Mine excavation silencer bracket vibration reduction and lightweight design analysis method based on NVH (Noise Vibration and Harshness)

Abstract

The invention discloses an NVH (Noise Vibration and Harshness)-based mining muffler bracket vibration reduction and lightweight design analysis method, which belongs to the technical field of mining machinery and comprises the following steps of: cleaning a bracket after modeling, extracting a middle surface of the bracket, meshing the bracket, carrying out material assignment on a bracket model, exciting the bracket at 0-200Hz, and carrying out modal analysis. The bracket mode is calculated to obtain a weighting coefficient, the strain energy superposition of the bracket mode is calculated, and the bracket is optimized according to the result. The bracket has the advantages that the problem of bracket resonance is solved, and the mass of the bracket is increased to the minimum as much as possible, so that better fuel economy is obtained, and the product cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of mining machinery, and in particular to a vibration reduction and lightweight design analysis method for a muffler bracket of a mining excavator based on NVH. Background Art

[0002] The mining excavator uses a high-power diesel engine. The engine itself has large vibrations, and the mining excavator has instantaneous impact vibrations during operation, which will cause the muffler bracket on the mining excavator to vibrate. If the natural frequency of the muffler bracket on the mining excavator is the same as the external excitation frequency, it will cause the bracket to resonate, further amplifying the vibration. Over time, it will cause vibration fatigue failure of the excavator muffler bracket.

[0003] In order to improve the vibration fatigue life of the excavator muffler bracket, the existing technology mainly increases the thickness of the bracket structural plate, adds reinforcing plates, and improves the structural strength of the bracket to improve the vibration fatigue life of the bracket.

[0004] Although the existing technical method can solve the problem of vibration fatigue failure of the bracket, it will significantly increase the mass of the bracket and cannot effectively solve the problem of bracket vibration or resonance. Summary of the Invention

[0005] The present invention aims to solve the technical problems mentioned in the above background art, and provides a vibration reduction and lightweight design analysis method for a muffler bracket of a mining excavator based on NVH, which solves the problem of bracket resonance and minimizes the increase in the mass of the bracket as much as possible to obtain better fuel economy and reduce product costs.

[0006] According to the content of the present invention, the technical solution provided by the present invention is: a vibration reduction and lightweight design analysis method for a muffler bracket of a mining excavator based on NVH, including the following steps:

[0007] S1. Perform simulation modeling of the muffler bracket in shell elements, and model the welds of the muffler bracket using 1D elements;

[0008] S2. Perform geometric cleaning on the muffler bracket;

[0009] S3. Extract the middle surface of the muffler bracket after geometric cleaning is completed;

[0010] S4. Perform meshing on the muffler bracket;

[0011] S5. Assign material properties to the muffler bracket, and perform simulation fixation on the welding positions and bolt fastening points on the muffler bracket;

[0012] S6. Set up modal analysis on the finite element model of the muffler bracket. Use the Lanczos method to calculate the modes of the excitation frequencies in the range of 0 - 200 Hz, and output the modal displacement and modal strain energy results.

[0013] S7. According to the magnitudes, durations, and occurrence frequencies of the main and secondary excitation sources of the muffler bracket, calculate the weighting coefficients of the modal strain energy of each order according to the following formula:

[0014] ,

[0015] M: Magnitude of the excitation source, normalized to . The larger the excitation source, the closer M approaches 1; conversely, M approaches 0.

[0016] I: Importance degree of the excitation source, normalized to . Based on objective facts and subjective judgments, the more important the excitation source, the closer I approaches 1; conversely, I approaches 0.

[0017] F: Occurrence frequency of the excitation source, normalized to . The higher the occurrence frequency of the excitation source, the closer F approaches 1; conversely, F approaches 0.

[0018] are the weights of the magnitude, importance, and occurrence frequency of the excitation source respectively, and satisfy: ,

[0019] Weighting coefficient of the modal strain energy of the nth order;

[0020] S8. Combine the output modal displacement and modal strain energy results, and calculate the total strain energy in the calculated frequency range according to the following formula: ,

[0021] = + + + …… + , where is the superposition of the total modal strain energy in the calculated frequency range, is the modal strain energy of the nth order, is the weighting coefficient of the modal strain energy of the nth order;

[0022] S9. Perform weighted superposition on the modal strain energy of the bracket in the excitation frequency range, and output the superposition result of the modal strain energy of the muffler bracket;

[0023] S10. According to the modal strain energy superposition result of the muffler bracket, strengthen and optimize the structure of the muffler bracket, conduct modal strain energy superposition analysis on the muffler bracket after structural strengthening and optimization, and output the analysis result.

[0024] Furthermore, geometric cleaning of the muffler bracket includes deleting standard parts such as bolts, nuts, and welded nuts in the three-dimensional model of the bracket geometry, deleting unnecessary process data such as points, lines, and surfaces in the geometry, and only retaining the entity of the bracket body structure.

[0025] Furthermore, in S4, the meshing process of the muffler bracket includes batch meshing of the muffler bracket using a mixed method of quadrilateral and triangular elements.

[0026] Furthermore, in S4, the meshing process of the muffler bracket includes checking and adjusting the mesh quality after mesh generation.

[0027] Furthermore, the main excitation sources include order excitations from the engine.

[0028] Furthermore, the secondary excitation sources include excitations from the rotational frequency of the plunger pump.

[0029] Furthermore, S10. According to the modal strain energy superposition result of the muffler bracket, including obtaining the areas where the structure of the muffler bracket needs to be strengthened or optimized for weight reduction based on the distribution characterization of the strain energy, strengthen and optimize the structure of the muffler bracket, conduct modal strain energy superposition analysis on the muffler bracket after structural strengthening and optimization, and output the analysis result.

[0030] Furthermore, S10. According to the modal strain energy superposition result of the muffler bracket, strengthen and optimize the structure of the muffler bracket, conduct modal strain energy superposition analysis on the muffler bracket after structural strengthening and optimization, and output the analysis result;

[0031] S101. According to the modal strain energy superposition result of the muffler bracket, conduct modal strain energy superposition analysis after strengthening the structure of the muffler bracket;

[0032] S102. According to the modal strain energy superposition analysis result of the muffler bracket in step S101, conduct modal strain energy superposition analysis after optimizing and reducing the weight of the structure of the muffler bracket;

[0033] S103. Output the modal strain energy superposition analysis result.

[0034] Furthermore, the means of strengthening and optimizing the structure of the muffler bracket include increasing the wall thickness of the muffler bracket, adding reinforcement plates to the muffler bracket, adding ribs to the muffler bracket, and optimizing the structure of the muffler bracket.

[0035] Further, the means for strengthening and optimizing the muffler bracket include reducing the wall thickness of the muffler bracket, hollowing out the muffler bracket, and digging pits in the muffler bracket.

[0036] The advantages of the present invention compared with the prior art are as follows: 1. When it is difficult to obtain the magnitude of the external excitation, it is still possible to calculate the superposition result of the strain energy by using the weighting coefficient, accurately predict the failure area of the component structure caused by vibration fatigue, and guide the optimization of the component structure; 2. By using shell elements to model, the model scale can be significantly reduced, the calculation time can be shortened, and the analysis efficiency can be improved.

[0037] The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flowchart of the muffler bracket vibration reduction and lightweight design analysis method according to an embodiment of the present invention;

[0039] Figure 2 It is a schematic diagram of the finite element mesh division of the muffler bracket according to an embodiment of the present invention;

[0040] Figure 3 It is a schematic diagram of the finite element model of the muffler bracket after being fixed according to an embodiment of the present invention;

[0041] Figure 4 It is a schematic diagram of the first-order modal displacement result of the muffler bracket according to an embodiment of the present invention;

[0042] Figure 5 It is a schematic diagram of the first-order modal strain energy result of the muffler bracket according to an embodiment of the present invention;

[0043] Figure 6 It is a schematic diagram of the superposition result of the modal strain energy of the muffler bracket according to an embodiment of the present invention;

[0044] Figure 7 It is a schematic diagram of the cracking position of the strain energy calculation result of the muffler bracket according to an embodiment of the present invention;

[0045] Figure 8 It is a schematic diagram of the comparison of the strain energy calculation results of the muffler bracket before and after strengthening according to an embodiment of the present invention;

[0046] Figure 9 It is a schematic diagram of the comparison of the strain energy calculation results of the muffler bracket before and after weight reduction according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] The following further describes the present invention in detail.

[0048] Strain energy is the energy stored in a material when it undergoes elastic deformation under the action of external forces. Modal strain energy is an important concept in structural dynamics and modal analysis. It is used to describe the strain energy distribution of each part of a structure under a certain order of modal vibration. The muffler bracket on a mining excavator is subjected to vibrations during the operation of the mining machine. The failure form of the bracket is mainly vibration fatigue failure. Therefore, modal strain energy can be used for calculation and evaluation. Areas with high modal strain energy indicate that the vibration deformation in these areas is more intense and the energy is more concentrated under the corresponding mode. These are the weakest and most easily damaged areas of the structure.

[0049] A mode is an inherent property of a structure, which reflects the vibration form of the structure at a specific frequency. Calculating the modes of the muffler bracket can analyze the vibration conditions of the bracket under the external excitation frequency and evaluate the risk of resonance of the bracket.

[0050] The strain energy distribution of a certain order of mode of a structure cannot fully reflect the strain energy distribution of the structure over the entire vibration frequency range. According to the frequency characteristics of the excitation source, the main excitation source and the secondary excitation source can be considered. Based on the excitation magnitude, occurrence frequency, and duration, the corresponding modal frequencies are weighted, and finally, the strain energies of all modal orders are weighted and superimposed, which can more fully represent the strain energy distribution of the structure over the entire vibration frequency range.

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0052] Combined with Figure 1 As shown, the process of this embodiment is as follows: S1 - S10:

[0053] S1. Conduct simulation modeling of the muffler bracket in the shell element. The welds of the muffler bracket are modeled using 1D elements.

[0054] The structure of the muffler bracket is mainly composed of flat parts and thin-walled profiles. The dimension in the thickness direction is much smaller than the dimension in the length direction. The geometric mid-surface can be extracted and modeled using shell elements. The welds can be modeled using 1D elements. The modal strain energy distribution calculated by using this method of modeling is completely consistent with the cracking area of the actual experimental bracket. Using this method of modeling significantly improves the modeling efficiency and calculation efficiency, shortens the calculation and analysis time, and saves the R & D cost.

[0055] S2. Conduct geometric cleaning on the muffler bracket, including deleting standard parts such as bolts, nuts, and welded nuts in the three-dimensional model of the bracket geometry, and deleting unnecessary process data such as points, lines, and surfaces in the geometry, and only retaining the solid of the bracket body structure.

[0056] S3. Extract the mid-surface of the muffler bracket after geometric cleaning to obtain a surface. Mesh generation through this surface can facilitate the coincidence of mesh nodes and reduce errors.

[0057] S4. Perform meshing on the muffler bracket, including batch meshing of the muffler bracket using a mixed method of quadrilateral and triangular elements. After mesh generation, perform mesh quality inspection and adjustment; as Figure 2 、 Figure 3 shown.

[0058] S5. Assign material properties to the muffler bracket. The material properties in this embodiment are elastic modulus 2.1x10^5 MPa, Poisson's ratio 0.3, and density 7.85x10^-9 ton / mm^3. And perform simulation fixation on the welding positions and bolt fastening points on the muffler bracket.

[0059] S6. Perform modal analysis settings on the finite element model of the muffler bracket. Use the Lanczos method to calculate the modes of the excitation frequencies in the range of 0 - 200 Hz, and output the modal displacement and modal strain energy results; as Figure 5 、 Figure 6 shown.

[0060] S7. According to the magnitudes, durations, and occurrence frequencies of the main and secondary excitation sources of the muffler bracket, calculate the weighting coefficients of the modal strain energy of each order according to the following formula,

[0061] ,

[0062] M: Magnitude of the excitation source, normalized to , the larger the excitation source, the closer M is to 1, and vice versa, M approaches 0.

[0063] I: Importance of the excitation source, normalized to , based on objective facts and subjective judgment, the more important the excitation source, the closer I is to 1, and vice versa, I approaches 0.

[0064] F: Occurrence frequency of the excitation source, normalized to , the higher the occurrence frequency of the excitation source, the closer F is to 1, and vice versa, F approaches 0.

[0065] are the weights of the magnitude, importance, and occurrence frequency of the excitation source respectively, satisfying: ,

[0066] Weighting coefficient of the modal strain energy of the nth order;

[0067] Example 1, the values of M, I, and F need to be calculated according to the characteristics of the excitation source corresponding to the modal frequency. For the case of a single excitation source, the value can be taken as 1. Within the modal frequency range of 0 - 200 Hz of the muffler bracket, within this frequency range, the main excitation source corresponding to the bracket modal frequency comes from the order excitation of the engine. The engine is the largest and main excitation source. For this excitation source of the engine, the values of M, I, and F are approximately equal to 1, , so the weighting coefficient is taken as 1.

[0068] Example 2, within the modal frequency range of 0 - 200 Hz of the muffler bracket, within this frequency range, the fundamental frequency of the excitation frequency of this excitation source of the plunger pump is the rotational frequency of the plunger pump, as well as the product of the plunger rotational frequency and the number of plungers. The excitation frequency of the plunger pump has no coupling with the modal of the exhaust system muffler bracket. Therefore, for this excitation source of the plunger pump, the values of M, I, and F are approximately equal to 0, , so the weighting coefficient is taken as 0.

[0069] S8. Combine the output modal displacement and modal strain energy results, and calculate the total strain energy within the calculation frequency range according to the following formula ,

[0070] = + + +… …+ , where, is the superposition of the total modal strain energy within the calculation frequency range, is the nth - order modal strain energy, is the weighting coefficient of the nth - order modal strain energy.

[0071] S9. Perform weighted superposition on the modal strain energy of the bracket within the excitation frequency range, and output the superposition result of the muffler bracket modal strain energy; as Figure 7 shown, the strain energy result of the muffler bracket highly coincides with the area where the bracket is actually damaged.

[0072] S10. According to the superposition result of the muffler bracket modal strain energy, including the area where the muffler bracket structure needs to be strengthened or optimized for weight reduction based on the characterization of the strain energy distribution, strengthen and optimize the structure of the muffler bracket, perform modal strain energy superposition analysis on the muffler bracket after structural strengthening and optimization, and output the analysis result.

[0073] S101. Based on the modal strain energy superposition results of the muffler bracket, after strengthening the structure of the muffler bracket, perform modal strain energy superposition analysis. The means of strengthening and optimizing the structure of the muffler bracket include increasing the wall thickness of the muffler bracket, adding reinforcement plates to the muffler bracket, adding ribs to the muffler bracket, and optimizing the structure of the muffler bracket. As Figure 8 shown, the mass of the original bracket scheme is 60.83 kg. After strengthening and optimizing the structure of the bracket, the weight of the optimized bracket increases by 13.4 kg. The modal strain energy of the optimized bracket is significantly lower compared to the strain energy of the bracket before optimization. The optimized bracket has not cracked or failed during actual use.

[0074] S102. Based on the modal strain energy superposition analysis results of the muffler bracket in step S101, after optimizing the structure of the muffler bracket to reduce weight, perform modal strain energy superposition analysis. The means of strengthening and optimizing the structure of the muffler bracket include reducing the wall thickness of the muffler bracket, hollowing out the muffler bracket, and digging pits in the muffler bracket. As Figure 9 shown, hollowing out the bracket reduces the weight by 6.5 kg. After weight reduction, the strain energy distribution table is improved, and the modal frequency is further increased.

[0075] S103. Output the modal strain energy superposition analysis results.

[0076] The calculation method of this application has been shown to be able to effectively guide the vibration reduction and weight reduction optimization of the muffler bracket through actual application.

[0077] In summary, for the technical solution disclosed in this embodiment, the external excitation frequency of the bracket is analyzed for excitation importance according to the magnitude, occurrence frequency, and duration of the excitation source, and the participation weighting factor is calculated within the entire frequency range; the modal strain energy of the bracket within the entire excitation frequency range is calculated, and the strain energy is weighted and superposed. The distribution of the strain energy is used to characterize the areas of the bracket structure that need to be strengthened or optimized for weight reduction; the modal and vibration modes of the bracket structure are calculated to obtain the natural frequency of the bracket, revealing the resonance risk of the bracket; in the case where it is difficult to obtain the magnitude of the external excitation, it is still possible to accurately predict the failure areas of the component structure due to vibration fatigue, guiding the optimization of the component structure.

[0078] Both the modeling and welding of the bracket assembly use shell elements for modeling, significantly reducing the model size, shortening the calculation time, and improving the analysis efficiency.

[0079] The calculation and analysis method of this application is also applicable to guiding the vibration reduction and lightweight design of other structural components of mining excavators.

[0080] The calculation and analysis method of this application is also applicable to guiding the vibration reduction and lightweight design of structural components of mining trucks and other mining machinery.

[0081] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A design analysis method for vibration reduction and lightweight of a mining excavator muffler bracket based on NVH, characterized in that It includes the following steps: S1. Conduct simulation modeling of the muffler bracket in the shell unit, and model the welds of the muffler bracket using 1D elements; S2. Conduct geometric cleaning on the muffler bracket; S3. Extract the mid-surface of the muffler bracket after geometric cleaning is completed; S4. Conduct meshing on the muffler bracket; S5. Assign material properties to the muffler bracket, and simulate and fix the welding positions and bolt fastening points on the muffler bracket; S6. Conduct modal analysis settings on the finite element model of the muffler bracket, adopt the Lanczos method, calculate the modes of the excitation frequencies in the range of 0 - 200 Hz, and output the modal displacement and modal strain energy results; S7. According to the magnitudes, durations, and occurrence frequencies of the main excitation source and secondary excitation source of the muffler bracket, calculate the weighting coefficient of the modal strain energy of each order according to the following formula, ， M: Magnitude of the excitation source, normalized to , the larger the excitation source, the closer M approaches 1, and vice versa, M approaches 0. I: Importance degree of the excitation source, normalized to , based on objective facts and subjective judgment, the more important the excitation source is, the closer I is to 1, otherwise I approaches 0. F: The occurrence frequency of the excitation source, normalized to , the higher the occurrence frequency of the excitation source, the closer F is to 1, otherwise F approaches 0. They are the weights of the magnitude, importance, and occurrence frequency of the excitation source respectively, and satisfy: , Weighting coefficient of the n-th order modal strain energy S8. Combine the output modal displacement and modal strain energy results and calculate the total strain energy within the calculated frequency range according to the following formula , = + + +… …+ , where is the sum of the total modal strain energy in the calculation frequency range, is the modal strain energy of the nth order, is the weighting coefficient of the modal strain energy of the nth order; S9. Perform weighted superposition on the modal strain energy of the bracket within the excitation frequency range, and output the superposition result of the modal strain energy of the muffler bracket; S10. According to the superposition result of the modal strain energy of the muffler bracket, strengthen and optimize the structure of the muffler bracket, conduct modal strain energy superposition analysis on the muffler bracket after structural strengthening and optimization, and output the analysis result.

2. The NVH-based vibration reduction and lightweight design analysis method for the muffler bracket of a mining excavator according to claim 1, characterized in that: Conducting geometric cleaning on the muffler bracket includes deleting standard parts such as bolts, nuts, and welding nuts in the three-dimensional geometric model of the bracket, deleting unnecessary process data such as points, lines, and surfaces in the geometry, and only retaining the entity of the bracket body structure.

3. The NVH-based vibration reduction and lightweight design analysis method for the muffler bracket of a mining excavator according to claim 1, wherein: The meshing of the muffler bracket in S4 includes batch meshing of the muffler bracket using a mixed method of quadrilateral and triangular elements.

4. The NVH-based vibration reduction and lightweight design analysis method for the muffler bracket of a mining excavator according to claim 1, characterized in that: The meshing of the muffler bracket in S4 includes checking and adjusting the mesh quality after the meshing is completed.

5. The NVH-based vibration reduction and lightweight design analysis method for the muffler bracket of a mining excavator according to claim 1, wherein: The main excitation source includes the order excitation from the engine.

6. The NVH-based vibration reduction and lightweight design analysis method for the muffler bracket of a mining excavator according to claim 1, characterized in that: The secondary excitation source includes the excitation from the rotation frequency of the plunger pump.

7. The NVH-based vibration reduction and lightweight design analysis method for the muffler bracket of a mining excavator according to claim 1, characterized in that: S10. According to the superposition result of the modal strain energy of the muffler bracket, including obtaining the areas where the structure of the muffler bracket needs to be strengthened or optimized for weight reduction based on the distribution characterization of the strain energy, strengthening and optimizing the structure of the muffler bracket, and conducting modal strain energy superposition analysis on the muffler bracket after structural strengthening and optimization, and outputting the analysis result.

8. The NVH-based vibration reduction and lightweight design analysis method for the mining excavator muffler bracket according to claim 1, wherein: S10. According to the superposition result of the modal strain energy of the muffler bracket, strengthen and optimize the structure of the muffler bracket, conduct modal strain energy superposition analysis on the muffler bracket after structural strengthening and optimization, and output the analysis result; S101. According to the superposition result of the modal strain energy of the muffler bracket, conduct modal strain energy superposition analysis after strengthening the structure of the muffler bracket; S102. According to the modal strain energy superposition analysis result of the muffler bracket in step S101, conduct modal strain energy superposition analysis after optimizing the weight reduction of the structure of the muffler bracket; S103. Output the modal strain energy superposition analysis result.

9. The NVH-based vibration reduction and lightweight design analysis method for the muffler bracket of a mining excavator according to claim 1, characterized in that: The means for strengthening and optimizing the structure of the muffler bracket include increasing the wall thickness of the muffler bracket, adding reinforcing plates on the muffler bracket, adding reinforcing ribs on the muffler bracket, and optimizing the structure of the muffler bracket.

10. The NVH-based vibration reduction and lightweight design analysis method for the muffler bracket of a mining excavator according to claim 1, wherein: Means for structurally strengthening and optimizing the muffler bracket include reducing the wall thickness of the muffler bracket, hollowing out the muffler bracket, and digging pits in the muffler bracket.

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