Contrast block preparation method for ultrasonic testing and contrast block

Abstract

The application aims to provide a contrast test block preparation method and contrast test block for ultrasonic detection, which comprises the following steps: obtaining the configuration of a woven preform, dividing the configuration of the woven preform into at least two detection partitions, determining the number, size and position distribution of artificial defects in each detection partition, preparing the artificial defects by using a large sound attenuation material, implanting the artificial defects into the corresponding detection partition of the woven preform, and detecting the woven preform with the pre-prepared artificial defects after glue injection and solidification molding. The test block prepared by the method can realize the detection of three-dimensional woven composite members.

Description

Technical Field

[0001] This invention relates to the field of nondestructive testing of aero-engine components, and in particular to a method for preparing a comparative test block for ultrasonic testing and the comparative test block itself. Background Technology

[0002] Using resin-based composite components in the cryogenic region of aero-engines can effectively achieve weight reduction goals. Three-dimensional weaving combined with RTM molding is one of the main methods for composite material molding, producing composite components with good isotropy, suitable for complex parts. However, due to the influence of structural form and molding process, porosity caused by localized resin deficiency is a common defect inside woven composite components. Among these, area-shaped porosity, similar to localized delamination in plywood composite components, has a large aspect ratio and exhibits significant anisotropy under stress, making it a weak point in the subsequent service life of the part. It easily acts as a crack initiation, leading to rapid part failure and significantly impacting the part's strength and lifespan. Therefore, ultrasonic testing after part molding is an important means to ensure part quality.

[0003] However, the development of complex resin-based composite components using three-dimensional woven molding is not yet mature in China, and the supporting testing methods are not precise enough. A commonly used ultrasonic testing method involves prefabricated flat-bottomed holes. However, because processing resin-based composites easily causes surface splitting and introduces internal delamination, high-precision flat-bottomed hole processing is difficult and costly. Furthermore, flat-bottomed holes are mainly suitable for pulse-echo methods and have poor applicability to penetration methods. In addition, the composite penetration method often uses external defect attachment for ultrasonic testing and evaluation. This method is affected by the consistency of ultrasonic attenuation within the composite material itself, as well as the external material and its bonding quality, resulting in poor stability. It is mainly used for non-batch, temporary testing or for parts with low quality requirements.

[0004] For three-dimensional woven composite material components, such as complex fan blades, there is currently no effective method for preparing ultrasonic testing blocks for internal area-type defects. This prevents the quantitative and accurate evaluation of defects in woven components through ultrasonic testing. Furthermore, for fan blades subjected to rotational conditions, internal quality inspection and evaluation are critical factors affecting the overall safety of the machine. Therefore, there is an urgent need to provide a comparative test block that can provide a foundation for accurate quantitative evaluation of defects in three-dimensional woven composite material components. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a comparative test block for ultrasonic testing, which can provide a test block for testing three-dimensional woven composite material components.

[0006] A method for preparing a contrast test block for ultrasonic testing to achieve the aforementioned objective includes the following steps:

[0007] a. Obtain the configuration of the woven preform, wherein the configuration of the woven preform is exactly the same as that of the composite part to be inspected;

[0008] b. Divide the configuration of the woven preform into at least two detection zones;

[0009] c. Determine the number, size, and location distribution of artificial defects within each detection zone;

[0010] d. The artificial defect is prepared using a sound attenuation material, and the artificial defect is in the form of a thin film;

[0011] e. Based on the number, size, and location of the artificial defects determined in step c, the artificial defects are implanted into the detection zone corresponding to the woven preform. During the implantation process, the artificial defects are inserted into the interlacing nodes of the warp and weft yarns and fixed to the inserted position by bonding.

[0012] f. Inject adhesive and cure the woven prefabricated body with the pre-made artificial defects into shape;

[0013] g. Use non-destructive testing methods to calibrate the artificial defect. If the artificial defect fails to meet the requirements, repeat step d, adjust the elements of the artificial defect, re-prepare the artificial defect, and implant it.

[0014] In one or more embodiments, in step b, the thickness, curvature, and weave structure of the composite parts to be inspected at the same location corresponding to each of the divided detection partitions are the same.

[0015] In one or more embodiments, in step c, the number, size, and location distribution of artificial defects in each detection zone are determined according to the detection sensitivity requirements of the detection zone.

[0016] In one or more embodiments, the artificial defect is made of a multilayer polytetrafluoroethylene film, with the edges of two adjacent polytetrafluoroethylene films bonded together and an air layer remaining between the two adjacent polytetrafluoroethylene films.

[0017] In one or more embodiments, during the implantation process of step e, room temperature curing adhesive is used to bond and fix the artificial defect to the pre-embedded position designed in each of the detection zones.

[0018] In one or more embodiments, the implantation process of step e is performed during the fiber weaving process of the woven preform.

[0019] In one or more embodiments, step f involves using the same injection curing process and the same molding die fixture as the composite material to be inspected for injection curing.

[0020] In one or more embodiments, in step g, the non-destructive testing method is industrial method or point-focused pulse reflection ultrasonic testing or pulse penetration ultrasonic testing.

[0021] In one or more embodiments, the composite material part to be inspected is a carbon fiber woven composite material component, and the artificial defect is a planar defect.

[0022] On the other hand, according to some embodiments of this application, a contrast test block is also provided, which is made using the contrast test block preparation method for ultrasonic testing as described above.

[0023] The beneficial effects of this invention are as follows:

[0024] In this method for preparing a comparative test block for ultrasonic testing, a thin-film-like artificial defect is implanted into a woven preform, enabling the provision of planar defects in the woven composite material component. This method is suitable for the inspection and calibration of area-like voids in components during ultrasonic testing, effectively improving the limited applicability of flat-bottomed hole test blocks and the poor accuracy and consistency caused by externally attached defects. Furthermore, since the preparation of comparative test blocks for components such as fan blades requires dry fiber weaving followed by an RTM (Reverse Motion Transformation) process, an adhesive method is used to fix the artificial defect at its insertion position to prevent it from being washed away or curled during the adhesive injection process. Additionally, by inserting the artificial defect into the interlacing node of the warp and weft yarns, it is positioned away from the warp yarns, especially at thickness transition points, thereby reducing the risk of deformation of the artificial defect during insertion.

[0025] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0026] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0027] Figure 1 A schematic flowchart of some embodiments of the method for preparing a contrast test block for ultrasonic testing is shown;

[0028] Figure 2 A schematic diagram of the configuration of a woven preform is shown in one embodiment;

[0029] Figure 3A partial schematic diagram of artificial defects in a calibration block is shown using the pulse penetration method for ultrasonic testing. Detailed Implementation

[0030] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0032] Penetrating ultrasonic testing: This method uses two probes, one transmitter and one receiver, placed on opposite sides of the specimen. Defects in the specimen are detected based on the energy changes after the probes penetrate the specimen.

[0033] Ultrasonic signals are reflected and refracted when they encounter interfaces. For example, if there are layers or pores inside the workpiece, the ultrasonic signal will be reflected and refracted at the gas-solid interface of the defect. The reflection method mainly judges the size of the defect by receiving the reflected wave, while the penetration method judges the size of the defect by receiving the pulse signal of the transmitted wave. To ensure the accuracy, repeatability, and comparability of the test results, the detection system must be calibrated using a defect test block of known size, and the size must be determined by comparing it with the detected defect.

[0034] The applicant found that for three-dimensional woven composite components with high operating conditions, such as fan blades, the allowable defects are usually small. Accurate and consistent detection of these small defects is currently a key issue in the inspection of composite components. If the reflection method is used, a common artificial defect is a flat-bottomed hole reflector. However, due to the low maturity of machining technology for resin-based composite materials, machining flat-bottomed holes with diameters of Φ3mm or less is difficult for complex parts with large thicknesses. The flatness and dimensional accuracy of the holes are low, and mechanical damage such as local delamination and splitting is easily introduced. If the penetration method is used, an external test piece can be used as the reflector. The external test piece can be made of polytetrafluoroethylene, polyester, or other sound-impermeable materials. The defect is then attached to the surface of the inspected part with transparent tape. However, each externally attached defect further attenuates the existing attenuation, which is affected by product quality stability. Furthermore, the consistency of the external material, number of layers, and thickness of the adhesive air layer is poor, making this method unsuitable for batch product inspection.

[0035] To provide a foundation for accurate quantitative evaluation of internal defects in three-dimensional woven composite components, on the one hand, according to some embodiments of this application, a method for preparing a comparative test block for ultrasonic testing is provided, such as... Figure 1 A schematic flowchart of some embodiments of the method for preparing a contrast sample block for ultrasonic testing is shown. The method for preparing a contrast sample block for ultrasonic testing includes the following steps:

[0036] S101: Obtain the configuration of the braided preform, which is identical to the configuration of the composite part to be inspected. In some optional embodiments, the obtained configuration of the braided preform may be a three-dimensional model of the braided preform generated within computer software.

[0037] S102: Divide the configuration of the woven preform into at least two detection zones.

[0038] S103: Determine the number, size, and location distribution of artificial defects within each inspection zone.

[0039] S104: Artificial defects are prepared using loud noise attenuation materials, and the prepared artificial defects are in the form of thin films.

[0040] S105: Based on the number, size, and location of the artificial defects determined in step S103, the artificial defects are implanted into the detection zone corresponding to the woven preform. During the implantation process, the artificial defects are inserted into the interlacing nodes of the warp and weft yarns and fixed to the inserted position by bonding.

[0041] S106: Inject adhesive and cure the woven prefabricated body with pre-fabricated artificial defects.

[0042] S107: Use non-destructive testing methods to calibrate the artificial defect. If the artificial defect fails to meet the requirements, repeat step S104 to adjust the elements of the artificial defect, re-prepare the artificial defect, and implant it. In some specific embodiments, the elements of the artificial defect include the material and number of layers of the artificial defect. By adjusting the material and number of layers of the artificial defect, the implanted artificial defect meets the requirements, thus completing the preparation of the comparison test block.

[0043] In this method for preparing a comparative test block for ultrasonic testing, a thin-film-like artificial defect is implanted into a woven preform, enabling the provision of planar defects in the woven composite material component. This method is suitable for inspecting and calibrating area-like voids in components during ultrasonic testing, effectively improving the limited applicability of flat-bottomed hole test blocks and addressing the poor accuracy and consistency caused by externally attached defects. Furthermore, since the preparation of comparative test blocks for components such as fan blades requires dry fiber weaving followed by an RTM (Reverse Motion Muting) process, an adhesive method is used to fix the artificial defect at its insertion position to prevent it from being washed away or curled during the adhesive injection process. Additionally, by inserting the artificial defect into the interlacing node of the warp and weft yarns, it is positioned away from the warp yarns, especially at thickness transition points, thereby reducing the risk of deformation of the artificial defect during insertion.

[0044] In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0045] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0046] In some embodiments of this comparative test block preparation method, in step S102, the thickness, curvature, and weave structure of the composite parts to be inspected at the same location corresponding to each divided test zone are the same. Specifically, the test zones are determined according to the structure and acceptance requirements of the woven composite material components to be inspected. In some specific embodiments, the required detection sensitivity and acceptance requirements within each test zone should also be kept uniform.

[0047] In some embodiments of this comparative test block preparation method, in step S103, the number, size, and location distribution of artificial defects within each detection zone are determined according to the detection sensitivity requirements of the detection zone. Specifically, the size of the artificial defects should meet the required detection sensitivity requirements of that area, such as Φ3mm, Φ6mm, 3mm×3mm, or 6mm×6mm. The location of the artificial defects should cover the near surface, middle thickness, and far surface of the detection area. If a certain detection area is large, such as greater than 300mm×300mm, the number of artificial defects within its detection range is increased and evenly distributed for convenient comparative evaluation.

[0048] In some embodiments of this comparative test block preparation method, the artificial defect is made of multiple layers of polytetrafluoroethylene (PTFE) film, with the edges of adjacent PTFE films bonded together, and an air layer maintained between adjacent PTFE films. Specifically, if the thickness of a single layer is approximately 0.1 mm, three layers are used; if the thickness of a single layer is approximately 0.15 mm, two layers are used. Vacuum should not be applied between layers; the air layer should be maintained normally. The edges are bonded with tape or other room temperature adhesive to ensure that the layers do not slip or detach. In some other suitable embodiments, other materials with higher sound attenuation can be used instead of PTFE film, such as prepreg with an adhesive backing paper. In some specific embodiments, the size deviation of the artificial defect should be controlled within ±0.2 mm.

[0049] In some embodiments of this comparative test block preparation method, during the artificial defect implantation process in step S105, room temperature curing adhesive is used to bond and fix the artificial defect to the pre-embedded position designed for each test zone, thereby reducing the curling or positional displacement of the artificial defect during RTM glue injection. In another embodiment, a prepreg with an adhesive backing paper is used as the artificial defect. In this embodiment, the adhesive properties of the paper itself can be used to fix it to the position to be implanted.

[0050] In some embodiments of this comparative test block preparation method, the artificial defect implantation process in step S105 is performed during the fiber weaving process of the woven preform. That is, step S105 includes the process of three-dimensional weaving according to the configuration of the woven preform and the process of implanting the artificial defect, both of which are performed simultaneously to prevent the fibers from becoming loose. In another embodiment, if the component thickness is small, the artificial defect implantation process can be performed after the fiber preform weaving is completed. However, it is necessary to ensure that the implantation process does not cause the fibers to become loose, and the tightness of the fiber weaving should be as consistent as possible with the surrounding area to be inspected.

[0051] In some embodiments of this comparative test block preparation method, in step S106, the same injection curing process and the same molding die tooling as the composite material to be tested are used for injection curing to ensure the reliability of the prepared comparative test block.

[0052] In some embodiments of the comparative test block preparation method, in step S107, in step g, the non-destructive testing method is industrial method or point-focused pulse reflection ultrasonic testing or pulse penetration ultrasonic testing.

[0053] In some embodiments of the comparative test block preparation method, the composite material part to be tested is a carbon fiber woven composite material component, and the artificial defect is a planar defect.

[0054] On the other hand, according to some embodiments of this application, a comparison test block is also provided, which is made using the comparison test block preparation method for ultrasonic testing as described in the preceding one or more embodiments.

[0055] The following example, using the ultrasonic testing block preparation scheme of a three-dimensional woven structure fan blade of a certain type of engine, further illustrates this application.

[0056] like Figure 2 A schematic diagram of the woven prefabricated body configuration in one embodiment is shown. Based on the shape and structure of the fan blades and the acceptance requirements, it is divided into five ultrasonic testing zones: A, B, C, D, and E.

[0057] Subsequently, the pre-embedding schemes for artificial defects in five zones were determined. Φ6mm and 6mm×6mm circular and square artificial defects were pre-embedded in zones A and B, while Φ3mm, Φ6mm, 3mm×3mm, and 6mm×6mm circular and square artificial defects were pre-embedded in zones C, D, and E. The pre-embedding depth included near-surface, intermediate thickness, and far-surface. All artificial defects were located in the relatively central part of the zone (at least 30mm away from the blade edge) and were evenly distributed.

[0058] Subsequently, artificial defect implants were prepared according to the above dimensions. Each artificial defect was prepared using two layers of adhesive backing paper, and the dimensional deviation was controlled within ±0.2mm.

[0059] Subsequently, the prepared artificial defects are implanted into the carbon fiber three-dimensional braided precast body of the component to be inspected, and the pre-embedded position is controlled to be within ±2mm of the design size using a clamping plate.

[0060] Subsequently, using the same resin, mold, and curing regime as the actual blade, the full-size test block was cured and molded.

[0061] Finally, the pulse penetration ultrasonic method was used to detect artificial defects in the calibration block, and the local manifestation of the artificial defects is shown in the figure below. Figure 3 As shown in the figure, reference numeral 1 indicates an external defect and the tape is visible, reference numeral 2 indicates a 3mm×3mm artificial defect, and reference numeral 3 indicates a 6mm×6mm artificial defect.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing a contrast test block for ultrasonic testing, characterized in that, Includes the following steps: a. Obtain the configuration of the woven preform, wherein the configuration of the woven preform is exactly the same as that of the composite part to be inspected; b. Divide the configuration of the woven preform into at least two inspection zones, and the thickness, curvature and weaving structure of the composite parts to be inspected at the same position corresponding to each of the inspection zones are the same. c. Determine the number, size, and location distribution of artificial defects within each detection zone; d. The artificial defect is prepared using a sound attenuation material. The artificial defect is in the form of a thin film and is made of multiple layers of polytetrafluoroethylene (PTFE) film. The edges of two adjacent PTFE films are bonded together, and an air layer is retained between two adjacent PTFE films. e. Based on the number, size, and location of the artificial defects determined in step c, the artificial defects are implanted into the detection zone corresponding to the woven preform. During the implantation process, the artificial defects are inserted into the interlacing nodes of the warp and weft yarns and fixed to the inserted position by bonding. f. Inject adhesive and cure the woven prefabricated body with the pre-made artificial defects into shape; g. Use non-destructive testing methods to calibrate the artificial defect. If the artificial defect fails to meet the requirements, repeat step d, adjust the elements of the artificial defect, re-prepare the artificial defect, and implant it.

2. The method for preparing a contrast test block for ultrasonic testing as described in claim 1, characterized in that, In step c, the number, size, and location distribution of artificial defects in each detection zone are determined according to the detection sensitivity requirements of the detection zone.

3. The method for preparing a contrast test block for ultrasonic testing as described in claim 1, characterized in that, During the implantation process in step e, room temperature curing adhesive is used to bond and fix the artificial defect to the pre-embedded position designed in each of the detection zones.

4. The method for preparing a contrast test block for ultrasonic testing as described in claim 1, characterized in that, The implantation process in step e is carried out during the fiber weaving process of the woven preform.

5. The method for preparing a contrast test block for ultrasonic testing as described in claim 1, characterized in that, In step f, the same injection curing process and the same molding mold tooling as the composite material to be inspected are used for injection curing and molding.

6. The method for preparing a contrast test block for ultrasonic testing as described in claim 1, characterized in that, In step g, the non-destructive testing method is industrial method or point-focused pulse reflection ultrasonic testing or pulse penetration ultrasonic testing.

7. The method for preparing a contrast test block for ultrasonic testing as described in claim 1, characterized in that, The composite material part to be inspected is a carbon fiber woven composite material component, and the artificial defect is a planar defect.

8. A comparative test block, characterized in that, It is prepared using the method for preparing a contrast test block for ultrasonic testing as described in any one of claims 1 to 7.

Images