JP6803766B2 - Strength evaluation method, structure manufacturing method, strength evaluation device, and strength evaluation program - Google Patents

Description

The present invention relates to a strength evaluation method, a structure manufacturing method, a strength evaluation device, and a strength evaluation program.

The electric power device is provided with a structure that supports conductors and electric components that serve as electric power paths. This structure is required to have insulating properties and mechanical strength, and is manufactured of an epoxy resin or the like. As a method for estimating and evaluating the strength of such a structure, an evaluation method based on the maximum principal stress theory is known. This evaluation method is an evaluation method assuming that fracture occurs when the maximum value of the maximum principal stress acting on the structure of a brittle fracture material such as epoxy resin reaches the strength determined by the material. Further, a method of predicting the fracture of the resin part by numerical simulation has been proposed (see, for example, Patent Document 1 and Patent Document 2 below).

In Patent Document 1, a plurality of nodes are selected based on the mounting state of the resin component in the finite element model corresponding to the resin component whose fracture state should be predicted. Then, a forced displacement is given to the finite element model to perform static structural calculation. Then, based on the plastic strain distribution obtained by the static structural calculation, when the plastic strain exceeds the reference value, the node is determined as the fracture site.

Further, in Patent Document 2, the parameter of the interface potential energy function of the coupling interface in the tire to be evaluated is determined based on at least one of the tensile peeling experiment and the shear peeling experiment. Then, an interface element containing the determined interface potential energy is created and arranged at the coupling interface in the analysis model created by dividing the tire into a finite number of elements. Then, the rigidity of the interface element is calculated based on the interface potential energy function. Then, the calculated rigidity is substituted into the total simultaneous equations of the analysis model, and the analysis is executed by solving the total simultaneous equations based on predetermined analysis conditions. Then, the propriety of crack growth is determined from the magnitude of the physical quantity of the interface obtained by solving the total simultaneous equations, and the tire fracture is evaluated.

Japanese Unexamined Patent Publication No. 2005-147806 Japanese Unexamined Patent Publication No. 2008-145200

There is room for improvement in the strength prediction accuracy of the strength evaluation method as described above. For example, in an actual test, a member may break at a stress of about 70% of the stress predicted to break the structure based on the maximum principal stress theory. As a factor, for example, it is considered that the influence of the dimensional effect and the stress distribution is not taken into consideration in the maximum principal stress theory and the maximum principal strain theory. Therefore, the accuracy of strength prediction is low, which leads to an increase in the number of trial productions, which leads to cost increase and delay in product development. Further, if the strength prediction accuracy is low, the safety factor is set excessively, which hinders miniaturization.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a strength evaluation method, a structure manufacturing method, a strength evaluation device, and a strength evaluation program capable of accurately evaluating the strength of a structure. To do.

According to the first aspect of the present invention , a strength evaluation method is provided. In the strength evaluation method, for each of a plurality of elements in a numerical model of a structure composed of a material that breaks brittlely, the reliability indicating the probability that each element does not break is calculated by using the stress acting on each element. May include that. Strength evaluation method, by subtracting the result of multiplying signal Yoriyukido of each element 1, and a calculation child destruction probability indicates the probability that at least one of the plurality of elements to destroy may Nde free.

According to the second aspect of the present invention, a method for producing a structure is provided. A method of making a structure may include designing a structure composed of a material that breaks brittlely . Method for manufacturing a structure based on the design, may Nde including that you evaluated by intensity above Symbol strength evaluation method of the structure. The method for manufacturing a structure may include manufacturing the structure when the strength satisfies a specific condition.

According to the third aspect of the present invention , a strength evaluation device is provided. The strength evaluator uses the stress acting on each element to calculate the reliability that indicates the probability that each element will not fracture for each of the multiple elements in the numerical model of the structure composed of the brittle fracture material. A degree calculation unit may be provided. Strength evaluation device subtracts the result of multiplying the signal Yoriyukido of each element 1, at least one of the plurality of elements may comprise breaking probability calculation unit for calculating the fracture probability indicating the probability of fracture.

According to a fourth aspect of the present invention , an intensity evaluation program is provided. The strength evaluation program tells the computer the reliability of each of the multiple elements in a numerical model of a structure composed of brittle fracture materials, using the stress acting on each element to indicate the probability that each element will not fracture. The calculation may be performed. Strength evaluation program, the computer subtracts the result of multiplying the signal Yoriyukido of each element 1, at least one of the plurality of elements by executing that you calculate the fracture probability indicating the probability of fracture Good .

Further, the material for brittle fracture may be an epoxy resin. In addition, the shape parameter, scale parameter, and position parameter representing the Weibull distribution of the strength of the structure are set to m, σ ₀ , and σ _u , respectively, and the stress and volume of the element whose number is i assigned to each of the plurality of elements are set, respectively. R _i (σ _i ), which is the reliability of the elements whose numbers are i, where σ _i and V _{i are used} and the reference volume of the plurality of elements is V ₀ , may be expressed by the following equation (1). ..

It may also include selecting the target element for calculating the reliability from a plurality of elements in the numerical model of the structure. When the stress acting on the elements of the structure is σ, the position parameter in the wibble distribution of the strength of the structure is σ _u , and the predetermined threshold value of 0 or more is σ _th , σ −σ _u > σ _An element satisfying _th may be selected as a target element. It also includes calculating the distribution of stress acting on the structure prior to calculating the reliability, calculating the representative value of the stress acting on each of the plurality of elements based on the stress distribution, and using the representative value. The reliability may be calculated.

According to the present invention, since the probability that at least one of the plurality of elements will be destroyed is calculated based on the probability that each element of the plurality of elements in the numerical model of the structure will not be destroyed, the strength of the structure can be evaluated accurately. Is.

Further, when the reliability of each element is expressed by the above equation (1), the reliability of each element is calculated based on the Weibull distribution, so that the reliability of each element can be predicted accurately, and a plurality of elements can be predicted. It is possible to accurately predict the destruction probability for the elements of. Further, when the target element for calculating the reliability is selected from a plurality of elements of the structure, the processing load can be reduced. Further, when an element satisfying σ _{−σ u} > σ _th is selected as the target element, the processing load can be reduced. In addition, when the distribution of stress acting on the structure is calculated and the reliability is calculated using the representative value of the stress acting on each element, the stress acting on each element can be evaluated accurately, so that the reliability and fracture The probability can be predicted accurately.

It is a figure which shows the manufacturing system which applied the strength evaluation apparatus which concerns on embodiment. It is a figure which shows an example of the evaluation target. It is a figure which shows the process of a stress distribution calculation part. It is a figure which shows the process of the reliability calculation part and the destruction probability calculation part. It is a flowchart which shows the strength evaluation method which concerns on embodiment. It is a figure which shows the evaluation example which applied the strength evaluation method which concerns on embodiment. It is a flowchart which shows the manufacturing method of the structure which concerns on embodiment.

An embodiment will be described. FIG. 1 is a diagram showing a manufacturing system to which the strength evaluation device according to the embodiment is applied. This manufacturing system is used for manufacturing structures that require insulation and mechanical strength. The above-mentioned structure is, for example, a mold provided in an electric power device such as a current transformer or a transformer, and supports a conductor or an electric component which is a path of electric power. The manufacturing system 1 includes a design device 2, a strength evaluation device 3, and a processing device 4.

The design device 2 is, for example, a computer on which a CAD application is implemented. The design device 2 is used to design a structure to be manufactured. The design device 2 outputs design data (eg, CAD data) that defines the shape and dimensions of the structure. This design data is supplied to each of the strength evaluation device 3 and the processing device 4. For example, the design device 2 is communicably connected to each of the strength evaluation device 3 and the processing device 4 by wire or wirelessly, and supplies design data by communication. The design data may be stored in a storage medium such as a USB memory and supplied to the outside of the design device 2 (eg, the strength evaluation device 3 and the processing device 4).

The processing device 4 is, for example, a device used for manufacturing a mold used for molding a structure. The processing device 4 performs various processing such as cutting, bending, and joining on the base material of the mold based on the design data of the structure. For example, the processing device 4 executes various types of processing by numerical control (NC) using design data supplied from the design device 2. The processing device 4 may be one of a plurality of devices (eg, laser processing machine, punch press machine, welding machine) that perform various types of processing, or may be a processing system including two or more devices. Further, the processing device 4 may be a device that performs processing other than manufacturing a mold, and may be, for example, a device that molds a structure using a mold.

The strength evaluation device 3 evaluates (predicts, estimates) the strength of the structure including the brittle fracture material by the weakest link model. The material of the structure is, for example, a resin based on an epoxy resin, and may be a resin to which a curing agent or a filler (eg, quartz) is added. The strength evaluation device 3 evaluates the strength of the structure based on the shape, dimensions, and material of the structure. The shape and dimensions of the structure are included in the above design data, and the strength evaluation device 3 evaluates the strength of the structure using, for example, the design data.

The evaluation result of the strength evaluation device 3 is used for determining whether or not the structure has a predetermined strength. This determination may be made by the strength evaluation device 3 or another device, or may be made by the user. When it is determined that the structure has a predetermined strength (for example, the strength is sufficient), the processing apparatus 4 executes processing for manufacturing the structure. When it is determined that the structure does not have a predetermined strength (for example, the strength is insufficient), the structure is redesigned using the design device 2. The strength evaluation device 3 may be a part of the design device 2 or an external device of the manufacturing system 1.

The strength evaluation device 3 includes a stress distribution calculation unit 5, a selection unit 6, a reliability calculation unit 7, a fracture probability calculation unit 8, and a storage unit 9. The strength evaluation device 3 generally operates as follows. The stress distribution calculation unit 5 calculates the stress distribution in the structure when a predetermined load is applied to the structure. The selection unit 6 selects the target element for strength evaluation based on the stress distribution calculated by the stress distribution calculation unit 5. The reliability calculation unit 7 calculates the reliability indicating the probability that the elements selected by the selection unit 6 will not be destroyed for each of the plurality of elements in the numerical model. The numerical model in this embodiment is a finite element analysis model to which the finite element method is applied. The destruction probability calculation unit 8 multiplies the reliability of a plurality of elements in the numerical model to calculate the probability that the plurality of elements will not be destroyed (non-destruction probability), and uses the non-destruction probability to at least the plurality of elements. Calculate the destruction probability indicating the probability that one will destroy. The storage unit 9 stores information (eg, calculation conditions, wible parameters) required for processing of each part of the strength evaluation device 3, processing results (example, calculation result) of each part of the strength evaluation device 3. Hereinafter, each part of the strength evaluation device 3 will be described with reference to FIGS. 2 to 4.

The stress distribution calculation unit 5 calculates the distribution of stress acting on the structure when a predetermined load is applied to the structure, based on the shape, dimensions, and mechanical properties of the structure. The above mechanical properties are values determined by the material of the structure (composition of epoxy resin). The stress distribution calculation unit 5 calculates the direction and magnitude of stress at the nodes (lattice points) of the calculation grid according to the structure by the finite element method (FEM) or the like.

FIG. 2 is a diagram showing an example of an evaluation target. FIG. 2A shows a test piece used for a JIS standard tensile test as a structure 11 as a structural example of the test piece when determining the Weibull parameter. The structure 11 is a dumbbell type, and both end portions 11a thereof are supported by a tensile tester. The central portion of the structure 11 is a rectangular parallelepiped parallel portion 11b, and this parallel portion 11b serves as a target region for obtaining the Weibull parameter.

FIG. 2B shows a coordinate system, a calculation grid, and calculation conditions as an example of a structure for strength evaluation. In this coordinate system, the X direction is the length direction connecting both end portions 11a, and corresponds to the direction in which the tensile load acts on the tensile tester. The Y direction is the plate thickness direction, and the Z direction is the width direction. Here, the structural grid is illustrated as the calculation grid 12, but the calculation grid may be an unstructured grid. Reference numeral 12a is a position constrained in the Y direction and the Z direction. Further, reference numeral 12b is a load applied to the structure to be evaluated (the structure represented by the calculation grid 12). An example of the evaluation result will be described later with reference to FIG.

FIG. 3 is a diagram showing the processing of the stress distribution calculation unit. FIG. 3A conceptually shows the stress distribution calculated by the stress distribution calculation unit 5. In FIG. 3B, one of the elements is enlarged and shown. The element E _i is surrounded by four nodes Ep, and the calculation result of the stress distribution calculation unit 5 includes the direction and magnitude of the stress at each of the four nodes Ep.

The stress distribution calculation unit 5 calculates a representative value (representative stress) of the stress acting on each of the plurality of elements based on the stress distribution. The representative stress is a value used for strength evaluation. The stress distribution calculation unit 5 calculates the average value (eg, additive average) of the stresses at the four nodes Ep as the representative stress. The representative value of the stress acting on the element E _i may be calculated by the weighted average. Weighted average coefficient of (weighting coefficients) may be, for example, a reciprocal of the distance between the center Ec and each node Ep elements E _i. Further, the representative value of the stress acting on the element E _i may be the maximum value or the minimum value of the stress among the plurality of nodes Ep, or the average value calculated by excluding the maximum value or the minimum value.

FIG. 3C conceptually shows the distribution of the representative stress σ _i of each element. In FIG. 3C, reference numeral 15 is a calculation grid used for strength evaluation, and reference numeral _Ei is a target element for strength evaluation. The calculation grid 15 used for strength evaluation may be the same as or different from the calculation grid 12 (see FIG. 2B) used for calculating the stress distribution. When the calculation grid 15 for strength evaluation is different from the calculation grid 12 for calculating the stress distribution, the representative stress can be calculated by interpolation using the calculation result of the stress distribution or the like. The stress distribution calculation unit 5 stores the calculated representative stress in the storage unit 9 (see FIG. 1).

The selection unit 6 of FIG. 1 selects the target element for which the reliability is to be calculated from the structure. In the selection unit 6, when the stress acting on the element of the structure is σ, the position parameter in the wibble distribution of the strength of the structure is σ _u , and the predetermined threshold value of 0 or more is σ _th , σ −σ Select the element that satisfies _u > σ _th as the target element. The position parameter σ _u is one of the parameters representing the Weibull distribution (Weibull parameter). Weibull parameters include shape parameters (m), scale parameters (σ ₀ ), and position parameters (σ _u ). The Weibull parameter has been obtained in advance by a test or the like, and is stored in the storage unit 9 of FIG.

The selection unit 6 reads out the representative stress calculated by the stress distribution calculation unit 5 and the position parameter σ _u from the storage unit 9. The selection unit 6 compares the difference between the representative stress and the position parameter σ _u for each element with the threshold value σ _th, and determines whether or not to calculate the reliability for each element. The threshold value σ _th is set to 0, for example, but may be set to a value larger than 0, such as a value of 1% or a value of 5% of the position parameter σ _u .

The reliability calculation unit 7 of FIG. 1 calculates the reliability of each of the plurality of elements _Ei ((see FIG. 3C)) selected by the selection unit 6 of the structure. The reliability is the probability that the element in the structure 11 will not be destroyed (non-destructive probability). The reliability calculation unit 7 calculates the reliability using the representative value of the stress acting on each element (representative stress σ _{i in} FIG. 3C). Here, the number assigned to each of the plurality of elements is i (integer). Further, number i of element (hereinafter, represented by _{E i)} a representative stress and sigma _i, and the volume of the element _{E i} and _{V i.} Further, let V ₀ be the reference volume of the plurality of elements. V ₀ is, for example, the average value of the volumes of a plurality of elements. Probability _{F i} of element _{E i} is destroyed is a function of sigma _i is expressed by the following equation (2). In equation (2), m and σ ₀ are Weibull parameters. m is a shape parameter, σ ₀ is a scale parameter, and σ _u is a position parameter.

Further, R _i (σ _i ), which is the reliability of the element E _i , is expressed by the following equation (3). The reliability calculation unit 7 reads the representative stress and the Weibull parameter from the storage unit 9, and calculates the reliability according to the following equation (3).

FIG. 4 is a diagram showing the processing of the reliability calculation unit and the destruction probability calculation unit. FIG. 4A conceptually shows the distribution of reliability calculated by the reliability calculation unit 7. Comparing FIG. 4 (A) with FIG. 3 (C), the reliability R _i is relatively small for an element having a relatively large representative stress σ _i (eg, the central portion of FIG. 3 (C)). Even if the representative stress σ _i is the same, if the size of the calculation grid used for strength evaluation is relatively large, the reliability _Ri is relatively small.

The destruction probability calculation unit 8 calculates the destruction probability by the weakest link model using the reliability of each element. FIG. 4B conceptually shows the weakest link model. In weakest link model, at least one of the plurality of elements (E 1 _{to E n)} and overall Disruption destroyed. At least one of the plurality of elements _(E 1 to E _n) the probability of fracture (fracture probability F) is expressed by the following equation (4). The second term on the right-hand side of Equation (4) is the probability that a plurality of elements _(E 1 to E _n) does not destroy any, represented by the multiplied value of the _{R 1} to _{R n.} The destruction probability calculation unit 8 calculates the destruction probability F according to the equation (4) using the reliability ( _Ri ) calculated by the reliability calculation unit 7.

Since the strength evaluation device 3 as described above calculates the reliability for each element and calculates the probability that at least one of the plurality of elements will break, the influence of the dimensional effect and the stress distribution can be added to the structure. Can be evaluated accurately. As a result, it is possible to know whether or not the strength of the structure is sufficient prior to the manufacture of the structure, so that, for example, the frequency of manufacturing and testing a prototype of the structure can be reduced.

Further, the strength evaluation device 3 of the present embodiment includes a stress distribution calculation unit 5. In this case, for example, the calculation grid for calculating the stress distribution and the calculation grid for strength evaluation can be shared. As a result, for example, it is possible to reduce the processing required for the conversion of the coordinate system and suppress the occurrence of an error due to the rounding of the numerical value when the coordinate system is converted. The calculation grid for calculating the strength may be different from the calculation grid for calculating the stress distribution. For example, the calculation grid for strength evaluation may have a smaller number of grids than the calculation grid for calculating the stress distribution.

The stress distribution calculation unit 5 may be provided in an external device of the strength evaluation device 3. For example, the strength evaluation device 3 may evaluate the strength of the structure based on the stress distribution supplied from the external device. In this case, the representative stress of the element may be calculated by the strength evaluation device 3 (eg, selection unit 6) or by an external device. Further, when the representative stress of the element is calculated by the strength evaluation device 3, the calculation of the representative stress may be executed by the selection unit 6 or by another part (eg, the reliability calculation unit 7). Good.

Further, the strength evaluation device 3 of the present embodiment includes a selection unit 6. In this case, the processing of the reliability calculation unit 7 and the processing of the destruction probability calculation unit 8 are omitted for the elements not selected by the selection unit 6, so that the processing load can be reduced. When the above threshold value σ _th is 0, it is possible to select necessary and sufficient elements for performing the strength evaluation with high accuracy. Further, when it is larger than the threshold value σ _th , the number of target elements is reduced, so that the processing load can be reduced. The strength evaluation device 3 does not have to include the selection unit 6, and for example, the reliability may be calculated for each of all the elements included in the portion specified by the user. In this case, the reliability calculation unit 7 may set the reliability R _i to a predetermined value (eg, 1) for the element E _i satisfying σ _i −σ _u ≦ 0.

Next, the strength evaluation method according to the embodiment will be described based on the configuration of the strength evaluation device 3 described above. FIG. 5 is a flowchart showing a strength evaluation method according to the embodiment. In step S1, for example, the user sets a portion of the structure for which strength is evaluated (eg, parallel portion 11b in FIG. 2A). In step S2, the selection unit 6 selects the element to be evaluated. For example, the selection unit 6 reads the representative stress σ _i , the position parameter σ _u , and the threshold value σ _th from the storage unit 9, and determines whether or not to calculate the reliability for each element.

In step S3, the reliability calculation unit 7 acquires the number (n) of the target elements. The strength evaluation device 3 calculates the reliability of each element in the processes of steps S4 to S7, and calculates the reliability of all the target elements by repeating the processes of steps S4 to S7. In step S4, the strength evaluation device 3 sets i to 1. In step S5, the stress distribution calculating unit 5, the stress value of the node belonging to the target element _{(E i),} calculating a representative stress of the target elements _{(E i) (σ i)} .

In step S6, the reliability calculation unit 7 calculates the reliability (R _i ) of the target element (E _i ) according to the above equation (3). In step S7, the strength evaluation device 3 determines whether or not the value of i has reached the number of target elements (n). When the strength evaluation device 3 determines that the value of i is less than n, the strength evaluation device 3 increments (+1) the value of i and repeats the processes of steps S5 to S7. When the strength evaluation device 3 determines that the value of i is n, the strength evaluation device 3 proceeds to the process of step S8.

In step S8, the destruction probability calculation unit 8 calculates the probability R that all the target elements are not destroyed. The destruction probability calculation unit 8 calculates the probability R by multiplying R1 by Rn. In step S9, the destruction probability calculation unit 8 calculates the destruction probability F that any target element destroys according to the above equation (4).

FIG. 6 is a diagram showing an evaluation example to which the strength evaluation method according to the embodiment is applied. In the graph of FIG. 6, the horizontal axis is the load [N], and the vertical axis is the cumulative failure probability. "Resin A" is an epoxy resin widely used for insulating electric power equipment, and contains quartz and the like as a filler in addition to a base resin and a curing agent. "Resin B" has lower elasticity than "Resin A", and contains particles having a core-shell structure in addition to a base resin, a curing agent, and quartz as a filler. The "analyzed value" is an evaluation result by the strength evaluation method according to the present embodiment. The "measured value" is a measurement result of a test using a plurality of samples. The "estimated value" is an estimated value based on the maximum stress theory.

As can be seen from FIG. 6, for both "resin A" and "resin B", the analysis values using the strength evaluation method according to the present embodiment are measured values as compared with the estimated values based on the maximum stress theory. Very close values were obtained. The following [Table 1] is a table showing the evaluation results of "resin A" and "resin B". The “prediction accuracy of the embodiment” is a value expressed as a percentage of the average fracture load calculated from the evaluation result according to the embodiment with the average fracture load calculated from the “measured value” as a reference. Further, the "prediction accuracy of the comparative example" is a value expressed as a percentage based on the average fracture load calculated from the "measured value" of the average fracture load based on the evaluation of the maximum principal stress theory.

Focusing on the prediction accuracy of "resin A", it is 68.7% in the comparative example, while it is 97.7% in the example, and the evaluation result according to the embodiment is often the measured value (measured value). It turns out that they match. Focusing on the prediction accuracy of "resin B", it is 72.4% in the comparative example and 98.4% in the example, and the evaluation result according to the embodiment is the measured value (measured value). It turns out that it matches well with. Further, for each of "resin A" and "resin B", strength evaluation was performed under a plurality of calculation conditions in which the number of elements was systematically changed from about 3500 to about 37000. As a result, the prediction accuracy of "resin A" was 97.7% to 100.3%, and the prediction accuracy of "resin B" was 98.4% to 99.4%. As the number of elements increases, the prediction accuracy tends to approach 100%, but even when the number of elements is 3500, sufficient prediction accuracy is obtained for grasping the intensity.

The Weibull parameter can be estimated by using, for example, a maximum likelihood estimation method. This estimation method is a method of preparing measurement data and obtaining a Weibull parameter so that the probability of obtaining the measurement data is maximized. First, a tensile test is performed a plurality of times using the test piece as shown in FIG. 2 (A) to obtain a measurement data group (σ _i ). Then, the shape parameter (m) and the position parameter (σ _u ) are obtained by using Newton's Rapson method or the like for the simultaneous equations shown in the following equation (5).

Then, by substituting the shape parameter (m) and the position parameter (σ _u ) obtained from the equation (5) into the following equation (6), the scale parameter (σ ₀ ) can be obtained.

Next, a method for manufacturing the structure according to the embodiment will be described based on the configuration of the manufacturing system shown in FIG. FIG. 7 is a flowchart showing a method of manufacturing the structure according to the embodiment. In step S11, the user designs the structure using the design device 2. In step S12, the strength evaluation device 3 determines whether or not there is a Weibull parameter. For example, the strength evaluation device 3 determines that there is a Weibull parameter when the user inputs the Weibull parameter (step S12; Yes). In this case, the strength evaluation device 3 uses the Weibull parameter input by the user in the following processing.

When the strength evaluation device 3 determines that there is no Weibull parameter (not specified) (step S12; No), the strength evaluation device 3 acquires the Weibull parameter stored in the storage unit 9 in step S13. For example, the storage unit 9 stores Weibull parameters according to the material of the structure as table data. The strength evaluation device 3 reads out the Weibull parameters corresponding to the material specified by the user and uses them in the following processing.

In step S14, the stress distribution calculation unit 5 calculates the stress distribution in the structure. For example, the stress distribution calculation unit 5 generates a calculation grid according to calculation conditions (eg, number of elements) specified by the user, and calculates the stress distribution by FEM or the like. In step S15, the strength evaluation device 3 evaluates the strength of the structure. The process of step S15 is a process to which the strength evaluation method according to the embodiment is applied, and is the same as the process shown in FIG.

In step S16, the user determines whether or not the strength of the structure satisfies a predetermined condition. For example, the user compares the strength required for the structure (hereinafter referred to as the required strength) with the evaluation result in step S15 in consideration of the safety factor, and the strength obtained from the evaluation result is equal to or higher than the required strength. In this case, it is determined that the strength satisfies a predetermined condition (step S16; Yes).

The process of step S16 may be automatically performed by the strength evaluation device 3 or another device. For example, the above-mentioned required strength is stored in advance in the storage unit 9 of the strength evaluation device 3, and the strength evaluation device 3 uses the required strength stored in the storage unit 9 as a threshold value and the strength obtained from the evaluation result as a threshold value. In comparison with, the process of step S16 may be performed. If it is determined in step S16 that the strength does not satisfy the predetermined condition (eg, the strength according to the evaluation result is less than the required strength) (step S16; No), the processes of steps S11 to S16 are repeated.

When it is determined in step S16 that the strength satisfies a predetermined condition (eg, the strength according to the evaluation result is equal to or higher than the required strength) (step S16; Yes), the processing apparatus 4 manufactures a mold. For example, in step S17, design data is supplied to the processing apparatus 4, and a mold is manufactured by numerical control (NC) using the design data. A prototype of the structure is produced in step S18 using the mold produced in step S17. The strength of the produced prototype is verified by testing in step S19. In step S20, it is determined whether or not the strength satisfies a predetermined condition. In step S16, the strength obtained from the evaluation result and the required strength were compared, but in step S20, the strength obtained from the test result (measured value) was used instead of the strength obtained from the evaluation result, and the strength was compared with step S16. Perform the same process.

If it is determined in step S20 that the strength does not satisfy the predetermined condition (eg, the strength obtained from the test result is less than the required strength) (step S20; No), the processes of steps S11 to S20 are repeated. When it is determined in step S20 that the strength satisfies a predetermined condition (eg, the strength according to the test result is equal to or higher than the required strength) (step S20; Yes), the product of the structure is manufactured based on the design data.

In FIG. 7, an example in which a prototype of the structure is manufactured (manufactured) in step S18 and a product of the structure is manufactured in step S21 has been described. However, the method of manufacturing the structure according to the embodiment is a prototype. It may be applied to manufacture only one of the product and the product. For example, a product may be manufactured instead of the prototype in step S18, and the processing of steps S19 to S21 may be omitted. Further, the method for manufacturing the structure according to the embodiment may be used to manufacture a prototype in step S18 and provide the prototype. Further, the method for manufacturing a structure according to the embodiment may be used to determine the design data of the structure in the processes up to step S20 and to provide the determined design data.

Although FIG. 7 has described an example in which the strength evaluation method according to the embodiment is applied to the structure manufacturing method, the strength evaluation method according to the embodiment may be applied to other than the manufacturing of the structure. For example, the strength evaluation method according to the embodiment can also be used for predicting fracture of an existing structure. In addition, the strength evaluation method according to the embodiment can also be used to elucidate the cause when the existing structure is damaged.

In the above-described embodiment, the strength evaluation device 3 includes, for example, a computer system. The strength evaluation device 3 reads out the strength evaluation program stored in the storage unit 9 and executes various processes according to the strength evaluation program. This strength evaluation program gives a computer a confidence that indicates the probability that each element will not break using the stress acting on each element for each of the multiple elements in the numerical model of the structure, including those molded with epoxy. The calculation is performed, and the reliability is multiplied by a plurality of elements to calculate the destruction probability indicating the probability that at least one of the plurality of elements is destroyed. This intensity evaluation program may be provided recorded on a computer-readable storage medium.

In the above-described embodiment, the material for brittle fracture is an epoxy resin, but a material other than the epoxy resin may be used. For example, the strength evaluation according to the embodiment can be widely applied to structures that require insulation and mechanical strength. For example, the strength evaluation according to the embodiment is widely applicable to a structure that supports a conductor or an electric component that serves as a path for electric power and is composed of a material that breaks brittlely. In the above-described embodiment, the finite element analysis model is used as the numerical model, but the numerical model may be a numerical model to which other discretization methods (eg, finite volume method, boundary element method) are applied.

The technical scope of the present invention is not limited to the embodiments described in the above-described embodiments. One or more of the requirements described in the above embodiments and the like may be omitted. In addition, the requirements described in the above-described embodiments can be combined as appropriate. In addition, to the extent permitted by law, the disclosure of all documents cited in the above-mentioned embodiments and the like shall be incorporated as part of the description in the main text.

1 ... Manufacturing system 2 ... Design equipment 3 ... Strength evaluation equipment 4 ... Processing equipment 5 ... Stress distribution calculation unit 6 ... Selection unit 7 ... Reliability calculation unit 8 ...・ Destruction probability calculation unit 9 ・ ・ ・ Storage unit

Claims (9)

For each of a plurality of elements in a numerical model of a structure composed of a material that breaks brittlely, the reliability indicating the probability that each element does not break is calculated by using the stress acting on each element.
Wherein the result of multiplying signal Yoriyukido of each element is subtracted from 1, the strength evaluation method comprising, comprising: at least one of said plurality of elements is to calculate the fracture probability indicating the probability of fracture. The strength evaluation method according to claim 1, wherein the brittle fracture material is an epoxy resin. The shape parameter, scale parameter, and position parameter representing the Weibull distribution of the strength of the structure are m, σ0, and σu, respectively, and the stress and volume of the element whose number is i assigned to each of the plurality of elements is σi, respectively. Li (σi), which is Vi, the reference volume of the plurality of elements is V0, and the reliability of the element whose number is i is represented by the following formula (1) , claim 1 or claim. Item 2. The strength evaluation method according to Item 2.
The strength evaluation method according to any one of claims 1 to 3, wherein the target element for calculating the reliability is selected from the structure. An element that satisfies σ−σu> σth when the stress acting on the element of the structure is σ, the position parameter in the Weibull distribution of the strength of the structure is σu, and the predetermined threshold value of 0 or more is σth. The strength evaluation method according to claim 4, wherein is selected as the target element. Including calculating the distribution of stress acting on the structure prior to the calculation of the reliability.
The method according to any one of claims 1 to 5, wherein a representative value of stress acting on each of the plurality of elements is calculated based on the stress distribution, and the reliability is calculated using the representative value. Strength evaluation method. Designing a structure that contains materials that break brittlely,
Based on the design, the strength of the structure is evaluated by the strength evaluation method according to any one of claims 1 to 6.
A method for manufacturing a structure, comprising manufacturing the structure when the strength satisfies a specific condition . For each of a plurality of elements in a numerical model of a structure composed of a material that breaks brittlely, a reliability calculation unit that calculates the reliability indicating the probability that each element does not break using the stress acting on each element.
Wherein the result of multiplying signal Yoriyukido of each element is subtracted from 1, the strength evaluation apparatus and a fracture probability calculation unit at least one of said plurality of elements is to calculate the fracture probability indicating the probability of fracture. On the computer
For each of the multiple elements in a numerical model of a structure composed of brittle fracture materials, the stress acting on each element is used to calculate the reliability that indicates the probability that each element will not fracture.
Wherein the result of multiplying signal Yoriyukido of each element is subtracted from 1, the strength evaluation program at least one of said plurality of elements is to execute, and calculating the fracture probability indicating the probability of fracture.