The present disclosure is directed to systems and methods for evaluating a bond between two components. More particularly, the present disclosure is directed to systems and methods for evaluating a bond between two components using an underwater spark discharge to generate a compression wave.
Laser bond inspection (LBI) is an inspection method that can be used to evaluate the quality of adhesive bonds in a structure. During laser bond inspection, a plasma is created by using a laser pulse to ablate a sacrificial layer to generate compression waves in the structure. The structure can be, for example, a composite structure including a carbon fiber reinforced polymer (CFRP)-to-CFRP bond or CFRP-to-metal bond. The compression wave mechanically creates a stress load on the adhesive bond. During exposure to this load, a weak bond will fail, and a strong bond will not. Structures with weak bonds are thus identified and repaired or discarded. However, current LBI systems require lasers and power supplies that are large and expensive. Therefore, an improved system and method for evaluating a bond that eliminates the laser is desired.
A system for evaluating a bond is disclosed. The system includes a first vessel having one or more sidewalls and an endwall, a liquid port configured to connect to a source to fill the first vessel with a liquid, and an open portion configured to be placed against a bonded structure to be inspected. The system also includes a second vessel surrounding the open portion of the first vessel, having a vacuum port configured to connect to a vacuum system to pull a vacuum in a space between an outer surface of the first vessel and an inner surface of the second vessel when the open portion of the first vessel and an open portion of the second vessel are adjacent to the bonded structure to be inspected. The system further includes a pair of electrodes disposed within the first vessel and a power supply connected to the pair of electrodes, wherein the power supply is configured to provide an electrical pulse to create an underwater plasma between the pair of electrodes to generate a compression wave.
A method for evaluating a bond is also disclosed. The method includes placing an open portion of a first vessel against a bonded structure being inspected, pulling a vacuum between an outer surface of the first vessel and an inner surface of a second vessel that encloses the first vessel, wherein pulling the vacuum seals the first vessel to the bonded structure, and filling the first vessel with a liquid, wherein the liquid contacts a surface of the bonded structure to be inspected at the open portion. The method also includes initiating a spark discharge in the liquid to form a plasma that generates a compression wave in the liquid, wherein the compression wave propagates from the liquid into the bonded structure through the open portion to apply a force to a bond in the bonded structure. The method further includes inspecting the bond in the bonded structure.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present teachings, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate aspects of the present teachings and together with the description, serve to explain the principles of the present teachings.
It should be noted that some details of the figures have been simplified and are drawn to facilitate understanding rather than to maintain strict structural accuracy, detail, and scale.
Reference will now be made in detail to the present teachings, examples of which are illustrated in the accompanying drawings. In the drawings, like reference numerals have been used throughout to designate identical elements. In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific examples of practicing the present teachings. The following description is, therefore, merely exemplary.
The present disclosure is directed to an inspection system and method that uses an underwater plasma to generate a compression wave to evaluate a strength of bonding parameters between two adjacent layers in a structure. Compression waves are also referred to herein as stress waves or longitudinal waves. The inspection system includes a first vessel containing a liquid in which an underwater plasma generates a compression wave. The compression wave propagates from the liquid into the structure to mechanically stress the bond, as described in greater detail below. While the compression wave stresses the bond in a manner similar to LBI, the disclosed inspection system and method using the underwater plasma eliminates the need for a laser and its power supply required for LBI thereby reducing the size and cost of the equipment for bond inspection. The reduced size further provides increased portability to allow easier and more efficient inspection of a greater range of shapes and sizes of bonded structures compared to, for example, ASTM Standard D5868—Lap Shear Adhesion for Fiber Reinforced Plastic (FRP) Bonding, ASTM Standard D1002—Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded, and ASTM Standard D3167—Standard Test Method for Floating Roller Peel Resistance of Adhesives.
System 100 also includes a second vessel 140 having one or more sidewalls 144, an endwall 142, an open portion 150, and a vacuum port 170 that can be connected to a vacuum system. Second vessel 140 surrounds open portion 130 of first vessel 110, and may completely enclose first vessel 110 as shown in
End of sidewall 114 at open portion 130 is depicted as planar to allow inspection of a bond within bonded structure 190 having a flat surface. A structure being inspected having a curved or shaped surface can be inspected by conforming ends of sidewalls of first vessel 110 and second vessel 140 to have a shape or curvature that matches a shape or curvature of the surface of the structure being inspected. As shown in
System 100 further includes a pair of electrodes 180 disposed in first vessel 110 and a power supply 185 connected to pair of electrodes 180. As used herein, pair of electrodes refers to an anode and a cathode separated by a gap. Pair of electrodes 180 can be, for example, part of a spark plug, e.g., a spark plug for a combustion engine. Pair of electrodes 180 are positioned so that the compression wave generated in the liquid can propagate towards the structure being inspected. For example, pair of electrodes 180 can be positioned in front of open portion 130 of first vessel 110 so that the compression wave can propagate through open portion 130 into the structure being inspected. Power supply 185 supplies an electrical pulse to initiate the spark discharge at electrodes 180. The electrical pulse generates a compression wave with high amplitude and short pulse width for bond inspection, for example, high amplitude and short pulse comparable to a compression wave generated by an LBI system. Power supply 185 can provide about 40 kV to about 60 kV to pair of electrodes 180 and can be, for example, one or more banks of capacitors. The one or more banks of capacitors can be variable capacitors including time delay capability. Power supply 185 can also provide a voltage (e.g., and electrical pulse) via a transformer to produce arcing at pair of electrodes 180 at a desired voltage. Examples of transformers include, but are not limited to, an oscillator transformer and flyback transformer. Power supply 185 can also be a Van de Graaff belt high voltage electrostatic generator or other sources of an electrical pulse.
As shown in
During inspection, a bonded structure is placed over open portion 230 of first vessel 210 and open portion 250 of second vessel 240. First vessel 210 is filled with the liquid through liquid port 220 and a vacuum is pulled within space 260 via vacuum port 270. Seals optionally located at the ends of the sidewalls that contact the bonded structure can keep the liquid within first vessel 210 from escaping and facilitate establishing a vacuum in space 260. Pair of electrodes 280, for example, part of a spark plug, immersed in the liquid are provided with an electrical pulse from a power supply 285. The electrical arc formed between pair of electrodes 280 generates a plasma within the liquid that in turn generates a compression wave directed towards the bonded structure through open portion 230 of first vessel 210.
At 310 of method 300, a system for evaluating a bond as disclosed herein can be placed against a structure to be inspected. Referring to
System 400 is placed against structure 490 so that open portions of a first vessel 410 and a second vessel 440 are closed by structure 490. In other words, structure 490 closes open portions of first vessel 410 to allow liquid to fill first vessel 410 and to contact a surface of structure 490. Structure 490 also closes open portions of second vessel 440 to allow a vacuum to be pulled in second vessel 440, for example, in space 460 between the inside of a sidewall of second vessel 440 and an outside of a sidewall of first vessel 410.
At 320 of method 300, a vacuum is pulled within second vessel 440. Referring to
At 330 of method 300, the first vessel is filled with a liquid. Referring to
At 340 of method 300, an electrical pulse is transmitted to a pair of electrodes that are immersed in the liquid in first vessel 410 to initiate a spark discharge. Referring again to
The electrical pulse is provided by a power supply 485, for example, a bank of capacitors, a voltage induction source, or voltage switching source, provides a voltage capable of forming an underwater plasma that generates a high amplitude, short wavelength compression wave for bond inspection. The high amplitude, short wavelength compression wave can have a pulse width of about 100 ns to about 300 ns and an energy of about 5 to about 40 Joules. The high amplitude, short wavelength compression wave can further be comparable to a compression wave generated during LBI inspection. Power supply 485 can provide about 40 kV to about 60 kV to pair of electrodes 480 to generate the underwater plasma and the resulting compression wave having a duration or pulse width of about 100 ns to about 300 ns and an energy of about 5 to about 40 Joules.
Although not wishing to be bound by any particular theory, it is believed that the electrical pulse when transferred to the pair of electrodes causes a high intensity electric field across the gap of the pair of electrodes within the liquid. This results in ionization of the liquid molecules and formation of a gaseous plasma. High temperature and pressure generated by the plasma and opposed by the liquid, results in an acoustic wave, e.g., a compression wave, that propagates outwards with an amplitude sufficient to change the density of the liquid.
The compression wave generated in liquid 425 by the plasma propagates through the liquid and into first component 492 of structure 490. The compression wave propagates through first component 492 and applies a force to bond 493. In various implementations, the force needed to damage or break a bond with a satisfactory/passing quality may be known prior to performing the disclosed method. Thus, the force can be a predetermined force, for example, from about 30% to about 70% (e.g., about 50%) of the force required to break bond 493, in a manner similar to adhesive bond testing by LBI or peel ply. The predetermined force applied by the compression wave is controlled by, for example, the length of the gap between the electrodes, the size and width of electrical pulse, and size and shape of the first vessel, and/or the liquid in the vessel. A force can further be applied to bond 493 from a reflected compression wave after the compression wave is reflected from a surface of first component 492, a surface of second component 494, and/or bond 493. The predetermined force can be based on, for example, peel ply testing in a manner similar to establishing a predetermined force in laser bond inspection.
At 340 of method 300, the bond can be inspected. For example, bond 493 can be inspected with a non-destructive inspection (NDI) system including but not limited to an ultrasound imaging system or an ultrasonic inspection system. The inspection detects inconsistencies and/or damage to the bond that occurs in response to the compression wave and/or a reflected compression wave reflected from a back surface of the structure. If the inspection reveals that bond 493 is fractured or broken, then the quality of the bond is determined to be bad (i.e., the bond did not pass inspection). If the inspection reveals that bond 493 (e.g., material forming the bond) is not fractured or broken, then the quality of the bond is determined to be good (i.e., the bond passes inspection). Such an inspection of the bond is comparable to inspection by LBI and ASTM D5528-13—Standard Test Method for Mode 1 Interlaminar Fracture Toughness of Unidirectional Fiber-reinforced Polymer matrix composites. Alternative or additional steps may also be performed.
The disclosed system and method can replace destructive testing such as peel ply tests, which use mechanically applied stress to pull a bond apart. The disclosed system and method can also replace LBI tests, which use an expensive and large laser/power supply and further requires a sacrificial material for ablation to generate a compression wave.
Further, the disclosure comprises examples according to the following clauses:
Clause 1. A system for evaluating a bond comprising: a first vessel comprising, one or more sidewalls and an endwall, a liquid port configured to connect to a source to fill the first vessel with a liquid, and an open portion configured to be placed against a bonded structure to be inspected; a second vessel surrounding the open portion of the first vessel, comprising a vacuum port configured to connect to a vacuum system to pull a vacuum in a space between an outer surface of the first vessel and an inner surface of the second vessel when the open portion of the first vessel and an open portion of the second vessel are adjacent to the bonded structure to be inspected; a pair of electrodes disposed within the first vessel; and a power supply connected to the pair of electrodes, wherein the power supply is configured to provide an electrical pulse to create an underwater plasma between the pair of electrodes to generate a compression wave
Clause 2. The system of any of Clauses 1 or 3-9, further comprising one or more seals configured to seal the first vessel against the structure when the vacuum is pulled in the space between the outer surface of the first vessel and the inner surface of the second vessel.
Clause 3. The system of any of Clauses 1, 2 or 4-9, further comprising a spark plug that comprises the pair of electrodes.
Clause 4. The system of any of Clauses 1-3 or 5-9, wherein the power supply provides about 40 kV to about 60 kV to the pair of electrodes.
Clause 5. The system of any of Clauses 1-4 or 6-9, wherein the pair of electrodes comprise a gap that discharges a spark to generate a compression wave with a pulse width of about 100 ns to about 300 ns and an energy of about 5 to about 40 Joules per pulse.
Clause 6. The system of any of Clauses 1-5 or 7-9, wherein the liquid port is configured to connect to a source of water, deionized water, mineral oil, or a non-conductive fluid.
Clause 7. The system of any of Clauses 1-6 or 8-9, further comprising an additional liquid port and/or an air vent.
Clause 8. The system of any of Clauses 1-7 or 9, wherein the first vessel and the second vessel comprise an endwall and/or a sidewall that is common to both the first vessel and the second vessel.
Clause 9. The system of any of Clauses 1-8, wherein an end of the one or more sidewalls of the first vessel comprise a shape and/or curvature that matches a shape and/or curvature of a surface of the structure to be inspected.
Clause 10. A method for evaluating a bond, comprising: placing an open portion of a first vessel against a bonded structure being inspected; pulling a vacuum between an outer surface of the first vessel and an inner surface of a second vessel that encloses the first vessel, wherein pulling the vacuum seals the first vessel to the bonded structure; filling the first vessel with a liquid, wherein the liquid contacts a surface of the bonded structure to be inspected at the open portion; initiating a spark discharge in the liquid to form a plasma that generates a compression wave in the liquid, wherein the compression wave propagates from the liquid into the bonded structure through the open portion to apply a force to a bond in the bonded structure; and inspecting the bond in the bonded structure.
Clause 11. The method for evaluating a bond of any of Clauses 10 or 12-20, wherein the bond in the bonded structure comprises a metal-to-composite adhesive bond or a composite-to-composite adhesive bond.
Clause 12. The method for evaluating a bond of any of Clauses 10, 11 or 13-20, wherein pulling the vacuum between the outer surface of the first vessel and the inner surface of a second vessel comprises compressing seals disposed between the first vessel and the bonded structure and compressing seals disposed between the second vessel and the bonded structure.
Clause 13. The method for evaluating a bond of any of Clauses 10-12 or 14-20, wherein filling the first vessel with a liquid comprises filling the first vessel with water or oil.
Clause 14. The method for evaluating a bond of any of Clauses 10-13 or 15-20, wherein filling the first vessel with the liquid comprises introducing a pressure of up to about 100 psi in the first vessel.
Clause 15. The method for evaluating a bond of any of Clauses 10-14 or 16-20, wherein initiating the spark discharge in the liquid comprises supplying about 40 kV to about 60 kV to a pair of electrodes disposed in the first vessel.
Clause 16. The method for evaluating a bond of any of Clauses 10-15 or 17-20, wherein initiating the spark discharge in the liquid to form the plasma generates a compression wave in the liquid having a pulse width of about 100 ns to about 300 ns.
Clause 17. The method for evaluating a bond of any of Clauses 10-16 or 18-20, wherein initiating a spark discharge in the liquid comprises providing an electrical pulse from a bank of capacitors to a spark plug.
Clause 18. The method for evaluating a bond of any of Clauses 10-17 or 19-20, wherein the force applied to the bond by the compression wave is from about 30% to about 70% of a force required to break the bond.
Clause 19. The method for evaluating a bond of any of Clauses 10-18 or 20, further comprising applying another force to the bond by a reflected compression wave.
Clause 20. The method for evaluating a bond of any of Clauses 10-19, wherein inspecting the bond in the bonded structure comprises using ultrasound to inspect the bond.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein.
While the present teachings have been illustrated with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the present teachings may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. As used herein, the terms “a”, “an”, and “the” may refer to one or more elements or parts of elements. As used herein, the terms “first” and “second” may refer to two different elements or parts of elements. As used herein, the term “at least one of A and B” with respect to a listing of items such as, for example, A and B, means A alone, B alone, or A and B. Those skilled in the art will recognize that these and other variations are possible. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” Further, in the discussion and claims herein, the term “about” indicates that the value listed may be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the intended purpose described herein. Finally, “exemplary” indicates the description is used as an example, rather than implying that it is an ideal.
It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompasses by the following claims.
This application claims priority to U.S. Provisional Patent Application No. 63/125,790, filed on Dec. 15, 2020, the entirety of which is incorporated by reference herein.
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Number | Date | Country | |
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20220187178 A1 | Jun 2022 | US |
Number | Date | Country | |
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63125790 | Dec 2020 | US |