Apparatus and associated method for detuning from resonance a structure

A system for detuning from resonance a support structure which receives vibratory energy is disclosed. In one embodiment, the system includes a substrate actuator having at least a first wire embedded in a substrate matrix material, the actuator being couplable to the support structure. The system may further include a heater for heating at least the first wire from a first to a second temperature to increase the modulus of elasticity of the first wire, which in turn increases the stiffness of the substrate actuator. Such an increase in the stiffness of the substrate actuator detunes from resonance structures supporting a device from which vibratory energy emanates, and also inhibits transmission of vibratory energy of specific frequencies into structures supporting equipment sensitive to vibrations.

FIELD OF THE INVENTION 
The present invention generally relates to an apparatus for detuning from 
resonance a structure which is subject to vibrations, and more 
specifically, to a substrate actuator capable of increasing its stiffness 
to detune from resonance a structure subject to vibratory energy from a 
vibrating device, the substrate actuator being couplable to the structure. 
BACKGROUND OF THE INVENTION 
Over the years, various techniques and systems have been developed for 
damping vibrating devices, such as motors and compressors. Generally, such 
techniques and systems attempt to reduce the effect of vibrating devices 
on surrounding structures by isolating the vibrating device. For example, 
vibration isolation mounts having a rubber cylinder positioned between a 
support structure and a vibrating device mounted thereon have been used to 
isolate the vibratory motion of the vibrating device by absorbing 
vibrations. However, the vibration absorbing ability of such visco-elastic 
cylinders degrades over time. In addition, such traditional vibration 
isolators may introduce undesirable compliance into an interface between 
the vibrating device and its structural support base. Furthermore, 
traditional vibration isolators may not be acceptable for use in aerospace 
applications, among others, due to the weight and complexity associated 
with such systems. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide an 
apparatus and method for damping vibrations emanating from a device 
mounted on a base or support structure. 
It is another object of the present invention to provide a lightweight and 
reusable apparatus for detuning from resonance a support member having a 
device from which vibratory energy emanates interconnected thereto. 
It is yet another object of the present invention to provide an apparatus 
for detuning from resonance a support member which does not warp, twist or 
otherwise alter the shape or configuration of the support member to 
accomplish such detuning. 
It is a further object of the present invention to provide a modular 
apparatus for detuning from resonance a structure. 
It is yet another object of the present invention to provide an apparatus 
for detuning from resonance a support structure, the apparatus offering 
dielectric protection, wire collimation and wire tendon registration 
within the support structure. 
It is still another object of the present invention to provide an apparatus 
for detuning from resonance a structure having equipment mounted thereon 
which may be adversely effected by vibratory energy emanating from a 
vibrating device positioned proximate the structure. 
The above objects are accomplished by providing a substrate actuator having 
at least a first wire embedded within a substrate matrix material. In one 
aspect of the present invention, for purposes of detuning from resonance a 
support structure upon which a device from which vibrations emanate is 
interconnected, at least one of the substrate actuators of the present 
invention is couplable to the support structure, and is operatively 
associated with a means for heating at least the first wire. In another 
aspect of the present invention, at least one of the substrate actuators 
of the present invention is couplable to a structure to which components 
adversely effectable by vibratory energy are interconnected to detune from 
resonance such structure. 
In one embodiment, heating of at least the first wire within the substrate 
actuator of the present invention from a first temperature to a second 
temperature increases the modulus of elasticity of at least the first wire 
embedded within the substrate matrix material from a first modulus of 
elasticity to a second modulus of elasticity, which in turn increases the 
stiffness of the substrate actuator. Such an increase in stiffness during 
operation of the vibrating device inhibits propagation of vibratory energy 
of specific frequencies from the vibrating device into the support 
structure and surrounding structures by detuning from resonance the 
support structure. 
To facilitate rapid installation and/or removal of the substrate actuators 
of the present invention into and from various support structures, and to 
facilitate access thereto, the substrate actuators of the present 
invention may be modular in nature. In this regard, a substrate actuator 
having features of the present invention may be embeddable in, on or 
otherwise couplable to a structure, as opposed to embedding wires directly 
into the support structure. As such, the substrate actuator of the present 
invention offers dielectric protection, wire or foil collimation and wire 
registration within the support structure. Such modularity also provides 
for efficient installation and/or removal of the substrate actuators from 
such support structures. 
In one embodiment, at least one substrate actuator of the present invention 
is sized and/or configured to substantially fit within a recessed or 
hogged-out portion in a surface of the structure upon which the vibrating 
device is interconnectable and/or a structure effected by the vibratory 
energy emanating from a vibrating device. In another embodiment, at least 
one substrate actuator of the present invention is embeddable within at 
least one cavity formed within the structure to be detuned from resonance. 
Substrate actuators of the present invention may also be positioned on one 
or more surfaces of such support structures. In yet another embodiment, at 
least one substrate actuator is interconnectable to the support structure 
such that at least a portion of the substrate actuator is interposed 
between the device from which vibratory energy emanates and the support 
structure. 
For purposes of significantly increasing the stiffness of the substrate 
actuator when desired, the substrate matrix material may be selected. 
Generally, at an elevated temperature, the modulus of elasticity of at 
least the first wire should be greater than or equal to the modulus of 
elasticity of the substrate matrix material, and, at lower temperatures, 
the modulus of elasticity of at least the first wire is comparable or can 
be lower than the modulus of elasticity of the substrate matrix material. 
In one embodiment, the matrix material comprises a nonconductive material 
having a relatively low modulus of elasticity, such as glass epoxy, or 
materials with relatively higher elastic modulii, such as glass polycynate 
or glass polyimide. The structure on or within which the substrate 
actuators of the present invention are couplable may comprise a composite 
material or a metal, such as aluminum, which has a relatively low modulus 
of elasticity. 
In one embodiment, for purposes of achieving a significant increase in the 
modulus of elasticity of at least the first wire, relative to the 
substrate matrix material, at least the first wire is fabricated from a 
shape memory alloy (e.g., nickel titanium, nickel titanium copper, nickel 
titanium palladium and nickel titanium hafnium) . In instances where at 
least the first wire comprises a shape memory alloy, the increase in 
modulus of elasticity and therefor, the increase in stiffness of the 
substrate actuator, is reversible, as repeated heating and cooling of at 
least the first wire produces a reversible crystalline phase 
transformation within the first wire. As such, increasing the temperature 
of a first wire comprising a shape memory alloy does not substantially 
alter the shape or configuration of the first wire, but only results in an 
increase in the modulus of elasticity of the first wire. In this regard, 
the shape or configuration of the substrate matrix material is not 
substantially altered, and detuning of the support structure from 
resonance is accomplished without twisting of the substrate actuator or 
structure coupled thereto. 
A plurality of shape memory alloy wires may be embedded in substrate matrix 
material to form a substrate actuator interconnectable to a support 
structure to detune from resonance the support structure. Detuning from 
resonance of the support structure is enhanced due to the combinative 
effect of the plurality of wires embedded within the substrate matrix 
material. Specifically, for a device having a given mass, the number of 
shape memory alloy wires utilized in the substrate actuator is selectable, 
depending upon the amount of modulus shift desired in the substrate 
actuator. In this regard, the degree to which the modulus of elasticity of 
the substrate actuator should increase to affect a frequency shift is 
dependent upon the number of wires embedded in the substrate matrix 
material, as well as the amount of heat applied to the wires within the 
phase transformation temperature range. 
At least the first wire may be uniformly distributed throughout the 
substrate matrix material to uniformly increase the stiffness of the 
substrate matrix material throughout the substrate (i.e., to avoid 
radiated stiffness across the substrate). In one embodiment, at least the 
first wire is distributed within the matrix material in one of a 
serpentine, circular and criss-cross pattern. Further, in instances where 
portions or segments of at least the first wire are positioned 
substantially adjacent one another, such portions are spaced apart a 
distance of at least one diameter of the first wire, with matrix material 
extending therebetween. In another embodiment, for purposes of 
sufficiently increasing the stiffness of the substrate actuator throughout 
the actuator, such portions of at least the first wire are spaced apart a 
distance of no more than ten diameters of the first wire. In addition, at 
least the first wire may be embedded within the matrix material such that 
at least the first wire is encapsulated within the matrix material. In 
this regard, the apparatus of the present invention offers dielectric 
protection. 
Heating of at least the first wire may be accomplished by convective and/or 
conductive heating means and/or by resistance heating means. In one 
embodiment, the heating means is in fluid connection with at least the 
substrate matrix material and comprises a means for passing a fluid (e.g., 
air) at an elevated temperature over the substrate actuator (e.g., for 
oven-type heating). Such convective heating increases the temperature of 
the substrate matrix material, which in turn increases the temperature of 
at least the first wire embedded therein. This increase in the temperature 
of at least the first wire increases the modulus of elasticity in at least 
the first wire, which results in an increase in the stiffness of the 
actuator. In another embodiment, the heating means is in electrical 
connection with at least the first wire and comprises a means for direct, 
resistance heating of at least the first wire. In this embodiment, at 
least the first wire may be electrically connected to a source for 
supplying an electric current. In this regard, the temperature of at least 
the first wire may be increased by resistance heating, which in turn, 
increases the modulus of elasticity of the first wire to thereby increase 
the stiffness of the actuator to thereby detune from resonance the support 
structure receiving vibratory energy. 
In another aspect, the present invention is directed to a method for 
detuning a structure effected by vibratory energy. In one embodiment, the 
method concerns detuning from resonance a structure upon which a vibrating 
device is interconnected. In another embodiment, the method concerns 
detuning from resonance a structure supporting components which are 
adversely effectable by vibratory energy. The method generally includes 
the steps of coupling with the structure at least a first modular 
substrate actuator having at least a first wire embedded within a 
substrate matrix material and heating at least the first wire to increase 
the stiffness of the substrate actuator. In instances where at least the 
first wire is a shape memory alloy, such heating of the first wire 
increases the modulus of elasticity of the first wire, which increases the 
stiffness of the modular substrate actuator to detune from resonance the 
structure coupled therewith. 
In one embodiment, the step of heating at least the first wire includes 
applying electrical current to at least the first wire to resistively heat 
at least the first wire. Alternatively, or in conjunction with the 
above-described applying step, the step of heating includes flowing a 
fluid at a temperature greater than the temperature of at least the first 
wire over the substrate actuator to heat at least the first wire to 
thereby increase the modulus of elasticity of at least the first wire. 
Such flowing of a fluid over the substrate actuator provides for 
convective and/or conductive heat transfer from the fluid to at least the 
first wire via the substrate matrix material. 
In one embodiment, the method further includes the steps of uniformly 
distributing at least the first wire within the matrix material in a 
selected pattern in order to provide for a uniform increase in stiffness 
across the substrate actuator when the first wire is heated. The uniformly 
distributing step may include configuring at least the first wire in the 
selected pattern within a mold cavity, filling the mold cavity with a 
matrix material (e.g., chipped fiber and resin mixture) and curing the 
matrix material to form the modular substrate actuator. 
In one embodiment, the step of coupling the first substrate actuator to the 
structure includes the step of interconnecting the substrate actuator to 
the structure by chemically bonding or mechanically fastening the 
substrate actuator to the structure. For purposes of enhancing coupling 
between the substrate actuator and the support structure to thereby 
enhance detuning from resonance the support structure, a plurality of 
substrate actuators may be interconnected to or embedded within one or 
more surfaces of the support structure. In another embodiment, for 
purposes of enhancing coupling between the substrate actuator and the 
support structure to thereby enhance detuning of the support structure, 
the step of interconnecting the first substrate actuator includes the 
steps of forming at least a first recessed area or cavity within the 
support structure and bonding the substrate actuator within the first 
recessed area or cavity via a chemical bond or mechanical fastener, the 
substrate actuator and first recessed area or cavity being of 
substantially corresponding volumes.

DETAILED DESCRIPTION OF THE INVENTION 
FIGS. 1-7 illustrate a substrate actuator embodying the various features of 
the present invention. Generally, for purposes of detuning from resonance 
a support structure having a vibrating device interconnected thereto, or 
otherwise having equipment mounted thereon which is effected by a 
vibrating device, the modular actuator 10 includes at least a first wire 
16, shown in FIG. 2, embeddable within a substrate matrix material 22. Of 
importance, at least the first wire 16 is operatively associated with a 
means for heating at least the first wire 16. In this regard, heating of 
at least the first wire 16 from a first temperature to a second 
temperature increases the modulus of elasticity of the first wire 16 from 
a first modulus of elasticity to a second modulus of elasticity, which, in 
turn, increases the stiffness of the substrate actuator. As such, the 
substrate actuator 10 detunes from resonance the support structure 36 upon 
which the vibrating device 42 is mounted and thus inhibits transmission of 
vibratory energy of specific frequencies from the vibrating device into 
the support structure and into surrounding structures. 
As illustrated in FIGS. 1 and 4, the actuator 10 is modular in nature, 
which facilitates the rapid installation and/or removal of the actuator 10 
into and/or from support structures 36 interconnected to vibrating devices 
42. In one embodiment, the support structure 36 upon which the vibrating 
device 42 (e.g., compressor, motor, electronic and optical component 
packages) is mounted, is "hogged out" and/or otherwise configured to 
receive the modular substrate actuator 10 therein. In this regard, the 
modular substrate actuator 10 may be sized to be embeddable within a first 
hogged-out portion 38 of the support structure 36. Further, in order to 
provide enhanced coupling between the modular actuator 10 and the support 
structure 36, the modular actuator 10 may be chemically bonded to the 
support structure, within the hogged-out portion 38, via an adhesive, such 
as a two part epoxy or paste. In an alternative embodiment, the modular 
actuator 10 may be interconnected to the support structure 36 via 
mechanical fastening devices. Such coupling of the modular actuator 10 to 
the support structure 36 enhances the detuning capabilities of the modular 
actuator 10 as increases in stiffness in the modular actuator 10 are 
transmittable into the support structure 36. 
Referring to FIGS. 1-5, for purposes of significantly increasing the 
stiffness of a modular actuator when a vibrating device is operating, the 
first wire 16 of the modular actuator 10 exhibits increased modulus of 
elasticity with increases in temperature of the first wire 16. More 
specifically, the first wire 16 of the present invention has a first 
modulus of elasticity at a first temperature and a second modulus of 
elasticity greater than the first modulus of elasticity at a second 
temperature greater than the first temperature. In this regard, when 
heated from a first temperature to a second temperature, the first wire 16 
exhibits an increase of modulus of elasticity, which, in turn, provides 
for a stiffer first wire 16. In one embodiment, for purposes of achieving 
a significant increase in the modulus of elasticity of the first wire, the 
first wire is fabricated from a shape memory alloy selected from the group 
consisting of nickel titanium, nickel titanium copper, nickel titanium 
palladium and nickel titanium hafnium. In this regard, increases in 
stiffness of the first wire 16 are reversible as heating of the first wire 
16 produces a reversible crystalline phase transformation within the first 
wire 16. When heat-actuated, the modulus of elasticity of the first wire 
16 fabricated from a shape memory alloy increases by a factor from about 
three to about seven times the original modulus of elasticity, as a 
function of wire conditioning and training, without substantially altering 
the shape or configuration of the first wire. 
As illustrated in FIGS. 1 and 4, at least the first wire 16 is embeddable 
into the substrate matrix material 22, which provides dielectric 
protection. Generally, for purposes of significantly increasing the 
stiffness of the modular actuator 10, the modulus of elasticity of the 
first wire 16 at an elevated temperature should be greater than or equal 
to the modulus of elasticity of the substrate matrix material 22, and, at 
lower temperatures, the modulus of elasticity of the first wire 16 should 
be comparable or lower than the modulus elasticity of the substrate matrix 
material 22. In this regard, the substrate matrix material 22 comprises a 
composite material having a modulus of elasticity of less than about 3 
million pounds per square inch (msi) to about 7 msi. In one embodiment, 
the substrate matrix material which encapsulates at least the first wire 
16 comprises a glass epoxy. The substrate matrix material 22 may be 
fabricated from a nonconductive material, as electric current may flow 
through wires 16 to heat the wires 16. In other embodiments, the substrate 
matrix material comprises glass polycynate or glass polyimide. 
FIGS. 2 and 3A-3B illustrate a few of the configurations in which at least 
the first wire 16 may be embedded within the substrate matrix material 22. 
Generally, at least the first wire 16 is uniformly distributed throughout 
the substrate matrix material 22 to uniformly increase the stiffness 
throughout the substrate actuator 10 when at least the first wire 16 is 
heated. In one embodiment, illustrated in FIGS. 1 and 2, at least the 
first wire 16 is distributed within the substrate matrix material 22 in a 
serpentine configuration. Alternatively, and as illustrated in FIGS. 
3A-3B, at least the first wire 16 may be configured in a circular or 
criss-cross pattern. These configurations of at least the first wire 16 
within the substrate matrix material 22 provide wire or foil collimation. 
The shape memory alloy wire packing density and wire orientation within the 
substrate material is dependent upon the mode shapes of the target 
frequencies to be shifted. The greatest effect will be when the mode shape 
deforms the structure in such a way as to stretch and compress the shape 
memory alloy wires. If the structure with the shape memory alloy is a beam 
that is being stretched axially and in the direction of the wires, the 
stiffness is determined as follows: 
EQU Stiffness=Area.sub.SMA *Modulus.sub.SMA *Area.sub.core *Modulus.sub.core 
+.SIGMA.Area.sub.plies *Modulus.sub.ply 
If the beam is being deformed in bending, the stiffness is determined by: 
EQU Stiffness=Inertia.sub.SMA *Modulus.sub.SMA *Inertia.sub.core 
*Modulus.sub.core +.SIGMA.Inertia.sub.plies *Modulus.sub.ply, 
where the inertia calculations are about the neutral axis of the structure. 
The change in the frequency of the beam is proportional to 
.sqroot.Stiffness.sub.actuated /Stiffness .sub.unactuated 
In most structures, the beam analogy may be too simplistic to be useful. 
The analysis to determine volume fraction and placement of the shape 
memory alloy wires is usually addressed using a Finite Element Model. The 
types of elements used in the analysis will depend on the fidelity of the 
desired answer. If shell elements are used, the material properties are 
best generated from a laminate or composite stackup. The ply properties 
that contain the shape memory alloy wires can be created using any of the 
standard micro-mechanics theories such as "Composite Cylinder Assemblage" 
or "Halpin-Tsai" to name just a few. Laminate properties such as stiffness 
need to be calculated for both the actuated and the un-actuated 
temperatures states. 
The overall change in stiffness of the structure is dependent upon the 
product of the magnitude of change in the modulus of the shape memory 
alloy and the volume fraction of shape memory alloy material relative to 
the stiffness of the matrix material. Matrix materials with a high modulus 
will require higher volume fractions of shape memory alloy material to 
experience similar changes in stiffness if a low modulus matrix material 
were employed. Typically, the volume fraction of shape memory alloy is 
increased by increasing the packing density of the substrate actuators of 
the present invention. 
In one embodiment, for purposes of adequately increasing stiffness of the 
substrate actuator throughout the actuator, adjacent segments or portions 
of at least the first wire 16 should be spaced no more than 10 diameters 
of the first wire 16 apart. In another embodiment, adjacent segments or 
portions of at least the first wire 16 should be positioned no closer than 
one diameter of the first wire 16 apart, with the matrix material 22 
extending between such portions of the first wire 16. Otherwise, the 
changes in the modulus of elasticity of the first wire 16, and resulting 
increases in stiffness of the substrate actuator are insignificant. And, 
if such portions of the first wire 16 contact one another, resistance 
becomes an issue. In a preferred embodiment, for substrate matrix 
materials comprising one of a glass epoxy, glass polycynate and glass 
polyimide, adjacent portions of the first wire 16 are between one diameter 
of the first wire 16 and six diameters of the first wire 16 apart (e.g., 
where the first wire 16 has a diameter of 0.020 inches, 0.60 inches, 0.80 
inches, etc.). 
The heating means is generally used to increase the modulus of elasticity 
of at least the first wire 16, which results in an increase in stiffness 
of the substrate actuator 10 to thereby detune from resonance the support 
structure 36 upon which the vibrating device 42 is interconnected. More 
specifically, for purposes of increasing the modulus of elasticity of at 
least the first wire 16, the heating means is capable of convectively 
and/or conductively heating at least the first wire or, alternatively, 
resistance heating the first wire 16. In one embodiment, the heating means 
is in fluid connection with the substrate matrix material 22. In this 
regard, the heating means comprises a means for passing a fluid (e.g., a 
gas, such as air, or a liquid) at an elevated temperature (e.g., greater 
than that of the first wire 16) over the modular actuator 10 and 
specifically, over the substrate matrix material 22. Such oven-type 
heating increases the temperature of the substrate matrix material which, 
in turn, increases the temperature of the first wire 16 embedded therein. 
In one embodiment, heat from the vibrating device 42 itself or from any 
nearby device (not shown) may be used to increase the temperature of the 
first wire 16 of the modular actuator 10. In another embodiment, the first 
wire 16 has wire ingress and egress points which are connectable to a 
heating means comprising an electric source. In this regard, the first 
wire 16 is resistance heated by applying a current through the first wire 
16 via the wire ingress and egress points of the first wire 16. 
In one embodiment, where the first wire 16 comprises a shape memory alloy 
having a diameter of about 0.020 inches, power of about 12 watts may be 
applied to the first wire 16 to increase the temperature thereof between 
about 20.degree. C. and about 80.degree. C., which may result in an 
increase in the elastic modulus of the shape memory alloy first wire 16 by 
a factor from about three to about seven times the original elastic 
modulus. Such an increase in the elastic modulus of the shape memory alloy 
first wire results in an increase in the stiffness of the substrate 
actuator. For example, in one embodiment, the increase in stiffness of the 
substrate actuator is between about 2:1 and about 7:1. 
As indicated herein above, a modular substrate actuator of the present 
invention may be used to detune from resonance a support structure which 
is interconnected to and supports a vibrating device. In order to detune 
from resonance such a structure, the modular substrate actuators of the 
present invention may be coupled to the support structure, such that the 
modular actuators are located about the vibrating device, and/or 
interposed between the vibrating device and the support structure. In one 
embodiment, illustrated in FIG. 5, at least a first modular actuator 110 
is interconnectable to (e.g., mechanically fastened) the support structure 
136 and has a sufficient cross-sectional area to detune the vibrating 
energy from the vibrating device 142 interconnected thereto. For purposes 
of providing an area of uniform increases in stiffness, a plurality of 
modular actuators 110 each having at least a first wire 116 embedded 
within substrate matrix material 122 may be interconnected to the 
vibrating device 142 and the support structure 136. A heating means 130 
for resistance heating of the first wire 116 is in electrical connections 
with at least the first wire 116. 
Referring to FIGS. 6 and 7, in another embodiment, for purposes of detuning 
from resonance a support structure 260, a plurality of substrate actuators 
210 of the present invention are couplable to one or more surfaces (e.g., 
top and/or bottom surfaces 262, 264) of the support structure 260 and are 
embeddable within the support structure 260. Components 150 (e.g., 
electronic, optical packages sensitive to vibratory energy) mounted to the 
top surface 262 of the support structure 260 may thus be protected from 
vibratory energy as the substrate actuators 210 of the present invention 
can detune from resonance the support structure 260 when actuated by the 
heating means described hereinabove. 
The foregoing description of the present invention has been presented for 
purposes of illustration and description. Furthermore, the description is 
not intended to limit the invention to the form disclosed herein. 
Consequently, variations and modifications commensurate with the above 
teachings, and the skill or knowledge of the relevant art, are within the 
scope of the present invention. The embodiments described hereinabove are 
further intended to explain best modes known for practicing the invention 
and to enable others skilled in the art to utilize the invention in such, 
or other, embodiments and with various modifications required by the 
particular applications or uses of the present invention. It is intended 
that the appended claims be construed to include alternative embodiments 
to the extent permitted by the prior art.