JP2008059274A - Vibration analysis system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology allowing accurate and intelligible visualization of the state of transmission of vibration energy. <P>SOLUTION: This vibration analysis system has: a transmission vector calculation means calculating a transmission vector showing magnitude of the vibration energy transmitted through an element and its transmission direction about each of a plurality of elements configuring a model; and an output means displaying the calculated transmission vector together with the model. Here, the output means represents the transmission vector of each the element by an arrowhead figure of the same size. A direction of a tip of the arrowhead figure shows the transmission direction of the vibration energy, and a color of the arrowhead figure shows the magnitude (a transmission amount) of the vibration energy. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for supporting analysis of a vibration phenomenon of a structure.

  In vehicle development, reduction of body vibration and noise is one of the important issues. However, since the vibration phenomenon is invisible, it is difficult to accurately grasp the cause of the phenomenon. Accordingly, there has been a demand for the emergence of a system that analyzes and visualizes vibration energy (kinetic energy, strain energy) distribution, phase-by-phase change, transmission path, and the like in a three-dimensional structure with high accuracy by a computer.

  Non-Patent Document 1 discloses a system that measures the transient vibration energy flow in the outer plate of a passenger car using the intensity method and displays the measured result with an arrow. As in the system of Non-Patent Document 1, conventionally, a display method in which the magnitude (transmission amount) of vibration energy is represented by the line length of an arrow and the transmission direction of vibration energy is represented by the direction of the arrow is common. .

However, the conventional display method has the following problems. Where the amount of energy transmitted is small, the arrow becomes very fine, making it difficult to determine the direction of the arrow. On the other hand, where the amount of transmission is large, the long arrows are dense and they overlap each other, making it difficult to grasp the energy transmission direction as a whole. Therefore, it is difficult to intuitively understand how vibration energy is transmitted, and it is difficult to specify the main transmission path.
JP-A-11-148858 JP 2001-255200 A Kojima, 3 others, “Measurement of transient vibration energy flow in passenger car skin using intensity method”, Automobile Engineering Society Proceedings, Vol. 31, no. 2, April 2000, p. 23-28

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique capable of accurately and easily visualizing the state of vibration energy transmission.

  In order to achieve the above object, the present invention employs the following configuration.

  According to a first aspect of the present invention, for each of a plurality of elements constituting a model, a transmission vector calculation means for calculating a transmission vector representing the magnitude of vibration energy transmitted through the element and its transmission direction, and the calculated transmission vector A vibration analysis system comprising: output means for displaying the model together with the model. Here, the output means represents the transmission vector of each element with an arrowhead figure of the same size.

  According to this configuration, the transmission vector is displayed as an arrowhead figure of the same size regardless of the magnitude of vibration energy. Therefore, the transmission direction can be accurately and easily determined even at a location where the amount of energy transmission is small, and the overlapping of transmission vectors is eliminated (or as small as possible) even at a location where the amount of energy transmission is large. It becomes easy. Therefore, the state of vibration energy transmission can be intuitively understood, and the main transmission path can be easily identified.

The output means preferably represents the transmission direction of vibration energy by the direction of the tip of the arrowhead figure.

  The output means preferably represents the magnitude of vibration energy by the color of the arrowhead figure. For example, the output means may change the color of the arrowhead figure continuously or stepwise according to the magnitude of vibration energy. At this time, the output means may change the color of the arrowhead figure linearly with respect to the magnitude of vibration energy, or may change non-linearly with respect to the magnitude of vibration energy. For example, a logarithmic scale can be used as the non-linear scale.

  The output means preferably hides a transmission vector whose vibration energy does not satisfy the display condition. By specifying only a noticeable transmission vector, the main transmission path can be easily identified. As the display condition, a lower limit value or an upper limit value of the vibration energy value can be preferably adopted. It is also preferable that the output means allows the user to input display conditions.

  The present invention can be understood as a vibration analysis system having at least a part of the above means. The present invention can also be understood as a vibration analysis method including at least a part of the above processing, a program for realizing the method, or a computer-readable recording medium storing the program. Each of the above means and processes can be combined with each other as much as possible to constitute the present invention.

  For example, in the vibration analysis method according to the second aspect of the present invention, the computer calculates, for each of a plurality of elements constituting the model, a transmission vector representing the magnitude of vibration energy transmitted through the element and its transmission direction. Processing and output processing for displaying the calculated transmission vector together with the model are executed, and in the output processing, the transmission vector of each element is represented by an arrowhead figure of the same size.

  The program as the third aspect of the present invention is a program for calculating a transfer vector for calculating a transfer vector representing the magnitude of vibration energy transmitted through the element and the transfer direction for each of a plurality of elements constituting the model. A program that functions as a means and an output means for displaying the calculated transfer vector together with the model, wherein the output means represents the transfer vector of each element as an arrowhead figure of the same size.

  According to the present invention, the state of vibration energy transmission can be visualized accurately and easily. As a result, it becomes easy to specify the main transmission path of vibration energy, which can be used for investigating the cause of vibration and planning countermeasures.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings.

  The vibration analysis system according to the embodiment of the present invention analyzes the state of vibration energy in a three-dimensional structure such as a vehicle body and visualizes the transmission path of the vibration energy, thereby investigating the cause of vibration and planning countermeasures. It is for support.

<Transmission vector calculation method>
Before describing the specific configuration of the vibration analysis system, the basic concept of the transfer vector calculation method in this embodiment will be described.

In order to analyze vibration energy in a three-dimensional structure with high accuracy, it is desirable to use state quantities (displacement) and internal forces (axial force, shear force, moment) inside the structure. However, it is extremely difficult to measure such internal state quantities and internal forces by experiments. Therefore, in this embodiment,
The internal state quantity and internal force are calculated by structural analysis using a computer.

As a structural analysis method, a finite element method (FEM) is used. In the finite element method, a three-dimensional structure is represented by an FE model composed of a large number of elements (plate elements, beam elements, etc.). For example, in the case of a vehicle body, an FE model composed of about one million elements is used. When an excitation condition such as an excitation point or an angular frequency is given to the FE model, an internal force acting on each element, a displacement of a node of each element, and the like are calculated. Each element of the FE model also has volume and material information, and a stiffness matrix and a mass matrix for each element are calculated from the information.

  The vibration analysis system calculates a transfer vector representing vibration energy transmitted through the element by using the displacement of the node of each element and the internal force acting on each element obtained as a result of the finite element analysis. As the internal force, axial force, shear force, lateral shear force, bending moment and torsion moment are taken into consideration.

  In this embodiment, the transmission vector is defined as the difference in power between two points under the assumption that “vibration energy is transmitted from the larger work to the smaller work in order to maintain an energy equilibrium state”. As a result, the transfer vector can be calculated with high accuracy by a relatively simple calculation. The work rate is the work per unit time, and can be calculated by multiplying the internal force by the speed (time derivative of displacement). The difference in work rate is the difference in work between two points when considered in one cycle in a system with no attenuation (or a system with extremely small attenuation). This is because it becomes 0 (or almost 0), and energy transfer between two points cannot be accurately captured.

Hereinafter, as illustrated in FIG. 1, a transmission vector calculation method will be described using a plate element having an xy plane that is rectangular and has a thickness in the z-axis direction as an example. The plate element has four nodes P1 to P4, and each node has six degrees of freedom of movement in the x, y, and z axis directions and rotation (angular displacement) around the x, y, and z axes. Therefore, the displacement u of the plate element is represented by a vector composed of 24 components as in the following equation. Note that x, y, and z here are element coordinate systems. If the result of finite element analysis is obtained in the global coordinate system, it is necessary to perform coordinate conversion from global coordinates to element coordinates.

The velocity of the node can be obtained as follows by differentiating the displacement with time.

  Here, two side surfaces facing in the x-axis direction are referred to as a surface A and a surface B, respectively, an axial force Fx on the x-axis, a transverse shear force Fxy, a shear force Vx on the x-axis, a bending moment My around the x-axis, and It is assumed that the torsional moment Mxy acts on points (mass points) PA and PB that are the centers of gravity of the surfaces A and B, respectively. Similarly, the two side surfaces facing in the y-axis direction are plane C and plane D, respectively, an axial force Fy on the y axis, a transverse shear force Fxy, a shear force Vy on the y axis, a bending moment Mx around the y axis, and It is assumed that the torsional moment Mxy acts on the points (mass points) PC and PD which are the centers of gravity of the surfaces C and D, respectively.

The speed of the point PA is obtained as follows by linearly interpolating the speeds of the nodes P1 and P3.

  Similarly, the speed of the point PB is obtained from the speeds of the nodes P2 and P4, the speed of the point PC is obtained from the speeds of the nodes P1 and P2, and the speed of the point PD is obtained from the speeds of the nodes P3 and P4.

(1) Axial Force FIG. 2 schematically shows the transmission direction of vibration energy when the axial force Fx on the x-axis acts. When the axial force Fx acts on the points PA and PB as shown in the figure, the vibration energy is considered to be transmitted in the x-axis direction (direction connecting the points PA and PB). The magnitude of vibration energy transmitted per unit time can be defined as the difference in power due to the axial force Fx between the point PA and the point PB, and specifically can be expressed by the following equation. .

(2) Lateral Shear Force FIG. 3 schematically shows the transmission direction of vibration energy when the transverse shear force Fxy is applied. When the transverse shear force Fxy acts on the points PA and PB as shown in the figure, the vibration energy is considered to be transmitted in the x-axis direction. The magnitude of vibration energy transmitted per unit time can be defined as the difference in power due to the transverse shear force Fxy between the point PA and the point PB. Specifically, it can be expressed by the following equation. it can.

(3) Shear Force FIG. 4 schematically shows the transmission direction of vibration energy when the x-axis shear force Vx is applied. When the shear force Vx acts on the points PA and PB as shown in the figure, the vibration energy is considered to be transmitted in the x-axis direction. The magnitude of vibration energy transmitted per unit time can be defined as the difference in power due to the shearing force Vx between the point PA and the point PB, and specifically can be expressed by the following equation. .

(4) Bending Moment FIG. 5 schematically shows the transmission direction of vibration energy when the bending moment My around the x axis acts. When the bending moment My acts on the points PA and PB as shown in the figure, the vibration energy is considered to be transmitted in the x-axis direction. The magnitude of vibration energy transmitted per unit time can be defined as the difference in power due to the bending moment My between the point PA and the point PB, and specifically can be expressed by the following equation. .

(5) Torsional moment FIG. 6 schematically shows the transmission direction of vibration energy when the torsional moment Mxy acts. When the torsional moment Mxy acts on the points PA and PB as shown in the figure, the vibration energy is considered to be transmitted in the x-axis direction. The magnitude of vibration energy transmitted per unit time can be defined as the difference in power due to the torsional moment Mxy between the point PA and the point PB, and specifically can be expressed by the following equation. .

From the above, the x-axis direction component VIx of the transmission vector can be expressed by Equation 4.

Similarly, the y-axis direction component VIy of the transmission vector can be expressed by Equation 5.

  Although the description has been given here taking the plate element shown in FIG. 1 as an example, the transmission vector is calculated using the above equations 4 and 5 if the mass points PA to PD are appropriately set for elements of other shapes. can do.

  Next, a configuration example of the vibration analysis system using the above formulas 4 and 5 will be specifically described.

<System configuration>
FIG. 7 is a block diagram illustrating a functional configuration of the vibration analysis system.

  The vibration analysis system includes a transmission vector calculation unit 1 that calculates a transmission vector, a characteristic value database 2 that stores a calculation result, and an output unit 3 that outputs the calculation result.

This vibration analysis system typically includes a general-purpose computer including an arithmetic processing unit (CPU), a main storage device (memory), an auxiliary storage device (hard disk, etc.), a display device, and an input device (mouse, keyboard, etc.). And a program that runs on this computer. The functional elements shown in FIG. 7 are realized by an arithmetic processing unit executing a program and controlling hardware resources such as a main storage device, an auxiliary storage device, a display device, and an input device as necessary. . However, a part of these functional elements may be replaced with a dedicated chip. Further, not all of these functional elements need to be executed by a single computer, and a plurality of computers may cooperate to constitute a vibration analysis system.

<Transmission vector calculation process>
FIG. 8 is a flowchart showing a flow of a transfer vector calculation process.

  The transfer vector calculation unit 1 acquires the result of the finite element analysis via a storage medium or a network (step S10). The information acquired here includes at least the displacement of each element when the FE model is vibrated at a predetermined angular frequency ω and the internal force acting on each element (axial force, shear force, lateral shear force, bending moment, Torsional moment).

  Next, the transmission vector calculation unit 1 calculates the velocity of the node from the displacement of the node of each element (step S11). Conversion from displacement to speed may be performed by time differentiation (see Equation 2).

  Next, the transmission vector calculation unit 1 calculates the speed at the action points PA to PD of the internal force from the speed of the node (step S12). The speed at the point of action can be calculated by linearly interpolating the speed of the node (see Equation 3).

  Next, the transfer vector calculation unit 1 converts the speed of the action point calculated in step S12 from the global coordinate system to the element coordinate system (step S13). However, if the displacement acquired in step S10 was originally in the element coordinate system, the coordinate conversion process here is unnecessary. It should be noted that the same result can be obtained regardless of the order of steps S11 to S13.

  Next, the transfer vector calculation unit 1 calculates the transfer vector of each element according to Expression 4 and Expression 5 from the internal force of each element acquired in Step S10 and the speed of each action point of each element calculated in Step S13. (Step S14). The calculation results are sequentially stored in the characteristic value database 2.

<Transmission vector output processing>
After the transmission vector calculation process is completed, the vibration energy transmission state of the entire FE model can be displayed and confirmed by the output unit 3 as a post processor.

  FIG. 9 shows a display example of the transmission vector on the flat plate. As a comparative example, FIG. 10 shows a display example using conventional arrows.

  In the conventional display example of FIG. 10, the direction of the arrow indicates the transmission direction of vibration energy, and the length of the arrow line indicates the magnitude (transmission amount) of vibration energy. However, in this display method, the arrow becomes very fine (unclear) when the energy transmission amount is small, and the arrows overlap or become complicated when the energy transmission amount is large. Difficult to grasp the direction of transmission.

  On the other hand, as shown in FIG. 9, the output unit 3 of the present embodiment employs a display method in which the transmission vectors of the respective elements are represented by arrowhead figures of the same size, and these are superimposed on the FE model and displayed. . Here, the direction of the tip of the arrowhead figure represents the transmission direction of vibration energy. The arrowhead figure is displayed in a so-called pseudo color, and the color changes continuously or stepwise according to the magnitude of vibration energy. That is, the color of the arrowhead figure represents the amount of vibration energy transmitted.

According to such a display method, the transmission direction can be accurately and easily determined even at a location where the amount of energy transmission is small, and transmission vectors do not overlap each other even at a location where the amount of energy transmission is large. Become. The amount of energy transfer can be grasped by looking at the color of the arrowhead shape. Therefore, the state of vibration energy transmission can be intuitively understood, and the main transmission path can be easily identified.

  Furthermore, the output unit 3 of the present embodiment has a display setting function for changing the display mode of the transmission vector. FIG. 11 is an example of a display setting function setting screen.

  In this setting screen, “angle” is an input field for designating the angle of the tip of the arrowhead graphic, and “size” is an input field for designating the size of the arrowhead graphic (see FIG. 12). By inputting desired values in these input fields, the user can freely change the shape and size of the arrowhead figure. As a result, the visibility of the transmission vector output screen (see FIG. 9) can be improved.

  Further, “logarithm” in the setting screen of FIG. 11 is a check box for changing the correlation between the color of the arrowhead figure and the magnitude of vibration energy. When unchecked, the color of the arrowhead shape changes linearly with the magnitude of vibration energy. On the other hand, when checked, the magnitude of vibration energy takes a logarithmic scale, and the color of the arrowhead figure changes nonlinearly with respect to the magnitude of vibration energy. When the dynamic range of vibration energy is wide, if the pseudo color is displayed in the former (linear scale), the arrowhead figure color is biased to the same hue, and it may be difficult to grasp the distribution of energy transmission amount. In such a case, display on a logarithmic scale is advantageous.

  Further, the “display condition” in the setting screen of FIG. 11 is an input field for designating the condition of the arrowhead figure to be displayed. Specifically, a lower limit value and an upper limit value of vibration energy can be input. For example, when the lower limit “3” is input as the display condition, the output unit 3 hides the arrowhead figure (transmission vector) whose vibration energy value is 3 or less. FIG. 13 is a display example in which an arrowhead figure with small vibration energy is not displayed. As can be seen from the comparison between FIG. 9 and FIG. 13, the main transmission path can be identified very easily by setting only the transmission vector having a certain level of vibration energy to the display state.

  FIG. 14 is a display example of a transmission vector in the vehicle body model. By viewing such a display, it is possible to intuitively and easily grasp what path the vibration generated at the excitation point is transmitted to each part of the structure. For example, assume that the analysis result of FIG. 14 is obtained when the vibration sound of the roof panel is a problem. From the display of FIG. 14, it can be seen that vibration energy in the engine compartment is transmitted to the roof panel via the front pillar and vibrates a part of the roof panel. As a result, it is possible to easily guess the mechanism by which the vibration noise of the roof panel is generated. If such consideration is obtained, it will be understood that it is only necessary to reinforce somewhere in the transmission path from the engine compartment to the roof panel or to attach damping materials as countermeasures, and it becomes easy to take appropriate countermeasures. . In addition, since the transmission path and transmission mechanism have been clarified, for example, the location of the countermeasures and the contents of the countermeasures such as reinforcement of the joint part in the engine compartment, change of the shape of the front pillar, and thickening of the roof panel. Since the degree of freedom increases, there is also an advantage that it is only necessary to take measures that are the easiest to cope with (design change).

  According to the configuration of the present embodiment described above, the state of vibration energy transmission can be visualized accurately and easily. As a result, it becomes easy to specify the main transmission path of vibration energy, which can be used for investigating the cause of vibration and planning countermeasures.

In addition, in this embodiment, the structure model to be analyzed is composed of a plurality of elements, and the transfer vector is obtained from the displacement and internal force for each element. Therefore, a complicated structure is obtained by calculation (computer simulation). It is possible to accurately estimate the vibration energy transmission path inside an object (particularly a three-dimensional structure).

  The above embodiment is merely an example of the present invention. The scope of the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the technical idea.

  For example, a transmission vector (a transmission amount and a transmission direction of vibration energy) calculated using another method can also be displayed by the display method according to the present invention using an arrowhead figure.

FIG. 1 is a diagram for explaining plate elements and internal forces acting thereon. FIG. 2 is a diagram schematically showing the transmission direction of vibration energy when the axial force Fx is applied. FIG. 3 is a diagram schematically showing the transmission direction of vibration energy when the transverse shear force Fxy is applied. FIG. 4 is a diagram schematically showing the transmission direction of vibration energy when the shearing force Vx is applied. FIG. 5 is a diagram schematically showing the transmission direction of vibration energy when the bending moment My is applied. FIG. 6 is a diagram schematically showing the transmission direction of vibration energy when the torsional moment Mxy is applied. FIG. 7 is a block diagram illustrating a functional configuration of the vibration analysis system. FIG. 8 is a flowchart showing a flow of a transfer vector calculation process. FIG. 9 is a display example of a transfer vector in the embodiment of the present invention. FIG. 10 is a display example of a conventional transmission vector. FIG. 11 is a diagram illustrating an example of a setting screen for the display setting function. FIG. 12 is a diagram illustrating an example of an arrowhead figure. FIG. 13 is a display example in which an arrowhead figure with small vibration energy is not displayed. FIG. 14 is a display example of a transmission vector in the vehicle body model.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transfer vector calculation part 2 Characteristic value database 3 Output part

Claims (8)

For each of a plurality of elements constituting the model, transmission vector calculation means for calculating a transmission vector representing the magnitude of vibration energy transmitted through the element and its transmission direction;
Output means for displaying the calculated transmission vector together with the model,
The output means represents the transmission vector of each element as an arrowhead figure of the same size.   The vibration analysis system according to claim 1, wherein the output unit represents a transmission direction of vibration energy by a direction of a tip of the arrowhead figure.   The vibration analysis system according to claim 1, wherein the output unit represents a magnitude of vibration energy by a color of the arrowhead figure.   4. The vibration analysis system according to claim 3, wherein the output means changes the color of the arrowhead figure in a non-linear manner with respect to the magnitude of vibration energy.   The vibration analysis system according to claim 1, wherein the output unit hides a transmission vector whose vibration energy does not satisfy a display condition. Computer
For each of a plurality of elements constituting the model, a calculation process for calculating a transmission vector representing the magnitude of vibration energy transmitted through the element and its transmission direction;
An output process for displaying the calculated transfer vector together with the model; and
In the output processing, the vibration analysis method, wherein the transmission vector of each element is represented by an arrowhead figure of the same size. Computer
For each of a plurality of elements constituting the model, transmission vector calculation means for calculating a transmission vector representing the magnitude of vibration energy transmitted through the element and its transmission direction;
A program for functioning as an output means for displaying the calculated transmission vector together with the model,
The said output means represents the transmission vector of each said element by the arrowhead figure of the same size, The program characterized by the above-mentioned.   A computer-readable storage medium storing the program according to claim 7.

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