Calculation method for heating plan used in bending of metal sheets using linear heating

Abstract

The present invention provides a method for calculating a heating pattern used in bending metal sheets using linear heating. The method comprises the following steps: performing a structural analysis under a first heating condition including a heating line set in an analysis model, repeatedly performing a first trial by varying the position of the heating line and comparing the analysis results with a first target shape; selecting as a first selected heating line the heating line set in the first trial whose analysis results approach the first target shape during the repeated first trial; performing a structural analysis under a second heating condition including the first selected heating line and the heating line set in the analysis model, repeatedly performing a second trial by varying the position of the heating line and comparing the analysis results with a second target shape; and selecting as a second selected heating line the heating line set in the second trial whose analysis results approach the second target shape during the repeated second trial.

Description

Technical Field

[0001] The present invention relates to a method for calculating a heating plan used in a bending process of a metal plate using linear heating. Background Art

[0002] Ships have complex curved surfaces, such as bows, bulbous bows, and sterns. To create these curved surfaces, multiple steel plates are bent and then joined by welding. Linear heating is a widely used bending technique in shipbuilding.

[0003] Linear heating, a technique that utilizes the thermal deformation generated when heating the surface of a steel plate with a gas burner, has long been used in many shipyards in Japan. When bending steel plates using linear heating, plastic deformation occurs when the steel plate is locally heated by the flame of a gas burner and then rapidly cooled by adding water to the heated area. This plastic deformation can be controlled by adjusting the amount of heat input to the steel plate, such as the speed of the heating gas burner, the mixture ratio of the combustion gas to the incoming oxygen, and the distance between the burner and the steel plate. Furthermore, bending using linear heating is a processing technique that allows the steel plate to approach the target curved shape by arranging multiple heating wires at appropriate positions.

[0004] However, the deformation produced during linear heating is a complex deformation with a mixture of longitudinal contraction / lateral contraction and longitudinal bending / lateral bending. It also depends on the input heat, the movement speed of the gas burner, the heating position, etc., and is very difficult to predict. Therefore, bending processing using linear heating is one of the technologies that is difficult to automate.

[0005] In order to automate bending processing using linear heating, a method for calculating a heating pattern to be used has been proposed (for example, see Patent Document 1).

[0006] Prior art documents

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2013-66902 Summary of the Invention

[0009] In the conventional heating method, since the heating method is calculated based on the target inherent strain calculated from the target shape, it is necessary to perform complicated corrections in areas where heating lines are densely packed.

[0010] The present invention has been made in view of such circumstances, and provides a calculation method capable of calculating a heating plan including a plurality of heating lines that are optimal for bringing a metal plate close to a target shape.

[0011] The present invention provides a calculation method for a heating scheme used in a bending process of a metal plate using linear heating. The calculation method of the present invention comprises: a first step of performing a finite element method structural analysis under a first heating condition including at least one first heating line set at a first position of an analysis model of the metal plate, and repeatedly performing a first trial comparing the analysis result with a first target shape by changing the position of the first heating line; a second step of selecting at least one first heating line set in a first trial whose analysis result in the repeated first trial is close to the first target shape as a first selected heating line; a third step of performing a finite element method structural analysis under a second heating condition including the first selected heating line and at least one second heating line set at a second position of the analysis model, and repeatedly performing a second trial comparing the analysis result with the first target shape by changing the position of the second heating line; a fourth step of selecting at least one second heating line set in a second trial whose analysis result in the repeated second trial is close to the first target shape as a second selected heating line; a fifth step of performing a finite element method structural analysis under a second heating condition including the first selected heating line and at least one second heating line set at a second position of the analysis model, and repeatedly performing a second trial comparing the analysis result with the first target shape by changing the position of the second heating line; In a sixth step, a finite element method structural analysis is performed under a third heating condition including the first, second, and third selected heating lines, and at least one third heating line set at a third position of the analysis model, and a third trial is repeated with the position of the third heating line changed; in a sixth step, the at least one third heating line set in the third trial whose analysis result is close to the second target shape in the repeated third trial is selected as the third selected heating line; in a seventh step, a finite element method structural analysis is performed under a fourth heating condition including the first, second, and third selected heating lines, and at least one fourth heating line set at a fourth position of the analysis model, and a fourth trial is repeated with the position of the fourth heating line changed; and in an eighth step, the at least one fourth heating line set in the fourth trial whose analysis result is close to the second target shape in the repeated fourth trial is selected as the fourth selected heating line. The heating scheme includes the first, second, third, and fourth selected heating lines.

[0012] The calculation method of the present invention repeatedly selects heating lines that approximate the target shape from heating lines set at various positions. This allows calculation of a heating plan that includes multiple heating lines that are optimal for bringing the metal plate closer to the target shape. Furthermore, by heating the metal plate based on the calculated heating plan, the metal plate can be deformed into a shape that approximates the target shape.

[0013] In the calculation method of the present invention, in steps 1 through 4, the heating lines set in the trials where the analysis results were compared with the first target shape and the results were close to the first target shape are selected as the selected heating lines. In steps 5 through 8, the heating lines set in the trials where the analysis results were compared with the second target shape and the results were close to the second target shape are selected as the selected heating lines. Therefore, a heating plan can be created by setting intermediate target shapes and a final target shape. Furthermore, even if the final target shape is complex, by setting intermediate target shapes and creating a staged heating plan, a heating plan capable of bending metal sheets with high precision can be created.

[0014] Furthermore, if the number of selected heater lines increases excessively during calculation, it may be necessary to reselect the heater lines. In this case, if an intermediate target shape is set, it is possible to return to the intermediate target shape without returning to the initial stage and reselecting the heater lines. This improves the efficiency of creating heating plans. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a flowchart of a calculation method according to one embodiment of the present invention.

[0016] Figure 2 This is a flowchart of a calculation method according to one embodiment of the present invention.

[0017] Figure 3 (a) to (c) are explanatory diagrams of a calculation method according to one embodiment of the present invention.

[0018] Figure 4 This is an explanatory diagram of a method for setting a heating line included in a calculation method according to one embodiment of the present invention.

[0019] Figure 5 This is an explanatory diagram of a method of selecting cells on a heating line included in a calculation method according to one embodiment of the present invention.

[0020] Figure 6 This is an explanatory diagram showing a comparison between an analysis result and a target shape included in a calculation method according to one embodiment of the present invention.

[0021] Figure 7 (a) to (e) are the heating schemes calculated in the simulation.

[0022] Figure 8 (a) to (d) are the analysis results of the structural analysis based on the calculated heating scheme.

[0023] Figure 9(a) is the target shape (bowl shape) used in the simulation, and (b) is the analysis result of the structural analysis based on the calculated heating scheme.

[0024] Figure 10 It is a comparison Figure 9 (a) (b) Graphs showing the target shape and analysis results at the dotted line AA'.

[0025] Figure 11 It is a comparison Figure 9 (a) (b) Graphs showing the target shape and analysis results at the dashed line BB'.

[0026] Figure 12 (a) is the target shape (saddle shape) used in the simulation, and (b) is the analysis result of the structural analysis based on the calculated heating scheme.

[0027] Figure 13 is the heating scheme calculated in the simulation.

[0028] Figure 14 It is a comparison Figure 12 (a) (b) Graphs showing the target shape and analysis results at the dotted line AA'.

[0029] Figure 15 It is a comparison Figure 12 (a) (b) Graphs showing the target shape and analysis results at the dotted line BB'.

[0030] Figure 16 (a) is the target shape (distorted type) used in the simulation, and (b) is the analysis result of the structural analysis based on the calculated heating scheme.

[0031] Figure 17 is the heating scheme calculated in the simulation.

[0032] Figure 18 It is a comparison Figure 16 (a) (b) Graphs showing the target shape and analysis results at the dotted line AA'.

[0033] Figure 19 It is a comparison Figure 16 (a) (b) Graphs showing the target shape and analysis results at the dotted line BB'. DETAILED DESCRIPTION

[0034] The present invention is a method for calculating a heating scheme used in a bending process of a metal plate using linear heating, comprising: a first step of performing a finite element method structural analysis under a first heating condition including at least one first heating line set at a first position of an analysis model of the metal plate, and repeatedly performing a first trial by changing the position of the first heating line and comparing the analysis result with a first target shape; a second step of selecting at least one first heating line set in a first trial whose analysis result in the repeated first trial is close to the first target shape as a first selected heating line; a third step of performing a finite element method structural analysis under a second heating condition including the first selected heating line and at least one second heating line set at a second position of the analysis model, and repeatedly performing a second trial by changing the position of the second heating line and comparing the analysis result with the first target shape; a fourth step of selecting at least one second heating line set in a second trial whose analysis result in the repeated second trial is close to the first target shape as a second selected heating line. hot line; a fifth step of performing a finite element method structural analysis under a third heating condition including a first selected heating line, a second selected heating line, and at least one third heating line set at a third position of the analysis model, and repeatedly performing a third trial of comparing the analysis result with the second target shape by changing the position of the third heating line; a sixth step of selecting at least one third heating line set in a third trial in which the analysis result approaches the second target shape in the repeated third trial as the third selected heating line; a seventh step of performing a finite element method structural analysis under a fourth heating condition including the first selected heating line, the second selected heating line, and the third selected heating line, and at least one fourth heating line set at a fourth position of the analysis model, and repeatedly performing a fourth trial of comparing the analysis result with the second target shape by changing the position of the fourth heating line; and an eighth step of selecting at least one fourth heating line set in a fourth trial in which the analysis result approaches the second target shape in the repeated fourth trial as the fourth selected heating line. In addition, the heating scheme includes the first selected heating line, the second selected heating line, the third selected heating line, and the fourth selected heating line.

[0035] If, in the fourth step, the finite element method structural analysis results under the second heating condition, including the first and second selective heating lines, show a significant difference from the first target shape, the first, second, third, and fourth steps can be repeated. If, in the eighth step, the finite element method structural analysis results under the fourth heating condition, including the first, second, third, and fourth selective heating lines, show a significant difference from the second target shape, the fifth, sixth, seventh, and eighth steps can be repeated. This prevents the heating plan from including too many selective heating lines, thus preventing the heating plan from becoming costly. Furthermore, the efficiency of heating plan production can be improved.

[0036] In the calculation method of the present invention, the positions of the first, second, third, or fourth heating lines can be determined based on stored processing data or artificial intelligence that has learned the stored processing data. This reduces the number of trials required in each heating line selection process and speeds up the calculation of heating plans.

[0037] In the calculation method of the present invention, the initial shape of the metal plate analysis model can be set to the shape of the metal plate after bending, and the shape of the metal plate before bending can be set to the first or second target shape. This allows calculation of an optimal heating plan.

[0038] In the calculation method of the present invention, the initial shape of the metal sheet analysis model can be set to the shape after the pre-bending process using linear heating. This allows the creation of a heating plan for processing the metal sheet by combining a pre-bending process such as a stamping process with a bending process using linear heating.

[0039] The present invention will be described in more detail below with reference to various embodiments. The structures shown in the drawings and the following description are merely exemplary, and the scope of the present invention is not limited to the structures shown in the drawings and the following description.

[0040] First embodiment

[0041] Figure 1 and Figure 2 is a flowchart of the calculation method of this embodiment, Figure 3 (a) to (c) are diagrams illustrating the calculation method. Figure 4 This is an illustration of how to set up the heating wire. Figure 5 This diagram explains how to select cells on a heating line.

[0042] The calculation method of the present embodiment is a calculation method for a heating scheme 6 used in a bending process of a metal plate using linear heating. Furthermore, the calculation method of the present embodiment comprises: a first step of performing a finite element method structural analysis under a first heating condition including at least one first heating line 4 set at a first position of an analysis model 2 of a metal plate, and repeatedly performing a first trial comparing the analysis result 3 with a first target shape 10 by changing the position of the first heating line 4; a second step of selecting as a first selected heating line 5 at least one first heating line 4 set in a first trial in which the analysis result 3 in the repeated first trial approaches the first target shape 10; a third step of performing a finite element method structural analysis under a second heating condition including the first selected heating line 5 and at least one second heating line 4 set at a second position of the analysis model 2, and repeatedly performing a second trial comparing the analysis result 3 with the first target shape 10 by changing the position of the second heating line 4; and a fourth step of selecting as a second selected heating line 5 at least one second heating line 4 set in a second trial in which the analysis result 3 in the repeated second trial approaches the first target shape 10; In a fifth step, a finite element method structural analysis is performed under a third heating condition including the first and second selective heating lines 5 and at least one third heating line 4 set at a third position of the analysis model 2, and a third trial is repeated to compare the analysis result with the second target shape 10 by varying the position of the third heating line 4. In a sixth step, the at least one third heating line 4 set in the third trial in which the analysis result approximates the second target shape 10 in the repeated third trial is selected as the third selected heating line 5. In a seventh step, a finite element method structural analysis is performed under a fourth heating condition including the first, second, and third selective heating lines 5 and at least one fourth heating line 4 set at a fourth position of the analysis model 2, and a fourth trial is repeated to compare the analysis result with the second target shape 10 by varying the position of the fourth heating line 4. In an eighth step, the at least one fourth heating line 4 set in the fourth trial in which the analysis result approximates the second target shape 10 in the repeated fourth trial is selected as the fourth selected heating line 5. Furthermore, the heating scheme includes the first, second, third, and fourth selective heating lines 5.

[0043] In the second, fourth, sixth or eighth step, the heating line 4 whose analysis result 3 is closest to the first or second target shape 10 may be selected, or the heating line 4 whose analysis result 3 is second or third closest to the first or second target shape 10 may be selected.

[0044] In addition, the program of this embodiment is produced so as to cause a computer to execute the calculation method of this embodiment.

[0045] The calculation method of the present embodiment is a method of calculating a heating pattern used in bending a metal plate using linear heating, using finite element method structural analysis (FEM structural analysis).

[0046] A heating plan is a plan for heating the metal sheet for the bending process.

[0047] In the calculation method of this embodiment, an analysis model 2 of a metal plate is used. The length, width, thickness, etc. of the metal plate are set in the analysis model 2. In addition, the analysis model 2 of the metal plate has a front surface and a back surface. In addition, the analysis model 2 is divided into a plurality of units (grids) 8. The unit 8 can be a shell such as a square or a triangle, or a solid such as a cube, a rectangular parallelepiped, a triangular pyramid, or a triangular prism. In addition, each vertex of the unit 8 becomes a node 9. For example, in Figure 3 In the analytical model 2 shown in (a), the analytical model 2 is divided into 20×20 (400) units 8, each of which is a quadrilateral shell. In this case, the analytical model 2 is in a lattice shape, and each intersection is a node 9.

[0048] In the calculation method according to the present embodiment, models of the first and second target shapes 10 are used. The first and second target shapes 10 are shapes that are targets for the bending process of the metal plate. Models of the first and second target shapes 10 are created by moving the nodes 9 so that the shape of the analysis model 2 of the metal plate becomes the first or second target shape 10. The second target shape 10 is the final target shape, while the first target shape 10 is an intermediate target shape before reaching the final target shape. Here, only one intermediate target shape is set, but multiple intermediate target shapes (for example, 3 to 10 intermediate target shapes) can be set. Thus, by setting the intermediate target shapes and the final target shape to create a heating scheme, even if the final target shape is a complex shape, a heating scheme that can bend the metal plate with high precision can be created.

[0049] Intermediate target shapes can be produced based on past machining data.

[0050] In the calculation method of this embodiment, for example, by causing a computer to execute a calculation based on Figure 1 、 Figure 2 The program created by the flowchart shown in the figure can calculate the heating scheme 6. Figure 1 、 Figure 2 The flowchart shown is used for explanation.

[0051] First, the computer reads the model of the first target shape 10 and the analysis model 2. The first target shape 10 is an intermediate target shape.

[0052] Next, a heater line 4 is set at a first position on the analysis model 2. The first position can be set randomly at any position on the analysis model 2. The first position can be a position on the surface of the metal plate analysis model 2 or a position on the back surface of the analysis model 2. The heater line 4 can be a straight line or a curved line. Furthermore, multiple heater lines 4 can be set. For example, five heater lines 4 can be set.

[0053] For example, when the heating line 4 is a straight line, Figure 4 As shown, any two nodes 9 (x1, y1) and (x2, y2) of the analysis model 2 can be randomly selected, and the heating line 4 can be set as a straight line connecting the two nodes 9. In this case, the set heating line 4 can be expressed by the formula: y = {(y2-y1) / (x2-x1)}x + {(x2y1-x1y2) / (x2-x1)}.

[0054] For example, you can set Figure 3 (a) shows the heating line 4a. In addition, when setting five heating lines 4, heating lines 4a to 4e can be set. Figure 3 In (a) to (c), although there is no difference between the heating wire 4 or the optional heating wire 5 set on the surface of the metal plate and the heating wire 4 or the optional heating wire 5 set on the back of the metal plate, some of the heating wires 4a to 4v and the optional heating wire 5 are set on the surface of the metal plate, and some are set on the back of the metal plate.

[0055] Then, select the unit 8 on the set heating line 4. If at least one of the sides of the unit 8 intersects the heating line 4, then the unit 8 can be considered to be on the heating line 4. For example, Figure 5 In the analytical model 2 shown, elements (1), (2), and (3) are on the heating line 4, but element (4) is not on the heating line 4. When multiple heating lines 4 are set, elements 8 on the multiple heating lines 4 are selected.

[0056] Next, a finite element method structural analysis is performed using analysis model 2. In this finite element method structural analysis, strain is applied to selected elements 8 under heating conditions in which the set heating wire 4 performs linear heating, resulting in analysis result 3 (analysis model deformed by structural analysis). Heating conditions can include not only the position of the heating wire 4 but also the amount of heat input. If the first heating wire 4 is positioned on the surface of the analysis model 2 of the metal plate, the metal plate is heated from the surface during analysis. If the first heating wire 4 is positioned on the back side of the analysis model 2 of the metal plate, the metal plate is heated from the back side during analysis.

[0057] Finite element structural analysis can be either FEM thermoelastic analysis or elastic analysis using the inherent strain method. Structural analysis can include linear heating using a gas burner, lasers (such as laser forming), or induction heating. Furthermore, material properties (such as Young's modulus, Poisson's ratio, and density) of the metal sheet being bent are used in structural analysis.

[0058] In FEM thermoelastic analysis, the inherent strain of four components (i.e., longitudinal contraction, lateral contraction, angular deformation, and longitudinal bending) of the selected element 8 is calculated relative to the heating conditions (the set position of the heating wire 4 (including the heated surface) and the heat input (J / mm)). In FEM thermoelastic analysis, deformation analysis is performed by sequentially reproducing the thermal and deformation history, enabling analysis of transitional conditions.

[0059] In the elastic analysis using the inherent strain method, it is considered that the deformation of the metal plate (analysis model 2) caused by linear heating is caused by the inherent deformation. If the inherent deformation is known, the deformation of the metal plate (analysis model 2) caused by linear heating can be predicted by applying the inherent deformation as a forced strain along the heating line 4 in the elastic analysis. Therefore, in the elastic analysis using the inherent strain method, the structural analysis is performed using the inherent strain calculated or measured in advance. For example, the inherent strain calculated using FEM thermoelastoplastic analysis or the inherent strain obtained by measuring the actual linearly heated deformed metal plate can be used for the elastic analysis using the inherent strain method. In addition, the elastic analysis based on the inherent strain method can be performed using a pre-calculated or measured formula representing the relationship between the input heat and the inherent strain.

[0060] In addition, the inherent strain method is an elastic analysis, so its calculation time is much shorter than that of thermoelastoplastic analysis as a characteristic.

[0061] Next, the analysis result 3 is compared with the first target shape 10, and an error is evaluated between the analysis result 3 and the first target shape 10. Then, the error and the set position of the heater line 4 are stored in the storage unit.

[0062] As an evaluation index, for example, the out-of-plane displacement amount (displacement amount) or curvature of the node 9 may be used.

[0063] Figure 6 1 is an explanatory diagram showing the comparison between the analysis result 3 and the first target shape 10 when the out-of-plane displacement 13 of the node 9 is used as an evaluation index. Figure 6As shown, the displacement (error) in the out-of-plane direction from node 9 in analysis result 3 to node 12 of the corresponding first target shape 10 is calculated. In this way, when the evaluation indicator is the displacement of node 9, a heating plan that can quickly bring the metal plate closer to the first target shape can be calculated.

[0064] When the curvature of node 9 is used as an evaluation indicator, the error between the curvature of node 9 in analysis result 3 and the curvature of node 12 in the first target shape 10 corresponding to node 9 is calculated. In this way, when curvature is used as the evaluation indicator, a heating plan that can accurately bring the metal sheet close to the first target shape can be calculated.

[0065] Whether to use the displacement amount or the curvature as the evaluation index may be determined in consideration of the first target shape, processing efficiency, and the like.

[0066] The flow from setting the heater wire 4 to saving the error and the set position of the heater wire 4 is referred to as a first trial.

[0067] When the first trial is completed, the second trial is carried out. The second trial is basically the same process as the first trial, but the heating line 4 of the second trial is set at a position different from the setting position of the heating line 4 of the first trial. The position can be randomly set at any position of the analysis model 2. In addition, the position can be a position included in the surface of the analysis model 2 of the metal plate, or a position included in the back of the analysis model 2. In the second trial, the heating line 4 can be a straight line or a curve. In addition, multiple heating lines 4 can also be set. For example, set Figure 3 (a) shows heating line 4b. Furthermore, when five heating lines 4 are set, for example, heating lines 4f to 4j can be set. Then, cells 8 on the set heating lines 4 are selected and a finite element method structural analysis is performed to obtain analysis results 3. The obtained analysis results 3 are compared with the first target shape 10, and the errors and the positions of the set heating lines 4 are stored in the memory unit.

[0068] Repeat this experiment X times. For example, Figure 3 As shown in (a), the positions of the heater wires 4 can be set to heater wires 4c to 4k, and trials can be performed at each position. Furthermore, multiple heater wires 4 can be set for each trial. For example, if five heater wires are set, five heater wires 4 can be set for each trial. The number of trials can be set to 500, for example.

[0069] In the second to X-th trials, the displacement amount or curvature may be used as an index for evaluating the error between the analysis result 3 and the first target shape 10 , but the same index as in the first trial is used.

[0070] The analysis result 3 in each trial has a shape corresponding to the heating wire 4 at a different position, and thus has a different shape. The error between the analysis result 3 and the first target shape 10 is different in each trial.

[0071] Then, the heating line 4 in the trial with the smallest error between the analysis result 3 in each trial and the first target shape 10 is selected as the selected heating line 5. Alternatively, the heating line 4 in the trial with the second smallest, third smallest, fourth smallest, or fifth smallest error between the analysis result 3 in each trial and the first target shape 10 can be selected as the selected heating line 5. Which heating line 4 in the trial is selected as the selected heating line 5 can be determined by taking into account the first target shape 10, the size of the bending amount, etc. In addition, when multiple heating lines 4 are set in the trial, multiple heating lines 4 are selected as the selected heating line 5. For example, Figure 3 The heating wire 4d is selected from the heating wires 4a to 4k shown in (a). In addition, when five heating wires 4 are set in each trial, for example, the heating wires 4f to 4j can be selected.

[0072] The process from the first trial to the selection of the heating wire 5 is referred to as the first heating wire selection process.

[0073] When the first heating line selection process is completed, the second heating line selection process is carried out. The second heating line selection process is basically the same as the first heating line selection process, but when the heating line 4 is randomly set at an arbitrary position of the analysis model 2, both the selected heating line 5 selected in the first heating line selection process and the heating line 4 randomly set in each trial of the second heating line selection process are set to select the unit 8 on the selected heating line 5 and the unit 8 on the set heating line 4. Moreover, by performing structural analysis under this heating condition, an analysis result 3 reflecting both the selected heating line 5 and the set heating line 4 can be obtained. In the second heating line selection process, multiple heating lines 4 can also be set in each trial. In addition, the number of heating lines 4 set in each trial of the first heating line selection process and the number of heating lines 4 set in each trial of the second heating line selection process can also be different numbers. For example, it can be set Figure 3 (b) shows the selected heating line 5 and the heating line 41. When five heating lines 4 are set in each trial, for example, the selected heating lines (heating lines 4f to 4j) and the heating lines 41 to 4p selected in the first heating line selection process can be set.

[0074] In the second heating line selection process, the trial is repeated until X times, and the heating line 4 in the trial with the smallest error between the analysis result 3 and the first target shape 10 in each trial is selected as the selected heating line 5. Alternatively, the heating line 4 in the trial with the second smallest or third smallest error between the analysis result 3 and the first target shape 10 in each trial can be selected as the selected heating line 5. In addition, if multiple heating lines 4 are set in the trial, multiple heating lines 4 can be selected as the selected heating line 5. For example, Figure 3 The heating wire 4s is selected from the heating wires 41 to 4v shown in (b). In addition, when five heating wires 4 are set in each trial, for example, the heating wires 41 to 4p can be selected.

[0075] The third, fourth, ..., nth heating line selection process is performed sequentially. Each heating line selection process (referred to as the Ath heating line selection process) is basically the same process as the first heating line selection process, but when at least one heating line 4 is randomly set at any position in the analysis model 2, the at least one heating line 4 randomly set in each trial of the Ath heating line selection process and all selected heating lines 5 selected in the (A-1)th and previous heating line selection processes are set. Furthermore, in each trial of the Ath heating line selection process, multiple heating lines 4 may be set for the trial. For example, when five heating lines 4 are set, the trial is set using the five heating lines 4 randomly set in each trial and all selected heating lines 5 selected in the (A-1)th and previous heating line selection processes.

[0076] For example, in the third heating line selection process, the selected heating line 5 (4d) selected in the first heating line selection process, the selected heating line 5 (4s) selected in the second heating line selection process, and at least one heating line 4 randomly set in each trial of the third heating line selection process are set. In other words, as the number of heating line selection processes increases, the number of selected heating lines 5 set increases.

[0077] Furthermore, by selecting all cells 8 on the selected heating lines 5 and cells 8 on the set heating lines 4 and performing structural analysis under the heating conditions, analysis results 3 reflecting all selected heating lines 5 and set heating lines 4 can be obtained.

[0078] In the Ath heating line selection process, trials are repeated until X times, and the heating line 4 in the trial with the smallest error between the analysis result 3 and the first target shape 10 among the trials is selected as the selected heating line 5. Alternatively, the heating line 4 in the trial with the second or third smallest error between the analysis result 3 and the first target shape 10 among the trials may be selected as the selected heating line 5. Furthermore, if multiple heating lines 4 are set in the trial, multiple heating lines 4 are selected as the selected heating line 5.

[0079] If it is determined that the error between the analysis result 3 under the heating conditions including the selected heating line 5 selected in the nth heating line selection process and the first target shape 10 is small, the iteration of the heating line selection process using the first target shape 10 is terminated.

[0080] An upper limit can be set for the number of times the heater selection process is repeated. This upper limit can be set to exceed the number of selected heaters 5 required to achieve the first target shape 10. If the number of heater selection processes reaches the upper limit and the error between the analysis result 3 and the first target shape 10 is large, the process restarts with the first heater selection process. This prevents the heating plan from including too many selected heaters 5, thereby preventing the heating plan from increasing processing costs.

[0081] When the repetition of the heating line selection process for making the analysis result close to the first target shape 10 is completed, then, as shown in FIG. Figure 2 As shown in the flowchart, the model of the second target shape 10 is read into the computer, the target shape is replaced from the first target shape 10 to the second target shape 10, and the heating line selection process is repeated (from the (n+1)th to the mth time). The second target shape 10 is the final target shape. The (n+1)th selected heating line is selected in the (n+1)th heating line selection process, the (n+2)th selected heating line is selected in the (n+2)th heating line selection process, and the Bth selected heating line is selected in the Bth heating line selection process.

[0082] Furthermore, if it is determined that the error between the analysis result 3 under the heating condition including the mth selected heating line 5 selected in the mth heating line selection process and the second target shape 10 is small, the iteration of the heating line selection process using the second target shape 10 is terminated, and the heating plan 6 including the selected heating lines 5 selected in the 1st to nth and (n+1)th to mth heating line selection processes is completed. The heating plan 6 is, for example, Figure 3 As shown in (c), it includes multiple optional heating wires 5.

[0083] exist Figure 2 In the flowchart shown, in each trial of the heating wire selection process using the second target shape 10, although the selected heating wire 5 selected in the heating wire selection process using the first target shape 10 is also set and the finite element method structural analysis is performed, it is also possible to read the analysis results that are smaller than the first target shape or the first target shape, and set the heating wire 4 in the read analysis model (in this case, the selected heating wire 5 selected in the heating wire selection process using the first target shape 10 is not set).

[0084] In the repetition of the heating wire selection process using the second target shape 10, an upper limit can also be set for the number of times the heating wire selection process is performed. The upper limit can be set to exceed the number of selected heating wires 5 required to reach the second target shape 10. If the number of times the heating wire selection process is performed reaches the upper limit and the error between the analysis result 3 and the second target shape 10 is large, the heating wire selection process is restarted from the (n+1)th time. In this way, it is possible to prevent the number of selected heating wires 5 included in the heating scheme from becoming too large, and it is possible to prevent the heating scheme from becoming a high processing cost. In addition, if the number of selected heating wires 5 included in the heating scheme increases too much, it is possible to return to the intermediate target shape instead of returning to the initial stage and reselecting the selected heating wires 5. Therefore, the production efficiency of the heating scheme can be improved.

[0085] The indicators used to evaluate the difference between the analysis result 3 and the first or second target shape 10 can be changed between the heating line selection process using the first target shape 10 and the heating line selection process using the second target shape 10. For example, the displacement can be used as an indicator in the heating line selection process using the first target shape 10, while the curvature can be used as an indicator in the heating line selection process using the second target shape 10. This allows for faster processing speed when heating with the selected heating line 5 selected in the heating line selection process using the first target shape 10, while improving processing accuracy when heating with the selected heating line 5 selected in the heating line selection process using the second target shape 10. This allows for a balance between processing efficiency and processing accuracy.

[0086] By linearly heating the metal sheet and performing the bending process based on the obtained heating plan 6, the metal sheet can be deformed into a shape close to the final target shape. In addition, even if the final target shape is complex, the metal sheet can be bent with high precision by using the heating plan 6 created by setting the intermediate target shape.

[0087] The bending process of the metal plate can be performed by an operator or automatically by a machine. When the metal plate is bent by a machine, a plurality of selective heating wires 5 can be heated simultaneously.

[0088] The heating plan 6 may include an order for selecting the heating wires 5 corresponding to the order of the heating wire selection process. When the metal sheet is subjected to linear heating and bending according to the heating plan 6, the selected heating wires 5 may be heated in this order. This allows the metal sheet to be deformed into a shape closer to the target shape.

[0089] The method for processing a metal plate based on the obtained heating scheme 6 may include: a step of linearly heating the metal plate under the heating conditions of the selected heating wire 5 selected in the Ath (A=1~n) or Bth (B=(n+1)~m) heating wire selection process to perform bending processing on the metal plate; a step of measuring the three-dimensional shape of the metal plate after the bending processing; a step of comparing the measured three-dimensional shape of the metal plate with the analysis result 3 of the finite element method structural analysis performed under the heating conditions of the selected heating wire 5 included in the Ath or Bth heating wire selection process; and a step of heating the metal plate based on the comparison result so that the three-dimensional shape of the metal plate is close to the analysis result 3.

[0090] The step of measuring the three-dimensional shape of the metal plate can be performed using a 3D measuring instrument. This instrument can be a contact type, a scanning laser probe type, or a non-contact optical type. This allows the metal plate to be deformed into a shape closer to the target shape.

[0091] The device for automatically processing a metal plate based on the heating plan 6 may include, for example, a heating unit for heating the metal plate and a control unit for controlling the processing device. The control unit is configured to read the heating plan 6 and control the heating unit to heat the metal plate according to the heating plan 6.

[0092] Second embodiment

[0093] In the first embodiment, the position of the heater wire 4 is randomly set in each trial. However, in the second embodiment, it is determined based on stored processing data or artificial intelligence that has learned the stored processing data. This reduces the number of trials performed in each heater wire selection process and speeds up the calculation of the heating plan.

[0094] The other configurations are the same as those of the first embodiment. In addition, the descriptions of the first embodiment also apply to the second embodiment unless there is any contradiction.

[0095] Third embodiment

[0096] In the calculation heating method of the third embodiment, the initial shape of the analysis model 2 of the metal plate is the shape of the metal plate after the bending process (the final target shape of the first embodiment), the first target shape is the shape during the process (the intermediate target shape of the first embodiment), and the second target shape is the shape of the metal plate before the bending process (the flat plate shape of the first embodiment). The calculation method of the heating scheme is the same as that of the first embodiment, but the order of the selected heating lines 5 included in the heating scheme is reversed. That is, in the heating scheme calculated in the first embodiment, the order is from the first selected heating line to the mth selected heating line, while in the heating scheme calculated in the second embodiment, the order is from the mth selected heating line to the first selected heating line. By such a calculation method, an excellent heating scheme can be calculated.

[0097] In addition, in the calculation method of the first embodiment, the first target shape and the second target shape are set, but in the calculation method of the third embodiment, only one target shape may be set.

[0098] The other configurations are the same as those of the first or second embodiment. In addition, the descriptions of the first or second embodiment also apply to the third embodiment unless there is any contradiction.

[0099] Fourth embodiment

[0100] In the heating plan calculation method of the fourth embodiment, the initial shape of the metal plate analysis model 2 is the shape after the previous step of bending the metal plate using linear heating. The previous step is, for example, a stamping process. This calculation method enables the creation of a heating plan for processing a metal plate by combining a previous step such as a stamping process with a bending process using linear heating.

[0101] The other configurations are the same as those of the first, second, or third embodiment. The descriptions of the first, second, or third embodiment also apply to the fourth embodiment unless there is any contradiction.

[0102] simulation

[0103] The calculation method of the present invention (structural analysis: elastic analysis using the inherent strain method) is used to calculate heating schemes (target shapes: bowl, saddle, and twisted), and the calculated heating schemes are used to simulate elastic analysis (structural analysis) using the inherent strain method.

[0104] The inherent strain applied to the element for deformation analysis using the inherent strain method is obtained by performing FEM thermoelastic analysis on the analysis model and from the deformation results.

[0105] In the structural analysis based on the inherent strain method, a plate-shaped analysis model with a plate length of 500 mm and a plate width of 500 mm was used. The analysis model was divided into quadrilateral shell elements so that the number of nodes and elements was 2,601 and 2,500, respectively. The metal plate material was assumed to be SM490A (rolled steel for welded structures) with a plate thickness of 16 mm. The material constants of SM490A are shown in Table 1. In addition, three target shapes (bowl, saddle, and torsion) were set for the simulation. The number of trials required to determine the position of a single selected heating line was set to 500.

[0106] [Table 1]

[0107] Young's modulus: 212000MPa Poisson's ratio: 0.3 <![CDATA[Density: 7.81×10 -3 g / cm 3 >

[0108] In the FEM thermoelastic-plastic analysis used to determine inherent strain, the analysis model was set to a plate length of 500 mm, a plate width of 500 mm, a plate thickness of 16 mm, and the number of nodes and elements was set to 61,711 and 50,000, respectively. Welding conditions were set to a current of 150 A, a voltage of 20 V, a welding speed of 2.286 mm / sec, and a welding efficiency of 0.8. The resulting inherent strains (longitudinal contraction, transverse contraction, longitudinal curvature, and transverse curvature) are shown in Table 2.

[0109] [Table 2]

[0110] <![CDATA[Longitudinal contraction ε x : -1.135476×10 -2 > <![CDATA[Longitudinal curvature ρ x : -4.790146×10 -4 > <![CDATA[Transverse contraction ε y : -8.340290×10 -3 > <![CDATA[Transverse curvature ρ y : -3.917135×10 -6 >

[0111] Target shape: Bowl

[0112] Figure 7 (a) to (e) are heating plans calculated by setting the number of selected heating lines to 10, 20, 30, 40, and 55, respectively. Figure 8 (a) to (d) are the analysis results of the structural analysis using the inherent strain method based on the heating schemes calculated with the number of selected heating lines set to 10, 20, 30, and 40, respectively. Figure 9 (a) is the target shape used in the structural analysis, Figure 9 (b) shows the analysis results of the structural analysis using the inherent strain method based on the heating pattern calculated with the number of selected heating wires set to 55. Figure 10 It is a comparison Figure 9 The target shape at the dotted line A-A' in (a) and (b) and the out-of-plane displacement distribution of the analysis results, Figure 11 It is a comparison Figure 9 The target shape at the dot-dash line BB' in (a) and (b) and the out-of-plane displacement distribution of the analysis results.

[0113] In simulations where the target shape was a bowl, the curvature at the nodes was used as an indicator to evaluate the difference between the target shape and the analysis result. Furthermore, the number of heating wires was selected to be 10, 20, 30, 40, or 55.

[0114] In this simulation, it is possible to calculate Figure 7 (a) to (e) are heating patterns. In addition, structural analysis using the inherent strain method based on the calculated heating pattern can be performed to obtain Figure 8 (a)~(d) Figure 9 (b) shows the analysis results. Figure 7 The solid lines represent the selective heating lines on the surface of the metal plate, and the dotted lines represent the selective heating lines on the back of the metal plate.

[0115] from Figure 8 (a) to (d) show that when 10 heating lines are selected, the bowl shape is captured, and when 20 heating lines are selected, the shape can be formed into a shape that is roughly consistent with the target shape. After that, it can be confirmed that fine-tuning the shape or adding more heating lines has almost no effect on the shape. In addition, if you pay attention to Figure 7 The heating positions shown in the figure show that more selective heating wires are placed diagonally along the base material. This is believed to be the result of selecting the heating wire positions to achieve uniform bending of the base material using both angular deformation and longitudinal bending in order to form a bowl-shaped shape with a concave center.

[0116] In addition, from Figure 9 (a)(b), Figure 10 、 Figure 11 Can confirm Figure 9 The analysis results shown in (b) capture the trend of the target shape well. Therefore, it can be seen that by heating the metal plate based on the heating plan calculated by the calculation method of the present invention, the metal plate can be bent into a shape close to the target shape.

[0117] Target shape: Saddle

[0118] Figure 12 (a) is the target shape for structural analysis, Figure 12 (b) shows the analysis results of the structural analysis using the inherent strain method based on the heating pattern calculated with the number of selected heating wires set to 40. Figure 13 This is a heating plan calculated by setting the number of selected heating lines to 40. Figure 14 It is a comparison Figure 12 The target shape at the dotted line A-A' in (a) and (b) and the out-of-plane displacement distribution of the analysis results, Figure 15 It is a comparison Figure 12The target shape at the dot-dash line BB' in (a) and (b) and the out-of-plane displacement distribution of the analysis results.

[0119] In the simulation with the target shape set to a saddle, the out-of-plane displacement at the node was used as an indicator to evaluate the error between the target shape and the analysis result. In addition, the number of heating wires was set to 40.

[0120] In this simulation, it is possible to calculate Figure 13 In addition, the structural analysis using the inherent strain method was performed based on the calculated heating scheme, and the results were Figure 12 (b) shows the analysis results.

[0121] from Figure 12 、 Figure 14 、 Figure 15 to Figure 12 The analysis results shown in (b) confirm that the tendency of the target shape is well captured.

[0122] Target shape: Distorted

[0123] Figure 16 (a) is the target shape for structural analysis, Figure 16 (b) shows the analysis results of the structural analysis using the inherent strain method based on the heating pattern calculated with 16 selected heating lines. Figure 17 This is a heating plan calculated by setting the number of selected heating lines to 16. Figure 18 It is a comparison Figure 16 The target shape at the dotted line A-A' in (a) and (b) and the out-of-plane displacement distribution of the analysis results, Figure 19 It is a comparison Figure 16 The target shape at the dot-dash line BB' in (a) and (b) and the out-of-plane displacement distribution of the analysis results.

[0124] In simulations where the target shape was a twisted one, the out-of-plane displacement of the nodes was used as an indicator to evaluate the difference between the target shape and the analysis results. Furthermore, the number of heating wires was set to 16.

[0125] In this simulation, it is possible to calculate Figure 17 In addition, the structural analysis using the inherent strain method was performed based on the calculated heating scheme, and the results were Figure 16 (b) shows the analysis results.

[0126] from Figure 16 、 Figure 18 、 Figure 19 Can confirm Figure 16 The analysis results shown in (b) capture the tendency of the target shape well.

[0127] Description of Reference Numerals

[0128] 2: Analysis model 3: Analysis results 4, 4a-4v: Heating lines 5: Select heating lines 6: Heating scheme 8: Elements 9: Nodes 10: Target shape 11: Elements of the target shape 12: Nodes of the target shape 13: Displacement between the analysis results and the target shape

Claims

1. A method for calculating a heating pattern used in bending a metal plate using linear heating, characterized in that: This calculation method has: In a first step, a finite element method structural analysis is performed under a first heating condition including at least one first heating line set at a first position of an analysis model of the metal plate, and a first trial is repeatedly performed to compare the analysis result with a first target shape while changing the position of the first heating line; In a second step, at least one first heating line set in a first trial whose analysis result in the repeated first trial is close to the first target shape is selected as a first selected heating line; a third step of performing a finite element method structural analysis under a second heating condition including the first selected heating line and at least one second heating line set at a second position of the analysis model, and repeatedly performing a second trial comparing the analysis result with the first target shape while changing the position of the second heating line; In a fourth step, at least one second heating line set in the second trial whose analysis result in the repeated second trial is close to the first target shape is selected as a second selected heating line; A fifth step of performing a finite element method structural analysis under a third heating condition including the first and second selected heating lines and at least one third heating line set at a third position of the analysis model, and repeatedly performing a third trial of comparing the analysis result with the second target shape by varying the position of the third heating line. In a sixth step, at least one third heating line set in the third trial whose analysis result in the repeated third trial is close to the second target shape is selected as a third selected heating line; A seventh step is to perform a finite element method structural analysis under a fourth heating condition including the first, second, and third selected heating lines, and at least one fourth heating line set at a fourth position of the analysis model, and repeatedly perform a fourth trial of comparing the analysis result with the second target shape while changing the position of the fourth heating line. as well as In an eighth step, at least one fourth heating line set in the fourth trial whose analysis result in the repeated fourth trial is close to the second target shape is selected as a fourth selected heating line; The heating scheme includes a first selected heating line, a second selected heating line, a third selected heating line, and a fourth selected heating line.

2. The calculation method according to claim 1, wherein: If the analysis result of the finite element method structural analysis under the second heating condition including the first selected heating line and the second selected heating line in the fourth step has a large error from the first target shape, the first, second, third and fourth steps are repeated, If in the eighth step the analysis results of the finite element method structural analysis under the fourth heating condition including the first selected heating line, the second selected heating line, the third selected heating line and the fourth selected heating line have a large error with the second target shape, the fifth, sixth, seventh and eighth steps are repeated.

3. The calculation method according to claim 1, wherein: The position of the first heating line, the second heating line, the third heating line, or the fourth heating line is set based on stored processing data or determined by artificial intelligence that has learned the processing data.

4. The calculation method according to claim 2, wherein: The position of the first heating line, the second heating line, the third heating line, or the fourth heating line is set based on stored processing data or determined by artificial intelligence that has learned the processing data.

5. The calculation method according to any one of claims 1 to 4, wherein: The initial shape of the analysis model of the metal plate is the shape of the metal plate after bending. The first target shape or the second target shape is the shape of the metal plate before bending.

6. The calculation method according to any one of claims 1 to 4, wherein: The initial shape of the analysis model of the metal plate is the shape after the previous step of the bending process.

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