Acoustic packet performance database based on polyurethane foaming and application

Abstract

The invention discloses an acoustic packet performance database based on polyurethane foaming and application, and the database is established by adopting the following steps: S1, determining initial analysis parameters of polyurethane foaming, and outputting three parameters with maximum influence factors based on an actual process adjustable range; and S2, determining final analysis parameters of polyurethane foaming. And calculating the correlation degree between the sequences by using a Pearson correlation coefficient to obtain respective correlation coefficients, and determining the selection of the initial analysis parameters according to the values of the coefficients to obtain final analysis parameters. And S3, establishing an acoustics including performance database. And the physical parameters are substituted into medium and low frequency acoustic performance analysis, the pore parameters are substituted into medium and high frequency acoustic performance analysis, the coating rate of the material is used as a calculation parameter, the influence trend of the coating rate on the acoustic performance is analyzed, and a final acoustic material database is established. According to the method, various requirements such as development and evaluation of the acoustic package, motor noise reduction scheme screening and process parameter adjustment can be met at the same time.

Description

Technical Field

[0001] The invention relates to an acoustic bag performance database based on polyurethane foaming and application thereof. Background Art

[0002] In recent years, the number of new energy vehicles in the Chinese market has continued to increase, and various automakers have continuously expanded new functions in the research and development of vehicle performance to attract consumers. As an important part of new energy vehicles, the electric drive assembly is also an important part of the noise source of vehicles running at medium and low speeds. The integration of electronic control and motor, coupled with consumers' demand for performance and the emergence of high-power motors, has further aggravated the deterioration of the assembly's NVH performance. Installing an acoustic package is one of the noise reduction treatment methods currently used by mainstream manufacturers.

[0003] On the one hand, due to its unique pore structure, polyurethane material has better formability and low compression permanent deformation rate compared to fiber-type sound-absorbing cotton. It is a porous sound-absorbing material widely used in automotive interior and exterior decoration. As a material in direct contact with the motor housing, in addition to its own sound absorption effect, it also needs to have a certain damping effect. As a typical foaming material, referring to the acoustic theory of porous foaming materials, its sound absorption performance is affected by nine parameters. However, in order to meet the actual state and production needs of the acoustic package, it is not practical to consider all parameters comprehensively. It is necessary to effectively improve the acoustics of the material while meeting the rapid adjustment of the production process.

[0004] On the other hand, the NVH performance of the electric drive assembly needs to be tested in a special acoustic semi-anechoic chamber and a supporting test bench. It is expensive and time-consuming to conduct an electric drive assembly test bench. It is not practical to directly verify the acoustic effect of the material on the test bench for the accumulation of material data, especially in the early material development stage. At the same time, as an electric drive manufacturer, due to various internal and external factors, it is impossible to provide sufficient resources for repeated verification of the acoustic package solution, so it is hoped that the supplier can provide an acoustic package that meets its acoustic noise reduction requirements at one time. Considering the wiring installation of the electric drive assembly, the actual state of the acoustic package is not close to the ideal coating, but to avoid various holes generated by the wiring, which greatly affects the acoustic performance of the material. In addition, electric drive manufacturers will propose to meet the trend of lightweighting of automobiles while meeting the acoustic performance, and the two themselves are also a pair of contradictions.

[0005] Therefore, a polyurethane foam-based acoustic bag performance database and its application are urgently needed. Summary of the invention

[0006] In order to solve the defects of the prior art, the present invention provides an acoustic package performance database based on polyurethane foam, which can not only effectively improve the acoustic performance, but also meet the rapid adjustment of the process, and at the same time can provide the parts expected by electric drive manufacturers at one time, and can also meet the overall lightweight requirements.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] The first object of the present invention is to provide an acoustic bag performance database based on polyurethane foaming, wherein the database is established by the following steps:

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

[0010] S11, determine the material parameters of the polyurethane foam in the initial state, there are k adjustable process parameters in total, and according to the upper and lower limits of each process parameter, produce 2 k material samples in different states, and then measure the material parameters of all material samples respectively, the material parameters include physical parameters and pore parameters, and obtain the maximum and minimum values ​​of each parameter;

[0011] S12, inputting 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, changing the value of a certain material parameter to the maximum value and the minimum value of the parameter, and keeping the other material parameters unchanged, to obtain two insertion loss curves of the parameter within the adjustable range, and the other parameters are deduced in this way, until two insertion loss curves of all parameters within the adjustable range are obtained;

[0012] S13, defining the frequency range of the acoustic material producing noise reduction effect as 500-10000 Hz, taking the arithmetic average of all insertion loss curves obtained in step S12 for all frequency bands, and taking the difference between the maximum value and the minimum value of each material parameter and the corresponding average value, selecting the first three parameters with the largest difference as initial analysis parameters, and arranging them in order of size;

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

[0014] S21, adjusting the foaming process parameters and preparing m polyurethane foaming samples, respectively testing the values ​​of the initial analysis parameters of these foaming samples to form a parameter matrix;

[0015] S22, using the Pearson correlation coefficient, respectively calculate the correlation between the series, obtain the respective correlation coefficients, and determine the selection of the initial analysis parameters in step S13 according to the coefficient values ​​to obtain the final analysis parameters;

[0016] S3. Establishing an acoustic package performance database, specifically including the following steps:

[0017] S31. In the low and medium frequency bands, the double-wall system composed of the sound insulation layer, polyurethane foam and electric drive shell has a natural frequency. As a viscoelastic body, the polyurethane foam layer has both propagation and attenuation effects on sound energy. Therefore, the physical parameters of polyurethane foam are used to establish a calculation method for low and medium frequency acoustic performance.

[0018] S32. In the medium and high frequency bands, the sound wave frequency is relatively short. The attenuation of sound energy by polyurethane foam is mainly based on 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, the pore parameters of polyurethane foam are used to establish a calculation method for the medium and high frequency acoustic performance.

[0019] S33. Based on the actual state of the acoustic package of the electric drive assembly, the insertion loss curves of the two states, with coverage and full coverage (no holes), were measured through 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 rate. The relationship between the coverage rate and the lowest influence frequency band is obtained, and a material acoustic performance database is established.

[0020] Preferably, the physical parameters in step S11 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 resistivity, tortuosity, viscosity 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 Represents the two parameter values ​​of the selected i-th sample block, It represents the average value of all samples for the two selected parameters, and r is the correlation coefficient;

[0024] In step S22, the selection 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, indicating that the parameter values ​​are not highly correlated or are negatively correlated, the three parameters are defined as independent variables as the final analysis parameters;

[0026] S222. When one of the correlation coefficients reaches 0.5 or above, and the other two correlation coefficients satisfy -1≤r<0.5, it indicates that the two parameters with correlation coefficients of 0.5 or above have a certain correlation, and according to the result of step S1, if the influence of one parameter is higher than that of the other parameter, the parameter with 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 above, it indicates that there is a strong correlation between the parameters, and according to the result of step S1, only the parameter with the highest influence is defined as the independent variable as the final analysis parameter.

[0028] Preferably, in step S31 and step S32, the low-medium frequency band is 500-2000 Hz, and the high-frequency band is 2000-10 kHz.

[0029] Preferably, in step S31, in the medium and low frequency bands, the physical parameters of polyurethane foaming are substituted into the acoustic performance analysis, and the 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 is the insertion loss curve in the medium and low frequency bands, M is the density of the sound insulation layer, f is the frequency, F[ρ, E, γ, η, d, f] is a function of physical parameters, ρ is the density, E is the Young's modulus, γ is the 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 middle and high frequency bands, the pore parameters of the polyurethane foam are substituted into the acoustic performance analysis, and the 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 HFis the insertion loss curve in the medium and high frequency bands, M is the density of the sound insulation layer, f is the frequency, G[φ, σ, α, Λ, Λ′, f] is a function of the polyurethane foaming parameters on the pore parameters, φ is the porosity, σ is the flow resistivity, α is the tortuosity, Λ is the viscous characteristic length, Λ′ is the thermal characteristic length, σ0 is the flow resistivity when the sound absorption coefficient of a certain thickness material in each frequency band reaches the maximum, C2 is the adjustment coefficient, G′[α, Λ, Λ′] is a function of the tortuosity, the viscous characteristic length and the thermal characteristic length, and the function is determined by the following steps:

[0037] S321, output the three parameters with the greatest influence according to step S1, if none of them contain α, Λ, Λ′, then G′[α, Λ, Λ′]=0; if at least one parameter among α, Λ, Λ′ is contained, proceed to step S322;

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

[0039] Preferably, the C1 and C2 are determined by least square method combined with experiment, the method is as follows:

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

[0041] S312. Determine the values ​​of C1 and C2 by using the least square method so that the residual square sum Q of the test values ​​of each frequency band of 500 to 10000 Hz in 1 / 3 octave is minimized, that is:

[0042]

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

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

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

[0046] S332, set the acoustic package coverage range of the electric drive assembly [S a , S b ], the insertion loss of the flat plate with openings is tested by the reverberation-anechoic chamber window method; the square scanning area of ​​the original window sound intensity probe is defined as A0, and then this area is divided into m*m small area arrays, and a circular hole is opened in each small area, and its area is respectively

[0047] S333, respectively conduct window insertion loss tests for two opening areas, and obtain horizontal line insertion loss values ​​in the high frequency band as IL sa IL sb , any coverage rate S within this coverage rate range k , use linear interpolation to determine its high frequency insertion loss IL sk ;

[0048] S334, compare the raw material insertion loss curve IL s0 And the insertion loss IL with aperture ratio in high frequency band sk , then the intersection of the two curves is the coverage rate S k Lowest frequency affected If it is lower than this frequency, its acoustic curve is consistent with the performance of the material without holes; if it is higher than this frequency, its acoustic curve is the insertion loss horizontal line of the high frequency band in the hole state.

[0049] The second purpose of the utility model is to provide an application of a polyurethane foam-based acoustic bag performance database, which uses the database to achieve the following functions:

[0050] (1) Forward input parameter query: Input the existing material parameters to obtain the material weight, cost and acoustic performance curve, 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: According to the noise reduction requirements that the electric drive assembly needs to achieve, the noise reduction value in the key frequency band is input, and the corresponding materials and corresponding parameters are reversely output to provide the electric drive assembly manufacturers with noise reduction solutions 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] The present invention proposes a material database establishment method for noise reduction of electric drive acoustic package based on polyurethane foaming. The method identifies the important parameters affecting the composite material of the acoustic package based on the numerous acoustic parameters of the polyurethane material and the adjustment parameters of the actual process, calculates the acoustic performance of different material parameters according to relevant theories, and establishes a corresponding data retrieval system. The method can provide a fast and effective evaluation of existing materials, find suitable material solutions for sample production, and provide material solutions of different costs for the noise reduction needs of drive assembly manufacturers, avoiding the waste of time and capital costs caused by blindly looking for material solutions for bench tests. By adjusting the process parameters, the foaming state of polyurethane can be quickly and effectively controlled, thereby meeting the different performance requirements of different customers for the acoustic package. The research on polyurethane foam materials, especially the development and application of materials and mechanisms of acoustic packages corresponding to the noise reduction requirements of different orders of noise in electric drive assemblies, provides a better solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Create a schematic diagram for the polyurethane composite acoustic database;

[0055] Figure 2 It is a schematic diagram of the identification process of important analysis parameters;

[0056] Figure 3 A schematic diagram of a method for determining acoustic performance taking coverage into account;

[0057] Figure 4 Schematic diagram of data retrieval for acoustic performance of materials under a certain process. DETAILED DESCRIPTION

[0058] The following detailed description of exemplary embodiments of the present invention refers to the accompanying drawings, which form a part of the description, and in which exemplary embodiments of the present invention that can be implemented are shown as examples. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be implemented and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but is only for the purpose of illustrating and not limiting the description of the characteristics and features of the present invention, so as to propose the best mode for performing the present invention and to enable those skilled in the art to implement the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

[0059] like Figures 1 to 4 As shown, this embodiment provides a method for establishing a polyurethane-based electric-driven acoustic package material database, comprising the following steps:

[0060] S1. Determine the initial analysis parameters of polyurethane foaming.

[0061] As a typical porous foaming sound-absorbing material, polyurethane foam can be made into different states of polyurethane foam according to different application occasions and requirements by adjusting the formulation process parameters. The sound absorption performance of the foam material is affected by the structure of the internal pores, which can be characterized by its physical parameters and pore parameters. The physical parameters include density, Young's modulus, Poisson's ratio, and damping factor. The pore parameters include porosity, flow resistivity, tortuosity, viscosity characteristic length, and thermal characteristic length. After the sound insulation layer is formed, the reaction process parameters are set, such as temperature, pressure, the proportion of each component in the combined material, the ratio of the combined material and isocyanate, etc. The raw material generates a conformable polyurethane foam in a closed mold. The process parameters directly affect the state of the generated foaming structure, and then affect the acoustic performance. Therefore, it is necessary to select several parameters that have an important influence and can be adjusted in practice from the material parameters as variable factors for establishing the material database of the electric-driven acoustic package.

[0062] S11. In the initial mass production state, polyurethane foaming sample preparation is performed. This state is defined as the initial state of polyurethane foaming, and the polyurethane foaming parameters of the initial state are measured and recorded as P0 = T (ρ0, E0, γ0, η0, φ0, σ0, α0, Λ0, Λ'0). Then, a total of k process parameters are set for adjustment, and 2 are made according to the upper and lower limits of each process parameter. k materials in different states, and measure the parameters of each material separately, namely Get the minimum and maximum values ​​of each parameter

[0063] S12, input any material parameter (such as density parameter) of the initial foaming state into the acoustic calculation software to calculate the insertion loss curve. ρ ,Maximum value ρ Replace the initial state density parameter value ρ0 respectively, keep the other parameters unchanged, and calculate the insertion loss curve after the density parameter is changed. Changes of other parameters are similar, until the insertion loss curves of all physical parameters and pore parameters are obtained.

[0064] S13. Set the frequency range of the acoustic material to produce noise reduction effect to 500Hz~10000Hz. Within this frequency range, perform arithmetic averaging on all the above insertion loss curves in each frequency band, calculate the difference between each parameter under maximum and minimum value changes, select the first three parameters with the largest difference, and arrange them in order of size, such as parameters ρ, η, and σ.

[0065] S2. Determine the final analysis parameters of polyurethane foaming.

[0066] Theoretically, the material property parameters obtained in step S1 are independent of each other, and can be used as a single variable to control the change in its acoustic performance. However, the chemical reaction process of polyurethane is very complicated, and is often affected by various factors in actual production. The change of a certain parameter will inevitably cause changes in other parameters. In this case, further correlation analysis is required to eliminate parameters with strong correlation. The beneficial effect is that the 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 foaming conditions under each state, and test the parameter ρ, η, and σ values ​​of n samples respectively to form a [ρ], [η], [σ] series.

[0068] S22, calculate the correlation between the three parameters, use the Pearson correlation coefficient theory to calculate the correlation between the series, get their respective correlation coefficients, and determine the parameters α, β, γ in step S13 according to 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 Represents the two parameter values ​​of the selected i-th sample block, It represents the average value of all samples for the two selected parameters, and r is the correlation coefficient;

[0072] Determine the parameters ρ, η, and σ according to the following method:

[0073] S221, when the three parameters have their respective correlation coefficients r ρη 、r ησ 、r σρ When all satisfy -1≤r<0.5, it indicates that the parameter values ​​are not highly correlated or are negatively correlated, and the three parameters are defined as independent variables as the final analysis parameters;

[0074] S222. When one of the correlation coefficients reaches 0.5 or above, and the other two correlation coefficients satisfy -1≤r<0.5 (such as r ρη ≥0.5, and -1≤r ησ 、r σρ <0.5), indicating that the parameters ρ and η have a certain correlation, and according to the result of step S1, if the influence of ρ is higher than 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 three parameters have their respective correlation coefficients 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 result of step S1, parameter α has the highest influence. Then, parameters η and σ are discarded, and only parameter ρ is defined as the independent variable as the final analysis parameter.

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

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

[0078] In the low and medium frequency bands, polyurethane foam is sandwiched between the sound insulation layer and the electric drive shell. Since the wavelength of the low and medium frequency bands is relatively long, the vibration energy on the shell surface can easily penetrate the surface of the acoustic package and radiate out, thereby weakening the noise reduction function of the acoustic package. Therefore, in this frequency band, the overall viscoelastic function of the polyurethane foam is emphasized, and the internal pore structure distribution is ignored. Based on the double-wall structure theory consisting of the sound insulation layer-polyurethane-electric drive shell, the natural frequency f0 of the system is:

[0079]

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

[0081] In the low and medium frequency bands, the 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 have a great influence on the noise radiation of the electric drive assembly. Since the wavelength of the low and medium frequency bands is relatively long, the vibration energy on the surface of the housing can easily penetrate the surface of the acoustic package and radiate, thereby weakening the noise reduction function of the acoustic package. It can be seen from the natural frequency formula of the system:

[0082] (1) The actual adjustable range of polyurethane foam thickness is generally between 0 and 30 mm. Within this range, the greater the thickness of polyurethane foam, 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 value of the sound insulation curve will move to the right, and the sound insulation performance of the structure will deteriorate.

[0084] Therefore, in the low and medium frequency bands, the physical parameters of polyurethane foam are substituted into the acoustic performance analysis. At the same time, the polyurethane foam density range of the actual acoustic package is clearly defined, and its variation is very small, basically a fixed value, and the variation range of Poisson's ratio is also not large. 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 is the insertion loss curve in the medium and low frequency bands, M is the density of the sound insulation layer, f is the frequency, F[ρ, E, γ, η, d, f] is a function of physical parameters, ρ is density, E is Young's modulus, γ is Poisson's ratio, η is damping factor, d is material thickness, and C1 is the adjustment coefficient.

[0088] In the high frequency band, due to the short frequency of sound waves, the cell structure of polyurethane foam can better absorb the noise in this high frequency band, which enhances the acoustic performance of the composite part to a certain extent. Therefore, in the high frequency band, the cell structure parameters of polyurethane are also substituted into the insertion loss analysis of the composite flat plate to establish a database.

[0089] According to the foaming sound absorption theory, under certain thickness, there is a suitable value for air permeability, so that under certain thickness, the sound absorption performance of the foaming material can reach the best level in both low-frequency and high-frequency bands. When it exceeds or falls below this range, the air permeability is not conducive to the material's absorption of sound energy. According to the leakage law of board sound insulation, the leakage area will have a great impact on the medium and high frequency bands. In particular, the high-frequency sound insulation performance will show a significant decline. Therefore, in order 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, no matter what state, a certain porosity needs to be guaranteed.

[0090] In the mid-high frequency band, the pore parameters of polyurethane foam are substituted into the acoustic performance analysis, and its acoustic performance is expressed as follows:

[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 HFis the insertion loss curve in the medium and high frequency bands, M is the density of the sound insulation layer, f is the frequency, G[φ, σ, α, Λ, Λ', f] is a function of the polyurethane foaming on the pore parameters, φ is the porosity, σ is the flow resistivity, α is the tortuosity, Λ is the viscous characteristic length, Λ' is the thermal characteristic length, σ0 is the flow resistivity when the sound absorption coefficient of a certain thickness material in each frequency band reaches the maximum, C2 is the adjustment coefficient, G'[α, Λ, Λ'] is a function of the tortuosity, the viscous characteristic length and the thermal characteristic length, and the function is determined by the following steps:

[0094] S321, output the three parameters with the greatest influence according to step S1, if none of them contain α, Λ, Λ′, then G′[α, Λ, Λ′]=0; if at least one parameter among α, Λ, Λ′ is contained, proceed to step S322;

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

[0096] The C1 and C2 are determined by the least square method combined with experiments, and the method is as follows:

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

[0098] S312. Determine the values ​​of C1 and C2 by using the least square method so that the residual square sum Q of the test values ​​of each frequency band of 500 to 10000 Hz in 1 / 3 octave is minimized, that is:

[0099]

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

[0101] According to the above steps, the analysis method of the insertion loss of polyurethane-based composite materials on high and low frequencies is obtained, and an acoustic database is established from the material perspective. Under ideal conditions, the material can significantly reduce the noise of the motor when it performs at its maximum performance. However, when the motor is actually installed, due to the installation of wiring harnesses and pipelines, these interfaces need to be avoided during design, holes are opened in the original materials, and even some areas need to be deleted on a large scale, so that the coverage rate of the final finished product is not high, resulting in the material being unable to exert its maximum acoustic performance. Therefore, the surface coverage rate of the material wrapped around the electric drive assembly should also be taken into account when establishing the database.

[0102] According to leakage theory, the acoustic performance of the material gradually decreases as the opening area increases. At the same time, the frequency gradually moves to low frequency as the opening area increases. That is, the larger the opening area, the greater the span from high frequency to low frequency affected by the decline in acoustic performance. Within the affected frequency range, its acoustic curve no longer shows an upward trend with increasing frequency, but is almost a horizontal straight line. The method for determining the value of the horizontal straight line with the change of the opening area is as follows:

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

[0104] S332, set the acoustic package coverage range of the electric drive assembly [S a , S b ], the insertion loss of the flat plate with openings is tested by the reverberation-anechoic chamber window method; the square scanning area of ​​the original window sound intensity probe is defined as A0, and then this area is divided into m*m small area arrays, and a circular hole is opened in each small area, and its area is respectively

[0105] S333, respectively conduct window insertion loss tests for two opening areas, and obtain horizontal line insertion loss values ​​in the high frequency band as IL sa IL sb , any coverage rate S within this coverage rate range k , use linear interpolation to determine its high frequency insertion loss IL sk ;

[0106] S334, compare the raw material insertion loss curve IL s0 And the insertion loss IL with aperture ratio in high frequency band sk , then the intersection of the two curves is the coverage rate S k Lowest frequency affected If it is lower than this frequency, its acoustic curve is consistent with the performance of the material without holes; if it is higher than this frequency, its acoustic curve is the insertion loss horizontal line of the high frequency band in the hole state.

[0107] According to the above steps, the calculation method of insertion loss of polyurethane foam and sound insulation layer composite material at low frequency, medium and high frequency and considering the open hole state is obtained. Based on the above theory, the corresponding data query and retrieval system is established. The system can quickly and effectively evaluate the noise attenuation of the drive motor after adding acoustic materials to the material, and can also find the corresponding materials, the weight and cost of various materials, which greatly improves the development efficiency of acoustic package products.

[0108] Application example: The acoustic package of a new energy electric drive assembly composed of a heavy-coated ethylene-vinyl acetate copolymer (EVA) and a polyurethane foam is evaluated by material insertion loss, and a material acoustic database with an open-pore structure is established.

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

[0110] In a polyurethane foam molding process, the actual adjustable process parameters are the mixing ratio (40%-70%), mold temperature (50℃-75℃), and molding time (90s-180s). According to the maximum and minimum values ​​of the adjustable range of each parameter, 8 different states of polyurethane foam can be formed, and the BIOT parameters of the 8 materials are tested separately to form a 9-row 8-column matrix. The minimum and maximum values ​​of each row of parameters are output respectively, such as curvature (1.213-1.951), etc., that is, the variation range of each material parameter obtained under the actual process adjustment.

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

[0112] In the frequency range of 500-10000Hz, all insertion loss curves are arithmetic averaged, and the difference of the average values ​​corresponding to the change of each parameter is calculated and arranged in order from large to small. The parameters with the largest final difference are Young's modulus E, resistivity σ, and density ρ.

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

[0114] According to the parameter selection method of step S2, the parameters Young's modulus E and flow resistivity σ are retained, and the density ρ is discarded. The retained parameters are used as independent variables affecting the insertion loss of the composite component, and the subsequent calculation method is defined to establish a corresponding database.

[0115] The final physical parameter only retains Young's modulus E, and the damping loss factor η does not enter the low-frequency influencing parameters. The actual value of η can be entered here, or the damping factor can be directly set to 1. The difference between the two lies in the different adjustment coefficient values. If the damping coefficient value is assumed to be 1, the adjustment coefficient value determined by the least squares method is 40.13. Therefore, in this embodiment, the low-frequency insertion loss curve of the structure can be expressed as:

[0116]

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

[0118] In the high frequency band, the wavelength of sound waves is short, and the physical parameters of the material have little effect on the acoustic performance of the structure, while the pore parameters have a greater impact. In this embodiment, the pore parameter that is finally retained is the flow resistivity σ, and the other parameters are discarded, that is, G′[α, Λ, Λ′] = 0. In this embodiment, when the overall sound absorption performance of the polyurethane foam reaches the best, its value is about 50000. The opening ratio is 0.96, and the C2 value is determined to be approximately 0.0001 according to the least squares method. The insertion loss curve of the structure at medium and high frequencies is expressed as:

[0119]

[0120] Where, M is the surface density of the sound insulation material, d is the thickness of the polyurethane foam, E is the foam Young's modulus, f is the frequency, IL HF This is the insertion loss curve for mid-high frequency.

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

[0122] Identify the intersection of the insertion loss curves of the same material under full coverage and different coverage, where the intersection frequency of 90% coverage is about 1600Hz, and the intersection frequency of 60% coverage is about 500Hz. This means that at this coverage, changing the material property parameters will only affect the acoustic performance below the intersection frequency band, and will basically have no effect above this frequency band. For example, the 60% coverage mentioned above only affects frequencies below 500Hz, and as an acoustic material for passive noise reduction solutions, the lowest frequency of acoustic impact is generally at least 400Hz. This method proves that if the coverage of the electric drive assembly is too low, no matter what kind of optimization is performed on the material body, there will be no obvious 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 electric drive assembly acoustic package with polyurethane foam under a certain coverage rate was obtained. Using this calculation method, the acoustic results of different combinations of changes in the sound insulation layer density, polyurethane foam Young's modulus, and flow resistivity parameters are integrated into a corresponding database system. Its interface can be used for forward input parameter query. For several materials, by inputting various material parameters, the acoustic performance comparison curve, total material weight, and corresponding cost data of the material can be obtained. Material parameters can also be obtained in reverse. Input the noise reduction performance that needs to be achieved under a known frequency range, and retrieve the best combination of materials that meet this requirement, that is, output light-weight and low-cost materials.

[0124] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A polyurethane foam-based acoustic package performance database, characterized in that: The database is established by following the steps: S1. Determine the initial analysis parameters of polyurethane foaming, specifically including the following steps: S11, determine the material parameters of the polyurethane foam in the initial state, there are k adjustable process parameters in total, and according to the upper and lower limits of each process parameter, produce 2 k material samples in different states, and then measure the material parameters of all material samples respectively, the material parameters include physical parameters and pore parameters, and obtain the maximum and minimum values ​​of each parameter; S12, inputting 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, changing the value of a certain material parameter to the maximum value and the minimum value of the parameter, and keeping the other material parameters unchanged, to obtain two insertion loss curves of the parameter within the adjustable range, and the other parameters are deduced in this way, until two insertion loss curves of all parameters within the adjustable range are obtained; S13, defining the frequency range of the acoustic material producing noise reduction effect as 500-10000 Hz, taking the arithmetic average of all insertion loss curves obtained in step S12 for all frequency bands, and taking the difference between the maximum value and the minimum value of each material parameter and the corresponding average value, selecting the first three parameters with the largest difference as initial analysis parameters, and arranging them in order of size; S2. Determine the final analysis parameters of polyurethane foaming, specifically including the following steps: S21, adjusting the foaming process parameters and preparing m polyurethane foaming samples, respectively testing the values ​​of the initial analysis parameters of these foaming samples to form a parameter matrix; S22, using the Pearson correlation coefficient, respectively calculate the correlation between the series, obtain the respective correlation coefficients, and determine the selection of the initial analysis parameters in step S13 according to the coefficient values ​​to obtain the final analysis parameters; S3. Establishing an acoustic package performance database, specifically including the following steps: S31. In the mid- and low-frequency bands, the physical parameters of polyurethane foaming are used to establish a mid- and low-frequency acoustic performance calculation method; S32. In the mid-high frequency band, the pore parameters of polyurethane foam are used to establish a mid-high frequency acoustic performance calculation method; 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 wrapping rate are measured respectively through 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 wrapping rate, and the material acoustic performance database is established.

2. The polyurethane foam-based acoustic package performance database according to claim 1, characterized in that: In the 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 resistivity, tortuosity, viscosity characteristic length, and thermal characteristic length; and the process parameters include at least one of mixing ratio, mold temperature, and molding time.

3. The polyurethane foam-based acoustic package performance database 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 Represents the two parameter values ​​of the selected i-th sample block, It represents the average value of all samples for the two selected parameters, and r is the correlation coefficient; In step S22, the selection 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, indicating that the parameter values ​​are not highly correlated or are negatively correlated, the three parameters are defined as independent variables as the final analysis parameters; S222. When one of the correlation coefficients reaches 0.5 or above, and the other two correlation coefficients satisfy -1≤r<0.5, it indicates that the two parameters with correlation coefficients of 0.5 or above have a certain correlation, and according to the result of step S1, if the influence of one parameter is higher than that of the other parameter, the parameter with 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 above, it indicates that there is a strong correlation between the parameters, and according to the result of step S1, only the parameter with the highest influence is defined as the independent variable as the final analysis parameter.

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

5. The polyurethane foam-based acoustic package performance database according to claim 4, characterized in that: In step S31, in the medium and low frequency bands, the physical parameters of polyurethane foaming are substituted into the acoustic performance analysis, and the acoustic performance is expressed as follows: IL LF =20*1g(fM)+F[ρ,E,γ,η,d,f]+C1,(500Hz≤f≤2000Hz) Among them, IL LF is the insertion loss curve in the medium and low frequency bands, M is the density of the sound insulation layer, f is the frequency, F[ρ, E, γ, η, d, f] is a function of physical parameters, ρ is the density, E is the Young's modulus, γ is the Poisson's ratio, η is the damping factor, d is the material thickness, and C1 is the adjustment coefficient.

6. The polyurethane foam-based acoustic package performance database according to claim 5, characterized in that: In step S32, in the middle and high frequency bands, the pore parameters of the polyurethane foam are substituted into the acoustic performance analysis, and the acoustic performance is expressed as follows: IL HF =20*1g(fM)+G[φ,σ,α,Λ,Λ',f],(2000Hz≤f≤10000Hz) G[φ,σ,α,Λ,Λ',f]=C2*φ(σ-σ0)*1g(f)+G'[α,Λ,Λ'] Among them, IL HF is the insertion loss curve in the medium and high frequency bands, M is the density of the sound insulation layer, f is the frequency, G[φ,σ,α,Λ,Λ',f] is a function of the polyurethane foaming on the pore parameters, φ is the porosity, σ is the flow resistivity, α is the tortuosity, Λ is the viscous characteristic length, Λ' is the thermal characteristic length, σ0 is the flow resistivity when the sound absorption coefficient of a certain thickness material in each frequency band reaches the maximum, c2 is the adjustment coefficient, G'[α, Λ, Λ'] is a function of the tortuosity, the viscous characteristic length and the thermal characteristic length, which is determined by the following steps: S321, output the three parameters with the greatest influence according to step S1, if none of them contain α, Λ, Λ', then G'[α, Λ, Λ'] = 0; if at least one parameter among α, Λ, Λ' is contained, then proceed to step S322; S322. If the final analysis parameters obtained in step S2 do not include α, Λ, Λ', then G'[α, Λ, Λ'] = 0; if the final analysis parameters obtained in step S2 include at least one parameter among α, Λ, Λ', then G'[α, Λ, Λ'] is the product of the output parameters.

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

8. The polyurethane foam-based acoustic package performance database according to claim 7, characterized in that: The step S33 specifically includes the following steps: S331. Select any combination of polyurethane foam and sound insulation layer and test to obtain the insertion loss curve IL of the material in the non-opening state. s0 ; S332, set the acoustic package coverage range of the electric drive assembly [S a ,S b ], the insertion loss of the flat plate with openings is tested by the reverberation-anechoic chamber window method; the square scanning area of ​​the original window sound intensity probe is defined as A0, and then this area is divided into m*m small area arrays, and a circular hole is opened in each small area, and its area is respectively S333, respectively conduct window insertion loss tests for two opening areas, and obtain the horizontal line insertion loss values ​​in the high frequency band as IL sa IL sb , any coverage rate S within this coverage rate range k , use linear interpolation to determine its high frequency insertion loss IL sk ; S334, compare the raw material insertion loss curve IL s0 And the insertion loss IL with aperture ratio in high frequency band sk , then the intersection of the two curves is the coverage rate S k Lowest frequency affected If it is lower than this frequency, its acoustic curve is consistent with the performance of the material without holes; if it is higher than this frequency, its acoustic curve is the insertion loss horizontal line of the high frequency band in the hole state.

9. An application of a polyurethane foam-based acoustic bag performance database as described in any one of claims 1 to 8, characterized in that: The database is used to implement the following functions: (1) Forward input parameter query: Input the existing material parameters to obtain the material weight, cost and acoustic performance curve, 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: According to the noise reduction requirements that the electric drive assembly needs to achieve, the noise reduction value in the key frequency band is input, and the corresponding materials and corresponding parameters are reversely output to provide the electric drive assembly manufacturers with noise reduction solutions with different materials and different costs that meet the performance requirements.

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