Subsurface patterning for diffraction-based strain measurement and damage detection in structures.

Abstract

To provide non-destructive inspection techniques for assessing strain in structural components.SOLUTION: A structural component 10 has a geometric pattern 12 of grooves 14 within the structural component 10, with the grooves in the geometric pattern 12 each having a groove width. A method for assessing strain in the structural component 10 comprises: projecting beams 142 of electromagnetic (EM) energy, where the beams 142 are transmitted through the structural component 10 to reach the geometric pattern 12 of the grooves 14 so as to create diffracted beams 144 of EM energy that are reflected from or transmitted through the geometric pattern 12 of the grooves 14, the diffracted beams 144 having diffracted wavelengths indicating changes in the groove widths due to strain caused when the structural component 10 is exposed to environmental conditions; detecting the diffracted wavelengths of the diffracted beams 144; and correlating the diffracted wavelengths of the diffracted beams 144 with the strain in the structural component 10.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present disclosure relates generally to non-destructive testing (NDI) of structural components, and more particularly to systems and methods for utilizing geometrically patterned grooves within a structural component to diffract invisible electromagnetic (EM) energy and produce a detectable change in the wavelength of the EM energy reflected or transmitted by the grooves, thereby indicating strain in the structural component and thereby detecting strain in the structural component caused by exposure to environmental conditions. [Background technology]

[0002] Many mechanical systems, such as commercial vehicles, manufacturing equipment, or other industrial systems, can be exposed to particularly energetic environmental conditions, including vibration, extreme temperatures, shock, and mechanical stress. For example, aircraft, even while grounded, can be subjected to significant stresses during loading and unloading of cargo, as well as impacts from support vehicles and ground support equipment. Stresses and impacts can also occur during flight, takeoff, and landing due to shifting or improperly secured cargo, or collisions with objects. Furthermore, some structural components can be thermally stressed when exposed to high temperatures. For example, some composite materials can be subject to thermal degradation, which can impair the mechanical properties of the composite, such as flexural strength, post-crash compression, and interlaminar shear strength.

[0003] Therefore, selected components in various industrial systems are typically subjected to periodic inspection and evaluation throughout their operational life. Even when the effects of environmental conditions on a structural component are not visually detectable, the integrity of the component may be compromised. Therefore, there is a need for non-destructive testing techniques that can indicate the cumulative effects on a structural component after it has been exposed to environmental conditions, such as repeated loads, impacts, and high temperatures, during operation. Such indications allow for timely scheduling of future evaluation, maintenance, and / or replacement of the structural component. Summary of the Invention

[0004] In one aspect of the present disclosure, a multilayer component is disclosed. The multilayer component can include a first outer layer, a second outer layer, and a first pattern layer disposed between the first and second outer layers. The first pattern layer includes a first geometric pattern of grooves on a first surface thereof, the grooves of the first geometric pattern including a first set of grooves, each having a first groove width. A first incident beam of EM energy having a first wavelength corresponding to the first groove width is diffracted upon striking the first set of grooves to form a first diffracted beam of diffracted EM energy having a first diffracted wavelength, the first diffracted wavelength indicating a change in the first groove width due to strain induced when the multilayer component is exposed to environmental conditions. At least one of the first and second outer layers is formed of an outer layer material that is transparent to the first incident beam of EM energy and the first diffracted beam of diffracted EM energy.

[0005] In another aspect of the present invention, an inspection system for assessing strain in a structural component is disclosed. The inspection system can include a first geometric pattern of grooves and a first EM energy source. The grooves in the first geometric pattern include a first set of grooves disposed within the structural component, each groove having a first groove width, and the first EM energy source projects a first incident beam of electromagnetic energy at a first wavelength corresponding to the first groove width. When the first incident beam of EM energy is projected onto the structural component, When the first EM energy source projects the first incident beam of EM energy onto the structural component, the first incident beam of EM energy passes through the structural component to the grooves of the first geometric pattern and is diffracted by the first set of grooves to form a first diffracted beam of diffracted EM energy having a first diffracted wavelength, the first diffracted wavelength indicative of a change in the first groove width due to strain when the structural component is exposed to an environmental condition. The inspection system may further include an EM energy detector and a processor. The EM energy detector detects the first diffracted wavelength of the first diffracted beam of EM energy from the first set of grooves when the first EM energy source projects the first incident beam of EM energy onto the structural component, and the processor is operatively connected to the EM energy detector and configured to receive the first diffracted wavelength of the first diffracted beam of diffracted EM energy by the EM energy detector and associate the first diffracted wavelength with the strain in the structural component.

[0006] In a further aspect of the present disclosure, a method for assessing strain in a structural component is disclosed. The structural component can have a first geometric pattern of grooves therein. The grooves of the first geometric pattern include a first set of grooves, each having a first groove width. The method for assessing strain can include projecting a first incident beam of EM energy through the structural component to the grooves of the first geometric pattern. The first incident beam of EM energy has a first wavelength corresponding to the first groove width, and the first set of grooves diffract the first incident beam of EM energy to form a first diffracted beam of diffracted EM energy having a first diffracted wavelength, the first diffracted wavelength indicative of a change in the first groove width due to strain when the structural component is exposed to an environmental condition. The method for assessing strain may further include detecting a first diffraction wavelength of the first diffracted beam of EM energy from the first set of grooves when the first incident beam of EM energy is incident on the structural component, and relating the first diffraction wavelength of the first diffracted beam of EM energy from the grooves of the first geometric pattern to a strain in the structural component.

[0007] Further aspects of the present application are defined by the claims. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an isometric view illustrating structural components of a mechanical system having grooves in a geometric pattern according to the present disclosure. FIG. [Figure 2] 2 is a partial cross-sectional view showing the structural component of FIG. 1 having grooves in a geometric pattern. [Figure 3] 10A-10C are partial cross-sectional views illustrating alternative embodiments of structural components having grooves in alternative geometric patterns. [Figure 4] 10A-10C are partial cross-sectional views illustrating further embodiments of structural components having grooves with different geometric patterns. [Figure 5] 1 is an isometric view illustrating structural components of a mechanical system having multiple layers and multiple geometric patterns of grooves according to the present disclosure. FIG. [Figure 6] 6 is a partial cross-sectional view of the structural component of FIG. 5 having an exemplary configuration of grooves in a plurality of geometric patterns. [Figures 7A-7G] 2 is a plan view illustrating an embodiment of a geometric pattern of grooves in the structural component of FIG. 1 in accordance with the present disclosure. [Figure 8] 1 is an isometric view of a portion of a structural component having a patch with a geometric pattern of grooves attached thereto in accordance with the present disclosure. FIG. [Figure 9] FIG. 1 is a block diagram illustrating electronic and control components for performing inspection of structural components according to the present disclosure. [Figure 10] 2 is a schematic diagram illustrating an exemplary embodiment of an inspection system and method for the structural component of FIG. 1 according to the present disclosure. [Figure 11] 2 is a schematic diagram illustrating an exemplary alternative embodiment of an inspection system and method for the structural component of FIG. 1. [Figure 12] FIG. 10 is a flow diagram illustrating an embodiment of a testing routine according to the present disclosure. [Figure 13] FIG. 10 is a flow diagram illustrating an alternative embodiment of a testing routine according to the present disclosure. [Figure 14] 1A-1C illustrate exemplary strain pattern displays according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1 and 2 illustrate a portion of a structural component 10 of a mechanical system configured for use in the NDI systems and NDI methods shown and described herein. The structural component 10 is any component in a mechanical system that may be exposed to environmental conditions that may cause stresses and strains in the structural component 10. For use in the NDI systems and NDI methods of the present disclosure, the structural component 10 has a geometric pattern 12 of grooves 14 formed therein. In the exemplary embodiment, the structural component 10 has a multi-layer structure having the geometric pattern 12 of grooves 14 formed therein. The structural component 10 includes a first outer layer 16, a second outer layer 18, and a first pattern layer 20 disposed between the outer layers 16 and 18. The geometric pattern 12 of grooves 14 is formed in the surface of the first pattern layer 20, which is covered by the second outer layer 18. This keeps the geometric pattern 12 hidden from view and protected from external elements that may scratch or damage the grooves 14 .

[0010] FIG. 2 illustrates a cross-section of the structural component 10 of FIG. 1. A first patterned layer 20 is disposed on the first outer layer 16. A second outer layer 18 overlies the first patterned layer 20 and the geometric pattern 12 of grooves 14. The grooves 14 and geometric pattern 12 are configured to produce a strain-sensitive detectable change in the wavelength of the EM energy reflected or transmitted by the grooves 14 of the geometric pattern 12 in response to EM energy outside the visible spectrum projected thereon. The reflected or transmitted EM energy is detected by a suitable detector, as described below. The detectable change in the wavelength and frequency of the reflected or transmitted EM energy is then identified by a processor and compared to a baseline value for the EM energy wavelength. This baseline value is the value that would be expected if the structural component 10 were not subjected to stresses and strains that may be caused by environmental conditions.

[0011] In the exemplary embodiment, grooves 14 are arranged with a groove width WG and groove separation distance DG to produce diffraction when EM energy having a corresponding wavelength is projected onto structural component 10. The wavelength of the projected EM energy is typically outside the visible range, between about 400 nm and 750 nm, unless outer layers 16, 18 are formed of a material that is visually transparent to EM energy in the visible range. Diffraction of the applied EM energy produces a detectable change in the diffracted wavelength of the reflected or transmitted EM energy. This change occurs as the groove width WG changes due to strain in structural component 10.

[0012] The groove width W G determines the optimal spectral range of EM energy that can be applied to the geometric pattern 12. Generally, the geometric pattern 12 does not diffract EM energy having a wavelength greater than twice the groove width W G. Examples of wavelength, frequency, and groove width W G combinations that can be used with the systems and methods of the present disclosure are as follows: [Table 1]

[0013] The combination of wavelength and groove width W G is selected so that, when EM energy is applied, geometric pattern 12 reflects or transmits EM energy having a corresponding diffracted wavelength without causing distortion in structural component 10 that changes groove width W G. When structural component 10 is exposed to environmental conditions that cause distortion, which increases or decreases groove width W G , the diffracted wavelength of EM energy reflected or transmitted by geometric pattern 12 shifts from one diffracted wavelength to another across the EM energy spectrum. Depending on the configuration of structural component 10, geometric pattern 12, and the environmental conditions to which structural component 10 is exposed, the change in groove width W G and the corresponding change in diffracted wavelength may be uniform throughout geometric pattern 12 or may be greater in some areas, indicating greater concentrations of stress and strain in those areas. The amount of distortion and the corresponding change in groove width W G and diffracted wavelength may be acceptable without requiring further inspection, or a significant change may indicate further inspection, maintenance, and / or replacement of structural component 10. Those skilled in the art will appreciate that the initial groove width WG and wavelength are set such that the groove width WG does not exceed two wavelengths before strains worthy of further investigation are induced in the structural component 10.

[0014] The embodiment of structural component 10 in Figures 1 and 2 illustrates a configuration in which outer layers 16, 18 and first pattern layer 20 are made of multiple different materials. Outer layers 16, 18 are formed of a composite material that is transparent to EM energy having a wavelength corresponding to the groove width WG of grooves 14, for example. Meanwhile, first pattern layer 20 is formed of a material that is opaque to the wavelength of EM energy. In this configuration, EM energy of the appropriate wavelength transmitted from an EM energy source passes through second outer layer 18 without diffraction and is diffracted and reflected from the geometric pattern 12 of first pattern layer 20, with the diffracted wavelengths being detected by an appropriate EM energy detector.

[0015] 1 and 2, the geometric pattern 12 of grooves 14 is provided throughout the entire extent of the structural component 10, with the first pattern layer 20 being generally centrally located within the structural component 10. However, other configurations and arrangements of the geometric pattern 12 of grooves 14 are contemplated. For example, the geometric pattern 12 may be configured to distribute stresses on the structural component 10, such as in areas of the structural component 10 where high stress concentrations are expected. The geometric pattern 12 may be positioned in areas that provide the most relevant information about the structural components 10, such as openings in the structural component 10 for routing wiring, piping, conduits, etc., corners, and bond lines where the structural component 10 engages or connects to other components in a mechanical system or where patches are applied to repair the structural component 10. In the latter areas, the layers 16-20 and the geometric pattern 12 may be configured so that the geometric pattern 12 is positioned at or near the contact points with other components or patches, as long as the connections and structural integrity of the mechanical system are maintained.

[0016] Alternatively, the structural component having the geometric pattern of grooves can be configured to diffract EM energy and then reflect or transmit the diffracted EM energy ("diffracted EM energy"). Figure 3 shows a first outer layer 32, a second outer layer 34, and a wire mesh, such as a wire mesh scrim 36 or conductive scrim. An alternative embodiment is shown in which a structural component 30 is formed with a first patterned layer 36 formed with a wire mesh. The wire mesh provides lightning strike protection or suppression in aircraft or other environments where the structural component 30 may be exposed to electrostatic discharge. The wire mesh scrim 36 has a geometric pattern 38 formed by interweaving a first set of wires 40 oriented in a first direction with a second set of wires oriented in a second direction (e.g., perpendicular to the first direction). As shown in FIG. 3 , the wire spacing between the first set of wires 40, the wire spacing between the second set of wires 42, and the thicknesses of the wires 40, 42 define groove widths WG and groove separations DG in the geometric pattern 38.

[0017] In some embodiments, the groove width W and groove separation DG may be the same in both directions. In other embodiments, the thickness and spacing of the first set of wires 40 may be different from the thickness and spacing of the second set of wires 42 so that different wavelengths of EM energy are diffracted by each set of wires 40, 42. Using this approach on an aircraft fuselage, for example, the first set of wires 40 may be configured to diffract EM energy in the near-infrared band to indicate hoop stress around the fuselage, while the second set of wires 42 may be configured to diffract EM energy in the far-infrared band to indicate tensile, compressive, or torsional stresses along the fuselage. The orientation of each set of wires 40, 42 may be set at an angle relative to each other other than perpendicular as shown and described herein, depending on the stress being monitored.

[0018] The spacing between the wires 40, 42 defines grooves in the geometric pattern 38, providing flexibility in determining where diffracted EM energy is detected. In one embodiment, the first outer layer 32 can be formed of a material that reflects EM energy, and the second outer layer 34 can be formed of a material that is transparent to EM energy. In this configuration, the EM energy source and the EM energy detector can be positioned on the second outer layer 34 side of the structural component 30. EM energy transmitted by the EM energy source passes through the second outer layer 34, is diffracted by the geometric pattern 38 formed by each pair of wires 40, 42, is reflected by the first outer layer 32, and is detected by the EM energy detector. In an alternative embodiment, both outer layers 32, 34 can be formed of a material that is transparent to the projected and diffracted EM energy. In this configuration, EM energy transmitted through one side of the structural component 30 is diffracted by the geometric pattern 38 formed by each pair of wires 40, 42, and the diffracted EM energy is transmitted through the other side of the structural component 30. In this manner, an EM energy source and an EM energy detector can be located on opposite sides of the structural component 30. This configuration may be advantageous for limited access inspections. The beam of EM energy may be generated by an appropriately sized transmitter located in a hard-to-reach space, or the diffracted EM energy may be generated by a suitable transmitter located in the hard-to-reach space. The diffracted EM energy may be manually or automatically guided into the space, and detected on the more accessible side of the structural component 30. Of course, the respective locations of the EM energy source and the EM energy detector may be reversed depending on the requirements of a particular embodiment.

[0019] FIG. 4 illustrates another alternative structural component 50 according to the present disclosure. In the structural component 50, a first outer layer 52 and a second outer layer 54 surround a first patterned layer 56, which is formed of a plurality of parallel wires or rods 58 forming a geometric pattern 60. The wires 58 can be used for lightning strike protection, as described above. Additionally, stronger wires or rods 58 can be used as mini-rebar to provide additional support for the structural component 50. Similar to the first set of wires 40, the size and spacing of the wires 58 can be varied to achieve the desired groove width WG and groove separation distance DG, thereby establishing the EM energy wavelength used. Additionally, the materials of the outer layers 52, 54 can be selected to reflect EM energy or to allow diffracted EM energy to be transmitted through the structural component 50.

[0020] It should be noted that various manufacturing methods can be employed to realize the structural component 10, 30, 50 and other embodiments described herein. For example, the outer layer may be a composite material fabricated using known manufacturing techniques. The patterned layer 20, 36, 56 may be formed of a metal or other material that diffracts EM energy and may be provided at the appropriate time and location during the placement of the composite material in forming the structural component 10, 30, 50. In an alternative process, the structural component 10, 30, 50 may be fabricated using other additive manufacturing techniques, such as three-dimensional (3D) printing. The 3D printer may be configured to provide multiple different materials for the structural component 10, 30, 50 at the appropriate time. Thus, a reflective or transparent material may be provided to form the first outer layer 16, 32, 52. At the appropriate time, material for the patterned layers 20, 36, 56 may be provided and formed to form the geometric patterns 12, 38, 60. In the case of the structural component 30, 50, material for the first outer layer 32, 52 or the second outer layer 34, 54 may be provided to fill the spaces between the wires 40, 42, 58. Finally, material for the second outer layer 18, 34, 54 is added to complete the construction of the structural component 30, 50. Note that although the first outer layer 32, 52 and the second outer layer 34, 54 are shown as separate layers, those skilled in the art will understand that additive manufacturing techniques can be used to fabricate the structural component 30, 50 as a single structure of homogenous material without any distinct layers other than the patterned layers 36, 56 in which the wires 40, 42, 58 are embedded. Still additional methods for making the structural components 10, 30, 50 according to the present disclosure are envisioned by the inventors.

[0021] In some embodiments, the wire 58 may be implemented as an induction susceptor, which functions to facilitate fabrication of the structural component 50 and to form grooves in the geometric pattern 60 after fabrication is complete. The induction susceptor may be positioned along the bond line to both create a bond between the outer layers 52, 54 and provide a means for monitoring stress and strain at the bond line. In one embodiment, the susceptor may be approximately 0.008 inches to 0.010 inches in diameter, with a center-to-center spacing of approximately twice the wire diameter. The induction susceptor wire is first embedded in neat resin to form a screen that is placed at the bond line. The wire is then used to weld the thermoplastic structure together by rapid heating via electromagnetic induction. Once the bond and structural component are fabricated, the internal wire is first inspected using an inspection process according to the present disclosure to determine its initial baseline diffraction response to EM energy. The structural component 50 is then exposed to normal environmental conditions. The changes in stress and strain at the bond line are checked periodically during installation or after exposure to unexpected loading conditions.

[0022] 5 and 6 illustrate an alternative embodiment of a structural component 70. The structural component 70 has multiple geometric patterns 72, 74 of grooves 76, 78 at various depths to indicate strain at different locations within the structural component. The structural component 70 includes a first outer layer 80, a second outer layer 82, and an intermediate layer 84 disposed therebetween. A first patterned layer 86 having a first geometric pattern 72, similar to the patterned layers described above, is disposed between the first outer layer 80 and the intermediate layer 84. A second patterned layer 88 having a second geometric pattern 74 is disposed between the intermediate layer 84 and the second outer layer 82. As shown, the first geometric pattern 72 is formed by multiple wires or rods 90 aligned in a first direction, and the second geometric pattern 74 is formed by multiple wires or rods 92 oriented in a second direction.

[0023] In this laminate structure, the materials of layers 80, 82, and 88, the groove width W, and the groove separation DG are selected so that EM energy diffracted by first geometric pattern 72 of grooves 76 is transmitted undiffracted by layers 80, 82, and 84 and second geometric pattern 74 of grooves 78, thereby providing useful strain measurements. Generally, lower frequency EM energy, having longer wavelengths, is incident deeper into structural component 70 than higher frequency EM energy, having shorter wavelengths. Thus, in the illustrated example, first geometric pattern 72 of grooves 76 is configured to diffract EM energy in the terahertz, microwave, or ultrasonic ranges, while second geometric pattern 74 of grooves 78, closer to the surface of second outer layer 82, is configured to diffract higher frequency EM energy in the ultraviolet or infrared ranges. In this configuration, the wavelengths of EM energy in the terahertz, microwave, and ultrasonic bands are longer than twice the groove width W of grooves 78 in second geometric pattern 74, allowing the EM energy to transmit through grooves 78 without diffraction on its way to first geometric pattern 72. The transmission of either type of EM energy through structural component 70 can be enhanced by increasing the intensity of the EM energy projected onto structural component 70. In an alternative embodiment, geometric patterns 72, 74 may be located in non-laminated regions of structural component 70 to prevent EM energy for one of geometric patterns 72, 74 from impinging on the other of geometric patterns 72, 74 as the EM energy transmits through structural component 70.

[0024] The appropriate geometric pattern for a structural component is determined by the characteristics of the structural component, the environmental conditions the structural component is expected to encounter, the results of development testing, knowledge of structural components in the art, and other factors. Figures 7A-7G show several examples of geometric patterns 12A-12G that may be optionally formed within a structural component. Figure 7A shows an example of a one-dimensional geometric pattern 12A formed by a series of parallel, linear grooves 14A. The linear geometric pattern 12A is suitable for cylindrical structural components, such as pipes (not shown), which are subject to circumferential, or hoop, stresses but little axial stress. The geometric pattern 12A can be wrapped around the cylindrical structural component with the grooves 14A parallel to the longitudinal axis of the component, so that strain due to the hoop stress widens the circumferential groove width W between the grooves 14A.

[0025] FIG. 7B shows an example of a two-dimensional geometric pattern 12B formed by a plurality of square or rectangular grooves 14B. The square or rectangular grooves 14B define a plurality of areas in order from a small area area to a large area area area, and are arranged concentrically to form the geometric pattern 12B. The rectangular geometric pattern 12B may have, for example, a rectangular opening 22 therethrough. 7C shows an example of an alternative two-dimensional geometric pattern 12C formed by a plurality of concentric grooves 14C defining regions in an order ranging from small to large area. Circular geometric patterns 12C can be used in structural components 10 where stress on the structural component 10 is directed radially outward from a center point of the geometric pattern 12C. FIG. 7D shows a further example of a geometric pattern 12D having concentric grooves 14D with more complex geometries corresponding to the shapes of openings or other components extending from the structural component 10. Additional irregular shapes are contemplated based on the needs of a particular implementation of the structural component 10.

[0026] 7E shows an example of a further alternative two-dimensional geometric pattern 12E having multiple grooves 14E extending radially outward from a center point 24. Geometric pattern 12E may be an alternative to geometric pattern 12C when hoop stresses are greater than radial stresses. FIG. 7F shows a geometric pattern 12F formed by multiple parallel curvilinear grooves 14F. Curvilinear grooves 14F may follow the contour of a curved component extending through structural component 10, such as an aircraft wing.

[0027] In some embodiments, the structural component 10 may have a region of interest that is desirably more sensitive to strain and changes in groove width W. In this case, the region of interest can be distinguished by varying the spacing between grooves 14, the groove width W, and the overall wavelength of the structural component 10. FIG. 7G illustrates a geometric pattern 12G, a variation of the circular geometric pattern 12C of FIG. 7C, in which the groove separation distance DG between adjacent grooves 14G increases as the geometric pattern 12G expands outward from a central location where radial stresses are to be more carefully examined. Regions with shorter groove separation distances DG and more grooves 14G concentrated together are more sensitive to strain and changes in groove width W. Such regions have a greater effect on the diffracted wavelength of reflected or transmitted EM energy for EM energy projected into the region of interest than regions where the grooves 14G have longer groove separation distances DG and are spaced farther apart.

[0028] As another alternative that may provide a more sophisticated strain indicator, geometric pattern 12 may have multiple sets of grooves 14 with different groove widths W and positioned at multiple angles relative to each other to independently monitor different levels or types of strain on the structural component. For example, geometric patterns 12C and 12E may be combined into a single geometric pattern 12 on the structural component. Circular geometric pattern 12C may be formed with a groove width W within a range that affects EM energy in the ultraviolet range, and geometric pattern 12E may be formed over geometric pattern 12C with a groove width W within a range that affects EM energy in the mid-infrared range. During inspection, radial strain can be determined by projecting EM energy in the ultraviolet range onto the structural component, and circumferential strain can be determined by projecting EM energy in the mid-infrared range onto the structural component. Alternate or additional geometric patterns 12 as shown and described herein can be further formed by using various groove widths W and corresponding wavelengths of EM energy in the structural component to test additional distortion patterns as needed in a particular embodiment.

[0029] 8 illustrates an embodiment in which a patch 102 is attached to a damaged area of ​​a structural component 100. The patch 102 has a shape suitable for covering the damaged area and is attached to the structural component 100 by rivets, welding, adhesives, lamination, or other suitable attachment means. The patch 102 includes a geometric pattern 12C, such as that shown in FIG. 7C, at or near the bond line between the structural component 100 and the patch 102. After the patch 102 is installed, it can be inspected using the systems and methods disclosed herein. In addition to detecting strain in the patch 102, the inspection can also assess the integrity of the patch 102's attachment to the structural component 100. If the patch 102 is properly attached to the structural component 100, stresses from the structural component 100 will be transferred to the patch 102, resulting in corresponding strains upon inspection. If the patch 102 is not properly attached, such as due to a delamination, the stresses will not be transferred, and inspection of the patch 102 will reveal lower than expected strains in the patch 102. In such cases, further inspection may be performed or the patch 102 may be reattached to the damaged area.

[0030] The geometric patterns 12 shown and described herein can be incorporated into an inspection system 110 for assessing strain in a structural component 10. FIG. 9, for example, illustrates an exemplary arrangement of electrical and control components that can be incorporated into an inspection system 110 according to the present disclosure that can identify strain in the structural component 10. The controller 112, using software stored therein, can process information received from the monitoring and control devices and output command and control signals to the devices of the monitoring system 110. The controller 112 can include a processor 114 for executing specific programs that control and monitor various functions associated with the monitoring system 110. The processor 114 is operatively connected to a memory 116, which can include a read-only memory (ROM) 118 for storing programs and a random access memory (RAM) 120 that serves as a working memory area used to execute the programs stored in the ROM 118. It is noted that although a processor 114 is illustrated, it is contemplated that other electronic components, such as a microcontroller, an application specific integrated circuit (ASIC) chip, or any other integrated circuit device, may be used.

[0031] Although the description herein is directed to the functionality of the monitoring system 110, the controller 112 may be configured to control other operational aspects of other systems. Furthermore, the controller 112 may refer collectively to multiple control and processing devices to which the functionality of the monitoring system 110 and other systems is allocated. For example, some of the functionality of the monitoring system 110 may be performed by a remote computing device 122 having a controller 124 operatively connected to the controller 112 by a communications module 126 of the monitoring system 110. The remote computing device 122 may be located at a centralized location of an enterprise utilizing the monitoring system 110 to perform inspections of mechanical systems. The controllers 112, 124 are operatively connected to receive and transmit information as needed to control the operation of the monitoring system 110. Other variations of integrating and distributing the processing of the controllers 112, 124 described herein are contemplated for use in the monitoring system 110 consistent with the present disclosure.

[0032] The monitoring system 110 may further include one or more EM energy sources 128, 130 capable of projecting EM energy at a predetermined wavelength corresponding to, for example, the groove width WG of the grooves 14 in the geometric pattern 12. The EM energy sources 128, 130 receive control signals from the processor 114, which cause the EM energy sources 128, 130 to project EM energy at the predetermined wavelength. In some embodiments, each EM energy source 128, 130 can project EM energy at one wavelength. In other embodiments, each EM energy source 128, 130, or a single EM energy source, can project EM energy at multiple different wavelengths. While the EM energy sources 128, 130 are shown and described as being operatively connected to the processor 114, those skilled in the art will understand that the EM energy sources 128, 130 may be stand-alone devices having associated input devices, such as an on / off switch, wavelength selection input, etc., for manual control of operation by an operator performing the inspection. It is also possible.

[0033] The monitoring system 110 may also include an EM energy detector 132 operatively connected to the processor 114. The EM energy detector 132 may be any device capable of detecting diffracted wavelengths of EM energy reflected or transmitted at the geometric pattern 12 when EM energy from the EM energy sources 128, 130 is projected onto the geometric pattern 12. In the embodiments described herein, the EM energy detector 132 may be an optical detector capable of detecting diffracted wavelengths of reflected or transmitted EM energy. For example, the EM energy detector 132 may be a charge-coupled device (CCD) camera, a video camera, photographic film, or other EM energy sensitive device. When activated by the processor 114 or manually activated via an appropriate input device, the EM energy detector 132 may capture diffracted EM energy and transmit an indication of the diffracted wavelength of the detected diffracted EM energy to the processor 114. The processor 114 may receive the diffracted wavelengths and store the wavelengths in the memory 116. Those skilled in the art will appreciate that detecting the wavelength or frequency of diffracted EM energy and determining changes in diffracted wavelength or frequency can be accomplished using alternative mechanisms as desired or required in particular embodiments of the systems and methods described herein, and the use of such alternative mechanisms is contemplated by the inventors. It should be noted that other mechanisms for detecting and analyzing the diffracted wavelength of diffracted EM energy can be used to equivalent effect in the systems and methods of the present disclosure.

[0034] The monitoring system 110 may have one or more input devices 134 that can be adjusted by an operator to control the inspection process. The input devices 134 may include switches, buttons, a keyboard, a mouse, a touch screen, etc. that can receive input commands from an operator. Output devices 136, such as a monitor, screen, touch screen, speakers, printer, etc., can communicate information from the monitoring system 110 to the operator.

[0035] 10 illustrates an exemplary embodiment of monitoring system 110. Processor 114, EM energy source 128, and EM energy detector 132 are integrated into inspection workstation 140. Inspection workstation 140 may be, for example, a workstation at a maintenance facility for a mechanical system of which structural component 10 is a part. With structural component 10 positioned at inspection workstation 140, EM energy source 128 can be activated to project a beam of EM energy 142 at an appropriate wavelength onto geometric pattern 12. Projected beam 142 is diffracted and reflected by geometric pattern 12 to produce a beam of diffracted EM energy 144. EM energy detector 132 receives and detects beam of diffracted EM energy 144 and transmits the detected EM energy to processor 114, which analyzes the detected diffracted wavelength or frequency of reflected beam of EM energy 144 and associates it with a corresponding strain value. The processor 114 may be programmed with algorithms well known in the art to convert the detected wavelength or frequency into a strain value.

[0036] FIG. 11 illustrates an alternative embodiment of monitoring system 110 in which EM energy source 128 and EM energy detector 132 are components of a portable inspection device 150, with processor 114 and memory 116 located at a central inspection workstation 152. Portable inspection device 150 may be a laptop computer, tablet, smartphone, personal digital assistant, or other portable processing device. Portable inspection device 150 may further include a communications module 154 that communicates wirelessly with communications module 126 at the central inspection workstation to transmit detected color from EM energy detector 132. 10, EM energy is projected from an EM energy source 128 and detected by an EM energy detector 132.

[0037] 11 also illustrates an embodiment in which the EM energy source 130 is located on the opposite side of the structural component 10 from the portable inspection device 150. The EM energy source 130 may be permanently mounted in a hard-to-reach location within the mechanical system. As shown, the EM energy source 130 may project a beam of EM energy 142 onto the structural component 10 and the geometric pattern 12. The EM energy is diffracted by the grooves 14 in the geometric pattern 12 into a beam 144 that is transmitted through the structural component 10. The diffracted beam of EM energy 144 is received by an EM energy detector 132 on the opposite side of the structural component 10 from the energy source and processed by the processor 114.

[0038] 12 illustrates an exemplary inspection routine 160 that may be performed by the monitoring system 110 on the structural component 10, 30, 50, 70, 100. The routine 160 begins at block 162, where a structural component is created (e.g., manufactured) including a groove 14, 14A-14G having one or more of the geometric patterns 12, 12A-12G therein. The groove 14, 14A-14G is formed in the structural component using any suitable manufacturing technique. After the structural component having the geometric patterns 12, 12A-12G is created, control passes to block 164, where the EM energy source 128 projects a beam 142 of EM energy having a corresponding wavelength onto the structural component and the geometric patterns 12, 12A-12G. The EM energy in the projected beam 142 is diffracted by the grooves 14, 14A-14G, and corresponding EM energy having diffracted wavelengths is reflected or transmitted at or through the geometric pattern 12, 12A-12G. The reflected or transmitted beam 144 of EM energy may have multiple diffracted wavelengths that vary at different locations in the geometric pattern 12, 12A-12G due to variations in the groove width W G caused by strain in the structural component.

[0039] Once the beam of EM energy 142 projected onto the geometric pattern 12, 12A-12G is diffracted, reflected, or transmitted, control passes to block 166 where the diffracted beam of EM energy 144 is detected by an EM energy detector to determine the diffracted wavelength. The diffracted wavelength of the beam of EM energy 144 is temporarily or permanently stored in memory 116.

[0040] Once the beam of diffracted EM energy 144 is detected, control passes to block 168, where the monitoring system 110 determines whether EM energy having the last EM energy wavelength (if there are multiple) has been projected onto the geometric pattern 12, 12A-12G. As described above, some embodiments may include a first set of grooves 14, 14A-14G having a first groove width W G onto which a first beam of EM energy 142 having a first wavelength is projected, and a second set of grooves 14, 14A-14G having a second groove width W G onto which a second beam of EM energy 142 having a second wavelength is projected. In these embodiments, it may be necessary to project only a beam 142 having a single wavelength at a time. Thus, if it is determined in block 168 that the beam of EM energy 142 having various wavelengths was not projected onto the geometric pattern 12, 12A-12G, control returns to blocks 164, 166, where EM energy having one of the different wavelengths is projected from the EM energy source 128, 130 onto the geometric pattern 12, 12A-12G, as described above, and the diffracted wavelength of the beam of EM energy 144 for the projected beam 142 associated with that wavelength is detected.

[0041] Once the beams of EM energy 142 having all the required wavelengths have been projected and the diffracted beams of EM energy 144 have been detected in block 168, control passes to block 170 where the diffracted wavelengths of the beams 144 are related to strain in the structural component. As mentioned above, the processor 114 can be programmed with algorithms known in the art for converting the wavelengths of EM energy in the diffracted beams 144 into strain values.

[0042] Once the strain values ​​are calculated for the beam of diffracted EM energy 144 in block 170, control passes to block 172, which determines whether any of the strain values ​​calculated from the diffraction wavelengths of the beam of diffracted EM energy 144 exceed a predetermined minimum strain value. The minimum strain value is a value that, if exceeded, indicates the need for further inspection or maintenance. As explained, some level of strain in a structural component is acceptable. As an alternative, the current strain value may be compared to a baseline strain value obtained for the structural component prior to the mechanical system being placed into service and exposed to environmental conditions. The baseline strain value for the geometric pattern 12, 12A-12G, is established by projecting the beam 142 onto the structural component with no strain or with a known strain on the structural component and determining the resulting change in the diffraction wavelength of the beam 144. In other embodiments, portions of the geometric patterns 12, 12A-12G may be positioned in areas where distortion does not occur during exposure to environmental conditions, and the diffracted wavelengths associated with the distortion-free areas may establish a real-time dynamic baseline when the inspection is performed.

[0043] The current strain value is compared to a baseline or other predetermined strain value to determine whether the current strain value differs from the previous strain value by more than a minimum amount or percentage. If the strain value is equal to or less than the minimum strain value and no further testing is required, control passes to block 174, where the structural component is exposed to environmental conditions. This exposure occurs during normal use in the mechanical system's normal environment. If the mechanical system is in the development stage, the environmental conditions are applied in a test environment. After exposure in block 174, control passes to block 164, where another instance of testing the structural component is initiated. If the strain value is greater than the minimum strain value in block 172, the structural component may require further testing, maintenance, or replacement. If the strain value is greater than the minimum strain value in block 172, control passes to block 176, where further testing of the structural component is performed.

[0044] The inspection routine 160 of Figure 12 is an example of a quantitative process for assessing strain on the structural component 10, 30, 50, 70, 100 and identifying when further inspection, maintenance, or replacement is required. In some embodiments, it may be appropriate to replace or supplement the quantitative inspection routine 160 with a qualitative process in which the experience of the inspector performing the inspection is used to analyze strain patterns in the structural component 10, 30, 50, 70, 100 and identify anomalies in the strain patterns that may require further inspection. Figure 13 illustrates an exemplary qualitative inspection that may be performed on the structural component 10, 30, 50, 70, 100 by the monitoring system 110 and an inspector, engineer, or other inspection technician using the inspection system 110. The inspection routine 180 begins similarly to the inspection routine 160, where in block 162, the structural component 10, 30, 50, 70, 100 is fabricated with a geometric pattern 12, 12A-12G of grooves 14, 14A-14G, in block 162, a beam of EM energy 142 is projected onto the structural component 10, 30, 50, 70, 100 in block 164, the diffracted beam of EM energy 144 is detected in block 166, and in block 170, In this case, the diffraction wavelength of the beam 144 of diffracted EM energy is related to the strain of the structural component 10 , 30 , 50 , 70 , 100 .

[0045] To perform the inspection routine 180, the inspection system 100 may be modified in blocks 164, 166, and 170 to determine the position of the beam 142, 144 relative to the inspected structural component 10, 30, 50, 70, 100 as the beam 142 is projected onto the surface of the structural component 10, 30, 50, 70, 100. Known techniques may be used to determine the position and movement of a body or device, such as the structural component 10 as it moves relative to the inspection workstation 140 shown in FIG. 10 or the portable inspection device 150 shown in FIG. 11 as it moves across the surface of the structural component 10. The position information for the beam 144 of diffracted EM energy may be stored in memory 116 along with the diffracted wavelength detected in block 166 and the associated strain value determined in block 170.

[0046] After the diffracted wavelengths are detected and strain values ​​determined, or dynamically as the monitoring system 110 progresses with the inspection of the structural component 10, 30, 50, 70, 100, control passes to block 182, where the diffracted wavelengths, strain values, and position of the beam relative to the structural component 10, 30, 50, 70, 100 are used to generate and display a strain pattern for the inspected structural component 10, 30, 50, 70, 100. FIG. 14 shows an example display 200 of a strain pattern 202 derived from information obtained by the monitoring system 110. The display 200 may be any suitable visual display that provides a graphical representation of the strain in the structural component 10, 30, 50, 70, 100. For example, the display 200 may be a video display on one of multiple output devices 136 located at the inspection workstation 140, the portable inspection device 150, the central inspection workstation 152, or another location where the display 200 can be viewed by an inspector. In an alternative embodiment, the display 200 may be a print output by one of the plurality of output devices 136 in an appropriate location. Additionally, alternative visual display output devices 136 for displaying the strain pattern 202 will be apparent to those skilled in the art and are contemplated by the inventors herein.

[0047] The strain pattern 202 provides a visual indication of the distribution of strain values ​​throughout the inspected structural component 10, 30, 50, 70, 100. In the illustrated example, the display of the strain pattern 202 utilizes grayscale shading to indicate the location and magnitude of strain values ​​within the structural component 10, 30, 50, 70, 100. White or light gray tones, for example, may indicate areas of low strain, with darker gray tones as strain values ​​increase. The spacing between shaded regions indicates the degree of change in strain values ​​throughout the structural component 10, 30, 50, 70, 100. In an alternative embodiment, the strain pattern may be color-coded. For example, blue may correspond to low strain values, and the color may graduate in a color spectrum to red, indicating high strain values. In other embodiments, the strain pattern may be shown as lines of constant strain value having an appearance similar to a weather map showing barometric pressure changes, or a topographic map showing elevation changes. Further alternative depiction methods are also envisioned.

[0048] In some embodiments where a grayscale or color spectrum is used, a scale may be added to the display 200 to indicate strain values ​​corresponding to various tones or colors of the strain pattern 202. The display 200 may also display minimum values ​​in a minimum strain region 204 and maximum strain values ​​in a maximum strain region 206. The display 200 may display the strain pattern 202 overlaid on an image or graphical representation of the structural component 10, 30, 50, 70, 100 to more clearly indicate the location of the strain pattern on the structural component 10, 30, 50, 70, 100. By displaying it, the quality can be improved.

[0049] Once the strain pattern 202 is generated and displayed on the display 200 in block 182, control passes to block 184, where an inspector, maintenance person, or other technician can review the strain pattern 202 to determine whether the strain pattern 202 is normal for the environmental conditions to which the structural component 10, 30, 50, 70, 100 is exposed. The inspector may evaluate, in light of their experience inspecting the current structural component and / or other structural components, whether the strain pattern 202 has expected characteristics or whether the strain pattern 202 indicates a problem that may require further inspection. This evaluation may include reviewing baseline information collected for the structural component 10, 30, 50, 70, 100 of the types described above. The baseline information may be displayed in any suitable format. In some embodiments, the baseline information may be used to generate a baseline strain pattern, which is displayed on the display 200 as a complement to the real-time strain pattern 202 for visual comparison.

[0050] If the inspector determines in block 184 that the strain pattern 202 is normal and the strain values ​​shown in the strain pattern 202 are at or below the strain values ​​that indicate a problem and do not require further inspection, control passes to block 174, where the structural component is exposed to environmental conditions, as described above. After exposure in block 174, control passes back to block 164, where another instance of inspecting the structural component 10, 30, 50, 70, 100 is initiated. If the strain values ​​in the strain pattern 202 are different from, i.e., greater or less than, expected in block 184, the structural component 10, 30, 50, 70, 100 may require further inspection, maintenance, or replacement. If, at block 184, the strain pattern 202 is abnormal compared to the expected strain pattern of the structural component 10, 30, 50, 70, 100, control passes to block 176 where further testing of the structural component 10, 30, 50, 70, 100 is performed. As noted above, the qualitative testing routine 180 can be implemented as an alternative to or a supplement to the quantitative testing routine 160 shown in FIG. 12. INDUSTRIAL APPLICABILITY

[0051] Monitoring system 110 and routine 160 may have broad applications in assessing the structural integrity of structural components in mechanical systems. For example, monitoring system 110 and routine 160 may be used in applications such as monitoring a repair, such as patch 102 for structural component 100 shown in FIG. 8 , to ensure bond quality in the repair and to ensure the response of patch 102 to stresses and strains over time before replacing structural component 100. If geometric pattern 12C for patch 102 is created and positioned near the bond line between structural component 100 and patch 102 prior to application of patch 102 to structural component 100, the bond strain can be imaged and analyzed according to routine 160 to detect residual stresses in patch 102 and the bond quality of patch 102 to structural component 100. A baseline image of the patch 102, prior to exposing the structural component 100 to environmental conditions, can show initial strain in the patch 102 and structural component 100, and periodic imaging after exposing the structural component 100 to environmental conditions can monitor the quality and integrity of the bond and show degradation of the repair over time. Strain values ​​derived from the monitoring system 110 and routine 160 can be input into a finite element analysis (FEA) model of the patch 102 on the structural component 100 for analysis to evaluate the performance of the patch 102, future inspection schedules, approaches to NDI, and predicted maintenance and repairs. This makes it possible to plan management.

[0052] The monitoring system 110 and routine 160 can also be applied in structural testing environments. Manufacturers typically perform sub-scale, mid-scale, and full-scale structural testing of components and repairs to ensure proper performance in the field. Such testing can include static and dynamic loading conditions. Several technologies are currently used in this type of structural testing. For example, strain gauges are used as point sensors on structural components to monitor stress and strain during testing, but their effectiveness in detecting the location of damage to the structural component depends on where the strain gauges are located on the structural component. Digital image correlation (DIC) can be used to provide stream mapping in structural testing, but it is expensive to process, requires specialized expertise in operation, and requires the application of spot patterns on the surface. For this reason, DIC is used in structural testing only after careful consideration. The monitoring system 110 and routine 160 may be used as an alternative or a supplement to currently used testing techniques to monitor and measure real-time strain patterns throughout the application of test load conditions. The detected strain patterns can be used to correlate analytical models and / or to locate initial failure locations in the structural component under test. As with repair monitoring applications, providing strain information directly to FEA tools can provide real-time or load-level damage progression information. Information on damage initiation and propagation can be used to refine structural models of structural components or to modify the structural design.

[0053] The monitoring system 110 and routine 160 can be used to improve the manufacturing process of composite parts, which are becoming more prevalent in mechanical systems, particularly aerospace systems. During the manufacturing development, routine process monitoring, and fabrication of composite parts, it would be advantageous to identify and track strains within the part caused by fabricating the composite part. Internal strains can be tracked in the composite part using strain indicator plies that include geometric patterns 12, 12A-12G. To form the strain indicator plies, the geometric patterns 12, 12A-12G are applied to the resin of selected plies during the manufacturing process, either as an additional resin layer that is subsequently sprayed onto the plies that include the geometric patterns 12, 12A-12G, or as an applique that forms a peelable ply that is removed after the composite part has cured. The patterned strain indicator plies indicate residual stresses and strains that occur in the composite part due to the curing process. Information from the patterned strain indicator plies can be used to modify the manufacturing process of a composite part to reduce warpage, predict performance, and ensure that the manufacturing process is within specifications.

[0054] The monitoring system 110 and routine 160 can also be used to monitor the structural integrity of structural components located in restricted access areas of mechanical systems. Restricted access structures in aircraft and other mechanical systems are critical to structural integrity and may be subject to high loads. Testing the structural integrity of such restricted access structures may require costly disassembly and reassembly processes. During the manufacturing process, strain witness surfaces in the form of geometric patterns 12, 12A-12G of grooves 14, 14A-14G may be formed in strategic locations within the restricted access structural components. Optical or video borescopes, or The miniature camera and extension mechanism can function as the EM energy source 128 or 130 and the EM energy detector 132 in the surveillance system 110, and access is restricted. The diffracted wavelengths of EM energy transmitted through the geometric patterns 12, 12A-12G in a confined structure can be detected. For example, the diffraction wavelength data can be analyzed to detect component degradation and monitor slowly developing damage until repair is necessary. As discussed above in connection with FIG. 11 , either the EM energy source 130 or the EM energy detector 132 can be permanently installed in a hard-to-reach space or can be installed during inspection in a manner that does not require complete disassembly of the structural component. The other of the EM energy source 130 or the EM energy detector 132 can be located on the opposite side of the structural component to detect the transmitted beam 144 of EM energy. When access is possible, EM energy inspection can be combined with other NDI methods, such as infrared thermography or terahertz imaging, to improve the assessment and location of components with limited access. The applications described herein and above for the monitoring system 110 and routine 160 are exemplary, and additional applications are envisioned by the inventors.

[0055] Furthermore, the present disclosure includes examples according to the following appendices.

[0056] Appendix 1. A multilayer component including a first outer layer, a second outer layer, and a first patterned layer disposed between the first and second outer layers, the first patterned layer having a first geometric pattern of grooves on a first surface thereof, the grooves of the first geometric pattern including a first set of grooves each having a first groove width, a first incident beam of electromagnetic (EM) energy having a first wavelength corresponding to the first groove width is diffracted upon striking the first set of grooves to form a first diffracted beam of diffracted EM energy having a first diffracted wavelength, the first diffracted wavelength indicative of a change in the first groove width due to strain induced when the multilayer component is exposed to an environmental condition, and at least one of the first and second outer layers being formed of an outer layer material that is transparent to the first incident beam of EM energy and the first diffracted beam of diffracted EM energy.

[0057] Appendix 2. The multilayer component of Appendix 1, wherein the first pattern layer is formed of a metal material.

[0058] Appendix 3. The multilayer component of Appendix 1, wherein the first outer layer is formed from the outer layer material, and the first patterned layer reflects the first incident beam of EM energy passing through the first outer layer and transmits the first diffracted beam of diffracted EM energy through the first outer layer.

[0059] Appendix 4. The multilayer structure component of Appendix 1, wherein the first outer layer and the second outer layer are formed from the outer layer material, and when the first incident beam of EM energy passes through the first outer layer to reach the first patterned layer, a first diffracted beam of diffracted EM energy passes through the second outer layer and exits the multilayer structure component.

[0060] and a second patterned layer, the intermediate layer being disposed between the first outer layer and the second outer layer, the first patterned layer being disposed between the first outer layer and the intermediate layer, the second patterned layer being disposed between the intermediate layer and the second outer layer and having a second geometric pattern of grooves on a second surface thereof, the grooves of the second geometric pattern including a second set of grooves each having a second groove width different from the first groove width, a second incident beam of EM energy having a second wavelength corresponding to the second groove width being diffracted upon striking the second set of grooves to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, the second diffracted wavelength being indicative of a change in the second groove width due to strain caused when the multilayered structural component is exposed to the environmental condition, and the outer layer material is transparent to the second incident beam of EM energy and the second diffracted beam of diffracted EM energy. The multilayer structure component according to claim 1.

[0061] Appendix 6. The multilayer component of Appendix 5, wherein the second groove width is greater than the first groove width and the second wavelength is greater than the first wavelength, such that the second incident beam of EM energy passes through the grooves of the first geometric pattern without diffraction.

[0062] Appendix 7. The multilayer component of Appendix 1, wherein the first geometric pattern of grooves includes a two-dimensional geometric pattern having a second set of grooves, each of the second set of grooves having a second groove width and spaced apart in a second direction non-parallel to the first direction in which the first set of grooves are spaced apart.

[0063] Clause 8. The multilayer component of Clause 7, wherein the second groove width is different from the first groove width, a second incident beam of EM energy having a second wavelength corresponding to the second groove width is diffracted upon striking the second set of grooves to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, the second diffracted wavelength indicating a change in the second groove width due to strain caused when the multilayer component is exposed to the environmental condition, and the outer layer material is transparent to the second incident beam of EM energy and the second diffracted beam of diffracted EM energy.

[0064] Appendix 9. The multilayer component of Appendix 1, wherein each groove in the first set of grooves has a similar geometric shape and defines a plurality of regions in order from small area to large area, and are concentrically arranged to form the grooves in the first geometric pattern.

[0065] Appendix 10. The multilayer component of Appendix 9, wherein the groove separation distance between adjacent grooves in the first geometric pattern increases as the first geometric pattern extends outward from a central point.

[0066] Clause 11. The multilayer component of Clause 1, wherein the grooves of the first geometric pattern include a second set of grooves, each having a second groove width; a second incident beam of EM energy having a second wavelength corresponding to the second groove width is diffracted upon striking the second set of grooves to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, the second diffracted wavelength indicating a change in the second groove width due to strain caused when the multilayer component is exposed to the environmental conditions; and the outer layer material is transparent to the second incident beam of EM energy and the second diffracted beam of diffracted EM energy.

[0067] Appendix 12. The multilayer component of Appendix 1, wherein the first pattern layer includes a plurality of parallel wires forming the first geometric pattern of grooves, and the first groove width of the grooves is equal to a wire spacing distance between adjacent wires of the plurality of parallel wires.

[0068] Appendix 13. The multilayer component of Appendix 1, wherein the first pattern layer includes a wire mesh scrim forming the first geometric pattern of grooves, the wire mesh scrim including a first set of parallel wires oriented in a first direction and a second set of parallel wires oriented in a second direction non-parallel to the first direction, the first groove width equal to a first wire separation distance between adjacent wires of the first set of parallel wires, and the second groove width of the grooves equal to a second wire separation distance between adjacent wires of the second set of parallel wires.

[0069] Clause 14. The multilayer component of clause 13, wherein the first set of parallel wires are interwoven with the second set of parallel wires.

[0070] Clause 15. The multilayer component of clause 13, wherein the first groove width is different from the second groove width.

[0071] Clause 16. An inspection system for assessing strain in a structural component, comprising: a first geometric pattern of grooves; a first electromagnetic (EM) energy source; an EM energy detector; and a processor; wherein the grooves of the first geometric pattern are disposed within the structural component and comprise a first set of grooves, each having a first groove width; the first EM energy source projects a first incident beam of EM energy at a first wavelength corresponding to the first groove width; and when the first incident beam of EM energy is projected onto the structural component, the first incident beam of EM energy transmits through the structural component to the grooves of the first geometric pattern and is diffracted by the first set of grooves to produce diffracted EM energy having a first diffracted wavelength. and forming a first diffracted beam of energy from the first set of grooves, the first diffracted wavelength indicative of a change in the first groove width due to strain caused when the structural component is exposed to an environmental condition; the EM energy detector detecting the first diffracted wavelength of the first diffracted beam of EM energy from the first set of grooves when the first EM energy source projects the first projected beam of EM energy onto the structural component; and the processor is operatively connected to the EM energy detector and configured to receive the first diffracted wavelength of the first diffracted beam of diffracted EM energy by the EM energy detector and associate the first diffracted wavelength with the strain in the structural component.

[0072] Addendum 17. The inspection system of Addendum 16, wherein the grooves of the first geometric pattern reflect the first incident beam of EM energy and transmit the first diffracted beam of diffracted EM energy back through the structural component, and the first EM energy source and the EM energy detector are positioned on the same side of the structural component.

[0073] Addendum 18. The inspection system of Addendum 16, wherein the first diffracted beam of diffracted EM energy passes through the structural component and arrives on an opposite side of the grooves of the first geometric pattern from the first projected beam of EM energy, and the first EM energy source and the EM energy detector are positioned on opposite sides of the structural component.

[0074] Clause 19. The grooves of the first geometric pattern include a second set of grooves each having a second groove width, and the inspection system includes a second EM energy source that projects a second incident beam of EM energy at a second wavelength corresponding to the second groove width, wherein when the second incident beam of EM energy is projected onto the structural component, the second incident beam of EM energy transmits through the structural component to the grooves of the first geometric pattern and is diffracted by the second set of grooves to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, and the second diffracted wavelength is inversely proportional to the incident wavelength of the structural component when exposed to the environmental condition. 17. The inspection system of claim 16, wherein when the second EM energy source projects the second projected beam of EM energy onto the structural component, the second diffracted beam of diffracted EM energy reflected from the second set of grooves has a second diffracted wavelength detected by the EM energy detector, and the processor is configured to receive the second diffracted wavelength of the second diffracted beam of diffracted EM energy by the EM energy detector and associate the second diffracted wavelength with the strain in the structural component.

[0075] Clause 20. A method for manufacturing a structural component, comprising: a second geometric pattern of grooves; and a second EM energy source, wherein the grooves of the second geometric pattern are positioned within the structural component to form a second EM energy source. the second EM energy source projects a second incident beam of EM energy at a second wavelength corresponding to the second groove width, the second incident beam of EM energy being projected onto the structural component such that the second incident beam of EM energy passes through the structural component to the grooves of the second geometric pattern and is diffracted by the second set of grooves to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, the second diffracted wavelength being such that the structural component is diffracted by the second set of grooves to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, the second diffracted wavelength being such that the structural component is diffracted by the second diffracted wavelength. 17. The inspection system of claim 16, wherein the second EM energy source projects the second projected beam of EM energy onto the structural component, wherein the second diffracted wavelength of the second diffracted beam of diffracted EM energy reflected from the second set of grooves is detected by the EM energy detector, and the processor is configured to receive the second diffracted wavelength of the second diffracted beam of diffracted EM energy by the EM energy detector and associate the second diffracted wavelength with the strain in the structural component.

[0076] Addendum 21. The inspection system of Addendum 20, wherein the second groove width is greater than the first groove width and the second wavelength is greater than the first wavelength, whereby the second incident beam of EM energy passes through the first set of grooves without diffraction.

[0077] Addendum 22. The inspection system of Addendum 16, wherein the grooves of the first geometric pattern include a two-dimensional geometric pattern having the first set of grooves spaced apart in a first direction and a second set of grooves spaced apart in a second direction non-parallel to the first direction.

[0078] Clause 23. The inspection system of Clause 22, wherein the first set of grooves have the first groove width and the second set of grooves have a second groove width different from the first groove width; the first EM energy source projects a second incident beam of EM energy having a second wavelength corresponding to the second groove width; the second incident beam of EM energy is diffracted by the second set of grooves to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, the second diffracted wavelength indicative of a change in the second groove width due to strain caused when the multilayer structural component is exposed to the environmental condition; when the first EM energy source projects the second incident beam of EM energy onto the structural component, the second diffracted wavelength of the second diffracted beam of diffracted EM energy reflected by the second set of grooves is detected by the EM energy detector; and the processor is configured to receive the second diffracted wavelength of the second diffracted beam of diffracted EM energy by the EM energy detector and associate the second diffracted wavelength with the strain in the structural component.

[0079] Addendum 24. The inspection system of Addendum 16, including a portable inspection device comprising the first EM energy source and the EM energy detector, and transmitting the first diffraction wavelength of the first diffracted beam of diffracted EM energy to the processor via wireless communication.

[0080] Clause 25. A method for assessing strain in a structural component, the structural component having a first geometric pattern of grooves therein, the grooves of the first geometric pattern including a first set of grooves each having a first groove width, the method for assessing strain comprising projecting a first incident beam of electromagnetic (EM) energy through the structural component to the grooves of the first geometric pattern, wherein the first incident beam of EM energy has a first wavelength corresponding to the first groove width, the first set of grooves diffracting the first incident beam of EM energy to form a first diffracted beam of diffracted EM energy having a first diffracted wavelength, the first diffracted wavelength being A structural component exhibits a change in width of the first groove due to strain caused when the structural component is exposed to an environmental condition, and the method includes detecting a first diffracted wavelength of the first diffracted beam of EM energy from the first set of grooves when the first projected beam of EM energy is projected onto the structural component, and relating the first diffracted wavelength of the first diffracted beam of EM energy from the grooves of the first geometric pattern to strain in the structural component.

[0081] Clause 26. The method of Clause 25, wherein the grooves of the first geometric pattern include a second set of grooves, each groove having a second groove width; and wherein the method for assessing strain includes projecting a second incident beam of EM energy through the structural component to the grooves of the first geometric pattern, wherein the second incident beam of EM energy has a second wavelength corresponding to the second groove width; and wherein the second set of grooves diffract the second incident beam of EM energy to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, the second diffracted wavelength indicative of a change in the second groove width due to strain when the structural component is exposed to the environmental condition; and wherein the method includes detecting the second diffracted wavelength of the second diffracted beam of EM energy from the second set of grooves when the second incident beam of EM energy is projected onto the structural component; and relating the second diffracted wavelength of the second diffracted beam of EM energy from the second set of grooves to strain in the structural component.

[0082] Clause 27. The method of Clause 25, comprising projecting the first incident beam of EM energy onto the structural component a first time before the structural component is exposed to the environmental condition; detecting a baseline diffraction wavelength of the first diffracted beam of EM energy from the first set of grooves when the first incident beam of EM energy is projected onto the structural component a first time; projecting the first incident beam of EM energy onto the structural component a second time after the structural component has been exposed to the environmental condition; detecting the first diffracted wavelength of the first diffracted beam of EM energy from the first set of grooves when the first incident beam of EM energy is projected onto the structural component a second time; and comparing the first diffracted wavelength of the first diffracted beam of EM energy to the baseline diffraction wavelength when the first incident beam of EM energy is projected onto the structural component a second time to identify a change in strain at the corresponding location of the structural component.

[0083] Clause 28. The method of Clause 25, wherein the structural component has grooves in a second geometric pattern disposed at a different depth within the structural component, relative to a surface of the structural component, than the grooves in the first geometric pattern, and including a second set of grooves each having a second groove width; and wherein the method for assessing strain includes projecting a second incident beam of EM energy through the structural component to the grooves in the second geometric pattern, wherein the second incident beam of EM energy has a second wavelength corresponding to the second groove width, and wherein the second set of grooves has a second incident wavelength corresponding to the second groove width. and diffracting the second incident beam of EM energy to form a second diffracted beam of diffracted EM energy having a second diffraction wavelength, the second diffraction wavelength indicative of a change in the second groove width due to strain when the structural component is exposed to the environmental condition, the method also including detecting the second diffraction wavelength of the second diffracted beam of EM energy diffracted from the grooves of the second geometric pattern when the second incident beam of EM energy is projected onto the structural component, and relating the second diffraction wavelength of the second diffracted beam of EM energy diffracted from the grooves of the second geometric pattern to strain in the structural component.

[0084] Clause 29. The method of clause 25, wherein the first set of grooves reflects the first incident beam of EM energy and transmits the first diffracted beam of EM energy back through the structural component, and wherein the method for assessing strain includes projecting the first incident beam of EM energy onto the structural component on the same side as the structural component and detecting the first diffracted wavelength.

[0085] Clause 30. The method of clause 25, wherein the first diffracted beam of EM energy is transmitted through the structural component on a side opposite the grooves of the first geometric pattern from a side on which the first projected beam of EM energy is present, and wherein the method for assessing strain includes projecting the first projected beam of EM energy onto the structural component on one side of the structural component and detecting the first diffracted wavelength on a side opposite the one side of the structural component.

[0086] Appendix 31. The method of Appendix 25, wherein the strain in the structural component is compared with a minimum strain value, and if it is determined that the strain in the structural component is greater than the minimum strain value, further testing of the structural component is performed accordingly.

[0087] Clause 32. The method of clause 25, including generating and displaying a strain pattern derived from strains in the structural component, wherein the strain pattern is a graphical representation of strain values ​​in an inspection area of ​​the structural component, and wherein the method includes, if it determines that the strain pattern differs from an expected strain pattern for the structural component, responsively performing further inspection of the structural component.

[0088] Although many different embodiments have been described in detail above, the legal scope of protection is defined by the language of the claims at the end of this document. The detailed description of the embodiments should be construed as exemplary only. Furthermore, not all possible embodiments are described below, as describing every possible embodiment would be impractical, if not impossible. Many alternative embodiments may be realized using current technology, or technology developed after the filing date of this application, and these embodiments are also within the scope of the claims that define the scope of protection.

[0089] Furthermore, unless a definition of a term is expressly set forth herein, there is no intention, expressly or implicitly, to limit that term beyond its plain or ordinary meaning. The scope of such a term is not limited by any statement in any section of this document (other than the language of the claims). Where a term in the claims at the end of this document is referred to as being consistent with one meaning, this is for the purpose of clarity to avoid confusion for the reader, and no intention, expressly or implicitly, to limit the term in the claims to that single meaning.

Claims

1. 1. An inspection system for assessing strain in a structural component, comprising: a first geometric pattern of grooves disposed within the structural component, the first geometric pattern including a first set of grooves each having a first groove width, wherein strains induced in the structural component upon exposure to environmental conditions cause changes in the first geometric pattern such that the first groove widths of at least some of the first set of grooves can increase or decrease; a first EM energy source that projects a first projected beam of EM energy at a first wavelength corresponding to the first groove width; an EM energy detector that detects a first diffracted wavelength of the first diffracted beam of EM energy formed by the first set of grooves when the first EM energy source projects the first diffracted beam of EM energy onto the structural component and the first diffracted beam of EM energy passes through the structural component and reaches the grooves of the first geometric pattern; and a processor operatively connected to the EM energy detector, the processor configured to receive from the EM energy detector the first diffraction wavelength possessed by the first diffracted beam of diffracted EM energy and to associate the first diffraction wavelength with the strain in the structural component; Equipped with The structural component includes a plurality of parallel wires forming grooves in the first geometric pattern, the first groove width being equal to a wire separation distance between adjacent ones of the plurality of parallel wires.

2. 2. The inspection system of claim 1, wherein the grooves of the first geometric pattern reflect the first incident beam of EM energy and transmit the first diffracted beam of EM energy back through the structural component, and the first EM energy source and the EM energy detector are positioned on the same side of the structural component.

3. 2. The inspection system of claim 1, wherein the first diffracted beam of diffracted EM energy passes through the structural component on a side opposite the grooves of the first geometric pattern from a side on which the first incident beam of EM energy is present, and the first EM energy source and the EM energy detector are positioned on opposite sides of the structural component.

4. the grooves of the first geometric pattern include a second set of grooves each having a second groove width, the inspection system including a second EM energy source that projects a second incident beam of EM energy at a second wavelength corresponding to the second groove width, wherein when the second incident beam of EM energy is projected onto the structural component, the second incident beam of EM energy transmits through the structural component to the grooves of the first geometric pattern and is diffracted by the second set of grooves to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, the second diffracted wavelength indicative of a change in the second groove width due to strain caused when the structural component is exposed to the environmental condition; when the second EM energy source projects the second incident beam of EM energy onto the structural component, the second diffracted beam of diffracted EM energy reflected from the second set of grooves has a second diffracted wavelength that is detected by the EM energy detector; 2. The inspection system of claim 1, wherein the processor is configured to receive the second diffraction wavelength of the second diffracted beam of diffracted EM energy from the EM energy detector and associate the second diffraction wavelength with the strain in the structural component.

5. a second geometric pattern of grooves; and a second EM energy source; the grooves of the second geometric pattern are disposed within the structural component at a different depth, as viewed from an exterior surface of the structural component, than the grooves of the first geometric pattern, and include a second set of grooves each having a second groove width; the second EM energy source projects a second incident beam of EM energy at a second wavelength corresponding to the second groove width, wherein when the second incident beam of EM energy is projected onto the structural component, the second incident beam of EM energy transmits through the structural component to the grooves of the second geometric pattern and is diffracted by the second set of grooves to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, the second diffracted wavelength indicative of a change in the second groove width due to strain caused when the structural component is exposed to the environmental condition; when the second EM energy source projects the second incident beam of EM energy onto the structural component, the second diffracted beam of diffracted EM energy reflected from the second set of grooves has a second diffracted wavelength that is detected by the EM energy detector; the processor receives the second diffraction wavelength of the second diffracted beam of diffracted EM energy from the EM energy detector and associates the second diffraction wavelength with the strain in the structural component; 2. The inspection system of claim 1, wherein the second groove width is greater than the first groove width and the second wavelength is greater than the first wavelength, such that the second incident beam of EM energy passes through the first set of grooves without diffraction.

6. the grooves of the first geometric pattern include a two-dimensional geometric pattern having the first set of grooves spaced apart in a first direction and a second set of grooves spaced apart in a second direction non-parallel to the first direction; 2. The inspection system of claim 1, wherein the first set of grooves have the first groove width and the second set of grooves have a second groove width different from the first groove width; the first EM energy source projects a second incident beam of EM energy having a second wavelength corresponding to the second groove width; the second incident beam of EM energy is diffracted by the second set of grooves to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, the second diffracted wavelength indicative of a change in the second groove width due to strain caused when the structural component is exposed to the environmental condition; when the first EM energy source projects the second incident beam of EM energy onto the structural component, the second diffracted wavelength of the second diffracted beam of diffracted EM energy reflected by the second set of grooves is detected by the EM energy detector; and the processor is configured to receive the second diffracted wavelength of the second diffracted beam of diffracted EM energy from the EM energy detector and associate the second diffracted wavelength with the strain in the structural component.

7. 10. The inspection system of claim 1, further comprising a portable inspection device comprising the first EM energy source and the EM energy detector, and configured to wirelessly transmit information about the first diffracted wavelength of the first diffracted beam of diffracted EM energy to the processor.

8. 1. A method for assessing strain in a structural component, the structural component having a first geometric pattern of grooves therein, the grooves of the first geometric pattern including a first set of grooves each having a first groove width, wherein strain induced in the structural component when exposed to an environmental condition causes a change in the first geometric pattern such that the first groove width can increase or decrease for at least a portion of the first set of grooves, the method for assessing strain comprising: projecting a first incident beam of electromagnetic (EM) energy through the structural component to the grooves of the first geometric pattern, wherein the first incident beam of EM energy has a first wavelength corresponding to the first groove width, the first set of grooves diffracting the first incident beam of EM energy to form a first diffracted beam of diffracted EM energy having a first diffracted wavelength, and wherein a change in the first groove width due to a strain of the structural component causes a change in the first diffracted wavelength corresponding to the strain of the structural component; detecting the first diffracted wavelength of the first diffracted beam of EM energy from the first set of grooves when the first incident beam of EM energy is incident on the structural component; relating the first diffraction wavelength of the first diffracted beam of diffracted EM energy from the grooves of the first geometric pattern to a strain in the structural component; The method, wherein the structural component includes a plurality of parallel wires forming grooves in the first geometric pattern, the first groove width being equal to a wire separation distance between adjacent ones of the plurality of parallel wires.

9. The grooves of the first geometric pattern include a second set of grooves each having a second groove width, and the method for assessing distortion comprises: projecting a second incident beam of EM energy through the structural component to the grooves of the first geometric pattern, wherein the second incident beam of EM energy has a second wavelength corresponding to the second groove width, and wherein the second set of grooves diffract the second incident beam of EM energy to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, the second diffracted wavelength indicative of a change in the second groove width due to strain caused when the structural component is exposed to the environmental condition; detecting the second diffracted wavelength of the second diffracted beam of EM energy diffracted from the second set of grooves when the second incident beam of EM energy is incident on the structural component; 9. The method of claim 8, comprising relating the second diffraction wavelength of the second diffracted beam of diffracted EM energy from the second set of grooves to a strain in the structural component.

10. projecting the first projected beam of EM energy onto the structural component before the structural component is exposed to the environmental condition; detecting a baseline diffraction wavelength of the first diffracted beam of EM energy from the first set of grooves when the first incident beam of EM energy is first incident on the structural component; projecting the first projected beam of EM energy onto the structural component a second time after the structural component has been exposed to the environmental conditions; detecting the first diffracted wavelength of the first diffracted beam of EM energy from the first set of grooves when the first incident beam of EM energy is incident on the structural component as a second incident; 10. The method of claim 8, further comprising comparing the first diffraction wavelength of the first diffracted beam of EM energy to the baseline diffraction wavelength when the first incident beam of EM energy is incident on the structural component for a second time to identify a change in strain at the corresponding location of the structural component.

11. The structural component has grooves in a second geometric pattern disposed at a different depth within the structural component from a surface of the structural component than the grooves in the first geometric pattern, the second set of grooves each having a second groove width, and the method for assessing strain comprises: projecting a second incident beam of EM energy through the structural component to the grooves of the second geometric pattern, wherein the second incident beam of EM energy has a second wavelength corresponding to the second groove width, and wherein the second set of grooves diffract the second incident beam of EM energy to form a second diffracted beam of diffracted EM energy having a second diffracted wavelength, the second diffracted wavelength indicative of a change in the second groove width due to strain caused when the structural component is exposed to the environmental condition; When the second projected beam of EM energy is projected onto the structural component, the second diffracted beam of EM energy from the grooves of the second geometric pattern is detecting the second diffracted wavelength having the 9. The method of claim 8, comprising relating the second diffraction wavelength of the second diffracted beam of diffracted EM energy from the grooves of the second geometric pattern to a strain in the structural component.

12. 9. The method of claim 8, wherein the first set of grooves reflects the first incident beam of EM energy and transmits the first diffracted beam of EM energy back through the structural component, and wherein the method for assessing strain comprises projecting the first incident beam of EM energy onto the structural component on a same side of the structural component and detecting the first diffracted wavelength.

13. 9. The method of claim 8, wherein the first diffracted beam of EM energy is transmitted through the structural component on a side opposite the grooves of the first geometric pattern from a side on which the first projected beam of EM energy is present, and wherein the method for assessing strain comprises projecting the first projected beam of EM energy onto the structural component on one side of the structural component and detecting the first diffracted wavelength on a side opposite the one side of the structural component.

14. comparing the strain in the structural component to a minimum strain value; The method of claim 8 , further comprising: if determining that the strain in the structural component is greater than the minimum strain value, then, in response, conducting further inspection of the structural component.

15. generating and displaying a strain pattern derived from the strain of the structural component, wherein the strain pattern is a graphical representation of strain values ​​in an inspection area of ​​the structural component; The method of claim 8 , further comprising: if determining that the strain pattern differs from an expected strain pattern for the structural component, then responsively conducting further inspection of the structural component.

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