Digital Analysis of the Effect of Gear Structure on the Earthquake Force

The finite element model of the vibration of the gear structure is complicated by the gear structure, and its structure is often simplified in the structural dynamic analysis. It is now simplified to a circular plate. The geometric parameters of the gear are: Z=30, m=40mm, inner diameter is 45mm, thickness is 15mm. The relevant physical parameters are: elastic modulus E=211011N/m2, Poisson's ratio is 0.3, material density=February 12, 2007 The National Natural Science Foundation of China (50575187) was received and the Natural Science Foundation of Shaanxi Province (2004E219) received 78,103kg/m3. The eight-node hexahedral element is used to divide the gear by finite element meshing by sweeping mesh division method. Its finite element model is divided into 2,160 units and 2,400 nodes as shown.
The vibration response analysis of the gear structure establishes the finite element model of the gear structure and then performs modal analysis. First, the constraint is imposed, usually the radial and axial displacement of the surface of the inner ring of the constraining gear, leaving only the rotational freedom in the axial direction. Through modal analysis, the natural frequency and mode shape of the gear structure can be obtained, ready for vibration response analysis.
The excitation force of the vibration of the gear structure is very complicated, and stiffness excitation, error excitation and meshing impact excitation are usually considered. Harmonic response analysis and transient analysis can be used for the vibration analysis of the gear structure, but the harmonic response analysis is used because the SYSNOISE software time domain analysis is not accurate enough. In ANSYS, the harmonic excitation amplitude is set to 500N, the frequency range is 05000Hz, and the action position is on the gear pitch circle. The result of the harmonic response analysis is saved to the result file File.RST, thereby obtaining the node normal velocity of the SYSNOISE acoustic boundary element model.
The surface angle at the point P on the surface S of the structure is discretized by the boundary element method, that is, the direct boundary element method is used to solve the equation. The external boundary problem in the SYSNOISE software is the direct boundary element method. The acoustic equation is [6]Ap=B(6) where: A and B are the influence matrix; p is the node sound pressure vector; v is the node normal velocity vector. The p and v at each node of the surface are solved. Interpolation can be used to obtain the sound pressure pX=a at any point X in the outer field point grid. a and b are matrixes of interpolation coefficients. The direct method is applicable to the calculation of the inner and outer sound fields with closed surface structure. In the process of solving, the sound pressure and normal velocity at the surface are first obtained, and the sound pressure, velocity and sound intensity of the inner and outer fields can be obtained by interpolation.
The 3D Acoustic Boundary Element Model SYSNOISE software does not provide a tool for meshing. When building an acoustic boundary element model, the previously created finite element model mesh can be used as an acoustic boundary element model mesh. The finite element model used for vibration analysis is exported in .cdb format and then imported into the SYSNOISE software. After clicking the menu Geometry\CoarsenMesh, select SkintheVolumes to convert the finite element model into the required boundary element model, but the node does not perform any processing. . The reason for maintaining the consistency of the finite element model nodes and the boundary element model nodes is to ensure the correctness of the vibration response data transmitted to the SYSNOISE model.
After establishing the above acoustic boundary element model, the SYSNOISE software is used to establish the field point mesh model to find the sound pressure value at any position in the radiated sound field. The spherical structure of the spherical sound field of the gear structure is established, and the center of the ball is located at the center of the gear structure.
Gear structure spherical sound field point mesh model 23 Gear structure vibration sound radiation analysis calculation reference sound pressure taken 2010-5Pa, air density = 121kg / m3, air sound speed c = 344m / s. Calculated frequency is (05000) Hz, frequency The incremental step is 100Hz. The sound pressure curve of the acoustic structure of the gear structure under harmonic excitation is shown. It can be seen from the figure that the sound pressure level of the gear structure radiates harmonic characteristics, that is, at 750Hz and its fundamental frequency. Frequency 1500Hz, 2250Hz, 3000Hz, 3750Hz, 4500Hz obvious echo pressure peaks, reflecting the connection between vibration and noise. The results of numerical calculations can only reflect the nature of structural acoustic radiation under specific constraints and excitations. Similarly, the acoustic radiation sound pressure and radiation efficiency of the gear structure under different geometric models can be obtained by changing the geometric parameters of the structure such as diameter, thickness, inner and outer diameter ratio, and the like.
Conclusion Structural acoustic radiation analysis requires mechanical dynamics, acoustics, finite element and other related theories. The computer-based numerical calculation method is used to analyze the structural vibration and acoustic radiation, which can realize the dynamic optimization design of the gear structure. The numerical results show that the analysis process of the radiated noise of the gear structure established in this paper is reasonable, and the analysis method of the radiated noise of the finite element combined with the boundary element is very convenient. At the same time of theoretical and simulation analysis, it is necessary to establish relevant experimental system optimization theory and analysis model.

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