Ultrasonic drilling method for forming holes in composite materials

Abstract

The present disclosure relates to an ultrasonic drilling method for forming perforations in a composite material. Specifically, an ultrasonic drilling method can be used to form a perforated plate by forming a hole through a workpiece using a needle or a needle array operatively coupled to an ultrasonic actuator. The needle is repeatedly contacted with the surface of the workpiece at an ultrasonic operating frequency to form a hole through the workpiece. Such steps are repeated to form a plurality of holes in the workpiece, thereby forming a perforated plate that can be used in an acoustic liner for noise attenuation. While the hole is being formed, the workpiece can be heated via a remote heating unit that locally heats a portion of the workpiece.

Description

Technical Field

[0001] The present disclosure relates generally to ultrasonic drilling methods and, more particularly, to using ultrasonic drilling to form perforations in composite materials. Background Art

[0002] Acoustic liners are typically formed using a thin material that is formed with many small holes or perforations. For example, an acoustic liner may be placed inside a jet engine (e.g., in an engine inlet inner barrel) for noise attenuation (i.e., to suppress engine noise and / or reduce noise pollution on an aircraft). These acoustic liners are typically formed by placing a sheet of perforated material (e.g., a metal sheet or graphite sheet) on a honeycomb core, the acoustic liner typically being sandwiched between a perforated sheet and an impermeable layer or backing sheet.

[0003] Perforated plates are formed by punching or drilling thousands or even millions or more of small holes through thin metal or composite plates. Conventional methods involve drilling these holes one at a time, which is intensive in time and money, and therefore very expensive from the perspective of the build cycle. In some cases, such drilling may require more than a week of robotic drilling operations, and each individual hole takes anywhere from one second to five seconds to drill. In addition, the tooling costs of forming such perforations are very expensive in terms of the wear of the drill bit that needs to be frequently replaced, especially for drilling holes in composite materials (e.g., carbon fiber or glass fiber reinforced polymer) and / or other thermoplastic materials. In addition, the drill bit usually needs to be made of expensive materials (such as tool steel) that are difficult to machine. Attempts have been made to drill multiple holes at a time, but due to the rotary motion requirements of this drilling operation, this attempt has been limited to drilling 4 to 12 holes at a time.

[0004] Ultrasonic drilling is a technique that uses high frequency, low amplitude vibrations of a tool or drill bit against the surface of a workpiece to remove material from the workpiece by micro-cutting or abrading with abrasive particles. Compared to traditional drilling methods that use rotation to cut through the material, ultrasonic drilling relies on axial vibrations to essentially hammer the drill bit into the material. Figure 1An example of a prior art ultrasonic drill 10 is illustrated. The ultrasonic drill 10 includes a piezoelectric actuator 12 as its power source and utilizes a variety of horns 14 to vibrate the drill bit through a workpiece 16 in the presence of abrasive particles to mix fine abrasive particles with water to form a slurry stored in a slurry tank 18. A slurry pump 20 distributes the slurry across the workpiece 16 and the tip of the drill bit via a pipeline and nozzle 22, which is required to remove material from the workpiece 16 while keeping the drill bit clean and effective. The slurry also acts as a coolant to keep the material and the drill bit cool, thereby preventing damage to the workpiece and the drill bit. The slurry is returned to the slurry tank 18 via a slurry return line 24, and the slurry is used to carry the debris away from the cutting area. The ability of the slurry or cutting fluid to reach the drill bit limits the depth to which the ultrasonic drill can be used, because the ultrasonic drill bit does not include a groove that allows the slurry to enter, as the slurry used with a rotary drill does.

[0005] Ultrasonic drilling has been successfully used to machine hard and / or brittle materials such as semiconductors, stainless steel, glass, ceramics, carbide, quartz, stone, tungsten, granite, rock, and medical bone. Attempts to utilize ultrasonic drilling methods for composite materials (e.g., carbon fiber reinforced plastics) have been limited by applying ultrasonic vibrations to a rotating drill bit, which must be cooled using a slurry or other cooling fluid during drilling. Furthermore, drilling through composite materials is often difficult and costly to perform and often results in damage to the composite part. Summary of the invention

[0006] In a disclosed method of performing ultrasonic drilling at a first location on a workpiece to form a hole in the workpiece, a surface of the workpiece is placed relative to a tool of an ultrasonic hone, and a hole is formed in the workpiece by vibrating the tool along a longitudinal axis so that the tool repeatedly contacts the surface of the workpiece at an operating frequency and amplitude sufficient to form the hole in the workpiece. The tool may have a longitudinal axis that is substantially orthogonal to the surface of the workpiece. In such a method, the tool is vibrated for a time sufficient to form the hole in the workpiece, but the tool is not rotated relative to the surface of the workpiece during the formation of the hole. In addition, the hole can be formed without the use of a slurry or a cooling fluid. In some methods according to the present disclosure, the workpiece is composed of a composite material.

[0007] In another method according to the present disclosure, a plurality of perforations are formed in a composite sheet. In such a method, the surface of the sheet is arranged with a needle array operatively coupled to an ultrasonic grinding stone so that the needle array is placed above a first region of the sheet. The needle array includes a plurality of needles extending along a longitudinal axis, the longitudinal axis being substantially orthogonal to the surface of the sheet. In the method, the surface of the sheet is repeatedly contacted in the first region by the needle array for a first period of time at an operating frequency greater than 20 kHz, the first period of time being sufficient to form a first plurality of holes in the first region of the sheet. This repeated contact of the surface of the sheet forms corresponding first holes in the sheet corresponding to respective corresponding needles of the needle array. In the method, the needles of the needle array contact the sheet without rotating the plurality of needles about the longitudinal axis, rotating the needles relative to the sheet, and without using a slurry or cooling fluid.

[0008] The method may also include the steps of translating the needle array relative to the sheet (and / or translating the sheet relative to the needle array) so that the needle array is placed over a second region of the sheet; and then, again repeatedly contacting the surface of the sheet in the second region with the needle array at the operating frequency for a second period of time sufficient to form a second plurality of holes in the second region of the sheet. Again, corresponding second holes corresponding to respective respective needles of the needle array may be formed in the sheet. Such steps of translating and repeatedly contacting subsequent regions of the sheet may be repeated any number of times to form a desired number of holes in the sheet. In each repetition, the surface of the sheet may be contacted by the plurality of needles of the needle array without rotating the plurality of needles about the longitudinal axis, without rotating the needles relative to the sheet, and without using a slurry or cooling fluid.

[0009] A method of forming an acoustic liner is also disclosed. In one example, a workpiece formed according to the disclosed method is coupled to a first side of a honeycomb structure. The honeycomb structure also includes a second side opposite the first side, and a plurality of internal cells extending between the first side and the second side. Each internal cell is sized to adapt an acoustic plane wave in the internal cell for a desired frequency range, so that the acoustic liner is configured to generate noise attenuation characteristics for a desired frequency range. In the method, a rigid backing plate is coupled to the second side of the honeycomb structure, thereby forming an acoustic liner.

[0010] An acoustic liner is disclosed. An example of the disclosed acoustic liner includes a thin plate material, which is composed of a carbon fiber reinforced polymer and has at least 100,000 circular or non-circular perforations formed through the thickness of the thin plate material. The thin plate material can be formed according to the method currently disclosed. The acoustic liner can also include a honeycomb structure and a rigid backplane. The honeycomb structure includes a first side, a second side opposite to the first side, and a plurality of internal cells extending between the first side and the second side. The first side of the honeycomb structure is connected to the thin plate material, and the second side of the honeycomb structure is connected to the rigid backplane. Each of the plurality of internal cells is sized to adapt the acoustic plane waves in the internal cell for a desired frequency range, so that the acoustic liner is configured to generate noise attenuation characteristics for a desired frequency range. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a front view of an ultrasonic drilling device in the prior art.

[0012] Figure 2 is a schematic representation of an apparatus that may include one or more acoustic liners according to the present disclosure and / or one or more acoustic liners formed according to the methods of the present disclosure.

[0013] Figure 3 is a schematic representation of an example of a system for performing an ultrasonic drilling method according to the present disclosure.

[0014] Figure 4 is a perspective view of an example of an acoustic liner formed according to the method of the present disclosure.

[0015] Figure 5 is a schematic representation from a bottom view of an example of a needle array according to the present disclosure.

[0016] Figure 6 is a schematic representation from a side view of an example of a needle array according to the present disclosure.

[0017] Figure 7 is a perspective view of an example of a needle array that may be used in the presently disclosed methods.

[0018] Figure 8 is a schematic representation of an example of the distribution of needles in a needle array according to the present disclosure.

[0019] Fig. 9 is a schematic representation of another example of the distribution of needles in a needle array according to the present disclosure.

[0020] Fig.10 is a flow chart representing a disclosed method of forming one or more holes in a workpiece.

[0021] Fig.11 is a flow chart representing a disclosed method of forming one or more holes in a workpiece.

[0022] Fig.12 is a flow chart representing the disclosed method of forming an acoustic liner.

[0023] Fig.13 is a schematic representation of an example of a needle tip for use with the presently disclosed needle arrays and systems, illustrating a side view of a portion of a needle.

[0024] Fig.14 is a schematic representation of an example of a needle tip for use with the presently disclosed needle arrays and systems, illustrating a bottom view of the needle tip. DETAILED DESCRIPTION

[0025] Reference Figure 2 , one or more perforated plates 100 may be included in the device 102. The perforated plates 100 may be used in a variety of different industries and applications, such as aerospace, automotive, electronics, construction, military, entertainment, and / or motorsports industries. Figure 2 , an example of an apparatus 102 that may include one or more perforated plates 100 is generally illustrated in the form of an aircraft 104. Aircraft 104 may take any suitable form, including a commercial aircraft, a military aircraft, or any other suitable aircraft. Figure 2 The aircraft 104 is illustrated as taking the form of a fixed-wing aircraft, but other types and configurations of aircraft are within the scope of the aircraft 104 according to the present disclosure, including, but not limited to, rotorcraft and helicopters.

[0026] The device 102 (e.g., the aircraft 104) may include one or more perforated panels 100. As an illustrative, non-exclusive example, the perforated panels 100 may be used in an engine case 116, although other components of the aircraft 104 (such as wings 106, fuselage 108 or fuselage segments 108a, 108b, 108c, horizontal stabilizers 110, overhead storage bins 112, vertical stabilizers 114, and other portions) may additionally or alternatively include one or more perforated panels 100. Other applications for the perforated panels 100 in the aircraft 104 may include: floors, interior walls, food handling galley assemblies, wing control surfaces, passenger luggage racks, thrust deflector assemblies, cabin panels, fairing ablative protection, instrument covers and racks, and bulkhead panels. In other industries, examples of devices 102 (including one or more perforated panels 100) may include or may be part of space satellites, electronic radome structures, transportation vehicles, shipping containers, shelters, large antenna or dish reflectors, refrigeration panels, rapid transit floors, shipboard electronic deck shelters, cargo pallets, automobile bodies, building curtain walls, partitions, spacer panels, expandable hospital shelters and / or the internal structure of components.

[0027] Figures 3 to 9 as well as Figure 13 to Figure 14 Illustrative, non-exclusive examples of systems 30, acoustic liners 33, 36, and / or needle arrays 60 according to the present disclosure are provided. Figures 3 to 9 as well as Figure 13 to Figure 14 In the various figures in the drawings (and generally throughout this specification), like reference numerals are used to designate elements serving similar or at least substantially similar purposes, and reference may not be made herein. Figures 3 to 9 as well as Figure 13 to Figure 14 The various figures in the Figures 3 to 9 as well as Figure 13 to Figure 14 Not all elements may be labeled in the various figures in the present disclosure, but the reference numerals associated with these elements may be used for consistency. Without departing from the scope of the present disclosure, references herein are made to Figures 3 to 9 as well as Figure 13 to Figure 14 The elements, components and / or features discussed in one or more of the figures may be included in Figures 3 to 9 as well as Figure 13 to Figure 14 any figure in, and / or with Figures 3 to 9 as well as Figure 13 to Figure 14 Any Figure 1Generally speaking, elements that are likely to be included in a given (i.e., particular) embodiment are illustrated in solid lines, while elements that are optional for a given embodiment are illustrated in dashed lines. However, elements shown in solid lines are not essential to all embodiments, and elements shown in solid lines may be omitted from a particular embodiment without departing from the scope of the present disclosure. Where appropriate, Figures 3 to 9 as well as Figure 13 to Figure 14 The numbers in the figures are used to designate Figures 3 to 9 as well as Figure 13 to Figure 14 The corresponding parts of other figures in . However, Figures 3 to 9 as well as Figure 13 to Figure 14 The examples in are non-exclusive and may be incorporated into Figures 3 to 9 as well as Figure 13 to Figure 14 The other figures and variations thereof illustrated in and referring to Figures 3 to 9 as well as Figure 13 to Figure 14 Any number of different aspects, configurations, features, characteristics, etc. discussed in other figures and variations thereof, without necessarily including all such aspects, configurations, features, characteristics, etc. For the purpose of brevity, reference may not be made again. Figures 3 to 9 as well as Figure 13 to Figure 14 The various figures in the drawings are used to discuss, illustrate and / or label various previously discussed components, parts, portions, aspects, regions, etc. or variations thereof; however, the components, parts, portions, aspects, regions, etc. or variations thereof are in a manner that can be related to Figures 3 to 9 as well as Figure 13 to Figure 14 Any Figure 1 It is within the scope of the present disclosure to utilize the previously discussed features, modifications, etc.

[0028] Figure 3A system 30 according to the present disclosure is schematically illustrated. Such a system 30 can be used to form one or more holes in a workpiece 32 (an example of a porous plate 100). In some examples, the system 30 can be used to perforate and / or form some or all of an acoustic liner 33 (which can be an example of a workpiece 32) on the workpiece 32. According to the present disclosure, and as will be described in more detail herein, one or more holes can be formed in a workpiece (32) (e.g., through the workpiece) by repeatedly contacting a surface 34 of the workpiece 32 along a longitudinal axis 40 with an ultrasonic operating frequency and amplitude for a time sufficient to form one or more holes in the workpiece 32. The one or more needles are operatively coupled to an ultrasonic actuator 38 configured to vibrate the one or more needles. The combination of the ultrasonic actuator 38 and the needle 36 (or the needle array 60) can be referred to herein as an ultrasonic drilling device 58. In some examples, the ultrasonic drilling apparatus 58 includes an arm coupling the needle array 60 to the ultrasonic actuator 38 , and the arm is configured to amplify vibrations along the longitudinal axis 40 .

[0029] In general, the system 30 is configured to form a corresponding hole through the workpiece 32 for each corresponding needle 36 operatively coupled to the ultrasonic actuator 38. The ultrasonic actuator 38 is configured to vibrate the needle 36 (or the needle array 60) at an ultrasonic frequency, such as via a piezoelectric transducer and an electrical oscillator. In various examples, the ultrasonic actuator 38 may include a mechanical, electromagnetic, and / or thermal energy source. In order to form one or more holes in different regions or ranges of the workpiece 32, the workpiece 32 may be translated relative to the needle 36, and / or the needle 36 may be translated relative to the workpiece 32 so that the needle 36 is located over a different region or section (region or area) of the workpiece 32. The needle 36 may then be repeatedly contacted with the surface 34 in the different regions of the workpiece 32 to form one or more additional holes in the workpiece 32. The needle 36 (e.g., the longitudinal axis 40 of the needle 36 or the needle 36 in the needle array 60) may be arranged so that it is at least approximately orthogonal to the surface 34 (e.g., such as Figure 6 In other examples, needle 36 may contact surface 34 at a non-orthogonal angle to surface 34.

[0030] The system 30 is configured to form a through hole 44 through the workpiece 32 in a manner different from conventional drilling. Rather than rotating the drill bit at a high speed to cut through the material (as in conventional drilling), the needle 36 does not rotate relative to the surface 34 of the workpiece 32 (nor does the workpiece 32 rotate relative to the needle 36) during the formation of the through hole 44. Similarly, the needle array 60 does not rotate relative to the surface 34 of the workpiece 32 (nor does the workpiece 32 rotate relative to the needle array 60) during the formation of the through hole 44. Moreover, conventional drilling requires the use of a cooling fluid to prevent damage to the drill bit and the part due to heat generated during rotary drilling, and conventional ultrasonic drilling, which still involves rotation of the drill bit, requires the use of a slurry to cool the part and / or carry away debris. On the other hand, the currently disclosed ultrasonic drilling apparatus 58 is configured to operate without the use of a slurry or cooling fluid (although either or both of the slurry or cooling fluid may be optionally used if desired).

[0031] Such a system 30 may be used to form any number of holes (including a single hole) in or through a variety of materials, but in some examples may be used to form an acoustic liner 33, Figure 4 An example of such an acoustic liner is shown in FIG. The acoustic liner 33 includes a sheet material 42 (the sheet material 42 is an example of the workpiece 32 and the perforated plate 100) having a plurality of perforations 44 formed therethrough. The perforations 44 are formed by extending through the entire thickness 46 ( Figure 3 ). In some specific examples, the thickness 46 of the sheet material 42 can be less than 0.25 inches, less than 0.1 inches, less than 0.05 inches, and / or less than 0.025 inches thick. The sheet material 42 is typically formed of a composite material, but can be formed of other materials, including metals and ceramics.

[0032] The acoustic liner 33 also includes a honeycomb structure 48 having a first side 50, a second side 52 opposite the first side 50, and a plurality of internal baffles or internal cells 54 extending between the first side 50 and the second side 52. The first side 50 is coupled to the sheet material 42, and the second side 52 is coupled to the rigid backing plate 56, such that the honeycomb structure 48 is sandwiched between the sheet material 42 and the rigid backing plate 56. Each internal cell 54 is sized to fit an acoustic plane wave in the internal cell 54 for a desired frequency range, such that the acoustic liner 33 is configured to generate noise attenuation characteristics for a desired frequency range. For example, the internal cell 54 can be sized according to a specific application for which the acoustic liner 33 is designed, and the size of the internal cell 54 can be selectively changed according to the expected noise frequency expected in a given use. In this manner, the acoustic liner 33 can be used to reduce noise pollution and / or achieve noise attenuation in a variety of applications. In one specific example, the acoustic liner 33 can be configured for use in a jet engine housing in an aircraft, and the internal unit 54 is sized to accommodate the range of acoustic plane waves generated by the jet engine, so that the acoustic liner 33 can be used to reduce noise pollution from the engine and / or achieve noise attenuation in an aircraft or other device. Jet engines including the acoustic liner 33 and aircraft including the acoustic liner 33 are within the scope of the present disclosure.

[0033] The sheet material 42 may be formed, for example, of a carbon fiber or glass fiber reinforced polymer, a thermoplastic material, a thermosetting material, a carbon fiber or peeled fiber reinforced polyether ether ketone (PEEK), a carbon fiber or glass fiber reinforced polyphenylene sulfide (PPS), a carbon fiber or glass fiber reinforced epoxy resin, and / or a carbon fiber or glass fiber reinforced polyether ketone ketone (PEKK). The rigid backplate 56 (which may also be referred to as an impermeable layer, back-sheet, or back-skin) may be formed of any material that provides adequate support for the sheet material 42 and the honeycomb structure 48, and suitable examples include metal, carbon fiber, and / or a fiber-based reinforced polymer. The honeycomb structure 48 may be made of The honeycomb material is formed, although other honeycomb structure materials are also within the scope of the present disclosure.

[0034] The sheet material 42 may include any number of perforations 44. In some examples, the sheet material 42 includes at least 100 perforations, at least 1,000 perforations, at least 10,000 perforations, at least 100,000 perforations, and / or at least 1,000,000 perforations formed therein. Figure 4 4, the perforations 44 are illustrated as being substantially elliptical, but the perforations 44 may be of a variety of different shapes. For example, the perforations 44 may include round (e.g., circular) and / or non-circular perforations 44, such as square, rectangular, triangular, polygonal, star-shaped, and / or diamond-shaped perforations 44. The perforations 44 of different shapes may be generated using needles 36 having various cross-sectional shapes and / or by lateral movement of the needle array 60 and / or the workpiece 32 during the formation of the perforations 44. In some examples of the acoustic liner 33, the perforations 44 may all have substantially uniform sizes and shapes. In other examples of the acoustic liner 33, one or more perforations 44 may have a size and / or shape different from one or more other perforations in the perforations 44. For example, one or more perforations 44 in a given area of ​​the workpiece 32 may be larger than one or more other perforations 44 in another area of ​​the workpiece 32. In some examples, the perforations 44 of different sizes and / or shapes may be interspersed with each other and distributed across the entire surface of the workpiece 32.

[0035] The currently disclosed system 30 (and the related ultrasonic drilling method using such system 30) can be configured to form a perforated plate using the following techniques and materials: the techniques and materials can reduce the time required to form such perforations in the acoustic liner 33, for example, by forming multiple holes at a time. In addition, the needles 36 of the disclosed ultrasonic drilling technology can be made of cheaper materials than conventional drill bits, and / or made via inexpensive design and manufacturing methods (e.g., additive manufacturing) that can reduce the costs associated with manufacturing and tool operations. The disclosed technology can also increase the life of tool operations, which can further reduce costs. For example, because the disclosed system and needle array effectively push fibers apart to form perforations instead of cutting through materials, such technology can improve the resulting material properties in the workpiece and / or reduce wear on tool operations. Compared with conventional drilling techniques, the disclosed technology can also reduce labor intensity, thereby reducing manufacturing process time.

[0036] Figure 5 to Figure 6 Schematically illustrates an example of a needle array 60 that can be used to form ultrasonic perforations in a workpiece 32 according to the present disclosure. The needle array 60 includes a plurality of needles 36 arranged to form the needle array 60. In the example, each needle 36 is oriented along the longitudinal axis 40 ( Figure 6) extends from a first end 62 to a second end 64. Each respective needle 36 is configured to repeatedly contact a surface of a workpiece (e.g., Figure 3 When the needle array 60 is vibrated at an ultrasonic operating frequency along the longitudinal axis 40 while simultaneously moving the needle array 60 toward the surface 34 of the workpiece 32 as shown in FIG. 1 , corresponding holes or perforations are formed in the workpiece. For example, a needle array 60 having ten needles 36 is configured to form ten holes or perforations at a time within a region of the workpiece. Such holes are formed without translating the needle array 60 relative to the workpiece, rotating the plurality of needles 36 about the longitudinal axis 40, and rotating the plurality of needles 36 relative to the workpiece while the holes are being formed.

[0037] Refer again Figure 3 , such a through hole 44 can be formed in the area 66 of the workpiece 32. In order to form the through hole 44 in a different area (e.g., the second area 98) of the workpiece 32, the workpiece 32 can be translated relative to the needle array 60, and / or the needle array 60 can be translated relative to the workpiece 32 so that the needle array 60 is placed over a different area of ​​the workpiece 32, and the device is operated again so that the needles 36 repeatedly contact the surface 34 of the workpiece 32 in different sections or regions, thereby forming more through holes 44 on the workpiece 32.

[0038] The perforations 44 are typically quite small in size. For example, each perforation 44 may have a diameter (or maximum size for non-circular perforations 44): less than 0.1 inches, less than 0.09 inches, less than 0.08 inches, less than 0.07 inches, less than 0.06 inches, less than 0.05 inches, less than 0.04 inches, less than 0.03 inches, less than 0.02 inches, and / or less than 0.01 inches. In a specific example, the perforations 44 may have a diameter between 0.04 inches and 0.05 inches. In some examples, each perforation 44 in a given workpiece 32 has a substantially uniform diameter. In some examples, a given workpiece 32 may include one or more perforations 44 having a size and / or shape different from one or more other perforations formed in the workpiece 32. For example, a given needle array 60 may include a plurality of needles 36 of different sizes and / or shapes that form a plurality of perforations 44 of different sizes and / or shapes in a given area of ​​the workpiece 32. Additionally or alternatively, a first needle array 60 may be used to form through-holes 44 of a first size and shape in one area of ​​the workpiece 32 , while a second needle array 60 may be used to form through-holes 44 of a different size and shape in a different area of ​​the workpiece 32 .

[0039] In a given workpiece 32, each hole or perforation 44 can be spaced apart from each adjacent hole at a minimum center distance. In a specific example, the minimum center distance can be less than 0.5 inches, less than 0.4 inches, less than 0.3 inches, less than 0.2 inches, and / or less than 0.1 inches. In a specific example, the minimum center distance is between 0.13 inches and 0.15 inches. Additionally or alternatively, the minimum center distance can be greater than or equal to the diameter of each corresponding hole. For example, the minimum center distance can be at least 1.25 times the diameter of each corresponding hole, at least 1.5 times the diameter of each corresponding hole, at least 1.75 times the diameter of each corresponding hole, at least 2 times the diameter of each corresponding hole, at least 2.5 times the diameter of each corresponding hole, at least 3 times the diameter of each corresponding hole, at least 4 times the diameter of each corresponding hole, and / or at least 5 times the diameter of each corresponding hole.

[0040] Refer again Figure 5 to Figure 6 , the needle array 60 may include a support plate 68. In an example, each needle 36 is coupled to the support plate 68 at its first end 62. In an example, each needle 36 may be integrally formed with the support plate 68. The support plate 68 may serve as a connection between the needle 36 and the ultrasonic actuator 38 ( Figure 3 ) so that the needle array 60 can be operatively coupled to the ultrasonic actuator 38 so that the needle array 60 vibrates at a desired ultrasonic operating frequency via the support plate 68. In some examples, when the needle array 60 is used to form a perforation in a workpiece according to the present disclosure, the needle array 60 acts like a grindstone that amplifies the ultrasonic vibrations from the ultrasonic actuator to increase the mechanical energy output. In some examples, the needle array is removably coupled to the ultrasonic drilling device 58 so that the needle array can be selectively removed from the ultrasonic actuator 38 and replaced with a different needle array 60.

[0041] The needle array 60 may include a variety of different numbers of needles depending on a given application of the needle array 60. For example, the needle array 60 may include at least five needles 36, at least six needles 36, at least seven needles 36, at least eight needles 36, at least nine needles 36, at least ten needles 36, at least twenty needles 36, at least thirty needles 36, at least forty needles 36, at least fifty needles 36, at least sixty needles 36, at least seventy needles 36, at least eighty needles 36, at least ninety needles 36, and / or at least one hundred needles 36. The needles 36 in the needle array 60 may be arranged in one or more rows 70 (e.g., row 70a, row 70b, etc.) of needles 36 and / or one or more columns 72 (e.g., column 72a, column 72b, etc.) of needles 36. The columns 72 may be disposed between the first side 74 of the support plate 68 and the second side 76 of the support plate 68 and generally parallel to the first side 74 of the support plate 68 and the second side 76 of the support plate 68. The row 70 may be disposed between the third side 78 of the support plate 68 and the fourth side 80 of the support plate 68 and generally parallel to the third side 78 of the support plate 68 and the fourth side 80 of the support plate 68. Figure 5 In the embodiment of the present invention, the support plate 68 is illustrated as having a square footprint, but the support plate 68 can have any desired footprint shape. Additionally or alternatively, the needles 36 in the needle array 60 can be arranged in a polar array (e.g., a circular arrangement), randomly placed, and / or arranged in any desired shape or pattern.

[0042] In an example, the needle array 60 includes: a plurality of rows 70 of needles 36, each row 70 having a plurality of needles 36; and a plurality of columns 72, each column 72 having a plurality of needles 36. The needles 36 may be arranged in rows 70 and / or columns 72 according to length. For example, the first row 70a may include needles 36 having a first length, and the second row 70b may include needles 36 having a second length. In some examples, the length of the needles 36 may increase row by row (e.g., from the first row 70a to the last row 70x). In some examples, the needles 36 of one or more corresponding rows 70 may include needles 36 having different lengths compared to one or more other corresponding rows 70. In some examples, each corresponding row 70 may include needles 36 having different corresponding dimensions compared to each other corresponding row 70. In some examples, the needles 36 in a given row 70 all have a uniform length, while in other examples, one or more needles 36 in a given row 70 may have different lengths compared to one or more other needles 36 in the row 70. Similarly, the first column 72a may include needles 36 having a first length, and the second column 72b may include needles 36 having a second length. In some examples, the length of the needles 36 may increase from column to column (e.g., from the first column 72a to the last column 72x). In some examples, the needles 36 of one or more corresponding columns 72 may include needles 36 of different lengths compared to one or more other corresponding columns 72. In some examples, each corresponding column 72 may include needles 36 having different corresponding dimensions compared to each other corresponding column 72. In some examples, the needles 36 in a given column 72 all have a uniform length, while in other examples, one or more needles 36 in a given column 72 may have a different length compared to one or more other needles 36 in the column 72.

[0043] Although Figure 5 The needles 36 are schematically shown as having a circular or round cross-section, but one or more of the needles 36 in the needle array 60 may have cross-sections of different shapes. For example, one or more of the needles 36 in the needle array 60 may have cross-sections of elliptical, square, rectangular, triangular, polygonal, star-shaped, diamond-shaped, and / or other shapes. Such differently shaped needles 36 may be amenable to the ultrasonic techniques of the present disclosure because the needles 36 are not rotated during the formation of the perforations. The cross-sectional shape of the needles 36 may be selected or optimized to generate perforations of corresponding shapes to improve the noise attenuation performance of the resulting acoustic liner formed according to the present disclosure.

[0044] The needles 36 may be formed of any suitable material, such as stainless steel, titanium, and / or other metals, as one of ordinary skill in the art will appreciate. The needles 36 may have a coating on some or all of the surfaces of the needles 36, such as a tungsten carbide coating, but other coatings are also within the scope of the present disclosure. As one of ordinary skill in the art will appreciate, the second ends 64 of some or all of the needles 36 in the needle array 60 may be beveled, shaped, coated, roughened, grooved, and / or otherwise shaped. The radius and / or roughness of the second ends 64 of the needles 36 may be selectively altered to the desired characteristics of the needles 36. Methods of making the needle array 60 and methods of forming the perforations 44 using the needle array are disclosed in attorney docket number 19-1160-US-NP[2], invented by Weidong Song, filed on February 20, 2020, and entitled “NEEDLE ARRAYSFOR FORMING ULTRASONIC PERFORATIONS, AND METHODS OF MAKING THE SAME,” which is disclosed in its entirety as a background example.

[0045] For example, Fig.13 An example of a needle 36 is illustrated (which may be one of a plurality of needles 36 in a needle array 60). Fig.13 As shown, the needle 36 may include a smooth shaft portion 118 and a textured or roughened tip portion 120 adjacent the second end 64. In some examples, the tip portion 120 may be tapered. The needle 36 may include: one or more grooves 122 formed in the shaft portion 118 and / or the tip portion 120. For example, Fig.13 The illustrated needle 36 includes two grooves 122 extending from the shaft portion 118 to the tip portion 120. Other examples of the needle 36 may include more or fewer grooves 122. In some examples, one or more grooves 122 may be located only in the shaft portion 118, and / or one or more grooves 122 may be located only in the tip portion 120. The grooves 122 may be configured to remove debris from the work area while the through hole 44 is being formed in the workpiece 32. Fig.14 An example of the needle 36 is shown as viewed from the bottom at the second end 64. Fig.141, the needle 36 includes a plurality of curved grooves 122 that meet at a center point 124 of the tip portion 120, but other arrangements of the grooves 122 are also within the scope of the present disclosure. In some examples, the tip portion 120 can have a surface roughness of less than 20 grit, less than 40 grit, less than 60 grit, less than 80 grit, less than 100 grit, less than 120 grit, less than 140 grit, and / or less than 160 grit. In a specific example, the tip portion 120 has a surface roughness between 80 grit and 120 grit. In another example, the tip portion 120 has a surface roughness between 40 grit and 60 grit.

[0046] Figure 7 An example of a needle array 60 is illustrated. Figure 7 In this example, the needle array 60 includes: a first row 70a of needles 36, each needle having a first length 82; a second row 70b of needles 36, each needle having a second length 84; a third row 70c of needles 36, each needle having a third length 86; a fourth row 70d of needles 36, each needle having a fourth length 88; a fifth row 70e of needles 36, each needle having a fifth length 90; and so on. In this example, the length of the needles 36 increases row by row between the first side 74 of the support plate 68 and the second side 76 of the support plate 68, such that the second length 84 is greater than the first length 82, the third length 86 is greater than the second length 84, and so on, wherein the length of the needles 36 in the last row 70x adjacent to the second side 76 of the support plate 68 is the longest, and the length of the needles 36 in the first row 70a is the shortest. In this example, the length of the needles in a given column 72 increases along the column between the first side 74 and the second side 76 of the support plate 68. Other arrangements are also within the scope of the present disclosure.

[0047] like Figures 8 to 9 As schematically shown in FIG. 1 , the second ends 64 of the needles 36 in a given needle array 60 may collectively define a contact plane 92 or a plurality of contact planes 92 disposed relative to one another to form a contact shape 94 ( Fig. 9 ) or contact contour. For example, Figure 8 As shown, the needles 36 can be arranged in a bilinear distribution according to their lengths so that the second ends 64 of the needles 36 together form an angled contact plane 92 for contacting the workpiece. As another example, Fig. 9As shown, the needles 36 can be arranged in a pyramid distribution according to their lengths, so that the second ends 64 of the needles 36 collectively form a pyramidal contact shape 94 for contacting a workpiece, wherein the pyramidal contact shape 94 is defined by a plurality of contact planes 92 collectively defined by the second ends 64 of the needles 36. Other different arrangements of the needles 36 can be formed to generate different contact planes 92 and / or contact shapes 94. In some examples, the needles 36 can be arranged to collectively define a contact profile having an arc or irregular shape. Additionally or alternatively, the needles 36 can be selectively arranged according to their lengths to optimize the energy consumption of an ultrasonic actuator operatively coupled to the needle array 60. Additionally or alternatively, the needles 36 of the needle array 60 can be selectively arranged to maximize perforation efficiency.

[0048] Refer again Figure 3 , the system 30 may include a remote heating unit 96 spaced apart from the ultrasonic drilling device 58. Additionally or alternatively, the ultrasonic drilling device 58 may include a heating unit coupled to the ultrasonic drilling device 58, and / or the ultrasonic drilling device 58 may effectively heat the workpiece 32 by vibrating the needle array 60 against the workpiece 32 without a cooling fluid or coolant. The remote heating unit 96 is configured to locally heat a portion of the workpiece 32 while the through-hole 44 is formed in the portion. For example, the remote heating unit 96 may be positioned relative to the workpiece 32 and the ultrasonic drilling device 58 such that the remote heating unit 96 locally heats the first region 66 while the needle array 60 is located above the first region 66 of the workpiece 32, such that the first region 66 is heated while the ultrasonic drilling device 58 contacts the surface 34 to form the through-hole 44 in the region 66. The remote heating unit 96 may be configured to maintain a temperature of a given region of the sheet material (e.g., the first region 66 of the workpiece 32) above a threshold temperature while the through-hole 44 is formed by the ultrasonic drilling device 58. For example, the threshold temperature may be the glass transition temperature of a resin used in forming the composite material of the workpiece 32. In particular examples, the threshold temperature may be at least 200 degrees Fahrenheit (°F), at least 210°F, at least 220°F, at least 230°F, at least 240°F, at least 250°F, at least 260°F, at least 270°F, at least 280°F, at least 290°F, and / or at least 300°F. In some systems 30, the remote heating unit 96 may be a heat lamp, although other types of heating units are also within the scope of the present disclosure.

[0049] Once the through-holes 44 are formed in the first region 66 of the workpiece 32, the needle array 60 may be translated relative to the workpiece 32 such that the needle array 60 is positioned over a different region (e.g., the second region 98 of the workpiece 32) so that the ultrasonic drilling apparatus 58 may be used to form the through-holes 44 in one or more other regions of the workpiece 32. Additionally or alternatively, the workpiece 32 may be translated relative to the needle array 60 such that a different region of the workpiece 32 is positioned below the needle array 60 to form through-holes in different regions of the workpiece 32.

[0050] The ultrasonic actuator 38 can be configured to operate at any suitable ultrasonic operating frequency. In some examples, the operating frequency is at least 15 kilohertz (kHz), at least 20 kHz, and / or at least 25 kHz.

[0051] Figures 10 to 12 Schematically provided are illustrative, non-exclusive examples representing methods according to the present disclosure. Figures 10 to 12 In the embodiment, some steps are illustrated with dashed boxes, indicating that these steps may be optional or may correspond to optional versions of the method according to the present disclosure. That is, it is not required that all methods according to the present disclosure include the steps illustrated with solid boxes. Figures 10 to 12 The methods and steps illustrated in are not limiting, and other methods and steps are also within the scope of the present disclosure, including methods having more or less than the number of steps illustrated, as will be understood from the discussion herein.

[0052] Fig.10 A method 200 of performing ultrasonic drilling at a first location of a workpiece (e.g., workpiece 32) to form a hole (e.g., perforation 44) in the workpiece is illustrated. The method 200 generally includes the following steps: At 202, a surface (e.g., surface 34) of the workpiece is placed relative to a tool (e.g., needle 36 or needle array 60 of ultrasonic drilling device 58) of an ultrasonic grinder, wherein the tool has a longitudinal axis (e.g., longitudinal axis 40) that is substantially orthogonal to the surface of the workpiece. The method 200 also includes the following steps: At 202, a hole is formed in the workpiece by vibrating the tool along the longitudinal axis so that the tool repeatedly contacts the surface of the workpiece at an operating frequency and a predefined speed sufficient to form the hole in the workpiece, wherein the step of vibrating the tool is performed for a time sufficient to form the hole in the workpiece. At 204, during the formation of the hole (or holes) in the workpiece, the tool is not rotated relative to the surface of the workpiece, and the step of forming the hole at 204 is performed without using a slurry or cooling fluid. In some methods 200 , the force with which the tool contacts the workpiece may be limited such that forming the hole at 204 may include vibrating the tool such that each time the tool contacts the workpiece, the tool applies a force on the surface of the workpiece that is less than a predetermined threshold.

[0053] In the method 200 including forming a plurality of holes in a workpiece, the method 200 may further include the steps of: at 206, translating the workpiece relative to the tool so that the tool is positioned above a position of the workpiece different from the first position where the first hole was formed; and at 210, while the tool is positioned above the different position, forming a second hole (or holes) in the workpiece by vibrating the tool again along the longitudinal axis. Additionally or alternatively, the method 200 may include the steps of: at 208, translating the tool relative to the workpiece so that the tool is positioned above a position of the workpiece different from the first position where the first hole was formed; and at 210, while the tool is positioned above the different position, forming a second hole (or holes) in the workpiece by vibrating the tool again along the longitudinal axis. These steps may be repeated any number of times to form a plurality of holes in a plurality of different positions of the workpiece. For example, after each execution of the step of forming one or more holes at 210, the workpiece may be translated a plurality of times at 206. Similarly, and additionally or alternatively, after each execution of the step of forming one or more holes at 210, the tool may be translated a plurality of times at 208. In this manner, the tool may be sequentially placed over a plurality of different corresponding locations of the workpiece and thereby form one or more corresponding holes in each corresponding location of the workpiece that are contacted by a needle or array of needles in accordance with the present disclosure.

[0054] The method 200 may include the step of locally heating a portion of the workpiece at 212. For example, locally heating a portion of the workpiece at 212 may include positioning a remote heating unit (e.g., remote heating unit 96) relative to the workpiece such that a first location where the through-hole is being formed is heated by the remote heating unit while the through-hole is being formed. Such heating at 212 may be performed before forming the hole at 204 and / or 210, and / or may be performed during forming the hole at 204 and / or 210. In some examples, locally heating the workpiece at 212 includes maintaining a temperature of the portion of the workpiece above a threshold temperature during forming the hole in the workpiece, such as above a glass transition temperature of a resin in a composite material forming the workpiece.

[0055] The method 200 may include the steps of coupling a tool to an ultrasonic actuator of an ultrasonic grinder (eg, ultrasonic actuator 38 ) at 214 ; removing the tool from the ultrasonic actuator at 214 ; and / or coupling a different tool to the ultrasonic actuator at 218 .

[0056] Fig.11A method 220 of forming a plurality of perforations in a composite sheet (e.g., sheet material 42) is illustrated, the method generally comprising the steps of: at 222, placing a surface of the sheet opposite a needle array operatively coupled to an ultrasonic device such that the needle array is positioned over a first region (e.g., first region 66) of the sheet; and at 224, repeatedly contacting the surface of the sheet in the first region with the needle array at an operating frequency greater than 20 kHz for a period of time sufficient to form a first plurality of holes in the first region of the sheet. The step of repeatedly contacting the surface of the sheet at 224 forms respective holes in the sheet corresponding to respective respective needles of the needle array, and the steps are performed without rotating the plurality of needles about a longitudinal axis, without rotating the needles relative to the sheet, and without using a slurry or cooling fluid.

[0057] The method 220 also includes the steps of translating the sheet and / or the needle array at 226 so that the sheet is positioned relative to the needle array so that the needle array is located over a second region of the sheet (e.g., second region 98), and then repeatedly contacting the sheet with the needle array again at 224. In this manner, corresponding holes corresponding to respective corresponding needles of the needle array are formed in the second region of the sheet. Such translating steps at 226 and the steps of repeatedly contacting the regions of the sheet at 224 may be repeated any number of times until a desired number of holes have been formed in the desired regions of the sheet. Each time the needle array and / or sheet is translated at 226, the needle array may be positioned over a different corresponding region of the plurality of regions of the sheet material, and the step of repeatedly contacting the surface of the sheet at 224 is performed each time the needle array is positioned over a different corresponding region of the sheet material.

[0058] Fig.12 A method 230 of forming an acoustic liner according to the present disclosure is illustrated. The method 230 includes the following steps: at 232, forming a perforated workpiece (e.g., workpiece 32, sheet material 42); at 234, coupling the perforated workpiece to a first side of a honeycomb structure (e.g., first side 50 of honeycomb structure 48); and at 236, coupling a backing plate (e.g., rigid backing plate 56) to a second side of the honeycomb structure (e.g., second side 52 of honeycomb structure 48), thereby forming an acoustic liner (e.g., acoustic liner 33). The step of forming the perforated workpiece at 232 may include: forming a plurality of perforations in a sheet of composite material in method 220 ( Fig.11 ), and / or a method 200 of performing ultrasonic drilling to form a hole in a workpiece ( Fig.10). The method 230 may also include the following steps: at 238, incorporating the acoustic liner into a jet engine casing of the aircraft; and at 240, using the acoustic liner to attenuate noise generated by a jet engine of the aircraft, wherein the jet engine is housed in the jet engine casing. For example, the acoustic liner 33 may be applied to the inner wall of a nacelle, an air intake, and / or a bypass duct for dissipating incident acoustic energy.

[0059] Illustrative, non-exclusive examples of the inventive subject matter according to the present disclosure are described in the following enumerated paragraphs:

[0060] A1. A method of performing ultrasonic drilling at a first location of a workpiece to form a hole in the workpiece, the method comprising the following steps:

[0061] placing the surface of the workpiece relative to a tool of an ultrasonic grinder, wherein the tool has a longitudinal axis that is generally orthogonal to the surface of the workpiece; and

[0062] The hole is formed in the workpiece by vibrating the tool along the longitudinal axis so that the tool repeatedly contacts the surface of the workpiece at an operating frequency and amplitude sufficient to form the hole in the workpiece, wherein the step of vibrating the tool is performed for a time sufficient to form the hole in the workpiece, wherein the tool is not rotated relative to the surface of the workpiece during the forming of the hole, wherein the step of forming the hole is performed without the use of a slurry or a cooling fluid, and wherein the workpiece is composed of a composite material.

[0063] A2. The method of paragraph A1, wherein the hole extends through the entire thickness of the workpiece.

[0064] A3. A method according to any of paragraphs A1 to A2, wherein the operating frequency is at least 15 kHz, at least 20 kHz and / or at least 25 kHz.

[0065] A4. The method of any of paragraphs A1 to A3, wherein the hole is a first hole, and wherein the method further comprises the steps of:

[0066] translating the workpiece relative to the tool so that the tool is positioned over a location of the workpiece different from the first location where the first hole is formed; and

[0067] A second hole is formed in the workpiece by again vibrating the tool along the longitudinal axis while the tool is positioned over the different location.

[0068] A5. According to the method described in paragraph A4, the method also includes the following steps: the step of translating the workpiece relative to the tool is repeated multiple times so that the tool is sequentially placed above multiple different corresponding positions of the workpiece, and between each translation of the workpiece, while the tool is placed above the corresponding position, additional corresponding holes are formed at the corresponding positions in the workpiece by vibrating the tool again along the longitudinal axis.

[0069] A6. The method of any of paragraphs A1 to A3, wherein the hole is a first hole, and wherein the method further comprises the steps of:

[0070] translating the tool relative to the workpiece so that the tool is positioned over a location of the workpiece different from the first location where the first hole is formed; and

[0071] A second hole is formed in the workpiece by again vibrating the tool along the longitudinal axis while the tool is positioned over the different location.

[0072] A7. According to the method described in paragraph A6, the method also includes the following steps: the step of translating the tool relative to the workpiece is repeated multiple times so that the tool is sequentially placed above multiple different corresponding positions of the workpiece, and between each execution of translating the tool, while the tool is placed above the corresponding position, additional corresponding holes are formed at the corresponding positions in the workpiece by vibrating the tool again along the longitudinal axis.

[0073] A8. The method according to any of paragraphs A1 to A7, further comprising the following steps:

[0074] A portion of the workpiece is locally heated, wherein the first location is within the portion of the workpiece.

[0075] A9. The method of paragraph A8, wherein the step of locally heating the portion of the workpiece is performed before forming the hole in the workpiece.

[0076] A9.1. The method of paragraph A8 or A9, wherein the step of locally heating the portion of the workpiece is performed during formation of the hole in the workpiece.

[0077] A10. A method as described in any of paragraphs A8 to A9.1, wherein the step of locally heating the portion of the workpiece includes: maintaining the temperature of the portion of the workpiece above a threshold temperature during the formation of the hole in the workpiece.

[0078] A11. The method of paragraph A10, wherein the threshold temperature is the glass transition temperature of the resin in the composite material.

[0079] A12. A method according to any of paragraphs A8 to A11, wherein the threshold temperature is at least 200 degrees Fahrenheit (℉), at least 210℉, at least 220℉, at least 230℉, at least 240℉, at least 250℉, at least 260℉, at least 270℉, at least 280℉, at least 290℉ and / or at least 300℉.

[0080] A13. The method of any of paragraphs A8 to A12, wherein locally heating the portion of the workpiece includes locally heating the portion of the workpiece via a remote heating unit.

[0081] A14. The method of paragraph A13, wherein the remote heating unit comprises a heating lamp.

[0082] A15. A method according to any of paragraphs A1 to A14, wherein the tool includes a needle array, the needle array includes a plurality of needles, wherein each of the plurality of needles is oriented to extend along the longitudinal axis, wherein each corresponding needle of the plurality of needles is configured to form a corresponding hole in the workpiece when the tool vibrates along the longitudinal axis, so that the step of forming the holes in the workpiece includes: forming a plurality of holes in an area of ​​the workpiece without translating the tool relative to the workpiece and without translating the workpiece relative to the tool.

[0083] A16. The method of paragraph A15, wherein the method further comprises the step of heating the region of the workpiece before forming the plurality of holes in the region.

[0084] A16.1. A method according to any of paragraphs A15 to A16, wherein the needle array includes at least ten needles, at least twenty needles, at least thirty needles, at least forty needles, at least fifty needles, at least sixty needles, at least seventy needles, at least eighty needles, at least ninety needles and / or at least one hundred needles.

[0085] A17. The method of any of paragraphs A1 to A16.1, wherein the step of forming the hole includes vibrating the tool along the longitudinal axis at a predefined speed.

[0086] A18. A method according to any of paragraphs A1-A17, wherein the step of forming the hole includes: vibrating the tool along the longitudinal axis so that each time the tool contacts the workpiece, the tool applies a force less than a predetermined threshold on the surface of the tool.

[0087] A19. The method of any of paragraphs A1 to A18, wherein the tool is removably coupled to an ultrasonic grinder.

[0088] A20. The method of any of paragraphs A1 to A19, further comprising the step of coupling the tool to an ultrasonic actuator of the ultrasonic grinder.

[0089] A21. The method of any of paragraphs A1 to A20, further comprising the step of coupling the tool to an arm of the ultrasonic grinder.

[0090] A22. The method according to any of paragraphs A1 to A21, further comprising the following steps:

[0091] removing the tool from the ultrasonic grinder; and

[0092] A second tool is coupled to the ultrasonic grinder.

[0093] B1. A method for forming a plurality of perforations in a thin sheet of a composite material, the method comprising the following steps:

[0094] placing the surface of the sheet opposite a needle array operatively coupled to an ultrasound device such that the needle array is positioned over a first region of the sheet; wherein the needle array comprises a plurality of needles extending along a longitudinal axis that is substantially orthogonal to the surface of the sheet;

[0095] repeatedly contacting the surface of the sheet with the array of needles in the first region for a period of time sufficient to form a first plurality of holes in the first region of the sheet at an operating frequency greater than 20 kHz, wherein the step of repeatedly contacting the surface of the sheet forms respective second holes in the sheet corresponding to respective respective needles of the array of needles, wherein the step of repeatedly contacting the surface of the sheet comprises: contacting the sheet with the plurality of needles of the array of needles without rotating the plurality of needles about the longitudinal axis, without rotating the plurality of needles relative to the sheet, and without using a slurry or cooling fluid;

[0096] translating the thin plate and / or the needle array so that the thin plate is positioned relative to the needle array so that the needle array is located above the second region of the thin plate; and

[0097] The needle array is used to repeatedly contact the surface of the thin plate in the second region for a period of time sufficient to form a second plurality of holes in the second region of the thin plate at an operating frequency greater than 20 kHz, wherein the step of repeatedly contacting the surface of the thin plate forms corresponding second holes in the thin plate corresponding to the respective corresponding needles of the needle array, wherein the step of repeatedly contacting the surface of the thin plate includes contacting the thin plate with the plurality of needles of the needle array without rotating the plurality of needles around the longitudinal axis, without rotating the plurality of needles relative to the thin plate, and without using slurry or cooling fluid.

[0098] B2. The method of paragraph B1, wherein the sheet has a thickness of less than 0.25 inches, less than 0.1 inches, less than 0.05 inches, and / or less than 0.025 inches.

[0099] B3. The method of any of paragraphs B1 to B2, wherein the sheet is configured to be incorporated into an acoustic liner.

[0100] B4. The method according to any of paragraphs B1 to B3, wherein the sheet includes a plurality of regions, and the method further comprises the following steps:

[0101] translating the sheet and / or the needle array a plurality of times such that the needle array is positioned over a different corresponding region of the plurality of regions of the sheet with each corresponding translation of the sheet and / or the needle array; and

[0102] At an operating frequency higher than 20kHz, the needle array is used to repeatedly contact the surface of the thin plate in each corresponding area of ​​the multiple areas of the thin plate for a certain period of time, and the period of time is sufficient to form a corresponding plurality of holes in each corresponding area of ​​the thin plate, wherein the step of repeatedly contacting the surface of the thin plate is repeated each time the needle array is placed over a different corresponding area of ​​the thin plate.

[0103] B5. A method according to paragraph B4, wherein the step of repeatedly contacting the surface of the thin plate is repeated at least multiple times as needed to form at least 1,000 holes, at least 10,000 holes, at least 100,000 holes and / or at least 1,000,000 holes in the thin plate.

[0104] B6. A method according to any of paragraphs B1 to B5, wherein the composite material includes a carbon fiber reinforced polymer, a glass fiber reinforced polymer, a thermoplastic material, a thermosetting material, a carbon fiber or peeled fiber reinforced polyetheretherketone (PEEK), a carbon fiber or glass fiber reinforced polyetherketoneketone (PEKK), a carbon fiber or glass fiber reinforced epoxy resin, and / or a carbon fiber or glass fiber reinforced polyphenylene sulfide (PPS).

[0105] B7. A method according to any of paragraphs B1 to B6, wherein each hole in the first plurality of holes, each hole in the second plurality of holes, and each hole in each corresponding plurality of holes has a diameter of less than 0.1 inch, less than 0.09 inch, less than 0.08 inch, less than 0.07 inch, less than 0.06 inch, less than 0.05 inch, less than 0.04 inch, less than 0.03 inch, less than 0.02 inch and / or less than 0.01 inch.

[0106] B8. A method according to any of paragraphs B1 to B7, wherein each hole in the first plurality of holes, each hole in the second plurality of holes, and each hole in each corresponding plurality of holes has a diameter between 0.04 inches and 0.05 inches.

[0107] B9. A method as described in any of paragraphs B1 to B8, wherein each hole in the first plurality of holes, each hole in the second plurality of holes, and each hole in each corresponding plurality of holes have a substantially uniform diameter.

[0108] B10. A method according to any of paragraphs B1 to B9, wherein each hole in the first plurality of holes, each hole in the second plurality of holes, and each hole in each corresponding plurality of holes are spaced apart from each adjacent corresponding hole at a minimum center distance.

[0109] B11. A method according to paragraph B10, wherein the minimum center distance is less than 0.5 inches, less than 0.4 inches, less than 0.3 inches, less than 0.2 inches and / or less than 0.1 inches.

[0110] B12. A method according to paragraph B10 or B11, wherein the minimum center distance is greater than or equal to the diameter of each corresponding hole.

[0111] B13. A method according to any of paragraphs B10 to B12, wherein the minimum center distance is at least 1.25 times the diameter of each corresponding hole, at least 1.5 times the diameter of each corresponding hole, at least 1.75 times the diameter of each corresponding hole, at least 2 times the diameter of each corresponding hole, at least 2.5 times the diameter of each corresponding hole, at least 3 times the diameter of each corresponding hole, at least 4 times the diameter of each corresponding hole, and / or at least 5 times the diameter of each corresponding hole.

[0112] C1. A method for forming an acoustic liner, the method comprising the following steps:

[0113] forming the workpiece according to the method of any of paragraphs A1 to A22;

[0114] coupling the workpiece to a first side of a honeycomb structure, wherein the honeycomb structure comprises:

[0115] the first side;

[0116] a second side opposite to the first side; and

[0117] a plurality of interior cells extending between the first side and the second side, wherein each interior cell of the plurality of interior cells is sized to fit an acoustic plane wave in the interior cell for a desired frequency range such that the acoustic liner is configured to generate noise attenuation characteristics for the desired frequency range; and

[0118] A rigid backing plate is coupled to the second side of the honeycomb structure, thereby forming an acoustic liner.

[0119] C2. A method of forming an acoustic liner, the method comprising the steps of:

[0120] Forming a sheet of the composite material according to the method of any of paragraphs B1 to B13;

[0121] coupling a sheet of the composite material to a first side of a honeycomb structure, wherein the honeycomb structure comprises:

[0122] the first side;

[0123] a second side opposite to the first side; and

[0124] a plurality of interior cells extending between the first side and the second side, wherein each interior cell of the plurality of interior cells is sized to fit an acoustic plane wave in the interior cell for a desired frequency range such that the acoustic liner is configured to generate noise attenuation characteristics for the desired frequency range; and

[0125] A rigid backing plate is coupled to the second side of the honeycomb structure, thereby forming an acoustic liner.

[0126] C3. The method according to any of paragraphs C1 to CA2, further comprising the following steps:

[0127] incorporating the acoustic liner into a jet engine casing of an aircraft; and

[0128] The acoustic liner is used to attenuate noise generated by a jet engine of the aircraft, wherein the jet engine is housed in the jet engine casing.

[0129] D1. An acoustic lining, comprising:

[0130] A sheet of material comprised of a composite material and comprising a plurality of perforations formed through the thickness of the sheet of material, wherein the sheet of material is the workpiece formed according to the method of any of paragraphs A1 to A22, and / or wherein the sheet of material is a sheet of the composite material formed according to the method of any of paragraphs B1 to B13;

[0131] a honeycomb structure having a first side, a second side opposite the first side, and a plurality of internal cells extending between the first side and the second side, wherein the first side is coupled to the sheet material, and wherein each of the plurality of internal cells is sized to fit an acoustic plane wave in the internal cell for a desired frequency range such that the acoustic liner is configured to generate noise attenuation characteristics for the desired frequency range; and

[0132] A rigid back plate is coupled to the second side of the honeycomb structure.

[0133] D2. An acoustic lining according to paragraph D1, wherein the composite material includes carbon fiber or glass fiber reinforced polymer, thermoplastic material, thermosetting material, carbon fiber or glass fiber reinforced PEKK, carbon fiber or glass fiber reinforced PPS, carbon fiber or glass fiber reinforced epoxy resin, and / or carbon fiber or glass fiber reinforced PEKK.

[0134] D3. An acoustic lining according to any of paragraphs D1 to D2, wherein the plurality of perforations includes at least 100 perforations, at least 1,000 perforations, at least 10,000 perforations, at least 100,000 perforations and / or at least 1,000,000 perforations formed in the thin sheet material.

[0135] D4. An acoustic liner as described in any of paragraphs D1 to D3, wherein the acoustic liner is configured for use in a jet engine casing.

[0136] D5. An acoustic liner as described in any of paragraphs D1 to D4, wherein the acoustic liner is formed according to the method described in any of paragraphs C1 to C3.

[0137] D6. An acoustic lining as described in any of paragraphs D1 to D5, wherein the rigid backing panel comprises: metal, carbon fiber and / or fiber-based reinforced polymer.

[0138] D7. An acoustic liner as described in any of paragraphs D1 to D6, wherein each of the plurality of perforations is non-circular.

[0139] D8. An acoustic liner as described in any of paragraphs D1 to D7, wherein one or more of the plurality of perforations are square, rectangular, triangular, polygonal, star-shaped and / or diamond-shaped.

[0140] E1. A jet engine comprising an acoustic liner according to any of paragraphs D1 to D8.

[0141] E2. An aircraft comprising an acoustic liner according to any of paragraphs D1 to D8.

[0142] F1. Use of an acoustic lining according to any of paragraphs D1 to D8 for reducing noise pollution and / or achieving noise attenuation.

[0143] F2. Use of an acoustic liner according to any of paragraphs D1 to D8 for reducing noise pollution from an engine and / or achieving noise attenuation in an aircraft.

[0144] As used herein, the terms "selective" and "selectively" in connection with an action, movement, configuration, or other activity that modifies one or more components or features of a device mean that the specific action, movement, configuration, or other activity is a direct or indirect result of user manipulation of that aspect of the device or one or more components.

[0145] As used herein, the terms "suitable for" and "configured" refer to elements, components, or other subjects that are designed and / or intended to perform a given function. Thus, the use of the terms "suitable for" and "configured" should not be interpreted as meaning that a given element, component, or other subject is simply "capable of" performing a given function, but rather that the element, component, and / or other subject is specifically selected, created, implemented, utilized, programmed, and / or designed for the purpose of performing that function. It is also within the scope of the present disclosure that the element, component, and / or other stated subject matter stated as being suitable for performing a particular function may additionally or alternatively be described as being configured to perform that function, and vice versa. Similarly, a subject matter stated as being configured to perform a particular function may additionally or alternatively be described as being operable to perform that function.

[0146] As used herein, with respect to a list of one or more entities, the phrase "at least one" should be understood to refer to at least one entity selected from any one or more entities in the entity list, but does not necessarily include at least one of each entity explicitly listed in the entity list, and does not exclude any combination of entities in the entity list. This definition also allows that in addition to the entities explicitly identified in the entity list to which the phrase "at least one" refers, other entities may optionally be present, whether related or unrelated to those entities specifically identified. Thus, as a non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B", or equivalently, "at least one of A and / or B") may refer to: in one embodiment, at least one (optionally including more than one) A, and no B (and optionally including entities other than B); in another embodiment, at least one (optionally including more than one) B, and no A (and optionally including entities other than A); in yet another embodiment, at least one (optionally including more than one) A and at least one (optionally including more than one) B (and optionally including other entities). In other words, the phrases "at least one", "one or more", and "and / or" are open-ended expressions that can be both conjunctive and disjunctive in operation. For example, the expressions "at least one of A, B, and C", "at least one of A, B, or C", "one or more of A, B, and C", "one or more of A, B, or C", and "A, B, and / or C" may refer to A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together, and optionally also to any of the foregoing in combination with at least one other entity.

[0147] For all devices and methods according to the present disclosure, the various disclosed elements of the devices disclosed herein and the steps of the methods are not required, and the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various elements and steps disclosed herein. In addition, one or more of the various elements and steps disclosed herein may define an independent invention theme that is separated and separated from the entire disclosed device or method. Therefore, such invention theme does not need to be associated with the specific devices and methods explicitly disclosed herein, and such invention theme may find use in devices and / or methods that are not explicitly disclosed herein.

[0148] As used herein, the phrase "for example," the phrase "as an example," and / or simply, the term "example," when used with reference to one or more components, features, details, structures, implementations, and / or methods according to the present disclosure, is intended to convey that the described components, features, details, structures, implementations, and / or methods are illustrative, non-exclusive examples of components, features, details, structures, implementations, and / or methods according to the present disclosure. Thus, the described components, features, details, structures, implementations, and / or methods are not intended to be limiting, requiring, or exclusive / exhaustive; rather, other components, features, details, structures, implementations, and / or methods (including structurally and / or functionally similar and / or equivalent components, features, details, structures, implementations, and / or methods) are also within the scope of the present disclosure.

Claims

1. A method of performing ultrasonic drilling at a first location of a workpiece (32) to form a hole (44) in the workpiece (32), the method comprising the following steps: placing (202) the surface (34) of the workpiece (32) relative to a tool of an ultrasonic grinding stone, wherein the tool has a longitudinal axis (40) that is generally orthogonal to the surface (34) of the workpiece (32); forming the hole (44) in the workpiece (32) by vibrating the tool along the longitudinal axis (40) such that the tool repeatedly contacts the surface (34) of the workpiece (32) at an operating frequency and amplitude sufficient to form the hole (44) in the workpiece (32), wherein the step of vibrating the tool is performed for a time sufficient to form the hole (44) in the workpiece (32), wherein the tool is not rotated relative to the surface (34) of the workpiece (32) during the forming of the hole (44), wherein the step of forming the hole (44) is performed without the use of a slurry or a cooling fluid, and wherein the workpiece (32) is composed of a composite material; and A portion of the workpiece (32) is locally heated (212), wherein the first location is within the portion of the workpiece (32) during formation of the hole (44) in the workpiece (32).

2. The method according to claim 1, wherein: The operating frequency is at least 20 kHz.

3. The method according to claim 1 or 2, wherein: The hole (44) is a first hole, and wherein the method further comprises the steps of: translating the workpiece (32) relative to the tool so that the tool is positioned over a location of the workpiece (32) different from the first location where the first hole is formed; forming a second hole in the workpiece (32) by again vibrating the tool along the longitudinal axis (40) while the tool is positioned over the different location; and The step of translating the workpiece (32) relative to the tool is repeated a plurality of times so that the tool is sequentially placed over a plurality of different corresponding positions of the workpiece (32), and between each execution of translating the workpiece (32), while the tool is placed over the corresponding position, additional corresponding holes (44) are formed at the corresponding positions in the workpiece (32) by again vibrating the tool along the longitudinal axis (40).

4. The method according to claim 1, wherein: The step of locally heating (212) the portion of the workpiece (32) includes maintaining a temperature of the portion of the workpiece (32) above a threshold temperature during formation of the hole (44) in the workpiece (32).

5. The method according to claim 4, wherein: The threshold temperature is the glass transition temperature of the resin in the composite material.

6. The method according to claim 1 or 2, wherein: The tool comprises a needle array (60), the needle array (60) comprising a plurality of needles (36), wherein each needle (36) of the plurality of needles (36) is oriented to extend along the longitudinal axis (40), wherein each corresponding needle (36) of the plurality of needles (36) is configured to form a corresponding hole (44) in the workpiece (32) when the tool is vibrated along the longitudinal axis (40), so that the step of forming the holes (44) in the workpiece (32) comprises: forming a plurality of holes (44) in a region of the workpiece without translating the tool relative to the workpiece (32) and without translating the workpiece (32) relative to the tool.

7. The method according to claim 6, wherein: The needle array (60) comprises a two-dimensional array including at least four needles (36).

8. The method according to claim 6, wherein: The needle array (60) is removably coupled to the ultrasonic grinder.

9. A method of forming a plurality of perforations (44) in a sheet (42) of composite material, the method comprising the steps of: placing (222) a surface (34) of the sheet (42) and a needle array (60) operatively coupled to an ultrasonic grinding stone such that the needle array (60) is positioned over a first region (66) of the sheet (42), wherein the needle array (60) includes a plurality of needles (36) extending along a longitudinal axis (40) that is generally orthogonal to the surface (34) of the sheet (42); repeatedly contacting (224) the surface (34) of a sheet (42) in the first region (66) with the needle array (60) for a first period of time at an operating frequency greater than 20 kHz, the first period of time being sufficient to form a first plurality of holes (44) in the first region (66) of the sheet (42), wherein the step of repeatedly contacting (224) the surface (34) of the sheet (42) forms respective first holes in the sheet (42) corresponding to respective respective needles (36) of the needle array (60), wherein the step of repeatedly contacting (224) the surface (34) of the sheet (42) comprises contacting the sheet (42) with the needles of the needle array (60) without rotating the needles about the longitudinal axis (40), without rotating the needles relative to the sheet (42), and without using a slurry or cooling fluid; translating the needle array (60) relative to the sheet (42) such that the needle array (60) is positioned over a second region (98) of the sheet (42); and The needle array (60) is configured to repeatedly contact (224) the surface (34) of the thin plate (42) in the second region (98) at the operating frequency for a second period of time, the second period of time being sufficient to form a second plurality of holes (44) in the second region (98) of the thin plate (42), wherein the step of repeatedly contacting the surface (34) of the thin plate (42) forms corresponding second holes in the thin plate (42) corresponding to respective corresponding needles (36) of the needle array (60), wherein the step of repeatedly contacting (224) the surface (34) of the thin plate (42) includes contacting the thin plate (42) with the needles (36) of the needle array (60) without rotating the needles (36) about the longitudinal axis (40), without rotating the needles (36) relative to the thin plate (42), and without using slurry or cooling fluid.

10. The method according to claim 9, wherein: The thin plate (42) has a thickness of less than 0.1 inches.

11. The method according to claim 9 or 10, wherein: The thin plate (42) is configured as an acoustic liner (33).

12. The method according to claim 9 or 10, wherein: The sheet (42) includes a plurality of regions (66), and the method further includes the following steps: translating the needle array (60) relative to the sheet (42) a plurality of times so that the needle array (60) is positioned over a different corresponding region (66) of the plurality of regions (66) of the sheet (42) with each corresponding translation of the needle array (60); and At the operating frequency, the needle array (60) is used to repeatedly contact (224) the surface (34) of the thin plate (42) in each corresponding area of ​​the multiple areas (66) of the thin plate (42) for a corresponding period of time, and the corresponding period of time is sufficient to form a corresponding plurality of holes (44) in each corresponding area (66) of the thin plate (42), wherein the step of repeatedly contacting (224) the surface (34) of the thin plate (42) is repeated each time the needle array (60) is placed over a different corresponding area (66) of the thin plate (42), and wherein the step of repeatedly contacting (224) the surface (34) of the thin plate (42) is repeated at least a plurality of times as needed to form at least 100,000 holes (44) in the thin plate (42).

13. The method according to claim 9 or 10, wherein: The composite material comprises a carbon fiber reinforced polymer and / or a glass fiber reinforced polymer.

14. The method according to claim 9 or 10, wherein: Each hole (44) in the first plurality of holes (44) and each hole (44) in the second plurality of holes (44) has a diameter between 0.01 inches and 0.06 inches.

15. The method according to claim 9 or 10, wherein: Each corresponding hole (44) in the first plurality of holes (44) and each corresponding hole (44) in the second plurality of holes (44) are spaced apart from each adjacent corresponding hole (44) by a minimum center distance, wherein the minimum center distance is at least 1.5 times the diameter of each corresponding hole (44).

16. The method according to claim 9 or 10, wherein: The composite material includes thermoplastic material and / or thermosetting material.

17. The method according to claim 9 or 10, wherein: The composite material comprises one or more materials selected from the group consisting of: carbon fiber reinforced polyetheretherketone, i.e., carbon fiber reinforced PEEK; Glass fiber reinforced PEEK; Carbon fiber reinforced polyetherketoneketone, i.e. carbon fiber reinforced PEKK; glass fiber reinforced PEKK; carbon fiber reinforced epoxy resin; Glass fiber reinforced epoxy resin; Glass fiber reinforced PPS; And carbon fiber reinforced polyphenylene sulfide, that is, carbon fiber reinforced PPS.

18. A method of forming an acoustic liner (33), the method The following steps are involved: Forming the workpiece (32) according to the method of claim 1; The workpiece (32) is coupled to a first side (50) of a honeycomb structure (48), wherein the honeycomb structure (48) includes: the first side (50); a second side (52) opposite the first side (50); and a plurality of interior cells (54) extending between the first side (50) and the second side (52), wherein each interior cell (54) of the plurality of interior cells (54) is sized to fit an acoustic plane wave in the interior cell (54) for a desired frequency range such that the acoustic liner (33) is configured to generate noise attenuation characteristics for the desired frequency range; and A rigid backing plate (56) is coupled to the second side (52) of the honeycomb structure (48), thereby forming the acoustic liner (33).

19. The method according to claim 18, further comprising the steps of: incorporating (238) the acoustic liner (33) into a jet engine casing of an aircraft (104); and The acoustic liner (33) is used to attenuate (240) noise generated by a jet engine of the aircraft (104), wherein the jet engine is housed in the jet engine casing.

20. A method of forming an acoustic liner (33), the method The following steps are involved: Forming a plurality of perforations (44) in the sheet (42) of composite material according to the method of claim 10; The composite material perforated sheet (42) is coupled to a first side (50) of a honeycomb structure (48), wherein the honeycomb structure (48) comprises: the first side (50); a second side (52) opposite the first side (50); and a plurality of interior cells (54) extending between the first side (50) and the second side (52), wherein each interior cell (54) of the plurality of interior cells (54) is sized to fit an acoustic plane wave in the interior cell (54) for a desired frequency range such that the acoustic liner (33) is configured to generate noise attenuation characteristics for the desired frequency range; and A rigid backing plate (56) is coupled to the second side (52) of the honeycomb structure (48), thereby forming the acoustic liner (33).

21. An acoustic lining (33), comprising: A sheet (42) composed of a carbon fiber reinforced polymer and comprising at least 100,000 non-circular perforations (44) formed through the thickness of the sheet (42); a honeycomb structure (48) having a first side (50), a second side (52) opposite the first side (50), and a plurality of internal cells (54) extending between the first side (50) and the second side (52), wherein the first side (50) is coupled to the thin plate (42), and wherein each of the plurality of internal cells (54) is sized to fit an acoustic plane wave in the internal cell (54) for a desired frequency range, such that the acoustic liner (33) is configured to generate noise attenuation characteristics for the desired frequency range; and A rigid back plate (56) is coupled to the second side (52) of the honeycomb structure (48).

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