JP2014006721A - Method of creating brittle fracture model - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of creating a brittle fracture model capable of simulating brittle fracture by generating the brittle fracture in a vertical direction when compression load is applied in the vertical direction.SOLUTION: In S10, a compression stress-distortion measured value and a compression fracture distortion measured value in each compression speed of a different test piece are inputted to a computer 10. In S20, the computer 10 extrapolates and interpolates the compression stress-distortion measured value and the compression fracture distortion measured value and calculates the extrapolated and interpolated values as a physical property of an FEM element group other than the compression speed. A value obtained by mutually multiplying the sum total of surface areas in each FEM shell element, a plate thickness value of the FEM shell element and mass density is balanced to measured mass of the test piece. In S40, at least either one of the plate thickness value and the compression fracture distortion of the column FEM shell element group and that of the row FEM shell element group are inputted to the computer 10 as a correction input so that fracture of the row FEM shell element group is generated prior to fracture of the column FEM shell element group.

Description

  The present invention relates to a method for creating a brittle fracture model.

  Conventionally, when a vehicle travels in a snowy area, snow bounced up from the tire may adhere to the lower surface of the body exterior part located behind the tire and become ice as it is. In this state, when the vehicle passes through a step with a difference in height of the road, if the tire moves from a high step to a low height, the ice collides with the high step and the ice The upper part may impact the lower surface of the body exterior part.

  The above case is a phenomenon related to the icing of the vehicle, but when an object is icing, if the icing object hits another object through the ice, the icing object If the degree of deformation and breakage can be simulated in advance, it can contribute to the improvement of impact resistance of the object.

Japanese Patent Application Laid-Open No. 2004-151561 discloses that when a vehicle collision analysis is performed, the impact absorber is modeled by a honeycomb structure with shell elements and the impact absorber is analyzed.
Patent Document 5 proposes a method for simulating the contact between ice and a rubber material, in which an ice model is disclosed.

  Patent Documents 2 to 4 disclose an object model creation method, a modeling method, and the like for using the finite element method at the time of filing this application.

JP 2011-53807 A JP 2001-282873 A JP 2003-320824 A Japanese Patent Laid-Open No. 9-91469 JP 2004-25963 A

By the way, in order to perform the simulation as described above, it is preferable to model the ice as compared with the actual test because it can reduce labor and the like.
It is known that when ice is compressed, ductile fracture or brittle fracture occurs depending on conditions. In particular, there has been no model of ice or brittle fracture that occurs when a compressive load is applied, as in the case of ice. By using such a brittle fracture model, the Finite Element Method is used. No analysis has been proposed. In addition, since the model of the shock absorber of patent document 1 comprises the honeycomb structure with the shell element, it does not reproduce the brittle fracture when ice is compressed. The ice model disclosed in Patent Document 5 is modeled by dividing a rectangular ice plate having a thickness, width, and length into small hexahedral solid elements. This model is not a model that assumes that the entire ice is divided vertically during compression, and is not a brittle fracture model.

  An object of the present invention is to provide a method for creating a brittle fracture model in which a brittle fracture occurs in the longitudinal direction when a compressive load is applied in the longitudinal direction and the brittle fracture can be simulated.

  In order to solve the above-mentioned problems, the invention of claim 1 is a method for creating a brittle fracture model using a computer for each of different compression speeds obtained for a test piece of an object that causes brittle fracture in the computer. Compressive stress-strain actual measurement value and compressive rupture strain actual measurement value are input as physical properties in the FEM element group having a configuration in which a plurality of vertically extending FEM shell element groups are bridged by a row FEM shell element group. A second step in which the computer extrapolates and interpolates the compression stress-strain actual measurement value and the compression fracture strain actual measurement value to calculate the physical properties of the FEM element group other than the compression speed; The computer measured the value obtained by multiplying the total surface area of each FEM shell element by the thickness value and mass density of the FEM shell element. A third step of balancing the mass of the strike pieces, and the computer of the column and row of FEM shell elements such that the computer breaks the row of FEM shell elements prior to the column of FEM shell elements. The gist of the present invention is a brittle fracture model creation method including a fourth step of correcting and inputting at least one of a thickness value and a compression fracture strain. Note that FEM is an abbreviation for Finite Element Method.

The invention of claim 2 includes a fifth step of storing in the computer data defining a brittle fracture model created by executing the first to fourth steps.
The invention of claim 3 is characterized in that, in the first step, the measured compressive stress-strain value is a measured compressive stress-strain value corrected for Young's modulus in the first step. .

According to a fourth aspect of the present invention, in the first or second aspect of the present invention, in the first step, the actual measured value of compressive fracture strain is a corrected actual value of compressed fracture strain.
The invention of claim 5 includes a group of quadrangular cylindrical portions in which the columnar FEM shell element group is formed by connecting a plurality of quadrilateral shell elements at nodes in any one of claims 1 to 4. In addition, the FEM shell element group in the row is formed by connecting quadrilateral shell elements.

  According to the first aspect of the present invention, it is possible to provide a method for creating a brittle fracture model in which a brittle fracture occurs in the longitudinal direction when a compressive load is applied in the longitudinal direction and the brittle fracture can be simulated.

According to the invention of claim 2, by storing data defining the brittle fracture model, it is possible to reconfigure the brittle fracture model and perform a simulator.
According to the invention of claim 3, since the Young's modulus obtained from the test piece is corrected, the brittle fracture time during compression of the brittle fracture model can be changed.

According to the fourth aspect of the present invention, since the actual measurement value of the compression fracture strain is corrected, the brittle fracture time at the time of compression of the brittle fracture model can be changed.
According to the invention of claim 5, the columnar FEM shell element group is composed of a group of quadrangular cylindrical portions formed by connecting a plurality of quadrilateral shell elements at nodes, and the row of FEM shell element groups is a quadrilateral shell element. By connecting these, the brittle fracture model of the invention of claim 1 can be easily realized.

The schematic perspective view of a brittle fracture model. (A) is a schematic perspective view of the FEM shell element group of the column of a brittle fracture model, (b) is a schematic perspective view of the FEM shell element group of a row. (A) And (b) is a true stress-true strain curve figure, (c) is an equivalent stress-equivalent plastic strain curve figure. (A) is a schematic block diagram of a brittle fracture model creation device, and (b) is a flowchart for creating a brittle fracture model. (A) is schematic explanatory drawing of the state before compressing a test piece, (b) is explanatory drawing of the state before compressing a brittle fracture model. (A) is a schematic explanatory drawing of the state where the brittle fracture occurred when the test piece was compressed, and (b) was the explanatory diagram of the state where the brittle fracture occurred when the brittle fracture model was compressed. Fig. 4 is a characteristic diagram of load and displacement obtained when a compression test is performed on an ice test piece. Equivalent stress-equivalent plastic strain curve diagram. The load-time curve figure of a test piece. Load-time curve diagram of test piece and brittle fracture model (A), (b) is explanatory drawing of the example of application when a model is made into ice. (A), (b) is a conceptual diagram of the model of a comparative example. The schematic perspective view of the brittle fracture model of other embodiment.

Hereinafter, a method for creating a brittle fracture model according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 4, a brittle fracture model creating apparatus used in the brittle fracture model creating method of the present embodiment is shown. Although not shown, the computer 10 of this apparatus includes a CPU for performing arithmetic processing, a ROM in which processing procedures of the CPU are stored in advance, a RAM serving as a working memory for the CPU, and a nonvolatile memory such as a hard disk. Storage device. Further, the computer 10 includes an input unit 12 such as a keyboard and mouse for inputting various commands and various data, and an output unit 14 such as a display and a printer for outputting the results calculated by the computer. Prepare. With this device, a brittle fracture model using the finite element method is created and various analyzes are performed.

Next, in the present embodiment, the computer 10 creates a brittle fracture model of a test piece of an object that undergoes brittle fracture during compression.
Examples of the brittle fracture model that undergoes brittle fracture during compression include ceramics, concrete, glass, and ice. Depending on the object, ductile fracture or brittle fracture may occur depending on the strain rate, that is, the compression rate.

  For example, ice is known to cause ductile fracture or brittle fracture depending on the strain rate, and it is known that brittle fracture occurs when the strain rate is high. For this reason, when brittle fracture or ductile fracture is caused by the compression speed, such as ice, the compression speed at which brittle fracture occurs is selected.

(Acquisition of physical property data of objects of brittle fracture model)
Next, acquisition of physical property data related to the object of the brittle fracture model will be described.
When the object of the brittle fracture model is ice, the compression test is performed at a temperature below the freezing point so that the test piece does not melt due to the environmental temperature. When the object of the brittle fracture model is not ice, the ambient temperature may be room temperature.

  As shown in FIG. 5A, the compression tester 50 is operated with the test piece 40 of the object of the brittle fracture model sandwiched between the crosshead 52 and the table 54 of the known compression tester 50. As a result, as shown in FIG. 6A, the load (load) and displacement applied to the test piece 40 until the brittle fracture occurs, and the fracture strain when the brittle fracture occurs (compressed fracture strain measured value). get. The load (load) and displacement at this time become the nominal stress and the nominal strain, respectively.

  In this embodiment, the compression speed of the compression tester 50 with respect to the test piece 40 is performed at a plurality of different speeds, and the nominal stress σn and the nominal strain εn of the test piece 40 are obtained at each compression speed, and brittle fracture occurs. Fracture strain at the time (compressed fracture strain measured value) is acquired.

Next, the true strain εtrue and the true stress σtrue are calculated from the nominal stress σn and the nominal strain εn obtained as described above based on the following formulas (1) and (2), respectively.
εtrue = ln (1 + εn) (1)
σtrue = σn (1 + εn) (2)
Further, as shown in FIG. 3A, the Young's modulus E and the yield stress at each compression rate are obtained from the graph of the true stress σtrue and the true strain εtrue. In the case of brittle fracture, the yield stress is the fracture strength.

Next, the equivalent stress σ and the equivalent plastic strain ε are obtained from the equations (3) and (4) and plotted.
ε = εtrue−σtrue / E (3)
σ = σtrue ...... (4)
3 (b) and 3 (c) show that the true stress-true strain curve A shown in FIG. 3 (b) is equivalent to the equivalent stress-of FIG. 3 (c) based on the equation (3). A place where a plastic strain curve B is changed is shown.

  Since this equivalent stress-equivalent plastic strain curve B is used for compression and not used for tension, as shown in FIG. 3C, the positive value is changed to a negative value, and this is the physical property of the test piece. Use as data. The equivalent stress-equivalent plastic strain curve corresponds to the actual measured value of compressive stress-strain.

(Operation of embodiment: creation of brittle fracture model)
Next, the creation of the brittle fracture model will be described with reference to the flowchart of FIG. It is assumed that the physical property data of the test piece has been obtained by acquiring the physical property of the test piece described above.

In general, in S10, the operator creates a brittle fracture model and inputs physical property data and the like to the computer 10.
The brittle fracture model of this embodiment is demonstrated with reference to FIG.1, FIG.2 (a) and FIG.2 (b). As shown in FIG. 1, the FEM element group of the brittle fracture model is composed of a plurality of FEM shell element groups 100 in a column and a plurality of FEM shell element groups 200 in a row. As shown in FIG. 2 (a), the vertical FEM shell element group 100 is formed of four square plate-shaped shells S and a plurality of rectangular cylinder portions 104 that open upper and lower ends are vertically connected. It includes a cylindrical body 106 and a longitudinally connected shell body 108 that is connected to the side of the cylindrical body 106 arranged on the outer periphery of the model or is independently arranged. In the vertically connected shell body 108, a plurality of square plate-shaped shells S are vertically connected. Note that the rectangular plate-like shells S constituting the FEM shell element group 100 and the FEM shell element group 200 described later have the same size or different sizes for the convenience of explanation. A sign shall be attached.

  When the planar view is seen in plan view, the cylindrical body bodies 106 are alternately arranged in the directions orthogonal to each other. The longitudinally connected shell body 108 is provided to form the outer shape of the model. In the present embodiment, the height (vertical length) of each rectangular tube portion 104 of the cylindrical body 106 is made the same, and the height (vertical length) of each shell of the vertically connected shell body 108 is made the same. ing. Note that the height of each layer in the vertical direction may be the same, or may be different for each layer.

  In this way, in the present embodiment, the nodes of the shells of the cylindrical portion 106 and the vertical connection shell body 108 in the respective layers in the vertical direction (height direction) of the cylindrical portion 106 and the vertical connection shell body 108 are the same. It arrange | positions so that it may be located in height, ie, the same plane.

Note that the nodes of the cylindrical portion 106 and the vertically connected shell body 108 of each layer do not necessarily have to have the same height, and may be arranged on a common slope, for example.
As shown in FIG. 2 (b), the FEM shell element group 200 in the row includes a rectangular plate-like shell S in each layer so that adjacent ones in the columnar body 106 are bridged. The rectangular tube portion 104 is connected to the nodes at both upper and lower ends. In FIG. 2B, in order to clearly indicate the shells S of the row FEM shell element group 200 in the uppermost layer, the shells are shown by hatching. The lower layers excluding the uppermost layer show the approximate vertical positional relationship with a two-dot chain line. In the present embodiment, the square plate-like shell S is an example of a quadrilateral shell element.

  In the present embodiment, the adjacent cylinder parts 106 in the column are cross-linked with each other, as shown in FIG. 2A, adjacent to the 360 degree periphery of the P part cylinder 106. This means that the cylindrical body 106 at positions P1 to P8 is cross-linked by the shell S as shown in FIG. In FIG. 2B, P and P1 to P8 indicate the positions of the cylindrical portion 106 of P and P1 to P8 in FIG.

Further, the shell S of each layer of the vertically connected shell body 108 in the peripheral part of the model is appropriately connected to the node of the shell S of each layer in the FEM shell element group 200.
Note that the longitudinally connected shell body 108 defines the peripheral shape of the model in this embodiment, but may be omitted because it can be replaced by the arrangement state of the cylindrical body 106.

  In addition, although the whole shape of the said brittle fracture model is made into the column shape in FIG. 1, it is not limited to a column shape, The shape similar to the shape of a test piece may be sufficient as the shape of the whole brittle fracture model. Accordingly, if the shape of the test piece is a three-dimensional shape such as a column having a polygonal cross section, a cone, a quadrangular column, or a quadrangular pyramid, the shape of the model similar to that shape may be used.

  In the present embodiment, the shell S has a square plate shape. However, the shell S is not limited to a square plate shape as long as the FEM shell element groups 200 in a row can be bridged by the FEM shell element groups 200 in a row.

  Therefore, in S10, the operator uses the input unit 12 of the brittle fracture model creation apparatus shown in FIG. 4A to provide various information necessary for creating the model, for example, the shape of the brittle fracture model. , Size, total number of elements, element size, etc. are input to the computer 10. The element size includes the thickness of the element.

  The element sizes include the thickness of the shell S of the FEM shell element group 100 and the thickness of the shell S of the FEM shell element group 200. In this case, the thickness of the shell S of the FEM shell element group 200 Is input with a value smaller than the plate thickness of the FEM shell element group 100.

  In addition, the operator inputs the fracture plastic strain of the shell S of the FEM shell element group 200 to the computer 10 with a value smaller than the fracture plastic strain of the FEM shell element group 100. Here, to make the plate thickness and fracture plastic strain of the shell S of the FEM shell element group 200 smaller than the plate thickness and fracture plastic strain of the shell S of the FEM shell element group 100, brittle fracture is caused in the longitudinal direction. This is to make it easier to occur.

In addition, the operator inputs the virtual Poisson's ratio and the virtual mass density of the brittle fracture model to the computer 10 using the input unit 12.
In S10, the operator can also obtain physical property data of the test piece obtained at different compression speeds, that is, mass, equivalent stress-equivalent plastic strain curve (compressed stress-strain measured value), and fracture strain (compression fracture strain). (Actual measurement value) is input to the computer 10.

  Further, in order to use the finite element method, boundary conditions (for example, a constraint condition and a load condition for constraining both upper and lower ends) of the brittle fracture model are input. The load condition includes a compression speed.

  In S20, the computer 10 calculates the equivalent stress-equivalent plastic strain curve (compressed stress-strain measured value) and the fracture strain (compression compression) at each compression speed based on the brittle fracture model and various data input in S10. Extrapolation and interpolation are performed for compression speeds other than the compression speed based on the fracture strain measurement value. Since extrapolation and interpolation are known methods, description thereof is omitted.

Further, the computer 10 calculates the total area of the input FEM shell element group 100 and the total area of the FEM shell element group 200, respectively.
The computer 10 calculates the mass of the FEM shell element group 100 by multiplying the total area, the plate thickness, and the mass density of the FEM shell element group 100, and calculates the total area, the plate thickness, and the mass density of the FEM shell element group 200. Multiply and calculate the mass of the FEM shell element group 200, and the total mass of both is taken as the mass of the brittle fracture model. Then, the computer 10 corrects the mass of the brittle fracture model so as to balance the mass of the test piece. The correction is performed, for example, by correcting the mass density, the plate thickness, and the like. In this case as well, the magnitude relationship between the thickness of the shell S of the FEM shell element group 200 and the thickness of the shell S of the FEM shell element group 100 is not broken.

  Next, the computer 10 compresses and simulates the brittle fracture model created based on the various input data under the boundary condition, and loads (reaction force) under the boundary condition. Create a time curve and output it to the output unit 14 (for example, a display).

  In S30, the operator determines “NO” if the output load (reaction force) -time curve is largely different from the load (reaction force) -time curve obtained with the test piece down. In step S40, correction input is performed from the input unit 12. The correction input includes, for example, increasing or decreasing the thickness value of the FEM shell element group in the column and the row. Further, the compression breaking strain may be corrected. Moreover, you may make it correct | amend both the plate | board thickness value and compression fracture | rupture distortion of the FEM shell element group of a column and a row. Thereafter, the computer 10 is caused to perform the process of S20.

  In S30, if the output load (reaction force) -time curve is little different from the load (reaction force) -time curve obtained with the test piece down, an appropriate brittle fracture model can be obtained. In step S50, the worker stores the various data defining the created brittle fracture model in a storage device (not shown) of the computer 10 and then ends this work.

  For example, as shown in FIG. 11 (a), the brittle fracture model created as described above is the same as the snow which the tire T jumps up on the lower surface of the body exterior part M located behind the tire T of the vehicle. The case where it becomes ice can be provided as the brittle fracture model MD.

  In this case, as shown in FIG. 11 (b), when the vehicle passes through a step D having a difference in height of the passage, if the tire T moves from a place where the step D is high to a place where the height is low, the brittle fracture occurs. It is possible to perform a simulation when the model MD collides with a high step and the upper part of the brittle fracture model MD gives an impact to the lower surface of the body exterior part.

  As shown in FIG. 12A, when the honeycomb structure is formed by the shell element Sh as shown in FIG. 12A or when the model is constituted by the solid element S0 as shown in FIG. Therefore, it is difficult to cause brittle fracture in the vertical direction, i.e., vertically split.

This embodiment has the following features.
(1) In the method for creating a brittle fracture model using the computer according to the present embodiment, in the first step (S10), compression at different compression speeds obtained for a test piece of an object that causes brittle fracture in the computer 10 is performed. The stress-strain actual measurement value and the compression rupture strain actual measurement value are input as physical properties in the FEM element group having a configuration in which a plurality of columnar FEM shell element groups 100 extending in the vertical direction are bridged by the row FEM shell element group 200. Further, as the second step (S20), the computer 10 extrapolates and interpolates the measured compressive stress-strain measured value and the measured compressive fracture strain, and calculates the physical property of the FEM element group other than the compression speed. To do. Furthermore, as a third step (S20), the computer 10 balances the value obtained by multiplying the total surface area of each FEM shell element, the thickness value of the FEM shell element, and the mass density with the measured mass of the test piece. .

  Then, as the fourth step (S40), the thickness values of the FEM shell element groups in the column and the row are set in the computer 10 so that the fracture of the FEM shell element group 200 in the row occurs before the FEM shell element group 100 in the column. And at least one of compression break strain and correction input. As a result, according to the present embodiment, it is possible to provide a method for creating a brittle fracture model in which when a compressive load is applied in the longitudinal direction, brittle fracture occurs in the longitudinal direction and the brittle fracture can be simulated.

  (2) In the brittle fracture model creation method of the present embodiment, as the fifth step (S50), data defining the brittle fracture model created by executing the first to fourth steps is stored in the computer 10. As a result, according to the present embodiment, by storing data defining the brittle fracture model, it is possible to reconfigure the brittle fracture model and perform a simulator.

  (3) In the method of creating the brittle fracture model, the FEM shell element group 100 in the column includes a group of quadrangular cylindrical portions 104 formed by connecting a plurality of quadrilateral shell elements at nodes, and the FEM shell element group 200 in the row includes The brittle fracture model (1) can be easily realized by connecting the square plate-shaped shells S (quadrangular shell elements).

In addition, embodiment of this invention is not limited to the said embodiment, You may change as follows.
In the embodiment, the Young's modulus is used as it is, but the Young's modulus may be corrected. The correction can be performed by multiplying the correction multiple or adding or subtracting a predetermined value. By using the corrected Young's modulus, the measured compressive stress-strain value in which the Young's modulus is corrected is used. In this way, the correction of the Young's modulus obtained from the test piece makes it possible to change the brittle fracture time during compression of the brittle fracture model.

  In the embodiment, the fracture strain (actual compression fracture strain measurement value) is used as it is. However, in the first step, the compression fracture strain measurement value may be a corrected compression fracture strain measurement value. As described above, by correcting the actual measurement value of the compression fracture strain, the brittle fracture time at the time of compression of the brittle fracture model can be changed.

  In the brittle fracture model of the above-described embodiment, in the FEM shell element group 100 in the column, the cylindrical part 106 in which a plurality of the rectangular cylindrical parts 104 that open the upper and lower ends are vertically connected is the other adjacent cylindrical part 106. Are arranged so as to be connected to a rectangular cylinder part of another adjacent cylinder part 106 through the shell S of the FEM shell element group 200 in a row, but the brittle fracture model is It is not limited to the structure of the said embodiment.

  For example, as shown in FIG. 13, each tubular body 106 is configured such that the rectangular tubular portions 104 are connected in a row of grids. Then, the FEM shell element group 200 connects the cylindrical body members 106 of each row arranged at intervals with a plurality of FEM shell element groups 200 arranged in layers above and below. In FIG. 13, in the uppermost FEM shell element group 200, a part of the shell S is indicated by hatching, the rest is indicated by virtual lines, and the FEM shell element group 200 from the uppermost layer to the lower layer is indicated by virtual lines. .

In addition, although not shown, it goes without saying that each cylindrical body 106 may have a square shape of two or more rows, in addition to the square shape of the square cylindrical portion 104.
-In the said embodiment, of course, it uses as brittle fracture models, such as earthenware other than ice, concrete, and glass.

(Example)
Next, an example will be described with reference to FIGS. This example is an example of the brittle fracture model shown in FIGS. First, a cylindrical ice test piece 40 (vertical height: 100 mm, diameter: 40 mm) is prepared, and the test piece 40 is sandwiched between the tables 54 and 52 of the compression tester 50 shown in FIG. The test piece 40 was compressed at four different compression speeds to cause brittle fracture, and the displacement and load at each compression speed were obtained. The compression test was performed at an ambient temperature of -15 ° C. The compression speed was 10 mm / min, 50 mm / min, 500 mm / min, and 1000 mm / min. The load-displacement curve (FS diagram) obtained at this time is shown in FIG.

Based on the acquired data, a graph of the true stress and true strain at each compression rate was created, and the Young's modulus and yield stress at each compression rate were determined based on this graph.
An equivalent stress-equivalent plastic strain (compressed stress-strain measured value) curve was obtained from the obtained graph of true stress and true strain at each compression rate (see FIG. 8).

Next, these physical property data were input to the computer 10, and the input of S10 described in the embodiment was performed to create the models of FIGS.
The values input in S10 are as follows.

The element size (mesh size) was a square plate of 3 mm × 3 mm, and the brittle fracture model was a cylinder with a vertical length (vertical length) of 100 mm and a diameter of 40 mm.
The plate thickness of the FEM shell element group 100 was 6.0 mm, and the breaking strain (breaking plastic strain) was 0.009. The thickness of the FEM shell element group 200 was 1.0 mm, and the breaking strain (breaking plastic strain) was 0.005.

The Poisson's ratio was generally 0.3, and the mass density was 1.0E-9.
In S20, a compression speed other than the compression speed is calculated by the computer 10 on the basis of the equivalent stress-equivalent plastic strain curve (compressed stress-strain measured value) and fracture strain (compressed fracture strain measured value) at each compression speed. Extrapolation and interpolation were performed.

  Then, the computer 10 calculates the total area of the input FEM shell element group 100 and the total area of the FEM shell element group 200, respectively, and multiplies the total area, plate thickness, and mass density of the FEM shell element group 100 by FEM. The mass of the shell element group 100 is calculated, and the mass of the FEM shell element group 200 is calculated by multiplying the total area, plate thickness, and mass density of the FEM shell element group 200, and the total mass of both is calculated as the mass of the brittle fracture model. did. The computer 10 balances the mass of the brittle fracture model with the mass of the test piece.

  Thereafter, the brittle fracture model created on the basis of the various input data is compressed and simulated under the boundary condition by a finite element method, and the load (reaction force) under the boundary condition is simulated. -A time curve was created and output to the output unit 14 (for example, a display).

  FIG. 5B shows a brittle fracture model before compression when simulated. In the brittle fracture model, for convenience of explanation, the FEM shell element group 100 is hatched. FIG. 6B shows a brittle fracture model showing a state when the brittle fracture occurs. Thus, it was confirmed that the brittle fracture model was brittle fracture in the vertical direction.

  FIG. 9 shows a load (reaction force) -time curve (load-time curve) when the test piece 40 is performed at a compression speed of 1000 mm / min. FIG. 10 illustrates the load-time curve when the test piece 40 is performed at a compression speed of 1000 mm / min and the load-time curve when the test piece 40 is performed at a compression speed of 1000 mm / min in the brittle fracture model. It is. As shown in FIG. 10, it is shown that the brittle fracture model and the load-time curve of the test piece can be approximated.

S ... Shell,
10 ... Computer, 12 ... Input unit, 14 ... Output unit,
DESCRIPTION OF SYMBOLS 100 ... FEM shell element group, 104 ... Square cylinder part, 106 ... Tube part body,
108: longitudinally connected shell body, 200: FEM shell element group.

Claims (5)

A method for creating a brittle fracture model using a computer,
The measured compressive stress-strain and measured compressive strain at different compression speeds obtained for the test piece of the object causing the brittle fracture in the computer are measured between a plurality of FEM shell element groups extending in the vertical direction. A first step of inputting as physical properties in a group of FEM elements having a structure crosslinked with a group of FEM shell elements in a row;
A second step in which the computer extrapolates and interpolates the compression stress-strain actual measurement value and the compression rupture strain actual measurement value to calculate the physical property of the FEM element group other than the compression speed;
A third step in which the computer balances the value obtained by multiplying the total surface area of each FEM shell element by the thickness value and mass density of the FEM shell element with the measured mass of the test piece;
At least one of the plate thickness value and compressive fracture strain of the column and row FEM shell element groups so that the computer breaks the row FEM shell element groups before the column FEM shell element groups. A method of creating a brittle fracture model, comprising a fourth step of correcting and inputting   The brittle fracture model creation method according to claim 1, further comprising a fifth step of storing data defining the brittle fracture model created by executing the first to fourth steps in the computer.   3. The method for creating a brittle fracture model according to claim 1, wherein, in the first step, the actual measured value of compressive stress-strain is an actual measured value of compressive stress-strain corrected for Young's modulus. .   3. The method for creating a brittle fracture model according to claim 1, wherein in the first step, the actual measured value of compressive fracture strain is a corrected actual measured value of compressive fracture strain.   The FEM shell element group in the column includes a group of quadrangular cylindrical portions formed by connecting a plurality of quadrilateral shell elements at nodes, and the FEM shell element group in the row includes a quadrilateral shell element. The method for creating a brittle fracture model according to any one of claims 1 to 4.