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Measurement
Published in Carl Hopkins, Sound Insulation, 2020
The bending stiffness can be determined with small strips of material acting as beams; this uses the same test set-up as for internal loss factor measurements (Section 3.11.3.4). When the stiffness varies with temperature, this measurement can be arranged inside a small temperature-controlled chamber. The peaks in the input impedance spectrum correspond to the resonance frequencies, fi. The bending stiffness for a plate of the material can be calculated at each resonance frequency from these beam measurements (Yoshimura and Kanazawa, 1984; ISO/PAS 16940) () Bp,i=ρs(πL2fi2Ci2)2
Beams
Published in Ever J. Barbero, Introduction to Composite Materials Design, 2017
Composite beams are thin walled and composed of an assembly of flat panels (Figure 10.1). Most beams are prismatic but they can be tapered. They are produced by pultrusion, filament winding, hand lay-up, etc. To reduce cost and weight, the cross-sectional area of a composite beam should be as small as possible. The required bending stiffness is achieved by increasing the second moment of area I as much as possible. This is done by enlarging the dimensions of the cross section while reducing the thickness of the walls. The typical example is the use of an I-beam as opposed to a rectangular solid beam. Furthermore, common processing methods used to produce beams, such as pultrusion, work best for relatively thin walls.
Introduction and Definitions
Published in Eugene I. Rivin, Stiffness and Damping in Mechanical Design, 1999
The most critical mode of loading is bending because bending deformations can be very large even for not very high forces; thus bending stiffness can be very low, and in many cases this determines the effective stiffness of the structure. Bending stiffness can be enhanced by reducing spans between supports of the components subjected to bending, by reducing the overhang length of cantilever components, and by increasing cross sectional moments of inertia ("beefing up'"). The first two techniques are frequently unacceptable due to design constraints, but 'beefing up', of cross sections can even be counterproductive since it inflates dimensions and increases weights of the components, as illustrated above in Section 7.1.
Fabrication and characterization of a novel facial mask substrates based on thermoplastic polyester elastomer fibers
Published in The Journal of The Textile Institute, 2020
Yi Zhao, Ranran Chen, Ruiyan Ni, Honggang Liu, Juan Li, Chen Huang
Besides mechanical properties, softness of the nonwoven is also important as it largely determines the comfortability and skin adhesion of facial mask. Bending stiffness represents the ability to resist bending deformation. The softness of the spunlaced nonwoven is expressed by the bendability (Deng et al., 2018). Figure 5(a) shows the relationship between bending stiffness and thickness. It is obvious that bending stiffness of the samples would increase with the increase of weight, thickness or proportion of PET. When the content of the hydrophobic fibers (PET fibers) increases, the energy from water jets cannot be sufficiently absorbed by the fibers, resulting in the increase of nonwoven thickness and the softness is deteriorated. Compared to V/PET, nonwoven formed by TPEE/PET is significantly softer under the same weight. That is ascribed to the lower thickness of TPEE/PET samples, for that a higher fiber density suggests a larger fabric thickness. In addition, TPEE fiber is softer than viscose fiber and PET.
An experimentally-verified approach for enhancing fluid drag force simulation in vertical oilwell drill strings
Published in Mathematical and Computer Modelling of Dynamical Systems, 2022
Mihiran Galagedarage Don, Geoff Rideout
The bending stiffness is defined as the force required to laterally displace the midpoint of the flexible beam by a unit displacement. One can argue that the fixed-fixed boundary condition may be too rigid to simulate the actual dynamics of the drill pipe, and instead, a flexible boundary condition is more appropriate. Nevertheless, the fixed-fixed boundary conditions were introduced to establish the computational stability of the FSI simulation as there are still some limitations that exist in commercial software, in the domain of FSI simulations, at the time of these experiments.