A calculation method for MNCT coverage of interior materials with uneven thickness

Abstract

The present invention discloses a method for calculating the MNCT coverage of interior materials with uneven thickness, which includes setting a covering on a flat plate, recording the thickness and sound insulation performance of the covering; changing the thickness of the covering, and testing multiple groups of corresponding sound insulation performance; drawing a thickness-sound insulation performance curve; dividing the interior materials with uneven thickness into finite element grids, and measuring the thickness of each grid respectively; and finding the corresponding sound insulation performance value in the thickness-sound insulation performance curve; finding the corresponding thickness value on the thickness-sound insulation performance curve, which is the average thickness value of the interior materials with uneven thickness; and calculating the MNCT coverage rate according to the ratio of the area of ​​the interior materials to the area of ​​the metal plate. In this scheme, through the relationship between thickness and sound insulation performance, the sound insulation performance is averaged and then the average thickness is inferred, so that the average thickness value of the material with uneven thickness is accurately obtained acoustically, and then the acoustic performance can be accurately evaluated.

Description

Technical Field

[0001] The invention belongs to the technical field of sound insulation, and in particular relates to a method for calculating the MNCT coverage of an interior material with uneven thickness. Background Art

[0002] As people's requirements for the comfort of modern cars are increasing, the NVH performance of cars has become one of the most important indicators affecting a car brand. The sound insulation performance of cars is one of the car qualities that users are most likely to perceive and complain about. The quality of sound insulation has an important impact on user reputation and brand image.

[0003] The interior materials of a car have a direct impact on the sound insulation performance of the entire vehicle. The sound insulation performance evaluation method of interior materials is mainly based on placing the entire component to be tested in a soundproof window for testing. However, the test tooling is complex to make, the cost is high, and the tooling is bulky and difficult to disassemble and assemble. In addition, for the development of multiple projects at the OEM, it is necessary to repeatedly disassemble and assemble the test tooling for different models, which is complicated to operate, the process is cumbersome, the cycle is long, and the efficiency is low.

[0004] To this end, acoustic package analysis can be used for simulation calculation. In acoustic package analysis, it is necessary to set the NCT (noise control treatment) of the interior material and calculate its MNCT (multiple noise control treatment) coverage to simulate its sound absorption and insulation characteristics. When calculating the MNCT coverage, for materials of uniform thickness, it can be calculated based on the ratio of the area of ​​the interior material and the area of ​​the metal plate. When calculating the coverage of interior materials of uneven thickness, only an approximate value of the thickness can be taken. However, although there is a certain relationship between thickness and sound insulation characteristics, it is not a completely linear relationship. In the existing method, the coverage is calculated by the arithmetic average thickness of the interior material of uneven thickness, which may lead to poor accuracy of the result. Summary of the invention

[0005] The purpose of the present invention is to provide a method for calculating the MNCT coverage of interior trim materials with uneven thickness, so as to solve the problems in the prior art.

[0006] The present invention is implemented by the following technical solution: a method for calculating the MNCT coverage of interior materials with uneven thickness, characterized in that it comprises the following steps:

[0007] Step 1, set a cover on the flat plate and test its sound insulation performance. When it meets the requirements, record the thickness of the cover and record it as T0; the sound insulation performance at this time is recorded as G0;

[0008] Step 2, changing the thickness T1 of the covering and testing its sound insulation performance G1; testing multiple groups of corresponding T1-G1 values;

[0009] Step 3, calculate the thickness change rate T'= T1 / T0; the sound insulation performance change rate G'= G1 / G0; and draw the thickness-sound insulation performance curve T'- G';

[0010] Step 4: Divide the interior material with uneven thickness into finite element meshes and measure the thickness T of each mesh separately. i ;

[0011] Step 5: Calculate the ratio of the thickness of each grid to T0, and find the corresponding sound insulation performance value G in the thickness-sound insulation performance curve. i ;

[0012] Step 6: G of all grids i The average of the values ​​is taken as the sound insulation performance value G of the entire covering;

[0013] Step 7, find the thickness value T corresponding to the G value on the thickness-sound insulation performance curve, and the thickness value T is the average thickness value of the interior material with uneven thickness;

[0014] Step 8: Calculate the MNCT coverage rate based on the ratio of the interior material area to the metal plate area; the area of ​​the interior material is calculated by the ratio of the volume to the average thickness.

[0015] Further: In step 2, T1=(0.5-2.0)T0.

[0016] Furthermore: the flat plate is a metal plate that is consistent with the material of the vehicle body.

[0017] Further: the covering is an interior decoration material.

[0018] Further: In step 2, at least 20 groups of corresponding T1-G1 values ​​are tested.

[0019] The advantages of the present invention are as follows: in this solution, through simulation testing, a thickness-sound insulation performance curve is obtained, and the curve can effectively express the relationship between thickness and sound insulation performance. Through the curve, the sound insulation performance corresponding to different thicknesses is obtained, and the average thickness is inferred after the sound insulation performance is averaged, so that the average thickness value of the material with uneven thickness is accurately obtained acoustically, and the value is applied to the acoustic calculation to accurately evaluate the acoustic performance. This method effectively solves the problem of poor calculation of sound insulation performance results caused by inaccurate thickness calculation methods in the prior art. DETAILED DESCRIPTION

[0020] The present invention discloses a method for calculating the MNCT coverage of interior materials with uneven thickness, which comprises the following steps:

[0021] Step 1, referring to the interior material and the metal plate of the vehicle body and their bonding relationship, a uniform covering is set on the flat plate, and its sound insulation performance is tested. When the sound insulation performance meets the requirements (the requirements can be the corresponding standards or expected values), the thickness of the covering is recorded and recorded as T0; the sound insulation performance at this time is recorded as G0; the larger G0 is, the better the sound insulation performance is;

[0022] Step 2, changing the thickness T1 of the covering and testing its sound insulation performance G1; repeating multiple times to test multiple groups of corresponding T1-G1 values;

[0023] Step 3, calculate the thickness change rate (i.e. the ratio of the changed thickness to T0) T'= T1 / T0; the sound insulation performance change rate G'= G1 / G0; and draw the thickness-sound insulation performance curve T'- G';

[0024] Step 4: Divide the upper and lower surfaces of the interior material with uneven thickness into finite element meshes and measure the thickness T of each mesh separately. i ; Specifically, the thickness of the grid midpoint can be used as T i ;

[0025] Step 5: Calculate the ratio of the thickness of each grid to T0, and find the corresponding sound insulation performance value G in the thickness-sound insulation performance curve. i ;

[0026] Step 6: G of all grids i The average of the values ​​is taken as the sound insulation performance value G of the entire covering (actually this value is the rate of change, and it can also refer to G0 to convert it into a specific value of sound insulation performance, which has no effect on the result);

[0027] Step 7, find the thickness value T corresponding to the G value on the thickness-sound insulation performance curve, and the thickness value T is the average thickness value of the interior material with uneven thickness;

[0028] Step 8: Calculate the MNCT coverage rate based on the ratio of the interior material area to the metal plate area; the area of ​​the interior material is calculated by the ratio of the volume to the average thickness.

[0029] Preferably: in step 2, T1=(0.5-2.0)T0; and the values ​​of multiple thicknesses are arithmetically distributed. In this solution, only the effect of thickness on sound insulation performance is considered. When the thickness is too small, a cavity effect will occur, affecting the overall sound insulation performance. When the thickness is large, the increase in sound insulation performance of a single grid will not bring too much advantage to the sound insulation performance of the entire interior material, so T1 is limited to (0.5-2.0)T0.

[0030] Preferably: in step 2, at least 20 groups of corresponding T1-G1 values ​​are tested.

[0031] Preferably, the volume of the interior material can be calculated by the ratio of the weight to the average density.

[0032] In this solution, through simulation tests, a thickness-sound insulation performance curve is obtained. This curve can effectively express the relationship between thickness and sound insulation performance. Through this curve, the sound insulation performance corresponding to different thicknesses is obtained, and the average thickness is inferred after averaging the sound insulation performance, so that the average thickness value of the material with uneven thickness is accurately obtained acoustically. This value is applied to acoustic calculations to accurately evaluate the acoustic performance. This method is particularly suitable for interior materials with little thickness variation, and does not consider the cavity effect, etc., but only considers the influence of thickness on acoustics. This method effectively solves the problem of poor sound insulation performance calculation results caused by inaccurate thickness calculation methods in the prior art. The average thickness and coverage calculated by this method can also be applied to other acoustic calculations, and has wide adaptability.

Claims

1. A method for calculating the MNCT coverage of interior materials with uneven thickness, characterized by: The steps include: Step 1, set a cover on the flat plate and test its sound insulation performance. When it meets the requirements, record the thickness of the cover and record it as T0; the sound insulation performance at this time is recorded as G0; Step 2, changing the thickness T1 of the covering and testing its sound insulation performance G1; testing multiple groups of corresponding T1-G1 values; Step 3, calculate the thickness change rate T'= T1 / T0; the sound insulation performance change rate G'= G1 / G0; And draw the thickness-sound insulation performance curve T'- G'; Step 4: Divide the interior material with uneven thickness into finite element meshes and measure the thickness T of each mesh separately. i ; Step 5: Calculate the ratio of the thickness of each grid to T0, and find the corresponding sound insulation performance value G in the thickness-sound insulation performance curve. i ; Step 6: G of all grids i The average of the values ​​is taken as the sound insulation performance value G of the entire covering; Step 7, find the thickness value T corresponding to the G value on the thickness-sound insulation performance curve, and the thickness value T is the average thickness value of the interior material with uneven thickness; Step 8, calculating the MNCT coverage rate according to the ratio of the interior material area to the metal plate area; wherein the area of ​​the interior material is calculated by the ratio of the volume to the average thickness.

2. The method for calculating the MNCT coverage of interior materials with uneven thickness according to claim 1, characterized in that: In step 2, T1=(0.5-2.0)T0.

3. The method for calculating the MNCT coverage of interior materials with uneven thickness according to claim 1, characterized in that: The flat plate is a metal plate that is consistent with the material of the vehicle body.

4. The method for calculating the MNCT coverage of interior materials with uneven thickness according to claim 1, characterized in that: The covering is an interior material.

5. The method for calculating the MNCT coverage of interior materials with uneven thickness according to claim 1, characterized in that: In step 2, at least 20 groups of corresponding T1-G1 values ​​are tested.