An initial crack presetting method for aircraft engine disk life assessment

Abstract

The present application provides an initial crack presetting method for aircraft engine disk life assessment, comprising: determining process parameters for initial crack presetting, the process parameters comprising electrode material, size and working current, the electrode being a graphite electrode, the radius size of the graphite electrode being consistent with the preset initial crack depth, the initial thickness of the graphite electrode being greater than the preset initial crack width, and the final thickness of the electrode being consistent with the preset initial crack width by reducing the electrode thickness; the working current comprising a high voltage current and a low voltage current, and a current parameter combination consistent with the preset initial crack depth is obtained by performing a combination test of different high voltage currents and low voltage currents on the electrode material; determining the position and direction of the preset initial crack, and determining the preset initial crack position according to the type of the aircraft engine disk and the stress magnitude, the initial crack position being in a stress concentration region, and the direction of the initial crack being perpendicular to the stress direction.

Description

Technical Field

[0001] The present application belongs to the field of aero-engine testing technology, and in particular relates to an initial crack presetting method for aero-engine disc life assessment. Background Art

[0002] As aircraft engines age, fatigue damage to rotor discs is becoming increasingly prominent. Disc damage tolerance is a crucial factor in ensuring aircraft engine safety. However, due to limitations in manufacturing processes and testing methods, the probability of manufacturing defects, micro-cracks, and other issues in service rotor discs increases, complicating disc lifespan assessment and verification.

[0003] Since the crack initiation life is difficult to predict accurately, the number of cycles required for the initiation of natural cracks is unknown, and the monitoring methods for initial crack initiation are immature, in order to save test time and labor costs and ensure the test progress, the method of artificially pre-setting initial cracks is generally adopted. After pre-setting the initial crack on the wheel, a crack extension test is carried out to verify the wheel cycle life.

[0004] Commonly used initial crack presetting methods include scratch presetting method, impact presetting method, corrosion presetting method, spot welding presetting method and electric spark presetting method, but the initial cracks of aircraft engine discs are usually tiny cracks, and the methods in the existing technology are usually difficult to produce crack sizes and shapes that meet the precision requirements. Summary of the Invention

[0005] The purpose of the present application is to provide an initial crack presetting method for life assessment of an aircraft engine disk, so as to solve or alleviate at least one problem in the background technology.

[0006] The technical solution of the present application is: an initial crack presetting method for aircraft engine disc life assessment, the initial crack presetting method comprising:

[0007] Determining process parameters for initial crack presetting, wherein the process parameters include electrode material, size, and operating current; the electrode is a graphite electrode, the radius of the graphite electrode is consistent with the preset initial crack depth, the initial thickness of the graphite electrode is greater than the preset initial crack width, and the electrode thickness is reduced so that the final thickness of the electrode is consistent with the preset initial crack width; the operating current includes high-voltage current and low-voltage current, and a current parameter combination consistent with the preset initial crack depth is obtained by conducting different high-voltage and low-voltage current combination tests on the electrode material;

[0008] The position and direction of a preset initial crack are determined, wherein the preset initial crack position is determined according to the type and stress magnitude of the aircraft engine wheel disc, the initial crack position is in a stress concentration area, and the direction of the initial crack is perpendicular to the stress direction.

[0009] Furthermore, the shape of the graphite electrode is the same as or similar to that of the initial crack.

[0010] Furthermore, the thickness of the electrode is reduced by reversing the connection of the electrode.

[0011] Furthermore, the current parameter combination is determined as follows:

[0012]

[0013] Where: I l and I h They represent low voltage current and high voltage current respectively, ρ represents the material parameter of the pre-cracked wheel, a, b, c, d represent the range of current parameter selection

[0014] Furthermore, the difference between the initial crack depth preset by combining the low-voltage current and the high-voltage current and the target initial crack depth does not exceed 5%.

[0015] Furthermore, the aircraft engine wheel types include fan and compressor wheels and turbine wheels. The stress concentration areas of the fan and compressor wheels are the wheel groove bottom and the wheel center, and the stress concentration areas of the turbine wheel are the wheel groove bottom, the wheel center and the wheel spoke plate.

[0016] Furthermore, the directions of the preset initial cracks on the wheel groove bottom and the wheel center are along the wheel meridian plane, and a plurality of initial cracks are preset at symmetrical positions along the wheel circumference;

[0017] The directions of the preset initial cracks of the wheel disc spokes are along the wheel disc meridian plane and perpendicular to the wheel disc meridian plane, and a plurality of initial cracks are preset at symmetrical positions along the wheel disc circumference.

[0018] The initial crack presetting method of the aircraft engine wheel of the present application clarifies the electric spark presetting process parameters and related technical requirements, provides quantitative parameters for the initial crack presetting of the relevant wheel structure, has high feasibility, and provides technical support for the damage tolerance research and crack propagation test of the aircraft engine wheel. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions provided by this application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of this application.

[0020] Figure 1 This is a schematic diagram of the initial crack presetting method of this application.

[0021] Figure 2 Schematic diagram of the graphite electrode structure according to one embodiment of the present application

[0022] Figure 3 Schematic diagram of a typical roulette wheel structure in this application DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below in conjunction with the drawings in the embodiments of this application.

[0024] To overcome the difficulty in controlling crack shape, depth, and width in existing methods of pre-setting cracks using electric sparks, a new method for pre-setting initial cracks was proposed. By determining a suitable combination of electrode materials, electrode dimensions, and optimal high and low voltage currents, the crack shape, depth, and width required for aircraft engine disc life assessment were achieved. Furthermore, parameters such as the location, number, and direction of the initial cracks were determined based on the structural form and stress characteristics of a typical aircraft engine disc.

[0025] like Figure 1 As shown, the initial crack presetting method proposed in this application mainly includes the following steps:

[0026] (1) Determine the process parameters for crack presetting;

[0027] Based on the initial crack requirements of the aircraft engine wheel, an electric spark method that is suitable for processing small defects is selected for initial crack presetting. The copper electrode commonly used in electric spark is prone to electrode melting and damage when the electrode size is relatively thin. Therefore, a graphite electrode with better temperature resistance is selected in this application. Among them, the graphite electrode has the same or similar shape as the initial crack, and the depth of the initially selected graphite electrode is the same or close to the depth of the initial crack. The width of the graphite electrode is greater than the width of the initial crack. By reducing the width of the graphite electrode, its width is the same or close to the width of the initial crack.

[0028] For example, in one embodiment of the present application, the initial crack parameters are a width of 0.1 to 0.2 mm, a depth of 0.38 mm, and a semicircular microcrack. The size diagram of the selected graphite electrode is shown in FIG. Figure 2 The graphite electrode is semicircular. Since the processing quality of the graphite electrode with a thickness t of 0.1 to 0.2 mm is difficult to guarantee, the initial graphite electrode size is selected as R = 0.38 mm and t = 0.5 mm. The thickness of the graphite electrode is thinned by reversely connecting the graphite electrode on the machine tool. When the thickness t of the graphite electrode reaches 0.1 mm to 0.2 mm, the graphite electrode is connected in a forward manner to preset the initial crack.

[0029] For aircraft engine discs made of different materials, different low-voltage and high-voltage current combinations are required to achieve a crack depth of 0.38 mm. According to the following formula, different current combinations are used to preset initial cracks on the simulated component. The specimens with different preset cracks are dissected and the crack depths are measured to determine the optimal current combination:

[0030]

[0031] Where: I l and I h Represent low voltage current and high voltage current respectively;

[0032] ρ represents the material parameter of the disc that needs to be pre-cracked;

[0033] a, b, c, and d represent the current parameter selection range.

[0034] As shown in Table 1, the current parameters and crack depth measurement results of a typical titanium alloy (TC17) wheel disc material in an embodiment of the present application are shown. According to the crack depth measurement results, the crack depth of 382.25 μm is relatively close to the initial crack depth of 0.38 mm. Therefore, it can be determined that the current process parameters of the titanium alloy wheel disc are more reasonable to select a low voltage current of 1A and a high voltage current of 0.5A.

[0035] Table 1

[0036]

[0037] According to the above-mentioned initial crack presetting process parameters, the electric spark method can be used to preset the initial crack depth and width that meet the requirements on the test piece. At the same time, the consistency and stability of the crack shape and dimensional accuracy are good, so the initial crack can be preset on the aircraft engine disk.

[0038] (2) Determine the preset position of the initial crack of the aircraft engine wheel and complete the production of the initial crack of the wheel.

[0039] like Figure 3 As shown, according to the structural form and stress characteristics of the aircraft engine wheel 10, for the fan and compressor wheels, the groove bottom 13 and the disk center 11 with higher stress are selected as the initial crack preset positions of the aircraft engine wheel in this application. For the turbine disk, in addition to selecting the groove bottom 13 and the disk center 11 with higher stress, the turbine disk's web 12 is also a part with greater stress and is also selected as the preset position of the initial crack.

[0040] The groove bottom and disc center of aircraft engine disc are mainly subjected to circumferential stress. The crack preset direction is along the disc meridian plane. Two initial cracks can be preset at symmetrical positions along the disc circumference.

[0041] The circumferential and radial stresses in the wheel spokes are both high. Cracks are pre-set along and perpendicular to the wheel's radial plane, with one to two initial cracks pre-set at symmetrical locations along the wheel's circumference. The specific pre-set locations can be adjusted based on operability and process requirements, but are typically selected in high-stress areas.

[0042] The direction of the preset crack is perpendicular to the stress direction, so the preset crack can be cracked.

[0043] The initial crack presetting method of the aircraft engine wheel of the present application clarifies the electric spark presetting process parameters and related technical requirements, provides quantitative parameters for the initial crack presetting of the relevant wheel structure, has high feasibility, and provides technical support for the damage tolerance research and crack propagation test of the aircraft engine wheel.

[0044] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. An initial crack presetting method for aircraft engine disk life assessment, characterized in that: The initial crack presetting method comprises: Determine the process parameters preset for the initial crack, wherein the process parameters include electrode material, size and working current, the electrode is a graphite electrode, the radius size of the graphite electrode is consistent with the preset initial crack depth, the shape of the graphite electrode is the same as or similar to the initial crack and the initial thickness of the graphite electrode is greater than the preset initial crack width, and the electrode thickness is reduced by reverse electrode connection so that the final thickness of the electrode is consistent with the preset initial crack width; the working current includes high voltage current and low voltage current, and a current parameter combination consistent with the preset initial crack depth is obtained by performing a combination test of different high voltage currents and low voltage currents on the electrode material, and the current parameter combination is determined as follows: Where: I l and I h They represent low voltage current and high voltage current respectively, ρ represents the material parameter of the pre-cracked wheel, and a, b, c, d represent the current parameter selection range; Determine the position and direction of the preset initial crack, wherein the preset initial crack position is determined according to the type of aircraft engine wheel and the stress magnitude, the initial crack position is in the stress concentration area, and the direction of the initial crack is perpendicular to the stress direction, wherein the aircraft engine wheel types include fan and compressor wheels and turbine wheels, the stress concentration areas of the fan and compressor wheels are the wheel groove bottom and the wheel center, the stress concentration areas of the turbine disk are the wheel groove bottom, the wheel center and the wheel spoke plate, the preset initial crack directions of the wheel groove bottom and the wheel center are along the wheel meridian plane, and a number of initial cracks are preset at symmetrical positions along the circumference of the wheel, the preset initial crack directions of the wheel spoke plate are along the wheel meridian plane and perpendicular to the wheel meridian plane, and a number of initial cracks are preset at symmetrical positions along the circumference of the wheel.

2. The initial crack presetting method for aircraft engine disk life assessment according to claim 1, characterized in that: The difference between the initial crack depth preset by combining the low voltage current and the high voltage current and the target initial crack depth does not exceed 5%.

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