A method for establishing a discrete model of a pipe clamp using matrix elements

Abstract

The application belongs to the field of aero-engine clamp design, and is a method for establishing a discrete model of a pipeline clamp using a matrix unit. A corresponding physical model is first established, and then node 1 and node 2 are set to simulate the two ends of the clamp in the physical model. A mechanical pipeline is set, thereby establishing a mechanical model. Then, a coordinate system corresponding to the mechanical model is established, the corresponding relationship between the coordinate system and the coordinate system in the physical model is obtained, and then the node 1 and the node 2 are both set to have 6 degrees of freedom, and a 12x12 order matrix is established, so as to convert the mechanical model into a mathematical model. The stiffness characteristics and the damping characteristics in each direction can be simultaneously equivalent, the modeling is simple and fast, and the calculation accuracy can be improved. When nonlinear simulation is performed, the values of each row and each column of the matrix unit are adjusted as appropriate, the nonlinear characteristics of the clamp can be simulated, the nonlinear calculation of the pipeline system is supported, and the simulation efficiency is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aero-engine clamp design, and particularly relates to a method for establishing a discrete model of a clamp for a pipeline using matrix units. BACKGROUND

[0002] The aero-engine clamp is mainly used for the relative fixation between a pipeline and a casing or between pipelines, the former generally uses a single clamp, and the latter generally uses a double clamp, and the system damping is formed by the metal rubber in the clamp. The stiffness and damping of the clamp have a significant influence on the dynamic characteristics of the pipeline system, and they play an important role in the frequency modulation and vibration reduction of the pipeline system, and the determination of the number and position of the clamps is one of the focuses of the pipeline system design.

[0003] How to accurately establish the discrete model of the aero-engine clamp is crucial to the study of the dynamic characteristics of the pipeline system, especially for the metal rubber clamp. The metal rubber is a large-damping nonlinear material, and the friction contact between the metal liner formed by the metal rubber and the pipeline also leads to the very obvious nonlinear characteristics of the clamp. At present, the modeling of the clamp is mainly through the discretization of shell elements or solid elements, and the displacement constraints of the public nodes between different structural parts are bound or the contact characteristics of the public nodes are set.

[0004] The method for establishing the discrete model of the clamp by using shell elements or solid elements has the following disadvantages:

[0005] 1) The aero-engine clamp has obvious multi-layer structure characteristics, and the use of shell elements for discretization requires that it be regarded as a multi-layer integrated structure containing several material layers, and the movement friction and other behaviors and effects between the upper and lower halves of the clamp and the metal rubber cannot be forcedly bound by the public nodes. The modeling process is complex, the solving speed is slow, and the calculation accuracy of the dynamic characteristics cannot be guaranteed;

[0006] 2) The overall size of the aero-engine clamp is small, and the use of solid elements for discretization requires that the grid of each layer of structural parts be refined to ensure that each layer can reflect the characteristics of the beam, and the public nodes are bound. It also cannot solve the problem of describing the behavior characteristics of the metal rubber, and the model is large, and the modeling process is complex, the solving time is too long, and the calculation accuracy of the dynamic characteristics is limited;

[0007] 3) The metal rubber clamp has very obvious nonlinear characteristics, and the binding of the public nodes or the setting of the contact characteristics of the public nodes cannot support nonlinear calculation.

[0008] Therefore, it is necessary to develop a method for establishing the discrete model of the aero-engine clamp to facilitate fast solving and ensure the calculation accuracy. SUMMARY

[0009] The application aims to provide a method for establishing a discrete model of a pipeline clamp using matrix units to solve the problems of complex modeling speed and slow solving speed of the discrete model of the existing aero-engine clamp.

[0010] The technical solution of the application is a method for establishing a discrete model of a pipeline clamp using matrix units, comprising:

[0011] Confirming the type of the clamp, establishing a corresponding physical model, setting node 1 and node 2 to simulate both ends of the clamp in the physical model, setting a mechanical pipeline, connecting the mechanical pipeline with the corresponding nodes to form a mechanical model of the clamp, and simulating the fluid influence of the mechanical model;

[0012] According to the selected one of the double-connection ground clamp and the single-connection ground clamp, a coordinate system corresponding to the mechanical model is established, and the corresponding relationship between the coordinate system and the coordinate system in the physical model is obtained;

[0013] Node 1 and node 2 are both set with 6 degrees of freedom, and a 12x12 order matrix is established, the values of each row and each column in the matrix unit are set according to the corresponding relationship between the coordinate system of the mechanical model and the coordinate system of the physical model, and the stiffness matrix unit and the damping matrix unit are respectively formed.

[0014] The value increment of one or more values in the stiffness matrix unit or the damping matrix unit is set in a loop to perform nonlinear simulation on the clamp.

[0015] Preferably, the stiffness matrix unit of the single-connection ground clamp is:

[0016]

[0017] In the formula, k x , k y and k z are the linear stiffness of the single-connection ground clamp along the directions of the coordinate axes, k θx , k θy and k θz are the angular stiffness of the single-connection ground clamp around the directions of the coordinate axes;

[0018] The damping matrix unit of the single-connection ground clamp is:

[0019]

[0020] In the formula, c x , c y and c z are the dampings of the clamp along the directions of the coordinate axes, c θx , c θy and c θz are the dampings of the clamp around the directions of the coordinate axes.

[0021] The stiffness matrix unit of the double suspension ground clamp is:

[0022]

[0023] wherein k x ′, k y ′ and k z ′ are linear stiffness of the clamp along the direction of each coordinate axis, k θ ′ x , k θ ′ y and k θ ′ z are angular stiffness of the clamp around the direction of each coordinate axis, respectively.

[0024] The damping matrix unit of the double suspension ground clamp is:

[0025]

[0026] wherein c′ x , c′ y and c′ z are damping of the clamp along the direction of each coordinate axis, c′ θx , c′ θy and c′ θz are damping of the clamp around the direction of each coordinate axis, respectively.

[0027] Preferably, when the coordinate system of the matrix unit is inconsistent with the coordinate system of the physical model, then one or more specific numerical values in the matrix are transformed according to the angle relationship between the coordinate system in the mechanical model and the coordinate system in the physical model.

[0028] Preferably, the coordinate system of the single suspension ground clamp is defined as:

[0029] Taking the center of the pipeline as the coordinate origin, the half-split opening direction is defined as the positive direction of the x-axis, the direction perpendicular to the x-axis and pointing to the lower half is defined as the positive direction of the y-axis, and the z-axis is determined according to the right-hand rule.

[0030] The coordinate system of the double suspension ground clamp is defined as:

[0031] Taking the center of one of the pipelines as the coordinate origin, the half-split opening direction is defined as the positive direction of the x-axis, the direction perpendicular to the x-axis and pointing to the lower half is defined as the positive direction of the y-axis, and the z-axis is determined according to the right-hand rule.

[0032] Preferably, the fluid influence of the mechanical model is simulated by using an acoustic-elastic coupling model or an additional mass model, and the mechanical pipeline is simulated by using a pipe element or a shell element.

[0033] Preferably, the specific method for nonlinear simulation of the clamp by the matrix unit is:

[0034] Determine the input parameters that need to be changed, set several nodes from small to large for the value of each input parameter, the difference value of each adjacent node is a value increment, according to the specific test project, select one or more input parameters that need to be changed, set a corresponding value increment for each input parameter, then obtain the changes of other parameters in the stiffness matrix element and the damping matrix element, calculate the regression curve, and finally obtain the stiffness value and the damping value of the clamp in each direction according to the regression curve.

[0035] The method for establishing a discrete model of a pipe clamp using a matrix element provided by the present application first establishes a corresponding physical model according to the type of the clamp, then sets node 1 and node 2 to simulate the two ends of the clamp in the physical model, sets a mechanical pipeline, simulates the fluid influence of the mechanical model, establishes a mechanical model, thereby simplifying the model, then establishes a coordinate system corresponding to the mechanical model, obtains the corresponding relationship between the coordinate system and the coordinate system in the physical model, realizes data conversion between the physical model and the mechanical model, sets 6 degrees of freedom for node 1 and node 2, and establishes a 12x12 order matrix, sets the values of each row and each column in the matrix element according to the corresponding relationship between the coordinate system of the mechanical model and the coordinate system of the physical model, converts the mechanical model into a mathematical model, which can simultaneously equivalent the stiffness characteristics and the damping characteristics in each direction, the modeling is simple and fast, and the calculation accuracy can be improved; the overall model has a small number of element units, and the matrix element has the characteristics of symmetry and sparsity, which facilitates fast solution; when nonlinear simulation is performed, the values of each row and each column in the matrix element can be adjusted to simulate the nonlinear characteristics of the clamp and support the nonlinear calculation of the pipeline system, thereby greatly improving the simulation efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions provided by the present application, the following will briefly introduce the drawings. Obviously, the drawings described below are only some embodiments of the present application.

[0037] Figure 1 It is a schematic diagram of the overall process of the present application;

[0038] Figure 2 It is a schematic diagram of the physical model of the single ground connection clamp of the present application;

[0039] Figure 3 It is a schematic diagram of the physical model of the double ground connection clamp of the present application;

[0040] Figure 4 It is a schematic diagram of the mechanical model of the single ground connection clamp of the present application;

[0041] Figure 5 It is a schematic diagram of the mechanical model of the double ground connection clamp of the present application;

[0042] Figure 6 A schematic diagram is defined for the direction of the coordinate system of the single-connection ground clamp of the present application.

[0043] Figure 7 A schematic diagram is defined for the direction of the coordinate system of the double-connection suspension clamp of the present application.

[0044] 1, first pipe; 2, single-connection clamp upper half; 3, single-connection clamp lower half; 4, first metal gasket; 5, second metal gasket; 6, first bolt; 7, nut; 8, second pipe; 9, third metal gasket; 10, double-connection clamp lower half; 11, fourth metal gasket; 12, spacer sleeve; 13, third pipe; 14, fifth metal gasket; 15, sixth metal gasket; 16, double-connection clamp upper half; 17, second bolt. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described in more detail below in combination with the drawings in the embodiments of the present application.

[0046] A method for establishing a discrete model of a clamp for a pipeline using a matrix unit. In the process of clamping discretization, the present application uses a matrix unit to equivalently perform stiffness or damping. The matrix unit has a total of 2 nodes, each node has 6 degrees of freedom, and one or more numerical values in the stiffness matrix unit or the damping matrix unit are cyclically set to a numerical increment. The clamp is nonlinearly simulated.

[0047] As shown in Figure 1 , the specific steps include:

[0048] Step S100, confirming the type of the clamp, establishing the corresponding physical model, setting node 1 and node 2 to simulate both ends of the clamp in the physical model, setting a mechanical pipeline, connecting the mechanical pipeline with the corresponding node to form a mechanical model of the clamp, and simulating the fluid influence of the mechanical model;

[0049] As shown in Figure 2 , for a single-connection ground clamp, one end is connected to a first pipeline 1, and the other end is connected to a casing, as shown in Figure 2 , including a single-connection clamp upper half 2, a single-connection clamp lower half 3, a first metal gasket 4, a second metal gasket 5, a first bolt 6, and a nut 7. The single-connection clamp upper half 2 and the single-connection clamp lower half 3 are respectively sleeved on the upper and lower sides of the first pipeline 1, the first metal gasket 4 is arranged between the single-connection clamp upper half 2 and the pipeline, the second metal gasket 5 is arranged between the single-connection clamp lower half 3 and the pipeline, and the first bolt 6 and the nut 7 are threadedly connected to the side of the single-connection clamp upper half 2 and the single-connection clamp lower half 3 away from the pipeline. The corresponding mechanical model is as shown in Figure 4 .

[0050] As shown in Figure 3As shown, for the double suspension ground clamp, its two ends are connected with the second pipeline 8 and the third pipeline 13 respectively, and it comprises a double clamp upper half 16, a double clamp lower half 10, a third metal gasket 9, a fourth metal gasket 11, a fifth metal gasket 14, a sixth metal gasket 15, a distance screw sleeve 12 and a second bolt 17. The third metal gasket 9, the fourth metal gasket 11, the double clamp upper half 16 and the double clamp lower half 10 are cooperatively sleeved on the second pipeline 8, the fifth metal gasket 14, the sixth metal gasket 15, the double clamp upper half 16 and the double clamp lower half 10 are cooperatively sleeved on the third pipeline 13, and the distance screw sleeve 12 and the second bolt 17 are threadedly connected in the middle of the double clamp upper half 16 and the double clamp lower half 10. The corresponding mechanical model is as shown in Figure 5

[0051] The two ends of the single ground clamp can be simulated by two nodes respectively, and the mechanical properties of the nodes can be directly compared from the physical model, which is more accurate and convenient.

[0052] The mechanical pipeline can be simulated by a tube unit or a shell unit.

[0053] The fluid influence can be established according to specific conditions to establish an acoustic-elastic coupling model or an additional mass model.

[0054] In this way, the corresponding mechanical model is established according to the physical model, the model is preliminarily simplified, and the modeling is simple.

[0055] In step S200, according to the selected one of the double suspension ground clamp and the single ground clamp, a coordinate system corresponding to the mechanical model is established, and the corresponding relationship between the coordinate system and the coordinate system in the physical model is obtained.

[0056] As shown in Figure 6 Preferably, the coordinate system of the single ground clamp is defined as:

[0057] The center of the pipeline is taken as the coordinate origin, the half-split opening direction is defined as the positive direction of the x-axis, the direction perpendicular to the x-axis and pointing to the lower half is defined as the positive direction of the y-axis, and the z-axis is determined according to the right-hand rule.

[0058] As shown in Figure 7 The coordinate system of the double suspension ground clamp is defined as:

[0059] One of the centers of the pipelines is taken as the coordinate origin, the half-split opening direction is defined as the positive direction of the x-axis, the direction perpendicular to the x-axis and pointing to the lower half is defined as the positive direction of the y-axis, and the z-axis is determined according to the right-hand rule.

[0060] When modeling by using commercial software, the initial coordinate system of the node is consistent with the overall coordinate system of the physical model by default, and if it is inconsistent with the defined coordinate system direction of the clamp, the node coordinate system in the model needs to be rotated to ensure the accuracy of the stiffness and damping values. ​

[0061] The data conversion between the coordinate system corresponding to the physical model and the coordinate system corresponding to the mechanical model can be realized by establishing the coordinate system.

[0062] In step S300, the node 1 and the node 2 are set with 6 degrees of freedom, and 12x12 order matrices are established. The values of each row and each column in the matrix unit are set according to the corresponding relationship between the coordinate system of the mechanical model and the coordinate system of the physical model, and the stiffness matrix unit and the damping matrix unit are respectively formed.

[0063] Preferably, the stiffness matrix unit of the single-coupling ground clamp is:

[0064]

[0065] In the formula, k x , k y and k z are the linear stiffness of the single-coupling ground clamp along the directions of the coordinate axes, respectively, k θx , k θy and k θz are the angular stiffness of the single-coupling ground clamp around the directions of the coordinate axes, respectively.

[0066] The damping matrix unit of the single-coupling ground clamp is:

[0067]

[0068] In the formula, c x , c y and c z are the damping of the clamp along the directions of the coordinate axes, respectively, c θx , c θy and c θz are the damping of the clamp around the directions of the coordinate axes, respectively.

[0069] The stiffness matrix unit of the double-coupling suspended clamp is:

[0070]

[0071] In the formula, k x ', k y ' and k z ' are the linear stiffness of the clamp along the directions of the coordinate axes, respectively, k θ ', x k θ ', y k θ ' and k z ' are the angular stiffness of the clamp around the directions of the coordinate axes, respectively.

[0072] The damping matrix unit of the double-coupling suspended clamp is:

[0073]

[0074] In the formula, c′ x , c′ y , and c′ z are the dampings of the clamp along the directions of the respective coordinate axes, c′ θx , c′ θy , and c′ θz are the dampings of the clamp around the directions of the respective coordinate axes.

[0075] When the coordinate system of the matrix unit is inconsistent with the coordinate system of the physical model, one or more specific values in the matrix are transformed according to the angle relationship between the coordinate system in the mechanical model and the coordinate system in the physical model, and the value of 0 in the matrix may be non-0 at this time.

[0076] By converting the mechanical model into a matrix unit, the equivalence between the mechanical model and the mathematical model is realized, the model is further simplified, and the calculation efficiency and accuracy are improved.

[0077] In step S400, a value increment of one or more values in the stiffness matrix unit or the damping matrix unit is set in a loop, and the clamp is nonlinearly simulated.

[0078] Preferably, the specific method for nonlinearly simulating the clamp by the matrix unit is as follows:

[0079] The input parameters that need to be changed are determined, a plurality of nodes are set from small to large for the value of each input parameter, the difference between each adjacent node is a value increment, one or more input parameters that need to be changed are selected according to a specific test item, each input parameter is set with a corresponding value increment, and then the changes of other parameters in the stiffness matrix unit and the damping matrix unit are obtained, a regression curve is calculated, and finally the stiffness values and the damping values of the clamp in each direction are obtained according to the regression curve.

[0080] In this way, when the nonlinear model is performed, the simulation of the nonlinear characteristics, including the hysteresis characteristics, the piecewise linearity, and the like, can be performed only by the transformation of the parameters, which is more simple and effective.

[0081] The application first establishes a corresponding physical model according to the clamp type, then sets node 1 and node 2 to simulate two ends of the clamp in the physical model, sets a mechanical pipeline, simulates fluid influence of the mechanical model, establishes a mechanical model, thereby simplifying the model, then establishes a coordinate system corresponding to the mechanical model, obtains a corresponding relationship between the coordinate system and a coordinate system in the physical model, realizes data conversion between the physical model and the mechanical model, then sets 6 degrees of freedom for node 1 and node 2, establishes a 12x12 order matrix, sets values of each row and each column in the matrix unit according to the corresponding relationship between the coordinate system of the mechanical model and the coordinate system of the physical model, converts the mechanical model into a mathematical model, can simultaneously equivalent stiffness characteristics and damping characteristics in each direction, is simple and fast in modeling, and can improve calculation accuracy; the overall model has a small number of unit quantities, and the matrix unit has the characteristics of symmetry and sparsity, facilitating fast solution; when nonlinear simulation is performed, the values of each row and each column in the matrix unit can be adjusted to simulate nonlinear characteristics of the clamp, support nonlinear calculation of the pipeline system, and greatly improve simulation efficiency.

[0082] The above merely provides a specific implementation manner of the application, but the protection scope of the application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A method for establishing a discretized model of pipe clamps using matrix elements, characterized in that, The application relates to a method for simulating a clamp. The method comprises the following steps: Confirming the type of the clamp, establishing a corresponding physical model, setting a node 1 and a node 2 to simulate two ends of the clamp in the physical model, setting a mechanical pipeline, connecting the mechanical pipeline with corresponding nodes to form a mechanical model of the clamp and simulating fluid influence of the mechanical model; According to the selected one of the double-suspension clamp and the single-connection clamp, a coordinate system corresponding to the mechanical model is established, and the corresponding relationship between the coordinate system and a coordinate system in the physical model is obtained; The node 1 and the node 2 are both provided with six degrees of freedom, and a 12x12 matrix is established; the values of each row and each column in the matrix unit are set according to the corresponding relationship between the coordinate system of the mechanical model and the coordinate system of the physical model, so as to form a stiffness matrix unit and a damping matrix unit; The values of one or more values in the stiffness matrix unit or the damping matrix unit are set in a value increment, and the clamp is simulated in a nonlinear manner; where k x , k y , and k z are linear stiffnesses of the single-coupling ground clamp in the directions of the respective coordinate axes, and k θx , k θy , and k θz are angular stiffnesses of the single-coupling ground clamp in the directions of the respective coordinate axes. The stiffness matrix unit of the single-connection clamp is as follows: where c x , c y , and c z are the dampings of the clamp in the directions of the respective coordinate axes, and c θx , c θy , and c θz are the dampings of the clamp around the respective coordinate axes.

2. The method of claim 1, wherein the matrix unit is used to establish a discrete model of the pipe clamp, and The damping matrix unit of the single-connection clamp is as follows: where k' x , k' y , and k' z are the linear stiffness of the clamp in the respective coordinate axis directions, and k' θx , k' θy , and k' θz are the angular stiffness of the clamp about the respective coordinate axis directions. The stiffness matrix unit of the double-suspension clamp is as follows: In the formula, c′ x c′ y and c′ z These represent the damping of the clamp along each coordinate axis, c′ θx c′ θy and c′ θz These represent the damping of the clamp around each coordinate axis.

3. The method of claim 2, wherein the matrix unit is used to establish a discrete model of the pipe clamp, and The damping matrix unit of the double-suspension clamp is as follows:

4. The method of claim 1, wherein the matrix unit is used to establish a discrete model of the pipe clamp, and When the coordinate system of the matrix unit is inconsistent with the coordinate system of the physical model, one or more specific values in the matrix are transformed according to the angle relationship between the coordinate system in the mechanical model and the coordinate system in the physical model. The coordinate system of the single-connection clamp is defined as follows: The center of the pipeline is taken as the coordinate origin, the half-split opening direction is defined as the positive direction of the x-axis, the y-axis is defined as the positive direction of the downward half direction which is perpendicular to the x-axis, and the z-axis is determined according to the right-hand rule; The coordinate system of the double-suspension clamp is defined as follows:

5. The method of claim 1, wherein the matrix unit is used to establish a discrete model of the pipe clamp, and the method further comprises: The center of one of the pipelines is taken as the coordinate origin, the half-split opening direction is defined as the positive direction of the x-axis, the y-axis is defined as the positive direction of the downward half direction which is perpendicular to the x-axis, and the z-axis is determined according to the right-hand rule. ​ 6. The method of claim 1, wherein the matrix unit is used to establish a discrete model of the pipe clamp, and The acoustic-elastic coupling model or the additional mass model is adopted to simulate the fluid influence of the mechanical model, and the pipe unit or the shell unit is adopted to simulate the mechanical pipeline. The specific method for simulating the clamp through the matrix unit in a nonlinear manner is as follows: The input parameters that need to be changed are determined, a plurality of nodes are set for the values of each input parameter from small to large, the difference between each adjacent node is a value increment, one or more input parameters that need to be changed are selected according to a specific test item, each input parameter is provided with a corresponding value increment, the changes of other parameters in the stiffness matrix unit and the damping matrix unit are obtained, a regression curve is calculated, and finally the stiffness values and the damping values of the clamp in each direction are obtained according to the regression curve.

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