JP6222467B2 - Vibration analysis model creation device and vibration analysis model creation method - Google Patents

Description

  The present invention relates to a vibration analysis model creation device and a vibration analysis model creation method, and in particular, vibration analysis for creating a vibration analysis model of a vehicle body floor panel structure having a frame member and a floor panel fixed to the frame member. The present invention relates to a model creation device and a vibration analysis model creation method.

  It is known that vibrations from the frame members to which the engine and suspension are connected are transmitted to the floor panel, causing the floor panel to vibrate, resulting in uncomfortable vehicle interior vibration and noise radiated from the floor panel. It has been. In this case, vibrations of the engine itself and road noise transmitted from the suspension become a problem as the vibration source. This road noise is generally caused by tire cavity resonance and suspension resonance. Such unpleasant vibration transmitted from the engine or suspension is mainly 400 Hz or less in an automobile, and has a peak at a frequency around 250 Hz, which is road noise caused by tire cavity resonance.

  Conventionally, in order to suppress these vibration noises, a vibration damping material and a vibration proof material are generally pasted on the floor panel and various parts of the vehicle body in the vicinity thereof as various vibration proof and sound proof measures. It is also known to increase the rigidity by forming a large number of beads on the floor panel or increasing the panel thickness, thereby shifting the natural frequency of the floor panel to a high band higher than 400 Hz. That is, the floor panel does not resonate at the resonance frequency of the suspension, the cavity resonance frequency band of the tire, or the like, thereby reducing unpleasant vibration noise.

  In order to effectively implement these various anti-vibration and anti-sound measures, vibration analysis of the floor panel structure of the vehicle body is performed by the finite element method (FEM), and the peak frequency of the floor panel vibration and the location where the peak occurs are specified. (For example, refer to Patent Document 1 and Patent Document 2).

Japanese Patent No. 3536813 JP 2006-65466 A

By the way, the vibration mode of the floor panel is (1) a mode in which the floor panel itself resonates with the input from the frame member to the floor panel, and (2) the frame member resonates with an input from the engine or suspension to the frame member. Accordingly, it can be classified into two types of modes: a mode in which the floor panel vibrates. Of these, if the mode due to resonance of the floor panel itself becomes a problem, the natural frequency of the floor panel can be reduced by changing the bead pattern of the floor panel or changing the wall thickness of the floor panel as a countermeasure. It is effective to change On the other hand, if the mode due to the resonance of the frame member becomes a problem, the natural frequency of the frame member can be changed by changing the framework or cross section of the frame, changing the thickness of the frame, or adding a node. It is effective to do.
That is, in order to effectively perform vibration isolation and soundproofing measures based on vibration analysis of the floor panel structure of the vehicle body, each vibration mode of the floor panel output by vibration analysis is one of the two types of modes described above. It is necessary to identify the mode and take appropriate measures according to each mode.

  Therefore, in the past, the floor panel mode has been confirmed from the vibration analysis results, and the analysis model has been changed (for example, bead position or shape change, node addition, frame cross-sectional shape change, etc.). By confirming the sensitivity of the panel vibration, it is determined whether each vibration mode of the floor panel output by the vibration analysis is a mode caused by resonance of the floor panel itself or resonance of the frame member.

  However, in order to determine whether each vibration mode of the floor panel is caused by the resonance of the floor panel itself or the resonance of the frame member, expertise and experience in the vibration analysis field are required. But it's hard to say that you can make accurate decisions. In addition, when checking the sensitivity of floor panel vibration to the change of the analysis model, the analysis model must be changed, which increases the design cost.

  The present invention has been made to solve the above-described problems of the prior art, and each vibration mode of the floor panel is divided into a mode caused by resonance of the floor panel itself and a mode caused by resonance of the frame member. An object of the present invention is to provide a vibration analysis model creation apparatus and a vibration analysis model creation method capable of creating a vibration analysis model of a floor panel structure useful for accurate and easy discrimination.

In order to achieve the above object, according to the present invention, a vibration analysis model creating apparatus creates a vibration analysis model for creating a vibration analysis model of a floor panel structure of a vehicle body having a frame member and a floor panel fixed to the frame member. A model creation device, comprising: a base model creation means for creating a base model obtained by dividing a floor panel structure into finite elements; and a floor panel sorting means for sorting frame members and floor panels included in the base model. Panel part model extraction means that extracts only the floor panel part from the base model as a panel part model, and a contraction that reduces the mass of the entire extracted panel part model to the position of the node set at the boundary between the floor panel and the frame member. Panel mass excluding means for excluding approx. Means and floor panel part mass in the base model The mass of the floor panel in the floor panel structure is obtained by incorporating the panel partial model whose mass is reduced to the position of the node set at the boundary between the floor panel and the frame member into the base model excluding the mass of the floor panel part. And a contracted model creating means for creating a contracted model by contracting to a position of a boundary node set between the floor panel and the frame member.
The vibration analysis model creation method, computer, a vibration analysis model creation method for creating a vibration analysis model car body floor panel structure having a floor panel which is fixed to the frame member and the frame member, the base model The creating means creates a base model obtained by dividing the floor panel structure into finite elements, the floor panel sorting means sorts the frame member and the floor panel included in the base model, and the panel partial model extracting means Extracting only the sectioned floor panel part from the base model as a panel part model, and the contracting means calculates the mass of the whole extracted panel part model as the position of the node set at the boundary between the floor panel and the frame member. the condensed promises step, the panel mass excluding means, in base model And mass excluding step of the lower panel portion, reduced model creation means, mass position of node set of the boundary between the floor panel and the frame member a contracted panel portion model, the mass of the floor panel part is excluded Creating a contracted model in which the mass of the floor panel in the floor panel structure is contracted to the position of the boundary node set between the floor panel and the frame member.
According to the present invention configured as described above, a base model in which the floor panel structure of the vehicle body is divided into finite elements is created, and the mass of the floor panel in the floor panel structure is calculated as a set of boundary nodes between the floor panel and the frame member. Since a reduced model that is contracted to a position is created, a vibration analysis is performed on each of the base model and the reduced model, so that a mode caused by resonance of the floor panel itself and a mode caused by resonance of the frame member Thus, the analysis result of the base model including both vibration modes and the analysis result of the contracted model not including the mode caused by the resonance of the floor panel itself can be compared. Therefore, a vibration analysis model of a floor panel structure useful for accurately and easily distinguishing each vibration mode of the floor panel from a mode caused by resonance of the floor panel itself and a mode caused by resonance of the frame member is created. be able to.

In the present invention, it is preferable that the floor panel sorting means divides a region inside a fixing portion between the frame member and the floor panel as a floor panel in the floor panel structure.
In the present invention configured as described above, the floor panel dividing means can accurately classify the portion contributing to the resonance of the floor panel itself in the floor panel structure, and each vibration mode of the floor panel can be divided into the floor panel itself. It is possible to create a contraction model useful for reliably distinguishing between a mode caused by resonance of the frame and a mode caused by resonance of the frame member.

In the present invention, it is preferable that the contracting means uses a mass matrix representing a mass set at each node position of the extracted panel partial model as a mass matrix at the position of the node set at the boundary between the floor panel and the frame member. Reduce to
In the present invention configured as described above, the contracting means uses a mass matrix representing a mass set at each node position of the panel partial model extracted from the base model as a node set at the boundary between the floor panel and the frame member. Therefore, the mass of the floor panel in the floor panel structure can be appropriately distributed to the position of the boundary node set between the floor panel and the frame member. It is possible to create a reduced model useful for reliably distinguishing between a mode caused by resonance of itself and a mode caused by resonance of the frame member.

  According to the vibration analysis model creation apparatus and the vibration analysis model creation method according to the present invention, each vibration mode of the floor panel is accurately and easily converted into a mode caused by resonance of the floor panel itself and a mode caused by resonance of the frame member. It is possible to create a vibration analysis model of a floor panel structure that is useful for distinguishing between the two.

1 is a block diagram illustrating an electrical configuration of a vibration analysis apparatus including a vibration analysis model creation apparatus according to an embodiment of the present invention. It is a perspective view of the simple model which modeled the floor panel structure of the vehicle body. It is a flowchart of the vibration analysis process which the vibration analyzer by embodiment of this invention performs. FIG. 4A is a plan view conceptually showing a mass setting state in a simple model, FIG. 4A is a diagram showing a mass setting state in a base model of the simple model, and FIG. It is a figure which shows the setting state of mass. It is a diagram which shows the analysis result output to the display by the output part of the vibration analyzer by embodiment of this invention. FIG. 6A is a cross-sectional view showing a vibration mode of a simple model in the frequency band I in FIG. 5, FIG. 6A is a view showing a vibration mode of a base model of the simple model, and FIG. It is a figure which shows the vibration mode of. FIG. 7A is a cross-sectional view showing a vibration mode of a simple model in the frequency band II in FIG. 5, FIG. 7A is a view showing a vibration mode of a base model of the simple model, and FIG. It is a figure which shows the vibration mode of. It is a top view which shows a part of floor panel structure of a vehicle body. It is a flowchart of the reduction model creation process which the vibration analysis model creation apparatus by embodiment of this invention performs. It is a top view which shows the panel extracted from the base model of the floor panel structure of a vehicle body. It is a top view which shows the reduction panel which reduced the mass of the whole panel of FIG. 10 to the boundary of a panel and a flame | frame. It is a top view of the contraction model of the floor panel structure incorporating the contraction panel of FIG. FIG. 9 is a diagram in which results of frequency response analysis of a base model and a contracted model of the floor panel structure of the vehicle body shown in FIG. 8 are superimposed.

  Hereinafter, a vibration analysis model creation device and a vibration analysis model creation method according to embodiments of the present invention will be described with reference to the accompanying drawings.

  First, the configuration of a vibration analysis apparatus including a vibration analysis model creation apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing an electrical configuration of a vibration analysis apparatus including a vibration analysis model creation apparatus according to an embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes a vibration analyzer. The vibration analysis apparatus 1 analyzes a response when an external force is applied to the floor panel structure of the vehicle body. Based on the design data of the floor panel structure, the vibration analysis apparatus 1 creates a vibration analysis model of the floor panel structure. Based on the analysis model creation device 2, the vibration analysis model created by the vibration analysis model creation device 2, the vibration analysis unit 4 that executes the vibration analysis of the floor panel structure by the finite element method, and the analysis by the vibration analysis unit 4 And an output unit 8 that generates display data from the result and outputs the display data to the display 6.

The vibration analysis model creation device 2 includes a base model creation unit 10 that creates a finite element model (hereinafter referred to as a “base model”) obtained by dividing a floor panel structure of a vehicle body into meshes, and a panel in the floor panel structure based on the base model. And a contracted model creating unit 12 for creating a contracted model in which the mass of the contracted material is contracted to the boundary between the panel and the frame. Each of the base model creation unit 10 and the contracted model creation unit 12 outputs the created model to the vibration analysis unit 4.
Each of these components includes a CPU, various programs that are interpreted and executed on the CPU (including basic control programs such as an OS and application programs that are activated on the OS to realize specific functions), programs, and various types It is constituted by a computer having an internal memory such as a ROM or RAM for storing data.

  Next, with reference to FIG. 2 to FIG. 7, each process of vibration analysis executed by the vibration analysis apparatus 1 according to the embodiment of the present invention will be described. FIG. 2 is a perspective view of a simplified model schematically illustrating the floor panel structure of the vehicle body, and FIG. 3 is a flowchart of vibration analysis processing executed by the vibration analysis apparatus 1 according to the embodiment of the present invention. 4 is a plan view conceptually showing a mass setting state in the simple model, FIG. 4 (a) is a diagram showing a mass setting state in the base model of the simple model, and FIG. 4 (b) is a simple model. It is a figure which shows the setting state of the mass in the contraction model of. FIG. 5 is a diagram showing an analysis result output to the display 6 by the output unit 8 of the vibration analysis apparatus 1 according to the embodiment of the present invention. FIG. 6 is a simplified model in the frequency band I in FIG. FIG. 6A is a diagram showing the vibration mode of the base model of the simple model, and FIG. 6B is a diagram showing the vibration mode of the reduced model of the simple model. 7 is a cross-sectional view showing the vibration mode of the simple model in the frequency band II in FIG. 5, FIG. 7A is a view showing the vibration mode of the base model of the simple model, and FIG. It is a figure which shows the vibration mode of the reduction model of a simple model.

  The floor panel structure of the vehicle body has a frame constituting the skeleton and a panel fixed to the frame. For example, the simplified model 14 schematically shown in FIG. 2 includes a square frame 16 and a square panel 18 coupled to the inner peripheral side of the frame 16. The outer shape of the frame 16 is a square having a side length of 550 mm in plan view, and the cross-sectional shape of the frame 16 is a square closed section having a side length of 50 mm. Further, the outer shape of the panel 18 is a square having a side length of 450 mm in plan view. Both the frame 16 and the panel 18 have a plate thickness of 1 mm.

Next, as shown in FIG. 3, when the vibration analysis process is started, the base model creation unit 10 creates a base model of the floor panel structure of the vehicle body in step S1. For example, the base model creation unit 10 acquires shape data and physical property data (density, elastic modulus, etc.) of the floor panel structure, and creates a base model from these data. The created base model is output to the vibration analysis unit 4.
For example, when the simplified model 14 shown in FIG. 2 is acquired as the shape data of the floor panel structure, the base model creation unit 10 creates a base model from the simplified model 14 as a shell element made up of quadrilateral elements.

Next, in step S2, the vibration analysis unit 4 performs frequency response analysis of the base model by the finite element method based on the base model created by the base model creation unit 10. In the example of the simple model 14 shown in FIG. 2, one corner of the frame 16 is set as an excitation point A, and excitation is performed in the direction perpendicular to the panel 18 (Z direction in FIG. 2) with respect to this excitation point A. The displacement of each node of the base model is calculated.
Furthermore, various indexes can be used as an evaluation index for evaluating the result of the frequency response analysis, but the vibration analysis unit 4 according to the present embodiment is an index for evaluating the magnitude of noise generated by the panel 18. Equivalent Radiation Energy (ERP) corresponding to the acoustic power radiated from the panel 18 is calculated from the displacement of each node of the base model.

Next, the process proceeds to step S <b> 3, and the contracted model creating unit 12 contracts the mass of the panel 18 in the floor panel structure to the boundary between the panel 18 and the frame 16 based on the base model created by the base model creating unit 10. Create a reduced model.
Here, with reference to FIG. 4, the setting state of mass in the base model and the contracted model of the simplified model 14 shown in FIG. 2 will be described. In FIG. 4, among the nodes of each element constituting the panel 18, nodes for which a predetermined density is set are indicated by circles. For the frame 16, there is no difference between the base model and the contracted model, so the mesh and nodes are omitted.

As shown in FIG. 4A, in the base model 20 of the simplified model 14, a predetermined density corresponding to the material of the panel 18 is set at the nodes of the entire panel 18. On the other hand, as shown in FIG. 4B, in the contracted model 22 of the simplified model 14, the mass matrix of the entire panel 18 is contracted to a mass matrix at the node set position at the boundary between the panel 18 and the frame 16, The density of nodes inside the panel 18 is zero. That is, in the contracted model 22, the mass inside the panel 18 is distributed to the boundary between the panel 18 and the frame 16, and the panel 18 itself has rigidity but does not have mass. Resonance will not occur. Therefore, it can be said that the displacement of the panel 18 in the contracted model 22 is not caused by the resonance of the panel 18 itself, but is entirely caused by the deformation of the frame 16.
Details of creating the contracted model 22 in step S3 will be described later.

  Next, proceeding to step S4, the vibration analysis unit 4 is based on the contracted model 22 created by the contracted model creating unit 12 under the same conditions as the frequency response analysis of the base model 20 in step S2. 22 frequency response analysis is performed.

  Next, proceeding to step S5, the output unit 8 displays the result of the frequency response analysis of the base model 20 in step S2 and the result of the frequency response analysis of the contracted model 22 in step S4 using a common coordinate axis. 6 is superimposed and output. Thereafter, the vibration analysis apparatus 1 ends the vibration analysis process.

FIG. 5 is a diagram in which the results of frequency response analysis of the base model 20 and the contracted model 22 of the simplified model 14 are superimposed and displayed using a common coordinate axis, with the horizontal axis representing frequency (Hz) and the vertical axis. Indicates ERP (W). In FIG. 5, the frequency response of the base model 20 is indicated by a solid line, and the frequency response of the contracted model 22 is indicated by a broken line.
As shown in FIG. 5, since the frequency response of the base model 20 includes modes caused by the resonance of the panel 18 itself and the resonance of the frame 16, there are a plurality of ERP peaks over a wide frequency band. Yes. On the other hand, since the resonance of the panel 18 itself does not occur in the contracted model 22 as described above, the frequency response of the contracted model 22 includes only the mode caused by the resonance of the frame 16. There is only one ERP peak.

  For example, in the frequency band I in which the ERP peak occurs in the base model 20 and the ERP peak does not occur in the contracted model 22, the panel 18 itself is deformed in the base model 20 as shown in FIG. On the other hand, as shown in FIG. 6B, in the contracted model 22, the panel 18 itself is hardly deformed. That is, it can be said that the ERP peak in this frequency band I is due to the resonance of the panel 18, and the vibration mode of the panel 18 in this frequency band I can be determined to be the vibration mode due to the resonance of the panel 18 itself. .

  On the other hand, in the frequency band II in which peaks occur in both the base model 20 and the contracted model 22, both the frame 16 and the panel 18 are deformed in the base model 20, as shown in FIG. On the other hand, as shown in FIG. 7B, the panel 18 is deformed along with the deformation of the frame 16 in the contracted model 22. That is, it can be said that the peak of ERP in the frequency band II is caused by the deformation of the panel 18 due to the resonance of the frame 16, and therefore the vibration mode of the panel 18 in the frequency band II is a vibration mode caused by the resonance of the frame 16. It can be judged that there is.

That is, according to the diagram shown in FIG. 5, the vibration mode in the frequency band I in which the ERP peak occurs only in the frequency response of the base model 20 is a vibration mode caused by the resonance of the panel 18 itself. It can be determined at a glance that the vibration mode of the frequency band II in which the ERP peak occurs in the frequency response of both the 20 and the contracted model 22 is a vibration mode caused by the resonance of the frame 16.
In other words, the range in which the difference between the frequency response of the base model 20 and the frequency response of the contracted model 22 (shown by hatching in FIG. 5) is within the resonance of the panel 18 itself with respect to the ERP of the entire panel 18. Indicates the range to which.

Next, with reference to FIG. 8 to FIG. 12, a procedure for creating a contracted model by the vibration analysis model creating apparatus 2 according to the embodiment of the present invention will be described in detail.
8 is a plan view showing a part of the floor panel structure of the vehicle body, FIG. 9 is a flowchart of the contracted model creation process executed by the vibration analysis model creation device 2 according to the embodiment of the present invention, and FIG. 10 is the floor of the vehicle body. FIG. 11 is a plan view showing a panel extracted from the base model of the panel structure, and FIG. 11 is a plan view showing a reduced panel in which the mass of the entire panel in FIG. 10 is reduced to the boundary between the panel and the frame. FIG. 12 is a plan view of a contracted model of a floor panel structure in which the contracted panel of FIG. 11 is incorporated.

  FIG. 8 shows the floor panel structure 24 below the seat on the left side of the front row of the vehicle. As shown in FIG. 8, the floor panel structure 24 of the vehicle body includes a frame member 26 that extends in the front-rear direction of the vehicle, and a floor panel 28 that extends horizontally below the frame member 26. The frame member 26 has a closed cross-sectional shape, and a floor panel 28 is spot-welded to the lower surface side of the frame member 26.

  When the contracted model creation process is started in step S3 of the vibration analysis process described with reference to FIG. 3, as shown in FIG. 9, in step S11, the contracted model creation unit 12 performs a step of the vibration analysis process. In S1, the base model created by the base model creation unit 10 is acquired.

  Next, proceeding to step S12, the contracted model creation unit 12 classifies the frame member 26 and the floor panel 28 included in the base model acquired at step S11. For example, as indicated by a broken line in FIG. 8, the contracted model creating unit 12 divides the area on the floor panel 28 inside the welded portion between the frame member 26 and the floor panel 28 as the floor panel 28.

  Next, the process proceeds to step S13, and the contracted model creation unit 12 sets only the portion of the floor panel 28 divided in step S12 as the panel partial model 30 from the base model acquired in step S11, as shown in FIG. Extract.

  Next, proceeding to step S14, the contracted model creating unit 12 sets the node set 32 (that is, the panel portion) at the boundary between the floor panel 28 and the frame member 26 among the nodes of the panel partial model 30 extracted at step S13. Node set located on the outer periphery of the model 30).

  Next, proceeding to step S15, the contracted model creating unit 12 uses the mass matrix that is a set of densities set at each node of the panel partial model 30 extracted at step S13 as the boundary node specified at step S14. Reduce to a mass matrix at the location of set 32. Accordingly, as indicated by a circle in FIG. 11, the mass of the entire panel partial model 30 is the node set 32 at the boundary between the floor panel 28 and the frame member 26 (that is, the node set positioned on the outer periphery of the panel partial model 30). ).

  Next, proceeding to step S16, the contracted model creation unit 12 sets the density set to each node in the floor panel 28 divided in step S12 among the nodes in the base model acquired in step S11 to 0. To. Thereby, the mass of the floor panel 28 in the base model acquired in step S11 becomes zero.

  Next, the process proceeds to step S17, and the contracted model creating unit 12 displays the panel partial model 30 in which the mass matrix is contracted to the mass matrix at the position of the boundary node set 32 between the floor panel 28 and the frame member 26 in step S15. In step S16, the floor panel 28 is incorporated into the base model in which the mass is zero. As a result, as shown in FIG. 12, a contracted model 34 in which the mass of the floor panel 28 is contracted to the position of the boundary node set 32 between the floor panel 28 and the frame member 26 is created. After step S17, the vibration analysis unit 4 returns to the main routine of FIG. 3 and performs frequency response analysis of the contracted model 34 (step S4).

FIG. 13 is a diagram in which the results of frequency response analysis of the base model and the contracted model 34 of the floor panel structure 24 of the vehicle body shown in FIG. 8 are superimposed, with the horizontal axis representing frequency (Hz) and the vertical axis Indicates ERP (W). In FIG 13, illustrates the frequency response of the base model with a solid line, according to the diagram shown in FIG. 13 shows the frequency response of the reduced model 34 in broken lines, at frequencies F ₁ following ranges, based model Since the frequency response and the frequency response of the contracted model 34 almost overlap, it can be seen that the vibration mode of the floor panel structure 24 in this range is a vibration mode caused by the resonance of the frame. On the other hand, in the range above the frequency F ₁ , an ERP peak occurs only in the frequency response of the base model. Therefore, the vibration mode of the floor panel structure 24 in this range is a vibration mode caused by resonance of the floor panel 28 itself. I understand that. In other words, in the range above the frequency F ₁ , there is a difference between the frequency response of the base model and the frequency response of the contracted model 34. Therefore, in this frequency band, the floor panel is compared with the ERP of the floor panel structure 24. It can be seen that the resonance of 28 itself contributes.
That is, in order to reduce the ERP in the range below the frequency F ₁ , it is sufficient to take measures against the frame member 26 so as to suppress the resonance of the frame member 26, and in order to reduce the ERP in the range above the frequency F _1. It can be seen that it is sufficient to take measures against the floor panel 28 so as to suppress the resonance of the floor panel 28 itself.

  Next, the effects of the vibration analysis apparatus 1 and the vibration analysis method of the present embodiment described above will be described.

  First, the base model creation unit 10 creates a base model obtained by dividing the floor panel structure 24 of the vehicle body into finite elements, and the contracted model creation unit 12 determines the mass of the floor panel 28 in the floor panel structure 24 as the floor panel 28. Since the contracted model 34 contracted to the position of the boundary node set 32 between the frame member 26 and the frame member 26 is created, the vibration analysis is performed on each of the base model and the contracted model 34, thereby the floor panel 28 itself. The analysis result of the base model including both the vibration mode and the mode caused by the resonance of the frame member 26, and the analysis result of the reduced model 34 that does not include the mode caused by the resonance of the floor panel 28 itself. Can be compared. Therefore, the vibration analysis of the floor panel structure 24 useful for accurately and easily distinguishing each vibration mode of the floor panel 28 from a mode caused by resonance of the floor panel 28 itself and a mode caused by resonance of the frame member 26. A model can be created.

  In particular, the contracted model creation unit 12 divides the area inside the fixing portion between the frame member 26 and the floor panel 28 in the floor panel structure 24 as the floor panel 28, so that the floor panel 28 itself has the floor panel structure 24. A portion contributing to resonance can be accurately distinguished, and each vibration mode of the floor panel 28 is reliably distinguished into a mode caused by resonance of the floor panel 28 itself and a mode caused by resonance of the frame member 26. A reduction model 34 useful for the above can be created.

  Further, the contracted model creating unit 12 extracts only the floor panel 28 portion in the base model from the base model as the panel partial model 30, and a mass matrix representing a set of masses at the respective node positions of the extracted panel partial model 30. Is reduced to a mass matrix at the position of the node set at the boundary between the floor panel 28 and the frame member 26, the mass of the floor panel 28 in the floor panel structure 24 is reduced to the boundary node set 32 between the floor panel 28 and the frame member 26. The vibration mode of the floor panel 28 can be appropriately assigned to the position of the floor panel 28, and is useful for reliably distinguishing the vibration mode of the floor panel 28 from the mode due to the resonance of the floor panel 28 itself and the mode due to the resonance of the frame member 26. About a model 34 can be created.

  The base model creation unit 10 creates a base model obtained by dividing the floor panel structure 24 into finite elements, and the contracted model creation unit 12 calculates the mass of the floor panel 28 in the floor panel structure 24 based on the base model. A contracted model 34 contracted to the boundary position between the floor panel 28 and the frame member 26 is created, and the vibration analysis unit 4 executes vibration analysis of the floor panel structure 24 based on the base model and the contracted model 34. Since the output unit 8 displays and outputs the analysis results of the base model and the contracted model 34 using a common coordinate axis, it results from the mode caused by the resonance of the floor panel 28 itself and the resonance of the frame member 26. Analysis results of the base model including both vibration modes and modes resulting from resonance of the floor panel 28 itself. The analysis result of not reduced model 34 can be easily compared. That is, the vibration analysis of the floor panel structure 24 is performed in such a manner that each vibration mode of the floor panel 28 can be accurately and easily distinguished from a mode caused by resonance of the floor panel 28 itself and a mode caused by resonance of the frame member 26. The result can be output.

  Further, since the output unit 8 displays and outputs the frequency response of the equivalent radiant energy of the base model and the frequency response of the equivalent radiant energy of the contracted model 34 using a common coordinate axis, the output unit 8 is radiated from the floor panel 28. Results of vibration analysis of the floor panel structure 24 in such a manner that the range in which the resonance of the floor panel 28 itself contributes to the equivalent radiant energy of the entire floor panel 28 can be clearly distinguished using the equivalent radiant energy corresponding to the acoustic power as an index. Can be output.

DESCRIPTION OF SYMBOLS 1 Vibration analysis apparatus 2 Vibration analysis model creation apparatus 4 Vibration analysis part 6 Display 8 Output part 10 Base model creation part 12 Reduction model creation part 14 Simple model 16 Frame 18 Panel 20 Base model 22 Reduction model 24 Floor panel structure 26 Frame Member 28 Floor panel 30 Panel partial model 32 Boundary node set 34 Reduction model

Claims (4)

A vibration analysis model creation device for creating a vibration analysis model of a floor panel structure of a vehicle body having a frame member and a floor panel fixed to the frame member,
Base model creating means for creating a base model obtained by dividing the floor panel structure into finite elements;
Floor panel dividing means for dividing the frame member and the floor panel included in the base model;
Panel part model extraction means for extracting only the divided floor panel part from the base model as a panel part model;
Contraction means for reducing the mass of the entire extracted panel partial model to the position of the node set at the boundary between the floor panel and the frame member;
Panel mass exclusion means for excluding the mass of the floor panel portion in the base model;
In the floor panel structure, the panel part model whose mass is reduced to the position of the node set at the boundary between the floor panel and the frame member is incorporated into the base model from which the mass of the floor panel part is excluded. And a contracted model creating means for creating a contracted model in which the mass of the floor panel is contracted to the position of a boundary node set between the floor panel and the frame member. The vibration analysis model creating apparatus according to claim 1 , wherein the floor panel sorting unit sorts an area inside a fixing portion between the frame member and the floor panel as the floor panel in the floor panel structure.   The contraction means contracts a mass matrix representing a set of masses at each node position of the extracted panel partial model into a mass matrix at a position of a node set at a boundary between the floor panel and the frame member. The vibration analysis model creation apparatus according to 1 or 2. A vibration analysis model creation method in which a computer creates a vibration analysis model of a floor panel structure of a vehicle body having a frame member and a floor panel fixed to the frame member,
A base model creating means creating a base model obtained by dividing the floor panel structure into finite elements;
Floor panel sorting means for sorting the frame member and the floor panel included in the base model;
A panel part model extracting means for extracting only the sectioned floor panel part from the base model as a panel part model;
A contracting means for contracting the mass of the whole extracted panel partial model to the position of the node set at the boundary between the floor panel and the frame member;
Panel mass excluding means excluding the mass of the floor panel portion in the base model;
The reduced model creating means incorporates the panel partial model whose mass is reduced to the position of the node set at the boundary between the floor panel and the frame member into the base model excluding the mass of the floor panel portion. Accordingly, vibration analysis model creation method characterized by comprising the steps of: creating a reduced model which contracted the mass of the floor panel to the position of the boundary node set between the floor panel and the frame member in the floor panel structure.

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