Spline connection structure contact stiffness identification device and identification method

Abstract

The application belongs to the field of aerospace transmission, and proposes a spline connection structure contact stiffness identification device and identification method. The device comprises spaced supports and centering support bearing seats; the inner spline seat is rigidly fixed with the support; the outer spline shaft is fixed at one end of the centering support bearing seat and is a free end at the other end and passes through the inner spline seat, and a counterweight disc is rigidly fixed on the outer spline shaft; the outer spline shaft is locked with the inner spline seat; a torque loading arm is connected to one end of the outer spline shaft; two jacks are respectively located at both ends of the torque loading arm; two pressure sensors and two acceleration sensors are used to measure the torque load and vibration acceleration of the structure. Through the inherent frequency test and the spline connection structure modal simulation data based on the thin layer element, the contact stiffness of the contact surface of the spline connection structure can be accurately identified. The spline connection structure contact stiffness identification device and identification method are ingenious in design, simple in structure, strong in repeatability and high in identification accuracy.

Description

Technical Field

[0001] This invention relates to the field of aerospace transmission, and more particularly to a device and method for identifying the contact stiffness of spline connection structures. Background Technology

[0002] Spline (also known as toothed) connections offer advantages such as large contact area, high load-bearing capacity, good centering and guiding performance, and high reliability. They can also compensate for torque transmission errors and are widely used in shaft connections of high-speed rotating machinery rotor systems, such as aero-engines. Complex power transmission is achieved through the contact of the spline meshing surface, cylindrical positioning surface, and bolt connection surface. Finite element analysis of the coordinated contact of multiple spline teeth requires complex setups and significant computational resources. To achieve accurate and rapid finite element modeling and iterative calculations for splines, it is necessary to identify the contact stiffness of the spline connection structure. Machined surfaces are microscopically rough, and surface contact involves the contact between micro-protrusions; therefore, contact stiffness is related to load parameters and surface processing technology. Direct measurement of the contact stiffness of spline connections introduces significant sensor measurement errors and bolt deformation errors. Generally, contact stiffness is identified indirectly by measuring the natural frequency of the spline connection structure. Summary of the Invention

[0003] This invention addresses the shortcomings of existing experimental devices and methods for measuring the performance of spline connection structures by proposing a device and method for identifying the contact stiffness of spline connection structures.

[0004] The technical solution of the present invention: a spline connection structure contact stiffness identification device, comprising a tightening sleeve 1, a counterweight plate 2, an acceleration sensor 3, an external spline shaft 4, a stop 5, a pressure sensor 6, a torque loading arm 7, a digital display 8, a holding charge amplifier 9, a spline stiffness test bench base 10, a jack 11, a centering support bearing seat 12, a support 13, a main nut 14, an internal spline seat 15, an industrial control computer 16, and a dynamic data acquisition instrument 17;

[0005] Support 13 and centering support bearing seat 12 are fixed at intervals on the base 10 of the spline stiffness test bench; inner spline seat 15 is rigidly fixed to support 13; one end of outer spline shaft 4 is fixed to centering support bearing seat 12, and the other end passes through inner spline seat 15, and the counterweight plate 2 is rigidly fixed on it by expansion sleeve 1; the stop 5 on outer spline shaft 4 cooperates with main nut 14 to lock outer spline shaft 4 and inner spline seat 15; torque loading arm 7 is detachably vertically connected to the fixed end of outer spline shaft 4; two jacks 11 are located at both ends of torque loading arm 7, and are located above one end and below the other end, respectively, and are equidistant from the central axis of outer spline shaft 4;

[0006] Two pressure sensors 6 are located between the jack 11 and the torque loading arm 7 and are connected to the holding charge amplifier 9. The pressure signal is amplified by the holding charge amplifier 9 and displayed in real time on the digital display 8. Two acceleration sensors 3 are located on the surface of the external spline shaft 4 and the surface of the counterweight plate 2, respectively, and are connected to the dynamic data acquisition instrument 17 and the industrial control computer 16 to measure the vibration acceleration of the structure.

[0007] A method for identifying the contact stiffness of a spline connection structure includes the following steps:

[0008] Step 1: Assemble a spline connection structure contact stiffness identification device;

[0009] Step 2: Apply torque load T using jack 11 at torque loading arm 7;

[0010] Step 3: After the torque load T is applied, wait until the entire spline connection structure is stable, and then hammer the other end of the external spline shaft 4 and different positions of the counterweight plate 2.

[0011] Step 4: Obtain the frequency value of the spline connection structure corresponding to the torque T using the accelerometer 3 and the industrial computer 16.

[0012] Step 5: Apply a gradually increasing torque load using the jack 11 at the torque loading arm 7. After reaching the maximum torque Tmax, gradually unload the torque load.

[0013] Step Six: Repeat Step Five above at least four times;

[0014] Step 7: Change the applied torque load and repeat Step 6 until all torque load conditions have been tested.

[0015] Step 8: Using the thin-layer element method, a ring-shaped thin-layer element of a certain thickness is applied to the spline connection structure model. By changing the elastic modulus E of the ring-shaped thin-layer element, finite element modal analysis is performed on the spline connection structure model to obtain the relationship between the elastic modulus E and the natural frequency.

[0016] Step 9: Method for identifying the contact stiffness of spline connection structures:

[0017] S9.1 defines the squared error function for experimental results and simulation model modal results:

[0018]

[0019] in, These represent the first, fourth, and sixth natural frequencies under a specific torque force during the inherent characteristic test of the spline connection structure. η represents the first, fourth, and sixth order frequency fitting functions obtained through simulation calculations using the thin-layer element method. iThe weighting ratio of each natural frequency measured in the experiment represents the sensitivity of each natural frequency to changes in torque, and is defined as follows:

[0020]

[0021] S9.2 The elastic modulus value that minimizes R(N) is obtained using Matlab software, through the formula: h represents the thickness of the thin-layer unit, and the unit contact stiffness value of the spline contact surface corresponding to different torque loads is identified.

[0022] The spline connection structure contact stiffness identification device and method described herein measure the contact stiffness of the spline connection structure as follows: A vertically upward force is applied to the loading arm by jacks 11 located on both sides of the torque loading arm 7, thus applying a torque load T to the spline connection structure. The vibration characteristics of the spline connection structure are measured by various acceleration sensors 3 after the excitation hammer strikes the right end surface of the outer spline shaft 4 and the surface of the counterweight plate 2. The acceleration sensor signals are then processed and analyzed to obtain the variation law of each natural frequency and vibration characteristic of the spline connection structure under different torque loads T. Based on the relationship between the torque load T and the vibration frequency, combined with finite element analysis, the contact stiffness of the spline connection structure is inferred.

[0023] The beneficial effects of this invention are:

[0024] (1) By centering the bearing housing 12, the centering of the spline connection structure is adjusted, avoiding stiffness test errors caused by misalignment.

[0025] (2) The torque loading arm 7 and the jack 11 are used to achieve uniform torque loading and avoid introducing additional lateral force to reduce the contact stiffness recognition accuracy. Attached Figure Description

[0026] Figure 1 This is the main view of the spline connection structure contact stiffness identification device;

[0027] Figure 2 The spline contact stiffness per unit area is shown in the diagrams for different torque loads T.

[0028] In the figure: 1. Expansion sleeve, 2. Counterweight plate, 3. Accelerometer, 4. External spline shaft, 5. Stop, 6. Pressure sensor, 7. Torque loading arm, 8. Digital display, 9. Retaining charge amplifier, 10. Spline stiffness test bench base, 11. Jack, 12. Centering support bearing seat, 13. Support, 14. Main nut, 15. Internal spline seat, 16. Industrial computer, 17. Dynamic data acquisition instrument. Detailed Implementation

[0029] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0030] like Figure 1 As shown, the spline connection structure contact stiffness identification device and identification method of the present invention include a tightening sleeve 1, a counterweight plate 2, an acceleration sensor 3, an external spline shaft 4, a stop 5, a pressure sensor 6, a torque loading arm 7, a digital display 8, a holding charge amplifier 9, a spline stiffness test bench base 10, a jack 11, a centering support bearing seat 12, a support 13, a main nut 14, an internal spline seat 15, an industrial control computer 16, and a dynamic data acquisition instrument 17.

[0031] The specific implementation process is as follows:

[0032] 1) Construct a spline connection structure contact stiffness identification device;

[0033] 2) Apply torque load T using jack 11 at torque loading arm 7;

[0034] 3) After the torque T is applied, wait until the entire spline connection structure is stable, then hammer the other end of the external spline shaft 4 and different positions of the counterweight plate 2.

[0035] 4) Obtain the frequency value of the spline connection structure corresponding to the torque T using the accelerometer 3 and the industrial computer 16;

[0036] 5) Apply a gradually increasing torque load using the jack 11 at the torque loading arm 7. After reaching the maximum torque Tmax, gradually unload the torque load.

[0037] 6) Repeat step 5) above at least 4 times;

[0038] 7) Change the applied torque load T and repeat step 6) until all torque load conditions are tested to obtain the relationship between torque load T and natural frequency.

[0039] 8) Using the thin-layer element method, a certain thickness of annular thin-layer elements are applied to the spline connection structure model. By changing the elastic modulus E of the annular thin-layer elements, finite element modal analysis is performed on the spline connection structure model to obtain the relationship between the elastic modulus E and the natural frequency.

[0040] 9) Method for identifying the contact stiffness of spline connection structures:

[0041] ① Define the squared error function for the experimental results and the modal results of the simulation model:

[0042]

[0043] in, These represent the first, fourth, and sixth natural frequencies under a specific torque force during the inherent characteristic test of the spline connection structure. η represents the first, fourth, and sixth order frequency fitting functions obtained through simulation calculations using the thin-layer element method. i The weighting ratio of each natural frequency measured in the experiment represents the sensitivity of each natural frequency to changes in torque, and is defined as follows:

[0044]

[0045] ② Use Matlab software to find the elastic modulus value that minimizes R(N), using the formula: h represents the thickness of the thin-layer unit, and the unit area contact stiffness value of the spline contact surface corresponding to different torque loads is identified.

[0046] Taking the contact stiffness identification of a spline connection structure as an example, the specific implementation steps of this invention are as follows:

[0047] (1) Test on the inherent characteristics of a certain spline connection structure:

[0048] 1.1 The test bench is installed and debugged to ensure that all test pieces are aligned; the sensitivity of pressure sensor 6 is adjusted to ensure that the displayed value is correct;

[0049] 1.2 According to Figure 1 At the position shown, the external spline shaft 4 is thin at one end and thick at the other end; an acceleration sensor 3 is installed on the thick end of the external spline shaft 4 and the counterweight plate 2, and the sensor is connected to the dynamic data acquisition instrument 17, and the relevant parameter settings are adjusted in the computer software.

[0050] 1.3. Operate both jacks 11 simultaneously, and keep the loading pace consistent according to the reading on the digital display 8;

[0051] 1.4 After the torque load T is applied and the entire structure stabilizes, tap the thick end of the external spline shaft 4 and different positions of the counterweight plate 2, and record the frequency values ​​corresponding to the peak values ​​in the 16FFT image of the industrial control computer. To prevent accidental influences on the experiment, the torque load T is applied sequentially from 15 Nm to 150 Nm and then unloaded at the same intervals. The experiment is repeated four times.

[0052] 1.5. Calculate the average of the first, fourth, and sixth natural frequencies corresponding to four test loadings under the same torque load T, so as to obtain the relationship between the first, fourth, and sixth natural frequencies corresponding to different torques under the test conditions.

[0053] (2) Simulation of the inherent characteristics of a spline connection structure based on the thin-layer element method:

[0054] 2.1 According to Figure 1 Establish a finite element model of the spline connection structure and make reasonable simplifications to some parts of the model;

[0055] 2.2 The key tooth structure that contacts the external spline shaft 4 and the internal spline seat 15 is simplified into an annular thin-layer unit. The thickness of the thin-layer unit is designed to be 0.05 mm, and the density and Poisson's ratio of the thin-layer unit are consistent with those of the external spline shaft 4.

[0056] 2.3. Import the finite element model of the spline connection structure containing thin-layer elements into the simulation software, and set the contact mode and boundary conditions. The boundary conditions should be consistent with the experimental conditions.

[0057] 2.4 Modal analysis was performed on the spline connection structure. By correcting the elastic modulus of the thin-layer element, the simulation results were made to continuously approximate the experimentally measured natural frequencies of the spline connection structure. When the simulation results reached the minimum difference from the experimental results, the correct elastic modulus of the thin-layer element and the corresponding first, fourth, and sixth natural frequencies were obtained, and the relationship between different elastic moduli and natural frequencies was obtained.

[0058] (3) Identification of contact stiffness of a spline connection structure:

[0059] 3.1 For a given torque load T, considering the weighted influence of each natural frequency of the spline connection structure, the squared error function of the experimental results and the modal results based on the thin-layer element simulation model is defined as follows:

[0060]

[0061] in, These represent the first, fourth, and sixth natural frequencies under a specific torque force during the inherent characteristic test of the spline connection structure. η represents the first, fourth, and sixth order frequency fitting functions obtained through simulation calculations using the thin-layer element method. i The weighting ratio of each natural frequency measured in the experiment represents the sensitivity of each natural frequency to changes in torque, and is defined as follows:

[0062]

[0063] 3.2. Use Matlab software to find the elastic modulus value that minimizes R(N), using the formula: h is the thickness of the thin-layer unit. The unit area contact stiffness value of the spline contact surface corresponding to different torque loads T is identified, as shown in Table 1.

[0064] 3.3 Table 1 shows the elastic modulus, error function values, and corresponding contact stiffness per unit area obtained based on the thin-layer element method under some different torque loads T; and plots the contact stiffness per unit area of ​​the splines identified under different torque loads T, as shown below. Figure 2 As shown.

[0065] Table 1. Parameters under different torque loads

[0066]

Claims

1. A spline connection structure contact stiffness identification device characterized by, The spline connection structure contact stiffness identification device comprises an expansion sleeve (1), a counterweight disc (2), an acceleration sensor (3), an outer spline shaft (4), a stop (5), a pressure sensor (6), a torque loading arm (7), a digital display instrument (8), a holding charge amplifier (9), a spline stiffness test bench base (10), a jack (11), a centering support bearing seat (12), a support (13), a main nut (14), an inner spline seat (15), an industrial computer (16) and a dynamic data acquisition instrument (17); The support (13) and the centering support bearing seat (12) are fixed at intervals on the spline stiffness test bench base (10); the inner spline seat (15) is rigidly fixed with the support (13); one end of the outer spline shaft (4) is fixed on the centering support bearing seat (12), and the other end passes through the inner spline seat (15), and the expansion sleeve (1) is rigidly fixed on the outer spline shaft (4) to fix the counterweight disc (2); the stop (5) on the outer spline shaft (4) cooperates with the main nut (14) to lock the outer spline shaft (4) and the inner spline seat (15); the torque loading arm (7) is detachably and vertically connected to the fixed end of the outer spline shaft (4); the two jacks (11) are respectively located above and below the two ends of the torque loading arm (7) and are equidistant from the central axis of the outer spline shaft (4); The two pressure sensors (6) are located between the jacks (11) and the torque loading arm (7) and are connected to the holding charge amplifier (9), and the pressure signal is amplified by the holding charge amplifier (9) and displayed in real time on the digital display instrument (8); the two acceleration sensors (3) are respectively located on the surface of the outer spline shaft (4) and the surface of the counterweight disc (2) and are connected to the dynamic data acquisition instrument (17) and the industrial computer (16) for measuring the vibration acceleration of the structure; The spline connection structure contact stiffness identification method comprises the following steps: Step one, assemble the spline connection structure contact stiffness identification device; Step two, use the jack (11) at the torque loading arm (7) to apply a torque load T; Step three, after the torque T is loaded, wait for the entire spline connection structure to be stable, and hammer different positions of the other end of the outer spline shaft (4) and the counterweight disc (2); Step four, obtain the corresponding frequency value of the spline connection structure under the torque T according to the acceleration sensor (3) and the industrial computer (16); Step five, use the jack (11) at the torque loading arm (7) to apply a gradually increasing torque load, and then gradually unload the torque load after reaching the maximum torque Tmax; Step six, repeat step five no less than 4 times; Step seven, change the applied torque load and repeat step six until all torque load conditions are tested; Step eight, use the thin layer element method to give the spline connection structure model a certain thickness of annular thin layer elements, change the elastic modulus E of the annular thin layer elements, and perform finite element modal analysis on the spline connection structure model to obtain the relationship between the elastic modulus E and the natural frequency; Step nine, the spline connection structure contact stiffness identification method: S9.1 define the square error function of the test results and the modal results of the simulation model: wherein, f1, f4, f6 represent the first, fourth and sixth natural frequencies under the specific torque force in the spline connection structure inherent characteristic test; f1, f4, f6 represent the first, fourth and sixth natural frequencies under the specific torque force in the spline connection structure inherent characteristic test; i f1, f4, f6 represent the first, fourth and sixth natural frequencies under the specific torque force in the spline connection structure inherent characteristic test; S9.2 The elastic modulus value that makes R(N) minimum is obtained by using Matlab software, through the formula: h is the thickness of the thin layer unit, and the unit area contact stiffness value of the spline contact surface corresponding to different torque loads is identified.

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