradual process which depends mainly on the flexural rigidity of the beam and not directly on the longitudinal strain in the plate. Debonding due to shear forces has been found to be a rapid process which depends on the shear strength of the reinforced concrete beam and not on the shear stress at the steel-plate/concrete-slab interface.

Changes in Cotton Fabric Bending Properties As a Result of Laboratory Wear

Abstract: The mechanical properties of four woven cotton fabrics have been analyzed in terms of the elastic (Go) and frictional (Co) resistance to bending deformation using a Shirley cyclic bending tester. Changes in bending properties of the cotton fabrics as a consequence of wear using an Accelerotor abrasion tester in the dry condition are illustrated. Statistical correlations between the elastic and frictional parameters of deformation and other parameters such as percentage loss in weight are shown. The correlations are shown to be highly significant between elastic flexural rigidity and frictional coercive couple parameters of the deformation and percentage loss in weight of fabrics given 25 min abrasion time. Correlations between elastic and frictional parameters of deformation before the abrasion test, and with 5 and 25 min abrasion time, are also highly significant. Relations between bending parameters, mass, thickness, density, and specific volume of these fabrics before and after abrasion are reported. The result shows that weight loss may be small as a result of short periods of accelerated wear, but the changes in the bending parameters are large.

Transverse strength and acoustic emission characteristics of commercial denture base resins

Abstract: Transverse strength and acoustic emission (AE) characteristics were measured by the transverse test in deionized water at 37 degrees C on commercial denture base resins (five heat-cured type resins and one polysulfone). Difference in flexural property of five heat-cured denture base resins was not shown from the transverse deflection according to JIS, but high toughness of polysulfone was recognized in transverse deflection, flexural strength, flexural modulus, flexural rigidity, flexural proof stress, and fracture energy. The five heat-cured denture base resins showed a low AE activity, but the polysulfone resin high AE activity. Significant rates of AE for polysulfone were detected at a kgf of approximately 50-60% the maximum load. The presence of Kaiser effect in its cycle transverse test was confirmed.

Transport and turning device for core structure part of nuclear reactor

Abstract: PURPOSE: To prevent the structural parts of a reactor core from receiving an untolerable load by supporting a cage which is used for housing the parts and has flexural rigidity and torsional rigidity below a cross beam so that the cage can rotate around the horizontal axis. CONSTITUTION: The upper structure 18 of a reactor core is put in a rotating cage 3 having a flexural rigidity and torsional rigidity and fixed to the cage 3 with screws. Two rotating disks 24 and two short shafts 6 are provided face to face at two points near the common center of gravity of the structure 18 and cage 3. The assembly of the structure 18 and cage 3 is rotatably supported by the shafts 6. During the rotation of the assembly, a bias pressure is displayed by means of a digital elongation measuring instrument and a recorder connected to the instrument and the force of a rope is continuously displayed and monitored. Therefore, the stable state caught by the cage 3 having flexural rigidity and torsional rigidity is guaranteed.

Core structure of light ski

Abstract: PURPOSE: To obtain a core structure of light skins which are light and excellent in turning characteristic and stability in high speed skiing, by superimposing and forming uneven thick materials which are thin in both ends of upper or lower face of the ski core material but thick in the middle of the ski. CONSTITUTION: An uneven thick plate material 2 is superimposed to make a pattern of required bending rigidity on the upper face of a ski core material 1 and an even thin plate 3 is superimposed on the lower face of the ski core material 1. The thickness distribution of the ski core material 1 is thick in the middle and thin in both ends in order to keep high the tortion rigidity. A fiber-reinforced plastic material is used to lighten the ski on the uneven thick material 2 and the even thin material 3 for giving this bending rigidity. For forming these light skis, plastic foamed material or wooden material are preferably used as the material of the ski core. Reinforced plastic materials with high relative rigidity made of carbon fiber, aramid fiber, alumina fiber, and silicon carbide fiber, etc., are preferable for the reinforced plastic materials. COPYRIGHT: (C)1991,JPO&Japio

Manufacture of speed ring for hydraulic machinery

Abstract: PURPOSE:To obtain a speed ring sufficiently bearable for flexural rigidity with a small welding quantity by welding only the part of which rigidity is elevated by fixedly securing ring-like main plates with stay vanes, except the other part, at welding reinforcing rings with flanges. CONSTITUTION:In a speed ring 1, a plurality of stay vanes 3 spaced in the circumferential direction are fixedly secured between ring-like main plates 2 arranged opposedly and in parallel. Further, a ring-like reinforcing ring 5 is arranged on the outside of the ring-like main plate 2, and a ring-like flange 6 is arranged on its outside. In this case, the connecting parts A between the ring-like main plate 2 and the reinforcing ring 5 and between the reinforcing ring 5 and the flange 6, where are corresponding to the elevated rigidity part by fixedly securing the ring-like main plate 2 with the stay vane 3, are respectively welded, and the other mutually connected parts B are not welded.

Study of flexural rigidity of weavable powder-coated towpreg

Abstract: An effort has been made to weave powder-impregnated tow into a two-dimensional preform, controlling process variables to obtain high flexural rigidity in the warp direction and greater flexibility in the fill direction. The resulting prepregs have been consolidated into laminates with LaRC-TPI matrices. Complementary SEM and DSC studies have been performed to deepen understanding of the relationship between tow flexibility and heat treatment. Attention is also given to the oven temperature and residence time variables' effects on power/fiber fusion.

Diaphragm for speaker

Abstract: PURPOSE:To obtain a diaphragm for speaker having a large bending rigidity and an inter-layer shearing strength by reinforcing a textile comprising high strength and high elastic modulus polyethylene fibers and glass fibers with a resin. CONSTITUTION:As threads constituting textile 1, blended yarns which are made by mixed spinning high strength and high elastic modulus polyethylene fibers and E glass fibers are used to weave a plane weave fabric whose weave density is 13 threads/inch for both weft and warp, a vinylester resin is subjected to prepleg processing, being heat press molded under the condition of 120 deg.C, 5 minutes and 5kg/cm (face pressure) for one ply to obtain a cone diaphragm 3 for a 10 inch speaker. Thus, the bending rigidity is improved, resulting that the cone molding with as large as 10 inches is attained without causing deformation at the mold releasing. Moreover, an ideal piston motion is obtained up to a high frequency band in the acoustic characteristic and the sound quality at the high sound frequency range is excellent.