A method for wide frequency vibration stress relief of a gearbox

Abstract

The application discloses a kind of machine case modal broadband vibration stress relief method, machine case is fixed on vibration table, and the vibration frequency scanning is carried out to machine case, determine several first exciting frequencies;First exciting frequency is screened based on ABAQUS software, obtain several second exciting frequencies;Different acceleration is applied to machine case based on second exciting frequency, and the strain of weld area on machine case is measured;When the strain is less than or equal to strain threshold value, the corresponding acceleration is selected, and the selected acceleration and corresponding second exciting frequency are combined as vibration aging treatment parameters;Vibration aging treatment is carried out to machine case based on vibration aging treatment parameters;The application can reduce and homogenize the residual stress of machine case welding position by screening exciting frequency and acceleration in vibration aging treatment respectively, and the service life and reliability of machine case are improved.

Description

Technical Field

[0001] This invention belongs to the field of casing stress relief technology, and particularly relates to a method for stress relief of casing modal broadband vibration. Background Technology

[0002] During the manufacturing process of an aero-engine casing, blades need to be connected to the inner and outer housings. Current technology involves assembling one end of the blade to the inner housing and then gluing it together. The other end of the blade is then passed through the outer housing and welded to the outer circumference of the outer housing. However, after the weld cools, a weld seam of a certain width and depth will be generated around each blade on the outer circumference of the casing housing, leaving a certain amount of residual tensile stress.

[0003] Therefore, after the casing has been in operation for a period of time, the residual tensile stress at the weld will accelerate the initiation and propagation of cracks, eventually leading to cracking around the blades, which will seriously affect the service life of the casing. Summary of the Invention

[0004] The purpose of this invention is to provide a method for stress relief by modal broadband vibration of a casing, so as to reduce and homogenize the residual stress at the welded parts of the casing and improve the service life and reliability of the casing.

[0005] This invention adopts the following technical solution: a method for stress relief of chassis modal broadband vibration, comprising the following steps:

[0006] The casing is fixed on the vibration table, and the vibration frequency of the casing is scanned to determine several first excitation frequencies.

[0007] Based on the ABAQUS software, several second excitation frequencies are obtained by filtering the first excitation frequency.

[0008] Different accelerations were applied to the casing based on the second excitation frequency, and the strain in the weld area on the casing was measured.

[0009] Select the acceleration corresponding to the strain value being less than or equal to the strain threshold, and combine the selected acceleration and the corresponding second excitation frequency as vibration aging treatment parameters;

[0010] The casing is subjected to vibration aging treatment based on vibration aging treatment parameters.

[0011] Furthermore, the selection of the first excitation frequency based on ABAQUS software includes:

[0012] Input the first excitation frequency and the property parameters of the casing into the ABAQUS software to generate stress cloud diagrams corresponding to different first excitation frequencies.

[0013] When the proportion of the dynamic stress coverage area in the stress cloud diagram is greater than or equal to the proportion threshold, the first excitation frequency is used as the second excitation frequency.

[0014] Furthermore, the strain in the weld area of ​​the casing is measured, including:

[0015] The strain in the weld area is measured in different strain directions; where the strain direction includes the direction of the casing cross section, the direction of the casing axis, and the intermediate direction between the direction of the casing cross section and the direction of the casing axis.

[0016] Furthermore, the accelerations corresponding to strain values ​​less than or equal to the strain threshold include:

[0017] Calculate the principal strain of the weld region based on the strain in different strain directions;

[0018] Select the acceleration corresponding to when the main strain is less than or equal to the strain threshold.

[0019] Furthermore, the calculation of the principal strain variables in the weld region based on strain variables in different strain directions includes:

[0020]

[0021] Where ε1 represents the principal dependent variable, ε x ε represents the strain in the cross-sectional direction of the casing. y ε represents the strain along the axis of the casing. 45° This indicates the dependent variable in the middle direction.

[0022] Furthermore, the vibration aging treatment of the casing based on vibration aging treatment parameters includes:

[0023] For each set of vibration aging treatment parameters, a corresponding vibration aging treatment time is matched to perform vibration aging treatment on the casing.

[0024] Furthermore, vibration aging treatment of the casing based on vibration aging treatment parameters also includes:

[0025] Different casing angles were matched for each set of vibration aging treatment parameters to perform vibration aging treatment.

[0026] The beneficial effects of this invention are: by screening the excitation frequency and acceleration in the vibration aging treatment, and finally combining them to form treatment parameters, and performing vibration aging treatment for different treatment parameters for different times, a combined vibration aging treatment method is formed, which can reduce and homogenize the residual stress in the welded parts of the casing, and improve the service life and reliability of the casing. Attached Figure Description

[0027] Figure 1This is a flowchart of a method for stress relief of a casing modal broadband vibration according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the blade numbering in an embodiment of the present invention;

[0029] Figure 3 This is a top view of the casing placed on the vibration table in an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of the residual stress test location in an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of the casing clamping method in an embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram of the casing fixing method in an embodiment of the present invention;

[0033] Figure 7 This is a flowchart illustrating the simulation process executed by the CAE simulation software in an embodiment of the present invention.

[0034] Figure 8 These are stress cloud diagrams corresponding to different first excitation frequencies in embodiments of the present invention;

[0035] Figure 9 This is a schematic diagram showing the bonding position of the strain gauge in an embodiment of the present invention;

[0036] Figure 10 This is a schematic diagram of different clamping positions when measuring dynamic strain of the casing in an embodiment of the present invention;

[0037] Figure 11 This is a diagram showing the state of the housing at different circumferential angles during vibration aging treatment in an embodiment of the present invention.

[0038] 10. Borehole probe base; 20. Casing; 30. Vibration table; 40. Pressure block; 50. Pad block. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0040] This invention discloses a method for stress relief of the modal broadband vibration of a casing, such as... Figure 1As shown, the process includes the following steps: fixing the casing on a vibration table and scanning the casing for vibration frequencies to determine several first excitation frequencies; filtering the first excitation frequencies using ABAQUS software to obtain several second excitation frequencies; applying different accelerations to the casing based on the second excitation frequencies and measuring the strain in the weld area of ​​the casing; selecting the acceleration corresponding to a strain threshold, and combining the selected acceleration and the corresponding second excitation frequency as vibration aging treatment parameters; and performing vibration aging treatment on the casing based on the vibration aging treatment parameters.

[0041] This invention selects the excitation frequency and acceleration in the vibration aging treatment separately, and finally combines them to form the treatment parameters. By performing vibration aging treatment for different parameters for different times, a combined vibration aging treatment method is formed, which can reduce and homogenize the residual stress in the welded parts of the casing, and improve the service life and reliability of the casing.

[0042] To verify the effectiveness of the method of the present invention, the residual stress in the welding area of ​​the casing to be treated should first be detected. Specifically, a blade numbering rule for the casing is first established, and the blades are numbered. Then, the measurement point location, test direction, and test angle for residual stress are specified. Finally, the corresponding welding area is selected for residual stress testing before vibration. The residual stress is measured using a residual stress meter. Before the test, a stress-free powder block is tested. The same test point is tested at least three times, and the average value is taken as the result.

[0043] More specifically, place the casing horizontally on the vibration table with the larger diameter end facing upwards, such as... Figure 2 As shown, the fifth blade counting clockwise from the borehole probe base 10 is numbered as blade #1, and counting counterclockwise from this blade, the remaining blades are labeled as #2, #3, ... In this embodiment, blades numbered #1 and #30 are used as detection blades. Figure 3 The image shown is a top view of the casing after it has been placed on the vibration table.

[0044] Mark the measuring points on blades #1 and #30, such as Figure 4 As shown in the figure, the black dots with numerical numbers are marked positions, which are the raised areas at the center of the weld. A and B are determined based on the actual situation. In this embodiment of the invention, the direction parallel to the weld (i.e., the direction of the casing cross-section) is defined as the 0° stress direction (x-direction), and the direction perpendicular to the weld (i.e., the direction of the casing axis) is defined as the 90° stress direction (y-direction). The bisector of the angle between the two directions is defined as the 45° stress direction. During testing, the blades are inspected in ascending order of blade number and test angle to complete the residual stress test for two blades. After the test, the equivalent stress is used to evaluate the test results, and the calculation formula is as follows:

[0045] τ xy=σ45°-(σ x +σ y ) / 2,

[0046]

[0047]

[0048]

[0049] Where, τ xy This represents the shear stress in the xoy plane. The equivalent stress is represented by σ1, the maximum principal stress is represented by σ2, and the minimum principal stress is represented by σ. x σ represents the stress value in the direction parallel to the weld. y σ represents the stress value perpendicular to the weld direction. 45° This indicates the stress value in the middle direction.

[0050] The target material used for residual stress testing was a Cu target with a Bragg angle of 142°, a Beta angle of 25°, and nine Beta angles. Before testing, stress-free powder blocks were tested; results within 0±20 MPa indicated accurate instrument testing. To prevent the residual stress tester from touching the casing end face, the large-diameter end of the casing was positioned with its back to the instrument, and the test point of the blade was placed directly below the laser spot. During focusing, the instrument handle needed to be adjusted until the laser displacement sensor displayed 0±0.1; this was to ensure accurate test results. Residual stress testing before vibration began, with three tests performed at the same test point, and the average value taken. The test results for test points 1 and 2 are shown in Table 1.

[0051] Table 1

[0052]

[0053]

[0054] Next, the casing frequency is scanned to determine the excitation frequency. First, the mounting method of the casing on the vibration table is determined, then the casing is frequency scanned. The vibration table is used for frequency scanning, and the same casing is scanned at least three times. When the scan differences are small, the average value is taken as the result. If there are individual values ​​with large differences during the scanning process, such as exceeding 80% of the average, the scan is canceled and repeated.

[0055] More specifically, the casing is placed with the large-diameter end facing upwards, and the excitation method is horizontal radial excitation. Considering the stability of the casing vibration process and the effectiveness of the vibration effect, the fixing points are located at the edge of the small end face, and the angle between each fixing point is 120°, such as... Figure 5 As shown. When fixed, as... Figure 6As shown, the pressure block 40 is placed on the edge of the small end face of the casing 20, and the small end face of the casing 20 is placed on the pad 50 on the vibration table 30. A fixing torque is applied to the fastening bolts using a torque wrench to complete the assembly connection between the casing 20 and the vibration table 30. This invention uses a vibration table to perform frequency scanning on the casing. Since the casing will generate strong vibrations when it reaches resonance, its own acceleration often changes significantly compared to the excitation acceleration. Therefore, the first six frequencies with higher resonance peaks are selected for finite element simulation of the casing. This is because the frequencies corresponding to the first four frequencies are relatively small, resulting in large vibration displacements within the same time period; the latter two frequencies have larger peak values, causing the casing 20 to generate larger accelerations, which has a better effect on reducing and homogenizing stress in the vibration direction, playing a dominant role. To ensure the accuracy of the frequency sweep results, the casing is swept three times, and the average value is taken as the result, as shown in Table 2.

[0056] Table 2

[0057]

[0058]

[0059] In one embodiment, the selection of the first excitation frequency based on ABAQUS software includes: inputting the first excitation frequency and the property parameters of the casing into ABAQUS software to generate stress cloud diagrams corresponding to different first excitation frequencies; when the proportion of the dynamic stress coverage area in the stress cloud diagram is greater than or equal to the proportion threshold, the first excitation frequency is used as the second excitation frequency.

[0060] In other words, the first excitation frequency is input into the ABAQUS software as a known parameter, and then the same values ​​are input for other parameters (such as material properties, fixed point mesh, acceleration magnitude, etc.) for simulation. The second excitation frequency is then selected based on the simulation results.

[0061] CAE simulation process as follows: Figure 7 As shown, stress distribution cloud maps of the casing at different frequencies were obtained. Since different frequencies correspond to different vibration modes, the magnitude of stress generated at different locations in the casing during vibration is also inconsistent. Therefore, a method of superimposing different frequencies was used to vibrate the casing. To achieve better stress relief at the weld area, [further details are needed]. Figure 8 The finite element simulation results shown indicate that five frequencies—120.5Hz, 163.8Hz, 219.7Hz, 382.5Hz, and 414.4Hz—were selected for vibration aging treatment.

[0062] Next, the corresponding excitation acceleration needs to be determined based on the second excitation frequency. Establish rules for strain gauge placement, specify the strain test direction, attach the strain gauges, and use a vibration table to bring the casing to resonance, thus determining the excitation acceleration. To ensure that the dynamic strain at each location meets the requirements during the casing's vibration aging process, dynamic strain tests at different locations need to be performed to understand the distribution of dynamic strain on the circumference.

[0063] To understand the strain condition of the weld area during vibration and determine a reasonable excitation acceleration, strain gauges should be attached near the weld, especially in areas prone to cracking. During testing, if... Figure 9 As shown, dynamic strain needs to be measured in three directions at each measuring point. The direction parallel to the weld (i.e., the direction of the casing cross-section) is the 0° direction, i.e., ε x The direction perpendicular to the weld (i.e., the direction of the casing axis) is 90°, i.e., ε. y The angle bisectors of x and y are in the 45° direction, i.e., ε. 45° direction.

[0064] Specifically, measuring the strain in the weld area of ​​the casing includes measuring the strain in the weld area in different strain directions; wherein the strain direction includes the direction of the casing cross-section, the direction of the casing axis, and the intermediate direction between the direction of the casing cross-section and the direction of the casing axis. Then, the principal strain of the weld area is calculated based on the strain in different strain directions; the acceleration corresponding to the principal strain being less than or equal to the strain threshold is selected.

[0065] More specifically, the calculation of the principal strain variables in the weld region based on strain variables in different strain directions includes:

[0066]

[0067] Where ε1 represents the principal dependent variable, ε x ε represents the strain in the cross-sectional direction of the casing. y ε represents the strain along the axis of the casing. 45° This indicates the dependent variable in the middle direction.

[0068] To ensure that the dynamic strain at all locations during the vibration aging process of the casing meets the requirements, it is necessary to understand the distribution of dynamic strain on the circumference of the casing. Considering the symmetrical clamping of the casing during vibration aging, the bonding position of the strain gauges is not changed during dynamic strain testing. Figure 10 As shown, the casing is rotated by the corresponding angle and then re-clamped to test the dynamic strain in six directions: 0° and 90°, 30° and 120°, and 60° and 150°. A total of three clamping operations are required. After obtaining the dynamic strain values ​​of different acceleration excitations at the selected frequency, the magnitude of the excitation acceleration is determined according to the requirements.

[0069] Once the excitation frequency and acceleration are obtained, they are combined into parameters for vibration aging treatment. A corresponding vibration aging treatment time is matched for each set of parameters to perform vibration aging treatment on the casing. Furthermore, to ensure uniform vibration aging treatment results, different casing angles are matched for each set of parameters, thereby achieving vibration aging treatment across the entire casing angle.

[0070] Specifically, the excitation parameters determined for the casing are shown in Table 3. To ensure the residual stress achieves a homogenization effect, during the modal broadband aging process, based on the actual stress relief effect, after one excitation is completed, the casing is rotated 90° circumferentially for another treatment, as shown below. Figure 11 As shown.

[0071] Table 3

[0072] Excitation frequency / Hz 120.5 163.8 219.7 382.5 414.4 Excitation acceleration / g 1.8 1.4 2.1 1.8 1.6 Excitation time / min 2 2 2 2 2

[0073] Finally, residual stress tests were conducted on the measuring points of the blades. The specific process is as follows: Residual stress tests were performed on the same blades using the method described above, and the test results are shown in Table 4. Compared with the residual stress before vibration, the average equivalent residual stress decreased from 181.87 MPa to 83.19 MPa, and the peak equivalent stress decreased from 308.63 MPa to 103.99 MPa, representing reductions of 54.26% and 66.31% respectively, thus improving the service life and reliability of the casing.

[0074] Table 4

[0075]

[0076] In summary, the method provided by this invention aims to reduce and homogenize the residual stress at the welded parts of the casing. It utilizes a dynamic strain testing system and a residual stress testing instrument to monitor the vibration test process and results. Furthermore, it employs CAE simulation and a vibration test bench to conduct vibration stress relief tests, analyzes the relationship between vibration test parameters and residual stress, and selects appropriate excitation frequency, excitation acceleration, and excitation time to perform vibration aging treatment on the casing. The design and analysis methods of this invention are simple and reliable, and can quickly and conveniently obtain the processing results.

Claims

1. A method for stress relief of a casing modal broadband vibration, characterized in that, Includes the following steps: The casing is fixed on a vibration table, and the casing is scanned for vibration frequency to determine several first excitation frequencies. Based on the ABAQUS software, several second excitation frequencies are obtained by filtering the first excitation frequency. Different accelerations were applied to the casing based on the second excitation frequency, and the strain in the weld area on the casing was measured. Select the acceleration corresponding to the strain variable being less than or equal to the strain threshold, and combine the selected acceleration and the corresponding second excitation frequency as vibration aging treatment parameters; The casing is subjected to vibration aging treatment based on the aforementioned vibration aging treatment parameters; Vibration aging treatment of the casing based on the aforementioned vibration aging treatment parameters includes: The casing is subjected to vibration aging treatment by matching the corresponding vibration aging treatment time to each set of vibration aging treatment parameters. For each set of vibration aging treatment parameters, different casing angles are matched for vibration aging treatment; The selection of the first excitation frequency based on ABAQUS software includes: Input the first excitation frequency and the property parameters of the casing into the ABAQUS software to generate stress cloud diagrams corresponding to different first excitation frequencies. When the proportion of the dynamic stress coverage area in the stress cloud diagram is greater than or equal to the proportion threshold, the first excitation frequency is used as the second excitation frequency.

2. The method for stress relief of a casing modal broadband vibration as described in claim 1, characterized in that, Measuring the strain in the weld area on the casing includes: The strain in the weld area is measured in different strain directions; wherein the strain direction includes the direction of the casing cross section, the direction of the casing axis, and the intermediate direction between the direction of the casing cross section and the direction of the casing axis.

3. A method for stress relief of a casing modal broadband vibration as described in claim 1 or 2, characterized in that, The accelerations corresponding to strain variables less than or equal to the strain threshold include: The principal strain of the weld region is calculated based on the strain in different strain directions; Select the acceleration corresponding to the main strain variable being less than or equal to the strain threshold.

4. The method for stress relief of a casing modal broadband vibration as described in claim 3, characterized in that, The principal strain variables of the weld region calculated based on strain variables in different strain directions include: ， in, Indicates the main dependent variable. This represents the strain in the cross-sectional direction of the casing. The strain represents the strain along the axis of the casing. This indicates the dependent variable in the middle direction.

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