Abstract:
Methods and apparatus for inspecting a component are provided. The method includes receiving a plurality of data points that define a shape of the component, fitting the received data points to a curve that defines a predetermined model shape, and comparing the received data points to the curve defining the predetermined model shape to determine a break radius of the component.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to non-destructive inspection and, more particularly, to dimensional inspection of fabricated components. 
   Dimensional inspection techniques are used in many applications where the non-destructive evaluation (NDE) of a workpiece or component is desired. At least some known inspection techniques include a visual or manual inspection to facilitate determining a service condition of a component. A knowledgeable and skilled technician may be able to ascertain the worthiness of a particular component for replacement using visual or manual inspection, however visual or manual inspection may not be accurate enough for modem components, nor repeatable for quality verification purposes. For example, a compressor blade dovetail outer edge break radii may be small and span only a few degrees of arc, which may require a relatively accurate relative measurement to determine the actual radius. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one embodiment, a method of inspecting a component is provided. The method includes receiving a plurality of data points that define a shape of the component, fitting the received data points to a curve that defines a predetermined model shape, and comparing the received data points to the curve defining the predetermined model shape to determine a break radius of the component. 
   In another embodiment, a dimensional inspection system is provided. The inspection system includes a fixture configured to maintain a component in a predetermined fixed position during a scan of the component, a profileometer configured to trace a profile of the component, and a controller communicatively coupled to the profileometer, the controller configured to compare the traced profile to a curve defining a predetermined model shape to determine whether a break radius of the traced profile substantially equals a predetermined allowable break radius of the component. 
   In yet another embodiment, a computer program embodied on a computer readable medium is provided. The computer program includes a code segment that prompts a user to select a predetermined profile specification and then determines an initial position of at least one of a tracing shaft and a measurement unit, receives a plurality of data points that define a profile of a component, determines, using the predetermined profile specification and the plurality of received data points, whether the component profile is substantially equal to the predetermined profile specification, and transmits an indication of the determination to at least one of a display and a computer readable file. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view of an exemplary embodiment of a profile measuring gauge system; 
       FIG. 2  is an exemplary screen shot of an output that may be generated by the profile measuring gauge system shown in  FIG. 1  in response to measuring a quality indicator gauge; 
       FIG. 3  is an exemplary screen shot of an output that may be generated by the profile measuring gauge system shown in  FIG. 1  in response to measuring a component contour; and 
       FIG. 4  is a flow chart illustrating an exemplary method of evaluating a radius of the component shown in  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As used herein, the term “component” may include any component configured to be coupled within a gas turbine engine, wherein the component may include dimensional characteristics indicative of component wear and/or failure The turbine blade dovetail illustrated is intended as exemplary only, and thus is not intended to limit in any way the definition and/or meaning of the term “component”. Furthermore, although the invention is described herein in association with a gas turbine engine, and more specifically for use with a rotor for a gas turbine engine, it should be understood that the present invention is applicable to other components, such as gas turbine engine stationary components, and components associated with machines other than gas turbine engines. Accordingly, practice of the present invention is not limited to gas turbine engines. 
     FIG. 1  is a schematic view of an exemplary embodiment of a profile measuring gauge system  10 . System  10  includes a base  12  that supports a column  14 . A main housing  16  is coupled to column  14  such that main housing  16  may translate substantially vertically in a first direction, indicated by arrow  18  and in an opposite direction, indicated by arrow  20 . Main housing  16  includes electronic circuitry to facilitate controlling operation of gauge system  10  and pre-processing data. A support arm  22  is slidably coupled to main housing  16  such that support arm  22  may be translated horizontally along a longitudinal axis  24 . A stylus  26  coupled to support arm  22  may be mounted such that it can pivot in order to enable a tip  27  of stylus  26  to trace a surface  28  of a workpiece or component  29  during relative movement of stylus  26  and surface  28 . 
   The displacement of stylus  26  as it follows surface  28  is detected using a transducer  30  and an output of the transducer may be transmitted to data logging and processing equipment  32  (e.g. a personal computer) through a cable  34  or other communications link, including optic and wireless communication devices. Data indicating a relative position of tip  27  of stylus  26  along component  29  also may be transmitted to data logging and processing equipment  32  to provide data indicative of a measurement of a surface profile or form of component  29 . Either Stylus  26 , surface  28 , or both may be moved with respect to the other member so as to allow the generation of a two- or three-dimensional surface map which can then be displayed on a visual display unit  36  or printed as a hard copy. In the exemplary embodiment, a linear variable differential transducer (LVDT) is used in combination with stylus  26  to detect the position of tip  27  as it traces surface  28  of component  29 . 
   A turntable  38  for supporting component  29  on a high accuracy air bearing spindle, may be coupled directly to base  12 , or maybe coupled to a common support, such as a work bench  40 . Turntable  38  may incorporate a clamping device or retaining member that may be used to secure component  29  in a fixed position relative to stylus  26 . 
   Support arm  22  may be pivotally mounted within main housing  16  such that support arm  22  is pivotable about an axis  23  extending in a direction parallel to work bench  40 . For example, in one embodiment, support arm  22  is pivotable generally horizontally and as such, is substantially perpendicular to axis  24 . 
   In operation, component  29  including surface  28  whose profile is to be measured is mounted to turntable  38 . In the exemplary embodiment, surface  28  of component  29  includes a curved portion, or break edge, that has a radius of curvature, or break radius (see  FIG. 3 ). In the exemplary embodiment, component  29  is a gas turbine engine compressor blade having a dovetail outer break edge. The break edge radii may bc relatively small and span only a few degrees of arc. Component  29  may be mounted on turntable  38  and secured such that component  29  is maintained in position at a predetermined height and distance such that tip  27  may be positioned to contact surface  28 . During a scan, support arm  22  may be retracted axially from a first starting position, which also defines a starting position of tip  27 . During retraction of support arm  22 , tip  27  traces the contour of surface  28 . Contact between tip  27  and surface  28  is facilitated to be maintained by a biasing mechanism, such as, for example, gravity, a spring, or any other suitable biasing member (not shown). Any displacement of tip  27  from the starting position is detected by transducer  30  and a corresponding output is generated. 
     FIG. 2  is an exemplary screen shot  200  of an output that may be generated by profile measuring gauge system  10  in response to measuring a quality indicator gauge (not shown). A quality indicator gauge may be used as a standard for a calibration and/or performance check of profile measuring gauge system  10 . In the exemplary embodiment, the quality indicator gauge includes four lobes that each have a different radius with respect to each other lobe. Screen shot  200  includes a display area  202  and a control panel  204 . Control panel  204  may be used to control a display of data in display area  202 . 
   In the exemplary embodiment, display area  202  illustrates a curve  206  of data points of the quality indicator gauge collected by profile measuring gauge system  10 . A first portion  208  of curve  206  is generated in response to data collected from a first lobe of the quality indicator gauge. A radius of first portion  208  is indicated by a line  210  and a value of the radius may be displayed in display area  202 . A second portion  212  of curve  206  is generated in response to data collected from a second lobe of the quality indicator gauge. A radius of second portion  212  is indicated by a line  214  and a value of the radius may be displayed in display area  202 . A third portion  216  of curve  206  is generated in response to data collected from a third lobe of the quality indicator gauge. A radius of third portion  216  is indicated by a line  218  and a value of the radius may be displayed in display area  202 . A fourth portion  220  of curve  206  is generated in response to data collected from a fourth lobe of the quality indicator gauge. A radius of fourth portion  208  is indicated by a line  222  and a value of the radius may be displayed in display area  202 . 
     FIG. 3  is an exemplary screen shot  300  of an output that may be generated by profile measuring gauge system  10  in response to measuring component  29 . In the exemplary embodiment, component  29  is a dovetail portion of a gas turbine engine blade. In an alternative embodiment, component  29  may be any component, or portion of a component, that a user desires measuring to obtain dimensional information. Screen shot  300  includes a display area  302  that displays information regarding the operation of a curve fitting algorithm utilized by profile measuring gauge system  10 . In various embodiments, the curve-fitting algorithm may be executed by another machine using data accessible from profile measuring gauge system  10  through a network, communication media, data storage media or other data communications device. A first CAD curve  304  defines a specification profile for a shape of component  29  traced by profile measuring gauge system  10 . Cad curve  304  may be stored in a database containing data associated with component  29 , such as the specification for the profile measured by profile measuring gauge system  10 . A limit curve  306  defines a limit for the maximum radius for a contour of component  29  traced by profile measuring gauge system  10 . In the exemplary embodiment, the maximum radius is selected to be about 0.015 inches. 
   A curve  308  displays data received by profile measuring gauge system  10  during a scan of component  29 . Curve  308  includes a plurality of discrete data points sampled by profile measuring gauge system  10  as tip  27  traces surface  28  of component  29 . In the exemplary embodiment, an iterative curve-fitting algorithm selects a portion of the plurality of discrete data points, such as forty points on each side of a selected midpoint  310 , to “best fit” to CAD curve  304 . A break radius  312  for each of the selected midpoints  310  may be calculated and the calculated midpoint break radius  314  values may then be combined, for example, by averaging a selectable number of the calculated midpoint break radius values, to generate an output. 
     FIG. 4  is a flow chart of an exemplary method  400  of evaluating a radius of a component, such as component  29  (shown in  FIG. 1 ). Method  400  includes determining  400  a inspection plan for the component being inspected, based at least partially on a part number of component  29 . An inspection plan for each configuration of component  29  is used to generate the measurement. The scan plan may be used to control system  10  to generate scans at one or more locations across a leading edge side of the dovetail, for example, at three locations, such as, one at the center and one each side of center on the leading edge dovetail side. The determined scan plan may control system  10  to generate scans at one or more locations on a trailing edge dovetail side, for example, three locations, such as, one at the center and one each side of the trailing edge side of the dovetail. 
   Depending on the component being inspected, a setup  404  of system  10  may include a check scan using a quality indicator gauge or gauge master to conduct a calibration check of system  10 . The gauge master may be positioned in fixture  37  such that a dovetail surface of the gauge master is oriented generally horizontally such that fixture  37  grips the gauge master on opposing sides that are substantially perpendicular to the dovetail. In the exemplary embodiment, the scan X-zero is started at approximately 0.030 inches from a dovetail valley of the gauge master. The scan Z-zero is started at approximately the depth of the dovetail valley. The X-scan increment may be selected to be a predetermined value, for example, fifteen micro-inches. After the gauge master is scanned, an evaluation macro is processed by system  10  or another processor. In the exemplary embodiment, for an acceptable scan, the radius measurement may be verified to be within approximately 0.002 inches of previous measurements. 
   Component  29  may be oriented within fixture  37 , for example, along a Y-axis of system  10 . Component  29  may be clamped or coupled, for example, along the dovetail sides using fixture  37 . A locator (not shown), for example, a notch may be used to facilitate positioning the dovetail such that the dovetail to be inspected is oriented approximately horizontally. 
   After system  29  is checked for calibration, an inspection scan  408  may be conducted. The scan plan is initiated such that arm  22  is withdrawn axially while tip  27  remains in contact with surface  28 . Tip  27  is biased to maintain contact with surface  28 . The X and Z values of arm  22  are measured and preprocessed by system  10 . An evaluation  410  of the inspection scan is conducted using a software algorithm, such as UltraContour Software. Evaluation  410  is used to generate the edge radius of the contour traced by tip  27  during inspection scan  408 . During the evaluation  410 , CAD data is extracted from component  29  contour. The CAD data is trimmed to fit into a selectable length of scan data. The scan data is includes the area of the maximum edge radius. 
   The scan data is acquired from approximately 0.010″ before the maximum edge radius to approximately 0.100″ beyond the radius along the traced length. Evaluation  410  reads in the CAD data and the scan data. For each of the scans performed on component  29 , the scan data is fitted to the CAD data by iterating, for example, ten times. The CAD data is then deleted. An arc is fitted to the scan data between the start and end of the maximum edge radius. The fitted arc is dimensioned and the maximum edge radius value is reported. In the exemplary embodiment, six measurements (three on each side of the blade) are made and the average measurement is reported  412  as the blade value. A passing criteria for each component  29  may include, for example, the average of the six edge radii may exceed a predetermined value, the average radius may not exceed 100% of a drawing specification, and/or none of the reported values may exceed 200% of a drawing maximum edge break. 
   A technical effect of the various embodiments of the systems and methods described herein include at least one of the accurate and repeatable determination of component dimensions and comparison of those dimensions to a predetermined specification to facilitate inspection and maintenance of various components. 
   The above-described methods and apparatus are cost-effective and highly reliable for determining a dimension, such as a maximum break radius of a component. The methods and apparatus describe repeatable data sets using a profileometer, fitting collected scan data to a specification curve, and determining whether the scanned data meets predetermined specification criteria. The methods and apparatus described above facilitate fabrication, assembly, and reducing the maintenance cycle time of components in a cost-effective and reliable manner. 
   An exemplary embodiment of a component inspection system is described above in detail. The system illustrated is not limited to the specific embodiments described herein, but rather, components of each may be utilized independently and separately from other components described herein. 
   While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.