Patent Description:
In many applications, near surface cracks, voids, discontinuities, flaws, and defects in ferrous or nonferrous materials must be detected in order to ensure the structural integrity of a material. For example, the material integrity of components comprising many air and space vehicles is critical for their proper operation, especially with regard to components subjected to high stresses, such as turbine and fan blades.

A number of non-destructive testing techniques are utilized to detect cracks, flaws, defects or the like in materials. For example, fluorescent penetrant inspection (FPI) can be used to visualize defects that are in communication with the surface of a material. However, FPI is unable to detect internal defects in a material that lack an opening to the surface of a material.

There is a need for simple, flexible, and effective system for visualizing defects in a material.

<CIT> discloses a magneto-optic device to be used in industrial applications to investigate articles for flaws or defects. The magneto-optic device is capable of revealing defects in articles of nonmagnetic and magnetic conducting material. These results are achieved by designing a magneto-optic device having a magneto-optic transformer element on its bottom surface and incorporating a front electrical contact and a rear electrical contact on the bottom surface of the magneto-optic device. The respective electrical contacts are connected by wire conductors to the respective positive and negative terminals of a source of electrical current. The defect pattern of an article can be either visually viewed or the defect pattern can be recorded on a tape or magnetic rubber sheet placed between the bottom surface of the magneto-optic device and the top surface of the article being analyzed.

In an aspect, there is provided an apparatus for visualizing defects in a component using a magneto-optical effect in accordance with claim <NUM>. In a further aspect, there is provided a method of detecting defects in a component in accordance with claim <NUM>.

A full and enabling disclosure of the aspects of the present description, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which refers to the appended figures, in which:.

For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present teachings. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present teachings. Certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required.

One method utilized to detect defects or cracks in materials is the "eddy current" technique. Eddy current techniques typically utilize a time varying electromagnetic field which is applied to the target material. Non-contact coils may then be used to excite eddy currents in the target material, such that these currents tend to flow around defects and result in field distortions which allow the defect to be detected in a number of ways. For example, circuit parameters characterizing the mutual interaction between the exciting coil and the responding material may comprise the parameters of capacitance, inductance, or reactance. However, conventional eddy current techniques require a considerable amount of support equipment and most techniques do not result in a defect image but rather produce data from which defect information can be obtained only after appropriate analysis has been completed. Further, conventional eddy current techniques are considerably impacted by lift-off variations and surface anomalies.

The following embodiments illustrate magneto-optic visualization apparatuses and systems that allow for visualization of defects in materials using existing imaging devices, such as smartphones, tablet computers, and borescopes. The apparatuses and systems also allow for improved visualization of defects in components with non-planar surfaces, through provision of one or more flexible and/or conformable optical elements and a flexible coil for inducing a magnetic field in the component. The magneto-optic visualization systems may advantageously be combined with other devices such as arms to extend the reach of a user to visualize defects in difficult to reach places. In addition, the magneto-optic visualization systems may be implemented with a crawling robot to allow for magnet-optic visualization and/or scanning of remote or difficult to access locations. The magneto-optic visualization system may also be configured to transmit magneto-optically derived images or video to a computing device and/or display so that the images or video may be viewed by a remote user or processed and stored by a remote computing system.

The terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein. The word "or" when used herein shall be interpreted as having a disjunctive construction rather than a conjunctive construction unless otherwise specifically indicated.

Accordingly, a value modified by a term or terms such as "about", "approximately", and "substantially", are not to be limited to the precise value specified.

The foregoing and other benefits may become clearer upon making a thorough review and study of the following detailed description. Referring now to the drawings, and in particular to <FIG>, there is illustrated an exemplary gas turbine engine <NUM>. The gas turbine engine <NUM> defines an axial direction <NUM>, a radial direction <NUM>, and a circumferential direction <NUM> (i.e., a direction extending about the axial direction <NUM>). The gas turbine engine <NUM> includes an outer casing <NUM> about a fan section <NUM> followed by a core section <NUM>. The core section <NUM> includes an inner casing <NUM> that may be substantially tubular and that defines an annular inlet <NUM>. The inner casing <NUM> encases, in the axial direction <NUM>, a compressor section including a low-pressure compressor (LPC) <NUM> and a high-pressure compressor (HPC) <NUM>, a combustion section <NUM>, a turbine section including a high-pressure turbine (HPT) <NUM> and a low-pressure turbine (LPT) <NUM>, and a jet exhaust nozzle section <NUM>. A low pressure (LP) shaft <NUM> drivingly connects the LPC <NUM> to the LPT <NUM>. A high pressure (HP) shaft <NUM> drivingly connects the HPC <NUM> to the <NUM> HPT.

The fan section <NUM> includes a fan <NUM> having a plurality of fan blades <NUM> extending in the radial direction <NUM> from a disc <NUM>. The LPT <NUM> drives rotation of the fan <NUM>. More specifically, the fan blades <NUM>, the disc <NUM>, and an actuation member <NUM> are rotatable together in the circumferential direction <NUM> by LP shaft <NUM> in a "direct drive" configuration. Accordingly, the LPT <NUM> rotates the fan <NUM> at the same rotational speed of the LPT <NUM>.

A rotatable front hub <NUM> covers the disc <NUM> and is aerodynamically contoured to promote an airflow through the plurality of fan blades <NUM>. Additionally, the fan section <NUM> includes an outer nacelle <NUM> that circumferentially surrounds the fan section <NUM> and a portion of the core section <NUM>. More specifically, the nacelle <NUM> includes an inner wall <NUM> with a section that extends over the core section <NUM> to define a bypass airflow passage <NUM> therebetween. Additionally, the nacelle <NUM> is supported relative to the core section <NUM> by a plurality of circumferentially spaced struts <NUM> that extend in the radial direction <NUM> and are shaped as guide vanes.

During operation of the gas turbine engine <NUM>, a volume of air <NUM> enters the gas turbine engine <NUM> through an associated inlet <NUM> of the nacelle <NUM>. As the volume of air <NUM> passes the fan blades <NUM>, a first portion of the air <NUM> flows into the bypass airflow passage <NUM>, and a second portion of the air <NUM> flows into the LPC <NUM>. The pressure of the second portion of air <NUM> is then increased as it flows through the HPC <NUM> and into the combustion section <NUM>, where it is mixed with fuel and burned to provide combustion gases <NUM>.

The combustion gases <NUM> flow through the HPT <NUM> where a portion of thermal and/or kinetic energy from the combustion gases <NUM> is extracted via sequential stages of HPT stator vanes that are coupled to an inner casing <NUM> and HPT rotor blades that are coupled to the HP shaft <NUM>, thus causing the HP shaft <NUM> to rotate, which causes operation of the HPC <NUM>. The combustion gases <NUM> then flow through the LPT <NUM> where a second portion of thermal and kinetic energy is extracted from the combustion gases <NUM> via sequential stages of LPT stator vanes that are coupled to the inner casing <NUM> and LPT rotor blades that are coupled to the LP shaft <NUM>, thus causing the LP shaft <NUM> to rotate, which causes operation of the LPC <NUM> and/or the fan <NUM>.

The combustion gases <NUM> subsequently flow through the jet exhaust nozzle section <NUM> to provide propulsive thrust. Simultaneously, the pressure of the first portion of air <NUM> is substantially increased as the first portion of air <NUM> flows through the bypass airflow passage <NUM> before it is exhausted from a fan nozzle exhaust section <NUM>, also providing propulsive thrust. The HPT <NUM>, the LPT <NUM>, and the jet exhaust nozzle section <NUM> at least partially define a hot gas path for routing the combustion gases <NUM> through core section <NUM>.

It should be appreciated, however, that the exemplary gas turbine engine <NUM> depicted in <FIG> and described above is by way of example only, and that in other exemplary embodiments, the gas turbine engine <NUM> may have any other suitable configuration. For example, in other exemplary embodiments, the engine <NUM> may include any other suitable number of compressors, turbines and/or shaft. Additionally, the gas turbine engine <NUM> may not include each of the features described herein, or alternatively, may include one or more features not described herein. Additionally, although described as a "turbofan" gas turbine engine, in other embodiments the gas turbine engine may instead be configured as any other suitable ducted gas turbine engine.

Referring now to <FIG>, an illustrative magneto-optic defect visualization or imaging apparatus <NUM> and system <NUM> that is compatible with many of these teachings will now be presented. A sample component <NUM> is provided which may include a defect <NUM>, such as a flaw, a crack, or corrosion, within the surface <NUM> or subsurface <NUM> of the component <NUM>. The magneto-optic imaging apparatus <NUM> for visualizing a defect <NUM> includes a housing <NUM> which in one form includes an imaging device mounting interface <NUM> at a proximal end of the housing configured for removably attaching a separate imaging device <NUM> to the housing <NUM>. A variety of imaging devices <NUM> may be used together with the housing <NUM>. In general, the imaging device <NUM> will include a light source <NUM> and a camera <NUM>, and optionally a display <NUM>, which may be integrated with the imaging device <NUM> or provided separately. Non-limiting examples of suitable imaging devices <NUM> include mobile telephones or smartphones, tablet computers, laptop computers, borescopes, cameras, and the like. The imaging device mounting interface <NUM> may take a variety of forms suitable for securely attaching the imaging device <NUM> to the housing <NUM>, and may include straps, hooks, a slot or slots, a sleeve, magnets, hook and loop fasteners, threaded fasteners, snaps, clamps, and the like. The imaging device <NUM> is attached to the imaging device mounting interface <NUM> with its light source <NUM> and camera <NUM> oriented in a distal direction toward the component <NUM> and a display <NUM> (if present) facing proximally away from the component <NUM>.

The magneto-optic imaging apparatus <NUM> is preferably adapted to attach or mount an existing imaging device <NUM> thereto and advantageously provides the existing imaging device <NUM> with magneto-optic imaging capabilities. This allows a user to easily conduct magneto-optic imaging of components <NUM>, such as fan blades <NUM>, simply by attaching the magneto-optic imaging apparatus <NUM> to an imaging device <NUM> which, in the case of a smartphone, they may already have in their pocket. By using the camera functionality of the imaging device <NUM>, such as a smartphone, images or videos of visualized defects <NUM> in a component <NUM> may be easily viewed, stored, and shared, such as via SMS, e-mail, video call, livestream, Bluetooth link, Wi-Fi connection or other known communication methods. Magneto-optically derived images or videos may also be further analyzed by a special purpose application of the imaging device <NUM> or a remote computing device <NUM>. In another form, the imaging device <NUM> may be specially designed to be integrated with the housing <NUM>.

The magneto-optic imaging apparatus <NUM> includes a plurality of optical elements for enabling magneto-optic imaging of a component. One or more white light filters <NUM> are provided within the housing <NUM> and optically aligned with the light source <NUM> for filtering the light <NUM> emitted by the light source <NUM> to one or more wavelengths of filtered light <NUM>. A conventional polarizer <NUM> is provided distal to the filter or filters <NUM> and in optical alignment therewith for linearly polarizing the filtered light <NUM> to produce polarized light <NUM> having a polarization state. At a distal end <NUM> of the housing <NUM> opposite from the imaging device mounting interface <NUM>, a distally-oriented face <NUM> is provided, which includes a flat, transparent, non-conformable surface that allows the polarized light <NUM> to pass through the face <NUM>.

A translucent or transparent conformable body <NUM> in optical alignment with the polarizer <NUM> is attached to the distally-oriented face <NUM> and is adapted to allow the polarized light <NUM> to pass therethrough. The conformable body <NUM> is of a material or combination of materials that are adapted to conform with a non-planar surface of the component <NUM> when the distal end <NUM> of the housing <NUM> is pressed against the component <NUM>, as shown in <FIG>. For example, the conformable body <NUM> may be a gel-like material, a solid material, such as a transparent flexible elastomer, such as polydimethylsiloxane, or a fluid or gel-like material encapsulated by a transparent or translucent conformable thin-walled container or a deformable membrane. The fluid contained within the container or membrane of the conformable body <NUM> may be a gas, such as air, or a liquid, such as water, an oil, or an alcohol. The material or materials of the conformable body <NUM> may be elastic such that the conformable body <NUM> has an uncompressed shape and is adapted to resume its uncompressed shape after being compressed. For example, the conformable body <NUM> may be a fluid-filled flexible membrane which deforms and conforms to a shape of a component <NUM> when pressed against the component <NUM> and which resumes its relaxed form when the external pressure is removed.

A conventional magneto-optic or garnet film <NUM> is attached to or integrated with a distal side of the conformable body <NUM>. The magneto-optic or garnet film <NUM> is preferably flexible and has maximum sensitivity. A flexible coil <NUM> is positioned at a distal side of the magneto-optic film <NUM> and may be attached thereto or to the conformable body <NUM>. The flexible coil <NUM> preferably has a sheet-like or planar configuration. Both the magneto-optic or garnet film <NUM> and planar flexible coil <NUM> are adapted to conform, along with the conformable body <NUM>, to a non-planar surface <NUM> of a component <NUM>, so that defects or flaws <NUM> in a wide variety of non-planar components may be visualized. Instead of a planar flexible coil <NUM>, a pair of spaced-apart electrical terminals <NUM> may be provided at the distal end of the housing <NUM> for inducing a current and a resultant magnetic field in the component <NUM>.

The planar flexible coil <NUM> or electrical terminals <NUM> are connected via an electrical connection <NUM> to a current source <NUM>. The current source <NUM> may be integral to the imaging device <NUM> or may be provided separately therefrom. For example, an adapter <NUM> may be used to access the imaging device's <NUM> host power via an electrical interface <NUM>, such as a bus connection or charging port of the imaging device <NUM>, such that a battery of the imaging device <NUM> is used to generate the required current in the planar flexible coil <NUM> or electrical terminals <NUM>. The adapter <NUM> may also include a DC to AC inverter to convert the current provided by the imaging device <NUM> from direct to alternating current. In another form, a conventional current source <NUM> external from the imaging device <NUM> and the magneto-optic imaging apparatus <NUM> may be implemented.

The polarized light <NUM>, after passing through the transparent face <NUM> of the housing <NUM> and the conformable body <NUM>, is reflected by the magneto-optic or garnet film <NUM>. The reflection causes variations in the polarization state of the polarized light <NUM>, and particularly in the angle of the plane of polarization due to the variations in the magneto-optic film caused by induced magnetic fields. The reflected light <NUM> then passes through the conformable body <NUM> and transparent face <NUM> of the housing <NUM> again. The reflected light <NUM> then passes through a conventional analyzer (a second polarizer) <NUM>, which converts the variations in the polarization state of the reflected light <NUM> (with respect to the polarization state of the polarized light <NUM> transmitted through the polarizer <NUM>) to variations in light intensity that are visible. The reflected light <NUM> may be directed towards the camera <NUM> of the imaging device <NUM> with one or more reflective surfaces or refractive units <NUM>, such as mirrors or prisms positioned in optical alignment with the analyzer <NUM>.

The reflected light <NUM> thus provides a visual image of how the magneto-optic film <NUM> reacts to the induced magnetic fields from eddy-currents in the component surface <NUM> and subsurface <NUM>. Accordingly, any defects <NUM> in the component are thereby rendered visible, and can be viewed with a display, such as display <NUM> of the imaging device <NUM>. If no crack or defect <NUM> is present in the component surface <NUM> or subsurface <NUM>, the image seen by the camera <NUM> is a completely dark or light image. If a crack or defect <NUM> is present, the image seen by the camera <NUM> will include contrasting dark or light patterns corresponding to the crack or defect <NUM>.

The camera <NUM> of the imaging device <NUM> includes at least a lens <NUM>, an aperture, a sensor, and an image signal processor. The light source <NUM> of the imaging device <NUM> in some forms may be a flash associated with the camera <NUM>. In some forms, the light source <NUM> may be one or more LEDs. In other forms, the light source <NUM> may comprise an incandescent bulb, a fluorescent lamp, or a laser. The display <NUM> may take the form of an LCD or LED screen, and may be a touch screen. Remote displays <NUM> (e.g., see <FIG>) may include any kind known in the art. The imaging device <NUM> may include wireless functionality in the form of a wireless module <NUM> for transmitting data, including image or video data, from the camera <NUM>, to a remote computing device <NUM>, such as a smartphone, tablet computer, computer, remote server, or cloud computing resource, including a display <NUM> thereof, as shown in <FIG>.

As shown in <FIG>, the magneto-optic imaging apparatus <NUM> is adapted to visualize defects <NUM> in a component <NUM> with a non-planar surface <NUM>. In particular, when the magneto-optic film <NUM>, flexible coil <NUM>, and conformable body <NUM> at the distal end <NUM> of the housing <NUM> are pressed against the surface <NUM> of component <NUM>, they are sandwiched between the non-conformable face <NUM> of the housing <NUM> and the surface <NUM> and conform to the shape of the surface <NUM>. This allows the flexible coil <NUM> and magneto-optic film <NUM> to be in close and uniform proximity to the surface <NUM> of the component <NUM>, which improves the induction of a magnetic field into the surface <NUM> of the component <NUM> by the flexible coil <NUM> and improves the visualization of magnetic fields in the magneto-optic film <NUM>.

The magneto-optic imaging apparatus <NUM> and imaging device <NUM> may advantageously be connected to other devices for positioning the combined magneto-optic imaging system <NUM> in position for magneto-optically visualizing defects <NUM> within a component <NUM>. In one form shown in <FIG>, the combined magneto-optic imaging system <NUM> may be attached to a distal end <NUM> of an elongate arm <NUM>, which may be a rigid or collapsible pole, a selfie stick, a robotic arm, or the like. Accordingly, a user may directly or indirectly manipulate the arm <NUM> from a proximal end <NUM> of the arm or from another location remote from the component <NUM> to position the magneto-optic imaging system <NUM> in contact with the component <NUM> and move the magneto-optic imaging system <NUM> along the surface <NUM> of the component <NUM> to detect defects <NUM> in the component <NUM>.

In another form, the magneto-optic imaging system <NUM> may be operably connected to a robotic vehicle <NUM>, such as a crawler, as shown in <FIG>. In each embodiment, images or video acquired from the imaging device <NUM> may be advantageously transmitted via a wired connection or a wireless communication module <NUM> of the imaging device <NUM>. The wireless communication module <NUM>, such as a Wi-Fi or cellular module, may be configured to transmit data, including image or video data, via a wireless gateway <NUM> to a network <NUM>, such as a LAN, WAN, the internet, etc., and on to one or more remote computing devices <NUM> and displays <NUM>. Similarly, the robotic vehicle <NUM> and magneto-optic imaging system may be controlled by a user of a remote device <NUM> via network <NUM>.

Claim 1:
An apparatus (<NUM>) for visualizing defects (<NUM>) in a component (<NUM>) using a magneto-optical effect, comprising:
a housing (<NUM>) having a proximal interface (<NUM>) configured to be removably connected to an imaging device (<NUM>) having a camera (<NUM>) and a light source (<NUM>);
a filter (<NUM>) disposed in the housing (<NUM>) adapted to filter light (<NUM>) from the light source (<NUM>) directed therethrough;
a polarizer (<NUM>) disposed in the housing (<NUM>) adapted to polarize the filtered light (<NUM>) into polarized light (<NUM>) having a polarization state;
a transparent or translucent conformable body (<NUM>) operably connected to the housing (<NUM>) at a distal end (<NUM>) thereof and adapted to:
allow the polarized light (<NUM>) to pass therethrough; and
conform to a non-planar surface (<NUM>) of the component (<NUM>);
a magneto-optic film (<NUM>) operably connected to the transparent or translucent conformable body (<NUM>) configured to reflect the polarized light (<NUM>);
at least one of:
a flexible coil (<NUM>) operably connected to the magneto-optic film (<NUM>); and
electrical terminals (<NUM>) disposed at a distal end (<NUM>) of the housing (<NUM>), wherein the at least one of the flexible coil (<NUM>) and the electrical terminals (<NUM>) is adapted to induce a magnetic field in the component (<NUM>); and
an analyzer (<NUM>) disposed in the housing (<NUM>) configured to convert variations in a polarization state of the reflected light (<NUM>) relative to the polarization state of the polarized light (<NUM>) to visible variations in light intensity.