Ultrasonic drilling method for forming holes in composite materials - Patent Application 20070122967

Abstract

To provide an implementation method of ultrasonic drilling for forming a hole on a workpiece at a first portion of the workpiece.SOLUTION: A method of ultrasonic drilling may be used to form perforated sheets 100 by forming holes 44 through a workpiece 32 using a needle 36 or needle array 60 operatively coupled to an ultrasonic actuator 38. The needle 36 is repeatedly brought into contact with the surface of the workpiece 32 at an ultrasonic operating frequency, thereby forming the hole 44 through the workpiece 32. Such steps are repeated to form a plurality of holes 44 in the workpiece 32, thereby forming a perforated sheet 100 which may be used in an acoustic liner 33 for noise attenuation. The workpiece 32 may be heated while the holes 44 are formed, via a remote heating unit 96 that locally heats a portion of the workpiece 32.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Acoustic liners are often formed using thin material with numerous small holes or perforations formed therein. For example, acoustic liners may be placed inside jet engines (e.g., within the inner barrel of the engine inlet) for noise attenuation (i.e., to dampen engine sound and / or reduce noise pollution in aircraft). These acoustic liners are often formed by placing a perforated sheet of material (e.g., a metal or graphite sheet) over a honeycomb core material, which is sandwiched between the perforated sheet and an impermeable layer or backing.

[0003] Perforated sheets are formed by punching or drilling hundreds of thousands, or even millions, of small holes through thin metal or composite sheets. Traditional methods involve drilling these holes one at a time, which is time- and capital-intensive and therefore costly in terms of production cycles. In some cases, such drilling can require robotic drilling operations lasting more than a week, with each hole taking 1-5 seconds to drill. Additionally, tooling costs for forming such holes are high in terms of wear on drill bits, which require frequent replacement, especially when drilling composite materials (e.g., carbon fiber or glass fiber reinforced polymers) and / or other thermoplastic materials. Additionally, drill bits often need to be made of expensive materials, such as tool steel, which are difficult to machine. While attempts have been made to drill multiple holes at once, such attempts have been limited to drilling 4-12 holes at a time due to the rotational motion required by such drilling operations.

[0004] Ultrasonic drilling is a technique that uses high-frequency, low-amplitude vibration of a tool or bit against the workpiece surface to remove material from the workpiece by microchipping or erosion with abrasive particles. In contrast to traditional drilling methods that use rotation to penetrate the material, ultrasonic drilling primarily relies on axial vibration to drive the bit into the material. FIG. 1 illustrates an example of a prior art ultrasonic drilling machine 10. The ultrasonic drilling machine 10 includes a piezoelectric actuator 12 as its power source and utilizes various horns 14 to vibrate the bit to penetrate the workpiece 16 in the presence of fine abrasive particles. The fine abrasive particles are mixed with water to form a slurry that is stored in a slurry reservoir 18. A slurry pump 20 distributes the slurry across the workpiece 16 and the tip of the bit via lines and nozzles 22. This slurry is necessary to remove material from the workpiece 16 while keeping the bit clean and effective. The slurry also serves as a refrigerant liquid to keep the material and bit cool to prevent damage to the workpiece and bit. The slurry is returned to the slurry reservoir 18 via a slurry return line 24 and serves to remove debris from the cutting area. Because ultrasonic drill bits do not include slots that allow for the use of slurries as used with rotary drills, the ability of the slurry or cutting fluid to reach the bit limits the depth at which an ultrasonic drilling machine can be used.

[0005] Hard and / or brittle materials have been successfully machined using ultrasonic drills, such as semiconductors, stainless steel, glass, ceramics, carbides, quartz, stone, tungsten, granite, rock, and delicate bone for medical applications. Attempts to utilize ultrasonic drilling methods with composite materials (e.g., carbon fiber reinforced plastics) have been limited to 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 tends to be difficult and costly to perform and often results in damage to the composite part. Summary of the Invention [Means for solving the problem]

[0006] In one disclosed method of performing ultrasonic drilling to form a hole in a workpiece at a first location on the workpiece, the surface of the workpiece is positioned relative to a tool of an ultrasonic horn, and the 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 sufficient to form the hole in the workpiece. The tool may have a longitudinal axis substantially perpendicular to the surface of the workpiece. In such a method, the tool is not rotated relative to the surface of the workpiece during hole formation, but is vibrated for a time sufficient to form the hole in the workpiece. Furthermore, the hole may be formed without the use of a slurry or cooling fluid. In some methods according to the present disclosure, the workpiece is composed of a composite material.

[0007] Another method according to the present disclosure forms a plurality of perforations in a thin composite sheet. In such a method, a surface of the thin sheet and a needle array operably coupled to an ultrasonic horn are positioned such that the needle array is positioned above a first region of the thin sheet. The needle array includes a plurality of needles extending along a longitudinal axis substantially perpendicular to the surface of the thin sheet. In this method, the surface of the thin sheet within the first region is repeatedly contacted with the needle array at an operating frequency greater than about 20 kHz for a first time period sufficient to form a first plurality of perforations in the first region of the thin sheet. Such repeated contact of the surface of the thin sheet forms a respective first perforation in the thin sheet corresponding to each respective needle of the needle array. In this method, the needles of the needle array contact the thin sheet without rotating the plurality of needles about the longitudinal axis, without rotating the needles relative to the thin sheet, and without using a slurry or cooling fluid.

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

[0009] A method for forming an acoustic liner is also disclosed. In one example, a workpiece formed according to the disclosed method is bonded to a first side of a honeycomb structure. The honeycomb structure also includes a second side opposite the first side and a plurality of interior cells extending between the first and second sides. Each interior cell is sized to accommodate an acoustic plane wave within the interior cell in a desired frequency range, such that the acoustic liner is configured to provide noise attenuation characteristics for the desired frequency range. In this method, a rigid backing is bonded to the second side of the honeycomb structure, thereby forming the acoustic liner.

[0010] Acoustic absorbing liners are also disclosed. One example of the disclosed acoustic absorbing liner is a thin sheet material composed of a carbon fiber reinforced polymer and at least 100,000 circular or non-circular perforations formed through the thickness of the thin sheet material. The thin sheet material can be formed according to the method of the present disclosure. The acoustic absorbing liner can also include a honeycomb structure and a rigid backing. The honeycomb structure includes 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. The first side of the honeycomb structure is bonded to the thin sheet material, and the second side of the honeycomb structure is bonded to the rigid backing. Each internal cell of the plurality of internal cells is sized to accommodate an acoustic plane wave within the internal cell in the desired frequency range, such that the acoustic absorbing liner is configured to provide noise attenuation characteristics for a desired frequency range. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an elevational view of a prior art ultrasonic drilling device. [Figure 2] 1 is a schematic diagram 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. [Figure 3] 1 is a schematic diagram of an example system for implementing an ultrasonic drilling method according to the present disclosure; [Figure 4] 1 is a perspective view of an example acoustic liner formed according to the method of the present disclosure. [Figure 5] 1 is a schematic diagram of an example needle array according to the present disclosure, viewed from a bottom view. [Figure 6] 1 is a schematic diagram of an example needle array according to the present disclosure, viewed from a side view. [Figure 7] FIG. 1 is a perspective view of an example of a needle array that may be used in the methods of the present disclosure. [Figure 8] 1A-1C are schematic diagrams of examples of needle distribution in a needle array according to the present disclosure. [Figure 9] FIG. 10 is a schematic diagram of another example of needle distribution in a needle array according to the present disclosure. [Figure 10]FIG. 1 is a flow diagram illustrating the disclosed method of forming one or more holes in a workpiece. [Figure 11] FIG. 1 is a flow diagram illustrating the disclosed method of forming one or more holes in a workpiece. [Figure 12] FIG. 1 is a flow diagram depicting the disclosed method of forming an acoustic liner. [Figure 13] 1 is a schematic diagram of an example needle tip used in needle arrays and systems of the present disclosure, illustrating a side view of a portion of a needle. [Figure 14] 1A-1C are schematic diagrams of examples of needle tips used in needle arrays and systems of the present disclosure illustrating a bottom view of the needle tip. DETAILED DESCRIPTION OF THE INVENTION

[0012] With reference to FIG. 2 , one or more perforated sheets 100 may be included in an apparatus 102. The perforated sheets 100 may be utilized in many different industries and applications, such as the aerospace, automotive, electronics, construction, military, recreational, and / or motorsport industries. In FIG. 2 , an example of an apparatus 102 that may include one or more perforated sheets 100 is depicted generally in the form of an aircraft 104. The aircraft 104 may take any suitable form, including a commercial aircraft, a military aircraft, or any other suitable aircraft. While FIG. 2 depicts the aircraft 104 in the form of a fixed-wing aircraft, 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.

[0013] The apparatus 102 (e.g., the aircraft 104) may include one or more perforated sheets 100. As illustrative, non-exclusive examples, the perforated sheets 100 may be utilized within the engine housing 116, although other components of the aircraft 104, such as the wings 106, the fuselage 108, i.e., fuselage sections 108a, 108b, 108c, the horizontal stabilizer 110, the overhead bins 112, the vertical stabilizer 114, and others, may additionally or alternatively include one or more perforated sheets 100. Other uses for the perforated sheets 100 in the aircraft 104 include floor panels, interior walls, food galley assemblies, wing control surfaces, passenger storage racks, thrust vectorer assemblies, capsule panels, ablation shields for nose cones, equipment enclosures and shelving, and bulkhead panels. In other industries, examples of apparatus 102 (including one or more perforated sheets 100) may include or be part of the interior structure of a space satellite, an electronic radome structure, a transportation vehicle, a shipping container, a shelter, a large antenna or disc reflector, a refrigeration panel, a high-speed transportation floor panel, a shipboard electronic deck shelter, a cargo pallet, an automobile body, an architectural curtain wall, a partition, a dividing panel, an expandable hospital shelter, and / or an assembly.

[0014] 3-9 and 13-14 present illustrative, non-exclusive examples of systems 30, acoustic liners 33, needles 36, and / or needle arrays 60 according to the present disclosure. Elements serving similar or at least substantially similar purposes are similarly numbered in each of FIGS. 3-9 and 13-14 (and generally throughout this specification), and these elements may not be described in detail herein with reference to each of FIGS. 3-9 and 13-14. Similarly, not all elements are numbered in each of FIGS. 3-9 and 13-14, and reference numbers associated with these elements may be used herein for consistency. Elements, components, and / or features described herein with reference to one or more of FIGS. 3-9 and 13-14 may be included in and / or utilized in any of FIGS. 3-9 and 13-14 without departing from the scope of the present disclosure. Generally, elements likely to be included in a given (i.e., particular) embodiment are illustrated with solid lines, while elements that are optional in a given embodiment are illustrated with dashed lines. However, elements shown with solid lines are not required for all embodiments, and elements shown with solid lines may be omitted from particular embodiments without departing from the scope of the present disclosure. Where appropriate, reference numerals in each of Figures 3-9 and 13-14 are used to designate other corresponding parts in Figures 3-9 and 13-14, but the examples in Figures 3-9 and 13-14 are non-exclusive and may include any number of the various aspects, configurations, features, characteristics, etc. shown and described with reference to others of Figures 3-9 and 13-14 and variations thereof, and need not include all such aspects, configurations, features, characteristics, etc. For purposes of brevity, each of the aforementioned components, parts, portions, aspects, regions, etc., or variations thereof, may not be described, illustrated, and / or labeled again with respect to each of Figures 3-9 and 13-14, but it is within the scope of this disclosure that the aforementioned features, variations, etc. may be utilized with any of the same.

[0015] FIG. 3 schematically illustrates a system 30 according to the present disclosure. Such a system 30 may be used to form one or more holes in a workpiece 32 (which is an example of a perforated sheet 100). In some examples, the system 30 may be used to drill holes in the workpiece 32 and / or form part or all of an acoustic liner 33 (which may be an example of the workpiece 32). According to the present disclosure, as described in more detail herein, one or more holes may be formed in (e.g., through) the workpiece 32 by repeatedly contacting a surface 34 of the workpiece 32 with one or more needles 36 (which may be arranged as a needle array 60) operably coupled to an ultrasonic actuator 38 configured to vibrate the one or more needles 36 along a longitudinal axis 40 at an ultrasonic operating frequency and amplitude for a time sufficient to form one or more holes in the workpiece 32. The combination of the ultrasonic actuator 38 and the needles 36 (or needle array 60) may be referred to herein as an ultrasonic drilling apparatus 58. In some examples, the ultrasonic drilling device 58 includes a horn that couples the needle array 60 to the ultrasonic actuator 38 , the horn being configured to amplify vibrations along the longitudinal axis 40 .

[0016] Generally, the system 30 is configured to form a respective hole through the workpiece 32 for each needle 36 operably coupled to an ultrasonic actuator 38. The ultrasonic actuator 38 is configured to vibrate the needle 36 (or needle array 60) at ultrasonic frequencies, 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. To form one or more holes in different regions or areas 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 positioned over different regions or areas of the workpiece 32. The needle 36 may then be repeatedly contacted with the surface 34 of the workpiece 32 in the different areas to form one or more additional holes in the workpiece 32. The needles 36 (e.g., the longitudinal axes 40 of the needles 36 or of the needles 36 of the needle array 60) may be positioned so as to be at least substantially perpendicular to the surface 34 (e.g., as shown in FIG. 6). In other examples, the needles 36 may contact the surface 34 at an angle that is not perpendicular to the surface 34.

[0017] The system 30 is configured to form the perforations 44 through the workpiece 32 in a manner different from conventional drilling. Rather than rotating the drill bit at high speed to penetrate the material (as is done in conventional drilling), the needles 36 are not rotated relative to the surface 34 of the workpiece 32 (and the workpiece 32 is not rotated relative to the needles 36) during the formation of the perforations 44. Similarly, the needle array 60 is not rotated relative to the surface 34 of the workpiece 32 (and the workpiece 32 is not rotated relative to the needle array 60) during the formation of the perforations 44. Furthermore, conventional drilling requires the use of a cooling fluid to prevent damage to the drill bit and part due to heat generated during rotary drilling, and conventional ultrasonic drilling, which still involves rotating the drill bit, requires the use of a slurry to cool the part and / or remove debris. In contrast, the ultrasonic drilling apparatus 58 of the present disclosure is configured to operate without the use of a slurry or a cooling fluid (although either or both can optionally be used if desired).

[0018] Such a system 30 may be used to form an acoustic liner 33, an example of which is shown in FIG. 4, in some instances, but may also be used to form any number of holes (including a single hole) in or through a variety of materials. The acoustic liner 33 includes a thin sheet material 42 (an example of a workpiece 32 and a perforated sheet 100) having a plurality of perforations 44 formed therethrough. The perforations 44 are holes that extend entirely through a thickness 46 (FIG. 3) of the thin sheet material 42. In some implementations, the thickness 46 of the thin sheet material 42 may 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 thin sheet material 42 is generally formed of a composite material, although it may be formed of other materials, including metals and ceramics.

[0019] 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 interior partitions, or interior cells 54, extending between the first side 50 and the second side 52. The first side 50 is bonded to the thin sheet material 42, and the second side 52 is bonded to a rigid backing 56, such that the honeycomb structure 48 is sandwiched between the thin sheet material 42 and the rigid backing 56. To ensure that the acoustic liner 33 provides noise attenuation characteristics for a desired frequency band, each interior cell 54 is sized to accommodate acoustic plane waves within the interior cell 54 in the desired frequency band. For example, the interior cells 54 may be sized according to the particular application for which the acoustic liner 33 is designed, with the size of the interior cells 54 selectively varied depending on the anticipated frequency of noise anticipated in a given use. In this manner, the acoustic liner 33 can be used to reduce noise pollution and / or for noise attenuation in a variety of applications. In one specific example, the acoustic liner 33 may be configured for use within a jet engine housing in an aircraft, with the interior cells 54 sized to accommodate a band of acoustic plane waves generated by the jet engine such that the acoustic liner 33 may be used to reduce noise pollution from the engine and / or for noise attenuation within an aircraft or other device. Jet engines including the acoustic liner 33 and aircraft including the acoustic liner 33 are within the scope of this disclosure.

[0020] The thin sheet material 42 may be formed of, for example, carbon fiber or glass fiber reinforced polymer, thermoplastic material, thermoset material, carbon fiber or glass fiber reinforced polyetheretherketone (PEEK), carbon fiber or glass fiber reinforced polyphenylene sulfide (PPS), carbon fiber or glass fiber reinforced epoxy, and / or carbon fiber or glass fiber reinforced polyetherketoneketone (PEKK). The rigid backing plate 56 (sometimes referred to as an impermeable layer, backing sheet, or backing skin) may be formed of any material that provides sufficient support for the thin sheet material 42 and honeycomb structure 48; suitable examples include metal, carbon fiber, and / or fiber-reinforced polymer. The honeycomb structure 48 may be formed of Nomex® honeycomb material, although other honeycomb structure materials are within the scope of this disclosure.

[0021] The thin sheet material 42 can include any number of perforations 44. In some examples, the thin 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 in the thin sheet material. While the perforations 44 can be a variety of different shapes, in FIG. 4 the perforations 44 are illustrated as being generally elliptical. For example, the perforations 44 can 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. Perforations 44 of different shapes can be created using needles 36 with various cross-sectional shapes and / or by lateral movement of the needle array 60 and / or workpiece 32 during the formation of the perforations 44. In some examples of the acoustic liner 33, the perforations 44 may all have a substantially uniform size and shape. In other examples of the acoustic liner 33, one or more perforations 44 may be a different size and / or shape than one or more other perforations 44. For example, one or more perforations 44 may be larger in a given area of ​​the workpiece 32 than one or more other perforations 44 in another area of ​​the workpiece 32. In some examples, perforations 44 of different sizes and / or shapes may be interspersed with one another and distributed across the surface of the workpiece 32.

[0022] The disclosed system 30 (and related ultrasonic drilling methods using such system 30) can be configured to form perforated sheets using techniques and materials that may reduce the time required to form such perforations in the acoustic liner 33, for example, by forming multiple holes at once. Additionally, needles 36 for the disclosed ultrasonic drilling techniques may be made from cheaper materials than conventional drill bits and / or using less expensive designs and manufacturing techniques (e.g., additive manufacturing), which may reduce costs associated with tool manufacturing. The disclosed techniques may also increase the tool life cycle, further reducing costs. For example, the disclosed systems and needle arrays effectively displace fibers to form perforations rather than penetrate the material; as a result, such techniques may enhance the resulting material properties in the workpiece and / or reduce tool wear. The disclosed techniques may also be less labor-intensive than conventional drilling techniques, thereby reducing manufacturing flow time.

[0023] 5-6 schematically illustrate 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 one example, each needle 36 is oriented to extend from a first end 62 to a second end 64 along a longitudinal axis 40 (FIG. 6). Each needle 36 is configured to form a respective hole or perforation in the workpiece when the needle array 60 is vibrated along the longitudinal axis 40 at an ultrasonic operating frequency while the needle array 60 is positioned to repeatedly contact the surface of the workpiece (e.g., the surface 34 of the workpiece 32 shown in FIG. 3). For example, a needle array 60 having ten needles 36 is configured to form ten holes or perforations in an area of ​​the workpiece at one time. Such holes are formed without translating the needle array 60 relative to the workpiece, without rotating the plurality of needles 36 about the longitudinal axis 40, and without rotating the plurality of needles 36 relative to the workpiece while the holes are being formed.

[0024] 3 , such perforations 44 may be located within region 66 of workpiece 32. To form perforations 44 in a different region of workpiece 32 (e.g., second region 98), the workpiece 32 may be translated relative to needle array 60, and / or the needle array 60 may be translated relative to workpiece 32 so that it is positioned over a different region of workpiece 32, and the apparatus is again operated so that needles 36 repeatedly contact surface 34 of workpiece 32 in different areas or regions, thereby forming more perforations 44 in the workpiece 32.

[0025] The perforations 44 are generally fairly small in size. For example, each perforation 44 may have a diameter (or maximum dimension, in the case of non-round perforations 44) 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. In specific examples, the perforations 44 may have a diameter between 0.04 inch and 0.05 inch. 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 different size and / or shape than one or more other perforations 44 formed in the workpiece 32. For example, a given needle array 60 may include a plurality of different sized and / or shaped needles 36 that form a plurality of different sized and / or shaped perforations 44 in a given region of the workpiece 32. Additionally or alternatively, a first needle array 60 may be used to form perforations 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 perforations 44 of different sizes and / or shapes in a different area of ​​the workpiece 32.

[0026] In a given workpiece 32, each hole or perforation 44 may be spaced a minimum center-to-center distance from each adjacent hole. In particular examples, the minimum center-to-center distance may 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 one example, the minimum center-to-center distance is between 0.13 inches and 0.15 inches. Additionally or alternatively, the minimum center-to-center distance may be greater than or equal to the diameter of each hole. For example, the minimum center-to-center distance may be at least 1.25 times the diameter of each hole, at least 1.5 times the diameter of each hole, at least 1.75 times the diameter of each hole, at least 2 times the diameter of each hole, at least 2.5 times the diameter of each hole, at least 3 times the diameter of each hole, at least 4 times the diameter of each hole, and / or at least 5 times the diameter of each hole.

[0027] 5-6 , the needle array 60 may include a support plate 68. In one example, each needle 36 is coupled to the support plate 68 at its first end 62. In one example, each needle 36 may be integrally formed with the support plate 68. The support plate 68 may serve as an interface between the needles 36 and the ultrasonic actuator 38 ( FIG. 3 ), such that the needle array 60 may be operably coupled to the ultrasonic actuator 38 via the support plate 68 to vibrate the needle array 60 at a desired ultrasonic operating frequency. In some examples, the needle array 60 acts like a horn, amplifying ultrasonic vibrations from the ultrasonic actuator to increase mechanical energy output when the needle array 60 is used to form perforations in a workpiece in accordance with the present disclosure. In some examples, the needle array is removably coupled to the ultrasonic drilling device 58, such that the needle array may be selectively detached from the ultrasonic actuator 38 and replaced with a different needle array 60.

[0028] 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 5 needles 36, at least 6 needles 36, at least 7 needles 36, at least 8 needles 36, at least 9 needles 36, at least 10 needles 36, at least 20 needles 36, at least 30 needles 36, at least 40 needles 36, at least 50 needles 36, at least 60 needles 36, at least 70 needles 36, at least 80 needles 36, at least 90 needles 36, and / or at least 100 needles 36. The needles 36 of the needle array 60 may be arranged in one or more rows 70 of needles 36 (e.g., row 70a, row 70b, etc.) and / or one or more columns 72 of needles 36 (e.g., column 72a, column 72b, etc.). The columns 72 may be positioned between a first side 74 of the support plate 68 and a second side 76 of the support plate 68 substantially parallel to the first side 74 of the support plate 68 and the second side 76 of the support plate 68, and the rows 70 may be positioned between a third side 78 of the support plate 68 and a fourth side 80 of the support plate 68 substantially parallel to the third side 78 of the support plate 68 and the fourth side 80 of the support plate 68. Although the support plate 68 may have a footprint of any desired shape, in FIG. 5 the support plate 68 is illustrated as having a square footprint. Additionally or alternatively, the needles 36 of the needle array 60 may be arranged in a polar array (e.g., a circular arrangement), randomly positioned, and / or arranged in any desired shape or pattern.

[0029] In examples, the needle array 60 includes multiple rows 70 of needles 36, with each row 70 including multiple needles 36, and multiple columns 72, with each column 72 including multiple needles 36. The needles 36 may be arranged in the rows 70 and / or columns 72 according to length. For example, a first row 70a may include needles 36 having a first length, and a second row 70b may include needles 36 having a second length. In some examples, the length of the needles 36 may increase from row to row (e.g., from the first row 70a to the last row 70x). In some examples, one or more respective rows 70 of needles 36 may include needles 36 of a different length than one or more other respective rows 70. In some examples, each respective row 70 may include needles 36 of a different length than each of the other respective rows 70. In some examples, the needles 36 in a given row 70 may all have a uniform length, whereas in other examples, one or more needles 36 in a given row 70 may have a different length than one or more other needles 36 in that row 70. Similarly, a first column 72a may include needles 36 having a first length, and a 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, one or more respective columns 72 of needles 36 may include needles 36 of a different length than one or more other respective columns 72. In some examples, each respective column 72 may include needles 36 having a different respective length than each of the other respective columns 72. In some examples, all of the needles 36 in a given column 72 have a uniform length, whereas in other examples, one or more needles 36 in a given column 72 may have a different length than one or more other needles 36 in that column 72.

[0030] While FIG. 5 schematically depicts needles 36 having a circular or round cross-sectional area, one or more needles 36 of needle array 60 may have cross-sectional areas of different shapes. For example, one or more needles 36 of needle array 60 may have cross-sectional areas that are oval, square, rectangular, triangular, polygonal, star-shaped, diamond-shaped, and / or other shapes. Such differently shaped needles 36 may be suitable for the ultrasonic techniques of the present disclosure because the needles 36 do not rotate during the formation of the perforations. The cross-sectional shapes of the needles 36 may be selected or optimized to create correspondingly shaped perforations for improved noise attenuation performance of the resulting acoustic liner formed in accordance with the present disclosure.

[0031] The needles 36 may be formed of any suitable material, such as stainless steel, titanium, and / or other metals, as will be appreciated by those skilled in the art. The needles 36 may have a coating on some or all of their surfaces, such as a tungsten carbide coating, although other coatings are within the scope of this disclosure. As will be appreciated by those skilled in the art, the second ends 64 of some or all of the needles 36 in the needle array 60 may be chamfered, shaped, coated, roughened, grooved, and / or otherwise shaped or treated. The radius and / or roughness of the second ends 64 of the needles 36 may be selectively modified for desired needle 36 characteristics. Methods for making the needle array 60 and using the needle array to form the perforations 44 were invented by Weidong Song, whose entire disclosure is an example of background art. No. 16 / 796,658 Attorney Docket No. 19-1160-US-NP, filed February 20, 2020, entitled "NEEDLE ARRAYS FOR FORMING ULTRASONIC PERFORATIONS, AND METHODS OF MAKING THE SAME" , U.S. Patent Application Publication No. 2021-0260713, published August 2021 It is disclosed in

[0032] For example, FIG. 13 illustrates an example of a needle 36 (which may be one of the multiple needles 36 of the needle array 60). As shown in FIG. 13, the needle 36 may include a smooth shaft portion 118 and a textured or roughened tip portion 120 adjacent the second end 64. The tip portion 120 may, in some examples, be conical. The needle 36 may include one or more grooves 122 formed in the shaft portion 118 and / or the tip portion 120. For example, the needle 36 as shown in FIG. 13 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 positioned only in the shaft portion 118 and / or one or more grooves 122 may be positioned only in the tip portion 120. The grooves 122 may be configured to allow for the removal of debris from the work area while the perforations 44 are being formed in the workpiece 32. FIG. 14 shows an example of a needle 36 viewed from the bottom at the second end 64. While other arrangements of the grooves 122 are within the scope of this disclosure, the needle 36 includes multiple curved grooves 122 that intersect at a center point 124 of the tip portion 120, as seen in FIG. 14. In some examples, the tip portion 120 may 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 specific examples, the tip portion 120 has a surface roughness of 80-120 grit. In another example, the tip portion 120 has a surface roughness of 40-60 grit.

[0033] 7 illustrates one example of a needle array 60. In this example of FIG. 7, the needle array 60 includes a first row 70a of needles 36, each having a first length 82, a second row 70b of needles 36, each having a second length 84, a third row 70c of needles 36, each having a third length 86, a fourth row 70d of needles 36, each having a fourth length 88, and a fifth row 70e of needles 36, each having a fifth length 90, etc. In this example, the lengths of the needles 36 increase from row to 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, etc., with the needles 36 in the last row 70x adjacent the second side 76 of the support plate 68 having the longest length and the needles 36 in the first row 70a having the shortest length. In this example, the length of the needles in a given column 72 increases along the column between a first side 74 and a second side 76 of the support plate 68. Other arrangements are within the scope of this disclosure.

[0034] As shown generally in FIGS. 8-9 , the second ends 64 of the needles 36 in a given needle array 60 may collectively define a contact plane 92 or multiple contact planes 92 positioned relative to one another to form a contact shape 94 ( FIG. 9 ) or contact contour. For example, as shown in FIG. 8 , the needles 36 may be arranged in a bilinear distribution along the length of the needles 36 so as to collectively form an angled contact plane 92 where the second ends 64 of the needles 36 contact the workpiece. As another example, as shown in FIG. 9 , the needles 36 may be arranged in a pyramidal distribution along the length of the needles 36 so as to collectively form a pyramidal contact shape 94 where the second ends 64 of the needles 36 contact the workpiece, the pyramidal contact shape 94 being defined by multiple contact planes 92 collectively defined by the second ends 64 of the needles 36. Other different arrangements of the needles 36 may be formed to create different contact planes 92 and / or contact shapes 94. In some examples, the needles 36 may be arranged to collectively define a contact contour having a curved or irregular shape. Additionally or alternatively, the needles 36 may be selectively arranged by their length to optimize energy consumption by the ultrasonic actuator to which the needle array 60 is operably coupled. Additionally or alternatively, the needles 36 of the needle array 60 may be selectively arranged to maximize piercing efficiency.

[0035] 3 , the system 30 may include a remote heating unit 96 positioned remotely 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 relative to the workpiece 32 in the absence of a cooling fluid or liquid. The remote heating unit 96 is configured to locally heat a portion of the workpiece 32 while the perforations 44 are formed in the workpiece. 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 a first region (e.g., region 66) of the workpiece 32 while the needle array 60 remains positioned over the first region 66 such that the first region 66 is heated while the ultrasonic drilling device 58 contacts the surface 34 to form the perforations 44 in region 66. The remote heating unit 96 may be configured to maintain the temperature of a given region of the thin sheet material (e.g., the first region 66 of the workpiece 32) above a threshold temperature while the perforations 44 are formed by the ultrasonic drilling device 58. For example, the threshold temperature may be the glass transition temperature of a resin used in the composite material from which the workpiece 32 is formed. In specific 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. The remote heating unit 96 may be a heat lamp in some systems 30, although other types of heating units are within the scope of this disclosure.

[0036] Once perforations 44 have been formed in the first region 66 of the workpiece 32, the needle array 60 may be translated relative to the workpiece 32 so that the needle array 60 is positioned above a different region (e.g., a second region 98 of the workpiece 32) so that the ultrasonic drilling device 58 may be used to form perforations 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 so that a different region of the workpiece 32 is positioned below the needle array 60 to form perforations in the different region of the workpiece 32.

[0037] The ultrasonic actuator 38 may be configured to operate at any suitable ultrasonic operating frequency, hi some examples, the operating frequency is at least 15 kilohertz (kHz), at least 20 kHz, and / or at least 25 kHz.

[0038] 10-12 generally present flow diagrams representing illustrative, non-exclusive examples of methods according to the present disclosure. In FIGS. 10-12, some steps are depicted with dashed blocks, indicating that such steps may be optional or may represent optional versions of methods according to the present disclosure. That said, not all methods according to the present disclosure need include steps depicted with solid boxes. The methods and steps depicted in FIGS. 10-12 are not limiting, and as will be understood from the discussion herein, other methods and steps, including methods having more or fewer steps than those depicted, are within the scope of the present disclosure.

[0039] 10 illustrates a method 200 of performing ultrasonic drilling to form a hole (e.g., bore hole 44) in a workpiece (e.g., workpiece 32) at a first location on the workpiece. Method 200 generally includes, at 202, positioning a surface (e.g., surface 34) of the workpiece relative to a tool of an ultrasonic horn (e.g., a stylus 36 or stylus array 60 of an ultrasonic drilling device 58), the tool having a longitudinal axis (e.g., longitudinal axis 40) substantially perpendicular to the surface of the workpiece. Method 200 also includes, at 204, forming a hole in the workpiece by oscillating the tool along the longitudinal axis so that the tool repeatedly contacts the surface of the workpiece at an operating frequency and / or predetermined speed sufficient to form the hole in the workpiece, the oscillating of the tool being performed for a time sufficient to form the hole in the workpiece. During the formation of the hole (or holes) in the workpiece at 204, the tool is not rotated relative to the surface of the workpiece, and forming the holes at 204 is performed without the use of a slurry or cooling fluid. In some methods 200, the force with which the tool contacts the workpiece may be reduced, such that forming the holes at 204 may include vibrating the tool such that the tool exerts a force on the workpiece surface that is less than a predetermined threshold force each time the tool contacts the workpiece surface.

[0040] In a method 200 that includes forming a plurality of holes in a workpiece, the method 200 may also include translating the workpiece relative to the tool at 206 so that the tool is positioned over a location on the workpiece that is different from a first location where the first hole was formed, and forming a second hole (or holes) in the workpiece at 210 by again oscillating the tool along the longitudinal axis while the tool is positioned over the different location. Additionally or alternatively, the method 200 may include translating the tool relative to the workpiece at 208 so that the tool is positioned over a location on the workpiece that is different from the first location where the first hole was formed, and forming a second hole (or holes) in the workpiece by again oscillating the tool along the longitudinal axis while the tool is positioned over the different location. Such steps may be repeated any number of times to form a plurality of holes in a plurality of different locations on the workpiece. For example, the workpiece may be translated multiple times at 206 after each performance of forming one or more holes at 210. Similarly, additionally or alternatively, the tool may be translated multiple times at 208 after each performance of forming one or more holes at 210. In such a manner, the tool may be sequentially positioned over multiple different respective locations on the workpiece, thus forming a respective one or more holes at each respective location of the workpiece that is contacted with a needle or needle array in accordance with the present disclosure.

[0041] Method 200 may include 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 perforation is to be formed is heated by the remote heating unit while the perforation is being formed. Such heating at 212 may be performed before the hole is formed at 204 and / or 210, and / or heating at 212 may be performed during the formation of 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 the formation of the hole in the workpiece, e.g., above a glass transition temperature of a resin of a composite material from which the workpiece is formed.

[0042] The method 200 may include coupling a tool to an ultrasonic actuator (e.g., ultrasonic actuator 38) of the ultrasonic horn at 214, removing the tool from the ultrasonic actuator at 216, and / or coupling a different tool to the ultrasonic actuator at 218.

[0043] 11 illustrates a method 220 for forming a plurality of perforations in a thin sheet of composite material (e.g., thin sheet material 42) generally including: positioning a surface of the thin sheet relative to a needle array operably coupled to an ultrasound device at 222 so that the needle array is positioned over a first region of the thin sheet (e.g., first region 66); and repeatedly contacting the surface of the thin sheet within the first region with the needle array at an operating frequency greater than about 20 kHz for a time sufficient to form a first plurality of perforations in the first region of the thin sheet at 224. The repeatedly contacting the surface of the thin sheet at 224 forms a respective perforation in the thin sheet corresponding to each respective needle of the needle array, and this repeated contacting is performed without rotating the needles about a longitudinal axis, without rotating the needles relative to the thin sheet, and without the use of a slurry or cooling fluid.

[0044] Method 220 also includes translating the thin sheet and / or the needle array at 226 so that the thin sheet is positioned relative to the needle array such that the needle array is positioned over a second region of the thin sheet (e.g., second region 98), and then repeatedly contacting the thin sheet with the needle array again at 224. In this manner, respective holes are formed in the second region of the thin sheet corresponding to each respective needle of the needle array. Such translating at 226 and repeatedly contacting the surface of the thin sheet at 224 may be repeated any number of times until a desired number of holes are formed in a desired area of ​​the sheet. Each time the needle array and / or thin sheet is translated at 226, the needle array may be positioned over a different respective region of the multiple regions of thin sheet material, and repeatedly contacting the surface of the thin sheet at 224 may be performed each time the needle array is positioned over a different respective region of the thin sheet.

[0045] 12 illustrates a method 230 for forming an acoustic liner according to the present disclosure. Method 230 includes forming a perforated workpiece (e.g., workpiece 32, thin sheet material 42) at 232, bonding the perforated workpiece to a first side of a honeycomb structure (e.g., first side 50 of honeycomb structure 48) at 234, and bonding 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) at 236, thereby forming an acoustic liner (e.g., acoustic liner 33). Forming the perforated workpiece at 232 may include method 220 ( FIG. 11 ) for forming a plurality of perforations in a thin sheet of composite material and / or method 200 ( FIG. 10 ) for performing ultrasonic drilling to form holes in a workpiece. The method 230 may also include incorporating the acoustic liner into a jet engine housing of an aircraft at 238 and using the acoustic liner to attenuate noise generated by a jet engine of the aircraft, the jet engine being housed within the jet engine housing, at 240. For example, the acoustic liner 33 may be applied to the inner walls of the engine nacelle in the intake duct and / or bypass duct for dissipation of acoustic energy incident thereon.

[0046] Illustrative, non-exclusive examples of the inventive subject matter according to the present disclosure are described in the following enumerated paragraphs.

[0047] A1. A method of performing ultrasonic drilling to form a hole in a workpiece at a first location on the workpiece, comprising: positioning a surface of a workpiece relative to a tool of an ultrasonic horn, the tool having a longitudinal axis substantially perpendicular to the surface of the workpiece; forming a hole in a workpiece by vibrating the tool along a longitudinal axis such that the tool repeatedly contacts a surface of the workpiece at an operating frequency and amplitude sufficient to form a hole in the workpiece, wherein vibrating the tool is performed for a time sufficient to form the hole in the workpiece, the tool is not rotated relative to the surface of the workpiece during hole formation, forming the hole is performed without the use of a slurry or cooling fluid, and the workpiece is composed of a composite material; A method comprising:

[0048] A2. The method of paragraph A1, wherein the holes extend through the entire thickness of the workpiece.

[0049] A3. The method of paragraph A1 or A2, wherein the operating frequency is at least 15 kHz, at least 20 kHz, and / or at least 25 kHz.

[0050] A4. The hole is a first hole and the method comprises: translating the workpiece relative to the tool so that the tool is positioned over a location on the workpiece different from the first location where the first hole was formed; forming a second hole in the workpiece by again oscillating the tool along the longitudinal axis while the tool is positioned over a different location; The method of any one of paragraphs A1-A3, comprising:

[0051] A5. The method described in paragraph A4, further comprising repeating the steps of translating the workpiece relative to the tool a plurality of times so that the tool is sequentially positioned over a plurality of different respective locations on the workpiece, and between each translation of the workpiece, again oscillating the tool along the longitudinal axis while the tool is positioned over the respective locations to form additional respective holes in the workpiece at the respective locations.

[0052] A6. The hole is a first hole, and the method comprises: translating the tool relative to the workpiece so that the tool is positioned over a location on the workpiece different from the first location where the first hole was formed; forming a second hole in the workpiece by again oscillating the tool along the longitudinal axis while the tool is positioned over a different location; The method of any one of paragraphs A1-A3, comprising:

[0053] A7. The method described in paragraph A6, further comprising repeating the steps of translating the tool relative to the workpiece a plurality of times so that the tool is sequentially positioned above a plurality of different respective locations on the workpiece, and between each translation of the tool, again oscillating the tool along the longitudinal axis while the tool is positioned above the respective locations to form additional respective holes in the workpiece at the respective locations.

[0054] A8. The method of any one of paragraphs A1-A7, further comprising the step of locally heating a portion of the workpiece, the first location being located within the portion of the workpiece.

[0055] A9. The method of paragraph A8, wherein the step of locally heating a portion of the workpiece is performed before the step of forming a hole in the workpiece.

[0056] A9.1. The method of paragraph A8 or A9, wherein the step of locally heating a portion of the workpiece is performed during the step of forming a hole in the workpiece.

[0057] A10. The method of any one of paragraphs A8-A9.1, wherein the step of locally heating a portion of the workpiece includes maintaining the temperature of the portion of the workpiece above a threshold temperature during formation of a hole in the workpiece.

[0058] A11. The method of paragraph A10, wherein the threshold temperature is the glass transition temperature of the resin of the composite material.

[0059] A12. The method of any one of paragraphs A8-A11, wherein the threshold temperature is 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.

[0060] A13. The method of any one of paragraphs A8-A12, wherein locally heating the portion of the workpiece includes locally heating the portion of the workpiece via a remote heating unit.

[0061] A14. The method of paragraph A13, wherein the remote heating unit includes a heat lamp.

[0062] A15. A method according to any one of paragraphs A1-A14, wherein the tool includes a needle array including a plurality of needles, each needle of the plurality of needles being oriented to extend along a longitudinal axis, and each needle of the plurality of needles being configured to form a respective hole in the workpiece when the tool is vibrated along the longitudinal axis, such that the step of forming 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.

[0063] A16. The method of paragraph A15, wherein the method further includes heating the region of the workpiece prior to forming the plurality of holes in the region.

[0064] A16.1. The method of paragraph A15 or A16, wherein the needle array comprises at least 10 needles, at least 20 needles, at least 30 needles, at least 40 needles, at least 50 needles, at least 60 needles, at least 70 needles, at least 80 needles, at least 90 needles, and / or at least 100 needles.

[0065] A17. The method of any one of paragraphs A1-A16.1, wherein forming the hole includes oscillating the tool along the longitudinal axis at a predetermined rate.

[0066] A18. The method described in paragraphs A1-A17, wherein the step of forming the hole includes a step of oscillating the tool along the longitudinal axis so that the tool exerts a force on the surface of the workpiece that is less than a predetermined threshold force each time the tool contacts the workpiece.

[0067] A19. The method of any one of paragraphs A1-A18, wherein the tool is removably coupled to the ultrasonic horn.

[0068] A20. The method of any one of paragraphs A1-A19, further comprising further coupling the tool to an ultrasonic actuator of the ultrasonic horn.

[0069] A21. The method of any one of paragraphs A1-A20, further comprising coupling a tool to the horn of the ultrasonic horn.

[0070] A22. The method of any one of paragraphs A1-A21, further comprising the steps of removing the tool from the ultrasonic horn and coupling a second tool to the ultrasonic horn.

[0071] B1. A method for forming a plurality of perforations in a thin sheet of composite material, comprising: positioning a surface of the thin sheet relative to a needle array operably coupled to an ultrasound device such that the needle array is positioned over a first region of the thin sheet, the needle array including a plurality of needles extending along a longitudinal axis substantially perpendicular to the surface of the thin sheet; repeatedly contacting a surface of the thin sheet with the needle array within a first region at an operating frequency greater than 20 kHz for a time sufficient to form a first plurality of holes in the first region of the thin sheet, wherein the repeatedly contacting the surface of the thin sheet forms respective holes in the thin sheet corresponding to each respective needle of the needle array, and wherein the repeatedly contacting includes contacting the thin sheet with the plurality of needles of the needle array without rotating the plurality of needles about a longitudinal axis, without rotating the plurality of needles relative to the thin sheet, and without using a slurry or cooling fluid; translating the thin sheet and / or the needle array such that the thin sheet is positioned relative to the needle array such that the needle array is positioned over a second region of the thin sheet; repeatedly contacting the surface of the thin sheet with the needle array in the second region at an operating frequency greater than 20 kHz for a time sufficient to form a second plurality of holes in the second region of the thin sheet, wherein the repeatedly contacting the surface of the thin sheet forms respective holes in the thin sheet corresponding to each respective needle of the needle array, and wherein the repeatedly contacting includes contacting the thin sheet with the plurality of needles of the needle array without rotating the plurality of needles about the longitudinal axis, without rotating the plurality of needles relative to the thin sheet, and without using a slurry or cooling fluid; A method comprising:

[0072] B2. The method of paragraph B1, wherein the thin 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.

[0073] B3. The method of paragraph B1 or B2, wherein the thin sheet is configured to be incorporated into an acoustic liner.

[0074] B4. The thin sheet comprises a plurality of regions, and the method comprises: translating the thin sheet and / or the needle array multiple times such that each translation of the thin sheet and / or the needle array positions the needle array over a different respective region of the multiple regions of the thin sheet; repeatedly contacting a surface of the thin sheet within each of the plurality of regions of the thin sheet with a needle array at an operating frequency of greater than 20 kHz for a time sufficient to form a respective plurality of holes in each of the respective regions of the thin sheet, the step of repeatedly contacting the surface of the thin sheet being repeated each time the needle array is positioned over a different respective region of the thin sheet; The method of any one of paragraphs B1-B3, further comprising:

[0075] B5. The method of paragraph B4, wherein the step of repeatedly contacting the surface of the thin sheet is repeated at least a number of times necessary to form at least 1,000, at least 10,000, at least 100,000, and / or at least 1,000,000 holes in the thin sheet.

[0076] B6. The method of any one of paragraphs B1-B5, wherein the composite material comprises carbon fiber reinforced polymer, glass fiber reinforced polymer, thermoplastic material, thermoset material, carbon fiber or glass fiber reinforced polyetheretherketone (PEEK), carbon fiber or glass fiber reinforced polyetherketoneketone (PEKK), carbon fiber or glass fiber reinforced epoxy, and / or carbon fiber or glass fiber reinforced polyphenylene sulfide (PPS).

[0077] B7. The method of any one of paragraphs B1-B6, wherein each hole of the first plurality of holes, each hole of the second plurality of holes, and each hole of each respective plurality of holes has a diameter of 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.

[0078] B8. The method of any one of paragraphs B1-B7, wherein each hole of the first plurality of holes, each hole of the second plurality of holes, and each hole of each respective plurality of holes has a diameter between 0.04 inches and 0.05 inches.

[0079] B9. The method of any one of paragraphs B1-B8, wherein each hole of the first plurality of holes, each hole of the second plurality of holes, and each hole of each respective plurality of holes has a substantially uniform diameter.

[0080] B10. The method of any one of paragraphs B1-B9, wherein each hole of the first plurality of holes, each hole of the second plurality of holes, and each hole of each respective plurality of holes is spaced apart from each adjacent respective hole by a minimum center-to-center distance.

[0081] B11. The method of paragraph B10, wherein the minimum center-to-center spacing 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.

[0082] B12. The method of paragraph B10 or B11, wherein the minimum center-to-center distance is greater than or equal to the diameter / diameter of each respective hole.

[0083] B13. The method of any one of paragraphs B10-B12, wherein the minimum center-to-center distance is at least 1.25 times the diameter of each respective hole, at least 1.5 times the diameter of each respective hole, at least 1.75 times the diameter of each respective hole, at least 2 times the diameter of each respective hole, at least 2.5 times the diameter of each respective hole, at least 3 times the diameter of each respective hole, at least 4 times the diameter of each respective hole, and / or at least 5 times the diameter of each respective hole.

[0084] C1. A method of forming an acoustic liner, comprising: forming a workpiece according to the method of any one of paragraphs A1-A22; Bonding the workpiece to a first side of the honeycomb structure, the honeycomb structure comprising: A first side; a second side opposite the first side; and a plurality of interior cells extending between the first side and the second side, each interior cell of the plurality of interior cells sized to accommodate an acoustic plane wave within the interior cell in a desired frequency range, such that the acoustic liner is configured to provide noise attenuation characteristics for the desired frequency range; and bonding a rigid backing to the second side of the honeycomb structure, thereby forming an acoustic liner; A method comprising:

[0085] C2. A method of forming an acoustic liner, comprising: forming a thin sheet of composite material according to the method of any one of paragraphs B1-B13; bonding a thin sheet of composite material to a first side of a honeycomb structure, the honeycomb structure comprising: A first side; a second side opposite the first side; and a plurality of interior cells extending between the first side and the second side, each interior cell of the plurality of interior cells sized to accommodate an acoustic plane wave within the interior cell in a desired frequency range, such that the acoustic liner is configured to provide noise attenuation characteristics for the desired frequency range; and bonding a rigid backing to the second side of the honeycomb structure, thereby forming an acoustic liner; A method comprising:

[0086] C3. Assembling the acoustic liner into a jet engine housing of an aircraft; using an acoustic liner to attenuate noise generated by a jet engine of an aircraft, the jet engine being housed within a jet engine housing; The method of paragraph C1 or C2, further comprising:

[0087] D1. An acoustic liner, a thin sheet material constructed from a composite material and including a plurality of perforations formed through a thickness of the thin sheet material, wherein the thin sheet material is a workpiece formed in accordance with the method of any one of paragraphs A1-A22 and / or the thin sheet material is a thin sheet of composite material formed in accordance with the method of any one of paragraphs B1-B13; a honeycomb structure having a first side, a second side opposite the first side, and a plurality of interior cells extending between the first side and the second side, wherein the first side is bonded to a thin sheet material and each interior cell of the plurality of interior cells is sized to accommodate an acoustic plane wave within the interior cell in a desired frequency range, such that the acoustic liner is configured to provide noise attenuation characteristics for the desired frequency range; a rigid backing plate bonded to a second side of the honeycomb structure; Including, sound absorbing liner.

[0088] D2. The acoustic liner of paragraph D1, wherein the composite material includes carbon fiber or glass fiber reinforced polymer, thermoplastic material, thermoset material, carbon fiber or glass fiber reinforced PEEK, carbon fiber or glass fiber reinforced PPS, carbon fiber or glass fiber reinforced epoxy, and / or carbon fiber or glass fiber reinforced PEKK.

[0089] D3. The acoustical liner of paragraph D1 or D2, wherein the plurality of perforations comprises 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.

[0090] D4. The acoustic liner of any one of paragraphs D1-D3, wherein the acoustic liner is configured for use within a jet engine housing.

[0091] D5. The acoustic liner of any one of paragraphs D1-D4, wherein the acoustic liner is formed according to the method of any one of paragraphs C1-C3.

[0092] D6. The acoustic liner of any one of paragraphs D1-D5, wherein the rigid backing comprises metal, carbon fiber, and / or fiber-reinforced polymer.

[0093] D7. The acoustical liner of any one of paragraphs D1-D6, wherein each perforation of the plurality of perforations is non-circular.

[0094] D8. The acoustical liner of any one of paragraphs D1-D7, wherein one or more perforations of the plurality of perforations are square, rectangular, triangular, polygonal, star-shaped, and / or diamond-shaped.

[0095] E1. A jet engine comprising the sound-absorbing liner of any one of paragraphs D1-D8.

[0096] E2. An aircraft comprising an acoustic liner according to any one of paragraphs D1-D8.

[0097] F1. Use of an acoustic liner according to any one of paragraphs D1-D8 for reducing noise pollution and / or for noise attenuation. G1. A needle array for forming ultrasonic perforations in a workpiece, the needle array comprising: a plurality of needles arranged to form a needle array, each needle of the plurality of needles oriented to extend along a longitudinal axis from a first end to a tip, each needle of the plurality of needles configured to form holes in the workpiece when the needle array is vibrated along the longitudinal axis at an ultrasonic operating frequency while the needle array is positioned to repeatedly contact a surface of the workpiece, each needle of the plurality of needles having a non-circular cross-section, the needle array configured to form a plurality of holes in a region of the workpiece without translating the needle array relative to the workpiece, without rotating the plurality of needles about the longitudinal axis, and without rotating the plurality of needles relative to the workpiece, the needle array comprising a plurality of needles configured to be operably coupled to an ultrasonic actuator to vibrate the needle array at the ultrasonic operating frequency. G1.1. The needle array of paragraph G1, further comprising a support plate, wherein each needle of the plurality of needles is coupled to the support plate at a respective first end, and wherein the needle array is configured to be operably coupled to an ultrasonic actuator to vibrate the needle array at an ultrasonic operating frequency via the support plate. G2. The needle array of paragraph G1 or G1.1, wherein the needle array includes at least 5 needles, at least 6 needles, at least 7 needles, at least 8 needles, at least 9 needles, at least 10 needles, at least 20 needles, at least 30 needles, at least 40 needles, at least 50 needles, at least 60 needles, at least 70 needles, at least 80 needles, at least 90 needles, and / or at least 100 needles. G3. Needle array a plurality of rows of needles, each row of the plurality of rows comprising a plurality of needles; and A plurality of columns of needles, each column of the plurality of columns comprising a plurality of needles. The needle array of any of paragraphs G1-G2, comprising: G4. The needle array of paragraph G3, wherein a first row of the plurality of rows of needles is formed with needles having a first length. G5. The needle array of any of paragraphs G3-G4, wherein a second row of the plurality of rows of needles is formed with needles having a second length. G6. The needle array of any of paragraphs G3-G5, wherein each row of the plurality of rows of needles is formed with needles having different lengths. G7. The needle array of any of paragraphs G3 through G6, wherein the plurality of rows of needles includes: (i) a first row of needles each having a first length; (ii) a second row of needles, each having a second length greater than the first length; (iii) a third row of needles, each having a third length greater than the second length; (iv) a fourth row of eights, each having a fourth length greater than the third length; and (v) a fifth row of needles, each having a fifth length greater than the fourth length; G8. The needle array of paragraph G7, further comprising an additional plurality of rows of needles, each additional row of needles in the additional plurality of rows being formed with needles having a respective length greater than at least one other respective row of needles. G9. The needle array of paragraph G7 or G8, wherein the plurality of rows of needles includes a last row of needles having a last length. G10. The needle array of any of paragraphs G3-G9, wherein the plurality of rows of needles comprises: (i) a first row of needles, each having a first length; (ii) a row of needles between a plurality of needles; and (iii) The needles in the last row, each having the final length. G11. A needle array of paragraph G10, the first length of which is different from the last length. G12. The needle array of any of paragraphs G10-G11, wherein each row of the plurality of inter-row rows is formed from respective needles having different lengths, and wherein the length of each inter-row row of the plurality of inter-row rows is different from the first length and the last length. G13. A needle array described in any of paragraphs G10 to G12, wherein a first row of needles is positioned near a first side of the needle array and / or a first side of the support plate, and a last row of needles is positioned near a second side of the needle array and / or a second side of the support plate, the second side of the needle array being opposite the first side of the needle array and / or the second side of the support plate being opposite the first side of the support plate. G14. The needle array of paragraph G13, wherein a plurality of intervening rows are located between the first row of needles and the last row of needles. G15. The needle array of paragraph G14, wherein each inter-row of the plurality of inter-rows is arranged such that a respective length of each needle forming each inter-row is greater than a respective length of a first adjacent respective needle forming a first adjacent inter-row, and a respective length of each needle forming each inter-row is less than a respective length of a second adjacent respective needle forming a second adjacent inter-row. G16. The needle array of paragraph G14, wherein the plurality of inter-rows are arranged consecutively in order of increasing length of the respective needles forming each inter-row. G17. The needle array of any of paragraphs G1-G16, wherein the needle array comprises a polar array of needles. G18. The needle array of any of paragraphs G1-G17, wherein each needle of the plurality of needles extends longitudinally from a respective first end to a respective second end. G19. The needle array of paragraph G18, wherein the first ends of the plurality of needles are all coupled to the support plate. G20. The needle array of any of paragraphs G18-G19, wherein the second ends of the plurality of needles collectively form a contact surface, and the plurality of contact surfaces are arranged relative to one another to form a contact shape or contact contour. G21. The needle array of any of paragraphs G1-G20, wherein the needles of the plurality of needles are arranged in a bilinear distribution through their lengths such that the second ends of the plurality of needles collectively form an inclined contact surface for contacting the workpiece. G22. A needle array according to any of paragraphs G1 to G20, wherein the needles of the plurality of needles are arranged in a pyramidal distribution along their lengths so that the second ends of the plurality of needles collectively form a contact shape for contacting the workpiece, and the contact shape is pyramidal. G23. The needle array of any of paragraphs G1-G22, wherein needles of the plurality of needles are selectively positioned by their length to optimize energy consumption by the ultrasonic actuator. G24. The needle array of any of paragraphs G1-G23, wherein needles of the plurality of needles are selectively positioned to maximize perforation efficiency. G25. The needle array of any of paragraphs G1-G24, wherein the needle array is formed of steel and / or tungsten carbide. G26. The needle array of any of paragraphs G1-G25, wherein the needle array is configured to act like a horn to amplify ultrasonic vibrations from the ultrasonic actuator to increase mechanical energy output. G27. The needle array of any of paragraphs G1-G26, wherein the needle array is a monolithic structure. G28. The needle array of any of paragraphs G1-G26, comprising a plurality of needles individually bonded to a support plate to form the needle array. G29. The needle array of any of paragraphs G1-G28, wherein each needle of the needle array has an oval, square, rectangular, triangular, polygonal, star-shaped, and / or diamond-shaped cross section. H1. A method for forming a plurality of perforations in a thin sheet of composite material, comprising: Positioning a surface of the thin sheet relative to the needle array of any of paragraphs G1-G29, the needle array being operably coupled to an ultrasonic drilling device, and the needles of the needle array sharing a longitudinal axis substantially perpendicular to the surface of the thin sheet; forming a plurality of holes in the thin sheet by vibrating the needle array along the longitudinal axis such that the needle array repeatedly contacts the surface of the thin sheet at an operating frequency sufficient to form a plurality of holes in the thin sheet, wherein the vibration of the needle array is performed for a time sufficient to form a plurality of holes in the thin sheet, the needle array is not rotated relative to the surface of the thin sheet during the formation of the plurality of holes, and the formation of the plurality of holes is performed without the use of a slurry or a coolant; A method comprising: H2. A method for forming a plurality of perforations in a thin sheet of composite material, comprising: Positioning a surface of the thin sheet relative to the needle array of any of paragraphs G1-G29, the needle array being operably coupled to an ultrasonic drilling device such that the needle array is positioned over a first region of the thin sheet, the needle array comprising a plurality of needles extending along a longitudinal axis substantially perpendicular to the surface of the thin sheet; repeatedly contacting a surface of the thin sheet in a first region with the needle array at an operating frequency greater than 20 kHz for a time sufficient to form a first plurality of holes in the first region of the thin sheet, wherein the repeatedly contacting the surface of the thin sheet forms respective holes in the thin sheet corresponding to each needle of the needle array, and the repeatedly contacting the surface of the thin sheet is performed without rotating the plurality of needles about a longitudinal axis, without rotating the needles relative to the thin sheet, and without using a slurry or a coolant; translating the thin sheet and / or the needle array such that the thin sheet is positioned relative to the needle array such that the needle array overlies a second region of the thin sheet; repeatedly contacting a surface of the thin sheet in a second region with the needle array at an operating frequency greater than 20 kHz for a time sufficient to form a second plurality of holes in the second region of the thin sheet, wherein the repeatedly contacting the surface of the thin sheet forms respective holes in the thin sheet corresponding to each needle of the needle array, and the repeatedly contacting the surface of the thin sheet is performed without rotating the plurality of needles about a longitudinal axis, without rotating the plurality of needles relative to the thin sheet, and without using a slurry or a coolant; A method comprising: I1. A system for forming perforations in thin sheets of composite material, comprising: An ultrasonic drilling device, the needle array of any of paragraphs G1 through G29; an ultrasonic actuator configured to vibrate the needle array along a longitudinal axis such that the needle array repeatedly contacts a surface of the thin sheet at an operating frequency sufficient to form a plurality of holes through the thin sheet within a first region of the thin sheet, wherein the needle array does not rotate relative to the surface of the thin sheet while the plurality of holes are formed, and the ultrasonic drilling apparatus is configured to operate without the use of a slurry or cooling fluid; an ultrasonic drilling device comprising: a remote heating unit spaced from the ultrasonic drilling apparatus, the remote heating unit configured to locally heat a first region of the thin sheet while the plurality of holes are being formed by the ultrasonic drilling apparatus; A system comprising: I2. The system of paragraph I1, wherein the operating frequency is at least 15 kHz, at least 20 kHz, and / or at least 25 kHz. I3. The system of any of paragraphs I1-I2, wherein the needle array is removably coupled to the ultrasonic drilling device. I4. The system of any of paragraphs I1-I3, wherein the needle array is configured to be translated relative to the thin sheet to form a second plurality of holes through the thin sheet in a second region of the thin sheet. I5. The system described in any of paragraphs I1-I4, wherein the remote heating unit is configured to maintain the temperature of the first region of the thin sheet above a threshold temperature while the plurality of holes are formed by the ultrasonic drilling device. I6. The system of paragraph I5, wherein the threshold temperature is the glass transition temperature of a resin of the composite material. I7. The system of any of paragraphs I5-I6, wherein the threshold temperature is at least 200°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. I8. The system of any of paragraphs I1-I7, wherein the remote heating unit comprises a heat lamp. J1. Use of the needle array of any of paragraphs G1-G29 to form perforations in a thin sheet of composite material. J2. Use of the system of any of paragraphs I1-I8 to form perforations in thin sheets of composite material J3. Use of the system of any of paragraphs I1-I8 to reduce noise pollution and / or to form an acoustic liner for attenuating noise. J4. Use of the system of any of paragraphs I1-I8 to reduce noise pollution from engines and / or to form an acoustic liner for attenuating noise inside an aircraft. J5. Use of the needle array of any of paragraphs G1-G29 to reduce noise pollution and / or form a sound-absorbing liner for attenuating noise. J6. Use of the needle array of any of paragraphs G1 through G29 to reduce noise pollution from an engine and / or to form an acoustic liner for attenuating noise inside an aircraft.

[0098] F2. Use of an acoustic liner according to any one of paragraphs D1-D8 to reduce noise pollution from an engine and / or for noise attenuation inside an aircraft.

[0099] As used herein, the terms "selective" and "selectively" mean that when changing the operation, movement, configuration, or other action of one or more components or characteristics of a device, a particular operation, movement, configuration, or other action is the direct or indirect result of a user's manipulation of an aspect of the device or one or more components of the device.

[0100] As used herein, the terms "adapted" and "configured" mean that an element, component, or other subject matter is designed and / or intended to perform a given function. Thus, use of the terms "adapted" and "configured" should be interpreted to mean that a given element, component, or other subject matter is specifically selected, created, executed, utilized, programmed, and / or designed to perform a function, rather than that a given element, component, or other subject matter is simply "capable" of performing a given function. It is within the scope of this disclosure that elements, components, and / or other subject matter described as adapted to perform a particular function may additionally or alternatively be described as configured to perform that function, and vice versa. Similarly, subject matter described as configured to perform a particular function may additionally or alternatively be described as operable to perform that function.

[0101] As used herein, the phrase "at least one" in connection with a list of one or more entities should be understood to mean at least one entity selected from any one or more of the entities in the list of entities, but not necessarily including at least one of each and every entity specifically listed in the list of entities, nor excluding any combination of entities in the list of entities. This definition may also allow for the optional presence of entities other than those specifically identified in the list of entities to which the phrase "at least one" refers, whether related or unrelated to the specifically identified entity. 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") can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including entities other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including entities other than A); and in yet another embodiment, to 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 terms "at least one," "one or more," and "and / or" are open-ended expressions that are both conjunctive and disjunctive in operation. For example, the phrases "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" can each mean A only, B only, C only, A and B together, A and C together, B and C together, or A, B, and C together, as well as any of the above, optionally in combination with at least one other entity.

[0102] The various apparatus elements and method steps disclosed herein are not required for all apparatus and methods according to the present disclosure, and the present disclosure includes all novel and non-obvious combinations and subcombinations of the various elements and steps disclosed herein. Moreover, one or more of the various elements and steps disclosed herein may define separate and independent inventive subject matter separate and apart from any of the disclosed apparatus or methods. Thus, such inventive subject matter need not relate to the specific apparatus and methods explicitly disclosed herein, and such inventive subject matter may find utility in apparatus and / or methods not explicitly disclosed herein.

[0103] As used herein, the terms "for example," "for example," and / or simply "example," when used in reference to one or more components, features, details, structures, embodiments, and / or methods according to the present disclosure, are intended to convey that the described components, features, details, structures, embodiments, and / or methods are exemplary, non-exclusive examples of components, features, details, structures, embodiments, and / or methods according to the present disclosure. Thus, the described components, features, details, structures, embodiments, and / or methods are not intended to be limiting, required, or exclusive / exhaustive, and other components, features, details, structures, embodiments, and / or methods, including structurally and / or functionally similar and / or equivalent components, features, details, structures, embodiments, and / or methods, are also within the scope of the present disclosure. [Explanation of symbols]

[0104] 30 systems 32 Workpiece 33 Sound-absorbing liner 34 Surface 36 needles 38 Ultrasonic Actuator 40 Longitudinal axis 42 Thin Sheet Materials 44 Perforation 48 Honeycomb structure 50 First Side 52 Second Side 54 internal cells 56 Rigid back plate 58 Ultrasonic drilling equipment 60 needle array 68 Support plate 96 Remote Heating Unit 118 Shaft part 120 Tip part 122 curved groove 124 Center point

Claims

1. 1. A method (200) of performing ultrasonic drilling to form a plurality of holes (44) in a workpiece (32) at a first location of the workpiece (32), the method comprising: A step (202) of positioning a surface (34) of the workpiece (32) relative to a tool of an ultrasonic horn, the tool having a longitudinal axis (40) substantially perpendicular to the surface (34) of the workpiece (32), the tool including a needle array (60) including a plurality of needles (36), each needle (36) of the plurality of needles (36) oriented to extend along the longitudinal axis (40), each needle (36) of the plurality of needles (36) configured to form a respective hole (44) in the workpiece (32) when the tool is vibrated along the longitudinal axis (40), the plurality of holes being in contact with the workpiece (32). forming a needle (36) within a region of the workpiece without translating (208) a tool and without translating (206) the workpiece (32) relative to the tool, the needles (36) being arranged in a distribution selected from the group consisting of a bilinear distribution, the needles (36) being arranged according to their lengths such that ends of each needle of the plurality of needles collectively form an inclined contact surface for contacting the workpiece, and the pyramidal distribution, the needles (36) being arranged such that ends of each needle of the plurality of needles collectively form a pyramidal contact shape for contacting the workpiece; forming the plurality of holes in the workpiece by vibrating the tool along the longitudinal axis such that the tool repeatedly contacts the surface of the workpiece at an operating frequency and amplitude sufficient to form the plurality of holes in the workpiece, wherein the vibrating the tool is performed for a time sufficient to form the holes in the workpiece, the tool is not rotated relative to the surface of the workpiece during the forming of the plurality of holes, the forming of the plurality of holes is performed without the use of a slurry or cooling fluid, and the workpiece is comprised of a composite material; a step (212) of locally heating a portion of the workpiece (32), the first location being located within the portion of the workpiece (32) during the step (204) of forming the plurality of holes (44) in the workpiece (32); A method (200) comprising:

2. The method (200) of claim 1, wherein the operating frequency is at least 20 kHz.

3. the plurality of holes (44) is a first plurality of holes, and the method (200) comprises: translating (206) 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 plurality of holes are formed; forming (210) a second plurality of holes in the workpiece (32) by again oscillating the tool along the longitudinal axis (40) while the tool remains positioned over the different location; repeating the steps of: translating (206) the workpiece (32) relative to the tool a plurality of times so that the tool is sequentially positioned over a plurality of different respective locations on the workpiece (32); and forming (210) an additional respective plurality of holes (44) in the workpiece (32) at the respective locations by again oscillating the tool along the longitudinal axis (40) while the tool remains positioned over the respective locations between each translation (206) of the workpiece (32). The method (200) of claim 1 or 2, further comprising:

4. 4. The method (200) of claim 1, wherein the step (212) of locally heating a portion of the workpiece (32) comprises maintaining a temperature of the portion of the workpiece (32) above a threshold temperature during the formation (204) of the hole (44) in the workpiece (32).

5. The method of claim 4 , wherein the threshold temperature is the glass transition temperature of a resin of the composite material.

6. The method (200) of claim 1, wherein the needle array (60) comprises a two-dimensional array including at least four needles (36).

7. The method (200) of claim 1, wherein the needle array (60) is removably coupled to the ultrasonic horn.

8. 1. A needle array for ultrasonically drilling holes in a workpiece, comprising: a plurality of needles arranged to form the needle array, each needle of the plurality of needles oriented to extend along a longitudinal axis from a first end to a second end, each needle of the plurality of needles configured to form a respective hole in the workpiece when the needle array is vibrated along the longitudinal axis at an ultrasonic operating frequency while positioned in repeated contact with a surface of the workpiece, each needle of the plurality of needles having a non-circular cross-section, the needle array configured to form a plurality of holes in a region of the workpiece without translating the needle array relative to the workpiece, without rotating the plurality of needles about the longitudinal axis, and without rotating the plurality of needles relative to the workpiece; a support plate, each needle of the plurality of needles coupled to the support plate at a respective first end, the needle array configured to be operably coupled to an ultrasonic actuator via the support plate to vibrate the needle array at the ultrasonic operating frequency; Equipped with the needle array a plurality of rows of needles, each row of the plurality of rows of needles comprising a plurality of needles; a plurality of columns of needles, each column of the plurality of columns of needles comprising a plurality of needles; a two-dimensional array including A needle array wherein the plurality of rows of needles are selectively arranged sequentially in order of increasing length of the respective needles forming each needle row.

9. The needle array of claim 8 , wherein the needle array comprises at least nine needles.

10. The needle array of claim 8 , wherein each needle of the plurality of needles has a polygonal cross section.

11. The needle array of claim 8 , wherein the second ends of the plurality of needles collectively form a contact surface, the plurality of contact surfaces being arranged relative to one another to form a contact shape or contact contour.

12. 9. The needle array of claim 8, wherein the needles of the plurality of needles are arranged in a bilinear distribution along the length of the needles such that the second ends of the plurality of needles collectively form an inclined contact surface for contacting the workpiece.

13. 1. A needle array for ultrasonically drilling holes in a workpiece, comprising: a plurality of needles arranged to form the needle array, each needle of the plurality of needles oriented to extend along a longitudinal axis from a first end to a second end, each needle of the plurality of needles configured to form a respective hole in the workpiece when the needle array is vibrated along the longitudinal axis at an ultrasonic operating frequency while positioned in repeated contact with a surface of the workpiece, each needle of the plurality of needles having a non-circular cross-section, the needle array configured to form a plurality of holes in a region of the workpiece without translating the needle array relative to the workpiece, without rotating the plurality of needles about the longitudinal axis, and without rotating the plurality of needles relative to the workpiece; a support plate, each needle of the plurality of needles coupled to the support plate at a respective first end, the needle array configured to be operably coupled to an ultrasonic actuator via the support plate to vibrate the needle array at the ultrasonic operating frequency; Equipped with A needle array, wherein the needles of the plurality of needles are arranged in a pyramidal distribution according to the length of the needles so that the second ends of the plurality of needles collectively form a pyramidal contact shape for contacting the workpiece.

14. 1. A system for forming perforations in a thin sheet of composite material, comprising: An ultrasonic drilling device, The needle array of claim 10; an ultrasonic actuator configured to vibrate the needle array along a longitudinal axis such that the needle array repeatedly contacts a surface of the thin sheet at an operating frequency sufficient to form a plurality of holes through the thin sheet within a first region of the thin sheet, wherein the needle array does not rotate relative to the surface of the thin sheet while the plurality of holes are formed, and the ultrasonic drilling apparatus is configured to operate without the use of a slurry or a cooling fluid; an ultrasonic drilling device comprising: a remote heating unit spaced from the ultrasonic drilling apparatus, the remote heating unit configured to locally heat the first region of the thin sheet while the plurality of holes are being formed by the ultrasonic drilling apparatus; and A system comprising:

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