WO2020248460A1 - Damping analysis method for pedestrian warning loudspeaker - Google Patents

Abstract

Disclosed in the present invention is a damping analysis method for a pedestrian warning loudspeaker, which solves the problems existing in a traditional test method of the necessity of preparing a sample in advance, time-consuming and laborious sample development, high costs, investment, etc. A damping analysis method for a pedestrian warning loudspeaker, comprises: providing a geometric model of a damping system of a pedestrian warning loudspeaker, the damping system comprising a loudspeaker box, a damper and a support; establishing a finite element model of the damping system according to the geometric model, solving the finite element model, and obtaining, by means of post-processing, a change relationship between a displacement transmissibility of the damping system and a frequency; wherein the finite element model is solved by using a steady state analysis method, and the theoretical equations for solving are as follows: (I); and the displacement transmissibility satisfies the following equation: (II).

Description

A method of vibration reduction analysis of pedestrian warning loudspeaker

Cross references to related applications

This application claims the priority of the Chinese patent application with the application number CN 201910510485.1 filed on June 13, 2019, the entire content of which is incorporated into this application by reference.

Technical field

The invention belongs to the field of pedestrian warning loudspeakers, and relates to a shock absorption analysis method of the pedestrian warning loudspeaker.

Background technique

With the promotion of new energy vehicles, pedestrian warning speakers have also become a focus. Since the pedestrian warning device is usually installed in the engine compartment, the pedestrian warning speaker not only needs to ensure its normal operation, but also needs to ensure that it does not affect the surrounding structure during normal operation. The shock absorber is an important component to maintain the stability of the pedestrian warning speaker structure, and it plays a role of buffering and damping. The shock absorber can reduce the influence of the pedestrian warning speaker itself on the surrounding structure, and it can also reduce the influence of the surrounding structure on the pedestrian warning speaker itself.

The traditional method is to test the damping effect of pedestrian warning speakers through experimental methods. However, the test method has a series of problems: first, it must be done after the warning device samples are made; second, in the development of shock absorbers, in order to obtain a shock absorber that meets the requirements, repeated samples are often required It is very time-consuming and labor-intensive to test multiple times; thirdly, the production of shock absorbers requires mold opening, which is expensive.

Summary of the invention

In view of the above problems, the present invention provides a method for analyzing the shock absorption of the pedestrian warning loudspeaker, which solves the need to make samples in advance in the traditional test method, the development of samples is time-consuming and laborious, high cost and investment, and has an effect on finding vulnerable points. Minor problems.

In order to achieve the above-mentioned objective, the technical solution adopted by the present invention is:

A method for analyzing the shock absorption of a pedestrian warning loudspeaker provides a geometric model of a shock absorbing system of the pedestrian warning loudspeaker. The shock absorbing system includes a speaker cabinet, a shock absorber, and a bracket; the structure of the shock absorbing system is established according to the geometric model The finite element model is used to solve the finite element model, and the relationship between the displacement transmission rate of the shock absorption system and the frequency is obtained through post-processing; wherein,

The steady-state analysis method is used to solve the finite element model, and the solved theoretical equation is as follows:

In the formula, [M] is the mass matrix, [C] is the damping matrix, [K] is the static stiffness matrix,

Is the nodal acceleration vector,

Is the nodal velocity vector, {X} is the nodal displacement vector, {F} is the excitation load vector;

The displacement transfer rate satisfies the following equation:

In the formula, T is the displacement transmission rate, ζ is the relative damping coefficient, and λ is the frequency ratio.

In one embodiment, through the post-processing, the spatial distribution of deformation, stress and strain of the shock absorption system, the relationship between the displacement amplitude and the frequency, the relationship between the speed amplitude and the frequency, and the acceleration amplitude as One or more of the frequency changes. By establishing the finite element simulation analysis model of the pedestrian warning loudspeaker, the stress, strain, displacement, velocity and acceleration of any point on the system can be calculated and the relationship between the stress, strain, displacement, velocity and acceleration of any point on the system can be calculated. The relationship between the displacement transmission rate and the frequency is used to determine whether the damping effect of the pedestrian warning speaker meets the demand. Further, the results obtained by solving the finite element model are imaged or displayed in a list through post-processing.

Preferably, establishing the finite element model for shock absorption according to the geometric model includes the following steps:

S21. Import the geometric model of the shock absorption system into the finite element analysis software;

S22. Set up physical field and material model;

S23. Define fixed boundary conditions and designated displacement;

S24. Define material properties;

S25. Divide the mesh.

More preferably, in step 21, after the geometric model is imported into the finite element analysis software, redundant points, lines, surfaces or bodies are removed.

More preferably, in step S22, a solid mechanics physics field is selected to simulate the deformation of the shock absorption system of the pedestrian warning speaker, and the material model is set as a linear elastic model.

More preferably, in step S23, the boundary of the mounting point of the support of the shock absorption system is set as a fixed constraint boundary, and displacement is loaded on the shock absorption system.

More preferably, in step S24, the material properties include Young's modulus, density, Poisson's ratio, and damping.

In a specific and preferred embodiment, establishing the finite element model of the shock absorption according to the geometric model includes the following steps:

1. Establish a simulation analysis geometric model of the shock absorption system. The specific modeling steps are as follows:

A. Import the geometric model of the shock absorption system: import the three-dimensional geometric model of the shock absorption system of the pedestrian warning loudspeaker into the finite element analysis software;

B. Geometry cleanup: In the process of finite element model construction, the redundant points, lines, surfaces and volumes in the geometric model will have a greater impact on the mesh quality, so after importing the geometric model, use the geometric cleanup function to clean the model Redundant points, lines, areas and volumes in the middle to improve mesh quality;

2. Set up the physical field and material model, the detailed steps are as follows:

A. Set up the physical field: select the "solid mechanics" physical field to simulate and analyze the pedestrian warning speaker;

B. Set the material model: set the shock absorption system as a linear elastic material model, and set the material damping;

3. Define boundary conditions and loads. The detailed steps are as follows:

A. Boundary fixed constraint: set the boundary of the bracket installation point as a fixed constraint boundary;

B. Specified displacement: load the displacement perpendicular to the surface on the speaker;

4. Define material properties: The material properties of the finite element simulation model are related to the physical field, material model and boundary conditions. The set material parameters include Young's modulus, density, Poisson's ratio, and damping;

5. Grid division: Specify the grid unit type and grid size to generate the finite element grid unit, and the pedestrian warning speaker adopts the free tetrahedral grid type; here you need to customize the grid size and perform appropriate mesh refinement. Make the calculation result more accurate.

In one embodiment, the seismic reduction analysis method further includes the step of simplifying the geometric model, using three-dimensional drawing software to simplify the geometric model and importing it into finite element analysis software, or using finite element software (such as COMSOL Multiphysics) simplify the geometric model.

The present invention adopts the above scheme and has the following advantages compared with the prior art:

There is no need to make the pedestrian warning loudspeaker shock absorption samples (including loudspeakers, loudspeaker brackets and shock absorbers) in advance, and use numerical simulation analysis methods to analyze the shock absorption system model and calculate the displacement transfer at any point on the shock absorption system through post-processing calculations The relationship between the rate and the frequency change, and then determine whether the shock absorption effect of the shock absorber meets the demand, thereby greatly improving the efficiency of product design and saving research and development costs and time.

Description of the drawings

In order to explain the technical solution of the present invention more clearly, the following will briefly introduce the drawings used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. Ordinary technicians can obtain other drawings based on these drawings without creative work.

Fig. 1 is a flowchart of a method for analyzing vibration reduction of a pedestrian warning speaker according to an embodiment of the present invention;

Figure 2 is a schematic diagram of a shock absorption system of a pedestrian warning speaker;

Fig. 3 is a simulation geometric model of the shock absorption system of the pedestrian warning speaker shown in Fig. 2;

Figure 4 shows the fixed restraining surface of the shock absorption system;

Figure 5 shows the designated displacement body of the shock absorption system;

Figure 6 shows the finite element network model of the shock absorption system;

Figure 7 shows a stress distribution diagram of the shock absorption system;

Figure 8 shows the strain distribution diagram of the shock absorption system;

Figure 9 shows the displacement size distribution and deformation of the shock absorption system;

Figure 10 shows the relationship between the displacement amplitude of a point on the shock absorption system and the frequency;

Figure 11 shows the relationship between the speed amplitude of a point on the shock absorption system and the frequency;

Figure 12 shows the relationship between the acceleration amplitude of a point on the shock absorption system and the frequency;

Figure 13 shows the relationship between the displacement transmission rate of a point on the shock absorption system and the frequency.

Detailed ways

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted here that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

In this embodiment, a pedestrian warning loudspeaker is taken as an example, and the vibration reduction effect of the pedestrian warning loudspeaker is analyzed by a numerical simulation method. Fig. 1 shows a flow chart of the vibration reduction analysis method of the pedestrian warning loudspeaker of this embodiment. The specific steps are as follows.

1. Preparation

The analysis object of the shock absorption analysis method is specifically the shock absorption system of the pedestrian warning speaker. Fig. 2 shows the three-dimensional geometric model of the shock absorption system of the pedestrian warning loudspeaker analyzed in this embodiment, which is drawn by the three-dimensional drawing software. As shown in Figure 2, the damping system specifically includes a speaker cabinet 1, a shock absorber 2, and a bracket 3. The speaker is installed in the speaker cabinet 1, the shock absorber 2 is installed on the speaker cabinet 1, and the bracket 3 is connected. Install the entire pedestrian warning speaker on the shock absorber 2, such as in the engine compartment.

Second, establish a finite element model

1. Add spatial dimensions, physics interfaces and research types. Open the COMSOL Multiphysics software, set the spatial dimension to "3D", select the physical field as "Solid Mechanics", and select the research type as "Frequency Domain".

2. Establish a finite element model of the shock absorption system of the pedestrian warning speaker. The modeling process is as follows:

A. Import the simplified geometric model of the damping system: use "geometry" related operations to import the three-dimensional geometric model of the damping system.

B. Geometry cleanup: Under the "geometry" operation, the geometry cleanup function is used to clean up redundant points, lines, surfaces and bodies in the model, as shown in Figure 3.

3. Set the physical field: In the setting window of "Solid Mechanics", set the geometric field of "Solid Mechanics" applicable to pedestrian warning speakers.

4. Set the material model: set the material model of the speaker cabinet, shock absorber and bracket to "linear elastic material" under the "solid mechanics" physics field, and add the "damping" function interface for the linear elastic material, and make " Damping is applied to the geometric domain of the shock absorption system.

5. Set boundary conditions and loads: set boundary fixed constraints and designated displacements under the "solid mechanics" physics field. The detailed setting steps are as follows:

A. Boundary fixation constraint: Set the surface corresponding to the bracket mounting hole 30 shown in FIG. 4 as "solid mechanics".

B. Designated displacement: As shown in Figure 5, load a displacement of U0y=1mm, and the direction of displacement is along the -Y direction.

6. Defining material properties: Use "material" related operations to set the material parameters of the speaker cabinet, shock absorber and bracket geometry in the model. The material parameters defined in this embodiment are shown in Table 1.

Table 1

7. Meshing: Figure 6 shows the finite element mesh model used in this embodiment. The meshing steps are as follows:

Specify the mesh type of the speaker cabinet geometric domain as "free tetrahedral mesh", "custom" free tetrahedral mesh size: "refine" the grid of the bracket; default the grid of the speaker cabinet Setting; defines the maximum grid of the shock absorber as 1mm. Finally, "build all" generates the finite element mesh shown in Figure 6.

Three, solution and post-processing

1. Frequency domain research.

A. Set the solver: set the frequency range of the "frequency domain" study: 10^{range(log10(1),1/20,log10(8000))}.

B. Calculation: After the setting is completed, the finite element model is solved, and the calculation process is realized by the built-in algorithm of COMSOL software.

2. Post-processing. The results that can be viewed through post-processing are as follows:

A. Add a "three-dimensional drawing group", use "solid" drawing, enter the expression solid.mises, modify the viewing frequency point to 1415.9Hz, and draw a stress distribution diagram on the pedestrian warning speaker at 1415.9Hz, as shown in Figure 7. It can be seen from Figure 7 that the stress near the mounting hole of the bracket is greater than other positions.

B. Add "three-dimensional drawing group", use "solid" drawing, enter the expression abs(solid.evol), modify the viewing frequency point to 1415.9Hz, and draw the strain distribution map on the pedestrian warning speaker at 1415.9Hz, as shown in Figure 8. Shown.

C. Add "3D drawing group", use "body" drawing, enter the expression solid.disp, add "deformation" under "body" drawing, enter the expressions of X component, Y component, and Z component as u, v, w, set the zoom factor to 10, modify the viewing frequency point to 1415.9Hz, and draw the displacement distribution map and the amount of deformation (zoomed) on the speaker frame at 1415.9Hz, as shown in Figure 9. It can be seen from Figure 9 that the deformation of the pedestrian warning speaker is mainly concentrated on the bracket.

D. Add "one-dimensional drawing group", use "point diagram" to draw, select the point on the boundary load surface (point number: 233), enter the expression: solid.uAmpY, draw the variation of the displacement amplitude Y component with frequency The relationship is shown in Figure 10.

E. Add "one-dimensional drawing group", use "point diagram" to draw, select the point on the boundary load surface (point number: 233), enter the expression: solid.uAmp_tY, draw the velocity amplitude Y component with frequency The relationship is shown in Figure 11.

F. Add "one-dimensional drawing group", use "point diagram" to draw, select the point on the boundary load surface (point number: 233), enter the expression: solid.uAmp_ttY, draw the acceleration amplitude Y component with frequency The relationship is shown in Figure 12.

G. Add "one-dimensional drawing group", use "point diagram" to draw, select the point on the boundary load surface (point number: 233), enter the expression: abs(v)/1[mm]*100, draw pedestrians The relationship between the displacement transmission rate of the warning speaker and the frequency is shown in Figure 13.

The above results are used to provide reference for the design and manufacture of the shock absorption system of pedestrian warning speakers.

The above-mentioned embodiments are only to illustrate the technical concept and features of the present invention, and are a preferred embodiment. The purpose is that those familiar with the technology can understand the content of the present invention and implement it accordingly, and cannot limit the present invention. protected range.

Claims (9)

1. A method for damping analysis of pedestrian warning loudspeakers is characterized in that a geometric model of a pedestrian warning loudspeaker damping system is provided. The damping system includes a speaker cabinet, a shock absorber and a bracket; The finite element model of the damping system is solved, and the relationship between the displacement transmission rate of the damping system and the frequency is obtained through post-processing; wherein,

   The steady-state analysis method is used to solve the finite element model, and the solved theoretical equation is as follows:

   

   In the formula, [M] is the mass matrix, [C] is the damping matrix, [K] is the static stiffness matrix,

   

   Is the nodal acceleration vector,

   

   Is the nodal velocity vector, {X} is the nodal displacement vector, {F} is the excitation load vector;

   The displacement transfer rate satisfies the following equation:

   

   In the formula, T is the displacement transmission rate, ζ is the relative damping coefficient, and λ is the frequency ratio.
2. The shock absorption analysis method according to claim 1, characterized in that the spatial distribution of the deformation, stress and strain of the shock absorption system, the relationship between the displacement amplitude and the frequency, and the velocity amplitude of the shock absorption system are also obtained through the post-processing. One or more of the relationship between changes with frequency and the relationship between acceleration amplitude and frequency.
3. The seismic reduction analysis method according to claim 1, wherein the establishment of the finite element model of the seismic reduction according to the geometric model comprises the following steps:

   S21. Import the geometric model of the shock absorption system into the finite element analysis software;

   S22. Set up physical field and material model;

   S23. Define fixed boundary conditions and designated displacement;

   S24. Define material properties;

   S25. Divide the mesh.
4. The shock absorption analysis method according to claim 3, wherein in step 21, after the geometric model is imported into the finite element analysis software, redundant points, lines, surfaces or bodies are removed.
5. The shock absorption analysis method according to claim 3, wherein in step S22, a solid mechanics physics field is selected to simulate the deformation of the shock absorption system of the pedestrian warning speaker, and the material model is set as a linear elastic model.
6. The shock absorption analysis method according to claim 3, wherein in step S23, the boundary of the bracket installation point of the shock absorption system is set as a fixed constraint boundary, and a displacement is loaded on the shock absorption system.
7. The shock absorption analysis method according to claim 3, wherein in step S24, the material properties include Young's modulus, density, Poisson's ratio, and damping.
8. The seismic reduction analysis method according to claim 1, wherein the seismic reduction analysis method further comprises the step of simplifying the geometric model, using three-dimensional drawing software to simplify the geometric model and importing it into finite element analysis software Or use finite element software to simplify the geometric model.
9. The seismic reduction analysis method according to claim 1, wherein the establishment of the finite element model of the seismic reduction according to the geometric model comprises the following steps:

   1). Establish a simulation analysis geometric model of the shock absorption system:

   A. Import the geometric model of the shock absorption system: import the three-dimensional geometric model of the shock absorption system of the pedestrian warning loudspeaker into the finite element analysis software;

   B. Geometry cleanup: After importing the geometric model, use the geometry cleanup function to remove redundant points, lines, surfaces and bodies in the model to improve mesh quality;

   2). Set up physical field and material model:

   A. Set up the physical field: select the "solid mechanics" physical field to simulate and analyze the pedestrian warning speaker;

   B. Set the material model: set the shock absorption system as a linear elastic material model, and set the material damping;

   3). Define boundary conditions and loads:

   A. Boundary fixed constraint: set the boundary of the bracket installation point as a fixed constraint boundary;

   B. Specified displacement: load the displacement perpendicular to the surface on the speaker;

   4) Define material properties: material parameters include Young's modulus, density, Poisson's ratio, and damping;

   5) Grid division: Specify the grid unit type and grid size to generate finite element grid units, the pedestrian warning loudspeaker adopts the free tetrahedral grid type; customize the grid size, and perform appropriate mesh refinement.

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