JP2010230644A - Structural analysis apparatus and structural analysis method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform breakage generating prediction of high accuracy and high versatility. <P>SOLUTION: This structural analysis apparatus performs numerical analysis of a structure including breakage using a finite element method of virtually dividing the structure into a plurality of elements and calculating change in each element. This structure analyzer includes a breaking strain storing means 4 for storing the breaking strain in each element in association with the stress three-axis degree of the element and the size of the element, a breakage determining means 6 for determining the breakage in each element based on the breaking strain stored in the breaking strain storing means 4, and a calculating means 8 for calculating the change in each element based on a change condition different depending on the determination result of the breakage determining means 6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a structural analysis apparatus and a structural analysis for performing numerical analysis of the structure including fracture using a finite element method that virtually divides the structure into a plurality of elements and calculates a change in each of the elements. It is about the method.

For example, a fan case of a jet engine or the like is required to have a design in which the flying pieces do not penetrate even when the fan blades are scattered due to an unexpected situation.
For example, there are experimental formulas such as the Stanford formula and the BRL formula as prediction formulas for the penetration of the scattering pieces with respect to the steel plate.
On the other hand, a method has been proposed in which an existing numerical simulation code is applied to the finite element method, and the occurrence of fracture in the high-speed collision problem is predicted by numerical analysis of a structure including fracture.

  In addition, the occurrence of fracture in such a high-speed collision problem is not only performed in the field of jet engines, but is performed in general fields in which an object moving at high speed may collide with a predetermined structure. .

JP-A-8-61086 JP-A-2005-283130

  However, it is difficult to predict the occurrence of fracture using the above empirical formula because it has a limited range of application of the empirical formula, and it is difficult to make a strict prediction under actual design conditions. For this reason, it is necessary to set a large safety factor when performing fracture occurrence prediction using empirical formulas in actual design. In other words, the failure occurrence prediction using the empirical formula cannot be performed with high accuracy. Therefore, the safety measures for the structure are likely to be excessive with respect to the conditions for which they are originally required.

On the other hand, the fracture occurrence prediction performed by applying an existing numerical simulation code in the finite element method can be performed with high accuracy.
However, such a fracture occurrence prediction uses a numerical simulation code acquired under a predetermined condition as in Non-Patent Document 1, although the application range is wider compared to the fracture occurrence prediction using an empirical formula. . For this reason, there is no guarantee that accurate fracture occurrence prediction can be performed when the element size when the element is divided into a plurality of elements of the structure or the stress triaxiality of each element changes due to a change in conditions. For this reason, the failure occurrence prediction performed by applying an existing numerical simulation code in the finite element method has a problem of low versatility.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to make it possible to predict fracture occurrence with high accuracy and high versatility.

  The present invention adopts the following configuration as means for solving the above-described problems.

  A first invention is a structural analysis apparatus that performs numerical analysis of the structure including fracture using a finite element method that virtually divides the structure into a plurality of elements and calculates a change in each of the elements. A fracture strain storage means for storing the fracture strain in each of the elements in association with the stress triaxiality of the element and the element size of the element, and based on the fracture strain stored in the fracture strain storage means A configuration is adopted in which a destruction determination unit that determines the destruction of each of the above elements and a calculation unit that calculates a change in each of the above elements based on a change condition that varies depending on the determination result of the destruction determination unit.

  According to a second invention, in the first invention, the fracture strain storage means stores a fracture strain in each of the elements in association with a strain rate in addition to the stress triaxiality and the element size. adopt.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a stress-strain relationship storage unit that stores a relationship between stress and strain in each of the elements in association with a strain rate in the element is provided. A configuration is adopted in which a change in each element is calculated based on the relationship between the stress and strain stored in the stress-strain relationship storage means.

  A fourth invention is a structural analysis method for performing numerical analysis of the structure including fracture using a finite element method that virtually divides the structure into a plurality of elements and calculates a change in each of the elements. In addition, the fracture strain in each of the above elements is determined by using the fracture strain related data associated with the stress triaxiality of the element and the element size of the element, and varies depending on the determination result of the fracture. A configuration is adopted in which a change in each of the above elements is calculated based on a change condition.

  In a fifth aspect based on the fourth aspect, the fracture strain in each element is stored in the fracture strain-related data in association with the strain rate in addition to the stress triaxiality and the element size. The configuration is adopted.

  According to a sixth invention, in the fourth or fifth invention, a change in each element is calculated using stress-strain relationship data in which the relationship between stress and strain in each element is related to the strain rate in the element. Adopting a configuration to do.

  According to the present invention, since the numerical analysis of the structure is performed using a so-called finite element method, it is possible to perform the failure occurrence prediction with higher accuracy than the failure occurrence prediction using the conventional empirical formula.

Further, according to the present invention, the fracture strain in each element is stored in association with the stress triaxiality of the element and the element size of the element, and the determination of the fracture in each element is made based on the stored fracture strain. Done. That is, according to the present invention, when the stress triaxiality of an element or the element size of an element changes, the fracture strain of the element also changes according to the change.
For this reason, according to the present invention, even when the stress triaxiality of the element and the element size of the element are changed, it is possible to perform an appropriate numerical analysis corresponding to the change. Therefore, it is possible to predict the occurrence of destruction with high versatility.

  Therefore, according to the present invention, it is possible to perform fracture prediction with high accuracy and high versatility.

It is a functional block diagram which shows schematic structure of the structure analysis apparatus of one Embodiment of this invention. It is a graph which shows the result of having performed the tension test with respect to the test piece which consists of SUS304 so that it may become strain rate 0.001 / s. It is a test result which shows the change of coefficient (alpha) and coefficient (beta) when changing the strain rate as a parameter with respect to the test piece which consists of SUS304. It is a graph which shows the relationship between the stress triaxiality obtained by using the result of having performed the torsion test performed with respect to the test piece which consists of SUS304, and the numerical simulation result using the same test piece, and a fracture | rupture strain. . It is a perspective view which shows the test piece for acquiring the graph shown in FIG. It is a graph which shows the relationship between the rotation angle and torque which were acquired from the torsion tester, and the relationship between the rotation angle and torque which were acquired from the numerical simulation using the above-mentioned finite element method. It is a graph which shows the relationship between the rotation angle obtained from numerical simulation, and an equivalent plastic strain, and the torsion angle at the time of a maximum torque. For a test piece made of SUS304, the strain rate is 0.0006 / s, 0.007 / s, 0.07 / s, 0.6 / s, 8.6 / s, 81 / s, 266 / s, It is a graph which shows the result of having done the tension test so that it might become 1037 / s. It is a flowchart for demonstrating the structure analysis method of one Embodiment of this invention. It is a flowchart for demonstrating the calculation process in the structure analysis method of one Embodiment of this invention.

  Hereinafter, an embodiment of a structural analysis apparatus and a structural analysis method according to the present invention will be described with reference to the drawings.

The structural analysis apparatus S of the present embodiment performs numerical analysis of a structure including fracture using a finite element method that virtually divides a structure into a plurality of elements and calculates changes in each element. Yes, embodied by a personal computer or workstation.
FIG. 1 is a functional block diagram showing a schematic configuration of the structural analysis apparatus S of the present embodiment. As shown in this figure, the structural analysis apparatus S includes an element creation unit 1, a material data storage unit 2, a calculation condition storage unit 3, a fracture strain storage unit 4 (fracture strain storage unit), and a stress strain relation storage unit 5 (stress strain). A relationship storage unit), a destruction determination unit 6 (destruction determination unit), a yield determination unit 7 (yield determination unit), a calculation unit 8 (calculation unit), an evaluation unit 9, an operation input unit 10, and an output unit 11. .

The element creation unit 1 virtually divides a structure into a plurality of elements based on a command from the operation input unit 10.
For example, the element creating unit 1 divides an area estimated to have a large change in structure in numerical analysis into elements having a small element size, and divides an area estimated to have a small change into elements having a large element size. . Thus, by changing the element size in the region of the structure, it is possible to shorten the time for numerical analysis and perform highly accurate prediction. In addition, in the element creation part 1, you may make it divide | segment a structure into the element size of the same magnitude | size uniformly. In addition, the element size and the element shape of the element once created in the element creating unit 1 can be arbitrarily changed via the operation input unit 10.
And in the structure analysis apparatus S of this embodiment, the element creation part 1 has memorize | stored the element size of each element.

The material data storage unit 2 stores the material data of the structure required for performing numerical analysis. For example, the material data storage unit 2 stores the density of the structure, the elastic constant (Young's modulus) of the structure in the elastic deformation region, the elastic constant of the structure in the plastic deformation region, and the yield point. And in the structural analysis apparatus S of this embodiment, in order to enable the numerical analysis of the structure including the destruction, the material data storage unit 2 also stores the material data used after the destruction.
In addition, these material data are input into the material data storage part 2 via the operation input part 10, for example.

The calculation condition storage unit 3 stores calculation conditions necessary for performing numerical analysis. For example, the calculation condition storage unit 3 includes a boundary condition in each element, a load condition acting on the structure, a contact condition between parts when the structure is composed of a plurality of parts, an initial condition indicating an initial state of the structure, and Other calculation formulas and calculation parameters are stored. And in the structural analysis apparatus S of this embodiment, in order to enable the numerical analysis of the structure including the destruction, the calculation condition storage unit 3 also stores the calculation conditions used after the destruction.
These calculation conditions are input to the calculation condition storage unit 3 via the operation input unit 10, for example.

The fracture strain storage unit 4 relates to fracture strain related to the fracture strain associated with the element triaxiality (value obtained by dividing the average stress by the equivalent stress), the element size of the element, and the strain rate of the element. Stores data.
The fracture strain related data is acquired by a tensile test or the like with respect to the material forming the structure, and is input to the fracture strain storage unit 4 via the operation input unit 10.

  FIG. 2 is a graph showing the results of a tensile test performed on a test piece made of SUS304 so that the strain rate is 0.001 / s, where the horizontal axis indicates the element size and the vertical axis indicates the fracture strain. Yes. From this figure, it can be seen that the fracture strain decreases as the element size increases, that is, the fracture strain changes depending on the element size.

Moreover, the approximate straight line obtained from the experimental result shown in FIG. 2 can be represented by the approximate expression (1) shown below. In the approximate expression (1), ε _f indicates fracture strain, L indicates element size, and α and β are coefficients.
ε _f = αL ^β (1)
FIG. 3 shows test results showing changes in the coefficients α and β when the element size is constant and the test piece made of SUS304 is changed using the strain rate as a parameter. From this figure, it can be seen that the coefficient α and the coefficient β change depending on the strain rate. That is, it can be seen from this figure that the fracture strain changes depending on the strain rate.

  FIG. 4 is a graph showing the relationship between the stress triaxiality and the fracture strain obtained by using the result of the torsion test performed on the test piece and the numerical simulation result using the same test piece. Yes, the abscissa indicates the stress triaxiality and the ordinate indicates the fracture strain. From this figure, it can be seen that the fracture strain increases as the stress triaxiality decreases, that is, the fracture strain changes depending on the stress triaxiality. In addition, the graph shown in FIG. 4 was acquired using the test piece which consists of SUS304 similarly to FIG.

Here, a method for obtaining the graph shown in FIG. 4 will be described.
For example, a graph is first drawn using the theoretical solution described in “FA McClintock, A Criterion for Ductile Fracture by the Growth of Holes, Journal of Applied Mechanics, June 1968, pp.363-371”. However, the theoretical solution tends to require a maximal fracture strain when the stress triaxiality is extremely close to zero. For this reason, the graph shown in FIG. 4 is obtained by measuring the fracture strain in the region where the stress triaxial is very close to zero by a torsion test and numerical simulation, and correcting the graph obtained by using the theoretical solution using the measured value. Get. Specifically, the curved portion shown in FIG. 4 is obtained using the above theoretical solution, and the straight portion shown in FIG. 4 is obtained by a torsion test. In practice, it is preferable to confirm the validity of the theoretical solution by conducting a tensile test.

Next, a method for obtaining the fracture strain when the stress triaxiality is extremely close to zero by the torsion test and the numerical simulation will be described.
First, as shown in FIG. 5, a cylindrical test piece 100 having both ends having a large diameter and a center having a small diameter is prepared. In this test piece 100, both ends 100a are locations where the torsion tester grips. Moreover, it is a measurement location twisted until the center 100b of the test piece 100 breaks.
The diameter of both ends 100a of the test piece 100 is determined by the shape of the gripping tool of the torsion tester. On the other hand, the diameter of the center 100b of the test piece 100 is set so that the destruction of the test piece 100 occurs at about half the load capacity of the torsion tester.
Then, such a test piece 100 is twisted by a torsion tester, and a torque and a rotation angle (a torsion angle at the maximum torque) when a crack occurs in the surface layer of the test piece 100 to which the largest load acts are obtained. At the same time, the relationship between the rotation angle and the torque is acquired.

  Subsequently, the relationship between the rotation angle and the torque and the relationship between the rotation angle and the equivalent plastic strain are obtained by calculation by a numerical simulation using the finite element method. The numerical simulation is performed without considering the destruction of the test piece 100. Further, this numerical simulation may be performed before the above-described torsion test.

Subsequently, as shown in FIG. 6, the relationship between the rotation angle and torque acquired from the above-described torsion tester and the relationship between the rotation angle and torque acquired from the numerical simulation using the above-mentioned finite element method are compared. Confirm the validity of the numerical simulation.
Here, when the result obtained from the numerical simulation is greatly different from the result obtained from the torsion tester and lacks validity, the calculation conditions in the numerical simulation are changed until the validity is obtained.

Then, when the validity of the result obtained from the numerical simulation is obtained, as shown in FIG. 7, from the relationship between the rotation angle obtained from the numerical simulation and the equivalent plastic strain, the maximum torque twist angle is obtained. Acquire equivalent plastic strain.
FIG. 7 also shows the relationship between the rotation angle and the stress triaxiality obtained by numerical simulation. As shown in this figure, the scale of the stress triaxiality is one tenth of the display scale, and the stress triaxiality is in the range of 0 to 0.01, which is extremely close to zero, until reaching the torsion angle at the maximum torque. It can be seen that changes. That is, the result obtained by this numerical simulation is obtained in a state where the stress triaxiality is extremely close to zero.
Therefore, the equivalent plastic strain at the torsion angle at the maximum torque described above is a value indicating the fracture strain in a state where the stress triaxiality is extremely close to zero.
In this way, the fracture strain when the stress triaxiality is extremely close to zero is obtained by the torsion test and the numerical simulation.

  As shown in FIGS. 6 and 7, it is preferable to obtain a plurality of maximum torque twist angles using a plurality of test pieces 100 in consideration of a measurement error of a torsion tester. And when calculating | requiring a fracture | rupture distortion | strain, considering safety | security, the thing with the smallest value is employ | adopted among several torsion angles at the time of maximum torque, for example.

  Then, the graph obtained using the above theoretical solution is notched with the fracture strain when the stress triaxiality is very close to zero as the upper limit value, and the stress triaxiality and fracture strain shown in FIG. A graph showing the relationship can be acquired.

As can be seen from the test results shown in FIGS. 2 to 4, the fracture strain changes depending on the stress triaxiality of the element, the element size of the element, and the strain rate of the element.
The fracture strain storage unit 4 stores the fracture strain using the stress triaxiality, element size, and strain rate as parameters.

  In actual numerical analysis, the structure is divided into a large number of elements, and the stress triaxiality, element size, and strain rate of each element change from moment to moment. If the element size of the element and the distortion speed in the element are set finely, the calculation load and the storage capacity may become enormous. For this reason, the stress triaxiality of the element, the element size of the element, and the strain rate in the element have the triaxiality of the element, the element size of the element, and the strain rate in the element according to the analysis capability of the structural analysis apparatus S. You may make it group by every fixed range. For example, when the analysis capability of the structural analysis apparatus S is low, for example, the element sizes of elements may be grouped into three, large, medium, and small.

Returning to FIG. 1, the stress-strain relationship storage unit 5 stores stress-strain relationship data in which a curve indicating the relationship between stress and strain in an element is associated with the strain rate in the element.
Note that the stress-strain related data is acquired by a tensile test or the like for the material forming the structure, like the fracture strain-related data, and is input to the stress-strain related storage unit 5 via the operation input unit 10. The

FIG. 8 shows a strain rate of 0.0006 / s, 0.007 / s, 0.07 / s, 0.6 / s, 8.6 / s, 81 / s, and a test piece made of SUS304. It is a graph which shows the result of having done the tension test so that it may become 266 / s and 1037 / s, and a horizontal axis shows distortion and a vertical axis shows stress. From this figure, it can be seen that the curve indicating the relationship between stress and strain changes as the strain rate changes.
The stress-strain relationship storage unit 5 stores a plurality of curves indicating the relationship between stress and strain using the strain rate as a parameter.

The destruction determination unit 6 determines whether or not the region including the element has been destroyed based on the destruction strain related data (that is, the destruction strain) stored in the destruction strain storage unit 4.
The destruction determination unit 6 refers to the fracture strain related data based on the stress triaxiality of the element input from the calculation unit 8 and the element size stored in the material data storage unit 2. The strain is calculated, and the stress in the element input from the calculation unit 8 is compared with the calculated fracture strain to determine the fracture. The destruction determination unit 6 determines that the element has been destroyed when the stress at the element input from the calculation unit 8 exceeds the calculated fracture strain.

The yield determination unit 7 determines whether or not the element has yielded.
The yield determination unit 7 determines whether or not the element has yielded based on whether or not the stress in the element input from the calculation unit 8 exceeds the yield point of the material forming the structure. The yield determination unit 7 determines that the element has yielded when the stress input from the calculation unit 8 exceeds the yield point.

  When the yield point of the material forming the structure changes depending on the strain rate, the yield point is prepared with data associated with the strain rate, and the yield determination unit 7 refers to the data to obtain the yield point. May be calculated.

The calculation unit 8 calculates strain (change) of each element by numerical analysis from the material data stored in the material data storage unit 2 and the calculation conditions stored in the calculation condition storage unit 3.
In the structural analysis apparatus S of the present embodiment, the calculation unit 8 calculates the distortion of each element based on the change conditions (material data and calculation conditions) that differ depending on the determination result of the fracture determination unit 6 and the determination result of the yield determination unit 7. Etc. are calculated.
Specifically, the calculation unit 8 calculates the distortion of each element using the Young's modulus, density, and the like when the determination result in the yield determination unit 7 is a determination that the yield has not yielded. The calculation unit 8 calculates the stress of each element with reference to the stress-strain relation data based on the calculated strain and the strain rate that can be calculated from the strain. Furthermore, the calculation unit 8 calculates the stress triaxiality of each element from the calculated stress of each element.

  Then, the calculation unit 8 determines that the determination result in the yield determination unit 7 is yielding and the determination result in the fracture determination unit 6 is determination that the breakdown is not broken, the elasticity in the plastic deformation region. The distortion of each element is calculated using constants and density. Further, when it is determined that the determination result of the destruction determination unit 6 is destroyed, the calculation unit 8 calculates the change of each element based on the material data after destruction and the calculation conditions after destruction.

The evaluation unit 9 evaluates the result of the numerical analysis of the structure based on the deformation amount and the movement amount of each element calculated by the calculation unit 8, and stores a program for evaluating the result of the numerical analysis. The evaluation result calculated using the program is output.
The operation input unit 10 inputs a program and parameters from the network or external media to the structural analysis device S in addition to the function of the man-machine interface between the structural analysis device S and the worker of the present embodiment.
The output unit 11 outputs the evaluation result of the evaluation unit 9, the calculation result of the calculation unit 8, and the like.

The structural analysis device S of the present embodiment is embodied by a personal computer or workstation as described above, and more specifically, an arithmetic device such as a CPU, an internal storage device such as a memory, a hard disk drive. It is embodied by an external storage device such as an output device such as a display or a printer, an input device such as a mouse or a keyboard.
For example, in the structural analysis apparatus S of the present embodiment, the material data storage unit 2, the calculation condition storage unit 3, the fracture strain storage unit 4, and the stress strain relation storage unit 5 are internal storage devices such as memories or external devices such as hard disk drives. Embodied by a storage device. In addition, the element creation unit 1, the destruction determination unit 6, the yield determination unit 7, the calculation unit 8, and the evaluation unit 9 are embodied by an arithmetic device such as a CPU. The operation input unit 10 is embodied by an input device such as a mouse or a keyboard. The output unit 11 is embodied by an output device such as a display or a printer.

  Next, the operation (structure analysis method) of the structure analysis apparatus S of the present embodiment configured as described above will be described with reference to the flowcharts of FIGS. 9 and 10.

In the structural analysis apparatus S of the present embodiment, first, the element creation unit 1 performs element creation by virtually dividing a structure to be numerically analyzed into a plurality of elements (step S1).
Here, the element creation unit 1 divides the structure into a plurality of elements based on an instruction input via the operation input unit 10, and stores the element size of each element.

Subsequently, calculation conditions are set by storing the calculation conditions input via the operation input unit 10 in the calculation condition storage unit 3 (step S2).
Here, boundary conditions in each element, load conditions acting on the structure, contact conditions between parts when the structure consists of multiple parts, initial conditions indicating the initial state of the structure, other calculation formulas and parameters The calculation condition storage unit 3 stores (for example, a calculation period) and calculation conditions used after the destruction.

Subsequently, material definition is performed by storing material data input via the operation input unit 10 in the material data storage unit 2 (step S3).
Here, the density of the structure, the elastic constant in the elastic deformation region, the elastic constant in the plastic deformation region, and the material data used after fracture are stored in the material data storage unit 2.

Subsequently, fracture strain related data is set by storing the fracture strain related data input via the operation input unit 10 in the fracture strain storage unit 4 (step S4).
Further, the stress-strain relationship data set via the operation input unit 10 is stored in the stress-strain relationship storage unit 5 to set the stress-strain relationship data (step S5).

  The order of steps S1 to S5 described above is an example, and the order of steps S1 to S5 can be arbitrarily changed.

  Then, the calculation process which calculates the change in each element produced in step S1 by the destruction determination part 6, the yield determination part 7, and the calculation part 8 is performed (step S6).

FIG. 10 is a flowchart showing the flow of processing performed on one element in this calculation step.
As shown in FIG. 10, in the calculation step, first, the calculation unit 8 calculates the strain of the element in the elastic deformation range (step S6a). Specifically, the calculation unit 8 includes material data such as Young's modulus and density stored in the material data storage unit 2, boundary conditions, load conditions, and contact conditions in the elastic deformation range stored in the calculation condition storage unit 3. Then, the distortion of the element is calculated using calculation conditions such as initial conditions.

Subsequently, the calculation unit 8 calculates the stress in the element from the strain calculated in step S6a (step S6b). Here, the calculation unit 8 first calculates the strain rate from the strain change amount calculated in step S6a. Then, the calculation unit 8 determines a curve indicating the relationship between the stress and the strain stored in the stress strain relationship storage unit 5 based on the calculated strain rate, and the stress in the element from the curve and the strain calculated in step S6a. Is calculated.
That is, the calculation unit 8 calculates the change in the element by calculating the stress in the element based on the stress-strain relationship data stored in the stress-strain relationship storage unit 5 and the strain calculated in step S6a.

  Subsequently, whether or not the element has yielded is determined by the yield determination unit 7 (step S6c). Specifically, it is determined whether or not the element has yielded based on whether or not the stress calculated in step S6b exceeds the yield point stored in the material data storage unit 2. The yield determination unit 7 determines that the element has yielded when the stress input from the calculation unit 8 exceeds the yield point.

  When the yield determination unit 7 determines that the element has not yielded in step S6c, the calculation unit 8 determines whether the calculation period has ended (step S6d). As a result of this determination, if the calculation period has not ended, the time is advanced by the calculation unit 8 (step S6e), and step S6a is performed again. On the other hand, if the result of determination is that the calculation period has ended, the calculation process ends.

On the other hand, when the yield determination unit 7 determines that the element has yielded in step S6c, the calculation unit 8 calculates the strain of the element in the plastic deformation range (step S6f). That is, the calculation unit 8 calculates the element distortion based on the calculation conditions (change conditions) that differ depending on the determination result of the yield determination unit 7.
Specifically, the calculation unit 8 includes material data such as the elastic constant and density of the plastic deformation range stored in the material data storage unit 2, boundary conditions and loads in the plastic deformation range stored in the calculation condition storage unit 3. The element distortion is calculated using calculation conditions such as conditions and contact conditions.

  Subsequently, the calculation unit 8 calculates the stress in the element from the strain calculated in step S6f (step S6g). Here, the calculation unit 8 first calculates the strain rate from the strain change amount calculated in step S6f. Then, the calculation unit 8 determines a curve indicating the relationship between the stress and the strain stored in the stress-strain relationship storage unit 5 based on the calculated strain rate, and the stress in the element from the curve and the strain calculated in step S6f. Is calculated.

  Subsequently, the destruction determination unit 6 determines whether or not the element is destroyed (step S6h). Here, the calculation unit 8 first calculates the stress triaxiality of the element from the stress calculated in step S6b. Then, the fracture determination unit 6 calculates an element fracture strain from the stress triaxiality and strain rate calculated by the calculation unit 8 and the element size stored in the element creation unit 1, and the calculation unit 8 performs step S6g. It is determined whether or not the element is broken by comparing the stress calculated in step 1 with the calculated fracture strain. The failure determination unit 6 determines that the element has been destroyed when the stress calculated by the calculation unit 8 in step S6g is greater than the fracture strain.

  When the destruction determination unit 6 determines that the element has not yielded in step S6h, the calculation unit 8 determines whether the calculation period has ended (step S6i). As a result of this determination, if the calculation period has not ended, the time is advanced by the calculation unit 8 (step S6j), and step S6f is performed again. On the other hand, if the result of determination is that the calculation period has ended, the calculation process ends.

  On the other hand, if it is determined in step S6h that the element has been destroyed by the destruction determination unit 6, the calculation unit 8 performs calculation using the calculation conditions after destruction stored in the calculation condition storage unit 3 ( Step S6k). Then, the calculation unit 8 repeats the determination of whether the calculation period has ended (step S61), the step of advancing time (step S6m), and step S6k until the calculation period ends.

When the calculation step (step S6) shown in FIG. 9 is thus completed, the evaluation unit 9 evaluates the calculation result obtained in the calculation step (step S7).
The calculation result in step S6 and the evaluation result in step S7 are visualized in the output unit 11. That is, when the output unit 11 is a display, the calculation result and the evaluation result are displayed, and when the output unit 11 is a printer, the calculation result and the evaluation result are printed.

  According to the structure analysis apparatus S and the structure analysis method of the present embodiment as described above, a structure is virtually divided into a plurality of elements and changes (strain changes, stress changes, state changes, etc.) in each element are calculated. To do. That is, according to the structural analysis apparatus S and the structural analysis method of the present embodiment, a numerical analysis of a structure is performed using a so-called finite element method. For this reason, it becomes possible to perform the fracture occurrence prediction with higher accuracy compared to the fracture occurrence prediction using the conventional empirical formula.

Further, according to the structural analysis apparatus S and the structural analysis method of the present embodiment, the fracture strain in each element is stored in association with the stress triaxiality of the element, the element size of the element, and the strain rate of the element. Determination of destruction in each element is performed based on the stored destruction strain. That is, according to the structural analysis device S and the structural analysis method of the present embodiment, when the stress triaxiality of an element, the element size of the element, or the strain rate in the element changes, the element is destroyed according to the change. The distortion also changes.
For this reason, according to the structural analysis device S and the structural analysis method of the present embodiment, even when the stress triaxiality of the element, the element size of the element, or the strain rate in the element changes, an appropriate response according to the change Numerical analysis can be performed. Therefore, it is possible to predict the occurrence of destruction with high versatility.

  Therefore, according to the structural analysis apparatus S and the structural analysis method of the present embodiment, it is possible to perform a fracture occurrence prediction with high accuracy and high versatility.

  As mentioned above, although preferred embodiment of this invention was described referring drawings, this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

For example, in the above embodiment, in order to enhance versatility, in the fracture strain-related data stored in the fracture strain storage unit 4, the fracture strain is represented by the element triaxiality of the element, the element size of the element, and the strain rate of the element. The configuration in which the three parameters are stored in association with each other has been described.
However, the present invention is not limited to this. For example, even if the fracture strain is not stored in association with all of the above three parameters, the versatility is improved compared to the fracture occurrence prediction using the conventional empirical formula. be able to. That is, for example, the fracture strain may be stored in association with the stress triaxiality of the element and the element size of the element.

In the above embodiment, in order to further improve versatility, the stress-strain relationship data is obtained by associating the stress-strain relationship (stress-strain relationship curve) in the element with the strain rate in the element. About the structure which memorize | stores in the memory | storage part 5, calculates the stress (change) in each element based on the said stress strain relation data, and also determines the yield of an element based on the stress calculated with reference to the said stress strain relation data explained.
However, the present invention is not limited to this, and it is not always necessary to calculate the stress in each element based on the stress-strain relationship data.

  DESCRIPTION OF SYMBOLS 1 ... Element preparation part, 2 ... Material data storage part, 3 ... Calculation condition storage part, 4 ... Destructive strain storage part (destructive strain storage means), 5 ... Stress-strain relation storage part (Stress-strain relation storage) Means), 6 ... destruction determination unit (destruction determination unit), 7 ... yield determination unit (yield determination unit), 8 ... calculation unit (calculation unit), 9 ... evaluation unit, 10 ... operation input unit, 11 …… Output unit, S …… Structural analysis device

Claims (6)

A structure analysis apparatus that performs numerical analysis of the structure including fracture using a finite element method that virtually divides the structure into a plurality of elements and calculates a change in each of the elements,
Breaking strain storage means for storing the breaking strain in each of the elements in association with the stress triaxiality of the element and the element size of the element;
Destruction determination means for determining destruction in each of the elements based on the destruction strain stored in the destruction strain storage means;
A structural analysis apparatus comprising: a calculation unit that calculates a change in each of the elements based on a change condition that varies depending on a determination result of the destruction determination unit.   2. The structural analysis apparatus according to claim 1, wherein the fracture strain storage means stores a fracture strain in each of the elements in association with a strain rate in addition to the stress triaxiality and the element size. Stress-strain relationship storage means for storing the relationship between stress and strain in each of the elements in association with the strain rate in the element;
The structural analysis apparatus according to claim 1, wherein the calculation unit calculates a change in each element based on a relationship between the stress and strain stored in the stress-strain relationship storage unit. A structure analysis method for performing numerical analysis of the structure including fracture using a finite element method that virtually divides the structure into a plurality of elements and calculates a change in each of the elements,
Determining the fracture in each of the elements using fracture strain related data in which the fracture strain in each of the elements is related to the stress triaxiality of the element and the element size of the element;
A structural analysis method, comprising: calculating a change in each of the elements based on a change condition that varies depending on a determination result of destruction.   5. The structural analysis method according to claim 4, wherein the fracture strain in each of the elements in the fracture strain-related data is stored in association with a strain rate in addition to the stress triaxiality and the element size. .   The structural analysis method according to claim 4 or 5, wherein a change in each element is calculated using stress-strain relation data in which a relation between stress and strain in each element is related to a strain rate in the element. .

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