Damping element connected to a vibrating structure, and damping device including at least one such element
Damping element bonded to a vibrating structure, and device damping having at least one such element . The present invention relates to a damping element bonded to a vibrating structure, and also a damping device comprising at least one such element. Such damping elements are, in a known manner, in the form of a plate of a viscoelastic material such as a rubber. These members are bonded to a vibrating structure which can be one-piece, such as a single blade, or which can be composed of several parts rigidly assembled, such as a frame. These elements are therefore linked to a vibrating structure. The connection, between the plate and the vibrating structure, of adhering the plate such that bending vibrations of the structure create tensile stresses-compression in the material to permit the energy dissipation in the material. The efficiency will be greater that the plate is thick, and the stiff material and damped, but these two criteria Box high stiffness and damping reduce the possible choices for the material. Furthermore, the viscoelastic materials support harsh environments (cold, hot, oils, ...) but their performance are generally influenced, and they are strong thermal and electrical insulating, this can be a disadvantage. There are also known, mechanical elements made of woven or knitted threads, called cushions when thick, and two mat when they are large relative to a third, the thickness. The cushions or mats are always used as suspension installed between a structure and a floor or other structure, optionally in combination with other springs and/or dampers. Then mainly They provide a spring function. But they have, their quality also spring, a potentiality energy dissipation by friction of the wires on each other, and always has the potentiality been considered insufficient by the specialists to be considered to be able to have damping functions structures, these specialists and then merely use these pads or mats as insulators interposed between two structures. Or, tests on models have shown that the cushions or mats, bonded to a structure, provide structural damping values equal, see even higher, than those obtained with plates of a viscoelastic material very damped. The present invention, the aim of which is to enhance the damping of structure, is provided for this purpose, or to replace the viscoelastic by the plates or mats which are then bonded only to the vibrating structure, without providing a link between the structure and a floor or other structure. The present invention relates to a damping element monoblock linked to a vibrating structure or composed of a plurality of parts rigidly assembled, characterized in that it is in the form of a pillow or a fiber mat woven or knitted. The fibers may be coated with another material, as, for example, an elastomer, a grease or a resin providing a particular characteristic. The present invention also relates to a damping device using at least one damping element as described above, characterized in that at least one element includes a stress plate which in shear. Of course, if the mass of the stress plate is large relative to the structure, the plate then acts as mixer. It is described below, with reference to the accompanying drawings, a plurality of devices according to the invention provided with at least one damping is in the form of a cushion. Figure 1 shows a device comprising two cushions installed on a vibrating structure planar. Figure 2 shows a device having a cushion opera- the planar on a vibrating structure, the cushion having a stress plate which causes it to shear. Figure 3 shows a device comprising a cushion assembly installed on a cylindrical structure and distributed circumferentially. In Figure 1, the device consists of two cushions 10 planar vibrating structure 1. In Figure 2, the device consists of a cushion 10 covered by a stress plate 2, causing the plate the cushion shear, providing further 1' damping. In Figure 3, the device consists of eight cushions 10 distributed on the circumference of a cylindrical structure 3, which is in this case piping. Two adjacent cushion are connected to a stress plate, the stress plate 4 for the two pillows upper and the stress plate 5 for the two pillows lower. The other two plates and the other four cushions are not represented. The mass of each of the four plates is large enough so that they act as beaters. This combining the structural dampening with effectiveness of a vibration damper. In this example, may also be used a system for providing prestressing, for example a collar controlling the efficiency. In these three devices described, the stiffness and the damping provided to the cushions, are adjustable at will by changing various parameters such as, for example, the nature and the diameter of the yarns, the knitting mode, and the geometric dimensions of the cushions. The cushions can be fabricated using wires which have the advantage of supporting high-temperature and chemical insensitivity, very wide therefore is effective regardless of the environment in which the cushions are used. Cushions can also be achieved with glass fibers, aramid or carbon for example. Cushions can be linked to the vibrating structure by gluing, welding, brazing, or by the use of an additional material for interfacing, such as an elastomer or a resin impregnating the cushion base or the embedding. An assembly may also be envisioned by mechanical techniques, riveting for example, if the distance between two consecutive cushions is low compared to the wavelength corresponding to the frequency band where one wants of the damping. The cushions or mats, are particularly suitable when one tries to achieve in a large temperature range, a gain in stiffness and strength viscoelastic relative to the plates, to have a good resistance to harsh environments, to provide good thermal conductivity and/or electrical, in particular in all aeronautical applications ambient-hot or for supporting large temperature gradients. The present invention relates to a damping element 10 connected to a vibrating structure 1 which is monobloc or composed of several rigidly assembled parts, characterised in that it is in the form of a cushion or mat of woven or knitted fibres. It also relates to a damping device including at least one such element. Application to the damping of vibrating structures. <IMAGE> 1/Damping element (10) bonded to a vibrating structure (1, 2) integral or composed of several parts rigidly assembled, characterized in that it is in the form of a cushion or a fiber mat woven or knitted. 2/Element according to claim 1, characterized in that the fibres are coated with another material. 3/Damping device using at least an element according to claim 1 or 2, characterized in that at least one element (10) has, on its face opposite that connected to the structure, a stress plate (3, 4, 5) which in shear. 4/Damping device according to claim 3, characterized in that the stress plate (4, 5) has a large mass which act as a mixer. 5/A damping device according to any one of claims 3 or 4, characterized in that the elements (10) are applied locally onto a planar structure (1). 6/A damping device according to any one of claims 3 or 4, characterized in that the elements (10) are distributed circumferentially over the cylindrical structure (2).