A method for calculating the basic vibration parameters of a pulse wind tunnel balance

Abstract

The present invention provides a method for calculating the basic vibration parameters of a pulse wind tunnel balance. In this method, the form of aerodynamic load action is selected, and the corresponding vibration parameter calculation model is established. This method can calculate the vibration parameters such as the amplitude in the vertical direction, the amplitude in the horizontal slip direction, and the deflection angle of the pulse wind tunnel balance foundation under the action of aerodynamic load. The finite element method is used for numerical simulation verification, which proves the reliability of this method. Through the method of the present invention, the vibration parameters of the pulse wind tunnel balance foundation can be calculated more simply, which has certain guiding significance for mastering the vibration characteristics of the overall structure of the pulse wind tunnel and also provides a reference for the research in related fields.

Description

Technical Field

[0001] The present invention belongs to the technical field of impulse wind tunnel tests, and particularly relates to a method for calculating the basic vibration parameters of an impulse wind tunnel balance. Background Art

[0002] With the continuous development of science and technology, more and more technicians have begun to pay attention to the basic design problems of vibrating equipment. What they mainly concern is how to separate the natural vibration frequency of the foundation from the forced frequency to prevent the occurrence of resonance. Before the 20th century, the design calculation methods for vibrating machine foundations usually adopted the methods for solving static problems, multiplying the dynamic load amplitude by a dynamic coefficient greater than 1 for dynamic analysis. Until the early 20th century, two calculation methods, namely the mass-spring calculation model and the elastic half-space theory, emerged. Later, lumped parameter models for vertical, torsional, rocking, and horizontal vibrations of the foundation were further proposed, but these do not conform to the actual situations of the foundation soil and the foundation, and it is still very difficult to calculate the foundation vibration under impulse loads. Although the finite element method can analyze vibrating machine foundations, the rationality and reliability of its analysis results depend on the simulation degree of the actual foundation-foundation soil system. In the existing simplified calculation methods for the vertical dynamic impedance of any rigid foundation, the calculations of the stiffness and damping coefficients still do not match the test environment.

[0003] The impulse wind tunnel test time does not exceed 1 second. It is an important test equipment in the research and development process of hypersonic aircraft, and can achieve high Mach number and high total temperature flow field states that are difficult to achieve by other wind tunnel equipment. As an essential key equipment for simulating the flow of hypersonic and high-enthalpy real gases, it plays an important role in the research and development process of hypersonic aircraft. During startup and operation, the impulse wind tunnel airflow acts on the test model in the form of an approximate step impulse load, causing the structural vibration of the test system including the model, balance, support, and balance foundation. When the impulse load acts on the model and the balance, it will be transmitted to the lower balance foundation through the support. If the strength and vibration prevention performance of the balance foundation itself are not good, it will cause the vibration of the balance foundation, even the test section foundation and even the foundation, thus having a greater adverse impact on the response characteristics and measurement accuracy of the upper balance model. Therefore, figuring out the vibration parameters of the impulse wind tunnel balance foundation has practical reference value for mastering the vibration characteristics of the overall structure of the impulse wind tunnel. However, the existing foundation vibration calculation methods do not pay attention to this special action type of impulse load, and there is currently a lack of research content in this regard. Therefore, it is necessary to develop a method for calculating the vibration parameters of the impulse wind tunnel balance foundation. Summary of the Invention

[0004] For the foundation of a pulse wind tunnel balance under the action of pulse loads, the existing general methods for calculating foundation vibration are no longer applicable. The present invention aims to solve the deficiencies of the prior art. By establishing a model of the foundation of a pulse wind tunnel balance under the action of pulse loads, its vibration characteristics are investigated, its vibration mode is grasped, and finally a method for calculating the vibration parameters of the balance foundation is proposed.

[0005] The technical solution of the present invention is: a method for calculating the vibration parameters of the foundation of a pulse wind tunnel balance. Select the form of aerodynamic load action, propose a calculation model for the vibration parameters of the foundation of a pulse wind tunnel balance, establish a calculation method for the vibration parameters of the foundation of a pulse wind tunnel balance under the action of aerodynamic loads, and use the finite element method for numerical simulation verification; it includes the following steps:

[0006] Step 1: According to the actual parameters, establish a calculation model for the vibration parameters of the foundation of a pulse wind tunnel balance. When a pulse-shaped force acts on the balance model, establish a calculation domain;

[0007] Step 2: According to the structure of the balance foundation and the characteristics of the aerodynamic load action, decompose the vibration of the balance foundation into vertical vibration under the action of vertical disturbing force and horizontal deflection coupled damped forced vibration under the action of horizontal slip disturbing force and bending moment force;

[0008] Step 3: The connections between the balance model and the support plate, and between the support plate and the balance foundation are all rigid connections. The pulse force acting on the calculation model of the vibration parameters of the foundation of a pulse wind tunnel balance is directly transmitted to the balance foundation. When a rigid rectangular block foundation embedded in the soil medium is subjected to a horizontal slip disturbing force, determine its equivalent target parameters in the horizontal slip direction of the foundation-soil system, the dynamic response under the coupled steady-state vibration of horizontal slip and rocking, and the dynamic dissipated energy within each horizontal slip steady-state vibration period and the coupled steady-state vibration period of rocking; the coupled steady-state vibration of rocking is decomposed into rocking motion and coupled motion;

[0009] Step 4: When a rigid rectangular block foundation embedded in the soil medium is subjected to a vertical disturbing force, determine its equivalent target parameters in the vertical direction of the foundation-soil system and the dynamic response of the rigid rectangular block foundation under vertical vibration;

[0010] Step 5: Simplify the study of the foundation of a pulse wind tunnel balance, establish a three-dimensional analysis numerical model using ABAQUS finite element, calculate the parameters and their constitutive models, and use the finite element method for numerical model calculation;

[0011] Step 6: Obtain the basic mechanical property parameters of the soil of the rigid rectangular block foundation. Through the theoretical calculations in the third and fourth steps, compare the theoretical calculation results with the numerical simulation calculation results in the fifth step.

[0012] Among them, the vertical disturbing force is perpendicular to the balance foundation;

[0013] The steady-state vibration period refers to the periodic stable state reached by a vibration system under the action of a periodic external force and the time duration of maintaining this state; the specific calculation method depends on the free vibration equation of the vibration system and the form of the external force action; in the case of simple harmonic vibration, the steady-state vibration period is equal to the natural period of the vibration system, that is, an integer multiple of the natural period of the vibration unit.

[0014] The specific steady-state vibration period of the rocking coupling is the time of the period of each pendulum in the rocking coupling system (a complete round-trip vibration motion from one extreme point to another and back to the origin) when the vibration reaches the steady state.

[0015] Vertically specifically refers to the direction perpendicular to the balance foundation;

[0016] Horizontally specifically refers to the direction parallel to the balance foundation.

[0017] Preferably, in the first step, the calculation model of the vibration parameters of the pulse wind tunnel balance foundation is a rigid rectangular block foundation, and its balance foundation engineering overview is as follows: The balance foundation adopts a reinforced concrete structure, the concrete material is C30 concrete, the steel bars adopt HRB400, the top surface of the foundation is connected to the steel support plate by bolts, and then the balance model 1 is fixed on it, and a pulsed force acts on the balance model.

[0018] Preferably, in the third step, the motion equation of the rigid rectangular block foundation is:

[0019]

[0020] K x = K sx (k x + a0c x )

[0021] K β = K sβ (k β + a0c β )

[0022] K c = K sc (k c + a0c c )

[0023] a0 = ωR / V s

[0024] In the formula: M is the mass of the rigid rectangular block foundation; I β is the moment of inertia when the rigid rectangular block foundation deflects around the center of gravity; h is the buried depth of the rigid rectangular block foundation; t is the time; U bis the horizontal slip amplitude of the rigid rectangular block foundation pedestal; Φ β is the deflection of the rigid rectangular block foundation about the center; is the second derivative of the horizontal slip amplitude of the rigid rectangular block foundation pedestal; is the second derivative of the deflection of the rigid rectangular block foundation about the center; H is the horizontal slip force; M oβ is the rocking moment; K x , K β and K c are the dynamic impedance functions based on the center of the rigid rectangular block foundation pedestal, K sx , K sβ and K sc are the static stiffnesses under horizontal slip motion, rocking motion, and coupled motion respectively; k x , k β and k c are the normalized stiffness coefficients, c x , c β and c c are the normalized damping coefficients, where the subscripts x, β, and c represent horizontal slip motion, rocking motion, and coupled motion respectively; a0 is the dimensionless frequency, V s is the shear wave velocity of the soil, and R is the characteristic length.

[0025] Preferably, in the third step, the dynamic dissipation energy equation of the foundation-soil system in each steady-state vibration cycle of horizontal slip is:

[0026]

[0027] In the formula: u s is the static amplitude of the coupling effect; M x is the horizontal slip amplification factor; θ x is the phase angle; K sx is the static stiffness; e Dx is the dynamic dissipation energy factor of horizontal slip forced vibration; P x1 is the amplitude of the horizontal slip force; E Dx is the horizontal slip dynamic dissipation energy.

[0028] Preferably, in the third step, the dynamic dissipation energy equation of the foundation-soil system in each steady-state vibration cycle of rocking coupling is:

[0029]

[0030] In the formula: φ s is the static position deflection without coupling effect; M β is the rocking amplification factor; θ β is the phase angle; K sβ is the static stiffness; eDβ is the dynamic dissipation energy factor of rocking vibration; m oβ is the torque amplitude; E Dβ is the rocking dynamic dissipation energy.

[0031] Preferably, in the third step, the equivalent target parameter equation of the horizontal sliding to the foundation-soil system is:

[0032] M x = u t / u s

[0033] M c = hφ β / u s

[0034] M β = φ β / φ s

[0035] Where: u t is the horizontal sliding amplitude; u s is the static amplitude of the coupling effect; φ β is the dynamic amplitude; φ s is the static deflection without coupling effect, h is the foundation embedment depth; M x is the horizontal sliding amplification factor; M c is the coupling amplification factor; M β is the rocking amplification factor.

[0036] Preferably, in the fourth step, the balance model transfers the vertical disturbing force to the balance foundation, that is, when the rigid rectangular block foundation is subjected to the vertical disturbing force, according to the foundation-soil system, the equivalent target parameter equation in its balance model is:

[0037] K ez = K sz

[0038] C ez = k ez c ez ×ρV s R 2

[0039]

[0040] Where: K sz is the static stiffness; k ez is the equivalent stiffness factor; c ez is the equivalent damping factor; ρ is the density; a0 is the dimensionless frequency, V s is the shear wave velocity of the soil, R is the characteristic length; k z is the coefficient, depending on the dimensionless frequency; Kez is the equivalent stiffness; C ez is the equivalent damping; M ez equivalent mass

[0041] Preferably, in the fifth step, the basic assumptions introduced by the numerical model calculation method are: the model under aerodynamic load and the supporting material are completely elastic; the contact between the foundation and the ground satisfies Coulomb friction

[0042] Preferably, in the fifth step, when the three-dimensional analysis numerical model is under aerodynamic load, the balance model, the support plate, and the balance foundation are always in contact. The Tie connection method of bonded constraint is adopted; the normal behavior between the foundation and the ground is set as hard contact, and the tangential behavior is set as the penalty function; to ensure the correctness of the numerical simulation, a grid independence test is carried out; the concrete damage plasticity constitutive model is adopted, and the Mohr-Coulomb elastoplastic model is adopted for the ground; in order to simulate the aerodynamic load acting conditions of the wind tunnel on the test model, a horizontal sliding load, a vertical load, and a moment are applied at the centroid of the model. The load forms are the measured vertical disturbing force, the horizontal sliding disturbing force, and the pitching moment

[0043] Preferably, in the sixth step, the basic mechanical property parameters of the rigid rectangular block foundation soil are obtained, including the dynamic shear modulus G of the foundation soil, the average shear wave velocity V s , the density ρ of the rigid rectangular block foundation soil, the damping coefficient of the foundation soil, the Poisson's ratio v, and the side length of the given rigid rectangular block foundation. At the same time, the site intensity is less than 6 degrees, and there is no saturated sand within a depth of 20m, and the influence of seismic liquefaction is not considered; combined with the grid independence test scheme and the calculation results with the reference values recommended in the "Design Standard for Dynamic Machine Foundations" GB50040-2020; the vibration parameters of the pulse wind tunnel balance foundation are obtained through the theoretical calculation model and numerical simulation

[0044] The present invention has the following beneficial effects: At present, the "Design Code for Dynamic Machine Foundations" (GB50040-2020) in China proposes calculation methods and construction measures for vibration parameters under different load types for rotating machines, reciprocating machines, impact machines, presses, crushers and grinders, vibration test benches, and metal cutting machines. However, for the vibration characteristics of the pulse wind tunnel balance foundation under pulse load, the calculation methods in this code are not applicable, and there is no other applicable calculation method at present. Therefore, the present invention selects the action form of aerodynamic load, studies its vibration characteristics, proposes a calculation model for the vibration parameters of the pulse wind tunnel balance foundation, and establishes calculation methods for vibration parameters such as the amplitude in the vertical and sliding directions and the deflection angle (i.e., the dynamic response under the rocking coupling vibration of the rigid rectangular block foundation), and verifies its reliability by numerical simulation methods, which can further promote the development of the design theory of dynamic machine foundations Description of the Drawings

[0045] Figure 1 This is a simplified diagram of the calculation model for the basic vibration parameters of the pulse wind tunnel balance of the present invention.

[0046] Figure 2 This is a simplified diagram of the calculation of the coupled damped forced vibration of the horizontal deflection under the action of the horizontal sliding disturbing force and bending moment of the rigid rectangular block foundation of the present invention.

[0047] Figure 3 This is a simplified diagram of the rigid rectangular block foundation of the present invention under the action of a vertical disturbing force.

[0048] Figure 4 This is a three-dimensional vertical mesh division diagram of the present invention.

[0049] Figure 5 This is a comparison diagram between the theoretical calculation results and the finite element calculation results in the vertical direction of the present invention.

[0050] Figure 6 This is a comparison diagram between the theoretical calculation results and the finite element calculation results in the horizontal sliding direction of the present invention.

[0051] Figure 7 This is a comparison diagram between the theoretical calculation results (i.e., the dynamic response under the rocking coupling vibration of the rigid rectangular block foundation) and the finite element calculation results of the deflection angle of the present invention.

[0052] In the figure, 1. balance model, 2. support plate, 3. balance foundation, 4. vertical disturbing force, 5. horizontal sliding disturbing force, 6. bending moment force, 7. rocking moment, 8. deflection angle, 9. horizontal sliding amplitude at the top of the rigid rectangular block foundation, 10. horizontal sliding amplitude at the base of the rigid rectangular block foundation, 11. characteristic length, 12. burial depth of the rigid rectangular block foundation, 13. vertical amplitude of the rigid rectangular block foundation, 14. equivalent stiffness, 15. equivalent mass, 16. equivalent damping. Specific embodiments

[0053] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0054] See Figures 1 to 7 . Figure 1 This is a simplified diagram of the calculation model for the basic vibration parameters of the pulse wind tunnel balance of the present invention, including the balance foundation 3, the support plate 2 above the balance foundation 3, and the balance model 1 above the support plate 2; and both between the balance model 1 and the support plate 2 and between the support plate 2 and the balance foundation 3 are rigidly connected.

[0055] Point P in the figure y represents the vertical disturbing force in the form of a pulse, and P x represents the horizontal slip disturbing force in the form of a pulse; Figure 1 The schematic diagram of is a common existing structure. Mz is the bending moment force.

[0056] Example 1

[0057] The example provides a method for calculating the vibration parameters of the pulse wind tunnel balance foundation. Taking a certain pulse wind tunnel as an example, the form of the aerodynamic load action is selected, a calculation model for the vibration parameters of the pulse wind tunnel balance foundation is proposed, a calculation method for the vibration parameters of the pulse wind tunnel balance foundation under the action of the aerodynamic load is established, and finally the vibration response characteristics of the balance foundation are calculated, and the finite element method is used for numerical simulation verification. The steps are as follows:

[0058] Step 1: According to the actual parameters, establish a calculation model for the vibration parameters of the pulse wind tunnel balance foundation. When a force in the form of a pulse acts on the balance model, establish a calculation domain;

[0059] Step 2: According to the structure of the balance foundation and the characteristics of the aerodynamic load action, decompose the vibration of the balance foundation into vertical vibration under the action of the vertical disturbing force and horizontal deflection coupled damped forced vibration under the action of the horizontal slip disturbing force and the bending moment force;

[0060] Step 3: The connections between the balance model and the support plate and between the support plate and the balance foundation are all rigid connections. The pulse force acting on the calculation model of the vibration parameters of the pulse wind tunnel balance foundation is directly transmitted to the balance foundation. When a rigid rectangular block foundation embedded in the soil medium is subjected to a horizontal slip disturbing force, determine its equivalent target parameters in the horizontal slip direction of the foundation-soil system, the dynamic response under the coupled steady-state vibration of horizontal slip and rocking, and the dynamic dissipated energy within each horizontal slip steady-state vibration period and rocking coupled steady-state vibration period; The rocking coupled steady-state vibration is decomposed into rocking motion and coupled motion;

[0061] Step 4: When a rigid rectangular block foundation embedded in the soil medium is subjected to a vertical disturbing force, determine its equivalent target parameters in the vertical direction of the foundation-soil system and the dynamic response of the rigid rectangular block foundation under vertical vibration;

[0062] Step 5: Simplify the research on the pulse wind tunnel balance foundation, establish a three-dimensional analysis numerical model using ABAQUS finite element, calculate the parameters and their constitutive models, and use the finite element method to calculate the numerical model;

[0063] Step 6: Obtain the basic mechanical property parameters of the rigid rectangular block foundation soil. Through the theoretical calculations in the third and fourth steps, compare the theoretical calculation results with the numerical simulation calculation results in the fifth step.

[0064] Example 2

[0065] The present application will be described in detail below in conjunction with the accompanying drawings and examples.

[0066] A method for calculating the basic vibration parameters of a pulse wind tunnel balance includes the following steps

[0067] (1) Step 1: According to the actual parameters, establish a calculation model for the basic vibration parameters of the pulse wind tunnel balance. When a pulse - form force acts on the balance model, establish a calculation domain;

[0068] As Figure 1 shown, in Step 1, the calculation model for the basic vibration parameters of the pulse wind tunnel balance is a rigid rectangular block foundation. The general situation of the balance foundation project is as follows: The balance foundation adopts a reinforced concrete structure, the concrete material is C30 concrete, the steel bars are HRB400, the top surface of the foundation is connected to a steel support plate by bolts, and then a balance model 1 is fixed on it. A pulse - form force acts on the balance model.

[0069] (2) Step 2: According to the structure of the balance foundation and the characteristics of the aerodynamic load action, decompose the balance foundation vibration into vertical vibration under the action of vertical disturbing force, and horizontal deflection coupled damped forced vibration under the action of horizontal slip disturbing force and bending moment force;

[0070] (3) Step 3: The connections between the balance model and the support plate, and between the support plate and the balance foundation are all rigid connections. The pulse force acting on the calculation model of the basic vibration parameters of the pulse wind tunnel balance is directly transmitted to the balance foundation. When a rigid rectangular block foundation embedded in the soil medium is subjected to a horizontal slip disturbing force, determine its equivalent target parameters in the horizontal slip direction of the foundation - soil system, the dynamic response under the coupled steady - state vibration of horizontal slip and rocking, and the dynamic dissipated energy within each horizontal slip - direction steady - state vibration period and the rocking - coupled steady - state vibration period; The rocking - coupled steady - state vibration is decomposed into rocking motion and coupled motion;

[0071] Figure 1 The sketch of the calculation model for the basic vibration parameters of the pulse wind tunnel balance of the present invention includes a balance foundation 3, a support plate 2 above the balance foundation 3, and a balance model 1 above the support plate 2; and the connections between the balance model 1 and the support plate 2, and between the support plate 2 and the balance foundation 3 are all rigid connections.

[0072] Figure 1 In the figure, P y represents the vertical disturbing force in pulse form, and P x represents the horizontal slip disturbing force in pulse form; Figure 1 The sketch of... is a common existing structure. Mz is the bending moment force.

[0073] The pulse force acting on the balance model is directly transmitted to the balance foundation 3, and its equivalent target parameters are obtained according to the horizontal sliding and vibration characteristics of the balance foundation 3.

[0074] Since the balance foundation of the pulse wind tunnel adopts a reinforced concrete structure, the top surface of the balance foundation 3 is connected to the steel support plate 2 by bolts, and then the balance model 1 is fixed on it. The balance model is rigidly connected to the support plate and the support plate is rigidly connected to the balance foundation. It can be considered that the aerodynamic load acting on the model can be transmitted to the lower foundation without loss; from the first step, it can be seen that the foundation will perform horizontal sliding and deflection coupling damped forced vibration. See Appendix Figure 2 In step three, the motion equation of the rigid rectangular block foundation is:

[0075]

[0076] K x =K sx (k x +a0c x )

[0077] K β =K sβ (k β +a0c β )

[0078] K c =K sc (k c +a0c c )

[0079] a0 = ωR / V s

[0080] Where: M is the mass of the rigid rectangular block foundation; I β is the moment of inertia of the rigid rectangular block foundation when deflecting around the center of gravity; h is the buried depth of the rigid rectangular block foundation; t is the time; U b is the horizontal sliding amplitude of the base of the rigid rectangular block foundation; Φ β is the deflection of the rigid rectangular block foundation around the center; is the second derivative of the horizontal sliding amplitude of the base of the rigid rectangular block foundation; is the second derivative of the deflection of the rigid rectangular block foundation around the center; H is the horizontal sliding force; M oβ rocking moment; K x , K β and K c are the dynamic impedance functions based on the center of the base of the rigid rectangular block foundation, K sx , K sβ and K sc are the static stiffness under horizontal sliding motion, rocking motion and coupling motion respectively; k x , kβ and k c is the normalized stiffness coefficient, c x , c β and c c are the normalized damping coefficients, where the subscripts x, β, and c represent the horizontal sliding motion, rocking motion, and coupled motion, respectively; a0 is the dimensionless frequency, V s is the shear wave velocity of the soil, and R is the characteristic length.

[0081] The dynamic dissipation energy equation of the foundation-soil system in each steady-state vibration period of the horizontal sliding direction is:

[0082]

[0083] In the formula: u s is the static amplitude of the coupling effect; M x is the horizontal sliding amplification coefficient; θ x is the phase angle; K sx is the static stiffness; e Dx is the dynamic dissipation energy factor of the horizontal sliding forced vibration; P x1 is the amplitude of the horizontal sliding disturbing force; E Dx Horizontal sliding dynamic dissipation energy.

[0084] The dynamic dissipation energy equation of the foundation-soil system in each rocking-coupled steady-state vibration period is:

[0085]

[0086] In the formula: φ s is the static deflection angle without coupling effect; M β is the rocking amplification coefficient; θ β is the phase angle; K sβ is the static stiffness; e Dβ is the dynamic dissipation energy factor of the rocking vibration; m oβ is the torque amplitude; E Dβ Rocking dynamic dissipation energy.

[0087] The equivalent target parameter equation of the horizontal sliding direction for the foundation-soil system is:

[0088] M x = u t / u s

[0089] M c = hφ β / u s

[0090] M β = φ β / φ s

[0091] In the formula: u t is the horizontal sliding amplitude; u s is the static amplitude of the coupling effect; φ β is the dynamic amplitude; φ s is the static position deflection without coupling effect, and h is the foundation embedment depth; M x is the horizontal sliding amplification coefficient; M c is the coupling amplification coefficient; M β is the rocking amplification coefficient.

[0092] (4) Step Four: When a rigid rectangular block foundation embedded in the soil medium is subjected to a vertical disturbing force, determine the equivalent target parameters of the vertical foundation-soil system and the dynamic response of the rigid rectangular block foundation under vertical vibration;

[0093] Refer to Appendix Figure 3 . The balance model transfers the vertical disturbing force to the balance foundation, that is, when the rigid rectangular block foundation is subjected to a vertical disturbing force, according to the foundation-soil system, the equivalent target parameter equation in its model is:

[0094] K ez = K sz

[0095] C ez = k ez c ez ×ρV s R 2

[0096]

[0097] In the formula: K sz is the static stiffness; k ez is the equivalent stiffness factor; c ez is the equivalent damping factor; ρ is the density; a0 is the dimensionless frequency, V s is the shear wave velocity of the soil, R is the characteristic length; k z is the coefficient, depending on the dimensionless frequency; K ez is the equivalent stiffness; C ez is the equivalent damping; M ez equivalent mass.

[0098] (5) Step Five: Simplify and study the pulse wind tunnel balance foundation, establish a three-dimensional analysis numerical model using ABAQUS finite element, calculate the parameters and their constitutive models, and perform numerical model calculations using the finite element method; as Figure 4 shown;

[0099] In step 5, the basic assumptions introduced in the numerical model calculation method are: the model and the supporting material under the action of the aerodynamic load are completely elastic; and the contact between the foundation and the base satisfies the Coulomb friction.

[0100] In step five, when the three-dimensional analysis numerical model is subjected to load, the balance model and the support plate, and the support plate and the balance foundation are always in contact, and the binding constraint Tie connection method is adopted; the normal behavior between the foundation and the foundation is set to hard contact, and the tangential behavior is set to a penalty function; to ensure the correctness of the numerical simulation, a grid independence test is carried out; the concrete damage plasticity constitutive model is adopted, and the Mohr-Coulomb elastoplastic model is adopted for the foundation; in order to simulate the load conditions of the wind tunnel on the test model, horizontal slip loads, vertical loads and bending moments are applied at the centroid of the model, and the load forms adopt the measured vertical disturbance force, horizontal slip disturbance force and pitching moment.

[0101] (6) Step 6: Obtain the basic performance parameters of the rigid rectangular block foundation soil, and compare the theoretical calculation results with the numerical simulation calculation results of the fifth step through the theoretical calculations of the third and fourth steps.

[0102] In step 6, the basic mechanical performance parameters of the rigid rectangular block foundation soil are obtained, including the dynamic shear modulus G of the foundation soil, the average shear wave velocity V s , rigid rectangular block foundation soil density ρ, foundation soil damping coefficient, Poisson's ratio v and the side length of a given rigid rectangular block foundation, while the site intensity is less than 6 degrees, and there is no saturated sand within a depth of 20m, and the influence of seismic liquefaction is not considered; combined with the grid independence test scheme and calculation results in Table 1 and the reference values recommended in the "Design Standard for Power Machinery Foundations" (GB50040-2020); the vibration response characteristics of the pulse wind tunnel balance foundation are obtained through theoretical calculation models and numerical simulations.

[0103] In order to ensure the accuracy of numerical simulation, it is necessary to first perform a grid independence test; the present invention sets four grids with different numbers of units and nodes to verify the grid independence. The test scheme and calculation results are shown in Table 1.

[0104] The calculation results in Table 1 are the calculation results obtained by setting different units and grids when the present invention performs numerical simulation; in numerical simulation, a grid independence test is generally required. When the influence of the increase in the number of grids on the simulation results can be ignored, the grid independence meets the requirements. The numerical simulation technology should belong to the existing known technology.

[0105] The basic vibration parameters were calculated by the present invention and compared with the results of ABAQUS fine finite element calculation, and Table 2 was obtained. It can be seen from Table 2 that the calculation results of this method are basically consistent with the accurate results of finite element calculation. Figure 5 , Figure 6 andFigure 7 Compared with the finite element modeling calculation, the present invention greatly reduces the modeling difficulty while ensuring the calculation accuracy, and the calculation efficiency is also significantly improved.

[0106] Table 1 Grid independence test scheme and calculation results

[0107]

[0108] Table 2 Comparison between theoretical calculation results and numerical simulation calculation results

[0109]

[0110] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for calculating the basic vibration parameters of a pulse wind tunnel balance, characterized in that: Select the form of pneumatic load action, propose a calculation model for the vibration parameters of the pulse wind tunnel balance foundation, establish a calculation method for the vibration parameters of the pulse wind tunnel balance foundation under pneumatic load, and use the finite element method for numerical simulation verification; including the following steps: Step 1: According to the actual parameters, establish a calculation model for the vibration parameters of the pulse wind tunnel balance foundation. When a pulse-form force acts on the balance model, establish a calculation domain; Step 2: According to the structure of the balance foundation and the characteristics of pneumatic load action, decompose the vibration of the balance foundation into vertical vibration under the action of vertical disturbing force, and horizontal deflection coupled damped forced vibration under the action of horizontal slip disturbing force and bending moment force; Step 3: The connections between the balance model and the support plate, and between the support plate and the balance foundation are all rigid connections. The pulse force acting on the calculation model of the pulse wind tunnel balance foundation vibration is directly transmitted to the balance foundation. When a rigid rectangular block foundation embedded in the soil medium is subjected to a horizontal slip disturbing force, determine its equivalent target parameters in the horizontal slip direction of the foundation-soil system, the dynamic response under horizontal slip and rocking coupled steady-state vibration, and the dynamic dissipated energy within each horizontal slip direction steady-state vibration period and rocking coupled steady-state vibration period; The rocking coupled steady-state vibration is decomposed into rocking motion and coupled motion; Step 4: When a rigid rectangular block foundation embedded in the soil medium is subjected to a vertical disturbing force, determine its equivalent target parameters in the vertical direction of the foundation-soil system and the dynamic response of the rigid rectangular block foundation under vertical vibration; Step 5: Simplify the research on the pulse wind tunnel balance foundation, use ABAQUS finite element to establish a three-dimensional analysis numerical model, calculate parameters and their constitutive models, and use the finite element method for numerical model calculation; Step 6: Obtain the basic mechanical property parameters of the rigid rectangular block foundation soil. Through the theoretical calculations in the third and fourth steps, compare the theoretical calculation results with the numerical simulation calculation results in the fifth step.

2. The method for calculating the basic vibration parameters of the pulse wind tunnel balance according to claim 1, characterized in that: In the first step, the calculation model for the vibration parameters of the pulse wind tunnel balance foundation is a rigid rectangular block foundation. The general situation of the balance foundation project is as follows: The balance foundation adopts a reinforced concrete structure, the concrete material is C30 concrete, the steel bars are HRB400, the top surface of the foundation is connected to the steel support plate by bolts, and then the balance model (1) is fixed on it. A pulse-form force acts on the balance model.

3. The method for calculating the basic vibration parameters of a pulse wind tunnel balance according to claim 1, wherein: In the third step, the motion equation of the rigid rectangular block foundation is: K x = K sx (k x + a0c x ) K β = K sβ (k β + a0c β ) K c = K sc (k c + a0c c ) a0 = ωR / V s Where: M is the mass of the rigid rectangular block foundation; I β is the moment of inertia of the rigid rectangular block foundation when deflecting about the center of gravity; h is the embedment depth of the rigid rectangular block foundation; t is time; U b is the horizontal slip amplitude of the base of the rigid rectangular block foundation; Φ β is the deflection of the rigid rectangular block foundation about the center; is the second derivative of the horizontal slip amplitude of the base of the rigid rectangular block foundation; is the second derivative of the deflection of the rigid rectangular block foundation about the center; H is the horizontal slip force; M oβ is the rocking moment; K x , K β and K c are the dynamic impedance functions based on the center of the base of the rigid rectangular block foundation, K sx , K sβ and K sc are the static stiffnesses under horizontal slip motion, rocking motion and coupled motion respectively; k x , k β and k c are the normalized stiffness coefficients, c x , c β and c c are the normalized damping coefficients, where the subscripts x, β and c represent horizontal slip motion, rocking motion and coupled motion respectively; a0 is the dimensionless frequency, V s is the shear wave velocity of the soil, and R is the characteristic length.

4. The method for calculating the basic vibration parameters of a pulsed wind tunnel balance according to claim 1, characterized in that: In the third step, the equation for the dynamic dissipated energy of the foundation-soil system within each horizontal slip direction steady-state vibration period is: where: u s is the static amplitude of the coupling effect; M x is the horizontal slip amplification factor; θ x is the phase angle; K sx is the static stiffness; e Dx is the dynamic dissipation energy factor of the horizontal slip forced vibration; P x1 is the amplitude of the horizontal slip disturbing force; E Dx Horizontal slip dynamic dissipation energy.

5. The method for calculating the basic vibration parameters of a pulse wind tunnel balance according to claim 1, characterized in that: In the third step, the equation for the dynamic dissipated energy of the foundation-soil system within each rocking coupled steady-state vibration period is: Where: φ s is the static position deflection without coupling effect; M β is the swing amplification factor; θ β is the phase angle; K sβ is the static stiffness; e Dβ is the dynamic dissipation energy factor of swing vibration; m oβ is the torque amplitude; E Dβ Swing dynamic dissipation energy.

6. The method for calculating the basic vibration parameters of a pulsed wind tunnel balance according to claim 1, wherein: In the third step, the equation for the equivalent target parameters of the horizontal slip direction foundation-soil system is: M x = u t / u s M c = hφ β / u s M β = φ β / φ s Where: u t is the amplitude of horizontal slip; u s is the static amplitude of the coupling effect; φ β is the dynamic amplitude; φ s is the static deflection of the position without the coupling effect, and h is the foundation embedment depth; M x is the horizontal slip amplification factor; M c is the coupling amplification factor; M β is the rocking amplification factor.

7. The method for calculating the basic vibration parameters of a pulsed wind tunnel balance according to claim 1, characterized in that: In the fourth step, the balance model transmits the vertical disturbing force to the balance foundation, that is, when the rigid rectangular block foundation is subjected to a vertical disturbing force, according to the foundation-soil system, the equation for the equivalent target parameters in the balance model is: K ez = K sz C ez = k ez c ez × ρV s R 2 Where: K sz is the static stiffness; k ez is the equivalent stiffness factor; c ez is the equivalent damping factor; ρ is the density; a0 is the dimensionless frequency, V s is the shear wave velocity of soil, R is the characteristic length; k z is a coefficient, depending on the dimensionless frequency; K ez is the equivalent stiffness; C ez is the equivalent damping; M ez Equivalent mass.

8. The method for calculating the basic vibration parameters of the pulse wind tunnel balance according to claim 1, characterized in that: In the fifth step, the basic assumptions introduced by the numerical model calculation method are as follows: the model and the supporting material under the action of aerodynamic load are completely elastic; the contact between the foundation and the ground meets Coulomb friction.

9. The method for calculating the basic vibration parameters of a pulse wind tunnel balance according to claim 1, wherein: In the fifth step, when the three-dimensional analysis numerical model is under the action of aerodynamic load, the balance model and the support plate, and the support plate and the balance foundation are always in contact. The Tie connection method of bonded constraint is adopted; the normal behavior between the foundation and the ground is set as hard contact, and the tangential behavior is set as the penalty function; to ensure the correctness of the numerical simulation, a grid independence test is carried out; the concrete damage plasticity constitutive model is adopted, and the Mohr-Coulomb elastoplastic model is adopted for the ground; in order to simulate the aerodynamic load action conditions of the wind tunnel on the test model, a horizontal sliding load, a vertical load and a moment are applied at the centroid of the model, and the load forms are the measured vertical disturbing force, the horizontal sliding disturbing force and the pitching moment.

10. The method for calculating the basic vibration parameters of a pulse wind tunnel balance according to claim 1, characterized in that: In the sixth step, the basic mechanical property parameters of the rigid rectangular block foundation soil are obtained, including the dynamic shear modulus G of the foundation soil, the average shear wave velocity V s , the density ρ of the rigid rectangular block foundation soil, the damping coefficient of the foundation soil, the Poisson's ratio v, and the side length of the given rigid rectangular block foundation. At the same time, the site intensity is less than 6 degrees, there is no saturated sand within a depth of 20 m, and the influence of seismic liquefaction is not considered; combining the grid independence test scheme and the calculation results with the reference values recommended in the Design Standard for Dynamic Machine Foundations GB50040-2020; The vibration parameters of the pulse wind tunnel balance foundation are obtained through the theoretical calculation model and numerical simulation.

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