Computed tomography (CT) detection device and method for internal dimension of complex casting of aero-engine

Abstract

The invention relates to the technical field of industrial CT detection, and discloses an aero-engine complex casting internal dimension CT detection device comprising a positioning tool used for bearing and positioning a detected casting, the positioning tool is provided with a vertical core rod at the center of a base, and an angular positioning block and an angular positioning pin which can move along the direction close to or far away from the core rod; during detection, the detected casting is placed on the base, and the positioning tool provides reference, so that the accuracy of the detection result of the detected casting is higher. The invention also provides a detection method, which adopts the positioning tool and ensures the accuracy of relevant dimension measurement through different system calibration methods. Scanning parameters are optimized through a scanning test, reconstruction parameters are optimized through an analysis test of image reconstruction, and it is guaranteed that the image can meet the size measurement requirement; a measuring tool is selected to measure the wall thickness of the pipeline, different concentric circles are drawn with the center as the circle center according to different machining sizes, and the conformity of the size of a machined part is measured through a virtual circle.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial CT detection, and in particular to a CT detection device and method for the internal dimensions of complex castings of an aero-engine. Background Art

[0002] Compared with the external dimensions of the casting, which can be directly measured, in order to detect the internal features of the casting, the relevant dimensions are generally checked by regular sectioning inspection. However, the disadvantages of this method are obvious: first, the sectioning result only represents the conformity of the sampled castings, and the sectioning inspection destroys the integrity of the castings, and the castings are directly scrapped after the sectioning inspection; second, after sectioning, the position of the internal features to be inspected relative to the casting processing datum is destroyed, which is only convenient for checking the relevant dimensions of the internal features themselves, and cannot accurately reflect the overall position dimensions. It may result in the problem that the dimensions themselves are qualified, but the position of the pipeline outlet is biased and cannot be connected after processing, and the internal features are thin from the blank surface to the machined surface after machining or are machined through.

[0003] Industrial Computed Tomography (Industrial CT) technology has been widely used in non-destructive testing in important industrial fields in my country.

[0004] Industrial CT is the best means of non-destructive testing (NDT) and non-destructive evaluation (NDE) of products, which can achieve non-destructive visual measurement of products, assembly defects or material analysis. Industrial CT replaces traditional destructive monitoring and analysis, non-destructive slicing and imaging in any direction, without being blocked by surrounding detailed features, and can directly obtain the spatial position, shape and size information of the target features. The three main components of industrial CT equipment are X-ray source, rotating console and detector. The distance from X-ray source to detector and the distance from X-ray source to scanning target determine the geometric magnification of CT scanning and the voxel size of 3DCT component model. The use of variable X-ray source to detector distance provided in the X-ray equipment product family is essential for obtaining accurate data in product inspection. The output of industrial CT scanning is a 3D model of the component, on which very accurate measurements can be performed without any form of contact, cutting or destruction. CT can also inspect materials and identify internal defects such as voids, cracks, etc. When inspecting composite materials, CT can also be used for layer identification.

[0005] Industrial CT is an industrial application of computer tomography technology, which uses high-energy X-rays to penetrate the workpiece to obtain projection data, and then obtains a two-dimensional or three-dimensional image of the workpiece through a reconstruction algorithm. Industrial CT can clearly, accurately and intuitively display the size, position, shape, composition, material and defect status of the internal structure of the workpiece to be inspected without contact or damage, and is not affected by the material, shape and surface of the workpiece. However, the existing industrial CT directly places the workpiece to be inspected on the inspection platform for scanning, and can only obtain the scanned image of the workpiece to be inspected and the subsequent reconstructed image. When measuring the image of the workpiece to be inspected, due to differences in CT detection conditions and the influence of image clarity, there are errors in the measurement of the workpiece to be inspected. Summary of the invention

[0006] The purpose of the present invention is to provide a CT detection device and method for the internal dimensions of complex castings of aircraft engines with high accuracy.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a CT detection device for the internal dimensions of complex castings of aircraft engines, including a positioning tool, the positioning tool including a base, a core rod, an angular positioning block and an angular positioning pin, the base is used to support the casting, the top surface of the base is provided with a positioning groove, the positioning groove is concentrically arranged with the base, the core rod is vertically connected to the center of the base, the angular positioning block can be movably installed on the base in a direction close to or away from the core rod, and the angular positioning pin can be movably connected to the angular positioning block in the height direction of the angular positioning block.

[0008] As a preferred solution, the angular positioning block is provided with a plurality of guide holes, the plurality of guide holes are distributed at intervals along the height direction of the angular positioning block, and the angular positioning pins are inserted into the guide holes.

[0009] As a preferred solution, the base is circular, and the angular positioning block moves along the radial direction of the base.

[0010] As a preferred solution, a weight-reducing hole is provided on the base.

[0011] As a preferred solution, the bottom surface of the base is provided with reinforcing ribs.

[0012] The present invention also provides a CT detection method for the internal dimensions of complex castings of an aircraft engine, using the above-mentioned detection device, characterized in that it comprises:

[0013] The casting to be inspected is placed on the base, wherein the central reference cylindrical surface of the casting to be inspected coincides with the central reference cylindrical surface of the base, and the height plane reference starting surface of the casting to be inspected coincides with the central reference cylindrical surface of the base;

[0014] Adjust the position of the angular positioning needle on the angular positioning block according to the angular feature height of the casting to be inspected, and rotate the casting to be inspected so that the angular feature of the casting to be inspected is aligned with the needle tip of the angular positioning needle;

[0015] Place the positioning tooling and the casting to be inspected as a whole on the industrial CT scanning operation platform;

[0016] Perform industrial CT scanning on the positioning tool and the casting to be inspected as a whole to obtain the projection image of the positioning tool and the casting to be inspected as a whole;

[0017] Perform image reconstruction based on the projection images of the positioning tool and the entire casting to be inspected, to obtain a reconstructed image;

[0018] Perform surface measurement on the reconstructed image to achieve initial calibration and obtain the initial dimensional measurement values ​​of the positioning fixture and the entire casting being inspected;

[0019] According to the error between the initial dimension measurement value of the positioning tool and the actual dimension value of the positioning tool, accurate calibration is performed to obtain the accurate dimension measurement value of the positioning tool and the casting to be inspected as a whole.

[0020] As a preferred solution, it also includes measuring the wall thickness after removing the allowance during circular machining: first, the center of machining is determined on the reconstructed image of the machining position, and then a virtual circle for removing the machining allowance is drawn with the center of machining as the center, and the wall thickness after removing the allowance is measured through the virtual circle, wherein the position of the center of the virtual circle is guaranteed by the reference surface of the positioning tool and the machining of the inspected casting.

[0021] As a preferred solution, before performing industrial CT scanning on the positioning fixture and the entire casting to be inspected, scanning parameters are first determined. The scanning parameters include the number of projection frames, scanning frequency and slice thickness during scanning.

[0022] As a preferred solution, when performing image reconstruction, a clear reconstructed image is obtained by setting and adjusting reconstruction parameters, and the reconstruction parameters include reconstruction area, grayscale magnification, and reconstruction size.

[0023] As a preferred solution, when performing initial calibration, the reconstructed image is subjected to surface measurement, that is, the middle value between the maximum grayscale value and the minimum grayscale value in the image is taken to define the boundary contour of the image.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention sets a positioning tool for carrying and positioning the casting to be inspected. The positioning tool sets a vertical core rod and an angular positioning block and an angular positioning needle that can move in a direction close to or away from the core rod at the center of the base. The casting to be inspected is placed in the positioning groove, and the axis of the casting to be inspected and the core rod are located in the same straight line. During industrial CT inspection, the positioning tool and the casting to be inspected are scanned and processed as a whole, wherein the imaging result of the core rod can be used to determine the center position of the casting on the inspection surface and provide the casting center reference information; the base provides the height plane reference starting surface and the center reference cylindrical surface of the casting inspection process; the angular positioning block and the angular positioning needle can determine and adjust the casting to a specified angular position when the casting is placed, and their imaging results can be used to determine the angular information of the casting. Therefore, the positioning tool is set in the present invention to provide a reference, which can make the inspection result of the inspected casting more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic structural diagram of a positioning tool according to an embodiment of the present invention.

[0027] Figure 2 It is a cross-sectional view of a positioning tool according to an embodiment of the present invention.

[0028] Figure 3 Schematic diagram of the structure of the mandrel according to an embodiment of the present invention.

[0029] Figure 4 4 is a top view of a base according to an embodiment of the present invention.

[0030] Figure 5 It is a bottom view of the base according to the embodiment of the present invention.

[0031] Figure 6 is a cross-sectional view of a base according to an embodiment of the present invention.

[0032] Figure 7 It is a side view of an angular positioning block and an angular positioning pin according to an embodiment of the present invention.

[0033] Figure 8 It is a front view of the angular positioning block according to an embodiment of the present invention.

[0034] Fig. 9 It is a schematic diagram of placing the casting to be inspected on a positioning tool in an embodiment of the present invention.

[0035] Fig.10 It is a cross-sectional view of a casting to be inspected placed on a positioning tool according to an embodiment of the present invention.

[0036] Fig.11 It is a front view of a casting to be inspected placed on a positioning tool according to an embodiment of the present invention.

[0037] Fig.12It is a rendering of the inspection process of the inspected casting and the positioning tooling according to the embodiment of the present invention.

[0038] Fig.13 is a flow chart of a detection method according to an embodiment of the present invention.

[0039] Fig.14 It is a schematic diagram of a CT scanning reference of a casting to be inspected according to an embodiment of the present invention.

[0040] Fig.15 Schematic diagram of CT inspection scanning of a workpiece according to an embodiment of the present invention.

[0041] Fig.16 Schematic diagram of image reconstruction operation according to an embodiment of the present invention.

[0042] Fig.17 4 is a comparison diagram of the influence of the center calibration value on the reconstructed image according to an embodiment of the present invention.

[0043] Fig.18 It is a reconstructed image of the T+160mm section of the detected casting according to an embodiment of the present invention.

[0044] Fig.19 It is a schematic diagram of measuring the wall thickness of a local area of ​​the oil passage of the T+24mm section of the tested casting according to an embodiment of the present invention.

[0045] Fig. 20 It is a schematic diagram of a virtual circle drawn on the T=253mm section of the casting to be inspected according to an embodiment of the present invention.

[0046] Fig.21 It is a schematic diagram of the embodiment of the present invention after the excess is removed by circular machining.

[0047] Fig. 22 It is an enlarged view of the center position of the virtual circle in the embodiment of the present invention.

[0048] Fig.23 Schematic diagram of virtual circle boundary extraction according to an embodiment of the present invention.

[0049] In the figure, 1-base; 101-positioning groove; 102-reinforcement rib; 103-weight reduction hole; 104-slide groove; 2-core rod; 201-working section; 202-assembly section; 3-angular positioning block; 301-guide part; 302-sliding part; 303-guide hole; 4-angular positioning pin; 5-mounting seat; 501-mounting hole; 6-inspected casting; 7-angular feature of the inspected casting; 8-central reference cylindrical surface of the inspected casting; 9-height plane reference starting surface of the inspected casting; 10-virtual circle; 11-center of the virtual circle. DETAILED DESCRIPTION

[0050] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0051] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0052] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0054] Embodiment 1

[0055] like Figures 1 to 9As shown, a CT detection device for the internal dimensions of a complex casting of an aircraft engine according to a preferred embodiment of the present invention includes a positioning tool, the positioning tool includes a base 1, a core rod 2, an angular positioning block 3 and an angular positioning pin 4, the base 1 is used to support the casting, the top surface of the base 1 is provided with a positioning groove 101, the positioning groove 101 is arranged concentrically with the base 1, the core rod 2 is vertically connected to the center of the base 1, the angular positioning block 3 can be movably installed on the base 1 in a direction close to or away from the core rod 2, and the angular positioning pin 4 can be movably connected to the angular positioning block 3 in the height direction of the angular positioning block 3. In this embodiment, a positioning tool is provided to carry and position the casting 6 to be inspected. The positioning tool is provided with a vertical core rod 2 and an angular positioning block 3 and an angular positioning needle 4 which can move in a direction close to or away from the core rod 2 at the center of the base 1. The casting 6 to be inspected is placed in the positioning groove 101, and the axis of the casting 6 to be inspected is located in the same straight line as the core rod 2. During industrial CT inspection, the positioning tool and the casting 6 to be inspected are scanned and processed as a whole, wherein the imaging result of the core rod 2 can be used to determine the center position of the casting on the inspection surface and provide the casting center reference information; the base 1 provides the height plane reference starting surface and the center reference cylindrical surface of the casting inspection process; the angular positioning block 3 and the angular positioning needle 4 can determine and adjust the casting to a specified angular position when placing the casting, and their imaging results can be used to determine the angular information of the casting. Therefore, the positioning tool is provided in this embodiment to provide a reference, which can make the inspection result of the casting 6 to be inspected more accurate.

[0056] When in use, the core rod 2 and the angular positioning block 3 are installed on the base 1, and the angular positioning pin 4 is installed from the angular positioning block 3 at a suitable height as required. The above matching parts are all clearance assembly, and the verticality requirement is ≤0.1. During production, the contact surface requirements can be required to be matched with coloring inspection, and the coloring area ≥70%.

[0057] Embodiment 2

[0058] The difference between this embodiment and the first embodiment is that, based on the first embodiment, this embodiment further illustrates the positioning tooling.

[0059] The core rod 2 needs to form reliable detection data during the CT detection process. Considering the penetration of CT detection rays and the consistency of results, the material of the core rod 2 should be close to the detected casting 6 and have certain processing performance. In this solution, the core rod 2 is made of 7075 aluminum alloy, which is suitable for aluminum alloy and magnesium alloy casting detection.

[0060] In this embodiment, a mounting seat 5 is provided on the base 1, and a mounting hole 501 is provided on the mounting seat 5, and the mounting hole 501 is a threaded hole. The core rod 2 includes a working section 201 and an assembly section 202, and the diameter of the assembly section 202 is larger than the diameter of the working section 201. The assembly section 202 is provided with an external thread, and the assembly section 202 is threadedly installed in the mounting hole 501 of the mounting seat 5. During the detection process, the working section 201 and the detected casting 6 are simultaneously penetrated by the rays generated by the CT device, and the imaging result of the core rod 2 can be used to determine the center position of the casting on the detection surface and provide the casting center reference information. The assembly section 202 is used to ensure the verticality and stability of the core rod 2 and the base plate.

[0061] Considering the CT detection radiation penetration and the processability of the measurement results, the diameter of the working section 201 of the core rod 2 is preferably The diameter of the assembly section 202 of the mandrel 2 is larger than the diameter of the working section 201 to provide a reliable assembly and fixing effect. The diameter of the assembly section 202 may be within the range of The diameter of the assembly section 202 in this embodiment is

[0062] The total height of the mandrel 2 should be determined according to the total height of the casting 6 to be tested, and is generally within 10 mm of the total height of the casting 6 to be tested. Under the condition of ensuring the assembly and fixing effect, the length of the assembly section 202 is generally slightly larger than the diameter of the assembly section 202. However, since the mandrel 2 is a long-axis part, the length of the assembly section 202 can be appropriately increased for the convenience of clamping during processing.

[0063] In this embodiment, the base 1 is circular, and the angular positioning block 3 moves along the radial direction of the base 1. The positioning groove 101 is also a circular groove concentric with the base 1.

[0064] The base 1 is used to position the casting, which requires good processing performance and dimensional stability, so the material of the base 1 selected in this embodiment is cast steel. The base 1 is used to place and position the casting during the inspection process, and provides a height plane reference starting surface and a center reference cylindrical surface for the casting inspection process.

[0065] The diameter of the positioning groove 101 must be consistent with the center reference size of the detected casting 6. During the inspection, the casting is placed in the positioning groove 101, and the starting surface of the height plane reference of the casting is the bottom surface of the positioning groove 101. The height difference between the top surface of the base 1 and the bottom surface of the positioning groove 101 determines the height of the cylindrical surface on the base 1 used to locate the center reference of the casting. This size can be determined based on the center reference of the detected part.

[0066] In addition, the bottom surface of the base 1 of this embodiment is provided with reinforcing ribs 102. The reinforcing ribs 102 are used to provide strength to the base 1. In this embodiment, three reinforcing ribs 102 are provided, and the three reinforcing ribs 102 are distributed along the radial direction of the base 1 and are arranged radially from the center of the base 1.

[0067] In addition, a weight-reducing hole 103 is provided on the base 1. The weight-reducing hole 103 passes through the bottom surface of the positioning groove 101 and the bottom surface of the base 1. In addition to the weight-reducing function, the weight-reducing hole 103 can also be used to quickly clean dirt and excess materials on the casting placement surface, because the detected casting 6 may have molding sand and other excess materials that are easy to fall during the casting stage. In this embodiment, three weight-reducing holes 103 are provided, and the three weight-reducing holes 103 are distributed circumferentially around the center of the base 1, and the weight-reducing holes 103 are tangent to the outer edge of the positioning groove 101 and the outer edge of the mounting seat 5.

[0068] The base 1 of this embodiment is further provided with a slide groove 104 which is in communication with the positioning groove 101 . The slide groove 104 runs through the side surface of the base 1 . The slide groove 104 is arranged along the radial direction of the base 1 . The angular positioning block 3 is slidably installed in the slide groove 104 .

[0069] In this embodiment, the angular positioning block 3 is provided with a plurality of guide holes 303, which are spaced apart along the height direction of the angular positioning block 3, and the angular positioning pins 4 are passed through the guide holes 303. The angular positioning pins 4 are installed in different guide holes 303 to achieve height adjustment on the angular positioning block 3.

[0070] In addition, the angular positioning block 3 of the present embodiment includes a guide portion 301 and a sliding portion 302 which are perpendicular to each other, and a guide hole 303 is provided in the guide portion 301 .

[0071] The angular positioning block 3 needs to form reliable detection data during the CT detection process. Its material should be close to the detected casting 6 and have certain processing performance. The angular positioning block 3 of this embodiment is made of 7075 aluminum alloy; the angular positioning needle 4 can be made of common mold steel. The angular positioning needle 4 of this embodiment is made of 45 steel.

[0072] By means of the angular positioning block 3 and the angular positioning needle 4, the casting can be determined and adjusted to a specified angular position when the casting is placed; and during the detection process, the guide portion 301 and the detected casting 6 are simultaneously penetrated by the CT device rays, and the imaging result of the angular positioning block 3 can be used to determine the angular information of the casting.

[0073] The total height of the angular positioning block 3 is determined by the angular reference feature height of the detected casting 6 and the internal feature height to be detected of the detected casting 6. Generally speaking, the angular reference feature of the casting is located in the middle of the casting, so the total height of the angular positioning block 3 is greater than or equal to two-thirds of the total length of the core rod 2.

[0074] The diameter of the guide hole 303 is equal to the diameter of the angular positioning needle 4. In order to ensure that the angular positioning needle 4 is easy to operate and accurately positioned during use, the range of 5 to 15 mm can generally be selected. The guide holes 303 are evenly distributed in the guide part 301 of the angular positioning block 3, and the distance between two adjacent guide holes 303 is 3 to 5 times the diameter of the guide hole 303. Considering the size of the guide hole 303 and the stability of the angular positioning block 3 after assembly, the width of the guide part 301 of the angular positioning block 3 can be 3 to 5 times the diameter of the guide hole 303. Considering the stability of the placement of the angular positioning block 3, the length of the sliding part 302 of the angular positioning block 3 can be set at 1 / 2 to 1 / 3 of the total height of the angular positioning block 3. The angular positioning needle 4 needs to ensure that when its needle part contacts the angular feature of the casting, the middle part of the angular positioning needle 4 is at the position of the guide hole 303 of the angular positioning block 3. Taking into account the observation, manufacturing convenience, alignment convenience, etc., the needle cone angle of the angular positioning needle 4 is 30-70°, and the needle cone angle of the angular positioning needle 4 in this embodiment is 60°. The thickness of the guide portion 301 of the angular positioning block 3 determines the contact area between the angular positioning block 3 and the angular positioning needle 4. Therefore, the thickness of the guide portion 301 of the angular positioning block 3 is greater than or equal to 1 / 2 of the diameter of the angular positioning needle 4. Appropriate thickening can improve the stability of the angular positioning needle 4 after assembly.

[0075] When the positioning tool of this embodiment is in use, the casting 6 to be inspected is placed on the base 1, the center reference cylindrical surface 8 of the casting to be inspected coincides with the center reference cylindrical surface of the base 1, the height plane reference starting surface coincides with the center reference cylindrical surface of the base 1, and the angular feature 7 of the casting to be inspected (the engraved line in this embodiment) is aligned with the needle tip of the angular positioning needle 4.

[0076] Place the positioning fixture and the casting 6 to be inspected as a whole on the turntable of the industrial CT equipment, and the bottom surface of the reinforcing rib 102 of the positioning fixture base 1 coincides with the height starting surface of the industrial CT equipment turntable, and then the subsequent inspection can begin. During CT scanning inspection, when the equipment scanning height is set to (the height difference between the bottom surface of the positioning groove 101 and the bottom surface of the reinforcing rib 102) + T1, the measurement data corresponds to the T1 height section of the casting, so that the height position of the inspection result can be accurately determined.

[0077] The detection results include casting information, core rod 2 information and angular positioning block 3 information. The center and angular position of the casting measurement results can be accurately determined through the center of the core rod 2 information and the long side direction in the angular positioning block 3 information.

[0078] During the machining stage, the casting inherits the height plane datum, center datum and angular datum used in CT inspection, which can ensure that the inspection results are highly consistent with the actual machining situation.

[0079] And by using the tooling of this embodiment, the internal features of the casting can be accurately inspected in size at the blank stage. The inspection results include the internal feature size and position size, and are highly consistent with the expected processing, thereby improving the conformity of the internal features of the final part, so that it can safely and reliably meet the design function. At the same time, quality problems such as the position of the pipeline outlet in the machining process is biased, cannot be connected, and the size of the internal feature blank surface to the machining surface is thin or is processed through can be predicted in advance.

[0080] The other structures of this embodiment are the same as those of the first embodiment and will not be described again here.

[0081] Embodiment 3

[0082] like Figures 9 to 23 As shown, a CT detection method for the internal dimensions of a complex casting of an aircraft engine according to a preferred embodiment of the present invention adopts the detection device of the first embodiment or the second embodiment, comprising:

[0083] The casting 6 to be inspected is placed on the base 1, wherein the central reference cylindrical surface 8 of the casting to be inspected coincides with the central reference cylindrical surface of the base 1, and the height plane reference starting surface 9 of the casting to be inspected coincides with the central reference cylindrical surface of the base 1;

[0084] Adjust the position of the angular positioning needle 4 on the angular positioning block 3 according to the height of the angular feature 7 of the casting to be inspected, and rotate the casting to be inspected 6 to align the angular feature 7 of the casting to be inspected with the needle tip of the angular positioning needle 4;

[0085] Place the positioning fixture and the casting 6 to be inspected as a whole on the industrial CT scanning operation platform;

[0086] Performing industrial CT scanning on the positioning tool and the casting 6 to be inspected as a whole, to obtain a projection image of the positioning tool and the casting 6 to be inspected as a whole;

[0087] Perform image reconstruction based on the overall projection image of the positioning tool and the casting 6 to be inspected, to obtain a reconstructed image;

[0088] Perform surface measurement on the reconstructed image to achieve initial calibration and obtain initial dimensional measurement values ​​of the positioning fixture and the casting 6 to be inspected as a whole;

[0089] According to the error between the initial dimension measurement value of the positioning tool and the actual dimension value of the positioning tool, accurate calibration is performed to obtain the accurate dimension measurement value of the positioning tool and the detected casting 6 as a whole.

[0090] The detection method of this embodiment first requires that the casting 6 to be detected be placed on the positioning tooling. Specifically, (1) the core rod 2 is assembled on the mounting seat 5 on the base 1; (2) the casting 6 to be detected is placed on the base 1, the central reference cylindrical surface 8 of the casting to be detected coincides with the central reference cylindrical surface of the base 1, and the height plane reference starting surface 9 of the casting to be detected coincides with the central reference cylindrical surface of the base 1; (3) the angular positioning block 3 is assembled on the slide groove 104 of the base 1; (4) according to the angular feature height of the casting to be detected, a suitable guide hole 303 is selected on the angular positioning block 3, and the angular positioning needle 4 is inserted; (5) the casting 6 to be detected is rotated as needed, so that the angular feature 7 of the casting to be detected is aligned with the needle tip of the angular positioning needle 4; (6) the tooling and the casting 6 to be detected are placed as a whole on the industrial CT scanning operation platform, and subsequent detection and analysis can be started.

[0091] In this embodiment, the casting 6 to be inspected is an air intake casing. The CT inspection of the air intake casing mainly scans the following: Fig.14 Shown with large end face ( Fig.14 Assuming that the large end blank margin is T, the height of the CT scanning section is respectively: T+X.

[0092] The inspection plan is as follows: (1) Design a positioning fixture according to the rough processing reference of the inspected casting 6. After the inspected casting 6 is clamped in the positioning fixture, the accuracy of the slice position and the center of the part should be ensured. (2) Use different system calibration methods to ensure the accuracy of related dimensional measurements. (3) Through scanning tests, optimize the scanning parameters. Through image reconstruction analysis tests, optimize the reconstruction parameters to ensure that the image can meet the requirements of dimensional measurement. (4) Select a suitable measuring tool to measure the wall thickness of the pipeline. With the center as the center of the circle, draw different concentric circles according to different processing dimensions. Use the virtual circle 10 to measure the conformity of the size of the processed parts.

[0093] Specifically, before performing industrial CT scanning on the positioning fixture and the casting 6 to be inspected as a whole, scanning parameters are first determined. The scanning parameters include the number of projection frames, scanning frequency and slice thickness during scanning.

[0094] The scanning method of this embodiment adopts RO scanning method. RO scanning is to make the fan-shaped area formed by the ray source and the linear array detector array include the entire range of the workpiece to be detected. Fig.15 As shown, the complete data of the reconstructed CT image can be obtained only by rotating the detected casting 6.

[0095] For the accelerator industrial CT system, the ray energy is fixed. Other main scanning parameters include scanning frequency, projection number and slice thickness. The more projections, the more information collected and the better the imaging effect. Experiments have shown that when the number of projections exceeds 2000 within the standard scanning range, the imaging effect will not change substantially. Therefore, the number of projections is set to 2000 during scanning. The scanning frequency of the accelerator is 50-250Hz. The higher the frequency, the higher the ray intensity and the higher the signal-to-noise ratio. However, for the accelerator ray source, the higher the frequency, the easier it is to generate pulse overcurrent during the scanning process, resulting in high voltage interruption, causing repeated scanning and affecting the scanning efficiency. Experiments have shown that pulse overcurrent is prone to occur when the scanning frequency is higher than 150Hz, and the frequency of pulse overcurrent increases with the increase of scanning frequency. Therefore, the scanning frequency is set to 100Hz. A large slice thickness is conducive to improving the signal-to-noise ratio and improving density resolution. A small slice thickness is conducive to the detection of small defects and improves spatial resolution. In order to meet the contrast requirements, a larger slice thickness should be selected. After comprehensive consideration, the slice thickness is determined to be 2.0mm.

[0096] In addition, when performing image reconstruction, a clear reconstructed image is obtained by setting and adjusting reconstruction parameters, including reconstruction area, grayscale magnification, and reconstruction size.

[0097] The main parameters that can be changed to affect image reconstruction include reconstruction area, grayscale magnification, reconstruction size, etc. By setting and adjusting the reconstruction parameters, a clear reconstructed image of the super-large part industrial CT detection is obtained. In this embodiment, the reconstruction software nACTiS Recon 6.0 is used for image reconstruction.

[0098] like Fig.16 As shown, during image reconstruction, parameters such as reconstruction area, grayscale magnification, and reconstruction size can be adjusted.

[0099] The reconstruction area (0.2, 0.3-1) is determined by the size range of the detected casting 6. The larger the size range of the detected casting 6, the larger the reconstruction area should be. Otherwise, the reconstructed image cannot fully display the size range of the detected casting 6. If the size range of the detected casting 6 is small and the reconstruction area is large, the details of the reconstructed image will be affected. Therefore, the reconstruction area should be adapted to the size range of the scanned detected casting 6.

[0100] Grayscale magnification can be set to 1, 100, 1000 and 10000. Experiments show that grayscale magnification settings above 1000 have little effect on the reconstructed image.

[0101] A large reconstruction size (reconstruction matrix) is beneficial to improving spatial resolution, but the reconstruction speed is slow. The reconstruction sizes are generally 512×512, 1034×1034, 2048×2048 and 4096×4096. For small-size measurements, a large reconstruction size should be selected to improve measurement accuracy.

[0102] This embodiment points out that the center calibration of the reconstruction software has a great influence on the image quality. The center calibration value is determined by the deviation between the actual center and the theoretical center of each scan, and should be adjusted in real time during each image reconstruction. Fig.17 As shown in the figure, other parameters are the same but the image changes with different center calibration values. It can be seen that the change of the center calibration value affects the clarity of the reconstructed image.

[0103] In summary, the key parameters of CT detection in this embodiment are shown in Table 1. After the key parameters of CT detection are determined, the intrinsic nature of the CT reconstructed image is determined. Fig.18 This is a relatively clear reconstructed image of the intake casing T+160mm section under certain parameters. Only by obtaining a clear image can we better observe the internal condition of the parts and meet the requirements for accurate measurement.

[0104] Table 1 Key parameters of CT detection

[0105]

[0106] In addition, after obtaining the reconstructed image of the detected casting 6, the size of the detected casting 6 is measured. Optionally, all the size measurements in this embodiment are achieved by importing the reconstructed image into VG studio MAX 2.2 software for image processing and then using the measurement module of the software.

[0107] When measuring the dimensions of the casting 6 to be inspected, it is necessary to perform initial calibration and precise calibration of the system.

[0108] VG studio MAX 2.2 software can only accurately measure the required data using measurement tools such as distance, caliper, minimum and maximum values ​​after importing the reconstructed image, entering the appropriate resolution value and performing surface measurement on the image, that is, after calibrating the system.

[0109] The surface measurement adopts the automatic mode, that is, the middle value of the maximum grayscale value and the minimum grayscale value in the image is taken to define the boundary contour of the image, so that the formation of the boundary can reach a relatively ideal state. Before importing the data of the detected casting 6, the image reconstruction of this embodiment uses a cylinder and a scanning section to calibrate the system. The resolution value R can be obtained by measuring the known cylinder scanning image. The resolution value r, the actual size value D of the part, and the measured value d of the part image are arbitrarily input, then R = Dr / d, and the calculated resolution value is input to measure the part image size again. If the actual part size value and the part image size are inconsistent, repeat the above steps until the actual part size value and the part image size are basically consistent. Then, the image resolution values ​​of the system when the reconstruction matrix is ​​4096 and 2048 are: 0.1631 and 0.3262 respectively.

[0110] When using VG studio MAX 2.2 software for dimensional measurement, the image import resolution value has nothing to do with the material type and scanning parameters, but is only related to the image reconstruction matrix. Different image reconstruction matrices have corresponding fixed image import resolution values. The error between the system measurement value and the actual value does not exceed 0.05mm.

[0111] After the system is initially calibrated, the data of the casting 6 to be inspected can be imported for initial dimensional measurement.

[0112] Since the CT detection conditions are different each time, the shape of the detected casting 6 may also be different, and the noise level at the edge of the scanned image may also be different. Therefore, the actual measured value may have an error of several percent while ensuring the image is clear. If there is a certain actual size value in the image each time scanning, if the measured value is inconsistent with the actual value, a more accurate system calibration can be performed through resolution adjustment to achieve better measurement accuracy. In this embodiment, the adjustment is made using the mandrel 2 of the positioning fixture as a reference. The actual accurate size of the mandrel 2 is known, and the adjustment is made based on the actual accurate size of the mandrel 2 and the error of the initial size measurement value obtained by the system measurement. For example, the actual value of the radius of the cross-section circle of the mandrel 2 is 10.00, and the initial size measurement value is 10.02. Click Adjust Resolution in the drop-down menu of the measurement module, change the nominal value to 10.00 in the pop-up menu, and then click OK. In this way, the nominal value becomes 10.00, and the resolution of the entire system is also changed, making the measurement value closer to the actual value.

[0113] After the system is calibrated, the distance of all determined points on the image, the thickness of the entity, the space, etc. can be accurately measured. The distance measurement tool can be used to directly measure the point-to-point size, the caliper measurement tool can be used to directly measure the point-to-surface or surface-to-surface size, and the minimum and maximum distances within the area can be directly measured using the minimum and maximum measurement tool. Fig.19It is the minimum wall thickness measurement of the local area of ​​the oil passage of the intake casing T+24mm section, where the wall thickness is relatively thin.

[0114] In addition, the detection method of this embodiment also includes the measurement of the wall thickness after the circumferential machining is removed: first, the center of the machining is determined on the reconstructed image of the machining position, and then a virtual circle 10 for removing the machining allowance is drawn with the center of the machining as the center of the circle. The wall thickness after the allowance is removed is measured by the virtual circle 10, and the image after the allowance is removed can be obtained, and the relevant wall thickness can also be accurately measured. Among them, the position of the center of the virtual circle 10 is guaranteed by the reference surface of the positioning tool and the machining of the detected casting 6. In this embodiment, the boundary of the solid circle of the precision-machined round bar slice is automatically fitted into a circle showing the radius and the center position. If the radius value of the measured circle has a large error with the actual value during machining, the system can be accurately calibrated by adjusting the system resolution. The position of the center of the circle is guaranteed by the reference surface of the tool and the part machining.

[0115] After determining the center of the circle, you can draw a circle of any radius. Since VG studio MAX 2.2 software cannot draw a circle directly through the center of the circle like CAD, it can only fit a circle through certain points. The minimum number of points on the circumference to fit a circle is three points, such as Fig. 20 For the T=253mm cross-sectional measurement of the tested casting 6 (intake casing), three points with a radius of 37.50mm are found evenly spaced through the center of the circle. Select Fit Circle in the software menu. When fitting the circle, click on all the automatic point fitting options and select the marked points. In this way, a circle with a radius of 37.50mm is drawn in the reconstructed image. The same method can also be used to draw a circle with a radius of 46.15mm. At the same time, the measurement tool is used to complete the design inspection requirements of the T=253mm section.

[0116] The inspection requirements of other sections can be completed in sequence. Fig.21 This is the inspection requirement for the T+160mm section of the tested casting 6 (intake casing) after removing the excess. After one round of processing, the wall thickness of the oil pipe is clear at a glance.

[0117] When drawing the virtual circle 10, three points of the same radius are taken on the cross-section through the center of the circle, and then the three points are fitted into a circle of the same radius. During this process, due to manual operation, whether the error is too large to affect the measurement accuracy can be confirmed by measuring the T+253mm section of the intake casing. In order to minimize the error generated during the operation, all points should be taken when the image is enlarged to the maximum. Fig. 22It is an enlarged image of the center of the mandrel 2 fitting circle and the center of the circle automatically generated by drawing circles with radii of 37.50 mm and 46.15 mm. The distance between the two farthest points is measured, and the measured value is 0.00 mm. Therefore, the position deviation of the manually selected point is less than 5‰. In this embodiment, the center of the virtual circle 11 is calibrated by the center of the mandrel 2.

[0118] Specifically, when measuring the size of the virtual circle 10, all measuring tools will automatically extract the measurement boundary after the surface measurement boundary. However, when measuring the distance between the part boundary and the drawn circle, the measuring tool cannot automatically identify the virtual boundary of the circle. The boundary of the drawn circle should be manually extracted in the magnified state, such as Fig.23 As shown, in order to improve the measurement accuracy.

[0119] Finally, the detection method of this embodiment solidifies the scanning parameters, reconstruction parameters and position information of each cross section in the above-mentioned intake casing test process into the process of industrial CT detection of the part.

[0120] The working process of the present invention is as follows: (1) Design a positioning fixture according to the rough processing benchmark of the casting 6 to be inspected. After the casting 6 to be inspected is clamped in the positioning fixture, the accuracy of the slice position and the center of the part should be ensured. (2) Through different system calibration methods, the accuracy of related dimension measurement is ensured. (3) Through scanning tests, the scanning parameters are optimized, and through image reconstruction analysis tests, the reconstruction parameters are optimized to ensure that the image can meet the requirements of dimension measurement. (4) Select a suitable measuring tool to measure the wall thickness of the pipeline, take the center as the center of the circle, draw different concentric circles according to different processing dimensions, and measure the compliance of the size of the processed parts through the virtual circle 10.

[0121] In summary, an embodiment of the present invention provides a CT detection device and method for the internal dimensions of complex castings of aircraft engines, which is used to carry and position the detected casting 6 by setting a positioning tool. The positioning tool is provided by setting a vertical core rod 2 and an angular positioning block 3 and an angular positioning needle 4 that can move in a direction close to or away from the core rod 2 at the center of the base 1. The detected casting 6 is placed in the positioning groove 101, and the axis of the detected casting 6 is located in the same straight line as the core rod 2. During industrial CT detection, the positioning tool and the detected casting 6 are scanned and processed as a whole, wherein the imaging result of the core rod 2 can be used to determine the center position of the casting on the detection surface and provide the casting center reference information; the base 1 provides the height plane reference starting surface and the center reference cylindrical surface of the casting detection process; the angular positioning block 3 and the angular positioning needle 4 can determine and adjust the casting to the specified angular position when placing the casting, and their imaging results can be used to determine the angular information of the casting. Therefore, the positioning tool is provided in the present invention to provide a reference, which can make the detection result of the detected casting 6 more accurate.

[0122] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A CT detection device for the internal dimensions of complex castings of aircraft engines, characterized in that: The invention comprises a positioning tool, wherein the positioning tool comprises a base (1), a core rod (2), an angular positioning block (3) and an angular positioning needle (4); the base (1) is used to support a casting; a positioning groove (101) is provided on the top surface of the base (1); the positioning groove (101) is arranged concentrically with the base (1); the core rod (2) is vertically connected to the center of the base (1); the angular positioning block (3) can be movably installed on the base (1) in a direction approaching or moving away from the core rod (2); and the angular positioning needle (4) can be movably connected to the angular positioning block (3) in a height direction of the angular positioning block (3).

2. The CT detection device for the internal dimensions of complex aircraft engine castings according to claim 1 is characterized in that: The angular positioning block (3) is provided with a plurality of guide holes (303), the plurality of guide holes (303) are distributed at intervals along the height direction of the angular positioning block (3), and the angular positioning needles (4) are inserted into the guide holes (303).

3. The CT detection device for the internal dimensions of complex aircraft engine castings according to claim 1 is characterized in that: The base (1) is circular, and the angular positioning block (3) moves along the radial direction of the base (1).

4. The CT detection device for the internal dimensions of complex aircraft engine castings according to claim 1, characterized in that: The base (1) is provided with a weight-reducing hole (103).

5. The CT detection device for the internal dimensions of complex aircraft engine castings according to claim 1, characterized in that: The bottom surface of the base (1) is provided with reinforcing ribs (102).

6. A CT detection method for the internal dimensions of complex aircraft engine castings, using the detection device according to any one of claims 1 to 5, characterized in that: include: The casting to be inspected is placed on the base, wherein the central reference cylindrical surface of the casting to be inspected coincides with the central reference cylindrical surface of the base, and the height plane reference starting surface of the casting to be inspected coincides with the central reference cylindrical surface of the base; Adjust the position of the angular positioning needle on the angular positioning block according to the angular feature height of the casting to be inspected, and rotate the casting to be inspected so that the angular feature of the casting to be inspected is aligned with the needle tip of the angular positioning needle; Place the positioning tooling and the casting to be inspected as a whole on the industrial CT scanning operation platform; Perform industrial CT scanning on the positioning tool and the casting to be inspected as a whole to obtain the projection image of the positioning tool and the casting to be inspected as a whole; Perform image reconstruction based on the projection images of the positioning tool and the entire casting to be inspected, to obtain a reconstructed image; Perform surface measurement on the reconstructed image to achieve initial calibration and obtain the initial dimensional measurement values ​​of the positioning fixture and the entire casting being inspected; According to the error between the initial dimension measurement value of the positioning tool and the actual dimension value of the positioning tool, accurate calibration is performed to obtain the accurate dimension measurement value of the positioning tool and the casting to be inspected as a whole.

7. The method for CT detection of internal dimensions of complex aircraft engine castings according to claim 6, characterized in that: It also includes the measurement of wall thickness after circumferential machining to remove allowances: first, determine the center of machining on the reconstructed image of the machining position, then draw a virtual circle for machining allowance removal with the machining center as the center, and measure the wall thickness after removing the allowance through the virtual circle. The position of the center of the virtual circle is guaranteed by the reference surface of the positioning tooling and the machining of the inspected casting.

8. The method for CT detection of internal dimensions of complex aircraft engine castings according to claim 6, characterized in that: Before performing industrial CT scanning on the positioning fixture and the entire casting to be inspected, the scanning parameters are determined first. The scanning parameters include the number of projection frames, scanning frequency and slice thickness during scanning.

9. The method for CT detection of internal dimensions of complex aircraft engine castings according to claim 6, characterized in that: When performing image reconstruction, a clear reconstructed image is obtained by setting and adjusting reconstruction parameters, which include reconstruction area, grayscale magnification, and reconstruction size.

10. The method for CT detection of internal dimensions of complex aircraft engine castings according to claim 6, characterized in that: When performing initial calibration, the surface of the reconstructed image is measured, that is, the middle value of the maximum grayscale value and the minimum grayscale value in the image is taken to define the boundary contour of the image.

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