Structure analysis method and computer-readable recording medium

Abstract

The present invention achieves highly accurate and efficient prediction of strength of an additive-manufactured object. In order to solve this problem, a structure analysis method according to the present invention includes dividing the shape of an additive-manufactured object exhibiting anisotropy into a plurality of elements, imparting direction information corresponding to a movement direction of a discharge head to each of the divided elements on the basis of forming path information indicating a movement path of the discharge head when the additive-manufactured object exhibiting anisotropy is formed by a 3D printer, creating a structure analysis model of the additive-manufactured object exhibiting anisotropy by imparting, to the element, physical property value information corresponding to the imparted direction information, and executing structure analysis using the created structure analysis model.

Description

Structural analysis method and computer-readable recording medium

[0001] The present disclosure relates to a structural analysis method and a computer-readable recording medium.

[0002] Generally, anisotropic injection molded articles obtained by injection molding a thermoplastic resin or a thermoplastic resin composition are widely used as industrial products, for example. Such anisotropic injection molded articles are required to be manufactured into a shape faithful to the design drawing in order to exhibit the functions as industrial products. For this reason, when manufacturing an anisotropic injection molded article by injection molding, it takes time to manufacture the mold, and dimensional stability problems such as warpage may occur.

[0003] Therefore, in recent years, it has been studied to manufacture prototypes and products of structures made of a thermoplastic resin or a thermoplastic resin composition using a 3D printer, and significantly shorten the lead time of design and manufacturing. That is, for example, molten thermoplastic resin is discharged from the discharge head of a 3D printer to form a layer corresponding to the cross-sectional shape of a desired structure, and the structure is manufactured as a laminated molded body having anisotropy by laminating the layers thus formed. When manufacturing a laminated molded body having anisotropy using a 3D printer, strength design may be performed by numerical analysis.

[0004] Japanese Patent Application Laid-Open No. 2021-109401, Japanese Patent Application Laid-Open No. 2017-177462, Japanese Patent Application Laid-Open No. 2021-028164

[0005] However, there is a problem that it is difficult to accurately predict the strength of a laminated molded body having anisotropy at the time of strength design. Specifically, for the strength design of a laminated molded body having anisotropy, physical property values such as Young's modulus and Poisson's ratio are required, for example. However, when manufacturing a laminated molded body using a 3D printer, since the physical property values depend on the shaping path (tool path) which is the movement path of the discharge head, it is not easy to accurately predict the strength and rigidity of the laminated molded body.

[0006] Furthermore, numerical analysis for strength design employs computational methods such as finite element models. However, the quality of the finite element model can hinder the improvement of accuracy in numerical analysis and result in enormous computational costs. In this regard, high-quality computational methods for anisotropic additively fabricated structures are not yet known, making highly accurate and efficient structural analysis difficult.

[0007] The technology disclosed herein has been made in view of the above, and aims to provide a structural analysis method and a computer-readable recording medium that can achieve highly accurate and efficient prediction of the strength of anisotropic additively manufactured bodies.

[0008] According to one aspect of the present disclosure, a structural analysis method comprises: dividing the shape of an anisotropic additively manufactured body into a plurality of elements; assigning direction information corresponding to the direction of movement of the ejection head to each of the divided elements based on manufacturing path information indicating the movement trajectory of the ejection head when manufacturing the anisotropic additively manufactured body by a 3D printer; creating a structural analysis model of the anisotropic additively manufactured body by assigning physical property information corresponding to the assigned direction information to the elements; and performing a structural analysis using the created structural analysis model.

[0009] Furthermore, according to another aspect of the present disclosure, the computer-readable recording medium stores a structural analysis program that causes a computer to perform the following actions: divide the shape of an anisotropic additive manufacturing body into a plurality of elements; assign direction information corresponding to the direction of movement of the ejection head to each of the divided elements based on manufacturing path information indicating the movement trajectory of the ejection head when manufacturing the anisotropic additive manufacturing body by a 3D printer; create a structural analysis model of the anisotropic additive manufacturing body by assigning physical property value information corresponding to the assigned direction information to the elements; and perform a structural analysis using the created structural analysis model.

[0010] Figure 1 is a flowchart showing a structural analysis method according to one embodiment. Figure 2 is a diagram showing a specific example of finite element division. Figure 3 is a diagram showing a specific example of fabrication path information. Figure 4 is a diagram showing a specific example of a model for structural analysis. Figure 5 is a flowchart showing the process of creating a model for structural analysis. Figure 6 is a diagram explaining the division path. Figure 7 is a diagram explaining the correspondence between finite elements and division paths. Figure 8 is a diagram showing a specific example of the direction of implementation of a bending test. Figure 9 is a diagram showing a specific example of the method of implementing a bending test. Figure 10 is a diagram showing finite element division according to Example 1. Figure 11 is a diagram schematically showing a part of the fabrication path. Figure 12 is a diagram schematically showing direction information associated with finite elements. Figure 13 is a diagram showing specific examples of boundary conditions and calculation conditions for structural analysis. Figure 14 is a diagram showing a specific example of deformation amount distribution according to Example 1. Figure 15 is a diagram showing finite element division according to Example 2. Figure 16 is a diagram showing a specific example of deformation amount distribution according to Example 2. Figure 17 is a block diagram showing an example of the hardware configuration of an information processing device.

[0011] An embodiment of the present disclosure will be described below with reference to the attached drawings. The embodiment described below is illustrative and should not be interpreted as limiting.

[0012] [Structural Analysis Method for Anisotropic Additive-Manufactured Structures] Figure 1 is a flowchart showing a structural analysis method for an anisotropic additive-manufactured structure according to one embodiment.

[0013] As shown in Figure 1, a structural analysis method according to one embodiment includes the steps of: acquiring physical property information of an anisotropic additive manufacturing body (step S101); dividing the shape of the anisotropic additive manufacturing body into finite elements (step S102); acquiring fabrication path information for creating the anisotropic additive manufacturing body (step S103); creating a structural analysis model in which physical property information is assigned to each finite element (step S104); and performing a structural analysis calculation using the structural analysis model (step S105).

[0014] [Anisotropic Physical Property Information Acquisition Step (Step S101)] In the anisotropic physical property information acquisition step, information on the physical properties of an anisotropic additively manufactured body made using thermoplastic resin (hereinafter referred to as "anisotropic physical property information") is acquired.

[0015] Generally, when manufacturing anisotropic additive-built bodies using a 3D printer, a manufacturing method such as material extrusion (MEX) is used. In fused filament fabrication (FFF), a type of material extrusion, a filament-shaped thermoplastic resin is used, the thermoplastic resin is melted in a filament heating device, and the molten single-fiber resin is extruded from an extrusion head to form layers, and the additive-built body is created by stacking these layers. In addition, anisotropic additive-built bodies can also be created by melting pellet-shaped thermoplastic resin without using filaments. Since the physical properties of such anisotropic additive-built bodies differ depending on the direction, this information on physical properties (anisotropic physical property information) can be obtained, for example, by creating a rectangular parallelepiped-shaped test piece and performing a bending test by applying force to the test piece from multiple different directions.

[0016] Specifically, in the step of acquiring anisotropic physical property information (step S101), a bending test is performed on the long side of a rectangular parallelepiped-shaped test piece, applying a force parallel to the lamination direction of the thermoplastic resin, and another bending test is performed applying a force perpendicular to the lamination direction of the thermoplastic resin. Anisotropic physical property information such as Young's modulus and Poisson's ratio is acquired from each bending test. In other words, anisotropic physical property information is acquired for both the direction parallel to and perpendicular to the lamination direction of the thermoplastic resin. Thus, in the anisotropic physical property information acquisition step, anisotropic physical property information showing different physical properties depending on the direction is obtained.

[0017] In the case of a thermoplastic resin composition containing a thermoplastic resin and a fibrous or plate-shaped anisotropic filler, the physical properties of the thermoplastic resin composition may be calculated from the physical properties of the resin portion and the physical properties of the filler, and the obtained physical properties may be used as anisotropic physical property information. Alternatively, anisotropic physical property information may be calculated from the composition information of the thermoplastic resin composition.

[0018] [Finite element division step (step S102)] In the finite element division step, the shape of the anisotropic additive body to be manufactured is divided into finite elements of a predetermined shape and size.

[0019] Specifically, as shown in Figure 2, for example, the anisotropic additive-built body 10 is divided into a plurality of finite elements 11. These finite elements 11 are elements that constitute a structural analysis model of the anisotropic additive-built body 10.

[0020] The method of element division is not particularly limited. For example, first, the shape of the anisotropic additive manufactured body 10 is imported into a computer using a CAD interface or the like, or the shape of the anisotropic additive manufactured body 10 is created by a CAD system and the modeling range is set. Next, the anisotropic additive manufactured body 10 is divided into multiple finite elements 11 by performing element division using a finite element method or the like with an element division preprocessor.

[0021] The shape of the finite element 11 is not particularly limited, and a tetrahedron linear element, a tetrahedron quadratic element, a hexahedron linear element, or a hexahedron quadratic element can be selected. The shape should be selected appropriately according to the specifications of the finite element method software, the specifications of the computer system used for calculation, and the computational cost.

[0022] The number of finite elements 11 is not particularly limited and can be appropriately selected considering the calculation accuracy and calculation time.

[0023] [Building path information acquisition step (step S103)] In the building path information acquisition step, building path information is acquired that shows the movement trajectory of the extrusion head when an anisotropic additive body 10 is built by a 3D printer.

[0024] The build path information of 3D printers used in manufacturing methods such as material extrusion (MEX) is generally described using G-code, which is also used for controlling NC (Numerical Control) machine tools. Build path information using G-code includes the movement position, direction and speed of the extrusion head, as well as the amount of resin extruded. For example, the build path information for creating an anisotropic additive body 10 includes information on the movement trajectory of the extrusion head when forming one layer of the anisotropic additive body 10, as shown in Figure 3. In the build path information acquisition step, build path information including the movement trajectory of the extrusion head is acquired in this manner.

[0025] [Structural Analysis Model Creation Step (Step S104)] In the structural analysis model creation step, a structural analysis model is created that will be used for structural analysis of the anisotropic additively fabricated body 10.

[0026] Here, a structural analysis model is created by assigning anisotropic physical property information to each finite element 11 obtained in the finite element division step (step S102) based on the molding path information obtained in the molding path information acquisition step (step S103). That is, as shown in Figure 4 for example, each finite element 11 constituting the anisotropic additive manufactured body 10 is assigned direction information corresponding to the movement direction of the ejection head, and anisotropic physical property information corresponding to the direction is assigned from the direction information of each finite element 11. Therefore, the structural analysis model consists of elements to which different physical property information is assigned depending on the direction, enabling structural analysis that takes anisotropy into account.

[0027] The specific procedures for the structural analysis model creation step (step S104) will be described in detail later.

[0028] [Structural Analysis Calculation Step (Step S105)] In the structural analysis calculation step, a simulation using a structural analysis model is performed to predict the strength of the anisotropic additive fabricated body 10.

[0029] In other words, the structural analysis model created in the structural analysis model creation step (step S104) is used to perform a structural analysis of the anisotropic additive manufactured body 10. The structural analysis simulates the deformation and stress of the anisotropic additive manufactured body 10, and the presence or absence of damage to the anisotropic additive manufactured body 10 is determined from the simulation results. Since the structural analysis model used in this structural analysis has anisotropic material property information set, a simulation that takes anisotropy into account is performed, and the strength of the anisotropic additive manufactured body 10 can be accurately predicted.

[0030] Next, the specific process of creating a structural analysis model (step S104) will be explained with reference to the flowchart shown in Figure 5.

[0031] As described above, in the structural analysis model creation step, a structural analysis model used for structural analysis is created. In this structural analysis model, anisotropic material property information is assigned to the finite elements 11. When creating such a structural analysis model, first, the centroid of each finite element 11 of the anisotropic additive fabricated body 10 is derived (step S201). That is, the centroid position is determined for each finite element 11 from the position of the vertex of each finite element 11. The centroid position of the finite element 11 is used to associate the finite element 11 with the fabrication path.

[0032] Once the centroids of all finite elements 11 are derived, a divided path is set from the manufacturing path information for creating the anisotropic additive body 10 to be manufactured, by dividing the manufacturing path (step S202). Specifically, for example, the manufacturing path shown in Figure 6(a) is divided into predetermined lengths to set a divided path 21 as shown in Figure 6(b). The length of the divided path 21 may be a length corresponding to the size of the finite element 11, such as being approximately the same length as the longest side of the finite element 11.

[0033] Then, the positions of the anisotropic additive manufactured body 10 and the manufacturing path are superimposed, and directional information based on the manufacturing path is assigned to each finite element 11 (step S203). Specifically, first, the distance between the centroid of the finite element 11 and the center point of each division path 21 is calculated, and for each finite element 11, the division path 21 whose center point is closest to the centroid is identified. That is, for example, in the example shown in Figure 7, there are division paths 21a, 21b, 21c, and 21d near the centroid 11a of the finite element 11, but of these division paths 21a, 21b, 21c, and 21d, the division path 21a has its center point closest to the centroid 11a. For this reason, the division path closest to the finite element 11 is identified as division path 21a. Then, based on the identified nearest division path 21, directional information corresponding to the movement direction of the ejection head is assigned to the finite element 11. In other words, since the division path 21 includes information about the direction of movement of the discharge head, directional information corresponding to the nearest division path 21 is assigned to the finite element 11.

[0034] Once directional information is assigned to all finite elements 11, physical property information is set for each finite element 11 (step S204). That is, since anisotropic physical property information for each direction is obtained by measurement using test specimens, anisotropic physical property information corresponding to the assigned directional information is assigned to each finite element 11. As a result, each finite element 11 in the structural analysis model is assigned anisotropic physical property information that shows different physical properties depending on the direction.

[0035] Once such a structural analysis model is created, various conditions such as boundary conditions and calculation conditions for the structural analysis are set (step S205). These conditions are not particularly limited and may, for example, follow the specifications of the structural analysis software used for the structural analysis. Furthermore, the setting of these conditions does not necessarily have to be performed after the structural analysis model has been created; it may be performed at any time after the anisotropic additively fabricated body 10 has been divided into finite elements 11.

[0036] As described above, according to this embodiment, a structural analysis model is created in which anisotropic physical property value information is set for each finite element based on the fabrication path information, and structural analysis of an anisotropic additively manufactured body is performed using this structural analysis model. Therefore, by considering the different physical properties depending on the direction of the anisotropic additively manufactured body, it is possible to achieve highly accurate and efficient prediction of the strength of the anisotropic additively manufactured body.

[0037] The following describes an embodiment relating to one of the embodiments described above. The technology of this disclosure is not limited to the following embodiments.

[0038] (Example 1) In Example 1, a liquid crystalline resin (Laperos® LCP A950, manufactured by Polyplastics Co., Ltd.) was used as the thermoplastic resin, and a rectangular parallelepiped-shaped test specimen with a width of 10 mm, a thickness of 4 mm, and a length of 80 mm was fabricated using the filament fusing (FFF) method. A three-point bending test in accordance with ISO 178 was performed on this test specimen in two different directions. Specifically, bending tests were performed when force was applied in directions A and B as shown in Figure 8. In this bending test, as shown in Figure 9, the distance between the fixing jigs was set to 64 mm, an indenter was placed in the center of the test specimen, the indenter was moved so that the strain rate was 1% / min, and the load was measured by a load sensor mounted on the testing equipment. Then, the Young's modulus was calculated from the bending strain and the measured load. As a result, the Young's modulus was 23200 MPa in direction A of Figure 8 and 7850 MPa in direction B of Figure 8.

[0039] Next, the shape of the anisotropic additively manufactured object was created as CAD data, and finite element division was performed. As shown in Figure 10, in Example 1, an anisotropic additively manufactured object with a width of 13 mm, a length of 130 mm, and a thickness of 0.8 mm was divided into cubic hexahedral primary elements. When the length of one side of these hexahedral primary elements was matched to the layer size, the number of divisions became 10,816,000. The number of divisions of nodes became 11,540,638.

[0040] Next, the shaping path information described in the G-code was read, and the trajectory of the ejection head was determined. FIG. 11 is a diagram schematically showing a part of the movement trajectory of the ejection head. Based on this movement trajectory, by specifying the nearest divided path for each of the plurality of divided finite elements, the moving direction of the ejection head was associated with each finite element. FIG. 12 is a diagram schematically showing the direction information associated with the finite elements at the longitudinal end of the anisotropic laminated structure.

[0041] Then, from the direction information set for each finite element, anisotropic physical property value information such as Young's modulus corresponding to the direction was assigned to each finite element, and the boundary conditions and calculation conditions for the structural analysis were set. FIG. 13 is a diagram showing a specific example of the boundary conditions and calculation conditions.

[0042] Structural analysis calculation was performed using the obtained structural analysis model. For the structural analysis calculation, the structural analysis software AdventureCluster 2023 was used.

[0043] FIG. 14 shows the strain distribution obtained by the structural analysis according to Example 1. Since Young's modulus is obtained by dividing the total reaction force by the true strain obtained from the cross-sectional area and the strain, Young's modulus was obtained by calculation. The Young's modulus in Example 1 was 22,920 MPa. Also, the time required for the calculation was 17 minutes.

[0044] As shown in FIG. 12, since there is a path perpendicular to the longitudinal direction at the longitudinal end of the anisotropic laminated structure, the Young's modulus is reduced by that amount, and it can be said that the prediction accuracy of the Young's modulus in Example 1 is extremely good.

[0045] (Example 2) In Example 2, for the anisotropic laminated structure having the same anisotropy as in Example 1, structural analysis was performed by changing only the shape of the finite elements. As shown in FIG. 15, in Example 2, an anisotropic laminated structure with a width of 13 mm, a length of 130 mm, and a thickness of 0.8 mm was divided into hexahedral first-order elements in the shape of a rectangular parallelepiped with a width of 1 mm, a length of 1 mm, and a thickness of 0.2 mm. The number of divisions was 7,616, and the number of divided nodes was 10,276.

[0046] For such a structural analysis model, structural analysis was performed under the same conditions as in Example 1. Fig. 16 shows the amount of deformation distribution obtained by the structural analysis according to Example 2. The Young's modulus in Example 2 was 22,940 MPa. Also, the time required for the calculation was 5 seconds.

[0047] In Example 2 as well, the same results as in Example 1 were obtained. Therefore, even if the number of divisions is reduced to shorten the calculation time, good analysis accuracy can be obtained, and according to the technology of the present disclosure, the calculation cost can be reduced.

[0048] The structural analysis method of the anisotropic laminated structure according to the above-described embodiment can be executed by an information processing apparatus. Fig. 17 is a block diagram showing a hardware configuration example of an information processing apparatus 100 that executes the structural analysis method of the anisotropic laminated structure. As shown in Fig. 17, the information processing apparatus 100 includes a processor 101, a main storage device 102, an auxiliary storage device 103, an I / O (Input / Output) interface 104, and a network interface (hereinafter abbreviated as "NW interface") 105.

[0049] The processor 101 includes, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor), etc., and comprehensively controls the entire information processing apparatus 100 and executes various arithmetic processes.

[0050] The main storage device 102 includes, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory), etc., and stores information used for the arithmetic processes executed by the processor 101.

[0051] The auxiliary storage device 103 includes, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive), etc., and stores various programs and data.

[0052] The I / O interface 104 is an interface that allows the user to input information or output information to the user. The I / O interface 104 may include, for example, a keyboard, display, touch panel, microphone, or speaker.

[0053] The NW interface 105 is an interface that connects to a network via wired or wireless connection.

[0054] The information processing device 100 receives input such as the shape and anisotropic physical property information of an anisotropic additive manufacturing body via the I / O interface 104 and the NW interface 105. The processor 101 then uses the main memory 102 to execute a program stored in the auxiliary storage device 103 to create a structural analysis model of the anisotropic additive manufacturing body, and performs structural analysis using the structural analysis model.

[0055] Furthermore, the above structural analysis method can also be described as a program that can be executed by a computer. In this case, the program can be stored in a computer-readable and non-transitory recording medium and installed on the computer. Examples of such recording media include portable recording media such as CD-ROMs, DVD discs, and USB memory, as well as semiconductor memory such as flash memory.

[0056] In relation to the technology described above, the following is further disclosed:

[0057] [1] A structural analysis method comprising: dividing the shape of an anisotropic additive manufacturing body into multiple elements; assigning direction information corresponding to the direction of movement of the ejection head to each of the divided elements based on manufacturing path information showing the movement trajectory of the ejection head when manufacturing the anisotropic additive manufacturing body with a 3D printer; creating a structural analysis model of the anisotropic additive manufacturing body by assigning physical property information corresponding to the assigned direction information to the elements; and performing a structural analysis using the created structural analysis model.

[0058] [2] The structural analysis method according to [1] above, wherein the assignment includes: deriving the center of gravity position of the element; dividing the movement trajectory indicated by the molding path information to set division paths; identifying the nearest division path to the element based on the distance between the derived center of gravity position and the set division path, and assigning direction information corresponding to the identified division path to the element.

[0059] [3] The structural analysis method described in [1] or [2] above, wherein the creation is to create a structural analysis model by assigning physical property information measured using a test piece formed by a material extrusion method to the elements.

[0060] [4] The structural analysis method described in [3] above, wherein the preparation involves creating a structural analysis model by assigning physical property information obtained by measuring different physical properties depending on the orientation of the test specimen to the elements.

[0061] [5] A computer-readable recording medium that stores a structural analysis program that causes a computer to perform the following: divide the shape of an anisotropic additive manufacturing body into multiple elements; assign direction information corresponding to the direction of movement of the ejection head to each of the divided elements based on manufacturing path information that shows the movement trajectory of the ejection head when manufacturing the anisotropic additive manufacturing body by a 3D printer; create a structural analysis model of the anisotropic additive manufacturing body by assigning physical property value information corresponding to the assigned direction information to the elements; and perform a structural analysis using the created structural analysis model.

Claims

1. A structural analysis method comprising: dividing the shape of an anisotropic additively manufactured body into multiple elements; assigning direction information corresponding to the direction of movement of the extrusion head to each of the divided elements based on manufacturing path information indicating the movement trajectory of the extrusion head when manufacturing the anisotropic additively manufactured body by a 3D printer; creating a structural analysis model of the anisotropic additively manufactured body by assigning physical property information corresponding to the assigned direction information to the elements; and performing a structural analysis using the created structural analysis model.

2. The structural analysis method according to claim 1, wherein the assignment includes: deriving the center of gravity position of the element; dividing the movement trajectory indicated by the molding path information and setting division paths; identifying the nearest division path to the element based on the distance between the derived center of gravity position and the set division path, and assigning direction information corresponding to the identified division path to the element.

3. The structural analysis method according to claim 1, wherein the above-mentioned creation involves assigning physical property information measured using a test piece fabricated by a material extrusion method to elements to create a structural analysis model.

4. The structural analysis method according to claim 3, wherein the above-mentioned creation is to create a structural analysis model by assigning physical property value information obtained by measuring different physical properties depending on the orientation of the test specimen to the elements.

5. A computer-readable recording medium that stores a structural analysis program that causes a computer to perform the following actions: divide the shape of an anisotropic additively manufactured body into multiple elements; assign direction information corresponding to the direction of movement of the extrusion head to each of the divided elements based on manufacturing path information showing the movement trajectory of the extrusion head when manufacturing the anisotropic additively manufactured body by a 3D printer; create a structural analysis model of the anisotropic additively manufactured body by assigning physical property information corresponding to the assigned direction information to the elements; and perform a structural analysis using the created structural analysis model.

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