Abstract:
A method of calculating an amount of visible damage on a component includes capturing an image of the component, identifying an area of visible damage, calculating a size of the area, and communicating the size of visible damage to a storage device. A system for evaluating coating loss is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/905,930, filed Nov. 19, 2013. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    This invention was made with government support under Contract No. F-33657-99-D-2051 0027 awarded by the United States Air Force. The Government has certain rights in this invention. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    This application relates to the use of image technology to calculate the amount of visible damage of a part or structure, e.g., the distress for the coating on a gas turbine engine component. While the exemplary embodiment is in reference to a gas turbine engine, it will be apparent to one of ordinary skill in the art that these teachings apply equally to visible damage in other mechanical devices, aircraft structures, civil structures such as bridges and roadways, etc. 
         [0004]    Gas turbine engines are known and, typically, include a fan delivering air into a compressor. The air is compressed and delivered into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors driving them to rotate. 
         [0005]    The turbine sections and the compressor sections typically include rotors carrying blades having airfoils. There are typically several stages of such airfoils in each of the compressor and turbine sections. Intermediate the stages are static airfoils which are called vanes. 
         [0006]    Many components in a gas turbine engine are provided with protective coatings. As an example, the turbine and exhaust components are subjected to very high temperatures and, thus, they often have a thermal coating to assist in resisting the high temperatures. 
         [0007]    Over time and with use, these coatings can become distressed and erode, or otherwise are lost. 
         [0008]    Routine maintenance requires calculation of the amount of lost coating on airfoils or structures. Historically, the amount of lost coating on the surface area of the airfoils has been calculated manually. 
         [0009]    Image processing software is known in the prior art for calculating metric areas based upon photographic images given an a priori known perspective projection and fiducial marks to establish scale. However, no such system has been utilized to evaluate visible damage, e.g., coating loss, on airfoils, or parts or structures in general, because of the difficulty of establishing in practice the perspective projection and scale. While an area measurement in relative units is occasionally useful, a metric area is frequently required to quantify the area in absolute units for subsequent assessment. 
       SUMMARY OF THE INVENTION 
       [0010]    In a featured embodiment, a method of calculating an amount of visible damage on a component includes capturing an image of the component, identifying an area of visible damage, calculating a size of the area, and communicating the size of visible damage to a storage device. 
         [0011]    In another embodiment according to the previous embodiment, the communication step is performed by a one of a hardwired and wireless connection between an image capture tool and the storage device. 
         [0012]    In another embodiment according to any of the previous embodiments, capturing an image of the component is performed by an image capturing tool including a display and a camera. 
         [0013]    In another embodiment according to any of the previous embodiments, lasers assist in providing a scale to the captured image. 
         [0014]    In another embodiment according to any of the previous embodiments, the area of visible damage is contoured on the captured image. 
         [0015]    In another embodiment according to any of the previous embodiments, a size of the contoured area is calculated. 
         [0016]    In another embodiment according to any of the previous embodiments, the image capture tool includes a wireframe used to align the image capture tool with the component to be evaluated. 
         [0017]    In another embodiment according to any of the previous embodiments, capturing an image of the component is performed by an image capturing tool including a display and a camera. 
         [0018]    In another embodiment according to any of the previous embodiments, the image capture tool includes a wireframe used to align the image capture tool with the component to be evaluated. 
         [0019]    In another embodiment according to any of the previous embodiments, lasers assist in providing a scale to the captured image. 
         [0020]    In another embodiment according to any of the previous embodiments, the area of visible damage is contoured on the captured image. 
         [0021]    In another embodiment according to any of the previous embodiments, a size of the contoured area is calculated. 
         [0022]    In another embodiment according to any of the previous embodiments, the component is a gas turbine engine component. 
         [0023]    In another embodiment according to any of the previous embodiments, the gas turbine engine component includes one of a blade, a vane, a panel, a flame holder, a lining, a tail cone, a duct, a cover, a heat shield, a flap. 
         [0024]    In another embodiment according to any of the previous embodiments, the visible damage is damage to the thermal barrier coating on the gas turbine engine component. 
         [0025]    In another featured embodiment, a system for evaluating coating loss includes an image capture device, which is capable of capturing an image of a component to be evaluated. The image capture device is capable of communicating with an analyzing unit capable of distinguishing a visible damage area from an visible undamaged area and calculating a size of the visible damage area. 
         [0026]    In another embodiment according to the previous embodiment, the image capture device is provided with a camera for capturing the image, and lasers to assist in providing a scale to the captured image. 
         [0027]    In another embodiment according to any of the previous embodiments, a location of projected laser points on the captured image is utilized to calculate the size of the visible damage on the captured image. 
         [0028]    In another embodiment according to any of the previous embodiments, a change in the visible damage area is monitored over time. 
         [0029]    In another embodiment according to any of the previous embodiments, there is a display and a wireframe on the image capture device that allows a user to align the image capture device with one of a component and a structure to be evaluated. 
         [0030]    These and other features may be best understood from the following drawings and specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  shows a gas turbine engine component. 
           [0032]      FIG. 2A  shows a tool for evaluating the component. 
           [0033]      FIG. 2B  is a rear view of the tool. 
           [0034]      FIG. 2C  is another view of the tool. 
           [0035]      FIG. 3A  shows a first step. 
           [0036]      FIG. 3B  shows a subsequent step. 
           [0037]      FIG. 3C  shows another step. 
           [0038]      FIG. 4  schematically shows an overall system. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    A gas turbine engine component  20 , which may be a turbine blade, is shown in  FIG. 1 . In other embodiments, the turbine component  20  might be part of any other type of turbine, such as a steam turbine, or the component might be another part of a turbine such as a vane, lining, flame holder, flap, etc., or the component might be part of any machine or structure susceptible to visibly discernable damage. In the preferred embodiment, an airfoil  22  is formed as part of the component  20 . As known, the airfoil  22  may be provided with a protective coating  25 . As shown at  24 , areas of this coating may become distressed and lost. It is a routine maintenance requirement to evaluate the amount of lost coating or damage to the coating as shown at  24 . This area must be evaluated over time to determine a lifespan of the component  20 . 
         [0040]    A tool  30  for calculating the amount of visible damage is illustrated in  FIG. 2A . An image  32  of the component is taken and displayed on a screen  31 . An area of visible damage  34  will be readily apparent to any number of image processing software systems. As an example, the visible damage might be that coated areas of a part may be brighter in the visible spectrum than the areas where the coating has been compromised. It will be obvious to one of ordinary skill in the art that the damage may be visible in imaging devices, including cameras, lidars, sonars, and radars, sensitive to other parts of the electromagnetic or acoustic spectrum such as ultraviolet or infrared cameras. Area  34  corresponds to area  24 . 
         [0041]      FIG. 2B  shows a rear view of the tool  30 . In an embodiment, a visible spectrum camera  36  is utilized to capture the image  32  of the component. 
         [0042]    One of more laser pointers  38  are disposed orthogonally to the camera to provide projected points on the part and visible in the image as will be shown below, such that the metric area of visible damage  34  can be calculated. 
         [0043]      FIG. 2C  shows a “wireframe”  40  which is included on the display  31 . Preferably, a wireframe  40  is stored for each component that may be evaluated utilizing the tool  30 . Thus, when initially capturing the image  32 , a user will align the wireframe  40  such that it meets with the contours of the component  20  to be evaluated. In this manner, the user insures that the images are repeatedly captured at an a priori known perspective. 
         [0044]      FIG. 3A  shows a portion of a captured image  32 . A defective area  34  is shown within an uncompromised area  35 . The area  35  and, perhaps area  34  depending on the nature of the damage, may have visible non-damage features  51 ,  52  in regular patterns or irregularly spaced across the areas  34 ,  35 . 
         [0045]    Image analytic software can calculate the metric area of the visible damage  34  initially by establishing scale, such as evaluating the distance between some of the projected laser points, such as shown at  60 ,  62  and  64 , between each other or from the origin of a reference coordinate system as shown in  FIG. 3B . 
         [0046]    Then, the entire area  34  can be contoured as shown at  78  and the overall area calculated, as shown in  FIG. 3C . 
         [0047]    While any number of mathematical techniques for contouring can be utilized, one particular technique is a geometric active contour, possibly with manual initialization. In another embodiment, level set methods are used. Since either embodiment produces a closed, simple, polygonal contour, the well-known product of adjacent point sums algorithm is used to compute the area (in pixels), see, e.g., “Ultra-Easy Polygon Area Algorithm with C Code Sample” by D. R. Finley. While the image could be rectified based on the wireframe or estimated pose, this rectification is unnecessary. The metric area is calculated from the area in pixels, the scale, and the trigonometric relations from the pose. 
         [0048]      FIG. 4  shows a system  90  incorporating the tool  30  and a connection  99  to a processing unit and storage, such as a computer  100 . In one embodiment, the connection  99  is hardwired. In another embodiment, the connection is wireless. The computer  100  will store a total amount of visible damage for a particular component, and will calculate the change in the amount of damage by well-known image registration techniques and will compare the newly detected damage to previous images and damage estimates. 
         [0049]    Once a particular amount of damage has been detected, it may be necessary to replace the part or send it for repair. 
         [0050]    The disclosed embodiments, thus, provide a system which evaluates visible damage, and in particular coating loss, in a very efficient manner compared to the prior art. Further, the accuracy of the overall measurement may be improved. 
         [0051]    Although an embodiment of this invention has been disclosed, one of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.