US 5,345,514 AGranted

Method for inspecting components having complex geometric shapes

AssigneeGeneral Electric Company

InventorsYaghoub Mahdavieh, Kristina H. V. Hedengren

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Abstract

A method for inspecting a component of a gas turbine engine or the like having a plurality of similarly shaped structural portions, such as the gear teeth of a gear, the dovetail slots of a turbine disk or the like, includes the steps of: scanning a surface of at least one of the similarly shaped structural portions with an eddy current probe to induce eddy currents in the component; generating a two-dimensional image of the at least one portion from eddy current signals received during scanning, the image including a multiplicity of pixels arranged in a two-dimensional array and each pixel having a gray scale intensity responsive to the eddy current induced in the component at a component location corresponding to a position of the pixel in the matrix array; preprocessing the image to substantially reduce any signals or changes in the gray scale intensity of any pixels relative to the background pixel intensities of the image caused by geometrical characteristics and background noise common to all similarly shaped structuaral portions; identifying any suspected defect regions from the preprocessed image; determining a defect signal for each suspected defect region; and rejecting the component if any defect signal exceeds a predetermined reference value.

Claims34

Dependent claims

A method for inspecting a component having a plurality of similarly shaped structural portions, comprising the steps of:

(a) scanning a surface of at least one of the similarly shaped structural portions with an eddy current probe means to induce eddy currents in the component;
(b) generating a two-dimensional image of the at least one portion from eddy current signals received during scanning, the image including a multiplicity of pixels arranged in a two-dimensional matrix array and each pixel having a gray scale intensity responsive to the eddy current induced in the component at a component location corresponding to a position of the pixel in the two-dimensional matrix array;
(c) preprocessing the image to substantially reduce any signals caused by geometrical characteristics and background noise common to all of the similarly shaped structural portions;
(d) identifying any suspected defect regions in the two-dimensional image from corresponding regions in the preprocessed image of step (c);
(e) determining a defect signal from the gray scale intensities for each suspected defect regions in the two-dimensional image;
and
(f) rejecting the component if any defect signal exceeds a predetermined reference value, wherein step (c) comprises the steps of:
(c1) repeating steps (a) and (b) to generate a two-dimensional image for a second and third similarly shaped structural portion;
(c2) selecting a test portion and an associated test image, a first reference portion and an associated first reference image, and a second reference portion and an associated second reference image from the three similarly shaped portions;
(c3) taking a difference between the first reference image and the test image to provide a first resulting image by taking a difference between the gray scale intensity of each pixel of the first reference image and the gray scale intensity of a corresponding pixel of the test image;
(c4) taking a difference between the second reference image and the test image to provide a second resulting image by taking a difference between gray scale intensities of corresponding pixels of each image;
(c5) converting each of the first and second reference images from a gray scale image to respective first and second binary images;
and
(c6) combining the first and second binary images by a logic AND operation to provide a preprocessed composite binary image.

11 more elements

A method for inspecting dovetail slots of a gas turbine engine component, comprising the steps of:

(a) scanning a surface of a dovetail slot with an eddy current probe means to induce eddy currents in the component;
(b) generating a two-dimensional image of the dovetail slot surface from eddy current signals received during scanning, each image including a multiplicity of pixels arranged in a two-dimensional matrix array and each pixel having a gray scale intensity responsive to the eddy current induced in the component at a component location corresponding to a position of the pixel in the two-dimensional matrix array;
(c) repeating steps (a) and (b) to generate a two-dimensional image for three dovetail slots;
(d) selecting a test slot and an associated test image, a first reference slot and an associated first reference image, and a second reference slot and an associated second reference image from the three dovetail slots;
(e) taking a difference between the first reference image and the test image to provide a first resulting image by taking a difference between the gray scale intensity of each pixel of the first reference image and the gray scale intensity of a corresponding pixel of the test image;
(f) taking a difference between the second reference image and the test image to provide a second resulting image by taking a difference between gray scale intensities of corresponding pixels of each image;
(g) converting each of the first and second resulting images from a gray scale image to respective first and second binary images by thresholding;
(h) combining the first and second binary images by a logic AND operation to provide a composite binary image;
(i) identifying any sections within the composite binary image which contain a cluster of pixels with predominantly all pixels having a predetermined binary value;
(j) identifying any suspected defect regions in one of the first and second resulting images of step (e) which correspond to the identified sections of step (i);
(k) calculating a defect signal for each suspected defect region;
and
(l) comparing the defect signal for each region with a predetermined reference value to determine whether a defect is present in the test slot at a location corresponding to the suspected defect region.

10 more elements

A method for inspecting gear teeth and the like of a component, comprising the steps of:

(a) scanning a surface of a gear tooth with an eddy current probe means to induce eddy currents in the component;
(b) generating a two-dimensional image of the gear tooth surface from eddy current signals received during scanning, each image including a multiplicity of pixels arranged in a two-dimensional matrix array and each pixel having a gray scale intensity responsive to the eddy current induced in the component at a component location corresponding to a position of the pixel in the matrix array;
(c) repeating steps (a) and (b) to generate a two-dimensional image for three gear teeth;
(d) selecting a test tooth and an associated test image, a first reference tooth and an associated first reference image, and a second reference tooth and an associated second reference image from the three gear teeth;
(e) taking a difference between the first reference image and the test image to provide a first resulting image by taking a difference between the gray scale intensity of each pixel of the first reference image and the gray scale intensity of a corresponding pixel of the test image;
(f) taking a difference between the second reference image and the test image to provide a second resulting image by taking a difference between the gray scale intensities of corresponding pixels of each image;
(g) converting each of the first and second resulting images from a gray scale image to respective first and second binary images by thresholding;
(h) combining the first and second binary image by a logic AND operation to provide a composite binary image;
(i) identifying any sections within the composite binary image which contain a cluster of pixels with predominantly all pixels having a predetermined binary value;
(j) identifying any suspected defect regions in one of the first and second resulting images of step (e) which correspond to the identified sections of step (i);
(k) calculating a defect signal for each suspected defect region;
and
(l) comparing the defect signal for each region with a predetermined reference value to determine whether a defect is present in the test tooth at a location corresponding to the suspected defect region.

10 more elements

Dependencies are inferred from the claim text.