JP3136204B2 - Vibration / noise prediction method for vibration control material molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for predicting vibration and noise of a vibration damping material molded article used for transportation machines such as automobiles, railways, aircrafts, etc., industrial machines, building structures and the like.

[0002]

2. Description of the Related Art Generally, in order to reduce radiation noise of a molded product using a material having a small vibration damping capacity (for example, a steel plate),
Measures have been taken to replace the material with a damping material having a large vibration damping capacity (for example, a damping steel plate which is a three-layer viscoelastic material). Conventionally, only the loss coefficient of the damping material is used to predict the effect of reducing vibration and noise when the damping material is replaced.

[0003]

When the conventional material is replaced with a vibration damping material, the resonance frequency or the anti-resonance frequency of the molded product changes as shown in FIG.
Depending on the frequency of the excitation force applied to the molded product, the vibration response magnification may increase due to replacement.

However, in the prediction using only the loss coefficient of the vibration damping material, it is impossible to predict only the difference of the vibration response magnification at each resonance frequency when the conventional material or the vibration damping material is used. The prediction evaluation cannot be performed when the vibration response magnification increases. In other words, the prediction based on only the loss coefficient of the damping material does not consider the change in rigidity when the conventional material is replaced with the damping material, so that it was not possible to accurately predict the vibration reduction effect due to the replacement of the damping material. .

Further, it has been desired to accurately predict the vibration of the surface of a vibration-damping steel sheet molded product during actual operation so that the effect of the vibration-damping steel sheet can be evaluated by hearing.

SUMMARY OF THE INVENTION The present invention is intended to solve such a problem, and makes it possible to easily and accurately predict the vibration characteristics and vibration reduction effect of a molded article made of a vibration damping material. It is an object of the present invention to provide a vibration / noise prediction method that allows the user to experience the effect of reducing vibrations with his / her ear.

[0007]

In order to achieve the above object, a method for predicting vibration and noise of a vibration damping material molded product according to the present invention comprises:
A frequency response function of the vibration-damping material molded article based on the vibration characteristics of the ordinary material molded article obtained by the experiment and the loss coefficient and bending rigidity of the vibration-damping material molded article having the same shape as the ordinary material molded article. By calculating the impulse response of the vibration damping material molded product by performing an inverse Fourier transform of the predicted frequency response function, and then giving the impulse response to a digital filter, thereby obtaining the It is characterized by outputting the vibration of the surface of the vibration damping material molded product during actual operation.

[0008]

According to the method for predicting vibration and noise of a vibration-damping material molded article of the present invention described above, the frequency response function of the vibration-damping material molded article is predicted while considering the loss coefficient and bending rigidity of the vibration-damping material molded article. The vibration of the surface of the damped steel sheet molded product during operation is predicted. In addition, since the vibration of the surface of the vibration-damping material molded product during actual operation is output from the digital filter based on the prediction result, the effect of reducing the vibration of the vibration-damping material molded product can be simulated by hearing.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for predicting vibration and noise of a vibration damping material molded product according to one embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining the procedure, and FIG.
Is a graph showing specific examples of the transfer mobility response function calculated by the present method in comparison with experimental values, and FIGS. 3A and 3B are graphs showing characteristics of impulse response of a damping steel sheet and a normal steel sheet, respectively. is there.

Normally, the vibration characteristics of a molded product of ordinary steel plate (molded product of ordinary material) can be experimentally obtained by conducting a vibration experiment. In other words, one point of the molded product is
When the transfer mobility response function a [= (ΔX / Δt) / F; vibration magnification frequency response function] of the response (vibration velocity ΔX / Δt) at an arbitrary point is measured, each vibration mode Every
Modal parameters such as the equivalent mass m, the equivalent rigidity k, and the equivalent damping c are obtained (step S1 in FIG. 1). For example, when there are n modes in the frequency range of interest, the vibration characteristics of a molded product using a normal steel plate (normal material) are expressed using n sets of modal parameters for these n modes. be able to.

The vibration characteristics of a damped steel sheet molded product (damping material molded product) are basically considered to be similar to the vibration characteristics of a normal steel sheet molded product if the shape is the same as that of the ordinary steel sheet molded product. Can be Therefore, taking into account changes in the surface properties and the Young's modulus, which are the differences in the material properties, the arbitrary point p
Modal parameters (equivalent mass m _pi ', equivalent stiffness k _pi ', equivalent damping coefficient c _pi ')
Is expressed by the following equations (1) to (3) using the equivalent mass m _pi , equivalent stiffness k _pi , and equivalent damping coefficient c _pi which are the modal parameters of the i-th vibration mode at the point p of the ordinary steel sheet molded product. Can be represented.

M _pi ′ = m _pi (ρ ₁ t ₁ + ρ ₂ t ₂ + ρ ₃ t ₃ ) / (ρ ₀ t ₀ ) (1) k _pi ′ = k _pi E (t ₁ + t ₂ + t ₃ ) ³ / (E ₀ t ₀ ³ ) (2) c _pi ′ = c _pi + ηk _pi ′ / ω (3) In the above equations (1) to (3), ρ ₀ t ₀ is the surface density of the ordinary steel sheet, and E ₀ Is the Young's modulus of the ordinary steel sheet, and ω is the angular velocity.
The damping steel plate, which is a three-layer viscoelastic material, is constructed by interposing a viscoelastic resin layer between upper and lower steel plates.
In (1) to (3), ρ ₁ t ₁ and ρ ₃ t ₃ are the areal densities of the upper and lower steel sheets constituting the damping steel sheet, ρ ₂ t ₂ are the areal densities of the viscoelastic resin layer constituting the damping steel sheet, t ₀ is the thickness of ordinary steel plate, t _1, t ₃ is the thickness of the upper and lower steel plates constituting the vibration damping steel plate, t ₂ is the thickness of the viscoelastic resin layer constituting the vibration damping steel plate, E is the vibration damping steel plate The Young's modulus (flexural rigidity) and η are the loss coefficients of the damping steel sheet. These Young's modulus E and loss coefficient η are calculated using the RKU model (Ross-Kerwin
-Ungar model; obtained from the following equations (4) to (6) by the Japan Society of Automotive Engineers of Japan Academic Lecture Preprint 912 1991-10 229 "Study on the prediction of dynamic characteristics of damped steel beams" Figure 1
Step S2).

[0013]

(Equation 1)

However, in the above equations (4) to (6), E ₁ , E ₃
Is the Young's modulus of the upper and lower steel sheets constituting the damping steel sheet, G ₁ + jG ₂
Is the complex shear modulus of the viscoelastic resin that constitutes the damping steel sheet,
I is the second moment of area of the three-layer beam (t ₁ + t ₂ + t ₃ ) ³ /
Given as 12.

The modal parameters m _pi ′, k _pi ′, and c _pi ′ of the i-th vibration mode calculated using the above equations (1) to (6).
Based on the above, the mobility response function (vibration magnification frequency response function) a of the vibration damping steel sheet molded product is calculated using the following equations (7) and (8) (step S3 in FIG. 1).

[0016]

(Equation 2)

Here, the mobility response function a of the damping steel plate beam is calculated from the driving point mobility response function measurement result of the ordinary steel plate beam.
Is predicted as described above, and compared with the experimental result, the predicted mobility response function a of the damped steel plate beam is obtained.
2 is shown in FIG. In FIG. 2, the points plotted by white square marks indicate the calculated frequency response of the damped steel sheet molded product, the solid line indicates the frequency response experimental value of the damped steel sheet molded article, and the dashed line indicates the ordinary steel sheet molded article. The frequency response experimental value of the product is shown for reference. As is clear from FIG.
The calculated value and the experimental value agree well, and it can be confirmed that the frequency response function a of the vibration damping steel sheet molded product can be predicted with sufficient accuracy for practical use by this method.

In this embodiment, an inverse Fourier transform is performed on the transfer mobility response function a predicted as shown in FIG. 2 (step S4 in FIG. 1). Inverse Fourier transform finds impulse response for damped steel sheet molding
(Step S5 in FIG. 1). FIGS. 3A and 3B show specific examples of impulse responses of the vibration damping steel sheet molded article and the ordinary steel sheet molded article calculated by the inverse Fourier transform, respectively. As can be seen by comparing FIGS. 3A and 3B, the vibration is rapidly reduced by replacing the ordinary steel plate with the damping steel plate.

The characteristics of the impulse response of the vibration-damping steel sheet molded product obtained by the inverse Fourier transform are evaluated by, for example, FIR
Type digital filter 1, as shown in FIG.
When the exciting force data of the molded article mounting portion at the time of actual operation is inputted to the digital filter 1, the vibration of the surface of the molded article at the time of actual operation is output from the digital filter 1 in a pseudo manner.

As described above, according to the vibration / noise prediction method of the vibration-damping material molded product of the present embodiment, the vibration test results (equivalent mass m, equivalent rigidity k,
Based on the equivalent damping c modal parameter) and the complex Young's modulus E and loss coefficient η of the damped steel sheet molded product obtained from the RKU model, the vibration characteristics of the damped steel sheet molded article are predicted, and a comparison between calculation and experiment Thus, the vibration characteristics of the vibration damping steel sheet molded product can be predicted with practical accuracy by the present method.

Further, the effect of replacing the damping steel sheet is simulated by using the FIR digital filter 1 to simulate the vibration of the surface of the damping steel sheet molded product during actual operation. There are also advantages that can be evaluated.

In the above embodiment, the case where the ordinary steel plate is replaced with a damping steel plate which is a damping material has been described as an example. However, a damping material in which the upper and lower steel plates of the damping steel plate are made of another material such as plastic is used. If so, the method of the invention applies analogously. Further, in the above embodiment, the case where the molded product has a beam shape is described, but the method of the present invention is not limited to this, and may be applied to molded products of other various shapes, It goes without saying that the same operation and effect as in the above embodiment can be obtained.

[0023]

As described above in detail, according to the method for predicting vibration and noise of a vibration-damping material molded product of the present invention, the vibration-damping material molded product is taken into consideration while considering the loss coefficient and bending rigidity of the vibration-damping material molded product. In addition to predicting the frequency response function of, the vibration of the surface of the damped steel sheet molded product during actual operation can be predicted easily and accurately.
Based on the prediction result, the digital filter outputs the vibration of the surface of the vibration-damping material molded product during actual operation, so that the vibration reduction effect of the vibration-damping material molded product can be simulated by hearing.
There is also an effect that the replacement effect of the vibration damping material can be confirmed audibly.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining a procedure of a method for predicting vibration and noise of a vibration damping material molded product as one embodiment of the present invention.

FIG. 2 is a graph showing a specific example of a transfer mobility response function calculated by the present method in comparison with experimental values.

FIGS. 3A and 3B are graphs showing characteristics of impulse responses of a damping steel sheet and a normal steel sheet, respectively.

FIG. 4 is a graph showing a comparison of a transfer mobility response function between a conventional material and a damping material.

[Explanation of symbols]

 1 FIR digital filter

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshimitsu Tanaka 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Kobe Steel, Ltd. Kobe Research Institute (72) Inventor Yoshio Inoue Nishi-ku, Kobe-shi, Hyogo 1-5-5 Takatsukadai Kobe Steel, Ltd. Kobe Research Institute (58) Field surveyed (Int. Cl. ⁷ , DB name) G01H 15/00

Claims (1)

(57) [Claims] 1. A method for forming a vibration damping material based on a vibration characteristic of a molded material of ordinary material obtained by an experiment and a loss coefficient and a bending rigidity of a vibration damping material having the same shape as the molded material of normal material. By calculating the impulse response of the vibration damping material molded article by predicting the frequency response function of the article and performing an inverse Fourier transform of the predicted frequency response function, the impulse response is given to a digital filter. A vibration / noise prediction method for a vibration damping material molded product, comprising: outputting the vibration of the surface of the vibration damping material molded product during actual operation from the digital filter.