Patent Publication Number: US-2022230041-A1

Title: Location of fastener accessory using sacrificial rf tag

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to U.S. Provisional Application No. 63/138,027 filed on Jan. 15, 2021, which is hereby incorporated by reference in its entirety. 
    
    
     INTRODUCTION 
     Modern aircraft, spacecraft, and other complex mobile and stationary systems are constructed of a vast number of component parts. For instance, a modern jet-powered passenger airplane uses several million different parts in its construction. Many of the parts are interconnected using specialized or off-the-shelf fastener hardware such as screws, bolts, nuts, washer, rivets, and river stems, as well as cable tie-downs, electrical clips, end connectors, and the like. The myriad of different sizes, shapes, and materials of construction in the vast array of fastener hardware can complicate manufacturing and assembly processes. This is particularly true when relatively small and difficult to handle fasteners are inadvertently dropped or misplaced and thus lost within a workspace. 
     An example scenario is that of assembling, overhauling, or repairing a modern aircraft or other complex system. In such a scenario, maintenance personnel are often required to work within or in proximity to confined workspaces. Space restrictions and the small size of many of the above-noted fasteners often results in lost fasteners. In a typical aircraft passenger cabin or fuselage interior, for instance, a fastener could make its way through openings in the floor or between adjacent ribs of the fuselage, behind a control panel, or into another undesirable space. Over time, the lost fastener could cause adjacent components to wear or short out, thus leading to a condition referred to in the art as Foreign Object Damage/FOD. 
     SUMMARY 
     The present disclosure provides a solution to the above-noted problem of Foreign Object Damage (FOD) during a manufacturing process. While the particular manufactured end product may vary within the scope of the present disclosure and appended claims, the present teachings are of particular benefit in reducing instances of FOD during the manufacturing and assembly of aircraft, spacecraft, and other vehicles, as well as other stationary or mobile systems in which the risk of FOD is elevated due to the use of easily dropped, misplaced, or otherwise lost fastener hardware in proximity to damage-sensitive components or subsystems. 
     In particular, the solutions presented herein involve the use of low-cost sacrificial radio frequency (RF) tags in conjunction with mechanical or electrical fastener bodies for the purpose of enabling remote detection of the fastener body, thereby reducing instances of the above-described FOD. The disclosed solutions may also be used in any manufacturing environment in which FOD is a concern, and in which determining a resting location of an inadvertently dropped or misplaced fastener body would be desirable. 
     In an exemplary embodiment, a fastener accessory as described herein includes a fastener body and a sacrificial RF tag. The fastener body includes a contact surface configured to receive an installation force during connection of the fastener body to a component. The sacrificial RF tag includes a dielectric substrate affixed to the contact surface, as well as an RF antenna trace connected to or imprinted on the dielectric substrate. The sacrificial RF tag transmits an RF response signal when the RF antenna trace is excited by an external exciter/RF tracking circuit. The installation force is configured to plastically deform or destroy the sacrificial RF tag to prevent transmission of the RF response signal, and thus the RF tag communicates with the RF tracking circuit solely in pre-installation use scenarios. 
     The RF antenna trace contemplated herein may optionally include separate receiver (Rx) and transmitter (Tx) antenna traces positioned on or within the dielectric substrate. In such a configuration, the Tx antenna trace is spaced a distance apart from the Rx antenna trace on or within the dielectric substrate. An RF modulating circuit interconnects the Rx and Tx antenna traces. The sacrificial RF tag is configured to transmit the RF response signal at a predetermined response frequency via the Tx antenna trace when the Rx antenna trace is excited by an RF interrogation signal from the external RF tracking circuit noted above. 
     In some embodiments, the RF modulating circuit includes a fixed-value receiver. Alternatively, the RF modulating circuit may include a system-on-a-chip (SoC) configured to actively frequency-modulate a frequency of the RF interrogation signal to thereby generate the predetermined response frequency. Representative embodiments are described in which the RF interrogation signal is on the order of about 10 MHz, while the predetermined response frequency is on the order of 100 MHz, i.e., about 10 times the frequency of the RF interrogation signal. Other embodiments may exist at other frequencies, provided the response frequency is readily distinguishable from the interrogation frequency, thus enabling detection in accordance with the disclosed solutions. 
     The fastener body in some configurations includes an externally-threaded shaft and a fastener head integrally connected thereto at or along an underside of the fastener head. The contact surface in such an embodiment includes the underside of the fastener head. 
     Alternatively, the fastener body may be an internally-threaded nut configured to surround and engage an externally-threaded shaft during installation, with the contact surface in such an embodiment including a surface of the internally-threaded nut. 
     The dielectric substrate in some aspects of the present disclosure is constructed from a flexible polymer film. 
     The Rx and Tx antenna traces may each be laser-etched, printed, or micro-imprinted directly onto the dielectric substrate in some embodiments, and/or the Rx and Tx traces may be integrated together as described herein. 
     The RF tag may be non-serialized, such that the RF tag does not transmit data as part of its RF response signal. 
     Also disclosed herein is a method for locating a fastener body within a search area. The method according to a possible embodiment includes attaching a dielectric substrate of a sacrificial RF tag to a contact surface of the fastener body, the RF tag including an Rx antenna trace positioned on or within the dielectric substrate, a Tx antenna trace spaced apart from the Rx antenna trace on or within the dielectric substrate, and an RF modulating circuit interconnecting the Rx antenna trace and the Tx antenna trace. The method includes exciting the Rx receiver trace at an interrogation frequency using an RF interrogation signal, and then frequency-modulating the interrogation frequency using the RF modulating circuit. 
     The method also includes transmitting an RF response signal at a predetermined response frequency via the Tx antenna trace. The RF response signal is then detected as part of the method using the RF tracking circuit to thereby locate the fastener body within the search area. 
     Another embodiment of the present method for locating a fastener body within a search area includes adhering a sacrificial RF tag to the fastener body using a dielectric adhesive material, with the sacrificial RF tag containing an antenna array. Within the search area, the method includes exciting an Rx antenna trace of the antenna array after adhering the sacrificial RF tag to the fastener body, including directing a calibrated RF interrogation signal with a predetermined interrogation frequency from an RF tracking circuit into the search area. 
     After exciting the Rx antenna trace, the method in this particular embodiment includes receiving an RF response signal having a predetermined response frequency. The RF response signal is received from a Tx antenna trace of the antenna array using the RF tracking circuit, with the predetermined response frequency being higher than the predetermined excitation/interrogation frequency, e.g., by a factor of 10× in some embodiments. The method thereafter includes using the RF response signal to locate the fastener body within the search area, with the RF response signal in this embodiment also being characterized by an absence of data. 
     The method may, in some approaches, include installing the fastener body to a component of an aircraft or a spacecraft by applying an installation force to the fastener body. The installation force plastically deforms the sacrificial RF tag to a level sufficient for preventing further transmission of the RF response signal. 
     Adhering the sacrificial RF tag to the fastener body using the dielectric adhesive material may include loading a stack of the sacrificial RF tags onto a clamping tool having an anvil and spring-biased arms or handles, and manually clamping the sacrificial RF tag from the stack of the sacrificial RF tags directly onto the fastener body using forces imparted by the clamping tool. 
     The above summary is not intended to represent every possible embodiment or every aspect of the present disclosure. Rather, the foregoing summary is intended to exemplify some of the novel aspects and features disclosed herein. The above features and advantages, and other features and advantages of the present disclosure, will be readily apparent from the following detailed description of representative embodiments and modes for carrying out the present disclosure when taken in connection with the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a representative workspace in the form of an aircraft fuselage interior in which a lost fastener body could present a foreign object damage (FOD) risk of the type mitigated by the solutions presented herein. 
         FIG. 2  is a schematic plan view illustration of an exemplary sacrificial radio frequency (RF) tag usable as part of a fastener accessory within the scope of the present disclosure. 
         FIG. 3  is a schematic partial cross-sectional side view illustration of a portion of the RF tag shown in  FIG. 2 . 
         FIGS. 4A and 4B  are schematic plan view illustrations of opposing surfaces of the sacrificial RF tag depicted in  FIG. 2 . 
         FIG. 5  is a schematic partial cross-sectional perspective view illustration of a fastener accessory having an externally-threaded fastener shaft and integral fastener head according to an exemplary embodiment. 
         FIG. 6  is a schematic cross-sectional perspective view illustration of a fastener accessory in the form of an internally-threaded nut according to another exemplary embodiment. 
         FIG. 7  is schematic cross-sectional perspective view illustration of a fastener accessory according to yet another exemplary embodiment. 
         FIG. 8  is a schematic cross-sectional side view illustration of the RF tag shown in  FIG. 7 . 
         FIG. 9  is a schematic cross-sectional side view illustration of a fastener accessory during installation to a component. 
         FIG. 10  is a schematic circuit diagram of an external exciter/RF tracking circuit usable for locating a fastener accessory configured as described herein. 
         FIG. 11  is a schematic cross-sectional side view illustration of a representative stack of sacrificial RF tags configured for use in attachment to a fastener body in accordance with an aspect of the disclosure. 
         FIG. 12  is a schematic illustration of a representative clamping tool loaded with the stack of sacrificial RF tags shown in  FIG. 12 . 
     
    
    
     The present disclosure is susceptible to modifications and alternative forms, with representative embodiments shown by way of example in the drawings and described in detail below. Inventive aspects of this disclosure are not limited to the disclosed embodiments. Rather, the present disclosure is intended to cover modifications, equivalents, combinations, and alternatives falling within the scope of the disclosure as defined by the appended claims. 
     DETAILED DESCRIPTION 
     The present disclosure is susceptible of embodiment in many different forms. Representative examples of the disclosure are shown in the drawings and described herein in detail as non-limiting examples of the disclosed principles. To that end, elements and limitations described in the Abstract, Introduction, Summary, and Detailed Description sections, but not explicitly set forth in the claims, should not be incorporated into the claims, singly or collectively, by implication, inference, or otherwise. 
     For purposes of the present description, unless specifically disclaimed, use of the singular includes the plural and vice versa, the terms “and” and “or” shall be both conjunctive and disjunctive, “any” and “all” shall both mean “any and all”, and the words “including”, “containing”, “comprising”, “having”, and the like shall mean “including without limitation”. Moreover, words of approximation such as “about”, “almost”, “substantially”, “generally”, “approximately”, etc., may be used herein in the sense of “at, near, or nearly at”, or “within ±5% of”, or “within acceptable manufacturing tolerances”, or logical combinations thereof. 
     Referring to the drawings, wherein like reference numbers refer to the same or like components in the several Figures, a workspace  10  is shown in  FIG. 1 . The workspace  10  is depicted in a non-limiting exemplary embodiment as an aircraft fuselage interior or passenger cabin as it might appear during manufacturing, or in the course of an extended maintenance overhaul. In such a state, the workspace  10  is devoid of interior wall panels, seats, and flooring, which in turn exposes transverse ribs  12  and longitudinal beams  14 . An external fuselage skin  16  defining window openings  15  is thus visible between the transverse ribs  12  and the longitudinal beams  14 . Other workspaces  10  may be envisioned, such as interiors or exteriors of spacecraft, surface and subsurface marine vessels and watercraft, robotics, industrial equipment, etc., and therefore the depicted scenario of  FIG. 1  is just one possible embodiment of the workspace  10  within the scope of the present disclosure and the appended claims. 
     Floor supports  18  are present within a cavity (arrow A) of the workspace  10 , which in the representative embodiment of  FIG. 1  is surrounded by the above-noted transverse ribs  12 , longitudinal beams  14 , and fuselage skin  16 . The floor supports  18  may include transverse and longitudinal joists  20  and  22 , respectively. When a floor surface is eventually installed along with seat pallets, passenger seats, and other equipment, the interconnected floor supports  18  support and distribute the collective weight via the joists  20  and  22 . 
     Prior to installation of these and other components, however, the interconnected joists  20  and  22 , the transverse ribs  12 , the longitudinal beams  14 , and possibly other structural components within the workspace  10  may define openings  24  of various sizes therebetween. Workspaces  10  other than the representative aircraft embodiment depicted in  FIG. 1  may be envisioned in which similar openings  24  are present. When working within the workspace  10 , and in particular when transporting, handling, or installing fastening hardware for connection to a component, opportunities abound for inadvertently dropping and losing such hardware. The final resting locations of such dropped or misplaced hardware complicates location and removal thereof, often leading to time consuming and often fruitless searches of the workspace  10 . 
     As noted above, a lost or misplaced fastener such as a screw, bolt, nut, washer, or rivet poses a short-term or long-term risk of foreign object damage (FOD). This is particularly true in an aviation or aerospace content. For instance, although omitted for illustrative simplicity, the representative workspace  10  of  FIG. 1  may include one or more additional levels located below that of the floor supports  18 . In the non-limiting exemplary aircraft manufacturing or overhaul scenario depicted in  FIG. 1 , such a level may include a cargo bay and an equipment bay, with the identity of the lower bay depending on the particular location along the floor supports  18  relative to a bulkhead  25  disposed at a distal end of the workspace  10 . 
     In addition to housing cargo, an aircraft cargo bay may also contain emergency oxygen supplies, compressors, cooling systems, and potable water. One or more separate equipment bays may include electrical and hydraulic flight control equipment such as electrical distribution panels, circuit breakers, wiring, battery compartments, weather radar, flight and onboard systems control equipment, and the like. Any or all of these important systems may experience FOD as they are degraded or damaged over time due to abrasion, interference, or contact with a lost fastener of the types considered herein. The present radio-frequency (RF)-based location and tracking solutions therefore address this particular problem, with various embodiments now discussed with reference to  FIGS. 2-12 . 
     Referring to  FIG. 2 , the above-noted fastener, or more specifically a fastener body  50  thereof as shown in an exemplary embodiment in  FIG. 5 , is equipped herein with a sacrificial radio frequency (RF) tag  26 . In the ring-shaped or annular configuration of  FIG. 2  which the RF tag  26  includes a circular inner circumferential wall  27 , an inner diameter (ID) of the RF tag  26  may receive an externally-threaded shaft  50 - 1  of the fastener body  50  therein, with the externally-threaded shaft  50 - 1  likewise shown in  FIG. 5 . When the RF tag  26  is remotely interrogated and thereby excited by an RF interrogation signal  30  transmitted at a first frequency, e.g., from an external exciter/RF tracking circuit  60  as shown in detail in  FIG. 10 , the sacrificial RF tag  26  responds with a RF response signal  130  at a predetermined second frequency. The RF response signal  130  thus provides a unique signature that can be detected by the RF tracking circuit  60  for the purpose of locating the fastener body  50  to within an application-suitable level of accuracy. 
     The sacrificial RF tag  26  as described herein is “sacrificial” in the sense that installation forces applied to the fastener body  50  of  FIG. 5  or other embodiments thereof plastically deform or totally destroy the sacrificial RF tag  26 , which in turn prevents transmission of the RF response signal  130  after installation. The sacrificial RF tag  26  thus communicates with the RF tracking circuit  60  only when in a pre-installed state. That is, once a fastener body  50  equipped with the sacrificial RF tag  26  is fully installed, the equipped fastener body  50  is no longer detectable, thereby eliminating false location alarms and possible electromagnetic interference by the sacrificial RF tag  26  with other equipment. 
     In the illustrated construction of  FIG. 2 , the sacrificial RF tag  26  includes a dielectric substrate  28  and an RF antenna trace  32 , the latter of which is connected to or imprinted on the dielectric substrate  28 , e.g., via laser etching, surface printing, or micro-imprinting in different embodiments. The RF antenna trace  32  in the illustrated embodiment includes a receiver (Rx) antenna trace  34  and a transmitter (Tx) antenna trace  36 . The Tx antenna trace  36  is spaced apart from the Rx antenna trace  34  on or within the dielectric substrate  28 . 
     As part of the illustrated embodiment of  FIG. 2 , an RF modulating circuit  38  interconnects the Rx antenna trace  34  and the Tx antenna trace  36 . In this particular configuration, the sacrificial RF tag  26  is configured to transmit the RF response signal  130  at the above-noted predetermined response frequency, via the Tx antenna trace  36 , whenever the Rx antenna trace  34  is excited by the RF interrogation signal  30  from the RF tracking circuit  60 . Other configurations may be envisioned for constructing the RF antenna  32 . For example, a modulated pulse tone may be applied to a single fixed antenna to incite a unique frequency response, as appreciated in the art. 
     With respect to the particular embodiment of  FIG. 2 , the RF modulating circuit  38  may be optionally embodied as a fixed-value receiver, or as a combination resistor, inductor, and/or capacitor to produce a desired modulation to the received RF interrogation signal  30 . Other embodiments may be envisioned in which the RF modulating circuit  38  is a system-on-a-chip (SoC) or an application-specific integrated circuit (ASIC) configured to actively frequency-modulate the frequency of the RF interrogation signal  30  to thereby generate the RF response signal  130  having a predetermined response frequency. 
     In general, search and location may proceed by transmitting a fixed frequency from the RF tracking circuit  60 , e.g., 10 MHz, which is then received by the RF tag  26 . The sacrificial RF tag  26  converts the received RF energy to DC power to power transmission of the RF response signal  130  at a different frequency, e.g., 100 MHz. The higher frequency signal is then detected using a handheld RF tracker such as the non-limiting RF tracking circuit  60  as described in detail below with reference to  FIG. 10 . 
     As depicted schematically in  FIG. 3 , the sacrificial RF tag  26  is constructed from relatively low-cost, one-time use materials in which the RF antenna  32  is formed in or etched or printed on a surface  128  of the above-noted dielectric substrate  28 , e.g., between layers  28 A and  28 B thereof. The sacrificial RF tag  26  may be constructed from a thin, flexible dielectric polymer film of a thickness T, e.g., on the order of less than 1 mm. When attached as set forth below, therefore, the thin profile and flexible materials are easily plastically deformed or completely destroyed by an applied torque or other installation forces. 
     In contrast to conventional RFID tags, the sacrificial RF tag  26  contemplated herein and shown in  FIG. 2  is not serialized, i.e., the sacrificial RF tag  26  does not transmit data or information as part of a programmed function. Its functions are instead limited in the described embodiments to transmission of the RF response signal  130  as a waveform having a uniquely identifiable response frequency relative to the frequency of the incident RF interrogation signal  30 . 
     In terms of the above-noted one-time use, installation-based destruction of the sacrificial RF tag  26  prevents undesirable post-installation transmission of the RF response signal  130  of  FIG. 2 . In this way, the RF tracking circuit  60  of  FIGS. 2 and 10  may be maneuvered by an operator within a space in which a lost or dropped fastener is likely to have fallen. The strength of the RF response signal  130  is then used to locate the fastener body  50  to a reasonable degree of accuracy within such a space. Roughly speaking, location to within 10 feet of the fastener body  50  may be sufficient, with the operator thereafter manually conducting the search. Other embodiments may be constructed in which the accuracy is much higher, e.g., to within 1 foot of the actual location. As properly installed fasteners cannot respond to the RF interrogation signal  30 , false alarms are effectively eliminated, with any received RF response signal  130  likely belonging to the lost fastener. 
     As shown in  FIGS. 4A and 4B , the sacrificial RF tag  26  of  FIGS. 2 and 3  in the depicted annular embodiment has primary surface  29  on which is applied a layer of a suitable dielectric adhesive material  40 . Specialty electrically-insulative two-part epoxies, silicones, or other quick-set suitable polymer materials may be used for this purpose. A primary surface  129  diametrically opposite to the surface  29  is characterized by a lack of the adhesive material  40 , with surface  129  treated with materials or constructed of a particular material to which the adhesive material  40  will not adhere. Such a construction would facilitate the application variation described below with reference to  FIGS. 11 and 12 . 
     Referring now to  FIG. 5 , the above-described sacrificial RF tag  26  is adhesively attached to a contact surface  55  of the fastener body  50  to form a fastener accessory  70 . In a representative embodiment, the fastener body  50  may be a screw or bolt having a centerline  51 , the externally-threaded shaft  50 - 1 , and an integral fastener head  50 - 2 . In this configuration, external threads  52  of the externally-threaded shaft  50 - 1  are adjacent to the inner circumferential surface  27  ( FIGS. 4A and 4B ) of the sacrificial RF tag  26  once the sacrificial RF tag  26  is securely adhered to the contact surface  55 , with the contact surface  55  in this instance being an underside of the fastener head  50 - 2 . 
     For example, a screwdriver or torque wrench may be applied to the fastener head  50 - 2  to deliver a torque (arrow T) about the centerline  51 . This ultimately results in linear and rotational installation forces (arrow F) being directed to primary surface  129  once primary surface  129  contacts an external component (not shown in  FIG. 5 ), e.g., a surface of a fuselage panel or a control board in the representative aviation embodiment of  FIG. 1 . Due to such installation forces (arrow F), the sacrificial RF tag  26  is ultimately twisted and crushed during installation of the fastener body  50 , thereby causing plastic deformation and destruction of the sacrificial RF tag  26  attached thereto. 
     The scope of the present disclosure may be extended to other fastener types. For example, and as shown in  FIG. 6 , a fastener body  50 A with an attached sacrificial RF tag  26  forms another fastener accessory  70 A. The fastener body  50 A is in the form of an internally-threaded nut  50 - 3  or, in other embodiments, an unthreaded planar washer, and includes a contact surface  155 . In a possible configuration, the sacrificial RF tag  26  may be adhered to the contact surface  155  as shown. An externally-threaded fastener body  50  such as shown in  FIG. 5  may be inserted along a centerline  151 . Once the nut  50 - 3  is tightened against the fastener head  50 - 2 , the installation forces (arrows F) likewise deform/destroy the installed sacrificial RF tag  26 . 
     Referring briefly to  FIG. 9 , the embodiments of  FIGS. 5 and 6  may be combined in some configurations. That is, an alternative fastener accessory  70 B may include the above-noted externally-threaded fastener body  50  of  FIG. 5  and the nut or washer-type fastener bodies  50 A of  FIG. 6 . During a representative installation process, the externally-threaded shaft  50 - 1  of the fastener body  50  is threaded into an internally-threaded opening  64  of a component  65  along the centerline  51  using the applied torque (arrow T). Once the contact surface  155  of the fastener body  50 A is in close proximity to a surface  62  of the component  65 , continued application of the torque (arrow T) transmits the installation forces (arrows F) to the installed sacrificial RF tag  26  located on the fastener body  50 A. Soon thereafter, the installation forces (arrows F) are transferred to the contact surface  55  of the fastener head  50 - 2 . Both installed sacrificial RF tags  26  are thereby twisted, torn, crushed, and otherwise plastically deformed/destroyed as the fastener body  50 A is tightened against the surface  62 . 
     Yet another possible configuration is shown in  FIGS. 7 and 8 . Here, the alternatively configured sacrificial RF tag  126  of  FIG. 8 , inclusive of an Rx antenna trace  134 , a Tx antenna trace  136 , and an RF modulating circuit  138  disposed in/on dielectric substrate  28  of a thickness T may be adhered using the adhesive material  40  to the externally-threaded shaft  50 - 1  in proximity to the contact surface  55 , e.g., on the underside of the integral fastener head  50 - 2 , thus functioning in the manner of a sleeve. Installation forces (arrows F) on the contact surface  55 , along with threaded contact between the threads and mating threads (not shown) of the component and/or the nut of  FIG. 6 , ultimately crush and twist the installed sacrificial RF tag  126  to the same desired destruction effect. 
     Referring now to  FIG. 10 , the external RF tracking circuit  60  noted briefly above is used as part of a method for locating the fastener body  50  or its other described embodiments within a search area, e.g., within a general location in which a lost or inadvertently dropped fastener body  50  is expected to have come to rest. For illustrative simplicity, the following description is taken with respect to a generic embodiment of the sacrificial RF tag  260  having an Rx antenna trace  234 , a Tx antenna trace  236 , and an RF modulating circuit  238  connected therebetween, all of which are situated on a dielectric substrate  228 . 
     An initial part of such a method includes attaching the dielectric substrate  228  to the contact surface  55  of the fastener body  50 , a process that could be performed manually in a piece-by-piece manner. Such a process could include peeling a backing material (not shown) away from the adhesive material  40  of  FIG. 4A  to expose the dielectric adhesive material  40 , for instance, and then adhering the dielectric substrate  228  to the contact surface  55 . Alternatively, the attachment process could be facilitated using a handheld clamping tool such as the representative clamping tool  90  of  FIG. 12  described below. 
     With respect to the RF tracking circuit  60  shown in  FIG. 10 , such a device may include an RF exciter antenna  87  connected to a fixed RF exciter circuit  82 , itself energized via a low-voltage power supply  83 , e.g., a 5V battery. An RF receiver antenna directional array  86  may be connected to a fixed RF receiver circuit  84 , the latter possibly including a directional visual LED system  85 . Using such a setup, the directional array  86  provides sufficient detection bandwidth for which to detect the RF response signal  130  in the event the sacrificial RF tag  260  is excited by the RF interrogation signal  30  emitted by the RF tracking circuit  60 . Variation in signal strength of the received RF response signal  130  would produce a different drive voltage to the LED system  85 , thereby providing intuitive/visual feedback to the operator of the RF tracking circuit  60  as to proximity of the lost fastener accessory  70  with its attached sacrificial RF tag  26 . 
     Referring now to  FIGS. 11 and 12 , attaching the sacrificial RF tag  26  to a given fastener body  50  optionally includes clamping the sacrificial RF tag  26  from a stack  80  onto the fastener body  50  using a clamping tool  90 . To that end, the stack  80  of the representative annular sacrificial RF tags  26  of  FIG. 3  may be situated on a spool  81 , with the spool  81  circumscribed by a plunger  82  at a proximal end E 1  of the stack  80 . Such a stack  80  is then placed over the externally-threaded shaft  50 - 1  in the position of  FIG. 11 . An application force (arrows FA) is then applied to the plunger  82  to transmit the application force (arrow FA) to one of the sacrificial RF tags  26  disposed at a distal end E 2  of the stack  80 . The RF tag  26  at the distal end E 2  is thereby adhered to the contact surface  55 . 
     The clamping tool  90  shown in  FIG. 12  may be used for this purpose. In the representative configuration, the clamping tool  90  includes a pair of spring-biased arms  94  and  95  connected at a pivot point P 1  and biased by a return spring  92 . The stack  80  of  FIG. 11  may be inserted between an anvil  91  and an apply mechanism  97 . In the illustrated embodiment of the clamping tool  90 , an outer surface  57  of the fastener head  50 - 2  shown in  FIG. 11  rests against a surface  910  of the anvil  91 , with the plunger  82  likewise resting against a surface  197  of the apply mechanism  97 . The apply mechanism  97  may define a pocket  96  within which the spool  81  of  FIG. 11  is received and retained. 
     In order to attach one of the sacrificial RF tags  26  from the stack  80  to the fastener body  50 , an operator would insert the fastener body  50  into the stack  80 , which is prepositioned within the pocket  96 . Thereafter, the operator would gently squeeze together distal ends (not shown) of the spring-biased arms  94  and  95  to compress the return spring  92 . This compressing action in turn creates an apply force (arrows FA) that compresses the stack  80  between the surfaces  910  and  197 . A sacrificial RF tag  26  located adjacent to the fastener head  50 - 2  of  FIG. 11 , with its adhesive material  40  facing the contact surface  55 , is thus adhered to the contact surface  55 . The next sacrificial RF tag  26  in the stack  80  of  FIG. 11  is then in position to be applied to another fastener body  50  once the latter is inserted into the stack  80 . When the operator releases pressure on the arms  94  and  95 , the return spring  92  forces the arms  94  and  95  apart again via a return force (arrow FR). 
     Referring again to  FIG. 10 , once the sacrificial RF tag  26  has been adhered to the contact surface  55 , the method next includes exciting the Rx receiver trace  234  at a predetermined interrogation frequency using the RF interrogation signal  30 , which occurs by virtue of the RF tracking circuit  60  being brought into proximity of the sacrificial RF tag  260 , i.e., of the above-described fastener accessory  70 . The method also includes frequency-modulating the interrogation frequency using the RF modulating circuit  238  aboard the sacrificial RF tag  260 , which as described above causes oscillation to occur at the predetermined response frequency. The method thereafter includes transmitting the RF response signal  130  at the predetermined response frequency via the Tx antenna trace  236 . The RF response signal  130  is ultimately detected using an RF tracking device, e.g., the representative RF tracking circuit  60  of  FIG. 10  or a similar setup, to thereby locate the fastener body  50  within the search area. 
     After detecting the RF response signal  130  in this manner, the method may include installing the fastener body  50 , e.g., to the component  65  of  FIG. 9 . Such an action includes applying the installation force to the fastener body  50  to plastically destroy or plastically deform the sacrificial RF tag  26  to a level sufficient for preventing transmission of the RF response signal  130 . 
     Those skilled in the art will appreciate that various other embodiments of the method may be envisioned for locating the fastener body  50  within a search area. For example, alternative methods may include adhering the sacrificial RF tag  26  to the fastener body  50  using the dielectric adhesive material  40  of  FIG. 4A , with the sacrificial RF tag  26  containing the antenna array  32  of  FIG. 2 . Within the search area, the method may include exciting the Rx antenna trace  34  of the antenna array  32  after adhering the sacrificial RF tag  26  to the fastener body  50 , including directing the calibrated RF interrogation signal  30  with its excitation or interrogation frequency from the RF tracking circuit  60  or another handheld RF tracking device into the search area. 
     After exciting the Rx antenna trace  34 , the method may include receiving the RF response signal  130 , with its predetermined response frequency, from the Tx antenna trace  36  using the handheld RF tracking circuit  60 . Exemplary embodiments include transmitting the RF interrogation frequency  30  at a fixed frequency, e.g. 10 MHz, and receiving the RF response signal at a different frequency, e.g., 100 MHz. The method then proceeds by using the RF response signal  130  to locate the fastener body  50  within the search area, with the RF response signal  130  being characterized by an absence of data as noted above. 
     The method in this embodiment may include installing the fastener body  50  to a component of an aircraft or a spacecraft, e.g., the component  65  of  FIG. 9 , by applying the apply force to the fastener body  50 . The apply force plastically deforms the sacrificial RF tag  26  to a level sufficient for preventing further transmission of the RF response signal  130 . Adhering the sacrificial RF tag  26  to the fastener body using the dielectric adhesive material  40  as part of the method may include loading the stack  80  of the sacrificial RF tags  26 , as shown in  FIGS. 10 and 11 , into the clamping tool  90  of  FIG. 11 . In a representative embodiment, the clamping tool  90  includes the anvil  91  and spring-biased arms  94  and  95 , such that the method includes manually clamping the sacrificial RF tag  26  from the stack  80  directly onto the fastener body  50  using the clamping tool  90 . 
     As will be appreciated by those skilled in the art in view of the foregoing disclosure, the sacrificial RF tag  26  in its various embodiments may be attached to relatively expensive fastener bodies  50 , e.g., those constructed of titanium for aviation or aerospace uses, as well as to relatively inexpensive constructions such as aluminum and plastic. Likewise, the fastener bodies  50  may be of different configurations inclusive of rivets, threaded screws, nuts, and bolts, washers, and other small and easily dropped or misplaced fastener hardware. 
     The size and shape of the sacrificial RF tag  26  may likewise vary with the configuration of the fastener body  50  to which the sacrificial RF tags  26  are attached. Representative tag types and applications suitable for aviation use in non-limiting embodiments include planar annular/donut tags for use with any of the above fastener bodies  50 , circular sleeve tags having an extended axial length to wrap around the externally-threaded shaft  50 - 1 , line tags for use with rivet stems, ground straps, zip tie tails, etc., and beveled or conical angle tags for rivets, screws, conical washers, collars, and similar fastener bodies  50 . Regardless of the size, shape, and materials of construction of the fastener body  50 , instances of FOD may be greatly reduced using the above-described tracking solutions and associated hardware, with the sacrificial construction rendering the underlying sacrificial RF tag  26  inoperable, thus eliminating post-installation false alarms and errant signal transmission. These and other benefits will be readily appreciated by those skill in the art in view of the foregoing disclosure. 
     While some of the best modes and other embodiments have been described in detail, various alternative designs and embodiments exist for practicing the present teachings defined in the appended claims. Those skilled in the art will recognize that modifications may be made to the disclosed embodiments without departing from the scope of the present disclosure. Moreover, the present concepts expressly include combinations and sub-combinations of the described elements and features. The detailed description and the drawings are supportive and descriptive of the present teachings, with the scope of the present teachings defined solely by the claims.