A method for evaluating the working characteristics of a bellows for a high-pressure swing device

Abstract

The application discloses a bellows working characteristic evaluation method for a high-pressure swing device, which is based on a multi-layer bellows two-dimensional finite element model and a multi-layer bellows three-dimensional finite element model to respectively perform axial stiffness simulation and bending stiffness simulation, and to perform fatigue test to obtain bellows life; the multi-layer bellows is respectively subjected to axial stiffness test and bending stiffness test; the multi-layer bellows is subjected to swing examination based on the bellows life value, if the swing examination is qualified, the results of the axial stiffness simulation and the axial stiffness test and the results of the bending stiffness simulation and the bending stiffness test are respectively compared and analyzed, if the multi-layer bellows two-dimensional finite element model and the multi-layer bellows three-dimensional finite element model meet the design requirements, the designed multi-layer bellows is put into use. The application can simulate the high-pressure bellows load working condition, and effectively improves the reliability and accuracy of the high-pressure bellows working characteristic evaluation.

Description

Technical Field

[0001] This invention relates to a method for evaluating the working characteristics of bellows in a high-pressure swing device, belonging to the field of spacecraft engine pump rear swing technology. Background Technology

[0002] Post-pump swing technology is one of the key technologies in the development of liquid rocket engines. This technology can effectively reduce the engine's swing mass, lower the swing torque, and significantly improve the swing characteristics of the engine system. The key component of the swing mechanism is the high-pressure swing device, whose core technology lies in the design and experimental verification of the high-pressure bellows. The high-pressure bellows includes a tube blank, an armor ring, and an interface ring. Currently, the method of verifying the effectiveness and accuracy of the finite element model involves finite element modeling and remanufacturing of the high-pressure bellows, followed by pressure and swing tests on the manufactured high-pressure bellows workpiece. However, this method lacks a method for evaluation from the source, resulting in complex verification, long cycles, and low reliability. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a method for evaluating the working characteristics of bellows in high-pressure swing devices. This method simulates the working conditions of high-pressure bellows under load, effectively improving the reliability and accuracy of the evaluation of the working characteristics of high-pressure bellows. The method includes simulation methods for bellows tension and compression stiffness, bending stiffness, fatigue life, tension and compression stiffness testing, bending stiffness testing, fatigue testing simulation, and finally, evaluation and judgment.

[0004] The technical solution of this invention is:

[0005] A method for evaluating the operating characteristics of bellows in a high-voltage swing device includes:

[0006] Axial stiffness simulation was performed based on a two-dimensional finite element model of a multi-layer bellows with armored rings. A preset pressure load was applied inside the bellows, a fixed support boundary was set at one end, and a concentrated load that gradually increased according to the preset load step was applied to the other end to compress the bellows. The axial displacement of the bellows and the strain of the bellows peaks and valleys under different concentrated loads were extracted.

[0007] Bending stiffness simulation was performed based on a three-dimensional finite element model of a multi-layered bellows with armored rings. A preset pressure load was applied inside the bellows, a fixed boundary was set at one end, and a forced displacement and a deflection angle that increased by a preset step value were applied to the other end. The reaction force and reaction moment at the center point of the interface ring and the strain at the peak and trough of the bellows were extracted under different deflection angles to obtain the bending moment of the bellows under different deflection angles. Fatigue tests were then conducted to obtain the life of the bellows.

[0008] An axial stiffness test was conducted on a multi-layered bellows. Pressure was applied to the bellows to make its axial direction reach several set displacements. The strain of the bellows at the peaks and troughs during the compression process was obtained from the measuring points based on the pre-pressure.

[0009] A bending stiffness test was conducted on a multi-layer corrugated pipe. A servo mechanism was used to apply a transverse load to the corrugated pipe, causing it to generate several predetermined offset angles under the transverse load. The bending moment, deflection angle, and strain of the corrugated pipe at the crest and trough were recorded during the loading process.

[0010] Based on the obtained bellows life value, several bending stiffness tests were conducted on the multi-layer bellows to perform a sway test. If the sway test is qualified, the results of axial stiffness simulation and axial stiffness test, and the results of bending stiffness simulation and bending stiffness test are compared and analyzed to evaluate whether the two-dimensional finite element model and the three-dimensional finite element model of the multi-layer bellows meet the design requirements.

[0011] If the two-dimensional finite element model and the three-dimensional finite element model of the multi-layer corrugated pipe meet the design requirements, the designed multi-layer corrugated pipe will be delivered for use.

[0012] Preferably, an axial stiffness test is performed on the multi-layer corrugated pipe. Pressure is applied to the corrugated pipe to achieve a certain set axial displacement. The pre-pressure is obtained based on the measuring points. Specifically, this includes:

[0013] Place the multi-layer corrugated pipe on the measuring platform of the testing instrument, place the pressure plate on the top, apply pre-pressure to the corrugated pipe to make the corrugated pipe produce the set nominal displacement; record the pre-pressure value under different nominal displacements, and the nominal displacement test points shall not be less than 10.

[0014] For each nominal displacement, the multi-layer corrugated pipe is measured 3 to 5 times, and the pre-pressure under the nominal displacement is obtained by averaging the values.

[0015] Preferably, the indicating accuracy of the prestress measuring device is less than 1 / 10 of the allowable deviation of the corrugation stiffness, and the graduation value of the displacement measuring device is not less than 0.01 mm.

[0016] Preferably, a bending stiffness test is performed on the multi-layer corrugated pipe. A servo mechanism applies a lateral load to the corrugated pipe, and the bending moment and deflection angle are recorded during the loading process, including:

[0017] Seal both ends of the bellows and fill it with water and pressurize it to the set pressure. Place the bellows on the fatigue testing machine, fix one end of the bellows, and apply a transverse load to the other end through a servo mechanism so that the bellows produces a predetermined offset angle under the action of the transverse load. Record the concentrated force of the angular displacement at different predetermined offset angles. There are no less than 10 predetermined offset angles.

[0018] For each offset angle, the multi-layer corrugated pipe is measured 3 to 5 times, and the concentrated force of the angular displacement is obtained by averaging the values. According to the bending moment M = FL, the correspondence between the bending moment and the offset angle is obtained; F is the concentrated force that causes the corrugated pipe to produce angular displacement; L is the lever arm from the servo mechanism to the center of the corrugated pipe.

[0019] Preferably, the bending test is performed on the test fixture, the angle measurement scale is not less than 0.01 mm, and the measurement accuracy is not less than ±1% of the indicated value.

[0020] Preferably, after the sway test is passed, the results of axial stiffness simulation and axial stiffness test are compared and analyzed to evaluate whether the two-dimensional finite element model of the multi-layer bellows meets the design requirements, including:

[0021] Based on several preload values ​​obtained from axial stiffness tests and the corresponding displacements under preload, a linear relationship between preload and displacement is established by fitting, and the slope and intercept of the test line are obtained.

[0022] Based on several load values ​​and corresponding displacements obtained from axial stiffness simulation experiments, a linear relationship between load and displacement is established by fitting, and the slope and intercept of the simulated straight line are obtained.

[0023] Using the slope and intercept of the experimental line as the true value, if the error of the simulated slope and intercept relative to the experimental slope and intercept is not greater than 10%, then the simulated slope and intercept are deemed to meet the requirements. Then, using the strain value obtained from the experiment as the true value, if the error of the simulated strain value relative to the true value is not greater than 20%, then the two-dimensional finite element model of the multilayer corrugated pipe is determined to meet the design requirements.

[0024] Preferably, after the sway test is passed, the results of the bending stiffness simulation and the bending stiffness test are compared and analyzed to evaluate whether the three-dimensional finite element model of the multi-layer corrugated pipe meets the design requirements, including:

[0025] Based on several bending moments and corresponding offset angles obtained from bending stiffness tests, a linear relationship between bending moment and offset angle is established by fitting, and the slope and intercept of the test line are obtained.

[0026] Based on several bending moments and corresponding deflection angles obtained from bending stiffness simulation experiments, a linear relationship between bending moment and deflection angle is established by fitting, and the slope and intercept of the simulated straight line are obtained.

[0027] Using the slope and intercept of the experimental line as true values, if the error of the simulated slope and intercept relative to the experimental slope and intercept is no greater than 10%, then the simulated slope and intercept are deemed to meet the requirements. Then, using the strain value obtained from the experiment as the true value, if the error of the simulated strain value relative to the true value is no greater than 20%, then the three-dimensional finite element model of the multilayer corrugated pipe is determined to meet the design requirements.

[0028] Preferably, the method for calculating the life of the bellows is as follows:

[0029] The lifespan of the bellows is calculated based on the maximum and average strain values ​​recorded in the bending stiffness simulation strain cloud map.

[0030] Preferably, based on the obtained bellows life value, a number of bending stiffness tests are conducted on the multi-layer bellows to perform a sway test, including:

[0031] A servo mechanism is used to apply a lateral load to the bellows to conduct a bending stiffness test. The number of tests is 1.5 to 2 times the life value of the bellows, and the deflection angle range is ±4°. After the test, the bellows is inspected to see if it is intact. If it is intact, the swing test is qualified.

[0032] Preferably, in the two-dimensional finite element model and the three-dimensional finite element model of the multi-layer corrugated pipe, contacts are set between the pipe blanks, between the pipe blank and the armor ring, and between the pipe blank and the interface ring, and the contact type is surface-to-surface contact.

[0033] The advantages of this invention compared to the prior art are:

[0034] This invention provides a complete solution from the simulation methods of bellows tension and compression stiffness, bending stiffness, fatigue life, tension and compression stiffness test methods, bending stiffness test methods, fatigue test simulation methods to the final evaluation and judgment method. It can simulate the working conditions of high-pressure bellows under load and plays an important role in the development of pump-driven liquid rocket engines. Attached Figure Description

[0035] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0036] Figure 1 This is a flowchart of the bellows working characteristic evaluation method according to an embodiment of the present invention;

[0037] Figure 2 This is a simulation diagram of the bending stiffness of the bellows in an embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of load decomposition during the bending process of a bellows according to an embodiment of the present invention. Detailed Implementation

[0039] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0040] This invention proposes a method for evaluating the working characteristics of bellows in a high-voltage swing device, such as... Figure 1 As shown, it includes:

[0041] Step S1: In the simulation software, based on the actual mechanism, establish two-dimensional and three-dimensional finite element models of the multi-layer bellows blank, armor ring, and interface ring. Set the material of each part to stainless steel. The two-dimensional finite element model is an axisymmetric model, and the multi-layer bellows needs to be modeled independently. The three-dimensional finite element model is an axisymmetric model, the multi-layer bellows is modeled independently and is a shell element, and the interface ring and armor ring are solid elements.

[0042] Step S2: Simulate the axial stiffness of the bellows under internal pressure load.

[0043] In the two-dimensional finite element model, contact friction pairs are set between tube blanks, between tube blanks and armor rings, and between tube blanks and interface rings. The contact type is surface-to-surface contact, and the friction coefficient is set to 0.15. A fixed boundary is set at one end of the bellows. A pressure load of 10 MPa is applied inside the inner bellows. The end face of the bottom interface ring is fixed, and a concentrated load is applied to the top interface ring to compress the bellows. The concentrated load ranges from 500 to 20000 N, with a load step set every 1000 N. The axial compression of the bellows and the strain at the peaks and troughs of the bellows are calculated and extracted.

[0044] Step S3: Simulate the bending stiffness of the bellows under internal pressure load.

[0045] In the 3D simulation model, contact friction pairs are set between tube blanks, between tube blanks and armor rings, and between tube blanks and interface rings. The contact type is surface-to-surface contact, and the friction coefficient is set to 0.15. A fixed boundary is set at one end of the bellows, and a pressure load of 10 MPa is applied inside the bellows. Forced displacement and deflection angle are applied to the other end, ranging from 0° to 4°, with a load step set every 0.5°. The reaction force RF at the loading point is extracted. x RF y and reaction torque RM z Obtain the strain at the peaks and troughs of the bellows and the maximum plastic strain Δε from the strain contour plot. p and mean strain ε m ,based on Figure 3 The force composition rule shown is used to combine forces and moments to obtain force F. v Composite bellows bending moment.

[0046] In step S4: Calculate the bellows life.

[0047] The maximum plastic strain Δε is calculated using step S3. p and mean strain ε m Calculate the bellows life N using the formula below. f :

[0048]

[0049] Among them, the fatigue elongation index c takes a value of -0.26, and the fatigue elongation coefficient ε' f The value is 0.45, ε b The value is 0.45, which corresponds to the strain when the local stress of the structure reaches the strength limit.

[0050] Step S5: Conduct axial stiffness test on the bellows product.

[0051] The bellows must be sealed at both ends during testing, and the interior must be filled with water and pressurized to 10 MPa. A dedicated stiffness tester or a combined stiffness tester should be used to check the axial stiffness of the bellows. The force testing instrument's indication accuracy should be less than 1 / 10 of the allowable deviation, and the displacement measurement graduation value should be no less than 0.01 mm. During measurement, the bellows is placed on the measuring platform of the testing instrument, with a pressure plate placed on top. A preload is applied to the bellows to induce the specified nominal displacement. The measurement accuracy should be no less than ±10% of the indicated value. A preload test should be performed first, followed by the formal test. The preload values ​​at different nominal displacements should be recorded, with no fewer than 10 nominal displacement test points.

[0052] Based on each nominal displacement, the multi-layer corrugated pipe is measured three times, and the preload under the nominal displacement is obtained by averaging the values.

[0053] Step S6: Conduct a bellows bending stiffness test

[0054] Under the constraint of no axial elongation of the bellows, ensure that the bellows can deform normally in the angular direction. Both ends of the bellows are sealed, and the inside is filled with water and pressurized to 10 MPa. One end is fixed, and a lateral load is applied to the other end using a servo mechanism. The displacement and force of the servo mechanism during the loading process are recorded. Bending tests are performed on a fatigue testing machine and special tooling, see [link to documentation]. Figure 2 As shown. The displacement measurement scale division is not less than 0.01 mm, and the measurement accuracy is not less than ±1% of the indicated value. The bellows is subjected to a predetermined offset angle under lateral load, and the concentrated force of the angular displacement is recorded at different predetermined offset angles, with no fewer than 10 predetermined offset angles.

[0055] For each offset angle, the multi-layer bellows is measured three times, and the concentrated force of the angular displacement is obtained by averaging the values. Based on the bending moment M = FL, the relationship between the bending moment and the offset angle is derived; F is the concentrated force that causes the bellows to produce angular displacement; L is the lever arm from the servo mechanism to the center of the bellows. The strain at the crests and troughs of the bellows during compression is recorded.

[0056] Step S7: Conduct a bellows life test

[0057] The loading method is the same as in S6. Based on the lifespan calculated in step S4, perform a swing test with 2 times the number of cycles ±4°. The bellows should not be damaged after the test.

[0058] Step S8: Analyze and evaluate the test results to confirm the design status of the high-pressure bellows.

[0059] Linear fitting is performed on the simulation and experimental results of axial tensile and compressive stiffness obtained in steps S2 and S5. The axial load F and displacement x should satisfy F = kx + c, and the errors of k and c obtained from simulation and experiment should not exceed 10%. The errors of strain values ​​obtained from simulation and experiment should not exceed 20%.

[0060] Linear fitting is performed on the bending stiffness simulation and experimental results obtained in steps S3 and S6. The bending moment M and the deflection angle θ should satisfy M = a + bθ, and the errors of a and b obtained from simulation and experiment should not exceed 10%. The errors of strain values ​​obtained from simulation and experiment should not exceed 20%.

[0061] If the errors of both meet the requirements, it indicates that the high-pressure bellows design has been closed-loop and can be put into use; if one does not meet the requirements, the finite element model needs to be corrected.

[0062] The embodiments described above are merely preferred embodiments of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for evaluating the working characteristics of a bellows used in a high-pressure swing device, characterized in that, include: Axial stiffness simulation was performed based on a two-dimensional finite element model of a multi-layer bellows with armored rings. A preset pressure load was applied inside the bellows, a fixed support boundary was set at one end, and a concentrated load that gradually increased according to the preset load step was applied to the other end to compress the bellows. The axial displacement of the bellows and the strain of the bellows peaks and valleys under different concentrated loads were extracted. Bending stiffness simulation was performed based on a three-dimensional finite element model of a multi-layered bellows with armored rings. A preset pressure load was applied inside the bellows, a fixed boundary was set at one end, and a forced displacement and a deflection angle that increased by a preset step value were applied to the other end. The reaction force and reaction moment at the center point of the interface ring and the strain at the peak and trough of the bellows were extracted under different deflection angles to obtain the bending moment of the bellows under different deflection angles. Fatigue tests were then conducted to obtain the life of the bellows. An axial stiffness test was conducted on a multi-layered bellows. Pressure was applied to the bellows to make its axial direction reach several set displacements. The strain of the bellows at the peaks and troughs during the compression process was obtained from the measuring points based on the pre-pressure. A bending stiffness test was conducted on a multi-layer corrugated pipe. A servo mechanism was used to apply a transverse load to the corrugated pipe, causing it to generate several predetermined offset angles under the transverse load. The bending moment, deflection angle, and strain of the corrugated pipe at the crest and trough were recorded during the loading process. Based on the obtained bellows life value, several bending stiffness tests were conducted on the multi-layer bellows to perform a sway test. If the sway test is qualified, the results of axial stiffness simulation and axial stiffness test, and the results of bending stiffness simulation and bending stiffness test are compared and analyzed to evaluate whether the two-dimensional finite element model and the three-dimensional finite element model of the multi-layer bellows meet the design requirements. If the two-dimensional finite element model and the three-dimensional finite element model of the multi-layer corrugated pipe meet the design requirements, the designed multi-layer corrugated pipe will be delivered for use.

2. The method for evaluating the working characteristics of a bellows used in a high-pressure swing device according to claim 1, characterized in that, An axial stiffness test was conducted on a multi-layered bellows. Pressure was applied to the bellows to induce several predetermined axial displacements. The preload was obtained from measuring points, specifically including: Place the multi-layer corrugated pipe on the measuring platform of the testing instrument, place the pressure plate on the top, apply pre-pressure to the corrugated pipe to make the corrugated pipe produce the set nominal displacement; record the pre-pressure value under different nominal displacements, and the nominal displacement test points shall not be less than 10. For each nominal displacement, the multi-layer corrugated pipe is measured 3 to 5 times, and the pre-pressure under the nominal displacement is obtained by averaging the values.

3. The method for evaluating the working characteristics of a bellows used in a high-pressure swing device according to claim 2, characterized in that, The indicating accuracy of the prestress measuring device is less than 1 / 10 of the allowable deviation of the corrugated stiffness, and the graduation value of the displacement measuring device is not less than 0.01 mm.

4. The method for evaluating the working characteristics of a bellows used in a high-pressure swing device according to claim 1, characterized in that, A bending stiffness test was conducted on a multi-layered corrugated pipe. A servo mechanism was used to apply a lateral load to the corrugated pipe, and the bending moment and deflection angle were recorded during the loading process, including: Seal both ends of the bellows and fill it with water and pressurize it to the set pressure. Place the bellows on the fatigue testing machine, fix one end of the bellows, and apply a transverse load to the other end through a servo mechanism so that the bellows produces a predetermined offset angle under the action of the transverse load. Record the concentrated force of the angular displacement at different predetermined offset angles. There are no less than 10 predetermined offset angles. For each offset angle, the multi-layer corrugated pipe is measured 3 to 5 times, and the concentrated force of the angular displacement is obtained by averaging the values. According to the bending moment M = FL, the correspondence between the bending moment and the offset angle is obtained; F is the concentrated force that causes the corrugated pipe to produce angular displacement; L is the lever arm from the servo mechanism to the center of the corrugated pipe.

5. The method for evaluating the working characteristics of a bellows used in a high-pressure swing device according to claim 4, characterized in that, The bending test was carried out on the test fixture, with the angle measurement scale division value not less than 0.01 mm and the measurement accuracy not less than ±1% of the indicated value.

6. The method for evaluating the working characteristics of a bellows used in a high-voltage swing device according to claim 1, characterized in that, After the sway test is passed, the results of axial stiffness simulation and axial stiffness test are compared and analyzed to evaluate whether the two-dimensional finite element model of the multi-layer bellows meets the design requirements, including: Based on several preload values ​​obtained from axial stiffness tests and the corresponding displacements under preload, a linear relationship between preload and displacement is established by fitting, and the slope and intercept of the test line are obtained. Based on several load values ​​and corresponding displacements obtained from axial stiffness simulation experiments, a linear relationship between load and displacement is established by fitting, and the slope and intercept of the simulated straight line are obtained. Using the slope and intercept of the experimental line as the true value, if the error of the simulated slope and intercept relative to the experimental slope and intercept is not greater than 10%, then the simulated slope and intercept are deemed to meet the requirements. Then, using the strain value obtained from the experiment as the true value, if the error of the simulated strain value relative to the true value is not greater than 20%, then the two-dimensional finite element model of the multilayer corrugated pipe is determined to meet the design requirements.

7. The method for evaluating the working characteristics of a bellows used in a high-voltage swing device according to claim 1, characterized in that, After passing the sway test, the results of bending stiffness simulation and bending stiffness test are compared and analyzed to evaluate whether the three-dimensional finite element model of the multi-layer bellows meets the design requirements, including: Based on several bending moments and corresponding offset angles obtained from bending stiffness tests, a linear relationship between bending moment and offset angle is established by fitting, and the slope and intercept of the test line are obtained. Based on several bending moments and corresponding deflection angles obtained from bending stiffness simulation experiments, a linear relationship between bending moment and deflection angle is established by fitting, and the slope and intercept of the simulated straight line are obtained. Using the slope and intercept of the experimental line as true values, if the error of the simulated slope and intercept relative to the experimental slope and intercept is no greater than 10%, then the simulated slope and intercept are deemed to meet the requirements. Then, using the strain value obtained from the experiment as the true value, if the error of the simulated strain value relative to the true value is no greater than 20%, then the three-dimensional finite element model of the multilayer corrugated pipe is determined to meet the design requirements.

8. The method for evaluating the working characteristics of a bellows used in a high-voltage swing device according to claim 1, characterized in that, The method for calculating the life of a bellows is as follows: The maximum strain value Δε is recorded from the strain contour plot of the bending stiffness simulation. p and the average strain value ε m Calculate the lifespan N of the bellows. f : In the formula, c is the fatigue elongation index, and ε' f ε is the fatigue elongation coefficient. b This represents the strain corresponding to the local stress of the structure reaching its strength limit.

9. A method for evaluating the working characteristics of a bellows used in a high-voltage swing device according to claim 1 or 8, characterized in that, Based on the obtained bellows life value, several bending stiffness tests were conducted on the multi-layer bellows to perform sway assessment, including: A servo mechanism is used to apply a lateral load to the bellows to conduct a bending stiffness test. The number of tests is 1.5 to 2 times the life value of the bellows, and the deflection angle range is ±4°. After the test, the bellows is inspected to see if it is intact. If it is intact, the swing test is qualified.

10. The method for evaluating the working characteristics of a bellows used in a high-voltage swing device according to claim 1, characterized in that, In both the two-dimensional and three-dimensional finite element models of the multi-layer corrugated pipe, contacts are set between the pipe blanks, between the pipe blank and the armor ring, and between the pipe blank and the interface ring. The contact type is surface-to-surface contact.

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