Structural component and method for assessing strain in a structural component

Abstract

The present invention relates to a structural component and a method for evaluating strain in a structural component. The structural component can have a geometric pattern of diffractive cavities within the structural component, where each of the diffractive cavities in the geometric pattern has a cavity width and is spaced apart from one another by a cavity spacing distance. The method can include projecting a projected beam of electromagnetic (EM) energy through the structural component to a first geometric pattern of diffractive cavities to form a diffracted beam of EM energy that is reflected or transmitted through the geometric pattern of diffractive cavities and has a diffracted wavelength indicative of a change in the cavity spacing distance due to strain caused when the structural component is exposed to environmental conditions; detecting the diffracted wavelength of the diffracted beam; and correlating the diffracted wavelength of the diffracted beam to strain in the structural component.

Description

Technical Field

[0001] This disclosure generally relates to nondestructive inspection (NDI) of structural components, and more specifically, to systems and methods for detecting strain in structural components caused by exposure to environmental conditions using the geometry of a diffraction cavity within the structural component, the structural component diffracting invisible electromagnetic (EM) energy to produce a detectable change in the wavelength of the EM energy reflected or transmitted by the structural component, the change indicating strain in the structural component. Background Technology

[0002] Many mechanical systems, such as commercial vehicles, manufacturing equipment, and other industrial systems, can be exposed to particularly harsh environmental conditions such as vibration, extreme temperatures, shock, and mechanical stress. For example, even on the ground, aircraft can experience significant stress during cargo loading and unloading, as well as impacts from support vehicles and ground support equipment. During flight, stress and / or impacts can occur due to improper cargo shifting or securing, or collisions with objects during flight. Additionally, certain structural components experience thermal stress when exposed to high temperatures. For instance, some composite materials are susceptible to thermal degradation, which can impair their mechanical properties, including flexural strength, post-impact compression, interlaminar shear strength, and other mechanical properties.

[0003] Therefore, routine inspections and evaluations of selected components are typically performed throughout the service life of various industrial systems. The integrity of one or more structural components may be compromised without accompanying visually detectable indications of the effects of environmental conditions on the components. Therefore, there is a need for non-destructive inspection techniques that can indicate the cumulative effects on structural components exposed to environmental conditions such as repetitive loads, shocks, and high temperatures during operation. Such indications can lead to the scheduling of further evaluation, repair, and / or replacement of structural components at appropriate times. Summary of the Invention

[0004] In one aspect of this disclosure, a structural component is disclosed. The structural component may include a first outer surface, a second outer surface, and a first geometric pattern of diffraction cavities formed by the first surface within the structural component. The first geometric pattern of the diffraction cavities may have a first set of diffraction cavities spaced apart from each other by a first cavity spacing distance, wherein when a first projected beam having EM energy of a first wavelength corresponding to the first cavity spacing distance encounters the first set of diffraction cavities, the first projected beam of EM energy is diffracted, forming a first diffracted beam of EM energy having a first diffraction wavelength indicating a change in the first cavity spacing distance due to strain caused by strain when the structural component is exposed to environmental conditions.

[0005] In another aspect of the invention, an inspection system for evaluating strain in a structural component is disclosed. The inspection system may include: a first geometric pattern of diffraction cavities within the structural component, the first geometric pattern having a first set of diffraction cavities spaced apart from each other by a first cavity spacing distance; and a first EM energy source that projects a first projected beam of EM energy at a first wavelength corresponding to the first cavity spacing distance. When the first projected beam of EM energy is projected onto the structural component, the first projected beam of EM energy can pass through the structural component to reach the first geometric pattern of the diffraction cavities and can be diffracted by the first set of diffraction cavities to form a first diffracted beam of EM energy having a first diffraction wavelength indicating the change in the first cavity spacing distance due to strain caused by the structural component being exposed to environmental conditions. The detection system may further include: an EM energy detector that detects a first diffraction wavelength of a first diffracted beam of diffracted EM energy from a first set of diffraction cavities when a first EM energy source projects a first projected beam of EM energy onto a structural component; and a processor operatively connected to the EM energy detector and configured to receive the first diffraction wavelength of the first diffracted beam of diffracted EM energy from the EM energy detector and correlate the first diffraction wavelength with strain in the structural component.

[0006] In other aspects of this disclosure, a method for evaluating strain in a structural component is disclosed. The structural component may have a first geometric pattern of diffraction cavities within the structural component, the first geometric pattern of diffraction cavities comprising a first set of diffraction cavities each having a first cavity spacing distance. The method for evaluating strain may include: projecting a first projected beam of EM energy through the structural component to the first geometric pattern of the diffraction cavities, wherein the first projected beam of EM energy has a first wavelength corresponding to the first cavity spacing distance, and wherein the first set of diffraction cavities diffracts the first projected beam of EM energy to form a first diffracted beam of EM energy having a first diffraction wavelength indicating a change in the first cavity spacing distance due to strain caused when the structural component is exposed to environmental conditions. The method may further include: detecting a first diffraction wavelength of the first diffracted beam of EM energy from the first set of diffraction cavities when the first projected beam of EM energy is projected onto the structural component; and correlating the first diffraction wavelength of the first diffracted beam of EM energy from the first geometric pattern of the diffraction cavities with strain in the structural component. Attached Figure Description

[0007] Figure 1 It is an isometric view of a structural component of a mechanical system according to the present disclosure, the structural component having a geometric pattern of a diffraction cavity;

[0008] Figure 2 yes Figure 1A cross-sectional view of a portion of a structural component having a geometric pattern of a diffraction cavity;

[0009] Figure 3 From and Figure 2 The cross-section is cut from a plane perpendicular to the cross-section. Figure 1 A sectional view of a part of the structural component;

[0010] Figure 4 This is an isometric view of an alternative embodiment of a structural component of a mechanical system according to the present disclosure, the structural component having multiple geometric patterns of a diffraction cavity;

[0011] Figure 5 yes Figure 4 A cross-sectional view of a portion of a structural component having an exemplary configuration of multiple geometric patterns of a diffraction cavity;

[0012] Figure 6 This is a cross-sectional view as part of another alternative embodiment of a structural component according to the present disclosure, which has an exemplary configuration of a three-dimensional geometric pattern of a diffraction cavity;

[0013] Figures 7A to 7G It is used for Figure 1 A plan view of the structural components according to an embodiment of the geometric pattern of the diffraction cavity of the present disclosure;

[0014] Figure 8 It is an isometric view of a portion of a structural component according to this disclosure, wherein a patch mounted on the structural component has a geometric pattern of a diffraction cavity;

[0015] Figure 9 It is a block diagram of electrical and control components that enable structural component inspection according to this disclosure;

[0016] Figure 10 yes Figure 1 A schematic diagram of an exemplary implementation of the inspection system and inspection method according to this disclosure on a structural component;

[0017] Figure 11 Is Figure 1 A schematic diagram of an alternative exemplary implementation of an inspection system and inspection method on structural components;

[0018] Figure 12 This is a flowchart illustrating an implementation of the inspection routine according to this disclosure;

[0019] Figure 13 This is a flowchart of an alternative implementation of the inspection routine according to this disclosure; and

[0020] Figure 14 This is a diagram showing an exemplary strain pattern according to the present disclosure. Detailed Implementation

[0021] Figure 1 and Figure 2 This is an illustration of a structural component 10 of a mechanical system configured for applying the NDI systems and methods illustrated and described herein. The structural component 10 can be any component of the mechanical system subject to environmental conditions that can cause stress and strain to the structural component 10. For use in the NDI systems and methods of this disclosure, the structural component 10 includes a geometric pattern 12 of a diffraction cavity 14 formed by surfaces within the interior of the structural component 10. In the illustrated embodiment, the structural component 10 has a single-layer construction in which the geometric pattern 12 defining the diffraction cavity 14 is defined. The structural component 10 includes a first outer surface 16 and a second outer surface 18, wherein the geometric pattern 12 of the diffraction cavity 14 is disposed within the structural component 10, between the outer surfaces 16 and 18. With the diffraction cavity 14 defined within the structural component, the geometric pattern 12 is hidden and thus invisible and protected from environmental elements that may damage or harm the diffraction cavity 14.

[0022] Figure 2 and Figure 3 An example is shown in a sectional view. Figure 1 The structural component 10. The geometric pattern 12 of the diffraction cavity 14 is disposed within the structural component 10, inside the outer surfaces 16 and 18. In the illustrated embodiment, the diffraction cavity 14 is an elongated cylindrical cavity, perpendicular to the... Figure 2 When viewed in cross-section, the cylindrical cavity appears circular, but when viewed perpendicularly... Figure 3 When viewed in cross-section, the cylindrical cavity appears as a linear channel within structural member 10. In alternative embodiments, the diffraction cavity 14 may have other cross-sectional geometries and may be shaped to conform to structural member 10 as needed to provide a meaningful indication of strain. The diffraction cavity 14 and the geometric pattern 12 are configured to form a strain-sensitive detectable change in the wavelength of the EM energy reflected or transmitted through the geometric pattern 12 in response to the projection of EM energy beyond the visible spectrum onto it. The reflected or transmitted EM energy can be detected by a suitable detector discussed below, and a processor can determine the detectable change in the wavelength and frequency of the reflected or transmitted EM energy and compare it to a reference value of the expected EM energy wavelength when structural member 10 has not yet been subjected to stress and strain caused by environmental conditions. The elongated cylindrical diffraction cavity 14 of the illustrated embodiment is exemplary, and the diffraction cavity according to this disclosure may have alternative geometries as needed to provide a meaningful representation of the strain encountered by a particular structural member in which the diffraction cavity is implemented.

[0023] Structural components with diffraction cavities according to this disclosure can be manufactured using addition manufacturing techniques in which diffraction cavities are formed within the structural component during its construction. Such addition manufacturing techniques may include VAT photopolymerization, material jetting, binder jetting, powder bed fusion with laser sintering, material extrusion, direct energy treatment, sheet lamination, investment casting, or casting, etc. These manufacturing techniques allow for the isolated formation of diffraction cavities within the structural component without the need for openings through the outer surface of the structural component, which can then be backfilled to isolate the diffraction cavities within the structural component. However, those skilled in the art will understand that other alternative manufacturing techniques can be used in manufacturing structural components with diffraction cavities according to this disclosure, and the inventors anticipate such techniques.

[0024] In the illustrated embodiment, the diffraction cavity 14 is arranged with a cavity width WC and a cavity spacing DC to generate diffraction when EM energy of a corresponding wavelength is projected onto the structural member 10. An acoustic boundary is generated within the structural member 10, in which the inner surface defines the diffraction cavity 14. The wavelength of the EM energy projected onto the structural member 10 is coordinated with the cavity width WC and cavity spacing DC of the diffraction cavity 14 to facilitate the determination of strain in the structural member 10 due to exposure to environmental conditions.

[0025] The wavelength of the projected EM energy is typically outside the visible range of approximately 400 nm to 750 nm, unless the structural component 10 is made of a material that is visually transparent to EM energy in the visible range. Diffraction of the applied EM energy produces a detectable variation in the diffraction wavelength of the reflected or transmitted EM energy, which changes as the cavity spacing distance DC changes due to strain in the structural component 10.

[0026] The cavity spacing distance DC, corresponding to the center-to-center distance between adjacent diffraction cavities 14 of the geometric pattern 12, will determine the optimal spectral range of EM energy that can be applied to the geometric pattern 12. Typically, the geometric pattern 12 will diffract EM energy when the cavity spacing distance DC is greater than the wavelength of the EM energy. In some embodiments, the target value of the cavity spacing distance DC may be approximately twice the wavelength of the EM energy. However, depending on the requirements of the specific implementation of patterning and strain measurement according to this disclosure, the cavity spacing distance DC may be greater than or less than twice the wavelength of the EM energy. These conditions are derived from the following diffraction gratings known in the art:

[0027] d×sinθ=n×λ (1)

[0028] Where d is equal to the cavity spacing distance DC between adjacent diffraction cavities 14, λ is the wavelength of the EM energy, n is the maximum order of the diffracted EM energy to be observed or detected, and θ is the observation angle or the angle between the incident direction of the EM energy projected onto the structural component 10 and the direction of the observed maximum value. Based on formula (1), when the cavity spacing distance DC is approximately twice the wavelength λ of the incident EM energy, a first-order maximum value (n=1) is observed at an observation angle θ of approximately 30° (sin 30°=0.5).

[0029] Examples of combinations of wavelength, frequency, and cavity spacing DC that can be used in the systems and methods of this disclosure are as follows:

[0030] Table 1

[0031]

[0032]

[0033] Therefore, for example, for ultrasonic EM energy in the wavelength range of 1 mm to 5 mm, the cavity spacing DC can be in the same range or larger (e.g., 1 mm to 10 mm), and the diffraction cavity 14 can have a cavity width WC sufficient to diffract the ultrasonic EM energy at a sufficient observation angle θ to measure the desired order maximum value of the diffracted EM energy. For example, for ultrasonic EM energy with a wavelength of 1 mm, the cavity spacing DC can be approximately 4 mm, and the diffraction cavity 14 can have a cavity width WC equal to approximately 2 mm. The cavity spacing DC is approximately four times the wavelength, and for the first order maximum value, solving Equation (1) yields sinθ equal to approximately .25, thus the observation angle θ equals approximately 14.5°. For a structural component 10 with a thickness of 20 mm between outer surfaces 16 and 18, when ultrasonic EM energy is projected onto the first outer surface 16, the first two order maximum values ​​will be separated by approximately 5 mm at the second outer surface 18, i.e., by the spacing that enables currently known ultrasonic sensors to measure the diffracted EM energy.

[0034] The combination of wavelength / cavity spacing DC can be selected such that when EM energy is applied and structural component 10 is not subjected to strain that causes a change in cavity spacing DC, geometry 12 will reflect or transmit EM energy with the corresponding diffraction wavelength. The size of the diffraction cavity 14 is also related to the wavelength / cavity spacing DC, because the cavity width WC must be large enough to ensure that impedance mismatch at the boundary will affect the propagated EM energy without compromising the structural integrity of structural component 10. When structural component 10 is subjected to environmental conditions that cause strain, as the strain causes the cavity spacing DC to increase or decrease, the diffraction wavelength of the EM energy reflected or transmitted by geometry 12 will evolve into other diffraction wavelengths through the EM energy spectrum. Depending on the configuration of structural component 10, the environmental conditions exposed to geometry 12 and structural component 10, the change in cavity spacing DC, and the corresponding change in diffraction wavelength can be uniform across geometry 12 or larger in certain regions, indicating greater stress and strain concentration in these regions. The amount of strain, and the corresponding changes in cavity spacing DC and diffraction wavelength, can be acceptable without further inspection, while larger changes may indicate the need for further inspection, repair, and / or replacement of structural component 10. An initial cavity spacing DC and wavelength can be selected to allow timely detection of strain in structural component 10 that requires further inspection. It will be apparent to those skilled in the art from this discussion that various combinations of cavity spacing DC, cavity width WC, and EM energy wavelengths are available for the diffraction cavities 14 and the spacing between them. As long as sufficient EM energy penetrates structural component 10 and passes through the geometry 12 of the diffraction cavities 14 according to this disclosure, the diffraction angle θ will be sufficient to produce a pattern of EM energy of diffraction that can be detected and measured to indicate strain in structural component 10.

[0035] like Figure 1 and Figure 2 As illustrated, the geometry 12 of the diffraction cavity 14 may cover the entire extent of the structural member 10 and may be substantially centered within the structural member 10. However, other configurations and locations of the geometry 12 of the diffraction cavity 14 are contemplated. For example, the geometry 12 may be strategically positioned within the structural member 10 at locations that provide the most relevant information about the stress and strain on the structural member 10 (e.g., in areas where high stress concentration is expected). Such areas may include openings, corners, and joints through the structural member 10 for wiring, tubing, conduits, etc., where the structural member 10 is joined or attached to another component of the mechanical system, or where a patch is applied to repair the structural member 10. In these latter areas, the geometry 12 may be configured such that it is located at or near intersections with another component or patch, provided that the structural integrity of the connection and the mechanical system is maintained.

[0036] Alternative configurations of structural components with a geometric pattern of diffraction cavities can diffract EM energy and reflect or transmit the diffracted EM energy. For example, geometry 12 can be modified to have a second set of elongated diffraction cavities (not shown) that are parallel to each other and substantially perpendicular to diffraction cavity 14. The second set of diffraction cavities may be curved to follow... Figure 1 The outline of structural component 10. The second set of diffraction cavities may be positioned at the same depth as and intersect with diffraction cavity 14, or may be deeper or shallower and not intersect with diffraction cavity 14. In some embodiments, the cavity width WC and cavity spacing DC may be the same in both directions. In other embodiments, the cavity width WC and cavity spacing DC of the first set of diffraction cavities 14 may be different from those of the second set of diffraction cavities, such that EM energy of different wavelengths will be diffracted by each set of diffraction cavities. For example, by using this method in an aircraft fuselage, the first set of diffraction cavities 14 may be configured to diffract EM energy in the near-infrared band to indicate circumferential strain around the fuselage, while the second set of diffraction cavities may be configured to diffract EM energy in the far-infrared band to indicate tensile, compressive, or torsional strain in the longitudinal direction of the fuselage. Depending on the strain to be monitored, as described herein, the groups of diffraction cavities may be angled relative to each other in directions other than orthogonal.

[0037] The geometry 12 of the diffraction cavity 14 provides flexibility in the location where the diffracted EM energy can be detected. A portion of the diffracted EM energy is reflected back in the direction of the EM energy source, while another portion is transmitted through the structural member 10 to the side opposite the EM energy source. In one embodiment, the EM energy source and the EM energy detector can be located on the same side of the structural member 10. The EM energy transmitted by the EM energy source will pass through the structural member 10, be diffracted by the geometry 12 of the diffraction cavity 14, be reflected back in the opposite direction, and be detected by the EM energy detector. In an alternative embodiment, the EM energy transmitted through one side of the structural member 10 will be diffracted at the geometry 12 of the diffraction cavity 14, and the diffracted EM energy will be transmitted through the opposite side of the structural member 10. This allows the EM energy source and the EM energy detector to be located on opposite sides of the structural member 10. This arrangement can be advantageous in situations requiring limited access inspection. The EM energy beam can be generated by an appropriately sized transmitter located in or manually or automatically guided into an inaccessible space, and the diffracted EM energy can be detected from the accessible side of structural component 10. Of course, depending on the requirements of a particular implementation, the positions of the EM energy source and the EM energy detector can be reversed.

[0038] Figure 4 and Figure 5An alternative embodiment of the structural component 30 is illustrated, having multiple geometric patterns 32, 34 of grooves 36, 38 at different depths to provide strain indication at different depths within the structural component 30. The structural component 30 may include a first outer surface 40 and a second outer surface 42 opposite to the first outer surface 40. As illustrated, the diffraction cavities 36 of the first geometric pattern 32 and the diffraction cavities 38 of the second geometric pattern 34 are aligned in the same direction, but the second diffraction cavities 38 of the second geometric pattern 34 may be oriented in a second direction in a manner similar to that discussed above. In the case of an overlapping arrangement, cavity widths WC1, WC2 and cavity spacing distances DC1, DC2 are selected for the diffraction cavities 36, 38 respectively (as shown), such that the EM energy diffracted by the second geometric pattern 34 of the diffraction cavity 38 will pass through the first geometric pattern 32 of the diffraction cavity 36 without diffraction, thus enabling meaningful strain measurements. Generally, low-frequency EM energy with longer wavelengths penetrates deeper into the structural component 30 than high-frequency EM energy with shorter wavelengths. Therefore, in an exemplary example, the second geometric pattern 34 of the diffraction cavity 38 can be configured to diffract EM energy in the terahertz, microwave, or ultrasonic bands, and the first geometric pattern 32 of the diffraction cavity 36 closer to the first outer surface 40 can be configured to diffract higher-frequency EM energy in the ultraviolet or infrared bands. In this configuration, the cavity spacing DC1 of the diffraction cavities 36 of the first geometric pattern 32 is set such that EM energy in the terahertz, microwave, and ultrasonic bands can pass through the diffraction cavities 36 to reach the second geometric pattern 34 without diffraction. Penetration of any type of EM energy through the structural member 30 can be enhanced by increasing the intensity of the EM energy projected onto the structural member 30. In an alternative embodiment, the geometric patterns 32, 34 can be located in a non-overlapping region of the structural member 30 such that when EM energy passes through the structural member 30, EM energy for one geometric pattern 32, 34 does not encounter the other geometric pattern 32, 34.

[0039] Figure 6Other exemplary embodiments of the structural component 50 are illustrated, wherein the structural component 50 has a three-dimensional (3D) geometric pattern 52 of diffraction cavities 54. Between a first outer surface 56 and a second outer surface 58 of the structural component 50, the diffraction cavities 54 are arranged in multiple rows at different depths within the structural component 50. Each row is aligned with an adjacent row such that the corresponding diffraction cavities 54 are aligned row-wise. In this embodiment, the diffraction cavities 54 in each row may be spaced apart from adjacent rows by the same cavity spacing distance DC, such that a given diffraction cavity 54 is spaced apart from each of four adjacent diffraction cavities 54 by the cavity spacing distance DC. The 3D geometric pattern 52 enhances the ability of applied EM energy with corresponding wavelengths to produce diffracted EM energy and to indicate strain aspects in the structural component 50. In an alternative embodiment, the alternating multiple rows of diffraction cavities 54 may be laterally offset such that the diffraction cavities 54 are not aligned front-to-back, as... Figure 6 As shown in the diagram. In this embodiment, each diffraction cavity 54 is spaced at the same cavity spacing distance DC as each of the six adjacent diffraction cavities 54. This type of 3D geometry also enables the applied EM energy to produce diffracted EM energy and has a stronger effect on indicating strain aspects in the structural component 50. Furthermore, the 3D geometry 52 allows for the guidance of EM energy transmitted from directions other than those perpendicular to the outer surfaces 56, 58, and produces a meaningful response indicating strain in the structural component 50.

[0040] The elongated diffraction cavities 14, 36, 38, and 54 illustrated and described herein are exemplary, and diffraction cavities with other geometric configurations are contemplated. For example, a geometric pattern can be formed by spherical diffraction cavities arranged in a two-dimensional (2D) or 3D array. The cavity spacing DC between the spherical diffraction cavities and the cavity width CW or cavity diameter of the spherical diffraction cavities will be similar to those discussed above for elongated cylindrical diffraction cavities, to form boundaries within the structural component that will diffract EM energy of corresponding wavelengths. The spherical diffraction cavities may have a consistent cavity spacing DC in two directions of the 2D geometry or in all three directions of the 3D geometry, such that an EM energy of one wavelength will be diffracted to reveal strain in each direction. Alternatively, the spherical diffraction cavities may have different cavity spacing DCs in each direction, such that EM energies of different wavelengths will be used to evaluate the corresponding strains. For example, a 3D pattern of spherical diffraction cavities can be implemented in a cylindrical object such as a pipe or shell, which can withstand internal pressure from a gas or other pressurized fluid. The 3D geometry of a spherical diffraction cavity can have a first cavity spacing DC in the axial direction that diffracts EM energy of a first wavelength to indicate axial strain, a second cavity spacing DC in the circumferential direction that diffracts EM energy of a second wavelength to indicate annular strain, and a third cavity spacing DC in the radial direction that diffracts EM energy of a third wavelength to indicate radial strain. Other configurations of the 2D and 3D geometries of the spherical diffraction cavity are contemplated depending on the geometry of the specific structural component and the strain that the structural component will experience.

[0041] The appropriate geometry for a structural component can be determined by the characteristics of the structural component, the environmental conditions it is expected to encounter, the results of development and testing, the experience of the structural component in the field, and other factors. Figures 7A to 7G Several examples of geometric patterns 12A-12G that can be appropriately formed within structural components are provided. Figure 7A An exemplary one-dimensional geometric pattern 12A is shown, formed by a series of parallel linear diffraction cavities 14A. Geometric pattern 12A can be implemented in a planar structure subjected to tension or compression in one direction. Linear geometric pattern 12A can also be applied to cylindrical structural components such as pipes (not shown) that can withstand circumferential or circumferential strain, but with minimal strain in the axial direction. Geometric pattern 12A can be wrapped around the cylindrical structural component such that the diffraction cavities 14A are aligned parallel to the longitudinal axis of the structural component, such that the strain caused by circumferential strain increases the circumferential cavity spacing DC between the diffraction cavities 14A.

[0042] Figure 7BAn example of a two-dimensional geometric pattern 12B formed by multiple square or rectangular diffraction cavities 14B is shown. The square or rectangular diffraction cavities 14B define an increased region and are concentrically arranged to form the geometric pattern 12B such that adjacent square or rectangular diffraction cavities 14B are separated by the same cavity spacing distance DC. For example, the rectangular geometric pattern 12B can be used in a structural component 10 having a rectangular opening 22 extending therethrough. Figure 7C An alternative two-dimensional geometric pattern 12C is shown, formed by a plurality of concentric circular diffraction cavities 14C defining an increased region. The concentric circles can be sized such that adjacent circular diffraction cavities 14C are separated by the same cavity spacing distance DC. The circular geometric pattern 12C can be applied to a structural component 10 in which stresses can be radially directed outward from a point at the center of the geometric pattern 12C. Figure 7D Other examples of geometric patterns 12D with concentric diffraction cavities 14D are illustrated, the concentric diffraction cavities 14D having more complex geometries corresponding to the shapes of openings or other components extending from structural member 10. Other irregular shapes are contemplated based on the needs of specific implementations in structural member 10.

[0043] Figure 7E Other alternative two-dimensional geometries 12E are illustrated, having multiple diffraction cavities 14E extending radially outward from a center point 24. Geometries 12E can replace geometries 12C in which circumferential stress is more prevalent than radial stress. Figure 7F A geometric pattern 12F formed by multiple parallel curved diffraction cavities 14F is shown. The curved diffraction cavities 14F may follow the contour of a component with a curved shape that extends through a structural component 10 such as an aircraft wing.

[0044] In some implementations, structural component 10 may have regions of interest in which greater sensitivity to changes in strain and cavity spacing DC is expected. In this case, the regions of interest can be distinguished by varying the cavity spacing DC between the diffraction cavities 14 and the wavelength across structural component 10. Figure 7G Examples are given as Figure 7C A variation of the circular geometric pattern 12C, the geometric pattern 12G, is described, wherein the cavity spacing DC between adjacent diffraction cavities 14G increases as the geometric pattern 12G extends outward from the center (where close examination of radial stress is more critical). Regions with smaller cavity spacing DC and correspondingly higher concentrations of diffraction cavities 14G are more sensitive to changes in strain and cavity spacing DC, and exhibit a stronger response to the EM energy projected onto the region of interest in terms of the diffraction wavelength of the reflected or transmitted EM energy compared to regions with larger cavity spacing DC and more distantly spaced diffraction cavities 14G.

[0045] As an alternative form that can provide a more intelligent strain indicator, the geometric pattern 12 may have multiple sets of diffraction cavities 14 placed at angles relative to each other with different cavity spacing distances DC to independently monitor different levels or types of strain appearing in the structural component. For example, geometric patterns 12C, 12E may be combined on the structural component to form a single geometric pattern 12. A circular geometric pattern 12C may be formed such that the cavity spacing distance DC is within the range responsive to ultraviolet EM energy, and a geometric pattern 12E may be formed over the geometric pattern 12C such that the cavity spacing distance DC is within the range responsive to mid-infrared EM energy. During inspection, radial strain can be inquired by projecting ultraviolet EM energy onto the structural component, and circumferential strain can be inquired by projecting mid-infrared EM energy onto the structural component. Alternative or additional geometric patterns 12, such as those illustrated and described herein, may also be formed within the structural component, wherein, in a particular implementation, additional strain patterns are inspected as necessary by changing the corresponding wavelengths of the cavity spacing distance DC and the EM energy.

[0046] Figure 8 An example is illustrated in which structural member 100 has a patch 102 applied over a damaged area. The patch 102 is suitably shaped to cover the damaged area and attached to structural member 100 via rivets, welding, adhesives, lamination, or other suitable attachment means. The patch 102 includes, for example, at or near the joint line between structural member 100 and patch 102. Figure 7C The geometric pattern 12C. The patch 102 can be manufactured by addition processing. The diffraction cavity 14C of the geometric pattern 12C can be disposed slightly below the surface facing and engaging the structural member 100, so that there is complete surface-to-surface contact between the structural member 100 and the patch 102. Alternatively, the diffraction cavity 14C can be formed in the surface of the patch 102 such that the surface of the structural member 100 closes the open side of the diffraction cavity 14C, even without compromising the integrity of the bonding line. After the patch 102 is installed, it can be inspected according to the system and method disclosed herein. In addition to detecting strain in the patch 102, the inspection can also assess the integrity of the patch 102 applied to the structural member 100. If the patch 102 is properly applied and attached to the structural member 100, the stress in the structural member 100 will be transferred to the patch 102 and corresponding strain will appear during the inspection. If patch 102 is not applied properly and conditions such as delamination exist, stress will not be transferred, and inspection of patch 102 will reveal that the strain within patch 102 is less than expected. Such results may prompt further investigation of patch 102 in the damaged area and reapplication of patch 102.

[0047] The geometric pattern 12 illustrated and described herein can be incorporated into the inspection system 110 to assess strain in structural components such as structural component 10. Figure 9 An exemplary arrangement of electrical and control components that can be integrated into an inspection system 110 according to this disclosure is illustrated, which can, for example, determine strain in a structural component 10. A controller 112 may be able to process information received from monitoring and control devices using software stored at the controller 112 and output command and control signals to the means of the inspection system 110. The controller 112 may include a processor 114 for executing a specified program that controls and monitors various functions associated with the inspection system 110. The processor 114 is operatively connected to a memory 116, which may have a read-only memory (ROM) 118 for storing a program and a random access memory (RAM) 120 serving as a working storage area for use in executing the program stored in the ROM 118. Although a processor 114 is shown, other electronic components such as microcontrollers, application-specific integrated circuit (ASIC) chips, or any other integrated circuit devices are contemplated.

[0048] Although the discussion provided herein relates to the functionality of inspection system 110, controller 112 can be configured to control other aspects of the operation of other systems. Furthermore, controller 112 may collectively refer to multiple control and processing devices across which the functionality of inspection system 110 and other systems can be distributed. For example, some portions of the functionality of inspection system 110 may be executed at a remote computing device 122 having controller 124 operatively connected to controller 112 via communication module 126 of inspection system 110. Remote computing device 122 may be located at a centralized location for the enterprise, utilizing inspection system 110 to perform inspections on mechanical systems. Controllers 112 and 124 are operatively connected to exchange information as needed to control the operation of inspection system 110. Other variations of merging and distributing the processing of controllers 112 and 124, as described herein, are contemplated for use in inspection system 110 according to this disclosure.

[0049] The inspection system 110 may also include one or more EM energy sources 128, 130, which are capable of projecting EM energy at a predetermined wavelength corresponding to, for example, the cavity spacing distance DC of the diffraction cavities 14 in the geometric pattern 12. The EM energy sources 128, 130 may receive control signals from the processor 114 causing them to project EM energy at the predetermined wavelength. In some embodiments, each EM energy source 128, 130 may be capable of projecting EM energy of one wavelength. In alternative embodiments, each EM energy source 128, 130 or a single EM energy source may be capable of projecting EM energy of different wavelengths. Although the EM energy sources 128, 130 are illustrated and described as operatively connected to the processor 114, those skilled in the art will understand that the EM energy sources 128, 130 may be standalone devices having associated input devices such as on / off switches, wavelength selection inputs, etc., to allow manual control of operation by a person performing the inspection.

[0050] The inspection 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 the diffracted wavelength of EM energy reflected or transmitted by the geometry 12 when EM energy from EM energy sources 128, 130 is projected onto the geometry 12. In the embodiments illustrated herein, the EM energy detector 132 may be an optical detector capable of detecting the diffracted wavelength of reflected or transmitted EM energy. For example, the EM energy detector 132 may be a charge-coupled device (CCD) camera, camcorder, photographic film, or other EM energy sensing device. When activated by the processor 114 or manually actuated by an appropriate input device, the EM energy detector 132 may capture the diffracted EM energy and send a representation of the detected diffracted wavelength of the diffracted EM energy to the processor 114. Once the diffracted wavelength is received, the processor 114 may store the diffracted wavelength in memory 116. Those skilled in the art will understand that the detection of the wavelength or frequency of the EM energy of diffraction and the determination of variations in the diffraction wavelength or frequency can be achieved using alternative mechanisms desired or necessary for the specific implementations of the systems and methods described herein, and the inventors anticipate using such alternative mechanisms. It should be understood that the use of any other mechanism for detecting and analyzing the diffraction wavelength of the EM energy of diffraction is equally applicable to the systems and methods of this disclosure.

[0051] The inspection system 110 may have one or more input (I / P) devices 134 that can be adjusted by an operator to control the inspection process. Input devices 134 may include switches, buttons, keyboards, mice, touchscreens, etc., capable of receiving input commands from the operator. Output (O / P) devices 136, such as monitors, screens, touchscreens, speakers, printers, etc., can transmit information from the inspection system 110 to the operator.

[0052] exist Figure 10 An exemplary implementation of the inspection system 110 is illustrated. A processor 114, an EM energy source 128, and an EM energy detector 132 are integrated into an inspection workstation 140. For example, the inspection workstation 140 may be a workstation at a maintenance facility for a mechanical system, to which the structural component 10 is part. With the structural component 10 located at the inspection workstation 140, the EM energy source 128 can be activated to project one or more EM energy beams 142 of appropriate wavelengths onto a geometric pattern 12. The projected beams 142 are diffracted and reflected by the geometric pattern 12 to produce a diffracted EM energy beam 144. The EM energy detector 132 receives and detects the diffracted EM energy beam 144 and transmits the detected EM energy to the processor 114 to analyze the detected diffracted wavelengths or frequencies of the reflected EM energy beams 144 and correlate them with corresponding strain values. The processor 114 may be programmed with algorithms known in the art to perform the conversion of the detected wavelengths or frequencies into strain values.

[0053] Figure 11 An alternative implementation of inspection system 110 is illustrated, in which EM energy source 128 and EM energy detector 132 are components of portable inspection device 150, and processor 114 and memory 116 are located at 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 also include communication module 154, which is capable of wirelessly communicating with communication module 126 at the central inspection workstation to transmit detected color from EM energy detector 132. EM energy can be... Figure 10 Similar to the illustrated and described manner, energy is projected from EM energy source 128 and detected by EM energy detector 132.

[0054] Figure 11An implementation in which the EM energy source 130 is located on the side of the structural component 10 opposite to the portable inspection device 150 is also illustrated. The EM energy source 130 can be permanently installed in a hard-to-reach location within the mechanical system. As shown, the EM energy source 130 can project a beam 142 of EM energy onto the structural component 10 and the geometric pattern 12. The EM energy is diffracted in the form of a beam 144 by the diffraction cavity 14 at the geometric pattern 12 and transmitted through the structural component 10. The diffracted beam 144 of EM energy is received at the EM energy detector 132 on the opposite side of the structural component 10 and processed by the processor 114.

[0055] Figure 12 A flowchart illustrating an exemplary inspection routine 160 that the inspection system 110 can perform on structural components 10, 30, 50, and 100 is shown. Routine 160 may begin at block 162, in which structural components 10, 30, 50, and 100 are formed (e.g., manufactured), and one or more geometric patterns 12, 12A-12G of diffraction cavities 14, 14A-14G are formed within the structural components 10, 30, 50, and 100. For example, any suitable manufacturing technique such as the manufacturing technique described above can be used to form the diffraction cavities 14, 14A-14G in the structural components 10, 30, 50, and 100. After forming structural components 10, 30, 50, and 100 with geometric patterns 12, 12A-12G, control can be switched to frame 164, in which EM energy source 128 projects a beam 142 with EM energy of corresponding wavelengths onto structural components 10, 30, 50, and 100 and onto geometric patterns 12, 12A-12G. The EM energy in the projected beam 142 is diffracted by diffraction cavities 14, 14A-14G, and the corresponding EM energy with diffraction wavelengths is reflected or transmitted by geometric patterns 12, 12A-12G. Due to the change in cavity width WC caused by strain on structural components 10, 30, 50, and 100, the diffraction wavelength of the reflected or transmitted EM energy beam 144 can vary at different positions on geometric patterns 12, 12A-12G.

[0056] When the EM energy beam 142 is projected onto the geometric patterns 12, 12A-12G and is diffracted, reflected, or transmitted, control can be switched to box 166, in which the EM energy detector 132 detects the diffracted wavelength of the reflected or transmitted EM energy beam 144. The diffracted wavelength of the EM energy beam 144 can be temporarily or permanently stored in memory 116.

[0057] After detecting the diffracted beam 144 with EM energy, control can proceed to block 168, where the inspection system 110 can determine whether EM energy with the final EM energy wavelength has been projected onto the geometric patterns 12, 12A-12G. As discussed above, some implementations may include a first set of diffracting cavities 14, 14A-14G with a first cavity spacing DC1 and a second set of diffracting cavities 14, 14A-14G with a second cavity spacing DC2. The EM energy source 128 projects a beam 142 with EM energy of the first wavelength onto the first set of diffracting cavities 14, 14A-14G, and the EM energy source 128 projects a beam 142 with EM energy of the second wavelength onto the second set of diffracting cavities 14, 14A-14G. In these implementations, it may be necessary to project a beam 142 with one wavelength at a time. Therefore, if the beam 142 with various wavelengths of EM energy determined in block 168 has not yet been projected onto the geometric patterns 12, 12A-12G, control can return to blocks 164, 166 to project EM energy with different wavelengths of these wavelengths from EM energy sources 128, 130 onto the geometric patterns 12, 12A-12G and detect the corresponding diffraction wavelength in the beam 144 of EM energy for the next projected beam 142, as described above.

[0058] If a beam 142 with EM energy of all necessary wavelengths has been projected and a diffracted beam 144 with EM energy has been detected in block 168, control can proceed to block 170 to associate the diffraction wavelength of beam 144 with strain values ​​in structural components 10, 30, 50, and 100. As discussed above, processor 114 can be programmed with algorithms known in the art to associate the wavelength of EM energy in diffracted beam 144 with strain values.

[0059] After the strain value is determined in box 170 for the diffracted beam 144 with EM energy, control can proceed to box 172 to determine whether any of the strain values ​​calculated from the diffraction wavelength in the diffracted beam 144 with EM energy exceeds a predetermined minimum strain value. If this minimum strain value is exceeded, further inspection or repair should be performed. As discussed, a certain level of strain is acceptable in structural components 10, 30, 50, and 100. Alternatively, before the mechanical system is put into use and exposed to environmental conditions, the current strain value can be compared with a reference strain value obtained for structural components 10, 30, 50, and 100. By projecting beam 142 onto structural components 10, 30, 50, and 100 when no strain is applied to them or when a known strain is applied to them to determine the diffraction wavelength in the responding beam 144, a reference strain value in geometric patterns 12, 12A-12G can be established. In other embodiments, a portion of geometric patterns 12, 12A-12G can be applied to regions that do not experience strain during exposure to environmental conditions, and the diffraction wavelength from the unstrained regions can establish a real-time dynamic reference during inspection.

[0060] The current strain value can be compared with a baseline or other previously determined strain value to determine if the difference between the current strain value and the previous strain value is greater than a minimum amount or percentage. If the strain value is not greater than the minimum strain value and no further inspection is required, control can proceed to box 174, where structural components 10, 30, 50, and 100 are exposed to environmental conditions. Exposure can result from normal use in the normal environment of the mechanical system. In the case of a mechanical system under development, environmental conditions can be applied in a test environment. After exposure in box 174, control can return to box 164 to initiate another inspection of structural components 10, 30, 50, and 100. In box 172, a strain value greater than the minimum strain value indicates that further inspection, repair, or replacement of structural components 10, 30, 50, and 100 may be necessary. If the strain value in box 172 is greater than the minimum strain value, control proceeds to box 176 for further inspection of structural components 10, 30, 50, and 100.

[0061] Figure 12 Inspection routine 160 is an example of a quantitative procedure used to assess strain in structural components 10, 30, 50, and 100 and to identify when further inspection, repair, or replacement may be required. In some implementations, it may be appropriate to replace or supplement quantitative inspection routine 160 with a qualitative procedure in which the experience of the inspector performing the inspection is used to analyze the strain patterns in structural components 10, 30, 50, and 100 and to identify any anomalies in the strain patterns that may require further inspection. Figure 13A flowchart illustrating an inspection system 110 and an exemplary qualitative inspection routine 180 that an inspector, engineer, or other inspection technician utilizing the inspection system 110 can perform on structural components 10, 30, 50, 100 is shown. Inspection routine 180 may begin in a manner similar to inspection routine 160, wherein: in block 162, structural components 10, 30, 50, 100 are formed having geometric patterns 12, 12A-12G having diffraction cavities 14, 14A-14G; in block 164, a beam 142 of EM energy is projected onto structural components 10, 30, 50, 100; in block 166, the diffracted beam 144 of EM energy is detected; and in block 170, the diffraction wavelength from the diffracted beam 144 of EM energy is correlated with strain in structural components 10, 30, 50, 100.

[0062] To implement inspection routine 180, inspection system 110 can be modified in frames 164, 166, and 170 to confirm the position of beams 142 and 144 relative to structural components 10, 30, 50, and 100 when beam 142 is projected over the surfaces of the inspected structural components 10, 30, 50, and 100. For example, this is used to determine the position of a body or device, such as structural component 10, relative to... Figure 10 Inspection workstation 140 or Figure 11 When the portable inspection device 150 moves (when the portable inspection device 150 moves past the surface of the structural component 10), the position and movement technique of the main body or device are known. The position information of the diffracted EM energy beam 144 can be stored in memory 116 together with the diffraction wavelength detected in frame 166 and the associated strain value determined in frame 170.

[0063] After the diffraction wavelength is detected and the strain value is determined, or dynamically while the inspection system 110 is inspecting structural components 10, 30, 50, 100, control can be switched to box 182 to generate and display strain patterns of structural components 10, 30, 50, 100 using the diffraction wavelength, strain value, and position of beam 144 relative to the structural components 10, 30, 50, 100 being inspected. Figure 14An example of a display 200 for a strain pattern 202 that can be derived from information obtained from inspection system 110 is illustrated. Display 200 can be any suitable visual display that conveys a graphical representation of the strain in structural components 10, 30, 50, 100. For example, display 200 can be a video display at one of the output devices 136 located at inspection workstation 140, portable inspection device 150, central inspection workstation 152, or another location where an inspector can view display 200. In an alternative embodiment, display 200 can be a printed output from one of the output devices 136 at an appropriate location. Furthermore, alternative visual display output devices 136 for displaying strain pattern 202 will be readily apparent to those skilled in the art and are contemplated by the inventors.

[0064] Strain pattern 202 is a visual representation of the distribution of strain values ​​on the inspected structural components 10, 30, 50, and 100. In the illustrated example, the display of strain pattern 202 utilizes grayscale shading to depict the location and magnitude of strain values ​​in structural components 10, 30, 50, and 100. White or lighter gray shading can indicate areas of low strain, while the gray shading can darken as the strain value increases. The spacing between shading areas provides an indication of the rate of change of strain values ​​on structural components 10, 30, 50, and 100. In alternative embodiments, the strain pattern can be color-coded. For example, blue can correspond to low strain values, and colors can progress through a color spectrum to red, which can represent high strain values. In other embodiments, the strain pattern can be represented as a line of constant strain values, resembling a weather map representing changes in atmospheric pressure or a topographic map representing changes in altitude. Other alternative depiction strategies are contemplated.

[0065] In some embodiments using grayscale or color gradation, scales may be added to display 200 to indicate strain values ​​corresponding to various shades or colors in strain pattern 202. Display 200 may also display minimum strain values ​​at minimum strain regions 204 (e.g., lighter colors or shades) and maximum strain values ​​at maximum strain regions 206 (e.g., darker colors or shades). Other representations, such as different colors for representing different strain value ranges, may be used. Display 200 may be further enhanced by displaying strain pattern 202 overlaid on and positioned on captured images or graphical representations of structural components 10, 30, 50, 100 to more clearly illustrate the position of the strain pattern on the structural components 10, 30, 50, 100.

[0066] With strain pattern 202 generated in box 182 and displayed on display 200, control can move to box 184, where inspectors, maintenance personnel, or other technicians can view strain pattern 202 to determine whether it is normal for the environmental conditions that structural components 10, 30, 50, and 100 have been subjected to. Inspectors can refer to their experience inspecting current and / or other structural components when assessing whether strain pattern 202 has the expected characteristics or whether it indicates potential problems requiring additional inspection. Assessment may include reviewing baseline information collected for structural components 10, 30, 50, and 100 of the types discussed above. Baseline information can be presented in any suitable format. In some implementations, baseline information can be used to generate a baseline strain pattern, which can be displayed on display 200 as a supplement to the real-time strain pattern 202 used for visual comparison.

[0067] If the inspector determines in box 184 that strain pattern 202 is normal, and the strain values ​​illustrated in strain pattern 202 are not greater than or less than strain values ​​that would indicate a problem, and further inspection is not required, control can proceed to box 174, where structural components 10, 30, 50, and 100 are exposed to environmental conditions as discussed above. Following exposure in box 174, control can return to box 164 to initiate another scenario for inspecting structural components 10, 30, 50, and 100. If strain pattern 202 differs from expectations in terms of strain values ​​in box 184 (either larger or smaller than expected), it may indicate that further inspection, repair, or replacement of structural components 10, 30, 50, and 100 is necessary. If strain pattern 202 is abnormal relative to the expected strain pattern of structural components 10, 30, 50, and 100 in box 184, control proceeds to box 176 for further inspection of structural components 10, 30, 50, and 100. As discussed above, the qualitative check routine 180 can be implemented as follows: Figure 12 The quantitative test routine 160 can be used as an alternative or supplement.

[0068] Industrial applicability

[0069] The inspection system 110 and routine 160 can be widely used to evaluate the structural integrity of structural components in mechanical systems that have diffraction cavities according to this disclosure. For example, the inspection system 110 and routine 160 can be used in maintenance monitoring applications to ensure, for example... Figure 8The quality of the joint between the repair piece 102 and the structural component 100, and the response of the patch 102 to stress and strain over time before the structural component 100 is replaced, are assessed. If a geometric pattern 12C is formed on the patch 102 before it is applied to the structural component 100 and positioned near the joint line between the structural component 100 and the patch 102, then the strain due to the joint can be imaged and analyzed according to routine 160 to detect residual stress in the patch 102 and the quality of the joint between the patch 102 and the structural component 100. A reference image of the patch 102 before the structural component 100 with the patch 102 is exposed to environmental conditions can show any initial strain in the patch 102 and the structural component 100, and periodic imaging after the structural component 100 is exposed to environmental conditions will monitor the quality and integrity of the joint and the patch 102, and indicate the deterioration of the repair over time. The strain values ​​derived by checking system 110 and routine 160 can be input into the finite element analysis (FEA) model of patch 102 on structural component 100 and analyzed to provide performance evaluation of patch 102, prospective inspection plans, and methods for NDI and predictive maintenance and repair plans.

[0070] Inspection system 110 and routine 160 can be applied to structural testing environments. Manufacturers typically perform sub-scale, medium-scale, and full-scale structural tests on components to ensure appropriate performance in the field. Such testing can involve both static and dynamic load conditions. Several techniques are currently used in this type of structural testing. For example, strain gauges are applied to structural components as point sensors to monitor stress and strain during testing, but their effectiveness in detecting the location of damage initiation and propagation depends on the placement of the strain gauges on the structural component. Digital image correlation (DIC) can be used to provide flow mapping during structural testing, but this process can be costly, requires operational expertise, and necessitates the spraying of spot patterns on the surface. Therefore, DIC can be used prudently in structural testing. Inspection system 110 and routine 160 can be used as an alternative to or supplement to currently used testing techniques and can be used to monitor and measure real-time strain patterns across the entire test load conditions. The detected strain patterns can be used to correlate analysis models and pinpoint or indicate the initial fault location in the structural component being tested. In maintenance monitoring applications, feeding strain information directly into FEA tools can provide real-time or load-level damage growth information. Information on the onset and growth of damage can be used to improve the structural model of structural components and modify the structural design.

[0071] Inspection system 110 and routine 160 can be used to improve the manufacturing process of composite components, which are becoming increasingly common in mechanical systems, particularly in aerospace systems. It can be beneficial to identify and track internal strains in composite components that arise from component manufacturing during the development and periodic process monitoring and manufacturing of the composite components. Internal strain can be tracked by using a strain indicator layer in the composite component configured with geometric patterns 12, 12A-12G of diffraction cavities 14, 14A-14G. To form the strain indicator layer, the geometric patterns 12, 12A-12G are formed in a selected layer with resin during manufacturing or in an appliqué that forms a peelable layer that can be removed after the composite component has cured. The patterned strain indicator layer will exhibit residual stresses and strains present in the composite component due to the curing process. Information from the patterned strain indicator layer can be used to modify the manufacturing process of the composite component to reduce warpage, predict performance, and verify that the manufacturing process remains within specifications.

[0072] Inspection system 110 and routine 160 can also be used to monitor the structural health of structural components located in the limited-touch areas of their mechanical systems. Limited-touch structures on aircraft and other mechanical systems are critical to structural integrity and withstand high loads. Structural health testing of such limited-touch structures may necessitate costly disassembly and reassembly processes. During manufacturing, strain-witnessing surfaces in the form of geometric patterns 12, 12A-12G of diffraction cavities 14, 14A-14G can be formed at critical locations within the limited-touch structural components. Optical or video conduit lenses or small cameras, along with extension mechanisms, can act as EM energy sources 128 or 130 and EM energy detectors 132 in inspection system 110 and are used to detect the diffraction wavelengths in the EM energy transmitted in the geometric patterns 12, 12A-12G on the limited-touch structure, enabling the analysis of diffraction wavelength data to, for example, detect component degradation and monitor slow loss growth until repair is required. As described above for... Figure 11 As discussed, the EM energy source 130 or EM energy detector 132 can be permanently installed in hard-to-reach spaces or deployed during inspection in a manner that does not require complete disassembly of the structural component. The other of the EM energy source 130 and EM energy detector 132 can be located on the opposite side of the structural component to detect the beam 144 of transmitted EM energy. Where accessibility is possible, EM energy inspection can be combined with other NDI methods such as infrared thermal imaging or terahertz imaging to improve the evaluation and handling of components with limited access. This and the above applications of the inspection system 110 and routine 160 are exemplary, and the inventors anticipate additional applications.

[0073] In addition, this disclosure includes the following examples, and the scope of protection is provided by the claims.

[0074] Example 1. A structural component comprising: a first outer surface; a second outer surface; and a first geometric pattern of diffraction cavities formed by the first surface within the structural component, the first geometric pattern of diffraction cavities having a first set of diffraction cavities spaced apart from each other by a first cavity spacing distance, wherein when a first projected beam of electromagnetic (EM) energy having a first wavelength corresponding to the first cavity spacing distance encounters the first set of diffraction cavities, the first projected beam of EM energy is diffracted and forms a first diffracted beam of EM energy having a first diffraction wavelength indicating a change in the first cavity spacing distance caused by strain due to the structural component being exposed to environmental conditions.

[0075] Example 2. The structural component according to Example 1, wherein the first geometric pattern of the diffraction cavity reflects a first projected beam of EM energy passing through the structural component, so that the first diffracted beam of the diffracted EM energy is transmitted through the first outer surface.

[0076] Example 3. A structural component according to any one of Examples 1-2, wherein when a first projected beam of EM energy passes through a first outer surface and reaches a first geometric pattern of a diffraction cavity, a first diffracted beam of EM energy passes through a second outer surface and reaches outside the structural component.

[0077] Example 4. A structural component according to any one of Examples 1-3, the structural component comprising a second geometric pattern of a diffraction cavity formed by a second surface between a first geometric pattern of a diffraction cavity and a second outer surface within the structural component, the second geometric pattern of the diffraction cavity having a second set of diffraction cavities spaced apart from each other by a second cavity spacing distance different from the first cavity spacing distance, wherein when a second projected beam having EM energy of a second wavelength corresponding to the second cavity spacing distance encounters the second set of diffraction cavities, the second projected beam of EM energy is diffracted and a second diffracted beam of EM energy having a second diffraction wavelength indicating the change in the second cavity spacing distance caused by strain when the structural component is exposed to environmental conditions.

[0078] Example 5. The structural component according to Example 4, wherein the second cavity spacing distance is greater than the first cavity spacing distance, and the second wavelength is greater than the first wavelength, such that the second transmitted beam of EM energy passes through the first geometric pattern of the diffraction cavity without being diffracted.

[0079] Example 6. The structural component according to any one of Examples 1-5, wherein the first geometric pattern of the diffraction cavity includes a two-dimensional geometric pattern having a second set of diffraction cavities, each of the second set of diffraction cavities having a second cavity spacing distance and being spaced apart in a second direction, the second direction not being parallel to the first direction in which the first set of diffraction cavities are spaced apart.

[0080] Example 7. The structural component according to Example 6, wherein the second cavity spacing distance is not equal to the first cavity spacing distance, wherein when a second projected beam having EM energy of a second wavelength corresponding to the second cavity spacing distance encounters the second set of diffraction cavities, the second projected beam with EM energy is diffracted and forms a second diffracted beam with diffracted EM energy having a second diffraction wavelength indicating the change in the second cavity spacing distance caused by strain when the structural component is exposed to environmental conditions.

[0081] Example 8. The structural component according to any one of Examples 1 to 7, wherein the diffraction cavities in the first set of diffraction cavities have similar geometries and define an increased area, wherein the diffraction cavities are concentrically arranged to form a first geometric pattern of diffraction cavities.

[0082] Example 9. The structural component according to Example 8, wherein, as the first geometric pattern extends outward from the center point, the first cavity spacing distance between adjacent diffraction cavities of the first geometric pattern increases.

[0083] Example 10. A structural component according to any one of Examples 1 to 9, wherein the first geometric pattern of the diffraction cavities includes a second set of diffraction cavities, each having a second cavity spacing distance, wherein when a second projected beam having EM energy of a second wavelength corresponding to the second cavity spacing distance encounters the second set of diffraction cavities, the second projected beam of EM energy is diffracted, and a second diffracted beam of EM energy with a second diffraction wavelength indicating the change in the second cavity spacing distance caused by strain when the structural component is exposed to environmental conditions.

[0084] Example 11. An inspection system for evaluating strain in a structural component, the inspection system comprising: a first geometric pattern of diffraction cavities within the structural component, the first geometric pattern of diffraction cavities having a first set of diffraction cavities spaced apart from each other by a first cavity spacing distance; a first electromagnetic (EM) energy source that projects a first projected beam of EM energy of a first wavelength corresponding to the first cavity spacing distance, wherein, when the first projected beam of EM energy is projected onto the structural component, the first projected beam of EM energy passes through the structural component to reach the first geometric pattern of the diffraction cavities and is diffracted by the first set of diffraction cavities to form a first diffraction wavelength. The first diffracted beam of diffracted EM energy, the first diffracted wavelength indicating the change in the first cavity spacing distance caused by strain when the structural component is exposed to environmental conditions; an EM energy detector that detects the first diffracted wavelength of the first diffracted beam of diffracted EM energy from the first set of diffracting cavities when the first EM energy source projects the first projected beam of EM energy onto the structural component; and a processor operatively connected to the EM energy detector and configured to receive the first diffracted wavelength of the first diffracted beam of diffracted EM energy from the EM energy detector and correlate the first diffracted wavelength with strain in the structural component.

[0085] Example 12. The inspection system according to Example 11, wherein a first geometric pattern of the diffraction cavity reflects a first projected beam of EM energy to return a first diffracted beam of diffracted EM energy transmitted through the structural component, and wherein a first EM energy source and an EM energy detector are located on the same side of the structural component.

[0086] Example 13. An inspection system according to any one of Examples 11 to 12, wherein a first diffracted beam of EM energy is transmitted through a structural member on the side of a first geometric pattern of a diffracting cavity opposite to the first projected beam of EM energy, and wherein a first EM energy source and an EM energy detector are located on opposite sides of the structural member.

[0087] Example 14. An inspection system according to any one of claims 11-13, wherein the first geometric pattern of the diffraction cavity has a second set of diffraction cavities spaced apart from each other by a second cavity spacing distance, wherein the inspection system includes a second EM energy source that projects a second projected beam of EM energy corresponding to a second wavelength of the second cavity spacing distance, wherein when the second projected beam of EM energy is projected onto the structural member, the second projected beam of EM energy passes through the structural member to reach the first geometric pattern of the diffraction cavity and is diffracted by the second set of diffraction cavities to form a second diffracted beam of EM energy having a second diffracted wavelength, the second diffracted wavelength indicating the change in the second cavity spacing distance caused by strain when the structural member is exposed to environmental conditions, wherein when the second EM energy source projects the second projected beam of EM energy onto the structural member, the second diffracted wavelength of the second diffracted beam of EM energy reflected by the second set of diffraction cavities is detected by an EM energy detector, and wherein a processor is configured to receive the second diffracted wavelength of the second diffracted beam of EM energy from the EM energy detector and correlate the second diffracted wavelength with strain in the structural member.

[0088] Example 15. An inspection system according to any one of claims 11-14, the inspection system comprising: a second geometric pattern of diffraction cavities within a structural component, the second geometric pattern of diffraction cavities being located at a depth different from the depth of the outer surface of the structural component and the depth of the first geometric pattern of the diffraction cavities, the second geometric pattern of the diffraction cavities having a second set of diffraction cavities spaced apart from each other by a second cavity spacing distance; and a second EM energy source projecting a second projected beam of EM energy of a second wavelength corresponding to the second cavity spacing distance, wherein, when the second projected beam of EM energy is projected onto the structural component, the second projected beam of EM energy passes through the structural component and reaches the second set of diffraction cavities. A geometric pattern is formed and diffracted by a second set of diffraction cavities to form a second diffracted beam of EM energy with a second diffraction wavelength, the second diffraction wavelength indicating the change in the second cavity spacing distance caused by strain when the structural component is exposed to environmental conditions. The second diffraction wavelength of the second diffracted beam of EM energy reflected by the second set of diffraction cavities is detected by an EM energy detector when the second EM energy source projects the second projected beam of EM energy onto the structural component. The processor is configured to receive the second diffraction wavelength of the second diffracted beam of EM energy from the EM energy detector and correlate the second diffraction wavelength with strain in the structural component.

[0089] Example 16. The inspection system according to Example 15, wherein the second cavity spacing distance is greater than the first cavity spacing distance, and the second wavelength is greater than the first wavelength, such that the second transmitted beam of EM energy passes through the first set of diffraction cavities without being diffracted.

[0090] Example 17. An inspection system according to any one of Examples 11 to 16, wherein the first geometric pattern of the diffraction cavity comprises a two-dimensional geometric pattern having a first set of diffraction cavities spaced apart in a first direction and a second set of diffraction cavities spaced apart in a second direction, the second direction being non-parallel to the first direction.

[0091] Example 18. The inspection system according to Example 17, wherein a first set of diffraction cavities has a first cavity spacing distance and a second set of diffraction cavities has a second cavity spacing distance unequal to the first cavity spacing distance, wherein a first EM energy source projects a second projected beam of EM energy having a second wavelength corresponding to the second cavity spacing distance, wherein the second projected beam of EM energy is diffracted by the second set of diffraction cavities to form a second diffracted beam of EM energy having a second diffracted wavelength, the second diffracted wavelength indicating the change in the second cavity spacing distance due to strain caused when the structural component is exposed to environmental conditions, wherein when the first EM energy source projects the second projected beam of EM energy onto the structural component, the second diffracted wavelength of the second diffracted beam of EM energy reflected by the second set of diffraction cavities is detected by an EM energy detector, and wherein a processor is configured to receive the second diffracted wavelength of the second diffracted beam of EM energy from the EM energy detector and associate the second diffracted wavelength with strain in the structural component.

[0092] Example 19. An inspection system according to any one of Examples 11 to 18, the inspection system comprising a portable inspection device, the portable inspection device including a first EM energy source and an EM energy detector, and transmitting a first diffraction wavelength of a first diffracted beam of diffracted EM energy to a processor via wireless communication.

[0093] Example 20. A method for evaluating strain in a structural component, the structural component having a first geometric pattern of diffraction cavities within the structural component, the first geometric pattern of diffraction cavities comprising a first set of diffraction cavities each having a first cavity spacing distance, the method comprising: projecting a first projected beam of electromagnetic (EM) energy through the structural component to the first geometric pattern of the diffraction cavities, wherein the first projected beam of EM energy has a first wavelength corresponding to the first cavity spacing distance, and wherein the first set of diffraction cavities diffracts the first projected beam of EM energy to form a first diffracted beam of EM energy having a first diffraction wavelength indicating a change in the first cavity spacing distance due to strain caused when the structural component is exposed to environmental conditions; detecting the first diffraction wavelength of the first diffracted beam of EM energy from the first set of diffraction cavities when the first projected beam of EM energy is projected onto the structural component; and correlating the first diffraction wavelength of the first diffracted beam of EM energy from the first geometric pattern of the diffraction cavities with strain in the structural component.

[0094] Example 21. A method for evaluating strain in a structural component according to Example 20, wherein a first geometric pattern of diffraction cavities includes a second set of diffraction cavities, each having a second cavity spacing distance, and wherein the method for evaluating strain includes the steps of: projecting a second projected beam of EM energy through the structural component onto the first geometric pattern of the diffraction cavities, wherein the second projected beam of EM energy has a second wavelength corresponding to the second cavity spacing distance, and wherein the second set of diffraction cavities diffracts the second projected beam of EM energy to form a second diffracted beam of EM energy with a second diffraction wavelength indicating a change in the second cavity spacing distance due to strain caused when the structural component is exposed to environmental conditions; detecting the second diffraction wavelength of the second diffracted beam of EM energy from the second set of diffraction cavities when the second projected beam of EM energy is projected onto the structural component; and associating the second diffraction wavelength of the second diffracted beam of EM energy from the second set of diffraction cavities with strain in the structural component.

[0095] Example 22. A method for evaluating strain in a structural component according to any one of Examples 20 to 21, the method comprising the steps of: firstly projecting a first projected beam of EM energy onto the structural component before the structural component is exposed to environmental conditions; detecting a reference diffraction wavelength of a first diffracted beam of EM energy from a first set of diffraction cavities when the first projected beam of EM energy is first projected onto the structural component; secondly projecting the first projected beam of EM energy onto the structural component after the structural component is exposed to environmental conditions; detecting a first diffraction wavelength of a first diffracted beam of EM energy from the first set of diffraction cavities when the first projected beam of EM energy is secondly projected onto the structural component; and comparing the diffraction wavelength of the first diffracted beam of EM energy with the reference diffraction wavelength when the first projected beam of EM energy is secondly projected onto the structural component to determine the strain change at a corresponding location of the structural component.

[0096] Example 23. A method for evaluating strain in a structural component according to any one of Examples 20-22, wherein the structural component has a second geometric pattern of diffraction cavities within the structural component, the second geometric pattern of the diffraction cavities being located at a depth different from the depth of the surface of the structural component and the depth of the first geometric pattern of the diffraction cavities, the second geometric pattern of the diffraction cavities comprising a second set of diffraction cavities each having a second cavity spacing distance, the method for evaluating strain comprising: projecting a second projected beam of EM energy through the structural component to the second geometric pattern of the diffraction cavities, wherein the second projected beam of EM energy has a second cavity spacing distance corresponding to the second cavity spacing distance. The second wavelength, wherein the second set of diffraction cavities diffracts a second projected beam of EM energy to form a second diffracted beam of EM energy with a second diffraction wavelength, the second diffraction wavelength indicating the change in the second cavity spacing distance caused by strain when the structural component is exposed to environmental conditions; the second diffraction wavelength of the second diffracted beam of EM energy from the second geometric pattern of the diffraction cavities is detected when the second projected beam of EM energy is projected onto the structural component; and the second diffraction wavelength of the second diffracted beam of EM energy from the second geometric pattern of the diffraction cavities is correlated with the strain in the structural component.

[0097] Example 24. A method for evaluating strain in a structural component according to any one of Examples 20 to 23, wherein a first set of diffraction cavities reflects a first projected beam of EM energy to return a first diffracted beam of EM energy transmitted through the structural component, and wherein the method for evaluating strain comprises: projecting the first projected beam of EM energy onto the structural component on the same side of the structural component and detecting a first diffraction wavelength.

[0098] Example 25. A method for evaluating strain in a structural component according to any one of Examples 20 to 24, wherein a first diffracted beam of EM energy is transmitted through the structural component on the side of a first geometric pattern of a diffraction cavity opposite to the first projected beam of EM energy, and the method for evaluating strain comprises: projecting the first projected beam of EM energy onto the structural component on opposite sides of the structural component and detecting a first diffraction wavelength.

[0099] Example 26. A method for evaluating strain in a structural component according to any one of Examples 20 to 25, the method comprising the steps of: comparing the strain on the structural component with a minimum strain value; and performing further inspection on the structural component in response to determining that the strain on the structural component is greater than the minimum strain value.

[0100] Example 27. A method for evaluating strain in a structural component according to any one of Examples 20 to 26, the method comprising the steps of: generating and displaying a strain pattern derived from the strain in the structural component, wherein the strain pattern is a graphical representation of strain values ​​in an inspected area of ​​the structural component; and further inspecting the structural component in response to determining that the strain pattern differs from an expected strain pattern on the structural component.

[0101] While the foregoing text provides detailed descriptions of numerous different implementations, it should be understood that the legal scope of protection is defined by the wording of the claims set forth at the end of this document. Specific embodiments will be interpreted as merely exemplary and not as describing every possible implementation, as describing every possible implementation would be impractical, if not impossible. Numerous alternative implementations may be achieved using current technology developed after the filing date of this patent, which will still fall within the scope of the limiting claims.

[0102] It should also be understood that unless a term is expressly defined herein, it is not intended to explicitly or implicitly limit the meaning of that term beyond its general or ordinary meaning, and such term should not be construed as limited in scope based on any statement made in any part of this patent (other than in the claims). If any term set forth in the claims at the end of this patent is referenced herein in a manner consistent with its single meaning, this is done for clarity and without confusing the reader, and this claim entry is not intended to be implicitly or otherwise limited to that single meaning.

Claims

1. A single-layer structural component, the structural component comprising: First outer surface; Second outer surface; as well as A first geometric pattern of diffraction cavities formed by a first surface within the structural component, the first geometric pattern of diffraction cavities having a first set of diffraction cavities spaced apart from each other by a first cavity spacing distance, wherein the diffraction cavities are unfilled spaces within the structural component, and wherein when a first projected beam of electromagnetic energy (EM energy) having a first wavelength corresponding to the first cavity spacing distance encounters the first set of diffraction cavities, the first projected beam of EM energy is diffracted and forms a first diffracted beam of EM energy having a first diffraction wavelength, the first diffraction wavelength indicating the change in the first cavity spacing distance caused by strain due to the structural component being exposed to environmental conditions, wherein the first geometric pattern of the diffraction cavities is a two-dimensional geometric pattern, wherein each diffraction cavity in the first set of diffraction cavities is an elongated cavity defining the same geometry, wherein the geometry defined by the diffraction cavities is concentrically arranged around the center of the two-dimensional geometric pattern, and wherein the area of ​​the geometry defined by each diffraction cavity increases with the increase of the distance from the center of the two-dimensional geometric pattern to the diffraction cavity.

2. The structural component according to claim 1, wherein, The first geometric pattern of the diffraction cavity reflects the first projected beam of the EM energy passing through the structural component, so that the first diffracted beam of the diffracted EM energy is transmitted through the first outer surface.

3. The structural component according to claim 1, wherein, The first projected beam of EM energy passes through the first outer surface and reaches the first geometric pattern of the diffraction cavity, and the first diffracted beam of EM energy passes through the second outer surface and reaches outside the structural component.

4. The structural component according to claim 1, wherein, As the first geometric pattern extends outward from the center point, the distance between the first cavity spaces between adjacent diffraction cavities in the first geometric pattern increases.

5. A single-layer structural component, the structural component comprising: First outer surface; Second outer surface; as well as A first geometric pattern of diffraction cavities formed by a first surface within the structural component, the first geometric pattern of diffraction cavities having a first set of diffraction cavities spaced apart from each other by a first cavity spacing distance, wherein the diffraction cavities are unfilled spaces within the structural component, and wherein, when a first projected beam of electromagnetic energy (EM energy) having a first wavelength corresponding to the first cavity spacing distance encounters the first set of diffraction cavities, the first projected beam of EM energy is diffracted, forming a first diffracted beam of EM energy having a first diffraction wavelength, the first diffraction wavelength indicating the change in the first cavity spacing distance caused by strain due to the structural component being exposed to environmental conditions; and The second geometric pattern of the diffraction cavity, formed by a second surface between the first geometric pattern of the diffraction cavity and the second outer surface within the structural component, has a second set of diffraction cavities spaced apart from each other by a second cavity spacing distance different from the first cavity spacing distance. When a second projected beam with EM energy having a second wavelength corresponding to the second cavity spacing distance encounters the second set of diffraction cavities, the second projected beam with EM energy is diffracted, forming a second diffracted beam with diffracted EM energy having a second diffraction wavelength indicating the change in the second cavity spacing distance caused by strain when the structural component is exposed to environmental conditions.

6. The structural component according to claim 5, wherein, The second cavity spacing is greater than the first cavity spacing and the second wavelength is greater than the first wavelength, such that the second projected beam of the EM energy passes through the first geometric pattern of the diffraction cavity without being diffracted.

7. A single-layer structural component, the structural component comprising: First outer surface; Second outer surface; as well as A first geometric pattern of diffraction cavities formed by a first surface within the structural component, the first geometric pattern of diffraction cavities having a first set of diffraction cavities spaced apart from each other by a first cavity spacing distance, wherein the diffraction cavities are unfilled spaces within the structural component, and wherein, when a first projected beam of electromagnetic energy (EM energy) having a first wavelength corresponding to the first cavity spacing distance encounters the first set of diffraction cavities, the first projected beam of EM energy is diffracted and forms a first diffracted beam of EM energy having a first diffraction wavelength, the first diffraction wavelength indicating the change in the first cavity spacing distance caused by strain when the structural component is exposed to environmental conditions, wherein the first geometric pattern of diffraction cavities includes a two-dimensional geometric pattern having a second set of diffraction cavities, the second set of diffraction cavities each having a second cavity spacing distance and spaced apart in a second direction, the second direction not being parallel to the first direction in which the first set of diffraction cavities are spaced apart.

8. The structural component according to claim 7, wherein, The second cavity spacing distance is not equal to the first cavity spacing distance. When a second projected beam with EM energy of a second wavelength corresponding to the second cavity spacing distance hits the second set of diffraction cavities, the second projected beam with EM energy is diffracted and forms a second diffracted beam with diffracted EM energy of a second diffraction wavelength, the second diffraction wavelength indicating the change in the second cavity spacing distance caused by strain when the structural component is exposed to environmental conditions.

9. A single-layer structural component, the structural component comprising: First outer surface; Second outer surface; as well as A first geometric pattern of diffraction cavities formed by a first surface within the structural component, the first geometric pattern of diffraction cavities having a first set of diffraction cavities spaced apart from each other by a first cavity spacing distance, wherein the diffraction cavities are unfilled spaces within the structural component, and wherein, when a first projected beam of electromagnetic energy (EM energy) having a first wavelength corresponding to the first cavity spacing distance encounters the first set of diffraction cavities, the first projected beam of EM energy is diffracted, and a first diffracted beam of EM energy having a first diffraction wavelength is formed, the first diffraction wavelength indicating the effect of exposure when the structural component is exposed to light. The change in the first cavity spacing distance caused by strain due to exposure to environmental conditions, wherein the first geometric pattern of the diffraction cavity includes a second set of diffraction cavities, each having a second cavity spacing distance, wherein when a second projected beam with EM energy having a second wavelength corresponding to the second cavity spacing distance encounters the second set of diffraction cavities, the second projected beam with EM energy is diffracted, and a second diffracted beam with diffracted EM energy having a second diffraction wavelength is formed, the second diffraction wavelength indicating the change in the second cavity spacing distance caused by strain due to exposure of the structural component to environmental conditions.

10. An inspection system for evaluating strain in a structural component of a single-layer structure, the inspection system comprising: A first geometric pattern of diffraction cavities within the structural component, the first geometric pattern of diffraction cavities having a first set of diffraction cavities spaced apart from each other by a first cavity spacing distance, wherein the diffraction cavities are unfilled spaces within the structural component; The first electromagnetic energy source, namely the first EM energy source, projects a first projected beam of EM energy with a first wavelength corresponding to the first cavity spacing distance. When the first projected beam of EM energy is projected onto the structural component, the first projected beam of EM energy passes through the structural component to reach the first geometric pattern of the diffraction cavity and is diffracted by the first set of diffraction cavities to form a first diffracted beam of EM energy with a first diffraction wavelength. The first diffraction wavelength indicates the change in the first cavity spacing distance caused by strain when the structural component is exposed to environmental conditions. An EM energy detector that detects the first diffraction wavelength of the first diffracted beam of EM energy from the first set of diffraction cavities when the first EM energy source projects a first projected beam of EM energy onto the structural component; and A processor, operatively connected to the EM energy detector and configured to receive the first diffraction wavelength of the first diffracted beam of the diffracted EM energy from the EM energy detector and correlate the first diffraction wavelength with strain in the structural component.

11. The inspection system according to claim 10, wherein, The first geometric pattern of the diffraction cavity reflects the first projected beam of the EM energy to return the first diffracted beam of the diffracted EM energy through the structural component, and wherein the first EM energy source and the EM energy detector are located on the same side of the structural component.

12. The inspection system according to claim 10, wherein, The first diffracted beam of the diffracted EM energy is transmitted through the structural component on the side of the first geometric pattern of the diffraction cavity opposite to the first projected beam of the EM energy, and wherein the first EM energy source and the EM energy detector are located on opposite sides of the structural component.

13. The inspection system according to claim 10, wherein, The first geometric pattern of the diffraction cavity has a second set of diffraction cavities spaced apart from each other by a second cavity spacing distance. The inspection system includes a second EM energy source that projects a second projected beam of EM energy at a second wavelength corresponding to the second cavity spacing distance. When the second projected beam of EM energy is projected onto the structural component, it passes through the structural component to reach the first geometric pattern of the diffraction cavity and is diffracted by the second set of diffraction cavities to form a second diffracted beam of EM energy with a second diffraction wavelength indicating the change in the second cavity spacing distance due to strain caused by exposure of the structural component to environmental conditions. Specifically, when the second EM energy source projects the second projected beam of EM energy onto the structural component, the second diffraction wavelength of the second diffracted beam of EM energy reflected by the second set of diffraction cavities is detected by the EM energy detector, and The processor is configured to receive the second diffraction wavelength of the second diffraction beam of the diffracted EM energy from the EM energy detector and associate the second diffraction wavelength with the strain in the structural component.

14. The inspection system of claim 10, wherein the inspection system comprises: The second geometric pattern of the diffraction cavity within the structural component is located at a depth different from the depth of the first geometric pattern of the diffraction cavity at the outer surface of the structural component. The second geometric pattern of the diffraction cavity has a second set of diffraction cavities spaced apart from each other by a second cavity spacing distance. as well as A second EM energy source projects a second beam of EM energy with a second wavelength corresponding to the second cavity spacing distance. When this second beam of EM energy is projected onto the structural component, it passes through the structural component to reach the second geometric pattern of the diffraction cavity and is diffracted by the second set of diffraction cavities to form a second diffracted beam of EM energy with a second diffraction wavelength indicating the change in the second cavity spacing distance caused by strain when the structural component is exposed to environmental conditions. Specifically, when the second EM energy source projects the second projected beam of EM energy onto the structural component, the second diffraction wavelength of the second diffracted beam of EM energy reflected by the second set of diffraction cavities is detected by the EM energy detector, and The processor is configured to receive the second diffraction wavelength of the second diffraction beam of the diffracted EM energy from the EM energy detector and associate the second diffraction wavelength with the strain in the structural component.

15. The inspection system according to claim 14, wherein, The second cavity spacing is greater than the first cavity spacing, and the second wavelength is greater than the first wavelength, such that the second transmitted beam of the EM energy passes through the first set of diffraction cavities without being diffracted.

16. The inspection system according to claim 10, wherein, The first geometric pattern of the diffraction cavity includes a two-dimensional geometric pattern having a first set of diffraction cavities spaced apart in a first direction and a second set of diffraction cavities spaced apart in a second direction, the second direction being non-parallel to the first direction.

17. The inspection system according to claim 16, wherein, The first set of diffraction cavities has a first cavity spacing distance and the second set of diffraction cavities has a second cavity spacing distance that is not equal to the first cavity spacing distance. The first EM energy source projects a second projected beam of EM energy having a second wavelength corresponding to the second cavity spacing distance. The second projected beam of EM energy is diffracted by the second set of diffraction cavities to form a second diffracted beam of EM energy with a second diffracted wavelength. The second diffracted wavelength indicates the change in the second cavity spacing distance due to strain caused when the structural component is exposed to environmental conditions. When the first EM energy source projects the second projected beam of EM energy onto the structural component, the second diffracted wavelength of the second diffracted beam of EM energy reflected by the second set of diffraction cavities is detected by the EM energy detector. The processor is configured to receive the second diffracted wavelength of the second diffracted beam of EM energy from the EM energy detector and correlate the second diffracted wavelength with strain in the structural component.

18. The inspection system of claim 10, the inspection system comprising a portable inspection device, the portable inspection device including the first EM energy source and the EM energy detector, and transmitting the first diffraction wavelength of the first diffracted beam of the diffracted EM energy to the processor via wireless communication.

19. A method for evaluating strain in a single-layer structural component, the structural component having a first geometric pattern of diffraction cavities within the structural component, the first geometric pattern of diffraction cavities comprising a first set of diffraction cavities each having a first cavity spacing distance, wherein, The diffraction cavity is an unfilled space within the structural component, and the method for evaluating strain includes the following steps: A first projected beam of electromagnetic energy, i.e., EM energy, is projected through the structural component to a first geometric pattern of the diffraction cavity, wherein the first projected beam of EM energy has a first wavelength corresponding to the first cavity spacing distance, and wherein the first set of diffraction cavities diffracts the first projected beam of EM energy to form a first diffracted beam of EM energy with a first diffraction wavelength, the first diffraction wavelength indicating the change in the first cavity spacing distance caused by strain when the structural component is exposed to environmental conditions; When the first projected beam of EM energy is projected onto the structural component, the first diffraction wavelength of the first diffracted beam of EM energy from the first set of diffraction cavities is detected; and The first diffraction wavelength of the first diffracted beam, which is the EM energy of the first diffracted beam from the first geometric pattern of the diffraction cavity, is correlated with the strain in the structural component.

20. The method for evaluating strain in a single-layer structural component according to claim 19, wherein, The first geometric pattern of the diffraction cavities includes a second set of diffraction cavities, each having a second cavity spacing distance, and wherein the method for evaluating strain includes the following steps: A second projected beam of EM energy is projected through the structural component to a first geometric pattern of the diffraction cavity, wherein the second projected beam of EM energy has a second wavelength corresponding to the second cavity spacing distance, and wherein the second set of diffraction cavities diffracts the second projected beam of EM energy to form a second diffracted beam of EM energy with a second diffraction wavelength, the second diffraction wavelength indicating the change in the second cavity spacing distance caused by strain when the structural component is exposed to environmental conditions; When the second projected beam of EM energy is projected onto the structural component, the second diffraction wavelength of the second diffracted beam of EM energy from the second set of diffraction cavities is detected; and The second diffraction wavelength of the second diffraction beam, which is the EM energy of the diffraction from the second set of diffraction cavities, is correlated with the strain in the structural component.

21. The method for evaluating strain in a single-layer structural component according to claim 19, the method comprising the steps of: Before the structural component is exposed to environmental conditions, a first projected beam of EM energy is first projected onto the structural component; The reference diffraction wavelength of the first diffracted beam of EM energy from the first set of diffraction cavities is detected when the first projected beam of EM energy is first projected onto the structural component. and After the structural component is exposed to environmental conditions, the first projected beam of EM energy is projected onto the structural component a second time; The first diffraction wavelength of the first diffraction beam of the first diffraction EM energy from the first set of diffraction cavities is detected when the first projected beam of the EM energy is projected onto the structural component for the second time. and When the first projected beam of EM energy is projected onto the structural component for the second time, the first diffraction wavelength of the first diffracted beam of the diffracted EM energy is compared with the reference diffraction wavelength to determine the strain change at the corresponding position of the structural component.

22. The method for evaluating strain in a single-layer structural component according to claim 19, wherein, The structural component has a second geometric pattern of diffraction cavities within the structural component. The second geometric pattern of the diffraction cavities is located at a depth different from the depth of the surface of the structural component and the depth of the first geometric pattern of the diffraction cavities. The second geometric pattern of the diffraction cavities includes a second set of diffraction cavities, each having a second cavity spacing distance. The method for evaluating strain includes the following steps: A second projected beam of EM energy is projected through the structural component to a second geometric pattern of the diffraction cavity, wherein the second projected beam of EM energy has a second wavelength corresponding to the second cavity spacing distance, and wherein the second set of diffraction cavities diffracts the second projected beam of EM energy to form a second diffracted beam of EM energy with a second diffraction wavelength, the second diffraction wavelength indicating the change in the second cavity spacing distance caused by strain when the structural component is exposed to environmental conditions; When the second projected beam of EM energy is projected onto the structural component, the second diffraction wavelength of the second diffracted beam of EM energy from the second geometric pattern of the diffraction cavity is detected; and The second diffraction wavelength of the second diffracted beam, which is the EM energy of the diffracted second geometric pattern from the diffraction cavity, is correlated with the strain in the structural component.

23. The method for evaluating strain in a single-layer structural component according to claim 19, wherein, The first set of diffraction cavities reflects a first projected beam of EM energy to return the first diffracted beam of EM energy transmitted through the structural component, and wherein the method for evaluating strain includes: projecting the first projected beam of EM energy onto the structural component on the same side of the structural component and detecting the first diffraction wavelength.

24. The method for evaluating strain in a single-layer structural component according to claim 19, wherein, The first diffracted beam of EM energy is transmitted through the structural component on the side of the first geometric pattern of the diffraction cavity opposite to the first projected beam of EM energy, and the method for evaluating strain includes: projecting the first projected beam of EM energy onto the structural component on opposite sides of the structural component and detecting the first diffraction wavelength.

25. The method for evaluating strain in a single-layer structural component according to claim 19, the method comprising the steps of: The strain on the structural component is compared with the minimum strain value; and Further inspection of the structural component is performed in response to the determination that the strain on the structural component is greater than the minimum strain value.

26. The method for evaluating strain in a single-layer structural component according to claim 19, the method comprising the steps of: Generate and display a strain pattern derived from the strain in the structural component, wherein the strain pattern is a graphical representation of the strain values ​​in the inspected area of ​​the structural component; and In response to the determination that the strain pattern is different from the expected strain pattern on the structural component, the structural component is further inspected.

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