A design method for mounting a vibration pickup to prevent resonance of a boundary

Abstract

The present application relates to the technical field of vibration test, and discloses a kind of installation boundary uncertain vibration measuring seat anti-resonance design method, comprising: obtaining the measured natural frequency under the actual installation state of vibration measuring seat;Equivalent stiffness model is established, and elastic unit with fixed constraint is established at each mounting hole of vibration measuring seat finite element model, respectively, and the stiffness of each elastic member of elastic unit is adjusted repeatedly and iteratively, when the natural frequency of vibration measuring seat finite element model is consistent with the measured natural frequency, the stiffness determined as equivalent stiffness is simulated;With equivalent stiffness as boundary condition, the structural optimization simulation of vibration measuring seat is carried out.The natural frequency of the present application avoids the basic frequency of rotor, and the accuracy of finite element simulation result can be ensured when the installation boundary is uncertain, and the vibration measuring seat obtained by simulation optimization is not prone to resonance.The method can obtain reliable optimization direction without accurately measuring actual installation stiffness, and significantly improves the anti-resonance design efficiency of vibration measuring seat.

Description

Technical Field

[0001] This invention relates to the field of vibration testing technology, and specifically to a design method for anti-resonance of a vibration measuring base with uncertain installation boundaries. Background Technology

[0002] When rotating machinery such as aircraft engines or gearboxes undergo vibration testing, if the natural frequency of the vibration measuring base falls within the engine's operating speed frequency, it is very easy to cause resonance of the vibration measuring base, affecting the measurement results and even affecting normal testing.

[0003] In related technologies, finite element simulations of vibration measuring seats often rely on empirically defined boundary constraints, typically assuming fixed constraints or simple frictional contact at the mounting holes. However, after actual installation, various factors such as installation location, fastener preload, mating surface roughness, and gasket material can influence the finite element simulation results, leading to deviations. Sometimes, the simulation results avoid the rotor's fundamental frequency and have a large margin, but actual testing may still result in vibration seat resonance, causing vibration response to exceed limits. Therefore, when the installation boundaries are uncertain, finite element simulation results cannot provide reliable guidance for the structural optimization of vibration measuring seats. Summary of the Invention

[0004] In view of this, the present invention provides a design method for anti-resonance of vibration measuring base with uncertain installation boundaries, so as to solve the problem that the finite element simulation results are prone to deviation when the installation boundaries are uncertain.

[0005] In a first aspect, the present invention provides a design method for anti-resonance of a vibration measuring base with uncertain installation boundaries, comprising: Obtain the measured natural frequency of the vibration measuring base under its actual installation condition; Establish an equivalent stiffness model and determine the equivalent stiffness; Using the equivalent stiffness as a boundary condition, structural optimization simulation of the vibration measuring seat is performed. The establishment of the equivalent stiffness model and the determination of the equivalent stiffness include: Three elastic elements with fixed constraints in mutually perpendicular directions are established at each mounting hole of the vibration measuring seat finite element model to simulate the constraint effect of the mounting holes of the vibration measuring seat. The stiffness of each elastic element in the elastic unit is repeatedly adjusted iteratively. When the natural frequency of the finite element model of the vibration measuring base is consistent with the measured natural frequency, the equivalent stiffness is obtained.

[0006] Beneficial Effects: This invention establishes three mutually perpendicular elastic elements with fixed constraints at each mounting hole of the vibration measuring seat finite element model. These elastic elements simulate the constraint effect of the mounting holes. By iteratively adjusting the stiffness of each elastic element, the natural frequency of the vibration measuring seat finite element model is made consistent with the measured natural frequency of the vibration measuring seat under the installed state. The stiffness obtained from the simulation is determined as the equivalent stiffness, which is then used as the constraint boundary condition for structural optimization simulation of the vibration measuring seat. This ensures that the natural frequency of the vibration measuring seat avoids the rotor fundamental frequency of rotating machinery. Even when the installation boundary is uncertain, the accuracy of the finite element simulation results is still guaranteed. The vibration measuring seat optimized by the simulation is less prone to resonance. This method obtains a reliable optimization direction without requiring precise measurement of the actual installation stiffness, significantly improving the efficiency of vibration measuring seat anti-resonance design.

[0007] In one optional embodiment, each elastic unit includes elastic elements arranged along three directions: X, Y, and Z, respectively designated as X-direction elastic elements, Y-direction elastic elements, and Z-direction elastic elements; the first ends of the X-direction elastic elements, the first ends of the Y-direction elastic elements, and the first ends of the Z-direction elastic elements are each fixedly constrained, and the second ends of the X-direction elastic elements, the second ends of the Y-direction elastic elements, and the second ends of the Z-direction elastic elements are connected to the center point of the mounting hole.

[0008] Beneficial effects: By arranging elastic elements in the X, Y, and Z directions at the center points of each mounting hole in the finite element model of the vibration measuring seat, a spatial orthogonal elastic element is constructed. This restores the multi-dimensional force constraint characteristics of the X, Y, and Z directions on the mounting surface of the vibration measuring seat, enabling it to match the multi-directional stiffness deformation characteristics of the vibration measuring seats of aero-engines and gearboxes after assembly with fasteners. Each of the X, Y, and Z elastic elements has a fixed constraint at one end and the other ends converge at the center of the mounting hole. The modeled force transmission path is completely consistent with the tightening force path of the actual fasteners. The equivalent stiffness in the three orthogonal directions can be independently iteratively calibrated, further improving the accuracy of the equivalent stiffness calibration, reducing the error in the simulation calculation of the natural frequency, and further enhancing the reliability of the vibration measuring seat's anti-resonance structure optimization.

[0009] In one optional implementation, modal analysis is performed on the finite element model of the vibration measuring base to calculate the natural frequency. The stiffness of the X-axis elastic element, the Y-axis elastic element, and the Z-axis elastic element are adjusted until the natural frequency is close to the fundamental frequency of the rotor of the rotating machinery mounted on the vibration measuring base. The equivalent stiffness of the X-axis elastic element, the Y-axis elastic element, and the Z-axis elastic element is recorded.

[0010] Beneficial effects: By using finite element modal analysis to solve for the natural frequency, the stiffness of the three elastic components in the X, Y, and Z directions can be adjusted individually. The stiffness parameters can be iteratively adjusted by comparing them with the fundamental frequency of the rotating machinery rotor. In turn, the three-dimensional equivalent stiffness that fits the actual installation conditions can be calculated in reverse. This facilitates the subsequent improvement and optimization of the vibration measuring base structure, making the natural frequency of the vibration measuring base far away from the rotor's operating frequency, effectively avoiding resonance of the vibration measuring base during vibration testing, reducing the amount of debugging work, and improving the overall design efficiency.

[0011] In an optional implementation, when the natural frequency and the rotor fundamental frequency satisfy the relationship... When the natural frequency is close to the rotor's fundamental frequency, it is determined that the natural frequency is close to the rotor's fundamental frequency.

[0012] Beneficial effects: Finite element calculations have calculation errors. If the natural frequency is calculated as equal to the rotor fundamental frequency, it will lead to an increase in the number of iterations and reduce the calculation efficiency. In engineering, a difference of less than 1% is considered to be approximately equal. Therefore, the stiffness of the elastic element when the ratio of the difference between the natural frequency and the rotor fundamental frequency to the rotor fundamental frequency is no greater than 1% can be used as the equivalent stiffness, thereby reducing the number of iterations and improving the calculation efficiency.

[0013] In one optional implementation, the structural optimization simulation of the vibration measuring base includes: Using the equivalent stiffness of the X-axis elastic element, the Y-axis elastic element, and the Z-axis elastic element as boundary constraints, the vibration measuring base is structurally optimized to ensure that the safety margin is equal to or greater than the preset margin.

[0014] Beneficial effects: The equivalent stiffness in the X, Y, and Z axes obtained through reverse engineering is directly used as the simulation boundary constraint for optimizing the vibration measuring base structure, closely reflecting the actual installation stress conditions. By optimizing the vibration measuring base structure, the frequency safety margin of the vibration measuring base is controlled to meet the standards, ensuring a safe distance between the vibration measuring base frequency and the rotor operating frequency. Resonance problems are avoided from the design level, making the optimized vibration measuring base structure results closely match the actual operating conditions. This avoids situations where simulations are successful but actual tests still produce resonance, improving the stability of the vibration measuring base and ensuring smooth testing.

[0015] In one optional implementation, the preset margin value ranges from [15%, 20%].

[0016] Beneficial effects: Limiting the safety margin to the 15%-20% range balances the rationality of the vibration measuring base structure with its anti-resonance safety performance. A lower margin of 15% can meet the vibration damping requirements under normal working conditions, preventing resonance caused by small fluctuations in rotational speed and preload. Generally, a safety margin of more than 15% is required, but due to the uncertainty of the installation boundary, the margin is increased to 20% to further ensure the reliability of the optimized vibration measuring base structure.

[0017] In one optional implementation, the structural optimization of the vibration measuring base includes any or any combination of adding reinforcing ribs, changing the size, and adjusting the local shape.

[0018] Beneficial effects: The vibration measuring seat can be structurally optimized by adding reinforcing ribs, changing dimensions, or optimizing local shape without altering the mounting hole positions and assembly structure, and without changing the original installation compatibility; the natural frequency of the vibration measuring seat can be adjusted as needed at low cost to meet frequency safety margin requirements. The above optimization and modification methods are easy to implement, convenient to process, and easy to improve the design.

[0019] In one optional implementation, the iterative adjustment of the stiffness of each elastic element of the elastic unit includes: The stiffness of the X-axis elastic element, the Y-axis elastic element, and the Z-axis elastic element can be adjusted independently or proportionally.

[0020] Beneficial effects: The stiffness of the elastic components in the X, Y, and Z directions can be adjusted independently or proportionally to adapt to the iterative stiffness requirements of different installation and assembly conditions. The independent adjustment mode allows for individual modification of the stiffness of the elastic components in a single direction, adapting to conditions such as uneven constraints in all directions, asymmetrical fastener preload, and unilateral wear on the mating surfaces, correcting unidirectional stiffness deviations. The proportional adjustment mode simultaneously and proportionally modifies the stiffness of the elastic components in all three directions, adapting to conventional conditions with uniform installation forces and symmetrical assembly, making iterative adjustments simpler.

[0021] In one optional implementation, before iteratively adjusting the stiffness of each elastic element of the elastic unit, the method further includes: pre-assigning an initial value to the model interface stiffness.

[0022] Beneficial effects: Setting initial stiffness values ​​for the model interface in advance is essential for initiating finite element modal calculations, providing a computational foundation for subsequent iterative parameter tuning. Randomly selecting initial stiffness values ​​without any basis significantly lengthens the iterative search interval, generating a large amount of invalid simulation calculations and reducing overall design computational efficiency. Providing reasonable initial stiffness values ​​based on experience in advance narrows the search range for subsequent iterations, reduces the number of iterations, and allows for faster finding of the equivalent stiffness that satisfies the requirement that the ratio of the difference between the natural frequency and the rotor fundamental frequency to the rotor fundamental frequency is no greater than 1%, effectively shortening the calculation cycle and improving overall calibration efficiency.

[0023] In one optional implementation, after completing the structural optimization simulation of the vibration measuring base, the method further includes: The optimized vibration measuring base was subjected to modal testing under actual installation conditions to obtain the natural frequency of the vibration measuring base under actual installation conditions and to verify the simulation calculation results.

[0024] Beneficial effects: After completing the simulation optimization of the vibration measuring base, modal measurements were conducted on the machined vibration measuring base under actual assembly conditions to obtain the natural frequency of the vibration measuring base under actual installation conditions, thereby verifying the calculation results obtained from the simulation optimization. Through physical testing, deviations in the simulation modeling, equivalent stiffness determination, and structural optimization processes can be identified, confirming that the natural frequency of the optimized vibration measuring base meets the preset safety margin with the rotor fundamental frequency, ensuring the reliability of the vibration measuring base's anti-resonance performance, and guaranteeing the stable conduct of subsequent vibration testing. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the specific embodiments or related technologies of the present invention, the drawings used in the description of the specific embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a structural diagram of the vibration measuring base before structural optimization. Figure 2 The diagram shows the structure of the vibration measuring seat after structural optimization using the design method of this invention. Figure 3 The results of finite element analysis are obtained using traditional constraint methods in related technologies; Figure 4 This is a schematic diagram showing the state of the vibration measuring seat mounting holes constrained by elastic elements in the finite element model of the vibration measuring seat of the present invention; Figure 5 The finite element analysis results of the grounding stiffness are set before the optimization of the vibration measuring seat structure; Figure 6 The finite element analysis results of the grounding stiffness were set after the vibration measuring seat structure was optimized; Figure 7 To measure the curve of the natural frequency of the vibration seat as a function of the stiffness of the grounding spring; Figure 8 This is a first flowchart of the design method for anti-resonance of a vibration measuring seat with uncertain installation boundaries according to the present invention. Figure 9 This is a second flowchart of the design method for anti-resonance of vibration measuring base with uncertain installation boundaries according to the present invention.

[0027] Explanation of reference numerals in the attached figures 1. Mounting holes.

[0028] Explanation of symbol meanings f. Natural frequency; f0, rotor fundamental frequency; δ, safety margin. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In the description of the invention, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0032] Aero-engines have complex structures with numerous pipes and accessories. During vibration measurements, the sensor installation is typically affected by factors such as installation location, bolt preload, joint roughness, and the natural frequency of the vibration measuring base. When the natural frequency of the vibration measuring base falls within the engine's operating speed frequency, it can easily cause resonance, affecting measurement results and even disrupting normal testing. In a certain aero-engine test, around 48,000 r / min, the vibration amplitude at a certain vibration measuring point on the casing exceeded the limit. Modal testing of the vibration measuring base revealed its natural frequency to be 795.5 Hz. When the speed reached 48,000 r / min, resonance occurred in the measuring base, causing the vibration amplitude at that point to exceed the limit, and the test was terminated.

[0033] In related technologies, when performing modal analysis on vibration measuring seats using finite element simulation, it is usually assumed that the mounting holes are under fixed constraints or have simple frictional contact. However, after actual installation, the connection is affected by various factors such as bolt preload, surface roughness, and gasket material, making accurate simulation difficult. This leads to significant discrepancies between simulation and actual measurement results. Therefore, when the installation boundaries are uncertain, finite element simulation results cannot provide reliable guidance for the structural optimization of vibration measuring seats.

[0034] Research in related technologies has shown that the rotor's operating frequency can be avoided by changing the sensor's mass. However, vibration sensors are precision measuring instruments, and their mass, stiffness, etc., cannot be adjusted after purchase, thus limiting their widespread application. Therefore, this invention is proposed.

[0035] It should be noted that the installation boundary of the vibration measuring seat referred to in this invention is uncertain. This can be understood as the installation connection stiffness of the vibration measuring seat being uncertain due to the influence of uncertain factors such as the installation position, the pre-tightening force of the fasteners, the roughness of the connection between the rotating machinery and the vibration measuring seat, and the natural frequency of the vibration measuring seat.

[0036] The following is combined with Figures 1 to 9 Embodiments of the present invention are described.

[0037] According to an embodiment of the present invention, see, in one aspect, Figure 8 This paper provides a design method for anti-resonance of vibration measurement bases with uncertain installation boundaries, including: Obtain the measured natural frequency of the vibration measuring base under its actual installation condition; Establish an equivalent stiffness model and determine the equivalent stiffness; Using the equivalent stiffness as a boundary condition, structural optimization simulation of the vibration measuring seat is performed. The establishment of the equivalent stiffness model and the determination of the equivalent stiffness include: Three elastic elements with fixed constraints in mutually perpendicular directions are established at each mounting hole 1 of the vibration measuring seat finite element model to simulate the constraint effect of the mounting hole 1 of the vibration measuring seat. The stiffness of each elastic element in the elastic unit is repeatedly adjusted iteratively. When the natural frequency f of the finite element model of the vibration measuring base is consistent with the measured natural frequency, the equivalent stiffness is obtained.

[0038] This invention establishes three mutually perpendicular elastic elements with fixed constraints at each mounting hole 1 of the vibration measuring seat finite element model. These elastic elements simulate the constraint effect of the mounting holes 1. By iteratively adjusting the stiffness of each elastic element, the natural frequency f of the vibration measuring seat finite element model is made consistent with the measured natural frequency of the vibration measuring seat under the installed state. The equivalent stiffness is then derived and used as the constraint boundary condition for structural optimization simulation of the vibration measuring seat. This ensures that the natural frequency f avoids the fundamental frequency f0 of the rotor of the rotating machinery mounted on the vibration measuring seat. Even when the installation boundary is uncertain, the accuracy of the finite element simulation results is guaranteed, and the vibration measuring seat optimized by the simulation is less prone to resonance. This method obtains a reliable optimization direction without requiring precise measurement of the actual installation stiffness, significantly improving the efficiency of vibration measuring seat anti-resonance design.

[0039] In some embodiments, a method for designing resonance-resistant vibration measurement bases with uncertain installation boundaries includes: Obtain the measured natural frequency of the vibration measuring base under its actual installation condition; An equivalent stiffness model is established, and elastic elements with fixed constraints are established at each mounting hole 1 of the vibration measuring seat finite element model to simulate the constraint effect of the mounting hole 1 of the vibration measuring seat. Each elastic element includes elastic elements arranged in three directions: X, Y, and Z, respectively designated as X-direction elastic elements, Y-direction elastic elements, and Z-direction elastic elements. The first ends of the X-direction elastic elements, the Y-direction elastic elements, and the Z-direction elastic elements are each fixedly constrained, and the second ends of the X-direction elastic elements, the Y-direction elastic elements, and the Z-direction elastic elements are connected to the center point of the mounting hole 1. The stiffness of the X-axis, Y-axis and Z-axis elastic elements of the elastic unit is repeatedly adjusted iteratively. When the natural frequency f of the finite element model of the vibration measuring seat is consistent with the measured natural frequency, the equivalent stiffness is obtained. Using equivalent stiffness as a boundary condition, structural optimization simulation of the vibration measuring seat is performed.

[0040] By arranging elastic elements in the X, Y, and Z directions at the center points of each mounting hole 1 in the finite element model of the vibration measuring seat, a spatial orthogonal elastic element is constructed. This restores the multi-dimensional force constraint characteristics of the vibration measuring seat mounting interface in the X, Y, and Z directions, which can match the multi-directional stiffness deformation characteristics of the vibration measuring seat after assembly with fasteners for aero-engines and gearboxes. Each of the X, Y, and Z elastic elements has a fixed constraint at one end and the other end converges at the center of mounting hole 1. The modeled force transmission path is completely consistent with the fastening force path of the actual fasteners. The equivalent stiffness in the three orthogonal directions can be independently iteratively calibrated, further improving the accuracy of the equivalent stiffness calibration, reducing the error between the natural frequency f and the measured natural frequency, and further improving the reliability of the vibration measuring seat's anti-resonance structure optimization.

[0041] In some embodiments, modal analysis is performed on the finite element model of the vibration measuring base to calculate the natural frequency f. The stiffness of the X-axis elastic element, the Y-axis elastic element, and the Z-axis elastic element are adjusted until the natural frequency f approaches the fundamental frequency f0 of the rotor of the rotating machinery mounted on the vibration measuring base. The equivalent stiffness of the X-axis elastic element, the Y-axis elastic element, and the Z-axis elastic element is recorded and denoted as K. x Ky and Kz.

[0042] Finite element modal analysis is used to solve for the natural frequency f. The stiffness of the three elastic components in the X, Y, and Z directions is adjusted individually. The stiffness parameters are iteratively adjusted by referring to the fundamental frequency of the rotating machinery rotor. Then, the three-dimensional equivalent stiffness that fits the actual installation conditions is calculated in reverse. This facilitates the subsequent improvement and optimization of the vibration measuring base structure, so that the vibration frequency of the vibration measuring base is far away from the rotor's operating frequency. This effectively avoids resonance between the vibration measuring base and the rotor during vibration testing, while reducing the amount of debugging work and improving the overall design efficiency.

[0043] In some embodiments, modal analysis is performed on the finite element model of the vibration measuring base to calculate the natural frequency f, and the stiffness of the X-axis elastic element, the Y-axis elastic element, and the Z-axis elastic element are adjusted until the natural frequency f and the rotor fundamental frequency f0 satisfy the relationship. At that time, the equivalent stiffness of the X-direction elastic element, the Y-direction elastic element, and the Z-direction elastic element is recorded and denoted as K. x Ky, Kz. When the natural frequency f is close to the rotor fundamental frequency f0, it is determined that...

[0044] Finite element method calculations are subject to computational errors. If the calculation is performed with the natural frequency f equal to the rotor fundamental frequency f0, it will lead to an increase in the number of iterations and reduce computational efficiency. In engineering practice, a difference of less than 1% is considered to be approximately equal to the natural frequency f and the rotor fundamental frequency f0. Therefore, the stiffness of the elastic element when the ratio of the difference between the natural frequency f and the rotor fundamental frequency f0 to the rotor fundamental frequency f0 is no greater than 1% can be used as the equivalent stiffness to reduce the number of iterations and improve computational efficiency.

[0045] In some embodiments, the structural optimization simulation of the vibration measuring base includes: Using the equivalent stiffness of the X-axis elastic element, the Y-axis elastic element, and the Z-axis elastic element as boundary constraints, the vibration measuring base is structurally optimized to ensure that the safety margin δ is equal to or greater than the preset margin.

[0046] The equivalent stiffness in the X, Y, and Z axes obtained through reverse engineering is directly used as the simulation boundary constraint to optimize the vibration measuring base structure, closely matching the actual installation stress conditions. By optimizing the vibration measuring base structure, the frequency safety margin δ of the vibration measuring base is controlled to meet the standard, ensuring a safe distance between the vibration measuring base frequency and the rotor operating frequency. This avoids resonance problems from the design level, making the optimized vibration measuring base structure results closely match the actual operating conditions. This prevents situations where the simulation is qualified but resonance still occurs in actual testing, improves the stability of the vibration measuring base in use, and ensures smooth testing.

[0047] In some embodiments, the preset margin value range is [15%, 20%].

[0048] The safety margin δ is limited to the range of 15%-20%, balancing the rationality of the vibration measuring base structure with its anti-resonance safety performance. A lower limit of 15% can meet the vibration isolation requirements under normal working conditions, preventing resonance caused by small fluctuations in speed and preload. In the industry, the safety margin δ is generally required to exceed 15%.

[0049] Preferably, the safety margin δ satisfies .

[0050] Due to the uncertainty of the installation boundary, the margin is increased to 20%, further ensuring the reliability of the vibration measuring base structure optimization.

[0051] Specifically, the structural optimization of the vibration measuring base includes any or any combination of adding reinforcing ribs, changing the size, and adjusting the local shape.

[0052] The vibration measuring seat can be structurally optimized by selecting any one or a combination of modifications such as adding reinforcing ribs, changing dimensions, and optimizing local shape. This does not require changing the hole position and assembly structure of the vibration measuring seat mounting hole 1, and does not change the original installation compatibility. The natural frequency of the vibration measuring seat can be adjusted as needed at low cost to meet the frequency safety margin δ requirement. The above-mentioned optimization and modification methods are low in difficulty, easy to process, and convenient for design improvement.

[0053] In some embodiments, the iterative adjustment of the stiffness of each elastic element of the elastic unit includes: The stiffness of the X-axis elastic element, the Y-axis elastic element, and the Z-axis elastic element can be adjusted independently or proportionally.

[0054] The stiffness of the elastic components in the X, Y, and Z directions can be adjusted independently or proportionally to adapt to the iterative stiffness requirements of different installation and assembly conditions. The independent adjustment mode allows for individual modification of the stiffness of the elastic components in a single direction, adapting to conditions such as uneven constraints in all directions, asymmetrical fastener preload, and unilateral wear on the mating surfaces, correcting unidirectional stiffness deviations. The proportional adjustment mode simultaneously and proportionally modifies the stiffness of the elastic components in all three directions, adapting to conventional conditions with uniform installation forces and symmetrical assembly, making iterative adjustments simpler.

[0055] Specifically, a two-way gradient iteration method can be adopted, starting from large to small and then from small to large. Initially, a large step size is used to quickly define the stiffness range. After the frequency value is reversed from the measured value, the iteration is refined by reducing the step size by ten times until the ratio of the difference between the natural frequency f and the rotor fundamental frequency f0 to the rotor fundamental frequency f0 value is no greater than 1%. This method balances iteration speed and stiffness accuracy, reduces invalid simulation calculations, and efficiently determines the equivalent stiffness.

[0056] In some embodiments, before iteratively adjusting the stiffness of each elastic element of the elastic unit, the method further includes: pre-assigning an initial value to the model interface stiffness.

[0057] Setting initial stiffness values ​​for the model interface in advance is essential for initiating finite element modal calculations and providing a computational foundation for subsequent iterative parameter tuning. Randomly selecting initial stiffness values ​​without any basis will significantly lengthen the iterative search interval, generate a large number of invalid simulation calculations, and reduce overall design computational efficiency. Providing reasonable initial stiffness values ​​based on experience in advance can narrow the search range for subsequent iterations, reduce the number of iterations, and more quickly find the equivalent stiffness that satisfies the requirement that the ratio of the difference between the natural frequency f and the rotor fundamental frequency f0 to the rotor fundamental frequency f0 is no greater than 1%, effectively shortening the calculation cycle and improving overall calibration efficiency.

[0058] It should be noted that, in the embodiments of the present invention, after completing the structural optimization simulation of the vibration measuring seat, the following steps are also included: The optimized vibration measuring base was subjected to modal testing under actual installation conditions to obtain the natural frequency of the vibration measuring base under actual installation conditions and to verify the simulation calculation results.

[0059] After completing the simulation optimization of the vibration measuring base, modal measurements were conducted on the machined vibration measuring base under actual assembly conditions to obtain the natural frequency of the vibration measuring base under actual installation conditions. This was used to verify the calculation results obtained from the simulation optimization. Through physical testing, deviations in the simulation modeling, equivalent stiffness determination, and structural optimization processes can be identified. It is confirmed that the natural frequency f of the optimized vibration measuring base and the rotor fundamental frequency f0 meet the preset safety margin δ, ensuring the reliability of the vibration measuring base's anti-resonance performance and guaranteeing the stable conduct of subsequent vibration testing.

[0060] The following specific embodiment illustrates the design method for anti-resonance of vibration measuring base with uncertain installation boundaries according to the present invention.

[0061] A method for optimizing the natural frequency design of a vibration measuring base, see [link to relevant documentation]. Figure 9 It includes the following steps: S1. Obtain the natural frequency of the vibration measuring base under actual installation conditions; In the installed state, modal testing is performed on the vibration measuring base to obtain the natural frequency of the vibration measuring base under actual installation conditions.

[0062] S2. Establish an equivalent stiffness model; An equivalent stiffness model is established in the finite element model. Grounding spring elements are established at each mounting hole 1 of the vibration measuring base along the three directions of X-axis, Y-axis and Z-axis. One end of the spring is connected to the center node of mounting hole 1, and the other end is fixed. An initial stiffness value is assigned based on empirical values.

[0063] S3. Confirm the equivalent stiffness model; Modal analysis was performed on the vibration measuring base model with a grounding spring to calculate its natural frequency f. The spring stiffness in three directions was adjusted (independently or proportionally) until the natural frequency f approached the rotor's fundamental frequency f0, and the ratio of the difference between the two to the fundamental frequency was no greater than 1%. The spring stiffness values ​​at this point were recorded, along with the equivalent stiffnesses Kx, Ky, and Kz. The above relationships are as follows:

[0064] When adjusting proportionally, a stiffness value is assigned based on experience for calculation, such as 1×10. 7 The frequency value is calculated by substituting N / m into the value. If the value is too large, the stiffness value is reduced and the calculation continues. When the frequency value and the actual value are reversed, the stiffness value is compared with the previous stiffness value. The calculation is then iterated between the two stiffness values. When the ratio of the difference between the natural frequency f and the rotor fundamental frequency f0 to the rotor fundamental frequency f0 is equal to or less than 1%, the calculation is stopped and the stiffness value of the last result is taken as the stiffness value of the boundary condition.

[0065] Stiffness iteration can proceed from large to small or from small to large, with a relatively large initial step size, such as a difference of 1 × 10⁻⁶ between two stiffness values. 7 N / m, if the result is reversed, iterate again with a smaller step size, such as 1×10. 6 For N / m, repeat the above process until the result is reversed. Calculate the natural frequency value and compare it with the measured value. If one value is larger than the other, calculate again to determine if the above relationship is satisfied. If it is satisfied, stop the iteration. If not, continue to perform step-by-step iterative calculation between the two stiffness values ​​where the result is reversed. The step size of each iteration is 1 / 10 of the previous one, gradually narrowing the gap until a stiffness value that meets the conditions is found.

[0066] S4. Vibration measuring base structure optimization; Using the equivalent stiffnesses Kx, Ky, and Kz calibrated by S3 as boundary constraints, the vibration measuring base is structurally optimized, such as by adding stiffeners, changing dimensions, and adjusting local shapes, to ensure that its natural frequencies meet the following requirements:

[0067] In the formula The safety margin is δ.

[0068] S5. Vibration test fixture verification test; If the safety margin δ condition is met, output the optimized vibration measuring base structure scheme; if the safety margin δ condition is not met, return to S4 to continue optimization until the requirements are met.

[0069] Modal testing was performed on the optimized vibration measuring base under actual installation conditions to obtain the natural frequency of the vibration measuring base under actual installation conditions and to verify the simulation calculation results.

[0070] During a full-engine test of an aero-engine, vibration exceeded limits due to resonance of the vibration measuring base near the operating speed of 48,000 r / min, forcing the test to be suspended. The three-dimensional model of the vibration measuring base is shown below. Figure 1 The natural frequency of the vibration measuring base, measured under installed conditions, is 795.5Hz, which is close to the rotor's fundamental frequency of 800Hz. Therefore, structural optimization of the vibration measuring base is needed to adjust its natural frequency to avoid the rotor's fundamental frequency of 800Hz.

[0071] If the vibration measuring base is subjected to finite element analysis using the traditional method, and the two bolt mounting holes 1 of the vibration measuring base are fully constrained using the traditional constraint method, the calculated frequency is 3163Hz. The finite element calculation results are shown below. Figure 3 The simulation results differed significantly from the measured results, and analysis confirmed that the simulation of the installation boundary was inaccurate.

[0072] Therefore, using the design method of this invention, a grounding spring is established for finite element calculation of the vibration measuring base.

[0073] To simulate actual installation stiffness, three grounding springs (X, Y, and Z) are installed at each of the two mounting holes 1. The initial stiffness of the springs can be determined empirically (1×10⁻⁶). 7 (N / m). Then, adjust the spring stiffness according to the simulation calculation results until the difference between the simulation calculation result and the measured result is no greater than 1%. Record the grounding spring stiffness value at this time as 0.62×10 N / m. 7 N / m. This simulated stiffness value is selected as the stiffness value of the actual installation boundary, and used as the boundary condition for subsequent vibration meter structure optimization simulation calculations.

[0074]

[0075] Optimizing the vibration meter structure can involve adjusting its dimensions or changing its shape. The optimized 3D model of the vibration meter is shown below. Figure 2 .

[0076] Finite element analysis was performed on the optimized vibration measuring base, which had identical grounding springs installed at the bolt holes. The stiffness of the grounding springs was taken as 0.62 × 10⁻⁶. 7 N / m, finite element calculation results are shown in Figure 6The natural frequency f is calculated to be 975Hz, and the safety margin δ = (975-800) / 800 = 21.9%.

[0077] The optimized vibration measuring base has a safety margin δ of more than 20%, which meets the requirements and can avoid vibration exceeding the limit due to resonance of the vibration measuring base during the test, thus ensuring that the test is carried out reliably.

[0078] Simulation model diagram: STEP: Load step; SUB: sub-step; FREQ: Frequency; USUM: Total displacement; RSYS: Result coordinate system; DMX: Maximum displacement; SMX: Maximum stress / strain value.

[0079] To address the issue of distorted finite element simulation results for the vibration measuring base due to the difficulty in simulating installation boundary conditions, this invention proposes establishing grounding springs in the X, Y, and Z directions at each mounting hole 1 in the finite element model to simulate the constraint effect of the mounting hole 1. By continuously adjusting and optimizing the stiffness of the springs, the natural frequency of the model is made consistent with the measured value of the whole machine test, and the equivalent stiffness is derived. Using the equivalent stiffness as the boundary condition, the structure of the vibration measuring base is optimized so that its natural frequency avoids the rotor fundamental frequency f0.

[0080] This invention utilizes the boundary condition equivalence method, replacing the complex and unknown installation connection stiffness with grounding springs in the X, Y, and Z directions at the vibration measuring base mounting hole 1. When determining the equivalent stiffness value, the finite element simulation calculation result is back-calculated from the vibration measuring base frequency test result until the difference between the two is less than 1%, allowing the finite element calculation result to gradually approach the measured result, thus determining the equivalent stiffness value in the three directions. The determined equivalent stiffness model is used for vibration measuring base structural optimization. By continuously changing parameters such as structural dimensions, stiffeners, and thickness, the difference between the simulation calculation result and the rotor fundamental frequency f0 is increased to more than 20% of the fundamental frequency. Frequency tests are then conducted on the optimized vibration measuring base under installation conditions to verify the optimization method. This invention obtains reliable optimization directions without requiring precise measurement of the actual installation stiffness, significantly improving the efficiency of vibration measuring base anti-resonance design.

[0081] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by this application.

Claims

1. A method for designing an anti-resonance vibration measuring base with uncertain installation boundaries, characterized in that, include: Obtain the measured natural frequency of the vibration measuring base under its actual installation condition; Establish an equivalent stiffness model and determine the equivalent stiffness; Using the equivalent stiffness as a boundary condition, structural optimization simulation of the vibration measuring seat is performed. The establishment of the equivalent stiffness model and the determination of the equivalent stiffness include: Three elastic elements with fixed constraints in mutually perpendicular directions are established at each mounting hole (1) of the finite element model of the vibration measuring seat to simulate the constraint effect of the mounting hole (1) of the vibration measuring seat. The stiffness of each elastic element of the elastic unit is repeatedly adjusted iteratively. When the natural frequency (f) of the finite element model of the vibration measuring base is consistent with the measured natural frequency, the equivalent stiffness is obtained.

2. The design method for anti-resonance of vibration measuring base with uncertain installation boundaries according to claim 1, characterized in that, Each of the elastic units includes elastic elements arranged along three directions: X, Y, and Z, respectively designated as X-direction elastic elements, Y-direction elastic elements, and Z-direction elastic elements; the first end of the X-direction elastic element, the first end of the Y-direction elastic element, and the first end of the Z-direction elastic element are each fixedly constrained, and the second end of the X-direction elastic element, the second end of the Y-direction elastic element, and the second end of the Z-direction elastic element are connected to the center point of the mounting hole (1).

3. The design method for anti-resonance of vibration measuring base with uncertain installation boundaries according to claim 2, characterized in that, Modal analysis is performed on the finite element model of the vibration measuring base to calculate the natural frequency (f). The stiffness of the X-axis elastic element, the Y-axis elastic element and the Z-axis elastic element are adjusted until the natural frequency (f) is close to the fundamental frequency (f0) of the rotor of the rotating machinery installed on the vibration measuring base. The equivalent stiffness of the X-axis elastic element, the Y-axis elastic element and the Z-axis elastic element is recorded.

4. The design method for anti-resonance of vibration measuring base with uncertain installation boundaries according to claim 3, characterized in that, When the natural frequency (f) and the rotor fundamental frequency (f0) satisfy the relationship When the natural frequency (f) is close to the rotor fundamental frequency (f0), it is determined that the natural frequency (f) is close to the rotor fundamental frequency (f0).

5. The design method for anti-resonance of vibration measuring base with uncertain installation boundaries according to claim 3, characterized in that, The structural optimization simulation of the vibration measuring base includes: Using the equivalent stiffness of the X-axis elastic element, the Y-axis elastic element, and the Z-axis elastic element as boundary constraints, the vibration measuring seat is structurally optimized to ensure that the safety margin (δ) is equal to or greater than the preset margin.

6. The design method for anti-resonance of vibration measuring base with uncertain installation boundaries according to claim 5, characterized in that, The preset margin value range is [15%, 20%].

7. The design method for anti-resonance of vibration measuring base with uncertain installation boundaries according to claim 5, characterized in that, The structural optimization of the vibration measuring base includes any or any combination of adding reinforcing ribs, changing the size, and adjusting the local shape.

8. The design method for anti-resonance of vibration measuring base with uncertain installation boundaries according to claim 2, characterized in that, The iterative adjustment of the stiffness of each elastic element in the elastic unit includes: The stiffness of the X-axis elastic element, the Y-axis elastic element, and the Z-axis elastic element can be adjusted independently or proportionally.

9. The design method for anti-resonance of vibration measuring base with uncertain installation boundaries according to claim 1, characterized in that, Before iteratively adjusting the stiffness of each elastic element of the elastic unit, the method further includes: pre-assigning an initial value to the model interface stiffness.

10. The design method for anti-resonance of a vibration measuring base with uncertain installation boundaries according to any one of claims 1 to 9, characterized in that, After completing the structural optimization simulation of the vibration measuring base, the following steps are also included: The optimized vibration measuring base was subjected to modal testing under actual installation conditions to obtain the natural frequency of the vibration measuring base under actual installation conditions and to verify the simulation calculation results.

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