Classifications

• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
  • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/162—Selection of materials
  • G10K11/168—Plural layers of different materials, e.g. sandwiches
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64C—AEROPLANES; HELICOPTERS
  • B64C1/00—Fuselages; Constructional features common to fuselages, wings, stabilising surfaces or the like
  • B64C1/40—Sound or heat insulation, e.g. using insulation blankets
• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
  • E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
  • E04B1/62—Insulation or other protection; Elements or use of specified material therefor
  • E04B1/92—Protection against other undesired influences or dangers
  • E04B1/98—Protection against other undesired influences or dangers against vibrations or shocks; against mechanical destruction, e.g. by air-raids
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F9/00—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium
  • F16F9/30—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium with solid or semi-solid material, e.g. pasty masses, as damping medium
  • F16F9/306—Springs, vibration-dampers, shock-absorbers, or similarly-constructed movement-dampers using a fluid or the equivalent as damping medium with solid or semi-solid material, e.g. pasty masses, as damping medium of the constrained layer type, i.e. comprising one or more constrained viscoelastic layers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T50/00—Aeronautics or air transport
  • Y02T50/40—Weight reduction

Definitions

• This invention relates to vibration damping and, more particularly, to methods and apparatus for reducing the noise produced by, and increase the sonic fatigue life of, structural elements.
• the invention can be used in other types of reinforced skin structures to reduce interior noise and vibration, including all types of transportation vehicles — uto ⁇ mobiles, buses, trucks-, ships, submarines, hovercraft and hydrofoils, for examples.
• the invention can also be used in the exterior and interior walls of buildings and enclosures where noise 'reduction is desired.
• the invention can also be used in reinforced skin bulkheaks, partitions or walls in any or all of the ' transportation vehicles listed above and others, including aircraft.
• Noise and vibration inside of reinforced skin structures affects passenger speech communication, comfort and sleep. Noise and vibration can also cause material fatigue and, thus, the malfunction of equipment mounted in regions of high noise and vibration. Since most transportation structures are designed to be as light in weight as possible (commensurate with structural requirements), in order to obtain maximum fuel efficiency, limitations are placed on what designers can do to reduce interior noise and vibration levels. These constraints are particularly severe in the aircraft design field where weight is extremely critical.
• noise in an aircraft can be segregated into n contributing to the overall sound pressure level (OASPL) and noise contribut to the speech interference level (SIL).
• OASPL is essentially determined the low audio frequency content of the noise and the SIL is determined by mid to high audio frequency content of the noise. Since both the OASPL and affect passengers, noise reduction over the entire, or any portion of the au frequency range is desirable.
• the cabin noise of an aircraft in the mid and high au frequency range (above 600 Hz) is reduced by applying skin damping tape, l vinyl sheeting and fiberglass insulation to the walls of the aircraft fusela While the use of such items to reduce noise are effective in the mid and h audio frequengy range, they are essentially ineffective in the low au frequency range, defined as frequencies below 300 Hz. Further, they are o moderately effective in the mid-audio frequency range defined as frequen between 300 and 600 Hz. As a result, the reduction of low and mid-au frequency cabin noise has remained a problem in present day commer aircraft.
• This invention is directed to a method and apparatus for cooperatively damping the vibration of the flanges and webs of such structural elements in order to reduce the noise created by such vibration and improve the sonic fatigue life of the vibrating elements.
• the method generally comprises the step of viscoelastically attaching a rigid constraining element to at least two transverse (normally orthogonal) legs of the structural element to be damped.
• the viscoelastic attachment material is coupled together via the rigid constraining layer such that the viscoelastic attachment to one of the legs assists in the vibration damping of the other leg and vice versa. More specifically, viscoelastic attachment to the vibrating leg directly damps the vibrations of t leg.
• the constraining layer couples the vibrations of the vibrating to the viscoelastic attachment to the other leg, which provides indirect dampi
• the vibration is damped in two ways.
• viscoelastic medium attaching the rigid constraining element to the vibrating provides direct damping.
• the constraining element couples vibrations to the viscoelastic medium attaching the constraining element to other leg, which provides indirect damping. Even though the mode of vibrat (e.g., twist, as opposed to bending or vice versa) of the two legs is differe indirect or supplemental damping is still provided.
• Vibration damping apparatus formed in accordance with invention comprises a rigid constraining layer and a viscoelastic attach material for attaching the constraining layer to at least two transverse legs the structural element to be damped.
• the rigid constraining layer a configuration that mates with the configuration of the legs of the structu element to be damped.
• the constraining element defines a mating ri angle.
• the constraining element will be formed so as to mate with the legs structural element to be damped.
• the structural element is Z-shap the rigid constraining layer will be Z-shaped.
• the rigid constraining layer will be Z-shaped.
• layer and the viscoelastic attachment medium may be segmented or may ext along the entire length of the structural element. If desired, the segments be linked together by links forming part of the rigid constraining layer. Or, constraining layer can include apertures through which items can be attached the structural member.
• the segmented and apertured versions are particula valuable where weight is " at a premium.
• the rigid constraining layer can be formed of t layers, each of which mates with, and is viscoelastically attached to, one of two surfaces of the structural element. Or multiple layers can be attached one or both surfaces of the structural element.
• the invention provides grea increased vibration damping without significantly increasing the weight of damped structural element over the weight added when separate damp treatment is applied to each of the at least two transverse legs.
• Grea increased vibration damping is provided because of the indirect damping that added to the direct damping provided by the viscoelast ⁇ cal attachment to the vibrating legs.
• the indirect or supplemental damping decreases the total treatment required to achieve a particular level of damping, whereby the additional weight required to achieve a particular level of damping is reduced.
• FIGURE 1 is a perspective view of a Z-shaped structural element wherein the web and both flanges are damped in accordance with the invention
• FIGURE 2 is a series of exaggerated cross-sectional views showing twist vibration of a Z-shaped structural element of the type illustrated in FIGURE 1
• FIGURE 3 is a series of exaggerated side views showing the bend vibration of a Z-shaped structural element of the type illustrated in FIGURE 1;
• FIGURE 4 is a partial perspective view of a Z-shaped structural element damped in accordance with the invention wherein the damping treatment layer is segmented;
• FIGURE 5 is a partial perspective view of a Z-shaped structural element wherein the constraining layer is segmented and the segments are linked together;
• FIGURE 6 is a partial perspective view of a Z-shaped structural element wherein a constraining layer is viscoelastically attached to both surfaces of the Z-shaped structural element;
• FIGURE 7 is a partial pictorial view of a Z-shaped structural element wherein an L-shaped constraining layer is viscoelastically attached to the inner surface defined by one flange and the web of the Z-shaped structural element;
• FIGURE 8 is a partial pictorial view of a Z-shaped structural element wherein an L-shaped constraining layer is viscoelastically attached to the exterior surface defined by one flange and the web of the Z-shaped structural element;
• FIGURE 9 is a partial pictorial view of an l-shaped structural element having constraining layers viscoelastically attached to all of its surfaces;
• FIGURE 10 is a partial pictorial view of an L-shaped structural element constraining layers viscoelastically attached to both the inner and outer surfaces defined by the legs of the element;
• FIGURE 11 is a partial pictorial view of a C-shaped structu element having constraining layers viscoelastically attached to both surfaces both flanges and to the web of the element; 5 .
• FIGURE 12 is a partial pictorial view of a T-shaped structu element having constraining layers viscoelastically attached to both surfaces the web and flanges of the element; and,
• FIGURE 13 is a pictorial view of a Z-shaped structural elem illustrating that the region of the constraining layer connecting together
• FIGURE 1 illustrates a Z-shaped structural element 21 damped
• the Z-shaped structural element 2 elongate and includes a web 23 and a pair of flanges 25a and 25b. The flan
• a rigid constraining layer 27 20 attached by a layer of viscoelastic material 29 to one of the surfaces defined the web 23 and the flanges 25a and 25b of the Z-shaped structural element
• the cross sectional configuration of the rigid constraining layer 27 is Z-sha and mates with the surface of the structural component 21 to which it attached by the layer- of viscoelastic material 29.
• the ri 25 constraining layer 27 is shown as continuous and unapertured.
• rigid constraining layer is formed of the same material as the Z-sha structural element 21 and is of the same thickness.
• the constrain layer can also be made from fiber reinforced composite materials of h stiffness to weight ratio.
• FIGURES 2 Prior to describing the operation of the damping treatm illustrated in FIGURE 1 (which comprises the rigid constraining element 27 the attaching viscoelastic layer 29) a brief discussion of the types of vibrat that occurs in a Z-shaped structural element when it is used to form the frame an aircraft is described. In this regard, attention is directed to FIGURES 2
• FIGURE 2 is a series " of three cross-sectional views of a Z-sha structural element.
• the left-most view illustrates an untwisted Z-sha structural element oriented such that the web is vertical, the upper fla extends outwardly to the left and the lower flange extends outwardly to the right.
• the flanges lie orthogonal (e.g., 90°) to the web of the Z- shaped structural element.
• the middle view of FIGURE 2 illustrates in an exaggerated manner what happens to a Z-shaped structural element when a counterclockwise twist force is applied to it. In this case, the angle between the flanges and the web changes from orthogonal to obtuse.
• the increased size of the angle is related to the magnitude of the twist force.
• the right ⁇ most view of FIGURE 2 illustrates in an exaggerated manner what happens to the Z-shaped structural element when a clockwise twist is applied to it. In this case, the angle between the flanges and the web change from orthogonal to acute. Again, the reduced size of the angle is related to the magnitude of the twist force.
• FIGURE 3 is a series of three longitudinal views illustrating the second type of vibration, commonly occurring in Z-shaped structural elements forming an aircraft frame. While the illustrated Z-shaped structural element is shown as straight, as will be readily appreciated by those skilled in the aircraft frame art, in actuality aircraft frame elements are longitudinally curved. (They may also have a longitudinally changing cross-sectional size.) The illustrated frame element is shown as straight to better illustrate bending vibration, which occurs in a similar (but. not as easily seen manner) in curved frame elements.
• the top view of FIGURE 3 shows the Z-shaped structural element as unbent, i.e., straight; the middle view of FIGURE 3 illustrates a concave curvature (viewed from above) in the Z-shaped structural element; and the bottom view illustrates a convex curvature (viewed from above) in the Z-shaped structural element 21.
• Z-shaped structural elements can also bend in a plane lying parallel to the pl of the flanges 25a and 25b.
• Z-shaped structural eleme can bend in any longitudinal plane, which bends can, of course, be mat matically resolved into planes lying parallel to the web 23 and the flanges and 25b, using conventional vector analysis techniques. Further, studies h shown that aircraft frame bend and twist vibration frequencies lying in the l (below 300 Hz) audio frequency range control the fuselage structural vibrati and sound transmission into the aircraft cabin.
• the viscoelastic materials used in actual embodime of the invention will have a vibration to internal heat energy dissipation p that lies at or near the temperature of the environment in which the structu elements are to be used. More specifically, as will be readily appreciated those familiar with viscoelastic materials, viscoelastic materials damp vibrati by dissipating vibration energy as heat. As will also be appreciated by th familiar with viscoelastic materials, the magnitude of the vibration energy t can be converted to heat by a particular material peaks " at a cert temperature.
• the layer of viscoelastic material 29 located between the ri constraining layer 27 and the Z-shaped structural element 21 illustrated FIGURE 1 damps vibration in two different manners.
• the vibration sou is twisting of the web 23
• the region of the viscoelastic material layer ly between the web 23 and the adjacent region of the rigid constraining layer provides direct damping.
• the rigid constraining layer coup web vibration to the region of the viscoelastic material layer 29 lying betw the flanges 25a and 25b and the adjacent -region of the rigid constraining la 27, these regions of the viscoelastic material layer provide indirect damping.
• the total weight of the damping treatment provided in accordance with the invention is substantially less than the weight of the damping treatment that would be. required if separate damping treatment in the form of a separate constraining layer viscoelastically attached to each of the webs and the two flanges of the Z-shaped structural element 21 illustrated in FIGURE 1.
• adequate vibration damping can be provided by segmenting and/or aperturing the rigid constraining layer and the layer of viscoelastic material attaching the rigid constraining layer to the structural
• FIGURE 4 illustrates a Z-shaped structural element 31 comprising a web 33 and a pair of orthogonal outwardly projecting flanges 35a and 35b.
• FIGURE 4 illustrates spaced-apart rigid constraining layers 37a and 37b, each of which is formed to mate with the same surface of the web and flanges of the Z-shaped structural element 31.
• Layers of,, viscoelastic material 29a and 29b attach the spaced apart rigid constraining layers to the same surface of the web and flanges of the Z-shaped structural element 31. While attached to the same surface of the web and flanges, the rigid constraining layers are independent of one another.
• two rigid constraining layer segments are illustrated in FIGURE 4 obviously this by way of example only. In an actual embodiment of the invention various numbers of segments of the same or different lengths can be used.
• FIGURE 5 illustrates an embodiment of the- invention similar to FIGURE 4 except that the rigid constraining layer segments are linked together. More specifically, FIGURE 5 illustrates a Z-shaped structural element 41 comprising a web 43 and a pair 4 of orthogonal outwardly projecting flanges 45a and 45b. FIGURE 5 also illustrates a segmented rigid constraining layer formed to a plurality of segments 47a and 47b having a cross-sectional configuration that mates with one of the surfaces of the web and flanges of the Z-shaped structural element 41. The segments are attached to the mating surface of the web 43 and flanges 45a and 45b of the Z-shaped structural element 41 by layers of viscoelastic material 49a and 49b.
• the segments 47a and 47b are joined by a plurality of connecting links 48a, 48b, 48c and 48d. While the FIGUR embodiment of the invention is slightly heavier than the embodiment illustra in FIGURE 4 it produces substantially the same amount of damping as embodiment of the invention illustrated in FIGURE 1 because of the links 4 48b, 48c and 48d between the segments 47a and 47b. It should be noted that apertures between the links 48a, 48b, 48c and 48d provide space for various ite to be attached to the web and flanges of the structural element 41. In t regard, the links can take on a wide variety of shapes other than that illustra in FIGURE 5. The links can be longer, narrower, wider, shorter,- etc. Furth obviously the number of linked segments can be other than two, as illustrat And, of course, other apertures can be included to provide access to structural element at non-uniform positions.
• FIGURE 6 illustrates a -further embodiment of the invent wherein a Z-shaped structural element 51 has damping treatment applied to b surfaces of its web 53 and the flanges 55a and 55b. More specifically, first second rigid constraining layers 57a and 57b mate with, and are viscoelastic attached by first and second viscoelastic layers 59a and 59b to, opposed surfa of the web 53 and flanges 55a and 55b of the Z-shaped structural element 53. a result, direct and indirect damping of the web and flanges of the Z-sha structural element 51 is provided.
• direct damping is provided by the regions of the first and second viscoelas layers attaching the first -and second rigid constraining layers to the web.
• indirect damping is provided by the regions of the first and sec viscoelastic layers attaching the first and second constraining layers 57a and 5 to the flanges 55a and 55b.
• the ri constraining layers 57 and 57b can be segmented; and, the segments can be lin together as illustrated in FIGURE 5.
• FIGURE 7 illustrates an embodiment of the invention where damping treatment is applied to the web 63 and only one flange 65a of Z-shaped structural element 61.
• the other flange 65b does not receive dampi treatment.
• FIGURE 7 illustrates a rigid constraining layer that mates with one side of the web 63 and the outer surface of one of flanges 65a of the Z-shaped structural element 61 and is attached to this surfa by a layer of viscoelastic material 69.
• direct and indirect vibration damping of w vibrations is provided by this embodiment of the invention.
• indir damping is provided only by the viscoelastic attachment to one flange, rat than by viscoelastic attachment to two flanges. And, of course only one flange ⁇ j directly and indirectly vibration damped. The other flange is undamped.
• the rigid constraining layer 67 can be segmented (FIGURE 4) and the segments can be linked together (FIGURE 5), if desired.
• FIGURE 8 also illustrates an embodiment of the invention wherein damping treatment is applied to the web 73 and only one flange 75a of a Z-shaped structural element 71.
• the other flange 75b is undamped.
• the damping treatment is attached to the inside surface of the angle defined by the damped flange and the web, as opposed to being attached to the outside surface.
• FIGURE 8 illustrates a rigid constraining layer 77 that mates with one surface of the web 73 and the inner surface of one of ' the flanges 75a of the Z-shaped structural element 71 and is attached to this composite surface by a layer of viscoelastic material 79.
• the rigid constraining layer 77 can be segmented with or without the segments being linked together, if desired.
• damping treatments can be applied to * Z-shaped structural elements.
• the nature of the damping treatment chosen for an actual embodiment of the invention will depend upon the magnitude of the vibration that occurs in the structural element to be damped and acceptable weight additions. That is, whether the chosen damping treatment will cover both sides of the structural component as illustrated in FIGURE 6, or only the web and one of the flanges as illustrated in FIGURE 7 and 8, or lie somewhere ⁇ nbetween these two extremes, as illustrated in the other FIGURES, will depend upon two factors.
• the first factor is the magnitude of the vibration that occurs in the structural element and the second factor is the- amount of acceptable weight that can be added to the structural element in order to reduce the noise created by the vibration to an acceptable leveL Whether or not the damping treatment formed by the rigid constraining and the viscoelastic material layers is continuous, apertured or segmented will depend upon similar factors, plus other factors, such as nature, amount and type " of -items to be attached to
• the rigid constraining layer attached to the structural element by the layer of viscoelastic material is of the same material as, and has a thickness generally " equal to the thickness of the web or flanges of, the structural element. While this is the preferred material and thickness, obviously, other materials and thickness can be utlized, if desired, keeping in mind that the important factor to be met is that the constraining layer be rigid so that it can prov ⁇ de the coupling effect previously described.
• FIGURES 9-12 and hereinafter described .
• invention is not limited to use with Z-shaped structural elements. Rather, invention can be utilized with other types of structural elements, for exa the I, L, C and T-shaped structural elements illustrated in FIGURES 9-12 hereinafter described.
• FIGURES Prior to describing these FIGURES, it is pointed out while these FIGURES illustrate damping treatment applied to all of the surf of the illustrated structural components, less than all of the surfaces can b treated if desired.
• the damping treatment formed by r constraining layers and viscoelastic attachment material is illustrated continuous, it can be apertured or segmented (with or without the segments b linked) if desired.
• the extent of damping treatment can vary and in an actual embodimen the invention will depend upon the amount of vibration reduction desi commensurate with weight restrictions.
• FIGURE 9 illustrates an elongate l-shaped structural element which includes a web 83 and upper and lower flanges 85a and 85b.
• flanges 85a and 85b are longitudinally centered along the edges of the web 8 that the cross sectional configuration of the structural element 81 has the sh of an I, as previously noted.
• planar r constraining layers 91a and 91b are viscoelastically attached by layers viscoelastic material 93a and 93b to the outer surfaces of the flanges 85a 85b of the l-shaped structural element 81.
• all of the potentially vibra surfaces (e.g., the web and the flanges 85a and 85b) of the l-shaped struct element 81 are covered by two rigid constraining layers and their attac layers of viscoelastic material.
• the C-shaped constraining layers 87a and couple the vibration region of the structural element (e.g., web 83 or flanges and 85b) to the other regions so that indirect as well as direct dampin provided, as heretofore described.
• FIGURE 10 illustrates an L-shaped structural element 101 ha first and second legs 103 and 105.
• First and second L-shaped rigid constrai - ' layers 107a and 107b are attached by first and second layers of viscoela material 109a and 109b to the inner and outer surfaces of the legs 103 and 10 the L-shaped structural element 101. More specifically, the first L-shaped r constraining layer 107a is attached by the first layer of viscoelastic mate
• the second L-shaped rigid constraining layer 107b is attached by the second layer of viscoelastic material 109b to the outer surface of the legs 103 and 105.
• vibration of one of the legs of the L- shaped structural element is directly damped by the regions of the layers of viscoelastic material attached to the vibrating leg and indirectly damped by the regions of the layers of viscoelastic material attached to the other leg as a result of the coupling provided by the L-shaped rigid constraining layers 107a and 107b.
• FIGURE 11 illustrates an elongate C-shaped structural element 111, comprising a web 113 and first and second flanges 115a and 115b projecting orthogonally outwardly on the same side, but from opposite longitudinal edges of, the web 113.
• a first C-shaped rigid constraining layer 117a is attached by a first layer of viscoelastic -material 119 a to the interior surface of the C-shaped structural element 111.
• a second C-shaped rigid constraining layer 117b is attached by a second layer of viscoelastic material 119b to the outer surface of the C-shaped structural element 111.
• vibration of the web or the flanges of the C-shaped structural element is directly damped by the layer of viscoelastic material attached to the vibrating region and indirectly damped by the layer of viscoelastic material attached to the other regions of the C-shaped structural element due to the coupling provided by the L-shaped rigid constraining elements 117a and 117b.
• FIGURE 12 illustrates an elongate T-shaped structural element 121 comprising a web 123 and a cross member flange 125.
• the cross member flange 125 is centered along one longitudinal edge of the web 123 so that the cross- sectional configuration of the combination is in the shape of a T.
• a first L- shaped rigid constraining layer 127a is attached by a first layer of viscoelastic material 129a to one surface defined by the web 123 and the cross member flange 125 of the T-shaped structural element 121.
• a second L-shaped rigid constraining layer 127b is viscoelastically attached by a second layer of viscoelastic material 129b to the other surface defined by the web 123 and the cross member flange 125 of the T-shaped structural element 121.
• a planar rigid constraining layer 131 is attached by a third layer of viscoelastic material 133 to the top or outer surface of the cross member flange 125 of the T-shaped structural element 121.
• the vibration of either the web or the ⁇ cross member flange of the T- shaped structural element 121 is directly damped by the layer of viscoelastic material attached to the vibrating region and indirectly damped by the layer of viscoelastic material attached to other regions, as a result of the coupling provided by the first and second L-shaped rigid constraining layers 127a a 127b.
• FIGURE 5 illustrates that the rigid constrai ing layer and the layer of viscoelastic material attaching the rigid constraini layer to the structural element can be longitudinally segmented, with t segments coupled together by links.
• FIGURE 13 also illustrates a linked ri constraining layer; however, the links connect together the regions of the ri constraining layer attached to the various areas of the structural element.
• FIGURE 13 illustrates an elongate Z-shaped structural element 1 comprising a web 143 and a pair of flanges 145a and 145b that proje orthogonally outwardly from opposite longitudinal edges of the web 143 and opposite sides thereof.
• the Z-shaped rigid constraining layer 147 has three distin regions— a web 149 and two flanges 151a and 151b.
• the links 15 . . . 1531 lie at the bends in the Z-shaped rigid constraining layer.
• a first layer viscoelastic material 155 attaches the web 149 of the Z-shaped rigid constraini layer 147 to the web 143 of the Z-shaped structural element.
• Second and thi layers of viscoelastic material 157a and 157b attach the flanges 151a and 151b the Z-shaped rigid constraining layer 147 to the flanges 145a and 145b of the shaped structural element 141. Since the links 153a . . . 1531, couple t vibration of one region (web or flanges) of the Z-shaped structural element to t other region or regions, the embodiment of the invention provides indirect well as direct damping similar to that provided by the previously describ embodiments of the invention.
• a rig constraining layer link configuration of the type illustrated in FIGURE 13 can used in other embodiments of the invention such as those illustrated in FIGUR 1 and 4-12, and variations thereof.
• a linked rigid constraining layer has, course, a weight advantage over a continuous type rigid constraining layer.
• the invention provides a method a apparatus for vibration damping structural elements having at least t transverse .legs.
• the method generally comprises viscoelastically attaching rigid contrain ⁇ ng layer to the at least two transverse legs of the undamp structural element to be damped.
• the vibration of one of the legs directly damped by the viscoelastic layer attached thereto.
• Additional indire ⁇ J damping of the vibrating leg is provided by the viscoelastic layer attached to the other leg as a result of the link created by the rigid constraining layer.
• such vibration damping treatment can be applied to one or both sides of the two legs, if desired.
• damping treatment can be applied to one or both sides of the legs.
• the structural component includes more than two legs, similar damping treatment can be applied to the other leg or legs.
• the constraining element can run the entire length of the structural element or can be apertured or segmented in various ways. If desired, the segments can be linked together. Consequently, the invention can be practiced in a wide variety of manners all of which are not specifically illustrated and described herein. Thus, it is to be understood that the invention can be practiced otherwise than as specifically described herein.

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• 1981
  • 1981-03-04 WO PCT/US1981/000279 patent/WO1981002718A1/en not_active Application Discontinuation
  • 1981-03-04 EP EP19810901037 patent/EP0047786A4/de not_active Withdrawn
  • 1981-03-04 JP JP56501394A patent/JPS57500330A/ja active Pending

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