JP2007033405A - Simulation device and simulation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simulation device which can significantly simplify input work and improve working efficiency, thus reducing time required for simulation. <P>SOLUTION: This device is provided with a form file which presents a predetermined space region consisting of a plurality of materials by an image consisting of a plurality of pixels and stores an image which gives identification information indicative of a form and a kind of each material to each pixel, a material file which stores information on the plurality of materials in correspondence to the identification information, and an arithmetic unit 1 which performs the simulation over a predetermined time range for the predetermined space region consisting of the plurality of materials for every pixel having the same size as a minimum unit of space division in the simulation based on the form file and the material file. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a simulation apparatus and a simulation method for calculating various values inside a material.

  In recent years, the calculation speed of computers has been developed, and various simulations can be realized. One example is a wave propagation simulation by the FDTD method. The FDTD method is a simulation method for obtaining propagation of electromagnetic waves by alternately calculating an electric field and a magnetic field temporally and spatially. Moreover, it may be applied not only to electromagnetic waves but also to acoustic waves propagating in the air and water and elastic waves propagating in solids. In these cases, instead of calculating the electric and magnetic fields, the particle velocity and sound pressure or the particle velocity and stress are calculated.

  In general, there are various shapes and materials of a medium through which a wave propagates. For example, in ultrasonic flaw detection, in order to simulate the propagation of ultrasonic waves in a test object by the FDTD method, it is necessary to input information on the shape and material of the test object to a computer. What is a test object in ultrasonic flaw detection? In some cases, it is a steel welded part, in various alloys, or in a material such as ceramic, and the shape and material of the test object are various. In addition, in the case of the water immersion method in which a test body is immersed in water for flaw detection, it is necessary to obtain propagation of ultrasonic waves in the water. As described above, there are various shapes and materials of the medium through which ultrasonic waves propagate in ultrasonic flaw detection.

  As described above, in order to perform the simulation by the FDTD method, it is necessary to input information on the shape and material of the medium through which the wave propagates to the computer. As a method for this, there is a method in which the shape is expressed by a mathematical expression, and the range surrounded by the mathematical expression line is handled as a certain material. In this method, if the shape is simple such as a circle or a rectangle, it can be adequately handled. However, if the shape of the medium through which the ultrasonic wave propagates varies, such as the ultrasonic flaw detection described above, the method is complicated. The shape needs to be expressed by a mathematical formula, and the mathematical formula itself becomes complicated. For this reason, there is a difficulty that processing takes time in the stage of expressing the shape.

  A method of expressing a shape without using a mathematical formula has been proposed (see, for example, Patent Document 1). Patent Document 1 discloses a method for expressing a cross-sectional structure of a semiconductor device, which is different from the field of wave propagation simulation, but is included in the prior art in the sense of “expressing a shape”. In Patent Document 1, a material type is defined by a pixel value assigned to each pixel on the screen, and a pixel whose adjacent pixel value is different from its own pixel value is determined as a boundary of the material. is there. If this method is used, even if it is a complicated shape, it is thought that a shape can be expressed easily compared with the method of expressing with a numerical formula. However, Patent Document 1 does not show information on the pixel size.

  In the FDTD method, since a simulation is performed by dividing a space, coordinates for calculating a value (for example, particle velocity) exist discretely in the medium. In the present specification, these discrete coordinates are referred to as a lattice, and the interval between the lattices is referred to as a lattice interval. In the FDTD method, values (for example, particle velocities) are calculated in each grid. Therefore, in order to represent the shape with pixels, it is desirable to represent the shape so that pixel values can be individually given to each grid. In other words, it is necessary to have a one-to-one correspondence between the grid and the pixel. In order to realize this, it is necessary to match the lattice spacing and the pixel size. However, in Patent Document 1, since there is no concept of lattice spacing, no special mention is made with respect to the pixel size. That is, it is difficult to express the shape using the technique disclosed in Patent Document 1 as it is and to perform a simulation of the FDTD method.

  Another method for expressing the shape has been proposed (see, for example, Patent Document 2). The shape expression method disclosed in Patent Document 2 is a technique related to the processing of a semiconductor device as in Patent Document 1, and the shape expression method is almost the same as that in Patent Document 1. This is an improvement that can be applied to the case where particles fly obliquely, which was difficult in Patent Document 1.

  On the other hand, a simulation of the FDTD method in which the lattice spacing and the pixel size are matched has been proposed (for example, see Non-Patent Document 1). In Non-Patent Document 1, binary data in which a flaw area is “0” and a non-flaw area is “1” is created on a lattice point of the FDTD method, and this data is input to a computer for calculation. It is shown. However, the method disclosed in Non-Patent Document 1 is a method in which the stress is calculated as zero in the “0” region and is calculated as it is in the “1” region. Only two materials can be considered.

JP-A-6-53099 JP-A-8-306600 "Simulation of scattered sound field and echo of flaws with complex shape by hybrid FDTD method", 25th Symposium on Fundamentals and Applications of Ultrasonic Electronics, pp. 79-80

  As described above, when a wave simulation propagating in a complex-shaped material is performed by the FDTD method, it is difficult to input the shape to a computer, and as a result, the time required for the simulation becomes long. there were.

  Moreover, although the prior art of expressing a shape by the pixel on a screen is shown, since there is no description regarding a pixel size in this prior art, the application to a wave propagation simulation is difficult.

  Furthermore, there is a conventional technique in which the lattice spacing of the FDTD method and the pixel size are matched, but this conventional technique has a problem that it cannot be applied when there are three or more kinds of materials.

  The present invention has been made to solve the above-described problems, and its purpose is to greatly simplify the input work when performing simulation by inputting shape and material information to a computer. It is possible to obtain a simulation apparatus and a simulation method that can improve the working efficiency and can reduce the time required for the simulation.

  The simulation apparatus according to the present invention expresses a predetermined spatial region composed of a plurality of materials by an image composed of a plurality of pixels, and provides an image in which identification information representing the shape and type of each material is given to each pixel. A shape file to be stored, a material file that stores information on the plurality of materials corresponding to the identification information, and a pixel having the same size as the smallest unit of space division in the simulation based on the shape file and the material file Each is provided with a calculation means for performing simulation over a predetermined time range for a predetermined space region composed of the plurality of materials.

  The simulation apparatus according to the present invention can greatly simplify the input operation, improve the work efficiency, and consequently reduce the time required for the simulation.

Embodiment 1 FIG.
A simulation apparatus according to Embodiment 1 of the present invention will be described with reference to FIGS. In the first embodiment, a two-dimensional elastic wave propagation simulation by the FDTD method will be described as an example. Hereinafter, the term “pixel” is used, which is synonymous with “pixel”.

  1 is a diagram showing a configuration of a simulation apparatus according to Embodiment 1 of the present invention. In addition, in each figure, the same code | symbol shows the same or equivalent part.

  In FIG. 1, the simulation apparatus according to the first embodiment includes an arithmetic unit (arithmetic unit) 1, a shape file content (for example, an identification number) and a material file content (for example, longitudinal wave velocity, shear wave velocity, and A memory 2 for storing (density), a shape file input device 3 for reading a shape file, and a material file input device 4 for reading a material file are provided.

  Next, the shape file will be described with reference to FIGS. FIG. 2 is a diagram for explaining a situation where a lateral hole is flawed with an oblique probe. FIG. 3 is a diagram illustrating an example of a shape file.

  In FIG. 2, a horizontal hole 6 exists in the test body 5. Further, the wedge 7 and the vibrator 8 constitute an oblique angle probe. The shape of the horizontal hole 6 is a circle, and the shape of the wedge 7 is a shape including not only a horizontal line and a vertical line but also an inclined straight line.

  In FIG. 2, the wedge 7 and the lateral hole 6 have relatively simple shapes, but the simulation apparatus according to the first embodiment can handle not only a circle and a straight line but also a curved line. In this example, in order to compare with the experimental results described later, the shape is actually easy to process.

  FIG. 2 is a diagram drawn with a straight line and a curve, but when expressed in color in the pixel, the pixels on the straight line and the curve are black, and the other pixels are white. In the first embodiment, a pixel not only represents a line but also represents identification information of a material in a certain region. The material identification information given to the pixels corresponding to the material in the region and stored as a file will be called a shape file here.

  FIG. 3 shows an example in which the test body 5, the lateral hole 6, the wedge 7, and the vibrator 8 shown in FIG. A small square in FIG. 3 is one pixel. In the figure, the value for each pixel is shown. In the shape file of FIG. 3, the value of the pixel inside the specimen 5 is represented by “1”, the value of the pixel inside the wedge 7 is represented by “2”, and the value of the pixel inside the vibrator 8 is represented by “11”. The inside of the horizontal hole 6 is the same as the surrounding air portion, and the pixel value is represented by “0”. In FIG. 3, FIG. 2 is overlaid for easy understanding of the region. The size of each pixel is the same as the lattice interval of the FDTD method described later.

  As shown in FIG. 3, if the values of the pixels in each region are stored, it is possible to identify what the material of that portion is. In other words, the value of the pixel is material identification information, and if the identification information is a number, it is an identification number. In FIG. 3, the pixels are shown to be coarse for the sake of clarity, but the actual pixels (that is, the lattice spacing of the FDTD method) are finer than the wavelength.

Next, the material file will be described with reference to FIGS. FIG. 4 is a diagram illustrating an example of a material file. FIG. 5 is a diagram showing the lattice of the FDTD method and the pixels of the shape file. The material file is a table that associates the identification information (identification number) of each pixel included in the shape file with the material information. Here, the identification number “0” is air, “1” is steel, “2” is acrylic, “3” is polystyrene, “4” is aluminum, “5” is titanium, “6” is gold, “7” Corresponds to silver, “8” corresponds to copper, “9” corresponds to tungsten, and “10” corresponds to water information. In the example of the material file shown in FIG. 4, “longitudinal wave sound velocity [m / s]”, “transverse wave sound velocity [m / s]”, and “density [kg / m ³ ]” are used as material information. . When the solid is isotropic, the properties of the material can be expressed by these three parameters. Of course, a Lame constant, elastic stiffness, or elastic compliance may be used. In short, it is assumed that material information necessary for the simulation is stored in the material file. In addition, since it is assumed that a wave does not propagate in the air, information on air is not given.

  By the way, when calculating an elastic wave propagating through an isotropic solid by the two-dimensional elastic wave FDTD method, the calculation is performed using the following calculation formula.

Here, v _x and v _z are the particle velocities in the x and z directions, respectively, and T _xx , T _zz , and T _xz are stress tensors, respectively. V _l and _{V s,} respectively, a longitudinal acoustic velocity and shear wave velocity of the medium. ρ is the density of the medium. In the two-dimensional elastic wave FDTD method, the particle velocity and stress are alternately calculated temporally and spatially based on the equations (1) to (5).

FIG. 5 shows a lattice in the two-dimensional elastic wave FDTD method. In the figure, a lattice for calculating the particle velocity and stress is shown. The white square mark is v _x , the white circle mark is v _z , the black square mark is T _xx and T _zz , and the black circle mark is a lattice for calculating T _xz. Represents. The lattice spacing is shown as Δh in both the x and z directions. Although there is an idea that the lattice spacing is, for example, the inter-lattice distance for calculating v _x and T _xz , in FIG. 5, the distance between the lattices for calculating the same parameter (for example, v _z and v _z ) is the lattice spacing. . In the first embodiment, the lattice spacing is the minimum unit of space division.

  Further, in FIG. 5, the borders of the pixels of the shape file are indicated by bold lines. In other words, a rectangle surrounded by a thick line corresponds to a pixel in the shape file, and the size of the pixel and the lattice interval Δh are the same.

  Now, the operation of the simulation apparatus according to the first embodiment will be described with reference to the drawings.

  FIG. 6 is a diagram illustrating a state of information transmission between the arithmetic device and the memory. FIG. 7 is a diagram showing a lattice of the FDTD method and pixels of the shape file. FIG. 8 is a flowchart showing the operation of the simulation apparatus according to Embodiment 1 of the present invention. FIG. 9 is a diagram showing a relative positional relationship between the probe and the test body in the oblique angle flaw detection. FIG. 10 is a diagram showing a sound field snapshot obtained using the simulation apparatus according to Embodiment 1 of the present invention. FIG. 11 is a diagram showing echoes obtained by experiments. FIG. 12 is a diagram showing echoes obtained by the simulation apparatus according to Embodiment 1 of the present invention. FIG. 13 is a diagram showing a relative positional relationship between the probe and the test body when the test body is in water. FIG. 14 is a diagram showing a sound field snapshot obtained using the simulation apparatus according to Embodiment 1 of the present invention.

  It is assumed that the shape file and material file have already been created at the start of simulation. First, a shape file is read using the shape file input device 3 and the contents are stored in the memory 2. In the case of the shape file as shown in FIG. 3, the identification number is stored in the memory 2. Next, the material file is read using the material file input device 4 and the contents are stored in the memory 2. In the case of the material file as shown in FIG. 4, the longitudinal wave sound velocity, the shear wave sound velocity, and the density are stored in the memory 2.

  Next, the computing device 1 determines a grid for calculation. The coordinates of the lattice are converted into the address of the memory 2 where the shape file is stored, and the address is designated. From the memory 2, the identification number is read from the designated address. For example, when the coordinates of the grid to be calculated are inside the wedge 7, since the wedge region has the identification number “2” in the shape file, the value “2” is read out.

The arithmetic device 1 converts the read identification number into an address of the memory 2 where the material file is stored, and designates the address. For example, if the identification number is “2”, the second address is designated. Material information is read from the commanded address. If the address number is the second, the material file shown in FIG. 4 reads values of longitudinal wave sound speed 2730 m / s, shear wave sound speed 1430 m / s, and density 1180 kg / m ³ . Calculations are performed using these values.

That is, at a certain coordinate, the identification number of the shape file corresponding to the coordinate is “2”, and the second address of the material file is “longitudinal wave velocity 2730 m / s, transverse wave velocity 1430 m / s, density 1180 kg / m ³ ”. Is stored as V ₁ = 2730 m / s, V _s = 1430 m / s, and ρ = 1180 kg / m ³ . Since the calculation formula is a common formula (formulas (1) to (5)) in all coordinates, various materials can be handled by changing the material information without changing the calculation formula. In addition, since the shape file provides identification information for each pixel, even if the shape of the material is complicated, it can be handled by a simple operation of changing the pixel identification information. In this way, V _l , V _s , and ρ can be changed for each coordinate by using a shape file and a material file. Therefore, even in a test body having a complicated shape mixed with various materials, the FDTD method is used. Elastic wave propagation can be calculated.

  Here, for the sake of simplicity, the case where the value of the identification number and the address number of the material file are the same has been described, but the two do not necessarily have to be the same. Since it is only necessary to know the material information of the coordinates to be calculated, for example, when the identification number of the shape file is “2”, a process of designating the third address of the material file may be performed.

In the simulation apparatus according to the first embodiment, the above processing is performed over the entire calculation region. For example, in the shape file shown in FIG. 3, the area of the specimen 5 is the identification number “1”. Therefore, if the calculated coordinate is within the specimen, the first address of the material file shown in FIG. Since there are “longitudinal wave sound velocity 5930 m / s, shear wave sound velocity 3240 m / s, density 7700 kg / m ³ ”, V ₁ = 5930 m / s, V _s = 3240 m / s, and ρ = 7700 kg / m ³ are calculated.

  In addition, after the above processing is performed over the entire calculation area, the calculation is performed by advancing the time. The wave propagation can be obtained by simulation by calculating with increasing time.

Here, the effect produced by making the lattice spacing Δh of the FDTD method the same as the pixel size of the shape file will be described again. As described above, in the method using the shape file and the material file, the simulation is performed by changing the material information for each coordinate to be calculated. Therefore, when the lattice spacing Δh and the pixel size of the shape file are not the same, for example, as shown in FIG. 7, when the number of pixels is 1 with respect to the number 4 of lattices (for example, v _z ), The correspondence between the identification number and the lattice cannot be taken. In order to perform calculation in such a case, some kind of treatment must be newly provided, and as a result, the time required for the simulation becomes long. In other words, the merit of using the shape file is greatly reduced. In addition, there is a demerit that the spatial resolution for representing the shape is reduced. Furthermore, when the ratio is not a good ratio such as 4 to 1, but a ratio such as 9 to 2, for example, the newly required processing becomes more complicated and the calculation time becomes longer.

On the other hand, if the grid interval Δh is the same as the pixel size of the shape file, the grid (for example, v _z ) and the number of pixels have a one-to-one correspondence as shown in FIG. Therefore, it is possible to perform a simulation using the shape file as it is, and the calculation time can be shortened. Further, if the lattice spacing Δh and the size of the pixel in the shape file are the same, there is an effect that the correspondence between the size of the actual test object and the shape file can be simplified.

Note that when the number of pixels in the shape file is reduced so that the number of pixels is 4 with _{respect to} the number 1 of the grid (for example, v _z ), the same effect as the one-to-one correspondence can be obtained. It is not practical because it only grows. Further, when the ratio is not a good ratio such as 1: 4, but a ratio such as 2: 9, for example, a new process is required, so the effect of reducing the calculation time is reduced.

  The series of processes shown above is shown in a flowchart in FIG. FIG. 8 shows processing when a simulation of the two-dimensional elastic wave FDTD method in the XZ plane is performed using the simulation apparatus according to the first embodiment.

  First, in step 101 and step 102, the shape file and the material file are read into the memory 2. Either order may be the order.

  Next, in step 103, a simulation start time T in the FDTD method is determined. In general, T = 0.

  Next, in step 104, the coordinates (x, z) of the lattice are determined. This is a spatial calculation start point. Any point that is easy to understand (for example, a coordinate origin) may be selected.

  Next, in step 105, the coordinates (x, z) are converted into the address of the memory 2 where the shape file is stored, and the address is designated.

  Next, in step 106, the identification number is read from the designated address in the memory 2.

  Next, in step 107, the identification number is converted into the address of the memory 2 where the material file is stored, and the address is designated.

  Next, in step 108, material information is read from the designated address in the memory 2.

  Next, in step 109, the information necessary for the calculation of the FDTD method has been prepared up to step 108. Therefore, the calculation of the FDTD method (calculation for obtaining stress and particle velocity) is performed using the equations (1) to (5). .

  Next, in steps 110 to 111, the processing up to step 109 is performed on the entire region represented by the shape file. It is determined whether or not the calculation of the entire area has been completed. If not, the coordinates (x, z) are changed and the processing returns to step 105, where the memory 2 stores the coordinates (x, z) in the shape file. The same processing is performed from the point where the address is converted to.

  Next, in step 112, if the calculation of the entire region has been completed, the calculation results of equations (1) to (5) are output to a file as necessary. In elastic wave simulation, the particle velocity or stress at a certain time is output to a file.

  Next, in steps 113 to 114, it is determined whether or not the calculation of the predetermined time range has ended. If not, the time T is changed and the coordinates (x, z) in step 104 are obtained. The same processing is repeated from the processing.

  In step 115, if the necessary time range is calculated, an output signal is output to a file as necessary, and the series of processes is terminated. This output signal is an echo received by a vibrator in a simulation such as ultrasonic flaw detection.

  In the flowchart shown in FIG. 8, processing other than processing of the shape file and the material file is normal FDTD processing. In the first embodiment, even if the calculation area has a complicated shape, or even when various materials are mixed in the calculation area, the shape and the material can be obtained by using the shape file and the material file. Can be easily input to the computer, so that the FDTD method can be efficiently simulated and the calculation time can be shortened.

  An example in which the simulation apparatus according to the first embodiment is actually developed and simulated is shown below. The shape file and material file shown in FIGS. 3 and 4 were used, respectively. That is, the wedge 7 is acrylic and the test body 5 is steel. The relative positional relationship between the probe and the test body 5 is shown again in FIG. The dimensions of the vibrator 8 were 6 mm, the incident angle was 36.6 °, the diameter of the horizontal hole 6 was 2 mm, the depth was 7.5 mm, and the horizontal distance from the incident point to the center of the horizontal hole 6 was 8 mm.

  FIGS. 10A to 10F show sound field snapshots every 3 μs from when the vibrator 8 is excited to 15 μs. In FIG. 10, the intensity of the particle velocity is shown in shades. It can be seen that the elastic wave excited by the vibrator 8 passes through the boundary surface between the acrylic 7 and the steel 5, is scattered by the horizontal hole 6, and propagates again into the acrylic 7.

  An experiment was performed to confirm the validity of the simulation apparatus according to the first embodiment. The relative positional relationship between the probe used in the experiment and the specimen was the same as that shown in FIG. The echo obtained in the experiment is shown in FIG. Further, FIG. 12 shows echoes obtained using the simulation apparatus according to the first embodiment. Comparing FIG. 11 and FIG. 12, the waveform and the reception time are almost the same. From this result, the validity of the simulation apparatus according to the first embodiment was confirmed.

  The results shown in FIGS. 10 and 12 are examples in which the simulation of the two-dimensional elastic wave FDTD method in the XZ plane is performed using the simulation apparatus according to the first embodiment. The simulation apparatus according to the present invention can be applied to other than elastic waves. For example, the present invention can be applied to acoustic waves that propagate in water or air. The result of having performed the simulation in case solid and water coexist using the simulation apparatus which concerns on this Embodiment 1 is shown below.

  As a simulation example, a water immersion method in which a test body is in water was used. FIG. 13 shows a relative positional relationship between the probe and the test body 5 in the water immersion method. It was assumed that aluminum having a diameter of 2 mm was present as the impurity 6 </ b> A in the steel specimen 5 having a thickness of 10 mm, and ultrasonic flaw detection was performed through the water 10 having a thickness of 2 mm.

  The relative positional relationship between the probe and the test body 5 was simulated as shown in FIG. 13 using the FDTD method for ultrasonic flaw detection by the water immersion method using the simulation apparatus according to the first embodiment. FIGS. 14A to 14H show sound field snapshots every 2 μs from when the vibrator 8 is excited to 14 μs. Also in this simulation, the material file shown in FIG. 4 was used. That is, in the shape file, the identification number is “10” for water and “4” for aluminum. From FIG. 14, it can be seen that the elastic wave in the wedge reaches water, is refracted and converted into an acoustic wave. Moreover, when the underwater acoustic wave reaches the test body 5, it can be seen that it is refracted and converted into an elastic wave. Since the incident angle with respect to the test body 5 is large, a transverse wave mainly propagates in the test body. After the transverse wave is reflected from the bottom surface of the specimen, it reaches the impurity 6A of φ2. When the test body 5 is steel and the impurity 6A is aluminum, since the acoustic impedance is different, a scattered wave is generated with respect to the incident wave. There are also transmitted waves. In the simulation, these situations are visualized and reproduced. That is, in the simulation apparatus according to the first embodiment, even in a situation where elastic waves and acoustic waves are mixed, simulation can be easily performed by using a shape file and a material file, so that work efficiency is greatly improved. There is an effect of doing. In addition, as shown in the material file of FIG. 4, the acoustic wave which propagates in water was calculated by making the transverse wave sound velocity of water into zero (0).

  In the first embodiment, the pixels in the shape file need not be square. It may be rectangular. When the pixels are rectangular, the lattice spacing of the FDTD method also differs in the vertical direction and the horizontal direction. Furthermore, although the case where a number is used as the pixel identification information, that is, the case where the identification number is used is described here, the pixel identification information is not limited to only a number. It can be a symbol or alphabet. Further, the pixels may be represented by color or shading. In short, it is only necessary to show that the pixel is different from other pixels.

  Moreover, although description is abbreviate | omitted here, the simulation apparatus which concerns on this Embodiment 1 is applicable also to calculation of electromagnetic waves. The FDTD method for electromagnetic waves calculates an electric field and a magnetic field, but the calculation formula is similar to formulas (1) to (5). That is, a method in which pixel identification information is given to a pixel is saved as a shape file, the material information is saved as a material file, and simulation is performed using the shape file and the material file. It can be applied regardless of the properties of waves such as electromagnetic waves.

  The first embodiment can be applied not only in two dimensions but also in three dimensions. In this case, the equations (1) to (5) are equations corresponding to three dimensions. Of course, the present invention can also be applied to a three-dimensional acoustic wave and a three-dimensional electromagnetic wave.

  Furthermore, it can be applied to other than the FDTD method. The present invention can be applied to all simulations in which a space is divided and a value is obtained in each lattice. For example, it can be applied to the difference method.

  Finally, a supplementary explanation of the shape file will be given. In the simulation example described here, the format of the shape file representing the probe and the specimen is a bitmap file. Since the bitmap file is a format in which an image is stored with a value for each pixel, it is suitable as a file used when a simulation is performed by the simulation apparatus according to the first embodiment. In addition, since the number of pixels in the vertical and horizontal directions is stored in the header of the bitmap file, the information on the number of pixels is also used in the simulation shown here. However, in the first embodiment, the shape file format is not limited to the bitmap file, and any type of file may be used as long as the material identification information is stored in each pixel. It doesn't matter.

  In addition, as a method of creating the shape file, it may be created based on a real photograph, or may be created based on a diagram created by a computer. In addition, a figure written on paper may be read into a computer by a scanner and created based on the read figure.

  As described above, using a shape file in which material identification information is given to pixels with the same size as the lattice spacing of the simulation, and performing a simulation using a material file in which material information is stored, the simulation can be simplified. As a result, the time required for calculation can be shortened.

Embodiment 2. FIG.
A simulation apparatus according to Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 15 is a diagram showing a configuration of a simulation apparatus according to Embodiment 2 of the present invention. FIG. 16 is a diagram for explaining a situation in which a test body is flawed with an array probe. FIG. 17 is a diagram illustrating an example of a shape file including an array probe. FIG. 18 is a diagram illustrating an example of a signal file.

  In FIG. 15, the simulation apparatus according to the second embodiment includes an arithmetic device (arithmetic means) 1, a memory 2, a shape file input device 3, a material file input device 4, and a signal file for reading a signal file. An input device 9 is provided.

  In the second embodiment, the simulation is performed using the shape file and the material file as in the first embodiment. In the second embodiment, this is further developed, identification information is given to the transducers of the array probe, and a response to the simulation in the case where a plurality of transducers are present is intended.

  Next, the transducer of the array probe will be described. FIG. 16 shows a situation in which a specimen is flawed with an array probe. In FIG. 16, the lateral hole 6 exists in the test body 5. The periphery of the test body 5 is water 10, and the array probe is only the vibrator 11. Although an actual array probe is not composed of only the transducers 11, it is assumed here that it is composed of only a plurality of transducers 11 for simplicity.

  FIG. 17 shows an example in which the vibrator 11, the test body 5, and the horizontal hole 6 shown in FIG. A small square in FIG. 17 is one pixel. In the figure, the value for each pixel is shown. FIG. 17 is an enlarged view of the upper left portion of the shape file, showing the vibrator 11, water 10, the test body 5, the lateral hole 6, and air. In the shape file of FIG. 17, the pixel value inside the test body 5 is “1”, the inside of the horizontal hole 6 is the same as the surrounding air portion, and the pixel value is “0”. The values of these pixels are material identification numbers as in the first embodiment. Further, the values of the pixels inside the vibrator 11 are represented by “11”, “12”, “13”, “14”, and “15”. Since it is shown in an enlarged manner, it is limited to “15”. For example, in the case of a 64-element array probe, the pixel values are “11” to “74”. In FIG. 17, FIG. 16 is overlaid for easy understanding of the region. The size of each pixel is the same as the lattice interval of the FDTD method as in the first embodiment.

  Next, the signal file will be described. The signal file is a table that associates the identification information of each pixel included in the shape file with the information of the signal source of the array probe. In the case of an ultrasonic probe, the signal source is a transducer. FIG. 18 shows an example of a signal file. Here, as the information of the signal source, “incident angle [deg]”, “delay time [s]”, and “amplitude intensity (magnitude of signal for exciting the vibrator)” are used. Further, information other than the three may be stored in the signal file. In other words, any information may be used as long as the signal source information, but here, as a representative example, description will be made on an incident angle, a delay time, and an amplitude intensity.

  The incident angle of the signal file shown in FIG. 18 indicates the angle of the ultrasonic wave radiated from the transducer 11. With reference to the vertical direction, when radiating vertically (lower side in FIG. 16), the angle is 0 °. The delay time is a delay time of excitation timing when operating as an array probe. The amplitude intensity is used when weighting the intensity of the ultrasonic wave radiated from each transducer 11. When simulating that no ultrasonic wave is emitted from the transducer 11, “0” is set.

  The operation of the simulation apparatus according to the second embodiment will be described with reference to FIGS. It is assumed that the shape file, material file, and signal file have already been created at the start of the simulation. As in the first embodiment, first, a shape file is read using the shape file input device 3 and the contents are stored in the memory 2. In the case of the shape file as shown in FIG. 3, the identification number is stored in the memory 2. Next, the material file is read using the material file input device 4 and the contents are stored in the memory 2. In the case of the material file as shown in FIG. 4, the longitudinal wave sound velocity, the shear wave sound velocity, and the density are stored in the memory 2. Further, in the second embodiment, the signal file is read using the signal file input device 9 and the contents thereof are stored in the memory 2. In the case of the signal file as shown in FIG. 18, the incident angle, the delay time, and the amplitude intensity are stored in the memory 2.

  Since the operation in the portion other than the vibrator 11 is the same as that in the first embodiment, the description thereof will be omitted, and a case where the coordinates of the lattice for calculation are within the region of the vibrator will be described. The coordinates to be calculated are converted into the address of the memory 2 where the shape file is stored, and the address is designated. From the memory 2, the identification number is read from the designated address. In the shape file of FIG. 17, since the identification number of the leftmost vibrator is “11”, the value “11” is read when the coordinates to be calculated are in the leftmost vibrator.

  In the arithmetic unit 1, the identification number is converted into the address of the memory 2 in which the signal file is stored, and the address is designated. For example, if the identification number is “11”, the first address is designated. The probe control parameters are read from the commanded address. If the address number is the first, the signal file shown in FIG. 18 reads values of an incident angle of 0 °, a delay time of 0 [s], and an amplitude intensity of “0”. That is, there is no ultrasonic radiation from the transducer “11”.

  For example, if the identification number is “22”, the 12th address is designated. The probe control parameters are read from the commanded address. If the address number is 12, the signal file shown in FIG. 18 reads values of an incident angle of 0 °, a delay time of 7.080E-08 [s], and an amplitude intensity of “0”.

  Each transducer emits ultrasonic waves based on the read signal source information. In the FDTD method, there are various methods of emitting ultrasonic waves from the vibrator. Here, a method is used in which values are given to all particle velocity lattices in the region of the vibrator. First, in the signal source information, when the incident angle is α and the amplitude intensity is A, the following values are obtained.

A _x = A × sin α,
A _z = A × cos α (6)

  Next, in the signal source information, when the delay time is τ, a signal s (t−τ) is generated with respect to a separately prepared sound source signal s (t).

Subsequently, in all lattices of particle velocities in the region of the vibrator, the particle velocities v _x and v _z are set as follows, so that ultrasonic waves based on the control information are emitted from the vibrator. be able to.

v _x = A _x × s (t−τ),
v _z = A _z × s (t−τ) (7)

Even if the value of the equation (7) is not given to all the particle velocity lattices in the region of the vibrator, the ultrasonic wave is emitted if the value of the equation (7) is given only to the lattice in contact with the ultrasonic radiation surface. can do. However, since another work of specifying the radiation surface is required, here, a method is used in which the value of equation (7) is given to all particle velocity lattices in the region of the vibrator. For example, when the identification number is “22” in the region of the vibrator, it is as follows. This value is given to v _x and v _z of the grid whose all identification numbers correspond to “22”.

v _x = 0 × s (t−7.080E−8) = 0,
v _z = 1 × s (t−7.080E−8)

  Thus, since the ultrasonic wave radiated from the transducer of the array probe can be controlled by using the shape file and the signal file, the sound field simulation of the array probe can be easily performed. That is, the calculation time can be shortened. In addition, although the case where the signal file was used for the radiation of the ultrasonic wave was described, the signal file may be used for reception of the ultrasonic wave propagating in the medium. Furthermore, not only ultrasonic waves but also acoustic waves and electromagnetic waves may be used for radiation and reception.

  The second embodiment can also be applied to various variations as in the first embodiment. That is, the pixels in the shape file may not be square. In addition, since it is only necessary to indicate that the pixel is different from the other pixels, the pixel identification information may not be a number but may be a symbol or an alphabet. Further, the pixels may be represented by color or shading. In short, it is only necessary to show that the pixel is different from other pixels.

  As in the first embodiment, the simulation apparatus can be applied to electromagnetic waves, acoustic waves, and the like. It can also be applied to a three-dimensional simulation. Furthermore, the present invention can be applied to, for example, a difference method other than the FDTD method.

  Further, the shape file format is the same as that of the first embodiment, and the file format may be a bitmap file or another format. The shape file can be created based on a real photograph or based on a diagram created on a personal computer. A figure written on a paper may be read by a scanner and created based on the read figure.

  As explained above, using a shape file that gives material identification information to pixels of the same size as the lattice spacing of the simulation, using a material file that saves material information, and a signal file that saves signal source information By using the simulation, it is possible to simplify the simulation, simplify the simulation when there are a plurality of signal sources, and as a result, reduce the time required for the calculation.

It is a figure which shows the structure of the simulation apparatus which concerns on Embodiment 1 of this invention. It is a figure explaining the condition which flaws a horizontal hole with an oblique angle probe. It is a figure which shows the example of a shape file. It is a figure which shows the example of a material file. It is a figure showing the grid of the FDTD method and the pixel of a shape file. It is the figure which showed the mode of the information transmission between an arithmetic unit and memory. It is a figure showing the grid of the FDTD method and the pixel of a shape file. It is a flowchart which shows operation | movement of the simulation apparatus which concerns on Embodiment 1 of this invention. It is the figure which showed the relative positional relationship of the probe and a test body in an oblique inspection. It is a figure which shows the sound field snapshot obtained using the simulation apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the echo obtained by experiment. It is a figure which shows the echo obtained by the simulation apparatus which concerns on Embodiment 1 of this invention. It is the figure which showed the relative positional relationship of a probe and a test body when a test body is in water. It is a figure which shows the sound field snapshot obtained using the simulation apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the simulation apparatus which concerns on Embodiment 2 of this invention. It is a figure explaining the condition which tests a test body with an array probe. It is a figure which shows the example of the shape file containing an array probe. It is a figure which shows the example of a signal file.

Explanation of symbols

  1 arithmetic device, 2 memory, 3 shape file input device, 4 material file input device, 5 specimen, 6 horizontal hole, 6A impurity, 7 wedge, 8 transducer, 9 signal file input device, 10 water, 11 transducer.

Claims (7)

Representing a predetermined spatial region composed of a plurality of materials by an image composed of a plurality of pixels, a shape file for storing an image in which identification information representing the shape and type of each material is given to each pixel,
A material file storing information of the plurality of materials corresponding to the identification information;
Based on the shape file and the material file, a computing means for performing simulation over a predetermined time range for a predetermined spatial region composed of the plurality of materials for each pixel having the same size as the smallest unit of space division in the simulation A simulation apparatus comprising: and. A predetermined spatial region composed of a plurality of materials and a plurality of signal sources is represented by an image composed of a plurality of pixels, and identification information representing the shape and type of each material and the type of each signal source is given to each pixel. A shape file to save the saved image,
A material file storing information of the plurality of materials corresponding to the identification information;
A signal file for storing information of the plurality of signal sources corresponding to the identification information;
Based on the shape file, the material file, and the signal file, a predetermined spatial region composed of the plurality of materials and a plurality of signal sources is determined for each pixel having the same size as the smallest unit of space division in the simulation. A simulation device comprising: an arithmetic means for performing simulation over a time range of The simulation apparatus according to claim 1, wherein the calculation unit performs a simulation on wave propagation. The simulation apparatus according to claim 3, wherein the calculation unit performs a simulation by an FDTD method. The simulation apparatus according to claim 3, wherein the calculation unit performs a simulation by a difference method. Each material given to each pixel for each pixel whose size is the same as the smallest unit of space division in the simulation from a shape file that expresses a predetermined spatial region composed of multiple materials with an image composed of multiple pixels Reading identification information representing the shape and type of
Reading information on the plurality of materials from a material file that stores information on the plurality of materials corresponding to the identification information;
Performing a simulation over a predetermined time range for a predetermined space region composed of the plurality of materials based on the read information of the plurality of materials. From a shape file representing a predetermined spatial region composed of a plurality of materials and a plurality of signal sources with an image composed of a plurality of pixels, each pixel has the same size as the smallest unit of spatial division in the simulation. Reading identification information representing the shape and type of each material given to each and the type of each signal source;
Reading information on the plurality of materials from a material file that stores information on the plurality of materials corresponding to the identification information;
Reading the information of the plurality of signal sources from a signal file that stores the information of the plurality of signal sources corresponding to the identification information;
Performing a simulation over a predetermined time range for a predetermined spatial region composed of the plurality of materials and the plurality of signal sources based on the read information on the plurality of materials and the information on the plurality of signal sources. A simulation method characterized by that.

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