An acoustic package performance database based on polyurethane foaming and applications

Abstract

The application discloses an acoustic package performance database based on polyurethane foaming and application, and the database is established by the following steps: S1, determining initial analysis parameters of polyurethane foaming, and outputting three parameters with the largest influence factor based on an actual process adjustable range; S2, determining final analysis parameters of polyurethane foaming; utilizing a Pearson correlation coefficient, calculating a correlation degree between sequences, obtaining respective correlation coefficients, determining selection of the initial analysis parameters according to the coefficient values, and obtaining the final analysis parameters; S3, establishing an acoustic performance database; substituting physical parameters into middle-low-frequency acoustic performance analysis, substituting pore parameters into middle-high-frequency acoustic performance analysis, taking a material covering rate as a calculation parameter, analyzing an influence trend of the covering rate on acoustic performance, and establishing a final acoustic material database. The application can simultaneously satisfy various requirements such as development and evaluation of acoustic packages, motor noise reduction scheme screening, process parameter adjustment and the like.

Description

Technical Field

[0001] This invention relates to a performance database of acoustic packages based on polyurethane foam and its application. Background Technology

[0002] In recent years, the number of new energy vehicles in the Chinese market has been increasing, and automakers are constantly expanding new features in the research and development of vehicle performance to attract consumers. The electric drive system, as a crucial component of new energy vehicles, is also a significant source of noise during low-speed driving. The integration of the electronic control system and the motor, coupled with consumer demands for performance and the emergence of high-power motors, has further exacerbated the deterioration of the system's NVH performance. Installing acoustic packages is currently one of the mainstream noise reduction methods used by manufacturers.

[0003] On the one hand, polyurethane, due to its unique pore structure, has better formability and lower compression set compared to fibrous sound-absorbing cotton, making it a widely used porous sound-absorbing material in automotive interiors and exteriors. As a material in direct contact with the motor housing, it needs to provide not only sound absorption but also damping. As a typical foamed material, according to the acoustic theory of porous foamed materials, its sound absorption performance is affected by nine parameters. However, to meet the actual acoustic package requirements and production needs, considering all parameters comprehensively is impractical. It is necessary to effectively improve the material's acoustic properties while simultaneously allowing for rapid adjustments to the production process.

[0004] On the other hand, the NVH performance of the electric drive assembly needs to be tested in a specialized semi-anechoic chamber and on a dedicated test bench. Conducting a single test bench test on an electric drive assembly is expensive and time-consuming. Furthermore, for data accumulation, especially in the early material development stages, directly verifying the acoustic effects of materials on a test bench is unrealistic. Simultaneously, as an electric drive manufacturer, due to various internal and external factors, there are insufficient resources for repeated verification of acoustic package solutions. Therefore, they expect suppliers to provide acoustic packages that meet their acoustic noise reduction requirements in one go. Considering the wiring and installation of the electric drive assembly, the actual acoustic package is not a near-ideal cover, but rather designed to avoid various holes created by wiring, which significantly affects the acoustic performance of the materials. Moreover, electric drive manufacturers often demand that while meeting acoustic performance requirements, they also comply with the trend of automotive lightweighting, which is inherently contradictory.

[0005] Therefore, a performance database and application of acoustic packages based on polyurethane foam are urgently needed. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a polyurethane foam-based acoustic package performance database that can effectively improve acoustic performance, meet the requirements for rapid process adjustment, provide the parts desired by electric drive manufacturers in one go, and also meet the overall lightweight requirements.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] The first objective of this invention is to provide a performance database of acoustic packages based on polyurethane foam, which is established using the following steps:

[0009] S1. Determine the initial analytical parameters for polyurethane foaming, specifically including the following steps:

[0010] S11. Measure the material parameters of the polyurethane foam in its initial state. There are k adjustable process parameters in total. Based on the upper and lower limits of each process parameter, produce 2... k Material samples in different states were used, and the material parameters of all samples were measured. The material parameters included physical parameters and pore parameters, and the maximum and minimum values ​​of each parameter were obtained.

[0011] S12. Input the material parameters of the polyurethane foam in the initial state into the acoustic calculation software VA One to obtain the insertion loss curve of the composite material. Then, change the value of a certain material parameter to the maximum and minimum values ​​of that parameter, while keeping the other material parameters unchanged, to obtain two insertion loss curves of that parameter within the adjustable range. Repeat this process for the other parameters until two insertion loss curves of all parameters within the adjustable range are obtained.

[0012] S13. Define the frequency range of the acoustic material that produces noise reduction effect as 500-10000Hz. Take the arithmetic mean of all the insertion loss curves obtained in step S12 for all frequency bands, and take the difference between the maximum and minimum values ​​of each material parameter and its corresponding average value. Select the three parameters with the largest differences as the initial analysis parameters and arrange them in order of size.

[0013] S2. Determine the final analytical parameters for polyurethane foaming, specifically including the following steps:

[0014] S21. Adjust the foaming process parameters and prepare m polyurethane foam samples. Test the initial analytical parameters of these foam samples respectively to form a parameter matrix.

[0015] S22. Using the Pearson correlation coefficient, calculate the correlation between the data series respectively, obtain their respective correlation coefficients, and determine the selection or rejection of the initial analysis parameters in step S13 according to the magnitude of the coefficient values ​​to obtain the final analysis parameters.

[0016] S3. Establish an acoustic package performance database, which includes the following steps:

[0017] S31. In the mid-to-low frequency band, the double-wall system composed of sound insulation layer-polyurethane foam-electric drive shell has an inherent frequency. As a viscoelastic material, the polyurethane foam layer has both propagation and attenuation effects on sound energy. Therefore, a method for calculating the mid-to-low frequency acoustic performance is established by using the physical parameters of polyurethane foam.

[0018] S32. In the mid-to-high frequency range, the sound wave frequency is relatively short. The attenuation of sound energy by polyurethane foam is mainly due to the absorption of sound by the microporous structure in the foam. The pore structure parameters affect both the absorption of sound and the overall sound leakage of the composite. Therefore, a method for calculating the mid-to-high frequency acoustic performance of polyurethane foam is established based on the pore parameters of polyurethane foam.

[0019] S33. Based on the actual state of the acoustic package of the electric drive assembly, the insertion loss curves with two states, namely coverage and full coverage (no opening), are measured by the reverberation chamber-anechoic chamber window sound insulation test method. These two insertion loss curves are the starting points of the influence frequency bands corresponding to the coverage. The relationship between the coverage and the lowest influence frequency band is obtained, and a material acoustic performance database is established.

[0020] Preferably, in step S11, the physical parameters include at least one of density, Young's modulus, Poisson's ratio, and damping factor; the pore parameters include at least one of porosity, flow resistance, tortuosity, viscous characteristic length, and thermal characteristic length; and the process parameters include at least one of mixing ratio, mold temperature, and molding time.

[0021] Preferably, the correlation coefficient in step S22 is obtained according to the following formula:

[0022]

[0023] in, x i y i This represents the two parameter values ​​of the selected i-th sample block. This represents the average value of all samples for the two selected parameters, where r is the correlation coefficient.

[0024] In step S22, the selection or rejection of initial analysis parameters is determined according to the following method:

[0025] S221. When the correlation coefficients of the three parameters all satisfy -1≤r<0.5, it indicates that the parameter values ​​are not highly correlated or are negatively correlated. In this case, all three parameters are defined as independent variables and used as the final analysis parameters.

[0026] S222. When one of the correlation coefficients reaches 0.5 or above, and the other two correlation coefficients each satisfy -1≤r<0.5, it indicates that the two parameters with a correlation coefficient of 0.5 or above have a certain correlation. According to the results of step S1, if the influence of one parameter is higher than that of the other parameter, the parameter with the lower influence is discarded, and the other two parameters are defined as independent variables as the final analysis parameters.

[0027] S223. When the correlation coefficients of the three parameters are all 0.5 or higher, it indicates that there is a strong correlation between the parameters. Based on the results of step S1, the parameter with the highest influence is defined as the independent variable and used as the final analysis parameter.

[0028] Preferably, in steps S31 and S32, the low-to-mid frequency band is 500–2000 Hz, and the high-frequency band is 2000–10 kHz.

[0029] Preferably, in step S31, in the mid-to-low frequency range, the physical parameters of polyurethane foam are substituted into the acoustic performance analysis, and its acoustic performance is expressed as follows:

[0030] IL LF =20*lg(fM)+F[ρ,E,γ,η,d,f]+C1, (500Hz≤f≤2000Hz)

[0031]

[0032] Among them, IL LF The insertion loss curve is shown in the low-to-mid frequency range. M is the density of the sound insulation layer, f is the frequency, F[ρ, E, γ, η, d, f] is a function of a certain physical parameter, where ρ is the density, E is Young's modulus, γ is Poisson's ratio, η is the damping factor, d is the material thickness, and C1 is the adjustment coefficient.

[0033] Preferably, in step S32, in the mid-to-high frequency range, the pore parameters of the polyurethane foam are substituted into the acoustic performance analysis, and its acoustic performance is expressed as follows:

[0034] IL HF =20*lg(fM)+G[φ,σ,α,Λ,Λ′,f], (2000Hz≤f≤10000Hz)

[0035] G[φ,σ,α,Λ,Λ′,f]=C2*φ(σ-σ0)*lg(f)+G′[α,Λ,Λ′]

[0036] Among them, IL HFThe insertion loss curve is shown in the mid-to-high frequency band. M is the density of the sound insulation layer, f is the frequency, G[φ, σ, α, Λ, Λ′, f] is a function of polyurethane foam with respect to pore parameters, where φ is porosity, σ is flow resistance, α is tortuosity, Λ is viscous characteristic length, Λ′ is thermal characteristic length, σ0 is the flow resistance when the sound absorption coefficient of a material of a certain thickness reaches its maximum in each frequency band, C2 is an adjustment coefficient, and G′[α, Λ, Λ′] is a function of tortuosity, viscous characteristic length, and thermal characteristic length, which is determined by the following steps:

[0037] S321. Based on the three parameters with the greatest impact output in step S1, if none of them contain α, Λ, Λ′, then G′[α, Λ, Λ′] = 0; if at least one of the parameters α, Λ, Λ′ is contained, then proceed to step S322.

[0038] S322. If the final analysis parameters obtained after step S2 do not include α, Λ, Λ′, then G′[α, Λ, Λ′] = 0; if the final analysis parameters obtained after step S2 include at least one of α, Λ, Λ′, then G′[α, Λ, Λ′] is the product of the output parameters.

[0039] Preferably, C1 and C2 are determined using the least squares method combined with experiments, as follows:

[0040] S311. Select a sound insulation material with a specific surface density, and for polyurethane foam with the same Young's modulus, cut three different thicknesses, and after compositing them with the sound insulation material, conduct window tests in an acoustic reverberation-anechoic chamber to obtain three corresponding insertion loss curves.

[0041] S312. Use the least squares method to determine the values ​​of C1 and C2, so that the sum of squared residuals Q of the test values ​​in each frequency band from 500 to 10000 Hz in 1 / 3 octave band is minimized, that is:

[0042]

[0043] Among them, IL ie Indicates according to IL LF IL HF The estimated value, IL i This represents the measured value. When the Q value is at its minimum, the values ​​of the adjustment coefficients C1 and C2 can be obtained.

[0044] Preferably, step S33 specifically includes the following steps:

[0045] S331. Select any combination of polyurethane foam and sound insulation layer in any state, and test the insertion loss curve IL of the material in the non-porous state. s0 ;

[0046] S332, Set the acoustic package coverage range of the electric drive assembly [S a S b The insertion loss of a flat plate sample with an opening was tested using the reverberation-anechoic chamber window method. The area of ​​the square scanning region of the original test window acoustic intensity probe was defined as A0. This region was then divided into an array of m*m small regions, with a circular opening in each region, the areas of which were respectively...

[0047] S333. Window insertion loss tests were conducted for two different aperture areas, and the horizontal line insertion loss values ​​in the high-frequency band were obtained as follows: IL sa IL sb Any coverage S within this coverage range k The high-frequency insertion loss IL was determined using linear interpolation. sk ;

[0048] S334, Compare the raw material insertion loss curves IL s0 and insertion loss IL with aperture ratio at high frequencies sk The intersection of the two curves is where the coverage ratio is S. k The lowest frequency affected If the frequency is below this value, its acoustic curve is consistent with the performance of the material in the unopened state; if the frequency is above this value, its acoustic curve is the insertion loss level line in the high-frequency band of the open state.

[0049] The second objective of this invention is to provide an application of a polyurethane foam-based acoustic package performance database, which utilizes the database to achieve the following functions:

[0050] (1) Forward input parameter query: Input existing material parameters to obtain the material's weight, cost and acoustic performance curves, evaluate the overall noise reduction performance after the material covers the motor, and provide developers with an overall evaluation of the material, weight, cost and performance.

[0051] (2) Reverse acquisition of material parameters: Based on the noise reduction requirements to be achieved by the electric drive assembly, input the noise reduction value in the key frequency band, and output the corresponding materials and parameters in reverse, providing electric drive assembly manufacturers with different materials and different costs that meet the performance requirements.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] This invention proposes a method for establishing a material database for noise reduction in electric drive acoustic packages based on polyurethane foam. This method starts from numerous acoustic parameters of polyurethane materials and adjustment parameters of actual processes, identifies key parameters affecting the composite material of the acoustic package, calculates the acoustic performance of different material parameters based on relevant theories, and establishes a corresponding data retrieval system. This method can provide rapid and effective evaluation of existing materials, find suitable material solutions for prototype fabrication, and offer material solutions with different costs to meet the noise reduction needs of drive assembly manufacturers, avoiding the waste of time and money caused by blindly searching for material solutions and conducting bench tests. By adjusting process parameters, the polyurethane foam state can be quickly and effectively controlled, thereby meeting the different performance requirements of different customers for acoustic packages. This provides a better solution for the research of polyurethane foam materials, especially for the development and application of materials and mechanisms for acoustic packages corresponding to noise reduction needs of different orders in electric drive assemblies. Attached Figure Description

[0054] Figure 1 A schematic diagram illustrating the establishment of an acoustic database for polyurethane composite materials;

[0055] Figure 2 A schematic diagram illustrating the process for identifying key analytical parameters;

[0056] Figure 3 A schematic diagram illustrating a method for determining acoustic performance considering coverage.

[0057] Figure 4 This is a schematic diagram illustrating the retrieval of acoustic performance data for materials under a certain process. Detailed Implementation

[0058] The following detailed description of exemplary embodiments of the invention is taken with reference to the accompanying drawings, which form part of the description and illustrate exemplary embodiments in which the invention may be practiced. While these exemplary embodiments have been described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be implemented and various changes may be made to the invention without departing from the spirit and scope thereof. The more detailed description of embodiments of the invention below is not intended to limit the scope of the claimed invention, but is merely illustrative and not restrictive of the description of the features and characteristics of the invention, to suggest the best mode for carrying out the invention, and is sufficient to enable those skilled in the art to practice the invention. Therefore, the scope of the invention is defined only by the appended claims.

[0059] like Figures 1 to 4 As shown, this embodiment provides a method for establishing a database of polyurethane-based electroacoustic package materials, including the following steps:

[0060] S1. Determine the initial analytical parameters for polyurethane foaming.

[0061] Polyurethane foam, as a typical porous foamed sound-absorbing material, can be produced in different states by adjusting the formulation and process parameters according to different applications and needs. The sound absorption performance of foamed materials is affected by the internal pore structure, which can be characterized by its physical parameters and pore parameters. Physical parameters include density, Young's modulus, Poisson's ratio, and damping factor, while pore parameters include porosity, flow resistance, tortuosity, viscous characteristic length, and thermal characteristic length. After the sound insulation layer is formed, the reaction process parameters, such as temperature, pressure, the proportion of each component in the composite material, and the ratio of composite material to isocyanate, are set. The raw materials are then used to generate conformal polyurethane foam in a closed mold. The process parameters directly affect the resulting foam structure, and thus the acoustic performance. Therefore, it is necessary to select several parameters that have a significant impact and are practically adjustable from the material parameters as variable factors for establishing the electro-acoustic package material database.

[0062] S11. Under the initial mass production state, polyurethane foaming sample preparation is carried out. This state is defined as the initial state of polyurethane foaming. The polyurethane foaming parameters in the initial state are measured and denoted as P0 = T(ρ0, E0, γ0, η0, φ0, σ0, α0, Λ0, Λ'0). Then, k process parameters are set for adjustment. Based on the upper and lower adjustable limits of each process parameter, 2... k For materials in different states, the parameters of each material were measured. Obtain the minimum and maximum values ​​of each parameter.

[0063] S12. Input any material parameter (e.g., density parameter) from the initial foaming state into the acoustic calculation software to calculate the insertion loss curve. Find the minimum value of the density parameter, Min. ρ Maximum value (Max) ρ Replace the initial density parameter value ρ0 with each value, keeping the other parameters unchanged, and calculate the insertion loss curve after changing the density parameter. Repeat this process for other parameters until the insertion loss curves for all physical parameters and pore parameters are obtained.

[0064] S13. Set the frequency range for the noise reduction effect of the acoustic material to be 500Hz to 10000Hz. Within this frequency range, perform an arithmetic average of all the above insertion loss curves in each frequency band, calculate the difference between the maximum and minimum values ​​of each parameter, select the three parameters with the largest differences, and arrange them in order of size, such as parameters ρ, η, and σ.

[0065] S2. Determine the final analytical parameters for polyurethane foaming.

[0066] Theoretically, the material property parameters obtained in step S1 are independent of each other and can be used to study changes in acoustic performance by controlling a single variable. However, the chemical reaction process of polyurethane is very complex and is often affected by various factors in actual production. A change in one parameter inevitably causes changes in other parameters. In such cases, further correlation analysis is needed to eliminate parameters with strong correlations. The beneficial effects are that subsequent theoretical calculations for establishing a database are simpler, and the adjustment of process parameters and the provision of foaming samples in different states are also more convenient.

[0067] S21. Set n kinds of process parameters, corresponding to n polyurethane foams under each state, and test the parameter ρ, η, σ values ​​of n samples respectively to form the [ρ], [η], [σ] sequence.

[0068] S22. Calculate the correlation between the three parameters. Using Pearson correlation coefficient theory, calculate the degree of correlation between the series respectively to obtain their respective correlation coefficients. Determine whether to include or exclude parameters α, β, and γ in step S13 according to the magnitude of the coefficient values ​​to obtain the final analysis parameters.

[0069] The correlation coefficient is obtained according to the following formula:

[0070]

[0071] in, x i y i This represents the two parameter values ​​of the selected i-th sample block. This represents the average value of all samples for the two selected parameters, where r is the correlation coefficient.

[0072] The selection of parameters ρ, η, and σ should be determined using the following method:

[0073] S221, When the correlation coefficients of the three parameters are r ρη r ησ r σρ When all three parameters satisfy -1≤r<0.5, it indicates that the parameter values ​​are not highly correlated or are negatively correlated. In this case, all three parameters are defined as independent variables and used as the final analysis parameters.

[0074] S222. When one set of correlation coefficients reaches 0.5 or higher, and the other two sets of correlation coefficients each satisfy -1 ≤ r < 0.5 (e.g., r ρη ≥0.5, and -1≤r ησ r σρ When the value is less than 0.5, it indicates that the parameters ρ and η are correlated to a certain extent. According to the results of step S1, if the influence of ρ is greater than that of η, then η is discarded, and the parameters ρ and σ are defined as independent variables as the final analysis parameters.

[0075] S223, When the correlation coefficients of the three parameters are r ρη r ησ r σρ When γ≥0.5 is satisfied, it indicates that there is a strong correlation between the parameters. According to the results of step S1, the influence of parameter α is the highest. Therefore, parameters η and σ are discarded, and only parameter ρ is defined as the independent variable as the final analysis parameter.

[0076] S3. Establish an acoustic package performance database.

[0077] In this embodiment, the low-to-mid frequency band is 500–2000 Hz, and the mid-to-high frequency band is 2000–10 kHz.

[0078] In the low-to-mid frequency range, polyurethane foam is sandwiched between the sound insulation layer and the electric drive housing. Due to the relatively long wavelengths in this range, vibrational energy from the housing surface easily penetrates and radiates outwards, thus weakening the noise reduction function of the acoustic package. Therefore, in this frequency range, the overall viscoelasticity of the polyurethane foam is emphasized, while the internal cell structure distribution is ignored. Based on the theory of a double-wall structure consisting of a sound insulation layer, polyurethane, and electric drive housing, the natural frequency f0 of the system is:

[0079]

[0080] Where M1 and M2 are the areal densities of the electric drive housing and the sound insulation material, respectively, E is the Young's modulus of the foam material, and d is the thickness of the intermediate layer material.

[0081] In the low-to-mid frequency range, polyurethane foam is sandwiched between the sound insulation layer and the electric drive housing. The structural resonance characteristics of the housing, polyurethane foam, and sound insulation layer significantly affect the noise radiation of the electric drive assembly. Because the wavelengths in the low-to-mid frequency range are relatively long, the vibration energy on the housing surface can easily penetrate and radiate through the acoustic package, thus weakening its noise reduction function. This can be seen from the system's natural frequency formula:

[0082] (1) The actual adjustable range of polyurethane foam thickness is generally between 0 and 30 mm. Within this range, the greater the polyurethane foam thickness, the better the structural sound insulation performance.

[0083] (2) The higher the elastic modulus of polyurethane foam, the higher the natural frequency of the structure, the valley of the sound insulation curve will shift to the right, and the sound insulation performance of the structure will deteriorate.

[0084] Therefore, in the mid-to-low frequency range, the physical parameters of polyurethane foam are substituted into the acoustic performance analysis. Meanwhile, the polyurethane foam density range of the actual acoustic package is clearly defined, with very little variation, essentially remaining constant, and the Poisson's ratio also exhibits minimal variation. In summary, the acoustic performance of polyurethane foam is expressed as follows:

[0085] IL LF=20*lh(fM)+F[ρ,E,γ,d,f]+C1, (500Hz≤f≤2000Hz)

[0086]

[0087] Among them, IL LF The insertion loss curve is shown in the low-to-mid frequency range. M is the density of the sound insulation layer, f is the frequency, F[ρ, E, γ, η, d, f] is a function of a certain physical parameter, where ρ is the density, E is Young's modulus, γ is Poisson's ratio, η is the damping factor, d is the material thickness, and C1 is the adjustment coefficient.

[0088] In the high-frequency band, due to the shorter frequency of sound waves, the pore structure of polyurethane foam can effectively absorb noise in this high-frequency band, thus enhancing the acoustic performance of the composite component to some extent. Therefore, the pore structure parameters of polyurethane are also incorporated into the insertion loss analysis of the composite flat panel component in the high-frequency band to establish a database.

[0089] According to the theory of foamed sound absorption, for a given thickness, there exists a suitable value for air permeability. This value allows the sound absorption performance of the foamed material to reach its optimal level in both low and high frequency ranges at a given thickness. When the air permeability exceeds or falls below this range, it becomes detrimental to the material's absorption of sound energy. Furthermore, based on the leakage characteristics of sound insulation panels, the leakage area has a significant impact on the mid-to-high frequency range. In particular, high-frequency sound insulation performance will show a marked decline. Therefore, to improve the sound insulation performance of composite materials, the air permeability of polyurethane should be reduced as much as possible. At the same time, regardless of the specific conditions, a certain level of porosity must be maintained.

[0090] In the mid-to-high frequency range, the acoustic performance is expressed as follows by substituting the pore parameters of polyurethane foam into the acoustic performance analysis:

[0091] IL HF =20*lg(fM)+G[φ,σ,α,Λ,Λ',f], (2000Hz≤f≤10000Hz)

[0092] G[φ,σ,α,Λ,Λ',f]=C2*φ(σ-σ0)*lg(f)+G'[α,Λ,Λ']

[0093] Among them, IL HFThe insertion loss curve is shown in the mid-to-high frequency band. M is the density of the sound insulation layer, f is the frequency, G[φ, σ, α, Λ, Λ', f] is a function of polyurethane foam with respect to pore parameters, where φ is porosity, σ is flow resistance, α is tortuosity, Λ is viscous characteristic length, Λ′ is thermal characteristic length, σ0 is the flow resistance when the sound absorption coefficient of a material of a certain thickness reaches its maximum in each frequency band, C2 is an adjustment coefficient, and G′[α, Λ, Λ′] is a function of tortuosity, viscous characteristic length, and thermal characteristic length, which is determined by the following steps:

[0094] S321. Based on the three parameters with the greatest impact output in step S1, if none of them contain α, Λ, Λ′, then G′[α, Λ, Λ′] = 0; if at least one of the parameters α, Λ, Λ′ is contained, then proceed to step S322.

[0095] S322. If the final analysis parameters obtained after step S2 do not include α, Λ, Λ′, then G′[α, Λ, Λ′] = 0; if the final analysis parameters obtained after step S2 include at least one of α, Λ, Λ′, then G′[α, Λ, Λ′] is the product of the output parameters.

[0096] C1 and C2 are determined using the least squares method combined with experiments, as follows:

[0097] S311. Select a sound insulation material with a specific surface density, and for polyurethane foam with the same Young's modulus, cut three different thicknesses, and after compositing them with the sound insulation material, conduct window tests in an acoustic reverberation-anechoic chamber to obtain three corresponding insertion loss curves.

[0098] S312. Use the least squares method to determine the values ​​of C1 and C2, so that the sum of squared residuals Q of the test values ​​in each frequency band from 500 to 10000 Hz in 1 / 3 octave band is minimized, that is:

[0099]

[0100] Among them, IL ie Indicates according to IL LF IL HF The estimated value, IL i This represents the measured value. When the Q value is at its minimum, the values ​​of the adjustment coefficients C1 and C2 can be obtained.

[0101] Based on the above steps, an analysis method for the insertion loss of polyurethane-based composite materials on high and low frequencies was obtained. An acoustic database was established from a material perspective, demonstrating the material's ability to significantly reduce motor noise when it performs at its maximum capacity. However, in actual motor installation, due to the installation of wiring harnesses and conduits, these interfaces need to be avoided during design, requiring openings in the original material, and even large-scale deletion in some areas. This results in low coverage of the final product, preventing the material from achieving its maximum acoustic performance. Therefore, the surface coverage of the material surrounding the electric drive assembly must also be considered when establishing the database.

[0102] According to leakage theory, the acoustic properties of a material gradually decrease as the opening area increases. Simultaneously, the frequency also gradually shifts to lower frequencies as the opening area increases. In other words, the larger the opening area, the greater the range of acoustic performance degradation from high to low frequencies. Within this affected frequency range, the acoustic curve no longer shows an upward trend with increasing frequency, but rather becomes almost a horizontal straight line. The method for determining the change of this horizontal straight line value with the opening area is as follows:

[0103] S331. Select any combination of polyurethane foam and sound insulation layer in any state, and test the insertion loss curve IL of the material in the non-porous state. s0 ;

[0104] S332, Set the acoustic package coverage range of the electric drive assembly [S a S b The insertion loss of a flat plate sample with an opening was tested using the reverberation-anechoic chamber window method. The area of ​​the square scanning region of the original test window acoustic intensity probe was defined as A0. This region was then divided into an array of m*m small regions, with a circular opening in each region, the areas of which were respectively...

[0105] S333. Window insertion loss tests were conducted for two different aperture areas, and the horizontal line insertion loss values ​​in the high-frequency band were obtained as follows: IL sa IL sb Any coverage S within this coverage range k The high-frequency insertion loss IL was determined using linear interpolation. sk ;

[0106] S334, Compare the raw material insertion loss curves IL s0 and insertion loss IL with aperture ratio at high frequencies sk The intersection of the two curves is where the coverage ratio is S. k The lowest frequency affected If the frequency is below this value, its acoustic curve is consistent with the performance of the material in the unopened state; if the frequency is above this value, its acoustic curve is the insertion loss level line in the high-frequency band of the open state.

[0107] Based on the above steps, calculation methods for insertion loss in low-frequency, mid-to-high-frequency, and pore-considered states of polyurethane foam and sound insulation layer composite materials are obtained. Based on this theory, a corresponding data query and retrieval system is established. This system can quickly and effectively evaluate the noise attenuation of drive motors after adding acoustic materials, and can also find corresponding materials, displaying the weight and cost of various materials, greatly improving the development efficiency of acoustic package products.

[0108] Application Example: An acoustic package for a new energy electric drive assembly, composed of a composite of recoated ethylene-vinyl acetate copolymer (EVA) and polyurethane foam, is used as the evaluation target to establish a material acoustic database with an open structure.

[0109] First, key parameters were identified based on the actual process. In the initial production process, a certain polyether polyol compound was mixed with isocyanate raw materials in a certain proportion to generate polyurethane foam in its initial state. Various parameters of the polyurethane foam were tested: density ρ, Young's modulus E, Poisson's ratio υ, damping η, porosity φ, flow resistance σ, tortuosity α, viscoelastic characteristic length Λ, and thermal characteristic length Λ′.

[0110] In a polyurethane foam molding process, the adjustable process parameters are: mixing ratio (40%-70%), mold temperature (50℃-75℃), and molding time (90s-180s). Based on the maximum and minimum adjustable ranges of each parameter, eight different states of polyurethane foam can be formed. The BIOT parameters of the eight materials were tested, forming a 9x8 matrix. Output the minimum and maximum values ​​of each parameter in each row, such as the curvature (1.213-1.951), which is the range of variation of each material parameter under actual process adjustment.

[0111] The EVA weight of the sound insulation layer is selected to be 3.5 kg / m³. 2 The initial polyurethane foam and EVA parameters are input into the acoustic calculation software to calculate the material insertion loss IL. Keeping other parameters constant, the minimum and maximum values ​​of each parameter obtained above are input into the software for calculation. For example, if the curvature parameter is changed from the initial 1.503 to 1.213 and 1.951 respectively, the corresponding insertion loss curves IL1(γ) and IL2(γ) are obtained. The remaining parameters are calculated using the same method to obtain their corresponding curves.

[0112] Within the 500–10000 Hz frequency range, all insertion loss curves were arithmetically averaged, and the difference between the average values ​​corresponding to the changes in each parameter was calculated and arranged in descending order. The parameters with the largest final differences were Young's modulus E, flow resistivity σ, and density ρ.

[0113] Among the aforementioned adjustable process parameters, 10 foaming parameters are arbitrarily defined to produce 10 different states of polyurethane foam. The Young's modulus E, flow resistance σ, and density ρ of each state are then tested. Each parameter forms a 10×1 matrix, namely [E], [σ], and [ρ]. Using Pearson correlation coefficient theory, the correlation coefficient r of each of the three parameter matrices is calculated. Eσ r σρ r ρE Their values ​​are 0.375, 0.681, and 0.752, respectively.

[0114] Based on the parameter selection method in step S2, the parameters Young's modulus E and flow resistance σ are retained, while the density ρ is discarded. The retained parameters are used as independent variables affecting the insertion loss of the composite component. Subsequent calculation methods are defined, and a corresponding database is established.

[0115] The final physical parameters retain only the Young's modulus E, while the damping loss factor η is not included in the low-frequency influence parameters. Here, the actual value of η can be entered, or the damping factor can be directly set to 1; the difference lies in the different adjustment coefficient values. If the damping coefficient is assumed to be 1, then according to the least squares method, the determined adjustment coefficient value is 40.13. Therefore, in this embodiment, the low-frequency insertion loss curve of the structure can be expressed as:

[0116]

[0117] In the formula, M is the surface density of the sound insulation material, d is the thickness of the polyurethane foam, E is the Young's modulus of the foam, f is the frequency, and IL is the molecular weight. LF This is the low-frequency insertion loss curve.

[0118] In the high-frequency band, the sound wave wavelength is relatively short, and the material physical parameters have a smaller impact on the structural acoustic performance, while the pore parameters have a greater impact. In this embodiment, the final retained pore parameter is the flow resistance σ, and all other parameters are discarded, i.e., G′[α, Λ, Λ′]=0. In this embodiment, the overall sound absorption performance of the polyurethane foam reaches its optimal value of approximately 50000. With an aperture ratio of 0.96, and C2 determined to be approximately 0.0001 using the least squares method, the insertion loss curve of the structure at mid-to-high frequencies is as follows:

[0119]

[0120] In the formula, M is the surface density of the sound insulation material, d is the thickness of the polyurethane foam, E is the Young's modulus of the foam, f is the frequency, and IL is the molecular weight. HF This is the insertion loss curve for medium to high frequencies.

[0121] Finally, an acoustic performance database was established based on the actual coverage. The acoustic package coverage of a certain electric drive assembly was determined to be approximately 60%–90%. The scanning area of ​​the reverberation-anechoic chamber window was defined as 0.5m*0.5m, divided into 25 small area arrays. The opening area of ​​each area was 0.001m²–0.004m². Window acoustic tests were conducted, and the insertion loss levels in the high-frequency band were 4.5dB and 11.7dB, respectively. Linear interpolation was used to calculate other insertion loss values ​​within this coverage range.

[0122] The intersection points of insertion loss curves for the same material under full coverage and different coverage rates were identified. The intersection frequency at 90% coverage was approximately 1600Hz, and at 60% coverage, it was approximately 500Hz. This means that at these coverage rates, changing material property parameters only affects acoustic performance below the intersection frequency band; above this band, there is virtually no impact. For example, at 60% coverage, only frequencies below 500Hz are affected, while for acoustic materials used in passive noise reduction, the lowest frequency affected is generally at least 400Hz. This method demonstrates that if the coverage of the electric drive assembly is too low, no matter what optimizations are made to the material itself, there will be no significant effect on the overall noise reduction of the electric drive.

[0123] Based on the above method, a calculation method for the acoustic performance of an acoustic package containing polyurethane foam in an electric drive assembly with a certain coverage ratio was obtained. Using this calculation method, acoustic results from different combinations of variations in sound insulation layer density, Young's modulus of polyurethane foam, and flow resistance parameters were integrated into a corresponding database system. The interface allows for both forward parameter input and querying. For several materials, inputting various material parameters can yield acoustic performance comparison curves, total material weight, and corresponding cost data. It also allows for reverse parameter retrieval. By inputting the desired noise reduction performance at a known frequency range, the optimal combination of materials that meets this requirement is retrieved, outputting lightweight and low-cost materials.

[0124] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A performance database for acoustic packages based on polyurethane foam, characterized in that, The database was established using the following steps: S1. Determine the initial analytical parameters for polyurethane foaming, specifically including the following steps: S11. Measure the material parameters of the polyurethane foam in its initial state. There are k adjustable process parameters in total. Based on the upper and lower limits of each process parameter, produce 2... k Material samples in different states were used, and the material parameters of all samples were measured. The material parameters included physical parameters and pore parameters, and the maximum and minimum values ​​of each parameter were obtained. S12. Input the material parameters of the polyurethane foam in the initial state into the acoustic calculation software VA One to obtain the insertion loss curve of the composite material. Then, change the value of a certain material parameter to the maximum and minimum values ​​of that parameter, while keeping the other material parameters unchanged, to obtain two insertion loss curves of that parameter within the adjustable range. Repeat this process for the other parameters until two insertion loss curves of all parameters within the adjustable range are obtained. S13. Define the frequency range of the acoustic material that produces noise reduction effect as 500-10000Hz. Take the arithmetic mean of all the insertion loss curves obtained in step S12 for all frequency bands, and take the difference between the maximum and minimum values ​​of each material parameter and its corresponding average value. Select the three parameters with the largest differences as the initial analysis parameters and arrange them in order of size. S2. Determine the final analytical parameters for polyurethane foaming, specifically including the following steps: S21. Adjust the foaming process parameters and prepare m polyurethane foam samples. Test the initial analytical parameters of these foam samples respectively to form a parameter matrix. S22. Using the Pearson correlation coefficient, calculate the correlation between the data series respectively, obtain their respective correlation coefficients, and determine the selection or rejection of the initial analysis parameters in step S13 according to the magnitude of the coefficient values ​​to obtain the final analysis parameters. S3. Establish an acoustic package performance database, which includes the following steps: S31. In the mid-to-low frequency range, establish a method for calculating the acoustic performance of polyurethane foam in the mid-to-low frequency range based on the physical parameters of the polyurethane foam. S32. In the mid-to-high frequency range, establish a method for calculating the mid-to-high frequency acoustic performance of polyurethane foam based on the pore parameters. S33. Based on the actual state of the acoustic package of the electric drive assembly, the insertion loss curves of the two states of full coverage and with coverage ratio are measured by the sound insulation test method of the reverberation chamber-anechoic chamber window. These two insertion loss curves are the starting points of the frequency bands affected by the corresponding coverage ratio, and a material acoustic performance database is established.

2. The acoustic package performance database based on polyurethane foam according to claim 1, characterized in that, In step S11, the physical parameters include at least one of density, Young's modulus, Poisson's ratio, and damping factor; the pore parameters include at least one of porosity, flow resistance, tortuosity, viscous characteristic length, and thermal characteristic length; and the process parameters include at least one of mixing ratio, mold temperature, and molding time.

3. The acoustic package performance database based on polyurethane foam according to claim 2, characterized in that, The correlation coefficient in step S22 is obtained according to the following formula: in, x i y i This represents the two parameter values ​​of the selected i-th sample block. This represents the average value of all samples for the two selected parameters, where r is the correlation coefficient. In step S22, the selection or rejection of initial analysis parameters is determined according to the following method: S221. When the correlation coefficients of the three parameters all satisfy -1≤r<0.5, it indicates that the parameter values ​​are not highly correlated or are negatively correlated. In this case, all three parameters are defined as independent variables and used as the final analysis parameters. S222. When one of the correlation coefficients reaches 0.5 or above, and the other two correlation coefficients each satisfy -1≤r<0.5, it indicates that the two parameters with a correlation coefficient of 0.5 or above have a certain correlation. According to the results of step S1, if the influence of one parameter is higher than that of the other parameter, the parameter with the lower influence is discarded, and the other two parameters are defined as independent variables as the final analysis parameters. S223. When the correlation coefficients of the three parameters are all 0.5 or higher, it indicates that there is a strong correlation between the parameters. Based on the results of step S1, the parameter with the highest influence is defined as the independent variable and used as the final analysis parameter.

4. The acoustic package performance database based on polyurethane foam according to claim 3, characterized in that, In steps S31 and S32, the low-to-mid frequency band is 500–2000 Hz, and the high-frequency band is 2000–10 kHz.

5. The acoustic package performance database based on polyurethane foam according to claim 4, characterized in that, In step S31, in the low-to-mid frequency range, the physical parameters of polyurethane foam are substituted into the acoustic performance analysis, and its acoustic performance is expressed as follows: IL LF =20*lg(fM)+F[ρ,E,γ,η,d,f]+C1,(500Hz≤f≤2000Hz) Among them, IL LF The insertion loss curve is shown in the low-to-mid frequency range. M is the density of the sound insulation layer, f is the frequency, F[ρ,E,γ,η,d,f] is a function of a certain physical parameter, where ρ is the density, E is Young's modulus, γ is Poisson's ratio, η is the damping factor, d is the material thickness, and C1 is the adjustment coefficient.

6. The acoustic package performance database based on polyurethane foam according to claim 5, characterized in that, In step S32, in the mid-to-high frequency range, the pore parameters of polyurethane foam are substituted into the acoustic performance analysis, and its acoustic performance is expressed as follows: IL HF =20*lg(fM)+G[φ,σ,α,Λ,Λ',f],(2000Hz≤f≤10000Hz) G[φ,σ,α,Λ,Λ',f]=C2*φ(σ-σ0)*lg(f)+G'[α,Λ,Λ'] Among them, IL HF The insertion loss curve is shown in the mid-to-high frequency band. M is the density of the sound insulation layer, f is the frequency, G[φ,σ,α,Λ,Λ',f] is a function of polyurethane foam with respect to pore parameters, where φ is porosity, σ is flow resistance, α is tortuosity, Λ is viscous characteristic length, Λ' is thermal characteristic length, σ0 is the flow resistance when the sound absorption coefficient of a material of a certain thickness reaches its maximum in each frequency band, c2 is an adjustment coefficient, and G'[α,Λ,Λ'] is a function of tortuosity, viscous characteristic length, and thermal characteristic length. This function is determined using the following steps: S321. Based on the three parameters with the greatest impact output in step S1, if none of them contain α, Λ, Λ', then G'[α, Λ, Λ'] = 0; if at least one of the parameters α, Λ, Λ' is contained, then proceed to step S322. S322. If the final analysis parameters obtained after step S2 do not include α, Λ, Λ', then G'[α, Λ, Λ'] = 0; if the final analysis parameters obtained after step S2 include at least one of α, Λ, Λ', then G'[α, Λ, Λ'] is the product of the output parameters.

7. The acoustic package performance database based on polyurethane foam according to claim 6, characterized in that, C1 and c2 are determined using the least squares method combined with experiments, as follows: S311. Select a sound insulation material with a specific surface density, and for polyurethane foam with the same Young's modulus, cut three different thicknesses, and after compositing them with the sound insulation material, conduct window tests in an acoustic reverberation-anechoic chamber to obtain three corresponding insertion loss curves. S312. Use the least squares method to determine the values ​​of C1 and C2, so that the sum of squared residuals Q of the test values ​​in each frequency band from 500 to 10000 Hz in 1 / 3 octave band is minimized, that is: Among them, IL ie Indicates according to IL LF IL HF The estimated value, IL i This represents the measured value. When the Q value is at its minimum, the values ​​of the adjustment coefficients C1 and C2 can be obtained.

8. The acoustic package performance database based on polyurethane foam according to claim 7, characterized in that, Step S33 specifically includes the following steps: S331. Select any combination of polyurethane foam and sound insulation layer in any state, and test the insertion loss curve IL of the material in the non-porous state. s0 ; S332, Set the acoustic package coverage range of the electric drive assembly [S a ,S b The insertion loss of a flat plate sample with an opening was tested using the reverberation-anechoic chamber window method. The area of ​​the square scanning region of the original test window acoustic intensity probe was defined as A0. This region was then divided into an array of m*m small regions, with a circular opening in each region, the areas of which were respectively... S333. Window insertion loss tests were conducted for two different aperture areas, and the horizontal line insertion loss values ​​in the high-frequency band were obtained as follows: IL sa IL sb Any coverage S within this coverage range k The high-frequency insertion loss IL was determined using linear interpolation. sk ; S334, Compare the raw material insertion loss curves IL s0 and insertion loss IL with aperture ratio at high frequencies sk The intersection of the two curves is where the coverage ratio is S. k The lowest frequency affected If the frequency is below this value, its acoustic curve is consistent with the performance of the material in the unopened state; if the frequency is above this value, its acoustic curve is the insertion loss level line in the high-frequency band of the open state.

9. An application of a polyurethane foam-based acoustic package performance database as described in any one of claims 1-8, characterized in that, Implement the following functions using a database: (1) Forward input parameter query: Input existing material parameters to obtain the material's weight, cost and acoustic performance curves, evaluate the overall noise reduction performance after the material covers the motor, and provide developers with an overall evaluation of the material, weight, cost and performance. (2) Reverse acquisition of material parameters: Based on the noise reduction requirements to be achieved by the electric drive assembly, input the noise reduction value in the key frequency band, and output the corresponding materials and parameters in reverse, providing electric drive assembly manufacturers with different materials and different costs that meet the performance requirements.

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