Stiffener design support device, stiffener design support method, and stiffener design support program

Abstract

To provide a stiffener design support device capable of further reducing an information processing amount, a stiffener design support method, and a stiffener design support program.SOLUTION: A stiffener design support apparatus 1000 according to the present invention is an apparatus for supporting design of a stiffener in a structure including a pair of first and second plate-like members and the stiffener disposed between the first and second plate-like members, the apparatus being configured to generate, as a first design structure, the structure in which the stiffener includes a plurality of sub members each having a predetermined dimension set in advance, and generate, as a second design structure, the structure by a total stress design method so as to reduce a total weight of the stiffener with a first target value of static stiffness, the structure is generated as a third design structure by the total stress design method so that the total weight of the stiffener is reduced with the second target value of the dynamic stiffness, and the structure is generated as a fourth design structure by the genetic algorithm so that the first to third design structures are included in the individuals of the first generation and the total weight of the stiffener is reduced, and the fourth design structure is output.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a stiffener design support device, a stiffener design support method, and a stiffener design support program that support the design of stiffeners in structures. [Background technology]

[0002] A method using a genetic algorithm (GA) is known for designing structures (for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Masateru Asayama, Hiroshi Hasegawa, Keiji Kawatsura, "A Numerical Experiment on Size Optimization of Truss Structures under Stress Constraints Using GA (Mainly Study of a Hybrid Method Combining Total Stress Design and GA)," Transactions of the Japan Society of Mechanical Engineers (Series A), Vol. 62, No. 597 (May 1996) Summary of the Invention [Problem to be solved by the invention]

[0004] In a genetic algorithm, generations are replaced until a preset number of generations is reached or until the differences between generations are substantially eliminated, and the optimal individual (the individual with the highest fitness or highest evaluation value) is selected as the solution from the individuals in the final generation. For this reason, information processing such as individual evaluation, individual selection, crossover, and mutation is required for each generation, and it is desirable to reduce the amount of information processing work.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a stiffener design support device, a stiffener design support method, and a stiffener design support program that can further reduce the amount of information processing when a genetic algorithm is used to design a stiffener in a structure. [Means for solving the problem]

[0006] After various studies, the inventors have found that the above object can be achieved by the present invention described below. That is, a stiffener design support device according to one aspect of the present invention is a stiffener design support device that supports the design of a stiffener in a structure including a pair of first and second plate-like members and a stiffener disposed between the first and second plate-like members, and includes a first design structure generation unit that generates, as a first design structure, the structure including a plurality of sub-members with a predetermined dimension that has been set in advance, and a second design structure that generates, as a second design structure, the structure by a total stress design method so that the total weight of the stiffener is reduced at a first target value of static stiffness. a third designed structure generation unit that generates the structure as a third designed structure by a total stress design method so that the total weight of the stiffener is reduced at a second target value of dynamic stiffness; a fourth designed structure generation unit that includes the first to third designed structures determined by the first to third designed structure generation units, respectively, in a first generation of individuals and generates the structure as a fourth designed structure by a genetic algorithm so that the total weight of the stiffener is reduced; and an output unit that outputs the fourth designed structure generated by the fourth designed structure generation unit.

[0007] When designing a stiffener for a structure using a genetic algorithm, such a stiffener design support device includes the first to third design structures as individuals in the first generation (initial generation), so that individuals more suitable for the solution can be expected to emerge in fewer generations, thereby reducing the amount of information processing.

[0008] In another aspect, in the above-mentioned stiffener design support device, the fourth design structure generation unit uses a linear sum or a weighted linear sum of the total weight of the stiffener and a multiplication result obtained by multiplying the total weight by a penalty value that is assigned depending on whether or not predetermined constraint conditions are satisfied, as an evaluation function for evaluating the quality of an individual, wherein the predetermined constraint conditions include a first sub-constraint condition regarding static stiffness and a second sub-constraint condition regarding dynamic stiffness, the penalty term is a simple average of a first sub-penalty value that is assigned depending on whether or not the first sub-constraint condition is satisfied and a second sub-penalty value that is assigned depending on whether or not the second sub-constraint condition is satisfied, and the evaluation function evaluates the individual as being better the smaller the value. Preferably, in the above-described stiffener design support device, when an individual satisfies the first sub-constraint condition, the first sub-penalty value is 0, and when the individual does not satisfy the first sub-constraint condition, the first sub-penalty value is a predetermined first value that is set in advance, and when the individual satisfies the second sub-constraint condition, the second sub-penalty value is 0, and when the individual does not satisfy the second sub-constraint condition, the second sub-penalty value is a predetermined second value that is set in advance.

[0009] Such a stiffener design support device can obtain a structure that satisfies a first sub-constraint condition regarding static stiffness and a second sub-constraint condition regarding dynamic stiffness.

[0010] In another aspect, in the above-described stiffener design support device, the penalty term is weighted with a weight that increases as the number of generations increases and becomes a constant value when the number of generations becomes equal to or greater than a predetermined threshold value.

[0011] In such a stiffener design support device, the penalty term is weighted with a weight that increases as the number of generations increases, so that individuals that do not satisfy at least one of the first and second sub-constraint conditions can be eliminated in a fewer number of generations, and therefore individuals that are more suitable for the solution can be selected in a fewer number of generations.

[0012] In another aspect, in the above-mentioned stiffener design support device, the stiffener comprises a plurality of sub-members within a predetermined weight range, and the third design structure generation unit determines an overlapping normalized stress range of a first normalized stress range at the time of natural vibration in the structure comprising the plurality of sub-members in which the stiffener has a minimum weight in the predetermined weight range and a second normalized stress range at the time of natural vibration in the structure comprising the plurality of sub-members in which the stiffener has a maximum weight in the predetermined weight range, and calculates a total stress range so that the total weight of the stiffener is small at each target value of the maximum value, median value, and minimum value in the overlapping normalized stress range. Using the force design method, each of the structures is determined as a maximum value design structure, a median value design structure, and a minimum value design structure, and for each of the determined maximum value design structure, median value design structure, and minimum value design structure, the straight lines that best fit when coordinate points are plotted on a total weight-static stiffness Cartesian coordinate system with total weight and static stiffness as two axes, a static stiffness-dynamic stiffness Cartesian coordinate system with static stiffness and dynamic stiffness as two axes, and a dynamic stiffness-total weight Cartesian coordinate system with dynamic stiffness and total weight as two axes are determined, and the total weight is determined by setting up simultaneous linear equations that represent each of the determined straight lines, and a normalized stress is determined as a second target value for the dynamic stiffness based on the determined total weight.

[0013] Such a stiffener design support device can determine a second target value for dynamic stiffness by specifying the weight range of the sub-member, and can determine a structural part that takes dynamic stiffness into account using the full stress design method.

[0014] In another aspect, in the above-mentioned stiffener design support device, the stiffener is a rectangular plate whose thickness can be designed, and includes a plurality of sub-members arranged in a lattice pattern.

[0015] This makes it possible to provide a stiffener design support device that supports the design of a stiffener having a rectangular plate shape whose thickness can be designed and that includes a plurality of sub-members arranged in a lattice pattern.

[0016] A stiffener design support method according to another aspect of the present invention is a stiffener design support method for supporting the design of a stiffener in a structure including a pair of first and second plate-like members and a stiffener disposed between the first and second plate-like members, the method including a first design structure generation step of generating, as a first design structure, the structure including a plurality of sub-members with predetermined dimensions set in advance for the stiffener; and a second design structure generation step of generating, as a second design structure, the structure using a total stress design method so that the total weight of the stiffener is reduced at a first target value of static stiffness. The method comprises a designed structure generation process, a third designed structure generation process for generating the structure as a third designed structure by a total stress design method so that the total weight of the stiffener is reduced at a second target value of dynamic stiffness, a fourth designed structure generation process for generating the structure as a fourth designed structure by a genetic algorithm, including each of the first to third designed structures obtained in the first to third designed structure part generation processes, respectively, in a first generation individual so that the total weight of the stiffener is reduced, and an output process for outputting the fourth designed structure obtained in the fourth designed structure generation process.

[0017] In this stiffener design support method, when designing a stiffener for a structure using a genetic algorithm, the first to third design structures are included in the individuals of the first generation (initial generation), so that individuals more suitable for the solution can be expected to appear in fewer generations, thereby reducing the amount of information processing.

[0018] A stiffener design support program according to another aspect of the present invention is a stiffener design support program that supports the design of a stiffener in a structure comprising a pair of first and second plate-like members and a stiffener disposed between the first and second plate-like members, and causes a computer to function as a stiffener design support device for either of these members.

[0019] This makes it possible to provide a stiffener design support program, which has the same effects as the stiffener design support devices described above. [Effects of the Invention]

[0020] The stiffener design support device, stiffener design support method, and stiffener design support program according to the present invention can further reduce the amount of information processing when a genetic algorithm is used to design a stiffener in a structure. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a block diagram showing a configuration of a stiffener design support device according to an embodiment. [Figure 2] As an example, it is a diagram for explaining a structure. [Figure 3] FIG. 10 is a diagram illustrating a first normalized stress range, a second normalized stress range, and an overlap normalized stress range, as an example. [Figure 4] As an example, this figure shows changes in the total plate thickness (objective function), static stiffness (bending load displacement amount), and dynamic stiffness (natural frequency) in repeated calculations. [Figure 5] As an example, this figure shows the relationship between total plate thickness and static stiffness, the relationship between static stiffness and dynamic stiffness, and the relationship between dynamic stiffness and total plate thickness for a maximum value design structure, a median design structure, and a minimum value design structure. [Figure 6] FIG. 10 is a diagram showing, as an example, the relationship between the total weight and the normalized stress (reference normalized stress) determined based on the total weight. [Figure 7] As an example, this is a diagram showing the transition of stiffeners in a third design structure obtained by the iterative calculation. [Figure 8] FIG. 10 is a diagram showing, as an example, histograms of normalized stresses occurring in each stiffener in each of the first and third design structures. [Figure 9] 4 is a flowchart showing the operation of the stiffener design support device in the embodiment. [Figure 10] FIG. 10 is a diagram showing, as an example, the results of comparison between an example and first to third comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. In addition, components with the same reference numerals in each drawing indicate the same components, and their description will be omitted as appropriate. In this specification, when referring to a general term, a reference numeral without a subscript is used, and when referring to an individual component, a reference numeral with a subscript is used.

[0023] A stiffener design support device in an embodiment is a device for supporting design of a stiffener in a structure including a pair of first and second plate-like members and a stiffener disposed between the first and second plate-like members, and includes first to fourth design structure generation units and an output unit. The first design structure generation unit generates, as a first design structure, the structure including a plurality of sub-members each having a predetermined dimension set for the stiffener. The second design structure generation unit generates, as a second design structure, the structure using a full stress design method so that the total weight of the stiffener is reduced at a first target value for static stiffness. The third design structure generation unit generates, as a third design structure, the structure using a full stress design method so that the total weight of the stiffener is reduced at a second target value for dynamic stiffness. The fourth designed structure generation unit includes the first to third designed structures determined by the first to third designed structure generation units, respectively, in first-generation individuals, and generates the structure as a fourth designed structure using a genetic algorithm so that the total weight of the stiffener is reduced. The output unit outputs the fourth designed structure generated by the fourth designed structure generation unit. Such a stiffener design support device, as well as a stiffener design support method and stiffener design support program implemented therein, will be described in more detail below.

[0024] FIG. 1 is a block diagram showing the configuration of a stiffener design support device according to an embodiment. FIG. 2 is a diagram illustrating a structure, as an example. FIG. 2A is an external perspective view of the structure, and FIG. 2B is an external perspective view of a stiffener in the structure. FIG. 3 is a diagram illustrating, as an example, a first normalized stress range, a second normalized stress range, and an overlap normalized stress range. The horizontal axis of FIG. 3 represents thickness [mm], and the vertical axis represents normalized stress. FIG. 4 is a diagram illustrating, as an example, changes in the total plate thickness (objective function), static stiffness (bending load displacement), and dynamic stiffness (natural frequency) during repeated calculations. FIG. 4A shows changes in the total plate thickness (objective function) during repeated calculations, with the horizontal axis representing the number of repeated calculations and the vertical axis representing the total plate thickness (objective function) [mm]. FIG. 4B shows changes in the static stiffness (bending load displacement) during repeated calculations, with the horizontal axis representing the number of repeated calculations and the vertical axis representing the static stiffness (bending load displacement) [mm]. FIG. 4C shows the change in dynamic stiffness (natural frequency) during repeated calculations, with the horizontal axis representing the number of repeated calculations and the vertical axis representing dynamic stiffness (natural frequency) [Hz]. FIG. 5 shows, as an example, the relationship between total plate thickness and static stiffness, the relationship between static stiffness and dynamic stiffness, and the relationship between dynamic stiffness and total plate thickness for a maximum-value design structure, a median-value design structure, and a minimum-value design structure. FIG. 5A shows the relationship between total plate thickness and static stiffness, with the horizontal axis representing static stiffness (bending load displacement) [mm] and the vertical axis representing total plate thickness (objective function) [mm]. FIG. 5B shows the relationship between static stiffness and dynamic stiffness, with the horizontal axis representing static stiffness (bending load displacement) [mm] and the vertical axis representing dynamic stiffness (natural frequency) [Hz]. FIG. 5C shows the relationship between dynamic stiffness and total plate thickness, with the horizontal axis representing dynamic stiffness (natural frequency) [Hz] and the vertical axis representing total plate thickness (objective function) [mm]. Fig. 6 is a diagram showing, as an example, the relationship between total weight and normalized stress (reference normalized stress) calculated based on the total weight. The horizontal axis of Fig. 6 is total plate thickness [mm], and the vertical axis is reference normalized stress. Fig. 7 is a diagram showing, as an example, the transition of stiffeners in the iterative calculations in a third designed structure calculated by the iterative calculations. Fig. 8 is a diagram showing, as an example, histograms of normalized stresses occurring in each stiffener in each of the first and third designed structures.Figure 8A shows the case of the first design structure, and Figure 8B shows the case of the third design structure. The horizontal axis of each of Figures 8A and 8B is normalized stress, and the vertical axis of each of these is frequency.

[0025] The stiffener design support device 1000 in the embodiment is a device that supports the design of a stiffener (stiffener, reinforcing material) in a structure, and includes, for example, a control processing unit 1, an input unit 2, an output unit 3, an interface unit (IF unit) 4, and a memory unit 5, as shown in FIG. 1 .

[0026] The structure may be any structure as long as it includes a pair of first and second plate-shaped members and a stiffener disposed between the first and second plate-shaped members. The first and second plate-shaped members may have flat surfaces entirely, but do not necessarily have to have flat surfaces entirely; all or part of the surface may be curved. The stiffener may be any member that reinforces the structure. In one example, as shown in FIG. 2, a structure Ob includes a first plate-shaped member PT1 that is a rectangular (square in this example) top panel, a second plate-shaped member PT2 (not shown) that is a rectangular (square in this example) bottom panel, four rectangular side panels, first to fourth side plate-shaped members SP1 to SP4 (third and fourth side plate-shaped members SP3 and SP4 are not shown), and a stiffener SF. The first and second plate-shaped members PT1 and PT2 face each other and have the same shape, and the first through fourth side plate-shaped members SP1 to SP4 also have the same shape and are arranged to surround the sides of the first and second plate-shaped members PT1 and PT2, which are arranged to face each other. The stiffener SF is composed of a plurality of sub-members ST within a predetermined weight range. The predetermined weight range is set in advance as appropriate depending on, for example, the specifications of the structure Ob. In the example shown in FIG. 2, the stiffener SF is composed of 40 sub-members ST1 to ST40 arranged in a lattice pattern. The reference symbols ST1 to ST40 of the sub-members ST are given in order from ST1 to ST40, from the top left to the bottom right of the page, but due to space limitations, some of the reference symbols ST1 to ST40, such as ST10 to ST12, ST15 to ST17, ST19 to ST22, ST24 to ST26, ST28 to ST30, and ST33 to ST35, are not shown in the illustration. Each of the first to fortieth sub-members ST1 to ST40 is a rectangular plate with the same horizontal and vertical lengths, and whose volume and therefore weight (mass) change when its thickness is changed. The stiffener SF is arranged within a rectangular box formed by the first and second plate-shaped members PT1, PT2 and the first to fourth side plate-shaped members SP1 to SP4 so that its upper end is connected to the first plate-shaped member PT1, its lower end is connected to the second plate-shaped member PT2, and each side end is connected to the first to fourth side plate-shaped members SP1 to SP4.

[0027] In addition, the grid lines drawn on each member PT1, SP1, SP2, ST1 to ST40 are lines drawn to indicate each element, since in this embodiment, stresses, etc. are determined by numerical analysis using the finite element method, as described below.

[0028] 1, the input unit 2 is connected to the control processing unit 1 and is a device that inputs various data necessary for operating the stiffener design support device 1000, such as various commands such as a command to start calculations, the name of the structure Ob to be designed, and various quantities, to the stiffener design support device 1000, and is, for example, a keyboard, a mouse, a plurality of input switches to which predetermined functions are assigned, etc. The output unit 3 is connected to the control processing unit 1 and is a device that outputs commands, data, calculation results, etc. input from the input unit 2 in accordance with the control of the control processing unit 1, and is, for example, a display device such as a CRT display, an LCD (liquid crystal display), or an organic EL display, or a printing device such as a printer.

[0029] The input unit 2 and the output unit 3 may be configured as a touch panel. In the case of configuring this touch panel, the input unit 2 is a position input device that detects and inputs an operation position, for example, of a resistive film type or a capacitive type, and the output unit 3 is a display device. In this touch panel, a position input device is provided on the display surface of the display device, and one or more input content candidates that can be input are displayed on the display device. When a user touches a display position that displays the input content that the user wants to input, the position is detected by the position input device, and the display content displayed at the detected position is input to the stiffener design support device 1000 as the user's operation input content. With such a touch panel, the user can easily intuitively understand the input operation, and therefore a stiffener design support device 1000 that is easy for the user to use is provided.

[0030] The IF unit 4 is connected to the control processing unit 1 and is a circuit that inputs and outputs data to and from, for example, an external device under the control of the control processing unit 1, and is, for example, an interface circuit for RS-232C, which is a serial communication method, an interface circuit using the Bluetooth (registered trademark) standard, an interface circuit using the USB standard, etc. The IF unit 4 may also be, for example, a communication interface circuit that transmits and receives communication signals to and from an external device, such as a data communication card or a communication interface circuit conforming to the IEEE802.11 standard, etc.

[0031] The storage unit 5 is connected to the control processing unit 1 and is a circuit that stores various predetermined programs and various predetermined data under the control of the control processing unit 1.

[0032] The various predetermined programs include, for example, a control processing program, and the control processing program includes, for example, a control program and first to fourth design structure part generation programs. The control program controls each of the parts 2 to 5 of the stiffener design support device 1000 according to the function of each part. The first design structure part generation program is a program that generates, as a first design structure, the structure in which the stiffener comprises a plurality of sub-members having predetermined dimensions. The second design structure generation program is a program that generates, as a second design structure, the structure by a full stress design method so that the total weight of the stiffener is reduced at a first target value of static stiffness. The third design structure generation program part is a program that generates, as a third design structure, the structure by a full stress design method so that the total weight of the stiffener is reduced at a second target value of dynamic stiffness. The fourth designed structure generation program is a program that includes the first to third designed structures obtained by the first to third designed structure part generation programs, respectively, in first generation (initial generation) individuals and generates the structure as a fourth designed structure by a genetic algorithm so that the total weight of the stiffeners is reduced. Then, the control program outputs the fourth designed structure generated by the fourth designed structure generation program to an output unit 3.

[0033] The various predetermined data include, for example, the name of the structure Ob to be designed, various quantities such as the dimensions and physical properties of the structure Ob, various calculation results during the calculation, and the final calculation results, etc., data necessary for executing each of these programs.

[0034] The storage unit 5 includes, for example, a ROM (Read Only Memory), which is a nonvolatile storage element, and an EEPROM (Electrically Erasable Programmable Read Only Memory), which is a rewritable nonvolatile storage element. The storage unit 5 also includes a RAM (Random Access Memory), which serves as a working memory for the control processing unit 1 and stores data generated during execution of the predetermined program. The storage unit 5 may also be configured with a hard disk drive or solid state drive (SSD) with a relatively large storage capacity.

[0035] The control processing unit 1 is a circuit that controls each of the units 2 to 5 of the stiffener design support device 1000 in accordance with the function of each unit and supports the design of a stiffener. The control processing unit 1 is configured to include, for example, a CPU (Central Processing Unit) and its peripheral circuits. In the control processing unit 1, a control unit 11 and first to fourth design structure generation units 12 to 15 are functionally configured by executing the control processing program.

[0036] The control unit 11 controls each of the units 2 to 5 of the stiffener design support device 1000 in accordance with the function of each unit, and is in charge of overall control of the stiffener design support device 1000.

[0037] The first designed structure generation unit 12 generates, as the first designed structure, the structure comprising a plurality of sub-members, each of which has a stiffener of a predetermined dimension that has been set in advance. More specifically, the first designed structure generation unit 12 obtains, as the first designed structure, the structure comprising a plurality of sub-members, each of which has a stiffener of the same dimension and shape. For example, in the example shown in FIG. 2, in one numerical example, the first to fortieth sub-members ST1 to ST40 are each an iron plate of 10 [mm] × 20 [mm] × t [mm] (thickness t = 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8), and their Young's modulus is 1.96 × 10 5 [MPa], and its density is 8.01×10 -6 [kg / mm 3 ] and the Poisson's ratio was set to 0.3. In this example, the predetermined weight range (mass range) was set to 10×20×0.4×8.01×10 -6 (=640.8×10 -6 ) [kg], 10 × 20 × 1.8 × 8.01 × 10 -6 (=2883.6×10 -6 ) [kg], and can be expressed as a plate thickness range from 0.4 [mm] to 1.8 [mm]. In the example shown in FIG. 2, the first designed structure generation unit 12 determines a structure Ob comprising the first to fortieth sub-members ST1 to ST40 with t=1.0 [mm] as the first designed structure Base. The external dimensions of the structure Ob are 50 [mm] × 50 [mm] × 20 [mm]. Note that it is not necessarily necessary for the structure Ob comprising the first to fortieth sub-members ST1 to ST40 with t=1.0 to be the first designed structure Base, but here a value approximately in the middle of the weight range (plate thickness range in this example) is used.

[0038] The second design structure generation unit 13 generates the structure as a second design structure using a fully stressed design method so that the total weight of the stiffeners is reduced at a first target value of static stiffness. More specifically, the second design structure generation unit 13 generates the structure as a second design structure using a fully stressed design method so that the stress distribution of the stiffeners is leveled and the total weight is reduced at the first target value of static stiffness. In other words, the second design structure generation unit 13 generates the structure as a second design structure using a fully stressed design method so that the static stiffness for each plate thickness of each stiffener is reduced, thereby reducing the total weight of the stiffeners. The fully stressed design method (FSD) is generally a known technique for minimizing weight (mass) by uniformly distributing the stress σ generated in a member throughout the entire member to the minimum necessary level. More specifically, the second design structure generation unit 13 optimizes the thickness of element n so that the von Mises stress (hereinafter simply referred to as "stress") generated in element n of the finite element method in the structural part Ob when subjected to static load becomes the first target value of static stiffness (stress target value). [k] The load applied to element n in F n [k] and this load F n [k] The stress generated in element n by σ n [k] and the thickness is t n [k] The target stress value is σ st Then, the following equation 1 holds, and from this equation 1, the thickness t n [k+1] is given by the following equation 2.

[0039]

number

[0040]

number

[0041] The second design structure generation unit 13 generates an initial structure Ob [1] For example, the first design structure Base is used, and the structure Ob [k] A static bending load is applied to the thickness t n [k] The stress σ generated in each element n n [k] is calculated using the finite element method, and the thickness t n [k+1] The static bending load is calculated as follows. In the example shown in FIG. 2, the static bending load is 100 [N] each and is applied from top to bottom to both end points of the upper edge of one side plate member SP (e.g., the third side plate member SP3) facing the first side plate member SP, with the four vertices (four corners) of the other side plate member SP (the first side plate member SP1 in this example) fixed. The static stiffness is expressed (evaluated) as the average downward displacement of both end points (bending load displacement = ((displacement of one end point) + (displacement of the other end point)) / 2) a2 [mm] when the static bending load is applied from top to bottom to the both end points, with the positions of the both end points of the other side plate member SP (the first side plate member SP1 in this example) when the static bending load is not applied to the structure Ob as reference 0. The finite element method may be, for example, the Lanczos method implemented in MSC Nastran, a vibration structural analysis software manufactured by HEXAGON. The number of elements in each of the first to fortieth sub-members ST1 to ST40 was set to 5×10=50, the number of elements in each of the first and second plate-shaped members PT1 and PT2 was set to 25×25=625, and the number of elements in each of the first to fourth side plate-shaped members SP1 to SP4 was set to 25×10=250, and element n was set to a shell element in the finite element method. n [k+1] and thickness t n [k] The k+1-th thickness t is repeatedly measured until the difference between the thickness t and the k+1-th thickness t is equal to or less than the predetermined first tolerance value set appropriately in advance. n [k+1] The second design structure generation unit 13 calculates the thickness t n [k+1] (|t n [k+1] -t n[k] A structure Ob having a plurality of sub-members ST (the first to fortieth sub-members ST1 to ST40 in the example shown in Figure 2) each having a first tolerance | or less) is designated as the second design structure FSD-Bending.

[0042] The third design structure generation unit 14 generates the structure as a third design structure using a total stress design method so that the total weight of the stiffener is reduced at a second target value of dynamic stiffness. More specifically, the third design structure generation unit 14 generates the structure as a third design structure using a total stress design method so that the stress distribution of the stiffener is leveled and the total weight is reduced at the second target value of dynamic stiffness. More specifically, the third design structure generation unit 14 generates the structure as a third design structure using a total stress design method so that the quotient of the normalized stress generated in the stiffener divided by its plate thickness is reduced at the second target value of dynamic stiffness. When a structure vibrates at the frequency of its natural vibration, resonance often causes the amplitude to become significantly large, leading to destruction. For this reason, the dynamic stiffness of a structure can be evaluated using the frequency of its natural vibration. Designing a structure to have a high frequency of its natural vibration makes it less likely to resonate, resulting in excellent dynamic stiffness. Here, the mass matrix is ​​[M], the damping matrix is ​​[C], the stiffness matrix is ​​[K], and the acceleration vector is {X ··} and the velocity vector is {X ·} and the displacement vector is {X}, the equation of motion when no external force is acting is expressed by the following equation 3. If the natural vibration is in an undamped state, [C] = 0, so ω 2 If is the eigenvalue (ω is the angular frequency of the natural vibration) and Φ is the eigenvector, then Equation 3 can be transformed into the following Equation 4. Note that for convenience of description, the "··" and "·" immediately above X in Equation 3 are written as superscripts of X in the text. Others will be written in the same way hereinafter.

[0043]

number

[0044]

number

[0045] Equation 4 represents a general eigenvalue problem, and the normalization conditions are given by the following equations 5-1 and 5-2.

[0046]

number

[0047] From Equation 5-1 and Equation 5-2, the normalized eigenvector {Φ} is obtained, and the normalized von Mises stress σ ~ The normalized eigenvector {Φ} and normalized stress σ ~ The Lanczos method (an iterative method for solving eigenvalue problems) implemented in the eigenvalue analysis software SOL103 of the linear analysis software MSC Nastran is used for the calculation.

[0048] Therefore, the third design structure generation unit 14 calculates the normalized stress σ at the time of natural vibration, which is generated in the element n of the finite element method in the structural unit Ob and is obtained as described above. ~ is the second target value of dynamic stiffness (normalized stress target value) σ ~ st The thickness t of element n is optimized so that: In the example shown in Figure 2, the dynamic stiffness is expressed (evaluated) by the natural frequency in the first torsional mode. For the eigenvalue analysis, the Lanczos method implemented in SOL103 of the MSC Nastran is used. More specifically, in the repeated calculation, the thickness t of the kth element is n [k] and the (k+1)-th thickness t n [k+1] Similar to Equation 2, Equation 6 holds between the thickness t n [k+1] and thickness t n [k] The k+1-th thickness t is repeatedly measured until the difference between the thickness t and the k+1-th thickness t is equal to or less than the predetermined second tolerance value set appropriately in advance. n [k+1] and calculate the thickness t n[k+1] (|t n [k+1] -t n [k] A structure Ob having a plurality of sub-members ST (the first to fortieth sub-members ST1 to ST40 in the example shown in FIG. 2) each having a second tolerance value | or less) is defined as a third design structure FSD-EigenF.

[0049]

number

[0050] To perform the above-mentioned repeated calculations, the second target value of dynamic stiffness (normalized stress target value) σ ~ st In this setting, the third design structure generation unit 14 first determines an overlapping normalized stress range of a first normalized stress range at natural vibration of the structure including the plurality of sub-members in which the stiffener has a minimum value within the predetermined weight range, and a second normalized stress range at natural vibration of the structure including the plurality of sub-members in which the stiffener has a maximum value within the predetermined weight range. Next, the third design structure generation unit 14 determines each of the structures as a maximum value design structure, a median value design structure, and a minimum value design structure using a total stress design method so that the total weight of the stiffener is small at each target value of the maximum value, median value, and minimum value within the overlapping normalized stress range. Next, the third design structure generation unit 14 finds straight lines that best fit when plotting coordinate points for each of the found maximum value design structure, median value design structure, and minimum value design structure on a total weight-static stiffness Cartesian coordinate system with total weight and static stiffness as two axes, a static stiffness-dynamic stiffness Cartesian coordinate system with static stiffness and dynamic stiffness as two axes, and a dynamic stiffness-total weight Cartesian coordinate system with dynamic stiffness and total weight as two axes, and then finds the total weight by solving simultaneous linear equations representing each of the found straight lines.The third design structure generation unit 14 then calculates the normalized stress based on the found total weight to the second target value of dynamic stiffness (normalized stress target value) σ ~ st In this way, the normalized stress is calculated based on the total weight as the second target value (normalized stress target value) σ of the dynamic stiffness. ~ stBy calculating as above, the third design structure FSD-EigenF in the case of dynamic stiffness can be obtained using the full stress design method.

[0051] In the example shown in FIG. 2, the weight range is expressed by the plate thickness range, and the plate thickness range is 0.4 [mm] to 1.8 [mm]. Therefore, the design structure T min The first normalized stress range σ at natural vibration ~ n (T min ) is obtained, and the maximum value of the designed structure T max The second normalized stress range σ at natural vibration ~ n (T max ) is required. More specifically, the design structure T min Normalized stress σ occurring in element n during natural vibration ~ is calculated in the same manner as above by using the above formulas 5-1 and 5-2, and the maximum value is σ ~ n-max (T min ) and the minimum value is σ ~ n-min (T min ), then σ ~ n-min (T min )≦σ ~ n (T min )≦σ ~ n-max (T min ) as the first normalized stress range σ ~ n (T min ) is required. Design structure T max Normalized stress σ occurring in element n during natural vibration ~ is calculated in the same manner as above by using the above formulas 5-1 and 5-2, and the maximum value is σ ~ n-max (T max ) and the minimum value is σ ~ n-min (T max ), then σ ~n-min (T max )≦σ ~ n (T max )≦σ ~ n-max (T max ) as the second normalized stress range σ ~ n (T max ) is obtained. Then, the first normalized stress range σ ~ n (T min ) and the second normalized stress range σ ~ n (T max ) is calculated as the overlap normalized stress range σS. In the example shown in Figure 2, as shown in Figure 3, σ ~ n-min (T min )=4437, σ ~ n-max (T min )=14219, σ ~ n-min (T max )=2504, σ ~ n-max (T max )=7924, 4437≦σS≦7924.

[0052] Next, the maximum value in the overlap normalized stress range σS is the target value σ ~ st n-H The target value σ ~ st n-H The structure is determined as a maximum design structure by the total stress design method so that the total weight of the stiffener is reduced. In the example shown in Figure 2, the target value σ ~ st n-H More specifically, the third design structure generation unit 14 calculates the normalized stress σ ... ~ is the target value σ ~ st n-H Similarly, the median value in the overlap normalized stress range σS is the target value σ ~ st n-Average The target value σ ~ stn-Average The structure is determined as a median design structure by the total stress design method so that the total weight of the stiffener is reduced. In the example shown in Figure 2, the target value σ ~ st n-Average = (7924 + 4437) / 2 = 6180.5 ≒ 6181. Similarly, the minimum value in the overlap normalized stress range σS is the target value σ ~ st n-L The target value σ ~ st n-L The structure is determined as a minimum design structure by the total stress design method so that the total weight of the stiffener is reduced. In the example shown in Figure 2, the target value σ ~ st n-L =4437.

[0053] 4A to 4C show the changes in total plate thickness (objective function), static stiffness (bending load displacement), and dynamic stiffness (natural frequency) during repeated calculations until the maximum value design structure, median value design structure, and minimum value design structure are obtained. ■ indicates the value for the maximum value design structure, ▲ indicates the value for the median value design structure, and ● indicates the value for the minimum value design structure. The maximum value design structure, median value design structure, and minimum value design structure were each obtained through five repeated calculations. In the total stress design method, the objective function is total weight. In this embodiment, the total weight, which is the sum of the weights of the first through fortieth sub-members ST1 to ST40, is expressed as the total plate thickness a1 [mm], which is the sum of the thicknesses of the first through fortieth sub-members ST1 to ST40. As shown in Figure 4, the maximum design structure had a total plate thickness of 25 mm, a bending load displacement of 0.0185 mm, and a natural frequency of 500 Hz. As shown in Figure 4, the median design structure had a total plate thickness of 36 mm, a bending load displacement of 0.0182 mm, and a natural frequency of 487 Hz. As shown in Figure 4, the minimum design structure had a total plate thickness of 65 mm, a bending load displacement of 0.0179 mm, and a natural frequency of 468 Hz.

[0054] Next, for each of the maximum value design structure, median value design structure, and minimum value design structure, coordinate points are plotted on a total weight-static stiffness Cartesian coordinate system with total weight and static stiffness as the two axes, and a first straight line α1 that best fits this is determined. As described above, total weight is represented by total plate thickness a1, and static stiffness is represented by bending load displacement a2. Therefore, as shown in Figure 5A, the coordinate points of the maximum value design structure (0.0185, 25), the coordinate points of the median design structure (0.0182, 36), and the coordinate points of the minimum value design structure (0.0179, 65) are plotted on an a2-a1 Cartesian coordinate system with total plate thickness a1 and bending load displacement a2 as the two axes, and a first straight line α1; a1 = -59987 a2 + 1124.2 that best fits these points is determined, for example, by the least squares method. Similarly, for each of the maximum design structure, median design structure, and minimum design structure, coordinate points are plotted on a static stiffness-dynamic stiffness Cartesian coordinate system with static stiffness and dynamic stiffness as the two axes, and a second line α2 that best fits the plot is determined. As shown in Figure 5B, the coordinate points of the maximum design structure (0.0185, 500), the median design structure (0.0182, 487), and the minimum design structure (0.0179, 468) are plotted on an a2-a3 Cartesian coordinate system with bending load displacement a2 and natural frequency a3 as the two axes, and a second line α2;a3=48101a2-391.2 that best fits these points is determined. Similarly, for each of the maximum design structure, median design structure, and minimum design structure, coordinate points are plotted on a dynamic stiffness-total weight Cartesian coordinate system with dynamic stiffness and total weight as the two axes, and a third line α3 that best fits the plot is determined. As shown in Figure 5C, the coordinate points of the maximum value design structure (500, 25), the coordinate points of the median value design structure (487, 36), and the coordinate points of the minimum value design structure (468, 65) are plotted in an a3-a1 Cartesian coordinate system with the natural frequency a3 and the total plate thickness a1 as the two axes, and the third straight line α3;a1 = -1.2551a3 + 650.24 that best fits these points is obtained.

[0055] Next, the linear equations representing the first to third straight lines α1 to α3 are simultaneously established, and the total weight a1 is determined by solving these simultaneous equations. In the example shown in Figure 2, a1 = 36.8. Note that a2 = 0.018294 and a3 = 488.7.

[0056] Then, based on this total weight a1, the normalized stress is set to the second target value (normalized stress target value) σ of the dynamic stiffness. ~ st In this example, a1=36.8, so σ ~ st =6598 is required.

[0057] In this way, the second target value (normalized stress target value) σ ~ st is required.

[0058] In addition, in FIG. 6, the total plate thickness a1 and the normalized stress σ calculated based on the total plate thickness a1 are shown. ~ st (Reference normalized stress σ ~ tst ) is shown. When linearly approximated, the relationship between the total plate thickness a1 and the reference normalized stress σ ~ tst The relationship between ~ tst =-82.255a1+9625.8.

[0059] FIG. 7 also shows the changes in the stiffeners in the third design object FSD-EigenF obtained by the iterative calculation. In the example shown in FIG. 2, the third design object FSD-EigenF was obtained by five iterative calculations using the full stress design method with the first design object Base as the initial value. That is, the stiffener on the far right side of the page in FIG. 7 is the stiffener in the third design object FSD-EigenF. The thickness of the stiffener in this third design object FSD-EigenF is symmetrical with respect to a diagonal line from the upper left to the lower right in the figure, being thin at the center and thicker in the area surrounding it in a square shape, with the thickest thickness at 1.8 mm at the inverted L-shaped area.

[0060] Moreover, Fig. 8A shows a histogram of normalized stresses occurring in the stiffeners in the first designed structure Base, and Fig. 8B shows a histogram of normalized stresses occurring in the stiffeners in the third designed structure FSD-EigenF. As can be seen from comparing Fig. 8A and Fig. 8B, the normalized stress distribution range of the third designed structure FSD-EigenF is narrower than the normalized stress distribution range of the first designed structure Base, and the normalized stresses of the third designed structure FSD-EigenF are more level than the normalized stresses of the first designed structure Base.

[0061] Returning to Figure 1, the fourth design structure generation unit 15 includes the first to third design structures Base, FSD-Bending, and FSD-EigenF obtained by the first to third design structure generation units 12 to 14, respectively, in the first generation individuals, and uses a genetic algorithm to obtain the structure as a fourth design structure so that the total weight of the stiffener SF is small.

[0062] In a genetic algorithm, the number of individuals in each generation (number of individuals in a generation) is set in advance. When generating individuals from the current generation to the next generation, first, a predetermined number (number of selected individuals) of individuals with high evaluation values ​​according to a predetermined evaluation function are selected from all individuals in the current generation, and these selected individuals are designated as individuals for the next generation (a so-called tournament selection method). Second, individuals equal to the number of individuals in the first generation minus the number of selected individuals are generated through genetic operations such as crossover, mutation, and duplication with a predetermined probability, and these generated individuals are designated as individuals for the next generation. Third, the generated next generation individuals replace the current generation. Fourth, these first through third processes are repeated until the predetermined number of generations is reached or until the difference between generations is substantially eliminated, and the individual with the highest evaluation value from the individuals of the final generation is selected as the solution. The crossover process involves selecting two individuals and swapping some of the components (genes) that make up the individuals between the selected individuals. The mutation is a process of selecting one individual and changing some of the components (genes) that make up the selected individual. The duplication is a process of selecting one individual and using the selected individual as an individual for the next generation. In addition to the tournament selection method, genetic algorithms also include roulette selection and ranking selection methods, and any of these may be used.

[0063] In such a genetic algorithm, a predetermined evaluation function f is required to evaluate the quality of the individual. In this embodiment, the objective is to minimize the total weight of the stiffener SF, more specifically, the total plate thickness of the stiffener. Therefore, if each individual (design structure to be evaluated) of a generation in the genetic algorithm is designated as x, the total plate thickness of the stiffener (f(x)=Σt i , Σ may be the sum of i=1 to i=40), but in this embodiment, the evaluation function f AOFFor (x), a linear sum (or a weighted linear sum) of the total weight of the stiffener SF (total plate thickness of the stiffener SF in this embodiment) f(x) and the multiplication result of this total weight (total plate thickness in this embodiment) f(x) by a penalty value p(x) that is assigned depending on whether or not a predetermined constraint condition is satisfied is used (f AOF (x)=f(x)+f(x)×p(x), or f AOF (x) = f(x) + w × f(x) × p(x), where w is the weight. AOFFor each of (x), the smaller the evaluation value, the higher the evaluation, and therefore the smaller the evaluation value, the better the individual is evaluated. The predetermined constraint condition may be one or more predetermined conditions set in advance, and in this embodiment, since the structure is designed using static stiffness and dynamic stiffness, the predetermined constraint condition includes a first sub-constraint condition g1(x) regarding static stiffness and a second sub-constraint condition g2(x) regarding dynamic stiffness. More specifically, the first and second sub-constraints g1(x) and g2(x) are based on the bending load displacement u0 (=0.01824 mm) and natural frequency v0 (=479 Hz) of the first design structure Base. The first sub-constraint g1(x) requires that the bending load displacement u(x) of the design structure x to be evaluated be less than or equal to the bending load displacement u0 of the first design structure Base (u(x)≦u0). The second sub-constraint g2(x) requires that the natural frequency v(x) of the design structure x to be evaluated be greater than or equal to the natural frequency v0 of the first design structure Base (v0≦v(x)). In other words, the constraints require that the design structure x to be evaluated be equivalent to or superior to the first design structure Base in terms of both static stiffness and dynamic stiffness. When the constraints include first and second sub-constraints g1(x) and g2(x), the penalty term p(x) is a simple average of a first sub-penalty value p1(x), which is assigned depending on whether the first sub-constraint g1(x) is satisfied, and a second sub-penalty value p2(x), which is assigned depending on whether the second sub-constraint g2(x) is satisfied (p(x)=(p1(x)+p2(x)) / 2). The first sub-penalty value p1(x) is set to 0 if the first sub-constraint g1(x) is satisfied, and is set to a predetermined value (e.g., 0.2) that is appropriately set in advance if the first sub-constraint g1(x) is not satisfied. Similarly, the second sub-penalty value p2(x) is set to 0 if the second sub-constraint g2(x) is satisfied, and is set to a predetermined value (e.g., 0.2) that is appropriately set in advance if the second sub-constraint g2(x) is not satisfied.The penalty term p(x) may be a constant value regardless of the number of generations, but in this embodiment, from the viewpoint of encouraging the attainment of a solution while maintaining an appropriate search range for the solution, the penalty term p(x) is weighted by a weight w that increases as the number of generations increases and becomes a constant value when the number of generations reaches a predetermined threshold value. For example, from the first generation to the tenth generation, the weight w increases by 0.2 from 3, and from the eleventh generation onwards it becomes a constant value of 5. Therefore, in this embodiment, f. AOF (x)=f(x)+w×f(x)×p(x)=f(x)+w×f(x)×((p1(x)+p2(x)) / 2).

[0064] To apply a genetic algorithm, each individual (design structure) in a generation is represented by a binary number. In the example shown in Fig. 2, there are eight thicknesses: 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, and 1.8. If each is assigned an identifier (ID) of 1, 2, 3, 4, 5, 6, 7, or 8, one sub-member ST is represented by 3 bits, and the 40 first through 40th sub-members ST1 to ST40 are represented by 3 bits x 40 = 120 bits. In other words, a structure equipped with this stiffener SF is represented by these 120 bits.

[0065] In the genetic algorithm, the number of individuals in a generation, the number of selected individuals, the probability of applying a genetic operation, and the number of operations of a genetic operation are each appropriately set in advance. In this embodiment, for example, the number of individuals in a generation is 20, the number of selected individuals is 6, crossover is a one-point crossover with an application probability of 80% and mutation is a one-point mutation with an application probability of 3%. For example, six individuals with the highest evaluations are selected from the 20 individuals in the current generation, and these six selected individuals are designated as individuals for the next generation. Genetic operations are then performed on each of the remaining 14 individuals. In this genetic operation, first, a number between 0 and 100 is generated randomly for crossover. If the generated number is equal to or less than the application probability of crossover of 80%, the individual is crossed over. If the generated number is greater than the application probability of crossover of 80%, the individual is not crossed over. When crossing the individuals, two sets of four individuals are randomly selected from all individuals, and the individual with the best performance from each set is selected to select one set. A number between 1 and 120 is generated by random numbers, the bit to be crossed is determined, and the bit string (gene string) between the two individuals in the pair is swapped starting from the determined bit. This changes the thickness of one of the sub-components ST among the first through 40th sub-components ST1 through ST40, and one-point crossover is performed. While a number between 1 and 120 is generated in the above example, the bit to be crossed may be determined by multiplying any number between 0 and 100 generated in the crossover determination by 1.2. The crossover point may also be set to any value greater than or equal to 1. After the crossover process is performed, a new number between 0 and 100 is generated by random numbers for each of the 14 individuals (the individual after crossover if crossover has been performed, and the original individual if crossover has not been performed). If the generated number is less than or equal to the mutation application probability of 3, the individual is mutated. If the generated number exceeds the mutation application probability of 3, the individual is not mutated. When mutating the individual, a number between 1 and 120 is generated randomly, the bit to be mutated is determined, and if the determined bit is 0, it is changed to 1, and if the determined bit is 1, it is changed to 0. This changes the thickness of one of the sub-components ST1 to ST40, and mutation is performed. After this mutation process is performed, 14 individuals are selected as the next-generation individuals: the individual after crossover if only crossover was performed, the individual after mutation if only mutation was performed, the individual after crossover and mutation if both crossover and mutation were performed, and the original individual (in other words, a copy individual) if neither crossover nor mutation was performed. This process generates 20 next-generation individuals.

[0066] Then, the control unit 11 outputs the fourth design structure generated by the fourth design structure generation unit 14 to the output unit 3. The output unit 3 outputs the fourth design structure. For example, the output unit 3 displays the fourth design structure in the same manner as in the case of the third design structure FSD-EigenF shown in FIG.

[0067] The control processing unit 1, input unit 2, output unit 3, IF unit 4 and storage unit 5 can be configured by, for example, a desktop or notebook computer.

[0068] Next, the operation of this embodiment will be described with reference to a flowchart of FIG.

[0069] When the stiffener design support device 1000 having such a configuration is powered on, it initializes the necessary parts and starts operation. By executing the control processing program, the control processing unit 1 functionally configures a control unit 11, a first designed structure generation unit 12, a second designed structure generation unit 13, a third designed structure generation unit 14, and a fourth designed structure generation unit 15.

[0070] 9, when a start command is input to the input unit 2, first, the stiffener design support device 1000 causes the first designed structure generation unit 12 of the control processing unit 1 to generate a structure including a plurality of sub-members ST whose stiffeners SF have predetermined dimensions as a first designed structure Base, and stores the first designed structure Base in the storage unit 5 (S11). Note that it is assumed that data necessary for generating the first to fourth designed structures, such as various quantities such as the dimensions and physical properties of the structure Ob, are stored in the storage unit 5.

[0071] Next, the stiffener design support device 1000 generates a structure as a second design structure FSD-Bending using the total stress design method so that the total weight of the stiffener SF is small at the first target value of static stiffness using the second design structure generation unit 13 of the control processing unit 1, and stores it in the memory unit 5 (S12).

[0072] Next, the stiffener design support device 1000 generates a third design structure FSD-EigenF of the structure using the total stress design method so that the total weight of the stiffener SF is reduced at the second target value of dynamic stiffness using the third design structure generation unit 14 of the control processing unit 1, and stores the third design structure FSD-EigenF in the memory unit 5 (S13).

[0073] Next, the stiffener design support device 1000 causes the fourth designed structure generation unit 15 of the control processing unit 1 to generate a structure as a fourth designed structure using a genetic algorithm so that the first generation individuals include the first to third designed structures Base, FSD-Bending, and FSD-EigenF determined by the first to third designed structure generation units 12 to 14, respectively, and the total weight of the stiffener SF is reduced, and stores the generated structure in the storage unit 5 (S14). Of the first generation individuals, the remaining individuals excluding the first to third designed structures Base, FSD-Bending, and FSD-EigenF are generated by, for example, determining the plate thickness of each of the first to fortieth sub-members ST1 to ST40 using random numbers.

[0074] Then, the stiffener design support device 1000 causes the control unit 11 of the control processing unit 1 to output the fourth design structure generated by the fourth design structure generation unit 15 to the output unit 3 (S15), and ends this process. Note that the control unit 11 may output each calculation result to an external device via the IF unit 4 as necessary.

[0075] As explained above, the stiffener design support device 1000 in the embodiment and the stiffener design support method and stiffener design support program implemented therein include the first to third design structures Base, FSD-Bending, and FSD-EigenF in the individuals of the first generation (initial generation) when designing a stiffener for a structure using a genetic algorithm, and therefore it is possible to expect the emergence of individuals more suitable for the solution in fewer generations, thereby reducing the amount of information processing.

[0076] An example and first and third comparative examples will be described. Fig. 9 is a diagram showing the results of a comparison between the example and the first to third comparative examples, as an example. The horizontal axis of Fig. 9 represents the generation number, and the vertical axis represents the total plate thickness [mm].

[0077] In the first comparative example, the first designed structure Base is included in the first generation individuals, and a structure is generated as the first comparative example designed structure CM1 using a genetic algorithm so that the total weight of the stiffeners SF is small (Method 1).

[0078] In the second comparative example, the first and second design structures Base and FSD-Bending are included in the first generation individuals, and a structure is generated as the second comparative example design structure CM2 using a genetic algorithm so that the total weight of the stiffener SF is small (Method 2).

[0079] In the third comparative example, the first and third design structures Base and FSD-EigenF are included in the first generation individuals, and a structure is generated as the third comparative example design structure CM3 using a genetic algorithm so that the total weight of the stiffener SF is small (Method 3).

[0080] In the example, the fourth designed structure PM is generated as described above (Example method).

[0081] For each of the Example and the first through third Comparative Examples, three genetic algorithm optimization calculations were performed up to 50 generations using three different random number tables, and the Example with the smallest total weight was selected from the three Examples for each Example. The three different random number tables applied to each Example were all the same. Figure 10 plots the individual with the smallest total thickness that satisfied the first and second constraints g1(x) and g2(x) among the Examples obtained by the selected optimization calculation for each generation. The results of the first Comparative Example are plotted with ● in Figure 10, the results of the second Comparative Example are plotted with ◆ in Figure 10, the results of the third Comparative Example are plotted with ▲ in Figure 10, and the results of the Example are plotted with ■ in Figure 10.

[0082] As can be seen from Figure 10, the first comparative example did not show any improvement in total thickness until the fifth generation, while the second comparative example, the third comparative example, and the working example showed significant improvements by the fifth generation. The third comparative example had a total thickness of 30.0 mm, the second comparative example had a total thickness of 29.4 mm, and the working example had a total thickness of 28.4 mm, showing the greatest improvement. In the final 50th generation, the first comparative example had a total thickness of 32.2 mm, the third comparative example had a total thickness of 28.8 mm, and the second comparative example had a total thickness of 28.2 mm, while the working example had a total thickness of 27.0 mm, showing the greatest improvement.

[0083] Therefore, by including the first to third design structures Base, FSD-Bending, and FSD-EigenF in the individuals of the first generation (initial generation), it is possible to expect the emergence of individuals more suitable for the solution in fewer generations, thereby reducing the amount of information processing.

[0084] Furthermore, the stiffener design support device 1000, stiffener design support method, and stiffener design support program can obtain a structure that satisfies the first sub-constraint condition regarding static stiffness and the second sub-constraint condition regarding dynamic stiffness.

[0085] In the above stiffener design support device 1000, stiffener design support method, and stiffener design support program, the penalty terms are weighted with weights that increase as the number of generations increases, so that individuals that do not satisfy at least one of the first and second sub-constraint conditions can be eliminated in a fewer number of generations, and therefore individuals that are more suitable for the solution can be selected in a fewer number of generations.

[0086] The above-mentioned stiffener design support device 1000, stiffener design support method, and stiffener design support program can determine a second target value for dynamic stiffness by specifying the weight range of the sub-member ST, and can determine a structural part that takes dynamic stiffness into consideration using the total stress design method.

[0087] According to the embodiments, it is possible to provide a stiffener design support device 1000, a stiffener design support method, and a stiffener design support program that support the design of a stiffener that is a rectangular plate-shaped stiffener whose thickness can be designed and that includes a plurality of sub-members arranged in a lattice pattern.

[0088] In order to express the present invention, the present invention has been properly and sufficiently described above through the embodiments with reference to the drawings, but it should be recognized that those skilled in the art can easily change and / or improve the above-mentioned embodiments. Therefore, unless the changes or improvements made by those skilled in the art are at a level that causes departure from the scope of the claims described in the claims, such changes or improvements are interpreted as being included in the scope of the claims. [Explanation of symbols]

[0089] 1 Control processing section 3 Output section 5 Storage section 11 Control section 12 1st Design Structure Generation Department 13 2nd Design Structure Generation Department 14 3rd Design Structure Generation Department 15 4th Design Structure Generation Department Ob structure PT1 First plate-shaped member PT2 Second plate-shaped member SF Stiffner ST sub-member

Claims

1. A stiffener design support device for supporting design of a stiffener in a structure including a pair of first and second plate-like members and a stiffener disposed between the first and second plate-like members, comprising: a first design structure generation unit that generates, as a first design structure, the structure including a plurality of sub-members, the stiffeners of which have predetermined dimensions; a second design structure generation unit that generates the structure as a second design structure by a total stress design method so that a total weight of the stiffener is reduced at a first target value of static stiffness; a third design structure generation unit that generates the structure as a third design structure by a total stress design method so that a total weight of the stiffener is reduced at a second target value of dynamic stiffness; a fourth designed structure generation unit that includes the first to third designed structures obtained by the first to third designed structure generation units, respectively, in a first generation individual and generates the structure as a fourth designed structure by a genetic algorithm so that the total weight of the stiffener is reduced; an output unit that outputs the fourth designed structure generated by the fourth designed structure generation unit. Stiffener design support device.

2. the fourth designed structure generation unit uses a linear sum or a weighted linear sum of a total weight of the stiffener and a multiplication result obtained by multiplying the total weight by a penalty value that is assigned depending on whether a predetermined constraint condition is satisfied, as an evaluation function for evaluating the acceptability of an individual; the predetermined constraint comprises a first sub-constraint on static stiffness and a second sub-constraint on dynamic stiffness; the penalty term is a simple average of a first sub-penalty value that is assigned depending on whether the first sub-constraint condition is satisfied and a second sub-penalty value that is assigned depending on whether the second sub-constraint condition is satisfied, The smaller the value of the evaluation function, the better the individual is evaluated. The stiffener design support device according to claim 1 .

3. The penalty term is weighted with a weight that increases as the number of generations increases and becomes a constant value when the number of generations is equal to or greater than a predetermined threshold. The stiffener design support device according to claim 2.

4. the stiffener comprises a plurality of sub-members within a predetermined weight range; The third design structure generation unit determining an overlapping normalized stress range between a first normalized stress range at natural vibration in the structure including the plurality of sub-members in which the stiffener has a minimum value within the predetermined weight range and a second normalized stress range at natural vibration in the structure including the plurality of sub-members in which the stiffener has a maximum value within the predetermined weight range; determining each of the structures as a maximum value design structure, a median value design structure, and a minimum value design structure by a total stress design method so that the total weight of the stiffener is reduced at each target value of the maximum value, median value, and minimum value in the overlap normalized stress range; For each of the maximum value design structure, median value design structure, and minimum value design structure obtained above, when each coordinate point is plotted on a total weight-static stiffness Cartesian coordinate system with total weight and static stiffness as two axes, a static stiffness-dynamic stiffness Cartesian coordinate system with static stiffness and dynamic stiffness as two axes, and a dynamic stiffness-total weight Cartesian coordinate system with dynamic stiffness and total weight as two axes, each straight line that best fits is obtained, and the total weight is obtained by setting up simultaneous linear equations that represent each of the obtained straight lines; determining a normalized stress as the second target value of the dynamic stiffness based on the determined total weight; The stiffener design support device according to claim 1 .

5. The stiffener has a rectangular plate shape whose thickness can be designed and includes a plurality of sub-members arranged in a lattice pattern. The stiffener design support device according to claim 1 .

6. 1. A stiffener design support method for supporting design of a stiffener in a structure including a pair of first and second plate-like members and a stiffener disposed between the first and second plate-like members, comprising: a first design structure generating step of generating, as a first design structure, the structure including a plurality of sub-members, the stiffeners of which have predetermined dimensions; a second design structure generation step of generating the structure as a second design structure by a total stress design method so that the total weight of the stiffener is reduced at a first target value of static stiffness; a third design structure generating step of generating the structure as a third design structure by a total stress design method so that the total weight of the stiffener is reduced at a second target value of dynamic stiffness; a fourth designed structure generating step of generating a fourth designed structure by using a genetic algorithm to include the first to third designed structures obtained in the first to third designed structure generating steps, respectively, in a first generation individual so that the total weight of the stiffeners is reduced; an output step of outputting the fourth design structure obtained in the fourth design structure generating step. A method for supporting stiffener design.

7. 6. A stiffener design support program for supporting design of a stiffener in a structure comprising a pair of first and second plate-like members and a stiffener disposed between the first and second plate-like members, the stiffener design support program causing a computer to function as the stiffener design support device according to any one of claims 1 to 5.

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