Structure design support device and method, program and recording medium

Abstract

To provide a design guideline that, even under conditions that depend on mass of each part, quantitatively evaluates a deformation form and reduces the mass while ensuring rigidity required for a structure.SOLUTION: An initial natural frequency of a structure f0, a natural frequency ft of the structure when a plate thickness is changed to an arbitrary positive number α times and a density thereof is respectively changed to 1 / α times, and a natural frequency fE of the structure when a Young-modulus is changed to α times are calculated, and then a natural frequency fluctuation ratio b=Δft / ΔfE of the structure is calculated from Δft=ft-f0 and ΔfE=fE-f0.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a structure design support device and method, a program, and a recording medium. [Background technology]

[0002] In recent years, there has been a demand for lighter vehicle bodies, especially in the automotive field. A common countermeasure is to reduce the plate thickness of vehicle body parts. However, reducing the plate thickness also leads to a decrease in the rigidity of the vehicle body. In particular, reducing the plate thickness of a part that is subject to bending deformation results in a significant decrease in rigidity, since bending rigidity is proportional to the cube of the plate thickness. Therefore, a technology has been proposed for selecting vehicle body parts that have deformation forms that make it difficult to reduce rigidity (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-8787 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology disclosed in Patent Document 1 is a technology that deals with so-called static stiffness. Therefore, under conditions where the mass of a structure cannot be ignored, such as during natural vibration of the structure, it is difficult to apply the technology disclosed in Patent Document 1 to quantitative evaluation of the deformation form of the structure.

[0005] The present invention has been made in consideration of the above problems, and aims to provide a structure design support device and method, as well as a program and a recording medium, that can quantitatively evaluate the deformation form of a structure even under conditions that depend on the mass of the structure, such as when the structure is in natural vibration. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention has been proposed in the following aspects as a result of extensive research.

[0007] [1] A calculation unit that calculates an initial natural frequency f0 of a structure and a natural frequency f of the structure when at least one of a plate thickness, a density, and a Young's modulus of an analysis target portion included in the structure is changed based on numerical analysis data; An output unit that outputs a value including Δf=f−f0 as an evaluation point regarding the vibration mode of the structure; A structure design support device comprising:

[0008] [2] The calculation unit is The natural frequency f0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed by an arbitrary positive number α and the density of the analysis target part is changed by 1 / α. t and the natural frequency f of the structure when the Young's modulus of the analysis target portion is changed by α times. E A first calculation unit that calculates Δf t =f t -f0 and Δf E =f E -f0 to the natural frequency fluctuation ratio of the structure b = Δf t / Δf E A second calculation unit that calculates It has The structure design support device according to [1], wherein the output unit outputs the natural frequency fluctuation ratio b calculated by the second calculation unit as the evaluation point.

[0009] [3] The calculation unit calculates the natural frequency f0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed by an arbitrary positive number α, the density of the analysis target part is changed by 1 / α, and the Young's modulus of the analysis target part is changed by 1 / α. N Calculate The output section is Δf N =f NThe structure design support device according to [1], wherein −f0 is output as the evaluation point.

[0010] [4] The calculation unit is The natural frequency f0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed by an arbitrary positive number α times and the density of the analysis target part is kept constant s and the natural frequency f of the structure when the Young's modulus of the analysis target portion is changed by α times and the density of the analysis target portion is changed by α times. E A first calculation unit that calculates Δf s =f s -f0 and Δf E =f E -f0 to the natural frequency fluctuation ratio of the structure b = Δf s / Δf E A second calculation unit that calculates It has The structure design support device according to [1], wherein the output unit outputs the natural frequency fluctuation ratio b calculated by the second calculation unit as the evaluation point.

[0011] [5] The structure design support device according to any one of [1] to [4], further comprising a storage unit that stores the numerical analysis data for the structure.

[0012] [6] The structure design support device according to any one of [1] to [5], characterized in that the vibration mode is one or more selected from all vibration modes occurring in the structure between 20 Hz and 2000 Hz and less, and vibration modes resulting from superpositions thereof.

[0013] [7] A computer-implemented structural design support method, comprising: Based on numerical analysis data, The aboveA calculation step of calculating an initial natural frequency f0 of the structure and a natural frequency f of the structure when at least one of a plate thickness, a density, and a Young's modulus of an analysis target portion included in the structure is changed; An output step of outputting a value including Δf=f−f0 as an evaluation point regarding the vibration mode of the structure; A structure design support method comprising:

[0014] [8] The calculation step includes: The natural frequency f0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed by an arbitrary positive number α and the density of the analysis target part is changed by 1 / α. t and the natural frequency f of the structure when the Young's modulus of the analysis target portion is changed by α times. E A first calculation step of calculating Δf t =f t -f0 and Δf E =f E -f0 to the natural frequency fluctuation ratio of the structure b = Δf t / Δf E A second calculation step of calculating It has The structural design support method according to [7], wherein the output step outputs the natural frequency fluctuation ratio b calculated in the second calculation step as the evaluation point.

[0015] [9] The calculation step is a step of calculating the natural frequency f0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed by an arbitrary positive number α, the density of the analysis target part is changed by 1 / α, and the Young's modulus of the analysis target part is changed by 1 / α. N Calculate The output step is Δf N =f N The structure design support method according to [7], wherein −f0 is output as the evaluation point.

[0016]

[10] The calculation step includes: The natural frequency f0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed by an arbitrary positive number α times and the density of the analysis target part is kept constant s and the natural frequency f of the structure when the Young's modulus of the analysis target portion is changed by α times and the density of the analysis target portion is changed by α times. E A first calculation step of calculating Δf s =f s -f0 and Δf E =f E -f0 to the natural frequency fluctuation ratio of the structure b = Δf s / Δf E A second calculation step of calculating It has The output step is Out The structural design support method according to [7], characterized in that the natural frequency fluctuation ratio b calculated in step is output as the evaluation point.

[0017]

[11] The structure design support method according to any one of [7] to

[10] , characterized in that the numerical analysis data stored in a predetermined storage unit is used.

[0018]

[12] The structure design support method according to any one of [7] to

[11] , characterized in that the vibration mode is one or more selected from all vibration modes occurring in the structure between 20 Hz and 2000 Hz and less, and vibration modes resulting from superpositions thereof.

[0019]

[13] A calculation step of calculating an initial natural frequency f0 of a structure and a natural frequency f of the structure when at least one of a plate thickness, a density, and a Young's modulus of an analysis target portion included in the structure is changed based on the numerical analysis data; An output step of outputting a value including Δf=f−f0 as an evaluation point regarding the vibration mode of the structure; A structure design support program characterized by causing a computer to execute the above steps.

[0020]

[14] The calculation step includes: The natural frequency f0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed by an arbitrary positive number α and the density of the analysis target part is changed by 1 / α. t and the natural frequency f of the structure when the Young's modulus of the analysis target portion is changed by α times. E A first calculation step of calculating Δf t =f t -f0 and Δf E =f E -f0 to the natural frequency fluctuation ratio of the structure b = Δf t / Δf E A second calculation step of calculating It has The structural design support program according to

[13] , wherein the output step outputs the natural frequency fluctuation ratio b calculated in the second calculation step as the evaluation point.

[0021]

[15] The calculation step is a step of calculating the natural frequency f0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed by an arbitrary positive number α, the density of the analysis target part is changed by 1 / α, and the Young's modulus of the analysis target part is changed by 1 / α. N Calculate The output step is Δf N =f N The structure design support program according to

[13] , wherein -f0 is output as the evaluation point.

[0022]

[16] The calculation step includes: The natural frequency f0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed by an arbitrary positive number α times and the density of the analysis target part is kept constant sand the natural frequency f of the structure when the Young's modulus of the analysis target portion is changed by α times and the density of the analysis target portion is changed by α times. E A first calculation step of calculating Δf s =f s -f0 and Δf E =f E -f0 to the natural frequency fluctuation ratio of the structure b = Δf s / Δf E A second calculation step of calculating It has The output step is Out The structural design support program according to

[13] , characterized in that the natural frequency fluctuation ratio b calculated in step 1 is output as the evaluation point.

[0023]

[17] The structure design support program according to any one of

[13] to

[16] , characterized in that the vibration mode is one or more selected from all vibration modes occurring in the structure between 20 Hz and 2000 Hz and less, and vibration modes resulting from superpositions thereof.

[0024]

[18] A computer-readable recording medium having recorded thereon the structure design support program according to any one of

[13] to

[17] . Effect of the Invention

[0025] According to the present invention, the deformation form of a structure can be quantitatively evaluated even under conditions that depend on the mass of the structure, such as when the structure is in natural vibration. [Brief description of the drawings]

[0026] [Figure 1] 1 is a block diagram showing a structure design assistance device according to a first embodiment. [Diagram 2] FIG. 2 is a flow diagram showing a structure design support method according to the first embodiment. [Diagram 3]FIG. 11 is a block diagram showing a structure design assistance device according to a second embodiment. [Figure 4] FIG. 11 is a flow diagram showing a structure design support method according to a second embodiment. [Diagram 5] FIG. 11 is a block diagram showing a structure design assistance device according to a third embodiment. [Figure 6] FIG. 11 is a flow diagram showing a structure design support method according to a third embodiment. [Figure 7] FIG. 2 is a schematic diagram showing the internal configuration of a personal user terminal device. [Figure 8] FIG. 4 is a characteristic diagram showing the sensitivity of each part in a single-node torsional vibration mode in the first embodiment. [Figure 9] FIG. 4 is a characteristic diagram showing the sensitivity of each part in a single-node bending vibration mode in the first embodiment. [Figure 10] FIG. 4 is a characteristic diagram showing the sensitivity of each part in a two-node bending vibration mode in the first embodiment. [Figure 11] FIG. 11 is a characteristic diagram showing evaluation points for each part in ascending order in the first embodiment. [Figure 12] FIG. 11 is a characteristic diagram showing evaluation points for each part in Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] (Basic concept of the present invention) In the present invention, when designing a structure, the deformation form of the structure is expressed in simple numerical values, and the following basic concepts are the basis for designing an excellent structure that can be made lighter more efficiently while maintaining the rigidity of the structure.

[0028] First, consider the torsional rigidity of a structure. When a bending moment M is applied to a structure, the structure rotates by an angle θ. In this case, the torsional rigidity K is expressed as K=M / θ. Here, the change in stiffness K of the structure before and after the change when the Young's modulus of at least one part of the structure is changed by a constant factor ΔK Eand the change in the stiffness K of the structure before and after the change when the plate thickness of the same part is changed by the same factor ΔK t Ratio ΔK E / ΔK t Consider ΔK E / ΔK t When is 1, the deformation of the structure is 100% in-plane deformation. On the other hand, ΔK E / ΔK t When ΔK is 3, the deformation of the structure is 100% out-of-plane deformation. E / ΔK t The deformation of the structure can be evaluated simply and quantitatively by the value of

[0029] By the way, the natural frequency f of a structure is expressed as s Then, f=(1 / 2π)·(K / m s ) 1 / 2 It is expressed as: Here, only the Young's modulus of the structure is virtually changed. In this case, the mass of the structure m S Therefore, the change in the natural frequency f of the structure before and after changing the Young's modulus Δf E From the above, the change in stiffness K of the structure, ΔK E can be sought. On the other hand, when only the plate thickness of the structure is changed virtually, the mass of the structure m S Therefore, the change in the natural frequency f of the structure before and after changing the plate thickness, Δf t The change in stiffness K of the structure from t It is difficult to ask for. That is, the mass of the structure m S When the change occurs, the ratio of change in the stiffness K of the structure is ΔK E / ΔK t It is difficult to calculate the deformation of the structure, and it is difficult to quantitatively evaluate the deformation of the structure.

[0030] In the present invention, the natural frequency of a structure is calculated when the plate thickness, density, and Young's modulus of an analysis target portion consisting of a part or all parts of the structure are changed. Specifically, the plate thickness, density, and Young's modulus are changed in one analysis process to obtain one type of natural frequency, or two types of natural frequencies are obtained by appropriately selecting two from the plate thickness, density, and Young's modulus in two analysis processes. Here, the plate thickness, density, and Young's modulus are changed under the restriction that the mass of the structure is not changed, or the mass of the structure is the same value in two analysis processes. As will be described later, a value including Δf=f-f0 can be regarded as an index that quantitatively represents the deformation form of the structure. In the present invention, this value is adopted as an evaluation point regarding the vibration mode. Various aspects of the present invention will be described below.

[0031] [First aspect] In the first mode, the plate thickness of the analysis target portion consisting of a part or all of the structure is virtually changed by an arbitrary positive number α times, and the density of the analysis target portion is virtually changed by 1 / α times. As a result, the mass m s Therefore, the natural frequency f of the structure before and after changing the plate thickness of the analysis target part is t The change in Δf t The change in stiffness K from ΔK t Therefore, the natural frequency fluctuation ratio of the structure b = Δf t / Δf E The ratio of change in stiffness K of the structure to ΔK E / ΔK t can be obtained, and the deformation of the structure can be quantitatively evaluated. This will be described in more detail below.

[0032] The initial natural frequency f0 of the structure is

[0033]

number

[0034] Here, K0 is the initial stiffness of the structure, m S0represents the initial mass of the structure. In the following, the natural frequency f of the structure when the plate thickness of the analysis target part included in the structure is hypothetically changed to an arbitrary positive number α times and the density of the analysis target part is hypothetically changed to 1 / α times is t f t =f0+Δf t In this case, the rigidity of the structure is K t In addition, the natural frequency f of the structure when the Young's modulus of the analysis target part is virtually changed by a factor of α is E f E =f0+Δf E In this case, the rigidity of the structure is K E Furthermore, the mass of the structure after changing the plate thickness and density of the analysis target part as described above is m St The mass of the structure after changing the Young's modulus of the analysis target part as described above is m SE Then, the natural frequency fluctuation ratio of the structure is b=Δf t / Δf E can be expressed as the following equation (2).

[0035]

number

[0036] Here, the initial mass of the part to be analyzed is m P0 , plate thickness is t P0 , density ρ P0 The mass of the part to be analyzed after changing the plate thickness and density as described above is m Pt , plate thickness is t Pt , density ρ Pt This leads to the following equation (3).

[0037]

number

[0038] In addition, when the Young's modulus of the analysis target part is changed, the mass of the analysis target part does not change, so the mass of the analysis target part after the change in Young's modulus m PE is expressed by the following equation (4).

[0039]

number

[0040] As mentioned above, m P0 =m Pt =m PE It can be seen that the mass of the analyzed part does not change. Therefore, the mass of the structure does not change, and m S0 =m St =m SE Therefore, the above formula (2) becomes the following formula (5).

[0041]

number

[0042] Here, K t K0+ΔK t , K E K0+ΔK E And K t ,K E Change ΔK from K0 t ,ΔK E If we use Taylor expansion assuming that is infinitesimal, the above equation (5) becomes the following equation (6).

[0043]

number

[0044] From the above equation (6), the natural frequency of the structure, f t The change in Δf t and natural frequency f E The change in Δf E Ratio to Δf t / Δf E is stiffness K t The change in ΔK t and stiffness K E The change in ΔK E Relative to ΔK E / ΔK t Therefore, Δf t / Δf E This allows for a quantitative evaluation of the deformation of the structure.

[0045] [Second aspect] In the second mode, the thickness of the analysis target part consisting of a part or all parts of the structure is virtually changed by an arbitrary positive number α times, the density of the analysis target part is virtually changed by 1 / α times, and the Young's modulus of the analysis target part is virtually changed by 1 / α times. In this case, the mass of the structure can be considered not to change due to [plate thickness α times + density 1 / α times]. The natural frequency f of the structure when the plate thickness, density, and Young's modulus of the analysis target part are changed by one analysis process is calculated. N The natural frequency f of the structure before and after the change can be calculated. N The change in Δf N can be used as an index capable of quantitatively evaluating the deformation of a structure, as described below in more detail.

[0046] In the first embodiment, the natural frequency of [plate thickness α times + density 1 / α times] is f t , [Young's modulus α times]'s natural frequency is f E When the plate thickness, density, and Young's modulus of the analysis target part are changed simultaneously as in this embodiment, the natural frequency corresponding to [plate thickness α times + density 1 / α times] is f t The natural frequency corresponding to [Young's modulus 1 / α times] is f E ', where f E '-f E From the above, the natural frequency f1 corresponding to [plate thickness α times + density 1 / α times + Young's modulus 1 / α times] is f t and f E ' and the natural frequency f N The change in Δf N =f N -f0 can be assumed as follows:

[0047] Δf N =Δf t +Δf E ' =Δf t -Δf E ...(7) Here, similarly to the formula (6) in the first aspect, the following relationship holds:

[0048]

number

[0049] Δf E Since is the Young's modulus sensitivity, using equation (8), equation (7) can be rewritten as follows: Δf N =Δf E (b-1) = (Young's modulus sensitivity) × (b-1) (9)

[0050] Thus, in this embodiment, Δf N is expressed as the product of Young's modulus sensitivity and natural frequency fluctuation ratio b, both of which are evaluation indexes for the deformation form of a structure. Therefore, when it is not necessary to separate Young's modulus sensitivity and natural frequency fluctuation ratio (bending degree), for example, when it is desired to evaluate Young's modulus sensitivity as well, Δf N can be used as an evaluation index for the deformation of the structure.

[0051] [Third aspect] In the third embodiment, two analysis processes (analysis A and analysis B) are performed in the same manner as in the first embodiment, and the natural frequency f of the structure is calculated when the plate thickness of the analysis target part consisting of a part or all parts of the structure is changed. s , and the natural frequency f of the structure when the density of the analyzed part is changed E Request.

[0052] In analysis A, the density of the analysis target part is kept constant, and the plate thickness of the analysis target part is virtually changed by an arbitrary positive number α times. In this case, the mass m t is the initial mass of the structure, m S0 , the mass of the analysis target part after changing the plate thickness is m Pt So, it becomes as follows. m t =m S0 +(α-1)m Pt...(10)

[0053] In analysis B, both the Young's modulus and density of the analysis target part are virtually changed by a factor of α. Since the mass of the analysis target part does not change even if the Young's modulus of the analysis target part is changed, the mass mρ of the structure after changing the Young's modulus and density depends only on the change in density. This mass mρ is calculated by multiplying the initial mass of the structure by m S0 , the mass of the analyzed part after the change in Young's modulus and density is m P As for ρ, it becomes as follows. mρ=m S0 +(α-1)m P ρ (11)

[0054] m Pt is the plate thickness multiplied by α, and the mass m P Since ρ is the mass of the part to be analyzed when the density is multiplied by α, m Pt =m P ρ. Therefore, from equations (10) and (11), the mass of the structure for analysis A and B is the same (m t =mρ).

[0055] The initial natural frequency of the structure is f0, and the natural frequency of the structure obtained by analysis A is f A (=f0+Δf A ) and Δf A When calculating × f0, using equations (1), (2), (5), (6), etc., we get the following. Note that if the mass of the structure in analysis A is m A (=m t )

[0056]

number

[0057] From equation (12), ΔK A would be as follows:

[0058]

number

[0059] Similarly, the natural frequency of the structure obtained in analysis B is f B (=f0+Δf B ) and ΔK B The mass of the structure in analysis B is m B (=mρ).

[0060]

number

[0061] From the above, ΔK A / ΔK B would be as follows:

[0062]

number

[0063] ΔK A / ΔK B = ΔK s / ΔK E ≡b' (the natural frequency fluctuation ratio of the structure), m A (m t )=m B Using (mρ), the natural frequency fluctuation ratio b' is given as follows:

[0064]

number

[0065] From equation (16),

[0066]

number

[0067] The effect of m on equation (16) is negligibly small, e.g. t M S0 If the value is close enough to

[0068]

number

[0069] It is possible to quantitatively evaluate the deformation form of a structure using the natural frequency fluctuation ratio b' as an index.

[0070] (Embodiments of the present invention) In the following embodiments, the body of an automobile is the structure to be evaluated. A part included in the body, a predetermined portion including at least a part of the part, or a portion consisting of a plurality of parts included in the body is the part to be analyzed. In the following description, the part or portion included in the body may be simply referred to as a "part." The present invention is a technology that can be applied not only to the body of an automobile but also to all structures. For example, the technology of the present invention can be applied to mechanical parts such as engines, buildings themselves, and parts of buildings such as pillars, and is particularly preferably applied to structures that may be subjected to mechanical vibrations.

[0071] (First embodiment) The structure design support system and method of this embodiment in which the evaluation target and the analysis target portion are set as described above will be described in detail below with reference to the drawings. Figure 1 is a block diagram showing the structure design support system of this embodiment, and Figure 2 is a flow diagram showing the structure design support method of this embodiment.

[0072] [Structure design support device] The structure design support apparatus according to this embodiment includes a first calculation unit 1, a second calculation unit 2, an output unit 3, and a storage unit 4, as shown in FIG. The storage unit 4 stores numerical analysis data of a single or multiple parts that configure at least a part of the vehicle body. The numerical analysis data is, for example, finite element analysis (FEM) data that is initial design data of the vehicle body, and load data acting on the vehicle body (boundary conditions of the FEM data), etc.

[0073] The first calculation unit 1 sequentially performs calculation A, calculation B, and calculation C based on the numerical analysis data stored in the storage unit 4. Hereinafter, the subscript k of each variable indicates the part number given to each part. Calculation A is a calculation of the initial natural frequency f0 of the car body by analytical processing. Calculation B is a calculation of the natural frequency f0 of the car body when the plate thickness of a specific part k included in the car body is virtually changed by an arbitrary positive number (positive real number) α times and the density of part k is virtually changed by 1 / α times. tk Calculation C is the calculation of the natural frequency f of the car body when the Young's modulus of part k is virtually changed by a factor of α without changing the plate thickness and density of part k (with the initial data unchanged) through analytical processing. Ek This is the calculation.

[0074] The second calculation unit 2 sequentially performs calculations D and E. Calculation D is the natural frequency fluctuation amount Δf tk =f tk -f0 and Δf Ek =f Ek -f0 is calculated. Calculation E is the natural frequency fluctuation ratio b k =Δf tk / Δf Ek This is the calculation.

[0075] The initial stiffness of the car body is K0, and the stiffness of the car body when the plate thickness and density of part k are virtually changed as described above is K tk , the stiffness of the car body when the Young's modulus of part k is virtually changed as above is defined as K Ek Then, Δf tk / Δf Ek (K tk -K0) / (K Ek -K0). That is, ΔK tk =K tk -K0, ΔK Ek =K Ek If we set it to -K0, then Δf tk / Δf Ek is ΔK tk / ΔK Ek can be considered to be equal to

[0076] The output unit 3 outputs the calculation result of the calculation E by the second calculation unit 2 as information related to the vibration mode of the vehicle body under the boundary conditions. When outputting the information related to the vibration mode of the vehicle body, the output unit 3 may output the information to a display unit such as a monitor, or may store the information in the storage unit 4, for example.

[0077] [Structure design support method] In the structural design support method according to this embodiment, as shown in FIG. 2, first, in the FEM data (initial FEM data) created based on the initial design data, a number is assigned to each part or a group of parts that constitutes the body of an automobile (step 1).

[0078] Next, the first calculation unit 1 calculates the initial natural frequency f0 of the vehicle body by analysis processing using the initial FEM data as calculation A (step 2). Next, as a calculation B, the first calculation unit 1 performs an analysis process to calculate the natural frequency f of the vehicle body when the plate thickness of a given part k is virtually changed by an arbitrary positive number (positive real number) α times and the density of the part k is virtually changed by 1 / α times. tk Calculate (Step 3). Next, the first calculation unit 1 performs a calculation C by performing an analysis process to calculate the natural frequency f of the vehicle body when the Young's modulus of the part k is virtually changed by a factor of α without changing the plate thickness and density of the part k (with the initial data unchanged). Ek Calculate (Step 4).

[0079] Next, the second calculation unit 2 calculates the natural frequency fluctuation amount Δf tk =f tk -f0 and Δf Ek =f Ek -f0 is calculated (step 5). Steps 1 to 5 may be performed for multiple components in the same way. After that, if it is necessary to exclude components with small natural frequency fluctuations from the range of consideration, Δf tk or Δf Ek It is also possible to perform filtering using the value of , and extract only the data of the necessary parts.

[0080] Next, the second calculation unit 2 calculates the natural frequency fluctuation ratio b k =Δf tk / Δf Ek (Step 6) As mentioned above, the natural frequency fluctuation ratio b k ΔK tk / ΔK Ek This natural frequency fluctuation ratio b k is the sensitivity of each part to the vibration mode of the vehicle body. When focusing on multiple vibration modes, the vehicle body's natural frequency fluctuation ratio b k The average value of these is the evaluation score V k In addition, when focusing on multiple vibration modes of the vehicle body, the natural frequency fluctuation ratio b k The weighted sum of these is the evaluation score V k For example, when focusing on three vibration modes, X, Y, and Z, the natural frequency fluctuation ratio b kX ,b kY ,b kZ Then, multiply them by a specified coefficient and calculate the evaluation score V using the following formula: k You may also ask for: V k =(xb kX +yb kY +zb kZ ) / (x+y+z) Although the above example focuses on three vibration modes, the number of vibration modes to be focused on is not particularly limited.

[0081] The natural frequency variation ratio can be used as a parameter that expresses the deformation form of one part of the body under certain boundary conditions. Based on the value of this natural frequency variation ratio, it is possible to easily select parts to be stiffened and parts to have their plate thickness reduced, making it possible to simultaneously achieve weight reduction and improved rigidity. In particular, in the case of an automobile body, it becomes possible to significantly reduce the weight reduction index (the value obtained by dividing the body weight by the torsional rigidity and effective area), which evaluates the performance of the body rigidity and weight. For example, by increasing or decreasing the plate thickness by a factor proportional to the value of the natural frequency variation ratio, it is possible to easily design a body that reduces the weight reduction index.

[0082] Also, in step 1 above, the designer may freely divide the parts to be analyzed, rather than dividing them into parts by component. For example, in the case of an automobile body, dividing large parts such as the roof and side panels into multiple regions makes it possible to extract more suitable stiffening points. Furthermore, if numerical analysis capabilities and time permit, targeting each element of the FEM data will clarify the distribution of deformation in the structure, enabling more detailed design.

[0083] By using this method, it is possible to quantitatively and easily know the deformation form of a structure accompanied by the change in mass of each part or each part. Moreover, since the above steps 2 to 6 are routine processes, they can be easily automated by computer, reducing the workload of the designer.

[0084] Second embodiment The structure design support system and method of this embodiment will be described in detail below with reference to the drawings. Fig. 3 is a block diagram showing the structure design support system according to this embodiment, and Fig. 4 is a flow chart showing the structure design support method according to this embodiment.

[0085] [Structure design support device] The structure design support apparatus according to this embodiment includes a calculation unit 11, an output unit 12, and a storage unit 13, as shown in FIG. The storage unit 13 stores numerical analysis data of a single or multiple parts that configure at least a part of the vehicle body. The numerical analysis data is, for example, finite element analysis (FEM) data that is initial design data of the vehicle body, and load data acting on the vehicle body (boundary conditions of the FEM data), etc.

[0086] The calculation unit 11 sequentially performs calculation A, calculation B, and calculation C based on the numerical analysis data stored in the storage unit 13. Hereinafter, the subscript k of each variable indicates the part number given to each part. Calculation A is a calculation of the initial natural frequency f0 of the vehicle body by analytical processing. Calculation B is a calculation of the natural frequency f0 of the vehicle body when the plate thickness of a specific part k included in the vehicle body is virtually changed by an arbitrary positive number (positive real number) α times, the density of part k is virtually changed by 1 / α times, and the Young's modulus of part k is virtually changed by 1 / α times. Nk Calculation C is the calculation of the natural frequency fluctuation Δf Nk =f Nk This is the calculation of -f0.

[0087] where b k =Δf tk / Δf Ek Using Δf Nk is Δf Ek (b k -1). Therefore, when it is not necessary to separate the Young's modulus sensitivity and the natural frequency fluctuation ratio, Δf Nk can be used as an evaluation index for the deformation form of each part of the vehicle body.

[0088] The output unit 12 outputs the calculation result of the calculation C by the calculation unit 11 as information on the vibration mode of the vehicle body under the boundary conditions. When outputting the information on the vibration mode of the vehicle body, the output unit 12 may output this information to a display unit such as a monitor, or may store this information in the storage unit 13, for example.

[0089] [Structure design support method] In the structural design support method according to this embodiment, as shown in FIG. 4, first, in the FEM data (initial FEM data) created based on the initial design data, a number is assigned to each part or a group of parts that constitutes the body of an automobile (step 11).

[0090] Next, the calculation unit 11 calculates the initial natural frequency f0 of the vehicle body by analysis processing using the initial FEM data as calculation A (step 12). Next, as a calculation B, the calculation unit 11 performs an analysis process to calculate the natural frequency f of the vehicle body when the plate thickness of a predetermined part k included in the vehicle body is virtually changed by an arbitrary positive number (positive real number) α times, the density of the part k is virtually changed by 1 / α times, and the Young's modulus of the part k is virtually changed by 1 / α times. Nk Calculate (step 13). Next, the calculation unit 11 calculates the natural frequency fluctuation amount Δf of the vehicle body as a calculation C. Nk =f Nk -f0 is calculated (step 14). As described above, the natural frequency fluctuation amount Δf Nk is the evaluation value for the vibration mode of the vehicle body due to each part.

[0091] Steps 11 to 14 may be performed for multiple components in the same manner. After that, if it is necessary to exclude components with small natural frequency fluctuations from the range of consideration, Δf Ak It is also possible to perform filtering using the value of , and extract only the data of the necessary parts.

[0092] When focusing on multiple vibration modes, the natural frequency fluctuation Δf of the vehicle body in each vibration mode Nk The average value of these is the evaluation score V k In addition, when focusing on multiple vibration modes of the vehicle body, the natural frequency fluctuation Δf of a specific vibration mode may be quantitatively evaluated. Nk The weighted sum of these is the evaluation score V k For example, when focusing on the three vibration modes of X, Y, and Z, the natural frequency fluctuation Δf of each vibration mode may beNX ,Δf NY ,Δf NZ Then, multiply them by a specified coefficient and calculate the evaluation score W by the following formula: k You may also ask for: W k =(xΔf NX +yΔf NY +zΔf NZ ) / (x+y+z) Although the above example focuses on three vibration modes, the number of vibration modes to be focused on is not particularly limited.

[0093] In the case where it is not necessary to separate the Young's modulus sensitivity and the natural frequency variation ratio, the natural frequency variation amount can be used as a parameter expressing the deformation form of one part of the body under certain boundary conditions. In this embodiment, the natural frequency variation amount can be obtained by one analysis process. Based on the value of this natural frequency variation amount, the parts to be stiffened and the parts to be reduced in plate thickness can be easily selected, making it possible to simultaneously achieve weight reduction and rigidity improvement. In particular, in the case of an automobile body, it becomes possible to significantly reduce the weight reduction index (the value obtained by dividing the body weight by the torsional rigidity and the effective area) that evaluates the performance of the body rigidity and weight. For example, a design that easily reduces the weight reduction index can be performed by increasing or decreasing the plate thickness by a factor proportional to the value of the natural frequency variation ratio.

[0094] Also, in step 11 above, the designer may freely divide the parts to be analyzed, rather than dividing them into parts by component. For example, in the case of an automobile body, dividing large parts such as the roof and side panels into multiple regions makes it possible to extract more suitable stiffening points. Furthermore, if numerical analysis capabilities and time permit, targeting each element of the FEM data will clarify the distribution of deformation in the structure, enabling more detailed design.

[0095] By using this method, it is possible to quantitatively and easily know the deformation form of the structure accompanied by the change in the mass of each part or each part. Moreover, since the above steps 12 to 14 are routine processes, they can be easily automated by a computer, and the workload of the designer can be reduced.

[0096] (Third embodiment) The structure design support system and method of this embodiment in which the evaluation target and the analysis target portion are set as described above will be described in detail below with reference to the drawings. Fig. 5 is a block diagram showing the structure design support system of this embodiment, and Fig. 6 is a flow chart showing the structure design support method of this embodiment.

[0097] [Structure design support device] The structure design support apparatus according to this embodiment includes a first calculation unit 21, a second calculation unit 22, an output unit 23, and a storage unit 24, as shown in FIG. The storage unit 24 stores numerical analysis data of one or more parts that constitute at least a part of the vehicle body. The numerical analysis data is, for example, finite element analysis (FEM) data that is initial design data of the vehicle body, and load data acting on the vehicle body (boundary conditions of the FEM data).

[0098] The first calculation unit 21 sequentially performs calculation A, calculation B, and calculation C based on the numerical analysis data stored in the storage unit 24. Hereinafter, the subscript k of each variable indicates the part number given to each part. Calculation A is a calculation of the initial natural frequency f0 of the car body by analytical processing. Calculation B is a calculation of the natural frequency f0 of the car body by analytical processing when the plate thickness is virtually changed by an arbitrary positive number (positive real number) α times without changing the density of a specific part k included in the car body (with the initial data unchanged). sk Calculation C is the calculation of the natural frequency f of the vehicle body when the Young's modulus and density of a specific part k included in the vehicle body are both changed by a factor of α through analytical processing. Ek This is the calculation.

[0099] The second calculation unit 22 sequentially performs calculation D and calculation E. Calculation D is a calculation of the natural frequency fluctuation amount Δf of the vehicle body.sk =f sk -f0 and Δf Ek =f Ek -f0 is calculated. Calculation E is the natural frequency fluctuation ratio b k =Δf sk / Δf Ek This is the calculation.

[0100] Here, the initial stiffness of the car body is K0, and the stiffness of the car body when the plate thickness is virtually changed by a factor of α while keeping the density of part k constant as described above is K tk As described above, the Young's modulus and density of part k are virtually changed by a factor of 1 / α to define the rigidity of the vehicle body as K Ek When 1-(m so / m tk ) 1 / 2 If is small enough, b k = ΔK sk / ΔK Ek ≒Δf sk / Δf Ek Then, b k can be used as an evaluation index for the deformation form of each part of the vehicle body.

[0101] The output unit 23 outputs the calculation result of the calculation E by the second calculation unit 22 as information about the vibration mode of the vehicle body under the boundary conditions. When outputting the information about the vibration mode of the vehicle body, the output unit 23 may output this information to a display unit such as a monitor, or may store this information in the storage unit 24, for example.

[0102] [Structure design support method] In the structural design support method according to this embodiment, as shown in FIG. 6, first, in the FEM data (initial FEM data) created based on the initial design data, a number is assigned to each part or a group of parts that constitutes the body of an automobile (step 21).

[0103] Next, the first calculation unit 21 calculates, as calculation A, an initial natural frequency f0 of the vehicle body by analysis processing using the initial FEM data (step 22). Next, the first calculation unit 21 performs a calculation B by performing an analysis process to calculate the natural frequency f of the vehicle body when the plate thickness is virtually changed by an arbitrary positive number (positive real number) α times without changing the density of a predetermined part k included in the vehicle body (with the initial data unchanged). sk is calculated (step 23). Next, as a calculation C, the first calculation unit 21 performs an analysis process to calculate the natural frequency f of the vehicle body when the Young's modulus and density of a predetermined part k included in the vehicle body are both changed by a factor of α. Ek is calculated (step 24).

[0104] Next, the second calculation unit 22 calculates the natural frequency fluctuation amount Δf sk =f sk -f0 and Δf Ek =f Ek -f0 is calculated (step 25). Steps 21 to 25 may be performed similarly for multiple components. After that, if it is necessary to exclude components with small natural frequency fluctuations from the range of consideration, Δf sk or Δf Ek It is also possible to perform filtering using the value of , and extract only the data of the necessary parts.

[0105] Next, the second calculation unit 22 calculates the natural frequency fluctuation ratio b k =Δf sk / Δf Ek (Step 26) As described above, the natural frequency fluctuation ratio b k is the evaluation value for the vibration mode of the vehicle body due to each part.

[0106] When focusing on multiple vibration modes, the vehicle body's natural frequency fluctuation ratio b k The average value of these is the evaluation score V k In addition, when focusing on multiple vibration modes of the vehicle body, the natural frequency fluctuation ratio b k The weighted sum of these is the evaluation score V kFor example, when focusing on three vibration modes, X, Y, and Z, the natural frequency fluctuation ratio b kX ,b kY ,b kZ Then, multiply them by a specified coefficient and calculate the evaluation score U k You may also ask for: U k =(xb kX +yb kY +zb kZ ) / (x+y+z) Although the above example focuses on three vibration modes, the number of vibration modes to be focused on is not particularly limited.

[0107] The natural frequency variation ratio can be used as a parameter that expresses the deformation form of one part of the body under certain boundary conditions. Based on the value of this natural frequency variation ratio, it is possible to easily select parts to be stiffened and parts to have their plate thickness reduced, making it possible to simultaneously achieve weight reduction and improved rigidity. In particular, in the case of an automobile body, it becomes possible to significantly reduce the weight reduction index (the value obtained by dividing the body weight by the torsional rigidity and effective area), which evaluates the performance of the body rigidity and weight. For example, by increasing or decreasing the plate thickness by a factor proportional to the value of the natural frequency variation ratio, it is possible to easily design a body that reduces the weight reduction index.

[0108] Also, in step 21 above, the designer may freely divide the parts to be analyzed, rather than dividing them into parts by component. For example, in the case of an automobile body, dividing large parts such as the roof and side panels into multiple regions makes it possible to extract more suitable stiffening points. Furthermore, if numerical analysis capability and time permit, targeting each element of the FEM data will clarify the distribution of deformation forms in the structure, enabling more detailed design.

[0109] By using this method, it is possible to quantitatively and easily know the deformation form of the structure accompanied by the change in the mass of each part or each part. Moreover, since the above steps 22 to 26 are routine processes, they can be easily automated by a computer, and the workload of the designer can be reduced.

[0110] (Other embodiments) The first calculation unit 1, the second calculation unit 2, and the output unit 3 shown in Fig. 1, which are components of the structure design support device according to the first embodiment, the calculation unit 11 and the output unit 12 shown in Fig. 3, which are components of the structure design support device according to the second embodiment, and the first calculation unit 21, the second calculation unit 22, and the output unit 23 shown in Fig. 5, which are components of the structure design support device according to the third embodiment, may be realized by dedicated hardware. Also, the first calculation unit 1, the second calculation unit 2, and the output unit 3, the calculation unit 11 and the output unit 12, and the first calculation unit 21, the second calculation unit 22, and the output unit 23 may be configured by a memory and a CPU (Central Processing Unit), and the functions of the first calculation unit 1, the second calculation unit 2, and the output unit 3, the calculation unit 11 and the output unit 12, and the first calculation unit 21, the second calculation unit 22, and the output unit 23 may be realized by loading a program for realizing the functions of the first calculation unit 1, the second calculation unit 2, and the output unit 3, the calculation unit 11 and the output unit 12, and the first calculation unit 21, the second calculation unit 22, and the output unit 23 into the memory and executing the program.

[0111] The memory unit 4 shown in FIG. 1, the memory unit 14 shown in FIG. 3, and the memory unit 24 shown in FIG. 5 may be composed of a hard disk device, a magneto-optical disk device, a non-volatile memory such as a flash memory, a read-only storage medium such as a CD-ROM, a volatile memory such as a RAM (Random Access Memory), or a combination of these.

[0112] Furthermore, a program for realizing the functions of the first calculation unit 1, the second calculation unit 2, and the output unit 3, the calculation unit 11 and the output unit 12, and the first calculation unit 21, the second calculation unit 22, and the output unit 23 may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read into a computer system and executed to execute each process of the first calculation unit 1, the second calculation unit 2, and the output unit 3, the calculation unit 11 and the output unit 12, and the first calculation unit 21, the second calculation unit 22, and the output unit 23. Note that the term "computer system" used here includes hardware such as an OS and peripheral devices.

[0113] Furthermore, if a WWW system is used, the "computer system" may also include the homepage providing environment (or display environment). In addition, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into computer systems. Furthermore, the term "computer-readable recording medium" may also include devices that dynamically hold a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and devices that hold a program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client in such cases. Furthermore, the above-mentioned program may be one that realizes part of the above-mentioned functions, or may be one that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

[0114] As a specific example, the structure design support apparatus shown in this embodiment has a computer function 100 as shown in FIG. 7, and the operations in this embodiment are carried out by a CPU 101 thereof. 7, the computer function 100 includes a CPU 101, a ROM 102, and a RAM 103. It also includes a controller (CONSC) 105 for an operation unit (CONS) 109, and a display controller (DISPC) 106 for a display (DISP) 110 serving as a display unit such as a CRT or LCD. It also includes a controller (DCONT) 107 for a hard disk (HD) 111 and a storage device (STD) 112 such as a flexible disk, and a network interface card (NIC) 108. These functional units 101, 102, 103, 105, 106, 107, and 108 are connected to each other via a system bus 104 so as to be able to communicate with each other.

[0115] The CPU 101 executes software stored in the ROM 102 or HD 111, or software supplied from the STD 112, thereby generally controlling each component connected to the system bus 104. That is, the CPU 101 reads out a processing program (structure design support program) for performing the above-mentioned operations from the ROM 102, HD 111, or STD 112, and executes it, thereby performing control for realizing the operations in this embodiment. The RAM 103 functions as the main memory, work area, etc. of the CPU 101.

[0116] CONSC 105 controls instruction input from CONS 109. DISPC 105 controls the display of DISP 110. DCONT 107 controls access to HD 111 and STD 112 which store the boot program, various applications, user files, network management program, and the above-mentioned processing programs in this embodiment. NIC 108 exchanges data bidirectionally with other devices on network 113. Instead of using a normal computer terminal device, a specific computer specialized for a structure design support device may be used.

[0117] (Example) Specific examples of the various embodiments will be described below.

[0118] [Example 1] In Example 1, when carrying out the structural design support method (steps 1 to 6) of the first embodiment, an eigenvalue analysis of an automobile body was carried out using the analysis software NASTRAN. The car body model is created from data on 500 parts, data on spot welding that joins each part, and bolt fastening data. In step 1, of the data on these 500 parts, 62 pairs of parts were assigned numbers to create initial FEM data. Note that equivalent parts on the left and right sides of the car body were treated as one pair.

[0119] In step 2, eigenvalue analysis is performed using NASTRAN to calculate the initial natural frequency f 0i Here, the subscript i indicates the type of vibration mode. In this embodiment, attention is focused on three representative vibration modes: single-node torsional vibration mode (i=1), single-node bending vibration mode (i=2), and double-node bending vibration mode (i=3). In the following, the subscript k indicating the part number assigned to the 62 sets of parts as described above is added, and the natural frequency of the car body when the plate thickness and density of any part (analysis target part) included in the car body (structure) are changed is expressed as f tki , the natural frequency of the body when the Young's modulus of any part of the body is changed is f Eki As above, the subscript i is an integer between 1 and 3, and the subscript k is an integer between 1 and 62.

[0120] The analysis targets of the present invention are not limited to the vibration modes listed in this embodiment. For example, one or more vibration modes selected from all vibration modes occurring in a structure between 20 Hz and 2000 Hz and vibration modes resulting from superposition of these vibration modes are the analysis targets.

[0121] In step 3, the thickness of part 1 (k=1) is changed to 50% of the initial FEM data, the density of the part is doubled, and an eigenvalue analysis is performed using NASTRAN to obtain the natural frequency f of the car body in each vibration mode.t11 ~f t13 Similarly, the natural frequency f tk1 ~f tk3 was calculated.

[0122] In step 4, the Young's modulus of part 1 is changed to 50% of the initial FEM data, and eigenvalue analysis is performed using NASTRAN to obtain the natural frequency f E11 ~f E13 Similarly, the natural frequency f Ek1 ~f Ek3 was calculated.

[0123] In step 5, the f calculated in steps 3 and 4 is tk1 ~f tk3 and f Ek1 ~f Ek3 Using the above, the natural frequency fluctuation Δf of the vehicle body in each vibration mode tki =f tki -f 0i , and Δf Eki =f Eki -f 0i Furthermore, Δf was calculated from all 62 sets of parts. tki or Δf Eki The Δf of the remaining 43 parts was calculated by removing the parts with a value of 0.001 or less. tki and Δf Eki The subscript k is an integer between 1 and 43.

[0124] In step 6, the natural frequency fluctuation ratio b ki =Δf tki / Δf Eki were calculated and used as the sensitivities (component sensitivities). Figure 8 shows the component sensitivity in the single-node torsional vibration mode, Figure 9 shows the component sensitivity in the single-node bending vibration mode, and Figure 10 shows the component sensitivity in the two-node bending vibration mode. Furthermore, in this embodiment, the sensitivities (natural frequency fluctuation ratio b ki) is weighted as the most important vibration mode, and the evaluation score V k was calculated using the following formula: Rating: V k =(b k1 +b k2 +5b k3 ) / 7 In Fig. 11, the evaluation scores V of each part are arranged in ascending order from left to right. k Shows.

[0125] Rating: V k The value fell within the range of 1 to 3. Next, the evaluation score V k The thickness of the parts is increased by 20% from the side with a large value, and the evaluation point V k The plate thickness of the parts starting from the smallest side was reduced by 20%, and eigenvalue analysis was performed again. The results are shown in Table 1 below. Modified FEM model 1 shown in Table 1 is a model in which the plate thickness of each part was adjusted so that the vehicle weight does not change from the initial FEM model. Modified FEM model 2 shown in Table 1 is a model in which the plate thickness of each part was adjusted so that the natural frequency of the vehicle body during two-node bending deformation does not change from the initial FEM model.

[0126] [Table 1]

[0127] As shown in Table 1, in modified FEM model 1, the natural frequency at two-node bending deformation was improved, i.e., the rigidity against two-node bending deformation was improved, without increasing the vehicle weight. Also, in modified FEM model 2, the natural frequency at two-node bending deformation was maintained, i.e., the rigidity against two-node bending deformation was maintained, even if the vehicle weight was reduced.

[0128] As described above, according to the first embodiment, it is possible to quantitatively evaluate the deformation form of a structure even under conditions that depend on the mass of the structure, such as when the structure is at its natural vibration. Therefore, according to this embodiment, it is possible to contribute to a design guideline that reduces the mass of a structure while ensuring the rigidity required for the structure (e.g., a car body). Furthermore, according to this embodiment, it is also possible to contribute to a design guideline that efficiently improves the rigidity of a structure against a vibration mode of importance without increasing the mass of the structure.

[0129] [Example 2] In Example 2, when carrying out the structural design support method (steps 11 to 14) of the second embodiment, an eigenvalue analysis of an automobile body was carried out using the analysis software NASTRAN. The car body model is created from data on 500 parts, spot welding data for joining each part, and bolt fastening data. In step 11, of the 500 parts data, 62 pairs of parts were assigned numbers to create initial FEM data. Note that equivalent parts on the left and right sides of the car body were treated as one pair.

[0130] In step 12, eigenvalue analysis is performed using NASTRAN to calculate the initial natural frequency f 0i Here, the subscript i indicates the type of vibration mode. In this embodiment, attention is focused on three representative vibration modes: single-node torsional vibration mode (i=1), single-node bending vibration mode (i=2), and double-node bending vibration mode (i=3). In the following, the subscript k indicating the part number assigned to the 62 sets of parts as described above is added, and the natural frequency of the car body when the plate thickness, density, and Young's modulus of any part (analysis target part) included in the car body (structure) are changed is expressed as f Nki As above, the subscript i is an integer between 1 and 3, and the subscript k is an integer between 1 and 62.

[0131] The analysis targets of the present invention are not limited to the vibration modes listed in this embodiment. For example, one or more vibration modes selected from all vibration modes occurring in a structure between 20 Hz and 2000 Hz and vibration modes resulting from superposition of these vibration modes are the analysis targets.

[0132] In step 13, the thickness of part 1 (k=1) is changed to 50% of the initial FEM data, the density of the part is doubled, and the Young's modulus is doubled. Then, eigenvalue analysis is performed using NASTRAN to obtain the natural frequency f of the car body in each vibration mode. N11 ~f N13 Similarly, the natural frequency f Nk1 ~f Nk3 was calculated.

[0133] In step 14, the f calculated in step 13 is Nk1 ~f Nk3 Using the above, the natural frequency fluctuation Δf of the vehicle body in each vibration mode Nki =f Nki -f 0i These were used as evaluation indices for the deformation form of each part. Furthermore, Δf Nki The Δf of the remaining 43 parts was calculated by removing the parts with a value of 0.001 or less. Nki The subscript k is an integer between 1 and 43.

[0134] In the second embodiment, the sensitivities (natural frequency fluctuation Δf Nki ) is weighted as the most important vibration mode, and the evaluation score W k was calculated using the following formula: Evaluation score W k =(Δf Nk1 +Δf Nk2 +5Δf Nk3 ) / 7 Figure 12 shows the evaluation score V k Shows.

[0135] Evaluation score W kThe value fell within the range of 1 to 3. Next, the evaluation score W k The thickness of the parts is increased by 20% from the side with the larger value, and the evaluation point W k The plate thickness of the parts starting from the smallest side was reduced by 20%, and eigenvalue analysis was performed again. The results are shown in Table 2 below. Modified FEM model 1 shown in Table 2 is a model in which the plate thickness of each part was adjusted so that the vehicle weight does not change from the initial FEM model. Modified FEM model 2 shown in Table 2 is a model in which the plate thickness of each part was adjusted so that the natural frequency of the vehicle body during two-node bending deformation does not change from the initial FEM model.

[0136] [Table 2]

[0137] As shown in Table 2, in modified FEM model 1, the natural frequency at two-node bending deformation was improved, i.e., the rigidity against two-node bending deformation was improved, without increasing the vehicle weight. Also, in modified FEM model 2, the natural frequency at two-node bending deformation was maintained, i.e., the rigidity against two-node bending deformation was maintained, even if the vehicle weight was reduced.

[0138] As described above, according to Example 2, it is possible to quantitatively evaluate the deformation form of a structure even under conditions that depend on the mass of the structure, such as when the structure is at its natural vibration. Therefore, according to this embodiment, it is possible to contribute to a design guideline that reduces the mass of a structure while ensuring the rigidity required for the structure (e.g., a vehicle body). Furthermore, according to this embodiment, it is also possible to contribute to a design guideline that efficiently improves the rigidity of a structure against a vibration mode of importance without increasing the mass of the structure. [Explanation of symbols]

[0139] 1,21 First calculation section 2,22 Second calculation section 3,12,23 Output section 4,13,24 Storage part 11 Calculation section

Claims

1. Based on the numerical analysis data, the initial natural frequency f 0 a calculation unit that calculates a natural frequency f of the structure when at least one of a plate thickness, a density, and a Young's modulus of an analysis target portion included in the structure is changed; Δf=f−f 0 An output unit that outputs a value including the above as an evaluation score regarding the vibration mode of the structure; A structure design support device comprising:

2. The calculation unit is The natural frequency f 0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed by an arbitrary positive number α and the density of the analysis target part is changed by 1 / α. t and the natural frequency f of the structure when the Young's modulus of the analysis target portion is changed by α times. E A first calculation unit that calculates Δf t = f t -f 0 , and Δf E = f E -f 0 From the above, the natural frequency fluctuation ratio b of the structure is Δf t / Δf E A second calculation unit that calculates It has 2. The structure design support device according to claim 1, wherein the output unit outputs the natural frequency fluctuation ratio b calculated by the second calculation unit as the evaluation point.

3. The calculation unit calculates the natural frequency f 0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed to an arbitrary positive number α times, the density of the analysis target part is changed to 1 / α times, and the Young's modulus of the analysis target part is changed to 1 / α times. N Calculate The output section is Δf N = f N -f 0 2. The structure design support device according to claim 1, wherein the evaluation point is output as the evaluation point.

4. The calculation unit is The natural frequency f 0 and the natural frequency f of the structure when the plate thickness of the analysis target portion is changed by an arbitrary positive number α and the density of the analysis target portion is kept constant. s and the natural frequency f of the structure when the Young's modulus of the analysis target portion is changed by α times and the density of the analysis target portion is changed by α times. E A first calculation unit that calculates Δf s = f s -f 0 , and Δf E = f E -f 0 From the above, the natural frequency fluctuation ratio b of the structure is Δf s / Δf E A second calculation unit that calculates It has 2. The structure design support device according to claim 1, wherein the output unit outputs the natural frequency fluctuation ratio b calculated by the second calculation unit as the evaluation point.

5. 5. The structure design support device according to claim 1, further comprising a storage unit for storing said numerical analysis data for said structure.

6. The structure design support device according to any one of claims 1 to 5, characterized in that the vibration mode is one or more selected from all vibration modes occurring in the structure between 20 Hz and 2000 Hz and less, and vibration modes resulting from superpositions thereof.

7. A method for supporting the design of a structure using a computer, comprising: Based on the numerical analysis data, the initial natural frequency f 0 and a calculation step of calculating a natural frequency f of the structure when at least one of a plate thickness, a density, and a Young's modulus of an analysis target portion included in the structure is changed. Δf=f−f 0 an output step of outputting a value including the above as an evaluation score for the vibration mode of the structure; A structure design support method comprising:

8. The calculation step includes: The natural frequency f 0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed by an arbitrary positive number α and the density of the analysis target part is changed by 1 / α. t and the natural frequency f of the structure when the Young's modulus of the analysis target portion is changed by α times. E A first calculation step of calculating Δf t = f t -f 0 , and Δf E = f E -f 0 From the above, the natural frequency fluctuation ratio b of the structure is Δf t / Δf E A second calculation step of calculating It has 8. The structural design support method according to claim 7, wherein the output step outputs the natural frequency fluctuation ratio b calculated in the second calculation step as the evaluation point.

9. The calculation step is performed by calculating the natural frequency f 0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed to an arbitrary positive number α times, the density of the analysis target part is changed to 1 / α times, and the Young's modulus of the analysis target part is changed to 1 / α times. N Calculate The output step is Δf N = f N -f 0 8. The method for supporting structural design according to claim 7, further comprising the step of outputting as said evaluation point:

10. The calculation step includes: The natural frequency f 0 and the natural frequency f of the structure when the plate thickness of the analysis target portion is changed by an arbitrary positive number α and the density of the analysis target portion is kept constant. s and the natural frequency f of the structure when the Young's modulus of the analysis target portion is changed by α times and the density of the analysis target portion is changed by α times. E A first calculation step of calculating Δf s = f s -f 0 , and Δf E = f E -f 0 From the above, the natural frequency fluctuation ratio b of the structure is Δf s / Δf E A second calculation step of calculating It has 8. The structure design support method according to claim 7, wherein the output step outputs the natural frequency fluctuation ratio b calculated in the second calculation step as the evaluation point.

11. 11. The structure design support method according to claim 7, wherein the numerical analysis data stored in a predetermined storage unit is used.

12. The structure design support method according to any one of claims 7 to 11, characterized in that the vibration mode is one or more selected from all vibration modes occurring in the structure between 20 Hz and 2000 Hz and less, and vibration modes resulting from superpositions thereof.

13. Based on the numerical analysis data, the initial natural frequency f 0 and a calculation step of calculating a natural frequency f of the structure when at least one of a plate thickness, a density, and a Young's modulus of an analysis target portion included in the structure is changed. Δf=f−f 0 an output step of outputting a value including the above as an evaluation score for the vibration mode of the structure; A structure design support program characterized by causing a computer to execute the above steps.

14. The calculation step includes: The natural frequency f 0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed by an arbitrary positive number α and the density of the analysis target part is changed by 1 / α. t and the natural frequency f of the structure when the Young's modulus of the analysis target portion is changed by α times. E A first calculation step of calculating Δf t = f t -f 0 , and Δf E = f E -f 0 From the above, the natural frequency fluctuation ratio b of the structure is Δf t / Δf E A second calculation step of calculating It has 14. The structural design support program according to claim 13, wherein the output step outputs the natural frequency fluctuation ratio b calculated in the second calculation step as the evaluation score.

15. The calculation step is performed by calculating the natural frequency f 0 and the natural frequency f of the structure when the plate thickness of the analysis target part is changed to an arbitrary positive number α times, the density of the analysis target part is changed to 1 / α times, and the Young's modulus of the analysis target part is changed to 1 / α times. N Calculate The output step is Δf N = f N -f 0 14. The structure design support program according to claim 13, wherein the evaluation score is output as the evaluation score.

16. The calculation step includes: The natural frequency f 0 and the natural frequency f of the structure when the plate thickness of the analysis target portion is changed by an arbitrary positive number α and the density of the analysis target portion is kept constant. s and the natural frequency f of the structure when the Young's modulus of the analysis target portion is changed by α times and the density of the analysis target portion is changed by α times. E A first calculation step of calculating Δf s = f s -f 0 , and Δf E = f E -f 0 From the above, the natural frequency fluctuation ratio b of the structure is Δf s / Δf E A second calculation step of calculating It has 14. The structural design support program according to claim 13, wherein the output step outputs the natural frequency fluctuation ratio b calculated in the second calculation step as the evaluation score.

17. The structure design support program according to any one of claims 13 to 16, characterized in that the vibration mode is one or more selected from all vibration modes occurring in the structure between 20 Hz and 2000 Hz and vibration modes resulting from superposition thereof.

18. A computer-readable recording medium having recorded thereon the structure design support program according to any one of claims 13 to 17.

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