Preparation method of reference block for ultrasonic detection and reference block

Abstract

The invention aims to provide a preparation method of a reference block for ultrasonic detection and the reference block, and the preparation method comprises the following steps: obtaining the configuration of a woven preform, dividing the configuration of the woven preform into at least two detection subareas, determining the number, size and position distribution of artificial defects in each detection subarea, and determining the number, size and position distribution of the artificial defects in each detection subarea; and preparing the artificial defect by adopting a loud sound attenuation material, implanting the artificial defect into the detection subarea corresponding to the woven preform, injecting glue into the woven preform with the prefabricated artificial defect, curing and molding, and then detecting. Through the preparation method, the test block for detecting the three-dimensional woven composite material component can be provided.

Description

Technical Field

[0001] The invention relates to the field of nondestructive testing of aviation engine parts, and in particular to a method for preparing a comparison test block for ultrasonic testing and a comparison test block. Background Art

[0002] The use of resin-based composite components at the low-temperature end of aircraft engines can effectively achieve the goal of weight reduction. Three-dimensional weaving combined with RTM molding is one of the main methods for composite molding. The formed composite components have good isotropy and are suitable for complex parts. However, affected by the structural form and molding process, pores caused by local lack of glue are common defects inside woven composite components. Among them, area-shaped pores are similar to local delamination in laminated composite components. Due to the large length-to-width ratio of the defects, the anisotropy is more obvious when subjected to force. It is a weak point in the subsequent service process of the parts and is easy to serve as a crack source, causing rapid failure of the parts, which has a greater impact on the strength and life of the parts. Therefore, ultrasonic testing after the parts are formed is an important means to ensure the quality of the parts.

[0003] However, complex components of three-dimensional woven resin-based composite materials are not yet mature in China, and the supporting detection methods are not sophisticated enough. The commonly used ultrasonic inspection test block is the method of prefabricating flat-bottom holes. Since the processing of resin-based composite materials can easily cause surface splitting and introduce internal stratification, it is difficult and costly to process high-precision flat-bottom holes. Flat-bottom holes are mainly suitable for pulse reflection methods and are less suitable for penetration methods. In addition, the composite penetration method often uses the method of external defects for ultrasonic detection and evaluation. Affected by the consistency of ultrasonic attenuation of the composite body, and affected by the external materials and the quality of the paste, the stability of this method is poor. It is mainly used for non-batch temporary detection or parts detection with low quality requirements.

[0004] For three-dimensional woven composite components, such as fan blades with complex structures, there is no effective method for preparing ultrasonic test blocks for internal area defects, which makes it impossible to quantitatively and accurately evaluate the ultrasonic testing of woven components. For fan blades that are subjected to rotating conditions, internal quality inspection and evaluation are also key factors affecting the safety of the entire machine. Therefore, it is urgent to provide a comparison test block that can provide a basis for accurate quantitative evaluation of defects in three-dimensional woven composite components. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a comparison test block for ultrasonic testing, which can provide a test block for testing a three-dimensional woven composite material component.

[0006] To achieve the above-mentioned purpose, a method for preparing a comparative test block for ultrasonic testing comprises the following steps:

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

[0008] b. Dividing the configuration of the braided preform into at least two detection partitions;

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

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

[0011] e. According to the number, size and position of the artificial defects determined in step c, the artificial defects are implanted into the detection partition corresponding to the woven preform, and the artificial defects are inserted into the interlaced nodes of the lining warp and weft yarns during the implantation process, and fixed to the inserted position by bonding;

[0012] f. The braided preform with the artificial defects preformed is injected and cured;

[0013] g. Use non-destructive testing means to calibrate the artificial defect. If the artificial defect cannot 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 weaving structure of the composite part to be inspected at the same position corresponding to each of the divided inspection zones are the same.

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

[0016] In one or more embodiments, the artificial defect is made of a multi-layer polytetrafluoroethylene film, the edges of two adjacent polytetrafluoroethylene films are bonded and connected, and an air layer is retained between the two adjacent polytetrafluoroethylene films.

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

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

[0019] In one or more embodiments, in step f, the same glue injection and curing process and the same molding mold tooling as those of the composite part to be inspected are used for glue injection and curing molding.

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

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

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

[0023] The beneficial effects of the present invention are:

[0024] In the preparation method of the comparison test block for ultrasonic testing, by implanting a film-like artificial defect into a woven preform, it is possible to provide a planar defect in a woven composite material component, which is suitable for the inspection and calibration of area-shaped gaps in the component during ultrasonic testing, and can effectively improve the current situation that the flat-bottom hole test block has a small application range and the external defects lead to poor detection accuracy and consistency. At the same time, since the comparison test blocks of parts such as fan blades need to be prepared by dry fiber weaving first and then by glue injection RTM process, in order to prevent the artificial defects from being washed away or curling during the glue injection process, they are fixed to the inserted position by bonding. At the same time, by inserting the artificial defects into the interlaced nodes of the lining warp and the weft yarn, it can be kept away from the binding warp yarn, especially the thickness transition point, thereby reducing the risk of deformation of the artificial defects during the insertion process.

[0025] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0027] Figure 1 A schematic diagram of the process of preparing a comparison test block for ultrasonic testing according to some embodiments of the present invention is shown;

[0028] Figure 2 A schematic diagram of the configuration of a braided preform under an embodiment is shown;

[0029] Figure 3A local schematic diagram of using the pulse penetration method to ultrasonically detect artificial defects in a calibration test block is shown. DETAILED DESCRIPTION

[0030] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0032] Penetrating ultrasonic testing: A method of detecting defects in a specimen by placing two probes, one transmitting and one receiving, on opposite sides of the specimen, based on the energy change after penetrating the specimen.

[0033] When an ultrasonic signal encounters an interface, it will be reflected and refracted. For example, if there are stratifications 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, and the penetration method judges the size of the defect by receiving the pulse signal of the penetrating wave. In order to ensure the accuracy, repeatability and comparability of the test results, the detection system must be calibrated with a defect test block of known size and compared with the found defect to determine its size.

[0034] The applicant found that for three-dimensional woven composite components with high requirements for operating conditions, such as fan blades, the defects allowed are usually small. Accurate and consistent detection of small defects is a key issue in the current detection of composite components. If the reflection method is used, the common artificial defect is a flat-bottom hole reflector. However, due to the low maturity of the mechanical processing technology of resin-based composite materials, it is difficult to process flat-bottom holes with a diameter of Φ3mm or less for complex parts with large thickness. The flatness and dimensional accuracy of the holes are low, and mechanical damage such as local delamination and splitting are easily introduced. If the penetration method is used, an external test piece can be used as a reflector. The external test piece can be made of polytetrafluoroethylene, polyester or other sound-impermeable materials. The defects are pasted to the surface of the inspected part with transparent tape. However, each external defect causes further attenuation on the basis of the attenuation of the main body, which is affected by the stability of product quality. In addition, the consistency of the external material, number of layers, and thickness of the pasted air layer is poor. This method is not suitable for batch product testing.

[0035] In order to provide a basis for accurate quantitative evaluation of internal defects of three-dimensional woven composite components, on the one hand, according to some embodiments of the present application, a method for preparing a comparison test block for ultrasonic testing is provided, such as Figure 1 The flowchart of some embodiments of the method for preparing a comparative test block for ultrasonic testing is shown. The method for preparing a comparative test block for ultrasonic testing comprises the following steps:

[0036] S101: Acquire a configuration of a braided preform, wherein the configuration of the braided preform is identical to that of the composite part to be inspected. In some optional embodiments, the acquired configuration of the braided preform may be a three-dimensional model of the braided preform generated in computer software.

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

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

[0039] S104: an artificial defect is prepared by using a sound attenuation material, and the prepared artificial defect is in a film shape.

[0040] S105: According to the number, size and position of the artificial defects determined in step S103, the artificial defects are implanted into the detection partition corresponding to the woven preform. During the implantation process, the artificial defects are inserted into the interlaced nodes of the lining warp yarn and the weft yarn, and fixed to the inserted position by bonding.

[0041] S106: injecting glue to solidify the braided preform with the prefabricated artificial defects.

[0042] S107: Use non-destructive testing means to calibrate the artificial defect. If the artificial defect cannot meet the requirements, repeat step S104, 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, and the preparation of the comparison test block is completed.

[0043] In the preparation method of the comparison test block for ultrasonic testing, by implanting a film-like artificial defect into a woven preform, it is possible to provide a planar defect in a woven composite material component, which is suitable for the inspection and calibration of area-shaped gaps in the component during ultrasonic testing, and can effectively improve the current situation that the flat-bottom hole test block has a small application range and the external defects lead to poor detection accuracy and consistency. At the same time, since the comparison test blocks of parts such as fan blades need to be prepared by dry fiber weaving first and then by glue injection RTM process, in order to prevent the artificial defects from being washed away or curling during the glue injection process, they are fixed to the inserted position by bonding. At the same time, by inserting the artificial defects into the interlaced nodes of the lining warp and the weft, it can be kept away from the binding warp, especially the thickness transition point, thereby reducing the risk of deformation of the artificial defects during the insertion of the artificial defects.

[0044] In the description of the embodiments of the present application, “plurality” means more than two, unless otherwise clearly and specifically defined.

[0045] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0046] In some embodiments of the comparative test block preparation method, in step S102, the thickness, curvature, and weaving structure of the same position of the composite material part to be inspected corresponding to each divided inspection zone are the same. Specifically, the inspection zone is determined according to the structure and acceptance requirements of the woven composite material component to be inspected. In some specific embodiments, the required detection sensitivity and acceptance requirements in each inspection zone should also be kept uniform.

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

[0048] In some embodiments of the comparative test block preparation method, the artificial defect is made of a multilayer polytetrafluoroethylene film, the edges of two adjacent polytetrafluoroethylene films are bonded and connected, and an air layer is retained between two adjacent polytetrafluoroethylene films. Specifically, if the thickness of a single layer is about 0.1 mm, a three-layer preparation is adopted. If the thickness of a single layer is about 0.15 mm, a two-layer preparation is adopted. The layers should not be evacuated, and the air layer is normally retained. The edges are bonded with tape, or other room temperature adhesives are used to fix them to ensure that the layers do not slip and detach. In some other suitable embodiments, other materials with greater sound attenuation can also be used instead of polytetrafluoroethylene film, such as backing paper with a prepreg tape adhesive layer. In some specific embodiments, the deviation in the size of artificial defects should be controlled within ±0.2 mm.

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

[0050] In some embodiments of the comparative test block preparation method, the artificial defect implantation process of 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 artificial defects, and the two 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 is woven, but it is necessary to ensure that the implantation process does not cause the fibers to become loose, and the fiber weaving tightness should be kept as consistent as possible with the nearby area to be inspected.

[0051] In some embodiments of the comparison test block preparation method, in step S106, the same glue injection and curing process and the same molding mold tooling as those of the composite part to be tested are used for glue injection and curing molding, thereby ensuring the reliability of the prepared comparison test block.

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

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

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

[0055] The following further illustrates the present application by taking the ultrasonic inspection test block preparation scheme of a certain type of engine three-dimensional woven structure fan blade as an example.

[0056] like Figure 2 A schematic diagram of the configuration of a braided preform under an embodiment is shown, which is divided into five ultrasonic testing zones A, B, C, D, and E according to the fan blade shape structure and acceptance requirements.

[0057] Subsequently, the artificial defect embedding plan for the five partitions was determined. Φ6mm and 6mm×6mm circular and square artificial defects were embedded in areas A and B, and Φ3mm, Φ6mm, 3mm×3mm, and 6mm×6mm circular and square artificial defects were embedded in areas C, D, and E. The embedded depth included the near surface, middle thickness, and far surface. All artificial defects were located in the middle part of the area (at least 30mm away from the edge of the blade) and were evenly arranged.

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

[0059] Subsequently, the prepared artificial defects were implanted into the carbon fiber three-dimensional braided preform of the component to be inspected, and the pre-embedded position was controlled to have a deviation within ±2 mm from the designed size using a card plate;

[0060] Subsequently, the full-scale test block was cured into shape using the same resin, mold and curing system as the actual blade;

[0061] Finally, the pulse penetration method is used to detect the artificial defects in the calibration test block. The local display of the artificial defects is as follows: Figure 3 As shown, reference numeral 1 in the figure is an external defect and tape display, reference numeral 2 is an artificial defect of 3mm×3mm, and reference numeral 3 is an artificial defect of 6mm×6mm.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for preparing a comparative test block for ultrasonic testing, characterized in that: The steps include: a. Obtaining the configuration of the braided preform, the configuration of the braided preform is exactly the same as that of the composite part to be inspected; b. Dividing the configuration of the braided preform into at least two detection partitions; c. Determine the number, size and location distribution of artificial defects within each of the detection zones; d. The artificial defect is prepared by using a sound attenuation material, and the artificial defect is in the form of a film; e. According to the number, size and position of the artificial defects determined in step c, the artificial defects are implanted into the detection partition corresponding to the woven preform, and the artificial defects are inserted into the interlaced nodes of the lining warp and weft yarns during the implantation process, and fixed to the inserted position by bonding; f. The braided preform with the artificial defects preformed is injected and cured; g. Use non-destructive testing means to calibrate the artificial defect. If the artificial defect cannot 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 comparison test block for ultrasonic testing according to claim 1, characterized in that: In the step b, the thickness, curvature and weaving structure of the composite part to be inspected at the same position corresponding to each of the divided inspection zones are the same.

3. The method for preparing a comparison test block for ultrasonic testing according to claim 1, characterized in that: In the 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.

4. The method for preparing a comparison test block for ultrasonic testing according to claim 1, characterized in that: The artificial defect is made of multiple layers of polytetrafluoroethylene films, the edges of two adjacent polytetrafluoroethylene films are bonded and connected, and an air layer is reserved between the two adjacent polytetrafluoroethylene films.

5. The method for preparing a comparison test block for ultrasonic testing according to claim 1, characterized in that: During the implantation process of step e, the artificial defect is bonded and fixed at the pre-embedded position designed for each detection partition using room temperature curing glue.

6. The method for preparing a comparison test block for ultrasonic testing according to claim 1, characterized in that: The implantation process of step e is performed during the fiber weaving process of the braided preform.

7. The method for preparing a comparison test block for ultrasonic testing according to claim 1, characterized in that: In the step f, the same glue injection and curing process and the same molding mold tooling as those of the composite part to be inspected are used for glue injection and curing molding.

8. The method for preparing a comparison test block for ultrasonic testing according to claim 1, characterized in that: In step g, the non-destructive testing method is industrial method or point-focused pulse reflection method ultrasonic testing or pulse penetration method ultrasonic testing.

9. The method for preparing a comparison test block for ultrasonic testing according to 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 surface defect.

10. A comparative test block, characterized in that: The comparative test block is made by the method for preparing the comparative test block for ultrasonic testing as claimed in any one of claims 1 to 9.

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