WO1999067548A2

WO1999067548A2 - Vibration dampening device for tubular structures

Info

Publication number: WO1999067548A2
Application number: PCT/US1998/022310
Authority: WO
Inventors: Terry L. Schneider
Original assignee: Schneider Terry L
Priority date: 1998-06-25
Filing date: 1998-10-20
Publication date: 1999-12-29
Also published as: AU1111599A

Abstract

A device for dampening vibrational energy propagated along a beam has contact surfaces made of a shape memory alloy. The dampening device is positioned either within a hollow beam, or around and outer surface of the beam to be dampened. When the device is placed within a hollow beam, the device has an outer dimension that is slightly larger than an inner diameter of the beam, thereby placing the shape memory alloy contact surfaces in a selected pre-stressed condition. If the dampening device is placed around an outer surface of the beam, the device has an inner diameter that is slightly smaller than an outer diameter of the beam, thereby placing the shape memory alloy contact surfaces in a selected pre-stressed condition. Preferably, the contact surfaces are pre-stressed at a level sufficient to be near the threshold of the pseudo-elastic plateau region of the alloy's stress-strain property curve. Alternatively, the SMA may be selected and subjected to a heat processing treatment such that it is in the martensitic phase at a desired range of temperatures, in which it is believed the device will be used. As a result, the device made of SMA exhibits superelastic properties when used in the selected range of temperatures, omitting the need to pre-stress the SMA elements.

Description

VIBRATION DAMPENING DEVICE FOR TUBULAR STRUCTURES

Related Patent Applications This application claims priority from U.S. Provisional Patent Application o. 60/090,657, filed June 25, 1998, and U.S. Provisional Patent Application o. 60/095,803, filed August 7, 1998.

Field of the Invention This invention relates to a device for dampening vibrations in tubular structures.

Background of the Invention In a wide variety of situations, it is desirable to dampen vibration in structural, i.e., load-bearing, and nonstructural tubes or beams of various cross-sectional geometries. Such applications include, but are not limited to, automotive, aerospace and sports implements or structures that are exposed to repeated shock or vibration. For example, vibration dampening is desirable for high-speed rotating composite shafts in automotive and industrial application, in critical satellite support structures and in civil engineering applications requiring improved seismic and durability. Examples of sports applications include tubes or beams that form golf shafts, tennis racquets, hockey sticks, ski poles, polo sticks, baseball bats and bicycle tubing.

Conventionally, beams or similar structures that are repeatedly exposed to shock or vibration must absorb and dampen the vibrational energy. Repeated exposure to vibrational energy may therefore result in structural damage and reduce the long-term durability of the structure, particularly if the structure is thin-walled or brittle. In the context of sports implements, vibrational energy is often transferred to the user, creating an undesirable "feel" when the piece of equipment is exposed to a shock or vibration. Repeated transfer of vibrational energy to a user's body may also result in injuries.

Accordingly, there is a need in the art for an improved device for dampening vibration in tubular structures. The present invention fulfills these needs, and provides further related advantages.

Summary of the Invention Briefly, the present invention provides a device for dampening vibrational energy propagated along a beam. As used throughout the specification, a "beam" refers to a hollow or solid member having one of various cross-sectional geometries, diameters or tapers. In a preferred embodiment of the present invention, the device for dampening vibration has a body provided with a plurality of contact surfaces made of shape memory alloy. The body is positioned in a hollow beam at a selected location where dampening is desired. The body has an outer dimension that is greater than an inner dimension of the hollow beam As a result, the plurality of contact surfaces contact the inner surface of the hollow beam and are pre-stressed when the body is positioned in the hollow beam. In an alternative embodiment, the body has a plurality of contact surfaces made of shape memory alloy, and is positioned around an outer surface of a beam. The body has an inner dimension that is smaller than the outer dimension of the beam, such that the plurality of contact surfaces contact the outer surface of the beam and are pre-stressed by the contact.

In a preferred embodiment, the contact surfaces are made from a shape memory alloy (SMA) which include alloys with elements selected from the group comprising: Ni, Ag, Au, Cd, In, Ga, Mn, Cr, Co, C, N, Si, Ge, Sn, Sb, Zn, Nb, Cu, Fe, Pt, Al and Ti. In a preferred embodiment, the shape memory alloy has superelastic (reversible strain) properties, and preferably is able to exhibit stress- induced martensitic phase transformations. As discussed previously, the contact surfaces of a device provided in accordance with the present invention are pre-stressed, due to the difference between the inner and outer diameters of the device and the beam being dampened. In a preferred embodiment, the contact surfaces are pre-stressed at a level sufficient to be near the threshold of the pseudo-elastic plateau region of the alloy's stress-strain property curve, thereby maximizing the dampening properties of the device.

Alternatively, the SMA may be selected and subjected to a heat processing treatment such that it is in the martensitic phase at a desired range of temperatures, in which it is believed the device will be used. As a result, the device made of SMA exhibits superelastic properties when used in the selected range of temperatures, omitting the need to pre-stress the SMA elements.

Brief Description of the Drawings The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a partial cross-sectional elevational view of a device provided in accordance with a preferred embodiment of the present invention; FIGURE 2 is a cross-sectional elevational view of a device provided in accordance with an alternative embodiment of the present invention;

FIGURE 3 is a partial cross-sectional elevational view of a device provided in accordance with an alternative embodiment of the present invention;

FIGURE 4 is a front isometric view of a spool used in connection with the device illustrated in FIGURE 3 ;

FIGURE 5 is a front isometric view of an alternative spool provided in accordance with the present invention;

FIGURE 6 is a cross-sectional elevational view of a device provided in accordance with an alternative embodiment of the present invention; FIGURE 7 is cross-sectional plan view taken along line 7-7 of FIGURE 6;

FIGURE 8 is a front isometric view of a retaining ring used in the device of FIGURE 6;

FIGURE 9 is a partial cross-sectional elevational view of a device provided in accordance with an alternative embodiment of the present invention; FIGURE 10 is a partial cross-sectional elevational view of a device provided in accordance with an alternative embodiment of the present invention;

FIGURE 11 is a cross-sectional plan view taken along line 11-11 of FIGURE 10;

FIGURE 12 is an exploded front isometric view of the device illustrated in FIGURE 10;

FIGURE 13 is a partial cross-sectional elevational view of a device provided in accordance with an alternative embodiment of the present invention;

FIGURE 14 is a cross-sectional plan view taken along line 14-14 of FIGURE 13; FIGURE 15 is front elevational view of a device provided in accordance with an alternative embodiment of the present invention;

FIGURE 16 is a cross-sectional elevational view of a device provided in accordance with an alternative embodiment of the present invention; FIGURE 17 is a cross-sectional plan view of the device of FIGURE 15 installed in a baseball bat;

FIGURE 18 is cross-sectional elevational view of the devices illustrated in FIGURES 15 and 16, provided in a golf club shaft and head;

FIGURE 19 is an elevational plan view of a device provided in accordance with an alternative embodiment of the present invention;

FIGURE 20 is a cross-sectional elevational view taken along 20-20 of FIGURE 19;

FIGURE 21 is an elevational plan view of a device provided in accordance with an alternative embodiment of the present invention; FIGURE 22 is an elevational plan view of a device provided in accordance with an alternative embodiment of the present invention; and

FIGURE 23 is an elevation plan view of a device provided in accordance with yet another alternative embodiment of the present invention.

Detailed Description of the Invention A device for dampening vibration in a beam is provided in accordance with a preferred embodiment of the present invention. As is discussed in greater detail below, the dampening performance of the device is optimized by providing a body having a plurality of contact surfaces made of shape memory alloy that are in contact with either the inner surface or outer surface of the beam being dampened. If the beam is hollow and the body is placed within the beam, the contact surfaces contact the inner surface of the hollow beam. The body is configured to have an outer dimension that is slightly larger than the inner diameter of the beam, thereby pre- stressing the contact surfaces. If the body is positioned around the outer surface of the beam, the contact surfaces of the device are in contact with the outer surface of the beam, which may be hollow or solid. The body has an inner diameter that is slightly smaller than the outer diameter of the beam, thereby pre-stressing the contact surfaces of the device.

In a preferred embodiment, the contact surfaces are made from a shape memory alloy (SMA) which include alloys with elements selected from the group comprising: Ni, Ag, Au, Cd, In, Ga, Mn, Cr, Co, C, N, Si, Ge, Sn, Sb, Zn, Nb, Cu, Fe, Pt, Al and Ti. In a preferred embodiment, the shape memory alloy has superelastic (reversible strain) properties, and preferably is able to exhibit stress- induced martensitic phase transformations. Although a variety of shape memory alloys may be used, in a preferred embodiment, the shape memory alloy is Nitinol. Nitinol is a known SMA of nickel and titanium. As discussed previously, the contact surfaces of a device provided in accordance with the present invention are pre- stressed, due to the difference between the inner and outer diameters of the device and the beam being dampened. In a preferred embodiment, the contact surfaces are pre-stressed at a level sufficient to be near the threshold of the pseudo-elastic plateau region of the alloy's stress-strain property curve. It is believed that by pre-stressing the contact surfaces to this level, the dampening properties of the device are maximized. For example, when using Nitinol, the device provided in accordance with the present invention is configured to be pre-stressed to a level of 2-3% strain when the contact surfaces are in contact with the beam being dampened. A strain level of 2-3% corresponds to the threshold of the martensitic phase transformation for this material. Alternatively, the SMA may be selected and subjected to a heat processing treatment such that it is in the martensitic phase at a desired range of temperatures, in which it is believed the device will be used. As a result, the device made of SMA exhibits superelastic properties when used in the selected range of temperatures, omitting the need to pre-stress the SMA elements.

In a first preferred embodiment, as illustrated in FIGURE 1, a dampening device 10 comprises a length of continuously coiled SMA wire 19. The SMA wire may be wound at any selected angle relative to a longitudinal axis of the beam. The coil or body is positioned within a hollow beam 11 at a selected location where it is desired to dampen vibration. The coil has an outer dimension 18 that is slightly larger than an inner diameter 12 of beam 11. As a result, the contact surfaces 17 of the coil or body 16 are pre-stressed to a desired level against the inner surface 13 of the beam.

Alternatively, as illustrated in FIGURE 2, the device 10 comprises a length of continuously coiled SMA hollow tubing 20 positioned within the hollow beam 11. The SMA hollow tubing may be wound at any selected angle relative to a longitudinal axis of the beam. An outer diameter of the coil is slightly larger than the inner diameter of the beam, thereby pre-stressing the coil to a desired degree, as discussed previously.

If desired, as illustrated in FIGURES 3-5, the length of solid or hollow SMA wire 19 is wound around a spool 21 that is positioned coaxially within the hollow beam 11. In a preferred embodiment, the spool 21 is provided with a plurality of holes 22 that are sized to receive and engage ends of the solid or hollow SMA wire. The SMA wire may therefore be mechanically constrained along the length of the spool in this manner. Alternatively, to further constrain the SMA wire, the spool 21 is provided with a first annular collar 23 coupled to a first end 24 of the spool, and a second annular collar 25 coupled to a second end 26 of the spool. The solid or hollow SMA wire is wound around the spool 21 between the first and second annular collars 23, 25. Preferably, the width 56 of the spool 21 is less than the inner diameter 12 of the beam. As an alternative to SMA wire, a length of SMA hollow tubing may be wound around the spool.

In an alternative embodiment of the present invention, as illustrated in FIGURE 6-8, the body of the device comprises a tube 27 provided with a first plurality of holes 28 circumferentially spaced adjacent a first end 62 of the tube and a second plurality of holes 29 circumferentially spaced adjacent a second end 63 of the tube. The first plurality of holes 28 are laterally aligned with the second plurality of holes 29. A length of SMA wire 30, and alternatively SMA hollow tubing, extends along an outer surface 31 of the tube 27 between the first and second sets of holes. The SMA wire passes through and is secured to the tube by the two sets of holes. In a preferred embodiment, a single length of SMA wire or hollow tubing is alternately threaded through the first and second pluralities of holes in a continuous manner. Alternatively, multiple strands of SMA wire or hollow tubing are threaded through a first hole adjacent the first end of the tube and through an aligned second hole adjacent the second end of the tube. The body has an outer dimension 64 that is slightly larger than the inner diameter 12 of the beam 11, thereby pre-stressing the contact surfaces comprising SMA wire or hollow tubing.

In an alternative embodiment as illustrated in FIGURE 9, the body of the device comprises a tube 32 having a plurality of threads 33 extending around a circumference of the outer surface 34 of tube 32. The threads 33 are preferably, but not necessarily, integral to the main body of the device. The contact points comprising the threads may be either discrete rings of threads or continuous, spiraled rings along the length of the device. The angled surfaces of the threads may be either equivalent or variable in angle relative to the angled surfaces of adjacent threads. The threads are made of SMA, and the outer edges 57 of the threads are either flat or pointed. The device has an outer dimension 65 that is slightly greater than the inner diameter 12 of beam 11 to create a selected pre-stressed condition in the contact surfaces comprising the edges of the threads. The thread edges 57 may vary in contact area and in thickness to achieve a desired pre-stress level when positioned within the beam.

In an alternative embodiment, as illustrated in FIGURES 10-12, the body of the device comprises a tube 35 having a plurality of holes 36 spaced longitudinally along the tube. The device 10 further includes a plurality of washers 37 formed from SMA. Each washer 37 has an opening 38 extending through the washer and one or more tabs 39 extending into the opening. As best seen in FIGURES 10 and 11, the tube 35 extends through the opening in each of the washers such that the tab 39 of each of the washers engages one of the holes 36, thereby coupling the washer to the tube. The outer diameter 58 of the washer 37 is slightly greater than the inner diameter 12 of the beam 11, thereby placing the washers in a selected pre-stressed state. The level to which the contact surfaces comprising the washer edges are pre- stressed may be varied by varying the outer diameter and thickness of the washers. In an alternative embodiment, as illustrated in FIGURES 13 and 14, the body of the device comprises a tube 40 positioned coaxially in the hollow beam 11 and having pairs of holes 41 spaced longitudinally along the tube. Each pair of holes has a first hole 43 and a second hole 44 that are spaced diametrically from each other, and that extend through a wall 42 of the tube. A length of SMA wire 45 extends through each pair of holes and has a first end 59 and a second end 60 that are both in contact with the inner surface 13 of the beam. Alternatively, SMA hollow tubing may be used. As best seen in FIGURE 14, the length of SMA wire or hollow tubing is sufficiently long to contact the inner surface of the beam and place the length of SMA wire or hollow tubing in a selected pre-stressed state. In an alternative embodiment, as illustrated in FIGURE 15, the outer surface 46 of the body 66 is pleated to created a plurality of annular edges 47 that are spaced longitudinally from each other and that define a maximum diameter 48. The contact points comprising the annular edges 47 may be discreet rings of threads or continuous, spiraled rings along the length of the device. The angles θ_j, θ₂ of the pleats may vary. When the device is positioned within a hollow beam, for example within the handle of a baseball bat 70 as illustrated in FIGURE 17 or within the shaft 71 and head 72 of a golf club as illustrated in FIGURE 18, the annular edges 47 are in contact with the inner surface of the beam. The maximum diameter 48 is slightly larger than the inner diameter of the beam being dampened, such that the contact surfaces comprised of the annular edges 47 are in a desired pre-stressed condition. If desired, for example, to minimize weight, a bore is provided through the body 66.

As illustrated in FIGURES 16 and 18, a device is provided in accordance with a preferred embodiment of the present invention having an internal surface 49 that is pleated to create a plurality of annular edges 51 that define a minimum inner diameter 50 of the body. The angles θi, θ₂ of the pleats may vary. When the device is positioned on the outer surface 15 of the beam, the annular edges 51 contact the outer surface 15 of the beam. The minimum inner diameter 50 is slightly smaller than the outer diameter 14 such that the contact surfaces comprising the annular edges 51 are in a selected pre-stressed condition. Such a device may be used alone, or in combination with an internal device, as illustrated in FIGURE 18. It will also be understood that other embodiments described previously for placement within a hollow beam may be adapted for use external to a beam. For example, a length of SMA wire or hollow tubing may be wound around an outer surface of a beam. Similarly, the device illustrated in FIGURE 9 may be threaded internally, such that the threads 33 extend from an inner surface of the tube. As such, when the tube is positioned around an outer surface of a beam, the threads provided on the inner surface of the tube contact and are pre-stressed against the outer surface of the beam being dampened. In another alternative embodiment, as illustrated in FIGURES 19-20, an annular retaining ring 52 is positioned around and is radially spaced from the outer surface 15 of a beam 67. A length of SMA wire 53 or hollow tubing is positioned between the outer surface 15 of the beam and the inner surface 54 of the retaining ring 52. The SMA wire 53 may be oriented substantially parallel to a longitudinal axis 55 of the beam, as illustrated in FIGURES 19 and 20. Alternatively, the SMA wire may be wound around the beam transverse to the longitudinal axis, as illustrated in FIGURE 21. Although these two orientations are preferred for ease of manufacturing, it will be understood that the SMA wire may be oriented at any angle along the outer surface of the tube. The outer retaining ring 52 is sized to pre-stress the SMA wire or hollow tubing against the outer surface of the beam. The ring 52 may be opaque or transparent to allow visual detection of the SMA elements.

Alternatively, as illustrated in FIGURE 22 and discussed previously, a coil 73 made of SMA wire or hollow tubing is wound around an external surface of a beam 74. An inner diameter of the coil 73 is slightly smaller than the outer diameter 75 of the beam, such that the SMA wire or hollow tubing is pre-stressed against the outer surface of the beam, without the use of a retaining ring. As an alternative to an SMA coil 73, a solid SMA band 76 may be provided around the outer surface of a beam, as illustrated in FIGURE 23. Similar to the discussion above, the band 76 has an inner diameter that is slightly smaller than the outer diameter of the beam 74, thereby pre-stressing the SMA band against the outer surface of the beam.

By providing a device in accordance with a preferred embodiment of the present invention, having contact surfaces made of SMA that are pre-stressed when brought into contact with either the inner or outer surface of the beam being dampened, vibrational energy propagated along the beam is efficiently absorbed and dampened. The pre-stressed condition of the alloy allows it to more efficiently absorb stresses applied by vibrational energy in the beam due to the device being nearer to the stress-induced, reversible, change-in-phase state of the shape memory alloy, known as the "superelastic" or "pseudo-elastic" state of the alloy. The degree of pre- stress, and hence degree of efficiency of vibration dampening, of the contact surfaces is controlled by the geometry, thickness, number of contact points along the device's main body, and the degree of dimensional difference between the device and the structural beam. More particularly, the wall thickness of SMA flexible, hollow tubing may vary, as well as the length, outer and inner dimensions, and number of contact points of devices provided in accordance with the present invention, to achieve a desired pre-stress level. The desired pre-stress level in turn is determined by the material being used, and the particular application, which will dictate the desired degree of vibrational energy dampening. Alternatively, the SMA may be selected and subjected to a heat processing treatment such that it is in the martensitic phase at a desired range of temperatures, in which it is believed the device will be used. As a result, the device made of SMA exhibits superelastic properties when used in the selected range of temperatures, omitting the need to pre-stress the SMA elements.

A device for dampening vibrational energy in a beam has been shown and described. From the foregoing, it will be appreciated that although embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit of the invention. Thus, the present innovation is not limited to the embodiments described herein, but rather is defined by the claims which follow.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A device for dampening vibration in a hollow beam having an inner dimension and an inner surface, comprising: a body having a plurality of contact surfaces made of shape memory alloy, the body being positioned in the hollow beam at a selected location and having an outer dimension that is greater than the inner dimension of the hollow beam such that the plurality of contact surfaces contact the inner surface of the hollow beam and are pre- stressed when the body is positioned in the hollow beam.

2. The device according to Claim 1, wherein the body further comprises a length of continuously coiled shape memory alloy wire.

3. The device according to Claim 2, wherein the length of continuously coiled shape memory alloy wire is wound around a spool that is positioned coaxially in the hollow beam.

4. The device according to Claim 3, wherein the spool has an outer surface provided with a plurality of holes that are sized to receive and engage ends of the length of continuously coiled shape memory alloy wire.

5. The device according to Claim 3, wherein a first annular collar is coupled to a first end of the spool and a second annular collar is coupled to a second end of the spool, the length of continuously coiled shape memory alloy wire being wound around the spool between the first and second annular collars.

6. The device according to Claim 1, wherein the body further comprises a length of continuously coiled shape memory alloy hollow tubing.

7. The device according to Claim 6, wherein the length of continuously coiled shape memory alloy hollow tubing is wound around a spool that is positioned coaxially in the hollow beam.

8. The device according to Claim 7, wherein the spool has an outer surface provided with a plurality of holes that are sized to receive and engage ends of the length of continuously coiled shape memory alloy hollow tubing.

9. The device according to Claim 7, wherein a first annular collar is coupled to a first end of the spool and a second annular collar is coupled to a second end of the spool, the length of continuously coiled shape memory alloy hollow tubing being wound around the spool between the first and second annular collars.

10. The device according to Claim 1, wherein the body further comprises a tube having a first plurality of holes circumferentially spaced adjacent a first end of the tube and a second plurality of holes circumferentially spaced adjacent a second end of the tube, and a length of shape memory alloy wire extends along an outer surface of the tube between the first plurality of holes and the second plurality of holes, the length of shape memory alloy wire passing through and being secured to the tube by the first and second plurality of holes.

11. The device according to Claim 1 , wherein the body further comprises a tube having a first plurality of holes circumferentially spaced adjacent a first end of the tube and a second plurality of holes circumferentially spaced adjacent a second end of the tube, and a length of shape memory alloy hollow tubing extends along an outer surface of the tube between the first plurality of holes and the second plurality of holes, the length of shape memory alloy hollow tubing passing through and being secured to the tube by the first and second plurality of holes.

12. The device according to Claim 1, wherein the body further comprises a tube having an outer surface and a plurality of shape memory alloy threads extending around a circumference of the outer surface of the tube.

13. The device according to Claim 12, wherein the shape memory alloy threads are provided with flat outer edges in contact with the inner surface of the hollow beam.

14. The device according to Claim 12, wherein the shape memory alloy threads are provided with pointed outer edges in contact with the inner surface of the hollow beam.

15. The device according to Claim 1, wherein the body further comprises a tube having a plurality of holes spaced longitudinally along the tube, and a plurality of washers formed from shape memory alloy, each washer having an opening extending through the washer and a tab extending into the opening, the tube passing through the opening of each of the washers such that the tab of each of the washers engages one of the holes, thereby coupling the washer to the tube.

16. The device according to Claim 1 further comprising: a tube positioned coaxially in the hollow beam and having pairs of holes spaced longitudinally along the tube, each pair of poles having a first hole extending through a wall of the tube and spaced diametrically from a second hole extending through the wall of the tube, a length of shape memory alloy wire extending through each pair of holes and having a first end and a second end that are both in contact with the inner surface of the hollow beam.

17. The device according to Claim 1 further comprising: a tube positioned coaxially in the hollow beam and having pairs of holes spaced longitudinally along the tube, each pair of poles having a first hole extending through a wall of the tube and spaced diametrically from a second hole extending through the wall of the tube, a length of shape memory alloy hollow tubing extending through each pair of holes and having a first end and a second end that are both in contact with the inner surface of the hollow beam.

18. The device according to Claim 1, wherein the body is formed of shape memory alloy and an outer surface of the body is provided with a plurality of annular edges spaced longitudinally from each other and defining a maximum outer diameter of the body, the annular edges being in contact with the inner surface of the hollow beam.

19. The device according to Claim 18, wherein the body is further provided with a bore extending longitudinally through the body.

20. The device according to Claim 1 further comprising: a second body formed of shape memory alloy and having an internal surface that is provided with a plurality of annular edges spaced longitudinally from each other and defining a minimum inner diameter of the second body, the second body being positioned around an outer surface of the hollow beam such that the plurality of annular edges contact the outer surface of the hollow beam.

21. The device according to Claim 1, wherein the shape memory alloy is pre-stressed at a level sufficient to be near the threshold of the pseudo-elastic plateau region of the alloy's stress-strain property curve.

22. The device according to Claim 1, wherein the shape memory alloy is selected so as to be in a martensitic phase at a temperature at which the device is used.

23. A device for dampening vibration in a beam having an outer dimension and an outer surface, comprising: a body having a plurality of contact surfaces made of shape memory alloy, the body being positioned around the outer surface of the beam at a selected location and having an inner dimension that is less than the outer dimension of the beam such that the plurality of contact surfaces contact the outer surface of the beam and are pre-stressed when the body is positioned around the outer surface of the hollow beam.

24. The device according to Claim 23, wherein the body is formed of shape memory alloy and has an internal surface that is pleated to create a plurality of annular edges spaced longitudinally from each other and defining a minimum inner diameter of the body, the body being positioned around the outer surface of the beam such that the plurality of annular edges contact the outer surface of the beam.

25. The device according to Claim 23, wherein the body further comprises an annular retaining ring positioned around and radially spaced from the outer surface of the beam, a length of shape memory alloy wire being positioned between the outer surface of the beam and an inner surface of the annular retaining ring, the length of shape memory alloy wire extending around the circumference of the beam substantially along the length of the annular retaining ring.

26. The device according to Claim 23, wherein the body further comprises an annular retaining ring positioned around and radially spaced from the outer surface of the beam, a length of shape memory alloy hollow tubing being positioned between the outer surface of the beam and an inner surface of the annular retaining ring, the length of shape memory alloy hollow tubing extending around the circumference of the beam substantially along the length of the annular retaining ring.

27. The device according to Claim 23, wherein the body further comprises an annular retaining ring positioned around and radially spaced from the outer surface of the beam, a length of shape memory alloy wire positioned between the outer surface of the beam and an inner surface of the annular retaining ring and extending along the outer surface of the beam substantially along the length of the annular retaining ring.

28. The device according to Claim 23, wherein the body further comprises an annular retaining ring positioned around and radially spaced from the outer surface of the beam, a length of shape memory alloy hollow tubing positioned between the outer surface of the beam and an inner surface of the annular retaining ring and extending along the outer surface of the beam substantially along the length of the annular retaining ring.

29. The device according to Claim 23, wherein the shape memory alloy contact surfaces are pre-stressed at a level sufficient to be near the threshold of the pseudo-elastic plateau region of the alloy's stress-strain property curve.

30. The device according to Claim 23, wherein the shape memory alloy is selected so as to be in a martensitic phase at a temperature at which the device is used.

31. The device according to Claim 23, wherein the body further comprises a coil of shape memory alloy wire.

32. The device according to Claim 23, wherein the body further comprises a coil of shape memory alloy hollow tubing.

33. The device according to Claim 23, wherein the body further comprises a band of shape memory alloy.