Assembly method of dynamic balance testing tool and dynamic balance testing tool thereof

Abstract

The application relates to an assembling method of a dynamic balance test tool and the dynamic balance test tool. The assembling method of the dynamic balance test tool comprises the following steps: processing initial raw materials to form a balance mandrel; the balance mandrel is gradually increased in outer diameter from one end to the other end, so that small-diameter ends and large-diameter ends are formed at the two ends of the balance mandrel; a part to be tested is provided, and the part to be tested is formed with a through hole; the small-diameter end of the balance mandrel is inserted into the through hole, the small-diameter end is in clearance fit with the through hole of the part to be tested, the balance mandrel is guided without resistance; an insertion force F is continuously applied in the axial direction, so that the surface of the balance mandrel is attached to part of the through hole, and the axial displacement of the balance mandrel is prevented; and the overall vibration amplitude of the balance mandrel and the part to be tested is detected to verify the stability of the assembly between the balance mandrel and the part to be tested and the absence of additional unbalance.

Description

Technical Field

[0001] This application relates to the field of liquid rocket engine turbopump manufacturing technology, and in particular to the assembly method of dynamic balancing test fixtures and the dynamic balancing test fixtures thereof. Background Technology

[0002] In the aerospace field, the engine, as the core power unit, directly affects the operational stability and safety of the entire system through its performance and reliability. The turbopump, as a key component of aerospace engines, undertakes the crucial task of providing high-pressure, high-speed fluid transport to the engine; its performance has a decisive impact on the entire engine system.

[0003] Centrifugal impellers and inducer wheels are core components of turbopumps that rotate at high speeds. However, during manufacturing, these components inevitably encounter problems due to various factors. From a material perspective, the inherent inhomogeneity of the material leads to differences in mass distribution across different parts of the component. Furthermore, errors during machining and assembly further exacerbate this uneven mass distribution, ultimately causing mass eccentricity in the component. When the turbopump operates at high speed, this mass eccentricity generates unbalanced centrifugal forces and torques. These unbalanced forces can have numerous negative impacts on the engine, triggering harmful high-frequency vibrations. This can not only damage the normal operation of bearings and seals, reducing their service life, but also potentially affect the overall performance of the engine and even lead to safety accidents.

[0004] Given the above, balancing tests on rotating parts in turbopumps are a crucial step in engine manufacturing. Balancing tests effectively reduce unbalanced forces and torques on rotating components, controlling engine vibration and stress on turbopump bearings within permissible limits, thus ensuring normal and stable engine operation. For shaftless parts such as centrifugal wheels and inducer wheels, specialized balancing mandrels are required for balancing tests.

[0005] Currently, while the design and application of dynamic balancing testing fixtures for turbopump parts meet production needs to a certain extent, some problems still need to be addressed. On the one hand, the fixtures in related technologies primarily rely on pre-tightening lock nuts to fix the parts. However, lock nuts themselves have a certain imbalance, which is added to the tested part during testing, reducing the accuracy of the test and preventing the results from accurately reflecting the true balance state of the part. On the other hand, the positioning accuracy of some fixtures is not high. In dynamic balancing testing, the accuracy of positioning directly affects the reliability of the test results. Insufficient positioning accuracy can lead to significant errors in the test results, making it difficult for engineers to accurately judge the quality of the parts, thus affecting the determination of whether the parts are qualified. This may result in unqualified parts entering subsequent production stages or unnecessary reprocessing of qualified parts, increasing production costs and time. Summary of the Invention

[0006] Based on this, an assembly method for a dynamic balancing test fixture and the dynamic balancing test fixture itself are provided, which can improve testing efficiency and balancing accuracy.

[0007] An assembly method for a dynamic balancing test fixture, comprising:

[0008] The initial raw materials are processed to form a balancing mandrel; wherein the balancing mandrel includes a variable diameter fitting section, the outer diameter of which gradually increases from one end to the other, so that its two ends form a small diameter end and a large diameter end respectively;

[0009] A part to be tested is provided, wherein the part to be tested has a through hole;

[0010] The smaller diameter end of the variable diameter fitting section is inserted into the through hole, and the smaller diameter end is clearance-fitted with the through hole of the part to be tested, so that the balance mandrel can be introduced without resistance.

[0011] An insertion force F is continuously applied along the axial direction to make the surface of the variable diameter mating section partially fit with the through hole and prevent the axial displacement of the balance mandrel.

[0012] The overall vibration amplitude of the balance mandrel and the part under test is detected to verify the stability of the assembly between the balance mandrel and the part under test and the absence of additional unbalance.

[0013] In one embodiment, the continuous application of an axial insertion force F to cause the surface of the variable-diameter mating section to fit against the through hole includes:

[0014] The insertion force F is continuously applied along the axial direction. The surface of the variable diameter fitting section contacts the through hole and generates a radial component force. The radial component force drives the test part to move automatically until the coaxiality error between its axis and the axis of the balance mandrel is ≤ ±0.01mm.

[0015] In one embodiment, the detection of the overall vibration amplitude of the balance mandrel and the part under test must meet the following criteria:

[0016] When the dynamic balancing machine is pre-rotated at a speed of 500 r / min, the overall vibration amplitude is ≤0.005 mm / s, and there is no additional imbalance in the assembly between the balancing mandrel and the part to be tested.

[0017] In one embodiment, the processing of the initial raw materials to form a balanced mandrel includes at least the following steps:

[0018] The initial raw materials are processed to form an initial balanced mandrel;

[0019] The initial balancing mandrel is precision machined to form an intermediate balancing mandrel; wherein, the intermediate balancing mandrel has a preset thickness D, such that the small diameter end of the intermediate balancing mandrel is Φ(A-0.05-D) mm, and the large diameter end of the intermediate balancing mandrel is Φ(A+0.05-D) mm, where A is the reference dimension;

[0020] An electroplating process is used to treat the surface of the intermediate balance mandrel, forming a coating on its surface; the thickness of the coating is 0.15±0.02mm, and the hardness of the coating is HV≥800.

[0021] The intermediate balancing mandrel is precision machined to form the balancing mandrel; wherein the small diameter end of the balancing mandrel is Φ(A-0.05) mm, the large diameter end of the balancing mandrel is Φ(A+0.05) mm, and the surface roughness Ra of the balancing mandrel is ≤0.4 μm.

[0022] In one embodiment, the processing of the initial raw materials to form an initial balanced mandrel includes:

[0023] The residual stress of the initial balancing mandrel is eliminated by liquid nitrogen immersion to control the deformation to ≤0.003mm.

[0024] In one embodiment, the assembly method of the dynamic balancing test fixture controls the assembly quality through the following parameters:

[0025] A continuous insertion force F≤50N is applied along the axial direction;

[0026] The measured radial runout of the outer circle of the part to be tested is ≤0.01mm.

[0027] In one embodiment, the step of inserting the smaller diameter end of the variable diameter mating section into the through hole further includes the following steps:

[0028] Clean the balancing mandrel and the part to be tested.

[0029] In one embodiment, the cleaning of the balancing mandrel and the part to be tested needs to meet the following conditions:

[0030] The particle size of residual impurities on the inner wall of the through hole and / or the outer wall of the balance mandrel is <0.005 mm.

[0031] The inner diameter of the through hole is Φ(A±0.003) mm, where A is the reference dimension, and the surface roughness of the inner wall of the through hole is Ra≤0.8μm;

[0032] The deviation of the balancing mandrel is ≤0.005mm.

[0033] In one embodiment, the assembly method of the dynamic balancing test fixture is adapted to a dynamic balancing machine, the balancing mandrel includes a support section, and the variable diameter fitting section is provided with a support section on both sides along its axial direction;

[0034] The dynamic balancing machine clamps the support section of the balancing mandrel and the part to be tested.

[0035] A dynamic balancing test fixture, comprising:

[0036] The balancing mandrel includes a variable diameter fitting section, wherein the outer diameter of the variable diameter fitting section gradually increases from one end to the other, so that its two ends form a small diameter end and a large diameter end, respectively.

[0037] and the part to be tested, wherein the part to be tested has a through hole;

[0038] The variable diameter fitting section is inserted into the through hole of the part to be tested through the small diameter end. The surface of the variable diameter fitting section is partially fitted with the through hole, thereby preventing axial displacement of the balance mandrel.

[0039] The assembly method and fixture described above for dynamic balancing testing involve a variable-diameter fitting section of the balancing mandrel with a small-diameter end and a large-diameter end. The small-diameter end of the fitting section is inserted into the through-hole of the part to be tested, and an insertion force is continuously applied axially. As the balancing mandrel is pushed further axially, the surface of the variable-diameter fitting section gradually comes into contact with the through-hole, forming a gradient fit. With further assembly, the variable-diameter fitting section gradually fits against the inner wall of the through-hole. This gradual fitting process achieves a "self-centering fastening" mode. The gradient structure automatically corrects any deviations that may occur during assembly, achieving coaxiality calibration of the cylindrical hole and the cone without the need for additional positioning fixtures. This keeps the coaxiality error within 0.01 mm, significantly improving assembly accuracy. When the surface of the variable-diameter mating section is fully engaged with the through hole, an interference fit is formed. This fit effectively eliminates assembly clearance, ensuring a stable connection between the balance mandrel and the test part during high-speed operation. This fundamentally improves the balance quality accuracy of the overall rotating system, providing a reliable guarantee for the efficient and stable operation of the turbine pump. The entire assembly process, guided by the axial movement of the balance mandrel along the through hole, achieves a transition from initial guidance to final tight fit, forming a mating structure that combines positioning accuracy and fastening performance. Attached Figure Description

[0040] Figure 1 This is a flowchart illustrating the assembly method of a dynamic balancing test fixture in an exemplary embodiment.

[0041] Figure 2 This is a flowchart illustrating the assembly method of a dynamic balancing test fixture in another exemplary embodiment.

[0042] Figure 3 This is a cross-sectional schematic diagram of a dynamic balancing test fixture in an exemplary embodiment.

[0043] Figure 4 This is a schematic diagram of the structure of a balancing mandrel in an exemplary embodiment.

[0044] Figure label:

[0045] 1. Balancing mandrel; 11. Small diameter end; 12. Large diameter end; 13. Variable diameter fitting section; 14. Support section; 2. Part to be tested; 21. Through hole; 3. Dynamic balancing machine. Detailed Implementation

[0046] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0047] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0048] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0049] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0050] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0051] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0052] In some exemplary embodiments, a method for assembling a dynamic balancing test fixture is provided, which is applied to the dynamic balancing test fixture for performing dynamic balancing tests on the parts to be tested. This dynamic balancing test fixture is also applicable to the dynamic balancing tests of high-speed rotating components such as aerospace and marine gas turbines and industrial turbines, and can be applied according to specific circumstances.

[0053] like Figure 1 As shown, the assembly method of the dynamic balancing test fixture mainly includes processing the initial raw material to form a balancing mandrel, and then assembling and connecting the balancing mandrel with the part to be tested and the dynamic balancing machine to complete the assembly of the dynamic balancing test fixture, thereby performing dynamic balancing tests on the part to be tested. Specifically, it includes the following steps:

[0054] S100. Process the initial raw materials to form a balanced mandrel.

[0055] In step S100, refer to Figure 3 , Figure 4 As shown, the initial raw material is provided, such as a φ50mm x 200mm No. 45 steel round bar. It should be noted that the initial raw material is not limited to this specification and material; other suitable materials and sizes can be selected according to actual needs. The No. 45 steel round bar must have a flaw detection grade ≥ GB / T4162-2008 Class III to ensure the absence of internal cracks and inclusions, effectively avoiding defects in the raw material that could lead to subsequent processing failures and guaranteeing the quality and performance of the balance mandrel 1.

[0056] The balancing mandrel 1, formed by machining, includes a variable-diameter fitting section 13. The outer diameter of the variable-diameter fitting section 13 gradually increases from one end to the other, thus forming a small-diameter end 11 and a large-diameter end 12 at its two ends, respectively. The variable-diameter fitting section 13 of the balancing mandrel 1 is used to fit and connect with the part 2 to be tested, achieving stable assembly between the two. It should be noted that the balancing mandrel 1 is not limited to including the variable-diameter fitting section 13; it may also include a support section 14. A support section 14 is provided on both sides of the variable-diameter fitting section 13 along its axial direction. The support section 14 is used to connect with the dynamic balancing machine 3. The support section 14 mainly provides support and connection functions; it does not contact the part 2 to be tested. Therefore, the radial dimension of the support section 14 is determined according to actual needs, as long as it is smaller than the radial dimension of the small-diameter end 11 of the variable-diameter fitting section 13.

[0057] The dynamic balancing machine 3 can clamp the support section 14 of the balancing mandrel 1 and the part 2 to be tested. The clamping process includes two aspects: positioning and clamping.

[0058] The positioning process is crucial for ensuring the correct installation positions of the balancing mandrel 1 and the part to be tested 2 on the dynamic balancing machine, guaranteeing that their axes are aligned with the rotation axis of the dynamic balancing machine 3. Misalignment will lead to eccentricity, resulting in testing errors and affecting the accuracy of the dynamic balancing test.

[0059] Clamping involves using fixtures, fixing devices, centers, or supports to securely fix the support section 14 of the balancing mandrel 1 and the part 2 to be tested. During testing, the part and mandrel rotate at high speed. If they are not securely fixed, they are prone to displacement or falling off, which can damage the equipment and pose a safety threat to the operator. Therefore, clamping effectively ensures operational safety and also helps improve testing accuracy.

[0060] To ensure the dynamic balancing testing fixture operates without additional vibration during testing, the surface roughness Ra of the support section 14 of the balancing mandrel 1 must be ≤0.8μm, and the coaxiality must be ≤0.005mm. Excessive surface roughness can lead to uneven friction during high-speed rotation, causing additional vibration; similarly, excessive coaxiality deviation can result in imbalance during rotation, affecting test results. Strict control of these two parameters ensures the accuracy and stability of the dynamic balancing test.

[0061] Connect the support section 14 of the machined balance mandrel 1 to the corresponding support part of the dynamic balancing machine 3 to ensure a firm and stable connection.

[0062] The following detailed explanation, with specific steps and operational details, elaborates on step S100 of the dynamic balancing test fixture assembly method in this disclosure, which involves processing the initial raw material to form a balancing mandrel. This process includes multiple sub-steps, sequentially performing rough processing, heat treatment, semi-finishing, residual stress elimination, and finishing operations on the initial raw material, ultimately obtaining a compliant balancing mandrel 1, providing a foundation for the subsequent assembly and testing of the dynamic balancing test fixture. Figure 2 As shown, the specific steps include the following:

[0063] S1001. Process the initial raw materials to form an initial balance mandrel.

[0064] In step S1001, the initial raw material undergoes rough machining. For example, an initial raw material, such as a φ50mm x 200mm No. 45 steel round bar, is selected and rough-machined using a CNC lathe. During rough machining, a machining allowance of 3mm-5mm is reserved to remove the oxide scale on the surface of the steel round bar. The presence of oxide scale will affect the subsequent machining accuracy and part quality. Simultaneously, it quickly removes excess material, forming an initial prototype of the steel round bar, laying the foundation for subsequent semi-finishing. It should be noted that if sufficient machining allowance is not reserved, the ideal machining effect may not be achieved when removing oxide scale and excess material, leading to difficulties in subsequent machining.

[0065] After rough machining, the steel round bar undergoes quenching and tempering treatment. The purpose is to adjust the internal structure of the material to achieve a "strength-toughness balance" in mechanical properties, resulting in a final hardness of HRC28-32. The specific procedures are as follows:

[0066] First, the steel bar undergoes quenching treatment. It is heated to 840℃±10℃ and held for 2 hours, followed by water quenching. Quenching can give the surface and core of the steel bar high hardness and high wear resistance, but it also generates large internal stresses in the material, causing it to become brittle.

[0067] Next, tempering is performed. The quenched steel bar is heated to 520℃±10℃ and held for 3 hours, followed by air cooling. Tempering can eliminate the internal stress generated during quenching, improve the toughness and plasticity of the material, and give it excellent comprehensive mechanical properties, including high strength, good toughness, and plasticity. For example, a balancing mandrel that has undergone tempering treatment can maintain sufficient strength to prevent breakage when subjected to centrifugal force generated by high-speed rotation, while also possessing a certain degree of toughness to avoid damage due to excessive local stress.

[0068] After heat treatment, the steel bar is semi-finished using a CNC lathe. During semi-finishing, a machining allowance of 0.1mm-0.2mm is reserved. At this stage, the initial balancing mandrel is preliminarily machined. The initial balancing mandrel can be frustum-shaped or conical, primarily a variable-diameter cylindrical structure. A 0.02mm deviation is temporarily reserved for the taper of its profile; this near-final dimension machining method effectively reduces stress during finishing. For example, if the machining allowance during semi-finishing is too large, subsequent finishing removal of a significant amount of material will generate substantial internal stress, leading to part deformation and affecting machining accuracy.

[0069] After the initial balanced mandrel is formed, residual stress is eliminated by liquid nitrogen immersion to control the deformation to ≤0.003mm. The specific operation is as follows:

[0070] The initial balancing mandrel was immersed in liquid nitrogen at -196°C for 3 hours, then heated to room temperature in the furnace. Liquid nitrogen immersion completely eliminates residual stress generated during rough machining and tempering, improving overall dimensional stability and preventing subsequent dimensional deformation. For example, if residual stress is not eliminated, parts may deform during subsequent machining, assembly, or use due to the release of residual stress, leading to inaccurate dynamic balancing tests and even affecting the performance of the entire dynamic balancing test fixture.

[0071] Through the above series of steps, the initial raw materials are processed to form an initial balancing mandrel that meets the requirements, which prepares for further processing into the final balancing mandrel and assembly of the dynamic balancing test fixture.

[0072] S1002. The initial balancing mandrel is precision machined to form the intermediate balancing mandrel.

[0073] In step S1002, after the initial balancing mandrel is machined, the finishing stage begins. Through precise machining operations, the initial balancing mandrel is further processed into an intermediate balancing mandrel, while reserving suitable adhesion space for subsequent plating treatment, ensuring that the dimensional accuracy and performance of the entire balancing mandrel meet the requirements of the dynamic balancing test fixture.

[0074] A high-precision CNC lathe is selected as the machining equipment. Before machining begins, the CNC lathe undergoes a comprehensive inspection and adjustment to ensure that all performance indicators are normal, such as the spindle rotation accuracy, tool mounting position, and angle. Simultaneously, based on the material of the initial balancing mandrel and the machining requirements, appropriate turning tools, such as carbide tools, are selected to ensure cutting efficiency and machining quality. The initial balancing mandrel is accurately installed on the CNC lathe's chuck or center and aligned to ensure that the axis of the initial balancing mandrel coincides with the axis of the CNC lathe's spindle, avoiding dimensional errors caused by installation deviations during machining.

[0075] Based on actual design requirements and usage needs, the preset thickness D and reference dimension A of the intermediate balancing mandrel are determined. It should be noted that the aforementioned support section 14 has little impact on the part to be tested 2; therefore, this embodiment mainly focuses on the variable diameter fitting section 13 connected to the part to be tested 2 for further explanation.

[0076] For example, the preset thickness D is set to 0.1 mm, and the reference dimension A of the variable diameter mating section 13 is set to 42 mm. Determining the preset thickness D requires comprehensive consideration of factors such as the type and thickness of the subsequent coating, as well as the adhesion between the coating and the mandrel, to ensure that the coating can firmly adhere to the mandrel surface without affecting the overall dimensional accuracy and performance of the mandrel. The reference dimension A is the basis for the intermediate balancing mandrel dimension design; the subsequent dimensions of the small diameter end 11 and the large diameter end 12 will be calculated and processed based on this reference dimension.

[0077] Based on the preset thickness D and the reference dimension A, calculate the dimensions of the small diameter end 11 and the large diameter end 12 of the variable diameter fitting section 13 of the intermediate balancing mandrel. The calculation formula is as follows:

[0078] The minor diameter end 11 of the intermediate balance mandrel has a size of Φ(A-0.05-D) mm. Substituting A=42mm and D=0.1mm into the formula, we can obtain the minor diameter end 11 size as Φ(42-0.05-0.1)mm=Φ41.85mm.

[0079] The major diameter of the central balancing mandrel is Φ(A+0.05-D) mm. Substituting A=42mm and D=0.1mm into the formula, we can obtain the major diameter of the central balancing mandrel as Φ(42+0.05-0.1)mm=Φ41.95mm.

[0080] The purpose of setting the dimensions in this way is to ensure that a variable diameter structure is formed in the balance mandrel 1, while reserving a suitable space for subsequent coating, and to ensure that the dimensional accuracy of the balance mandrel 1 meets the design requirements by controlling the dimensional deviation of ±0.05mm.

[0081] Through the above implementation steps, the initial balancing mandrel is finished, forming an intermediate balancing mandrel that meets the design requirements, laying a solid foundation for subsequent coating treatment and the assembly of dynamic balancing test fixtures.

[0082] S1003. An electroplating process is used to treat the surface of the intermediate balance mandrel, forming a coating on its surface.

[0083] In step S1003, after the intermediate balancing mandrel is machined, the electroplating surface treatment stage begins. Through the electroplating process, a coating with a specific thickness and hardness is formed on the surface of the intermediate balancing mandrel, thereby improving the wear resistance of the mandrel, extending its service life, and meeting the performance requirements of the dynamic balancing test fixture under high-intensity and high-frequency use scenarios.

[0084] The intermediate balancing mandrel is immersed in a degreasing solution for degreasing treatment. For example, prepare a degreasing solution and soak the mandrel in it for 10-15 minutes, while simultaneously using appropriate agitation or ultrasonic cleaning to remove oil, dust, and other impurities adhering to the mandrel surface. If the oil is not thoroughly removed, it will affect the adhesion between the electroplated layer and the mandrel surface, leading to the plating peeling off.

[0085] After degreasing, the mandrel is immersed in a pickling solution to remove surface oxide scale and rust. Immerse the mandrel in the pickling solution for 3-5 minutes. During the pickling process, carefully control the time and temperature to avoid over-pickling, which could lead to excessive corrosion of the mandrel surface and affect dimensional accuracy and surface quality.

[0086] After pickling, rinse the mandrel surface with clean water to remove the pickling solution, and then immerse it in an activation solution for activation treatment. The purpose of activation treatment is to further clean the mandrel surface, improve surface activity, and enhance the adhesion between the coating and the mandrel surface.

[0087] The hard chrome plating process is employed, using a standard hard chrome plating bath. Its main components include chromium anhydride and sulfuric acid. The chromium anhydride content is typically 200-250 g / L, and the sulfuric acid content is 2-2.5 g / L. Appropriate bath component ratios are crucial for forming a high-quality plating layer. Chromium anhydride is the primary source of chromium ions, while sulfuric acid stabilizes the plating bath and improves the plating layer's performance.

[0088] The temperature of the plating solution should be controlled between 50-60℃. If the temperature is too low, the diffusion rate of ions in the plating solution will slow down, the electroplating reaction rate will decrease, and the coating deposition speed will be slow and the quality will be poor. If the temperature is too high, the evaporation of the plating solution will be accelerated, and it may also cause the coating crystals to be rough, affecting the hardness and wear resistance of the coating.

[0089] The appropriate current density should be set according to the size and shape of the intermediate balancing mandrel. For example, the current density should be controlled between 30-50 A / dm². If the current density is too low, the coating deposition rate will be slow and the production efficiency will be low; if the current density is too high, defects such as burning and roughness will occur in the coating, reducing the coating quality.

[0090] Calculate the electroplating time based on the required plating thickness and the set current density. Given a required plating thickness of 0.15 ± 0.02 mm, the approximate plating time can be calculated using Faraday's law and relevant empirical formulas. For example, at the aforementioned current density, achieving a plating thickness of 0.15 mm would require approximately 40-60 minutes of electroplating. During the electroplating process, the time must be strictly controlled to ensure a uniform and satisfactory plating thickness.

[0091] The pretreated intermediate balancing mandrel is mounted on the anode conductive rod in the electroplating tank using a suitable clamp, ensuring good contact between the mandrel and the conductive rod to guarantee that the current can pass evenly through the mandrel surface. At the same time, attention should be paid to the spacing between the mandrels to avoid mutual obstruction and affecting the electroplating effect.

[0092] Turn on the electroplating power supply and perform the electroplating operation according to the set current density and electroplating time. During the electroplating process, closely observe the changes in parameters such as the temperature, current, and voltage of the plating solution, and make timely adjustments to ensure a stable electroplating process. For example, if the temperature of the plating solution rises too quickly, cooling measures can be taken; if fluctuations occur in the current or voltage, check whether the power supply equipment and conductive system are functioning properly.

[0093] To ensure that ions in the plating solution are evenly distributed on the mandrel surface and to improve the uniformity of the coating, stirring is necessary during the electroplating process. Mechanical stirring or air stirring can be used. Mechanical stirring is achieved by rotating a stirrer in the plating solution; air stirring involves introducing compressed air into the plating solution to create flow. The stirring speed should be moderate to avoid excessive stirring, which could lead to plating solution splashing or uneven coating on the mandrel surface.

[0094] Post-electroplation processing includes cleaning, passivation, and quality inspection. The intermediate balancing mandrel undergoes quality inspection after electroplating. A thickness gauge is used to measure the plating thickness, ensuring it meets the requirement of 0.15±0.02mm. A hardness tester is used to test the plating hardness, requiring a hardness HV≥800. Simultaneously, the surface quality of the plating is observed, checking for defects such as peeling, bubbles, and cracks. If the plating quality is found to be unsatisfactory, the cause must be analyzed and appropriate measures taken for rework.

[0095] The balance mandrel treated with the above electroplating process exhibited good wear resistance and a long service life during actual testing. Comparative testing with unplated balance mandrel fixtures in related technologies revealed that the balance mandrel with hard chrome plating in this embodiment has a service life at least 2.5 times that of the unplated balance mandrel fixture, effectively improving the overall performance and reliability of the dynamic balancing testing fixture.

[0096] Through the above implementation steps, the electroplating surface treatment of the intermediate balancing mandrel is completed, forming a coating that meets the requirements, thus ensuring the long-term stable operation of the dynamic balancing test fixture.

[0097] S1004. The intermediate balance mandrel is precision machined to form a balance mandrel.

[0098] In step S1004, refer to Figure 3 , Figure 4 As shown, after completing the preliminary processing and electroplating of the intermediate balance mandrel, the intermediate balance mandrel is precision machined to form a balance mandrel 1 with accurate dimensions and good surface quality, thereby ensuring its self-centering and positioning function with the part to be tested and meeting the high precision requirements of the dynamic balancing test fixture.

[0099] The reference dimension A is the basis for the design of the diameter-changing fitting section 13 of the balancing mandrel 1, and its value is determined according to the specifications of the part 2 to be tested and the requirements for self-centering and positioning. For example, if the design reference for the inner hole size of the part 2 to be tested is 42mm, then the reference dimension A can be set to 42mm.

[0100] The generatrix length of the variable-diameter fitting section 13 of the balancing mandrel 1 is determined based on the actual assembly depth requirements. In practical applications, the assembly structure of the dynamic balancing test fixture can be analyzed first, and the assembly depth range of the variable-diameter fitting section 13 between the part to be tested 2 and the balancing mandrel 1 can be measured. Then, considering factors such as machining processability and operational stability, a suitable generatrix length can be determined. For example, in this embodiment, the generatrix length is set to 22mm, but it is not limited to this and can be adjusted according to specific circumstances.

[0101] Based on the determined datum dimension A, calculate the dimensions of the small diameter end 11 and the large diameter end 12 of the variable diameter fitting section 13 of the balancing mandrel 1. The calculation formula is as follows:

[0102] The minor diameter end 11 of the balancing mandrel 1 has a size of Φ(A-0.05) mm. Substituting A=42mm into the formula, we can get the minor diameter end 11 size as Φ(42-0.05)mm=Φ41.95mm.

[0103] The major diameter end 12 of the balancing mandrel 1 has a size of Φ(A+0.05) mm. Substituting A=42mm into the formula, we get the size of the major diameter end 12 as Φ(42+0.05)mm=Φ42.05mm.

[0104] The purpose of setting the dimensions in this way is to ensure good self-centering and positioning between the balance mandrel 1 and the part to be tested 2, while leaving a certain dimensional tolerance to accommodate errors in the machining process and assembly requirements in actual use.

[0105] Using high-precision measuring tools, such as micrometers and calipers, measure the dimensions of the small diameter end 11 and the large diameter end 12 of the variable diameter fitting section 13 of the balance mandrel 1 to check whether they meet the requirements of Φ(A-0.05) mm and Φ(A+0.05) mm. At the same time, measure whether the length of the busbar meets the design requirements.

[0106] The surface roughness of the variable diameter fitting section 13 of the balancing mandrel 1 is tested using a surface roughness tester to ensure that the surface roughness Ra ≤ 0.4 μm. If the surface roughness does not meet the requirements, the grinding parameters can be further adjusted, or the mandrel surface can be polished or subjected to other subsequent treatments. The surface roughness of the support section 14 can be greater than that of the variable diameter fitting section 13, such as Ra ≤ 0.8 μm.

[0107] Through the above steps, the intermediate balancing mandrel 1 is finished, forming a balancing mandrel 1 that meets the requirements, thus ensuring the accurate assembly and reliable operation of the dynamic balancing test fixture.

[0108] S110. Provide a part to be tested, which has through holes.

[0109] In step S110, refer to Figure 3 , Figure 4 As shown, in the test scenarios involved in this disclosure, the test part 2 has various types, such as centrifugal wheel, inducer wheel, etc. In order to make the explanation clearer, this disclosure uses the inducer wheel as a specific example of the test part 2 for detailed description. However, it should be noted that the technical solution provided by this disclosure is also applicable to centrifugal wheel and other parts with similar structures and test requirements.

[0110] The part 2 to be tested has a through hole 21. For the inducer wheel, the through hole 21 is usually machined by boring and grinding. For example, if the reference size A is 42mm, according to the requirement that the inner diameter of the through hole 21 is Φ(A±0.003)mm, that is, the inner diameter range is Φ(42-0.003)mm to Φ(42+0.003)mm, which is Φ41.997mm to Φ42.003mm, it can be first bored to Φ41.85mm, and then the dimensional accuracy of the through hole can be ensured by subsequent finishing processes such as grinding.

[0111] The surface roughness of the inner wall of through hole 21 is Ra≤0.8μm.

[0112] Part 2 to be tested has an end face, and the end face positioning datum L is set to, for example, 15mm. During machining, the starting point and direction of the measurement for the end face positioning datum L must first be clearly defined. For example, using a specific structural feature of the idler wheel (such as a shoulder) as the measurement starting point, the distance measured axially to the end face is 15mm. During machining, the dimensional accuracy of the end face positioning datum L can be ensured through processes such as turning or milling. Simultaneously, the end face flatness must be ≤0.01mm.

[0113] S120. Insert the smaller diameter end of the variable diameter fitting section into the through hole. The smaller diameter end is clearance fitted with the through hole of the part to be tested, so that the balance mandrel can be introduced without resistance.

[0114] In step S120, refer to Figure 3 , Figure 4 As shown, before performing the insertion operation, it is necessary to ensure that both the balancing mandrel 1 and the part to be tested 2 are in a suitable condition. For the balancing mandrel 1, its appearance should be carefully inspected to ensure that the small-diameter end 11 is free of obvious burrs, scratches, or deformation, as these defects may affect the fitting accuracy with the through hole 21, or even prevent smooth insertion. Simultaneously, the balancing mandrel 1 should be cleaned using cleaning tools to remove any dust, oil, or other impurities that may be present on its surface, ensuring a smooth insertion process.

[0115] For part 2 to be tested, the internal condition of its through hole 21 should also be checked. Check whether there are any residual chips, rust or other foreign objects inside the through hole 21. If so, use appropriate tools to clean them.

[0116] For example, before inserting the small diameter end 11 of the variable diameter mating section 13 into the through hole 21 of the part to be tested 2, in order to avoid impurities causing abnormal mating clearance and thus affecting coaxiality, the balance mandrel 1 and the part to be tested 2 need to be cleaned.

[0117] The specific cleaning method involves using anhydrous ethanol as the cleaning agent. A clean cloth soaked in anhydrous ethanol is used to carefully wipe the inner wall of the through-hole 21 of the part to be tested 2, ensuring that all parts of the inner wall are cleaned to remove oil, iron filings, and other impurities. Simultaneously, at least the variable-diameter fitting section 13 of the balance mandrel 1 is wiped clean, similarly removing oil, iron filings, and other impurities from its surface. After cleaning, the residual impurity particle size on the inner wall of the through-hole 21 and / or the outer wall of the variable-diameter fitting section 13 should be <0.005mm to ensure the accuracy and quality of subsequent assembly.

[0118] After cleaning, the cleaning effect needs to be tested to determine if the cleanliness meets the requirements. For the through hole 21 of the part to be tested 2, the actual parameter of its inner diameter is measured using an inside micrometer. During the testing process, it is necessary to ensure that the measuring head of the inside micrometer is in full contact with the inner wall of the through hole 21, and to take multiple measurements and average the results according to the correct measurement method to ensure the accuracy of the measurement results. The required inner diameter of the through hole 21 is Φ(A±0.003) mm, where A is the reference dimension. At the same time, the surface roughness of the inner wall of the through hole 21 also needs to be tested using a surface roughness measuring instrument to ensure that the surface roughness of the inner wall of the through hole 21 is Ra≤0.8μm.

[0119] For the variable diameter fitting section 13, its taper is checked using a dial indicator. During actual measurement, the dial indicator's measuring head is brought into contact with the surface of the variable diameter fitting section 13, and the dial indicator is slowly moved along the axial direction. Measurement data at different positions are recorded, and the taper is calculated. The deviation of the variable diameter fitting section 13 must be ≤0.005mm, i.e., the taper deviation must be ≤0.005mm. Subsequent assembly operations can only proceed when the inner diameter of the through hole 21, the surface roughness, and the taper of the balancing mandrel 1 all meet the above requirements.

[0120] In addition, it is necessary to reconfirm whether the dimensional accuracy and surface roughness of the through hole 21 meet the design requirements, because only when the size and surface quality of the through hole 21 meet the standards can a good clearance fit be achieved with the small diameter end 11 of the variable diameter mating section 13.

[0121] After cleaning and cleanliness testing are completed, the small diameter end 11 of the variable diameter fitting section 13 is inserted into the through hole 21 of the part 2 to be tested.

[0122] The small diameter end 11 of the variable diameter fitting section 13 is fitted with the through hole 21 of the part to be tested 2 using a clearance fit. The purpose is to allow the balancing mandrel 1 to be inserted into the through hole 21 without resistance. The size range of the clearance fit needs to be determined according to the specific design requirements and application scenarios.

[0123] Generally, during the design phase, the size of the minor diameter end 11 is determined based on the nominal size of the through hole 21 (for example, when the reference size A of the inner diameter of the through hole 21 is 42mm, the nominal size is 42mm) and the required fitting accuracy. The size of the minor diameter end 11 should be slightly smaller than the nominal size of the through hole 21, and the difference is the clearance. The selection of the clearance must take into account multiple factors. If the clearance is too small, although it can ensure high positioning accuracy, it may lead to increased insertion resistance or even jamming. If the clearance is too large, although insertion is easy, it will affect the relative positional accuracy between the variable diameter mating section 13 and the part 2 under test, thus affecting the subsequent test results.

[0124] For example, when the inner diameter of the through hole 21 is Φ (42±0.003) mm, the diameter of the small diameter end 11 can be designed to be Φ41.99 mm. In this case, the clearance is between 0.007 and 0.013 mm, ensuring smooth insertion of the balance mandrel 1 while meeting certain positioning accuracy requirements. During actual machining, the dimensional accuracy of the small diameter end 11 and the through hole 21 must be strictly controlled. High-precision measuring tools, such as micrometers or inside gauges, should be used to accurately measure the dimensions to ensure they meet design requirements.

[0125] Place the part to be tested 2 on a suitable workbench, ensuring that it does not move or wobble during insertion. The design of the positioning fixture should be based on the shape and size characteristics of the part to be tested 2 to ensure positioning accuracy and stability. For example, for an inducer wheel-type part to be tested 2 with an end face, an end face positioning fixture can be used to fix the part by pressing the end face.

[0126] Then, holding the balance mandrel 1, slowly bring the small diameter end 11 close to the entrance of the through hole 21. During the approach, carefully observe the relative position of the small diameter end 11 and the through hole 21 to ensure that their axes are aligned.

[0127] Once the small-diameter end 11 is aligned with the axis of the through hole 21, slowly insert the small-diameter end 11 of the balancing mandrel 1 into the through hole 21. Maintain a uniform speed during insertion, avoiding excessive force or speed. Excessive force may damage the balancing mandrel 1 or the part 2 under test, while excessive speed may generate a large inertial force, affecting the insertion accuracy or even causing the small-diameter end 11 to collide with the through hole 21.

[0128] Meanwhile, closely observe the insertion process. If a sudden increase in insertion resistance or abnormal sounds are detected, immediately stop the insertion operation and check for interference between the small-diameter end 11 and the through hole 21, or foreign objects stuck in the hole. If any problems are found, troubleshoot them promptly before continuing insertion.

[0129] Through the above operation process and key point control, it can be ensured that the small diameter end 11 of the variable diameter mating section 13 can be smoothly and accurately inserted into the through hole 21 of the part to be tested 2, achieving resistance-free introduction and providing a good foundation for subsequent testing work.

[0130] S130. Continuously apply an insertion force F along the axial direction to make the surface of the variable diameter mating section partially fit with the through hole and prevent the axial displacement of the balance mandrel.

[0131] In step S130, refer to Figure 3 , Figure 4As shown, after inserting the smaller diameter end 11 of the variable diameter fitting section 13 into the through hole 21 of the part to be tested 2 and completing the initial positioning, an insertion force F is continuously applied along the axial direction. The magnitude of the insertion force F needs to be controlled within the range of F≤50N. The method of applying the insertion force is relatively flexible, and mechanical pushing or manual pushing can be selected according to the actual production conditions and equipment conditions.

[0132] As the balancing mandrel 1 is continuously pushed axially, the surface of its variable-diameter fitting section 13 gradually comes into contact with the through hole 21. During this contact process, the contact between the surface of the variable-diameter fitting section 13 and the through hole 21 generates a radial force. This radial force drives the part under test 2 to move automatically, causing its axis to continuously approach the axis of the balancing mandrel 1 until the coaxiality error between the two is ≤ ±0.01mm.

[0133] The variable-diameter fitting section 13 has a small-diameter end 11 and a large-diameter end 12, forming a gradient fit with the through hole 21 of the part to be tested 2. At the beginning of assembly, the small-diameter end 11 with a size of (A-0.05) mm serves as the guide end. Since this size is smaller than the reference size A of the through hole 21, it can be easily inserted into the initial position of the through hole 21 to achieve initial guidance. As assembly progresses, the diameter of the variable-diameter fitting section 13 gradually transitions to the (A+0.05) mm region, forming a progressive fit with the inner wall of the through hole 21. This progressive fit process achieves a "self-centering fastening" mode. The gradient structure can automatically correct deviations that may occur during assembly, achieving coaxiality calibration of the cylindrical hole and the cone without the need for additional positioning fixtures, controlling the coaxiality error within 0.01 mm, thereby significantly improving assembly accuracy.

[0134] For example, during assembly, if the actual size of the through hole 21 deviates to a certain extent, when the actual size is too large (e.g., A+0.03mm), the variable diameter fitting section 13 can be moved towards the smaller diameter end 11, so that the contact position falls in the larger variable diameter fitting section 13 area (e.g., at A+0.03mm); if the actual size of the through hole 21 is too small (e.g., A-0.02mm), it can be moved towards the larger diameter end 12, so that the contact position falls at A-0.02mm. This self-adjusting characteristic allows the fitting clearance / interference to be controlled within ±0.01mm, which can accommodate machining dimensional deviations of ±0.03mm, reducing the precision requirements of the machining equipment.

[0135] When the surface of the variable-diameter fitting section 13 is fully engaged with the through hole 21, an interference fit is formed between them. This fit effectively eliminates assembly clearance, ensuring a stable connection between the balance mandrel 1 and the test part 2 during high-speed operation. This fundamentally improves the balance quality accuracy of the overall rotating system, providing a reliable guarantee for the efficient and stable operation of the turbine pump. The entire assembly process, guided by the axial movement of the balance mandrel 1 along the through hole 21, achieves a transition from initial guidance to final tight fit, forming a fitting structure that combines positioning accuracy and fastening performance.

[0136] During this process, the gradient structure of the variable diameter fitting section 13 automatically corrects the coaxiality deviation between the through hole 21 and the variable diameter fitting section 13. To verify whether the coaxiality meets the requirements, a dial indicator is used to detect the radial runout of the outer diameter of the part under test 2. For example, the root of the blade of the part under test 2 is selected as the detection position. The measuring head of the dial indicator is brought into contact with the outer diameter surface of the blade root. The part under test 2 is slowly rotated, and the change in the dial indicator reading is recorded. The radial runout is calculated, and this radial runout is the measured coaxiality error. The measured coaxiality error is 0.008mm, which meets the accuracy requirement of ≤0.01mm, indicating that the assembly coaxiality of the balance mandrel 1 and the part under test 2 is good, and subsequent dynamic balancing tests and other related operations can be performed.

[0137] S140. Detect the overall vibration amplitude of the balance mandrel and the part under test to verify the stability of the assembly between the balance mandrel and the part under test and the absence of additional unbalance.

[0138] In step S140, refer to Figure 3 , Figure 4 As shown, after assembling the variable diameter fitting section 13 and the test part 2, since they use an interference fit, no additional structure is needed for fixation. At this point, the test part 2 is manually rotated. The operator carefully feels for any jamming or loosening during the rotation, while simultaneously observing whether the surface mounting of the variable diameter fitting section 13 and the test part 2 is secure. If the manual rotation feels smooth and the surface mounting is secure, the next step, dynamic balancing, can be performed.

[0139] The dynamic balancing machine 3 is used to perform a dynamic balancing test on the balance mandrel 1 and the part to be tested 2. First, the assembled assembly is installed on the dynamic balancing machine 3, and the pre-rotation settings are performed according to the operating instructions of the dynamic balancing machine 3. When the speed of the dynamic balancing machine 3 reaches 500 r / min, the overall vibration amplitude is recorded. The overall vibration amplitude is required to be ≤0.005 mm / s. If the measured vibration amplitude meets this requirement, it indicates that there is no additional imbalance between the balance mandrel 1 and the part to be tested 2, and the assembly quality is qualified. If the vibration amplitude exceeds this requirement, the assembly needs to be adjusted or reassembled until the requirement is met.

[0140] To verify the advantages of the dynamic balancing test fixture in this disclosure, please refer to Table 1 for a comparison of key performance parameters between the dynamic balancing fixtures (including locking nuts and cylindrical interference fits) in related technologies and the dynamic balancing fixture in this disclosure.

[0141] Table 1 shows the parameters and objectives of each process of the dynamic balancing fixture. Specific comparative data are as follows:

[0142]

[0143] As can be seen from the comparative data in the table above, the dynamic balancing test fixture in this disclosure has significant advantages. In terms of assembly, the gradient fit between the variable-diameter fitting section 13 and the part to be tested 2 achieves stress-free, high-precision assembly without the need for forced pressing or heating / cooling methods throughout the process. In related technologies, cylindrical surface fits require forced fitting through presses, heating holes / cooling shafts, etc., which can easily lead to localized stress concentration due to uneven interference fit, resulting in micro-cracks and deformations in the parts (such as out-of-roundness of through holes, and tapered distortion of cones). The assembly method in this disclosure avoids these problems, reduces the risk of part damage, and improves the assembly qualification rate.

[0144] Regarding precision adjustment, the variable diameter fitting section 13 in this disclosure exhibits a linearly gradual change in size. The contact position between the through hole 21 and the fitting surface of the variable diameter fitting section 13 can be dynamically adjusted through axial movement, possessing self-adjusting precision characteristics. This allows for compatibility with dimensional deviations and expands the applicable scenarios. In contrast, symmetrical tolerance fittings in related technologies require extremely high machining precision; any dimensional deviation can lead to an excessively loose or tight fit.

[0145] Regarding load distribution, in the cylindrical surface fit of related technologies, the load is concentrated at both ends of the fit surface, which easily leads to localized wear. However, in this disclosure, the conical surface of the variable diameter fit section 13 and the cylindrical hole of the through hole 21 form a continuous annular fit surface, allowing the load to be evenly transmitted along the conical surface, avoiding localized stress concentration. Experimental verification shows that under the same load conditions, the wear of parts using the assembly structure in this embodiment is only 1 / 5 of that of traditional cylindrical fits, and the service life is extended by 2-3 times.

[0146] In summary, the dynamic balancing test fixture disclosed herein fully meets the manufacturing requirements of "high reliability and high efficiency" for aerospace turbopump parts, and is also suitable for dynamic balancing tests of similar high-speed rotating parts such as aerospace and ship gas turbines.

[0147] In some exemplary embodiments, reference is made to Figure 3 , Figure 4As shown, a dynamic balancing test fixture includes a balancing mandrel 1 and a part 2 to be tested. The balancing mandrel 1 includes a variable diameter fitting section 13. This dynamic balancing test fixture achieves the dynamic balancing test related functions of the part 2 to be tested through a specific fitting method between the variable diameter fitting section 13 and the part 2 to be tested.

[0148] The variable diameter fitting section 13 has a unique structural feature, with its outer diameter gradually increasing from one end to the other. This design results in distinct small-diameter end 11 and large-diameter end 12 at both ends of the variable diameter fitting section 13. The outer diameter of the small-diameter end 11 is relatively small, making it easy to insert into the corresponding hole of the part 2 to be tested; the outer diameter of the large-diameter end 12 is relatively large, playing a certain supporting and positioning role in the overall structure.

[0149] When manufacturing the balance mandrel 1, appropriate materials, such as high-strength, wear-resistant alloy steel, can be selected according to the specifications and testing requirements of the actual part 2 to be tested. Through precision machining processes such as turning and grinding, the outer diameter dimensions of each part of the variable diameter mating section 13 are precisely controlled to ensure that its outer diameter changes uniformly and gradually from one end to the other, forming a smooth transition surface. This avoids problems such as abrupt changes in size or substandard surface roughness, thereby ensuring the quality and performance of the balance mandrel 1.

[0150] A through hole 21 is formed on the part 2 to be tested. The through hole 21 is usually circular in shape, and its size and position are designed according to the specific structure of the part 2 to be tested and the testing requirements. When manufacturing the part 2 to be tested, high-precision machining equipment and methods, such as precision grinding machines and boring machines, are required for machining the through hole 21 to ensure the dimensional accuracy and positional accuracy of the through hole 21. For example, the diameter tolerance of the through hole 21 can be controlled within ±0.01mm to ensure the fitting accuracy with the balance mandrel 1.

[0151] When assembling the dynamic balancing test fixture, align the small diameter end 11 of the variable diameter fitting section 13 with the through hole 21 of the part 2 to be tested, and slowly insert the small diameter end 11 into the through hole 21. During the insertion process, ensure that the axis of the balancing mandrel 1 is basically coincident with the axis of the through hole 21 to avoid misalignment or other issues.

[0152] When the variable diameter fitting section 13 is inserted to a certain depth, its surface will fit tightly against part of the inner wall of the through hole 21. As the outer diameter of the variable diameter fitting section 13 gradually changes, when it fits against part of the through hole 21, a certain amount of friction and resistance will be generated in the axial direction, thereby effectively preventing the balance mandrel 1 from axially displacing within the through hole 21.

[0153] For example, when the variable-diameter fitting section 13 is inserted to a position where its outer diameter matches the diameter of the through hole 21, that part of the surface of the variable-diameter fitting section 13 is in close contact with the inner wall of the through hole 21, forming a stable fit. At this time, even if subjected to a certain axial force, the balancing mandrel 1 will not easily move within the through hole 21, thus ensuring the relative positional stability of the balancing mandrel 1 and the part 2 under test during the dynamic balancing test, providing a reliable guarantee for accurate dynamic balancing testing.

[0154] Through the above structural design and assembly method, the dynamic balancing test fixture of this application can effectively realize the dynamic balancing test function of the part 2 to be tested, and has the advantages of simple structure, convenient assembly and accurate positioning.

[0155] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0156] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. An assembly method for a dynamic balancing testing fixture, characterized in that, include: The initial raw materials are processed to form a balancing mandrel; wherein the balancing mandrel includes a variable diameter fitting section, the outer diameter of which gradually increases from one end to the other, so that its two ends form a small diameter end and a large diameter end respectively; A part to be tested is provided, wherein the part to be tested has a through hole; The smaller diameter end of the variable diameter fitting section is inserted into the through hole, and the smaller diameter end is clearance-fitted with the through hole of the part to be tested, so that the balance mandrel can be introduced without resistance. An insertion force F is continuously applied along the axial direction to make the surface of the variable diameter mating section partially fit with the through hole and prevent the axial displacement of the balance mandrel. The overall vibration amplitude of the balance mandrel and the part under test is detected to verify the stability of the assembly between the balance mandrel and the part under test and the absence of additional unbalance. The continuous application of an insertion force F along the axial direction to make the surface of the variable-diameter mating section fit against the through hole includes: The insertion force F is continuously applied along the axial direction. The surface of the variable diameter fitting section contacts the through hole and generates a radial component force. The radial component force drives the test part to move automatically until the coaxiality error between its axis and the axis of the balance mandrel is ≤ ±0.01mm. The overall vibration amplitude of the balancing mandrel and the part under test must meet the following standards: When the dynamic balancing machine is pre-rotated at a speed of 500 r / min, the overall vibration amplitude is ≤0.005 mm / s, and there is no additional imbalance in the assembly between the balancing mandrel and the part to be tested. The process of processing the initial raw materials to form a balanced mandrel includes at least the following steps: The initial raw materials are processed to form an initial balanced mandrel; The initial balancing mandrel is precision machined to form an intermediate balancing mandrel; wherein, the intermediate balancing mandrel has a preset thickness D, such that the small diameter end of the intermediate balancing mandrel is Φ(A-0.05-D) mm, and the large diameter end of the intermediate balancing mandrel is Φ(A+0.05-D) mm, where A is the reference dimension; An electroplating process is used to treat the surface of the intermediate balance mandrel, forming a coating on its surface; the thickness of the coating is 0.15±0.02mm, and the hardness of the coating is HV≥800. The intermediate balancing mandrel is precision machined to form the balancing mandrel; wherein the small diameter end of the balancing mandrel is Φ(A-0.05) mm, the large diameter end of the balancing mandrel is Φ(A+0.05) mm, and the surface roughness Ra of the balancing mandrel is ≤0.4 μm; The assembly method of the dynamic balancing test fixture controls the assembly quality through the following parameters: A continuous insertion force F≤50N is applied along the axial direction; The measured radial runout of the outer circle of the part to be tested is ≤0.01mm.

2. The assembly method of the dynamic balancing test fixture according to claim 1, characterized in that, The process of processing the initial raw materials to form an initial balanced mandrel includes: The residual stress of the initial balancing mandrel is eliminated by liquid nitrogen immersion to control the deformation to ≤0.003mm.

3. The assembly method of the dynamic balancing test fixture according to claim 1, characterized in that, Before inserting the smaller diameter end of the variable diameter fitting section into the through hole, the method further includes the following steps: Clean the balancing mandrel and the part to be tested.

4. The assembly method of the dynamic balancing test fixture according to claim 3, characterized in that, The cleaning of the balance mandrel and the part to be tested must meet the following conditions: The particle size of residual impurities on the inner wall of the through hole and / or the outer wall of the balance mandrel is <0.005 mm. The inner diameter of the through hole is Φ(A±0.003) mm, where A is the reference dimension, and the surface roughness of the inner wall of the through hole is Ra≤0.8μm; The deviation of the balancing mandrel is ≤0.005mm.

5. The assembly method of the dynamic balancing test fixture according to claim 1, characterized in that, The assembly method of the dynamic balancing test fixture is adapted to a dynamic balancing machine. The balancing mandrel includes a support section, and a support section is provided on both sides of the variable diameter fitting section along its axial direction. The dynamic balancing machine clamps the support section of the balancing mandrel and the part to be tested.

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